JPH0422517B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a developing device for electrophotography in a copying machine or the like.

<Summary of the Invention> In summary, the electrophotographic developing device of the present invention is capable of accurately detecting toner concentration by regulating the amount of developer flowing into the sensor head by providing a regulating plate on the upstream side of the sensor head. This is what I am trying to do.

<Prior art and its drawbacks> In a developing device that uses a two-component developer consisting of a magnetic carrier and a non-magnetic toner,
When controlling toner concentration by detecting changes in magnetic permeability, the sensor head of the magnetic permeability sensor is placed upstream of the doctor. However, since the doctor is used to regulate the amount of developer conveyed by the developing roller toward the photoreceptor surface, the blocked developer stays upstream of the doctor, and the flow at the sensor head is interrupted. will not be carried out smoothly. Additionally, if the developer is left unused for a long time, the particles become clogged and the density increases, so if the magnetic permeability sensor detects it as it is, it will falsely detect that the toner density is low due to the large amount of carrier. There is a risk. For this reason, in the past, it took a long time for the developer density on the upstream side of the doctor to return to normal at startup, and until then, a magnetic permeability sensor detected the drop in toner concentration and supplied additional toner from the hopper. Therefore, the toner concentration cannot be accurately controlled for a while after the device is first used.

<Object of the Invention> The present invention has been made in view of the above circumstances, and provides an electrophotographic developing device in which the toner concentration can be accurately detected by providing a regulating plate on the upstream side of the sensor head. The purpose is to provide

<Configuration and Effects of the Invention> The electrophotographic developing device of the present invention regulates the amount of developer conveyed by the developing roller toward the surface of the photoreceptor to a constant amount by a doctor, and detects the toner concentration. The sensor head of the magnetic permeability sensor is arranged on the upstream side of this doctor in the developer conveyance direction,
Furthermore, in a developing device that is provided with an agitation roller that rotates in the same direction as the developing roller on the side facing the photoreceptor and below the toner hopper with the developing roller at the center, the tip of the developing roller is located further upstream of the sensor head. A regulating plate is provided with a slight distance from the roller and has a plurality of aperture holes opened only at a position facing the sensor head surface, and further,
The stirring roller is provided at a position where a mixing area for mixing the toner developer supplied from the toner hopper is formed between the stirring roller and the regulating plate.

When the electrophotographic developing device of the present invention is configured as described above, the developer does not stay between the doctor and the regulating plate more than necessary, so the flow between them becomes smooth, and the developer is released at the time of startup. Even if the density has increased, it can be quickly restored to normal density. Therefore, the sensor head placed between the doctor and the regulation plate can detect the correct toner concentration in a short time, quickly eliminating the effects of false detection when starting up after being left unused for a long time. can do. Therefore, the present invention can prevent image quality from deteriorating when starting up the apparatus. In addition, the toner supplied from the toner hopper is sent to the mixing area by the rotation of the stirring roller, mixed with the developer in this mixing area, and then a portion is sent to the sensor head through the aperture hole, so when toner is replenished. The toner concentration detection time is shortened.

<Example> Hereinafter, a case will be described in which the present invention is implemented in a developing device of a copying machine.

FIG. 1 is a cross-sectional side view of a developing device of a copying machine according to an embodiment of the present invention, and FIG. 2 is a perspective view of a regulating plate viewed from the direction of arrow A in FIG.

This embodiment shows an example in which the developing roller 2 rotates forward (in the driven direction) with respect to the photosensitive drum 1.
The developing roller 2 is a cylindrical magnet 3 with odd number of poles.
A cylindrical sleeve 4 that is rotatably driven is fitted around the sleeve 4, and as the sleeve 4 rotates in the normal direction, the developer 6 in the developer tank 5 is absorbed and conveyed, and is kept at a constant level by a doctor 7 placed above. After regulating the amount, it is brought into contact with the surface of the photoreceptor drum 1. The magnetic permeability sensor 8 is attached above the ceiling portion 11 of the developer tank 5, and a sensor head 9 is disposed upstream of the doctor 7, and detects the toner concentration of the developer 6 at this portion. The developer 6 consists of two components: a non-magnetic toner and a magnetic carrier.
The magnetic permeability sensor 8 attempts to detect the relative toner concentration by detecting the density of the carrier in the developer 6. Therefore, when the density of the developer 6 itself increases, the magnetic permeability sensor 8 may falsely detect that the density of only the carrier increases and the amount of toner decreases relatively, resulting in a low toner concentration. become. When the magnetic permeability sensor 8 detects a decrease in toner concentration, a control circuit (not shown) operates the hopper 10 to supply replenishment toner 11 into the developer tank 5 and stir it into the developer 6 with the stirring roller 15, thereby increasing the toner concentration. Increase. Therefore, if the magnetic permeability sensor 8 makes an erroneous detection, the actual toner density will increase more than necessary, causing fog or stains on the copy paper and deteriorating the image quality.

