JPH0440485A - Toner concentration controller - Google Patents

Abstract

PURPOSE:To stably keep a toner concentration constant by carrying out toner replenishing based on compared data with respective to a standard toner concentration. CONSTITUTION:A toner concentration deference calculating means 3 calculates a deference in data detected by a first toner concentration sensor 1 detecting the toner concentration before development is carried out, and by a toner concentration sensor 2 detecting the toner concentration after the development is carried out, and the reduction rate of the concentration of the toner in accordance with the consumption of the toner when actual development is carried out. On the other hand, a toner concentration correcting data producing means 4 compares the concentration data of the data inside a developing unit with the standard value of the toner concentration set in advance, and produces the correcting data of the toner concentration. Then, a toner replenishing data operating means 5 operates a toner replenishing quantity according to toner correcting data outputted from the toner concentration correcting data producing means 4, and a toner replenishing means 6 replenishes the toner into the developing unit. Thus, the concentration of the toner inside the developing unit can be kept constant.

Description

[Detailed Description of the Invention] [Summary] A toner concentration control device for a developing device that uses a two-component developer consisting of toner and carrier as a developer, which accurately detects the toner concentration and controls the toner concentration to a constant value. In a toner concentration control device for a developing device that performs a developing process using a developer consisting of toner and carrier, the device includes a toner concentration control device for a developing device that performs a developing process using a developer consisting of toner and a carrier. first and second toner concentration sensors provided at positions; toner concentration difference calculation means for calculating a difference in toner concentration detected by the first and second toner concentration sensors;
1 to 1 density correction data creating means for creating density correction data corresponding to the toner density difference between the toner density detection data detected by the toner density sensor and the toner density standard value data; and the toner density difference calculation means. toner replenishment data calculating means for calculating the toner density difference data outputted by the means based on the density correction data outputted by the toner density correction data creating means to create toner replenishment data; and a toner replenishing means for replenishing toner to the developing device according to toner replenishment data.

[Industrial application field]

The present invention provides a laser beam printer that forms an image using an electrophotographic process5. The present invention relates to an image forming apparatus such as an LED blink or an LCS printer, and more particularly to a toner concentration control device for a developing device that uses a two-component developer consisting of toner and carrier as a developer.

[Conventional technology]

Image forming apparatuses such as laser beam printers and LED printers that form images using an electrophotographic process have a photoreceptor drum disposed therein as an image carrier, and a charger is installed near the circumference of the photoreceptor drum. , an exposure section, a developing device, a transfer device, and other image forming members are sequentially arranged. Then, the photoreceptor drum, whose circular surface is charged with a negative charge by the charger, is exposed to light in accordance with the image data, and the formed electrostatic latent image is turned into a toner image (visualized) by the developer. After the toner image is transferred onto paper using a transfer device, the toner image is thermally fixed onto the paper using a fixing device to form an image. In the image forming process as described above, a two-component development method consisting of toner and carrier is generally adopted as a development method for developing the above-mentioned electrostatic latent image formed on the circumferential surface of the photoreceptor drum.

FIG. 8 is a schematic diagram of a developing device using a two-component developing system. In the figure, the developing device 7 includes a developing roll 8, a stirring member 9, a blade 10, a toner hopper 11, and a supply roll 1.
2. Consists of a toner concentration sensor 13. The developing roll 8 has a magnet roll 8a inside and a developing sleeve 8 on the circumference.
b, the developing sleeve 8b attracts developer and rubs against a photoreceptor tram (not shown) to develop an electrostatic latent image on the circumferential surface of the photoreceptor drum. The stirring member 9 stirs the developer made of toner and carrier contained in the developing device 7, and keeps the toner concentration in the developing device 7 uniform. Further, the blade 10 regulates the layer thickness of the developer adsorbed onto the circumferential surface of the developing sleeve 8b, and maintains the layer thickness at a constant value.

2 As the developing process by the developing device 7 continues, the toner in the developing device 7 is gradually consumed, and the toner concentration sensor 13 detects a decrease in toner concentration. The replenishing roll 12 is rotated a predetermined number of times to replenish the toner in the 1-ner printer 11 to the developing device 7.

On the other hand, conventionally, in the vicinity of the developing sleeve 8b, the flade 1
A device has also been devised in which a toner density sensor is attached between the rubbing position (development area) between the toner 0 and the photosensitive drum to detect the densities 1 to 1. FIG. 9 is a block diagram of a toner density control device having this configuration, and the same members as in FIG. 8 described above are given the same numbers. i~lunar degree sensor 13 disposed at a position immediately before the developing area 15, which is the sliding position with the photoreceptor drum 14;
'The detection signal of the toner density detected by the signal line 13
The control circuit 16b controls the rotation/non-rotation of the motor 17 based on the toner concentration signal which is output to the amplifier circuit 16a disposed in the control unit 16 through the amplifier circuit 16a and amplified to a predetermined voltage value by the amplifier circuit 16a. Then, by driving the motor 17 in accordance with the control signal output from the control circuit 16b, the replenishment roll 12 is rotationally driven and toner is supplied to the developing unit 7.

[Problem to be solved by the invention]

In the conventional toner density control device as described above, the eighth
In the toner concentration control device having the configuration shown in the figure, since the toner concentration sensor 13 is disposed near the stirring member 9, a certain amount of developer must always pass over the toner concentration sensor 13 at a constant speed. - Toner concentration sensor] 3's output value varies.

Furthermore, in the apparatus shown in FIG. 9, since the toner and carrier are charged and rubbed in the developing device 7 as described above, electrostatic noise is constantly generated due to minute discharges, and furthermore, the toner density sensor 13' Since the output voltage output from the toner concentration sensor 13' is extremely small on the order of mV, the signal line 1 from the toner concentration sensor 13'
3''. Figure 10 shows the output voltage after the toner concentration detection signal from the above device is amplified by the above-mentioned amplifier circuit 16a. As can be seen from the figure, the toner concentration detection output voltage is extremely low. Accuracy is poor and accurate toner density control cannot be performed.

Further, in both the conventional 1-toner density control devices shown in FIGS. 8 and 9, when the toner density reaches the lower limit of the preset toner density tolerance, the replenishment roll 12 is driven, and the toner is transferred to the developing device 7. This is a control in which toner replenishment is performed, and when the upper limit of the toner density tolerance is reached, the drive of the replenishment roll 12 is stopped and toner replenishment is stopped. Therefore, the actual toner density within the developing device 7 is not constant as shown in FIG. That is, after the toner concentration sensor 13 or 13' detects that the concentration of henna has decreased, toner is actually replenished into the developing device 7 by driving the replenishment roll 12, and by the stirring process by the stirring member 9. This is because it takes time for the concentration to increase.

An object of the present invention is to accurately detect toner concentration and to maintain the toner concentration constant.

[Failure to solve the problem]

The means of the present invention are as follows.

FIG. 1 is a block diagram of the present invention. The present invention is based on the case where development processing is performed using a developer consisting of toner and carrier.

The first toner concentration sensor 1 is disposed on the upstream side in the moving direction of the developer with respect to the developing position in the developing device, and is disposed at a predetermined distance from the developer position, and Detects the toner density for developing the latent image. Further, this toner concentration sensor 1.2 is covered with a non-magnetic conductive material. It is disposed at a predetermined distance from the toner position and detects the toner density after developing the electrostatic latent image.

The toner concentration difference calculation means 3 calculates the difference between the first and second toner concentration sensors 1.2 from the detection data detected by the first toner concentration sensor 1 and the data detected by the second toner concentration sensor 2. Calculate the difference in 1-ner concentration.

The toner density correction data creation means 4 creates density correction data corresponding to the toner density difference between the toner density detection data detected by the first toner density sensor 1 and the preset toner density standard value data. .

The toner replenishment data calculation means 5 calculates the toner density difference data output from the toner density difference calculation means 3 based on the density correction data output from the toner density correction data creation means 4, and calculates the toner to be replenished into the developing device. Create toner replenishment data.

1 to 1 replenishment means 6 is the toner replenishment data calculation means 5.
Toner is replenished to the developing device according to the toner replenishment data calculated in .

[For production]

The operation of the means of the invention is as follows.

The toner concentration difference calculation means 3 calculates the difference between detection data between a first toner concentration sensor I that detects the toner concentration before development and a second toner concentration sensor 2 that detects the toner concentration after development. Then, the rate of decrease in toner density corresponding to toner consumption during actual development is calculated. Further, the toner concentration correction data creation means 4 compares the toner concentration data in the developing device, which is the detection data of the first toner concentration sensor 1, with a preset standard value of l-toner concentration, and generates toner concentration correction data. Create. The toner replenishment data calculation means 5 then uses the toner concentration difference data outputted from the toner concentration difference calculation means 3 based on the actual toner consumption, in accordance with the toner correction data outputted from the toner concentration correction data creation means 4. The amount of toner replenishment is calculated, and the L-toner replenishing means 6 replenishes toner into the developing device based on the calculated value.

By controlling the toner flow rate in this way, it is possible to replenish toner according to the amount of toner actually consumed in the developing process, and also to replenish the toner based on the difference between the toner concentration in the developing device and the standard toner concentration. Since toner replenishment is performed according to the toner replenishment correction data created by the toner replenishment correction data, the toner concentration in the developing device can always be kept constant.

Further, by incorporating an amplifier circuit into the toner concentration sensor 1.2 and covering it with a non-magnetic conductive material, toner concentration control can be performed without being affected by electrostatic noise.

〔Example〕

Examples will be described below with reference to FIGS. 2 to 7.

FIG. 2 is a diagram showing the overall configuration of a toner density control device according to one embodiment, and FIG. 3 is an enlarged diagram showing a partial configuration of the developing device shown in FIG. 2. However, FIG. 3 also shows a part of the photosensitive drum that is not shown in FIG. 2. In both figures, the developing device 20 includes a developing roll 21, a stirring member 22,
Toner concentration difference 23, blade 24, toner concentration sensor 2
It is composed of 5a and 25b. The developing roll 21 includes a rotating shaft 21a to which rotational force is transmitted from a motor (not shown), a developing sleeve 721c fixed to the rotating shaft 21a, and a predetermined gap maintained with respect to the developing sleeve 21c. It consists of a magnet 1-roll 21b.

N poles and S poles are alternately arranged on the magnet roll 21b, each magnetic pole is fixed at a predetermined position, and the developer is attracted to the circumferential surface of the developing sleeve 21c by magnetic force.

Further, the developer adsorbed to the circumferential surface of the developing sleeve 21c is
In reality, the carrier is attracted to the circumferential surface of the developing sleeve 21c, and the toner is attracted to the carrier by static electricity. As the developing sleeve 21c rotates, the developer on the developing sleeve 21c is conveyed in the direction of the arrow, and the layer thickness of the developer is regulated to be constant at the position where the blade 24 is disposed.

The agitating member 22 is rotated as described above to uniformize the toner concentration in the developing device 20, and also causes the carrier and I/toner to rub against each other, thereby charging the toner with a certain electric charge.

The I/toner density sensor 25a is arranged at an intermediate position between the development position 27 with the photosensitive drum 26 and the arrangement position of the blade 28, and the toner density sensor 25b is arranged downstream of the development position 27. Therefore, toner concentration sensor 2
5b is a configuration for detecting the toner density after developing the electrostatic latent image on the photoreceptor drum 26 at the development position.

The toner concentration detection signals from the toner concentration sensors 25a and 25b described above are output to the toner concentration control circuit 28. The toner concentration control circuit 28 includes toner concentration side sections 29a and 29b, a toner consumption calculation section 30, and a control signal output section 31. The output of the above-mentioned toner concentration sensor 25a (for example, output voltage V) is supplied to the concentration measuring section 29a, and the toner concentration measuring section 29a creates toner concentration data (T c + ) from the input voltage value. do. Further, the output (for example, output voltage V2) of the above-mentioned toner concentration sensor 25b is supplied to the toner concentration measurement section 29b, and the toner concentration measurement section 29b creates toner concentration data (TC2) from the input voltage value. Toner concentration data is created in the above-mentioned 1-toner concentration measuring sections 29a and 29b using an 1-toner concentration sensor 25a, which corresponds to the toner concentration shown in FIG.
25b according to the characteristic data.

Toner consumption calculation unit 30 and standard toner density setting unit 30a
, a coefficient section 30b, a difference detection section 30c, and a conversion section 30d. The standard toner concentration setting section 30a contains data on the toner concentration in the standard and suitable developing device 20 (Tco
) is set.

The coefficient section 30b combines the standard toner concentration data (Tco) set in the standard toner concentration setting section 30a and the output data (toner concentration data (Tco) of the toner concentration measuring section 29a).
C+)) and outputs comparison data A to the converter 30d in synchronization with the clock signal (CLOCK). The above-mentioned clock signal converts the comparison data A into the converter 30 at a predetermined period.
This is a signal to inform d.

The difference detection section 30c is connected to the above-mentioned toner concentration measurement sections 29a and 2.
9b is detected, and the difference data is outputted to the converter 30d.

The conversion unit 30d calculates the toner consumption amount based on the comparison data A from the difference data (ΔTc) output from the coefficient unit 30b, and outputs data (Ts) of the amount of toner to be replenished to the control signal output unit 31. .

The output of the control signal output section 31 is sent to the motor driver circuit 32.
supplied to The motor driver circuit 32 is a circuit that controls the rotation speed of the motor 33 according to a control signal, and the motor 33 is driven to rotate according to the output from the motor driver circuit 32.

