JP2021085926A - Density detection device and image forming apparatus - Google Patents

Abstract

To provide a density detection device that can reduce the number of times to clean an optical sensor to reduce time and effort for a user and cost for visit of a service person, and an image forming apparatus.SOLUTION: A density detection device comprises: an IDC sensor 120 (optical sensor) that includes a light emitting unit 122 (light emitting element) that irradiates an intermediate transfer belt with light and a P-wave light receiving unit 130 and an S-wave light receiving unit 140 (light receiving elements) that receive reflected light reflected on the intermediate transfer belt, and detects the density of a toner image; and a control unit 50 (correction unit) that corrects a detection value detected by the IDC sensor 120. The IDC sensor 120 can adjust the densities of toner images of at least two or more colors. The control unit 50 corrects the detection value detected by the IDC sensor 120 for each of the colors in accordance with the amount of dirt on the IDC sensor 120.SELECTED DRAWING: Figure 2

Description

The disclosure relates to a density detector for detecting the density of a toner image formed on an image carrier, and an image forming apparatus including the density detection device.

In recent years, in an image forming apparatus, an optical sensor for forming a toner image of a predetermined test pattern on an image carrier and detecting the density of the toner image is provided in order to obtain a high-quality image, and an image is imaged based on the detected density. The concentration of is adjusted. However, as the image is formed (printed) by the image forming apparatus, the optical sensor may become dirty and the density of the toner image may not be detected accurately. Therefore, patent documents 1 and 2 disclose methods for detecting the amount of dirt on the optical sensor that detects the density of the toner image.

In Patent Document 1, the light-receiving amount in a state where the toner image is not placed on the image carrier (bare surface state) and the light-receiving amount at the time of the current measurement are measured by an optical sensor, respectively, and the difference between the two light-receiving amounts. The amount of dirt on the optical sensor is calculated from. Further, in Patent Document 2, the change in surface gloss due to the wear of the intermediate rotation belt is estimated, and the amount of dirt on the optical sensor is calculated by using the information. Further, in Patent Document 3, the amount of contamination of the optical sensor is calculated at the timing when the difference between the two input values of the P wave and the S wave received by the optical sensor changes significantly.

JP-A-2002-214851 Japanese Unexamined Patent Publication No. 2005-221523 Japanese Unexamined Patent Publication No. 2005-150244

In recent years, in image forming apparatus, a shutter that protects an optical sensor has been abolished in order to increase the speed and reduce the cost, and the amount of dirt on the optical sensor tends to increase. Patent Documents 1 to 3 only disclose a method for calculating the amount of dirt on the optical sensor, and when the optical sensor becomes dirty, it is necessary for a user or a service person to clean the optical sensor.

However, when cleaning the optical sensor, as the amount of dirt increases, the number of cleanings increases, which requires time and effort for the user and the cost of visiting the service person. In addition, when cleaning the optical sensor, there is a possibility that the optical sensor may be damaged during cleaning.

Therefore, the present disclosure has been made to solve the above-mentioned problems, and is a concentration detection device that can reduce the number of cleanings of the optical sensor, the labor of the user, and the cost of visiting the service person. It is to provide an image forming apparatus.

According to a certain embodiment, it is a concentration detection device that detects the density of a toner image formed on an image carrier, and receives a light emitting element that irradiates the image carrier with light and the reflected light reflected by the image carrier. The optical sensor includes an optical sensor that detects the density of the toner image, and a correction unit that corrects the detection value detected by the optical sensor. The optical sensor measures the density of the toner image of at least two colors or more. It can be adjusted, and the correction unit corrects the detection value detected by the optical sensor for each color according to the amount of dirt on the optical sensor.

Preferably, the amount of dirt on the optical sensor is determined based on the amount of change of the reflected light from the bare surface of the image carrier in the initial state with respect to the amount of light, and the amount of reflected light received by the light receiving element is the amount of reflected light in the initial state. The amount of light emitted from the light emitting element is corrected so as to be.

Preferably, the correction unit determines the amount of contamination of the optical sensor by subtracting the amount of change due to deterioration of the image carrier from the amount of change of the reflected light in the initial state with respect to the amount of light.

Preferably, the correction unit estimates the amount of change due to deterioration of the image carrier from the number of images formed or the toner coverage of the image carrier facing the optical sensor.

Preferably, the correction unit increases the correction amount of the optical sensor as the amount of dirt on the optical sensor increases.

Preferably, the correction unit changes the correction amount of the optical sensor according to the usage state of the optical sensor.

Preferably, the correction unit changes the application rate of the correction amount of the optical sensor according to the usage state of the optical sensor.

Preferably, the optical sensor includes a first optical sensor and a second optical sensor.
When the first optical sensor has a larger amount of dirt than the second optical sensor, the first optical sensor is made to detect the density of the toner image of the first color, and the second optical sensor has a larger correction amount than the first color. The density of the two-color toner image is detected.

Preferably, the correction unit is an optical sensor that detects the density of the toner image of another color when the stain amount of the optical sensor that detects the density of the toner image of one color becomes a predetermined value or more. The density of the toner image is detected.

Preferably, the correction unit notifies the cleaning information when the amount of dirt on the optical sensor exceeds a predetermined value.

Preferably, when the image carrier is replaced, the correction unit compares the estimated value of the amount of change in the amount of reflected light due to the deterioration of the image carrier with the actual value, and averages the difference between the estimated value and the actual value. Is used as an estimate of the image carrier after replacement.

According to a certain embodiment, an image forming apparatus for forming (printing) an image on a sheet, which detects the density of the image carrier on which the toner image is formed and the density of the toner image formed on the image carrier. Includes the concentration detector described in.

The density detection device and the image forming device according to a certain embodiment can reduce the number of times of cleaning the optical sensor and reduce the labor of the user and the visit cost of the service person while maintaining the image quality of the image to be formed.

