Patent Description:
Sensors for detecting the presence or absence of fluid and/or temperature have numerous applications. One known sensor type for detecting the presence or absence of fluid is an electro-optic liquid sensor. Electro-optic liquid sensors are described in <CIT>. Known electro-optic sensors generally do not perform well in high temperature environments. There is a need for improved electro-optic sensors that can perform well in wider ranges of temperatures. There is also a need for electro-optic liquid sensors that also have the capability of measuring temperature.

<CIT> relates to sensor having: a light source for illuminating a remote surface, a detector for receiving returned illumination from the remote surface and providing a signal representative of the returned illumination, and a controller which samples the signal to obtain sample data representative of amplitude of light of the source returned from the surface by the detector; the controller determines the presence of water on the remote surface in accordance with the sample data. Each of the light source and the detector may be provided with optics including a prism.

<CIT> relates to an optical sensor to detect a level of fluid in a vessel; the sensor is composed of a light emitting device, a light receiving device and a prism.

The invention relates to an electro-optic liquid sensor as defined in claim <NUM>. The present disclosure provides an electro-optic sensor that performs well in a wide range of temperatures. The fluid sensors of the present disclosure can be used in high temperature applications. According to the invention, the sensor detects the presence or absence of fluid as well as measure temperature.

The following drawings are illustrative of particular embodiments of the present disclosure and therefore do not limit the scope of the present disclosure. The drawings are not to scale and are intended for use in conjunction with the explanations in the following detailed description. Embodiments of the present disclosure will hereinafter be described in conjunction with the appended drawings, wherein like numerals denote like elements.

Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate embodiments of the invention, and such exemplifications are not to be construed as limiting the scope of the invention in any manner.

Reference will now be made in detail to embodiments of the present disclosure, examples of which are described herein and illustrated in the accompanying drawings. While the invention will be described in conjunction with embodiments, it will be understood that they are not intended to limit the invention to these embodiments.

Referring to the figures, in which like reference numerals refer to the same or similar features in the various views, <FIG> is a block diagram view of a system <NUM> including a component <NUM> for which determining the presence or absence of liquid may be desirable. The component <NUM> may include a liquid chamber <NUM>, and the system <NUM> may further include a liquid sensor <NUM> and an electronic control unit (ECU) <NUM>.

The component <NUM> may be any component in any field that includes or may be exposed to liquid in its operation. For example, the component <NUM> may be or may be included in a mechanical, electrical, hydraulic, pneumatic, or other known actuator or actuation system. The component <NUM> may include a liquid chamber <NUM> configured to store or receive a liquid. The liquid may be, for example only, of a type necessary for the functionality of the component <NUM> (e.g., hydraulic fluid, liquid for lubrication, fuel, etc.), liquid incidental to the environment of the component <NUM>, and/or liquid that is detrimental to the function of the component <NUM>.

In one embodiment, the component <NUM> could be, for example, a gearbox that houses gears and high temperature lubricating oil. The gearbox could be a high performance type gearbox in an aerospace application, such as the gearbox of a jet engine. The temperature of the oil in the gearbox could be between <NUM> to <NUM> degrees Celsius. It should be appreciated that many alternative applications are possible.

The liquid sensor <NUM> may be coupled with the component <NUM>. For example, the liquid sensor <NUM> may be disposed within the liquid chamber <NUM> of the component <NUM>. The liquid sensor <NUM> may be an electro-optic sensor according to the present disclosure, such as that described in conjunction with <FIG> and <FIG>. It should be appreciated that alternative embodiments are possible.

The ECU <NUM> may be electrically coupled to the liquid sensor <NUM> and may be configured to drive the liquid sensor <NUM>, receive feedback from the liquid sensor <NUM>, assess whether liquid is present or absent in the liquid chamber <NUM>, and/or assess the operational state of the liquid sensor <NUM>. The ECU <NUM> may comprise, in embodiments, one or more of a processor, a non-volatile computer-readable memory, an application-specific integrated circuit (ASIC), field-programmable gate array (FPGA), and/or other known processing or memory devices. The ECU <NUM> may be or may comprise a dedicated processing resource for the liquid sensor <NUM>, or may be or may comprise processing resources for numerous sensors, components, and/or systems. The ECU <NUM> may be electrically coupled to the liquid sensor <NUM> through known wired and/or wireless connections.

<FIG> illustrates a multicomponent system wherein the ECU <NUM> (also referenced herein as Sensor Signal Conditioning Circuitry) is connected to the liquid sensor <NUM> via an electrical cable and electrical connector interface. In the depicted embodiment, some of the hardware components including the light emitter, sensor, and temperature sensors are remote from the signal conditioning unit.

<FIG> illustrates an alternative embodiment wherein the ECU/Sensor Signal Conditioning Circuitry <NUM> is integrated with the hardware components of the liquid sensor <NUM>. <FIG> illustrates an embodiment wherein the ECU/Sensor Signal Conditioning Circuitry <NUM> is directly mounted to the sensor housing.

<FIG> depicts an example physical housing of the integrated sensor of <FIG>. In the depicted embodiment, the sensor can be mounted via a single aperture into a tank and provide both fluid presence sensing and temperature sensing. It should be appreciated that alternative embodiments are possible.

In addition to assessing the data from the liquid sensor <NUM> to determine whether liquid is present or absent at the liquid sensor <NUM>, the ECU <NUM> can be configured to ascertain the temperature at the liquid sensor <NUM>.

The liquid sensor <NUM> may include a light source <NUM>, a light detector <NUM>, and a prism <NUM>, which may be generally disposed within a housing <NUM>.

