JP2004354904A - Toner residual amount detecting device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably and accurately detect a toner decreasing process with simple constitution. <P>SOLUTION: In a state where toner D in a developer tank 41 is decreased to be under a fixed level, the vicinity of the edge of a flexible member 53 slides on the surface of the toner D, and a body to be detected 54 also slides and moves on the surface of the toner D. Furthermore, when the toner D in the tank 41 is gradually decreased and the level of the surface of the toner D is gradually lowered, the position of the body to be detected 54 sliding and moving on the surface of the toner D is also gradually lowered, so that a distance between the body to be detected 54 and an electrostatic capacity sensor 55 is shortened. An electrostatic capacity detection circuit 68 inputs the detection output of the sensor 55 so as to detect electrostatic capacity between the body to be detected 54 and the sensor 55. The electrostatic capacity is changed in accordance with the distance between the body to be detected 54 and the sensor 55. Therefore, the residual amount of the toner D is detected based on the electrostatic capacity. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a toner remaining amount detecting device used in an electrophotographic image forming apparatus such as a printer, a copying machine, a facsimile, and the like, for detecting a remaining amount of toner in a developer tank, and an image forming apparatus including the same.
[0002]
[Prior art]
As a conventional device for detecting the remaining amount of toner, there is, for example, a device disclosed in Japanese Patent Application Laid-Open No. H11-163,837. Here, while stirring the toner in the developer container, a stir bar that deforms from a refracted state to a straight state with increasing resistance received from the toner is provided, and a sensor that detects the position of the tip of the stir bar is provided. When provided, the toner decreases, the resistance of the toner decreases, the stirring rod deforms into a refraction state, and when the tip of the stirring rod moves, based on the position of the tip of the stirring rod detected by the sensor, Detects decrease in toner.
[0003]
[Patent Document 1]
JP-A-10-319704
[0004]
[Problems to be solved by the invention]
However, in the above-described conventional apparatus, the position of the tip of the stirring rod is detected based on whether or not the tip of the stirring rod has contacted the sensor. Therefore, only one position of the tip of the stirring rod is detected by one sensor. However, it was only possible to detect whether or not the toner was reduced to a certain level.
[0005]
Further, in order to detect the stepwise decrease of the toner, it is necessary to provide a plurality of sensors for detecting the respective positions of the tip of the stirring rod, and the configuration of the apparatus is complicated.
[0006]
Further, in the toner, the contact between the tip of the stirring rod and the sensor may become unstable, and the reliability of the detection output of the sensor is low.
[0007]
Accordingly, the present invention has been made in view of the above-described conventional problems, and has a toner remaining amount detecting apparatus and a toner remaining amount detecting apparatus capable of stably and accurately detecting a toner decreasing process while having a simple configuration. It is an object of the present invention to provide an image forming apparatus including:
[0008]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the present invention provides a toner remaining amount detecting device for detecting the remaining amount of toner in a developer tank, wherein the stirring is performed by rotating the developer tank and stirring the toner in the developer tank. A member, a flexible member that is connected to the agitating member, rotates following, and enters or moves into the toner, or moves on the toner surface, and a detection target attached to the tip of the flexible member, It is arranged at the lower part of the developer tank, and detects the capacitance between the flexible member and the detected object when the detected object at the tip of the flexible member comes close to the rotation of the flexible member. And capacitance detecting means.
[0009]
According to the present invention having such a configuration, the flexible member is connected to the agitating member, rotates following, and moves into the toner. At this time, when the flexible member enters the toner at the connection point with the stirring member, the entire flexible member is flexibly deformed, and the entire flexible member is continuously and continuously inserted into the toner at the same position. As the flexible member enters, the entire flexible member rotates and moves along the same trajectory in the toner. Therefore, the object to be detected at the tip of the flexible member also rotates and moves along the same trajectory as the flexible member. As long as the toner is at a certain level or more and the connecting portion of the flexible member enters the toner, the trajectory drawn by the flexible member and the detection target hardly changes in the toner.
[0010]
Also, when the toner decreases below a certain level and the connecting portion of the stirring member does not enter the toner, the vicinity of the tip of the flexible member slides on the toner surface, and the object to be detected also slides on the toner surface and moves. I do.