It is a figure which shows schematic the whole structure of the image forming apparatus in Embodiment 1. FIG. It is a block diagram which shows the outline of the structure of the image forming apparatus in Embodiment 1. FIG. It is a figure which shows the main part structure of the IDC sensor of the image forming apparatus in Embodiment 1. FIG. It is a graph which shows the relationship of the detection result at the time of adjusting the light emitting amount so that it becomes the light receiving amount when it is not dirty in the IDC sensor. It is a graph which shows the relationship between the detection result of the IDC sensor and the correction value in the image forming apparatus which concerns on Embodiment 1. FIG. It is a flowchart for demonstrating operation of density correction of the image forming apparatus which concerns on Embodiment 1. FIG. It is a figure which shows the relationship between the amount of light emission of a light emitting part, the amount of change of light emission, and the number of printed sheets. It is a graph which shows the change of the application rate of the correction before and after the exchange of the intermediate transfer belt in the image forming apparatus which concerns on Embodiment 2. It is a flowchart for demonstrating operation of density correction of the image forming apparatus which concerns on Embodiment 2. FIG.

The present embodiment will be described in detail with reference to the drawings. The same or corresponding parts in the drawings are designated by the same reference numerals and the description thereof will not be repeated.
<Embodiment 1>
FIG. 1 is a diagram schematically showing the overall configuration of the image forming apparatus according to the first embodiment. The image forming apparatus 100 according to the first embodiment has an adjustment function for adjusting the variation of each color of the IDC sensor (optical sensor) 120 used in the image correction operation for correcting the density of an image. The adjustment function adjusts the variation of each color by detecting the density of the toner image of the adjustment patch P formed on the intermediate transfer belt 8.

As shown in FIG. 1, the image forming apparatus 100 is called a tandem type image forming apparatus, and includes an automatic document conveying unit 80 and an apparatus main body 102. The automatic document transfer unit 80 is attached to the upper part of the apparatus main body 102, and feeds the paper set on the transfer table to the image reading unit 90 of the apparatus main body 102 by a transfer roller or the like.

The apparatus main body 102 includes an image reading unit 90, an image forming unit 10, an intermediate transfer belt 8 as an example of an image carrier, an IDC sensor 120 as an example of an optical sensor, a paper feeding unit 20, and a fixing unit 44. And an automatic paper reversal transfer unit 60 (Auto Duplex Unit: hereinafter referred to as ADU). The image reading unit 90 scans and exposes the document placed on the platen by the optical system of the scanning dew device, and photoelectrically converts the image of the document scanned by the CCD (Charge Coupled Devices) image sensor to generate an image information signal. Generate. The image information signal is output to the image forming unit 10 after being subjected to analog processing, analog / digital (hereinafter referred to as A / D) conversion processing, shooting correction, image compression processing, etc. by an image processing unit (not shown).

The image forming unit 10 forms an image by an electrophotographic method, and includes an image forming unit 10Y for forming a yellow (Y) color image, an image forming unit 10M for forming a magenta (M) color image, and the like. It has an image forming unit 10C for forming a cyan (C) color image and an image forming unit 10K for forming a black (K) color image. In this example, the common function names, for example, Y, M, C, and K indicating the colors to be formed after the reference numerals are added.

The image forming unit 10Y includes a photoconductor drum 1Y, a charging unit 2Y arranged around the photoconductor drum 1Y, an exposure unit (optical writing unit) 3Y, a developing unit 4Y, and a cleaning unit 6Y. The image forming unit 10M includes a photoconductor drum 1M, a charging unit 2M, an exposure unit 3M, a developing unit 4M, and a cleaning unit 6M arranged around the photoconductor drum 1M. The image forming unit 10C includes a photoconductor drum 1C, a charging unit 2C, an exposure unit 3C, a developing unit 4C, and a cleaning unit 6C arranged around the photoconductor drum 1C. The image forming unit 10K includes a photoconductor drum 1K, a charging unit 2K, an exposure unit 3K, a developing unit 4K, and a cleaning unit 6K arranged around the photoconductor drum 1K.

Photoreceptor drums (image carriers) 1Y, 1M, 1C, 1K, charged parts 2Y, 2M, 2C, 2K, exposed parts 3Y, 3M, 3C, 3K, developed in the image forming units 10Y, 10M, 10C, 10K, respectively. The parts 4Y, 4M, 4C, 4K and the cleaning parts 6Y, 6M, 6C, 6K have common contents. Hereinafter, unless a distinction is necessary, Y, M, C, and K are not added.

The charging unit 2 charges the surface of the photoconductor drum 1 substantially uniformly. The exposure unit 3 is composed of, for example, an LPH (LED Print Head) having an LED array and an imaging lens, or a polygon mirror type laser exposure scanning device, and uses laser light on the photoconductor drum 1 based on an image information signal. Scan to form an electrostatic latent image. The developing unit 4 develops the electrostatic latent image formed on the photoconductor drum 1 with toner. As a result, a toner image, which is a visible image, is formed on the photoconductor drum 1.

The intermediate transfer belt 8 is stretched by a plurality of rollers and is supported so as to be able to travel. When the primary transfer roller operates, the intermediate transfer belt 8 runs, and the toner image formed on each photoconductor drum 1 is transferred to the image transfer position of the intermediate transfer belt 8 (primary transfer). Further, a plurality of patches Q composed of a plurality of gradations (densitys) are formed on the intermediate transfer belt 8 during the image correction operation, and the variation of each color of the IDC sensor 120 is adjusted.

The IDC sensor 120 is arranged on the belt surface of the intermediate transfer belt 8 opposite to the side on which the photoconductor drum 1 and the like are arranged. The IDC sensor 120 irradiates the surface of the intermediate transfer belt 8 with light during the image correction operation or the balance adjustment operation, and detects the amount of reflected light (toner adhesion amount) reflected on this surface. Depending on the density of the toner image on the intermediate transfer belt 8 detected by the IDC sensor 120, the exposure unit 3 controls the amount of light (laser power, etc.), the developing unit 4 controls the development bias voltage, and the like, thereby controlling the image density. Correction etc. are performed. Details of the IDC sensor 120 will be described later.

The paper feed unit 20 has a plurality of paper feed trays 20A and 20B in which paper M such as A3 and A4 is housed. The paper M conveyed from the paper feed trays 20A and 20B by the transfer rollers 22, 24, 26, 28 and the like is conveyed to the resist roller 32 via the loop making roller 30. The number of paper feed trays is not limited to three. Further, a single or a plurality of large-capacity paper feeding devices capable of accommodating a large-capacity paper M may be connected as needed.

