U.S. patent application number 11/547823 was filed with the patent office on 2008-01-31 for flat-blade windscreen wiper blade comprising an aerodynamic deflector.
This patent application is currently assigned to Valeo Systemes d'Essuyage. Invention is credited to Flavien Dubief, Sebastien Jallet, Jean-Michel Jarasson.
Application Number | 20080022478 11/547823 |
Document ID | / |
Family ID | 34946576 |
Filed Date | 2008-01-31 |
United States Patent
Application |
20080022478 |
Kind Code |
A1 |
Jarasson; Jean-Michel ; et
al. |
January 31, 2008 |
Flat-Blade Windscreen Wiper Blade Comprising An Aerodynamic
Deflector
Abstract
The invention provides a blade (10) comprising a central
rigidifying element (20), a wiping strip (14) and an element (16)
forming an aerodynamic deflector that has a contour (AE-FM-MA) with
an overall triangular shape comprising a front side (AE) that
delimits the side of the aerodynamic deflector (16) that faces the
wind, characterised in that the ratio (H/L) of the total height (H)
of the windscreen wiper blade (10) to the overall transversal width
(L) of the windscreen wiper blade (10), is comprised between 1.5
and 2.
Inventors: |
Jarasson; Jean-Michel;
(Elancourt, FR) ; Jallet; Sebastien; (Maurepas,
FR) ; Dubief; Flavien; (Montigny-Le-Bretonneux,
FR) |
Correspondence
Address: |
OSHA LIANG L.L.P.
1221 MCKINNEY STREET, SUITE 2800
HOUSTON
TX
77010
US
|
Assignee: |
Valeo Systemes d'Essuyage
La Verriere
FR
|
Family ID: |
34946576 |
Appl. No.: |
11/547823 |
Filed: |
April 4, 2005 |
PCT Filed: |
April 4, 2005 |
PCT NO: |
PCT/EP05/03507 |
371 Date: |
July 31, 2007 |
Current U.S.
Class: |
15/250.201 |
Current CPC
Class: |
B60S 1/3848 20130101;
B60S 1/381 20130101; B60S 1/3881 20130101; B60S 2001/382
20130101 |
Class at
Publication: |
15/250.201 |
International
Class: |
B60S 1/38 20060101
B60S001/38 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 7, 2004 |
FR |
04/03619 |
Claims
1. Windscreen wiper blade of a motor vehicle of the type
comprising: a rigidifying central longitudinal element; a strip for
wiping the window to be wiped, which extends longitudinally below
the central element and which comprises a bottom longitudinal
wiping edge that cooperates with the top face of the window to be
wiped; and an element forming an aerodynamic deflector, which
extends longitudinally above the central rigidifying element and
along at least one section of the latter, and which, in a
cross-section according to a vertical plane, has a contour with an
overall triangular shape comprising a bottom horizontal side
forming a base, a front side which delimits the side of the
aerodynamic deflector that faces the wind, said front side
comprising a bottom section, an intermediate section substantially
forming a concave arc of circle, and a top end section, a rear side
with an overall vertical orientation that delimits the side behind
the wind of the deflector and which is connected to the front side
by a section that delimits the top longitudinal edge with a top
free end of the deflector, characterised in that the ratio (H/L) of
the total height (H) of the windscreen wiper blade separating the
top edge of the aerodynamic deflector from the bottom wiping edge,
to the overall transversal width (L) of the windscreen wiper blade,
measured on the plane of the rigidifying element, is comprised
between 1.5 and 2.
2. Windscreen wiper blade according to the preceding claim,
characterised in that the bottom section is substantially
rectilinear and forms an acute angle in relation to the bottom
horizontal edge.
3. Windscreen wiper blade according to the preceding claim,
characterised in that said acute angle is comprised between 5 and
35 degrees.
4. Windscreen wiper blade according to claim 2, characterised in
that the bottom section extends substantially to the right of a
median vertical plane of the central rigidifying element and of the
bottom wiping strip.
5. Windscreen wiper blade according to claim 1, characterised in
that the radius R of said concave intermediate section is comprised
between 50% and 70% of said total overall width.
6. Windscreen wiper blade according to claim 1, characterised in
that said top end section of the front side is substantially
rectilinear and has a vertical orientation.
7. Windscreen wiper blade according to claim 1, characterised in
that the top end section of the front side substantially forms a
convex arc of circle.
8. Windscreen wiper blade according to claim 6, characterised in
that said top end section of the front side extends over a marginal
vertical height comprised between 15% and .ltoreq.25% of the total
height of the aerodynamic deflector.
9. Windscreen wiper blade according to claim 1, characterised in
that the rear side of the triangular contour comprises a top
section that is overall parallel to a top section of the front
side.
10. Windscreen wiper blade according to claim 1, characterised in
that the rear side of the triangular contour comprises an
intermediate section that is overall parallel to an intermediate
section of the front side.
11. Windscreen wiper blade according to claim 9, characterised in
that the top rectilinear section of the rear side extends to the
right of the rear lateral edge of the central rigidifying
element.
12. Windscreen wiper blade according to claim 1, characterised in
that the rear side of the triangular contour comprises a bottom
section forming a concave arc of circle.
13. Windscreen wiper blade according to the preceding claim,
characterised in that the most transversally internal point of the
bottom section forming a concave arc of circle of the rear side is
located transversally set back towards the inside in relation to
the rear lateral edge of the central rigidifying element.
14. Windscreen wiper blade according to the preceding claim,
characterised in that the horizontal distance that separates the
most internal point of the rear lateral edge from the central
support element is comprised between 15% and 25% of said total
overall width.
15. Windscreen wiper blade according to claim 1, characterised in
that the section that delimits the top edge of the aerodynamic
deflector is semi-circular in shape.
16. Windscreen wiper blade according to claim 9, characterised in
that the thickness of the top part of the aerodynamic deflector
separating the two vertical and rectilinear top sections is
comprised between 8% and 15% of said total overall width.
17. Windscreen wiper blade according to claim 3, characterised in
that the bottom section extends substantially to the right of a
median vertical plane of the central rigidifying element and of the
bottom wiping strip.
18. Windscreen wiper blade according to claim 7, characterised in
that said top end section of the front side extends over a marginal
vertical height comprised between 15% and .ltoreq.25% of the total
height of the aerodynamic deflector.
Description
[0001] The present invention relates to a flat-blade windscreen
wiper blade for a motor vehicle.
[0002] The invention relates, in particular to a windscreen wiper
blade of a motor vehicle of the type that comprises
[0003] a support frame with a longitudinal main orientation, which
comprises bottom means for supporting a wiping strip and a tubular
body with a longitudinal main axis, which is delimited by a
horizontal bottom wall and by two vertical longitudinal lateral
walls;
[0004] a structural element in the shape of a longitudinal
horizontal strip, which is accommodated inside the tubular
body.
[0005] With a view to improving the aerodynamic performance of such
a windscreen wiper blade, as proposed in particular in documents
U.S. Pat. No. 6,292,974, B1 US-A1-2003/0145412 and
US-A-2002/0000018, a known windscreen wiper blade for a motor
vehicle exists, of the type that comprises:
[0006] a central longitudinal rigidifying element;
[0007] a strip for wiping the window to be wiped, which extends
longitudinally below the central element and which comprises a
bottom longitudinal wiping edge that cooperates with the face of
the window to be wiped; and
[0008] an element forming an aerodynamic deflector, which extends
longitudinally above the central rigidifying element and along at
least one section of the latter and which, in a vertical
cross-section, has a contour with an overall triangular shape
comprising a horizontal base side, a front side that delimits the
part of the aerodynamic deflector that faces the wind, and a rear
side with an overall vertical orientation, which delimits the side
of the deflector that is behind the wind and which is connected to
the front side by a section that delimits the top free end top
longitudinal edge of the deflector.
[0009] In order further to improve the aerodynamic performance of
the windscreen wiper blade and its aerodynamic deflector, the
invention provides a windscreen wiper blade of the preceding type,
characterised in that the H/L ratio of the total height H of the
windscreen wiper blade separating the top edge of the aerodynamic
deflector from the bottom wiping edge of the wiping strip to the
overall transversal width of the windscreen wiper blade, measured
on the plane of the rigidifying element, is comprised between 1.5
and 2.
[0010] According to other characteristics of the invention:
[0011] the front side of the triangular contour comprises a
substantially rectilinear bottom section that forms an acute angle
B in relation to the bottom horizontal edge;
[0012] said acute angle B is comprised between 5 and 35
degrees;
[0013] said bottom section extends substantially to the right of a
median vertical plane of the central rigidifying element and of the
bottom wiping strip;
[0014] said bottom section of the front side of the triangular
contour is followed by an intermediate section substantially
forming a concave arc of circle;
[0015] the radius R of said intermediate concave section is
comprised between 50% and 70% of said total overall width;
[0016] the front side of the triangular contour comprises a top end
section;
[0017] said top end section of the front side is substantially
rectilinear and has a vertical orientation;
[0018] the top end section of the front side is substantially
forming a convex arc of circle;
[0019] said top end section of the front side extends over a
marginal vertical height Hv comprised between 15% and .ltoreq.25%
of the overall height Hsp of the aerodynamic deflector;
[0020] the rear side of the triangular contour comprises a top
section that is overall parallel to the top section of the front
side;
[0021] the rear side of the triangular contour comprises an
intermediate section that is overall parallel to the intermediate
section of the front side;
[0022] the top rectilinear section of the rear side extends to the
right of the rear lateral edge of the central rigidifying
element;
[0023] the rear side of the triangular contour comprises a bottom
section forming a concave arc of circle;
[0024] the transversally most internal point of the bottom section
forming a concave arc of circle of the rear side is located
transversally set back towards the inside in relation to the rear
lateral edge of the central rigidifying element;
[0025] the horizontal distance P separating said most internal
point of the rear lateral edge from the central support element is
comprised between 15% and 25% of said total overall width L;
[0026] the section that delimits the top edge of the aerodynamic
deflector is semi-circular in shape;
[0027] the thickness e of the top part of the aerodynamic deflector
separating the two vertical and rectilinear top sections is
comprised between 8% and 15% of said total overall width L.
[0028] Further characteristics and advantages of the invention will
become apparent from reading the following detailed description,
for the understanding of which the appended figures can be
consulted, in which:
[0029] FIG. 1 is a diagrammatic large-scale view that shows, in a
cross-section across a vertical plane, a section that is
characteristic of a first embodiment of a windscreen wiper blade
manufactured according to the instructions of the invention;
[0030] FIG. 2 is a view similar to that shown in FIG. 1, which
illustrates a first alternative embodiment of the general
confirmation of the aerodynamic deflector;
[0031] FIG. 3 is a view similar to that shown in FIG. 1, which
illustrates the top part of the windscreen wiper blade with a
second alternative embodiment of the general confirmation of the
aerodynamic deflector;
[0032] FIGS. 4 and 5 are two detail views that illustrate two
alternative embodiments of the top part of the aerodynamic
deflector of the windscreen wiper blade according to the
invention;
[0033] FIG. 6 is a detail view that illustrates an alternative
embodiment of the leading edge.
[0034] In the following description and in the claims--by way of
non-limiting example and with a view to facilitating their
understanding--the terms vertical, horizontal, bottom, top will be
adopted in reference to the orientation of the figures and to the
trihedron L, V, T shown in FIG. 1, which corresponds to the
Longitudinal (main direction of the windscreen wiper blade),
Vertical and Transversal (also corresponding to the horizontal
reference) directions
[0035] Identical, similar or analogous elements and components will
be referred to using the same reference numbers.
