Wind tunnel balance

Abstract

The invention relates to a wind tunnel balance, having at least one belt unit that has at least one belt unit frame equipped with at least one conveyor belt that is wound around at least two rollers. The wind tunnel balance also has at least one fastening device that is suitable for fastening a vehicle to the conveyor belt in a predetermined position, a frame, and a platform that is supported so that it is able to move relative to the frame; force measuring elements are provided between the platform and the frame and are able to detect forces between the frame and platform, and the fastening device is attached to the platform in stationary fashion. The invention permits a high-precision detection of aerodynamic forces in wind tunnel measurements or tests.

Claims

1. A wind tunnel balance, comprising: at least one belt unit that has at least one belt unit frame equipped with at least one conveyor belt that is wound around at least two rollers; at least one fastening device configured to fasten a vehicle to the conveyor belt in a predetermined position; a frame; and a platform that is supported so that it is configured to move relative to the frame, wherein force measuring elements are provided between the frame and the platform and are configured to detect forces between the frame and platform, the fastening device is attached to the platform, the at least one belt unit is supported on the frame, the platform is coupled to the at least one belt unit by means of at least one connecting mount such that forces in the x and/or y direction are transmitted from the belt unit to the platform, the connecting mount connects the platform to the belt unit in the z direction, and the belt unit is supported on the frame by means of a floating mount.

2. The wind tunnel balance according to claim 1, wherein the floating mount permits a relative movement of the belt unit in relation to the frame in the x and y direction.

3. The wind tunnel balance according to claim 1, wherein at least one connecting mount is a hydrostatic and/or pneumatic mount, and at least one guide pin is arranged in at least one guide socket.

4. The wind tunnel balance according to claim 1, wherein at least one connecting mount permits a transmission of forces in the x direction from the belt unit to the platform and the connecting mount connects the platform to the belt unit frame in the y and z directions.

5. The wind tunnel balance according to claim 1, wherein the force measuring elements include at least one x force measuring element, at least one y force measuring element, and/or one z force measuring element is/are provided between the platform and the frame, the at least one x force measuring element is arranged so that it is possible to detect a force in the x direction between the platform and the frame, the at least one y force measuring element is arranged so that it is possible to detect a force in the y direction between the platform and the frame, and the at least one z force measuring element is arranged so that it is possible to detect a force in the z direction between the platform and the frame.

6. The wind tunnel balance according to claim 1, wherein the force measuring elements include at least one ventilation loss force measuring element is provided, which is arranged between the belt unit and the platform so that it is possible to detect a force in the x direction between the platform and the belt unit, thus making it is possible to separately detect a ventilation loss of the vehicle wheels.

7. The wind tunnel balance according to claim 1, wherein at least one rocker pad is situated underneath an upper run of the at least one conveyor belt, the rocker pad is arranged so that the vehicle, when it is affixed to the conveyor belt, rests on the conveyor belt with the vehicle wheels on top of the at least one rocker pad, and the at least one rocker pad detects forces in the z direction, in particular the weight force of the vehicle as well as lift forces and/or negative lift forces.

8. The wind tunnel balance according to claim 1, wherein the fastening device secures the vehicle to the conveyor belt in a fixed position above the at least one rocker pad, and the fastening device affixes to the vehicle so that forces in the x, y, and/or z directions are transmitted from the vehicle to the platform via the fastening device.

9. The wind tunnel balance according to claim 1, wherein at least one z force measuring element is configured to separately measure parasitic forces in the z direction (z forces) that are transmitted to the z force measuring element via the fastening device and the platform.

10. The wind tunnel balance according to claim 1, which includes one, three, five, or seven belt units.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be described by way of example below with reference to the accompanying schematic drawings. In the drawings:

(2) FIG. 1 shows a sketch of a side view of the wind tunnel balance according to the invention, according to example 1,

(3) FIG. 2 shows a sketch of a top view of the wind tunnel balance according to the invention, according to example 1,

(4) FIG. 3 shows a sketch of a side view of the wind tunnel balance according to the invention, according to example 2, and

(5) FIG. 4 shows a sketch of a top view of the wind tunnel balance according to the invention, according to example 2.

DETAILED DESCRIPTION OF EMBODIMENTS

(6) FIG. 1 shows a preferred example of the wind tunnel balance according to the invention. A platform (1) is used, which is connected or coupled to the belt unit (3) and/or a belt unit frame (3a) by means of a connecting mount (7) with frictional, nonpositive engagement only with regard to the x and y directions. The forces in the z direction are diverted via (essentially) frictionless mounts (8), e.g. floating mounts or sliding mounts. The frictionless mounts (8) can also be embodied as articulated mounts, i.e. the mounts are then composed of rod-shaped or column-shaped supports that have cross-sectionally tapered sections (curves, recesses) that are that are oriented so that they are skew relative to each other by for example 90 in the axial direction. It is also possible to provide each support with more than two cross-sectionally tapered sections.

(7) FIG. 1 shows that a belt unit frame (3a) of the belt unit (3) has two rollers (3c) supported in rotary fashion. A continuous conveyor belt (3b) is arranged (wound) around these rollers (3c) and can be set into motion, for example, by a rotating motion of the rollers (3c). The belt unit frame (3a) has stand elements (3d) that support the weight of the belt unit (3) and are each supported on a frame (4) by means of a respective floating mount (8). Consequently, the weight force of the belt unit (3) and of the motor vehicle (9) possibly resting on it is diverted into the frame (4). In addition, the frame (4) can be supported so that it is able to rotate around the z axis relative to its surroundings (not shown).

(8) The platform (1) is for example a unit that is arranged centrally in the frame (4). The distances shown in FIG. 1 between the platform (1) and the frame (4) are provided for better illustration, i.e. much smaller or larger distances can be provided. The shape of the platform (1) can be embodied in plate-like fashion, in the basic shape of a rectangle, as shown in FIG. 1. A more complex form of the platform (1), however, is also possible according to the invention. The platform (1) does not necessarily have to be embodied as plate-shaped.

(9) It is also clear from FIG. 1 that two connecting mounts (7) make it possible to couple the x and y movement between the belt unit (3) and/or its belt unit frame (3a) and the platform (1). FIG. 1 shows that the connecting mounts (7) have guide pistons (7a) mounted on the side oriented toward the belt unit, which engage in associated guide sockets (7b) that are mounted on the platform (1). The guide pistons (7a) slide in (essentially) frictionless fashion inside the guide sockets in the z direction, i.e. up and down. A support in the z direction is embodied, for example, in a hydraulic or pneumatic fashion so that no forces or essentially no forces are transmitted from the belt unit (3) to the platform (1) in the z direction. By contrast, the positive, form-fitting engagement of the guide piston (7a) in the preferably complementarily shapedin this case cylindricalguide socket (7b) permits x and y movements of the belt unit (3) and/or its belt unit frame (3a) to be transmitted/transferred to the platform (1).

(10) By means of z force measuring elements (2c)only two are shown, but it is particularly preferable to provide three or fourthe platform (1) is supported in the frame (4) in the direction of the vertical axis (z direction). Forces detected can, for example, be displayed by means of an evaluation unit (not shown).

(11) The forces along the driving axis (x forces) are detected with at least one x force measuring device (2a), which in FIG. 1 is provided between a front end of the platform (1) in the x direction and a section of the frame (4).

(12) The forces perpendicular to the driving axis (y forces) are detected/measured with at least one, preferably two, y force measuring element(s) (2b). Two y force measuring elements can be provided that are arranged on the side of the platform (1) and are spaced apart from each other in the x direction. The opposite end of the y force measuring element (2b) is solidly attached to the frame (4).

(13) In the figures, all of the force measuring elements (2) are schematically depicted in the form of spring elements. In the real device, preferably load cells or strain gauges (or strain gauges integrated into load cells) are used (it is also possible, however, to use other force measuring devices), which are arranged centrally in one or between two Eulerian columns or pillars. It is naturally also possible to provide an alternative fastening and/or arrangement of the force measuring elements.

(14) FIG. 1 also shows that the platform (1) is connected to at least two (or possibly also three or more) first fastening elements (6a) (fastening brackets) of a fastening device (6) (restraint system). The two fastening brackets (6a) stand in the z direction, preferably vertically and respectively to the side of the conveyor belt (3b), preferably in a central positionwith regard to the x directionof the wind tunnel balance on the platform (1). FIG. 1 also shows that the upper endsin the z directionof the fastening brackets (6a) protrude beyond the z height of the upper run of the conveyor belt (3b). Preferably, at least one second fastening element (6b) is fastened in the protruding end section of the fastening brackets (6a). The second fastening element (6b) is preferably a cable, a belt, a very thin rod, or an arrangement of various components such as cables, belts, etc. and, at the end oriented toward the vehicle (9), can have a rocker fitting. Preferably, at least two second fastening elements (6b) are provided for each side of the vehicle (in the y direction), which are arranged in corresponding sockets on the vehicle (9) by means of rocker fittings. The second fastening elements (6b) hold the vehicle (9) in a predetermined position on (relative to) the conveyor belt (3b). Any x/y forces acting on the cables are diverted via the cables (6b) and only act as internal forces, i.e. these forces are not detected by the force measuring elements (2a, 2b).

(15) If the second fastening elements (6b) are not guided exactly in the horizontal direction, for example, this produces parasitic z forces that are detected by at least one rocker pad (5) underneath the upper run of the conveyor belt (3b). In addition, these parasitic z forces are also separately conveyed to the z force measuring element (2c) via the fastening device (6). This permits an offsetting/correction of the measured z forces at the rocker pad (5) and at the z force measuring elements (2c) and thus enables an increased measurement precision.

(16) FIG. 2 schematically depicts a top view of the example according to FIG. 1. It is clear from the depiction in FIG. 2 that a one-sided arrangement of y force measuring elements (2b) is sufficient to allow a precise measurement to be carried out. It also shows that the platform (1) protrudes laterally (in the y direction) at least far enough beyond the outer lateral edge of the conveyor belt (3b) that there is room for the fastening brackets (6a) in the protruding sections.

(17) FIG. 2 also shows the arrangement of the platform (1) that is situated in the middle of the frame (4) or is at least essentially centered in it.

(18) Underneath the conveyor belt (3b), shown by means of squares in FIG. 2, rocker pads (5) are provided on which the vehicle wheels are positioned. The vehicle (9) is not shown in FIG. 2. The rocker pads (5) use a through-the-belt measurement to detect a weight force, i.e. a z force here, that can have various components. For example, the z force detected by means of the rocker pads (5) can in particular be the sum of the weight force of the vehicle (9), lift forces, negative lift forces, and parasitic z forces. As has already been described several times, the wind tunnel balance according to the invention can detect the parasitic z forces separately so that they can be offset (corrected) with the z forces measured at the rocker pads (5).

(19) FIG. 2 also shows the second fastening elements (6b) whose ends respectively connect a socket on the vehicle frame and the associated first fastening element (6a) to each other.

(20) In another example of the wind tunnel balance according to the invention (FIGS. 3 and 4), the at least one belt unit (3) or the belt unit frame (3a) or the conveyor belt(s) (3b) is/are connected to the platform (1) via an additional force measuring element (10). This makes it possible to separate forces occurring in the wheels, e.g. roll forces, walk forces, and/or ventilation losses that are measured at the ventilation loss force measuring element (10). The other aerodynamic forces continue to be available at the force measuring elements (2a-2c). Specifically, FIG. 3 shows that the ventilation loss force measuring element (10) is solidly mounted to a front end of the platform (1) in the x direction (but a different position is also possible). By contrast with the other force measuring elements (2a-2c), the second end of the ventilation loss force measuring element (10) is situated on the belt unit (6). In this case, it is situated on one of the stand elements (3d). It is thus possible, for example, to detect the relative movement in the x direction between the platform (1) and the belt unit (3), thus permitting an additional, separate determination of the ventilation losses in the wheels of the vehicle (9). These ventilation losses can, for example, be offset with the other detected force values in order to increase the measurement precision of the wind tunnel balance.

(21) In addition, FIG. 3 together with FIG. 4 also shows another example of the connecting mount (7) according to the invention. It should be noted here that the additional example of the connecting mount (7) is only shown together with the example of the additional ventilation loss force measuring element (10) for illustration purposes. Naturally, the example according to FIG. 1 can also have the additional ventilation loss force measuring element (10).

(22) As is particularly shown in FIG. 3, two rails (7c) are solidly mounted onto the belt unit and are spaced apart from each other in the x direction. Two engaging elements (7d) solidly mounted to the platform (1) on each side engage in the receiving opening of the rails (7c) so thatas in the example according to FIG. 1a coupling of the x/y movements is possible, but a frictionless support is provided in the z direction.

(23) Naturally, examples or embodiments of the wind tunnel balance are also possible in which, for example, a movement coupling only in the x direction or only in the y direction is implemented and a frictionless support is provided in the z direction and in the x or y direction.

(24) In summary, the wind tunnel balance according to the invention has the advantage that parasitic forces in the z direction can be conveyed via the fastening device (6) to the z force measuring element (2c) and measured by the latter in an isolated fashion. As a result, the measuring values of the rocker pads (5) can be corrected and more precise measurements can be carried out. The measurement precision is further increased by the fact that the weight force of the wind tunnel balance is diverted via the floating mounts (8) and therefore does not exert strain on the platform (1).

(25) The examples shown can be arbitrarily combined with one another in any way that would be obvious to the person skilled in the art. 1 platform 2 force measuring element 2a x force measuring element 2b y force measuring element 2c z force measuring element 3 belt unit 3a belt unit frame 3b conveyor belt 3c roller 3d stand elements 4 frame (of the wind tunnel balance) 5 rocker pad 6 fastening device 6a first fastening element (side brackets) 6b second fastening element (belts, cables, etc.) 7 connecting mount 7a guide pin/driving pin 7b guide socket 7c rail 7d engagement element 8 floating/sliding mount 9 (motor) vehicle 10 ventilation loss force measuring element