JPH03261980A - Toner density controller for electrophotographic device - Google Patents

Abstract

PURPOSE:To maintain an optimum printing density at all times even if temperature or humidity varies by performing calculating processes for the temperature and humidity compensation of the output voltage value of a toner density detector and the temperature and humidity compensation of toner density-printing density characteristics with a central processing unit and controlling the supplementary amount of toner. CONSTITUTION:The detection signals from the toner density detector 7 and a temperature and humidity detector 8 are led to the central processing unit 9, which corrects the signals and then sends a control signal to a toner supplementing device 2, thereby adjusting the supplementary amount of toner from a hopper unit 1. When the temperature or humidity is different, print density indicates a different value in the relation between toner density and printing density even if the toner density is equal, so the data on them are found previously by experimentation and stored in the central processing unit 9. Consequently, even if the temperature or humidity veries, the optimum printing density can be maintained at all times.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a toner concentration control device for an electrophotographic device using a two-component powder developer consisting of a mixture of magnetic carrier and toner.

Conventional technology Two-component powder developer made of a mixture of magnetic carrier and toner has a toner concentration that decreases as printing is performed, so toner must be replenished one after another.

In general, the developing device in this type of electrophotographic apparatus consists of a developing unit and a hopper unit that supplies toner to the developing unit, and a toner replenishing device installed in the hopper unit to maintain a constant toner concentration in the developing unit. The structure is such that the required amount of toner is replenished to the developing unit each time so that it is within the range. In order to maintain the toner concentration inside the developing unit at a predetermined value, it is necessary to detect the toner concentration inside the developing unit. A method of detecting concentration was used. As a specific detection device, a magnetic circuit having a magnetic core wound with a primary coil and a secondary coil having a gap near the developer or in the developer has been used.

When the toner in the developer is consumed and the composition ratio of toner to magnetic carrier in the developer changes, the magnetic permeability of the developer changes. Therefore, since the magnetic permeability in the magnetic circuit gap changes, the coupling coefficient between the primary and secondary coils changes. The change is extracted as a voltage value change. The output voltage value is then input to the central processing unit and compared with a preset control reference (voltage) value.

If a value below the control reference value is detected here, it is determined that the toner concentration of the developer is necessary and sufficient, and as printing progresses, the toner concentration decreases until the detected value becomes larger than the reference value. If a value larger than this value is detected, it is determined that the toner concentration is low, and a command is given to the toner replenishing device to replenish toner, and printing is temporarily interrupted.

Such a toner concentration detection device has a problem in that the detection signal is affected by changes in the external environment such as temperature and humidity, and the output signals obtained are different even when the toner concentration is the same. On the other hand, a toner concentration detection device has been proposed that uses two magnetic circuits to compare each output signal and output a signal that compensates for the effects of temperature and humidity.
(See Publication No. 0814).

Problems to be Solved by the Invention However, the relationship between the toner concentration in the developing unit and the print density of characters and images finally printed on paper is also a function of temperature and humidity, and the relationship between the toner concentration in the developing unit and the print density of characters and images finally printed on paper is also a function of temperature and humidity. In this case, the optimum toner density will be a different value. Therefore, it is difficult to always maintain an optimum print density by simply maintaining a constant toner density as in the conventional apparatus described above.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a toner density control device for an electrophotographic apparatus that always maintains optimum print density even when temperature and humidity conditions vary.

Means for Solving the Problems In order to achieve the above object, the present invention includes a toner concentration detecting device as in the prior art, but also includes a central processing unit for signal processing, and at the same time, the internal processing of an electrophotographic apparatus. A temperature and humidity detection device (hereinafter referred to as temperature and humidity detection device) is provided near the developing device, and information signals regarding temperature and humidity are transmitted from the center.

Function: The present invention has the above-described configuration; the toner concentration detection signal is processed based on the information regarding the environment in which the electrophotographic apparatus is installed, which is obtained by the temperature/humidity detection device, and necessary correction processing is performed. , the central processing unit issues an optimal toner replenishment signal, making it possible to maintain optimal print density at all times.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to FIGS. 1 to 3.

As shown in FIG. 1, toner loaded into a hopper unit 1 is supplied to a developing unit 3 while being controlled by a toner replenishing device 2 of the hopper unit 1. In the developing unit a, the toner is stirred and mixed with a magnetic carrier and charged, and an electrostatic latent image on the photoreceptor drum 6 is developed by a magnetic brush 6 formed on a rotating magnet roller 4. The developing unit 3 is provided with a toner concentration detection device 7 and a temperature/humidity detection device 8 . Toner concentration detection device 7
The detection signals from the temperature and humidity detection device 8 are guided to the central processing unit 9. After signal correction processing is performed in the central processing unit 9, a control signal is sent to the toner replenishment device 2, and the amount of toner replenishment from the hopper unit 1 is adjusted. The relationship between the toner concentration in the developing unit 3 and the output signal of the toner i concentration detection device 7 is represented by a characteristic curve as shown in FIG.

As shown in the figure, when the temperature and humidity are different, the output signal of the toner concentration detection device 7 shows different values even if the toner concentration is the same. The relationship between toner density and print density is shown by a characteristic curve as shown in FIG. 3, and if the temperature and humidity are different, the print density will show different values even if the toner density is the same.

Data on these characteristic curves are obtained in advance through experiments and stored in the central processing unit 9.

Assume now that the output signal voltage of the toner concentration detection device 7 is as shown in FIG. 2a. Temperature and humidity conditions are 72. If it is RH2, then curve A2 in FIG. 2 can be applied to the relationship between the output voltage and the toner concentration, and the toner concentration is represented by b. Under these temperature and humidity conditions, the relationship between toner concentration and print density is shown by the characteristic curve B2 in FIG. B2, and in this case, since the toner density is out of the optimum range b1-b2, the central processing unit 9 sends a replenishment signal to the toner replenishing device 2 of the hopper unit 1 until the print density reaches cl-C2. be done.

The toner replenishing device of the hopper unit 1 receives a signal sent from the toner concentration detector 7 to the central processing unit 9 until the toner concentration falls within the range al-B2 in FIG. 2, which corresponds to the range b1-b2 in FIG. A replenishment signal is sent to the hopper unit 1, and when the range is within this range, a stop signal is sent and toner replenishment from the hopper unit 1 is stopped. In this way, optimum print density is always maintained.

Effects of the Invention As is clear from the above embodiments, according to the present invention, in addition to the toner concentration detection device, the temperature and humidity detection device is provided, so the toner concentration detection device does not require a complicated structure, and the toner concentration detection device can be easily used. Accurate temperature and humidity correction processing is applied to the output voltage of the device, making it possible to always accurately detect toner density. At the same time, since the toner concentration that provides the optimum print density is calculated based on the characteristic curve corrected for temperature and humidity, the electrophotographic apparatus can always be operated at an appropriate print density even if the temperature or humidity changes. Furthermore, since the relationship among toner concentration, toner concentration detection device output voltage, print density, etc. is stored as data in the central processing unit, replacement is easy and learning functions can be easily added. Furthermore, even if the structure or specifications within the electrophotographic apparatus are changed, new conditions can be easily dealt with.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of the present invention, FIG. 2 is a characteristic curve diagram showing the relationship between the output voltage of the toner concentration detection device and toner concentration in an embodiment of the present invention, and FIG. 3 is a printed diagram of the same. FIG. 3 is a characteristic curve diagram showing the relationship between density and toner density. 1...Hopper unit, 2...Toner supply device, 3...Development unit, 6...
...Magnetic brush, 6...Photoreceptor drum, 7...
. . . Toner concentration detection device, 8 . . . Temperature and humidity detection device, 9., . 10. Central processing unit.

Claims (1)

[Claims] Central processing that performs temperature and humidity detection device and signal processing in the development device of an electrophotographic device that uses a two-component powder developer composed of magnetic carrier and toner and is equipped with a toner supply device and a toner concentration detection device. The toner concentration of an electrophotographic device is equipped with a central processing unit that controls the amount of toner replenishment by performing calculation processing for temperature and humidity compensation of the output voltage value of the toner concentration detection device and temperature and humidity compensation of the toner density-print density characteristic. Control device.