JP3135150B2 - Developing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus, comprising: a toner carrier that is rotatably driven; After regulating the layer thickness of the toner, the electrostatic latent image formed on the latent image carrier in the developing region where the latent image carrier and the toner carrier are opposed to each other is transferred to the toner carried on the toner carrier. The present invention relates to a developing device for visualizing an image by using the developing device.

[0002]

2. Description of the Related Art In an image forming apparatus such as an electronic copying machine, a laser printer or a facsimile for obtaining a recorded image by visualizing an electrostatic latent image formed on a latent image carrier, an auxiliary agent may be removed as necessary. It has been well known that a developing device of the above-described type using an added toner, that is, a one-component developer, is employed.

A developing device of this type has the advantage that the maintenance of the device can be simplified and the structure of the device can be reduced, as compared with a developing device using a two-component developer containing a carrier.

By the way, in this type of developing device,
For example, the toner is carried on the surface of a toner carrier having a roller shape, and in the developing area, the electrostatic latent image on the latent image carrier is visualized by the carried toner. Prior to this, The layer thickness of the carried toner sent toward the developing area is regulated by a toner layer thickness regulating member such as an elastic doctor blade.

[0005] This type of toner carrier is driven to rotate at a relatively high speed, and a toner layer thickness regulation comprising a doctor blade is provided on the surface of such a high-speed rotating toner carrier via a toner layer. When the members are in contact with each other, frictional heat is easily generated between the toner layer thickness regulating member and the toner layer.

Conventionally, a toner layer thickness regulating member
Since the contact position with respect to the toner carrier was not changed, when toner adhered to the toner layer thickness regulating member, it did not separate from the toner layer thickness regulating member, and remained attached to the toner layer thickness regulating member. Due to the above-mentioned action of frictional heat and the like, a situation in which the adhered toner is softened and solidified and stuck to the toner layer thickness regulating member tends to occur.

If such toner sticking occurs, "white streaks" or the like appear on the developed solid image, which causes deterioration in image quality.

Therefore, in order to deal with such a problem,
The toner layer thickness regulating member is formed in a roller shape, and by rotating the member, the toner layer thickness is regulated to regulate the toner layer thickness. Tends to be non-uniform, and it is difficult to uniformly regulate the thickness of the toner layer. Further, since the roller occupies a large space, it is difficult to take advantage of a developing device using a one-component developer such as light weight, compact size, and low cost.

In this type of developing device, a minute closed electric field is formed near the surface of the toner carrier, and the toner carrier is used to suck the charged toner by the closed electric field and carry the toner. Although a toner carrier has been proposed (for example, refer to Japanese Patent Application No. 2-275061), when such a toner carrier is used, the amount of toner transported increases, so that the toner is more likely to be fixed as described above. .

[0010]

[0011]

SUMMARY OF THE INVENTION It is an object of the present invention to prevent a toner from sticking to a toner layer thickness regulating member in a developing device using a toner carrier for forming a minute closed electric field, or to prevent the toner from sticking. An object of the present invention is to provide a developing device capable of removing toner so as not to deteriorate an image.

[0012]

[0013]

According to the present invention, in order to attain the above object, the thickness of a toner layer which is carried and conveyed on a surface of a rotatable toner carrier is brought into contact with the surface of the toner carrier. After regulating the layer thickness of the toner on the toner carrier by the regulating member, the electrostatic latent image formed on the latent image carrier in the developing area where the latent image carrier and the toner carrier are opposed to each other, In a developing device that visualizes an image with toner carried on a toner carrier, a minute closed electric field is formed near the surface of the toner carrier, and the charged electric toner is sucked by the closed electric field to carry the toner. The present invention proposes a developing device that uses a toner carrier that performs the above operation, and further includes means for moving and driving the toner layer thickness regulating member so that the contact position of the toner layer thickness regulating member with respect to the toner carrier changes.

It is effective to use a bimetal for the moving drive means.

Further, it is effective to use a piezoelectric element for the movement driving means.

Furthermore, it is effective to use a rotationally driven eccentric cam for the moving drive means.

Furthermore, it is effective to use a solenoid for the moving drive means.

[0018]

Embodiments of the present invention will be described below.

FIG. 1 is a schematic view showing an example of the developing device. First, the overall structure and operation will be clarified.

In FIG. 1, a drum-shaped photosensitive member 1, which is an example of a latent image carrier, is driven in the direction of arrow A, and a developing device 2 is provided opposite to the photosensitive member. In the toner container 3 of the developing device 2, a toner 4, in which an auxiliary agent is mixed as necessary, that is, a one-component developer is stored. The toner 4 may be a magnetic toner or a non-magnetic toner. When using a color toner, it is desirable to use a non-magnetic toner. The specific volume resistivity of the toner is, for example, about 10 ⁷ to 10 ¹² Ω · cm.

On the front and rear side plates of the toner container 3, a developing roller 5 is supported in a state where a part thereof is exposed from an opening of the container 3, and the roller 5 is opposed to the photoreceptor 1 in a counterclockwise direction in FIG. (In the direction of arrow Y). The developing roller 5 is an example of a toner carrier, but a belt-shaped toner carrier may be used instead of the roller 5. Further, a toner supply roller 6 is supported on the front and rear side plates of the toner container 3, and the roller 6 is a developing roller 5.
, And is driven to rotate, for example, counterclockwise.

The toner 4 in the toner container 3 is carried to the toner supply roller 6 while being stirred by the agitator 7 rotating clockwise, and then supplied to the developing roller 5 by the roller 6. At the time of this supply, the toner is frictionally charged to a predetermined positive or negative polarity (in this example, negative polarity),
The toner adheres electrostatically to the peripheral surface of the developing roller 5 and is carried by the developing roller 5.

As described above, the toner supplied and carried on the peripheral surface of the developing roller 5 is conveyed by the rotation of the roller 5, and is leveled by the doctor blade 8, which is an example of a toner layer thickness regulating member, to regulate the thickness. Is done. As described above, the doctor blade 8 comes into contact with the surface of the developing roller 5 via the toner, and functions to regulate the layer thickness of the toner on the developing roller 5. Next, this toner is
Is transported to the developing area 9 opposite to the developing roller 5, where it is electrostatically transferred to an electrostatic latent image formed on the photoconductor 1,
The latent image is visualized.

The toner that has not passed through the developing area 9 without being used for development is returned to the toner supply roller 6 while being carried on the developing roller 5. Further, the visible image formed on the photoreceptor 1 is transferred to a transfer sheet (not shown) and fixed on the transfer sheet by a fixing device.

By the way, as described above, a minute closed electric field is formed in the vicinity of the surface of the toner carrier of such a developing device, and the charged toner is sucked by the closed electric field to carry the toner. When the toner carrier is used, the amount of toner transported by the toner carrier can be increased.

The developing roller 5 shown in FIG. 1 is constructed in accordance with such a concept, and FIG. 2 schematically shows the surface portion of the developing roller 5 and the toner in an enlarged manner. The developing roller 5 includes a conductive base made of a conductive roller 10 made of, for example, aluminum and the like.
The surface of the developing roller 5 is provided with a conductive surface 12 of a conductive roller surface and a surface of the dielectric 11 buried in the groove 100. As shown in FIG. 3, it is exposed regularly or irregularly, and its surface is formed smooth.

In the example shown in FIG. 3, the dielectric 11 extends in the directions of arrows Z and W in an iris shape on the surface of the developing roller 5 (X in FIG. 2 indicates the axial direction of the developing roller, and Y indicates the developing roller). 5 shows the rotation direction, that is, the circumferential direction). The widths W1 and W2 of the dielectric 11 and the conductive surface 12 are minute, for example, about 30 to 500 μm, and the area ratio of the entire conductive surface 12 to the total surface area of the developing roller 5 is, for example, 20 to 80. %, Especially about 30 to 60%. In FIG. 3, a horizontal line is given to the dielectric 11 so that the surface of the dielectric 11 can be easily distinguished from the conductive surface.