A replenishment roll 19 disposed below the toner hopper 23 is provided on the rotating shaft of the motor 33, and is driven according to the rotation of the motor 33 to transfer the toner in the toner hopper 12 to the developer 20.
It is configured to supply internally.

By configuring the 1 henna 1 density control device of this embodiment as described above, the toner density of the developer stored in the developing device 20 is controlled as follows.

First, toner is gradually consumed by the developer in the developing device 20 rubbing against the photoreceptor drum 26, and the toner concentration in the developing device 20 decreases. This decrease in toner concentration is detected by the toner concentration sensor 25a, and its output voltage V1 is supplied to the toner concentration measuring section 29a.
Toner density data (T e l) is calculated from a. This toner density data is the standard toner density data (
Tco), and coefficient data A is calculated.

Calculation of this coefficient data A is A = A o - T c
It is performed based on the calculation formula of o/Tc. That is,
Coefficient data A is conversion constant A. It is the product of the deviation rate of toner density data with respect to the set value Tc of i/toner density. Therefore, the more the detected value of the toner concentration sensor 25a deviates from the standard toner concentration data (Tco), the larger the value of the coefficient data A becomes.

On the other hand, the difference detection unit 30c detects the toner density data (
T c + ) and the toner density data (Te3) output from the toner density measuring section 29b are compared. Here, the toner concentration data (Te3) is calculated from the output voltage value detected by the toner concentration sensor 25b according to the characteristics shown in FIG. 4 as described above. The difference detection unit 30c calculates the difference data between both toner density data and creates difference data Tc (Tc+TC2). In other words,
The difference data 8Tc calculated by the difference detection section 30C corresponds to the amount of toner consumed from the toner concentration sensor 25a to the toner concentration sensor 25b. Therefore, corresponding to the amount of toner consumed at the developing position 27 of the developing sleeve 21c,
For example, during so-called solid black printing, this difference data △Tc becomes large, and conversely, when printing with a low printing rate, the difference data △T
c becomes a small value.

The difference data ΔTc calculated as in 1 is converted to the converter 30.
output to d. The conversion unit 30d converts this difference data according to the conversion constant A described above. This conversion process is performed by T, where T represents the amount of toner consumed at the developing position 27 of the developing sleeve 21c.

This is performed based on the calculation formula =A·ΔTc. Therefore, the toner consumption amount Ts varies depending on the magnitude of the difference data ΔTc, and also varies depending on the magnitude of the conversion constant A.

That is, for example, when the toner concentration in the developing device 2o is significantly lower than the standard toner concentration data (Tco), even if development is performed at the same printing rate (even if △Tc is the same), the toner consumption amount Ts data becomes larger. Conversely, when the toner concentration in the developing device 2o has a relatively small decrease with respect to the standard toner concentration data (TCO), the data of toner consumption MTs becomes small even when printing an image at the same printing rate.

Toner consumption amount T calculated as described above.

The data is output from the control signal output unit 31 to the motor 1 driver circuit 32, and the motor 33 is driven to rotate according to the drive control of the motor driver circuit 32, driving the replenishment roll 19, and transferring the toner in the toner hopper 23 to the developing device 20. Replenish.

As described above, in this embodiment, toner is replenished by detecting toner consumption at the developing position where toner consumption actually occurs, and moreover, the toner replenishment takes into account the rate of decrease in the 1-toner concentration in the developing device 20. Therefore, it is possible to replenish the exact amount of toner. FIG. 5 shows measurements of changes in toner density when toner density control was performed according to this embodiment. As shown in the figure, by controlling the toner concentration according to this embodiment, stable toner replenishment becomes possible.

Next, another embodiment of the present invention will be described using FIGS. 6(a), (b), and FIG. 7. Incidentally, in FIG. 6(a), the same members as those in the configuration of FIG. 2 described above are designated by the same numbers, and the explanation of the configuration will be omitted.

In this embodiment, the toner concentration sensors 25a and 25b have a different configuration from those of the above-described embodiments, and are configured to prevent the influence of electrostatic noise caused by charged friction between toner and carrier. In other words, the toner concentration sensors 25a' and 25b' (however, the toner concentration sensor 25b' is not shown) are disposed in a shield container 35, and the shield container 35 is made of, for example, aluminum (AI) or copper. It is made of a non-magnetic conductive material such as (Cu). Further, the thickness of the shield container 35 used in this embodiment is 0.5 m, n, and is configured to completely block external electrostatic noise.

Further, inside the shield container 35, a Hall element section 36 and an amplifier circuit 37 are housed. FIG. 6(b) is a diagram showing the circuit configuration of the Hall element section 36 and the amplifier circuit 37. The ball element section 36 is composed of a Hall element 36a and a constant current circuit 36b, and the constant current circuit 36b is composed of a Hall element 36a and a constant current circuit 36b.
This is a circuit that supplies a constant current to a. Hall element 36
A detects a change in the magnetic force of the magnet roll 21b through a space between carriers due to a difference in toner concentration in the developer. The toner concentration signal detected by the Hall element 36a is output to the operational amplifier 37' in the amplifier circuit 37.
The output signal from the Hall element 36a is amplified by about 1000 times, for example, and is outputted via the signal line 38 to the toner replenishment control circuit 28 described in the previous embodiment. Therefore, in the case of the toner concentration control device of this embodiment, since the amplification circuit 37 is built into the toner concentration sensor 25a' etc., the signal level output from the toner concentration sensor 25a' etc. is extremely large. Toner concentration sensor 25a'
etc. are covered by the shield container 35, so they are not affected by electrostatic noise. FIG. 7 shows the above-mentioned amplifier circuit 37.
As shown in the figure, the toner concentration control device of this embodiment can obtain a stable toner concentration detection output.

In the toner replenishment control circuit 28, the toner concentration sensor 25a'
The rotation of the motor 33 is controlled in the same manner as in the previous embodiment in accordance with the signals outputted from the components, etc., and the replenishment roll 19 is rotationally driven to replenish toner from the developing device 20-11. As described above, by performing toner replenishment, accurate toner replenishment can be performed without being affected by electrostatic noise.

〔Effect of the invention〕

According to the present invention, since toner replenishment is performed based on comparison data with respect to standard toner density, toner replenishment can be performed accurately and the toner density within the developing device can be stably maintained at a constant level.

Further, since the influence of electrostatic noise can be prevented, toner density control can be performed accurately from this point of view as well.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the present invention, FIG. 2 is an overall configuration diagram of a toner concentration control device according to an embodiment, FIG. 3 is a configuration diagram of a part of a developing device of a toner concentration control device according to an embodiment, and FIG. Fig. 4 is a characteristic diagram showing the relationship between the output voltage value of the toner density sensor and the toner density, Fig. 5 is a diagram showing the measured values of toner density control by the toner density control device of one embodiment, Fig. 6 (a) 6(b) is a circuit diagram of a toner concentration sensor used in the toner concentration control device of another embodiment, and FIG. 7 is another embodiment of the toner concentration control device. 8 and 9 are block diagrams of a conventional toner concentration control device. FIG. 10 is a diagram showing the output voltage of a toner concentration sensor in a conventional toner concentration control device. FIG. 11 is a diagram showing the measured value of toner density by a conventional toner density control device. DESCRIPTION OF SYMBOLS 1...First toner density sensor, 2...Second toner density sensor, 3...Toner density difference detection means, 4...Toner density correction data creation means, 5...Toner replenishment data Calculating means, 6... Toner replenishing means, 20... Developing device, 21... Developing roll, 21b... Magnet roll, 21c ・ 22 ・ ・ 23 ・ ・ 24 ・ ・ 5 al Toner concentration sensor 28 ・9a1 30... 30a, 30b, 30c, 30d, 32,... 33... Developing sleeve, - Stirring member, - Toner hopper, - Blade, 25b, 25a', 25b' - Toner replenishment control circuit , 29b... Toner concentration measurement section, - Toner consumption calculation section, ... Toner concentration setting section, ... Coefficient section, ... Difference detection section, ... Conversion section, - Motor driver circuit, - Motor,

Claims (1)

[Scope of Claims] 1) In a toner concentration control device for a developing device that performs a developing process using a developer made of toner and carrier, upstream and downstream in the moving direction of the developer with respect to the development position in the developing device. First and second toner concentration sensors (1) and (2) provided at predetermined positions on the side, and toner concentration detection values detected by the first and second toner concentration sensors (1) and (2). a toner concentration difference calculation means (3) for calculating the difference between the toner concentration and the toner concentration difference between the toner concentration detection data detected by the first toner concentration sensor (1) and the toner concentration standard value data; Toner density correction data creation means (4) for creating correction data Based on the toner density difference data outputted by the toner density difference calculation means (3) based on the density correction data outputted by the toner density correction data creation means (4). toner replenishment data calculation means (5) for calculating and creating toner replenishment data; toner replenishment means (6) for replenishing toner to the developing device according to the toner replenishment data calculated by the toner replenishment data calculation means (5); A toner density control device comprising: 2) The toner concentration control device according to claim 1, wherein the toner concentration sensors (1) and (2) have built-in amplifier circuits and are covered with a non-magnetic conductive material.