JPS62135857A - Developing device for electrophotographic method - Google Patents

Abstract

PURPOSE:To detect toner concentration accurately by providing a slight gap at the upstream side of a sensor head between the sensor head and a developing roller and further providing a control plane which has bored reducing holes as necessary. CONSTITUTION:The control plate 12 provided on the upstream side of the sensor head 9 is a plate made of a nonmagnetic material which has plural round holes (reducing hole) 13 bored in the center, the front end is bent to the downstream side to form the slight gap on the peripheral surface of the sleeve 4 of the developing roller 2, and the base end side is fixed to a ceiling part 14. The developer 6 in the developing tank 5 is controlled by the control plate 12 and not supplied to the side of the sensor head 9 by more than required, and even when the developer is cut off by a doctor 7, it never stays at this part and the flow becomes smooth. Consequently, even when the sensor head is left without being used for a long period and the concentration of the developer 6 nearby the sensor head 9 is high, the agitated developer 6 from the developing tank 5 flows in immediately on the start of a copying machine and the concentration recovers in a short time, so that correct toner concentration is detected. Consequently, picture quality is prevented from degradation at the start of the copying machine.

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 provided with a regulating plate on the upstream side of the sensor head to regulate the amount of developer flowing into the sensor head side, thereby achieving accurate toner concentration. The aim is to detect the

<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 trying to control 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 that the developing roller generally feeds toward the surface of the photoconductor to a certain amount, the blocked developer stays upstream of the doctor, causing damage to the sensor head area. The flow will not run smoothly. Additionally, if the developer is left unused for a long time, the particles become clogged and the density increases, and if the magnetic permeability sensor continues to detect it, it will falsely detect that the toner density is low due to the large amount of carrier. There is a risk. For this reason, conventionally, it takes 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 detects a drop in toner concentration and supplies additional toner from the hopper. Therefore, the toner density 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 method 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 equipment.

<Structure 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 uses a transparent plate for detecting toner concentration. In a developing device in which the sensor head of the magnetic sensor is disposed upstream of this doctor in the developer conveyance direction, there is a gap between the sensor head and the developing roller further upstream of the sensor head in order to regulate the amount of developer flowing into the sensor head side. leave a small gap between
Further, the present invention is characterized in that a regulating plate is provided with an aperture hole as required.

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 is high, 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 erroneous detection when starting up after being left unused for a long time. It can be resolved. Therefore, the present invention can prevent image quality from deteriorating when starting up the apparatus.

<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) relative to the photosensitive drum 1.

The developing roller 2 has a cylindrical sleeve 4 fitted around a cylindrical magnet 3 having an odd number of poles, and as the sleeve 4 rotates forward, it attracts the developer 6 in the developer tank 5. After being conveyed and regulated to a certain amount by a doctor 7 disposed above, it is brought into contact with the surface of the photosensitive drum 1. The magnetic permeability sensor 8 is connected to the ceiling 11 of the developer tank 5.
The sensor head 9 is installed on the upper side of the doctor 7 and is placed upstream of the doctor 7 to detect the toner concentration of the developer 6 at this portion. The developer 6 is composed of two components: non-magnetic toner and magnetic carrier, and the magnetic permeability sensor 8 attempts to detect the relative toner concentration by detecting the density of the carrier in the developer 6. It is something to do. Therefore, when the density of the developer 6 itself increases, the magnetic permeability sensor 8 will erroneously detect that the density of only the carrier increases and the amount of toner decreases relatively, resulting in a low toner concentration. 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 the stirring roller 1 .
The toner concentration is increased by stirring the toner into the developer 6 in step 5. 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 form a small gap between it and the circumferential surface of the sleeve 4 of the developing roller 2. is arranged in an open manner, 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.

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. There will be no need to do anything, and the flow will be smoother. Therefore, even if the density of the developer 6 near the sensor bend 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 the image quality from deteriorating when starting up the copying machine.

Further, when the regulation plate 12 is provided with the round holes 13 as in the embodiment, the flow in the lower part of the sensor head 9 can be made even smoother, and the recovery of toner density is further promoted. The toner supplied by the toner can be stirred into the developer 6 by the stirring roller 15 and then immediately supplied to the lower part of the sensor head 9 through the round hole 13. Therefore, the effect of toner supply can be quickly detected, and the control mechanism It is possible to stabilize the toner density and accurately adjust the toner density. However, in order to obtain the effects of the present invention, it is not necessarily necessary to provide the round hole 13, and the shape of the hole is also arbitrary.

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 31 mm, but experimental results show that the highest effect is obtained in the range of 1.5 mm to 2 ml. Ta.

[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. 1-photosensitive drum (photosensitive member), 2-developing roller, 6-developer, 7-doctor, 8-magnetic permeability sensor, 9-sensor head, 12-regulating plate, 13-round hole (diaphragm 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 the magnetic permeability sensor for detecting toner concentration is installed upstream of the doctor in the developer conveyance direction. In the developing device located on the side, a small gap is provided between the developing roller and the developing roller on the upstream side of the sensor head in order to regulate the amount of developer flowing into the sensor head side, and an aperture hole is provided as necessary. 1. A developing device for electrophotography, characterized in that it is provided with a regulation plate having an opening.