JP3507364B2 - Developing device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copying machine, a printer, and a recording image display device for developing a visible image by developing an electrostatic latent image formed on an image carrier by an electrophotographic system or an electrostatic recording system. Or a developing device used in an image forming apparatus such as a facsimile.

[0002]

2. Description of the Related Art Conventionally, a dry developer as a developing agent is carried and conveyed near the surface of an image bearing member carrying an electrostatic latent image on the surface of the developer bearing member, and the image bearing member and the developer bearing member are carried. A developing device that develops and visualizes an electrostatic latent image by applying an alternating (alternating) electric field between them is well known.

A developing sleeve is generally used as the developer carrying member, so that it will be referred to as a "developing sleeve" in the following description, and a photosensitive drum is generally used as the image carrying member. Therefore, in the following description, the term "photosensitive drum" is used.

As the above-mentioned developing method, conventionally, for example, 2
A magnetic brush was formed on the surface of a developing sleeve having a magnet inside by a developer (two-component developer) composed of a component system composition (carrier particles and toner particles), and a small developing gap was held to face each other. The magnetic brush is rubbed or brought close to the photosensitive drum, and an alternating electric field is continuously applied as a developing bias between the developing sleeve and the photosensitive drum (between SD), so that the toner particles are exposed to light from the developing sleeve side. A so-called magnetic brush developing method is known in which development is performed by repeatedly performing transfer to the body drum side and reverse transfer. (See, for example, JP-A-55-3060 and JP-A-59-165082).

As shown in FIG. 5, the developing device 18 for developing the two-component magnetic brush has a partition 19 for developing chamber R1.
And a developing container 18a divided into a stirring chamber R2, and stirring screws 23 and 24 as stirring means are rotatably housed in the developing chamber R1 and the stirring chamber R2, respectively. In the opening of the developing chamber R1, a developing sleeve 25 that rotates in a predetermined direction is arranged to face the photosensitive drum 3 that rotates in a predetermined direction at a minute interval, and a magnet roller 29 is fixedly arranged inside thereof. Has been done. Further, a regulating blade 28 for forming a thin layer of developer on the surface of the developing sleeve 25 is arranged opposite to the developing sleeve 25.

The developing container 18a contains a developer 22 in which toner particles and magnetic carriers are mixed, and the mixing ratio of toner particles and magnetic carriers (hereinafter referred to as "T / C ratio") is consumed by the development. The amount of toner commensurate with the supplied toner is dropped and replenished from the toner storage chamber 21 in which the replenishment toner 20 is stored, so that it is kept constant.

At this time, various methods have been proposed for detecting and maintaining the mixing ratio of the toner particles and the magnetic carrier in the developing container 18a. For example, by providing a detection means around the photosensitive drum 3, irradiating the toner transferred from the developing sleeve 25 side to the photosensitive drum 3 side with light, and adjusting the toner replenishment amount from the transmitted light and the reflected light at this time, T / C ratio is maintained, detection means is provided near the surface layer of the developing sleeve 25, and the T / C ratio is detected from reflected light when light is applied to the developer coated on the developing sleeve 25. A method in which a sensor is provided in the sensor 18, the change in the apparent permeability of the developer within a certain volume in the vicinity of the sensor is detected by using the inductance of the coil, and the T / C ratio is detected has been proposed and put into practical use. .

However, the method of maintaining the T / C ratio based on the amount of developing toner on the photosensitive drum 3 causes fluctuations in the distance between the photosensitive drum 3 and the developing sleeve 25, fluctuations in the latent image potential, and the like.
The amount of toner on the photosensitive drum 3 may change due to factors other than the fluctuation of the T / C ratio, and as a result, malfunction of toner replenishment may occur, and the developer coated on the developing sleeve 25 may be exposed to light. T / C from reflected light when applying
The method of detecting the ratio has a problem that the T / C ratio cannot be accurately detected when the detection unit is soiled due to toner scattering or the like.

On the other hand, by utilizing the inductance of the coil, the developer 22 in a constant volume in the vicinity of the sensor is used.
The detection means of the method of detecting the apparent magnetic permeability change to detect the T / C ratio, that is, the toner concentration control means (hereinafter referred to as “toner concentration sensor”) is low in cost of the sensor alone, and also due to toner scattering. Since it is not affected by the problem of dirt, it can be said to be the optimum T / C ratio detecting means in a low-cost, small-space copying machine or image forming apparatus.

The toner concentration sensor utilizing the change in magnetic permeability of the developer means that the T / C ratio in the developer becomes low within a certain volume when the magnetic permeability becomes large, which means that This means that the amount of toner in the developer has decreased, so when toner replenishment is started and conversely the magnetic permeability decreases, it means that the T / C ratio in the developer has increased within a fixed volume. Therefore, since it means that the amount of toner in the developer has increased, the T / C ratio is controlled based on a sequence in which toner supply is stopped or reduced.

[0011]

However, since the toner concentration sensor utilizing the above-mentioned inductance, that is, the inductance detection sensor, detects the change in the apparent magnetic permeability of the developer within a certain volume, the sensor surface is developed in the developing container. The developer must have such a thickness that it can contact the developer and can detect the toner concentration, and the developer shows a constant flow when the developer is stirred. As described above, in the toner concentration sensor, if the developer does not show a constant flow when the developer is stirred, the sensor output cannot follow the change in the T / C ratio of the developer. It is preferable that they are opposed to and close to each other.

On the other hand, the toner concentration sensor described above generates a magnetic flux by the oscillation circuit and detects the change in the apparent permeability of the developer within a fixed volume. Therefore, if a conductive member is present in the vicinity of the sensor, the conductive member is detected. There is a problem that an eddy current is generated due to the magnetic flux from the sensor and the operating point of the output of the toner concentration sensor is changed. On the other hand, if there is no problem if the operating point of the output of the toner concentration sensor is readjusted, as described in Japanese Patent Publication No. 3-42676, the stirring screw arranged in the vicinity of the sensor surface is It is preferably an insulating and non-magnetic member.

By the way, in recent years, there has been a demand for downsizing of image forming apparatuses, particularly full-color copying machines, and accordingly, the developing apparatus must be further downsized. As a result, not only a developing container but also a developing sleeve having a small diameter, a small amount of developer and a small stirring screw are used, and a highly reliable device which is the same as the conventional one is desired.

However, when an insulating non-magnetic member is used with a small-diameter stirring screw, the strength of the stirring screw cannot be ensured, and the developer cannot be agitated when it is agitated / conveyed or when it is used for agitation. There are problems that the rotating shaft of the screw is deformed, the stirring screw comes into contact with the developing container or the toner concentration sensor, and stirring and conveying of the developer cannot be performed as usual.

Especially, the radius of the rotating shaft of the stirring screw is 3 m.
The above tendency becomes stronger under the condition of m or less.

To solve the above problems, if the outermost radius of the stirring screw is fixed to increase the strength of the rotating shaft of the stirring screw and only the diameter of the rotating shaft of the stirring screw is increased, the developer is stirred. The number of agitating parts for the developer is reduced, which causes a problem in agitability of the developer, which causes problems such as poor agitation of the replenished toner and a decrease in toner charge amount. Therefore, the outermost diameter of the stirring screw is preferably 2.5 times or more the diameter of the rotating shaft.

With the downsizing of the developing device, when the outermost radius of the stirring screw becomes 7.5 mm or less, or when the radius of the rotating shaft of the stirring screw becomes 3 mm or less, the rotating shaft of the stirring screw is deformed. Therefore, a strong member such as iron or stainless steel must be used for the rotating shaft of the stirring screw.

However, when a conductive member is used for the rotating shaft of the stirring screw, the AC component of the developing bias is induced on the rotating shaft of the stirring screw, and a problem arises in that it enters the circuit portion of the toner concentration sensor as noise.

According to a study made by the present inventors, a toner concentration sensor utilizing inductance was used, iron was used as a rotating shaft, and a stirring screw using a non-magnetic / insulating member was used as a stirring portion near the sensor surface. In this case, it was found that the sensor sensitivity (change in sensor output with respect to change in sensor ratio) was reduced by about 30% when the AC component of the developing bias was affected, compared to when there was no influence of the AC component of the developing bias. .

Therefore, when the toner density sensor is initially set (sensitivity setting) with no influence of the AC component of the developing bias when the sensor sensitivity is initially set, the AC component of the developing bias is applied during image formation. When, the toner density cannot be detected accurately.

For example, as shown in FIG. 6, the T / C ratio is 6
In an image forming apparatus capable of obtaining a good image at 8%,
The sensor sensitivity is a sensor having a characteristic like A, and the toner density control is initialized without being affected by the AC component of the developing bias, and the sensor sensitivity like B due to the influence of the AC component of the developing bias during image formation. If the T / C ratio is 6% because the toner density control is performed with the sensitivity A sensor as the reference, the A sensor can accurately detect the output a with respect to the T / C ratio. However, since a sensor sensitivity such as sensitivity B detects a sensor output such as b, B is 6. on the sensitivity table of A.
The sensor output of 5% will be detected, and T /
The sensor output with respect to the C ratio cannot be detected accurately.

Due to such an erroneous sensor detection, a sensor output indicating that the toner amount has not decreased even though the toner amount has decreased is produced, and toner is not replenished or toner is replenished. A sensor output indicating insufficient toner supply is output, and problems such as further toner supply occur. In the former case, problems such as image deterioration due to a decrease in the amount of toner in the developer, low image density, and low image density due to an increase in the toner charge amount are caused. On the other hand, in the latter case, there is a problem that the image density becomes dark due to excessive toner supply, a problem that the developer amount increases as the toner amount increases, and the developer overflows from the developing container, or the toner ratio in the developer increases. This causes problems such as toner scattering due to a decrease in the toner charge amount.

[0023]

The object of the present invention is to provide a developing apparatus capable of eliminating electrical impacts on both the toner density control means to achieve the downsizing.

[0025]

SUMMARY OF THE INVENTION The above object is achieved according to the present invention
It is achieved by the developing device. In summary, the present invention is, toner
Developer container containing a developer containing a magnetic carrier
And a partition for partitioning the developing container into a developing chamber and a stirring chamber,
A developer carrying member carrying a developer in the developing chamber;
Stirring means for stirring and transporting the developer in the stirring chamber, and
Use the change in magnetic permeability of the developer to detect the toner concentration in the container.
And a toner concentration sensor used for carrying the developer.
Applying a developing bias that superimposes DC voltage and AC voltage on the body
In a developing device that develops by
The means is a conductive rotary shaft and an insulating material fixed to the rotary shaft.
And a pair of stirrers, and a pair of stirrers are provided through the stirrer.
The toner concentration sensor is installed in the stirring chamber so that
The rotation shaft is grounded and the
Characterized by preventing erroneous detection of the toner concentration sensor
It is a developing device .

According to one embodiment of the present invention, the toner
-Place a conductive member between the detection surface of the concentration sensor and the circuit section.
And the conductive member is grounded together with the rotating shaft.

[0027]

[0028]

BEST MODE FOR CARRYING OUT THE INVENTION The developing device according to the present invention will be described below in more detail with reference to the drawings. In the embodiments described below, the present invention is described as being embodied in an electrophotographic image forming apparatus as shown in, for example, FIG. 2, but the present invention is not limited to this.

In FIG. 2, the electrophotographic image forming apparatus is
A photoconductor drum 3, which is an image carrier, is rotatably provided, the photoconductor drum 3 is uniformly charged by a primary charger 1, and then,
An information signal is exposed by a light emitting element 2 such as a laser to form an electrostatic latent image, which is visualized by a developing device 32. Then, the visible image is transferred onto the transfer paper 5 by the transfer charger 4 and further fixed by the fixing device 6 to obtain a permanent image. Further, the transfer residual toner on the photosensitive drum 3 is removed by the cleaning device 7.

An embodiment of the developing device according to the present invention will be described with reference to FIGS. 1 and 3 to 5.

In FIG. 1, the developing device 32 includes a developing container 31, and the inside of the developing container 32 is divided by a partition wall 44 into a developing chamber R1 and a stirring chamber R.
The toner storage room R3 is divided into two parts, and above the stirring room R2.
Is provided in which the replenishment toner 33 is stored. From the replenishment port 34 at the bottom of the toner storage chamber R3, an amount of toner commensurate with the toner consumed in the development is supplied to the stirring chamber R
Dropped within 2 and replenished. On the other hand, in the developing chamber R1 and the stirring chamber R2, a developer 35 in which the toner particles and the magnetic carrier are mixed is contained.

A spiral-shaped first conveying screw (stirring means) 36 having a function of agitating the developer and excellent transportability is housed in the developing chamber R1, and the developer is driven by rotation in the arrow direction. Are conveyed along the longitudinal direction of the developing sleeve 38 which is a developer carrying member.

In the stirring chamber R2, similarly, a spiral second conveying screw (stirring means) 37 is housed rotatably in the direction of the arrow, and the developer conveying direction by the second conveying screw 37 is the developing chamber. The direction is opposite to that of the first conveying screw 36 of R1. The partition 44 has openings (not shown) on the front side and the back side in the drawing, and the developer conveyed by the first conveying screw 36 is transferred to the second conveying screw 37 from one of the openings. The developer carried by the second carrying screw 37 is delivered to the first carrying screw 36 from the other one of the openings.

Further, an opening is provided in a portion of the developing container 31 close to the photosensitive drum 3, and the opening is made of a material such as aluminum or non-magnetic stainless steel, and has a suitable unevenness on the surface thereof. A developing sleeve 38, which is a carrier, is provided.

In the present embodiment, the developing sleeve 38 has a peripheral velocity V in the direction of arrow b (the same direction as the photoconductor rotating direction).
After being rotated by b and regulated to an appropriate developer layer thickness by a layer thickness regulating blade 41 provided at the upper end of the opening of the developing container 32, the developer is carried and conveyed to the developing area 39. The magnetic brush of the developer carried on the developing sleeve 38 is the developing area 3
9, the photosensitive drum 3 rotating in the direction of arrow a at the peripheral speed Va.
, And the electrostatic latent image is developed in this development area 39.
The peripheral speed Vb of the developing sleeve 38 is 1 to the peripheral speed ratio of the photosensitive drum.
30 to 200% is desirable, and 150 to 180% is even better. If the amount is less than the above range, sufficient image density cannot be obtained, and if the amount is more than the above range, the developer scatters.

Inside the developing sleeve 38, a magnet 42, which is a roller-shaped magnetic field generating means, is fixedly arranged. The magnet 42 has a developing magnetic pole N1 facing the developing area 39. A magnetic brush of developer is formed by the developing magnetic field formed in the developing region 39 of the developing magnetic pole N1, and the magnetic brush comes into contact with the photosensitive drum 3 to develop the electrostatic latent image. At that time, the toner adhering to the magnetic brush and the toner adhering to the surface of the sleeve are also transferred to the image area of the electrostatic latent image and developed. In this embodiment, the magnet is the developing magnetic pole N.
In addition to 1, it has N2, S1, S2, and S3 carrier poles.

With this structure, the developer 3 applied at the S2 pole by the rotation of the developing sleeve 38 as in the conventional case.
5 passes through the layer thickness regulating blade 41 to reach the developing magnetic pole N1, and the developer 35 that stands up in the magnetic field develops the electrostatic latent image on the photosensitive drum 3. Then, the repulsive magnetic field between the S2 pole and the S3 pole causes the developer 35 on the developing sleeve 38 to drop into the stirring chamber R1. The developer 35 that has dropped into the stirring chamber R1 is stirred and conveyed by the first and second conveying screws 36 and 37.

The inductance detecting sensor 43, which is the toner concentration detecting means in the present embodiment, is arranged on the side surface of the stirring chamber R2 in the vicinity of the second conveying screw 37 as shown in FIG. The side surface of the second conveying screw 37 has a regular flow rate of the developer and is unlikely to accumulate. Therefore, when the inductance detection sensor 43 is arranged in this portion, it is considerably larger than in other portions in the developing container 32. Detection accuracy increases.

As described in the section "Prior Art", the toner concentration detecting inductance detecting sensor 43 has a T / C ratio of the developer unless the developer 35 shows a constant flow when the developer is stirred. Since the sensor output cannot follow the change, the sensor surface (detection surface) 4
5 is preferably opposed to and close to the second stirring screw 37.

It should be noted that the inductance detecting sensor 43 may be installed on the sensor surface 45 where the developer thickness is such that toner concentration can be detected and the developer 35 shows a constant flow when the developer is stirred. However, it does not matter if it is in another place.