The resist roller 32 has a driving roller and a driven roller, and a loop is formed by abutting the tip of the paper M with the loop making roller 30 to correct the skew of the paper M. The paper M is conveyed to the secondary transfer unit 34 at a predetermined timing. In the secondary transfer unit 34, the color image transferred to the image forming position of the intermediate transfer belt 8 is collectively transferred to the surface of the paper M conveyed from the paper feed unit 20 (secondary transfer). The secondary transferred paper M is conveyed to the fixing unit 44.

The fixing portion 44 is provided on the downstream side in the paper transport direction with respect to the secondary transfer portion 34, and has a pressure roller and a heating roller. The fixing unit 44 fixes the toner image on the surface of the paper M to the paper M by applying pressure and heat treatment to the paper M on which the toner image is transferred by the secondary transfer unit 34.

On the downstream side of the fixing unit 44 in the paper transport direction, a transport path switching section 48 for switching the transport path of the paper M to the paper discharge path side or the ADU60 side is provided. The transport path switching unit 48 is composed of, for example, a solenoid, a motor, or the like, and performs transport path switching control based on a selected printing mode (single-sided printing mode, double-sided printing mode, etc.).

Paper M for which single-sided printing has been completed in the single-sided printing mode or paper M for which double-sided printing has been completed in the double-sided printing mode has been fixed in the fixing section 44 and then in the paper transport direction with respect to the fixing section 44. The paper is discharged onto the paper discharge tray by the paper discharge roller 46 provided on the downstream side.

Further, when the paper M is re-fed to the image forming unit 10 in the double-sided printing mode, the paper M on which the image is formed on the front surface side is conveyed to the ADU 60 via the conveying path switching unit 48. The paper M conveyed to the ADU 60 is conveyed to the switchback path via the transfer roller 62 and the like. In the switchback path, the paper is conveyed to the U-turn path section with the rear end of the paper M at the head by the reverse rotation control of the ADU roller 64, and the sheet is conveyed to the resist roller 32 by the transfer rollers 66, 68 and the like provided in the U-turn path section. The paper is re-fed in a state where the front and back of M are reversed. The paper M re-fed to the resist roller 32 is subjected to the same image forming process as in the case of the front side of the paper M. The paper M whose image is transferred to the back surface by the image forming unit 10 is discharged onto the paper ejection tray via the transport path switching portion 48 and the paper ejection roller 46 after the fixing process is performed by the fixing portion 44.

Next, a block configuration example of the image forming apparatus 100 according to the first embodiment will be described. FIG. 2 is a block diagram showing an outline of the configuration of the image forming apparatus 100 according to the first embodiment. As shown in FIG. 2, the image forming apparatus 100 includes a control unit 50 that controls the overall operation of the apparatus.

The control unit 50 has a CPU (Central Processing Unit) 52, a ROM (Read Only Memory) 54 for storing control software and data, and a RAM 56 (Random Access Memory) forming a work area of the CPU 52. ing. The CPU 52 expands the software and data read from the ROM 54 on the RAM 56, activates the software, and controls each part of the image forming apparatus 100 to execute a balance adjustment operation, an image correction operation, and an image forming operation.

The IDC sensor 120, the operation display unit 70, the memory unit 72, the image forming unit 10, the image density control unit 58, and the temperature measuring unit 74, which is an example of the measuring unit, are connected to the control unit 50, respectively. ing. The light emitting unit 122 of the IDC sensor 120 irradiates a single polarized light such as a P wave under the control of the control unit 50. The P wave light receiving unit 130 of the IDC sensor 120 receives the P wave reflected by the toner image or the like and supplies the output signal SP to the control unit 50, and the S wave light receiving unit 140 receives the S wave reflected by the toner image or the like. The output signal SS is supplied to the control unit 50.

The operation display unit 70 is configured by combining a touch panel type position input device and a display unit, and accepts, for example, selection of a balance adjustment operation, a toner adhesion amount confirmation operation, and selection of image formation conditions such as paper type and size. An operation signal corresponding to the receiving operation is supplied to the control unit 50. The operation display unit 70 displays an operation screen for accepting selection of a balance adjustment operation or the like, or when the patch P does not satisfy the condition of a high adhesion amount in the toner adhesion amount confirmation operation of the patch P, the patch P is displayed. Display that it is abnormal.

The memory unit 72 is composed of, for example, a non-volatile semiconductor memory, an HDD (Hard Disk Drive), or the like. The memory unit 72 determines, for example, a correction value for correcting the detected value of each color of the light receiving unit of the IDC sensor 120, the relationship between the amount of change in light emission and the amount of dirt on the IDC sensor 120, and the amount of dirt on the IDC sensor 120. A predetermined threshold value (predetermined value), an initial amount of light on the bare surface of the intermediate transfer belt 8 and the like are stored.

The image density control unit 58 performs laser output and development in the image forming unit 10 in order to form the density of the plurality of patches P for density correction so as to be high and gradually different during the density correction operation. Controls the bias voltage, etc. The image density control unit 58 can also be controlled by the control unit 50.

When the density correction operation is executed, the exposure unit 3 of the image forming unit 10 outputs a laser under the condition of higher laser power than during the image correction operation under the control of the image density control unit 58. Further, when the density correction operation is executed, the development unit 4 of the image forming unit 10 is placed between the developing unit 4 and the photoconductor drum 1 under the condition of a development bias voltage higher than that during the image correction operation under the control of the image density control unit 58. Apply development bias voltage.

The temperature measuring unit 74 is provided inside the image forming apparatus 100. The temperature measuring unit 74 measures the temperature inside the image forming apparatus 100, and supplies the temperature information obtained by the measurement to the control unit 50.

In the first embodiment, the IDC sensor (optical sensor) 120 attached to detect the density of the toner image of the patch P formed on the intermediate transfer belt 8 which is an example of the image carrier of the image forming apparatus 100 is used. Let's take an example. FIG. 3 is a diagram showing a main configuration of the IDC sensor 120 of the image forming apparatus according to the first embodiment.

In FIG. 3, the IDC sensor 120 has a light emitting unit 122, a P wave receiving unit 130, an S wave receiving unit 140, a polarizing plate 130a on the light receiving surface side of the P wave receiving unit 130, and a light receiving surface side of the S wave receiving unit 140. The polarizing plate 140a and the like are housed in the hanging. The IDC sensor 120 is attached so as to detect a predetermined position of the intermediate transfer belt 8. Light is emitted from the light emitting unit 122, reflected on the surface of the intermediate transfer belt 8, and received by the P wave receiving unit 130 and the S wave receiving unit 140.

On the other hand, the P wave receiving unit 130 receives the P wave component of the reflected light of the light emitted by the light emitting unit 122. The other S-wave light receiving unit 140 receives the S-wave component of the reflected light of the light emitted by the light emitting unit 122. The P wave component means a vibration component parallel to the intermediate transfer belt 8, and the S wave component means a vibration component perpendicular to the P wave component.

The IDC sensor 120 may become dirty as the image forming apparatus 100 forms (prints) an image, and the density of the toner image may not be accurately detected. When the IDC sensor 120 becomes dirty, in addition to cleaning the optical sensor by the user or a service person, there is a method of correcting the detected value of the IDC sensor 120 and adjusting the density of the toner image by feedback.

However, the IDC sensor 120 may not be able to correct the detected value with sufficient accuracy even if the detected value is corrected and the density of the toner image is adjusted by feedback. FIG. 4 is a graph showing the relationship between the detection results when the light emission amount is adjusted so as to be the light reception amount when the IDC sensor 120 is not dirty. In the graph shown in FIG. 4, the detection result of the received light amount when the IDC sensor 120 is not dirty is shown by a broken line, and the detection result of the received light amount when the IDC sensor 120 adjusts the dirty light emission amount is shown by a solid line. Further, FIG. 4 (a) shows the detection results of magenta, FIG. 4 (b) shows the detection results of cyan, FIG. 4 (c) shows the detection results of black, and FIG. 4 (d) shows the detection results of yellow. Shown.

As can be seen from FIG. 4, the IDC sensor 120 that receives specular reflected light (P wave) and diffuse reflected light (S wave), respectively, emits light so that when the amount of dirt increases, the amount of received light becomes the same as when the amount of dirt is not dirty. Even if the amount is adjusted, it can be seen that the difference for each color is different from that when the detection result is not dirty. In particular, it can be seen that in the IDC sensor 120, the difference between magenta and cyan is larger than that when the detection result is not dirty.

This is because the balance of the light receiving amount of each color is lost due to the difference in the stain color tendency and the stain method of the window of the IDC sensor 120. Therefore, even if the IDC sensor 120 is uniformly corrected according to the amount of dirt, a correction error occurs depending on the color of the toner, and it becomes more remarkable as the amount of dirt increases, and the detection accuracy of the IDC sensor 120 is lowered. .. In particular, when a plurality of colors are detected by one IDC sensor 120, it is affected by the correction error for each color of the toner.

The image forming apparatus 100 according to the first embodiment is provided with, for example, two IDC sensors 120, and one IDC sensor 120 (first IDC sensor 120) detects magenta and cyan. Then, the other IDC sensor 120 (second IDC sensor 120) detects black and yellow. The color combination of each IDC sensor 120 is not limited to this. Then, in the IDC sensor 120 according to the first embodiment, the detection values of the P wave light receiving unit 130 and the S wave light receiving unit 140 are corrected according to the amount of dirt. The amount of dirt on the IDC sensor 120 is detected by subtracting the deterioration amount of the intermediate transfer belt 8 based on the detected value from the bare surface of the intermediate transfer belt 8.

In the image forming apparatus 100, a correction value for each color of the toner with respect to the amount of stain is determined in advance from the tendency of stain. The image forming apparatus 100 calculates the amount of stain from the value detected from the bare surface of the intermediate transfer belt 8, and applies a correction value for each toner color to the detected value of the IDC sensor 120 according to the calculated amount of stain. , Calculate the density of the toner image of each color. As a method for detecting the amount of dirt on the IDC sensor 120, various previously developed methods can be applied. Further, it can be considered that the image forming apparatus 100 includes a density detecting apparatus including an IDC sensor 120 for detecting the density of the toner image and a control unit 50 for correcting the detection value detected by the IDC sensor 120.

FIG. 5 is a graph showing the relationship between the detection result of the IDC sensor 120 and the correction value in the image forming apparatus 100 according to the first embodiment. In FIG. 5A, the horizontal axis shows the output value (detection value) of the IDC sensor 120, and the vertical axis shows the detected adhesion amount. The horizontal axis of FIG. 5A is the output value (detection value) of the IDC sensor 120 after the correction value is applied. In the graph shown in FIG. 5A, the relationship between the detected value and the detected adhesion amount is set in advance as a table, and the detected adhesion amount is calculated from the detected value using the table. The table is set for each toner color.

FIG. 5B is a graph showing the relationship between the output value (detection value) of the IDC sensor 120 and the corrected output value (detection value). In FIG. 5B, the horizontal axis shows the output value (detection value) of the IDC sensor 120 after correction, and the vertical axis shows the output value (detection value) of the IDC sensor 120 before correction. In the graph shown in FIG. 5B, the correction amount of the output value (detection value) of the IDC sensor 120 after correction is shown with respect to the output value (detection value) of the IDC sensor 120 before correction for each toner color. ing. In the image forming apparatus 100, the correction amount for each color of the toner shown in FIG. 5B is preset.

Next, the operation of the density correction of the image forming apparatus 100 will be described with a flowchart. FIG. 6 is a flowchart for explaining the operation of density correction of the image forming apparatus according to the first embodiment. First, the control unit 50 of the image forming apparatus 100 determines whether or not the intermediate transfer belt 8 is in the initial state before use (step S11). When the intermediate transfer belt 8 is in the initial state (YES in step S11), the control unit 50 corrects the amount of light reflected on the bare surface of the intermediate transfer belt 8 (step S12).

The control unit 50 determines whether or not the initial amount of light reflected on the bare surface of the intermediate transfer belt 8 is stored in the memory unit 72 (step S13). When the initial light amount is not stored in the memory unit 72 (NO in step S13), the control unit 50 stores the detected value of the IDC sensor 120 as the initial light amount in the memory unit 72 (step S14). When the initial light amount is stored in the memory unit 72 (YES in step S13), the control unit 50 calculates the dirt amount of the IDC sensor 120 (step S15). Specifically, the control unit 50 calculates the amount of dirt on the IDC sensor 120 based on the most recently detected value detected by the IDC sensor 120 and the initial amount of light stored in the memory unit 72.

As the image forming apparatus 100 forms (prints) an image, the amount of light emitted from the light emitting unit 122 decreases. The causes are rough surface due to deterioration of the intermediate transfer belt 8 and dirt on the IDC sensor 120. FIG. 7 is a diagram showing the relationship between the amount of light emitted from the light emitting unit 122 and the amount of change in light emission and the number of printed sheets. In FIG. 7, the number of prints is set on the horizontal axis, the amount of light emitted is set on the positive side of the vertical axis, and the amount of change in light emission is set on the negative side of the vertical axis. The solid line A1a shows the measured value of the light emission amount of the IDC sensor 120 when the IDC sensor 120 before the replacement of the intermediate transfer belt 8 is dirty, and the solid line A2a shows the measured value of the light emission amount of the IDC sensor 120 after the replacement of the intermediate transfer belt 8. The measured value of the light emission amount of the IDC sensor 120 when there is. The solid line B1a shows the estimated value of the light emission amount of the IDC sensor 120 when the IDC sensor 120 before the replacement of the intermediate transfer belt 8 is clean, and the solid line B2a considers the measured value before the replacement of the intermediate transfer belt 8. The estimated value of the light emission amount of the IDC sensor 120 when the IDC sensor 120 is clean is shown.

The solid line A1b shows the measured value of the amount of change in light emission of the IDC sensor 120 when the IDC sensor 120 before the replacement of the intermediate transfer belt 8 is dirty, and the solid line A2b is the IDC sensor 120 after the replacement of the intermediate transfer belt 8. The measured value of the amount of change in light emission of the IDC sensor 120 when there is dirt is shown. The solid line B1b shows an estimated value of the amount of change in light emission of the IDC sensor 120 when the IDC sensor 120 before the replacement of the intermediate transfer belt 8 is clean, and the solid line B2b considers the measured value before the replacement of the intermediate transfer belt 8. Then, the estimated value of the amount of change in light emission of the IDC sensor 120 when the IDC sensor 120 is clean is shown.

In the image forming apparatus 100, the change in the amount of light emitted from the IDC sensor 120 due to the deterioration of the intermediate transfer belt 8 is stored in the memory unit 72 in advance as a solid line B1a. Therefore, the control unit 50 subtracts the estimated value of the light emission change amount of the IDC sensor 120 of the solid line B1b from the measured value of the light emission change amount of the IDC sensor 120 of the solid line A1b, so that the light emission change amount T1 due to the dirt of the IDC sensor 120 Can be sought. After the intermediate transfer belt 8 is replaced, the control unit 50 subtracts the estimated value of the light emission change amount of the IDC sensor 120 of the solid line B2b from the measured value of the light emission change amount of the IDC sensor 120 of the solid line A2b, thereby performing the IDC. The amount of change in light emission T2 due to dirt on the sensor 120 can be obtained.

Further, when the intermediate transfer belt 8 is replaced, the control unit 50 can measure the amount of dirt on the IDC sensor 120 as the measured value I from the difference between the solid line A1a and the solid line B1a when the intermediate transfer belt 8 is replaced. Further, when the intermediate transfer belt 8 is replaced, the control unit 50 calculates a change in the amount of light emitted due to the roughness of the surface of the intermediate transfer belt 8 to obtain an actually measured value II indicating deterioration of the intermediate transfer belt 8. The control unit 50 feeds back the measured value I of the dirt amount of the IDC sensor 120 to the measured value II indicating the deterioration of the intermediate transfer belt 8 and considers it, so that the amount of light emitted from the IDC sensor 120 after the replacement of the intermediate transfer belt 8 is taken into consideration. (Solid line B2a) is corrected. Since the measured value measured by the IDC sensor 120 also includes variations, the measurement accuracy of the IDC sensor 120 can be improved by averaging the preset estimated value and the actual value. The amount of change in deterioration of the intermediate transfer belt 8 may be estimated from the number of prints (the number of images formed) or the toner coverage of the intermediate transfer belt 8 facing the IDC sensor 120.

Returning to FIG. 6, the control unit 50 calculates the amount of dirt on the IDC sensor 120 in step S15, and then estimates the amount of change (solid line B2a shown in FIG. 7) such as deterioration of the intermediate transfer belt 8 (roughness of the belt). ) Is corrected (step S16).

Next, the control unit 50 determines whether or not to perform a process for stabilizing the image formation (step S17). The control unit 50 determines that the process of stabilizing the image formation is performed by a predetermined time unit or by exchanging the intermediate transfer belt 8. When performing the process of stabilizing the image formation (YES in step S17), the control unit 50 determines the amount of bare surface light so that the amount of light reflected from the bare surface of the intermediate transfer belt 8 becomes a predetermined amount (for example, the initial amount of light). The correction is performed (step S18). The control unit 50 determines the amount of light emitted by the light emitting unit 122 based on the correction result in step S18 (step S19). The control unit 50 calculates the amount of change in light emission changed from the amount of light emission determined in step S19 from the detected value of the IDC sensor 120 (step S20).

The control unit 50 calculates the amount of dirt on the IDC sensor 120 from the amount of change in light emission calculated in step S20 (step S21). The control unit 50 sets, for example, the relationship between the amount of change in light emission and the amount of dirt on the IDC sensor 120 as a table in advance and stores it in the memory unit 72. Using the table, the IDC sensor 120 is used to obtain the amount of change in light emission. Calculate the amount of dirt.

The control unit 50 determines whether or not the calculated dirt amount of the IDC sensor 120 is equal to or greater than a predetermined threshold value (predetermined value) (step S22). As shown in FIG. 7, when the solid line A1b indicating the amount of change in light emission of the IDC sensor 120 becomes a threshold value of 1 or more, the control unit 50 determines that the amount of dirt on the IDC sensor 120 is large. When the amount of dirt on the IDC sensor 120 is equal to or greater than a predetermined threshold value (YES in step S22), the control unit 50 displays an instruction prompting cleaning on the operation display unit 70 or contacts a serviceman by a service call (step). S23). When the amount of dirt on the IDC sensor 120 exceeds a predetermined threshold value, the control unit 50 cannot correct the detected value according to the amount of dirt on the IDC sensor 120, so that the IDC sensor 120 needs to be cleaned.

The image forming apparatus 100 uses a plurality of IDC sensors 120, and one IDC sensor 120 detects the amount of change in the color emission of the plurality of toners. Therefore, when the dirt amount of the IDC sensor 120 is less than a predetermined threshold value (NO in step S22), the control unit 50 confirms the difference in the dirt amount for each color detected by one IDC sensor 120, and the dirt amount. It is determined whether or not the difference between the above is equal to or greater than a predetermined difference (step S24). When the difference in the amount of stain is equal to or greater than a predetermined difference (YES in step S24), the control unit 50 changes the color assignment detected by the plurality of IDC sensors 120 (step S25). For example, when one IDC sensor 120 detects magenta and cyan, and the other IDC sensor 120 detects black and yellow, the control unit 50 becomes dirty. Magenta and Black, which are strong against dirt (small correction amount), are detected by one of the IDC sensors 120, and Cyan and Yellow, which are weak against dirt (large correction amount), are detected. It may be rearranged so as to be detected by the other IDC sensor 120. As a result, by changing the color assignment of the IDC sensor 120, it is possible to make it less susceptible to stains. Further, the control unit 50 detects the density of the toner image of one color. When the stain amount of the IDC sensor 120 for detecting the density of the toner image of one color becomes a predetermined value or more, the control unit 50 detects the density of the toner image of the other color. The density of the toner image of one color may be detected at 120.

When the difference in the amount of stain is less than a predetermined difference (NO in step S24), the control unit 50 determines the correction value according to the amount of stain in each color (step S26). As shown in FIG. 4, the control unit 50 sets the correction value for each color as a table in advance from the amount of stain, and determines the correction value for each color using the table.

After that, the control unit 50 adjusts the maximum concentration in steps S27 to S31. Specifically, the control unit 50 prints a plurality of patches of the adhesion amount changed under each bias condition (step S27), and obtains the detection value of the IDC sensor 120 of each patch (step S28). Further, the control unit 50 corrects the detection value of the IDC sensor 120 of each color using the correction table of each color (step S29), calculates the adhesion amount of the toner image of each patch (step S30), and intermediate transfer belt. The development pier of 8 is determined (step S31). Thereby, the control unit 50 can determine the development bias in which the toner image of an appropriate amount of adhesion is formed on the intermediate transfer belt 8 even if the IDC sensor 120 is dirty. It is desirable that the control unit 50 increases the correction amount for each color as the amount of dirt on the IDC sensor 120 increases and the density increases.

The control unit 50 determines whether or not the operation for ending the process has been accepted (step S32). When the operation to end is not accepted (NO in step S32) and the process for stabilizing the image formation is not performed (NO in step S17), the control unit 50 returns the process to step S11. When the operation to end is accepted (YES in step S32), the control unit 50 ends the process.

As described above, the image forming apparatus 100 according to the first embodiment includes a density detecting apparatus for detecting the density of the toner image formed on the intermediate transfer belt 8 (image carrier). The concentration detection device includes a light emitting unit 122 (light emitting element) that irradiates the intermediate transfer belt 8 with light, a P wave receiving unit 130 that receives the reflected light reflected by the intermediate transfer belt 8, and an S wave receiving unit 140 (light receiving element). ), An IDC sensor 120 (optical sensor) that detects the density of the toner image, and a control unit 50 (correction unit) that corrects the detection value detected by the IDC sensor 120. The IDC sensor 120 can adjust the density of the toner image of at least two colors or more. The control unit 50 corrects the detection value detected by the IDC sensor 120 for each color according to the amount of dirt on the IDC sensor 120. As a result, the density detection device according to the first embodiment can reduce the number of times the IDC sensor 120 is cleaned while maintaining the image quality of the image to be formed, and can reduce the time and effort of the user and the cost of visiting the service person.

Preferably, the amount of dirt on the IDC sensor 120 is determined based on the amount of change of the reflected light from the bare surface of the intermediate transfer belt 8 in the initial state with respect to the amount of light, and the reflected light received by the P wave receiving unit 130 and the S wave receiving unit 140. The amount of light emitted from the light emitting unit 122 is corrected so that the amount of light of is the amount of reflected light in the initial state.

The control unit 50 may determine the amount of dirt on the IDC sensor 120 by subtracting the amount of change due to deterioration of the intermediate transfer belt 8 from the amount of change of the reflected light in the initial state with respect to the amount of light. As a result, the control unit 50 can more accurately detect the amount of dirt on the IDC sensor 120.

The control unit 50 may estimate the amount of change due to deterioration of the intermediate transfer belt 8 from the number of images formed or the toner coverage of the intermediate transfer belt 8 facing the IDC sensor 120. As a result, the control unit 50 can more accurately detect the amount of change due to deterioration of the intermediate transfer belt 8.

The control unit 50 may increase the correction amount of the IDC sensor 120 as the amount of dirt on the IDC sensor 120 increases. As a result, the control unit 50 can appropriately correct the detected value of the IDC sensor 120.

The IDC sensor 120 includes a first IDC sensor 120 and a second IDC sensor 120, and when the first IDC sensor 120 has a larger amount of dirt than the second IDC sensor 120, the first IDC sensor 120 may be used. The density of the toner image of the first color may be detected, and the density of the toner image of the second color having a correction amount larger than that of the first color may be detected by the second IDC sensor 120. As a result, the IDC sensor 120 can be made less susceptible to dirt.

When the amount of dirt on the IDC sensor 120 that detects the density of the toner image of one color exceeds a predetermined value, the control unit 50 uses the IDC sensor 120 that detects the density of the toner image of another color to detect the density of the toner image of one color. The density of the toner image may be detected. As a result, even if the IDC sensor 120 that detects the density of the toner image of one color cannot detect the density, the control unit 50 takes over by the IDC sensor 120 that detects the density of the toner image of another color. , The detected value of the IDC sensor 120 can be appropriately corrected.

When the amount of dirt on the IDC sensor 120 exceeds a predetermined value, the control unit 50 may notify the cleaning information. This enables appropriate measures such as cleaning the IDC sensor 120.

When the intermediate transfer belt 8 is replaced, the control unit 50 compares the estimated value of the amount of change in the amount of reflected light due to the deterioration of the intermediate transfer belt 8 with the actual value, and averages the difference between the estimated value and the actual value. May be used as an estimated value of the intermediate transfer belt 8 after replacement. As a result, the control unit 50 can appropriately correct the detected value of the IDC sensor 120 after the replacement of the intermediate transfer belt 8.

