JPH05197269A - Developing device - Google Patents

Abstract

PURPOSE:To stably measure the resistance of developer in a state where an excessive current does not flow in a measurement circuit which measures the resistance of developer by interposing a current restricting means for restricting the potential difference of counter electrodes in the measurement circuit. CONSTITUTION:A magnet roller 2 and a doctor 3 for regulating the napping of the developer on the roller 2 are provided in a developing tank 1, and a power source circuit 4 impressing bias voltage on the roller 2 is provided. In a state where the roller 2 and the doctor 3 are set as the counter electrodes, the measurement circuit 5 measuring the resistance of the developer according to the current flowing between the roller 2 and the doctor 3 through the developer is provided, and the current restricting means 6 for restricting the potential difference of the counter electrodes is interposed in the circuit 5. When the bias voltage is impressed on the roller 2, the current flows in the doctor 3 through the developer. The current passing through the developer has a value in proportion to the bias voltage impressed on the roller 2 by the means 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device for visualizing a latent image formed on a photoreceptor or the like with a developer, and to a method for measuring the resistance of the developer.

[0002]

2. Description of the Related Art In a developing device using a two-component developer composed of toner and carrier, the toner concentration of the developer has a great influence on the image quality. That is, if the toner density is low,
The image density decreases, and if the toner density is high, fogging to the non-image area is likely to occur.

Therefore, in order to control the toner concentration of the developer, conventionally, the permeability of the developer or the volume change is measured, and the toner replenishment and the like are controlled based on the measured permeability.

[0004]

However, the developer is
Deterioration may occur with repeated use, or the resistance value may change due to changes in environmental conditions, resulting in poor image quality even though the toner concentration is controlled to be constant.

Therefore, the change in the resistance value of the developer is measured by detecting the bias current when the bias voltage is applied to the magnet roller of the developing device.

However, when trying to obtain a stable measurement current when measuring the resistance of the developer, there is a linear relationship between the bias voltage and the bias current, and it is difficult to perform reproducible measurement. It was Because the carrier of the developer and the counter electrode come into direct contact with each other, sometimes an excessive current flows, which destroys the measurement circuit, or the measurement result is abnormal, resulting in stable and reproducible measurement. I couldn't do it.

In view of the above, it is an object of the present invention to provide a developing device capable of stably measuring the resistance of a developer.

[0008]

As shown in FIG. 1, the means for solving the problems according to the first aspect of the present invention regulates the magnet roller 2 in the developing tank 1 and the spike of the developer on the magnet roller 2. A doctor circuit 3 for applying a bias voltage to the magnet roller 2, and a current flowing between the magnet roller 2 and the doctor 3 as a counter electrode via a developer. A measuring circuit 5 for measuring the resistance of the developer is provided, and the current limiting means 6 for limiting the potential difference of the counter electrode is interposed in the measuring circuit 5.

According to a second aspect of the present invention, as shown in FIG. 6, a developing tank 1 is internally provided with a magnet roller 2 and a doctor 3 for regulating the rising of the developer on the magnet roller 2. A power supply circuit 24 for applying a bias voltage to the magnet roller 2 and the magnet roller 2 and the doctor 3 as counter electrodes, and the resistance of the developer is measured by a current flowing through the developer between them. Circuit 20
An opening / closing unit 21 for opening / closing the measurement circuit 20 and a control unit 22 for driving and controlling the opening / closing unit 21 and the power supply circuit 24. The control unit 22 is provided with the opening / closing unit 21 during non-measurement.
Is provided so as to shut off the measuring circuit 20 and a measuring means for closing the opening / closing part 21 at the time of measurement and applying a voltage lower than the bias voltage at the time of image formation.

