DE102008023255A1 - Vehicle-interval radar for use as protective shield for motor vehicle, has defrosting device including connection device, in which compressed air and liquid mixture are combined, and is connected with pneumatic and hydraulic devices - Google Patents

Abstract

The radar (100) has a defrosting device (10) for defrosting an acryl glass panel (36) i.e. Plexiglas(RTM: light, transparent, weather-resistant thermoplastic). The device (10) has a connection device (14), in which compressed air and a liquid mixture (23) are combined. The device (10) is connected with a pneumatic device (10a) and a hydraulic device (16) and with an injector device (35) provided with an injector (35) by supply lines (13a, 13b, 24, 28, 33, 34). The device (16) is formed from a gear pump (17) and a spraying pump (18), and a throttle valve (19) and a check valve (20). An independent claim is also included for a method for defrosting an acryl glass panel of vehicle-interval radar.

Description

The The invention relates to a distance radar with an acrylic glass pane as a protective shield for a motor vehicle.

moreover The invention relates to a method for deicing an acrylic glass pane a distance radar.

distance radars of the type mentioned are known from the prior art and are the expert in a variety of designs known and common.

In general, the object of a distance radar in automobiles is to measure, depending on the vehicle speed, the distance of the moving vehicle to the vehicle in front, to optimally calculate this distance, to control it in a controlled manner and, if necessary, to trigger a braking operation. If the automatically triggered braking acceleration of -2 m / s ^{2 is} insufficient, the driver is prompted by a signal tone to control the braking process himself.

This Distance radar can be extraordinary for the driver to be helpful. It can be him during a long drive Relieving strain and, moreover, it helps rear-end collisions to avoid. A habituation is achieved quickly and so This device will be for the motorist with time almost indispensable.

The However, experience shows that during certain meteorological events the distance radar fails, without a time evaluable, unmistakable Warning to the driver to produce, namely to turn off the distance radar immediately, which for the road users have serious consequences can.

These critical weather situations are:
In case of precipitation: snowfall, especially at air temperatures around 0 ° C as well as freezing rain, but also
without precipitation: with hoarfrost and especially undercooled fog (possible, even without drastic reduction in visibility!).

While A ride can be done by the driver of this meteorological Conditions are not always correctly assessed.

In several critical weather situations was scary through the Driving behavior of the vehicle found that the distance radar, ge coupled with the cruise control failed. As a cause, it turned out that in two cases a layer of snow, in a third However, a hard encrusted layer of ice on the surface the acrylic glass of the distance radar, which during the ride in snowfall, or formed in subcooled fog would have.

To investigate the physical causes of the observed failures, it should be noted that to protect against precipitation and falling rocks of the distance radar head a Plexiglas, ie acrylic glass, in the radiator grille of the vehicle as a "shield" is installed. This amorphous polymethylacrylate (so-called plexi or acrylic glass) is characterized by a very low thermal conductivity value of λ = 0.158 kcal / mhgrd, Ernst Eckert: Introduction to heat and mass transfer. Publisher: Springer, Berlin, Göttingen, Heidelberg, 2nd edition, year of publication 1959, page 278 ]. This makes it a high grade thermal insulation material.

To meet z. As rainfall particles, such as raindrops or wet snow on the surface of the Plexiglas disk and lies the Driving temperature below 2 ° C, so its surface temperature, due to the heat of evaporation of the water, under 0 ° C so that the precipitating particles on its surface freeze up. They form a layer of ice. Your thickness can be during a few minutes increase in travel by several millimeters. From a certain layer thickness (the critical strength is different depending on how the crystal structure the frozen snow layer on the Plexiglas surface is just created) can the radar beams first no longer received, later no longer sent because of the ice or snow deposits on the Plexiglas surface are no longer "transparent" to them. The consequence of this is that the distance radar "blinds". It can, for. B. a preceding vehicle as a traffic obstacle not recognize more and the distance to him not at all determine more.

An indication on a display in the vehicle: "distance radar off", or "distance radar passive" and a short beep do not generally cause the driver to switch off the distance radar and the associated cruise control without delay and even adjust the driving speed to the traffic situation.

Around the temperature of a layer of ice 5 mm thick on the Plexiglas surface (120 mm × 130 mm) to increase a Kelvin would have an amount of heat of 0.0233 kcal be applied, whereas their Increase by 10 Kelvin but 10 times this value would require. When the vehicle is stationary that does not Problem dar. With a moving vehicle, this is due to the airstream, but hardly or not at all possible. It should be noted that the radar system radiate freely and the reflected beams can receive without interference effects got to.

The Generation or transmission of the necessary amount of heat to prevent icing or deicing in the direction of travel facing side of the acrylic glass can, for. B. by attaching Heating coils or not caused by ceramic heating elements become. This fact is due to the airstream and thereby that the radar beams in their propagation through any kind of metal parts would be disturbed, so that they are no longer with the required intensity emitted or received could; it would be no longer evaluable "phantom images". Another technical problem arises z. B. from the heat engineering Properties of acrylic glass.

Also due to the wind, the application fails convection heat originating from the engine compartment.

The Generation of a certain amount of heat in the immediate lower, rear space of the plexiglass disturbed the radar beams Not. However, by convection to the rear part of the Acrylic glass body transferred amount of heat not to his, in the direction of travel side ice-free too get or keep ice-free, since this amorphous material the Heat is highly isolated, and thus, at its transfer prevents.

Also extend the (long-wave) heat rays pointing in the direction of travel, which are generated by the hot engine parts, not to do this, the temperature on the, pointing in the direction of travel Side of the acrylic glass in wintry conditions To keep 0 ° C.

outgoing from the problems outlined and in appreciation of cited prior art in distance radars of the beginning mentioned type, the present invention is therefore the object of to provide a distance radar such that effective de - icing of the acrylic sheet as a protective shield of the Distance radar is guaranteed.

These The object is achieved with the features of claim 1.

advantageous Embodiments of the invention are manifested in the subclaims.

The The core idea of the invention is the combination of pneumatics with hydraulics, with a sufficient supply of heat to compressed air and secured to a liquid mixture. The use of nozzles causes the de-icing of the acrylic glass surface with the warm compressed air flow or with the jets of the liquid mixture. These jets are designed to be carried by the Compressor provided compressed air even for the extremely fine Atomization of the special liquid components are suitable and thus lead a cyclic regenerating Surface treatment of the acrylic glass, under consideration the airstream components, targeted and high quality enough.

The Automatic de-icing of the acrylic glass pane can only be successful be carried out when the influence of the airstream considered and an air jet or a liquid jet certain composition of this disc is imposed. This assumes that the center lines of these particle beams when Reaching the acrylic glass pane a predetermined track length and speed. In addition, the particle web, largely independent of the wind, the acrylic glass pane to hit at a suitable angle. The airstream may the Do not change the particle path length beyond a certain level. Experience has shown that the tolerance is max. + 25% the calculated optimal track length. Is this difference higher, so the wind can blow the particle to flutter bring or even carry. This is explained by that the airstream the flow angle of the particle beam basically enlarged and as a result whose ray the acrylic glass u. U. umschwenkt.

A meaningful specification of the particle track length, taking into account the direction of the center line of the particle flow and its Final speed (when hitting the acrylic surface) can only do so after a sufficient vector analysis of the airstream respectively. These parameters decide on the coordinates the impact of these currents on the acrylic glass pane.

The mathematically obtained results also provide the significant Statement that for a flutter-free particle beam a Nozzle outlet speed of at least 200 m / s to to a speed of 180 km / h is required.

For the analysis of the wind vectors, the so-called conformal mappings to the flow of curved plates as well as the superimposition of a parallel flow with a circulatory flow can be applied. These methods can be very effectively applied to planar, two-dimensional flows, as is the case here. Please refer [ Prandtl-Tietjens: Hydro- and Aeromechanics. Publisher: Julius Springer, Berlin, 2nd volume, year of publication 1931, page 185 ff. ] such as [ Bruno Eck: Technical Fluid Mechanics, Publisher: Julius Springer, Berlin, Göttingen, Heidelberg, 3rd edition, year of publication 1949, page 24, 29, 59, 63, 76 ].

To different are horizontal and vertical wind loads.

Horizontal wind load of the acrylic glass pane:
The horizontal cross section of the acrylic glass body, based on its front sides, shows that the side wings together form an obtuse angle of about 170 degrees. The sides are each about 66 mm long.

