The invention relates to an air mass flowmeter for measuring the air mass taken in by the internal combustion engine.
Air mass flowmeters in the intake duct or charge duct of the internal combustion engine are known. They serve to measure the mass flow or the intake/charge air, in order to be able to determine and control the mass ratios accordingly during the chemical process of combustion.
An air mass flowmeter is known from EP 0 908 704 A1 that measures the air flow thermally. The air mass flowmeter is arranged with one end in a principal air stream in the intake duct to the internal combustion engine. A specific proportion of the principal air stream is directed into a first channel that leads to an air mass sensor. The air mass sensor determines thermally the air mass passing by it. The air stream is then diverted and channeled back into the principal air stream in order to be fed to the combustion operation. One disadvantage of the known air mass sensor is that the air flow is separated from the inner channel wall. Such separation causes the measurement signals of the downstream air mass sensor to be disturbed. It has proven that the position of the point of separation from the inner channel wall can vary significantly even with strong flows. Even small disturbances to the flow conditions result in major displacement of the position of the point of separation. The changing point of separation from the inner channel wall however results in areas with a separated flow of different sizes and positions.
The object of the invention is to provide an air mass sensor, with which falsification and influencing of the detected air mass by the separation of the air flow from the inner channel wall are prevented.
The air mass flowmeter according to the invention has a sensor unit arranged in the air flow path to detect the passing air mass. The air mass is directed from a first section of the channel via a turning area into a second section of the channel. In the turning area at least one flow element is provided that projects in the turning area in such a way that the air flow is separated from the inner channel wall. The flow element creaces a defined point of separation or a defined separating edge for the air flow. This solution of using a flow element is based on the consideration that an area with separated flow should not be avoided but that controlled separation should take place at the flow element with a defined position that can be taken into account when calibrating the sensor unit. The flow element and sensor unit are at such a distance from each other that the flow element creates largely defined flow conditions for the sensor unit.
It proves, to be particularly effective to locate a flow element at a turning area that diverts the air flow by approximately 90°. With such a diversion the passing air is separated from the channel wall in the area of the bend. Separation then takes place from the inside of the turning area, i.e. the side facing the central point of the curve of the turning area.
In a possible embodiment of the air mass flowmeter the side walls of the first and second channel sections meet directly or when extended in the turning area. The right angle of the turning area is preferably located on the side facing the central point of the curve of the turning area. The side facing the central point of the curve of the turning area is then referred to as the inside of the turning area.
The flow element preferably comprises an element projecting into the turning area that is secured on the inside to the side wall of one of the channel sections. A plate-shaped insert is preferably provided as the element, projecting into the turning area and secured to the side wall of the preferably, downstream channel section and creating a breaking edge for the air flow with its free end. The plate-shaped insert preferably extends over the entire side wall to which it is secured.
The insert is preferably a metal holder for the sensor unit.
In an alternative embodiment the flow element comprises a barrier surface inclined towards the direction of flow in the first channel section, coining into contact at an acute angle with a downstream wall of the element to form a breaking edge. The element can be configured in a, bar shape with a triangular cross-sectional contour. The element is preferably made of a plastic material. In a preferred arrangement of the flow element in the turning area its downstream wall terminates flush with the side wall of the downstream channel section. Alternatively the element can also be configured as a shaped section of the channel wall projecting into the turning area.
Preferred embodiments of the air mass flowmeter according to the invention are described in more detail below with reference to the figures, in which:
The air flow from the channel section 22 exits via the descending channel section 28 at the opening 30 and re-enters the principal air flow in the intake manifold. The opening 30 is screened by the tapering first channel section from the direct principal air flow so that the principal air flow generates suction at the opening 30 for the exiting air flow.
Disturbances always occur in the air flow when an air mass flowmeter is used. Disturbances cause displacement of the point of separation 34, 40, which result in clear changes to t-he recirculation area even with small displacements. These changes however bring about a change in the measurement signals so that the detected values are disturbed.
During operation the flow comes up against the insert 42 as shown in
As shown in
Number | Date | Country | Kind |
---|---|---|---|
101 41 909 | Aug 2001 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/DE02/03013 | 8/16/2002 | WO | 00 | 2/20/2004 |
Publishing Document | Publishing Date | Country | Kind |
---|---|---|---|
WO03/02761 | 4/3/2003 | WO | A |
Number | Name | Date | Kind |
---|---|---|---|
5712425 | Hecht et al. | Jan 1998 | A |
6220090 | Kohno et al. | Apr 2001 | B1 |
6336360 | Weber | Jan 2002 | B1 |
Number | Date | Country |
---|---|---|
10019149 | Nov 2001 | DE |
10135142 | Oct 2002 | DE |
0908704 | Apr 1999 | EP |
0940657 | Sep 1999 | EP |
2128754 | May 1984 | GB |
Number | Date | Country | |
---|---|---|---|
20040231405 A1 | Nov 2004 | US |