JPH02144582A - Developing device - Google Patents

Abstract

PURPOSE:To accurately detect a state that the toner remaining in a developing tank becomes less by applying an AC voltage to a specific counter electrode and detecting the voltage induced in the detecting electrode by the AC voltage. CONSTITUTION:A counter electrode 6 having a closed shape so that the electrode can be free from an induced voltage from a developing sleeve 3 is provided facing to a detection electrode 4. Then, by applying an AC voltage to the counter electrode 6 and detecting the voltage induced corresponding it, the quantity of toner interposing the electrodes 6 and 4 is detected. Therefore, it can be detected surely and accurately without receiving any influences from a developing sleeve side that the remaining quantity of the toner becomes less.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an improvement of a developing device of an image forming apparatus such as a copying machine, a laser beam printer, or a facsimile machine, and more specifically, to an improvement of a developing device of an image forming apparatus such as a copying machine, a laser beam printer, or a facsimile machine. The present invention relates to a developing device.

[Prior art]

FIG. 8 shows a developing device of a general electrostatic type AZIF image forming apparatus. In f51, toner is stored in the developing tank 52, and by rotating the developing sleeve 53 within the developing tank 52, the toner adhering to the outer peripheral surface of the gA@sleeve 53 is removed onto the photosensitive drum 58 outside the developing tank 52. The toner is transported to an electrostatic layer image developing section of the photosensitive drum 58 outside the developer tank 52, and the toner is transferred to the electrostatic latent image on the photosensitive drum 58.
A toner image is formed on the photosensitive drum 58.

This figure shows a type of developing device 5 in which the amount of toner is regulated by a doctor blade 62 pressed against a developing sleeve 53.
1 is shown. The stirring rod 55 functions to uniformly stir the toner and prevents the formation of cavities and toner clumps within the toner.

In the developing device 51, the amount of toner is detected by detecting the induced voltage induced in the detection electrode 54 by the alternating current voltage applied to the developing sleeve 53, which is a conductive material.

Therefore, as shown in this figure, the detection electrode 54 for detecting toner is provided near the bottom of the developer tank 52, which is suitable for extracting the toner Ta that is running low as accurately as possible.

[Problem to be solved by the invention]

Broken lines a, b, and c shown in FIG. 8 structurally indicate lines of electric force generated between the developing sleeve 53 and the detection electrode 54 due to the alternating current voltage applied to the developing sleeve 53. In this case, most of the electric lines of force are not affected by the toner Ta as shown in c, but some electric lines of force pass through the toner Ta as shown in a, and as a result, the toner Ta
affected by Therefore, the induced voltage induced in the detection electrode 54 by the AC voltage applied to the developing sleeve 53 is caused by the presence of the electric force lines a, which causes the toner to reach the developing tank 54.
The value is almost the same as when the value is sufficiently within.

Therefore, the conventional method has a limit in accurately detecting the state shown in FIG. 8 where the amount of toner remaining in the developer tank 52 is low.

Therefore, it is an object of the present invention to provide a developing device capable of solving the problems of the prior art described above.

[Means to solve the problem]

In order to achieve the purpose described above, the present invention has been developed in accordance with 1J! A detection electrode is provided near the bottom of @v, and an alternating current voltage is applied to the sleeve provided inside the developer tank, and at the same time, the toner in the developer tank is stirred by a stirring means! lf! In the developing device, a counter electrode having a shape that shields the detection electrode from the influence of the induced voltage from the developing sleeve is provided opposite to the detection electrode, and an alternating current voltage is applied to the counter electrode. The amount of toner interposed between the counter electrode and the protruding electrode is detected by applying the voltage and detecting the induced voltage of the detection electrode correspondingly induced. In addition, in order to avoid the influence of external disturbances, a detection electrode is provided near the bottom of the developer tank, and an AC voltage is applied to the developing sleeve provided in the developer tank. Along with applying
In a developing device in which the toner in a bipedal developing tank is stirred by a stirring means, a counter electrode having a shape that shields the detection electrode from being affected by the induced voltage from the developing sleeve is provided with a counter electrode configured to The toner interposed between the counter electrode and the detection electrode is detected by applying an alternating current voltage to the counter electrode and detecting the induced voltage of the detection electrode correspondingly induced. The developing device is configured as a developing device that is provided with a shield plate that is configured to detect the quantity and to block the detection electrode, facing the counter electrode with the detection electrode in between.

[Effect]

In the developing device configured as described above, as the amount of toner is consumed, the toner between the counter electrode and the detection electrode also decreases reliably, and eventually disappears completely at fL (7), and the induced voltage between By measuring the amount of toner, the absence of toner can be accurately detected.

Moreover, the counter electrode has a shape that blocks the detection electrode, and as a result, the AC fL voltage applied to the developing sleeve has almost no effect on the detection electrode.

Further, by using a shield plate shaped to shield the detection electrode, for example, the influence of disturbances from outside the machine can be eliminated.

