JPS62266579A - Developing device - Google Patents

Abstract

PURPOSE:To eliminate toner leakage and to scrape toner without generating the filming of toner by arranging a rotating roller contactlessly opposed to a toner layer on a developing roller approximately in parallel with the toner layer on an aperture end part of a developer hopper where the developing roller is arranged. CONSTITUTION:The developer roller 1 is pivotally arranged on the aperture part 9 formed on the developer hopper 4. When voltage is impressed between the developing roller 1 and the rotating roller 2 so that an electric field is generated in a direction allowing toner on a toner layer 3 to electrostatically disperse in the direction on the rotating roller 2, the toner on the developing roller 1 can be contactlessly removed in the direction to the roller 2. The toner removed to the roller 2 is stuck to the roller 2 and rotated in the arrow direction. Since the roller 2 adheres to a filler 7, the toner stuck to the roller 2 is scraped at the end part 7a of the filler and recovered into the hopper 4.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a developing device for a copying machine, a printer, or the like to which an electrophotographic process is applied.

BACKGROUND OF THE INVENTION Development methods employed in electrophotographic processes using dry developers can be roughly divided into two types: methods using a two-component developer and methods using a one-component developer.

The method using a two-component developer uses a mixed developer of carrier and toner, as opposed to the method using a one-component developer, that is, the method using a developer containing only toner, so the mixing ratio of toner and carrier is kept constant. This method requires a toner concentration detection device to maintain the toner density, and has drawbacks such as deterioration of image quality due to deterioration of the carrier and periodic replacement of the carrier.

Therefore, recently, methods using the above-mentioned -component type developer have been attracting attention, and several developing devices have been proposed.

As an example, FIG. 5 shows a developing device described in Japanese Patent Publication No. 69-5253. 26 is an electrostatic latent image carrier, 1
1 is a developing roller capable of carrying a one-component non-magnetic toner 5 on its surface; 6 is an elastic blade for regulating the layer thickness of the toner carried on the surface of the developing roller 1; 4 is a toner 51;
This is a container that stores the developing roller 1. 27 is blade 6
This is a cam for changing the pressing force against the developing roller 1, but this is not related to the present invention. Further, the electrostatic latent image carrier 26 and the developing roller 1 each rotate in the direction of the arrow. Further, a part of the outer circumferential surface of the developing roller 1 is covered with a surrounding member 28 having an arcuate inner surface.

Now, in Japanese Patent Publication No. 159-6253, there is a container 4
Although there is no particular mention of a sealing means for preventing the non-magnetic component toner 6 stored inside the container from leaking out of the container, it is possible to use a sealing means for preventing the non-magnetic component toner 6 stored in the container from leaking out of the container. According to experiments, if the gap 29 between the developing roller 21 and the surrounding member 28 is appropriately narrow and the length of the surrounding member 28 is appropriately long, the angle of repose of the toner or the rotational direction of the developing roller 1 will change. In combination, it is possible to prevent toner from leaking out of the container 4 through the gap 29 due to the action of gravity. However, as you can easily understand, its sealing performance is extremely unreliable. For example, if an impact is transmitted to the developing device from the outside, toner will pass through the gap 29 and leave the hopper 4. This may cause contamination within the electrophotographic device or significant deterioration of development quality.

Furthermore, another major problem in the developing device shown in FIG. 5 is overcharging of the toner on the developing roller 1 or filming of toner that occurs on the surface of the developing roller 1.

In FIG. 5, a layer 30 of toner is formed on the developing roller 1, which is frictionally charged by a blade 6 and whose thickness is regulated. Then, as the developing row 21 rotates in the direction of the arrow, this toner layer passes through the developing section of the electrostatic latent image carrier 26 and returns to the developer hopper 4 again. At this time, it is preferable that the toner on the developing roller 1 that has returned into the developing hopper 4 is once scraped off from the surface of the developing roller. Otherwise, the toner remaining on the surface of the developing roller 1 will be charged again by friction with the blade 6, and the charge of the toner will increase, which will have an unfavorable effect on the developing characteristics.

For example, when the density of excessively charged toner particles increases, the charged toner on the developing roller will remain attached to the developing roller due to the action of its own electric field, even though a developing bias is applied. , development may not be performed.

Such excessive charging can be solved if a self-discharge type toner can be used, but it is difficult to say that such a developer has been put into practical use yet. Also,
Even if excessive charging can be solved by using such toner, the toner that is not scraped off will deteriorate due to mechanical friction with the blade 6, and the deteriorated toner will increase on the developing roller. There are some inconveniences.

Therefore, regardless of whether self-discharge type toner is used or not, it is preferable to always scrape off the toner on the developing roller.

