JP2005077685A - Powder sticking amount conversion method, powder sticking amount detector, and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make it possible to detect the sticking amount of powder such as toner always stably and correctly over the whole range. <P>SOLUTION: In the powder sticking amount conversion method, the sensitivity correction of diffused light output is performed on the basis of arithmetic processing result of an arithmetic processing means by using a plurality of gradation patterns of powder having different sticking amount which are continuously formed on the surface to be detected, an optical detection means which is arranged on a position opposite to the surface to be detected and is capable of detecting regular reflection light and diffused reflection light concurrently and the arithmetic processing means which arithmetically processes a regular reflection light output voltage and a diffused light output voltage obtained by detecting the surface to be detected and the gradation patterns by means of the optical detection means. Thereby, the diffused light output correction value is converted into a value determined unequivocally with respect to the powder sticking amount. Therein, the sticking amount range of powder patterns used in the calculation of sensitivity correction coefficient of the diffused light output is determined so as to satisfy a prescribed conditional relation among particle size, density and roundness of the powder to be detected. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a powder adhesion amount conversion method in powder adhesion amount detection of toner or the like, a powder adhesion amount detection apparatus for detecting the powder adhesion amount by performing the above method, and a copy using the above method or apparatus. The present invention relates to an image forming apparatus such as a printer, a printer, a facsimile, or a plotter.

Conventionally, in an image forming apparatus such as an electrophotographic copying machine or a laser beam printer, a density detection toner patch is provided on an image carrier such as a photoconductor in order to always obtain a stable image density. (Hereinafter also referred to as a density pattern or density detection pattern), the patch density is detected by an optical detection means, and the development potential is changed based on the detection result (specifically, LD power, charging bias) , Change of development bias).
In the case of the two-component development method, image density control is performed such that the maximum target adhesion amount (adhesion amount for obtaining a target ID) becomes a target value by changing the toner density control target value in the developing device. It is carried out.

As such a density detection patch detection means, a reflection type sensor in which an LED as a light emitting element (light emitting means) and a PD (photodiode) or PTr (phototransistor) as a light receiving element (light receiving means) is generally combined. Are known.
As the sensor configuration, (1) as shown in FIG. 2, a type that detects only specularly reflected light (see Patent Document 1 (Japanese Patent Laid-Open No. 2001-324840) etc.), (2) as shown in FIG. , A type that detects only diffuse reflected light (refer to Patent Document 2 (Japanese Patent Laid-Open No. 5-249787), Patent Document 3 (Japanese Patent No. 3155555), etc.), (3) As shown in FIG. There are three types (see Japanese Patent Application Laid-Open No. 2001-194843). 2, 3, and 4, reference numerals 50 </ b> A, 50 </ b> B, and 50 </ b> C denote element holders, 51 denotes an LED, 52 denotes a regular reflection light receiving element, 53 denotes a detection target surface, and 54 denotes a toner patch on the detection target surface. , 55 denotes a diffuse reflection light receiving element.
In recent years, (4) as shown in FIG. 5, a type in which a beam splitter is provided on the light path on the light emitting side and the light receiving side (Patent Document 5 (Patent No. 2729976)), Patent Document 6 (Japanese Patent Laid-Open No. 10-221902). Gazette), and patent document 7 (Japanese Patent Laid-Open No. 2002-72612) etc. have also been widely used. In FIG. 5, 56 is an LED, 57 and 58 are beam splitters, 59 is a photodiode as a light receiving means for P wave light (regular reflection light), and 60 is a light receiving means for S wave light (diffuse reflected light). Each photodiode is shown.

JP 2001-324840 A JP-A-5-249787 Japanese Patent No. 3155555 JP 2001-194443 A Japanese Patent No. 2729976 JP-A-10-221902 JP 2002-72612 A JP 2001-215850 A

As many of the above-mentioned publications and patent publications relate to a color image forming apparatus, since color density fluctuations in the color image forming apparatus lead to color fluctuations, density detection is required to stabilize the image density. It is important to accurately detect the amount of the applied pattern and control the density.
Since the image density to be stabilized here is the “image density of the output image”, the conventional monochrome image forming apparatus detects the density on the photoconductor, whereas the color image forming apparatus transfers it to the paper. It is desirable to carry out on the transfer belt immediately before being applied, and the aim of the image density control is to control so that the maximum target adhesion amount becomes a target value, so that even a high adhesion amount region can be accurately detected. desirable.
However, with the conventional detection method, it is difficult to always perform stable and accurate adhesion amount detection over the entire adhesion amount.

  The present invention relates to a powder adhesion amount conversion method capable of always detecting stable and accurate adhesion amount detection over the entire adhesion amount in powder adhesion amount detection such as toner, and a powder adhesion amount using the above method. An object of the present invention is to provide a detection apparatus, and further to provide an image forming apparatus using the powder adhesion amount conversion method or the powder adhesion amount detection apparatus.

In order to achieve the above object, the present invention employs the following means.
The first means of the present invention comprises: a plurality of powder gradation patterns having different adhesion amounts formed continuously on the detection target surface; and a light emitting means and a light receiving means arranged at positions facing the detection target surface. Optical detection means capable of simultaneously detecting specular reflection light and diffuse reflection light, and a specular reflection light output voltage and a diffuse light output voltage obtained by detecting the detection target surface and the gradation pattern by the optical detection means. Using an arithmetic processing means for performing arithmetic processing, the diffused light output correction value is converted to a value uniquely determined with respect to the amount of powder adhering by performing sensitivity correction of the diffused light output based on the arithmetic processing result of the arithmetic processing means. In the powder adhesion amount conversion method to be performed, the powder pattern adhesion amount range used for calculating the sensitivity correction coefficient of the diffused light output depends on the particle size and density of the powder to be detected and the circularity of the powder. Set to satisfy the following conditional expression And wherein the Rukoto.

  According to a second means of the present invention, in the powder adhesion amount conversion method of the first means, the powder is a toner.

  The third means of the present invention comprises means for continuously forming a plurality of powder gradation patterns having different adhesion amounts on the surface to be detected, light emitting means and light receiving means arranged at positions facing the surface to be detected. Optical detection means capable of simultaneously detecting specular reflection light and diffuse reflection light, and specular reflection output voltage and diffuse light output voltage obtained by detecting the detection target surface and the gradation pattern by the optical detection means And a plurality of gradation patterns formed on the detection target surface using the powder adhesion amount conversion method of the first or second means. And detecting the amount of adhered powder.

The fourth means of the present invention is an image forming method capable of obtaining a color image by sequentially superimposing and transferring images formed on a plurality of image carriers onto a sheet-like recording medium carried on a transfer member. In the apparatus, the powder adhesion amount conversion method of the first or second means or the powder adhesion amount detection apparatus of the third means is used, and the detection target surface is the transfer body.
Further, the fifth means of the present invention can obtain a color image by sequentially superimposing and transferring images formed on a plurality of image carriers onto a sheet-like recording medium carried on the transfer member. In the image forming apparatus, the powder adhesion amount conversion method of the first or second means or the powder adhesion amount detection apparatus of the third means is used, and the detection target surface is the image carrier. To do.

According to the sixth means of the present invention, a toner image formed on a plurality of image carriers can be sequentially transferred onto an intermediate transfer member and then transferred onto a sheet-like recording medium to obtain a color image. In another image forming apparatus, the powder adhesion amount conversion method of the first or second means or the powder adhesion amount detection apparatus of the third means is used, and the detection target surface is the intermediate transfer member. And
The seventh means of the present invention obtains a color image by transferring the toner images formed on a plurality of image carriers in succession to the intermediate transfer member and then transferring them onto a sheet-like recording medium. In the image forming apparatus capable of performing the above, the detection target surface is the image carrier using the powder adhesion amount conversion method of the first or second means or the powder adhesion amount detection apparatus of the third means. It is characterized by.

The eighth means of the present invention can obtain a color image by transferring the toner images formed on one image carrier in succession to the intermediate transfer member and then transferring them all at once to a sheet-like recording medium. In another image forming apparatus, the powder adhesion amount conversion method of the first or second means or the powder adhesion amount detection apparatus of the third means is used, and the detection target surface is the intermediate transfer member. And
The ninth means of the present invention obtains a color image by transferring a toner image formed on one image carrier in succession to an intermediate transfer member and then transferring it onto a sheet-like recording medium. In the image forming apparatus capable of performing the above, the detection target surface is the image carrier using the powder adhesion amount conversion method of the first or second means or the powder adhesion amount detection apparatus of the third means. It is characterized by.

According to a tenth means of the present invention, in any one of the fourth to ninth means, the plurality of gradation patterns formed on the detection target surface are converted into an adhesion amount, and the adhesion is performed. Image density control is performed based on the amount conversion value.
The eleventh means of the present invention is the image forming apparatus according to any one of the fourth to ninth means, wherein the powder is a toner, and the particle size r of the powder of the conditional expression is a toner particle It is characterized by a lower limit value of the diameter tolerance.

In the powder adhesion amount conversion method of the present invention, the upper limit value of the adhesion amount range of the gradation pattern (toner patch) used for calculating the sensitivity correction coefficient of the diffused light output is determined based on the particle diameter, density, Further, since the sensitivity calculation can be performed in a wider range by obtaining it more rationally from the circularity, more accurate sensitivity correction can be performed. Thereby, it becomes possible to correct the sensitivity variation of the sensor of the optical detection means with higher accuracy. In the powder adhesion amount detection apparatus using this powder adhesion amount conversion method, accurate adhesion amount detection can be performed.
In addition, by mounting the powder adhesion amount conversion method or powder adhesion amount detection device of the present invention in actual machine control, accurate adhesion amount detection can be performed, so that a color image that can always obtain a stable image density over time. A forming apparatus can be provided.

Hereinafter, the configuration, operation and action of the present invention will be described in detail with reference to the drawings.
First, before describing the configuration and function of the present invention, the background of the study that has led to the realization of the present invention will be described.
[Selection of optical detection means and consideration of its function]
When considering which type of sensor is used to detect the density pattern on the transfer belt as the detection target surface, among the sensor types mentioned above, the type with only specular reflection (1) cannot detect even the high adhesion amount range. There is a drawback. In the case of only the diffusely reflected light type (2), if the transfer belt is black (in many cases, the transfer belt is often black because carbon is used as a resistance adjusting agent), black toner is used. Have a fatal defect that the sensor cannot be detected, and the diffuse reflected light output at the transfer belt background is almost zero, so that the sensor sensitivity cannot be calibrated.
In order to deal with such a problem, the difference between the outputs of the two light receiving sensors is obtained by using both types (3) and (4) (Patent Document 3 (Patent No. 3155555) or Patent Document 4). (Refer to Japanese Patent Laid-Open No. 2001-194843) or a ratio (see Patent Document 6 (Japanese Patent Laid-Open No. 10-221902), etc.), and many methods for detecting the amount of adhesion have been proposed. It seems to have been.