〔Example〕

Hereinafter, embodiments embodying the present invention will be described with reference to the accompanying drawings to provide an understanding of the present invention.

The following examples embody the present invention and are merely examples, and are not intended to limit the technical scope of the present invention.

FIG. 1 is a schematic cross-sectional view of a developing device according to an embodiment of the present invention, FIG. 2 is a toner empty detection circuit diagram of the developing device,
Fig. 3 is a waveform diagram showing the signal waveform of each element in the circuit diagram shown in Fig. 2, and Fig. 4 (fat 5 peaks) shows changes in the toner detection signal and changes in the toner empty signal in the same circuit diagram. Fig. @5 is a flowchart showing the operation of the toner empty LED in the U path diagram, Fig. 6 is a perspective view of a portion showing the counter electrode etc. of the developing device, and Fig. 7 is a schematic cross-sectional view of the same portion. .

The developing device 1 according to this embodiment will be explained with reference to FIG. 1, FIG. 6, and FIG. 7. The developing device 1 is of a type that supplies minute amounts of toner T from the developing sleeve 3 to the photosensitive drum 8 using a so-called jumping phenomenon. The doctor pad 12 is pressed against the developing sleeve 3 and is rotated by the rotating developing sleeve 3.
The amount of toner conveyed to the developing section between the photosensitive drum 8 and the photosensitive drum 8 is regulated.

Further, a stirring means 5 is provided inside the developing device 1112. The stirring means 5 constantly stirs the toner contained in the developer tank 2 in order to prevent the toner from solidifying or to prevent the formation of cavities in the toner. 6 and 7 show the stirring means 5 and the detection electrode 4. The mounting positional relationship of the counter electrode 6 is shown, and the stirring bar 5. is attached so as to pass between the picture electrodes.

The stirring rod 51 is rotatably supported around a fulcrum 5c attached to a central shaft 5. When the central shaft 5c is rotated as shown by arrow X by a drive motor (not shown), the stirring rod 5. moves to the birch (not shown by arrow Y) and stirs the toner.

Further, in FIG. 1, the detection electrode 4 is provided near the bottom of the developer 12, which is suitable for accurately detecting the toner T that is running low, as shown in the figure.

In this embodiment, the developing sleeve 3 is a conductor and is applied with an alternating current voltage for jumping control and the like.

(FIG. 3(A)) Then, facing this detection electrode 4,
A counter electrode 6 is provided on the side facing the developing sleeve 3 and has a shape that shields the detection electrode 4 from being affected by the induced voltage from the developing sleeve 3. This counter electrode 6
The AC voltage is applied in parallel to the developing sleeve 3.

Furthermore, in order to prevent the detection electrode 4 from being affected by external disturbances, a grounded shield plate 7 is installed in the developing tank 2 and has a shape that blocks the detection electrode 4 and is opposite to the counter electrode 6 with the detection electrode 4 in between. It is installed along the inner surface of the case song.

Next, the circuit shown in FIG. 2 and its operation will be explained using FIG. 2.3.4.5.5 When the AC voltage shown in FIG. In response to the alternating current signal induced in the detection pole 4, an alternating current signal as shown in FIG. 3(B) is generated at point B in FIG.

The amplitude of the waveform of this AC signal B is determined by the counter electrode 6 detection electrode 4
This represents the size of the capacitance of the capacitor formed by the amount of toner between the picture electrodes 4 and 6. Therefore,
Toner detection signal C obtained through peak hold circuit 9
is as shown in FIG. 3(C), and its value is related to the amount of toner between the detection electrode 4 and the counter electrode 6.

When there is sufficient toner in the developer tank 2, the space between the detection electrode 4 and the counter electrode 6 is filled with toner, and the capacitance is large. Therefore, the toner detection signal C shows the value of α shown in FIG. 4 (dark).

The toner T in the developer tank 2 is consumed due to the continuation of image processing, and there is little left (then, air 1'WAR shown in FIG. 1 is formed between the detection electrode 4 and the counter electrode 6, and the toner is further consumed. As a result, toner is no longer present between the detection electrode 4 and the counter electrode 6.

Therefore, the detection electrode 4 and the opposing electrode 1! All lines of electric force between the winding 6 and the winding 6 come to pass through this air layer AR.

Therefore, the capacitance between the detection electrode 4 and the counter electrode 6 is
It will suddenly become smaller due to the influence of this air 1iAR, so
The moment the air ff1AR is generated, the toner detection signal C suddenly becomes smaller and reaches the value of β shown in FIG. 4 (at).

Therefore, the appropriate threshold level signal vth as shown in Figure 4) and the toner detection signal C are input to the comparator 1.
0, and when the toner detection signal C falls below the threshold level signal vth, the toner empty signal Tamp is input to the microcomputer CPU.

FIG. 4(b) shows such a toner empty signal Tam.
A waveform diagram of p is shown.

