JP4523345B2 - Developing device and image forming apparatus - Google Patents

Description

  The present invention relates to a developing device and an image forming apparatus, and more particularly to replacement control of a deteriorated developer.

In an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a printing machine, an electrostatic latent image formed on a photosensitive member that is a latent image carrier is subjected to a visible image processing by a developing device, and a visible image is obtained. A recording output can be obtained by transferring to a sheet or the like.
In addition to the configuration in which one photoconductor is provided for only a single color, there is a configuration in which a plurality of photoconductors are provided for forming images of a plurality of colors. In the latter case, a multicolor image including a full color image is formed. Used in cases.

By the way, as a developer used for development, there is a two-component developer in which a toner and a carrier are mixed in addition to a one-component developer containing only a magnetic or non-magnetic toner.
The two-component developer is composed of a toner and a carrier that carries the toner, and the toner can be charged by a frictional charging action that occurs during agitation and mixing so that the toner can be electrostatically attracted to the electrostatic latent image on the photoreceptor. Is done.

  The toner and the carrier may be contaminated by a part of the toner that is repeatedly rubbed and collided by stirring and mixing, and the carrier coating layer may be peeled off. When such a phenomenon occurs, the charging ability of the carrier with respect to the toner gradually decreases, and the fogging phenomenon of the image due to the charging failure of the toner tends to occur. In this case, the fog phenomenon means a phenomenon in which toner charged to a reverse polarity due to a decrease in the charge amount of the developer adheres to a non-image portion of the photoreceptor, and this may cause a decrease in image quality.

  Conventionally, the decrease in toner concentration that causes a decrease in image quality is to detect the magnetic permeability that changes depending on the mixing ratio of the toner with respect to the magnetic carrier when using a two-component developer in which the toner and the magnetic carrier are mixed. The toner density is stabilized by replenishing the toner when the change in magnetic permeability corresponds to the shortage of toner.

  On the other hand, the charging function of the carrier contained in the developer is deteriorated due to a phenomenon such as peeling off of the surface coating layer as described above. For this reason, it is necessary to replace the developer separately from the replenishment of the toner. However, if the replacement is performed for all the developers in the developing device, maintenance labor and cost are increased, and further image formation can be performed. Inconveniences such as an increase in waiting time for the user due to no downtime occur.

  Conventionally, instead of replacing all of the developer described above when preventing image quality degradation, in addition to replenishing new toner, a part of the developer is forced to overflow from the developing device, resulting in a decrease in charging performance. There is a configuration in which the developer is replaced by discharging the developed developer from the developer container and newly replenishing carrier and toner (for example, Patent Document 1).

  If a part of the developer overflows from the developer container, the overflow part may face downward due to the inclination or impact of the device when the user can carry it like a small machine. In some cases, the developer overflows and is discharged. On the contrary, if the developer is replenished but the overflow does not occur properly, the amount of the developer may be extremely increased. Even if such an inclination of the overflow portion does not occur, the amount of overflow may not be constant due to the powder surface not being constant due to the flow of the developer during normal use. The dosage may vary. Moreover, such instability of the developer amount is not limited to the movement of the developing device, but also occurs at the overflow portion or the replenishment portion of the developing device.

  On the other hand, when the developer is not replaced, the amount of the developer may change significantly from the steady state due to carrier adhesion or damage to the device over time.

Changes in the developer amount cause the following problems.
Stabilization of the developer amount is a precondition for determining the mixing ratio of the toner to the carrier contained therein. Therefore, if the developer amount fluctuates, a toner concentration sensor whose magnetic permeability is to be detected is used. When the detection output from the toner concentration sensor is high, the actual toner concentration is low and the developer amount. When the detected output is low, it may not be possible to distinguish between the case where the actual toner density is high and the case where the developer amount is small. That is, since the bulk density varies depending on the amount of developer that contacts the toner density sensor, an excessive or insufficient state of the developer may occur even when toner replenishment control is performed according to the detection output. For this reason, if the amount is excessive, the driving load on the developer supplying member is increased. If the amount is insufficient, the developer pumping amount is decreased. As a result, the image reproducibility may be deteriorated, or even if the image is not a solid image, unevenness in image may occur due to unevenness in supply. In addition, when the developer is insufficient, the friction and collision caused by the agitation between the carrier and the toner is likely to be repeated, so that the carrier film is easily peeled off. It may become difficult to proceed or the amount of carrier contacting the toner density sensor may be reduced, so that an accurate toner mixing ratio cannot be detected, and it may be difficult to maintain an appropriate image density.

  Incidentally, an increase in the load on the supply member that occurs when the amount of developer is excessive leads to an increase in the drive torque in the developer supply member, which hinders the normal operating state of the drive unit, and the gear in the drive unit. This causes a problem that damage and wear due to an increased burden on the seal and the like become severe.

  Therefore, it is necessary to stabilize the image quality by increasing the supply amount and the discharge amount of the developer. However, such a measure causes an increase in the consumption amount of the developer, resulting in wasteful consumption of resources.

In view of such problems, particularly problems due to changes in the developer amount, developer requirements for measuring the weight of the developing device and calculating the weight difference between the current time point and the previous time point to maintain the weight of the developing device constant. The structure which performs control is proposed (for example, patent document 2).
Instead of calculating the developer amount from the weight of the developing device, the weight of the developer discharged and collected from the developing device is calculated based on the difference over time, and the developer corresponding to the collected developer amount is replenished Has also been proposed (for example, Patent Document 3).

JP 59-1000047 (Claims) Japanese Patent No. 2891848 (Claims) Patent No. 29986001 (paragraph "0040" column)

  However, in the configurations disclosed in Patent Documents 2 and 3, as a configuration used for indexing the developer amount, a weight measuring device which is a special means for detecting the weight of the developing device or the collected developer Alternatively, it is necessary to specially provide a collected developer amount detection means. For this reason, there is a possibility that adding a component for coping with the variation in the developer amount may lead to an increase in the number of parts and an increase in the number of parts assembly steps.

  The object of the present invention is to solve the above problems in the conventional developing device, in particular, the configuration for detecting the fluctuation of the developer level. It is an object of the present invention to provide a developing device and an image forming apparatus having a configuration that enables supply control to stabilize image quality, save resources, and reduce costs.

According to the first aspect of the present invention, a two-component developer having a carrier and toner adhered to the carrier by frictional charging is brought into contact with the electrostatic latent image to perform a visible image processing, and at least an excess developer. A developing device having a configuration capable of partially discharging to the outside, wherein the toner concentration sensor detects a ratio of toner contained in the two-component developer by a change in magnetic permeability, and the two-component developer. A scraping member which is provided in a developer supply means for transporting the toner toward the electrostatic latent image and can periodically scrape the developer in contact with the toner density sensor, and the two-component development A toner replenishment drive unit for supplying toner contained in the developer, a developer replenishment drive unit for supplying the two-component developer, a discharge drive unit for the two-component developer, and the toner concentration sensor are connected to the input side, Toner on the output side A control unit to which a replenishment drive unit and a developer discharge drive unit are connected, respectively, and the control unit detects an upper limit value and a lower limit of a detection result by the toner density sensor during one rotation of the scraping member. The difference between the upper limit value and the lower limit value based on the detection result by the toner density sensor is the difference between the predetermined upper limit value and the lower limit value so that the difference between the values approaches the difference between the predetermined upper limit value and the lower limit value. When the toner density control is performed, the toner replenishment drive unit is driven to replenish toner, and after the toner density control is performed, the average value of the detection output from the toner density sensor is determined in advance. so as to approach the obtained average value, when the average value by a detection result of the toner density sensor is smaller than the average value set in advance performs a new supply of the two-component developer, It is characterized by performing discharge control in the case of an off come.
According to a second aspect of the invention is characterized by using a developing apparatus according to claim 1 Symbol mounting to the image forming apparatus.