As described above, the stirring screw used in the system of the present invention needs to have a small diameter in order to downsize the device. Therefore, if this stirring screw is made of an insulating and non-magnetic material and has a small diameter, the strength of the stirring screw cannot be ensured, and it cannot be endured under the load of developer stirring / conveying or durability, and it deforms. Since there is a problem that the container and the toner concentration sensor are contacted with each other , or the stirring / conveying of the developer cannot be performed as usual, the rotating shafts 46 and 47 of the stirring screws 36 and 37 have strong iron. -Stainless steel etc. must be used.

As described above, conductive members are used for the rotating shafts 46 and 47 of the first and second stirring screws 36 and 37, and the AC component of the developing bias is the first and second stirring screws 36 and 37. Since there is a problem that the circuit portion 43a of the inductance detection sensor 43 induced on the rotating shafts 46 and 47 of the second embodiment is mounted as noise, the present invention faces the inductance detection sensor 43 and is disposed close to the second portion.
By connecting the rotating shaft 47 of the stirring screw 37 to the ground 48, the influence of the AC component of the developing bias is eliminated.

The conditions of the inductance detection sensor and the developing device used in the study by the present inventors and the T at that time are as follows.
The relationship between the / C ratio and the sensor output value is shown in FIG.

In the developing device 32 where a good image can be obtained in the range of T / C ratio of 6 to 8%, stirring means; spiral screw, stirring part material ABS, rotary shaft material iron, outermost shell Turning radius 7m
m, rotation axis radius 2 mm-toner concentration control means; inductance detection sensor,
Sensor surface radius 5 mm-The distance between the outermost portion of the stirring means and the sensor surface of the inductance detection sensor 0.5 mm-The distance between the outermost portion of the rotating shaft and the sensor surface of the inductance detection sensor 5.5 mm In Fig. 3, under the above conditions. The system of the present invention in which the rotating shaft 47 of the second stirring screw 37, which is arranged close to and faces the sensor surface 45 of the inductance detection sensor 43, is connected to the ground 48 while the developing bias is OFF and the AC component of the developing bias is ON. The relationship between the T / C ratio and the output value of the inductance detection sensor is shown.

In the figure, straight line X: development bias OFF state straight line Y: development bias AC component ON state straight line Z: development bias AC component ON state, facing the detection surface 45 of the inductance detection sensor 43 and approaching This is a system of the present invention in which the rotating shaft 47 of the arranged second stirring screw 37 is grounded 48.

From the above examination results, the output change amount (sensor sensitivity) of the inductance detection sensor 43 when the T / C ratio changes by 1% is the developing bias OFF state: 0.42 V /%, and the AC component of the developing bias is ON. State: 0.3 V /% In the system of the present invention: 0.4 V /%, the system of the present invention was able to suppress the decrease in sensor sensitivity.

With the above-described configuration of the present embodiment, the influence of the AC component of the developing bias can be eliminated, and the AC component of the developing bias is applied during the initial image formation of the toner density sensor and during the image formation. Since the sensor sensitivities of the states are the same and the toner density can be accurately controlled, it is possible to prevent adverse effects due to excessive toner supply, insufficient toner supply, and the like.

Second Embodiment Next, a second embodiment of the present invention will be described with reference to FIG. In the first embodiment, the inductance detection sensor 43
It was possible to suppress the influence of the AC component of the developing bias by connecting the conductive rotating shaft 47 of the second stirring screw 37, which is arranged in proximity to the sensor surface 45, and is connected to the ground 48.

In this embodiment, as shown in FIG. 4, a conductive seal member 50 is further sandwiched between the circuit portion 43a of the inductance detection sensor 43 and the developing container 31, and the conductive seal member 50 is grounded. It is characterized by being connected.

With the same combination of the inductance detecting sensor 43 and the developer 35 as the system used in the first embodiment,
The conductive rotating shaft 47 of the second stirring screw 37, which is arranged close to the sensor surface 45 of the inductance detection sensor 43, is connected to the ground 48, and the conductive seal member 5 is connected.
0 is sandwiched between the circuit portion 43a of the inductance detection sensor 43 and the developing container 31 so as to face the member to which the developing bias is applied, and the conductive seal member 50 is connected to the ground 4
Similar to the first embodiment, in the system connected to 8, the output change amount (sensor sensitivity) of the toner concentration sensor when the T / C ratio changes by 1% when the developing bias is turned on and off is examined. , Conductive seal member + Connect conductive seal member to earth +
Development bias OFF: 0.42V /% Conductive seal member + Connect conductive seal member to ground +
AC component of developing bias: 0.42 V /%, the influence of AC component of developing bias could be further eliminated. As a result, accurate toner density control can be performed.

Further, the conductive rotary member 47 of the second stirring screw 37, which is arranged close to the sensor surface 45 of the inductance detection sensor 43, is not connected to the ground 48, but the conductive seal member 50 is connected to the ground 48. Even in a system in which the conductive seal member 50 is connected and sandwiched between the circuit portion 43a of the inductance detection sensor 43 and the developing container 31 so as to face the member to which the developing bias is applied, the T / C
The output change amount (sensor sensitivity) of the inductance detection sensor when the ratio changes by 1% is 0.4 V /%, and the influence of the AC component of the developing bias can be eliminated. Therefore, it is effective even when the conductive rotating shaft of the stirring screw cannot be connected to the ground due to the configuration.

[0052]

As is apparent from the above description, the present invention
According to the above, the developer containing the toner and the magnetic carrier is collected.
Partition the developing container into a developing chamber and a stirring chamber.
And a developer carrier that holds the developer in the developing chamber.
And stirring means for stirring and transporting the developer in the stirring chamber, and
Use the change in magnetic permeability of the developer to detect the toner concentration in the container.
Used as a developer concentration carrier
Apply a developing bias that superimposes DC voltage and AC voltage
In a developing device that develops by
The electric rotating shaft and the insulating stirring unit fixed to the rotating shaft
Toner concentration so that it faces the partition through the stirring means.
A sensor is installed in the stirring chamber and the rotary shaft is grounded for development.
Prevented false detection of toner concentration sensor due to bias
As a result, the toner density sensor is
Can eliminate the influence of the AC component of the developing bias for Sir, therefore, it is possible to control the correct toner density in the same sensor sensitivity and the initial setting of the toner density sensor, it is possible to obtain a high quality image. In addition, overflow of the developer from the developing container and toner scattering can be prevented.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of a developing device according to the present invention.

FIG. 2 is a schematic configuration diagram showing an electrophotographic image forming apparatus that can use the developing device of the present invention.

FIG. 3 is a graph showing the relationship between the T / C ratio and the sensor output value in the first embodiment.

FIG. 4 is a configuration diagram illustrating a developing device according to a second embodiment.

FIG. 5 is a configuration diagram showing an example of a conventional developing device.

FIG. 6 is a graph showing a relationship between a T / C ratio and a sensor output value in a conventional developing device.

[Explanation of symbols]

3 Photoreceptor Drum (Image Carrier) 31 Developing Container 32 Developing Device (Developing Means) 36, 37 Stirring Screws (Stirring Means) 36a, 37a Stirring Section 38 Developing Sleeve (Developer Carrier) 43 Inductance Detection Sensor (Toner Density Control) Means) 43a Circuit part 45 Sensor surface (detection surface) 46, 47 Rotating shaft part 48 Grounding 50 Conductive seal member

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ichiro Ozawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) References: Kaihei 4-28659 (JP, U) Japanese Patent Publication 3 −42676 (JP, B2) J. Kohei 4-52755 (JP, Y2) (58) Fields investigated (Int.Cl. ⁷ , DB name) G03G 15/08 G03G 15/06 101

Claims (2)

(57) [Claims] 1. A developing container for containing a developer in which a toner and a magnetic carrier are mixed, a developing chamber and a stirring chamber for the developing container.
A partition wall, a developer carrier that carries the developer in the developing chamber, a stirring unit that stirs and conveys the developer in the stirring chamber, and a toner concentration in the developing container is detected. developing
In the developing apparatus for developing by applying a magnetic permeability has changed toner density sensor using a, a, a developing bias obtained by superimposing a DC voltage and an AC voltage to the developer carrying member of agents, said agitating means conducting A rotary shaft and an insulating stirrer fixed to the rotary shaft, and the toner is disposed so as to face the partition through the stirring means.
-Providing a concentration sensor in the stirring chamber and the rotating shaft
The toner concentration sensor by grounding the developing bias
A developing device characterized by preventing erroneous detection of . 2. A detection surface and a circuit of the toner concentration sensor
A conductive member between the part and the conductive member.
The developing device according to claim 1, wherein the developing device is grounded together with the rotating shaft.
Place