JP3391627B2 - Toner density control method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner density control method, and more specifically, in a developing device using a two-component developer composed of a carrier and a toner, the toner density always has an optimum mixing ratio of the carrier and the toner. The present invention relates to a toner density control method capable of obtaining

[0002]

2. Description of the Related Art Conventionally, a developing device using a two-component developer composed of a carrier formed of a magnetic material such as ferrite and a toner formed of a non-magnetic material such as resin or carbon has been known. In such a developing device,
The image quality of a recorded image is greatly affected by the toner density, which is the mixture ratio of the carrier and the toner. Moreover, in the above-mentioned two-component developer, only the toner is consumed with the recording and development even when the optimum mixing ratio is initially set, so that the toner concentration in the developer gradually decreases. As a result, if nothing is done, the development is finally impossible.

Therefore, conventionally, focusing on the fact that the magnetic permeability of the developer and the inductance of the magnetic coil around the developer change due to the change of the toner concentration, based on the detection output of the magnetic permeability and the inductance. There has been proposed a device for appropriately replenishing a predetermined amount of toner into a developer so as to keep the toner density constant (Japanese Patent Publication No. 51-14).
896).

However, the conventional toner concentration control device described above has a drawback in that the toner is likely to be excessively supplied due to the response delay of the detecting means. In order to eliminate such a defect, a vibration waveform component that swings positively and negatively on both sides of the optimum concentration level (control reference level) as the zero center is generated, and it is determined according to the difference from the reference voltage corresponding to the control reference level. A toner concentration control method has been proposed in which the toner replenishment amount can be adjusted (JP-A-2-6456).
No. 0).

[0005]

However, the above-mentioned conventional techniques have the following problems. That is, in the above toner concentration control method, a rotating stirring member or the like creates a flow in the developer, a toner waveform detection output has a vibration waveform component, and a magnetic permeability sensor or the like detects the magnetic force mainly by the carrier near the sensor. .

This phenomenon will be described with reference to FIG.
As shown in FIG. 7A, the analog signal is converted into a digital signal as shown in FIG. 7B so that the digital signal is turned ON when the analog signal of the toner density detection value exceeds the control reference level. Then, the toner replenishment is performed while the digital signal is ON, and the toner replenishment is stopped while the digital signal is OFF.

However, in the above-mentioned conventional toner concentration control method, if the developer is reduced by an external factor or the carrier charge amount is extremely changed by an environmental factor, the detection error of the magnetic permeability sensor becomes large, and the toner is not accurately measured. There is a problem that it becomes difficult to control the toner density.

That is, when the amount of toner decreases, the carrier is developed on the photosensitive drum, and the amount of carrier in the developing device decreases. In such a case, the flow of the developer for producing the vibration waveform component becomes insufficient, and the detected amplitude of the vibration waveform component becomes small. Further, since the amount of carrier is small, the magnetic permeability decreases, and the magnetic permeability sensor determines that the toner is sufficient and does not replenish the toner. Therefore, not only the toner concentration decreases, but also the carrier is developed and the amount of carrier decreases. .

This phenomenon will be described with reference to FIG.
In (a), the analog signal of the toner concentration detection value of the developer in the normal state is represented by a solid line, and the analog signal of the toner concentration detection value in which the amplitude of the vibration waveform component is reduced due to the decrease of the developer due to the external factor Is represented by a dotted line. The toner concentrations of the two detected analog signals are completely different from each other, but when the two analog signals are converted into digital signals at the control reference level, as shown in FIG. 8B, digital signals having exactly the same length are obtained. Is converted to. Therefore, the magnetic permeability sensor cannot discriminate the state of the developer, and it becomes impossible to accurately control the toner supply.

In the two-component developer, when the charge amount of the carrier in the developer decreases, the toner separates from the surface of the carrier to increase the magnetic permeability, and the magnetic permeability sensor lacks the toner amount in the developing device. If it is wrong, the toner is replenished. The replenished toner is also unlikely to adhere to the carrier whose charge amount has dropped, so the magnetic permeability sensor determines that the toner is still insufficient, and the toner is excessively supplied. Further, since the magnetic permeability is high, the amplitude of the vibration waveform component detected becomes large.

Therefore, in order to solve the above-mentioned problems, the present invention is capable of determining the toner state by detecting the state of the developer, and controlling the toner concentration so that the toner replenishment can be controlled appropriately. The challenge is to provide a method.

[0012]

In order to solve the above-mentioned problems, the present invention detects a toner concentration change in a two-component developer by superimposing a vibration waveform component and compares the detected value with a predetermined reference level. the toner density control method for controlling the toner replenishment Te, optimization criteria as the predetermined reference level
There are two levels, a high level and a lower auxiliary reference level.
And the detection value of the toner density changes, the optimum of the higher
The time when the level is above the reference level is x ₁ ,
When the time when the level exceeds the auxiliary reference level is x ₂ , x
_The toner replenishment is controlled using a predetermined arithmetic expression with ₁ as a variable, and x ₁ and x ₂ are compared to obtain x ₁
Is less than the first predetermined ratio with respect to x ₂ , the toner
Supplement the above formula to supply a larger amount than usual.
Correct, larger than said first predetermined percentage _{x 1} is relative to _{x 2}
If the threshold second predetermined ratio or more, the toner supply amount
It is characterized in that the arithmetic expression is corrected so that the supply amount is smaller than usual .

According to such a toner density control method,
By preparing two predetermined reference levels to be compared with the toner concentration detection value detected by superimposing the vibration waveform component and comparing the toner concentration detection value with each of the two reference levels, the two-component developer It is possible to determine the state. Therefore, it is possible to accurately detect the toner density, and it is possible to appropriately control the toner replenishment.

That is, according to the above technical means, the developer is reduced or / and the charge amount of the developer carrier is increased depending on the relationship between the detection signal corresponding to the sensor output from the toner concentration sensor and the two control reference levels. By changing (correcting) the calculation formula of the toner replenishment control in accordance with the extreme change of the toner replenishment control, it is possible to perform highly accurate toner replenishment control according to the actual toner concentration in the developing device.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings. However, the dimensions, shapes, materials of the components described in this embodiment,
Unless otherwise specified, the relative arrangement and the like are merely examples and are not intended to limit the scope of the present invention thereto.

FIG. 1 shows the internal structure of a developing device according to the first embodiment of the toner density control method of the present invention. To briefly explain the configuration of the main part of the developing device, a mag roll (fixed magnet assembly) (not shown) is provided on the opening side facing the photosensitive drum 3 in the developing container 1 in which the carrier and the toner are stored in a predetermined concentration ratio. The sleeve 4 containing the toner is rotatably supported, and the toner container 2 is mounted above the developing container 1 via the partition plate 5.

A slit opening 6a is provided on the bottom side of a tapered guide recess 6 formed at an arbitrary position of the partition plate 5, and a toner replenishing roller 7 covered with sponge is rotatably attached to the opening 6a. By controlling the rotation of the DC motor (M) 9 connected to the roller 7, the toner replenishment amount can be arbitrarily adjusted.

On the other hand, the developing container 1 is provided with a rotatable stirring member 8 at substantially the center thereof, and the toner replenishing roller 7 is provided.
The toner replenished in the developing container 1 can be agitated together with the carrier. A magnetic permeability sensor 10 for detecting the toner concentration from the magnetic permeability of the developer is attached to the bottom side of the container below the stirring member 8, and a detection signal from the sensor 10 is input to the CPU 19 to drive the drive circuit (DRIV.) 20.
The rotation control of the DC motor 9, in other words, the control of toner replenishment is performed via the.

Further, a sensor scraper 8a is attached to the tip of the stirring member 8, and the stirring member 8 is rotated at a constant speed in a cycle T so that the scraper 8a is rotated.
Rubs against the surface of the magnetic permeability sensor 10,
A waveform signal having a vibration component with a period T is generated.

As shown in FIG. 2, the CPU 19 inputs the detection signal from the magnetic permeability sensor 10 on which the vibration waveform component is superimposed, and outputs the reference voltage V ₁ corresponding to the optimum reference level and the reference corresponding to the auxiliary reference level. The reference voltage setting circuits 11 and 12 for respectively setting the voltage V ₂ are compared with the respective reference voltages V ₁ and V ₂ and the detection signal, and an ON signal is output when the detection signal exceeds the reference voltage. Comparator 13, 1
4, counters 16 and 17 for counting ON signals from the comparators 13 and 14 based on a reference clock 15 and outputting counter values x ₁ and x ₂ , respectively, and counter values x from the counters 16 and 17. An arithmetic circuit 18 for generating a toner replenishment control signal from an arithmetic expression based on ₁ and x ₂ is provided, and the rotation control of the motor 9 is performed by outputting the toner replenishment control signal to the motor drive circuit 20.

According to the toner density control method using such a developing device, two kinds of control reference levels, that is, the optimum reference level 1 and the auxiliary reference level 2 are provided as shown in FIG. An analog signal detection signal on which the vibration waveform component from the magnetic permeability sensor 10 is superimposed is compared with the respective control reference levels 1 and 2 to be converted into a digital signal.

The two analog signals in FIG. 3 (a) have the same period but different amplitudes. Each of the digital signals converted by comparing the two analog signals with the optimum reference level 1 becomes a digital signal whose ON time is exactly the same as shown in FIG. 3B. The digital signal converted at the reference level 2 is shown in FIG.
As shown in (c) and (d), a clear difference appears in the length of ON time.

That is, the analog signal whose amplitude has changed small is compared with the optimum reference level 1 even if the difference from the normal analog signal cannot be discriminated.
Since the ON time of the digital signal obtained by comparison with is longer (see FIG. 3D), it can be distinguished from the digital signal of the normal analog signal (see FIG. 3C).

From this, the counter value x ₁ corresponding to the digital signal converted by comparison with the optimum reference level 1 (see FIG. 3B) and the digital signal converted by the auxiliary reference level 2 (see FIG. 3). Accurate toner replenishment control is performed by performing toner replenishment control using the following arithmetic expression based on the counter value x ₂ corresponding to (d). Y = F ₁ (x ₁ ) (eg, A ₁ x ₁ + B ₁ ) (when condition 1) F ₂ (x ₁ ) (eg, A ₂ x ₁ + B ₂ ) (when condition 2) F ₃ (x ₁ ) (Example, A ₃ x ₁ + B ₃ ) (When conditions other than 1 and 2) Condition 1: Example, when the counter value x ₁ is 50% or less of the value x ₂ Control so as to replenish more: Condition 2, such as when the counter value x ₁ is 80% or more of the value x ₂ , control so as to replenish the toner supply amount less than usual Y: Development Toner replenishment control signal length considering the state of the agent

When toner replenishment is executed based on the above equation, Y (length of toner replenishment control signal) <T (cycle of vibration waveform), that is, the detection signal crosses the reference level. Applies when In other cases, that is, when the counter values x ₁ and x ₂ are not output, a continuous OFF signal is output from the arithmetic circuit 18, and when the counter values x ₁ and x ₂ ≧ T, the arithmetic expression is A continuous ON signal may be output regardless of the above, or an arithmetic expression in which the counter value x ₁ is replaced with the period T may be used.

The features of the present invention are as follows.
The state of the developer is determined from a plurality of digital signals obtained by comparing an analog signal corresponding to the toner concentration detection value obtained from the toner concentration sensor in the component developer and two types of control reference levels, According to the state, a calculation formula for converting into a toner replenishment control signal is corrected to generate a toner replenishment control signal, and toner replenishment control is performed based on the generated toner replenishment control signal.

[0027]

EXAMPLES For example, the toner amount is 10% and the total amount of the developer is 50.
In the 0 g developing device, the vibration waveform period T given by the stirring member 8 is 1 second, the optimum reference level 1 is 10.0 V,
Suppose auxiliary reference level 2 is provided at 7.0V. When the state of the developer is normal, it is represented as shown in FIG. 4, and in a printer that prints 10 sheets per minute, the toner replenishment time Y is calculated by the following equation (1) using the counter value x ₁ . Y = x ₁ +300 [msec] (1)

Toner replenishment is controlled at the optimum reference level 1, and when printing with a print density of about 5%, x ₁ = 200 [m
sec], x ₂ = 300 [msec], and x ₁ / x ₂ = 67%
And Y = 500 [msec] is calculated. Ie 1
The motor rotates for 5 seconds (= 500 [msec] × 10) per minute, and toner is replenished to the developer by about 0.3 g.

Next, consider a case where the toner density is lowered, the carrier is developed on the photosensitive drum, and the developer weight is reduced to 400 g. As shown by the broken line graph in FIG. 5A, the amplitude of the vibration waveform component is smaller than when the developer is in a normal state (solid line graph), and the counter value x ₁ is smaller than the normal value. Will be represented. That is, when x ₁ = 100 [msec] and x ₂ = 300 [msec], x ₁ / x ₂ = 33%, and the value of x ₁ is 50% of the value of x _2.
It becomes the following. At this time, the calculation formula for toner replenishment is corrected as in the following formula (2). Y = x ₁ +400 [msec] (2)

When print quality is guaranteed, x ₁ =
Although it is reduced to 100 [msec], the toner replenishment time is Y = 500 [msec]. Further, the toner is further reduced, and x ₁ = 200 as shown in FIG.
Even if [msec] is indicated, Y = 600 [msec] and more toner is supplied than the standard.

Next, consider the case after being left in a high temperature and high humidity environment. When the charge amount of the carrier decreases, the toner separates from the carrier surface, and the magnetic permeability increases, the amplitude of the vibration waveform component increases and the counter value x ₂ of the counter value x ₂ increases, as shown by the broken line graph in FIG. The value becomes smaller than that in the normal case with respect to x ₁ . That is, x ₁ = 30
When 0 [msec] and x ₂ = 350 [msec], x ₁ / x ₂ =
86%, the value of x ₁ becomes 80% or more of the value of x ₂ . At this time, the calculation formula for toner replenishment is corrected as in the following formula (3). Y = x ₁ +200 [msec] (3)

When the print quality is guaranteed, x ₁ =
Although it is increased to 300 [msec], the toner replenishment time is Y = 500 [msec]. Further, as the toner is excessively supplied, x ₁ = 2 as shown in FIG.
Even if 00 [msec] is indicated, Y = 400 [mse
c] and the toner is supplied in a small amount.

[0033]

As described above, according to the present invention, two predetermined reference levels to be compared with the toner concentration detection value detected by superposing the vibration waveform component are prepared, and the toner concentration detection value is obtained. By comparing with each of the two reference levels, it becomes possible to determine the state of the two-component developer.
Therefore, it is possible to accurately detect the toner density,
It is possible to perform appropriate toner supply control.

That is, according to the present invention, basically, the toner replenishment can be adjusted according to the difference between the detection signal and the control reference level as in the prior art, but the developer is reduced and the carrier is reduced. The calculation formula for the toner replenishment signal is corrected according to the change in the charge amount, etc., whereby highly accurate toner replenishment control can be realized.

Further, since the correction is not for correcting the analog signal itself but for correcting the digital signal obtained by comparing with the control reference level, the correction is performed not by hardware but by software. Therefore, the circuit configuration is not complicated and highly accurate toner replenishment control is possible.

[Brief description of drawings]

FIG. 1 shows a first toner concentration control method according to the present invention.
FIG. 3 is a schematic diagram for explaining the developing device according to the embodiment.

FIG. 2 is a functional block diagram showing the configuration and operation of a CPU 19 shown in FIG.

FIG. 3 is an analog waveform signal of a toner density detection value to be compared with two control reference levels 1 and 2 (FIG. 3A).
FIG. 4 is a diagram showing a digital rectangular signal (FIGS. 3B to 3D) created by comparing them.

FIG. 4 is a diagram showing a relationship between a toner concentration detection waveform signal of a developer in a normal state and two reference levels 1 and 2.

FIG. 5 shows a toner concentration detection waveform signal of a developer in a normal state (solid line), a toner concentration detection waveform signal when the developer decreases due to an external factor (broken line), and two reference levels 1 and 2. It is a figure which shows a relationship.

FIG. 6 is a toner concentration detection waveform signal of a normal developer (solid line) and a toner concentration detection waveform signal when there is an extreme change in carrier charge amount due to environmental factors (dashed line).
It is a figure which shows the relationship between two reference levels 1 and 2.

7 is a diagram showing a relationship between a vibration waveform component of a conventional toner density detection signal and a control reference level (FIG. 7A), and a diagram showing a digital rectangular signal created by comparing them (FIG. 7 ( b)).

FIG. 8 shows a toner concentration detection waveform signal of a developer in a normal state (solid line), and a toner concentration detection waveform signal (dashed line) when a state of the developer erroneously recognized by the toner concentration sensor changes.
FIG. 9 is a diagram showing a relationship with a control reference level (FIG. 8A) and a diagram showing a digital rectangular signal created by comparing these signals (FIG. 8B).

[Explanation of symbols]

1 developer 2 Toner container 3 photoconductor drum 4 sleeve 5 partition boards 6 Guide recess 6a slit opening 7 Toner supply roller 8 stirring member 8a Sensor scraper 9 motors 10 Permeability sensor 11 Reference voltage V1 setting circuit 12 Reference voltage V2 setting circuit 13,14 Comparator 15 Reference clock 16,17 counter 18 Arithmetic circuit 19 CPU 20 drive circuit

Continuation of the front page (56) Reference JP 58-194066 (JP, A) JP 5-307325 (JP, A) JP 6-236109 (JP, A) (58) Fields investigated (Int .Cl. ⁷ , DB name) G03G 15/08 115 G03G 15/08 507

Claims (4)

(57) [Claims] 1. A toner concentration control method for detecting a toner concentration change in a two-component developer by superposing a vibration waveform component, and comparing the detected value with a predetermined reference level to control toner replenishment. Optimal reference level and more than this as the reference level of
Two high and low auxiliary reference levels are prepared, and the detected value of the toner density change is the higher optimum reference level.
The time above the level is set as x ₁ , and the lower assistance
When the time becomes higher than a reference level set to x _2, the toner replenishment using a predetermined arithmetic expression for the x ₁ and variable
Control performs the, by comparing the x ₁ and x _2, when x ₁ is less than a first predetermined percentage of the x ₂ Toner
The above formula is used to supply more than usual
And x ₁ is larger than the first predetermined ratio with respect to x ₂ .
When the ratio is 2 or more, the toner supply amount is
A method for controlling toner density, characterized in that the above-mentioned arithmetic expression is corrected so as to replenish a little . Wherein said arithmetic expression is a toner replenishment time and Y
Then, using the time x ₁ and the predetermined constants A and B, Y =
Expressed by the formula A x ₁ + B, comparing x ₁ and x _2, and when x ₁ is less than or equal to the first predetermined ratio with respect to x ₂ , either one of the constants A or B Alternatively, both values are corrected to a value larger than a normal value, and when x ₁ is equal to or larger than the second predetermined ratio with respect to x ₂ , either or both of the constants A and B are changed. The toner density control method according to claim 1, wherein the toner density is corrected to a value smaller than a normal value. 3. The method according to claim 1, wherein the detected value is an analog signal, and the result of comparing the detected value of the analog signal with each of the two reference levels is expressed as a digital signal for processing. 5. The toner concentration control method according to. 4. The toner concentration control method according to claim 1, wherein the calculation and correction of the calculation formula are performed using a digital signal.