GB2211946A - Thermal air flow meter - Google Patents
Thermal air flow meter Download PDFInfo
- Publication number
- GB2211946A GB2211946A GB8825645A GB8825645A GB2211946A GB 2211946 A GB2211946 A GB 2211946A GB 8825645 A GB8825645 A GB 8825645A GB 8825645 A GB8825645 A GB 8825645A GB 2211946 A GB2211946 A GB 2211946A
- Authority
- GB
- United Kingdom
- Prior art keywords
- flow
- air
- stream
- electric current
- path
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
- G01F1/68—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using thermal effects
- G01F1/684—Structural arrangements; Mounting of elements, e.g. in relation to fluid flow
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
- G01F1/68—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using thermal effects
- G01F1/684—Structural arrangements; Mounting of elements, e.g. in relation to fluid flow
- G01F1/688—Structural arrangements; Mounting of elements, e.g. in relation to fluid flow using a particular type of heating, cooling or sensing element
- G01F1/69—Structural arrangements; Mounting of elements, e.g. in relation to fluid flow using a particular type of heating, cooling or sensing element of resistive type
- G01F1/692—Thin-film arrangements
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P5/00—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft
- G01P5/10—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft by measuring thermal variables
- G01P5/12—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft by measuring thermal variables using variation of resistance of a heated conductor
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Fluid Mechanics (AREA)
- Engineering & Computer Science (AREA)
- Aviation & Aerospace Engineering (AREA)
- Measuring Volume Flow (AREA)
Description
221194o 1 DEVICE FOR MEASURING THE RATE OF FLOW OF THE ASPIRATED AIR IN AN
INTERNAL COMBUSTION ENGIN The invention relates to a device for measuring the rate of flow of the aspirated air in an internal combustion engine.
To satisfy the official regulations on the exhaust gases of motor vehicles it is necessary to control accurately the composition of the combustible mixture fed to the engine, and for this one has to measure the rate of flow of the aspirated air. For this purpose it is known to use electric heating-wire anemometers of various constructions.
From the German Patent Specification DE-PS 3127 081 a device is known in which an electric current flow-path applied to a support is arranged so that the electric resistance per unit of area, and therefore the heat output per unit of area, decreases in the downstream direction of the airflow proportionately with the decrease in heat loss per unit of area. The intention is to keep the temperature of the entire resistor constant irrespective of the rate of flow of the air-strearn. But in this known device no allowance is made for the fact that heat is removed from the electrical resistor not only by the air-stream but also by the holder which holds the support in the air-stream. The holder can hold the support from one side only, or froin both sides, the support being positioned transverse to the air-stream. In the operation of the device the support is heated by electrical film-resistors and transfers heat to the holder. Consequently, there is a greater loss of heat from near the edges of the support than there is from near its middle, the extra heat not being carried away by the air-stream but by the holder. The signal produced does therefore not truly represent the rate of flow of the air- stream.
The intention of the invention is to provide a measuring device which is free from this source of error.
2 1 According to this invention there is provided a device for measuring the rate of flow of the aspirated air in an internal combustion engine, with one or more temperature-dependent electrical resistors in contact with the air-stream, at least one being controllably heatable by an electric current, each electrical resistor being in the form of a thin metal film applied, in order to provide an electric current flow-path, to an electrically insulated support which is itself supported in the airstrearn with the help of at least one holder, in such a way that the electric current flow-paths run parallel and transverse to the air-stream, and in which the flow-paths are so dimensioned that they decrease linearly in cross section towards each holder within an edge-marginal region of specified width.
X, Such an arrangement achieves an approximately rectangular temperature profile extending across tile support, transverse to te air-stream.
Preferably the desired effect is obtained by reducing the cross section of each electrical flow-path in the region of the edge-margiii near the holder, increasing the electrical resistance here and increasing the output of heat.
With advantage, the cross sections of the electrical flow-paths can decrease constantly in the direction of flow of the air-strearn.
Alternatively, if necessary, the cross sections can decrease less in the downstream direction, in order to allow for the varying losses of heat from the air-stream to the holders.
One embodiment will now be described by way of example with reference to the accompanying drawing showing essential parts of a support for electrical resistors and the holding means at one end thereof 3 The drawing shows a support 1 to which meandering electric current flow- paths 2 have been applied in the form of thin-fihn metal-layer heating resistors. The support 1 is supported at each end by a holder 3, only one being shown in the drawing, to simplify representation. The current of air aspirated by the engine is indicated by the arrows 4. Each holder 3 is itself supported in the passage (not shown) carrying the air-strearn by a bracket 5, only one bracket 5 being shown in the drawing.
