JP2006171361A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of more accurately detecting the remaining amount of toner in a toner container. <P>SOLUTION: The image forming apparatus, having a development unit 4 which performs development, by using a developer containing toner and a carrier, the toner container 46 which contains toner to be supplied, a toner supply means 47, a toner density detecting means 42 for detecting the toner density of the developer in the development unit 4, and an image density detecting means 15 of detecting the density of a developed reference toner image T has a toner remaining amount detection mode, including a 1st step of driving the toner supply means 47 and also detecting the toner density of the developer in the development unit 4 by the toner density detecting means 42 and a 2nd step of forming the reference toner image T, after the 1st step and detecting its density by the image density detecting means 15, and in the 2nd step, it is decided whether the 1st step is to be performed again or that the toner remaining amount detection mode is to be finished, according to the detection result of the density of the reference toner image T. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a copying machine or a laser beam printer using an electrostatic recording system or an electrophotographic system that develops an electrostatic image formed on an image carrier using a developer including a toner and a carrier. It is about.

  For example, in an electrophotographic image forming apparatus, image formation is generally performed by image forming processes of charging, exposure, development, transfer, fixing, and cleaning. That is, after the surface of an electrophotographic photoreceptor (hereinafter referred to as “photoreceptor”) is uniformly charged, exposure according to image information is performed to form an electrostatic image (latent image). The electrostatic latent image is developed as a toner image with toner, and the toner image is transferred from the photoreceptor onto a recording material such as paper. The photoreceptor after the toner image is transferred is cleaned by removing the transfer residual toner remaining on the surface. On the other hand, the recording material onto which the toner image has been transferred is heated and pressurized to fix the toner image on the surface. This completes image formation.

  As a developer used in the image forming apparatus as described above, a two-component developer in which a non-magnetic toner and a magnetic carrier are mainly mixed is widely used with the recent improvement in image quality and speed of a full-color image forming apparatus. ing.

  In a developing device using a two-component developer, since the mixing ratio (toner concentration) of toner and carrier in the developing device changes depending on toner consumption, it is necessary to always maintain the toner concentration appropriately. When the toner density is inappropriate, image defects such as image density fluctuation, roughness, fogging, carrier adhesion, and toner scattering may occur. For this reason, in forming a high-quality and highly-stabilized image, it is very important to accurately detect the toner concentration and appropriately control the toner replenishment amount.

  Therefore, conventionally, as means for detecting the toner density, for example, a light detection method, an inductance detection method, and the like have been proposed and implemented. The light detection method detects changes in the developer's reflection density, and the inductance detection method detects changes in the magnetic permeability with a sensor to directly detect changes in the physical properties of the two-component developer itself, based on the detection results. To control the toner supply amount.

  Since the toner density detection means of these light detection system and inductance detection system can directly detect the toner density, it is relatively easy to keep the toner density constant. On the other hand, if the charge amount of the toner fluctuates due to environmental fluctuations such as temperature and humidity or deterioration with time, the toner density may not be accurately controlled. In other words, even if the toner concentration is appropriate, if the toner charge amount fluctuates due to environmental fluctuations or carrier deterioration, the binding force between the toner and the carrier fluctuates, and the amount of toner movement onto the photoreceptor is reduced. Since it fluctuates, it may be difficult to maintain a stable image density.

  On the other hand, there is a so-called patch detection type toner supply control method as described below. That is, a reference image (patch image) is formed by developing the reference latent image formed on the photosensitive member (or recording material carrier or intermediate transfer member), and the reflection density of the patch image is detected by the image density detection means. To do. Then, the toner replenishment amount is controlled based on the detection result.

  In the patch detection method, the target of detection is the amount of toner deposited on the photosensitive member (or recording material carrier or intermediate transfer member), so the toner charge is caused by environmental fluctuations such as temperature and humidity and deterioration with time. Even when the amount varies, it is possible to always maintain an appropriate toner density in image formation. However, in the patch detection method, the toner density of the developer is not directly controlled. Therefore, when the toner density greatly fluctuates, fogging, carrier adhesion, toner scattering, and the like may occur.

  Therefore, the toner replenishment control using the toner concentration detecting means for directly detecting the toner concentration of the developer in the developing device such as the light detection method and the inductance detection method described above and the toner replenishment control by the patch detection method are used in combination. Is called.

  By the way, if the image forming apparatus is continuously used for a long time, the toner in the toner storage unit (toner container) for storing the toner to be replenished to the developing device disappears. Therefore, the remaining amount (presence / absence) of the toner remaining in the toner container is determined, and the user is supplied with a new toner, or the toner container is replaced (a part or all of the toner container forms an image). If it is possible to attach to and detach from the main body, it is necessary to prompt.

  Conventionally, a piezo method, an antenna method (capacitance detection method), a light detection method, and the like have been proposed and implemented as toner remaining amount detection means for detecting the remaining amount of toner in the toner container.

  On the other hand, as another method for detecting the remaining amount of toner in the toner container, in recent years, the image density detecting means used in the toner replenishment control of the above-described patch detection system, or the toner density of the developer in the developing container is directly used. A method for detecting the remaining amount of toner using a toner density detecting means of a light detecting method or an inductance detecting method for detecting has been proposed and implemented. According to this method, there is no need to provide a special sensor in the toner container in order to detect the remaining amount of toner in the toner container, which is advantageous in terms of simplification of the apparatus configuration and cost reduction.

  However, by merely determining whether the detection output from the image density detection means or the toner density detection means is higher or lower than a predetermined fixed value, whether the toner is really present or the patch image density depends on factors other than the toner density. It is difficult to determine whether the is low.

  The problem is that the toner remaining amount is not determined based on the detection output during normal operation, but forced toner supply is performed, and the toner remaining amount is determined based on whether or not the detection output after the forced toner supply exceeds a predetermined threshold. This is improved with the method. This is because if the toner remains in the toner container, the detection output is surely increased by the forced toner supply, and the remaining amount of toner can be accurately determined regardless of the state of the developer at that time.

  Patent Document 1 and Patent Document 2 describe a toner container in which a detected output does not satisfy a predetermined reference value even when a toner replenishing operation is performed with respect to toner remaining amount detection using a patch detection method and an inductance detection method, respectively. It is disclosed to determine that there is no toner in (toner bottle, toner cartridge). These methods can perform both the toner remaining amount detection and the toner replenishment control with a common sensor, so there is no need to provide a dedicated sensor for toner remaining amount detection, and the cost is very excellent. It can be said that it is a method.

  However, when forced toner supply is performed and the remaining toner amount is determined by the patch detection method, it is usually necessary to frequently form patch images during forced toner supply in order to prevent oversupply of toner. Therefore, it takes a long time to detect the remaining amount of toner, and a downtime in which image formation cannot be performed occurs. Further, if patch image formation is frequently performed, toner consumption increases for patch image formation. When a patch image whose density has been detected is collected by the cleaner mechanism, the patch image cannot be sufficiently collected by the cleaner mechanism, and so-called slip-through occurs in which the toner that could not be collected contaminates the photoconductor. There is. In addition, the life of the cleaner mechanism is shortened. Conversely, if the frequency of patch image detection is reduced, toner may be replenished excessively. In this case, image density defects, fogging, and toner scattering may occur.