According to the first and second aspects of the present invention, the developer amount is determined by comparing the detection output from the toner density sensor with a preset threshold value, and the developer supply amount corresponding to the result is determined. Since the control unit capable of controlling the discharge amount is provided, the amount control necessary for the replenishment and discharge of the developer can be executed using only the toner density sensor which is an existing component in the developing device. Therefore, it is not necessary to provide a special configuration for determining the developer amount. As a result, it is possible to maintain the stabilization of the toner concentration only by using a simple configuration by eliminating the increase in the number of components and the increase in assembly cost.
In particular, the difference between the upper limit value and the lower limit value of the detection output from the toner density sensor is compared, and at least one of developer replenishment and discharge is controlled so that the difference is equal, or a preset predetermined value By controlling at least one of developer replenishment and discharge so that the above-mentioned difference and / or the average value of the difference are equal, the developer amount is determined while keeping the toner concentration constant. Can do. In other words, assuming that the toner concentration is constant, the developer amount can be based on the change in the magnetic permeability by the toner concentration sensor, and if the developer amount is constant, the toner concentration Can be determined by the change in the magnetic permeability of the toner concentration sensor.

  The best mode for carrying out the present invention will be described below with reference to the embodiments shown in the drawings.

  FIG. 1 is a schematic diagram showing a main part of an image forming apparatus using a developing device according to an embodiment of the present invention. The image forming apparatus described as the present embodiment includes a copying machine, a printer, a facsimile machine, a printing machine, and the like.

  In FIG. 1, an image forming apparatus 1 has a configuration related to the present embodiment, a photosensitive member 2 that is a latent image carrier that carries an electrostatic latent image to be developed, and an electrostatic latent image on the photosensitive member 2. And a developing device 3 for processing a visible image. In addition to the photoreceptor 2 and the developing device 3, the image forming apparatus 1 includes a charging device, a writing device, a transfer device, a cleaning device, and a fixing device for fixing an image after transfer, although not shown. It is.

The developing device 3 uses a two-component developer in which a toner and a magnetic carrier are agitated and mixed to carry a charged toner on the carrier.
The developing device 3 includes a casing 3A that forms a casing of the device, a developing sleeve 3B that is disposed at a position facing the photoreceptor 2 in the casing 3A, and each space that is partitioned by a partition wall 3A1 in the casing 3A. Rotating transport augers 3C and 3D which are arranged inside and have a lead direction capable of transporting the developer in opposite directions, and a doctor blade 3E which defines the layer thickness of the developer carried on the developing sleeve 3B. And.

  In the developing device 3, the electrostatic latent image carried on the photoreceptor 2 is brought into contact with a developer mixed with toner that is agitated and mixed by the conveying augers 3 </ b> C and 3 </ b> D and frictionally charged, and the toner is brought into contact with the electrostatic latent image. The electrostatic latent image is subjected to visible image processing by being electrostatically attracted to the electrostatic latent image.

The developing device 3 in this embodiment has a configuration in which the developer is replaced with a new developer. Hereinafter, this configuration will be described.
In FIG. 1, the casing 3A has a developer replenishing section 4 in the upper part of the space where the conveyance auger 3D adjacent to the conveyance auger 3C that conveys the developer toward the developing sleeve 3B, and the conveyance auger 3D. Developer collecting portions 5 are respectively provided on the wall portions away from the developing sleeve 3B in the rotation direction (in the direction of the arrow in the drawing). The developer supply unit 4 and the developer recovery unit 5 are communicated with a space in which the transport auger 3D is disposed through an opening that penetrates the casing 3A.

FIG. 2 is a diagram showing the configuration of the developer replenishing unit 4 and the developer collecting unit 5 for the developing device 2, in which the developer replenishing unit 4 is a toner feeding pipe for feeding only toner. One end of 4A1 and one end of developer feeding pipe 4B1 for feeding a developer consisting of only the carrier or a carrier mixed with a small amount of toner are connected to face each other with an opening in casing 3A. .
Each of the toner feeding pipe 4A1 and the developer feeding pipe 4B1 is provided with a conveying screw (indicated by reference numeral 4A10 for only one conveying screw in FIG. 1). The toner can be transported while being agitated and mixed in the axial direction by being rotationally driven by a toner transport motor 4A2 and a developer transport motor 4B2 provided at the other end of each of the pipes 4A1 and 4B1.

In FIG. 2, a toner cartridge 4A and a carrier cartridge (including a case where a developer mixed with a small amount of toner is used) 4B are connected in the middle of each of the feed pipes 4A1 and 4B1, and are accommodated inside. A developer replenishing unit 4 that discharges only the toner or carrier that is being mixed or a developer mixed with a small amount of toner, and the discharged toner, carrier, or developer communicates with the inside of the casing 3A as the conveying screw rotates. It is designed to be conveyed.
As shown by an arrow A in FIG. 1, the toner or carrier or developer from the developer replenishing section 4 is dropped into the space where the conveyance auger 3D is arranged.

On the other hand, the developer recovery unit 5 includes a recovery chamber 5A having a space communicating with a space where the transport auger 3D in the casing 3A of the developing device 3 is disposed. One end of the pipe 6 is connected. Disposed inside the developer discharge pipe 6 is a discharge screw 5C that is rotationally driven by a developer discharge motor 5B.
The other end of the developer discharge pipe 6 communicates with the inside of a developer recovery container 7 that is detachably attached to the developing device 3.
The developer discharge motor 5B sets the rotation timing and the rotation amount in a control unit (a member indicated by reference numeral 100 in FIG. 9), thereby allowing the developer discharged in the developer discharge pipe 6 to be filled. The developer can be recovered by moving it toward the developer recovery container 7. In this embodiment, the toner cartridge 4A, the carrier cartridge 4B, and the developer collection container 7 provided in the developer collection unit provided in the developer supply unit 4 are all detachable from the developing device 3. The toner cartridge 4A and the carrier cartridge 4B are replaced with new ones when the stored toner, carrier or developer is consumed, and the developer recovery container 7 is full. Emptyed out.

The toner concentration of the developer accommodated in the developing device 3, that is, the mixing ratio of the toner in the developer, is a toner concentration sensor embedded in the casing 3A and having a detection surface facing the outer peripheral portion of the transport auger 3D. 8 is determined by detecting a change in magnetic permeability. When the mixing ratio is determined, toner replenishment control is executed according to this result.
Further, the detection of the image density is performed by the image density sensor 9 facing the photoconductor 2, and toner replenishment control is performed when it is determined that the toner density is low according to the result. The image density sensor 9 used in this embodiment is an optical sensor that can detect light irradiated from a light emitting element and reflected on the photoreceptor 2. Usually, the image density sensor 9 using an optical sensor often detects the toner density in the image area, but in this embodiment, by detecting the amount of reflected light on the non-image area of the photosensitive member 2, the image density sensor 9 other than the image area is detected. It is used to determine the degree of developer deterioration by detecting the amount of poorly charged toner adhering to the toner.
As a means for conveying toner and developer for the feeding pipes 4A1 and 4B1 and the developer discharging pipe 6 provided in the developer replenishing section 4 and the developer collecting section 5, suction is used instead of a screw. It is also possible to adopt a conveyance form using negative pressure by a pump.

  In FIG. 2, the toner concentration sensor 8 is disposed on a substantially bottom surface of the casing 3 </ b> A corresponding to the lower side in the gravity direction of the casing 3 </ b> A, and is provided at a position where the developer is easily collected when the developer moves. This makes it possible to inevitably make contact with the developer by utilizing the movement of the developer in the direction of gravity, and accurately detects a change in permeability determined by the mixing ratio of the toner with respect to the carrier. Yes.

A part of the conveyance auger 3D that faces the toner density sensor 8 is provided with a scraping member 10 that can scrape off the developer and foreign matters adhering to the detection surface of the toner density sensor 8.
FIG. 3 is a view showing a position where the transport augers 3 </ b> C and 3 </ b> D are accommodated in the developing device 3 in order to explain the configuration of the scraping member 10.
In FIG. 3, the casing 3A is provided with a partition wall 3A1 between the respective transport augers 3C and 3D, which constitutes a space that is removed from the vicinity of both ends in the axial direction of the transport augers 3C and 3D and serves as a developer movement path. Yes, as the direction of rotation of the transport augers 3C and 3D is the direction in which the developer moves in the opposite direction, as shown by the arrows, toward the adjacent spaces near both ends in the axial direction of the transport augers 3C and 3D. The flow direction is switched and the developer circulates.

As shown in FIG. 3 (B), a part of the transport auger 3D in the axial direction is fixed to the rotary shaft 3D1 in which the spiral fins constituting the auger are integrated by using an adhesive or a tape. There is provided a film-like scraping member 10 having
The scraping member 10 is made of a resin film that is softer than the hardness of the detection surface of the toner concentration sensor 8 and rubs the detection surface of the toner concentration sensor 8 to remove the developer and foreign matter adhering to the detection surface. The detection surface is not damaged when scraped and rubbed.

  In the developing device 3, toner replenishment control is performed on the basis of a change in detection output from the toner density sensor 8, in other words, a change in magnetic permeability due to a change in toner mixing ratio, and a developer amount control is also performed. To do. That is, when the amount of poorly charged toner adhering to the non-image portion of the photoreceptor 2 is increased by the image density sensor 9, the developer needs to be replaced. For this reason, when the developer is replenished and discharged, the developer amount changes, and accordingly, a constant amount of developer, which is a precondition for controlling the toner density, may not be maintained. Therefore, in this embodiment, when the developer amount is made constant, the developer amount is controlled using only the toner concentration sensor 8 without providing a special developer amount detecting means. This will be described below.

FIG. 4 is a diagram showing the relationship between the output of the toner density sensor 8 and the toner density when the change in magnetic permeability is a detection target.
Normally, when the magnetic permeability is to be detected, as shown in FIG. 4 and FIG. 5 described later, the detection output of the toner concentration sensor 8 according to the amount of toner (toner concentration) contained in the developer. The average value shows a linear change.

On the other hand, in the developing device 3 of this embodiment in which the developer is replenished and discharged, the detection output shown in FIG. 6 is obtained according to the rotational phase of the scraping member 10 with respect to the toner concentration sensor 8. That is, as indicated by reference numerals (A) to (C) in FIG. 6, the toner density sensor 8 corresponds to the change in the bulk density of the developer contacting the toner density sensor 8 depending on the rotational phase of the scraping member 10. The detection output from changes.
6A shows a state immediately after the scraping member 10 has passed through the toner density sensor 8. In this state, the developer deposited on the periphery of the toner density sensor 8 is scraped off. The bulk density is lowered by being beaten by 10 rotations. As a result, the magnetic permeability decreases, and as a result, the detection output of the toner density sensor 8 shows the lowest lower limit value. The bulk density in this case corresponds to an aggregated state of the developer, and the high bulk density corresponds to a state where the toner and carrier in the developer are easily condensed.
6B shows a state in which the scraping member 10 is at a position facing the toner density sensor 8 with the rotation center interposed therebetween. In this state, FIG. 6A shows the case shown in FIG. In contrast, the developer is collected by the scraping member 10 so that the developer slowly flows toward the detection surface of the toner density sensor 8, and the bulk density is higher than that shown in FIG. Get higher. As a result, the detection output of the toner density sensor 8 shows a steady state that is almost close to the average value.

