JP2005107446A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of grasping the amount of remaining toner in a developing device with a simple constitution and at a low cost without disposing a specified sensor for the developing device. <P>SOLUTION: The image forming apparatus is composed of an image carrier on which an electrostatic latent image is formed in accordance with image information of an image forming job, a developer carrier which is arranged opposite to the image carrier, conveys the toner while being deposited on the surface thereof, develops the electrostatic latent image and forms a job toner image, a toner storage chamber that stores the toner and supplies the same to the developer carrier, a bias power source that applies a developing bias between the image carrier and the developer carrier, a means that measures an electric-resistance value of a circuit for applying the developing bias containing the image carrier and the developer carrier, a consumption grasping means for grasping the toner consumption from the measured resistance value and a remaining amount judging means that accumulates the grasped consumption and grasps the amount of remaining toner in the toner storage chamber from the accumulated consumption. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus using a so-called electrophotographic process in which an electrostatic latent image formed on an image carrier such as a photosensitive drum is developed with toner to form a recorded image. The present invention relates to a technique for grasping the remaining amount of toner in a developing device for developing an electrostatic latent image.

JP 2001-31195A JP 2001-051498 A

  In an image forming apparatus such as a copying machine or a printer that employs an electrophotographic process, after uniformly charging the surface of an image carrier such as a photosensitive drum, the surface of the photosensitive drum is exposed according to image information. Then, an electrostatic latent image is formed, and the electrostatic latent image is developed with toner to form a visible toner image. Finally, the toner image is electrostatically transferred to a recording sheet, and the recorded image is recorded. Forming. As a method of developing an electrostatic latent image with toner, there are a developing method using a two-component developer in which a toner and a carrier are mixed at a certain ratio, and a method using a one-component developer consisting only of toner.

  In the method using the two-component developer, if the mixing ratio of the toner and the carrier in the developing device changes, the developing density of the toner image obtained by developing the electrostatic latent image fluctuates. Therefore, the mixing ratio is kept constant. Therefore, it is necessary to replenish the developing device with an amount of toner corresponding to the amount of toner consumed by developing the electrostatic latent image. For this reason, a toner replenishment system is required separately from the developing device, and it is difficult to reduce the size of the image forming apparatus itself.

  On the other hand, the one-component developer, although it contains some external additives such as a charge control agent, is almost composed only of toner, so it does not require a complicated toner replenishment system, and the developer itself is used up with toner. This cartridge has the characteristic that it is easy to configure. In recent years, small-sized laser beam printers use a single-use process cartridge in which a photosensitive drum and a developing device are integrated in order to simplify maintenance by a user. For example, most of them use the one-component developer, so that it can be said that the process cartridge can be miniaturized.

  As described above, most of the developing devices using a one-component developer are configured as a single use type process cartridge, and the problem is that the toner is stored in a toner storage chamber in the developing device. One component developer, that is, grasping the remaining amount of toner. If the remaining amount of toner cannot be accurately grasped, the process cartridge will be replaced in spite of the remaining toner, and if the toner is used up before the user notices, Until a new process cartridge is obtained, the printing operation must be interrupted. Therefore, in an image forming apparatus using a one-component developer, a means for accurately grasping the remaining amount of toner in the developing device is indispensable.

  Conventionally, as a method of grasping the remaining amount of toner in the developing unit, a sensor for detecting the remaining amount of toner is provided in the toner storage chamber in the developing unit, and the remaining amount of toner is estimated from the detection signal of this sensor. Known (Japanese Patent Laid-Open No. 2001-51489). The sensor includes a magnetic sensor for detecting a magnetic field generated by magnetic toner, a sensor for electrically measuring a change in electrostatic capacity in the toner storage chamber as the toner decreases, and a change in pressure caused by toner accumulation is converted into an electrical signal. Piezo-type sensors are used. However, when only a specific recorded image is printed in a large amount, only a specific area of toner in the toner storage chamber is consumed in a large amount, and the toner may partially accumulate in the toner storage chamber. There is a problem in that the remaining amount of toner in the toner storage chamber cannot be accurately grasped depending on the mounting position of the sensor. Moreover, if a plurality of sensors are provided in order to increase the certainty, the manufacturing cost will increase.

  In addition, as a method of grasping the toner consumption amount and grasping the toner remaining amount in the developing device therefrom, a so-called pixel counter for integrating the exposure time of the photosensitive drum by the laser beam is provided, and the accumulated value of this pixel counter is used. What knows the amount of toner consumption is known. Further, as disclosed in Japanese Patent Laid-Open No. 2001-312195, a method of using this pixel counter in combination with a sensor for detecting the remaining amount of toner in the developing device is also known.

  This method using the pixel counter is based on the premise that the toner consumption corresponds one-to-one with the exposure amount of the photosensitive drum, that is, the image density of the recorded image to be printed. The developer using the agent has a characteristic that the amount of toner consumption varies even when an electrostatic latent image having the same image density is developed according to the usage history. There is a problem that the amount of consumption cannot be accurately grasped.

  For example, the toner stored in the developing device preferably has a uniform particle size, but it contains some toners with irregular particle sizes and is repeatedly stirred in the developing device. In the meantime, the particle size may change gradually. Such unevenness of the particle size also affects the charge amount of each toner in the developing unit. As a result, toner that is easily consumed in developing the electrostatic latent image (hereinafter referred to as “appropriate” in the developing unit). Toner ”) and toner that is difficult to be consumed (hereinafter referred to as“ degraded toner ”). For this reason, in a state where the use of the developing device has progressed to some extent, more deteriorated toner remains in the developing device, and even if an electrostatic latent image having the same image density is developed, the toner in the developing device remains. When the remaining amount decreases, the amount of toner consumption differs, and as a result, the remaining amount of toner cannot be accurately predicted only from the integrated value of the pixel counter. On the other hand, the change in the particle size of the toner described above occurs remarkably when the toner is agitated for a long time in the developing unit, so if the toner in the developing unit is used up in a short period of time, The change in particle size is not a problem. Therefore, if the recorded image with high image density is printed frequently and the process cartridge is replaced in a short period of time, the remaining amount of toner in the developing device can be accurately adjusted even if only the integrated value of the pixel counter is used. It is possible to predict. That is, in order to accurately predict the remaining amount of toner in the developing device, it is necessary to consider the toner consumption history in the developing device.

  SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide toner in the developing device with a simple configuration and low cost without providing a special sensor for the developing device. An object of the present invention is to provide an image forming apparatus capable of grasping the remaining amount.

  Another object of the present invention is to provide an image forming apparatus capable of more accurately grasping the remaining amount of toner in the developing device by taking into account the toner consumption history in the development.

  In the developing method using a one-component developer, a developer carrying body having a toner attached to the surface is disposed opposite to an image carrying body such as a photosensitive drum, and the image carrying body and the developer carrying body. A developing bias voltage containing an alternating current component is applied between them, and the toner adhering to the surface of the developer carrying member flies and adheres to the photosensitive drum to develop the electrostatic latent image. Since the flying and adhesion of the toner is performed based on the charged charge of the toner, when the electrostatic latent image is developed with the toner, the amount of toner consumed depends on the amount of toner consumed between the developer carrier and the image carrier. The charge is moved. That is, during the development of the electrostatic latent image, the electrical resistance value of the developing bias application circuit including the developer carrier and the image carrier varies according to the amount of toner consumed.

  Therefore, by measuring the electrical resistance value of the developing bias application circuit including the developer carrier and the image carrier during development of the electrostatic latent image, it is possible to grasp the toner consumption during the measurement. In addition, the resistance value is sequentially measured at a predetermined sampling interval, and the toner consumption amount obtained from each measurement result is accumulated, whereby the remaining amount of toner in the developing device can be grasped.

  That is, in the first invention, an image carrier on which an electrostatic latent image corresponding to image information of an image forming job is formed, the toner is attached to the surface of the image carrier, the toner is attached to the image carrier, and conveyed. A developer carrier that develops the electrostatic latent image to form a job toner image, a toner storage chamber that stores toner and supplies it to the developer carrier, and the image carrier and developer carrier A bias power source for applying a development bias between the image carrier and a means for measuring an electrical resistance value of a developing bias application circuit including the image carrier and the developer carrier during formation of a job toner image, and a measured resistance A consumption amount grasping means for grasping the toner consumption amount from the value; and a remaining amount judgment means for accumulating the grasped consumption amount and grasping the remaining toner amount in the toner storage chamber from the accumulated consumption amount. To do.

  Here, the job toner image means a toner image related to a copy job or a print job instructed by the user, and the image density of the job toner image differs depending on the contents of the job.

  According to the first aspect of the present invention, the electrical resistance value of the developing bias application circuit including the image carrier and the developer carrier is measured during the formation of the job toner image, and the toner consumption is grasped from the measured resistance value. It is possible to grasp the remaining amount of toner in the toner storage chamber by accumulating the consumption amount. Then, based on the result of grasping the toner remaining amount, a warning is given to notify the so-called near empty when the toner remaining amount in the toner storage chamber is low, and the user is prompted to prepare a new cartridge unit, or the toner empty is It is possible to perform an action such as giving a warning to notify and prohibiting the image forming operation of the image forming apparatus itself.

  In the first aspect of the invention, it is assumed that there is a one-to-one correspondence between the electrical resistance value of the developing bias application circuit and the amount of toner (toner consumption) flying from the developer carrier to the image carrier. However, when the developing device is used over time, a lot of deteriorated toner remains in the toner storage chamber, and the charge amount of the deteriorated toner is different from the charge amount of the proper toner. Therefore, even when a job toner image having the same image density is formed, the ratio of the deteriorated toner is increased compared to the case where the job toner is formed in a state where there is abundant appropriate toner in the toner storage unit. When the job toner is formed, the electric resistance value of the developing bias application circuit is different, and as a result, there is a possibility that the toner consumption amount may be misunderstood.

  From this point of view, taking into account the accumulated usage time of the developing device, when grasping the toner consumption amount from the measured resistance value, the toner consumption amount grasped based on the accumulated usage time of the developing device is corrected. Is preferred. As a method of grasping the cumulative usage time of the developing device, it is considered to count the number of rotations of the image carrier, the number of printed sheets and the number of copies of the recording sheet after replacing the developing device, and grasp the value from the counted value. It is done.

  On the other hand, as described above, when the developing unit is used and the toner in the toner storage unit is consumed, the toner storage unit has deteriorated toner, that is, the particle size is irregular from the beginning, or the particle size is increased by agitation over time. A lot of toner having changed remains. Since these deteriorated toners have slightly different charge amounts compared to the proper toner consumed at the beginning of use of the developing device, the electric resistance of the developing bias application circuit is developed while developing an electrostatic latent image of a predetermined image density. When the value is measured, there is a difference between the measured value at the beginning of use of the developing device and the measured value after a certain amount of use, and this difference increases as the use of the developer progresses over time. It tends to spread gradually. Accordingly, a reference toner image having a predetermined image density is periodically formed on the image carrier, and an electric resistance value of a developing bias application circuit is measured during the formation of the reference toner image, and this resistance value is measured by a developing device. In comparison with the reference resistance value corresponding to the beginning of use of the toner, it is possible to grasp the toner remaining amount in the toner storage unit based on the comparison result.

  That is, in the second invention, an image carrier on which an electrostatic latent image corresponding to image information of an image forming job is formed, the toner is attached to the surface of the image carrier, and the toner is attached to the image carrier. A developer carrier that develops the electrostatic latent image to form a job toner image, a toner storage chamber that stores toner and supplies it to the developer carrier, and the image carrier and developer carrier A bias power source for applying a developing bias between the image carrier, a reference image generator for periodically forming a reference toner image having a predetermined image density on the image carrier, and the image carrier during formation of the reference toner image And means for measuring the electrical resistance value of the developing bias application circuit including the developer carrying member, means for comparing the measured resistance value with a reference resistance value held in advance, and a comparison result of the comparison means Based on the toner storage chamber Further comprising a remaining amount determining means for grasping the definitive amount of remaining toner is characterized in.

  According to such technical means, the electrical resistance value of the developing bias application circuit including the image carrier and the developer carrier is measured during the formation of the reference toner image, and the measured resistance value is held in advance. By comparing with the reference resistance value, it is possible to grasp the unevenness of the particle size of the toner remaining in the toner storage chamber, in other words, the remaining amount of toner in the toner storage chamber. Similarly, it is possible to warn the user of toner near-empty or empty, prompt the user to prepare a new cartridge unit, or take measures such as prohibiting the image forming operation of the image forming apparatus itself.

  On the other hand, the occurrence of deteriorated toner is closely related to the accumulated usage time of the developing device. If the accumulated use time is short, the amount of deteriorated toner is small, and the amount of remaining toner in the toner storage chamber is not always large. Absent. As described above, when a high-density toner image is frequently developed and the toner in the toner storage chamber is consumed in a short period of time, there is little generation of deteriorated toner, and a reference toner image is formed regularly. Even if the resistance value of the developing bias application circuit is measured, the difference between the reference resistance value and the measured resistance value is not expected to increase. Therefore, if the remaining amount of toner in the toner storage chamber is determined based only on the difference between the reference resistance value and the measured resistance value, it may not be possible to accurately determine the remaining toner amount.

