JP3021086B2 - 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 developer carrying a two-component type developer carried on a developer carrying member to a developing area between the developer carrying member and a latent image carrier. The present invention relates to a developing device that visualizes an electrostatic latent image formed on a latent image carrier.

[0002]

2. Description of the Related Art It has been well known that an image forming apparatus such as an electronic copying machine, a printer or a facsimile employs a developing apparatus of the above-described type using a two-component developer having a toner and a carrier. In such a developing device, the carrier in the developer deteriorates with time, and if the carrier is used as it is, the quality of the visible image deteriorates. Therefore, conventionally, the deterioration state of the developer is detected, and when the life of the developer has expired, the developer is replaced with a new one.

However, in this type of conventional developing device, the detection current for detecting the life of the developer fluctuates due to the influence of various elements of the image forming apparatus, and it is difficult to accurately detect the life of the developer. Was. In addition, since the detection current itself is very weak, there is a disadvantage that the detection current is easily buried in noise.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a developing apparatus which eliminates the above-mentioned disadvantages of the prior art and which can detect the life of a developer correctly with a simple structure.

[0005]

According to the present invention, in order to achieve the above object, in a developing device of the type described at the outset, an opposing device arranged at a predetermined distance from an outer surface of the developer carrying member is provided. and the electrode, when the non-image area between the electrostatic latent image and the next electrostatic latent image on the latent image bearing member is passing through the developer carrying member, a predetermined voltage V ₀ to the developer carrying member Means for applying voltage, and a voltage V ₁ induced on the counter electrode through the developer on the developer carrying member when the voltage V ₀ is applied.
An induced voltage detecting means for calculating the voltage ratio R ₁ between the voltage V ₁ and the applied voltage V _0, and an operation comparing means for comparing the voltage ratio R ₁ with the reference voltage ratio R ₀ ; And a control unit that determines that the life of the developer is satisfied when ₁ ≦ R ₀ .

Further, it is advantageous to use a conductive agent regulating member for regulating the amount of the developer carried on the developer carrying member and conveyed to the developing area as the counter electrode.

[0007]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows an electronic copying machine which is an example of an image forming apparatus provided with a developing device according to the present invention.

An original 3 is placed on a contact glass 2 fixedly mounted on an upper part of a copying machine main body 1, and the original 3 is illuminated and scanned by an optical system 4 during an image forming operation. That is, light from the halogen lamp 6 of the first scanner 5 moving rightward in FIG. 1 is applied to the document 3, and light from the document is reflected by the first mirror 7 of the first scanner 5. This reflected light is also moved to the right by the second mirror 9 of the second scanner 8.
And after being sequentially reflected by the third mirror 10 and passing through the lens 11, the fourth mirror 12, the fifth mirror 13, and the sixth mirror 1
The light is reflected at 4, passes through the dustproof glass 15, and exposes the drum-shaped photoconductor 16 rotating clockwise, thereby forming a document image on the surface thereof.

The above-mentioned dustproof glass 15 prevents a floating substance such as toner or paper dust from entering the optical system 4 and contaminating the optical element. The illustrated optical system 4 has a maximum of 2
It has a zooming function for every 1% from 00% to a minimum of 50%. Further, the background density of the original 3 is detected by using an optical fiber (not shown), and based on the detected density, the developing bias voltage to the developing sleeve 17 described later is corrected, so that an image having a clear background can be obtained. An automatic density adjustment system can also be provided.

The photosensitive member 16 is an example of a configuration of a latent image carrier, and is driven to rotate clockwise in FIG. 1 by a driving device (not shown). Further, the illustrated photoconductor 1
Reference numeral 6 denotes an organic photoconductor formed by laminating an organic photoconductive layer on a drum-shaped conductive support.

The photoreceptor 16 is uniformly charged to a predetermined polarity, in this example, negatively by the charging charger 18 during its rotation. That is, a high voltage is applied to the charge wire of the charger 18 in the dark to generate a corona discharge, thereby applying a negative charge uniformly on the photoconductor. At this time, the surface potential of the photoconductor 16 is, for example, −8.
00V. A grid 19 is provided between the charge wire and the photoreceptor 16 for controlling the potential uniformly and uniformly.
Is provided.

The surface of the photoreceptor charged as described above is subjected to image exposure as described above, thereby forming an electrostatic latent image.

Next, the photoreceptor 16 is irradiated with light from the eraser 20 on the non-image portion, and unnecessary charges are erased. This facilitates a cleaning operation described later. The eraser 20 is composed of a long LED,
Erasing the front and rear ends.

When the electrostatic latent image formed as described above passes through the developing device 21, it is visualized as a toner image.

The surface of the photoreceptor that has passed through the developing device 21 is irradiated with light by a pre-transfer charge removing lamp 22. The neutralization lamp 22 is turned on at the same time as the start of a main motor (not shown), and irradiates the photosensitive member 16 with light that erases residual charges on the photosensitive member 16 while being diffused by a filter. This operation is performed in the same manner in the neutralization lamp 23 described later.

On the other hand, transfer paper 24, which is an example of a transfer material fed from a paper supply unit (not shown),
5, the toner is sent toward the photoconductor 16 at a predetermined timing and adheres to the photoconductor 16, and the toner image on the photoconductor 16 is transferred to the transfer paper 24 by the corona discharge action of the transfer charger 26. Next, the transfer paper 24 is separated from the photoconductor 16 by the separation charger 27. In this case, if the transfer paper cannot be separated, the separation claw 2
8 forcibly separates the transfer paper. The transfer paper 24 after separation is conveyed to the fixing device 30 by the conveyance belt 29,
Then it is discharged outside the machine.

The cleaning device 131 includes a cleaning brush 3 for scraping off toner remaining on the surface of the photoconductor 16.
1 and a cleaning blade 32, and the cleaning blade 32 is supported at one point at the center so that the contact pressure at each end in the axial direction of the photoconductor becomes uniform.
The cleaning brush 31 rotates in the same clockwise direction as the photoconductor 16 and removes foreign matter such as a piece of paper which is difficult to remove with the cleaning blade 32. Cleaning blade 32
The toner scraped off by the brush 31 is collected by the toner collecting section. The surface of the photoreceptor that has passed through the cleaning device 131 is subjected to a charge removing operation by the charge removing lamp 23.

The fixing device 30 applies a constant temperature and pressure to the transfer paper conveyed by the conveyance belt 29 and fixes the toner image by bringing the toner image into contact with the transfer paper. The temperature of the heater is controlled.

The developing device 21 is provided with a developing container 34 having an opening at a portion facing the photoreceptor 16, and the developing container 34 contains a powdery two-component developer D having toner and carrier. Is housed. As the carrier, for example, a resin-coated carrier having an average particle size of 70 μm can be used.

In the developing container 34, a developing sleeve 17 which is located opposite to the photoreceptor 16 is supported. Inside the developing sleeve 17, a magnet 35 in which a plurality of different magnetic poles are alternately arranged is fixed from the inner surface of the developing sleeve 17. Are provided at intervals. The developing sleeve 17 shown in FIG. 1 is formed of a cylindrical body made of a conductive non-magnetic material such as aluminum, and the gap with the photoconductor 16 is, for example, 0.75 mm.

The developer D in the developing container 34 is stirred by rotating stirring rollers 36 and 37, and the toner and the carrier are frictionally charged to different polarities. In this example, the toner is charged positively and the carrier is negatively charged. Further, the developer is transferred to the developing sleeve 1 by one stirring roller 36.
7 and the developing sleeve 1
7 carried.

At this time, the developing sleeve 17 rotates counterclockwise, and the developer carried on the sleeve 17 is conveyed counterclockwise while forming a magnetic brush, and is made of a nonmagnetic conductive material such as aluminum. The excess developer is scraped off by a doctor blade 38 consisting of The scraped developer is guided by the separator 39,
Fall down. Instead of rotating the developing sleeve 17, the magnet 35 may be rotated clockwise, or the sleeve 17 and the magnet 35 may be driven to rotate to transport the developer.

The developer that has passed through the doctor blade 38 is transported to a developing area between the developing sleeve 17 and the photosensitive member 16 and passes there. At this time, the magnetic brush made of the developer contacts or comes close to the surface of the photoconductor 16 on which the electrostatic latent image is formed, and the positively charged toner electrostatically forms the negatively charged electrostatic latent image. Then, the latent image is visualized as a toner image.

The above-described developing sleeve 17 is a member for transporting the developer to the developing area, and constitutes an example of the configuration of the developer carrying member. Instead of the sleeve 17, a developer carrying member formed of a belt can be used. Further, the magnet 35 provided inside the developing sleeve 17 constitutes an example of a configuration of a magnetic field generating means for attracting and holding the developer on the developer carrying member. Further, the doctor blade 38 disposed above the developing sleeve 17 constitutes an example of a developer regulating member for controlling the amount of the developer carried on the developer carrying member and conveyed to the developing area. Then, as described above, the developing device of this embodiment transfers the two-component developer carried on the developer carrying member made up of the developing sleeve 17 to the latent image carrier made up of the developer carrying member and the photoconductor 16. The electrostatic latent image formed on the latent image carrier is visualized by the developer.

When the above-described developing operation is performed, the photosensitive member 1
Although the conductive support member 6 is grounded, a bias voltage is applied to the developing sleeve 17 by the bias power supply 40 shown in FIG. Such a bias voltage is applied to the photoconductor 16.
The bias voltage is applied to prevent the above-described background contamination and adjust the image density. In this example, assuming that the surface potential of the electrostatic latent image is −800 V and the background potential is −40 V as described above, the bias voltage is It is set to about -200V. However, the final bias voltage value is determined according to the original density or the demand of the operator.

When the toner concentration of the developer in the developing container 34 decreases, the toner in the toner container 41 is sprinkled on the toner replenishing roller 42 by the rotation of the toner replenishing bar 41a. The developer D is supplied into the developer container 34 through a hole (not shown) formed in the slitter 42a. The outer diameter of the developing sleeve 17 is set to, for example, 30 mm, and the magnet 35 has a surface magnetic force of, for example, about 800 mm.
The magnetic force is set to be Gaussian.

Although the developing operation is performed as described above, the carrier in the developer deteriorates as such an operation is repeatedly performed. If the deteriorated developer is continuously used, the image quality of the visible image deteriorates. Therefore, it is necessary to detect the state of deterioration of the developer, and when it reaches the end of its life, replace the developer with a new one.

In this embodiment, the life of the developer is checked as shown in FIG. 3 according to the configuration shown in FIG. Such a check can be performed in a timely manner including a developing operation in which the developing device 21 actually visualizes the electrostatic latent image on the photoconductor 16, but in this example, each of the developing devices 21 A developer life check is performed when a non-image portion between one electrostatic latent image on the photoreceptor 16 and the next electrostatic latent image passes through the developing device 21 although the element is operating. Shall be.

First, a non-image portion between a certain electrostatic latent image and the next electrostatic latent image on the photosensitive member 16 passes through the developing sleeve 17 by a bias power supply 40 as a voltage applying means shown in FIG. 3, a predetermined DC voltage V ₀ is applied to the developing sleeve 17 rotating counterclockwise (see FIG. 3).
(A)). At this time, the doctor blade 38 made of a conductor arranged at a predetermined distance from the outer surface of the developing sleeve 17 is, for example, grounded or floated in voltage.

As described above, the voltage V ₀ is applied to the developing sleeve 17.
Is applied, the doctor blade 38 opposite thereto is applied.
The developer D magnetically supported on the developing sleeve 17
A voltage V ₁ is induced through the capacitor. Thus, in this example, the doctor blade 38 serves as a counter electrode for the developing sleeve 17.

The above-mentioned induced voltage V ₁ is detected by the induced voltage detecting means 43 shown in FIG. 2 (FIG. 3B).
As this detection means, a contact-type voltmeter or a non-contact surface voltmeter for forming a closed circuit can be appropriately used.
When the earth is grounded, the contact-type electrometer
When 8 is floated, a non-contact type surface electrometer is usually used.

If the ratio V ₁ / V ₀ between the two voltages V ₁ and V ₀ is represented by R ₁ , the voltage ratio R ₁ and the use time of the developer, that is, the number of copies, are as shown in FIG. Has the relationship indicated by B in FIG. From this figure, according to usage time of the developer is increased, it is possible to voltages V ₁ induced in the doctor blade 38 to understand that the decrease. this is,
As the number of copies increases and the usage time of the developer increases, the toner is spent on each carrier in the developer, thereby increasing the resistance of the developer, and is induced by the doctor blade 38 as a counter electrode. it is considered that the voltages V ₁ decreases.

From this point of view, in this example, FIG.
As shown in the figure, the voltage V ₀ of the bias power supply 40 and the voltage V ₁ detected by the induced voltage detecting means 43 are calculated by the arithmetic comparing means 44.
And the voltage ratio R ₁ = V ₁ / V ₀ is calculated (FIG. 3C). Further, the reference voltage ratio R ₀ stored in the control reference data storage unit 45 in advance is given to the arithmetic comparison unit 44, and the voltage ratio R ₁ and the reference voltage ratio R ₀ (reference data of developer deterioration) are compared. They are compared (FIG. 3D).

Here, when the developer has not deteriorated yet, the above-mentioned comparison result is R ₁ > R ₀ , but the number of copies becomes P ₀ or more as shown in FIG. When the developer deteriorates and the voltage ratio R ₀ becomes equal to or less than the threshold value L, the above comparison result satisfies R ₁ ≦ R ₀ . Thus, the control means 46 determines that the life of the developer has been reached when R ₁ ≤R _0, and that fact is considered as the copying machine body 1 (FIG. 1).
Display means 47 comprising a display unit attached to the operation unit of
The control unit 46 sends a developer life signal, and displays on the display unit that the developer has reached the end of its life and needs to be replaced (FIG. 3E). The operator can know from the display that the life of the developer has reached the end of its life, and the operator or a service person can immediately perform the replacement operation of the developer. As described above, the developing device according to the present embodiment includes the counter electrode including the doctor blade 38 disposed at a predetermined interval from the outer surface of the developer carrying member including the developing sleeve 17 and the latent electrode including the photosensitive member 16. bias non-image area between the electrostatic latent image and the next electrostatic latent image on the image bearing member, to be applied when passing through the developer carrying member, a predetermined voltage V ₀ to the developer carrying member and voltage applying means consisting of a power supply 40, the voltage V induced in the counter electrode through the developer on the developer carrying member at the time of application of the voltage V ₀
An induced voltage detection means 43 for detecting _one, calculates the voltage ratio R ₁ between the voltages V ₁ and the applied voltage V _0, the voltage ratio R ₁
An operation comparing means 44 for comparing the reference voltage ratio R ₀ with the reference voltage ratio R ₀ ;
And control means 46 for judging the life of the developer when ₁ ≦ R ₀ .

As described above, the voltage value induced in the doctor blade 38 is compared with the reference value indicating the degree of deterioration of the developer, and based on the result, the deterioration of the developer is determined, and the fact is displayed. Since it is displayed in the section, the replacement time of the life can be accurately detected with a simple configuration.

In this embodiment, the life of the developer is checked when the actual developing operation is not being performed, such as when the non-image portion on the photosensitive member 16 passes through the developing device 21. Detection accuracy can be improved. That is, at the time when the electrostatic latent image is actually visualized, the above-described developer life check operation is performed, and when a current flows through the developer D between the developing sleeve 17 and the doctor blade 38,
Although the amount of toner adhering to the developing sleeve 17 or the doctor blade 38 may be increased and the accuracy of detecting the life of the developer D may be slightly reduced, such a problem can be eliminated in the present embodiment.

In the embodiment described above, a conductive agent regulating member comprising a doctor blade 38 for regulating the amount of the developer carried on the developer carrying member and conveyed to the developing area is used as the counter electrode. Thus, simplification of the configuration can be achieved. Of course, an independent counter electrode separate from the doctor blade 38 may be provided, and may be arranged at a predetermined distance from the outer surface of a developer carrying member such as a developing sleeve.

Similarly, in the illustrated example, the bias power supply 40 used during the normal image forming operation is used as a voltage applying means for applying a voltage to the developing sleeve 17 for checking the life of the developer. Yes, but it is also possible to use separate power supplies.

The voltage applied to the developer carrying member such as the developing sleeve at the time of the developing operation or at the time of checking the life of the developer may be a DC voltage, or may be an AC voltage or a superimposed voltage of AC and DC.

The operation comparison means 44, control reference data storage means 45, and control means 46 shown in FIG. 2 can be easily constituted by a microcomputer, for example.

[0042]

According to the first aspect of the invention, the life of the two-component developer can be accurately detected with a simple configuration.

According to the second aspect of the present invention, since the agent regulating member is used as the counter electrode, the structure can be simplified and the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional configuration diagram of an electronic copying machine having a developing device according to the present invention.

FIG. 2 is an explanatory view showing a developing device according to one embodiment of the present invention.

FIG. 3 is a flowchart corresponding to the block diagram shown in FIG. 2;

4 is a diagram showing an example of the relationship between the number of copies and the voltage ratio R _1.

[Explanation of symbols]

 21 Developing device 43 Induced voltage detecting means 44 Calculation comparing means 46 Control means D Developer

Claims (1)

(57) [Claims] 1. A two-component developer carried on a developer carrying member is transported to a developing area between the developer carrying member and a latent image carrier, and is formed on the latent image carrier by the developer. A developing device for visualizing the formed electrostatic latent image, a counter electrode arranged at a predetermined distance from an outer surface of the developer carrying member, and an electrostatic latent image on the latent image carrier. And the next electrostatic latent image
When the non-image portion between is passing through the developer carrying member,
Voltage applying means for applying a predetermined voltage V ₀ to said developer carrying member, the induced voltage to detect the voltages V ₁ induced in the counter electrode through the developer on the developer carrying member upon application of the voltage V ₀ Detecting means, the voltage V ₁ and the applied voltage V ₀
Is calculated, and the voltage ratio R ₁ and the reference voltage ratio R ₁ are calculated.
A developing device, comprising: an arithmetic comparing unit that compares ₀ with _0; and a control unit that determines the life of the developer when R ₁ ≦ R ₀ .