JP2007304208A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To process determination of adequacy of a toner attaching amount to an image carrier in a simple composition and in a short time. <P>SOLUTION: A detection patch 45A is formed in a central part of a photoreceptor drum 20 (step 202) and the toner attaching amount "n'" and position from a home position "l'" are read by a sensor and stored (step 204) in an image forming apparatus. A difference "u" of a position which is closest to the read position is read among a reference distribution (distribution of the difference between an average value and the toner attached amount in each position) of the toner attached amount stored to a memory 76 beforehand (step 206) and added to the toner attached amount "n'" (n''=n'+u)(step 208). Default and tolerance for the toner attached amount are read from the memory 76, a difference value from the calculated value "n''" is calculated (step 210) and whether the difference value in included in the tolerance is judged (step 212). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus that forms an image on continuous paper at high speed.

  As an example of an image forming apparatus, a tandem image forming apparatus that forms an image on a continuous sheet at a high speed is known. In general, the image forming apparatus includes a photoconductive drum as an image carrier, the photoconductive drum is uniformly charged by a charging device, an LED array is emitted by an image recording head, and the photoconductive drum is charged. Is exposed to an electrostatic latent image. Toner is attached to the electrostatic latent image by a developing device to form a toner image on the photosensitive drum, and the toner image is transferred to a recording medium by a transfer device. The transferred toner image is fixed on a recording medium by a fixing device.

In general, in an image forming apparatus, the toner adhesion amount of toner adhering on a photosensitive drum varies depending on the characteristics of the toner, the internal and external environment of the image forming apparatus, the characteristics of the photosensitive drum, and the like. This change in the toner adhesion amount is one of the factors that greatly affect the image density of the image fixed on the recording medium. Therefore, an image forming apparatus is known that maintains a constant toner adhesion amount on a photosensitive drum in order to stabilize an image fixed on a recording medium. For example, by detecting the toner adhesion amount on the photosensitive drum, the process conditions relating to image formation such as the grid voltage applied to the charging device and the development bias voltage applied to the developing device are determined so that the toner adhesion amount is constant. An image forming apparatus is known (for example, see Patent Document 1). In this image forming apparatus, the density of the toner image on the photosensitive drum is read by a sensor at the time of warm-up after turning on the power to the image forming apparatus, the toner adhesion amount is obtained, and the process condition is determined when the warm-up is completed.
JP-A-6-175449

  However, it is not sufficient to stabilize the image quality if the process conditions are determined only from the toner adhesion amount obtained during warm-up as in the conventional image forming apparatus. For example, in order to obtain a stable image quality, it is necessary to adjust process conditions with respect to fluctuations in toner adhesion amount, not only during warm-up. However, it is difficult to determine process conditions that are executed during warm-up during image formation. In recent years, there has been a call for faster processing time for image formation. However, it is not preferable to perform a process for determining process conditions to be executed during warm-up because the process time increases.

  SUMMARY OF THE INVENTION The present invention has been made in consideration of the above facts, and an object of the present invention is to obtain an image forming apparatus that can process the determination of whether or not the amount of toner adhered to an image carrier is simple and can be processed in a short time.

  In order to achieve the above object, the image forming apparatus of the present invention performs development processing by adhering toner to an image carrier on which an electrostatic latent image is formed when an image is formed by main scanning and sub-scanning. Storage means for preliminarily storing a relationship between a position on the image carrier and a toner adhesion amount at the position as a reference distribution over the entire surface of the image carrier, a toner adhesion amount adhered to the image carrier, and A detecting means for detecting a position on the image carrier; and a toner is attached to at least one portion of the image carrier; the attached toner is detected by the detecting means; and the detected toner is detected on the image carrier. Control means for determining whether or not the toner adhesion amount detected by the detection means is included in a predetermined allowable range for the toner adhesion amount in the reference distribution corresponding to the position.

  In the image forming apparatus of the present invention, when an image is formed by main scanning and sub-scanning, an electrostatic latent image is formed on an image carrier, and toner is attached to the image carrier. Generally, the amount of toner deposited on the image carrier varies depending on the position of the image carrier due to the characteristics of the image carrier. Therefore, the storage means stores in advance the relationship between the position on the image carrier and the toner adhesion amount at the position as the reference distribution over the entire surface of the image carrier. The amount of toner adhering to the image carrier and the position on the image carrier are detected by detection means. The control means causes the toner to adhere to at least one location of the image carrier and causes the detection means to detect the attached toner. In many cases, the variation in the toner adhesion amount due to the change over time of the image carrier is uniform throughout the image carrier. For this reason, the tendency of the entire image carrier can be detected only by detecting at least one location of the image carrier. At the same time, the control means obtains the toner adhesion amount in the reference distribution corresponding to the position on the image carrier detected by the detection means. The toner adhesion amount in this reference distribution may be the position on the image carrier detected by the detection means or the nearest position. An allowable range is predetermined for the toner adhesion amount, and it is determined whether or not the toner adhesion amount detected by the detection unit is included in the allowable range. As described above, in the image forming apparatus of the present invention, the toner adhesion amount and the position on the image carrier are detected for the toner adhered to at least one place, and compared with the toner adhesion amount of the reference distribution corresponding to the position. As a result, the tendency of the entire image carrier can be determined. As described above, whether or not the toner adhesion amount is appropriate is determined only by detecting the toner adhering to at least one position of the image carrier without detecting the toner adhesion amount of the entire image carrier that requires a long time. be able to. As described above, in the image forming apparatus of the present invention, the toner adhesion amount on the image carrier is determined based on the reference distribution. For example, the toner adhesion amount is included in the allowable range according to the determination result. If not, process conditions such as grid voltage applied to the charging device can be changed, so that the amount of toner adhering to the image carrier can be kept constant.

