JP2003186309A - Toner concentration measuring method of wet developer, and device thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably and accurately measure the toner concentration of a wet developer. <P>SOLUTION: A rotating body 1, endlessly forming a groove 20b holding the wet developer along an outer peripheral face, is provided rotatably in the wet developer (a toner ink T) in a developer tank constituting a developing device arranged in an electrophotographic image-forming apparatus by centering a horizontal rotary shaft 11, in a state of the downward part of a diametral direction thereof being immersed. A metering blade 4 for making the layer thickness of a wet developer layer (a toner ink thin layer Ta), formed by pumping the developer to the groove 20b equal to the depth of the groove 20b, is provided in the upstream side of the rotary direction of the rotating body 1. An optical sensor 30, provided with a light-emitting element and a light-receiving element, is provided directly above the top part of the rotating body 1 as a toner concentration detection means. A cleaning blade 5 for stratching off the developer layer is provided on the downstream side of the rotating direction of the rotating body 1. The optical sensor 30 is equipped with a toner concentration totalizing means, a toner concentration totalizing result recording means and a toner concentration determination means in a prescribed mode. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for measuring toner concentration of a wet type developer (toner ink) used in an electrophotographic image forming apparatus, and more particularly to a developing apparatus provided in the image forming apparatus. By incorporating
The present invention relates to a toner concentration measuring device for a wet type developer, which is capable of simply and accurately measuring the toner particle concentration with a simple structure.

[0002]

2. Description of the Related Art Wet developers are highly insulating liquids in which a colorant, a resin, a charge control agent and the like are dispersed and have a particle size of 0.01.
The toner particles are positively or negatively charged to about 3 μm. That is, the developer used in the wet development is a resin toner having a pigment such as carbon in an isoparaffin solvent which is an insulating carrier, a charge control agent that determines the charging characteristics and charge amount of toner particles, and a toner after evaporation of the carrier liquid. It is a dispersion of a fixing agent for hardening the particles.
The wet development method is a method in which toner particles are dispersed in an insulating liquid as described above to form a developer, and the electrostatic latent image on the image carrier is electrophoresed to develop the electrostatic latent image. In the wet method of the direct method, the toner concentration of the developer decreases with the development, so it is necessary to supply fresh developer.

As a method for detecting the toner concentration of a wet type developer,
The developer is pumped to the sensor section (developer reservoir),
It is known that the amount of transmitted light of the developer is detected. In this case, the layer thickness of the developer layer between the light emitting element and the light receiving element facing each other is about 0.5 mm, and this gap can be adjusted. Another known method for detecting the toner concentration of a wet developer is one in which a developer is made to flow from an overflow reservoir to form a thin film, and the amount of transmitted light of the flowing thin film is detected.

[0004]

However, in the conventional toner concentration measuring apparatus for wet type developer described above, the structure of the apparatus tends to be complicated, and the toner concentration can be stably and accurately measured. There was a problem that it was difficult.

Therefore, a first object of the present invention is to provide a toner concentration measuring method for a wet type developer, which can stably and accurately measure the toner concentration. A second object of the present invention is to provide an apparatus capable of simply carrying out such a toner concentration measuring method, that is, to incorporate it in a developing device provided in an image forming apparatus because of its simple structure. It is an object of the present invention to provide a toner concentration measuring device for a wet type developer, which can stably and accurately measure the toner concentration by a simple operation. The third object of the present invention is to
(EN) Provided is a toner concentration measuring device for a wet type developer, which is capable of suppressing the generation of a poor quality image to a minimum by stopping the driving of the image forming apparatus when an abnormality occurs in the measured toner concentration value. Is.

[0006]

The invention according to claim 1 is
In the wet developer in the developer tank that constitutes the developing device provided in the electrophotographic image forming apparatus, the holding groove for the wet developer is formed in an endless shape along the outer peripheral surface of the rotating body in the diametrical downward direction. The portion is dipped, and in this state, the rotary body is rotated about the horizontal rotation axis to draw up the wet developer into the holding groove, and metering is performed so that the layer thickness of the wet developer becomes equal to the depth of the holding groove. Then, while the processed wet developer layer is positioned at the top portion of the rotating body by the rotation of the rotating body, the wet developer layer is directly irradiated with the light from the light source without passing through another member. However, the reflected light or the transmitted light is directly received by the light receiving portion without passing through another member, and the light reflectance or the light transmittance of the wet developer layer is detected. Toner concentration measurement method .

According to the second aspect of the invention, when the detection operation of the light reflectance or the light transmittance is performed a plurality of times, the wet developer layer after the previous detection is scraped before each detection operation. The method for measuring toner concentration of a wet type developer according to claim 1, characterized in that.

According to a third aspect of the present invention, the light reflectance of the wet developer layer is detected by irradiating the light from the light source onto the wet developer layer located at the apex portion of the rotating body from directly above. The method for measuring toner concentration of a wet type developer according to claim 1 or 2, characterized in that.

According to a fourth aspect of the present invention, the light from the light source is horizontally directed to the wet developer layer located at the top portion of the rotating body,
3. The toner concentration measuring method for a wet developer according to claim 1, wherein the light transmittance of the wet developer layer is detected by irradiating the rotary member in a direction orthogonal to the rotation axis of the rotary member. Is.

According to a fifth aspect of the present invention, the wet developer holding groove is endless along the outer peripheral surface of the wet developer in the developer tank constituting the developing device provided in the electrophotographic image forming apparatus. The rotatably formed in a circular shape is rotatably provided around a horizontal axis of rotation in a state where the lower portion in the diametrical direction is immersed, and the wet developer is pumped up to the holding groove on the upstream side in the rotating direction of the rotator. A metering blade for making the thickness of the formed wet developer layer equal to the depth of the holding groove was contacted with a predetermined contact pressure, and a light emitting element and a light receiving element were provided immediately above the top portion of the rotating body. A toner concentration measuring device for a wet type developer, comprising an optical sensor as a toner concentration detecting means.

According to a sixth aspect of the present invention, a wet developer holding groove is endless along an outer peripheral surface of a wet developer in a developer tank constituting a developing device provided in an electrophotographic image forming apparatus. The rotatably formed in a circular shape is rotatably provided around a horizontal axis of rotation in a state where the lower portion in the diametrical direction is immersed, and the wet developer is pumped up to the holding groove on the upstream side in the rotating direction of the rotator. A metering blade for making the thickness of the formed wet developer layer equal to the depth of the holding groove is contacted with a predetermined contact pressure, and an optical sensor as a toner concentration detecting means is provided in the vicinity of the top portion of the rotating body. Provided,
The optical sensor is configured to include a light emitting element disposed on one of the upstream side and the downstream side in the rotation direction of the rotating body, and a light receiving element disposed on the other side, and the light from the light emitting element is directed to the top portion of the rotating body. The toner concentration measuring device for a wet type developer is characterized in that the wet type developer layer positioned is irradiated horizontally and in a direction orthogonal to the rotation axis of the rotating body.

According to a seventh aspect of the present invention, a cleaning blade for scraping off the wet developer layer after irradiation of light from the light emitting element is provided on the downstream side in the rotation direction of the rotating body and in contact with a predetermined contact pressure. The toner concentration measuring device for a wet type developer according to claim 5 or 6, characterized in that.

According to an eighth aspect of the invention, the rotating body is a cylindrical rotating body comprising a reference cylinder which rotates about a rotating shaft provided at a diametrical center of the cylindrical body and an eccentric cylinder which rotates integrally with the reference cylinder. A reference cylinder is integrally provided at both ends in the longitudinal direction of the eccentric cylinder, and the eccentric cylinder rotates eccentrically around the rotation axis of the reference cylinder, and has an outer diameter smaller than that of the reference cylinder and an outer peripheral surface. The whole is retracted from the outer peripheral surface of the reference cylinder to the center side of the reference cylinder (in the axial cross section, the outer peripheral surface contour line of the eccentric cylinder is included in the outer peripheral surface contour line of the reference cylinder), and the center of the eccentric cylinder The axis is in the same vertical plane as the center line of rotation of the reference cylinder, and the holding groove is formed so that the outer peripheral surface of the eccentric cylinder serves as the bottom surface of the holding groove due to the difference in outer diameter between the reference cylinder and the eccentric cylinder. 6. The method according to claim 5, wherein 7 is a toner concentration measuring apparatus of a liquid developer according to.

According to a ninth aspect of the present invention, in addition to the toner concentration detecting means including an optical sensor, a concentration totalizing means for totalizing the toner concentrations detected by the density detecting means, and a totaling output from the density totalizing means. A totaling result recording unit for recording the result and a toner concentration determining unit for obtaining the toner concentration from the totaling result recorded in the totaling result recording unit,
The toner concentration measuring device for a wet type developer according to any one of claims 5 to 8, which is further provided.

According to a tenth aspect of the present invention, the toner concentration measuring device for a wet developer according to the ninth aspect is characterized in that the toner concentration is detected once while the rotating body makes one revolution.

According to an eleventh aspect of the present invention, in the toner concentration measuring apparatus for a wet type developer according to the ninth aspect, the toner concentration detection is started after the rotation of the rotating body reaches a steady state. is there.

The invention according to claim 12 is characterized in that the toner concentration is obtained from the detection result of the toner concentration obtained by continuously rotating the rotating body for two or more revolutions. It is a toner concentration measuring device for the agent.

According to a thirteenth aspect of the present invention, when the variation between the toner densities obtained for each rotation of the rotator exceeds a predetermined value, the rotational speed of the rotator is adjusted, and when the toner concentration with the large variation is obtained. 11. The toner concentration measuring device for a wet developer according to claim 10, wherein the variation is set within a predetermined value by increasing or decreasing the rotation speed of the rotating body.

According to a fourteenth aspect of the present invention, when the toner density measurement result exceeds the specified range, the image forming operation is stopped and a warning is issued to the user that the toner density exceeds the specified range. Claim 12 or 1
3 is a toner concentration measuring device for a wet type developer according to item 3;

According to the fifteenth aspect of the present invention, when the toner density measurement result shows that the toner density tends to decrease with the passage of time, the image forming operation is stopped and the toner density shows the tendency. The toner concentration measuring device for a wet type developer according to claim 12 or 13, characterized in that a warning is issued to the user.

According to the sixteenth aspect of the present invention, when the variation in the toner density measurement result exceeds the specified range, the image forming operation is stopped and the user is warned that the variation has occurred. Claim 12
The toner concentration measuring device for a wet developer described in 1.

According to the seventeenth aspect of the present invention, when the variation rate of the toner concentration measurement result tends to increase as compared with the past toner concentration variation rate, the image forming operation is stopped and the toner concentration variation rate is increased. 13. The toner concentration measuring device for a wet type developer according to claim 12, wherein a warning indicating that there is a tendency of expansion is issued to the user.

According to the eighteenth aspect of the present invention, when the variation in the toner concentration measurement result does not converge within the specified time,
13. The toner concentration measuring device for a wet type developer according to claim 12, wherein the image forming operation is stopped and a warning is issued to the user that the variation does not converge within a specified time.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic sectional view showing the structure of a main part of a toner concentration measuring device for toner ink which is a wet type developer, and FIG. 2 is a perspective view thereof.

A cylindrical rotating body 1, that is, a cylindrical body rotatable by a drive mechanism (not shown) is immersed in toner ink T (wet developer) stored in a developer tank (not shown). A toner concentration sensor (optical sensor) 30 for detecting the light reflectance of a thin layer of toner ink (wet developer layer) described below is provided immediately above the top of the cylindrical rotating body 1. The cylindrical rotating body 1 includes a reference cylinder 10 that rotates about a horizontal rotation shaft 11 provided at a diametrically central position of the cylindrical body,
It is composed of an eccentric cylinder 20 which rotates integrally with this. The reference cylinder 10 is provided on both axial sides of the eccentric cylinder 20.
A toner ink discharge groove 12 is formed on the outer peripheral surface of the reference cylinder 10 as shown in FIG.

