Patent Application
20060217946
This application claims the priority of German patent document 103 06 162.2, filed Feb. 14, 2003 (PCT International Application No. PCT/EP2003/013770, filed Dec. 5, 2003), the disclosure of which is expressly incorporated by reference herein.
The invention relates to a driver's cab of a motor vehicle, such as a truck, having optimized air flow characteristics or aerodynamics, and to a method for optimizing the aerodynamics of a driver's cab of a motor vehicle.
The aerodynamic properties of vehicles vary as a function of the shape of the bodyshell (such as the unity of an external bodyshell shape, for example) and efforts have been made to obtain the lowest possible air resistance and hence the lowest possible drag coefficient (cw value). Because low air resistance also achieves a reduction in the vehicle fuel consumption, in modern vehicle development extensive wind tunnel testing is carried out before the ultimate shape of a vehicle bodyshell or a driver's cab of a truck is finalized.
Other design measures can also be taken to improve the aerodynamics and hence the drag coefficient of vehicle cabs for trucks. For example, German patent document DE 3823161 A1 discloses height-adjustable wind baffles which can be fitted, in particular, to truck cabs to improve the drag coefficient of the truck. Such wind baffles, however, are fitted to a given truck cab by means of separate fixing devices, and the transitions between the cab and the wind baffle constitute aerodynamic problem zones. All in all the aerodynamic improvement is unsatisfactory.
German patent document DE 8119436.6 U1 discloses a wind and or flow baffle that is mounted on an existing driver's cab, finishing flush with the front and side edges of the driver's cab. Even in this case, however, the improvement in the drag coefficient is nevertheless still limited, the given external shape of the cab bodyshell preventing any further improvement. The external shape of the driver's cab, influenced decisively by the technical design construction, is relatively angular and leads to turbulence, and hence to an increased air resistance.
Accordingly, one object of the present invention is to provide a driver's cab for a vehicle having optimized aerodynamic properties and air flow characteristics.
Another object of the invention is to provide a method for optimizing the aerodynamic properties of a driver's cab of a motor vehicle.
These and other objects and advantages are achieved by the method and apparatus according to the invention, in which the driver's cab of a vehicle has a plurality of design parameters which determine the drag coefficient of the vehicle, and which are optimized for airflow purposes. The aerodynamic influence of each of the design parameters on the vehicle bodyshell can be determined in air flow tests. The design parameters of the driver's cab according to the invention can each be varied within a predefined fixed range, and within the predefined range of variation they are optimized jointly (as a function of one another) with a view to optimum overall air flow characteristics of the external shape of the driver's cab.
In this manner, an overall optimum drag coefficient for the driver's can be achieved by varying a number of design parameters of the driver's cab. The driver's cab is still formed within a given design framework, but nevertheless has improved aerodynamic properties in terms of a reduced drag coefficient compared to those driver's cabs or vehicles in which design parameters, such as the windshield inclination or the integrity of the external shape would only have been optimized in isolation by means of wind tunnel testing. According to the invention, all the design parameters for overall aerodynamics are determined jointly and in coordination with one another on the driver's cab, so that the driver's cab has a better overall drag coefficient than existing driver's cabs. Extreme values for the individual design parameters, such as an extremely shallow windshield inclination, which are unacceptable for non-aerodynamic reasons, are avoided. The driver's cab retains, within certain limits, a bodyshell shape consistent with the functionality and the vehicle-specific requirements, but is fully optimized in terms of the aerodynamics.
In an advantageous embodiment of the invention, the design parameters of the driver's cab that influence its air flow characteristics are optimized in conjunction with one another and in predefined steps by means of a computer. The predefined stages or steps in which the parameters are varied reduces the design and development costs of the driver's cab. Coherent optimization by means of a computer ensures that the individual design values of the driver's cab are determined in overall correlation and not each in their individual effect on the aerodynamics of the vehicle. The latter approach would only result in a less than optimum drag coefficient.
In a further advantageous embodiment of the invention the external geometric shape and the edge shape of the driver's cab are aerodynamically optimized as a function of one another. It has been determined that the edge shape of the bodyshell, in particular, and the external geometric shape (that is, the width, height and length) of driver's cabs, have a substantial influence on the overall aerodynamics of a driver's cab and a vehicle bodyshell. The aerodynamically and coherently optimized parameters of the edge shape and external geometric shape of the driver's cab serve largely to prevent turbulence, and thereby sources of air resistance. The flow resistance is thus reduced.
According to still another embodiment of the invention the end face area of the driver's cab is optimized, coordinating its external shape with the air flow within predefined limits and in predefined steps for the design parameters of the end face area. This measure alone makes it possible to achieve a considerable improvement in the aerodynamics, and hence a considerable reduction in the fuel consumption. Merely through the number of design parameters which affect the end face area of a driver's cab (which in the state of the art generally has a relatively angular front inclining downwards in a straight line), it is possible to improve the aerodynamics of the driver's cab without greatly influencing the technically essential design shaping.
According to another feature of the invention, the driver's cab design parameters which are optimized as a function of one another in predefined steps are selected from the following group:
a) Width of driver's cab
b) Height of driver's cab
c) Length of driver's cab
d) Corner radius
e) Sweepback
f) Taper
g) Roof radius
h) Windshield inclination
Surprisingly, it has been determined that these particular cab design parameters, in their overall correlation, have a considerable influence on the aerodynamic properties of the driver's cab, which can be optimized by varying such parameters, provided that they are set within given limits. The driver's cabs according to the invention therefore do not have any extreme individual parameter values, such as an extremely shallow inclination of the windshield or an extremely rounded corner radius. Rather, they are optimized within the context of an acceptable design modification of the aforementioned parameters relevant to the aerodynamics. A considerable improvement was obtained in terms of the drag coefficient (cw value).
The method according to the invention for optimizing the aerodynamics of a driver's cab of a motor vehicle by determining a plurality of design parameters includes:
In this way it is possible to improve the drag coefficient of driver's cabs solely by a specific variation of design parameters that strongly influence its aerodynamic properties. In each case, the design parameters are optimized in overall correlation, and observing limits. Extreme values for individual parameters are thus avoided. The costs of the method are contained, since the scope for varying individual parameters is defined on the one hand by upper and lower limits, and on the other by predefined steps in the parameter values. It has been shown that in this way, within the framework of design and vehicle construction limits, it is possible to achieve a considerable improvement in the aerodynamics of driver's cabs, particularly of trucks.
According to a further advantageous embodiment of the method according to the invention the parameters are each predefined in a specific graduation in the range of variation, which reduces the cost of implementing the method. The results in the parameter values are, moreover, unambiguous and avoid odd intermediate values. The graduation of the parameter values also has the advantage that relatively few computer calculations and relatively short computer times are required for carrying out the method.
In another advantageous embodiment of the invention, the design parameters undergo two-dimensional analysis for their respective influence on the aerodynamic resistance of the driver's cab, and are then fixed by means of a computer through three-dimensional evaluation and synthesis of each of the optimum values. The individual steps of analyzing the individual influences by two-dimensional evaluation and then combining them in a computer step for overall optimization have proved expedient. The cost of calculating and determining the resulting parameter values is minimized.
According to the invention a number of design parameters can be optimized, selected from the following group:
a) Width of driver's cab
b) Height of driver's cab
c) Length of driver's cab
d) Corner radius
e) Sweepback
f) Taper
g) Roof radius
h) Windshield inclination
These design measures can each be varied within predefined limits without excessive restrictions on the design or feasibility requirements for driver's cabs for vehicles, especially trucks, and each has a separate and determinable individual influence on the air resistance and the aerodynamics of the driver's cab. In the case of a negative influence on the air flow or the air resistance it is precisely these parameters which cumulatively produce an extremely negative drag coefficient of the overall vehicle. For this reason it has been determined that a joint, coordinated optimization of these parameters leads, within prescribed limits, to unexpected improvements in the aerodynamics of vehicles.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.
The driver's cab 10, represented schematically in a top view in
A: Width of driver's cab
B: Length of driver's cab
C: Corner radius (or edge rounding)
D: Sweepback
E: Taper
F: Roof radius
G: Windshield inclination
H: Height of driver's cab (not visible in the figure)
These design parameters of the driver's cab all have a specific value, which is optimized from a predefined variation range, and as a function of the individual influences of the parameters on the aerodynamics of the driver's cab having regard to the overall aerodynamics. The external shape of the driver's cab 10 is nevertheless arrived at within the essential technical and feasibility limits. None of the individual parameters is exaggerated through extreme design, for example the windshield inclination G, which obviously by itself, would have an optimum drag coefficient at an extremely shallow angle of inclination.
In this exemplary embodiment according to
After fixing these limits and gradations for the parameters, according to the invention the aerodynamic influence of each individual parameter within a predefined range is analyzed by means of wind tunnel tests. The individual parameters can also be analyzed by simulation programs or the like. The joint optimization of the values with a view to the overall drag coefficient of the driver's cab leads to the parameter values for the taper E, the sweepback D, the corner radius C, the roof radius F and the windshield inclination G given as examples. The sweepback D is in this case the taper of the cab front from the center towards the side (see
The invention is obviously not limited to the design parameters given and may comprise just some of the parameters or also other design parameters of driver's cabs.
The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.
| Number | Date | Country | Kind |
|---|---|---|---|
| 103 06 162.2 | Feb 2003 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP03/13770 | 12/5/2003 | WO | 4/6/2006 |