[0036] The windscreen wiper blade 10 shown in FIG. 1 consists
essentially of a support frame with a longitudinal main
orientation, which comprises bottom means for supporting a wiping
strip and a tubular body with a longitudinal main axis which is
delimited by a top horizontal wall, a bottom horizontal wall and
two vertical longitudinal lateral walls.
[0037] The central tubular body 12 is, for example, made by
moulding from a rigid or semi-rigid plastic material.
[0038] The windscreen wiper blade 10 shown in FIG. 1 also consists
of a bottom wiping strip 14 made from rubber or a natural or
synthetic elastomer, made by extrusion, and of a top aerodynamic
deflector or spoiler 16 made from a rigid or flexible synthetic
material attached to the central body 12 or made by co-extrusion or
co-moulding with this body 12.
[0039] The central body 12 has an overall rectangular section, with
its long side placed according to the horizontal plane and its
short side placed according to the vertical plane. The central body
12 has a general symmetry of design in relation to the median
vertical plane PVM, which is also the plane of symmetry of the
bottom wiping strip 14.
[0040] The hollow central body 12 delimits an internal hollow
housing 18 with a rectangular contour which accommodates, with free
play in order to allow slight relative movements, in particular in
the longitudinal direction, a structural element in the form of a
longitudinal horizontal strip, a central longitudinal element 20
with a rectangular section which is a structural element in the
form of a longitudinal horizontal strip, or a rigidifying spine
which, in association with the hollow body 12, constitutes the
structure of the flat-blade windscreen wiper blade 10 and which
also affords the windscreen wiper blade its elasticity in the
vertical and longitudinal planes, allowing it to adapt to the
confirmation and, in particular, to the curve of the outside face
or top face 22 of the window 24 to be wiped.
[0041] The top face of the central body 12 comprises a top housing
or recess 26 with a flat horizontal bottom that accommodates the
bottom part of the deflector 16.
[0042] The central body 12 is extended vertically downwards from
its bottom face 30 by sections of two opposing ribs 32 with an
L-shaped cross-section forming hooks that delimit a bottom housing
34 with a rectangular section, which accommodates, with free play,
the top flat heel 36, with rectangular section, of the bottom
wiping strip 14.
[0043] The strip 14 is of a generally known design and includes, at
the bottom, a bottom wiping blade 38 which ends in a bottom edge 40
for wiping the face 22 of the window 24.
[0044] The following is a detailed description of the top part of
the windscreen wiper blade 10 which essentially consists of the
aerodynamic deflector 16 and, more particularly, of the various
shape and profile aspects of its contour in a cross-section across
a vertical plane.
[0045] This contour is overall triangular with:
[0046] a bottom side or base AM which is rectilinear and horizontal
and which extends above the flat base 28 of the central body
12;
[0047] a front side AE, overall curved and concave;
[0048] and a rear side FM with overall vertical orientation, which
is connected to the top end E of the front side AE by the top
longitudinal edge 42 at the end of the deflector 16.
[0049] The top edge 42 in this case has a convex semi-circular
section EF whose diameter defines the width or marginal thickness
"e" of the thin top part 44 of the aerodynamic deflector 16.
[0050] The total height of the windscreen wiper blade is defined as
being the vertical distance "H" that separates the tip of the top
edge 42 of the deflector 16 from the bottom wiping edge 40 of the
bottom wiping blade 38
[0051] The front side AE comprises a first bottom section AC that
is substantially rectilinear or concavely curved with a very large
radius which, in the example shown in FIG. 1, extends from point A
to point C, which is located substantially at the level of the
plane of symmetry PVM. The straight line AC forms, together with
the horizontal plane and, for example, the bottom side AM, an acute
angle "B" also called angle of incidence of the deflector 16.
[0052] The angle B is positive, that is to say that the section AC
is "above" the bottom horizontal side AM.
[0053] After the point C at the top end of the first bottom section
AC, the front side AE comprises a concavely curved intermediate
section CD which in this case, by way of example, is a section
forming a concave arc of circle with a constant radius "R".
[0054] By way of an alternative, not shown, the concave
intermediate section CD can comprise several successive parts with
different radii.
