JP2003228228A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely prevent the occurrence of a trouble that no image is outputted in image forming processing by accurately detecting a state in which a developing device which is not filled with developer is attached to an image forming apparatus by using only an existing functional part and a detecting means or the like in the image forming apparatus. <P>SOLUTION: In the developing device 5 freely attachable/detachable to/from a printer 1, comparison is made for oscillation frequency outputted from a detection sensor 11 in accordance with toner concentration in the developer stored in a developing tank 52 before and after the stirring operation of the developer D by the rotation of a stirring blade 54 over a specified period after attaching the developing device 5, and it is discriminated that the developer is not stored in the attached developing device 5 when a difference between them is less than a specified value, so that warning is generated. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for forming an electrophotographic image, such as a copying machine, a printer or a facsimile apparatus, and more particularly, it is housed in a developing device which is detachably attached to the apparatus. The present invention relates to an image forming apparatus that forms an image using a two-component developer.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine or a printer for performing electrophotographic image formation, image light is radiated onto the surface of a photoconductor uniformly charged with a single polarity to cause static electricity due to photoconductive action. An electrostatic latent image is formed, and the electrostatic latent image is electrostatically attracted with a developer, and the visualized developer image is transferred to a recording medium such as paper. When a two-component developer including a non-magnetic toner (hereinafter simply referred to as toner) and a magnetic carrier (hereinafter simply referred to as carrier) is used as a developer that forms a visible image in such an image forming apparatus. There is. In this two-component developer, since only the toner is electrostatically adsorbed to the electrostatic latent image and consumed in the developing process for visualizing the electrostatic latent image, the toner concentration in the developer is formed on the recording medium. Affect the image density.

Therefore, in the conventional image forming apparatus using the two-component developer, the toner density in the developer is detected and the toner is replenished according to the decrease in the toner density in order to always obtain a constant image density. The toner concentration in the two-component developer is maintained within an appropriate range. As a method of detecting the toner concentration in the developer, there is a method of using the oscillation frequency change of the LC oscillation circuit.

That is, the apparent magnetic permeability of the developer, which is a mixture of a carrier that is a magnetic material and toner, changes depending on the toner concentration (carrier density). Therefore, when the detection coil is appropriately covered with a case, the inductance of the detection coil changes depending on the magnetic permeability of the atmosphere when the detection coil is brought close to the developer by a method such as indirectly or directly embedding it in the developer. . The oscillation frequency of the LC oscillator circuit is f = 1 /
Since it is given by (2π√ (LC)), it is possible to detect the change in toner density by measuring the frequency f. Various types of toner concentration detecting means for detecting the toner concentration using this LC oscillation circuit have been proposed.

For example, as shown in FIG. 1, the toner concentration detecting means 141 for detecting the toner concentration has a developing device 14 adjacent to a photosensitive drum 142 having a photosensitive layer formed on the surface thereof.
It is located within 0. The developing device 140, which supplies toner to the surface of the photosensitive drum 142 on which the electrostatic latent image is formed to visualize the electrostatic latent image into a toner image, includes a toner cartridge 143 in which unused toner is stored. , A developing tank 146 filled with a two-component developer composed of toner and a magnetic carrier. The developing tank 146 rotatably supports a developing roller 144 and an agitating roller 145 inside, and a toner concentration detecting means 141 is attached thereto. The toner stored in the toner cartridge 143 is replenished into the developing tank 146 as needed.

The developing roller 144 is disposed so as to be exposed from the developing tank 146 so that a part of its peripheral surface is in contact with the photosensitive drum 142. The toner concentration detecting means 141 has a detection surface 141a which is always in contact with the developer, and the developing roller 14
It is located far away from the No. 4. Since the toner concentration detecting means 141, which is a magnetic permeability sensor, is easily affected by the magnetic field, the toner concentration detecting means 141 is arranged at a position away from the developing roller 144, which is a magnet roller having a magnet housed therein. Detecting means 141
Makes it less susceptible to the magnetic field of the developing roller 144.

