EP0096255B1 - Electric motor-driven axial fan, especially for motor vehicle cooling fans - Google Patents

Description

The invention relates to an electric motor driven statorless axial fan, in particular for motor vehicle radiator fans, according to the preamble of claim 1; such an axial fan is known from US-A-3 885 888.

In what is known from U.S.-A-3,885,888, including The fan provided for motor vehicle radiators consists of a one-piece plastic part with radially projecting blades that are integrally molded onto a hub. On the outside of the end face of the hub, radially extending additional blades for producing an air flow are also cast, which is supplied to the outer air flow of the main blades and is intended to reinforce the latter. Further design parameters for the axial fan are not included in the publication; the impeller shown corresponds to the usual design.

From US-A-4123 198 a publication on the impeller of a fan is known, in which some design parameters are mentioned, but the resulting construction is within the scope of the usual design of an impeller, which, among other things, according to the object of the present invention. should be improved.

The object of the present invention is namely to provide an axial fan driven by an electric motor, in particular for motor vehicle radiator fans, which, despite being technically and structurally simple in construction, stands out from previous solutions by a lower power-to-weight ratio.

The problem is solved in an axial fan of the type mentioned according to the invention by the teaching according to the characterizing part of claim 1; advantageous embodiments of the invention are the subject of the dependent claims.

It has surprisingly been found that an axial fan designed according to the invention with the hitherto unusual design parameters for the impeller, assuming the same materials and a constant strength compared to axial fans with conventional impellers, due to the impeller having a significantly smaller surface area, with a weight reduction of 30% to 40 % enables the impeller efficiency to be increased to 45% and the power-to-weight ratio can be reduced even further by the easily achievable airflow sucked into the interior of the hub through the ventilation openings and the additional blades on the inner end face of the hub and flowing through the subsequent motor.

The combination of low weight and good strength at the same time can be further improved in that the hub diameter of the impeller is in the range from 0.3 to 0.4 times the outer diameter of the impeller.

• Fig. 1 eine Seitenansicht des Axialventilators mit im Schnitt dargestellten Laufrad gemäß Schnittverlauf I-I in Fig. 2.
• Fig. 2 eine stirnseitige Draufsicht auf das Laufrad,
• Fig. 3 eine Seitenansicht des Laufrades gemäß Fig. 2 mit geschnittener Laufradschaufel gemäß Schnittwerlauf III-III.

The invention is explained below with reference to a schematically illustrated embodiment in the drawing. In it show:

• 1 is a side view of the axial fan with the impeller shown in section according to section II in Fig. 2nd
• 2 is a front plan view of the impeller,
• Fig. 3 is a side view of the impeller of FIG. 2 with a cut impeller blade according to section III-III.

Fig. 1 shows an electric drive motor 1 of an axial fan, on the free shaft end 11, an impeller 2 is fixedly mounted. The entire axial fan is e.g. held in a guide device of a motor vehicle (not shown) by means of screws 3 and via three mounting brackets 4 fastened to the housing of the drive motor 1.

The impeller 2 has a cup-shaped hub 21 fastened on the shaft end 11 of the drive motor 1 with an end face 212 and a cylindrical wall 211; are arranged in a star shape on the outside of the cylindrical wall 211 and five blades 22 are integrally formed in one piece on the circumference. Radially projecting ribs 214 are also integrally formed in one piece within the cup-shaped hub 21, likewise uniformly distributed over the circumference. Ventilation openings 213 are provided in each case between the radial inner ends of the ribs 214 in the end face 212 of the top-shaped hub 21, such that an air flow sucked in by the driven sound wheel 2 accelerates in the area of the ribs 214 in the radial direction and then on the inside of the cylindrical wall 211 the cup-shaped hub 21 is deflected axially against the surface of the drive motor 1. The ribs 214 molded inside the hub 21 of the sound wheel 2 behave together with the ventilation openings 213 in the end face 211 of the hub 21 like a radial fan. In this sense, particular care should be taken to ensure that the ventilation openings 213 are placed as close as possible to the motor shaft end 11 together with the inner ends of the ribs 214, taking into account optimal structural and strength-related Gesielit tracks on the one hand and a streamlined design on the other hand.

• 1 = 0,15...0,18 D₂
• D_N = 0,3...0,4 D₂
• d_ma ≦ 0,01 D₂
• _dmin < 1/2 dmax
• R_su = 0,35...0,45 D₂
• _{Rso = Rsu} + dmax
• ß_s = 16°...24°

dabei bedeuten:

• D₂ = Außendurchmesser des Lautrades,
• 1 = Abstandslänge zwischen vorderer und hinterer Schaufelkante,
• D_N = Nabendurchmesser des Lautrades,
• d_max = größte Schaufeldicke,
• d_mi_n = kleinste Schaufeldicke,
• R_su = Krümmungsradius an der

Schaufelunterseite,

• R_so = Krümmungsradius an der

Schaufeloberseite,

• β_s = Anstellwinkel des Schaufelprofils, gegen Umtangsrichtung gemessen.

The impeller 2 is determined by the following design parameters:

• 1 = 0.15 ... 0.18 D ₂
• D _N = 0.3 ... 0.4 D ₂
• d _ma ≦ 0.01 D ₂
• _dmin <1/2 dmax
• R _su = 0.35 ... 0.45 D ₂
• _{Rso = Rsu} + dmax
• ß _s = 16 ° ... 24 °

mean:

• D ₂ = outer diameter of the sound wheel,
• 1 = distance between front and rear blade edge,
• D _N = hub diameter of the sound wheel,
• d _max = maximum blade thickness,
• d _m i _n = smallest blade thickness,
• R _su = radius of curvature at the

Blade underside,

• R _so = radius of curvature at the

Bucket top,

• β _s = angle of attack of the blade profile, measured against the circumferential direction.

If the construction parameters of a sound wheel are in the aforementioned range, the desired effectiveness improvement is achieved despite the simplest construction.

In the construction of an axial fan according to the invention, the blade length 1 can first be determined for a specific impeller, taking into account the ranges specified for the respective construction parameters, for example starting from a selected outer diameter D _{2 of} the impeller; taking into account the proposed parameter value for the constant angle _ß can then the circular arcs R _su and R _as for the radii of curvature of the blade lower side and the blade top side, taking into account the maximum and minimum wall thickness of the blade (d _max and d _m i _n) are determined . The blades defined in this way with the aid of the two circular arc lines are then to be rounded off only in the region of the front edge or the rear edge in the transition between the lower and upper radius of curvature from the previously described circular arc lines, but adapted to these.

Claims (3)

1. An electric motor-driven axial fan, without a guide wheel, in particular for motor vehicle cooling fans, comprising an impeller which is secured to the shaft end of a drive motor and has non-twisted blades arranged on the outer periphery of its hub in a star-fashion at a constant setting angle β_S in the range of 16°...24° and which has both axially and radially extending ribs on the inner periphery of its cup-shaped hub, characterised by the following features:

a) the length (1) of the distance between the front and rear blade edges lies in the range of 0.15 times to 0.18 times the outer dimater (D₂) of the impeller (2);

b) the greatest blade thickness (d_max) on the rounded front edge of each blade (22) is smaller than or the same as 0.01 times the outer diameter (D₂) of the impeller (2), and the smallest blade thickness (d _min) is less than 0.5 times the greatest blade thickness;

c) the radius of curvature (R_su) at the underside of the blade is in the range between 0.35 times and 0.45 times the outer diameter (D₂) of the impeller (2), and the radius of curvature (R so) at the upper side of the blade corresponds to the sum of the radius of curvature (R_su) at the upper side of the blade and the greatest blade thickness (^d max);

d) between the ribs (214) which extend radially on the inner end face (212) of the hub (21), in the region of their radially inner ends, there are arranged ventilation openings (213) on the end face (212) of the hub (21).

2. An electric motor-driven axial fan as claimed in Claim 1, characterised in that the hub diameter (D_N) of the impeller (2) lies in the range of 0.3 times to 0.4 times the outer diameter (D₂) of the impeller (2).

3. An electric motor-driven axial ventilator as claimed in one of Claims 1 and 2, characterised in that the impeller (2) consists of a unitary synthetic resin injection moulded component which can only be produced with mould parts which can be drawn in a mould-opening direction.

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