However, with the conventional detection method using the combination type of (3) and (4), it is considered difficult to always stably and accurately detect the adhesion amount for the reasons described below.
[1] Lot variation of light emitting element output and light receiving element output is not considered (sensor variation).
[2] Temperature characteristics of light emitting element output, light receiving element output, and deterioration with time are not taken into consideration (sensor fluctuation).
[3] The influence of deterioration over time of the transfer belt, which is the detection target surface, is not considered (belt fluctuation).
This point will be described in detail below.

Explanation of [1] In order to investigate how much the sensor element varies, several lots (1 lot = 197 pieces) of LEDs (light emitting elements) and PTr (phototransistors) are measured by the following method. The variation width was evaluated.
[Light emitting element side]
The light receiving element when the light emitting element is sequentially switched and light is irradiated to a certain reference plate under the condition that the sensor head shown in FIG. 2 is used, Vcc = 5 V, LED current: If = 14.2 mA, and the light receiving element is fixed. The photocurrent: IL was measured, and the magnitude of the light emission output was determined.
[Light receiving element side]
The light receiving element when the light receiving element is sequentially replaced and light is irradiated to a certain reference plate under the condition that the sensor head shown in FIG. 2 is used, Vcc = 5 V, LED current: If = 14.2 mA, and light emitting element fixed. The photocurrent: IL was measured, and the magnitude of the light receiving sensitivity was determined. The measurement results are shown in Table 1 below.

From Table 1, it was found that the output variation was slightly less than twice on the light emitting element side and slightly less than four times on the light receiving element side.
The size of the element variation seems to vary depending on the type of element (top view type, side view type) and manufacturer, but at least the variation at the level that requires adjustment should be no matter which element is used. It is.
This point is not mentioned at all in each of the above prior arts. It seems that this is a matter of course, but in order to accurately detect the amount of adhesion using the method described in the prior art, strict output is required at the inspection stage of the sensor (element). Adjustment is required.

Therefore, what happens when there is no adjustment will be described below based on the prediction result based on experimental data.
FIG. 6 shows the result of measuring the amount of color toner adhering to the transfer belt using the sensor shown in FIG. 4. The horizontal axis: the amount of adhesion, the vertical axis represents the specular reflection light output voltage, and the diffuse reflection light output. The voltage is plotted.
Here, even when there is element variation in each of the light emitting element, the specular reflection light receiving element, and the diffuse reflection light element, at least for the specular reflection light output, since it has the characteristic that the output is maximum at the belt background, If the LED current is adjusted so that the output at the belt background becomes a certain value (3.0 V in this case), output variations due to variations in light emitting elements and regular reflection light receiving elements can be absorbed. An almost unique output characteristic can be obtained as the sensor output with respect to the quantity.
The large squares in FIG. 6 are the points where the diffused light output after LED adjustment is plotted. If the variation in the light receiving element is doubled, the light receiving element with the diffuse reflected light output has a light receiving sensitivity of 1/2. , The diffused light output at that time is an output (Vd / 2) represented by a small □ mark, and taking the difference from the specularly reflected light (Vr) in each case, as shown in FIG. The output relationship with the amount of adhesion is not uniquely determined. This is the same even when the ratio is taken.
In addition, as shown in FIG. 7, when the values of the two conditions coincide with each other at the point where the amount of adhesion is zero, and when these values are deviated in the high amount of adhesion region, the regular output of the specular reflection light output conventionally known is normal. Even if an operation such as a conversion process is performed, it cannot be determined uniquely.

Based on the above, the relationship between “regular reflection light output” and “diffuse reflection light output” when the amount of adhesion is converted based on the difference between “regular reflection light output” and “diffuse reflection light output” or ratio data. It is necessary to always satisfy a certain relationship, and for this purpose, for example, at the sensor shipping inspection stage, it is necessary to correct variations such as strictly adjusting the relationship between the specular reflection light output and the diffuse reflection light output with respect to a certain reference plate. Become.
Even if the technique described in the above-mentioned prior art is a story after the adjustment as described above, it is still [2], [3] that simply taking the difference or taking the ratio. ] Cannot be detected accurately due to the fluctuation factors (sensor fluctuation, belt fluctuation) listed above. Here, the variation factors listed in [3] will be described.

Explanation for [3] Since the transfer belt is always in contact with the transfer paper as the sheet-like recording medium during image output, the surface of the belt becomes rough over time due to wear. In addition, when the transfer paper containing a large amount of white agent is continuously fed, the belt surface becomes white over time.
Before showing the experimental result about this, the state change factor of regular reflection light output and diffuse reflection light output is demonstrated.
The specularly reflected light output is light that is specularly reflected by the detection target surface (incident angle and reflection angle are equal), and when the detection target surface is smooth (= high specular gloss), it is shown in FIG. As described above, the irradiated light 61 is only slightly diffused on the detection target surface 53, and most of the light is specularly reflected as the regular reflection light 62. In FIG. 8, reference numeral 63 indicates the specular reflection light sensitivity, and 64 indicates the diffuse reflection light sensitivity in a distributed area.
As shown in FIG. 9, when the toner 65 as powder adheres to the detection target surface 53, the incident light 61 is diffused by the toner 65, so that the regular reflection light 62 is reduced and conversely diffuse reflection. Light 66 increases. However, the diffuse reflected light 66 increases when the toner 65 is a color toner. When the toner 65 is a black toner, the irradiated light 61 is almost absorbed. Little increase.
That is, the output of specularly reflected light changes due to the “change in state of surface property (glossiness, surface roughness, etc.) of the object to be detected, and the diffuse reflected light output is the“ color characteristic (lightness, etc.) of the object to be detected. The output changes due to factors completely independent of each other, such as the output changing due to the “state change”.

Next, experimental results will be described. In the quadruple tandem direct transfer type color image forming apparatus shown in FIG. 1, assuming that the surface of the transfer belt is rough and whitened over time, “specular gloss (Gs)” and “lightness (L ^* ) A 16-tone pattern was formed on three types of transfer belts with different "", and the results were predicted when they varied over time by comparing the sensor detection output of these patterns. The conditions of the experiment are shown below.
<Transfer belt (detection target surface)>
Black belt: Specular gloss: Gs (60) = 57, Brightness: L ^* = 10
Brown belt: Specular gloss: Gs (60) = 27, Brightness: L ^* = 25
Gray belt: Specular gloss: Gs (60) = 5, Brightness: L ^* = 18
<Detection sensor (optical detection means)> Detailed specification of the sensor shown in FIG. 4 [light emission side]
Element: GaAs infrared light emitting diode (peak emission wavelength: λp = 950 nm), top view type Spot diameter: φ1.0 mm
[Light receiving side]
Element: Si phototransistor (peak spectral sensitivity: λp = 800 nm), top view type Spot diameter: specular reflection light receiving side: φ1.0 mm
Diffuse reflected light receiving side: φ3.0mm
Detection distance: 5 mm (distance from the top of the sensor to the detection target surface)
LED current: 25 mA fixed
<Line speed>
125mm / sec
<Sampling frequency>
500 Sampling / sec (= 2 msec)
Note 1: The specular gloss value is a value measured at a measurement angle of 60 ° using a gloss meter PG-1 made by Nippon Denshoku.
Note 2: Brightness is a value measured using a spectrocolorimeter: X-Rite 938 manufactured by X-Rite, with a light source of D50 and a viewing angle of 2 °.

FIG. 10 shows the regular reflection light output characteristic with respect to the black toner adhesion amount, and FIG. 11 shows the regular reflection light output characteristic with respect to the color toner adhesion amount.
In this experiment, the sensor side input condition is fixed (LED current: If = 25 mA fixed), so in the high adhesion amount region (M / A = 0.4 mg / cm ² or more) where the influence of the belt background is not exerted. Although the specularly reflected light output (voltage) is substantially the same for the three types of belts, it is not the same in the low adhesion amount region (M / A = 0.4 mg / cm ² or less) affected by the belt background.
As can be seen from this result, when the mirror glossiness of the transfer belt decreases with time, that is, when the surface roughness deteriorates, as indicated by the arrow in the low adhesion amount region where the belt background portion where the adhesion amount is zero is exposed. It can be seen that the specular reflection light output (voltage) decreases.

[Consideration of defects in conventional technology (when using type (1) sensor)]
Based on the above experimental facts, if the amount of adhesion is detected with a sensor of type (1) that has only specular reflection output, the biggest difficulty is that the amount of adhesion that can be detected is the gloss of the transfer belt. That is, it becomes narrower with time as the temperature decreases.
The reason for this is that, in the prior art, the adhesion amount detection of the color adhesion amount is performed by the following adhesion amount detection algorithm, so that the sensor output characteristic with respect to the adhesion amount is an adhesion amount greater than the inflection point (minimum value) shown in FIG. This is because cannot be detected.

<Conventional specular light output type adhesion amount conversion formula>
Normalized value = (pattern part output voltage−Vmin) / (background part output voltage−Vmin)
Vmin: Minimum value of multiple pattern output

In FIG. 11, when the output minimum value of each belt is obtained by calculating the inflection point of the approximate curve, the maximum detectable amount of adhesion is 0.36 (57), 0.30 (27) as the belt deteriorates over time. ), 0.17 (5), and the like (see the gloss value in parentheses ()). The adhesion amount detectable range is the output value and the adhesion amount that is the minimum value.
As for the black toner adhesion amount detection, the maximum detectable adhesion amount can be detected with little change, although the output SN ratio is simply lowered, and the detection accuracy is slightly reduced.

Next, the horizontal axis: the diffused light output characteristic with respect to the black toner adhesion amount is shown in FIG. 12, and the horizontal axis: the diffuse reflected light output characteristic with respect to the color toner adhesion amount is shown in FIG.
Diffuse reflected light output is almost unaffected by the belt background, but the output is almost the same for the three types of belts. However, in the low adhesion amount area, which is affected by the change in brightness of the belt background, the effect of the change in brightness is low. Output does not match.
That is, it can be seen that when the transfer belt becomes white over time, the diffuse reflected light output of the transfer belt background portion increases.

[Consideration of defects in conventional technology (when using type (2) sensor)]
Based on the above experimental facts, the biggest difficulty when the amount of adhesion is detected with the sensor of type (2) that has only diffuse reflected light output. Secondly, the sensor sensitivity calibration cannot be performed on the detection target surface, particularly when the detection target surface is black, such as lightness: L ^* <20.
The reason why the sensitivity cannot be calibrated when the lightness is L ^* <20 is that the diffuse reflected light output from the background becomes almost zero.
For reference, the sensor sensitivity calibration method that the applicant has done for the conventional machine will be described. After the sensor is attached to the image forming apparatus at the factory, the sensor output for a certain white reference plate is a certain value. The LED light emission side adjustment of the sensor light emission side was performed so that it might become. However, even if it can be adjusted initially in this way, since there is no means for correcting the change in sensitivity due to the temperature characteristics of the sensor, LED degradation over time, etc., a reliable guarantee for quality over time cannot be obtained.

FIG. 14 shows the result of examining the correlation between the specular gloss and the specular reflection light output, and FIG. 15 shows the result of examining the correlation between the brightness and the diffuse reflection light output.
FIG. 14 shows the specular reflection light output when 42 types of transfer belts having different “glossiness” and “lightness” are fixed to LED current: 20 mA using the reflection type photosensor shown in FIG. Horizontal axis: plotted against 60 ° gloss.
The gloss value measured on the horizontal axis is a value measured at a measurement angle of 60 ° using a Nippon Denshoku gloss meter PG-1.
As shown in FIG. 9, since the regular reflection light output includes a diffuse reflection light component, if the results are sorted for each brightness range, the regular reflection light output voltage has a relationship that is approximately linearly proportional to the glossiness. It turns out that it is obtained.
The reason why the linear proportional relationship is obtained in this way is that the specular reflection itself is measured with respect to the specular glossiness. (Refer to JISZ8741 Specular Gloss-Measurement Method)

FIG. 15 is a graph in which the diffuse reflected light output measured at the same time is plotted with respect to the horizontal axis: the brightness of the belt. In FIG. 15, [-] means that there is no unit.
The brightness on the horizontal axis is a value measured using a spectrocolorimeter: X-Rite 938 manufactured by X-Rite Co., Ltd., with a light source: D50 and a viewing angle: 2 °.
The relationship between the two is not a linear relationship because of differences in the light source, measurement angle, etc., but since it is plotted on the same curve without being affected by the glossiness, the diffuse reflected light output is positive. It can be seen that it is independent of the reflected light output.

When the surface of the transfer belt becomes rough with time and the specular reflection light output of the belt background portion decreases, or when the diffuse reflection light output of the background portion increases due to whitening, or when these two progress simultaneously, either of these Since the relationship between “regular reflection light output” and “diffuse reflection light output” is broken, the output cannot be made the same as the initial state simply by taking the difference between the two outputs or taking the ratio.
Therefore, even if the adhesion amount conversion is performed based on this, the same result as the initial stage can never be obtained. Even if the amount of adhesion is not converted and this result is directly fed back to the density control, the result only deviates from the initial value.

Therefore, when the specular reflection light output decreases due to the belt glossiness decrease, it is conceivable to correct the LED current by increasing that amount.For example, adjustment is made so that the regular reflection light output of the belt background becomes the initial value. If this is done, at least the belt background portion is the same as the initial value, but as shown in FIG. 16, in the case of color toner, the output increases over the entire amount of adhesion.
In addition, since the output of the diffuse reflected light output voltage increases as the amount of received light increases, the resulting differential output is managed together with the initial value in the low coverage area as shown in FIG. However, since the deviation occurs in the high adhesion amount region, the same result as the initial stage cannot be obtained. This is the same even when the ratio is taken instead of the differential output.

Explanation for [2] Even if there is no change over time as described above, if the output characteristics of the light emitting element and the light receiving element, which are semiconductors, change due to an increase in the ambient temperature, the initial stage is similarly performed. The output result differs from the determined state.

As described above, the means for detecting the adhesion amount in the high adhesion amount region, and particularly the means for detecting the toner adhesion amount up to the high adhesion amount region on the black belt often used in the color image forming apparatus. In the method shown in the related art proposed as: (a) In order to make full use of the gradation pattern detection technique, the two outputs of the density detection sensor used for this are strictly adjusted in advance, that is, at the shipping inspection stage. It seems to be a major premise that a very strict adjustment is required. (B) There is no countermeasure against the environmental variation with time of the density detection sensor, and (c) the countermeasure with respect to the temporal variation of the detection target surface (transfer belt). Considering that there is no problem, it can be said that there are still many technical problems in the detection of gradation patterns.
In other words, on the black belt where the diffused reflected light output sensitivity cannot be adjusted, (a) output variations due to sensor lot variations, (b) aging and environmental variations of the density detection sensor, (c) detection target surface (transfer belt) (2) It is not influenced by any factor of the time-dependent fluctuations)), and a technical problem to be solved is how to always detect the toner adhesion amount in a stable high adhesion amount region.

The present invention has been made to solve the above-mentioned problems hidden in the prior art,
(1) Strict adjustment of the output relationship between “regular reflected light output” and “diffuse reflected light power” on the sensor side (hardware side) is not required, that is, it is manufactured with a greater degree of freedom at the shipping stage. Contributes to cost reduction,
(2) In spite of the presence of the above three factors, it is possible to automatically correct by the feature on the software side, and to achieve high accuracy of gradation pattern detection.
The above-described aim of the present invention is achieved by a powder adhesion amount conversion method of the present invention described below, a powder adhesion amount detection apparatus using the same, and an image forming apparatus using them.
Specifically, the reflection pattern optical sensor (optical detection means) with two outputs of “regular reflection light output” and “diffuse reflection light output” which are the types of (3) and (4). In the adhesion amount region where the amount of adhesion can be detected by reading and specular reflection light, these two outputs are converted into values having a linear relationship with the adhesion amount, and each output (regular reflection light output, diffuse light output) In the adhesion amount range linear with respect to the adhesion amount, that is, the adhesion amount range determined by the particle size r, density ρ, and circularity of the toner to be detected as shown in the first means, the diffused light output By calculating the sensitivity correction coefficient and performing the sensitivity correction, the sensitivity variation of the sensor is corrected so that the stable adhesion amount detection can be performed at all times.

Hereinafter, a first embodiment of the present invention will be described based on a specific configuration.
First, a schematic configuration of a color laser printer of a quadruple tandem direct transfer system as an image forming apparatus using the powder adhesion amount detection apparatus in this embodiment will be described with reference to FIG.
This color laser printer has three paper feed trays, one manual feed tray 36, two paper feed cassettes 34 (first paper feed tray), and 34 (second paper feed tray). Transfer sheets (not shown) as the fed sheet-like recording medium are separated one by one from the uppermost one by the paper feeding roller 37 and conveyed toward the registration roller pair 23. The transfer sheets fed from the first sheet feed tray 34 or the second sheet feed tray 34 are separated one by one from the uppermost one by the sheet feed roller 35 and are transferred to the registration roller pair 23 via the transport roller pair 39. It is conveyed toward.
The fed transfer paper is temporarily stopped by the pair of registration rollers 23, the skew is corrected, and then the leading edge of the image formed on the photosensitive drum 14Y positioned at the uppermost stream described later and the transfer paper in the transport direction. At a timing coincident with the predetermined position, the sheet is conveyed toward the transfer belt 18 by the rotation operation of the registration roller pair 23 by ON control of a registration clutch (not shown).
When the transfer paper passes through a paper suction nip composed of the transfer belt 18 and a paper suction roller 41 in contact with the transfer belt 18, the transfer paper is attracted to the transfer belt 18 by an electrostatic force by a bias applied to the paper suction roller 41. For example, it is conveyed at a process linear velocity of 125 mm / sec.

The transfer paper adsorbed by the transfer belt 18 has toner transferred to the transfer brushes 21B, 21C, 21M, and 21Y disposed at positions facing the photosensitive drums 14B, 14C, 14M, and 14Y of the respective colors with the transfer belt 18 interposed therebetween. By applying a transfer bias (plus) opposite to the charging polarity (minus), the toner images of the respective colors formed on the photoconductor drums 14B, 14C, 14M, and 14Y are converted into yellow (Y) and magenta (M ), Cyan (C), and black (Bk).
The transfer paper that has undergone the transfer process of each color is separated from the transfer belt 18 by the downstream drive roller 19 and is conveyed to the fixing device 24. By passing through a fixing nip formed by the fixing belt 25 and the pressure roller 26 in the fixing device 24, the toner image is fixed on the transfer paper by heat and pressure. In the single-sided printing mode, the fixed transfer paper is discharged to an FD (face-down) tray 30 formed on the upper surface of the apparatus main body.
When the double-sided printing mode is selected in advance, the transfer paper that has exited the fixing device 24 is sent to a reversing unit (not shown), and the front and back sides are reversed by the unit, and then the double-sided transport unit positioned below the transfer unit. It is conveyed to 33. The transfer paper is fed again from the double-sided conveyance unit 33 and conveyed to the registration roller pair 23 through the conveyance roller pair 39. Thereafter, it passes through the fixing device 24 through the same operation as in the single-sided printing mode, and is discharged to the FD tray 30.

Next, the configuration and image forming operation in the image forming unit of the color laser printer will be described in detail.
Since the image forming unit has the same configuration and operation for each color, the configuration and operation for forming a yellow image will be described as a representative, and the other components are denoted by reference numerals corresponding to the respective colors and description thereof is omitted.
An image forming unit 12Y having a charging roller 42Y and a cleaning unit 43Y, a developing unit 13Y, an optical writing unit 16, and the like are provided around the photosensitive drum 14Y positioned on the most upstream side in the transfer paper conveyance direction.
At the time of image formation, the photosensitive drum 14Y is rotated in the clockwise direction by a main motor (not shown), is neutralized by an AC bias (DC component is zero) applied to the charging roller 42Y, and the surface potential is a reference of approximately −50V. It becomes a potential.

Next, the photosensitive drum 14Y is uniformly charged to a potential approximately equal to the DC component by applying a DC bias with an AC bias superimposed on the charging roller 42Y, and the surface potential thereof is approximately −500 V to −700 V (target charging). The potential is determined by the process control unit).
Digital image information sent from a controller unit (not shown) as a print image is converted into a binarized LD light emission signal for each color, and a cylinder lens, a polygon motor, an fθ lens, first to third mirrors, and a WTL. Exposure light 16Y is irradiated onto the photosensitive drum 14Y by an optical writing unit 16 having a lens or the like.
The drum surface potential of the irradiated portion becomes approximately −50 v, and an electrostatic latent image corresponding to the image information is formed.

The electrostatic latent image corresponding to the yellow image information on the photosensitive drum 14Y is visualized by the developing unit 13Y. By applying DC (−300 to −500 V) with an AC bias superimposed on the developing sleeve 44Y of the developing unit 13Y, toner (Q / M: −20 to −30 μC / g) is developed to form a toner image.
The formed toner images on the photosensitive drums 14B, 14C, 14M, and 14Y of the respective colors are transferred onto the transfer paper adsorbed on the transfer belt 18 by the transfer bias.

In the color laser printer according to the present embodiment, in addition to the image forming mode as described above, a process control operation (hereinafter referred to as a process controller) is performed in order to optimize the image density of each color when the power is turned on or after a predetermined number of sheets have passed. (Abbreviated as operation).
In this process control operation, a plurality of density detection patches (hereinafter abbreviated as “P patterns”) for each color are formed on the transfer belt by sequentially switching the charging bias and the developing bias at appropriate timing, and the output of these P patterns is performed. The voltage is detected by a density detection sensor (hereinafter abbreviated as P sensor) 40 disposed outside the transfer belt 18 in the vicinity of the drive roller 19, and the output voltage is detected as an adhesion amount conversion algorithm (powder adhesion amount conversion) of the present invention. The amount of adhesion is converted by (Method) to calculate (development γ, Vk) representing the current developing ability, and based on this calculated value, control is performed to change the developing bias value and the toner density control target value. .

The configuration of the P sensor is as shown in FIG. 4, and the specifications are as described above.
Here, PTr (phototransistor) is used as the light receiving element, but a light receiving element such as PD (photodiode) may be used.

Below, the algorithm of the adhesion amount conversion method in the present embodiment will be described based on the experimental results shown in FIGS. In this algorithm, the diffused light output is converted into an adhesion amount value according to the following procedure.
(1) Sampling the regular reflection light output and diffuse reflection light output of the gradation pattern (see FIGS. 11 and 13);
(2) Extracting specularly reflected light output into [specularly reflected light component] and [diffuse reflected light component] to extract only [specularly reflected light component]
(3) Extracting [diffuse light component from toner] by removing [diffuse reflection light component from belt background] from the diffuse reflection output,
(4) A deposition amount range in which each output is linear with respect to the deposition amount by using a linear relationship with the deposition amount of two output conversion values that are independent (intersect) obtained from (2) and (3). (That is, the adhesion amount range determined by the particle diameter, density, and circularity of the toner shown in the above solution), a value of a diffuse reflection light output conversion value of a certain regular reflection light output conversion value (or adhesion amount). The diffuse reflected light output conversion value is corrected for sensitivity so that the diffuse reflected light output (correction value) for the amount of adhesion is uniquely determined.
(5) The adhesion amount conversion process is performed from the relationship between the “adhesion amount” and the “diffuse reflected light output correction value” obtained in advance.

(1) to (5) will be described below in order.
Description of (1) FIGS. 11 and 13 show “regular reflection output voltage” obtained by detecting the density detection P pattern 70 shown in FIG. 18 formed on the transfer belt 18 by the P sensor 40 shown in FIG. The “diffuse reflected light output voltage” is plotted against the color toner adhesion amount [mg / cm ² ] precisely measured by the electronic balance. In the gradation pattern 70, the toner adhesion amount increases on the upstream side in the belt moving direction.
As described above, three types of transfer belt 18 having different “specular gloss” and “brightness” are used.

Explanation of (2) Here, when the regular reflection light output characteristic with respect to the black toner adhesion amount shown in FIG. 10 is compared with the regular reflection light output characteristic with respect to the color toner adhesion amount shown in FIG. It can be seen that the reflected light output shifts from monotonic decrease to monotonic increase at a certain adhesion amount (in this case 0.2 to 0.4 mg / cm ² ) or more, as shown in FIGS. 19 and 20. The light received by the regular reflection light receiving element 52 as regular reflection light includes, in addition to pure [regular reflection light component], [diffuse reflection light component from belt surface] and [diffuse reflection light component from toner layer]. It is because it is included. In FIG. 19B, reference numeral 54 denotes a cyan solid portion.
Considering that the irradiation light from the LED 51 is evenly diffused on the detection target surface as shown in FIG. 19, the diffuse reflected light component received by the regular reflection light receiving element 52 and the diffusion entering the diffuse light receiving element 55. There should be an n-fold relationship with the reflected light.
The value of n times used here is a value determined by the optical layout such as the light receiving diameter and arrangement of the light receiving elements 52 and 55.

The actual output is output as a voltage after the reflected light entering each of the light receiving elements 52 and 55 is IV-converted in the circuit by the OP amplifier. The difference between these is also accumulated, and the α-fold relationship should be established.
If such a coefficient α can be obtained, it is considered that the specular reflection light output can be decomposed into “regular reflection component” and “diffuse reflection component”.
Here, considering how to obtain the coefficient α, the diffuse reflection component of Bk toner is so small that it is almost equal to zero. Therefore, the regular reflection light output characteristic of Bk shown in FIG. This is considered to be almost equal to the regular reflection component output characteristic from which the component is removed.
As shown in FIG. 10, the specular reflection light output characteristic of Bk toner becomes almost zero or slightly positive as the adhesion amount increases, and never becomes negative. Find the minimum value of the ratio between the specular reflection light output and the diffuse reflection light output every time, multiply the diffuse reflection light output by the minimum value of this ratio, and subtract it from the specular reflection light output. It should be possible to extract the output characteristics.

A processing flow based on the output result of the brown belt (Gs = 27, L ^* = 25) shown in FIG. 11 will be described below. In addition, the meaning of the symbol (abbreviation) in the following description is as follows.
Vsg: Output voltage of the background portion of the transfer belt 18 Vsp: Output voltage of each pattern portion Voffset: Offset voltage (output voltage when the LED 51 is off)
_reg. ・ ・ ・ Specular reflection output (Regular Reflection)
_dif .... Diffuse reflected light output (Diffuse Reflection, see JISZ8105 color terminology)
[n] ... Number of elements: n array variables

(STEP 1): Data sampling: calculation of ΔVsp and ΔVsg (see FIGS. 21 and 22)
First, the difference from the offset voltage is calculated for all points [n] for both regular reflection light output and diffuse reflection light output.
This is because, in the end, it is desired to express only “the increment of the sensor output by the change of the amount of color toner attached”.
<Processing formula>
Regular reflection light output increment: ΔVsp_reg. [N] = Vsp_reg. [N] −Voffset_reg.
Diffuse reflected light output increment: ΔVsp_dif. [N] = Vsp_dif. [N] −Voffset_dif.
However, an OP amplifier in which each offset output voltage value (Voffset_reg: 0.0621V, Voffset_dif: 0.0635V) when the LED 51 is OFF is sufficiently small to a negligible level as in this embodiment is used. In such a case, such difference processing is not necessary.

(STEP2): Calculation of sensitivity correction coefficient α (see FIG. 22)
[Delta] Vsp_reg. [N] / [Delta] Vsp_dif. [N] is calculated for each point from [Delta] Vsp_reg. [N] and [Delta] Vsp_dif. [N] obtained in STEP1, and the component of the specular reflection light output is decomposed in STEP3. Then, the coefficient α multiplied by the diffuse reflected light output (ΔVsp_dif. [N]) is calculated.
<Processing formula>
α = min {ΔVsp_reg. [n] / ΔVsp_dif. [n]}
The reason why α is obtained from the minimum value of the ratio is that it is known in advance that the minimum value of the regular reflection component of the regular reflection light output is almost zero and is a positive value. Here, the gradation pattern has at least one, preferably three or more adhesion amount patterns in the vicinity of the adhesion amount that provides the minimum value of the ratio between the specular reflection light output and the diffuse reflection light output. . At least one or more, preferably three or more, in the vicinity of the amount of adhesion at which the minimum value of the ratio between the specular reflection light output increment and the diffuse reflection light output increment obtained from the difference from each output value when the light emitting means is off is obtained. You may make it have an adhesion amount pattern. In addition, the regular reflection light output conversion value may have at least one, preferably three or more adhesion amount patterns within an adhesion amount range in which the linear reflection relationship with the adhesion amount is linear.

(STEP3): Component decomposition of specularly reflected light (see FIG. 23)
The component decomposition of the regular reflection light output is performed by the following equation.
<Processing formula>
Diffuse light component of regular reflection light output: ΔVsp_reg._dif. [N] = ΔVsp_dif. [N] × α
Regular reflection component of regular reflection light output: ΔVsp_reg._reg. [N] = ΔVsp_reg. [N] -ΔVsp_reg._dif. [N]
When the components are decomposed in this way, the regular reflection component of the regular reflection light output becomes zero in the pattern portion where the sensitivity correction coefficient α is obtained.
By this processing, as shown in FIG. 23, the regular reflection light output is decomposed into [regular reflection light component] and [diffuse reflection light component].

(STEP 4): specular reflection light output_regular reflection component normalization (see FIG. 24)
Next, in order to correct the difference in the specular reflection light output of the three types of belt background portions, the ratio of each pattern portion output to the belt background portion output is taken and converted to a normalized value from 0 to 1.
<Processing formula>
Normalized value: β [n] = ΔVsp_reg._reg. / ΔVsg_reg._reg. (= Exposure rate of transfer belt background)

FIG. 24 shows the results of conversion into normalized values obtained by performing the same processing for all three types of belts shown in FIG.
In this way, by analyzing the components of the specularly reflected light, only the specularly reflected light component is extracted and converted into a normalized value, thereby uniquely determining the relationship between the specularly reflected light component and the amount of adhesion. Can do. This value represents the exposure rate of the belt background portion, and in the adhesion amount range from zero to one layer formation, this normalized value (= belt background exposure rate) is relative to the adhesion amount. There is a linear relationship. However, the upper limit value of the adhesion amount range from zero adhesion amount to one layer formation is a value determined by the toner particle size, density, and circularity shown in the above-mentioned solving means. This will be described later.
If the adhesion amount per unit area: M / A} = 0 to 0.4 mg / cm ² is desired to obtain the toner adhesion amount in the low adhesion amount region, the adhesion amount as shown in FIG. If the relationship with the conversion value is experimentally obtained in advance as a mathematical expression or table data, the adhesion amount can be converted by inversely converting this or referring to the table.

Here, a comparison with the prior art will be made. In claim 4 of Patent Document 8 (Japanese Patent Laid-Open No. 2001-215850), specular reflection light + (diffuse reflection light−diffuse reflection light output min) × predetermined coefficient is shown. There is a description that the predetermined coefficient is “−6” so that the post-output becomes a first order correlation. However, as described above, the characteristic coefficient of the optical detection means is multiplied by such a predetermined coefficient. It can be said that it is practically meaningless in that it is not considered.
On the other hand, in this embodiment, since the coefficient calculated based on the sensor output of the specular reflection light and the diffuse reflection light is multiplied as the predetermined coefficient, a high accuracy considering the characteristic variation of the optical detection means is taken into consideration. Detection can be performed.

Explanation for (3) Next, processing for removing [diffuse reflected light output component from the belt background portion] from [diffuse reflected light output voltage] will be described.
What is finally determined by the adhesion amount conversion algorithm in this embodiment is a unique relationship between the diffuse reflection light output and the toner adhesion amount.
However, as shown in FIG. 20, the light that enters the diffuse reflection light receiving element 55 includes diffuse reflection light (noise component) from the belt background in addition to the diffuse reflection light from the toner layer. This component needs to be removed from the output.
In FIG. 20, the ratio between the “background part output” and the “pattern part output” of the regular reflection component is uniquely determined with respect to the adhesion amount (adhesion amount detectable range: 0 to 0.4 mg / cm ² ).
In addition, in the diffuse reflection component from the toner layer, if the irradiation light to the detection target surface is constant, the relationship with the adhesion amount is uniquely determined (attachment amount detectable range: 0 to 1.0 mg / cm ² ).
As a continuation of STEP 4, the processing flow will be described based on the output result of the brown belt (Gs = 27, L ^* = 25) shown in FIG.
As shown in the results of FIG. 13, the diffuse reflected light output from the belt background portion becomes maximum at the belt background portion where the toner is not attached, and the component gradually decreases as the toner adheres.
The relationship with the amount of adhesion of the diffuse reflection light output voltage increment due to the light that directly enters the diffuse reflection light receiving element 55 from the belt background is the exposure ratio of the transfer belt 18, that is, the specular reflection component of the specular reflection light output obtained previously. In order to be proportional to the normalized value (see FIG. 24), processing for removing [diffuse reflected light output component from the belt background portion] from [diffuse reflected light output voltage] is as follows.

