Measuring and testing – Liquid level or depth gauge
Reexamination Certificate
2002-03-13
2003-12-23
Kwok, Helen (Department: 2856)
Measuring and testing
Liquid level or depth gauge
C073S291000
Reexamination Certificate
active
06666084
ABSTRACT:
FIELD OF THE INVENTION
In modern motor vehicles, fluid-level measuring devices are used to measure the level of fuel (e.g., gasoline, diesel, etc.) in the fuel tank. The instantaneous fluid level is communicated to the driver by a display, so that he or she may estimate the expected range of the motor vehicle with the fuel remaining in the tank, as well as the necessity of filling up the tank.
BACKGROUND INFORMATION
Fluid-level measuring devices for tanks, where the floating member of a pivoted float floats in the region of the fluid level of the liquid in the tank in question, have been known for more than twenty years. The rotational axis of the float, which is normally below the highest possible liquid level, is connected to the input of a mechanical gear box, the output of which has a magnet mounted. The angular position of the float, which is a function of the level of the liquid, is transmitted to the magnet, whose angular position is therefore a measure of the fluid level. The magnet is situated near the outside of the tank. In other embodiments of fluid-level measuring devices, the rotational position of the magnet is detected through a housing wall, by a second pivoted magnet, which is mechanically coupled to a display device. This fluid-level measuring device is suitable for tanks in which flammable or explosive liquids are stored, for, in the case of the gearbox that is situated in the explosive region, no duct posing a problem with regard to imperviousness needs to pass through the tank wall. In other embodiments of fluid-level measuring devices, the magnet supported outside the tank interior is replaced by a magnetic-field sensor, which is connected to an electronic evaluation unit. This sensor detects the magnetic field, which is a function of the angular position of the magnet, is a measure of the fluid level, and can be converted to a fluid-level value with the aid of the evaluation unit.
German Published Patent Application No. 199 25 185 relates to a fluid-level measuring device for a tank, having a float pivoted about an axis of rotation, and having a tube, which possesses a first end and a second end, is set so that its second end extends to the outside of the tank, and is sealed with respect to the interior of the tank. A magnet is mounted in the region of the first end of the tube, and outside the tube on the rotational axis of the float. Situated opposite the magnet, in the interior of the tube, is a magnetic-field sensor which is set up to output a signal dependent on the angular position of the float, to an evaluation unit, via an electrical line.
A multi-sensor design, which allows data to be exchanged in a motor vehicle, via a data bus, is described in D. Sparks, T. Noll, D. Agrotis, T. Betzner, K. Gschwend, “Multi-Sensor Modules with Data Bus Communication Capability,” SAE Technical Paper Series 1999-01-1277. A plurality of sensors in a housing is combined into a group. This multi-sensor module shares a single set of communication chips and thereby becomes an “intelligent” sensor network.
German Published Patent Application No. 40 25 184 relates to a sensor for measuring the acceleration or inclination, in particular for motor vehicles. It has a cylindrical fluid tank, which contains an electrically conductive fluid. Two electrodes coated with a dielectric extend from below, into the fluid tank. The electrodes and the conductive liquid function as a capacitor. The position of the sensor and, consequently, its inclination are ascertained from the capacitances of these capacitors.
Various acceleration sensors are known in the automotive field. According to the “Kraftfahrtechnischen Taschenbuch” (Automotive Handbook), Bosch, 23rd edition, Viehweg Publishing House (1999), pages 103 to 109, the followings sensors are, for example, suitable for monitoring acceleration in a turn, as well as changes in speed: inductive sensors, Hall-effect sensors, micromechanical silicon rpm sensors, Hall-effect accelerometers, piezoelectric sensors, or capacitive silicon accelerometers.
Devices and methods for ascertaining the instantaneous fuel consumption in a motor-vehicle engine are known.
The disadvantages of the above-described fluid-level measuring devices include that the measured values are invalidated by sloshing movements, in particular during the acceleration and deceleration of the motor vehicle, which are caused by curves and by driving on an incline, so that the fuel-level indicator displays values that are not correct or fluctuate sharply. In addition, inaccuracies caused by the float striking the bottom of the tank occur mainly in the residual-amount range.
SUMMARY
The present invention relates to a method for determining the instantaneous fluid level of a motor-vehicle tank, which includes the following steps: designating a beginning fluid level of the motor-vehicle tank as the input value, upon starting the motor-vehicle engine; ascertaining a first fluid-level value from a fluid level measured by a fluid-level measuring device, and ascertaining a second fluid-level value and a window around the second fluid-level value, from a consumption value of the motor-vehicle engine and from the input value; comparing the first fluid-level value to the window around the second fluid-level value; determining whether the first or the second fluid-level value should be a new input value; displaying the new input value as the fluid level; and terminating method if the motor-vehicle engine is switched off or repeating the method from the ascertaining step if the motor-vehicle engine is running.
The instantaneous fluid level means the fraction of the tank volume filled with fuel at a particular time. The beginning fluid level is the fluid level, which is ascertained from the fluid level measured by the fluid-level measuring device, immediately after the motor-vehicle engine is started, and which is subsequently used as an input value for the subsequent method steps until a new input value is obtained.
The fluid-level measuring device may be a conventional tank fluid-level measuring device and may include a fluid-level measuring device containing a float, which is pivoted about an axis of rotation, and the angular position of which is ascertained, for example, with the aid of a magnet and a magnetic-field sensor, or using a potentiometer. Fluid-level sensors, which measure the capacitance or the resistance between electrodes situated in the tank, may be provided. However, any other type of fluid-level measuring device is suitable for the present invention.
In the case of engines having fuel-injection, the consumption value of the motor vehicle, e.g., the instantaneous fuel consumption, may be determined.
In this context, a window around a fluid-level value means a range surrounding the fluid-level value, i.e., a range of values, which includes the fluid-level value itself and also the fluid-level value of larger and/or smaller surrounding values.
The new input value may be displayed as the current fluid-level, using a display already present in the motor vehicle. In this context, the display may be, for example, an analog display, which is situated in the driver-information area of the motor vehicle and is possibly a component of the instrument cluster.
If the motor-vehicle engine is switched off, the fluid level does not change. Therefore, it is superfluous to redetermine the fluid level of the tank.
The method according to the present invention may provide that the accuracy of the fluid-level display is increased, and that it is possible to more accurately determine the range of the motor vehicle. The accuracy is primarily increased by eliminating the effect of the dynamics of the tank contents on the display, especially in the case of sloshing and cornering. Inaccuracies, which may occur in the residual-amount range due to the float striking the bottom of the tank, may be largely eliminated. The measuring devices, sensors, and computers needed for implementing the method may already be present in the motor vehicle. The tank display only has to be expanded in the form
Braun Hans
Marx Klaus
Muelders Stefan
Schelhas Peter
Frank Rodney
Kenyon & Kenyon
Kwok Helen
Robert & Bosch GmbH
LandOfFree
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