1. Field of the Invention
The present invention relates to a capacitive fluid sensor and more specifically to a fluid sensor for sensing the dielectric constant of fluid flowing through a sensor housing. By sensing a change in capacitance influenced by the dielectric constant, it is possible to ascertain the concentration or mixture ratio of two substances, for instance.
2. Descritpion of the Prior Art
Recently, fuel mixtures of petroleum fuel (gasoline or petrol) and alcohol fuel (methanol or methyl alcohol) has been used to drive engines for the purpose of reducing the dependency of the vehicles upon petroleum fuel. In the mixed fuel, it is necessary to detect a mixture ratio of petroleum fuel to alcohol fuel in order to regulate the quantity of fuel to be supplied to an engine, ignition timing, etc. In other words, an optimum engine output is required, even when the mixture ratio changes.
As sensors for detecting mixture ratios of petroleum and alcohols fuels, a capacitive fluid sensor for detecting dielectric constants of fluid flowing therethrough has been known, because the dielectric constant of petroleum fuel differs from that of alcohol. In the prior-art capacitive fluid sensor, however, there exists a problem in that fuel tends to leak from the sensor housing through an electric connector portion, when the pressure of fuel flowing through the fluid sensor housing increases.
The structure of the prior-art capacitive fluid sensor will be described in more detail hereinbelow for comparison purposes with reference to the detached drawings under DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS.