JPS59155865A - Developing device - Google Patents

Abstract

PURPOSE:To prevent generation of an uneven density of a picture and a background fog by making at least one of a toner supplying means and an applied quantity controlling means have elasticity, and providing a contact pressure compensating mechanism for equalizing a control pressure of a nip part formed by both the means. CONSTITUTION:A rigid plate 9 whose one end contacts by pressing to a control roller 3 is provided along the revolving shaft direction of this control roller 3. This rigid plate 9 in constituted of a comparatively hard material such as steel, copper, etc., and a rigid body core 3a contacts by pressing with a feed roller 2, by which it is prevented that its center parts floats up. That is to say, both the rollers 2, 3 contact with each other by an equal pressure in the whole area of its nip part at all times. This rigid plate 9 is fixed to a housing 5 with a screw 10, and in this case a hold whose diameter is a little larger than the diameter of the screw 10 is provided on the rigid body 9 side, by which a press- contact force of the rigid body 9 can be adjusted. According to such a constitution, an applied quantity of a toner and an electrostatic charge quantity are equalized, and an uneven density and a fog are prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a developing device using insulating powder toner, particularly for developing an electrostatic latent image formed on a photoreceptor, an insulator, etc., or a magnetic latent image formed on a magnetic material. This relates to a developing device.

Conventionally, various development methods have been proposed for developing the entire latent image formed on the image bearing member such as the photoreceptor. A one-component development method in which development is performed using only toner is widely known. This method is further divided into those using magnetic toner and those using non-magnetic toner.

However, in any case, it may be necessary to form a uniform layer of toner on the surface of a means such as a roller that supplies toner to the image carrier, or to sufficiently charge this single layer of toner. . It becomes more difficult to uniformly apply toner to the surface of such a toner supply means as the coating layer becomes thinner.

In order to solve this problem, an elastic blade plate is pressed against the surface of the toner supply means according to the moving direction of this supply means, and the toner is passed between these blade plates and the supply means, thereby making the layer thinner. It has been proposed to carry out both the charging and the charging at the same time. However, with the above configuration, foreign matter tends to get stuck between the supply means and the elastic plate, and as a result, a striped area is formed on the supply means where toner is not applied. This will result in a decrease in the quality of the image obtained by development.

Furthermore, when non-magnetic toner is used, since it cannot be transported by a magnetic field, application to the supply means and transport are more difficult than for magnetic toner.

An object of the present invention is to solve the problems of a developing device using a toner of the above-mentioned one-component developer. More specifically, it is an object of the present invention to provide a developing device that can satisfactorily apply toner to toner supply means and charge the toner. Furthermore, it is an object of the present invention to provide a developing device which is capable of forming a uniform thin layer over the entire surface of a toner supplying means, regardless of magnetic or non-magnetic toner, with a simple structure, and which can sufficiently charge the toner.

A developing device of the present invention that achieves the above object includes a toner storage container that stores insulating powder toner, a toner supply means that rotates to supply the toner to an image bearing member, and a toner supply means that rotates to supply the toner to an image bearing member. a toner application amount regulating means for rotating and preventing the toner from flowing out from the toner outlet portion and forming a single layer of toner of a constant thickness on the surface of the toner supplying means; the toner supplying means and the application amount regulating means; At least one of the two means has elasticity, and a contact pressure compensating mechanism is provided so that when the two means form a nip and come into pressure contact, both means are brought into pressure contact with uniform contact pressure.

Hereinafter, the present invention will be explained in more detail according to examples and explanatory drawings thereof.

FIG. 1 shows a sectional view of essential parts of a developing device before the present invention is fully applied. In the figure, reference numeral 1 denotes a photosensitive drum as an image carrier that rotates in the direction of the arrow, and an electrostatic image is formed on the rear surface by a latent image forming means (not shown). A toner supply roller 2 facing the photosensitive drum 1 at a development position j heat supplies insulating non-magnetic toner on its surface to the photosensitive drum while rotating in the direction of the arrow.

The toner supply roller 2 is made of a metal sleeve made of stainless steel or aluminum, or hard synthetic resin, and its surface is coated with sandblast, sandpaper, etc.
The surface is roughened to have an unevenness of about 2μ to 107z, preferably about 0.5 to 4μ. The rough surface of the toner prevents the toner from slipping between the nip and allows it to be sufficiently charged by friction.

A regulation roller 3 for regulating the amount of toner applied is opposed to the roller 2 upstream of the development position, and the regulation roller 3 and the supply roller 2 cause the toner 4 to flow out from the toner storage section. It prevents The regulating roller 3 rotates in the same direction as the position facing the supply roller 2, and its speed is different from that of the supply port and the roller 2. The regulating roller 3 has elasticity and faces the supply roller 2 in pressure contact with the supply roller 2 forming a nip.

The structure of this regulation roller is such that a rigid core 3a serving as a rotation center axis is used.
It has an intermediate elastic layer 3b surrounding the core 3ak, and a surface elastic layer 3ci provided as needed. As the intermediate elasticity 7% 3b, a particularly flexible resin such as a foamed resin having continuous or discontinuous cells or silicone rubber can be used. The appropriate rubber hardness of the elastic body used for these intermediate elastic layers 3b is about 30 degrees to 90 degrees under Asker, and the hardness of this rubber is such that a nip is formed between both rollers without applying more pressure than necessary. Take this into consideration when deciding.

If the upper intermediate elastic layer 3b has open cells and the toner enters into the cells and changes the elasticity, or if the composition of the toner causes deterioration, the intermediate elastic layer 3b has open cells. It is preferable to provide 3ci of surface elastic layers covering the surface. Such a surface elastic layer 3c has a thickness of, for example, 0.3 to 2 m.
A resin tube having a rubber hardness of approximately 60 to 90 degrees with Asker C may be used, or the periphery of the intermediate elastic layer may be coated with a separated material. Of course, if the surface of the elastic layer 3b has open cells without undesirable porosity or a relatively smooth surface and is not affected by toner, there is no need to further provide a surface elastic layer.

The surface layer of the regulating roller 3 regulates the thickness of the toner adhesion layer to the supply roller at the nip portion with the supply roller, and also performs frictional electrification on the toner. This w: frictional charging is mainly performed between the surface of the supply roller in the nip portion and the toner, and it is preferable to select a material for the surface of the supply roller that can triboelectrically charge all the toner on the supply roller to a predetermined polarity. For example, positive (+
) Teflon (trade name) can be used to fully charge the toner, and synthetic resin gold such as nylon (trade name) can be used to charge the toner negatively (-).

However, if the surface of the regulation roller is made smooth by using a material with low frictional resistance such as Teflon, the toner will easily pass through the nip, and the toner thickness will be controlled and the toner will be sufficiently triboelectrically charged. The nip width at 1 is set by taking into account conditions such as the pressure between both rollers 2 and 2, the busyness of the regulating roller 3, and the speed difference between the circular rollers.

The toner 4 storage section in the current 1 house design shown in FIG. 1 above is as follows:
The image rollers 2 and 3 and the housing 5 of the device form a +1 structure. Additionally, film-like seal members 6 and 7 are provided between the housing 5 and each of the rollers 2 and 3 to prevent toner from leaking from the storage section. A stirring blade 8 is provided in the center of the toner storage section for completely stirring the toner and transporting the toner toward the nip portion of both rollers.
It rotates in the direction of the arrow in conjunction with the movement of the supply roller.

Next, the rotation of the supply roller 2 and the regulating roller 3 in the developing device shown in FIG. 1 will be described. In this embodiment, it has already been described that both rollers rotate in the same direction at the nip portion, but it is preferable that the circumferential speed of the regulating roller is lower than the circumferential speed of the supply roller. On the other hand, if the speeds of both cylinders are exactly the same, the toner on the supply roller may be caught between the regulating roller and the toner and may pass through. Such passage of toner not only does not restrict the toner on the supply roller to a predetermined toner thickness, but also does not generate an appropriate amount of charge related to the thickness required during development. Failure to develop or unevenness may cause the toner on the supply roller to scatter.

Therefore, both rollers preferably vary their circumferential speed,
The amount of change is preferably such that the speed of the regulating roller 4 is at least 5 times slower than the supply roller 3, preferably at least 50 times slower. Furthermore, the rotation of the regulation roller 4 may be not only continuous rotation but also intermittent rotation.

As described above, the effect of setting the rotation directions of the supply roller 2 and the regulation roller 3 in the same direction instead of in opposite directions at the position where they face each other is that solidified toner and foreign matter caught between the nip can be removed from the nip. This prevents the occurrence of streak-like areas where no toner exists on the supply roller 2. Furthermore, by rotating in the same direction, the rollers are not rotated in the opposite direction to the supply roller while in contact with the supply roller or with toner present, and therefore high rotational torque is not required. That is, when rotating in the opposite direction, the toner adhering to the regulating roller must be removed, and the toner removing member for this purpose also acts in a direction that prevents the rotation of the regulating roller. Therefore, it is inevitable that the structure of the drive system will be larger or heavier than that of this embodiment.

By setting the rotational directions of the supply roller 2 and the regulation roller 3 as in the embodiment shown in FIG. 1 in this way, it is possible to reduce the rotational torque and simplify the device structure.

By the way, in the developing device configured as described above, although one of the regulating rollers has elasticity and is in pressure contact with the opposing supply roller forming a nip, the amount of applied toner and the amount of charge is smaller than that of the supply roller. may not be uniform in the direction of the rotation axis. Specifically, a total pressure difference of about 40% to 60% may occur between the center and both ends forming the nip.

Atsushi: A possible reason for this current increase is that the rigid core 3a of the regulation roller 3, which is in pressure contact with the toner supply roller 2, is supported at both ends by support plates and is pressurized by spring pressure or air pressure. It becomes. For this reason, the pressing force of the regulating roller against the supply roller increases at both ends due to the deflection of the first side body core 3a. This non-uniformity of pressure causes the amount of toner applied and, if the toner is insulating, the amount of charge to differ between the edges and the center, resulting in uneven density and background bulges depending on the total pressure. This will occur.

As a solution to this phenomenon, in order to maintain sufficient strength of the rigid core of the regulating roller, it is possible to increase the diameter of the rigid core 3a, but this increases the size of the developing device and the arrangement with the photoreceptor. There may be cases where it cannot be put to practical use due to the following reasons. The present invention reduces the diameter of this regulating roller and provides a developing device that can be arranged in any manner.

Hereinafter, an example of a mechanism for checking the above-mentioned contact pressure will be explained with reference to the drawings.

Figure 2 shows a complete improvement of the developing device shown in Figure 1 above.
Components that are the same as those in the figures and components that have the same functions are given the same reference numerals.

In this embodiment, a rigid plate 9 is provided along the direction of rotation I11 of the regulating roller 3, with one end entirely in contact with the regulating roller. The rigid plate 9 is made of a relatively hard material such as iron or brass, and the rigid core 3a is in pressure contact with the supply roller 2 to prevent its central portion from floating. That is, the rigid plate 9 acts to press the regulating roller 3 toward the supply roller 2 side, and allows both rollers 2 and 3 to be in constant contact with uniform pressure over their entire area. The rigid plate 9 may be fixed to the housing 5 with screws 1o. In this case, by loosening the screws 10, the pressure force of the rigid body 9 against the regulating roller can be fully adjusted. Specifically, if the screw 1o is fixed to the housing and a hole with a small diameter slightly larger than the diameter of the screw 10 is provided on the rigid plate 9 side, the above adjustment can be made arbitrarily by tightening the screw 1°. be able to.

To protect the surface of the roller 3, it may be rounded or bent to form a flat surface. Then, the rigid plate 9 is fixed at a position where the rigid plate 9 presses the regulating roller 3 in a vertical or nearly vertical direction.

In order to make the pressure contact between the regulating roller and the supply roller 2 more uniform, the distance between the center of the mounting hole provided in this rigid plate 9 and the tip of the rigid plate 9 on the regulating roller 3 side is 2t. In this case, if the distance at the center is t1 and the distance at both ends is 62, then 2. ＞If you set up a solid board for the relationship between the two, it will be tough. As a result, a particularly strong pressing force acts on the center portion of the regulating roller 3, so that the pressure at the nip portion can be made uniform over the entire area.

[Experiment example]

A hollow cylinder made of non-magnetic stainless steel and having a diameter of 30 mm and having a concave portion with an average roughness of 2 μm was used for the toner supply port. On the other hand, the roller has a diameter of 5
The stainless steel core of the lock was coated with urethane rubber having a rubber hardness of 10° by cast molding, and a heat-shrinkable resin film was wrapped around the surface of the core, using a roller with a diameter of 20 mm.

The image roller is configured as shown in Fig. 1, a total pressure of I kg is applied between both rollers 2 and 3, a 100μ thick polyethylene film is inserted into the nip formed by the meat roller, and the film is pulled out. The pressure between the nip was measured by According to this, about 2,002 g of pressure was required at the center of both rollers in the rotational axis direction, while about 350 g of pressure was required at both ends.

The gap between the photoreceptor 1 and the roller-shaped toner supply means 2 is approximately 3
00 μ, frequency 1.5 KH as developing bias
z, DC voltage is applied to the alternating electric field of positive peak [from negative peak to negative peak (direct 1.3 KVl) p - 280 V
Superimposed.

Incidentally, the latent image potential on the photoreceptor 1 was set to a dark area potential of -700v and a bright area potential of -200v.

We have confirmed that this phenomenon may occur.

On the other hand, using a stainless steel plate approximately 1 mx thick, the second
As shown in the figure, a portion of the regulating roller side was bent to form a rigid plate 9, which was pressed and fixed to the regulating roller of the developing device with a force of about 1.5 kg. In addition, in this case, the relationship of the above-mentioned t of the rigid plate 9 was made constant over the entire area. Therefore, when the pressure between the nip was measured as described above, it was found to be about 3009 at the center and both ends, and similar development results showed that a homogeneous image without fogging could be obtained over the entire area.

3.1 is a perspective view showing another embodiment of the present invention, and as in the previous case, the same parts and parts having the same function as in FIG. The same applies to the embodiment.

In this embodiment, a driven roller 11 is used in place of the rigid plate 9 as a contact pressure compensation mechanism.

The rotation shafts 2a and 3a of the upper ml rollers 2 and 3 are fixed to the side surface Bit 5a of the housing 5, and both rollers 2 and 3 are in pressure contact with each other in advance. On the other hand, the ronilla 11 that presses against the regulating roller 3 and applies a pressing force in the axial direction is rotatably attached to a support 12, and the support 12 is rotatable about the entire center of the shaft 13. Further, the rotation limit of the support body 12 is determined by a rod 14, and the screw 14 is supported by a mounting plate 15 fixed to the side surface 5a of the housing 5.

With the above structure, by tightening the screw 14, the support body 12 is rotated counterclockwise in the figure, and the roller 1 is pressed against the regulating roller 11. That is, the roller 11 is
It becomes possible to finely adjust the pressing force against the regulating roller 11.

The effect of this embodiment is that since the roller 11 rotates as a result of the regulation roller 3, it is effective when the surface of the roller 3 is weak against frictional force. The material of this roller 11 is not limited in any way, but it must satisfy the hardness required to press the regulating roller 3. Of course you can. Further, by making the diameter of the roller 11 larger at the center than at both ends, it is possible to compensate for the entire history of the pressure contact force at the center of the regulation and supply roller.

FIG. 4 shows another embodiment of the present invention, in which the rotation center axes of the supply roller 2 and the regulation roller 3 are made to intersect with each other, without using another member as a contact pressure compensation mechanism, and the rotation of both rollers 2 and 3 is made to cross each other. The pressure contact force in the axial direction is uniform over the entire range. When each roller having the above configuration is used, a sufficient effect can be obtained when the intersection angle θ is approximately 2 degrees. Generally, it is easier to configure the device by bending the rotation center axis on the regulating roller side.

Figure TA5 is another embodiment of the present invention, similar to the case of Figure 4,
A contact pressure compensation mechanism is applied to the regulating roller side. In this embodiment, the thickness of the elastic layer of the regulating roller is made thicker at the center than at the ends. If the regulating roller has a diameter of about 20mm, the diameter between the ends and the center is about 0.5~
The diameter changes continuously by about two fins.