  The detection unit is configured to be able to detect at a plurality of positions in the main scanning direction, and the control unit is configured to detect the detection position of the detection unit at the time of executing the development process when forming an image based on the image data. Control is performed such that detection is performed at a position different from the detection position of the detection means at the time of execution.

  In the present invention, the detection means is configured to be able to detect at a plurality of positions in the main scanning direction. As for the detection position of the toner adhesion amount, there is a high possibility that an average detection value can be obtained near the center in the main scanning direction of the image carrier (in the case of a rotating body such as a photosensitive drum, the rotational axis direction). For example, it cannot be used during image formation. For this reason, the control means detects the detection position of the detection means at the time of executing the development processing when forming an image based on the image data, and the detection position at a position different from the detection position of the detection means at the time of non-execution in the main scanning direction. Control to do. As a result, the position in the main scanning direction detected by the detection unit can be set to a different position when executing the developing process when forming an image based on the image data and when not performing it. For example, at the time of development processing when forming an image based on image data, the detection position of the detection means is set to an area outside the range where an electrostatic latent image is formed on the image carrier, and the main portion of the image carrier is not used when it is not executed. Since it can be near the center in the scanning direction, it can be determined whether or not the toner adhesion amount on the image carrier is within the allowable range even during image formation.

  The storage means has an average value of the toner adhesion amount when the detection means detects a distribution of the toner adhesion amount adhered over the entire surface of the image carrier in order to form a predetermined reference image, and the image. The distribution of the difference value of the average value with respect to the toner adhesion amount detected at each position on the carrier is stored as the reference distribution, and the control means at the position on the image carrier detected by the detection means A difference value of the reference distribution corresponding to the position is subtracted from the toner adhesion amount, and it is determined whether or not the subtraction value is included in the allowable range.

  In the present invention, the storage means stores an average value of the toner adhesion amount when the detection means detects the distribution of the toner adhesion amount adhered over the entire surface of the image carrier in order to form a predetermined reference image. To do. The reference image is, for example, an image that has the same image density and covers the entire surface of the image carrier. Further, the storage means stores, as a reference distribution, a distribution of difference values of average values with respect to the toner adhesion amount detected at each position on the image carrier. Accordingly, the storage unit stores the difference value of the average value, that is, the variation in the toner adhesion amount compared to the average value, as the reference distribution. Since the difference value of the average value with respect to the detected toner adhesion amount is handled, the control unit subtracts the difference value of the reference distribution corresponding to the position from the toner adhesion amount at the position on the image carrier detected by the detection unit. Then, it is determined whether or not the subtraction value is included in the allowable range. As described above, the storage unit does not correspond to the toner adhesion amount itself detected by the detection unit with respect to the toner adhered to the image carrier, but to the average value of the toner adhesion amount and the toner adhesion amount detected at each position on the image carrier. Since the distribution of average difference values is stored as a reference distribution, the amount of data stored in advance can be reduced.

  The storage means distributes the amount of toner adhering over the entire surface of the image carrier to form a predetermined reference image, and the amount of toner adhering around the image carrier at a plurality of positions in the main scanning direction. And calculating the reference distribution based on the detection result, and storing the calculated reference distribution.

  In general, the toner adhesion amount on the image carrier has a distribution as illustrated in FIG. 9 depending on the position in the main scanning direction on the image carrier, and varies as illustrated in FIG. 8 depending on the position in the sub scanning direction. There is a case. Therefore, in the present invention, the storage means is configured to make a round of the image carrier at a plurality of positions in the main scanning direction with respect to the distribution of the amount of toner adhering over the entire surface of the image carrier in order to form a predetermined reference image. Detect the toner adhesion amount. That is, the toner adhesion amount around the image carrier in the sub-scanning direction is detected. Then, based on the detection result, the reference distribution is calculated and stored. Accordingly, the storage unit stores a distribution including variations in the sub-scanning direction as the reference distribution. Therefore, it is possible to determine whether or not the toner adhesion amount is within the allowable range regardless of the variation in the toner adhesion amount on the image carrier in the sub-scanning direction.

  The detecting means detects a toner adhesion amount when the surface potential of the image carrier is stable.

  If the surface potential on the photosensitive drum is not stable, the amount of toner attached to the photosensitive drum may vary. Therefore, in the present invention, the detection means detects the toner adhesion amount when the surface potential of the image carrier is stable. As a result, a stable toner adhesion amount can be detected.

  The storage means stores the reference distribution for forming a predetermined reference image according to a predetermined reference process condition for forming an image, and the control means is configured such that the detected toner adhesion amount is within an allowable range. Output means for obtaining and outputting an instruction amount for instructing to change the process condition based on the detected toner adhesion amount.

  In the present invention, the storage means stores a reference distribution for forming a predetermined reference image according to a predetermined reference process condition for forming an image. The control means includes an output means, and when it is determined that the detected toner adhesion amount is not within the allowable range, the output means obtains an instruction amount for instructing to change the process condition based on the detected toner adhesion amount. Output. Thereby, the process condition can be changed more accurately and promptly based on the output instruction amount. As described above, since the process condition can be changed according to the determination result, for example, the toner adhesion amount when the toner is adhered on the image carrier under the changed process condition can be included in the allowable range.

  As described above, according to the present invention, the relationship between the position on the image carrier and the toner adhesion amount at the position as the reference distribution is stored in advance over the entire surface of the image carrier, so that at least one location can be obtained. Since the adequacy of the toner adhesion amount can be determined based on the reference distribution only by detecting the adhered toner, the determination of the adequacy of the toner adhesion amount to the image carrier can be processed with a simple configuration in a short time. There is an effect.

  Hereinafter, an example of implementation of the present invention will be described in detail with reference to the drawings.