Generally, in an image forming apparatus using a two-component developer (hereinafter, simply referred to as a developer), the developer is agitated to charge the toner by friction, and the charged toner is placed on a photosensitive drum. A visible image is formed by electrostatically adhering to the formed electrostatic latent image. The toner concentration detecting means in such an image forming apparatus reflects a change in the inductance of the detection coil, that is, a change in the density of magnetic carriers (hereinafter, simply referred to as carriers) in the atmosphere. Therefore, as shown in FIG. 2, when the toner concentration is low (when the carrier density in the atmosphere is high), the inductance of the coil increases, so that the oscillation frequency of the toner concentration detecting means becomes low and when the toner concentration is high. Since the inductance of the coil decreases (when the carrier density in the atmosphere is low), the oscillation frequency of the toner concentration detecting means becomes high. That is, since the oscillation frequency of the toner concentration sensor reflects the carrier density with respect to the space, the air contained in the developer is also detected as toner.

[0008]

However, in the maintenance work for the apparatus such as the periodical developer replacement, the developing apparatus in which the developing tank is not filled with the developer is erroneously mounted in the image forming apparatus. When the initial setting process for toner concentration control is performed, the toner concentration detecting means detects a low magnetic permeability from the air present on the detection surface, and there is no developer in the developing tank. Nevertheless, from the low magnetic permeability, it is considered that the toner density is saturated by idling drive, and the oscillation frequency obtained at this time is adopted as the reference value for controlling the toner density. Then, the preparation for use is completed similarly to the case where the developing device filled with the developer is mounted, and the image forming apparatus shifts to the standby mode. However, there is a problem in that the toner cannot be supplied and the image is not output.

An object of the present invention is to provide an image forming apparatus with only existing functional parts, detecting means, etc. even when a developing apparatus in a state where the developer is not filled is attached to the image forming apparatus due to an operation error or the like. By using this, it is possible to accurately detect the state in which the developing device is not filled with the developer, and it is possible to reliably notify the operator of that fact and prevent the trouble that no image is output during the image forming process. An object is to provide an image forming apparatus.

[0010]

The present invention has the following structure as means for solving the above problems.

(1) A toner concentration detecting means for accommodating a developer consisting of a carrier and toner and detecting the concentration of toner in the developer by a frequency change of the oscillation circuit due to the inductance and capacitance of the toner concentration detecting coil is provided. In the image forming apparatus, the developing device is detachably attached, and the control device controls the toner density in the developer based on the oscillation frequency of the toner density detecting means.
When the developing device is mounted, the control means determines whether or not the developer is stored in the developing device based on the oscillation frequency of the toner concentration detecting means before and after the idling of the developing device. .

In this structure, when a new developing device is mounted, the toner concentration detecting means provided in the mounted developing device is based on the oscillation frequency difference between before and after the idling of the developing device, and the inside of the mounted developing device. The presence or absence of the developer is determined. Therefore, by using only the existing functional parts and the detecting means in the developing device and the image forming device, the developing device which does not store the developer by mistake when the image forming device is installed or the developer is replaced is used. The state of being attached to the device is accurately determined.

(2) Toner concentration detecting means for accommodating a developer consisting of a carrier and toner and for detecting the toner concentration in the developer by the frequency change of the oscillation circuit due to the inductance and capacitance of the toner concentration detecting coil is provided. In the image forming apparatus, the developing device is detachably attached, and the control device controls the toner density in the developer based on the oscillation frequency of the toner density detecting means.
When the developing device is mounted, the control means detects the oscillation frequency when the developing device is stationary, continues the idling operation of the developing device for a predetermined period, and detects the oscillation frequency when the developing device idles. Is sequentially executed, and it is determined whether or not the developer is stored in the developing device based on the oscillation frequency difference before and after the idling of the developing device.

In this structure, when a new developing device is mounted, the toner concentration detecting means provided in the mounted developing device is installed in the developing device mounted on the basis of the oscillation frequency difference before and after the idle rotation of the developing device. A process for determining the presence / absence of the two-component developer is executed. Therefore, by using only the existing functional parts and detection means in the developing device and the image forming apparatus, and only changing the processing contents of the control means, it is possible to make mistakes when installing the image forming apparatus or when replacing the two-component developer. It is possible to accurately determine the state in which the developing device that does not contain the developer is attached to the image forming apparatus. Further, the determination as to whether or not the developer is stored in the developing device is made based on the difference in the oscillation frequency of the toner concentration detecting means before the idling of the developing device is started and after the idling of the developing device is executed. Even if there is an error in the oscillation output characteristic, erroneous determination is suppressed.

(3) The control means determines that the developer is not stored in the developing device when the oscillation frequency difference before and after the idling of the developing device is less than a predetermined value, and when the difference is more than the predetermined value. It is characterized in that it is determined that the developer is stored in the developing device.

In this structure, whether the developer is stored in the attached developing device or not depending on whether or not the oscillation frequency difference of the toner concentration detecting means before and after the idling of the developing device is more than a predetermined value. Is determined. Therefore, even if there is an error in the oscillation output characteristics of the individual toner concentration detecting means, erroneous determination can be reliably suppressed.

(4) The control means detects the oscillation frequency immediately before the end of the idling operation of the developing device, which is continuously performed for a predetermined period, as the oscillation frequency of the toner concentration detecting means during idling of the developing device. And

In this structure, the determination as to whether or not the developer is stored in the mounted developing device is performed by the toner concentration detecting means before and immediately before the idling operation of the developing device is continued for a predetermined period. It is determined based on the difference in oscillation frequency. Therefore, as the oscillation frequency of the toner concentration detecting means after the idling operation of the developing device, the detection result for the developer after the flow state is stabilized by being sufficiently stirred by the idling operation for a predetermined period is used and mounted. The presence or absence of the developer in the developing device is accurately determined.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 3 is a sectional view showing a schematic configuration of a printer which is an image forming apparatus according to an embodiment of the present invention.
The printer 1 is connected to an external terminal device (not shown) and performs an electrophotographic image forming operation based on image data input from the terminal device. This printer 1
The exposure scanning unit 2 and the image forming unit 3 are roughly classified, and a control unit 4 that integrally controls these operations is provided. Control unit 4
Performs predetermined image processing on the input image data and supplies the image data to the exposure scanning unit 2.

The exposure scanning unit 2 includes a semiconductor laser 21, a non-scanning optical system 22, a polygon mirror 23, and a scanning optical system 24. In the exposure scanning unit 2, the semiconductor laser 21 is driven based on the image data supplied from the control unit 4,
A laser beam corresponding to the image data is emitted. The laser light emitted from the semiconductor laser 21 is collimated by a collimating lens included in the non-scanning optical system 22, and then reflected by a reflecting surface of a polygon mirror 23 rotating at a constant speed to be deflected into scanning light in the main scanning direction. To be done. The deflected laser light is changed from the constant angular velocity light to the constant velocity light in the main scanning direction by the f-θ lens included in the scanning optical system 24, and then the folding mirror included in the scanning optical system 24 changes the image forming unit 3. Is reflected toward the inside.

In the image forming section 3, a charger 32, a developing device 5, a transfer device 33, a cleaner 34 and a charge eliminator 35 are provided around the photosensitive drum 31 having a photoconductive layer formed on the surface thereof. Are arranged in this order along the rotation direction of arrow A. Photoreceptor drum 3 that rotates in the direction of arrow A
The surface of No. 1 is uniformly exposed to electric charges of a single polarity by the charger 32, and then exposed to laser light via the scanning optical system 24 of the exposure scanning unit 2. As a result, an electrostatic latent image is formed on the surface of the photoconductor drum 31 by the photoconductive action. Next, the surface of the photoconductor drum 31 receives the supply of the developer from the developing device 5 to visualize the electrostatic latent image, and carries the developer image.

In the image forming section 3, a paper feed roller 38, a registration roller 39, a conveyor belt are provided between the paper feed cassette 36 and the photoconductor drum 31 and the transfer unit 33 to reach the paper discharge tray 37. 40, fixing device 41 and half-paper roller 4
A paper transport path in which 2 is arranged is configured. The sheets fed one by one from the sheet feeding cassette 36 by the sheet feeding roller 38 prior to the rotation of the photosensitive drum 31 are stopped with the front end portion abutting on the registration rollers 39, and then the photosensitive drum 31 The registration roller 39, which starts rotating in synchronization with the rotation, guides the front end portion between the photosensitive drum 31 and the transfer unit 33 at a timing facing the front end portion of the electrostatic latent image carried by the photosensitive drum 31.

The transfer device 33 applies an electrostatic force to the paper located between the photoconductor drum 31 and the paper, and transfers the developer image carried on the surface of the photoconductor drum 31 to the surface of the paper. Photoreceptor drum 3 after transfer of the developer image
The surface of No. 1 is subjected to removal of paper powder and residual developer by the cleaner 34, and further to removal of residual charge by the static eliminator 35, and then charged again by the charger 32 to be repeatedly used for image forming processing. To be done.

On the other hand, the sheet on which the developer image has been transferred is guided to the fixing device 41 by the conveyor belt 40. The fixing device 41 heats and presses the paper between a pair of rollers including a heating roller and a pressure roller, melts the developer image transferred onto the paper, and firmly fixes the surface of the paper. The paper on which the image is formed by the developer in this manner is discharged onto the paper discharge tray 37 by the paper discharge roller 42.

In the printer 1, the exposure scanning unit 2
Is configured such that the upper surface of the image forming unit 3 can be freely opened and closed by using one side surface side as a hinge, and it is possible to easily perform a work for clearing a paper jam in the image forming unit 3, a work for replacing the developing device 5, and the like. ing.

FIG. 4 is a diagram showing the construction of the developing device mounted on the printer. In the developing tank 52 of the developing device 5, a magnet roller 53 and a stirring blade 54 are rotatably provided. The developer D including the carrier and the toner in the developing tank 52 is stirred by the stirring blade 54,
The carrier and the toner are electrostatically attracted to each other by frictional charging. The developer D, in which the carrier and the toner are electrostatically attracted to each other, is magnetically attracted to the surface of the magnet roller 53 having a permanent magnet housed therein, and the magnet roller 53.
When the toner image is conveyed in accordance with the counterclockwise rotation, the toner comes into contact with the electrostatic latent image on the photoconductor 31 rotating at a predetermined position, and the toner is attracted to the electrostatic latent image for development.

Therefore, the agitated developer D is always conveyed to a predetermined position (developing area) for development, but the toner T is not replenished from the toner cartridge by the rotation of the toner replenishing roller 56. The ratio of carriers in the developer D (carrier density) gradually increases.
On the resin wall surface of the developing tank 52, the detection sensor 11 which is the toner concentration detecting means of the present invention is attached.
The detection sensor 11 is provided with a coil 12.

Developing tank 5 to which the detection sensor 11 is attached
The agitated developer D is constantly in contact with the wall surface of 2,
When the ratio of carriers in the developer D (carrier density) increases, the rotation / stop of the toner replenishing roller 56 provided at the lower opening of the toner cartridge is controlled based on the detection signal of the detection sensor 11 that detects this state. Then, a required amount of toner is replenished into the developing tank 52 to maintain a constant toner concentration.

FIG. 5 is a circuit diagram showing the configuration of the detection sensor and control means. The detection sensor 11 is composed of the inductance L of the coil 12 and the capacitor C, and constitutes, for example, a part of the Kolwitz oscillation circuit 17.

When the ratio of carriers in the developer housed in the developing tank 52 increases, the inductance of the coil 12 increases, and the oscillation frequency f becomes the inductance of the coil L,
If the capacities of the capacitors 13 and 14 are C1 and C2, respectively, it can be calculated by the following equation.

Oscillation frequency: f = 1 / (2π√ (LC)) where C is the synthetic capacitor capacity, and C = C1 · C2
/ (C1 + C2).

Oscillation circuit 17 including the above detection sensor 11
The method of processing the signal output from the will be described below. First, as a method of converting into a DC signal by the phase locked loop type circuit, as is clear from the above equation, the oscillation frequency f is inversely proportional to the square root of the value of the inductance L of the coil 12 which changes depending on the ratio of carriers in the developer. And a phase locked loop (PLL) circuit 15
Outputs a DC signal proportional to the input oscillation frequency f. In the comparison circuit 16, when the signal voltage output from the PLL circuit 15 becomes equal to or lower than a predetermined constant value, it is assumed that the toner concentration in the developer has decreased, and the toner replenishment signal is output as a control signal.

Next, as a method of directly counting the oscillation frequency, the frequency of the oscillation circuit 17 is directly taken into the counter, the gate of the gate generation circuit is opened for a predetermined time via the control CPU, and within that period. Count the number of pulses taken. Then, the CPU compares the count value of the number of pulses with a preset reference count number (threshold value), and when the count difference exceeds a predetermined value, toner replenishment is performed.

The detection sensor 11 faces the coil 12 of the resonance circuit in the vicinity of the position where the developer flows in the developing tank 52. The amount of carriers (carrier density), which are magnetic particles flowing in the magnetic field generated by the coil 12, decreases as the toner concentration in the developer increases, while
The toner concentration increases as the toner concentration decreases, and the inductance L of the coil changes. In this method, in order to detect a change in magnetic permeability, that is, a change in inductance L with high sensitivity, a change in frequency of the oscillation circuit 17 (f = 1 / 2π√ (LC)).
, The frequency signal corresponding to the density output from the detection sensor 11 is shaped into a pulse signal, the frequency is detected by the number of occurrences of this pulse signal within a predetermined gate time, and the toner density is determined based on the frequency (pulse number). Is detected and the toner replenishment is controlled so that the toner density becomes constant.

In the above structure, the PLL circuit 15, the comparison circuit 16 and the oscillation circuit 17 are included in the control means of the present invention.

The control means of the present invention is specifically shown in FIG.
As shown in, the detection signal from the detection sensor 11 is input to the analog multiplexer 61 in the magnetic permeability detection circuit 6, and in this analog multiplexer 61, the output of the detection sensor 11 is buffered based on the signal from the CPU. To 62.

The output of the detection sensor 11 via the buffer transistor 62 is input to the comparator 71 in the toner replenishment control circuit 7, where it is shaped into a pulse signal. The pulse signal is output to the counter 72, and the gate of the counter 72 has a predetermined period (for example, 12 msec).
When released, the number of pulses within that period (gate period) is counted by the counter 72, and the frequency of the detection signal from the detection sensor 11 is counted by this count number.
That is, the toner density is detected.

The predetermined period in which the gate of the counter 72 is opened is controlled by the counter 74 to which the clock signal from the oscillator 73 is input. Comparator 7 above
1, counter 72, oscillator 73, counter 74 and CP
The toner supply control circuit 7 is constituted by U75. In actual density detection, counting the number of pulses in the gate period is repeated about 20 times, the peak value of the sampling data of 20 times is obtained, and the peak value is compared with the reference level obtained in the initial state of the developing device. The calculation of the toner density is repeated during the printing operation. Then, the toner replenishing operation is controlled so that the detected toner density approaches the reference level.

When the developing tank 52 of the developing device 5 mounted on the printer 1 is filled with the developer, the printer 1
A change in the flow state of the developer (change in carrier density) always occurs due to the idling drive in the initial setting processing (initialization of the developer) after being mounted on the coil, and the inductance L of the coil 12 of the detection sensor 11 changes accordingly. Occurs, and the oscillation frequency of the oscillation circuit 17 changes. On the other hand, when the developing tank 52 of the developing device 5 mounted on the printer 1 is not filled with the developer, the carrier density does not change even when the idling drive is performed, and the toner density is apparently very high. Similarly, the inductance L of the coil 12 of the detection sensor 11 becomes small and the inductance L does not change, so that the oscillation frequency generated by the oscillation circuit 17 becomes higher than that when the developer is supplied, and This oscillation frequency hardly changes before and after the idling drive.

FIG. 7 is a flowchart showing a processing procedure executed by the printer controller after the developing device is mounted on the printer. When the power of the printer 1 is turned on (s1), the control unit of the printer 1 detects the oscillation frequency as the toner concentration in the developer housed in the developer tank 52 immediately before the start of the idling drive through the detection toner 11. After detecting and storing the detection result (s2), idling drive of the developing device 5 is started (s3), and this idling drive is continued for a predetermined time (s4).

