JP2010122537A - Development device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a development device which includes constitution for determining a deterioration in developer by using a change in flowability with the entire developer as a target even when temperature and humidity environment and toner concentration are changed, and which thereby always prevents a degradation in image quality. <P>SOLUTION: The development device 3 which develops an electrostatic latent image to be visible with two-component developer containing toner and carrier includes: a development portion including a developer carrier and a developer regulating member 34 regulating a carried amount of the developer; a developer agitating portion 40 prepared separately from the development portion and storing and agitating the developer collected from the development portion; and circulation portions 41 and 42 making the developer circulate between the development portion and the developer agitating portion 40. The developer agitating portion 40 is provided with an agitating member 45 whose revolving speed is optionally controlled, and a torque sensor 40B which is capable of detecting torque of the agitating member 45, and the development device 3 is provided with configuration 100 for detecting the deterioration in the developer based on an output value of the torque sensor 40B when the revolving speed of the agitating member 45 is caused to change. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a developing device and an image forming apparatus, and more particularly to a stirring mechanism for a two-component 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 as a latent image carrier is subjected to visible image processing by a developing device, and the visible image is converted into a sheet. A recording output can be obtained by transferring to the above.

  As a developer used for development, there is a two-component developer obtained by mixing a toner and a carrier 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 electrostatically attracted to the electrostatic latent image on the photosensitive member by charging the toner by a frictional charging effect that occurs during stirring and mixing. It is said.

  The developing device includes a developing sleeve for supplying a developer toward the electrostatic latent image on the photosensitive member by causing the developer to rise on the peripheral surface by magnetic force, and an agitation for supplying the developer mixed with stirring to the developing sleeve. A configuration including a sleeve is known, and a developer in which toner is consumed for visible image processing of an electrostatic latent image on a photoreceptor is collected by a developing device.

  On the other hand, the toner contained in the developer is an object to be replenished because the image density decreases when consumed, and at the time of replenishment, the upper part or axial end of the conveying screw provided with a screw auger as a stirring sleeve May be replenished in a state of being poured from.

  The toner is replenished by controlling the amount of rotation of a replenishing member that feeds out the toner stored in the toner replenishing portion in accordance with the detection result of the developer concentration by a detecting means such as a toner concentration sensor.

  When the replenished toner is poured into the developer contained in the developing tank, it is agitated and mixed with the carrier by a conveying screw arranged in the vicinity of the replenishing member, and is maintained at a predetermined concentration and is triboelectrically charged. Thus, the toner is supplied to the developing sleeve in a state where a predetermined charge amount is applied.

  When mixing the toner replenished in the developing device with the carrier in the developing device, it is a short time until the replenished toner is pumped up to the developing sleeve which is a developer carrier. When there is a large balance, there may be cases where the replenished toner is stirred and dispersed, and the charging action is not sufficient. For this reason, there is a possibility that the toner with poor charging will adhere to the background on the photosensitive member or may be scattered to the peripheral part, resulting in a decrease in image quality.

  Therefore, a configuration is proposed in which replenished toner and carrier are mixed at a position different from the developing device, and the developer in a state where the amount of stirring is increased and the amount of charge is not insufficient is conveyed to the developing device. ing. (For example, Patent Documents 1 to 3).

  In each of the above patent documents, a developer agitation unit is provided in the circulation path or at a position different from this through the circulation path, and a stirring member such as a screw auger provided in the developer agitation part is used. A configuration is disclosed in which a developer and newly supplied toner are dispersed in the developer and conveyed to a developing device.

  In the configuration disclosed in each of the above patent documents, an increase in stress on development that occurs when agitation is performed in the developing device can be reduced, but on the other hand, by being circulated between the developing devices, the conveyance process thereof is reduced. Therefore, physical stress may occur on the developer.

  The physical stress in this case corresponds to rubbing on the conveyance path, and the developer may be carelessly deteriorated.

  The deterioration of the developer means that the spent external additives are peeled off or buried, the carrier coat film is scraped, and the toner external additives adhere to the carrier surface.

  The deterioration of the developer may cause changes in bulk density, resistance value, fluidity and chargeability as characteristics of the entire developer. Such a change in the developer characteristics due to the deterioration of the developer causes a change in the dispersibility of the toner due to the disturbance of the image density and the deterioration of the fluidity, and the above-mentioned background contamination and scattering when the toner is pumped up to the developing sleeve. As a result, the image quality is degraded.

  Conventionally, in order to cope with such deterioration of the developer, the developer agitating unit detects the change in the developer volume and the change in the pressure with which the developer presses the inner wall of the storage unit to determine the deterioration of the developer. It has been proposed (for example, Patent Document 4).

  Apart from such a configuration intended for a change in developer accommodation, a configuration for detecting a change in the developer by detecting a torque variation in the stirring member of the developer is also proposed (for example, Patent Documents 5 and 6). ).

  In Patent Document 4, a sensor for detecting the volume of the developer in the developing device or a pressure sensor for detecting the pressure of the developer in contact with the inner wall of the developer accommodating portion is provided, and the fluidity that causes the deterioration of the developer is provided. The structure which discriminate | determines the rise change of the volume which arises when it deteriorates, and the rise change of a pressure is disclosed.

  Patent Documents 5 and 6 disclose a configuration for detecting an increase in torque due to deterioration of developer fluidity.

Japanese Patent No. 3733496 Japanese Patent No. 3349286 JP-A-11-143196 JP 2008-76428 A JP-A-11-160978 JP 2008-83409 A

  In the configuration disclosed in the above-described patent document, in the configuration in which a change in pressure or torque is detected, a change in developer fluidity due to an environmental change may be determined as developer deterioration. False detection occurs.

