JPH04106572A - Developer life detector - Google Patents

Abstract

PURPOSE:To exactly detect the life of a developer by impressing a prescribed voltage between a magnetic brush carrying member and a counter electrode and detecting the current flowing between both through a developer layer. CONSTITUTION:The DC voltage from a bias power source 12 is impressed to a developing roller 3 and the current I flowing through the developer to a doctor blade 6 is detected by a detecting section 13 as a detecting means. The current I and the reference current value data previously stored by a control reference data memory section 14 are compared in a comparing section 15 as a comparing means. The end of the developer life is judged by a control section 16 which is a control means when the resistance by the developer layer exceeds the prescribed value. A signal is then transmitted from the control section 16 to a display section 17 which is a display means so as to display that the developer life ends. The need for the exchange of the developer is thereby announced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a developer life detection device in an image forming bag W using an electrophotographic process.

[Conventional technology]

In a dry type developing device that uses a two-component developer consisting of toner and carrier, the developer deteriorates over time due to toner consumption due to multiple executions of the image forming process and other reasons. If this deterioration is left unaddressed and the image forming process is continued, the image quality will deteriorate and units such as the photoreceptors and the developing device will be adversely affected, so it is necessary to detect the lifespan of the developer early.

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

For example, Japanese Patent Application Laid-Open No. 63-14258 discloses a current measuring means for measuring the inflow current flowing from the photoreceptor to the developing roller via the developer, and a current measuring means that measures the inflow current flowing from the photoconductor to the developing roller via the developer, and when the measured value of the inflow current becomes less than a predetermined value. A technique has been disclosed for detecting the lifespan of a developer by providing a developer lifespan determining means that determines the lifespan of the developer and outputs a developer replacement signal.

[Problem to be solved by the invention]

However, in the above-described conventional technology, the current flowing into the developing roller through the developer layer fluctuates due to the current flowing into the photoreceptor from the charging charger, transfer/separation charger, etc., making it difficult to accurately detect the current. Furthermore, since the current value itself is very weak, there is a drawback that the detected current is easily buried in noise.

SUMMARY OF THE INVENTION An object of the present invention is to provide a developer lifespan detection device that eliminates the drawbacks of the above-mentioned prior art and can accurately detect the lifespan of a developer with a simple configuration.

[Means to solve the problem]

The above purpose is to provide a developer life detecting device for a developing device that performs dry development using spike-shaped developer formed on a magnetic brush carrier having a built-in magnetic field generating means. a counter electrode arranged at a distance,
A voltage applying means for applying a predetermined voltage between the counter electrode and the magnetic brush carrier, and a current value flowing between the magnetic brush carrier and the counter electrode through a developer layer attracted onto the magnetic brush carrier. A detecting means for detecting, a comparing means for comparing preset reference data and actually detected current value data or resistance value data, and determining and controlling the deterioration of the developer based on the comparison result of the comparing means. This is achieved by including a control means that outputs a command, and a display means that displays the deterioration of the developer based on the output of the control means.

Moreover, in the above, by detecting the measurement data by the detection means in the non-image area, the counter electrode can further be constituted by a conductive peg restriction member.

[Effect]

As the number of copies is increased, toner is spent on the carrier, which increases the resistance of the developer. Therefore, the voltage applied between the magnetic brush carrier and the opposing electrode and the developer attracted onto the magnetic brush carrier between the two increase. The lifespan of the developer can be determined by determining the apparent resistance value of the developer layer, which is determined by Ohm's law from the current flowing through the layer. Alternatively, if the voltage is fixed, the life of the developer can be determined from the current value.

The present invention is based on this principle, and compares predetermined reference current value data with actual measured current value data or reference resistance value data, determines whether the developer has reached the end of its life due to deterioration, and displays this. do.

Note that accurate doctor current is detected by detecting measurement data in the non-image area.

Furthermore, the configuration is simplified by using the developer control member (doctor blade) as the counter electrode.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

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

As shown in the figure, a photosensitive drum 1 as a latent image carrier is rotationally driven in the direction of arrow A, that is, clockwise, by a drive mechanism (not shown). This photoreceptor drum 1 is made of an organic photoreceptor (○PC), and the polarity of the electrostatic latent image formed on the photoreceptor drum 1 is negative (-). Therefore, toner for development, which will be described later, is charged to a positive (+) polarity opposite to this.