Usually, to scrape off toner on a rotating roller, PE
It is conceivable to bring a blade made of T, rubber, etc. into contact with the roller surface in the axial direction. However, if this is done, toner filming will occur on the developing roller. This toner filming may not occur completely uniformly depending on the state of contact between the blade and the developing roller, but in some cases, it may occur concentratedly at several locations on the surface of the developing roller. It becomes non-uniform. As a result, the developing characteristics also become non-uniform due to the influence of filming.

In summary, it can be said that the main problems in developing devices using -component type developers are (1) toner sealing, and (2) overcharging of the developer or toner filming. Developer overcharging and toner filming have a complicated relationship in that trying to solve one problem will cause the other problem.

In the conventional one-component type developing apparatus, there is no one that has been able to solve these problems.

Problems to be Solved by the Invention It is an object of the present invention to provide a developing device capable of scraping off toner without causing toner leakage or toner filming.

Means for Solving the Problems The technical means of the present invention for solving the above-mentioned problems is to connect a rotating roller that faces substantially parallel without contact with a layer of toner on the developing roller to a developing roller on which the developing roller is disposed. It is provided at the open end of the agent hopper so that a voltage can be applied between the developing roller and the rotating roller.

For production The effect of this technical means is as follows.

In other words, an electric field is formed between the developing roller and the rotating roller so that an electric field is formed in the direction in which the charged toner on the developing roller electrostatically flies toward the rotating roller, depending on the charging polarity of the toner on the surface of the developing roller. Apply voltage. As a result, the toner on the developing roller is removed toward the rotating roller without contact.
Toner filming does not occur on the developing roller.

If the rotating direction of this rotating roller is set in the opposite direction to the direction in which the toner inside the developer hopper tends to leak out of the hopper, combined with the effect of the electric field mentioned above, toner leakage can be completely prevented. becomes possible.

Embodiment Hereinafter, one embodiment of the present invention will be described based on the accompanying drawings.

In FIG. 1, 1 is a rotatable developing roller that carries a layer of toner 3 on its outer peripheral surface, and 2 is a toner layer 3 on the developing roller 1.
4 is a developer hopper containing developer 5, and 6 is for forming a layer 3 of toner on the developing roller 1. The layer thickness of the toner layer 3 is properly regulated mainly by the pressing force of the rubber blade 6 against the developing roller 1, and also by the contact between the rubber blade 6 and the developing roller 1. It is charged to a predetermined polarity by friction near the contact portion. 7 is an elastic filler that fills the gap between the rotating roller 2 and the hopper 4 without leaving a gap;
It is arranged substantially integrally on the side and is in contact with the rotating roller 2. The material is PT for the reason explained later.
FE fiber felt is used. A latent image carrier 8 faces the developing roller 1 in a non-contact manner. Reference numeral 9 denotes an opening provided in the developer hopper 4, and a developing row 21 is rotatably disposed in this opening. 9a and 9b are this opening 9
This is the open end along the longitudinal direction (direction perpendicular to the plane of the paper).

q is a so-called development gap, and the toner in the toner layer 3 flies to a desired portion on the surface of the latent image carrier 8 under the action of the electric field from the voltage source Eb to perform development. G is the gap between the developing roller 1 and the rotating roller 2, and is usually 0.2, which is about the same as q. These are the values before and after. As shown in the figure, the rotating roller 2 is provided near the open end 9b of the hopper 4, which is the side where the developing roller 1 rotates in the direction of the arrow from the outside to the inside of the hopper 4. The other open end 9
At point a, the surface of the developing roller 1 moves from the inside of the hopper 4 to the outside, so naturally a rubber blade 6 as a means for forming the toner layer 3 is provided at this position. Further, the developing roller 1 and the rotating roller 2 are both made of stainless steel metal material, and a voltage E can be applied between them. This voltage E is applied in the direction shown in the figure when the charge polarity of the toner in the toner layer 3 is ◯, and in the opposite direction when it is ◯. That is, a voltage is applied between the developing roller 1 and the rotating roller 2 so that an electric field is generated in such a direction that the toner in the toner layer 3 electrostatically flies toward the rotating row 22 . As a concrete value, the amount of charge of toner of toner layer 3 is 3X per gram.
If the voltage is about 10 -6 C, one layer 3 of toner on the developing roller 1 can be flown toward the rotating roller 22 by applying a voltage of about E = 500 V for G = = 0.2.

That is, the toner on the developing roller 1 can be removed toward the rotating roller 2 without contact. The toner is thus removed from the surface of the developing roller 1 at the portion facing the rotating roller 2, but after that, as the developing roller 1 rotates, the toner adheres to the surface again due to contact with the toner 5 in the hopper 4. The blade 6 forms a toner layer 3 having a predetermined thickness.

