Apparatus for detecting residual quantity of toners

#1. Field of the Invention

#The present invention relates to a toner residual quantity detecting apparatus for detecting a toner empty, i.e., a residual quantity of toners in a developing unit.

#2. Description of the Related Art

#The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate presently preferred embodiments of the invention, and together with the general description given above and the detailed description of the preferred embodiments given below, serve to explain the principle of the invention, in which:

#FIG. 1 is a view showing the principle of the present invention;

#FIG. 2 is a view illustrating a construction of one embodiment of the present invention;

#FIG. 1 is a view showing the principle of the present invention.

#As illustrated in FIG. 1, a temperature detecting element 30 is provided on the bottom of a developing unit 20. This temperature detecting element 30 detects an internal temperature of the developing unit 20 and generates an output corresponding to the detected temperature. The temperature detecting element 30 is constructed of, e.g., a thermistor or the like. In this temperature sensor 30, there is produced a difference between the detected temperatures when covered with toners and when not covered with the toners. A detecting circuit 31 determines this detected temperature difference from an output of the temperature detecting element 30. An existence or non-existence of the toners can be thereby detected.

#FIG. 2 is a view illustrating a construction of one embodiment of the present invention. FIG. 3 is an explanatory diagram showing an attaching position of the sensor of FIG. 2. FIG. 4 is a circuit diagram illustrating the detecting circuit of FIG. 3.