In the figure, numeral 2 denotes a developing tank having an opening in a portion facing the photosensitive drum 1, and a developing roller 3 serving as a magnetic brush carrier is disposed at the front portion of the developing tank 2. Inside the developing roller 3, a developing magnet roller constituted by a plurality of different magnetic poles (not shown) arranged alternately is provided at a constant interval from the inner surface of the developing roller 3. A magnetic brush 4 containing magnetic carrier and toner is formed on the surface of the developing roller 3 by the magnetic force. This magnetic blank 4 is moved in the direction of arrow B, that is, counterclockwise, by rotation of at least one of the developing roller 3 and the developing magnet roller.

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

The rear lower part of the developing tank 2 is a developer storage section that stores a two-component developer consisting of toner and carrier, and an agitation roller 5 is disposed in this developer storage section. The toner and carrier are stirred to cause good frictional electrification on the toner, and the developer can be conveyed to the developing roller 3. The developing roller 3 is a non-magnetic cylindrical roller made of aluminum or the like, and is arranged near the photosensitive drum 1 (with a gap of 0.75 fl from the photosensitive drum 1).

Further, a developing bias voltage of the same polarity is applied to the developing roller 3 and the photosensitive drum 1 by a bias power supply 12 serving as a voltage applying means.

The magnetic blank 4 on the developing roller 3 comes into contact with the photoreceptor tram l on which the electrostatic latent image is formed while moving, and applies toner to the electrostatic latent image to form a developed image. .

In this embodiment, the developing roller 3 has an outer diameter of 30 gauss, and the developing magnet roller has a surface magnetic force of about 800 gauss.

Further, the developing bias is applied to prevent background smearing and adjust image density. In this embodiment, the latent image potential is set to 1800V, the background potential is set to 140V, and the developing bias voltage is set to 200V. Note that the final developing bias value is determined depending on the original density or the user's wishes.

A doctor blade 6 is arranged above the developing roller 3 to regulate the thickness of the developer magnetic brush 4 and to constitute a counter electrode. Further, a separator 7 is provided above the stirring roller 5 to return the developer regulated by the doctor blade 6 to the rear of the developer tank 2 .

The toner in the toner hopper 8 is sprinkled onto the toner replenishment roller 10 by the rotation of the toner replenishment bar 9, and the toner is sprinkled onto the slitter 11 by the rotation of the toner replenishment roller IO.
The developer is supplied to the developer storage section through the.

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

A DC voltage (-200V 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 detection unit 13 serving as a detection means. Then, the obtained current value I and reference current value data stored in advance in the control reference data storage section 14 are compared by a comparison section 15 serving as a comparison means.

Alternatively, the resistance value R obtained from Ohm's law V=IR is compared with pre-stored reference resistance value data.

When the resistance due to the developer layer exceeds a predetermined value, the control unit 16, which is a control means, determines that the developer life has reached its limit, and the control unit 16 instructs the display unit 17, which is a display means, to display that the developer life has come to an end. Sends a signal to notify that the developer needs to be replaced.

FIG. 2 is a flowchart of the above control operation, and as described above, the current flowing between the voltage V applied to the developing roller 3 (Sl) and the doctor blade 6 (doctor current)
(S2), resistance R8 (-V
/I) (S3), and if RD is greater than or equal to the control reference resistance value R8 (Y at 34), that fact is displayed on the display (S5).

FIG. 3 is a characteristic diagram showing changes in the current flowing from the developing roller 3 to the doctor blade 6 through the developer layer.

As seen in the figure, as the number of sheets of developer used increases, the doctor current value decreases. It is determined that the developer has deteriorated after the intersection point P between the threshold value and the doctor current value shown in the figure is the boundary.

It is desirable that the doctor current detection in this embodiment be performed between non-image areas. This is because, in the image area, since toner moves from the developing roller 3 to the photosensitive drum 1, a current is generated accordingly. This is because the current value fluctuates depending on the surface potential of the latent image on the photoreceptor, making it difficult to detect a positive FrM doctor current.

Although a DC developing bias was used in this example, an AC developing bias could also be used by detecting the DC component of the current.
It is possible to judge the deterioration of the developer in the same way as when using a DC developing bias.

Next, an example of a copying machine employing the above-described developing device will be functionally explained based on FIG.

First, to explain the optical system, light emitted from the halogen lamp 31 hits the document 32 on the contact glass 20,
The image passes through the first 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, and is formed on the photoreceptor drum I. Ru. The dustproof glass 40 is provided to prevent floating objects from entering the optical system. In addition, this device has a maximum of 200% and a minimum of 50%.
It is equipped with a zoom magnification function. Furthermore, an automatic density adjustment system is provided which detects the background density of the original 32 using an optical fiber and corrects the developing bias based on the detected background density, thereby making it possible to obtain an image with a clear background. .

Around the photoconductor tram 1, a charging section 41 and an eraser 42 are installed.
, a developing device 43, a static eliminating section 44, a transfer separation section 45, a cleaning section 47, and the like are arranged. In the charging section 41, a high voltage is applied to the charge wire in the dark to cause corona discharge, and the photoreceptor drum 1 is uniformly charged with negative charges. The potential of the photoreceptor drum at this time is set to -800V. A grid 48 is arranged between the charge wire and the photosensitive drum 1 in order to control the potential uniformly and constant. The eraser 42 is a long LED that illuminates the charged photoreceptor drum 1 to erase unnecessary charges and facilitate cleaning.
It consists of a site eraser and a tip eraser. As the developing device 43, the one described in FIG. 1 is adopted.

The static eliminator 44 includes a pre-transfer static eliminator LED 44a and a static eliminator lamp 44b. Both are turned on at the same time as the main motor is started, and light is emitted to erase residual charges on the photosensitive drum 1 while being diffused by a filter. The transfer separation unit 45 separates the transfer paper 49, which is the transfer material sent out from the registration roller 2I.
While bringing the toner into close contact with the photoreceptor drum 1, the transfer charger 45a transfers the toner onto the transfer paper 49, and the separation charger 45b transfers the toner from the photoreceptor drum 1 to the transfer paper 49.
9 is separated.

If separation is not possible, the separation claws 5o force the separation. The transfer paper 49 after separation is transferred to the conveyor belt 5
1 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 photoreceptor drum 1.

The cleaning blade 47b is configured to be supported at a center point so that the left and right contact pressures are equalized. The cleaning brush 47a is rotated in the same direction as the photosensitive drum 1. This cleaning brush 47a has a function of removing foreign matter such as pieces of paper that are difficult to remove with the cleaning blade 47b. The toner scraped off by the cleaning brush 47a and the cleaning blade 47b is collected in a toner collection section.

The fixing section 52 is connected to the transfer paper 49 sent from the conveyance section.
By applying constant temperature and pressure to the transfer paper 49, the toner is transferred to the transfer paper 49.
It is fused onto the top. Further, in this fixing section 52,
The temperature of the heater 52b is controlled while the thermistor 52a detects the temperature.

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

[Effects of the Invention] As described above, according to the invention described in claim 1, a predetermined voltage is applied between the magnetic brush carrier and the opposing electrode, and a current flowing between the two through the developer layer is detected. With this, it is possible to accurately detect the lifespan of the developer.

Furthermore, according to the second aspect of the invention, more accurate lifespan detection can be performed by detecting current in the non-image area.

Further, according to the third aspect of the invention, the developer regulating member that is originally provided in the developing device is also used as the counter electrode, thereby simplifying the device.

[Brief explanation of drawings]

FIG. 1 is a control conceptual diagram of a developer life detection device according to an embodiment of the present invention, FIG. 2 is a control flowchart, FIG. 3 is a characteristic diagram showing the relationship between the number of copies and doctor current value, and FIG. The figure is a configuration diagram showing an example of a copying machine to which the present invention is applied. 1... Photosensitive drum, 3... Developing roller, 6...
Doctor blade, 12...Bias power supply, 13...
・Detection unit, 14... Control reference data storage unit, 15...
- Comparison section, 16... Control section, 17... Display section. Agent Patent Attorney Junji Takeshi Department (1 other person) Figure 2'-Pe N-1-Less than $1

Claims (3)

[Claims] (1) In a developer life detection device for a developing device that performs dry development using spike-shaped developer formed on a magnetic brush carrier with a built-in magnetic field generating means, a slight gap is placed on the outer periphery of the magnetic brush carrier. a voltage applying means for applying a predetermined voltage between the counter electrode and the magnetic brush carrier, and a developer layer attracted onto the magnetic brush carrier to pass through the magnetic brush carrier. a detection means for detecting the current value flowing between the and the opposing electrodes, a comparison means for comparing preset reference data and at least one of the actually detected current value data or resistance value data, and a comparison of the comparison means. A developer life detection device comprising: a control means for determining developer deterioration based on the result and outputting a control command; and a display means for displaying developer deterioration based on the output of the control means. (2) The developer life detection device according to claim 1, wherein the detection means detects the measurement data in a non-image area. (3) The developer life detecting device according to claim 1, wherein the counter electrode is constituted by a conductive developer regulating member.