The shape of the acrylic glass body with its two wings can be approximated by the mantle of a circular cylinder with a suitable radius and axial tilt. The in 1 drawn circular cylinder arc is created by the intersection of a plane with the cylinder jacket, which is perpendicular to its axis and on the surface of the acrylic glass.

In the 1 The center line of the front of the acrylic glass (the so-called "fold line" of the acrylic glass), shown in the drawing, encloses an angle of approximately 70 ° with the horizontal plane (see also FIG 4 ). It follows that the axis of the fictitious circular cylinder must also include an angle of 70 ° with this plane.

For the setting up of a mathematical model became the acrylic glass body placed on a horizontal plane that the "crease line" of his Front with her an angle of 180 ° - 70 ° = 110 ° included. His wing cross sections were recorded and measured. Subsequently, the radius became of a spare arc and calculated fluidically optimized. It was found a radius of 70.8 cm, which inevitably also gives the radius of the circular cylinder.

The Indian 1 shown vertical cross-section in the middle of the acrylic glass body (with two wings) was replaced by a circular cylinder arc.

The Vector analysis of the wind moving on the acrylic glass screen horizontal was thus mathematically through this "artifice" allows.

The Results shown in Table 1, Table 2a, and Table 2b summarized, can be physically believable, in particular for distances of more than 1 m from the acrylic surface (i.e., from the cylinder jacket), clearly explained become.

The Calculations are for the largest wind load of the acrylic glass body (at 180 km / h) performed Service. For others, any wind speeds are to apply the results, it is only necessary to take into account that the amount of wind vectors is linear of the driving speed is dependent.

The Amounts for the horizontal wind vectors, for a travel speed of V = 50 m / s (180 km / h), 44 mm away from the fold line, are summarized in Table 1.

Of the Amount of horizontal wind load, at any point on the acrylic sheet, is linearly dependent on his Distance from the traffic jam point. For the horizontal wind components the stagnation points are on the crease line, for the vertical ones Wind components, however, on the lower edge of the acrylic glass pane.

It It can be assumed that on the fold line of the acrylic glass the horizontal wind vectors, approximated by the dynamic pressure 0 m / s. The wind vectors, which at the same, on the cylinder axis belong to vertical plane and the same distance from the acrylic glass fold line have (left and right), point out Symmetry reasons on the same amounts. This follows from the fact that here is an approximately two-dimensional level flow is present.

The fictional circular cylinder, whose shell replaces the acrylic glass panel and was used to calculate the horizontal wind components, has a radius of a = 70.8 cm ( 1 u. 2 ).

The Connecting line of the two upper attachment points of the liquid jet centerlines cuts the fold line of the acrylic glass at a height of 35 mm, measured from its lower edge.

Of the Center of the projection of the round distance radar head is located on the fold line of the acrylic glass, is about 50 mm from its bottom Edge removed and has a diameter of 88 mm.

A plane perpendicular to the acrylic surface and to the cylinder axis should cut this circle in the middle. It creates a circle on the cylinder as a cut surface with a radius of 70.8 cm ( 2 ) and on the acrylic glass two straight lines which result in two "sinews" of the "shell circle". These tendons have a length of approximately 44 mm ( 2 ). They represent, in the horizontal direction, to the right and left of the fold line, the radius of the projection of the spacer radar head ( 6 ). These distances, viewed from the center of the circular cylinder, can be seen at an opening angle of φ = 3.56 ° ( 2 ). This angle is also called the central angle. It remains constant for the calculation of wind amounts for different distances from the acrylic surface. The wind components for a distance of 1.6 mm from the surface of the acrylic glass serve as reference values for the investigation of the processes on its surface. The changes in their amounts, in the same direction, within 5 mm of their surface, are within the range of 0.03 m / s, or 0.5%.

V:

Ist die Fahrtwindgeschwindigkeit;

V_n:

stellt die auf die Acrylglasoberfläche senkrecht stehende Komponente, die sog. Normalkomponente des Fahrtwindes, dar; Da die Acrylglasplatte (die aus zwei zusammenhängenden Flügel besteht) mit dem Horizontalen einen Winkel von 70° bildet, wird die Normalkomponente des Fahrtwindes V_n berechnet nach der Formel: V_n = V·cos(90° – 70°) = V·cos(20°) ≈ 47 m/s (bei einer Fahrgeschwindigkeit von 180 km/h);

w_I:

Ist die sog. imaginäre Komponente von V. Sie steht senkrecht auf die Strömungsrichtung; verläuft parallel zur Ebene der Acrylglasoberfläche (vgl. 3 und 5). Ihr Betrag ist von der Fahrtwindgeschwindigkeit, von der Entfernung aus der Faltenlinie der Acrylglasplatte und vom Abstand von ihrer Oberfläche, abhängig. Es sind hier nur diejenige Komponenten entscheidend, die im Bereich von 0,0 mm bis 5,0 mm über der Acrylglasoberfläche entstehen;

w_R:

Ist die Realteil-Komponente von V_n und zeigt in Strömungsrichtung. Sie greift senkrecht auf die Acrylglasplatte bzw. auf den fiktiven Kreiszylinder an. Ihr Betrag ist ebenfalls von der Fahrtwindgeschwindigkeit, von der Entfernung aus der Mitte der Acrylglasplatte und vom Abstand von seiner Oberfläche, abhängig. In der Mitte der Platte ist Windstille (Staudruck!). Dies ist der Punkt am umströmten Körper, wo die Strömung sich aufteilt;

w:

Ist der resultierende Windvektor aus den Komponenten w_I und w_R. In größerer Entfernung von der Acrylglasplatte ist er identisch mit V_n (siehe Tabellen 1, 2a und 2b);

δ:

Ist der Tangentenwinkel (die Steigung), den der resultierende Windvektor w mit seiner Projektion auf der Acrylglasoberfläche einschließt;

a:

Ist der Radius des fiktiven Kreiszylinders. Er beträgt für die Analyse der horizontalen Windbelastung der Acrylglasscheibe (Tabelle 1) a = 70,8 cm und für die vertikale Windbelastung (Tabelle 2a und Tabelle 2b) a = 16,15 cm;

r:

Ist der Radius eines Kreises um die fiktive Kreiszylinderachse und stellt die Entfernung eines Bezugspunktes von seiner Achse dar. Es ist stets r ≥ a;

Δ:

Ist der Abstand von der Acrylglasscheibe: r – a;

φ:

Ist der Zentriwinkel. Er ist der Mittelpunktswinkel, zwischen zwei Kreisradien des Kreiszylinders. Siehe auch 2.

In the following, the characters or abbreviations used in Tables 1, 2a and 2b will be explained.

V:

Is the airstream speed;

V _n:

represents the perpendicular to the acrylic glass surface component, the so-called. Normal component of the wind, dar; Since the acrylic sheet (consisting of two continuous wings) forms an angle of 70 ° with the horizontal, the normal component of the wind V _{n is} calculated according to the formula: V _n = V × cos (90 ° -70 °) = V × cos (20 °) ≈ 47 m / s (at a driving speed of 180 km / h);

w _I :

Is the so-called imaginary component of V. It stands perpendicular to the flow direction; runs parallel to the plane of the acrylic glass surface (cf. 3 and 5 ). Their amount depends on the speed of air travel, the distance from the fold line of the acrylic sheet and the distance from its surface. Only those components which arise in the range of 0.0 mm to 5.0 mm above the acrylic glass surface are decisive here;

w _R :

Is the real part component of V _n and points in the flow direction. It attacks perpendicular to the acrylic glass plate or on the fictitious circular cylinder. Their amount is also dependent on the airspeed, the distance from the center of the acrylic sheet and the distance from its surface. In the middle of the plate is calm (dynamic pressure!). This is the point on the body around which the flow is divided;

w:

Is the resulting wind vector of the components w _I and w _R. At a greater distance from the acrylic sheet it is identical to V _n (see Tables 1, 2a and 2b);

δ:

Is the tangent angle (the slope) that the resulting wind vector w encloses with its projection on the acrylic surface;

a:

Is the radius of the fictitious circular cylinder. It is a = 70.8 cm for the analysis of the horizontal wind load of the acrylic sheet (Table 1) and a = 16.15 cm for the vertical wind load (Table 2a and Table 2b);

r:

Is the radius of a circle around the fictitious circular cylinder axis and represents the distance of a reference point from its axis. It is always r ≥ a;

Δ:

If the distance from the acrylic glass pane is: r - a;

φ:

Is the central angle. It is the midpoint angle between two circle radii of the circular cylinder. See also 2 ,

Each row of data in Table 1, 2a and 2b gives information about the position and tangent slope in a point of a preselected flow line. The flock of these streamlines, which belong to the same plane, gives the 2-dimensional plane flow around a curved plate, z. B. to this of the circular cylinder, which replaces the surface of the acrylic glass with a part of his coat. Each of these flow lines is characterized by its own constant. It can be determined by the angle φ, a, r and by the travel speed V.

The imaginary components of the wind vectors, starting from the center of the circle, the projection of the distance radar head here decide on the distribution of air and liquid particles on the acrylic glass surface in a horizontal direction. Through these components takes place the de-icing of this surface, mainly in a horizontal direction. They also create a surface boundary layer a thickness γ, which in turn is a cyclic-regenerating Surface treatment of acrylic glass allows.

The wind amounts for a distance of 1.6 mm from the surface of the acrylic glass are used as reference values for the determination of the parameters on its surface. The wind components, within the space of 4.8 mm above its surface, have a difference of no greater than 0.03 m / s or 0.5% (see Table 1). On the next page the Table 1. Table 1 follows V = 50 m / s (180 km / h) → V _n = 47 m / s a = 70.8 cm horizontal direction, wherein a central angle of φ = 3.56 ° [Mm] [cm] [M / s] [M / s] [M / s] Δ ₁ = 1.6 r ₁ = 70.96 w _I = 5.82 w _R = 0.12 W = 5.82 δ = 2.06 ° Δ ₂ = 3.22 r ₂ = 71.123 w _I = 5.81 w _R = 0.425 W = 5.82 δ = 4.24 ° Δ ₃ = 4.83 r ₃ = 71.285 w _I = 5.79 w _R = 0.636 W = 5.83 δ = 6.27 ° Δ ₄ = 6.44 r ₄ = 71.447 w _I = 5.78 w _R = 0.846 W = 5.84 δ = 8.29 ° Δ ₅ = 16.3 r ₅ = 72.429 w _I = 5.70 w _R = 2.09 W = 6.07 δ = 19.98 ° Δ ₆ = 179.0 r ₆ = 88.713 w _I = 4.77 w _R = 17.03 W = 17.68 δ = 74.35 ° Δ ₇ = 0.392 m r ₇ = 1.10 m w _I = 4.12 w _R = 27,47 W = 27.78 δ = 81.47 ° Δ ₈ = 2.661 m r ₈ = 3.397 m w _I = 3.04 w _R = 44.83 W = 44.94 δ = 86.12 ° Δ ₉ = 5.811 m r ₉ = 6.519 m w _I = 2.95 w _R = 46.36 W = 46.45 δ = 86.35 ° Δ ₁₀ = 31.52 m r ₁₀ = 32.225 m w _I = 2.92 w _R = 46,887 W = 46.98 δ = 86.44

Vertical wind load of the acrylic glass pane:

Of the vertical cut in the middle of the two wings of the acrylic glass body ("Crease line") is a straight line, which is a Angle of about 70 ° with its projection on the horizontal Includes level. The height of the acrylic glass pane along this straight line is about 120 mm.

If the acrylic glass body is mirrored on the horizontal plane while its lower edge remains in this plane, then two bodies are obtained, similar to an open book, which enclose an angle of (2 × 70 °) 140 ° with each other. Its lower edge forms the symmetry axis, which at the same time represents the so-called locus of all stagnation points (cf. 3 ).

Their two wing surfaces can be approximately replaced by the shell of a horizontal circular cylinder of suitable diameter. The in 3 drawn circular arc of the cylinder (its mirror image is shown in dashed lines) replaces the two wings. On the acrylic glass surface acting wind can be calculated and analyzed in detail for the real area. A plane which is perpendicular to the above-mentioned axis produces a straight line or its mirror image on the acrylic glass. She was by one continuous line, however, its mirror image shown in dashed lines (see. 3 ).

Of the Radius of the circular cylinder was determined graphically and fluidically optimized. He is a = 16.15 cm.

The landing points of the air and liquid beam centerlines, which are aligned by the nozzles of the nozzle means of the deicer, impinge on their surface at a height of about 19.5 mm measured from the lower edge of the plexiglass disk. The center of gravity of the larger elliptical scattering surfaces of the particles lie at a height of 35 mm (the associated central angle is 11 °), their upper edge approximately at 75 mm (the associated central angle is 19 °) away from the lower edge of the acrylic glass (cf. , 4 and 5 ).

The amounts of the vertical wind components were therefore determined at a distance of 35 mm and 75 mm from its lower edge (this edge is also the locus of all stagnation points for the vertical wind components, cf. 5 ).

The next page is followed by Table 2a, followed by Table 2b. Table 2a φ = 11 °; V = 50 m / s (180 km / h) → V _n = 47 m / sa = 16.15 cm vertical direction, 35 mm from the lower edge of the acrylic glass [Mm] [cm] [M / s] [M / s] [M / s] Δ ₁ = 1.6 r ₁ = 16.31 w _I = 17.76 w _R = 0.9 W = 17.8 δ = 2.9 ° Δ ₂ = 3.22 r ₂ = 16.47 w _I = 17.59 w _R = 1.79 W = 17.7 δ = 5.81 ° Δ ₃ = 4.83 r ₃ = 16.63 w _I = 17.42 w _R = 2.64 W = 17.62 δ = 8.62 ° Δ ₄ = 6.44 r ₄ = 16.79 w _I = 17.26 w _R = 3.47 W = 17.61 δ = 11.4 ° Δ ₅ = 16.3 r ₅ = 17.78 w _I = 16.4 w _R = 8.07 W = 18.25 δ = 26.2 ° Δ ₆ = 179.0 r ₆ = 34.05 w _I = 10.99 w _R = 35.76 W = 37.41 δ = 72.91 ° Δ ₇ = 0.392 m r ₇ = 0.554 m w _I = 9.73 w _R = 42.21 W = 43.32 δ = 77.01 ° Δ ₈ = 2.661 m r ₈ = 2.823 m w _I = 9.0 w _R = 45.99 W = 46.86 δ = 78.93 ° Δ ₉ = 5.811 m r ₉ = 5.973 m w _I = 8.97 w _R = 46.1 W = 46.97 δ = 79.0 ° Δ ₁₀ = 31.52 m r ₁₀ = 31.682 m w _I = 8.97 w _R = 46.14 W = 46.99 δ = 79.0 ° Table 2b φ = 19 °; V s = V → _n = 47 m / sa = 16,15 cm vertical direction, 75 mm 50 m / (180 km / h) from the lower edge of the acrylic glass [Mm] [cm] [M / s] [M / s] [M / s] Δ ₁ = 1.6 r ₁ = 16.31 w _I = 30.30 w _R = 0.87 W = 30.31 δ = 1.64 ° Δ ₂ = 3.22 r ₂ = 16.47 w _I = 30.01 w _R = 1.72 W = 30.06 δ = 3.28 ° Δ ₃ = 4.83 r ₃ = 16.63 w _I = 29.73 w _R = 2.54 W = 29.83 δ = 4.9 ° Δ ₄ = 6.44 r ₄ = 16.79 w _I = 29.45 w _R = 3.34 W = 29.64 δ = 6.47 ° Δ ₅ = 16.3 r ₅ = 17.78 w _I = 27.93 w _R = 7.77 W = 29.0 δ = 15.56 ° Δ ₆ = 179.0 r ₆ = 34.05 w _I = 18.74 w _R = 34.44 W = 39.21 δ = 61.45 ° Δ ₇ = 0.392 m r ₇ = 0.554 m w _I = 16.60 w _R = 40.65 W = 43.91 δ = 67.79 ° Δ ₈ = 2.661 m r ₈ = 2.823 m w _I = 15.35 w _R = 44.29 W = 46.88 δ = 71.00 ° Δ ₉ = 5.811 m r ₉ = 5.973 m w _I = 15.31 w _R = 44.41 W = 46.97 δ = 71.0 ° Δ ₁₀ = 31.52 m r ₁₀ = 31.682 m w _I = 15.30 w _R = 44.45 W = 46.99 δ = 71.0 °

The particle beam without consideration of the airstream has the vertical component at the point of impact: A V = 50 m / s · cos (90 ° -70 °) · sin (φ 2 ) = 45.4 m / s. Where φ ₂ = 75 °
(φ ₂ is the angle that the particle beam encloses with the horizontal plane or with the nozzle tube).

Its horizontal component has an impact at the point of impact of: A H = 50 m / s · cos (90 ° -70 °) · cos (φ 2 ) = 11.5 m / s

These Speed components of the particle beam are responsible for the targeted distribution of the particles as well as for Breaking up or removing the ice particles during slow-moving or when the vehicle is stationary.

About that In addition, they are responsible for the formation of a so-called. Boundary layer on the acrylic surface. Within this The boundary layer becomes the individual liquid particles due to the friction on the surface of the acrylic glass in slowed her movements. So the particles that can a size of not more than 0.1 mm, even easier to adhere to the surface of the acrylic glass and they coat. It is for a high quality wetting the acrylic surface indispensable.

The In detail here presented vector analysis of the airstream has it at all allows to recognize what physical conditions must meet a defrosting device, so also at higher speeds for acrylic glass surfaces Any form can be successfully used.

in the These conditions are shown below.

Horizontal component of the airstream:

The horizontal velocity component of the particle beam without wind is: A _H = 11.5 m / s.

The both Aufsetzpunkte the main particle beams are approximately 22 mm, to the left and right of the fold line of the acrylic glass. The particles flow with no airflow at 11.5 m / s from both Pages in the middle on the acrylic glass fold line too.

The calculation results in Table 1 show:
The normal airstream component (at a vehicle speed of 180 km / h) has a horizontal component of 5.8 m / s, 44 mm from the center of the acrylic glass and is approximately constant (see Table 1, in the range of 1.6 mm to 4.83 mm from the acrylic surface). Their direction points from the center of the circle to the right and to the left side of the acrylic glass plate (cf. 6 ).

The resulting horizontal flow velocity has the amount in the touchdown points: V GesHor = [11.5 2 + 2.9 2 + 2 x 11.5 x 2.9 x cos (0 ° to 180 °)] 1.2 = 8.6 m / s

Your Direction points to the fold line of the acrylic glass.

The Direction of particle flow is thus maintained, their however, horizontal propagation speed becomes (at a vehicle speed of 180 km / h) slowed down by about 25%.

The effect of the horizontal component of the wind (W _I ) on the particle path can be defined mathematically as follows:
Mathematically formulated path inclination at any point of the particle path: tgφ = B / (E - X) (Eq. 1)

tgφ indicates the tangent slope (steepness) in the individual points of the particle web on the way from the nozzle exit to the acrylic glass surface under the action of the travel wind (W _I ) in the horizontal direction.

Of the Variable X is equal to 5.05 mm (smallest distance of the nozzle exit to acrylic surface) minus distance (the smallest distance) a point of the particle web to the acrylic surface.

By integration, one obtains therefrom the coordinates of the particle web, under the influence of the horizontal component of the airstream (W _I ):
Mathematically formulated course of the particle web: y (X) = -B ln (1-X / E) (equation 2)

B and E are constant and have for the nozzle exit velocity of w ₀ = 300 m / s and for W I = (5.8 m / s) / 2 = 2.9 m / s; φ 1 = 180 °, A _H = 11.5 m / s; φ ₂ = 75 °
the following amounts:
B = 335.77 mm; E = 89.57 mm

These mathematical relationships with the constants mentioned here at a distance of 1.6 mm above the acrylic glass pane give the following results: φ = 75.83 ° Δφ = 75.83 ° - 75 ° = + 0.83 ° y (X) = 18.61 mm Δy (X) = 0.0 mm

Which values do these values assume for the nozzle exit velocity of w ₀ = 100 m / s, if all other values remain unchanged?

This is calculated for
B = 111.92 mm
E = 29.32 mm φ = 77.66 ° Δφ = 77.66 ° - 75 ° = + 1.66 ° y (X) = 20.15 mm Δy (X) = +1.49 mm

One Comparison of these results shows that the horizontal component the wind a rel. little influence on the particle beam exercises. The role of the nozzle exit velocity but for the stability of the particle beam is already recognizable here.

As it became visible here, the particle beam raises slightly before reaching the acrylic sheet by 1.66 ° and hits the spot from 20.15 mm to a higher wind speed. Thereby if he is forcibly taken one step further, etc., until he finally reaches a distance y (X) where this Difference sizes have a negligible amount. There then the stability of the particle beam is temporary reached.

In this process, it should be noted that the opening angle of the particle beam is about 14 ° [ Bruno Eck: Technical Fluid Mechanics, Publisher: Julius Springer, Berlin, Göttingen, Heidelberg, 3rd edition, year of publication 1949, page 153 ]. The side winds while driving are also still to be considered.

By an iterative calculation method, the limits below accurately determined.

Vertical component of the airstream A _V :
Mathematically defined consequences for the particle web:
The particle beam without wind has a vertical component at the attachment points: A V = 50 m / s · sin (75 °) · cos (90 ° - 70 °) = 45.4 m / s.

The both main particle beam attachment points are approximately 19.5 mm from removed the bottom edge of the acrylic sheet.

The Vertical components of the wind in these points can be from Tables 2a and 2b. It is important to take into account that their amount, at constant speed, grows linearly with the distance from the bottom of the acrylic sheet.

The Tables 2a and 2b show that the vertical velocity components, in the range of 1.6 mm to 4.83 mm above the acrylic sheet, are largely constant. On the contour line of 35 mm on this disc gave an average for the vertical flow velocity, according to Table 2a, of 17.5 m / s (at a speed of 180 km / h).

This yields, for the 19.5 mm contour line, that is to say in the attachment points of the particle beam center lines, the vertical velocity components of the travel wind to A _V = 9.75 m / s (symmetrical to the acrylic glass fold line).

The resulting vertical flow velocity in the touchdown points thus has the amount: V GesVer = [45.4 2 + 9.75 2 + 2 · 45.4 · 9.75 · cos (90 ° - 90 °)] 1.2 = 55.15 m / s

The effect of the vertical component of the wind (W _I ) on the particle path can be defined mathematically as follows:
Mathematically formulated path inclination at any point of the particle path: tgφ = 2D + tgφ 2 + D / C · X (equation 3)

tgφ indicates the tangent slope (steepness) in the individual points of the path of the particle beam under the action of the travel wind (W _I ) in the vertical direction. This mathematical relationship states that the farther a particle moves away from the nozzle exit, the more forced it, forced by the vertical component of the wind, onto a railway line whose tangent slope increases linearly with the distance!

By integration, one obtains therefrom the coordinates of the individual points of the particle web under the action of the airstream (W _I ) in the vertical direction:
Mathematically formulated course of the particle web: y (X) = (2D + tgφ 2 ) · X + D / 2C · X 2 (Equation 4)

Out In this context, it can be seen that the further the particles of the Remove the outlet of the nozzles, the more they go through brought the vertical component of the airstream, instead of at a straight line to move on a parabolic-shaped railway line and thus experience a constant acceleration. she leads to make them more and more of the acrylic surface remove.

C and D are constants and have for the nozzle exit velocity of w ₀ = 300 m / s
also for
W _I = 9.75 m / s, φ ₁ = 90 °
and
A _V = 45.4 m / s and φ ₂ = 75 °
the following values:
C = 0.104 mm
D = 1.49 10 ^-2
and
tgφ ₂ = 3.732
2D + tgφ ₂ = 3.7618
D / C = 0.143 mm ^-1
D / 2C = 0.0716 mm ^-1

The above mathematical relationships (Eqs. 3 and Eq. 4) give the following results with these constants: φ = 77.34 ° and Δφ = 77.34 ° - 75 ° = + 2.34 ° y (X) = 19.84 mm Δy (X) = +0.53 mm

When the nozzle exit velocity of
w ₀ = 100 m / s is:
Step 1: 2D + tgφ 2 = 3,821 D / C = 0.43 mm -1 D / 2C = 0.215 mm -1

Using Eqs. (3) and Eq. (4): φ = 80.4 ° and Δφ = 80.4 ° - 75 ° = + 5.4 ° y (X) = 23.5 mm Δy (X) = 23.5 - 19.31 = + 4.19 mm

By a multiple stepwise calculation one receives almost the exact final results:
At the new attachment point of the particle beam, 23.5 mm along the particle path, there is a vertical wind speed of
W _I = 11.75 m / s.

