Method and device for indicating liquid volume in a tank

#The present invention relates to systems and methods for determining the level of a liquid contained within a storage tank carried on an automotive vehicle.

#Automotive vehicles today contain a variety of liquids for use in the operation of the vehicle. For example, the fluids may include fuel, engine coolant, window washer fluid, brake fluid, and engine lubrication fluid. To ensure proper operation of the automotive vehicle, it is essential that liquid levels are accurately determined.

#There are several phenomena that can affect the liquid level reading. These phenomena include agitation of the liquid within the container during movement of the vehicle. For example, during acceleration, deceleration, and driving on inclines and declines. Also, the change in level but not volume occurring from parking on inclines and declines as well as the change in level and volume due to the addition of liquid or a leak from the container can cause an inaccurate liquid level reading. Although prior art systems and methods work for their intended purpose, these and other problems have not been adequately addressed.

#FIG. 1 is a block diagram illustrating a liquid level indication system, in accordance with the present invention;

#FIG. 2 is a flowchart illustrating a liquid level filter routine, in accordance with the present invention;

#FIG. 3 is a flowchart illustrating a fuel filter initialization routine, in accordance with the present invention;

#With reference to FIG. 1 a liquid level indication system 10 is illustrated, in accordance with the present invention. System 10 includes a storage tank 12, a liquid level sender card 14, a processor 16, memory devices 18 and 20, liquid level indicator gauge 22 and a low level indicator light 24. Processor 16 is in communication with a vehicle bus 26. Vehicle bus 26, in one embodiment of the present invention, is an in-vehicle communications network for sending and receiving control and data signals. In another embodiment of the present invention, a vehicle speed sensor 28 is in communication with the vehicle bus 26 for sending speed data to the processor 16. Other sensors such as an ignition key sensor 30 and a gear select sensor 32 are provided for sending information related to ignition key position and transmission gear position to processor 16.

#Liquid level indication system 10 includes software code executable on processor 16 and stored in memory devices 18 and 20 for carrying out system functions. For example, a liquid level processing routine is provided to read an analog to digital converter on sender card 14. The liquid level processing routine provides a ratio (RAD) of the liquid level to battery voltage periodically. In an embodiment of the present invention, liquid level processing routine is completed at least every 120 milliseconds in order to capture an accurate profile of the liquid level.

#There are two basic types of liquid level senders 14, forward and reverse. The present invention contemplates using either a forward or a reverse liquid level sender. A forward sender is one in which the sender card resistance increases with increasing liquid level volume, in contrast, a reverse sender is one in which the sender card resistance decreases with increasing liquid level volume. Preferably, a forward sender is used in system 10 to provide a more accurate liquid level reading since the liquid level sender reading error is smaller at lower resistance values, providing better accuracy at a near empty tank condition.