JP4732261B2 - Image forming apparatus - Google Patents

Description

  The present invention is used in, for example, copying machines, printers, facsimiles, and the like, and develops an electrostatic latent image formed on an image carrier with toner, and transfers and fixes the image onto a recording material. It is about.

  In recent years, in an image forming apparatus using an electrophotographic system, the flow of speeding up, colorization, high image quality, and high reliability is accelerating. In addition to this, research and development are being conducted to meet various market demands such as reducing toner consumption and considering the environment.

  Along with the advancement of various detection / control technologies, electrophotographic image forming apparatuses also perform so-called process control (hereinafter referred to as “procon”), and many controls are used to stably maintain high image quality. Implemented or proposed. The following methods are used for general process control.

(A-1) The optical reflectance (reflected light density) of the reference toner patch formed on the photoconductor is detected, and based on this, each unit is controlled so that the amount of toner contained in the toner image is optimized. Method Since a monochrome machine or the like does not have an intermediate transfer member or a transfer belt also used for paper conveyance, a method of detecting a toner adhesion amount (toner density) of a reference toner patch formed on a photosensitive member is generally used. Then, based on the obtained toner adhesion amount (toner concentration), a developing bias condition for obtaining a desired developing toner amount is adjusted.

(A-2) A method of detecting the optical reflectance (reflected light density) of the reference toner patch on the intermediate transfer member and controlling each part based on this. This method is often used in a color machine, and is applied on the photosensitive member. The formed reference toner patch is temporarily transferred onto an intermediate transfer member (such as a transfer belt also used for paper conveyance), and the toner adhesion amount (toner density) of the transferred reference toner patch is detected, and the obtained toner adhesion amount Based on (toner density), the development conditions and transfer conditions are controlled so that a desired amount of developed toner or transferred toner can be obtained.

  In addition to the above methods, a method of detecting the surface potential of the photosensitive member (exposure potential including charging potential and halftone state) and controlling each part so as to obtain optimum charging conditions and exposure conditions, and two components In a development system of the type, there is a case where a method of detecting the toner concentration (ratio of carrier to toner) and controlling the toner replenishment condition so as to obtain a desired toner concentration may be used together.

  However, these methods have the following problems. For example, according to the technique (A-1), although the toner image immediately after the development process has a desired toner amount, the toner amount of the toner image after the transfer process is not always optimal. This is because the charge amount of the toner patch is unknown, so that the optimum transfer voltage condition cannot be obtained, and the toner image may not have the optimum toner amount after the transfer process. In particular, in a two-component development system, the toner density is detected and controlled so as to control the developed toner image to have a predetermined charge amount. However, environmental conditions and usage conditions (change over time) Depending on the toner replenishment history and the like, the developed toner image may not have a predetermined charge amount. For this reason, even if a predetermined amount of toner is present on the photosensitive member, the transfer efficiency is lowered when the charge amount is high, and vice versa, retransfer and scattering are likely to occur. A problem occurs.

  On the other hand, the method (A-2) also has the same problem as the method (A-1). In addition, since this method detects the state of the toner patch after the development process and the transfer process, if the toner patch on the intermediate transfer body does not have the desired toner amount, the cause is derived from the development process. It is difficult to specify whether it is derived from the transfer process. For this reason, there may be a problem that the time required for the process control becomes longer or the accuracy is lowered.

  In image formation using an electrophotographic system, the most basic and important physical phenomenon is a behavior in which toner, which is a charged particle, is transferred in accordance with an electric field formed around in a development process or a transfer process. At this time, the force Ft acting on the toner strongly depends on the product of the charge amount (charge amount) Qt of the toner and the electric field strength E in each step. Here, the electric field strength in each step can be set to a desired state by optimizing the configuration requirements and design conditions of the image forming apparatus in advance, but the toner charge amount varies depending on the surrounding environment and changes over time. Since it is strongly affected, it cannot be brought into a desired state only by the configuration requirements and design conditions of the image forming apparatus. Therefore, it is necessary to actually determine the charge amount of the toner image formed on the photoconductor and to appropriately control each part so that the charge amount becomes an appropriate value. This process improves the quality of the formed image. It is an important key. Based on this idea, several techniques for obtaining the toner charge amount in the process computer have been proposed.

  In Patent Document 1, the charge amount of the toner image is obtained by detecting the surface potential of the toner image formed on the photosensitive member and the toner adhesion amount, and various procomputers are provided based on the obtained charge amount of the toner image. It is disclosed to do.

Patent Document 2 discloses that the charge amount of a toner image formed on an intermediate transfer member is obtained by the same method as in Patent Document 1.
JP 2004-226533 A (released on August 12, 2004) JP 2004-70251 A (published March 4, 2004)

  Although the quality of the formed image can be improved by performing the process control using the techniques of Patent Documents 1 and 2, the conventional techniques have the following problems.

  The toner used in the reference toner patch for the process control is collected by the cleaning blade of the photosensitive member or intermediate transfer member after detecting the toner amount and the surface potential, and is processed as waste toner. Further, in order to improve the accuracy of the process control, when the patch creation, patch detection, and control of each unit are repeated a plurality of times, toner consumption is further increased.

  Recently, emphasis has been placed on reducing environmental impact, and electrophotographic devices are also required to reduce power consumption, reduce the generation of harmful substances, reduce toner consumption, and so on. It is not preferable that a large amount of toner is consumed by forming the reference toner patch.

  By the way, as a method of forming a reference toner patch on the photoreceptor, an electrostatic latent image of the reference patch is created by exposing a predetermined area of the uniformly charged photoreceptor surface in accordance with the principle of a normal electrophotographic process. In addition, there is a method of developing the electrostatic latent image to obtain a reference toner patch. However, since the photosensitivity characteristics of the photoreceptor change according to environmental conditions and usage conditions, the potential of the exposed portion (exposure potential) in the electrostatic latent image is not stable. As a result, the development electric field in the development process changes, and the amount of toner contained in the developed reference toner patch may change, or an error may occur in the detection accuracy of the surface potential of the reference toner patch.

  Therefore, in order to prevent this, without charging or exposing the photoconductor in accordance with a normal electrophotographic process, the substrate layer (usually ground potential or arbitrary bias potential) of the photoconductor and the developing roller are used. There is also a method of performing bias development in which a potential difference (development bias) is generated between them and toner is transferred onto the photoreceptor using this potential difference (development bias). According to this method, it is possible to suppress the influence due to the change in the photosensitivity characteristics of the photoconductor. However, when bias development is performed, since the reference toner patch is formed over the entire length of the developing roller, the amount of toner discarded at the time of the process control is further increased, and the burden on the environment is further increased.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to perform high-precision process control and reduce an environmental load in an image forming apparatus that performs process control.

  In order to solve the above-described problems, an image forming apparatus according to the present invention is configured to attach an image carrier that rotates and carries an electrostatic latent image and a toner image, and toner to the electrostatic latent image carried by the image carrier. A developing device for forming a toner image, a transfer member provided in contact with the image carrier for transferring the toner image on the image carrier to a transfer object, and formed on the image carrier. An electrophotographic image forming apparatus comprising process control means for performing process control based on a reference toner image so that the reference toner image formed on the image carrier is not transferred to the transfer object. A transfer member separating means for separating the transfer member from the image carrier, and a toner cycle for collecting the toner of the reference toner image on the image carrier that has passed through the transfer member so as to be reused by the developing device. And means, said process control means, and performs the process control based on the toner amount and the toner charge amount of the reference toner image.

  According to the above configuration, the process control by the process control unit is performed based on the toner amount and the toner charge amount of the reference toner image. As described above, the process control is performed in consideration of not only the toner amount of the reference toner image but also the toner charge amount of the reference toner image, so that the accuracy of the process control can be improved and high-quality image formation is possible. become.

  In addition, according to the above configuration, the transfer member is separated from the image carrier by the transfer member separation unit, so that the reference toner image used for the process control is the transfer object (for example, the transfer member itself or the transfer member). The toner image is not transferred to an intermediate transfer member or a recording sheet sandwiched between the member and the image carrier. The reference toner image on the image carrier that has not been transferred to the transfer object is recovered downstream by the toner recovery means. As a result, the toner consumption can be reduced by reusing the reference toner image used for process control, so the burden on the environment can be reduced.

  Further, the image forming apparatus includes, as the toner collecting unit, a cleaning member that removes the reference toner image on the image carrier that has passed through the transfer member, and a toner of the reference toner image that is removed by the cleaning member. And a toner conveying means for conveying the toner to the developing device.

  According to the above configuration, the reference toner image on the image carrier that has passed through the transfer member is removed by the cleaning unit, and then conveyed to the developing device by the toner conveyance unit. Therefore, the reference toner image on the image carrier can be collected relatively easily.

  The developing device may collect the toner of the reference toner image on the image carrier that has passed through the transfer member as the toner collecting unit.

  According to the above configuration, the cleanerless system can be realized, and the toner of the reference toner image on the image carrier can be collected by the developing device. According to this method, it is not necessary to provide a new member for collecting the toner of the reference toner image, and the cost can be reduced.

  In this case, the image forming apparatus is disposed downstream of the transfer member in the rotation direction of the image carrier, and the toner image on the image carrier that has passed through the transfer member is applied to the image carrier. A cleaning member that contacts and removes, and a cleaning member separation unit that separates the cleaning member from the image carrier so that the reference toner image formed on the image carrier is not removed by the cleaning member; The developing device may collect the toner of the reference toner image on the image carrier that has passed through the cleaning member.

  According to the above configuration, the reference toner image is collected by the developing device in a cleanerless manner, while the normal toner image other than the reference toner image is removed by the cleaning member after being transferred by the transfer member. Is done. Therefore, during normal image formation other than during process control, it is possible to reduce the risk that paper dust and dust that may be collected together with toner during cleaning will be mixed into the developing device. In this way, it is possible to perform higher-quality image formation by suppressing substances that adversely affect the developing process from entering the developing device.

  In addition, the image forming apparatus includes a potential detection unit that detects a surface potential of the reference toner image formed on the image carrier and a toner that detects a toner amount of the reference toner image formed on the image carrier. An amount detection unit, wherein the process control unit is configured to calculate the reference amount calculated from the toner amount of the reference toner image detected by the toner amount detection unit and the detection results of the potential detection unit and the toner amount detection unit. The process control is preferably performed based on the toner charge amount of the toner image.

  According to the above configuration, the toner amount of the reference toner image is detected by the toner amount detection unit. Further, the toner charge amount of the reference toner image is calculated from the detected toner amount of the reference toner image and the surface potential of the reference toner image detected by the potential detection means. Then, process control is performed based on the obtained toner amount and toner charge amount of the reference toner image. As described above, the process control is performed in consideration of not only the toner amount of the reference toner image but also the toner charge amount of the reference toner image, so that the accuracy of the process control can be improved and high-quality image formation is possible. become.

  Alternatively, the reference toner image on the image carrier is formed by developing the reference electrostatic latent image on the image carrier by the developing device, and the surface of the reference toner image formed on the image carrier. A potential detecting means for detecting a potential; and a developing current detecting means for detecting a developing current flowing from the developing device to the image carrier when the developing device develops the reference electrostatic latent image. The control unit may perform the process control based on a toner charge amount and a toner amount of the reference toner image calculated from detection results by the potential detection unit and the development current detection unit.

  According to the above configuration, the toner charge amount and toner amount of the reference toner image are calculated from the detection results of the potential detection means and the development current detection means, and the process control is based on the calculated toner amount and toner charge amount of the reference toner image. Done. As described above, the process control is performed in consideration of not only the toner amount of the reference toner image but also the toner charge amount of the reference toner image, so that the accuracy of the process control can be improved and high-quality image formation is possible. become.

  Further alternatively, the reference toner image on the image carrier is formed by developing the reference electrostatic latent image on the image carrier by the developing device, and the reference toner image formed on the image carrier is A toner amount detecting means for detecting a toner amount; and a developing current detecting means for detecting a developing current flowing from the developing device to the image carrier when the developing device develops the reference electrostatic latent image; The process control means includes: a toner amount of the reference toner image detected by the toner amount detection means; a toner charge amount of the reference toner image calculated from detection results of the toner amount detection means and the development current detection means; The process control may be performed based on the above.

  According to the above configuration, the toner amount of the reference toner image is detected by the toner amount detection unit. Further, the toner charge amount of the reference toner image is calculated from the detected toner amount of the reference toner image and the detection result by the developing current detecting means. Then, process control is performed based on the obtained toner amount and toner charge amount of the reference toner image. As described above, the process control is performed in consideration of not only the toner amount of the reference toner image but also the toner charge amount of the reference toner image, so that the accuracy of the process control can be improved and high-quality image formation is possible. become.

  The image forming apparatus further includes a developing device separating means for separating the developing device from the image carrier so that the electrostatic latent image on the image carrier is not developed by the developing device. The means is disposed downstream of the developing device in the rotational direction of the image carrier and upstream of the toner collecting means in the rotational direction of the image carrier, and is formed on the image carrier by the developing device. The surface potential of the developed reference toner image and the surface of the electrostatic latent image on the image carrier that was not developed by the developing device by the developing device separating means separating the developing device from the image carrier. The process control means detects the toner in the reference toner image from the surface potential of the reference toner image and the electrostatic latent image detected by the potential detection means. Surface of layer - together with obtaining the toner layer potential is the potential difference between the bottom, it is preferable to calculate the toner charge amount of the reference toner image based on the toner layer potential difference obtained.

  Since the surface potential of the reference toner image corresponds to the surface potential of the electrostatic latent image plus the toner layer potential difference, according to the above configuration, the reference toner image and electrostatic latent image detected by the potential detecting means The toner layer potential difference of the reference toner image is obtained from the surface potential. The toner charge amount of the reference toner image is calculated based on the toner layer potential difference. Thus, since the toner charge amount is calculated using the toner layer potential difference obtained using the actual measured value of the surface potential of the electrostatic latent image, the toner charge amount can be obtained accurately.

  Further, according to the above configuration, when the surface potential of the electrostatic latent image is detected by the potential detecting means, the developing device is separated from the image carrier by the developing device separating means. It is possible to prevent adverse effects on the electrostatic latent image, such as changing the potential. Accordingly, the surface potential of the electrostatic latent image can be accurately determined, and thus the toner charge amount can be accurately determined.

  In the developing device, it is preferable that the developing device forms the reference toner image on the image carrier by attaching toner to the image carrier using a developing bias having only a DC voltage.

  Usually, for the purpose of improving developability and uniformity, a development bias in which an alternating voltage is superimposed is often used at the time of development. However, when such a development bias is used for detection of a development current at the time of a process control. In other words, the development current cannot be detected accurately, and the toner charge amount may not be detected correctly.

  Here, according to the above configuration, the development current of only the DC voltage can be used to form the reference toner image, so that the development current can be accurately detected, and as a result, the toner charge amount can be accurately detected. . Therefore, the accuracy of the process control can be improved.

  The image forming apparatus also includes a charging device that uniformly charges the image carrier and an electrostatic latent image on the image carrier by exposing the image carrier that has been uniformly charged by the charging device. And an exposure device that forms an image, and the developing device attaches toner to the image carrier, which is not charged by the charging device and exposed by the exposure device, using a developing bias. The reference toner image may be formed on the image carrier by bias development.

  According to the above configuration, a normal toner image is formed by uniformly charging a predetermined area on the surface of the image carrier with the charging device and then exposing the predetermined area to the electrostatic latent image by exposing the predetermined area. It is formed by an electrophotographic process in which the electrostatic latent image is formed and developed by a developing device. However, in this electrophotographic process, the charging potential or the exposure potential varies depending on the variation in the characteristics of the image carrier, and the intended conditions may not be achieved. Therefore, when this electrophotographic process is used to form a reference toner image for process control, the process control conditions become inaccurate, and as a result, the accuracy of process control may be reduced. Also, in the process of measuring the surface potential of the reference toner image, if the potential of the surface of the image carrier under the toner layer (that is, the potential of the exposure area) fluctuates, the toner layer potential difference of the reference toner image can be accurately measured. It may disappear.

  According to the above configuration, the reference toner image is formed by bias development using only the development bias without charging and exposing the image carrier. Accordingly, it is possible to prevent a decrease in the accuracy of process control due to a change in characteristics of the image carrier.

