JP2009145488A - Developer carrier refreshing method, image forming apparatus, image forming method, process cartridge, and developing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developer carrier refreshing method for moving developer adhering to a developer carrier onto an image carrier considering degree of deterioration in the developer, an image forming method using the method, an image forming method using the two methods, a process cartridge used for them, and a developing device used for them and having the developer carrier. <P>SOLUTION: The developer carrier refreshing method uses: a two-or-more-density-image forming step for forming two or more images having different image density; an image density detection step for detecting the image density of each of the two or more images formed in the two-or-more-density-image forming step by using an image density detection means; and a refreshing mode implementation judging step for judging whether or not the refreshing mode is performed on the basis of the image density of each of the two or more images detected by the image density detection step. In the refreshing mode, developing bias is formed by a bias forming means 80Y, to move the developer on the developer carrier 51Y onto the image carrier 20Y. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a developer carrier refreshing method for removing toner adhering to a developer carrier such as a developing roller used in an image forming apparatus such as a copying machine, a facsimile, and a printer, and such an image forming apparatus using the same. Further, the present invention relates to an image forming method using these, a process cartridge used for these, and a developing device using such a developer carrying member.

  Image forming apparatuses such as copying machines, facsimiles, and printers are generally image bearing members such as photoreceptors on which electrostatic latent images are formed as described in, for example, [Patent Document 1] to [Patent Document 3]. And a developer carrying member such as a developing roller for carrying the developer and developing the image carrying member with toner contained in the carried developer.

In such an image forming apparatus, the developer may adhere to the developer carrying member due to deterioration of the developer or the like, and the developing performance may be deteriorated. Therefore, for example, as described in [Patent Document 1] and the like, an image forming apparatus that performs a fresh operation for moving the developer attached on the developer carrying member onto the image carrying member has been proposed.
[Patent Document 2] and [Patent Document 3] describe techniques for forcibly consuming a developer in consideration of deterioration of the developer.

JP-A-9-258553 Japanese Patent No. 3029648 JP 2001-75438 A

  However, although it is desirable that the timing at which the developer adhered on the developer carrier is moved on the image carrier is preferably determined in consideration of the degree of deterioration of the developer, such a technique is still proposed. Not.

  The present invention relates to a developer carrying member refreshing method in which the developer attached on the developer carrying member is moved onto the image carrying member in consideration of the degree of deterioration of the developer, such an image forming apparatus using the same, and the like. It is an object of the present invention to provide an image forming method, a process cartridge used in the image forming method, and a developing device including the developer carrier used in the image forming method.

  In order to achieve the above object, an invention according to claim 1 includes an image carrier that carries an electrostatic latent image, and a developer that carries the developer and develops the image carrier with toner contained in the developer. And a bias forming means for forming a developing bias for developing the image carrier by moving toner contained in the developer carried on the developer carrier onto the image carrier. An image density detecting means for detecting the density of the developed image, the developing bias is formed by the bias forming means, and the developer on the developer carrying body is moved onto the image carrying body to carry the developer A developer carrier refreshing method for performing a refresh mode for refreshing a body, wherein a multi-density image forming step for forming a plurality of images having different image densities and the multi-density image forming step An image density detection step for detecting the image density of each of the plurality of images using the image density detection means, and the refresh based on the image density of each of the plurality of images detected in the image density detection step The developer carrier refreshing method includes a refresh mode execution determination step for determining whether or not to perform a mode.

  According to a second aspect of the present invention, in the developer carrier refreshing method according to the first aspect, in the refresh mode execution determining step, the ratio of the change in image density of each of the plurality of images detected in the image density detecting step It is determined that the refresh mode is performed on the condition that is greater than a predetermined ratio.

  According to a third aspect of the present invention, in the developer carrier refreshing method according to the first or second aspect, in the refresh mode, the ratio of the change in the image density of each of the plurality of images detected in the image density detection step. Accordingly, the length of time for forming the developing bias is changed by the developing bias forming means.

  According to a fourth aspect of the present invention, in the developer carrier refreshing method according to any one of the first to third aspects, when the refresh mode is determined to be performed in the refresh mode execution determining step, the refresh mode is set. Dividing the plurality of times at a predetermined time interval, and changing the predetermined time interval according to a rate of change in image density of each of the plurality of images detected in the image density detection step. To do.

  According to a fifth aspect of the present invention, in the developer carrier refreshing method according to any one of the first to fourth aspects, the absolute value of the potential difference between the latent image potential of the image carrier and the developing bias is set as the absolute value of the potential difference. The refresh mode is different from that at the time of normal image formation.

  According to a sixth aspect of the present invention, in the developer carrier refreshing method according to the fifth aspect, the absolute value is larger when the refresh mode is executed than when a normal image is formed.

  According to a seventh aspect of the present invention, in the developer carrier refreshing method according to the sixth aspect, the developing bias at the time of executing the refresh mode is set to a level at which development characteristics are saturated.

  According to an eighth aspect of the present invention, in the developer carrying member refreshing method according to the seventh aspect, a change in the image density of each of the plurality of images detected in the image density detection step is a level at which the development characteristic is saturated. It is characterized by determining based on the ratio of.

  According to a ninth aspect of the present invention, in the developer carrier refreshing method according to any one of the first to eighth aspects, the multi-density image forming step includes the step that the number of formed images reaches a predetermined number and / or Alternatively, it is performed on condition that the traveling distance of the image carrier has reached a predetermined distance and / or that a predetermined change has occurred in the atmosphere environment.

  A tenth aspect of the present invention includes the image carrier, the developer carrier, the bias forming unit, and the image density detecting unit, and the image density detecting unit according to any one of the first to ninth aspects. The image forming apparatus uses a developer carrier refreshing method.

  An eleventh aspect of the present invention is the developer carrying member refreshing method according to any one of the first to ninth aspects, or the image forming method using the image forming apparatus according to the tenth aspect.

  According to a twelfth aspect of the present invention, there is provided the developer carrier refreshing method according to any one of the first to ninth aspects, the image forming apparatus according to the tenth aspect, or the image forming method according to the eleventh aspect. It is in the process cartridge to be used.

  The invention described in claim 13 has at least the developer carrier, and the developer carrier refresh method according to any one of claims 1 to 9, or the image forming apparatus according to claim 10, or The image forming method according to claim 11 or the developing device used for the process cartridge according to claim 12.

  The present invention relates to an image carrier that carries an electrostatic latent image, a developer carrier that carries a developer and develops the image carrier with toner contained in the developer, and a carrier that is carried on the developer carrier. Bias forming means for forming a developing bias for moving the toner contained in the developed developer onto the image carrier to develop the image carrier, and image density detecting means for detecting the density of the formed image And developing the developing bias by the bias forming means and moving the developer on the developer carrier onto the image carrier to perform a refresh mode for refreshing the developer carrier. In the agent carrier refreshing method, a plurality of density image forming steps for forming a plurality of images having different image densities, and the respective image densities of the plurality of images formed in the plurality of density image forming steps An image density detection step for detecting the image density using the image density detection means, and a refresh for determining whether to perform the refresh mode based on the image density of each of the plurality of images detected in the image density detection step Since the developer carrying member refreshing method includes a mode execution judging step, the image carrying the developer adhered on the developer carrying member at a relatively simple timing in consideration of the degree of developer deterioration. It is possible to move the developer on the image bearing member, and it is also possible to move the deteriorated developer near the developer bearing member onto the image bearing member, which contributes to good image formation by maintaining the developing performance over time. It is possible to provide a developer carrier refreshing method that can be applied.

  In the refresh mode execution determination step, it is determined that the refresh mode is performed on the condition that the rate of change in image density of each of the plurality of images detected in the image density detection step is greater than a predetermined rate. If this is the case, it is possible to move the developer adhering to the developer carrying member onto the image carrying member at a more appropriate timing that is determined relatively easily, taking into account the degree of deterioration of the developer. It is also possible to move the deteriorated developer in the vicinity of the developer carrier onto the image carrier, and to maintain the development performance better over time and to contribute to better image formation An agent carrier refreshing method can be provided.

  In the refresh mode, the length of time for forming the developing bias by the developing bias forming means is changed in accordance with the rate of change in the image density of each of the plurality of images detected in the image density detecting step. Then, the developer attached on the developer carrier can be sufficiently moved onto the image carrier at a relatively simple timing that better considers the degree of deterioration of the developer, It is also possible to move the deteriorated developer in the vicinity of the developer carrier onto the image carrier, and maintain the development performance better over time and contribute to better image formation. A body refreshing method can be provided.

  When it is determined in the refresh mode execution determination step that the refresh mode is performed, the refresh mode is divided into a plurality of times at a predetermined time interval, and the predetermined time interval is detected in the image density detection step. If it is changed in accordance with the rate of change in the image density of each of the plurality of images, it adheres to the developer carrier at a relatively simple timing considering the degree of deterioration of the developer. The developer can be moved onto the image carrier, and the deteriorated developer in the vicinity of the developer carrier can also be moved onto the image carrier. In addition to contributing to image formation, the developer moved to the image carrier side can be well cleaned, and the effect of the developer on image formation can be improved. A developer carrying member refresh method that can prevent or reduce can be provided.

  If the absolute value of the potential difference between the latent image potential of the image carrier and the development bias is made different between the execution of the refresh mode and the normal image formation, the degree of deterioration of the developer is taken into consideration. It is possible to efficiently move the developer adhering to the developer carrier onto the image carrier at a relatively simple timing, and the deteriorated developer in the vicinity of the developer carrier can be removed from the image carrier. It is possible to provide a developer carrier refreshing method that can be moved upward and that can contribute to good image formation while maintaining development performance over time.

  If the absolute value is larger during execution of the refresh mode than during normal image formation, the developer carrier is determined at a relatively simple timing in consideration of the degree of deterioration of the image agent. The developer adhering to the image carrier can be efficiently moved onto the image carrier, and the deteriorated developer near the developer carrier can be moved onto the image carrier. Thus, it is possible to provide a developer carrier refreshing method that can contribute to good image formation while maintaining the required time and shortened the required time.

  If the developing bias at the time of executing the refresh mode is set to a level at which the developing characteristics are saturated, the developer bias is placed on the developer carrier at a relatively simple timing in consideration of the degree of deterioration of the image agent. It is possible to move the adhered developer onto the image carrier more efficiently, and it is also possible to move the deteriorated developer near the developer carrier onto the image carrier. Thus, it is possible to provide a developer carrier refreshing method that can contribute to good image formation while maintaining the required time and can further reduce the required time.

  If the degree of saturation of the development characteristics is determined based on the rate of change in the image density of each of the plurality of images detected in the image density detection step, the degree of deterioration of the image agent is taken into consideration. The developer attached on the developer carrier can be moved onto the image carrier more efficiently by using a multiple density image forming step and an image density detection step at a relatively simple timing. It is also possible to move the deteriorated developer in the vicinity of the developer carrier onto the image carrier, and it is possible to maintain development performance over time and contribute to good image formation. It is possible to provide a developer carrier refreshing method capable of shortening the above.

  In the multi-density image forming step, the image forming number has reached a predetermined number and / or the traveling distance of the image carrier has reached a predetermined distance and / or a predetermined change has occurred in the atmosphere environment. If the condition is satisfied, the developer attached on the developer carrier is image-bearing at a relatively simple timing, considering the degree of deterioration of the developer more appropriately using these conditions. It is possible to move the developer on the image bearing member, and it is also possible to move the deteriorated developer near the developer bearing member onto the image bearing member, which contributes to good image formation by maintaining the developing performance over time. It is possible to provide a developer carrier refreshing method that can be applied.

  The present invention is an image forming apparatus that includes the image carrier, the developer carrier, the bias forming unit, and the image density detecting unit, and uses the developer carrier refreshing method. The developer adhering to the developer carrying member is moved onto the image carrying member at a relatively simple timing in consideration of the degree of deterioration of the developer, and the deteriorated developer near the developer carrying member is removed. Since it can also be moved onto the image carrier, it is possible to provide an image forming apparatus capable of performing good image formation while maintaining development performance over time.

  Since the present invention is in such a developer carrier refreshing method or an image forming method using such an image forming apparatus, the developer carrying is carried out at a relatively simple timing in consideration of the degree of deterioration of the developer. The developer attached on the body can be moved onto the image carrier, and the deteriorated developer in the vicinity of the developer carrier can be moved onto the image carrier, thereby maintaining the development performance over time. Thus, it is possible to provide an image forming method capable of performing good image formation.

  Since the present invention is in the developer carrier refreshing method, the image forming apparatus, or the process cartridge used in the image forming method, it is determined relatively easily in consideration of the degree of deterioration of the developer. At the timing, the developer attached on the developer carrier can be moved onto the image carrier, and the deteriorated developer near the developer carrier can be moved onto the image carrier, It is possible to provide a developer carrier refreshing method, an image forming apparatus, and a process cartridge that contributes to an image forming method that can contribute to good image formation while maintaining development performance over time.

  The present invention includes at least the developer carrier, and the developer carrier refresh method, or the image forming apparatus, the image forming method, or the developing device used for the process cartridge. The developer adhering to the developer carrier can be moved onto the image carrier at a relatively simple timing considering the degree of deterioration of the developer, and the vicinity of the developer carrier has deteriorated. In the developer carrier refreshing method, image forming apparatus, and image forming method, it is possible to move the developer onto the image carrier and maintain development performance over time and contribute to good image formation. A contributing developing device can be provided.

  FIG. 1 shows an outline of an image forming apparatus to which the present invention is applied. The image forming apparatus 100 is a color laser printer capable of forming a color image. However, the image forming apparatus 100 may be another type of image forming apparatus such as a printer, a facsimile machine, a copier, a copier-printer multifunction machine, or the like. good. The image forming apparatus 100 performs an image forming process based on an image signal corresponding to image information received from the outside. The image forming apparatus 100 can form an image using plain paper generally used for copying, OHP sheets, thick paper such as cards and postcards, and envelopes as sheet-like recording media. .

  The image forming apparatus 100 includes photosensitive drums 20Y, 20C, 20M, and 20BK as image carriers that can form images as images corresponding to colors separated into yellow, magenta, cyan, and black, respectively. The installed tandem structure, in other words, the tandem system is adopted. Y, C, M, and BK added after the numerals of the respective symbols indicate members for yellow, cyan, magenta, and black.

  The photosensitive drums 20Y, 20C, 20M, and 20BK are on the outer peripheral surface side of the transfer belt 11 as an intermediate transfer body, that is, an endless belt disposed almost at the center inside the main body 99 of the image forming apparatus 100, that is, image formation. Located on the surface side.

  The transfer belt 11 is movable in the direction of the arrow A1 while facing each of the photosensitive drums 20Y, 20C, 20M, and 20BK. The photosensitive drums 20Y, 20C, 20M, and 20BK are arranged in this order from the upstream side in the A1 direction.

  Visible images, that is, toner images formed on the respective photosensitive drums 20Y, 20C, 20M, and 20BK are respectively superimposed and transferred onto the transfer belt 11 that moves in the direction of the arrow A1, and then collectively onto the transfer sheet S that is a recording medium. It is designed to be transcribed. Therefore, the image forming apparatus 100 is an intermediate transfer type image forming apparatus.

  The lower portion of the transfer belt 11 is opposed to the photosensitive drums 20Y, 20C, 20M, and 20BK, and the opposed portions receive the toner images on the photosensitive drums 20Y, 20C, 20M, and 20BK. A transfer portion 98 for transferring to the transfer belt 11 is formed.

  In the superimposing transfer to the transfer belt 11, the toner images formed on the photosensitive drums 20Y, 20C, 20M, and 20BK are transferred to the same position on the transfer belt 11 while the transfer belt 11 moves in the A1 direction. As described above, voltage application by primary transfer rollers 12Y, 12C, 12M, and 12BK disposed at positions facing the respective photosensitive drums 20Y, 20C, 20M, and 20BK across the transfer belt 11 causes the A1 direction upstream. The timing is shifted toward the downstream side.

  The transfer belt 11 has a multilayer structure in which the base layer is made of a material with little elongation, the surface of the base layer is covered with a smooth material, and the coat layer is formed on the base layer. Examples of the material of the base layer include a fluororesin, a PVD sheet, and a polyimide resin. Examples of the material of the coat layer include a fluorine resin.

  The transfer belt 11 has a base portion as a non-image forming portion (not shown) on which a toner image is not transferred in a part in the A1 direction. The base portion is used instead of a reference plate for adjusting so that an output value of an image density detecting means 81 described later becomes constant.

  Each of the transfer belts 11 has a detent guide (not shown) as a detent member at each edge thereof. The offset guide is provided to prevent the transfer belt 11 from being biased in any direction perpendicular to the paper surface in FIG. 1 when the transfer belt 11 rotates in the A1 direction. The stopper guide is made of urethane rubber, but can be made of various rubber materials such as silicon rubber.

  Each of the photosensitive drums 20Y, 20C, 20M, and 20BK has image forming units 60Y, 60C, and 60M as toner image forming portions as image forming portions for forming yellow, cyan, magenta, and black images, respectively. , 60BK.

  The image forming apparatus 100 includes four image forming units 60Y, 60C, 60M, and 60BK, and is disposed to face the photosensitive drums 20Y, 20C, 20M, and 20BK. The image forming apparatus 100 includes a transfer belt 11. Below the transfer belt unit 10, the secondary transfer roller 5 as a transfer member that is disposed opposite to the transfer belt 11 and is driven by the transfer belt 11, and the image forming units 60Y, 60C, 60M, and 60BK. And an optical scanning device 8 as a writing unit disposed so as to face each other.

  The image forming apparatus 100 also includes a sheet feeding device 61 as a sheet feeding cassette on which the transfer sheets S transported between the photosensitive drums 20Y, 20C, 20M, and 20BK and the transfer belt 11 are stacked, and a sheet feeding apparatus. The recording paper S conveyed from the feeding device 61 is transferred to the respective photosensitive drums 20Y, 20C, 20M, and 20BK at a predetermined timing that matches the toner image formation timing by the image forming units 60Y, 60C, 60M, and 60BK. A registration roller pair 4 that feeds toward the transfer unit 98 between the belt 11 and a sensor (not shown) that detects that the leading edge of the transfer sheet S has reached the registration roller pair 4 is provided.

  The image forming apparatus 100 also includes a fixing device 6 as a roller fixing type fixing unit for fixing the toner image onto the transfer paper S to which the toner image is transferred, and the fixed transfer paper S outside the main body 99. A discharge roller 7 for discharging, and a toner bottle 9Y as a toner replenishing member which is disposed above the transfer belt unit 10 and is filled with toner of each color of yellow, cyan, magenta, and black and is attached to and detached from the main body 99; 9C, 9M, 9BK, a discharge tray 17 on the upper side of the main body 99, on which the transfer paper S discharged from the main body 99 by the discharge roller 7 is stacked, and waste toner that stores unnecessary materials such as waste toner And a tank 83.

  The image forming apparatus 100 also includes an image density detecting unit 81 that detects the density of the image formed on the photosensitive drums 20Y, 20C, 20M, and 20BK and transferred to the transfer belt 11, and toner bottles 9Y, 9C, 9M, and 9BK. And a toner supply mechanism as a toner replenishing means (not shown) that supplies the toner in the image forming units 60Y, 60C, 60M, and 60BK to the developing devices 50Y, 50C, 50M, and 50BK. .

  The image forming apparatus 100 also includes a use environment of the image forming apparatus 100, in other words, an environment detection unit (not shown) that detects an atmospheric environment, and a secondary transfer bias application unit (not shown) that applies a secondary transfer bias to the secondary transfer roller 5. A secondary transfer roller driving unit (not shown) that contacts and separates the secondary transfer roller 5 from the transfer belt 11 is provided.

  The image forming apparatus 100 also includes an operation panel (not shown) as input means for making various settings for the image forming apparatus 100, and a CPU, memory, timer, etc. (not shown) that control the operation of the entire image forming apparatus 100. Control means.

  In addition to the transfer belt 11, the transfer belt unit 10 includes primary transfer rollers 12Y, 12C, 12M, and 12BK, a drive roller 72 that is a drive member around which the transfer belt 11 is wound, a transfer inlet roller 73, The cleaning counter roller 74 and a spring 75 as a biasing unit that biases the cleaning counter roller 74 in a direction to increase the tension of the transfer belt 11 are provided.

  The transfer belt unit 10 is also detachably supported by the main body 99 and holds a driving roller 72, a transfer inlet roller 73, a cleaning counter roller 74, and a spring 75, and forms an intermediate transfer belt case 14 that forms a casing of the transfer belt unit 10. And a cleaning device 13 as an intermediate transfer belt cleaning device which is integrated with the intermediate transfer belt case 14 and is disposed opposite to the transfer belt 11 and is a transfer belt cleaning means for cleaning the transfer belt 11. Yes.

  The transfer belt unit 10 also includes a drive system (not shown) that rotates the drive roller 72 and a power source as a primary transfer bias application unit (not shown) that applies a primary transfer bias to the primary transfer rollers 12Y, 12C, 12M, and 12BK. And bias control means.

  The transfer entrance roller 73 and the cleaning counter roller 74 are driven rollers that rotate along with the transfer belt 11 that is rotationally driven by the drive roller 72. The primary transfer rollers 12Y, 12C, 12M, and 12BK press the transfer belt 11 from the back surface thereof toward the photosensitive drums 20Y, 20C, 20M, and 20BK to form primary transfer nips, respectively. The primary transfer nip is formed in a portion of the transfer belt 11 that extends between the transfer entrance roller 73 and the cleaning counter roller 74. The transfer entrance roller 73 and the cleaning counter roller 74 have a function of stabilizing the primary transfer nip.

  In each primary transfer nip, a primary transfer electric field is formed between the photosensitive drums 20Y, 20C, 20M, and 20BK and the primary transfer rollers 12Y, 12C, 12M, and 12BK by the action of the primary transfer bias. . The toner images of the respective colors formed on the photosensitive drums 20Y, 20C, 20M, and 20BK are primarily transferred onto the transfer belt 11 due to the influence of the primary transfer electric field and nip pressure.

  The driving roller 72 is in contact with the secondary transfer roller 5 via the transfer belt 11 to form a secondary transfer portion 90. The rotation control of the transfer belt 11 by energizing the drive system is performed by a control unit, and the control unit recognizes the phase of the transfer belt 11. Specifically, the control means recognizes the position of the base portion on the transfer belt 11 and recognizes the timing at which the base portion passes the detection position of the image density detection means 81.

The cleaning counter roller 74 has a function as a tension roller as a pressure member that applies a predetermined tension suitable for transfer to the transfer belt 11 by the action of the spring 75.
The secondary transfer roller 5 is brought into contact with and separated from the transfer belt 11 by the secondary transfer roller driving unit under the control of the control unit.

The cleaning device 13 is disposed to face the transfer belt 11 at a position on the left side of the cleaning facing roller 74 in FIG.
Although not shown in detail, the cleaning device 13 includes a cleaning brush and a cleaning blade disposed so as to face and contact the transfer belt 11, and residual toner and reverse transfer toner on the transfer belt 11. The toner constituting the solid image adhered to the photosensitive drums 20Y, 20C, 20M, and 20BK in the refresh mode to be described later is scraped off and removed with a cleaning brush and a cleaning blade. Thus, the transfer belt 11 is cleaned. Unnecessary items such as waste toner generated by this cleaning are stored in a waste toner tank 83 through a waste toner path (not shown).

  The sheet feeding device 61 accommodates a plurality of transfer sheets S in a stacked state, and is provided at the bottom of the main body 99 and is in contact with the upper surface of the uppermost transfer sheet S. The uppermost transfer sheet S is fed toward the registration roller pair 4 by being driven to rotate counterclockwise. Yes.

  The registration roller pair 4 is precisely machined in outer diameter to match the image forming speed, in other words, the moving speed of the transfer belt 11 and the paper feeding speed. The accuracy is within 0.03 mm in outer diameter.

  In the secondary transfer unit 90, a secondary transfer electric field is formed between the driving roller 72 and the transfer belt 11 and the secondary transfer roller 5 by the action of the secondary transfer bias by the secondary transfer bias applying unit. The toner image formed on the transfer belt 11 is secondarily transferred onto the transfer paper S due to the influence of the secondary transfer electric field and nip pressure. The drive roller 72 also serves as a secondary transfer counter roller.

  The fixing device 6 includes a fixing roller 62 having a heat source therein, and a pressure roller 63 pressed against the fixing roller 62. The fixing sheet 62 carrying the toner image is transferred to the fixing roller 62 and the pressure roller 63. By passing through a fixing portion that is a pressure contact portion, the carried toner image is fixed on the surface of the transfer paper S by the action of heat and pressure.

  The yellow, cyan, magenta, and black toners in the toner bottles 9Y, 9C, 9M, and 9BK are respectively provided in the image forming units 60Y, 60C, 60M, and 60BK by a predetermined supply amount by the toner supply mechanism. The developing devices 50Y, 50C, 50M, and 50BK are supplied. The toner bottles 9Y, 9C, 9M, and 9BK are consumables that are replaced when the toner in the interior is exhausted, and are removed from the main body 99 and replaced when the toner is exhausted.

  The cleaning device 13 and the cleaning counter roller 74 are configured to move upward together with the primary transfer rollers 12Y, 12C, and 12M when the black image is formed, and to separate the transfer belt 11 from the photosensitive drums 20Y, 20C, and 20M. Has been.

  The environment detection means includes a temperature detection sensor and a humidity detection sensor, and is provided inside the main body 99. In the temperature detection sensor and the humidity detection sensor, detection signals related to temperature and humidity are input to the control means, respectively, and the control environment recognizes the image forming atmosphere environment related to temperature and humidity. .

  Various types of information input through the operation panel are recognized and identified by the control means. Examples of information that can be input through the operation panel include image quality settings. The operation panel has a display unit as output means for performing predetermined display under the control of the control means.

  Although not shown, the image density detection means 81 adjusts the current that flows through the light emitting element constituted by the LED, the light receiving element that receives the light emitted from the light emitting element and reflected by the transfer belt 11, and the light emitting element. And a light emission amount adjusting circuit for adjusting the light emission amount of the light emitting element. The current value If passed through the light emitting element by the issue amount adjustment circuit is controlled by the control means. The amount of light detected by the light receiving element is recognized by the control means as a value Vref converted into a voltage.

The control means corrects the image density detection means 81 by adjusting the current value If so that the value Vref becomes the reference value Vba at a timing described later (FIG. 3 (S3)).
In addition, the control means functions as an engine controller that controls each component necessary for image formation, and in order to maintain the image quality when the density of the formed image, that is, the toner density varies, a predetermined toner density is set. In addition to performing process control such as process control for setting the density to a predetermined level, a refresh mode described later is performed, which will be described later.

  The configuration of the image forming units 60Y, 60C, 60M, and 60BK will be described as a representative of the configuration of the image forming unit 60Y including the photosensitive drum 20Y. Since the configurations of the other image forming units 60C, 60M, and 60BK are substantially the same, in the following description, for the sake of convenience, reference numerals corresponding to the reference numerals assigned to the configuration of the image forming unit 60Y are used for other configurations. It attaches | subjects to the structure of image formation unit 60C, 60M, and 60BK, and shall abbreviate | omit suitably for detailed description.

  As shown in FIG. 2, the image forming unit 60Y including the photosensitive drum 20Y includes a primary transfer roller 12Y and a cleaning device around the photosensitive drum 20Y along a rotation direction B1 that is a clockwise direction in the drawing. A cleaning device 40Y as a means, a charging device 30Y as a charging device as a charging means, and a developing device 50Y as a developing unit as a developing means.

  The photosensitive drum 20Y is rotationally driven at a peripheral speed of 150 mm / sec by driving means (not shown). The image carrier may not be a drum like the photosensitive drum 20Y but may be a belt.

  A predetermined voltage suitable for primary transfer is applied to the primary transfer roller 12Y by the primary transfer bias applying means based on the control by the bias control means.

  The charging device 30Y includes a charging roller 31Y that is pressed against the surface of the photosensitive drum 20Y and is driven to rotate, and a cleaning roller (not shown) that is in contact with the charging roller 31Y and is driven to rotate. The charging roller 31Y is connected to a high voltage power source (not shown) that applies a bias of an alternating current component to a direct current, and the surface of the photosensitive drum 20Y is neutralized in a charging region facing the photosensitive drum 20Y. At the same time, it is charged to -500V.

The cleaning roller rotates following the charging roller 31Y to clean the charging roller 31Y.
As described above, in this embodiment, the charging system using the contact roller is adopted, but the charging system may be one using a proximity roller or one using a corotron system. .

  The optical scanning device 8 shown in FIG. 1 is a laser beam scanner using a laser diode (not shown) as a light source. As shown in FIG. 2, the optical scanning device 8 is placed in a region between the charged region and the developing region on the photosensitive drum 20Y. The surface of the photosensitive drum 20Y after being irradiated with the light-modulated laser light L and charged by the charging roller 31Y is exposed, and the potential of the exposed portion is lowered to electrostatically adhere to the surface of the photosensitive drum 20Y. An electrostatic potential image is formed by providing a sufficient potential difference. Yellow toner is supplied and adhered to the portion where the potential is lowered by the developing device 50Y, and a visible image is formed as a yellow toner image. The light source may be an LED.

  The cleaning device 40Y has a cleaning case 43Y having an opening at a portion facing the photoconductor drum 20Y, and scrapes off unnecessary materials such as residual toner, carrier, and paper dust on the photoconductor drum 20Y in contact with the photoconductor drum 20Y. The cleaning brush 45Y for cleaning and the rotating direction B1 of the photosensitive drum 20Y are in contact with the photosensitive drum 20Y at a position downstream of the cleaning brush 45Y and scrape off unnecessary materials on the photosensitive drum 20Y for cleaning. And a cleaning blade 41Y.

  The cleaning device 40Y is also rotatably supported by the cleaning case 43Y, scraped off from the photosensitive drum 20Y by the cleaning brush 45Y and the cleaning blade 41Y, and removed unnecessary materials such as waste toner generated by the removal of the waste toner. A discharge screw 42 </ b> Y that constitutes a part of a waste toner path (not shown) for transporting toward the tank 83 is provided.

  The developing device 50Y performs one-component contact development, and includes a developing roller 51Y as a developer carrying member disposed so as to contact and face the photosensitive drum 20Y, and the developing roller 51Y and the photosensitive drum 20Y. In the developing area between the toner and the toner, the yellow toner is electrostatically transferred to an electrostatic latent image formed on the surface of the photosensitive drum 20Y, and the electrostatic latent image is visualized as a yellow toner image. is there.

  In addition to the developing roller 51Y, the developing device 50Y thins the developing case 55Y as a case as a casing as a developer container having an opening in a portion facing the photosensitive drum 20Y, and the developer on the developing roller 51Y. And a developing blade 52Y as a layer regulating member to be layered. The developing roller 51Y rotates counterclockwise in the figure so that it moves in the same direction as the photosensitive drum 20Y at a position facing the photosensitive drum 20Y.

  The developing device 50Y also includes a toner supply chamber 56Y that is a space inside the developing case 55Y that houses a part of the developing roller 51Y, and a developer that is located in the space inside the developing case 55Y and opposite to the developing roller 51Y. And a partition wall 58Y forming a part of the developing case 55Y that partitions the toner supply chamber 56Y and the toner storage chamber 57Y. The partition wall 58Y has an opening 58Ya through which the toner supply chamber 56Y communicates with the toner storage chamber 57Y and the developer in the toner storage chamber 57Y passes through the toner supply chamber 56Y toward the toner supply chamber 56Y.

  The developing device 50Y is also disposed in contact with the developing roller 51Y in the toner supply chamber 56Y, and is disposed in the vicinity of the opening 58Ya in the toner storage chamber 57Y and a supply roller 59Y that rotates counterclockwise in the drawing. The first toner conveying member 53Y that feeds the developer in the toner storage chamber 57Y into the toner supply chamber 56Y through the opening 58Ya by rotation in the counterclockwise direction in the figure, and the opposite side of the opening 58Ya in the toner storage chamber 57Y. And a second toner transport member 54Y that moves the developer in the toner storage chamber 57Y toward the first toner transport member 53Y by rotating counterclockwise in FIG.

  The developing device 50Y also supplies a high-voltage power supply 80Y as a bias forming unit as a bias applying unit that applies a DC component developing bias to the developing roller 51Y, and supplies a supply bias described later to the supply roller 59Y. Supply bias applying means, a regulating bias applying means for applying a regulating bias described later to the developing blade 52Y, a developing roller 51Y, a supplying roller 59Y, a first toner conveying member 53Y, and a second toner conveying member 54Y. Driving means (not shown) for rotationally driving in the direction.

  The bias applied by the high-voltage power supply 80Y, the supply bias applying means, and the regulation bias applying means is adjusted by the control means. Here, the control unit functions as a development bias application control unit, a supply bias application control unit, and a regulation bias application control unit, respectively.

  The developing device 50Y performs development using a developer that is a one-component developer mainly containing yellow toner that is magnetic toner. The developer 50Y accommodates the developer in a developing case 55Y, and the yellow of the toner bottle 9Y. The toner is supplied by the toner supply mechanism into the developing case 55Y, specifically into the toner storage chamber 57Y.

  The developing roller 51Y is disposed in contact with the photosensitive drum 20Y so as to face the photosensitive drum 20Y from the opening of the developing case 55Y. When the developing roller 51Y rotates, the developer blade 52Y faces the developer carried on the surface, and the developing blade The toner is conveyed to the abutting portion where 52Y abuts, and further to the developing area between the photosensitive drum 20Y.

  The developing roller 51Y rotates at a peripheral speed of 225 mm / sec. Therefore, the peripheral speed ratio with respect to the photosensitive drum 20Y is 1.5. Hereinafter, this peripheral speed ratio is referred to as development Θ (theta). The developing roller 51Y may be non-contact with the photosensitive drum 20Y.

  Although not shown, the developing roller 51Y is charged to a polarity opposite to that of the toner, which is a core metal that forms the center of rotation, an elastic rubber layer that is covered with the metal core, and a surface layer that is provided on the surface of the elastic rubber layer. And a surface coat layer made of an easy-to-use material.

The elastic rubber layer is set to a hardness of 60 degrees or less according to JIS-A in order to prevent toner deterioration due to pressure concentration at the contact portion with the developing blade 52Y. The surface roughness of the elastic rubber layer is set to 0.3 to 2.0 μm in Ra so that a necessary amount of toner is held on the surface. Since a developing bias for forming an electric field between the developing roller 51Y and the photosensitive drum 20Y is applied from the high voltage power supply 80Y, the elastic rubber layer is set to a resistance value of 10 ³ to 10 ¹⁰ Ω.

The supply roller 59Y is disposed in contact with the developing roller 51Y. The surface of the supply roller 59Y is covered with a foam material having a structure having pores, that is, cells, so that the developer adhesion amount on the supply roller 59Y, in other words, the toner adhesion amount is ensured and the developer roller 51Y is in contact Toner deterioration due to pressure concentration in the area is suppressed. As the foam material, a conductive material containing carbon fine particles is used, and the electric resistance value of the supply roller 59Y is set to 10 ³ to 10 ¹² Ω.

  The supply bias applying unit applies a supply bias having a value offset in the same direction as the charging polarity of the toner to the developing bias to the supply roller 59Y. This supply bias acts in the direction in which the precharged toner is pressed against the developing roller 51Y at the contact portion between the developing roller 51Y and the supply roller 59Y. The supply roller 59Y applies and supplies the toner adhered to the surface to the surface of the developing roller 51Y by rotation.

  The developing blade 52Y uses a metal leaf spring material such as SUS or phosphor bronze, and has a free end brought into contact with the surface of the developing roller 51Y with a pressing force of 10 to 40 N / m. And a charge is applied by triboelectric charging. The regulating bias applying means applies a regulating bias to the developing blade 52Y with a value offset in the same direction as the charging polarity of the toner with respect to the developing bias in order to assist the developing blade 52Y with frictional charging of the toner on the developing roller 51Y. Apply.

  Of the photoconductor drum 20Y, the primary transfer roller 12Y, the cleaning device 40Y, the charging device 30Y, and the developing device 50Y constituting the image forming unit 60Y, the one excluding the primary transfer roller 12Y, that is, the photoconductor. The drum 20Y, the cleaning device 40Y, the charging device 30Y, and the developing device 50Y constitute a process cartridge 95Y that is a process cartridge unit as a process unit, and the process cartridge 95Y is integrated with the image forming apparatus. The main body 100 can be detached from the front side of the sheet in FIG.

  In addition, the photosensitive drum 20Y is detachable from the image forming apparatus 100 main body on the front side in FIG. 1, and is detachable, and also constitutes a process cartridge 95Y. Of the cleaning device 40Y, the charging device 30Y, and the developing device 50Y, the one excluding the photosensitive drum 20Y, that is, the cleaning device 40Y, the charging device 30Y, and the developing device 50Y constitute a unit. The unit is integrated, and is detachable from the image forming apparatus 100 main body toward the front side of the sheet in FIG. 1, and is detachable.

  Further, the developing device 50Y is detachable from the image forming apparatus 100 main body on the front side of the paper surface in FIG. The charging device 30Y is also detachable from the image forming apparatus 100 main body to the front side in FIG. When the process cartridge 95Y is detached from the main body 99 and the cleaning device 40Y, the charging device 30Y, and the developing device 50Y are detached from the process cartridge 95Y main body, a stopper (not shown) is released.

  In the image forming apparatus 100 having such a configuration, when a signal indicating that a color image should be formed is input, the driving roller 72 is driven, and the transfer belt 11, the transfer inlet roller 73, and the cleaning counter roller 74 are driven and rotated. The photosensitive drums 20Y, 20C, 20M, and 20BK are rotationally driven in the B1 direction.

  As the photosensitive drum 20Y rotates in the B1 direction, the surface is uniformly charged by the charging roller 31Y, and an electrostatic latent image corresponding to the yellow color is formed by exposure scanning of the laser beam L from the optical scanning device 8. The electrostatic latent image is developed with the yellow toner by the developing device 50Y to be visualized, and the yellow toner image obtained by the development is moved in the A1 direction by the primary transfer roller 12Y. Unnecessary materials including toner that has been primarily transferred to the transfer belt 11 and remained after the transfer are removed well by the cleaning device 40Y, and used for the next charge removal and charging by the charging roller 31Y.

  Similarly, toner images of the respective colors are formed on the other photosensitive drums 20C, 20M, and 20BK, and the formed toner images that are single-color images of the respective colors are moved in the A1 direction by the primary transfer rollers 12C, 12M, and 12BK. Primary transfer is sequentially performed at the same position on the moving transfer belt 11. The toner image superimposed on the transfer belt 11 moves to the secondary transfer portion 90 that is the position facing the secondary transfer roller 5 as the transfer belt 11 rotates in the A1 direction, and is transferred by the secondary transfer portion 90. Secondary transfer is performed on the paper S.

  The transfer sheet S conveyed between the transfer belt 11 and the secondary transfer roller 5 is fed from the sheet feeding device 61 by the feeding roller 3 and fed, and is detected by the registration roller pair 4 as a detection signal by the sensor. Based on this, the leading edge of the toner image on the transfer belt 11 is sent out at a timing facing the secondary transfer roller 5.

  When the transfer paper S has transferred and carried toner images of all colors, the transfer paper S enters the fixing device 6 and acts by heat and pressure when passing through the fixing portion between the fixing roller 62 and the pressure roller 63. As a result, the carried toner image is fixed, and a color image which is a composite color image is fixed on the transfer paper S. The fixed transfer paper S that has passed through the fixing device 6 passes through the paper discharge roller 7 and is stacked on the paper discharge tray 17 at the top of the main body 99. On the other hand, the transfer belt 11 that has finished the secondary transfer is cleaned by a cleaning brush and a cleaning blade provided in the cleaning device 13 to prepare for the next charging step and developing step.

  In such an image forming process, the yellow, cyan, magenta, and black toners are consumed by the developing devices 50Y, 50C, 50M, and 50BK, respectively. , 9C, 9M, and 9BK are supplied to the developing devices 50Y, 50C, 50M, and 50BK, respectively, by a predetermined replenishment amount of yellow, cyan, magenta, and black toner.

  In the image forming process, in the developing devices 50Y, 50C, 50M, and 50BK, the toner adheres to the developer carrying member, for example, the developing roller 51Y in the developing device 50Y with time.

  This is because, in the developing devices 50Y, 50C, 50M, and 50BK, various mechanical stresses applied to the toner, such as pressing by a blade such as the developing blade 52Y, the first toner conveying member 53Y, the second toner conveying member 54Y, and the like. The external additive added to the developer for the purpose of improving the fluidity is buried in the toner or peeled off due to the stirring action, transport action, etc. by the stirring member, and the charging characteristics of the toner itself deteriorate. This is because the toner deteriorates.

  For example, toner adhesion to the developer carrying member may cause toner charging characteristics to become unstable and cause abnormal images such as background stains and density reduction when toner filming occurs. It is known that the filming is a film deposited on the developer carrier by, for example, the toner being repeatedly pressed against the developer carrier by a blade or the like.

  Therefore, toner filming is likely to occur when a document with a very low printing rate of about 1% or less is repeatedly printed over a long period of time, particularly during color image formation. This is because the toner that is not consumed but remains on the developer carrying member is repeatedly rubbed with a blade or the like, and the toner with reduced chargeability stays on or near the developer carrying member and increases. It is.

  In addition, when the toner is deteriorated, the reproducibility of the highlight portion is reduced due to deterioration of the charging characteristics of the toner, the granularity of the entire image is increased, and the image quality is lowered. The toner remaining on the developer carrying member is charged with a reverse polarity and adheres to the non-latent image portion of the image carrying member, causing a problem called background stains, or causing toner sticking to the blade and causing image loss. It is known to become. Further, the toner deteriorated on the developer carrying member is pressed against the developer carrying member by a blade or the like, and adheres to the blade or the like, or peels off from the developer carrying member and stays around the developer carrying member to develop again. Although these are sometimes supplied to the agent carrier, these phenomena similarly lead to a decrease in image quality.

  Therefore, the control means performs control such as setting an appropriate development bias in advance of image formation requested by the user in order to perform good image formation by good development. In performing this control, the control unit specifically forms a solid patch image of each color and reads it by the image density detection unit 81, and refers to a look-up table stored in the memory so that proper development is performed. Set the bias. The look-up table describes the correlation between the output result of the image density detection unit 81 and the solid variation correction value of the image density detection unit 81, and the control unit functions as an engine controller to set an appropriate development bias. Is read from the memory.

  In the image forming apparatus 100, as a component of at least part of the control by the control unit, the development bias is applied by the bias forming unit such as the high-voltage power supply 80Y in each of the image forming units 60Y, 60C, 60M, and 60BK. A developer carrying unit that performs a refresh mode in which the developer on the developer carrying member such as the developing roller 51Y, that is, the toner is moved onto the image carrying member such as the photosensitive drum 20Y and released to refresh the developer carrying member. The body refresh method is implemented.

  The refresh mode and developer carrier refreshing method are specifically performed as follows with reference to FIG.

  After the power is turned on, if an image formation request is made from a terminal such as a PC connected to the image forming apparatus 100, when this is recognized by the control means (S1), then the developer carrier refreshing method is executed in the control means. It is determined whether or not it is time to execute (S2).

  Specifically, the determination of the timing is that the number of formed images has reached a predetermined number, and that the traveling distance of the image carrier, that is, the photosensitive drums 20Y, 20C, 20M, and 20BK has reached a predetermined distance. This is performed when any of the predetermined changes in the atmospheric environment is satisfied.

  These conditions are used in order to suppress the toner consumption and cost caused by this in the later-described image density measurement (S6) that consumes the toner by using an index of stress on the toner as a trigger for executing the method. It is.

  The fact that the number of formed images has reached a predetermined number and that the traveling distances of the photosensitive drums 20Y, 20C, 20M, and 20BK have reached a predetermined distance are due to mechanical stress on the toner, and are in an atmospheric environment. The occurrence of the predetermined change takes into account the stress caused by the temperature and humidity environment on the toner.

  Specifically, whether or not the number of formed images has reached a predetermined number is determined based on whether or not the number of image formed since the previous execution of the method has reached 1000. Note that this number is used as an index by which mechanical stress on the toner changes the development characteristics, and may be another number. The same applies to the next travel distance.

  Specifically, the fact that the travel distance of the photoconductor drums 20Y, 20C, 20M, and 20BK has reached a predetermined distance means that the rotation of the photoconductor drums 20Y, 20C, 20M, and 20BK since the previous method was executed. Judgment is made based on whether the number reaches 5000 revolutions. In this embodiment, the same method is performed only for the image forming units 60Y, 60C, 60M, and 60BK that include the image carrier that has reached the same rotational speed, but all the image forming units 60Y, 60C, 60M, and 60BK are used. The same method may be performed for all the image forming units 60Y, 60C, 60M, and 60BK when the rotational speeds of all the image carriers reach the same rotational speed.

  Specifically, the predetermined change in the atmospheric environment includes that the temperature has reached 50 degrees, that the temperature has changed by a predetermined width, for example, 10 ° C. within a predetermined time, for example, 1 hour, and that the humidity has been changed by a predetermined time, for example, It is 90% or more for 24 hours or more. The temperature / humidity environment is used as an index because it affects the flowability of the developer or changes the charging characteristics to change the developing characteristics. For example, specifically, in a high temperature and high humidity environment, the charging characteristics of the toner are reduced, and the toner tends to be charged to the opposite polarity on the developer carrying member, and the charging characteristics change.

  In this embodiment, the method is executed if any one of these conditions is satisfied. However, the method may be executed when all the conditions are satisfied, or may be executed in other combinations. You may make it do.

If it is determined that it is the timing for executing the method that satisfies the above conditions, the image density detecting means 81 is corrected as described above (S3), and then steps S4 to S8 are performed as shown in FIG. As described above, a solid pattern patch image (P _{1 to} P _n ) is formed while changing the developing bias Vb _n a plurality of times (seven times in this embodiment) sequentially, and is detected by the image density detecting means 81. Based on the result, the control means obtains the toner amount (M _{1 to} M _n ) that is the toner density of each pattern patch image. Change of the developing bias Vb _n is equidistant at -50 V. That is, Vb _n-1 −Vb _n = −50 (V).

  Other process conditions excluding the developing bias are constant, for example, the exposure amount is constant at a. However, the size of the pattern patch image is smaller than a width L and a length W, which will be described later with reference to FIG. 9 in order to suppress toner consumption, and the size and position that can be detected by the image density detection unit 81. Is done.

  As described above, from step S4 to step S8, prior to image formation requested by the user, a plurality of different development biases are applied to a pattern patch image, which is a plurality of images having different image densities, during non-image formation. A multi-density image forming step that forms continuously under process conditions, and an image density detection step that detects the image density that is the toner density of each of the plurality of pattern patch images using the image density detection means 81 are performed.

FIG. 5 shows an example of the relationship between the developing bias Vb _n and the toner adhesion amount M _n obtained as a result. In this embodiment, the developing bias is gradually decreased. However, the developing bias may be gradually increased or may be changed at random. The intervals between the developing biases are equal. However, the intervals may not be equal. Further, if the value of n is plural, it may not be 7.

  Subsequently, in step S9 to step S16, the control unit performs a refresh mode execution determination step for determining whether or not it is necessary to perform the refresh mode based on the image densities of the plurality of pattern patch images. Here, the control unit functions as a refresh mode execution determination unit.

  In the refresh mode execution determination step, first, in order to improve the efficiency when performing the refresh mode, a saturation value removal step for removing a region where the toner adhesion amount is saturated is performed in steps S9 to S13.

The region where the toner adhesion amount is saturated is a portion from Vb ₅ to Vb ₇ where the slope of the toner adhesion amount is substantially constant, as described in the example shown in FIG. The saturation of the toner adhesion amount is determined by the amount of toner carried on the developer carrying member. For example, in the image forming apparatus 100, the developer carried by the developer carrying member, in other words, the toner conveyance amount is 5 g / m. ^{2. When} the primary transfer efficiency is 98%, the development Θ = 1.5, which is the ratio of the peripheral speed of the developer carrier to the peripheral speed of the image carrier, so that these products are 7.35 g / m ^2. Therefore, the toner adhesion amount to the image carrier, in other words, the toner supply capability to the image carrier is saturated at 7.35 g / m ² and becomes the limit.

Therefore, in the saturation value removing step, the toner densities of the corresponding pattern patch images are arranged in the order of the magnitude of the applied developing bias, and these are set as M _{1 to} M _n and the developing bias corresponding to this n is set to Vb ₁ to Vb ₁ . Vb _n , and the control means sets the slope R of the toner density in each of the arranged development bias sections,
R = | M _n −M _n−1 | / | Vb _n −Vb _n−1 |
The toner adhesion amount is saturated or is equal to the saturation condition.
R ≦ 10 ⁻²
When satisfying the above, the data of n (<7) or less is used to determine the slope of the toner adhesion amount with respect to the developing bias as the slope S by linear approximation, and when there is no n satisfying R ≦ 10 ⁻² , all data are used. The inclination of the toner adhesion amount with respect to the developing bias is obtained as an inclination S by linear approximation.

  The slope S is obtained in the refresh mode execution determination step in which the change rate of the toner density of the corresponding pattern patch image arranged in order of the magnitude of the development bias, in other words, the slope of the change in the toner density is a predetermined rate. That is, it is for determining that the refresh mode is to be performed on the condition that the inclination is larger than a predetermined inclination.

  The reason why the slope S is obtained is that the degree of toner deterioration can be known from the slope S, and the necessity of the refresh mode due to toner adhesion to the developer carrying member can be determined. The fact that the degree of toner deterioration can be understood from the slope S is apparent from the fact that the slope of the developer is larger at the initial stage and the elapsed time as shown in FIGS. Therefore, by performing the above-described saturation value removal step, such a ratio is accurately obtained, the degree of toner deterioration, that is, the slope S is accurately measured, and the necessity of the refresh mode is accurately determined.

  As described above, it is determined in step S2 whether or not it is the timing to execute the developer carrier refreshing method, that the number of image formation has reached a predetermined number, the image carrier, that is, the photosensitive drum 20Y, The fact that the traveling distance of 20C, 20M, and 20BK has reached a predetermined distance is suitable for the fact that the slope S becomes larger and the need for the refresh mode tends to increase with time, It effectively functions as a preliminary screening for accurately determining the necessity of the refresh mode using S.

The control means stores the calculated slope S in the memory (S15), and S ≧ 2 compared with 2.3 × 10 ⁻² that is quantitatively obtained as a condition that the refresh mode is required. When satisfying 3 × 10 ⁻² , it is determined that the refresh mode needs to be performed (S16).

  When it is determined that the refresh mode needs to be performed, the control means starts the operation of the timer (S17), and determines whether the timer measurement time ΔT is equal to or longer than Tr (S18). Since the timer is stopped in the initial state with the measurement time ΔT being 0, when the first determination is made in step S18, the process proceeds to step S19 in which execution of the refresh mode is started.

  As shown in FIG. 8, the time Tr is a time for performing the refresh mode every time the developer carrier refreshing method is performed, and is equal to the developing bias formation time. Therefore, the time Tr is shorter than the time from when it is determined at the execution timing of the developer carrying member refreshing method at step S2 that the number of formed images reaches a predetermined number, and until the next determination is made. At the same time, the time is necessary and sufficient for executing one refresh mode, that is, the time necessary and sufficient for discharging the toner on the developer carrier to the image carrier.

In the refresh mode, as shown in FIG. 9, a solid image is formed.
The width L in the width direction of the developer carrier corresponding to the direction perpendicular to the paper surface of FIG. 2 of the solid image is set to be the entire width of the region where the developer carrier carries the developer in the same direction. The width L is substantially equal to the maximum image forming area of the image carrier in the same direction.

  The length W of the solid image along the rotation direction of the developer carrier, that is, the length W in the A1 direction is equal to or longer than the length of one circumference of the developer carrier. When the refresh mode is performed with such a width L and length W, the developer on the developer carrier moves toward the image carrier for the entire developer carrying region of the developer carrier.

  The toner attached to the image carrier in the refresh mode is transferred to the transfer belt 11 and then cleaned by the cleaning device 13. At this time, a bias in the direction opposite to the normal direction is applied by the secondary transfer bias applying unit, and the secondary transfer roller 5 is separated from the transfer belt 11.

  In this embodiment, the toner attached to the image carrier in the refresh mode is transferred to the transfer belt 11 and then cleaned, but without being transferred to the transfer belt 11, the cleaning device 40Y for the photosensitive drum 20Y or the like can be used. You may clean using the cleaning apparatus for image carriers. In this case, the secondary transfer roller 5 does not need to be in contact with or separated from the transfer belt 11.

  The absolute value of the potential difference between the latent image potential of the image carrier and the developing bias in the refresh mode is different from that in normal image formation. Specifically, such an absolute value is set to be larger during execution of the refresh mode than during normal image formation.

  As a result, a large amount of deteriorated toner adhering to the developer carrying member can be discharged in a short time, and the waiting time of the user, in other words, the time until the end of image formation is shortened. In addition, the deteriorated toner that cannot be removed by the normal developing bias is removed from the developer carrying member, and it becomes possible to prevent or suppress the occurrence of abnormal images, the background stain is reduced, and the toner filming of the developer carrying member is prevented or suppressed. This will extend the life of the equipment.

More specifically, the magnitude of the developing bias at the time of executing the refresh mode is set so that the developing characteristics are saturated. This will be described with reference to the example shown in FIG. 5. Among the development biases Vb _{1 to} Vb ₇ arranged in order of magnitude, the development characteristics are saturated at Vb _{5 to} Vb ₇ , so the magnitude of the development bias is Vb. ₅ as either through Vb ₇ and applies the.

  As described above, since the magnitude at which the development characteristic is saturated is determined based on the slope S after the saturation value removal step, which is relatively easily calculated in the above-described image density detection step, the development characteristic is saturated. High reliability. Therefore, the effect obtained by increasing the absolute value at the time of executing the refresh mode is better than that at the time of normal image formation. In addition to this, depending on the usage environment, the developer carrying amount by the developer carrier and the toner charge amount also change the development bias at which the development characteristics are saturated, but depending on the developer carrying amount and the toner charge amount Since the developing bias is changed, the developer carrying member is refreshed satisfactorily and efficiently even if the carrying amount of the developer and the charge amount of the toner are changed.

  Assuming that the amount of toner adhering to the image carrier at the normal developing bias is Mi, the time required to discharge the same amount of toner from the developer carrier to the image carrier in the refresh mode as in normal image formation. Is reduced by a factor of Mi / Mn when the toner adhesion amount Mn on the image carrier during the refresh mode is used.

The magnitude of the developing bias at the time of executing the refresh mode is desirably a minimum value in a range where the developing characteristics are saturated. This value corresponds to Vb ₅ in the example shown in FIG. In this way, the above-described effect is satisfactorily exhibited without applying an excessively strong bias and thus suppressing power consumption.

  It is desirable to change the development bias formation time Tr during the refresh mode, that is, the solid image formation time, in other words, the length W in accordance with the slope S. As described above, since the slope S increases as the degree of toner deterioration progresses, the length W is increased when the slope S is large.

For example, the time Tr is
Tr = A × Sα (A and α are weighting factors)
Ask for.

  In this way, the developer carrying member can be refreshed more accurately and more accurately. Thereby, useless toner consumption is suppressed.

  Further, as shown in FIG. 8, the solid image formation time Tr when the refresh mode is executed is divided into a plurality of times at a time interval Tw. The time interval Tw is changed in accordance with the slope S. It has become.

  This is because, when the solid image, that is, the length W of the refresh toner, that is, the patch width is determined according to the slope S as described above, a large patch width is required in the degraded state, but the patch width is too large. If a large amount of deteriorated toner is to be cleaned by the cleaning device 13, the cleaning performance of the cleaning device 13 may be insufficient and a cleaning failure may occur. Therefore, the time interval Tw is long when the toner deterioration is small, that is, when the slope S is small, and conversely, when the toner deterioration is severe, that is, when the slope S is large, the time interval Tw is short.

For example, the time interval Tw is
Tw = B × Sβ (B and β are weighting factors)
Ask for. Note that the time interval Tw may have a length W corresponding to the time interval Tw equal to or longer than the length of one round of the developer carrier.

  After starting the execution of the refresh mode, it is monitored whether or not the measurement time ΔT of the timer has reached the time interval Tw (S20). When the time interval Tw is reached, the formation of the solid image is stopped and the formed solid image is displayed. The toner is transferred to the transfer belt 11 and cleaned by the cleaning device 13 (S21). Note that the timer is stopped while step S21 is being executed.

  After the cleaning is completed, Step S18 is performed again, and Steps S19 to S21 are repeated until the timer measurement time ΔT reaches the time Tr. When the measured time ΔT of the timer reaches the time Tr, the timer is reset and stopped (S22), and according to the image formation request made from the terminal, the image is formed according to the above-described image forming operation, and with this, the developer is carried The execution of the body refresh method ends.

  As described above, in the refresh mode in the image forming apparatus 100, an appropriate developing bias is applied at an appropriate timing and time suitable for the use state of the image forming apparatus 100 without performing a large number of tables and complicated calculations. The deteriorated toner on the developer carrier is discharged to the image carrier and the deteriorated toner is forcibly consumed, and the deteriorated toner on the developer carrier is cleaned to maintain the image quality. . Further, the life of the developer carrying member and the life of the developing device are thereby prolonged, and wasteful toner consumption and associated cost increase are suppressed.

  In addition, the toner deteriorated on the developer carrying member is pressed against the developer carrying member by a blade such as the developing blade 52Y, or the toner adheres to the developer carrying member or peels off from the developer carrying member around the developer carrying member. It may stay and be supplied again to the developer carrier, but when the developer carrier is refreshed, the toner that has adhered to the blade or the developer carrier is peeled off from the developer carrier and the periphery of the developer carrier Since the deteriorated toner staying in the toner is also attached to the image carrier, the developer around the blade and the developer carrier is refreshed or cleaned, and the blade and developer This extends the life of the developing device, thereby extending the life of the developing device and maintaining the image quality.

  If it is determined in step S2 that it is not time to execute the developer carrier refreshing method, the image forming operation is performed without executing the developer carrier refreshing method, and the process ends. In step S1, the image forming operation and the developer carrier refreshing method are not executed until the image forming request is made, without waiting.

  However, in the image forming apparatus 100, in order to adjust the toner density of the toner images formed on the photosensitive drums 20Y, 20C, 20M, and 20BK and the transfer paper S, in other words, in the same manner as in a general image forming apparatus. Therefore, the condition for executing the process control is the same as the condition for executing the developer carrier refreshing method in step S2, and the developer carrier described above is part of the process control. A refresh method may also be executed. In this way, there is an advantage that the required time and toner consumption are suppressed as compared with the case where these are performed alone.

  As part of the process control, not the whole developer carrier refreshing method described above, but a part thereof, for example, a part excluding execution of the refresh mode, such as a part of steps S3 to S16, may be performed. This also has similar advantages.

  Further, the whole or part of the developer carrier refreshing method may be performed after the end of the image forming operation. If the image forming request is for a plurality of transfer sheets S, it may be performed between pages. Also good.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the specific embodiments, and the present invention described in the claims is not specifically limited by the above description. Various modifications and changes are possible within the scope of the above.

  For example, in the embodiment described above, an example in which a one-component developer is used as a developer containing toner is shown, but a two-component developer containing a carrier together with toner may be used as the developer containing toner. Good.

  Since the image density detecting means only needs to detect the density of the developer moved from the developer carrying body to the image carrying body, the image density detecting means is not limited to the one that detects the density on the transfer belt 11 as described above. Such density may be detected on the image carrier.

  In addition, the present invention is not a so-called tandem image forming apparatus such as the image forming apparatus 100, but sequentially forms toner images of each color on a single photosensitive drum and sequentially superimposes the color toner images to form a color image. The present invention can be similarly applied to a so-called one-drum type image forming apparatus, and can be applied not only to a color image forming apparatus but also to a monochrome image forming apparatus.

  The effects described in the embodiments of the present invention are only the most preferable effects resulting from the present invention, and the effects of the present invention are limited to those described in the embodiments of the present invention. is not.

1 is a schematic front view of an image forming apparatus to which the present invention is applied. FIG. 2 is a schematic front view showing a process cartridge including a developing device provided in the image forming apparatus shown in FIG. 1. 2 is a flowchart relating to a developer carrier refreshing method performed in the image forming apparatus shown in FIG. 1. The image formed in the multiple density image forming step performed in the developer carrier refreshing method shown in FIG. 3, and the image, the development bias for forming the image, and the image for detecting the image density of the image It is the conceptual diagram which showed the relationship with the image density detected by the density | concentration detection step. In order to explain the rate of change in image density detected in a region where development characteristics are saturated and in a range other than this, which is performed in the developer carrier refreshing method shown in FIG. It is a correlation diagram. FIG. 6 is a correlation diagram between a developing bias and an image density, showing how the rate of change in image density changes during the initial period and time. FIG. 6 is a correlation diagram between development bias and image density showing how development characteristics change between an initial stage and time. FIG. 4 is a timing chart regarding a refresh mode performed in the developer carrier refreshing method shown in FIG. 3. FIG. FIG. 6 is a perspective view showing an image formed by moving toner from a developer carrier to an image carrier in a refresh mode.

Explanation of symbols

20Y, 20M, 20C, 20BK image carrier 50Y, 50M, 50C, 50BK developing device 51Y developer carrying member 80Y biased forming means 81 image density detection means 95Y, 95M, 95C, 95BK process cartridge 100 image forming apparatus M ₁ ~M time interval for dividing the length Tw refresh mode time to form a respective image density P ₁ to P _n more images Tr developing bias _n plurality of images

Claims (13)

An image carrier for carrying an electrostatic latent image;
A developer carrier for carrying the developer and developing the image carrier with toner contained in the developer;
Bias forming means for forming a developing bias for developing the image carrier by moving toner contained in the developer carried on the developer carrier onto the image carrier;
Using image density detection means for detecting the density of the formed image,
Developer carrying member refresh that performs a refresh mode for forming the developing bias by the bias forming means and moving the developer on the developer carrying member onto the image carrying member to refresh the developer carrying member. A method,
A multiple density image forming step for forming a plurality of images having different image densities;
An image density detecting step for detecting the image density of each of the plurality of images formed in the multiple density image forming step using the image density detecting means;
A developer carrier refreshing method comprising: a refresh mode execution determination step of determining whether or not to perform the refresh mode based on the image density of each of the plurality of images detected in the image density detection step. In the developer carrier refreshing method according to claim 1,
In the refresh mode execution determination step,
The developer carrying, characterized in that it is determined to perform the refresh mode on condition that a rate of change in image density of each of the plurality of images detected in the image density detection step is greater than a predetermined rate. Body refresh method. The developer carrying member refreshing method according to claim 1 or 2,
In the refresh mode,
The development characterized in that the length of time for forming the developing bias is changed by the developing bias forming means in accordance with the rate of change in image density of each of the plurality of images detected in the image density detecting step. Agent refreshing method. In the developer carrier refreshing method according to any one of claims 1 to 3,
When it is determined in the refresh mode execution determination step that the refresh mode is performed, the refresh mode is divided into a plurality of times at a predetermined time interval, and the predetermined time interval is detected in the image density detection step. A developer carrying member refreshing method, wherein the developer carrying member is changed in accordance with a rate of change in image density of each of a plurality of images. In the developer carrier refreshing method according to any one of claims 1 to 4,
A developer carrier refreshing method, wherein an absolute value of a potential difference between a latent image potential of the image carrier and the developing bias is made different between the execution of the refresh mode and the normal image formation. In the developer carrier refreshing method according to claim 5,
The developer carrying member refreshing method, wherein the absolute value is larger when the refresh mode is executed than when performing normal image formation. The developer carrying member refreshing method according to claim 6,
The developer carrying member refreshing method, wherein the developing bias at the time of executing the refresh mode is set to a level at which developing characteristics are saturated. The developer carrying member refreshing method according to claim 7,
The developer carrier refreshing method, wherein the degree of saturation of the development characteristics is determined based on a rate of change in image density of each of the plurality of images detected in the image density detection step. The developer carrying member refreshing method according to any one of claims 1 to 8,
In the multi-density image forming step, the image forming number has reached a predetermined number and / or the traveling distance of the image carrier has reached a predetermined distance and / or a predetermined change has occurred in the atmosphere environment. A developer carrier refreshing method, characterized in that the method is performed under conditions. The image carrier, the developer carrier, the bias forming unit, and the image density detection unit,
An image forming apparatus using the developer carrying member refreshing method according to claim 1.   A developer carrying member refreshing method according to any one of claims 1 to 9, or an image forming method using the image forming apparatus according to claim 10.   A process cartridge used in the developer carrier refreshing method according to claim 1, the image forming apparatus according to claim 10, or the image forming method according to claim 11. Having at least the developer carrier,
The developer carrier refreshing method according to any one of claims 1 to 9, the image forming apparatus according to claim 10, the image forming method according to claim 11, or the process according to claim 12. Developing device used for cartridge.

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