JPS6227391B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a toner concentration detection device used in devices such as copying machines.

Conventionally, methods for detecting the toner concentration of developer include means for detecting toner concentration by pouring developer onto a transparent plate, shining light from the side of the transparent plate, and measuring the intensity of the reflected light; There is a means of separating toner from the toner, attaching the toner to an electrode, and detecting the transmitted light of the electrode to detect the toner concentration. In addition to such optical means, there are also means for detecting the fluidity of the developer by converting it into a change in the inductance of a coil, and means for detecting the bulk density of the developer by changing the inductance of a coil. A two-component developer is a mixture of a carrier and a toner at a constant ratio, and the specific gravity of the carrier containing a large amount of iron is about 7 to 8 times that of the toner.

Then, to measure the toner concentration of the developer,
This is done by detecting changes in the inductance of the coil and determining the ratio of toner to carrier.

The bulk density of the developing agent is the value obtained by dividing the weight of the developer by the bulk volume of the developer in the container when the developer is allowed to fall freely into the container. Therefore, a large bulk density means a large amount of carrier in the developer and a low toner concentration. Conversely, a low bulk density means a high toner concentration.

Further, the fluidity of the developer refers to the amount of developer flowing down from the orifice portion per unit time. This flow rate is
Generally, as the toner concentration increases, it decreases, and when the fluidity deteriorates, it is judged that the toner concentration has become low.

However, when these are used alone, the detection output changes as the number of running sheets increases with respect to the initial state, and as a result, the toner concentration of the developer changes based on fluctuations in the detection device.
The problem is that it is difficult to maintain a constant concentration.

For this reason, as shown in Japanese Patent Application Laid-Open No. 50-26550, there are methods in which a program is set up in advance to control the detection signal, and
As seen in Publications Nos. 50 to 26549, there is a method in which a reference signal is obtained and compared using a developer used for development and a developer not used for development, but in the former method, the program is programmed in advance. The latter method has drawbacks such as the need to use a developer that is not used for development.

The present invention has been made in view of the above points, and an object of the present invention is to provide a toner concentration detection device that can obtain more reliable detection data and stabilize the toner concentration of a developer.

The present invention uses two types of sensors that detect toner concentration based on different physical property values that change in accordance with changes in toner concentration, and the variation in the output level of one sensor Δ _A ' based on an increase in the number of running sheets. and the variation Δ in the output level of the other sensor
Two types of sensors whose _B ' varies at a ratio of approximately 1:K (K is a constant) and the output level Δ of the other sensor.
An electrical output signal is generated by calculating the value obtained by subtracting the output level Δ _A of one sensor from _B and multiplying it by 1/(K-1) from the output level Δ _A of one sensor. The present invention is characterized in that an arithmetic circuit is provided, and the toner concentration is detected based on an output signal of the arithmetic circuit. Therefore, even if the output from the sensor fluctuates due to an increase in the number of sheets being run, it is possible to offset the fluctuations in the output from the two types of sensors and obtain the correct value.
In this way, the density of the developer can be maintained constant.

Embodiments of the present invention will be described based on the drawings. First, a hole 3 is formed in a part of the flow plate 2 through which the developer 1 flows, and two sensors 4 and 5 are installed below the hole 3.
is provided. That is, the first sensor 4
A coil 8 is attached to the outer periphery of a cylinder 7 having an orifice 6.
The second sensor 5 is located below the orifice 6 and has a coil 10 wound around a cylinder 9 having a predetermined inner diameter.

Therefore, the coil 8 includes an oscillation circuit 11,
A frequency voltage conversion circuit 12 and a level adjustment circuit 13 are connected in sequence, and an oscillation circuit 1 is connected to the coil 10.
5. Frequency-voltage conversion circuit 16 is connected in sequence, and this level adjustment circuit 13 and frequency-voltage conversion circuit 16
is connected to the toner replenishment signal generation circuit.
This toner replenishment signal generation circuit 18 is connected to the arithmetic circuit 1
9 and a discrimination circuit 20. Further, a toner replenishment circuit 21 for driving a toner replenishment device and the like is connected to the toner replenishment signal generation circuit 18.

