JP5418128B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an electrophotographic image forming apparatus applied to a copying machine, a facsimile, a printer, and the like.

  Conventionally, a photosensitive member surface is uniformly charged to a predetermined potential by a charging unit, an electrostatic latent image is formed by an exposure unit, and the electrostatic latent image is developed by a developing unit using a two-component developer composed of at least a toner and a carrier. In an electrophotographic image forming apparatus that develops and forms a toner image, the image density varies depending on the toner density of the developer, the toner charge amount, and the like. Therefore, a predetermined toner patch is formed on the photosensitive member, the intermediate transfer belt, the secondary transfer roller, or the paper transport belt, and this is detected by an optical sensor to detect the toner adhesion amount. The toner density of the developer is detected to determine image forming conditions, toner supply conditions, and the like. As a result, even when the developing ability fluctuates, image density fluctuations are suppressed by optimizing the control parameters. Some image forming apparatuses perform toner replenishment control for controlling the amount of toner replenished during printing, and potential control for mainly adjusting an image forming potential at a timing other than printing.

  Here, the potential control will be described. A plurality of toner patches (gradation patterns) having different densities are formed on the photosensitive member, the latent image potential of each toner patch is detected by the potential sensor, and transferred to the intermediate transfer belt. The toner adhesion amount of each toner patch is detected by a toner image detection sensor (P sensor). For this reason, the potential control is executed after a certain amount of time when the power of the image forming apparatus is turned on, when a print job is not received, or when the print job ends. At this time, the developing potential (the difference between the developing bias Vb and the latent image potential Vl) is obtained from the output of the potential sensor, and the toner adhesion amount is obtained from the P sensor output. In an image forming apparatus in which no potential sensor is installed, exposure is performed so that the latent image potential is constant, and a development potential is obtained by changing the development bias, and a plurality of toner patches having different densities are formed. . Then, from the relationship between the development potential and the toner adhesion amount, a development potential that achieves a predetermined toner adhesion amount is obtained, and image forming conditions such as a development bias, a charging bias, and an exposure light amount are determined.

  The detection timing and control method of the toner density sensor (T sensor) provided in the developing device and the toner image detection sensor (P sensor) provided facing the intermediate transfer belt are as follows. That is, since the T sensor can perform sensing at any time regardless of the presence or absence of printing, the sensing interval is set short, and the sensor output is mainly used for controlling the toner replenishment amount. The detection timing of the T sensor is generally to detect the toner density for each printed sheet. On the other hand, toner image detection is performed by forming predetermined toner patches on the intermediate transfer belt and detecting them with a P sensor. Accordingly, during printing, these cannot be imaged and detected, and toner is consumed. Therefore, the detection frequency by the P sensor is generally lower than the detection frequency by the T sensor.

  Several types of optical sensors are known as optical sensors that are P sensors used to detect the amount of toner adhesion, and include an LED as a light emitting element and a photodiode (PD) or phototransistor (PTr) as a light receiving element. A combined reflective sensor is generally known. As the sensor configuration, as shown in FIG. 4, a type that detects only specularly reflected light (see Patent Document 1, etc.), and as shown in FIG. 5, a type that detects only diffusely reflected light (Patent Documents 2 and 3). As shown in FIG. 6, there are three types that detect both (see Patent Document 4 and the like). 4, 5, and 6, reference numeral 10 denotes an optical sensor, 20 denotes an LED, 21 denotes a regular reflection light receiving element, 8 denotes a detection target surface, 23 denotes a toner patch on the detection target surface, and 22 denotes diffuse reflection. Each of the light receiving elements is shown.

In any type of optical sensor, processing for converting the sensor detection value (the amount of received light) into the toner adhesion amount is performed. The conversion process is broadly divided into calibration of sensor output and conversion of sensor output into toner adhesion amount.
Calibration of the sensor output is necessary to detect an accurate amount of adhesion, and several calibration methods are disclosed. For example, a sensor has a white reference plate inside, and a method for periodically calibrating the sensor output using this white reference plate (see Patent Document 5) and a mechanism for detecting regular reflection light and diffuse reflection light are provided. There is a method of detecting a plurality of patches having different densities and performing self-calibration by an internal calculation from the array of sensor outputs (see Patent Document 6).
As the conversion of the sensor output into the toner adhesion amount, a method of performing conversion using a relational expression between the toner adhesion amount and the sensor output (after calibration), which is experimentally obtained in advance, is generally used.

  Patent Document 7 discloses an image forming unit that forms a toner image on an image carrier that is detachable from an image forming apparatus, and light reflection characteristics of an unfixed toner image formed on the image carrier or transfer material carrier. Forming an image sensor, an image gradation control means for controlling the image gradation according to the detection result detected by the optical sensor, and a non-volatile memory for storing data provided in the image forming unit In the apparatus, density conversion information corresponding to the detection result and density is stored in a nonvolatile memory, and when image gradation control is performed, each image is referred to by referring to the density conversion information stored in the nonvolatile memory. It discloses that gradation control is performed based on density conversion information suitable for a forming unit.

  However, a detachable image forming unit is an indispensable constituent element. In particular, as in the case of the one-component developing method, the process cartridge is replaced when the toner in the developing device is used up. . When a toner bottle is used in the two-component development system, when the toner bottle is replaced, the old toner before replacement remains in the developer in the developing device. The toner is mixed. The toner detection signal detected by the optical sensor is converted into a density by referring to a density conversion table (density conversion information) stored in the non-volatile memory. A mismatch occurs between the density conversion table for toner and the old toner. Since the density conversion table itself is stored in a non-volatile memory for storing data provided in the image forming unit, the conversion table for the old toner can no longer be referred to. Correction cannot be performed. Further, although it is disclosed that the user corrects the density conversion table, it is necessary to use an expensive density measuring device instead of a scanner, or it is necessary to perform correction whenever new and old toners are mixed, which is not realistic.

  Patent Document 8 includes a developing device, a memory, and a T sensor in a detachable cartridge, and information (toner end / near end information) for switching between memory information and toner supply based on T sensor output or toner supply based on pixel information. ) To switch the toner replenishment mode.

In an image forming apparatus having such image density control, the image density may fluctuate during printing.
Usually, the image forming apparatus is provided with a detachable toner cartridge. When the toner in the toner cartridge runs out, the user replaces the toner cartridge. However, since the toner characteristic value depends on the time when the toner cartridge is manufactured, unintended changes in manufacturing conditions, etc., the same toner cannot be created, and the toner characteristic value may vary within a tolerance range. . If toner whose toner characteristic value has greatly fluctuated is supplied to the image forming apparatus, the image density control cannot be performed as intended. That is, in an image forming apparatus that detects a toner image with an optical sensor, the detection output may vary depending on the characteristic value of the toner, and the control unit may adjust to the shifted image density. As a result, when the toner cartridge is replaced during continuous printing of 1000 sheets, the image density varies between the first and 1000th sheets. In particular, in the PP market, higher quality image quality is required compared to the general office market, and such repeat density fluctuations and left and right density differences in one sheet can be problematic. In particular, no solution has been disclosed for the deviation in detection output when old and new toners are mixed.

In order to prevent such a problem in advance, it is only necessary to supply a uniform quality toner by narrowing the tolerance of the toner characteristic value. However, the yield of the toner is reduced, which causes an increase in the cost of the toner and the like.
In view of the above, even when the toner characteristic value fluctuates due to the replacement of the toner bottle or the process cartridge, the present invention replaces the image forming apparatus by performing the control process in consideration of the mixed state of the old and new toner. The object is to provide a high quality image with a constant image density before and after.

An object of the present invention is to provide an image forming apparatus according to the present invention , which includes an image carrier, a developing device that includes a developer container and forms a toner image on the image carrier, a toner image detector that detects the toner image, and image formation Detected by toner storage means configured to be detachable from the apparatus main body, first storage means associated with the toner storage means, second storage means associated with the developer storage section, and toner image detection means Control means for appropriately controlling the image density based on the detected value of the toner image, and the toner in the toner storage means is supplied to the developer storage portion of the developing device via the toner transport means, storage means has data on toner particle diameter in the toner storage means, second storage means has data on initial toner particles having a particle diameter in the developer accommodating portion, the first storage means and second storage door in means Taking into account the data relating to over particle size, the control means is bets toner image detecting means is solved Converting open the detection value of the toner image detected in the current toner adhesion amount. Even when the toner before and after the replacement is mixed immediately after the toner storage means is replaced, it is possible to prevent the adhesion amount detection accuracy from being lowered by using the toner particle size information. By storing the toner particle size information in the developer storage unit and the toner storage unit, the current toner particle size can be specified regardless of which is replaced. Image density stability can be provided.

  The control means has a first algorithm for converting the detected value of the toner image detected by the toner image detecting means into a relationship between the current toner adhesion amount and the normalized value. In the first algorithm, At this time, it is preferable to use the toner particle size which is one of the data of the storage means and convert the detected value of the toner image into the toner adhesion amount using the relationship between the toner adhesion amount and the normalized value. Since the error due to the toner particle size generated when the optical sensor output is converted into the toner adhesion amount by the adhesion amount conversion algorithm can be reduced, high quality image quality can be provided.

  In addition, after the toner storage unit is replaced, the control unit further calculates, in the first algorithm, a new and old toner replacement ratio representing a ratio of new toner in the entire developer in the developer storage unit, and calculates the calculated The control means preferably converts the detected value of the toner image detected by the toner image detecting means into a relationship between the toner adhesion amount and the normalized value based on the old / new toner replacement ratio and the toner particle size. Even if the toner before and after the replacement is mixed immediately after the toner storage means is replaced, the conversion processing is performed using the two characteristic value information of the old and new toner until all the toner in the image forming apparatus becomes the replaced toner. By doing so, high quality image quality can be provided.

  Further, the control means has a second algorithm for controlling the developing bias applied to the developing device and the exposure light amount of the exposure device for exposing the image carrier from the detected value of the toner image detected by the toner detecting means, In the second algorithm, it is preferable to use a coloring degree, which is one of the data in the storage unit, which is an image density when a predetermined adhesion amount of toner is formed on the transfer paper. Even when the degree of coloring differs for each toner bottle, the image forming conditions are determined according to the degree of coloring, so that stable image quality can be provided. Further, since the variation in coloring degree can be absorbed on the control side, the tolerance of the manufacturing variation of toner can be widened, which can contribute to cost reduction. In addition, waste toner can be reduced because defective toner can be reduced.

  The toner image detection means is preferably an optical sensor having a light emitting element and a light receiving element for optically detecting a toner image. When the toner particle size changes, the optical sensor output shows a different value even with the same adhesion amount. In order to avoid this, the toner adhesion amount can be converted based on the detected toner particle diameter, so that stable image quality can be provided. Further, since the variation in particle diameter can be absorbed on the control side, the tolerance of the manufacturing variation of toner can be widened, which can contribute to cost reduction.