The light source <NUM> may be configured to emit light of a chosen frequency and power (or powers) appropriate for a given application (i.e., appropriate for the characteristics of the other elements of the sensor, such as shape, orientation, materials, reflectivity, etc., and/or according to characteristics of the liquid to be detected, such as density, scattering properties, etc.). As used herein, a light frequency should be understood to include either/or both of a specific frequency of light and a frequency band. In an embodiment, the light source <NUM> may be configured to emit light in the infrared portion and/or the near-infrared portion of the electromagnetic spectrum. The light source <NUM> may be or may include one or more of a light-emitting diode (LED), a laser, or other known light source, in an embodiment.

The light detector <NUM> may be configured, in an embodiment, to detect light of one or more frequencies of light, including at least the frequency of light emitted by the light source <NUM>. In the depicted embodiment, the light detector <NUM> is a LED. The LED is not used to generate light but rather it is used in reverse to detect light. The light detecting LED is configured to generate a voltage or current when it detects light (e.g., when light is shined on the detecting LED). Whether a voltage or current is generated depends on the configuration of the diode arrangement within the system. In one embodiment, the LED diode is an <NUM> nanometer peak emission Gallium-Aluminum-Arsenide (GaAlAs) type device. It should be appreciated that many alternatives are possible. For example, the LED light emitter and/or LED light detector can alternatively have GaAS or GalnAs construction.

The combination of the paired LED emitter and detector provides a liquid sensor that performs well in high temperature applications. In addition, as discussed above, the LED emitter can be configured to measure temperature as well.

In the depicted embodiment, the LED light detector and the LED light emitter can be two of the same component. Using the same model LED for both the emitter and detector ensures that they are paired. It should be appreciated that the LED can be of different models and brands as well. As discussed above, the LED light detector is paired to the light emitting LED so long as the LED light detector can detect light of the frequency or wavelength that is emitted by the light emitting LED. To decrease susceptibility to ambient light noise, it can be desirable to further match the LED so that the nominal operable wavelength substantially overlaps. For example, in some embodiments, it can be desirable that the emitting LED only emits light in the range that the detecting LED can detect light. This decreases the likelihood that light from another source creates a false reading on the light detecting LED and increases the system's light immunity.

The prism <NUM> may be a member, article, or device comprising one or more components configured in size, shape, and materials to reflect a light signal from the light source <NUM> to the light detector <NUM> in certain conditions, and to pass light from the light source <NUM> through the prism <NUM> in certain conditions. For example only, the prism <NUM> may be configured to reflect light from the light source <NUM> to the light detector <NUM> when liquid is not present around the prism <NUM>, and to pass light from the light source <NUM> through the prism <NUM> when liquid is present around the prism <NUM>. In an embodiment, for example only, the prism <NUM> may comprise borosilicate glass, fused silica (quartz), one or more polymers, etc., that is optically-transmissive at least to light of the frequency emitted by the light source <NUM>. Thus, in an embodiment, the prism <NUM> may be optically-transmissive to light in the infrared and/or near-infrared portions of the electromagnetic spectrum, for example only.

Referring to <FIG>, a block diagram of an embodiment of the system of the present disclosure is shown. In the depicted embodiment, the IR emitter and temperature sensor diode (e.g., LED emitter) are operably connected to a constant current source. In the depicted embodiment, the constant current source supplies current to the IR emitter for level sensing and/or temperature sensing functions. The temperature constant current source supplies a small current and offset current sufficient to mitigate component and environmental effects such as diode self-heating. This current could be, for example, within <NUM> to <NUM> mA range depending on the diode used and application temperature range. The level sensing excitation current source could be, for example, within <NUM> to <NUM> mA depending on the particular diode and application.

In the depicted embodiment, the IR emitter and temperature sensor diode (e.g., LED emitter) are operably connected to temperature signal conditioning circuitry. In the depicted embodiment, the temperature signal conditioning circuit converts the signal from the temperature diode to a °C/V signal mapped to the range of the temperature processing circuit and corrects for environmental offsets. For example, the temperature from -<NUM> to <NUM> could be mapped to <NUM> to 5V range for processing.

In the depicted embodiment, the temperature signal conditioning circuitry is operably connected to temperature processing circuitry. In the depicted embodiment, the temperature processing circuit converts the signal from the conditioning circuit to the temperature output interface. For example, the processing circuit could provide signal sampling and buffering for a digital serial output.

In the depicted embodiment, the IR detector diode (e.g., LED detector) is operably connected to signal conditioning circuitry. In the depicted embodiment, the signal conditioning circuit converts the raw signal from the IR detector to a format suitable for the signal processing circuit. For example, this circuit could amplify and filter the raw signal for further signal processing.

In the depicted embodiment, the signal conditioning circuit is operably connected to signal processing circuitry. In the depicted embodiment, the signal processing circuitry converts the signal from the signal conditioning circuitry to a discrete liquid level output interface. For example, sampling and buffering the signal for a digital serial output or triggering a digital on/off signal.

In the depicted embodiment, the system includes built-in test circuitry. In the depicted embodiment, the built-in test circuitry includes self-test capabilities to test level and temperature sensing functions.

Claim 1:
An electro-optic liquid sensor comprising:
an LED light emitter (<NUM>);
an LED light detector (<NUM>); and
a prism (<NUM>) configured to reflect light emitted from the LED light emitter to the LED light detector,
characterized in that at least one of the LED light emitter (<NUM>) or LED light detector (<NUM>) is also a temperature sensor, wherein a signal conditioning unit (<NUM>) is configured to determine the temperature of liquid in a tank.