After that, the control unit oscillates immediately before the idling drive is stopped as the toner concentration in the developing case (saturated toner concentration) after a predetermined time has elapsed from the start of the idling drive while maintaining the idling drive. After detecting the frequency through the detection sensor 11 and storing it (s5),
The idling drive is stopped (s6).

Next, the control unit determines whether or not the frequency difference between the oscillation frequency immediately before the start of idling drive and the oscillation frequency immediately before the stop of idling drive is equal to or more than a threshold value.
The presence / absence of the developer in the developing device is determined (s7). As a result of the determination, if the difference in the oscillation frequency before and after the idling drive is less than the threshold value, it is determined that the developing device 5 not loaded with the developer is attached to the printer 1. Judgment, display an error message on the main unit display of the printer 1, turn on the alarm lamp,
Alternatively, the operator is informed of the fact that the developer has not been input through a notification means such as the generation of a warning sound (s8).

On the other hand, if it is determined in s7 that the difference between the oscillation frequencies before and after the idling drive is equal to or greater than the threshold value, the control unit determines that the developing device 5 filled with the developer is attached to the printer 1, The oscillation frequency immediately before the idling drive is stopped, which is stored in s5, is adopted as the reference value for executing the subsequent toner density control, and the standby mode is set (s9, s10), and the preparation for use is completed.

As described above, in the printer 1 according to this embodiment, when the developing device 5 in a normal state in which the developer is stored in the developing device 52 is attached to the printer 1, It is mounted on the printer 1 by utilizing the fact that the oscillation frequency output from the oscillation circuit 17 including the detection sensor 11 immediately before and immediately before the stirring operation in the developing tank 52 by the idling drive causes a difference of a certain value or more. It is determined whether or not the developer is normally stored in the developing device 5 that is being stored, and the developer is stored when there is no difference of a certain value or more between the oscillation frequency before the start of idling drive and immediately before the end of idling drive. If it is determined that the improper developing device 5 is attached to the printer 1, a warning is issued.

As a result, it is possible to prevent the image forming process from being executed while the improper developing device 5 containing no developer is attached to the printer 1.
It is possible to prevent the inconvenience that no image is output even by the image forming process.

The processes of s1 to s10 may be executed only when a new developing device 5 is attached to the printer 1.

In the above embodiment, the printer has been described as an example of the image forming apparatus of the present invention. However, the present invention can be applied to other image forming apparatuses such as copying machines for performing electrophotographic image forming processing. Can be similarly implemented.

[0048]

According to the present invention, the following effects can be obtained.

(1) When a new developing device is installed, the development in the installed developing device is based on the difference in the oscillation frequency of the toner concentration detecting means provided in the developing device before and after the idle of the developing device. By determining the presence or absence of the developer, only the existing functional parts and detection means are used in the developing device and the image forming device, and the developer is mistakenly stored when the image forming device is installed or the developer is replaced. It is possible to accurately determine the state in which the developing device that is not installed is attached to the image forming apparatus. As a result, even when the developing device that is not filled with the developer is attached to the image forming apparatus due to a work error or the like, it is possible to accurately detect the state that the developing device is not filled with the developer. It is possible to surely prevent a trouble in which an image is not output when the image forming process is executed in this state.

(2) When a new developing device is mounted, the developer in the developing device mounted on the basis of the oscillation frequency difference of the toner concentration detecting means provided in the developing device before and after the idle rotation of the developing device. When the image forming apparatus is installed, only the existing functional parts and detecting means are used in the developing device and the image forming apparatus by executing the processing for determining the presence or absence of the image forming apparatus, and only the processing content of the control means is changed. It is possible to accurately determine the state in which a developing device that does not store the developer by mistake is mounted in the image forming apparatus when the developer is replaced or the like. As a result, even when the developing device that is not filled with the developer is attached to the image forming apparatus due to a work error or the like, it is possible to accurately detect the state that the developing device is not filled with the developer. It is possible to surely prevent a trouble in which an image is not output when the image forming process is executed in this state.

