JP3248288B2 - 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 a developing device used in an image forming apparatus such as a copying machine, a facsimile, a printer, and the like. More specifically, the present invention relates to a developing device for an image forming apparatus. The present invention relates to a developing device having a developer carrier disposed opposite to a carrier and visualizing a latent image on the latent image carrier using a one-component or two-component developer. .

[0002]

2. Description of the Related Art Conventionally, in a developing device of this type, when a developing roller that is driven to rotate, for example, is used as a developer carrier, the developing roller is rotated so that the developer ( In the case of the one-component developer, there is a problem that the toner, and in the case of the two-component developer composed of the toner and the carrier), the toner attached to the carrier is scattered. Therefore, conventionally, a developing device configured to control the airflow on the downstream side of the developing roller in the developer conveyance direction from a region facing the latent image carrier of the developing roller to guide the scattered toner into the developing container, 2. Description of the Related Art A developing device configured to be guided outside the apparatus and collected at one location is known. Also,
A rotating roller that is provided downstream of the developing roller in the developer transport direction with respect to the region facing the latent image carrier, and that catches toner to be scattered; and a rotating roller that contacts the surface of the rotating roller and is caught on the rotating roller. 2. Description of the Related Art A developing device having a scraper that scrapes off toner and stores the toner in a toner collecting section is known (for example, see Japanese Patent Application Laid-Open No. 62-27776).

[0003]

However, in a developing device configured to control the airflow to guide the scattered toner, the toner concentration in the developer (for example, 2
As the component developer has a higher ratio of toner adhering to the carrier), the charge amount of the toner decreases and the amount of toner scattered increases. As a result, the balance with the airflow control ability is lost, and the toner becomes There was a problem of scattering. Further, in the developing device of this configuration, there is a developing device in which the toner guided by the airflow and conveyed into the developing device is collected by a filter through a filter provided in the developing device. According to this configuration, the toner concentration is high. When the amount of floating toner is large, there is a problem that the filter is immediately clogged and the airflow control ability is reduced. Further, even when the toner concentration is low, the filter is clogged with time, so that there is a problem that the filter needs to be periodically replaced. Further, in the developing device disclosed in Japanese Patent Application Laid-Open No. 62-27776, it is necessary to rotationally drive the rotary roller, and further, toner is scattered from the rotary roller due to poor scraping due to wear of the scraper. There was a problem.

The present invention has been made in view of the above problems, and an object of the present invention is to stably collect satisfactorily the developer scattered from a developer carrier over time, and An object of the present invention is to provide a developing device capable of preventing a problem caused by scattering.

[0005]

According to a first aspect of the present invention, there is provided an image forming apparatus, comprising: an opening provided to face a latent image carrier; A developing device that transports a two-component developer with the developed developer carrier to develop a latent image on the latent image carrier, wherein the developer is located in a region where the developer carrier is opposed to the latent image carrier. in the downstream side in the conveying direction
Where the developer scatters from the developer carrier
Further, a developer collector having an electrostatic actuator for transporting the developer is provided on the inner side of the apparatus , facing the surface of the developer carrier. According to a second aspect of the present invention, in the first aspect of the present invention, a toner density detecting means for detecting a toner density of the developer in the apparatus conveyed by the developer carrier, and a detection result of the toner density detecting means. And control means for controlling the voltage applied to the electrostatic actuator. According to a third aspect of the present invention, in the first aspect of the present invention, a toner concentration detecting means for detecting a toner concentration of the developer in the apparatus conveyed by the developer carrier, and a detection result of the toner concentration detecting means. And control means for controlling the switching speed of the voltage applied to the electrostatic actuator based on the control signal.

[0006]

According to the first aspect of the present invention, the developer scattered after passing through the region between the developer carrier and the latent image carrier is more developed than the region of the developer carrier facing the latent image carrier. The developer is caught by a developer collector having an electrostatic actuator provided on the downstream side in the developer transport direction, and is transported to the inner side inside the developing device. According to a second aspect of the present invention, in the first aspect, the toner concentration detecting means for detecting the toner concentration of the developer in the apparatus conveyed by the developer carrier increases the toner concentration of the developer in the apparatus. Control means for controlling the voltage applied to the electrostatic actuator based on the detection result of the toner concentration detecting means, the voltage applied to the electrostatic actuator is increased, and the developer in the developer collector is increased. The ability to collect is increased. According to a third aspect of the present invention, in the first aspect, the toner concentration detecting means for detecting the toner concentration of the developer in the apparatus conveyed by the developer carrier increases the toner concentration of the developer in the apparatus. Control means for controlling the voltage applied to the electrostatic actuator based on the detection result of the toner concentration detecting means, the switching speed of the voltage applied to the electrostatic actuator is increased, and the developer collector Of the developer is increased.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a developing device used in an electrophotographic copying machine (hereinafter referred to as a copying machine) as an image forming apparatus will be described. In the following, a two-component developing device using a two-component developer composed of a toner and a carrier as a developer will be described as an example. FIG. 1 is a schematic configuration diagram of a developing device according to the present embodiment. In this developing device, an opening 21 is formed in a portion opposed to a drum-shaped photoreceptor 1 as a latent image carrier, and a developing tank 2 as a developing container containing a developer including a toner and a carrier therein is provided. And a toner tank 3 containing toner to be supplied to the developing tank 2 therein. The developing tank 2 is provided with a developing roller 4 as a developer carrying member which is disposed to face the photoconductor 1 and visualizes an electrostatic latent image on the photoconductor 1. A doctor blade 5 disposed at an interval to regulate the amount of the developer on the developing roller 4 to a predetermined amount, and a developing device disposed at the back of the developing tank 2 to agitate the developer and supply the developer to the developing roller 4 A paddle 6 as a developer supply member, a toner collection roller 7 as a developer collection device disposed downstream of a region of the development roller 4 facing the photoconductor 1 in the developer conveyance direction, and an end portion. A scraping member 8 which comes into contact with the surface of the toner collection roller 7 and scrapes the toner on the toner collection roller 7, and the toner is scattered from the upstream side of the developing roller 4 in the developer conveyance direction with respect to the area where the developing roller 4 faces the photoconductor 1. Seal 9 and a developing tank 2 for preventing A toner concentration sensor 10 as toner concentration detecting means is provided for detecting the toner concentration in the developer. The toner tank 3 includes a toner replenishing roller 11 for replenishing toner in the toner tank 3 to the developing tank 2 based on a signal from the toner density sensor 10, and a rotatable toner replenishing roller 11 for supplying toner in the toner tank 3. And a toner agitator 12 to be supplied to the printer. Further, the photoconductor 1, the developing roller 4, the paddle 6, and the toner replenishing roller 11 are configured to be rotatable in a direction indicated by an arrow in FIG.

In this developing device, the developer in the developing tank 2 is agitated by the paddle 6 and supplied to the developing roller 4. The excess developer on the developing roller 4 is scraped off by a doctor blade 5 and regulated to a predetermined amount. Then, the developer is conveyed to a region facing the photoconductor 1 by rotation of the developing roller 4. Then, the developer is supplied to the electrostatic latent image on the photoreceptor 1 in the above-described facing area to visualize the electrostatic latent image. When the toner concentration sensor 10 detects that the toner concentration in the developer in the developing tank 2 has decreased, a signal is sent to a control device (not shown), and the control device rotates the toner supply roller 11. First, the toner supplied by the toner agitator 12 is supplied from the toner tank 3 to the developing tank 2 by a predetermined amount.

Here, when the developing roller 4 rotates in the direction of the arrow shown in the figure, centrifugal force acts to cause the toner on the developing roller 4 to be located downstream of the area where the developing roller 4 faces the photosensitive member 1 in the developer conveying direction. May fly. Therefore, in the present embodiment, the scattered toner is collected by the toner collection roller 7 and returned to the developing tank 2.

