JP5804356B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile machine. Specifically, a toner image obtained by developing a latent image on a latent image carrier with a two-component developer is finally formed on a recording material. The present invention relates to an image forming apparatus that performs image formation by transferring to the above.

When toner in a two-component developer (hereinafter simply referred to as “developer”) that is circulated and conveyed along the developer circulation conveyance path in the developing device (developing means) is consumed by image formation, The toner is supplied to the developer by the toner supply means. The following methods are known as conventional toner replenishment control methods employed in this toner replenishment.
For example, a toner density detection unit is provided at a predetermined location (toner detection location) on a circulation transport path for circulating and transporting the developer in the developing device, and the toner density detected by the toner density detection unit is used as a target toner density. A necessary target toner supply amount is calculated. A control method is known in which replenished toner is replenished to the developer all at once or at regular intervals so that the calculated target toner replenishment amount is replenished. Hereinafter, this control method is referred to as feedback supply control (FB supply control). In addition, toner consumption that is expected to be consumed by developing the latent image from pixel writing information (image information) used when the exposure device (latent image forming means) forms the latent image on the latent image carrier. (Predicted value) is obtained. A control method is also possible in which the target toner replenishment amount is calculated from the calculated predicted value, and the replenishment toner is replenished to the developer all at once or at regular intervals so that the target toner replenishment amount of toner is replenished. Are known. Hereinafter, this control method is referred to as feedforward supply control (FF supply control). Also, a control method that combines FF supply control with FB supply control has been proposed.

  In general, there are individual differences in toner replenishing devices, and the amount of toner replenished per unit replenishing operation (unit toner replenishing amount) differs depending on the individual toner replenishing device. Even if the same toner replenishing device is used, the usage environment such as the temperature and humidity of the place where the image forming apparatus on which the toner replenishing device is installed is installed, the remaining amount of toner in the toner replenishing device, and the gear for driving the toner replenishing device. Unit toner replenishment amount varies depending on factors such as motor deterioration. Therefore, even if an accurate target toner supply amount is calculated, the actual toner supply amount does not become the target toner supply amount, and a supply error occurs.

  Patent Document 1 discloses an image forming apparatus capable of correcting a replenishment error caused by an error in unit toner replenishment amount caused by individual differences of such toner replenishment devices. In this image forming apparatus, first, prior to the toner supply operation, the toner density before toner supply is detected by the toner density detection means. Thereafter, a target toner replenishment amount is calculated from the detection result of the toner density detection means, and a toner replenishment operation for replenishing the toner of the target toner replenishment amount is executed. After this toner replenishment operation, the toner concentration after toner replenishment is detected by the toner concentration detecting means. At this time, if the target toner replenishment amount calculated from the detection result of the toner concentration detection means before replenishment is accurate and the toner of the target toner replenishment amount is replenished accurately, the toner concentration after toner replenishment is Should match the target toner density. However, in reality, the toner concentration after the toner replenishment does not match the target toner concentration because the toner of the target toner replenishment amount is not accurately replenished due to the replenishment error due to the individual difference of the toner replenishing devices.

  In the conventional image forming apparatus disclosed in Patent Document 1, the actual toner replenishment amount (actual replenishment amount) by the current toner replenishment is obtained by multiplying the toner density difference before and after toner replenishment by the toner replenishment amount per unit toner density difference. Amount). Since the toner replenishment amount per unit toner density difference can be obtained with high accuracy in advance, the actual replenishment amount calculated here coincides with the toner replenishment amount actually replenished with high accuracy. The ratio between the target toner supply amount calculated at the current toner supply and the actual supply amount is set as a correction coefficient (correction value), and the target toner supply amount is calculated using the correction coefficient at the subsequent toner supply. Thereby, the replenishment error due to the individual difference of the toner replenishing device is corrected, and the originally necessary amount of toner is appropriately replenished.

  However, in the conventional image forming apparatus described in Patent Document 1, image formation is performed during a period from the detection of the toner concentration before toner replenishment to the detection of the toner concentration after toner replenishment in order to calculate the correction coefficient. The operation cannot be performed. This is because if toner is consumed during this period, the actual toner replenishment amount (actual replenishment amount) replenished by the toner replenishment cannot be calculated from the toner density difference before and after toner replenishment, and an appropriate correction coefficient cannot be calculated. Because. Therefore, in the conventional image forming apparatus described in Patent Document 1, it is necessary to provide a period in which only the toner replenishing operation is performed without executing the image forming operation in order to calculate the correction coefficient. There was a problem that increased.

  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 that does not increase the standby time of an image forming operation when calculating a correction value for correcting a replenishment error. Is to provide.

In order to achieve the above object, a first aspect of the present invention provides a latent image carrier, latent image forming means for forming a latent image on the latent image carrier based on image information, and the surface of the developer carrier. The two-component developer carried on the toner is conveyed to the development area by rotation of the developer carrier, and the toner in the two-component developer is adhered to the latent image on the surface of the latent image carrier in the development area. A developing device for developing a latent image, a toner replenishing unit for replenishing toner to the two-component developer in the developing device, and a target toner replenishment necessary for setting the toner concentration in the two-component developer to a target toner concentration And a toner replenishment control means for controlling the toner replenishing means so that the calculated target toner replenishment amount of toner is replenished, and the latent image carrier is developed by the developing device. The toner image formed above is finally transferred onto the recording material. Toner in an image forming apparatus not form an image by a toner concentration detecting means for detecting the toner density of the two-component developer in the developing device, in parallel with the image forming operation in the image forming operation by the toner replenishing means The toner concentration of the two-component developer before and after image formation before and after the toner replenishment when the toner is replenished is detected by the toner concentration detection means to calculate the difference in toner density before and after the image formation before and after the toner replenishment. acquiring image information in the image forming operation during the previous imaging before the toner supply by the toner concentration detecting means from the time of the toner density detection until image formation after the toner concentration detecting after the toner supply according to the toner concentration detecting means, correction value for calculating a correction value for correcting the target toner supply amount of the next subsequent image formation after the image formation operation is completed and a said toner density difference and the image information A correction value calculation processing unit for performing a discharge process, wherein the toner replenishment control unit supplies the toner so that a target toner replenishment amount of toner corrected by the correction value calculated by the correction value calculation processing unit is replenished. The means is controlled.
According to a second aspect of the present invention, in the image forming apparatus of the first aspect, a plurality of toner patches are formed on the latent image carrier, and the plurality of toner patches or the latent image carrier on the latent image carrier. The toner adhesion amount of the plurality of toner patches after being transferred from the body onto the transfer body is detected by the toner adhesion amount detection means, and image density adjustment control for obtaining a target image density is executed based on the detection result An image density adjustment control means, and the correction value calculation processing means executes the correction value calculation processing in parallel with the image forming operation during the image forming operation immediately after the image density adjustment control is executed. It is a feature.
According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the correction value calculation processing means has passed a predetermined unstable replenishment time after starting toner replenishment by the toner replenishing means. The correction value calculation process is not performed when the toner supply by the toner supply means is completed until the toner supply is completed, and the correction is performed when the toner supply by the toner supply means ends after the unstable supply time has elapsed. A value calculation process is performed.
According to a fourth aspect of the present invention, in the image forming apparatus according to the first or second aspect, the correction value calculation processing means is an unstable replenishment time in which a total time of a plurality of times of toner replenishment by the toner replenishing means is predetermined. The correction value calculation process is not performed when the time is less than the value, and the correction value calculation process is performed when the time is equal to or longer than the unstable replenishment time.
According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, the toner supply unit includes a plurality of toner supply units, and the toner supply control unit includes the plurality of toner supply units. The correction value calculation processing means individually performs the correction value calculation processing for the plurality of toner replenishing means.
According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the first to fifth aspects, the correction value calculation processing means repeatedly performs the correction value calculation processing after a predetermined period. It is characterized by.
According to a seventh aspect of the present invention, in the image forming apparatus according to the sixth aspect, the predetermined period is a fixed period determined in advance or a period determined according to a use environment or an accumulated toner consumption amount. It is characterized by.

  In the present invention, not only the toner density difference before and after toner replenishment obtained by detecting the toner density before and after toner replenishment but also the period from the time of toner density detection before toner replenishment to the time of toner density detection after toner replenishment. A correction value for correcting the target toner supply amount is calculated using the image information in the image forming operation. When the image forming operation is performed during this period and the toner is consumed, the actual toner replenishment amount during the period and the image forming operation during the period are actually consumed from the toner density difference before and after the toner replenishment. The difference value from the toner consumption can be calculated with high accuracy. The amount of toner consumed by the image forming operation during the period can be grasped with high accuracy using the image information of the image forming operation. Therefore, even when the image forming operation is performed during the period and the toner is consumed, the toner consumption due to the image forming operation obtained from the toner density difference before and after the toner replenishment and the image information of the image forming operation during the period From the amount, the actual toner replenishment amount during the period can be calculated with high accuracy. Thus, an error (that is, a replenishment error) between the target toner replenishment amount used at the time of toner replenishment during the period and the toner amount actually replenished during the period can be grasped, and the replenishment error can be reduced. It is possible to calculate an appropriate correction value.

  As described above, according to the present invention, an appropriate correction value can be calculated even when an image forming operation is performed while the toner density before and after replenishment used for calculating the correction value is detected. An excellent effect of not increasing the operation standby time can be obtained.

1 is a schematic configuration diagram illustrating a printer according to an embodiment. FIG. 3 is a schematic diagram illustrating a configuration of a process unit for generating a Y toner image in the printer. FIG. 3 is an explanatory diagram showing a development unit configuration around a developer circulation conveyance path in which the developer circulates in the development unit in the process unit. FIG. 3 is a block diagram illustrating an example of a control system that executes toner supply control according to the embodiment. 5 is a flowchart showing a flow of toner supply control. 6 is a flowchart illustrating a flow of processing for calculating a target toner supply amount correction value in the embodiment. 6 is a graph showing an example of increase / decrease of the toner amount in the developing unit from the start of the image forming operation to the end of the image forming operation when the actual toner replenishment amount is larger than the actual toner consumption amount. 7 is a graph showing an example of increase / decrease in the toner amount in the developing unit from the start of the image forming operation to the end of the image forming operation when the actual toner replenishment amount is smaller than the actual toner consumption amount. (A) is explanatory drawing which shows the total image formation time in the case of performing correction value calculation regularly in the conventional apparatus which required the time for exclusive use for calculating a correction value. (B) is explanatory drawing which shows the total image formation time in the case of performing correction value calculation with the same frequency, performing the same image formation as the conventional apparatus in embodiment. FIG. 10 is an explanatory diagram for explaining an effect obtained by correcting a target toner supply amount with a correction value. 10 is a flowchart showing a flow of correction value calculation processing in Modification 1; 10 is a flowchart showing a flow of toner replenishment control in Modification 3.

An embodiment in which the present invention is applied to an electrophotographic printer (hereinafter simply referred to as “printer”) as an image forming apparatus will be described below.
First, a basic configuration of the printer according to the present embodiment will be described.
FIG. 1 is a schematic configuration diagram illustrating a printer according to the present embodiment.
This printer includes four process units 1Y, 1C, 1M, and 1K for yellow, magenta, cyan, and black (hereinafter referred to as Y, C, M, and K). These use Y, C, M, and K toners of different colors as image forming substances for forming an image, but the other configurations are the same.

FIG. 2 is a schematic diagram showing a configuration of a process unit 1Y for generating a Y toner image.
The process unit 1Y includes a photoreceptor unit 2Y and a developing unit 7Y. The photoconductor unit 2Y and the developing unit 7Y are configured to be detachable from the printer main body as a process unit 1Y. However, in a state where it is detached from the printer main body, the developing unit 7Y can be attached to and detached from a photosensitive unit (not shown).

The photoreceptor unit 2Y includes a drum-shaped photoreceptor 3Y as a latent image carrier, a drum cleaning device 4Y, a static eliminator (not shown), a charging device 5Y, and the like.
The charging device 5Y, which is a charging unit, uniformly charges the surface of the photoreceptor 3Y, which is driven to rotate clockwise in FIG. 2 by a driving unit (not shown), by the charging roller 6Y. Specifically, a charging bias is applied from a power source (not shown) to the charging roller 6Y that is driven to rotate counterclockwise in FIG. 2, and the charging roller 6Y is brought close to or in contact with the photosensitive member 3Y, whereby the photosensitive member 3Y. Is uniformly charged. Instead of the charging roller 6Y, another charging member such as a charging brush may be used in proximity or contact. Further, a charger that uniformly charges the photosensitive member 3Y by a charger method, such as a scorotron charger, may be used. The surface of the photoreceptor 3Y uniformly charged by the charging device 5Y is exposed and scanned by a laser beam emitted from an optical writing unit 20 serving as a latent image forming unit, which will be described later, and carries an electrostatic latent image for Y.

FIG. 3 is an explanatory diagram showing the configuration of the developing unit around the developer circulation conveyance path through which the developer circulates in the developing unit.
As shown in FIGS. 2 and 3, the developing unit 7 </ b> Y that is a developing device has a first conveying screw 8 </ b> Y as a developer conveying means disposed in the developer stirring and conveying path 9 </ b> Y. Further, a second conveying screw 11Y as a developer conveying means is disposed in the developer supply conveying path 14Y. Further, the developing unit 7Y includes a toner concentration sensor 10Y including a magnetic permeability sensor as a toner concentration detecting unit, a second conveying screw 11Y as a developer conveying unit, a developing roll 12Y as a developer carrying member, and a developer regulating member. The doctor blade 13Y is also provided. In these two transport paths, a Y developer (not shown) that is a two-component developer composed of a magnetic carrier and a negatively chargeable Y toner is accommodated.

  The first conveying screw 8Y is rotationally driven by a driving means (not shown) to convey the Y developer in the developer stirring and conveying path 9Y to the front side in FIG. 2 (direction of arrow A in FIG. 3). The Y developer in the middle of conveyance is supplied by a toner concentration sensor 10Y fixed on the first conveyance screw 8Y to the replenishment point (in this embodiment, the developer agitation conveyance path) facing the toner replenishing port 17Y in the developer agitation conveyance path 9Y. The toner concentration of the Y developer passing through a predetermined detection location (near the downstream end of the developer stirring and conveying path 9Y in the present embodiment) located downstream of the developer circulation direction in the vicinity of the upstream end of 9Y) is detected. . Then, the Y developer conveyed to the downstream end of the developer agitation conveyance path 9Y by the first conveyance screw 8Y enters the upstream end of the developer supply conveyance path 14Y from the end communication port 18Y.

  The second transport screw 11Y in the developer supply transport path 14Y is rotationally driven by a driving unit (not shown) to transport the Y developer to the back side in FIG. 2 (in the direction of arrow A in FIG. 3). In this way, the developing roll 12Y is arranged in a posture parallel to the second conveying screw 11Y above the second conveying screw 11Y that conveys the Y developer in FIG. The developing roll 12Y has a configuration in which a fixedly arranged magnet roller 16Y is included in a developing sleeve 15Y as a developer carrying member made of a non-magnetic sleeve that is driven to rotate counterclockwise in FIG. . A part of the Y developer conveyed by the second conveying screw 11Y is pumped up to the surface of the developing sleeve 15Y by the magnetic force generated by the magnet roller 16Y. Then, after the layer thickness is regulated by a doctor blade 13Y disposed so as to maintain a predetermined gap from the surface of the developing sleeve 15Y, the layer is conveyed to a developing region facing the photosensitive member 3Y, and is transferred onto the photosensitive member 3Y. Y toner is adhered to the electrostatic latent image for Y. This adhesion forms a Y toner image on the photoreceptor 3Y. The Y developer that has consumed Y toner by the development is returned onto the second conveying screw 11Y as the developing sleeve 15Y rotates. Then, the Y developer transported to the downstream end of the developer supply transport path 14Y by the second transport screw 11Y returns to the upstream end of the developer stirring transport path 9Y through the end communication port 19Y. In this way, the Y developer is circulated and conveyed in the developing unit.

  The Y toner image formed on the photoreceptor 3Y is intermediately transferred to an intermediate transfer belt 41 that is an intermediate transfer body. The drum cleaning device 4Y of the photoreceptor unit 2Y removes toner remaining on the surface of the photoreceptor 3Y after the intermediate transfer process. As a result, the surface of the photoreceptor 3Y subjected to the cleaning process is neutralized by a neutralizing device (not shown). By this charge removal, the surface of the photoreceptor 3Y is initialized and prepared for the next image formation. Similarly, in the process units 1C, 1M, and 1K for other colors, C toner images, M toner images, and K toner images are formed on the photoreceptors 3C, 3M, and 3K, and the intermediate transfer belt 41 is subjected to intermediate transfer. Is done.

  An optical writing unit 20 is disposed below the process units 1Y, 1C, 1M, and 1K in FIG. The optical writing unit 20 irradiates the photoconductors 3Y, 3C, 3M, and 3K of the process units 1Y, 1C, 1M, and 1K with the laser light L emitted based on the image information. As a result, electrostatic latent images for Y, C, M, and K are formed on the photoreceptors 3Y, 3C, 3M, and 3K, respectively. The optical writing unit 20 deflects the laser light L emitted from the light source by the polygon mirror 21 that is rotationally driven by a motor, and passes through the photoreceptors 3Y, 3C, 3M, and 3K via a plurality of optical lenses and mirrors. Is irradiated. Instead of such a configuration, an LED array may be used.

  A first paper feed cassette 31 and a second paper feed cassette 32 are disposed below the optical writing unit 20 so as to overlap in the vertical direction. In each of these paper feed cassettes, a plurality of recording papers P, which are recording materials, are stored in a stack of recording papers, and a first paper feed roller is placed on the top recording paper P. 31a and the second paper feed roller 32a are in contact with each other. When the first paper feed roller 31a is driven to rotate counterclockwise in FIG. 1 by driving means (not shown), the uppermost recording paper P in the first paper feed cassette 31 is vertically oriented on the right side of the cassette in FIG. The paper is discharged toward the paper feed path 33 arranged so as to extend. When the second paper feed roller 32a is rotated counterclockwise in FIG. 1 by driving means (not shown), the uppermost recording paper P in the second paper feed cassette 32 is discharged toward the paper feed path 33. The A plurality of transport roller pairs 34 are arranged in the paper feed path 33, and the recording paper P fed into the paper feed path 33 is sandwiched between the rollers of the transport roller pair 34 while being fed between the paper feed paths 33. 1 is conveyed from the lower side to the upper side in FIG. A registration roller pair 35 is disposed at the end of the paper feed path 33. The registration roller pair 35 temporarily stops the rotation of both rollers as soon as the recording paper P sent from the conveyance roller pair 34 is sandwiched between the rollers. Then, the recording paper P is sent out toward a later-described secondary transfer nip at an appropriate timing.

  Above each process unit 1Y, 1C, 1M, and 1K in FIG. 1, a transfer unit 40 is disposed to endlessly move the intermediate transfer belt 41 counterclockwise in FIG. In addition to the intermediate transfer belt 41, the transfer unit 40 includes a belt cleaning unit 42, a first bracket 43, a second bracket 44, and the like. Also provided are four primary transfer rollers 45Y, 45C, 45M, 45K, a secondary transfer backup roller 46, a drive roller 47, an auxiliary roller 48, a tension roller 49, and the like. The intermediate transfer belt 41 is endlessly moved counterclockwise in FIG. 1 by the rotational driving of the driving roller 47 while being stretched around these rollers. The four primary transfer rollers 45Y, 45C, 45M, and 45K sandwich the intermediate transfer belt 41 that moves endlessly between the photoreceptors 3Y, 3C, 3M, and 3K to form primary transfer nips, respectively. Yes. A transfer bias having a polarity opposite to that of the toner (in this embodiment, a positive polarity) is applied to the inner peripheral surface of the intermediate transfer belt 41. The intermediate transfer belt 41 sequentially passes through the primary transfer nips for Y, C, M, and K along with the endless movement thereof, and the photoreceptors 3Y, 3C, 3M, and 3K are disposed on the outer peripheral surface thereof. The upper color toner images are primarily transferred so as to overlap each other. As a result, a four-color superimposed toner image (hereinafter referred to as “four-color toner image”) is formed on the intermediate transfer belt 41.

  The secondary transfer backup roller 46 sandwiches the intermediate transfer belt 41 with the secondary transfer roller 50 disposed outside the loop of the intermediate transfer belt 41 to form a secondary transfer nip. The registration roller pair 35 described above feeds the recording paper P sandwiched between the rollers toward the secondary transfer nip at a timing at which the recording paper P can be synchronized with the four-color toner image on the intermediate transfer belt 41. The four-color toner image on the intermediate transfer belt 41 is affected by the secondary transfer electric field formed between the secondary transfer roller 50 to which the secondary transfer bias is applied and the secondary transfer backup roller 46, and the influence of the nip pressure. The secondary transfer is batch-transferred onto the recording paper P in the secondary transfer nip. Then, combined with the white color of the recording paper P, a full color toner image is obtained.

  Untransferred toner that has not been transferred to the recording paper P adheres to the intermediate transfer belt 41 after passing through the secondary transfer nip. This is cleaned by the belt cleaning unit 42. In the belt cleaning unit 42, the cleaning blade 42a is brought into contact with the front surface of the intermediate transfer belt 41, whereby the transfer residual toner on the belt is scraped off and removed.

  The first bracket 43 of the transfer unit 40 swings at a predetermined rotation angle about the rotation axis of the auxiliary roller 48 as the solenoid (not shown) is turned on / off. In the case of forming a monochrome image, the printer according to the present embodiment rotates the first bracket 43 a little counterclockwise in the drawing by driving the solenoid described above. By this rotation, the Y, C, and M primary transfer rollers 45Y, 45C, and 45M are revolved counterclockwise in the drawing around the rotation axis of the auxiliary roller 48, whereby the intermediate transfer belt 41 is moved to the Y direction. , C and M photoconductors 3Y, 3C and 3M. Of the four process units 1Y, 1C, 1M, and 1K, only the K process unit 1K is driven to form a monochrome image. Accordingly, it is possible to avoid exhaustion of the process units due to wastefully driving the process units for Y, C, and M during monochrome image formation.

  A fixing unit 60 as a fixing unit is disposed above the secondary transfer nip in the figure. The fixing unit 60 includes a pressure heating roller 61 that includes a heat source such as a halogen lamp, and a fixing belt unit 62. The fixing belt unit 62 includes a fixing belt 64, a heating roller 63 containing a heat source such as a halogen lamp, a tension roller 65, a driving roller 66, a temperature sensor (not shown), and the like. Then, the endless fixing belt 64 is endlessly moved in the counterclockwise direction in FIG. 1 while being stretched by the heating roller 63, the tension roller 65, and the driving roller 66. In the process of endless movement, the fixing belt 64 is heated from the back side by the heating roller 63. A pressure heating roller 61 that is driven to rotate in the clockwise direction in FIG. 1 is in contact with the surface of the fixing belt 64 that is heated in this manner. Thereby, a fixing nip where the pressure heating roller 61 and the fixing belt 64 abut is formed.

  Outside the loop of the fixing belt 64, a temperature sensor (not shown) is disposed so as to face the front surface of the fixing belt 64 with a predetermined gap, and the fixing belt 64 just before entering the fixing nip. Detect surface temperature. This detection result is sent to a fixing power supply circuit (not shown). The fixing power supply circuit performs on / off control of power supply to the heat generation source included in the heating roller 63 and the heat generation source included in the pressure heating roller 61 based on the detection result of the temperature sensor. As a result, the surface temperature of the fixing belt 64 is maintained at about 140.degree. The recording paper P that has passed through the secondary transfer nip is separated from the intermediate transfer belt 41 and then fed into the fixing unit 60. Then, in the process of being conveyed from the lower side to the upper side in the drawing while being sandwiched by the fixing nip in the fixing unit 60, the full-color toner image is applied to the recording paper P by being heated or pressed by the fixing belt 64. To settle.

  The recording paper P subjected to the fixing process in this manner is discharged outside the apparatus after passing between the rollers of the paper discharge roller pair 67. A stack unit 68 is formed on the upper surface of the housing of the printer main body, and the recording paper P discharged to the outside by the discharge roller pair 67 is sequentially stacked on the stack unit 68.

  Above the transfer unit 40, toner cartridges 72Y, 72C, 72M, and 72K, which are four toner containers that respectively store Y toner, C toner, M toner, and K toner, are disposed. The color toners in the toner cartridges 72Y, 72C, 72M, and 72K are appropriately supplied to the developing units 7Y, 7C, 7M, and 7K of the process units 1Y, 1C, 1M, and 1K by the toner replenishing device 70, respectively. The toner cartridges 72Y, 72C, 72M, and 72K are detachable from the printer main body independently of the process units 1Y, 1C, 1M, and 1K.

Hereinafter, toner replenishment control, which is a characteristic part of the present invention, will be described.
In this embodiment, the toner replenishment operation can be executed independently for each of yellow, magenta, cyan, and black, but the toner replenishment operations are the same. Therefore, in the following description, description of color-coded codes Y, C, M, and K is omitted.

FIG. 4 is a block diagram illustrating an example of a control system that executes toner supply control according to the present embodiment.
In the control system shown in FIG. 4, the toner density information is input from the toner density sensor 10 attached to the developing unit 7 to the control device 100 as the toner replenishment control means. Further, image information used for forming a latent image is input from the optical writing unit 20 to the control device 100. The control device 100 according to the present embodiment executes toner supply control using both FB supply control using toner density information and FF supply control using image information. Specifically, the control device 100 determines the amount of toner replenishment (required for restoring the current toner density to the target toner density based on the difference value between the toner density information from the toner density sensor 10 and the target toner density. FB replenishment amount) is calculated. Further, the control device 100 predicts the amount of toner consumed by the image forming operation based on the image information based on the image information from the optical writing unit 20, and suppresses a decrease in toner density due to the toner consumption. A necessary toner supply amount (FF supply amount) is calculated. The control device 100 adds the FB replenishment amount and the FF replenishment amount thus calculated, and calculates the added value as a target toner replenishment amount (hereinafter referred to as “target toner replenishment amount before correction”). . After calculating the pre-correction target toner supply amount, the control device 100 corrects the pre-correction target toner supply amount using the correction value stored in the storage device 101. Then, the toner replenishing device 70 is controlled so that the corrected target toner replenishment amount toner thus obtained is replenished to the developing unit 7.

FIG. 5 is a flowchart showing the flow of toner supply control in the present embodiment.
When a print job is input (S1), first, the toner density sensor 10 detects the toner density of the developer in the developing unit 7 (hereinafter referred to as “pre-image toner density”) (S2), and the detection result. The pre-image toner density value is stored in the storage device 101. In the present embodiment, the unit of toner concentration will be described by the mass ratio [wt%] of toner and carrier. Further, the amount of toner is expressed by mass [g], and will be described as a positive value when the toner is replenished and a negative value when the toner is consumed.

After the pre-image toner density is detected, an image forming operation according to the contents of the print job is started (S3), and the control device 100 forms a latent image for the current image formation on the photoreceptor 3. In this case, image information used by the optical writing unit 20 is acquired (S4). The acquired image information is stored in the storage device 101. Specifically, the image information here refers to, for example, the toner adhesion amount to the photoreceptor 3 per unit image area or the image area ratio per unit image area (when the predetermined toner adhesion amount is 1). The ratio of the amount of toner adhering to the unit image area). The unit image area here can be arbitrarily set, for example, the area of one sheet of paper on which an output image is formed, or the area of one region obtained by further dividing the area of one sheet of paper. Further, for example, the area of the output image output within a specified time may be the unit image area. However, if the unit image area is set to be large, for example, the area of a plurality of sheets of paper is set as the unit image area, the timing for obtaining the image information is delayed, and therefore the supply operation start timing of the FF supply control may be delayed. Therefore, it is desirable that the unit image area be as small as possible.
Note that the image information is any information as long as it is information that can specify the toner adhesion amount (toner amount consumed by the developing unit) that adheres to the photoreceptor by the image forming operation corresponding to the image information. Good.

Next, the control device 100 reads out from the storage device 101 correction values calculated by a method described later during the previous image forming operation (S5). Thereafter, the control device 100 uses the pre-image toner density detected by the toner density sensor 10 in S2 and the image information acquired in S4, and the toner replenishment amount necessary for setting the toner density to the target toner density. (Pre-correction target toner supply amount) is calculated. Then, using the correction value read in S5, the target toner supply amount before correction is corrected, and the final target toner supply amount is calculated (S6). In this embodiment, the final target toner replenishment amount is calculated from the following equation (1), but how to correct the pre-correction target toner replenishment amount using the correction value is appropriately determined.
Target toner supply amount = Target toner supply amount before correction x Correction value (1)

  The calculated final target toner replenishment amount is stored in the storage device 101. However, since the correction value has not yet been calculated in the first image forming operation, the storage device 101 stores the initial value of the correction value in advance. deep. At the time of the first image forming operation, the final target toner supply amount is calculated using this initial value. This initial value may be an arbitrary value, but if the initial value is too large or too small, the amount of toner replenishment will be excessive or too small during the first image forming operation. Therefore, it is desirable to set the initial value to a value in which the target toner supply amount before correction is directly calculated as the final target toner supply amount.

  When the calculation of the final target toner supply amount is completed, the control device 100 controls the toner supply operation of the toner supply device 70 so that the toner of the target toner supply amount is supplied to the developing unit 7 (S7). If there is an image to be formed next (Yes in S8), the process returns to S4, the image information is acquired, the target toner replenishment amount is calculated again, and the toner is replenished (S4 to S7). ). When returning to the process of S4, the image information of the next image is stored cumulatively with respect to the image information in the storage device 101. Further, the final target toner supply amount calculated using the image information of the next image is added to the target toner supply amount stored in the storage device 101.

  When there are no more images to be formed next (No in S8), the image forming operation is terminated (S9). The toner density sensor 10 detects the toner density of the developer in the developing unit 7 (hereinafter referred to as “post-image toner density”) (S 10), and stores the post-image toner density value that is the detection result. Store in the device 101. Thereafter, the control device 100 stores the four pieces of stored information stored in the storage device 101, specifically, the entire image information of the image formed during the current image formation, and the toner supply operation during the current image formation. Using the four stored information of the final target toner replenishment amount, the pre-image toner density and the post-image toner density used in the above, a correction value calculation process to be used next time is executed (S20).

Next, the correction value calculation process in this embodiment will be described.
FIG. 6 is a flowchart showing a flow of processing for calculating a target toner supply amount correction value in the present embodiment.
In the correction value calculation process of this embodiment, the control device 100 firstly stores four pieces of storage information stored in the storage device 101, that is, image information of an image formed during the immediately preceding image formation, and the immediately preceding image formation. Final target toner replenishment amount used for toner replenishment operation performed in the image, pre-image toner density detected before the start of the previous image formation, and post-image formation toner detected after the end of the previous image formation The density is acquired (S21).

  It can be considered that the total amount of toner adhering to the photoreceptor by the image forming operation during the immediately preceding image formation coincides with the toner consumption amount consumed by the developing unit 7 during the immediately preceding image forming. The image information stored in the storage device 101 is a cumulative value of all image information of images formed during the immediately preceding image formation. Therefore, the toner consumption amount consumed during the last image formation can be calculated from this image information. At this time, the toner consumption calculated from the image information coincides with the actual toner consumption actually consumed by the developing unit 7 during the previous image formation with high accuracy. Therefore, in this embodiment, the toner consumption calculated from the image information is calculated as the actual toner consumption (S22).

Further, from the following equation (2), from the difference value between the pre-image toner density and the post-image toner density stored in the storage device 101, before and after the previous image formation (before and after toner supply during the previous image formation). ) Can be directly grasped. If the toner density change amount [wt%] before and after the immediately preceding image formation can be grasped, the actual toner amount change amount [g] in the developing unit 7 before and after the immediately preceding image formation can be grasped from the following equation (3). it can. Therefore, from the difference value between the pre-image toner density and the post-image toner density stored in the storage device 101, the actual toner amount change amount (actual toner amount change amount) before and after the previous image formation is accurately determined. It can be calculated. In this embodiment, the toner amount change amount calculated from the difference value between the pre-image toner density and the post-image toner density is calculated as the actual toner amount change amount (S23).
Toner density change amount = Toner density after image formation-Toner density before image formation (2)
Actual toner amount change amount = toner density change amount × ΔTn (3)

  When calculating the toner amount change amount calculated from the difference value between the pre-image toner density and the post-image toner concentration, the toner amount change amount per unit toner concentration change amount [wt%] (unit toner amount change) Amount) ΔTn [g / wt%] must be specified in advance by experiments or the like. Strictly speaking, since the unit toner amount change amount ΔTn slightly varies depending on the toner concentration, it is desirable to prepare a plurality of unit toner amount change amounts ΔTn according to the toner concentration.

7 and 8 are graphs showing an example of increase and decrease of the toner amount in the developing unit from the start of the image forming operation to the end of the image forming operation.
Temporarily, during the last image formation, the change in the actual toner replenishment amount is as shown by the graph b in FIG. 7, and the change in the actual toner consumption is as shown by the graph c in FIG. In this case, the change amount of the actual toner amount during the previous image formation is shown by the graph indicated by symbol a in FIG.
On the other hand, if the actual toner replenishment amount changes as shown by the graph indicated by symbol e in FIG. 8 and the actual toner consumption amount changes by the graph indicated by symbol f in FIG. In the case where the actual toner amount is changed, the change amount of the actual toner amount during the immediately preceding image formation is indicated by a graph d in FIG.

The actual toner amount change amount indicates an actual increase / decrease amount of the toner in the two-component developer in the developing unit during the previous image formation. That is, the actual toner amount change amount corresponds to the total value of the toner replenishment amount actually replenished during the immediately preceding image formation and the toner consumption amount actually consumed during the immediately preceding image formation. It can be expressed as (4). Further, when the equation (4) is modified, the following equation (5) is obtained.
Actual toner amount change amount = Actual toner replenishment amount + Actual toner consumption amount (4)
Actual toner supply amount = Actual toner amount change amount-Actual toner consumption amount (5)

  As described above, the actual toner consumption amount is calculated from the image information during the previous image formation in S22, and the actual toner amount change amount is calculated from the toner density before and after image formation in S24. Therefore, in the present embodiment, an appropriate actual toner supply amount can be calculated even when toner supply is performed in parallel with the image forming operation (image forming operation) (S24).

  On the other hand, the target toner replenishment amount stored in the storage device 101 is the same as the target toner replenishment amount when the toner replenishment device 70 can replenish the development unit 7 with the target toner replenishment amount. It matches the amount of toner replenished actually. However, since there are individual differences in the toner replenishing device 70, the toner replenishing device 70 cannot always replenish the developing unit 7 with the toner according to the target toner replenishment amount, and a replenishment error occurs. Therefore, the target toner replenishment amount stored in the storage device 101 is determined as the toner replenishment amount estimated to have been replenished to the developing unit 7 during the immediately preceding image formation (hereinafter referred to as “estimated toner replenishment amount”). S25).

Thereafter, the control device 100 calculates a ratio between the actual toner replenishment amount and the estimated toner replenishment amount as a replenishment error ratio from the following equation (6) (S26). The actual toner replenishment amount is a value representing the toner replenishment amount actually replenished during the previous image formation, and the estimated toner replenishment amount is the calculated toner replenishment when the toner replenishing device 70 is properly replenished. A value indicating the quantity. Accordingly, the replenishment error ratio calculated here is a value indicating a replenishment error due to individual differences of the toner replenishing device 70.
Replenishment error ratio = actual toner replenishment amount / estimated toner replenishment amount (6)

In the present embodiment, the control device 100 calculates a correction value by the following equation (7) from the replenishment error ratio calculated by the above equation (6) (S27). The correction value calculated in this way is overwritten with the correction value stored in the storage device 101, and when calculating the target toner replenishment amount for the next and subsequent image formation as shown in the above equation (1). Used for. After calculating the correction value, the control device 100 resets four pieces of stored information in the storage device (S28).
Correction value = 1 / correction error ratio (7)

  According to the present embodiment, the correction value can be calculated in parallel with the image forming operation without providing a dedicated time for calculating the correction value (a time during which the image forming operation cannot be performed). Therefore, the replenishment error can be corrected without increasing the waiting time for the image forming operation. Further, in the case of a conventional apparatus that requires a dedicated time for calculating a correction value, as shown in FIG. 9 (a), it is periodically performed between image forming (print job) and image forming. While it is necessary to include a dedicated time for calculating the correction value, in the case of the present embodiment, such a dedicated time is provided between image formations as shown in FIG. 9B. The correction value can be calculated without entering. As a result, when correction values are calculated at the same frequency while performing the same image formation as the conventional apparatus, the time required for all image formation can be shortened by ΔTime at the maximum, as shown in FIG.

FIG. 10 is an explanatory diagram for explaining the effect obtained by correcting the target toner supply amount with the correction value.
When the target toner replenishment amount before correction is as indicated by the symbol n in FIG. 10, when the toner replenishment amount (unit toner replenishment amount) per unit replenishment operation of the toner replenishing device 70 is larger than the reference value, before correction. When the replenishment operation for replenishing the target toner replenishment amount n is executed, the actual toner replenishment amount is as indicated by reference numeral 1 in FIG. On the other hand, when the unit toner replenishment amount of the toner replenishing device 70 is smaller than the reference value, when a replenishment operation for replenishing the toner of the target toner replenishment amount n before correction is executed, the actual toner replenishment amount is as indicated by the symbol m in FIG. It will be something. Here, the supply error ratio calculated in the former case is L, and the supply error ratio calculated in the latter case is M.

  Since the actual toner replenishment amount l> the estimated toner replenishment amount n, the replenishment error ratio L takes a value larger than 1 from the above equation (6). The replenishment error ratio L indicates that the unit toner replenishment amount of the actual toner replenishing device 70 is L times the reference value. On the other hand, the correction value at this time is the reciprocal of the replenishment error ratio L as shown in the above formula (7), and therefore the correction value is smaller than 1. Then, the correction value (1 / L) is multiplied by the target toner replenishment amount n before correction to correct the target toner replenishment amount, so that the actual unit toner replenishment amount of the toner replenishing device 70 is equal to the reference value. Thus, the actual toner replenishment amount l can be reduced. That is, by executing a replenishment operation to replenish the target toner replenishment amount of toner after correction with the correction value (1 / L), the actual toner replenishment amount of the toner replenishing device 70 having the replenishment error ratio L can be obtained. The toner replenishment amount can be matched. The pre-correction target toner replenishment amount indicates the toner replenishment amount necessary for setting the toner density to the target toner density. Therefore, even in the toner replenishing device 70 having the replenishment error ratio L, by correcting the target toner replenishment amount with the correction value (1 / L), the amount of toner necessary for setting the toner concentration to the target toner concentration Can be replenished properly.

  Similarly, in the case of the replenishment error ratio M, the target toner replenishment amount is corrected by the correction value (1 / M) to appropriately replenish the amount of toner necessary for setting the toner concentration to the target toner concentration. Can do.

  Actually, the amount of toner consumed during image formation, that is, the amount of toner adhering to the photoreceptor 3, has relatively long-term fluctuations due to individual differences in the developing unit 7 and the photoreceptor 3, the usage environment, and the like. There is a case. When such a long-term fluctuation exists, an error corresponding to the fluctuation is added to the actual toner replenishment amount calculated by the above equation (5). Therefore, when such a long-term fluctuation in the toner consumption exists, image density adjustment control is executed at a predetermined timing to adjust the toner adhesion amount on the photosensitive member 3 and the long-term fluctuation. Is preferably suppressed. In the image density adjustment control, for example, a plurality of toner patches are formed on the photoconductor 3 so that the image densities are different from each other, and the toner adhesion amount on the photoconductor or the intermediate transfer belt is determined for the plurality of toner patches. It is detected by the adhesion amount detection means. Based on the detection result, the charging bias applied to the charging device 5, the intensity of the laser light irradiated from the optical writing unit 20, and the developing sleeve 15 of the developing unit 7 are applied so as to obtain the target image density. Adjust the development bias. At this time, in the image formation immediately after the image density adjustment control and the image formation after a while have passed since the image density adjustment control, the toner consumption amount is more immediately after the image density adjustment control. Small fluctuation. For this reason, it is desirable that the correction value calculation process described above is performed by image formation immediately after image density adjustment control is performed.

  Further, although the toner consumption varies somewhat depending on the difference in toner density, the replenishment error caused by the variation in toner consumption is much smaller than the replenishment error due to the individual difference of the toner replenishing device 70 described above. Therefore, the replenishment error ratio calculated from the above equation (6) can be regarded as a replenishment error due to individual differences in the toner replenishing device 70. Therefore, by using the correction value calculated by the above formula (7), the replenishment error due to the individual difference of the toner replenishing device 70 can be sufficiently corrected.

  When toner supply is not performed during the immediately preceding image formation, the actual toner supply amount and the estimated toner supply amount are both zero, and the correction value calculation process is not required. Therefore, the correction value calculation process is performed when toner is replenished at least once during image formation, and is not performed when toner replenishment is not performed once during image formation. Good.

  In addition, when the replenishment drive time during image formation is short, even in the same toner replenishing device 70, the actual toner replenishment amount varies greatly due to the influence of the environment and toner state at that time. There is. Therefore, a time (unstable replenishment time) until the toner amount (unit toner replenishment amount) to be replenished per unit replenishment operation is stabilized in advance by an experiment or the like is obtained, and the correction value calculation process is the unstable replenishment time. It is desirable to perform when a replenishment operation exceeding the above is performed.

  In the present embodiment, the toner replenishing devices 70Y, 70C, 70M, and 70K are individually provided for the developing units 7Y, 7C, 7M, and 7K of the respective colors. The toner replenishing devices 70Y, 70C, 70M, and 70K have different unit toner replenishment amounts due to individual differences. For this reason, it is desirable that the correction value for correcting the replenishment error due to the difference in unit toner replenishment amount due to the individual difference is calculated individually for each toner replenishing device.

[Modification 1]
Next, a modified example of the toner replenishment control in the above embodiment (hereinafter, this modified example is referred to as “modified example 1”) will be described.
In the toner replenishment control of the above embodiment, the controller 100 calculates the replenishment error ratio from the above equation (6), and calculates the reciprocal of the replenishment error ratio as a correction value. On the other hand, in the first modification, the correction value is calculated using the correction value calculation table shown in Table 1 below.

FIG. 11 is a flowchart showing a flow of correction value calculation processing in the first modification.
In the first modification, when the actual toner replenishment amount and the estimated toner replenishment amount are obtained (S31 to S35) as in S21 to S25 of the above embodiment, the control device 100 calculates the actual toner replenishment from the following equation (8). The difference between the amount and the estimated toner supply amount is calculated as a supply amount error (S36).
Supply amount error = Actual toner supply amount-Estimated toner supply amount (8)

After calculating the replenishment amount error in this way, the control device 100 refers to the correction value calculation table as shown in Table 1 stored in advance in the storage device 101, and corresponds to the calculated replenishment amount error. The correction value correction parameter is read (S37). Then, the control device 100 calculates a correction value using the read correction value correction parameter from the following equation (9) (S38). The correction value calculated in this way is overwritten on the correction value stored in the storage device 101. After calculating the correction value, the four pieces of stored information in the storage device are reset as in the above embodiment (S39).
Correction value = Correction value before correction + Correction value correction parameter (9)

  Each correction value correction parameter described in the correction value calculation table shown in Table 1 has a value determined in advance for each replenishment amount error. For example, when the replenishment amount error is 0, proper toner replenishment can be realized with the current correction value, so there is no need to correct the correction value. Therefore, the correction value correction parameter in this case may be 0. On the other hand, when the replenishment amount error is smaller than 0, even if the target toner replenishment amount is corrected with the current correction value, the actually replenished toner replenishment amount is smaller. Therefore, the correction value correction parameter P2 in this case is a positive value. On the other hand, when the replenishment amount error is larger than 0, even if the target toner replenishment amount is corrected with the current correction value, the toner replenishment amount actually replenished is larger. Therefore, the correction value correction parameter P1 in this case is a negative value. However, if the corrected correction value becomes a negative value, the target toner replenishment amount after correction according to the above equation (1) becomes a negative value, so it is preferable to put a condition that correction value ≧ 0.

  Here, since the absolute values of the correction value correction parameters P1 and P2 directly become the correction value correction resolution, the smaller the value is set, the more accurately the toner replenishment amount can be corrected. However, in the first modification, the correction value is increased / decreased depending on whether the replenishment amount error is positive or negative. Therefore, if the absolute value of the correction value correction parameters P1 and P2 is small, if the replenishment amount error is large, the error is corrected. Takes time. Therefore, it is preferable to set the absolute values of the correction value correction parameters P1 and P2 in the first modification as large as possible within a range in which a necessary resolution can be obtained.

  In the above-described embodiment, an appropriate correction value can be calculated by a single correction value calculation process. However, in the first modification, an appropriate correction value is normally calculated through a plurality of correction value calculation processes. However, when the toner consumption amount or the toner supply amount temporarily shows an abnormal value due to, for example, a failure of the developing unit 7 or the toner supply device 70, an abnormal correction value is calculated as it is in the above embodiment. Inappropriate toner supply may be performed. On the other hand, according to the first modification, even when the toner consumption amount and the toner replenishment amount temporarily show abnormal values, the calculated correction value hardly changes and inappropriate toner replenishment is performed. There is little possibility of being.

[Modification 2]
Next, another modified example of the toner replenishment control in the above embodiment (hereinafter, this modified example is referred to as “modified example 2”) will be described.
Also in the second modification, the correction value is calculated using the correction value calculation table as in the first modification. In the second modification, the number of correction value correction parameters corresponding to the replenishment amount error is the above-described modification. More than Example 1. Specifically, in the first modification, the number of correction value correction parameters is three, whereas in the second modification, as shown in Table 2 below, the number of correction value correction parameters is five. It is.

  Also in the second modification, the difference between the actual toner replenishment amount and the estimated toner replenishment amount is calculated as a replenishment amount error from the above formula (8), and a correction value correction parameter corresponding to the replenishment amount error is stored in the storage device 101 in advance. It reads out from the stored correction value calculation table as shown in Table 2 above. Then, the control device 100 calculates a correction value using the read correction value correction parameter from the above equation (9).

  The correction value correction parameters P3 and P4 when the correction amount error is larger than 0 are set to positive values as in the first modification. However, the absolute value of the correction value correction parameter P4 corresponding to the case where the correction amount error is relatively small is smaller than the absolute value of the correction value correction parameter P3 corresponding to the case where the correction amount error is relatively large. Set. On the other hand, the correction value correction parameters P5 and P6 when the correction amount error is smaller than 0 are also set to negative values as in the first modification. However, the absolute value of the correction value correction parameter P5 corresponding to the case where the correction amount error is relatively small is smaller than the absolute value of the correction value correction parameter P6 corresponding to the case where the correction amount error is relatively large. Set.

  As described in the first modification, the smaller the absolute value of the correction value correction parameter used for calculating the correction value, the higher the correction value correction resolution and the higher the correction accuracy of the toner replenishment amount. The time required for correction in the case of large is long. Conversely, the larger the absolute value of the correction value correction parameter used when calculating the correction value, the shorter the time required for correction when the correction amount error is large, but the correction value correction resolution becomes lower and the toner supply amount is reduced. The correction accuracy becomes low. As in the second modification, the absolute values of the correction value correction parameters P4 and P5 corresponding to the case where the correction amount error is relatively small are used as the absolute values of the correction value correction parameters P3 and P6 corresponding to the case where the correction amount error is relatively large. By setting the value to be smaller than the absolute value, the time required for correction when the correction amount error is large can be shortened, and when the correction amount error is small, the toner supply amount can be corrected with high resolution.

  In the second modification, the number of correction value correction parameters corresponding to the replenishment amount error is five. However, this number can be set arbitrarily, and the number of correction value error parameters can be further increased. May be increased.

[Modification 3]
Next, still another modified example of the toner replenishment control in the above embodiment (hereinafter, this modified example is referred to as “modified example 3”) will be described.
In the above-described embodiment, it has been described that the correction value calculation process is preferably performed when the time of toner replenishment operation (replenishment drive time) performed during one image formation exceeds the unstable replenishment time. However, in the third modification, even when the replenishment drive time of the toner replenishment operation performed during one image formation is less than the unstable replenishment time, the total replenishment drive of the toner replenishment operation performed during a plurality of image formations. If the time exceeds the unstable replenishment time, a correction value is calculated. In the following description, the correction value calculation process will be described in the case where the correction value calculation process of the above-described embodiment is adopted, but the correction value calculation process described in Modification 1 and Modification 2 is adopted. Alternatively, other correction value calculation processing may be employed.

FIG. 12 is a flowchart showing the flow of toner supply control in the third modification.
In the third modification, when a print job is input (S1), it is first determined whether or not a correction value has been calculated at the previous image formation (S41). If it is determined in this determination that the correction value has been calculated at the time of the previous image formation (Yes in S41), the storage information for correction value calculation in the storage device 101 has been reset in S28. After detecting the previous toner density (S2), the image forming operation is started (S3). On the other hand, when it is determined that the correction value is not calculated at the previous image formation (No in S41), the image forming operation is started without detecting the pre-image toner density (S3). The operation during image formation in the third modification is the same as that in the above embodiment (S4 to S8).

  In the third modification, when the image forming operation is completed (S9), a replenishment drive time for toner replenishment performed during the current image formation is calculated (S42). Then, the calculated replenishment drive time is added to the total replenishment drive time stored in the storage device 101. Thereafter, it is determined whether or not the total replenishment drive time exceeds a predetermined unstable replenishment time (S43). When the total replenishment drive time exceeds the unstable replenishment time (Yes in S43), after the toner density after image formation is detected (S10), correction value calculation processing is executed (S10) (S10). S20). This correction value calculation process is the same as the correction value calculation process of the above-described embodiment shown in FIG. 6, but in S28, in addition to the four pieces of stored information in the storage device 101, the total replenishment drive time is also reset.

  On the other hand, when the total replenishment drive time does not exceed the unstable replenishment time (No in S43), the process ends without calculating a correction value. At this time, the replenishment drive time for toner replenishment performed during the current image formation is added to the total replenishment drive time of the storage device 101 and remains. Even if the replenishment drive time at the next image formation does not exceed the unstable replenishment time, the replenishment drive time is added to the total replenishment drive time. Correction value calculation processing is executed.

As described above, the printer according to the present embodiment (including the first to third modifications) includes the photosensitive member 3 as a latent image carrier and the latent image formation that forms a latent image on the photosensitive member 3 based on the image information. An optical writing unit 20 as a means, and a two-component developer containing toner and carrier are circulated and conveyed along the developer circulation path, and in the developer supply and conveyance path that bears a part of the developer circulation path The two-component developer being conveyed is supplied to the surface of the developing roll 12 as a developer carrying member, and the two-component developer carried on the surface of the developing roll 12 is conveyed to the development region by the rotation of the developing roll 12. The developing unit 7 as a developing device that develops the latent image by adhering the toner in the two-component developer to the latent image on the surface of the photosensitive member in the developing area, and development at a predetermined supply position on the developer circulation path To two-component developer in unit 7 A toner replenishing device 70 serving as a toner replenishing unit that performs toner replenishment, a target toner replenishment amount necessary to set the toner concentration in the two-component developer to the target toner concentration, and the calculated target toner replenishment amount of toner are calculated. And a control device 100 as toner replenishment control means for controlling the toner replenishing device 70 so as to be replenished, and finally the toner image formed on the photoreceptor 3 by being developed by the developing unit 7 is finally obtained. An image forming apparatus that forms an image by transferring it onto a recording material. The printer further includes a toner concentration sensor 10 as a toner concentration detection means for detecting the toner concentration of the two-component developer passing through a predetermined toner concentration detection portion on the developer circulation path. The control device 100 determines the pre-image toner density and the post-image toner density, which are the toner concentrations of the two-component developer before and after the toner supply when the toner supply device 70 supplies the toner in parallel with the image forming operation. The toner density sensor 10 detects the toner density difference before and after the toner replenishment (pre-image toner density−post-image toner density) and detects the post-image toner density from the time of detecting the pre-image toner density. Correction value for acquiring the image information in the image forming operation until the time, and correcting the target toner replenishment amount from the toner density difference between the pre-image toner density and the post-image toner density, and the acquired image information It functions as a correction value calculation processing means for performing a correction value calculation process for calculating. Then, the control device 100 controls the toner replenishing device 70 so that the target toner replenishment amount corrected with the calculated correction value is replenished. With such a configuration, the correction value can be calculated in parallel with the image forming operation without providing a dedicated time (a time during which the image forming operation cannot be performed) for calculating the correction value. Therefore, the replenishment error can be corrected without increasing the waiting time for the image forming operation.
Further, in the present embodiment (including the above-described modification examples 1 to 3), a plurality of toner patches are formed on the photosensitive member 3, and the plurality of toner patches on the photosensitive member 3 or the photosensitive member 3 are transferred to the transfer body. An image on which a toner adhesion amount of a plurality of toner patches after being transferred onto a certain intermediate transfer belt 41 is detected by a toner adhesion amount detection means, and image density adjustment control for obtaining a target image density based on the detection result is executed. It is preferable to provide density adjustment control means and execute the correction value calculation process in parallel with the image forming operation immediately after the image density adjustment control is executed. In this case, an appropriate correction value can be calculated even if there is a relatively long-term variation in the amount of toner adhesion due to individual differences between the developing unit 7 and the photoreceptor 3 or the usage environment.
In addition, as described in the above embodiment, when the toner supply by the toner supply device 70 is completed after the toner supply by the toner supply device 70 is started and before the predetermined unstable supply time elapses. The correction value calculation process may be performed when the toner replenishment by the toner replenishing device 70 ends after the unstable replenishment time has elapsed without performing the correction value calculation process. As a result, it is possible to avoid a situation in which an inappropriate correction value is calculated based on information during an unstable replenishment time in which a variation in toner replenishment amount becomes large.
On the other hand, as in Modification 3 above, when the total time of toner replenishment by the toner replenishing device 70 is less than the predetermined unstable replenishment time, the correction value calculation process is not performed, and the unstable replenishment time is exceeded. In some cases, correction value calculation processing may be performed. In this case, it is possible to avoid a situation in which a new correction value is not calculated indefinitely by repeating image formation such that the replenishment drive time is less than the unstable replenishment time.
Further, in the present embodiment (including the above-described modifications 1 to 3), a plurality of toner replenishing devices 70 are provided, and toner replenishment control is individually performed for each toner replenishing device 70, and each toner replenishing device is performed. The correction value calculation process is performed individually for 70. Thereby, the replenishment error based on the individual difference of the plurality of toner replenishing devices 70 mounted on the same printer can be corrected.
In the present embodiment (including the above-described modification examples 1 to 3), the correction value calculation process is repeatedly performed after a predetermined period, so that the toner replenishment error can be corrected with an appropriate correction value according to the latest situation. it can. This predetermined period may be a predetermined fixed period, or may be a period that is appropriately determined according to the use environment and the accumulated toner consumption.

DESCRIPTION OF SYMBOLS 3 Photoconductor 7 Developing unit 10 Toner density sensor 20 Optical writing unit 41 Intermediate transfer belt 70 Toner replenishing device 72 Toner cartridge 100 Control device 101 Storage device

JP 2007-304524 A

Claims (7)

A latent image carrier;
Latent image forming means for forming a latent image on the latent image carrier based on image information;
The two-component developer carried on the surface of the developer carrier is transported to the development area by the rotation of the developer carrier, and the toner in the two-component developer is transferred to the latent image carrier surface on the surface of the latent image carrier. A developing device that adheres to the image and develops the latent image;
Toner replenishing means for replenishing toner to the two-component developer in the developing device;
Toner replenishment control for calculating the target toner replenishment amount necessary to set the toner concentration in the two-component developer to the target toner concentration and controlling the toner replenishing means so that the calculated target toner replenishment amount is replenished. Means and
In an image forming apparatus for forming an image by finally transferring a toner image formed on the latent image carrier by being developed by the developing device onto a recording material,
Toner density detecting means for detecting the toner density of the two-component developer in the developing device;
In parallel with the image forming operation during the image forming operation , the toner concentration of the two-component developer before and after image formation is detected by the toner concentration detection unit before and after the toner supply when the toner supply unit supplies toner. After calculating the toner density difference before and after the image formation before and after the toner replenishment, and after the image formation after the toner replenishment by the toner density detection means from the time of the toner density detection before the toner replenishment by the toner density detection means Correction value for acquiring image information in an image forming operation until the time of toner density detection, and correcting the target toner replenishment amount at the next and subsequent image formation from the toner density difference and the image information after the image forming operation is completed Correction value calculation processing means for performing correction value calculation processing for calculating
The image forming apparatus, wherein the toner replenishment control unit controls the toner replenishment unit so that a target toner replenishment amount of toner corrected by the correction value calculated by the correction value calculation processing unit is replenished. The image forming apparatus according to claim 1.
Toner of the plurality of toner patches after forming a plurality of toner patches on the latent image carrier and transferring the plurality of toner patches on the latent image carrier or the latent image carrier onto the transfer target Image density adjustment control means for detecting the adhesion amount by the toner adhesion amount detection means and executing image density adjustment control for obtaining a target image density based on the detection result;
The image forming apparatus characterized in that the correction value calculation processing means executes the correction value calculation processing in parallel with an image forming operation during an image forming operation immediately after the image density adjustment control is executed. The image forming apparatus according to claim 1 or 2,
The correction value calculation processing unit performs the correction when the toner supply by the toner supply unit is completed after the toner supply by the toner supply unit is started and before a predetermined unstable supply time elapses. An image forming apparatus, wherein the correction value calculation process is performed when the toner supply by the toner supply unit ends after the unstable supply time has elapsed without performing the value calculation process. The image forming apparatus according to claim 1 or 2,
The correction value calculation processing means does not perform the correction value calculation processing when the total time of toner replenishment by the toner replenishment means is less than a predetermined unstable replenishment time, An image forming apparatus characterized in that the correction value calculation processing is performed in some cases. The image forming apparatus according to any one of claims 1 to 4, wherein:
A plurality of toner replenishing means;
The toner replenishment control means individually controls the plurality of toner replenishment means.
The image forming apparatus, wherein the correction value calculation processing unit performs the correction value calculation processing individually for the plurality of toner supply units. The image forming apparatus according to any one of claims 1 to 5,
The image forming apparatus, wherein the correction value calculation processing means repeatedly performs the correction value calculation processing after a predetermined period. The image forming apparatus according to claim 6.
The image forming apparatus according to claim 1, wherein the predetermined period is a predetermined fixed period or a period determined according to a use environment or an accumulated toner consumption amount.

Images