  The toner image detecting means preferably detects an unfixed toner image before passing through the fixing device. By sensing unfixed toner having no particle size change with an optical sensor and utilizing this particle size information, the amount of adhesion is accurately calculated.

  The toner image detecting means preferably detects a toner patch that is a toner image transferred onto a transfer conveying member that conveys the transfer paper. By performing the detection by the optical sensor after the secondary transfer, the image density can be adjusted with the information including the influence of the variation up to the secondary transfer process depending on the time and environment, so that the influence of the variation can be further suppressed.

According to the present invention, the toner characteristic value information is acquired from the storage area associated with the toner bottle or the process cartridge and fed back to the control. Therefore, the toner characteristic value varies greatly from toner bottle to toner bottle. Even in the case where the toner image is mixed, the detected value of the toner image detected by the toner image detecting means is converted into the toner adhesion amount in consideration of this, and thus a high-quality image can be provided.
In addition, even if the toner characteristic value fluctuates greatly, the image forming apparatus performs control to keep the image density constant. Conversely, the tolerance of the toner characteristic value can be widened, and the toner yield is improved. Thus, cost reduction can be expected, and waste toner in the manufacturing process is also reduced.

1 is a schematic cross-sectional view of a full-color printer that is an example of an image forming apparatus according to the present invention. It is a figure which shows the input / output information of the electric potential control apparatus in this invention. It is a figure which shows the control flow of the electric potential control apparatus in this invention. It is a schematic sectional drawing of the optical sensor of the type which detects only regular reflection light. It is a schematic sectional drawing of the optical sensor of the type which detects only diffuse reflection light. It is a schematic sectional drawing of the optical sensor of the type which detects regular reflection light and diffuse reflection light. FIG. 6 is a diagram illustrating a relationship between a normalized value of toners having different toner particle sizes and a toner adhesion amount. FIG. 6 is a diagram illustrating a relationship between a normalized value of toners having different toner particle sizes and a toner adhesion amount. It is a figure which shows the method of calculating | requiring the optimal image development potential using the relationship between coloring degree, image development potential, and adhesion amount. It is a figure which shows the update method of the toner characteristic value in the control flow of an electric potential control apparatus. FIG. 6 is a diagram illustrating a toner information update flow when a toner bottle is replaced. FIG. 10 is a diagram illustrating a toner information update flow when a process cartridge is replaced. FIG. 10 is a diagram illustrating a toner information update flow when a process cartridge and a toner bottle are replaced. It is a figure which shows the update method of the toner characteristic value in the control flow of an electric potential control apparatus. FIG. 6 is a diagram illustrating a toner information update flow when a toner bottle is replaced. FIG. 10 is a diagram illustrating a toner information update flow when a process cartridge is replaced. FIG. 10 is a diagram illustrating a toner information update flow when a process cartridge and a toner bottle are replaced.

Hereinafter, an embodiment of an image forming apparatus of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a cross-sectional configuration diagram showing an outline of a full-color printer as an example of an image forming apparatus according to the present invention.
At the center of the main body of the full-color printer shown in FIG. 1, four drum-shaped photoreceptors (referred to as photoreceptor drums) 1Y, 1M, 1C, and 1Bk as image carriers are arranged in parallel at equal intervals. ing. Y, M, C, and Bk represent yellow, magenta, cyan, and black colors, respectively. Here, the following description will be given focusing on the photosensitive drum 1Y for yellow image. The photosensitive drum 1Y is rotationally driven by a drive motor (not shown) in the clockwise direction in the drawing. Image forming means such as a charging device (charging roller in the illustrated example) 2, a developing device 4 having a developing roller 3, a cleaning device 7 and the like are sequentially formed around the lower side of the photoreceptor 1Y in accordance with an electrophotographic process. It is arranged. The same applies to magenta, cyan, and black image forming means.

  The surface of the photosensitive drum 1 (1Y, 1M, 1C, 1Bk) is uniformly charged by the charging roller 2 of the charging device, and then the optical drum of the optical writing device (not shown) shows the arrow in the drawing. Thus, an electrostatic latent image corresponding to the image information is formed. The developing roller 3 in the developing device 4 transports the developer in the developing device 4 to a developing nip region facing the photosensitive drum 1, and attaches toner to the electrostatic latent image formed on the photosensitive drum 1. , Visualize. The toner image formed on the photosensitive drum 1 is disposed on the upper side of the photosensitive drum 1, and the primary transfer device (on the intermediate transfer belt 8 stretched between the driving roller 18 and the plurality of driven rollers 15. In the illustrated example, the image is transferred by a primary transfer roller 6. As the intermediate transfer belt 8 moves, the toner images transferred onto the intermediate transfer belt 8 are sequentially transferred onto the intermediate transfer belt 8 as toner images of colors Y, M, C, and Bk are overlaid. . The color-superposed toner images are moved to a secondary transfer portion that faces a secondary transfer device (secondary transfer roller provided so as to be able to contact and separate in the example shown), and a paper feed portion (paper cassette) (not shown). A recording medium (for example, a paper feed tray, etc.) fed by a paper feed means (paper feed roller, separation roller, transport roller, etc.) and fed to the secondary transfer unit at a predetermined timing by a registration roller 11 (for example, The image is transferred to the transfer paper P by the secondary transfer device 12 and an image is formed on the transfer paper P. On the other hand, the cleaning device 7 wipes away unnecessary toner remaining on the photosensitive drum 1 after transfer, and stores unnecessary toner in a waste toner bottle (not shown). Also, a belt cleaning device 14 is provided for the intermediate transfer belt 8. The belt cleaning device 14 wipes off unnecessary toner remaining on the intermediate transfer belt 8 after the secondary transfer, and waste toner (not shown). Store unnecessary toner in the bottle. After the photosensitive drum 1 and the intermediate transfer belt 8 are cleaned, the above-described procedure is repeated to repeatedly form an image.

  The developing device 4 of the image forming means for each color of Y, M, C, and Bk includes a developing roller 3 that is a developer carrier, and the developing roller 3 is disposed so as to face the photosensitive drum 1. The developing roller 3 includes a cylindrical developing sleeve that carries and conveys a two-component developer composed of a non-magnetic toner and a magnetic carrier, and a plurality of magnetic poles (a plurality of magnets or a plurality of magnetic poles) that are fixedly arranged inside the developing sleeve. A magnetic roller having magnetic poles). Further, the developing device 4 includes a biaxial conveying screw including a first screw 13 and a second screw 19. A toner concentration sensor 5 serving as a toner concentration detecting unit is provided at a lower portion of the developer chamber on the second screw 19 side. The toner concentration sensor 5 or the developing device 4 is accompanied by a non-illustrated nonvolatile memory. In this nonvolatile memory, in the initial state in the developing device 4, the particle size of the toner, the degree of coloring, the inspection value of the control voltage Vtcnt which is information relating to the toner density sensor 5, the latest developing ability, the toner density, the new article Information, serial number, etc. are stored.

  In this embodiment, the photosensitive member 1, the charging roller 2, the developing device 4, and the cleaning device 7 are integrated into a detachable process cartridge. Members that can be replaced by the user are a process cartridge and a toner bottle 9 as a toner supply container.

Here, the image density control in the image forming apparatus of the present embodiment includes the potential control device 100 and toner supply control (not shown).
The toner control device that performs toner replenishment control compares the output value Vt of the toner density sensor 5 with the toner density control target value Vtref, calculates a toner replenishment amount from an arithmetic expression according to the difference, and supplies a toner replenishment container (toner bottle). ) The toner stored in 9 is replenished to the developing device 4 by the toner replenishing device 17 which is a toner replenishing means. Further, the toner bottle 9 is provided with a nonvolatile memory 16. The non-volatile memory 16 stores the toner particle size as the characteristic value of the toner in the toner bottle 9, the degree of coloration, the manufacturing number as the toner bottle ID information, the new product information, the refill information, and the remaining amount information of the toner in the toner bottle. The amount of toner replenishment and the remaining amount of toner are stored. As described above, by storing the toner characteristic value information in the toner bottle, the processing can be changed in the potential control flow in accordance with the toner characteristic value information, so that high quality image quality can be provided.

  Input / output information in the potential control apparatus 100 is as shown in FIG. That is, the detected value of the toner image detected by the optical sensor 10 as the toner image detection sensor, the toner concentration detected by the toner density sensor 5, and the temperature / humidity sensor (FIG. 5) which is an environmental sensor disposed in the vicinity of the developing device 4. When the temperature / humidity detected by the sensor (not shown), the surface potential after exposure of the photosensitive member detected by the potential sensor 30, and the developing bias are input, the potential control device 100 sets the toner density control target value Vtref, the charging device A charging bias, a developing bias of the developing device, and an exposure light amount of the exposure device are output. By controlling each bias and toner supply in accordance with these optimum image forming conditions, a stable image density is maintained.

  The optical sensor 10 of the present embodiment is a one-emission two-reception type optical sensor as shown in FIG. The optical sensor 10 mainly includes a light emitting element 20 as a light emitting means such as an LED, a regular reflection light receiving element 21 as a first light receiving means for receiving specular reflected light, and a light for receiving diffusely reflected light. It comprises a diffuse reflection light receiving element 22 as a second light receiving means. Light emitted from the light emitting element 20 is emitted toward the surface of the intermediate transfer belt 8 which is a detection target surface. Then, the specularly reflected light regularly reflected by the surface of the intermediate transfer belt 8 and the toner patch 23 transferred to the surface is received by the specular reflection light receiving element 21 and a voltage corresponding to the amount of received light is output. Further, the diffuse reflection light diffused and reflected by the surface of the intermediate transfer belt 8 and the toner patch 23 transferred to the surface is received by the diffuse reflection light receiving element 22, and a voltage corresponding to the amount of received light is output.

Next, the control flow of the potential control apparatus 100 will be described in detail using the flowchart of FIG. Image density control by the potential control device 100 is periodically executed when a printing operation is not performed, such as when the power is turned on or after printing a predetermined number (250 sheets). The reason why the image density control is performed when the printing operation is not performed is that a plurality of toner patches (tone patterns) having different densities need to be formed.
The potential control device first updates the toner characteristic value. This will be described in detail later. Next, adjustment of the LED light quantity of the optical sensor 10 is performed. After completion of the adjustment, a plurality of toner patches having different densities are formed on the photosensitive drum, the latent image potential of each toner patch is detected by the potential sensor 30, and the development potential (development bias Vb and latent potential is detected from the detected potential sensor output. (Difference in image potential Vl). At the same time, the output of each toner patch is detected by the optical sensor 10 on the intermediate transfer belt, the sensitivity of the optical sensor 10 is calibrated to calculate the accurate toner adhesion amount, and the toner adhesion amount is calculated from the output of each toner patch. To do. Further, the temperature and humidity in the image forming apparatus main body at this time are detected by a temperature and humidity sensor (not shown), and the toner density in the developing device 4 is detected by the toner density sensor 5.

  In the optical sensor of this embodiment, the output of the regular reflection light receiving element 21 in Bk toner is used to convert it into an adhesion amount. The C toner, M toner, and Y toner are converted based on the output of the diffuse reflection light receiving element 22 in addition to the regular reflection light receiving element 21. The regular reflection output of C toner, M toner, and Y toner is used to calibrate the diffuse reflection output. The calibration of the optical sensor 10 and the conversion of the sensor output into a normalized value are performed using the same algorithm as known in Patent Document 6. Here, the normalized value is an integer from 0 to 100, and is a value obtained by removing noise from the sensor output so as to have a one-to-one relationship with the toner adhesion amount. Then, the sensor output is converted into the toner adhesion amount from the relational expression MAnow [n] including a predetermined normalization value and the toner adhesion amount parameter.

In brief, this algorithm is converted into an adhesion amount using the regular reflection light output from the Bk toner according to the following procedure.
(1) Sampling the regular reflection light output of the belt background and the gradation pattern of Bk toner,
(2) Calculate the normalized value,
Normalized value = (regular reflection output of gradation pattern) / (regular reflection output of belt background) × 100
= Vsp_reg / Vsg_reg × 100
Vsp: Output voltage Vsg of each gradation pattern: Output voltage _reg. Of the background portion of the intermediate transfer belt 8 ... Specular reflection light output (Regular Reflection)
(3) An adhesion amount conversion process is performed from the relationship between the “adhesion amount” and the “normalized value” obtained in advance.
Here, the present invention is characterized in that the relationship between the adhesion amount and the normalized value in (3) is changed according to the toner characteristic value.

Further, the diffuse reflected light output from the C toner, M toner, and Y toner is converted into an adhesion amount value according to the following procedure.
(1) Sampling the regular reflection light output and diffuse reflection light output of the gradation pattern,
(2) Extracting only the regular reflection light component by decomposing the regular reflection light output into a regular reflection light component and a diffuse reflection light component,
(3) By extracting the “diffuse reflected light component from the belt background” from the diffuse reflected light output, the “diffused light component from the toner” is extracted,
(4) An adhesion amount range in which the adhesion amount can be detected by specular reflection light using a linear relationship with the adhesion amount of two output conversion values that are independent (intersect) obtained from (2) and (3). By adjusting the sensitivity of the diffuse reflection light output conversion value so that the diffuse reflection light output conversion value of a certain regular reflection light output conversion value (or adhesion amount) becomes a certain value in the (low adhesion amount region), the adhesion amount Diffuse reflected light output (correction value) is uniquely determined for
(5) Multiply the diffuse reflection light output correction value by 20 to convert it to a normalized value,
(6) The adhesion amount conversion process is performed from the relationship between the “adhesion amount” and the “normalized value” obtained in advance.

From the relationship between the development potential and the toner adhesion amount obtained as described above, the development potential, which is an inclination when the development potential is taken on the horizontal axis and the toner adhesion amount is taken on the vertical axis, is obtained (FIGS. 3 and 9). Then, a developing potential that gives a predetermined image density is calculated from the developing ability and the coloring degree Cnow. Thereby, image forming conditions such as a developing bias, a charging bias, and an exposure light amount are determined (FIGS. 3 and 9). Further, the temperature and humidity in the apparatus main body at this time are detected by a temperature and humidity sensor, the toner density in the developing device 4 is detected by the toner density sensor, and the toner density suitable for the environment at that time is calculated to control the toner density. Determine or correct the target value.
Although not shown in the series of potential control flows as described above, an appropriate output range is determined in advance for all the detected values, and an abnormal stop means is provided for abnormally stopping the machine operation if it is outside the proper output range. . In the case of an output abnormality, the notification means can notify the user or service person of the abnormality.

  By the way, although the output of the optical sensor 10 is calibrated, there is a case where a shift occurs in the conversion of the sensor output into the toner adhesion amount. As a result of this cause analysis, it has been found that this deviation depends on the toner characteristic value, particularly the toner particle diameter, and the deviation between the normalized value and the toner adhesion amount is caused by the conversion of the toner particle diameter. As described above, the calibration of the optical sensor converts the diffuse reflection output when a predetermined toner adhesion amount is detected into a predetermined value. Since calibration of the optical sensor is in principle calibrating the sensitivity of the optical sensor, the diffuse reflection output and the converted value should be in a proportional relationship. However, if the toner particle size changes, the profile of the relationship between the normalized value and the toner adhesion amount changes as shown in FIGS. 7 and 8, and the normalized value and the toner adhesion amount have a one-to-one relationship. As a result, it is impossible to calibrate with a constant multiple calibration such as that performed during the sensor calibration process. The reason for this is considered to be that the way in which light is reflected fluctuates due to a change in toner particle diameter. Due to such fluctuations, the toner adhesion amount is erroneously detected, causing the image density to fluctuate. Therefore, in this embodiment, the conversion to the toner adhesion amount is performed in consideration of the change in the toner particle size, that is, the toner particle size in a mixed state of old and new toner.

Next, a control / calculation method relating to the toner characteristic value update flow in FIG. 3 will be described. First, the calculation of the relational expression MAnow [n] including the normalized value and the toner adhesion amount parameter will be described.
In the present embodiment, the relationship between the normalized value depending on the toner particle diameter Dv obtained in advance by experiments as shown in FIGS. 7 and 8 and the toner adhesion amount is stored in a non-illustrated nonvolatile memory of the apparatus main body. . The normalized value is an integer from 0 to 100 and has a one-to-one relationship with the toner adhesion amount. The level of the toner particle diameter Dv includes the toner value of the central value and the upper and lower tolerance values. In FIGS. 7 and 8, the central value is Dv = 5.0 μm, the upper limit value is Dv = 6.5 μm, and the lower limit value. The value is expressed as Dv = 4.3 μm. The information on the toner particle diameter Dv stored in the nonvolatile memory of the apparatus main body and the toner particles in the nonvolatile memory (not shown) associated with the toner density sensor 5 or the nonvolatile memory 16 associated with the toner bottle 9 are used. Based on the diameter information, the relationship between the normalized value of the toner in the developing device 4 and the adhesion amount in the mixed state of old and new toner is calculated.

  First, in order to derive the relationship between the normalized value of toner in the developing device 4 and the adhesion amount, the toner particle size in the nonvolatile memory associated with the toner density sensor 5 in which the toner particle size information in the developing device 4 is stored is stored. Use information. This initial toner particle size information before another toner is replenished in the developing device 4, the normalized value for the toner having the toner particle size of the center value and the upper and lower tolerances in the nonvolatile memory of the apparatus main body, and the toner Based on the adhesion amount, the relationship between the toner normalization value in the developing device 4 and the toner adhesion amount is obtained.

The relational expression MAdev [n] between the normalized value of the toner in the developing device 4 (at the initial time and at the time of replacement) and the toner adhesion amount is calculated as follows.
When the particle size is larger than the center value 5.0 μm MAdev [n] = (MAup [n] −MAc [n]) × (Gdev−Gc) / (Gup−Gc) + MAc [n]
When the particle size is a median value of 5.0 μm or less MAdev [n] = (MAlow [n] −MAc [n]) × (Gdev−Gc) / (Glow−Gc) + MAc [n]

  Here, n is an ordinal number of normalized values and is an integer from 0 to 100, MA is the toner adhesion amount, and G is the toner particle size. In the subscript, dev refers to the toner in the developing device, low means the particle size tolerance lower limit, c means the particle size tolerance center value, and up means the particle size tolerance upper limit. Therefore, MAup [n] represents the toner adhesion amount of the normalized value n that is the upper limit of the particle size tolerance, and Gdev represents the toner particle size of the toner in the developing device. In this way, the toner adhesion amount MAdev [n] of the toner in the developing device can be calculated. After the calculation, MAdev [n] is stored in a non-volatile memory in the image forming apparatus.

  Further, in order to derive the relationship between the normalized value of the toner in the toner bottle 9 and the adhesion amount, the toner particle size in the nonvolatile memory 16 attached to the toner bottle 9 in which the toner particle size information in the toner bottle 9 is stored is stored. Use information.

The relational expression MAbot [n] between the normalized value of the toner in the toner bottle 9 and the toner adhesion amount is calculated as follows using the subscript dev of the above expression as bot.
When the particle size is larger than the center value of 5.0 μm MAbot [n] = (MAup [n] −MAc [n]) × (Gdev−Gc) / (Gup−Gc) + MAc [n]
When the particle size is less than or equal to the central value 5.0 [μm] MAbot [n] = (MAlow [n] −MAc [n]) × (Gdev−Gc) / (Glow−Gc) + MAc [n]
Here, the suffix bot indicates a toner bottle. The calculated MAbot [n] is similarly stored in a nonvolatile memory in the image forming apparatus.

Next, the replacement ratio R (%) of the new and old toner is calculated as follows.
The bottle toner ratio R (%) in the developing device is as follows using the accumulated toner replenishment amount Ts (mg) and the initial toner weight Mt (mg) that are updated each time printing is performed.
R (%) = Ts / (Mt + Ts) × 100

  Here, Mt indicates the weight of toner remaining in the developing device 4 and the toner replenishing device 17 when any replacement is performed. Mt is calculated at the following timing, and thereafter, the calculated value is used.

When new:
Mt = (initial toner weight)
When the process cartridge is replaced or the process cartridge and toner bottle are replaced at the same time:
Mt = (initial toner weight)
When the toner bottle is replaced:
Mt = (Mt−S × M / A) + Ts
Here, M / A is a target toner adhesion amount M / A (mg / cm ² ) stored in the apparatus main body, and S is a written image area cumulative value S (cm ² ) updated for each printing. . After the bottle toner ratio R (%) in the developing device 4 is calculated, the upper limit processing is performed at 100 (%).

  In summary, the relational expression MAdev [n] between the normalized value of toner in the developing device 4 and the adhesion amount, the relational expression MAbot [n] between the normalized value of toner in the toner bottle 9 and the adhesion amount, and development The bottle toner ratio R (%) in the apparatus 4 was calculated. From these pieces of information, a relational expression MAnow [n] between the current normalized value and the toner adhesion amount is obtained.

Calculation of the relational expression MAnow [n] between the current normalized value and the toner adhesion amount is as follows.
MAnow [n] = MAbot [n] × R / 100 + (1−R / 100) × MAdev [n]
That is, since the bottle toner ratio R increases as the toner is consumed, the first term on the right side increases, and the contribution of the new toner in the bottle toner increases. On the other hand, since the old toner in the developing device decreases, the second term on the right side decreases accordingly, and the contribution of the old toner in the developing device decreases. The relational expression MAnow [n] between the current normalized value and the adhesion amount is also stored in the nonvolatile memory of the apparatus main body.

