JP3090989B2 - Image forming 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 such as a copying machine, a facsimile, a printer and the like, and more particularly to a developing apparatus for transporting a developer or a toner to the surface of a latent image bearing member for development. .

[0002]

2. Description of the Related Art Conventionally, in a developing device of this type of image forming apparatus, a developer or a toner stirred 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. To carry the latent image on the photoconductor to a position facing the surface of the photoconductor as the electrostatic latent image carrier. After the development, the developer or toner not transferred to the photoreceptor was collected in the developing device by rotation of the developing roller, and the developer or toner was newly stirred and charged, and was again carried on the developing roller and transported. .

[0003]

However, according to the above configuration, when the developing roller rotates, toner enters between the developing roller and the developing side plate, and the toner is rubbed to cause an abnormality such as toner fixation. Was adversely affected.
In the case where the developing roller is constituted by a developing sleeve including a magnet roller, an eddy current is generated when the developing sleeve crosses the magnetic field of the magnet roller, thereby increasing the torque of rotation of the developing roller and causing the developing roller to generate heat. In some cases, the toner may be melted in the developing device.

Accordingly, the present applicant has filed a patent application for an image forming apparatus that conveys a developer or toner on a developing roller without using an electrostatic actuator member to rotate the developing roller (Japanese Patent Application No. Hei 10-214,752). 3-1
95901). According to the invention according to the earlier application, the above problems can be solved and the configuration of the developing device can be simplified. However, in the image forming apparatus of the invention according to the earlier application, the amount of toner carried per unit area on the surface of the electrostatic actuator member depends on the arrangement of the plurality of electrodes of the electrostatic actuator. For this reason, depending on the setting of the arrangement, the amount of toner carried per unit area on the surface of the electrostatic actuator member may be insufficient, resulting in insufficient development density. In order to solve such a shortage of development density, it is conceivable to make the toner conveying speed by the electrostatic actuator sufficiently higher than the moving speed of the latent image carrier. There is a possibility that an abnormal image in which the toner concentrates and adheres to the background portion near the end portion may occur. This is because, as is well known in a conventional developing device, the rotational speed of the developing roller is changed to increase the toner supply amount per unit time for the electrostatic latent image on the latent image carrier. This is the same phenomenon that occurs when the speed is higher than the surface moving speed.

The present invention has been made in view of the above problems, and has as its object to transfer toner without moving a developer carrying member, and
An object of the present invention is to provide an image forming apparatus capable of obtaining a sufficient image density even when the toner conveying speed in the developing area is set to be substantially equal to the moving speed of the surface of the latent image carrier.

[0006]

A latent image on a latent image carrier is displayed.
In an image forming apparatus having a developing device provided with a toner for forming an image , a developing area which is a portion facing the latent image carrier is provided.
As a toner conveying means of the developing device for conveying the toner to
First to third adjacent three electrodes are sequentially different from each other
To form the first to third drive electrode groups by being connected to the
Number of electrodes in the transport direction at a pitch of 1/3 of the particle size of the toner
Using the electrostatic actuator member which is arranged in, said
One of the first to third electrode terminals has one polarity opposite to that of the toner and the other polarity.
Two sets the voltage of the pattern of the same polarity as the toner,
Electrodes are shifted one by one in the first to third electrodes
The application is performed while switching to .

[0007]

