JPH01200379A - Developing device and multicolor image forming device equipped with this device - Google Patents

Abstract

PURPOSE:To prevent magnetic particles from sticking on a latent image carrier by setting magnetic particles to a specific occupation rate with respect to the capacity of a development area formed in the space sandwiched between a developer carrier and the latent image carrier, and stopping a driving means for the developer carrier when no image is formed. CONSTITUTION:The magnetic particles are set to a 1.5-40% occupation rate with respect to the capacity of the development area formed in the space sandwiched between the developer carrier 41 and latent image carrier 1. Further, a control means 46' stops the rotation of a developing sleeve 41 in image formation and no-image formation as a next image formation time. No centrifugal force by the rotation of the sleeve 41 from the developing sleeve 41 to a photosensitive drum 1, therefore, exerts on carriers on the developing sleeve 41. Further, a shock at the time of the napping of carriers is eliminated and the amount of carriers to the amount of toner is suppressed small. Consequently, no carrier sticks on the photosensitive drum 1.

Description

Detailed Description of the Invention (Industrial Applicability!!?) The present invention is used in the field of electrophotography, and is particularly applicable to two-component developers consisting of magnetic particles (carriers) and a so-called magnetic brush. The present invention relates to an apparatus for forming and developing images, and a multicolor image forming apparatus using the apparatus.

(Prior Art and Problems) As a conventionally known apparatus for forming an image by forming a magnetic flap, the one shown in FIG. 4 is known.

In this device, a photosensitive drum C, which is a latent image carrier having a conductive substrate and a photoconductive layer applied thereto, is uniformly charged, for example, negatively, by a charger 2, and then an image signal 3 is transferred to a photosensitive drum 1 using a laser or the like. ~
An electrostatic latent image is formed by scanning over the ram l.

This electrostatic m-image is then reversely developed by the negatively charged toner at the area irradiated with light by the developing device 4. The developing device 4 in this case has a developing sleeve 41 as a developer carrier disposed so as to partially protrude between the front portions of the developing device 4, and this developing sleeve 41 is located between the photosensitive drum l and A developing area is formed facing the toner, and a magnetic brush (not shown) of so-called magnetic particles (hereinafter referred to as carrier) and toner is created in this area to perform development.

Furthermore, in the image forming apparatus as described above, when there is no latent image to be developed on the photosensitive drum l, that is, when no image is being formed, the rotation of the developing sleeve 41 is stopped to prevent carriers from adhering to the photosensitive drum l, Transfer section, which is the process after development,
Measures have been taken to prevent many problems such as image disturbances caused by carriers in fixing sections and the like.

Further, it is also known that the above-mentioned magnetic brush development of carrier and toner is used in a multicolor image forming apparatus. An example of such an apparatus is the one for two-color development shown in FIG. This image forming apparatus has a first developing device 4 and a second developing device 7 disposed facing the photosensitive tram 1 in the order of developing in the rotational direction A of the photosensitive tram 1,
As the first developing device 4, the above-described developing device that performs development of carrier and toner using a magnetic brush is used. To explain this device along with its operation, the photosensitive drum l is uniformly charged, for example, negatively, by a charger 2, and then a first image signal 3 is scanned onto the photosensitive drum l using a laser or the like to generate a first static image. Forms an electrolatent image. This electrostatic latent image is developed by a first developing device 4, which is a two-component magnetic brush developing device, in a reversal manner using negatively charged toner. Subsequently, after being charged by the recharging device 5, a second image signal 6 is scanned to form a second electrostatic latent image, which is then reversely developed with negatively charged toner to become a visible image. The latent image formed on the photosensitive tram l by the above-described single image forming process is defined as a two-color 01 visual image. Then transfer charger 8
Thus, the image is transferred onto the transfer paper 9.

Similarly to the image forming apparatus shown in FIG. 4, the two-color image forming apparatus shown in FIG. It is made so that it does not adhere to the photosensitive tram 1.

In particular, in a multi-color device as shown in Figure 5, carrier leaked from the first developing device and toner attached to this carrier may enter the developing devices after the second developing device, causing new problems such as color mixing. It is necessary to more reliably prevent carriers from adhering to the photosensitive tram.

However, in the conventional image forming apparatus shown in FIGS. 4 and 5, the rotation of the developing sleeve is stopped during non-image formation, and a large amount of the developing sleeve that was present in the developing area immediately before stopping is removed. Since the carrier and toner remain as they are, a situation arises in which they adhere to the photosensitive drum and leak, and problems such as image disturbance and color mixing caused by the carrier have not yet been completely solved.

(Means for Solving the Problems) The present invention provides a developing device and a developing device using the same that solves the above-mentioned problems caused by adhesion of magnetic particles (carriers) to a latent image carrier, which have not been solved in the past. An object of the present invention is to provide a multicolor image forming apparatus.

In order to achieve the above-mentioned object, the present invention provides a developing device comprising: a two-component developer consisting of magnetic particles and toner; It has a developer carrier disposed opposite to the image carrier and a drive means for rotationally driving the developer carrier,
In a developing device that forms a development area using a magnetic brush of a two-component developer in the opposing portion to make a latent image on the latent image carrier visible, the magnetic particles are formed between the developer carrier and the latent image carrier. 1 for the volume of the development area formed in the space between
．． The occupancy rate is set at 5 to 30 percent, and the driving means for the developer carrier is provided with a control means for stopping the means when an image is not formed, and the developing device is arranged. The multicolor image forming apparatus forms two or more types of latent images on an electrostatic latent image carrier based on different image signals, and develops the first developing device in the order corresponding to each latent image. and in an apparatus which forms multicolor images in one image forming process by sequentially arranging subsequent developing devices, at least the first developing device is provided with the developing device having the above structure of the present invention.

It is composed of "C".

(Example) Hereinafter, an example device of the present invention will be described based on FIGS. 1 to 3 of the accompanying drawings. FIG. 1 shows a schematic configuration of a first example device of the present invention. is a photosensitive drum serving as a latent image carrier, and is arranged to rotate once in the direction of the arrow.The drum 1 is opposed to the photosensitive tram 1, and the circumferential surface of the photosensitive tram 1 is charged in the manner of -. A charger 2 is disposed for this purpose, and an image signal 3 by a laser beam or the like is scanned onto the circumferential surface of the photosensitive drum l downstream from the charger 2 in the direction A.This image signal 3 A developing device 4 for developing the latent image formed on the photosensitive tram 1 by the Shingetsu is disposed downstream from the scanning position.

, h The developing device 4 is made of magnetic particles (hereinafter referred to as carrier).
and a hopper 47 containing a two-component developer consisting of toner.
The hopper 47 has a grain size of 30 to 200 J, for example.
Lm of carrier and toner with a particle size of 3 to 30 m are accommodated. Further, at the front opening of the hopper 47, a developing sleeve 41 serving as a developer carrying member that carries the developer and rotates and conveys it in the direction of arrow B' is disposed facing the photosensitive drum l. A fixed macnet 43 is arranged inside the developing sleeve 41. This fixed magnet 43
As shown in FIG. S2, N2
It is said to have a four-pole configuration. The SI is the magnetic pole closest to the photosensitive drum l, which is arranged to form a development area 48 by a magnetic brush of a developer made of carrier and toner at the facing part of the photosensitive drum l and the developing sleeve 41, and the developing sleeve The photosensitive drum 41 is arranged at a position that is shifted in the circumferential direction from the closest position between the photosensitive drum 1 and the photosensitive drum l. The N1 pole is located upstream of the blade 42, which is disposed upstream of the development area 48 to regulate the developer conveyed in the B direction by the developing sleeve 41, and the S, N2 poles are located further upstream of the blade 42. They are arranged in sequence at positions inside the hopper 47 and closer to the bottom.

The developing device 4 includes a driving means 46 as a means for rotationally driving the developing sleeve 41, and a control means for controlling the driving means 46 to cut off power supply during non-image formation such as between image formation and the next image formation. It is arranged at 46°.

Furthermore, an AC power source 44 and a DC power source 45 are connected to the circumferential surface of the developing sleeve 41 in order to apply a bias voltage between the photosensitive drum 1 and the developing sleeve 4I. Next, the developing sleeve 41 of the developing device 4 and the photosensitive drum l
The occupancy rate of carrier in the developing area 48 formed in the opposing portion will be explained.

Here, in explaining the occupancy rate of carrier in the developing area 48, the "developing area" is an area where a magnetic brush of developer is formed and toner is transferred or supplied from the developing sleeve 41 to the photosensitive drum 1, "Carrier occupancy" is defined as the percentage of the volume occupied by the carrier present in the space formed between the developing sleeve 41 and the photosensitive drum 1 as the developing area 48.

In the developing device of this embodiment, the -2 occupancy has a significant influence, and this value is set to be 1.5 to 30%.

1- If the occupancy rate is less than 1.5%, it may be difficult to recognize that the developed density has decreased, a ghost phenomenon may occur, or there may be a noticeable difference in density between the area where magnetic flash is present and the area where it is not. This is undesirable because it causes problems such as the thickness of the developer layer formed on the surface of the developing sleeve 11 becoming non-uniform as a whole. On the other hand, 3 (if it exceeds 3%, the degree of closing of the circumferential surface of the developing sleeve 41 will increase 1), fogging will occur on the image, and the spikes of the carrier forming the magnetic brush will damage the surface of the photosensitive drum l. This is not desirable as it causes problems such as:

In addition, the image quality does not monotonically deteriorate or increase as the carrier occupancy increases or decreases;
．． Sufficient image density can be obtained in the range of 5 to 30%, and 1.5
This is based on the fact that the inventor discovered that if the value is less than 30% or more than 30%, the image quality deteriorates, but within the range of the above-mentioned numerical value, which is sufficient for this image quality, neither ghost nor image fogging occurs.

The lower image quality in the former is thought to be due to negative characteristics, and the latter is because the amount of carrier present increases and the surface of the developing sleeve 41 becomes unable to be opened, resulting in a significant decrease in the amount of toner supplied from the surface of the developing sleeve 41. It is predicted when it occurs.

Next, the developer layer (total of carrier and toner) of the developer sleeve 41 is applied to the developer sleeve 41 per unit area, that is, after the developer is regulated by the plate 12. weight).

In the developing device 4 of the present embodiment, when the carrier is substantially spherical, - - Coating! The amount of σ is 0.5 to 5, Ox
10-'Ir/cm2 is preferred.

Furthermore, coating '4't" Fn is 5.OX Hl-2g
If it exceeds 7cm2, it will be noticeable in the image, especially if it is 6.
At Ox 01-2g /clfi2 or more, fogging occurs particularly strongly. Conversely, +1.5 x 1O-2H/cm
If it is less than 2, ``1'' was visually recognized as a sweep by the carrier's spikes.

Roughly speaking, the toner mixing ratio in the development area 48, that is, toner weight/carrier weight, is 4 to 40%.
is preferred. If the mixing ratio exceeds 40%, fogging will occur regardless of the amount of developer applied, and if it is less than 4%, sufficient image density will not be obtained regardless of the amount of developer applied.

Hereinafter, the above embodiment apparatus will be explained using specific numerical values. To explain based on FIG. 1, the surface of an aluminum sleeve with a diameter of 20 mm is used as the developing sleeve 41.
A fixed magnet 43 made of alundum and abrasive grains treated with a more amorphous Suntralast was arranged in the same manner as shown in FIG. 1, with quadrupole magnetization and alternating N and S poles. The maximum value of the surface magnetic flux density due to this magnet 43 is approximately 900
It was G (Gauss).

Further, as the plate 42, non-magnetic stainless steel with a thickness of 1.2 mm was used. Further, the developer regulation position of the blade 42 and the first magnetic pole N1 on the upstream side of the blade 42 are shown.
The angle 0 formed with respect to the center of rotation of the developing sleeve 41 is 15
°.

As a carrier, particle size 70-50 ILm (250/300 mesh) coated with silicone resin on the surface.
ferrite (maximum magnetization 60 emu/g) was used. Further, the toner used had an average particle size of 12 gm.

