JPS5926024B2 - developing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a developing device such as a copying machine or a printer that uses a magnetic developer, and more particularly to a detection device that detects the level of the developer.

Devices that develop electrostatic images using magnetic developers, especially single-component developers whose toner itself is magnetic, use the so-called two-component developer method, which consists of a conventional magnetic carrier and toner. The image quality of the developed image is greatly affected and the mixing ratio must be constantly controlled. However, since this problem is eliminated, there is an advantage that the apparatus and maintenance are extremely simple.

However, considering the size of the apparatus, it is natural that the developer container needs to be replenished as the developer is consumed.

Incidentally, conventionally, the presence or absence of developer has been determined by monitoring the state of the developed copy.

In other words, if there is no developer in the developing device due to developer consumption, the object to be developed will not be developed, and in the case of copying machines, the lack of developer will be detected by the fact that a white sheet of paper that has not been copied will come out. Know. On the other hand, compared to the two-component developer method, the positional relationship between the tip of the magnetic brush and the object to be developed with the dead-component developer requires precision, and the height of the magnetic brush tip due to lack of developer A small change in the developed image quality will change greatly, so the image quality will gradually deteriorate like in the two-component developer method, and it will be difficult to replenish the developer by looking at the degraded image. This was especially inconvenient when a large number of sheets were being automatically developed.

Therefore, it has been desired to know when to replenish developer by detecting the amount of developer in a developer container of a developing device.

However, since the one-component developer is a lightweight fine powder, it is difficult to use mechanical displacement such as a lever.

Furthermore, since it is a magnetic material, detection using a Hall element is also considered, but accurate detection is difficult because it is affected by the fluctuating magnetic field caused by the rotation of the magnet roll, which is a magnetic carrier.

Furthermore, a method of detecting changes in the dielectric constant due to the presence or absence of developer has been considered, but this method has the drawback that the dielectric constant of the developer is low and the detection accuracy is low due to changes in humidity.

Furthermore, by using a resonant circuit consisting of a coil placed in the developer in the replenishment developer container and a capacitor, the remaining amount of replenishment developer is converted into a change in inductance due to its disappearance into a change in resonance frequency. (Unexamined Japanese Patent Publication No. 1983
-87655) has also been proposed. However, this method detects the remaining amount of replenishment developer from changes in the resonance frequency, so in addition to the resonance circuit as an oscillator, other resonance circuits and auxiliary oscillators are required, resulting in a large number of parts and a complex configuration. There was a drawback. SUMMARY OF THE INVENTION An object of the present invention is to provide a developing device capable of detecting the level of a one-component developer with high accuracy using a simple configuration, while eliminating the drawbacks of the prior art described above.

To achieve this object, the present invention provides a detection coil having two coil elements provided at the lower part of a developer container and whose mutual inductance changes depending on the amount of developer in the developer container; and an anti-coupling oscillation circuit configured to change between an oscillating state and a non-oscillating state according to a change in the mutual inductance with a change in the amount of the developer, and the anti-coupling oscillating circuit has an oscillation output. According to the invention, the amount of developer in the developer container is detected. Hereinafter, the present invention will be explained in detail based on the drawings. FIG. 1 is a sectional view of a developing device according to an embodiment of the present invention, FIG. 2 is a view along arrow P showing a portion where the detection unit of FIG. 1 is attached, and FIG. 3 is a detailed sectional view of the detection unit. In these figures, 1 is the side plate,
Reference numerals 2 and 3 denote first and second panels that act as supply guide plates, and these constitute a developer container having a discharge port at the bottom.

4 is a spacer for correctly assembling the side plate 1 and the panels 2 and 3; 5 is a developer; the amount of developer 5 discharged from the developer container is controlled by the supply regulating end surface 3a at the lower end of the second panel 3; Therefore, it is regulated.

Reference numeral 6 denotes a roll magnet for conveying the developer 5, which is supported by the side plate 1 so as to be rotatable in the direction of the arrow in FIG.

