JPH0844187A - Method for detecting and controlling toner concentration and device therefor - Google Patents

Abstract

PURPOSE:To stably detect toner concentration with accuracy and reliability over a long period by installing an acoustic energy element in a developing part and detecting the toner concentration in developing by the acoustic output of a frequency peculiar to carrier, or toner. CONSTITUTION:The acoustic energy detecting element 16 is installed on the outer surface of a bristle cutting board 7 in a closely contact state in order to detect the toner concentration in developer in a case 3. And a mechanism 17 for detecting and controlling the toner concentration based on an electroacoustic output from the acoustic energy detecting element 16 is installed. The detecting and controlling mechanism 17 is constituted of a discriminating mechanism for taking out the acoustic output of the frequency peculiar to the carrier, or the toner from the electroacoustic output from the acoustic energy detecting element 16, a computing element for comparing the output from the discriminating mechanism with a reference value and outputting a control signal, and a control mechanism for controlling a toner supply motor based on the control signal from the computing element.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for acoustically detecting the toner concentration in a developer in an electrophotographic apparatus using a developer in which a carrier and toner are mixed, and a method and apparatus for controlling the concentration. Regarding

[0002]

2. Description of the Related Art Image formation in electrophotography is roughly classified into a system using a one-component developer and a system using a two-component developer. Although the conditions can be set easily and the tolerance of the conditions is large, the toner is consumed as the image formation progresses, and the toner density decreases.Therefore, the toner density is detected and the toner is replenished accordingly, and the toner density is set to a predetermined value. It is necessary to maintain the level.

Conventionally, the following various methods have been proposed for detecting and controlling the toner concentration in a two-component developer.

(A) Method for detecting change in physical property value of developer: (1) Permeability ... Detecting change in inductance of coil,
After converting this into a frequency change, it is extracted as a voltage change. (2) Fluidity: A method of detecting a change in magnetic permeability due to a change in fluidity due to a change in toner concentration and extracting the change as a voltage (JP-A-58-55952). A method of detecting a staying state of the developer scraped off from the magnetic roll by a piezoelectric element (Japanese Patent Laid-Open No. 184970/1983). (3) Volume ... A method of detecting a change in toner concentration as a change in developer volume (Japanese Patent Publication No. 57-22182). (4) Color tone: A method in which a white carrier is used and the amount of toner attached to the carrier is detected by an optical detection means (photosensor) (JP-A-58-55954). (5) Electric conductivity: A method of detecting the toner concentration by measuring the electric resistance of the developer by utilizing the difference in electric resistance between the toner and the carrier. (6) Pressure: A method of detecting the toner concentration using a piezoelectric vibrator (Japanese Patent Laid-Open No. 58-158668).

(B) Method for detecting toner adhesion amount: (1) On the photosensitive member ... A patch having a constant density is provided on a part of the original plate, and a toner image of this patch is formed on a part of the photosensitive drum. A method of detecting the toner image density with an optical sensor (Japanese Patent Laid-Open No. 54-143144). (2) Conductive probe: a method in which a conductive probe is provided in the flow path of the developer, toner is attached to the surface by applying a bias voltage, and photoelectrically detected (Japanese Patent Laid-Open No. 58-5595).
3 gazette). (3) Transfer paper: An optical method that detects the density of toner transferred to the transfer paper.

(C) Other methods: A method of supplying a predetermined amount of toner for a constant developing operation or for each number of copies.

[0007]