The image forming apparatus 100 according to the first embodiment is an image forming apparatus that forms (prints) an image on a sheet, and is an intermediate transfer belt 8 on which a toner image is formed and a toner formed on the intermediate transfer belt 8. The density detection device according to any one of the above for detecting the density of an image is included. As a result, the image forming apparatus 100 according to the first embodiment can reduce the number of times the IDC sensor 120 is cleaned while maintaining the image quality of the formed image, and can reduce the time and effort of the user and the cost of visiting the service person.
<Embodiment 2>
In the first embodiment, the set correction value is applied to the dirt amount as it is. However, since the set correction value is an estimated value, an error may occur depending on the situation of the image forming apparatus 100 (for example, whether or not the intermediate transfer belt 8 is replaced), the usage state of the IDC sensor 120 (for example, the number of printed sheets), and the like. It can occur. Therefore, in the image forming apparatus according to the second embodiment, the application rate of the correction value for each color is set according to the situation of the image forming apparatus, the usage state of the IDC sensor 120, and the like. The image forming apparatus according to the second embodiment is designated by the same reference numerals for the same configuration as the image forming apparatus 100 according to the first embodiment, and detailed description thereof will not be repeated.

FIG. 8 is a graph showing changes in the correction application rate before and after the replacement of the intermediate transfer belt 8 in the image forming apparatus according to the second embodiment. In FIG. 8, the number of prints is set on the horizontal axis and the correction application rate is set on the vertical axis. As shown in FIG. 8, the correction value of the detection value of the IDC sensor 120 has an application rate set according to the number of printed sheets. Before the replacement of the intermediate transfer belt 8, the correction application rate increases from 50% to 80% as the number of printed sheets increases. After replacing the intermediate transfer belt 8, the correction application rate is set to 100%. This is because the correction application rate has been raised from 80% to 100% by feeding back the measured value of the dirt amount of the IDC sensor 120 when the belt is replaced. The correction application rate shown in FIG. 8 is an example, and the initial application rate and the inclination of the application rate depend on the error of the correction value caused by the situation of the image forming apparatus 100, the usage state of the IDC sensor 120, and the like. You may adjust.

Next, the operation of the density correction of the image forming apparatus 100 according to the second embodiment will be described with a flowchart. FIG. 9 is a flowchart for explaining the operation of density correction of the image forming apparatus according to the second embodiment. First, the control unit 50 of the image forming apparatus 100 determines whether or not the intermediate transfer belt 8 is in the initial state before use (step S51). When the intermediate transfer belt 8 is in the initial state (YES in step S51), the control unit 50 corrects the amount of light reflected on the bare surface of the intermediate transfer belt 8 (step S52).

The control unit 50 determines whether or not the initial amount of light reflected on the bare surface of the intermediate transfer belt 8 is stored in the memory unit 72 (step S53). When the initial light amount is not stored in the memory unit 72 (NO in step S53), the control unit 50 stores the detected value of the IDC sensor 120 as the initial light amount in the memory unit 72 (step S54). When the initial light amount is stored in the memory unit 72 (YES in step S53), the control unit 50 calculates the dirt amount of the IDC sensor 120 (step S55). Specifically, the control unit 50 calculates the amount of dirt on the IDC sensor 120 based on the most recently detected value detected by the IDC sensor 120 and the initial amount of light stored in the memory unit 72.

After calculating the amount of dirt on the IDC sensor 120 in step S55, the control unit 50 corrects the estimated value of the amount of change (solid line B2a shown in FIG. 7) such as deterioration of the intermediate transfer belt 8 (roughness of the belt). (Step S56).

Next, the control unit 50 determines whether or not to perform a process for stabilizing the image formation (step S57). The control unit 50 determines that the process of stabilizing the image formation is performed by a predetermined time unit or by exchanging the intermediate transfer belt 8. When performing the process of stabilizing the image formation (YES in step S57), the control unit 50 determines the amount of bare surface light so that the amount of light reflected from the bare surface of the intermediate transfer belt 8 becomes a predetermined amount (for example, the initial amount of light). The correction is performed (step S58). The control unit 50 determines the amount of light emitted by the light emitting unit 122 based on the correction result in step S58 (step S59). The control unit 50 calculates the amount of change in light emission changed from the amount of light emission determined in step S59 from the detected value of the IDC sensor 120 (step S60).

The control unit 50 calculates the amount of dirt on the IDC sensor 120 from the amount of change in light emission calculated in step S60 (step S61). The control unit 50 sets, for example, the relationship between the amount of change in light emission and the amount of dirt on the IDC sensor 120 as a table in advance and stores it in the memory unit 72. Using the table, the IDC sensor 120 is used to obtain the amount of change in light emission. Calculate the amount of dirt.

The control unit 50 determines whether or not the calculated dirt amount of the IDC sensor 120 is equal to or greater than a predetermined threshold value (predetermined value) (step S62). As shown in FIG. 7, when the solid line A1b indicating the amount of change in light emission of the IDC sensor 120 becomes a threshold value of 1 or more, the control unit 50 determines that the amount of dirt on the IDC sensor 120 is large. When the amount of dirt on the IDC sensor 120 is equal to or greater than a predetermined threshold value (YES in step S62), the control unit 50 displays an instruction prompting cleaning on the operation display unit 70 or contacts a serviceman by a service call (step S62). S63). When the amount of dirt on the IDC sensor 120 exceeds a predetermined threshold value, the control unit 50 cannot correct the detected value according to the amount of dirt on the IDC sensor 120, so that the IDC sensor 120 needs to be cleaned.

The image forming apparatus 100 uses a plurality of IDC sensors 120, and one IDC sensor 120 detects the amount of change in the color emission of the plurality of toners. Therefore, when the stain amount of the IDC sensor 120 is less than a predetermined threshold value (NO in step S62), the control unit 50 confirms the difference in the stain amount for each color detected by one IDC sensor 120, and confirms the stain amount. It is determined whether or not the difference between the above is equal to or greater than a predetermined difference (step S64). When the difference in the amount of stain is equal to or greater than a predetermined difference (YES in step S64), the control unit 50 changes the color assignment detected by the plurality of IDC sensors 120 (step S65).

