JP4107550B2 - Toner adhesion amount detection method, program, apparatus, and image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to detection of toner adhesion using a light-reflective light quantity sensor and an image forming apparatus that performs the detection, and is applied to, for example, an electrophotographic copying machine, a facsimile, a printer, and the like.
[0002]
[Prior art]
  In this type of image forming apparatus, in order to keep the image density on the transfer paper constant and good, it is necessary to stabilize the toner adhesion amount on the surface of the image carrier. The amount of toner is detected by a toner density sensor, which is a reflection type optical sensor, and image forming conditions such as developer toner density (toner replenishment), development bias, charge amount, exposure level and the like are adjusted according to the detected value. Japanese Patent Application Laid-Open No. 2000-131900 discloses a density control apparatus and method for applying toner on a photoconductor under reference conditions, detecting the amount of adhesion with a toner density sensor, and adjusting a developing bias according to the detected value. Is disclosed.
[0003]
  Recently, a toner density sensor that measures the amount of diffuse reflected light has been proposed in order to more accurately detect the amount of color toner adhering (for example, JP-A-5-249787). When infrared light is applied to the color toner, diffuse reflected light is generated. The amount of diffusely reflected light increases with the amount of toner attached.RuSince it shows characteristics, it can be measured with high sensitivity from a low adhesion amount to a high adhesion amount.
[0004]
  Also, some full-color image forming apparatuses have been proposed that detect the toner adhesion amount on an intermediate transfer member rather than on a photosensitive member.
[0005]
  The output of the toner density sensor changes due to a change in reflectance due to deterioration over time of the opposing reflection object, that is, the photosensitive member or intermediate transfer member that is the detection target surface, contamination with time of the sensor, variation in each lot, and the like. Therefore, it is common to calibrate the sensor before detecting the toner adhesion amount. Here, calibration means adjusting the amount of light emitted from the sensor light emitting element (LED or the like) to adjust the toner adhesion amount sensor output to a constant value. For example, Japanese Patent Laid-Open No. 2000-131900 discloses one form thereof.
[0006]
  For example, assuming that the toner adhesion amount sensor output is Vs, the toner adhesion amount sensor output without toner on the surface of the image carrier is Vsg, and the toner concentration sensor output when the LED is off with the toner adhesion amount sensor output being the lowest level is Vso. (Black) As the toner adhesion amount increases, Vs decreases and eventually changes. That is, it saturates to a low level. This characteristic is shown in FIG. When the toner density sensor output is saturated in the Bk density detection, Vs = Vso. Using this characteristic, in the toner adhesion amount sensor, the light amount of the LED as the light emitting element is adjusted so that Vsg−Vso = constant, and the output level of the sensor is always kept constant with respect to the error factor. Yes. In the color toner, as shown in FIG. 5, the amount of reflected light increases as the toner adhesion amount increases, so that the sensor output level increases. The amount of color toner attached can also be grasped by the sensor output Vs.
[0007]
[Problems to be solved by the invention]
  However, since the detection target surface is an image carrier, it is difficult to accurately set Vsg−Vso = constant due to deterioration of the surface of the image carrier over time, resolution limit and tolerance of LED emission intensity control. . Therefore, an error occurs in the toner adhesion amount calculated from the toner adhesion amount sensor output Vs. Logically, by increasing the resolution of the LED emission intensity control, that is, reducing the A / D conversion quantization error of the sensor output, and reducing the allowable error when determining that the sensor output has reached the target value. The accuracy of emission intensity control is improved. However, the total time for focusing the light emission amount to the target value step by step becomes longer as the amount is reduced. Moreover, in practice, since the reflectance varies at each point in the circumferential direction of the image carrier, increasing the sensor output Vs reading resolution and reducing the allowable error will actually lead to convergence to the target value. It is also conceivable that the LED emission intensity control becomes unstable.
[0008]
  The first object of the present invention is to increase the accuracy of toner adhesion amount measurement by a toner density sensor, which is a light reflection type optical sensor, and to adjust the amount of light with the target amount of light emitted from the sensor in a relatively short time. In addition, a second object is to enable stable execution, and a third object is to stably control the toner adhesion amount to an optimum state at all times.
[0009]
[Means for Solving the Problems]
  (1) A light receiving element by irradiating the detection target surface with light from a light emitting elementLight ofRead the level signal level (Vsg)The level and the level of the light amount signal of the light receiving element that does not emit light (Vso) Difference from (Vsg-Vso) TheLight intensity adjustment to adjust the irradiation light quantity (B) of the light emitting element so that it is within the target value range (A ± 3%), and thenInIn order to detect the toner adhesion amount, the toner is applied to the detection target surface under the reference condition, and the detection target surface is irradiated with light with the adjusted irradiation light quantity (B) to receive the light.Light ofIn the toner adhesion amount detection method including the adhesion amount detection that reads the level (Vs) of the quantity signal,
  In the adhesion amount detection, reading is performed.LightQuantity signal level (Vs)And the light level signal level of the light receiving element that does not emit light (Vso) Difference from (Vs − Vso)And saidIrradiation light quantity within the target value range during light intensity adjustment (B) Level of the light amount signal of the light receiving element when the detection target surface is irradiated with (Vsg, Vsgf) And the light level signal level of the light receiving element that does not emit light (Vso) Difference from (Vsg, Vsgf − Vso) Target value within the target value range for (A) Ratio of (K = A / (Vsg, Vsgf − Vso)) Level multiplied by (k ・ (Vs − Vso)) Is the toner adhesion level detection level.And a toner adhesion amount detection method.
[0010]
  In addition, in order to make an understanding easy, the code | symbol of the corresponding element or the corresponding matter of the Example shown in drawing and mentioned later in parentheses is added for reference. The same applies to the following.
[0011]
  According to this, the toner in which the light amount adjustment error (A− (Vsg, Vsgf−Vso)) due to the allowable error (± 3%) is corrected in the light amount adjustment with the light amount of the light emitting element as the target value (A). An adhesion amount detection value is obtained. Therefore, it is possible to obtain a highly accurate toner adhesion amount detection value without reducing the tolerance (± 3%) in each step, and to converge the light amount of the light emitting element to the target range (A ± 3%). An increase in the time required for adjustment can be avoided.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
  (2) A light receiving element by irradiating the detection target surface with light from the light emitting elementLight ofRead the level signal level (Vsg)The level and the level of the light amount signal of the light receiving element that does not emit light (Vso) Difference from (Vsgf-Vso) TheLight intensity adjustment to adjust the irradiation light quantity (B) of the light emitting element so that it is within the target value range (A ± 3%), and thenInIn order to detect the toner adhesion amount, the toner is applied to the detection target surface under the reference condition, and the detection target surface is irradiated with light with the adjusted irradiation light quantity (B) to receive the light.Light ofIn the toner adhesion amount detection method including the adhesion amount detection that reads the level (Vs) of the quantity signal,
  In the light amount adjustmentIs a first average level obtained by irradiating a plurality of points b on the detection target surface with light of the light emitting element and reading a light amount signal level of the light receiving element. (Vsg) The first average level and the light level signal level of the light receiving element that does not emit light (Vso) Difference from (Vsg-Vso) Target value range (A ± Three % ) The amount of light emitted from the light emitting element (B) And adjusting the second average level by irradiating the light of the light emitting element to a plurality of d points, d> b, on the detection target surface and reading the level of the light quantity signal of the light receiving element. (Vsgf) Seeking
  In the adhesion amount detection, the level (Vs) of the read reflected light amount signalAnd the light level signal level of the light receiving element that does not emit light (Vso) Difference from (Vs − Vso)In addition,Second average level (Vsgf) And the light level signal level of the light receiving element that does not emit light (Vso) Difference from (Vsgf − Vso) Target value within the target value range for (A) Ratio of (K = A / (Vsgf − Vso)) Level multiplied by (k ・ (Vs − Vso)) Is the toner adhesion level detection level.And a toner adhesion amount detection method.
[0013]
  According to this, the toner in which the light amount adjustment error (A− (Vsg, Vsgf−Vso)) due to the allowable error (± 3%) in the light amount adjustment with the light amount of the light emitting element as the target value (A) is corrected. An adhesion amount detection value is obtained. Therefore, it is possible to obtain a highly accurate toner adhesion amount detection value without reducing the tolerance (± 3%) in each step, and to converge the light amount of the light emitting element to the target range (A ± 3%). An increase in the time required for adjustment can be avoided.
[0014]
  In addition, when the adjustment in the light amount adjustment is finished, the adjusted level (Vsgf) of the reflected light amount signal of the light receiving element is read and this is corrected to the subsequent toner adhesion amount detection value correction (K = A / (Vsgf− Vso)), for example, the tolerance is increased, and the reflected light amount signal at the time of light amount adjustment is quickly converged to the target value and / or the number of samples (measured value = the number of samplings for obtaining the average value)b) To reduce the time required for light intensity adjustment, and high density and / or large area(D)Then, the amount of reflected light is detected, and the correction value is accurately determined based on the average value thereof. According to this, an accurate correction value can be obtained even with a relatively rough light amount adjustment, and a highly accurate toner adhesion amount detection value can be obtained.
[0015]
  (3) The detection target surface is a visible image carrier that orbits,Used for the ratio,SaidIrradiation light quantity within the target value range during light intensity adjustment (B) Of the light intensity signal of the light receiving element when the target surface is irradiated withThe toner adhesion amount detection method according to (1) or (2), wherein the levels (Vsg, Vsgf) are average values of reading levels over a range of one circumference or more of the visible image carrier.
[0016]
  In addition to the functions and effects described in (1) or (2) above, the variation in reflectance in the circumferential direction of the image carrier is measured by measuring and averaging the change in reflectance in the circumferential direction of the image carrier. The correction error due to the toner can be suppressed to the minimum, and more accurate and stable toner adhesion amount detection can be performed.
[0017]
  (4) The above (1), (2) or (3)Includes light intensity adjustment and adhesion detectionA computer-executed program for detecting the toner adhesion amount. According to this, in the computer-controlled image forming apparatus, the toner adhesion amount detection of (1), (2) or (3) is performed, and the operation described in (1), (2) or (3), An effect can be obtained.
[0018]
  (5) A sensor (8) including a light emitting element that irradiates light on a detection target surface, and a light receiving element that receives reflected light from the direction of the detection target surface and generates a light amount signal whose level indicates a received light amount;
  Read the light intensity signal (Vsg) in the light intensity adjustment mode,TheLight intensity signalLevel and level of light quantity signal of light receiving element that does not irradiate light (Vso) Difference from (Vsg-Vso) Target value range (A ± Three % ) InsideA light amount adjusting means (30, 33) for adjusting the irradiation light amount (B) of the light emitting element so that;
  In order to detect the toner adhesion amount, toner is applied to the detection target surface under the reference conditions, and the light amount signal of the light receiving element is read by irradiating the detection target surface with the adjusted irradiation light amount (B).TheLevel of read light signal (Vs)And the light level signal level of the light receiving element that does not emit light (Vso) Difference from (Vs − Vso)And saidIrradiation light quantity within the target value range during light intensity adjustment (B) Level of the light amount signal of the light receiving element when the detection target surface is irradiated with (Vsg, Vsgf) And the light level signal level of the light receiving element that does not emit light (Vso) Difference from (Vsg, Vsgf − Vso) Target value within the target value range for (A) Ratio of (K = A / (Vsg, Vsgf − Vso)) Level multiplied by (k ・ (Vs − Vso)) Is a toner adhesion amount detection level. (30,33);
A toner adhesion amount detection device.
[0019]
  Using this toner adhesion amount detection device, the toner adhesion amount detection described in (1) or (2) can be performed, and the operation and effect described in (1) or (2) can be obtained. .
[0020]
  (6) Photoconductor (1), means for charging the photoconductor (4), exposure means for irradiating light on the charged surface of the photoconductor to display an image (5), and the electrostatic latent image formed thereby is converted into toner. Development means (6a to 6d) for visualizing the toner, means for transferring the visualized toner image directly or indirectly to the transfer paper via the intermediate transfer medium (9), light emitted to the photoreceptor or intermediate transfer medium Light receiving element by irradiating the light of the elementLight ofRead the level signal level (Vsg)The level and the level of the light amount signal of the light receiving element that does not emit light (Vso) Difference from (Vsg-Vso) TheSensor light intensity adjustment means (30, 33) that adjusts the light intensity (B) of the light emitting element so that it is within the target value range (A ± 3%), and then the photosensitivity is performed under reference conditions to detect the toner adhesion amount. The toner is applied to the body or intermediate transfer medium, and the light intensity level (Vs) of the light receiving element is read corresponding to the read value by irradiating the photoreceptor or intermediate transfer medium with the adjusted irradiation light quantity (B). In an image forming apparatus comprising an image density adjusting means (30, 33) for adjusting image forming conditions,
  The image density adjusting means (30, 33) is a level (Vs) of the read light amount signal in the adhesion amount detection.And the light level signal level of the light receiving element that does not emit light (Vso) Difference from (Vs − Vso)And saidIrradiation light quantity within the target value range during light intensity adjustment (b) Level of light quantity signal of light receiving element when irradiating photoconductor or intermediate transfer medium (Vsg, Vsgf) And the light level signal level of the light receiving element that does not emit light (Vso) Difference from (Vsg, Vsgf − Vso) Target value within the target value range for (A) Ratio of (K = A / (Vsg, Vsgf − Vso)) Level multiplied by (k ・ (Vs − Vso))On the basis of the,An image forming apparatus that adjusts image forming conditions.
[0021]
  According to this, the accuracy of toner density measurement is improved, and the toner adhesion amount can always be stably controlled to an optimal state to prevent image quality deterioration and abnormal images. Can be stabilized.
[0022]
  Other objects and features of the present invention will become apparent from the following description of embodiments with reference to the drawings.
[0023]
【Example】
  FIG. 1 shows a color printer 40 according to an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a flexible photosensitive belt as a belt-like image carrier. The photosensitive belt 1 is installed between the rotating rollers 2 and 3, and is rotated by the rotating roller 2. It is conveyed in the middle arrow A direction (clockwise). In the figure, reference numeral 4 denotes a charging charger for uniformly charging the surface of the photosensitive belt 1, and reference numeral 5 denotes a laser exposure apparatus which is an image writing unit. In the figure, 6 is a color developing device, 6a is magenta, 6b is cyan, 6c is yellow, and 6d is a black developing unit.
[0024]
  Further, 9 in the figure is an intermediate transfer belt as an image carrier and an intermediate transfer medium. The intermediate transfer belt 9 is installed on a rotating roller 10-12, and is rotated in the direction of arrow B ( (Counterclockwise) The photosensitive belt 1 and the intermediate transfer belt 9 are in contact with each other by a blank rotation roller portion of the photosensitive belt 1. On the intermediate transfer belt 9 side of the contact portion, a conductive bias roller 13 is in contact with the back surface of the intermediate transfer belt 10 under predetermined conditions.
[0025]
  The photosensitive belt 1 is uniformly charged by the charging charger 4 and then exposed by scanning with laser light modulated by the image recording signal by the laser exposure device 5. As a result, an electrostatic latent image is formed on the photosensitive belt 1. Here, the image recording signal for modulating the laser beam is for each color (single color) obtained by decomposing a desired full color image into magenta, cyan, yellow, and black (Bk) color information. The formation of the electrostatic latent image and the development by the one addressed to the color in the developing devices 6a-6d are repeated by the number of colors (for example, magenta, cyan, yellow, and black, a total of four times). The developed images (toner images) appearing by development are transferred onto the intermediate transfer belt 9 in a superimposed manner.
[0026]
  That is, each single-color image (toner image) formed on the photosensitive belt 1 rotating in the direction of arrow A in the drawing is synchronized with the photosensitive belt 1 on the intermediate transfer belt 9 rotating in the direction of arrow B in the drawing. , Magenta, cyan, yellow, and black are sequentially superimposed and transferred by a predetermined transfer bias applied to the bias roller 13. Magenta, cyan, yellow, and overlaid on the intermediate transfer belt 9The blackThe image is collectively transferred from the paper feed cassette 16a of the paper feed tray 16 onto the transfer paper transported to the transfer roller 14 through the paper feed roller 17, the transport roller pairs 18a and 18b, and the registration roller pairs 19a and 19b. After the transfer is completed, the toner image on the transfer paper is fixed (heat-pressed) to the transfer paper by the fixing device 20. As a result, a full-color image is completed, and the transfer paper is discharged to the paper discharge stack unit 22 through the paper discharge roller pair 21a and 21b.
[0027]
  In the figure, reference numeral 7 denotes a cleaning blade that is always in contact with the photosensitive belt 1 and wipes off the toner on the photosensitive belt 1, and reference numeral 15 denotes a cleaning device for the intermediate transfer belt 9, which is a cleaning brush of the cleaning device 15. 15a is held at a position separated from the surface of the intermediate transfer belt 10 during the image forming operation, and a formed image is transferred onto the above-described transfer paper and then brought into contact with the surface of the intermediate transfer belt 10.
[0028]
  Further, the photosensitive belt 1, the charger 4, the intermediate transfer belt 9, and the cleaning devices 7 and 15 are integrally assembled into a process cartridge to form a unit.
[0029]
  Reference numeral 8 denotes a toner adhesion amount sensor for detecting the toner adhesion amount on the photosensitive belt 1. The toner adhesion amount sensor 8 used this time generates and outputs a voltage Vs, that is, a detection signal of a level corresponding to the amount of light received by the photodiode, in which the light emitting portion is an infrared light emitting diode and the diffuse reflection light receiving portion is a photodiode. That is, a toner density sensor that measures the amount of diffusely reflected light.
[0030]
  FIG. 2 shows an outline of the electrical system of the full-color printer shown in FIG. FIG. 2 illustrates the control device with the main controller 30 as the center. The main controller 30 controls the entire printer 40. The main controller 30 is connected to an operation / display board OPB that performs display for the operator and function setting input control from the operator, controls the additional scanner 60 and the additional automatic document feeder ADF, and displays the original image. A scanner controller 32, a printer controller 36, and an image processing unit (IPU) 50 are also connected to perform control for writing to the memory and control for image formation from the image memory. Further, a dispersion control device such as an engine controller 33 for controlling an image forming engine in the color printer 40 that performs charging, exposure, development, paper feeding, transfer, fixing, and transfer paper transfer is connected. Each distributed control device and the main controller 30 exchange machine states and operation commands as necessary. A main motor and various clutches necessary for paper conveyance and the like are also connected to a driver (not shown) in the main controller 30. The engine controller 33 includes a sensor driver that drives the toner concentration sensor 8 and supplies the detection signal to the A / D conversion port of the main controller 30.
[0031]
  The printer controller 36 analyzes an image from the outside such as a personal computer and a command for instructing printing, develops a bitmap as image data into a printable state, and drives the printer 40 via the main controller 30 to print the image data. Out. In order to receive and operate images and commands through the LAN and parallel I / F, there is a LAN control 39 and a parallel I / F 38.
[0032]
  When there is a facsimile transmission instruction, the FAX controller 37 drives the scanner 60 and the IPU 50 via the main controller 30 to read the image of the original, and sends the image data to the facsimile communication line via the communication control 40 and the PBX. Send it out. When a facsimile call is received from the communication line and image data is received, the printer 40 is driven via the main controller 30 to print out the image data.
[0033]
  FIG. 3 shows a main flow of image formation control of the main controller 30. First, when power is turned on, initialization (IL) is performed (step 1: hereinafter, the word “step” is omitted in parentheses). Initialization (IL) is used to monitor various port settings, register clearing, output port resetting, abnormality check (EM) for processing when an abnormality such as door open or jam occurs, and monitoring the light intensity adjustment interval. Clear the number n of prints. Thereafter, standby mode processing (WT) is performed (2). In standby mode processing (WT), key input reading from the operation unit, fixing temperature (start-up) processing, abnormality check (EM), and the like are performed. Next, the copy is ready (3). When a start instruction is given, (4) pre-image formation mode processing (FT) is performed (5). In the pre-mode processing (FT), preparation processing such as determination of output to devices around the drive motor and belts 1 and 9 is performed, setting of the set number of prints (NK) in the register Nset, abnormality check (EM), and the like are performed. . Next, it is checked whether the number n of prints for monitoring the light quantity adjustment interval is 0 (immediately after the power is turned on) or more than the set value Nsh (light quantity adjustment timing) (6). The process proceeds to the mode process (CP) (9). If any of the conditions is satisfied, a “sensor calibration” (7) described later is performed and the print number n is cleared (8), and then the print mode process (CP) (9) ) And toner replenishment processing (10) is performed.
[0034]
  In print mode processing (CP) (9), image forming process processing, paper transport processing, abnormality check (EM), and the like corresponding to the print cycle are performed.
[0035]
  When both the print mode process (9) and the toner supply process (10) are completed (11), the register n and the register C indicating the number of copies are stored._COPYIs incremented by 1 (12, 13) and the number of prints (C_COPY) Has reached the set number of sheets (Nset) (14). If not, the process proceeds to the print mode process (9) and the processes of steps 9 to 14 are repeated.
[0036]
  Number of prints (C_COPY) Reaches the set number (Nset) (14), the register C_COPYIs set to 0 (15), and post-mode processing (LT) is performed (16). In the post-mode processing (LT), post-processing such as turning off the output to the devices around the belts 1 and 9, paper discharge processing, abnormality check (EM), and the like are performed. Then, the process returns to the standby mode process (WT) (2). Therefore, in this embodiment, the “sensor calibration” (7) is practically performed when the number of prints equal to or greater than the set number Nsh is printed at power-on and after power-on, and when a new print start instruction is issued. carry out.
[0037]
  FIG. 4 shows the contents of “sensor calibration” (7). When the process proceeds to “Sensor calibration” (7), the main controller 30 first measures the output Vso of the toner adhesion amount sensor 8 with the LED of the toner density sensor 8 turned off (no power supply: no light emission) to measure NVRAM, that is, a nonvolatile memory. Store in memory. At this time, the photosensitive belt 1 is in a constant speed rotation state, and reading of the output of the sensor 8 by A / D conversion is performed a (several tens) times or more, and the average value thereof is written in NVRAM as Vso (21 ). This is to eliminate as much as possible the influence of detection noise during measurement and variations due to the detection position on the belt. In the following detection, the detection value is read many times and the average value is calculated for the same purpose.
[0038]
  Next, the controller 30 initializes the measurement operation count c to 0 while keeping the photosensitive belt 1 rotating at a constant speed (22), and turns on the LED of the sensor 8 (23). At this time, the energization level instruction value B to the sensor 8 is obtained when the light amount value Vsgf (the result value adjusted by the previous sensor calibration) stored in the NVRAM is obtained, and the light amount value Vsg.f andBoth are stored in NVRAM. In this document, what the controller 30 operates to adjust the light amount of the sensor 8 (the amount of light reflected by the belt 1) to a target value is the LED energization level instruction value B to the sensor 8. When the state of the detection target surface and the environment around the sensor are the same and the sensor does not change with time, if the energization level instruction value B is the same, the detected light amount is the same, and the light amount value and the LED energization level instruction value B are There is substantially a one-to-one correspondence.
[0039]
  Further, the controller 30 reads the output of the sensor 8 b (several tens) times or more by A / D conversion, calculates an average value Vsg thereof, and increments the number of measurement operations c by 1 (23). A value obtained by subtracting Vso from Vsg is a substantial amount of reflected light from the photoconductor, and the accuracy of toner adhesion detection is improved by calibrating this value with higher accuracy. The target value A of the reflected light amount of the photosensitive member is generally about 1 to 5V.
[0040]
  Next, the controller 30 first determines whether or not Vsg−Vso falls within A ± 20% in order to bring Vsg−Vso closer to the target value A (24). If not, the LED energization level instruction value to the sensor 8 is determined. B is changed (25). In this case, B is a resolution that can be set from 0 to 255 represented by 8 bits. For example, when B = 150 and Vsg−Vso> A, B is set to 140, and measurement is performed once again to obtain Vsg (23) and repeated until Vsg-Vso reaches A ± 20% (23-24-25-25-23). If n = 25 times or more due to this repetition, it is considered that the LED energization level instruction value B has reached 0 or 255, and it is determined that the calibration is NG (calibration is impossible), and the sensor calibration (7) is terminated as an error. (26-27-36-return).
[0041]
  When A ± 20% is entered, in order to bring Vsg-Vso close to A with high accuracy, the LED energization level instruction value B is changed by 1 (30), and this time whether Vsg-Vso has become A ± 3% Check (28-29). If n = 35 times or more due to this repetition, it is considered that the LED energization level instruction value B has reached 0 or 255, and it is determined that the calibration is NG (calibration is impossible), and the sensor calibration (7) is terminated as an error. (31-32-36-return). When Vsg−Vso falls within A ± 3% within n = 35 times, the search for the LED energization level instruction value B is finished. In this high-precision adjustment, the target value range was set to A ± 3%. If the energization level instruction value and A / D conversion resolution are made larger than 8 bits (256 values) by making this a narrower range, the light quantity adjustment accuracy can be further improved. This leads to an increase in the cost of the A / D converter to be read and an increase in calibration time.
[0042]
  When Vsg−Vso falls within the target value A ± 3%, the LED light amount setting value and the LED energization level instruction value B are determined. However, this light quantity set value has an error of ± 3%, and a fluctuation within 6% is expected at every calibration.
[0043]
  Therefore, in order to correct the fluctuation within 6%, the correction coefficient K is calculated from the photoreceptor reflected light amount Vsg−Vso and the target value A at the LED light amount setting value (LED energization level instruction value B).
            K = A / (Vsg−Vso)
Ask for.
[0044]
  At this time (Vsg−Vso), it is desirable to measure and average the circumference of the photosensitive belt 1 for at least one circumference in order to eliminate the influence of the reflected light unevenness in the circumferential direction of the photosensitive belt and the detection noise at the time of measurement.
[0045]
  Therefore, in this embodiment, the controller 30 continues to drive the photosensitive belt 1 at a constant speed and causes the sensor 8 to emit light at the LED energization level instruction value B when Vsg−Vso falls within the target value A ± 3%. Continuously, the output of the sensor 8 is read by A / D conversion for d (several tens) times or more over the circumference of the photosensitive belt 1, and an average value Vsgf thereof is calculated, and the correction coefficient K,
            K = A / (Vsgf-Vso)
(33, 34), and the LED energization level instruction value B, the light amount setting value Vsgf and the correction coefficient K = A / (Vsgf-Vso) at this time are written in the NVRAM (35). d> a, b. In order to shorten the time required for sensor calibration, it is preferable to set a and b to small values, and in order to increase the accuracy of sensor calibration, it is preferable to set d to a large value.
[0046]
  FIG. 5 shows output characteristics of the toner adhesion amount sensor 8. In the toner replenishing process (10) shown in FIG. 3, the controller 30 sequentially forms toner marks of the respective colors on which the image is formed by the print mode process (CP) on the photosensitive belt 1 under the standard image forming conditions for the respective colors. Then, the light quantity of the sensor 8 is set to the value adjusted in “sensor calibration” (7), that is, the Vso written in NVRAM in step 21 and the LED conduction level command value written in step 35 (FIG. 4). B and the correction value K are read, the LED energization level command value B is given to the sensor 8, the LED is turned on, and the detection level of the sensor 8 of each color toner mark is A / D converted and read. After subtracting and multiplying the difference value (Vs−Vso) by the correction value K, K is determined based on the read signal / toner adhesion amount conversion characteristics (conversion ROM: conversion characteristics in FIG. 5) for each color. The (Vs-Vso), into a toner attached amount. When the toner adhesion amount is equal to or lower than the lower limit setting value, the toner is supplied to the corresponding developing device. When the lower limit set value is exceeded and less than the upper limit set value, nothing is done with respect to the developed color. If it is equal to or greater than the upper limit setting value, the development bias value of the corresponding color is changed to the low density development side by the amount exceeding the upper limit setting value.
[0047]
  At this time, there may be a variation in the light amount adjustment error that is expected to be 6% at the maximum, but in K · (Vs−Vso), the error variation is almost 0%, and the toner adhesion amount measurement value K · (Vs−Vso). ) Is highly accurate.
[0048]
  In the above embodiment, after Vsg−Vso reaches the target value A ± 3%, the output of the sensor 8 is A / D more than d (several tens) times over the circumference of the photosensitive belt 1. Reading by conversion, calculating an average value Vsgf thereof, and obtaining a correction coefficient K, in one modification of the above embodiment, Vsg when Vsg−Vso falls within the target value A ± 3% is calculated. Based on this, a correction value K = A / (Vsg−Vso) is calculated. Also in this case, in order to eliminate the influence of the reflected light amount unevenness in the circumferential direction of the photoreceptor belt 1 and the detection noise at the time of measurement, the circumference of the photoreceptor belt 1 is measured and averaged. That is, reading of the sensor detection value at step 28 is performed in the same manner as at step 33.
[0049]
  As a result, the multipoint sensor detection value reading (sampling) in step 33 of the above embodiment is omitted, but in the above modification, the step 28 may be repeated many times, so that the number of times of sampling in step 28 is small. The more preferable. From this point of view, the above-described embodiment is considered preferable in terms of increasing the calibration accuracy and shortening the time required for the entire sensor calibration.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing an outline of the mechanism of a full-color printer 40 embodying the present invention in one aspect.
FIG. 2 is a block diagram showing an outline of an electrical system of the printer 40 shown in FIG.
FIG. 3 is a flowchart showing an outline of image formation process control of the main controller 30 shown in FIG. 1;
FIG. 4 is a flowchart showing the contents of “sensor calibration” (7) shown in FIG. 3;
FIG. 5 is a graph showing toner adhesion amount detection characteristics of the toner density sensor 8 shown in FIG. 1;
[Explanation of symbols]
1: Photoconductor belt 2, 3: Rotating roller
4: Charging charger 5: Laser exposure device
6a-6d: Development unit 7: Cleaning blade
8: Toner adhesion sensor 9: Intermediate transfer belt
10-12: Rotating roller 13: Bias roller
14: Transfer roller 15: Cleaning device
15a: Cleaning brush
16: Cleaning device 17: Paper feed roller
18a, 18b: pair of transport rollers
19a, 19b: Registration roller pair
20: Fixing device 21a, 21b: Paper discharge roller pair
22: Paper discharge stack

Claims (6)

Is irradiated with light of light emitting elements to the detection target surface reads the level of the optical amount signal of the light receiving element, light emission difference between the level of the intensity signal of the light receiving element is not irradiated with the level and the light to be within the target value range light amount adjustment for adjusting the light quantity of the element, and, thereafter, the toner is applied to the detection target surface at the reference conditions in order to detect the toner adhesion amount, by irradiating light to the detection target surface at the irradiation amount of light the adjusted in the toner adhesion amount detection method comprising the adhesion amount detection, to read the level of light amount signal of the light receiving element,
In the adhesion amount detection, the difference between the level of the intensity signal of the light receiving element is not irradiated with the level and the light of the light amount signal Tsu read, the detection target surface with light of the irradiation light amount falls within the target value ranges in the light amount adjustment A level obtained by multiplying the ratio of the target value within the target value range to the difference between the level of the light amount signal of the light receiving element when the light is irradiated and the level of the light amount signal of the light receiving element that does not irradiate the light is a toner adhesion amount detection level. to that, the toner adhesion amount detection method characterized by. Is irradiated with light of light emitting elements to the detection target surface reads the level of the optical amount signal of the light receiving element, light emission difference between the level of the intensity signal of the light receiving element is not irradiated with the level and the light to be within the target value range light amount adjustment for adjusting the light quantity of the element, and, thereafter, the toner is applied to the detection target surface at the reference conditions in order to detect the toner adhesion amount, by irradiating light to the detection target surface at the irradiation amount of light the adjusted in the toner adhesion amount detection method comprising the adhesion amount detection, to read the level of light amount signal of the light receiving element,
Wherein the light amount adjustment obtains a first mean level by reading the level of irradiating light of the light emitting element into a plurality point b of the detection target surface intensity signal of the light receiving element, the light receiving element is not irradiated with the first mean level and the light The light quantity of the light emitting element is adjusted so that the difference from the level of the light quantity signal falls within the target value range, and then the light of the light emitting element is irradiated to a plurality of d points, d> b, on the detection target surface. Read the level of the light amount signal of the element to obtain the second average level,
In the adhesion amount detection, the difference between the read reflected light amount signal level and the light amount signal level of the light receiving element that does not emit light is the difference between the second average level and the light amount signal level of the light receiving element that does not emit light. wherein the level obtained by multiplying the ratio of the target value in the target value range, shall be the toner adhesion amount detection level, the toner adhesion amount detection method characterized in that for. The detection target surface is a visible image carrier that orbits and is used for the ratio, and a light amount signal of a light receiving element when the detection target surface is irradiated with light having an irradiation light amount that falls within a target value range in the light amount adjustment. The toner adhesion amount detection method according to claim 1, wherein the level is an average value of a reading level over a range of one circumference or more of the visible image carrier. A program executed by a computer for performing toner adhesion amount detection including light amount adjustment and adhesion amount detection according to claim 1, 2 or 3. A sensor including a light emitting element that irradiates light to the detection target surface, and a light receiving element that receives reflected light from the direction of the detection target surface and generates a light amount signal whose level indicates the amount of received light;
Reading the light quantity signal when the light intensity adjustment mode to adjust the irradiation light amount difference emitting element so that to the in the target value range between the level of the intensity signal of the light receiving element is not irradiated with the level and the light of the light quantity signal quantity Adjusting means; and
The toner was applied to the detection target surface at the reference conditions in order to detect the toner adhesion amount, the Ri adjusted to the detection target surface by irradiation light amount is irradiated with reading light of intensity signal of the light receiving element, the level of the light quantity signals read And the light amount signal level of the light receiving element when the detection target surface is irradiated with light of the light amount within the target value range in the light amount adjustment. wherein the level obtained by multiplying the ratio of the target value in the target value range, the adhesion amount detection unit shall be the toner adhesion amount detection level for the difference between the level of the intensity signal of light receiving elements not irradiated;
A toner adhesion amount detection device. Photoconductor, means for charging it, exposure means for irradiating light on the charged surface of the photoconductor to express an image, developing means for developing the electrostatic latent image formed thereby with toner, and developing the image a toner image, means for transferring the transfer sheet indirectly directly or via an intermediate transfer medium, reads the level of the optical amount signal of the light receiving element is irradiated with light from the light emitting element to the photoreceptor or intermediate transfer medium, the level Sensor light amount adjusting means for adjusting the amount of light emitted from the light emitting element so that the difference between the level of the light amount signal of the light receiving element and the light receiving element that does not emit light is within the target value range, and then a reference condition for detecting the toner adhesion amount The toner is applied to the photosensitive member or the intermediate transfer medium, and the photosensitive member or the intermediate transfer medium is irradiated with light with the adjusted irradiation light amount, and the light amount signal level of the light receiving element is read and the image forming condition is set corresponding to the read value. Image density adjusting means to be adjusted; An image forming apparatus comprising,
The image density adjusting means detects an amount of irradiation light that falls within a target value range in the light amount adjustment due to a difference between a read light amount signal level and a light amount signal level of a light receiving element that does not emit light. Multiplied by the ratio of the target value within the target value range to the difference between the level of the light amount signal of the light receiving element when the light of the photosensor or the intermediate transfer medium is irradiated and the level of the light amount signal of the light receiving element not irradiated with the light. based on the level, the toner adhesion amount detection method characterized by adjusting the image forming condition.

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