Next, correction of the target toner adhesion amount will be described.
Even if the toner adhesion amount can be controlled at the time of image formation, since the toner coloring level may be different for each toner bottle, the image density is changed by the change in the toner coloring degree in a mixed state of old and new toners. May fluctuate. Therefore, in this embodiment, the color degree information is stored in the nonvolatile memory (not shown) of the toner density sensor 5 and the nonvolatile memory 16 of the toner bottle 9, and the current coloring in the mixed state of old and new toner is used by using these. The target toner adhesion amount is corrected using the calculated degree. Here, the coloring degree is an image density on paper when a predetermined toner adhesion amount is printed. The predetermined adhesion amount in the present example is 0.45 (mg / cm ² ).

The current coloring degree Cnow is calculated as follows.
Cnow = Cbot × R / 100 + (1−R / 100) × Cdev
Here, C indicates the coloring degree, the subscript bot indicates the toner bottle, and dev indicates the developing device. Therefore, Cbot indicates the color level of the toner in the toner bottle, and Cdev indicates the color level of the toner in the developing device. Similarly, since the ratio R of the bottle toner increases as the toner is consumed, the contribution of the new toner in the bottle toner increases (the first term increases). On the other hand, since the amount of old toner in the developing device is decreasing, the contribution of the second term is reduced accordingly. The current coloring degree Cnow is also stored in the nonvolatile memory of the apparatus main body. Cdev uses a value in the nonvolatile memory of the toner density sensor 5.

FIG. 9 shows a method for obtaining an optimum development potential using the coloration degree Cnow thus obtained.
The straight line in the right half of the figure shows the relationship between the development potential obtained in the control flow of the potential control apparatus 100 and the toner adhesion amount. (1) is a plot for a black (Bk) toner patch, and (2) is a plot for a cyan (C) toner patch.
The curve in the left half of the figure shows the relationship of the target adhesion amount according to the coloring degree stored in the nonvolatile memory of the apparatus main body. For example, the upper right plot indicates that an adhesion amount of 0.5375 (mg / cm ² ) is necessary to obtain a predetermined image density when the coloring degree is 1.2. From the above relationship, the predetermined target adhesion amount in this embodiment is corrected. Specifically, the target adhesion amount is changed from 0.45 (mg / cm ² ) to 0.5375 (mg / cm ² ) when the coloring degree Cnow is 1.2. As described above, the target toner adhesion amount is calculated (corrected) using the previously calculated coloring degree Cnow, and the developing ability (relationship between the development potential and the toner adhesion amount) obtained in the control flow of the potential control device 100 is used. Find the optimal development potential (right half of the figure).
In this way, it is possible to obtain an optimum development potential and to obtain optimum image forming conditions such as a development bias, a charging bias, and an exposure light amount according to the toner characteristic value at that time, so that an image with more stable image density can be obtained. Formation is realized.

  These MAnow [n] and Cnow information are updated at the time of “updating toner characteristic values” in the control flow of the potential control apparatus 100 shown in FIG. A specific update flow is as shown in FIG. 10, and the toner mixing ratio R is updated to update the current MAnow [n] and Cnow.

Next, control when the toner bottle and the process cartridge are replaced will be described.
When the toner bottle is replaced, as shown in FIG. 11, it is necessary to update the toner information in the toner bottle, so MAbot [n] is updated. On the other hand, since the value of the coloring degree Cnow is referred from the nonvolatile memory, nothing is done. Also, as shown in FIG. 11, the current MAnow [n] and Cnow are substituted into MAdev [n] and Cdev in the developing device. This operation corresponds to the case where the mixed toner contained in the developing device is regarded as one type of toner after the toner bottle or the like is replaced. Here, Cdev is stored in a non-volatile memory in the developing device 4.

  When the process cartridge is replaced, as shown in FIG. 12, the relational expression MAdev [n] is calculated using the toner particle size information in the nonvolatile memory associated with the replaced toner density sensor 5. Next, the calculated MAdev [n] is substituted into the relational expression MAnow [n] between the current normalized value and the toner adhesion amount. At the same time, the current coloring degree Cnow is also updated to Cdev in the nonvolatile memory of the toner density sensor 5.

  When both the toner bottle and the process cartridge are exchanged, both toners are changed. Therefore, as shown in FIG. 13, the respective relational expressions MAdev [n] and MAbot [n] are calculated and the current relations are calculated. The calculated MAdev [n] is substituted into the expression MAnow [n]. At the same time, the current Cnow is also updated to Cdev in the nonvolatile memory of the toner density sensor 5.

In this way, even when the toner in the toner bottle and the toner in the developing device have different particle sizes, the old toner in the developing device gradually changes to the new toner in the toner bottle. Thus, the relationship between the normalized value and the toner adhesion amount can be optimized.
It should be noted that at the end of the flow after some replacement, the old and new toner ratio R, the written image area cumulative value S, and the toner replenishment amount cumulative value Ts are cleared and the old toner weight Mt is calculated at the same time.

As described above, by correcting the relational expression between the normalized value and the toner adhesion amount and the target toner adhesion amount, erroneous detection of the toner adhesion amount can be greatly reduced, so that the image density stability particularly during repeat printing is improved. .
Further, in such an image forming apparatus, it is possible to widen the tolerance of the toner characteristic value while maintaining the conventional image density stability. As a result, the yield of toner is improved, and the range of toner manufacturing methods or material selection is widened, so that the cost of the toner and the apparatus can be expected to be reduced.

  In this embodiment, the relational expression between the normalized value and the toner adhesion amount is corrected. However, the correction is not limited to the normalized value, and the raw value of the optical sensor output or the output (V) after calibration is used. There may be.

  Next, another embodiment of the image forming apparatus of the present invention will be described. The second embodiment is substantially the same as the first embodiment, but differs from the first embodiment in that a nonvolatile memory is not mounted on the toner density sensor 5. In this embodiment, since the information about the toner in the developing device 4 cannot be acquired, the image density may become unstable due to the fluctuation of the toner characteristic value as compared with the first embodiment. The image density is more stable than the apparatus.

  Information on MAnow [n] and Cnow is updated at the time of “updating the toner characteristic value” in the control flow of the potential control apparatus 100 shown in FIG. A specific update flow is as shown in FIG. 14, and the toner mixing ratio R is updated to update the current MAnow [n] and Cnow.

Next, control when the toner bottle and the process cartridge are replaced will be described.
When the toner bottle is replaced, the toner information update flow in this embodiment is the flow shown in FIG. 15, which is the same as the flow in FIG. 11 in the first embodiment. Since the characteristic value of the toner entered at the time of replacement is updated, a stable image density can be provided. Usually, since the toner bottle is exchanged more than the process cartridge, the image density is stabilized only in the second embodiment.

When the product is new, when the process cartridge is replaced, or when the process cartridge and the toner bottle are replaced, since the toner density sensor 5 is not equipped with a non-volatile memory, the characteristic value of the toner in the developing device 4 cannot be referred to. Use the tolerance center value. As shown in FIGS. 16 and 17, MAdev [n] is a relational expression MAc [n] at the tolerance center value of the toner particle diameter. Also, instead of Cdev, a value Cc of the tolerance center of the toner coloring degree is substituted for Cnow.
At the end of the flow, the new and old toner ratio R, the image area cumulative value S, and the toner replenishment amount cumulative value Ts are cleared, and the old toner weight Mt is calculated at the same time.

1Y, 1M, 1C, 1Bk photoconductor (image carrier)
2 Charging device 3 Developing roller 4 Developing device 6 Primary transfer device 8 Intermediate transfer belt (transfer conveying member)
9 Toner bottle (toner storage means)
10 Optical sensor (toner image detection means)
16 Nonvolatile memory (storage means)
17 Toner supply device (toner conveying means)

Japanese Patent Application Laid-Open No. 2001-324840 JP-A-5-249787 Japanese Patent No. 315555 Japanese Patent Application Laid-Open No. 2006-139179 Japanese Patent No. 3982188 Japanese Patent Application Laid-Open No. 2004-354624 JP 2009-42538 A Japanese Patent Application Laid-Open No. 2005-99750

Claims (7)

An image carrier, a developing device that includes a developer container and forms a toner image on the image carrier, a toner image detector that detects the toner image, and a toner that is detachable from the image forming apparatus main body. An image based on a detected value of the toner image detected by the storage unit, a first storage unit associated with the toner storage unit, a second storage unit associated with the developer storage unit, and the toner image detection unit. In an image forming apparatus having a control means for appropriately controlling the density,
The toner in the toner storage unit is supplied to the developer storage unit of the developing device via a toner transport unit,
The first storage means has data relating to the toner particle size in the toner storage means,
The second storage means has data relating to an initial toner particle size in the developer accommodating portion;
The control means converts the detected value of the toner image detected by the toner image detecting means into the current toner adhesion amount in consideration of data relating to the toner particle size in the first storage means and the second storage means. an image forming apparatus comprising and to Turkey. The image forming apparatus according to claim 1 .
The control means has a first algorithm for converting a detected value of the toner image detected by the toner image detecting means into a relationship between a current toner adhesion amount and a normalized value, and in the first algorithm, In this case, the toner particle diameter which is one of the data of the storage means is used, and the detected value of the toner image is converted into the toner adhesion amount using the relationship between the toner adhesion amount and the normalized value. apparatus. The image forming apparatus according to claim 2 .
After the toner storage means is replaced, the control means further calculates, in the first algorithm, a new and old toner replacement ratio representing a ratio of new toner in the entire developer in the developer storage section,
The control unit converts the detected value of the toner image detected by the toner image detecting unit into a relationship between the toner adhesion amount and the normalized value based on the calculated old / old toner replacement ratio and the toner particle size. An image forming apparatus. The image forming apparatus according to any one of claims 1 to 3 ,
The control means has a second algorithm for controlling a developing bias applied to the developing device and an exposure light amount of the exposure device for exposing the image carrier based on a detected value of the toner image detected by the toner detecting means. In the second algorithm, an image forming apparatus is used, which is one of the data of the storage unit, and a coloring degree which is an image density when a predetermined adhesion amount of toner is formed on a transfer paper. . The image forming apparatus according to any one of claims 1 to 4 ,
The image forming apparatus, wherein the toner image detecting means is an optical sensor having a light emitting element and a light receiving element for optically detecting a toner image. The image forming apparatus according to any one of claims 1 to 5 ,
The image forming apparatus, wherein the toner image detecting means detects an unfixed toner image before passing through the fixing device. In the image forming apparatus according to any one of claims 1 to 6 ,
The image forming apparatus, wherein the toner image detecting unit detects a toner patch that is a toner image transferred onto a transfer conveyance member that conveys transfer paper.

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