Land vehicles: bodies and tops – Bodies – With distinct wind deflector
Patent
1987-10-28
1990-04-17
Kashnikow, Andres
Land vehicles: bodies and tops
Bodies
With distinct wind deflector
98 2, 105 12, 293102, 296 91, B62D 3502, B62D 3200
Patent
active
049174347
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to characteristics of aerodynamics of a motor vehicle, and more particularly to a construction of side corner portions of the motor vehicle.
BACKGROUND ART
When a motor vehicle is subjected to the crosswind during running at high speed, a vehicle body may be carried away to the leeward or the running may become unsteady due to the correcting control by steering against the crosswind.
Furthermore, when the motor vehicle tries to outrun a plurality of large-sized vehicles on the leeward against the crosswind, the motor vehicle is intermittently subjected to the crosswind, whereby, above-described unsteadiness of the running may be caused, and it becomes necessary to perform steering control to correct the running against the unsteadiness.
As means for improving the control stabiltiy of the motor vehicle during running at high speed against the aforesaid crosswind, there is a method of improving the chassis (suspension and tires) or the characteristics of aerodynamics of the body (particularly, decreases in the yawing moment coefficient CY and the lift coefficient CL).
The above-described yawing moment coefficient CY is a coefficient of moment for rotating the vehicle in the lateral direction, and generated when the vehicle is subjected to the crosswind, i.e., the running wind has an yaw angle .psi. to the vertical center surface in the longitudinal direction of the vehicle.
This will hereunder be described in detail. As shown in FIG. 11, when a motor vehicle 1 is subjected to the crosswind and the yaw angle .psi. of a running wind 2 becomes .psi. .noteq. 0, a running wind 2 is divided at left corner portion 3 of a front side of the motor vehicle 1 into two air streams including an air stream flowing along the left side surface of the motor vehicle 1 and another air stream flowing along the front surface and to the right side surface of the motor vehicle 1.
At this time, there occurs a difference in flow velocity between these divided air streams, and a difference in pressure distribution around the vehicle body of the motor vehicle 1 is generated due to the difference in flow velocity as shown in FIG. 11.
As apparent from this drawing, in general, positive pressure is generated at the left side surface on the windward side of the motor vehicle 1 and negative pressure is generated at the right side surface on the leeward side.
Consequently, due to this difference in pressure, a moment for rotating the motor vehicle 1 to the right in the drawing is generated to the motor vehicle, and this coefficient is the above-described yawing moment coefficent CY.
Here, the relationship between the yaw angle .psi. and the yawing moment coefficient CY differs depending on the configuration of the vehicle body, however, in general, CY has the maximum value in the proximity of .psi.=25.degree..
The characteristics of CY as described above is mainly due to change in pressure (change in flow velocity) on the leeward side, i.e., in the right side corner portion of the motor vehicle 1 in the drawing.
More specifically, on the leeward side in the right corner portion 4 of the front side, the air stream flows along the outer surface of the vehicle body, and, even when the air stream is separated, the air stream is immediately attached again, so that the flow velocity is high and the negative pressure is high.
When the yaw angle reaches a certain value (in general, 25.degree.-30.degree.) or thereabove, the air stream is separated the outer surface of the vehicle body in the corner portion of the front side, whereby the negative pressure is lowered as compared with that when the air stream flows along the outer surface of the vehicle body.
Consequently, it is known that, when this corner portion is made angular or the radius of curvature thereof is decreased, separation of the air stream occurs and the yawing moment coefficient CY is reduced.
Now, regarding the relationship between the yawing moment coefficient CY and the drag coefficient CD, when the radius of curvature of the corner portio
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SAE Technical Paper, "Development of Aero-Slit", Sumitani and Yamada, No. 890370, Feb. 27, 1989.
Graham Matthew C.
Kashnikow Andres
Toyota Jidosha & Kabushiki Kaisha
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