  In the case of performing bias development, since the reference toner image is formed over the entire longitudinal direction of the image carrier, the amount of toner necessary for forming the reference toner image is increased. As described above, since the toner of the reference toner image is not collected by the toner collecting means, it is preferable that the toner consumption does not increase.

  In addition, the process control means, as the process control, a charging potential when the image carrier is uniformly charged, an exposure amount to the image carrier when forming an electrostatic latent image on the image carrier, A development voltage used when developing the electrostatic latent image on the image carrier, a transfer voltage used when transferring the toner image on the image carrier to the transfer object, and an electrostatic latent image on the image carrier. It is preferable to adjust at least one of the toner concentrations of the two-component toner used to develop the image.

  According to the above configuration, various conditions at the time of image formation can be adjusted by the process control means.

  As described above, in the image forming apparatus according to the present invention, the transfer member that separates the transfer member from the image carrier so that the reference toner image formed on the image carrier is not transferred to the transfer object. A separation unit, and a toner collection unit that collects the toner of the reference toner image on the image carrier that has passed through the transfer member so as to be reused by the developing device. The process control unit includes: The process control is performed based on the toner amount and the toner charge amount.

  Therefore, as described above, it is possible to perform highly accurate process control and to reduce the load on the environment.

Embodiment
An embodiment of the present invention will be described below with reference to FIGS. The following description is an example embodying the present invention, and does not limit the technical scope of the present invention. In this section, a configuration common to the embodiments will be described.

  FIG. 2 is a cross-sectional view showing a schematic configuration of the image forming apparatus 10 according to an embodiment of the present invention. As shown in FIG. 2, the image forming apparatus 10 includes an electrophotographic device (image carrier) 1, a charging device 2, an exposure device 3, a developing device 4, a transfer member 5, a fixing device 6, and a charge eliminating device 7. This is an image forming apparatus of the type.

  The photosensitive member 1 has a cylindrical shape and is driven to rotate in the direction of the arrow shown in FIG. Around the photoreceptor 1, a charging device 2, an exposure device 3, a developing device 4, a transfer member 5, and a charge eliminating device 7 are arranged in this order from the upstream side to the downstream side in the rotation direction of the photoreceptor 1. . Moreover, in each embodiment mentioned later, another member may be arrange | positioned. Between the photosensitive member 1 and the transfer member 5, a paper conveyance path for conveying a paper (recording medium) P such as PPC paper is disposed. A fixing device 6 is disposed on the downstream side of the conveyance direction with respect to the photosensitive member in the sheet conveyance path.

  As shown in FIG. 2, the photoconductor has a photoconductive layer 1b formed on a substrate 1a and carries an electrostatic latent image or a toner image. As the substrate 1a, for example, a metal drum such as aluminum can be used. On the other hand, as the photoconductive layer 1b, for example, amorphous silicon (a-Si), selenium (Se), or an organic optical semiconductor (OPC) is a thin film. Although what was formed in the shape can be used, it is not specifically limited.

  The charging device 2 charges the surface of the photoreceptor 1 so as to have a predetermined uniform potential. As the charging device 2, for example, a charging wire such as a tungsten wire, a non-contact charging corona charger including a metal shield plate and a grid plate, a contact charging charging roller or a charging brush, or the like can be used. However, it is not particularly limited.

  The exposure device 3 forms an electrostatic latent image on the surface of the photosensitive member 1 by exposing the surface of the uniformly charged photosensitive member 1 to light. As the exposure apparatus 3, a semiconductor laser that emits laser light, a light emitting diode, or the like can be used, but is not particularly limited.

  The developing device 4 forms toner images by attaching toner to the electrostatic latent image on the photoreceptor 1. The developing device 4 includes a container 16, and a developing roller 17 including a magnet roller and stirring transport screws 18 and 19 as stirring means are rotatably disposed inside the container 16. In FIG. 2, a screw type is used as the stirring means, but the present invention is not limited to this, and a paddle type may be used.

  The container 16 contains a two-component developer containing toner and a carrier. In the container 16, the toner is mixed so that the weight ratio with respect to the carrier is about several percent. The carrier has a resin coating layer on the surface of magnetic particles for controlling charging properties and suppressing toner adhesion. A resin carrier in which magnetic fine powder is dispersed in resin particles can also be used.

  When the carrier and toner are agitated by the agitating and conveying screws 18 and 19, the toner is charged by friction. The developing roller 17 composed of a magnet roller attracts the carrier by magnetic force to form a magnetic brush. Further, the developing device 4 is provided with a doctor 20 facing the developing roller 17 so that the height of the ears of the magnetic brush formed on the developing roller 17 is regulated.

  Further, a predetermined electric field (developing bias) is formed between the developing roller 17 and the photosensitive member 1 by applying a predetermined voltage to the developing roller 17 by a power supply device (not shown).

  A replenishment opening is provided in the upper wall portion of the container 16, and a replenishment developer supply unit 25 is fitted into the replenishment opening from above. At the bottom of the replenishment developer supply unit 25, a developer supply roller 22 that is driven and controlled by a control device (not shown) is provided. The developer supply roller 22 is rotationally driven to supply the developer into the container 16 by an amount corresponding to the driving time.

  A toner concentration sensor 21 that detects the toner concentration in the container 16 is provided inside the container 16. The toner concentration sensor 21 includes a magnetic permeability sensor, and detects the magnetic permeability by contacting the developer conveyed in the container 16. The magnetic permeability detected here is used for calculating the ratio of the carrier and the toner in an arithmetic unit (not shown).

  For example, when the amount of carrier contained in the developer near the toner concentration sensor 21 is small, it is determined that the toner ratio is high. On the other hand, when the amount of carrier in contact with the toner concentration sensor 21 is large, the toner ratio is Judged to be low. The detection signal of the toner density sensor 21 is input to a control device (not shown), the developer supply roller 22 of the replenishment developer supply unit 25 is driven based on the detection signal, and the roller 22 is replenished and developed in the container 16. By appropriately supplying the agent, the developer in the container 16 is adjusted to have an appropriate toner concentration (toner ratio).

  The transfer member 5 transfers a toner image formed on the surface of the photoreceptor 1 onto a sheet (transfer object) P. The transfer member 5 is in contact with the photoreceptor 1 at a predetermined pressure, and an electric field (transfer electric field) necessary for transferring the toner image is formed at the contact portion. As the transfer member 5, the transfer roller shown in FIG. 2 can be used, but the present invention is not limited to this, and may be a transfer belt, a corona charger, or a transfer brush.

  In the present embodiment, the toner image on the photoconductor 1 is directly transferred to the paper P by the transfer member 5, but the present invention is not limited to this, and the toner image on the photoconductor 1 The image may be transferred once to an intermediate transfer member such as a transfer roller or an intermediate transfer belt, and then transferred to the paper P.

  The transfer member 5 is provided so as to be detachable from the photoreceptor 1. That is, the transfer member 5 is provided with a transfer member separation / contact mechanism (transfer member separation means) 30, and the transfer member separation / contact mechanism 30 causes the transfer member 5 to contact the photoreceptor 1 as necessary, or the photoreceptor 1. Or away from it. Specifically, the transfer member separating / connecting mechanism 30 can be realized by an eccentric cam or by combining a spring and an electromagnetic clutch.

  The fixing device 6 includes a pair of heating roller and pressure roller, and fixes the toner image on the paper P by heating and pressing the paper P on which the toner image is transferred.

  The static eliminator 7 removes charges remaining on the surface of the photoreceptor 1. For example, a static elimination lamp can be used as the static elimination device 7, but is not particularly limited.

  Next, an image forming process by the image forming apparatus 10 will be described.

  First, the charging device 2 uniformly charges the surface of the photoreceptor 1 to a predetermined potential (charging process). Then, the uniformly charged region on the surface of the photoreceptor 1 reaches the exposure device 3 by rotating the photoreceptor 1. Subsequently, the exposure apparatus 3 performs exposure according to the image to be formed on the surface of the uniformly charged photoreceptor 1 to form an electrostatic latent image (exposure process). This electrostatic latent image is an image corresponding to document image data read by a scanner or image data transmitted from a host computer.

  When the electrostatic latent image formed on the surface of the photosensitive member 1 reaches the developing device 4 by the rotation of the photosensitive member 1, the developing device 4 rotates the developing roller 17 so that the toner contained in the magnetic brush is electrostatically charged. Contact the latent image. At this time, the toner contained in the magnetic brush is transferred from the carrier to the electrostatic latent image by the developing electric field (developing bias). As a result, the electrostatic latent image is visualized, and a toner image corresponding to the electrostatic latent image is formed (development process).

  Subsequently, the toner image formed on the surface of the photoconductor 1 reaches the vicinity of the transfer member 5 by the rotation of the photoconductor 1. Here, when a reference toner patch for process control is not created, the transfer member 5 is pressed against the photosensitive member 1 and the paper P is conveyed between the photosensitive member 1 and the transfer member 5. Then, the toner image on the photoreceptor 1 is transferred to the paper P by the transfer electric field (transfer process). The paper P on which the toner image is transferred is conveyed to the fixing device 6 and the fixing device 6 fixes the toner image on the paper P (fixing step).

  On the other hand, when a cleaning member (such as a cleaning blade) is provided on the surface of the photoreceptor 1 to which the toner image has been transferred, residual toner and paper dust are removed by a cleaning device (cleaning step). Then, the static elimination device 7 neutralizes the charge on the surface of the photoreceptor 1 (static elimination process). On the other hand, in the case of the cleanerless system in which no cleaning member is provided, the surface of the photoreceptor 1 is neutralized by the neutralizing device 7 and the remaining toner is collected by the developing device 4.

  The image forming process is completed by the series of processes as described above.

  In the above-described embodiment, the image forming apparatus that forms a monochromatic image has been described. However, the present invention is not limited to this, and may be an image forming apparatus that forms a color image. In the case of an image forming apparatus for forming a color image, a tandem type having at least three sets of developing devices and photoconductors for different toner colors, or 3 to 4 rotations having one photoconductor and sequentially superimposing colors. It may be a type of image forming apparatus. A known technique may be used for these, and detailed description thereof is omitted in this specification.

[Embodiment 1]
A first embodiment of the present invention will be described with reference to FIG. FIG. 1 shows an embodiment of the present invention and is a cross-sectional view showing a schematic configuration of an image forming apparatus 10a.

  In addition to the members of the image forming apparatus 10 described above, the image forming apparatus 10a of the present embodiment further includes a potential sensor (potential detection means) 31, a patch density sensor (toner amount detection means) 32, and a cleaning member (toner recovery). Means) 33, a toner circulation collection mechanism (toner collection means, toner transport means) 34, an arithmetic device (potential detection means, toner amount detection means) 35, and a control device (process control means) 36.

  The potential sensor 31 detects the surface potential of each part of the photoreceptor 1 in a non-contact manner. The potential detected by the potential sensor 31 includes (a) a potential of a uniformly charged area on the surface of the photoreceptor 1, (b) a potential of an exposed area on the surface of the photoreceptor 1, and (c) a reference toner formed on the photoreceptor 1. Patch surface potential, and the like. The potential sensor 31 is disposed opposite the photoconductor 1 at a predetermined position downstream of the developing device 4 in the rotation direction of the photoconductor 1 and upstream of the transfer member 5 in the rotation direction.

  The patch density sensor 32 irradiates light to the reference toner patch formed at the time of the process control, receives light reflected from the patch, and optically determines the toner amount of the reference toner patch based on the amount of the received reflected light. Is detected automatically. The patch density sensor 32 is a combination of a light emitting element such as an LED and a light receiving element that detects reflected light, and is located downstream of the developing device 4 in the rotation direction of the photosensitive member 1 and the transfer member 5. It is arranged opposite to the photoreceptor 1 at a predetermined position upstream of the rotation direction.

  The transfer member 5 is in contact with the photoconductor during normal image formation, but is separated from the photoconductor 1 by the transfer member separation / contact mechanism 30 during the process control. Thereby, the toner of the reference toner patch used for the process control does not adhere to the transfer member 5.

  The cleaning member 33 removes the toner remaining on the surface of the photoreceptor 1 that has passed through the transfer member 5. For example, a cleaning blade that removes the toner image by scraping off the toner image can be used. It is not a thing. The cleaning member 33 is provided in contact with the photoconductor 1 on the downstream side of the transfer member 5 in the rotation direction of the photoconductor 1 and on the upstream side of the charge removal device 7 in the rotation direction. During normal image formation, the cleaning member 33 removes residual toner that has not been transferred from the surface of the photoreceptor 1 to the paper P in the transfer process, and on the other hand, a reference that has passed through the transfer member 5 during process control. Remove the toner patch.

  The toner circulation recovery mechanism 34 conveys the toner of the reference toner patch removed by the cleaning member 33 to the developing device 4. The toner circulation and recovery mechanism 34 can be realized by, for example, providing a screw or the like as a toner conveying member in a rotatable manner inside a conveying tube that connects the cleaning member 33 and the developing device 4. The toner circulation / recovery mechanism 34 may return the toner removed by the cleaning member 33 to the replenishment developer supply unit 25 of the developing device 4 or return it to the container 16. The toner circulation and recovery mechanism 34 preferably has a filter for removing foreign matters such as paper dust from the toner to be conveyed.

  The arithmetic unit 35 acquires the detection results of the potential sensor 31 and the patch density sensor 32, and obtains the toner adhesion amount and toner charge amount of the reference toner patch based on these detection results.

  The control device 36 performs a process control. Specifically, the toner adhesion amount (for example, toner weight per unit area) and toner charge amount (for example, specific charge of toner) obtained by the arithmetic device 35 are calculated. ) To adjust various conditions of the image forming process.

  For example, when the toner adhesion amount of the toner image transferred onto the paper P or the transfer belt is small, how much the development bias or the transfer voltage should be increased depends on the toner charge amount of the toner image. Here, as in the image forming apparatus 10a of the present embodiment, by detecting the toner charge amount of the reference toner patch formed on the photoreceptor 1, the toner charge amount can be reduced even for a predetermined toner adhesion amount, for example. If it is detected that the transfer rate is high, the voltage in the transfer process can be increased so that the desired transfer efficiency can be obtained.

  In addition, when the toner charge amount is high, it is necessary to increase the developing bias in order to obtain a developing toner amount necessary in the developing process. In this case, in order to prevent background fogging on the photoreceptor 1. Control is performed such as increasing the potential (uniform charging potential) Vo of the non-image portion of the photoreceptor, and further increasing the exposure amount in order to maintain the exposure portion potential VL at a constant level.

  Alternatively, in the case of a two-component development system, the toner replenishment conditions are controlled so that an appropriate toner density is obtained depending on the toner charge amount.

  In this way, by detecting the toner charge amount of the reference toner patch, it is possible to optimize the conditions of the charging, exposure, development, and transfer processes.

  In the present embodiment, the conditions adjusted by the control device 36 include (1) the applied voltage to the transfer member 5 (that is, the strength of the transfer electric field), and (2) the developing voltage applied to the developing roller 17 of the developing device 4 (that is, Intensity of development electric field), (3) charging voltage applied to the photosensitive member 1 by the charging device 2 (that is, charging potential on the photosensitive member 1), and (4) exposure amount to the photosensitive member 1 by the exposure device 3 (that is, photosensitive member 1). (5) the toner concentration of the two-component developer contained in the container 16 of the developing device 4 is adjusted.

  If the above (1) is adjusted to an appropriate value according to the charge amount of the actual toner image, the transfer efficiency is improved. Therefore, it is possible to improve the image quality of the formed image and to suppress an increase in toner consumption due to an increase in untransferred toner.

  If the above (2) is adjusted to an appropriate value according to the charge amount of the actual toner image, an appropriate amount of toner will be attached to the electrostatic latent image in the development process. The toner image is formed. Therefore, there are effects that the image quality of the formed image can be improved and the reproducibility of the output image with respect to the input image data can be improved.

  On the other hand, when adjusting the above (2) in order to cope with the change in the charge amount of the toner image, if the above (3) or (4) is also adjusted, the desired toner amount is attached to the electrostatic latent image. There is an effect that image defects such as ground fog and carrier adhesion can be suppressed.

  Further, by adjusting the above (5) based on the actual charge amount of the toner image, there is an effect that the toner image formed on the photoreceptor 1 can be set to a desired charge amount.

  Next, a process control operation by the image forming apparatus 10a of the present embodiment will be described. First, the charging device 2 charges the surface of the photoreceptor 1 to a predetermined uniform potential. Next, the exposure device 3 exposes the uniformly charged surface of the photoreceptor 1 to form a reference patch latent image that is an electrostatic latent image corresponding to the reference toner patch. Subsequently, the developing device 4 develops the reference patch latent image with toner to form a reference toner patch.

  The potential sensor 31 detects the surface potential of the reference toner patch, and the patch density sensor 32 detects the intensity of reflected light from the reference toner patch. Then, the arithmetic unit 35 acquires the surface potential and reflected light intensity detected by the sensors 31 and 32, and calculates the toner charge amount and toner adhesion amount of the reference toner patch. Details of this process will be described later. Then, based on the toner charge amount and the toner adhesion amount obtained by the arithmetic unit, the control device 36 performs the process control.

  On the other hand, when the reference toner patch image passes through the potential sensor 31 and the patch density sensor 32, the transfer member separation mechanism 30 separates the transfer member 5 from the photoreceptor 1. As a result, the reference toner patch on the photoreceptor 1 passes through the transfer member 5 without being transferred to the transfer member 5 or the paper P. Note that the timing of the separation operation may be immediately after the start of the process control, and is not particularly limited.

  The reference toner patch on the photoreceptor 1 is scraped off and removed by the cleaning member 33, and the toner is conveyed to the developing device 4 by the toner circulation recovery mechanism 34. Thereby, the collection of the reference toner patch is completed.

  After that, you may return to the normal image formation mode to execute image formation, check if the charge amount and toner adhesion amount are really appropriate under the adjusted image formation conditions, and again if necessary. The adjustment may be continued by executing the process control so that a desired image forming condition is obtained.

  As described above, according to the image forming apparatus 10a of the present embodiment, the toner used for the process control can be effectively reused without being discarded, so that the burden on the environment can be reduced and the running cost can be reduced. it can.

  Next, how to obtain various parameters necessary for the process control by the arithmetic unit 35 will be described.

  The arithmetic unit 35 acquires the reflectance of the reference toner patch detected by the patch density sensor 32, and obtains the toner adhesion amount mt that is the toner weight per unit area of the reference toner patch from the reflectance. As a method of calculating the toner adhesion amount mt from the reflectance, the relationship between the reflectance detected by the patch density sensor 32 and the toner adhesion amount mt is previously examined by experiment, and the value of the toner adhesion amount mt for each reflectance is calculated. The data is stored in a storage unit (not shown) as a table, and the arithmetic device 35 may obtain it by referring to this table.

  In addition, the arithmetic unit 35 acquires the value of the surface potential Vs of the reference toner patch detected by the potential sensor 31. Here, the surface potential Vs of the reference toner patch is the sum of the potential (exposure potential) VL of the exposure area of the photoreceptor 1 and the potential difference (toner layer potential difference) Vt between the surface and the bottom of the toner layer of the reference toner patch. Therefore, the toner layer potential difference Vt can be obtained by subtracting the exposure potential VL from the surface potential Vs.

  Since the value of the exposure potential VL changes according to the charging condition and the exposure condition, a value for each condition is obtained in advance by experiments or the like, stored as a table in a storage unit (not shown), and the arithmetic unit refers to this. It is preferable to configure so as to. Further, if the values of the toner adhesion amount mt and the exposure potential VL are prepared as a table in consideration of environmental conditions and secular change, it becomes possible to perform more accurate control.

The toner charge amount of the reference toner patch, in other words, the toner specific charge qt (C / g) is obtained from the toner adhesion amount mt (g / cm ² ) and the toner layer potential difference Vt (V) as follows. be able to.

Although not actually measured, the thickness of the toner layer when the toner adhesion amount mt is dt (cm), the apparent dielectric constant of the toner layer is εt (F / cm), and the apparent density (bulk density) of the toner layer is kt. Assuming that (g / cm ³ ), the total toner charge amount Qt (C / cm ² ) of the reference toner patch per unit area is expressed by the following equation (1):
Qt = mt × qt (1)
Can be represented by The thickness dt of the toner layer of the reference toner patch is expressed by the following formula (2)
dt = mt / kt (2)
Can be represented by Further, when the volume charge density of the toner layer is ρt, ρt is expressed by the following equation (3).
ρt = Qt / dt (3)
Can be represented by Further, the toner layer potential difference Vt is expressed by the following equation (4).

（ただし、ｘはトナー層厚みを示す変数である）
によって表すことができる。

(Where x is a variable indicating the thickness of the toner layer)
Can be represented by

  From the above equation (4), the following equation (5)

が導かれ、この式（５）に、上記の式（１），（３）を代入すると、次の式（６）

When the above equations (1) and (3) are substituted into this equation (5), the following equation (6)

が得られ、式（６），（２）から、比電荷ｑｔは、次の式（７）
ｑｔ＝２×Ｖｔ×εｔ×ｋｔ／（ｍｔ＾２） …（７）
によって求めることができる。

From the equations (6) and (2), the specific charge qt is expressed by the following equation (7)
qt = 2 × Vt × εt × kt / (mt ^ 2) (7)
Can be obtained.

  Therefore, if the apparent relative dielectric constant εt of the toner to be used and the bulk density kt of the toner layer are obtained in advance, the toner specific charge qt can be estimated from the surface potential Vs and the toner adhesion amount mt.

  The actual toner layer may not have a uniform volume charge density. This is because there is particle size selectivity and charge amount selectivity in the development process (transfer process), and the volume charge density changes along the toner layer thickness direction. Therefore, the surface potential change when the developing toner amount is changed under an arbitrary charge amount condition is obtained in advance, and the value of the toner specific charge derived by the above equation (7) is corrected based on the information. The charge amount in the process computer may be used.

  As described above, according to the image forming apparatus 10a of this embodiment, the toner charge amount of the reference toner patch is obtained from the detection values of the potential sensor 31 and the patch density sensor 32, and the process control is performed in consideration of the toner charge amount. Therefore, a highly accurate process control can be performed.

[Embodiment 2]
A second embodiment of the present invention will be described with reference to FIG. FIG. 3 shows an embodiment of the present invention and is a cross-sectional view showing a schematic configuration of the image forming apparatus 10b.

  The image forming apparatus 10b according to the present embodiment is different from the image forming apparatus 10a according to the first embodiment described above in that the cleaning member 33 and the toner circulation recovery mechanism 34 are omitted, and the developing device 4 is replaced with the developing device 4 ′. The other points are the same. Description of the same configuration is omitted.

  The image forming apparatus 10b of the present embodiment employs a so-called cleanerless system. In other words, by optimizing the setting condition of the developing bias potential in the developing roller 17, the developing device 4 performs the development and cleaning at the same time.

  According to this configuration, the residual toner and the reference toner patch on the photoreceptor 1 that have passed through the transfer member 5 reach the charging device 2 without being removed by the cleaning member. Then, the surface of the photoreceptor and the toner itself are charged in the charging process, and are exposed in the exposure process. At this time, since the non-image area of the photoreceptor 1 is not exposed, the toner in the non-image area is transferred to the developing roller 17 and collected in the development process.

  As described above, in the present embodiment, the developing device 4 functions as a toner collecting unit, and collects the toner of the reference toner patch on the photoreceptor 1 that has passed through the transfer member 5. Accordingly, there is no need to provide a cleaning member, a reflux mechanism for the developing device, and the like, and the image forming apparatus can be reduced in cost and size.

  In the case of this configuration, the exposure device 3 does not expose the area where the reference toner patch is already formed on the photosensitive member 1 during the process control (that is, when the reference toner patch is formed). It is preferable that all the toner of the patch is collected by the developing device 4. In other words, it is preferable that the exposure apparatus 3 forms a new reference patch latent image corresponding to the reference toner patch by exposing a region where the reference toner patch is not formed. Thus, the newly formed reference toner patch is not affected by the previously formed reference toner patch, and has an appropriate surface potential and toner adhesion amount.

[Embodiment 3]
A third embodiment of the present invention will be described with reference to FIG. FIG. 4 shows an embodiment of the present invention and is a cross-sectional view showing a schematic configuration of the image forming apparatus 10c.

