JP4625348B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a printer, a copier, or a facsimile, and in particular, an image formed according to a predetermined set value is read by an optical reflection density sensor, and a print image forming condition is adjusted by the output value. The present invention relates to the image forming apparatus.

  Conventionally, in the field of electrophotographic copying machines and laser printers, a test pattern is created on a photosensitive member or an intermediate transfer member under predetermined image forming conditions for toner replenishment and image stabilization. The density of the printed image has been controlled by detecting the amount of adhesion with an optical reflection density sensor to control the toner supply to the developing machine or the image forming conditions.

  When creating such a test pattern and controlling the image forming conditions, it is important that the optical reflection density sensor is stable over time against contamination, deterioration, and the like. However, it is difficult for an optical reflection density sensor to be used in practice to always obtain a stable output due to contamination of the sensor or deterioration of the LED and PD over time.

  Therefore, a calibration standard for the sensor is provided, the sensitivity variation of the sensor is corrected, and the toner image adhesion amount is measured. In Patent Document 1, a toner image in which the sensor output is saturated by increasing the developing bias and the like is formed and read by the sensor, and the output value of the toner image is calibrated by this output.

JP 2003-5465 A

  However, a saturated toner image cannot always be formed when the image forming apparatus is difficult to develop toner in a low humidity environment or a change with time. Therefore, calibration is performed in a situation where the saturated toner adhesion amount is not sufficient, and a calibration error occurs.

The present invention possess an image forming unit, and the optical reflection density sensor for reading an image formed by the image forming means, and means for adjusting the image forming conditions of the image forming means by using an optical reflection density sensor, In an electrophotographic image forming apparatus using an intermediate transfer member , the light amount adjustment image of the optical reflection density sensor and a partial region of the light amount adjustment image are laminated under specified image forming conditions. a sensor calibration image for calibrating the optical reflection density sensor, formed of two or more and the density adjustment image simultaneously on the intermediate transfer member by the provision of an image forming condition different from the image forming conditions, the amount of light the adjustment image measured by the optical reflection density sensor, determine the LED current of the optical reflection density sensor based on the sensor output of the light amount adjustment image, measuring the sensor calibration image image based on the LED current And obtains the calibration coefficients from the sensor output of the sensor calibration image, the density adjustment image is measured by the optical reflection density sensor, by the calibration factor to calibrate the sensor output of the density adjustment image, two or more It is characterized in that adhesion amount control is performed to obtain the latest image forming condition that becomes the target sensor output from the post-calibration output value of the density adjustment image.
In addition, at least the light amount adjustment image and the sensor calibration image, when the latest image forming condition is obtained by the previous adhesion amount control, the latest image forming condition is used instead of the prescribed image forming condition. It is formed based on.
In addition, when the prescribed image forming conditions are not determined at power-on, an image is formed by applying the environment-corrected reference image forming conditions as initial values of the prescribed image forming conditions. It is characterized by that.
In addition, when the latest image forming condition obtained so as to become a target sensor output value is in the direction of decreasing the image density compared to the reference image forming condition, the reference image forming condition is used, and when the image density is increasing. Is characterized in that, based on the latest image forming conditions, the prescribed image forming conditions of the light quantity adjustment image and the sensor calibration image in the next adhesion amount control are adjusted.
Further, the image forming condition correction value according to the comparison result between the latest image forming condition and the reference image forming condition has a correction table defined as a table, and the latest value obtained to be a target sensor target value. The image forming condition correction value is obtained from the image forming condition and the reference image forming condition using the correction table, and image formation of the light amount adjustment image and the sensor calibration image in the next adhesion amount control is performed. The condition is obtained from the reference image forming condition and the image forming condition correction value.
Also, a printing unit comprising at least a photosensitive member, a charger, an exposure device, a developing machine, and an intermediate transfer member, an optical reflection density sensor for reading a toner image formed by the printing unit, and the optical reflection density sensor A toner image for adjusting the amount of light for adjusting the amount of light of an optical reflection density sensor on an intermediate transfer member in an electrophotographic image forming apparatus having means for adjusting the image forming conditions of the printing portion using A sensor calibration toner image for calibrating the optical reflection density sensor, and two or more density adjustment toner images under different image forming conditions, and a partial region of the light amount adjustment toner image A sensor calibration toner image is formed on top of each other, the light quantity adjustment image is measured by the optical reflection density sensor, and an optical reflection density sensor is measured based on the sensor output of the light quantity adjustment toner image. A sensor current is determined, the sensor calibration toner image is measured based on the LED current, a calibration coefficient is obtained from a sensor output of the sensor calibration toner image, and the density adjustment toner image is converted into an optical reflection density sensor. The sensor output of the density adjustment toner image is calibrated by the calibration coefficient, and the image forming conditions are adjusted so that the target sensor output is obtained from the post-calibration output values of two or more density adjustment toner images. It is characterized by that.

  According to the present invention, the light amount of the optical reflection density sensor is adjusted using the toner image for adjusting the light amount, and if the toner image of two or more layers is thin, the toner image for adjusting the concentration is corrected using the toner image of three or more layers. Therefore, even if the sensor output value of the calibration toner image is not saturated, the optical reflection density sensor can be calibrated without increasing the calibration error, and stable adhesion amount control can be provided.

  Embodiments of the present invention will be described below with reference to the drawings. The image forming apparatus according to the following embodiment is applied to an electrophotographic color printer, but can be applied to a monochrome printer, a copying machine, and a facsimile in the same manner. Further, the present invention can be similarly applied to an electrophotographic system in which toner is directly transferred from a photoreceptor to paper, and an electrophotographic system using a transfer drum. Further, the present invention can be applied to an image forming apparatus using other color materials.

  FIG. 1 schematically shows the overall configuration of a tandem color image forming apparatus according to an embodiment of the present invention. 1 is an image forming apparatus, 2 is a photosensitive member, 3 is an intermediate transfer member, 4 is a developing device, 5 is an exposure device, 6 is a charger, 7 is a cleaner, 8 is an optical reflection density sensor, 9 is a fixing device, 10 Is a paper tray, 11 is an intermediate transfer member cleaner, and 12 is a toner image.

  The basic movement during image formation is to charge the surface of the photoreceptor 2 cleaned by the cleaner 7 using a charger 6. Thereafter, an electrostatic latent image is formed on the surface of the photoreceptor 2 by arbitrarily irradiating light from the exposure unit 5. The electrostatic latent image formed on the photoreceptor 2 is developed with toner by the developing device 4. The developed toner is transferred to the intermediate transfer body 3, and the toner image 12 is temporarily stored while sequentially stacking the toner developed in each color.

  At this time, the intermediate transfer body cleaner 11 is retracted from the intermediate transfer body 3 so as not to disturb the toner image 12 stored on the surface of the intermediate transfer body 3. Thereafter, the toner image 12 stored in the intermediate transfer body 3 is transferred to a sheet conveyed from the paper tray 10 and is heated and fixed by the fixing device 9. At the same time, the toner remaining on the surface of the intermediate transfer member 3 is removed by the intermediate transfer member cleaner 11.

  Next, the control system of the image forming apparatus 1 shown in FIG. 1 will be described. FIG. 2 is a schematic block diagram of a control system of the image forming apparatus 1. As shown in FIG. 2, a CPU 13 as a component, a ROM 14 that stores a control program and various data, a RAM 15 that temporarily stores various data as a work area, parameters that determine the operating conditions of the device, and information necessary for device management NVRAM 16 of a non-volatile memory for storing the data.

  Further, this control system is connected via an I / O interface 17 to a charging control unit 18, an exposure control unit 19, a developing bias control unit 20, a photoconductor control unit 21, a transfer body control unit 22, an optical reflection density sensor 8, a temperature. The humidity detector 23 is connected.

  The charging control unit 18 controls the charger 6 to charge the photoreceptor 2. The exposure control unit 19 controls the exposure unit 5 to form a latent image on the photoreceptor 2. The development bias controller 20 controls the development bias applied to the developing machine 4 to form a toner image for the latent image.

  The photoconductor control unit 21 controls the rotation of the photoconductor 2, and the transfer body control unit 22 controls the rotation of the intermediate transfer body 3. The optical reflection density sensor 8 detects the adhesion amount of the toner formed on the intermediate transfer body 3, and the CPU 13 that receives the detection data obtains an adjustment value of the development bias from the toner adhesion amount and sets it in the development bias controller 20. Then, the toner density is controlled.

  The temperature / humidity detector 23 detects the temperature / humidity outside or inside the apparatus, and the CPU 13 that receives the detected data sets a value for correcting the environmental characteristics of the image forming apparatus 1 as an image forming condition. This is a reference value for image forming conditions.

  The optical reflection density sensor 8 includes an LED that irradiates light and a photodetector (PD) that receives reflected light, and is disposed so as to face the intermediate transfer member 3. The optical reflection density sensor 8 can adjust the light receiving sensitivity of the PD by changing the current passed through the LED.

  Next, the basic movement of the adhesion amount control for controlling the developing bias using the optical reflection density sensor 8 will be described with reference to FIGS.

  FIG. 3 shows a patch pattern formation status. In the tandem method, C (cyan), M (magenta), Y (yellow), and K (black) are formed on the intermediate transfer member 3 in one round, so that the light quantity adjustment patch 24, the calibration patch 25, and the density adjustment are performed. A patch 26 is simultaneously formed on the intermediate transfer member 3. Reference numeral 27 denotes a background area when the intermediate transfer member 3 is temporarily expanded.

  The light amount adjustment patch 24 is formed of a solid patch of C, M, or Y. Two or more density adjustment patches 26 are formed by changing the developing bias. The calibration patches 25a and 25b are formed of two-layer and three-layer solid patches. The order of the patch positions is not limited to that shown in FIG. Also, the order of C, M, and Y is not limited to FIG. Here, the K density adjustment patch is omitted.

  FIG. 4 is a flowchart showing the operation of the adhesion amount control. The cleaning process and the surface reflection measurement process of the intermediate transfer body 3 are omitted. Based on the temperature and humidity information detected by the temperature / humidity detector 23 of the image forming apparatus 1 in step 100, image forming conditions of the calibration patch 25, the light amount adjustment patch 24, and the density measurement patch 26 are set. More specifically, the exposure power, charging voltage, and development bias are corrected and set based on temperature and humidity information. The developing bias at this time is described below as a reference value Vb.

  If the development bias correction value Vc obtained in the previous adhesion amount control is determined in step 101, the development bias correction value Vc is added to the reference development bias Vb to obtain the patch formation development bias Vp (step 102). Otherwise, the reference development bias Vb is used as Vp (step 103). In step 104, the light amount adjustment patch 24 and the two-layer and three-layer calibration patches 25a and 25b are formed of Vp. A fixed correction value may be added to Vp. Further, three density adjustment patches 26a, 26b, and 26c are formed with the developing biases Vp-30V, Vp, and Vp + 30V (step 105). ± 30V is an example.

In step 106, the optical reflection density sensor 8 measures the light amount adjustment patch 24 with one or more LED currents set in advance. In step 107, an LED current Ip that falls within a predetermined sensor output voltage range is determined. In step 108, the two-layer calibration patch 25a is measured by the LED current. If this measured value is greater than or equal to a preset threshold value in step 109, the measured value of the two-layer calibration patch is used for calibration (step 110). The measured value is below the threshold, or using measured values of the calibration patches 2 5b three layers unless the calibration beyond it (step 111).

  In step 112, the calibration coefficient of the optical reflection density sensor 8 is obtained from the measurement value of the calibration patch 25 of two or three layers. Here, the calibration coefficient is obtained by a value obtained by dividing a preset calibration target value by the measured value. In step 113, the three density adjustment patches 26a, 26b, and 26c are measured with a predetermined LED current. In step 114, the sensor output values of the density adjustment patches 26a, 26b, and 26c are calibrated with the calibration coefficient.

  In step 115, a linear approximation formula is obtained from the three sensor output values after calibration. In step 116, a developing bias Vs that is a preset target sensor output value is obtained. Similarly, for M and Y, the developing bias is obtained.

  Each color developing bias Vs is set in the RAM 15 or NVRAM 16, and printing is performed with these latest developing bias Vs until the next adhesion amount control (step 117). Further, using a value obtained by subtracting the reference developing bias Vb from the latest developing bias Vs, a developing bias correction value Vc for the next adhesion amount control is set using a correction table as shown in Table 1 (step 118).

In other words, below a certain value, the developing bias correction value Vc is set to 0, and above the certain value, the developing bias correction value Vc is increased. This suppresses at least a decrease in density of the light amount adjustment patch 24 and the calibration patch 25. Depending on the value in the correction table, no correction can be made. The developing bias correction value Vc may be obtained by function calculation.

  In step 119, the development bias correction value Vc for each color is stored in the RAM 15 or NVRAM 16. In the next adhesion amount control, each patch is formed by adding the developing bias correction value Vc to the reference developing bias Vb.

  According to this embodiment, the light amount of the optical reflection density sensor is adjusted by the toner image for light amount adjustment, and if it is determined that the two-layer calibration toner image is thin, the three-layer calibration toner image is used. Since the calibration of the density adjustment patch is performed, the calibration error can be reduced even if the sensor output value of the calibration toner image is not saturated, and if it is determined that the calibration toner image is thin, Since the developing bias of the toner image is increased, stable adhesion amount control can be provided.