According to the present invention, an electrostatic actuator member is used as a toner conveying means of a developing device, and a voltage whose polarity is changed in a predetermined pattern is applied to a plurality of electrodes of the electrostatic actuator. The toner is conveyed by generating a driving force electrostatically by interaction with the electric charges of the plurality of electrodes of the electrostatic actuator. Then, the plurality of electrodes, disposed in a third of the pitch of the toner particle diameter in the toner transfer direction, thereby, in which so as to deposit approximately no clearance toner to an electrostatic actuator surface.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described based on embodiments. First,
FIG. 1 illustrates a schematic configuration of an entire image forming apparatus according to an embodiment.
, The overall configuration and operation will be described. A photoconductor drum 1 (for example, an organic photoconductor; OPC), which is a configuration example of a latent image carrier, is driven to rotate clockwise. When a document is placed on the contact glass 2 and a print switch (not shown) is pressed, a scanning optical system 5 including a document illumination light source 3 and a mirror 4 and a scanning optical system 8 including mirrors 6 and 7 move. Scanning of a document is performed. Then, the scanned image is read as an image signal by an image reading element 10 provided behind the lens 9. The read image signal is digitized and processed. Then, the laser diode (LD) is driven by the image-processed signal. The laser light from the LD is reflected by a polygon mirror 13 and then applied to the photosensitive drum 1 via a mirror 14. As a result, the optical writing by the laser beam is performed on the photosensitive drum 1, and an electrostatic latent image is formed on the surface of the photosensitive drum that is already uniformly charged by the 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. The transfer paper on which the visible image has been transferred is separated from the surface of the photoreceptor belt 1 by the separation charger 19, and then conveyed by the conveyance belt 21. It is fixed and discharged out of the machine. On the other hand, the toner remaining on the photoreceptor surface after the transfer is removed by the cleaning device 23.

Next, the developing device 16 will be described. FIG.
, The developing device 16 transports the toner in the toner hopper to the vicinity of the charging roller 162, the developing roller 161 which is a toner transporting unit, the charging roller 162 which rotates in contact with the surface of the developing roller 161 to frictionally charge the toner. And an agitator 163 for it. Developing roller 1
61 is on the base roller 161a which is supported non-rotatably,
An electrostatic actuator member including a stator 165 made of an insulator and a plurality of electrodes 164 embedded therein is provided. The plurality of electrodes (hereinafter, referred to as drive electrodes) 16
Numeral 4 is a strip that is elongated in the axial direction of the base roller 161. Adjacent electrodes are connected to any of the first to third electrode terminals 164a, 164b, 164c different from each other, and three driving electrodes are connected. An electrode group is formed. The pitch of the drive electrodes 164 in the circumferential direction of the developing roller 161 may be set to, for example, about 10 to 20 μm so that toner particles having a diameter of about 10 μm adhere to one drive electrode 164 in a line. (Refer to FIG. 3).
A plurality of rows of toner particles may be attached to one drive electrode. And these electrode terminals 164
By applying a voltage to a, 164b, and 164c as described later, a driving force is generated by the interaction between the charge of the toner and the charge of the drive electrode 164, and the toner is transported.

In the toner hopper, the charging roller 1 is provided.
For example, black toner that is frictionally charged to a positive polarity (+) by 62 is stored. This toner needs to have a predetermined resistance as described later. The toner end detection is performed by detecting the rotation torque of the agitator 163, and assuming that the toner has disappeared in the developing device 16 due to the rotation torque having decreased to a predetermined value or less, and the toner end has been detected. For example, a not-shown toner end indicator on the operation unit is turned on to notify the user of the toner end.

