GB2089303A - Adjustable air deflector assembly - Google Patents

Abstract

An adjustable air deflector assembly comprises an air deflector member 20 pivotally mounted at one edge 22 to a motor vehicle cab roof 14 and being adjustable in inclination relative to said cab roof 14 by means of a compressed air operated adjustable strut assembly 24, 26, 28 and 30, said strut assembly being automatically adjustable in length in response to an air flow pressure signal generated, when the vehicle is in forward motion, by air flow over an air pressure sensor 36, 38 mounted adjacent a leading edge of a body roof portion 18 of the motor vehicle. <IMAGE>

Description

SPECIFICATION Adjustable air deflector assembly This invention relates to air deflector assemblies on motor vehicles, in particular to adjustable air deflector assemblies in which the inclination of an air deflector member pivotally mounted at one edge on a cab roof of a motor vehicle is adjustable relative to said cab roof in order to deflect the air flow created during forward motion of the motor vehicle over a higher body portion of the motor vehicle.

Recently attempts have been made to increase the fuel economy of motor vehicles, in particular commercial motor vehicles, by equipping such motor vehicles with air deflectors on the cab roofs of such vehicles in order to reduce the aerodynamic resistance experienced by these vehicles when they are in forward motion. The concept of using fixed air deflectors in the cab roof of a commercial vehicle has long been known. Such fixed air deflectors are effective on commercial motor vehicles in which the shape and size of the body portion of the vehicle remains constant.

They are not so effective, however, with motor vehicles in which the elevation of the body portion of the vehicle above the cab roof can vary, i.e. in commercial vehicles having a flat bed loading area which can be loaded to a variable height, or in tractor-trailer articulated vehicles in which the tractor may be hauling trailers of different heights. Consequently, there is a need for the air deflector to be adjustable in inclination, so that it can be set at an optimum angle with respect to the height of the body porton of the commercial vehicle above the cab roof of the vehicle. One such adjustable air deflector is disclosed in British Patent Specification No. 1,520,554.

One problem that is met with in adjustable air deflectors of this type is the problem of judging correctly the optimum angle at which the deflector should be inclined in order to achieve the maximum possible reduction in the aerodynamic resistance experienced by the motor vehicle during forward motion thereof.

An adjustable air deflector assembly according to the present invention, mounted on a motor vehicle having a cab roof portion and a body roof portion higher than said cab roof portion, comprises an air deflector member pivotally mounted at one edge on said cab roof portion and being adjustable in inclination relative to said cab roof portion by means of an adjustable strut assembly, said strut assembly being automatically adjustable in length in response to an air flow pressure signal generated, when the vehicle is in forward motion, by air flow over an air pressure sensor mounted adjacent a leading edge of said body roof portion, the strut assembly being gradually lengthened in response to said pressure signal so as to raise the air deflector member until the change in inclination of the air deflector member during forward motion of the vehicle is sufficient to reduce the air flow pressure on the sensor to a predetermined pressure level, and the strut assembly being gradually decreased in length, so as to lower the air deflector member, whenever the air flow pressure on the sensor falls below said predetermined pressure level.

In motor vehicles having an elevated body portion mounted directly behind the vehicle cab, the air pressure sensor can be mounted on the body portion immediately adjacent the leading edge of the body roof. In the situation where there are variations in the total height of the body portion of the vehicle above the cab roof of the vehicle, that is, in the situation where the motor vehicle is a tractor-trailer articulated vehicle, the cab of the vehicle is provided with an adjustable sub-frame on which is mounted said air pressure sensor, the height of said sub-frame being adjustable to position said air pressure sensor adjacent the leading edge of the body portion of the vehicle.

Preferably the adjustable strut assembly of the invention includes a piston and cylinder arrangement for adjusting the overall length of the strut assembly, said piston and cylinder arrangement being powered by a source of pressure fluid, and said air pressure sensor is a vane-operated valve governing the flow of said pressure fluid from said source to the piston and cylinder arrangement. In a preferred embodiment of the present invention the pressure fluid used is compressed air and the source of pressure fluid is an air compressor driven by the engine of the motor vehicle.

Advantageously, in such a preferred embodiment of the invention, the vane-operated valve gradually vents the pressure fluid from the piston and cylinder arrangement as soon as the air flow pressure on the vane of said valve drops below said predetermined pressure level.

A preferred embodiment of the present invention will now be described with reference to the accompanying drawings, in which: Figure 1 shows a partial side view of a commercial motor vehicle fitted with an adjustable air deflector assembly according to the present invention; Figure 2 shows a vane-operated valve of the air deflector assembly shown in Fig. 1, viewed in the direction of the arrow A"; Figure 3 is a side view of the motor vehicle shown in Fig. 1, with the air deflector assembly in a lowered position; and Figure 4 shows a side view of the motor vehicle shown in Fig. 1 with the air deflector assembly in a raised position.

Fig. 1 of the drawings shows a side view of a portion of a motor vehicle 10 having a vehicle cab 1 2 with a vehicle cab roof 14, and a vehicle body portion 1 6 having a vehicle body roof 1 8 at a higher level than the vehicle cab roof 14. A substantially flat air deflector member 20 is pivotally connected at one end to a roof bracket 22 mounted adjacent a leading edge of the vehicle cab roof 14. A rigid link 24 is pivotally connected at one end to a bracket 26 on the other end of the air deflector member 20.The other end of the rigid link 24 is pivotally connected to a free end of a piston rod 28, which is con- nected to a piston of a piston and cylinder arrangement 30, the cylinder 32 of which is mounted adjacent the rear of the vehicle cab 1 2. The base of the cylinder 32 is connected via a compressed air-line 34 to a vane-operated compressed air valve 36 mounted on a forward surface 37 of the vehicle body portion 16.

As can be seen in Fig. 2, the vane-operated compressed air valve 36 comprises a rectangular vane connected to the body of the air valve 36 by means of an operating arm 40, the vane 38 and operating arm 40 being movable between a first position, indicated in solid lines in Fig. 1, in which the valve is closed, and a second position, indicated in dotted outline in Fig. 1, in which the valve is open. As can be seen in Fig. 1, the top edge of the vane 38 is arranged to coincide with the level of the vehicle body roof 18. Compressed air is supplied to the air valve 36 through a compressed air feed line 42 coupled to an air compressor (not shown) housed in the engine compartment of the motor vehicle 10.The compressed air valve 36 is provided with a bleed means (not shown) which becomes operable when the valve 36 is in its closed position to gradually bleed the air pressure from the compressed air-line 34, thus causing the air deflector member 20 to gradually be lowered, as will be discussed in detail hereinafter.

The initial operating position of the adjustable air dei9ector assembly according to the present invention is shown in Fig. 3, where it can be seen that the air deflector member 20 is in a fully lowered position, that is, it is laying effectively parallel with the vehicle cab roof 14. Whilst the motor vehicle 10 is stationary, the vane 38 of the compressed air valve 36 is in the first position, and no compressed air is being supplied to the piston and cylinder arrangement 30, even when the engine of the motor vehicle 1 0 is started up.

Once the engine of the motor vehicle 10 is started up, the air compressor associated with the engine quickly builds up a pressure of compressed air in the air valve feed line 42.

When the motor vehicle 10 is set in forward motion, the air flow passing over the lowered air deflector member 20 strikes the vane 38 of the compressed air valve 36. Movement of the vane 38 from its first position, where the valve 36 is closed, to its second position, where the valve 36 is open, does not occur until the air pressure on the vane 38 corresponds to a predetermined pressure level equivalent, for example, to a wind speed of 30 miles per hour. Once this predetermined pressure level is reached, the vane 38 moves from its first position to its second position, and the valve 36 opens.

Once the valve 36 is opened, compressed air is supplied to the piston and cylinder arrangement 30 in order to raise the air deflector member 20 into the air stream passing over the cab of the vehicle. Elevation of the air deflector member 20 continues until the position shown in Fig. 4 is reached, in which the air deflector member 20 is diverting the air flow passing over the air deflector rnerniber 20 over the vehicle roof 1 8. When this position of the air deflector member is reached, the pressure of the air stream on the vane 38 decreases below said predetermined pressure level and, since vane 38 is biased towards its first position, movement of vane 38 from its second position to its first position occurs.Once valve 36 is in its closed position, the air pressure is gradually bled from the compressed air-line 34, thus causing the air deflector 20 gradually to be lowered. This lowering of the air deflector member 20 will, in turn, result in the air stream deflected by the air deflector member coming again into contact with the vane 38, and thus moving it from its closed position to its open position.

