JP3069006B2 - 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 two-component developer comprising a toner and a carrier for visualizing an electrostatic latent image on the surface of a photoreceptor in an electrophotographic apparatus such as a copying machine. The present invention relates to a developing device for supplying a surface.

[0002]

2. Description of the Related Art For example, in a dry copying machine, a developing device for visualizing (developing) an electrostatic latent image on a photoreceptor surface with a two-component developer comprising a carrier and a toner is often used. In such a developing device, the toner is consumed by the developing operation, while the carrier is not consumed and remains in the developing device. Therefore, as the stirring frequency of the carrier stirred with the toner in the developing device increases,
A situation such as peeling of the resin coat layer on the surface or sticking of the toner to the surface occurs to cause deterioration, and as a result, the charging performance of the developer gradually decreases.

Therefore, in addition to the replenishment of the toner consumed by the developing operation, a device in which the carrier is replenished little by little into the developing device so as to suppress the deterioration of the charging performance is disclosed in, for example, Japanese Patent Application Laid-Open No. 1-267670. It is disclosed in the gazette. In this publication, in a developing device that performs development using a developer including a carrier and a toner, a developer discharge opening for discharging the developer is provided at a predetermined position of the developing device, and a new developer supply unit is used by a developer supply unit in accordance with copying. The developer is supplied to the developing device, and the excess developer is discharged from the developer discharge opening to prevent the deterioration of the developer. A so-called developer successively changing developing device for forming an image is disclosed. By successively repeating such supply and discharge, the deteriorated developer in the developing tank is replaced by newly supplied toner and carrier, thereby maintaining the charging performance and reducing the copy image quality. It is designed to suppress.

Further, a toner density sensor for detecting the toner density is provided in the developing tank, and the toner is supplied into the developing tank by the output of the toner density sensor.
The toner concentration in the developing tank is kept constant.
Further, as the toner concentration sensor, a magnetic permeability sensor that contacts a carrier in a developer and detects the magnetic permeability is used. In this case, the ratio of toner to carrier is detected from the detected magnetic permeability, and whether or not toner is replenished is controlled by increasing or decreasing the toner ratio, and the toner concentration in the developing tank is kept constant. To keep it.

[0005]

However, since the magnetic permeability detected by the magnetic permeability sensor is determined by the amount of the carrier contained in a fixed volume, even if the mixing ratio between the toner and the carrier is constant, the development is not performed. If the density of the agent changes, the magnetic permeability changes. For this reason, if the amount of the developer in the developing tank changes due to the inclination of the developing device and the developer density changes, the amount of the carrier in contact with the magnetic permeability sensor changes, and the determination of the toner concentration of the developer is incorrect. May be caused.

For example, when the developing device is tilted due to the movement of a copying machine and the amount of the developer in the developing tank is reduced, an accurate toner ratio cannot be detected due to a decrease in the amount of the carrier in contact with the magnetic permeability sensor. This causes a problem that the toner ratio is reduced and the image density is reduced.

On the other hand, when the developing device is tilted due to the movement of a copying machine or the like and the amount of developer in the developing tank increases, the accurate toner ratio cannot be detected due to the increase in the amount of carrier in contact with the magnetic permeability sensor. In addition, there is a problem that the toner amount is excessive with respect to the appropriate amount, which adversely affects the image quality and lowers the copy image quality.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and has as its object to detect the detection level of a toner density sensor without being affected by a change in the amount of developer in a developing tank due to the inclination of a developing device. Accordingly, it is an object of the present invention to provide a developing device capable of maintaining the toner density in the developing tank constant, thereby maintaining a good copy image.

[0009]

According to the present invention, there is provided a developing apparatus comprising: a stirring means for rotating and stirring and transporting a developer in a developing tank to a developing tank containing a developer comprising toner and carrier; A developing roller for supplying the developer to the photoreceptor is rotatably provided, and the developer is sequentially supplied from the developer supply section to the developing tank in accordance with the detection output of the toner concentration detecting means provided in the developing tank. while being, in the developing device in which the developer in the developer tank is discharged from the developer discharge opening formed in the developing tank, the toner concentration detecting means, provided on the bottom surface of the developer tank Rutotomoni, the stirring Means are formed so as to collectively convey the developer to the vicinity of the disposition position of the toner concentration detecting means, and on the bottom of the developing tank,
The developer is blocked in the direction of the rotation axis of the stirring means and overflows.
The overflow member to be sandwiched sandwiches the toner concentration detecting means.
It is characterized by being provided in .

[0010]

According to the developing device of the present invention , the agitating means is formed so as to collectively convey the developer to the vicinity of the position where the toner concentration detecting means is provided. The developer can be transported.

In addition, the above-mentioned stirring tank is provided on the bottom of the developing tank.
An overflow that dams and overflows the developer in the rotation axis direction of the means.
An output member is provided so as to sandwich the toner concentration detecting means.
The toner concentration of the transported developer.
It is possible to collect and overflow between the overflow members near the outlet means.
You.

Thus, the toner is collected near the toner concentration detecting means.
The obtained developer is sandwiched between the toner concentration detecting means.
Since it is blocked by the overflow member provided as
Even if the developing device is tilted, the development near the toner concentration detecting means
A change in the amount of the agent can be suppressed.

[0013] was but I, along with the amount of developer toner concentration detector vicinity can be greater than the amount of developer other developer tank, the fluctuation of the developer amount by the tilt of the developing device
Since it can be made smaller, it is possible to always obtain a stable detection signal by the toner density detecting means . This result
Fruit, without being affected by changes in the developer amount in the developer tank, it is possible to detect a more accurate toner concentration, as a result, it is possible to maintain good copy image.

[0014]

EXAMPLES Example 1 Before describing the examples of the present invention, the developing device of the present invention
A general developing device as a premise of the installation will be described below with reference to FIGS.

As shown in FIG. 4, a copying machine constituted by applying a developing device as a premise of the present invention has a document table 1 provided on an upper surface thereof, and an exposure optical system is provided below the document table 1. System 2 is provided. The exposure optical system 2 includes a light source lamp 3 that scans a document (not shown) placed on the document table 1 while irradiating the document with light, and a plurality of reflecting mirrors that guide reflected light from the document to the photoconductor 4. 5 and a lens unit 6 arranged in the optical path of the reflected light.

On the outer periphery of the photosensitive member 4, a charging charger 7 for charging the surface to a predetermined potential, an inter-image eraser (not shown), and a developing device 8 for developing an electrostatic latent image formed on the surface of the photosensitive member 4 A transfer charger 9 for transferring a toner image on the surface of the photoconductor 4 to a sheet, a cleaning device 10 for collecting residual toner on the surface of the photoconductor 4, and a static eliminator (not shown) are provided. A timing roller 11, a feeding roller 12, a paper feed cassette 13, and a paper feed roller 14 for supplying paper at a predetermined timing are provided on the paper input side with respect to the photoreceptor 4, while the timing output roller 11 supplies paper with predetermined timing. Is provided with a fixing device 15 for fixing the toner image transferred onto the sheet to the sheet.

Further, the developing device 8 is shown in FIGS.
As shown in FIG. 2, a developing tank 16 having a container shape is provided. Inside the developing tank 16, a developing roller 17 composed of a magnet roller, a stirring screw 18 as a second stirring means,
An agitator 19 as first stirring means, and a first conveying screw 20a and a second conveying screw 20b as conveying means are rotatably arranged.

The developing roller 17 and the stirring screw 1
8, the agitator 19, the first transport screw 20a, and the second transport screw 20b are each configured to rotate in the direction of the arrow as shown in FIG. As a result, the developer supplied from the developer supply unit (developer supply unit) 25 disposed above the developing tank 16 is transported in the direction of arrow C by the first transport screw 20a and the second transport screw 20b. The developer is stirred together with the developer transported by the agitator 19 and the stirring screw 18. Therefore, the agitator 19
The stirring screw 18 serves as means for stirring and transporting the developer in the developing tank 16.

The developer contained in the developing tank 16 is composed of a carrier and a toner. The carrier made of a magnetic material has a resin coating layer on its surface for suppressing the adhesion of the toner. The carrier and the toner are mixed with a stirring screw 1
When stirred by 8, the toner is triboelectrically charged. The developing roller 17 attracts the carrier by a magnetic force, forms a magnetic brush, and conveys the toner. Thus, the toner adhered to the carrier by the Coulomb force is supplied to the photoreceptor 4.
The development is performed by being attracted to the electrostatic latent image on the photoconductor 4.

As shown in FIG. 1, a developer supply opening 16a is formed in the upper wall of the developing tank 16, and the developer supply unit 25 is fitted into the supply opening 16a from above. ing. The inside of the developer supply unit 25 is partitioned into two chambers, a toner storage chamber and a carrier developer storage chamber. In one toner storage chamber, toner is stored. In the other carrier developer storage chamber, a developer composed of only a carrier or a developer in which toner is mixed with a carrier at a predetermined ratio (hereinafter, referred to as carrier developer) That)
Is stored.

On the other hand, on the side wall of the developing tank 16, there is provided a developer discharging portion 23 in which a developer overflow 23a is formed. The developer discharge portion 23 is provided with the developer overflow 23
The developer overflowing from a is discharged to a developer collection container (not shown).

A toner supply roller 21 driven and controlled by a control device 32 shown in FIG.
And the carrier developer supply roller 22 are provided, respectively. When the toner supply roller 21 is driven to rotate, the toner in the toner storage chamber is rotated, and when the carrier developer supply roller 22 is driven to rotate, The carrier developer in the carrier developer storage chamber is supplied to each roller 2.
In this case, the toner flows down by an amount corresponding to the drive time of the drive motor No. 1.22 and is supplied from the supply opening 16 a into the developing tank 16.
Transfer screw 20a and second transfer screw 20b
Is conveyed to the agitator 19 and the stirring screw 18 side.

Further, inside the developing tank 16, a toner density sensor 34 as a toner density detecting means for detecting the toner density in the developing tank 16 is provided. The toner density sensor 34 is, for example, a magnetic bridge type toner sensor manufactured by Hitachi Metals, Ltd. as a magnetic permeability sensor. The magnetic bridge type toner sensor is used for a two-component developer which is a mixture of a magnetic substance (carrier) and a non-magnetic substance (toner) used in the present description .
The change in the apparent magnetic permeability due to the mixing ratio of the magnetic carrier and the non-magnetic toner is detected and converted into an electric signal.

That is, the apparent magnetic permeability of the developer is
It is determined by the amount of the carrier occupying a certain volume, and under normal use conditions, the amount of the carrier in the certain volume is determined by the mixing ratio of the toner and the carrier.
For example, if the amount of the carrier that contacts the toner concentration sensor 34 is small, the apparent magnetic permeability decreases, and it is detected that the toner ratio is high. If the amount of the carrier that contacts the toner concentration sensor 34 is large, the apparent magnetic permeability increases. That is, it is detected that the toner ratio is low.

The detection signal of the toner density sensor 34 is
The toner supply roller 21 of the developer supply unit 25 is output to the control device 32 shown in FIG.
And the carrier developer supply roller 22 are driven to supply toner or carrier developer into the developing tank 16.

The toner density sensor 34 is provided as shown in FIG.
As shown in (1), it is disposed below the agitator 19 in the developing tank 16. Thereby, the uniformly stirred developer always comes into contact with the toner concentration sensor 34 regardless of the increase or decrease in the amount of the developer in the developing tank 16.

Further, when the agitator 19 is rotated in the direction of the arrow shown in FIG. 3, the developer is conveyed in the direction of the arrow B around the toner density sensor 34 as shown in FIG. And a second stirring unit 19b having a screw formed to convey the developer in the direction of arrow A. Thus, the developer stirred by the agitator 19 is conveyed in the direction of arrow B by the first stirring unit 19a, and is conveyed in the direction of arrow A by the second stirring unit 19b. Therefore, when the agitator 19 rotates and stirs the developer, the developer is transferred to the toner density sensor 34.
Are conveyed in a concentrated manner at the disposition position. For this reason, the toner concentration sensor 34 can always contact a fixed amount of the developer without being affected by the increase or decrease of the developer in the developing tank 16.

Here, the transport of the developer in the developing tank 16 will be described with reference to FIGS.

First, based on the detection signal of the toner concentration sensor 34, the toner supply roller 21 or the carrier developer supply roller 22 of the developer supply unit 25 rotates, and the toner or carrier developer is supplied to the developing tank 16 for supply. It is supplied from the opening 16a.

Next, the developer supplied from the supply opening 16a of the developing tank 16 is transported in the direction of arrow A by the first transport screw 20a and transported in the direction of arrow B by the second transport screw 20b. . Further, the developer is transported in the direction of arrow C by the first transport screw 20a and the second transport screw 20b, and is transported to the position where the agitator 19 is provided.

Next, the developer conveyed to the position where the agitator 19 is disposed is stirred by the rotation of the agitator 19 so that the toner and the carrier are uniformly mixed.
At this time, the developer stirred on the stirring screw 18 side and the first conveying screw 20a and the second conveying screw 2
Ob is mixed with the new developer conveyed. Further, the developer mixed by the agitator 19 is transported to the position where the toner density sensor 34 is disposed by the first stirring unit 19a and the second stirring unit 19b of the agitator 19.

Thereafter, the developer overflowing from the agitator 19 in the direction of arrow C is sufficiently stirred by the stirring screw 18 to frictionally charge the toner. Thereafter, the developing roller 17 attracts the carrier by a magnetic force, forms a magnetic brush, and conveys the toner. Thus, the toner adhered to the carrier by the Coulomb force is supplied to the photoconductor 4, and the electrostatic latent image on the photoconductor 4 is supplied. And is developed.

On the other hand, the excess developer in the developing tank 16 is conveyed by the agitator 19 to the developer discharge section 23 and discharged outside through the developer overflow 23a of the developer discharge section 23.

The control of the driving of the developing roller 17, the stirring screw 18, the agitator 19, the first transport screw 20a and the second transport screw 20b is performed by a controller 32.

When the tilt sensor (not shown) detects the tilt state of the developing device 8 exceeding the allowable tilt limit, the controller 32 includes an alarm comprising a light emitting diode as a warning means for notifying the tilt state. Lamp 3
5 is connected.

Next, a copying operation in the copying machine having the above configuration will be described.

When a power switch (not shown) is turned on, a warm-up process is first performed. After this is completed, a copy start switch 31 described later is turned on.
Then, the original placed on the original placing table 1 is scanned by the light source lamp 3 of the exposure optical system 2. The reflected light from the original at this time is irradiated on the photoconductor 4 via the reflecting mirrors 5 and the lens unit 6, and an electrostatic latent image is formed on the surface of the photoconductor 4 charged to a predetermined potential by the charging charger 7. It is formed. Next, this electrostatic latent image is developed with toner supplied from the developing device 8. The toner image on the surface of the photoreceptor 4 is transferred to a sheet supplied from a sheet feeding cassette 13 by a transfer charger 9 and is thermally fixed on the sheet by a fixing device 15. As a result, a copy image corresponding to the document image is formed on the sheet.

In order to control such a series of copying operations, the control device 3 including the microcomputer described above is used.
2 is provided in the copying machine.
An ON operation signal of the copy start switch 31 is input. Further, a copy counter 33 for counting the cumulative number of copying operations is further provided, and this count value (hereinafter, referred to as a copy count value) n is also input to the control device 32.

When the above-described copying operation is repeated, the toner in the developer stored in the developing tank 16 of the developing device 8 is gradually consumed, and the ratio of the toner to the carrier, that is, the toner concentration decreases. To go. The drive control of the toner supply roller 21 based on the output of the toner density sensor 34 is further performed by the control device 32.
That is, when it is detected that the detection signal from the toner density sensor 34 has fallen to the lower limit of the appropriate range required for development, the driving of the toner supply roller 21 is started. As a result, the toner in the toner storage chamber of the developer supply unit 25 is supplied into the developing tank 16, and the toner concentration in the developing tank 16 increases. When it is detected that the toner concentration has reached the upper limit of the above-described appropriate range, the driving of the toner supply roller 21 is stopped. With such control,
The toner concentration in the developing tank 16 is maintained within the above-mentioned appropriate range.

The toner replenished as described above is agitated with the developer in the developing tank 16, controlled to a fixed charge amount, supplied to the photoconductor 4, and used for development. on the other hand,
Since the carrier in the developer does not decrease and is used repeatedly, the carrier gradually deteriorates due to stirring by the developing roller 17 and the stirring screw 18 and contact with the photoconductor 4. When the carrier deteriorates in this manner, a predetermined charge amount cannot be given to the toner, and the image quality deteriorates. Thus, by additionally replenishing the carrier in the developing tank 16 and replacing the carrier with the deteriorated carrier in the developing tank 16, the above-described decrease in the charging performance can be suppressed.
For this purpose, the control unit 32 also controls supply / discharge of supplying the carrier developer from the carrier developer storage chamber and discharging the developer in the developing tank 16.

In the magnetic bridge type toner sensor used as the toner concentration sensor 34, even if the mixing ratio of toner and carrier is constant, if the density of the developer itself changes, the amount of carrier in a fixed volume changes. However, this changes the apparent magnetic permeability of the developer. In this case, the magnetic bridge type toner sensor cannot determine whether the density of the developer has changed or the mixing ratio of the toner and the carrier has changed, and the toner concentration in the developing tank 16 may be erroneously detected. There is. For this reason, it is necessary to keep the density of the developer near the toner density sensor 34 constant.

In general, in a developing device of a successive replacement type in which a developer overflows from a developer overflow formed in a developing tank and discharges the developer, the inclination of the developing device causes
When the developer overflow is lower than the reference position, the amount of developer discharged from the developer overflow increases, the amount of the developer in the developing tank decreases, and the developer overflow moves to the reference position. If it becomes higher, the discharge amount of the developer from the developer overflow decreases, and the developer amount in the developing tank increases. As a result, the amount of the developer near the toner density sensor changes, and the density of the developer also changes.

That is, when the amount of the developer in the developing tank decreases, the density of the developer near the toner density sensor decreases, and the magnetic permeability also decreases, so that the sensor output value of the toner density sensor also decreases. Even if the toner concentration is normal, it is detected as over toner. The developer is not replenished until it is determined from the sensor output value of the toner density sensor that the toner density in the developing tank is normal. Therefore, when it is determined that the toner concentration in the developing tank is normal, the actual toner concentration is low, and the inside of the developing tank is in an under toner state.

When the amount of the developer in the developing tank increases, the density of the developer near the toner density sensor increases, and the magnetic permeability also increases, so that the sensor output value of the toner density sensor also increases. Even under normal toner density, it is detected as under toner. The developer is supplied until the toner concentration in the developing tank is determined to be normal based on the sensor output value of the toner concentration sensor. Therefore, when it is determined that the toner concentration in the developing tank is normal, the actual toner concentration is high, and the inside of the developing tank is in an over toner state.

In the present description , if the initial amount of the developer in the developing tank 16 is set to 480 g, if the copying machine is inclined by 1 °, when the amount of the developer decreases,
g, and becomes 560 g when the developer amount increases. As described above, if the copier is only tilted by 1 °, the initial amount of the developer changes by about 17%. As a result, the influence on the toner density sensor, that is, the change in the developer density increases, and the toner in the developing tank 16 becomes large. It will greatly affect the concentration.

However, in the developing device having the above structure, the developer in the developing tank 16 is conveyed by the agitator 19 to the vicinity of the position where the toner density sensor 34 is provided. The developer amount can be made larger than in the other developing tanks 16. As a result, even if the developing device 8 tilts and the amount of developer in the developing tank 16 changes, the amount of change in the amount of developer near the toner density sensor 34 becomes small. Even if it changes, the change in the density of the developer near the toner density sensor 34 can be kept small. Therefore, the toner concentration sensor 34 can always detect the toner concentration in the developing tank 16 more accurately.

Therefore, the density of the developer in the vicinity of the toner density sensor 34 can always be kept constant, so that the toner density control based on the output value of the toner density sensor 34 can be performed accurately.

Here, in the developing device 8 having the above structure,
FIG. 6 shows the relationship between the developer weight change value (g) in the developing tank 16 and the toner concentration sensor output value (V) from the toner concentration sensor 34.

However, in the developing device 8, the rotation speed of the developing roller 17 is 292 rpm, the rotation speed of the stirring screw 18 is 120.9 rpm, and the rotation speed of the agitator 19 is 1
67.9 rpm, the first transport screw 20a and the second
The rotation speed of the transport screw 20b is 167.9 rpm, and the rotation direction of each member is the direction of the arrow shown in FIG. The pitch of the stirring plate of the stirring screw 18 is 23.5 mm, the pitch of the screw of the agitator 19 is 18 mm, and the pitch of the screws of the first conveying screw 20a and the second conveying screw 20b is 16 mm. Further, the initial amount of the developer stored in the developing tank 16 is 480 g. In addition, the faster the developer conveying speed (in the case of extremely high speed, the distribution of the developer becomes uneven and unsuitable),
As the amount of the developer increases and the size of the developing device increases, the influence on the change in the amount of the developer decreases.

As a comparative example with respect to FIG. 6, the developer weight change value (g) in the developing tank 16 when the developing device 8 'shown in FIG. FIG. 8 shows the relationship with V).

The developing device 8 'shown in FIG. 7 uses an agitator 19' instead of the agitator 19 provided in the developing device 8 having the above-described structure . The agitator 19 ′ has a configuration in which a plurality of fins extending in the longitudinal direction are provided, and the rotation speed is the same as that of the agitator 19. Also,
Other members of the developing device 8 'are the same as those of the developing device 8.

From the above, when the copier is tilted by about 3 ° from the time when the developer stored in the developing tank 16 is in the initial state, the toner when the amount of the developer in the developing tank 16 changes by ± 60 g. The density sensor output value changes by ± 0.2 V to 0.25 V in the developing device 8 ′ of the comparative example, as shown in FIG. This change is a change of about 1% in terms of toner density. This means that the toner concentration in the developer is 4% to 6%
Therefore, if the toner density changes by 1%, problems such as toner fogging, toner scattering, and carrier rise due to an increase in toner concentration occur, while problems such as image blurring due to a decrease in toner concentration occur.

In general, when the toner density in the developer changes, the effect is most apparent in the case of a solid black image. If the toner density is too low, the black solid becomes light. Therefore, to obtain the required image density,
The entire copied image becomes dark. For example, there is a Macbeth densitometer for measuring the black solid density of an image, and the black solid density for obtaining a normal image requires a density value of 1.3 or more by the Macbeth densitometer. At this time, the density value 1.3 corresponds to a change value of the toner density of 0.5%.