[0028]

A DC voltage, an alternating voltage (AC, pulse voltage, or the like) or a superimposed voltage of both is applied to the conductive roller 10 of the developing roller 5 as necessary to improve the quality of a visible image. Alternatively, the conductive roller 10 may be configured to be directly grounded. In the example of FIG. 1, a superimposed voltage of a direct current and an alternating voltage is applied by the power supply 50. The same applies to the toner supply roller 6.

In this example of the apparatus, a material having a polarity opposite to the charging polarity of the toner, that is, a material that is frictionally charged to a positive polarity is selected as the dielectric 11.

On the other hand, the toner supply roller 6 which is in contact with the developing roller 5 comes into contact with the dielectric 11 of the developing roller 5 and frictionally charges the same to a polarity opposite to the charging polarity of the toner, and frictionally charges the toner to the negative polarity. It is made of a material to be charged. In the example shown in FIG. 1, the toner supply roller 6 includes a conductor core member 14 and a cylindrical foam body 1 laminated therearound.
The foam 15 is pressed against the developing roller 5 while being elastically deformed. A fur brush or the like can be used instead of the foam 15.

In FIG. 1, the portion of the developing roller that has passed through the developing area 9 moves to the toner supply roller 6 and contacts the roller 6. Here, the toner that has not been subjected to development and is carried on the developing roller 5 is mechanically and electrically scraped off by the toner supply roller 6. At the same time, the dielectric 11 of the developing roller 5 comes into contact with the toner supply roller 6, and the friction opposite to the polarity opposite to the charged polarity of the toner.
In this example, it is charged to a positive polarity (see FIG. 2).

On the other hand, the toner 4 carried to the developing roller 5 while being in contact with the peripheral surface of the toner supply roller 6 has a predetermined polarity due to friction with the toner supply roller 6, as shown schematically in FIG. In this case, the developing roller 5 is frictionally charged to a negative polarity and is supplied to the developing roller 5. At this time, the developing roller 5 is further frictionally charged to a negative polarity by friction with the dielectric 11.

At this time, the dielectric 11 of the developing roller 5 is positively charged by friction with the toner supply roller 6, and a large number of conductive surfaces 1 having a small area are adjacent to the dielectric 11.
2, the conductive surface 12 and the surface of the dielectric 11 are mixed. In this state, a positive charge is selectively held at the dielectric 11 on the surface of the developing roller 5, and the surface of the developing roller 5 corresponds to the surface shape of the dielectric 11. The formed charge pattern is formed.

Therefore, a large potential difference is generated between each conductive surface 12 and the surface of the dielectric 11, and a closed electric field is formed between them. That is, a minute closed electric field (microfield) is formed near the surface of the developing roller 5 by the above-described charge pattern.

Due to such a closed electric field, the negatively charged toner is strongly attracted to the surface of the dielectric 11 and is held on the developing roller 5 in a state where it is difficult to separate a large amount. At this time, the toner is strongly frictionally charged due to the friction between the toner supply roller 6 and the developing roller 5 and is held on the surface of the developing roller 5 by the action of a strong micro electric field. A large amount of toner having

Instead of charging the dielectric 11 with the polarity opposite to that of the toner 4, the dielectric 11 may be charged with the same polarity as the toner 4 and a large amount of toner may be attached to the conductive surface 12. Further, the form of the dielectric 11 exposed on the surface of the developing roller may be any suitable form other than the iris shape.

As will be understood from the above description, when a toner carrier having such a configuration is used, the amount of toner transported increases, and the development effect can be further enhanced.

Here, as described at the beginning, in the configuration in which the doctor blade 8 shown in FIG. 1 is in contact with the developing roller 5, if the contact position does not change, toner adheres to the doctor blade 8. In this case, it does not separate from the doctor blade, remains attached to the doctor blade, and tends to adhere to the doctor blade.

When a toner carrier that forms a minute closed electric field near the surface is used as the toner carrier, a large amount of toner can be conveyed and the development effect can be further enhanced. When the toner carrier is used, the toner is easily fixed to the toner layer thickness regulating member.