  The configuration of the image forming apparatus 10 according to the present embodiment will be described with reference to FIGS. FIG. 1 is a diagram showing a schematic configuration of an image forming apparatus 10 according to the present embodiment. The image forming apparatus 10 according to the present embodiment is a tandem printer that forms an image on the continuous paper 11 at a high speed. Note that the image forming apparatus 10 of the present embodiment uses a photosensitive drum, but the image carrier is not limited to this.

  In the image forming apparatus 10, yellow (Y), magenta (M), cyan (C), and black (K) toner images of respective colors are sequentially transferred onto the continuous paper 11 and superimposed on the printing units 12K, 12C, 12M, and so on. 12Y (hereinafter referred to as print units 12K to Y) are arranged in order from the upstream side in the transport direction. A paper transport unit 14 that transports the continuous paper 11 to the print units 12K to Y is provided upstream of the print units 12K to Y in the transport direction. Further, on the downstream side in the transport direction of the printing units 12K to Y, the fixing unit 16 that fixes the unfixed toner image transferred by the printing units 12K to 12Y to the continuous paper 11 and the continuous paper 11 that has passed through the fixing unit 16 are discharged. A paper discharge unit 17 for paper is provided.

  In addition, when it is necessary to distinguish KCMY, it explains by adding any one of K, C, M, and Y after the code, and when it is not necessary to distinguish KCMY, K, C, M, and Y are used. Omitted.

  The paper transport unit 14 includes a main drive roll 18 around which the continuous paper 11 is wound. The main drive roll 18 is driven by a paper conveyance motor (not shown) that is an AC servo motor, and a main controller 70 (70 in FIG. 4) that controls the entire image forming apparatus 10 is provided with this paper conveyance motor (not shown). ) To control the feed amount of the continuous paper 11. For example, the paper counter 13 counts up for each specified paper length of the continuous paper 11.

  Further, idle rolls 19A and 19B around which the continuous paper 11 is wound are provided on the upstream side in the conveyance direction of the main drive roll 18 of the paper conveyance unit 14, and the continuous paper is provided on the downstream side in the conveyance direction of the main drive roll 18. An idle roll 19C around which 11 is wound is disposed. Further, the idle roll 19D is in pressure contact with the main drive roll 18. The idle roll 19D and the main drive roll 18 sandwich and convey the continuous paper 11.

  A transport guide 26 and an aligning roll 27 are disposed between the idle roll 19A and the idle roll 19B. The conveyance guide 26 is formed with a U-shaped curved surface on which the continuous paper 11 is wound and a guide rib (not shown) that guides one end of the continuous paper 11 in the width direction (a direction orthogonal to the conveyance direction). Yes.

  The aligning roll 27 is a roll having a roll width that is significantly narrower than the idle rolls 19 </ b> A, 19 </ b> B, 19 </ b> C, and 19 </ b> D, and a rotation axis that obliquely intersects the conveyance direction of the continuous paper 11. Further, the aligning roll 27 abuts against one end of the continuous paper 11 in the width direction and brings the continuous paper 11 toward one end in the width direction. As a result, one end in the width direction of the continuous paper 11 is abutted against a guide rib (not shown) of the conveyance guide 26, and the skew of the continuous paper 11 is corrected.

  The main drive roll 18, idle rolls 19A, 19B, 19C, and 19D, a paper transport motor (not shown), a transport guide 26, and an aligning roll 27 are supported on the paper transport frame 22 directly or via a support member. Has been. The paper transport frame 22 is supported on the base 23.

  In addition, the printing units 12 </ b> K to 12 </ b> Y include a photosensitive drum 20. Details of the photosensitive drum 20 are shown in FIG. Around the photosensitive drum 20, the transfer roll 24, the cleaning device 28, the charger 30, the LED 32, the photosensitive member surface potential sensor 42, respectively, in the rotation direction of the photosensitive drum 20 (the direction of arrow A shown in FIG. 1). A developing device 34 and toner adhesion amount detection sensors 44 and 44A are provided. In FIG. 2, the toner adhesion amount detection sensor 44A is disposed at a position overlapping the toner adhesion amount detection sensor 44. However, for convenience, the toner adhesion amount detection sensor 44A is indicated by a dotted line. The print units 12K to Y include print frames 38K to Y that support the photosensitive drum 20, the cleaning device 28, the charger 30, and the LEDs 32, respectively. Adjacent print frames 38K to Y are connected to each other by connecting bases 40 that support the print frames 38K to Y so as to be movable up and down with bolts and nuts (both not shown), and connect the print frames 38K to Y to each other. This is done by positioning and screwing through a plate (not shown). The base 40 that supports the print frame 38 </ b> Y is connected to the base 23 that supports the paper transport frame 22.

  Two toner adhesion amount detection sensors 44, 44 </ b> A are disposed along the main scanning direction with respect to the photosensitive drum 20. The arrangement positions of the toner adhesion amount detection sensors 44 and 44A with respect to the photosensitive drum 20 are shown in FIG. The right side of FIG. 3 (hereinafter referred to as the drum front side) is the side shown in FIG. A toner adhesion amount detection sensor 44 is disposed at the front end of the photosensitive drum 20, and a toner adhesion amount detection sensor 44 A is disposed at the center of the photosensitive drum 20. The toner adhesion amount detection sensor 44 reads a detection patch 45 formed outside the effective image area (area outside the range where the electrostatic latent image is formed) of the photosensitive drum 20, and the toner adhesion amount detection sensor 44A The detection patch 45 </ b> A formed at the center of the body drum 20 is read. Further, an AC servo motor (not shown) that drives the photosensitive drum 20 is provided with a position detection sensor 48 that detects the positions of the detection patches 45 and 45A in the sub-scanning direction on the surface of the photosensitive drum 20. ing. The detection patches 45 and 45A are discretely formed on the surface of the photosensitive drum 20, but are shown continuously in FIG. 3 for convenience.

  The charger 30 charges the surface of the photosensitive drum 20, and the LED 32 is controlled to emit light based on the image data, and the surface of the photosensitive drum 20 is line-exposed to form a latent image. The developing unit 34 forms a toner image by attaching toner onto the latent image formed on the surface of the photosensitive drum 20, and the transfer roll 24 converts the toner image formed on the surface of the photosensitive drum 20. Transfer to continuous paper 11. Further, the cleaning device 28 scrapes off and removes untransferred residual toner remaining on the surface of the photosensitive drum 20 without being transferred to the detection patches 45 and 45A and the continuous paper 11.

  Further, the fixing unit 16 includes a flash fixing device 52, idle rolls 54 </ b> A, 54 </ b> B, 54 </ b> C, and a paper discharge roll 56. The idle rolls 54A, 534, 54C, the flash fixing device 52, and the paper discharge roll 56 are arranged in this order in the transport direction, and these are supported by the fixing frame 58 at both ends in a direction orthogonal to the transport direction. .

  The idle rolls 54A, 54B, 54C are disposed on the back side of the printing surface of the continuous paper 11, and the idle roll 54C is disposed above the idle roll 54B. For this reason, the continuous paper 11 wound around the idle rolls 54A, 54B, 54C is reversed and conveyed with the printing surface facing upward.

  The flash fixing device 52 is disposed on the printing surface side of the continuous paper 11 conveyed with the printing surface facing upward, and irradiates the printing surface of the continuous paper 11 with infrared rays. As a result, the unfixed toner on the continuous paper 11 is heated and melted, and then solidified and fixed on the continuous paper 11.

  The paper discharge roll 56 discharges the toner-fixed area of the continuous paper 11 from the image forming apparatus 10, but the continuous paper 11 that has passed through the flash fixing device 52 is once discharged from the fixing unit 16 and discharged. After passing through 17, the paper returns to the fixing unit 16 and is discharged to the outside of the image forming apparatus 10 by the paper discharge roll 56.

  In the paper discharge unit 17, an idle roll 59A, a tension applying roll 60, a sub drive roll 61 as a transport means, an idle roll 59B, a transport guide 62, an aligning roll 63, and an idle roll 59C are arranged in order in the transport direction. These are supported by the paper discharge frame 65 directly or via a support member at both ends in a direction perpendicular to the transport direction. The paper discharge frame 65 is connected to the print frame 38K and the fixing frame 58.

  The sub drive roll 61 is disposed above the idle roll 59A, and the continuous paper 11 wound around the idle roll 59A and the sub drive roll 61 is changed in direction and conveyed upward. The idle roll 59 </ b> B is in pressure contact with the sub drive roll 61, rotates following the rotation of the sub drive roll 61, and sandwiches and conveys the continuous paper 11 together with the sub drive roll 61.

  Further, a tension applying roll 60 is disposed between the idle roll 59A and the sub drive roll 61, and the continuous paper 11 is between the idle roll 59A and the tension applying roll 60, and between the tension applying roll 60 and the sub drive roll. It is meandering between 61 and being conveyed.

  The tension applying roll 60 is supported at both ends in the main scanning direction so as to be swingable by arms (not shown). The arm is biased toward the continuous paper 11 by a biasing means (not shown) such as a spring, and the tension applying roll 60 is biased toward the continuous paper 11. As a result, tension is applied to the continuous paper 11.

  Further, the position of the arm is detected by a sensor (not shown), and the rotation speed of the sub drive roll 61 is controlled so that the position of the arm is always in a fixed position.

  Further, a transport guide 62 and an aligning roll 63 are disposed downstream of the sub drive roll 61 in the transport direction. The conveyance guide 62 and the aligning roll 63 have the same configuration as the conveyance guide 26 and the aligning roll 27 disposed in the paper conveyance unit 14 and correct the skew of the continuous paper 11.

  An idle roll 59 </ b> C is disposed downstream of the conveyance guide 62 in the conveyance direction. The continuous paper 11 is wound around the idle roll 59 </ b> C, and the direction is changed toward the paper discharge roll 56 of the fixing unit 16.

  FIG. 4 is a block diagram of a control system of the image forming apparatus 10 according to the present embodiment. Here, only one of the four KCMY colors is shown as a representative.

  The main controller 70 is constituted by a microcomputer including a CPU, a ROM, a RAM, and the like. In the main controller 70, the toner adhesion amount detection sensors 44 and 44A, the position detection sensor 48, the image data of the detection patches 45 and 45A, the predetermined value and the allowable amount of the toner adhesion amount, and the position length on the photosensitive drum 20 A memory 76 for storing in advance the distribution of toner adhesion amount and the like is connected. In order to compare with the sensor measurement values inputted from the toner adhesion amount detection sensors 44 and 44A and the position detection sensor 48, the toner adhesion from the memory 76 to the predetermined value and the allowable amount of the toner adhesion amount and the position length on the photosensitive drum 20 The amount distribution can be read out.

  In addition, a user interface 80 is connected so that an instruction regarding image formation or the like is given by a user's operation, and information on the image formation or the like is notified to the user. Further, the main controller 70 is connected to a network line with an external host computer (not shown) so that image data is input.

  When the image data is input, the main controller 70 analyzes, for example, the print instruction information included in the image data and the image data, and converts them into a format suitable for the image forming apparatus (for example, bitmap data). Image data is transmitted to the image formation processing control unit 72.

  In the image formation control unit 72, based on the input image data, the optical scanning system control unit 33, the drive system control unit 21, the charger control unit 31, the developing device control unit 35, the cleaning device control unit 29, and the fixing device control. The unit 15 is synchronously controlled to execute image formation.