(STEP 5): Correction of background variation of diffused light output (see FIG. 25)
<Processing formula>
Diffuse light output after correction: ΔVsp_dif '
ΔVsp_dif ′ = [diffuse light output voltage] − [belt background output] × [normalized value of specular reflection component]
= ΔVsp_dif (n) −ΔVsg_dif × β (n)

The results are shown in FIG. By performing such correction processing, the influence of the background portion of the transfer belt 18 can be eliminated. Accordingly, the [diffuse reflected light component directly reflected from the belt background portion] can be removed from the [diffuse reflected light output] in the low adhesion amount region where the regular reflected light output has sensitivity.
By performing such processing, the corrected diffuse reflection light output in the adhesion amount range from zero adhesion to one layer formation is converted to a value having a linear relationship with the adhesion amount through the origin. . However, the upper limit value of the adhesion amount range from zero adhesion amount to one layer formation is a value determined by the toner particle size, density, and circularity shown in the above-mentioned solving means. This will be described later.

Here, a supplementary explanation of the diffuse reflected light will be given. Since the specularly reflected light is light reflected from the surface of the detection target surface, as shown in FIG. 24, when the detection target surface is 100% covered with toner, the output changes substantially in the adhesion amount region beyond that. The normalized conversion value becomes almost zero. On the other hand, the diffuse reflected light is light that is reflected from the LED 51 and enters the toner layer, and thus is reflected multiple times. Therefore, as shown in FIG. 13, a high adhesion amount region in which the toner layer is covered 100% or more. However, the sensor output has a monotonically increasing characteristic. Therefore, as shown in FIG. 26, the light reflected from the belt background portion also includes a primary component directly reflected from the belt background portion and secondary and tertiary components reflected through the toner layer. is there.
In this embodiment, only the primary component is corrected in STEP 5, but this correction alone can remove the influence of the belt background portion almost accurately only in the low adhesion amount region where sensitivity correction is performed. Since the second-order and third-order components are sufficiently smaller than the first-order components, practically sufficient accuracy can be obtained even by correcting only the first-order components.

Explanation for (4) By the above processing, in the low adhesion amount region where the specular reflection light output has sensitivity, the relationship between the toner adhesion amount and the specular reflection light can be uniquely expressed in (2) [regular reflection light component ], And in (3), it was possible to remove [diffuse reflected light component directly reflected from the belt background] from the diffuse reflected light, and based on these, the sensitivity of the diffuse reflected light output Make corrections.
Here, the reason for performing the sensitivity correction is to perform the following correction as described above.
(1) Correction for lot variation in light emitting element output and light receiving element output.
(2) Correction for temperature characteristics and temporal deterioration characteristics of light emitting element output and light receiving element output.
The biggest point in this processing is that in the low adhesion amount region where only one toner layer is formed,
[1] The normalized value of the regular reflection light output (regular reflection component), that is, the exposure rate of the transfer belt background portion, has a linear relationship with the toner adhesion amount.
[2] [Diffusion reflection component from toner layer] has a linear relationship that passes through the origin with respect to the toner adhesion amount.
That is, the sensitivity of the diffuse reflected light output is corrected by utilizing the fact that the two corrected outputs of the specular reflected light and the diffuse reflected light are both in a linear relationship with the toner adhesion amount.
Hereinafter, an example of a method for performing the sensitivity correction will be described.

(STEP 6): Sensitivity correction of diffuse reflected light output (see FIG. 25)
According to the inverse conversion formula obtained from the relationship between the adhesion amount (measured value) obtained in FIG. 24 and the normalized value of the specular reflection light (specular reflection component), or by referring to the conversion table, “specular reflection light (regular reflection component) ) Normalized value ”is converted into adhesion amount (conversion value), and the diffuse reflected light output after correction of background fluctuation is plotted against this adhesion amount (conversion value), and diffused from the linear relationship in the low adhesion amount region. The sensitivity of the reflected light output is obtained, and correction is performed so that this sensitivity becomes a predetermined target sensitivity.
Here, the sensitivity of the diffuse reflected light output is the slope of the straight line shown in FIG. 28, and the diffuse reflected light output after the background portion fluctuation correction of a certain adhesion amount (conversion value) is a certain value (here, 0). The correction coefficient by which the current inclination is multiplied is calculated and corrected so as to be 1.2) when .175. Since this point must pass through the origin, it is calculated by the following zero point approximation formula.

(1). The slope of the straight line is obtained by the method of least squares.
Straight line slope = (Σx [i] × y [i]) / Σ (x [i]) ²
x [i]: Adhering amount (conversion value)
y [i]: Diffuse light output after correction of background variation However, the range of x used for the calculation is 0 ≦ x ≦ 0.3 [mg / cm ² ].
In this embodiment, the upper limit value of the range of x used for the calculation is 0.3, but this upper limit value is a value determined by the toner particle size, density, and circularity shown in the solution means described above. This will be described later.

(2) A sensitivity correction coefficient γ is calculated so that a certain adhesion amount: a calculated from the sensitivity thus obtained becomes a certain value: b.
Sensitivity correction coefficient: γ = b / (Slope of straight line × a)

(3) The diffused reflected light output after the background portion fluctuation correction obtained in STEP 5 is corrected by multiplying by this sensitivity correction coefficient γ.
Diffuse light output after sensitivity correction: ΔVsp_dif ''
ΔVsp_dif '' = [diffuse light output voltage after background fluctuation correction] × [sensitivity correction coefficient γ]
= ΔVsp_dif [n] '× γ

FIG. 29 shows the results of conversion into normalized values obtained by performing the same processing for all three types of belts.
Here, since the diffuse reflected light output voltage before correction is as shown in FIG. 13, the above processing is the object of the present invention.
(1) Correction for lot variation in light emitting element output and light receiving element output,
(2) Correction for temperature characteristics and temporal deterioration characteristics of light emitting element output and light receiving element output,
I was able to confirm that it was done enough.
By such processing, the diffuse reflected light output after the sensitivity correction can be uniquely expressed with respect to the toner adhesion amount. Therefore, if it is experimentally obtained in advance as an equation or table data, By referring to the conversion table, it is possible to accurately convert the adhesion amount up to the high adhesion amount region.

FIG. 30 shows the result of plotting the adhesion amount (conversion value) obtained by actually inversely transforming the normalized value against the adhesion amount measurement value by an electronic balance.
As shown in FIG. 30, it can be confirmed that the adhesion amount can be converted almost accurately up to the high adhesion amount region. Since accurate adhesion amount detection up to a high adhesion amount region becomes possible, it becomes possible to accurately control the maximum target adhesion amount in image density control, so regardless of time, environment, and sensor lot variation. , You can always get a stable image quality.

FIG. 31 shows a color produced on the transfer belt 18 of the laser color printer A shown in FIG. 1 with three sensors extracted as the upper and lower limit products and the center product of the variation among 200 prototypes of density detection sensors. A diffuse reflected light output voltage obtained by detecting a total of 30 P patterns (gradation patterns) of 10 toner colors is shown. FIG. 32 shows the diffuse reflected light conversion values according to the conversion algorithms of STEP1 to STEP6. The LED current at this time is a value when the regular reflected light output voltage of the background portion of the transfer belt 18 is adjusted to 4.0V.
As a result, by using the algorithm of the present embodiment (the present invention), the output variation of the light receiving element due to various factors in the optical detection means as described above can be achieved without requiring strict adjustment on the hardware side. It is possible to automatically and accurately correct the algorithm side, that is, the software side.

Next, the relationship between the upper limit value of the adhesion amount range for performing sensitivity correction of the diffused light output in the present invention and the toner particle size, density, and circularity will be described.
As shown in FIG. 32, in order to accurately correct the sensitivity variation of the sensor, it is important to obtain the diffuse light output sensitivity correction coefficient γ obtained in STEP 6 very accurately. As described above, as described above, the adhesion amount range used for the sensitivity calculation is an adhesion amount range in which a linear relationship is established for each sensor output correction value with respect to the adhesion amount, that is, toner from the adhesion amount zero to one layer formation. It is important to calculate the sensitivity using only data points (pattern output) in the adhesion amount range.
Hereinafter, how this adhesion amount range is obtained will be described based on experimental results.

FIG. 33 shows the diffused light output characteristics with respect to the adhesion amount: M / A when the transfer belt 18 is a black belt (60 ° glossiness: 120, brightness: 1.8) using the image forming apparatus shown in FIG. It is a graph which shows (measured value).
The reason why the transfer belt 18 is a black belt in this experiment is that, as shown in FIG. 15, the diffused light output from the background portion of the transfer belt 18 is made zero as much as possible, and the diffused light output of the P sensor is changed by the change in the amount of toner attached Because I wanted to increase only.
As the toner, a toner having a volume average particle diameter: Dv = 5.5 [μm], a density: ρ = 0.43 [g / cm ³ ], and a circularity of 0.98 was used.

In this way, it is understood that the diffused light output from the background portion of the transfer belt 18 becomes substantially zero, so that the diffused light output with respect to the adhesion amount can be approximated substantially linearly for each adhesion amount section.
In other words, the adhesion amount is in this example: 0~0.284 [mg / cm ^2] to a range of, also adhesion amount: from 0.284 to 0.535 in the range of ^{[mg / cm 2], R} 2 = 0.99 It can be seen that the above and very high linearity can be obtained. Incidentally, when the intersection of these two straight lines is obtained, it is obtained as 0.284 [mg / cm ² ].

Next, why the diffusion light with respect to the adhesion amount becomes a straight line for each adhesion amount section will be described.
FIG. 34 is a diagram showing only the “component from the toner layer” of the diffused light output in FIG.
As described above, when the toner layer is composed of only the first layer, the amount of diffused light from the toner, that is, the output of the diffused light is very simple and is proportional to the number of vectors, that is, the amount of adhered toner.

Next, FIG. 35 is a diagram illustrating a state where the diffused light emitted from the toner is component-decomposed for each toner layer when the second layer is formed in the toner layer. Here, the toner layer (uppermost layer) is the first layer.
The diffuse light output emitted from the uppermost toner layer is considered to emit light having the same intensity as that shown in FIG. 34, but is emitted from the second layer toner covered with the uppermost toner. The incident light to the second layer toner is attenuated by the passage of the uppermost toner layer and is attenuated by the passage of the uppermost toner layer when it is radiated next time. The light output is an output attenuated by some percent from the amount of radiation from the uppermost toner layer.
Therefore, the output in the adhesion amount range of the first layer to the second layer can be expressed as the sum of the diffused light component from the toner layer (first layer) and the diffused light component from the toner layer (second layer). Therefore, a linear output characteristic is obtained for each section as shown in FIG.
From this, it can be seen that the intersection point of the two straight lines obtained previously: 0.284 [mg / cm ² ] is the maximum adhesion amount of the toner layer (first layer).
Therefore, the amount of adhesion that gives the intersection of these two straight lines is the upper limit value of the amount of adhesion in the calculation of the sensitivity correction coefficient for the diffused light output, and the amount of adhesion used in the sensitivity calculation in this embodiment is:
0 ≦ Adhesion amount ≦ 0.284 [mg / cm ² ]
It becomes.

Next, 0.284 [mg / cm ² ], which is the maximum adhesion amount of the toner layer (first layer) obtained by this experiment, is obtained by calculation.
FIG. 36 is a diagram illustrating a state in which one layer of toner having a radius of r [μm] is closely packed on the transfer belt. Here, for the sake of simplicity, the case where the toner is a true sphere will be considered.
The dimensions of each part in FIG.
a = {(2 / √3) −1} × r,
b = (1 / √3) × r,
c = (2-√3) × r
d = 2 × {1− (1 / √3)} × r
e = (2 / √3) × r
f = 2 × (2 + √3) × r
It is.

First, the area of the large triangle in FIG. 36 and the area of the toner inside thereof are obtained, and the area ratio of the toner particles is calculated from these areas.
Triangular area: S
S = (base) x (height) ÷ 2
= (Base) x (base ÷ 2 x √3) ÷ 2
= (2 × (2 + √3) × r) × ((2 + √3) × √3 × r) / 2
= √3 × (2 + √3) ² × r ² Formula (A)

The area of the toner in the triangle: T can be expressed as the sum of “the area of 6 circles” and “the area of 12 (the area of the hatched portion H shown in FIG. 37)”. Obtained from the area of the part H.
Area of hatched portion H = (Area of fan) − (Area of triangle)
= (R ² × θ) − ((r−h) ² × tan θ)
(However, θ = acos ((r−h) / r), h = (2−√3) × r)
= 12 × r ² × (θ− (√3-1) ² × tan θ)
(∵ h = (2-√3) × r)

Therefore, the area of the toner in the triangle: T is
T = (area of 6 circles) + ((area of hatched portion H shown in FIG. 37) × 12)
= (6 × π × r ² ) + 12 × r ² × (θ− (√3−1) ² × tan θ)
= 6 × r ² × (π + 2 × (θ− (√3−1) ² × tan θ)) Formula (B)
It becomes.
From the expressions (A) and (B), the area ratio of the toner inside the triangle, that is, the toner layer (first layer) is as follows.

As described above, the toner particle (first layer) area ratio when the toner is assumed to be a true sphere and is packed most closely disappears from the term of toner particle size: r [μm]. Thus, when the above equation is calculated, 90.608 [%] can be obtained.
When this is converted into a volume and the amount of adhesion is converted from the density of the toner, the result is as follows.
Maximum adhesion amount of toner layer (first layer) = (area ratio of toner (first layer)) × (4/3 × toner particle size) × (toner density) Formula (D)
Therefore, it becomes as follows from Formula (C) and Formula (D).

  The above is the calculation when the toner is a true sphere (circularity = 1). However, when the toner is not a true sphere, the degree of circularity can be applied to the equation (E), and is as follows. .

The toner physical properties used in the above experimental results were particle size: r = 5.5 [μm] and density: ρ = 0.43 [g / cm ³ ], and these were substituted into the above equation. When calculated, it was 0.280 [mg / cm ³ ], and it was confirmed that a value very close to the value 0.284 obtained by experiment was obtained.
From the above, the adhesion amount range used for calculating the sensitivity correction coefficient of the diffused light output can be expressed by the following equation.

  Finally, the result of the above verification performed by changing the toner particle diameter is shown. In the experiment, four levels of toner having different toner particle diameters shown in Table 2 below were used.

FIG. 38 shows the maximum adhesion amount of the toner layer (first layer) and the calculated value obtained experimentally in the manner shown in FIG.
As shown in FIG. 38, it was confirmed that even when the particle diameter was varied, a result in which the experimental value almost coincided with the calculated value was obtained.

  As shown in the above formula (F), the adhesion amount range used for the calculation of sensitivity correction is proportional to the toner particle size: r. Therefore, when mounted on an actual machine, the toner particle size tolerance is taken into consideration. It is important to calculate the sensitivity within the adhesion amount range equal to or less than the adhesion amount obtained by substituting the lower limit of the particle size tolerance.

In the embodiment described above, the optical detecting means having the light emitting means, the specular reflection light receiving element and the diffuse reflection light receiving element shown in FIG. 4 is used. However, the beam splitter shown in FIG. A similar detection function can be obtained even if an optical detection means having the above is used (second embodiment).
In the above embodiment, the detection target surface is the transfer belt 18 as a transfer body, but each photosensitive drum may be a detection target surface (third embodiment). In this case, the P sensor 40 is provided to face each photosensitive drum.

In the above embodiment, an example of a color image forming apparatus of a four-tandem direct transfer method is shown. However, as shown in FIG. 39, after being transferred onto an intermediate transfer body in a four-tandem tandem configuration, it is transferred to a transfer sheet. The same can be applied to a batch image transfer type color image forming apparatus (fourth embodiment).
In the embodiment shown in FIG. 39, the P pattern for density detection shown in FIG. 18 is formed on the intermediate transfer belt 2 as an intermediate transfer member, and this is detected by the P sensor 40 arranged in the vicinity of the support roller 2B. To do. That is, the intermediate transfer belt 2 is a detection target surface. The detection method and operation (equivalent handling of detection data, etc.) are the same as in the first embodiment.

The outline of the configuration and operation of a tandem type color copier as an image forming apparatus in this embodiment will be described below. The color copying machine 1 has an image forming unit 1A located at the center of the apparatus main body, a paper feeding unit 1B located below the image forming unit 1A, and an image reading unit 1C located above the image forming unit 1A. doing.
An intermediate transfer belt 2 as a transfer body having a transfer surface extending in the horizontal direction is disposed in the image forming unit 1A, and an image of a color complementary to the color separation color is disposed on the upper surface of the intermediate transfer belt 2. The structure for forming is provided. That is, the photosensitive drums 3Y, 3M, 3C, and 3B as image carriers capable of carrying an image of complementary color toners (yellow, magenta, cyan, and black) are arranged along the transfer surface of the intermediate transfer belt 2. It is juxtaposed.

Each of the photosensitive drums 3Y, 3M, 3C, and 3B is composed of a drum that can rotate in the same counterclockwise direction, and around the charging device 4 is a charging unit that performs image forming processing in the rotation process. The optical writing device 5 as an exposure unit for forming an electrostatic latent image having a potential _VL based on the image information on each of the photosensitive drums 3Y, 3M, 3C, and 3B. A developing device 6 as a developing unit that develops the electrostatic latent image with toner having the same polarity as the electrostatic latent image, a transfer bias roller 7 as a primary transfer unit, an applied voltage member 15, and a cleaning device 8 are arranged. The alphabets attached to the respective symbols correspond to the colors of the toner as in the photosensitive drum 3. Each developing device 6 accommodates each color toner.
The intermediate transfer belt 2 is configured to be wound around a plurality of rollers 2A to 2C and to move in the same direction at a position facing the photosensitive drums 3Y, 3M, 3C, and 3B. A roller 2C, which is different from the rollers 2A and 2B that support the transfer surface, faces the secondary transfer device 9 with the intermediate transfer belt 2 interposed therebetween. In FIG. 39, reference numeral 10 indicates a cleaning device for the intermediate transfer belt 2.

The surface of the photosensitive drum 3Y is uniformly charged by the charging device 4Y, and an electrostatic latent image is formed on the photosensitive drum 3Y based on the image information from the image reading unit 1C. The electrostatic latent image is visualized as a toner image by a two-component (carrier and toner) developing device 6Y containing yellow toner, and the toner image is formed on the intermediate transfer belt 2 as a first transfer step. The image is attracted and transferred by the electric field generated by the voltage applied to the transfer bias roller 7Y.
The applied voltage member 15Y is provided on the upstream side of the transfer bias roller 7Y in the rotation direction of the photosensitive drum 3Y. The applied voltage member 15Y applies a voltage to the intermediate transfer belt 2 that has the same polarity as the charging polarity of the photosensitive drum 3Y and has an absolute value that is larger than the solid _VL , and before the toner image enters the transfer area, the photosensitive drum 3Y. From the toner to the intermediate transfer belt 2 is prevented, and the disturbance due to dust during the transfer of the toner from the photosensitive drum 3Y to the intermediate transfer belt 2 is prevented.

The other photoconductor drums 3M, 3C, and 3B also form similar images only with different toner colors, and the toner images of the respective colors are sequentially transferred onto the intermediate transfer belt 2 and superimposed.
After the transfer, the toner remaining on the photosensitive drum 3 is removed by the cleaning device 8, and after the transfer, the electric potential of the photosensitive drum 3 is initialized by a neutralizing lamp (not shown), and is prepared for the next image forming process.
The secondary transfer device 9 includes a transfer belt 9 </ b> C that is wound around the charging drive roller 9 </ b> A and the driven roller 9 </ b> B and moves in the same direction as the intermediate transfer belt 2. By charging the transfer belt 9C with the charging drive roller 9A, it is possible to transfer a multicolor image superimposed on the intermediate transfer belt 2 or a supported single color image onto a paper 28 as a sheet-like recording medium.

The paper 28 is fed from the paper feed unit 1B to the secondary transfer position. The paper feed unit 1B has a plurality of paper feed cassettes 1B1 in which papers 28 are stacked and housed, and a paper feed roller 1B2 that separates and feeds the papers 28 contained in the paper feed cassette 1B1 one by one in order from the top. A pair of conveying rollers 1B3, a pair of registration rollers 1B4 positioned upstream of the secondary transfer position, and the like.
The paper 28 fed from the paper feed cassette 1B1 is temporarily stopped by the registration roller pair 1B4, and after correcting the oblique displacement and the like, the front end of the toner image on the intermediate transfer belt 2 and a predetermined position at the front end in the transport direction are set. Are sent to the secondary transfer position by the registration roller pair 1B4. A manual feed tray 29 is provided on the right side of the apparatus main body so that it can be turned up and down, and the paper 28 accommodated in the manual feed tray 29 joins the paper feed path from the paper feed cassette 1B1 fed by the paper feed roller 31. The paper is sent toward the registration roller pair 1B4 by the conveying path.

In the optical writing device 5, writing light is controlled by image information from the image reading unit 1C or image information output from a computer (not shown), and the photosensitive drums 3Y, 3M, 3C, and 3B correspond to the image information. Writing light is emitted to form an electrostatic latent image.
The image reading unit 1C includes an automatic document feeder 1C1, a scanner 1C2 having a contact glass 80 as a document table, and the like. The automatic document feeder 1C1 has a configuration capable of reversing the document fed on the contact glass 80, and can perform scanning on each surface of the document.
The electrostatic latent image formed on the photosensitive drum 3 formed by the optical writing device 5 is subjected to visible image processing by the developing device 6 and is primarily transferred to the intermediate transfer belt 2. When the toner images for each color are superimposed and transferred onto the intermediate transfer belt 2, they are secondarily transferred onto the paper 28 by the secondary transfer device 9. The second-transferred paper 28 is sent to the fixing device 11 where the unfixed image is fixed by heat and pressure. Residual toner on the intermediate transfer belt 2 after the secondary transfer is removed by the cleaning device 10.

  The paper 28 that has passed through the fixing device 11 is selectively guided to the conveyance path toward the paper discharge tray 27 and the reverse conveyance path RP by the conveyance path switching claw 12 provided on the downstream side of the fixing apparatus 11. When the paper is conveyed toward the paper discharge tray 27, it is discharged onto the paper discharge tray 27 by the paper discharge roller pair 32 and stacked. When guided to the reversal conveyance path RP, it is reversed by the reversing device 38 and sent again toward the registration roller pair 1B4.

With the above configuration, in the color copying machine 1, the photosensitive drum 3 that is uniformly charged is statically exposed by scanning the document placed on the contact glass 80 or by image information from the computer. An electrostatic latent image is formed, and the electrostatic latent image is subjected to visible image processing by the developing device 6, and then the toner image is primarily transferred to the intermediate transfer belt 2.
In the case of a single image, the toner image transferred to the intermediate transfer belt 2 is transferred as it is to the paper 28 fed out from the paper supply unit 1B. In the case of a multi-color image, the images are superimposed by repeating primary transfer, and then secondary transferred onto the paper 28 at once.
After the secondary transfer, the paper 28 is fixed with an unfixed image by the fixing device 11 and then discharged to the paper discharge tray 27 or reversed and sent again toward the registration roller pair 1B4 for double-sided image formation.
In this embodiment, the detection target surface is the intermediate transfer belt 2 as a transfer member, but each photosensitive drum may be a detection target surface (fifth embodiment). In this case, the P sensor 40 is provided to face each photosensitive drum.

Further, each color toner image is formed by using one photosensitive drum and a revolver type developing device, and each toner image is transferred onto an intermediate transfer member, and then transferred onto a transfer sheet as a sheet-like recording medium. The same can be applied to the type of color image forming apparatus (sixth embodiment). An example is shown in FIG.
In the embodiment shown in FIG. 40, the P pattern for density detection shown in FIG. 18 is formed on an intermediate transfer belt 426 as an intermediate transfer member, and this is detected by a P sensor 40 disposed in the vicinity of the drive roller 444. . That is, the intermediate transfer belt 426 is a detection target surface. The detection method and operation (handling of detection data, etc.) are the same as in the first embodiment.

The outline of the configuration of a color copying machine as an image forming apparatus in this embodiment will be described below.
In a color copying machine, a writing optical unit 400 serving as an exposure unit converts color image data from the color scanner 200 into an optical signal and performs optical writing corresponding to a document image, on a photosensitive drum 402 serving as an image carrier. An electrostatic latent image is formed on the surface. The writing optical unit 400 includes a laser diode 404, a polygon mirror 406, a rotation motor 408 thereof, an fθ lens 410, a reflection mirror 412, and the like.
The photosensitive drum 402 is rotated in the counterclockwise direction as indicated by an arrow, and a photosensitive member cleaning unit 414, a static elimination lamp 416, a potential sensor 420, and a rotary developing device 422 are selected around the photosensitive drum 402. A developing device, a development density pattern detector 424, an intermediate transfer belt 426 as an intermediate transfer member, and the like are arranged.

The rotary developing device 422 includes a black developing unit 428, a cyan developing unit 430, a magenta developing unit 432, a yellow developing unit 434, and a rotation driving unit (not shown) that rotates each developing unit. Each developing device is a so-called two-component developing type developer containing a mixed developer of carrier and toner, and has the same configuration as the developing device 4 shown in the above embodiment. The conditions and specifications of the magnetic carrier are the same.
In the standby state, the rotary developing device 422 is set at the black development position. When the copying operation is started, the color scanner 200 starts reading the black image data from a predetermined timing. Based on the above, optical writing with a laser beam and formation of an electrostatic latent image (black latent image) are started.

In order to develop from the leading edge of the black latent image, before the leading edge of the latent image reaches the developing position of the black developing device 428, the developing sleeve is started to rotate and the black latent image is developed with black toner. A negative polarity toner is formed on the photosensitive drum 402.
Thereafter, the development operation of the black latent image area is continued, but when the trailing edge of the latent image passes the black development position, the rotary development is quickly performed from the development position for black to the development position for the next color. The device 422 rotates. This operation is completed at least before the leading edge of the latent image by the next image data arrives.
When the image forming cycle is started, first, the photosensitive drum 402 is rotated counterclockwise as indicated by an arrow, and the intermediate transfer belt 426 is rotated clockwise by a drive motor (not shown). As the intermediate transfer belt 426 rotates, black toner image formation, cyan toner image formation, magenta toner image formation, and yellow toner image formation are performed. Finally, black (Bk), cyan (C), and magenta (M) are formed. , Yellow (Y) in this order (primary transfer) on the intermediate transfer belt 426 to form a toner image.

The intermediate transfer belt 426 includes a primary transfer electrode roller 450 that faces the photosensitive drum 402, a drive roller 444, a secondary transfer counter roller 446 that faces the secondary transfer roller 454, and a cleaning unit that cleans the surface of the intermediate transfer belt 426. It is stretched between the supporting members of the cleaning facing roller 448A facing the surface 452, and is driven and controlled by a driving motor (not shown).
The black, cyan, magenta, and yellow toner images sequentially formed on the photosensitive drum 402 are accurately and sequentially aligned on the intermediate transfer belt 426, thereby forming a four-color superimposed belt transfer image. This belt transfer image is collectively transferred onto a sheet by a secondary transfer counter roller 446.

Each of the recording paper cassettes 458, 460, and 462 in the paper supply bank 456 contains various sizes of paper different from the size of the paper stored in the cassette 464 in the apparatus body. The designated paper is fed and conveyed in the direction of the registration roller pair 470 by the paper feed roller 466 from the size paper storage cassette. In FIG. 34, reference numeral 468 denotes a manual paper feed tray for OHP paper, thick paper, and the like.
At the time when image formation is started, the paper is fed from the paper feed port of one of the above cassettes and waits at the nip portion of the registration roller pair 470. Then, when the leading edge of the toner image on the intermediate transfer belt 426 approaches the secondary transfer counter roller 446, the registration roller pair 470 is driven so that the leading edge of the sheet exactly coincides with the leading edge of the image. Is done.

In this manner, the sheet is overlapped with the intermediate transfer belt 426 and passes under the secondary transfer counter roller 446 to which a voltage having the same polarity as the toner is applied. At this time, the toner image is transferred to the paper. Subsequently, the sheet is neutralized, peeled off from the intermediate transfer belt 426, and moved to the sheet conveying belt 472.
The sheet onto which the four-color superimposed toner images have been collectively transferred from the intermediate transfer belt 426 is conveyed to the belt fixing type fixing device 470 by the paper conveying belt 472, and the toner image is fixed by the fixing device 470 by heat and pressure. The sheet that has been fixed is discharged out of the apparatus by the discharge roller pair 480 and stacked on a tray (not shown). Thereby, a full color copy is obtained.
In this embodiment, the detection target surface is the intermediate transfer belt 426 as a transfer body, but the photosensitive drum 402 may be the detection target surface (sixth embodiment). In this case, the P sensor 40 is provided to face the photosensitive drum 402.

In each of the above embodiments, the processing is based on the minimum value of the ratio between the specular reflection light output and the diffuse reflection light output, but the regular reflection light output increment obtained from the difference from each output value when the light emitting means is off. A similar detection function can be obtained as a method of processing based on the minimum value of the ratio to the diffuse reflection light output increment.
In each of the above embodiments, the image forming apparatus having the powder adhesion amount detection device is illustrated. However, in the adhesion amount detection field in which powder other than the toner is handled, the same detection function can be obtained by the same processing method. it can.

The effects obtained in the above embodiments will be described below.
In the prior art, as described above, the detectable range of the color adhesion amount gradually narrows due to the decrease in the glossiness of the detection target surface over time, so wear deterioration of the detection target surface over time becomes the rate-determining factor of the life. However, by performing the conversion process as described above, compared to the conventional specular reflection light detection, the adhesion amount detection range is expanded, and accurate adhesion amount detection can be performed without depending on the glossiness. . Moreover, in the said Example, since it does not depend on the wear deterioration of a detection target surface, the lifetime of a detection target surface can be extended.
Then, by applying the algorithm of the powder adhesion amount conversion method of the present invention to the adhesion amount detection using the image carrier, the transfer body, or the intermediate transfer body as the detection target surface in the color image forming apparatus, the conventional technique detects density. Even if it is a belt having a low glossiness, which is said to be difficult, and even if the detection target surface is a black belt, the amount of adhesion can be detected with high accuracy up to a high adhesion amount region. As a result, the solid adhesion amount that is the maximum adhesion amount target value can be detected, and stable image density control can always be performed regardless of environmental changes over time.
Further, in the powder adhesion amount conversion method of the present invention, the upper limit value of the adhesion amount range of the gradation pattern (toner patch) used for calculating the sensitivity correction coefficient of the diffused light output is determined by the particle size, density, and Since the sensitivity calculation can be performed in a wider range by reasonably obtaining from the circularity, sensitivity correction with higher accuracy can be performed. Thereby, it becomes possible to correct the sensitivity variation of the sensor of the optical detection means with higher accuracy.

Furthermore, by performing the powder adhesion amount conversion processing of the present invention, the diffuse reflected light output is set to a value that can obtain a linear relationship with the adhesion amount in the low adhesion amount range from zero adhesion amount to one powder layer formation. Can be converted.
In addition, by performing the above conversion process (automatic correction function of diffused light output sensitivity), the diffused light output variation (hardware side) due to the output variation of the light emitting element and the light receiving element of the density detection sensor is converted into an adhesion amount conversion algorithm. Adjustment is possible on the sensor side (software side), so adjustment work on the sensor side (hardware side) at the time of sensor shipment inspection as previously done is unnecessary, or the adjustment range can be greatly expanded. It becomes.
Thereby, the productivity in sensor manufacturing can be dramatically improved, and the cost of the sensor can be reduced, and hence the cost of the image forming apparatus can be reduced.

In addition, even with the decrease in the amount of LED light over time of the density detection sensor and the output fluctuation due to the temperature characteristics of the light emitting element and the light receiving element, an automatic correction function of the diffuse reflected light output sensitivity always performs stable adhesion amount conversion. Can do.
In the conventional technology, it was difficult to calibrate the sensitivity with a sensor with only diffuse reflected light output (type (2)). Even when the detection target surface is black, accurate sensitivity calibration and adhesion amount detection can be performed. .
In addition, with conventional specular reflection light output and diffuse reflection light output type sensors (types (3) and (4)), the amount of adhesion detection accuracy decreases over time due to changes in characteristics of the detection target surface over time. However, the automatic correction function of the diffuse reflected light output sensitivity allows the algorithm side (software side) to absorb changes in the characteristics of the detection target surface over time. Even if it is very low, the diffuse reflected light output can be accurately converted into an adhesion amount regardless of the glossiness, and even in the case of black, over a high adhesion amount region. As a result, the life of the detection target surface can be extended, and the running cost can be reduced.

  In addition, the life of the image carrier, the transfer belt, or the intermediate transfer belt, which is the detection target surface, can be extended. In particular, the detection target surface such as an image carrier is generally united with a charging device, a developing device, a cleaning device, and the like, and a method of batch replacement is adopted. Since it is not necessary to perform early collective replacement due to a decrease, the running cost can be greatly reduced in relation to other unit parts that have not reached the end of their service life.

  INDUSTRIAL APPLICABILITY The powder adhesion amount conversion method and the powder adhesion amount detection apparatus using the same of the present invention are effectively used for detecting the adhesion amount of toner adhering to an image carrier, transfer body or intermediate transfer body of an image forming apparatus. can do. In addition to the image forming apparatus, this powder adhesion amount conversion method and powder adhesion amount detection apparatus using the same can be detected in the same manner in the adhesion amount detection field that handles powder other than toner. Function can be obtained.

1 is a schematic front view of a color laser printer as an image forming apparatus according to a first embodiment of the present invention. It is a block diagram of the optical detection means of the type which detects only regular reflection light. It is a block diagram of the optical detection means of the type which detects only diffuse reflection light. It is a block diagram of the optical detection means of the type which detects a regular reflection light and diffuse reflection light simultaneously. FIG. 5 is a configuration diagram of an optical detection means using a beam splitter, which is a type that detects specular reflection light and diffuse reflection light simultaneously. It is a graph which shows the detection result of the regular reflection light output with respect to color toner adhesion amount, and a diffuse reflection light output. 6 is a graph showing a relationship between a color toner adhesion amount and a difference between specular reflection light. It is a schematic diagram which shows the reflection state of irradiation light in case the mirror surface glossiness of a detection target surface is high. FIG. 6 is a schematic diagram illustrating a reflection state of irradiation light when toner is attached and the specular glossiness of a detection target surface is decreased. It is a graph which shows the regular reflection light output characteristic with respect to the black toner adhesion amount. It is a graph which shows the regular reflection light output characteristic with respect to the color toner adhesion amount. It is a graph which shows the diffuse reflected light output characteristic with respect to black toner adhesion amount. It is a graph which shows the diffuse reflected light output characteristic with respect to the color toner adhesion amount. It is a graph which shows the regular reflection light output characteristic with respect to the mirror surface glossiness of a detection target surface. It is a graph which shows the diffuse reflected light output characteristic with respect to the brightness of a detection target surface. It is a graph which shows the relationship between the fall of the glossiness of a detection target surface with time, and correction | amendment of a regular reflection light output. It is a graph which shows the relationship between the color toner adhesion amount and the difference of regular reflection light in the fall of the glossiness with time of a detection object surface. It is a top view which shows a gradation pattern. Indicates that the light received by the specular reflection light receiving element as specular reflection light includes a diffuse reflection light component from the detection target surface and a diffuse reflection light component from the toner layer in addition to a pure specular reflection light component. It is a schematic diagram. It is a block diagram which shows the relationship between the reflected light component which should be actually detected by the optical detection means, and the reflected light component which should be removed. It is a graph which shows the relationship between the adhesion amount at the time of data sampling, and a detection output. It is a graph which shows the relationship between the sensitivity correction coefficient multiplied by a diffuse reflection light output, the adhesion amount, and a detection output. It is a graph which shows component decomposition | disassembly of regular reflection light. It is a graph which shows normalization of the regular reflection component of a regular reflection light output. It is a graph which shows the relationship between the surface part fluctuation | variation correction amount of a diffuse reflected light output, the adhesion amount, and a detection output. It is a schematic diagram which shows that a some component exists also in the component reflected from a belt background part. It is a graph which shows the relationship between the normalization value of a regular reflection component, and the diffuse reflected light output after background part fluctuation | variation correction | amendment. It is a graph which shows the sensitivity of a diffuse reflected light output. It is a graph which shows the conversion result to a normalized value. It is a graph which shows the result of having plotted the adhesion amount obtained by carrying out reverse conversion of the normalization value with respect to the adhesion amount measurement value by an electronic balance. It is a graph which shows the relationship between the lot dispersion | variation in the optical detection means extracted from many prototypes, and the diffuse reflected light output in a gradation pattern detection. It is a graph which shows the relationship between the lot dispersion | variation of the optical detection means extracted from many prototypes, and the diffuse reflected light output after the sensitivity correction | amendment in gradation pattern detection. 2 is a graph showing diffused light output characteristics with respect to an adhesion amount (measured value) when the transfer belt is a black belt using the image forming apparatus shown in FIG. 1. FIG. 27 is a diagram showing only components from the toner layer of diffused light output in FIG. 26 extracted. FIG. 6 is a diagram illustrating a state in which diffused light emitted from a toner is component-decomposed for each toner layer when a second layer is formed in the toner layer. FIG. 6 is a diagram illustrating a state in which a toner having a radius r is closest packed on a transfer belt. FIG. 37 is an explanatory diagram of a method for calculating the area of a part of toner in contact with a triangle shown in FIG. 36 when the toner shown in FIG. 36 is a perfect circle. It is a figure which shows the maximum adhesion amount of the toner layer (1st layer) calculated | required experimentally in the way shown in FIG. 33, and a calculated value. FIG. 2 is a schematic front view of a color image forming apparatus of a system in which transfer is performed onto a transfer sheet after being transferred onto an intermediate transfer body in a four-tandem configuration. FIG. 2 is a schematic front view of a color image forming apparatus of a type in which toner images are transferred onto an intermediate transfer body by superimposing and transferring them onto a transfer sheet by a single photosensitive drum.

Explanation of symbols

2, 426: Intermediate transfer belt (intermediate transfer member)
14Y, 14M, 14C, 14B: photosensitive drum (image carrier)
18: Transfer belt (transfer body)
51: LED as light emitting means
52: Regular reflection light receiving element as light receiving means 53: Detection target surface 54: Tone pattern (toner patch)
55: Diffuse reflected light receiving element as light receiving means 70: Tone pattern (toner pattern)
402: Photosensitive drum (image carrier)

Claims (11)

A plurality of powder gradation patterns with different adhesion amounts formed continuously on the surface to be detected, and a specular reflection light and a diffuse reflection having a light emitting means and a light receiving means arranged at a position facing the surface to be detected Using optical detection means capable of simultaneously detecting light, and arithmetic processing means for calculating the specular reflection light output voltage and diffused light output voltage obtained by detecting the detection target surface and the gradation pattern by the optical detection means, In the powder adhesion amount conversion method for performing the conversion process of the diffused light output correction value to a value uniquely determined with respect to the powder adhesion amount by performing sensitivity correction of the diffused light output based on the arithmetic processing result of the arithmetic processing unit,
The powder pattern adhesion amount range used to calculate the sensitivity correction coefficient for diffused light output is determined so as to satisfy the following conditional expression in relation to the particle size and density of the powder to be detected and the circularity of the powder. A powder adhesion amount conversion method characterized by the above.

In the powder adhesion amount conversion method according to claim 1,
A powder adhesion amount conversion method, wherein the powder is toner.   Means for continuously forming a plurality of gradation patterns of powders with different amounts of adhesion on the surface to be detected, and light emitting means and light receiving means arranged at positions facing the surface to be detected and diffused with specularly reflected light Optical detection means capable of simultaneously detecting reflected light, and arithmetic processing means for calculating a regular reflection light output voltage and a diffused light output voltage obtained by detecting the detection target surface and the gradation pattern by the optical detection means. And detecting a powder adhesion amount by converting a plurality of gradation patterns formed on the detection target surface into an adhesion amount using the powder adhesion amount conversion method according to claim 1 or 2. A powder adhesion amount detection device. In an image forming apparatus capable of obtaining a color image by sequentially superimposing and transferring images formed on a plurality of image carriers onto a sheet-like recording medium carried on a transfer member,
An image forming apparatus using the powder adhesion amount conversion method according to claim 1 or 2, or the powder adhesion amount detection apparatus according to claim 3, wherein the detection target surface is the transfer body. In an image forming apparatus capable of obtaining a color image by sequentially superimposing and transferring images formed on a plurality of image carriers onto a sheet-like recording medium carried on a transfer member,
An image forming apparatus using the powder adhesion amount conversion method according to claim 1 or 2, or the powder adhesion amount detection device according to claim 3, wherein the detection target surface is the image carrier. In an image forming apparatus capable of obtaining a color image by transferring toner images formed on a plurality of image carriers in succession to an intermediate transfer member, and then transferring them collectively to a sheet-like recording medium.
An image forming apparatus using the powder adhesion amount conversion method according to claim 1 or 2, or the powder adhesion amount detection device according to claim 3, wherein the detection target surface is the intermediate transfer member. In an image forming apparatus capable of obtaining a color image by transferring toner images formed on a plurality of image carriers in succession to an intermediate transfer member, and then transferring them collectively to a sheet-like recording medium.
An image forming apparatus using the powder adhesion amount conversion method according to claim 1 or 2, or the powder adhesion amount detection device according to claim 3, wherein the detection target surface is the image carrier. In an image forming apparatus capable of obtaining a color image by transferring a toner image formed on one image carrier in succession on an intermediate transfer member and then transferring the toner image to a sheet-like recording medium at once.
An image forming apparatus using the powder adhesion amount conversion method according to claim 1 or 2, or the powder adhesion amount detection device according to claim 3, wherein the detection target surface is the intermediate transfer member. In an image forming apparatus capable of obtaining a color image by transferring a toner image formed on one image carrier in succession on an intermediate transfer member and then transferring the toner image to a sheet-like recording medium at once.
An image forming apparatus using the powder adhesion amount conversion method according to claim 1 or 2, or the powder adhesion amount detection device according to claim 3, wherein the detection target surface is the image carrier. The image forming apparatus according to any one of claims 4 to 9,
An image forming apparatus that converts a plurality of gradation patterns formed on the detection target surface into an adhesion amount and performs image density control based on the adhesion amount conversion value. The image forming apparatus according to any one of claims 4 to 9,
An image forming apparatus, wherein the powder is toner, and the particle diameter r of the powder of the conditional expression is a lower limit value of the toner particle diameter tolerance.

Images