  Therefore, Patent Document 4 that discloses a configuration for detecting pressure fluctuations discloses that temperature and humidity, which are environmental fluctuation factors, are disclosed. Is not taken into consideration, and does not take into account the deterioration of toner concentration, environmental changes such as temperature and humidity, and deterioration of fluidity, which are causes of developer deterioration.

  On the other hand, in Patent Documents 5 and 6 in which a configuration using a torque sensor is disclosed, the mixing ratio between the toner and the carrier contained in the developer, in other words, the bulk fluctuation that changes due to the change in toner concentration and temperature and humidity is not. Because it is only for simple bulk fluctuations, for example, it is for torque fluctuations affected by the goodness of the developer at a position close to the conveying stirring member on the side where the torque sensor is provided. In addition, it is impossible to judge the deterioration of the entire developer.

  An object of the present invention is to develop using the conventional developing device, in particular, the change in fluidity for the entire developer even when the temperature / humidity environment or the toner concentration changes, in view of the problem in determining the deterioration of the developer. It is an object of the present invention to provide a developing device and an image forming apparatus which have a configuration capable of determining deterioration of an agent and can always prevent deterioration of image quality.

In order to achieve this object, the present invention has the following configuration.
(1) A developing device that performs visible image processing of an electrostatic latent image using a two-component developer containing toner and a carrier,
A developing section provided with a developer carrying member and a developer regulating member that regulates the end area of the developer; a developer stirring section provided separately from the developing section and stirring the developer recovered from the developing section; A circulation unit for circulating the developer between the developing unit and the developer stirring unit,
The developer stirring section is provided with a stirring member capable of arbitrarily controlling the rotation speed and a torque sensor capable of detecting the torque of the stirring member, and the torque when the rotation speed of the stirring member is changed. A developing device comprising a configuration for detecting deterioration of a developer based on an output value of a sensor.
(2) In the configuration for detecting the deterioration of the developer, a control unit to which drive control to the stirring member and an output value from the torque sensor are input is used. The developing device according to (1), wherein the deterioration of the developer is determined based on a difference in an output value from the torque sensor by changing a rotation speed of the member.
(3) The developing device according to (1) or (2), wherein the control unit sets a stop time of the developing unit as a time to change the rotation speed of the stirring member.
(4) The control unit is connected to a concentration sensor provided in the circulation path of the circulation unit in addition to the torque sensor, and outputs from the concentration sensor in addition to the output value from the torque sensor. 4. The developing device according to (2) or (3), wherein deterioration of the developer is discriminated using a value (developing apparatus according to 2 or 3).
(5) A temperature / humidity sensor is connected to the control unit in addition to the torque sensor, and the developer is deteriorated by using the output value from the temperature / humidity sensor in addition to the output value from the torque sensor. The developing device according to (2) or (3), wherein the developing device is discriminated.
(6) The control unit is connected to a level sensor capable of detecting the developer powder level in addition to the torque sensor, and uses the output value from the level sensor in addition to the output value from the torque sensor. The developing device according to (2) or (3), wherein deterioration of the developer is discriminated.
(7) The developer agitation unit includes a developer container having a shape that moves the developer in the direction of gravity, and the agitation member is disposed in the developer container and moves the developer in the direction of gravity. The developing device according to any one of (1) to (6), wherein the developing device is configured to be movable.
(8) Replenishing means for replenishing a replenisher containing a carrier or carrier and toner and a collecting means for collecting surplus developer are connected to the control section, and the control section is connected to the developing section. The developing device according to any one of (2) to (7), wherein when the deterioration of the agent is determined, the supply unit is driven to supply the supply agent.
(9) The control unit sets the mixing ratio of the carrier and the toner contained in the replenisher based on the image area ratio or the operating time in the developing unit. The developing device according to any one of the above.
(10) An image forming apparatus using the developing device according to any one of (1) to (9).
(11) The image according to (10), wherein the control unit is capable of adjusting a charging bias, a developing bias, and a writing light power used for image forming processing according to a degree of deterioration of the developer. Forming equipment.
(12) (10) or (11), wherein the control unit is configured to be able to indicate to the outside that the developer has deteriorated when determining the deterioration of the developer. Image forming apparatus.
(13) The image forming apparatus according to any one of (10) to (12), wherein the developer can be replenished by a user.

  According to the present invention, when the deterioration of the developer using the torque sensor is determined, the rotation speed of the stirring member is changed. Therefore, the deterioration of the developer is caused by the generation of torque in the rotation speed range. It is possible to determine the deterioration of the developer only by utilizing the influence on the developer. In particular, the position where the deterioration of the developer is judged is performed not in the developing device but in the developer stirring unit provided at a position different from the developing device. Therefore, it is possible to detect the deterioration of the developer without changing the supply amount of the developer to the latent image carrier.

  In addition, the fluidity of the developer is affected by environmental changes, toner concentration, and the like, and may be in the same state as when the fluidity deteriorates due to factors different from the actual developer degradation. For example, by excluding the change in fluidity caused by factors other than the deterioration factors in the actual developer itself, the deterioration of the developer is determined by using only the above-described developer deterioration and the torque change in the rotation speed range. Therefore, it is possible to prevent false detection caused by a change in liquidity caused by factors other than actual deterioration factors.

  The best mode for carrying out the present invention will be described below with reference to embodiments shown in the drawings. FIG. 1 is a schematic diagram for explaining the configuration of an image forming apparatus using a developing device according to the present invention.

  The image forming apparatus shown in FIG. 1 forms an image corresponding to each color (yellow, magenta, cyan, black) facing the lower surface of an intermediate transfer belt 10A used as an unfixed image carrier used in the intermediate transfer unit 10. The parts 6Y, 6M, 6C and 6K are arranged in parallel. These image forming units 6Y, 6M, 6C, and 6K have the same structure except that the color of the toner used in the image forming process is different. In the following description, only the numerical symbols common to the image forming units will be described, and the alphabetic symbols indicating the toner colors will be omitted.

  Each image forming unit 6 includes a photosensitive drum 1 as a latent image carrier, a charging unit 2, a developing device 3, a cleaning unit 4 and the like disposed around the photosensitive drum 1.

  An image forming process (charging process, exposure process, developing process, transfer process, cleaning process) is performed on the photosensitive drum 1, and a desired toner image is formed on the photosensitive drum 1.

  The photosensitive drum 1 is rotationally driven in the clockwise direction in the drawing by a driving unit (not shown), and the surface is uniformly charged at the position of the charging means 2 (charging process).

  The surface of the photosensitive drum 1 reaches an irradiation position of a laser beam emitted from an exposure unit (not shown), and an electrostatic latent image is formed by exposure scanning at this position (exposure process). When the position reaches this position, a visible image is processed by the toner contained in the developer supplied therefrom, and the development process is executed.

  The surface of the photosensitive drum 1 carrying the toner image that has been subjected to the visible image processing in the development process reaches a position facing the intermediate transfer belt 10A and the primary transfer bias roller 5, and at this position on the photosensitive drum 1. The toner image is transferred onto the intermediate transfer belt 10A (primary transfer step).

  After the transfer, the surface of the photosensitive member 1 reaches a position facing the cleaning unit 4, and untransferred toner remaining on the photosensitive drum 1 is collected at this position (cleaning step). After cleaning, the potential of the surface of the photosensitive drum 1 is initialized by a neutralizing roller (not shown). By passing through such steps, a series of image forming processes performed on the photosensitive drum 1 is completed.

  The image forming process described above is performed at the time of forming a single image of only a monochrome image and at the time of forming a full color image. At the time of forming a full color image, each of the four image forming units 6Y, 6M, 6C, and 6K shown in FIG. Each step is performed. That is, a laser beam based on image information from an exposure unit (optical writing device) (not shown) disposed below the image forming unit is applied to the photosensitive drums of the image forming units 6Y, 6M, 6C, and 6K. Irradiated toward. Thereafter, the toner images of the respective colors formed on the respective photosensitive drums through the developing process are transferred onto the intermediate transfer belt 8 in an overlapping manner. Thus, a color image is formed on the intermediate transfer belt 10A.

  The four primary transfer bias rollers 5Y, 5M, 5C, and 5K respectively sandwich the intermediate transfer belt 10A with the photosensitive drums 1Y, 1M, 1C, and 1K to form a primary transfer nip. The primary transfer bias rollers 5Y, 5M, 5C, and 5K are applied with a transfer bias having a polarity opposite to the polarity of the toner.

  The intermediate transfer belt 10A travels in the direction of the arrow and sequentially passes through the primary transfer nips of the primary transfer bias rollers 5Y, 5M, 5C, and 5K. Thus, the toner images of the respective colors on the photosensitive drums 1Y, 1M, 1C, and 1K are primarily transferred while being superimposed on the intermediate transfer belt 10A.

  The intermediate transfer belt 10A onto which the toner images of the respective colors are transferred in a superimposed manner reaches a position facing the secondary transfer roller 7 as a secondary transfer unit. The color toner image formed on the intermediate transfer belt 10A is collectively transferred onto a transfer sheet P as a recording medium conveyed to the secondary transfer nip position.

  A plurality of transfer sheets P are stored in a paper supply unit 8 disposed in the lower part of the apparatus main body 100, and are separated and fed one by one by a paper supply roller 9. The fed transfer paper P is temporarily stopped by the registration roller pair 10, and after the oblique deviation is corrected, it is conveyed toward the secondary transfer nip by the registration roller pair 10 at a predetermined timing. As described above, a desired color image is transferred onto the transfer paper P at the secondary transfer nip.

  The transfer paper P on which the color image is transferred at the position of the secondary transfer nip is conveyed to the fixing unit 11 where the color image transferred to the surface is fixed by heat and pressure generated by the fixing roller and the pressure roller. The

  After the fixing, the transfer sheet P is discharged as an output image to the paper discharge unit 100A formed on the upper surface of the apparatus main body 100 by the paper discharge roller pair 12 and stacked. Thus, a series of image forming processes in the image forming apparatus is completed. In FIG. 1, reference numeral 13 denotes a cleaning device for the intermediate transfer belt 10A.

  Next, the configuration of the developing device according to the present invention will be described.

  FIG. 2 is a diagram showing the overall configuration of the developing device according to the embodiment of the present invention.

  In FIG. 2, the developing device will be described in detail later. A developing unit that executes a developing process with a two-component developer in which a carrier and a toner are mixed with a photosensitive drum, and a developer collected from the developing unit. A circulation unit that transports the developer again toward the developer supply unit of the development unit is provided.

  In FIG. 2, the developing device 3 includes a developing tank 30 that can store a developer for developing the electrostatic latent image on the photosensitive drum 1, a developer collected from the developing tank 30 at a position away from the developing tank 30, and A developer container 40 serving as a stirring unit for stirring and mixing new toner corresponding to the consumed toner, a toner cartridge 52 for supplying new toner toward the developer container 40, and agitation discharged from the developer container 40 A rotary feeder 50 for transporting the mixed developer, an air pump 51 corresponding to a developer circulation drive source for transporting the developer toward the developer tank 30 by air pressure, and a new toner toward the developer accommodating portion 40 And a toner replenishing unit 60 for replenishing the toner. In FIG. 1, the developing tank 30 is configured in a cartridge shape.

  The developer tank 30 and the developer container 40 are connected by a developer recovery channel 41 and a rotary feeder 50 connected from the developer tank 30 and a developer supply channel 42 connected to the upper part of the developer tank 30. Thus, a developer circulation path is formed, and a circulation portion is formed by members provided in the circulation path.