  Furthermore, the paper counter 13 is connected to the main controller 70. During printing, the paper counter is read to read the number of printed sheets of the continuous paper 11 and determine when to detect the toner adhesion amount described later. .

  In the present embodiment, the toner adhering amount detection sensors 44 and 44A are arranged at two locations, the center portion and the front end portion of the photosensitive drum 20, as sensors for reading the detection patches 45 and 45A. However, the present invention is not limited to this, and one sensor may be moved to detect both the central portion and the front end portion of the photosensitive drum 20. In the present embodiment, the front side is detected as the end of the photosensitive drum 20, but the present invention is not limited to this. The end of the side (back side) may be detected.

  Next, the operation of the present embodiment will be described.

  A flow of processing for storing the reference distribution executed in the image forming apparatus 10 of the present embodiment will be described with reference to FIG. The process shown in FIG. 5 is a process executed at the initial time, for example, when the image forming apparatus 10 is turned on, when the photosensitive drum 20 is replaced, or when the toner adhesion amount detection sensors 44 and 44A are replaced. A program for executing processing is stored in advance in a ROM (not shown) of the main controller 70. In the image forming apparatus 10 according to the present embodiment, the photosensitive drum 20 having a circumference of 30 inches is used.

  First, when the image forming apparatus 10 is powered on, the processing routine of FIG.

  In step 100, the surface potential of the photoconductor drum 20 is read by the photoconductor surface potential sensor 42. In the next step 102, based on the surface potential read in step 100, it is determined whether or not the surface potential of the photosensitive drum 20 is stabilized. The determination of whether or not it is stable includes, for example, whether or not a certain time has elapsed since the image forming apparatus 10 was turned on. Here, the stable potential value and the allowable range are stored in the memory 76 in advance. This is done by reading several surface potentials in the sub-scanning direction of the photosensitive drum 20 and determining whether the average value is within the allowable range of the stable potential value. If the surface potential (average value) read in step 100 is outside the allowable range, the determination is negative and the process returns to step 100. If it is within the allowable range, it is determined that the surface potential is stable, and the routine proceeds to step 104. The state of the photosensitive drum 20 when it is determined that the surface potential of the photosensitive drum 20 is stable is an example corresponding to the state where the surface potential of the image carrier of the present invention is stable.

  In step 104, the photosensitive drum 20 is set to the home position (HP: initial position), and the process proceeds to step 106. In step 106, a variable x = 1 indicating the number of repetitions of toner adhesion amount detection is set in a counter (not shown), and in the next step 108, a detection patch 45Ax is formed at the center of the photosensitive drum 20. Note that image data of a toner image for forming the detection patch 45A may be stored in the memory 76 in advance. The shape and size of the detection patches 45 and 45A may be changed for each toner color depending on the characteristics of the sensor that reads the detection patch. From the viewpoint of reducing the amount of toner consumption, the detection patches 45 and 45A A smaller shape is preferred.

In the next step 110, the toner adhesion amount Nx of the detection patch 45Ax is read from the toner adhesion amount detection sensor 44A. Further, the position detection sensor 48 reads the position Lx from the home position in the sub-scanning direction of the photosensitive drum 20 of the detection patch 45Ax. The process of reading the toner adhesion amount of the detection patch from the toner adhesion amount detection sensor and the process of reading the position of the detection patch from the home position in the sub-scanning direction of the photosensitive drum 20 from the position detection sensor are the detection means of the present invention. This corresponds to an example of a function.
The read toner adhesion amount Nx and the position Lx from the home position are stored in the memory 76. In the present embodiment, ten detection patches 45Ax are formed per rotation of the photosensitive drum 20 (detection patches 45A _{1 to} 45A ₁₀ in FIG. 6 are equally spaced), and the toner adhesion amount N ₁ to N ₁ . N ₁₀ and positions L _{1 to} L ₁₀ from the home position are read and stored.

  In the next step 112, it is determined whether the detection and storage of the toner adhesion amount has been completed a predetermined number of times (10 times) (x = 10), that is, whether the entire circumference of the photosensitive drum 20 has been completed. to decide.

If the result in Step 112 is negative, the program proceeds to Step 114, where the variable x is incremented, and in Step 116, the photosensitive drum 20 is rotated by a predetermined amount (3 inches in the present embodiment), and the process returns to Step 108 to Repeat detection and storage. On the other hand, when the result in step 112 is affirmative, the routine proceeds to step 118, where an average value F of the toner adhesion amounts N _{1 to} N ₁₀ is calculated. The average value F in the present embodiment is calculated by averaging the remaining eight values of the toner adhesion amounts N _{1 to} N ₁₀ excluding the maximum value and the minimum value.

In the next step 120, the predetermined value and allowable range of the toner adhesion amount are read from the memory 76, and a difference value from the average value F of the toner adhesion amount calculated in step 118 is calculated. When the difference value from the average value F is larger than the average value F (for example, in the region above the average value F shown in FIG. 8), such as the detection patches 45A ₁ , 45A ₂ , 45A _3, etc., − ( Negative value. Further, for example, as such detecting patches 45A _10, when the average value F is smaller than (if than the average value F of FIG. 8 in the lower region) is the value of + (plus). In the present embodiment, the allowable range is the same range as + and − centering on the average value F. Note that the allowable range is not limited to this, and may be, for example, a range biased toward the + side or the − side, a range only on one side, or the like. Note that the permissible range that defines a range for the average value of the toner adhesion amount in the present embodiment is an example of the permissible range that is predetermined for the toner adhesion amount of the present invention.

  In the next step 122, it is determined whether or not the difference value calculated in step 120 is within the read allowable range. If it is out of the allowable range, the process proceeds to step 124, where the difference value calculated in step 120 is instructed to the image forming control unit 72 as an instruction to change the process condition. In step 126, the surface of the photosensitive drum 20 is detected by the cleaning device 28. The toner adhering to is cleaned, and the process returns to Step 104. Note that the process condition when the amount of toner adhering to the photosensitive drum 20 becomes a predetermined value is set as a reference process condition, and the image formation control unit 72 determines a change amount that is determined in advance according to the output difference value. For example, the process conditions are changed by changing the grid voltage applied to the charger 30, the development bias voltage applied to the developer 34, the exposure amount of the LED 32, and the like. This standard process condition corresponds to the process condition of the present invention.

  On the other hand, if it is within the allowable range in step 122, the process proceeds to step 128 where the cleaning device 28 cleans the toner adhering to the surface of the photosensitive drum 20, and in the next step 130, the photosensitive drum 20 is moved to the home position. To step 132. In step 132, a variable y = 1 representing the number of repetitions of toner adhesion amount detection is set in a counter (not shown), and in the next step 134, the detection patch 45A'y and the front side end portion are arranged at the center of the photosensitive drum 20. The detection patch 45y is formed. The shape and size of the toner images of the detection patch 45A ′ and the detection patch 45A may be different, and the shape and size of the toner images of the detection patch 45A ′ and the detection patch 45 may be different.

In the next step 136, the toner adhesion amount ny of the detection patch 45A'y is read from the toner adhesion amount detection sensor 44A, and the toner adhesion amount my of the detection patch 45y is read from the toner adhesion amount detection sensor 44. Further, the position detection sensor 48 reads the position ly of the detection patch 45A′y and the detection patch 45y from the home position of the photosensitive drum 20 in the sub-scanning direction. The read toner adhesion amounts ny and my and the position ly from the home position are stored in the memory 76. In this embodiment, ten detection patches 45A′y and 45y are formed for each circumference of the photosensitive drum 20 (detection patches 45A ′ _{1 to} 45A ′ ₁₀ and 45 _{1 to} 45 ₁₀ in FIG. The intervals between the detection patches in the sub-scanning direction of the body drum are equal), and the toner adhesion amounts n _{1 to} n ₁₀ , m _{1 to} m ₁₀ and the positions l _{1 to} l ₁₀ from the home position are read and stored.

  In the next step 138, it is determined whether or not the detection and storage of the toner adhesion amount has been completed a predetermined number of times (10 times) (y = 10), that is, whether or not the entire circumference of the photosensitive drum 20 has been completed. to decide.

If the result in Step 138 is negative, the program proceeds to Step 140, where the variable y is incremented. In Step 142, the photosensitive drum 20 is rotated by a predetermined amount (3 inches in the present embodiment), and the routine returns to Step 134 to return to the photosensitive drum 20. The detection and storage of the toner adhesion amount at the center portion and the front end portion are repeated. On the other hand, when the result in step 138 is affirmative, the process proceeds to step 144, and an average value f of the toner adhesion amounts n _{1 to} n ₁₀ is calculated. The average value f in the present embodiment is calculated by averaging the remaining eight values of the toner adhesion amounts n _{1 to} n ₁₀ excluding the maximum value and the minimum value. The average value f is an example of the average value of the toner adhesion amount of the present invention.

  In the next step 146, the difference between the average value f and the toner adhesion amount at each detection point at the center and the front end of the photosensitive drum 20 (center difference u: f−ny and front end difference w: f). -My) is calculated, and the correspondence (see Table 1) with the position ly from the home position is stored in the memory 76. The correspondence relationship shown in Table 1 shows the distribution of the toner adhesion amount with respect to the position length of the photosensitive drum on the photosensitive drum 20 in the sub-scanning direction. Note that the average value f, the center difference u of the toner adhesion amount, and the front side edge difference w are examples of the difference value of the average value with respect to the toner adhesion amount of the present invention, and the correspondence relationship shown in Table 1 is the standard of the present invention. It is an example of distribution and the memory 76 which memorize | stores this Table 1 respond | corresponds to the memory | storage means of this invention.

  In the next step 148, the toner adhering to the surface of the photosensitive drum 20 is cleaned by the cleaning device 28, and this process is terminated.

  By this processing, the image forming apparatus 10 according to the present exemplary embodiment distributes the toner adhesion amount with respect to the position length in the sub-scanning direction on the photosensitive drum 20 at the center portion and the front end portion of the photosensitive drum 20 (Table 1). Is stored in the memory 76 in advance.

  Therefore, processing during and during printing by the image forming apparatus 10 according to the present embodiment will be described in detail with reference to FIG. In addition, since the process substantially the same as the process (FIG. 5) at the time of the said initial is included, the same code | symbol is attached | subjected to the same process and detailed description is abbreviate | omitted. The process illustrated in FIG. 7 is, for example, a process executed when image data is printed in the image forming apparatus 10.

  When the image forming apparatus 10 receives a print instruction from the user interface 80, the processing routine of FIG. In step 200, if printing is not started, the process proceeds to step 100. If printing is started, the process proceeds to step 218. When the potential of the surface of the photosensitive drum 20 is stabilized by the processing of step 100 and step 102, the process proceeds to step 202, and the detection patch 55A is formed at the center of the photosensitive drum 20 in the main scanning direction. An example of the detection patch 55A in the present embodiment is shown in FIG. The central portion of the photosensitive drum 20 in the main scanning direction is an example of the detection position of the detection unit when the development processing of the present invention is not executed.

  In the next step 204, the toner adhesion amount n 'of the detection patch 55A is read from the toner adhesion amount detection sensor 44A. Further, the position detection sensor 48 reads the position l ′ of the detection patch 55A from the home position of the photosensitive drum 20 in the sub-scanning direction. The read toner adhesion amount n ′ and the position l ′ from the home position are stored in the memory 76.

In the next step 206, among the positions ly from the home position stored in the memory 76 by the above process (the process shown in FIG. 5), the position closest to the position l ′ from the home position read in step 204 is selected. Select as approximate position. Here, since the detection patch 45A ₃ (see FIG. 6) with y = 3 is at the closest position, the position l ₃ from the home position is selected. Thereby, the detection patch 55A is approximated to the detection patch 55A ′ shown in FIG. Further, the distribution of the toner adhesion amount corresponding to the position l ₃ from the home position, that is, the difference u from the average value f (see f−n ₃ Table 1) is read from the memory 76.

In the next step 208, a difference u from the average value f read in step 206 is added to the toner adhesion amount n ′ read in step 204 (n ″ = n ′ + (f−n ₃ )). As a result, the detection patch 55A ′ approximated in step 206 becomes the detection patch 55A ″ shown in FIG. The process of setting the detection patch 55A ′ as the detection patch 55A ″ subtracts the difference value of the reference distribution corresponding to the position from the toner adhesion amount at the position on the image carrier detected by the detection means of the present invention. It is an example of the process to perform.

  In the next step 210, a predetermined value and an allowable range of the toner adhesion amount are read from the memory 76, and a difference value from the calculated value n ″ calculated in step 208 is calculated. In the next step 212, it is determined whether or not the difference value calculated in step 210 is within the read allowable range. If it is outside the allowable range, the process proceeds to step 124, where the difference value calculated in step 210 is instructed to the image forming control unit 72 as a process condition change instruction, and in step 126, the difference value is attached to the surface of the photosensitive drum 20. Then, the process returns to step 202, a detection patch is formed at the center of the photosensitive drum 20, the toner adhesion amount is read, and the above processing is repeated. Note that the processing of steps 124 and 202 to 212 is an example of the control means of the present invention, the processing of step 124 is an example of processing for instructing to change the process conditions of the present invention, and the difference value is Corresponding to the instruction amount, the processing of step 210 and step 124 is an example of output means.

  On the other hand, if it is within the allowable range in step 212, the process proceeds to step 214 to clean the toner adhering to the surface of the photosensitive drum 20, and in the next step 216, a print instruction is output to the image formation control unit 72. .

  Printing is started because printing is started by the printing instruction in step 216, and printing is in progress. In the next step 218, the number of printed sheets I is read from the paper counter 13, and the process proceeds to step 220. In step 220, it is determined whether or not a predetermined number (here, 1000) has been printed (I = 1000). If the predetermined number of sheets has not been reached, the result is negative and the process proceeds to step 234 to determine whether or not to end printing. For example, when the number of print ends is reached or when a print end command is received from the user interface 80, the process is terminated. On the other hand, if the printing is not finished, the process returns to step 218, and the process is repeated until a predetermined number of sheets are printed. In the present embodiment, the paper counter 13 is reset when printing is completed.

  If the predetermined number of sheets has been printed, the result in step 220 is affirmative and the routine proceeds to step 222. In step 222, a detection patch 55 is formed at the front end portion outside the effective image area of the photosensitive drum 20 in order to detect the toner adhesion amount of the photosensitive drum 20 at the present time (during printing). An example of the detection patch 55 in the present embodiment is shown in FIG. The front end of the photosensitive drum 20 is an example of the detection position of the detection means when executing the development processing of the present invention.

  In the next step 224, the toner adhesion amount m ′ of the detection patch 55 is read from the toner adhesion amount detection sensor 44. Further, the position l ″ of the detection patch 55 from the home position in the sub-scanning direction of the photosensitive drum 20 is read from the position detection sensor 48. The read toner adhesion amount m ′ and the position l ″ from the home position are stored in the memory 76.

In the next step 226, the position closest to the position l ″ from the home position read in step 224 among the positions ly from the home position stored in the memory 76 by the above processing (the processing shown in FIG. 5). Is selected as the approximate position. Here, since the detection patch 45A ₁ (see FIG. 6) with y = 2 is at the closest position, the position l ₁ from the home position is selected. Thereby, the detection patch 55 is approximated to the detection patch 55 ′ shown in FIG. Further, the distribution of the toner adhesion amount corresponding to the position l ₁ from the home position, that is, the difference w from the average value f (see fm ₁ Table 1) is read from the memory 76.

In the next step 228, the difference w from the average value f read in step 226 is added to the toner adhesion amount m ′ read in step 204 (m ″ = m ′ + (f−m ₁ )). As a result, the detection patch 55 ′ approximated in step 226 becomes the detection patch 55 ″ shown in FIG.

  In the next step 230, the predetermined value and allowable range of the toner adhesion amount are read from the memory 76, and a difference value from the calculated value m ″ calculated in step 228 is calculated. In the next step 232, it is determined whether or not the difference value calculated in step 230 is within the read allowable range. If it is out of the allowable range, the process proceeds to step 124 where the difference value calculated in step 230 is instructed to the image formation control unit 72 as a process condition change instruction, and the process returns to step 222 to return the front end of the photosensitive drum 20. A detection patch is formed outside the effective image area, the toner adhesion amount is read, and the above processing is repeated.

  On the other hand, if it is within the allowable range in step 232, the process proceeds to step 234, where it is determined whether or not to end printing. If not, the process proceeds to step 236, the paper counter 13 is reset, the process returns to step 218, and printing is performed again. The number I is read, and when the predetermined number is reached, the detection of the toner adhesion amount is repeated. On the other hand, if the result in step 234 is affirmative, this process ends.