  Next, another embodiment of the present invention will be described. FIG. 5 shows the formation status of another patch pattern in the tandem method. A solid image of any one of C, M, and Y is formed in advance in the first round, and a solid image of two layers, three layers, and four layers is formed thereon in C, M, and Y in the second round. The order of patch positions is not limited to that shown in FIG. Further, the order of C, M, and Y is not limited to FIG.

  The intermediate transfer body cleaner 11 is retracted so as not to erase the toner image in the first round. Here, the two-layer solid is referred to as a light amount adjustment patch 24. The three-layer and four-layer solids are referred to as calibration patches 25a and 25b. If there are only two colors of C, M, and Y, the solid patch of one layer is the patch 24 for light amount adjustment, and the solid patch of two layers and three layers is the calibration patches 25a and 25b.

  When there is only one color among C, M, and Y, the single-layer solid patch is the light amount adjustment patch 24 and the two-layer solid patch is the calibration patch 25a. It is assumed that the sensor output value of the calibration patch 25b is obtained by multiplying the sensor output value of the second layer by the value corresponding to the sensor output value of the third layer. Two or more density adjustment patches 26 are formed by changing the developing bias.

  FIG. 6 is a flowchart showing an operation for controlling the amount of adhesion to the patch pattern. The cleaning process and the surface reflection measurement process of the intermediate transfer body 3 are omitted. Based on the temperature and humidity information detected by the temperature / humidity detector 23 of the image forming apparatus 1 in step 200, the image forming conditions of the calibration patch 25, the light amount adjustment patch 24, and the density measurement patch 26 are set. More specifically, the exposure power, charging applied voltage, and development bias are corrected and set based on temperature and humidity information. The developing bias at this time is set as a reference value Vb.

  If the development bias correction value obtained by the previous adhesion amount control is determined in step 201, the development bias correction value Vc is added to the reference development bias Vb to obtain the patch formation development bias Vp (step 202). Otherwise, the reference development bias Vb is used as Vp (step 203). In step 204, a long solid patch is formed of any one of C, M, and Y. In step 205, the light amount adjustment patch 24 and the three-layer and four-layer calibration patches 25a and 25b are formed so as to overlap the longer solid patch. Further, three density adjustment patches 26a, 26b, and 26c are formed with the developing biases Vp-30V, Vp, and Vp + 30V (step 206).

  In step 207, the light amount adjustment patch 24 is measured by the optical reflection density sensor 8 with one or more LED currents set in advance. In step 208, an LED current Ip that falls within a predetermined sensor output voltage range is determined. In step 209, the three-layer calibration patch 25a is measured by the LED current. If this measured value is equal to or smaller than a preset threshold value in step 210, the measured value of the three-layer calibration patch is used for calibration (step 211). If the measured value is not more than the threshold value or does not exceed the threshold value, the measured value of the four-layer calibration patch 25b is used for calibration (step 212).

  In step 213, the calibration coefficient of the optical reflection density sensor 8 is obtained from the measurement value of the calibration patch 25 of three or four layers. Here, the calibration coefficient is obtained by a value obtained by dividing a preset calibration target value by the measured value. In step 214, the three density adjustment patches 26a, 26b, and 26c are measured with a predetermined LED current. In step 215, the sensor output values of the density adjustment patches 26a, 26b, and 26c are calibrated with the calibration coefficient. In step 216, a linear approximation formula is obtained from the sensor output values at three points after calibration. In step 217, a developing bias that is a preset target sensor output value is obtained. Similarly, for M and Y, the developing bias is obtained.

  Each color developing bias Vs is set in the RAM 15 or NVRAM 16, and printing is performed with these latest developing bias Vs until the next adhesion amount control (step 218). Further, using the value obtained by subtracting the reference developing bias Vb from the latest developing bias Vs, the developing bias correction value Vc for the next adhesion amount control is set using the correction table as shown in Table 1 above (step 219). In step 220, the development bias correction value Vc for each color is stored in the RAM 15 or NVRAM 16. In the next adhesion amount control, each patch is formed by adding the developing bias correction value Vc to the reference developing bias Vb.

  According to the present embodiment, a more stable calibration patch can be formed, so that stable adhesion amount control can be provided.

1 is a schematic diagram showing an embodiment of an image forming apparatus of the present invention. 1 is a schematic block diagram showing a control system of an image forming apparatus of the present invention. FIG. 3 is a schematic diagram of a patch pattern in adhesion amount control of the image forming apparatus of the present invention. 6 is a flowchart showing an operation of adhesion amount control of the image forming apparatus of the present invention. FIG. 6 is a schematic diagram of a patch pattern according to another embodiment of the present invention. FIG. 6 is a flowchart showing an operation for controlling the amount of adhesion in the patch pattern of FIG. 5. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 2 ... Photoconductor, 3 ... Intermediate transfer body, 4 ... Developing machine, 5 ... Exposure device, 6 ... Charger, 7 ... Cleaner, 8 ... Optical reflection density sensor, 9 ... Fixing device, 10 ... Paver tray, 11 ... Intermediate transfer body cleaner, 12 ... Toner image, 13 ... CPU, 14 ... ROM, 15 ... RAM, 16 ... NVRAM, 17 ... I / O interface, 18 ... Charge controller, 19 ... Exposure controller, DESCRIPTION OF SYMBOLS 20 ... Development bias control part, 21 ... Photoconductor control part, 22 ... Transfer body control part, 23 ... Temperature / humidity detector, 24 ... Light quantity adjustment patch, 25 ... Calibration patch, 26 ... Density adjustment patch, 27 ... The scalp area.

Claims (6)

An image forming unit; an optical reflection density sensor that reads an image formed by the image forming unit; and a unit that adjusts image forming conditions of the image forming unit using the optical reflection density sensor. In the electrophotographic image forming apparatus to be used,
At prescribed imaging condition, an optical reflection light amount adjusting image density sensor, are laminated to a partial area of the light amount adjusting image optical reflection density sensor calibration image for calibrating the sensor And two or more density adjustment images are simultaneously formed on the intermediate transfer member under image forming conditions different from the prescribed image forming conditions ,
The light quantity adjustment image is measured by the optical reflection density sensor, and the LED current of the optical reflection density sensor is determined based on the sensor output of the light quantity adjustment image.
The sensor calibration image based on the LED current is measured to obtain the calibration factor from the sensor output of the sensor calibration image,
The density adjustment image is measured by an optical reflection density sensor, the sensor output of the density adjustment image is calibrated by the calibration coefficient, and the target sensor output is obtained from the post-calibration output values of two or more density adjustment images. An electrophotographic image forming apparatus characterized in that adhesion amount control for obtaining the latest image forming conditions is performed . At least the light amount adjustment image and the sensor calibration image, if you are been determined that the latest image forming conditions by the previous adhesion amount control, instead of the prescribed image forming condition, based on the latest image forming conditions The electrophotographic image forming apparatus according to claim 1, wherein the electrophotographic image forming apparatus is formed. When the prescribed image forming conditions are not fixed at power- on, the image is formed by applying the environmentally corrected reference image forming conditions as the initial values of the prescribed image forming conditions. The electrophotographic image forming apparatus according to claim 1 or 2. The latest image forming conditions determined to be the sensor output values of targets are compared to the reference image forming conditions, when the direction to lower the image density using the reference image forming conditions, when the direction of increasing the image density on the basis of the latest image forming conditions, the next claim 3, wherein said light amount adjusting image in adhesion amount control it has to adjust the prescribed image forming condition of said sensor calibration image An electrophotographic image forming apparatus. An image forming condition correction value according to a comparison result between the latest image forming condition and the reference image forming condition;
Using the correction table, the image forming condition correction value is obtained from the latest image forming condition and the reference image forming condition obtained so as to be a target sensor target value.
3. The image forming condition of the light amount adjustment image and the sensor calibration image in the next adhesion amount control is obtained from the reference image forming condition and an image forming condition correction value. An electrophotographic image forming apparatus. Using at least a printing unit comprising a photosensitive member, a charger, an exposure device, a developing machine, an intermediate transfer member, an optical reflection density sensor for reading a toner image formed by the printing unit, and the optical reflection density sensor And an electrophotographic image forming apparatus having means for adjusting the image forming conditions of the printing portion.
Two or more light adjustment toner images for adjusting the light quantity of the optical reflection density sensor on the intermediate transfer member and two or more sensor calibration toner images for calibration of the optical reflection density sensor under different image forming conditions Simultaneously with the toner image for density adjustment,
In addition, a sensor calibration toner image is laminated and formed on a partial region of the light amount adjustment toner image ,
The light quantity adjustment image is measured by the optical reflection density sensor, and the LED current of the optical reflection density sensor is determined based on the sensor output of the light quantity adjustment toner image.
Said sensor calibration toner image based on the LED current is measured to obtain the calibration factor from the sensor output of the sensor calibration toner image,
The density adjustment toner image is measured by an optical reflection density sensor, the sensor output of the density adjustment toner image is calibrated by the calibration coefficient, and the target sensor is calculated from the post-calibration output values of two or more density adjustment toner images. An electrophotographic image forming apparatus characterized in that image forming conditions are adjusted so as to be output.

Images