When such toner sticking occurs, "white stripes" appear on a developed solid image or the like, which causes deterioration in image quality.

The features of the developing device of the present invention are as follows.
In order to cope with the above problem, a means for moving and driving the toner layer thickness regulating member such as a doctor blade is provided so that the contact position of the toner layer thickness regulating member with respect to the toner carrier is changed.

In FIG. 1, the doctor blade 8 which comes into contact with the developing roller 5 at the contact point T is moved by the moving driving means 16 so that the contact point T changes.
Is driven to move in a direction orthogonal to the axial direction.

For the moving drive means, for example, a bimetal can be used. What is indicated by reference numeral 17 in FIG. 4 is the bimetal,
It is attached to one end of the doctor blade 8. In the vicinity of the bimetal 17, a heater 19 is provided. When the heater 19 is turned on, the bimetal portion is in a linearly extended state, and when the heater 19 is turned off, the bimetal portion is in a bent state as shown in the figure.

When the bimetal 17 extends or bends in this manner, the doctor blade 8 moves in the disposing direction, that is, the direction of the arrow shown in the figure, and changes the position of the contact point T.

For example, during the copying cycle, the heater 19 may be turned on and off to make the doctor blade 8 reciprocate intermittently. Alternatively, the doctor blade 8 may be rotated before the start of the copy cycle or after the end of the copy cycle. May be moved.

By changing the position of the contact point in this way, it is possible to prevent the toner from remaining on the doctor blade 8 beforehand. This makes it possible to prevent the toner from sticking to the doctor blade 8. Even if the toner is stuck to the doctor blade 8, the doctor blade 8 is moved and driven,
Such a fixed toner can be removed. By using such a bimetal as the movement driving means, the doctor blade 8 can be moved with a simple configuration, the reliability for removing the toner is increased, and the cost is promising.

In the embodiment shown in FIG. 5, the doctor blade 8 can be moved by attaching, for example, a piezoelectric element 20 to one end of the doctor blade 8.
By applying a predetermined voltage to the piezoelectric element 20 or releasing the application of the voltage, for example, when a piezoelectric actuator or the like is used as the piezoelectric element, the doctor blade 8 can reciprocate with a stroke of about 2 mm. .
Since the reciprocating cycle is relatively short and the effect of vibration can be expected, it is possible to make it more difficult for toner to adhere to the doctor blade.

In the embodiment shown in FIG. 6, the doctor blade 8 which contacts the developing roller 5 with toner
1, the position of the contact point T is changed by moving in the disposing direction.

The doctor blade 8 is given a movement behavior in the direction of pressing against the eccentric cam 21 by the force of the spring 22, and when the eccentric cam 21 makes one rotation in this applied state, the doctor blade 8 Reciprocates by the eccentric amount of the cam. Even in this case, the contact position is changed. However, if the eccentric cam 21 is rotated by a predetermined angle after a certain period of time, and such rotation is repeated as time elapses, the contact position is changed. The position of the contact point T can be gradually changed.

When such an eccentric cam 21 or the like is used as a moving drive means of the doctor blade 8, the doctor blade 8 can be purely mechanically operated without requiring a dedicated power supply or the like.
Can also be moved.

The embodiment shown in FIG.
The solenoid 23 is used as the moving drive means. The doctor blade 8 is pulled leftward in the figure by the force of the spring 24. When the solenoid 23 is excited, the doctor blade 8 moves rightward in the figure against the elasticity of the spring 24, and the position of the contact point T changes. Can be When such a solenoid is used for the movement driving means, the doctor blade 8 can be moved only by giving an on / off signal to the solenoid.

The doctor blade 8 shown in FIG.
Is an elastic supporting member 8a made of a conductor such as a metal.
Is provided at the tip of for example a regulating portion 8b made of synthetic resin,
The regulating portion 8b is brought into contact with the developing roller 5 via toner. However, in the present invention, the doctor blade 8 shown in FIGS. 4, 6, and 7, and the doctor blade 8 shown in FIG. The present invention can be widely applied to a developing device using a doctor blade 8 of another type or a doctor blade of another type.

