JPS6215873B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for controlling the toner content (mixing ratio of carrier and toner) of a developer in a developing device used in an electrostatic recording device.

As is well known, in image creation methods such as electrophotographic copying, in which a photoconductor on which an electrostatic latent image has been formed is brought into contact with a developer consisting of a carrier and toner, the image is visualized. It is necessary to always maintain the amount of toner contained in the developer at a constant ratio. That is, when the toner content in the developer becomes abnormally high, the toner adheres to the white background area of the image, resulting in so-called fog development.On the other hand, when the toner content becomes abnormally low, the entire image becomes pale.
This is because it becomes difficult to reproduce fine line parts and unusual color parts.

In order to solve such problems, conventionally, (1)
A device that attaches toner to a photoreceptor or auxiliary object, detects the optical density or charge amount of the attached toner, and replenishes toner according to these detected values (Jikkosho).
39-38339), (2) A device that detects the electrical characteristics of the developer and replenishes toner according to the change in the electrical characteristics (Japanese Patent Laid-Open No. 48-38157, Japanese Patent Laid-Open No. 57638, Publication No. 19458, Japanese Patent Publication No. 122277
(3) A device that detects the magnetic properties of developer and replenishes toner according to changes in the magnetic properties (Japanese Patent Publication No. 46-8280, Japanese Patent Application Laid-open No. 161247-1982),
(4) Device that utilizes the color tone change of developer
(17245 Publication), (5) Device for detecting fluidity, density, and volume change of developer (Japanese Unexamined Patent Application Publication No. 1972-19459), (6)
A device for estimating toner consumption from the original image density (Japanese Patent Application Laid-open No. 79247/1983); (7) A device in which a solid toner block is housed in a developer (Japanese Patent Publication No. 1979-79247);
36078) etc. have been proposed. However, these conventional toner content control devices each have the following drawbacks.

A: The device in (1) has a complicated structure and is prone to failure.

B In the devices of (2) and (3), the developer itself changes over time, and the electrical characteristics change accordingly, making them impractical.

In the case of the apparatus of C (4), since there is little change in color tone, it is difficult to measure the toner content, and the toner content cannot be controlled within a certain range.

D With the device described in (5), it is difficult to measure the fluidity and volume change of the developer, and in particular, the measurement of the weight and volume of the developer is easily affected by vibration, so it is impossible to put it into practical use. .

In the device of E (6), the adjustment range of the toner content is too wide, so sensitive response control is difficult.

F (7) In the device, the particle size of the toner becomes non-uniform,
This causes the electrical characteristics of the developer to change, making it difficult to obtain a good quality image.

In order to solve the problems of the conventional toner content control device as described above, the present invention provides a developing device that has a relatively simple structure, is less likely to malfunction, and can reliably control the toner content in the developer. This paper proposes a device.

Hereinafter, the present invention will be specifically explained with reference to embodiments shown in the drawings.

FIG. 1 is an overall schematic diagram of an electrophotographic copying apparatus according to the present invention, in which an exposure device 2, a magnetic brush 3 (for applying developer), and a magnetic brush 3 are arranged adjacent to each other in the rotational direction of the photoconductor drum 1. a roll-shaped carrier carried on the surface), a transfer paper guide 4, a separating corona discharger 5,
The addition of a transfer paper separation device 6, a cleaning brush 7, and a charging corona discharger 8 is exactly the same as in the conventional case. Facing the transfer paper guide 4, there is a transfer paper supply device 9, and the transfer paper 10 of this transfer paper supply device 9 is passed through the transfer paper guide 4 by a transfer paper supply roll 11 to the photoconductor drum 1. Supplied. Further, the transfer paper 10 separated from the photoconductor drum 1 by the transfer paper separation device 6 is transferred to the fixing device 12 while being transported by the conveyor belt device 12a.
The toner is fixed thereon and transferred to the receiving table 13.

FIG. 2 is an enlarged view of the area around the magnetic brush 3 described above, and clearly shows the features of the present invention. The magnetic brush 3 to which a DC voltage is applied between it and the photoconductor drum 1 is a normal magnetic brush in which a plurality of permanent magnets are embedded. It is rotated counterclockwise. Further, the developer tray 14 in which the lower half of the magnetic brush 3 is immersed contains a developer X consisting of a mixture of toner X1 and a carrier, and the toner X1 in the developer X is caused by electrostatic friction with the carrier. It is charged by. Therefore, ears 15 of the developer X are formed on the circumferential surface of the magnetic brush 3 as the magnetic brush 3 rotates, and after the length of the ears 15 is regulated by the scraper 16, the ears 15 of the developer The tip of the toner X1 is brought into contact with the circumferential surface of the photoconductor drum 1, which is charged with a polarity opposite to that of the toner X1, and a portion of the charged toner X1 contained in the ears 15 of the developer X is electrostatically attracted to the photoconductor drum 1. will be done.

Further, a replenishment tray 17 containing toner X1 is provided above the rear part of the developer tray 14, and the toner X1 falls into the developer tray 14 in fixed amounts by the rotational movement of a measuring roller 18 that closes the bottom of the replenishment tray 17. Supplied. That is, this metering roller 18 rotates 1/4 rotation per minute, and two recesses 19 capable of storing 2 g of toner are formed on its circumferential surface.
Therefore, the developer tray 14 is replenished with toner X1 at a rate of 1 g per minute. However, the rotation speed of this metering roller 18, the capacity and number of recesses 19 can be freely modified as necessary;
Any structure known in the art may be used as long as it replenishes a certain amount of toner X1 into the developer tray 14 for a certain period of time.

According to the present invention, a roll 20 is provided at a position close to the circumferential surface of the magnetic brush 3, the roller 20 having its circumferential surface in contact with the spikes of developer formed on the circumferential surface of the magnetic brush 3. Although not shown, this roll 20 is rotated at a constant speed in the same direction as the magnetic brush 3, that is, in a counterclockwise direction, by an appropriate driving device. As schematically shown, a DC power supply 21 is installed between the roll 20 and the magnetic brush 3, and a bias voltage having a polarity opposite to that of the toner X1 is applied to the roll 20 by this DC power supply 21. be done. Although this example uses a conductive roll, the present invention can also be carried out using a conductive roll with an insulating coating formed on its surface. In this case, the surface of the insulating film is An electrostatic voltage with a polarity opposite to that of the toner used may be applied to the toner. Also. The tip of the scraper blade 22 is brought into contact with the circumferential surface of the roll 20, and as the roll 20 is rotated, the scraper blade 22 removes the toner X1 electrostatically attracted to the circumferential surface of the roll 20. It acts to collect the stripped toner X1 into the supply tray 17. However, the present invention is not limited to such an embodiment. For example, the present invention is not limited to such an embodiment. The toner may be collected periodically or irregularly.

Since the present invention has the above-described structure, the ears 15 of the developer X are formed on the circumferential surface of the magnetic brush 3 by the rotational movement of the magnetic brush 3, and the tips of the ears 15 of the developer Image-charged photoconductor drum 1
After developing the electrostatic latent image by slidingly contacting the circumferential surface of the roll 20, the roll 20 is brought into contact with the roll 20. In this case, since a bias voltage having a polarity opposite to that of the toner X1 is applied to the roll 20 as described above, a portion of the toner X1 contained in the ears 15 of the developer X remains static on the circumferential surface of the roll 20. It is electrostatically attracted. In other words, the toner content in the developer tray 14, which tends to be increased by toner X1 replenishment from the replenishment tray 17, is
Because it tends to be reduced by the recovery action of
Even if the amount of toner supplied from the replenishment tray 17 is kept constant, the toner content in the developer can be controlled simply by varying the voltage applied to the roll 20. This fact will be specifically explained using an experimental example.

