U.S. patent application number 09/866721 was filed with the patent office on 2001-10-04 for device for measuring the mass of a flowing medium.
Invention is credited to Konzelmann, Uwe, Marberg, Henning, Reymann, Klaus, Tank, Dieter.
Application Number | 20010025526 09/866721 |
Document ID | / |
Family ID | 25934374 |
Filed Date | 2001-10-04 |
United States Patent
Application |
20010025526 |
Kind Code |
A1 |
Reymann, Klaus ; et
al. |
October 4, 2001 |
Device for measuring the mass of a flowing medium
Abstract
Known devices for measuring the mass of a flowing medium by
means of a temperature-sensitive measuring element have the
disadvantage that considerable measuring errors may occur in the
event of a pulsating flow characterized by flow fluctuations. In
order to counteract these measuring errors, the device (1)
possesses an axially extending measuring duct (33), in which a
temperature-sensitive measuring element (20) is accommodated. The
measuring duct (33) extends from the inlet mouth (36) to a
deflecting duct (34), out of which the flowing medium flows out
from an outlet orifice (46) without any axial distance from the
inlet mouth (36) and radially underneath the latter. The invention
is provided for measuring the mass of a flowing medium, in
particular for measuring the intake air mass of internal combustion
engines.
Inventors: |
Reymann, Klaus; (Gerlingen,
DE) ; Tank, Dieter; (Eberdingen, DE) ;
Konzelmann, Uwe; (Asperg, DE) ; Marberg, Henning;
(Weil der Stadt, DE) |
Correspondence
Address: |
EDWIN E. GREIGG
GREIGG & GREIGG P.L.L.C.
1423 POWHATAN STREET, UNIT ONE
ALEXANDRIA
VA
22314
US
|
Family ID: |
25934374 |
Appl. No.: |
09/866721 |
Filed: |
May 30, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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09866721 |
May 30, 2001 |
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08545583 |
Nov 3, 1995 |
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08545583 |
Nov 3, 1995 |
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PCT/DE95/00184 |
Feb 15, 1995 |
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Current U.S.
Class: |
73/114.35 |
Current CPC
Class: |
G01F 1/6842 20130101;
G01F 5/00 20130101 |
Class at
Publication: |
73/118.2 |
International
Class: |
G01P 005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 4, 1994 |
DE |
P 44 07 209.0 |
Claims
1. A device for measuring the mass of a flowing medium, in
particular the intake air mass of internal combustion engines, with
a temperature-sensitive measuring element, round which the flowing
medium flows and which is arranged in a measuring duct running in
the device and extending in the axial direction from an inlet mouth
of the measuring duct to a deflecting duct, into which the medium
flowing out of the measuring duct flows and flows out of an outlet
orifice of the deflecting duct, wherein there is a short axial
distance (a) or no axial distance at all between an entry plane
(55) of the inlet mouth (36) of the measuring duct (33) and a
centroid (S) of the outlet orifice (46) of the deflecting duct
(34).
2. The device as claimed in claim 1, wherein the axial distance (a)
from the entry plane (55) of the inlet mouth (36) to the centroid
plane (56) limited by the centroid (S) of the outlet orifice (46)
is at most approximately 50 percent of a minimum dimension (b) of
the cross section of the inlet mouth (36).
3. The device as claimed in claim 1, wherein there is a measuring
part (17) of cuboid shape.
4. The device as claimed in claim 1, wherein the inlet mouth (36)
of the measuring duct (33) has a rectangular cross section.
5. The device as claimed in claim 4, wherein the measuring duct
(33) has a rectangular cross section and narrows in the axial
direction.
6. The device as claimed in claim 1, wherein the outlet orifice
(46) of the deflecting duct (34) has a rectangular cross
section.
7. The device as claimed in claim 1, wherein the inlet mouth (36)
of the measuring duct (33) has rounded edge faces (41).
8. The device as claimed in claim 1, wherein the measuring element
(20) is designed in the form of a micromechanical component.
9. The device as claimed in claim 1, said device (1) being designed
as a pluggable component.
Description
PRIOR ART
[0001] The invention proceeds from a device for measuring the mass
of a flowing medium according to the preamble of the main claim.
There is already a known device (EP 0,547,595 A2) which possesses a
tubular inner housing and a tubular outer housing and in which a
temperature-sensitive measuring element is accommodated in a
central measuring duct of the inner housing, said measuring duct
extending in the axial direction in the inner housing and being
open on one side, in order to determine the mass of a flowing
medium, in particular the intake air mass of an internal combustion
engine. The device is provided as a mountable intermediate piece,
for example of an intake conduit through which the internal
combustion engine can suck in air from the environment via an air
filter. The tubular inner housing connected to the outer housing by
means of a plurality of ribs possesses, furthermore, a bypass duct
which is cut out from the inner housing and is arranged
concentrically to the measuring duct and which, taking the form of
an annular gap, surrounds the measuring duct with a smaller axial
extension. A part stream of the medium flowing in the outer housing
flows from an inlet mouth coaxial relative to the outer housing
first into the measuring duct and flows round the
temperature-sensitive measuring element arranged in the region of
its downstream end, after which the flowing medium, reversing its
direction of flow, flows from the measuring duct into the bypass
duct. The medium flowing upstream in the bypass duct leaves the
latter through a slit-shaped outlet orifice cut out on the
circumference of the inner housing relatively far downstream of the
inlet mouth and is mixed again with the medium flowing past between
the inner housing and the outer housing. However, the design of the
device as a mountable intermediate piece with an inner housing and
with an outer housing necessitates a considerable overall size, so
that the device is suitable to only a limited extent for confined
conditions of installation, particularly in the engine region of a
motor vehicle.
[0002] In the case of an internal combustion engine, as a result of
the opening and closing of the inlet valves of the individual
cylinders there occur considerable fluctuations or pulsations of
the flow, the intensity of which depends on the intake frequency of
individual pistons or on the rotational speed of the internal
combustion engine. The pulsations of the flow are propagated from
the inlet valves via the intake conduit as far as the measuring
element in the inner housing and beyond this. The pulsations cause
the measuring element, as a result of thermal inertia and
directional insensitivity, depending on the intensity of the
pulsations, to provide a measurement result which deviates
considerably from the flow velocity prevailing on average in the
measuring duct and from the intake air mass of the internal
combustion engine which can be calculated from it.
ADVANTAGES OF THE INVENTION
[0003] In contrast to this, the advantage of the device according
to the invention for measuring the mass of a flowing medium, having
the defining features of the main claim, is that a uniformly
accurate measurement result can be achieved virtually independently
of a fluctuating or pulsating flow.
[0004] Advantageous developments and improvements of the device
specified in the main claim are possible as a result of the
measures listed in the subclaims. It is particularly advantageous
that the device is distinguished by a compact design and small
overall size and therefore requires only a small installation
space. The device is therefore particularly suitable as a pluggable
component especially for confined conditions of installation, for
example in the engine region of a motor vehicle.
DRAWING
[0005] An exemplary embodiment of the invention is represented in
simplified form in the drawing and is explained in more detail in
the following description.
[0006] FIG. 1 shows a partial sectional representation of a side
view of a device designed according to the invention and
[0007] FIG. 2 shows a section along the line II-II in FIG. 1.