This embodiment is constructed by providing a regulating plate 12 further upstream of the sensor head 9. The regulating plate 12 is a non-magnetic plate material with a plurality of round holes (diaphragm holes) 13 formed in the center, and its tip is bent downstream to prevent the sleeve 4 of the developing roller 2 from forming.
It is arranged with a slight interval between it and the peripheral surface, and its base end side is fixed to the ceiling part 14. The plurality of round holes 13 are opened at positions facing the sensor head 9 on the downstream side, as shown in FIG.

Further, the stirring roller 15 is disposed between the stirring roller 15 and the regulating plate 12 at a position where a mixing portion 16 is formed for mixing the toner and developer supplied from the toner hopper 10 .

When this embodiment is configured as described above, the developer 6 in the developer tank 5 is regulated by the regulation plate 12 and is not supplied to the sensor head 9 side more than necessary, and even if it is blocked by the doctor 7, it remains in this part. This will no longer be the case and the flow will be smoother. Therefore, even if the density of the developer 6 near the sensor head 9 has increased due to being left unused for a long time, the agitated developer 6 from the developer tank 5 will flow in as soon as the copying machine is started. , the density recovers to normal in a short time and the correct toner density can be detected. Therefore, this embodiment can prevent image quality from deteriorating when starting up the copying machine.

Furthermore, by providing the round holes 13 in the regulating plate 12 as in the embodiment, the flow below the sensor head 9 can be made smoother, further promoting recovery of toner density, and the hopper 10 is The supplied toner is conveyed by the stirring roller 15 to the mixing section 16 located on the upper left side of the roller, and after being stirred into the developer 6 there, it can be immediately supplied to the lower part of the sensor head 9 through the round hole 13. , the effect of toner supply can be quickly detected, the control mechanism can be stabilized, and the toner concentration can be adjusted accurately. In this embodiment, the aperture hole is a round hole, but it may have any shape.

Note that the appropriate distance between the tip of the regulating plate 12 and the circumferential surface of the sleeve 4 is in the range of 0.5 mm to 3 mm;
The experimental results also showed that the highest effect was obtained in the range of 1.5 mm to 2 mm.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional side view of a developing device of a copying machine according to an embodiment of the present invention, and FIG. 2 is a perspective view of a regulating plate viewed from the direction of arrow A in FIG. DESCRIPTION OF SYMBOLS 1... Photosensitive drum (photosensitive member), 2... Developing roller, 6... Developer, 7... Doctor, 8... Magnetic permeability sensor, 9... Sensor head, 12... Regulating plate, 13... Circle Hole (aperture hole).

Claims (1)

[Claims] 1. The amount of developer conveyed by the developing roller toward the surface of the photoconductor is regulated to a constant amount by a doctor, and the sensor head of a magnetic permeability sensor for detecting toner concentration is controlled by the doctor. In a developing device which is arranged on the upstream side in the agent conveying direction, and further provided with an agitation roller that rotates in the same direction as the developing roller on the side facing the photoreceptor with the developing roller as the center and below the toner hopper, A regulating plate is provided at an upstream position, the tip of which is positioned with a slight spacing between it and the developing roller, and which has a plurality of aperture holes opened only at a position facing the sensor head surface, and further,
A developing device for electrophotography, characterized in that the stirring roller is provided at a position where a mixing area for mixing toner and developer supplied from a toner hopper is formed between the stirring roller and the regulating plate.