However, all of these conventional methods have the following drawbacks. A-1 When the developer is used for a long time, the developer deteriorates and its magnetic permeability changes. It becomes difficult to control the toner stably for a long time. A-2 (i) The developer deteriorates after a long time of use and its magnetic permeability changes. It becomes difficult to control the toner stably for a long time. A new mechanism is needed to guide the developer to the sensor section. Complex and expensive (ii) Susceptible to vibration. A new mechanism is needed to guide the developer to the sensor section. Complex and costly A-3 easily affected by vibration. A new mechanism is needed to guide the developer to the sensor section. The detection accuracy is poor because it is complicated, costly, and changes in volume are small. Although the unit price is low due to the mechanical method, since contact points are used, there is a risk of malfunction due to intrusion of toner. A-4 It is difficult to obtain accuracy because the amount of color change is small. Even if a white carrier is used, the combination with the toner is limited and it is not versatile. A-5 Since the S / N ratio of the electric conductivity of the developer is small, it is difficult to detect with high accuracy. A-6 It is unstable because it also detects changes in the physical properties of the developer due to changes in the environment (changes in temperature and humidity). As with volume change, the accuracy is poor. B-1 Since the developer density is indirectly measured, the toner density becomes unstable immediately when the standard density pattern changes over time or due to stains. Further, when the surface potential of the photoconductor changes with temperature and humidity, the standard density on the photoconductor changes. Therefore, it becomes unstable. B-2 The mechanism is complicated, the cost is high, and the toner concentration becomes unstable due to the contamination of the sensor unit. B-3 The density detection feedback is slow. Although the C structure is relatively simple, the amount of toner actually used is unknown, and the toner concentration varies easily because it depends on the document concentration.

Therefore, an object of the present invention is to provide a method and an apparatus capable of solving the above-mentioned drawbacks in the conventional toner concentration detection, and performing a highly accurate and reliable detection of the toner concentration over a long period of time. There is.

Another object of the present invention is to provide a toner concentration detecting and controlling apparatus which is free from the influence of malfunction and contamination by toner and which is compact and capable of always detecting and controlling with stable accuracy.

[0010]

According to the present invention, an acoustic energy detecting element is provided in a developing portion of an electrophotographic apparatus in which a toner and a carrier are mixed to use an acoustic energy of a frequency peculiar to the carrier or the toner. A toner concentration detecting method is provided, which is characterized in that the toner concentration in the developer is detected by the output.

In general, it is effective to set the relationship (calibration curve) between the carrier or toner concentration and the output in advance continuously or stepwise, and detect the toner concentration based on this set value.

According to the present invention, there is further provided an electrophotographic apparatus having a developing section having a stirring roller for stirring the toner and the carrier, a developing roller for applying the toner to the photosensitive member, and a replenishing mechanism for replenishing the toner, An acoustic energy detecting element provided in close contact with a wall or member of the developing section, a discrimination mechanism for selectively extracting an acoustic output of a carrier or a frequency peculiar to toner among signals from the detecting element, a carrier or There is provided a toner concentration detection control device including a comparator that compares a toner acoustic output with a reference value and outputs a control signal, and a control mechanism that operates a toner replenishment mechanism by the control signal.

[0013]

[Function] Acoustic E is a phenomenon in which the energy released by deformation and destruction of a solid propagates as an acoustic pulse.
Called mission (AE), acoustic emission. Since the AE signal is a weak ultrasonic wave of usually several KHz to several MHz, humans cannot directly hear it. Since AE is a method of directly and in real time observing the energy emitted by the defects themselves of the material, the process of plastic deformation and fracture can be dynamically observed. Although applied in various fields, the present invention is applied to toner concentration detection.

That is, even when the carrier particles or toner particles of the two-component electrophotographic developer rub or collide with the wall surface of the developing device or the developing member, an AE signal having a frequency peculiar to the carrier particles or toner particles is generated. I found out that

According to the present invention, the acoustic energy detecting element is thus provided in the developing section of the electrophotographic apparatus in which the toner and the carrier are mixed, so that the acoustic output of the frequency peculiar to the carrier or the toner can be obtained. It is possible to take out an acoustic output of a frequency peculiar to the toner, and thereby, it is possible to detect the toner concentration in the developer with high accuracy and in a stable and reliable manner.

1 to 4 of the accompanying drawings show an AE signal from an AE sensor when an AE sensor is attached to a scissors plate of a developing unit which contains a two-component developer composed of toner and carrier and the developing unit is operated. FIG. 1 shows the relationship between the frequency and the AE count when frequency analysis is performed on the (pulse signal). FIG. 1 shows toner concentration 0%, FIG. 2 shows toner concentration 1%, FIG. 3 shows toner concentration 3%, and FIG. The results for the toner concentration of 5% are shown.

In FIGS. 1 to 4, it can be seen that the peak at 150.3 kHz is the acoustic output of the carrier-specific frequency, which output decreases with increasing toner concentration.

That is, the magnitude of the carrier signal of the above specific frequency is closely related to the toner concentration in the two-component developer. FIG. 5 shows a result of plotting the toner concentration and the AE power value (db) at a frequency of 150.3 kHz when the toner concentration in the two-component developer is changed. According to this result, the output of the signal also decreases as the toner concentration increases, and there is a 1: 1 correspondence between the toner concentration and the magnitude of the acoustic output peculiar to the toner, and a negative proportional relationship. (Inverse proportional relationship) is established, and it is clear that the toner concentration can be obtained by extracting this acoustic output.

In the present invention, it is possible to detect only the above carrier signal and obtain the toner concentration from the output thereof and the calibration curve shown in FIG. In this case, the toner replenishment mechanism is operated when the acoustic output of the carrier is higher than the set upper limit value, and the toner replenishment mechanism is stopped when the acoustic output of the carrier is lower than the set lower limit value.

Although the detection of the carrier signal has high sensitivity and is excellent in accuracy and reproducibility, it is possible for those skilled in the art to detect the AE signal peculiar to the toner and directly determine the toner concentration from the acoustic output. Will understand. In the latter case, the toner replenishment mechanism is activated when the acoustic output of toner is lower than the set lower limit value, and the toner replenishment mechanism is stopped when the acoustic output of toner is higher than the set upper limit value.

INDUSTRIAL APPLICABILITY The present invention can be widely applied to an electrophotographic apparatus having a developing section having a stirring roller for stirring toner and carrier, a developing roller for applying toner to a photosensitive member, and a replenishing mechanism for replenishing toner. In addition, an acoustic energy detecting element for extracting AE as an electric signal is provided in close contact with the container wall or member of the developing section, and the acoustic energy of the frequency peculiar to the carrier or toner is included in the signal from this detecting element. A discriminating mechanism is provided for selectively taking out the output, or further for selectively taking out the acoustic output of the frequency peculiar to the carrier or toner in the signal from the detection element.
The acoustic output of the carrier from the discrimination mechanism is set as a reference value (Fig. 5).
If it is higher than the reference value, the toner replenishing mechanism can be operated by this control signal to maintain the toner concentration in the developing unit at the set level.

In the toner concentration detecting method of the present invention, since the acoustic output of the frequency peculiar to the carrier or the toner is detected, there is no influence of disturbance by the developing device, environmental change, and temporal change, and it is highly accurate. The toner density can be detected reliably, the response is quick, the detection operation can be remarkably speeded up, and the toner density can be quickly controlled. Further, since it is only necessary to attach the acoustic energy detecting element to the container wall or the member of the developing section, the detecting mechanism can be made compact, and the detecting mechanism can be placed outside the container, and the toner can be contaminated. In addition, there is an advantage that it does not have any adverse effect on development.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 6 shows a main part of a developing section of an electrophotographic apparatus to which the toner density detecting and controlling method of the present invention is applied. The developing section 1 is provided so as to come into contact with or come close to the photoconductor drum 2. On the upstream side of the developing section of the photoconductor drum 2, a main charging mechanism A for charging the photoconductor to a constant charge and a charging photoconductor are provided. Image exposure mechanism B that irradiates with a light image
However, on the downstream side of the developing unit, a transfer mechanism C that transfers the toner image on the surface of the photoconductor to the paper, a separation mechanism (not shown) that separates the paper on which the toner is transferred from the photoconductor, A cleaning mechanism (not shown) for removing the residual toner, a charge removing mechanism (not shown) for removing the residual charges on the surface of the photoconductor, and the like are arranged.

The developing section 1 includes a case 3 for containing a developer.
A developing roller (magnetic brush roller) 5 that faces the opening 4 facing the drum 2 and develops the latent image on the photosensitive drum 2 in the developing state; and agitating that agitates the developer in the case 3. The roller 6, the spike cutting member 7 that regulates the layer thickness of the developer 9 that is adhered and formed on the surface of the developing roller 6, the guide plate 8 that regulates the flow of the developer, and the developing toner 10 in the case 3. And a toner replenishing tank 12 having a toner replenishing roller 11 for replenishing.