Next, the detailed structure of the toner collecting roller 7 will be described. FIG. 2 is a schematic configuration diagram of the toner collection roller 7. At least the surface of the toner collection roller 7 is formed of an electrostatic actuator member. The electrostatic actuator member includes a stator 71 made of an insulator, which is a functional member, and a plurality of electrodes 72 embedded therein. Become. The plurality of electrodes (hereinafter referred to as drive electrodes) 72
Has an elongated band shape, and adjacent electrodes have different first to third electrode terminals 72a and 72a, as shown in FIG.
It is connected to either of 72b and 72c to form three drive electrode groups. Incidentally, the first to third electrode terminals 72a, 72b, 72c toner scavenged connector 73 provided on the roller 7 is connected to (see FIG. 2), V ₁ respectively, V _2, V ₃ of the voltage Is applied. By applying a voltage to these electrode terminals 72a, 72b, 72c from a power supply device (not shown) as described later, based on the principle of electrostatic actuator conveyance,
The driving force is generated by the interaction between the charge of the toner and the charge of the stator, and the toner is conveyed on the surface of the stator 71.

Referring to FIG. 3, a description will be given of the principle of operation in which toner used by being charged positively (+) by, for example, the electrostatic actuator member is conveyed, for example, rightward in the drawing on the electrostatic actuator member. As shown in FIG. 3A, when no voltage is applied to any of the electrode terminals 72a, 72b, 72c, there is no charge on the drive electrode 72. On the other hand, the toner is charged by friction with the carrier,
However, since there is no charge on the stator side, the toner is not controlled at all by the drive electrode 72, and the toner is not conveyed. At this time, the toner floats around the developing roller 7 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 72a, and the second electrode terminal 72b
, And 0 V is applied to the third electrode terminal 72c. 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 stator on the drive electrode 72 to which -V is applied. At this time, the toner is not attracted to the drive electrode 72 to which the voltage of + V having the same polarity as the toner is applied and the drive electrode 72 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 charge of the third drive electrode group attracts the toner at the upper left, and the charge of the first drive electrode group opposite to the toner transport direction is Since the toner has the same polarity as the toner, the toner on the upper right is repelled, and a rightward driving force is generated in the toner. The friction between the toner and the surface of the stator decreases due to the floating force, and the toner moves about one pitch of the driving electrode by the driving force due to the electric charge. Next, the voltage of the pattern for repelling and driving the toner (see FIG. 3)
(C) and (d) of FIG.
Each applied voltage is switched as shown in FIGS. Thereafter, similarly, the toner is continuously moved by applying the driving electrodes one by one while shifting them one by one. Here, FIG.
Table 1 summarizes the switching of the applied voltage to each drive electrode group from (b) to FIG. 3 (f) and thereafter. Figure 3 shows the steps in the table.
FIGS. 3C and 3D correspond to step (b), and FIGS. 3E and 3F correspond to step. The steps are + V, -V, + 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. (Hereinafter, margin)

[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.

In the above configuration, the toner scattered by the centrifugal force on the downstream side of the developing roller 4 in the developer conveying direction is captured by the electric field formed by the electrostatic actuator member of the toner collecting roller 7 provided thereon. The toner adheres to the surface of the toner collection roller 7. The attached toner is conveyed to the rear side of the developing tank 2 on the surface of the toner collection roller 7 in accordance with the principle described with reference to FIG. While the toner is being conveyed, the toner is scraped off from the surface of the toner collecting roller 7 by the scraping member 8 and returned into the developing tank 2.

By the way, as shown in FIG. 4, the amount of scattered toner rapidly increases when the toner concentration in the developing tank 2 exceeds 3% by weight. This is because when the toner concentration increases, the number of toners adhering to one carrier increases, so that the frictional charge with the carrier is not sufficiently performed, the charge amount is reduced, and the toner having an insufficient adhesive force with the carrier increases. it is conceivable that.

Therefore, in this embodiment, the toner density sensor 1 detects that the toner density exceeds 3 wt%, for example.
When it is detected as 0, the voltage applied to the electrostatic actuator member of the toner collection roller 7 is increased by a control device (not shown). With this configuration, the electric field formed by the electrostatic actuator member is increased, and the toner collecting ability of the toner collecting roller 7 can be improved.

In the present embodiment, when the toner concentration sensor 10 detects that the toner concentration exceeds 3 wt%, for example, as described above, the control device (not shown) applies a force to the electrostatic actuator member of the toner collection roller 7. It is also possible to increase the frequency of the applied three-phase alternating current. With this configuration, the amount of toner transported per unit time by the electrostatic actuator member is increased, and the toner transporting ability of the toner collection roller 7 is increased.
Thereby, the toner collecting ability of the toner collecting roller 7 can be improved.

