JP4827333B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus such as a copying machine or a printer such as an electrophotographic system or an electrostatic recording system in which a developer is attached to a latent image formed on an image carrier to form a visible image. The present invention relates to an image forming apparatus using a two-component developer containing toner and carrier as an agent and provided with a toner replenishing device for replenishing toner.
[0002]
[Prior art]
FIG. 9 shows a schematic cross-sectional configuration of an example of a developing device using a two-component developer containing toner and carrier as a developer. FIG. 10 is a top view of the developing device shown in FIG.
[0003]
In this example, the developing device 2 includes a developing container 10, and a developing sleeve 2 </ b> A serving as a developer carrying member is provided at an opening facing the image carrying member 1. A magnet roller 3 as a magnetic field generating means is fixedly disposed in the developing sleeve 2A.
[0004]
In the developing container 10, an A screw 5 and a B screw 6 are arranged as conveying stirring means for conveying the developer to the developing sleeve 2A. The A screw 5 and the B screw 6 are arranged substantially in parallel, and an inner wall 7 is provided between the A screw 5 and the B screw 6 so as to partition the developer so as not to come and go.
[0005]
As can be understood from FIG. 10, there are no inner walls 7 at both longitudinal ends, and the developer can travel between the A and B screws 5 and 6. The A screw 5 and the B screw 6 are configured to convey the developer in opposite directions.
[0006]
The developing sleeve 2A, the A screw 5 and the B screw 6 are connected by a gear (not shown) or the like, and when the developing sleeve 2A, the A screw 5 and the B screw 6 are rotated in the direction of the arrow, the developer is shown in FIG. It circulates inside without interruption as shown by the arrow.
[0007]
In the vicinity of the B screw 6, an inductance sensor 12 as a toner concentration detecting means is installed. The two-component developer is basically composed of a non-magnetic toner and a magnetic carrier, and the magnetic permeability of the developer is determined by the amount of carrier in a certain volume. Therefore, it is installed to measure the ratio of toner and carrier (hereinafter referred to as “toner concentration”) by measuring the magnetic permeability of the developer with the inductance sensor 12.
[0008]
A toner replenishing device 9 for replenishing a necessary amount of toner is installed above the developing container 10 of the developing device 2. There is a toner supply port 8 slightly downstream of the inductance sensor 12. When toner is used for image formation and the toner concentration in the developer decreases, the amount of decrease in the toner concentration when the developer passes through the inductance sensor 12 is reduced. The required amount of toner is replenished into the developing container 10 from the toner replenishing device 9 through the replenishing port 8, and the toner concentration of the developer is always kept constant.
[0009]
In addition to the inductance sensor described here, an optical density detection type or the like is also used as the toner density detection means 12.
[0010]
A new developing device 2 is prepared with a standard developer that is adjusted in advance to a predetermined toner concentration. When a new developing device 2 is set in the image forming apparatus, the agitating means 5 and 6 rotate for a certain period of time, the developer is evenly distributed to the A screw 5 and the B screw 6, and the developer circulation becomes a steady state. The charge amount is also settled. In this state, the toner density is measured by the toner density detector 12. The value measured at this time is stored in a storage device (for example, a writable EP-ROM) mounted on the developing device, and used as a toner density reference value T unique to the developing device.
[0011]
At the time of controlling the toner density during the printing operation, by comparing the difference between the measured value S and the reference value T, it is possible to know how much the current toner density is deviated from the toner density of the standard developer. The amount of toner to be replenished can be calculated. By providing the developing device with a toner density reference value T specific to the developing device, it is possible to perform optimum toner concentration control for each developing device 2.
[0012]
Then, when the toner replenishment of the toner replenishing device 9 is delayed and the measured value S decreases and reaches a predetermined value (hereinafter referred to as “limit value L”), toner is not replenished from the toner replenishing device 9. When the image forming apparatus is determined to be in the state, the image forming apparatus is stopped, and the toner supply to the toner supply device 9 is requested.