  On the other hand, FIG. 6C shows a state in which the scraping member 10 approaches the toner concentration sensor 8, and in this state, the developer that contacts the detection surface of the toner concentration sensor 8 increases at a stretch. It will be. For this reason, the density of the developer is concentrated on the detection surface of the toner density sensor 8, and the bulk density is also increased, and the detection output from the toner density sensor 8 is increased by corresponding to the so-called compressed state of the developer. The upper limit value will be indicated.

  While the scraping member 10 continues to rotate, the detection output of the toner density sensor 8 shown in (A) to (C) in FIG. 6 is repeatedly obtained by the rotational phase of the scraping member 10.

FIG. 5 shows the case where the developer bulk density changes as shown in FIGS. 6A and 6B in correspondence with the rotational phase of the scraping member 10 shown in FIGS. FIG. 6 is a diagram schematically illustrating a change in detection output from the toner density sensor 8 when the amount changes.
In the figure, when the amount of developer is larger than that in a steady state (constant developer amount), the developer is easily compressed (condensed) by gravity during the stirring and mixing, so that the bulk density increases, and the toner concentration sensor 8 The detection output becomes high in combination with an increase in the amount of developer in contact with the toner.
On the other hand, when the amount of the developer is small, air is easily mixed between the carrier and the toner in the developer at the time of stirring and mixing, so that the bulk density is reduced and the developer in contact with the toner concentration sensor 8 is contacted. The detection output is lowered in combination with a decrease in the amount of the signal.

When the present inventor constructs the control configuration, the change in the detection output of the toner concentration sensor 8 corresponding to the developer amount shown in FIG. 5 is targeted for the case where the toner concentration is constant and the case where the toner concentration is changed. As a result of experiments, the results shown in FIGS. 7 and 8 were obtained.
FIG. 7 shows a case where the toner concentration is constant and the developer amount changes, and FIG. 8 shows a case where the toner amount changes when the developer amount is a predetermined amount.
In FIG. 7, when the toner concentration is constant, the flowability of the developer does not change depending on the amount of the developer, and the difference between the upper limit value and the lower limit value of the detection output due to the rotation phase at one rotation of the scraping member 10. It has been found that the average value does not change regardless of the detection output, and the average value translates on the output level (indicated by the symbols VaveA and VaveB in FIG. 7). In this case, the detection output is the detection output at the time of initial setting, and separately from the detection output at the time of detection output performed at a different opportunity from the initial setting, for example, when a new developer is replenished. Both are targeted.

  On the other hand, when the toner density changes in FIG. 8, the difference between the upper limit value and the lower limit value of the detection output due to the rotation phase of the scraping member 10 due to the difference in the fluidity of the developer (reference symbols VppA and VppB in FIG. 8). It was found that the detection output differs depending on the detection output.

  What can be said from the experimental results shown in FIGS. 7 and 8 is that when the toner density is constant and the developer amount changes, the average value may be corrected to be equal to the initially set average value. In addition, when the developer amount is constant and the toner density is changed, the difference between the upper limit value and the lower limit value is set within a predetermined range with respect to the difference between the upper limit value and the lower limit value, and the initial value is set in detail. That is, it is only necessary to set the toner replenishment amount so as to be within the range of the difference between the upper limit value and the lower limit value.

In the present embodiment, based on such experimental results, the control unit 100 having the configuration shown in FIG. 9 executes the different types of control described above using the detection output from only the toner density sensor 8.
In FIG. 9, the control unit 100 uses a microprocessor provided for executing sequence control for image formation, and an image density as a member related to the present embodiment is provided on the input side via an interface (not shown). The sensor 9, the toner density sensor 8, and the agent discharge driving unit 50 are connected, and on the output side, a toner conveying motor 4A2 for supplying toner in the developer supplying unit 4 and a developer conveying motor 4B2 for supplying developer. Are connected to each other. In FIG. 9, the developer transport motor 4B2 is expressed as a carrier transport motor for convenience.
The developer discharge drive unit 50 is provided to drive the developer discharge motor 5B provided in the developer recovery unit 5.

  In the control unit 100, as an initial setting, a difference between the upper limit value and the lower limit value of the detection output from the toner density sensor 8 at a predetermined density and an average value are registered, and these registered values are obtained from the image density sensor 9. This is used for the developer replacement process that is executed when it is determined that the deterioration of the developer has progressed based on the detection output.

  In the developer replacement process, the toner transport motor 4A2 and the developer transport motor 4B2 in the developer supply section 4 and the developer discharge motor 5B in the developer recovery section 5 are selected according to the amount of the developer. In this embodiment, when the detection output from the image density sensor 9 corresponds to the start of replacement, the toner density is first set. A procedure for controlling the developer amount after the control is set.

  In the toner density control, the difference between the upper limit value and the lower limit value of the detection output from the toner density sensor 8 at the time when the developer replacement process is started is initially set to the upper limit value and the lower limit value of the detection output. So as to correspond to the difference between the upper limit value and the lower limit value set in the initial setting. This processing corresponds to the case where the value indicated by the symbol VppB falls within the range of the symbol VppA when the value indicated by the symbol VppA in FIG. 8 is the difference between the initially set upper limit value and lower limit value. .

  When controlling the toner density, that is, when correcting the toner density, the toner conveying motor 4A2 is driven to rotate so that the detection output from the toner density sensor 8 satisfies the above-described conditions, and new toner is fed into the developing device 3. Introduce.

  On the other hand, when the toner density control is completed, the average value of the detection output from the toner density sensor 8 at that time is compared with the initially set average value, and the average of the detection output when the toner density control is completed. A new developer replenishment and / or developer discharge from the developing device 3 is selected such that the value is equal to the initially set average value. This process corresponds to making the average value indicated by the symbol VaveB equal to the average value VaveA when the average value indicated by the symbol VaveA in FIG. 7 is a predetermined average value.

  In the control unit 100, toner density control and developer amount control, that is, the toner transport motor 4A2, the developer transport motor 4B2 and the developer discharge motor 5B which are provided in the developer replenishment unit 4 according to some extent. And the amount of rotation are set respectively.

On the other hand, the control unit 100 has a timer 101 connected to its input side and an alarm device 102 connected to its output side.
The warning device 102 is a device for warning when the developer replacement process is started in the control unit 100 and the developer replenishment or discharging operation does not end even after a predetermined time has elapsed by the timer 101. That is, in the control unit 100, when the difference between the upper limit value and the lower limit value of the detection output from the toner density sensor 8 does not reach the predetermined condition even after the predetermined time has elapsed, or when the average value does not reach the predetermined condition. By giving an alarm, it is possible to let the user know that there are problems such as equipment damage in the apparatus and clogging in the developer movement path.

Since the present embodiment is configured as described above, the operation of the control unit 100 will be described with reference to the flowchart shown in FIG.
It is determined whether or not the developer replacement process is necessary depending on whether or not the detection output from the image density sensor 9 is a predetermined value (ST1). If it is determined that the developer is deteriorated and needs to be replaced, the toner density is changed. It is determined whether the density is a predetermined concentration (ST2).
If the toner density is not at the predetermined density, the toner conveying motor 4A2 is driven until new toner is supplied until the detection output from the toner density sensor 8 corresponds to the initially set density (ST3).

When the toner density reaches a predetermined density, the developer amount is discriminated (shown as “quantity of agent amount” in FIG. 10) (ST4).
The developer amount determination processing uses the above-described comparison processing of the average value of the detection output from the toner density sensor 8 based on the experimental results shown in FIGS. 7 and 8, and determines whether or not the developer amount is small. (ST5) When the amount is small, a new developer is replenished (ST6). When the amount is large, the developer is discharged from the developing device 3 (ST7). As for the processes of steps ST6 and ST7, either one of them is performed alone or both are performed in association with each other.

  It is determined whether a predetermined time has elapsed for the developer replenishment and / or discharge processing (ST8). If the predetermined time has elapsed, an alarm processing is performed (ST9).

  In this embodiment, the description has been made on the assumption that the developer replacement process is performed, but the present invention is not limited to such a premise. That is, even if the developer replacement process is not performed without the recovery unit, the toner density control can be performed using the difference between the upper limit value and the lower limit value of the detection output from the toner density sensor 8. In addition, the developer amount can be determined using the output average value. As a result, even in the case of an apparatus in which the developer is not replaced, the amount of the developer is abnormally decreased due to the attachment of the carrier to the photoconductor due to the deterioration of the developer or the damage of the equipment due to the movement of the apparatus. It is possible to detect a defect and to prevent a decrease in image quality regardless of the presence or absence of the developer replacement process. Further, since an alarm can be given when the apparatus is turned on, it is possible to prevent an unnecessary increase in the number of prints by preventing image formation processing before image quality deterioration.

1 is a cross-sectional view illustrating a configuration of a main part of an image forming apparatus to which a developing device according to an embodiment of the present invention is applied. It is a figure which shows the structure of the developer supply part and developer collection | recovery part used for the image development apparatus by the Example of this invention. 2A and 2B are diagrams for explaining a developer agitation and mixing unit in the developing device illustrated in FIG. 1, and FIG. 2B is an enlarged view of a part indicated by a symbol B in FIG. It is a diagram for explaining the relationship between the output of a toner concentration sensor capable of detecting a change in magnetic permeability and the toner concentration. FIG. 5 is a diagram for explaining a relationship between an output change of the toner density sensor shown in FIG. 4 and a change in developer amount. FIG. 2 is a diagram for explaining a relationship between a rotational phase of a scraping member used in the developing device shown in FIG. 1 and a detection output of a toner density sensor. FIG. 6 is a diagram for explaining an output change of a toner density sensor with respect to a change in developer amount. FIG. 6 is a diagram for explaining the relationship between a change in toner density of a developer and an output change of a toner density sensor. It is a block diagram for demonstrating the structure of the control part used for the image development apparatus shown in FIG. It is a flowchart for demonstrating the effect | action of the control part shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Photoconductor 3 Developing apparatus 3C, 3D Conveying auger 4 Developer supply part 4A Toner cartridge 4B Carrier cartridge 5 Developer collection part 7 Developer collection container 8 Toner density sensor 9 Image density sensor 10 Scraping member 100 Control Part 101 Timer 102 Alarm part

Claims (2)

A two-component developer having a carrier and toner attached thereto by frictional charging is brought into contact with the electrostatic latent image for visual image processing, and at least a part of the excess developer can be discharged to the outside. A developing device having a configuration,
A toner concentration sensor for detecting a ratio of toner contained in the two-component developer by a change in magnetic permeability;
A scraping member provided in developer supplying means for transporting the two-component developer toward the electrostatic latent image and capable of periodically scraping the developer in contact with the toner density sensor; ,
A toner replenishment drive unit included in the two-component developer;
A developer replenishment drive for supplying the two-component developer;
The two-component developer discharge drive unit,
The toner concentration sensor is connected to the input side, and the output side includes a control unit to which the toner replenishment drive unit and the developer discharge drive unit are respectively connected.
The control unit is configured so that the difference between the upper limit value and the lower limit value of the detection result by the toner density sensor during one rotation of the scraping member approaches the difference between the predetermined upper limit value and the lower limit value. Toner that replenishes toner by driving the toner replenishment drive unit when the difference between the upper limit value and the lower limit value detected by the toner density sensor is smaller than the difference between the predetermined upper limit value and lower limit value After the toner density control is performed, the average value based on the detection result by the toner density sensor is set in advance so that the average value of the detection output from the toner density sensor approaches a predetermined average value. A developing device characterized in that when the average value is smaller than a predetermined average value, the two-component developer is newly supplied, and when the average value is larger, discharge control is performed. An image forming apparatus using the developing device according to claim 1.

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