[0055] Beyond the concave intermediate section CD, the front side
AE--which delimits the main front lateral face of the aerodynamic
deflector 16, facing the wind--comprises a third top end section DE
which, in the example of FIG. 1, is a rectilinear section with a
vertical orientation, that is to say, parallel to the vertical
plane of symmetry PVM.
[0056] Due to the situation of the point C at the level of the
plane PVM, the main active part of the aerodynamic deflector
16--made up of the concave intermediate section CD and by the top
section or tip DE--is situated overall behind or to the rear of the
median vertical plane PVM.
[0057] Marginal height "Hv" refers to the vertical distance that
separates the lowest point D of the third top section DE from the
tip of the top edge 42 of the deflector 16.
[0058] The height Hsp of the deflector 16 refers to the vertical
distance that separates the bottom side AM from the tip of the top
edge 42 of the deflector 16.
[0059] The rear side MF comprises a first concavely curved bottom
section MJ which in this case, by way of example, is a section
substantially forming an arc of circle.
[0060] The first concave bottom section MJ comprises an
intermediate point K which is the most transversally internal point
of this section, that is to say, which is as close as possible to
the plane of symmetry PVM.
[0061] The point K is therefore situated at a horizontal distance
"P" from the rear vertical edge NQ of the central body 12 which in
this case is a vertical rectilinear section that is vertically in
line with the third top end section GF of the rear side MF, which
is a rectilinear vertical section parallel to the section DE of the
front side AE. P is therefore the distance separating the point K
from the rearmost point of the top rear section FG, that is to say,
the most distant point from the plane PVM.
[0062] In the example shown in FIG. 1, the length or height of the
section GF is greater than the length or height of the section
DE.
[0063] Between the first bottom section MJ and the third top
section GF, the rear side MF comprises a second intermediate
section JG which is a convexly curved section, in this case overall
forming an arc of circle and substantially parallel to the concave
section CD, but with a radius that is slightly greater than the
latter and not concentric.
[0064] The lowest point M of the rear side MF in this case is
connected to the top point N of the rear vertical edge NQ of the
central body 12 by a section MN forming a convex arc of circle, in
the same way as the bottom point Q is connected to the bottom edge
or face 30 of the central body 12 by a section QS forming a convex
arc of circle.
[0065] The front edge or leading edge 46 of the windscreen wiper
blade in this case is the leading edge of the central body 12 which
is the edge, or profile surface, that is situated the furthest
forward in the fluid flow or relative flow of air to which the
windscreen wiper blade 10 is subjected.
[0066] The leading edge 46 comprises a front rectilinear vertical
section VU, the top point of which is connected to the lowest point
A of the front side AE of the aerodynamic deflector 16 by a
convexly curved section VA substantially forming an arc of circle,
and in which the bottom point U Q is connected to the bottom edge
or face 30 of the central body 12 by a section UT forming a convex
arc of circle.
[0067] The total overall width "L" of the windscreen wiper blade
thus corresponds to the horizontal distance separating the front VU
and rear NO external vertical sections or edges of the central body
12.
[0068] According to a first aspect of the invention, the ratio of
total width L/total height H is such that:
1.5.ltoreq.H/L.ltoreq.2.
[0069] For example, in FIG. 1, for a total height H of around 20
mm, the total width L is around 10 mm.
[0070] According to another aspect of the invention, the angle of
incidence B is positive and is preferably such that:
5 degrees.ltoreq.B.ltoreq.35 degrees.
[0071] For example, in FIG. 1 the angle B is around 15 degrees.
[0072] The radius R of the concave intermediate section CD is
comprised between 50% and 70% of the total overall width L.
[0073] The radius of curvature R of the concave intermediate
section CD is thus comprised between 5 mm and 7 mm and the total
height Hsp of the aerodynamic deflector 16 is equal to around 7.5
mm.
[0074] The smaller the angle B, the smaller the radius R and the
more the aerodynamic deflector 16 can be said to be "dipped".