Further, when the toner remaining amount is determined by the light detection method or the inductance detection method when the toner is forcibly replenished, for example, in a state where the developer has deteriorated due to long-term use, the forced toner is used until the toner concentration reaches a predetermined value. When the replenishment is performed, there may be a case where an abrupt increase in image density, fogging, or toner scattering occurs. This phenomenon occurs because the ability to impart charge to the toner is lowered due to the deterioration of the developer as compared with the state of the new developer. That is, it is very difficult to control the charge amount of the toner even if the toner density is detected during the forced replenishment.
Japanese Patent Laid-Open No. 5-66669 JP 2002-287479 A

  An object of the present invention is to provide an image forming apparatus capable of more accurately detecting the remaining amount of toner in a toner container with a simple configuration.

  One of the more detailed objects of the present invention is to forcibly replenish toner from the toner container to the developing device, and determine the remaining amount of toner remaining in the toner container by detecting the toner concentration of the developer in the developing device. In this case, the image can be formed with a stable density by reducing the downtime of the apparatus due to the time taken to detect the remaining amount of toner, and suppressing the fluctuation of the image density after detecting the remaining amount of toner. A forming apparatus is provided.

  The above object is achieved by the image forming apparatus according to the present invention. In summary, the present invention relates to a developing unit that develops an electrostatic image formed on an image carrier using a developer including toner and a carrier, and a toner container that contains toner to be replenished to the developing unit. Toner replenishing means for replenishing the toner contained in the toner container to the developing device, toner concentration detecting means for detecting the toner concentration of the developer in the developing device, and the developer supplying the developer. And an image density detecting means for detecting the density of the developed reference toner image. The toner supply means is driven and the toner density of the developer in the developing device is adjusted by the toner density detecting means. A first step of detecting, and a second step of forming the reference toner image after the first step and detecting the density thereof by the image density detecting means. Determining whether to execute the first step again or end the remaining toner amount detection mode in accordance with the detection result of the density of the reference toner image in the second step. The image forming apparatus is characterized.

  According to an embodiment of the present invention, in the first step, when the toner concentration of the developer detected by the toner concentration detection unit is equal to or higher than a predetermined value, after the driving of the toner supply unit is stopped, The second step is executed. According to an embodiment of the present invention, in the second step, when the density of the reference toner image detected by the image density detection means is a predetermined value or more, the toner remaining amount detection mode is terminated. To do. According to an embodiment of the present invention, when the density of the reference toner image detected by the image density detecting means is lower than a predetermined value in the second step, the first step is executed again. . Further, according to an embodiment of the present invention, in the first step, the toner density of the developer detected by the toner density detecting means is a predetermined value even when the driving time of the toner replenishing means is a predetermined value or more. If not, it is detected that the remaining amount of toner in the toner container has become a predetermined value or less.

  According to the present invention, the remaining amount of toner in the toner container can be detected more accurately with a simple configuration. More specifically, according to the present invention, the toner remaining in the toner container (presence / absence) is detected by forcibly supplying toner from the toner container to the developing device and detecting the toner concentration of the developer in the developing device. ) Is reduced, the downtime of the apparatus due to the time taken to detect the remaining amount of toner is reduced, and fluctuations in image density after the remaining amount of toner is detected are suppressed to form an image with a stable density. be able to.

  Further objects, characteristic configurations and operational effects of the present invention will become apparent from the following description.

  The image forming apparatus according to the present invention will be described below in more detail with reference to the drawings.

Example 1
[Overall Configuration and Operation of Image Forming Apparatus]
First, the overall configuration and operation of the image forming apparatus of this embodiment will be described. FIG. 1 is a schematic configuration diagram of an image forming apparatus 100 of the present embodiment. The image forming apparatus 100 is an electrophotographic full-color printer that is provided corresponding to four colors of magenta, cyan, yellow, and black and has four image forming units 1M, 1C, 1Y, and 1Bk. The image forming apparatus 100 includes a document reading device (not shown) connected to the image forming apparatus main body, or four image signals in response to an image signal from a host device such as a personal computer connected to the image forming apparatus main body. A color full-color image can be formed on a recording material (recording paper, plastic film, cloth, etc.). Recording in which the toner images formed on the electrophotographic photoreceptors 2M, 2C, 2Y, and 2Bk as image carriers in the image forming units 1M, 1C, 1Y, and 1Bk are moved to face the electrophotographic photoreceptor. The recording material P is transferred onto the recording material P conveyed by the material carrier 8. This will be described in detail below.

  In this embodiment, the four image forming units 1M, 1C, 1Y, and 1Bk included in the image forming apparatus 100 have substantially the same configuration except that the development colors are different. Accordingly, in the following, unless there is a particular distinction, the subscripts M, C, Y, and Bk attached to the reference numerals to indicate that the element belongs to any one of the image forming units will be omitted, and a general description will be given. .

  The image forming unit 1 is provided with a cylindrical photosensitive member, that is, a photosensitive drum 2 as an image carrier. The photosensitive drum 2 is rotationally driven in the arrow direction in the figure.

  Around the photosensitive drum 2, a primary charger 3 as a charging unit, a developing unit 4 as a developing unit, a transfer charging unit 5 as a transfer unit, and a cleaning device 6 as a cleaning unit are arranged. A laser scanner (exposure device) 7 as an exposure unit is disposed above the photosensitive drum 2 in the drawing. Further, a transfer belt 8 serving as a recording material carrier is disposed facing the photosensitive drum 2 of each image forming unit 1. The transfer belt 8 is wound around a driving roller 9, a tension roller 10, and a driven roller 11. The transfer belt 8 circulates in the direction of the arrow in the figure by driving the drive roller 9, and conveys the recording material P electrostatically attracted to the surface to contact portions (transfer nips) with the respective photosensitive drums 2. A transfer charger is disposed at a position facing the photosensitive drum 2 via the conveyance belt 7.

  When the image forming operation starts, first, the surface of the rotating photosensitive drum 2 is uniformly charged by the primary charger 3. At this time, a charging bias is applied to the primary charger 3 from a charging bias power source. Next, the photosensitive drum 2 is exposed with a laser beam corresponding to the image signal emitted from the exposure device 7. As a result, an electrostatic image (latent image) corresponding to the image signal is formed on the photosensitive drum 2. The electrostatic image on the photosensitive drum 2 is visualized by toner accommodated in the developing device 4 and becomes a visible image. In this embodiment, a reversal development method is used in which toner is attached to the bright portion potential exposed by laser light.

  The recording material P stored in a recording material storage cassette (not shown) is conveyed by the supply roller 14 in accordance with the toner image formation timing, and is electrostatically attracted to the surface of the transfer belt 8.

  For example, when a four-color full-color image is formed, the recording material P is first conveyed to a transfer unit between the photosensitive drum 2M of the magenta image forming unit 1M and the transfer charger 5M. Then, a magenta toner image is transferred onto the recording material P by the action of the transfer charger 5. At this time, a transfer bias is applied to the transfer charger 5 from a transfer power source. Similarly, as the recording material P conveyed by the transfer belt 8 moves to the image forming units, the toner images of the respective colors are sequentially recorded in the cyan, yellow, and black image forming units 1C, 1Y, and 1Bk. Overlaid on the material P. Thus, a full-color image is formed on the recording material P.

  Next, the recording material P is separated from the transfer belt 8 and conveyed to a fixing device 13 as fixing means. The toner on the recording material P is melted and mixed by being heated and pressed by the fixing roller 13a and the pressure roller 13b included in the fixing device 13, and a full-color permanent image is obtained. Thereafter, the recording material P is discharged out of the apparatus.

  Further, the toner remaining on the photosensitive drum 2 without being completely transferred at the transfer portion is collected by the cleaning device 6. Further, foreign matters such as toner adhering to the transfer belt 8 are removed by the transfer belt cleaner 12. Thereby, a series of operations are completed.

  Note that it is also possible to form a single-color or multi-color image of a desired color using only a desired image forming unit.

[Developer and toner supply device]
The developing device 4 and the toner replenishing device 49 for replenishing toner will be described with reference to FIG. In this embodiment, the configurations of the developing device 4 and the toner replenishing device 49 are the same in the image forming units 1M, 1C, 1Y, and 1Bk for all colors. 2, the developing device 4 is shown as a plan view as viewed from above in FIG. 1, and the toner replenishing device 49 is shown as a sectional view along the axial direction of the photosensitive drum 1 (direction perpendicular to the surface movement direction).

  The developing device 4 includes a developing container (developing device main body) 44 in which a two-component developer including non-magnetic toner particles (toner) and magnetic carrier particles (carrier) as main components is accommodated. In the developing container 44, two screws, a first stirring and conveying screw 43a and a second stirring and conveying screw 43b, are arranged as developer stirring and conveying members. A portion of the developing container 44 facing the photosensitive drum 2 is partially opened, and a developing sleeve 41 as a developer carrying member is rotatably disposed so as to be partially exposed from the opening. Inside the developing sleeve 41, a magnet roll (not shown) as a magnetic field generating means is fixedly arranged. The magnet roll has a plurality of magnetic poles in the circumferential direction, attracts the developer in the developing container 44 by the magnetic force and carries it on the developing sleeve 41, and at the developing portion facing the photosensitive drum 2, the developer spikes ( Magnetic brush).

  The developing sleeve 41 and the first and second agitating and conveying screws 43a and 43b are arranged in parallel to each other. The developing sleeve 41 and the first and second agitating / conveying screws 43 a and 43 b are arranged in parallel to the axial direction of the photosensitive drum 2. The inside of the developing container 44 is divided into a first chamber (developing chamber) 44a and a second chamber (stirring chamber) 44b by a partition wall 44d. The developing chamber 44a and the stirring chamber 44b communicate with each other at both ends in the longitudinal direction of the developing container 44 (left end and right end in FIG. 2).

  The first stirring and conveying screw 43a is disposed in the developing chamber 44a, and the second stirring and conveying screw 43b is disposed in the stirring chamber 44b. These first and second agitating and conveying screws 43 a and 43 b are rotationally driven in the same direction via the gear train 54 by the rotation of the motor 52. By this rotation, the developer in the stirring chamber 44b moves to the left in FIG. 2 while being stirred by the second stirring and conveying screw 43b, and then moves into the developing chamber 44a through the communicating portion. Further, the developer in the developing chamber 44a moves to the right in FIG. 2 while being stirred by the first stirring and conveying screw 43a, and then moves into the stirring chamber 44b through the communicating portion. That is, the developer is circulated and conveyed in the developing container 44 while being agitated by the two screws of the first and second agitating and conveying screws 43a and 43b.

  The toner in the developer is charged by the agitation and conveyance as described above. In this embodiment, the toner is replenished from a toner replenishing port 44c provided in the upper part on the upstream end side in the developer transport direction in the stirring chamber 44b. On the right end side of the stirring chamber 44b in the drawing, a window portion for visually checking the internal state from the outside is provided. Further, a magnetic permeability sensor 42 is attached as a toner concentration detecting means for detecting the toner concentration of the developer (mixing ratio of toner and carrier) in the stirring chamber 42. In this embodiment, the magnetic permeability sensor 42 is disposed on the side wall of the developer container 44 upstream of the toner supply port 44c in the developer transport direction in the stirring chamber 44b.

  If the position where the toner is replenished from the toner replenishing device 49 is the most upstream side of the developer circulation, the position where the toner density detection sensor 42 is attached is the most downstream side. That is, the toner concentration detection sensor 42 is arranged so as to detect the concentration of the developer that has been most stirred.

  The developing sleeve 41 is rotationally driven by a motor 51 in the direction indicated by an arrow (counterclockwise) in FIG. The developing sleeve 41 conveys the developer applied in a layered manner on the surface by a regulating blade (not shown) to the developing unit facing the photosensitive drum 1 by its rotation. In the developing unit, the developer on the developing sleeve 41 rises due to the magnetic force of the magnet roll to form a magnetic brush that is in contact with or close to the surface of the photosensitive drum 2. The toner is supplied to the electrostatic image on the photosensitive drum 1 from the developer (two-component developer) thus transported to the developing unit. Thereby, toner selectively adheres to the image portion of the electrostatic image, and the electrostatic image is developed as a toner image. More specifically, when the electrostatic image on the photosensitive drum 2 reaches the developing portion, a developing bias in which an AC voltage and a DC voltage are superimposed is applied to the developing sleeve 41 by a developing bias application power source (not shown). . At this time, the developing sleeve 41 is driven to rotate in the direction indicated by the arrow in FIG. 1 by the motor 51, and the toner in the developer is transferred onto the photosensitive drum 2 according to the electrostatic image on the surface of the photosensitive drum 1 by the above-described developing bias. Metastasize.

  The toner in the two-component developer is consumed by the developing operation as described above. Then, the toner concentration of the developer in the developing container 44 gradually decreases. Accordingly, toner is supplied to the developing container 44 by the toner supply device 49. The toner replenishing device 49 has a toner container (toner replenishing tank, toner storage unit) 46 that stores toner to be replenished to the developing device 4. A toner discharge port 48 is provided at the lower left end of the toner container 46 in the drawing. The toner discharge port 48 is connected to the toner supply port 44 c of the developing device 4. Further, the toner container 46 is provided with a toner replenishing screw 47 as toner replenishing means for conveying the toner toward the toner discharge port 48. The toner supply screw 47 is driven to rotate by a motor 53.

  The rotation of the motor 53 is controlled by a CPU (control means) 61 of an engine control unit 60 provided in the image forming apparatus main body. The rotation time of the motor 53 in a state where a predetermined amount of toner is stored in the toner container 46, and the toner supply screw 47 replenish the developer container 44 through the toner discharge port 48 (toner supply port 44c). A correspondence relationship with the amount of toner is obtained in advance by experiments or the like. The result is stored in ROM 62 (or in CPU 61) connected to CPU 61 as table data, for example. That is, the CPU 61 adjusts the toner replenishment amount to the developing container 44 by controlling (adjusting) the rotation time of the motor 53.

  As will be described in detail later, according to the present embodiment, no special sensors for detecting the remaining amount (presence / absence) of toner in the toner container 46 are provided in the toner container 46 without providing the toner container 46 or the like. It is possible to detect the remaining amount of toner (presence / absence). However, one or a plurality of sensors for detecting whether or not a larger amount of toner than the predetermined amount is stored in the toner container 46 are provided, and measurement is performed in advance corresponding to the state in which the predetermined sensor detects the presence of toner. The toner supply screw 47 may be driven based on the relationship between the amount of toner supplied by the toner supply screw 47 and the rotational speed of the motor 53.

[Toner supply control]
Next, toner supply control by the inductance detection method will be described.

  As described above, the toner in the developing container 44 is reduced by the image forming operation. Therefore, the toner concentration in the developer is reduced. In this embodiment, a magnetic permeability sensor 42 is disposed in the developing container 44 of the developing device 4, and the magnetic permeability of the developer is detected by the magnetic permeability sensor 42 in order to detect the toner concentration of the developer in the developing container 44. Is detected. When the toner concentration in the developer is low, the carrier ratio increases, so that the magnetic permeability of the developer increases and the output level of the magnetic permeability sensor 42 increases.

  As shown in FIG. 3, the magnetic permeability sensor 42 is integrated with the main body portion 42c in a shape in which the detection head 42a is mounted in a columnar shape. A detection signal is exchanged with the CPU 61 of the engine control unit 60 provided in the image forming apparatus main body via the input / output signal line 42b. A detection transformer is embedded in the detection head 42a. The detection transformer includes a total of three windings, one primary winding and two secondary windings including a reference winding and a detection winding. The detection winding is disposed on the top side of the detection head 42a, and the reference winding is disposed on the back side of the detection head 42a with the primary winding interposed therebetween. When a current having a signal having a constant waveform is input from the transmitter provided in the sensor body 42c to the primary winding, the two secondary windings including the reference winding and the detection winding are also caused by electromagnetic induction. A current having a signal with a certain waveform flows. At this time, the detection head 42a determines a signal having a constant waveform from the transmitter and a signal having a waveform having a current flowing from the detection winding by electromagnetic induction by a comparison circuit provided in the sensor body 42c. The density of the magnetic material is detected on the top surface side of the.

  Here, the relationship between the toner concentration of the developer and the output of the magnetic permeability sensor 42 will be described. FIG. 4 shows an example of output characteristics of the magnetic permeability sensor 42. In the illustrated example, the output voltage value is saturated at a large value in the range where the toner density is small, the sensor output gradually decreases as the toner density increases, and the output voltage value is saturated at a small value in the range where the toner density is large. In this embodiment, when the toner concentration is a normal value of 8% (weight%: the same applies hereinafter), the detected output voltage value of the magnetic permeability sensor 42 is adjusted to 2.5V. When the voltage value is around 2.5 V, the detected output value changes almost linearly with respect to the toner density.

  As described above, the developer concentration in the developing device 4 is detected by the magnetic permeability sensor 42. Then, based on the detection result, the toner replenishing device 49 storing replenishing toner is driven to keep the toner concentration in the developing container 44 constant. That is, based on the detection result of the magnetic permeability sensor 42, the CPU 61 determines the rotation time of the motor 53, and rotates the motor 53 by that time. In the ROM 62 (or in the CPU 61), the developer 4 should be replenished from the detection output of the magnetic permeability sensor 42 based on the relationship between the detection output of the magnetic permeability sensor 42 and the toner density of the developer as shown in FIG. Information for obtaining the toner amount is stored as table data or the like. Accordingly, the CPU 61 obtains the number of rotations of the toner supply screw 47 from this information and the table data indicating the correspondence between the rotation time of the motor 53 and the amount of toner to be supplied as described above, and determines the toner supply amount. Can be controlled.

  Normally, in the inductance detection type toner replenishment control, the toner replenishment is performed by obtaining the rotation speed of the toner replenishment screw 47 every time an image forming operation is performed on one recording material P.

  Next, toner supply control by the patch detection method will be described.

  As described above, the inductance detection method may not be able to accurately control the toner density when the charge amount of the toner fluctuates due to environmental fluctuations such as temperature and humidity and deterioration with time. For this reason, in this embodiment, patch detection type toner supply control is also used. That is, in this embodiment, after a predetermined reference latent image is formed on the photosensitive drum 2, the latent image is developed under a predetermined developing condition, whereby a reference toner image (reference toner image, patch image) is formed on the photosensitive drum 1. T is formed. The density of the reference toner image is detected by an image density detecting means (image density sensor) 15. In this embodiment, the image density sensor 15 is disposed opposite to the photosensitive drum 2 in each of the image forming units 1M, 1C, 1Y, and 1Bk. The image density sensor 15 inputs a density signal corresponding to the image density of the reference toner image to the CPU 61. The CPU 61 compares the density signal from the image density sensor 15 with the initial reference signal stored in advance in the ROM 62 (or in the CPU 61), and controls the driving time of the toner replenishing device 49 based on the comparison result.

  More specifically, when a patch latent image for image density detection is formed on the surface of the photosensitive drum 2, a developing bias is applied to the developing sleeve 41 by a developing bias applying power source (not shown). 1 is driven to rotate in the direction indicated by the arrow. Thereby, the patch latent image on the photosensitive drum 2 is developed. The density of the patch image T as a test pattern developed in this way is detected by the image density sensor 15 and read as an image density signal. The CPU 61 compares the value of the image density signal with a reference value and drives the toner replenishing device 49. Typically, it is possible to obtain an appropriate image by controlling the image density by supplying toner so that the output of the image density sensor 15 is always constant. As the image density sensor 15, a general light reflection type optical sensor that detects the amount of reflected light when the patch image T is irradiated with light can be used.

  In the present embodiment, the patch detection method is used at a predetermined timing other than the time of image formation for forming an image to be recorded and output on the recording material P every predetermined period (for example, a predetermined number of image formations). Perform toner replenishment control. As a predetermined timing other than the time of image formation (during non-image formation), during the preparation operation before or after the image forming operation, the recording material and the recording material when the image is continuously formed on a plurality of recording materials are used. There are timings corresponding to those in between. As a result, the toner replenishment control is corrected by the inductance detection method. The toner replenishment control by the patch detection method is not limited to being performed every predetermined period. For example, when the environment detection sensor provided in the image forming apparatus main body detects a predetermined environmental change, or the image forming apparatus This can be done at any timing such as when the power is turned on.

[Detecting remaining toner amount in toner container]
Next, characteristic toner remaining amount (presence / absence) detection in this embodiment will be described.

  In this embodiment, a special sensor for detecting the remaining amount of toner in the toner container 46 is not provided in the toner replenishing device 49 or the like, and is provided for toner replenishment control by the above-described inductance detection method. The remaining amount of toner in the toner container 46 is also detected by using the magnetic permeability sensor 42 and the image density sensor 15 provided for toner supply control by the patch detection method. As a result, it is possible to simplify the apparatus configuration and reduce the cost for a sensor dedicated to detecting the remaining amount of toner.

  In the inductance detection operation for toner replenishment control (normal replenishment mode) by the inductance detection method executed during normal operation, the CPU 61 detects the detection result (detection output) Vsig of the magnetic permeability sensor 42 and the ROM 62 (or in the CPU 61). Is compared with a predetermined threshold value Vlimit stored in the table, and it is determined whether or not Vsig is lower than Vlimit. Therefore, if Vsig <Vlimit, it is determined that sufficient toner still remains in the toner container 46, and the rotation time of the toner replenishing screw 47 is determined.

  On the other hand, when Vsig ≧ Vlimit, it can be determined that the remaining amount of toner in the toner container 46 is decreasing. However, the detection output of the magnetic permeability sensor 42 in the normal replenishment mode may change due to factors other than the toner concentration, such as a change in developer tribo (charged charge amount) and a change in fluidity. For this reason, if the remaining toner amount is determined only by the detected output value of the magnetic permeability sensor 42, the remaining toner amount in the toner container 46 may be erroneously detected.

  Here, it is considered that the detection accuracy of the remaining amount of toner can be improved by detecting the absence of toner in a state in which the toner density is extremely lowered by increasing the threshold value Vlimit. However, when there is actually no toner, the toner density is significantly reduced, so that the image density may be reduced, and the image quality may be impaired.

