Measuring and testing – Volume or rate of flow – Thermal type
Patent
1998-04-29
2000-04-11
Patel, Harshad
Measuring and testing
Volume or rate of flow
Thermal type
7320423, G01F 168
Patent
active
060475978
DESCRIPTION:
BRIEF SUMMARY
PRIOR ART
The invention is based on a device for determining the throughput of a flowing medium, for example the aspirated amount of air of an internal combustion engine, in accordance with the species of the main claim.
Sensors, as well as associated evaluation circuits, by means of which the throughput of a flowing medium can be determined, are known from DE-OS 43 24 040, for example. With these known mass flow sensors the sensor element is exposed to the flowing medium, for example the air flow. Here the sensor element comprises a heater, which is brought to an high temperature in relation to the medium to be detected by the application of a controlled current. A heater temperature sensor, as well as a temperature sensor, which detects the temperature of the flowing medium, are associated with this heater. Two temperature-dependent resistors are located in the spatial vicinity which, in respect to the flow direction of the medium to be detected, are placed laterally to the heated resistor, so that they are evenly heated by the latter. But they are cooled at different rates by the flowing medium, since the resistor reached first by the flow is cooled more than the other. The temperature difference resulting from this provides a measured voltage at a diagonal of the bridge of the proposed bridge circuit. The mass of the flowing medium is determined as a function of this measured voltage.
A device for determining the throughput of a flowing medium is described, wherein a heater resistor heats at least one upstream and downstream located, temperature-dependent resistor, wherein the resistors, which are cooled at different rates by the flowing medium, are wired to form a bridge, whose diagonal voltage is a function of the temperature difference of the resistors. In the end the mass of the flowing medium is determined from this processed voltage (UM). The control of the temperature of the resistor is performed with the aid of its own heater control circuit which regulates the current through the heater resistor in such a way that the temperature of the heater resistor is a predeterminable function of the temperature of the flowing medium. A temperature compensation, with the aid of which the measuring voltage (UM) is compensated at high temperatures, is performed with the aid of a high temperature compensation stage (DT) and of a converter circuit (UMS).
ADVANTAGES OF THE INVENTION
The device in accordance with the invention for determining the throughput of a flowing medium with the characteristics of the main claim has the advantage in comparison with the known device that a further improvement of the temperature behavior is achieved. This applies in particular to the high temperature behavior of the claimed device. This advantage is obtained in that the known circuit arrangement is complemented by an additional resistor bridge circuit, wherein this additional resistor bridge circuit permits high temperature compensation.
Further advantages of the invention are obtained by the steps recited in the dependent claims.
DRAWINGS
An exemplary embodiment of the invention is represented in the drawings and will be explained in more detail in what follows. The single drawing figure here shows the entire circuitry of the device in accordance with the invention with a heater control circuit and a so-called Delta T bridge circuit, such as is known at least in part from DE-OS 43 42 040. In addition, the circuit in accordance with the drawing figure also contains the additional high temperature compensation stage.
DESCRIPTION OF THE EXEMPLARY EMBODIMENT
A device in accordance with the invention for determining the throughput of a flowing medium is represented in the drawing figure, wherein the entire arrangement is placed on a substrate and is exposed in a suitable manner to the medium to be detected, for example the airflow in an aspirating tube of an internal combustion engine.
The heater control circuit HK comprises a bridge circuit with the resistors R1, R2, R3, RHF and RLF, wherein RHF is the heater temper
REFERENCES:
patent: 4196382 (1980-04-01), Bryzek
patent: 4836027 (1989-06-01), Hannappel et al.
patent: 5369994 (1994-12-01), Hecht et al.
Patel Harshad
Robert & Bosch GmbH
Striker Michael J.
LandOfFree
Device for finding the flow rate of a flowing medium does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Device for finding the flow rate of a flowing medium, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Device for finding the flow rate of a flowing medium will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1168829