DESCRIPTION OF THE EXEMPLARY EMBODIMENT
[0008] FIG. 1 shows a partial sectional representation of a side
view of a device, designated by 1, which serves for measuring the
mass of a flowing medium, particularly the intake air mass of
internal combustion engines. The device 1 preferably has a slender
cuboid shape extending elongately radially in the direction of a
longitudinal axis 10 and is introduced, for example pluggably, into
an orifice 6 of an intake conduit 7, said orifice 6 being cut out
from a wall 5. The device 1 is sealed off by means of a sealing
ring 3 in the wall 5 and is fixedly connected to the latter, for
example by means of a screw connection not represented in any more
detail. The wall 5 represented by hatching is part of the, for
example, cylindrically designed intake conduit 7, through which the
internal combustion engine can suck in air from the environment via
an air filter not shown in any more detail. The wall 5 of the
intake conduit 7 limits a flow cross section which, in the case of
a cylindrical intake conduit 7, has approximately a circular cross
section, in the middle of which extends in the axial direction,
parallel to the wall 5, a mid-axis 11 oriented perpendicularly to
the longitudinal axis 10. The device 1 projects into the flowing
medium by means of a part designed below as a measuring part 17,
the measuring part 17 being divided symmetrically by the mid-axis
11, for example approximately in the middle of the intake conduit
7, so that the medium can flow against a temperature-sensitive
measuring element 20 accommodated in the measuring part 17, if
possible without any disturbing marginal influences from the wall
5. In the exemplary embodiment shown in FIGS. 1 and 2, the medium
flows from right to left, the direction of flow being identified by
corresponding arrows 30.
[0009] The device 1 is composed, in one piece, of the measuring
part 17, of a carrier part 18 and of a holding part 19 and is
produced, for example, from plastic by the plastic injection
molding technique. The measuring element 20 is designed, for
example, in the form of a plate-shaped ceramic substrate and, as is
to be taken from the prior art, for example from German
Offenlegungsschrift 3,844,354, possesses one or more
temperature-dependent resistors which are applied to the
plate-shaped ceramic substrate in the form of resistive films,
so-called hot-film resistors. It is also possible, as proposed, for
example, in German Patent Application P 4,338,891, to design the
measuring element 20 as a micromechanical component which has a
dielectric membrane. The individual resistive films of the
measuring element 20 are electrically connected, by means of
connecting leads 21 extending inside the device 1, to an electronic
evaluation circuit 22 which is represented by broken lines in FIG.
1 and which contains, for example, a bridge-like resistance
measuring circuit. The evaluation circuit 22 is accommodated, for
example, in the carrier part 18 or in the holding part 19 of the
device 1. By means of a plug connection 24 provided on the holding
part 19, electrical signals supplied by the evaluation circuit 22
can be fed for evaluation, for example, to a further electronic
control unit which controls inter alia functions of the electronic
idling control or engine power control of the internal combustion
engine. A detailed description of the function and construction of
temperature-dependent measuring elements is dispensed with, since
the average person skilled in the art can take this from the prior
art.
[0010] As represented in FIG. 2, which is a sectional
representation along a line II-II in FIG. 1, the measuring part 17
of the device 1 has a cuboid shape and has a measuring duct 33
extending in the axial direction in the measuring part 17 and an
S-shaped deflecting duct 34. The measuring duct 33 extends axially
in the measuring part 17 from an inlet mouth 36 having, for
example, a rectangular cross section as far as a mouth 35 and is
limited by an upper face 38 further from the mid-axis 11 and a
lower face 37 nearer to the mid-axis 11 and by two side faces 39,
40, in the exemplary embodiment of FIG. 1 the measuring duct 33
being arranged eccentrically relative to the mid-axis 11. It is
also possible to arrange the measuring duct 33 centrically or in
the region of the mid-axis 11 of the intake conduit 7. The
plate-shaped measuring element 20 is oriented in the measuring duct
33 with its greatest extension radially in the direction of the
longitudinal axis 10 and is divided symmetrically by the latter.
