JP2000056555A - Developing device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the detecting accuracy and reliability of an inductance sensor by optimizing the shapes of each small-diameter screw and the sensor, the gap therebetween, and the relation in size therebetween, in a combination of a small developing machine and the inductance sensor. SOLUTION: The relation between screws 4, 5 and a toner density sensor 10 having an approximately circular detecting surface 10a detecting changes in toner density of a two-component developer as changes in magnetic permeability is set to satisfy the three expressions: 0<=Dmin<=1×10-3, 0.4<=r/R<=0.75 and 0.6<=Dmin/Dmax<=1.0 wherein Dmin is the closest distance (m) between the outermost hull surface of each screw and the detecting surface; (r) is the radius (m) of the detecting surface; R is the turning radius (m) of the outermost hull of each screw; and Dmax is the longest distance (m) between a perpendicular on the detecting surface and the outermost hull surface of an agitating member, with the radius R(m) of the outermost hull of the screw 4 in the range of 1.0×10-2<=R<=1.6×10-2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Conventionally, a dry developer as a developer is carried on the surface of a developer carrying member, and the developer is conveyed and supplied to the vicinity of the surface of the image carrying member carrying an electrostatic latent image. A developing device that develops an electrostatic latent image to make it visible while applying an alternating (alternating) electric field between a body and a developer carrying member is well known.

Since the developer carrier generally uses a developing sleeve in many cases, it is referred to as a "developing sleeve" in the following description, and the image carrier generally uses a photosensitive drum. Therefore, in the following description, it is referred to as “photosensitive drum”.

As the above-mentioned developing method, conventionally, for example, 2
A magnetic brush is formed on the surface of a developing sleeve in which a magnet, which is a magnetic field generating means, is disposed by using a developer (two-component developer) composed of a component system composition (carrier particles and toner particles) to maintain a minute developing gap. The magnetic brush is rubbed or brought close to the photoconductor drum opposed to the photoconductor drum, and a continuous alternating electric field is applied between the development sleeve and the photoconductor drum (between S and D). A so-called magnetic brush developing method in which development is performed by repeatedly performing transfer and reverse transfer to the photosensitive drum side is known. (For example, Japanese Patent Application Laid-Open No. 55-32060,
See JP-A-59-165082).

The developing device for developing a two-component magnetic brush includes a developing container divided by a partition into a developing chamber and a stirring chamber. The developing chamber and the stirring chamber are each capable of rotating a stirring and conveying screw as a stirring member. Is housed in At the opening of the developing chamber, a developing sleeve that rotates in a predetermined direction is arranged facing the photosensitive drum that rotates in a predetermined direction at a small interval, and a magnet is fixed inside the developing sleeve.

A developer in which toner particles and a magnetic carrier are mixed is contained in a developing container, and a mixing ratio between the toner particles and the magnetic carrier (hereinafter referred to as “T / C ratio”) is consumed by the development. An amount of toner corresponding to the toner is kept constant by being dropped and replenished from a toner storage chamber containing replenishing toner.

[0007] The dropped and replenished toner is stirred with the developer in the developing container by stirring by a screw in the stirring chamber, and is conveyed. The developer is conveyed along the longitudinal direction of the container opposite to the developer conveying direction of the conveying screw in the developing chamber. The partition is provided with openings on the near side and the back side, and the developer is delivered through the opening.

Meanwhile, maintaining the mixing ratio between the toner particles of the two-component developer and the magnetic carrier in the developing container is very important for stabilizing the output image, and various methods for detecting and maintaining the output image have conventionally been proposed. Have been.

For example, a detecting means is provided around the photosensitive drum to irradiate the developed toner image on the photosensitive drum with light, and the amount of toner replenishment is adjusted based on the transmitted light or reflected light. A method for detecting the C ratio, a method for providing a detecting means near the developing sleeve, and a method for detecting the T / C ratio from reflected light when the developer applied on the developing sleeve is irradiated with light, and a sensor in the developing container A method of detecting the change in the apparent magnetic permeability of the developer in a certain volume near the sensor using the inductance of the coil and detecting the T / C ratio has been proposed and put into practical use.

However, the method of maintaining the T / C ratio based on the amount of the developing toner on the photosensitive drum is based on, for example, the gap between the photosensitive drum and the developing sleeve, the fluctuation of the latent image potential, and the like. Irrespective of the T / C ratio, the amount of developing toner fluctuates. As a result, there is a problem that the toner cannot be properly replenished. In addition, the amount of reflected toner when the developer applied on the developing sleeve is irradiated with light is reduced. The method of detecting the T / C ratio is an accurate T / C ratio in the case where the surface of the reflected light detecting means is contaminated by toner scattering caused when the charge amount of the toner is reduced in a high humidity environment or the like. There is a problem that cannot be detected.

On the other hand, a sensor of a system that detects a change in the magnetic permeability of a developer in a fixed volume near the sensor using the inductance of the coil and detects a T / C ratio (hereinafter referred to as an "inductance detection sensor"). In addition to the low cost of the sensor alone, the erroneous detection described above is small, and the T / C ratio of the developer can be accurately detected.

The inductance detecting sensor is disposed near the screw. For example, when the magnetic permeability of the developer in a certain volume increases, it is determined that the T / C ratio of the developer has decreased, and toner supply is started. Conversely, when the magnetic permeability decreases, it is determined that the T / C ratio of the developer has increased,
The T / C ratio of the developer is controlled based on a sequence for stopping toner supply.

[0013]

By the way, in recent years, in image forming apparatuses, in particular, in full-color copying machines, downsizing of the apparatuses has been required, and accordingly, the development apparatus has been required to pursue further downsizing. is there. As a result, not only the developing container but also the developing sleeve and the agitating member must be miniaturized to form a highly reliable apparatus unchanged from the conventional one.

On the other hand, since the above-mentioned inductance detecting sensor detects a change in the magnetic permeability of the developer in a certain volume, the bulk of the developer due to standing, environmental change, or the like.
If the density fluctuates, there is a problem that it is determined that the magnetic permeability is different even if the T / C ratio is the same. It is arranged near the circulating and flowing stirring member.

At this time, depending on the bulkiness of the small diameter stirring member and the developer, and the shape and size of the sensor, the following problems may occur.

As shown in FIG. 7, with respect to the developing container 101 substantially along the rotation diameter and the curvature of the stirring member 105,
The size of the sensing surface 110a of the sensor 110, for example,
When the detection surface 110a has a substantially circular shape and the diameter is considerably large, a space such as a hatched portion c and a portion d is formed in a gap between the sensor 110 and the stirring member 105.

When the developer is agitated in the developing container 101 in a state where there is such a space, the developer entering the space of the hatched portions c and d, particularly the portion c, remains without being conveyed by the stirring member 105. Would.

The change in the developer T / C ratio with respect to the consumption and replenishment of the toner due to the developing operation is mainly due to the developer in the hatched portion e circulating in the developing container 101 by the stirring member 105. The developer existing in the space between the hatched portions c and d where the developer stays, particularly the portion c, has a very small change in the T / C ratio.

In this state, the inductance detecting sensor 1
When it is attempted to detect the T / C ratio at 10, the developer in the hatched portions c and d where the change in the developer T / C ratio is small together with the developer in the hatched portion e where the T / C ratio fluctuates. Therefore, the output value of the toner concentration detection sensor 110 with respect to the T / C ratio cannot be accurately obtained.

In FIG. 8, a straight line X indicates the relationship between the T / C ratio of the developer and the output value of the toner density detection sensor.

The relationship of the straight line X is an ideal state. Even if the toner is consumed and replenished from the center T / C ratio, an error occurs in the toner replenishing amount if the toner does not change on the straight line X. On the other hand, a straight line Y in the figure shows a change in the output value of the inductance detection sensor when the consumption and replenishment are actually performed in the state where the space exists. When the T / C ratio is low, the output of the inductance detection sensor is lower than that of the straight line X, and when the T / C ratio is high, the output of the inductance detection sensor is a straight line X.
It can be seen that there is a tendency to be higher than in the case of.

This is because even if the T / C ratio of the developer in the hatched portion e circulating in the developing container decreases, the staying developer in the hatched portions c and d remains close to the center T / C ratio. As a result, the inductance detection sensor detects both the developer having a low T / C ratio, so that the output value becomes lower than the output value on the straight line X, and conversely, the T / C of the developer in the hatched portion e.
Even when the ratio is increased, the developer remaining in the hatched portions c and d has the center T /
Since the ratio remains close to the C ratio, the inductance detection sensor detects both the developer having a high T / C ratio and the developer having the central T / C ratio. It is because it becomes high.

Although the output value of the inductance detection sensor with respect to the T / C ratio cannot be obtained accurately for the above reason, in this case, if the staying developer in the hatched portions c and d does not move, the sensor sensitivity (T / C ratio 1% change), but if the output value of the inductance detecting sensor always changes on the straight line Y with respect to the change of the T / C ratio, the change of the T / C ratio will occur. It can detect enough.

However, if the staying developer moves due to the vibration of the image forming apparatus itself, the vibration of the developing device due to the copying operation, the change in the fluidity of the developer, the change in the bulk density of the developer, etc., the T / C
The ratio following line Y will not be reproduced.

Conversely, the size of the detection surface of the sensor, for example, if the detection surface is substantially circular, the diameter of the development container is substantially equal to the rotation diameter of the stirring member and the curvature thereof.
If the size is very small, the above-mentioned problem of the dead space is solved, but first, a problem of a decrease in the absolute output of the sensor occurs. This reduction in absolute output can be prevented by improving members such as coils and cores inside the sensor, but in that case, the cost is increased. Also,
If the area of the sensor detection surface is reduced, the possibility of detecting a local change in magnetic permeability of the developer in the developing container (for example, a developer locally containing the aggregated toner) increases, and As a result, also in this case, a malfunction of toner supply occurs.

Therefore, it is desired to optimize the positional relationship, the size relationship, the shape, the gap, and the like between the small diameter stirring member and the inductance detection sensor.

Accordingly, a main object of the present invention is to provide a developing device and an image forming apparatus which can achieve both miniaturization of the device and improvement of the reliability of the toner density detecting means.

It is another object of the present invention to provide a developing device and an image forming apparatus in which the relationship between the developer stirring member and the toner concentration detecting means is optimized.

Another object of the present invention is to provide a developing apparatus and an image forming apparatus which can improve the detection accuracy of the toner density detecting means.

[0030]

The above object is achieved by a developing device and an image forming apparatus according to the present invention. In summary, the present invention provides a two-component developer containing a non-magnetic toner and a magnetic carrier facing the image carrier in order to develop the electrostatic latent image formed on the image carrier into a visible image. A rotatable developer carrier that carries and conveys therein a fixed magnetic field generating means, a developing container that contains a two-component developer, and a developer container that circulates and agitates the two-component developer. An agitating member disposed, and a toner concentration detecting means having a substantially circular detection surface for detecting a change in toner concentration of the two-component developer as a change in magnetic permeability in a position outside and close to the outermost surface of the stirring member; In order to reduce the stagnation of the developer near the detection surface, the outermost radius R (m) of the stirring member is set to 1.0 × 10 ⁻² ≦ R ≦ 1.6 × 1.
0 ^-2 in the range of, Dmin: minimum distance between the outermost surface and the detection surface of the stirring member (m), r: radius of the sensing surface (m), R: outermost rotation of the agitating member Radius (m), Dmax: when the longest distance (m) between the perpendicular to the detection surface and the outermost surface of the stirring member, 0 ≦ D
min ≦ 1 × 10 ⁻³ , 0.4 ≦ r / R ≦ 0.75,
A developing device characterized by satisfying three expressions of 0.6 ≦ Dmin / Dmax ≦ 1.0.

According to another aspect of the present invention, there is provided an image carrier on which an electrostatic latent image is formed, and in order to develop the electrostatic latent image formed on the image carrier into a visible image, A rotatable developer carrier in which a fixed magnetic field generating means is disposed, which carries and conveys a two-component developer including a non-magnetic toner and a magnetic carrier, facing the image carrier, and contains the two-component developer. A developing container, a stirring member arranged in the developing container for circulating and stirring the two-component developer, and a toner concentration of the two-component developer located outside and close to the outermost surface of the stirring member. In an image forming apparatus including a developing device having a toner density detecting unit having a substantially circular detection surface for detecting a change as a magnetic permeability change, in order to reduce stagnation of developer near the detection surface, the stirring member Outer radius R
(M) is in the range of 1.0 × 10 ⁻² ≦ R ≦ 1.6 × 10 ⁻² , and Dmin: the closest distance (m) between the outermost surface of the stirring member and the detection surface, r: Radius (m) of the detection surface, R: outermost radius of rotation of the stirring member (m), D
max: the longest distance (m) between the perpendicular to the detection surface and the outermost surface of the stirring member, 0 ≦ Dmin ≦ 1 × 1
0 ^-3 , 0.4 ≦ r / R ≦ 0.75, 0.6 ≦ Dmin /
An image forming apparatus is provided which satisfies the following three expressions: Dmax ≦ 1.0.

In the above invention, it is preferable that the stirring member has a spiral shape. It is preferable to process the surface of the detection surface that does not follow the wall shape of the developing container so that the developer does not contact the surface. It is preferable that the detection surface protrudes inside the developing container from an inner wall surface of the developing container. The toner concentration detecting means detects when the agitating member rotates when the developing device is driven, and determines a location where the developing device is driven, in which the flow rate of the developer flowing through the detecting surface during the stirring of the developer is constant and the flow is regular. It is preferable that the location is

[0033]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a developing device and an image forming apparatus according to the present invention will be described in more detail with reference to the drawings. In the following embodiments, the present invention will be described as being embodied in an electrophotographic image forming apparatus as shown in FIG. 2, for example, but the present invention is not limited to this.

Referring to FIG. 2, in the electrophotographic image forming apparatus, a photosensitive drum 6 serving as an image carrier is rotatably provided, and the photosensitive drum 6 is uniformly charged by a primary charger 21. For example, an information signal is exposed by a light emitting element 22 such as a laser to form an electrostatic latent image, and is visualized by the developing device 1.
Next, the visible image is transferred to a transfer paper 24 by a transfer charger 23 and further fixed by a fixing device 25 to obtain a permanent image. The transfer residual toner on the photosensitive drum 6 is removed by the cleaning device 26.

Embodiment 1 FIGS. 1, 3 and 4 show a first embodiment of the present invention.
This will be described below.

In FIG. 1, a developing device 1 includes a developing container 1a.
The inside is partitioned into a developing chamber R1 and a stirring chamber R2 by a partition 2, and a toner storage chamber (not shown) is provided above the stirring chamber R2, and a replenishing toner 12 is accommodated therein. From the supply port 13 at the bottom of the toner storage chamber,
An amount of toner 12 corresponding to the toner consumed in the development is dropped and supplied into the stirring chamber R2. On the other hand, the developer 11 in which the toner particles and the magnetic carrier are mixed is accommodated in the developing chamber R1 and the stirring chamber R2.

In the developing chamber R1, a first screw (stirring member) 4 having a spiral shape and having excellent functions of stirring and transporting the developer is accommodated. Is transported along the longitudinal direction of the developing sleeve 7 which is a developer carrier.

Similarly, a spirally shaped second screw (stirring member) 5 is accommodated in the stirring chamber R2 so as to be rotatable in the direction of arrow f. 4 in the opposite direction. The partition 2 is provided with openings (not shown) on the near side and the back side in the figure, and the developer 11 conveyed by the first screw 4 is delivered to the second screw 5 from one of the openings, The developer 11 conveyed by the second screw 5 is transferred to the first screw 4 from another of the openings.

An opening is provided in a portion of the developing container 1a adjacent to the photoreceptor drum 6, and the opening is made of a material such as aluminum or non-magnetic stainless steel, and has a developing sleeve having moderate unevenness on its surface. 7 are provided.

In this embodiment, the developing sleeve 7 is
After rotating at a peripheral speed Vb in the direction of arrow b (the direction opposite to the photoconductor rotation direction) and being regulated to an appropriate developer layer thickness by a layer thickness regulating blade 8 provided at the upper end of the opening of the developing container 1, The developer is carried and transported to the developing area. The magnetic brush of the developer carried on the developing sleeve 7 contacts the photosensitive drum 6 rotating at the peripheral speed Va in the direction of arrow a in the developing area, and the electrostatic latent image is developed in this developing area. The peripheral speed Vb of the developing sleeve 7 is desirably 130 to 200% of the peripheral speed of the photosensitive drum.
150-180% is even better. Below the above range, a sufficient image density cannot be obtained, and above this range, the developer is scattered.

In the developing sleeve 7, a magnet 9 as a roller-shaped magnetic field generating means is fixedly arranged. This magnet 9
Has a development magnetic pole S1 facing the development area. The developing magnetic pole S1 forms a magnetic brush of a developer by a developing magnetic field formed in the developing area, and the magnetic brush contacts the photosensitive drum 3 to develop the electrostatic latent image. At this time, the toner adhering to the magnetic brush and the toner adhering to the surface of the sleeve are transferred to the image area of the electrostatic latent image and developed. In the present embodiment, the magnet 9 is N in addition to the developing magnetic pole S1.
It has transport poles of 1, N2, N3 and S2.

With this configuration, the developer applied on the N2 pole and the S2 pole by the rotation of the developing sleeve 7 passes through the layer thickness regulating blade 8 and the developing magnetic pole S1 as in the conventional case.
Then, the developer rising in the magnetic field develops the electrostatic latent image on the photoconductor 6. Thereafter, the developer on the developing sleeve 7 falls into the stirring chamber R1 due to the repulsive magnetic field between the N2 pole and the N3 pole. The developer dropped into the stirring chamber R1 is the first and second developers.
It is stirred and transported by the screws 4 and 5.

The inductance detecting sensor 10, which is the toner concentration detecting means in this embodiment, is disposed at a position close to the second screw 5 on the side surface of the stirring chamber R2 as shown in FIG. The side surface of the second screw 5 has a high flow rate of the developer, is regular, and is unlikely to cause stagnation. Therefore, if the inductance detecting sensor 10 is arranged in this part, it is more difficult to arrange the inductance detecting sensor 10 in other parts in the developing container 1. , Detection accuracy is considerably increased. As described in the section of "Prior Art", the toner concentration detecting inductance detection sensor 10 is of a type that detects a change in the magnetic permeability of the developer using the inductance of the coil. In addition, this sensor 1
The location 0 is near the screw, where the sensor surface (detection surface) 10a has a thickness of the developer sufficient to detect the toner concentration, and where the developer flows when the screw rotates. It can be in another place.

Next, the configuration of this embodiment and the effect of the configuration will be described in detail.

The relationship between the diameter of the substantially circular inductance detection sensor 10 used in this embodiment and the outermost radius of rotation of the spiral second screw 5 which is a small diameter stirring member disposed in the vicinity thereof. Is set to satisfy the following three equations. (1) 0 ≦ Dmin ≦ 1 × 10 ⁻³ Dmin: closest distance between the outermost surface of the stirring member and the detection surface (m) (2) 0.4 ≦ r / R ≦ 0.75 r: of the detection surface Radius (m) R: Outermost rotation radius of screw (m) (3) 0.6 ≦ Dmin / Dmax ≦ 1.0 Dmax: Longest distance (m) between perpendicular to sensing surface and outermost surface of stirring member Satisfying these three equations is indispensable when the rotation diameter of the second screw 5 is as small as 10 to 16 mm. The reason is that when the rotation diameter of the second screw 5 is sufficiently larger than the diameter of the detection surface 10a of the sensor 10, the dead space in the gap between the second screw 5 and the sensor 10 is small, and the second screw 5 This is because the developer conveyance force accompanying the rotation of the roller is also hard to stay.