As shown in FIG. 7, the means for solving the problem according to the third aspect is such that the developing tank 1 is provided with a magnet roller 2 and at least two magnet rollers.
A power supply circuit 32, which internally includes agitating rollers 30 and 31, and applies a bias voltage to the magnet roller 2.
A voltage supply circuit 33 that applies a voltage to the two stirring rollers 30 and 31, a measuring unit that measures the resistance of the developer by the current flowing through the voltage supply circuit 33, and the magnet roller 2 or the magnetic roller 2 depending on the measurement result. A control unit 37 for controlling the bias voltage of the photoconductor is provided.

[0011]

In the means for solving the problems according to the first aspect, when a bias voltage is applied to the magnet roller 2, a current flows through the doctor 3 through the developer. This developer passing current has a value proportional to the bias voltage applied to the magnet roller 2 by the current limiting means 6. Therefore, the change in the resistance of the developer can be detected from the measurement result.

According to a second aspect of the present invention, the opening / closing section 2 is used during image formation.
By opening 1 to shut off the measuring circuit 20, an excessive current due to an increase in developer passing current does not flow to the measuring circuit 21. When measuring the resistance of the developer, the opening / closing unit 21 is closed and the power supply circuit 24 applies a voltage lower than the bias voltage at the time of image formation to the magnet roller 2. Then, an electric current flows from the doctor 3 through the developer to the measuring circuit 20.
And the resistance of the developer can be detected.

According to claim 3, the stirring rollers 30, 31
When a voltage is applied to the developer, a current flows through the developer, and the resistance of the developer is detected by measuring the current. Based on this measurement result, when the resistance of the developer increases due to the deterioration of the developer, the bias voltage to the magnet roller 2 is decreased or the surface potential of the photoconductor is increased to increase the image density. Prevent the decline.

[0014]

【Example】

(First Embodiment) FIG. 1 is a block diagram of a developing device showing a first embodiment of the present invention, in which a developing tank 1 and a magnet roller 2 are provided.
And a doctor 3 for regulating the rising of the developer on the magnet roller 2, the power supply circuit 4 for applying a bias voltage to the magnet roller 2, the magnet roller 2 and the doctor 3. The counter electrode is provided with a measuring circuit 5 for measuring the resistance of the developer by a current flowing through the developer, and the current limiting means 6 for limiting the potential difference of the counter electrode is provided in the measuring circuit 5. It is equipped.

The magnet roller 2 is disposed so as to face the photoconductor 7, and is composed of a cylindrical sleeve made of a conductive non-magnetic metal and a plurality of magnets fixedly arranged inside the sleeve. Is rotatable by a motor.

The doctor 3 is made of a conductive non-magnetic material, for example, an aluminum extrusion molded product, SUS304 stainless steel, and is developed above the magnet roller 2 with a distance of 0.5 mm from the magnet roller 2. It is fixed to tank 1.

A toner hopper 8 is mounted on the developing tank 1, and a toner replenishing roller 10 is rotatably arranged at a toner replenishing port 9.

Below the toner supply port 9, a stirring roller 11 for stirring the toner and performing stable triboelectric charging is arranged.
A conveying roller 12 that conveys the developer to the magnet roller 2 is arranged between the stirring roller 11 and the magnet roller 2, and the rollers 11 and 12 are rotatably supported by the developing tank 1. In the figure, 13 is a toner concentration sensor.

The power supply circuit 4 is equipped with a power supply for applying a bias voltage of about 200 V to the sleeve of the magnet roller 2 in order to prevent toner from adhering to the non-image portion of the photosensitive member 7, and constant voltage control is performed. Has been done.

The measuring circuit 5 is a circuit in which a power source circuit 4 connected to the magnet roller 2 and a doctor 3 are connected, and a resistor 14 for detecting a developer passing current and a resistor 6 as a current limiting means are interposed. The detected value is detected by the amplifier 1
It is amplified by 5 and sent to the analog port of the CPU 16.

In the developing device configured as described above,
By applying a bias voltage to the magnet roller 2 and detecting the current flowing from the doctor 3 to the measuring circuit 5 through the developer, the resistance of the developer is measured.
Is.

As can be seen from the figure, when the applied voltage is 100 V or more, the reproducibility is lost and the current voltage is out of the linear relationship. The developer used here was a carrier obtained by coating a ferrite with a silicone resin and having an average particle diameter of 80 μm, and a toner made of styrene acrylic resin and having an average particle diameter of 10.5 μm, which was mixed by stirring so as to be 4% by weight. It is a two-component developer.

Bring this developing device to the environmental test room,
FIG. 3 shows the results of resistance measurement under various environmental conditions. From this figure, it can be seen that the resistance change of the developer due to environmental conditions can be measured.

Next, the toner concentration of this developer is set to 2% and 6
FIG. 4 shows the result of adjusting the resistance to% and performing resistance measurement in the same manner. It is clear that the resistance value is different due to the difference in toner concentration, and more stable measurement results can be obtained only when the applied voltage is 100 V or less, as in the previous example.

By utilizing these characteristics and the measurement results, it becomes possible to detect the characteristic change of the developer due to the environmental change and correct the image change. Alternatively, it is possible to increase or decrease toner supply so that the toner density is controlled to a constant value.

Next, when the distance between the magnet roller 2 and the doctor 3 is set to 0.7 mm and 0.4 mm, the result of resistance measurement of the developer having a toner concentration of 4% is shown in FIG. From this figure, when the interval is 0.7 mm, the applied voltage for which a stable resistance measurement result is obtained can be slightly increased and can be measured up to about 140 V. On the other hand, when the interval is 0.4 mm, it is stable unless it is 80 V or less. You can see that you cannot measure. It is considered that this is because the pressure of the developer conveyed between the magnet roller 2 and the doctor 3 changed and the actual resistance value changed.

As described above, the voltage to be applied in measuring the resistance of the developer depends on the positional relationship of the counter electrodes, the magnetic force arrangement pattern of the magnet roller 2, the physical properties of the developer (carrier particle size,
It can be appropriately determined according to (saturation magnetization) and the like, but stable resistance measurement can be performed by setting it to about 100 V or less. As a result, it is possible to accurately detect changes in resistance caused by repeated use of the developer and changes in resistance due to changes in environmental conditions, and perform appropriate process control according to this information to suppress changes in image quality and always stabilize the image. It is possible to provide the copied image.

Moreover, according to this method, it is possible to use the existing magnet roller 2 and the doctor 3 without providing a new electrode, and the power source can also use the existing developing bias voltage. Is possible. However,
When the existing developing bias voltage is used, it is desirable that the current limiting resistor 6 has a resistance value of 10 ⁶ to 10 ⁷ Ω so that the potential difference between the counter electrodes is about 100V.

Further, since the developer on the sleeve of the magnet roller 2 is kept to have a uniform thickness by the doctor, there is an effect that a constant measurement can be always performed.

(Second Embodiment) FIG. 6 is a block diagram of a developing device showing a second embodiment of the present invention. In the developing device of the present embodiment, the magnet roller 2 and the doctor 3 are used as opposed electrodes, and a measuring circuit 20 for measuring the resistance of the developer by a current flowing between the measuring roller 20 and the measuring circuit 20 is opened and closed. There are provided an opening / closing part 21 for controlling the opening / closing part 21 and a control part 22 for driving and controlling the opening / closing part 21 and the power supply circuit 24.

The measuring circuit 20 has one end connected to the doctor 3 and the other end grounded through a passing current detecting resistor 23. The intermediate point is connected to the analog port of the CPU 22.

The opening / closing section 21 is composed of an opening / closing switch and is interposed in the measuring circuit 20. In the power supply circuit 24, the output voltage of the power supply is variable according to the output signal from the CPU 22.

The control unit 22 is composed of a CPU, and includes a protection means for opening the opening / closing unit 21 to cut off the measuring circuit 20 when the measurement is not performed, and a bias voltage for closing the opening / closing unit 21 for the measurement and bias voltage at the time of image formation. It is provided with measuring means for applying a low voltage to the magnet roller 2.

The other structure is the same as that of the first embodiment.

In the case of the present embodiment, when the resistance of the developer is measured, the open / close switch 21 is output by the output signal from the CPU 22.
And close the magnet roller 2 at low voltage 100
The power supply circuit 24 is changed so that the bias voltage of V is applied.

At the time of image formation, the open / close switch 21 is opened to shut off the measuring circuit 20, so that the magnet roller 2 is turned on.
A bias voltage of 00V is applied.

As a result, the same effect as that of the first embodiment is obtained, and the increase of the developer passing current (short-circuit state) due to the high electric field, the damage of the measuring circuit, and the inhibition of the electric field formation for development are prevented. Therefore, the measurement circuit can be protected.

(Third Embodiment) FIG. 7 is a block diagram of a developing device showing a third embodiment of the present invention. The developing device of this embodiment includes a developing tank 1, a magnet roller 2, and a conveying roller 1.
Two and two stirring rollers 30 and 31 are rotatably installed.

The magnet roller 2 is the same as that shown in the first embodiment, and a power supply circuit 32 capable of varying the bias voltage to the magnet roller 2 is connected.

The stirring rollers 30 and 31 are arranged below the toner supply port 9 and efficiently stir the toner supplied from the toner hopper to perform stable triboelectric charging.

Between the stirring rollers 30 and 31,
A voltage supply circuit 33 for applying a voltage for measuring the resistance of the developer is connected. A power supply 34 for applying a measurement voltage and a resistor 35 for detecting a developer passing current are interposed in the voltage supply circuit 33, and an amplifier circuit 36 for amplifying the detected value is connected to the voltage supply circuit 33. The measuring unit is composed of the circuit 36. The signal amplified by this is the CPU 37.
Is output to the analog port of.

The control unit 37 composed of this CPU has a function of controlling the bias voltage to the magnet roller 2 according to the measurement result of the resistance of the developer.

For example, when the resistance increases due to the deterioration of the developer, the function of decreasing the bias voltage to the magnet roller 2 and the fact that the image density does not decrease but the background fog increases, that is, This is a function of increasing the bias voltage to the magnet roller 2 when the resistance of the developer increases due to toner charging failure due to spent toner that adheres to the carrier during long-term use.

FIG. 8 shows the result of measuring the resistance of the developer by applying a voltage to the stirring rollers 30 and 31 using such a developing device. As can be seen, the stirring roller 3
It is understood that stable resistance measurement can be performed even when the applied voltage to 0 and 31 is about 5 to 24V. The developer used in this case was a carrier having an average particle size of 80 μm coated with a silicone resin on a ferrite and a toner having an average particle size of 10.5 μm made of styrene acrylic resin in a weight ratio of 4%.
It is a two-component developer that is agitated and mixed so as to have a ratio of%.

FIG. 9 shows a change in the developer resistance value along with the image density when the life test was carried out by mounting the developing device in a usual electrophotographic copying machine. From the figure, it can be seen that the developer resistance increases as the number of copies increases, and the image density decreases accordingly. It is presumed that this is because as the carrier coating material in the developer is peeled off, the triboelectric charge of the toner is increased and the image density is reduced.

Therefore, FIG. 11 shows the result of carrying out the life test while detecting the developer resistance value and controlling the developing bias voltage in a constant relationship as shown in FIG. In this case, the decrease in image density can be suppressed by decreasing the developing bias voltage as the developer deteriorates.

Further, instead of controlling the developing bias voltage, the same effect can be obtained by controlling the charging condition of the main charger, for example, the grid bias voltage in the scorotron charger. As shown in FIG. 12, by changing the grid bias voltage value with respect to the developer resistance value, as in the case of the development bias voltage,
FIG. 13 shows the result of a life test performed while controlling the grid bias voltage in this proportional relationship. This can be compensated for by deterioration of the developer by increasing the surface potential of the photoconductor, and the image density can be stabilized.

Next, a carrier having an average particle size of 80 μm coated with a silicone resin on a ferrite as a developer and an average particle size of 8.0 μm made of styrene acrylic resin.
A two-component developer obtained by stirring and mixing the above toner in an amount of 6% by weight was subjected to a life test, and the results shown in FIG. 14 were obtained.

In this case, the image density did not decrease, but the background fogging tended to increase remarkably. At the same time, the developer resistance value tends to decrease. It is presumed that this is because the spent toner adheres to the carrier in the developer, hinders normal triboelectric charging of the toner, and so-called reversely charged toner and weakly charged toner increase. This is a characteristic deterioration of the developer when the toner particle size is small.

On the other hand, when a life test was conducted while controlling the developing bias voltage in the relationship shown in FIG. 15, it was possible to suppress the increase in fog of the background over the life, and to obtain a stable copy without background stains. I was able to obtain image quality. This compensates for an increase in background stain due to developer deterioration by increasing the developing bias voltage.

As described above, the image change occurring in the life test depends on the deterioration factor of the employed developer and the environmental condition, and when the image density is changed or the background is contaminated, the transfer is performed. Although there are cases where efficiency and toner consumption increase, it is possible to use the change in the resistance value of the developer as process control information for preventing changes in the image by knowing each change factor correctly. is there.

Moreover, according to this method, the stirring roller 3
Since a stable developer current signal can be taken out even with an applied voltage extremely low with respect to 0 and 31, the secondary side voltage used in the copying machine can be used.

Moreover, it is not necessary to provide a new electrode, and the existing stirring roller can be used. The stirring roller is for efficiently stirring and mixing the developer and the toner to be newly supplied to give a stable triboelectric charge, and since the contact area with the developer is large and is rotated at high speed,
It is suitable as an electrode for measuring the resistance of the developer. Moreover, since the agitating roller exists just below the toner to be replenished, it is possible to measure the change in the toner concentration of the developer due to the toner replenishment without sending the response time, and it is possible to perform a quick process control. ..

The present invention is not limited to the above embodiment, and it goes without saying that many modifications and changes can be made to the above embodiment within the scope of the present invention.

[0055]

As is apparent from the above description, according to the first aspect of the present invention, the resistance of the developer is reduced by the electric current flowing between the magnet roller and the doctor as opposed electrodes through the developer. By providing a measuring circuit for measurement and interposing a current limiting means for limiting the potential difference of the counter electrode in the measuring circuit, stable resistance measurement of the developer can be performed without an excessive current flowing in the measuring circuit. ..

Moreover, it is not necessary to provide a new electrode for measuring the resistance of the developer, and the existing magnet roller and doctor can be used. Further, the power source uses the existing developing bias voltage. Because it is possible
It can be performed inexpensively without increasing the number of parts.

Further, since the developer on the sleeve of the magnet roller is kept in a uniform thickness by the doctor, it is possible to always obtain a constant measurement result.

According to a second aspect of the present invention, in the measuring circuit for measuring the resistance of the developer by the electric current flowing between the magnet roller and the doctor as the counter electrodes,
By providing an opening / closing part that opens / closes this circuit, the opening / closing part is opened during non-measurement to shut off the measurement circuit, the opening / closing part is closed during measurement, and a voltage lower than the bias voltage at the time of image formation is applied. It is possible to prevent damage to the measurement circuit due to an increase in the developer passing current, and it is possible to protect the measurement circuit.

According to the third aspect, the resistance of the developer is measured by the voltage supply circuit for applying a voltage to the two stirring rollers and the current flowing in the voltage supply circuit, and the magnet roller or the magnet roller is measured according to the measurement result. By controlling the bias voltage of the photoconductor, when the density of the image changes or the background is contaminated, it is possible to use the change in the resistance value of the developer as the process control information for preventing the image change. In addition, it is possible to prevent a decrease in image density throughout the life of the developer, suppress an increase in fog in the background, and always obtain a stable copy image quality.

Moreover, since it is not necessary to provide a new electrode for measuring the resistance of the developer and the existing stirring roller is used, the developer and the toner to be newly supplied are stirred and mixed, and Since resistance measurement can be performed, it is suitable as an electrode. Moreover, since a stirring roller exists just below the toner to be replenished, it is possible to immediately respond to changes in the characteristics of the developer due to toner replenishment, and rapid process control. It can be performed.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a developing device showing a first embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a resistance measurement value of a developer and a voltage applied to a magnet roller.

FIG. 3 is a diagram showing changes in characteristics of a developer due to environmental changes.

FIG. 4 is a diagram showing changes in characteristics of a developer due to changes in toner concentration.

FIG. 5 is a diagram showing a change in the characteristics of the developer due to a change in the distance between the magnet roller and the doctor.

FIG. 6 is a configuration diagram of a developing device showing a second embodiment of the present invention.

FIG. 7 is a configuration diagram of a developing device showing a third embodiment of the present invention.

FIG. 8 is a diagram showing a relationship between a resistance measurement value of a developer and a voltage applied to a stirring roller.

FIG. 9 is a diagram showing changes in developer resistance and image density due to a life test.

FIG. 10 is a graph showing the relationship between the bias voltage applied to the magnet roller and the resistance change of the developer.

FIG. 11 is a diagram showing a change in image density due to a life test when the voltage applied to the magnet roller is controlled.

FIG. 12 is a graph showing the relationship between the change in the resistance of the developer and the grid voltage for charging the photoconductor.

FIG. 13 is a diagram showing changes in image density due to a life test when the grid voltage to the photoconductor is controlled.

FIG. 14 is a diagram showing changes in developer resistance and fogging density by a life test.

FIG. 15 is a diagram showing the relationship between the bias voltage applied to the magnet roller and the resistance change of the developer.

[Explanation of symbols]

 1 Developing Tank 2 Magneto Roller 3 Doctor 4 Power Supply Circuit 5 Measuring Circuit 6 Current Limiting Means 21 Opening / Closing Unit 22,37 Control Unit 30,31 Stirring Roller 33 Voltage Supply Circuit

Claims (3)

[Claims] 1. A developing tank is internally provided with a magnet roller and a doctor for controlling the rising of the developer on the magnet roller, and a power supply circuit for applying a bias voltage to the magnet roller is provided. In the developing device, the magnet roller and the doctor are used as counter electrodes, and a measuring circuit for measuring the resistance of the developer by the current flowing through the developer is provided, and the measuring circuit is provided with a potential difference between the counter electrodes. A developing device, wherein a current limiting means for limiting the temperature is interposed. 2. The developing tank is internally provided with a magnet roller and a doctor for controlling the rising of the developer on the magnet roller, and a power supply circuit for applying a bias voltage to the magnet roller is provided. In the developing device, using the magnet roller and the doctor as counter electrodes, a measuring circuit for measuring the resistance of the developer by a current flowing through the developer, an opening / closing unit for opening and closing the measuring circuit, A control unit for driving and controlling the opening / closing unit and the power supply circuit is provided, and the control unit opens the opening / closing unit during non-measurement and shuts off the measurement circuit, and closes the opening / closing unit during measurement.
Further, the developing device is provided with a measuring means for applying a voltage lower than a bias voltage at the time of image formation. 3. A developing device in which a developing roller is internally provided with a magnet roller and at least two stirring rollers, and a power supply circuit for applying a bias voltage to the magnet roller is provided, the two stirring rollers. A voltage supply circuit for applying a voltage to the voltage sensor, a measurement unit for measuring the resistance of the developer by the current flowing through the voltage supply circuit, and a control unit for controlling the bias voltage of the magnet roller or the photosensitive member according to the measurement result. And a developing device.