  Therefore, from this point of view, in the second invention as well, when the reference resistance value and the measured resistance value are compared with each other based on the accumulated usage time of the developing device, the comparison is made based on the accumulated usage time of the developing device. It is preferable to correct the result.

  Further, when the ratio of the deteriorated toner in the toner storage chamber increases, the density of the toner image tends to decrease when the electrostatic latent image is developed. In the second aspect of the invention, the development bias application circuit for the reference toner image By measuring the resistance value and comparing the measured resistance value with the reference resistance value, the degree of progress of the toner deterioration is grasped. From this comparison result, the difference between the measured resistance value and the reference resistance value is more than a certain value. When it is determined, it is preferable to determine that the toner in the toner storage chamber is deteriorating, and to start density correction control when forming a toner image. Further, it is preferable to change the correction amount of the density correction parameter based on the difference between the two resistance values. Here, as the density correction parameter, a developing bias voltage and its waveform, the amount of light for exposing the image carrier, and the like can be considered. Further, if the charge amount of the toner itself increases, the toner easily flies from the developer carrier to the image carrier, and the density of the toner image is improved. Therefore, the toner prior to the start of the copy job or print job is improved. When the toner in the storage chamber is stirred, the stirring time is also a density correction parameter.

  Further, the comparison result between the reference resistance value in the second invention and the measured resistance value related to the reference toner image expresses the degree of progress of the toner deterioration in the toner storage chamber, in other words, the cumulative usage time of the developing device itself. Therefore, the correction value of the toner consumption amount is calculated based on the comparison result, while the apparent toner consumption amount is grasped from the measured resistance value related to the job toner image as in the first aspect of the invention. The actual toner consumption amount can be grasped by adding the correction value to the toner consumption amount.

  That is, the third invention is an image carrier on which an electrostatic latent image corresponding to image information of an image forming job is formed, and is opposed to the image carrier and is transported with toner attached to the surface. A developer carrier that develops the electrostatic latent image to form a job toner image, a toner storage chamber that stores toner and supplies it to the developer carrier, and the image carrier and developer carrier A bias power source for applying a developing bias between the image carrier, a reference image generator for periodically forming a reference toner image having a predetermined image density on the image carrier, and during the formation of the job toner image and the reference toner image Means for measuring an electrical resistance value of a developing bias application circuit including the image carrier and the developer carrier; and a resistance value measured in advance during formation of the reference toner image. Compare toner consumption A correction amount calculation unit for calculating a positive value and an apparent toner consumption amount from the resistance value measured during the formation of the job toner image, and the toner consumption amount by adding the correction value to the apparent toner consumption amount And a remaining amount determining means for accumulating the grasped consumption amount and grasping the remaining amount of toner in the toner storage chamber from the accumulated consumption amount.

  According to the third aspect of the present invention, without providing a counter or the like for counting the cumulative usage time of the developing device, the degree of progress of toner deterioration in the toner storage chamber is taken into account, and the resistance value of the developing bias application circuit is used to determine the toner storage chamber. It is possible to accurately grasp the remaining toner amount.

  In the third aspect of the invention, since the resistance value of the developing bias application circuit relating to the reference toner image is measured and the measured resistance value is compared with the reference resistance value, the degree of progress of the toner deterioration is grasped. If it is determined from this comparison result that the difference between the measured resistance value and the reference resistance value is greater than a certain value, it is determined that the toner in the toner storage chamber is deteriorating, as in the second aspect of the invention. It is preferable to start density correction control when forming an image. Further, it is preferable to change the correction amount of the density correction parameter based on the difference between the two resistance values.

  According to the image forming apparatus of the present invention configured as described above, by measuring the electrical resistance value of the developing bias application circuit including the image carrier and the developer carrier, a special developing device is provided. Without providing a sensor, the remaining amount of toner in the toner storage chamber of the developing device can be grasped with a simple configuration and at low cost.

  Further, according to the present invention, by measuring the electrical resistance value of the developing bias application circuit, it is possible to grasp the degree of progress of the developer deterioration in the toner storage chamber, and the development is performed in consideration of the degree of deterioration. It becomes possible to grasp the toner remaining amount in the container more accurately.

Hereinafter, an image forming apparatus of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 schematically shows a monochrome laser beam printer to which the present invention is applied. In the figure, reference numeral 1 denotes a photosensitive drum as an image carrier, reference numeral 2 denotes a charging roll for charging the photosensitive drum 1 to a predetermined background portion potential, and an arrow 3 denotes a laser scanning unit (ROS) (not shown). ) And a laser beam for writing an electrostatic latent image on the photosensitive drum 1, reference numeral 4 denotes a developing unit for developing the electrostatic latent image formed on the photosensitive drum 1 with toner, and reference numeral 5 denotes a photosensitive member. A sheet supply tray that feeds the recording sheet 6 at a predetermined timing synchronized with the timing of writing the electrostatic latent image on the drum 1. Reference numeral 7 denotes a transfer for electrostatically transferring the toner image developed on the photosensitive drum 1 to the recording sheet 6. Roll, reference numeral 8 is a cleaner provided with a cleaning blade 9 in contact with the surface of the photosensitive drum 1 after the transfer of the toner image, and reference numeral 10 is a toner image transferred to the recording sheet 6. A fixing device for fixing on the recording sheet 6.

  In this laser beam printer, the photosensitive drum 1, the charging roll 2, the developing device 4 and the cleaner 8 constitute one process cartridge, and the toner empty (empty) in the developing device is detected by a method described later. Then, the entire process cartridge is exchanged. Therefore, by replacing this process cartridge, it is possible to replace the deteriorated photosensitive drum, to supply toner, and to collect the waste toner collected by the cleaner.

  Under such a configuration, a toner image corresponding to the image information is formed on the photosensitive drum 1 through a charging process using the charging roll 2, an exposure process using the laser beam 3, and a developing process using the developing device 4. The toner image is transferred to the recording sheet 6 at a position where the photosensitive drum 1 and the transfer roll face each other. The recording sheet on which the toner image has been transferred is discharged to a sheet discharge tray (not shown) through a fixing device, and the photosensitive drum 1 after the transfer process is adhered to the toner, such as residual toner and paper dust, by the cleaning blade. Is removed.

FIG. 2 shows a specific structure of the process cartridge.
In the figure, reference numeral 11 denotes a cleaner housing that rotatably holds the photosensitive drum 1. The cleaning blade 9 is fixed to the cleaner housing 11, and the cleaning blade 9 removes the photosensitive drum 1 from the surface of the photosensitive drum 1. The collected waste toner, paper dust, and other deposits are accumulated inside. Further, the charging roll 2 is also rotatably held in the cleaner housing 11, and the charging roll 2 is pressed against the photosensitive drum 1 by a spring 12. Accordingly, when the photosensitive drum 1 is rotated, the charging roll 2 is also rotated following the rotation.

  The developing device 4 is swingably connected to the cleaner housing 11 via a pin 13, and a spring 14 interposed between the cleaner housing 11 and the developing device 4 serves as a developing device. Energized in one direction. As a result, a developing gap between the developing roll (developer carrier) 20 provided in the developing device 4 and the photosensitive drum 1 held by the cleaner housing 11 is maintained.

  On the other hand, the developing device 4 includes a cylindrical developing roll 20 that rotates while holding a thin layer of toner on a peripheral surface, a toner storage chamber 21 that supplies toner to the developing roll 20, and the toner storage A layer forming blade 22 for forming toner adhering to the developing roll 20 from the chamber 21 into a thin layer having a predetermined thickness, a peeling blade 23 for peeling the toner thin layer from the peripheral surface of the developing roll 20, and the inside of the toner storage chamber 21 And an agitator (agitating means) 24 that agitates the toner in the room by rotating at the same time.

  Here, magnetic toner is used as the toner, and the toner is held on the peripheral surface by the magnetic force generated by the developing roll 20. That is, the developing roll 20 includes a magnet roll (not shown), and the toner in the toner storage chamber 21 is attracted to the peripheral surface of the developing roll 20 by the magnetic force of the magnet roll.

  Further, the agitator 24 rotating in the toner storage chamber 21 prevents the toner from being blocked in the chamber, and also functions to feed the toner toward the developing roll 20, so that the latter function can be exhibited more effectively. A flexible film 25 such as PET is attached to the tip of the agitator 24. The flexible film 25 rubs against the inner wall of the toner storage chamber 21 as the agitator 24 rotates, and the toner present in the corner of the toner storage chamber 21 is also sent toward the developing roll without waste. In addition, the broken line circle in the drawing indicates the range where the advanced flexible film 25 reaches, in other words, it indicates the stirring range of the toner by the agitator 24.

  Further, one end of the layer forming blade 22 is pressed against the developing roll 20 with a predetermined pressing force, and the other end is fixed to the mounting block 28, and the toner adhering to the developing roll 20 is frictionally charged by magnetic force. Thinning to a predetermined layer thickness. A synthetic resin tube 26 having a substantially cylindrical cross section is sandwiched between the layer forming blade 22 and the mounting block 28 in parallel with the developing roll 20, and the tube 26 faces the developing roll 20 to form the layer forming blade. 22 is pressed uniformly from the back side.

  Then, the toner thinned on the peripheral surface of the developing roll 20 as described above is carried out to the developing area facing the photosensitive drum 1 as the developing roll 20 rotates, and a part of the toner is transferred to the photosensitive body. The electrostatic latent image is developed by adhering to the drum 1. On the other hand, the toner remaining on the developing roll 20 without adhering to the photosensitive drum 1 is collected into the developing device 4 as the developing roll 20 rotates, and is peeled off from the developing roll by the peeling blade 23. .

  FIG. 3 is a block diagram showing a first embodiment of a control system for grasping the remaining amount of toner in the process cartridge. A bias power source 30 is connected between the developing roll 20 and the photosensitive drum 1, and a so-called alternating voltage obtained by superimposing a DC voltage on an AC voltage is applied as a developing bias. The toner stirred in the toner storage chamber 21 and rubbed by the layer forming blade 22 is triboelectrically charged, and an alternating electric field corresponding to the developing bias is generated between the photosensitive drum 1 and the developing roll 20. Thus, when the toner adhering to the surface of the developing roll 20 is carried out to a position facing the photosensitive drum 1 by the rotation of the developing roll 20, it flies by electrostatic attraction and After migrating with the developing roll 20 by the action of an alternating electric field, the image is attracted to the electrostatic latent image on the photosensitive drum 1 and attached to the photosensitive drum 1 or developed without attaching to the photosensitive drum 1. It is pulled back to the roll 20. Thereby, the electrostatic latent image formed on the photosensitive drum 1 is developed.

  When a part of the toner thinned on the developing roll 20 in this way adheres to the photosensitive drum 1, each toner has a charge, and therefore the photosensitive drum 1 and the developing roll A current corresponding to the amount of toner movement, in other words, the amount of toner consumed by developing the electrostatic latent image flows between the photosensitive drum 1 and the photosensitive drum 1 during development of the electrostatic latent image. Then, the electrical resistance value of the developing bias application circuit including the developing roll 20 is sequentially changed. Since the developing bias applied to the developing roll 20 includes an alternating current component, the electrical resistance value of the developing bias application circuit is the impedance of the circuit. FIG. 4 is a graph showing the relationship between the image density of the toner image formed on the photosensitive drum and the resistance value of the developing bias application circuit. As shown in this graph, when the developed toner image has a high image density, the resistance value of the developing bias application circuit decreases. Conversely, when the developed toner image has a low true image density, the resistance of the developing bias application circuit decreases. The value rises. FIG. 5 is a graph showing the relationship between the image density of the toner image developed on the photosensitive drum 1 and the amount of toner consumed. For ease of measurement, the amount of toner consumed is the amount per recording sheet. Is shown. As is apparent from this graph, the image density and the toner consumption amount are substantially proportional to each other. When the image density increases, the toner consumption amount increases in proportion to this. Therefore, based on these results, the larger the amount of toner consumed for developing the electrostatic latent image, the lower the resistance value of the developing vise application circuit at that moment, and conversely, It can be seen that the smaller the amount, the higher the resistance value of the developing vise application circuit.

  Therefore, in the laser beam printer of this embodiment, the impedance meter 31 is provided in the developing bias application circuit including the photosensitive drum 1 and the developing roll 20, and the resistance of the developing bias application circuit during the development of the electrostatic latent image. The value (impedance) is measured, and the toner consumption during the print job is grasped based on the measured resistance value. While the electrostatic latent image is being developed in the print job, in other words, while the developing bias is being applied to the developing roll 20, the impedance meter 31 has an impedance at a predetermined time interval. The measurement is repeated, and each measurement result is sequentially transmitted to the consumption amount grasping means 32 composed of a microcomputer. The non-volatile memory of the consumption amount grasping means 32 stores in advance a table showing the relationship between the resistance value of the developing bias application circuit and the toner consumption amount as shown in FIG. 6, and based on this table, the consumption amount grasping means. 32 converts the resistance value received from the impedance meter 31 into a toner consumption amount, and sequentially reports the toner consumption amount to the remaining amount determination means 33 also realized by a microcomputer.

