JPS6377069A - Bias developing device - Google Patents

Abstract

PURPOSE:To perform excellent bias development at all times by detecting a current which flows through a developer layer with constant thickness by a bias voltage at all times and controlling the bias voltage so that the current has a desired current value. CONSTITUTION:A developer is attracted and conveyed by a magnetic roll 4 and passes between an electrode member 7 and the magnetic roll 4 and is controlled by a shaping member 5 to a prescribed conveyance quantity, thereby developing an electric latent image on a photosensitive drum 12 by the bias voltage 8 which is applied to the magnetic roll 4 and has the same polarity with toner electrostatic charging polarity. A current which flows to the electrode member 7 is detected and compared with an optional reference voltage 8 by a comparing device 10 to control the bias voltage 8 with the comparison output so that the current has an optional constant value. Consequently, a bias development effect is made constant and printing of excellent quality is carried out continuously with constant print density.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an electrophotographic bias developing device that is operated by applying one bias voltage to a two-component developer consisting of toner and a magnetic carrier. [Prior Art] In the magnetic brush development method in which bias development is performed using a two-component developer consisting of toner and a magnetic carrier in electrophotography, the life of the developer, that is, the deterioration of the developer is a major problem. The deterioration of the developer is caused by a phenomenon in which the toner is fused to the surface of the magnetic carrier, that is, the spent amount increases, the resistance of the magnetic carrier itself becomes high, and the frictional charging efficiency between the toner and the magnetic carrier decreases. Therefore, as the resistance as a developer increases, the bias current during bias development decreases, the bias development ability decreases, and the printing density becomes thinner. Conventionally, this problem has been dealt with by determining the lifespan of the developer empirically and replacing the developer, or by adjusting the bias voltage and increasing the bias current for each appropriate number of pages used. However, the lifespan of the developer is greatly affected by the operating conditions of the developing device, and it is not preferable to increase the bias current regardless of the degree of deterioration of the developer.

The above conventional technology uses a developer based on experience to deal with a decrease in bias development ability associated with toner and magnetic carrier. This was done without paying sufficient attention to the usage conditions and degree of deterioration of the developer, such as replacing the developer or adjusting the bias voltage according to the appropriate number of pages used. There was a problem.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and provide an electrophotographic bias developing device that can always perform good bias development.

[Means for solving problems]

The above object is to install electrode members at regular intervals opposite to a magnetic roll that conveys a developer to which a bias voltage is applied, and to generate a current that flows to the electrode member via the developer due to the bias voltage. This can be achieved by providing a resistor for converting the bias voltage into a voltage, and a comparator for controlling the bias voltage based on the comparison output with a reference voltage.

[Function] The present invention focuses on the fact that there is always a constant relationship between the degree of deterioration of the developer and the resistance of the developer. By constantly detecting the current and controlling the bias voltage so that the current reaches a desired current value, it is possible to always perform good bias development.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the drawings. FIG. 1 is a configuration diagram of a bias developing device according to an embodiment of the present invention.
FIG. 2 is a diagram showing the relationship between the number of pages of developer used and the current flowing through the developer, in which 1 is the developing device, 2 is the developer container, and 3
a two-component developer, 4 a magnetic roll, 5 a magnetic brush shaping member, 6 a developer scraping member, 7 an electrode member, 8
is a bias voltage, 9 is a resistor, 10 is a comparator, and 11 is a reference voltage. In this embodiment, the bias developing device 1 includes a developer container 2, a magnetic roll 4 for magnetically conveying the developer 3, a shaping member 5 for uniformly aligning the tips of the magnetic brushes, and a developer after development. 3 from the outer circumferential surface of the magnetic roll 4, and an electrode member 7 installed at a constant interval opposite the magnetic roll 4.The magnetic roll 4 is capable of voltage conversion. Bias voltage 8
is applied. Then, the bias voltage 8 is applied to the developer 3.
The current flowing through the electrode member 7 is converted into voltage by a resistor 9 and guided to a comparator 10. On the other hand, the comparator 10 includes:
A plurality of reference voltages 11 having different voltages, such as AlB, are connected.

In this configuration, the developer 3 is attracted and conveyed by the magnetic roll 4, passes between the electrode member 7 and the magnetic roll 4, is regulated to a predetermined conveyance amount by the shaping member 5, and is transferred to the photosensitive drum 12. The target latent image is developed using a bias voltage 8 having the same polarity as the toner charge polarity applied to the magnetic roll 4.

The developer 3 after development is scraped off from the top of the magnetic roll 4 by a scraping member 6, and falls to the bottom of the developer container 2.

If the bias voltage 8 is constant, the current flowing through the electrode member 7 is 1/7
'11 Nei Rika 1t total h knowledge Q M&I
F”;;卆 r ＾謔”Decreases as the number of oil field pages increases. Therefore, the bias development effect is reduced and the printing density becomes thinner.

However, the current flowing through the electrode member 7 is detected and the comparison device 10
By comparing with an arbitrary reference voltage 11 and controlling the bias voltage 8 so that the current returns to an arbitrary constant value with the comparison output, from K, the bias developing effect remains unchanged and at a constant printing density, Good quality printing can continue. Further, for example, if the printing density is to be increased, the reference voltage 11 can be switched to A, and if it be to be decreased, it can be switched to B, thereby making it easier to adjust the reference voltage 11 from K. Note that the reference voltage 11 may be operated by a continuously variable method instead of a switching method.

[Effects of the Invention] As explained above, according to the present invention, the bias voltage can be appropriately controlled according to the degree of deterioration of the developer, and good bias development can always be performed permanently. Can be done.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a bias developing device according to an embodiment of the present invention, and FIG. 2 is a diagram showing the relationship between the number of pages of developer used and the current flowing through the developer. DESCRIPTION OF SYMBOLS 1... Developing device, 3... Developer, 4... Magnetic roll, 7... Electrode member, 8... Bias voltage, engineering 0.
... Comparison device, 11... Reference voltage. Name of wheat flour Hitachi Koki Co., Ltd.rrn OzrfB

Claims (1)

[Claims] 1. A two-component developer consisting of toner and magnetic carrier,
In an electrophotographic bias developing device that is operated by applying a bias voltage, electrode members are installed at regular intervals opposite a magnetic roll that conveys the developer to which a bias voltage is applied. A resistor is provided to convert the current flowing through the electrode member through the developer into a voltage, and a comparison device is provided to control the bias voltage based on a comparison output with a reference voltage. Bias developing device.