JP4189563B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus used for a copying machine, a printer, or the like. More specifically, the present invention relates to an image forming apparatus having a function of creating a gradation test pattern and detecting the toner adhesion amount in order to control image density and gradation.
[0002]
[Prior art]
In the image forming apparatus, the amount of toner adhered per unit area on the image carrier in the development process affects the image density and gradation. Therefore, a gradation test pattern is created on the image carrier, and the image forming conditions are controlled so that the toner adhesion amount in each density region (toner pattern of each density) in this gradation test pattern is constant. (Hereinafter, this control is referred to as “AIDC control”). For this purpose, it is necessary to measure a reference toner adhesion amount in each density region.
[0003]
Therefore, conventionally, an adhesion amount sensor composed of an infrared light emitting element and a light receiving element that detects the reflected light is used to measure the toner adhesion amount of each density region in the gradation test pattern created on the image carrier. To measure. That is, the toner adhesion amount in each density region is measured by detecting the intensity of infrared light emitted from the light emitting element and reflected in each density region by the light receiving element.
[0004]
Specifically, first, a gradation test pattern KP as shown in FIG. 6 is created on the image carrier. Then, according to the moving direction of the image carrier (see FIG. 6), the toner adhesion amount in each density area in the gradation test pattern KP is sequentially detected from the high density side by the adhesion amount sensor, and the detection result as shown in FIG. 7 is obtained. It is done. Next, an average value of detection results in each concentration region is calculated. Then, by connecting each average value with a curve, waveform data indicating the relationship between the density and the toner adhesion amount as shown in FIG. 8 is acquired. And AIDC control is performed based on the waveform data acquired in this way.
[0005]
[Problems to be solved by the invention]
However, the conventional image forming apparatus has a problem that the entire length of the KP of the gradation test pattern created on the image carrier becomes very long, and thus the toner is unnecessarily consumed. The total length of the gradation test pattern KP is increased in this way in order to detect an accurate toner adhesion amount for each density region (each density toner pattern). That is, when a portion other than the density region (the surface of the image carrier) enters the detection region of the adhesion amount sensor, reflected light from other than the density region is also detected by the adhesion amount sensor, so the intensity of the reflected light from the density region is reduced. This is because it cannot be detected accurately. Therefore, each density area must be larger than the detection area of the adhesion amount sensor.
[0006]
On the other hand, in order to reduce the amount of toner consumed when creating the gradation test pattern KP, the length of each density area may be shortened. However, if the length of each density area is simply shortened, the area other than the density area (the surface of the image carrier) also enters the detection area of the adhesion amount sensor, and the intensity of infrared light reflected by each density area Cannot be measured accurately. For this reason, an accurate toner adhesion amount cannot be detected, which may adversely affect AIDC control.
[0007]
Therefore, the present invention has been made to solve the above-described problems, and the toner adhesion amount can be accurately detected even when the total length of the gradation test pattern is shortened. It is an object to provide an image forming apparatus that does not adversely affect control (AIDC control).
[0008]
[Means for Solving the Problems]
According to the image forming apparatus of the present invention made to solve the above-described problems, the image carrier, the intermediate density including a plurality of density regions of different density with the highest density region, the lowest density region on the image carrier. A test pattern creating means for creating a gradation test pattern comprising: a density pattern; and a detecting means for detecting a toner adhesion amount on the image carrier. The test pattern creating means comprises a highest density area and a lowest density area. Is created longer than the detection area of the detection means, and the intermediate density pattern is created so that two or more density areas of the plurality of density areas included in the intermediate density pattern fall within the detection area of the detection means. Features.