[0011]
Here, when the toner decreases below a certain level, the remaining amount of the toner gradually decreases, and the height of the toner surface gradually decreases, the position of the detection object that slides and moves on the toner surface also gradually decreases. I do. That is, when the toner decreases below a certain level, the position of the detection target moving on the toner surface decreases according to the remaining amount of the toner.
[0012]
On the other hand, the capacitance detecting means can detect the capacitance between the capacitance detecting means and the detection target moving on the toner surface. Then, the capacitance between the capacitance detecting means and the object to be detected changes according to the distance between them. Further, since the capacitance detecting means is disposed at the lower part of the toner tank, the toner decreases to less than a certain level, the height of the toner surface gradually decreases, and the detected object moves on the toner surface. When the position is lowered, the distance between the capacitance detecting means and the object to be detected is reduced, and the capacitance between the two is reduced. That is, the capacitance between the capacitance detecting means and the detection target changes according to the remaining amount of toner.
[0013]
Therefore, the remaining amount of toner can be detected based on the capacitance detected by the capacitance detecting unit.
[0014]
Further, in the present invention, the capacitance detection means may determine a distance between the capacitance detection means and the detection target based on a capacitance between the capacitance detection means and the detection target. It is detected as the remaining amount of toner inside.
[0015]
As described above, the capacitance between the capacitance detecting means and the detected object corresponds to the distance between the capacitance detecting means and the detected object, and this distance corresponds to the remaining amount of toner in the developer tank. Accordingly, if the capacitance between the capacitance detecting means and the object to be detected is detected, the remaining amount of the toner in the developer tank can be detected.
[0016]
Further, in the present invention, the capacitance detection means forms a detection signal whose frequency or phase changes according to the capacitance between the capacitance detection means and the object to be detected, and based on this detection signal, The distance between the capacitance detecting means and the object to be detected is detected as the remaining amount of toner in the developer tank.
[0017]
By forming a detection signal whose frequency or phase changes in accordance with the capacitance between the capacitance detecting means and the object to be detected, the remaining amount of toner in the developer tank is determined based on the detection signal. Can be detected.
[0018]
Further, in the present invention, the object to be detected contains a conductive material to be an electrode of capacitance.
[0019]
In order to detect the capacitance between the capacitance detecting means and the object to be detected, a conductive material serving as an electrode of the capacitance may be provided on the object to be detected.
[0020]
Further, in the present invention, the capacitance detecting means is provided on the inner wall of the developer tank. Alternatively, the capacitance detecting means is provided on an outer wall of the developer tank.
[0021]
When the capacitance detecting means is provided on the inner wall of the developer tank, the capacitance detecting means is closer to the object to be detected, and is less susceptible to external noise. Can be improved. Further, when the electrostatic capacity detecting means is provided on the outer wall of the developer tank, the electrostatic capacity detecting means and the developer tank can be separated from each other. Need not be replaced, and an increase in running costs can be suppressed.
[0022]
Next, the image forming apparatus of the present invention includes the toner remaining amount detecting device of the present invention.
[0023]
According to the image forming apparatus of the present invention, the same operation and effect as those of the toner remaining amount detecting apparatus of the present invention can be achieved.
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
[0025]
FIG. 1 is a side view showing an image forming apparatus to which an embodiment of a toner remaining amount detecting device according to the present invention is applied. The image forming apparatus 1 forms an image by an electrophotographic method, and includes an exposure scanning unit 10 and an image forming unit 20.
[0026]
In the exposure scanning unit 10, the control unit 30 receives an image signal from an external host computer or the like. The control unit 30 performs necessary processing on the image signal to form image data, outputs a drive signal corresponding to the image data to the laser diode 11, and outputs a laser beam emitted from the laser diode 11. Is modulated. This laser light is converted into parallel light by a collimating lens 12, then reflected and deflected by a polygon mirror 14, which is driven to rotate at a constant speed by a motor 13, and passes through an fθ lens 15 and a folding mirror 16 to form an image forming unit 20. The surface of the photosensitive drum 21 is exposed and scanned.
[0027]
In the image forming unit 20, while rotating the photosensitive drum 21 in one direction, the residual developer on the surface of the photosensitive drum 21 is removed by the cleaner 22, and the light of the eraser lamp 23 is irradiated on the surface of the photosensitive drum 21. Then, the surface of the photosensitive drum 21 is neutralized, and the surface of the photosensitive drum 21 is further uniformly charged by the charging charger 24. Then, the surface of the photosensitive drum 21 is exposed and scanned by the laser beam from the exposure scanning unit 10. Then, an electrostatic latent image is formed on the surface of the photosensitive drum 21, and the electrostatic latent image on the surface of the photosensitive drum 21 is developed by the developing device 25 to form a developer image on the surface of the photosensitive drum 21. I do.
[0028]
On the other hand, in synchronization with the rotation operation of the photosensitive drum 21, the recording paper (not shown) is pulled out of the paper cassette 27 by the feed roller 26, and the recording paper is transported to the photosensitive drum 21 by each transport roller 28. The developer image on the surface of the photosensitive drum 21 is transferred onto a recording sheet by the transfer charger 31. Further, the recording paper is transported to the fixing device 32 by the transport belt 29, and the recording paper is heated and pressed by the fixing device 32 to fix the developer image on the recording paper. The paper is discharged to the paper discharge tray 34.
[0029]
The exposure scanning unit 10 is pivotally supported by a hinge so as to be openable and closable upward so as to be able to exchange the developer tank 41 of the developing device 25 and to handle a paper jam generated inside the image forming unit 20. ing.
[0030]
FIG. 2 is a side view showing the photosensitive drum 21 and the developing device 25. The developing device 25 includes a developer tank 41 that stores and stores the toner, a developing container 42 that stores a developer that is a mixture of the toner and the carrier, a stirring roller 43 that stirs the developer in the developing container 42, A developing roller 44 for supplying the toner in the developer from the developing container 42 to the surface of the photosensitive drum 21; and a toner for detecting a toner concentration that decreases with respect to the carrier when the toner in the developer is consumed by the developing operation. And a density sensor 45. By the supply of the developer from the developing device 25, toner adheres to the electrostatic latent image on the surface of the photosensitive drum 21, and the electrostatic latent image is developed to form a developer image.
[0031]
Further, the developer tank 41 includes a developer replenishing roller 51 for replenishing toner from the developer tank 41 to the developing container 42, a stirring member 52 for stirring the toner in the developer tank 41, and one end of the stirring member 52. A flexible belt-shaped member 53 connected to the flexible belt-shaped member 53, a detection target 54 fixed to the end of the flexible belt-shaped member 53, and a capacitance sensor 55 for detecting a capacitance between the detection target 54. It has.
[0032]
The developing device 25 is controlled by the control device 61. The control device 61 includes a CPU 62, a ROM 63, a RAM 64, and the like.
[0033]
The ROM 63 stores a program for controlling the entire image forming apparatus and a program for controlling replenishment of the developer. Further, the RAM 33 is used as a working area of the CPU 62 and stores various data.
[0034]
The CPU 62 controls the rotation of the stirring roller 43 and the developing roller 44 of the developing container 42 and the stirring member 52 of the developer tank 41 according to a program in the ROM 63.
[0035]
The comparator 69 compares the detection output of the toner density sensor 45 with a preset threshold value, and when the detection output becomes equal to or less than the threshold value, it is regarded that the toner density of the developer in the developing container 42 has become equal to or less than a specified amount. Then, the driving motor 67 for the developer supply roller 51 is driven through the developer supply motor drive circuit 66 to rotate the developer supply roller 51 to supply toner from the developer tank 41 to the developing container 42.
[0036]
The capacitance detection circuit 68 receives the detection output of the capacitance sensor 55, forms a detection signal indicating the capacitance between the detection target 54 and the capacitance sensor 55, and outputs the detection signal. The CPU 62 measures the remaining amount in the developer tank 41 based on the detection signal from the capacitance detection circuit 68, and when the remaining amount of the toner in the developer tank 41 becomes equal to or less than a specified amount, the developer tank 41 Is displayed on the display screen of the notifying unit 65 to prompt the exchange of the information. When the user sees the display screen of the notification unit 65 and knows that the replacement of the developer tank 41 is prompted, the user replaces the developer tank 41 with a new one. As a result, the toner is replenished without interruption.
[0037]
Next, detection of the remaining amount of toner in the developer tank 41 will be described in more detail.
[0038]
FIG. 3 is a perspective view schematically showing the developer tank 41. As shown in FIG. 3, in the developer tank 41, the support shaft 52 a of the stirring member 52 is rotatably supported, and the support shaft 52 a is rotated by a driving motor to rotate the stirring member 52 in the direction of arrow A. The toner in the agent tank 41 is agitated. The stirring member 52 is formed by combining a plurality of plate pieces 52b vertically and horizontally and fixing a stirring blade 52c to one side thereof. In addition, a flexible strip 53 is connected and fixed to one end of the stirring member 52. Further. The detection target 54 is fixed to the distal end of the flexible strip 53, and the capacitance sensor 55 is disposed outside the bottom of the developer tank 41.
[0039]
The flexible band-shaped member 53 is, for example, a thin band-shaped synthetic resin plate, and its original shape is substantially linear. The flexible band-shaped member 53 is fixed to one end of the stirring member 52, and the flexible band-shaped member 53 is disposed in the developer tank 41 by being curved.
[0040]
Here, in a state where the toner D in the developer tank 41 is at a certain level or more as shown in FIG. Intrudes into D. Then, while the entire flexible member 53 is flexibly deformed, the entire flexible member 53 continuously enters the toner D at the same location C, and the entire flexible member 53 is within the toner D. Rotate and move along the same trajectory E. Therefore, the detection target 54 at the distal end of the flexible member 53 also rotates and moves along the same trajectory E as the flexible member 53.
[0041]
As long as the toner D is at a certain level or more and the connecting portion C of the flexible member 53 penetrates into the toner D, the trajectory E drawn by the flexible member 53 and the detection object 54 in the toner D hardly changes. Instead, the detection target 54 passes above the capacitance sensor 55 with a certain separation distance.
[0042]
Further, as shown in FIG. 5, when the toner D in the developer tank 41 is reduced below a certain level, the connecting portion C of the flexible member 53 does not enter the toner D, and The vicinity slides on the surface of the toner D, and the detection target 54 also slides and moves on the surface of the toner D.
[0043]
Further, when the toner D in the developer tank 41 gradually decreases and the height of the surface of the toner D gradually decreases, the position of the detection target 54 that slides and moves on the surface of the toner D also gradually decreases.
[0044]
Therefore, when the toner D decreases below a certain level, the position of the detection target 54 that moves on the surface of the toner D decreases according to the remaining amount of the toner D. Then, the separation distance between the detection target 54 and the capacitance sensor 55 is reduced. Therefore, if the distance between the detection target 54 and the capacitance sensor 55 is known, the remaining amount of the toner D can be known.
[0045]
On the other hand, the capacitance detection circuit 68 receives the detection output of the capacitance sensor 55 and detects the capacitance between the detected object 54 and the capacitance sensor 55. This capacitance changes according to the separation distance between the detection target 54 and the capacitance sensor 55. Therefore, if the capacitance is detected, the separation distance between the detection target 54 and the capacitance sensor 55 is known, and the remaining amount of the toner D is known.
[0046]
Further, the detection target 54 slides on the surface of the toner D with the rotation of the stirring member 52, gradually approaches the capacitance sensor 55 from the right, passes over the capacitance sensor 55, and becomes static. The process of gradually moving leftward from the capacitance sensor 55 is repeated. When the detection target 54 comes closest to the capacitance sensor 55, the detection target 54 and the capacitance sensor 55 face each other. The capacitance at this time corresponds to the separation distance between the detection target 54 and the capacitance sensor 55, and corresponds to the remaining amount of the toner D.
[0047]
As shown in FIGS. 6A and 6B, the capacitance sensor 55 has a center electrode 55a and an annular electrode 55b fixed on an insulator plate 55c. Further, the detection target 54 has an electrode 54a fixed on an insulator plate 54b.
[0048]
Here, the capacitance between the center electrode 55a of the capacitance sensor 55 and the electrode 54a of the detection target 54 is C1, and the capacitance between the annular electrode 55b of the capacitance sensor 55 and the electrode 54a of the detection target 54 is C1. Let the capacity be C2. If the ring electrode 55b is grounded and a signal voltage v is applied to the electrode 55a, it can be equivalently represented as a circuit in which the capacitances C1 and C2 are connected in series as shown in FIG. Then, assuming that the combined capacitance of the respective capacitances C1 and C2 is Cs, the combined capacitance Cs can be expressed by the following equation (1).
[0049]
Cs = (C1 × C2) / (C1 + C2) (1)
FIG. 8 shows a configuration of a capacitance detection circuit 68 for detecting a combined capacitance Cs between the detection target 54 and the capacitance sensor 55. The capacitance detection circuit 68 includes a combined capacitance Cs, an inductance L, a capacitor Cc having a constant capacitance, an inverter 71, a comparator 72, and a dividing cycle 73.
[0050]
The combined capacitance Cs, the inductance L, the capacitor Cc, and the inverter 71 constitute a Colpitts oscillation circuit, and the oscillation frequency fo changes according to the combined capacitance Cs. The comparator 72 receives a sine wave signal from the oscillation circuit, converts the sine wave signal into a pulse signal, and outputs a pulse signal. The dividing period 73 divides the frequency (oscillation frequency) of the pulse signal by 1 / n, and applies a detection signal of the 1 / n frequency to the CPU 62.
[0051]
Since the oscillation frequency of the oscillation circuit changes according to the combined capacitance Cs, the 1 / n frequency of the detection signal applied to the CPU 62 also changes according to the combined capacitance Cs. As described above, when the detection target 54 and the capacitance sensor 55 face each other, the capacitance between them (the combined capacitance Cs) is the separation distance between them or the remaining amount of the toner D. Corresponding to Therefore, based on the 1 / n frequency of the detection signal applied to the CPU 62, the separation distance between the detection target 54 and the capacitance sensor 55 or the remaining amount of the toner D can be obtained.
[0052]
Therefore, the CPU 62 samples the 1 / n frequency of the detection signal at the timing when the detection target 54 and the capacitance sensor 55 face each other while controlling the rotation of the stirring member 52, and Is obtained, and the remaining amount of the toner D corresponding to this separation distance is obtained.
[0053]
FIG. 9 is a graph showing an oscillation frequency characteristic of the oscillation circuit with respect to a separation distance between the detection target 54 and the capacitance sensor 55. As is clear from the graph of FIG. 9, the oscillation frequency of the oscillation circuit decreases as the separation distance between the detection target 54 and the capacitance sensor 55 decreases. Therefore, based on the oscillation frequency of the oscillation circuit, the separation distance between the detection target 54 and the capacitance sensor 55 or the remaining amount of the toner D can be obtained.
[0054]
When the remaining amount of the toner D is obtained in this way, the CPU 62 determines whether the remaining amount of the toner D is equal to or less than a specified amount. Then, when the remaining amount of the toner D becomes equal to or less than the specified amount, the CPU 62 displays on the display screen of the notifying unit 65 that the replacement of the developer tank 41 is urged. Therefore, the user can replace the developer tank 41 with a new one at an appropriate timing.
[0055]
As described above, in the present embodiment, the flexible band-shaped member 53 is connected and fixed to one end of the stirring member 52, the detection target 54 is fixed to the tip of the flexible band-shaped member 53, and the flexible band-shaped member 53 is stirred. The detection target 54 is rotated above the electrostatic capacity sensor 55 outside the bottom of the developer tank 41 by rotating the member 52 following the member 52. Then, since the combined capacitance Cs between the detection target 54 and the capacitance sensor 55 corresponds to the remaining amount of the toner D, the toner D based on the oscillation frequency that changes according to the combined capacitance Cs is used. I'm looking for the remaining amount.
[0056]
Accordingly, the measurement of the remaining amount of the toner D is realized with a simple configuration. Further, since the detection target 54 and the capacitance sensor 55 are not in contact with each other, the combined capacitance Cs between the two can be stably and accurately detected. Therefore, the remaining amount of the toner D can be stably and accurately detected.
[0057]
Further, since the center electrode 55a of the capacitance sensor 55 is surrounded by the ring-shaped electrode 55b and the ring-shaped electrode 55b is grounded, it is hardly affected by external noise. This also makes it possible to stably and accurately detect the combined capacitance Cs, and to stably and accurately detect the remaining amount of the toner D.
[0058]
As the capacitance detection circuit 68, a circuit that forms and outputs a detection signal having a frequency corresponding to the combined capacitance Cs as shown in FIG. 8 is exemplified. A device that forms and outputs a detection signal having a phase corresponding to the combined capacitance Cs may be used.
[0059]
The capacitance detection circuit 68A of FIG. 10 includes a delay circuit 81 including a combined capacitance Cs and a resistor R, a square wave oscillation circuit 82, a first comparator 83, a second comparator 84, and a phase comparator 85.
[0060]
The first comparator 83 directly inputs the square wave signal S1 from the square wave oscillation circuit 82 and immediately outputs the square wave signal S2.
[0061]
The delay circuit 81 has a delay time Tw corresponding to the combined capacitance Cs, and delays the square wave signal S1 from the square wave oscillation circuit 82 by the delay time Tw. The second comparator 84 receives the signal from the delay circuit 81, compares the signal with a threshold voltage, and outputs a square wave signal S3.
[0062]
Upon receiving the square wave signal S2 from the first comparator 83 and the square wave signal S3 from the second comparator 84, the phase comparator 85 sets a delay time Tw corresponding to the phase difference between the square wave signal S2 and the square wave signal S3. And outputs a phase difference detection signal D indicating the delay time Tw. This phase difference detection signal D is applied to the CPU 62.
[0063]
As is apparent from FIG. 11, since the square wave signal S3 from the second comparator 84 corresponds to the signal from the delay circuit 81, it is delayed by the delay time Tw with respect to the square wave signal S2 from the first comparator 83. I have. Then, the phase difference detection signal S4 from the phase comparator 85 has a pulse width corresponding to the delay time Tw.
[0064]
Here, the delay time Tw of the delay circuit 81 changes according to the combined capacitance Cs. Further, when the detection target 54 and the capacitance sensor 55 face each other, the combined capacitance Cs between the two corresponds to the separation distance between the two or the remaining amount of the toner D. Therefore, based on the delay time Tw which is the pulse width of the phase difference detection signal S4, the separation distance between the detection target 54 and the capacitance sensor 55 or the remaining amount of the toner D can be obtained.
[0065]
The CPU 62 calculates the delay time Tw, which is the pulse width of the phase difference detection signal S4 from the phase comparator 85, at the timing when the detection target 54 and the capacitance sensor 55 face each other while controlling the rotation of the stirring member 52. Based on the delay time Tw, the separation distance between the detection target 54 and the capacitance sensor 55 is obtained, and the remaining amount of the toner D corresponding to the separation distance is obtained.
[0066]
FIG. 12 is a graph showing a characteristic of the delay time Tw of the delay circuit 81 with respect to the separation distance between the detection target 54 and the capacitance sensor 55. As is clear from the graph of FIG. 12, the shorter the separation distance between the detected object 54 and the capacitance sensor 55, the longer the delay time Tw of the delay circuit 81. Therefore, based on the delay time Tw of the delay circuit 81, the separation distance between the detection target 54 and the capacitance sensor 55 or the remaining amount of the toner D can be obtained.
[0067]
Note that the present invention is not limited to the above-described embodiment, and can be variously modified. For example, as shown in FIG. 13, two or more capacitance sensors 55 may be arranged outside the bottom of the developer tank 41. In this case, the remaining amount of toner in the developer tank 41 can be detected in a wider range.
[0068]
Further, the capacitance sensor 55 may be provided on the bottom inner wall of the developer tank 41. In this case, the capacitance sensor 55 comes closer to the detection target 54 and is less susceptible to external noise, so that the S / N of the detection signal from the capacitance sensor 55 can be improved. However, when the developer tank 41 is replaced, the capacitance sensor 55 is replaced together with the developer tank 41.
[0069]
Further, a single electrode is applied as the capacitance sensor 55, and the electrode of the detection object 5 is grounded or externally connected, so that a single capacitor is provided between the electrode of the capacitance sensor 55 and the detection object 54. May be formed.
[0070]
Further, the toner remaining amount detecting device of the present invention can be applied to various known developing devices and image forming devices.
[0071]
【The invention's effect】
As described above, according to the present invention, while the stirring member is rotated to stir the toner in the developer tank, the object to be detected at the tip of the flexible member is rotated following the stirring member. Then, when the toner decreases below a certain level, the height of the developer surface gradually decreases, and the position of the detected object moving on the developer surface decreases, the capacitance between the electrostatic capacitance detecting means and the detected object is reduced. The remaining amount of toner is detected based on the capacitance.
[0072]
Therefore, the remaining amount of toner can be detected with a simple configuration. Further, since the capacitance detecting means and the object to be detected are not in contact with each other, the capacitance between the two can be detected stably and accurately. Therefore, the remaining amount of toner can also be detected stably and accurately.
[Brief description of the drawings]
FIG. 1 is a side view illustrating an image forming apparatus to which an embodiment of a remaining toner amount detection device according to the present invention is applied.
FIG. 2 is a diagram illustrating a configuration of a photosensitive drum and a developing device in the apparatus of FIG.
FIG. 3 is a perspective view schematically showing a developer tank in the developing device of FIG. 2;
FIG. 4 is a cross-sectional view illustrating a state where the toner in a developer tank is at a certain level or more.
FIG. 5 is a cross-sectional view illustrating a state in which toner in a developer tank has decreased below a certain level.
FIG. 6A is a cross-sectional view illustrating a detection target of a developer tank and a capacitance sensor, and FIG. 6B is a plan view illustrating the capacitance sensor.
FIG. 7 is an equivalent circuit diagram showing a capacitance between a detection object in a developer tank and a capacitance sensor.
FIG. 8 is a block diagram illustrating a capacitance detection circuit for detecting a capacitance between a detection object in a developer tank and a capacitance sensor.
9 is a graph showing oscillation frequency characteristics of the oscillation circuit of FIG. 8 with respect to a separation distance between a detection target and a capacitance sensor.
FIG. 10 is a block diagram showing another capacitance detection circuit for detecting a capacitance between a detection object in a developer tank and a capacitance sensor.
11 is a timing chart showing signals in the capacitance detection circuit of FIG.
12 is a graph showing a delay time characteristic of the delay circuit of FIG. 10 with respect to a separation distance between a detection target and a capacitance sensor.
FIG. 13 is a sectional view showing a modification of the developing device.
[Explanation of symbols]
1 Image forming apparatus
10 Exposure scanning section
20 Image forming unit
21 Photoconductor drum
25 Developing device
41 Developer tank
51 Developer supply roller
52 Stirring member
53 Flexible strip
54 Detected object
55 Capacitance sensor
61 Controller
62 CPU
63 ROM
64 RAM
68 Capacitance detection circuit

Claims (7)

In a toner remaining amount detecting device that detects a remaining amount of toner in a developer tank,
A stirring member that rotates in the developer tank and stirs the toner in the developer tank;
A flexible member that is connected to the stirring member, rotates following, and enters and moves into the toner, or moves on the toner surface;
A detection target attached to the tip of the flexible member;
It is arranged at the lower part of the developer tank, and detects the capacitance between the flexible member and the detected object when the detected object at the tip of the flexible member comes close to the rotation of the flexible member. A toner remaining amount detecting device, comprising: a capacitance detecting unit. The capacitance detection unit determines a distance between the capacitance detection unit and the detection target as a remaining amount of toner in the developer tank based on a capacitance between the capacitance detection unit and the detection target. The developer remaining amount detecting device according to claim 1, wherein the developer remaining amount is detected. The capacitance detection means forms a detection signal whose frequency or phase changes according to the capacitance between the capacitance detection means and the object to be detected, and based on the detection signal, the capacitance detection means 2. The toner remaining amount detecting device according to claim 1, wherein a distance between the toner and the object to be detected is detected as a remaining amount of toner in the developer tank. 2. The toner remaining amount detecting device according to claim 1, wherein the object to be detected includes a conductive material serving as an electrode of capacitance. The toner remaining amount detecting device according to claim 1, wherein the capacitance detecting means is provided on an inner wall of the developer tank. The toner remaining amount detecting device according to claim 1, wherein the capacitance detecting means is provided on an outer wall of the developer tank. An image forming apparatus comprising the toner remaining amount detecting device according to claim 1.

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