By the way, if the above-mentioned elastic layer adopts the casting extrusion method, it is difficult to change the layer thickness of the elastic layer, so in this case, the diameter of the rigid core 3a is compared at both ends as shown in FIG. You may also make the center part thicker.

The embodiments described in FIGS. 5 and 6 above should be selected appropriately depending on the material and forming method of each part of the regulating roller, and are also valid for materials and forming methods other than those described. It is. Further, in particular, the method of changing the diameter of the roller or the diameter of the central axis of rotation described in FIGS. 4 to 6 can also be applied to the toner supply roller side. Specifically, this corresponds to a case where the supply roller has an elastic surface and is used by pressing the supply roller against the image carrier. Of course, it is also effective to apply all of the above embodiments in which the diameters of the rollers and rotation center shafts are changed for both the supply roller and the regulation roller.

By the way, in the present invention, the effect of roughening the roller surface can be obtained at the same time. Furthermore, it goes without saying that both rollers 2 and 3 may be made elastic and the surfaces of each roller may be roughened.

Furthermore, regarding the rotation directions of the supply roller 2 and the regulation roller 3, instead of rotating the regulation roller 3 in the same direction as the supply roller 2 as shown in FIG. 1, the regulation roller 3 may be rotated in opposite directions. In this case as well, since the surface of the rollers facing each other changes between the nip formed by both rollers, even if foreign matter enters between the nip, it can be removed from the nip.

The present invention is effective. In that case, a fixed or rotating magnet disposed within the supply roller may be used to convey the toner.

According to the present invention, the entire area of the supply means is magnetic.

A single layer of toner with a uniform thickness could be formed regardless of the non-staining toner. At the same time, the toner passes through the nip formed by providing elasticity to at least one of the supply means and the application amount regulating means, thereby making it possible to charge the toner to a sufficient potential. Furthermore, in the developing device of the present invention,
It is made of an elastic material, and uniform pressure is applied over the entire area to obtain the frictional charging effect due to the printing. Note that the toner supplying means and regulating means may be constructed in the form of a idle belt instead of a roller.

44. Brief description of the drawings Fig. 1 is a sectional view of a developing device to which the present invention is applicable, Fig. 2 is a sectional view of a developing device showing one embodiment of the present invention, and Fig. 3 is a sectional view of another embodiment. FIG. 4 is a perspective view showing an example, FIG. 4 is a plan view of a supply and regulation roller showing another embodiment, and FIGS. 5 and 6 are front views of the roller showing another embodiment.

In the figure,] 6i is a photoreceptor of an image carrier, 2 is a roller-shaped toner supply means, 3 is a roller-shaped regulating means, 4 is an insulating toner, and 9.10 is a contact pressure compensator. The rigid plate and rollers of the structure are shown.

Bow 3 f2

Claims (4)

[Claims] (1) a toner storage container for storing insulating powder toner;
a toner supply means that rotates to supply the toner to the image bearing member; a toner supply means that rotates opposite to the supply means and cooperates with the supply means to prevent the toner from flowing out from the toner outlet; Toner application amount regulating means for forming a single layer of toner of a constant thickness on the surface of the means, and at least one of the toner supplying means and the application amount regulating means having elasticity, and when both means form a nip and come into pressure contact. A developing device including a contact pressure compensation mechanism for bringing both means into pressure contact with uniform contact pressure. (2) The developing device according to claim (1), wherein the contact pressure compensation mechanism is a pressure contact member that presses a roller-shaped coating amount regulating means in a nip forming direction. (3) The developing device according to claim (1), wherein the contact pressure compensating mechanism is supported so that the centers of rotation of the roller-shaped coating amount regulating means and the supplying means intersect with each other. . (4) The above-mentioned contact pressure compensation mechanism is characterized in that the diameter of the central axis of rotation of at least one of the roller-shaped coating amount regulating means or the supplying means or the roller itself is made larger at the center than at the ends. The developing device according to the scope item (1).