Reference numeral 7 denotes a non-magnetic sleeve, which is supported by the roll magnet 6 so as to be rotatable in the opposite direction to the roll magnet 6.During the development process, the sleeve 7 and the roll magnet 6 are driven in the rotational direction shown in FIG. be done.

Reference numeral 8 denotes a magnetic brush formed on the surface of the sleeve 7 by the aforementioned rotation, and the lower part of the brush 8 is brought into contact with an electric latent image holder (not shown) for development.

The height of the ears of this magnetic brush is regulated by the ear height regulating end surface 2a at the lower end of the first panel 2. 9 is a developer level detection unit according to this embodiment.

Reference numeral 10 denotes a coil unit, which includes three independent coils 10a, 10b, 10a, 10b, and 10b wound concentrically in a flat oblong shape in order to averagely detect the developer level in the container.
It consists of 10c.

When the second panel 3 is made of a metal material such as aluminum, the coil unit 10 section is arranged as shown in FIG. 2 so that a closed conductor loop is not formed by the second panel 3 near the coil unit 10 section. As shown, it is desirable to install it in a notch 3b bored in the lower end of the second panel 3. A circuit board 9a includes a circuit unit 9b.

9c is a terminal.

The detection unit 9 is constructed as described above, and each component is integrally molded from resin 9d. 11 is a control plate, and 12 is a set screw, by means of which the detection unit 9 and control plate 11 are attached to the second panel 3.

As shown in FIG. 2, the control board 11 has one side 1 on the coil side.
1a is inclined with respect to the coil unit 10, and its mounting position can be adjusted with respect to the coil unit 10 by means of an elongated hole 11b.

; The slope of the side 11a is a shape to make the change in the electromagnetic induction relationship with the coil unit 10 gentle with respect to the positional displacement of the control board 11, and it goes without saying that the side 11a does not have to be a straight line. . Furthermore, the material of the control plate 11 is preferably made of a conductive member such as a metal, and is particularly preferably made of a non-magnetic material such as aluminum or copper which is not subjected to the magnetic induction of the roll magnet 6 for reasons described later. FIG. 4 shows another example of the detection unit 9, in which, instead of the control board 11,
A control screw 13 made of a conductor, preferably a non-magnetic conductor, is attached to the coil unit 10 through a screw hole 14 in an inclined manner so that its displacement can be adjusted. Furthermore, when the second panel 3 is made of a conductor such as aluminum, such a control plate 11 and control screws 13
Even without providing the coil unit 9, the same effect can be obtained by making the mounting position of the detection unit 9 adjustable and changing the relative position between the coil unit 10 and the second panel 3.

FIG. 5 shows a specific circuit example of the detection unit.

The coils 10a and 10b are connected to capacitors Cl and C2 as shown in the figure.
, C3, resistors Rl, R2, R3 and transistor Q1
This constitutes an anti-coupling oscillation circuit. If the developer 5 is present near the coil unit 10 as shown in FIG.
Since the developer 5 is a magnetic material, the coupling between the coils 10a and 10b is large, resulting in an oscillating state. Furthermore, if the developer 5 is not present near the coil unit 10, the coupling is rough and no oscillation occurs. The oscillation conditions basically change depending on the presence or absence of magnetic developer powder near the coil unit, but the oscillation conditions usually change depending on the characteristics of the circuit components including the coil, the type of developer, etc. 10, it is not clear to what position the developer 5 will run out to cause oscillation or not.

That is, the detection accuracy becomes unclear. Such problems can be dealt with by adjusting the detection level using the control plate 11 or the control screw 13. Control board 1
1, when the material of the control plate 11 is a magnetic material with low loss such as ferrite, the coils 10a and 10b are loosely coupled, and the control plate 11 is
By adjusting the positions of the coil unit 10 and the coil unit 10, the desired detection level can be adjusted.

In addition, when a conductor with a large loss due to electromagnetic induction, that is, a general metal material is selected as the material for the control board 11, the coils 10a and 10b are tightly coupled in advance, and the control board 11 is By controlling the amount of loss through position adjustment, the detection level can be adjusted.
This principle also applies to the control screw 13.

Further, in the coil unit 10 of this embodiment, since the coil is oval, it is possible to detect an average level over a certain length.

Note that when the detection level of the developer 5 is selected at a low level, that is, at a location close to the roll magnet 6, it is advantageous for the control plate 11 and the control screw 13 to be made of non-magnetic material.

That is, if the control member is made of a magnetic material, the control member is guided by the roll magnet 6, and the flow of the developer is obstructed. Returning to FIG. 5 again, the coil 10c is the coil 1
The coil is transformer-coupled with an anti-coupling oscillation circuit including 0a via coil 10a, and during oscillation, it is rectified by diode D1 and smoothed by capacitor C4, and the voltage of capacitor C4 fluctuates depending on the presence or absence of oscillation.

An amplifier circuit is constituted by resistors R4, R5, R6 and transistors Q2, Q3, and the output is transmitted through the resistors,
The light emitting diode 15 is added to indicate the presence or absence of developer. In the illustrated example, the system lights up to indicate when the developer level falls below a certain level, but this signal is not limited to just the display, but also causes the entire system, including the developing device, such as a copying machine, to come to a standby stop, for example. Of course, this can be controlled. In the figure, 16 is a power supply for operating the detection unit. As explained above, according to the present invention, since the anti-coupling oscillation circuit which oscillates and non-oscillates due to the change in the mutual inductance of the two coil elements as the amount of developer changes, the oscillation circuit itself also serves as a level determination (oscillation state→level high, non-oscillation state→level low), so the output of the oscillation circuit becomes the level determination result, and the configuration is simple. In addition, since the magnetic action of the developer acts on the positive feedback loop, this action is amplified and determines whether or not the oscillation circuit oscillates. Therefore, the operation of the oscillator circuit responds sensitively to changes in the level of the developer and is detected. Accuracy will not be high.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a developing device according to an embodiment of the present invention, FIG. 2 is a view along arrow P showing the mounting portion of the detection unit in FIG.
FIG. 3 is a detailed sectional view of the detection unit, FIG. 4 is a detailed sectional view showing another example of the detection unit, and FIG. 5 is an electric circuit diagram of the detection unit. 1... Side plate, 2, 3... Panel, 3a
...Notch, 5...One-component developer, 6
...Roll magnet, 7...Sleeve, 9
...Detection unit, 10...Coil unit, 10a-10c...Coil, 11...
...Control board, 13...Control screw.

Claims (1)

[Scope of Claims] 1. A one-component dry developer that integrates a magnetic material and a toner;
A developing device includes a developer container that stores the developer, and conveys the developer from the developer container to a surface to be developed by a magnetic conveyance means to develop the surface to be developed. A detection coil is provided at the bottom of the developer container and has two coil elements whose mutual inductance changes depending on the amount of developer in the developer container. An anti-coupling oscillation circuit configured to change between an oscillating state and a non-oscillating state according to a change in mutual inductance, and depending on the presence or absence of an oscillation output of the anti-coupling oscillating circuit, the amount of developer in the developer container is changed. A developing device characterized by detecting the amount. 2. The developing device according to claim 1, wherein the detection coil has a flat shape and forms a part of a developer container. 3. Claim 2 is characterized in that the replenishment guide plate of the developer container is made of a non-magnetic metal plate having a notch at its lower end, and the detection coil is disposed in this notch. A developing device. 4. In claim 1, a conductor is movably provided near the detection coil, and the mutual inductance of the detection coil is adjusted by moving the conductor relative to the detection coil. A developing device characterized by: 5. The developing device according to claim 4, wherein the conductor is made of a non-magnetic material. 6. In claim 1, a magnetic body is movably provided near the detection coil, and the mutual inductance of the detection coil is adjusted by moving the magnetic body relative to the detection coil. A developing device characterized by: