JP2003057938A - Toner concentration detecting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a toner concentration detecting method by which the consumption of a memory is restrained and toner concentration is accurately detected with simple constitution. SOLUTION: In this toner concentration detecting method for a two- component developing type image forming device, the cycle of reading the output of a toner concentration sensor is set so that one cycle may be equal to the half of the rotating cycle of a developer stirring screw. Then, the output value of the toner concentration sensor is read at three or more points, and measuring points other than a starting point and a finishing point at measuring time are doubly weighted to calculate a mean value. Furthermore, every time the output value of the toner concentration sensor is read, the mean value with the previous output value is calculated. Or the output of the toner concentration sensor is read at four or more points, and the number of measuring points is made even-numbered.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner density detecting method used in a two-component developing type image forming apparatus such as a copying machine, a printer and a facsimile.

[0002]

2. Description of the Related Art In a two-component developing type image forming apparatus, a toner concentration sensor for detecting the toner concentration is generally provided in order to control the toner concentration of a developer and obtain a stable image. The toner decreases from the developer as it is developed, and the toner is replenished to the developer based on the information detected by the toner concentration sensor, and the toner concentration is controlled. Conventionally, various technologies have been proposed for the toner concentration sensor.

In Japanese Laid-Open Patent Publication No. 03-256082, in order to deal with the periodical change in the toner concentration sensor output due to developer agitation, one cycle is defined as a cycle during which the developer agitating screw rotates in integral multiples, and a plurality of points are set. We propose a technology to read the sensor output and average it. However, the above technique has a problem in that the average value cannot be obtained correctly depending on the phase at which the detection is started. FIG. 7 is a graph showing a general output waveform of the toner density sensor. However, when the average value is calculated by detecting the points indicated by the black circles in FIG. 7, the average value becomes larger than the true average value. . In order to solve this problem, it is necessary to always set the same detection start phase or increase the number of measurement points. But,
If it is attempted to match the detection start phase, a mechanism for detecting the position of the stirring member is required, which complicates the configuration and increases the cost. Also, when the number of reading points is increased, the average value approaches the correct value, but the memory consumption increases. Considering cost and size, it is better to keep memory consumption as low as possible.

In Japanese Patent Laid-Open No. 06-242682, a cycle of detection output fluctuation of the toner concentration sensor is held in advance, and a peak value of the detection output is fetched as a detection output based on the held cycle of the detection output fluctuation. A technique for controlling toner density is proposed. However, the above technique has a problem that it is vulnerable to noise because only one peak value is detected.

[0005]

In view of the above problems, it is an object of the present invention to provide a toner concentration detecting method with a simple structure, which suppresses memory consumption and enables accurate toner concentration detection. It is an issue.

[0006]

In order to solve the above-mentioned problems, the present invention according to claim 1 discloses a toner concentration sensor for detecting the toner concentration of a developer, and a development for stirring the developer. In a toner concentration detecting method of a two-component developing type image forming apparatus having a developing device having a developer stirring screw, one reading cycle for detecting the output of the toner concentration sensor is the rotation cycle of the developer stirring screw. The toner density detection method is characterized by being equal to half the cycle. According to a second aspect of the present invention, in the toner concentration detecting method according to the first aspect, the output value of the toner concentration sensor is read at three or more points and is doubled at a measurement point other than the start point and the end point in the measurement time. A toner density detection method is characterized by weighting and calculating an average value. As a result, more accurate toner density detection can be performed.

According to a third aspect of the present invention, in the toner concentration detecting method according to the first or second aspect, every time the output value of the toner concentration sensor is read, an average value with the previous output value is calculated. And a toner density detecting method. This can save memory. According to a fourth aspect of the present invention, in the toner concentration detecting method according to the first aspect, the output of the toner concentration sensor is read at four points or more, and the number of measurement points is an even number. To do. As a result, the calculation speed can be increased.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an example of an overall schematic view of an image forming apparatus according to the present invention. The image forming apparatus shown in FIG. 1 is a color image forming apparatus, and is of a tandem type including developing devices 3 for four colors (black, yellow, magenta, and cyan) and a photoconductor 1. Images are sequentially transferred by the transfer device 5 to the transfer paper 8 conveyed from the paper feeding device 7, and the images are fixed on the transfer paper 8 by the fixing device 6. The developing device 3 and the toner bottle 9 are connected by a tube (not shown), and the toner is supplied from the toner bottle 9 to the developing device 3.

FIG. 2 is an enlarged view of the developing device 3 in FIG. The toner replenished from the toner bottle 9 by the toner replenishing pump 14 is agitated by the developer agitating screw 11 and mixed with the magnetic carrier, while
Circulate inside. The developing device 3 shown in FIG. 2 is equipped with a toner concentration sensor 12, which can detect the toner concentration of the developer. The toner concentration sensor 12 can detect the toner concentration by changing the magnetic permeability of the developer in proportion to the bulk density of the developer.

FIG. 3 is a flow chart showing the procedure of toner supply control according to the present invention. The toner replenishment control is performed every printing of each page. The output of the toner concentration sensor 12 is read at the end of the printing operation (at the end of the development), and the time for replenishment at the next printing operation is calculated. The time is set in a timer and subtracted, and when it reaches 0, toner supply is completed.

FIG. 4 is a graph showing an example of the output waveform of the toner concentration sensor. As can be seen from this figure, the toner concentration sensor output fluctuates periodically, and its waveform is almost a sine wave. This cycle matches the rotation cycle of the developer stirring screw 11. This is because the bulk density of the developer changes as the developer stirring screw 11 stirs and the developer stirring screw 11 rotates. Since this cycle can be calculated from the number of revolutions of the developer stirring screw 11 per unit time, it can be accurately determined. The output waveform V _{t which} is a function of time t is V _t = V ₁ × sin ((2π / T) × t) + V ₀ . ． ． It is expressed as (1). V ₁ is the width of the periodic fluctuation, which varies depending on the magnetic permeability of the developer, the toner concentration, the shape of the developer stirring screw, the positions of the toner concentration sensor and the developer stirring screw, and the like. In the case of FIG. 4, V ₁ is approximately 0.25. V ₀ is a true average value and is a value to be obtained. T is a cycle, and in this embodiment, one cycle of the developer stirring screw is 312 msec. In the present invention, the reading cycle of the toner concentration sensor output is half the rotation cycle of the developer stirring screw, so that the reading cycle of the toner concentration sensor is 156 msec in FIG. From the formula of the sine function, sin ((2π / T) × (t + T / 2)) = − sin ((2π / T) × t). ． ． Therefore, the average when measuring two points is (V ₁ × sin ((2π / T) × t) + V ₀ + V ₁ × sin ((2π / T) × (t + T / 2)) + V ₀ ) / 2 = V ₀ . ． ． (3) Since V ₀ can be obtained regardless of the number of t, the true average value V ₀ can be obtained regardless of the phase at which toner concentration detection is started.

In addition, reading only two points as shown above
Is effective, but considering the effects of noise and measurement errors, etc.
Therefore, it is more accurate to increase the number of measurement points.
Can be done. Therefore, the circumference of half the rotation cycle of the stirring screw
Period, and read multiple points of 3 points or more and average them
By calculating the value, it becomes possible to detect the toner concentration more accurately.
It However, if the average value is simply taken,
There is a similar problem with. For example, measure the black circle in Fig. 5
If you take the average value of multiple points, the true average value
Will be a lower value. Rotating circumference of stirring screw
If two or more points are read in the half cycle of the period, between two adjacent points
Is the average value of these two points because the phase is shifted by half a period
Is the true average. Therefore, in the present invention,
Take the average value between two adjacent points and add them
The average value of is taken as the value to be obtained. Measuring point is V₁,
V_Two,. ． ． V_n-1, V_nThen, the calculated value V is     V = ((V₁+ V_Two) / 2 + (V_Two+ V_Three) / 2 +. ． ． + (V_n-1 + V _n ) / 2) / (n-1). ． ． (4)       = (V₁+ V_n+ (V_Two+ V_Three+. ． ． + V_n-1) x 2) / (2n-2) ． ． ． (5) And the measurement values at the measurement points excluding the start and end points are weighted
Add 2 and average. For example, in Figure 5, the starting point is
V₁And the end point is V₅Therefore,     V = (V₁+ V₅+ (V_Two+ V_Three+ V_Four) × 2) / 8. ． ． (6) Becomes

In addition, it is often impossible to install a large memory in the software for incorporating the equipment due to the limitation of the cost and the size of the control board. Therefore, it is necessary to reduce the memory usage as much as possible. According to the present invention described above, if the calculation of two adjacent points is sequentially performed according to the equation (4), the memory required during the calculation is the measurement point counter C and the measurement value storage buffers V ₁ and V ₁ . ₂ , V ₃
No more memory is required even if more measurement points are added to improve accuracy. FIG. 6 is a flowchart showing the calculation procedure of the present invention. The mean value of two points adjacent while counting the number of points calculated continue adding the average value to the buffer V _3, the mean value from the value of the buffer V ₃ at which the measurement points counter reaches a desired value calculate.

In the present invention described above, when the number of measurement points is an even number, the true average value can be obtained by simply calculating the average, regardless of the phase at which the measurement is started. for that reason,
The calculation formula is simpler than the formula (5), and the calculation speed is increased, so that the system performance does not decrease. Particularly in the case of the tandem type, it is necessary to detect the toner densities in a plurality of developing devices at the same time, and in most cases, there is only one CPU that performs these processes. Will need to choose.

[0015]

As described above, according to the present invention as set forth in claim 1, the characteristics of the periodic fluctuation of the toner density sensor are utilized to make it possible to reduce the memory consumption with a simple structure and to realize an accurate operation. It is possible to provide a toner concentration detecting method capable of detecting toner concentration. Further, according to the present invention described in claim 2, it is possible to provide a toner concentration detection method capable of performing more accurate toner concentration detection. Further, according to the present invention described in claim 3, it is possible to provide a toner concentration detecting method capable of further saving the memory. Further, according to the present invention described in claim 4, it is possible to provide a toner concentration detection method capable of further increasing the calculation speed.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus according to the present invention.

FIG. 2 is a schematic configuration diagram of a developing device according to the present invention.

FIG. 3 is a flowchart showing toner supply control.

FIG. 4 is a graph showing an example of an output waveform of a toner concentration sensor.

FIG. 5 is a graph showing an example of detection points of a toner density sensor.

FIG. 6 is a flowchart showing a calculation procedure of the present invention.

FIG. 7 is a graph showing an example of detection points of a conventional toner density sensor.

[Explanation of symbols]

1 photoconductor 2 charging roller 3 developing device 4 Optical device 5 Transfer device 6 fixing device 7 Paper feeder 8 Transfer paper 9 Toner bottle 10 Development sleeve 11 Developer stirring screw 12 Toner density sensor 13 Developer regulating member 14 Toner supply pump 15 Toner supply port

Claims (4)

[Claims] 1. A toner concentration detecting method for a two-component developing type image forming apparatus, comprising a developing device having a toner concentration sensor for detecting the toner concentration of the developer and a developer stirring screw for stirring the developer. The reading cycle for detecting the output of the toner concentration sensor is 1
A toner concentration detecting method, wherein the cycle is equal to half the cycle of the rotation of the developer stirring screw. 2. The toner concentration detecting method according to claim 1, wherein the output value of the toner concentration sensor is read at three or more points, and the measurement points other than the start point and the end point in the measurement time are weighted twice and averaged. A method for detecting toner density, which comprises calculating a value. 3. The toner concentration detecting method according to claim 1, wherein each time the output value of the toner concentration sensor is read, an average value with the previous output value is calculated. . 4. The toner concentration detecting method according to claim 1, wherein four or more outputs of the toner concentration sensor are read and the number of measurement points is an even number.