JPH04204878A - Developing device - Google Patents

Abstract

PURPOSE:To eliminate the need for a toner concentration sensor by operating a toner replenishing means based on the result of a comparison between a reference current value generated from a reference current generator and a bias current value, thereby making the toner concentration constant. CONSTITUTION:During image formation, a bias voltage is applied to a magnet roller 3 from a bias circuit 11, and a bias current flows. The bias current is detected by a bias current detecting means 21. As the image formation is continuously carried out, toner is used; a bias current value is increased as the concentration of toner is developer is decreased. A current comparison means 23 compares this bias current value with a reference current value set by the reference current generator 22. Based on the result of the comparison, a signal is outputted to a toner replenishment operating means 24 so as to carry out toner replenishment. Thus, the need for the toner concentration sensor is eliminated, space can be saved, and costs can be reduced.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to one-time toner control in a developing device in an electrophotographic image forming apparatus.

[Conventional technology]

In a conventional developing device using a two-component developer, as shown in FIG. The interior is rotatable. The developer tank 2 is provided with a toner replenishing means 5 for replenishing toner. It consists of a toner supply roller 8 that supplies toner into the developer tank 2. Further, a toner concentration sensor 9 is attached below the magnet roller 3 of the developer tank 2, and the output of the toner concentration sensor 9 is used to drive a solenoid 10 for driving the toner replenishment roller.
is turned on and off, and the toner supply roller 8 is stopped. A bias circuit 1 is connected to the magnet roller 3 for applying a bias voltage to prevent the toner from being attracted to the residual potential in bright areas after exposure and to improve the Wji image. Further, in the figure, 12 is a doctor, 13 is a toner stirring plate, 14 is a developer supply chamber filled with developer in the developing device before use, and 15 is a sealing material, which can be peeled off to supply the developer. A developer is supplied from the chamber 14 into the developer tank 2. In the above-mentioned developing device, the amount of toner in the developer is detected by the toner concentration sensor 9, and when the amount of toner decreases, the toner concentration sensor 9 turns on the solenoid 10 for driving the toner replenishing roller, and the toner replenishing roller 8
rotates. Then, as the toner replenishing roller 8 rotates, toner is replenished into the developer tank 2 from the toner replenishing tank 6 and is stirred with the developer by the stirring roller 4. When the toner concentration reaches a predetermined value, the solenoid 10 is turned off and the rotation of the toner supply roller 8 is stopped.

[Problems to be Solved by the Invention] The conventional toner concentration sensor 9 brings the flowing developer into contact and reduces the resistance of the developer by 3iI! The toner concentration is detected by either measuring the inductance or by measuring the inductance. Therefore, it is necessary to install a toner concentration sensor 9 in the developer tank 2. However, in a cartridge-type developing device that is detachably installed in the main body of an image forming apparatus, when the developer reaches the end of its life, it is difficult to replace the developing device itself. In this way, the toner concentration sensor 9 is disposable even though it can still be used. Therefore, the toner concentration sensor 9 is wasted,
Costs are rising accordingly. In view of the above, it is an object of the present invention to provide a developing device that does not require a toner concentration sensor and can save space and reduce costs. [Means for Solving the Problems] As shown in FIG. 1.2, the means for solving the problems according to the present invention includes a magnet roller 3 rotatably installed in the developer tank 2;
A toner replenishing means 5 for replenishing toner in the developing tank 2 according to the decrease in toner is provided, and a bias circuit 1 for applying an image quality adjustment bias voltage to the magnet roller 3.
In the developing device to which 1 is connected, a toner density control unit 20 controls the I/toner density to a constant value based on the bias current value of the magnet roller 3 that changes depending on the amount of toner.
The toner density control section 20 includes a bias current detection means 21 for detecting the bias current value applied to the magnet roller 3, and a freeze detection means for detecting the reference current value generated by the reference current generator 22 and the bias. current comparison means 23 for comparing the bias current value detected by 21;
and a toner replenishment operating means 24 for operating the toner replenishment means 5 based on the comparison result of the flow comparison means 23.

[Effect]

In the above problem solving means, during image formation, a bias voltage is applied from the bias [Fll to the magnet roller 3, a bias current flows, and is detected by the bias current detection means 21. As image formation continues, the toner is consumed and the toner concentration in the developer decreases, and the bias current value increases. The current comparing means 23 determines the bias current value based on the value set by the reference current generator 22. When the noise current value exceeds the reference current value based on the comparison result, the toner concentration has become too low, and a signal is output to the toner replenishment operating means 24 to replenish toner. . Then, the toner replenishing means 5 is activated by the toner replenishing operation means 24, and toner is replenished into the developer tank 2. As the toner concentration increases, the bias current value applied to the magnet roller 3 decreases, and when the bias current value falls below the reference flow value, a stop signal is output to the toner replenishment operating means 24, and the toner replenishment operation means 24 is outputted. Means 5
stops, and the toner density becomes constant.

【Example】

Hereinafter, one embodiment of the present invention will be explained based on the drawings.
FIG. 2 is also a control block diagram. It should be noted that the same reference numerals are given to the same components as before. The developing device of this embodiment is of a cartridge type and is detachably attached to the main body of the image forming apparatus.As shown in FIG. a toner replenishing means 5 for replenishing toner into the developing tank 2 according to the toner, and a bias circuit 1 for applying an image quality adjustment bias voltage to the magnet roller 3.
1 is connected. The configurations of the developer tank 2 and the toner replenishing means 5 are the same as those of the prior art, so detailed explanations will be omitted. However, the toner concentration sensor installed in the conventional developing device has been abolished, and instead, the toner concentration is controlled to be constant based on the bias current value of the magnet roller 3, which changes depending on the amount of toner. Control unit 20
is provided. The toner density control section 20 includes a bias current detection means 21 for detecting a bias current value applied to the magnet roller 3, and a reference current value generated by a base current generator 22 and a reference current value detected by the bias current detection means 21. The current comparison means 23 compares the current value with the bias current value, and the toner replenishment operating means 24 operates the toner replenishment means 5 based on the comparison result of the 'S current comparison means 3. The magnet roller 3 is made up of a conductive non-magnetic sleeve and a magnet provided inside the sleeve, and a negative bias voltage is applied to the sleeve from a bias circuit 11 to separate the developer carrier and toner. The toner is attracted to the sleeve due to the filtration charge. Bias current detection means 21 of the toner concentration control section 20
is for detecting the value of the bias current flowing from the bias circuit 11 to the magnet roller 3. Here, the measurement results of investigating the relationship between the toner amount and the bias current value will be shown. Apply bias voltage to magnet roller 3 from -200 to -23
When 0V is applied, the bias current value is -1, 64m when the developing device is full of toner with new developer.
It becomes A. When the toner is being consumed and the toner l is decreasing and the developing car 1 ridge replacement lamp is turned on, the bias current value becomes -2.50 mA. in this way. The bias current value changes depending on the toner I in the developer,
When the amount of toner decreases, the resistance due to the toner decreases, so the bias current value increases. - Therefore, the reference current value generated from the reference $ flow generator 22 is set to the bias current value when the developer cartridge replacement lamp with a small amount of toner is lit. The current comparison means 23 compares the bias current value with a reference current value, and if the bias current value is larger than the reference current value, it determines that the toner concentration has become low and outputs a signal to replenish toner. Further, when the bias current value is smaller than the reference current value, it is determined that there is enough toner and the function is maintained. The toner supply operating means 24 is connected to the current comparing means 23.
When the amount of toner is low based on the output signal from
It has a function of turning on the solenoid 10 for driving the Q replenishing roller and turning it off when the amount of toner becomes appropriate. In the above configuration, when forming the image hill, the bias circuit 11
A bias voltage is applied to the magnet roller 3 from
1 has been detected. As image formation continues, the toner is consumed and the toner concentration in the developer decreases. As the toner concentration decreases, the resistance due to the toner decreases, so the bias current value increases. This bias current value is constantly compared with a reference current value set by the reference current generator 22 by the current comparison means 23. When the bias current value exceeds the reference current value, the toner concentration has become too low, so a signal is outputted from the current comparison means 23 to the toner replenishment operation means 24 to replenish toner. Then, the toner replenishment operating means 24 turns on the toner replenishment roller driving solenoid 10 of the toner replenishment means 5, and the toner replenishment roller 8 rotates to replenish toner from the toner replenishment tank 6 to the developer tank 2. The toner that has been
It is conveyed to the magnet roller 3 while being stirred with the developer. As the toner concentration increases, the bias current value applied to the -magnetic screw 1 to the roller 3 becomes smaller, and when the bias current value falls below the reference current value, the flow comparison means 23 changes the toner replenishment operation means 24. Outputs a signal to stop driving. In response to this signal, the toner replenishment operating means 24 turns off the solenoid 10, stops the rotation of the toner replenishment roller 8, and the toner concentration becomes constant. Therefore, instead of using a conventional toner concentration sensor, toner concentration can be detected by detecting changes in the flow value of the bias applied to the magnet roller 3. This makes it possible to eliminate the toner concentration sensor from the developing device. Cost reduction and space saving can be achieved. It should be noted that the present invention is not limited to the above-described embodiments, and it is of course possible to make many modifications and changes to the above-described embodiments within the scope of the present invention. For example, by changing the base current value set by the base current value generator 22, the concentration of a developer other than a two-component developer is controlled to be constant. Although the developing device of this embodiment is a cartridge-type one, it may also be applied to a developing device that is installed in the main wood of an image forming device and has a replaceable developer. The toner replenishing means 5 may be one that replenishes the toner from a toner cartridge that is detachably attached to the developer tank 2. [Effects of the Invention] As is clear from the above description, according to the present invention, a magnet that changes depending on the amount of toner is used. A toner density control unit is provided to keep the toner density constant based on the bias current value of the roller, so it detects the bias current value applied to the magnetic roller and compares it with the reference current value generated by the reference current generator. By comparing the bias current value,
Based on the comparison result of 2, the toner replenishment tank can be operated to keep the toner replenishment tank constant. Therefore, instead of the conventional toner concentration sensor, ) Since the toner concentration can be detected by detecting changes, it is possible to eliminate the toner IAa sensor from the developing device, which has excellent effects such as reducing the cost and space of the developing device. There is.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a developing device showing an embodiment of the present invention, FIG. 2 is a control block diagram, FIG. 3 is a sectional view of a conventional developing device, and FIG. 4 is a control block diagram. 2: Developer tank, 3: Magnet roller, 5: Toner supply means, 11: Bias circuit, 20. Toner density control section, 2
bias current detection means, 22 and reference current generator, 23
: Current comparison means, 24: Toner replenishment operation means. Applicant Sharp Corporation

Claims (1)

[Claims] The developing tank is provided with a rotatably built-in magnetic roller and a toner replenishing means for replenishing toner into the developing tank as the amount of toner decreases, and a bias voltage for applying an image quality adjustment bias voltage to the magnetic roller. The developing device to which the circuit is connected is provided with a toner density control section that controls the toner density to be constant based on a bias current value of the magnet roller that changes depending on the amount of toner, and the toner density control section is configured to control the toner density of the magnet roller. bias current detection means for detecting a bias current value applied to the bias current value; current comparison means for comparing a reference current value generated by a reference current generator with a bias current value detected by the bias current detection means; A developing device comprising: toner replenishment operation means for operating the toner replenishment means based on a comparison result of the means.