When the difference in the amount of stain is less than a predetermined difference (NO in step S64), the control unit 50 determines the correction value according to the amount of stain in each color (step S66). As shown in FIG. 4, the control unit 50 sets the correction value for each color as a table in advance from the amount of stain, and determines the correction value for each color using the table. Further, as shown in FIG. 8, the control unit 50 determines the correction application rate (correction rate) from a table or the like preset according to the situation of the image forming apparatus 100, the usage state of the IDC sensor 120, and the like. (Step S67).

After that, the control unit 50 adjusts the maximum concentration in steps S68 to S72. Specifically, the control unit 50 prints a plurality of patches of the adhesion amount changed under each bias condition (step S68), and obtains the detection value of the IDC sensor 120 of each patch (step S69). Further, the control unit 50 corrects the detection value of the IDC sensor 120 of each color using the correction table of each color (step S70), calculates the amount of toner image adhered to each patch (step S71), and intermediate transfer belt. The development pier of 8 is determined (step S72). Thereby, the control unit 50 can determine the development bias in which the toner image of an appropriate amount of adhesion is formed on the intermediate transfer belt 8 even if the IDC sensor 120 is dirty. It is desirable that the control unit 50 increases the correction amount for each color as the amount of dirt on the IDC sensor 120 increases and the density increases.

The control unit 50 determines whether or not the operation for ending the process has been accepted (step S73). When the operation for terminating is not accepted (NO in step S73) and the process for stabilizing the image formation is not performed (NO in step S57), the control unit 50 returns the process to step S51. When the operation to end is accepted (YES in step S73), the control unit 50 ends the process.

As described above, in the image forming apparatus 100 according to the first embodiment, the control unit 50 may change the correction amount of the IDC sensor 120 according to the usage state of the IDC sensor 120. Specifically, the control unit 50 may change the application rate of the correction amount of the IDC sensor 120 according to the usage state of the IDC sensor 120. As a result, the control unit 50 can appropriately correct the detection value of the IDC sensor 120 according to the situation of the image forming apparatus 100, the usage state of the IDC sensor 120, and the like. If the correction amount can be changed according to the usage state of the IDC sensor 120, it may be changed by a method other than the application rate of the correction amount.

In the example shown in FIG. 8, the application rate of the correction value is increased as the number of printed sheets increases. Before replacing the intermediate transfer belt 8 and before feeding back the measured value of the dirt amount of the IDC sensor 120, the dirt amount of the IDC sensor 120 can be further reduced by suppressing the correction application rate to about 50%. Even if the number increases, the detection accuracy of the IDC sensor 120 can be gradually improved.

It should be considered that the embodiments disclosed this time are exemplary in all respects and not restrictive. The scope of the present invention is shown by the scope of claims rather than the above description, and it is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

1 Photoreceptor drum, 2 Charging unit, 3 Exposure unit, 4 Developing unit, 6C, 6K, 6M, 6Y cleaning unit, 8 Intermediate transfer belt, 10 Image forming unit, 20 Paper feeding unit, 50 Control unit, 70 Operation display unit , 80 automatic document carrier, 90 image reader, 100 image forming device, 102 device body, 120 IDC sensor, 122 light emitting unit, 130 P wave receiving unit, 140 S wave receiving unit, 130a, 140a polarizing plate.

Claims (12)

A density detection device that detects the density of a toner image formed on an image carrier.
An optical sensor that includes a light emitting element that irradiates the image carrier with light and a light receiving element that receives the reflected light reflected by the image carrier, and detects the density of the toner image.
A correction unit for correcting a detection value detected by the optical sensor is provided.
The optical sensor can adjust the density of toner images of at least two colors.
The correction unit is a density detection device that corrects a detection value detected by the optical sensor for each color according to the amount of dirt on the optical sensor. The correction unit determines the amount of dirt on the optical sensor based on the amount of change of the reflected light from the bare surface of the image carrier in the initial state with respect to the amount of light, and the amount of reflected light received by the light receiving element is the amount of the reflected light in the initial state. The concentration detection device according to claim 1, wherein the light emission amount of the light emitting element is corrected so as to be the light amount of the reflected light of. The density detection device according to claim 2, wherein the correction unit determines the amount of contamination of the optical sensor by subtracting the amount of change due to deterioration of the image carrier from the amount of change of the reflected light in the initial state with respect to the amount of light. The concentration detecting device according to claim 3, wherein the correction unit estimates the amount of change due to deterioration of the image carrier from the number of images formed or the toner coverage of the image carrier facing the optical sensor. The concentration detecting device according to any one of claims 1 to 3, wherein the correction unit increases the correction amount of the optical sensor as the amount of dirt on the optical sensor increases. The concentration detecting device according to any one of claims 1 to 5, wherein the correction unit changes the correction amount of the optical sensor according to the usage state of the optical sensor. The concentration detection device according to claim 6, wherein the correction unit changes the application rate of the correction amount of the optical sensor according to the usage state of the optical sensor. The optical sensor includes a first optical sensor and a second optical sensor.
When the first optical sensor has a larger amount of dirt than the second optical sensor, the first optical sensor is made to detect the density of the toner image of the first color, and the second optical sensor is made to detect the density of the toner image of the first color. The density detection device according to any one of claims 1 to 7, which detects the density of a second color toner image having a large correction amount. The correction unit detects the density of a toner image of one color. When the amount of stain on the optical sensor exceeds a predetermined value, the correction unit detects the density of a toner image of another color with the optical sensor of the one color. The density detection device according to any one of claims 1 to 8, which detects the density of the toner image of the above. The concentration detecting device according to any one of claims 1 to 8, wherein the correction unit notifies cleaning information when the amount of dirt on the optical sensor exceeds a predetermined value. When the image carrier is replaced, the correction unit compares the estimated value of the amount of change in the amount of reflected light due to the deterioration of the image carrier with the actual value, and averages the difference between the estimated value and the actual value. The concentration detection device according to any one of claims 1 to 8, wherein the value is used as the estimated value of the image carrier after replacement. An image forming device that forms an image on a sheet.
An image carrier on which a toner image is formed and
An image forming apparatus including the density detecting apparatus according to any one of claims 1 to 11, which detects the density of a toner image formed on the image carrier.

Images