JP2594242B2 - Developing device for electrophotographic equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device for an image forming apparatus, and more particularly to a developing device using a two-component developer in which a carrier and a toner are mixed.

[0002]

2. Description of the Related Art An example of an interesting developing device of the present invention is as follows.
For example, it is disclosed in Japanese Patent Publication No. 60-19505 published on May 16, 1985.

This prior art is a developing apparatus in which a reverse transport portion is formed at the center of a screw conveyor to form a swelling of the developer, and a level detecting means detects the level of the swelling portion of the developer. is there.

[0004]

In the above-mentioned prior art,
Since the raised portion of the developer is formed by the reverse transport portion provided on the screw conveyor, the raised portion of the developer does not always accurately reflect the toner concentration, and therefore, the detection of the toner concentration is inaccurate. There was a disadvantage.

That is, in the prior art, when the toner concentration is low, the fluidity of the developer increases, the influence of the rotation of the blades increases, and the level pulsation increases. on the other hand,
Even when the toner concentration is high and the fluidity of the developer is small,
Levels and toner densities do not accurately correspond to each other, for example, due to collapse of a raised portion.

SUMMARY OF THE INVENTION Therefore, a main object of the present invention is to provide a developing device for an electrophotographic apparatus, which can more accurately detect the toner density.

[0007]

SUMMARY OF THE INVENTION The present invention comprises a shaft, a helical stirring blade attached to the shaft, and a conveyance interrupting portion in which the stirring blade is not attached to the shaft. Stirring means for stirring while transporting the developer mixed with the stirring blade from the beginning to the end of the stirring blade, provided at the transport interruption part of the stirring means, and detecting the level of the developer at the transportation interruption part A developing unit for the electrophotographic apparatus, wherein the developing unit detects a toner density based on the level detected by the level detecting unit.

[0008]

The stirring means stirs while transporting the developer. In the conveyance interruption portion where the stirring blade is not attached to the shaft, the conveyance is discontinuous, and the stagnation of the developer is formed in that portion. The level detecting means detects the level of the developer causing the stagnation. As the toner concentration increases, the fluidity of the developer decreases, so that the level of the developer at the conveyance interruption portion is higher than the increase in the volume of the developer due to the increase in the toner. Conversely, when the toner concentration decreases, the fluidity increases, and the level at the conveyance interruption portion falls below the decrease in the developer volume due to the decrease in toner. Thus, the toner density is detected by the level detecting means.

[0009]

FIG. 3 is a sectional view for explaining the internal structure of an electronic copying machine as one embodiment of the present invention.

Hereinafter, the present invention will be described as being applied to an electronic copying machine. However, the present invention can be applied to other electrophotographic apparatuses other than such an electronic copying machine, such as a printer and a facsimile. It should be pointed out in advance.

Referring to FIG. 3, an electronic copying machine 10 includes a copying machine body 12, and a document table 14 made of a transparent glass plate is fixedly provided on an upper surface of the copying machine body 12.
An automatic document feeder 16 is mounted above the document table 14. On the starting end side of the automatic document feeder 16, a document table 20 on which a document 18 before being copied is stored is stored.
A tray 22 is provided at the end of the automatic document feeder 16 for receiving copied documents.

A light source 24 as scanning means for exposing and scanning a document is provided below the document table 14 in the copying machine body 12, and this light source 24 is connected from one end to the other end of the document table 14. It is possible to move in and out of this direction. Associated with the light source 24 is a reflecting mirror 26 whose cross section is elliptical. A first movable mirror 28 is fixed to the reflecting mirror 26. When the light source 24 moves rightward in FIG. 3 by the servomotor, the document placed on the document table 14 is subjected to slit exposure.

A second movable mirror 30 is provided in association with the first movable mirror 28, and the second movable mirror 30 directs the original image reflected by the first movable mirror 28 to the zoom lens 32. To reflect the light again.

In front of the zoom lens 32, there is provided a fixed reflecting mirror 36 for reflecting the original image transmitted through the lens 32 toward the photosensitive drum 34.

The charging position for uniformly charging the photosensitive drum 34 with a charge of a specific polarity is located upstream of the exposure position of the photosensitive drum 34, that is, the position where the original image is formed by the reflecting mirror 36. A corotron 38 is provided.

A developing device 40 is provided on the downstream side of the above-described exposure position of the photosensitive drum 34, and is formed on the photosensitive drum 34 by the charging corotron 38, the light source 24 and the zoom lens 32 by the developing device 40. The developed electrostatic latent image is developed using toner. A toner hopper (not shown) for supplying toner is provided above the developing device 40.
Is provided. The developing device 40 further includes screw conveyors 42 and 44. The screw conveyors 42 and 44 are for stirring the carrier and the toner. The developing device 40 further includes a rotating sleeve 48. The present invention is directed to such a developing device 40.

One end of the copying machine main body 12 has a paper feeding section 5.
0 is formed in the sheet feeding unit 50 in this embodiment.
One paper cassette is detachably mounted. Of the sheets 52 stored in the sheet cassette, the uppermost sheet is pressed against the sheet feeding roller 54. Paper feed roller 54
When the paper 52 is rotated, the paper 52 pressed in this way is sequentially taken one by one from the paper cassette in the direction of the photosensitive drum 34.

On the downstream side of the developing device 40, a transfer corotron 56 and a separation corotron 58 are provided integrally.

When the paper 52 is supplied from the paper supply unit 50, the toner image formed on the photosensitive drum 34 is transferred onto the paper 52 by the transfer corotron 56. At the time of transfer by the transfer corotron 56, paper is transferred to the drum 34.
To move with the drum 34, but is separated by the separating corotron 58 and transferred to the vacuum conveyor 60 described later.

A cleaning device 62 is provided along the photoreceptor drum 34 on the downstream side of the transfer corotron 56 (upper left in FIG. 2).
Removes the toner remaining on the photosensitive drum 34 without being completely transferred.

The paper separated from the photosensitive drum 34 by the separating corotron 58 is sent to a fixing device 64 by a vacuum conveyor 60. The fixing device 64 includes a heating roller 66 having a built-in heater, and a pressure roller 68 for pressing a sheet against the heating roller 66. Therefore, the toner image transferred onto the paper 52 is heated and pressed by the two rollers 66 and 68 and is fixed on the paper 52. The paper after fixing is 1
The paper is discharged onto the paper discharge tray 70 by the pair of paper discharge rollers.

A control box 72 is formed above the fixing device 64 in the copying machine main body 12.
Within 2 are integrated electronic components for the control system.

In FIG. 2, the developing device 40 provided near the photosensitive drum 34 includes a container 40a. In the container 40a, a developer 74 is stored, and screw conveyors 42 and 44 extend along its length. They are juxtaposed so that the directions are parallel to each other. A partition wall 40b is formed between the screw conveyors 42 and 44. The partition wall 40b divides the conveying path of each of the screw conveyors 42 and 44 so that the starting end of the screw conveyor 42 and the end of the screw conveyor 44 communicate with each other, and the end of the screw conveyor 42 communicates with the starting end of the screw conveyor 44. That is, both ends of the screw conveyors 42 and 44 are formed so as to communicate with each other. The screw conveyor 42 stirs while transporting the developer 74 from the near side in a direction perpendicular to the paper surface, and the screw conveyor 44 mixes and agitates while transporting the developer in the opposite direction to the screw conveyor 42.

The developer 74 mixed and stirred by the two screw conveyors 42 and 44 in this way is formed as a magnetic brush in accordance with the rotation of the rotary sleeve 48. When the brush of the magnetic brush contacts the surface of the photosensitive drum 34, for example, the negatively charged toner is attracted to the positively charged electrostatic latent image, and the electrostatic latent image is Developed. At this time, the height of the spikes of the magnetic brush is regulated by the plate 76. The magnetic brush whose development has been completed is the rotating sleeve 4
8 is scraped off from its rotating sleeve 48 by a scraper 78 in accordance with the rotation of 8.

In connection with the screw conveyor 42, a level detector 80 is provided at a predetermined position of the container 40a of the developing device 40.
Is provided. In this embodiment, a load cell type pressure sensor is used as the level detector 80.

Referring to FIG. 1, one screw conveyor 42 is shown in FIG. Toner hopper 82
The toner supplied from FIG. 4 is dropped to the starting end of the screw conveyor 42. Screw conveyor 42
Has a stirring blade 42a formed in a spiral shape. Therefore, the supplied toner and the carrier contained in the container 40a are mixed while being conveyed in the direction of the arrow by the stirring blade 42a of the screw conveyor 42. Stirred. The stirring blade 42a is cut out or formed discontinuously at substantially the center of the screw conveyor 42. Then, in the interruption portion 42b of the stirring blade 42a, the transport of the developer is interrupted, and as shown in FIG. 1, stagnation of the developer 74 occurs.

The level detector 80 is arranged so that the level of the developer 74 can be detected at the interruption part 42b. In the case where the level detector 80 is a pressure sensor as in the embodiment, when the developer 74 comes into contact with a certain area or more of the detection surface, the level detector 80 starts developing at the stagnation portion, that is, the interruption portion 42b. It is detected that the agent 74 is at a certain level or higher.

