JPH1020636A - Developing device for electrophotographic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce toner density fluctuation with respect to printing density so as to obtain stable printing quality by changing the plural reference levels of a comparator circuit for controlling the magnetic permeability of developer to be constant based on the plural reference level of the comparator circuit, the detection level of the magnetic permeability sensor and the information of a printing density measuring device measuring the replenishing amount of the toner. SOLUTION: The magnetic permeability inside the developer 3 is detected by the magnetic permeability sensor 7, and the detection level is compared with the two (third one and fourth one) of five reference levels of the comparator circuit 8. When the low printing density printing condition of 2% printing density is recognized by the printing density measuring device 11 measuring the toner replenishment amount while having a relation that the magnetic permeability detection level is equal to or below the third reference level and equal to or above the fourth reference level, the comparison of the third one and the fourth one out of the five reference levels of the circuit 8 is changed to the comparison of the second one and the third one. When the low printing density printing condition of 1% printing density is recognized, the comparison of the second one and the third one out of the reference levels is changed to the comparison of the first one and the second one out of the reference levels.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a developing device for an electrophotographic apparatus.

[0002]

2. Description of the Related Art A developer in which a toner, which is a powder ink, and a carrier that is frictionally charged with the toner are mixed at a certain ratio (hereinafter referred to as a toner concentration) is used for printing (photoconductivity). Developing the toner in the developer on the photosensitive member having the toner), the toner in the developer is consumed, and as a result, the toner concentration is reduced.

FIG. 7 shows the relationship between the magnetic permeability detection level of the developer, the five reference levels of the comparison circuit, the operation timing of the toner replenishing device, and the printing density in the printing state of the conventional electrophotographic apparatus. FIG. 8 shows the relationship between the print density, the toner density, and the print density according to the related art.

Conventionally, it is generally assumed that the printing density which is most frequently used by customers is about 4% ± 1%, and even when printing at a printing density of rarely about 8% or 15%, it is stable. In order to obtain print quality, the relationship between the toner replenishment amount and the level detected by the magnetic permeability sensor and a plurality of reference levels are determined from the correlation between the toner concentration and the developer magnetic permeability detection level.

[0005] Therefore, as shown in FIG. 8, a customer who rarely prints at a low print density of about 1% is
There has been a phenomenon that the triboelectric charge increases, the toner density decreases, and as a result, the print density decreases.

[0006]

FIG. 5 shows the relationship between the triboelectric charge amount and the developer magnetic permeability detection level according to the prior art when the toner concentration is constant. FIG. 6 shows the relationship between the toner density and the print density according to the prior art.

In the prior art, as described above, it is generally assumed that the printing density most frequently used by customers is about 4% ± 1%, and the printing density is rarely about 8% or 15%. In order to obtain stable print quality even when
From the correlation between the toner density and the developer magnetic permeability detection level as shown in FIGS. 5 and 6, the relationship between the toner supply amount and the level detected by the magnetic permeability sensor is determined based on a plurality of reference levels.

However, when printing at a print density of 3% or less, the amount of triboelectric charge changes as shown in FIGS. 5 and 6, and the toner density changes even with the same magnetic permeability.

FIG. 8 shows the relationship among print density, toner density, and print density according to the prior art.
Because it is proportional to the time that the toner is in contact with the carrier,
When the printing density is increased and the toner replenished from the toner hopper is present only for a short time in the developer, the triboelectric charge amount is reduced. , The amount of triboelectric charge increases.

Therefore, in the conventional developing technology of an electrophotographic apparatus, when the print density is higher than 4%, the amount of triboelectric charge is reduced, the toner density is increased, and the toner density is increased. However, as shown in FIG. 8, when the print density is low, the amount of triboelectric charge increases, the toner density decreases, and the print density decreases. Therefore, the print quality for low print density printing was not stable.

SUMMARY OF THE INVENTION An object of the present invention is to improve the toner density control by the conventional magnetic permeability sensor, to reduce the toner density fluctuation with respect to the print density, and to obtain a stable print quality as compared with the related art. To provide a developing device for an electrophotographic apparatus.

[0012]

The object of the present invention is to provide a plurality of reference levels of a comparison circuit for controlling the magnetic permeability of a developer to be constant, a detection level of a magnetic permeability sensor, and a toner replenishing amount (the number of replenishments, Or by changing a plurality of reference levels of the comparison circuit based on information of a print density measuring device for measuring the time.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, a developing device of an electrophotographic apparatus according to the present embodiment includes a toner 1, a carrier 2,
Developer 3, photosensitive drum 4, frame 5, developing roll 6, magnetic permeability sensor 7, comparison circuit 8, toner hopper 9,
The print density of the electrophotographic apparatus is recognized by a print density measuring device 11 configured of a toner replenishing device 10 and connected to a comparison circuit 8 for measuring a toner replenishment amount (replenishment frequency or time), as shown in FIG. Perform the operation.

FIG. 2 shows the relationship among the detection level of the developer magnetic permeability, the five reference levels in the comparison circuit, the operation timing of the toner replenishing device, and the printing density in the printing state of the electrophotographic apparatus in this embodiment.

The developer 3 in which the toner 1 and the carrier 2 are mixed at a certain ratio is used for developing the toner 1 in the developer 3 by a developing roll 6 held by a frame 5 to form a photosensitive drum. 4 is carried.

By printing, the toner 1 in the developer 3
Is consumed, the magnetic permeability in the developer 3 is detected by the magnetic permeability sensor 7 and two of the detected magnetic permeability detection level and the five reference levels of the comparison circuit 8 (third and fourth positions) are used. ), The magnetic permeability detection level is lower than the third reference level and higher than the fourth reference level, and the print density measuring device 11 that measures the toner supply amount from the relation shown in FIG.
If the low-density printing state of 2% printing density is recognized, the comparison between the third and fourth places in the five reference levels of the comparison circuit 8 is replaced with the comparison between the second and third places. When the print density measuring device 11 recognizes that the print density is low and the print density is 1%, the print density measuring device 11 compares the second and third places in the reference level with the first and second places. Change to

FIG. 3 shows the relationship among the print density, toner density, and print density according to the present embodiment. The magnetic permeability detection level detected by the magnetic permeability sensor 7 and the magnetic permeability of the developer 3 are controlled to be constant. For simultaneously comparing a plurality of reference levels of a comparing circuit 8 and a printing density measuring device 1
By recognizing the print density by 1 and changing the reference level of the comparison circuit 8, it is possible to secure an optimum toner density for each of the print densities that fluctuate during printing, that is, stable print quality.

[0018]

According to the present invention, it is possible to compensate for the drawbacks of the toner density control by the conventional magnetic permeability sensor, to reduce the toner density fluctuation with respect to the print density, and to stabilize the print quality as compared with the prior art. it can.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of a developing device for an electrophotographic apparatus according to the present embodiment.

FIG. 2 is a diagram illustrating operation timings of the electrophotographic apparatus according to the embodiment.

FIG. 3 is a diagram illustrating the relationship between print density, toner density, and print density according to the present embodiment.

FIG. 4 is a diagram illustrating the relationship between print density and the number of toner replenishments according to the present embodiment.

FIG. 5 is a diagram illustrating a relationship between a triboelectric charge amount and a developer magnetic permeability detection level according to the related art.

FIG. 6 is a diagram illustrating the relationship between toner density and print density according to the related art.

FIG. 7 is a diagram illustrating the operation timing of a conventional electrophotographic apparatus.

FIG. 8 is a diagram illustrating the relationship between print density, toner density, and print density according to the related art.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Toner, 2 ... Carrier, 3 ... Developer, 4 ... Photoreceptor drum, 5 ... Frame, 6 ... Development roll, 7 ... Magnetic permeability sensor, 8 ... Comparison circuit, 9 ... Toner hopper, 10 ... Toner supply device, 11 ... Print density measuring instrument.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Katsuhiro Shinohara 1060 Takeda, Hitachinaka-shi, Ibaraki Pref. Hitachi Koki Co., Ltd.

Claims (3)

[Claims] 1. A developer obtained by mixing a toner that is a powder ink, a carrier that frictionally charges with the toner, a magnetic permeability sensor that detects the magnetic permeability of the developer, and a detection level of the magnetic permeability sensor. A comparison circuit having a plurality of reference levels, and a toner replenishing device for replenishing the developer with consumed toner, wherein two adjacent reference levels among the plurality of reference levels and the magnetic permeability sensor A developing unit for an electrophotographic apparatus that changes the amount of toner supplied from a toner hopper to a developer based on the result of the determination, and further comprises a print density measuring device for measuring a toner replenishing amount. Wherein the reference level is changed according to the information of the developing device. 2. The developing device for an electrophotographic apparatus according to claim 1, wherein said print density measuring device is a print density measuring device for measuring a toner replenishing amount based on a toner replenishing time. 3. The developing device for an electrophotographic apparatus according to claim 1, wherein the print density measuring device is a print density measuring device for measuring a toner supply amount based on the number of times of toner supply.