The drive means 46 for driving the developing sleeve 41 and the control means 46 for controlling the operation of the developing sleeve 41 are provided with a known motor and a control circuit for controlling the same.

When image formation was performed using the above-mentioned apparatus, the control means 46
It was confirmed that by stopping the rotation of the developing sleeve 41, the adhesion of carrier to the photosensitive drum 1 was prevented. At this time, the electric field applied between the photosensitive tram 1 and the developing sleeve 41 may be either only the DC component of the power source 45, only the AC component of the power source 44, or a combination of the DC component and the AC component. Similarly, it was confirmed that there is an effect of preventing carrier adhesion onto the photosensitive tram.

By stopping the rotation of the developing sleeve 4I during non-image formation as shown in the double series, the reason why carriers are prevented from adhering to the photosensitive tram is first caused by the rotation of the sleeve 41 on the carriers on the developing sleeve 41. Developing sleeve 41
This is because the centrifugal force from the photosensitive tram in one direction does not move, and the impact when the carrier ears are raised is eliminated.

Further, the developing device 4 of the individual packaging described above has a developing area 48.
As mentioned above, the fact that the amount of carrier relative to the amount of toner is suppressed to a small amount compared to the conventional device is effective in preventing the adhesion of carrier to the photosensitive drum 1. In other words, since there is less carrier than toner in the developing area 48, when the developing sleeve 41 is stopped, as shown in FIG. This is because the carrier is pushed downstream in the rotational direction A of the photosensitive tram 1, and a blank area with almost no carrier is formed in the developing area 48.

Note that the phenomenon in which almost no magnetic flanges exist in the developing area 48 when the developing sleeve 41 is stopped is caused by changing the facing distance between the developing sleeve 41 and the photosensitive drum 1 by 200 to 500.
This was particularly noticeable when it was set to Le I.

In addition, the inventor of the present invention has proposed that, in the developing device 4 shown in FIG. The pole position of the near pole S and the above rotation center 0
It has been confirmed that when the angle α between the magnetic brush and the line segment connecting the magnetic brushes is 5 to 2()0, the blank area where the magnetic brush is not formed expands in the developing area 48, and the effect of preventing carrier adhesion increases. The reason is that the Macnet 4 in the developing area 48
This is thought to be due to the fact that the gradient of the magnetic field due to 3 becomes large, so that the carrier moves smoothly to the downstream side.

Next, a developing device 4 having a configuration similar to that of the developing device 4 described above.
A case where 0 is applied to a multicolor image forming apparatus will be explained. FIG. 3 shows another example apparatus in which a two-color image forming apparatus as an example of a multi-color image forming apparatus is provided with a developing apparatus 40 as described above as a first developing apparatus.

The apparatus of this embodiment is characterized in that a developing device 40 is disposed as a first developing device, and the configuration of the developing device 40 is the same as that of the first embodiment described above. will be added and the explanation will be omitted. Further, regarding the Macnet 43, only the SI pole closest to the photosensitive drum 1 is shown.

Further, since the basic configuration of the two-color image forming apparatus is well known and has already been explained with reference to FIG. 5, the same reference numerals will be given to this point and the explanation will be omitted. Although the second developing device 7 can be a conventionally known developing device, it is necessary to use a non-contact developing device in order not to disturb the 1 to 3 toner images formed by the first developing device.

According to the apparatus of this embodiment, the first development '-! occurs between the time of image formation and the time of next image formation, or during a period in which there is no image information to be formed by the first development device 40. During non-image formation in the A position 40, the drive device 45 for the sleeve 41 of the first developing device 40 is controlled by the control means 46'' to move the sleeve 4L.
This effectively prevents carrier and toner from adhering to the photosensitive tram. As a result, there is no carrier and toner image failure in the first developing device 40.
It was possible to obtain a clear two-color image without fogging or color mixture.