[0013]
[Problems to be solved by the invention]
However, in the above configuration, the following problem may occur with respect to the setting of the limit value L.
[0014]
FIG. 8 is an explanatory diagram showing an example of the transition of the measured value S, where the horizontal axis indicates the number of printed sheets and the vertical axis indicates the toner density measured value S.
[0015]
During normal use, toner density control is performed so that the measured value S converges near the reference value T. However, when a high printing rate image such as a solid image is continuously printed, the toner in the developing device 2 is rapidly consumed, and thus the measured value S temporarily decreases rapidly (Smin). Therefore, unless the limit value L is set at a low position in anticipation of a certain safety factor with respect to Smin, the limit value L suddenly exceeds the limit value L when the high printing rate image is continuous, and the toner replenishing device 9. Even if there is still toner, the image forming apparatus may be erroneously determined to be out of toner and stopped.
[0016]
In order to avoid such erroneous detection, if the limit value L is set to a low developer concentration with a sufficient safety factor, the developer concentration is considerably lowered before the measured value S reaches the limit value L. Therefore, a decrease in image density occurs, and a good image cannot be guaranteed. Further, since image formation and stirring are performed in a state where the amount of toner is low, that is, in a carrier-rich state, carrier deterioration progresses, and when toner is replenished at once when toner is replenished to the toner replenishing device 9 There is a possibility that a fogging image or the like may occur. In this way, if the limit value L is set too high, the possibility of false detection increases, and if it is set too low, the possibility of problems occurring in the image and the developing device increases. It was very difficult to set up.
[0017]
In addition, since one limit value L is always used, it can be determined that the toner is not replenished from the toner replenishing device 9, but it is determined that there is no toner in the developing container 10. Is it a malfunction of the replenishing device 9 (defective toner discharge screw, clogged replenishing port, poor gear transmission, etc.) or a false detection that suddenly exceeds the limit value L when the high printing rate image is continuous? I couldn't tell.
[0018]
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image forming apparatus that can detect the absence of toner and a failure in a developing device having a toner replenishing device without causing erroneous detection or image failure.
[0019]
[Means for Solving the Problems]
  The above object is achieved by the image forming apparatus according to the present invention. In summary, the present inventionAccording to one aspect,
  Stores developer containing toner and carrierPresentAn image container,
  Developer in the developer containerToner insideConcentration to detect densityDetectionMeans,
  Contains tonerDoToner storage containerWhen,
  Based on the toner density detected by the density detecting means so as to keep the toner density at a reference value (T).Toner in the toner containerBy replenishing screwA toner replenishing device for replenishing the developer container;
In an image forming apparatus having
  The accumulated rotational speed of the replenishing screw has not reached the predetermined valueIn the state, the concentrationDetectionDetected by meanstonerWhen the density becomes smaller than a predetermined limit value (L1), it is determined that the toner replenishing device is out of order,
  The accumulated rotational speed of the replenishing screw has reached the predetermined value.In the state, the concentrationDetectionDetected by meanstonerAn image forming apparatus characterized in that when the density becomes lower than a limit value (L2) set to a value higher than the limit value (L1), it is determined that there is no toner in the toner storage container.Will be provided.
  The present invention, according to another aspect,
  A developer container containing a developer including toner and carrier;
  Density detecting means for detecting the toner density in the developer in the developer container;
  A toner storage container for storing toner;
  A toner replenishing device that replenishes the developing container with toner in the toner storage container by a replenishing screw based on the toner density detected by the density detecting means so as to keep the toner density at a reference value (T);
In an image forming apparatus having
  When the toner density detected by the density detecting means becomes smaller than a predetermined limit value (L1) in a state where the cumulative rotation speed of the replenishing screw has not reached a predetermined value, the toner replenishing device fails. Make a warning,
  In a state where the cumulative rotation speed of the replenishing screw has reached the predetermined value, the toner density detected by the density detecting means is higher than a limit value (L2) set higher than the limit value (L1). An image forming apparatus is provided that prompts replacement of the toner container when the toner container becomes smaller.
[0020]
By adopting the above configuration, the present invention does not determine that there is no toner even if the measured value S falls below the limit value L before the toner supply device issues a residual detection signal. Even if the developer concentration in the container is temporarily lowered, it is possible to prevent erroneous detection that erroneously determines that there is no toner even though the toner supply device still has toner.
[0021]
Further, since the limit value L is made effective for the first time after the toner replenishing device issues a residual detection signal, it becomes possible to set the limit value L a little higher, because the developer concentration is too low. Image density reduction and carrier deterioration can be prevented in advance, and a good image can be guaranteed until the end of the toner supply device without toner.
[0022]
In addition, since different limit values L are used depending on the remaining amount of toner in the toner storage container, it is possible to determine whether there is no toner in the toner storage container or whether the toner replenishing device is faulty. Useful warning display greatly improves usability.
[0023]
In this way, it is possible to realize control having both accurate toner absence detection and malfunction detection of the toner replenishing device with a simple configuration.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
The image forming apparatus according to the present invention will be described below in more detail with reference to the drawings.
[0025]
Example 1
FIG. 1 is a schematic configuration diagram of an electrophotographic image forming apparatus showing an embodiment of an image forming apparatus according to the present invention. The image forming apparatus according to this embodiment includes a drum-shaped electrophotographic photosensitive member, that is, a photosensitive drum 1 as an image carrier. The photosensitive drum 1 is rotatable in the direction of the arrow. Around the photosensitive drum 1, a charging device 20 that uniformly charges the photosensitive drum 1, an exposure device 21 that forms a latent image on the photosensitive drum, and the photosensitive drum 1 The developing device 2 for visualizing the latent image on the toner with the toner, the transfer device 22 for transferring the visualized toner image onto the transfer material P, and the cleaning for removing the transfer residual toner remaining on the photosensitive drum 1 A device 24 is arranged. The image forming apparatus also includes a fixing device 23 for fixing the toner image transferred onto the transfer material.
[0026]
FIG. 2 shows the developing device 2 according to this embodiment. In addition, a toner replenishing device 9 is installed in the developing device 2. In this embodiment, the toner replenishing device 9 is a toner cartridge (T-CRG) that is detachably attached to the developing device 2 as shown in FIGS. 2 and 3A and 3B.
[0027]
In FIG. 2, the developing device 2 includes a developing container 10 that stores a developer, and stores a developer in which toner particles and magnetic carrier particles are mixed.
[0028]
An opening is provided in a portion of the developing container 10 that faces and opposes the photosensitive drum 1, and a developing sleeve 2 </ b> A that is a nonmagnetic developer carrier such as aluminum or nonmagnetic stainless steel is provided in the opening. The developing sleeve 2A rotates in the direction of the arrow to carry and convey the developer mixed with toner and carrier to the developing unit. The developer magnetic brush carried on the developing sleeve 2A comes into contact with the photosensitive drum 1 rotating in the developing unit, and the electrostatic latent image on the photosensitive drum 1 is developed.
[0029]
The developing sleeve 2 is a hollow metal sleeve and includes therein a magnet roller 3 which is a magnetic field generating means. In the developing container 10, two screws 5 and 6 of A and B, which are stirring means, are installed. An A screw 5 is disposed substantially parallel to the developing sleeve 2A, and a B screw 6 is disposed on the opposite side of the developing sleeve 2A with respect to the A screw 5. Above the B screw 6, a toner cartridge 9 is detachably attached to the main body of the image forming apparatus.
[0030]
The toner cartridge 9 includes a toner storage container 11 that stores replenishment toner, an agitation device 13 for agitating the toner in the toner storage container 11, and a replenishment screw 14 for conveying the toner to the appropriate amount developing device 2. Have. A replenishing port 16 is provided at the end of the replenishing screw 14 and is connected to the toner replenishing port 8 of the developing device 2 in the image forming apparatus to replenish a required amount of toner into the developing device 2. Since the toner container 11 and the replenishing screw 14 are separated by the inner wall, the toner is transported through a narrow passage toward the replenishing port 16, so that the amount of toner discharged according to the rotation of the replenishing screw 14 is required. It can be adjusted accurately according to.
[0031]
As the toner, a known toner obtained by adding a colorant, a charge control agent and the like to a binder resin can be used. In this embodiment, a toner having a volume average particle diameter of 5 to 15 μm was used. On the other hand, as the magnetic carrier, a ferrite carrier, a resin-coated one or the like is preferably used, and an average particle size of 15 to 70 μm is preferable.
[0032]
Various methods such as light transmission type residual detection and stirring torque detection can be used as the remaining amount detection device of the toner cartridge 9. In this embodiment, the number of rotations of the replenishing screw 14 is integrated and provided in the toner cartridge 9. In addition, a method of storing in a non-volatile memory (EP-ROM) 15 and grasping the remaining amount of toner using the total number of revolutions of the replenishing screw 14 was used. Since the replenishing screw 14 has a small diameter, the amount of toner delivered is substantially proportional to the rotational speed, and the total rotational speed has a linear relationship with the total toner replenishing amount, so that there is an advantage that the remaining amount of toner can be grasped sequentially. When toner discharge progresses and the total number of revolutions reaches a predetermined value, it is determined that “remaining toner is low” and the remaining detection signal is turned ON.
[0033]
Next, the operation of the image forming apparatus according to this embodiment will be described. FIG. 4 is a flowchart showing the operation of the image forming apparatus regarding toner supply.
[0034]
After the power-on (s1) of the main body of the image forming apparatus, the standby state (s2) is entered when a predetermined start-up preparation is completed. When a print signal is received in the standby state, the print operation starts, and the photosensitive drum 1, the charging device 20, the exposure device 21 and the like are sequentially activated (s3). The developing device 2 is on standby until it is time to develop, and the developing device 2 rotates only when developing is performed (s4). Simultaneously with the rotation of the developing sleeve 2A, the screws 5 and 6 in the developing container 10 rotate to start stirring the developer. The exposure device 21 is activated to form a latent image at the time when the rotation of the developing device 2 is settled, and at the same time, the developer concentration is measured to obtain a measured value (signal value) S (s5).
[0035]
  Next, the residual toner information of the toner cartridge 9 is referred to (s6), and the residual detection signal isOFFIn this case, the limit value L1 is selected (s7), the measured value S is compared with the limit value L1 (s9), and if the measured value S> the limit value L1, toner is replenished as usual (s11). When the measured value S <the limit value L1, the toner density of the developing device 2 has decreased unnaturally even though the toner cartridge 9 still has toner, which means that some trouble has occurred in the toner cartridge 9. The image forming apparatus displays a message prompting replacement of the toner cartridge 9 (s14), and stops the operation (s15).
[0036]
  The residual toner information of the toner cartridge 9 is referred to (s6), and the residual detection signal isONIn this case, the limit value L2 is selected (s8), the measured value S is compared with the limit value L2 (s10), and if the measured value S> the limit value L2, toner is replenished as usual (s11). When measured value S <limit value L2, it is determined that the toner cartridge 9 is out of toner, and the image forming apparatus displays a message prompting replacement of the toner cartridge 9 (s16), and stops its operation (s17).
[0037]
After toner replenishment (s11) as usual with measured value S> limit value L (similar to L1 and L2), developing device 2 stops after the latent image has completely passed through developing device 2 (s12). Then, it is determined whether or not there is a remaining number of jobs (s13), and if it is still continuously printed, the image forming apparatus enters the next cycle again, and if there is no remaining number of jobs, returns to the standby state (s2).
[0038]
In the above configuration, FIG. 5 is a graph showing the transition of the measured value S as in FIG. 8 described in the related art. As is apparent from FIGS. 5 and 8, in this embodiment, unlike the case where a constant limit value is always valid, the limit value is switched based on the information of the toner cartridge. By doing so, the limit value (L2) after the residual detection signal of the toner cartridge is turned ON can be set a little higher, and the image density lowers due to the excessively low developer density or the carrier. Deterioration can be prevented in advance, and a good image can be guaranteed up to the end without the toner cartridge.
[0039]
In addition, when the residual detection signal of the toner cartridge is OFF, it is not necessary to detect the absence of toner. Therefore, the limit value (L1) is less than the limit value (L2) in order to avoid erroneous detection during continuous printing of high density images. If the toner cartridge has a malfunction such as a rotation failure or clogging of the replenishing screw, it can be used to detect the malfunction.
[0040]
As described above, according to the configuration of the present invention, different limit values are used depending on the remaining amount of toner in the toner storage container, so whether the toner storage container is out of toner or the toner replenishing device is faulty. Etc. can be discriminated, and the usability is greatly improved by displaying an appropriate warning. In this way, it is possible to realize control having both accurate toner absence detection and malfunction detection of the toner replenishing device with a simple configuration.
[0041]
Example 2
In the first exemplary embodiment, the limit value L is switched based on the residual detection information of the toner cartridge. When the measured value S <the limit value L (L1, L2), there is no toner in the toner storage container or there is a problem with the toner supply device. An example has been described in which an appropriate warning display is made by distinguishing and determining whether or not.
[0042]
In the present embodiment, the first embodiment is developed, and the number of times that the measured value S <the limit value L is continuously obtained for the purpose of more accurate determination (hereinafter referred to as “limit value excess count Z”). And the toner cartridge failure or the absence of toner is determined only when the limit value excess count Z exceeds 3.
[0043]
FIG. 6 is a flowchart illustrating the operation of the image forming apparatus relating to toner supply according to the present exemplary embodiment. Since the power supply is turned on (s1) and the developer concentration is measured to obtain the measured value S (s5), the process is the same as in the first embodiment, and the description is omitted.
[0044]
  After obtaining the measured value S, the residual toner information of the toner cartridge 9 is referred to (s6), and the residual detection signal isOFFIn this case, the limit value L1 is selected (s8), the measured value S is compared with the limit value L1 (s8), and if the measured value S> the limit value L1, toner is replenished as usual (s20). When the measured value S <the limit value L1, the limit value excess count Z is incremented by 1 (s9), and it is determined whether the value of Z is 3 times or less (s10). If it is equal to or smaller than 3, normal operation is continued, and when Z = 3, it is determined that some trouble has occurred in the toner cartridge, and the image forming apparatus displays a message prompting replacement of the toner cartridge (s11). Is stopped (s12).
[0045]
  The residual toner information of the toner cartridge 9 is referred to (s6), and the residual detection signal isONIn this case, the limit value L2 is selected (s13), the measured value S is compared with the limit value L2 (s14), and if the measured value S> the limit value L2, toner is replenished as usual (s20). When the measured value S <limit value L2, the limit value excess count Z is incremented by 1 (s15), and it is determined whether the value of Z is 3 times or less (s16). If it is 3 or less, normal operation is continued, and when Z = 3, it is determined that the toner cartridge is out of toner, and the image forming apparatus displays a message prompting replacement of the toner cartridge (s17), and stops the operation. (S18).
[0046]
When measured value S> limit value L (similar to L1 and L2), the limit value excess count Z is reset to 0 (s19), and the toner is replenished as usual (s20). After completely passing through the developing device 2, the developing device 2 stops (s21), determines whether or not there is a remaining number of jobs (s22), and if it is still to be continuously printed, the image forming apparatus goes to the next cycle again. If there is no remaining number of jobs, the process returns to the standby state (s2).
[0047]
By performing the operation as described above, the measured value S <limit value L (similar to L1 and L2) is determined three times continuously in a state where comparison with the limit value L (similar to L1 and L2) is performed. Since the following determination is made only when the toner concentration is detected, even if a low value is suddenly generated due to the measurement variation of the toner density detecting device, it is not erroneously stopped and the variation factor can be eliminated. It is possible to more accurately determine whether there is a malfunction or no toner.
[0048]
In the present embodiment, the limit value excess count Z is set to 3, but the present invention is not limited to this and may be set to another value.
[0049]
Example 3
FIG. 7 is a schematic cross-sectional view showing the overall configuration of an electrophotographic color printer according to another embodiment of the image forming apparatus of the present invention. The electrophotographic color printer of this embodiment is a four-drum type (inline) printer that has a plurality of image forming units arranged in parallel and adopts an intermediate transfer method.
[0050]
In this embodiment, the electrophotographic color printer includes a plurality of image forming portions Pa, Pb, Pc, and Pd arranged in parallel in this embodiment, and an intermediate transfer belt 40 is disposed below the image forming portion. Is done.
[0051]
The image forming portions Pa, Pb, Pc, and Pd have the same configuration. In each of the image forming portions Pa, Pb, Pc, and Pd, a drum-shaped electrophotographic photosensitive member as a first image carrier, that is, a photosensitive drum. 1 (1a, 1b, 1c, 1d) is rotatably supported and driven to rotate in the direction of the arrow. The primary chargers 20 (20a, 20b, 20c, 20d), the developing devices 2 (2a, 2b, 2c, 2d), and the cleaning devices 24 (24a, 24d) are opposed to the outer peripheral surfaces of the photosensitive drums 1a to 1d in the rotation direction. 24b, 24c, 24d) are arranged.
[0052]
In the primary chargers 20a to 20d, charges of a uniform charge amount are given to the surfaces of the photosensitive drums 1a to 1d. Next, the photosensitive drums 1a to 1d output an exposure unit (not shown) (color separation of a color original image, an imaging exposure optical system, and a laser beam modulated in accordance with a time-series electric digital pixel signal of image information. An electrostatic latent image is formed by receiving image exposure by a scanning exposure system or the like by laser scanning.
[0053]
Further, the electrostatic latent images are visualized by developing devices 2a to 2d each containing developer of four colors such as yellow, magenta, cyan and black (hereinafter referred to as “toner”). The visualized visible image is transferred to a belt-like intermediate transfer body, that is, a second image carrier, that is, an intermediate transfer belt 40 by transfer rollers 22a, 22b, 22c, and 22d arranged at a primary transfer position. .
[0054]
In this way, yellow, magenta, cyan, and black images are sequentially superimposed on the intermediate transfer belt 40 to form a full-color image.
[0055]
The intermediate transfer belt 40 is stretched and wound between a driving roller 41 that transmits driving force to the intermediate transfer belt 40, a driven roller 42, and a secondary transfer counter roller 43. A primary transfer plane A is formed between the driving roller 41 and the driven roller 42. As the intermediate transfer belt 40, for example, PET (polyethylene terephthalate), PVdF (polyvinylidene fluoride), or the like is used. The drive roller 41 is coated with rubber (urethane or chloroprene) having a thickness of several millimeters on the surface of the metal roller to prevent slippage with the belt. The drive roller 41 is rotationally driven by a pulse motor (not shown).
[0056]
Further, a cleaning device 45 for cleaning the image forming surface of the intermediate transfer belt 40 is disposed downstream of the secondary transfer position where the transfer roller 44 is disposed facing the secondary transfer counter roller 43 of the intermediate transfer belt 40. Is done.
[0057]
In the image forming apparatus having the above configuration, when an image forming operation start signal is issued, a high voltage is applied to the toner image formed on the photosensitive drum 1a that is the most upstream in the rotation direction of the intermediate transfer belt 40. The image is primarily transferred to the intermediate transfer belt 40 at the primary transfer position by the primary transfer roller 22a. The primarily transferred toner image is conveyed to the next primary transfer roller 22b. In this case, image formation is performed by delaying the time during which the toner image is conveyed between the image forming portions, and the next toner image is transferred by aligning the resist on the previous image. Thereafter, the same process is repeated, and eventually, four color toner images are primarily transferred onto the intermediate transfer belt 40.
[0058]
Thereafter, when the transfer material P enters the secondary transfer position and contacts the intermediate transfer belt 40, a high voltage is applied to the secondary transfer roller 44 in accordance with the passing timing of the transfer material P. As a result, the four color toner images formed on the intermediate transfer belt 40 by the process described above are transferred onto the surface of the transfer material P. Thereafter, the transfer material P is guided to a fixing device (not shown), the toner image is fixed on the surface of the transfer material P, and the transfer material P is discharged out of the apparatus.
[0059]
On the other hand, in each of the image forming portions Pa to Pd, the secondary remaining on the photosensitive drums 1a to 1d without being transferred to the intermediate transfer belt 40 by the cleaning devices 24a, 24b, 24c, and 24d on the downstream side of the transfer position. The transfer residual toner is scraped off to clean the drum surface and prepare for the next image forming step.
[0060]
Also in such a color image forming apparatus, the toner replenishing device 9 (9a, 9b, 9c, 9d) is installed in each developing device 2 (2a, 2b, 2c, 2d) to be used, and will be described in the first and second embodiments. By adopting the same configuration as that described above, the same effect as described in the first and second embodiments can be obtained.
[0061]
In particular, in the case of a color image forming apparatus, four color toners are consumed at different speeds. Therefore, if the accuracy of instructing the replacement of the toner cartridge is poor, it is very troublesome. However, the control according to the present invention, which accurately detects the absence of toner in the toner cartridge, uses up the toner to the end, and does not cause an image defect until just before the stop, is also very effective in a color image forming apparatus.
[0062]
  Less thanAs explained above, the bookExampleComprises a developing container for storing a developer including toner and a carrier, a means for detecting the developer concentration in the developing container, and a toner storing container for storing the toner, and the toner in the toner storing container is removed from the developing container. A toner replenishing device for replenishing an appropriate amount in the developer container, and a toner replenishing device having a developer concentration in the developing container that is smaller than a predetermined limit value (L). In the image forming apparatus that determines that the toner is not replenished, the limit value (L) has a plurality of levels, and one value is selected according to the remaining amount of toner in the toner storage container. Because it is configured to use
(1) Since the toner supply device does not determine that there is no toner even if the measured value S falls below the limit value L before issuing the residual detection signal, the developer concentration in the developing device is temporarily increased in continuous printing of high density images. Even if the toner drops suddenly, it is possible to prevent erroneous detection that erroneously determines that there is no toner even though the toner supply device still has toner.
(2) Since the limit value is made effective for the first time after the toner replenishing device outputs a residual detection signal, it is possible to set the limit value slightly higher, and an image caused by excessively low developer concentration Density reduction and carrier deterioration can be prevented in advance, and a good image can be guaranteed until the end of the toner replenishing device without toner.
(3) Different limit values are used depending on the amount of toner remaining in the toner storage container, so that it is possible to distinguish whether there is no toner in the toner storage container or the toner replenishing device is faulty. Useful warning display greatly improves usability.
(4) In this way, it is possible to realize control having both accurate toner absence detection and malfunction detection of the toner replenishing device with a simple configuration.
【The invention's effect】
  As described above, according to the present invention, different limit values are properly used according to the remaining amount of toner in the toner storage container. Therefore, it is distinguished whether there is no toner in the toner storage container or the toner replenishing device is defective. It becomes possible to make a judgment, and the usability is greatly improved by displaying an appropriate warning. In this way, it is possible to realize control having both accurate toner absence detection and malfunction detection of the toner replenishing device with a simple configuration.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an embodiment of an image forming apparatus according to the present invention.
FIG. 2 is a schematic configuration diagram of an embodiment of a developing device used in the image forming apparatus of the present invention.
FIG. 3 is a schematic configuration diagram of an embodiment of a toner replenishing device (toner cartridge) used in the image forming apparatus of the present invention.
FIG. 4 is a flowchart of an embodiment illustrating the operation of the image forming apparatus of the present invention.
FIG. 5 is an explanatory diagram showing a transition of a signal value (measured value) S;
FIG. 6 is a flowchart illustrating another example of the operation of the image forming apparatus of the present invention.
FIG. 7 is a schematic configuration diagram of another embodiment of the image forming apparatus according to the present invention.
FIG. 8 is an explanatory diagram showing a transition of a conventional signal value S.
FIG. 9 is a cross-sectional view of a conventional developing device.
FIG. 10 is a plan view of a conventional developing device.
[Explanation of symbols]
1 Image carrier (photosensitive drum)
2 Development device
2A developer carrier (developing sleeve)
3 Magnetic field generation means (magnet roller)
4 Developer regulating member
5 A screw
6 B screw
7 inner wall
8 Toner supply port
9 Toner supply device (toner cartridge)
10 Developer container
11 Toner container
20 Charging device
21 Exposure equipment
22 Transfer device
23 Fixing device

Claims (8)

And the current image container you accommodating a developer comprising a toner and a carrier,
Density detecting means for detecting the toner density in the developer in the developer container;
A toner storage container for storing toner ;
A toner replenishing device that replenishes the developing container with toner in the toner storage container by a replenishing screw based on the toner density detected by the density detecting means so as to keep the toner density at a reference value (T) ;
In an image forming apparatus having
When the toner density detected by the density detecting means becomes smaller than a predetermined limit value (L1) in a state where the cumulative rotation speed of the replenishing screw has not reached a predetermined value, the toner replenishing device fails. Judging
In a state where the cumulative rotation speed of the replenishing screw has reached the predetermined value, the toner density detected by the density detecting means is higher than a limit value (L2) set higher than the limit value (L1). An image forming apparatus that determines that the toner container is out of toner when the toner container becomes smaller. A developer container containing a developer including toner and carrier;
Density detecting means for detecting the toner density in the developer in the developer container;
A toner storage container for storing toner;
A toner replenishing device that replenishes the developing container with toner in the toner storage container by a replenishing screw based on the toner density detected by the density detecting means so as to keep the toner density at a reference value (T);
In an image forming apparatus having
When the toner density detected by the density detecting means becomes smaller than a predetermined limit value (L1) in a state where the cumulative rotation speed of the replenishing screw has not reached a predetermined value, the toner replenishing device fails. Make a warning,
In a state where the cumulative rotation speed of the replenishing screw has reached the predetermined value, the toner density detected by the density detecting means is higher than a limit value (L2) set higher than the limit value (L1). An image forming apparatus that prompts replacement of the toner container when the toner container becomes small. 3. The image according to claim 1, wherein when the toner density detected by the density detecting means becomes smaller than the limit value (L1) continuously a plurality of times, it is determined that the toner replenishing device is out of order. Forming equipment. The toner of the toner storage container is determined to be out of toner when the toner density detected by the density detection means becomes smaller than the limit value (L2) continuously several times . Any image forming apparatus. The toner replenishing device, any image forming apparatus according to claim 1-4, characterized in that the cartridge which is detachably attached to the apparatus main body of the image forming apparatus. 6. The image forming apparatus according to claim 5 , wherein a display prompting replacement of the cartridge is performed after determining that the toner container is out of toner or after determining that the toner supply device is out of order. The image forming apparatus according to claim 6 , wherein the operation is stopped after the display for prompting replacement of the cartridge is performed. The cartridge includes a replenishment screw that conveys toner in the toner storage container to the developer container, and a non-volatile memory that accumulates and stores the rotation speed of the replenishment screw, and is stored in the memory. 8. The image forming apparatus according to claim 6 , wherein when the total number of rotations of the replenishing screw reaches a predetermined value, it is determined that the remaining amount of toner in the toner storage container has become a predetermined amount or less.

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