When the measuring device is in operation electric current flows continually over the flow-paths 2 between electric terminals, which are also not shown in the drawing.
According to the invention and in order to compensate the extra loss of heat flowing away through the holders 3 at each end of the support 1, the current-paths are reduced in cross-section linearly over a marginal area of specified width near the supported ends of the support 1, terminating in points 6, as represented in the drawing or, alternatively, terminating as trapezes.
The widths of the current-paths can, if desired, decrease constantly near their ends from the one current-path to the next in the downstreain direction of the air-stream.
Or, alternatively, the decreasing in width can become less in the downstream direction, to compensate the decreasing cooling of the holder 3 by the airstream in the downstream direction.
These measures ensure that an approximately rectangular temperature profile is obtained across the support 1, preventing false measurements.
4
Claims (4)
1. A device for measuring the rate of flow of the aspirated air in an internal combustion engine, with one or more temperature-dependent electrical resistors is contact with the air-strearn, at least one being controllably heatable by an electric current, each electrical resistor being in the form of a thin metal film applied, in order to provide an electric current flow-path, to an electrically insulated support (1) which is itself supported in the air-stream, with the help of at least one holder (3), in such a way that the electric current flow-paths run parallel and transverse to the air-stream, and in which the flow-paths (2) are so dimensioned that they decrease linearly in cross section towards each holder (3) within an edge-marginal region of specified width.
2. A device as claimed in Claim 1, characterised in that the decrease in cross section is constant from the one flow-path (2) to the next in the down-stream direction of the air-flow.
3. A device as claimed in Claim 1, characterised in that the decrease in cross section becomes less from the one flow-path to the next in the downstream direction of the air-flow.
4. A device for measuring the rate of flow of the aspirated air in an internal combustion engine, according to claim 1 and substantially as hereinbefore described with reference to the accompanying drawing.
k Published 1989 atThe Patent Office. State I-louse, 6671 High Hc)lborn. LondonWCIR 4TP. Further copies nikybe obtainedfrorn The Patent office. Wes Branch, St Mary Cray, Orpington, Kent BR5 3RD. Printed by Multiplex techniques ltd, St Mary Cray, Kent, Con.. 1/87
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19873737188 DE3737188A1 (en) | 1987-11-03 | 1987-11-03 | DEVICE FOR MEASURING THE FLOW RATE OF THE INTAKE AIR OF COMBUSTION ENGINES |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB8825645D0 GB8825645D0 (en) | 1988-12-07 |
| GB2211946A true GB2211946A (en) | 1989-07-12 |
Family
ID=6339631
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8825645A Withdrawn GB2211946A (en) | 1987-11-03 | 1988-11-02 | Thermal air flow meter |
Country Status (3)
| Country | Link |
|---|---|
| DE (1) | DE3737188A1 (en) |
| FR (1) | FR2622701A1 (en) |
| GB (1) | GB2211946A (en) |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2103804A (en) * | 1981-07-09 | 1983-02-23 | Degussa | Device for measuring the flow velocity of gases and liquids |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS59162413A (en) * | 1983-03-07 | 1984-09-13 | Hitachi Ltd | Heat type flowmeter |
| DE3542788A1 (en) * | 1985-12-04 | 1987-06-19 | Degussa | DEVICE FOR THERMAL MASS CURRENT MEASUREMENT OF GASES AND LIQUIDS |
| DE3606849A1 (en) * | 1986-03-03 | 1987-09-10 | Vdo Schindling | ARRANGEMENT FOR MEASURING THE FLOW RATE |
-
1987
- 1987-11-03 DE DE19873737188 patent/DE3737188A1/en not_active Withdrawn
-
1988
- 1988-10-06 FR FR8813124A patent/FR2622701A1/en not_active Withdrawn
- 1988-11-02 GB GB8825645A patent/GB2211946A/en not_active Withdrawn
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2103804A (en) * | 1981-07-09 | 1983-02-23 | Degussa | Device for measuring the flow velocity of gases and liquids |
Also Published As
| Publication number | Publication date |
|---|---|
| FR2622701A1 (en) | 1989-05-05 |
| GB8825645D0 (en) | 1988-12-07 |
| DE3737188A1 (en) | 1989-05-18 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |