JPS6263969A - Developing device for electrophotographic device - Google Patents

Abstract

PURPOSE:To detect more accurately the toner concentration by providing a level detecting means, which detects the level of a developer, in a carrying interrupting part formed in a part of a carrying path of a stirring means. CONSTITUTION:The level of a developer 74 in an interrupting part 42a is dependent upon the fluidity of the developer itself, but if the toner concentration is raised, the fluidity of the developer is reduced and the level of the developer is raised more than the increment of the volume of the developer due to relative increase of a toner to a carrier in an interrupting part 42b. Consequently, it is detected that the toner concentration of the developer 74 is sufficiently high if the level in the interrupting part 42b is higher than a certain level. If the toner concentration is reduced, the fluidity of the developer 74 is increased and the level of the developer 74 falls more than the decrement of the volume of the developer due to relative reduction of the toner to the carrier in the interrupting part 42. Consequently, it is detected that the toner concentration is lower than a prescribed value if the level of the developer 74 in the interrupting part 42b is lower than the certain level. Thus, the more accurate toner concentration is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a developing device for an electrophotographic apparatus, and more particularly to a developing device using a two-component developer in which a carrier and a toner are mixed.

(Prior Art) An example of an interesting developing device of the present invention is, for example, the Japanese Patent Publication No. 6 (1-195
It is disclosed in Publication No. 05.

This prior art is a developing device in which a bulge of developer is formed in the center of a screw conveyor, and the level of the bulge of developer is detected by a level detection means.

(Problems to be Solved by the Invention) In the above-mentioned conventional technology, the raised part of the developer at the center of the screw conveyor does not necessarily reflect the toner concentration accurately, and therefore the detection of the toner concentration is inaccurate. There was a drawback.

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, when the toner concentration is high and the fluidity of the developer is low, the raised portions may collapse and the level and toner concentration will no longer correspond accurately.

Therefore, a main object of the present invention is to provide a developing device for an electrophotographic apparatus that can detect toner concentration more accurately.

(Means for Solving the Problems) To put it simply, the present invention provides a stirring means for stirring a developer in which carrier and toner are mixed while conveying it from its starting end to its terminal end, and a conveyance path of the stirring means. This is a developing device for an electrophotographic apparatus, comprising a conveyance interruption section formed in a part of the conveyance interruption section, and a level detection means provided in the conveyance interruption section for detecting the level of developer there.

(Function) The stirring means stirs the developer while conveying it. The conveyance becomes discontinuous at the conveyance interrupted portion, and stagnation of the developer is formed at that portion. The level detection means detects the level of the developer that has caused this stagnation. As the toner concentration increases, the fluidity of the developer decreases, so that the level of developer at the transport interruption increases by more than the increase in developer volume due to the increase in toner. Conversely, when the toner concentration decreases, the fluidity increases, and the level at the conveyance interrupted portion decreases by the amount of the decrease in developer volume due to the decrease in toner. In this way, the toner concentration is detected by the level detection means.

(Effects of the Invention) According to the present invention, since there is no stirring blade or the like in the conveyance interruption section, the level of the developer there accurately reflects the toner concentration, and therefore the toner concentration can be more accurately reflected than in the past. Concentration can be detected.

The above objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

(Embodiment) FIG. 3 is an illustrative cross-sectional view for explaining the internal structure of an electronic copying machine as an embodiment of the present invention.

Although the present invention will be described below as being applied to an electronic copying machine, it should be understood that the present invention can also be applied to other electrophotographic devices such as printers and facsimile machines. I would like to point out this in advance.

Referring to FIG. 3, electronic copying machine 10 includes a copying machine main body 12, and a document table 14 made of a transparent glass plate is fixedly provided on the upper surface of this copying machine main body 12. An automatic document feeder 16 is mounted above the document table 14. A document tray 20 is provided at the starting end of the automatic document feeder 16 to store originals I8 before being copied, and a tray 22 for receiving copied documents is provided at the end of the automatic document feeder 16. provided.

A light source 24 is provided below the document table 14 in the copying machine body 12 as a scanning means for exposing and scanning the document. Allowed to move in the opposite 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 this reflecting mirror 26 . When the light source 24 is moved rightward in FIG. 3 by the servo motor, the document placed on the document table 14 is exposed to slit light.

A second movable mirror 30 is provided in association with the first movable mirror 28 , and this second movable mirror 30 reflects the document image reflected by the first movable mirror 28 again toward the zoom lens 32 . It is for the purpose of

A fixed reflecting mirror 3G is provided in front of the zoom lens 32 to reflect the original image transmitted through the lens 32 toward the photosensitive drum 34.

Upstream of the exposure position of the photoreceptor drum 34, that is, the position where the original image is formed by the reflecting mirror 36, there is provided a charger for uniformly charging the photoreceptor drum 34 with a charge of a specific polarity.
A charging corotron 38 is provided.