[Experiment example]

In this experiment, U manufactured by Konishiroku Photo Industry Co., Ltd.
-The developing unit of BIX2000R (product name) was modified as shown in the second diagram. In this modified device, the distance between the circumferential surface of the photoconductor drum 1 and the circumferential surface of the magnetic brush 3 is set to 4.5 mm, and the distance between the circumferential surface of the magnetic brush 3 and the circumferential surface of the conductive roll 20 is set to 4.1 mm. A positively charged toner containing styrene-acrylic copolymer and carbon black as main components was used.
The amount of charge in this case is 2.0 × 10 coulombs/mg when the toner content is 5.0% by weight, and the amount of charge on the metering roller
Adjusted the supply rate of 8 to 2.2 to 2.68 per minute. The photoconductor drum 1 was also grounded, and a voltage of -200V was applied to the magnetic brush 3 with respect to the photoconductor drum 1, while a voltage of -250V was applied to the conductive roll 20. That is, a bias voltage of -50V is applied to the conductive roll 20 with respect to the magnetic brush 3.

In the electrostatic photographic apparatus having the toner content control device configured as described above, a total of 2000 copies were made, and the toner content in the developer tray 14 was measured every 200 copies. 3.1
It varied in the range of ~6.8% by weight. In this case, the obtained copy image was observed in detail, and it was confirmed that the image quality was stable and that this degree of variation in toner content had almost no adverse effect on the copy image.

FIGS. 3 and 4 show a photoconductor drum 1 installed in the experimental apparatus in order to confirm the function of the conductive roll.
It is a graph of various variable factors measured in a non-operating state.

FIG. 3 shows the relationship between the toner content and the applied bias voltage when a stable concentration is reached by changing the bias voltage applied to the conductive roll 20. As can be understood from the figure, as the bias voltage increases, the stable density decreases, so it is understood that the bias voltage can be adjusted to obtain the desired toner content.

Further, FIG. 4 shows the change over time in the toner content when the bias voltage applied to the conductive roll 20 is constant (-50V) and the amount of toner replenishment is taken as a parameter. As is clear from this figure, the necessary
Toner content of 4.4-5.3% is bias voltage −
In the case of 50V, the toner supply amount is approximately 1.2 to 1.5g/min.
It is sufficient to set the However, in an actual electrostatographic apparatus, the adjustment range of the above-mentioned variable factors is thought to be wider than the above-mentioned range due to the following factors.

In an actual electrostatographic apparatus, the amount of toner consumed by the photoconductor drum 1 varies depending on the black portion of the image and aging of the photoconductor.

Actual replenishment using a metering roller cannot perform quantitative replenishment in a strict sense.

It takes time for the replenishment toner to be evenly mixed with the carrier.

Although a conductive roll was used in the above experimental example, there was no difference in the results even when a roll was coated with an insulating film.

As is clear from the above description, according to the present invention, a roll to which a bias voltage of opposite polarity to the toner is applied is provided close to the conventional magnetic brush, and a part of the toner is collected by this roll. Toner content can be controlled simply by adjusting the amount of toner.
Further, in the toner content control device of the present invention,
There are advantages such as that in order to change the preset state, it is only necessary to change the bias voltage of the roll.

[Brief explanation of the drawing]

Figure 1 is a conceptual diagram of an electrophotographic copying machine to which the present invention is applied, Figure 2 is an enlarged view of the area around the magnetic brush of the copying machine, and Figure 3 is a diagram showing the relationship between the bias voltage and stable toner content. The graph shown in FIG. 4 is a toner content change curve using the toner supply amount as a parameter. X...developer, Sex roll, 21...DC power supply.

Claims (1)

[Claims] 1. A magnetic brush positioned close to a charged charge carrier and configured to carry a developer consisting of toner and carrier on its surface and to move this developer in a predetermined direction; A state in which the magnetic brush faces the circumferential surface of a magnetic brush located downstream of the developing device in a developing device having a developer tray for causing the developer to reach the developer tray, and a toner supply means for appropriately supplying toner to the developer tray. A rotatable roll having a conductive or insulating layer formed on the peripheral surface is provided, the peripheral surface of which is in contact with the magnetic brush, and the toner in the developer on the magnetic brush is transferred to the roll. A developing device for an electrophotographic copying machine, comprising means for applying a bias voltage to electrically attract the toner in the direction of the roll, and means for removing toner adhering to the roll.