  The image forming apparatus 10c of the present embodiment is different from the image forming apparatus 10b of the second embodiment described above in that a cleaning member 33 and a cleaning member separation / contact mechanism (cleaning member separation / contact means) 37 are provided. Others are the same. Description of the same configuration is omitted.

  The image forming apparatus 10c of the present embodiment can use the same cleanerless system as the image forming apparatus 10b of the second embodiment. However, at the time of normal image formation (that is, when the reference toner patch at the time of process control is not formed), the cleaner-less method is not used, and the residual toner on the photoreceptor 1 that has passed through the transfer member 5 is removed by the cleaning member 33. Remove. At the time of the process control, the cleaning member separation mechanism 37 separates the cleaning member 33 from the photosensitive member 1, so that the reference toner patch on the photosensitive member 1 that has passed through the transfer member 5 is not removed by the cleaning member 33. Then, the cleaning member 33 is passed. As in the image forming apparatus 10b of the second embodiment, the toner of the reference toner patch is collected by the developing device 4 '.

  The cleaning member separation / contact mechanism 37 can be realized by an eccentric cam or a combination of a spring and an electromagnetic clutch, as with the transfer member separation / contact mechanism 30.

  According to the configuration of the present embodiment, the cleaning member 33 is separated from the photoreceptor 1 during the process control (when the reference toner patch is formed) and the cleanerless system is used. The residual toner on the surface is removed. Therefore, it is possible to reduce the risk that paper dust or dust that may be collected together with the toner during cleaning is mixed into the developing device 4 ′, and the toner that has accumulated in the cleaning member 33 over a long period of time and becomes coarse is developed. The risk of refluxing to 4 'can also be reduced. As described above, since it is possible to suppress the substance that adversely affects the developing process from entering the developing device 4 ′, higher quality image formation can be performed.

  In addition, since the cleaner-less process (development cleaning) is performed only at the time of the process control, even if an adverse effect due to poor development cleaning occurs, there is no effect on image formation on the normal paper P. Is preferred.

[Embodiment 4]
A fourth embodiment of the present invention will be described with reference to FIG. FIG. 5 shows an embodiment of the present invention and is a cross-sectional view showing a schematic configuration of the image forming apparatus 10d.

  Compared to the image forming apparatus 10a of the first embodiment described above, the image forming apparatus 10d of the present embodiment is provided with a developing current detecting device 38 instead of the patch density sensor 32. The potential sensor 31 and the developing current detecting device 38 are used. The points for calculating the toner adhesion amount and the toner charge amount are different, and the others are the same. Description of the same configuration is omitted. In addition, since this embodiment shows another aspect of the calculation method of the toner adhesion amount and the toner charge amount, the method for collecting the toner is not particularly limited, and the cleanerless method of the above-described Embodiment 2 is used. You may employ | adopt and the method of using together the cleanerless system of Embodiment 3, and a normal cleaner system may be employ | adopted.

  In this embodiment, in order to detect the toner charge amount of the reference toner patch, the surface potential of the reference toner patch formed on the photoreceptor 1 and the reference patch latent image are developed to form the reference toner patch. A current flowing between the developing roller 17 and the photoreceptor 1 (hereinafter referred to as “developing current”) is detected. This developing current can be measured by detecting the current flowing through the developing roller 17 with the movement of the toner by the developing current detecting device 38 when forming the reference toner patch.

  Hereinafter, a method of obtaining the toner adhesion amount and the toner charge amount from the detection results of the potential sensor 31 and the developing current detection device 38 will be described.

It is assumed that the moving speed of the photosensitive member 1 at the time of forming the reference toner patch is vp (cm / s), the width of the reference toner patch is w (cm), and the developing current is Id (A). Here, assuming that the total charge amount of the toner developed during the time t (s) is Qt (C), the total charge amount Qt is expressed by the following equation (8).
Qt = Id × t (8)
Can be represented by The toner charge amount Qo (C / cm ² ) per unit area (1 cm ² ) in the reference toner patch is expressed by the following equation (9).
Qo = Qt / (vp × t × w)
= Id / (vp × w) (9)
Can be represented by

When the toner layer potential difference of the reference toner patch at this time is Vt (V) and the capacity of the toner layer per unit area is Ct (F), the capacity Ct is expressed by the following equation (10).
Ct = Qo / Vt
= Id / (Vt × vp × w) (10)
Can be represented by Here, the capacitance Ct is the following among the toner adhesion amount mt (g / cm ² ), the dielectric constant εt (F / cm), the bulk density kt (g / cm ³ ), and the toner layer thickness dt (cm). Formula (11)
Ct≈εt × S (= 1) / dt
= Εt / (mt / kt) (11)
And from the above equations (10) and (11), the following equation (12)
mt = εt × kt × (Vt × vp × w) / Id (12)
The toner specific charge qt (C / g) is calculated from the above equation (5) and the above equation (12) by the following equation (13).
qt = Vt × εt × kt / {εt × kt × (Vt × vp × w) / Id} ^ 2
= Id ^ 2 / {εt × kt × Vt × (vp × w) ^ 2} (13)
Can be obtained.

  Accordingly, if the process speed vp, the patch width w, the apparent relative dielectric constant εt of the toner to be used, and the bulk density kt of the toner layer are obtained in advance, the surface of the reference toner patch can be obtained. The specific charge of the toner can be estimated from the potential Vs and the developing current Id at the time of forming the reference toner patch. Further, the toner adhesion amount can be estimated without using the reflectance from the patch density sensor by using the above equation (12).

  In the case where the developing current is detected as in the image forming apparatus 10d of the present embodiment, it is preferable that the developing bias applied between the developing roller 17 and the electrostatic latent image on the photosensitive member 1 is only a DC voltage. . That is, it is preferable that the power source 39 applies a developing bias consisting only of a DC voltage between the developing roller 17 and the photosensitive member 1 during the process control (when the reference toner patch is formed).

  Usually, a development bias with an alternating voltage is used for the purpose of improving developability and uniformity, but when detecting the toner charge amount during the process control based on the development current, the alternating voltage is developed. It may adversely affect the accurate detection of current. Here, the developing current can be accurately detected by using a developing bias consisting of only a DC voltage during the process control, and as a result, the toner charge amount can be accurately detected.

When the toner adhesion amount is detected by a patch density sensor or the like in addition to the toner charge amount, it is desirable that the reference toner patch is uniform, and therefore, it is preferable to use a developing bias with an alternating voltage superimposed thereon. Therefore, when determining the toner charge amount based on the development current, the reference toner patch is formed by the development bias consisting only of a DC voltage, while when determining the toner adhesion amount by a patch density sensor or the like, an alternating voltage is set. If the reference toner patch is formed by the superimposed developing bias, the toner charge amount and the toner adhesion amount can be accurately obtained, and the accuracy of the process control can be improved.
Therefore, based on the information on the toner charge amount, it is possible to perform a more accurate process control by confirming the desired developer toner adhesion amount with an alternating voltage applied.

  Note that the volume charge density may not be constant in the actual toner layer, as in Embodiment 1 described above. This is because there is particle size selectivity and charge amount selectivity in the development process (transfer process), and the volume charge density changes along the thickness direction of the toner layer. Therefore, the relationship between the development current, the surface potential change, and the toner adhesion amount when the development toner amount is changed under an arbitrary charge amount condition is obtained in advance, and the above formulas are derived based on the information. It is also possible to correct the toner specific charge and the toner adhesion amount to obtain the charge amount and toner adhesion amount in the process control.

  As described above, according to the image forming apparatus 10d of this embodiment, the toner charge amount and the toner adhesion amount of the reference toner patch are obtained from the detection values of the potential sensor 31 and the development current detection device 38, and the toner charge amount is taken into consideration. Therefore, a highly accurate process control can be performed. Further, since the toner adhesion amount of the reference toner patch on the photoreceptor 1 can be estimated without using the patch density sensor, the cost can be reduced.

[Embodiment 5]
A fifth embodiment of the present invention will be described with reference to FIG. FIG. 6 shows an embodiment of the present invention and is a cross-sectional view showing a schematic configuration of the image forming apparatus 10e.

