The instant invention relates to sensor systems for sensing emulsions of oil and water, and more particularly to a sensor system including a sensor assembly for detecting the presence of water in an oil emulsion, and further including an alarm assembly for signaling when the presence of water is detected in the oil emulsion.
In outboard and/or inboard marine engines, the portion of the engine that houses the propeller extends below the surface of the water so that the propeller is situated beneath the surface of the water for propelling the boat. Within the portion of the engine housing which extends beneath the water, there is located an internal chamber in which the gearing elements that transfer power from the engine drive shaft to the propeller shaft are located. This internal chamber is filled with oil which lubricates the gearing elements during rotation thereof. The position of the chamber below the surface of the water allows cooling of the oil by heat conduction through the housing walls. However, one particular problem that has been associated with marine engines is the unwanted introduction of water into the internal oil-filled chamber from leaks in the engine housing or failure of a sealing member. The presence of water in the oil compartment reduces the lubricating ability of the oil thus causing excessive wear on the gearing and engine elements. This type of gradual wear on the gearing system often goes unnoticed because the parts are internal, and often leads to failure of the gearing system through a gradual deterioration of the gearing surfaces. In addition, any failure of a seal may cause an influx of water into the oil chamber leading to an eventual and complete failure of the gearing system, and/or seizure of the engine. In either event, the cost to repair and/or replace a marine engine is very expensive.
Despite the not uncommon occurrence of such lower gear unit failures, it has been found that there is a lack in the industry of any effective sensing system which could detect the presence of water within the oil chamber and which also warns the operator that there is water present so that the engine could be shut down before any damage occurs. In response to the stated problem, the instant invention provides a novel and effective sensor system which detects the presence of water in the oil chamber of a marine engine, and which provides an alarm signal to indicate to the boat operator that water is present in the oil chamber.
More specifically, the sensor system comprises a ring oscillator circuit and a symmetrical array of passive input probes which are disposed in the oil inside the oil chamber. Each of the passive input probes is electrically connected to the ring oscillator circuit wherein the probes function as fixed capacitors for measuring the electrical characteristics of the oil emulsion. When a voltage is applied to the oscillator circuit, the oscillator circuit generates an oscillating current that circulates at a frequency which varies according to the dielectric constant of the liquid emulsion. Accordingly, when water is introduced into the oil chamber it is emulsified with the oil and changes the dielectric properties of the oil. The sensor system further includes a frequency conversion circuit for sensing the frequency of the oscillating signal and linearly converting the frequency to a corresponding voltage signal. A frequency divider is utilized to divide the frequency by a factor of 32 to bring the operating frequency into an acceptable range for the frequency to voltage converter. The output voltage signal produced by the frequency to voltage converter is then compared to a predetermined voltage value by a comparator circuit which generates an output signal when the voltage signal exceeds the predetermined voltage value. More specifically, when the voltage signal exceeds the threshold value, the comparator triggers a circuit which permits current to flow through a relay. Actuation of the relay permits current to flow to external visual and audible alarm devices to provide recognizable alarm signals.
Accordingly, among the objects of the instant invention are: the provision of a sensor system which detects the presence of water in an oil chamber of a marine engine; the provision of a sensor system including a ring oscillator circuit and a plurality of passive probes situated within an oil emulsion for sensing changes in the electrical characteristics of the emulsion, i.e. the dielectric constant of the emulsion; the provision of a sensor system including a frequency to voltage converter wherein the frequency of the oscillating signal in the ring oscillator is converted to a corresponding voltage for more accurate comparison of the change in composition of the emulsion; and the provision of a sensor system including a comparator circuit to compare the voltage signal with a predetermined voltage and further including an alarm circuit which emits a recognizable alarm signal when the threshold voltage is exceeded.
Other objects, features and advantages of the invention shall become apparent as the description thereof proceeds when considered in connection with the accompanying illustrative drawings.