This value results in
2nd step: tgφ = 3.84 + 0.517x y (X) = 3.84 x X 0.2587 mm -1 · X 2 φ = 81.03 ° Δφ = 81.03 ° - 75 ° = + 6.03 ° y (X) = 24.6 mm Δy (X) = 24.6 mm - 19.31 = 5.29 mm

At this new distance of 24.6 mm but there is a vertical wind speed of
W _I = 12.3 m / s.

This results in
3rd step: tgφ = 3.845 + 0.542 mm -1 · X y (X) = 3.845 X + 0.22708 mm -1 · X 2

The new values are: φ = 81.2 ° Δφ = 81.2 ° - 75 ° = + 6.2 ° y (X) = 24.89 mm Δy (X) = 5.58 mm

This Value pair represents approximately the coordinates of the touchdown point of the particle beam with a temporary stability represents.

The particle path length is under the influence of the travel wind speed of 180 km / h and at a nozzle exit speed of w ₀ = 100 m / s 29% higher than the particle length without wind. The direction of the particle beam is raised by an angle of 6.2 ° and can hardly reach the acrylic glass pane. The particle beam tends to flutter.

Thus, it can be stated that at a travel speed of 180 km / h, a defined distribution of the fluid, at a nozzle exit speed of W ₀ = 100 m / s, is no longer present.

Calculation of the value pair for a nozzle exit velocity of W ₀ = 200 m / s:

With the newly calculated constants, the value pair becomes:
Step 1: φ = 78.3 ° Δφ = 78.3 ° - 75 ° = + 3.3 ° y (X) = 20.74 mm Δy (X) = 1.4 mm

At this point, the vertical wind speed of
W _I = 10.37 m / s
2nd step:
D = 2.374 10 ^-2
C = 0.104 mm φ = 78.42 ° Δφ = 78.42 ° - 75 ° = + 3.42 ° y (X) = 20.92 mm Δy (X) = 1.61 mm

This Pair of values was carried through one, in two steps Iteration and can be considered as the final result.

It can be deduced from this that a nozzle exit speed of W ₀ = 200 m / s must be taken as a minimum requirement, so that a sensible particle distribution is ensured on the acrylic glass pane under the action of the airstream up to 180 km / h.

Around to be able to uncover the true circumstances only vehicle pumps, which basically for the Windscreen cleaning are used.

Experiment design and determination of results:
A precisely measured amount of 4 cm ³ of liquid, which is also used in the de-icing device, was allowed to flow through the nozzle device (2 nozzle openings, each 0.4 mm in diameter) several times. Two pumps were connected in series (as they are also used in the deicing device) and operated with full battery voltage. The time for a full spray was stopped and averaged.

The Time for pumping this amount was on average 3.5 seconds. The speed is calculated as v = 4.55 m / s.

at Only 100 km / h driving speed (28 m / s) prevails at the touchdown points the upper beam center lines, 19.5 mm from the lower edge of the Plexiglas disk 5 m / s vertical wind speed.

To The calculation of the constants could be done for the higher ones Speeds derived in the vertical direction mathematical Relationships are also applied:

The Gl. 3 and Eq. 4 result: tgφ = 4.738 + 4.837 mm -1 · X y (X) = 4.738 X + 2.4183 mm -1 · X 2

They yielded the following results: φ = 87.96 ° Δφ = 87.96 ° - 75 ° + 13 ° y (X) = 79.3 mm Δy (X) ≈ 60 mm

from that can be seen that the liquid used, at a vehicle speed of 100 km / h, almost never the acrylic surface, at most its upper edge, and thus its de-icing only when the vehicle is stationary.

in the Within the scope of the present invention, the vector analysis of the airstream, based on the acrylic glass pane as a protective shield of the radar in automobiles, especially detailed. These is u. a. to justify that the icing of the acrylic sheet through a special, cyclic-regenerating surface wetting, prevented, at least made difficult, should be. Due to the friction effect of Liquid particles on the surface of this Acrylic glass plate should remain attached to the particles and so their Wetting. This is the formation of a boundary layer required on its surface, with a thickness which equal to or greater than the median size the liquid particles themselves.

From the substance constants: Kinematic toughness ν for ethylene glycol, at an air temperature of 0 ° C and at an air pressure of 1 at, as well as from the vertical and horizontal airstream components W _I , the boundary layer thicknesses were determined for certain levels on the acrylic glass plate. For this purpose, the wind speeds for the horizontal direction were taken from Table 1, 44 mm away from the fold line of the acrylic glass and 1.6 mm above the plate.
W _I = 5.82 m / s.

For ethylene glycol, ν = 0.22 cm2 / s, [ Gröber / Erk / Grigull: The basic laws of heat transfer, Publisher: Springer, Berlin, Heidelberg, New York 3rd edition, year of publication 1988, page 422 ].

This yields the Reynolds number: Re = [582 cm / s x 4.4 cm] / 0.22 cm 2 / s = 11640,0 (the flow is laminar) and from this the boundary layer thickness γ [ Bruno Eck: Technical Fluid Mechanics, Publisher: Julius Springer, Berlin, Göttingen, Heidelberg, 3rd edition, published in 1949, page 145 ], for ethylene glycol:
γ _ath = 408 μm

The boundary layer thickness is linearly dependent on the distance from the center of the acrylic glass and thus, at a distance of 22 mm from the fold line (in the middle of the spray surfaces), is half this value. (see also 6 ).

The boundary layer thickness γ _EtH for the horizontal direction, in the middle of the large striping strips is thus, at a travel speed of 180 km / h:
γ _eth = 204 μm,
at a driving speed of 100 km / h: ν GesHor = [11.5 2 + 3.25 2 + 2 · 11.5 · 3.25 · cos (0 ° - 180 °)] 1.2 = 8.25 m / s Re = [825 cm / s x 4.4 cm] / 0.22 cm 2 / s = 16500 you get
γ _etching = 171 microns

For the center of the strip, with the vertical wind component, from Table 2a: W _I = 17.6 m / s, at a distance of 35 mm from the lower edge of the acrylic sheet:
The boundary layer thickness γ _eth for the vertical direction, in the middle of the large striping chips, at a travel speed of 180 km / h:
γ _eth = 209 μm,
at a driving speed of 100 km / h:
γ _eth = 280 μm

The boundary layer thickness γ _EtH for the vertical direction, at the upper edges of the strip strips, results γ _EtH , with the vertical wind component, from Table 2b:
W _I = 30.3 m / s, at a distance of 75 mm from the lower edge of the acrylic sheet, at a speed of 180 km / h:
_eth γ = 233 microns,
at a driving speed of 100 km / h:
γ _eth = 312 μm

In the following, the invention is based on the 7 explained in more detail. It shows, in the part: "Summary", in a schematic representation:
A "space radar for all-weather use" according to the invention.

7 shows an inventive distance radar for all-weather use, with the reference numeral 100 is provided and in front of the embodiment shown here in addition to the de-icer 10 with its components only its protective shield in the form of plexiglass 36 lets recognize.

The pneumatic device 10a of the distance radar 100 has a compressor 11 in the form of a diaphragm pump, which is the air 12 from the area bounded by a side luggage room wall and an exterior body of an automobile via an air filter 12a sucked, compressed to a pressure of over 1 bar and through a flexible, reinforced with glass fiber tube 13a to flow into an engine room of an automobile. Here she is in a teflon tube 13b which can withstand an ambient temperature of well over 100 ° C. The hose 13b is to a connection device 14 connected by a metal box 15 protected with removable lid. It is permanently installed on the lower side of the engine cover in the car. Through the hose 13b is the compressed air, through the hose nozzle 25b , the connection device 14 fed.

The hydraulic device 16 consists mainly of a self-priming gear wheel 17 and a spray pump 18 which are interconnected to a cascade. The spray pump 18 is controlled by a controllable throttle valve 19 completed, at the output of a check valve 20 connected.

The gear pump 17 sucks out of the additional container 21 via a sintered filter 22a a liquid mixture 23 and thus feeds the connected to her spray pump 18 ,

By an interval control of the pump excitation as well as by the adjustment of the throttle valve 19 becomes the liquid mixture 23 , which at certain intervals in the fuel hose 24 pumped in, exactly adjusted. The fuel hose 24 , which is provided with a vulcanized Textilumflechtung, has an inner diameter of about 3.2 mm and a wall thickness of about 2 mm and is after DIN 73379 produced. He also becomes the connecting device 14 led and there to a metal hose nozzle 25a connected.