  The remaining amount determining means 33 accumulates each toner consumption amount received from the consumption amount grasping means 32, calculates the cumulative consumption amount of toner from the start of use of the process cartridge to the present time, and calculates the accumulated consumption amount to the process cartridge. The remaining amount of toner in the toner storage chamber 21 is grasped by comparing with the total amount of toner previously sealed in the toner storage chamber 21. When it is determined that the remaining amount of toner is less than or equal to the predetermined amount, a near empty warning signal indicating that the toner is about to run out is sent, and a near empty is displayed in a liquid crystal display provided in the printer casing as a user interface. A warning is displayed, or a warning message is displayed in the display of the client PC connected to the printer. On the other hand, when it is determined that the toner is further consumed and the toner in the toner storage chamber 21 is exhausted, an empty signal indicating that the toner has been exhausted is transmitted, and the user is warned in the same manner as the near empty warning signal. To prompt the user to replace the process cartridge. In addition, in order to prevent printing of a recorded image in which development omission has occurred, a signal for prohibiting the operation of the process cartridge is sent simultaneously with the sending of an empty warning signal.

  As described above, according to the first embodiment of the toner empty detection shown in FIG. 3, during the development of the toner image in the print job, by sequentially measuring the resistance value of the developing bias application circuit, no developing device 4 is obtained. The remaining amount of toner in the toner storage chamber 21 can be grasped without providing a sensor in the toner storage chamber 21.

  When the remaining amount of toner in the toner storage chamber 21 decreases, the density of the toner image formed by developing the electrostatic latent image on the photosensitive drum 1 tends to become lighter. If the remaining amount determining means 33 determines that the remaining amount of toner in the toner storage chamber 21 is less than a certain amount, various types of toner images are formed in order to maintain the toner image at an appropriate density. It is preferable to start density correction control such as changing a parameter. As parameters for density correction, a voltage value of a DC voltage component in the developing bias, a peak-to-peak voltage in an AC voltage component, a frequency, and a duty ratio can be considered. By changing these parameters, it is possible to enhance the electrostatic attraction force that attracts toner from the developing roll 20 toward the photosensitive drum 1, and as a result, it is possible to correct the developing density of the toner image. Further, as a parameter for density correction, it is conceivable to correct the exposure intensity of the photosensitive drum 1 by changing the light quantity of the laser beam 3 emitted by ROS. Further, when the toner in the toner storage chamber 21 is agitated before the start of the print job, increasing the agitation time as the remaining amount of toner decreases is effective for lowering the development density of the toner image. is there. This is because if the stirring time of the toner in the toner storage chamber 21 is increased, the toner can be reliably frictionally charged by that amount, and the toner can easily fly from the developing roll 20 to the photosensitive drum 1.

  On the other hand, the particle size of the toner filled in the toner storage chamber 21 of the process cartridge is not completely uniform, and a small amount of toner having irregular particle sizes is included. Further, even toner once thinned on the peripheral surface of the developing roll 20 by the layer forming blade 22 may be returned to the toner storage chamber 21 without adhering to the photosensitive drum 1. The toner gradually changes in particle size while repeatedly being rubbed by the layer forming blade 22. Such deteriorated toner is less likely to be consumed in the development of the electrostatic latent image due to its own charging failure and mass difference, and the amount of toner contained in the toner storage chamber 21 increases as the usage time of the process cartridge accumulates. It will gradually increase.

  For this reason, when the usage time of the process cartridge accumulates, even when the same amount of toner is consumed, the amount of charge moving from the developing roll 20 to the photosensitive drum 1 decreases, and as a result, the developing bias is increased. The resistance value of the application circuit tends to increase. Therefore, if the toner consumption is grasped only from the resistance value of the developing bias application circuit, the apparent toner consumption grasped from the measured resistance value is smaller than the actual toner consumption, and the remaining amount of toner is actually reduced. There is a concern that it will be estimated more than.

  In order to prevent such erroneous detection of the remaining amount of toner and to grasp the remaining amount of toner more accurately, a count counter 34 that can grasp the accumulated usage time of the developing device 4 is provided. It is preferable to correct the apparent toner consumption obtained from the measured resistance value based on the count value. For example, the correction coefficient corresponding to the count value of the count counter 34 can be set stepwise, and the apparent toner consumption grasped from the measured resistance value can be multiplied by the correction coefficient. Accordingly, it is possible to correct the prediction of toner consumption according to the ratio of the deteriorated developer in the toner storage chamber 21 and to grasp the remaining amount of toner in the toner storage chamber 21 more accurately. It is sufficient for the counting counter 34 to be able to grasp the accumulated usage time of the developing device 4. For example, even if the cumulative rotation number of the photosensitive drum 1 is counted, the recording sheet onto which the toner image has been transferred. It does not matter even if the number of P is counted.

  FIG. 7 is a block diagram showing a second embodiment of the control system for grasping the remaining amount of toner in the process cartridge. In the first embodiment shown in FIG. 3, the resistance value of the developing bias application circuit is sequentially measured during the progress of the print job designated by the user, and the measured resistance value is converted into toner consumption and accumulated. Thus, the remaining amount of toner in the toner storage chamber 21 was grasped. However, in this embodiment, the measured resistance value is not converted into the toner consumption amount, but the degree of deterioration of the toner remaining in the toner storage chamber 21 is determined from the measured resistance value, and the remaining toner amount is grasped from the degree of deterioration. It was configured as follows.

  That is, as described above, when the cumulative usage time of the process cartridge increases, the amount of deteriorated toner with poor charging gradually increases with respect to the remaining amount of toner in the toner storage chamber 21, and an electrostatic latent image having the same image density is obtained. Even when developing with toner, the amount of charge moving from the developing roll 20 to the photosensitive drum 1 tends to decrease. For this reason, a reference toner image corresponding to a predetermined image density is periodically formed on the photosensitive drum 1, and the resistance value of the developing bias application circuit at the time of developing the reference toner image is measured. Compared with a predetermined reference resistance value, it is possible to grasp the ratio of the deteriorated toner to the remaining toner amount in the toner storage chamber 21, and as a result, indirectly grasp the remaining toner amount itself. Is possible.

  A reference image generating unit 41 in FIG. 7 generates image data for forming the reference toner image and sends it to the ROS 42. As a result, the ROS 42 exposes the photosensitive drum, writes an electrostatic latent image having a predetermined image density on the surface of the photosensitive drum 1, and the developing roll 20 develops the electrostatic latent image to form a reference toner image. The impedance meter measures the resistance value of the developing bias application circuit during the development of the reference toner image, and sends the measured resistance value to the comparison means 40. The comparison means 40 compares the read measured resistance value with a reference resistance value held in advance in the nonvolatile memory, and notifies the remaining amount determination means 43 of the difference. The remaining amount determining means 43 grasps the toner remaining amount in the toner storage chamber using the comparison result of the comparing means.

  FIG. 8 is a flowchart showing the procedure of the toner remaining amount detecting method in the second embodiment. First, when the process cartridge is replaced, an image pattern signal having a predetermined image density is generated from the reference image generating unit 41, a reference toner image is formed on the photosensitive drum 1 (ST1), and the reference toner image is developed. The resistance value of the developing bias applying circuit when developing by the device 4 is measured by the impedance meter 31 (ST2). The comparison means 40 stores the resistance value measured by the impedance meter 31 at this time as a reference resistance value in the nonvolatile memory (ST3). Thereafter, when the use of the process cartridge is started, an image pattern signal is generated from the reference image generation unit 41 at a predetermined timing every time a print job designated by the user is completed or when the main power of the printer is turned on. The reference toner image is developed on the photosensitive drum 1 (ST4), and the resistance value of the developing bias application circuit when the reference toner image is developed by the developing device 4 is measured by the impedance meter 31 (ST5). The comparison means 40 compares the measured resistance value at this time with the reference resistance value stored in the nonvolatile memory, and calculates the difference (ST6). If the difference between the resistance values is equal to or greater than a predetermined amount (hereinafter referred to as “level 1”), the ratio of the deteriorated developer in the toner storage chamber 21 is increased to a certain level, that is, in the toner storage chamber 21. (ST7), a near-empty warning signal indicating that the toner will soon be exhausted is sent, and a near-empty warning is displayed in a liquid crystal display provided in the printer housing as a user interface. Or display a warning message in the display of the client PC connected to the printer (ST8). On the other hand, if the difference between the resistance values is equal to or less than the level 1, it is determined that the remaining amount of toner in the toner storage chamber 21 is sufficient, and the process returns to ST4 to form a reference toner image again at the end of the next print job. To do.

  Even when the near-empty warning is issued in ST8, the formation of the reference toner image at the end of the print job is continued (ST9), and the resistance of the developing bias application circuit when the developing device 4 develops the reference toner image. The value is measured with the impedance meter 31 (ST10). The comparing means 40 compares the measured resistance value at this time with the reference resistance value stored in the nonvolatile memory, and calculates the difference (ST11). If the difference between the resistance values is equal to or greater than a predetermined amount (hereinafter referred to as “level 2”) greater than level 1, it is determined that most of the toner in toner storage chamber 21 has become deteriorated toner (ST12). ), An empty signal indicating that the toner has been exhausted is transmitted, and a warning is issued to the user in the same manner as the near empty warning signal, prompting the user to replace the process cartridge (ST13).

  As described above, according to the second embodiment of the toner empty detection shown in FIG. 7, the reference toner image having a predetermined image density is developed between print jobs, and the development bias is applied during the development of the reference toner image. By sequentially measuring the resistance value of the circuit and comparing the measured resistance value with a reference resistance value that has been held in advance, the difference can be determined without providing a sensor in the toner storage chamber 21 of the developing device 4. The remaining amount of toner in the toner storage chamber 21 can be grasped.

  On the other hand, the amount of deteriorated toner in the toner storage chamber tends to increase as the cumulative usage time of the developing device increases. In other words, the toner is repeatedly stirred in the toner storage chamber or repeatedly rubbed by the layer forming blade. As a result, the toner particle diameter gradually changes and the deteriorated toner increases. For this reason, when a print job for forming a toner image having a very high image density, such as a solid black image, is frequently executed, the toner remaining in the toner storage chamber is not limited although the accumulated usage time of the developing device itself is short. The amount tends to decrease remarkably, and it is also assumed that the toner in the toner storage chamber is emptied in a state where the deteriorated toner is not generated so much. In the toner empty detection method of the second embodiment, there is a concern that in such a case, the remaining amount of toner may be determined more than the actual amount.

  In order to prevent such erroneous detection of the remaining amount of toner and to grasp the remaining amount of toner more accurately, a count counter 34 that can grasp the accumulated usage time of the developing device 4 is provided as in the first embodiment. It is preferable to correct the difference between the measured resistance value calculated by the comparison means 40 and the reference resistance value based on the count value of the count counter 34. For example, a correction coefficient corresponding to the count value of the count counter 34 can be set in stages, and the correction coefficient can be multiplied by the difference between the calculated measured resistance value and the reference resistance value. As a result, the degree of toner deterioration in the toner storage chamber 21 predicted from the difference between the measured resistance value and the pure resistance value can be corrected, and the remaining amount of toner in the toner storage chamber 21 can be grasped more accurately. . It is sufficient for the counting counter 34 to be able to grasp the accumulated usage time of the developing device 4. For example, even if the cumulative rotation number of the photosensitive drum 1 is counted, the recording sheet onto which the toner image has been transferred. It does not matter even if the number of P is counted.

  In the toner empty detection method of this embodiment, the ratio of the deteriorated toner in the toner storage chamber 21 is estimated by comparing the measured resistance value with the reference resistance value by the comparison unit 40. When the ratio of the deteriorated toner in the developing device 4 increases, it becomes difficult for the toner to fly from the developing roll 20 to the photosensitive drum 1, and as a result, the density of the toner image developed from the electrostatic latent image decreases. There is. Therefore, when the comparison means 40 determines that the difference between the measured resistance value and the reference resistance value is greater than or equal to a predetermined value, various parameters for forming the toner image are set in order to maintain the toner image at an appropriate density. It is preferable to start density correction control such as changing. As the parameters for density correction, the parameters described in the first embodiment can be used. Note that the difference between the measured resistance value serving as a trigger for starting the density correction control and the reference resistance value can be determined regardless of the level 1 and the level 2 when the toner remaining amount in the toner storage chamber is grasped. .

  FIG. 9 is a block diagram showing a third embodiment of a control system for grasping the remaining amount of toner in the process cartridge. In the third embodiment, as in the first embodiment shown in FIG. 3, the resistance value of the developing bias applying circuit is sequentially measured during the progress of the print job designated by the user, and the measured resistance value is used as the toner consumption amount. The remaining amount of toner in the toner storage chamber 21 is grasped by converting the amount into However, when the measured resistance value is converted into the toner consumption, the degree of deterioration of the toner remaining in the toner storage chamber 21 is judged, the correction amount is calculated according to the degree of deterioration, and the measured resistance value is converted into the toner consumption. The amount of correction is taken into account when converting to a quantity.

  As described in the second embodiment, as the cumulative usage time of the process cartridge increases, the amount of deteriorated toner with poor charging gradually increases with respect to the remaining amount of toner in the toner storage chamber 21, and the static density of the same image density is increased. Even when the electrostatic latent image is developed with toner, the amount of charge moving from the developing roll 20 to the photosensitive drum 1 tends to decrease. Therefore, if the resistance value of the developing bias application circuit is measured and simply converted into the toner consumption, the variation of the measured resistance value due to the deterioration of the toner in the toner storage chamber 21 is not taken into account. As a result, there is a concern that the accumulated toner consumption may be mistakenly grasped. On the other hand, the degree of deterioration of the toner in the toner storage chamber is such that, as shown in the second embodiment, a reference toner image having a predetermined image density is sequentially formed, and a developing bias application circuit during the development of the reference toner image. It is possible to easily grasp the measured resistance value by comparing the measured resistance value with a predetermined reference resistance value.

A reference image generation unit 41 in FIG. 9 generates image data for forming the reference toner image and sends it to the ROS 42. As a result, the ROS 42 exposes the photosensitive drum 1, writes an electrostatic latent image having a predetermined image density on the surface of the photosensitive drum 1, and the developing roll 20 develops the electrostatic latent image to form a reference toner image. . The impedance meter 31 measures the resistance value of the developing bias application circuit during the development of the reference toner image, and sends the measured resistance value to the correction amount calculation unit 50. The correction amount calculation unit 50 compares the read measured resistance value with a reference resistance value held in advance in the nonvolatile memory. Since the difference between the reference resistance value and the measured resistance value here indicates the degree of toner deterioration in the toner storage chamber, the correction amount calculation means calculates the correction value of the toner consumption amount from the difference and consumes the correction value. The amount grasping means 32 is notified. That is, the signal flow indicated by the broken line in FIG. 9 is the signal flow when calculating the correction value of the toner consumption amount. On the other hand, during execution of a print job designated by the user, image data relating to the print job is supplied to the ROS 42, and the ROS 42 exposes the photosensitive drum 1 based on this image data. As a result, an electrostatic latent image corresponding to the image data is formed on the photosensitive drum 1, and the electrostatic latent image is developed with toner by the developing device 4. The impedance meter 31 repeats measurement of impedance at predetermined time intervals during development of the toner image related to the print job, that is, the job toner image, and sequentially transmits each measurement result to the consumption amount grasping unit 32. The non-volatile memory of the consumption amount grasping means 32 stores in advance a table showing the relationship between the resistance value of the developing bias application circuit and the toner consumption amount as shown in FIG. 6, and based on this table, the consumption amount grasping means. A resistance value 32 measured during the formation of the job toner image is converted into an apparent toner consumption. Thereafter, the consumption amount grasping unit 32 grasps the toner consumption amount in the formation of the job toner image by adding the correction value of the toner consumption amount acquired from the correction amount calculation unit 50 to the apparent toner consumption amount. The toner consumption amount is sequentially reported to the remaining amount determination unit 33. The remaining amount determination unit 33 accumulates each toner consumption amount received from the consumption amount grasping unit 32, and accumulates toner from the start of use of the process cartridge to the present. The consumption amount is calculated, and the accumulated consumption amount is compared with the total amount of toner previously sealed in the toner storage chamber 21 of the process cartridge, so that the remaining amount of toner in the toner storage chamber 21 is grasped.
The remaining amount determining means 43 grasps the toner remaining amount in the toner storage chamber using the comparison result of the comparing means.

  FIG. 9 is a flowchart showing the procedure of the toner remaining amount detecting method in the third embodiment. First, when the process cartridge is replaced, an image pattern signal having a predetermined image density is generated from the reference image generating unit 41, a reference toner image is formed on the photosensitive drum 1 (ST21), and the reference toner image is developed. The resistance value of the developing bias applying circuit when developing by the device 4 is measured by the impedance meter 31 (ST22). The correction amount calculation unit 50 stores the resistance value measured by the impedance meter 31 at this time in the nonvolatile memory as a reference resistance value (ST23). Thereafter, when the use of the process cartridge is started, a job toner image based on the image data is formed in the print job (ST24), and the developing bias application circuit for developing the job toner image by the developing device 4 is used. The resistance value is measured by the impedance meter 31 (ST25), and the measured resistance value is converted into the toner consumption amount by the consumption amount grasping means 32. Here, the toner consumption amount converted from the measured resistance value is an apparent toner consumption amount that does not consider the deterioration of the toner in the toner storage chamber 21, and this apparent toner consumption amount is temporarily stored in the memory. On the other hand, when the print job is completed, an image pattern signal is generated from the reference image generator 41 to develop the reference toner image on the photosensitive drum 1 (ST26), and the reference toner image is developed by the developing device 4. The resistance value of the developing bias application circuit at this time is measured by the impedance meter 31 (ST27). The correction amount calculation unit 50 compares the measured resistance value at this time with the reference resistance value stored in the nonvolatile memory in ST23, calculates the difference (ST28), and determines the degree of deterioration of the toner from the difference between these resistance values. A correction value of the toner consumption amount corresponding to the toner consumption amount is calculated and notified to the consumption amount grasping means 32 (ST29). Upon receipt of the correction value notification, the consumption amount grasping means 32 reads the apparent toner consumption amount stored in the memory, and adds the correction value to the apparent toner consumption amount to determine the actual toner consumption amount. It grasps (ST30), and reports the actual toner consumption amount to the remaining amount determination means 33.

  The remaining amount determining means 33 accumulates each toner consumption amount received from the consumption amount grasping means 32 (ST31), calculates the cumulative consumption amount of toner from the start of use of the process cartridge to the present time, and the accumulated consumption amount. Whether or not exceeds a predetermined amount (hereinafter referred to as “level 3”) (ST32). As a result, if the level is 3 or higher, it is determined that the remaining amount of toner in the toner storage chamber 21 has become low, and a near-empty warning signal indicating that the toner will soon be exhausted is sent to the printer housing as a user interface. A near empty warning is displayed in the provided liquid crystal display, or a warning message is displayed in the display of the client PC connected to the printer (ST33). On the other hand, if the accumulated consumption amount is equal to or less than level 3 in ST32, it is determined that the remaining amount of toner in the toner storage chamber 21 is sufficient, the process returns to ST24, the next print job is performed, and ST25 to ST32 are repeated.

  Even when a near empty warning is issued in ST33, the next print job is executed, and as shown in FIG. 11, ST34 to ST41 exactly the same as ST24 to ST31 are performed, and the toner consumption amount in the print job is calculated as a consumption amount. The amount of toner consumed in the process cartridge is calculated by the remaining amount determining means 33 while being grasped by the means 32. Then, it is checked whether or not the cumulative consumption exceeds a predetermined amount (hereinafter referred to as “level 4”) (ST42). If it is determined that the cumulative consumption is above level 4, most of the toner in the toner storage chamber 21 is present. It is determined that the toner has been consumed, an empty signal indicating that the toner has been exhausted is transmitted, a warning is issued to the user in the same manner as the near empty warning signal, and a process cartridge replacement operation is urged (ST43).

  As described above, according to the third embodiment of the toner empty detection shown in FIG. 9, the resistance value of the developing bias application circuit is sequentially measured during the development of the toner image in the print job, as in the first embodiment. As a result, the remaining amount of toner in the toner storage chamber 21 can be grasped without providing a sensor in the toner storage chamber 21 of the developing device 4, and the degree of deterioration of the toner in the toner storage chamber In addition, the amount of toner consumed in a print job can be grasped, the amount of toner remaining in the toner storage chamber can be grasped, and the amount of toner remaining in the developing device can be grasped more accurately. It is possible to accurately determine the replacement time.

  Also in the toner empty detection method of the third embodiment, the correction amount calculation unit 50 estimates the ratio of deteriorated toner in the toner storage chamber 21 by comparing the measured resistance value with the reference resistance value. However, when the ratio of the deteriorated toner in the developing device 4 increases, it becomes difficult for the toner to fly from the developing roll 20 to the photosensitive drum 1, and as a result, the density of the toner image obtained by developing the electrostatic latent image. There is a problem that becomes thinner. Accordingly, when the correction amount calculation unit 50 determines that the difference between the measured resistance value and the reference resistance value is greater than or equal to a predetermined value, various types of toner images are formed in order to maintain the toner image at an appropriate density. It is preferable to start density correction control such as changing a parameter. As the parameters for density correction, the parameters described in the first embodiment can be used.

1 is a diagram illustrating a schematic configuration of a monochrome laser beam printer to which the present invention is applicable. FIG. 3 is a cross-sectional view showing a process cartridge in which a photosensitive drum and a developing device are integrated. FIG. 3 is a block diagram illustrating a first embodiment of a configuration for detecting the remaining amount of toner in the printer. It is a graph which shows the relationship between the resistance value (impedance) of the application circuit of development bias, and image density. 6 is a graph showing a relationship between image density and toner consumption. 5 is a graph showing a relationship between a resistance value (impedance) of a developing bias application circuit and toner consumption. FIG. 6 is a block diagram illustrating a second embodiment of a configuration for detecting the remaining amount of toner in the printer. 7 is a flowchart illustrating a procedure for detecting a remaining amount of toner in a second embodiment. FIG. 9 is a block diagram illustrating a third embodiment of a configuration for detecting the remaining amount of toner in the printer. 12 is a flowchart illustrating a first half procedure of toner remaining amount detection in a third embodiment. 12 is a flowchart illustrating a second half procedure of toner remaining amount detection in the third embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Photosensitive drum (image carrier), 20 ... Developing roll (developer carrier), 21 ... Toner storage chamber, 30 ... Bias power supply, 31 ... Impedance meter

Claims (7)

An image carrier on which an electrostatic latent image corresponding to image information of an image forming job is formed, and the image carrier is disposed opposite to the image carrier, and the toner is attached to the surface and conveyed, and the electrostatic latent image is developed. A developer carrier for forming a job toner image, a toner storage chamber for storing and supplying toner to the developer carrier, and applying a developing bias between the image carrier and the developer carrier A bias power source, a means for measuring an electric resistance value of a developing bias application circuit including the image carrier and the developer carrier during formation of a job toner image, and grasping a toner consumption amount from the measured resistance value An image forming apparatus comprising: a consumption amount grasping unit; and a remaining amount judgment unit that accumulates the grasped consumption amount and grasps the remaining toner amount in the toner storage chamber based on the accumulated consumption amount. The image forming apparatus according to claim 1, further comprising a counter that grasps the cumulative usage amount of the image carrier, and correcting the cumulative toner consumption amount in the consumption amount grasping unit based on a count value of the counter. An image carrier on which an electrostatic latent image corresponding to image information of an image forming job is formed, and the image carrier is disposed opposite to the image carrier, and the toner is attached to the surface and conveyed, and the electrostatic latent image is developed. A developer carrier for forming a job toner image, a toner storage chamber for storing and supplying toner to the developer carrier, and applying a developing bias between the image carrier and the developer carrier A bias power supply, a reference image generating unit for periodically forming a reference toner image having a predetermined image density on the image carrier, and development including the image carrier and the developer carrier during the formation of the reference toner image. A means for measuring the electrical resistance value of the bias application circuit, a means for comparing the measured resistance value with a reference resistance value held in advance, and the toner storage chamber based on the comparison result of the comparison means. Know the toner level An image forming apparatus comprising the remaining amount determining means that. 4. The image forming apparatus according to claim 3, wherein a counter for grasping the cumulative usage amount of the image carrier is provided, and the comparison result in the comparison means is corrected based on the count value of the counter. As a result of comparing the reference resistance value and the measured resistance value by the comparison means, when it is determined that the difference between the two resistance values is greater than or equal to a certain value, density correction control when forming the job toner image is started, 5. The image forming apparatus according to claim 3, wherein the density correction parameter is changed based on a difference between the two resistance values. An image carrier on which an electrostatic latent image corresponding to image information of an image forming job is formed, and the image carrier is disposed opposite to the image carrier, and the toner is attached to the surface and conveyed, and the electrostatic latent image is developed. A developer carrier for forming a job toner image, a toner storage chamber for storing and supplying toner to the developer carrier, and applying a developing bias between the image carrier and the developer carrier A bias power source, a reference image generator for periodically forming a reference toner image having a predetermined image density on the image carrier, and the image carrier and developer carrier during the formation of the job toner image and the reference toner image Means for measuring the electrical resistance value of the developing bias application circuit including the body, and correcting the toner consumption by comparing the resistance value measured during the formation of the reference toner image with a reference resistance value held in advance. Correction amount calculation to calculate the value A consumption amount grasping means for grasping the apparent toner consumption from the resistance value measured during the formation of the job toner image and grasping the toner consumption by adding the correction value to the apparent toner consumption. An image forming apparatus comprising: a remaining amount determining unit that accumulates the grasped consumption amount and grasps the remaining toner amount in the toner storage chamber from the accumulated consumption amount. As a result of comparing the reference resistance value and the measured resistance value in the correction amount calculation unit, when it is determined that the difference between the two resistance values is equal to or greater than a certain value, density correction control for forming the job toner image is started. The image forming apparatus according to claim 6, wherein the density correction parameter is changed based on a difference between the two resistance values.

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