Device for reducing vehicle aerodynamic resistance

A device for reducing vehicle aerodynamic resistance for vehicles having a generally rectangular body disposed above rear wheels, comprising a plurality of load bearing struts attached to the bottom of the rectangular body adjacent its sides, a plurality of opposing flat sheets attached to the load bearing struts, and angled flaps attached to the lower edge of the opposing sheets defining an obtuse angle with the opposing flat sheets extending inwardly with respect to the sides of the rectangular body to a predetermined height above the ground, which, stiffen the opposing flat sheets, bend to resist damage when struck by the ground, and guide airflow around the rear wheels of the vehicle to reduce its aerodynamic resistance when moving.

TECHNICAL FIELD

The invention relates to a device for reducing the aerodynamic resistance of a moving, rectangular shaped vehicle and more particularly to a pair of opposing airfoils that are mounted underneath the vehicle adjacent its sides.

BACKGROUND ART

It is well known that streamlining the undercarriage of a long vehicle such as a trailer truck or straight van truck will reduce the aerodynamic resistance of a moving vehicle and thus save fuel. However, streamlining the undercarriage of a long vehicle such as a semi-trailer is impractical because integrated enclosures are heavy, costly, easily damaged, interfere with standardized structural design, and prevent access to parts and equipment underneath the vehicle. Consequently, removable attachments have been designed to streamline the undercarriage of long vehicles. However, past designs for removable attachments have failed to achieve significant utilization because they are typically large and heavy enclosures or one piece structures, which are difficult to transport when not mounted on the trailer, difficult to mount, require drilling or welding the undercarriage when mounting, incompatible with different trailer and truck geometries, easily damaged, difficult to repair, become filled with snow and ice in winter driving conditions, do not provide the maximum drag decrease possible, and are too costly to generate a significant return on investment though associated fuel use reductions. The device described herein uses a minimal amount of material resulting in reduced weight and production costs and provides a maximized drag reduction. Prototypes of the device, constructed under U.S. Government contract No. DE-FC36-03G013173 awarded by the Department of Energy, weighed under 150 lbs and reduced a semi-trailer's fuel consumption by 4% in Society of Automotive Engineer's (SAE) J1321 type II standardized fuel economy tests conducted by a respected independent research center. The improved aerodynamic performance of the devise described herein when compared to past designs for aerodynamic attachments, that extend the side wall of the truck or trailer directly toward the ground, is due to the addition of angled flaps directed toward the center of the vehicle. The geometry of the angled flaps was tuned to provide the maximum drag reduction possible by directing crosswind airflow beneath the trailer's rear wheels and axles. The straight side extensions of past designs create low pressure vacuums that tend to direct crosswind airflow into the wheels and axles and can cause large side forces that push the vehicle off its intended course. The angled flaps also provide stiffing means, necessary to prevent the wind induced flapping or oscillations common to the straight side extensions of past designs. Unlike the straight side extensions of past designs, which tend to buckle or collapse in a random fashion if struck by protrusions on the ground (or the ground when the vehicle travels over uneven surfaces) and may sustain damage even if constructed of flexible materials, the angled flaps bend uniformly toward the vehicle if stuck by the ground and return to their original position. The device described herein is easily packaged and shipped, can be easily mounted on the undercarriage of trailers and trucks of different geometries and construction without modification, requires no welding or drilling in the undercarriage when mounting, resists damage, and damaged areas can be easily repaired with replacement parts. The device described herein does not enclose the undercarriage of the trailer like past designs, thereby preventing snow and ice build-up and allowing convenient access to parts underneath the trailer or truck. Unlike past designs, the device described herein also improves road safety by absorbing significant impact in the event of a side collision. Absorbing side impact helps prevent passenger vehicles from entering the area underneath the trailer, which often results in serious accidents because the vehicle is crushed by the trailers rear wheels.

DISCLOSURE OF THE INVENTION

In general, a device for reducing vehicle aerodynamic resistance disposed on the bottom of a vehicle having a generally rectangular body disposed above rear wheels, when made in accordance with this invention, comprises a plurality of load bearing struts of a predetermined size attached to the bottom of the rectangular body adjacent the sides thereof which can absorb impact in the event of a side collision. A plurality of impact absorbing members extending between adjacent load bearing struts and fastened thereto which can absorb impact in the event of a side collision. A plurality of opposing flat sheets attached to the load bearing struts. Front opposed flat sheets disposed toward the front of the rectangular body, intermediate opposed flat sheets disposed behind the front opposed flat sheets, and rear opposed flat sheets disposed toward the rear of the rectangular body, each having a top edge disposed adjacent the bottom and side of the rectangular body, and a lower edge disposed a predetermined height above the ground surface and below the bottom of the rectangular body. A plurality of angled flaps attached to the lower edges of the intermediate and rear opposed flat sheets, each defining an obtuse flap angle with respect to each attached opposed flat sheet, extending inwardly with respect to the sides of the rectangular body, to a predetermined height above the ground surface. Whereby the opposing flat sheets are stiffened by the angled flaps, which flex toward the rectangular body if struck by the ground surface to resist damage, and airflow is directed around the rear wheels to reduce the aerodynamic resistance of the vehicle when moving.

BEST MODE FOR CARRYING OUT THE INVENTION

Referring now to the drawings in detail and in particular toFIGS. 1 and 2, there is shown a vehicle1such as a trailer truck, having a generally rectangular body3having a front F, rear R, bottom B and opposed sides S mounted above rear wheels5and a device7for reducing the aerodynamic resistance of the vehicle1when it moves. The device7comprises a pair of opposed airfoils9disposed beneath the rectangular body3adjacent its sides S and are preferably made of aluminum, but of course other material could be utilized. Each opposing airfoil comprises load bearing struts13, which are removably attached to the vehicle cross members15. The load bearing struts13having predetermined dimensions are designed to carry loads from different directions and absorb impact from side collisions. They are shown fabricated from strips of flat sheets bent and joined to form a triangle. Opposed flat sheets16,17and18are attached to the load bearing struts13adjacent the sides S and bottom B of the rectangular body3and extend to a lower edge20,21and22, respectively, at a predetermined height above the ground surface G. The lower edges20,21and22of the opposing flat sheets16,17and18are approximately 20 inches above the ground surface G. Front opposed flat sheets16are disposed toward the front F of the vehicle. Rear opposed flat sheets18are disposed toward the rear R of the vehicle. Intermediate opposed flat sheets17are disposed behind the front opposed flat sheets16and in front of the rear opposed flat sheets and are generally rectangular. While only three intermediate opposed flat sheets17are shown, it is understood that any number of intermediate opposed flat sheets17could be used to accommodate rectangular bodies2of different lengths. Angled flaps23and24are bent to form an obtuse flap angle A, preferably less than 160 degrees, with their apexes adjacent the lower edges21and22. Forward angled flaps23are fastened to the intermediate opposed flat sheets17adjacent the front opposed flat sheets16. Rearward angled flaps24are fastened to the other intermediate opposed flat sheets17and rear opposed flat sheets18with their apexes adjacent the lower edges21and22. The angled flaps23and24extend to a predetermined height above the ground surface G, which is approximately 13 inches. The angled flaps23and24direct cross-wind airflow AF below the forward portion of the rear wheels5of the vehicle1to reduce associated drag forces. The angled flaps23and24can bend toward the rectangular body3, if struck by protrusions on the ground surface G or an uneven ground surface and return to their original position. Rolled shapes such as angles or channels may be utilized as impact absorbers25and are attached to the load bearing struts13adjacent the lower edges21of the intermediate opposed flat sheets17as an additional means of absorbing impact from side collisions. It is understood that the impact absorbers25are an optional addition to the aerodynamic devise7, which some users may choose not to employ because of increased weight and cost.

FIGS. 3 and 4show an intermediate opposed flat sheet17having a top portion bent at an angle B, generally about 90 degrees, to form flange27to stiffen the upper end of the intermediate opposed flat sheet17and help prevent wind induced oscillations. Front opposed flat sheets16and rear opposed flat sheets18are also bent to form the flange27but they are not shown. Rivets29or other fastening means are typically utilized to fasten the opposed flat sheets16,17and18to the load bearing struts13and the angled flaps23and24adjacent to the bottom edges21and22of the opposed flat sheets17and18so that they can be replaced if damaged. It is understood that the angled flaps23and24could also be bent into the opposed flat sheets17and18. The obtuse flap angle A, preferably less than 160 degrees, stiffens the lower edges21and22of the opposed flat sheets17and18and cooperates with the flanges27to stiffen the opposed flat sheets17and18to prevent wind induced oscillations.

FIG. 5shows a typical installation of an opposed airfoil9on a rectangular body3. Load bearing struts13are removably attached to vehicle cross members15approximately every 5 feet along the vehicles side S, but could be spaced differently. Impact absorbing members25extend between the load bearing struts13and are removably fastened thereto. The opposed flat sheets16,17and18are fastened to the load bearing struts13by rivets29. Adjacent opposed flat sheets overlap, when attached to a common load bearing strut13. The amount of overlap can be varied to accommodate different rectangular body lengths and overcome inconsistencies in the spacing of vehicle cross members15as shown by the extended overlap O. The front opposed flat sheets16have front edges33that form acute angles C, preferably less than 30 degrees, with respect to the bottom B of the rectangular body3, and rectangular portions32with bottom edges20. Front edges33of the opposed flat sheets16have angles, channels or other stiffeners attached adjacent thereto to form stiffening members35, which cooperate with the flanges27to prevent wind induced oscillations. Small load bearing struts37are removably attached to a vehicle cross member15to support the front opposed flat sheets16. The rear opposed sheets18have rear edges39, which form acute angles D, preferably less than 70 degrees, with respect to the bottom B of the rectangular body3and a rectangular portions41with bottom edges22. Forward angled flaps23have forward edges26below the apex of obtuse flap angle A that form acute angles E, preferably less than 20 degrees, with respect to the lower edges21.

FIGS. 6 and 8show a load bearing strut13that has opposing clamping sheets45and spacer sheets47fastened thereto by bolts49such that it can be removably attached to a vehicle cross member15. Rivet holes51allow the opposed flat sheets16,17and18to be attached to the load bearing struts13.

FIG. 7shows a small load bearing strut37that has opposing small clamping sheets53and small spacer sheets55fastened thereto by bolts49such that it can be removably attached to a vehicle cross member15. Rivet hole51allows the front opposed flat sheet16to be attached to the small load bearing strut37.

FIG. 9shows a preferred embodiment of the device7attached to a vehicle1of different geometry having a rectangular body3that is not a detachable trailer.

While the preferred embodiments described herein set forth the best mode to practice this invention presently contemplated by the inventor, numerous modifications and adaptations of this invention will be apparent to others of ordinary skill in the art. Therefore, the embodiments are to be considered as illustrative and exemplary and it is understood that the claims are intended to cover such modifications and adaptations as they are considered to be within the spirit and scope of this invention.

INDUSTRIAL APPLICABILITY

An aerodynamic reducing device7for a vehicle1as set forth in this invention provides a device7, which is economical to manufacture and to maintain, and is easily packaged, transported, and installed in the field on rectangular vehicles of varying geometry. It provides a pair of removable airfoil portions that will substantially reduce the aerodynamic resistance of the moving vehicle1, thus reducing fuel consumption, fuel cost and air pollution.