[0075] According to yet another aspect of the invention, the
marginal thickness e of the aerodynamic deflector 16 is such
that:
8% of L.ltoreq.e.ltoreq.15% of L.
[0076] The thickness e of the top end part of the aerodynamic
deflector 16 is substantially equal to 1 mm.
[0077] According to a further aspect of the invention, the marginal
height Hv of the aerodynamic deflector 16 is such that:
15% of Hsp.ltoreq.Hv.ltoreq.25% of Hsp.
[0078] In this way, still in FIG. 1, the resulting height Hv is
approximately 1.5 mm.
[0079] According to yet another aspect of the invention, the
distance or "dip" P of the rear face behind the wind of the
deflector is such that:
20% of L.ltoreq.P.ltoreq.25% of L.
[0080] In this way, P is, for example, equal to approximately 2
mm.
[0081] As regards the thinness of the leading edge 46, in other
words the vertical distance "Ha" that separates the point A from
the point V, it is such that:
Ha.ltoreq.1/3 of L.
[0082] Ha is therefore comprised between 0.5 mm and 3 mm.
[0083] The added or extruded or moulded deflectors are generally
defined by an overall shape or by an average angle of the wing in
relation to the plane of the windscreen to be wiped.
[0084] The deflectors thus manufactured have limited efficiency or
are inefficient, resulting in a loss of performance and therefore
of wiping quality and a risk in terms of safety
[0085] Some of these profiles even generate turbulence that
enhances the phenomenon of "water drag-back" or "water pull-back",
that is to say that the blade pulls the water it just wiped with it
when it returns to its position at the bottom of the
windscreen.
[0086] The aerodynamic performance of a profile is the combination
of several criteria including:
[0087] lift;
[0088] drag;
[0089] the re-attachment point, which defines the distance for
re-attachment of the air flows behind or to the rear of the
profile.
[0090] These different criteria change according to:
[0091] the overall dimensions of the profile and in particular the
height H/width L ratio;
[0092] the geometry of the leading edge, which is the foremost
surface of the profile in the flow of the fluid situated below the
active face of the aerodynamic deflector that faces the wind;
[0093] the actual geometry of the deflector 16 or spoiler and, in
particular, its angle of incidence B, its concave curvature R and
its marginal height Hv;
[0094] the projected lifting surfaces, at the front, at the middle
(deflector, tip included) or at the rear of the profile.
[0095] The state-of-the-art shows and theoretical two-dimensional
simulation confirms that a profile in which H=L in overall terms
(in other words H/L=1), with a level of lift performance
of.times.N/m can, according to the instructions of the invention,
be easily improved and notably so if H>L is obtained with a
ratio comprised between 1.5 and 2.
[0096] The higher the H/L ratio, the greater the lift performance,
while the drag performance drops, having a considerable "catch in
the wind" effect that influences the regularity of the wiping
cycle, but also the water drag-back phenomenon.
[0097] The principle of the solutions proposed according to the
present invention consists of obtaining the best dimensional
compromise and therefore an H/L dimensional ratio with a value
comprised between 1.5 and 2.
[0098] Below this range, average lift performance is obtained with
low drag, and above it, considerable lift performance is obtained
that can cause the phenomena mentioned above.
[0099] By reducing the width L and keeping an initial height H with
an H/L ratio equal to 1.5 to 2, the lift performance increases,
while the drag and the distance of the re-attachment point remain
stable.
[0100] The active part of the deflector is shifted towards the rear
of the profile such as to increase the performance, as is the dip
"P" formed in the rear of the profile, which enables a reduction in
the amount of turbulence.
[0101] By adapting, on the one hand, certain geometries that are
specific to the deflector, in particular the leading edge, the
angle of incidence B and the curvature R of the concave surface and
the marginal vertical height Hv of the deflector, the channelling
and the guiding of the air flows over the surface of the deflector
are improved such as to reduce the aerodynamic disturbances and
thereby improve the performance of the profile.
