JPH0519616A - Image forming device - Google Patents

Abstract

(57) [Summary] [Objective] Toner can be conveyed without rotating the developing roller 161, thereby preventing sticking of the toner in the developing device, increase in torque, and the like, and simplification of the developing device configuration. It is possible to obtain a good image. [Structure] A developing roller 161 is provided on a base roller 161a which is non-rotatably supported, and a stator 165 made of an insulating material.
And an electrostatic actuator member composed of a plurality of electrodes 164 embedded therein. The plurality of electrodes 1
64 is divided into three electrode groups, a voltage whose polarity is switched in a predetermined cycle is applied to each electrode group, and the toner is conveyed by the interaction between the charge of the toner and the charge of the stator. Then, to the electrode 164 in the developing area, a voltage having a voltage higher than that of the electrode 164 in the carrying area or a voltage having an alternating voltage superimposed thereon is applied to increase the toner repulsive force and enhance the developing efficiency.

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 such as a copying machine, a facsimile or a printer, and more particularly to a developing apparatus which conveys a developer or toner onto the surface of a latent image carrier to develop the image. .

[0002]

2. Description of the Related Art Conventionally, in a developing device of an image forming apparatus of this type, the developer or toner agitated in the developing device is carried on the surface of a developing roller which is a developer carrying member, and the developing roller is rotated. After thinning the developer or toner with a thin layer blade, etc., the latent image on the photoconductor is developed by transporting it to the developing area facing the surface of the photoconductor, which is the electrostatic latent image carrier. . After the development was completed, the developer or toner that was not transferred to the photosensitive member was collected in the developing device by rotating the developing roller, the developer or toner was newly stirred and charged, and the developer or toner was conveyed again to the developing area by the developing roller. .

[0003]

However, according to the above construction, when the developing roller rotates, the toner enters between the developing roller and the developing side plate, and the toner rubs to cause an abnormality such as toner sticking. Had a negative effect on.
Further, in the case where the developing roller is composed of a developing sleeve including a magnet roller, an eddy current is generated when the developing sleeve crosses the magnetic field of the magnet roller, which causes an increase in torque of rotation of the developing roller and heat of the developing roller. In some cases, the toner was tinged and melted in the developing device. Further, the developing roller requires a driving means to rotate the developing roller, and the developing roller has to be cylindrical, which is a great layout restriction. Further, in the case where the thinning blade is brought into contact with the surface of a rotating developing roller, a good toner thin layer is not formed and a good image cannot be obtained unless the thinning blade is attached with high accuracy. It was Further, the thinning blade is apt to be worn, and it was necessary to replace it at regular intervals. Further, an abnormality such as toner sticking may occur at the contact portion between the thin layer blade and the developing roller, which may adversely affect the image. Therefore, the present invention solves the above-mentioned problems by using the electrostatic actuator member to convey the developer or toner on the developing roller without rotating the developing roller, and simplifies the structure of the developing device. It is an object of the present invention to provide an image forming apparatus capable of achieving the above and capable of obtaining a good image.

[0004]

To achieve the above object, the present invention provides an image provided with a developing device for supplying toner onto a latent image carrier to develop the latent image on the latent image carrier. In the forming apparatus, at least a conveying area from the inside of the developing device to the developing area and the developing area are used as a toner conveying means for supplying the toner in the developing apparatus to the developing area which is a portion facing the surface of the latent image carrier. An electrostatic actuator member is used which has a plurality of electrodes to which a voltage whose polarity changes in a predetermined pattern is applied to a region, and among the plurality of electrodes, those in the developing region are in the carrying region. It is characterized by applying a voltage larger than that of the above.

[0005]

According to the present invention, the electrostatic actuator member is used as the toner conveying means of the developing device, and a voltage is applied to a plurality of electrodes of the electrostatic actuator, so that the charge of the charged toner and the plurality of electrodes of the electrostatic actuator are A driving force is electrostatically generated by the interaction with the electric charge, and thereby the toner is conveyed. Then, of the plurality of electrodes, a voltage higher than that in the transport area is applied to the electrode in the development area to transfer the toner transported to the development area to the latent image carrier side, This improves the development efficiency.