In such a configuration, the sensor 4 is connected to the cylinder body 7
The sensor 5 detects the bulk density of the developer 1 stored therein, and the sensor 5 detects the fluidity of the developer 1. and,
Each coil 8, 10 is an oscillation circuit 11, 15
The oscillation frequency value changes based on the change in inductance of each coil 8, 10, and is converted into a voltage by frequency-voltage conversion circuits 12, 16. The level adjustment circuit 13 is for matching the output levels of both.

Therefore, even if the output level V of each sensor 4, 5 is set to V _O in the initial state, as the number of running sheets increases, as shown in FIG.
The output level V _A of sensor 4 and the output level V _B of sensor 5 vary. Of course, what is shown in FIG. 2 is a state in which the toner concentration of the developer 1 is constant. And each output level V
The fluctuations of _A and _VB are almost similar, and the ratio is 1:K. Note that the constant K is determined by the developer used.

Therefore, the outputs from the frequency-voltage conversion circuits 12 and 16 are calculated in the calculation circuit 19,
Output level V determined by this arithmetic circuit 19
is calculated based on the formula: V=V _A -1/K-1 (V _B - V _A ).

That is, in FIG. 2, the basic formula V=V _A -V _A ' holds true. However, V _A ′:1=(V _B
-V _A ): (K-1), and the above equation is established by combining the basic equation and the main equation.
Note that V _A '=V _A -V _O , and V _O is the output level of the initial detection device. Therefore, the output V determined by the arithmetic circuit 19 is calculated from the values of the outputs V _A and V _B , which change due to an increase in the number of sheets being run, using the above formula to approximately become V _O , so that the detection device does not change. It is designed to constantly detect at the initial output level V _O.

The signal thus obtained is used by the determination circuit 20 to determine whether or not toner replenishment is required.
1 is given a replenishment signal.

To explain from another point of view, when the horizontal axis shows the toner concentration wt% and the vertical axis shows the output level V, as shown in Fig. 3, the actual state of the developer 1 is as shown by the solid line. Become. By the way, when copying 10,000 copies, the output level V _A from sensor 4
is the state shown by the dashed line, and the output level V _B from the sensor 5 is the state shown by the dotted line.
However, as a result of the above-mentioned calculation, these output levels V _A and V _B satisfy the state of the solid line, and accurate concentration detection is performed.

In addition, in the embodiment, each sensor 4,
Although we have explained the state in which the output level of No. 5 is obtained using the voltage V, this output level can also be obtained as an electrical quantity such as a current, and the symbols V _A , V _B , V
_A ′, V _B ′, etc. are expressed as Δ _A , Δ _B , Δ _A ′, Δ _B ′, etc., and mean not only voltage but also the output level and its fluctuation due to other electrical quantities such as current. It is.

The present invention uses two types of sensors that detect toner concentration based on different physical property values that change in accordance with changes in toner concentration, and the variation in the output level of one sensor Δ _A ' based on an increase in the number of running sheets. and the variation Δ in the output level of the other sensor
For two types of sensors in which _B ' varies at a ratio of approximately 1:K (K is a constant), the value obtained by subtracting the output level _ΔA of one sensor from the output level _ΔB of the other sensor is 1/( An arithmetic circuit is provided that generates an electrical output signal by calculating a value obtained by subtracting a value obtained by multiplying K-1) from one output level _ΔA , and detects toner concentration based on the output signal of the arithmetic circuit. As a result, even if the output from the sensor fluctuates due to an increase in the number of running sheets, it is possible to cancel out the fluctuations in the output from the two types of sensors and obtain the correct value. This has the effect of keeping the concentration constant.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a block diagram, FIG. 2 is a graph showing the relationship between the number of running sheets and output level, and FIG. 3 is a graph showing the relationship between toner density and output level. It is. 4 to 5...sensor, 18...toner replenishment signal generation circuit.

Claims (1)

[Claims] 1. There are two types of sensors that detect toner concentration based on different physical property values that change according to changes in toner concentration, and the variation in the output level of one sensor Δ _A ′ based on the increase in the number of running sheets and the change in the output level of the other sensor Two types of sensors whose output level fluctuations _ΔB ' vary at a ratio of approximately 1:K (K is a constant), and the output level _ΔA of one sensor is determined from the output level _ΔB of the other sensor. One output level Δ is the value obtained by multiplying the subtracted value by 1/(K-1).
1. A toner concentration detection device comprising: an arithmetic circuit that calculates a value subtracted from _A and generates an electrical output signal; and detects toner concentration based on the output signal of the arithmetic circuit.