JP5141664B2 - Developer amount adjusting device and image forming apparatus - Google Patents

Description

  The present invention relates to a developer amount adjusting device and an image forming apparatus, and in particular, a developer amount adjusting device and a developer amount for adjusting the amount of developer on a developing roller capable of supplying the developer to an image carrier of the image forming apparatus. The present invention relates to an image forming apparatus including an adjusting device.

  Some electrophotographic image forming apparatuses generally include an image forming unit, a fixing unit, a paper transport unit, and a discharge unit. The image forming unit includes an image carrier that can carry an electrostatic latent image on the surface, and a developing device that includes a developing roller that can supply a developer to the image carrier.

  In this image forming apparatus, an electrostatic latent image corresponding to image information is formed on an image carrier, and a developer is supplied to the electrostatic latent image from a developing roller. Then, the image is transferred from the image carrier to the paper. The sheet on which the image is transferred is conveyed to the fixing unit by the sheet conveying unit. Thereafter, the image is fixed on the sheet by the fixing unit. The sheet on which the image is fixed is transported to the discharge unit by the sheet transport unit, and is discharged out of the image forming apparatus from the discharge unit.

  Here, in order to supply an appropriate amount of developer to the electrostatic latent image, it is necessary to adjust the amount of developer on the developing roller. For this reason, there is one in which the amount of developer on the developing roller is detected by an optical sensor to adjust the developer supply amount (see Patent Document 1).

JP 2007-33863 A

  Here, when the optical sensor is used, when the thickness of the developer layer is equal to or less than a predetermined thickness, the reflection density (the amount of light emitted from the light emitting unit and the light reflected by the developer is reflected according to the thickness of the developer layer). The ratio to the amount of light. For this reason, the amount of developer on the developing roller can be detected with high accuracy. However, when the thickness of the developer layer is equal to or greater than a predetermined thickness, the reflection density is less likely to change depending on the thickness of the developer layer, so that it is difficult to detect the developer amount with high accuracy.

  In the developing device described in Patent Document 1, since the developer amount on the developing roller is detected using an optical sensor, the developing roller is used when the developer layer on the developing roller is thicker than a predetermined thickness. It is difficult to accurately detect the amount of developer above.

  For this reason, when the developer layer on the developing roller becomes thicker than a predetermined thickness, it becomes difficult to accurately adjust the developer amount on the developing roller. As a result, the amount of developer supplied from the developing roller to the electrostatic latent image may be too large. In this case, toner fog and toner scattering may occur, and the image quality of the image formed on the paper will be reduced.

  It is also conceivable to control the amount of developer conveyed by the developing roller based on the surface potential of the developer on the developing roller. However, since the surface potential varies depending on the toner charge amount, the amount of developer on the developing roller can be accurately adjusted. It cannot be detected and controlled well.

  An object of the present invention is to accurately detect and control the amount of developer on the developing roller, and to prevent deterioration in image quality due to an inappropriate amount of developer supplied to the electrostatic latent image.

  A developer amount adjusting device according to a first aspect of the present invention is a developer amount adjusting device that adjusts the amount of developer on a developing roller capable of supplying developer to an image carrier of an image forming apparatus, and includes a surface potential detecting unit and And a reflection density detecting means and a conveyance amount adjusting means. The surface potential detecting means is means for detecting the surface potential of the developer conveyed by the developing roller. The reflection density detecting means is means for detecting the reflection density of the developer conveyed by the developing roller. The conveyance amount adjusting unit is a unit that adjusts the developer conveyance amount based on the surface potential detected by the surface potential detection unit and the reflection density detected by the reflection density unit.

  In this developer amount adjusting device, the reflection density and surface potential of the developer conveyed by the developing roller are detected. Then, the developer conveyance amount is adjusted based on the detected reflection density and the surface potential.

  Here, not only the reflection density but also the developer transport amount is adjusted based on the developer surface potential, so compared to the case where the developer amount is adjusted based on either the reflection density or the surface potential. The amount of developer on the developing roller can be accurately adjusted. For this reason, it becomes easy to supply an appropriate amount of developer to the image carrier, and it is possible to prevent the image quality from deteriorating.

  A developer amount adjusting apparatus according to a second aspect of the present invention is the developer amount adjusting apparatus according to the first aspect, further comprising a storage unit, a first calculating unit, and a second calculating unit. The storage means can store the first relationship between the surface potential of the developer conveyed by the developing roller and the amount of the developer conveyed by the developing roller, and the second relationship between the developer amount on the developing roller and the reflection density. Means. The first calculation means is means for calculating the developer amount on the developing roller from the reflection density based on the second relationship. The second calculation means is means for calculating the first relationship based on the developer amount on the developing roller calculated by the first calculation means and the surface potential detected by the surface potential detection means.

  In this developer amount adjusting device, the developer amount on the developing roller is calculated based on the second relationship, and the first relationship is determined from the calculation result calculated by the first calculating means and the surface potential of the developer on the developing roller. Calculated.

  A developer amount adjusting apparatus according to a third aspect is the developer amount adjusting apparatus according to the second aspect, wherein the first calculating means calculates the amount of developer conveyed by the developing roller at a reflection density equal to or lower than a predetermined density. .

  Here, the developer amount at a reflection density equal to or lower than a predetermined density with good detection accuracy is detected. The calculation accuracy is improved as compared with the case of calculating the developer amount at a reflection density equal to or higher than a predetermined density. Here, the reflection density equal to or lower than a predetermined density means that the reflection density (which means the ratio between the light quantity emitted by the light emitting unit and the light quantity reflected by the developer) is accurately measured on the developing roller. The density in the range in which the developer amount changes, for example, a density of 1.2 or less in FIG. In the region where the developer amount is low, the toner charge amount and the reflection density have a substantially corresponding relationship.

  A developer amount adjusting apparatus according to a fourth aspect is the developer amount adjusting apparatus according to the second or third aspect, wherein the image forming apparatus includes a supply member that supplies the developer to the developing roller, a developing roller, and a supplying member. And a voltage applying device for applying a voltage to the power source. The carry amount adjusting means controls the voltage applying device based on the first relationship stored in the storage means.

  In this developer amount adjusting device, the applied voltage of the voltage applying device is controlled based on the first relationship. Here, since the applied voltage of the voltage application device is controlled using both the reflection density and the surface potential of the developer conveyed by the developing roller, the reflection density and the surface potential of the developer conveyed by the developing roller are controlled. Control can be performed with higher precision than in the case of controlling based on only one of them. For this reason, it becomes easy to supply an appropriate amount of developer to the image carrier, and it is possible to prevent the image quality from deteriorating.

  A developer amount adjusting device according to a fifth aspect of the present invention is the developer amount adjusting device according to any one of the first to fourth aspects, wherein the surface potential detecting means determines the surface potential of the developer conveyed by the developing roller as the developing roller. From the developer conveyed to the image carrier. The reflection density detecting means detects the reflection density of the developer conveyed by the developing roller from the developer conveyed from the developing roller to the image carrier.

  Here, in order to detect the reflection density and surface potential of the developer conveyed to the image carrier, a sensor can be disposed in the vicinity of the image carrier. For this reason, even when there is no space near the developing roller, the surface potential and reflection density of the developer can be detected.

  A developer amount adjusting apparatus according to a sixth aspect is the developer amount adjusting apparatus according to any one of the first to fourth aspects, wherein the image forming apparatus temporarily carries an image from an image carrier and transfers the image onto a sheet. And a transfer member. The surface potential detecting means detects the surface potential of the developer conveyed by the developing roller from the developer temporarily carried on the transfer member. The reflection density detecting means detects the reflection density of the developer conveyed by the developing roller from the developer temporarily carried on the transfer member.

  Here, in order to detect the reflection density and surface potential of the developer conveyed to the transfer member, a sensor can be disposed in the vicinity of the transfer member. For this reason, even when there is no space near the developing roller, the surface potential and reflection density of the developer can be detected.

  A developer amount adjusting apparatus according to a seventh aspect of the present invention is the developer amount adjusting apparatus according to any one of the first to fourth aspects, wherein the surface potential detecting means determines the surface potential of the developer conveyed by the developing roller as the developing roller. Detect from top developer. The reflection density detecting means detects the reflection density of the developer conveyed by the developing roller from the developer on the developing roller.

  Here, since the surface potential and reflection density of the developer on the developing roller are detected, the surface potential of the developer conveyed from the developing roller can be directly detected.

  An image forming apparatus according to an eighth aspect includes an image carrier, a developing device, a voltage applying device, and the developer amount adjusting device according to the first to seventh aspects. An electrostatic latent image is formed on the surface of the image carrier based on image information. The developing device can supply a developer to the image carrier and has a developing roller disposed so as to face the image carrier. The voltage application device is a device capable of applying a voltage to the developing roller.

  An image forming apparatus according to a ninth aspect is the image forming apparatus according to the eighth aspect, wherein the developing device can store toner and a carrier therein. The apparatus further includes a supply roller that supplies a developer to the developing roller and includes a mag roller having a plurality of magnetic poles therein and a sleeve disposed so as to cover the mag roller.

  Here, in an image forming apparatus using such a type of developing device, it is necessary to control the thickness of the developer layer with high accuracy, so the present invention is particularly effective.

  In the present invention, it is possible to accurately detect and control the amount of developer on the developing roller, and to prevent deterioration in image quality due to an inappropriate amount of developer supplied to the electrostatic latent image.

1 is an overall schematic cross-sectional view of a multifunction machine according to a first embodiment of the present invention. The elements on larger scale around a developing device. FIG. 3 is a block diagram illustrating a developer amount adjusting device. The figure which shows the 2nd relationship between toner adhesion amount and reflection density. The figure which shows the 1st relationship between a toner adhesion amount and surface potential. The table | surface which shows an experimental result. The table | surface which shows an experimental result. 6 is an example of an image forming unit according to another embodiment. 6 is an example of an image forming unit according to another embodiment.

[overall structure]
Hereinafter, a multifunction machine 1 as an image forming apparatus according to an embodiment of the present invention will be described with reference to FIG. Here, FIG. 1 shows an overall outline of a multifunction machine 1 according to an embodiment of the present invention. The multifunction device 1 is connected to an external computer or the like, and can form an image on a sheet based on image information read from a document or image information sent from a computer.

  The multifunction device 1 has various functions such as a function of copying a document and a function of transmitting image information of the document. As shown in FIG. 1, the multifunction device 1 includes a document reading unit 2, an image forming unit 3, a transfer unit 4, a sheet storage unit 5, a sheet transport unit 6, a fixing unit 7, and a discharge unit 8. The control unit 90 (see FIG. 3) is provided as a functional unit. The configuration of each functional unit will be described below.

{Original reading section}
The document reading unit 2 is a part for reading image information of a document. The document reading unit 2 is disposed at the top of the multifunction device 1.

{Image forming part}
The image forming unit 3 is a part for forming an image based on image information. The image forming unit 3 is disposed below the document reading unit 2. Further, the image forming unit 3 has four image forming units 30. The four image forming units 30 are arranged in a line. Each of the four image forming units 30 includes a photosensitive drum 31, a charging device 32, a laser unit 33, a developing device 34, a charge eliminating device 36, and a drum cleaning device 37. The four image forming units 30 can form yellow, magenta, cyan, and black toner images in order from the left side of FIG. The image forming units 30 have the same configuration. Therefore, the yellow image forming unit 30 will be described, and the description of the other image forming units 30 will be omitted.

  The photosensitive drum 31 is a member capable of carrying an electrostatic latent image on the surface. Further, the photosensitive drum 31 is rotatable around a rotation axis extending perpendicularly to the paper surface of FIG. The photosensitive drum 31 is disposed so as to contact a transfer belt 41 described later.

  The charging device 32 is a device for uniformly charging the surface of the photosensitive drum 31. The charging device 32 is disposed on the upper side of the photosensitive drum 31.

  The laser unit 33 is a device for irradiating the surface of the photosensitive drum 31 with laser light based on image information. The laser unit 33 is disposed on the upper side of the photosensitive drum 31.

  FIG. 2 shows a partially enlarged view around the developing device 34. The developing device 34 will be described with reference to FIG. The developing device 34 is a device capable of supplying a developer to the electrostatic latent image carried on the photosensitive drum 31. Further, each developing device 34 is disposed below the respective laser unit 33. Further, the developing device 34 includes a developing container 341, a developing roller 342, a magnetic roller 343, a regulating blade 344, two stirring screws 345, and a voltage applying device 346.

  The developing container 341 is a container that can store a developer of a color corresponding to each photosensitive drum 31 therein. The developing container 341 includes a replenishment toner storage unit 341a, a replenishment roller 341b, and a developer storage unit 341c.

  The replenishment toner storage portion 341a is a portion for storing replenishable toner in the developer storage portion 341c. Further, the replenishment toner storage portion 341a is located above the developer storage portion 341c. Further, the replenishment toner storage portion 341a is a box-shaped portion smaller than the developer storage portion 341c.

  The supply roller 341b is a member for supplying the toner stored in the supply toner storage unit 341a to the developer storage unit 341c. The replenishment roller 341b is disposed between the replenishment toner storage unit 341a and the developer storage unit 341c.

  The developer accommodating portion 341 c is a portion for accommodating a developer to be supplied to the photosensitive drum 31. The developer storage unit 341c stores toner and a carrier therein.

  The developing roller 342 is a member for supplying a developer to the photosensitive drum 31. The developing roller 342 is supported by the developing container 341. Further, the developing roller 342 is disposed so as to face the photosensitive drum 31.

  The magnetic roller 343 is a member for supplying the developer inside the developer accommodating portion 341c to the developing roller 342. The magnetic roller 343 is rotatably supported by the developing container 341. Further, the magnetic roller 343 is disposed in parallel with the developing roller 342. The magnetic roller 343 includes a roller member 343a having five magnetic poles and a sleeve 343b disposed so as to cover the roller member 343a.

  The roller member 343a has an N1 pole, an S1 pole, an N2 pole, an S2 pole, and an N3 pole. The N1 pole is disposed at a position facing the developing roller 342. The S1 pole is disposed at a position facing the regulating blade 344. The S1 pole is a magnetic pole for regulating the length of the magnetic brush formed on the surface. The S1 pole is disposed adjacent to the N1 pole. The N2 pole is a magnetic pole for attaching the developer in the developing device 34 to the surface of the sleeve 343b. The N2 pole is disposed adjacent to the S1 pole. The S2 pole is a magnetic pole for conveying the developer remaining on the sleeve 343b without being supplied from the N1 pole to the developing roller 342. The S2 pole is disposed adjacent to the N1 pole. The N3 pole is a magnetic pole for peeling off the residual toner from the sleeve 343b. The N3 pole is disposed between the N2 pole and the S2 pole.

  The sleeve 343b is a member for transporting the developer. The sleeve 343 b is a member that can rotate around a rotation axis parallel to the rotation axis of the photosensitive drum 31. Further, the sleeve 343b rotates in the direction of arrow A in FIG. The sleeve 343b is a cylindrical member.

  The regulating blade 344 is a member for regulating the thickness of the developer layer of the developing roller 342. The regulating blade 344 is disposed on the surface of the developing roller 342 with a predetermined space therebetween. Further, the regulation blade 344 is a plate-like member. The regulating blade 344 is a member that extends along the developing roller 342.

  The stirring screw 345 is a member for stirring the developer inside the developing container 341. Two stirring screws 345 are accommodated in the developing container 341 side by side. Further, the stirring screw 345 is disposed in parallel with the developing roller 342 and the magnetic roller 343.

  The voltage application device 346 is a device for applying a voltage to the developing roller 342 and the magnetic roller 343. Further, the voltage applying device 346 is connected to the developer amount adjusting device 9.

  The static eliminator 36 is a device for removing charges on the surface of the photosensitive drum 31. The static eliminator 36 is disposed above the photosensitive drum 31.

  The drum cleaning device 37 is a device for cleaning the developer remaining on the photosensitive drum 31 without being used for the developing operation. The drum cleaning device 37 includes a blade member 371 that contacts the surface of the photosensitive drum 31 and a waste developer storage container 372 (see FIG. 1) that can store toner scraped by the blade member 371.

{Transfer part}
As shown in FIG. 1, the transfer unit 4 includes a transfer belt 41, four primary transfer rollers 42, a secondary transfer roller 43, and a belt cleaning device 44.

  The transfer belt 41 is a member for transferring an image formed by the image forming unit 3 to a sheet. The transfer belt 41 is a member to which an image is primarily transferred from the photosensitive drum 31. Further, the transfer belt 41 is disposed below the photosensitive drum 31.

  The primary transfer roller 42 is a member for transferring the image on the photosensitive drum 31 onto the transfer belt 41. The primary transfer roller 42 is disposed so as to face the photosensitive drum 31 with the transfer belt 41 interposed therebetween. Further, each primary transfer roller 42 is connected to a voltage application device (not shown). Each primary transfer roller 42 is arranged in parallel with the direction in which the photosensitive drums 31 are arranged.

  The secondary transfer roller 43 is a member for transferring the image primarily transferred from the photosensitive drum 31 to the transfer belt 41 onto a sheet. The secondary transfer roller 43 is disposed so as to face the transfer belt 41 with the paper transport path of the paper transport unit 6 interposed therebetween.

  The belt cleaning device 44 is a device for cleaning toner, paper dust, dust and the like on the transfer belt 41. The belt cleaning device 44 is disposed on the right side of the transfer belt member 41 in FIG.

{Paper storage}
The paper storage unit 5 is a part for storing paper. The paper storage unit 5 is disposed at the lower part of the multifunction machine 1. Further, the paper storage unit 5 has a plurality of paper feed cassettes 51. Each paper cassette 51 stores different types (sizes, etc.) of paper. A plurality of paper feed cassettes 51 are stacked.

{Paper transport section}
The paper transport unit 6 is a part for transporting paper. The paper transport unit 6 has a paper transport path for transporting paper in the order of the paper storage unit 5, the transfer unit 4, the fixing unit 7, and the discharge unit 8. The paper transport unit 6 includes a paper transport guide pair 61 and a plurality of paper transport roller pairs 62.

  The paper transport guide pair 61 is a member for guiding the paper transport direction. The paper transport guide pair 61 has plate-like members arranged so as to face each other. A sheet can pass between these plate-like members.

  The paper transport roller pair 62 is a member for transporting paper in the paper transport direction. The pair of paper transport rollers 62 has two rollers arranged to face each other. The sheet can pass between the two rollers.

{Fixing part}
The fixing unit 7 is a part for fixing an image on a sheet. The fixing unit 7 is disposed on the downstream side of the transfer unit 4 in the sheet conveyance direction. Further, the fixing unit 7 includes a heating roller 71 that heats the image on the paper, and a pressure roller 72 that is disposed to face the heating roller 71 and presses the paper between the heating roller 71. .

{Discharge unit}
The discharge unit 8 is a part for discharging the sheet to the outside of the multifunction device 1. As shown in FIG. 1, the discharge unit 8 is disposed downstream of the fixing unit 7 in the sheet conveyance direction. The discharge unit 8 has a discharge roller 81. The discharge unit 8 is disposed below the document reading unit 2. The discharge unit 8 further includes a recess 82 that is recessed rightward from the left side surface of the multifunction device 1 in FIG. Then, the sheet is discharged into the recess 82.

{Control part}
FIG. 3 shows a block diagram of the control unit 90 and the like. The control unit 90 includes a storage unit 91 and a CPU (not shown). The control unit 90 is a part that can control the operation of each functional unit by executing a program. Further, the control unit 90 functions as the developer adjusting device 9 shown in FIG. 3 by executing the program.

  The developer amount adjusting device 9 is a device that adjusts the developer conveyance amount of the developing roller 342. The developer amount adjusting device 9 includes a storage unit 91, a surface potential detection unit 92, a toner concentration detection unit 93, a first calculation unit 94, a second calculation unit 95, and a conveyance amount adjustment of the control unit 90. Functions with the unit 96.

  The storage unit 91 is a part that stores various programs. In addition, the storage unit 91 stores the first relationship between the surface potential of the developer on the photosensitive drum 31 and the amount of developer conveyed by the developing roller 342 (see FIG. 5) and the development on the developing roller 342. The second relationship (see FIG. 4) between the agent amount and the reflection density is stored. Here, the reflection density means a ratio between the light emitted from the light emitting unit of the optical sensor 931 and the amount of light that is reflected by the developer and received by the light receiving unit.

  Here, in the first relationship, the relationship between the toner adhesion amount and the surface potential differs depending on the toner charge amount. For this reason, the storage unit 91 stores a first relationship between the toner adhesion amount and the surface potential, which differs for each toner charge amount. As shown in FIG. 5, in the present embodiment, four different first relationships, that is, a first relationship A of 40 μC / g, a first relationship B of 35 μC / g, and a first relationship C of 30 μC / g And only the first relationship D of 20 μC / g is illustrated.

  The surface potential detection unit 92 is a part that detects the surface potential of the developer conveyed by the developing roller 342. Specifically, the surface potential detector 92 detects the surface potential of the developer on the photosensitive drum 31. The surface potential detection unit 92 has a surface potential detection sensor 921. The surface potential detection sensor 921 is disposed in the vicinity of the photosensitive drum 31.

  The reflection density detector 93 is a part that detects the reflection density of the developer conveyed by the developing roller 342. Specifically, the reflection density detection unit 93 detects the reflection density of the developer on the photosensitive drum 31. Further, the reflection density detection unit 93 has an optical sensor 931 disposed in the vicinity of the photosensitive drum 31. The optical sensor 931 is arranged side by side with the surface potential sensor 921. The optical sensor 931 includes a light emitting unit and a light receiving unit that receives reflected light of light emitted from the light emitting unit.

The first calculator 94 is a part that calculates the amount of developer on the developing roller 342 from the reflection density based on the second relationship shown in FIG. For example, when the reflection density (ratio of reflected light to incident light) is 0.4, the developer conveyed to the photosensitive drum 31 of 1 g / m ² adheres to the developing roller 342 from the second relationship shown in FIG. Is calculated. The first calculation unit 94 calculates the amount of developer on the developing roller 342 at a density equal to or lower than a predetermined reflection density. Specifically, the amount of developer on the developing roller 342 at a reflection density of 1.2 or less in FIG. 4 is calculated.

  The second calculator 95 determines the first relationship based on the developer on the developing roller 342 calculated by the first calculator 94 and the surface potential of the developer on the photosensitive drum 31 detected by the surface potential detector 92. This is the part to calculate. Specifically, this is a part for detecting which of the plurality of first relationships stored in the storage unit 91 is appropriate.

The conveyance amount adjustment unit 96 is a part that adjusts the developer amount on the developing roller 342 based on the detection result of the surface potential detection unit 92 and the detection result detected by the reflection density detection unit 93. Specifically, the carry amount adjustment unit 96 controls the voltage application device 346 based on the first relationship stored in the storage unit 91. For example, when the relationship between the toner adhesion amount and the surface potential is the first relationship of 30 μC / g, when the toner adhesion amount of the developing roller 342 is 6 g / m ² , the developing roller 342 to the photosensitive drum When all the toner on the developing roller 342 is moved to 31, the voltage applying device 346 is applied so that a voltage that causes the surface potential on the photosensitive drum 31 to be −46 V is applied to the developing roller 342 and the magnetic roller 343. Control.

[Operation]
Next, the operation of the multifunction device 1 will be described.

  When image information of an original is read by the original reading unit 2 or image information is sent from a computer connected to the outside of the multifunction machine 1, an electrostatic latent image is formed on the photosensitive drum 31 based on the image information. . Specifically, the surface of the photosensitive drum 31 is charged by the charging device 32, and laser light is irradiated from the laser unit 33 to the photosensitive drum 31 based on the image information. When the electrostatic latent image is formed on the photosensitive drum 31 in this way, the developer is supplied from the developing roller 342 of the developing device 34 to the electrostatic latent image. When the developer is supplied from the developing device 34 to the electrostatic latent image, a toner image is formed on the photosensitive drum 31.

  Then, the toner image on each photosensitive drum 31 is transferred to the transfer belt 41. Then, the toner image on the transfer belt 41 is transferred to a sheet. The sheet on which the toner image is transferred is conveyed to the fixing unit 7 by the sheet conveying unit 6. After the toner image is fixed on the sheet by the fixing unit 7, the toner image is conveyed to the discharge unit 8. The sheet conveyed to the discharge unit 8 is discharged out of the multifunction machine 1.

  The operation of supplying the developer from the developing device 34 to the photosensitive drum 31 will be described in detail below with reference to FIG.

[Developer supply operation]
First, the developer stored in the developing container 341 is supplied to the developing roller 342 by the magnetic roller 343. Specifically, the developer stored in the developing container 341 is adsorbed to the N2 electrode. Then, it is moved toward the S1 pole with the rotation of the sleeve 343b. At this time, developer spikes are formed on the sleeve 343b, and the length of the spikes is regulated by the regulation blade 344. Thereafter, the spike of developer is moved to the N1 pole as the sleeve 343b rotates. The toner is electrically moved to the developing roller 342 from the developer spike that has moved to the N1 pole. When toner is supplied to the developing roller 342, the toner is moved to a position facing the photosensitive drum 31 as the developing roller 342 rotates. At this time, an electrostatic latent image based on image information is formed on the photosensitive drum 31. Then, toner is supplied from the developing roller 342 to the electrostatic latent image. At this time, the toner remaining on the developing roller 342 without being supplied to the electrostatic latent image is moved to the N3 pole via the S2 pole as the sleeve 343b rotates. The toner moved to the N3 pole is peeled off from the sleeve 343b and returned to the developing container 341.

  As described above, the toner is supplied to the electrostatic latent image on the photosensitive drum 31.

[Developer amount adjustment]
Next, the adjustment operation of the toner supply amount from the developing roller 342 to the photosensitive drum 31 will be described.

  First, a plurality of solid images, that is, images with uniform density are formed on the photosensitive drum 31. When this solid image is formed, a different voltage is applied to the developing roller 31 according to each solid image. Here, at least some of the applied voltages are set so that the reflection density of the solid image to be formed is not more than a predetermined value, that is, is located in a linear portion having a reflection density of 1.0 or less in FIG. . Then, the reflection density and surface potential of each solid image are measured. Thereafter, the toner adhesion amount adhered to the photosensitive drum 31 is calculated from the measured reflection density from the second relationship. Based on the toner adhesion amount and the surface potential, it is selected which of the plurality of first relationships stored in advance in the storage unit 91 corresponds to the first relationship. Thereafter, a surface potential necessary to obtain a desired toner adhesion amount is calculated based on the selected first relationship. A voltage applied to the developing roller 342 and the magnetic roller 343 necessary to obtain the calculated surface potential is determined. Thereafter, a voltage for obtaining a desired toner adhesion amount is applied from the voltage application device 346 to the developing roller 342 and the magnetic roller 343 during the image forming operation.

A specific example of the developer amount adjusting operation in the case where 6 g / m ² of developer is desired to adhere to the developing roller 342 will be described.

Three solid images are formed on the photosensitive drum 31. Specifically, voltages of −100 V, −200 V, and −300 V are applied to the developing roller 342, and three solid images are formed on the photosensitive drum 31. Then, the surface potential and reflection density of each solid image of −100V, −200V, and −300V are detected. For example, in a solid image of −100V, the surface potential is −9V and the reflection density is 0.8. In a solid image of -200V, the surface potential is -11V and the reflection density is 1.0. In a solid image of −300V, the surface potential is −15V and the reflection density is 1.25. In such a case, since the reflection density is 0.8 in the solid image of −100V, it can be seen from the relationship in FIG. 4 that the toner adhesion amount is about 1.9 g / m ² . This shows that the toner adhesion amount is about 1.9 g / m ^{2 at} the surface potential of −9V. Similarly, it can be seen that a solid image of −200 V has a toner adhesion amount of about 2.5 g / m ^{2 at} a surface potential of −11 V. It can be seen that in the solid image of −300V, the toner adhesion amount is about 3.3 g / m ^{2 when} the surface potential is −15V. From these relationships, the graph D of the first relationship of 20 μC / g shown in FIG. 5 is selected. From the first relationship of 20 μC / g, it can be seen that a surface potential of −32 V is necessary to deposit 6 g / m ² of developer on the developing roller 231.

An operation for detecting whether or not the developer on the developing roller 342 is 6 g / m ² when the surface potential is −32 V will be described.

When detecting whether the developer on the developing roller 342 is 6 g / m ² when the surface potential is −32 V, it is conceivable to directly detect the surface potential on the developing roller 342. However, it may be difficult to arrange a sensor for the purpose of detecting the amount of developer on the developing roller 342 in terms of securing a space for arranging the sensor. In this case, a sensor is provided in the vicinity of the photosensitive drum 31 as shown in FIG. 2 or in the vicinity of the transfer belt 41 as shown in FIG. 8, and the developer on the developing roller 342 is applied to the photosensitive drum 31 or the transfer belt 41. It is conceivable to detect the amount of developer on the developing roller 342 by moving it. In this case, it is necessary to move all the developer on the developing roller 342 to the photosensitive drum 31 side. The operation for setting the developing bias for moving all the developer on the developing roller 342 onto the photosensitive drum 31 will be described below.

  A voltage is applied to the developing roller 342 and the photosensitive drum 31 so that the initial developing bias acts between the developing roller 342 and the photosensitive drum 31. Then, developer is supplied from the developing roller 342 to the photosensitive drum 31, and a solid image is formed on the photosensitive drum 31. At this time, the surface potential H1 of the solid image formed on the photosensitive drum 31 is detected. Thereafter, a voltage is applied to the developing roller 342 and the photosensitive drum 31 such that a developing bias that is a predetermined amount lower than the initial developing bias acts between the developing roller 342 and the photosensitive drum 31. At this time, the surface potential H2 of the solid image formed on the photosensitive drum 31 is detected. And it is judged whether H1-H2 is 5V or less. When the voltage is 5 V or higher, it is considered that the developer on the developing roller 342 is not supplied to the photosensitive drum 31. Therefore, H3 calculated using a developing bias lower than the developing bias in the case of H2 is detected. A determination is again made as to whether H2-H3 is 5 V or less. When H2-H3 is 5 V or more, H4 calculated using a developing bias lower than the developing bias in the case of H3 is detected again, and the above operation is repeated. On the other hand, when the voltage is 5 V or less, it is considered that almost all of the developer on the developing roller 342 has been supplied to the photosensitive drum 31, and therefore the amount of developer on the photosensitive drum 31 at this time is the developer on the developing roller 342. The amount is considered to be.

For example, a voltage is applied to the photosensitive drum 31 and the developing roller 342 so that a developing bias of −300 V acts between the photosensitive drum 31 and the developing roller 342. At this time, the surface potential H1 of the solid image formed on the photosensitive drum 31 is detected. Thereafter, a voltage is applied to the photosensitive drum 31 and the developing roller 342 so that a developing bias of −350 V acts between the photosensitive drum 31 and the developing roller 342. At this time, the surface potential H2 of the solid image formed on the photosensitive drum 31 is detected. Then, it is determined whether or not H1−H2 is within 5V. If the voltage is 5V or more, the photosensitive drum 31 and the developing roller 342 are such that a developing bias of −400V acts between the photosensitive drum 31 and the developing roller 342. A voltage is applied to. At this time, the surface potential H3 of the solid image formed on the photosensitive drum 31 is detected. Then, it is determined whether or not H2-H3 is within 5V. When the voltage is 5 V or more, the same operation is repeated again. When the voltage is 5 V or less, it is determined that almost all the developer on the developing roller 342 has been supplied to the photosensitive drum 31. When it is detected from this developer transport amount that 6 g / m ² of developer has adhered to the developing roller 342, when 6 g / m ² of developer is supplied to the developing roller 342 during the image forming operation. Is applied to the developing roller 342 and the magnetic roller 343, and the voltage applying device 346 is controlled.

  The developer amount adjustment operation described above may be performed when the power is turned on, or may be performed between two jobs or for each predetermined number of printed sheets.

[effect]
Here, compared with the case where the developer amount is controlled only from the reflection density detected using the optical sensor 931 and the case where the developer amount is controlled only from the surface potential detected by the sensor, the amount on the developing roller 342 is increased. The amount of developer can be adjusted with high accuracy. For this reason, it is possible to prevent deterioration in image quality due to an inappropriate amount of developer supplied to the electrostatic latent image.

[Experimental example]
FIG. 6 shows experimental results in the image forming apparatus having the developing device of FIG.
In this experiment, a photosensitive drum having a diameter of 60 cm and a developing roller having a diameter of 20 cm were used. Further, “NEW” of the toner in the experimental result of FIG. 6 means that a new toner was used, and “deterioration” was 5% coverage (ratio of the print area to the paper area) and gave deterioration equivalent to 5000 sheets. This means that a developer was used. The “toner charge amount” is changed by changing the T / C of the developer (the ratio of the toner to the carrier). Furthermore, “◯” in the judgment part means that the measured value is within ± 0.5 g / m ² from the target adhesion amount. Then, as shown in FIG. 2, the “hybrid” returns the developer remaining on the photosensitive drum after the image forming operation among the developers supplied from the developing device to the photosensitive drum, to the developing device again. It means an image forming apparatus having a developing device which is used again for the image forming operation.

In Experimental Example 1, a new toner was used in the developing device 34 configured as shown in FIG. In this experimental example, the toner charge amount is 20 μC / g, and 6 g / m ² of toner is intended to adhere on the developing roller. As shown in the experimental results, about 6 g / m ² of toner can be adhered onto the developing roller 342, and a toner amount almost as intended can be adhered to the developing roller 342. Experimental Example 2 is an experiment performed under the same conditions as Experimental Example 1 except for the toner charge amount, and the toner charge amount is set to 25 μC / g. Also in this experimental example 2, it was possible to adhere the toner of the almost intended amount to the developing roller 342.

In Experimental Example 3, the conditions other than the toner charge amount and the target adhesion amount are the same as those in Experimental Example 1, and the toner charge amount is 40 μC / g and the target adhesion amount is 5 g / m ^2. . In Experimental Example 3, 4.8 g / m ² of toner could be adhered to the developing roller 342, and a toner amount almost as intended could be adhered.

In Experimental Example 4, the conditions other than the toner charge amount and the target adhesion amount were the same as those in Experimental Example 1, and the toner charge amount was 30 μC / g and the target adhesion amount was 7 g / m ^2. . In Experimental Example 4, 7.3 g / m ² of toner could be adhered to the developing roller 342, and a toner amount almost as intended could be adhered. Experimental Example 5 was performed under the same conditions as Experimental Example 1 except that the deteriorated toner was used, the toner charge amount, and the target adhesion amount, and the toner charge amount was 30 μC / g and the target adhesion amount was 5 g. / M ² . In Experimental Example 5, 4.7 g / m ² of toner could be adhered to the developing roller 342, and a toner amount almost as intended could be adhered. In Experimental Example 6, the conditions other than the toner charge amount and the target adhesion amount were the same as in Experimental Example 1, and the toner charge amount was 30 μC / g and the target adhesion amount was 5 g / m ^2. . In Experimental Example 6, 5.1 g / m ² of toner could be adhered to the developing roller 342, and the toner amount as intended could be adhered.

Here, an example in which the developer amount is adjusted based only on the surface potential or reflection density of the toner will be shown as a comparative example.
In Comparative Example 1, a new toner is used for the developing device 34 as shown in FIG. 2, the toner charge amount is 40 μC / g, and the aim is to attach 6 g / m ² of toner onto the developing roller 342. It is. In Comparative Example 1, the developer amount is adjusted based only on the surface potential of the toner. In Comparative Example 1, about 3 g / m ² of toner adhered to the developing roller 342. In this comparative example 1, the actual adhesion amount is about half of the target toner adhesion amount, which cannot be said to be the target adhesion amount. In Comparative Example 2, the experiment was performed under the same conditions as in Comparative Example 1 except that deteriorated toner was used. In Comparative Example 2, about 4.2 g / m ² of toner adhered to the developing roller 342. In Comparative Example 2, the actual adhesion amount is very small compared to the target toner adhesion amount, and cannot be said to be the intended adhesion amount. Comparative Example 3 is an experimental example in which the developer amount was controlled based on only the reflection density, not the surface potential, and the conditions other than the toner charge amount were the same as those in Comparative Example 1. In Comparative Example 3, the toner adhesion amount cannot be accurately measured, and it cannot be said that the intended adhesion amount can be adhered to the developing roller 342.

  Next, FIG. 7 shows experimental results in an image forming apparatus having the developing device of FIG. That is, an experimental example in which the amount of developer on the developing roller is detected by a sensor will be described. In this experiment, a photosensitive drum having a diameter of 60 cm and a developing roller having a diameter of 20 cm were used. Further, terms such as “NEW” in FIG. 7 have the same meaning as the terms in FIG.

In Experimental Example 7, a new toner was used for the developing device 34 having the configuration shown in FIG. In Experimental Example 7, the toner charge amount is 20 μC / g, and this is an experiment aimed at attaching 6 g / m ² of toner onto the developing roller 342. As shown in the experimental results, about 5.8 g / m ² of toner can be adhered on the developing roller 342, and a toner amount almost as intended can be adhered to the developing roller 342. Experimental Example 8 is an experiment performed under the same conditions as Experimental Example 7 except for the toner charge amount, and the toner charge amount is set to 25 μC / g. Also in this Experimental Example 8, it was possible to adhere the toner of the almost intended amount to the developing roller 342. In Experimental Example 9, the conditions other than the toner charge amount and the target adhesion amount were the same as in Experimental Example 7, and the toner charge amount was 40 μC / g and the target adhesion amount was 5 g / m ^2. . In Experimental Example 9, 4.9 g / m ² of toner could be adhered to the developing roller 342, and a toner amount almost as intended could be adhered.

  Here, an example in which the developer amount is adjusted based only on the surface potential or reflection density of the toner will be shown as a comparative example.

In Comparative Example 4, a new toner is used in the developing device shown in FIG. 9, the toner charge amount is 40 μC / g, and 7 g / m ² of toner is intended to adhere on the developing roller 342. In Comparative Example 4, the developer amount is adjusted based only on the surface potential of the toner. In Comparative Example 4, about 4 g / m ² of toner adhered to the developing roller 342. In Comparative Example 4, the actual adhesion amount is very small compared to the target toner adhesion amount, and cannot be said to be the intended adhesion amount. In Comparative Example 5, the deteriorated toner was used and conditions other than the target adhesion amount were performed under the same conditions as in Comparative Example 4. The target adhesion amount in Comparative Example 5 is about 4 g / m ² . In Comparative Example 5, about 3.8 g / m ² of toner adhered to the developing roller 342. In Comparative Example 5, the actual adhesion amount is very small compared to the target toner adhesion amount, and cannot be said to be the target adhesion amount. Comparative Example 6 is an experimental example performed under the same conditions as Comparative Example 4 except that the developer amount is controlled based on only the reflection density, not the surface potential, and the toner charge amount. In Comparative Example 6, the toner adhesion amount cannot be accurately measured, and it cannot be said that the intended adhesion amount can be adhered to the developing roller 342.

  From the above, it can be seen that the toner can be attached to the developing roller 342 with high accuracy by using the present invention.

[Other Embodiments]
(A) In the above embodiment, as shown in FIG. 2, the reflection density and surface potential of the toner on the photosensitive drum 31 are detected. However, the present invention is not limited to this, and as shown in FIG. In addition, the reflection density and surface potential of the toner on the transfer belt 41 may be detected. Further, as shown in FIG. 9, the reflection density and surface potential of the toner on the developing roller 342 may be directly measured.

