JPS6018064B2 - Toner concentration detection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for detecting toner concentration of a developer comprising a magnetic carrier and a non-magnetic toner used in a developing device of a copying machine.

Conventionally, as this type of toner concentration detection method, a method has been proposed in which the toner concentration of the developer is detected by passing a magnetic flux through the developer in a developing device and detecting the leakage magnetic field from the developer with a detector.

One method of implementing this method is to utilize a magnetic field generated by a permanent magnet in a Manette brush developing device as a magnetic field for passing magnetic flux through the developer. however,
This method targets the so-called DC magnetic field, so
It is necessary to use a sensitive element such as a Hall element as a detector to see the absolute value of its output, and fluctuations and dispersions in the DC level of the sensor can cause major problems and require complicated adjustment operations. . Further, the output of the detector is easily affected by the characteristics unique to each detector and the environmental conditions, and the detection accuracy is low. SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks and provide a toner concentration detection method with high detection accuracy in which direct current fluctuations and variations can be ignored.

An embodiment of the present invention will be described below with reference to the drawings. As shown in FIG. 1, a developer 1 made of a magnetic carrier and a non-magnetic toner is filled into an envelope 2 made of a non-magnetic material and formed into a fixed shape, and this fixed-shaped developer is the main material. AC magnet 3 is arranged so as to form a constant part of the magnetic path.

This AC magnet 3 is made of a coil and is wound around a core 4. Both end surfaces of the core 4 are joined to the outer surface of the outer envelope 2 on the left side in the figure, and a detector 5 using a magnetically sensitive element is arranged on the right side of the outer envelope 2 in the figure. Then, an alternating current is applied to the coil 3 from an alternating current power supply 6, and the developer 1 is passed from the coil 3 through the core 4.
When a constant alternating magnetic field is applied to the developer 1, the main magnetic flux Rm passes through the developer 1, and the leakage magnetic flux core 1 from the developer 1 is detected by the detector 5.
This leakage magnetic flux core IE appears in correlation with the toner concentration of the developer 1. Also, the coil 7 is an AC power source 8
An alternating current is supplied from the detector 5 to generate an alternating magnetic field having an opposite phase to the leakage magnetic flux JI, and a magnetic flux center r is applied to the detector 5. Therefore, the output of the detector 5 becomes zero when the magnitude of the magnetic flux R, Jr is equal, and the magnetic flux Jr from the coil 7 becomes equal to the magnitude of the leakage magnetic flux 1 when the toner concentration of the developer 1 is the appropriate reference toner concentration. is set so that the output of the detector 5 becomes zero. As a result, the toner concentration of the developer 1 is detected using the zero-level method based on the appropriate toner concentration, and the output of the detector 5 indicates whether there is excess or insufficient toner in the developer 1 and the toner concentration is higher than the reference toner concentration. Or, depending on whether the signal is low or not, a signal of normal phase or reverse phase is obtained. That is, the toner concentration of the developer 1 is higher than the proper toner concentration if the output from the detector 5 is in the same phase as the magnetic field applied by the coil 3, and is lower than the proper toner concentration if the output is in the opposite phase.
If it is zero, the toner density is appropriate. When automatically controlling the toner concentration of the developer in the developing device of a copying machine, there is no need to know the absolute value of the toner concentration of the developer, but it is necessary to know whether the toner concentration of the developer is lower than the appropriate toner concentration. It is sufficient to simply detect it, and to implement it, the output of the detector 5 may be synchronously detected.

FIG. 2 shows an example in which the present invention is applied to an automatic toner density control device in a developing device of a copying machine. In this example, in the above embodiment, the developer 1 is made of the developer used in the developing device of the copying machine, and the developer in the developing device is the developer in the outer container 2.
The toner concentration is constantly detected. The oscillation output of the oscillator 9 is amplified by an amplifier 10 and is supplied as the output of the AC power supply 6 to an AC magnetic field generator comprising the coil 3. The output of the oscillator 9 is phase-adjusted by a phase adjustment circuit 11, the output level is adjusted by an output adjustment circuit 12 according to a desired reference toner concentration, and the output is supplied as an output of an AC power source 8 to an inverse magnetic field generator made up of a coil 7. be done. The output of the detector 5 is amplified by the amplifier 13, and synchronously detected by the output of the oscillator 9 in the synchronous detection circuit 14. The toner concentration of the developer 1 is lower than the appropriate toner concentration and the toner in the developer 1 is insufficient. is detected. A toner replenishment mechanism 15 in the developing device is driven by the output of the synchronous detection circuit 14, replenishes toner to the developer 1, and controls the toner concentration of the developer 1 to an appropriate toner concentration. As described above, according to the toner concentration detection method according to the present invention, a fixed portion of the main magnetic path is formed by the developer used in the developing device, and an alternating current magnetic field is applied to the developer by an alternating current magnet, thereby reducing magnetic flux leakage from the developer. Since it detects the AC magnetic field, it is possible to exclude the DC component, which has been a problem in the past, and process it, making adjustment operations easy.

Furthermore, since a predetermined anti-phase alternating current magnetic field is applied to the detector and the toner concentration is detected using the zero-level method, the characteristics and variations of the detector can be ignored in principle, and high-precision detection can be performed. .

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention, and FIG. 2 is a block diagram showing an example of application of the present invention. 1...Developer, 3...Coil, 4...
... Core, 5 ... Detector, 6 ... AC power supply, 7 ... Coil, 8 ... AC power supply. Rare illustration Rare illustration 2

Claims (1)

[Claims] 1. In a developing device that uses a developer consisting of a magnetic carrier and non-magnetic toner, the developer forms a certain part of the main magnetic path, an AC magnet applies an AC magnetic field to the developer, and magnetic flux leakage from this developer is suppressed. A detector detects the toner, and an alternating magnetic field having an opposite phase to the leakage magnetic flux is applied to the detector, and the intensity of the alternating magnetic field is compared with the leakage magnetic flux, and the developer of the reference toner concentration is detected by the detector. A method for detecting toner concentration, characterized in that the output of the toner concentration is set to zero, and a signal is obtained from the detector according to the level of toner concentration of the developer with respect to the reference toner concentration.