  As will be described with reference to FIG. 3, the developer supply channel 42 connected to the developing tank 30 is connected to face one end in the axial direction of the transport screw 32. Further, the developer recovery flow path 41 is connected to a position on the opposite side to the side where the developer supply path 42 is connected in the axial direction of the other conveying screw provided in the developing tank 30.

  The developer container 40 has an appearance like a downward conical silo, and a stirring member described in the features of the present embodiment is provided inside. A driving motor 40 </ b> A that forms a driving unit for the stirring member and a torque sensor 40 </ b> B that detects the axial torque of the stirring member are provided above the developer storage unit 40.

  The developer agitated and mixed in the developer container 40 is fed to a rotary feeder 50 that is provided with a paddle that can adjust the supply amount and is driven to rotate by a drive motor 50A, and the supply amount is adjusted at this position. The developer is conveyed toward the developing tank 30 by the air flow generated by the air pump 51.

  The toner supply unit 60 includes a toner tank 61, a toner supply path 62 connected between the toner tank 61 and the developer container 40, and a conveying member such as a screw auger disposed in the toner supply path 62. And a drive motor 63 for driving (not shown).

  The internal structure of the developing tank 30 is shown in FIG.

In FIG. 3, in the developing tank 30, a developing sleeve 31 that bears a developer facing the photosensitive drum 1, and a conveying screw that is disposed in the vicinity of the developing sleeve 31 and has an opposite lead direction set. 32 and 33, and a doctor blade 34 for defining the developer carrying amount on the surface of the developing sleeve 31 are provided.
The developer in the developing tank 30 is transported from the front side to the back side in the drawing by the transport screws 32 and 33, and when a part of the developer is sucked and adsorbed by the magnetic force in the developing sleeve 31, the developer blade is evenly distributed. After being smoothed, the electrostatic latent image on the photosensitive drum 1 is developed with toner by contacting the photosensitive drum 1 to form a toner image.
The developed developer is transported to the developer accommodating section 40 from a developer recovery channel 41 (see FIG. 2) connected to the end of the transport screw 33.

Next, features of the developing device 3 used in the image forming apparatus having the above configuration will be described.
The characteristic of the developing device 3 in the present embodiment is in the deterioration determination of the developer to be stirred and mixed, and the following description corresponds to the embodiments of the inventions of claims 1 to 5 and 10.

  4 and 5 are diagrams for explaining the configuration of the developer accommodating portion used as a characteristic portion of the present embodiment. FIG. 4 shows the developer accommodating portion 40, the rotary feeder 50, and the air pump 51. Has been.

  In FIG. 4, the developer accommodating portion 40 has a funnel-like shape with a longitudinal cross section having a downward conical shape, and the discharge port 400 having the smallest diameter communicates with the rotary feeder 50 at the lowest position. In the developer container 40, the toner is charged by stirring and mixing by a stirring member 45, which will be described later, so that a developer having an appropriate toner concentration and charge amount is continuously applied using a funnel-shaped internal structure. The function that can be supplied stably is demonstrated.

A rotation shaft 43 extending in the vertical direction at the center position in the horizontal cross section and connected to the drive motor 40A is inserted into the internal space of the developer accommodating portion 51 from the upper surface.
The rotation shaft 43 is provided with paddles that are a plurality of stirring members 45 along the direction of gravity, and the stirring members 45 are provided so as to protrude in a relative direction while shifting the phase in the direction of gravity.

  A toner replenishing path 62 used for the new toner replenishing means 60 communicates with the upper surface of the developer accommodating portion 40 from the side of the peripheral wall. A screw auger 61 that is rotationally driven by a drive motor 63 (see FIG. 2) is disposed inside the toner supply path 62. New toner from the toner supply path 62 is poured toward the developer surface layer in the developer container 40.

  The developer mixed with the new toner or the carrier poured into the inside is efficiently stirred in a short time by the rotation of the stirring member 45, and the stress at the time of stirring is also reduced by the structure of the stirring member. ing.

  In FIG. 5, a stirring member provided in a developer container 40 (denoted by reference numeral 40 ′ for convenience) is provided with its rotating shaft 43 set in a direction perpendicular to the direction of gravity. 1 shows a configuration in which a stirring member (indicated by reference numeral 45 'for convenience) is provided. 5A shows a horizontal sectional structure on the stirring member 45 side, and FIG. 5B shows a sectional structure in the direction of gravity. In this case, the developer container 40 ′ has a rectangular cross section in the horizontal direction in order to align a plurality of stirring members in a direction perpendicular to the direction of gravity.

  The rotating shaft 43 of the stirring members 45 and 45 'shown in FIGS. 4 and 5 is connected to the drive motor 40A via the torque sensor 40B.

  The torque sensor 40B is used as a member for detecting the shaft torque by detecting the load acting on the stirring member 45 during the stirring process, and the change in the shaft torque is used for determining the deterioration of the developer.

  The drive motor 40A uses a format that can arbitrarily control the rotational speed, and the rotational speed is set by the control unit 100 described later.

  FIG. 6 is a block diagram for explaining the configuration of the control unit 100. In the figure, the control unit 100 uses a processor capable of managing the density of the developer including a sequence program for image forming processing. ing.

  In FIG. 6, the torque sensor 40B, the stirring member rotation speed sensor 101, the toner concentration sensor 102, the temperature / humidity sensor 103, the level sensor 104 for detecting the bulkiness, and the operation panel 105 are connected to the input unit of the control unit 100. On the output side, the stirring motor driving means corresponding to the driving motor 40A, the toner replenishing means 60, that is, the driving motor for the screw auger 61, the charging means 106, the developing bias means 107, the writing means 108, and the developing device driving means. 109 is connected.

  Among the units connected to the output side, the charging bias unit 106, the developing bias unit 107, the writing light source 108, and the developing device driving unit 109 are used in the charging device 2 and the developing device 3 shown in FIG. A drive motor for each member such as a bias power source, a light amount control unit in the writing device, and a developing sleeve in the developing device 3 corresponds to each other.

  When the controller 100 determines that the developer fluidity has deteriorated based on the relationship between the rotational speed range and the developer fluidity change obtained by an experiment described later, The actual deterioration of the developer is discriminated by excluding the change in fluidity due to a factor other than the cause of the deterioration of the developer. The principle will be described below.

First, FIG. 7 shows the result of an experiment on developer deterioration by torque measurement. This experiment was performed based on the following conditions.
Developer: toner particle size 6 μm, carrier particle size 35 μm
(The deteriorated developer in FIG. 7 is a developer obtained by operating the developing device in an idling state without consuming or replenishing toner, and after one hour has passed)
Stirring member: As shown in FIG. 8, a propeller PL having a diameter of 23.5 mm, a plate width of 6 mm, and an inclination angle of about 60 °
Using this condition, the propeller PL was rotated in the developer by the experimental apparatus shown in FIG. 8 and stirred, and the torque during stirring was obtained by a torque sensor (not shown). Torque was measured by stirring and measuring for a predetermined time (10 sec) at each rotational speed, obtaining a time-average torque, and obtaining the torque value as torque at the rotational speed.

  The experimental results are as shown in FIG. 7. In FIG. 7, since the fluidity varies depending on the concentration of toner contained in the developer, the torque value varies, and the torque varies depending on the rotational speed. Is different.

  In particular, when the toner concentration is 9%, it can be seen that the new developer has a smaller torque on the low rotation speed side than the deteriorated developer, and the above-described tendency is reversed on the high rotation speed side.

  It can be said that such a result is due to the change in the flow state due to the stirring conditions due to the deterioration of the developer. In other words, in the case of a deteriorated developer, fluidity deteriorates due to peeling or embedding of the toner external additive, scraping of the carrier coat film, and the occurrence of spent on the toner surface adhering to the carrier surface. I think that.

By the way, when observing the torque change according to the rotational speed and judging the deterioration of the developer based on the result, not only the fluidity of the developer but also the characteristics of the developer itself due to the above-mentioned mechanical phenomenon of the toner or carrier. The toner concentration is influenced by physical phenomena such as temperature and humidity and the toner content.
For this reason, judging the deterioration of the developer from the result of the torque measurement at a certain number of revolutions cannot be said to be the deterioration of the fluidity caused by the actual deterioration of the developer itself, and thus causes erroneous detection. There is a fear.

FIG. 9 shows the results of measuring the torque at the low speed and the high speed, and the torque difference at each speed was obtained.
Although it depends on the materials of the toner and the carrier, the difference in torque value between the low rotation and the high rotation tends to increase.

  In the control unit 100 of the present embodiment, by using the torque difference in the rotation speed range as an index of the deterioration degree of the developer, a false detection that occurs when determining the deterioration of the developer using the torque at a certain rotation speed. Is to prevent.

  In the present embodiment, since the change in the rotation speed is intended for the stirring member 45 of the developer container 40 provided at a position different from the developing device, the rotation speed is changed in the developing device. The developer supply amount can be prevented from changing. In other words, the developing device is equipped with a screw auger used as a stirring member, and it is conceivable to change the number of rotations. However, if the number of rotations of the stirring member in the developing device is changed, There is a possibility that the transport amount changes, and the supply of the developer becomes excessive or insufficient. However, in this embodiment, since it is on the right side of the rotational speed of the stirring member at a position different from the developing device, it is possible to determine the deterioration of the developer without causing a change in the developer transfer amount.

  The developer deterioration determination using the control unit 100 can be performed not only while the developing device 3 is in operation but also when the developing device 3 is stopped. That is, in the developer container 40, the developer is supplied and discharged simultaneously while stirring. For this reason, when bulkiness fluctuation or a large amount of replenishing toner is replenished, it is considered that the influence of toner density fluctuation before mixing / stirring is slightly affected on fluidity. Further, since the developer has fallen and moved, the flow has an effect on the torque. Therefore, in consideration of these influences, these influences are eliminated by detecting deterioration while the developing device is stopped. As a result, it is possible to perform the deterioration detection with higher accuracy by eliminating the factors of the change in torque due to the toner concentration and the falling movement of the developer described above than when the developing device is in operation.

On the other hand, the change in fluidity, which is a factor causing the torque difference, is affected not only by the change in the characteristics of the toner and carrier materials themselves, but also by the environmental change such as temperature and humidity and the difference in toner concentration as described above.
Therefore, the control unit 100 can determine deterioration due to deterioration in fluidity of the developer itself by excluding environmental changes and toner concentrations, which are deterioration factors other than deterioration due to material characteristics of the toner and carrier contained in the developer, from the determination conditions. It is like that. This will be described below.

  FIG. 10 shows a configuration of the agitating member disposed in the developer accommodating portion 40. The first agitating member 45 and the second agitating member 45 provided on the inner side and the outer side, respectively, around the rotating shaft 43 shown in FIG. The structure provided with stirring member 45 'is shown.

  The first stirring member 45 is a screw, the second stirring member 45 ′ is a blade provided with a plate extending in the direction of gravity, and the second stirring member 45 ′ has a rotating shaft. It is provided at a relative position with respect to the center. The developer container 40 is provided with replenishment ports 401 and 402 that can be introduced with toner and carrier or carrier alone at the top, and a developer recovery port 403 on the outer peripheral surface side. Inside the collection port 403, a screw auger 403A that collects and moves the developer is disposed.

  The first agitating member 45 has a rotational direction in which the developer can be raised from the lower side, and the second agitating member 45 ′ accommodates the developer using a centrifugal force generated during rotation. After being pushed up along the inner surface of the portion 40, it is dropped in the direction of gravity.

  In such a configuration, the developer is lifted in the direction opposite to the gravitational direction by the screw 45 at the center of the horizontal cross section of the developer containing portion 40, so that the stirring member is used below the developer containing portion 40. Stable and accurate development without causing a problem that the load applied to the stirring member becomes large due to the influence of the compressed developer because the developer is compressed by pushing or the dead weight of the developer. It is possible to detect the deterioration of the agent.

  On the other hand, FIG. 11 shows a case where a propeller 450 is used instead of the screw as the first agitating member, and in this case as well, the rotation direction is set to a direction in which the developer is raised. . In such a configuration using the propeller 450, a large torque acts as compared with the screw, so that it is possible to increase the sensitivity of torque change. In addition, by eliminating the compressing action on the developer, as will be described later, it is possible to eliminate an error in determining the deterioration of the developer that is influenced by the change in the powder surface position (bulk height) of the developer due to the compressing action.

  10 and 11, the screw 45 and the propeller 450 corresponding to the first stirring member are directly connected to the drive motor 40A, and the paddle corresponding to the second stirring member 45 ′ is rotated through the reduction gear group RG. It has come to be.

  The rotation shaft 43 is provided with a torque sensor 40B so that the shaft torque at the rotation shaft 43 is detected. In this case, the shaft torque detection method is the same as that described with reference to FIG. 10 and 11, the axial torque is detected by both the first and second agitating members. However, the present invention is not limited to this. It is also possible to detect.

  When detecting a change in the shaft torque by the torque sensor 40B and judging the deterioration of the developer, the fluidity of the developer also changes due to the environmental change such as temperature and humidity and the influence of the toner concentration. It is necessary to do.

Therefore, in the present embodiment, a density sensor 102 capable of detecting the toner density by the magnetic permeability is provided on the outer peripheral surface of the developer container 40 in the vicinity of the discharge port corresponding to the position where the developer flows down and collects. .
In addition, a temperature / humidity sensor 103 for detecting temperature / humidity is provided on the upper inner surface of the developer container 40.

  In the control unit 100, a map of data in which the relationship between the toner density and the torque change, and further the relationship between the temperature and humidity and the torque change is obtained in advance by experiments is registered. Accordingly, based on the detection results from the concentration sensor 102 and the temperature / humidity sensor 103, the torque change due to these detection results is excluded from the torque change obtained by the torque sensor 40B, and then the torque difference shown in FIG. The deterioration of the developer is discriminated based on the flowability of the developer.

As a result, it is possible to determine the deterioration of the developer using only the characteristics of the developer itself, excluding the torque change due to the toner concentration and temperature / humidity affecting the flowability of the developer.
The toner concentration sensor 102 is not limited to a configuration that targets magnetic permeability, but can be configured to detect an optical change.

  In the developer container 40 shown in this embodiment, the supply amount and the discharge amount of the developer have the same relationship (supply amount = discharge amount), and the developer stored in the developer container 40 is stored. The amount is always constant. If the bulk of the developer changes in such a state, the fluidity of the developer is affected in the same manner as the effects of the toner concentration and temperature and humidity described above. That is, the change in the bulkiness causes a change in the contact state between the stirring member and the developer, thereby changing the shaft torque.

  In the present embodiment, when determining the deterioration of the developer, the bulk of the developer is taken into consideration in addition to the above-described toner concentration and temperature / humidity as factors other than the characteristics of the developer itself.

In other words, the control unit 100 uses the level sensor 104 provided on a part of the side surface in the gravity direction of the developer accommodating unit 40, and uses the rotary feeder so as to maintain the bulkiness according to the detection result from the level sensor 104. 50 rotation control is performed.
The rotary feeder 50 is a member that sets the amount of developer discharged from the developer container 40 according to the amount of rotation. Therefore, by controlling the discharge amount, the bulk is kept constant, and the change in bulk is developed. The fluidity of the agent is not affected.
Accordingly, it is possible to determine the deterioration of the developer based on the characteristics of the developer itself, excluding the change in the fluidity of the developer due to the change in bulkiness.

  The control unit 100 also controls the image forming conditions according to the degree of developer deterioration. That is, the degree of deterioration of the developer leads to a decrease in the charge amount of the toner. For this reason, if the charging bias, the developing bias, and the writing light amount, which are image forming conditions set in advance when the deteriorated developer is used, are used as they are, the image quality is deteriorated.

  In the present embodiment, the control unit 100 adjusts at least one of a charging bias, a developing bias, and a writing light amount as a target according to the degree of developer deterioration.

As one means for changing the image forming conditions in accordance with the degree of deterioration of the developer, there is a means for changing the charging bias.
The meaning of changing the charging bias in accordance with the degree of developer deterioration is adjusting the density of the background or solid portion of the image. Depending on the system, whether the charge holding area on the photoconductor becomes the background or solid part of the image varies depending on the system, but due to fluctuations in the toner charge amount of the developer, background stains appear on the background part or the density decreases on the solid part May occur. Therefore, the charging bias value is adjusted so that the latent image potential changes in a direction to cancel these fluctuations.

Further, the developing bias can be an image forming condition that should be changed according to the degree of developer deterioration. The meaning of changing the developing bias according to the degree of developer deterioration is literally the adjustment of the developing ability, and by changing the developing bias, it is possible to cancel the toner charge amount fluctuation accompanying the developer deterioration. (Exposure power) may be set as an image forming condition to be changed according to the degree of developer deterioration. In this case, the meaning of changing the exposure power according to the degree of developer deterioration is almost the same as changing the charging bias. The change in the charging bias can adjust the latent image potential (dark portion potential) in the non-exposed area. Therefore, the latent image potential in the exposure area is adjusted so as to cancel the change in accordance with the developing ability of the developer that has changed due to the toner charge amount fluctuation. For example, when the toner charge amount increases and the developing capability decreases (the toner has a large amount of charge, the total amount of toner to be developed decreases), the development potential increases to compensate for this. The direction, that is, the exposure power may be increased. As a result, the same amount of toner as when the initial developer was used can be adhered to the photoreceptor. When the toner charge amount decreases and the developing ability increases, the reverse procedure may be performed.

  Furthermore, the developing bias can be set as an image forming condition that should be changed according to the degree of developer deterioration. In this case, the meaning of changing the developing bias in accordance with the degree of developer deterioration is literally the adjustment of the developing ability, and by changing the developing bias, it is possible to cancel the toner charge amount fluctuation accompanying the developer deterioration. it can.

  By adjusting such image forming conditions in accordance with the degree of deterioration of the developer, it is possible to cancel the deterioration of the developer and suppress a decrease in image quality.

  On the other hand, the control unit 100 considers that when the developer deterioration progresses, the image quality cannot be maintained only by adjusting the image forming conditions, and the developer deterioration is reduced to a predetermined condition, that is, the image quality. When the state becomes impossible to maintain, an alarm is given to the operation panel at 105, and when this state is obtained, the developer is replaced and the image is introduced by introducing a new developer. You can now take steps to restore quality. When replacing the developer, either or both of the toner and the carrier contained in the developer are targeted.

Hereinafter, the replacement of the developer will be described.
When toner deterioration is progressing alone, a forced toner consumption operation is activated (for example, solid development is performed), and after the deteriorated toner is discharged from the developing device through the photosensitive member, new toner is added. It is possible to replace only the toner that has deteriorated by replenishing the toner into the developing unit, the stirring unit, or the circulation path by the toner replenishing means.

  In the configuration shown in FIG. 10, since the toner supply path 62 is provided in the developer container 40, a large amount of new toner is supplied in order to recover the toner density lowered due to toner correction consumption. Even when such a large amount of new toner is replenished and poured into the developer container 40, the toner is stirred and mixed in the developer at a position different from the developing device 3 and dispersed. Therefore, the image quality can be prevented from being adversely affected.

  Next, a replacement method when the carrier alone or the deterioration of both the carrier and the toner is progressing will be described.

In the configuration shown in FIG. 10, the carrier alone or the carrier and toner is supplied from the supply port 401. As a result, the amount of the developer in the developing device increases, so that the developer powder surface rises and overflows and is recovered from the developer recovery port 403 by the screw auger 403A.
In this way, the developer can be replaced to maintain the state of the developer, and the image quality can be stabilized.

  Further, the developer container 40 of the present embodiment is provided with developer level adjustment means (rotary feeder 50 in the embodiment) of the developer in the agitating unit, so that the rotational speed of the rotary feeder 50 is reduced. Thus, it is possible to raise the powder level and forcibly discharge the developer, and then supply new toner and carrier from the replenishing port 401. By discharging the deteriorated developer before replenishing new toner and carrier, only the deteriorated agent can be selectively discharged, and can be efficiently replaced with a new developer. Further, since the replenished new developer is not discharged, the amount of the new developer to be replenished can be reduced, which leads to cost reduction.

Further, the developer can be replaced efficiently by taking into consideration the image area ratio and the driving time of the developing device. At low image area ratio, the toner consumption is low, so the carrier replenishment rate is increased to suppress carrier degradation, and at high image area ratio, the toner consumption is large, so the carrier ratio is decreased. The developer can be replenished according to the deterioration state of the developer, and the state of the developer can be maintained without wastefully replacing the developer that has not deteriorated. At this time, it is possible to change the replenishment ratio with respect to the developer deterioration state in more detail by considering the driving time of the developing device together with the image area ratio (in this case, the time change of the image area ratio is changed). Is considered).
In this way, along with the detection of developer deterioration due to torque, the image area ratio and the driving time of the developing device are taken into consideration, so that stable image quality can be maintained over time without wasteful toner and carrier discharge. Is possible.

  As described above, by replacing the deteriorated developer, the state of the developer is always kept in a fresh state, and image quality problems associated with the deterioration of the developer are not caused, and stable image quality is maintained over time. Is possible. Further, it is not necessary to replace the developing unit due to the deterioration of the developer, and it is possible to suppress downtime, labor and time for replacement, and cost associated with unit replacement.

  The above-described replacement of the developer may be automatically performed at a fixed timing, but the replenishment of the carrier or the developer can be adjusted by a user operation. That is, when the control unit 100 determines that the developer is deteriorated, the operation panel 105 is provided with a notification that the deterioration of the developer is detected in the image forming apparatus having the developing device provided with the deterioration detecting means. In this case, the user can adjust the replenishment of the carrier or the developer by the input device provided on the operation panel.

  For example, when the user looks at such a display, the developer replenishment adjustment evaluates the image formed on the paper and determines that the image quality is sufficient. The threshold used for determination can be set loosely by the input device. That is, when the image quality is not so demanded, the deterioration determination threshold value is set loosely so that the developer replenishment frequency can be reduced. On the other hand, when higher image quality is required, the threshold value for judging deterioration is set strictly, so that the developer replenishment frequency can be increased. An image quality selection key or the like corresponding to the setting of the threshold value can be provided to select the image quality.

Since this embodiment is configured as described above, the operation of the control unit 100 will be described with reference to the flowchart shown in FIG.
FIG. 12 is a flowchart for determining the deterioration of the developer and adjusting the developer.
When determining the deterioration of the developer and adjusting the developer, the bulkiness shown in FIG. 13 is adjusted.

  In FIG. 13, when the output value of the level sensor 104 is not appropriate, the bulkiness is adjusted using the rotary feeder 50. As a result, the bulkiness is maintained in a constant state.

After the above-described adjustment of the bulkiness, the temperature / humidity and the toner density are detected by the density sensor 102 and the temperature / humidity sensor 103 based on the flowchart shown in FIG.
The detection timing at this time is not only when the developing device 3 is operating but also when it is stopped, and the reason for performing it when it is stopped is as described above.

  When the temperature / humidity and toner density are detected, the data are stored, and the torque sensor 40B calculates the torque difference between the low rotation and the high rotation, and the developer difference is calculated from the obtained torque difference. The degree of deterioration is determined.

  The degree of deterioration of the developer fluidity is determined from the torque difference, but the torque difference includes the influence of the temperature and humidity and the toner concentration described above. The determination is performed by excluding the torque difference due to temperature and humidity and toner concentration from the obtained torque difference. As a result, the degree of deterioration due to the change in developer fluidity due to the characteristics of the developer itself is determined based on whether or not the torque change amount is within an appropriate range.

  When the degree of deterioration of the developer is determined, the image forming conditions are adjusted according to the degree of deterioration, and deterioration of image quality is prevented.

  On the other hand, when the deterioration of the developer is determined, the operation panel 105 displays that the developer has deteriorated (shown as an error display in FIG. 12), and develops by replenishing the carrier or carrier and toner. The original state of the agent is restored. Although not shown here, the above-described image forming conditions may be adjusted instead of restoring the developer to the original state.

  Further, when it is determined that the deterioration of the developer is progressing, the process may be shifted to a developer replacement process as necessary.

1 is a cross-sectional view illustrating a configuration of an image forming apparatus in which a developing device according to an embodiment of the present invention is used. 1 is a schematic diagram for explaining an overall configuration of a developing device according to an embodiment of the present invention. FIG. 3 is a schematic diagram for explaining a configuration of a developing unit in the developing device shown in FIG. 2. FIG. 2 is a schematic diagram illustrating an example of a main configuration of a developing device according to an embodiment of the present invention. It is a schematic diagram which shows the modification of the principal part structure shown in FIG. It is a block diagram for demonstrating the structure of the control part used for the image development measure by this embodiment. It is a diagram which shows the experimental result of rotation speed and a torque. It is a schematic diagram which shows the structure used for the experiment which calculates | requires the torque at the time of low rotation and high rotation. It is the result of measuring the torque at the time of low rotation speed and at the time of high rotation speed, and is a diagram showing the experimental result of the torque difference at each rotation speed. It is a schematic diagram for demonstrating the structure for detecting temperature / humidity and a toner density | concentration. It is a schematic diagram which shows the partial modification of the structure shown in FIG. It is a flowchart for demonstrating the degradation determination process performed by the control part shown in FIG. It is a flowchart for demonstrating the content of the process performed prior to the degradation determination process shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photoconductor 3 Developing apparatus 40, 40 'Developer accommodating part 40A Drive motor 40B Torque sensor 45, 45' Stirring member 60 Toner supply means 100 Control part 101 Stirring member rotation speed sensor 102 Concentration sensor 103 Temperature / humidity sensor 104 Level sensor 105 Operation panel 106 Charging bias means 107 Developing bias means 108 Writing light source 109 Developing device driving means

Claims (13)

A developing device that performs visible image processing of an electrostatic latent image using a two-component developer including a toner and a carrier,
A developing section provided with a developer carrying member and a developer regulating member that regulates the end area of the developer; a developer stirring section provided separately from the developing section and stirring the developer recovered from the developing section; A circulation unit for circulating the developer between the developing unit and the developer stirring unit,
The developer stirring section is provided with a stirring member capable of arbitrarily controlling the rotation speed and a torque sensor capable of detecting the torque of the stirring member, and the torque when the rotation speed of the stirring member is changed. A developing device comprising a configuration for detecting deterioration of a developer based on an output value of a sensor.   In the configuration for detecting the deterioration of the developer, a control unit to which drive control to the stirring member and an output value from the torque sensor are input is used, and the control unit rotates the stirring member at a predetermined timing. The developing device according to claim 1, wherein the deterioration of the developer is determined based on a difference in output value from the torque sensor by changing the number.   3. The developing device according to claim 1, wherein when the developing unit is stopped, the control unit sets a time when the rotation speed of the stirring member is changed. 4.   In addition to the torque sensor, a concentration sensor provided in the circulation path of the circulation unit is connected to the control unit, and an output value from the concentration sensor is used in addition to an output value from the torque sensor. 4. The developing device according to claim 2, wherein deterioration of the developer is discriminated.   In addition to the torque sensor, a temperature / humidity sensor is connected to the control unit, and the deterioration of the developer is determined using the output value from the temperature / humidity sensor in addition to the output value from the torque sensor. The developing device according to claim 2, wherein:   In addition to the torque sensor, a level sensor capable of detecting the developer powder level is connected to the control unit, and the developer is output using the output value from the level sensor in addition to the output value from the torque sensor. The developing device according to claim 2, wherein the deterioration is determined.   The developer agitation unit includes a developer container having a shape that moves the developer in the direction of gravity, and the agitation member is disposed in the developer container and moves to move the developer in the direction of gravity. The developing device according to claim 1, wherein the developing device has a possible configuration.   The control unit is connected to a replenishing unit that replenishes a carrier or a replenisher containing carrier and toner, and a collecting unit that collects excess developer, and the control unit is configured to deteriorate the developer. 8. The developing device according to claim 2, wherein the replenishing unit is driven to replenish the replenishment agent when it is determined.   9. The development according to claim 2, wherein the control unit sets a mixing ratio of the carrier and the toner contained in the replenisher based on the image area ratio or the operation time in the developing unit. apparatus.   An image forming apparatus using the developing device according to claim 1.   The image forming apparatus according to claim 10, wherein the control unit is capable of adjusting a charging bias, a developing bias, and a writing light power used for an image forming process according to a degree of deterioration of the developer.   12. The image forming apparatus according to claim 10, wherein the control unit is configured to be able to externally indicate that the developer has deteriorated when determining the deterioration of the developer.   13. The image forming apparatus according to claim 10, wherein the developer can be replenished by a user.

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