JPH03180880A - Image forming device - Google Patents

Abstract

PURPOSE:To uniformize transfer pressure and to simplify adjustment by providing a roller for transferring an image on the upper part of an image carrier and obtaining the transfer pressure by the dead weight of the transfer roller. CONSTITUTION:A printing sheet pulled out from a stacker 20 by a big roller 21 stands tentatively by a pair of resist rollers 22a and 22b, and a sheet position inspection sensor 23 transmits the completion of pulling out the sheet to a device main body. The transfer of the sheet 11 is started by a pair of resist rollers 22a and 22b when a signal to start printing, is received and the sheet is led to a transfer part through a pair of guide rollers 24. At this time, a carrying part 2 and the transfer roller 14 are provided on the upper part of the image carrier 10, and the photosensitive body 10 obtains contact pressure- by the dead weight of the roller 14. The sheet 11 is held between the drum 10 and the roller 14, and a toner image is transferred on the drum 10 and fixed at a fixing part 3. Therefore, transfer pressure is uniformized, adjustment is not needed as well and a device is miniaturized, simplified, and reduced in the cost.

Description

[Detailed description of the invention] [Table of contents] Overview Industrial field of application Prior art (Figure 4) Means for solving the problem to be solved by the invention (Figure 1) Working example (a) 1 Description of Examples (Figures 2 and 3) (b)
Description of other embodiments Effects of the invention [Summary] Regarding an image forming device that transfers an image formed on an image carrier to a print medium by a transfer roller, the necessary transfer pressure can be obtained without providing a spring on the transfer roller. An image carrier, an image forming section that forms an image on the image carrier, a transport section that transports a print medium, and a transfer roller that transfers the image of the image carrier onto the print medium. In the image forming apparatus, the conveyance section and the transfer roller are provided above the image carrier, and transfer pressure is obtained by the weight of the transfer roller.

[Industrial application field]

The present invention relates to an image forming apparatus that transfers an image formed on an image carrier onto a printing medium using a transfer roller.

In image forming devices such as electrophotographic devices and transfer-type electrostatic recording devices, a transfer device is provided to transfer a toner image or latent image formed on an image bearing member such as a photosensitive drum or dielectric drum to a printing medium. ing.

As this transfer device, a transfer roller, which has higher transfer efficiency than a transfer charger, is attracting attention, and even if a transfer roller is used, there is a demand for a device that can be miniaturized.

[Conventional technology]

FIG. 4 is an explanatory diagram of the prior art.

An image forming apparatus, such as an electrophotographic apparatus, is configured as follows.

After the rotating photosensitive drum 10 is pre-charged by a pre-charger 11, it is exposed to light by an image writing section 12 to form an electrostatic latent image.

The electrostatic latent image on the photosensitive drum 10 is developed by a developing device 13 to form a toner image.

On the other hand, the paper is taken out from the hopper 20 by the pick roller 21, hits the registration rollers 22a and 22b, and waits.

The paper being picked up by the pick roller 21 and waiting is detected by the paper position detection sensor 23.

The paper is conveyed from the registration rollers 22a and 22b in synchronization with the toner image on the photosensitive drum 10, and is pressed by the roller 24.
The paper is guided to the photosensitive drum 10 by the transfer roller 14.
The toner image is transferred to the paper.

The paper is further sent to the fixing section 3, where the toner image is fixed by a pressure roller 30 and a fixing roller 31.

On the other hand, after the transfer, the photosensitive drum 10 is cleaned by a cleaner 15 in preparation for the next image forming cycle.

Incidentally, in order to electrostatically clean the photosensitive drum 1O, there is a method in which static electricity is removed using a static eliminator such as a static electricity removal lamp.

The transfer roller 14 is generally a conductive or dielectric roller that applies a transfer bias voltage, but in order to satisfy appropriate transfer conditions, it needs to be pressed against the photosensitive drum 10 with an appropriate pressure. For this purpose, a pressure applying means such as a spring 16 is provided.

[Problem to be solved by the invention]

However, the conventional technology has the following problems.

(2) Since the transfer pressure of the transfer roller 14 is applied by the spring 16, it is difficult to obtain a uniform pressure, and its adjustment is also time-consuming.

(2) The need for the spring 16 increases the size of the transfer device, making it difficult to downsize the device.

(2) Since the spring 16 is required, it is difficult to construct it at low cost.

Therefore, it is an object of the present invention to provide an image forming apparatus that can obtain the necessary transfer pressure without providing a spring to the transfer roller.

[Means to solve the problem]

FIG. 1 is a diagram showing the principle of the present invention.