According to the detailed experiments of the present inventors, (1)
In the formula, when Dmin is below the above range, the screw and the sensor come into contact, and as a result, deterioration of the developer, increase of the screw torque, and failure of the sensor are caused. In addition, when the value exceeds the above range, the dead space between the second screw 5 and the sensor 10 is too large to cause a detection error even if the expressions (2) and (3) are satisfied.

In the equation (2), when the ratio r / R is below the above range, the detection surface 10a of the sensor becomes too small, resulting in a decrease in the absolute output. It becomes too large, and the detection malfunction of the sensor due to the increase of the dead space easily occurs.

Equation (3) defines the range of the gap unevenness between the second screw 5 and the sensor 10. When the gap is less than the above range, it means that the gap unevenness and inclination are large. Irregularities in the flow velocity of the developer in the gap are more likely to occur, and a sensor detection malfunction is more likely to occur. The conditions of the screw and the inductance detection sensor used in the present embodiment are described below.

Under these conditions, the standard T / C
FIG. 3 is a graph showing the relationship between the output of the inductance detection sensor and the actual T / C ratio when the specific developer is charged and the consumption and replenishment are actually performed. It can be seen that the configuration that satisfies the above three equations allows the inductance detection sensor to accurately detect the change in the T / C ratio of the developer in the developing container.

FIG. 4 shows a graph of the relationship between the conditions of the comparative example with respect to the present embodiment, the output of the sensor, and the T / C ratio. It can be seen that the sensor output sensitivity has decreased especially on the side where the T / C ratio is low.

The conditions of the stirring member and the toner concentration detecting sensor in this embodiment and the comparative example are as follows.

(Embodiment) Stirring member: spiral shaped screw, outermost rotation radius 7.0 × 10 ⁻² m Toner concentration detection sensor; inductance sensor, detection surface: circular, radius 0.5 × 10 ^{− 2} m, placed on the side of the developer container, facing the screw, the closest distance between the stirring member and the sensor: 0.5 × 10 ^-3 m,
Longest distance: 0.8 × 10 ⁻³ m In the above configuration, Dmin = 0.5 × 10 ⁻³ m, r /
R = 0.71 and Dmin / Dmax = 0.63.

(Comparative Example) Stirring member: spiral shaped screw, outermost rotation radius 0.6 × 10 ⁻² m Toner concentration detection sensor; inductance sensor, detection surface: circular, radius 0.5 × 10 ⁻² m, placed on the side of the developing container and facing the screw. The closest distance between the stirring member and the sensor: 0.5 × 10 ⁻³ m,
Longest distance: 0.9 × 10 ⁻³ m In the above configuration, Dmin = 0.5 × 10 ⁻³ m, r /
R = 0.83, Dmin / Dmax = 0.56,
It is outside the scope of the present invention. As a result, as shown in FIG. 4, the output sensitivity of the sensor decreases, and accurate T / C ratio detection becomes impossible.

Embodiment 2 Next, a second embodiment of the present invention will be described with reference to FIG.

The sensor 10 according to the present embodiment is arranged near the agitating member 4 and on the bottom surface of the developing container, and on the detection surface 10a, at a portion 30 not conforming to the wall shape of the developing container in the developing device used. Processes its surface so that the developer does not come into contact with it. Specifically, it is preferable to fill the location with a material 30 such as a mold. As a result, the dead space is drastically reduced, the generation of the staying developer is prevented, and the detection of the inductance detection sensor with respect to the T / C ratio becomes more reliable. In addition, the shape of the detection surface has a substantially circular shape even if it is processed.
The conditions of this embodiment are described below.

A stirring member; a spiral screw;
Outermost rotation radius 0.7 × 10 ^-2 m Toner concentration detection sensor; inductance sensor, detection surface: circular, radius 0.5 × 10 ^-2 m, placed on the bottom of the development container, facing the screw, facing the screw Areas that do not fit are filled with a mold.

The closest distance between the stirring member and the sensor; 0.5
× 10 ⁻³ m, longest distance; 0.6 × 10 ⁻³ m In the above configuration, Dmin = 0.3 × 10 ⁻³ m, r /
R = 0.71 and Dmin / Dmax = 0.83.

Embodiment 3 Next, a third embodiment will be described with reference to FIG.

The feature of the present embodiment is to reduce the dead space by extending the detection surface of the toner density detection sensor inside the wall surface of the developing container while satisfying the three expressions of the present invention. As a result, the closest distance between the sensor and the stirring member can be easily reduced, and the accuracy of sensor detection can be further improved.

The conditions of this embodiment are described below.

Stirring member; spiral shaped screw;
0.7 × 10 ^-2 m outermost rotation radius toner density detection sensor; inductance sensor, detection surface: circular, 0.4 × 10 ^-2 m, placed on the side of the development container, facing the screw, inside the container Projects 0.5 × 10 ^-3 m from the side.

The closest distance between the stirring member and the sensor; 0.3
× 10 ⁻³ m, longest distance; 0.5 × 10 ⁻³ m In the above configuration, Dmin = 0.2 × 10 ⁻³ m, r /
R = 0.57 and Dmin / Dmax = 0.6.

[0063]

As is apparent from the above description, according to the developing apparatus and the image forming apparatus of the present invention, a stirring member disposed in a developing container for circulating and stirring the two-component developer, Outside and close to the outermost surface of the stirring member,
Detecting means for detecting a change in toner density of the two-component developer as a change in magnetic permeability; and a toner density detecting means having a substantially circular detection surface, wherein the outermost radius R (m) of the stirring member is 1.0 × 10
^-2 ≦ R ≦ 1.6 × 10 ⁻² , Dmin: the closest distance (m) between the outermost surface of the stirring member and the sensing surface, r: radius of the sensing surface, R: the above The outermost radius of rotation of the stirring member (m), Dmax: when the longest distance (m) between the perpendicular to the detection surface and the outermost surface of the stirring member, 0 ≦ Dmin ≦ 1 × 10 ⁻³ , 0 .4 ≦ r / R
By satisfying ≦ 0.75 and 0.6 ≦ Dmin / Dmax ≦ 1.0, both miniaturization of the apparatus and improvement of the reliability of the toner concentration detecting means can be achieved, and the stirring member and the toner The relationship between the density detecting means is optimized, the detection accuracy of the toner density detecting means can be improved, and the image stability can be maintained.

[Brief description of the drawings]

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

FIG. 2 is a schematic configuration diagram illustrating an example of an electrophotographic image forming apparatus to which the present invention is applied.

FIG. 3 is a graph showing a relationship between a T / C ratio and an output of an inductance detection sensor according to the first embodiment of the present invention.

FIG. 4 shows T in a comparative example with respect to the first embodiment of the present invention.
4 is a graph showing the relationship between the / C ratio and the output of an inductance detection sensor.

FIG. 5 is an enlarged schematic sectional view showing a positional relationship between a stirring member and a sensor according to a second embodiment of the present invention.

FIG. 6 is an enlarged schematic sectional view showing a positional relationship between a stirring member and a sensor according to a third embodiment of the present invention.

FIG. 7 is a schematic configuration diagram showing an arrangement of a conventional inductance detection sensor.

FIG. 8 is a graph showing a relationship between a T / C ratio and an output of an inductance detection sensor in a conventional configuration.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Developing apparatus 1a Developing container 4 1st screw (stirring member) 5 2nd screw (stirring member) 6 Photoconductor drum (image carrier) 10 Inductance detection sensor (toner density detection means) 10a Detection surface R1 Developing room R2 Stirring room

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Masanori Shida 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Ichiro Ozawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon F term (reference) 2H077 AB02 AC02 AD02 AD06 AD13 AD18 BA08 DA10 DA42 DA52 EA03 FA01 FA26

Claims (10)

[Claims] 1. A two-component developer containing a non-magnetic toner and a magnetic carrier is carried and conveyed to face an image carrier in order to develop an electrostatic latent image formed on the image carrier into a visible image. A rotatable developer carrier having a fixed magnetic field generating means disposed therein, a developing container containing a two-component developer, and a developing container arranged in the developing container for circulating and stirring the two-component developer. A developing device having a stirring member and toner concentration detecting means having a substantially circular detection surface for detecting a change in the toner concentration of the two-component developer as a change in the magnetic permeability outside and close to the outermost surface of the stirring member; In the apparatus, the outermost radius R (m) of the stirring member is set to 1.0 × 10 ⁻² ≦ R ≦ in order to reduce the stagnation of the developer near the detection surface.
In the range of 1.6 × 10 ^-2, Dmin: minimum distance between the outermost surface and the detection surface of the stirring member (m), r: radius of the sensing surface (m), R: the agitating member , Where Dmax is the longest distance (m) between the perpendicular to the detection surface and the outermost surface of the stirring member, and the following three formulas are satisfied. apparatus. 0 ≦ Dmin ≦ 1 × 10 ⁻³ 0.4 ≦ r / R ≦ 0.75 0.6 ≦ Dmin / Dmax ≦ 1.0 2. The developing device according to claim 1, wherein said stirring member has a spiral shape. 3. The developing device according to claim 1, wherein a portion of the detection surface that does not follow the wall shape of the developing container is processed so that the developer does not contact the surface. 4. The developing device according to claim 1, wherein the detection surface protrudes inside the developing container from an inner wall surface of the developing container. 5. The toner concentration detecting means detects when the stirring member is rotating when the developing device is driven, and determines a location where the toner concentration detecting means is located at a constant flow velocity of the developer flowing on the detection surface when the developer is stirred. The developing device according to claim 1, wherein the flow is a place where the flow is regular. 6. An image carrier on which an electrostatic latent image is formed,
In order to develop the electrostatic latent image formed on the image carrier into a visible image, a two-component developer containing a non-magnetic toner and a magnetic carrier is carried and conveyed in opposition to the image carrier. A rotatable developer carrier on which a fixed magnetic field generating means is arranged, a developing container for containing a two-component developer, a stirring member arranged in the developing container for circulating and stirring the two-component developer, A developing device having a toner concentration detecting means having a substantially circular detection surface for detecting a change in the toner concentration of the two-component developer as a change in magnetic permeability, outside and close to the outermost surface of the stirring member. In the image forming apparatus, the outermost radius R (m) of the stirring member is set to 1.0 × 10 ⁻² ≦ R ≦
In the range of 1.6 × 10 ^-2, Dmin: minimum distance between the outermost surface and the detection surface of the stirring member (m), r: radius of the sensing surface (m), R: the agitating member , And Dmax: the longest distance (m) between the perpendicular to the detection surface and the outermost surface of the stirring member, wherein the following three formulas are satisfied. Forming equipment. 0 ≦ Dmin ≦ 1 × 10 ⁻³ 0.4 ≦ r / R ≦ 0.75 0.6 ≦ Dmin / Dmax ≦ 1.0 7. The image forming apparatus according to claim 6, wherein the stirring member has a spiral shape. 8. The image forming apparatus according to claim 6, wherein a portion of the detection surface that does not follow the wall shape of the developing container is processed so that the developer does not contact the surface. 9. The image forming apparatus according to claim 6, wherein the detection surface protrudes inside the developing container from an inner wall surface of the developing container. 10. The toner concentration detecting means detects when the stirring member rotates when the developing device is driven, and determines a location where the toner concentration detecting means has a constant flow velocity of the developer flowing through the detection surface when the developer is stirred. 7. The image forming apparatus according to claim 6, wherein the flow is a place where the flow is regular.