JPS5925220B2 - Toner remaining amount detection device for electrophotographic dry developing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for detecting the amount of developer remaining in a hopper in an electrophotographic dry developing device.

In a dry type developing device that uses a mixed type developer of iron powder carrier and toner to develop a latent image on a photoreceptor with a magnetic brush, and in a dry type developing device that uses magnetic toner that has been used in recent years. However, the remaining amount of toner is not automatically detected. It is common practice to manually replenish toner when the image density on the recording paper decreases, or to periodically check the toner in the hopper of the developing device and replenish it manually. This method requires constant attention,
Despite this, it is inevitable to overlook the lack of toner. The present invention proposes a device that automatically detects the amount of developer remaining in a hopper.

Embodiments of the present invention will be described below with reference to the accompanying drawings. In FIG. 1, a recording paper 1 having an electrostatic latent image on its surface is conveyed to a developing roller 4 via a guide plate 3 by a pair of developing rollers 2, 2. Toner stored in a toner receiving hopper 5 is supplied to the developing roller 4 via a doctor plate 6 from an outflow slit 5A provided at the bottom of the hopper. The developing roller 4 forms a magnet in which S poles and N poles are alternately located as shown in the figure, thereby forming a magnetic brush on its circumferential surface, and this magnetic brush touches the recording paper 1.
By contacting the latent image surface of the latent image, the latent image becomes a visible image.
The thus developed recording paper passes through the guide plate T and is transferred to the fixing roller 8.
, reaches 8. During development, the toner on the developing roller 4 is consumed, but as long as there is toner in the hopper 5, the developing roller 4 is replenished with toner.

However, when all the toner in the hopper 5 is consumed, the toner on the developing roller also disappears, and the base of the developing roller 4 is exposed. The present invention is based on the recognition that there is a difference in the optical reflectance of the developing roller between when there is toner on the developing roller 4 and when the toner is exhausted and the base of the developing roller is exposed. This was done based on the following. For this reason, a detection section 9 is disposed close to the developing roller 4, and this detection section is mounted on a bracket 10 fixed to the machine frame. Second
In the figure, the detection section 9 includes a toner remaining amount detection light source 11 and an optical semiconductor element 12 that captures the light projected by the light source when it hits the developing roller 4 and is reflected.

As the light source 11, a miniature bulb of about 6 W can be used, and as the optical semiconductor element 12, CdS or other material can be used. These light source 11 and optical semiconductor element 12 prevent disturbance of light from the outside! The case 13 is fixed to the bracket 10 in order to hold the device.
The optical semiconductor element 12 constitutes one side of the bridge circuit shown in FIG. 3, and as the resistance value of this element 12 changes, a potential difference is generated between the bridges, causing a detection, lighting of a lamp 15, or other alarm device. It is possible to perform the following operations.

Detecting a change in the resistance value of the optical semiconductor element 12 does not necessarily need to be performed using a bridge circuit, and other known means may be used. As described above, according to the present invention, it is possible to automatically detect the amount of developer remaining in the hopper accommodating the developer, and there is no risk of overlooking lack of developer.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of an electrophotographic dry developing device equipped with a toner remaining amount detection device according to the present invention, FIG. 2 is an enlarged view of the detection section, and FIG. 3 is an example of an electric circuit used in the detection device of the present invention. This shows that. 1...Recording paper, 4...Developing roller, 9
...Detection unit, 11... Remaining toner amount detection light source, 12... Optical semiconductor element, 14...
・Bridge circuit.

Claims (1)

[Claims] 1. Developer is supplied from a hopper containing a one-component developer to the circumferential surface of the developing roller, and the electrostatic latent image on the photoconductor is developed by supplying the developer on the circumferential surface to the photoconductor passing through it. In an electrophotographic dry type developing device, a detection unit includes a light source that irradiates the peripheral surface of the developing roller, an optical semiconductor element that captures the reflected light of the light source beam from the peripheral surface, and a detection unit of the optical semiconductor element. A device for detecting the amount of developer remaining in a hopper, characterized by being provided with means for detecting a change in resistance value.