The doctor blade movement driving means includes a bimetal 17, a piezoelectric element 20, an eccentric cam 2 and the like.
The configuration using the solenoid 1 or the solenoid 23 can be applied to a developing device using a normal developing roller that does not form a minute closed electric field. The basic configuration and operation of such a developing device using a normal developing roller are the same as those described above with reference to FIG. 1, and are different in that a minute closed electric field is not formed near the surface of the developing roller. Only.

[0055]

[0056]

According to the first aspect of the present invention, since the fixation of the toner is prevented or the fixed toner is removed, "streaks" or the like occur in the developed solid image. And the image quality can be further improved. Such a function is achieved in a developing device which is inexpensive, uses a toner layer thickness regulating member having a simple structure, and uses a toner carrier which forms a minute closed electric field and in which toner sticking is likely to occur. be able to.

According to the developing device of the second aspect, the movement of the toner layer thickness regulating member can be performed with a simple configuration, the reliability of removing the toner can be increased, and the cost can be reduced.

According to the third aspect of the present invention, the reciprocating cycle of the toner layer thickness regulating member can be shortened, and the vibration effect of the toner layer thickness regulating member can be expected. It can be made more difficult to adhere to the member.

According to the developing device of the fourth aspect, the toner layer thickness regulating member can be mechanically moved.

According to the developing device of the fifth aspect, the toner layer thickness regulating member can be moved only by giving the ON / OFF signal to the solenoid, and the control system for this movement is simplified. .

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a developing device according to an embodiment of the present invention.

FIG. 2 is a diagram schematically showing, in an enlarged manner, a surface portion of the toner carrier and toner in a developing device using the toner carrier that forms a minute closed electric field.

FIG. 3 is a diagram schematically illustrating an enlarged surface portion of a toner carrier in a developing device using the toner carrier that forms a minute closed electric field.

FIG. 4 is a diagram illustrating an example in which a bimetal is used as a movement driving unit of a toner layer thickness regulating member.

FIG. 5 is a diagram illustrating an example in which a piezoelectric element is used as a movement driving unit of the toner layer thickness regulating member.

FIG. 6 is a diagram illustrating an example in which an eccentric cam is used as a movement driving unit of a toner layer thickness regulating member.

FIG. 7 is a diagram illustrating an example in which a solenoid is used as a movement driving unit of the toner layer thickness regulating member.

[Explanation of symbols]

 2 Developing device 9 Developing area 16 Movement driving means 17 Bimetal 20 Piezoelectric element 21 Eccentric cam 23 Solenoid T Contact position

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Naoki Iwata 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company, Ltd. (72) Inventor Yuichi Ueno 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Co., Ltd. (56) References JP-A-59-5253 (JP, A) JP-A-2-16585 (JP, A) JP-B-63-16740 (JP, B2) (58) Fields surveyed (58) Int.Cl. ⁷ , DB name) G03G 15/08

Claims (5)

(57) [Claims] 1. A toner layer thickness regulating member contacting a surface of a toner carrier with a toner carried and conveyed on a surface of a toner carrier which is driven to rotate, thereby controlling a layer thickness of the toner on the toner carrier. After the regulation, the electrostatic latent image formed on the latent image carrier is visualized by the toner carried on the toner carrier in a developing region where the latent image carrier and the toner carrier are opposed to each other. In the developing device, as the toner carrier, a minute closed electric field is provided near the surface thereof.
Is formed, and the charged toner is sucked by the closed electric field to form the toner.
And a means for moving and driving the toner layer thickness regulating member so that the contact position of the toner layer thickness regulating member with respect to the toner carrier is changed. . 2. A moving drive means comprising a bimetal.
The developing device according to claim 1 . 3. The developing device according to claim 1, wherein a piezoelectric element is used as the moving drive unit. 4. The eccentric force that is rotationally driven is provided to the moving drive means.
The developing device according to claim 1 using a beam. 5. The developing device according to claim 1, wherein a solenoid is used as the moving drive means.