  As described above, in this embodiment, since the relationship between the position on the photosensitive drum and the toner adhesion amount at the position is stored in advance over the entire surface of the photosensitive drum as the reference distribution, the reference distribution is attached to at least one location. It is possible to determine whether or not the toner adhesion amount falls within a predetermined allowable range based on the reference distribution only by detecting the toner. Therefore, since it is not necessary to detect the toner adhesion amount of the entire photosensitive drum that requires a long time, whether or not the toner adhesion amount on the photosensitive drum is within an allowable range with a short time and a simple configuration. For example, it is possible to quickly process even immediately before the start of printing. Furthermore, since the process conditions can be changed according to the determination result, the amount of toner adhered on the photosensitive drum can be kept constant.

  In the present embodiment, toner is detected both at the center of the photosensitive drum and outside the range of the effective image area. Therefore, the position where toner is detected during printing and during non-printing is set in the main scanning direction. Different positions can be used. For example, it is possible to detect the central portion where there is little variation immediately before starting printing, and to detect out of the range of the effective image area during continuous paper printing in which no space is generated between the paper to be printed. . Therefore, it is possible to determine whether or not the toner adhesion amount on the photosensitive drum is within the allowable range even during printing.

  Furthermore, in the present embodiment, since the average value of the toner adhesion amount is used as a reference value, and the difference between the average value and the detected value is stored as a reference distribution, the amount of data stored in the memory in advance can be reduced.

  Furthermore, in this embodiment, since the distribution of the toner adhesion amount around the circumference of the photosensitive drum at the center and end positions of the photosensitive drum is stored in advance, the amount of toner adhesion on the photosensitive drum is determined as a secondary amount. Regardless of variations in the scanning direction, it can be determined whether or not the toner adhesion amount is within the allowable range.

  Furthermore, in this embodiment, after the surface potential of the photosensitive drum is stabilized, a detection patch is formed on the photosensitive drum, toner is detected, and the detection result is stored in the memory as a reference distribution. Since the surface potential of the body drum is not stable, there is no possibility that the toner adhesion amount varies, and therefore, a stable toner adhesion amount can be detected.

  Furthermore, in the present embodiment, when the toner adhesion amount is not included in the allowable range, a difference value between the predetermined value of the toner adhesion amount and the average value of the detection values is output. Based on this difference value, for example, Since the process conditions such as the grid voltage applied to the charger can be changed, the process conditions can be changed accurately and promptly. Since the process condition can be changed based on the difference value, the toner adhesion amount when the toner is adhered on the photosensitive drum under the changed process condition can be included in the allowable range.

It is a figure which shows the main structures of the image forming layer apparatus which concerns on embodiment of this invention. It is explanatory drawing explaining a photoconductor drum. FIG. 6 is an explanatory diagram for explaining the arrangement of detection patches and toner adhesion amount detection sensors. 2 is a block diagram of a control system of the image forming apparatus according to the embodiment of the present invention. FIG. 6 is a flowchart showing a flow of processing executed at the time of initialization in the image forming apparatus according to the embodiment of the present invention. It is explanatory drawing explaining the position of the detection patch on a photoconductor drum. 4 is a flowchart showing a flow of processing executed during printing and during printing in the image forming apparatus according to the embodiment of the present invention. FIG. 7 is an explanatory diagram for explaining a distribution of toner adhesion amount in the sub-scanning direction on the photosensitive drum according to the embodiment of the present invention. FIG. 6 is an explanatory diagram illustrating a distribution of toner adhesion amount in the main scanning direction on the photosensitive drum according to the embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 12 Print part 20 Photosensitive drum 44, 44A Toner adhesion amount detection sensor 45, 45A, 45A ', 55, 55A Detection patch 48 Position detection sensor 70 Main controller 72 Image formation control part 76 Memory

Claims (6)

When an image is formed by main scanning and sub-scanning, the toner is attached to the image carrier on which the electrostatic latent image is formed and development processing is performed. Storage means for storing in advance as a reference distribution over the entire surface of the image carrier,
Detection means for detecting the amount of toner attached to the image carrier and the position on the image carrier;
A toner is attached to at least one location of the image carrier, the attached toner is detected by the detection means, and a toner adhesion amount in the reference distribution corresponding to the detected position on the image carrier is determined in advance. Control means for determining whether or not the toner adhesion amount detected by the detection means is included in the allowable range;
An image forming apparatus comprising:   The detection unit is configured to be able to detect at a plurality of positions in the main scanning direction, and the control unit is configured to detect the detection position of the detection unit at the time of executing the development process when forming an image based on the image data. The image forming apparatus according to claim 1, wherein the detection unit is controlled to detect at a position different from a detection position of the detection unit at the time of execution.   The storage means has an average value of the toner adhesion amount when the detection means detects a distribution of the toner adhesion amount adhered over the entire surface of the image carrier in order to form a predetermined reference image, and the image. The distribution of the difference value of the average value with respect to the toner adhesion amount detected at each position on the carrier is stored as the reference distribution, and the control means at the position on the image carrier detected by the detection means The difference value of the reference distribution corresponding to the position is subtracted from the toner adhesion amount, and it is determined whether or not the subtraction value is included in the allowable range. Image forming apparatus.   The storage means distributes the amount of toner adhering over the entire surface of the image carrier to form a predetermined reference image, and the amount of toner adhering around the image carrier at a plurality of positions in the main scanning direction. 4. The image forming apparatus according to claim 1, wherein the reference distribution calculated by calculating the reference distribution based on the detection result is stored. 5.   5. The image forming apparatus according to claim 1, wherein the detection unit detects a toner adhesion amount when a surface potential of the image carrier is in a stable state. 6.   The storage means stores the reference distribution for forming a predetermined reference image according to a predetermined reference process condition for forming an image, and the control means is configured such that the detected toner adhesion amount is within an allowable range. 6. An output means for obtaining and outputting an instruction amount for instructing to change a process condition based on the detected toner adhesion amount when it is determined that it is not included. The image forming apparatus according to claim 1.

Images