JP2010204455A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To shorten processing to determine an output image forming condition, while accurately detecting a developing performance straight line. <P>SOLUTION: The image forming apparatus includes an absolute humidity sensor for detecting absolute humidity. A controller 500 is configured to perform processing to determine a patch image forming condition before performing the processing to determine the output image forming condition. If the absolute humidity higher than the previous one is detected in the processing to determine the patch image forming condition, developing potential corresponding to each of the individual patch toner images is made smaller in accordance with a difference from the previous one. On the contrary, if the absolute humidity lower than the previous one is detected, the developing potential corresponding to each of the individual patch toner images is made larger in accordance with a difference from the previous one. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention performs an image forming condition determination process for determining an image forming condition for an output image based on a result of grasping a development performance straight line based on a result of detecting a toner adhesion amount on a predetermined patch pattern image. The present invention relates to an image forming apparatus.

  In an electrophotographic image forming apparatus, when the characteristics of a developer, a latent image carrier, and the like change due to the environment (such as temperature and humidity) or deterioration over time, the image forming ability changes. Then, the image quality may be changed due to the change in the image forming ability. Specifically, when the characteristics of the developer and the latent image carrier change with environmental changes and usage over time, the development performance straight line of the image forming apparatus changes. This development performance straight line is a relationship between the latent image potential of the latent image carrier, the development potential that is the potential difference between the development bias for the developer carrier of the developing device, and the toner adhesion amount per unit area with respect to the toner image. It is the straight line shown. When the development performance line changes, the development potential at which the target image density is obtained changes. Nevertheless, if the development potential as the image forming condition is kept at a constant value, the image density is insufficient or the image density is excessive.

  Therefore, conventionally, an image forming apparatus that performs the following output image forming condition determination processing is known. That is, first, a patch pattern image composed of a plurality of patch-like toner images developed with different development potentials is formed. Next, the amount of toner attached to each patch-like toner image in the patch pattern image is detected by a reflective photosensor or the like. Based on the detection result, an approximate straight line indicating the relationship between the development potential and the toner adhesion amount is obtained as a development performance straight line, and then, based on the result, the development potential at which the target image density is obtained is specified. Thereafter, the development potential condition during image formation is set to a specific value. By periodically executing such output image forming condition determination processing, it is possible to obtain a stable image density regardless of environmental fluctuations and usage over time.

However, in general output image forming condition determination processing, the development performance straight line cannot be detected with high accuracy depending on the amount of environmental fluctuation. This is for the reason explained below. That is, in a general output image forming condition determination process, a fixed value is adopted as the developing potential when each patch-like toner image is formed. For example, the first, second, third,..., Tenth patch-like toner images are developed with fixed development potentials P ₁ , P ₂ , P ₃ ... P ₁₀ (P ₁ <P ₂ <P ₃ ... <P ₁₀ ). Under such conditions, the toner adhesion amount to the patch-like toner image is gradually increased to the first, second, third,..., Tenth. However, when the toner adhesion amount is detected by a reflection type photosensor or the like, since the detectable range of the toner adhesion amount is limited, the increase cannot be detected correctly. For example, when the development γ, which is the slope of the development performance line, is relatively large, the toner adhesion amount to the αth patch-like toner image smaller than the 10th reaches almost the upper limit of the detectable range, and the αth to the 10th. The detection result of the toner adhesion amount may be almost the same. In addition, in the first to βth (β <α) patch-like toner images, only a low toner adhesion amount (less than the lower limit value) is obtained so that a flaw on the surface of the image carrier is erroneously detected as toner. It may not be possible. In such a case, the straight line of the development performance cannot be accurately obtained because the straight line approximation process must be performed only based on the toner adhesion amount of a very small number of patch-like toner images between the βth and αth. . The case where the development γ becomes relatively large has been described, but when the development γ becomes relatively small, only a small number of patch-like toner images having a large number have a toner adhesion amount that exceeds the lower limit of the detectable range. The development performance straight line may not be obtained with high accuracy.

  In view of this, the image forming apparatus described in Patent Document 1 has been devised to increase the detection accuracy of the development performance straight line as follows. That is, first, as in a general output image forming condition determination process, each patch-like toner image is developed with a fixed development potential, and the toner adhesion amount is detected. Then, based on the detection result, the development potential for obtaining the toner adhesion amount per lower limit of the detectable range and the development potential for obtaining the toner adhesion amount per upper limit are specified. Next, by forming a patch-like toner image while changing the development potential stepwise between the two development potentials, a desired number of patch-like toner images having different toner adhesion amounts can be obtained within a detectable range. Thus, the development performance straight line can be detected with high accuracy by obtaining a desired number of samplings within the detectable range and performing straight line approximation processing.

  However, in this image forming apparatus, since the combination of the formation of the patch pattern image and the calculation process based on the detection result of the toner adhesion amount has to be repeated twice, a long time is required for the output image imaging condition determination process. There was a problem of doing.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an image forming apparatus capable of shortening an output image forming condition determination process while accurately detecting a development performance straight line. Is to provide.

In order to achieve the above object, a first aspect of the present invention provides a latent image carrier that carries a latent image, a latent image writing unit that writes an electrostatic latent image on the latent image carrier, and a developer carrier. Development means for developing the electrostatic latent image with a developer carried on the surface to obtain a toner image, and a toner image on the surface of the latent image carrier, or toner transferred from the latent image carrier to a transfer body An adhesion amount detecting means for detecting the toner adhesion amount per unit area with respect to the image, and a patch pattern image composed of a plurality of patch-like toner images developed under different image forming conditions, and toner for the plurality of patch-like toner images Based on the result of detecting the adhesion amount by the adhesion amount detection means, after grasping a development performance line indicating the relationship between the image forming condition and the toner adhesion amount, an image based on a user command based on the development performance line When forming In an image forming apparatus provided with a control means for executing an output image image formation condition determination process for determining an image condition at a predetermined timing, an environment grasping means for grasping an environmental situation is provided, and the output image image formation condition determination process Prior to the output image forming condition determination process, the amount of environmental change since the previous execution of the output image image forming condition determination process and the image forming conditions of the individual patch-like toner images in the previous output image image forming condition determination process are as follows. Based on this, the control means is configured to execute the patch image forming condition determining process for determining each of the image forming conditions of a plurality of patch-like toner images to be formed in the output image image forming condition determining process to be performed later. It is characterized by this.
According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, in the plurality of patch-like toner images when the previous output image image forming condition determining process is performed in the patch image forming condition determining process. Each image forming condition is corrected based on the amount of environmental variation, and processing for setting each image forming condition in the plurality of patch-like toner images formed in the output image image forming condition determination processing to be performed is performed. Thus, the control means is configured as described above.
According to a third aspect of the present invention, in the image forming apparatus of the second aspect, as the environment grasping means, a device for grasping the state of the absolute humidity is used. Is a positive absolute humidity fluctuation amount, a plurality of image formation conditions for the plurality of patch-like toner images in the output image image formation condition determination process to be performed are a plurality of image formation condition determination processes in the previous output image image formation condition determination process. The control means is configured to perform a process of determining an image forming capability lower than each image forming condition for the patch-like toner image.
According to a fourth aspect of the present invention, in the image forming apparatus of the second or third aspect, as the environment grasping means, a device for grasping the state of absolute humidity is used, and in the patch image forming condition determining process, the environment is determined. When the fluctuation amount is a negative absolute humidity fluctuation amount, as the respective imaging conditions for the plurality of patch-like toner images in the scheduled output image imaging condition determination process, the previous output image imaging condition determination process The control means is configured to perform a process of determining an image forming capability higher than image forming conditions for a plurality of patch-like toner images.
According to a fifth aspect of the present invention, in the image forming apparatus of the second aspect, when the patch image forming condition determining process determines that the current image forming ability is relatively high based on the environmental variation amount. While the development potential difference between the individual patch-like toner images in the patch pattern image formed in the output image imaging condition determination process to be performed later is made smaller on the high potential side than on the low potential side, The present invention is characterized in that, when it is determined that the current image forming ability is relatively low, the control means is configured so that the predetermined development potential difference is made smaller on the low potential side than on the high potential side. To do.

  In these inventions, for the reason described below, it is possible to shorten the output image forming condition determination process while accurately detecting the development performance straight line. In other words, there is a certain degree of correlation between the amount of environmental fluctuation and the amount of change in the slope of the development performance line. When the environment changes to the high temperature and high humidity side, the slope of the development performance line becomes larger. In this case, in the development performance straight line, the length of a line segment that falls within a predetermined toner adhesion amount detectable range becomes shorter. Then, a patch-like toner image in which the toner adhesion amount can be kept within a detectable range under a condition where the change pitch of the imaging conditions is constant, such as a potential pitch when forming a plurality of patch-like toner images with different development potentials. (Hereinafter referred to as the number of detectable patches) decreases. On the other hand, when the environment changes to the low temperature and low humidity side, the slope of the development performance line becomes smaller. Then, basically, the length of the above-mentioned line segment in the development performance straight line becomes longer and the number of detectable patches increases, but there are cases where this is not the case. Specifically, if the slope of the development performance line becomes too small, the amount of toner attached to most patch-like toner images will be below the lower limit of the detectable range, and the number of detectable patches will conversely decrease. Sometimes. As described above, when the environment changes to the low temperature and low humidity side, or when the environment changes to the high temperature and high humidity side, depending on the amount of change, the number of detectable patches may decrease, Based on the image forming conditions, it is possible to specify new image forming conditions for obtaining the target number of detectable patches. For example, if the environment changes to the high temperature and high humidity side and the slope of the development performance line becomes larger, the development potential for forming individual patch-like toner images will be reduced according to the amount of change in the environment. If the image forming ability is reduced, the same number of detectable patches as before the environment change can be obtained. In addition, when the environment changes to low temperature and low humidity, and the slope of the development performance line becomes smaller, the development potential for forming individual patch-like toner images can be increased according to the amount of change in the environment. (If the imaging ability is increased), it is possible to obtain the same number of detectable patches as before the environmental change. According to the first aspect of the present invention, in the patch image forming condition determining process performed prior to the output image image forming condition determining process, the amount of environmental variation and the individual patch-like toner images determined in the previous output image condition determining process are determined. Based on the image forming conditions, it is possible to determine the image forming conditions of individual patch-like toner images so that the same number of detectable patches as before the environment change can be obtained. Once the image forming conditions are determined in this way, the desired number of detectable patches can be obtained and the development performance can be achieved by performing only one combination of patch pattern image formation and calculation processing based on the detection result of the toner adhesion amount. Since the straight line can be grasped, the process control process can be shortened while accurately detecting the development performance straight line.

  In the invention of claim 5, the image forming conditions are determined as follows instead of determining the image forming conditions of individual patch-like toner images so that the same number of detectable patches as before the environmental change can be obtained. By doing so, the output image forming condition determination process is shortened. That is, when the image forming capability is relatively high depending on the environment, the toner adhesion amount to the patch toner image developed with a relatively low development potential among the plurality of patch toner images is the adhesion amount detection means. Enter the detectable range by. Therefore, in such a case, the difference in the development potential between the patch-like toner images is made smaller in the region having a relatively low development potential than in the region having a relatively high development potential. As a result, a desired number of patch-like toner images are formed within a detectable range by the adhesion amount detection means. On the other hand, when the image forming ability is relatively low due to the environment, the toner adhesion amount with respect to the patch-like toner image developed with a relatively high development potential falls within the detectable range by the adhesion amount detection means. Therefore, in such a case, the difference in development potential between the patch-like toner images is reduced in the relatively high development potential region as compared with the relatively low development potential region. As a result, a desired number of patch-like toner images are formed within a detectable range by the adhesion amount detection means.

1 is a schematic configuration diagram showing a copier according to a first embodiment. FIG. 3 is a partially enlarged configuration diagram illustrating a part of an internal configuration of a printer unit in the copier. FIG. 3 is an enlarged configuration diagram showing a process unit for Y and C together with an intermediate transfer belt in the copier. FIG. 2 is a block diagram showing a part of an electric circuit of the copier. The graph which shows the relationship between the toner adhesion amount and the sensor output based on the light reception amount by a diffuse reflection type light receiving element. The graph which shows the relationship between the toner adhesion amount and the sensor output based on the light reception amount by a regular reflection type light receiving element. 6 is a flowchart showing a control flow in output image forming condition determination processing executed by a control unit of the copier. FIG. 3 is a plan view showing an intermediate transfer belt and a K patch pattern image formed on the surface thereof. FIG. 4 is a schematic diagram showing from the side an intermediate transfer belt on which an M patch pattern image PpM and a K patch pattern image PpK are formed in order. The graph which shows the development performance straight line in the process unit of each color. The graph which shows the relationship between image development γ and absolute humidity. The chart which shows the imaging potential conditions of the "previous processing" and the imaging potential conditions of the "current processing" when the absolute humidity in the "current processing" is higher than the "previous processing". 6 is a graph showing a development performance straight line for “previous processing” and a development performance straight line for “current processing” when the absolute humidity in “current processing” is higher than “previous processing”.

Hereinafter, a first embodiment of an electrophotographic copying machine will be described as an image forming apparatus to which the present invention is applied.
FIG. 1 is a schematic configuration diagram showing a copying machine according to the first embodiment. The copying machine includes a printer unit 1 that forms an image on recording paper, a paper feeding device 200 that supplies the recording paper P to the printer unit 1, a scanner 300 that reads a document image, and automatically feeds a document to the scanner 300. An automatic document feeder (hereinafter referred to as ADF) 400 is provided.

  The scanner 300 is placed on the contact glass 301 as the first traveling body 303 equipped with a document illumination light source or mirror and the second traveling body 304 equipped with a plurality of reflecting mirrors reciprocate. Scanning of a document (not shown) is performed. The scanning light sent out from the second traveling body 304 is condensed on the imaging surface of the reading sensor 306 installed behind the imaging lens 305 and then read as an image signal by the reading sensor 306.

  On the side surface of the housing of the printer unit 1, a manual feed tray 2 for manually placing the recording paper P to be fed into the housing, and a paper discharge tray 3 for stacking the recording paper P after image formation discharged from the housing. Is provided.

  FIG. 2 is an enlarged partial configuration diagram illustrating a part of the internal configuration of the printer unit (1). In the housing of the printer section (1), there is disposed a transfer unit 50 as transfer means for stretching an endless intermediate transfer belt 51 as a transfer body by a plurality of stretching rollers. The intermediate transfer belt 51 is made of a material in which carbon powder for adjusting electric resistance is dispersed in a polyimide resin with little elongation. Then, while being stretched by a driving roller 52, a secondary transfer backup roller 53, a driven roller 54, and four primary transfer rollers 55Y, 55Y, 55C, and 55K that are driven to rotate in the clockwise direction in the drawing by a driving means (not shown). By the rotation of the driving roller 52, it is moved endlessly in the clockwise direction in the figure. Note that the suffixes Y, C, M, and K attached to the ends of the symbols of the primary transfer roller indicate the members for yellow, cyan, magenta, and black. Hereinafter, the subscripts Y, C, M, and K attached to the ends of the symbols are the same.

  The intermediate transfer belt 51 is greatly curved at the portions where the intermediate transfer belt 51 is wound around the driving roller 52, the secondary transfer backup roller 53, and the driven roller 54, so that the intermediate transfer belt 51 is stretched in an inverted triangular posture with the bottom side directed vertically upward. ing. The belt upper stretch surface corresponding to the base of the inverted triangle extends in the horizontal direction. Above the belt upper stretch surface, four process units 10Y, 10C, 10M, and 10K are provided on the upper stretch surface. It arrange | positions so that it may align with a horizontal direction along the extending direction.

  In FIG. 1 described above, an optical writing unit 60 is disposed above the four process units 10Y, 10C, 10M, and 10K. Based on the image information of the original read by the scanner 300, the optical writing unit 60 drives four semiconductor lasers (not shown) by a laser control unit (not shown) to emit four writing lights L. Then, the drum-shaped photoconductors 11Y, 11C, 11M, and 11K serving as latent image carriers of the process units 10Y, 10C, 10M, and 10K are scanned in the dark by the writing light L, respectively. , K, electrostatic latent images for Y, C, M, and K are written.

  In the first embodiment, the optical writing unit 60 performs optical scanning by deflecting a laser beam emitted from a semiconductor laser by a polygon mirror (not shown) and reflecting the laser beam by a reflection mirror (not shown) or passing through an optical lens. Use what you do. Instead of such a configuration, an LED array that performs optical scanning may be used.

  FIG. 3 is an enlarged configuration diagram showing the process units 10Y and C for Y and C together with the intermediate transfer belt 51. As shown in FIG. The Y process unit 10Y includes a charging member 12Y, a charge eliminating device 13Y, a drum cleaning device 14Y, a developing device 20Y as developing means, a potential sensor 49Y, and the like around a drum-shaped photoconductor 11Y. These are integrally attached to and detached from the printer unit while being held by a casing as a common holding body.

  The charging member 12Y is a roller-like member that is rotatably supported by a bearing (not shown) while being in contact with the photoreceptor 11Y. The surface of the photoconductor 11Y is uniformly charged to the same polarity as, for example, the charge polarity of Y toner by rotating in contact with the photoconductor 11Y while a charging bias is applied by a bias supply means (not shown). As a result, the surface of the photoreceptor 11Y is uniformly charged to, for example, −700 [V]. Instead of the charging member 12Y, a scorotron charger or the like that performs a non-contact uniform charging process on the photoconductor 11Y may be employed.

  A developing device 20Y in which a Y developer containing a magnetic carrier (not shown) and non-magnetic Y toner is contained in a casing 21Y has a developer conveying device 22Y and a developing unit 23Y. In the developing unit 23Y, a developing sleeve 24Y as a developer carrying member that is endlessly moved by being rotated by a driving unit (not shown) exposes a part of its peripheral surface to the outside through an opening provided in the casing 21Y. ing. As a result, a developing region is formed in which the photoconductor 11Y and the developing sleeve 24Y face each other with a predetermined gap.

  Inside the developing sleeve 24Y made of a non-magnetic hollow pipe-like member, a magnet roller (not shown) having a plurality of magnetic poles arranged in the circumferential direction is fixed so as not to rotate with the developing sleeve 24Y. The developing sleeve 24Y is driven to rotate while adsorbing the Y developer in the developer conveying device 22Y, which will be described later, to the surface by the magnetic force generated by the magnet roller, thereby pumping the Y developer from the developer conveying device 22Y. Then, the Y developer conveyed toward the developing area as the developing sleeve 24Y rotates, the doctor blade 25Y having the tip opposed to the surface of the developing sleeve 24Y with a predetermined gap, and the sleeve A doctor gap formed between the surface and the surface is entered. At this time, the layer thickness on the sleeve is regulated. When the developing sleeve 24Y is rotated and conveyed to the vicinity of the developing area facing the photoconductor 11Y, it receives a magnetic force of a developing magnetic pole (not shown) of the magnet roller and rises on the sleeve to become a magnetic brush. .

  For example, a developing bias having the same polarity as the charging polarity of the toner is applied to the developing sleeve 24Y by a bias supply unit (not shown). As a result, in the development region, non-development in which Y toner is electrostatically moved from the non-image portion side to the sleeve side between the surface of the development sleeve 24Y and the non-image portion (uniformly charged portion = background portion) of the photoreceptor 11Y. Potential acts. Further, a developing potential for electrostatically moving Y toner from the sleeve side toward the electrostatic latent image acts between the surface of the developing sleeve 24Y and the electrostatic latent image on the photoreceptor 11Y. The Y toner in the Y developer is transferred to the electrostatic latent image by the action of the developing potential, so that the electrostatic latent image on the photoreceptor 11Y is developed into the Y toner image.

  The Y developer that has passed through the developing area as the developing sleeve 24Y rotates is separated from the developing sleeve 24Y due to the influence of the repulsive magnetic field formed between the repelling magnetic poles provided in the magnet roller (not shown). The developer returns to the developer conveying device 22Y.

  The developer conveying device 22Y includes two first screw members 26Y, a second screw member 32Y, a partition wall interposed between the two screw members, a toner concentration detection sensor 45Y including a magnetic permeability sensor, and the like. The partition wall divides the first transport chamber, which is a developer transport section, in which the first screw member 26Y is accommodated, and the second transport chamber, which is a developer transport section in which the second screw member 32Y is accommodated. In the region facing both ends in the axial direction of the screw member, both the transfer chambers are communicated with each other through an opening (not shown).

  The first screw member 26Y and the second screw member 32Y as the agitating / conveying members are respectively provided with a rod-like rotary shaft member whose both ends are rotatably supported by a bearing (not shown), and a spiral projection on the peripheral surface thereof. And a spiral blade. Then, as it is driven to rotate by a driving means (not shown), the Y developer is conveyed in the rotation axis direction by the spiral blade.

  In the first transport chamber in which the first screw member 26Y is accommodated, the Y developer is transported from the near side to the far side in the direction orthogonal to the drawing surface as the first screw member 26Y is driven to rotate. . And if it conveys to the edge part vicinity of the back | inner side of casing 21Y, it will approach into a 2nd conveyance chamber via the opening which is not provided in the partition wall.

  The above-described developing unit 23Y is formed above the second transfer chamber in which the second screw member 32Y is accommodated, and the second transfer chamber and the developing unit 23Y communicate with each other in the entire area of the opposing part. ing. As a result, the second screw member 32Y and the developing sleeve 24Y disposed obliquely above the second screw member 32Y face each other while maintaining a parallel relationship. In the second transport chamber, the Y developer is transported from the back side to the near side in the direction orthogonal to the drawing sheet as the second screw member 32Y is driven to rotate. In this transport process, the Y developer around the rotation direction of the second screw member 32Y is appropriately pumped up to the developing sleeve 24Y, and the developed Y developer is appropriately collected from the developing sleeve 24Y. Then, the Y developer transported to the vicinity of the near end of the second transport chamber in the drawing returns to the first transport chamber through an opening (not shown) provided in the partition wall.

  A toner concentration detection sensor 45Y as a toner concentration detection means including a magnetic permeability sensor is fixed to the lower wall of the first conveyance chamber, and the toner concentration of the Y developer conveyed by the first screw member 26Y is lowered. And outputs a voltage according to the detection result. A control unit (not shown) replenishes an appropriate amount of Y toner into the first transfer chamber by driving a Y toner supply device (not shown) as necessary based on the output voltage value from the toner concentration detection sensor 45Y. As a result, the toner concentration of the Y developer, which has been lowered with the development, is recovered.

  The Y toner image formed on the photoreceptor 11Y is primarily transferred onto the intermediate transfer belt 51 at a Y primary transfer nip described later. The transfer residual toner that has not been primarily transferred onto the intermediate transfer belt 51 adheres to the surface of the photoreceptor 11Y after passing through the primary transfer process.

  The drum cleaning device 14Y cantilever-supports a cleaning blade 15Y made of, for example, polyurethane rubber, and the free end thereof is brought into contact with the surface of the photoreceptor 11Y. Further, a brush tip end side of a brush roller 16Y having a rotating shaft member that is driven to rotate by a driving means (not shown) and an infinite number of conductive brushes erected on the peripheral surface thereof is brought into contact with the photoreceptor 11Y. Yes. Then, the transfer residual toner described above is scraped off from the surface of the photoreceptor 11Y by the cleaning blade 15Y and the brush roller 16Y. A cleaning bias is applied to the brush roller 16Y via a metal electric field roller 17Y that is in contact with the brush roller 16Y, and the tip of the scraper 18Y is pressed against the electric field roller 17Y. The transfer residual toner scraped off from the photoconductor 11Y by the cleaning blade 15Y and the brush roller 16Y passes through the brush roller 16Y and the electric field roller 17Y, and then is scraped off from the electric field roller 17Y by the scraper 18Y and is placed on the recovery screw 19Y. Fall. Then, after the recovery screw 19Y is driven to rotate, the recovery screw 19Y is discharged out of the casing, and then returned to the developer transport device 22Y via a toner recycling transport means (not shown).

  The surface of the photoreceptor 11Y, from which the transfer residual toner has been cleaned by the drum cleaning device 14Y, is neutralized by the neutralizing device 13Y including a neutralizing lamp and then uniformly charged again by the charging member 14Y.

  Further, the potential of the non-image portion of the photoreceptor 11Y that has passed the optical writing position by the writing light L is detected by the potential sensor 49Y, and the detection result is sent to a control unit (not shown).

  The uniform charging potential of the photoconductor 11Y is −700 [V], for example, and the potential of the electrostatic latent image is −120 [V]. Further, the developing bias voltage is, for example, −470 [V], and a developing potential of 350 [V] is secured.

  Although the Y process unit 10Y has been described in detail, the process units (10C, M, K) of other colors have the same configuration as that of Y except that the color of the toner to be used is different. .

  In FIG. 2 shown above, the photoconductors 11Y, C, M, and K of the process units 10Y, 10C, 10M, and 10K are in contact with the upper stretched surface of the intermediate transfer belt 51 that is endlessly moved in the clockwise direction. Rotating to form primary transfer nips for Y, C, M, and K. As a material for the intermediate transfer belt 51, polyimide having excellent mechanical strength is used in order to suppress the occurrence of transfer position shift due to belt elongation. In this polyimide, carbon as an electric resistance adjusting agent is dispersed for the purpose of realizing a belt resistance value capable of exhibiting stable transfer performance without depending on the temperature and humidity environment. For this reason, the surface of the intermediate transfer belt 51 is black.

  On the back side of the primary transfer nips for Y, C, M, and K, the above-described primary transfer rollers 55Y, 55, C, M, and K are in contact with the back surface of the intermediate transfer belt 51. A primary transfer bias having a polarity opposite to the charging polarity of the toner is applied to each of the primary transfer rollers 55Y, 55C, 55M, 55K by a bias supply unit (not shown). Due to this primary transfer bias, a primary transfer electric field is formed in the primary transfer nips for Y, C, M, and K to electrostatically move the toner from the photoreceptor side to the belt side. The Y, C, M, and K toner images formed on the photoreceptors 11Y, 11C, 11M, and 11K are primary for Y, C, M, and K as the photoreceptors 11Y, 11C, 11M, and 11K rotate. When entering the transfer nip, primary transfer is performed by sequentially superimposing on the intermediate transfer belt 51 by the action of the primary transfer electric field and nip pressure. As a result, a four-color superimposed toner image (hereinafter referred to as a four-color toner image) is formed on the front surface (loop outer peripheral surface) of the intermediate transfer belt 51. Instead of the primary transfer rollers 55Y, 55C, 55M, 55K, a conductive brush to which a primary transfer bias is applied, a non-contact type corona charger, or the like may be employed.

  A toner adhesion amount sensor 61 is disposed on the right side of the K process unit 10K in the drawing so as to face the front surface of the intermediate transfer belt 51 with a predetermined gap. The toner adhesion amount sensor 61 is formed of a reflection type photosensor, reflects light emitted from a light emitting element (not shown) by a toner image on the front surface of the intermediate transfer belt 51 and the belt, and receives a reflected light amount (not shown). Detect by element. As the light receiving element, both a light receiving element that receives regular reflection light and a light receiving element that receives diffuse reflection light are provided. A control unit (not shown) detects a toner image on the intermediate transfer belt 51 based on an output voltage based on light reception by a regular reflection type light receiving element or an output voltage based on light reception by a diffuse reflection type light receiving element, The image density (toner adhesion amount per unit area) can be detected. By detecting both regular reflection light and diffuse reflection light, it is possible to detect the amount of adhesion not only with K toner but also with C, M, and K toners.

  A secondary transfer roller 56 is disposed below the intermediate transfer belt 51. The secondary transfer roller 56 abuts against the front surface of the intermediate transfer belt while being driven to rotate counterclockwise in the drawing by a driving means (not shown). To form a secondary transfer nip. Then, on the back side of the secondary transfer nip, a secondary transfer backup roller 53 that is electrically grounded is wound around the intermediate transfer belt 51.

  A secondary transfer bias having a polarity opposite to the charging polarity of the toner is applied to the secondary transfer roller 56 by a bias supply unit (not shown), whereby 2 is placed between the secondary transfer roller 56 and the grounded secondary transfer backup roller 53. A next transfer electric field is formed. The four-color toner image formed on the front surface of the intermediate transfer belt 51 enters the secondary transfer nip as the intermediate transfer belt 51 moves endlessly.

  In FIG. 1 described above, the paper feeding device 200 is fed with a paper feeding cassette 201 for storing the recording paper P, and a paper feeding roller 202 for feeding the recording paper P stored in these paper feeding cassettes 201 out of the cassette. A plurality of separation roller pairs 203 for separating the recording paper P one by one, a plurality of conveyance roller pairs 205 for conveying the separated recording paper P along the delivery path 204, and the like are provided. The sheet feeding device 200 is disposed directly below the printer unit 1 as shown in the figure. The feeding path 204 of the paper feeding device 200 is connected to the paper feeding path 70 of the printer unit 1. As a result, the recording paper P delivered from the paper feed cassette 201 of the paper feed device 200 is sent into the paper feed path 70 of the printer unit 1 via the feed path 204.

  A registration roller pair 71 is disposed near the end of the paper feed path 70 of the printer unit 1, and the recording paper P sandwiched between the rollers can be synchronized with the four-color toner image on the intermediate transfer belt 51. Send to the secondary transfer nip. In the secondary transfer nip, the four-color toner images on the intermediate transfer belt 51 are collectively transferred to the recording paper P due to the influence of the secondary transfer electric field and the nip pressure, and combined with the white color of the recording paper P, Become. The recording paper P on which the full-color image is formed in this way is separated from the intermediate transfer belt 51 when discharged from the secondary transfer nip.

  On the left side of the secondary transfer nip in the figure, a conveyor belt unit 75 is provided that moves the endless paper conveyor belt 76 endlessly in the counterclockwise direction in the figure while being stretched by a plurality of stretching rollers. . The recording paper P separated from the intermediate transfer belt 51 is transferred to the upper stretched surface of the paper conveying belt 76 and conveyed toward the fixing device 80.

  The recording paper P sent into the fixing device 80 is sandwiched in a fixing nip formed by a heating roller 81 containing a heat source such as a halogen lamp (not shown) and a pressure roller 82 pressed toward the heating roller 81. The full color image is sent to the outside of the fixing device 80 while being fixed on the surface by being heated while being pressurized.

  On the surface of the intermediate transfer belt 51 after passing through the secondary transfer nip, a slight amount of secondary transfer residual toner that has not been transferred to the recording paper P adheres. The secondary transfer residual toner is removed from the belt by a belt cleaning device 57 that is in contact with the front surface of the intermediate transfer belt 51.

  A switchback device 85 is disposed below the fixing device 80. When the recording paper P discharged from the fixing device 80 reaches the conveyance path switching position by the swingable switching claw 86, the paper discharge roller pair 87 or the switchback device according to the swing stop position of the switching claw 86. Sent to 85. When the paper is sent toward the paper discharge roller pair 87, the paper is discharged to the outside of the apparatus and then stacked in the form of the paper discharge tray 3.

  On the other hand, when it is sent toward the switchback device 85, it is turned upside down by the switchback conveyance by the switchback device 85 and then conveyed toward the registration roller pair 71 again. Then, it enters the secondary transfer nip again, and a full-color image is formed on the other side.

  The recording paper P manually fed onto the manual feed tray 2 provided on the side surface of the housing of the printer unit 1 passes through the manual feed roller 72 and the manual separation roller pair 73 and then toward the registration roller pair 71. Sent. The registration roller pair 71 may be grounded, or a bias may be applied to remove paper dust from the recording paper P.

  When copying a document by the copying machine according to the first embodiment, first, the document is set on the document table 401 of the automatic document feeder 400. Alternatively, the automatic document feeder 400 is opened, a document is set on the contact glass 301 of the scanner 300, and the automatic document feeder 400 is closed and pressed. Thereafter, when a start switch (not shown) is pressed, when the document is set on the automatic document feeder 400, the document is sent into the contact glass 301. Then, the scanner 300 is driven and reading scanning by the first traveling body 303 and the second traveling body 304 is started. At substantially the same time, driving of the transfer unit 50 and each color process unit 10Y, C, M, K starts. Furthermore, the feeding of the recording paper P from the paper feeding device 200 is also started. When recording paper P not set in the paper feed cassette 201 is used, the recording paper P set on the manual feed tray 2 is sent out.

  FIG. 4 is a block diagram showing a part of the electric circuit of the copying machine according to the first embodiment. As shown in the figure, the copying machine includes a control unit 500 as a control unit that controls various devices. The control unit 500 includes a ROM (Read Only Memory) 503 that stores in advance fixed data such as a computer program via a bus line in a CPU (Central Processing Unit) 501 that executes various calculations and drive control of each unit. A RAM (Random Access Memory) 502 that functions as a work area for storing data in a rewritable manner is connected. The ROM 503 stores an adhesion amount conversion algorithm that indicates the relationship between the output voltage value from the toner adhesion amount sensor 61 and the corresponding toner adhesion amount. FIG. 5 is a graph showing the relationship between the toner adhesion amount and the sensor output based on the light reception amount by the diffuse reflection type light receiving element. FIG. 6 is a graph showing the relationship between the toner adhesion amount and the sensor output based on the amount of light received by the regular reflection type light receiving element. The toner adhesion amount sensor 61 described above has an output terminal that outputs a voltage based on the amount of light received by the diffuse reflection type light receiving element, and an output terminal that outputs a voltage based on the amount of light received by the regular reflection type light receiving element. Yes. And the control part has memorize | stored both the algorithm which shows the graph of FIG. 5, and the algorithm which shows the graph of FIG. 6 in a data storage means as an adhesion amount conversion algorithm.

  The control unit 500 is connected to the printer unit 1, the paper feeding device 200, the scanner 300, and the ADF. In the figure, for convenience, only various sensors and the optical writing unit 60 are shown as devices in the printer unit 1, but these other devices (for example, a transfer unit and each color process unit) are also driven by the control unit 500. Is controlled. Output signals from various sensors of the printer unit 1 are sent to the control unit 500.

  FIG. 7 is a flowchart illustrating a control flow in the output image forming condition determination process performed by the control unit 500. This output image forming condition determination processing is performed when the copying machine is started, for each copying of a predetermined number of copies (between the preceding pudding and the operation and the subsequent printing operation in a continuous printing operation), at regular intervals, etc. However, FIG. 7 shows a processing flow at the time of activation. When the output image forming condition determination process starts, first, in order to distinguish the timing when the power is turned on from the time of abnormal processing such as a jam, the surface temperature of the heating roller (hereinafter referred to as the processing flow) is set as an execution condition of the processing flow. Is detected). Then, it is determined whether or not the fixing temperature exceeds 100 [° C.]. When the fixing temperature exceeds 100 [° C.] (N in step 1; hereinafter, step is denoted as S), the power is not on. As a result, the processing flow ends.

  If the fixing temperature does not exceed 100 [° C.] (Y in S1), a potential sensor check is performed (S2). In this potential sensor check, in the process units (10Y to K) of the respective colors, the surface potentials of the photosensitive members (11Y to K) are uniformly charged under a predetermined condition, respectively, and detected by a potential sensor (for example, 49Y in FIG. 3). Thereafter, Vsg adjustment of the toner adhesion amount sensor (61 in FIG. 4) is performed (S3). In this Vsg adjustment, for the toner adhesion amount sensor, the output voltage (Vsg) from the light receiving element that has detected the reflected light with respect to the non-image area of the intermediate transfer belt (51) is set to a constant value. Adjust the flash output. More specifically, the amount of emitted light of the toner adhesion amount sensor 61 is sequentially changed to obtain the amount of emitted light with a detection voltage of 4.0 [V] ± 0.2 [V]. Make it emit light. In the steps S2 to S3, the potential check and Vsg adjustment for each color are performed in parallel.

  When the Vsg adjustment is finished, it is next determined whether or not an error has occurred in the potential sensor check (S2) and the Vsg adjustment (S3) (S4). If there is an error (N in S4), an error code corresponding to the error is set (S11), and then a series of control flow ends. On the other hand, when there is no error (Y in S4), the flow of S5 to S10 described later is executed.

  In step S5, a patch pattern image composed of a plurality of patch-like toner images as shown in FIG. 8 is formed for each color on the front surface of the intermediate transfer belt 51. In the drawing, among the patch pattern images for Y, C, M, and K, the Y patch pattern image PpY is shown. As shown in the figure, the patch pattern image PpY is a first patch-like Y toner image Py1, a second patch-like Y toner image Py2,... Arranged in the belt moving direction (arrow direction in the figure) at a predetermined interval. ... It consists of n patch-like Y toner images called n-th patch-like Y toner images Pyn. These have different image densities, but the shapes and postures on the intermediate transfer belt 51 are the same. It is a rectangular shape that runs along the width direction in the belt width direction and along the length direction in the belt movement direction. Length (belt movement direction) = 13 [mm], width (belt width direction) L1 = 15 [Mm]. The interval G between the patches is 13 [mm]. In the first embodiment, since a patch pattern image composed of ten patch-like pattern images is formed, the length of the patch pattern image is 247 [mm]. As such patch pattern images, four Y, C, M, and K toners are formed side by side in the belt moving direction. The total length of the four patch pattern images is at least “247 × 4 + 13 × 3 = 1027 mm”, which is longer than the peripheral length of the intermediate transfer belt 51. Therefore, four patch pattern images are formed by moving the intermediate transfer belt 51 by one or more rounds. The order of forming the four patch pattern images is the order of Y, C, M, and K, as in the order of arrangement of the process units. FIG. 9 is a schematic diagram showing the upper side of the intermediate transfer belt 51 in which an M patch pattern image PpM and a K patch pattern image PpK are sequentially formed.

  Each patch-like toner image in each color patch pattern image (PpY, PpC, PpM, PpK) is formed on the photoreceptor (11Y, C, M, K) of each color process unit (10Y, C, M, K). The image is transferred onto the intermediate transfer belt 51. Then, when they pass directly under the toner adhesion amount sensor 61 as the intermediate transfer belt 51 moves endlessly, the light emitted from the sensor is reflected on its surface. This reflected light amount is a value correlated with the image density of the patch-like toner image. The controller (500) described above stores the sensor output voltage value for each patch-like toner image for each color in the RAM (502) as Vpi (i = 1 to N) (S7 in FIG. 7). Based on the sensor output voltage value and the above-described adhesion amount conversion algorithm stored in advance in the ROM (503), the toner adhesion amount per unit area for each patch-like toner image is calculated, and then the calculation result is obtained. The data is stored in the RAM (502) (S8 in FIG. 7). Before each color patch-like toner image is developed on each color photoconductor, the potential of each patch-like latent image that is a precursor of the patch-like toner image is the above-described potential sensor (for example, 49Y). The detection results are sequentially stored in the RAM (502) (S6 in FIG. 7).

  After calculating the toner adhesion amount for each patch-like toner image, next, an appropriate development potential is obtained for each color developing device (S9 in FIG. 7). Specifically, the following processing is performed for each color. That is, for each patch-like toner image, the development potential that is the difference between the latent image potential obtained in S6 and the development bias is calculated. Next, the relationship between the development potential and the toner adhesion amount is linear on the two-dimensional plane among the 10 data sets of the latent image potential and the toner adhesion amount corresponding to the 10 patch-like toner images, respectively. Only the data combinations in the section are selected. Then, an approximate straight line of the development characteristic straight line is obtained by applying the least square method to the data in this section. Then, based on the approximate line, the development potential at which the toner adhesion amount is maximized is specified (S9 in FIG. 7), and the development bias Vb and the laser writing intensity VD from which the development potential is obtained are set (FIG. 7). S10).

  FIG. 10 is a graph showing development performance straight lines (straight lines showing the relationship between the toner adhesion amount and the development potential) in the process units of the respective colors. In the figure, a straight line La shows an example of a development performance line when the development γ (which is the slope of the straight line and indicates development ability) becomes relatively large. A straight line Lb shows an example of a development performance straight line when the development γ becomes relatively small. Due to its characteristics, the toner adhesion amount sensor 61 has a detectable range as shown in FIG. In the adhesion amount range that exceeds the upper limit of the detectable range, even if the actual toner adhesion amount increases linearly, the sensor output does not increase linearly. The relationship cannot be detected. Similarly, even in the adhesion amount range below the lower limit of the detectable range, it is impossible to detect the linear relationship as shown in the figure. For this reason, with respect to the above-described approximate straight line, a straight line approximation process is performed based only on data (a combination of the toner adhesion amount and the development potential) in which the detection result of the toner adhesion amount is within the detectable range. Yes.

  In such a straight line approximation process, as development line γ becomes relatively large as in the case of straight line La, the number of patches that become the toner adhesion amount within the detectable range is remarkably reduced. End up. Further, even when the development γ becomes relatively small as shown by the straight line Lb, only the patch-like toner image having a larger number can enter the toner adhesion amount within the detectable range, so that the toner adhesion amount is within the detectable range. The number of patches is significantly reduced.

  As in the image forming apparatus described in Patent Document 1, after forming a patch pattern image and grasping the development γ, a patch pattern image is formed again based on the development γ and a desired number of patches within the detectable range. Therefore, it is possible to accurately detect the development performance straightness. However, in this case, the combination of the formation of the patch pattern image and the calculation process based on the detection result of the toner adhesion amount has to be repeated twice, so that it takes a long time to determine the output image forming condition. End up.

Next, a characteristic configuration of the copying machine according to the first embodiment will be described.
In the copying machine according to the first embodiment, an absolute humidity sensor (not shown) is provided in the housing of the printer unit (1), and the absolute humidity sensor can detect the absolute humidity. The development γ of the process unit shows a good correlation with the absolute humidity as shown in FIG. Specifically, as shown in the figure, the development γ increases as the absolute humidity increases, and decreases as the absolute humidity decreases.

  Here, it is assumed that a sufficient number of detectable patches are obtained within the detectable range when the previous output image imaging condition determination process is executed. After that, it is assumed that the development γ changes with the change of the absolute humidity. In this case, if each patch-like toner image in the patch pattern image is developed with the same development potential as in the previous output image imaging condition determination process, the desired number of detectable patches may not be obtained. However, since there is a correlation between the amount of change in absolute humidity and the amount of change in development γ, the development γ after change is predicted from the amount of change in absolute humidity, and each patch-like toner is based on the result. If the development potential of the image is corrected, it is possible to obtain a desired number of detectable patches even after the change in absolute humidity.

  Therefore, prior to performing the output image imaging condition determination process, the control unit of the copier according to the first embodiment calculates the absolute humidity fluctuation amount from the previous time when the output image imaging condition determination process was performed, and the previous time. Based on the development potential of each patch-like toner image in the output image imaging condition determination process, a patch for determining each development potential in a plurality of patch-like toner images to be formed in the output image imaging condition determination process to be performed from now on An image forming condition determination process is performed.

  In this patch image formation condition determination process, the development biases of the ten patch-like toner images in the patch pattern image are determined for each color as follows. That is, when the absolute humidity becomes higher than the previous execution (positive environmental fluctuation), a smaller development potential is determined for each patch-like toner image than the previous time (development ability as image forming ability is lowered). . On the other hand, when the absolute humidity is lower than the previous execution (negative environmental fluctuation), a higher development potential than the previous one is determined for each patch-like toner image (development capability is increased).

FIG. 12 shows an image forming potential condition of the former output image image forming condition determining process when the absolute humidity is higher during the subsequent output image condition determining process than the preceding output image image forming condition determining process, and the latter 6 is a chart showing image forming potential conditions of the output image image forming condition determining process. FIG. 13 is a chart showing a relationship between a graph showing a development characteristic line in the former output image imaging condition determination process and a graph showing a development characteristic line in the latter output image imaging condition determination process. Hereinafter, the former output imaging condition determination processing is referred to as “previous processing”. The latter output image image formation condition determination process is referred to as “current process”. Here, it is assumed that the image forming potential conditions in the “previous processing” are the photoreceptor surface potential Vd = Vd1, the developing bias Vb = Vb1, and the laser power (laser writing intensity) LD = LD1. The development potentials Vb1 ₁ , Vb1 ₂ ... Vb1 ₁₀ of the _ten patch-like toner images are laser powers LD1 ₁ , LD1 ₂ ,... Based on the photoreceptor surface potential Vd1, development bias Vb1, and laser power LD1. ..., latent image potential _VL 1 which is an optical writing in _{LD1 10,} VL 2, based on · · · _{VL 10,} obtained as follows. That is, it is obtained by calculation of (Vb1-VL ₁ ), (Vb1-VL ₂ ),..., (Vb1-VL ₁₀ ). LD1 ₁ = LD1 × e1, LD1 ₂ = LD1 × e2,..., LD1 ₁₀ = LD1 × e10 (0 <e1 <e2 <e10 = 1.5), and the values of e1 to e10 are experimentally determined in advance. It is decided.

When the absolute humidity in the “current process” is higher than that in the “previous process”, the photosensitive member surface potential is set to Vd1, the developing bias is set to Vb1, and the laser power is set to LD1 ′ (LD1 ′). = LD1 × α (0 <α <1)) smaller laser power LD1 _{'1, LD1'} than the last relative to the 2,..., by performing optical writing by LD1 _'10, "previous processing" A patch-like toner image is formed with a developing potential smaller than the time. The magnitude of the coefficient α is calculated based on a graph showing a relationship between an increase amount of absolute humidity and an appropriate value of α, which is obtained by a previous experiment. As a result, in the “current process” in which the development γ becomes larger, it is possible to obtain the same number of detectable patches as the previous time within the detectable range.

When the absolute humidity in the “current process” is lower than that in the “previous process”, the photosensitive member surface potential is set to Vd1, the developing bias is set to Vb1, and the laser power is set to LD1 ′ ( LD1 '= LD1 × beta large laser power LD1 than the last relative to the _{(1 <β)' 1,} LD1 '2, ···, LD1' by performing optical writing by _10, when the "previous processing" A patch-like toner image is formed with a larger development potential than the coefficient β based on a graph showing the relationship between the amount of decrease in absolute humidity and the appropriate value of β, which was obtained in advance through experiments. This makes it possible to obtain the same number of detectable patches as the previous time within the detectable range in the “current process” when the development γ becomes larger.

  In such a configuration, a desired number of detectable patches can be obtained and the development performance straight line can be obtained only by combining the formation of the patch pattern image and the calculation process based on the detection result of the toner adhesion amount on the patch-like toner image once. Can be grasped. Therefore, the process control process can be shortened as compared with the image forming apparatus described in Patent Document 1 in which the above combination is performed twice while accurately detecting the development performance straight line.

  In addition, although the example which provided the absolute humidity sensor which detects absolute humidity as an environment grasping | ascertainment means was demonstrated, this invention is applicable also when using what detects a relative humidity and temperature. In this case, although the accuracy is inferior to the case of detecting absolute humidity, the increase / decrease in development γ is grasped based on the fluctuation amount of relative humidity and the fluctuation amount of temperature, and the subsequent output image imaging condition determination It is possible to appropriately determine the development potential of each patch-like toner image formed by processing. Moreover, you may make it grasp | ascertain absolute humidity based on the detection result of relative humidity and temperature.

Next, a copying machine according to a second embodiment to which the present invention is applied will be described. Unless otherwise specified below, the configuration of the copying machine according to the second embodiment is the same as that of the first embodiment.
The control unit 500 of the copying machine according to the second embodiment performs the following patch image forming condition determination process. That is, the patch pattern formed by “current process” based on the amount of change in absolute humidity from “previous process” and the number of patch-like toner images formed in one patch pattern image formed by “previous process”. The number of patch toner images formed in the image and the potential pitch, which is the potential difference between the individual patch toner images, are determined. More specifically, when the absolute humidity in the “current process” is higher than that in the “previous process”, the ten patch-like toner images in the “previous process” have a low development potential in the “previous process”. Patch image forming conditions are added so that the number of patch-like toner images increases. That is, the photosensitive member surface potential Vd1, the developing bias Vb1, and the laser power LD1 (LD1 ₁ , LD1 ₂ ,..., LD1 ₁₀ ) at the time of “previous processing” are set, and the patch pattern LD1 _1H of the low developing potential portion is set. LD1 _2H and LD1 _3H (LD1 _1H = LD1 ₁ × α, LD1 _2H = LD1 ₂ × α, LD1 _3H = LD1 ₃ × α (0 <α <1)) are added. In the present description, one laser power smaller than LD1 _N is added, but a plurality of laser powers may be added, and the number and coefficient α to be added are calculated in advance by experiments. As a result, it is possible to obtain a sufficient number of detectable patches within the detectable range in the “current process” in which the development γ becomes larger.

In addition, when the absolute humidity in the “current process” is lower than that in the “previous process”, the 10 patch-like toner images in the “previous process” are added to the high development potential portion in the “previous process”. Patch image forming conditions are added so that the number of patch-like toner images increases. That is, the photosensitive member surface potential Vd1, the developing bias Vb1, and the laser power LD1 (LD1 ₁ , LD1 ₂ ,..., LD1 ₁₀ ) at the time of “previous processing” are set, and the patch pattern LD1 _8L of the high developing potential portion is set. LD1 _9L and LD1 _10L (LD1 _8L = LD1 ₈ × β, LD1 _9L = LD1 ₉ × β, LD1 _10L = LD1 ₁₀ × β (1 <β)) are added. Although in this description have added one larger laser power LD1 _N, may be added a plurality of laser power, the number and the coefficient β to be added is calculated determined by experiment. Thereby, in the “current process” in which the development γ becomes smaller, it is possible to obtain a sufficient number of detectable patches within the detectable range.

  Even in such a configuration, it is possible to obtain a desired number of detectable patches and develop the development performance straight line only by combining the formation of the patch pattern image and the calculation process based on the detection result of the toner adhesion amount on the patch-like toner image once. Can be grasped. Therefore, the process control process can be shortened as compared with the image forming apparatus described in Patent Document 1 in which the above combination is performed twice while accurately detecting the development performance straight line.

  As described above, in the copying machine according to the first embodiment, in the patch imaging condition determination process, the development potential of each patch-like toner image at the time of the “previous process” is corrected based on the amount of change in absolute humidity. Then, the control unit 500 serving as a control unit is configured so as to perform the process of setting each development potential in each patch-like toner image formed in the “current process” (scheduled output image forming condition determination process). is doing. In such a configuration, since the number of patch formations in the patch pattern image formed by the patch image formation condition determination process is constant every time regardless of the size of the development γ, the number of patch formations can be reduced even in the case of a relatively large development γ. Obtain the desired number of detectable patches without increasing it excessively. Accordingly, it is possible to avoid lengthening the output image forming condition determination process due to excessively increasing the number of patch formations in the case of relatively large development γ.

  In the copying machine according to the first embodiment, an absolute humidity sensor that grasps an absolute humidity state is used as an environment grasping means. When the environmental variation amount is a positive absolute humidity variation amount in the patch image formation condition determination processing, a plurality of development potentials for the plurality of patch-like toner images in the “current processing” The control unit 500 is configured to perform a process of determining a patch toner image having a smaller development potential than that of the patch-like toner image (that lowers the developing ability). In such a configuration, when the development γ becomes larger than that in the “previous processing” due to the increase in absolute humidity, the detection potential patch due to the increase in development γ is reduced by reducing the development potential in each patch-like toner image. A reduction in the number can be avoided.

  Further, in the copying machine according to the first embodiment, when the environmental fluctuation amount is a negative absolute humidity fluctuation amount in the patch imaging condition determination processing, each of the plurality of patch-like toner images in “current processing” is determined. The control unit 500 is configured to execute a process of determining a development potential larger than each development potential for the plurality of patch-like toner images in the “previous processing” (those that increase development capability) is doing. In such a configuration, when the development γ becomes smaller than that in the “previous processing” due to the decrease in absolute humidity, the detection potential patch due to the decrease in the development γ is increased by increasing the development potential in each patch-like toner image. A reduction in the number can be avoided.

  In the copying machine according to the second embodiment, in the patch imaging condition determination process, the process of reducing the potential difference and increasing the number of patches formed in the patch pattern image as the absolute humidity fluctuation amount increases. Thus, the control unit 500 is configured. In such a configuration, the number of detectable patches can be made substantially constant regardless of the absolute humidity by setting the potential pitch to a value commensurate with the development γ.

11Y, C, M, K: photoconductor (latent image carrier)
20Y, C, M, K: Developing device (developing means)
24Y: Development sleeve (developer carrier)
50: Transfer unit (transfer means)
60: Optical writing unit (latent image writing means)
61: Toner adhesion amount sensor (attachment amount detection means)
500: Control unit (control means)

JP-A-10-90961

Claims (5)

The latent image bearing member for carrying the latent image, the latent image writing means for writing the electrostatic latent image on the latent image bearing member, and the developer carried on the surface of the developer bearing member are used to develop the electrostatic latent image. Development means for obtaining a toner image and adhesion amount detection for detecting the toner adhesion amount per unit area on the toner image on the surface of the latent image carrier or the toner image transferred from the latent image carrier to the transfer body And a patch pattern image composed of a plurality of patch-like toner images developed under different image forming conditions, and a result of detection of the toner adhesion amount on the plurality of patch-like toner images by the adhesion amount detection means. After the development performance line indicating the relationship between the image formation condition and the toner adhesion amount is grasped, the output image formation for determining the image formation condition when forming an image based on the user's command based on the development performance line Condition decision processing In the image forming apparatus and a control means for performing a constant timing,
In addition to providing environmental grasping means to grasp the environmental situation,
Prior to the execution of the output image imaging condition determination process, the amount of environmental change from the previous execution of the output image imaging condition determination process and the individual patch shapes in the previous output image imaging condition determination process Based on the toner image forming conditions, the patch image forming condition determining process for determining the image forming conditions for a plurality of patch-like toner images to be formed in the output image forming condition determining process to be performed later is executed. An image forming apparatus comprising the control means. The image forming apparatus according to claim 1.
In the patch image formation condition determination process, each image formation condition in the plurality of patch-like toner images when the previous output image image formation condition determination process is performed is corrected based on the amount of environmental variation, An image forming apparatus characterized in that the control means is configured to perform a process of setting each image forming condition in a plurality of patch-like toner images formed in the output image forming condition determining process to be executed. The image forming apparatus according to claim 2.
As the environment grasping means, the one that grasps the situation of absolute humidity is used,
In the patch imaging condition determination process, when the environmental fluctuation amount is a positive absolute humidity fluctuation amount, each imaging condition for a plurality of patch-like toner images in the output image imaging condition determination process scheduled to be performed As described above, the control means is configured to perform a process of determining what makes the image forming ability lower than each image forming condition for the plurality of patch-like toner images in the previous output image image forming condition determining process. An image forming apparatus. The image forming apparatus according to claim 2 or 3,
As the environment grasping means, the one that grasps the situation of absolute humidity is used,
In the patch imaging condition determination process, when the environmental fluctuation amount is a negative absolute humidity fluctuation amount, each imaging condition for the plurality of patch-like toner images in the output image imaging condition determination process scheduled to be performed As described above, the control means is configured to execute a process for determining which image forming ability is higher than each image forming condition for a plurality of patch-like toner images in the previous output image image forming condition determining process. An image forming apparatus. The image forming apparatus according to claim 2.
In the patch imaging condition determination process, if it is determined that the current imaging capability is relatively high based on the environmental variation amount, a patch formed in the output image imaging condition determination process to be executed later When it is determined that the difference in development potential between individual patch-like toner images in the pattern image is smaller on the high potential side than on the low potential side while the current image forming capability is relatively low, the development is performed. An image forming apparatus characterized in that the control means is configured to carry out a predetermined step of making the potential difference smaller on the low potential side than on the high potential side.

Images