The eccentric cylinder 20 is a rotating shaft 11 of the reference cylinder 10.
The eccentric rotation is centered around, and the outer diameter is slightly smaller than that of the reference cylinder 10, and the entire outer peripheral surface is retracted closer to the center side of the reference cylinder 10 than the outer peripheral surface of the reference cylinder 10. In other words, as shown in FIG. 1, the outer peripheral surface contour line 20 a of the eccentric cylinder 20 is the outer peripheral surface contour line 10 of the reference cylinder 10 in the axial cross section.
It is included in a. Therefore, in the cylindrical rotating body 1, the eccentric cylinder 20 has a width between the reference cylinders 10 on both sides.
An endless groove 20b for holding a thin layer of toner ink is formed, which is equal to the axial length of the toner and has a depth gradually increasing / decreasing in the circumferential direction. The central axis of the reference cylinder 10 and the eccentric cylinder 20
Is in the same vertical plane as the central axis of the eccentric cylinder 20. Therefore, the groove 20b is formed so that the outer peripheral surface of the eccentric cylinder 20 becomes the bottom surface of the groove 20b due to the difference in outer diameter between the reference cylinder 10 and the eccentric cylinder 20. ing. The depth of the groove 20b varies depending on the outer peripheral surface portion of the eccentric cylinder 20, and is formed so as to gradually increase / decrease in the outer peripheral surface direction. In the state shown in FIG. 1 (rotational position of the cylindrical rotary body 1), the depth of the groove 20b is maximum at the top portion of the cylindrical rotary body 1 (for example, about 1.
0 mm), and the groove 20 is provided at the top portion.
b is substantially horizontal. The minimum depth of the groove 20b is, for example, about 0.5 mm.

At the outer peripheral surface portion of the cylindrical rotary member 1 on the toner ink drawing side (the right side of the cylindrical rotary member 1 in FIG. 1), the layer thickness of the toner ink thin layer on the outer peripheral surface of the eccentric cylinder 20 is set to the groove 20b. A metering blade 4 is provided as a metering member for making the depth equal to. The metering blade 4 is a flat plate made of spring steel that is swingable around a swing shaft 4a. The metering blade 4 can be brought into and out of contact with the outer peripheral surface of the reference cylinder 10 at a predetermined contact pressure. It is provided. In addition, on the outer peripheral surface of the eccentric cylinder 20, a portion facing the toner ink drawing side is
A cleaning blade 5 for scraping off a thin layer of toner ink on the outer peripheral surface of the eccentric cylinder 20 (in the groove 20b) is provided. Like the metering blade 4, the cleaning blade 5 is a flat plate made of spring steel and is used as the swing shaft 5.
It is swingable around a and is provided so as to come into contact with and separate from the outer peripheral surface of the eccentric cylinder 20 with a predetermined contact pressure.

As shown in FIG. 1, the toner concentration sensor 30 is a light emitting element (FIG. 1) for irradiating a thin layer of toner ink applied to the top portion of the rotating cylindrical rotor 1 with light of a predetermined luminous intensity. And a light receiving element (not shown) for receiving the reflected light from the toner ink thin layer. The toner concentration sensor 30 is connected to a toner ink concentration totaling unit, and the luminous intensity data of the reflected light obtained by the sensor is output to the toner concentration totaling unit. Further, a toner concentration totaling result recording unit is connected to the toner concentration totaling unit, and a toner concentration determining unit (all of these units are not shown) is connected to the totaling result recording unit.

Next, the operation of the toner concentration measuring device, that is, the method of measuring the toner concentration by this device will be described. In FIG. 1, the rotating body 1 is continuously rotated counterclockwise by a drive mechanism (not shown) as shown.
As a result, the toner ink T in the developer tank is pumped up into the groove 20b of the rotating body. A part of this pumped-up liquid is scraped off by the metering blade 4, and the layer thickness of the toner ink thin layer Ta (depth of the toner ink in the groove 20b) becomes equal to the depth of the groove 20b. Reference cylinder 10
The toner ink on the outer peripheral surface is discharged along the toner ink discharge groove 12.

When the rotating body 1 rotates, the toner concentration sensor 30 operates when the portion where the depth of the groove 20b is maximum is located on the top of the cylindrical rotating body 1 as shown in FIG. Light (irradiation light 30a) from a light emitting element (not shown) is irradiated on the toner ink thin layer Ta, and reflected light 30
b is received by a light receiving element (not shown). Then, the light reflectance of the thin layer Ta is obtained based on the light amounts of the irradiation light 30a and the reflected light 30b. Such detection of the light reflectance is performed once or continuously two or more times intermittently (one detection is performed while the rotating body 1 makes one rotation).

Then, the data from the toner density sensor 30 is output to the toner density totalizing means, and the totalization result output from the density totalizing means is recorded in the toner density totaling result recording means. Then, the totalization result recorded in the totalization result recording means is output to the toner concentration determining means, and the toner concentration is finally determined here. In addition,
The data from the toner density sensor 30 is recorded in the totalization result recording means as electric data and electronic data. Further, this totaling result recording means is in the form of a ring buffer, and old data is discarded every time new data is input.

Thin toner ink layer Ta in the groove 20b
Is scraped off by the cleaning blade 5, and a new toner ink thin layer Ta is formed in the groove 20b by the rotation of the cylindrical rotary member 1, and the toner concentration measuring operation is repeated. In FIG. 1, reference symbol L is the toner ink liquid surface, reference symbol Tb is the toner ink attached to the cylindrical surface of the rotating body 1, and reference symbol Tc is the scraped toner ink.

In the present embodiment, the toner density is detected once during one rotation of the rotating body. In this case, a filler is provided at an appropriate position of the cylindrical rotating body 1 or marking is performed and reading is performed. It is desirable to deploy a sensor (not shown). In this case, each time the rotating body 1 makes one rotation, the reading sensor detects the filler or the marking, and the detection signal (generation of pulse data) is output to the optical sensor 30 to detect the toner concentration. When the next pulse data is generated, the previous toner density detection data is output to the density totalizing means.

In the present embodiment, in order to obtain a more accurate toner density measurement result and to obtain an image of the highest possible quality, the toner density measurement operation and the driving operation of the image forming apparatus (image forming operation) are performed. ) Is performed as follows. In this case, the following method is executed alone, or a plurality of these methods are appropriately selected and executed. (1) The toner density detection is started after the rotating body is in the steady rotation state. To this end, a timer measures the elapsed time from the start of rotation of the rotating body, and the toner concentration detection is started when a predetermined time has elapsed. Alternatively, the cumulative number of rotations of the rotating body may be measured, and the toner concentration detection may be started when the cumulative value reaches a predetermined value. Further, after the rotation of the rotating body is started, the toner density is preliminarily detected for a while, and when the detection data becomes stable (when the variation rate of the toner density is below the specified value), the formal toner density detection is started. Is also effective. (2) Toner concentration is detected once during one rotation of the rotating body.
The toner concentration is obtained from the detection result of the toner concentration obtained by rotating the rotating body twice or more continuously while performing the rotation. In this case, the detection results are averaged. (3) When the variation between the toner densities obtained for each rotation of the rotator exceeds a predetermined value, the rotational speed of the rotator is made higher than the rotational speed of the rotator when the toner density with the large variation is obtained. , Or by lowering
The variation is kept within a predetermined value.

(4) When the toner density measurement result exceeds the specified range, the image forming operation is stopped and the user is warned that the toner density exceeds the specified range. (5) Normally, the density of the toner ink in the developing device gradually increases with time, but may decrease on the contrary. Therefore, when the toner density measurement result shows that the toner density tends to decrease with the passage of time, the image forming operation is stopped and the user is warned that the toner density shows the tendency. . (6) When the variation (variation rate) of the toner density measurement value exceeds the specified range, the image forming operation is stopped and the user is warned that the variation is occurring. To obtain the variation rate of the toner concentration measurement value, for example, the difference may be calculated from the concentration value stored as a memory or a log, or the distance from the variance may be obtained. (7) When the variation rate of the toner concentration measurement result tends to increase compared with the past toner concentration variation rate, the image forming operation is stopped and a warning that the toner concentration variation rate tends to increase is issued. Send to the user. (8) When the variation in the toner density measurement result does not converge within the specified time, the image forming operation is stopped and the user is warned that the variation does not converge within the specified time.

In the present embodiment, as shown in FIG.
(1) The metering blade 4 and the cleaning blade 5 are used together, and (2) the groove 20 is provided at the top portion of the rotating body 1.
When the depth of b is the maximum and the groove 20b is substantially horizontal, and (3) the thin layer of toner ink is directly irradiated with the light from the light source without passing through another member, and the reflected light is obtained. Is directly received by the light receiving portion without passing through another member, and the toner concentration is obtained by detecting the light reflectance of the wet developer layer, so that the toner concentration measurement accuracy is remarkably improved.

In FIG. 1, the toner density sensor 3
It is also possible to provide a plurality of 0s in the longitudinal direction of the eccentric cylinder 20 with appropriate intervals between them, to simultaneously detect the toner concentration, and average the plurality of detection data. Will be higher. Also,
Instead of the eccentric cylinder 20, a second cylindrical body having a larger diameter than the first cylindrical body is concentrically and coaxially provided on both sides of the first cylindrical body, so that the holding groove of the toner-ink thin layer is formed into It is also possible to provide a rotating cylinder formed at the same depth along the outer peripheral surface of the cylinder. Further, instead of irradiating the light from the light emitting element of the toner concentration sensor onto the toner ink thin layer from immediately above as shown in FIG. 1, the light is emitted in the direction orthogonal to the rotation axis 11 of the rotating body 1 and in the horizontal direction. By irradiating, it is also possible to measure the toner density by detecting the light transmittance of the toner ink thin layer.

[0038]

As is apparent from the above description, according to the toner concentration measuring method of the wet type developer of the present invention, the toner concentration can be measured stably and accurately. Further, according to the toner concentration measuring device for a wet type developer according to the present invention,
The above toner concentration measuring method can be easily implemented. That is, since the structure is simple, by incorporating it in the developing device of the image forming apparatus, it is possible to stably and accurately measure the toner concentration by a simple operation. Furthermore, according to the toner concentration measuring device for a wet type developer according to the present invention,
When an error occurs in the measured toner density value, by stopping the driving of the image forming apparatus, it is possible to minimize the occurrence of an image with poor quality and prevent the abnormal image from being printed. You can

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a main part structure of a toner concentration measuring device according to an embodiment of the present invention.

FIG. 2 is a perspective view of FIG.

[Explanation of symbols]

1: Cylindrical rotating body 4: Metering blade 4a: swing axis 5: Cleaning blade 5a: swing axis 10: Reference cylinder 10a: outline of outer peripheral surface 11: rotation axis 12: Toner ink discharge groove 20: Eccentric cylinder 20a: outline of outer peripheral surface 20b: groove 30: Toner concentration sensor (optical sensor) 30a: irradiation light 30b: reflected light L: Liquid level of toner ink T: Toner ink Ta: Toner ink thin layer Tb: Toner ink attached to the cylindrical surface Tc: Toner ink scraped off

Claims (18)

[Claims] 1. A rotation in which a wet developer holding groove is formed endlessly along an outer peripheral surface of a wet developer in a developer tank constituting a developing device provided in an electrophotographic image forming apparatus. The lower portion of the body in the diametrical direction is dipped, and in this state, the rotary body is rotated about the horizontal rotation axis to draw up the wet developer into the holding groove, and the layer thickness of the wet developer is equal to the depth of the holding groove. While the metered wet developer layer is positioned at the top portion of the rotating body by the rotation of the rotating body, the wet developer layer is exposed to light from a light source by another member. It is characterized in that the light reflectance or the light transmittance of the wet developer layer is detected by directly irradiating it without passing through and receiving the reflected light or transmitted light directly at the light receiving portion without passing through other members. Toner concentration of wet type developer Measuring method. 2. The wet developer layer after the previous detection is scraped before each detection operation when the detection operation of the light reflectance or the light transmittance is performed a plurality of times. 5. The method for measuring the toner concentration of the wet type developer according to. 3. By irradiating the wet developer layer located at the top portion of the rotating body with light from a light source from directly above it,
3. The method for measuring toner concentration of a wet developer according to claim 1, wherein the light reflectance of the wet developer layer is detected. 4. The light of the wet developer layer is obtained by irradiating light from a light source onto the wet developer layer located at the top portion of the rotating body in a horizontal direction and in a direction orthogonal to the rotation axis of the rotating body. The toner concentration measuring method of the wet type developer according to claim 1 or 2, wherein the transmittance of the toner is detected. 5. A rotation in which a wet developer holding groove is formed endlessly along an outer peripheral surface of a wet developer in a developer tank constituting a developing device provided in an electrophotographic image forming apparatus. A body is provided rotatably around a horizontal rotation axis with its lower portion in the diameter direction immersed, and a wet developer formed by pumping a wet developer into a holding groove on the upstream side in the rotation direction of the body. A metering blade for making the layer thickness of the layer equal to the depth of the holding groove is contacted with a predetermined contact pressure,
A toner concentration measuring device for a wet developer, comprising an optical sensor as a toner concentration detecting means, which is provided with a light emitting element and a light receiving element immediately above a top portion of a rotating body. 6. A rotation in which a wet developer retaining groove is formed endlessly along an outer peripheral surface of a wet developer in a developer tank constituting a developing device provided in an electrophotographic image forming apparatus. A body is provided rotatably around a horizontal rotation axis with its lower portion in the diameter direction immersed, and a wet developer formed by pumping a wet developer into a holding groove on the upstream side in the rotation direction of the body. A metering blade for making the layer thickness of the layer equal to the depth of the holding groove is brought into contact with a predetermined contact pressure, and an optical sensor is provided as toner concentration detecting means near the top portion of the rotating body. The sensor is configured to include a light emitting element disposed on one of the upstream side and the downstream side in the rotation direction of the rotating body and a light receiving element disposed on the other side, and the light from the light emitting element is located at the top portion of the rotating body. Horizontally on the wet developer layer, A toner concentration measuring device for a wet type developer, characterized in that irradiation is performed in a direction orthogonal to a rotation axis of a rotating body. 7. A cleaning blade for scraping off the wet developer layer after light irradiation from the light emitting element is provided on the downstream side in the rotation direction of the rotating body and in contact with a predetermined contact pressure. The toner concentration measuring device for a wet type developer according to claim 5 or 6. 8. The rotating body is a cylindrical rotating body composed of a reference cylinder that rotates about a rotation axis provided at a center position in the diameter direction of the cylindrical body, and an eccentric cylinder that rotates integrally with the reference cylinder,
Reference cylinders are integrally provided at both longitudinal ends of the eccentric cylinder, and the eccentric cylinder rotates eccentrically around the rotation axis of the reference cylinder, the outer diameter is smaller than the reference cylinder, and the entire outer peripheral surface is the reference cylinder. Of the eccentric cylinder, the central axis of the eccentric cylinder is in the same vertical plane as the rotation center line of the reference cylinder, and the holding groove is the difference in outer diameter between the reference cylinder and the eccentric cylinder. 8. The toner concentration measuring device for a wet developer according to claim 5, wherein the outer peripheral surface of the eccentric cylinder is formed so as to be the bottom surface of the holding groove. 9. In addition to the toner concentration detecting means including an optical sensor, a concentration totalizing means for totaling the toner concentrations detected by the density detecting means, and a totaling result for recording the totalization result output from the density totalizing means. 9. The wet development according to claim 5, further comprising a recording unit and a toner concentration determining unit that determines a toner concentration from the totalized result recorded in the totalized result recording unit. Toner concentration measuring device. 10. The toner concentration measuring device for a wet type developer according to claim 9, wherein the toner concentration is detected once during one rotation of the rotating body. 11. The toner concentration measuring device for a wet type developer according to claim 9, wherein the detection of the toner concentration is started after the rotation of the rotating body reaches a steady state. 12. The toner concentration measuring device for a wet developer according to claim 10, wherein the toner concentration is obtained from the detection result of the toner concentration obtained by continuously rotating the rotating body for two or more revolutions. . 13. The rotating speed of the rotating body when the variation between the toner densities obtained for each rotation of the rotating body exceeds a predetermined value, and the rotating speed of the rotating body is higher than the rotating speed of the rotating body when the toner concentration having a large variation is obtained. 11. The toner concentration measuring device for a wet developer according to claim 10, wherein the variation is set within a predetermined value by increasing or decreasing the variation. 14. The method according to claim 12, wherein when the toner density measurement result exceeds the specified range, the image forming operation is stopped and a warning is issued to the user that the toner density exceeds the specified range. 13. The toner concentration measuring device for a wet developer according to item 13. 15. When the toner density measurement result shows that the toner density tends to decrease with the passage of time, the image forming operation is stopped and a warning indicating that the toner density shows the tendency is displayed by the user. 14. The toner concentration measuring device for a wet type developer according to claim 12 or 13, characterized in that 16. The method according to claim 12, wherein when the variation of the toner density measurement result exceeds the specified range, the image forming operation is stopped and the user is warned that the variation is occurring. The toner concentration measuring device for a wet developer described in the above. 17. When the variation rate of the toner concentration measurement result tends to increase compared to the past toner concentration variation rate, the image forming operation is stopped and the toner concentration variation rate tends to increase. The toner concentration measuring device for a wet type developer according to claim 12, wherein a warning is given to the user. 18. When the variation in the toner density measurement result does not converge within a specified time, the image forming operation is stopped and a warning is issued to the user that the variation does not converge within the specified time. The toner concentration measuring device for a wet type developer according to claim 12.