JP2986872B2 - Developer life detector - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developer life detecting device in an image forming apparatus using an electrophotographic process.

[Conventional technology]

In a dry developing apparatus using a two-component developer composed of a toner and a carrier, the developer deteriorates with time due to consumption of toner due to execution of an image forming process many times and other reasons. If the image forming process is continued with the deterioration left unchecked, the image quality deteriorates or the unit such as each photoconductor and the developing device is adversely affected. Therefore, it is necessary to detect the life of the developer as soon as possible.

Therefore, various techniques for detecting the life of the developer have been conventionally proposed.

For example, Japanese Unexamined Utility Model Publication No. 63-14258 discloses a current measuring means for measuring a flowing current flowing from a photoconductor to a developing roller via a developer, and a method for measuring the flowing current when the measured value of the flowing current becomes a predetermined value or less. There is disclosed a technology for detecting the life of a developer by providing a developer life determining unit that determines the life of the developer and outputs a developer replacement signal.

[Problems to be solved by the invention]

However, in the above-mentioned conventional technology, the current flowing from the charging charger and the transfer / separation charger to the photoconductor fluctuates the current flowing into the developing roller through the developer layer, and it is difficult to accurately detect the current.
In addition, since the current value itself is very weak, there is a disadvantage that the detection current is easily buried in noise.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a developer life detecting device capable of solving the above-mentioned drawbacks of the related art and accurately detecting the life of the developer with a simple configuration.

[Means for solving the problem]

The object is to provide a photoconductor for carrying an electrostatic latent image, a magnetic brush carrier having a built-in magnetic field generating means, and an outer periphery of the magnetic brush carrier for regulating supply of a developer supplied to the photoconductor. A conductive developer regulating member disposed at a slight gap; and a voltage applying means for applying a predetermined voltage to the magnetic brush carrier and the developer regulating member. A current value flowing between the magnetic brush carrier and the developer regulating member through the attracted developer layer is detected by a detecting unit, and the detected value is compared with predetermined reference data by a comparing unit. In the developer life detecting device of the developing device that performs dry development to determine the deterioration of the developer based on the detection by the detecting unit,
This is achieved by performing the process between non-image portions where toner does not move from the magnetic brush carrier to the photoconductor.

Further, in the above, it is achieved by performing the comparison in the comparison unit with the reference resistance value in the reference data, and the resistance value obtained by the voltage from the voltage application unit and the current detected by the detection unit. You.

[Action]

Measure the current flowing through the developer layer sucked on the magnetic brush carrier between the magnetic brush carrier and the developer regulating member, compare this current value with preset reference data,
When judging whether or not the developer has reached the life due to the deterioration based on the comparison result, the detection by the detection unit is performed between the non-image portions where the toner does not move from the magnetic brush carrier to the photoconductor, so that the image portion is used. The developer does not move from the magnetic brush carrier to the photoconductor. Therefore, the current value does not fluctuate, and accurate current detection becomes possible.

As described above, according to the present invention, an accurate current value can be detected. Therefore, a resistance value can be obtained from the current value and the voltage from the voltage applying unit, and deterioration of the developer can be determined based on the resistance value. .

〔Example〕

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a control conceptual diagram of a developer life detecting device according to one embodiment of the present invention.

As shown in the figure, a photosensitive drum 1 as a latent image carrier
Are driven to rotate in the direction of arrow A, that is, clockwise by a drive mechanism (not shown). The photosensitive drum 1 is made of an organic photosensitive member (OPC), and the polarity of the electrostatic latent image formed on the photosensitive drum 1 is negative (-). Therefore, the developing toner described later is charged to positive (+) with the opposite polarity.

In the drawing, reference numeral 2 denotes a developing tank having an opening at a portion facing the photosensitive drum 1, and a front portion inside the developing tank 2 has
A developing roller 3 as a magnetic brush carrier is arranged. Inside the developing roller 3, a developing magnet roller configured by alternately arranging a plurality of different magnetic poles (not shown) is provided at a fixed distance from the inner surface side of the developing roller 3. A magnetic brush 4 containing a magnetic carrier and toner is formed on the surface of the developing roller 3 by the magnetic force. The magnetic brush 4 is moved in the direction of arrow B, that is, counterclockwise by rotating at least one of the developing roller 3 and the developing magnet roller.

As a carrier constituting the magnetic brush 4, a resin-coated carrier having an average particle diameter of 100 μm is used.

