JP4796436B2 - Toner supply controller and image forming apparatus - Google Patents

Description

  The present invention relates to a toner replenishment control technique in an electrophotographic image forming apparatus using a two-component developer, and more particularly, a toner replenishment control for controlling a toner replenishment amount based on a detection result of a toner concentration detection unit of a two-component developer. The present invention relates to an image forming apparatus such as a copying machine, a printer, a plotter, a facsimile, or a complex machine including the apparatus and the toner supply control device.

  2. Description of the Related Art Conventionally, in electrophotographic image forming apparatuses such as copying machines, facsimiles, and printers, a visible image is formed using a two-component developer composed of toner and carrier by a developing device, and this is recorded on a recording paper or the like. Although recorded on a medium, the toner density affects the density of the recorded image. For this reason, the toner density is detected by a toner density detector provided in the developing device, and when the toner density decreases, the toner is supplied to the developing device so that the toner density is maintained at the target density value. However, even if the toner density in the developing device is maintained at the target density value, the image density of the developed image is maintained at a desired density due to the deterioration of the characteristics of the image carrier such as the photoconductor and the developer characteristics over time. Therefore, toner replenishment control is performed while correcting the target density value at predetermined intervals.

  For example, when the toner density before and after the toner replenishment operation is detected by the toner density detection sensor, the ratio of the toner density difference before and after the detection is stored in the nonvolatile memory as a correction value, and the toner is actually replenished. There is a technique of determining the replenishment time based on the toner density value at that time and the correction value stored in the nonvolatile memory (see, for example, Patent Document 1). However, this conventional technique has a problem that the detection value of the toner density sensor has a difference, so that the correction value includes the variation.

JP-A-5-323787

  In the image forming apparatus according to the present invention, in the mechanism for transporting toner from the toner bottle to the developing device, the toner is transported by a mono pump and no toner hopper is provided. Therefore, it is based on the design concept that the toner replenishment amount is directly controlled by the MONO pump. However, there is a problem that the amount of toner replenished only by the mono pump varies greatly.

Since the toner replenishment amount directly affects the toner density (hereinafter referred to as TC) and the image density, if the toner replenishment amount varies, it immediately appears in the image density and is recognized as a defect.
There are several reasons why the toner replenishment amount varies. For example, the difference in mechanism includes a difference in height of the conveyance path, a difference in the length of the conveyance path from the toner bottle to the developing device, and a difference in the bending angle of the hose. These are different for each machine and each color (yellow (Y), magenta (M), cyan (C), black (K)). In addition, since the toner transported body is powder, differences in fluidity and bulk density occur due to differences in toner particle size, additives, and the like. Of course, these differ depending on the toner type, but also vary depending on the color and lot of the toner. The point is that it is very difficult to control the powder and voids.

  The toner replenishment control is precisely controlled in terms of timing and frequency. However, if the toner replenishment amount varies, the precise control is not effective. Therefore, it is an important technique to properly manage the toner replenishment amount. Therefore, if the toner replenishment amount per unit time varies depending on the color and mechanism, it is required to control the toner replenishment amount within a predetermined range by performing replenishment control (correction) corresponding to the color and mechanism. .

  The present invention has been made in view of the above circumstances, and provides a toner replenishment control device capable of more appropriately replenishing toner based on the detection result of the toner concentration detection means and obtaining a desired image density, and the same. Another object of the present invention is to provide an image forming apparatus.

In order to achieve the above object, the present invention employs the following technical means.
The first means of the present invention includes an image carrier on which a latent image is formed on the surface, and a developing device that develops the latent image on the image carrier using a two-component developer composed of toner and carrier. A toner replenishment control device provided in an image forming apparatus, comprising: a toner concentration detecting unit that detects a toner concentration in the developing device; a toner replenishing unit that replenishes toner to the developing device; and a predetermined condition. A toner replenishment control device having toner replenishment control means for controlling toner replenishment, wherein the toner density detecting means has a storage device for storing sensitivity information, and the toner replenishment control means comprises a toner replenishment amount, a toner replenishment time; has a calculating means for calculating a correction value of the toner supply rate and the toner supply amount, preparative toner dispense time calculated, and storage means for storing the toner supply rate and the toner supply amount correction value, before The toner replenishment amount is calculated as the product of the replenishment amount per unit time in the selected toner replenishment method and the toner replenishment time determined by the length of the transfer paper, and the toner replenishment time is calculated The toner replenishment amount is calculated as a value obtained by dividing the toner replenishment amount by a correction value of the toner replenishment amount based on a mechanism difference of the toner replenishing means, and the toner replenishment rate is a ratio of the toner replenishment time to the toner replenishment time. The calculated toner replenishment amount correction value is obtained by dividing the toner amount per unit weight% by the sensitivity of the toner concentration detection means stored in the storage device per unit output of the toner concentration detection means. The ratio of the actual supply amount to the toner supply amount when the product of the output difference of the toner density detecting means before and after toner supply is the actual supply amount. Is calculated by the recording compensation value of the toner supply amount in the storage means, it is characterized by using the calculation of the toner replenishing time.

According to a second means of the present invention, in the toner replenishment control device of the first means, the toner replenishment amount correction value is determined after at least one replenishment operation.
The third means of the present invention is characterized in that the toner replenishment control device of the first or second means calculates the toner replenishment amount correction value every predetermined period.
The fourth aspect of the present invention is a toner supply control apparatus of the third means, as a matter of determining the predetermined time period, characterized in that to consider the change in the regular time or environment.

It fifth means of the present invention is a toner supply control apparatus of the first to fourth any one means, the predetermined condition for calculating the toner replenishing amount and are each predetermined image forming single number It is characterized by.
According to a sixth means of the present invention, in the toner replenishment control device of any one of the first to fourth means, the predetermined condition for calculating the toner replenishment amount is for each predetermined image area ratio. It is characterized by.

According to a seventh means of the present invention, in the toner replenishment control device of any one of the first to sixth means, the calculated toner replenishment amount correction value is recorded in a nonvolatile memory of the storage means. Features.
According to an eighth means of the present invention, in the toner replenishment control device of any one of the first to seventh means, the toner replenishment is performed when the image forming apparatus has a plurality of developing devices having different development colors. The amount correction value can be set for each color.

According to a ninth means of the present invention, in the toner replenishment control device of any one of the first to eighth means, the toner concentration detecting means is a magnetic permeability detecting system.
According to a tenth means of the present invention, in the toner replenishment control device of any one of the first to eighth means, the toner density detecting means is a double resonance circuit system.
Further, according to an eleventh means of the present invention, in the toner supply control device of any one of the first to tenth means, the toner is a spherical toner.

The twelfth means of the present invention comprises: an image carrier on which a latent image is formed on the surface; a developing device that develops the latent image on the image carrier using a two-component developer comprising a toner and a carrier; An image forming apparatus having a toner replenishment control device for controlling toner replenishment to a developing device, wherein the toner replenishment control device includes a toner replenishment control device of any one of first to eleventh means. Features.
According to a thirteenth aspect of the present invention, the image forming apparatus of the twelfth aspect includes a plurality of developing devices having different developing colors, and can form a single color, a multicolor, or a full color image. .

There are individual differences in the function of the toner replenishing means, and the toner replenishment amount varies, but in the toner replenishment control device of the first means, the toner concentration detecting means has a storage device for storing sensitivity information, and the toner replenishment device control means, toner supply amount, the toner replenishment time, a calculating means for calculating a correction value of the toner supply rate and the toner supply amount, preparative toner dispense time calculated, stored for storing toner replenishment rate and the toner replenishment amount correction value And the toner replenishment amount is calculated as a product of a replenishment amount per unit time in the selected toner replenishment method and a toner replenishment time determined by a length between transfer sheets, The replenishment time is calculated as a value obtained by dividing the calculated toner replenishment amount by the correction value of the toner replenishment amount based on the difference in the mechanism of the toner replenishing means, and the toner replenishment rate is The toner replenishment amount correction value is calculated as a ratio of the toner replenishment time to the toner replenishment possible time. The toner amount per unit weight% is divided by the sensitivity of the toner density detecting means stored in the storage device. When the value is the toner amount per unit output of the toner density detecting means and the product of the output difference of the toner density detecting means before and after toner replenishment is the actual replenishing quantity, the actual replenishing quantity with respect to the toner replenishing quantity It is calculated as a ratio, and the correction value of the toner replenishment amount is recorded in the storage unit and used for calculation of the toner replenishment time . Therefore, the variation in the toner replenishment amount is known from the sensitivity of the toner density detection unit. The toner supply amount can be stably controlled by correcting the variation in the toner supply amount. Further, since the amount of toner replenishment is stabilized, noise with respect to toner density control is reduced, leading to stable image density.

In the toner replenishment control device of the second means, in addition to the configuration and effect of the first means, the toner replenishment amount correction value is determined after at least one replenishment operation. By taking the average value, it is possible to reduce variations in correction values.
Further, in the toner supply control device of the third means, in addition to the configuration and effect of the first or second means, the toner supply amount correction value is calculated every predetermined period. However, an appropriate correction value can be calculated as appropriate even when it changes depending on the state of the toner that is the transported body.
Further, the toner replenishment control device of the fourth means is characterized in that, in addition to the configuration and effect of the third means, periodic time or environmental changes are taken into consideration as a matter for determining the predetermined period. An appropriate correction value can be calculated as appropriate.

The toner supply control apparatus of the fifth means, in addition to the structure and effects of the first to fourth any one means, the predetermined condition for calculating the toner replenishing amount, are each given image forming single number Therefore, even when the toner replenishment amount depends on the usage situation of the user, it is possible to replenish the toner corresponding to the used (consumed) amount.
In the toner supply control device of the sixth means, in addition to the configuration and effect of any one of the first to fourth means, the predetermined condition for calculating the toner supply amount is for each predetermined image area ratio. Since there is a feature, even when the amount of toner replenishment depends on the usage status of the user, it is possible to replenish the toner corresponding to the amount used (consumed).

In the toner supply control device of the seventh means, in addition to the configuration and effect of any one of the first to sixth means, the calculated toner supply amount correction value is recorded in the nonvolatile memory of the storage means. Therefore, it is possible to periodically review the toner replenishment amount correction value with reference to the previous value recorded in the nonvolatile memory, and to reduce variation in the correction value.
In addition, in the toner supply control device of the eighth means, in addition to the configuration and effect of any one of the first to seventh means, when the image forming apparatus has a plurality of development devices having different development colors, the toner Since the replenishment amount correction value can be set for each color, even if the toner replenishment amount varies for each color or developing device, it is appropriate for each color or each developing device. Therefore, stable toner replenishment is possible in each case.

  In the toner supply control device of the ninth means, in addition to the configuration and effect of any one of the first to eighth means, the toner concentration detection means is a magnetic permeability detection system. The toner density in the toner can be reliably detected, and changes in toner density due to replenishment can be picked up sensitively. For example, there is a problem that the time lag is large when optically detecting a toner patch made on an image carrier, but by directly detecting the toner concentration in the developing device as a change in magnetic permeability, A change in toner density due to replenishment can be sensitively detected.

  In the toner replenishment control device of any one of the first to eighth means, when the sensitivity fluctuation due to the control voltage Vcnt of the toner density detection means is large, the storage device in the toner density detection means initially depends on Vcnt. Although multi-stage sensitivity information is required, the toner supply control device of the tenth means is characterized in that the toner density detection means is of a double resonance circuit system, and therefore, sensitivity fluctuations due to the control voltage Vcnt may occur. The sensitivity information is small and can be initially one level.

  In the toner replenishment control device of any one of the first to tenth means, the toner concentration and the toner replenishment amount are affected by the change in the bulk density of the toner. Is characterized by being a spherical toner, and the spherical toner has a narrower granular distribution than the pulverized toner, so that the change in bulk density can be suppressed smaller than that of the pulverized toner, and the toner replenishment amount is appropriate. Correction can be performed.

The image forming apparatus of the twelfth means is characterized by including the toner replenishment control apparatus of any one of the first to eleventh means as the toner replenishment control apparatus, so that stable toner replenishment amount control is possible. Thus, a stable image density can be obtained by stabilizing the toner replenishment amount.
In addition to the configuration of the twelfth means, the image forming apparatus of the thirteenth means has a plurality of developing devices with different development colors, and is capable of forming single-color, multicolor, and full-color images. However, even when the amount of toner replenishment varies between toner colors and each developing device, it is possible to make an appropriate correction for each color and each developing device. Therefore, it is possible to form single-color, multi-color, and full-color images with a stable image density.

  A toner replenishment control device according to the present invention includes a toner concentration detection unit that detects a toner concentration in a developing device, a toner replenishment unit that replenishes toner to the developing device, and a toner that controls toner replenishment based on predetermined conditions. Supply control means. Then, the transition of the change in the toner density in the developing device by stirring the toner supplied to the developing device by the toner replenishing means can be known from the output voltage Vt of the toner density sensor as the toner density detecting means. Then, the toner supply control unit can calculate the supply capability of the toner supply unit from the detection result of the toner density sensor. If the replenishment ability is different from the standard, the toner replenishment amount may be corrected for the difference in ability of the replenishing means. As a result, it is possible to prevent overshoot due to excessive replenishment.

  However, since the toner density sensor has sensitivity variations among the sensors, a difference in detection capability must be taken into consideration. Therefore, in the present invention, individual information of the toner density sensor is stored in advance in a storage device (memory function using a microcomputer chip, nonvolatile memory, etc.) mounted on the sensor itself, and necessary information (here, , Sensitivity information) is extracted, and the sensitivity of the toner density sensor used for detection is fed back to the toner replenishment control means, so that it is not necessary to take into account individual differences between the sensors.

  In addition, when the correction value of the toner replenishing means is calculated for the toner replenishment amount calculated based on the number of image formations and the image area ratio, it is highly likely that the correction value of the toner replenishing unit depends on the environment and toner state at that time. Rather, it is desirable to obtain a correction value from the results of a plurality of replenishment operations. The calculated correction amount is stored in the storage means (nonvolatile memory or the like) of the toner replenishment control means and can be used repeatedly. However, the change in the state of the toner gap may not be negligible from the initial time. The toner replenishment control means periodically calculates and updates the correction amount. In addition, there is a phenomenon in which the toner replenishment ability varies depending on the frequency and number of times of toner replenishment, such as the toner replenishment amount becomes more stable as the toner replenishment time becomes longer. The timing for calculating / updating the toner replenishment amount correction value can be changed depending on the use situation.

  As the toner concentration detecting means, a change in the magnetic permeability of the developer in the developing device is detected using a magnetic permeability detecting type toner concentration sensor installed in close contact with the wall in the developing device. By directly detecting the area where the replenished toner is stored with the toner density sensor, it takes time to stir the developer, but there is less time lag than optically detecting the toner density on the image carrier. It is possible to detect a change in toner density.

  Further, among the magnetic density detection type toner density sensors, there is a toner density sensor in which the sensitivity to the developer sensitivity changes depending on the control voltage Vcnt of the sensor. In this case, since the sensitivity changes depending on the Vcnt used, the sensitivity information stored in the memory function of the sensor needs information on Vcnt. On the other hand, even with the same magnetic permeability detection method, the double-resonance circuit type toner concentration sensor outputs an operational amplifier, and the output Vt of the sensor is proportional to Vcnt, so the sensitivity is almost constant regardless of Vcnt. The applicant has proposed in Japanese Patent Application No. 2003-322113 (Japanese Patent Laid-Open No. 2005-91516) filed earlier. As a result, it is not necessary to take into account the sensitivity change of the sensor due to Vcnt, so that the sensitivity information stored in the storage device in the sensor (memory function using a microcomputer chip, nonvolatile memory, etc.) can be reduced. The restriction of Vcnt involved was eliminated and it was considered effective. The circuit configuration and the like of the double-resonance circuit type toner density sensor are the same as those of the above-mentioned prior application.

  In the image forming apparatus provided with the toner replenishment control device of the present invention, it is more effective to use a spherical toner (for example, a small particle size polymerization toner) as the toner. Compared to pulverized toner, spherical toners (including small-sized polymerized toners as well as rugby ball types and dimple types having a plurality of irregularities on the surface) are less likely to cause shape changes. It can be said that there is little change in shape. In addition, the pulverized toner has a large variation in the shape of the toner particles, and thus the porosity and bulk density change are also large. In contrast, spherical toners (small particle size polymerized toner, etc.) have little change in the shape of the toner particles, so there is little change in the porosity and bulk density. The error of the detection signal of the toner density sensor of the magnetic permeability detection method that detects the toner is small. The spherical toner is not necessarily a polymerized toner as long as it has a small diameter and a spherical shape (including not only a true sphere but also a rugby ball type or a modified type such as a dimple type having a plurality of irregularities on the surface). There is no need.