Further, since it is determined whether or not the developer is stored in the developing device based on the oscillation frequency difference of the toner concentration detecting means before the idling of the developing device is started and after the idling of the developing device is executed, the individual toner concentration Even if there is an error in the oscillation output characteristic of the detection means, it is possible to suppress erroneous determination.

(3) Whether or not the developer is stored in the attached developing device depends on whether or not the oscillation frequency difference of the toner concentration detecting means before and after the idling of the developing device is more than a predetermined value. By making the determination, even if there is an error in the oscillation output characteristic of each toner concentration detection unit, it is possible to reliably suppress erroneous determination.

(4) The oscillation frequency of the toner concentration detecting means before and immediately before the start of the idling operation of the developing device, which is continued for a predetermined period, is judged whether or not the developer is stored in the installed developing device. By performing based on the difference, as the oscillation frequency of the toner concentration detecting means after the idling operation of the developing device, the detection result for the developer after the fluid state is stabilized by the sufficient stirring action by the idling operation for the predetermined period is obtained. It can be used and the presence or absence of the developer in the attached developing device can be accurately determined.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a configuration of a developing device in a general image forming apparatus.

FIG. 2 is a diagram showing a relationship between a toner concentration in a general developer and an oscillation frequency of a detection sensor.

FIG. 3 is a sectional view showing a schematic configuration of a printer which is an image forming apparatus according to an embodiment of the present invention.

FIG. 4 is a diagram showing a configuration of a developing device of the printer.

FIG. 5 is a circuit diagram showing a configuration of a detection sensor and control means in the printer.

FIG. 6 is a circuit diagram showing a specific configuration of the control means.

FIG. 7 is a flowchart showing a processing procedure executed by the printer control device after the developing device is attached to the printer.

[Explanation of symbols]

1-printer (image forming apparatus) 5-Developer 11-Detection sensor 12-coil 15-PPL circuit 16-comparator circuit 17-oscillation circuit 31-photosensitive drum 52-Development tank 54-stirring blade D-developer T-toner

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Jun Yamaguchi             22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka             Inside the company F term (reference) 2H077 AA15 AD06 DA10 DA16 DA42                       DA54 EA03

Claims (4)

[Claims] 1. A two-component developer composed of a magnetic carrier and a non-magnetic toner is stored, and the concentration of the non-magnetic toner in the two-component developer is adjusted by changing the frequency of the oscillation circuit due to the inductance and capacitance of the toner concentration detecting coil. In an image forming apparatus having a developing device equipped with a toner concentration detecting means for detecting, detachable, and comprising a controlling means for controlling the concentration of non-magnetic toner in the two-component developer based on the oscillation frequency of the toner concentration detecting means. When the developing device is mounted, the control means determines whether or not the two-component developer is stored in the developing device based on the oscillation frequency of the toner concentration detecting means before and after the idling of the developing device. A characteristic image forming apparatus. 2. A two-component developer composed of a magnetic carrier and a non-magnetic toner is stored, and the concentration of the non-magnetic toner in the two-component developer is adjusted by changing the frequency of the oscillation circuit due to the inductance and capacitance of the toner concentration detecting coil. In an image forming apparatus having a developing device equipped with a toner concentration detecting means for detecting, detachable, and comprising a controlling means for controlling the concentration of non-magnetic toner in the two-component developer based on the oscillation frequency of the toner concentration detecting means. When the developing device is mounted, the control means detects the oscillation frequency when the developing device is stationary, continues the idling operation of the developing device for a predetermined period, and detects the oscillation frequency when the developing device idles. , Are sequentially executed, and it is determined whether the two-component developer is stored in the developing device based on the oscillation frequency difference before and after the idling of the developing device. An image forming apparatus characterized by the above. 3. The control means determines that the two-component developer is not stored in the developing device when the difference between the oscillation frequencies before and after the idling of the developing device is less than a predetermined value, and is above the predetermined value. The image forming apparatus according to claim 2, wherein it is determined that the two-component developer is stored in the developing device. 4. The control means detects, as the oscillation frequency of the toner concentration detection means when the developing device is idling, the oscillation frequency immediately before the idling operation of the developing device is continued for a predetermined period. The image forming apparatus according to claim 2.