A lower portion of the rear portion in the developing tank 2 serves as a developer accommodating portion for accommodating a two-component developer composed of toner and carrier, and a stirring roller 5 is provided in the developer accommodating portion. The toner and the carrier are agitated to generate good frictional charge on the toner, and the developer can be transported to the developing roller 3. The developing roller 3 is a non-magnetic cylindrical member made of aluminum or the like, and is disposed in the vicinity of the photosensitive drum 1 (a gap with the photosensitive drum 1 is 0.75 mm).

Further, the developing roller 3 and the photosensitive drum 1 include:
A developing bias voltage of the same polarity is applied by a bias power supply 12 as voltage applying means. The magnetic brush 4 on the developing roller 3 contacts the photosensitive drum 1 on which the electrostatic latent image has been formed while moving, and applies toner to the electrostatic latent image to form a visible image. .

In this embodiment, the developing roller 3 having an outer diameter of 30 mm is used, and a developing magnet roller having a surface magnetic force of about 800 gauss is used as the developing magnet roller.

The developing bias is applied to prevent background contamination and adjust image density. In this embodiment, the latent image potential is set to −800 V, and the background potential is set to −40 V.
The developing bias voltage is set to -200V. Note that the final developing bias value is determined according to the original density or the user's desire.

A doctor blade 6 that regulates the thickness of the developer magnetic brush 4 and constitutes a counter electrode is disposed above the developing roller 3. Above the stirring roller 5, there is provided a separator 7 for returning the developer regulated by the doctor blade 6 to the rear of the developing tank 2.

The toner in the toner hopper 8 is sprinkled on the toner replenishing roller 10 by the rotation of the toner replenishing bar 9, and is supplied to the developer container through the slitter 11 by the rotation of the toner replenishing roller 10.

 Next, the control operation of the present invention will be described.

A DC voltage (−200 V in this embodiment) from a bias power supply 12 is applied to the developing roller 3, and a current I flowing through the developer layer to the doctor blade 6 is detected by a detecting unit 13 as detecting means.
To detect. Then, the obtained current value I is compared with reference current value data stored in advance in the control reference data storage unit 14 by a comparison unit 15 as a comparison unit. Alternatively, reference resistance data stored in advance and Ohm's law V =
The resistance value R obtained from IR is compared.

Then, when the resistance of the developer layer exceeds a predetermined value, the control unit 16 as control means determines that the developer life has elapsed, and the control unit 16 displays on the display unit 17 as display means that the agent life has expired. A signal is sent to indicate that the developer needs to be replaced.

FIG. 2 is a flow chart of the above control operation. As described above, the voltage V is applied to the developing roller 3 (S1), and the current flowing between the developing roller 3 and the doctor blade 6 (doctor current) is shown in FIG.
I is detected (S2), and the resistance R _{D of the} developer layer (= V / I)
Is determined (S3), and if _RD is greater than or equal to the control reference resistance value _R0 (Y in S4), this is indicated on the display unit (S5).

FIG. 3 is a characteristic diagram showing a change in a current flowing from the developing roller 3 to the doctor blade 6 through the developer layer. As can be seen from the figure, the doctor current value decreases as the number of developers increases. From the point of intersection P between the threshold value and the doctor current value shown in the drawing, it is determined that the developer has deteriorated thereafter.

The above-described doctor current detection is performed between the non-image portions of the photoconductor 1. That is, in the image portion of the photoconductor 1, the toner moves from the developing roller 3 to the photoconductor drum 1, and accordingly, a current is generated. As a result, the current value fluctuates due to the surface potential of the latent image on the photosensitive drum 1 and the like, and it becomes difficult to accurately detect the doctor current.

In this embodiment, the DC developing bias is used. However, by detecting the DC component of the current even with the AC developing bias, it is possible to determine the deterioration of the developer as in the case of using the DC developing bias. .

Next, an example of a copier employing the above-described developing device will be described in a fourth embodiment.
The function will be described based on the drawings.

First, the optical system will be described.
An image is formed on the photosensitive drum 1 through the mirror 33, the second mirror 34, the third mirror 35, the lens 36, the fourth mirror 37, the fifth mirror 38, the sixth mirror 39, and the dustproof glass 40 in order.
The dust-proof glass 40 is provided so that suspended matter does not enter the optical system. This device has a maximum of 200
From 1% to a minimum of 50%, a zoom magnification function of 1% is provided. Further, an automatic density adjustment system is provided which detects an image having a beautiful background by detecting the background density of the original 32 using an optical fiber and correcting the developing bias based on the detected density. .

Around the photosensitive drum 1, a charging unit 41, an eraser 42,
Developing device 43, static elimination unit 44, transfer separation unit 45, cleaning unit
47 and so on are arranged. In the charging section 41, a high voltage is applied to the charge wire in the dark to perform corona discharge, and negative charges are uniformly charged on the photosensitive drum 1. At this time, the potential of the photosensitive drum 1 is set to -800V. Between the charge wire and the photosensitive drum 1,
A grid 48 is provided to control the potential uniformly and uniformly. The eraser 42 includes a charged photosensitive drum 1
It is intended to erase unnecessary charges by irradiating light to facilitate cleaning, and is composed of a long LED, and performs side erase and tip erase. As the developing device 43, the one described in FIG. 1 is employed. The charge removing section 44 has a pre-transfer charge removing LED 44a and a charge removing lamp 44b. Both are turned on at the same time as the start of the main motor, and are irradiated with light for erasing residual charges on the photosensitive drum 1 while being diffused by the filter. The transfer / separation unit 45 transfers the toner onto the transfer paper 49 by the transfer charger 45a while keeping the transfer paper 49, which is the transfer material sent from the registration roller 21, in close contact with the photosensitive drum 1, and the transfer paper 49 on the separation charger 45b. Photoreceptor drum 1
The transfer paper 49 is separated from the paper. In the unlikely event that separation is not possible, separation is forcibly performed by the separation claw 50. The transfer paper 49 after separation is conveyed by the conveyance belt 51 to the fixing unit 52 side. The cleaning section 47 includes a cleaning brush 47a and a cleaning blade 47b for scraping off residual toner on the photosensitive drum 1. The cleaning blade 47b is supported by a single central point so that the contact pressures on the left and right are made uniform. The cleaning brush 47a is rotated in the same direction as the photosensitive drum 1. The cleaning brush 47a has a function of removing foreign matter such as a piece of paper that is difficult to remove with the cleaning blade 47b. The toner scraped off by the cleaning brush 47a and the cleaning blade 47b is collected by a toner collecting section.

The fixing unit 52 applies a certain temperature and pressure to the transfer paper 49 sent from the transport unit to fuse the toner onto the transfer paper 49. In the fixing unit 52, the temperature of the heater 52b is controlled while the temperature is detected by the thermistor 52a.

In the above-described apparatus, the developing roller 3 is used as the magnetic brush carrier, but a belt-shaped magnetic brush carrier may be employed.

〔The invention's effect〕

As described above, according to the first aspect of the present invention,
When the detection unit detects the value of the current flowing between the magnetic brush carrier and the developer regulating member through the developer sucked onto the magnetic brush carrier, the toner does not move from the magnetic brush carrier to the photoconductor. Since the operation is performed between the image portions, the current value is stable, and the current can be accurately detected.

According to the second aspect of the present invention, it is possible to determine the resistance value from the current value and the voltage from the voltage applying unit, and determine the deterioration of the developer based on the resistance value.

[Brief description of the drawings]

FIG. 1 is a control conceptual diagram of a developer life detecting device according to an embodiment of the present invention, FIG. 2 is a control flowchart of the same, FIG. 3 is a characteristic diagram showing a relationship between the number of copies and a doctor current value, FIG. 4 is a configuration diagram showing an example of a copying machine to which the present invention is applied. DESCRIPTION OF SYMBOLS 1 ... Photoreceptor drum, 3 ... Developing roller, 6 ... Doctor blade, 12 ... Bias power supply, 13 ... Detector, 14 ...
... control reference data storage unit, 15 ... comparison unit, 16 ... control unit, 17 ... display unit.

Claims (2)

(57) [Claims] 1. A photosensitive member carrying an electrostatic latent image, a magnetic brush carrying member having a built-in magnetic field generating means, and an outer periphery of the magnetic brush carrying member for regulating supply of a developer supplied to the photosensitive member. A conductive developer regulating member disposed at a slight distance from the magnetic brush carrier, and voltage applying means for applying a predetermined voltage to the magnetic brush carrier and the developer regulating member. A current value flowing between the magnetic brush carrier and the developer regulating member through the developer layer sucked into the developer regulating member is detected by a detecting means, and the detected value is compared with predetermined reference data by a comparing means. In the developer life detecting device of the developing device that performs dry development that determines the deterioration of the developer based on the result, the detection by the detecting unit detects the non-image portion where the toner does not move from the magnetic brush carrier to the photoconductor. Between And a developer life detecting device. 2. The comparison device according to claim 1, wherein the comparison is performed using a reference resistance value in the reference data, a resistance value obtained from a voltage from the voltage application unit and a current detected by the detection unit. The developer life detecting device according to claim 1, wherein