As described above, according to the present embodiment, the developing roller 4 rotates in the direction of the arrow shown in the figure, and the toner on the developing roller 4 is moved by the centrifugal force from the area of the developing roller 4 facing the photosensitive member 1 in the developer conveying direction. Even if the toner scatters on the downstream side, the scattered toner can be collected by the toner collection roller 7 and returned to the developing tank 2, so that the inside of the copying machine is contaminated with toner, It can be minimized that toner adheres to the portion. Further, since the toner is collected and transported by the electrostatic actuator member, there is no problem that the toner collecting ability is reduced due to clogging of the filter in the conventional apparatus. Further, since there is no need to rotate the toner collection roller 7, there is no need to provide a special member for rotating the toner collection roller 7, and the scraping member 8 is worn to cause poor scraping. There is no such thing. Further, the toner collecting ability of the toner collecting roller 7 can be controlled only by controlling the intensity or frequency of the voltage applied to the toner collecting roller 7.

[0017]

According to the first aspect of the present invention, the developer scattered by passing through the opposing region between the developer carrier and the latent image carrier is captured by the developer collector and is located inside the developing device. Side, so that there is no problem such as clogging of the filter or deterioration of the toner collection ability due to poor scraping due to abrasion of the scraper as in the conventional device. And a developing device capable of obtaining a developed image which is stable over time without any trouble due to toner scattering can be provided. According to the invention of claim 2, when the toner concentration detecting means detects that the toner concentration of the developer in the apparatus conveyed by the developer carrier has increased, the control means reduces the voltage applied to the electrostatic actuator. Since the developer collecting ability of the developer collecting device is increased by increasing the toner concentration, there is an excellent effect that the toner scattering can be completely prevented even if the toner concentration increases and the toner scattering amount increases. According to the invention of claim 3, when the toner concentration detecting means detects that the toner concentration of the developer in the apparatus conveyed by the developer carrier has increased, the control means controls the voltage applied to the electrostatic actuator. Since the switching speed is increased and the developer carrying capacity of the developer collector is increased, and thereby the developer collecting ability of the developer collector is increased, even if the toner concentration is increased and the toner scattering amount is increased, An excellent effect that a toner can be prevented from flowing out from a downstream side of a developer carrying member in a developer conveying direction from a region opposed to a latent image carrying member, a problem due to toner scattering is eliminated, and a highly reliable developing device can be provided. There is.

[Brief description of the drawings]

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

FIG. 2 is a schematic configuration diagram of a toner collection roller 7 in FIG.

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

FIG. 4 is a graph showing a relationship between a toner density and a toner scattering amount.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoreceptor 2 Developing tank 3 Toner tank 4 Developing roller 2 Doctor blade 6 Paddle 7 Toner collecting roller 8 Scraping member 9 Entrance seal 10 Toner density sensor 11 Toner supply roller 12 Toner agitator 21 Opening

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G03G 13/08-13/095 G03G 15/08-15/095

Claims (3)

(57) [Claims] An image forming apparatus, comprising: a two-component developer which is conveyed to an opening formed to face a latent image carrier by a developer carrier disposed so as to face the latent image carrier; In a developing device for developing a latent image on a body, a developer is transported downstream of a region where the developer carrier is opposed to the latent image carrier in a developer transport direction, and the developer is discharged from the developer carrier.
At the scattered point, face the developer carrier
And a developer collecting device having an electrostatic actuator for transporting the developer is provided on the inner side of the apparatus. 2. A toner concentration detecting means for detecting a toner concentration of a developer in an apparatus conveyed by the developer carrier, and a voltage applied to the electrostatic actuator based on a detection result of the toner concentration detecting means. 2. The developing device according to claim 1, further comprising control means for controlling the control of the developing device. 3. A toner concentration detecting means for detecting a toner concentration of the developer in an apparatus conveyed by the developer carrier, and an application to the electrostatic actuator based on a detection result of the toner concentration detecting means. 2. The developing device according to claim 1, further comprising control means for controlling a voltage switching speed.