  In addition, in the case of detecting the reflection density and surface potential of the developer on the transfer belt 41 other than the developing roller 342 and the photosensitive drum 31 including the case of the above embodiment, the rotational speed of the photosensitive drum 31 and the developing roller 342 are detected. It is necessary to pay attention to the relationship with the rotation speed. That is, for example, when the photosensitive drum 31 rotates at a rotational speed that is 2/3 of the rotational speed of the developing roller 342, the developer on the photosensitive drum 31 with respect to the layer thickness of the developer adhering to the developing roller 342. The layer thickness becomes 3/2. Therefore, in such a case, it is necessary to apply the relationship shown in FIGS. 4 and 5 in consideration of this point. In the above-described embodiments and experimental examples, values such as the layer thickness of the developer on the developing roller 342 are shown in consideration of this point.

  (B) In the above embodiment, the tandem developing device is used in the above embodiment. However, the present invention is not limited to this, and a configuration in which the developing device 34 is arranged around one photosensitive drum 31 or a developing device. The device 34 may be one monochrome format or the like.

  (C) In the above embodiment, the multifunction device 1 has been described. However, the present invention is not limited to this and may be a copying machine, a copying machine, or the like.

  (D) In the above embodiment, a sensor is provided in the vicinity of the photosensitive drum 31 and the relationship shown in FIG. 5 is experimentally obtained in advance for the developer on the photosensitive drum 31, but the present invention is not limited to this. If the configuration is different from the configuration of the present invention, it is necessary to experimentally obtain the relationship of FIG. 5 according to the configuration.

  For example, when a sensor is provided in the vicinity of the developing roller to detect the surface potential of the developer on the developing roller, the relationship corresponding to the relationship shown in FIG. 5 is experimentally detected using the developing roller. There is a need. Similarly, when a transfer belt is used, the relationship corresponding to FIG. 5 needs to be experimentally obtained in advance.

  This is because parameters, environments, and the like that affect the relationship corresponding to FIG. 5 such as the dielectric constant are different for each member, and the relationship corresponding to FIG. 5 is experimentally obtained in advance based on the members actually used. It is necessary to keep.

1 MFP (image forming device)
9 Developer amount adjusting device 31 Photosensitive drum (image carrier)
34 Developing Device 91 Storage Unit (Storage Unit)
92 Surface potential detection unit (surface potential detection means)
93 Reflection density detector (reflection density detector)
94 1st calculation part (1st calculation means)
95 Second calculation unit (second calculation means)
96 Conveyance amount adjustment unit (conveyance amount adjustment means)
342 Developing roller 343a Roller member 343b Sleeve

Claims (7)

A developer amount adjusting device for adjusting the amount of developer on a developing roller capable of supplying a developer to an image carrier of an image forming apparatus,
Surface potential detecting means for detecting the surface potential of the developer conveyed by the developing roller;
Reflection density detecting means for detecting the reflection density of the developer conveyed by the developing roller;
Information on the first relationship between the surface potential of the developer conveyed by the developing roller and the amount of developer conveyed by the developing roller, and the second of the amount of developer conveyed by the developing roller and the reflection density Storage means capable of storing information related to the relationship;
A developer amount on the developing roller under a condition indicating a plurality of different reflection densities that are equal to or lower than a predetermined reflection density is calculated based on the reflection density detected by the reflection density detecting unit and the information on the second relationship. First calculating means;
Using the developer amount on the developing roller calculated by the first calculating unit and the surface potential detected by the surface potential detecting unit, the developer amount on the developing roller corresponding to the predetermined reflection density Second calculation means for determining the first relationship in a larger developer amount range based on the information stored in the storage means;
A transport amount adjusting means for adjusting the amount of developer on the developing roller based on the first relationship determined by the second calculating means ;
A developer amount adjusting device. The image forming apparatus includes a supply member for supplying a developer to the development roller, and a voltage application device for applying a voltage to the development roller and the supply member.
The conveyance amount adjusting means controls the voltage applying device based on the stored first relationship to said storage means,
The developer amount adjusting device according to claim 1 . The surface potential detecting means detects the surface potential of the developer conveyed by the developing roller from the developer conveyed from the developing roller to the image carrier;
The reflection density detecting means detects the reflection density of the developer conveyed by the developing roller from the developer conveyed from the developing roller to the image carrier;
The developer amount adjusting device according to claim 1 or 2 . The image forming apparatus further includes a transfer member that temporarily holds an image from the image carrier and transfers the image to a sheet,
The surface potential detecting means detects the surface potential of the developer conveyed by the developing roller from the developer temporarily carried on the transfer member;
The reflection density detecting means detects the reflection density of the developer conveyed by the developing roller from the developer temporarily carried on the transfer member;
The developer amount adjusting device according to claim 1 or 2 . The surface potential detecting means detects the surface potential of the developer conveyed by the developing roller from the developer on the developing roller;
The reflection density detecting means detects the reflection density of the developer conveyed by the developing roller from the developer on the developing roller;
The developer amount adjusting device according to claim 1 or 2 . The image carrier on which an electrostatic latent image is formed on the surface based on image information;
A developing device capable of supplying a developer to the image carrier and having the developing roller arranged to face the image carrier;
A voltage applying device capable of applying a voltage to the developing roller;
A developer amount adjusting device according to any one of claims 1 to 5 ;
An image forming apparatus. The developing device includes:
A developer storage section capable of storing toner and carrier therein;
A developer roller for supplying developer to the developing roller, and further comprising a supply roller having a mag roller having a plurality of magnetic poles therein and a sleeve arranged to cover the mag roller;
The image forming apparatus according to claim 6 .

Images