JPH05306999A - Correcting device for sensor for density detection - Google Patents

Abstract

PURPOSE:To automatically control sensor output in a short time and very accurately, by controlling an amplifier gain so as to bring it near to a set point in an arbitrary position of an image carrier and a patch preparing position. CONSTITUTION:From a rotating sensitive body, a sensor 5 for density detection measures the quantity of reflected light of a part, on which a toner is not applied, becoming a reference value of output. The detected signal is amplified (11) with a set (14) amplifier gain and converted (12) into the digital value. A means 13 for controlling a sensor reference output value changes the amplifier gain with the converted digital value and feeds back it to the amplifier gain setting means 14. The means 14 converts the amplifier gain into the analog value and changes the amplifier gain of the amplifying means 11. The means 13 inputs a signal of a means 16 for synchronizing a patch preparing position on the basis of a signal 15 for recognizing a sensitive body position. Namely, the sensor output is measured with different amplifier gains, the amplifier gain nearest to the set point is selected, the rough control is made in an arbitrary position of the sensitive body, the fine control is made in a density patch preparing position, and OK or NG is displayed according to whether it corresponds to the set point or not. Very accurate control can be made in a short time by the control of two stages.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a correction device for a density detecting sensor in an image forming apparatus such as a copying machine, a facsimile machine or a printer which uses an electrophotographic method or an electrostatic recording method.

[0002]

2. Description of the Related Art In the above image forming apparatus, the image density is controlled to a predetermined density in order to prevent the deterioration of the image quality of an output image for a long time even when the environment or the characteristics of the photosensitive material and the developer are changed. There is an automatic toner density control method (ADC method) as a method for doing this. In this method, the photoconductor is uniformly charged to a predetermined potential by a charging device, and an electrostatic patch corresponding to a predetermined toner density that serves as a reference is formed in a non-image area by an exposure device, and the patch portion is powdered by a developing machine. After developing, the density detecting sensor detects the optical density, and controls the parameters for determining the image density such as the density of the developer, the developing bias, the exposure amount, and the charge amount according to the detection result.

The concentration detecting sensor is an optical sensor consisting of a light emitting element and a light receiving element. The light from the light emitting element is applied to the patch portion, and the reflected light is detected by the light receiving element and converted into an electric signal. is configured to amplify converted to the ratio of the reflected light amount V _clean in a clean part no toner riding patch portion, and the reflected light amount V _`patch portion toner is on the patch unit, i.e. reflection Rate R
= V _patch / V _clean has a characteristic as shown in FIG. 11 with respect to the toner density D, and the target value D * of the toner density is obtained.
The target value R * of the reflectance is set for the above, the change of the toner density is detected by the output of the density detection sensor, and the parameter for determining the image density according to the detection result is controlled.

However, since the image density depends on the characteristics of each unit such as charging, exposure, development and transfer of the image forming apparatus and the assembling accuracy, the density of the patch formed on the photoconductor with the same density pattern is It is not always constant.

Therefore, in the prior art, Japanese Patent Application Laid-Open No. 58-182650
As shown in Japanese Patent Laid-Open Publication No. 2003-242242, a sensor pattern of a reference density provided on a plane substantially the same as the original placement surface is exposed on a photoconductor,
A method has been proposed in which development is performed, a sensor for detecting the density of this pattern detects it as an electrical output, and the output of the sensor is adjusted to a target value of the image density using this output.

[0006]

By the way, when the photosensitive member is rotated and the sensor for density detection measures the reflected light amount V _{clean of a} portion where toner is not applied, which is the reference value of the sensor output, as shown in FIG. , In-plane variation of sensitive material characteristics,
Due to the eccentricity of the drum, the sensor output value changes depending on the position of the photoconductor. Therefore, conventionally, when the average value of the sensor output is set to V _a and a patch is created at the X position, the value of V _X / V _a is set to the reference V _clean value. However, this method has a problem that the image density cannot be accurately controlled because there is essentially a difference between the average value of the sensor output and the sensor output value of the patch creating unit.

The present invention solves the above problems and prevents the adverse effect of the density control caused by the in-plane unevenness of the photosensitive material characteristics, the eccentricity of the drum, and the like, and automatically outputs the sensor output accurately in a short time. An object of the present invention is to provide a correction device for a density detection sensor that can perform adjustment.

[0008]

In order to achieve the above object, a correction device for a density detecting sensor according to the present invention forms a density detecting patch on an image carrier and detects the amount of reflected light of the patch. In an image forming apparatus for controlling a parameter for determining an image density according to the detection result, an amplifying unit for amplifying a light receiving output of the density detecting sensor, and a reference output of the density detecting sensor. A means for setting the value as a sensor output value when detecting an image carrier on which toner is not adhered, and selecting an amplifier gain such that the sensor output value is the closest to the target value among the amplifier gains having different values, A means for adjusting the amplifier gain so as to approach the target value at an arbitrary position on the image carrier, and a means for adjusting the amplifier gain so as to approach the target value at the patch creation position for density detection are provided. And wherein the Rukoto.

[0009]

In the present invention, the sensor output is measured with different amplifier gains, the amplifier gain closest to the target value is selected, and then the coarse adjustment is performed to match the sensor output to the target value at an arbitrary position of the photoconductor. Furthermore, fine adjustment is performed to match the target value at the density patch creation position, and if the target value is entered, OK,
If it does not enter, NG is displayed and stored in the memory.
Therefore, as compared with the case where only the same location as the density patch is read from the beginning, the adjustment can be performed in two steps of the rough adjustment / fine adjustment, and the adjustment can be performed with high accuracy in a short time.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an image forming apparatus 1 to which the present invention is applied.
It is a block diagram which shows an example. On the outer periphery of the photoconductor 1, a uniform charger 2 made of scorotron or the like, an image writing device 3 made of laser or the like, a developing machine 4 (in the case of a color image forming apparatus, a plurality of developing machines for each color toner), and density detection The sensor 5 is provided. In this embodiment, the photoconductor is described as an example, but the present invention is also applicable to an image carrier such as an insulator, a toner support, and a charge carrier.

When density control (ADC) is performed, the photoconductor 1 is uniformly charged to a predetermined potential by the uniform charger 2, and the image writing device 3 forms a control patch in the non-image area of the photoconductor 1. The patch portion is developed by the developing device 4. The density detecting sensor 5 has a reflected light amount V _clean in a clean portion where toner is not on the patch portion.
And the amount of reflected light V at the part where the toner is on the patch part
_{The patch} is detected, the detection signal is amplified and output to the CPU 7.

In the CPU 7, the reflectance R = V _patch
/ _Vclean is calculated, the reflectance and the target value are compared and calculated, and the toner supply device 8, the bias power source 9 of the developing device 4, the exposure amount of the image writing device 3, and the high voltage power source 10 for controlling the uniform charger 2 are calculated. By controlling at least one of them, an image having an optimum toner density is formed on the photoconductor.

FIG. 2 is a block diagram showing an embodiment of a correction device for a density detecting sensor according to the present invention. This automatic adjustment is performed in the diagnostic mode at the time of shipping or maintenance of the apparatus, and the photoconductor 1 is rotated and the density detection sensor 5 is used to measure the amount of reflected light of a portion where toner is not on the sensor output reference value. Measure V _clean .

The detection signal of the concentration detecting sensor 5 is amplified by the amplifying means 11 at the amplification factor set by the amplifier gain setting means 14, and its output value V _A is A / D.
In the conversion means 12, as shown in FIG.
Converted to _D. In the sensor reference output value adjusting means 13, the amplifier gain is changed from the detected sensor output value V _D by a method to be described later and is fed back to the amplifier gain setting means 14. In the amplifier gain setting means 14, as shown in FIG. 4, the amplifier gain G _D is converted into an analog value G _A, and the amplification factor in the amplification means 11 is changed based on this. Further, the sensor reference output value adjusting means 13 receives a signal from the patch creation position synchronizing means 16 based on the photoconductor position recognition signal 15.

Next, a method for automatically adjusting the concentration detecting sensor according to the present invention will be described with reference to FIGS.

FIG. 6 shows the main flow. When the start button is pressed, the cleaning cycle of the photoconductor is performed to remove the residual toner, and then the coarse adjustment of the sensor output, the fine adjustment of the sensor output and the setting of the amplifier gain are performed. The unevenness of the entire surface of the photoconductor is detected.

FIG. 7 shows the rough adjustment of the sensor output in step S1 of FIG. 6. First, in step S5, the amplifier gain G _D (N1) is output and the photoconductor is rotated to reflect the reflected light amount V at arbitrary plural positions. _{The clean} value V _D (digital value) is detected. This processing is performed 5 times by changing the amplifier gain G _D (N1), and the detected sensor output V _D is used as the target value V _D *
The amplifier gain G _D (N1) closest to (FIG. 3) is output as G _D. For example, as shown in FIG. 5, different amplifier gains G _D (N1) [N1 = 0, 1, 2, 3, 4]
Then, the sensor output V _D is detected 8 times, and the average value of 6 points excluding the maximum and minimum values is calculated, respectively, and the amplifier gain G _D (1) closest to the target value V _D * among these average values is calculated.
Is output as G _D.

Next, in step S6, the sensor output V _D is detected at a plurality of arbitrary positions on the photosensitive member, and the step S6 is performed.
5 and calculates an average value in a similar manner, the sensor output V _D is determined whether the target value V _D * is greater than, if more larger target value V _D *, subtract 2 from the amplifier gain G _D, target if the value V _D * less sensor output V _D is determined whether the target value V _D * less than or smaller than the target value V _D *, add 2 to the amplifier gain G _D. This process is repeated 10 times.

FIG. 8 shows the fine adjustment of the sensor output in step S2 of FIG. 6. First, in step S7, the amplifier gain is output with G _D set in step S6, and this time, the density detection of the photoconductor is performed. The sensor output V _D is detected at the patch forming position for the. This is performed by the patch creation position synchronizing means 16 based on the photoconductor position recognition signal 15 described in FIG. Then, the average value is calculated by the same method as in step S5, and the process of adding or subtracting 2 to the amplifier gain G _D is performed five times by the same process as in step S6. Next, in step S8, the process of adding or subtracting 1 to / from the amplifier gain G _D is performed five times by the same method as in step S7.

FIG. 9 shows the process of amplifier gain setting in step S3 of FIG. 6. First, it is judged whether or not the sensor output V _D finally detected in step S8 is within a predetermined range, and within the predetermined range. If so, set the sensor output V _D to OK,
If it is not within the predetermined range, the sensor output V _{D is set} to NG.
Next, it is determined whether or not the amplifier gain G _D obtained in step S8 is within a predetermined range. If it is within the predetermined range, the amplifier gain G _{D is set} to OK. The gain G _{D is set} to NG.

In the process described above, in short, the sensor output is measured with different amplifier gains, the amplifier gain closest to the target value is selected, and then the coarse adjustment is performed to adjust the sensor output to the target value at an arbitrary position of the photoconductor. Then, fine adjustment is performed to match the target value at the density patch creation position. If the target value is entered, OK is displayed, and if not, NG is displayed and stored in the memory. Therefore, as compared with the case where only the same location as the density patch is read from the beginning, the adjustment can be performed in two steps of the rough adjustment / fine adjustment, and the adjustment can be performed with high accuracy in a short time.

FIG. 10 shows the processing of the amplifier gain setting in step S3 of FIG. 6. First, the amplifier gain is output by G _D set in step S9, and this time, at any desired plural positions of the photoconductor. The sensor output V _D is detected, an average value is calculated in the same manner as in step S5, this is repeated 10 times, and the difference between the maximum value and the minimum value of the sensor output V _D is calculated as V _DPP.
And then, the unevenness V _DPP of the photoreceptor entire surface determines whether within a predetermined range, if within a predetermined range, the unevenness V _DPP of the photoreceptor entire surface with OK, not within the predetermined range, the photoconductor The unevenness V _DPP on the entire surface is NG.

The present invention is not limited to the above embodiment, and various modifications can be made by those skilled in the art.
For example, in the above embodiment, the diagnostic mode is used at the time of shipping or maintenance of the device.
The automatic adjustment may be performed before the copy operation, during the copy operation, and after the copy operation.

[0024]

As is apparent from the above description, according to the present invention, the sensor output is measured with different amplifier gains, the amplifier gain closest to the target value is selected, and then the sensor output is obtained at any position on the photoconductor. Is adjusted to the target value, and fine adjustment is made to match the target value at the density patch creation position to prevent adverse effects of density control caused by unevenness of the surface of the photosensitive material characteristics, eccentricity of the drum, etc. Therefore, the sensor output can be automatically adjusted with high accuracy in a short time.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an example of an image forming apparatus to which the present invention is applied.

FIG. 2 is a configuration diagram showing an embodiment of a correction device for a density detecting sensor according to the present invention.

FIG. 3 is a diagram for explaining A / D conversion means according to the present invention.

FIG. 4 is a diagram for explaining an ADC gain setting means according to the present invention.

FIG. 5 is a diagram for explaining a sensor output detection method according to the present invention.

FIG. 6 is a main flow diagram for explaining the processing of the correction device for the density detection sensor of the present invention.

FIG. 7 is a flowchart showing a process of coarse adjustment of the sensor output in FIG.

FIG. 8 is a flowchart showing a process of finely adjusting the sensor output in FIG.

9 is a flowchart showing the processing of amplifier gain setting in FIG.

FIG. 10 is a flowchart showing a process for detecting unevenness of the photosensitive member in FIG.

FIG. 11 is a diagram for explaining the ADC according to the present invention, showing the relationship between toner density and reflectance.

FIG. 12 is a diagram for explaining the problems of the present invention and is a diagram showing unevenness of the photoconductor.

[Explanation of symbols]

1 ... Photoreceptor, 2 ... Uniform charger, 3 ... Image writing device, 4
... developing machine 5 ... density detection sensor, 7 ... CPU, 8 ... toner supply device, 9 ... bias power supply 10 ... high-voltage power supply, 11 ... amplification means, 12 ... A / D conversion means 13 ... sensor reference output value adjustment means, 14 ... Amplifier gain setting means 15 ... Photoconductor position recognition signal, 16 ... Patch creation position synchronizing means

 ─────────────────────────────────────────────────── (72) Inventor Shigeru Tsukada 2274 Hongo, Ebina-shi, Kanagawa Fuji Xerox Co., Ltd.Ebina business office (72) Inventor Shunichiro Shishikura 2274, Hongo, Ebina-shi, Kanagawa Fuji Xerox Co., Ltd. Ebina business (72) Inventor Toru Yoshida 2274 Hongo, Ebina City, Kanagawa Prefecture Fuji Xerox Co., Ltd.

Claims (1)

[Claims] 1. A density detecting patch is formed on an image carrier,
The amount of reflected light of the patch is detected by a density detection sensor,
In an image forming apparatus that controls a parameter that determines an image density according to the detection result, an amplification unit that amplifies a light reception output of the density detection sensor, and a reference output value of the density detection sensor are attached to toner. Means for setting a sensor output value when an unsupported image carrier is detected, and an amplifier gain that selects a sensor output value closest to a target value with a plurality of different amplifier gains, and selects an arbitrary value of the image carrier. Correction of the density detection sensor, which is provided with means for adjusting the amplifier gain so as to approach the target value at the position and means for adjusting the amplifier gain so as to approach the target value at the patch creation position for density detection. apparatus.