In the connection device 14 be the compressed air and the liquid mixture 23 in a Y-shaped pipe structure 26 brought together without feedback.

The common exit 27 forms a metal hose nozzle, on which a fuel hose 28 is appropriate. The hose 28 is guided on the lower side of the motor cover of an automobile in the direction of the radiator grille. It ends at the middle branch 32 a pipe structure 29 which has a T-shape and the side arms 30 . 31 having. The pipe structure 29 is suitably mounted in front of the radiator grille of the automobile, also on the lower side of the engine hood of the automobile. His job is in the middle branch 32 incoming compressed air or the liquid mixture 23 evenly distributed in the side arms 30 . 31 to flow in. To the side arms 30 . 31 is ever a piece of fuel hose 33 . 34 , a length of about 25 cm, connected. Through the hoses 33 . 34 becomes a nozzle device 35 from both sides with the compressed air or with the liquid uniformly charged.

The nozzle device 35 is the shape of the lower edge of the plexiglass 36 simulated. Their length depends on the width of the plexiglass 36 on its lower side. The nozzle device 35 is in the form of a tubular construction and is mounted on the grille edge of an automobile so as to cover the outer, lower edge of the plexiglass 36 touched. The tube construction is again in the form of a brass tube. In this brass tube, with an outer diameter of 6 mm and a wall thickness of 1 mm, are three nozzles 37 , which, relative to the vertical center line ("fold line") of the acrylic glass 36 , asymmetrically arranged, screwed in and after their alignment, be soldered. The nozzles 37 So are based on a centerline, which is the surface 38 of acrylic glass 36 divided into two equal halves, arranged asymmetrically. The whole nozzle device 35 is wrapped with a special, waterproof, black heat shrink tubing and welded by hot air on her. The openings of the nozzles 37 are then exposed.

This plastic casing serves to protect the nozzle device 35 against falling rocks and at the same time for its thermal insulation, so that the heated compressed air flowing in this pipe is not appreciably cooled by the wind.

The asymmetrical arrangement of the nozzles 37 has proved to be advantageous for fluidic reasons. It facilitates the destruction of, at the Plexiglas 36 possibly formed ice layer as well as the outflow of the mixture and the melt with stationary vehicle. The flow cross-sectional area of the nozzles 37 is about 0.13 mm ² . The nozzle centers are from the surface 38 of the plexiglass 36 about 5 mm away. They are aligned so that the jet of compressed air or liquid mixture 23 the surface 38 of the plexiglass 36 reached only at a distance of about 20 mm, measured along the fluid line.

From the flow rate of air, which per unit time in the nozzle device 35 flows in, is the average flow velocity of the air at the outlet of the nozzles 37 easy to calculate. It is at the first, detected by the flow nozzle 37 not less than 300 m / s.

By this high exit velocity is first achieved that the airstream, the flow direction of the compressed air or the liquid mixture 23 , to the surface 38 of the plexiglass 36 , not drastically influenced up to a driving speed of 180 km / h, since the flow velocity at the center of the flow cone is still min. 50 m / s (180 km / h). Thus, it is largely ensured that the air or particle flow the surface 38 of the plexiglass 36 reached there and parts where it must come to effect. The from the surface 38 of the plexiglass 36 detached ice or snow particles are "pushed" upwards or sidewards by the compressed air and by the wind. On the surface 38 of the plexiglass 36 form so first, due to the setting of the nozzles 37 and by the beam expansion, small elliptical ice or snow-free areas. In the ice layer thus forming small ice-free areas, namely where these streams of small particles, consisting of heated compressed air or at times from liquid droplets (during the pumping interval, it is the liquid jets, then it, at the beginning of the subsequent compressor phase, liquid particles , in the order of <100 microns, which are caused by the atomization of the liquid) impinge on their surface. They attack the ice layer at the formed edges from below. The warm air flow from the nozzles 37 Combined with the airstream components, the ice layer continually attacks and blows up at these edges.

A vehicle that has a speed of 100 km / h, deposited a distance of approximately 28 m per second, so much less than the above-mentioned nozzle exit velocity of the compressed air. The latter increases with the distance from the exit of the nozzles 37 to the surface 38 of the plexiglass 36 out asymptotically as 1 / s (if s means the length of the track on the particle path) and is still about 50 m / s (or 180 km / h) in still air after a running distance of 20 mm. At this speed, the air particles hit the surface when the vehicle is stationary 38 of the plexiglass 36 on. Due to the airstream components, the particle flows to the surface 38 of the plexiglass 36 easily nestled or, depending on the height of the driving speed, also be moved in an undefined direction, whereby, however, the efficiency of these particle streams, partially or completely, could be repealed.

The side arms 30 . 31 of the pipe structure 29 are each with a fuel hose 33 . 34 provided with a length of about 25 cm. Through the hoses 33 . 34 becomes the nozzle device 35 from both sides with compressed air or at times with the liquid mixture 23 evenly charged. Each side of the fuel hose 33 . 34 is provided with the vulcanized Textilindflechtung and bifilar with a resistance wire (made of Konstantan) evenly wound several times in such a way that these tubes 33 . 34 zweckmäß ig can be heated.

The heating power is, with a DC voltage of 13.0 volts, 45 watts. Thereby, the temperature of the compressed air can be increased, so that in a continuous operation and at a travel speed of 100 km / h, this min. 12 Kelvin above the air temperature. This is steadily through a at the nozzle device 35 fastened and 35 mm in front of the first nozzle 37 Placed Pt 100 sensor measured and displayed in the passenger compartment on an additional meter to control the so-called β-version.

This temperature increase is required to allow the surface 38 of the plexiglass 36 can also be kept free of ice, if during driving the air temperature drops down to -10 ° C and in the additional container 21 no antifreeze is available anymore. Below this air temperature, however, is the additional tank 21 with a mixture of antifreeze and water in a suitable ratio (according to the expected running wind temperature) and with a special polymer agent for regenerating surface treatment of the surface 38 of the plexiglass 36 fill.

The above-mentioned temperature gradient can only by a suitable heating and extensive heat insulation of the fuel hoses 33 . 34 be achieved. After seeing both sides of these tubes 33 . 34 wrapped with a resistance wire bifilar, they were plugged into a shrink tube. This was then by hot air on the hoses 33 . 34 vulcanized that the structure is completely waterproof. The resulting heated fuel hoses 33 . 34 several layers were heat-insulated with a glass cloth tape and wrapped several times with a tissue adhesive tape. The latter serves not only for external protection, but also for additional thermal insulation.

These flexible fuel hoses 33 . 34 are bent in shape, similar to the Greek letter Ω, and the back of the plexiglass 36 so generously framed and attached to the lower side of a hood and radiator grille bars of a motor vehicle. When the engine hood is closed, the molded pipe complex lies between the Plexiglas 36 and not shown here round radar head of the distance radar 100 , This shape and the mechanical suspension ensure that this complex does not interfere with the radar system. The nozzle device 35 is flexibly connected to the "feet" of this Greek character, through a special corner-tube combination.

The distance radar 100 is in an in 7 not shown round plastic housing installed. The housing has an outside diameter of 88 mm and is fixed in front of the heat exchanger of the engine of the automobile. Its surface thus has a maximum size of about 61 cm ² . It is through the Plexiglas 36 , which is integrated in the hood, completely concealed and serves as a shield against precipitation, rockfall, etc. This shield is z. B. slightly trapezoidal and has the dimensions: 120 mm × 140 mm × 120 mm (height, width of the upper edge, width of the lower edge) and thus a surface size of almost 156 cm ² .

The moving air and liquid particles form a stream of material before they reach the surface 38 of the plexiglass 36 to reach. You meet there with a rel. high speed and they melt (widen). It also form elliptical distribution surfaces, which, depending on the setting of the nozzles 37 , can easily overlap. These three elliptical areas form a nearly elliptical distribution of the scattered particles. The surface area thus generated is decisive for the assessment of the effective area size of the de-icing as well as the cyclic-regenerating treatment of the plexiglass 36 in its first phase (ice or snow layer on the Plexiglas 36 available). The large axis of the so-called "compensation ellipse" results from the distance of the outer nozzles (90 mm) in the nozzle device 35 , half of the minor axis was measured when the vehicle was at rest and is about 75 mm. This is the theoretical deicing area on the Plexiglas 36 a max. Size: π · b / 2 · a / 2) / 2, that is, (3.14 × 90/2 mm × 75 mm) / 2, or 53 cm ² . See also: [ Bronstein-Semendjajew: Taschenbuch der Mathematik, Publisher: Harri Deutsch Zurich and Frankfurt / M, 9th edition, year of publication 1969, page 177 ].

