JPS5854390B2 - Kankoutai cleaning method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic developing device having a photoreceptor cleaning function.

As is well known, in electrophotographic copying machines that repeatedly use the same photoreceptor, the electrostatic latent image formed on the photoreceptor is generally developed into a visible image, and the visible image is transferred onto a recording sheet. Thereafter, the photoreceptor is cleaned in order to remove toner remaining on the photoreceptor in preparation for a new copying process.

In the case of the magnetic development method, the carrier is held in the form of a brush in the same way as a magnetic brush is formed using a developer, and the tip of the carrier is brought into contact with the surface of the photoconductor to remove the toner remaining on the surface of the photoconductor. A method of cleaning the photoreceptor by trapping the developer in the above-mentioned ears is known, but recently it has become particularly popular to provide the developing device itself with a photoreceptor cleaning function and to clean the photoreceptor using a magnetic brush of the developer. This method has been proposed as seen in JP-A-47-11539.

By doing so, the copying apparatus can be simplified.

An object of the present invention is to provide a magnetic developing device having a photoconductor cleaning function that can further improve the photoconductor cleaning function provided to the magnetic development device itself.

Hereinafter, the present invention will be described by way of examples with reference to the drawings.

FIG. 1 shows only the essential parts of an example of a magnetic developing device embodying the present invention.

That is, in FIG. 1, reference numeral 1 indicates a photoreceptor, 2 indicates a non-magnetic sleeve, 3 indicates a developer tank, 4 indicates a doctor member, 5 indicates a developer, and 6 indicates a stirring blade. There is.

The photoreceptor 1 is formed in the shape of a drum, and rotates counterclockwise to carry out the copying process through charging, exposure, image formation, development, transfer, and cleaning stations (not shown), including static elimination. .

The photoreceptor 1 is used in a copying machine that uses two rotations and one copy, and the first rotation carries out the process from charging to transfer, and the second rotation carries out the cleaning process. It has become.

As mentioned above, the sleeve 2 is a developing device having a photoreceptor cleaning function, and is made of a non-magnetic material and is formed into a hollow cylindrical shape, and can be rotated counterclockwise around the shaft 2a. It is set in.

Inside the sleeve 2, there are a plurality of magnets (not shown) that are elongated rod-shaped and have magnetic poles perpendicular to the length direction, and are parallel to the length direction of the sleeve 2, that is, the direction perpendicular to the drawing in FIG. It is fixed in a fixed position.

The position and direction of the magnetic poles are such that the developer 5 is drawn up from the developer tank 3 by the magnetism of these magnets, development is performed in the part facing the photoreceptor, and the developer is reused without spilling or scattering. It is determined that the developer is collected in the developer tank 3.

The developer tank 3 is a box, and stores therein a developer 5 containing a magnetic carrier and toner.A replenishing device (not shown) supplies toner and developer as needed. Tank 3 can be replenished.

The doctor member 4 is formed into a hook shape by two plates 41 and 42.

The hand portion of the hook is pivotably attached to the end of the developer tank 3 by a support shaft 4a.

Two plates 41° 420 intersect in a hook shape, of which the plate 41 has a long width, and the plate 42 has a short width.When the length of the plate 41 is set as shown in Fig. 1, its tip is The height of the brush-like spikes formed at the development position is determined to be the optimum height for development due to the developer 5 whose conveyance amount is limited depending on the area.

The height of the ears is slightly larger than the distance between the sleeve 2 and the photoreceptor 10.

Now, development of an electrostatic latent image by the developing device is performed as follows.

That is, if the sleeve 2 is rotated counterclockwise with respect to the photoreceptor 1 which has an electrostatic latent image formed on its surface and rotates in the direction of the arrow, the magnetic force generated by the magnet provided inside the sleeve 2 will be applied. The developer 5 is drawn up and held on the circumferential surface of the sleeve 2 from the right side upward, and is conveyed together with the circumferential surface of the sleeve 20 by rotating the sleeve 20 counterclockwise.

At this time, the height of the spikes of the developer 5 in the developing device facing the photoreceptor 1 is adjusted to the height as described above by the tip of the plate 41 of the doctor member 4.

The brush-shaped developer 5 with the height of the spikes aligned in this manner is further conveyed to a development position, that is, a portion close to the sleeve 2 and the photoreceptor 1, and the tips of the developer 5 come into contact with the surface of the photoreceptor 10. Then, toner is supplied from the tip to the electrostatic latent image to make it a visible image.

When the developer that has contributed to the development passes through the development position, it is sent along the circumferential surface of the sleeve 20 by rotation of the sleeve 20, and is then released from the restraint by the magnetic force of the magnet in the sleeve 2 and collected into the developer tank 3. be done.