  The image forming apparatus 10e according to the present embodiment is provided with a developing current detecting device 38 instead of the potential sensor 31 as compared with the image forming apparatus 10a according to the first embodiment described above. The patch density sensor 32 and the developing current detecting device 38 are used. The points for calculating the toner adhesion amount and the toner charge amount are different, and the others are the same. Description of the same configuration is omitted. In addition, since this embodiment shows another aspect of the calculation method of the toner adhesion amount and the toner charge amount, the method for collecting the toner is not particularly limited, and the cleanerless method of the above-described Embodiment 2 is used. You may employ | adopt and the method of using together the cleanerless system of Embodiment 3, and a normal cleaner system may be employ | adopted.

  In this embodiment, in order to detect the toner charge amount of the reference toner patch, the toner adhesion amount of the reference toner patch formed on the photoreceptor 1 and the reference patch latent image are developed to form the reference toner patch. The developing current flowing between the developing roller 17 and the photosensitive member 1 is detected.

  Hereinafter, a method for obtaining the toner adhesion amount and the toner charge amount from the detection results of the patch density sensor 32 and the developing current detection device 38 will be described.

The toner adhesion amount mt (g / cm ² ) can be obtained from the detection result of the patch density sensor 32 in the same manner as in the first embodiment.

It is assumed that the moving speed of the photosensitive member 1 at the time of forming the reference toner patch is vp (cm / s), the width of the reference toner patch is w (cm), and the developing current is Id (A). Here, assuming that the total charge amount of the toner developed during the time t (s) is Qt (C), the total charge amount Qt is expressed by the following equation (14).
Qt = Id × t (14)
Can be represented by The toner charge amount Qo (C / cm ² ) per unit area (1 cm ² ) in the reference toner patch is expressed by the following equation (15).
Qo = Qt / (vp × t × w)
= Id / (vp × w) (15)
Can be represented by

The toner charge amount of the reference toner patch, in other words, the toner specific charge qt (C / g) is the toner adhesion amount mt (g / cm ² ) and the toner per unit area (1 cm ² ) in the reference toner patch. From the charge amount Qo (C / cm ² ), the following equation (16)
qt = Qo / mt
= Id / (mt × vp × w) (16)
Can be obtained.

  Accordingly, if the moving speed vp (cm / s) of the photosensitive member 1 at the time of forming the reference toner patch and the width w (cm) of the reference toner patch are obtained in advance, the toner adhesion amount mt and the reference toner patch forming time are formed. The specific charge of the toner can be estimated from the developing current Id.

  As in the first embodiment, the relationship between the toner adhesion amount and the development current when the development toner amount is changed under an arbitrary charge amount condition is obtained in advance, and each of the above-described information is based on the information. The toner charge amount in the process computer may be corrected by correcting the value of the toner specific charge amount derived by the equation.

  Also in the present embodiment, it is preferable that the developing voltage is only a DC voltage when the developing current is detected, as in the fourth embodiment.

  As described above, according to the image forming apparatus 10e of this embodiment, the toner charge amount and the toner adhesion amount of the reference toner patch are obtained from the detection values of the patch density sensor 32 and the development current detection device 38, and the toner charge amount is taken into consideration. Since the process control is performed, a highly accurate process control can be performed. In addition, since the toner charge amount (specific charge) of the reference toner patch on the photoreceptor 1 can be estimated without using a potential sensor, the cost can be reduced.

[Embodiment 6]
A sixth embodiment of the present invention will be described with reference to FIG. FIG. 7 illustrates an embodiment of the present invention and is a cross-sectional view illustrating a schematic configuration of the image forming apparatus 10f.

  Compared to the image forming apparatus 10a of the first embodiment described above, the image forming apparatus 10f of the present embodiment is provided with a developing device separating / contacting mechanism 40 that separates and contacts the developing device 4 with respect to the photoreceptor 1. They are different and the others are the same. Description of the same configuration is omitted. In addition, since the present embodiment shows a preferable aspect of the calculation method of the toner adhesion amount and the toner charge amount, the method for collecting the toner is not particularly limited, and the cleanerless method of the second embodiment described above is adopted. Alternatively, a method using both the cleaner-less method of the third embodiment and a normal cleaner method may be employed.

  In the image forming apparatus 10f according to the present embodiment, the potential sensor 31 has a function of measuring the surface potential Vs of the reference toner patch, in addition to the potential (exposure potential) VL of the exposure region in the reference patch latent image and the potential of the uniformly charged region. Also has a role to measure.

  Here, when measuring the exposure potential VL, since the potential sensor 31 is provided downstream of the developing device 4 in the rotation direction of the photosensitive member 1, the reference patch latent image is developed by the developing device 4. The exposure potential VL may not be measured accurately. In order to avoid this, for example, in a mode in which the exposure potential VL is detected, a developing bias is not applied to the developing device 4 so that toner does not adhere to the reference patch latent image on the photoreceptor 1. However, there is a concern that the exposure potential may change when the toner layer or the magnetic brush on the developing roller 17 comes into contact with the exposure area of the reference patch latent image.

  Therefore, in the image forming apparatus 10f of the present embodiment, when the potential sensor 31 measures the exposure potential VL in the reference patch latent image, the developing device separation / contact mechanism 40 separates the developing device 4 from the photoreceptor 1. ing. Therefore, an accurate exposure potential VL can be measured without the exposure area of the reference patch latent image being affected by the developing device 4.

  Then, the arithmetic unit 35 subtracts the exposure potential VL from the value of the surface potential Vs of the reference toner patch described in the first embodiment to obtain the toner layer potential difference Vt, and the exposure potential VL measured by the potential sensor 31 is obtained. Is used. As described above, when the toner layer potential difference Vt is obtained, the measured exposure potential VL is used, so that the toner layer potential difference Vt can be obtained accurately even if the characteristics of the photoreceptor 1 change, and the toner charge amount and adhesion can be determined. It becomes possible to further improve the accuracy of quantity detection and perform a more accurate process control.

  The developing device attaching / detaching mechanism 40 can be realized by an eccentric cam, or by combining a spring and an electromagnetic clutch, as with the transfer member attaching / detaching mechanism 30.

  Further, the configuration of the present embodiment can be applied to an image forming apparatus having the potential sensor 31, and can be applied to the image forming apparatus 10d of the fourth embodiment in addition to the image forming apparatus 10a of the first embodiment. .

[Embodiment 7]
A seventh embodiment of the present invention will be described. In the image forming apparatuses 10a to 10f according to the first to sixth embodiments described above, a normal electrophotographic process is used when forming a standard toner patch for a process computer. In the present embodiment, a standard toner patch for a process computer is used. Are formed by bias development.

  When a reference toner patch for a process computer is created by a normal electrophotographic process, the charging potential or the exposure potential VL may change due to the fluctuation of the characteristics of the photoreceptor 1. When such a problem occurs, there is a concern that the conditions at the time of the process control become inaccurate, and as a result, the process control accuracy decreases. Also, in the process of measuring the surface potential Vs of the reference toner patch, if the photoreceptor potential under the toner layer (that is, the exposure potential VL) fluctuates, the toner layer potential difference Vt of the reference toner patch cannot be measured accurately. There is.

  Therefore, in the image forming apparatus 10g of the present embodiment, when forming a reference toner patch for a professional computer, the photosensitive member is not charged and exposed, and a developing bias generated between the developing roller 17 and the photosensitive member 1 is generated. Utilizing this, a reference toner patch is formed on the photoreceptor 1. Hereinafter, this developing method is referred to as bias development.

  If bias development is used, uniform charging by the charging device 2 and exposure by the exposure device 3 are not required when forming the reference toner patch, and it is possible to prevent a decrease in the accuracy of the process control due to fluctuations in the characteristics of the photoreceptor 1. It becomes possible.

Examples of the method for generating the development bias include the following (1) to (3).
(1) The state where the surface potential of the photoconductor 1 is set to approximately 0 V (strictly, it is a potential formed by the static elimination lamp 7 and the like, and is about −10 to 50 V) without charging and exposing the photoconductor 1. Thus, a predetermined bias voltage is applied to the developing roller 17 by the power source 39 to change the potential of the developing roller 17.
(2) Without charging or exposing the photoconductor 1, a predetermined bias voltage is applied to the substrate 1a (such as an Al base tube) of the photoconductor 1 by a power supply device (not shown) to change the potential of the photoconductor 1. .
(3) The photosensitive member 1 is not charged and exposed, and a predetermined bias voltage is applied to the developing roller 17 by the power source 39 to change the potential of the developing roller 17. A predetermined bias voltage is applied to the material 1a to change the potential of the photosensitive member 1.