The distance radar 100 radiates over a round surface of max. 61 cm ² . Since the effective surface size at Plexiglas 36 thereafter about 80% of the cross-sectional size of the in 7 not shown Radarkopfes and mainly directly opposite the housing of the distance radar 100 Radar radiation can be radiated undisturbed after a successful de-icing process. In case of premature switching on the de-icing device 10 However, an icing of the entire Plexiglas 36 be prevented. Through the device 10 the radar system is in no way disturbed in its function.

The timing of the pneumatic device 10a , the pumps 17 . 18 , the valves 19 . 20 as well as the heating of the hoses 33 . 34 takes place by means of several programmable so-called multifunction time relays. These units are characterized among other things by differently adjustable switching intervals, turn-on or drop-off delay times. They are combined to form a so-called time and interval sequencer 39a , the time liche flow control of the pneumatic device 10a , the pumps 17 . 18 , the valves 19 . 20 as well as the heating of the hoses 33 . 34 as well as the cyclic repetition of the system tasks accomplished.

The Electronics is built in the so-called. C-MOS technology and has therefore a high interference immunity. It is powered by the vehicle battery voltage provided.

The compressor 11 and the heater, in the form of the above-described heating coil in the form of the wound resistance wire, the hoses 33 . 34 in front of the nozzle device 35 are coupled only in time, the relay contacts provided for their activation, however, are galvanically isolated from each other for safety reasons.

The pumps 17 . 18 are so excited that the pressure maximum to be established by the nozzles 37 only reached after the compressor 11 certainly no more air carried. By the duty cycle of the pumps 17 . 18 and by adjusting the throttle valve 19 that is achieved from the liquid mixture 23 in the form of the mixed liquid (mixture) in the additional container 21 Approximately 5 cm ³ in the, on the check valve 20 connected fuel hose 24 is pumped. The check valve 20 prevents the backflow of liquid through the pumps 17 . 18 in the additional container 21 and builds in the fuel hose 24 a liquid column. The fuel hose 24 extends to the connection device 14 , Behind it follows the fuel hose 28 , The total content of this branch, determined by its internal cross-section and by its total length, is a maximum of 4 cm ³ . The pumps 17 . 18 during excitation, carry a total amount of the liquid mixture 23 of about 5 cm ³ , passing through the side arms 30 . 31 the on the pipe structure 29 attached fuel hoses 33 . 34 a quantity of liquid not more than 4 cm ³ is pressed through. After that, the pumps are 17 . 18 off. As a result, it stays in the heated fuel hoses 33 . 34 a residual amount of liquid of about 1 cm ³ back.

After the pumping operation, the defrosting device is turned on for about 40 seconds 10 completely shut off. During this time, this residual fluid takes up in the heated fuel hoses 33 . 34 40 seconds lingers, the amount of heat stored there in part, so that their temperature is increased significantly. During the subsequent startup of the compressor 11 This residual liquid (at elevated temperature) is exposed to the compressed air. This warm liquid is passed through the compressed air to the outlet of the nozzles 37 accelerated very strong and then through the nozzles 37 atomized. These liquid droplets, barely larger than 100 μm, are targeted at the surface at a high speed 38 of the plexiglass 36 sprayed. Their final speed is barely below that of the air particles, that is approximately at 50 m / s.

The "driving force" of the particle beam (and thus the final velocity of the particles upon reaching the surface 38 ) is relevant for a variety of reasons. On the one hand, the dynamics of the particle beams should not be slowed down by the wind. On the other hand, for the cyclic-regenerative treatment of the surface 38 high quality wetting is required with the polymer agent present in the liquid mixture 23 is also included. However, this is only successful if this liquid component atomizes fine enough and so on the surface 38 is applied selectively. Finally, it is also relevant that the particle beam, also due to the kinetic energy of its constituents, helps to destroy the crystal structure of the ice.

The maximum speed, which is the distance radar 100 measured and still capable of measuring, namely 180 km / h = 50 m / s. If one chooses this value also for the particle velocity directly at the surface 38 Thus, one has two approximately equal velocity components, namely the maximum airstream normal component, perpendicular to the surface 38 and the particle velocity component of the direction 75 ° (it was recognized and determined after multiple trials as the optimum angle value) with respect to the horizontal nozzle device 35 , The nozzles 37 become in the manufacture of the nozzle device 35 set to this angle.

The nozzles 37 and the nozzle device 35 are adjusted so that the particle beam centerlines, from the exit of the nozzles 37 to the surface 38 calculated, a length of at most 20 mm and thus the beam center line speed is there 50 m / s. The nozzle device 35 is doing so to the surface 38 Assuming that this distance is given.

The determination of the force effect of the particle beam for the deicing results in:
For the force effect, only the impulse pressure of the particle beam is decisive: I = m * v = ρ * F * v * v = ρ * F * v ² with m = ρ · F · v (ρ = density of the spray jet, v = exit velocity at the nozzles, F = nozzle cross section, m = mass per unit time).

The kinetic energy is thus: E = ½ · m · v 2 = ½ · m · v · v = 1/2 · I · v

For the same momentum, ie for the same force effect, the energy to be expended becomes proportional to the velocity (linearly dependent). The force effect is proportional to the speed square. But because the flow velocity from the outlet of the nozzles 37 calculated as x ^-1 , but the impulse pressure decreases quadratically with distance, is the center line of the flow up to the surface 38 to a distance of 20 mm. This is because there is still a particle jet velocity of about 50 m / s and thus has a required pulse pressure.

The particle beam expands at 14 ° according to fluid mechanics and becomes steep from below onto the surface 38 directed, which encloses an angle of 15 ° with the surface of the acrylic glass. So elliptical conic sections (spray surfaces) are formed. The major axis has a length of 2a = 62 mm and the minor axis 2b = 35 mm. This results in an area of a × b × π = 17 cm ² . There are thus two spray surfaces in approximately the same size and a smaller, given with a spray area of about 10 cm ² . Thus, when the vehicle is stationary, a total area of at least 44 cm ^{2 is} directly sprayed.

By the pumping process, the liquid mixture 23 in an amount of 4 cm ³ on the surface 38 injected. Due to the pumping process, the liquid jet only reaches a speed of about 4.5 m / s. This will be the liquid mixture 23 through the nozzles 37 not atomized and can be taken up by the, on this surface frozen crystal structure (snow or ice, different strength), due to its capillary action to a large extent. This mixture loosens the crystal structure of the snow or ice covering on Plexiglas 36 on. For a first residence time of about 40 seconds is provided.

An amount of liquid of about 1 cm ³ remains in the heated hoses 33 . 34 for this period of time. Only then is this residual fluid accelerated to high speed by the compressed air flow through the nozzles 37 atomized and blown onto the ice or snow cover. This additionally enhances the dissolution of the crystals. As a result of the continuously flowing warm air flow and its impulse pressure, the surface becomes de-icing 38 continued. Is the surface 38 ice-free, a cyclic-regenerating treatment of the surface takes place every 4 minutes 38 with the components of the liquid mixture. This is to prevent a "disturbing coating" on the surface 38 can train soon and the distance radar 100 failed again in a short time. In addition, so, z. B. slush on the road, pollution of the surface 38 at least more difficult.

The electronics are set to pause for approximately 40 seconds every two minutes. 2 minutes after starting, as described above, the first pump spray is performed. This process is repeated every 4 minutes. How many such pump sprays are required, the Plexiglas 36 Deicing sufficiently depends on the initial ice sheet thickness on the plexiglass 36 and their structure as well as their temperature and vehicle speed.

In the additional container 21 , which is housed in the engine compartment, is the liquid mixture 23 , specially selected antifreeze, a small amount of pure alcohol and a special polymer agent, which mixes well with the other ingredients and the surface treatment of Plexiglas 36 suitable is.

The additional container 21 has a content of 1.5 liters. This amount of liquid is sufficient for the de-icing process and the cyclic-regenerating treatment of the surface 38 to maintain uninterrupted for at least 15 hours. Ongoing operation is indicated by an indicator 43 optically signaled.

If a lot of about 20% of the full additional container 21 is reached ("limit level"), closes the limit contact 22b a circuit and the driver is illuminated by the light of the visual display 39 made aware that the contents of the additional container 21 consumed after a continuous operation of about 3 hours.

The deicing device 10 can only be started while the engine is running. The start takes place z. Currently manual by the key 40 but stopping the de-icing process with the key 41 , The connection of the supply voltage U _B for the time and interval sequencer 39a done via the unit 42 , After a restart of the engine, the de-icing device must 10 be restarted manually.

The start could be automatic, if the wind temperature is evaluated so that a signal is generated at a temperature of 2 ° C and this is linked to the signal for automatic operation of the windscreen wiper system (ie if precipitation falls). By the so-called. AND signal thus produced could de-icing 10 be started automatically.

The possibility of a manual start and stop the de-icing process is provided in any case, as z. B. in freezing fog on the surface 38 an ice layer can form without the, in the vehicle built-in precipitation sensor could detect this. A layer of ice on the surface 38 to recognize automatically would be possible, however, with rel. high cost associated.

The pushbuttons 40 . 41 for the start and stop, the visual display 43 for the ongoing operation of the deicing device 10 as well as the optical display 39 for the below mentioned minimum amount of liquid 23 in the additional container 21 ("Mixture Level") are on one of the larger sides of a plastic housing 44 a size of 50 mm × 50 mm × 30 mm (H × W × D), functionally structured, built-in. The plastic housing is located on the lower side of the valve, to the left of the driver.

The spray pump 18 , the built-in throttle valve 19 and the check valve 20 are installed on a metal plate and installed in the engine compartment. The additional container 21 is placed next to this metal plate. They are placed so that they do not cause malfunction in the engine compartment and will not be a hindrance to vehicle maintenance.

While the compressor 11 is installed in an impact-resistant polystyrene housing, a size of 100 mm × 190 mm × 100 mm (H × W × D), the electronic control modules are housed in a so-called "Els" housing: EK 004, which has a transparent, hinged window, pluggable installed. Both the signals and the power supply are supplied via separate connectors to the individual functional units.

Drawings: 1 to 7

On the following pages the drawings follow:
"Distance radar for all-weather use":

Explanation:

1 to 5 :

are the outlines of models from the inventor to the mathematical treatment the wind from the wind on the acrylic glass, as a shield of the distance radar, applied wind load.

6 :

Shows the location of the wetting surfaces, that of liquid jets be produced on the acrylic glass pane for their de-icing.

100

distance radar

10

The de-icer

10a

pneumatic Facility

11

compressor

12

air

12a

air filter

13a

special hose

13b

Teflon tube

14

connecting device

15

metal box

16

hydraulic Facility

17

gear pump

18

injection pump

19

throttle valve

20

check valve

21

additional container

22a

Sinterfilter

22b

limit contact

23

liquid mixture

24

Fuel hose

25a

hose (Input 1)

25b

hose (Entrance 2)

26

Y-pipe structure

27

hose (Output)

28

Fuel hose

29

Tee, pipe structure

30

sidearm right

31

sidearm Left

32

Central branch

33

Fuel hose with the heating coil

34

Fuel hose with the heating coil

35

nozzle device

36

acrylic

37

jet

38

surface of acrylic glass

39

optical Limit level indicator (blue)

39a

Time- and interval sequencer

40

Start button

41

Stop button

42

connection the supply voltage after ignition of the engine

43

optical Display for operation (red)

44

Plastic housing

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited non-patent literature

• - Ernst Eckert: Introduction to heat and mass transfer. Publisher: Springer, Berlin, Göttingen, Heidelberg, 2nd edition, year of publication 1959, page 278 [0010]
• - Prandtl-Tietjens: hydro- and aeromechanics. Publisher: Julius Springer, Berlin, 2nd volume, year of publication 1931, page 185 ff. [0025]
• - Bruno Eck: Technical Fluid Dynamics, Publisher: Julius Springer, Berlin, Göttingen, Heidelberg, 3rd edition, year of publication 1949, page 24, 29, 59, 63, 76 [0025]
• - Bruno Eck: Technical Fluid Dynamics, Publisher: Julius Springer, Berlin, Göttingen, Heidelberg, 3rd edition, year of publication 1949, page 153 [0075]
• - Gröber / Erk / Grigull: The basic laws of heat transfer, Publisher: Springer, Berlin, Heidelberg, New York 3rd edition, year of publication 1988, page 422 [0114]
• - According to Bruno Eck: Technical Fluid Dynamics, Publisher: Julius Springer, Berlin, Göttingen, Heidelberg, 3rd edition, year of publication 1949, page 145 [0115]
• - DIN 73379 [0125]
• - Bronstein-Semendjajew: Taschenbuch der Mathematik, Publisher: Harri Deutsch Zurich and Frankfurt / M, 9th edition, year of publication 1969, page 177 [0140]

Claims (15)

Distance radar ( 100 ) for an all-weather use with an acrylic glass pane ( 36 ) as a protective shield for a motor vehicle, characterized in that the distance radar ( 100 ) a deicing device ( 10 ) for the de-icing of the acrylic glass pane ( 36 ), wherein the deicing device ( 10 ) a connection device ( 14 ), in the compressed air and a liquid mixture ( 23 ) and which are connected with a pneumatic device ( 10a ) and a hydraulic device ( 16 ) as well as with a nozzle ( 37 ) provided nozzle device ( 35 ) via supply lines ( 13a . 13b . 24 . 28 . 33 . 34 ) connected is. Distance radar according to claim 1, characterized in that the pneumatic device ( 10a ) a compressor ( 11 ) having. Distance radar according to claim 1 or 2, characterized in that the hydraulic device ( 16 ) from a gear pump ( 17 ) and from a spray pump ( 18 ) as well as from a throttle valve ( 19 ) and a check valve ( 20 ), wherein the gear pump ( 17 ) with an additional container ( 21 ) with a sintered filter 22a is coupled. Distance radar according to one of claims 1 to 3, characterized in that the connecting device ( 14 ) a Y-shaped pipe structure ( 26 ), in which the compressed air and the liquid mixture ( 23 ) are merge. Distance radar according to one of the preceding claims, characterized in that the supply line between linking device ( 14 ) and nozzle device ( 35 ) from a hose nozzle ( 27 ), on which a fuel hose ( 28 ) attached to a T-shaped pipe structure ( 29 ), which has two connections, at each of which a hose ( 33 . 34 ), whereby the hoses ( 33 . 34 ) with the nozzle device ( 35 ) are connected. Distance radar according to claim 5, characterized in that the hoses ( 33 . 34 ) are wrapped bifilarly with a resistance wire for their heating and are thermally insulated. Distance radar according to one of the preceding claims, characterized in that the nozzle device ( 35 ) follows the lower edge of the acrylic sheet exactly. Distance radar according to one of the preceding claims, characterized in that the nozzle device ( 35 ) is provided with a plastic casing. Distance radar according to one of the preceding claims, characterized in that the nozzles ( 37 ), relative to a center line, the surface ( 38 ) of the acrylic glass ( 36 ) in two equal halves divides, are arranged asymmetrically. Distance radar according to one of the preceding claims, characterized in that the nozzles ( 37 ) are aligned such that a jet of the compressed air and / or the liquid mixture ( 23 ) to the surface ( 38 ) of the plexiglass ( 36 ) has a length of 18 mm to 22 mm. Method for de-icing an acrylic glass pane ( 36 ) of a distance radar ( 100 ), characterized in that from a nozzle device ( 35 ) under the influence of compressed air, a liquid mixture ( 23 ) on the surface ( 38 ) of the acrylic glass pane ( 36 ) is sprayed. A method according to claim 11, characterized in that a particle jet of the liquid mixture ( 23 ) under the influence of compressed air at a speed of at least 200 m / s from the nozzle device ( 35 ) exit. A method according to claim 11 or 12, characterized in that the particle beam of the liquid mixture ( 23 ) under the influence of compressed air from three nozzles ( 37 ) of the nozzle device ( 35 ) exit. Method according to one of claims 12 or 13, characterized in that the core line of the particle beam has an average length of 20 mm. Method according to one of claims 11 to 14, characterized in that it is the de-icing device ( 10 ), a cyclic-regenerating treatment of the acrylic glass pane ( 36 ) through feed that on the surface ( 38 ) creates a temporary protective layer against rapid re-icing.