The collected developer 5 is stirred into the developer in the developer tank 3 by the counterclockwise rotation of the stirring blade 60.

The visible image formed on the surface of the photoreceptor 10 is transferred to a recording sheet (not shown).

Now, the switching of the posture of the doctor member 4 is controlled by the sequence system of the copying device, and as a predetermined copying process progresses, the photoconductor cleaning mode is set in preparation for a new copying process. At this point, the doctor member 4 is rotated 90 degrees clockwise from the state shown in FIG. 1, resulting in the state shown in FIG. 2.

That is, the tip of the shorter plate 42 of the doctor member 40 is close to the sleeve 2.

Therefore, while rotating the photoreceptor 1 in the direction of the arrow, the sleeve 2
When the developer 5 is rotated counterclockwise, the developer 5 is conveyed to the developing position as described above, but the plate 42 of the doctor member 4
Since the zero width is shorter than the width of the plate 41, a larger amount of developer is pumped up to the development position than during development.
The contact area and contact pressure between the developer 5 and the surface of the photoreceptor 10 are also
It becomes larger than during development.

The pumped up developer 5 rubs the surface of the photoreceptor 1 having the residual toner 1 and removes the residual toner 7 from the surface while applying an external force greater than the adhesion force of the toner remaining on the photoreceptor. .

The removed toner is sucked into the developer 5, and when it passes through the development position, it is collected into the developer tank 3 as described above.

The amount of developer 5 pumped up during photoconductor cleaning should be as large as possible without overflowing from the developer tank 3. As shown in FIG. The plate 41 can also be used to prevent the developer 5 from overflowing.

Furthermore, it has been confirmed through experiments that the cleaning effect can be significantly improved by increasing the speed of rotation of the sleeve 20 in the counterclockwise direction when cleaning the photoreceptor.

In addition, the sleeve 2 is made of a conductive material, and a bias voltage is applied to the sleeve 2 as appropriate in order to provide a counter electrode effect during development and to improve the cleaning effect during photoreceptor cleaning. Needless to say, it is a good thing.

Furthermore, it goes without saying that static elimination of the photoreceptor 1 by light irradiation and alternating current corona discharge may be performed in combination with photoreceptor cleaning according to the present invention.

Further, as shown in FIG. 3, a doctor member 40 having a semicircular cross section is used, and the position of its support shaft 4a is eccentric, and by rotating the doctor member 400, the doctor member 40 and the sleeve 2 are connected. The shortest distance may be changed continuously, and the height of the spikes of developer may be adjusted to the optimum height.

Further, as a method for transporting the developer 5 to the development position, the sleeve 2 may be rotated around a fixed magnet as in the above embodiment, and the magnet may be moved around the shaft 2 within the fixed sleeve 2.
The sleeve 5 and the magnet may both be rotated around a in a direction opposite to the direction in which the developer 5 is conveyed.

In addition, the sleeve does not necessarily have to be as in the above embodiment.
It does not have to be a hollow cylinder.

It goes without saying that the shape of the photoreceptor is not limited to a drum shape, but may also be a plate or belt shape.

As described above, according to the present invention, it is possible to provide a developing device having a simple structure, efficient photoconductor cleaning, and a photoconductor cleaning function.

[Brief explanation of the drawing]

FIG. 1 is a diagram schematically showing only the main parts of an example of a magnetic developing device embodying the present invention, FIG. 2 is a diagram showing a cleaning state of a photoreceptor by the device shown in FIG. The diagram is
FIG. 2 is a diagram schematically showing only the main parts of another example of a magnetic developing device embodying the present invention. 1...Photoreceptor, 2...Sleeve, 3.
...Developer tank, 4...Doctor part, 5...Developer, 7...Residual toner

Claims (1)

[Scope of Claims] The photoreceptor is provided opposite to a photoreceptor which undergoes each copying process of charging, exposure, development, and transfer in the 11th rotation, and undergoes the cleaning copying process including static elimination in the 2nd rotation, The magnetic force of the magnet provided inside the non-magnetic sleeve holds the developer made of a mixture of magnetic carrier and toner on the sleeve, and the relative movement between the sleeve and the magnet causes the developer to A magnetic developing device that develops an electrostatic latent image on a photoreceptor by conveying developer held on a sleeve to a developing position to create brush-like ears,
The height of the spikes of developer held on the sleeve is changed during development and when cleaning the photoconductor, and the height of the spikes is made higher during cleaning the photoconductor than during development. A magnetic developing device having a photoreceptor cleaning function. 2. A magnetic developing device having a photoconductor cleaning function as set forth in claim 1, wherein the conveyance speed of the developer held on the sleeve is made higher during photoconductor cleaning than during development. .