In addition, in the apparatus of this embodiment, as in the first embodiment described above, a line segment connecting the closest position of the photosensitive tram l to the developing sleeve 41 and the rotation center 0 of the developing sleeve, and a pole S1 nearest to the nearest position It was confirmed that the blank area where the magnetic flan of the developer is not formed expands when the angle β formed by the line segment connecting the pole position and the rotation center is 5 to 20 degrees. For example,
It has been confirmed that when the above-mentioned angle β is set to lOo from the nearest portion to the downstream side, the blank area in the circumferential direction of the developing sleeve 41 expands by about 1 mu+. When the angle β made above is less than 5°, no expansion of the blank area is observed,
If the angle is larger than 20°, the carrier will easily scatter, causing problems.

Also, JP-A-54-81855, JP-A-56-870
No. 60, etc., the potential of an image signal is applied to the latent image on the same surface or sequentially to the latent image on the photosensitive drum to form a so-called three-level potential, and the levels higher and lower than the intermediate level are set to different levels. Developed using toner with different polarity,
It is also possible to apply the present invention to a device intended to obtain a two-color image.

The above device exposes and scans the photosensitive drum with a laser beam as an image signal. This laser beam forms a latent image with three-level potential, and this latent image is continuously used for first development and second development. This is what we do. As a result, the carrier of the first developing device may adhere to the latent image to be developed in the second developing device, disturbing the image. By installing a developing device that could prevent carriers from adhering to the image, clear images were obtained.

(Effects of the Invention) With the developing device of the present invention configured as described above, adhesion of magnetic particles (carriers) to the latent image carrier can be reliably prevented, and a clear image without image disturbance can be provided. . Furthermore, since the developer carrying member is stopped during non-image formation, there is also the effect of preventing scattering of the developer.

By arranging the developing device as the first developing device of a multicolor image forming apparatus, adhesion of magnetic particles to the latent image carrier can be prevented, and image problems such as color mixing, which have been considered difficult in the past, can be eliminated. It now has 11 colors to provide clear, multi-colored images.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an apparatus according to an embodiment of the present invention; tSz diagram is an enlarged view of the developing area of the apparatus shown in FIG. 1; FIG. 3 is a diagram showing another embodiment of the apparatus; FIG. and FIG. 5 are diagrams showing an outline of a conventional device. 4...................................Phenomenon device 4I...Developer carrier (developing sleeve) 43...Magnetic field Generating means (magnet) 46... Drive means 1.
......Latent image carrier (photosensitive drum) 46
゛・・・・・・Control stage Fig. 1 Fig. 3 Fig. 4 Fig. 5

Claims (4)

[Claims] (1) A two-component developer consisting of magnetic particles and toner, and a developer that has a magnetic field generating means fixed therein, supports the two-component developer on its peripheral surface, and is disposed facing the latent image carrier. It has a carrier and a driving means for rotationally driving the developer carrier, and forms a development area of the two-component developer with a magnetic brush in the opposing portion, and makes the latent image on the latent image carrier visible. In the developing device, the magnetic particles have a volume of 1 with respect to the volume of the development area formed in the space sandwiched between the developer carrier and the latent image carrier.
．． A developing device having an occupancy rate of 5 to 30 percent, wherein the developer carrier driving means includes a control means for stopping the means when an image is not formed. (2) The magnetic field generating means inside the developer carrier is arranged such that the magnetic pole closest to the latent image carrier is shifted in the circumferential direction from the position of the developer carrier closest to the latent image carrier. A developing device according to claim (1), characterized in that: (3) Positional deviation is defined as a line segment extending from the rotation center of the developer carrier to the nearest position as a reference line, and the reference line and the rotation center position and the magnetic pole of the magnetic pole closest to the latent image carrier. Claim (2) characterized in that the angle formed by the line segment connecting the positions is set within a range of 5 to 20 degrees.
Developing device as described in section. (4) Two or more types of latent images are formed on the electrostatic latent image carrier based on different image signals, and the first developing device and subsequent developing devices are developed in the order in which they are developed corresponding to each latent image. An apparatus for forming multicolor images in a single image forming process by sequentially arranging the following: an apparatus for forming multicolor images in a single image forming process, characterized in that at least the first developing device is provided with the developing device according to claim (1); A multicolor image forming device.