A developing device 40 is provided downstream of the above-mentioned exposure position of the photoreceptor drum 34, and the charging corotron 38. An electrostatic latent image formed on the photoreceptor drum 34 by the light source 24 and zoom lens 32 is developed using toner. A toner hopper (not shown) is provided above the developing device 40 for supplying toner.

Developing device 40 further includes screw conveyors 42 and 44. The screw conveyors 42 and 44 are for stirring the carrier and toner. The developing device 40 further includes a rotating sleeve 48 built therein. The present invention is directed to such a developing device 40.

A paper feeding section 50 is formed at one side end of the copying machine main body 12, and two paper feeding force centers are detachably attached to this paper feeding section 50 in this embodiment.

Among the sheets 52 housed in these paper feed cassettes, the topmost paper is pressed against the paper feed roller 54 . As the paper feed roller 54 is rotated, it sequentially takes in the thus-pressed envelopes 52 from the paper feed cassette toward the photosensitive drum 34 one by one.

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

When the paper 52 is fed from the paper feed section 50, the photosensitive drum 3
The toner image formed on the paper 52 is transferred to the paper 52 by a transfer corotron 56.

During the transfer by the transfer corotron 56, the paper is attracted to the drum 34 and tries to move together with the drum 34, but is separated by the separation corotron 58 and transferred in the direction of a vacuum conveyor 60, which will be described later.

A cleaning device 62 is provided along the photoconductor drum 34 on the downstream side of the transfer corotron 56 (upper left in FIG. 2). Remove residual toner.

The paper separated from the photoreceptor drum 34 by the separating corotron 58 is sent to a fixing device 64 by a vacuum conveyor 60. This fixing device 64 includes a heating roller 66 that has a built-in heater, and a heating roller 66 that has a built-in heater.
A pressure roller 68 for pressing the paper is included. Therefore, the toner image transferred onto the paper 52 is heated and pressed by the two rollers 66 and 68, and the toner image is transferred onto the paper 52.
will be established. The paper that has been fixed is discharged onto the paper discharge tray 70 by a pair of paper discharge rollers.

A control box 72 is formed above the fixing device 64 in the copying machine main body 12, and electronic components for a control system are housed within the control box 72.

In FIG. 2, a developing device 40 provided near the photosensitive drum 34 includes a container 40a, in which a developer 74 is stored, and screw conveyors 42 and 44 are arranged in the longitudinal direction. placed parallel to each other.

A partition wall 40b is formed between the screw conveyors 42 and 44. This partition wall 40b divides the conveyance path of each screw conveyor 42 and 44 so that the starting end of the screw conveyor 42 and the terminal end of the screw conveyor 44 communicate with each other, and the terminal end of the screw conveyor 42 and the starting end of the screw conveyor 44 communicate with each other. That is, both ends of the screw conveyors 42 and 44 are formed to communicate with each other. The screw conveyor 42 agitates the developer 74 while conveying it from the front side in the direction perpendicular to the paper surface, and the screw conveyor 44 mixes and agitates the developer while conveying the developer in the opposite direction to the screw conveyor 42.

In this way the two screw conveyors 42 and 4
The developer 74 mixed and stirred by the rotating sleeve 4
It is formed as a magnetic brush according to the rotation of 8. When the spikes of the magnetic brush come into contact with the surface of the photoreceptor drum 34, for example, the negatively charged toner is attracted to the positively charged electrostatic latent image, and the electrostatic latent image is caused by the toner. Developed. At this time, the height of the spikes of the magnetic brush is regulated by the plate 76. The magnetic brush that has completed development is scraped off from the rotating sleeve 48 by a scraper 78 as the rotating sleeve 48 rotates.

In relation to the screw conveyor 42, a level detector 80 is provided at a predetermined position of the container 40a of the developing device 40. 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 illustrated in FIG. Toner hopper 82 (Figure 4)
The toner supplied from the screw conveyor 42
is dropped at the beginning of the The screw conveyor 42 has spirally formed stirring blades 4.23, and therefore:
The supplied toner and the carrier contained in the container 40a pass through the stirring blades 42 of the screw conveyor 42.
They are mixed and stirred while being conveyed in the direction of the arrow by a.

The stirring blade 42a is cut out or discontinuously formed approximately at the center of the screw conveyor 42. The conveyance of the developer is interrupted at the interrupted portion 42b of the stirring blade 42a, and stagnation of the developer 74 occurs there, as shown in FIG.

Level detector 80 is arranged so as to be able to detect the level of developer 74 at its interruption 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 detects the stagnation part, that is, the interrupted part 42b. It is detected that the developer 74 is at a level above a certain level.

In this manner, stagnation of the developer 74 occurs in the interrupted portion 42b, so that the pulsation of the developer that occurs in the case of a continuous screw conveyor is suppressed, and the level of the developer can be detected more accurately. That is, the interruption part 4
The level of the developer 74 at 2a also depends on the inherent fluidity of the developer, but as the toner concentration increases, the fluidity of the developer decreases, and at the interruption part 42b, the level of the developer 74 decreases due to the relative increase of toner to carrier. The increase is greater than the increase in developer volume. Therefore, when the toner concentration of the developer 74 is at a certain level or higher at the interrupted portion 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 at the interruption portion 42b, the level of the developer 74 decreases by the amount of the decrease in the volume of the developer due to the relative decrease of the toner to the carrier. . Therefore, when the level of the developer 74 is below a certain level in the interrupted portion 42b, the toner concentration is detected as being lower than a predetermined value.

In this way, since the level of stagnation of the developer 74 occurring in the interrupted portion 42b is detected, the toner concentration can be detected with high accuracy.

In the above embodiment, a pressure sensor is used as the level detector 80, but in addition to such a pressure sensor, the level detector 80 may also include an optical sensor, a magnetic sensor, an inductance sensor, or an inductance sensor. Any capacitance sensor could be used.

FIG. 4 is a circuit diagram showing an example of a control circuit for controlling toner density. A toner hopper 82 is provided above the developing device 40, and a first
As shown in the figure, toner is supplied to the starting end of the screw conveyor 42. A signal from a level detector 80 provided in the developing device 40 is applied to an input port of a microprocessor 84 via a suitable interface.

This microprocessor 84, although not shown, controls all operations of the electronic copying machine as shown in FIG. 3, but only the part related to toner supply control is depicted in FIG. Please note.

A given output port of the microprocessor 84 is connected to the base of a pnp transistor 86 via a suitable interface. The collector of this transistor 86 is connected to the power supply Vcc (for example, 5V), and the emitter is n
pn) connected to the base of transistor 88. The emitter of the transistor 88 is grounded, and the collector has a relay coil 9 connected between it and the power supply Vcc (for example, 24■).
0 is connected. Relay contacts 90a associated with this relay coil 90 constitute a power supply circuit for the motor 92. This motor 92 connects the toner hopper 82 to the developing device 4.
When this motor 92 rotates a certain amount, a certain amount of toner is supplied from the toner hopper 82 into the developing device 40 .

When the signal from the level detector 80 is at high level,
That is, the developer 74 at the interrupted portion 42b (FIG. 1)
When the level of is above a certain level, the microprocessor 8
No. 4 does not perform control for toner replenishment.

Conversely, when the signal from the level detector 80 is at a low level, that is, when the level of the developer 74 at the interruption section 42b is below a certain level, the microprocessor 84
Output a low level signal to that output port. In response, transistor 86 turns on and transistor 88 turns on. When transistor 88 turns on, relay coil 9
o is energized, and its relay contact 90a is turned on. For this purpose, power is supplied to the motor 92, and this motor 9
2 is energized, and a predetermined amount of toner is supplied from the toner hopper 82 to the developing device 40 .

In this way, the toner concentration within the developing device 40 is controlled based on the output from the level detector 8o.

[Brief explanation of the drawing]

FIG. 1 is an illustrative view showing an embodiment of the present invention. FIG. 2 is an illustrative view showing the developing device. FIG. 3 is an illustrative diagram for explaining the 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. In the figure, 40 is a developing device, 40a is a container, 42 and 44 are screw conveyors, 42a is a stirring blade, 42
74 is a developer, and 80 is a level detector. Patent applicant Sanyo Electric Co., Ltd. agent Patent attorney Yama 1) Yoshito (and 1 other person) 2. -Total
Ken〉Kishifudai

Claims (1)

[Scope of Claims] 1. An agitation means for agitating the developer in which carrier and toner are mixed while conveying it from its starting end to its end; a conveyance interruption portion formed in a part of the conveyance path of the agitation means; and a developing device of an electrophotographic apparatus, comprising a level detecting means provided at the conveyance interruption section and for detecting the level of the developer there. 2. The developing device for an electrophotographic apparatus according to claim 1, wherein the stirring means includes a stirring blade formed from a starting end to a terminal end thereof, and the conveyance interruption portion includes a discontinuous portion of the stirring blade. 3. The developing device for an electrophotographic apparatus according to claim 2, wherein the stirring blade is formed in a spiral shape. 4. The developing device for an electrophotographic apparatus according to claim 3, wherein the stirring means includes a screw conveyor. 5. The developing device for an electrophotographic apparatus according to any one of claims 1 to 4, further comprising toner supply means for supplying the toner to a starting end of the stirring means. 6. The developing device for an electrophotographic apparatus according to claim 5, further comprising means for controlling the supply of toner by the toner supply means in accordance with the output of the level detection means.