Referring to FIG. 3, a description will be given of the principle of operation in which toner is conveyed by the electrostatic actuator member, for example, rightward on the electrostatic actuator member. FIG.
As shown in (a), any of the electrode terminals 164a, 164
When no voltage is applied to b and 164c, there is no charge in the drive electrode 164. On the other hand, although the toner is frictionally charged by the charging roller 162 and is positively charged, the toner is not controlled at all by the drive electrode 164 because there is no charge on the stator side, and the toner is not conveyed. . At this time, the toner floats around the developing roller 161 or adheres to the stator by some force. From this state, as shown in FIG. 3B, a positive voltage is applied to the first electrode terminal 164a, a negative voltage is applied to the second electrode terminal 164b, 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, + toner adheres to the surface of the developing roller on the drive electrode 164 to which -V is applied. At this time, the toner is not attracted to the drive electrode 164 to which the voltage of + V having the same polarity as the toner is applied and the drive electrode 164 to which no applied voltage is applied. Next, as shown in FIG. 3C, + V, which is the same polarity as the toner, is applied to the second drive electrode group below the attached toner by applying the respective applied voltages to the toner in the toner transport direction ( In this example, on the right side, the adjacent third electrode group has -V, which is opposite in polarity to the toner, and the first drive electrode group, which is opposite to the toner transport direction of the second drive electrode, has the same polarity as the toner. Is switched so as to apply + V. As a result, since the charge of the toner and the charge of the drive electrode immediately below the toner have the same polarity, a repulsive force is generated, a floating force is generated for the toner, and the third drive electrode group in the toner transport direction is set to 0. To -V and have the same polarity as the toner, the electric charge of the third drive electrode group attracts the toner at the upper left, and
Since the charge of the first drive electrode group opposite to the toner transport direction has the same polarity as the toner, it repels the toner on the upper right, and generates a rightward driving force on the toner. The friction between the toner and the surface of the developing roller is reduced by the floating force, and the toner moves about one pitch of the drive electrode by the drive force due to the electric charge. Next, in order to shift the voltage (FIGS. 3 (c) and 3 (d)) of the pattern for repelling and driving the toner by one, as shown in FIGS. Switch.
Thereafter, similarly, the toner is continuously moved by applying the driving electrodes one by one while shifting them one by one. Here, Table 1 summarizes the switching of the voltage applied to each drive electrode group from FIG. 3B to FIG. 3F and thereafter. 3B corresponds to the steps in the table, FIGS. 3C and 3D correspond to the steps, and FIGS. 3E and 3F correspond to the steps. The steps are + V, -V, and -V for each of the first to third drive electrode groups.
+ V is applied, and the voltage of the pattern for repelling and driving the toner is shifted from the step by one to the right in the toner transport direction. Thereafter, by repeating the steps (1) to (4), the voltage of the pattern for repelling and driving the toner is shifted one by one.

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

Here, as the toner of this embodiment, any toner having a high resistance and a medium resistance can be used as long as it can be frictionally charged. However, in the case of a medium-resistance toner, the toner is instantaneously charged by the charge of the drive electrode after switching when the polarity of the voltage applied to the drive electrode is switched while the toner is attached to the surface of the developing roller above the drive electrode. If a charge having a polarity opposite to that of the triboelectric charge is guided to the lower portion of the toner, the charge may be attracted by the charge of the drive electrode and a sufficient repulsive force may not be obtained. Therefore, a resistor having such a resistance that a sufficient repulsive force can be obtained when the polarity of the voltage applied to the drive electrode is switched is used.

In the above configuration, the toner in the toner hopper is transported to the charging roller 162 by the agitator 163, charged to a predetermined polarity by the charging roller 162, and then transported to the surface of the developing roller 161. Developing roller 1
The toner on 61 is transported by an electrostatic actuator,
The photosensitive drum 1 reaches a portion facing the photosensitive drum 1 and adheres to the electrostatic latent image on the photosensitive drum 1 to visualize the electrostatic latent image. Photoconductor drum 1
The toner that has not adhered to the developing device returns to the inside of the developing device, and is removed from the developing roller 162 by the charging roller 162.

In the present embodiment, the plurality of drive electrodes 164 are divided into three drive electrode groups, and toner is attracted by one of the three drive electrode groups to thereby develop the developing roller 161. It is carried on the peripheral surface. That is, one toner is allocated to the three drive electrodes arranged side by side. Therefore, in order to supply a sufficient amount of toner to the latent image on the photoreceptor and perform uniform development, the necessary and sufficient conditions for carrying the toner so that there is almost no gap on the peripheral surface of the developing roller 161 are as shown in FIG. As shown in FIG. 4, the required width including the distance between the drive electrodes of all three drive electrodes arranged side by side is to be substantially equal to the particle size of one toner. If the arrangement pitch P is larger than this, a gap is generated between the toner particles. Conversely, if the arrangement pitch P is smaller than this,
As is clear when focusing on one layer of the toner, the toner cannot adhere to the peripheral surface of the developing roller 161 without a gap, and the toner that floats from the surface of the developing roller 161 is generated. Smooth toner conveyance based on the image cannot be performed. Therefore, in the present invention, the drive width is set so that the required width including the distance between the drive electrodes of all three drive electrodes arranged side by side as shown in FIG. 4 is substantially equal to the particle size of one toner. Electrode 164
Is set to approximately one third of the toner particle size.

