JP6217376B2 - Toner density control device, toner adhesion amount control device, and image forming apparatus - Google Patents

Description

  The present invention relates to a toner density control device used in an image forming apparatus such as a copying machine, a printer, and a facsimile, a toner adhesion amount control device including the same, and an image forming device including the same.

  An image forming apparatus having a developing device that develops with a toner using a two-component developer composed of toner and carrier for a latent image formed on the surface of the image bearing member. It is necessary to set the toner adhesion amount on the body or the toner charge amount (toner charge amount) to a target value.

  In order to measure the toner adhesion amount, a toner image for measurement is formed on the photosensitive member and detected. However, it is not preferable because the toner which is the user's asset is used for measuring the toner adhesion amount. In addition, while a toner image for measuring the toner adhesion amount is being formed, there is a problem in that productivity is reduced because normal printing cannot be performed.

  The toner charge amount is an electric force for bonding the carrier of the developer and the toner. Therefore, basically, the carrier and toner set are in an electrically neutral state. Here, the toner charge amount can be measured for the first time by forcibly peeling the carrier and the toner and measuring the charge. However, since the developer is individually taken out and measured, it is difficult to measure the toner charge amount online. Therefore, a method for estimating the toner charge amount in the developing device from the image density and the toner density is known.

  However, this method of estimating the toner charge amount has a problem that the estimation accuracy is not high and the toner density cannot be optimally controlled for correction.

  Further, as an alternative means for measuring the toner charge amount, a method of detecting the toner density of the developing device and correcting and controlling the toner density is already known. According to the method for correcting and controlling the toner density, the toner density can be corrected to a desired value.

  However, this toner density correction control system does not directly detect the toner charge amount. For this reason, there is a problem that image formation cannot be optimally performed by the method of correcting and controlling the toner density. In particular, the condition having a great influence is a state immediately after starting at the beginning of the holiday. In this case, the toner density is physically the same in the state where the machine has been used continuously and the state immediately after the first startup after the holiday. However, since the toner charge amounts are completely different, if the machine is operated under the same image forming conditions, the quality of the printed image will be greatly different.

  Also known is a method in which after development, the toner adhesion amount on the photosensitive member or transfer member is detected, the toner charge amount in the developing device is predicted from the detected value, and correction control is performed.

  However, since this correction control method includes various error factors in the development process, there is a problem that it is difficult to accurately predict the toner charge amount. Even if the prediction can be made with high accuracy, the toner charge amount is unknown until the process proceeds to the step of detecting the toner adhesion amount. Therefore, there is a problem that the image quality cannot be guaranteed for the time until the step of detecting the toner adhesion amount.

  On the other hand, image forming apparatuses that stabilize the image quality in consideration of the toner charge amount are also known (see, for example, Patent Documents 1 to 4).

  The image forming apparatus described in Patent Document 1 is configured to control the volume of the developer rising portion in the developing unit when the toner density is substantially within a predetermined range and the image density decreases. By having such a configuration, it is possible to prevent a decrease in image density due to a decrease in the toner charge amount of the developer.

  However, the image forming apparatus described in Patent Document 1 cannot know the change in the toner charge amount until the image density is lowered. Therefore, there is a problem that the image quality cannot be guaranteed for the time until the image density is lowered.

  The image forming apparatus described in Patent Document 2 has a configuration in which a magnetic sensor is added to detect a change in toner charge amount and image forming conditions are controlled in accordance with the change in toner charge amount. Specifically, the image forming conditions are controlled by detecting a moisture absorption state of the developer, that is, a change in toner charge amount, based on a deviation from a predetermined value such as a table measured and stored in advance. With such a configuration, a desirable image can be formed even if the environment changes.

  However, the image forming apparatus described in Patent Document 2 does not detect the value of the toner charge amount. Specifically, only a change in toner charge amount, particularly a difference from a predetermined value is detected. Therefore, the image forming conditions cannot always be optimized.

  The image forming apparatus described in Patent Document 3 is configured to correct the predicted toner charge amount from the toner density in the developing device and the toner density of the toner patch formed on the photosensitive member. With such a configuration, it is possible to grasp the toner charge amount of the developer and prevent the image density from being lowered.

  However, the image forming apparatus described in Patent Document 3 does not measure and measure the toner charge amount. Therefore, it is impossible to grasp the accurate toner charge amount. Furthermore, in order to correct from the toner density of the image actually formed on the photoreceptor, it is necessary to create a patch image. Therefore, the toner which is the user's asset is used for the prediction of the toner adhesion amount, which is not preferable.

  The image forming apparatus described in Patent Document 4 has a configuration in which a sensor for detecting the temperature in the developing device is provided, and the change amount of the toner charge amount is calculated from the temperature change amount and corrected. With such a configuration, it is possible to prevent a decrease in image density by calculating a toner charge amount change by grasping a temperature change in advance.

  However, the image forming apparatus described in Patent Document 4 cannot always know the toner charge amount in various situations. In addition, the change in toner charge amount due to changes in humidity, other environmental changes, and usage conditions cannot be calculated, and an accurate toner charge amount cannot be grasped.

  An object of the present invention is to provide a toner density control device having a simple configuration capable of providing desired image quality in consideration of the toner charge amount in the developing device.

In order to solve the above-described problem, a toner concentration control device according to claim 1 of the present invention provides:
In a toner concentration control device for controlling the amount of toner replenished to the developing means by the toner replenishing means based on information obtained from the toner density detecting means for detecting the toner density in the developing means main body using the magnetic permeability.
The developing unit includes a developing unit that develops the latent image formed on the image carrier with a two-component developer, and a conveying unit that conveys the two-component developer in the developing unit main body. A device,
At least two toner density detecting means are in the vicinity of the conveying means, and in the conveying direction in which the conveying means conveys the two-component developer, downstream of the position where the toner is replenished from the toner replenishing means. And the developer is disposed upstream of the position where the latent image on the image carrier is developed by a two-component developer,
First calculating means for calculating a toner charge amount from a difference between detection results of the at least two toner density detecting means;
The image forming apparatus includes a first control unit that controls a toner amount to be supplied from the toner supply unit to the developing unit based on calculation information of the first calculation unit.

  According to the present invention, it is possible to provide a toner density control device having a simple configuration capable of providing desired image quality in consideration of the toner charge amount in the developing device.

1 is a configuration diagram schematically showing an overall configuration of an image forming apparatus according to a first embodiment of the present invention. FIG. 2 is a configuration diagram schematically illustrating an image forming unit of the image forming apparatus illustrated in FIG. 1. FIG. 2 is a configuration diagram schematically illustrating an image forming unit of the image forming apparatus illustrated in FIG. 1. FIG. 2 is a configuration diagram schematically showing a developing unit of the image forming apparatus shown in FIG. 1. FIG. 2 is a perspective view schematically showing a toner supply device of the image forming apparatus shown in FIG. 1. FIG. 2 is a configuration diagram schematically showing a toner replenishing device and its periphery of the image forming apparatus shown in FIG. 1. FIG. 2 is an explanatory diagram schematically showing toner density control means of the image forming apparatus shown in FIG. 1. 3 is a graph for explaining a unit supply pattern of a toner supply device of the image forming apparatus shown in FIG. 1. FIG. 2 is an explanatory diagram schematically showing toner density control means of the image forming apparatus shown in FIG. 1. FIG. 2 is an explanatory diagram schematically showing toner density control means of the image forming apparatus shown in FIG. 1. FIG. 2 is an explanatory diagram illustrating a toner concentration sensor that uses the magnetic permeability of the image forming apparatus illustrated in FIG. 1. FIG. 2 is an explanatory diagram illustrating a toner concentration sensor of the image forming apparatus illustrated in FIG. 1. 3 is a graph illustrating sensor output of a toner density sensor of the image forming apparatus illustrated in FIG. 1. 2 is a graph showing a relationship between a difference in output value of a toner density sensor of the image forming apparatus shown in FIG. 1 and a toner charge amount. FIG. 2 is an explanatory diagram schematically illustrating a first pressure adjusting unit of the image forming apparatus illustrated in FIG. 1. FIG. 3 is an explanatory diagram schematically showing a second pressure adjusting unit of the image forming apparatus shown in FIG. 1. FIG. 6 is an explanatory diagram schematically showing a third pressure adjusting unit of the image forming apparatus shown in FIG. 1. FIG. 8 is an explanatory diagram schematically showing a fourth pressure adjusting unit of the image forming apparatus shown in FIG. 1. FIG. 7 is an explanatory diagram schematically showing a fifth pressure adjusting unit of the image forming apparatus shown in FIG. 1. FIG. 5 is a configuration diagram schematically showing an image forming unit of an image forming apparatus according to a second embodiment of the present invention. FIG. 21 is a graph for explaining the sensor output of the toner density sensor of the image forming apparatus shown in FIG. 20. FIG. FIG. 2 is an explanatory diagram illustrating a toner adhesion amount of the image forming apparatus illustrated in FIG. 1. 3 is a graph for explaining a relationship between a toner charge amount of the image forming apparatus shown in FIG. 1 and a toner amount entering a developing potential. FIG. 2 is an explanatory diagram schematically illustrating a toner adhesion amount control device of the image forming apparatus illustrated in FIG. 1. FIG. 6 is a diagram illustrating a relationship between a toner charge amount and a leaving time.

  Hereinafter, a first embodiment of the present invention will be described in detail with reference to the drawings. As shown in FIG. 1, an electrophotographic printer (hereinafter simply referred to as “printer”) as an image forming apparatus according to the present embodiment includes yellow, cyan, magenta, and black (hereinafter referred to as Y, C, M, and K). 4) image forming units 1Y, 1C, 1M, and 1K. 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, and in the following, Y, C, The description will be made with the M and K subscripts omitted as appropriate.

  Below the image forming units 1Y, 1C, 1M, and 1K in the drawing, an optical writing unit 20 as an exposure unit is disposed. The optical writing unit 20 irradiates the photoreceptors 3Y, 3C, 3M, and 3K as image carriers of the image forming units 1Y, 1C, 1M, and 1K with the laser light L emitted based on the image information. Thereby, electrostatic latent images (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 this 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 the figure by a driving means (not shown), the uppermost recording paper P in the first paper feed cassette 31 extends vertically on the right side of the cassette in the figure. The paper is discharged toward the paper feed path 33 arranged to exist. Further, when the second paper feed roller 32a is driven to rotate counterclockwise in the drawing by a driving means (not shown), the uppermost recording paper P in the second paper feed cassette 32 is discharged toward the paper feed path 33. . 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. 33 is conveyed from the lower side to the upper side in the figure. A registration roller pair (positioning 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 of the image forming units 1Y, 1C, 1M, and 1K, a transfer unit 40 that is endlessly moved counterclockwise in the drawing while an intermediate transfer belt 41 as an intermediate transfer member is stretched is disposed. . In addition to the intermediate transfer belt 41, the transfer unit 40 includes a belt cleaning unit (not shown), a bracket (not shown), and the like. Also provided are four primary transfer rollers 45Y, 45C, 45M, 45K, a secondary transfer backup roller 46, a drive roller 47, a tension roller 49, and the like. The intermediate transfer belt 41 is endlessly moved in the counterclockwise direction in the figure 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 a belt cleaning unit. In the belt cleaning unit, a cleaning blade (not shown) 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 bracket of the transfer unit 40 swings as the solenoid (not shown) is turned on / off. In the case of forming a monochrome image, the printer of this embodiment swings the bracket slightly by driving the solenoid described above. This swinging causes the Y, C, and M primary transfer rollers 45Y, 45C, and 45M to revolve counterclockwise in the drawing, so that the intermediate transfer belt 41 is exposed to Y, C, and M photosensitive. Separated from the bodies 3Y, 3C, 3M. Of the four image forming units 1Y, 1C, 1M, and 1K, only the K image forming unit 1K is driven to form a monochrome image. Accordingly, it is possible to avoid wasteful consumption of the image forming unit without driving the Y, C, and M image forming units 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 rotationally driven in the clockwise direction in the drawing 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 by 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 bottles 72Y, 72C, 72M, and 72K, which are four toner containers that respectively store Y toner, C toner, M toner, and K toner, are disposed. Each color toner in the toner bottles 72Y, 72C, 72M, and 72K is appropriately supplied to the developing units 7Y, 7C, 7M, and 7K of the image forming units 1Y, 1C, 1M, and 1K by a toner replenishing device as a toner replenishing unit. Is done. The toner bottles 72Y, 72C, 72M, and 72K are detachable from the printer main body independently of the image forming units 1Y, 1C, 1M, and 1K.

  Next, a schematic configuration of the image forming unit will be described. Here, since the image forming units 1K, 1Y, 1M, and 1C have the same configuration except for the color of the toner to be used, the configuration of one image forming unit 1Y will be described below, and other images will be described. The description of the configuration of the forming units 1C, 1M, and 1K is omitted. As shown in FIGS. 2 and 3, the image forming unit 1Y includes a photoreceptor unit 2Y and a developing unit 7Y. As shown in FIG. 3, the photoconductor unit 2Y and the developing unit 7Y are configured to be detachably attached to the printer body as an image forming unit 1Y. However, the developing unit 7Y can be attached to and detached from the photosensitive unit in a state where it is detached from the printer main body.

  As shown in FIG. 2, the photoconductor unit 2Y includes a drum-shaped photoconductor 3Y as an image carrier, a drum cleaning device 4Y, a static eliminator (not shown), a charging device 5Y, and the like. The charging device 5Y as a charging unit uniformly charges the surface of the photosensitive member 3Y, which is driven to rotate clockwise in FIG. 2 by a driving unit (not shown), by the charging roller 6Y. Specifically, in FIG. 2, a charging bias is applied from a power source (not shown) to the charging roller 6Y that is driven to rotate counterclockwise, and the charging roller 6Y is brought close to or in contact with the photosensitive member 3Y. 3Y is uniformly charged. In place 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 (exposure unit) described later, thereby generating an electrostatic latent image for Y. Carry.

  Next, a schematic configuration of the developing unit will be described. Here, since the developing units 7K, 7Y, 7M, and 7C have the same configuration except for the color of the toner to be used, the configuration of one developing unit 7Y will be described below, and the other developing units 7C will be described. , 7M, 7K will not be described. As shown in FIGS. 2 and 4, the developing unit 7 </ b> Y as the developing unit has a first agent storage chamber 9 </ b> Y in which a first conveying screw 8 </ b> Y as a conveying unit is disposed in the developing unit main body. Yes. In addition, a toner concentration sensor 10Y including a magnetic permeability sensor as a toner concentration detecting unit, a second conveying screw 11Y as a conveying unit, a developing roll 12Y as a developing device (developer carrying member), a doctor blade as a developer regulating member It also has a second agent storage chamber 14Y in which 13Y and the like are disposed. In these two agent storage chambers forming the circulation path, a Y developer (not shown) which is a two-component developer composed of a magnetic carrier and a negatively chargeable Y toner is contained. The first conveying screw 8Y is rotationally driven by a driving unit (not shown) to convey the Y developer in the first agent storage chamber 9Y to the front side in FIG. 2 (in the direction of arrow B in FIG. 4).

  In the toner density sensor 10Y, the Y developer in the middle of conveyance corresponds to the toner supply port 17Y in the first agent storage chamber 9Y, that is, the position where Y toner is supplied (hereinafter referred to as “supply position”). It is located downstream in the circulation direction (conveying direction) and is fixed below the first conveying screw 8Y. The toner density sensor 10Y is installed in the vicinity of the first conveying screw 8Y so as not to hinder the first conveying screw 8Y from conveying the Y developer. The toner concentration sensor 10Y detects the toner concentration of the Y developer when the Y developer passes a predetermined detection location. Then, the Y developer transported to the end of the first agent storage chamber 9Y by the first transport screw 8Y enters the second agent storage chamber 14Y through the communication port 18Y. The fixing position of the toner density sensor 10Y may be in the vicinity of the first conveying screw 8Y, and may be fixed above the first conveying screw 8Y.

  The second transport screw 11Y in the second agent storage chamber 14Y is rotationally driven by a driving means (not shown) to transport the Y developer to the back side in FIG. 2 (in the direction of arrow A in FIG. 4). In this way, a developing roll 12Y as a developing device 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 includes a magnet roller 16Y fixedly disposed in a developing sleeve 15Y 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 end of the second agent storage chamber 14Y by the second transport screw 11Y returns to the first agent storage chamber 9Y through the communication port 19Y. In this way, the Y developer is circulated and conveyed in the developing unit.

  In FIG. 1 described above, the Y toner image formed on the photoreceptor 3Y is intermediately transferred to the intermediate transfer belt 41. 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. In the image forming 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 in the same manner, and the intermediate transfer belt 41 has intermediate portions. Transcribed.

  The toner replenishing port 17Y is provided at a position for replenishing toner to the developer immediately after entering the first agent containing chamber 9Y from the second agent containing chamber 14Y. The toner concentration sensor 10Y detects the toner concentration of the developer at a position after the Y toner is supplied in the first agent storage chamber 9Y as a non-supply area. The toner concentration sensor 10Y detects the toner concentration of the developer at a position immediately before entering the second agent storage chamber 14Y as the supply region in the first agent storage chamber 9Y as the non-supply region. That is, in the first agent storage chamber 9Y, the toner concentration sensor 10Y is positioned downstream of the position where Y toner is supplied from the toner supply port 17Y in the developer transport direction, and the developing roller 12Y is located on the photoreceptor 3Y. It is located upstream from the position where the upper latent image is developed.

  Next, a schematic configuration of the toner replenishing device will be described. As shown in FIG. 5, a toner replenishing device as a toner replenishing unit includes a bottle placing table 95 on which four toner bottles 72K, 72Y, 72C, and 72M are placed, and a bottle driving unit that individually drives each bottle to rotate. 96 and the like. The toner bottles 72K, 72Y, 72C, and 72M include bottle-shaped bottle portions 73K, 73Y, 73C, and 73M that are powder storage portions that store toners (not shown) as powder, and cylindrical holders that are powder discharge portions. Parts 74K, 74Y, 74C, and 74M. On the inner peripheral surface of the bottle portion 73Y, a screw-like spiral protrusion protruding from the outside to the inside of the container is formed so as to extend in the bottle axis direction.

  The toner bottles 72K, 72Y, 72C, and 72M set on the bottle mounting table 95 engage the holder portions 74K, 74Y, 74C, and 74M with the bottle driving portion 96, respectively. As indicated by an arrow X1 in the figure, when the toner bottle 72M engaged with the bottle driving unit 96 is slid in the direction away from the bottle driving unit 96 on the bottle mounting table 95, the holder 74M of the toner bottle 72M is moved. The bottle drive unit 96 is detached. In this way, the toner bottle 72M can be removed from the toner supply device. Further, in the toner replenishing device in a state where the toner bottle 72M is not attached, when the toner bottle 72M is slid in the direction approaching the bottle driving unit 96 on the bottle mounting table 95 as indicated by an arrow X2 in the drawing, the toner The holder part 74 </ b> M of the bottle 72 </ b> M is engaged with the bottle driving part 96. In this way, the toner bottle 72M can be attached to the toner supply device. The toner bottles 72K, 72Y, and 72C for other colors can be attached to and detached from the toner supply device by performing the same operation.

  Gear portions (not shown) are formed on the outer peripheral surfaces of the head portions of the bottle portions 73K, 73Y, 73C, and 73M of the toner bottles 72Y, 72C, 72M, and 72K. The gear portions are the holder portions 74K, 74Y, and 74C. , 74M. However, a notch (not shown) for partially exposing the gear part is formed on a part of the peripheral surface of the holder part 74K, 74Y, 74C, 74M, and the gear part is a part of itself from the notch. Is exposed. When the holder parts 74K, 74Y, 74C, and 74M of the toner bottles 72K, 72Y, 72C, and 72M are engaged with the bottle driving part 96, the bottle driving motors for K, Y, C, and M (not shown) provided in the bottle driving part 96 are provided. The gear meshes with the gear portions of the bottle portions 73K, 73Y, 73C, and 73M through the aforementioned notches. Then, the bottle driving gears for the K, Y, C, and M of the bottle driving unit 96 are rotationally driven by a driving system (not shown), so that the bottles 73K, 73Y, 73C, and 73M become the holders 74K, 74Y, 74C, and 74M. It is driven to rotate.

  When the bottle portions 73K, 73Y, 73C, and 73M are thus rotated on the holder portions 74K, 74Y, 74C, and 74M, the color toners in the bottle portions 73K, 73Y, 73C, and 73M are screw-shaped spirals as described above. It moves from the bottle bottom side toward the bottle head side along the protrusion. And it flows into the cylindrical holder parts 74K, 74Y, 74C, and 74M through a bottle opening (not shown) provided at the tip of the bottle parts 73K, 73Y, 73C, and 73M, which are containers for containing powder.

  Next, a schematic configuration of the toner bottle mounted on the toner replenishing device and its peripheral configuration will be described. Here, since the toner bottle and its peripheral configuration are the same except for the color of the toner to be used, the configuration of the Y-color toner bottle and its peripheral configuration will be described below. Description of the toner bottle and its peripheral configuration is omitted. FIG. 6 is a schematic configuration diagram showing a toner bottle mounted on the toner replenishing device and its peripheral configuration. In the figure, the toner bottle is shown in a cross section at the holder portion 74Y in the longitudinal direction of the toner bottle. As described above, the Y toner in the bottle part is fed into the holder part 74Y by rotating the bottle part (not shown) that exists on the back side in the drawing relative to the holder part 74Y. The toner bottle holder 74Y is engaged with the hopper 76Y of the toner replenishing device. The hopper portion 76Y is formed in a flat shape in a direction perpendicular to the drawing sheet surface, and is located on the front side of the intermediate transfer belt 41 in the drawing. The toner discharge port 75Y formed at the bottom of the holder portion 74Y and the toner receiving port formed at the hopper portion 76Y of the toner replenishing device communicate with each other. The Y toner sent from the bottle portion of the toner bottle to the holder portion 74Y is dropped into the hopper portion 76Y by its own weight. In the hopper, a flexible pressing film 78Y fixed to the rotatable rotating shaft member 77Y rotates together with the rotating shaft member 77Y. A toner detection sensor 82Y made of a piezoelectric element that detects the presence or absence of toner in the hopper is fixed to the inner wall of the hopper 76Y. The pressing film 78Y made of a PET (polyethylene terephthalate) film or the like presses the Y toner toward the detection surface of the toner detection sensor 82Y as it rotates. As a result, the toner detection sensor 82Y can detect the toner in the hopper 76Y satisfactorily. The rotation driving control of the bottle portion of the toner bottle is performed so that the toner detection sensor 82Y can detect Y toner satisfactorily. Therefore, as long as the toner is sufficiently present in the bottle portion, a sufficient amount of Y toner is dropped from the bottle portion into the hopper portion 76Y via the holder portion 74Y, and the hopper portion 76Y is filled with a sufficient amount of toner. It is filled. If the state changes from this state to a state in which the toner detection sensor 82Y makes it difficult for the Y toner to be detected despite frequent rotation of the bottle portion, the control unit (not shown) has little Y toner remaining in the bottle portion. Assuming that there is an alarm, a warning of “toner near end” is notified to the user.

  A horizontal conveying pipe 79Y is connected to the lower part of the hopper section 76Y, and the Y toner in the hopper section 76Y slides down the taper due to its own weight and is dropped into the horizontal conveying pipe 79Y. A toner replenishing screw 80Y is disposed in the horizontal conveyance tube 79Y, and Y toner is laterally conveyed along the longitudinal direction of the horizontal conveyance tube 79Y as it is rotationally driven.

  A drop guide tube 81Y is connected to one end portion in the longitudinal direction of the horizontal conveyance tube 79Y in a posture extending in the vertical direction. The lower end of the drop guide tube 81Y is connected to the toner supply port 17Y of the first agent storage chamber 9Y of the developing unit 7Y. When the toner supply screw 80Y in the horizontal conveyance tube 79Y rotates, the Y toner conveyed to one end in the longitudinal direction of the horizontal conveyance tube 79Y passes through the drop guide tube 81Y and the toner supply port 17Y, and the first agent of the developing unit 7Y. It falls into the storage chamber 9Y. As a result, Y toner is supplied into the first agent storage chamber 9Y. In the other colors (C, M, K), toner is supplied in the same manner.

  Next, the toner concentration control means of the present invention will be described. As shown in FIG. 7, the toner supply amount is adjusted by a supply source for driving a toner supply member (not shown) of the toner supply device 70 by the supply control unit 102 of the control unit 100 functioning as the first control unit. This is done by controlling the drive timing, drive time, drive speed, etc. of 71Y, 71C, 71M, 71K. The toner replenishing member may be a known one as long as it can adjust the toner supply from the toner replenishing ports 17Y, 17C, 17M, and 17K to each color developer by the driving force of the driving sources 71Y, 71C, 71M, and 71K. Widely available.

  The detection result of the toner density of each color developer by the toner density detection means 10Y, 10C, 10M, and 10K is sent to the control unit 100 (not shown) as an electrical signal. The control unit 100 includes a CPU (Central ProCesing Unit), a RAM (Random ACCeSS MeMorY) as a data storage unit, a ROM (Read Only YMeMorY), and the like, and can execute various arithmetic processes and control programs. it can. The control unit 100 stores, in the RAM, the Vtref for Y, the Vtref for C, the Vtref for M, and the Vtref for K, which are target values of output voltages from toner density sensors 10Y, 10C, 10M, and 10K as toner density detecting means. Stores data.

  The control unit 100 compares the value of the output voltage from the toner density detection means 10Y with the Vtref for Y, and drives the toner replenishing device 70 so as to supply the amount of Y toner corresponding to the comparison result from the toner replenishing port 17Y. The source 71Y is controlled. With this control, an appropriate amount of Y toner is supplied to the Y developer whose Y toner density has decreased due to the consumption of Y toner during development in the first agent storage unit 9Y. For this reason, the toner concentration of the Y developer in the second agent container 14Y is maintained within the target toner concentration range. The same applies to the developers in the developing units 7C, 7M, and 7K for other colors.

  The replenishment control unit 102 controls one drive source 71Y of the toner replenishing device 70 based on the prediction data calculated by the calculation unit 101 of the control unit 100 functioning as the first calculation unit.

  Here, based on the detection result of the toner density detection unit 10Y, the calculation unit 101 uses the calculation program and the calculation table stored in the ROM to calculate prediction data of the temporal change in the Y developer toner density. And the replenishment control part 102 of the control part 100 which functions as a 1st control means performs drive control of one drive source 71Y by the combination of the unit replenishment pattern mentioned later based on the prediction data which the calculation part 101 calculated. This eliminates uneven toner density.

  Next, the unit supply pattern will be described. As shown in FIG. 8, the waveforms H1, H2, H3, H4, and H5 indicate the amount of toner that is replenished by a replenishment drive operation in which the developer is driven once by a drive source with no toner density unevenness. This is a result of detecting a change in toner density with time measured at an arbitrary specific position by a toner density sensor for measurement when toner is supplied with five different supply patterns. Here, a case where the amount of each waveform replenished in the order of H1, H2, H3, H4, and H5 increases is shown. This amount of replenishment can be calculated by changing the drive time and drive speed of the drive source.

  Next, the toner density control system will be described with reference to the block diagram shown in FIG. In FIG. 9, the toner density target value is first compared with the toner density sensor value from the toner density detecting means for detecting the current toner density, and input to the sensor calculation unit. This is input to the first supply amount calculation unit to calculate the necessary toner supply amount. Also, information related to the output image, such as image information and paper information, is input to the second supply amount calculation unit. The second replenishment amount calculation unit is a part that calculates the toner replenishment amount and timing for offsetting it from the toner consumption amount and the consumption timing obtained from the image information. The toner replenishment amount obtained from the first replenishment amount calculator and the toner replenishment amount from the second replenishment amount calculator are added together to obtain the final toner replenishment amount. The replenishment control unit 102 of the control unit 100 controls the toner replenishing device 70 based on the toner replenishment amount.

  Next, a case where PI control is used for the supply amount calculation unit will be described. As shown in FIG. 9, the difference between the toner density target value and the toner density sensor value is calculated and inputted by the sensor calculation unit. This is the toner density target difference value here. It can be seen that the larger the toner density target difference value is, the farther the current toner density is from the target toner density. At this time, as shown in FIG. 10, the toner density target difference value is branched and input to the P: proportional block and the I: integration block. P: In the proportional block, the toner density target difference value is multiplied by a gain, and a value is output according to the magnitude of the difference value. On the other hand, in the I: integration block, the toner density target difference value is accumulated at every calculation timing. For this reason, even if the difference value is small, for example, the value increases as time elapses, and the value can be reliably followed with respect to the target value. The values calculated by the P: proportional block and the I: integration block are added and output as a toner replenishment amount by FB control. In the present embodiment, an example in which PI control is used has been described. However, any other configuration may be used as long as it has a difference with respect to an input and a function of accumulating the difference.

Next, a toner concentration sensor using magnetic permeability will be described. As a sensor for detecting magnetic permeability, a method using an inductance component of a coil is most commonly used. Several methods are conceivable among them, but here, the operation principle of a magnetic bridge type sensor using a differential transformer will be described. As shown in FIG. 11, the differential transformer is constructed by a coil in which a drive coil L1, a reference coil L2, and a detection coil L3 are concentrically stacked. When L1 is driven at a high frequency, the differential output V0 is expressed by the following equation Is obtained.
V0 = (V2-V3)

Here, when the output voltages of the reference coil L2 and the detection coil L3 at the reference concentration of the developer are V2 and V3, and the coil is designed so that V2 = V3, the detection coil L3 corresponds to the change in the developer concentration. Output slightly changes. The minute change ΔV3 is obtained by the following equation. That is, the minute change ΔV3 becomes the differential output V0 as it is.
ΔV3 = (V3 + ΔV3) −V2 = −V0

  The above is the principle of operation of the magnetic bridge type sensor using the differential transformer in the toner density sensor using the magnetic permeability. However, since the value of ΔV3 is very small, practically, a considerable amplification process is required for detection as a change in voltage. Although detailed description is omitted here, an actual toner concentration detection sensor is configured by adding an amplification function by various methods.

  In this embodiment, at least two toner density sensors using magnetic permeability are used. Although it is desirable to reduce the solid variation between different sensors by configuring the sensor with as high accuracy as possible, it is difficult in reality. However, in order to reduce this solid variation as much as possible, in the circuit shown in FIG. 11, it is desirable to share a basic substrate including a power supply and GND.

  It is desirable that the at least two toner density sensors measure the sensor output characteristics before being incorporated in an actual product, and adjust the toner density sensor outputs so as to approximately match each other. Instead of this pre-adjustment, a configuration may be adopted in which automatic execution is performed at an arbitrary timing as in calibration after being incorporated into a product.

  Next, the toner density sensor will be described in more detail. The two toner density sensors 10Y_R and 10Y_B are arranged in the transport direction as shown in FIG. As described above, neither the developing sleeve nor the toner supply port is provided in the section where the two toner density sensors 10Y_R and 10Y_B are provided. Therefore, basically, a developer having the same toner concentration is conveyed and can be detected.

  Next, the sensor output waveform detected by the toner density sensor will be described. The developing device includes a screw that stirs and conveys the developer when detecting the toner concentration in the developing device. In general, a function is added to prevent the developer from staying in a portion where the toner density is detected. In that case, arbitrary bulk density is comprised with respect to the force which presses a developing agent. This is because the charged toners have the same polarity with respect to the force for pressing the developer, repel each other, and the balance of the force is balanced at a certain value. Since the pressing force is constant, the toner density can be detected stably.

  Here, the pressing force against the two toner density sensors 10Y_R and 10Y_B is changed. These two sensor sections do not perform toner replenishment or toner consumption, and are adjacent sections. Therefore, the toner density is considered to be approximately the same. At this time, the output of the toner concentration sensor 10Y_R with respect to time is indicated by a broken line in FIG. On the other hand, the output of the toner concentration sensor 10Y_B with respect to time is indicated by a solid line in FIG. As shown in FIG. 12, the toner density sensor 10Y_B is upstream of the toner density sensor 10Y_R in the developer transport direction. Therefore, the toner density sensor 10Y_B detects the peak of the toner density fluctuation earlier in time than the toner density sensor 10Y_R. Thereafter, the toner density sensor 10Y_R detects the peak of the toner density fluctuation. At that time, for example, there is a difference in peak values. Specifically, the pressing force at the detection position of each toner density sensor 10Y_R, 10Y_B is changed. For this reason, the force against this pressure varies depending on the toner charge amount, which changes the bulk density and appears as a difference in toner density sensor output. The above is based on the premise that the toner densities detected by the toner density sensors 10Y_R and 10Y_B are the same. In the present embodiment, toner replenishment or toner consumption is not performed in the section of the two toner density sensors 10Y_R and 10Y_B, and the toner density is considered to be approximately the same because it is a nearby section.

  Next, an example in which the toner charge amount is known from the sensor output will be described. FIG. 14 shows a correlation between the difference between the toner density sensor output values and the measured value of the toner charge amount at the time of output. As described above, since the toners have the same polarity, the repulsive force of each other increases as the toner charge amount increases. In order to make the bulk density the same even with the same toner concentration, it is necessary to increase the pressing force. Two toner density sensors 10Y_R and 10Y_B are installed in an area where the toner density is considered to be the same, and the pressing force to the sensors 10Y_R and 10Y_B is different from each other. If the pressing force against each of the toner density sensors 10Y_R and 10Y_B is different, the bulk density changes accordingly, and the output of each of the toner density sensors 10Y_R and 10Y_B is different. This difference becomes more noticeable as the toner charge amount is higher. Therefore, as shown in FIG. 14, the toner charge amount increases as the difference (difference) between the outputs of the toner density sensors 10Y_R and 10Y_B increases. The calculation unit 101 calculates the difference between the outputs of the toner density sensors 10Y_R and 10Y_B, and calculates the toner charge amount.

  In addition, for example, when the toner charge amount is high with respect to the calculated toner supply amount, the supply control unit 102 increases the toner supply amount according to the ratio or amount of the toner charge amount or increases the toner density target value to be high (darker). ) Control to change to the side. This increases the amount of new toner replenished into the developing device. The new toner is not charged. Therefore, the toner charge amount in the developing device can be reduced.

  On the other hand, when the toner charge amount is low with respect to the calculated toner replenishment amount, for example, the replenishment control unit 102 reduces the toner replenishment amount or decreases the toner density target value (lightens) by the ratio or amount of the toner charge amount. ) Control to change to the side. As a result, the amount of new toner replenished into the developing device is reduced. Therefore, it is possible to prevent the toner charge amount in the developing device from being reduced. Further, since the existing toner is charged by being stirred, as a result, the toner charge amount in the developing device can be increased.

  When the toner charge amount is high, an image may be formed outside the printing range and the toner may be discharged from the developing device. When the toner is discharged, the replenishment control unit 102 performs control so as to perform toner replenishment in order to supplement the toner. As a result, new uncharged toner is added, and the toner charge amount in the developing device can be reduced.

  On the other hand, when the toner charge amount is low, the toner consumption may be reduced by lowering the printed image density to a level at which it cannot be recognized. By reducing the toner consumption, the replenishment control unit 102 performs control so as to limit the execution of toner replenishment. That is, the supply of new uncharged toner is limited. Therefore, the toner in the developing device is continuously stirred, and the toner charge amount in the developing device increases.

  In order to increase the toner charge amount more effectively, even when printing with a low image area ratio, a consumption pattern as an arbitrary toner pattern is provided outside the printing range, and the first control means uses the toner consumption. It may be controlled so as to reduce the amount to be played and to play a buffer role. However, this promotes wasteful toner consumption and is not desirable as an actual mounting function.

  Specifically, it is not preferable that the designer intentionally dispose of the toner that is the customer's asset. The toner charge amount correction control is executed on the side where the toner is replenished, and the toner is preferably used only for forming an image. Moreover, it is not preferable from the spirit of making effective use of limited resources to the maximum.

  With the above operation, the toner charge amount in the developing device can be detected, and the toner charge amount can be corrected and controlled to a desired value.

  In this embodiment, the correlation between the output value of the toner density sensor and the measured value of the toner charge amount at the time of output is described as a linear relationship, but it approximates to a multi-order curve or other functions. Or, a section may be determined and used as a correction table. Although only one correlation is presented here, the correlation may change depending on the toner concentration and environment (temperature / humidity). In such a case, a method of selecting a correlation according to the change or providing a correction coefficient for changing the inclination or offset may be used. Further, the calculation unit calculates the toner charge amount from the difference between the two toner density sensors, but is not limited to this mode. For example, four toner density sensors may be used and arranged side by side in the developer conveyance direction. Then, the toner charge amount is calculated from the difference between the sum or average value of the two toner density sensors on the upstream side in the transport direction and the sum or average value of the two toner density sensors on the downstream side in the transport direction. You may do it.

  Next, various modes of pressure adjusting means for changing (adjusting) the force for pressing the developer against the toner density sensor 10 will be described. Although a plurality of configurations will be described below, in order to vary the pressing force, different configurations may be combined, or a configuration in which the shape of components is partially changed even in the same configuration. In addition, since the configuration is the same as that of each color, the reference numerals are omitted and will be described below.

  The first pressure adjusting means will be described. As shown in FIG. 15, the first conveying screw 8 includes a rotating shaft 27, a spiral spring 28 provided on the rotating shaft 27, and first pressure adjusting means 30. The first conveying screw 8 conveys the developer in the developing device. And the spiral spring 28 with which the 1st conveyance screw 8 is equipped is comprised in parallel with a conveyance direction. Therefore, it is possible to make the pressing force constant against the toner concentration detecting means (not shown) provided in the developing device without affecting the developer conveyance.

  The first pressure adjusting means 30 is a plate-like member disposed on the rotating shaft 27. Then, the working surfaces of the spiral spring 28 are bridged. With such a configuration, the developer in the first conveying screw space is applied with pressure to the first pressure adjusting means 30 as the first conveying screw 8 moves, and the escape space is generated in the first conveying screw 8. Disappear. Then, the vehicle passes over the first pressure adjusting means 30 and enters the first conveying screw space again. Therefore, the developer is pressed with an arbitrary pressure. At this time, the height of the first pressure adjusting means 30 can be changed to vary the force with which the developer is pressed.

  Next, the second pressure adjusting means will be described. As shown in FIG. 16, the first conveying screw 108 includes a rotating shaft 127, a spiral spring 128 provided on the rotating shaft 127, and a second pressure adjusting means 130. The first conveying screw 108 makes the force pressing the developer against a toner concentration detecting means (not shown) provided in the developing device constant.

  The second pressure adjusting means 130 includes a detection spring 130a and a sheet 130b as a sheet-like member having an arbitrary rigidity. The detection splash 130 a is a plate-like member disposed on the rotation shaft 127. The spiral helix 128 is disposed between the working surfaces. With such a configuration, the developer is present in the toner density sensor portion, and the toner density sensor reliably detects the toner density. Then, an elastically deformable sheet 130b is provided at the tip of the detection splash 130a. With such a configuration, the stay of the developer can be prevented, and the developer can be firmly pressed against the toner concentration detection sensor. For example, the sheet 130b rubs against the inner wall of the developing device in an elastically deformed state. If the developer in the toner density detection portion remains, the developer is removed by the sheet 130b. Further, the developer is pushed and conveyed by the sheet 130b and is pressed with an arbitrary pressure. At this time, it is possible to vary the force with which the developer is pressed by varying the length and material of the sheet 130b.

  Next, the third pressure adjusting means will be described. As shown in FIG. 17, the first conveying screw 208 includes a rotating shaft 227, a spiral spring 228 provided on the rotating shaft 227, and third pressure adjusting means 230. The first conveying screw 208 makes the force pressing the developer against a toner concentration detecting means (not shown) provided in the developing device constant.

  The third pressure adjusting means 230 is a plate-like member disposed on the rotation shaft 227. The spiral spring 128 is disposed substantially vertically between the working surfaces. The third pressure adjusting means 230 is provided around the detection position of the toner density sensor. The working surface of the third pressure adjusting unit 230 is orthogonal to the flow of the developer conveyed from one end of the first conveying screw 208 to the other end. For this reason, the conveyance of the developer is hindered. As a result, the developer is present in the toner concentration sensor, and the toner concentration of the developer can be reliably detected. Further, since the conveyance is hindered, the developer can be pressed with an arbitrary pressing force. Note that the force with which the developer is pressed can be made different by changing the attachment angle or length of the third pressure adjusting means 230.

  Next, the fourth pressure adjusting means will be described. As shown in FIG. 18, the first conveying screw 308 includes a rotating shaft 327, a spiral spring 328 provided on the rotating shaft 327, and fourth pressure adjusting means 330. The first conveying screw 308 makes the force pressing the developer against a toner concentration detecting means (not shown) provided in the developing device constant.

  The fourth pressure adjusting means 330 is a plate-like member that is disposed on the rotating shaft. The spiral spring 328 is disposed substantially vertically between the working surfaces. The fourth pressure adjusting means 330 is provided around the detection position of the toner density sensor. And it has the structure which bridge | crosslinks between the action surfaces of the spiral splash 328. FIG. Therefore, there is less space for the developer to escape compared to the third pressure adjusting means, and the developer can be pressed with a stronger pressing force. Note that the force with which the developer is pressed can be varied by changing the mounting angle, length, and the like of the fourth pressure adjusting means 330.

  Next, the fifth pressure adjusting means will be described. As shown in FIG. 19, the first conveying screw 408 includes a rotating shaft 427, a spiral spring 428 provided on the rotating shaft 427, and a fifth pressure adjusting means 430. The first conveying screw 408 makes the force pressing the developer against a toner concentration detecting means (not shown) provided in the developing device constant.

  The fifth pressure adjusting means 430 is a plate-like member arranged on the rotation axis. The spiral spring 428 is disposed substantially vertically between the working surfaces. The fifth pressure adjusting means 430 is provided around the detection position of the toner density sensor. And it has the structure which bridge | crosslinks between the action surfaces of the spiral spring 428. FIG. Further, the working surface of the fifth pressure adjusting means 430 is formed in a concave shape with respect to the rotation direction of the first conveying screw 408. Therefore, the amount of developer pressed against the detection position of the toner density sensor can be increased. As a result, it is possible to enhance the pressing force and improve the detection accuracy of the sensor. Note that the force with which the developer is pressed can be varied by changing the mounting angle, length, curvature, and the like of the fifth pressure adjusting means 430.

  The various pressure adjusting means for the first conveying screw for conveying the developer has been described above. However, the present invention is not limited to these embodiments, and it is sufficient that the force for pressing the developer against the toner concentration detecting means can be changed. Further, instead of providing pressure adjusting means on the screw, pressure adjusting means may be provided on the inner wall of the developing device. Specifically, the configuration of the detection position of the toner density sensor on the inner wall of the developing device is changed. For example, the inner wall of the developing device generally has a configuration that has a curvature that matches the rotation of the screw, but the configuration is such that only the detection position of the toner concentration sensor has a linear shape, or there are protrusions on the inside. You may do it. The force with which the developer is pressed can be varied by changing the length of the linear shape and the amount of protrusion. Further, the pressure adjusting means may be provided on both the screw and the inner wall of the developing device. With such a configuration, the pressing force of the developer can be further varied.

  In this embodiment, the pressure adjusting unit is configured to pressurize the developer, but is not limited to this mode, and may be configured to depressurize. For example, the pressure adjusting means may be configured to increase the interval (pitch) of the spiral splash of the first conveying screw at the position of the toner density sensor. Further, the pressure adjusting means may be configured such that the inner wall of the developing device main body has a concave shape on the outer side by the detection position of the toner density sensor. By adopting such a configuration, the pressure adjusting means can reduce the pressure at the position of the toner density sensor and cause a pressure difference in the toner density sensor.

  Next, the toner adhesion amount that adheres to the photoreceptor will be described. In an electrophotographic printer, toner is charged in the developing device. Then, the charged toner is attracted to the development potential formed on the photoconductor and developed. This attracted amount determines the toner adhesion amount, and finally determines the image density.

  As shown in FIG. 22, potential holes are formed on the surface of the photoreceptor by a laser. At this time, the depth of the hole where the toner adheres is determined by the laser intensity. On the other hand, the lid to which the toner adheres is determined by the developing bias. The charged toner enters a developing potential portion corresponding to the difference between the developing bias and the laser intensity, whereby the image is developed.

  Further, the entering toner enters in a form that cancels out the charge amount of the development potential. Therefore, the toner charge amount is a very important factor in determining the toner adhesion amount. Further, the development potential itself is determined almost mechanically. Therefore, it is no exaggeration to say that the toner adhesion amount is determined by the toner charge amount. However, in order to change the toner charge amount itself, a change in physical properties is required, and a certain amount of time is required. There are various states (situations) depending on the degree of change in the toner charge amount, the printing conditions, and the like, such as when the toner adhesion amount is to be changed immediately or gradually over time.

  Next, the relationship between the toner charge amount and the toner amount that enters the development potential will be described. The development potential is determined by the depth of the development potential hole formed by the laser intensity and the depth sandwiched between the lids of the development bias. Therefore, it is considered that it is almost mechanically determined. On the other hand, the toner charge amount becomes higher than the standard because, for example, the developer toner is continuously stirred. In addition, the toner charge amount becomes lower than the standard because the ratio of new toner increases due to frequent toner replenishment. When the development potential is an arbitrary value, as shown in FIG. 23, the amount of toner entering the development potential varies depending on the toner charge amount.

  The relationship between the development potential and the toner charge amount is a balance of electrical attraction. Therefore, when the toner charge amount is low, it is necessary to cover with the toner amount, and the amount of toner entering the development potential increases. On the other hand, when the toner charge amount is high, the development potential is balanced with a small amount of toner, and the amount of toner entering the development potential decreases. As a result, a deviation occurs between the target toner amount desired to enter the development potential and the toner amount that actually enters the development potential.

  The deviation in the toner amount is directly affected by, for example, the darkness and lightness of the image, causing a reduction in image quality. For this reason, it is important to control the toner amount to be constant by measuring the toner charge amount that is difficult to control and changing the developing bias and laser intensity that are relatively easy to control. From the above description, it can be seen that the toner charge amount has a great influence on the toner adhesion amount.

  Next, a change in toner charge amount will be described by taking a change with time as an example. FIG. 25 is a diagram illustrating the relationship between the toner charge amount and the leaving time. The toner charge amount is an amount of static electricity generated when the toner is mixed with the carrier, stirred, and rubbed. Therefore, the amount of static electricity decreases as time elapses in a stopped state. That is, the toner charge amount decreases as time elapses while the apparatus is stopped. Since the toner charge amount decreases as the leaving time becomes longer, even if the image forming conditions before and after the leaving are exactly the same, the toner amount entering the developing potential, that is, the toner adhesion amount changes as shown in FIG. .

  Next, the toner adhesion amount control device will be described with reference to FIG. A prescribed toner adhesion amount target value is acquired, and this value is input to the adhesion amount calculation unit 201 of the control unit 200 that functions as a second calculation unit. Further, the calculated value of the toner charge amount calculated by the first calculation means, that is, the calculated value (measured value) of the toner charge amount in the developing device is acquired as described above, and this value is also simultaneously calculated as the adhesion amount calculation unit 201. Is input.

  The adhesion amount calculation unit 201 calculates the toner adhesion amount from the obtained calculated value of the toner charge amount and the development potential obtained from the current set value. Further, as shown in FIG. 23, the toner adhesion amount varies depending on the change in the toner charge amount. Therefore, the difference between the toner adhesion amount target value and the calculated toner adhesion amount is also calculated at the same time. This difference is input to the parameter correction unit 202 of the control unit 200 that functions as the second control unit. The control unit 200 includes a CPU (Central ProCesSSing Unit), a RAM (Random ACCeSS MeMorY) as a data storage unit, a ROM (Read Only YMeMorY), and the like, and executes various arithmetic processes and control programs. Can do.

  The parameter correction unit 202 outputs a necessary parameter correction amount from the difference between the input toner adhesion amount target value and the calculated toner adhesion amount. Then, parameter correction is performed on the target value or setting value of the function of the image forming apparatus, and the toner amount is controlled to be constant, thereby preventing the image quality from being deteriorated.

  The calculated toner charge amount input to the toner adhesion amount calculation unit 201 may be input via a storage unit (not shown). The storage means is provided in the control unit 200 and has a function of measuring time and / or a function of receiving time information. The storage unit stores the calculated toner charge amount calculated by the first calculation unit at an arbitrary timing. This arbitrary timing is, for example, the elapsed time from the end of the operation of the image forming apparatus itself and / or the current time and / or the end of the print job. Then, the calculated toner charge amount stored in the storage unit is input to the adhesion amount calculation unit 201.

  Specifically, for example, an arbitrary number of sheets are printed. At that time, the storage unit stores the toner charge amount measured by the toner density detection unit when the last printing is completed. Then, the storage unit measures an elapsed time from the time when the last printing is completed. Then, when the first printing is executed after an arbitrary time has elapsed, the toner density detecting unit measures the toner charge amount when the developing device is first operated (current time). Then, the elapsed time and the toner charge amount are transmitted to the parameter correction unit 202. The calculation means (not shown) provided in the parameter correction unit 202 performs the first charge printing after the previous printing (when the last printing is finished) and the current printing (after an arbitrary time has elapsed). The toner charge amount at the time of execution) is compared, and the toner charge amount in the current state is calculated from the elapsed time.

  Then, the parameter correction unit 202 outputs a necessary parameter correction amount from the difference between the input toner adhesion amount target value and the calculated value of the toner adhesion amount in the current state from the elapsed time. Then, parameter correction is performed on the target value or setting value of the function of the image forming apparatus, and the toner amount is controlled to be constant, thereby preventing the image quality from being deteriorated. When the parameter elapsed time is short, almost no correction is required. On the other hand, if the machine is stopped during a certain period such as summer vacation or the year-end and New Year holidays, it is necessary to make corrections.

  Here, it is also conceivable to measure the toner charge amount immediately after the start of the image forming apparatus. However, immediately after startup, the operation is unstable, and the toner charge amount measurement is not sufficiently reliable with respect to variations and measurement accuracy. On the other hand, the image forming apparatus of the present embodiment can improve the accuracy by calculating the toner charge amount in consideration of the elapsed time.

  Next, various aspects of parameter correction executed by the parameter correction unit 202 will be described. Note that the parameter correction target executed by the parameter correction unit 202 is not limited to this mode, and may be a mode in which any mode is combined. Further, parameter correction may be performed for each function of the image forming apparatus.

  The first parameter correction executed by the parameter correction unit 202 will be described. The first parameter correction is performed on the developing unit 7. Specifically, as an example, the process is performed on the developing bias.

  When the measured value of the toner charge amount is higher than the target value, the amount of toner adhering from the developing device to the photosensitive member is reduced with the prescribed development potential. Therefore, the value of the developing bias is increased, the developing potential is deepened, and the amount of toner to be attached is increased. That is, the parameter correction unit 202 executes correction for increasing the value of the developing bias.

  On the other hand, when the measured toner charge amount is lower than the target value, the amount of toner adhering to the photoconductor becomes excessive at the prescribed development potential. Therefore, the value of the developing bias is lowered, the developing potential is made shallow, and the amount of toner to be attached is reduced. That is, the parameter correction unit 202 executes correction for reducing the value of the developing bias.

  The second parameter correction executed by the parameter correction unit 202 will be described. The second parameter correction is performed on the exposure unit 20. Specifically, as an example, the process is performed on the laser intensity.

  When the measured value of the toner charge amount is higher than the target value, the amount of toner adhering to the photosensitive member is reduced with the prescribed development potential. Therefore, the value of the laser intensity is increased, the development potential is deepened, and the amount of toner to be adhered is increased. That is, the parameter correction unit 202 executes correction for increasing the value of the laser intensity.

  On the other hand, when the measured value of the toner charge amount is lower than the target value, the amount of toner adhering to the photosensitive member becomes excessive at the specified development potential. Therefore, the value of the laser intensity is lowered, the developing potential is made shallow, and the amount of toner to be adhered is reduced. That is, the parameter correction unit 202 performs correction for reducing the value of the laser intensity.

  The third parameter correction executed by the parameter correction unit 202 will be described. The third parameter correction is performed on the toner density. Specifically, it is executed for the toner density in the developing means.

  When the measured value of the toner charge amount is higher than the target value, the amount of toner adhering to the photosensitive member is reduced with the prescribed development potential. Therefore, by increasing the amount of toner replenished in the developing device or increasing the toner density target value in the developing device, uncharged toner is added, and the toner charge amount of the developer is lowered. That is, the parameter correction unit 202 executes correction for increasing the toner supply amount or changing the toner density target value to a darker side.

  On the other hand, when the measured value of the toner charge amount is lower than the target value, the amount of toner adhering to the photosensitive member becomes excessive at the specified development potential. Therefore, by reducing the amount of toner replenished to the developing device or lowering the toner density target value in the developing device, the addition of uncharged toner is suppressed, and the chance of toner charging increases, and the developer toner Increase the amount of charge. That is, the parameter correction unit 202 executes correction for reducing the toner replenishment amount or changing the toner density target value to a lighter side.

  Next, a parameter correction method executed by the parameter correction unit 202 will be described. The simplest method is a method of changing each parameter to an optimum value from the measured change in the toner charge amount. However, this method is not desirable when image forming conditions change rapidly. When the image forming conditions change abruptly, a method of changing each parameter stepwise from the change in the measured toner charge amount may be employed. Since the change amount of the toner charge amount is clear, for example, a method of changing an amount of 1/10 with respect to the change amount for each number of printed sheets can be adopted. Further, the parameter may have a function of gradually returning to the initial value or the setting value before the change after the change, for example, when the correction is changed. As a result, it is possible to avoid such a situation that the upper and lower limit values of the parameter are reached while the parameter correction is repeated, and no further correction is possible.

  Note that the response speed to the control of the parameter correction unit 202 differs depending on each function of the image forming apparatus. That is, when the parameter correction unit 202 controls each function of the image forming apparatus, the response speed with respect to the control varies. Specifically, for example, the response speed is faster when the first parameter correction or the second parameter correction is executed than when the third parameter correction is executed. Therefore, when it is desired to change the toner adhesion amount immediately, for example, the developing unit (development bias as a specific example) or the exposure unit (exposure bias as a specific example) having a quick response is subjected to parameter correction (control). . On the other hand, when it is desired to gradually change the toner adhesion amount over time, for example, the toner density is parameter-corrected (controlled). Then, by making the control target changeable according to the response speed, it is possible to control the toner adhesion amount corresponding to various situations.

  In the present embodiment, the first calculation unit 101 and the second calculation unit 201 are provided separately, but are not limited to this mode, and may be integrated. In the present embodiment, the first control unit 102 and the second control unit 202 are provided separately, but are not limited to this mode, and may be integrated. Moreover, although the control part 100 and the control part 200 are provided separately, it is not limited to this aspect, It is good also as integral.

  Next, the operation of the image forming apparatus of this embodiment will be described. The two toner density sensors 10Y_B and 10Y_R are arranged on the downstream side of the position where the toner is supplied from the toner supply unit in the conveyance direction in which the conveyance unit conveys the developer, and the developing unit is a latent image on the image carrier. Is located upstream of the position where the toner is developed with toner, that is, in the area where the toner density is the same. Therefore, the first calculation unit 101 can calculate the toner charge amount from the difference between the values of the two toner density sensors 10Y_B and 10Y_R. As a result, an appropriate amount of toner can be supplied and image quality can be stabilized. Further, since the repulsive force between toners having an arbitrary charge amount not in contact with the carrier is used, the toner charge amount can be directly detected online. Therefore, the toner density can be optimally corrected and controlled without estimating the toner charge amount. Further, since the toner charge amount can be calculated even if the toner density does not decrease, there is no case where the image quality cannot be guaranteed.

  Further, by including a pressure adjusting unit that pressurizes or depressurizes the developer with respect to at least one toner concentration sensor, the bulk density of the developer detected by each toner concentration sensor becomes a different value. Therefore, an accurate toner charge amount can be calculated from the difference between the output values of the toner density sensors.

  Further, by including the second control unit that controls the toner adhesion amount based on the calculated value of the second calculation unit, the toner adhesion amount can be adjusted to a desired amount. Therefore, the image quality can be improved. Further, by making it possible to change the control target according to the response speed to the control of the second control means, it is possible to control the toner adhesion amount corresponding to various situations. For example, when it is desired to change the toner adhesion amount immediately, for example, the developing unit (development bias as a specific example) or the exposure unit (exposure bias as a specific example) having a quick response is subjected to parameter correction. On the other hand, when it is desired to gradually change the toner adhesion amount over time, for example, the toner density is parameter corrected. As a result, there is no problem that productivity is lowered because normal printing cannot be performed.

  Next, a second embodiment of the present invention will be described in detail with reference to the drawings. In addition, about the structure equivalent to embodiment mentioned above, a corresponding code | symbol is attached | subjected and detailed description is abbreviate | omitted. The image forming apparatus according to the present embodiment is different from the image forming apparatus according to the first embodiment in the configuration of toner density sensors 10Y_B ′ and 10Y_R ′ as toner density means.

  As shown in FIG. 20, the toner density sensors 10Y_B 'and 10Y_R' are provided in the rotation direction of the first transport screw 8Y. Since these sections are completely at the same position, basically the developer having the same toner density is conveyed. Then, it is possible to detect the developer having the same toner density that is conveyed. At this time, the toner density sensor output with respect to time is as shown in FIG. The positions of the toner density sensors 10Y_B ′ and 10Y_R ′ are basically the same positions in the developer transport direction. Therefore, the peak of the toner density fluctuation comes almost simultaneously. A difference appears in the sensor output as the pressing force is different. Strictly speaking, although the peak arrival time differs by the time difference obtained by the distance between the toner density sensors 10Y_B 'and 10Y_R' and the rotational speed of the screw 8, it is assumed that they are simultaneous for the sake of simplicity.

  In addition, when the inner wall configuration of the developing device near the toner density sensor is changed or is configured using an elastic sheet or the like, depending on the position in the screw rotation direction, even if it is the same position in the developer transport direction Different pressing force. In this case, the function can be satisfied by arranging the toner concentration means in the rotation direction of the screw. The toner density sensor may be a combination of a configuration arranged in the developer conveyance direction and a configuration arranged in the rotation direction of the first conveyance screw 8Y.

  As described above, the present invention is not limited to the above-described embodiment. The present invention is not limited to an image forming apparatus that employs a two-component developer, and can be applied to an image forming apparatus that employs a one-component developer. The image forming apparatus according to the embodiment of the present invention describes a laser printer. However, the present invention is not limited to this mode, and any one of a copying machine, a facsimile machine, a printer, and a printing machine, or at least two of these. The present invention can also be applied to an image forming apparatus in which two or more are combined.

  Note that the number, material, and dimensions of each component introduced in the above embodiment are merely examples, and it is needless to say that various numbers, materials, and dimensions can be selected within a range in which the operation of the present invention can be exhibited. .

3 Photoconductor (an example of an image carrier)
7 Development unit (an example of development means)
8 First conveying screw (an example of conveying means)
10 Toner density sensor (an example of toner density detection means)
11 Second conveying screw (an example of conveying means)
12 Developing roll (example of developing device)
20 Optical writing unit (an example of exposure means)
30, 130, 230, 330, 430 First to fifth pressure adjusting means (an example of pressure adjusting means)
70 Toner supply device (an example of toner supply means)
101 calculation unit (an example of first calculation means)
102 Supply control unit (an example of first control means)
201 Adhesion amount calculation unit (an example of second calculation means)
202 Parameter correction unit (an example of second control means)

Japanese Patent Laid-Open No. 11-174817 JP 2005-17713 A JP 2012-150293 A JP 2006-30877 A

Claims (17)

In a toner concentration control device for controlling the amount of toner replenished to the developing means by the toner replenishing means based on information obtained from the toner density detecting means for detecting the toner density in the developing means main body using the magnetic permeability.
The developing unit includes a developing unit that develops the latent image formed on the image carrier with a two-component developer, and a conveying unit that conveys the two-component developer in the developing unit main body. A device,
At least two toner density detecting means are in the vicinity of the conveying means, and in the conveying direction in which the conveying means conveys the two-component developer, downstream of the position where the toner is replenished from the toner replenishing means. And the developer is disposed upstream of the position where the latent image on the image carrier is developed by a two-component developer,
First calculating means for calculating a toner charge amount from a difference between detection results of the at least two toner density detecting means;
A toner density control apparatus comprising: a first control unit configured to control a toner amount to be supplied from the toner supply unit to the developing unit based on calculation information of the first calculation unit. In the vicinity of the detection position of at least one of the at least two toner density detecting means, there is a pressure adjusting means for adjusting the pressure applied to the two-component developer,
2. The bulk density of the two-component developer at the detection position of each toner concentration detection unit is changed by the pressure adjustment unit adjusting the pressure at the detection position of each toner concentration detection unit. The toner density control device described.   The toner concentration control apparatus according to claim 1, wherein the pressure adjusting unit is provided in the conveying unit.   The toner concentration control apparatus according to claim 1, wherein the pressure adjusting unit is provided in the developing unit main body.   5. The toner density control apparatus according to claim 1, wherein the at least two toner density detection units are arranged in parallel in a conveyance direction of the conveyance unit. The transport means is a screw that rotates to transport the two-component developer.
The toner density control device according to claim 1, wherein the at least two toner density detection units are arranged in parallel in a rotation direction of the screw.   7. The toner concentration control apparatus according to claim 1, wherein the shape and / or material of the pressure adjusting unit is different depending on a detection position of each toner concentration detecting unit.   The toner density control according to claim 1, wherein the first control unit controls a toner amount to be supplied to the developing unit when a toner charge amount is different from a specified value. apparatus.   9. The method according to claim 1, wherein the first control unit controls a toner amount supplied to the developing unit by the toner supplying unit based on image information formed by the developing unit. The toner concentration control device according to one item.   The first control means controls to form a toner pattern between printed images and / or out of a printed range to consume the toner when the toner charge amount is different from a specified value. The toner density control device according to claim 1. A toner concentration control device according to any one of claims 1 to 10, comprising:
A toner adhesion amount control device for controlling an amount of toner adhered to the image carrier from the developing means,
A toner adhesion amount is calculated from the calculated value of the toner charge amount calculated by the first calculation means and the development potential on the image carrier, and the calculated toner adhesion amount and the toner adhesion amount target. Second calculating means for calculating a difference from the value;
And a second control unit that controls the amount of toner that adheres to the image carrier from the developing unit based on the calculation information of the second calculation unit. Storage means for storing the calculated toner charge amount calculated by the first calculation means at an arbitrary timing;
The second calculation means calculates a comparison value obtained by comparing the storage values of the storage means;
12. The toner adhesion amount control device according to claim 11, wherein the second control unit controls the amount of toner adhered to the image carrier from the developing unit based on the comparison value.   13. The toner adhesion amount according to claim 12, wherein the timing at which the storage unit stores the calculated value by the first calculation unit is an elapsed time and / or a current time and / or an end time of a print job. Control device.   The second control means controls the developing means by controlling exposure means and / or developing means and / or toner density in the developing means for forming a latent image on the image carrier based on image information. The toner adhesion amount control apparatus according to claim 11, wherein the toner adhesion amount to the image carrier is controlled by a unit.   The toner adhesion amount control according to any one of claims 11 to 14, wherein the second control unit can change a control target according to a response speed to the control of the second control unit. apparatus.   16. The toner adhesion according to claim 11, wherein the response speed is faster when the exposure unit or the developing unit is controlled than when the toner density is controlled. Quantity control device.   An image forming apparatus comprising the toner concentration control device according to any one of claims 1 to 10 or the toner adhesion amount control device according to any one of claims 11 to 16.

Images