[0006]

EXAMPLES The present invention will be described based on examples. First,
FIG. 1 illustrates a schematic configuration of the entire image forming apparatus according to an embodiment.
Based on the above, the overall schematic configuration and operation will be described. A photosensitive drum 1 (for example, an organic photosensitive member; OPC), which is one configuration example of a latent image carrier, is rotationally driven in the clockwise direction. When a document is placed on the contact glass 2 and a print switch (not shown) is pressed, the scanning optical system 5 including the document illumination light source 3 and the mirror 4 and the scanning optical system 8 including the mirrors 6 and 7 are moved, Scanning of the original is performed. Then, the scanned image is read as an image signal by the image reading element 10 provided behind the lens 9. The read image signal is digitized and image-processed. Then, the laser diode (LD) is driven by the image-processed signal. The laser light from the LD is reflected by the polygon mirror 13 and then is irradiated onto the photosensitive drum 1 via the mirror 14. As a result, optical writing with the laser light is performed on the photoconductor drum 1, and an electrostatic latent image is formed on the surface of the photoconductor drum that has already been uniformly charged by the charging charger 15. The electrostatic latent image is visualized by the developing device 16, and the visible image is transferred to the transfer paper sent from the paper supply unit 17 by corona discharge of the transfer charger 18. Then, the transfer paper on which the visible image is transferred is separated from the surface of the photoconductor belt 1 by the separation charger 19, and then is conveyed by the conveyance belt 21 and passes through the pressure contact portion of the fixing roller pair 22 to form the visible image. It is fixed and discharged outside the machine. On the other hand, the toner remaining on the surface of the photoconductor after the transfer is removed by the cleaning device 23.

Next, the developing device 16 will be described. Figure 2
In the developing device 16, the developing device 16 is a developing roller 161, which is a toner conveying means, a charging roller 162 that abuts and rotates on the surface of the developing roller 161, and frictionally charges the toner, and conveys the toner in the toner hopper to the vicinity of the charging roller 162. And an agitator 163 for Developing roller 1
61 is a base roller 161a that is non-rotatably supported,
It has an electrostatic actuator member composed of a stator 165 made of an insulator and a plurality of electrodes 164 embedded therein. This plurality of electrodes (hereinafter referred to as drive electrodes) 16
4, each of which has a strip-like shape in the axial direction of the base roller 161, and as shown in FIG. 4, adjacent electrodes have different first to third electrode terminals 164a, 164b,
164c is connected to any one of them to form three drive electrode groups. Then, the drive electrode 164 in the developing area
And the drive electrode 164 in the transfer area separately from the first to third electrode terminals 164a, 164b, 164c.
It is connected to the. The developing roller 1 of this drive electrode 164.
The pitch in the 61 circumferential direction is, for example, 10 to 20 μ.
Alternatively, the toner particles having a diameter of about 10 μm may be attached in a line on one drive electrode 164 (see FIG. 3). It may be set large so that the toner particles adhere to one drive electrode in a plurality of rows. Then, by applying a voltage to these electrode terminals 164a, 164b, 164c as described later, a driving force is generated by the interaction between the electric charge of the toner and the electric charge of the stator to convey the toner.

In the toner hopper, two types of toner having different charging polarities are mixed and accommodated. The two types of toner may be of the same color or of different colors. However, each toner needs to have a predetermined resistance as described later. Then, the toner end detection is performed by detecting the rotation torque of the agitator 163, and assuming that the toner is exhausted in the developing device 16 due to the reduction of the rotation torque to a predetermined value or less, and the toner end is detected. Indicates the toner end to the user by lighting a toner end display (not shown) on the operation unit, for example.