As shown in FIG. 1, the present invention includes an image carrier lO, an image forming section l that forms an image on the image carrier 10, and a printing medium PP.
a conveying section 2 that conveys the image carrier l to the printing medium PP;
In an image forming apparatus having a transfer roller 14 for transferring an image of O, the conveyance section 2 and the transfer roller 14 are provided above the image carrier 10, and transfer pressure is obtained by the weight of the transfer roller 14. This is what I did.

[Effect]

In the present invention, the transfer roller 14 and the conveyance section 2 are connected to the image carrier lO
The transfer roller 14 is provided above the image carrier 10 so that the printing medium PP is moved away from the image carrier 10, and the transfer pressure is obtained by the weight of the transfer roller 14.

This makes the transfer pressure uniform, eliminating the need for adjustment, and eliminating the need for pressure applying means such as springs.
Smaller size and lower cost can be achieved.

〔Example〕

(a) Description of an Embodiment FIG. 2 is a block diagram of an embodiment of the present invention, and FIG. 3 is a block diagram of essential parts of an embodiment of the present invention.

In the figure, the same parts as shown in Figures 1 and 4 are:
Indicated by the same symbol.

In FIG. 2, the printing paper transport section 2, that is, the big roller 21, the registration rollers 22a and 22b, the guide roller 24, and the fixing section 3 are provided above the photosensitive drum IO, and the conveyance path is the photosensitive drum IO. is above.

Conversely, the image forming section 1 (pre-charger 11, image writing section 12, developing device 13) and cleaner 15 are provided below the transport bus.

The transfer roller 14 is provided above the photosensitive drum 10. As shown in the side view of FIG. .

The bracket 1/II is provided with a guide window 142, into which the tip of a guide rod 144 made of polyacetal resin fixed to the main body frame 143 is inserted.

Therefore, the bracket 141 is movable along the guide window in the near direction in the figure, thereby allowing the roller body 140 to
is guided in the vertical direction according to the eccentricity of the photosensitive drum 10.

To explain the operation of this embodiment, a toner image is formed on the photosensitive drum lO as in the conventional manner.

The printing paper pulled out from the stacker 20 by the big roller 21 is temporarily put on standby by a pair of registration rollers 22a and 22b, and an optical or mechanical copying type paper position detection sensor 23 detects that the paper has been pulled out to the main body of the apparatus. tell.

In response to a print start signal from the main body of the apparatus, the sheet 2 is started to be conveyed toward the transfer section by a pair of registration rollers 22a and 22b, and the sheet is transported by a pair of guide rollers 24 upstream of the transfer section.
is guided to the transfer section through the

The transfer roller 14 and the photosensitive drum 10 are already in contact,
The paper is sandwiched between the photosensitive drum IO and the transfer roller 14,
The toner image on the photosensitive drum 10 is transferred, sent to the fixing section 3, and fixed.

The contact pressure between the photosensitive drum 0 and the transfer roller 14 is preferably about 60 g/cm in linear pressure.

Since this pressure can be set by superimposing the transfer roller 14, the desired contact pressure can be obtained by appropriately setting the weights of the roller body 140 and the bracket 141.

In this way, transfer pressure can be obtained by the weight of the transfer roller 14.

(c) Description of other embodiments In the above embodiments, the image bearing member is described as a photosensitive drum, but it may also be belt-shaped, and electrostatic recording using not only a photosensitive member but also a dielectric material is possible. It may be.

Further, although the description has been made regarding the transfer of a toner image, latent image transfer may also be used.

Although the present invention has been described above using examples, the present invention can be modified in various ways according to the gist of the present invention, and these are not excluded from the present invention.

(Effects of the Invention) As explained above, according to the present invention, (1) Since the transfer pressure is obtained at zero ton of the transfer roller, the transfer pressure is uniform and there is no need for adjustment.

(2) Furthermore, since no pressure applying means such as a spring is required, the device can be made smaller, simpler, and cheaper.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the principle of the present invention, FIG. 2 is a block diagram of an embodiment of the present invention, FIG. 3 is a block diagram of essential parts of an embodiment of the present invention, and FIG. 4 is an explanatory diagram of the prior art. In the figure, an image forming section, a conveyance section, an image carrier, and a transfer roller.

Claims (1)

[Claims] An image carrier (10), an image forming section (1) that forms an image on the image carrier (10), a transport section (2) that transports a printing medium (PP), and In an image forming apparatus having a transfer roller (14) that transfers an image of the image carrier (10) to a printing medium (PP), the conveyance section (2) and the transfer roller are provided above the image carrier (10). An image forming apparatus comprising: a roller (14), and a transfer pressure is obtained by the weight of the transfer roller (14).