JPS602600Y2 - Dry developer toner density control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a toner concentration control device for a dry developing device used in electrophotography.

Conventionally, a dry type developer using a developer consisting of carrier and toner components includes a toner hopper having a passage communicating with the developer container and a toner replenishment mechanism into the developer container, and a part of the outer wall of the developer container. a toner concentration detection means for detecting a change in the amount of reflected light according to the mixture ratio of carrier and toner through the transparent plate; and a toner concentration detection means that is controlled according to the output of the detection means to drive the toner replenishment mechanism. A toner concentration control device of a so-called light reflection type is known.

In reality, in this type of toner density control device, little consideration is given to the light reflectance of the developer carrier and toner.

That is, the carbon-based toner generally used is black, and the carrier therefor is also a black material of almost the same type.

Therefore, the change in light reflectance caused by the change in the mixing ratio of toner and carrier corresponding to the density is extremely small, and the accuracy of the detection output of the toner density detection means is unsatisfactory.

Further, toner tends to adhere to the transparent plate separating the detection means and the developer, which also causes inaccurate detection output of the detection means.

The present invention has been devised in view of the above-mentioned conventional drawbacks, and an object of the present invention is to provide a toner concentration control device of this type with high accuracy and high reliability.

The present invention will be explained below based on the drawings of the embodiments.

FIG. 1 shows the configuration of the present invention.

The latent image on the photoreceptor 1 is visualized using a developer 4 carrier such as a magnetic roll 2 .

A developer 4 is stored in the developer container 3. The developer 4 is composed of, for example, a white-coated carrier and a black toner, which have significantly different light reflectances.

The toner concentration of the developer 4 is determined by receiving light from a light source 6 through a transparent plate 5 forming a part of the outer wall of the developer container 3, and detecting the amount of reflected light by a light receiver 7 in accordance with the toner concentration.

The detection level of the light receiver 7 determines toner replenishment timing by a comparison circuit 8, and a toner replenishment mechanism 10 in a toner hopper 9 having a passage communicating with the developer container 3 is driven by a toner replenishment driving means 11 to replenish toner 12. do.

The transparent plate 5 is movably supported by an outer wall via an elastic body 13, and is constantly vibrated by a vibration device 14 to prevent toner from adhering to its surface.

FIG. 2 shows the detection level characteristics of the detection means (light receiver 7) according to the present invention.

The horizontal axis is the toner concentration, and the vertical axis is the detection level of the light receiver 7.

Since the light reflectance of the black toner and the white-coated carrier are significantly different, it is possible to obtain a characteristic B of toner concentration versus detection level that is even more sensitive than the conventional characteristic line A.

As described above, the present invention coats the carrier with a material having a reflectance different from that of the toner, and
Since the transparent plate is movably supported relative to the developer container and a vibration device is installed to vibrate the transparent plate, the amount of reflected light changes greatly depending on the mixture ratio of carrier and toner, and moreover, toner adheres to the transparent plate. Therefore, it is possible to obtain a highly accurate and highly reliable toner concentration control device.

[Brief explanation of drawings]

FIG. 1 is a vertical side view showing one embodiment of the toner concentration control device for a dry type developing device according to the present invention, and FIG. 2 is a characteristic diagram of detection level with respect to toner concentration. In the figure, 3 is a developing container, 4 is a developer, 5 is a transparent plate,
6 is a light source, 7 is a light receiver, 9 is a toner hopper, 10 is a toner supply mechanism, 11 is a driving means, 12 is a toner 13
is an elastic body, and 14 is a vibration device.

Claims (1)

[Scope of utility model registration request] A toner hopper having a passage communicating with a developer container in which a developer consisting of two components of carrier and toner is stored and a toner replenishment mechanism into the developer container; a transparent toner hopper forming a part of the outer wall of the developer container; a toner concentration detecting means for detecting a change in the amount of reflected light according to the mixture ratio of carrier and toner through the transparent plate; and a driving means for driving the toner replenishing mechanism controlled in accordance with the output of the detecting means. In the carrier, the carrier is coated with a material having a light reflectance different from that of the toner, and a vibration device is provided which movably supports the transparent plate relative to the developer container and vibrates the transparent plate. A toner concentration control device for a dry developing device.