Once this happens, the supply of compressed air to compressed air-line 34 is restored, in order to raise the air deflector member 20.

The net result of this sequence of operation is that the air deflector member 20 will remain elevated at substantially the right angle to just deflect the air stream over the roof 1 8 all the time the motor vehicle is in motion. When the motor vehicle comes to a halt, the flow of air over the deflector member 20 ceases, and the biasing on vane 38 causes vane 38 to take up its first position again. on this position, the air bleed on compressed air-line 34 is re-established and the air deflector member is gradually lowered until it is parallel with the cab roof 14. Once the vehicle commences to move in a forward direction and the pressure level on the vance 38 builds up to said predetermined pressure level, the vane 38 moves to its second position and the cycle of raising and lowering the air deflector member into its optimum deflecting position recommences.

Of course, when the motor vehicle comes to a halt and the engine is switched off, the supply of compressed air to the piston and cylinder arrangement 30 ceases, the vane 38 moves into its first position, and the bleed of compressed air on the compressed air-line 34 gradually lowers the air deflector member 20 until it is again paraliel with the cab roof 14.

The present invention thus provides an ad justable air deflector which is capable of automatically adjusting its height relative to the cab roof of the vehicle on which it is mounted in order to deflect the air stream passing over the air deflector member when the vehicle is in motion smoothly and effectively over the roof of the vehicle body. The adjustable air deflector only becomes effective when it is required to become effective, namely after the vehicle has attained a predetermined forward speed. The "bleed off" facility provided on a preferred embodiment of the invention ensures that the adjustable air deflector can adjust its position to compensate for fluctuating wind velocities passing over the air deflector member due to the vehicle decelerating or to gusting winds passing over the vehicle.

Claims (6)

1. An adjustable air deflector assembly on a motor vehicle having a cab roof portion and a body roof portion higher than said cab roof portion, said deflector assembly comprising an air deflector member pivotally mounted at one edge on said cab roof portion and being adjustable in inclination relative to said cab roof portion by means of an adjustable strut assembly, said strut assembly being automaticaly adjustable in length in response to an air flow pressure signal generated, when the vehicle is in forward motion, by air flow over an air pressure sensor mounted adjacent a leading edge of said body roof portion, the strut assembly being gradually lengthened in response to said pressure signal so as to raise the air deflector member until the change in inclination of the air deflector member during forward motion of the vehicle is sufficient to reduce the air flow pressure on the sensor to a predetermined pressure level, and the strut assembly being gradually decreased in length, so as to lower the air deflector member, whenever the air flow pressure on the sensor falls below said predeterimined pressure level.

2. An adjustable air deflector assembly according to claim 1, in which the motor vehicle is a tractor-trailer articulated vehicle, and the cab of the tractor is provided with an adjustable sub-frame on which is mounted said air pressure sensor, the height of said sub-frame being adjustable to position said air pressure sensor adjacent the leading edge of the trailer.

3. An adjustable air deflector assembly according to claim 1 or 2, in which the adjustable strut assembly includes a piston and cylinder arrangement for adjusting the overall length of the strut assembly, said piston and cylinder arrangement being powered by a source of pressure fluid, and said air pressure sensor is a vane-operated valve governing the flow of said pressure fluid from said source to the piston and cylinder arrangement.

4. An adjustable air deflector assembly according to claim 3, in which the pressure fluid is compressed air and the source of pressure fluid is an air compressor driven by the engine of the motor vehicle.

5. An adjustable air deflector assembly according to claim 3 or 4, in which the vaneoperated valve gradually vents the pressure fluid from the piston and cylinder arrangement as soon as the air flow pressure on the vane of said valve drops below said predetermined pressure level.

6. An adjustable air deflector assembly on a motor vehicle substantially as hereinbefore particularly described and as shown in Figs. 1 to 4 of the accompanying drawings.