In the initial stage of the use of the developer, even if the change in the toner concentration in the developer is about 1%, the influence on the copied image is small, but the carrier and the toner in the developer deteriorate with the use of the developer. Then, when the toner density change is about 1%, the influence on the copied image increases. For this reason, in order to maintain a good copy image in consideration of the life of the developer, it is desirable to suppress the change in toner concentration in the developer to about 0.5%.

Therefore, in order to prevent the above-mentioned problems caused by the change in toner density, the change in toner density must be 0.5% or less.

On the other hand, if the copier is tilted about 3 ° from the time when the developer stored in the developing tank 16 is in the initial state, the toner density sensor output when the amount of the developer in the developing tank 16 changes by ± 60 g. In the developing device 8 having the above-described configuration, the value changes by ± 0.08 V to 0.12 V as shown in FIG. This change value is half of the output value of the toner density sensor in the developing device 8 'of the comparative example, and is approximately 0.5% in terms of the toner density.

Therefore, in the developing device 8 having the above structure ,
Since the change in the toner concentration in the developer in the developing tank 16 can be reduced, problems such as toner fogging and toner scattering due to the increase and decrease in the toner concentration can be eliminated, and as a result, a good copy image can be maintained. be able to.

From the above, the developing device 8 having the above-described configuration is used.
In this case, the developer in the developing tank 16 is collectively transported by the agitator 19 to the vicinity of the position where the toner density sensor 34 is provided.
Even if the amount of the developer inside changes, the amount of change in the amount of the developer near the toner density sensor 34 becomes small.

As a result, the density of the developer in the vicinity of the toner density sensor 34 can always be kept constant, so that the toner density can be accurately controlled by the output value of the toner density sensor 34. Can be favorably maintained.

Further , other developments based on the constitution presupposed by the present invention
The device 28 will be described below with reference to FIGS. 9 to 11. Members having the same functions as those of the developing device 8 are denoted by the same reference numerals, and description thereof will be omitted.

As shown in FIG. 9, the developing device 28
An agitator 29 is used in place of the agitator 19 of the developing device 8 shown in FIG. The agitator 29 includes a plurality of fins 2 extending perpendicularly to the axis and extending in the longitudinal direction.
9a are stirring means.

The developing tank 16 below the agitator 29
As shown in FIG. 10, a concave portion 30 is formed on the bottom surface of the. As shown in FIG. 11A, the recess 30 has a substantially rectangular parallelepiped shape of 100 mm in the directions of arrows A and B, and as shown in FIG. 11B, 20 mm in the directions of arrows C and D and a depth of 3 mm. ing. At substantially the center of the concave portion 30, a toner density sensor 34 is provided. The toner concentration sensor 34 is configured such that the upper contact surface with the developer, that is, the detection surface is substantially the same as the bottom surface of the concave portion 30. At this time, the developer level is set to the concave portion 3 of the developing tank 16.
The height from the bottom other than 0 is 12 mm.

A description will now be given, with reference to FIGS. 9 and 10, of the transfer of the developer in the developing device 28 having the above configuration.
The developing roller 17, the stirring screw 18, the agitator 29, the first transport screw 20a, and the second transport screw 20b rotate in the directions of the respective arrows as shown in FIG.

First, based on the detection signal of the toner density sensor 34, the toner supply roller 21 or the carrier developer supply roller 22 of the developer supply unit 25 is rotated, and the toner or carrier developer is supplied to the developing tank 16 for supply. It is supplied from the opening 16a.

Next, the developer supplied from the supply opening 16a of the developing tank 16 is transported in the direction of arrow A by the first transport screw 20a and transported in the direction of arrow B by the second transport screw 20b. . Further, the developer is transported in the direction of arrow C by the first transport screw 20a and the second transport screw 20b, and is transported to the position where the agitator 29 is provided.

Next, the developer conveyed to the position where the agitator 29 is disposed is stirred by the rotation of the agitator 29 so that the toner and the carrier are uniformly mixed.
At this time, the developer stirred on the stirring screw 18 side and the first conveying screw 20a and the second conveying screw 2
Ob is mixed with the new developer conveyed. The developer mixed by the agitator 29 collects in the concave portion 30 formed on the bottom surface of the developing tank 16 below the agitator 29 and is transported to the position where the toner density sensor 34 is provided.

Thereafter, the developer overflowing from the agitator 29 in the direction of arrow C is sufficiently stirred by the stirring screw 18 to frictionally charge the toner. Thereafter, the developing roller 17 attracts the carrier by a magnetic force, forms a magnetic brush, and conveys the toner. Thus, the toner adhered to the carrier by the Coulomb force is supplied to the photoconductor 4, and the electrostatic latent image on the photoconductor 4 is supplied. And is developed.

On the other hand, the excess developer in the developing tank 16 is conveyed by the agitator 29 to the developer discharge section 23 and discharged outside through the developer overflow 23 a of the developer discharge section 23.

As described above, by providing the toner density sensor 34 at substantially the center of the concave portion 30 of the developing tank 16, the vicinity of the position at which the toner density sensor 34 is disposed is depressed from the other bottom surface of the developing tank 16, The agent is conveyed in a concentrated manner. Thus, even if the amount of the developer in the developing tank 16 changes, the change in the developer density in the vicinity of the toner density sensor 34 can be reduced. Therefore, the output value of the toner density sensor 34 can be set to a more accurate value, so that the toner density in the developing tank 16 can be kept constant, and the copied image can be favorably maintained.

In the above-described developing device 28, the present inventor conducted an experiment. As a result, if the depth of the concave portion 30 is smaller than 2 mm, the developer hardly collects in the concave portion 30.
A change in the amount of the developer in the developing tank 16 causes a change in the developer density near the toner density sensor 34. For this reason, an appropriate toner density sensor output value cannot be obtained, and a copied image cannot be maintained satisfactorily. On the other hand, if the depth of the concave portion 30 is larger than 3 mm, the flow of the developer on the concave portion 30 is deteriorated, and the developer stays in the concave portion 30. In such a case, the developer that comes into contact with the toner density sensor 34 is always the same developer, so that a change in the toner density cannot be accurately detected, and a good copy image cannot be maintained.

Further, the depth of the recess 30 should be not less than 2 mm and not more than 3 mm.
The recess 30 is set in the following range so that the developing tank 16
Is about 25% deeper than the other portions, so that the developer is easily collected so that the developer does not stay. by this,
Since the developer having a constant density can always be brought into contact with the toner density sensor 34 without being affected by the change in the amount of the developer in the developing tank 16, the output value of the toner density sensor of the toner density sensor 34 is always adjusted to an appropriate value. Can be a value.

From the above, in order to maintain a good copy image, it is necessary to always obtain an appropriate output value of the toner density sensor without changing the amount of the developer contacting the toner density sensor 34. . Therefore, it is understood that it is desirable that the depth of the concave portion 30 be in the range of 2 mm or more and 3 mm or less.

Further, by the concave portion 30 provided in the developing tank 16, the vicinity of the position where the toner concentration sensor 34 is disposed in the developing tank 16 is formed lower than the other bottom surface of the developing tank 16, so that the developing tank 16 is formed. The developer in 16 is naturally conveyed to the vicinity of toner concentration sensor 34.

Thus, the agitator 29 does not have to be formed so that the developer is conveyed to the vicinity of the position where the toner density sensor 34 is provided, and the existing agitator 29 can be used as it is. Therefore, the manufacturing of the developing device 8 can be simplified, and the cost for manufacturing can be reduced.

Here, an embodiment of the present invention will be described with reference to FIGS. 12 to 15.
Members having the same functions as the members of the developing devices 8 and 28 are denoted by the same reference numerals, and description thereof will be omitted.

As shown in FIG. 12, the developing device 38 of this embodiment uses an agitator 39 instead of the agitator 29 of the developing device 28 . Agitator 39 above
Is a stirring means constituted by a plurality of fins 39a extending in the longitudinal direction.

The developing tank 16 below the agitator 39
On the bottom surface of the lens, a toner density sensor 34 is disposed substantially at the center, and as shown in FIG. 13, ribs 40 as overflow means orthogonal to the axis of the agitator 39 in the vicinity of the toner density sensor 34 (in the figure). (Indicated by shading).

The rib 40 is, as shown in FIG.
The developer tank 16 is provided below the agitator 39 in the directions of arrows A and B at intervals of 100 mm via the toner density sensor 34. At this time, the height of the rib 40 is 9 mm from the bottom of the developing tank 16, and the developer level is 12 mm from the bottom of the developing tank 16.

Further, as shown in FIG.
It is formed in a cut-out state so as not to contact the shaft of the agitator 39, that is, not to prevent the rotation of the agitator 39. Also, the fins 39a of the agitator 39 ...
Are cut off at the position where the ribs 40 are provided, so that the rotation of the agitator 39 is not prevented.

Accordingly, by providing the ribs 40 near the position where the toner density sensor 34 is provided as described above, the transported developer can be transferred between the ribs 40 near the position where the toner density sensor 34 is provided. The ribs 40 can be dammed and overflow. As a result, the developer collected near the toner density sensor 34 can be dammed by the ribs 40, so that a change in the amount of developer near the toner density sensor 34 can be suppressed even when the developing device 38 is inclined.

Here, the transport of the developer by the developing device 38 will be described with reference to FIGS. The developing roller 17, the stirring screw 18, the agitator 39, the first transport screw 20a, and the second transport screw 20b rotate in the directions of the arrows as shown in FIG.

First, based on the detection signal of the toner density sensor 34, the toner supply roller 21 or the carrier developer supply roller 22 of the developer supply unit 25 is rotated, and the toner or carrier developer is supplied to the developer tank 16 for supply. It is supplied from the opening 16a.

Next, the developer supplied from the supply opening 16a of the developing tank 16 is transported in the direction of arrow A by the first transport screw 20a and transported in the direction of arrow B by the second transport screw 20b. . Further, the developer is transported in the direction of arrow C by the first transport screw 20a and the second transport screw 20b, and is transported to the position where the agitator 39 is provided.

Next, the developer conveyed to the position where the agitator 39 is disposed is stirred by the rotation of the agitator 39 so that the toner and the carrier are uniformly mixed.
At this time, the developer stirred on the stirring screw 18 side and the first conveying screw 20a and the second conveying screw 2
Ob is mixed with the new developer conveyed. The developer mixed by the agitator 39 collects between the ribs 40 provided on the bottom surface of the developing tank 16 below the agitator 39, and the toner density sensor 34
Is transported to the disposition position.

Thereafter, the developer overflowing from the agitator 39 in the direction of arrow C is sufficiently stirred by the stirring screw 18 to frictionally charge the toner. Thereafter, the developing roller 17 attracts the carrier by a magnetic force, forms a magnetic brush, and conveys the toner. Thus, the toner adhered to the carrier by the Coulomb force is supplied to the photoconductor 4, and the electrostatic latent image on the photoconductor 4 is supplied. And is developed.

On the other hand, the excess developer in the developing tank 16 is transported by the agitator 39 to the developer discharge section 23 and discharged outside through the developer overflow 23 a of the developer discharge section 23.

As described above, by providing the toner density sensor 34 almost at the center between the ribs 40 formed on the bottom surface of the developing tank 16, the amount of developer near the position where the toner density sensor 34 is provided can be reduced. Can be increased more than other parts. Thus, even if the amount of the developer in the developing tank 16 changes, the change in the developer density in the vicinity of the toner density sensor 34 can be reduced. Therefore, the output value of the toner density sensor 34 can be set to a more accurate value, so that the toner density in the developing tank 16 can be kept constant, and the copied image can be favorably maintained.

Embodiment 2 The following will describe another embodiment of the present invention with reference to FIGS. Note that the above embodiment
Members having the same functions as those of the first member are denoted by the same reference numerals, and description thereof will be omitted.

As shown in FIG. 16, a developing device 48 according to the present embodiment uses the agitator 29 shown in FIG. 9 of the first embodiment as a stirring means. In the second transport screw 20b provided in the developing device 48, a rib 50 (shown by hatching in the figure) is provided in a screw portion facing the toner density sensor 34. As shown in FIGS. 17 and 18, the rib 50 is formed in the longitudinal direction of the second transport screw 20b and in a direction orthogonal to the axis of the second transport screw 20b.

Therefore, the second transport screw 20
b rotates in the direction of the arrow shown in FIG.
As shown in FIG. 16, the developer conveyed by the first conveying screw 20a is conveyed in the direction of arrow B, and is conveyed to the toner concentration sensor 34 side by the rib 50.

The first transport screw 20a is provided with a screw-free area E on the near side from the position of the rib 50 of the second transport screw 20b. As a result, the developer transported by the first transport screw 20a stays in the area E, and the developer overflowing from the area E is again moved by the arrow A by the first transport screw 20a.
While being transported in the direction of arrow B from the position where the rib 50 of the second transport screw 20b is provided.

Therefore, when the developer conveyed from the first conveying screw 20a is conveyed by the rib 50 from the position where the rib 50 of the second conveying screw 20b is provided to the direction of arrow C, that is, to the side where the toner density sensor 34 is provided. This eliminates the problem that the second conveying screw 20b is not conveyed in the direction of arrow B from the position where the rib 50 is provided.

Here, the transport of the developer by the developing device 48 will be described with reference to FIGS. The developing roller 17, the stirring screw 18, the agitator 29, the first transport screw 20a, and the second transport screw 20b rotate in the directions of the respective arrows as shown in FIG.

First, based on the detection signal of the toner concentration sensor 34, the toner supply roller 21 or the carrier developer supply roller 22 of the developer supply unit 25 is rotated, and the toner or the carrier developer is supplied to the developing tank 16 for supply. It is supplied from the opening 16a.

Next, the developer supplied from the supply opening 16a of the developing tank 16 is transported in the direction of arrow A by the first transport screw 20a and transported in the direction of arrow B by the second transport screw 20b. . Further, the developer is transported in the direction of arrow C by the first transport screw 20a and the second transport screw 20b, and is transported to the position where the agitator 29 is provided.

At this time, the developer replenished from the replenishing opening 16a is supplied by the first transport screw 20a to the arrow A.
And stays in the area E, overflows from the area E in the direction of arrow A of the first transport screw 20a, and overflows in the direction of arrow B from the position of the rib 50 of the second transport screw 20b. . Thus, the developer is transported again in the direction of arrow A by the first transport screw 20a, and is transported in the direction of arrow B by the second transport screw 20b.

The developer transported by the first transport screw 20a is transported to the rib 50 by the second transport screw 20b, and is transported to the toner density sensor 34 by the rib 50.

Next, the developer is stirred by the rotation of the agitator 29 so that the toner and the carrier are uniformly mixed. At this time, the developer stirred on the stirring screw 18 side and the new developer transported by the first transport screw 20a and the second transport screw 20b are mixed.

Thereafter, the developer overflowing from the agitator 29 in the direction of arrow C is sufficiently stirred by the stirring screw 18 to frictionally charge the toner. Thereafter, the developing roller 17 attracts the carrier by a magnetic force, forms a magnetic brush, and conveys the toner. Thus, the toner adhered to the carrier by the Coulomb force is supplied to the photoconductor 4, and the electrostatic latent image on the photoconductor 4 is supplied. And is developed.

On the other hand, the excess developer in the developing tank 16 is conveyed by the agitator 29 to the developer discharge section 23 and discharged outside through the developer overflow 23 a of the developer discharge section 23.

As described above, the developer transported by the second transport screw 20b is
Since the toner is forcibly conveyed to the toner density sensor 34 by the rib 50 formed in the developing tank 16, the amount of the developer near the toner density sensor 34 can always be larger than that of the other parts of the developing tank 16. Thus, even if the amount of the developer in the developing tank 16 changes, the change in the amount of the developer near the toner concentration sensor 34 can be reduced.

Therefore, the output value of the toner density sensor 34 can be set to a more accurate value.
Can be kept constant, and the copied image can be favorably maintained.

[Embodiment 3 ] FIGS. 19 to 21 show still another embodiment of the present invention.
This will be described below. The members having the same functions as those of the above-described embodiments are denoted by the same reference numerals, and description thereof will be omitted.

As shown in FIG. 19, the developing device 58 according to the present embodiment is provided with a stirring screw 59 in place of the stirring screw 18 provided in the developing device 28 of the first embodiment shown in FIG. .

The stirring screw 59 is provided with a rib 60 at a position on the shaft 59a of the stirring screw 59 opposite to the toner concentration sensor 34. This rib 60 is shown in FIG.
As shown in FIG. 21 and FIG. 21, the longitudinal direction on the shaft 59 a of the stirring screw 59 and the shaft 59
It is formed in a direction orthogonal to a.

Therefore, the stirring screw 59 is
By rotating in the direction of the arrow shown in FIG.
As shown in FIG. 5, the developer stirred in the developing tank 16 is conveyed to the developing roller 17 side, and is also conveyed to the toner density sensor 34 by the rib 60.

As described above, the rib 6 is attached to the stirring screw 59.
By providing 0, the developer can be forcibly conveyed to the vicinity of the toner concentration sensor 34 by rotating the stirring screw 59. As a result, the amount of the developer in the vicinity of the toner density sensor 34 can be made larger than that in the other portions in the developing tank 16.
4 can be stabilized.

Further, since the developer detected by the toner concentration sensor 34 is a developer after being developed by the developing roller 17, that is, a developer in an under toner state, a more accurate toner in the developer can be obtained. The concentration can be detected. As a result, the developer density can always be stabilized, so that the copied image can be favorably maintained.

[0109]

As described above, the developing device of the present invention has a stirring means for rotating and stirring and transporting the developer in the developing tank to the developing tank for storing the developer comprising the toner and the carrier. And a developing roller for supplying the developer to the photoconductor is provided rotatably, and the developer is sequentially supplied from the developer replenishing unit to the developing tank in accordance with the detection output of the toner concentration detecting means provided in the developing tank. while being replenished in the developing device in which the developer in the developer tank is discharged from the developer discharge opening formed in the developing tank, the toner concentration detecting means, provided on the bottom surface of the developer tank Rutotomoni, the The stirring means is formed so as to collectively convey the developer to the vicinity of the arrangement position of the toner concentration detecting means, and on the bottom of the developing tank,
The developer is blocked in the direction of the rotation axis of the stirring means and overflows.
The overflow member to be sandwiched sandwiches the toner concentration detecting means.
It is a structure provided in .

[0110] was but I, along with the amount of developer toner concentration detector vicinity can be greater than the amount of developer other developer tank, the fluctuation of the developer amount by the tilt of the developing device
Since it can be made smaller, it is possible to always obtain a stable detection signal by the toner density detecting means . This result
As a result, it is possible to detect the toner concentration more accurately without being affected by the change in the amount of the developer in the developing tank, and to obtain an effect that the copied image can be maintained satisfactorily.

[Brief description of the drawings]

FIG. 1 is a schematic plan view of a developing device on which the present invention is based .

FIG. 2 is a side view of the developing device shown in FIG.

FIG. 3 is a sectional view of the developing device shown in FIG.

FIG. 4 is a schematic configuration diagram of a copying machine including the developing device shown in FIG.

FIG. 5 is a control block diagram of the copying machine shown in FIG.

6 is a graph showing a relationship between a developer weight change value and an output value of a toner density sensor in the developing device shown in FIG.

FIG. 7 is a schematic plan view of a developing device of a comparative example with respect to a relationship between a developer weight change value and a toner density sensor output value of the developing device shown in FIG.

8 is a graph showing a relationship between a developer weight change value and a toner density sensor output value in the developing device shown in FIG. 7;

FIG. 9 is a schematic plan view of another developing device on which the present invention is based .

10 is a cross-sectional view of the developing device shown in FIG. 9 taken along line YY.

11 is a schematic cross-sectional view showing a structure near a toner concentration sensor provided on a bottom surface of a developing tank provided in the developing device shown in FIG. 9, wherein (a) is a cross-sectional view in the directions of arrows AB. (B) is a sectional view taken along line ZZ of (a).

FIG. 12 is a schematic plan view of a developing device according to an embodiment of the present invention.

13 is a cross-sectional view of the developing device shown in FIG. 12 taken along line WW.

14 is a schematic sectional view showing a structure near a toner concentration sensor provided on a bottom surface of a developing tank provided in the developing device shown in FIG.

15 is a perspective view of the vicinity of a rib formed on a bottom surface of a developing tank of the developing device shown in FIG.

FIG. 16 is a schematic plan view of a developing device according to another embodiment of the present invention.

17 is a cross-sectional view of the developing device shown in FIG. 16 taken along line VV.

18 is a cross-sectional view of the developing device shown in FIG. 16 taken along line RR.

FIG. 19 is a schematic plan view of a developing device according to still another embodiment of the present invention.

20 is a cross-sectional view of the developing device shown in FIG. 19 taken along line UU.

21 is a cross-sectional view of the developing device shown in FIG. 19, taken along line SS.

[Explanation of symbols]

 Reference Signs List 4 photoconductor 8 developing device 16 developing tank 17 developing roller 18 stirring screw (second stirring means) 19 agitator (first stirring means) 20a first transport screw (transport means) 20b second transport screw (transport means) 23 Developer discharging portion (developer discharging opening) 28 Developing device 29 Agitator (first stirring means) 30 Concavity 34 Toner density sensor (Toner density detecting means) 38 Developing device 39 Agitator (First stirring means) 40 Rib ( Spill member) 48 developing device 49 agitator (first stirring means) 50 rib (conveying member) 58 developing device 59 stirring screw (first stirring means) 60 rib (conveying member)

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Masatoshi Kanegashi 22-22, Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72) Inventor Takashi 22-22, Nagaikecho, Abeno-ku, Osaka-shi, Osaka Sharp Corporation (56) References JP-A-51-13249 (JP, A) JP-A-5-341649 (JP, A) JP-A-3-231272 (JP, A) JP-A-60-238877 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 15/08

Claims (1)

(57) [Claims] An agitating means for rotating and agitating and transporting the developer in the developing tank and a developing roller for supplying the developer to the photoreceptor; Each is provided rotatably, and the developer is sequentially replenished from the developer replenishing section to the developing tank in accordance with the detection output of the toner concentration detecting means provided in the developing tank, while the developer in the developing tank is in the developing device is discharged from the developer discharge opening formed in the developing tank, the toner concentration detecting means, that provided on the bottom surface of the developer tank
Together, the stirring means, a developer is formed so as to aggregate transported to the vicinity of the arrangement position of the toner concentration detection means, the bottom surface of the developer tank is present in the rotation axis direction of the stirring means
The overflow member that damps the image agent and overflows the toner
A developing device provided so as to sandwich the density detecting means .