As described above, since the stagnation of the developer 74 occurs in the interruption section 42b, the pulsation of the developer generated in the case of the continuous screw conveyor is suppressed, and the developer level can be detected more accurately. Can be. That is, although the level of the developer 74 in the interruption portion 42a also depends on the original fluidity of the developer, the fluidity of the developer decreases as the toner concentration increases, and the toner in the interruption portion 42b It is higher than the increase in the developer volume due to the relative increase. Therefore, when the level is at or above a certain level in the interruption section 42b, it can be detected that the toner concentration of the developer 74 is sufficiently high. Conversely, when the toner concentration decreases, the fluidity of the developer 74 increases, and the level of the developer 74 at the interruption portion 42b falls below the decrease in the developer volume due to the relative decrease of the toner with respect to the carrier. . Therefore, when the level of the developer 74 is lower than a certain level in the interruption section 42b, it is detected that the toner density is lower than the predetermined value.

As described above, since the stagnation level of the developer 74 generated in the interruption section 42b is detected,
The toner density can be accurately detected.

In the above embodiment, the level detector 80 is used.
Although the case where a pressure sensor is used has been shown, as the level detector 80, other than such a pressure sensor, an arbitrary sensor such as an optical sensor, a magnetic sensor, an inductance sensor, or a capacitance sensor may be used. .

FIG. 4 is a circuit diagram showing an example of a control circuit for controlling the toner density. A toner hopper 82 is provided above the developing device 40.
2, the toner is supplied to the starting end of the screw conveyor 42 as shown in FIG. A signal from the level detector 80 provided in the developing device 40 is supplied to an input port of the microprocessor 84 via an appropriate interface. Although not shown, the microprocessor 84 controls all operations of the electronic copying machine as shown in FIG. 3, but it should be noted that FIG. 4 shows only a portion related to toner supply control. I want to.

A predetermined output port of the microprocessor 84 is connected to a base of a pnp transistor 86 via an appropriate interface. Transistor 86 has its collector connected to power supply Vcc (for example, 5 V) and its emitter connected to the base of npn transistor 88. The emitter of transistor 88 is grounded, and the collector is connected to a relay coil 90 between power supply Vcc (for example, 24 V). A relay contact 90 a related to the relay coil 90 forms a power supply circuit of the motor 92. The motor 92 is a motor for supplying toner from the toner hopper 82 to the developing device 40. When the motor 92 is rotated at a constant speed, a fixed amount of toner is supplied from the toner hopper 82 into the developing device 40. You.

When the signal from the level detector 80 is at a high level, that is, when the level of the developer 74 in the interruption section 42b (FIG. 1) is higher than a certain level, the microprocessor 84 controls the toner supply. Not performed.

Conversely, when the signal from the level detector 80 is at a low level, that is, when the level of the developer 74 in the interruption section 42b is lower than a certain level, the microprocessor 84 outputs a low level to its output port. Output a signal. Accordingly, transistor 86 turns on and transistor 88 turns on. When the transistor 88 is turned on, the relay coil 90 is energized, and the relay contact 90a is turned on. To this end, power is supplied to the motor 92,
The motor 92 is energized to supply a predetermined amount of toner from the toner hopper 82 to the developing device 40.

As described above, the toner density in the developing device 40 is controlled based on the output from the level detector 80.

[0036]

According to the present invention, since there is no agitating blade in the conveyance interrupting portion, the developer level there accurately reflects the toner concentration. Can be detected.

[Brief description of the drawings]

FIG. 1 is an illustrative view showing one embodiment of the present invention;

FIG. 2 is an illustrative view showing a developing device of the present invention;

FIG. 3 is an illustrative view for explaining a structure of an electronic copying machine as an example of an electrophotographic apparatus to which the present invention is applied;

FIG. 4 is a circuit diagram showing an example of a control circuit for controlling toner supply according to the present invention.

[Explanation of symbols]

 Reference Signs List 40 developing device 40a container 42 screw conveyor 44 screw conveyor 42a stirring blade 42b interrupting part 74 developer 80 level detector

 ──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Akihiko Shuto 2-18 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (56) References JP-A-51-78343 (JP, A)

Claims (1)

(57) [Claims] 1. A developer comprising a shaft, a helical stirring blade attached to the shaft, and a conveyance interrupting portion in which the stirring blade is not attached to the shaft, wherein a developer in which a carrier and toner are mixed is provided. Stirring means for stirring while transporting from the beginning to the end of the stirring blade, provided at the transport interruption part of the stirring means, and a level detection means for detecting the level of the developer in the transport interruption part. A developing device for an electrophotographic apparatus, wherein a toner concentration is detected based on a level detected by the level detecting means.