On the other hand, the toner removed toward the rotating roller 2 adheres to the rotating roller 2 and rotates in the direction of the arrow. Since the rotating roller 2 is in close contact with the filler 7, it adheres to the rotating roller 2. The collected toner is scraped off at the end 7a of the filler and collected into the hopper 4. In this embodiment, the filler 7 is made of PTFEM fiber felt. This method has far less toner filming than scraping off the toner on the surface of the rotating roller 2 with a PET blade or rubber blade, and can reliably remove the developer on the surface. This is because it has a relatively low coefficient of friction and excellent wear resistance.

Furthermore, as shown in the figure, the rotating roller 2 rotates in the same direction as the developing roller at the portion facing the developing roller 1;
The wind speed does not necessarily have to be higher than the circumferential speed of the developing roller 1. If the gap G is appropriately large compared to the thickness of the first toner layer 3, even if the rotating roller is rotated at a peripheral speed that is somewhat slower than that of the developing roller, the toner flying toward the rotating roller 2 will remain in the gap. It will not accumulate enough to fill part G. In this embodiment, the outer diameter of the developing roller 1 is 16
mm, the circumferential speed is 120 mm/'S, the thickness of the toner layer 3 is about 25 to 30 μm, the outer diameter of the rotating roller 2 is s mm, the circumferential speed is about 80 mm/8, gear + lug G is 0.1
5 mm, and at this time, it was confirmed that the grip portion was not filled with flying toner and that the first layer of toner 3 was always removed stably by the rotating roller 2.

In addition, in the above-mentioned dimensions and positional relationship between the developing roller 1 and the rotating roller 2, when both are stationary, Ea==40
With a potential difference of 0V, the width in the circumferential direction is approximately 11-5mm.
I was able to make one layer of weak toner fly towards the rotating roller. Note that the amount of charge on the toner at this time was approximately 3×10 coulombs per gram of toner.Next, leakage of toner from the developer hopper 4 will be explained.

In FIG. 1, the toner 5 in the developer hole 4 does not pass through the gap G. It will not leak outside of Noku 4. Incidentally, this gap portion is very narrow, approximately 0.2 mm, and the rotation direction of the rotating roller 2 is such that the toner near the gap G is returned into the hopper 4. Therefore, these actions reliably prevent toner leakage.

In this example, no toner leakage occurred even during continuous operation for about 4.5 hours (development time equivalent to about 2000 A4 sheets).

As the developing device operates, the proportion of charged toner particles in the developer hopper 4 increases. Since the toner is reliably captured by the rotating roller 2 by the electric field, leakage of the toner is more reliably prevented.

In this manner, in this embodiment, the toner layer 3 on the developing roller 1 can be reliably removed without contact, and there is no toner leakage.

The toner layer 3 on the developing roller 1 is transferred to the rotating roller 22 in this way.
Since the toner is reliably removed, the unremoved toner on the developing roller 1 is not repeatedly charged by friction as in the conventional case. Therefore, the charge on the toner on the developing roller 1 becomes much more stable over time than in the past.

FIG. 2 shows the change in charge over time. a is the characteristic of the conventional developing device, and b is the characteristic of the developing device of this embodiment. In addition,
This electrical charge was measured while the developing device was operated alone, that is, when the developing device was operated without developing the latent image.

As can be seen from Figure 2, in a, approximately 1 gram of toner
The amount of charge increases at a rate of -8 x 10-6c/Hr, but no increase in the amount of charge is observed in case b.

FIG. 3 shows another embodiment of the invention. The same symbols as in FIG. 1 indicate the same contents. A fur brush 11 rotates in the direction of the arrow and triboelectrically charges the toner. Also, 1
A blade 2 lightly contacts the rotating roller 1o and scrapes off the toner on the rotating roller 10. In addition, rotating roller 1
There is no particular restriction on the direction of rotation of o, but in this embodiment it rotates in the direction of the arrow.

In particular, the present invention involves repeating charging, exposing, and developing multiple times,
The present invention is useful in a color electrophotographic apparatus in which a plurality of toner images of different colors are previously formed on a latent image carrier and then the toner images are transferred all at once onto plain paper to obtain a color image.

A conventional example of such a color electrophotographic apparatus and its image forming method will be explained with reference to FIG. First, corona charger 13
After positively charging the photoreceptor 14 as an electrostatic latent image carrier,
A yellow image signal is scanned and exposed using a laser beam scanner 16 to form a negative electrostatic latent image. Then, the electrostatic latent image is developed into a negative/positive state using a developing device 16 containing Y toner, thereby forming a yellow toner image on the photoreceptor 14.

At this time, a force (an electrical bias is applied between the developing roller and the photoconductor 14) by the developer 16 containing the Y toner, so that the toner electrostatically flies toward the photoconductor 14. The other developing devices 17 and 18 are kept in a state in which toner does not fly (described later).After developing with Y toner, the entire surface of the photoreceptor 14 is irradiated with a static elimination lamp 2o, and the yellow electrostatic latent image is optically neutralized. do.

Next, the steps of charging, exposing, developing, and optically removing charges are repeated in the same manner as the method used to form the yellow toner image, and all of the toner images of Y, M, C, and Bg are formed on the photoreceptor 14. After the toner development is completed, the electrostatic latent image is photo-neutralized in advance using a static eliminating lamp 22, and the toner image is electrostatically transferred onto plain paper 23 using a corona charger 21. The toner image transferred to the plain paper 23 is heated and fixed by a heating fixing device 24. On the other hand, toner remaining on the photoreceptor 14 after electrostatic transfer is removed by a cleaning blade 25, completing one cycle of color image formation (for example, Japanese Patent Laid-Open No. 60-95456).

Now, what is meant by "bringing the developing device into a state where toner does not fly" in the above description will be specifically explained. Specifically, for a developing device that does not develop a latent image, the developing device is installed on the photoreceptor so that the gap between the developing roller of the developing device and the photoreceptor widens to about one city. It makes them more spaced apart. By widening the gap, the electrostatic latent image is prevented from being developed. Note that the separation of the developing devices is usually performed by mechanical means such as a cam while being synchronized with the timing of latent image formation.

After a little thought, it seems that a complicated mechanism for mechanically separating the developing device is unnecessary in order to prevent the electrostatic latent image from being developed. That is, in the above example, it seems that development will not be performed if the developing bias voltage to the developing roller is set to about OV or if the developing roller is electrically floated. It is true that development will not occur if this is done, but at that time, the toner on the photoreceptor that has been recharged will fly toward the developing roller to which no developing bias is applied, and the image will be imaged. Not only is the toner not formed correctly, but different types of toner end up mixed into each developing device. In order to avoid such inconvenience, it is necessary to separate the developing devices.

However, in the developing device of this embodiment, if the power supply EC is connected between the rotating roller 10 and the developing roller 1 as necessary, all the toner is removed by the rotating roller 10 and no toner is left on the developing roller 1. It is possible to prevent the toner layer from being formed at all. Therefore, at this time, the developing device does not perform any development, and if an electrical bias is applied to the developing roller,
Toner does not fly backwards from the photoreceptor.

In this way, this embodiment can eliminate the complicated operation of separating the developing device, which was conventionally performed mechanically, and has great effects in improving reliability and reducing costs. be.

In FIG. 1, the same roller 2 is made of metal, but in relation to the filler 7, it may be made of an insulator. That is, the rotary row 22 may be an insulator as long as it is charged with a polarity opposite to that of the developer due to charging friction with the filler.

In addition, in FIGS. 1 and 3, the amount of developer removed by the rotating rollers 2 and 10 can be controlled by changing the output voltages of the power supplies E and EC.

Effects of the Invention As clarified in the above explanation, according to the present invention, toner sealing, which was extremely difficult in the past, can be performed reliably, and the charge on the developer can be kept stable over time. Furthermore, when applied to a color electrophotographic device, in addition to the above effects, it is possible to simplify the device and improve reliability.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of essential parts of a developing device according to the first embodiment of the present invention, FIG. 2 is a characteristic diagram showing the charging characteristics of the developing device of FIG. 1 and the conventional developing device of FIG. 5, and FIG. 3 is a characteristic diagram showing the charging characteristics of the developing device of FIG. is a cross-sectional view of the main parts of a developing device according to the second embodiment of the present invention, FIG. 4 is a diagram for explaining a color image creation process using electrophotography, and FIG. 5 is a main part of a conventional developing device. FIG. 1...Developing roller, 2, 10...Rotating roller, 4...Developer hopper, 5...
Developer (toner), 7... Filler, 9...
...opening, 9a, 9b...opening end. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 (a-) → Time [H and] Cb) 11111 Vinegar Replacement ra'% CHr) Figure 3 Ec. Figure 5

Claims (3)

[Claims] (1) A rotatable cylindrical developing roller that carries developer on its surface, and an opening in which the developing roller is disposed and has an opening approximately the same size as the axial cross section of the developing roller. A developer hopper containing the developer and a surface of the developer carried on the developing roller are provided so as to face each other in a non-contact manner and substantially parallel to each other in the vicinity of at least one end of the opening in the longitudinal direction of the opening. A developing device consisting of a rotatable rotating roller. (2) For a rotary roller whose surface rotates near the opening end side of the hopper from the outside to the inside of the hopper, the direction of rotation of the developing roller is the same as the direction of rotation of the developing roller at the portion facing the developing roller. Along with direction and
2. The developing device according to claim 1, wherein the rotating roller rotates in direct contact with the developing hopper or in contact with a member disposed substantially integrally with the developing hopper. (3) In the opposing portion of the developing roller and the rotating roller, an electric field is formed in a direction that causes the charged developer on the surface of the developing roller to electrostatically fly toward the rotating roller, or Developing device according to item 2.