JP2648143B2 - Developer remaining amount detection device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developer remaining amount detecting device for detecting a developer remaining amount state of a developing device used in an image forming apparatus or the like.

BACKGROUND OF THE INVENTION In many cases, a developing device provided in an image forming apparatus such as an electrophotographic apparatus is a dry developing device using a powder developer.
The developing device generally includes a box-shaped developer container containing a developer (toner) to be supplied to an electrostatic latent image carrier such as a photosensitive drum, and the developer is supplied from within the developer container. A rotary developer carrier that is carried out little by little toward the electrostatic latent image carrier,
have. During the operation of the image forming apparatus, the developer in the developer container is carried out by the developer carrier, so that the amount of the developer in the developer container decreases. And
When the level of the remaining amount of the developer in the developer container falls below a certain value, the amount of the developer carried out by the developer carrier also decreases, so that the image quality deteriorates. Therefore, in order to prevent such a state from occurring, the remaining amount of the developer in the developer container is constantly monitored so that the remaining amount of the developer in the developer container does not fall below a predetermined level. When the developer level in the developer container falls below a certain value, the developer must be supplied to the developer container immediately.

Conventionally, as a device for detecting the remaining amount of developer in a developing device, for example, a device having a configuration shown in FIG. 4 is known.

In FIG. 4, reference numeral 5 denotes a photosensitive drum of the image forming apparatus;
Is a developer container containing the developer T, 2 is a developer carrier or developing sleeve disposed at a side opening of the developer container 1, and 6 is the developing sleeve 2 in the developer container 2.
A conductive detector arranged in parallel with the developer container 3;
Are provided at the side openings of the developing sleeve 2 to adjust the thickness of the adhered developer layer on the developing sleeve 2;
An AC bias power supply for applying a developing bias to the detector 6; a rectifying circuit 8a for rectifying a current induced in the detector 6 in accordance with the amount of developer existing between the detector 6 and the developing sleeve 2; Is a current-voltage conversion circuit that converts a current signal generated by the rectifier circuit 7a into a voltage, 12 is a reference voltage generation circuit that generates a reference voltage signal, and 9 is a measurement voltage (detection voltage) generated from the current-voltage conversion circuit 8a. Is a comparator that generates an output when the two voltages match, and 10 is a display circuit that controls the display 11 in accordance with the output state of the comparator 9. 6, various circuits 7 a to 10 and 12 operating according to the output signal of the detector 6, and a display 11.

In the known developer remaining amount detecting device as described above, since the reference voltage generating circuit 12 for setting the reference value in the comparator 9 is completely independent of the AC bias power supply 4, the output of the AC bias power supply 4 Voltage (ie,
When the bias applied to the developing sleeve 2 fluctuates, a false detection is caused as if the thickness of the developer adhering to the developing sleeve 2 is not significantly reduced, as if the thickness was significantly reduced. was there. In the erroneous detection device, the output of the detector 6 depends on the voltage applied to the developing sleeve 2 and the thickness of the developer attached to the developing sleeve 2 (between the developing sleeve 2 and the detector 6). It is desirable that the output voltage of the AC bias power supply 4 does not fluctuate at all and always keeps a constant value. However, since the AC bias power supply 4 is manufactured with an output margin of ± 10%, the development in a known developing device is performed. Bias variation up to 10%
Therefore, even if the development that the layer thickness of the developer existing between the developing sleeve 2 and the detector 6 is remarkably reduced does not occur, the output fluctuation within the allowable range of the AC bias power supply 4 causes the detector to fail. At 6, a false (apparent) developer decrease detection signal is generated. Therefore, when such a false developer decrease detection signal is generated in the detector 6, it is necessary to automatically compensate for an apparent fluctuation such as the signal, thereby always enabling correct detection. In the remaining amount detecting device, the reference value set in the comparator 9 was constant irrespective of the fluctuation of the output of the AC bias power supply 4, so that the apparent fluctuation of the output of the detector 6 could not be compensated. When the output of the bias power supply 4 fluctuates, erroneous detection often occurs.

[Object of the Invention] It is an object of the present invention to provide an improved developer remaining amount detecting device which does not cause the erroneous detection as described above.

[Summary of the Invention] In order to achieve the above object, a developer remaining amount detecting device according to the present invention includes: a developer carrier for carrying a developer; an AC power supply for applying a bias voltage to the developer carrier; And a detector in which a current is induced by a bias voltage applied to the agent carrier, and formed by rectifying and transforming the measured value obtained by rectifying the output of the detector and the output of the AC power supply. It is characterized in that the remaining amount of the developer is detected by comparing with a reference value.

[Embodiment] The configuration and functions of an improved developer remaining amount detecting device according to the present invention will be described below with reference to FIGS.

FIG. 1 is a schematic configuration diagram of an embodiment of an improved developer remaining amount detecting device according to the present invention. In FIG. 1, the same parts as those of the conventional device of FIG. 4 are denoted by the same reference numerals as those of FIG. 4, and the description of the same parts will be omitted.

In the embodiment of the present invention shown in FIG.
Wherein the new variable reference voltage generating means 13 for setting a reference voltage V _S is provided in connection with the AC bias power source 4 to.