  Therefore, in this embodiment, when the CPU 61 detects that the detection output Vsig of the magnetic permeability sensor 42 is equal to or higher than the threshold value Vlimit (Vsig ≧ Vlimit) in the inductance detection operation in the normal supply mode, the normal image forming operation is temporarily suspended. Then, the mode shifts to a toner remaining amount (presence / absence) detection mode, which is a special mode for determining the remaining amount (presence / absence) of toner in the toner container 46. Determine the amount.

  In this embodiment, the toner remaining amount (presence / absence) detection mode includes a first step of driving the toner replenishing screw 47 and detecting the toner concentration of the developer in the developing device 4 by the magnetic permeability sensor 42. A second step of forming a patch image T after the first step and detecting the density thereof by the image density sensor 15. In the second step, the detection result of the density of the patch image T is provided. Accordingly, it is determined whether to execute the first step again or end the toner remaining amount (presence / absence) detection mode. In this embodiment, in the first step, when the toner concentration of the developer detected by the magnetic permeability sensor 42 exceeds a predetermined value, the driving of the toner supply screw 47 is stopped and then the second step. Execute. In the second step, when the density of the patch image T detected by the image density sensor 15 is equal to or higher than a predetermined value, the toner remaining amount (presence / absence) detection mode is terminated. Further, in the second step, when the density of the patch image T detected by the image density sensor 15 is lower than a predetermined value, the first step is executed again. In addition, in this embodiment, in the first step, the developer toner concentration detected by the magnetic permeability sensor 42 does not exceed the predetermined value even when the driving time of the toner replenishing screw 47 exceeds the predetermined value. In addition, it is detected that the remaining amount of toner in the toner container 46 has become a predetermined value or less.

  Hereinafter, the toner remaining amount detection mode will be described in detail with reference to FIG.

  When the CPU 61 starts the toner remaining amount detection mode in Step 1, first, the developing device 4 is idled for 2 seconds (the first and second agitating and conveying screws 43a and 43b are rotated. In addition, the inductance is detected by the magnetic permeability sensor 43 and the detection output is read. The detection output of the magnetic permeability sensor 42 at that time is VIref. Then, the CPU 61 uses a value obtained by subtracting 0.15V (corresponding to 0.5% in terms of toner density) from the obtained VIref, that is, VIref−0.15V as a target output value for inductance detection. .

  Next, in step 2, the CPU 61 rotates the toner supply screw 47 (forced toner supply operation), causes the developing device 4 to perform idle rotation, performs inductance detection by the magnetic permeability sensor 42, and reads the detection output. The detection output of the magnetic permeability sensor 42 at that time is VIsig. Then, the CPU 61 determines whether or not VIsig ≦ (VIref−0.15V) is satisfied, and if it is satisfied (that is, the toner concentration of the developer is increased by 0.5% by the forced toner supply operation). When a considerable amount of toner is supplied from the toner container 46 to the developing container 44), the forced toner supply operation and the inductance detection are stopped.

  Next, the CPU 61 forms a patch image T in step 3. Then, the CPU 61 detects the density of the patch image T by the image density sensor 15 and reads the density signal. The image density signal at that time is VPsig. Then, the CPU 61 compares VPsig with a threshold value VPtrg corresponding to a predetermined image density, and determines whether VPsig ≧ VPtrg is satisfied. Then, when VPsig ≧ VPtrg is satisfied (that is, when it is determined that the density of the patch image T is higher than the predetermined value), the CPU 61 determines that there is toner in the toner container 46 and ends the toner remaining amount detection mode. To do.

  On the other hand, if it is determined in step 2 that VIsig ≦ (VIref−0.15 V) is not established, the CPU 61 determines whether or not the integrated time Ttotal of the forced toner supply operation is 40 seconds or less. When Ttotal is 40 seconds or less, forced toner supply operation, inductance detection, and determination of whether or not VIsig ≦ (VIref−0.15 V) is continued. On the other hand, if VIsig ≦ (VIref−0.15 V) is not established even when Ttotal exceeds 40 seconds, the CPU 61 determines that there is no toner in the toner container 46 and ends the toner remaining amount detection mode. Then, the CPU 61 causes the operation unit 16 included in the image forming apparatus main body to display a message such as “no toner” to notify the user that there is no toner in the toner container 46. Note that the CPU 61 may transmit a signal for causing the host device such as a personal computer connected to the image forming apparatus main body to perform the same display as described above, or may record and output the signal on the recording material P. . Further, the same content may be notified by voice through sound generation means provided in the image forming apparatus main body or a host device communicably connected to the image forming apparatus main body. Further, during this display, use of the image forming apparatus (image forming operation) is prohibited.

  If VPsig ≧ VPtrg is not satisfied in step 3, it is determined that the toner density of the developer in the developer container 44 has not yet returned to an appropriate value for image formation, and the process returns to step 1 again. .

  The normal supply mode and the toner remaining amount detection mode are executed by the CPU 61 according to the normal supply program and the toner remaining amount detection program stored in the ROM 62, respectively. The ROM 62 stores threshold data and table data necessary for the normal replenishment mode and the toner remaining amount detection mode.

  The toner container 46 is a unit (toner cartridge, toner bottle) that can be attached to and detached from the toner supply device 49 and the image forming apparatus main body. In this case, when the toner in the toner container 46 runs out, the cartridge is replaced with a new one. The toner container 46 may be fixed to the image forming apparatus main body, and when the toner in the toner container 46 runs out, toner may be separately supplied from the toner supply means to the toner container 46. In this case, the toner supply means for supplying the toner to the toner container 46 may supply the toner to the toner container 46 at a time when the toner in the toner container 46 runs out. The unit (toner cartridge, toner bottle) that can be attached to and detached from the image forming apparatus main body may remain connected to the toner container 46 until the toner (and the toner in the toner container 46) therein is exhausted. (This toner supply unit corresponds to a part of the toner container 46).

  Here, an effect obtained by using both the inductance method and the patch detection method in order to detect the remaining amount of toner in the toner container 46 will be described.

  When the remaining amount of toner in the toner container 46 is detected only by the patch detection method, the following problems may occur. That is, in this case, the patch image T is formed during forced toner replenishment, and the remaining toner amount is detected based on whether or not the obtained image density signal value exceeds a predetermined threshold value. However, since it is difficult to accurately detect the toner concentration of the developer in the developer container 44 based on the density of the patch image T during forced toner replenishment, the toner concentration of the developer in the developer container 44 increases excessively. In image formation after completion of forced toner supply, image defects such as image density overshoot, toner scattering, and fogging may occur.

  It is considered that the above problems can be improved by increasing the frequency of patch detection during forced toner replenishment. Requires downtime. Further, the toner consumption increases by frequently forming the patch image T. Further, when the patch image T is collected by the cleaning 6 as in the image forming apparatus 100 of the present embodiment, the patch image T is frequently conveyed to the cleaning device 6, so that the entire patch image T is cleaned. (Recovery) cannot be completed and cleaning failure such as slipping may occur.

  On the other hand, when the remaining amount of toner in the toner container 46 is detected only by the inductance method, the following problems may occur. That is, in this case, the inductance detection is performed while forcibly supplying toner, and the toner remaining amount detection is performed based on whether or not the obtained signal value exceeds a predetermined threshold value. In this method, the toner concentration of the developer in the developer container 44 can be accurately detected during forced toner replenishment. However, the toner concentration for obtaining the optimum image density depends on the environmental conditions and the usage history of the developer. Due to the difference, it is difficult to measure and know the optimum toner density. Therefore, in image formation after forced toner supply, image density defects, fogging, and toner scattering may occur.

  In contrast, according to the present embodiment, during the forced toner replenishment operation, the toner replenishment operation is performed while accurately detecting the toner concentration of the developer in the developer container 44 by the inductance method. Whether or not to end the toner remaining amount detection mode is determined by temporarily stopping the replenishment operation and confirming the density of the patch image T by the subsequent patch detection method. Therefore, it is possible to restore the toner density for optimal image formation while reducing the formation frequency of the patch image T to the minimum.

  As described above, according to this embodiment, the remaining amount (presence / absence) of toner in the toner container 46 is more accurately detected without providing a special sensor in the toner container 46 that contains toner to be supplied to the developing device 4. be able to. In particular, when toner is forcedly supplied from the toner container 46 to the developing device 4 and the toner concentration of the developer in the developing device 4 is detected to determine the remaining amount (presence or absence) of toner remaining in the toner container 61, To reduce the downtime of the device due to the time taken to detect the remaining amount of toner (presence / absence) and to suppress fluctuations in the image density after detection of the remaining amount of toner (presence / absence), thereby forming an image with a stable density Can do. Thereby, the reliability of the image forming apparatus 100 can be improved.

  In this embodiment, the target output value for inductance detection in step 2 of FIG. 5 is set to VIref−0.15 V. However, the present invention is not limited to this, and environmental conditions in which the image forming apparatus is used, The target output value can be appropriately changed according to the type of developer, usage history, and the like.

  For example, as will be described in detail in Example 2, the charging ability of the carrier to the toner changes and the bulk density of the developer changes between the new developer and the developer deteriorated by use. Usually, a deteriorated developer has a high bulk density. Therefore, for example, by detecting the amount of developer used, the target output value for inductance detection should be set higher for a developer that has deteriorated due to increased usage and lower for a new developer. Can do. As a result, problems such as an image density defect, fogging, and toner scattering after execution of the toner remaining amount detection mode can be prevented more reliably. The developer usage amount information can be detected in the same manner as described in detail in the second embodiment, and a plurality of set inductance detection target output values are appropriately changed according to the detection result. be able to. Similarly, environmental information when executing the toner remaining amount detection mode detected by the environment detection means (temperature / humidity sensor, etc.) in consideration of environmental conditions, changes in the bulk density of the developer depending on the type of the developer, Alternatively, a plurality of set inductance detection target output values can be appropriately changed according to developer type information set automatically or manually.

  In this embodiment, the upper limit value of the total toner replenishment time Ttotal in step 2 of FIG. 5 is set to 40 seconds, but the present invention is not limited to this, and the image forming apparatus is used as described above. The upper limit value can be changed as appropriate according to environmental conditions, developer type, usage history, and the like.

  In addition, the target output value VPtrg for patch detection in step 3 of FIG. 5 can be changed as appropriate according to the environmental conditions in which the image forming apparatus is used, the type of developer, the usage history, and the like. .

  In this embodiment, the inductance method is adopted as the toner concentration detecting means of the developer in the developing container 44, but the invention is not limited to this. For example, a light detection system that detects the amount of reflected light when the developer is irradiated with light may be used. The present invention can be equally applied to any toner concentration detecting means that directly detects the toner concentration of the developer in the developing container 44.

  Further, in this embodiment, in the inductance detection operation for toner replenishment control by the inductance detection method executed during the normal operation, the toner remaining is detected when it is detected that the detection output of the magnetic permeability sensor 42 is equal to or higher than the threshold value Vlimit. The mode is shifted to the amount detection mode, that is, the toner remaining amount (presence / absence) detection mode is executed when the toner density of the developer detected by the magnetic permeability sensor 42 becomes a predetermined value or less. However, the present invention is limited to this. It is not a thing.

  For example, in the patch detection operation for toner replenishment control by the patch detection method executed during the normal operation, when it is detected that the image density signal is equal to or lower than the threshold value (that is, the density of the patch image T is lower than the predetermined density). When it is detected that the toner level is low, the toner remaining amount detection mode may be entered. That is, when the density of the patch image T detected by the image density sensor 15 becomes a predetermined value or less, the toner remaining amount (presence / absence) detection mode may be executed.

  Alternatively, as usage amount information of the toner replenishing device 49, for example, when the cumulative driving time of the toner replenishing screw 47 reaches a predetermined time (that is, it is theoretically estimated that the toner in the toner container 46 is equal to or less than a predetermined value). When the predetermined period elapses), the toner remaining amount detection mode may be entered. That is, when the usage amount of the toner replenishing screw 47 exceeds a predetermined value, the toner remaining amount (presence / absence) detection mode may be executed. In this case, in the same manner as described in the second embodiment, a counting unit that integrates the driving time of the toner replenishing device 49 and a storage medium that stores the integrated value are provided, and the integrated driving time is a predetermined value. In such a case, the remaining toner amount detection mode may be started. The accumulated drive time of the toner supply device 49 may be reset when new toner is supplied to the toner container 46 (or when the toner container 46 is replaced).

Example 2
Next, another embodiment of the present invention will be described. Since the basic configuration and operation of the image forming apparatus according to the present exemplary embodiment are the same as those of the first exemplary embodiment, elements having substantially the same or corresponding functions and configurations as those of the first exemplary embodiment are denoted by the same reference numerals. Detailed description will be omitted.

  In this embodiment, the toner container 46 of the toner replenishing device 49 is a toner cartridge that can be attached to and detached from the image forming apparatus main body.

  In this embodiment, when it is detected that there is no toner in the toner container 46 by the toner remaining amount detection mode described in the first embodiment, the toner remaining amount detection mode is changed to the new toner container 46 and then the toner remaining amount detection mode is set again. Do it automatically. That is, when part or all of the toner container 46 is a cartridge that can be attached to and detached from the image forming apparatus main body, when the replacement of the cartridge is detected by the replacement detection unit that detects that the cartridge has been replaced. The toner remaining amount (presence / absence) detection mode can be executed.

  More specifically, in this embodiment, as in the first embodiment, when it is detected that there is no toner in the toner container 46 by the toner remaining amount detection mode, the “toner” is displayed on the operation unit 16 provided in the main body of the image forming apparatus. A message for notifying that there is no toner in the toner container 46 such as “None” is displayed. While this display is being performed, the use of the image forming apparatus is prohibited.

  In the present exemplary embodiment, the image forming apparatus 100 opens the inside of the image forming apparatus main body, and an open / close member (front door) that allows the toner container 46 to be replaced. Not shown). Then, after opening the front door and replacing the toner container 46 with a new one, when the front door is closed again, the door open / close detection sensor detects the opening / closing of the door and inputs the detection signal to the CPU 61. As a result, the CPU 61 determines that the toner container 46 has been replaced. When the CPU 61 determines that the toner container 46 has been replaced in this way, the CPU 61 automatically performs the toner remaining amount detection mode along the flow of FIG. 5 described in the first embodiment.

  When the CPU 61 detects that there is toner in the toner container 46 in the toner remaining amount detection mode, the CPU 61 cancels the use prohibition of the image forming apparatus and enables normal use. Further, when it is detected that there is no toner in the toner container 46 by the toner remaining amount detection mode, the operation unit 16 provided in the image forming apparatus main body again notifies the operator that there is no toner in the toner container 46. Display a message. In this case, it is conceivable that a new toner container 46 is not mounted, the toner container 46 is not mounted correctly, or the replaced toner container 46 is empty. While this display is being performed, use of the image forming apparatus is prohibited.

  As described above, according to this embodiment, when it is detected that there is no toner in the toner container 46 by the toner remaining amount detection mode, the toner remaining amount detection mode is automatically performed again after replacement with a new toner container 46. It was. As a result, the same effects as those of the first embodiment can be obtained, and it is possible to accurately determine whether or not the new toner container 46 is correctly mounted, and stable image formation can be performed even after the toner container 46 is replaced. Can be performed.

  In this embodiment, in order to detect the replacement of the toner cartridge, the open / close detection sensor for detecting the opening / closing of the door is used. However, the present invention is not limited to this, and the replacement of the toner cartridge can be detected. Any means can be used as long as it is present.

Example 3
Next, still another embodiment of the present invention will be described. Since the basic configuration and operation of the image forming apparatus of the present embodiment are the same as those of the first embodiment, elements having substantially the same or corresponding functions and configurations as those of the first and second embodiments are denoted by the same reference numerals. A detailed description is omitted.

  In general, it is known that at the end of the life of a developer, the charging performance of the carrier is lowered due to the deterioration of the carrier.

  In such a case, when the forced toner supply in the toner remaining amount detection mode in the first exemplary embodiment is performed, the supplied toner may not be sufficiently charged, and fogging and toner scattering may occur. Further, when patch detection is performed in a state where the replenished toner is not sufficiently charged, the toner concentration of the developer in the developer container 44 has not yet recovered to the optimum toner concentration for image formation. Nevertheless, there is a concern that the remaining amount of toner may be erroneously detected by increasing the density of the patch image T or increasing the patch image T by a slight change in toner density.

  Therefore, in this embodiment, before the patch image T is formed in Step 3 of FIG. 5 described in Embodiment 1 according to the usage history of the two-component developer stored in the developing device 4, The idling operation of the developing device 4 (the first and second agitating and conveying screws 43a and 43b are rotated. At this time, the developing sleeve 41 is also driven) is performed. That is, the developer in the developing container 44 is stirred.

  As shown in FIG. 6, in this embodiment, the measuring means for measuring the usage time as the usage amount information of the developer stored in the developing device 4 and the storage for storing the integrated value of the usage time. A non-volatile memory is provided as a medium, and it is determined whether or not to perform the idling operation of the developing device 4 based on the accumulated usage time of the developer stored in the non-volatile memory. In this embodiment, the CPU 61 has a function of a counting means for the developer usage time. In this embodiment, a readable / writable RP-ROM (hereinafter referred to as “memory”) 45 is installed as a storage medium. The memory 45 is electrically connected to the CPU 61 by setting the developing device 4 in the image forming apparatus main body, and the usage time information of the developer in the developing device 4 can be read and written from the CPU 61. If the developing device 4 (developing container 44) is replaced, the accumulated usage time is newly accumulated in the memory 45. Alternatively, the accumulated usage time may be reset when the developer in the developing device 4 (developing container 44) is replaced.

  The storage medium is not limited to a nonvolatile memory, and any storage medium can be used. For example, a volatile memory and a backup battery may be used in combination. Further, a storage medium (memory) for storing developer usage time information may be provided in any other part such as in the engine control unit 60. Furthermore, in this embodiment, the accumulated usage time of the developer is obtained by counting the accumulated drive time of the developing device 4 (more specifically, the drive time of the first and second agitating and conveying screws 43a and 43b). In addition, an arbitrary index correlated with the usage amount of the developer, that is, information corresponding to the cumulative usage time of the developer in the developing device 4 can be used as the cumulative value of the usage time of the developer.

  In other words, in this embodiment, the remaining toner amount (presence / absence) detection mode is the same as in the first embodiment, in which the toner supply screw 47 is driven and the toner ratio of the developer in the developing device 4 is detected by the coincidence rate sensor 42. 1 and a second step in which a patch image T is formed after the first step and the density is detected by the image density sensor 15. In this embodiment, the toner remaining amount (presence / absence) detection mode further detects the toner remaining amount (presence / absence) after the driving of the toner supply screw 47 in the first step is stopped and before the second step. There is a third step of stirring the developer in the developing device 4 for a predetermined time based on the usage amount information of the developer in the developing device 4 at the time when the mode is started. In particular, in the present embodiment, the third step is executed when the accumulated usage time of the developer is a predetermined time or more as the usage amount information of the developer.

  Hereinafter, the toner remaining amount detection mode in this embodiment will be described in detail with reference to FIG.

  As in the first embodiment, when the CPU 61 starts the toner remaining amount detection mode in Step 1, first, the developing device 4 is idled for 2 seconds, and the inductance detection operation by the magnetic permeability sensor 42 is performed, and the detection output is read. . The detection output of the magnetic permeability sensor 42 at that time is VIref. Then, the CPU 61 uses a value obtained by subtracting 0.15V (corresponding to 0.5% in terms of toner density) from the obtained VIref, that is, VIref−0.15V as a target output value for inductance detection. . The CPU 61 always counts the usage time of the developing device 4 (more specifically, the driving time of the first and second agitating / conveying screws 43a and 43b). The accumulated usage time of the developing device 4 at the time of starting the remaining amount detection mode is held in the memory 45, and the driving time of the developing device 4 is continuously counted.

  Next, in step 2, the CPU 61 rotates the toner supply screw 47 (forced toner supply operation), causes the developing device 4 to perform idle rotation, performs inductance detection by the magnetic permeability sensor 42, and reads the detection output. The detection output of the magnetic permeability sensor 42 at that time is VIsig. Then, the CPU 61 determines whether or not VIsig ≦ (VIref−0.15V) is satisfied, and if it is satisfied (that is, the toner concentration of the developer is increased by 0.5% by the forced toner supply operation). When the toner to be supplied is supplied from the toner container 46 to the developing container 44), the forced toner supply operation and the inductance detection are stopped.

  Next, in step 3, the CPU 61 reads the accumulated usage time TDev of the developing device 4 at the time when the current toner remaining amount detection mode stored in the memory 45 is started, and whether or not TDev ≧ 50000 seconds is satisfied. Is not established, the process proceeds to step 4 to form the patch image T as it is. On the other hand, when TDev ≧ 50000 seconds is established, the developing device 4 is idled for 15 seconds, and then the process proceeds to step 4 where a patch image T is formed.

  In step 4, the CPU 61 detects the density of the patch image T by the image density sensor 15 and reads the density signal. The image density signal at that time is VPsig. Then, the CPU 61 compares VPsig with a threshold value VPtrg corresponding to a predetermined image density, and determines whether VPsig ≧ VPtrg is satisfied. Then, when VPsig ≧ VPtrg is satisfied (that is, when it is determined that the density of the patch image T is higher than the predetermined value), the CPU 61 determines that there is toner in the toner container 46 and ends the toner remaining amount detection mode. To do.

  On the other hand, if it is determined in step 2 that VIsig ≦ (VIref−0.15 V) is not established, the CPU 61 determines whether or not the integrated time Ttotal of the forced toner supply operation is 40 seconds or less. When Ttotal is 40 seconds or less, forced toner supply operation, inductance detection, and determination of whether or not VIsig ≦ (VIref−0.15 V) is continued. On the other hand, if VIsig ≦ (VIref−0.15 V) is not established even when Ttotal exceeds 40 seconds, the CPU 61 determines that there is no toner in the toner container 46 and ends the toner remaining amount detection mode. Then, the CPU 61 displays a message such as “no toner” on the operation unit 16 provided in the image forming apparatus main body. Further, during this display, use of the image forming apparatus (image forming operation) is prohibited.

  If VPsig ≧ VPtrg is not satisfied in step 4, it is determined that the toner density of the developer in the developer container 44 has not yet returned to an appropriate value for image formation, and the process returns to step 1 again. .

  As described above, according to the present embodiment, during the forced toner replenishment operation, the toner replenishment operation is performed while accurately detecting the toner concentration of the developer in the developer container 44 by the inductance method. The forced toner supply is temporarily stopped, and the density of the patch image T is confirmed by the subsequent patch detection method to determine whether or not to end the toner remaining amount detection mode. Therefore, it is possible to restore the toner density for optimal image formation while reducing the formation frequency of the patch image T to the minimum. In addition, stable image formation can be performed without image density fluctuation, fogging, and toner scattering even after forced toner replenishment.

  Further, in this embodiment, by performing the idling operation of the developing device 4 according to the usage state of the developer after the forced toner replenishment operation in the toner remaining amount detection mode, the charging ability of the carrier is lowered due to long-term use. Even in this case, the toner forcibly supplied to the developing container 44 is sufficiently charged. For this reason, it was possible to greatly suppress the occurrence of fog and toner scattering. Further, since patch detection is performed in a state where the toner replenished to the developing container 44 is sufficiently charged, the density of the patch image T is increased due to poor charging of the toner, or the patch image T is changed due to a slight change in toner density. It becomes possible to prevent erroneous detection of the remaining amount of toner by increasing the toner density.

  As mentioned above, although this invention was demonstrated according to the specific Example, this invention is not limited to the aspect of the said Example. For example, in each of the embodiments described above, toner is supplied from the toner supply device. However, the present invention can be equally applied to the case where the carrier is supplied together with the toner.

  In each of the above embodiments, the density of the patch image T is detected on the photosensitive drum 2. However, the present invention is not limited to this. The patch image T may be detected after being transferred to the transfer belt 8. In this case, the density of the patch image T for each of the image forming units 1M, 1C, 1Y, and 1Bk can be detected by a common image density sensor that is disposed to face the transfer belt 8.

  Further, as is well known to those skilled in the art, an intermediate transfer member (intermediate transfer belt or the like) is used instead of the recording material carrier in the image forming apparatus of each of the above embodiments, and the toner image formed in each image forming unit is intermediate. There is an image forming apparatus in which a primary transfer is performed on a transfer member, and the images are once superimposed, and then collectively transferred onto a recording material. The present invention is equally applicable to such an image forming apparatus. In this case, the density of the patch image T can be detected on the image carrier or intermediate transfer member of each image forming unit. In addition, a plurality of developing units are provided for one image carrier, and a plurality of color toner images are superimposed on the image carrier, or a plurality of color toner images sequentially formed on the image carrier are formed. There is an image forming apparatus that sequentially transfers and superimposes on a recording material or an intermediate transfer member. The present invention is equally applicable to such an image forming apparatus. Of course, the present invention is equally applicable to a monochrome image forming apparatus having a single image forming unit.

  Further, regarding the remaining amount of toner in the toner container, the absence of toner does not mean that the toner has been completely removed, but is determined in advance as an amount at which a desired toner replenishment operation cannot be performed. It also includes that the remaining amount of toner has fallen below a predetermined amount.

1 is a schematic configuration diagram of an example of an image forming apparatus to which the present invention can be applied. FIG. 4 is an explanatory diagram for explaining a developing device and a toner replenishing device to which one embodiment of a toner remaining amount detection mode according to the present invention is applied. It is the schematic which shows an example of a magnetic permeability sensor. It is a graph which shows an example of the output characteristic of a magnetic permeability sensor. It is a flowchart of one Example of the toner remaining amount detection mode according to the present invention. FIG. 7 is an explanatory diagram for explaining a developing device and a toner replenishing device to which another embodiment of a toner remaining amount detection mode according to the present invention is applied. FIG. 10 is a flowchart of another embodiment of the toner remaining amount detection mode according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image formation part 2 Photosensitive drum (image carrier)
4 Developer 15 Image density sensor (Image density detection means)
42 Magnetic permeability sensor (toner concentration detection means)
44 Developing container 46 Toner container 49 Toner replenishing device 61 CPU (control means)

Claims (14)

A developing device that develops an electrostatic image formed on an image carrier using a developer including toner and a carrier, a toner container that contains toner to be supplied to the developing device, and a toner container that contains the toner Toner replenishing means for replenishing the developed toner to the developing device, toner concentration detecting means for detecting the toner concentration of the developer in the developing device, and a reference toner image developed by the developer using the developer. In an image forming apparatus having image density detection means for detecting density,
A first step of driving the toner replenishing means and detecting a toner density of the developer in the developing device by the toner density detecting means; and forming the reference toner image after the first step and forming the density of the reference toner image And a second step of detecting the remaining amount of toner by the image density detecting means. In the second step, the first step is performed according to the detection result of the density of the reference toner image. An image forming apparatus that determines whether to execute the step again or to end the toner remaining amount detection mode.   In the first step, when the toner density of the developer detected by the toner density detecting means becomes a predetermined value or more, the second step is executed after the driving of the toner replenishing means is stopped. The image forming apparatus according to claim 1.   3. The toner remaining amount detection mode is ended when the density of the reference toner image detected by the image density detection means is equal to or higher than a predetermined value in the second step. Image forming apparatus.   The first step is executed again when the density of the reference toner image detected by the image density detection means is lower than a predetermined value in the second step. 3. Image forming apparatus of 3.   In the first step, when the toner concentration of the developer detected by the toner concentration detecting unit does not exceed the predetermined value even when the driving time of the toner replenishing unit exceeds the predetermined value, the toner in the toner container The image forming apparatus according to claim 1, wherein the image forming apparatus detects that the remaining amount is equal to or less than a predetermined value.   After the driving of the toner replenishing means in the first step is stopped and before the second step, the usage amount information of the developer in the developer at the time when the toner remaining amount detection mode is started. The image forming apparatus according to claim 1, further comprising a third step of stirring the developer in the developing unit for a predetermined time based on the image quality.   A storage medium for storing information corresponding to the accumulated usage time of the developer in the developing unit, and when the accumulated usage time at the time of starting the toner remaining amount detection mode is a predetermined time or more, The image forming apparatus according to claim 6, wherein step 3 is executed.   The image forming apparatus according to claim 1, wherein the toner concentration detection unit detects a magnetic permeability of a developer in the developing device.   The image forming apparatus according to claim 1, wherein the toner density detection unit detects a reflected light amount when the developer in the developing unit is irradiated with light.   The image forming apparatus according to claim 1, wherein the image density detection unit detects a reflected light amount when the reference toner image is irradiated with light.   11. The toner remaining amount detection mode is executed when the toner concentration of the developer detected by the toner concentration detection unit becomes a predetermined value or less. Image forming apparatus.   11. The toner remaining amount detection mode is executed when the density of a reference toner image detected by the image density detection unit becomes a predetermined value or less. Image forming apparatus.   11. The image forming apparatus according to claim 1, wherein the toner remaining amount detection mode is executed when a usage amount of the toner replenishing unit exceeds a predetermined value.   Part or all of the toner container is a cartridge that can be attached to and detached from the main body of the image forming apparatus, and has an exchange detection unit that detects that the cartridge has been exchanged, and the cartridge is exchanged. 14. The image forming apparatus according to claim 1, wherein the remaining toner amount detection mode is executed when the toner remaining amount is detected.

Images