When the microcomputer CPU receives such a toner empty signal Tamp, it lights up a toner empty LED made of a light emitting diode or the like according to the flowchart shown in FIG. 5 to prompt the operator to replenish toner.

Therefore, by using the above-described developing device 1, it is possible to rapidly change the toner detection signal C according to the degree of toner consumption, so that it is possible to accurately detect that the amount of toner remaining is low.

In addition, since the stirring means 5 stirs the toner by passing the stirring rod 51 between the detection electrode 4 and the counter electrode 6, the detection electrode 4
It is possible to prevent bridging caused by toner between the electrode 6 and the counter electrode 6, and when there is little toner remaining, the toner is uniformly stirred, so that the effect of reliably creating an air tank AR is brought about.
Note that the structure of the stirring means 5 is not limited to the above case.

In the above embodiment, the AC voltage applied to the developing sleeve 3 was applied in parallel to the counter electrode 6, but the AC voltage applied to the counter electrode 6 may be separately provided and can be selected arbitrarily.

However, if they are connected in parallel as described above, a separate AC voltage source can be omitted, resulting in cost reduction.

Moreover, since the counter electrode 6 has a shape that blocks the detection electrode 4, the detection electrode 4 is hardly affected by the AC voltage applied to the developing sleeve 3.

Furthermore, by using the shield plate 7, the detection electrode 4 is no longer affected by disturbances. Examples of disturbances include transformers, clutches, and other electrical components provided within the main body of the image forming apparatus, as well as influences from metal desks and large components outside the apparatus.

Furthermore, if the detection electrode 4 is formed into a loop shape to provide directivity, the amount of toner can be detected with high sensitivity.

In the above embodiment, the present invention was applied to a so-called jumping type image forming apparatus, but the present invention can of course also be applied to an image forming apparatus of a type in which a magnetic brush is formed by a so-called inspection plate. It is.

〔Effect of the invention〕

According to the present invention, a detection electrode is provided near the bottom of the developer tank, and an alternating current voltage is applied to the developing sleeve provided in the developer tank, and the toner in the developer tank is stirred by a stirring means. In the developing device, a counter electrode having a shape that shields the detection electrode from being influenced by the induced voltage from the development sleeve is provided opposite to the detection electrode, and an alternating current voltage is applied to the counter electrode, The developing device is characterized in that the amount of toner interposed between the opposing pole 1 and the detecting electrode is detected by detecting the induced voltage of the detecting electrode that is generated in response to this. is provided. Therefore, it is possible to reliably and accurately detect the state in which toner is low without being affected by the developing sleeve side. Furthermore, if a shield plate having a shape that shields the detection electrode is used in addition to the development device, the detection electrode will not be affected by disturbances.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of a developing device according to an embodiment of the present invention, FIG. 2 is a toner empty detection circuit diagram of the developing device,
Fig. 3 is a waveform diagram showing the signal waveform of each element in the circuit diagram shown in Fig. 2, and Fig. 4 +a+, peak) is a waveform diagram showing changes in the toner detection signal and toner empty signal in the same circuit diagram. , FIG. 5 is a flowchart showing the operation of the toner empty LED in the same circuit diagram, FIG. 6 is a perspective view of a portion showing the counter electrode etc. of the same developing device, FIG. 7 is a schematic cross-sectional view of the same portion, and FIG. 8 is a schematic cross-sectional view of a conventional developing device. [Explanation of symbols] 1...Developing device 2...Developing tank 3...Developing sleeve 4...Detecting electrode 5...Stirring means 6...Counter electrode 7...Shield plate.

Claims (1)

[Claims] 1. A detection electrode is provided near the bottom of the developer tank, and an AC voltage is applied to a developing sleeve provided in the developer tank, and the toner in the developer tank is stirred by a stirring means. In the developing device, a counter electrode having a shape that shields the detection electrode from the influence of induced voltage from the development sleeve is provided opposite to the detection electrode, and an alternating current voltage is applied to the counter electrode. The developing device is characterized in that the amount of toner interposed between the counter electrode and the detection electrode is detected by applying a voltage and detecting the induced voltage of the detection electrode correspondingly induced. . 2. A developing device in which a detection electrode is provided near the bottom of the developer tank, and an alternating current voltage is applied to a developing sleeve provided in the developer tank, and the toner in the developer tank is stirred by a stirring means. A counter electrode having a shape that shields the detection electrode from being influenced by the induced voltage from the developing sleeve is provided opposite to the detection electrode, an alternating voltage is applied to the counter electrode, and an alternating current voltage is applied to the counter electrode. By detecting the induced voltage of the detection electrode correspondingly induced, the amount of toner interposed between the counter electrode and the detection electrode is detected, and the toner located opposite to the counter electrode with the detection electrode in between is detected. . A developing device characterized in that a shield plate is provided in a shape that shields the detection electrode so as not to be affected by external disturbances.