  Note that when the bias development is used, the amount of toner required for the reference toner patch is increased as compared with the case where the bias development is not used because the reference toner patch formation region extends over the entire longitudinal direction of the photoreceptor 1. By using the toner collection configuration shown in each of the embodiments together, a stable process control can be performed while suppressing an increase in toner consumption.

  By the way, when the bias development described above is applied to the image forming apparatuses 10b and 10c of the second and third embodiments, it is preferable to further have the following configuration.

  When the reference toner patch is formed by bias development, as described above, the reference toner patch is an area that can be developed by the developing device 4/4 ′ in the longitudinal direction of the photoreceptor 1 (that is, an area facing the developing roller 17). It is formed over the entire area. In the image forming apparatuses 10b and 10c of the second and third embodiments, after the reference toner patch is formed, the developing device 4 ′ collects the toner of the patch. The developing device 4 collects the toner. The area that can be developed is an area that the developing roller 17 faces and is equal to an area that can be developed by the developing device 4.

  Accordingly, if the width of the reference toner patch extends in the longitudinal direction of the photoconductor 1 beyond the developable area, the toner at the end of the reference toner patch on the photoconductor 1 can be collected by the developing device 4 ′. Can not. As a result, the remaining toner of the reference toner patch may cause the image surface to become dirty or the inside of the machine to be contaminated.

  FIG. 8 shows an embodiment of the present invention and is a schematic view of the image forming apparatus as viewed from above. As shown in FIG. 8, in the image forming apparatus 10g of this embodiment, toner scraping members 41a and 41b are provided on the upstream side of the developing roller 17 of the developing device 4 'in the rotation direction of the photosensitive member 1. The toner scraping members 41a and 41b are arranged so that the end in the width direction of the reference toner patch formed on the photoreceptor 1 formed by bias development is moved toward the center, in other words, the width of the reference toner patch is narrowed. Scrape the reference toner patch. As a result, the width of the reference toner patch is shorter than the width (length in the longitudinal direction) of the developing roller 17, and the developing roller 17 can reliably collect the toner contained in the reference toner patch.

  Although the present invention has been described above based on the preferred embodiments, the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims, and different embodiments are possible. Embodiments obtained by appropriately combining the respective technical means disclosed are also included in the technical scope of the present invention.

  The present invention can be applied to an image forming apparatus using an electrophotographic system such as a copying machine, a facsimile machine, and a printer.

1 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention. 1 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention. 1 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention. 1 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention. 1 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention. 1 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention. 1 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention. 1 is a schematic diagram illustrating an image forming apparatus as viewed from above according to an embodiment of the present invention.

Explanation of symbols

1 Photoconductor (image carrier)
DESCRIPTION OF SYMBOLS 1a Base material 1b Photoconductive layer 2 Charging apparatus 3 Exposure apparatus 4 Developing apparatus 4 'Developing apparatus (toner collection means)
DESCRIPTION OF SYMBOLS 5 Transfer member 6 Fixing member 7 Static elimination apparatus 10a-10f Image forming apparatus 17 Developing roller 30 Transfer member separation / contact mechanism (transfer member separation means)
31 Potential sensor (potential detection means)
32 Patch density sensor (toner amount detection means)
33 Cleaning member 34 Toner circulation recovery mechanism (toner conveying means)
35 arithmetic unit (process control means)
36 Control device (process control means)
37 Cleaning member separation / contact mechanism (cleaning member separation means)
38 Development current detection device (development current detection means)
40 Developing device separation / contact mechanism (developing device separating means)
41a / 41b Toner scraping member P paper (transfer object)

Claims (8)

An image carrier that rotates and carries an electrostatic latent image and a toner image, a developing device that forms a toner image by attaching toner to the electrostatic latent image carried by the image carrier, and the image carrier A transfer member provided in contact with the transfer member for transferring a toner image on the image carrier to a transfer target; and a process control unit for performing process control based on a reference toner image formed on the image carrier. An electrophotographic image forming apparatus,
Transfer member separating means for separating the transfer member from the image carrier so that the reference toner image formed on the image carrier is not transferred to the transfer object;
A toner collecting means for collecting the toner of the reference toner image on the image carrier that has passed through the transfer member so as to be reused by the developing device;
The process control means performs the process control based on a toner amount and a toner charge amount of the reference toner image,
A cleaning member that is disposed downstream of the transfer member in the rotation direction of the image carrier and removes a toner image on the image carrier that has passed through the transfer member by contacting the image carrier;
Cleaning member separating means for separating the cleaning member from the image carrier so that the reference toner image formed on the image carrier is not removed by the cleaning member;
The developing device collects toner of a reference toner image on the image carrier that has passed through the cleaning member as the toner collecting unit. A potential detecting means for detecting a surface potential of the reference toner image formed on the image carrier;
A toner amount detecting means for detecting a toner amount of the reference toner image formed on the image carrier,
The process control means includes a toner amount of the reference toner image detected by the toner amount detection means and a toner charge amount of the reference toner image calculated from detection results by the potential detection means and the toner amount detection means. The image forming apparatus according to claim 1, wherein the process control is performed based on the process control. The reference toner image on the image carrier is formed by developing the reference electrostatic latent image on the image carrier by the developing device.
A potential detecting means for detecting a surface potential of the reference toner image formed on the image carrier;
A developing current detecting means for detecting a developing current flowing from the developing device to the image carrier when the developing device develops the reference electrostatic latent image;
2. The process control unit according to claim 1, wherein the process control unit performs the process control based on a toner charge amount and a toner amount of the reference toner image calculated from detection results of the potential detection unit and the development current detection unit. The image forming apparatus described in 1. The reference toner image on the image carrier is formed by developing the reference electrostatic latent image on the image carrier by the developing device.
A toner amount detecting means for detecting a toner amount of the reference toner image formed on the image carrier;
A developing current detecting means for detecting a developing current flowing from the developing device to the image carrier when the developing device develops the reference electrostatic latent image;
The process control means includes: a toner amount of the reference toner image detected by the toner amount detection means; a toner charge amount of the reference toner image calculated from detection results of the toner amount detection means and the development current detection means; The image forming apparatus according to claim 1, wherein the process control is performed based on the process. A developing device separating means for separating the developing device from the image carrier so that the electrostatic latent image on the image carrier is not developed by the developing device;
The potential detecting means is disposed downstream of the developing device in the rotational direction of the image carrier and upstream of the cleaning member in the rotational direction of the image carrier, and is developed by the developing device. And the electrostatic latent image on the image carrier that was not developed by the developing device by the developing device separating means separating the developing device from the image carrier. Detecting the surface potential of
The process control means obtains a toner layer potential difference which is a potential difference between the surface and bottom of the toner layer in the reference toner image from the surface potential of the reference toner image and the electrostatic latent image detected by the potential detection means. 4. The image forming apparatus according to claim 2, wherein a toner charge amount of the reference toner image is calculated based on the obtained toner layer potential difference.   5. The developing device according to claim 3, wherein the developing device forms the reference toner image on the image carrier by attaching toner to the image carrier using a developing bias having only a DC voltage. Image forming apparatus. A charging device for uniformly charging the image carrier;
An exposure device that forms an electrostatic latent image on the image carrier by exposing the image carrier after being uniformly charged by the charging device;
The developing device converts the reference toner image into the image by bias development in which toner is attached to the image carrier, which is not charged by the charging device and exposed by the exposure device, using a developing bias. The image forming apparatus according to claim 1, wherein the image forming apparatus is formed on a carrier. The process control means, as the process control,
A charging potential for uniformly charging the image carrier,
Exposure amount to the image carrier when forming an electrostatic latent image on the image carrier,
Development voltage used when developing the electrostatic latent image on the image carrier,
A transfer voltage used to transfer the toner image on the image carrier to the transfer object, and a toner concentration of a two-component toner used to develop the electrostatic latent image on the image carrier;
2. The image forming apparatus according to claim 1, wherein at least one of the two is adjusted.

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