The developing roller 5 is composed of a cylindrical developing sleeve 13 made of a non-magnetic material, and a magnet 14 provided inside the sleeve 13 and having a plurality of magnetic poles around it.

Thus, the two-component developer 9 in the case 3
Forms a magnetic brush of developer on the surface of the magnetic brush roller 5 after being sufficiently stirred and mixed by the stirring roller 6.
Toothed image 15 is developed by developing the electrostatic latent image on the surface of the photosensitive drum 2 by the roller 6, which is cut and aligned to have a fixed length by the brushing member 7 and conveyed so as to contact the surface of the photosensitive drum 2.
To form.

In the present invention, in order to detect the toner concentration of the developer in the case 3, the acoustic energy detecting element 16 is provided in close contact with the outer surface of the spike cutting plate 7. The position where the acoustic energy detecting element 16 is provided is not particularly limited, but it is preferable to provide the acoustic energy detecting element 16 on the ear cutting plate 7 in terms of sensitivity and accuracy.
It can also be provided on the outer surface of the case 3 close to the stirring roller. When the detecting element 16 is provided on the ear cutting plate 7, it is recognized that the detected acoustic signal is based on the friction of the carrier particles. However, in the case where it is close to the stirring roller, the acoustic signal due to the collision of the carrier particles is generated. In some cases, the characteristic output is detected, and in that case, the characteristic frequency is naturally different from that in the former case. In short, the detection frequency should be set so that the maximum acoustic output can be obtained.

The acoustic energy detecting element 16 has sensitivity to AE having a frequency peculiar to the carrier or toner, generally 100 to 400 kHz, and particularly 140.
A piezoelectric element having a sensitivity to a frequency (ultrasonic vibration) of 180 kHz to 180 kHz is used, and a preferable piezoelectric element is a perovskite type piezoelectric element, in particular, a lead zirconate titanate-based piezoelectric element. AE
It is available under the trade name of -901. The piezoelectric element may be provided with a preamplifier that amplifies an electric signal from the piezoelectric element, either integrally or separately.

The acoustic energy detecting element 16 may be fixed to the member 7 of the developing portion or the vessel wall (case) 3 as long as the ultrasonic vibration is effectively transmitted from the vessel wall to the acoustic energy detecting element. Generally, adhesion is preferred. Although it is desirable to bond them through silicone grease, a double-sided adhesive tape or an epoxy resin-based or isocyanate-based adhesive can also be used for the bonding.

A mechanism 17 is provided for detecting and controlling the toner concentration based on the electric acoustic output from the acoustic energy detecting element 16. As shown in the diagram of FIG. 7, the detection control mechanism 17 includes the acoustic energy detecting element 1
Discrimination mechanism 18 for taking out an acoustic output of a frequency peculiar to the carrier or toner from the electrical acoustic output from 6
And a calculator 19 for outputting a control signal by comparing the output from the discriminating mechanism with a reference value, and a control mechanism 21 for controlling the toner supply motor 20 based on the control signal from the calculator.
It consists of and. In the specific example shown in FIG. 7, an amplifier 22 for amplifying the electrical acoustic output from the acoustic energy detecting element 16 to a desired level is provided between the acoustic energy detecting element 16 and the discrimination mechanism 18. Further, an integrating circuit 23 that integrates the output from the discriminating mechanism 18, that is, the amplitude is provided between the discriminating mechanism 18 and the computing unit 19.

The amplification degree by the preamplifier or further the amplifier may be any as long as the concentration can be detected accurately.
Generally, 10 to 80 dB, especially about 20 to 40 dB is suitable. It is preferable to use an operational amplifier with a low distortion to obtain a constant amplification degree.

In order to extract the acoustic output of the frequency peculiar to the toner or the carrier from the output from the acoustic energy detecting element amplified if necessary, the discrimination mechanism 15 is a frequency analysis device for integrating the output value of the specific frequency. Of course, it is desirable to use a filter, especially a bandpass filter whose center frequency is at the carrier or toner specific frequency, because of the simplicity of the device. For example, a bandpass filter for a carrier is preferably 40 to 200 kHz, particularly 140 to 160 kHz, although it varies depending on the material of the carrier, the member of the developing section or the case. On the other hand, the bandpass filter for toner is generally 100 to 200 kHz, and particularly 170 to 190 kHz, although it depends on the material of the toner.
The ones are suitable. If the electric signal that has passed through the bandpass filter is attenuated, it can of course be amplified.

As the calculator 19, a comparator is generally used, and compares the toner density detection value with the toner density set value to generate a control signal. Generally, the toner density setting value, there is a set lower limit value (C _l) and set the upper limit value (C _u), the toner density detection value (C _x) is set lower limit value (C _l) less than or equal to the toner replenishment signal Occurs, and when the value exceeds the set upper limit (C _u ), a toner replenishment stop signal is generated. Based on these signals, the control mechanism 18 controls ON / OFF of the toner replenishment motor 17. In practice, the setting lower limit value ( _Cl ) is set slightly higher than the actual allowable toner concentration lower limit value, while the setting upper limit value ( _Cu ) is set slightly lower than the actual toner concentration allowable upper limit value. It is preferable in that the width of variation of is reduced.

When a frequency analyzer is used as the discriminator 18, the output of a specific frequency can be directly input to the arithmetic unit, but when a bandpass filter is used as the discriminator, the bandpass filter is used. The output of can be supplied to a half-wave rectification circuit or a full-wave rectification circuit to be a DC component, or can be supplied to an integration circuit to be integrated at regular time intervals and supplied as a pulse to a calculator.

The present invention is useful for the toner concentration of a two-component developer comprising a combination of an arbitrary toner and a carrier and its control. It is preferable that there is a difference in composition and physical properties between the toner and the carrier.

The carrier has an average particle size of 40 to 400 μm and a density ρ c of 3.0 to 6.0 g / c.
m3 Particularly, those having 4.8 to 5.0 g / cm ³ are preferable, and magnetic carriers known per se such as iron trioxide, ferrite, and iron powder are preferably used. The carrier used is
It may be an uncoated carrier or a resin-coated carrier coated with a resin known per se, for example, a silicone resin, an acrylic resin, an epoxy resin, a fluororesin or the like.

The toner used in the present invention is any toner known per se, which has a sensible property, a coloring property and a fixing property, and a coloring agent and a charge control agent in the fixing resin medium or a toner which is known per se. It is a mixture of ingredients. The particle diameter of this toner is generally in the range of 5 to 30 μm, and its density ρt is 1.00 to 1.40 g / c.
m ^3, is particularly preferred 1.10 to that of 1.20 g / cm ^3.

As the fixing resin medium, either a thermoplastic resin or a thermosetting resin in the form of an uncured or precondensate is used. For example, a vinyl aromatic resin such as polystyrene, an acrylic resin, a polyvinyl acetal resin, Examples thereof include polyester resins, epoxy resins, phenol resins, petroleum resins, polyolefin resins and the like, and among these, styrene resins, acrylic resins or styrene-acrylic copolymer resins are preferably used.

As the colorant to be contained in the resin, for example, the following inorganic or organic pigments and dyes may be used alone or in combination of two or more, but are not limited thereto. Carbon black such as furnace black and channel black; iron black such as ferrosoferric oxide; titanium dioxide such as rutile type or anatase type; phthalocyanine blue; phthalocyanine green; cadmium yellow; molybdenum orange; pyrazolone red; fast violet B etc.

As the charge control agent, any charge control agent known per se, for example, an oil-soluble dye such as nigrosine base (CI50415), oil black (CI20150), spirone black, or the 1: 1 type or 2: Type 1 metal complex salt dye, naphthenic acid metal salt, fatty acid, soap, resin acid soap and the like are used.

Further, the particle shape may be an amorphous one produced by a melt-kneading / pulverization method, or a spherical one produced by a dispersion or suspension polymerization method.

The toner weight concentration in the developer is generally in the range of 1 to 5%, preferably 3 to 4%.

[0043]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to the following examples.

Example 1 An acoustic energy detecting element (AE-901S manufactured by NF Circuit Design Block Co., Ltd.) was attached to a cutting board of a developing section of a DC-2556 type copying machine manufactured by Sanda Kogyo Co., Ltd. with silicone grease. An output terminal of this acoustic energy detecting element was connected to an AE analyzer (AS-709 manufactured by NUF Circuit Design Block Co., Ltd.) via a preamplifier.

Two-component type developers having toner concentrations of 0%, 1%, 3% and 5% were filled in the developing section, and the developing section was operated with the photosensitive drum separated from the developing roller under the following conditions. The acoustic output was measured. Measurement conditions: High-pass filter (HPF) THRU Low-pass filter (LPF) THRU Amplifier gain 40 dB Sensor resonance point 140 kHz Sampling frequency 4 MHz

Frequency analysis graphs when 64 samplings are averaged are shown in FIGS. 1 shows a toner concentration of 0%, FIG. 2 shows a toner concentration of 1%, FIG. 3 shows a toner concentration of 3%, and FIG. 4 shows a toner concentration of 5%.

According to FIGS. 1 to 4, of the acoustic output from the acoustic energy detecting element, the peak around 150.3 kHz is peculiar to the carrier, and the height of the peak changed depending on the toner concentration.

FIG. 5 is a plot of the relationship between the peak height (power value, dB) at 150.3 kHz and the toner density. It can be seen that there is an almost inverse proportional relationship between them. confirmed.

[0049]

According to the toner concentration detecting method of the present invention, since the acoustic output of the frequency peculiar to the carrier or the toner is detected, there is no influence of disturbance by the developing device, environmental change, and aging, and the high output. The toner density can be detected with high accuracy and reliability, the response is quick, the detection operation can be remarkably speeded up, and the toner density can be quickly controlled. Further, since it is only necessary to attach the acoustic energy detecting element to the member of the developing unit or the container wall, the detecting mechanism can be made compact, and since the detecting mechanism is outside the container, it is not contaminated by toner.
Further, there is an advantage that it does not have any adverse effect on the development.

[Brief description of drawings]

FIG. 1 is a frequency analysis curve of an AE signal (pulse signal) from an acoustic energy detecting element for a two-component developer having a toner concentration of 0%.

FIG. 2 is a frequency analysis curve of an AE signal (pulse signal) from an acoustic energy detecting element for a two-component developer having a toner concentration of 1%.

FIG. 3 is a frequency analysis curve of an AE signal (pulse signal) from an acoustic energy detecting element for a two-component developer having a toner concentration of 3%.

FIG. 4 is a frequency analysis curve of an AE signal (pulse signal) from an acoustic energy detecting element for a two-component developer having a toner concentration of 5%.

FIG. 5 is a graph showing a result of plotting the toner concentration and the AE power value (db) at a frequency of 150.3 KHz when the toner concentration in the two-component developer is changed.

FIG. 6 is a side view showing a main part of a developing unit of an electrophotographic apparatus to which a toner density detecting / controlling method of the present invention is applied.

FIG. 7 is a diagram showing a mechanism for detecting and controlling toner concentration based on electrical acoustic output from an acoustic energy detecting element.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Development part 2 Photosensitive drum 3 Case for accommodating developer 4 Opening part 5 Development roller 6 Stirring roller 7 Ear cutting member 8 Guide plate 9 Developer 10 Toner 11 Toner supply roller 12 Toner supply tank 13 Cylindrical development sleeve 14 Magnet 15 Toner image 16 Acoustic energy detecting element 18 Discrimination mechanism 19 Computing device 20 Toner supply motor 21 Control mechanism 22 Amplifier 23 Integrating circuit

[Procedure amendment]

[Submission date] August 30, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction content]

That is, the magnitude of the carrier signal of the above specific frequency is closely related to the toner concentration in the two-component developer. FIG. 5 shows a result of plotting the toner concentration and the AE power value (db) at a frequency of 150.3 kHz when the toner concentration in the two-component developer is changed. According to this result, when the toner concentration is larger output of the signal is decreased, the toner density and calibration
There is a 1: 1 correspondence with the magnitude of the acoustic output peculiar to the rear , and a negative proportional relationship (inverse proportional relationship) is established. By extracting this acoustic output, the toner concentration is obtained. It is clear that you can.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0020

[Correction method] Delete

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0028

[Correction method] Change

[Correction content]

The acoustic energy detecting element 16 has sensitivity to AE having a frequency peculiar to the carrier or toner, generally 100 to 400 kHz, and particularly 140.
A piezoelectric element having a sensitivity to a frequency (ultrasonic vibration) of 180 kHz to 180 kHz is used, and a preferable piezoelectric element is a perovskite type piezoelectric element, in particular, a lead zirconate titanate-based piezoelectric element. "N
It is available under the trade name of "FAE900S-WB" . The piezoelectric element may be provided with a preamplifier that amplifies an electric signal from the piezoelectric element, either integrally or separately.

[Procedure amendment 4]

[Document name to be amended] Statement

[Name of item to be corrected] 0032

[Correction method] Change

[Correction content]

In order to extract the acoustic output of the frequency peculiar to the toner or the carrier from the output from the acoustic energy detecting element amplified if necessary, the discrimination mechanism 15 is a frequency analysis device for integrating the output value of the specific frequency. Of course, it is desirable to use a filter, especially a bandpass filter whose center frequency is at the carrier or toner specific frequency, because of the simplicity of the device. For example, a bandpass filter for a carrier is generally 40 to 200 kHz, particularly 140 to 160 kHz, although it varies depending on the material of the carrier, the member of the developing section or the case.
Appropriate. If the electric signal that has passed through the bandpass filter is attenuated, it can of course be amplified.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0044

[Correction method] Change

[Correction content]

Example 1 An acoustic energy detecting element ( NFAE900S-WB manufactured by NF Circuit Design Block Co., Ltd.) was attached to a cutting board of a developing section of a DC-2556 type copying machine manufactured by Mita Kogyo Co., Ltd. with silicone grease. The output terminal of this acoustic energy detecting element is connected to the AE analysis device (AS-709 manufactured by NF Circuit Design Block Co., Ltd.) via a preamplifier.
Connected to.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koji Honda 1-22 Takumazo, Chuo-ku, Osaka Mita Engineering Co., Ltd.

Claims (5)

[Claims] 1. A toner concentration in a developer is detected by arranging an acoustic energy detecting element in a developing portion of an electrophotographic apparatus which uses a mixture of toner and a carrier and acoustically outputting a frequency peculiar to the carrier or the toner. A method for detecting toner density, comprising: 2. The relationship (calibration curve) between the toner concentration in the developer and the output is set in advance continuously or stepwise,
The detection method according to claim 1, wherein the toner density is detected based on the set value. 3. A toner concentration in a developer is detected by providing an acoustic energy detecting element in a developing portion of an electrophotographic apparatus that uses a mixture of toner and a carrier and acoustically outputting a frequency peculiar to the carrier or the toner. Then, the toner concentration control method is characterized in that the toner is supplied into the developer when the toner concentration falls below a set lower limit value, and the supply is stopped when the toner reaches the set upper limit value. 4. An electrophotographic apparatus comprising a developing roller having a stirring roller for stirring toner and carrier, a developing roller for applying toner to a photosensitive member, and a replenishing mechanism for replenishing toner, and a wall of the developing section. Alternatively, an acoustic energy detection element provided in close contact with a member, a discrimination mechanism for selectively extracting an acoustic output of a frequency peculiar to the carrier or toner among signals from the detection element, and an acoustic output of the carrier or toner Is compared with a reference value to output a control signal, and a toner concentration detection control device comprising a control mechanism for operating the toner replenishing mechanism in response to the control signal. 5. The acoustic energy detecting element is a detecting element having sensitivity to a carrier-specific frequency of 100 to 400 kHz, and activates the toner replenishing mechanism when the acoustic output of the carrier exceeds a set upper limit value. 5. The toner concentration detection control device according to claim 4, wherein the toner replenishing mechanism is stopped when the acoustic output of the carrier is lower than the set lower limit value.