[0102] The profile and the shape of the leading edge make up the
surface of the blade that is the furthest forward in the fluid
flow, for an angle of attack equal to zero, that is to say, when
the windscreen wiper blade is in its position shown in FIG. 1, in
which the plane PVM is orthogonal to the surface 22 to be
wiped.
[0103] The flow is, in a first approximation, separated into two
parts: a bottom part re-circulated at the bottom of the wiping
blade 38, and another top part that interacts with the aerodynamic
deflector 16 of the wiping blade 10. The role of the leading edge
is to suitably guide the flow over the deflector in order to obtain
the best push effect.
[0104] With a view to preventing any separation of the fluid at the
level of the leading edge, the latter must enter the flow in an
optimum manner. For various dimensional reasons to do with a
maximum width in order to remain within an H/L ratio of between 1.5
and 2, and for reasons relating to the methods of manufacturing and
obtaining the part, it is not always possible to obtain a leading
edge that is as thin as desired with the proportions mentioned
above. For this reason, the separation will be reduced as much as
possible by ensuring a small radius for the section VA and
"non-angularity", that is to say a lack of square edges, to disturb
the air flow as little as possible.
[0105] The angle of incidence B corresponds overall to the slope
between the end of the leading edge which corresponds to the point
A and the start of the concave curvature CE of the deflector
16.
[0106] In the context of the dimensional and manufacturing
constraints mentioned above, the angle of incidence B allows the
flow of air to be guided and to remain in contact with the active
surface CD+DE of the aerodynamic deflector 16. The value of this
angle B must be comprised between 5 and 35 degrees. Below 5
degrees, the air flow hits the active concave surface of the
deflector, creating a whirl and thus a disturbance. Above 35
degrees, the air flow is deflected by the slope of the first
section AC and is no longer guided along the active concave surface
CD of the aerodynamic deflector 16. Therefore, in extreme slopes,
the flow passes "above" the active concave surface, causing an
inefficiency of the deflector and therefore poor aerodynamic
performance.
[0107] The concave curvature CD with a radius R of the aerodynamic
deflector 16 makes it possible, the same as the angle of incidence
B, to guide the air flow towards the top vertical surface DE of the
aerodynamic deflector 16, ideally with no whipstall along the front
surface. The advantage of the concave curvature CD is that it
"brakes" the air flow at the level of the deflector and thus
creates an overpressure. A part of this overpressure is converted
into lift, that is to say a pushing force, opposed to the lifting
or separation of the blade and the wiping blade, and the other part
is converted into drag.
[0108] The effect is more predominant than for a substantially
rectilinear deflector facing the wind AE, which allows the fluid to
slide over this front surface without locally generating an
overpressure that is high enough to obtain a pushing effort.
[0109] On the contrary, an excessively hollow concave surface CD of
the aerodynamic deflector 16 does not provide acceptable
performance levels, especially for negative angles of attack, due
to the generation of a local low pressure area characterised by a
whirl, generated by the stalling of the fluid at the level of the
leading edge or along the deflector. Therefore, the shape of the
leading edge and the curvature of the deflector must be optimised
together for a range of angles of attack of the wiping blade
comprised between -10 and +10 degrees.
[0110] The relative increase of the marginal height Hv enables an
increase in the performance of the deflector, in particular for the
negative angles of attack. This also makes it possible to reduce
possible influence of the vortex areas that exist at the bottom of
the deflector and which can be caused by partial, incomplete
optimisation of the leading edge, due to manufacturing and
production-related constraints. This also makes it possible to
increase, for the negative angles of attack, the surface projected
for the overpressure lift (push effect). On the other hand, this
also leads to considerably increased drag for angles of incidence
equal to zero, which requires this marginal vertical height to be
optimised in order to find the best compromise between drag and
negative lift.
[0111] Indeed, it should be noted that the aerodynamic lift of the
profile must be optimum in every position of the windscreen wiper
blade in relation to the surface 22 of the windscreen or the window
to be wiped. The two-dimensional simulations show that a profile
can have good performance levels for an angle of incidence equal to
zero, and its performance can be considerably reduced in more
extreme positions. The value of the angle of attack of these
extreme positions, defined by experimentation, varies between -10
et +10 degrees in relation to the theoretical vertical position on
the windscreen, corresponding to the to and fro positions of the
windscreen wiper blade when wiping in an alternating sweeping
movement.