That is, in this embodiment, the AC bias power source 4 a predetermined electrostatic capacitance C _S capacitor 14 connected in parallel with the developing sleeve 2 with respect to the capacitor 14 rectifying circuit 7b connected in series, the rectifier circuit 7b Current connected in series on the downstream side
The variable reference voltage generating means 13 is constituted by the voltage conversion circuit 8b. Therefore, when only the output voltage of the AC bias power supply 4 fluctuates without changing the amount of the developer between the detector 6 and the developing sleeve 2, the detector 6 responds to the output fluctuation of the AC bias power supply 4. While the output of the detector 14 is generated, an output corresponding to the variation of the output voltage of the AC bias power supply 4 is also generated at the terminal of the capacitor 14, and the output of the detector 6 is subjected to current-voltage conversion after the rectifier circuit 7a removes the AC component. After being converted into a voltage signal by the circuit 8a and applied to one input terminal of the comparator 9, the output of the capacitor 14 is converted into a voltage signal by the current-voltage conversion circuit 8b after the AC component is removed by the rectification circuit 7b. The signal is applied to the other input terminal of the comparator 9.

Therefore, in the developer remaining amount detection device of the present invention, the detection signal voltage V _DC applied to one input terminal of the comparator 9
There therefore changes according to the voltage variation of the reference voltage V _S is also AC bias power source 4 is applied to the other input terminal of the comparator 9 when the varied by a voltage variation of the AC bias power source 4, no risk of causing false positives.

By accurately determining the capacitance of the capacitor 14 so that the relationship between the capacitance of the capacitor 14 and the remaining amount of the developer in the developer container 1 is linearly proportional, the remaining amount of the developer in the developer container 1 can be accurately detected. can do. Therefore, for example, when the remaining amount of the developer in the developer container 1 reaches 50 g, the display 11 indicates “the developer in the developer container 1 is almost empty (or
(Replenishment required) is assumed to be displayed as shown in FIG. 2, as shown in FIG. 2 showing the relationship between the remaining amount of developer and the capacitance of the capacitor 14 when the remaining amount of developer is 50 g. The capacitance C _S (pF) may be set as the capacitance of the capacitor 14. In FIG. 2, the horizontal axis represents the amount of developer (g) in the developer container 1, and the vertical axis represents the capacitance (pF) of the capacitor 14.

Figure 3 takes a developer remaining amount in the developer container 1 on the horizontal axis and the vertical axis represents the reference voltage V _S and the detection signal voltage V _DC and the detection signal voltage and the reference voltage of the AC bias power source 4 This shows the relationship with the output voltage fluctuation. When the output voltage of the AC bias power supply 4 is the regular voltage V _{PP as} shown by the solid line, the value of the detection signal voltage V _DC and the reference voltage V _S when the remaining amount of the developer in the developer container 1 is 50 g are obtained. The value is a regular value V _S0 , but when the output voltage of the AC bias power supply 4 is a voltage V _PP1 higher than the regular voltage V _{PP as} shown by a dotted line, a detection signal when the remaining amount of the developer is 50 g Voltage _VDC value and reference voltage
The value of V _S is increased in accordance with the output voltage of the _{V S1 (V S1> V S0} ) and turned with the detection signal voltage values and the reference values of voltage AC bias power source 4. When the output voltage of the AC bias power supply 4 is a value V _PP2 smaller than the regular value V _PP , the value of the detection signal voltage V _{DC and} the value of the reference voltage V _S are also smaller than the regular value V _{PP. As} shown in FIGS. 1 and 3, in the developer remaining amount detecting device of the present invention, a capacitor which is a part of variable reference voltage setting means for setting a reference voltage to the comparator 9 is provided.
14 is connected to the AC bias power supply 4, the output voltage of the capacitor 14, that is, the reference voltage of the comparator 9 fluctuates when the output voltage of the detector 6 fluctuates due to the fluctuation of the output voltage of the AC bias power supply 4. The influence of the apparent detection signal voltage resulting from the fluctuation of the output voltage of the bias power supply 4 can be eliminated.

Note that the developer remaining amount detection device of the present invention can be applied not only to the detection of the remaining state of the developer in the developing device but also to a developer supply control device for replenishing the developing device with the developer.

[Effects of the Invention] As described above, since the developer remaining amount detecting device of the present invention has the variable reference voltage generating means for changing the reference value of the comparator according to the fluctuation of the developing bias,
Even if the developing bias fluctuates, erroneous detection does not occur, and accurate detection can always be performed.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a developer remaining amount detecting device according to the present invention, FIG. 2 is a diagram showing a relationship between the capacitance of a capacitor included in the device of the present invention and the developer remaining amount, and FIG. 9
FIG. 4 is a diagram showing a state in which the detection signal voltage and the reference voltage applied to the AC power supply 4 fluctuate due to the output fluctuation of the AC bias power supply 4. FIG. 4 is a schematic diagram of a known developer remaining amount detecting device. DESCRIPTION OF SYMBOLS 1 ... Developer container 2 ... Developing sleeve (developer carrying body) 3 ... Blade 4 ... AC bias power supply 5 ... Photosensitive drum (electrostatic latent image carrying body) 6 ... Detectors 7a and 7b ... Rectifier circuits 8a and 8b Current-voltage conversion circuit 9 Comparator 10 Display circuit 11 Display 12 Reference voltage generation circuit 13 Variable reference voltage generation means 14 Capacitor

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yasumasa Otsuka 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Keiji Okano 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inside (72) Inventor Koichi Okuda 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (56) References JP-A-61-256355 (JP, A) JP-A-61-262769 (JP) JP-A-58-31363 (JP, A) JP-A-60-258570 (JP, A) JP-A-59-126568 (JP, A)

Claims (1)

(57) [Claims] A developer carrying member for carrying a developer, an AC power supply for applying a bias voltage to the developer carrying member, and a detector having a current induced by the bias voltage applied to the developer carrying member. And detecting a remaining amount of the developer by comparing a measured value obtained by rectifying the output of the detector with a reference value formed by rectifying and transforming the output of the AC power supply. Developer remaining amount detecting device.