[0009]
In this image forming apparatus, in order to obtain data relating to the toner adhesion amount used for image density and gradation control (AIDC control), first, a gradation test pattern is created on the image carrier by the test pattern creation means. The Next, the toner adhesion amount in the gradation test pattern is detected by the detection means. The toner adhesion amount is detected by irradiating each density region in the gradation test pattern created on the image carrier with infrared light and detecting the reflected light. Then, AIDC control is executed based on the data regarding the toner adhesion amount obtained by the detection means. It should be noted that the gradation test pattern may be created at a predetermined time (when a predetermined operating time or the number of processed sheets is reached, or when an operator gives an instruction). In addition to the photosensitive drum, the “image carrier” may be a transfer drum, a transfer belt, a recording paper, or the like.
[0010]
Here, the gradation test pattern created by the test pattern creating means includes an intermediate density pattern including a plurality of density areas having the highest density area, the lowest density area, and different densities. In the gradation test pattern, the lengths of the highest density area and the lowest density area are longer than the detection area of the detection means. Thus, when the detection unit detects the toner adhesion amount in the highest density region or the lowest density region, the detection unit detects only infrared light reflected by the highest density region or the lowest density region. Accordingly, the toner adhesion amount in the highest density region and the lowest density region is accurately detected (a true value is obtained). The “density area length” here means the length (width) of the density area in the moving direction of the image carrier (the same applies to the following description).
[0011]
In the intermediate density pattern, each density area is arranged so that two or more density areas having different densities are included in the detection area of the detection means. Thereby, the length of the intermediate density pattern is shortened. Therefore, the overall length of the gradation test pattern is short. For this reason, the amount of toner consumed when creating the gradation test pattern is reduced, and the cost is excellent. In addition, when the detection unit detects the toner adhesion amount of the intermediate density pattern, the detection unit detects infrared light reflected by two or more density regions, so that the detection value of the detection unit is the detection target. The average value in each density region. Therefore, it is not necessary to calculate the average value in each density area as in the conventional image forming apparatus.
[0012]
Here, when detecting the toner adhesion amount of the intermediate density pattern, the infrared light reflected by the portion other than the density area (the surface of the image carrier) is also slightly detected. For this reason, an error may occur when detecting the toner adhesion amount of the intermediate density pattern, which may adversely affect AIDC control. However, when the toner adhesion amount is detected, the part other than the density area that enters the detection area of the detection means is very small compared to the density area part, so that an error that causes a problem in the detection value of the detection means may occur. Unthinkable. Further, even if an error occurs in the detection value in the intermediate density pattern, the error is small, and an accurate detection value is obtained in the highest density region and the lowest density region. Therefore, the error can be corrected appropriately. it can. As described above, when detecting the toner adhesion amount of the intermediate density pattern, even if infrared light reflected by a portion other than the density area (the surface of the image carrier) is detected, there is no influence on the AIDC control. It is thought not to give.
[0013]
In the image forming apparatus according to the present invention, it is preferable that the test pattern creation unit creates the gradation test pattern so that the length of the intermediate density pattern is longer than the detection area of the detection unit.
[0014]
When measuring the toner adhesion amount of the intermediate density pattern, the detection means detects infrared light reflected by a portion other than the density area (the surface of the image carrier). If the length of the intermediate density pattern is shorter than the detection area of the detection means, a portion (surface of the image carrier) other than the density area occupying the detection area of the detection means becomes large. This is because the toner adhesion amount of the intermediate density pattern cannot be accurately detected (the error becomes large) and adversely affects AIDC control (particularly gradation control).
[0015]
Further, in the image forming apparatus according to the present invention, it is preferable to perform sampling by the detection means a plurality of times. This is because the toner adhesion amount can be detected with higher accuracy, and as a result, the accuracy of AIDC control is also improved.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying an image forming apparatus according to the present invention will be described below in detail with reference to the drawings. In the present embodiment, the case where the present invention is applied to an electrophotographic tandem color copying machine will be described.
[0017]
As shown in FIG. 1, the copying machine 1 according to the present embodiment includes an image reader unit IR that reads an image of a document, and a print unit PR that prints and reproduces the read image on a recording sheet S. Yes. First, the outline of the whole will be described.
[0018]
The image reader IR includes an image sensor such as a CCD, and reads an original image by separating the image into three colors of red (R), green (G), and blue (B). The printer unit PR includes a transport unit 2 that transports the recording paper S along the transport path L, and four image forming units 3C, 3M, 3Y, and 3K (hereinafter referred to as four image forming units for forming four color images on the recording paper S). C, M, Y, and K are added as color symbols to the numbers of the portions related to the reproduction colors of cyan, magenta, yellow, and black, respectively, except that they are handled differently. ).
[0019]
The image forming units 3C, 3M, 3Y, and 3K include image forming process units 4C, 4M, 4Y, and 4K arranged in parallel along the transport path L, and exposure scanning units (including optical systems) 5C and 5M. , 5Y, 5K. A control unit 100 that performs overall control of the entire copying machine 1 is provided, and an image memory and other various memories are provided therein. The control by the control unit 100 includes not only control for the copying operation itself but also control of each unit for detecting the toner adhesion amount of the test pattern described later.
[0020]
The transport unit 2 is configured around an endless transport belt 27 stretched through a drive roller 24, a driven roller 25, and a tension roller 26, and transports the recording paper S on the transport belt 27 at a constant speed. It has become. On the upstream side (feeding side) of the conveying belt 27, a paper feeding cassette 21 that stores and stores recording paper S of a predetermined size, and a paper feeding roller 22 that feeds the recording paper S from the paper feeding cassette 21 one by one. A timing roller 23 for feeding the fed recording sheet S onto the conveying belt 27 at a predetermined timing is disposed. On the other hand, on the downstream side of the conveying belt 27, a fixing device 28 for fixing the toner image transferred to the recording paper S and a paper discharge tray 29 for stacking and storing the recording paper S on which the image is copied are arranged. ing. Sensors SE1 and SE2 are provided on the upstream side and the downstream side of the conveyor belt 27, respectively, so as to detect paper feed timing, paper jam, and the like.
[0021]
The image forming process units 4C, 4M, 4Y, and 4K of the image forming units 3C, 3M, 3Y, and 3K form images by an electrostatic copying method, and follow the conveyance direction of the recording paper S on the conveyance belt 27. The photosensitive drums 41C, 41M, 41Y, and 41K are arranged in parallel. Around the photosensitive drums 41C, 41M, 41Y, and 41K, cleaners 42C, 42M, 42Y, and 42K, charging chargers 44C, 44M, 44Y, and 44K, developing devices 45C, 45M, 45Y, and 45K are arranged. Yes. Further, transfer chargers 46C, 46M, 46Y, and 46K are arranged via the conveyor belt 27 directly below the respective photosensitive drums 41C, 41M, 41Y, and 41K. Although details will be described later, an adhesion amount detection sensor for detecting the toner adhesion amount of a test pattern created on the photosensitive drums 41C, 41M, 41Y, and 41K includes photosensitive drums 41C, 41M, 41Y, and 41D. It is arranged at the bottom of 41K.
[0022]
Next, the operation of the copying machine 1 will be described. First, an image of an original is read by the image reader unit IR, and image data for each color component of red (R), green (G), and blue (B) is acquired. The obtained data is sent to the control unit 100, and necessary data processing such as shading correction, density conversion, edge enhancement and the like is performed. Further, it is converted into image data of each reproduction color of cyan (C), magenta (M), yellow (Y), and black (K). These color image data are temporarily stored in the image memory of the control unit 100.
[0023]
Then, the photosensitive drums 41C, 41M, 41Y, and 41K are rotated and charged by the charging chargers 44C, 44M, 44Y, and 44K. The rotational speeds of the photosensitive drums 41C, 41M, 41Y, and 41K are set to the conveyance speed of the recording paper S. In synchronization with this, a laser beam is irradiated from the exposure scanning units 5C, 5M, 5Y, and 5K based on the image data stored in the image memory, and exposure scanning is performed on the photosensitive drums 41C, 41M, 41Y, and 41K. The By this exposure, electrostatic latent images are formed on the photosensitive drums 41C, 41M, 41Y, 41K.
[0024]
Then, cyan (C), magenta (M), yellow (Y), and black (K) toners are supplied to the electrostatic latent images by the developing units 45C, 45M, 45Y, and 45K, and are visualized as toner images. It becomes. This is development. After development, the toner images formed on the photosensitive drums 41C, 41M, 41Y, and 41K are transferred onto the recording paper S by the transfer chargers 46C, 46M, 46Y, and 46K. After the transfer, the multiple toner image is heated and melted by the fixing device 28 to form a color image, and is fixed on the recording paper S. The recording paper S is discharged to the paper discharge tray 29. With the above operation, one copy operation is completed. Each of the photosensitive drums 41C, 41M, 41Y, and 41K is subjected to removal of residual toner by the cleaners 42C, 42M, 42Y, and 42K after being transferred by the transfer chargers 46C, 46M, 46Y, and 46K, and is prepared for the next copying operation. .
[0025]
Subsequently, the characteristic part of the present invention in the above-described copying machine 1 will be described. Therefore, FIG. 2 shows the photosensitive drum 41 (in the following description, the C, M, Y, and K color symbols are omitted unless otherwise required), the periphery thereof, and the control system. Around the photosensitive drum 41, an adhesion amount detection sensor 11 is provided in addition to the cleaner 42, the charging charger 44, the developing device 45, the conveying belt 27, and the transfer charger 46 described in FIG.
[0026]
The adhesion amount detection sensor 11 includes a light emitting element 12 and a light receiving element 13 as shown in FIG. 3, and detects the toner adhesion amount (mg / cm ² , the same applies hereinafter) of a toner image based on the intensity of reflected light. And provided downstream of the transfer position between the photosensitive drum 41 and the conveyor belt 27.
[0027]
Returning to FIG. 2, the developing device 45 is provided with a toner replenishing section 60 that replenishes toner and a developing roller 51 that imparts toner to the photosensitive drum 41. A sensor output Vs is sent from the adhesion amount detection sensor 11 to the control unit 100. On the other hand, the control unit 100 outputs a control signal of the grid voltage Vg to the charging charger 44, image data to the exposure scanning unit 5, a toner supply signal to the toner supply unit 60, and a bias voltage Vb to the developing roller 51. The control signal of the transfer voltage Vt is given to the transfer charger 46. In addition to what appears in FIG. 2, there are various types of signals in and out of the control unit 100 such as transmission of control signals to the image reader unit IR and reception of image data therefrom. The periphery of the photosensitive drum 41 is provided for each color of cyan (C), magenta (M), yellow (Y), and black (K).
[0028]
In the copying machine 1 having the periphery of the photosensitive drum 41 as described above, the test pattern toner is used to control the density and gradation of reproduced images (AIDC control) in addition to the normal operation of copying an original image. The amount of adhesion is appropriately measured. The toner adhesion amount of the test pattern is measured as follows. First, a test pattern is created on the photosensitive drum 41 under the control of the control unit 100. The test pattern itself is formed by forming an electrostatic latent image on the photosensitive drum 41 with the laser beam of the exposure scanning unit 5 and applying toner to the developer 45 in the same manner as in the normal copying operation. Is done. The test pattern created on the photosensitive drum 41 is measured by measuring the toner adhesion amount with the adhesion amount detection sensor 11.
[0029]
Here, the test pattern TP created on the photosensitive drum 41 when the toner adhesion amount is detected is a gradation pattern as shown in FIG. The gradation pattern gradually decreases in density from the upstream side to the downstream side in the rotation direction of the photosensitive drum 41 (see FIG. 4). In the test pattern TP, the lengths L1 and L2 of the highest density region P1 and the lowest density region P2 are respectively longer than the diameter of the detection window (detection region) W of the adhesion amount detection sensor 11. Thus, the adhesion amount detection sensor 11 can measure the toner adhesion amount in the highest density region P1 and the lowest density region P2 without being affected by reflected light from other than the density region (the surface of the photosensitive drum 41). it can. Accordingly, the toner adhesion amounts in the highest density region P1 and the lowest density region P2 are accurately measured by the adhesion amount detection sensor 11.
[0030]
Further, an intermediate density pattern P3 is formed between the highest density area P1 and the lowest density area P2, and the intermediate density pattern P3 includes a plurality of density areas having different densities. The length of each concentration region is such that the two concentration regions enter the detection window W of the adhesion amount detection sensor 11. That is, the length of each density region in the intermediate density pattern P3 is short. For this reason, the amount of toner consumed when creating the test pattern TP is reduced. On the other hand, when the adhesion amount sensor 11 measures the toner adhesion amount of the intermediate density pattern P3, the reflected light from other than the density region (the surface of the photosensitive drum 41) is also slightly detected. For this reason, an error may occur in the detection value of the adhesion amount sensor 11, and the AIDC control may be adversely affected.
[0031]
However, when the toner adhesion amount is measured, since the area of the photosensitive drum 41 that enters the detection window W of the adhesion amount detection sensor 11 is very small, an error that causes a problem in the detection value of the adhesion amount detection sensor 11 occurs. Is unthinkable. Further, even if an error occurs in the detection value of the adhesion amount detection sensor 11 in the intermediate density pattern P3, the error is small, and accurate detection values are obtained in the maximum density region P1 and the minimum density region P2. The error can be corrected appropriately. Therefore, it is considered that the AIDC control is not affected even if reflected light from the surface of the photosensitive drum 41 is detected when measuring the toner adhesion amount in the intermediate density pattern P3.
[0032]
The toner adhesion amount of the test pattern TP is first measured by the adhesion amount detection sensor 11 sequentially with respect to the high density region P1, the intermediate density pattern P3, and the lowest density region P2 according to the rotation of the photosensitive drum 41. Infrared light is irradiated and the intensity of the reflected light is detected. The sensor output Vs of the adhesion amount detection sensor 11 is sent to the control unit 100 to obtain waveform data as shown in FIG. This waveform data is almost the same as the waveform data (see FIG. 8) obtained by the conventional apparatus. Then, the control unit 100 refers to the detection characteristics of the adhesion amount detection sensor 11 stored in the memory, and calculates the toner adhesion amount of the test pattern TP. The measurement of the toner adhesion amount of the test pattern TP by the adhesion amount sensor 11 is performed three times. This is to increase the accuracy.
[0033]
In the test pattern TP, each density region is arranged so that two density regions always enter the detection window W of the adhesion amount detection sensor 11. For this reason, the adhesion amount detection sensor 11 detects the infrared light reflected by the two density regions. Thereby, the sensor output Vs of the adhesion amount detection sensor 11 is output as an average value of the two density regions. Therefore, it is not necessary to calculate an average value in each density region.
[0034]
Then, AIDC control is performed based on the fluctuation of the toner adhesion amount (sensor output Vs) measured in this way. Specifically, the image forming conditions such as the bias voltage Vb of the developing roller 51, the transfer voltage Vt of the transfer charger 46, and the grid voltage Vg of the charging charger 44 are appropriate so that a reproduced image based on the original image can be created. It is corrected to the value. In some cases, a toner replenishment signal is issued to the toner replenishment unit 60 to replenish toner. The adhesion amount measurement and control as described above is performed for each color of cyan (C), magenta (M), yellow (Y), and black (K). As a result, the copying machine 1 can always obtain a high-quality reproduced image.
[0035]
As described above in detail, according to the copying machine 1 according to the present embodiment, when the test pattern TP is created on the photosensitive drum 41 in order to measure the toner adhesion amount, the highest density region P1 and the lowest density. The region P2 is created longer than the diameter of the detection window W of the adhesion amount detection sensor 11, and each of the intermediate density patterns P2 includes two concentration regions so that the detection window W of the adhesion amount detection sensor 11 always includes A density region is arranged. As a result, the length of each density region in the intermediate density pattern P3 is shortened, so that toner consumption during the formation of the test pattern TP is suppressed.
[0036]
On the other hand, by shortening the length of each density area in the intermediate density pattern P3, when the adhesion amount sensor 11 measures the toner adhesion quantity of the intermediate density pattern P3, it is from other than the density area (the surface of the photosensitive drum 41). The reflected light is also slightly detected. However, when the toner adhesion amount is measured, since the area of the photosensitive drum 41 that enters the detection window W of the adhesion amount detection sensor 11 is very small, an error that causes a problem in the detection value of the adhesion amount detection sensor 11 occurs. Is unthinkable. Further, even if an error occurs in the detection value of the adhesion amount detection sensor 11 in the intermediate density pattern P3, the error is small, and accurate detection values are obtained in the maximum density area P1 and the minimum density area P2. The error can be corrected appropriately. Accordingly, even when the reflected light from the surface of the photosensitive drum 41 is detected when measuring the toner adhesion amount in the intermediate density pattern P3, the AIDC control is not adversely affected.
[0037]
In addition, this Embodiment is only a mere illustration and does not limit this invention at all. Accordingly, the present invention can be variously improved and modified without departing from the scope of the invention. For example, in the above embodiment, the present invention is applied to a copying machine. However, the present invention can be applied not only to a copying machine but also to a printer.
[0038]
【The invention's effect】
As described above, according to the present invention, the toner adhesion amount can be accurately detected even if the total length of the gradation test pattern is shortened, and the image density and gradation control (AIDC control) is adversely affected. No image forming apparatus is provided. That is, the total length of the gradation test pattern can be shortened without adversely affecting AIDC control. This suppresses toner consumption when creating the gradation test pattern.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a schematic configuration of a copier according to a first embodiment.
FIG. 2 is an enlarged view around a photosensitive drum of the copying machine shown in FIG.
FIG. 3 is a diagram showing a schematic configuration of an adhesion amount detection sensor.
FIG. 4 is a diagram showing a schematic configuration of a test pattern.
FIG. 5 is a graph showing an output waveform of an adhesion amount detection sensor.
FIG. 6 is a diagram illustrating a schematic configuration of a test pattern created in a conventional image forming apparatus.
FIG. 7 is a graph showing an output waveform (raw waveform) of an adhesion amount detection sensor obtained in a conventional image forming apparatus.
FIG. 8 is a graph showing an output waveform (after processing) of an adhesion amount detection sensor obtained in a conventional image forming apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Copier 11 Adhesion amount detection sensor 27 Conveyor belt 41 Photosensitive drum 45 Developer 46 Transfer charger 100 Control part TP Test pattern P1 Highest density area P2 Lowest density area P3 Intermediate density pattern

Claims (3)

An image carrier;
A test pattern creating means for creating a gradation test pattern comprising a maximum density area, a minimum density area, and an intermediate density pattern including a plurality of density areas of different densities on the image carrier;
Detecting means for detecting the toner adhesion amount on the image carrier,
The test pattern creation means includes
Creating the highest density area and the lowest density area longer than the detection area of the detection means;
2. The image forming apparatus according to claim 1, wherein the intermediate density pattern is created so that two or more areas out of a plurality of density areas included in the intermediate density pattern fall within a detection area of the detection unit. The image forming apparatus according to claim 1,
The image forming apparatus, wherein the test pattern creating unit creates a gradation test pattern so that a length of the intermediate density pattern is longer than a detection region of the detecting unit. The image forming apparatus according to claim 1,
An image forming apparatus characterized in that sampling by the detecting means is performed a plurality of times.

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