As described above, in the present embodiment, the toner is conveyed without rotating the developing roller 161 by using the principle of the electrostatic actuator. Therefore, there is no rubbing portion unlike the case where the developing roller 161 is rotated. There is no possibility that stress is applied to the toner in the rubbing part and the toner is fixed. Further, since the developing roller 161 does not rotate, the torque does not increase due to the generation of the eddy current, and the generation of heat is suppressed, so that the toner in the developing device does not melt.

In the above-described embodiment, the toner is used by frictionally charging the toner. However, the toner can be conveyed without frictionally charging the toner. In this case, FIG.
After the electric charge having the polarity opposite to the polarity of the applied voltage of the drive electrode is induced in the lower part of the toner in the state of (1), the voltage to each applied electrode is switched as shown in FIG. A repulsive force is generated to move the toner in the same manner as in the above embodiment. Also in this case, at the moment when the polarity of the voltage applied to the drive electrode is switched, the charge of the drive electrode after the switch instantaneously induces a charge having a polarity opposite to the triboelectric charge polarity of the toner to the lower portion of the toner. Since there is a possibility that a sufficient repulsive force may not be obtained by being attracted by the electric charge of the drive electrode, a resistor having a resistance enough to obtain a sufficient repulsive force when switching the polarity of the voltage applied to the drive electrode is used.

[0017]

As described above, according to the present invention, an electrostatic actuator member is used as a developer conveying means of a developing device, whereby toner is supplied to an electrostatic latent image carrier without rotating the developer carrier. Therefore, the toner is not fixed in the developing device, and the torque can be reduced. In addition, there is no problem that a voltage is applied via a bearing of a rotating member like a conventional developer carrier, resulting in a defective application of a developing bias voltage. Further, since the plurality of electrodes are arranged at a pitch of one third of the toner particle diameter in the toner conveying direction, and the toner is carried on the surface of the electrostatic actuator with almost no gap, the toner conveying in the developing area is performed. Even if the speed is set to be substantially the same as the moving speed of the surface of the latent image carrier, a sufficient amount of toner can be supplied to the electrostatic latent image carrier to obtain a sufficient image density.

[Brief description of the 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. 1;

FIGS. 3A to 3F are explanatory diagrams of the principle of toner transport operation.

FIG. 4 is an explanatory diagram of a drive electrode arrangement of an electrostatic actuator of the developing device.

[Explanation of symbols]

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

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Tomoji Ishikawa 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (56) References JP-A-3-21967 (JP, A) (58) Field surveyed (Int.Cl. ⁷ , DB name) G03G 15/08

Claims (1)

(57) [Claims] 1. A toner for developing a latent image on a latent image carrier.
In an image forming apparatus having a developing device provided with a developing device , a developing region, which is a portion facing the latent image carrier, is used for development.
As the toner conveying means of the developing device for conveying the toner, three adjacent electrodes are sequentially different from each other in first to
The first to third drive electrode groups are formed by being connected to the third electrode terminal.
Multiple electrodes at a pitch of 1/3 of the particle size of the toner
Using the electrostatic actuator member disposed side by side in a direction, to the first to third electrode terminal, one toner and opposite polarity
The other two apply a voltage of a pattern having the same polarity as the toner,
The electrodes to be polarized are shifted one by one in the first to third electrodes
The image forming apparatus is characterized in that the voltage is applied while switching .