The operation principle of toner conveyance by the electrostatic actuator member will be described with reference to FIG. Figure 3
As in (a), any of the electrode terminals 164a, 164
There is no charge in the drive electrode 164 when no voltage is applied to b and 164c. On the other hand, the toner is triboelectrically charged by the charging roller 162 and positively or negatively charged, but since there is no electric charge on the stator side, the toner is not controlled by the drive electrode 164 and the toner is not conveyed. Is. At this time, the toner is the developing roller 16
1 Floating around or attached to the stator by some force. From this state, as shown in FIG.
Positive voltage on the first electrode terminal 164a, second electrode terminal 164b
And a negative voltage, and 0 V is applied to the third electrode terminal 164c. Then, the toner is attracted to the drive electrode to which a voltage having a polarity opposite to the charging polarity is applied. That is, if the drive electrode is + V, −toner adheres to the surface of the developing roller on each drive electrode. At this time, the toner is not attracted to the drive electrode to which the applied voltage is not applied. Next, when each applied voltage is switched as shown in FIG. 3C (−V, + V, −V for each of the first to third electrodes), the electric charge of the toner and the electric charge of the drive electrode immediately therebelow have the same polarity. Therefore, the repulsive force is generated and the floating force is generated for the toner. In addition, the electric charge of the third drive electrode group (changed from 0 to −V) repels the upper right toner and attracts the upper left toner, so that a rightward driving force is generated to move the toner. . The levitation force reduces the friction between the toner and the surface of the developing roller, and the driving force of the electric charges causes the toner to move about one pitch of the driving electrode. Next, in order to shift the voltage (FIGS. 3 (c) and 3 (d)) of the pattern for repulsing and driving the toner,
Each applied voltage is switched as shown in FIGS. 3 (e) and 3 (f). Thereafter, in the same manner, by applying the driving electrodes while shifting them one by one, the toner is continuously moved. Here, a summary of the switching of the applied voltage to each drive electrode group from FIG. 3 (b) to FIG. 3 (f) and thereafter is as shown in Table 1. The steps in the table are shown in FIG. 3B, and the steps are shown in FIGS. 3C and 3D.
3 (e) and 3 (f) correspond to the steps. The step is + V for each of the first to third drive electrode groups,
A voltage of -V, -V is applied, and the voltage of the pattern for repulsing and driving the toner is shifted by one from the step to the right side in the toner conveyance direction. After that, by repeating steps 1 to 3, the voltages of the patterns for repulsing and driving the toner are shifted one by one.

[Table 1] Note that, for example, in FIG. 3C (step), if the voltage applied to the third drive electrode group is made positive, the drive can be performed in the opposite direction.

Here, as the toner of this embodiment, any toner having high resistance or medium resistance can be used as long as it can be triboelectrically charged. However, in the case of toner having a medium resistance, the toner is instantly attached to the surface of the developing roller above the drive electrode at the moment when the polarity of the voltage applied to the drive electrode is switched, by the charge of the drive electrode after the switching. If an electric charge having a polarity opposite to the triboelectric charge polarity is induced in the lower part of the toner, it may be attracted by the electric charge of the drive electrode and a sufficient repulsive force may not be obtained. Therefore, a resistor having a resistance sufficient to obtain a repulsive force when the polarity of the voltage applied to the drive electrode is switched is used.

In the above structure, the toner in the toner hopper is conveyed to the charging roller 162 by the agitator 163, charged to a predetermined polarity by the charging roller 162, and then conveyed to the surface of the developing roller 161. Developing roller 1
The toner on 61 is conveyed by the electrostatic actuator,
The developing area, which is a portion facing the photosensitive drum 1, is reached. In this development area, the positively charged toner and the negatively charged toner, which have been mixed in the developing device as described above and conveyed to the development area by the electrostatic actuator, are applied to the drive electrode 164 in the development area. By applying an appropriate voltage, the electrostatic latent image is adhered to the electrostatic latent image on the photosensitive drum 1 by the developing electric field formed by the interaction of the electrostatic latent image and the electric field of the driving electrode 164 to visualize it. The toner that has not adhered to the photosensitive drum 1 returns to the developing device again, and the charging roller 1
It is removed from the developing roller 161 by 62.

In the present embodiment, in order to improve the efficiency of toner supply to the photosensitive drum 1 in the developing area, the drive electrode 164 in the developing area is connected to the drive electrode 164 in the carrying area. A voltage larger than the applied voltage is applied. For this specific example,
This will be described below.

First, a latent image for regular development (hereinafter referred to as P / P latent image) is formed, and when the latent image passes through the developing area, for example, + toner (in this case, uniform charging is + charging). And then the photosensitive drum 1 is rotated with the toner image held without being transferred, or the photosensitive drum 1 is rotated after being transferred to a transfer paper or the like, and then the latent image for reversal development (N / P
Of the latent image) and the latent image is developed with, for example, −toner (in this case, uniform charging is −charged) when passing through the developing area. FIG. 5 (a) shows a P / P formed by using OPC as a photoconductor, for example, which is negatively charged by a charging device and then erased the charged electric charge of a portion corresponding to a background portion of an image with a laser beam. 6 schematically shows a state in which the electrostatic latent image has entered a developing area facing the surface of the developing roller 161. On the photoconductor shown in FIG.
The + toner carried on the surface of the developing roller 161 is attached to the portion where the charge remains. In order to promote this toner adhesion, in this example, a voltage as shown in FIG. 7B is applied to the drive electrode 164 in the developing area via the application electrodes 164a, b, c. This is a voltage in which the absolute value of the + polarity voltage portion is larger than the voltage applied to the drive electrode 164 in the transport area as shown in FIG. 7A. The drive electrode 164 is shown in FIGS.
Of the waveform of the voltage applied to, only the part whose polarity is switched is shown (the same applies to FIG. 7C and FIGS. 8A to 8C). In FIG. 5B, after being charged by a charging device, a portion of the image corresponding to the character or diagram of the image (a portion other than the background portion of the image) is erased by laser light to form. The developed N / P electrostatic latent image is the developing roller 161.
FIG. 3 is a schematic view showing a state of entering a developing area facing the surface. Toner is carried on the surface of the developing roller 161 on the portion of the photoreceptor where the charge has been erased, as shown in FIG. 5B. In order to promote this toner adhesion, in this example, a voltage as shown in FIG. 7C is applied to the drive electrode 164 in the developing area via the application electrodes 164a, b, c. As shown in FIG. 7A, these are voltages whose absolute value of the negative polarity voltage portion is larger than the voltage applied to the drive electrode 164 in the transport area.

As described above, the drive electrode 16 in the developing area
4 is larger than the voltage applied to the drive electrode in the transport area, and the absolute value of the voltage portion having the same polarity as the toner used for development is increased, so that the toner having the predetermined polarity is transferred to the photosensitive drum 1. It can be easily attached to the surface.
For example, when the toner carried on the surface of the developing roller 161 is attached to a portion of the N / P electrostatic latent image where the charge has been erased, as shown schematically in FIG. The toner of each polarity is levitated by the repulsive force of the electric charge of the drive electrode 164 having the same sign and is carried to the vicinity of the surface of the photoconductor.
As the distance from the surface of the photoconductor becomes smaller, the force F1 of the following formula (1) attracted to the photoconductor becomes larger, and this force F1 is attracted to the developing roller side F2.
It overcame and adheres to the photoreceptor and is developed. F1 = q × (ε × ΔV) / d (1) (where, q: charge of toner, ε: dielectric constant of toner, Δ
(V: potential difference between photoconductor and developing roller, d: distance between photoconductor and toner) At this time, the voltage applied to the drive electrode 164 in the developing area is the toner used for developing the latent image-the same polarity as the toner The repulsive force is increased by increasing the absolute value of the portion of, thereby increasing the force F1 that attracts the toner toward the photoconductor by bringing the toner closer to the photoconductor surface. It promotes adhesion. The toners having the same polarity may be used as the toners having different polarities, but the toners having different colors may be used and the toner images formed by the respective toners may be superposed on the photoconductor or the transfer paper. This makes it possible to obtain a two-color image.

Next, a latent image of P / P and a latent image of N / P are simultaneously formed on the photosensitive drum 1 by using, for example, two laser writing systems, and the latent image passes through the developing area. When, for example, the latent image of P / P is + toner (in this case, the portion corresponding to the character and diagram holds the + charging potential) and the latent image of N / P is − toner (in this case, the background The corresponding portion is −holding the charging potential), and the case of simultaneous development will be described. Here, in order to simultaneously form such a P / P latent image and an N / P latent image on the photoconductor drum 1, there is a known method.
A composite photoreceptor used for color development or the like can be used. In this example, in order to promote the adhesion of the predetermined toner to each latent image, the drive electrode 164 in the developing area is
A voltage as shown in FIG. 8B or a voltage as shown in FIG. 8C is applied. The applied voltage shown in each of FIGS. 8B and 8C is obtained by superimposing an alternating voltage on the applied voltage to the electrode 164 in the driving in the transport region shown in FIG. 8A. Is a superposition of an alternating electric field of a relatively short period with respect to the switching period of the applied voltage during transport,
FIG. 8B is a graph in which an alternating electric field having a cycle equivalent to the switching cycle of the applied voltage during conveyance is superimposed. As a result, the + toner and −toner in the developing area are floated by the repulsive force of the electric charge of the drive electrode 164 having the same sign, are carried to the vicinity of the photoconductor, and the force attracted to the photoconductor side is attracted to the development roller side. The force F1 that can overcome the generated force and adhere to the photoconductor to develop each latent image, and draws the respective toners closer to the photoconductor surface by the amount of the above-described alternating electric field and attracted to the photoconductor side. Is increased to promote the adhesion of toner to the latent image.
Also in this example, toners having the same color may be used as the toners having different polarities, but toners having different colors may be used and the toner images formed by the respective toners may be formed on the photoreceptor or A two-color image can be obtained by superposing them on the transfer paper.

In the present embodiment, the plurality of drive electrodes 164 are divided into three electrode groups, and the toner of each polarity is attached onto one of the three electrode groups. That is, the toners of the respective polarities are attached to approximately 1/3 of the entire peripheral surface of the developing roller 161. Therefore, when two-color images are formed by using toners having different colors as toners of respective polarities, the moving speed (conveying speed) of the toner on the developing roller 161 is tripled or more than the linear speed of the photoconductor. It is necessary to. When toners of the same color are used as the toners of the respective polarities, the toner moving speed of the developing roller 161 is 1.
It is necessary to make it 5 times or more.

As described above, in the present embodiment, since the toner is conveyed by using the principle of the electrostatic actuator without rotating the developing roller 161, there is no rubbing portion as in the case of rotating the developing roller 161, and thus, Since the toner is stressed at the rubbed portion, the torque is not increased due to the generation of the eddy current, and the heat generation is suppressed, so that the toner in the developing device is not melted. In addition, the drive electrode 164 in the developing area and the drive electrode 1 in the transport area are
Since a large voltage is applied so that the force of repulsing the toner to the vicinity of the surface of the photoconductor is larger than the voltage applied to 64, development can be accelerated.

Further, in the above embodiment, the charging roller 1
62 is arranged in the lower direction than the center of the developing roller 161. This is because when the charged toner that has passed through the charging roller 162 is stacked on the developing roller 161, it drops downward due to gravity. The toner is the developing roller 161.
In the above, since the development is better in the thin layer, the laminated toner is dropped by gravity to form a thin layer. On the contrary, when the charging roller 162 is located above the center of the developing roller, when the toner passes through the charging roller 162 in a stacked state, the toner is conveyed to the developing area with unevenness on the surface of the developing roller. Alternatively, the toner may be accumulated between the charging roller 162 and the developing roller 161.

In the above embodiment, the toner is frictionally charged and used, but it is also possible to carry the toner without frictionally charging the toner. In this case, FIG.
In this state, after the charge having the polarity opposite to the applied voltage polarity of the drive electrode is induced in the lower part of the toner, the voltage to each applied electrode is switched as shown in FIG. Repulsive force is generated to move the toner in the same manner as in the above embodiment. Also in this case, when the polarity of the applied voltage to the drive electrode is switched, the charge of the drive electrode after the switching instantly induces a charge having a polarity opposite to the triboelectrification polarity of the toner to the lower part of the toner. Since there is a risk that sufficient repulsive force will not be obtained due to the electric charge of the drive electrode, it is necessary to use a resistor having a resistance sufficient to obtain sufficient repulsive force when the polarity of the voltage applied to the drive electrode is switched.

Further, in the above embodiment, the toners having different polarities are contained in the developing device, but instead of this, even if one kind of toner charged to a predetermined polarity is contained, the electrostatic actuator can be used. The toner can be conveyed by using the toner. For example, when + toner is conveyed to the right side in FIG. 3, each of the application electrodes 164a, 164b, 164c.
Then, a voltage is applied as shown in Table 2 below.

[Table 2] Note that, for example, in FIG.
If the voltage applied to the drive electrode group of 1 is positive and the voltage applied to the first drive electrode group is negative, it is possible to drive in the opposite direction.
In this case, since the plurality of drive electrodes 164 are divided into three electrode groups and the toner of each polarity is attached onto one of the three electrode groups, the toner is not developed. Since the toner adheres to approximately 1/3 of the entire peripheral surface of the roller 161, it is desirable that the moving speed (conveying speed) of the toner on the developing roller 161 is 3 times or more the linear speed of the photoconductor. . In addition, the drive electrode 16 in the developing area
4, a voltage larger than the voltage applied to the drive electrode 164 in the transport area may be applied so that the force of repulsing the toner to the vicinity of the surface of the photoconductor is larger to accelerate development.

[0021]

As described above, according to the present invention, the electrostatic actuator member is used as the developer conveying means of the developing device, whereby the toner can be applied to the electrostatic latent image carrier without rotating the developer carrier. Since the toner is supplied, the toner is not fixed in the developing device, and the torque can be reduced. Further, the problem of improper application of the developing bias voltage due to the application of the voltage via the bearing of the rotating member unlike the conventional developer carrier does not occur. Further, by applying a voltage larger than that in the transport area to the electrode in the development area among the plurality of electrodes of the electrostatic actuator member, the development efficiency is improved and a high density image is formed. You can get it. Furthermore, if two types of toner having different polarities are accommodated in the developing device and development is performed, two types of latent images having different polarities of the toner attached to the toner adhering portion of the latent image on the latent image carrier are formed. Since development can be performed by one developing device, it is possible to reduce the space occupied by the developing device in the apparatus main body. Further, if toners having different colors are used as the toners having different polarities, it is possible to form an image of two colors by one development.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a developing device of the image forming apparatus of FIG.

FIG. 3A to FIG. 3F are explanatory views of the toner transport operation principle.

FIG. 4 is a schematic sectional view of a part of the electrostatic actuator of the developing device in FIG.

FIG. 5A is an explanatory diagram for explaining movement of toner in a developing region in regular development, and FIG. 5B is an explanatory diagram for explaining movement of toner in a developing region in reversal development.

FIG. 6 is an explanatory diagram for explaining a force that acts on toner in a developing area in reversal development.

7A is a waveform diagram showing a part of a waveform of a voltage applied to a drive electrode in a transfer area, and FIG. 7B is a part of a waveform of a voltage applied to a drive electrode in a developing area in a regular development. And (c) is a waveform diagram showing a part of the waveform of the voltage applied to the drive electrode in the development area in the reversal development.

FIG. 8A is a waveform diagram showing a part of a waveform of a voltage applied to a drive electrode in a transfer region, and FIG. 8B is a waveform diagram showing a waveform of a voltage applied to a drive electrode in a development region when normal development and reversal development are simultaneously performed. The waveform diagram which shows a part of waveform of applied voltage, (c) is a waveform diagram which shows a part of waveform of a voltage applied to the same drive electrode which concerns on a modification.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 photoconductor drum, 16 developing device 161, developing roller, 162 charging roller 163 agitator, 164 drive electrode 165 stator

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Shigeru Yoshiki             1-3-3 Nakamagome, Ota-ku, Tokyo Stocks             Company Ricoh

Claims (3)

[Claims] 1. An image forming apparatus comprising a developing device for supplying toner onto a latent image carrier to develop the latent image on the latent image carrier, wherein the toner in the developing device is replaced with the latent image carrier. As a toner conveying means for supplying the toner to the developing area which is a portion facing the surface, a voltage whose polarity changes in a predetermined pattern is applied to at least the conveying area from the developing device to the developing area and the developing area. An image forming apparatus using an electrostatic actuator member having a plurality of electrodes, wherein a voltage higher than that in the transport area is applied to one in the developing area among the plurality of electrodes. . 2. The image forming apparatus according to claim 1, wherein an alternating voltage is superposed on the voltage applied to the plurality of electrodes in the developing area. 3. The image forming apparatus according to claim 1, wherein the electrostatic actuator member is composed of an insulator forming a surface layer of the toner conveying means, and the plurality of electrodes provided in the insulator. .