Hereinafter, more specific configurations, operations, and actions of the present invention will be described in detail based on the illustrated embodiments.
FIG. 1 is a schematic configuration diagram of an image forming unit of an image forming apparatus showing an embodiment of the present invention. This is because an endless belt-like intermediate transfer member (hereinafter referred to as an intermediate transfer belt) 7 is disposed long in the horizontal direction, and a plurality of sets of image forming units 1Y, 1C, 1M, 1 shows an example of the configuration of a tandem type color image forming apparatus that can form an image ranging from monochromatic to full color by arranging 1K in parallel.

  In this embodiment, drum-shaped photosensitive members 2Y, 2C, 2M, and 2K as image carriers, charging rollers 3Y, 3C, 3M, and 3K as charging means, and laser exposure as image writing means (exposure means). As a unit having at least a cleaning device 6Y, 6C, 6M, 6K as a cleaning device for removing the transfer residual toner on the surface of the photoreceptor, a developing device 4Y, 4C, 4M, 4K as a developing device (not shown), a developing device. The image forming units 1Y, 1C, 1M, and 1K for each color are composed of a plurality of sets (four sets in this embodiment), and each of the colors for yellow (Y), magenta (M), cyan (C), and black (K) is used. The image forming units 1Y, 1C, 1M, and 1K are opposed to the horizontal stretched surface of the intermediate transfer belt 7 that runs in a loop shape, and Y, C, M, and K in that order from the left to the bottom thereof. It has been set. The four image forming units 1Y, 1C, 1M and 1K have the same configuration.

  The charging rollers 3Y, 3C, 3M, and 3K charge the photosensitive elements 2Y, 2C, 2M, and 2K by charging with the same polarity as the toner held at a predetermined potential (negative charging in this embodiment). To apply a uniform potential to the photoreceptors 2Y, 2C, 2M, and 2K. The charging means is not limited to the charging roller, and various devices such as a charging brush and a charging charger can be used as appropriate.

  The laser exposure device (not shown) is located downstream of the charging rollers 3Y, 3C, 3M, and 3K in the rotation direction of the photosensitive members 2Y, 2C, 2M, and 2K, and upstream of the developing devices 4Y, 4C, 4M, and 4K. Placed in. The laser exposure apparatus is arranged so as to perform exposure scanning in the main scanning direction parallel to the rotation axes of the photoreceptors 2Y, 2C, 2M, and 2K.

This laser exposure apparatus includes, for example, a light source composed of a semiconductor laser (LD), a coupling optical system (or beam shaping optical system) composed of a collimating lens, a cylindrical lens, etc., and an optical deflector composed of a rotating polygon mirror, Each color image data (or each image data (or image data) read by an image reading device (not shown) provided in a separate configuration and recorded in an image memory (or an image forming optical system for condensing the laser beam deflected by the optical deflector onto the photosensitive member) The photosensitive layers 2Y, 2C, 2M, and 2K for the respective colors are formed by laser beams L _Y , L _C , L _M , and L _{K that} are intensity-modulated in accordance with image data of each color input from an external device such as a personal computer. Image exposure is performed to form an electrostatic latent image for each color. As the image writing means (exposure means), in addition to the above laser exposure apparatus, an LED writing apparatus combining a light emitting diode array (LED array) and a lens array can be used.

  The photoreceptors 2Y, 2C, 2M, and 2K are, on the undercoat layer formed on the surface of a conductive cylindrical support made of aluminum or the like, a charge generation layer (lower layer) and a charge transport layer (upper layer) as the photosensitive layer. An organic photoreceptor (OPC) having a structure in which these photosensitive layers are laminated in the order of the above or in the reverse order. Further, a known surface protective layer such as an overcoat layer mainly composed of a thermoplastic or thermosetting polymer may be formed on the surface of the charge transport layer or the charge generation layer. In this embodiment, the conductive cylindrical supports of the photoreceptors 2Y, 2C, 2M, and 2K are grounded.

  The developing devices 4Y, 4C, 4M, and 4K maintain a predetermined gap with respect to the peripheral surfaces of the photoreceptors 2Y, 2C, 2M, and 2K, and rotate in the forward direction and the rotation direction of the photoreceptors 2Y, 2C, 2M, and 2K. Development sleeves 41Y, 41C, 41M, and 41K formed of cylindrical non-magnetic stainless steel or aluminum material are provided, and yellow (Y), magenta (M), cyan ( C) and black (K) one-component or two-component developers are accommodated. In this embodiment, as an example, a two-component developer composed of toner and a magnetic carrier (in this embodiment, the toner is negatively charged) is accommodated in the developing device. A fixed magnet or a magnet roll magnetized with a plurality of magnetic poles is disposed. Further, the developing devices 4Y, 4C, 4M, and 4K for each color are provided with a stirring / conveying member 42 that transports the developer in the container while stirring, and a toner replenishment unit 43 for each color. The toner replenishing unit 43 for each color is connected to a toner replenishing device (not shown) which is a toner replenishing unit via a flexible hose or the like. This toner replenishing device includes, for example, a toner bottle containing toner of each color and a transfer mechanism (for example, a mono pump) for transferring the toner in the toner bottle to the toner replenishing unit 43 via the hose. Further, the developing devices 4Y, 4C, 4M, and 4K for the respective colors are provided with a magnetic permeability detection type toner concentration sensor that detects the toner concentration of the developer in the container.

  The developing sleeves 41Y, 41C, 41M, and 41K of the developing devices 4Y, 4C, 4M, and 4K of the respective colors are placed on the drum surfaces of the photoreceptors 2Y, 2C, 2M, and 2K with a predetermined gap, for example, 100 to The development sleeve 41Y, 41C, 41M, 41K is maintained in a non-contact state with a gap of 500 μm. By applying a development bias in which a DC voltage and an AC voltage are superimposed on the development sleeves 41Y, 41C, 41M, 41K, contact or non-contact reversal development To form toner images on the surfaces of the photoreceptors 2Y, 2C, 2M, and 2K.

  The cleaning devices 6Y, 6C, 6M, and 6K include, for example, a cleaning blade 61 and a cleaning roller (or cleaning brush) 62, and the cleaning blade 61 is provided in contact with the counter surface of the photosensitive member surface.

The intermediate transfer belt 7 serving as an intermediate transfer member is stretched in contact with an intermediate transfer belt driving roller (also serving as a secondary transfer backup roller) 8, an intermediate transfer belt support roller 9, and intermediate transfer belt tension rollers 10a and 10b. The transfer belt 7 is provided so that the rotation direction thereof is counterclockwise as indicated by an arrow in the drawing.
A secondary transfer member (secondary transfer roller in this embodiment) 14 is provided through the intermediate transfer belt 7 so as to face the intermediate transfer belt driving roller (also serving as a secondary transfer backup roller) 8. A cleaning blade 12a of the belt cleaning device 12 is provided in contact with the intermediate transfer belt 7 at the position of the support roller 9 in the counter direction. Similarly, a release agent or lubricant application roller 11 is provided in contact with the intermediate transfer belt 7 at the position of the support roller 9. Further, primary transfer rollers 5Y, 5C, 5M, and 5K for each color are provided to face the photoreceptors 2Y, 2C, 2M, and 2K with the intermediate transfer belt 7 interposed therebetween.

The intermediate transfer belt 7 is an endless belt having a volume resistance of 10 ⁶ to 10 ¹² Ω · cm. Examples of belt materials include polycarbonate (PC), polyimide (PI), polyamideimide (PAI), and polyvinylidene fluoride. Ride (PVDF), tetrafluoroethylene-ethylene copolymer (ETFE) and other resin materials, rubber materials such as EPDM, NBR, CR, polyurethane, etc., and conductive fillers such as carbon are dispersed, or ionic conductive materials The thickness of the belt is preferably set to about 50 to 200 μm in the case of a resin material and about 300 to 700 μm in the case of a rubber material. A rubber layer may be provided on the resin belt, and a coating layer may be provided on the surface layer. Also, means for applying a release agent or lubricant such as a fluororesin to the surface of the belt in order to prevent the toner from adhering to the surface of the intermediate transfer belt 7 and to improve cleaning properties (the application roller). 11 is provided.

  The intermediate transfer belt 7 is driven by rotation of an intermediate transfer belt drive roller (also a secondary transfer backup roller) 8 by a drive motor (not shown). The intermediate transfer belt drive roller (also known as secondary transfer backup roller) 8 has a conductive cored bar (not shown) such as stainless steel, and a conductive material such as carbon or rubber such as polyurethane, EPDM, or silicon. A material coated with a conductive or semiconductive material in which a conductive filler is dispersed is used.

  The primary transfer rollers 5Y, 5C, 5M, and 5K are provided to face the photoreceptors 2Y, 2C, 2M, and 2K with the intermediate transfer belt 7 interposed therebetween, and the intermediate transfer belt 7 and the photoreceptors 2Y, 2C, 2M, and 2K are provided. A transfer zone is formed between the two. By applying a DC voltage having a polarity opposite to that of the toner (positive polarity in this embodiment) to the primary transfer rollers 5Y, 5C, 5M, and 5K by a DC power source (not shown) to form a transfer electric field in the transfer area, The toner images of the respective colors formed on the photoreceptors 2Y, 2C, 2M, and 2K are transferred onto the intermediate transfer belt 7.

The primary transfer rollers 5Y, 5C, 5M, and 5K, which are the first transfer means for each color, are made of polyurethane, EPDM, silicon on the peripheral surface of a conductive metal core (not shown) such as stainless steel having an outer diameter of 8 mm, for example. In a solid state or foamed sponge state with a volume resistance of about 10 ⁵ to 10 ⁹ Ω · cm by dispersing a conductive filler such as carbon in a rubber material such as carbon or containing an ionic conductive material Is formed by covering a semiconductive elastic rubber (not shown) having a thickness of 5 mm and a rubber hardness of about 20 to 70 ° (Asker-C).

  The secondary transfer roller 14 that performs transfer onto the surface of the transfer material S is provided opposite to the drive roller (also serving as a secondary transfer backup roller) 8 that is grounded with the intermediate transfer belt 7 interposed therebetween, and has a polarity opposite to that of the toner (this embodiment). In this example, a positive DC voltage is applied by a DC power source, and the superimposed toner image carried on the intermediate transfer belt 7 is transferred to the surface of the transfer material S via the secondary transfer roller 14.

The secondary transfer roller 14 serving as a second transfer unit that re-transfers the color toner image on the intermediate transfer belt 7 onto the transfer material is a peripheral surface of a conductive metal core (not shown) such as stainless steel having an outer diameter of 16 mm, for example. In addition, by dispersing a conductive filler such as carbon in a rubber material such as polyurethane, EPDM, or silicon, or by adding an ionic conductive material, a solid state having a volume resistance of about 10 ⁵ to 10 ⁹ Ω · cm Alternatively, it is formed by covering a semiconductive elastic rubber (not shown) having a thickness of 7 mm and a rubber hardness of about 20 to 70 ° (Asker-C) in a foamed sponge state. Unlike the primary transfer rollers 5Y, 5C, 5M, and 5K, the secondary transfer roller 14 may come in contact with toner and may coat the surface with a good releasability such as semiconductive fluorine resin or urethane resin. In addition, as described above, the driving roller (also serving as the secondary transfer backup roller) 8 is formed on a peripheral surface of a conductive metal core (not shown) such as stainless steel, on a rubber or resin material such as polyurethane, EPDM, or silicon, and on carbon or the like. It is formed by coating a semiconductive material in which a conductive filler is dispersed or an ionic conductive material is contained to a thickness of about 0.05 to 0.5 mm.

  The cleaning blades 61 and 12a in contact with the surfaces of the photoreceptors 2Y, 2C, 2M and 2K and the intermediate transfer belt 7 are plate-like urethane rubber having a thickness of 1 to 3 mm and a JIS-A hardness of 60 to 80 ° on the sheet metal holder. Are bonded so that the free length is about 5 to 12 mm, and is in contact with the photoreceptors 2Y, 2C, 2M, and 2K and the intermediate transfer belt 7 with a load of about 5 to 50 gf. Further, a fluorine coating may be applied to the blade tip so that the blade does not rise, or conductive urethane rubber may be used so that the other side is not charged.

  Here, the transfer material S such as transfer paper is conveyed one by one from a paper feeding unit (paper feeding cassette, paper feeding tray, etc.) not shown by a paper feeding device (paper feeding roller or paper feeding roller, separation roller, etc.), The sheet is conveyed so as to be superimposed on the intermediate transfer belt 7 sandwiched between the secondary transfer roller 14 and the driving roller (also serving as a secondary transfer backup roller) 8 through a conveyance roller (or registration roller) 13 and is intermediated at the secondary transfer unit. The toner image is transferred from the transfer belt 7 and sent to a fixing device 15 as a fixing unit. The fixing roller 15a and the pressure roller 15b of the fixing device 15 are fixed by heat welding and discharged to a paper discharge unit (not shown). Is done.

  In this embodiment, the charging rollers 3Y, 3C, 3M, and 3K are used as charging means for the photoreceptors 2Y, 2C, 2M, and 2K, and the primary transfer rollers 5Y, 5C, 5M, and 5K are used as primary transfer members. However, it is preferable from the viewpoint of suppressing the generation of harmful ozone, but is not limited to this, and the corotron discharger can be used as a non-contact charging means or a primary transfer means.

  In the image forming apparatus of this embodiment, after the toner images of the respective colors formed on the photoreceptors 2Y, 2C, 2M, and 2K through the processes of charging, exposure, and development are transferred (primary transfer) to the intermediate transfer belt 7. The toner image on the intermediate transfer belt 7 is transferred (secondary transfer) to the transfer material S such as transfer paper by the secondary transfer roller 14, and the intermediate transfer belt 7 is located downstream of the secondary transfer position in the rotational direction. In addition, an optical detection sensor (for example, a light reflection type photosensor composed of a light emitting element and a light receiving element) 16 having an image adjustment pattern opposed to the surface of the intermediate transfer belt 7 is provided.

  Then, a toner adhesion pattern (image adjustment pattern) for image adjustment is formed on the non-image areas on the photoreceptors 2Y, 2C, 2M, and 2K, and is primarily transferred onto the intermediate transfer belt 7, and an optical detection sensor. 16, the amount of toner adhering to the image adjustment pattern is detected, and the process control is performed so that an appropriate image can be obtained by changing the image forming condition of the next image based on the detection information of the detection sensor 16. This is performed by a control means (control unit) 19 including a microcomputer (CPU) 19a or the like, or the control unit 19 optimizes a toner replenishment amount for toner replenishment control.

  An embodiment of a toner replenishment control device that replenishes toner during printing will be described below. FIG. 2 is a block diagram illustrating an example of a control device that performs toner supply control. The control unit 19 serving as a toner replenishment control unit of the toner replenishment control device includes a CPU 19a having various arithmetic functions and the like, and a storage device (ROM, RAM (storage) for storing various control programs and arithmetic data, correction data to be described later, and the like. Including a non-volatile memory)) 19b and the like, and controls each part of the image forming apparatus together with toner replenishment control, and performs process control to obtain an appropriate image. The CPU 19a and the storage device 19b are connected by wire, and data exchange is performed between them. Further, an operation display unit 20, a toner concentration detection sensor 17, an optical detection sensor 16, a toner replenishing device 21, a driving device for each unit (not shown), and the like are connected to the CPU 19a. The operation display unit 20 includes, for example, a touch panel type liquid crystal display device and various keys such as an input / setting key, a numeric keypad, a start key, a clear / stop key, and provides predetermined information to the operator. This is for displaying or accepting key input from the operator.

The toner density detection sensor 17 detects the toner density in the developing devices 4Y, 4C, 4M, and 4K for the respective colors. In this embodiment, a toner density sensor of a magnetic permeability detection type and a double resonance circuit type is used. The detection output corresponding to the toner density is output to the CPU 19a. The toner concentration sensor 17 is provided with a storage device (nonvolatile memory or the like) 18 that stores sensor sensitivity information.
The optical detection sensor 16 detects the image density (toner adhesion amount) of the pattern formed on the intermediate transfer belt 7, and outputs a detection output corresponding to the toner adhesion amount to the CPU 19a.
The toner replenishing device 21 is composed of a toner bottle that stores toner of each color, a toner transfer mechanism (for example, a Mono pump), and the like, and is driven and controlled by the CPU 19a to supply toner to the developing devices 4Y, 4C, 4M, and 4K of each color. I do.

Next, the toner replenishment control of this embodiment will be described. An example of the control operation of the toner replenishment control by the control unit 19 is shown in the flowchart of FIG. The control operation program is stored in the ROM of the storage device 19a and is executed by the CPU 19a.
When the start of image formation is detected in step S1 in FIG. 3, a toner replenishment method is selected in step S2. This toner replenishment method includes quantitative replenishment (a replenishment amount is constant) and PID control (a replenishment amount is calculated based on at least the detection result of the toner density sensor 17, the number of pixels, or the image area ratio). Next, in step S3, a toner replenishable time is calculated. The toner replenishable time T1 [msec] is
T1 [msec] = (Transfer paper length [mm] + X) / Process linear velocity [mm / sec] × 1000
It is obtained by Here, X indicates the minimum inter-paper length including all modes and paper sizes.

In step S4, the toner replenishment amount calculated by the toner replenishment method selected in step S2 is calculated. In step S5, a toner replenishment time [msec] is calculated from the calculated toner replenishment amount. The toner supply time depends on the toner supply amount [mg] and supply characteristics. In particular, the replenishment characteristics vary depending on the replenishment control mechanism, the process linear velocity, the color / station, and the replenishment time. Toner replenishment time T2 [msec]
T2 [msec] = α (: conversion coefficient) × toner replenishment amount [mg] / B (: correction coefficient)
(The correction coefficient calculation method will be described later)
It is obtained by

Calculating the toner replenishing rate in step S 6. Toner replenishment rate [%]
Toner replenishment rate [%] = toner replenishment time T2 / toner replenishment possible time T1 × 100
Ask for. Using toner replenishment rate obtained here, perform the upper and lower limit limiter process at step S 7. Maximum toner replenishment rate than (previously determined predetermined had values), if greater in the toner replenishment rate determined in step S 6, the toner supply time, the maximum toner replenishing time. This maximum toner replenishment time is
Maximum toner replenishment time = toner replenishable time T1 x maximum toner replenishment rate.
Also, the minimum toner replenishment time, leave separately beforehand determined, the minimum toner replenishment time, when direction of the toner supply time determined in step S 5 is short, the toner supply time is set to 0 [msec] (minimum If this is the case, the toner supply rate is not affected.)

In step S8, the calculated toner replenishment time and toner replenishment rate are stored in a non-volatile memory of the storage device 19b of the control unit 19 or the like. Then, the toner replenishment control device is driven for the determined toner replenishment time to perform toner replenishment (step S9).
Next, in step S10, a correction value for the toner replenishment amount is calculated, and in step S11, the toner replenishment correction amount is recorded in a non-volatile memory or the like of the storage device 19b of the control unit 19. From the next time, this toner replenishment correction amount is fed back to step S5.

Hereinafter, calculation of the toner supply amount correction value in step S10 will be described.
The storage device 18 mounted on the toner concentration sensor 17 stores the sensitivity of the toner concentration sensor: η [V / wt%]. This is the sensitivity stored in this sensor at the time of shipment, and is different for each sensor.
The amount of toner (toner concentration) per unit [wt%]: m [mg / wt%] is obtained in advance by experiments from the developer capacity of the developing device. Since the toner amount [mg] corresponding to Δ1 [wt%] varies depending on the toner concentration, strictly speaking, it is desirable to have several levels, but at least the standard value;
From the above two pieces of information and the detection result of the output Vt of the toner density sensor 17, a correction value (correction coefficient) in the difference in the mechanism of the toner replenishing device 21 is calculated.

Here, the respective correction values when there are two machines (toner supply devices) are calculated.
If the toner amount per toner density sensor output Δ1 [V] (supplemented amount) is Mv,
Machine 1: Mv1 = m1 / η1 in sensor 1 with sensitivity η1
Machine 2: Mv2 = m2 / η2 in sensor 2 with sensitivity η2
It becomes.

If the difference in toner density sensor output before and after toner replenishment is ΔV1 [V] and ΔV2 [V], respectively,
Actual supply amount calculated from the toner density sensor result in the machine 1: Mreal1 = ΔV1 × Mv1
Actual supply amount calculated from the result of toner density sensor in machine 2: Mreal2 = ΔV2 × Mv2
It becomes.

Therefore,
Supply ability β = actual supply amount Mreal / calculated supply amount Mmath
Because it is found in
<Mmath; toner supply amount calculated in step S4>
Machine 1 supply capacity β1 = Mreal1 / Mmath1 = ΔV1 × m1 / η1 / Mmath1
Machine 2 supply capacity β2 = Mreal2 / Mmath2 = ΔV2 × m2 / η2 / Mmath2
It becomes.

Taking the average of each,
Machine 1 correction factor: B1 = Ave (β11... Β1n)
Correction factor of machine 2: B2 = Ave (β21... Β2n)
It becomes.
This B1 or B2 is stored as a correction coefficient in a nonvolatile memory or the like of the storage device 19b of the control unit 19, and is fed back in step S4. In the above example, two machines (toner supply devices) are used. However, in the image forming apparatus shown in FIG. 1, four toner supply devices 21 corresponding to the four developing devices 4Y, 4C, 4M, and 4K are used. In the same manner as described above, the correction coefficients for the four units are calculated individually.

  As described above, in the toner replenishment control device of the present invention, by calculating the correction coefficient for each toner replenishing device, it is possible to perform appropriate correction even if there is a difference in the replenishment control of each toner replenishing device. It becomes. Then, by correcting variations in the toner replenishment amount to each developing device, stable toner replenishment amount control can be performed. In addition, the image forming apparatus of the present invention includes the toner replenishment control device described above, so that the toner replenishment amount to the developing device for each color is stabilized, and the toner replenishment amount is stabilized, so that noise for toner density control is stabilized. Therefore, the image density is stabilized, and high-quality image formation without color unevenness can be performed.

1 is a schematic configuration diagram of an image forming unit of an image forming apparatus showing an embodiment of the present invention. FIG. 3 is a block diagram illustrating an example of a control device that performs toner supply control. 6 is a flowchart illustrating an example of a control operation of toner supply control by a control unit.

Explanation of symbols

1Y, 1C, 1M, 1K: Image forming unit 2Y, 2C, 2M, 2K: Photoconductor (image carrier)
3Y, 3C, 3M, 3K: Charging rollers 4Y, 4C, 4M, 4K: Developing devices 5Y, 5C, 5M, 5K: Primary transfer rollers 6Y, 6C, 6M, 6K: Cleaning devices 7: Intermediate transfer belt 8: Intermediate transfer Belt drive roller (also secondary transfer backup roller)
9: Intermediate transfer belt support roller 10a, 10b: Intermediate transfer belt tension roller 11: Lubricant application roller 12: Belt cleaning device 13: Conveyance roller (registration roller)
14: Secondary transfer roller 15: Fixing device 16: Optical detection sensor 17: Toner density detection sensor 18: Sensor storage device 19: Control unit (toner supply control means)
19a: CPU (calculation / control means)
19b: Storage device (storage means) of the control unit
20: Operation display unit 21: Toner supply device (toner supply means)

Claims (13)

Toner replenishment equipped in an image forming apparatus having an image carrier on which a latent image is formed and a developing device for developing the latent image on the image carrier using a two-component developer composed of toner and carrier A control device, a toner concentration detecting unit for detecting a toner concentration in the developing device, a toner supplying unit for supplying toner to the developing device, and a toner supply control for controlling toner supply based on a predetermined condition A toner replenishment control device comprising:
The toner density detecting means has a storage device for storing sensitivity information, and the toner replenishment control means is configured to calculate a toner replenishment amount, a toner replenishment time , a toner replenishment rate, and a correction value for the toner replenishment amount; have been collected by toner replenishment time, and a storage means for storing toner replenishment rate and the toner supply amount correction value,
The toner replenishment amount is calculated as a product of the replenishment amount per unit time in the selected toner replenishment method and the toner replenishment time determined by the length between transfer sheets,
The toner replenishment time is calculated as a value obtained by dividing the calculated toner replenishment amount by a correction value of the toner replenishment amount based on a difference in the mechanism of the toner replenishing means.
The toner replenishment rate is calculated as a ratio of the toner replenishment time to the toner replenishment possible time,
The correction value of the toner replenishment amount is obtained by dividing the toner amount per unit weight% by the sensitivity of the toner concentration detection unit stored in the storage device as the toner amount per unit output of the toner concentration detection unit. When the product of the output difference of the toner density detecting means before and after toner replenishment is defined as the actual replenishment amount, it is calculated as a ratio of the actual replenishment amount to the toner replenishment amount.
Wherein the correction value of the toner supply amount is recorded in the storage unit, the toner replenishment control device, which comprises using for the calculation of the toner replenishing time. The toner replenishment control device according to claim 1.
The toner replenishment control device, wherein the toner replenishment amount correction value is determined after at least one replenishment operation. The toner replenishment control device according to claim 1 or 2,
A toner replenishment control device that calculates the toner replenishment amount correction value every predetermined period. The toner supply control device according to claim 3.
As matter of determining the predetermined time period, the toner replenishment control device, characterized in that to consider the change in the regular time or environment. In the toner replenishment control device according to any one of claims 1 to 4,
Wherein the predetermined condition for calculating the toner replenishing amount, the toner replenishment control device, characterized in that the each predetermined image forming sheet number. In the toner replenishment control device according to any one of claims 1 to 4,
A toner replenishment control device, wherein the predetermined condition for calculating the toner replenishment amount is every predetermined image area ratio . In the toner replenishment control device according to any one of claims 1 to 6,
The calculated toner replenishment amount correction value is recorded in a non-volatile memory of the storage means. In the toner replenishment control device according to any one of claims 1 to 7,
A toner replenishment control device, wherein the toner replenishment amount correction value can be set for each color when the image forming apparatus has a plurality of developing devices having different development colors. The toner replenishment control device according to any one of claims 1 to 8,
The toner replenishment control device, wherein the toner concentration detection means is a magnetic permeability detection method. The toner replenishment control device according to any one of claims 1 to 8,
2. The toner replenishment control device according to claim 1, wherein the toner concentration detecting means is a double resonance circuit system. The toner replenishment control device according to any one of claims 1 to 10,
The toner replenishment control device, wherein the toner is a spherical toner. An image carrier on which a latent image is formed, a developing device that develops the latent image on the image carrier using a two-component developer composed of toner and a carrier, and control of toner supply to the developing device. In an image forming apparatus having a toner replenishment control device to perform,
An image forming apparatus comprising the toner supply control device according to claim 1 as the toner supply control device. The image forming apparatus according to claim 12.
An image forming apparatus comprising a plurality of developing devices having different developing colors and capable of forming a single color, a multicolor, or a full color image.

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