JPH0332790B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic developer developing device. 2. Description of the Related Art Apparatuses for developing latent images on latent image carriers such as photosensitive drums using magnetic developers such as magnetic toners are known.

Conventionally, in a developing device that develops an electrostatic latent image on a photosensitive drum with magnetic toner, the magnetic toner is conveyed in layers to a developing area by rotating one or both of a developing sleeve and a magnet roll. In order to develop the magnetic toner layer to a desired thickness, a doctor blade is provided at the opening of the magnetic developer container such as a toner hopper, and a doctor blade is provided at the opening of the magnetic developer container such as a toner hopper, and a doctor blade is installed at the opening of the magnetic developer container such as a toner hopper. interval
It is set to about 0.2 mm to 0.5 mm to regulate the thickness of the toner layer.

However, since the structure blocks the flow of toner, a large amount of pressure is applied to the toner, which tends to cause toner agglomerations, which clog the doctor blade and prevent a stable toner layer of uniform thickness. Formation may be prevented. This development is called blotting. In order to prevent blocking, a method has been proposed in which the hopper and the developing sleeve are separated, the amount of toner on the developing sleeve is detected, and the means for conveying the toner from the hopper onto the developing sleeve is controlled by the detection signal. . However, in practice, this method has the disadvantage that the toner amount detection accuracy is poor and the conveyance means has a complicated structure.

An object of the present invention is to solve this problem of blocking, and to solve this problem, a stopper is placed in contact with or close to the surface of a non-magnetic developing sleeve in the developing area along the rotational axis direction of the developing sleeve. By providing it upstream, the transport area, that is, the magnetic developer layer forming area is regulated, and both the developing sleeve and the magnet roll are separated from the magnetic developer container and the area where the latent image on the latent image carrier is developed. This is achieved by rotating the developing sleeve and the magnet roll toward the opening formed by the developing sleeve and setting the rotational speed of the developing sleeve and magnet roll depending on the desired thickness of the magnetic developer layer.

In the present invention, there is a magnetic developer that is restrained by the developing sleeve and directed toward the opening, and a magnetic developer that is directed toward the stopper by the magnet roll, and the thickness of the magnetic developer layer varies depending on the rotation speed of both. Therefore, the opening exists mainly for supplying the magnetic developer, and therefore, the gap may be sufficiently large compared to the desired thickness of the magnetic developer layer; Even if the gap is set to be smaller than the desired thickness of the magnetic developer layer, the magnetic developer that moves while being restrained by the developing sleeve enters the magnetic developer container from the conveying area, so the magnetic developer does not The applied pressure is small and agglomerations are unlikely to occur. Furthermore, since the developer transport area is restricted to a limited area between the opening and the stopper including the developing area, scattering of the developer and contamination of the developer with dust are reduced. Next, an explanation will be given using an example.

FIG. 1 is a side sectional view showing an embodiment of the present invention, in which 1 is a photosensitive drum that carries an electrostatic latent image and rotates, 2 is a toner hopper, 2a is a side plate of the opening thereof, and 3 is a magnetic material and plastic. 4 is a hopper side plate made of a rubber plate (or a metal plate covered with sponge rubber); 5 is a non-magnetic metal toner which rotates in the direction from the developing area of the photosensitive drum 1 toward the opening; A developing sleeve, 6 is a magnet roll in which S and N poles are arranged alternately in the developing sleeve 5 and rotates in the same direction as the developing sleeve, and 7 is a magnet roll that rotates in the direction of the rotation axis of the developing sleeve. It is provided in contact with or in close proximity to the surface of the developing sleeve to regulate the area in which magnetic toner is conveyed. If it is in contact with the surface, it is made of rubber material, and if it is in close contact with it, it is made of metal. It uses the configured one.

Further, the hopper side plate 4 is in contact with the surface of the developing sleeve 5, and prevents the magnetic toner 3 in the toner hopper 2 from leaking out of the toner hopper 2 as the developing sleeve rotates.

The side plate 2a of the opening is provided along the rotational axis direction of the developing sleeve 5 at an appropriate distance from the surface of the developing sleeve 5, and this distance is used as the opening of the toner hopper. As will be explained later, the opening does not have the function of a doctor blade that regulates the thickness of the magnetic toner 3, but functions as an entrance and exit through which the magnetic toner 3 is conveyed to the outside of the toner hopper 2. Therefore, the opening interval can be determined to a suitable value of about 0.2 mm to 2 mm.

Next, the rotation direction of the developing sleeve 5 and the magnet roll 6, and the conveyance direction of the magnetic toner 3 will be explained.

The developing sleeve 5 rotates in the direction of arrow a. In other words, the toner is transported back into the hopper 2.
The magnet roll 6 rotates in the direction of arrow b, that is, in the same direction as the developing sleeve 5. As the magnet roll 6 rotates, the lines of magnetic force substantially rotate, and the magnetic toner 3 is transported in a direction opposite to the direction of rotation of the magnet roll 6. In other words, Magnetroll 6
The direction of conveyance is the direction in which the toner is carried out from the toner hopper 2, and the direction opposite to the direction of conveyance by the developing sleeve 5.

Next, it will be explained using specific numerical values. saturation magnetization
Using magnetic toner with a particle size of 10 to 20 μm and 52 emu/g,
When rotating the developing sleeve at 60 rpm and the magnet roll at 1800 rpm using a developing sleeve with a diameter of 37 mm and a magnet roll with 16 poles and a magnetic flux density of 600 gauss, a toner height of 0.4 mm could be stably obtained. .

FIG. 2 is a diagram illustrating the thickness of the magnetic toner layer in the present invention in relation to the rotation speed of the developing sleeve and the rotation speed of the magnet roll.

The developing sleeve 5 used in the measurement had a diameter of 37 mm and a length of 300 mm, and the magnet roll 6 had a 12-pole configuration on the sleeve surface with each pole having a maximum magnetic flux density of 600 Gauss. The magnetic toner 3 used had a particle size distribution of 10 to 20 μm and a saturation magnetization of 60 emu/g.
An optical micro-displacement meter manufactured by Chienmar was used to measure the toner thickness. As will be explained in detail later, on the top of the magnet roll 6, chains formed of magnetic toner stand up along the lines of magnetic force, so that the toner layer forms peaks, and conversely, between the poles, the magnetic toner chains collapse and form valleys.

In Figure 2, the toner thickness is measured at the trough, and the two curves A and B show the toner thickness when the magnet roll rotation speed is fixed at 1000 rpm and 1500 rpm and the sleeve rotation speed is varied. Show relationships.

As a result of the measurements, the following things were found.

(A) When the magnet roll rotation speed is fixed, as the sleeve rotation speed increases, the toner thickness decreases in approximately inverse proportion to the rotation speed, and when it increases further, all of the magnetic toner 3 is eventually collected into the toner hopper 2. No magnetic toner 3 was present outside the toner hopper 2.

(B) The toner thickness is determined by the magnet roll rotation speed and the sleeve rotation speed, and the reproducibility and long-term stability were confirmed.

Furthermore, the following findings were discovered through experiments.

(C) Even if the amount of magnetic toner 3 in the toner hopper 2 was increased or decreased, the toner height did not change.

(D) Even if the magnetic toner 3 being conveyed is removed from the top of the developing sleeve 5 to the outside, the toner height decreases once, but the magnetic toner 3 is quickly supplied from the toner hopper 2 and returns to the original toner thickness. Ivy.

(E) The toner thickness was uniform in height from the vicinity of the outlet of the toner hopper 2 to the vicinity of the stopper 7.

(F) Other commercially available magnetic toner (saturation magnetization 52emu/
g, particle size distribution 10 to 20 μm), almost the same measurement results as those shown in FIG. 2 were obtained.

Next, the conveying action of the present invention will be explained using FIG. 3. In order to simplify the explanation, FIG. 3 is shown expanded linearly.

The present inventors observed the state of toner conveyance according to the present invention, and found that the lower layer of the toner layer is conveyed mainly depending on the rotation of the developing sleeve 5 (hereinafter, such conveyance is referred to as sleeve conveyance), and the upper layer is mainly dependent on the rotation of the developing sleeve 5. It has been separated into conveyance depending on the rotation of the rolls 6 (hereinafter, this conveyance will be referred to as magnet roll conveyance). As is generally known, the speed of sleeve conveyance is equal to the direction of rotation of the developing sleeve 5. The restraining force for conveying the sleeve is interpreted as a frictional force corresponding to the component of the magnetic attraction force to the magnet roll 6 perpendicular to the surface of the developing sleeve. Since the restraining force acts between the surface of the developing sleeve 5 and the magnetic toner 3, and also between the magnetic toner 3, the sleeve conveying ability is high and a sufficiently thick magnetic toner layer can be conveyed. In FIG. 3, the direction of rotation of the developing sleeve is in the direction of arrow a, and the direction of conveyance of the sleeve is in the direction of arrow c. On the other hand, magnet roll conveyance, as is generally known, is the rotational movement of a chain of magnetic toner accompanying the approximate rotation of magnetic lines of force, and the conveyance speed is determined by the number of poles of the magnet roll, the rotation speed of the magnet roll, and the magnetic It can be described as approximately equal to the product of the three toner chain lengths. The direction of conveyance of the magnet roll is shown by arrow d, which is the opposite direction since the direction of rotation of the magnet roll in FIG. 3 is the direction of arrow b, as described above. It is understood that the thickness of the toner restricted by the magnet roll transport, that is, the length of the above-mentioned chain of magnetic toner, is determined by the magnetic properties of the magnetic toner and the magnetic flux density of the magnet roll.

Generally, the thickness of magnetic toner that is restricted by magnet roll transport is small.

To specifically explain the conveyance state of the magnetic toner of the present invention with reference to FIG. 3, the magnetic toner restrained by the magnet roll conveyance is restrained by the sleeve conveyance because the magnet roll conveyance speed is slightly higher than the sleeve conveyance speed. The toner layer moves in the direction of arrow d at a speed equal to the difference between the two toner layers. Next, when it hits the toner stopper 7, the speed of the magnet roll transport naturally decreases, and as a result, it becomes smaller than the sleeve transport speed. For this reason, the magnetic toner that has been restricted to conveyance by the magnet roll is restricted to conveyance by the sleeve.
Therefore, the lower layer is conveyed in the c direction.

Next, since a toner pool is generated in the toner hopper 2 by the hopper side plate 4, the magnetic toner traveling in the direction c is absorbed into the toner pool. Alternatively, it is again restrained by magnet roll transport and transported in the direction of arrow d. As explained above, since the magnetic toner 3 is conveyed continuously, the toner thickness at that time is determined by the toner thickness constrained by the magnet roll conveyance and both conveyance speeds, that is, the magnet roll conveyance speed and the sleeve conveyance speed. It turns out.

In other words, the magnetic toner carried out by magnet roll transport is recovered by sleeve transport. on the other hand,
Since the restraining force of the sleeve conveyance is sufficiently high, the magnetic toner 3 forms a toner pool by the hopper side plate 4 that stops the sleeve conveyance. To explain this mathematically, let l _n be the thickness of the toner restricted by magnet roll transport, and l be the thickness of the entire toner layer.
Therefore, the thickness of the toner restricted by the sleeve conveyance is (l-l _n ). Further, when the magnet roll conveyance speed is v _n and the sleeve conveyance speed is v _s , the following equation holds true.

l _n (v _n −v _s )=(l−l _n )v _s The left side shows the conveyance amount by magnet roll conveyance, and the right side shows the conveyance amount by sleeve conveyance.

By transforming the above equation, it becomes easily the following equation.

l=l _n (v _n /v _s ) This formula shows that the height l of the toner layer is the ratio of the magnet roll transport speed to the sleeve transport speed when the toner thickness l _n restricted by the magnet roll transport is constant. Show that it is decided. This agrees with the tendency found in the experiment conducted by the present inventors as explained in FIG. However, it must be noted that in the results found through experiments, the toner thickness l _n that is restricted by the magnet roll transport is a variable of the magnet roll transport speed l _n . In development using magnetic toner, it is important for the quality and density of the developed image to have an appropriate thickness of the toner layer with respect to the gap between the photosensitive drum 1 and the developing sleeve 5. In the present invention, the magnetic properties of the magnetic toner and the magnetic flux density of the magnet roll are factors that have a large effect on the developing characteristics and cannot be easily changed, so they are fixed, and the number of rotations of the magnet roll and sleeve are appropriately selected. This allows the desired toner layer thickness to be determined.

Next, in the present invention, it is clear from the above description of conveyance that the gap between the openings of the toner hopper is not a factor that determines the height of the toner layer. Even if the gap is narrower than the gap between the openings, the toner will be carried out by the magnetic roll through the opening, and the same thickness as when the gap between the openings is wide enough will be formed, making it easy to replenish toner even during long-term development. I confirmed that there were no problems.
Even if the opening formed by the side plate 2a of the hopper 2 was set to about 0.2 mm, stable development could be performed for a long time. This can be interpreted to be because the magnet roll conveying force is weak and toner agglomeration does not occur even if there is an obstacle that blocks this flow. This is advantageous when the toner hopper is used in an environment where dust is likely to enter the toner hopper. Of course, if the gap between the openings becomes extremely narrow, the conveyance by the magnet roll is stopped. This is because the magnet roll conveyance speed is proportional to the chain of magnetic toner, so the minute gap shortens the chain of magnetic toner, reducing the conveyance speed of the magnet roll. As a result, it is explained that when the speed becomes lower than the sleeve conveyance speed, it is impossible to pass through this minute gap.

In experiments, this spacing was about 0.1 mm. This is also the basis for explaining that it is not necessary to bring the stopper 7 into contact with the surface of the developing sleeve 5. By placing the stopper 7 close to the surface of the developing sleeve 5 with an interval of about 0.1 mm or less, the magnetic toner can be removed. can be prevented from leaking out from the stopper 7.

Although the above explanation deals with the case where magnetic toner is used, other magnetic developers such as a mixture of non-magnetic toner and iron powder carrier, a mixture of magnetic toner and carrier, or non-magnetic developer may also be used. It can be applied to a magnetic developer developing device that uses a mixture of toner and magnetic toner.

In addition, although the explanation has been made with an example in which the stopper 7 and the hopper side plate 4 are provided, it is also possible to make both of them serve as the hopper side plate 4.
The outer wall of the developing sleeve should have the function of a stopper, or the hopper should largely surround the developing sleeve.
The stopper 7 may have the function of the hopper side plate 4.

As is clear from the above description, in the present invention, the magnetic developer transport area is regulated between the opening and the stopper, and the desired developer thickness is set by balancing the developing sleeve transport and the magnet transport. Therefore, the developer can be carried out without being subjected to large pressure, which has the effect of preventing the occurrence of agglomerates. Further, in the present invention, since the developer transport area is regulated by the position of the stopper, the stopper provided on the upstream side in the rotational direction of the developing sleeve and magnet roll when viewed from the developing area can be moved closer to the developing area. This has the effect of narrowing the area and preventing scattering of the developer and dust from being mixed into the developer.

[Brief explanation of drawings]

FIG. 1 is a side cross-sectional view showing an embodiment of the present invention, FIG. 2 is an explanatory diagram showing the relationship between toner thickness and rotation speed in the present invention, and FIG. 3 is a diagram for explaining the conveying action in the present invention. FIG. DESCRIPTION OF SYMBOLS 1... Photosensitive drum, 2... Toner hopper, 2a... Hopper side plate at opening, 3... Magnetic toner, 4... Hopper side plate at contact area, 5... Developing sleeve, 6... Magnet roll, 7... Stopper, a... Developing sleeve Rotation direction, b...Magnet roll rotation direction.

Claims (1)

[Scope of Claims] 1. A developing sleeve and a magnet roll built in the developing sleeve are rotated together in a direction from a latent image development area of a latent image carrier toward a developer container, and the developing sleeve and the magnet roll are A magnetic developer developing device in which the number of rotations of each nettrol is set according to a desired thickness of the developer layer in the development area, wherein the development is performed outside the developer container and viewed from the development area. A member for regulating the conveyance of the magnetic developer is provided in contact with or in close proximity to the surface of the developing sleeve at a position on the upstream side in the rotational direction of the sleeve and the magnet roll, and a member for controlling the conveyance of the magnetic developer is provided at a position on the downstream side in the rotational direction. A magnetic developer developing device characterized by having an opening for supplying a magnetic developer to the outside of the container.