The measuring element 20 is held with its narrow end on one side in
the carrier part 18 on the upper face 38, so that the medium flows
round said measuring element 20 together with its two side faces 23
in a manner approximately parallel to the mid-axis 11. As
represented in FIG. 2, the side faces 39, 40 of the measuring duct
33 extend obliquely relative to a plane 14 spanned by the mid-axis
11 and the longitudinal axis 10 and form an acute angle with said
plane 14, so that the measuring duct 33 narrows axially in the
direction of flow 30, in order to open into the deflecting duct 34
with a minimum cross section at the mouth 35. The narrowing of the
measuring duct 35 ensures that a uniform parallel flow as
undisturbed as possible prevails in the region of the measuring
element 20. In order to avoid flow breakaways in the region of the
inlet mouth 36, the latter possesses rounded edge faces 41. The
deflecting duct 34 has a rectangular cross section which
corresponds approximately to the cross-sectional area of the inlet
mouth 36 of the measuring duct 33, so that the flow cross section
increases abruptly at the mouth 35 between the measuring duct 33
and the deflecting duct 34. The axially flowing medium passes from
the measuring duct 33 into the approximately S-shaped deflecting
duct 34 and flows radially out of an outlet orifice 46 in the
direction of an arrow 31 marked in FIG. 1, in order thereafter to
mix again with the medium flowing past around the device 1. Like
the deflecting duct 34, the outlet orifice 46 possesses, for
example, a rectangular cross section and is provided on a lower
outer face 45 of the measuring part 17, said lower outer face being
oriented parallel to the mid-axis 11. In FIG. 1, a front face 50 of
the measuring part 17, said front face confronting the flow 30, is
adjacent transversely to the lower outer face 45 on the right of
the rectangular orifice 46 and leads in rounded form upstream of
the inlet mouth 36 from the lower outer face 45 to the lower face
37 of the measuring duct 33 as far as the inlet mouth 36.
[0011] According to the invention, the inlet mouth 36 of the
measuring duct 33 and the outlet orifice 46 of the deflecting duct
34 are designed to be located radially one under the other, so that
an axial distance, designated by a in FIGS. 1 and 2, is only
extremely small or is absent. The axial distance a is determined by
an entry plane 55, spanned by the inlet mouth 36, to a centroid
plane 56 passing through a centroid s of the outlet orifice 46
parallel to the entry plane 55. In the case, for example, of a
rectangular cross-section area of the outlet orifice 46, the
centroid S is located at the intersection point of the median. As
is known, the temperature-sensitive measuring element 20 is heated
to an excess temperature higher than that of the flowing medium
and, mainly as a result of convection, transmits heat to the
flowing medium, the heat quantity being dependent on the flow
velocity occurring in the measuring duct 33, so that the heating
voltage or heating current necessary, for example, for maintaining
the excess temperature is a measure of the flow velocity in the
measuring duct 33 and of the intake air mass calculable from this
in the intake conduit 7. Because the convective heat transmission
is based on non-linear physical laws, the measuring element 20 has
a non-linear characteristic, as a result of which, in the case of a
pulsating flow and a pulsating heat transmission to the flowing
medium, the measurement result does not correspond to the actual
time-averaged flow velocity in the measuring duct 33, but deviates
considerably from this, depending on the intensity of the
pulsations, as a consequence of a thermal inertia of the measuring
element 20. Because the outlet orifice 46 is arranged radially
underneath the inlet mouth 36 without or at only a short axial
distance a, it is possible that the pressure changes both at the
inlet mouth 36 and at the outlet orifice 46, which are triggered
during a pulsating flow, cancel one another out in terms of their
effect on the deflecting duct 34, so that a uniform velocity
independent of these pressure changes prevails in the deflecting
duct 34. The result of this effect of an air column flowing at
virtually constant velocity in the deflecting duct 34 is that the
medium also flows onto the measuring element 20 in the measuring
duct 33 at a constant velocity in a manner uninfluenced by the
pressure changes of the pulsations and their intensity and an exact
measurement result can be established. However, this effect occurs
only if the outlet orifice 46 is designed radially underneath the
inlet mouth 36 at a minimal axial distance a. The distance a is
itself dependent on the choice of the cross-sectional area of the
inlet mouth 36 or on the cross-sectional area of the measuring duct
33 and should be at most approximately 50% of a minimum dimension b
at the inlet mouth 36. The minimum dimension b of the inlet mouth
36 is marked accordingly in the exemplary embodiment in FIG. 1 and
corresponds to the radial distance from the surface 38 of the
carrier part 18 to the lower face 37 of the measuring duct 33. If
the measuring duct 33 is, for example, cylindrical with a circular
cross section, the minimum dimension b corresponds to the diameter
of the circular measuring duct 33 at the inlet mouth 36.
* * * * *