JP2009080185A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form an image where image thinning and image noise such as stripe noise made when variance is caused in an amount of toner in a developing device are suppressed by supplying toner so that the amount of the toner in the developing device may be constant even if fluidity of the toner in the developing device is varied. <P>SOLUTION: The image forming apparatus forms a toner image by forming an electrostatic latent image on an image carrier 1 and developing it by the developing device 4. The apparatus is equipped with a toner amount detection device 48 detecting the amount of the toner in the developing device 4 and a toner supply device 40 supplying the toner to the developing device 4. The toner is supplied by correcting the amount of the toner in the developing device obtained at least by the toner amount detection device 48 in accordance with a deterioration degree of the toner and supplying the insufficient amount of toner derived from the amount of the toner, which has been corrected, by the toner supply device 40. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus using an electrophotographic system, an electrostatic recording system, or the like, such as a copying machine, a printer, a facsimile machine, or a multi-function machine combining two or more of these.

  In an electrophotographic image forming apparatus, the surface of an electrostatic latent image bearing member such as a photosensitive member is charged by a charging device, and the charged area is exposed according to an image to be formed from an image exposure device to be static. An electrostatic latent image is formed, and the electrostatic latent image is developed by a developing device to form a visible toner image. Usually, the visible toner image is transferred to a transfer medium.

  In an electrostatic recording type image forming apparatus, a surface of an electrostatic latent image carrier such as a dielectric for electrostatic recording is charged by a charging device, and an image to be formed in the charged area by the electrostatic recording device. An electrostatic latent image can be formed by performing electrostatic recording according to the above, and a visible toner image can be formed by developing the electrostatic latent image with a developing device. Usually, the visible toner image is transferred to a transfer medium.

  In any type of image forming apparatus, in the monochrome image forming apparatus, the transfer target is a recording medium such as a normal recording paper, and the transferred toner image is fixed to the recording medium. In a color image forming apparatus, the transfer target is generally an intermediate transfer member, and the toner image primarily transferred to the intermediate transfer member is further transferred to a recording medium. It is fixed.

  In any of the image forming apparatuses, when the toner in the developing device is reduced due to consumption, if the development is continued with this being left as it is, image fading occurs or the toner amount distribution in the developing device becomes non-uniform and streaks. Uneven image noise may occur.

  For this reason, the developing device is usually provided with a means for detecting the toner amount in the developing device, and the toner supply device supplies the insufficient amount of toner to the developing device based on the detection output of the toner amount detecting means. It has been proposed to keep the amount constant.

  Various methods for detecting the amount of toner in the developing device have been proposed and put to practical use. For example, Japanese Patent Laid-Open No. 7-160073 discloses a two-component developer using a developer containing toner and a carrier. The document describes that the toner density is detected by a density detecting means to grasp the toner amount in the developing device. Japanese Patent Application Laid-Open No. 2004-184698 includes a light emitting unit and a light receiving unit, and the light concentration is detected by the light receiving unit detecting light reflected from the light emitting unit to the developer carrier of the developing device. And detecting the toner amount in the developing device.

JP-A-7-160073 JP 2004-184698 A

  However, the fluidity of the toner in the developing device varies depending on the usage history of the image forming apparatus. For example, if a low coverage image, in other words, an image with a low printing rate (an image with a low ratio of the number of pixels attached to the image forming area) is continuously formed, Since the amount of toner consumption is small, the same toner in the developing device is repeatedly stressed as the developing device is driven, so that the toner deterioration proceeds rapidly.

  The fluidity of the toner in the developing device varies depending on the degree of toner deterioration, and even if the same amount of toner is present in the developing device, the output of the toner amount detection means due to the difference in fluidity due to the difference in the degree of deterioration. Differ, and the detection accuracy of the toner amount detection means is lowered. As a result, if the toner is replenished based on the detection output of the toner detection unit as it is, the toner amount in the developing device is not fixed, and image noise such as variation, and consequently, image density reduction and stripe unevenness occurs.

  Such a phenomenon is observed in a developing device in which toner flows in the developing device as is generally the case even when there is a difference in the developing device type. In a developing device that circulates and stirs, variation in the toner amount detection means output due to fluctuations in toner fluidity is observed.

  Therefore, the present invention has one or two or more electrostatic latent image carriers and a developer provided corresponding to each electrostatic latent image carrier, and each developer has a corresponding electrostatic latent image carrier. An image forming apparatus capable of forming a toner image by developing an electrostatic latent image formed on a latent image carrier, wherein at least one of the developing devices, even if the fluidity of toner in the developing device varies The toner supply to the developing unit can be controlled so that the amount of toner in the developing unit is made constant, thereby suppressing image noise such as blurring and unevenness of the image that occurs when the toner amount in the developing unit varies. It is an object to provide an image forming apparatus.

In order to solve the above problems, the present invention provides:
One or two or more electrostatic latent image carriers and a developing device provided corresponding to each of the electrostatic latent image carriers, each developing device on the corresponding electrostatic latent image carrier An image forming apparatus capable of developing an electrostatic latent image formed into a toner image to form a toner image;
A toner amount detecting means provided corresponding to at least one developing device, for detecting the toner amount in the developing device, and a toner replenishing device for supplying toner to the developing device;
A toner replenishment control unit for causing the toner replenishing device to replenish toner to the corresponding developing device;
The toner replenishment control unit grasps the toner amount before correction in the developing device based on at least the detection output of the toner amount detecting means for the developing device subject to toner replenishment by the toner replenishing device. Determining the degree of deterioration of the toner in the developing device based on a predetermined factor among the factors affecting the deterioration, correcting the pre-correction toner amount according to the determined toner deterioration level, and determining the predetermined developing device An image forming apparatus is provided that replenishes an insufficient toner amount obtained by subtracting the corrected toner amount from an internal target toner amount from the toner replenishing device to the developing device.

  According to the image forming apparatus of the present invention, in the developing device provided with the toner amount detecting means and the toner replenishing device, the toner in the developing device is consumed to develop the electrostatic latent image on the electrostatic latent image carrier. Then, in order to stabilize the amount of toner in the developing device and stabilize the formed image, toner is replenished from the toner replenishing device under the instruction of the toner replenishment control unit.

  At this time, the toner replenishment control unit causes the toner replenishing device to replenish the insufficient toner based on the detection output of the toner amount detection means. However, the toner amount in the developing device cannot be immediately grasped with the detection output of the toner amount detection means. Absent.

  Depending on the degree of deterioration of the toner in the developing device, the fluidity of the toner in the developing device fluctuates, and even if there is the same amount of toner in the developing device, the toner amount detection means due to the difference in fluidity due to the difference in the degree of deterioration Therefore, the toner replenishment control unit is based on at least the detection output of the toner amount detecting means for the developer that is to be replenished by the toner replenishing device. Thus, the amount of toner before correction in the developing device is grasped. Further, the degree of deterioration of the toner in the developing unit is obtained based on a predetermined factor among the factors affecting the deterioration of the toner in the developing unit. Then, the pre-correction toner amount is corrected in accordance with the obtained degree of toner deterioration, and an insufficient toner amount obtained by subtracting the post-correction toner amount from the predetermined target toner amount in the developing device is supplied from the toner replenishing device. Replenish the developer.

  Thus, even if the fluidity of the toner in the developing device fluctuates, the toner replenishment to the developing device can be controlled so that the toner amount in the developing device is made constant, and if there is a variation in the toner amount in the developing device, it occurs. It is possible to suppress image noise such as blurred images and uneven stripes.

The toner replenishment control unit grasps the pre-correction toner amount at a predetermined timing, calculates the toner deterioration level in the developing device, and corrects the pre-correction toner amount according to the determined toner deterioration level. In addition, an insufficient toner amount obtained by subtracting the corrected toner amount from the target toner amount can be supplied from the toner supply device to the developing device.
As the predetermined timing, for example, the timing at the completion of the predetermined number of image formations can be exemplified.

  The fluidity of the toner in the developing device that affects the detection output of the toner amount detection means is also affected by the ambient environment (at least one of temperature and humidity). Therefore, when the toner replenishment control unit grasps the toner amount before correction in the developing device based on the detection output of the toner amount detection unit, the toner amount in the developing device based on only the detection output of the toner amount detection unit is determined. You may grasp | ascertain in the state by which it pre-corrected (pre correction | amendment) based on at least one among temperature and humidity around this developing device.

The factors that influence the deterioration of the toner in the developing device can be broadly classified as follows: toner consumption of the developing device, remaining toner amount of the toner replenishing device that replenishes toner to the developing device (in other words, toner by the toner replenishing device) Replenishment amount), the amount of residual toner in the developing device obtained based on these, the driving motor integrated driving time, and the like.
The toner replenishment control unit, for example, determines the degree of deterioration of the toner based on the toner consumption amount of the developing device and the replenishment toner remaining amount in the toner replenishing device that replenishes toner to the developing device. This can be obtained based on the remaining toner amount and the integrated driving time of the motor of the developing device.

  In this case, the toner replenishment control unit obtains, for example, the toner consumption amount of the developing device based on the consumption parameter and at least one of the temperature and humidity around the developing device, and the consumption parameter is a print rate in image formation. Further, it can be obtained on the basis of the system speed of the image forming apparatus, the developing motor drive integration time, and the fog coefficient.

Here, the “printing rate” can also be referred to as a ratio of the number of pixels to which the toner occupies in the image formable area, or a ratio of the area of the area to which the toner occupies in the image formable area. .
The “system speed” is the image forming speed, which is usually the surface moving speed of the electrostatic latent image carrier, and if the electrostatic latent image carrier is a drum type photoreceptor, it is the peripheral speed.
The “fogging coefficient” is a coefficient for assuming “image” + “fogging” as a toner consumption amount in consideration of so-called “fogging” generated during image formation (for example, about 1.0 to 1.4). It is.

  The toner replenishment control unit obtains the remaining amount of toner to be replenished in the toner replenishing device, for example, by subtracting the amount of toner replenished to the developing device by the toner replenishing device from the regular amount of toner stored in the toner replenishing device. In this case, the toner replenishment amount can be calculated by multiplying the toner replenishment amount per unit driving time of the toner replenishment motor in the toner replenishing device by the accumulated driving time of the toner replenishment motor.

  An example of a developing device to be replenished with toner by the toner replenishing device includes a toner circulating member that circulates toner in the developing device. In the case of this type of developing device, the toner amount detecting means can detect the toner amount in the developing device from the toner amount in the toner circulation path by the toner circulating member.

The image forming apparatus according to the present invention may be a monochrome image forming apparatus or a color image forming apparatus capable of forming a multicolor image.
In the case of a monochrome image forming apparatus, since only one developing device is used, the toner amount detecting means and the toner replenishing device are provided corresponding to the developing device, and the toner replenishing device is provided in the toner replenishing control unit. Under the instruction, toner is supplied to the developing device.

  In the case of a color image forming apparatus, a plurality of developing devices each capable of developing with the toner of the assigned color are employed. The toner amount detecting means and the toner replenishing device are provided for each of the plurality of developing devices. Although it is desirable, only a part may be provided. In any case, the toner replenishing device replenishes toner corresponding to the developer under the instruction of the toner replenishment control unit.

  As described above, according to the present invention, one or two or more electrostatic latent image carriers and a developer provided corresponding to each electrostatic latent image carrier are provided, and each developer is An image forming apparatus capable of developing a latent electrostatic image formed on a corresponding latent electrostatic image bearing member to form a toner image, wherein the fluidity of toner in the developing unit varies with respect to at least one developing unit. Even so, the toner supply to the developing device can be controlled so that the toner amount in the developing device is kept constant, thereby reducing image noise such as image blurring and streaks caused by variations in the toner amount in the developing device. An image forming apparatus that can be suppressed can be provided.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 shows an example of an image forming apparatus according to the present invention. The image forming apparatus shown in FIG. 1 is a tandem type full color printer. This printer has an endless intermediate transfer belt 7 wound around a driving roller 71 and a roller 72 facing the driving roller 71. The transfer belt 7 is rotated counterclockwise in the figure (arrow direction in the figure) by a driving roller 71 driven by a belt driving unit (not shown).

  The drive roller 71 is faced with a cleaner 73 for cleaning the secondary transfer residual toner and the like on the transfer belt 7 and the secondary transfer roller 8 is faced. The toner or the like collected by the cleaner 73 is sent to a waste container by a conveying means (not shown).

  The surface layer portion of the secondary transfer roller 8 is formed of an elastic material, and is pressed against a portion of the intermediate transfer belt 7 supported by the driving roller 71 by a pressing unit (not shown), so that a nip is formed between the secondary transfer roller 8 and the intermediate transfer belt 7. And can be rotated following the rotation of the intermediate transfer belt 7 or following the movement of the recording medium S fed into the nip as will be described later. A secondary transfer bias can be applied to the secondary transfer roller 8 from a power supply (not shown).

  A fixing device FX is disposed above the intermediate transfer belt 7 and the secondary transfer roller 8, a timing roller pair TR is disposed below, and a recording medium S such as recording paper is accommodated below the fixing device FX. The recording medium storage cassette 9 is disposed.

The fixing device FX includes a fixing heating roller incorporating a heat source such as a halogen lamp heater and a pressure roller pressed against the fixing heating roller.
The recording medium S accommodated in the recording medium accommodation cassette 9 can be pulled out one by one by the medium supply roller 91 and supplied to the timing roller pair TR.

  Between the rollers 71 and 72 around which the intermediate transfer belt 7 is wound, the yellow image forming unit Y, the magenta image forming unit M, the cyan image forming unit C, and the rollers 72 to 71 along the transfer belt 7. Black image forming portions K are arranged in this order.

  Each of the image forming units Y, M, C, and K includes a drum-type photoconductor 1 as an image carrier, and a charger 2, an image exposure device 3, a developing device 4, and a primary are provided around the photoconductor. The transfer roller 5 and the cleaning device 6 are arranged in this order.

The primary transfer roller 5 faces the photoconductor 1 with the transfer belt 7 therebetween, and rotates as the belt travels. A primary transfer bias for primary transfer of the toner image formed on the photoreceptor 1 to the belt 7 can be applied to the primary transfer roller 5 from a power supply (not shown).
The exposure apparatus 3 can perform image exposure on the photosensitive member 11 by dot (point) exposure using a laser beam in accordance with image information provided from a personal computer (not shown) or the like.

The photoconductor 1 in each image forming unit is a negatively chargeable photoconductor here, and can be driven to rotate clockwise in the drawing by a photoconductor drive motor (not shown).
The charger 2 in each image forming unit is not limited to this, but is a scorotron charger in this example, and a charging voltage is applied from a power supply (not shown) at a predetermined timing.

The developing device 4 in each image forming unit is also illustrated in FIG. 2, and although not limited thereto, in this example, an electrostatic latent image formed on the photosensitive member 1 using a negatively chargeable toner, Reversal development can be performed by a developing roller 41 to which a developing bias is applied from a power supply (not shown).
The developing device will be further described later.

FIG. 5 is a block diagram showing an outline of the control circuit of the printer of FIG. Each unit in the printer operates at a predetermined timing under the instruction of the control unit Cont that controls the operation of the entire printer.
According to this printer, an image can be formed using one or more of Y, M, C, and K image forming units.
Taking a case where a full color image is formed using all of the image forming portions Y, M, C, and K as an example, first, a yellow toner image is formed in the yellow image forming portion Y, and this is formed on the transfer belt 7 as a primary. Transcript.

  That is, in the yellow image forming portion Y, the photosensitive member 1 is rotationally driven in the clockwise direction in the drawing, and the surface is uniformly charged to a predetermined potential by the charger 2, and the image exposure device 3 applies the yellow image for the yellow image. The yellow electrostatic latent image is formed on the photoreceptor 1. The electrostatic latent image is developed by a developing roller 41 to which a developing bias of a developing unit 4 having yellow toner is applied to become a visible yellow toner image, and the toner image is transferred onto a transfer belt 7 by a primary transfer roller 5. Primary transfer is performed. At this time, a primary transfer bias is applied to the primary transfer roller 5 from a power supply (not shown).

  Similarly, a magenta toner image is formed in the magenta image forming unit M and transferred to the transfer belt 7. A cyan toner image is formed in the cyan image forming unit C and transferred to the transfer belt 7. In the black image forming unit K. A black toner image is formed and transferred to the transfer belt 7.

Yellow, magenta, cyan, and black toner images are formed at a timing when these toner images are transferred onto the intermediate transfer belt 7 in an overlapping manner.
Thus, the multiple toner image formed on the transfer belt 7 moves toward the secondary transfer roller 8 by the rotation of the transfer belt 7.

  On the other hand, the recording medium S is pulled out from the recording medium accommodating cassette 9 by the medium supply roller 91 and is supplied to the timing roller pair TR and is on standby.

  Thus, the recording medium S waiting at the timing roller pair TR7 is supplied to the nip portion between the transfer belt 7 and the secondary transfer roller 8 in accordance with the multiple toner images sent by the intermediate transfer belt 7. The multiple toner images are secondarily transferred onto the recording medium S by a secondary transfer roller 8 to which a secondary transfer bias is applied from a power supply (not shown). Thereafter, the recording medium S is passed through the fixing device FX, where the multiple toner images are fixed on the recording medium S under heat and pressure. The recording medium S is continuously discharged to the discharge tray DT by the discharge roller pair DR.

  In the primary transfer of the toner image to the belt 7, transfer residual toner or the like remaining on the photoreceptor 1 is cleaned by the cleaning device 6, and secondary transfer residual toner or the like remaining on the belt 7 by the secondary transfer is cleaned by the cleaner 73. To be cleaned. Each of these cleaned and removed toners is sent to a waste container by a conveying means (not shown).

  As described above, an image is formed, but the developing device 4 in each of the image forming units Y, M, C, and K is configured as shown in FIGS. 2 and 3, and an instruction from the control unit Cont. The toner supply from the toner supply device 40 can be received.

  FIG. 2 shows an outline of a cross-sectional structure of the developing device 4, and FIG. 3 shows an outline of an internal structure when the developing device 4 is viewed from the back (when viewed from the side opposite to the photoreceptor 1). However, the positions of the developing roller 41 and the supply roller 42 are indicated by chain lines).

Each developing device 4 includes an upper chamber 4U and a lower chamber 4L, and a partition 4W is formed between the upper and lower chambers.
The lower chamber 4L is provided with a developing roller 41 facing the photoreceptor 1 and a toner supply roller 42 for supplying toner to the developing roller 41. Both rollers are arranged in contact with each other, and both are rotated counterclockwise in FIG. 2 by a developing device motor M (see FIG. 5) not shown in FIGS. 2 and 3, and the developing roller 41 has a power supply not shown. To developing a latent image on the photoreceptor in a state where a developing bias is applied.

  In addition to the supply roller 42, the first and second toner regulating blades 43 and 44 and the charge removal member 45 are in contact with the developing roller 41. The toner regulating blades 43 and 44 are supplied onto the developing roller 41 by the supply roller 42, regulate the layer thickness of the toner conveyed toward the developing region to a predetermined level, and frictionally charge the toner. The neutralization member 45 neutralizes the toner returning to the developing unit without being consumed in the development area. The supply roller 42 also peels off the toner returning into the developing unit from the developing roller 41.

  An upper toner conveying screw 46 is provided in the upper chamber 4U of the developing device, and a lower toner conveying screw 47 is provided in the upper portion of the lower chamber 4L. In the partition wall 4W between the upper and lower chambers, a toner circulation opening P1 is formed in the vicinity of one end portion, and a toner circulation opening P2 is formed in the other end portion.

  The screws 46 and 47 are rotationally driven by a drive motor (not shown) (a motor for driving the developing roller 41 and the like), so that the toner circulates in the developing device 4. More specifically, some toner in the lower chamber 4L is used for development, while the lower toner conveying screw 47 conveys the toner from the lower region of the one partition opening P1 toward the partition opening P2, and the upper chamber passes through the opening. 4U is supplied to the upper toner conveying screw 46 from the opening P2 toward the opening P1, and circulates so as to move from the opening P1 to the lower chamber 4L.

For the developing device 4, a toner replenishing device 40 and a toner amount detecting device 48 in the developing device are provided.
First, the toner replenishing device 40 will be described. The replenishing device 40 can supply replenishing toner to the toner circulation path in the developing device 4. That is, the toner supply duct 402 is connected to the end of the upper chamber 4U on the side where the partition wall opening P1 is provided, and the toner storage unit 401 storing the supply toner can be replaceably connected to the supply duct 402. Yes. The replenishment duct 402 is provided with a toner replenishment screw 403 that supplies toner supplied from the toner storage unit 401 to the upper chamber 4U of the developing device. The screw is supplied to the toner replenishment motor 404 under the instruction of the control unit Cont. Turned around.

  The replenishment toner supplied from the toner accommodating portion 401 to the developing device upper chamber 4U via the replenishment duct 402 is sent to the partition opening P1 by the reverse feed screw portion below the replenishment duct 402 in the upper toner conveying screw 46. The toner is dropped into the lower chamber 4L together with the circulating toner sent from the opening P2, and is used for development while being circulated and agitated with the existing toner in the developing device.

  As shown in FIGS. 2 and 3, the toner amount detection device 48 is provided at a position where the toner amount in the toner circulation path by the toner conveying screws 46 and 47 can be detected as the toner amount in the developing device. Then, as shown in FIG. 2 and FIG. 3, it faces a region below the partition opening P1 where toner is started to be transported toward the opening P2 by the lower toner transport screw 47.

As shown in FIG. 5, the toner amount detection device 48 includes a light emitting element 48 a, a light receiving element 48 b, and a light guide member a and a light guide member a that guide light emitted from the light emitting element 48 a to a toner amount detection region in the developing device 4. The light guide member b which guides the light from the light emitting element 48a to the light receiving element 48b is included.
The light emitting element 48a is turned on under the instruction of the controller Cont, and the light receiving element 48b outputs a voltage corresponding to the amount of light coming from the light emitting element 48 through the light guide members a and b. That is, the output voltage of the light receiving element 48b is the detection output of the toner amount detection device 48, and this is input to the controller Cont as toner amount information in the developing device.

  A cleaning device 49 is provided for the toner amount detection device 48. As shown in FIG. 4, the cleaning device 49 holds flexible foam cleaning members 492 for wiping and cleaning the light guide members a and b on both side surfaces of the cleaning member support 491, and these are supported by a shaft 493. Is interlocked with the toner conveying screw 47 via a transmission mechanism (not shown) so as to be reciprocally driven. The pair of cleaning members 492 can intermittently clean the light guide members a and b by the reciprocating operation.

The toner amount detection device 48 detects the toner amount in the developing device based on the following principle.
In this example, in a state where there is no toner in the developing device, as shown in FIG. 6A, when the cleaning member 492 of the cleaning device 49 takes a position covering the light guide members a and b, the output of the light receiving element 48b. The voltage is approximately 5V, and when the cleaning member 492 is removed from between the light guides a and b, light passes between the light guide members, and the output voltage of the light receiving element 48b indicates approximately 0V. Etc. are set.

  Then, 2V between 0V and 5V is set in the control unit Cont as a threshold for determining the toner amount in the developing device 4, and the cleaning member 492 is not between the light guide members a and b (if there is no toner at all). The output of the light receiving element 48b is picked up by the control unit Cont for a predetermined number of detections (for example, 100 times) at predetermined time intervals in a state where the output of the element 48b is substantially 0V), and the output value is a threshold value (2V The amount of toner in the developing device 4 is determined based on the number of times less than.

  This is because when the amount of toner in the developing device is large, when the cleaning member 492 is not between the light guide members a and b, the toner easily flows between the light guide members a and b, and thus the light receiving element output is high. When the amount of toner is small, when the cleaning member 492 is not between the light guide members a and b, the amount of toner flowing between the light guide members a and b decreases, and thus the amount of light received by the light receiving element is large. This is based on the fact that the light receiving element output becomes low.

  For example, the control unit Cont picks up the output of the light receiving element 48b 100 times at a predetermined time interval in a state where the cleaning member 492 is not between the light guide members a and b, and the output value is set to a threshold value (2V). If the number of drops is less than 30 times (30%), the toner amount in the developing device is level 1, if it is 30 times or more and less than 70 times (30% or more and less than 70%), if the level is 2, and if it is 70 times or more (70% or more) Level 3 is assumed. In this case, the magnitude relationship of the toner amount in the developing device is level 1> level 2> level 3, and the level 3 is the smallest.

  Here, the fluidity of the toner in the developing device further changes due to the deterioration of the toner and the environment around the developing device, and when the toner fluidity varies, the light guide member a, Consider the fact that the amount of toner flowing between b fluctuates, whereby the output of the light receiving element 48b fluctuates, and the light receiving element output may not reflect the actual toner amount in the developing device.

  That is, as the above countermeasure, here, in the control unit Cont, the detection output of the light receiving element 48b and the developing device at a predetermined timing (for example, at a timing for each predetermined number of image forming sheets from a range of 1 to 100 sheets). The toner amount in the developing device is grasped based on the temperature and humidity environment of the toner, the grasped toner amount in the developing device is corrected according to the toner deterioration, and the insufficient toner amount derived from the corrected toner amount in the developing device is calculated. The toner replenishing device 40 is replenished.

  Here, the “insufficient toner amount” is not an insufficient toner amount relative to the full toner amount of the developing device, but is a target toner amount (predetermined according to the developing device) that is suitable for normal and smooth operation of the developing device. That is, the amount of toner that is deficient with respect to the amount of toner that is usually smaller than the amount of toner full of the developing device.

First, the toner amount in the developing device 4 grasped based on the detection output of the light receiving element 48b and the temperature and humidity environment of the developing device will be described.
Since the fluidity of the toner in the developing device changes according to the temperature and humidity environment around the developing device (the fluidity of the toner is lower in the high temperature and high humidity environment than in the low temperature and low humidity environment), the control unit Cont sets this point. The developing device detected by the temperature / humidity sensor S1 (see FIG. 5) at the toner amount level in the developing device (level 1, level 2, level 3) determined based on the output of the light receiving element 48b in consideration. The amount of toner in the developing device is grasped by combining the ambient temperature and humidity environment level [level 1 (low temperature and low humidity environment), level 2 and level 3 (high temperature and high humidity environment)].

Specifically, the toner amount in the developing device is grasped based on the next table 1 previously stored in the control unit Cont. In Table 1, level 1 in the temperature and humidity sensor output level is a low temperature and low humidity environment (temperature 10 ° C. or less, relative humidity 30% or less), level 3 is a high temperature and humidity environment (temperature 26 ° C. or more, relative humidity 70% or more), level 2 is a temperature and humidity environment level other than these.
The toner amount information in the developing device shown in Table 1 is information obtained in advance according to the output value of the light receiving element 48b and the measured value of the toner amount in the developing device corresponding to the temperature and humidity environment.

  In this way, the required toner amount in the developing device is further corrected according to the degree of toner deterioration, and the toner replenishing device 40 is supplied with the insufficient toner amount according to the corrected toner amount. In this example, the shortage toner amount is a shortage toner amount with respect to a preferable target toner amount (for example, about 23 g to 24 g) in the developing device.

The degree of toner deterioration in the developing device is obtained by the control unit Cont according to the following procedure.
(1) The amount of toner consumed by the developing device is obtained.
The toner consumption amount of the developing device 4 affects the amount of residual toner that is not consumed but is repeatedly subjected to stress in the developing device and deteriorates.
(2) The toner remaining amount (replenished toner remaining amount) in the toner replenishing device 40 is obtained.
In other words, the remaining amount of replenished toner indicates the cumulative toner replenishment amount of the toner replenishing device, which affects the charge amount of the toner in the developing device and is considered when determining the degree of deterioration.
(3) The remaining toner amount in the developing device is obtained from the toner consumption amount of the developing device (1) and the remaining toner amount (replenishing toner remaining amount) in the toner replenishing device (2).
(4) The degree of toner deterioration is obtained from the remaining toner amount in the developing device obtained in (3) above and the accumulated driving time of the developing device motor M.

These procedures will be further described.
(1) Amount of toner consumed by the developing device The amount of toner consumed by the developing device is obtained by combining the consumption parameter with the temperature and humidity environment around the developing device.
The consumption parameter is obtained by the following equation in the control unit Cont.
Consumption parameter = [Coverage (printing rate) [percentage] x system speed [mm / sec]
× Developer motor drive integration time (seconds) × Cover coefficient] / 1000

Here, the “coverage (printing rate)” is the ratio of the area of the toner adhesion area in the image formable area, in other words, the ratio of the number of images to which toner has adhered to the total number of pixels in the image formable area. The number of toner attached images is counted by a dot counter in the control unit Cont. Further, an average printing rate can be adopted as the printing rate here.
The system speed is the same as the photoreceptor peripheral speed.
The “fogging coefficient” is a so-called “fogging” phenomenon, so that the amount of toner consumed is actually larger than the consumption by “image”. Therefore, in order to consider the consumption by “fogging”, the fogging coefficient is determined in advance. Multiply this. Here, the fog coefficient is a value of about 1.1 to 1.4.

For example, if the coverage (printing rate) is 5% (0.05), the system speed is 180 mm / second, the development motor drive integration time is 20,000 seconds, and the fog coefficient is 1.1,
Consumption parameter = 0.05 × 180 × 20000 × 1.1 / 1000 = 198.

  Consumption parameters are level 1 for less than 200, level 2 for more than 200 and less than 350, and level 3 for 350 and more, and ambient temperature / humidity environment level detected by temperature / humidity sensor S1 (see FIG. 5) [level 1 ( Low temperature and low humidity environment), level 2 and level 3 (high temperature and high humidity environment)] are combined to determine the amount of toner consumed by the developing device.

Specifically, the toner consumption is grasped based on the next table 2 stored in advance in the control unit Cont. In Table 2, Level 1 in the temperature / humidity sensor output level is a low temperature and low humidity environment (temperature 10 ° C. or less, relative humidity 30% or less), Level 3 is a high temperature and humidity environment (temperature 26 ° C. or more, relative humidity 70% or more), level 2 is a temperature and humidity environment level other than these.
The toner consumption information of the developing device shown in Table 2 is information obtained in advance according to consumption parameters and actual measured values of toner consumption corresponding to the temperature and humidity environment.

(2) Toner remaining amount in toner replenishing device The toner remaining amount in the toner replenishing device (replenished toner remaining amount) is calculated by the control unit Cont according to the following equation.
Replenished toner remaining amount = (toner amount before replenishment in toner replenishing device)
-(Toner replenishment amount per unit time by toner replenishment motor 404 of replenishing device 40 x toner replenishment motor drive integration time)

In this example, the amount of toner before replenishment in the toner replenishing device is 500 g.

(3) Residual toner amount in the developing device The toner consumption amount of the developing device is level 2 when the consumption amount is 2500 g or more, less than 2500 g, level 2 when it is 2200 g or more, and level 3 when it is less than 2200 g. The remaining toner amount in the developing device is grasped by combining this with the level of the remaining amount of replenished toner (level 1 for 400 g or less but 400 g or more, level 2 for less than 200 g or 200 g or more and level 3 for less than 200 g).

  Specifically, the remaining toner amount in the developing device is grasped based on the next table 3 previously stored in the control unit Cont. The in-developer residual toner amount information shown in Table 3 is information obtained in advance according to an actual measurement value of the residual toner amount corresponding to the toner consumption amount and the replenishment toner remaining amount.

(4) Deterioration degree of toner The amount of toner remaining in the developing device obtained from Table 3 is 27, 30 g or less, and the amount is 27 g or less. Further, the level of toner deterioration is grasped by combining this with the level of integrated driving time of the developing device drive motor (level 1 is less than 4000 seconds, level 2 is 4000 seconds or more and less than 10,000 seconds is level 3).

Specifically, the degree of toner deterioration is grasped based on the next table 4 stored in advance in the control unit Cont. The toner deterioration degree information shown in Table 4 is obtained by previously obtaining the toner deterioration degree corresponding to the remaining toner amount in the developing device and the driving integration time of the developing device drive motor through experiments or the like.
In Table 4, the degree of deterioration is expressed as a relative value with respect to 100 having the smallest degree of deterioration. In Table 4, the degree of deterioration when deterioration is most advanced is “20”.

  The control unit Cont stores in advance the toner amount information in the developing device based on the light receiving element output and temperature / humidity environment obtained in the table 1 according to the toner deterioration degree obtained in the above procedure. The toner amount in the developing device after correction is obtained, and the toner amount that is insufficient based on the toner amount is supplied from the toner supply device 40 to the developing device 4.

  In the correction table 5, the degree of deterioration of the toner is obtained from the table 1 with the level 1 exceeding 80 and 100 or less, the level 2 exceeding 50 and 80 or less, and the level 3 being 50 (less than the most advanced level). The toner amount information in the developing device based on the output of the light receiving element and the temperature / humidity environment is set such that the level exceeds 27 g, 30 g or less, level 1, 23 g exceeds 27 g, level 2 and 23 g or less as level 3.

  As described above, by supplying toner to the developing device, toner supply to the developing device can be controlled so that the amount of toner in the developing device is made constant even if the fluidity of the toner in the developing device fluctuates. As a result, image noise such as image fading and streak can be suppressed as much as there is variation in the toner amount in the developing device.

  In each of the developing device 4 using cyan toner in the image forming portion C and the developing device 4 using magenta toner in the image forming portion M in the printer shown in FIG. Continuously start printing on size recording paper and print up to 400 sheets. During that time, the table 1 is changed based on the light receiving element output of the toner amount detecting device 48 including the light emitting element and the light receiving element and the ambient temperature and humidity environment. The toner amount information in the developing device is obtained, the toner amount information in the developing device is corrected using the table 5, and the insufficient toner amount grasped from the corrected residual toner amount in the developing device is supplied to the replenishing device 40. When replenished, as shown in FIG. 7A, the toner amount in the developing device was stably maintained around the target toner amount (about 23 g to 24 g in this example).

  Further, in the printer shown in FIG. 1, each of the developing device 4 using cyan toner in the image forming portion C and the developing device 4 using magenta toner in the image forming portion M has a deterioration level already shown in the table 4 and is about 60 levels. Continuously start printing on A4 size recording paper at a printing rate of 4% with deteriorated toner, and print up to 400 sheets. Meanwhile, the light receiving element output of the toner amount detection device 48 and the ambient temperature and humidity environment Based on the above, the toner amount information in the developing device is obtained using the table 1, the toner amount information in the developing device is corrected using the table 5, and the shortage grasped from the residual toner amount in the developing device after the correction. When the toner amount is replenished to the replenishing device 40, the toner amount in the developing device is maintained around the target toner amount (about 23g to 24g in this example) as shown in FIG. 7B. .

  Further, in each of the developing device 4 using cyan toner in the image forming unit C and the developing device 4 using magenta toner in the image forming unit M in the printer shown in FIG. Then, continuous printing is started on A4 size recording paper to print up to 400 sheets, and during that time, based on the light receiving element output of the toner amount detection device 48 and the ambient temperature and humidity environment, the table 1 is used to The internal toner amount information is obtained, the toner amount information is used as it is as the residual toner amount in the developing device, and the replenishment device 40 is made to supply the insufficient toner amount ascertained therefrom, as shown in FIG. As the number of images formed increases, the toner amount in the developing unit deviates greatly from the target toner amount (about 23 to 24 g in this example).

  Further, in the printer shown in FIG. 1, for each of the developing device 4 using cyan toner of the image forming unit C and the developing device 4 using magenta toner of the image forming unit M, the deterioration degree already shown in the table 4 is set to “60”. Continuously start printing on A4 size recording paper at a printing rate of 4% with deteriorated toner that has deteriorated to a certain extent, and print up to 400 sheets. During this time, the light receiving element output of the toner amount detection device 48 and the ambient temperature Based on the humidity environment, the toner amount information in the developing device is obtained using the table 1, the toner amount information in the developing device is used as it is as the remaining toner amount in the developing device, and the insufficient toner amount grasped therefrom is replenished. As shown in FIG. 8B, the toner amount in the developing device is increased as the number of images formed increases (in this example, the target toner amount in the developing device (in this example)). It went far off against about 3g~24g).

  From the above, based on at least the detection output of the toner amount detection device 48, the pre-correction toner amount in the developing device 4 is grasped, and this is corrected in accordance with the degree of deterioration of the toner in the developing device. The toner amount in the developing device 4 can be made constant by supplying the toner amount supplied from the toner supply device 48 to the developing device 4, and if there is a variation in the toner amount in the developing device 4, it will occur. It can be seen that image noise such as blurred image and streaks can be suppressed accordingly.

  The present invention replenishes the toner so that the toner amount in the developing device is kept constant even if the fluidity of the toner in the developing device fluctuates. If the toner amount in the developing device varies, image blurring, streak noise, etc. The present invention can be used to provide an image forming apparatus capable of forming an image with reduced image noise.

1 is a diagram schematically illustrating a configuration of an example of an image forming apparatus according to the present invention. FIG. 2 is a diagram illustrating an outline of a cross-sectional structure of a developing device in the image forming apparatus of FIG. 1. It is a figure which shows the outline of an internal structure when the developing device of FIG. 2 is seen from back. It is a perspective view showing a part of a light guide member cleaning device of the toner amount detection device. FIG. 2 is a block diagram illustrating an outline of a control circuit of the image forming apparatus in FIG. 1. FIG. 4 is a diagram for explaining a principle of toner amount information detection in a developing device by a toner amount detection device. FIG. 7A shows the toner in the developing device under the toner supply control according to the present invention when printing is started using the new toner, and FIG. 7B shows the printing started when using the deteriorated toner. It is a figure which shows the fluctuation state of quantity. FIG. 8A shows the amount of toner in the developer under conventional toner replenishment control when printing is started using new toner, and FIG. 8B is when printing starts using deteriorated toner. It is a figure which shows a fluctuation state.

Explanation of symbols

Y Yellow image forming portion M Magenta image forming portion C Cyan image forming portion K Black image forming portion 1 Photoconductor 2 Charger 3 Image exposure device 4 Developer 41 Developing roller 42 Toner supply rollers 43, 44 Toner regulating blade 45 Static elimination member 4U Upper chamber 4L Lower chamber 4W Partition P1, P2 Partition opening 46 Upper toner transport screw 47 Lower toner transport screw M Developer motor 40 Toner supply device 401 Toner storage unit 402 Toner supply duct 403 Toner supply screw 404 Toner supply motor 48 Developer Inner toner amount detection device 48a Light emitting device 48b Light receiving device a, b Light guide member 49 Cleaning device 491 Cleaning member support 492 Cleaning member 493 Shaft 5 Primary transfer roller 6 Cleaning device 7 Intermediate transfer belt 71 Drive roller 72 Opposing roller 73 Cleaner 8 Secondary transfer La 9 recording medium supply cassette 91 recording medium supply roller TR timing roller pair FX fixing device DR recording medium discharge rollers DT recording medium discharge tray S recording medium Cont controller

Claims (7)

One or two or more electrostatic latent image carriers and a developing device provided corresponding to each of the electrostatic latent image carriers, each developing device on the corresponding electrostatic latent image carrier An image forming apparatus capable of developing an electrostatic latent image formed into a toner image to form a toner image;
A toner amount detecting means provided corresponding to at least one developing device, for detecting the toner amount in the developing device, and a toner replenishing device for supplying toner to the developing device;
A toner replenishment control unit for causing the toner replenishing device to replenish toner to the corresponding developing device;
The toner replenishment control unit grasps the toner amount before correction in the developing device based on at least the detection output of the toner amount detecting means for the developing device subject to toner replenishment by the toner replenishing device. Determining the degree of deterioration of the toner in the developing device based on a predetermined factor among the factors affecting the deterioration, correcting the pre-correction toner amount according to the determined toner deterioration level, and determining the predetermined developing device An image forming apparatus characterized in that an insufficient toner amount obtained by subtracting the corrected toner amount from an internal target toner amount is replenished from the toner replenishing device to the developing device.   The toner replenishment control unit grasps the pre-correction toner amount at a predetermined timing, calculates the toner deterioration level in the developing device, and corrects the pre-correction toner amount according to the determined toner deterioration level. The image forming apparatus according to claim 1, wherein an insufficient toner amount obtained by subtracting the corrected toner amount from the target toner amount is supplied from the toner supply device to the developing device.   The image forming apparatus according to claim 2, wherein the predetermined timing is a timing at the completion of a predetermined number of image formations.   The toner replenishment control unit is configured to determine the toner amount before correction in the developing device based on at least the detection output of the toner amount detecting unit for the developing device subject to toner replenishment by the toner replenishing device. 4. The image forming apparatus according to claim 1, wherein the toner amount in the developing device based on only the detected output is grasped in a state in which the toner amount is precorrected based on at least one of the temperature and humidity around the developing device.   The toner replenishing control unit determines the degree of deterioration of the toner based on a toner consumption amount of the developing device and a replenishing toner remaining amount in a toner replenishing device that replenishes the developing device with toner. The image forming apparatus according to claim 1, wherein the image forming apparatus is obtained on the basis of the amount and the integrated driving time of the developing device motor.   The toner replenishment control unit obtains a toner consumption amount of the developing device based on a consumption parameter and at least one of a temperature and a humidity around the developing device, and the consumption parameter includes a print rate in image formation, an image forming apparatus 6. The image forming apparatus according to claim 5, wherein the image forming apparatus is obtained on the basis of the system speed, the developing device motor drive integration time and the fog coefficient.   The toner replenishment controller determines the remaining amount of toner to be replenished in the toner replenishing device by subtracting the amount of toner replenished to the developer by the toner replenishing device from the normal amount of toner to be replenished in the toner replenishing device. 7. The image forming apparatus according to claim 5, wherein the toner replenishment amount is calculated by multiplying a toner replenishment amount per unit drive time of the toner replenishment motor in the toner replenishment device by a drive integration time of the toner replenishment motor.