JP4661217B2 - Liquid developer characteristic detecting device, liquid developing device, and image forming apparatus - Google Patents

Description

The present invention relates to a liquid developer characteristic detecting device, a liquid developing device, and an image forming apparatus for detecting a toner concentration of a liquid developer used for developing an electrostatic latent image in an image forming apparatus such as a copying machine or a printer.

  In an image forming apparatus such as a copying machine or a printer, generally, the surface of an electrostatic latent image carrier such as a photoconductor is charged, and an image is exposed to the charged area based on image information to form an electrostatic latent image. The latent image is developed into a visible toner image, and the toner image is transferred to a recording material such as paper and fixed. A liquid developing device is known as one of developing devices that develop a latent image with a developer to form a visible toner image.

  In a liquid developing device, a liquid developer in which toner is dispersed in a carrier liquid is used as a developer. The carrier liquid usually contains a dispersant and a charge imparting agent.

  The liquid developing device typically has a developing roller that is rotationally driven as a developing member. A part of the developing roller is immersed in the liquid developer and faces the electrostatic latent image carrier. The liquid developer is carried to the development area while being held as a thin layer on the developing roller by the rotation of the developing roller, and the charged toner in the developer is applied to the electrostatic latent image carrier under the development bias. It adheres to the formed electrostatic latent image, and this latent image is made a visible toner image. Excess developer is returned to the original liquid developer as the developing roller rotates.

  In this way, the liquid developer is held in a thin layer on the developing roller and supplied to the development area. In liquid development, the toner moves in the insulating carrier liquid and develops the latent image. This is for shortening the moving distance of the toner during development and increasing the moving speed of the toner so that development can be performed.

  In such development, the distance (developer layer thickness) between the electrostatic latent image carrier and the developing roller is usually about 10 μm, which is considerably small. In order to maintain the image density with the toner existing during this period, a high toner density of 10 wt% (wt%) to 30 wt% (wt%) is required.

  On the other hand, the characteristics of the liquid developer differ from a predetermined regular one, such as the toner concentration decreasing while being used in this manner. Therefore, it is necessary to detect the characteristics of the liquid developer, such as detecting the toner concentration in the liquid developer, and to replenish the toner according to the detection result, thereby normalizing the liquid developer characteristics. .

  Taking toner density detection as an example, a toner density detection sensor including a light emitting element and a light receiving element is usually employed for toner density detection. That is, the liquid developer to be measured is disposed between the light emitting element and the light receiving element, and the toner density is detected based on the output of the light receiving element corresponding to the amount of light transmitted from the light emitting element to the light receiving element.

At this time, it is necessary to transmit light in the liquid developer according to the toner concentration. If the layer thickness of the liquid developer to be measured is too large, the light transmittance is reduced due to high concentration toner or the like. This makes it difficult to detect the toner density. However, if the distance between the light emitting element and the light receiving element installed in the liquid developer is reduced, the liquid developer whose viscosity is increased due to high-density toner or the like is between the light emitting element and the light receiving element. It becomes difficult to enter, and if it enters one end, it becomes difficult to get out, and replacement of the liquid developer between both elements becomes difficult.
In addition, there is a problem that the toner dispersed in a high concentration in the liquid developer adheres to the light emitting element and the light receiving element and the detection accuracy of the toner density is lowered.

  In this regard, for example, in Japanese Patent Laid-Open No. 2001-5299, the light emitting element and the light receiving element arranged in the liquid developer are separated from the density detection when the toner density is not detected, and the density detection is performed when the density is detected. It is described that the distance is approached.

  Japanese Patent Laid-Open No. 2001-305867 discloses that a light emitting element and a light receiving element are arranged inside and outside a transparent tube, and a liquid developer is applied to the surface of the tube with a coating roller in a thin layer. It describes that a toner layer is detected by arranging a thin layer between a light emitting element and a light receiving element.

  Japanese Patent Laid-Open No. 5-133890 adopts a configuration in which a liquid developer flows between a light emitting element and a light receiving element, and a portion of the light emitting element and the light receiving element that contacts the liquid developer is a substance having the same charge polarity as the toner. And thereby preventing the toner from adhering to both elements.

JP 2001-5299 A JP 2001-305867 A JP-A-5-133890

  However, in the toner density detection method described in Japanese Patent Application Laid-Open No. 2001-5299, when the light emitting element and the light receiving element are brought close to the density detection interval at the time of toner density detection, an error occurs between the two element intervals obtained by the approach. Therefore, an error is likely to occur in toner density detection.

  In the toner concentration detection method described in Japanese Patent Application Laid-Open No. 2001-305867, when a thin layer of liquid developer is applied and formed on the surface of a transparent tube, the thickness of the thin layer is likely to be uneven. Incurs errors.

  In the toner density detection method described in Japanese Patent Application Laid-Open No. 5-133890, when the space between the light emitting element and the light receiving element is set narrow for toner density detection, a clogged portion between both elements cannot be excluded.

  In any case, the problem with liquid developer property detection is that the liquid developer in which the toner is dispersed is so viscous that it does not have much fluidity, and if it is thick, it becomes difficult to transmit light. This is largely due to

SUMMARY OF THE INVENTION Accordingly, a first object of the present invention is to provide a liquid developer characteristic detection device that can accurately detect liquid developer characteristics , particularly toner density, with less error than conventional ones.
Further, the present invention can accurately detect the characteristics of the liquid developer used for development , particularly the toner concentration, with less error than conventional ones, and by using the detection result, the liquid used for development. A second object is to provide a liquid developing device capable of maintaining the characteristics of the developer , particularly the toner concentration, at a predetermined regular level .

Furthermore, the present invention can accurately detect the characteristics of the liquid developer used for development , particularly the toner concentration, with less error than conventional ones, and by using the detection result, the liquid developer used for development. It is a third object to provide an image forming apparatus capable of forming a good image by maintaining the characteristics of the agent , particularly the toner density, at a predetermined regular level .

The present invention is intended to provide the above-described liquid developer characteristic detection apparatus, liquid development apparatus, and image forming apparatus, but also relates to a liquid developer characteristic detection method described below for reference. (1) Liquid developer characteristic detection method
A method for detecting characteristics of a liquid developer in which toner is dispersed in a carrier liquid , wherein a predetermined amount of a liquid developer to be measured is diluted with a carrier liquid for dilution, and the liquid developer characteristics in the diluted liquid developer A liquid developer characteristic detection method for detecting a liquid developer characteristic to be measured based on the amount of liquid developer to be measured, the amount of carrier liquid used for dilution, and a detection value by the characteristic detection sensor It is.

  According to this detection method, the liquid developer to be measured (the liquid developer to be subjected to characteristic detection) is not subjected to characteristic detection as it is, but is diluted with a carrier solution for dilution, and the characteristic is detected in the state of the diluted liquid developer. To be served. Furthermore, if it is as it is, the liquid developer with low light transmittance and high viscosity due to high-concentration toner or the like is used as a diluted liquid developer with high light transmittance and high fluidity for characteristic detection. Provided.

Since such a diluted liquid developer is rich in fluidity, it can be easily flowed and disposed with respect to the characteristic detection sensor, and can also be easily flowed and replaced with respect to the characteristic detection sensor.
In addition, the characteristic detection sensor includes, for example, a light emitting element and a light receiving element, a diluted liquid developer is disposed between the two elements, and the characteristic is detected by the output of the light receiving element according to the amount of light transmitted from the light emitting element to the light receiving element. Even when detecting diluted liquid developer, since the light transmittance of the diluted liquid developer is increased, the distance between the two elements should be set at a fixed distance sufficient to dispose and replace the diluted liquid developer and to prevent clogging of foreign substances. When set, characteristics can be detected with little error while maintaining high detection sensitivity.

Further, since the distance between the two elements can be set to a fixed distance, the layer thickness of the diluted liquid developer to be detected by the characteristic detection sensor can be made constant. In this respect, the characteristic can be detected with little error.
Furthermore, since characteristic detection is performed using a diluted liquid developer having a low toner concentration and low viscosity, contamination of the characteristic detection sensor is also suppressed.
As a result, the characteristics of the liquid developer can be accurately detected with less error than in the prior art.
The toner density may be detected by measurement using reflection density, which is another method for measuring toner density. In this case, a reflection density detection sensor may be used as the sensor.

In such a detection method , the liquid developer property to be measured is obtained based on the amount of the liquid developer to be measured, the amount of the carrier liquid used for dilution, and the detection value by the characteristic detection sensor. On the other hand, the following two methods can be given as typical examples. (a) When diluting the liquid developer to be measured with a carrier liquid for dilution, the carrier liquid is supplied and diluted until the detection value by the characteristic detection sensor shows a predetermined detection value, and the carrier liquid supply amount Is the amount of the carrier liquid used for the dilution.
(b) When diluting the liquid developer to be measured with the carrier liquid for dilution, the liquid developer is diluted with a predetermined amount of the carrier liquid, and the predetermined amount of the carrier liquid is used as the amount of the carrier liquid used for the dilution. Method.

In the case of the former (a), the amount of liquid developer to be measured and the value detected by the characteristic detection sensor are predetermined known values. Then, if the amount of carrier liquid used for dilution is known, the liquid developer characteristics are obtained. be able to.
In the case of the latter (b), the amount of liquid developer to be measured and the amount of carrier liquid used for dilution are known in advance. Can be sought.

Such a liquid developer characteristic detection method can be applied, for example, when manufacturing a liquid developer, but also when detecting characteristics in order to maintain the characteristics of the liquid developer in the liquid developing device to a predetermined regular one. Applicable.
That is, the liquid developer to be measured may be collected from a liquid developer tank in the liquid developing device.

In this case, the following methods (1-1) and (1-2) can be cited as methods for detecting the liquid developer characteristics.
(1-1)
The liquid developer characteristic detection method of (1) above,
There is provided a detection tank that communicates with a liquid developer tank in the liquid developing device, and through the communication, the same liquid developer as the liquid developer in the liquid developer tank may exist, and the characteristic detection sensor is provided in the detection tank. The liquid developer present in the detection tank is disposed and the liquid developer present in the detection tank is used as the predetermined amount of liquid developer to be measured by communicating with the liquid developer tank. The developer is diluted with the carrier solution for dilution in a state where the detection tank is disconnected from the liquid developer tank, and the property detection sensor detects the liquid developer characteristics in the diluted liquid developer. A method that uses a diluted liquid developer in a detection tank.

(1-2)
The liquid developer characteristic detection method of (1) above,
A detection tank is provided for the liquid developer tank in the liquid developing device, and a position where the liquid developer tank is immersed in the liquid developer to a predetermined depth and a position where the liquid can be discharged to the detection tank. A nozzle that is reciprocally conveyed between them, the characteristic detection sensor is disposed in the detection tank, and the nozzle is used as the liquid developer in the liquid developer tank as the predetermined amount of liquid developer to be measured. An amount of liquid developer retained in the nozzle is adopted by immersing the nozzle in the predetermined depth and then removing the nozzle from the liquid developer, and the predetermined amount of the liquid developer to be measured For dilution with the carrier liquid for dilution, the nozzle holding the liquid developer is moved to the detection tank, and the liquid developer held and the carrier liquid for dilution are detected from the nozzle. The liquid developer is discharged into the tank and the diluted liquid developer is obtained in the detection tank, and the liquid developer characteristic in the diluted liquid developer is detected by the characteristic detection sensor, and the diluted liquid developer in the detection tank is detected. How to use it.

  As described above, when using a sample collected from the liquid developer tank in the liquid developing device as the liquid developer to be measured, the diluted liquid developer is detected after the liquid developer characteristics are detected in order to suppress loss of the liquid developer. May be returned to the liquid developer tank. In that case, an amount of toner corresponding to the amount of the carrier liquid for dilution is supplied to the liquid developer tank so that the toner concentration of the liquid developer in the liquid developer tank is maintained at a predetermined regular concentration. Also good.

  In addition, when using liquid developer collected from the liquid developer tank in the liquid developing device as the liquid developer to be measured, the carrier liquid is replenished to the liquid developer tank in the liquid developing device in order to make the detection device more compact and smaller. The carrier liquid for dilution may be supplied from the carrier liquid supply device.

A typical example of the characteristics of the liquid developer to be detected is a toner concentration.
Examples of the characteristics of the liquid developer to be detected include the toner concentration and the current value of the developer.
As the characteristic detection sensor, a sensor capable of detecting the characteristic to be detected may be employed.

When detecting the toner density, a sensor including a light-emitting element and a light-receiving element for detecting the toner density and having a fixed interval between the two elements can be employed as a representative example of the characteristic detection sensor. In the case of adopting this sensor, in detecting the liquid developer characteristics in the diluted liquid developer, the diluted liquid developer is disposed between the light emitting element and the light receiving element and transmitted from the light emitting element to the light receiving element. The toner concentration may be detected as the liquid developer characteristic based on the output of the light receiving element based on the amount of light.
As described above, the toner density may be detected by measuring the reflection density, which is another method for measuring the toner density. In this case, a reflection density detection sensor may be used.

  In any case, the liquid developer may contain a toner dispersant and a charge imparting agent. It is desirable to use a carrier liquid for dilution that contains a toner dispersant and a charge imparting agent.

The present invention provides a liquid developer property detection apparatus capable of performing the liquid developer property detection method described above , and in particular, the following detection device (1-2-1) capable of performing the method (1-2). To do. For reference, the following detection apparatus (1-1-1) that can implement the method (1-1) is also described below.

(1-1-1) detection device is a device for detecting the characteristics of a liquid developer in which toner is dispersed in a carrier liquid.
A detection tank that communicates with a liquid developer tank of the liquid developing device, and allows the liquid developer in the liquid developer tank to exist in a predetermined amount by the communication;
A communication blocking device for blocking communication of the detection tank to the liquid developer tank when liquid developer characteristics are detected;
A liquid developer characteristic detection sensor disposed in the detection tank;
A carrier liquid supply device for supplying a carrier liquid for dilution into the detection tank, which is disconnected from the liquid developer tank by the communication blocking device when the liquid developer characteristics are detected; and the liquid developer by the communication blocking device. The predetermined amount of liquid developer present in the detection tank when communication with the tank is interrupted, and the amount of carrier liquid supplied to the detection tank by the carrier liquid supply device; Means for obtaining developer characteristics based on a value detected by the liquid developer characteristic detection sensor for the liquid developer characteristics of the diluted liquid developer diluted with the carrier liquid in the detection tank. Agent property detection device.

(1-2-1) detection device ( detection device according to the present invention)
An apparatus for detecting the characteristics of a liquid developer in which toner is dispersed in a carrier liquid,
A detection tank disposed adjacent to the liquid developer tank of the liquid developing device;
A liquid developer characteristic detection sensor disposed in the detection tank;
A nozzle that is reciprocally conveyed between a position immersed in the liquid developer in the liquid developer tank to a predetermined depth and a position where liquid can be discharged to the detection tank;
A carrier liquid supply device for supplying a carrier liquid to the nozzle; and a liquid developer amount held in the nozzle by immersing the nozzle in a liquid developer in the liquid developer tank in a predetermined depth; The amount of carrier liquid supplied from the carrier liquid supply device into the detection tank through the nozzle and the discharge of the liquid developer and carrier liquid from the nozzle holding the liquid developer into the detection tank. A liquid developer characteristic detecting device comprising: means for obtaining a developer characteristic based on a value detected by the liquid developer characteristic detection sensor for the liquid developer characteristic of the diluted liquid developer obtained.

More specifically, in order to solve the first problem, the present invention provides:
A liquid developer characteristic detecting device for detecting a toner concentration of a liquid developer contained in a liquid developer tank of a liquid developing device and having the toner dispersed in a carrier liquid;
A detection tank provided separately from the liquid developer tank;
A diluent supply device for supplying a diluent for diluting the liquid developer;
A nozzle commonly used for conveying the liquid developer in the liquid developer tank to the detection tank and supplying the diluent from the diluent supply device to the detection tank;
A light emitting element and a light receiving element are included, and the toner concentration of the diluted liquid developer is detected based on the amount of light transmitted through the diluted liquid developer obtained in the detection tank by discharging the liquid developer and the diluted liquid from the nozzle. A toner density detection sensor
The amount of the liquid developer conveyed from the liquid developer tank to the detection tank by the nozzle, the amount of the diluent supplied into the detection tank via the nozzle, and the amount in the detection tank Means for determining the toner concentration of the liquid developer in the liquid developer tank based on the detected value by the toner concentration detection sensor for the toner concentration of the diluted liquid developer, and the diluted liquid developer is provided in the detection tank. The liquid developer characteristic detecting device for supplying the diluent to the detection tank by the nozzle after transporting the liquid developer in the liquid developer tank to the detection tank by the nozzle is provided.

The present invention also provides a liquid developing device including such a liquid developer characteristic detecting device, and an image forming apparatus including the developing device.
According to the liquid developing device according to the present invention, the liquid developer characteristic detecting device according to the present invention is provided so that the characteristics of the liquid developer used for development can be accurately detected with less error than in the past. Thus, by using the detection result, it is possible to maintain the characteristics of the liquid developer subjected to development at a predetermined regular value.

  In addition, according to the image forming apparatus of the present invention, by adopting the liquid developing device including the liquid developer characteristic detecting device according to the present invention, the characteristics of the liquid developer used for the development are more different from the conventional ones. Therefore, the detection result can be used to maintain the characteristics of the liquid developer used for the development at a predetermined regular level and form an image as well. is there.

As described above, according to the present invention, it is possible to provide a liquid developer characteristic detecting device that can accurately detect the characteristics of the liquid developer , particularly the toner concentration, with less error than conventional ones.
In addition, according to the present invention, the characteristics of the liquid developer used for development , particularly the toner density , can be detected with less error than in the past, and the detection result is used for development. It is possible to provide a liquid developing apparatus capable of maintaining the characteristics of the liquid developer , particularly the toner concentration, at a predetermined regular level .

Furthermore, according to the present invention, the characteristics of the liquid developer used for development , in particular, the toner concentration can be detected with less error than in the past , and the liquid used for development can be detected using the detection result. It is possible to provide an image forming apparatus capable of forming an image satisfactorily while maintaining the characteristics of the developer , in particular, the toner density at a predetermined regular level .

In the following, an embodiment of the present invention will be described with reference to the toner concentration detection apparatus of FIGS. 2 and 3 shown for reference .
In the following description, “liquid developer” is referred to as “developer” and “liquid developer characteristics” is referred to as “developer characteristics”.

FIG. 1 shows an example of an image forming apparatus according to the present invention.
This image forming apparatus has a photosensitive drum PC, and around it, a charger CH, a liquid developing device 1, a transfer roller Tr, a blade type cleaner CL, and a static elimination lamp IR are arranged in this order. An image exposure apparatus EX is provided above the photosensitive drum PC.
Although part of the liquid developing device 1 (developer tank 2) is omitted, the whole is shown together with the toner concentration detecting device S1 in FIG.

  According to the image forming apparatus of FIG. 1, the photosensitive drum PC is rotated in the clockwise direction in the figure, the surface thereof is uniformly charged to a predetermined potential by the charger CH, and the document is transferred from the image exposure apparatus EX to the charged area. Image exposure according to image information is performed, and an electrostatic latent image is formed. This electrostatic latent image shifts to the developing area as the photosensitive drum PC rotates, and is developed by the liquid developing device 1 to become a visible toner image.

  The liquid developing device 1 is supported by a developing tank 10, a developing roller 11 rotatably supported by the developing tank 10, a developer regulating blade 12 in contact with the developing roller 11, and a partition wall 14 in the developing tank. A cleaning blade 13 or the like is provided.

  In the developing tank 10, the developing solution D pumped up by the pump 21 from the developing solution tank 2 shown in FIG. The developer D is obtained by dispersing toner, a toner dispersant, a charge imparting agent, and the like in an insulating carrier liquid, and the toner concentration is constant within a range of 20 wt% to 30 wt%.

  Part of the developing roller 11 is immersed in the developing solution D, and the developing solution D is pumped up by being rotated counterclockwise in the drawing. The developer D pumped up is regulated to a constant film thickness (for example, 7 μm) by a regulating blade 12 that is in contact with the developing roller 11, and is conveyed to a developing area facing the photosensitive drum PC, in which the photosensitive drum It is used for developing an electrostatic latent image on a PC. At this time, a developing bias voltage is applied to the developing roller from a power supply (not shown).

  The developer having a changed toner density on the developing roller 11 after the development is collected by the cleaning blade 13 and returned to the collection chamber 10 ′ in the developing tank 10. The developer collected in this manner is separated from the developer D to be used for development by the blade 13 and the partition wall 14 that supports the blade 13, and is supplied to the developer tank 2 as shown in FIG. It is returned by its own weight, mixed with the developer, and reused. Note that the recovery of the developed developer into the tank 2 may be performed using a pump.

  A visible toner image developed and formed by the liquid developing device 1 is transferred onto a recording material (paper or the like) supplied from a recording material supply unit (not shown), and a transfer roller Tr applied with a transfer voltage from a power supply (not shown). And then fixed on the recording material by a fixing device (not shown).

  The toner, paper dust, and the like remaining on the photosensitive drum PC after the transfer are removed by the cleaner CL, and the residual charges are erased by the static elimination lamp IR to prepare for the next image formation.

The developing device 1 will be further described with reference to FIG.
The developing device 1 includes a developer tank 2 below the developer tank 10, and stores the developer D in the tank 2. The tank 2 is provided with a stirring device 23 for stirring the developer D. The agitator is periodically operated under the control of the control unit Cont.

As described above, the developing solution D in the tank 2 is pumped and supplied to the developing tank 10 by the pump 21. The pump 21 has a predetermined liquid supply amount per unit time.
The developing tank 10 is provided with a liquid level sensor 101 for detecting the position of the liquid level. When the liquid level in the developing tank 10 falls below the allowable range, the sensor 101 detects this and informs the control unit Cont of the information. input. In response to this, the controller Cont drives the pump 21 to supply the developer D from the tank 2 to the developing tank 10. Then, the supply is stopped at an output value indicating the normal liquid level position of the sensor 101.

Further, a concentrated toner liquid tank 3 and a carrier liquid tank 4 are provided above the developer tank 2. Here, the concentrated toner liquid is a liquid for replenishing toner to the developer D, and is obtained by dispersing toner in a carrier liquid at a higher concentration than the developer D.
The concentrated toner liquid in the tank 3 can be supplied to the tank 2 by the pump 31, and the carrier liquid in the tank 4 can be supplied to the tank 2 by the pump 41. The carrier liquid in the carrier liquid tank 4 contains a dispersant and a charge imparting agent at a predetermined concentration. The concentration is such that the dispersant and the charge imparting agent in the developing solution D in the tank 2 can be maintained at a predetermined concentration even if the developing solution in the tank 2 is diluted by adding the carrier solution from the tank 4 to the developing solution D.

Both pumps 31 and 41 have a fixed amount of liquid delivered per unit time.
The pumps 31 and 41 are also operated under the instruction of the control unit Cont, and the amount of liquid delivered by these pumps can be grasped by the pump operation time measured by the control unit Cont.

  A liquid level sensor 22 is also provided in the developer tank 2, and the sensor 22 detects when the liquid level in the tank 2 falls below an allowable range, and inputs the information to the controller Cont. In response to this, the controller Cont drives the pump 41 to replenish the carrier liquid from the carrier liquid tank 4. Then, the supply is stopped at the output value of the sensor 22 indicating the normal liquid level position.

The developer tank 2 is provided with a toner concentration detection device S1 for detecting the toner concentration in the developer D, which is a typical example of the liquid developer characteristics.
The detection device S1 includes a detection tank 5 installed in the developer tank 2 and a toner concentration detection sensor 6 provided in the detection tank 5. The lower portion of the detection tank 5 is immersed in the developer in the tank 2 and has an opening 51 communicating with the tank 2 on the bottom wall. A communication cutoff device ST including a valve V that opens and closes the opening and a solenoid SOL that drives the valve is provided for the opening 51.
As can be seen later, this device ST, the carrier liquid tank 4, the pump 41, and the controller Cont also constitute the toner concentration detection device S1.

The opening 51 remains open when the toner concentration is not detected, and the detection tank 5 communicates with the developer tank 2 through the opening 51. Therefore, the developing solution D in the tank 2 exists in the detection tank 5 at the same liquid level. Furthermore, when the opening is opened, the developer D whose amount is known is present in the detection tank 5.
The carrier liquid from the carrier liquid tank 4 can be supplied to the tank 2 via the detection tank 5.

  The toner concentration detection sensor 6 includes a light emitting element 61 and a light receiving element 62 that are arranged to face each other. The distance between the light emitting element 61 and the light receiving element 61 is fixed (1 mm in this example). Both elements are arranged at a position where the carrier liquid from the carrier liquid tank 4 just falls, and are positioned higher than the liquid level in the detection tank 5 when the toner concentration is not detected, but will be described later. Further, when the carrier liquid is supplied from the carrier liquid tank 4 at the time of toner concentration detection and the liquid level of the diluted developer formed in the detection tank 5 rises, the liquid is placed at a height position soaked in the liquid in the tank 5. ing.

  The toner concentration detection sensor 6 is a dilute liquid developer based on the output of the light receiving element 62 corresponding to the amount of light transmitted from the light emitting element 61 to the light receiving element 62 in a state in which a diluted developer described later enters between both elements 61 and 62. The toner density can be detected.

  When the toner concentration is detected, the valve V closes the opening 51 by energizing the solenoid SOL under the instruction of the control unit Cont, whereby the communication between the detection tank 5 and the developer tank 2 is blocked, and the detection tank 5 The developer D in the tank is placed in a state independent of the developer in the tank 2.

When the toner concentration is detected, the pump 41 is operated under the instruction of the control unit Cont with the opening 51 closed, and the carrier liquid is supplied from the carrier liquid tank 4 into the detection tank 5 to detect the detection tank. 5 is a diluted developer. The supply of the carrier liquid for dilution from the tank 5 is performed until the sensor 6 shows a predetermined output value (detection value), and the carrier liquid supply amount by that is obtained from the pump operation time measured by the control unit Cont. It is done.
The output of the light receiving element 62 is input to the control unit Cont.

  The controller Cont develops from the known amount of the developer D present in the detection tank 5 when the toner concentration is not detected, the amount of carrier liquid supplied to the detection tank 5 when detecting the toner concentration, and the output of the sensor 6. The toner concentration of the liquid D is calculated and obtained. In this example, the amount of liquid developer to be measured and the output (detected value) of the sensor 6 are predetermined known values, and then the liquid developer is obtained by obtaining the carrier liquid amount used for dilution by the control unit Cont. The toner concentration of the agent D can be obtained. Thus, the toner concentration of the developer D is detected.

When the measurement target liquid developer is diluted with the carrier liquid for dilution, the liquid developer may be diluted with a predetermined amount of carrier liquid. In this case, since the amount of liquid developer to be measured and the amount of carrier liquid used for dilution are known in advance, the liquid developer D is obtained by obtaining the detection value by the sensor 6 in the control unit Cont. The toner density can be obtained.
In any case, the supply amount of the dilution carrier liquid may be obtained from the liquid level in the detection tank 5.

  Based on the toner concentration thus determined, the control unit Cont sets the toner amount to be replenished to the developer tank 2 (concentrated toner solution amount), that is, the toner concentration within a predetermined normal range of the developer D. A supply toner amount (concentrated toner liquid amount) for maintenance is calculated, and the pump 31 is driven so that the concentrated toner liquid of that amount is supplied. Further, if necessary, the pump 41 is also driven to replenish the carrier liquid. Thus, the toner density of the developer tank 2 and, consequently, the developer D used for development is maintained within a predetermined normal range, and a good and stable image can be obtained in terms of image density and the like.

  The toner density detection by the toner density detection device S1 starts under the instruction of the control unit Cont. The timing of the density detection is, for example, the operator's density by an operation panel (not shown) connected to the control unit Cont. This is a detection instruction, timing immediately after replenishment of carrier liquid from the carrier liquid tank 4 to the tank 2, immediately after printing a certain number of sheets, power ON / OFF of the image forming apparatus.

  According to the toner concentration detection device S1 and the toner concentration detection method implemented by the device, the developer D to be measured is not used for toner concentration detection as it is, but is diluted with a carrier solution, and the diluted developer state To be used for detection. Furthermore, if it is as it is, the light transmittance is low due to the high-concentration toner, and the developer D having a high viscosity is used as a diluted developer having a high fluidity and a high fluidity. To be served.

Since such a diluted developer is rich in fluidity, it can be easily flowed between the light emitting element 61 and the light receiving element 62 of the sensor 6 and can be easily flowed and replaced between the two elements.
In addition, the distance between the elements 61 and 62 is set to a fixed distance sufficient for the arrangement and replacement of the diluted liquid developer and for suppressing the clogging of the foreign matter, but the diluted developer has an increased light transmittance. Therefore, the toner density can be detected with a small error while maintaining high detection sensitivity.

In addition, since the distance between the elements 61 and 62 is set to a fixed distance, the layer thickness of the diluted developer to be detected by the detection sensor 6 can be made constant. it can.
Furthermore, since the toner concentration is detected using a diluted developer having a low toner concentration and low viscosity, contamination of the detection sensor 6 is also suppressed. In the detection device S1, the light emitting element 61 and the light receiving element 62 are provided at a position where the carrier liquid supplied from the carrier liquid tank 4 just falls, so that both elements can be washed away with the carrier liquid. it can. Further, the dispersant and the charge imparting agent contained in the carrier liquid also act as a detergent for washing away the toner or the like that is to adhere to the sensor 6, and in this respect, the toner concentration can be detected with little error.
As a result, the toner density of the developer D can be accurately detected with less error than in the past.

  The diluted developer after the toner concentration detection can be returned to the developer tank 2 by opening the opening 51 of the detection tank 5, and at this time, depending on the amount of carrier liquid used for diluting the concentrated toner solution as necessary. Alternatively, the toner density in the tank 2 may be maintained within a predetermined range.

FIG. 3 shows another example of the toner concentration detection device together with the liquid developing device 1. The toner concentration detection device S2 in FIG. 3 is attached to the liquid developing device 1 in the same manner as the toner concentration detection device S1, but differs from the device S1 in the following points.
That is, in the apparatus S2, a midway portion 50 is narrowed as a detection tank, and a tank 5 ′ formed of a translucent material is adopted, and the light emitting element 61 and the light receiving element 62 of the sensor 6 are narrowed. The portion 50 is disposed outside the tank 5 ′. Further, the squeezed portion 50 is arranged at a position where the carrier liquid just falls so that the carrier liquid supplied from the carrier liquid tank 4 can be washed away.

The throttle portion 50 is positioned higher than the liquid level in the detection tank 5 ′ when the toner concentration is not detected, but diluted and developed in the detection tank 5 ′ when the carrier liquid is supplied from the carrier liquid tank 4 when the toner concentration is detected. When the liquid level of the liquid rises, it is arranged at a height position where it is immersed in the liquid in the tank 5 '.
The other points are substantially the same as the device S1. In FIG. 3, the same reference numerals as those in FIG. 2 are assigned to substantially the same parts and components as those of the liquid developing device 1 and the toner concentration detecting device S1 shown in FIG. Illustration of the control part Cont is omitted.

According to the toner concentration detection device S2, the diluted developer in the detection tank 5 ′ is not in contact with the sensor 6, and thereafter the toner concentration of the diluted developer in the tank 5 ′ is set in the same manner as the toner concentration detection device S1. It can be detected by the sensor 6, and the toner density of the developer D can be obtained.
Also with the toner concentration detection device S2, the toner concentration of the developing solution D can be accurately detected with less error than in the past.

FIG. 4 shows an example of the toner concentration detecting device according to the present invention together with a part of the liquid developing device. In FIG. 4, the same reference numerals as those in FIG. 2 are assigned to substantially the same parts and components as those of the liquid developing device 1 and the toner concentration detecting device S1 shown in FIG. Illustration of the control part Cont is omitted.

The toner concentration detection device S3 of FIG. 4 is attached to the liquid developing device 1 like the toner concentration detection device S1, but differs from the device S1 in the following points.
In other words, in the apparatus S3, the detection tank 50 is disposed adjacent to the tank 2 outside the developer tank 2 of the developing device 1. The toner concentration detection sensor 6 is disposed at the bottom of the detection tank 50.

Further, the carrier liquid tank 4 is connected to the nozzle N via the flexible pipe F below the pump 41.
The nozzle N can be reciprocally conveyed between the developer tank 2 and the detection tank 50 by the nozzle conveying device 7.
Furthermore, the nozzle N is a position where the liquid can be discharged into the detection tank 50 from a position (position shown in FIG. 4A) where it is immersed in the developer D in the developer tank 2 to a predetermined depth. (It can be reciprocated between the positions shown in FIG. 4B.

The details of the nozzle conveying device 7 are as shown in FIG. FIG. 5A shows a state in which the nozzle conveyance device 7 is viewed from the front, and FIG. 5B shows a top view of the device.
FIG. 5C shows a state of the device viewed from the side [state viewed from the left in FIG. 5A], and FIG. 5D shows a state in which the nozzle N is lifted by the cam 74. Show.

  The nozzle transport device 7 extends from above the developer tank 2 to above the detection tank 50, and is supported by a screw rod 71 rotatably supported by a support member (not shown), and a movable member 72 screwed to the screw rod. And a nozzle support arm 73 supported by the movable member so as to be swingable by a pin P, and a plate cam 74 having a trapezoidal shape in plan view, which is provided below them. The nozzle N is supported by the nozzle support arm 73.

  The screw rod 71 can be rotated forward and backward by the motor M, and the movable member 72 is moved by the rotation of the screw rod 71. At this time, the movable member 72 is being prevented from rotating along a rail member (not shown). It slides in the same posture. Further, the nozzle support arm 73 is limited in its downward movement by a stopper 75 provided on the movable member 72. Thus, when the nozzle N is not in contact with the cam 74, the nozzle N is directed directly below. To support. The motor operation is controlled by a control unit Cont (not shown).

  According to the nozzle conveying device 7, by rotating the screw rod 71 in the forward direction, the movable member 72 is at the position shown in FIG. 5A, that is, the position where the nozzle N is immersed in the developer D in the tank 2 to a predetermined depth. Can be moved rightward in the figure. In the rightward movement, the nozzle N moves while being in contact with the left inclined surface 741 of the cam 74 and is gradually lifted, and as shown in FIG. In this state, the position can be moved to the detection tank 50 side without colliding with the walls 2W and 50W of the tanks 2 and 50, and swings downward along the right slope 743 of the cam 74 so that the liquid can be discharged into the tank 50. Can take. By reversing the screw rod 71, the nozzle N can be returned to the tank 2 side from the position where the liquid can be discharged into the tank 50.

  According to the toner concentration detection device S3, the nozzle N is disposed at a position where the nozzle N is immersed in a predetermined depth in the developer D of the developer tank 2, as shown in FIG. The nozzle is lifted from the developer D in the tank 2 by moving it toward the detection tank 50 while being in contact with the cam 74, thereby holding the measuring developer D whose amount is known in the nozzle N. Then, the nozzle N is moved to the detection tank 50, where the carrier liquid for dilution is supplied from the carrier liquid tank 4 to the nozzle N, and the developer D and the developer D held in the nozzle N are supplied. Both carrier liquids are discharged into the detection tank 50, whereby a diluted developer is obtained in the detection tank 50.

  The toner concentration of the diluted developer thus obtained is detected by the toner concentration detection sensor 6, and the detected value and the amount of the nozzle N are immersed in the developer D in the tank 2 to a predetermined depth. The toner concentration of the developing solution D is obtained by calculating the toner concentration of the developing solution D by the control unit Cont (not shown) from the known amount of the developing solution for measurement and the supplied carrier liquid amount. Can do.

Also in the toner concentration detection device S3, when the carrier liquid for dilution is supplied to the detection tank 50, the carrier liquid may be supplied until the detection value by the sensor 6 shows a predetermined detection value, or a predetermined value may be set. An amount of carrier liquid may be supplied.
In the former case, the amount of developer to be measured and the value detected by the sensor 6 are predetermined known values, and then the toner concentration of the developer D can be obtained by obtaining the amount of carrier liquid used for dilution. it can.
In the latter case, since the amount of developer to be measured and the amount of carrier liquid used for dilution are known in advance, the toner concentration of developer D is obtained by obtaining the detection value by sensor 6 later. Can do.
Also with the toner concentration detection device S3, the toner concentration of the developer D can be accurately detected with less error than in the past.
The diluted developer in the detection tank 50 after detection may be discarded or returned to the developer tank 2 of the developing device 1.

A device 7 ′ shown in FIG. 6 may be employed as the nozzle conveying device. The nozzle conveyance device 7 ′ is a device in which a plate cam 74 ′ is used instead of the plate cam 74 in the nozzle conveyance device 7 described above. The other points are the same as those of the device 7.
The plate cam 74 ′ has a gentler slope on the left side slope (slope on the developer tank 2 side) than the plate cam 74. The front surface 742 and the slope 743 on the right side (detection tank 50 side) of the cam 74 ′ are the same as the cam 74.

  According to the nozzle transport device 7, the nozzle N remains immersed in the developer D when positioned on the developer tank 2 side. However, in the nozzle transport device 7 ′, the nozzle N is located on the developer tank side. Even when the toner density is not detected, the nozzle N is disposed at the position P2 in FIG. 6 and is lifted in contact with the cam inclined surface 741 ′ and separated from the developer D. In detecting the toner density, the nozzle N is once moved to the left in FIG. 6 and is thereby immersed in the developer D at the position P1, where it holds the developer D and is then driven to the right. It moves to the detection tank 50.

  According to the nozzle conveying device 7 ′, when the toner concentration is not detected, the nozzle N is lifted and separated from the developer D, so that the replacement of the liquid in the nozzle N becomes more reliable, and thus the toner concentration is detected with less error. can do.

  INDUSTRIAL APPLICABILITY The present invention can be used for accurately detecting characteristics such as the toner concentration of the liquid developer with little error, and using the detection result, the characteristics such as the toner concentration of the liquid developer in the liquid developing apparatus can be normalized. It can also be used to keep things.

1 is a diagram illustrating a schematic configuration of an example of an image forming apparatus according to the present invention. FIG. 4 is a diagram illustrating an example of a liquid developing device provided with a reference example of a toner concentration detecting device . It is a figure which shows the other reference example of a toner density | concentration detection apparatus . 4A and 4B are diagrams illustrating a toner concentration detection device according to the present invention, in which FIG. 4A shows a state in which the nozzle is disposed on the developer tank side, and FIG. 4B is a state in which the nozzle is disposed on the detection tank side. Is shown. 5A and 5B are diagrams illustrating a nozzle conveyance device in the toner concentration detection device illustrated in FIG. 4, in which FIG. 5A illustrates the nozzle conveyance device viewed from the front, and FIG. 5B illustrates the device viewed from the top. FIG. 5C is a view showing the device viewed from the side, and FIG. 5D is a view showing a state where the nozzle is lifted by the cam. It is a figure which shows the other example of a nozzle conveying apparatus.

Explanation of symbols

PC Photosensitive drum CH Charger Tr Transfer roller CL Cleaner IR Static elimination lamp EX Image exposure apparatus 1 Liquid image apparatus 10 Developing tank 10 'Collection chamber 11 Developing roller 12 Regulation blade 13 Cleaning blade 14 Partition wall (supporting member for the blade 13)
101 Liquid Level Sensor D Liquid Developer (Developer)
2 Developer tank 21 Developer supply pump 22 Liquid level sensor 23 Stirrer 3 Concentrated toner liquid tank 31 Concentrated toner liquid supply pump 4 Carrier liquid tank 41 Carrier liquid supply pumps S1, S2, S3 Toner concentration detectors 5, 5 ′, 50 Detection tank 51 Tank bottom opening 6 Toner concentration detection sensor 61 Light emitting element 62 Light receiving element ST Opening / closing valve V Opening / closing valve SOL Solenoid Cont Control unit 7, 7 'Nozzle transport device 71 Screw rod 72 Movable member P Pin 73 Nozzle support Arm 74, 74 'Plate cam 741, 741', 743 Cam slope 742 Cam front surface 2W Developer tank wall 50W Detection tank wall

Claims (4)

A liquid developer characteristic detecting device for detecting a toner concentration of a liquid developer contained in a liquid developer tank of a liquid developing device and having the toner dispersed in a carrier liquid;
A detection tank provided separately from the liquid developer tank;
A diluent supply device for supplying a diluent for diluting the liquid developer;
A nozzle commonly used for conveying the liquid developer in the liquid developer tank to the detection tank and for supplying the dilution liquid from the dilution liquid supply device to the detection tank;
A light emitting element and a light receiving element are included, and the toner concentration of the diluted liquid developer is detected based on the amount of light transmitted through the diluted liquid developer obtained in the detection tank by discharging the liquid developer and the diluted liquid from the nozzle. A toner density detection sensor
The amount of the liquid developer conveyed from the liquid developer tank to the detection tank by the nozzle, the amount of the diluent supplied into the detection tank via the nozzle, and the amount in the detection tank Means for determining the toner concentration of the liquid developer in the liquid developer tank based on the detected value by the toner concentration detection sensor for the toner concentration of the diluted liquid developer; When obtaining the diluted liquid developer in the detection tank, the liquid developer in the liquid developer tank is transported to the detection tank by the nozzle, and then the diluent is supplied to the detection tank by the nozzle. A liquid developer characteristic detection device. The nozzle is reciprocated between a position where the nozzle is immersed in a predetermined depth in the liquid developer in the liquid developer tank and a position where the liquid developer can be discharged into the detection tank. The liquid developer characteristic detection device according to claim 1, wherein: A liquid developing device comprising a liquid developer tank and the liquid developer characteristic detecting device according to claim 1. 4. An image forming apparatus comprising: a photosensitive member; means for forming an electrostatic latent image on the photosensitive member; and a liquid developing device according to claim 3 for developing the electrostatic latent image formed on the photosensitive member. apparatus.