[0112] The geometry of the top tip of the aerodynamic deflector 16
is also dimensioned and positioned with precision since it
influences the overall performance of the profile of the
aerodynamic deflector 16. Indeed, the smaller the projected
surface, the better the performance of the profile when positioned
at +10 degrees.
[0113] The tip of the deflector must be as thin as possible in
order to reduce the projected lift surface, the limit being set by
the production constraints. It must also allow the air flow to
remain attached and it must direct the latter such as to reduce the
size of the recirculation area behind the blade.
[0114] The following is a description of several alternatives of
embodiment shown in FIGS. 2 and following.
[0115] The windscreen wiper blade 10 shown in FIG. 2 is overall
similar to that of FIG. 1.
[0116] The leading edge sections AV and MN are symmetrical in
relation to the plane PVM and have a convex profile forming an arc
of circle.
[0117] The thin top part with vertical orientation 44 of the
aerodynamic deflector 16 is overall shifted transversally towards
the inside in the direction of the plane PVM. In this way there
exists a gap "d", which is the horizontal distance.
[0118] The top part of the windscreen wiper blade 10 shown in FIG.
3 is overall similar to that of FIG. 1.
[0119] The leading edge sections AV and MN are symmetrical in
relation to the plane PVM and have a convex profile forming an arc
of circle with a larger radius.
[0120] The thin top part with vertical orientation 44 of the
aerodynamic deflector 16 is overall shifted transversally towards
the inside in the direction of the plane PVM. In this way there
exists a gap "d", which is the horizontal distance.
[0121] Furthermore, below the horizontal plane that passes through
the opposing symmetrical points V and N, in other words, below the
leading edge, the front VU and rear NQ sections are no longer
vertical, instead they are tilted in the direction of the plane PVM
in order to facilitate the division of the air flow into two parts,
without any excessive square edges thanks to the transition between
the section forming an arc of circle with a large radius AV and the
rectilinear section VU.
[0122] In the alternative embodiment shown in FIG. 4, when compared
with FIG. 1, it can be seen that the third front DE and rear FG top
sections are no longer rectilinear and vertical, but rather curved,
respectively forming convex and concave arcs of circles.
[0123] In this way, the top end point E of the section DE is higher
than the top end point F of the section GF with a flat free top
"edge" of the thin part 44, that is to say that the section EF is
rectilinear.
[0124] In the alternative embodiment shown in FIG. 5, when compared
with FIG. 1, it can be seen that the third top rear section FG is
rectilinear and vertical with its top end point F being the highest
point of the deflector 16, while the section EF which corresponds
to the top edge of the fine part 44 is a convex quarter circle.
[0125] In the alternative embodiment shown in FIG. 6, when compared
with FIG. 1, it can be seen that the leading edge AV comprises
longitudinal ribs 48. In a section view along the plane of the
figure, each rib can have a triangular or substantially square or
trapezoidal profile. The height of the ribs, the number of them and
their distribution can vary without departing from the context of
the invention, as is the case with their profile, which can also
be, for example, rounded and convex.
[0126] According to further alternative embodiments not shown:
[0127] the top edge of the aerodynamic deflector corresponding to
the section EF can comprise holes or notches or crimped sections,
longitudinally distributed along the trailing edge of the
aerodynamic deflector;
[0128] the concave section profile CE of the active part of the
aerodynamic deflector facing the wind does not necessarily form an
arc of circle with a constant radius, but can also comprise several
consecutive concave parts with different radii;
[0129] in a known manner, it is also possible to provide passages
or channels that pass transversally through the bottom part of the
aerodynamic deflector, forming venturi tubes that open through to
the rear face behind the wind in order to reduce the drag and the
water pull-back phenomenon.
* * * * *