JPH01222278A - Developing device - Google Patents

Abstract

PURPOSE:To prevent the generation of deterioration of the image density by detecting a toner of a first hopper part in the vicinity of a toner supplying part to a second hopper of the first hopper. CONSTITUTION:A toner 3 which is replenished into the first hopper part 1 is fed to the second hopper part 2 being adjacent thereto by a replenishing roller 4 which is provided so as to occupy the greater part of a supply port 12 and driven to rotate. In the second hopper part 2, a toner detector 9 is provided, and by a signal which is detected by the detector 9, a motor for driving the replenishing roller 4 is controlled through a controller, and the rotation of the replenishing roller 4 is controlled. A quantitative relation of the toner quantity in the second hopper part 2 which can execute an optimum development and the replenishing quantity of the toner 3 is optimized in advance. In such a way, the image of a high quality can always be obtained without allowing an old toner to remain behind in the first hopper part.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] "Industrial Application Field" The present invention relates to an image forming apparatus, particularly a developing device for an electrophotographic image forming apparatus.

"Prior Art and Problems to be Solved" Conventionally, one of the most important issues in obtaining high-quality images in electrophotographic apparatuses has been the problem of how stable development can be performed. In order to make this possible, the state of the toner around the developing sleeve must be made most suitable for development in accordance with the characteristics of the developer, such as tribo or fluidity. In other words, it is necessary to stir a certain amount of toner in advance before sending it onto the developing sleeve in order to provide the toner particle base with a certain tribo value and to form a stable coating on the developing sleeve. be.

Usually this is done by the following method. In other words, a first hopper section stores a large amount of toner, and a second hopper section internally stirs a fixed amount of toner within a certain range and always supplies toner in a stable state to the developing sleeve. In this method, toner is supplied from the first hopper section to the second hopper section little by little so as not to cause a sudden change in tribo every time the amount of toner in the second hopper section becomes insufficient. Now, it is necessary to display an out-of-toner display at the same time or before the amount of toner in the if hopper section runs out to inform the user of the time to replenish toner to the first hopper section. However, the old toner remains in the first hopper and mixes with new toner, gradually deteriorating the quality of the toner and causing a long-term decrease in density.
Care must also be taken to avoid image defects. For this reason, it is not desirable to detect the remaining amount in the first hopper section too quickly.

"Problems to be Solved by the Invention" The present invention solves the problems of the conventional example described above, and by preventing old toner from remaining in the first hopper section,
It is an object of the present invention to provide a developing device that can always obtain high-quality images.

"Means for Solving the Problems" The present invention has a first hopper section and a second hopper section equipped with a developing means and a remaining toner amount detecting means adjacent to each other, and detects the remaining amount of toner in the second hopper section. , in the developing device that supplies toner from the first hopper section to the second hopper section, a remaining toner amount detection means located in the final passage area of the toner and near the supply section of the first hopper to the second hopper;
The developing device includes means for generating a signal for permitting toner replenishment in response to a signal of the remaining toner amount detecting means detecting a zero remaining amount of toner in the first hopper.

“Examples” Examples of the present invention will be described below. FIG. 1 is a longitudinal sectional view of the developing device. Around the photosensitive drum 10, there is a primary charger that performs an electrophotographic process (not shown), and the photosensitive drum 1.
A well-known electrophotographic process is performed by sequentially disposing a window through which the image light sent to the image sensor 1 passes, a developing device 11, a transfer device, a separating device, a cleaning device, and the like.

The developing device 11 has a first hopper section 1 at the top and a second hopper section 2 at the bottom, and both hopper sections 1.degree.2 are adjacent to each other. Both hopper sections 1 and 2 communicate with each other through a supply port 12. The toner 3 replenished into the first hopper section 1 is sent to the second hopper section 2 by a replenishment roller 4 which occupies most of the supply port 12 and is driven to rotate in the direction of the arrow in the figure. It has become.

A developing sleeve 7 is provided in the second hopper section 2 so as to be close to or in contact with the photosensitive drum 10, and the developing sleeve 7 rotates in the direction of the arrow in the figure during operation, and a doctor blade 8 provided in the second hopper section 2 causes the developing sleeve 7 to The toner 3 sucked by the toner 7 is made into a negative layer and supplied to the photosensitive drum 10. A stirring rod 6 is provided inside the second hopper section 2 to stir the toner 3 inside.

A toner detector 9 is provided in the second hopper section 2, and a signal detected by the detector 9 controls a motor that drives the replenishment roller 4 via a control device (not shown), so that the rotation of the replenishment roller 4 is controlled. It's about to be controlled. As a result, when the toner detector 9 detects the lower limit amount of toner A in the second hopper section 2, the replenishment roller 4 is rotated by a certain angle to replenish a small amount of toner 3 from the first hopper section 1. The toner detector 9 includes, for example, a capacitive type, a magnetic sensor type, a piezoelectric sensor type, etc., in which a wire is stretched apart from the developing sleeve 7, and the amount of toner is detected by the capacitance between these wires.

Fluctuations in the amount of toner in the second hopper section 2 vary depending on the black area of the original to be copied, but assuming that the amount of toner X in the second hopper section 2 that allows optimal development is between xl and xl. (XI<X2), the lower limit amount xO detected by the toner detector 9 must be larger than xl. Further, the replenishment amount ΔX of the toner 3 must be smaller than: t7−XQ.

These quantitative relationships shall be optimized in advance. As the stirring rod 6 rotates, the toner 3 in the second hopper 2 is given an appropriate tribo effect, is evenly supplied to the developing sleeve 7, and is sent onto the photosensitive drum 10.

Detection when the toner 3 runs out in the first hopper section 1 can be carried out by making the entire or surface of the replenishment roller 4 conductive and detecting the electric capacitance C between it and the opposing conductive plate 5. can. The first and second hopper parts 1 and 2 are made of electrically insulating material. The conductive plate 5 is provided so as to be integrated with the green of the supply port 12.

Thereby, the size of the supply port 12 is also determined by the distance between the conductive plate 5 and the supply roller 4. That is, the conductive plate 5 also serves as a member constituting the supply port 12. The remaining amount of toner detection means is not limited to this, but there is a supply port 1 near the supply port 12.
It can also be constructed by a member separate from the member constituting 2.

If there is toner 3 in the first hopper section 1, the replenishment roller 4
Since the toner is filled in the vicinity of the conductive plate 5, there is a larger electric capacity than in the case where there is no toner 3. Here, it is only necessary to display a toner replenishment indication when the capacitance C becomes less than a certain value CG.

The above-described detection method of the first hopper section 1 is carried out at the boundary between the first hopper section 1 and the second hopper section 2, and serves both as a toner supply means and a detection means. Therefore, when performing the detection at the upper part of the first hopper section 1, it is possible to perform accurate detection without comparative variation, and detection can be performed until just before the toner 3 is used up. When the critical value of the capacitance detection is set to a value where the toner 3 completely disappears in the first hopper section 1 or a value close to it, consider the case where there is no toner 3 in the first hopper section 1 during continuous large-volume copying △X It is desirable that the conductive plate 5 be designed to have a certain degree of thickness (with some margin between Xl and put.

FIG. 2 shows a control device including a capacitive sensing circuit, ie, means 16 for generating a signal authorizing toner replenishment. Means 16 for generating a signal authorizing toner replenishment
The circuit 13 overlooked the capacitance between the supply roller 4 and the conductive plate 5.
The comparator 14 compares the critical capacitance value CO with the corresponding reference voltage Vo, outputs the presence or absence of the toner 3, and generates a toner replenishment detection signal S when the toner 3 in the first hopper section 1 runs out. emits. Upon receiving the signal S, the toner replenishing device 22 such as a lamp is released via the control circuit 17 including a power amplification circuit. As a result, the user is pivotally attached to the main body of the first hopper section 1 by the hinge 26! Open i21 and replenish toner 6.

When the door 21 is closed, the lock device 22 is activated and cannot be opened until the toner 6 in the first hopper section 21 is exhausted. As a result, toner cannot be replenished unless the toner 6 is completely exhausted in the first hopper section 1.
Old toner is no longer left in the first hopper section 1.

In Figure 3, the horizontal axis represents the amount of toner 3 in the first hopper section 1.
The electric capacity fc between the supply roller 4 and the conductive plate 5 is plotted on the vertical axis.
Toner in the first hopper section 1! It is a diagram showing the relationship between fiy and electric power ic. C1 is the electric capacity when toner 6 is not present in the supply port 12, that is, when there is no toner 3 in the first hopper section 1. When the amount of toner is 72 or more, the capacitance reaches a nearly saturated value C2 and hardly increases beyond that value. The toner detection level y3 is C1 and C2.
It can be taken as C& between.

These quantitative relationships and detection characteristic curves are based on the supply roller 4.
and can be freely changed depending on the shape of the conductive plate 5. In this figure, the larger the slope between <ystcs) and (72,02), the more precise the detected amount.

Although the toner amount detection in the first hopper section 1 has been described so far as capacitance detection, it is also possible to use a similar structure to detect a DC resistance value change.

〔Effect of the invention〕

As explained above, the toner detection in the first hopper section is
By performing this in the vicinity of the toner supply section to the second hopper of the hopper, accurate and stable toner detection is possible, and toner replenishment is indicated at an appropriate time. When replenishing new toner, the toner in the first hopper is used up, so it will not mix with old toner that has completely deteriorated and reduce the quality of the toner, so even if used for a long time, the image quality will be maintained. No decrease in concentration occurs.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal sectional view of an embodiment of the present invention, Fig. 2 is a detection system circuit diagram of the first hopper section, and Fig. 3 is the relationship between the amount of toner in the first hopper section and the capacitance between the roller and the conductive plate. FIG. 1. 1st hopper section 211. 2nd hopper section 3.
- Toner 4... Replenishment roller 5... Conductive plate 13...
Oscillation circuit 14... Comparator. Patent applicant Canon Co., Ltd.

Claims (1)

[Claims] 1. A first hopper section and a second hopper section equipped with a developing means and a remaining toner amount detecting means are adjacent to each other, and the remaining amount of toner in the second hopper section is detected, and the toner is transferred from the first hopper section to the second hopper section. In a developing device that supplies toner, remaining toner amount detection means is located in the final passage area of the toner and near a supply section of the first hopper to the second hopper, and the toner remaining amount detection means is located in the first hopper. A developing device comprising means for receiving a signal detecting a zero remaining amount state and generating a signal for permitting toner replenishment.