Abstract:
An aeronautical high-lift system comprising a drive unit, elements for the transmission of the drive energy to drive stations of individual segments of landing flap/slat flap systems as well as comprising an overload safety device, with the overload safety device having at least one electrical overload sensor which is arranged in the drive chain between the drive unit and an output drive station.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to an aeronautical high-lift system comprising a drive unit, elements for the transmission of the drive energy to drive stations of individual segments of landing flap/slat flap systems and comprising an overload safety device. 
     Aeronautical high-lift systems comprising a central drive unit which is in connection with an auxiliary drive for two wing halves are known.  FIG. 4  shows such a high-lift system in accordance with the prior art. The transmission of the right wing is illustrated. The drive unit  10  is in connection with the transmissions of the two wings via the auxiliary drive  20 . The system load limiter  50  is located between the heavy duty transmission  30  and the low load transmission  40  of the wing. Load stations of the wing flaps are designated by the reference numeral  60 . The reference symbol  62  designates the transmission brake. 
     The required drive torque of the drive unit  10  is determined by the loads of the two wing transmissions. If a jam or seizure occurs in the system (e.g. at the load stations  60  of the wing flaps), then the load in the transmission of the affected wing rises until the system load limiter  50  prevents a further load rise in the low load transmission  40 . In this situation, the entire drive torque is conducted into one wing up to the system load limiter  50 . It has the task of protecting at least a portion of the transmission of a wing from the drive torque of two wings. 
     A spring biased ball ramp mechanism is usually used as a system load limiter  50  and in the event of an overload actuates a further mechanism which leads off the overload into the airplane structure and in this way protects the low load transmission  40 . 
     It cannot be prevented by the braking of the drive unit  10  that a large torque builds up in the heavy duty transmission  30  as a result of the kinetic drive energy and of the blocking torque. The heavy duty transmission  30  and the devices which are located within it must thus be designed for a very heavy load/load peak. There results from this the disadvantage of a large weight of the heavy duty transmission  30  and of the affected devices. 
     SUMMARY OF THE INVENTION 
     It is the object of the present invention to achieve a load reduction and thus a weight reduction in an aeronautical high-lift system of the initially named kind. 
     This object is solved in accordance with the invention by an aeronautical high-lift system. 
     The overload safety device accordingly comprises at least one electrical overload sensor which is arranged in the drive chain between the drive unit and an output drive station. This also comprises the case in which the overload sensor is arranged in an output drive station or measures its load. An overload state can be rapidly detected by means of the electrical overload sensor, whereby the load in the transmission can be rapidly reduced and consequently the weight of the transmission and of the devices concerned can be reduced. 
     In a preferred embodiment of the invention the overload safety device comprises a mechanically actuated electrical overload sensor. 
     The overload sensor can be arranged in the drive chain within the output drive station disposed closest to the drive unit. 
     In a further embodiment of the present invention, an electronic regulator is provided which is in connection with the overload sensor or sensors as well as with the drive unit and which has means by which an electrical signal can be fed into the drive unit on reception of a load which exceeds a threshold value. 
     In order to be able to reduce the drive energy very rapidly and preferably to hold the system at a low load level, provision can be made for the signal to result in a reversed operation and preferably in a stopping of the drive unit. Provision can be made for the regulator algorithm of the regulator to be designed such that, after the arrival of an overload signal, a reversal of the desired value of the direction of rotation specified to the drive unit is generated until the actual value of the speed of rotation of the drive assumes the value zero. 
     Furthermore, provision can be made for the drive unit to comprise high-dynamic drives, in particular hydraulic motors with an adjustable displacement volume or brushless direct current motors, for the rapid regulation of the drive power. 
     It is particularly advantageous for the overload sensor or sensors to comprise or to be in connection with a mechanical element which reduces the stiffness to twisting of the unit when a set maximum torque is exceeded. This mechanical element can, for example, be a ball ramp mechanism. 
     Furthermore, provision can be made for the overload sensor or sensors to have or to consist of an electromagnetic switch or an inductive proximity switch. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further details and advantages of the invention will be explained in more detail with reference to an exemplary embodiment which is illustrated in the drawings. There are shown: 
         FIG. 1 : a schematic view of the aeronautical high-lift system in accordance with the invention, 
         FIG. 2 : a schematic view of the spring biased ball ramp mechanism with various characteristic curves, 
         FIG. 3 : a schematic view of the digital monitoring conception and 
         FIG. 4 : a schematic view of an aeronautical high-lift system in accordance with the prior art. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  shows the drive unit  10 , which is connection with the transmissions of the two wings via the auxiliary drive  20 . The transmission serves to transmit the drive energy over the entire wing span. The system load limiter  70  or a sensor unit is provided in the transmission and is located in the drive chain or in the central drive shaft between the drive unit  10  or the auxiliary drive  20  and the load stations  60  of the wing flaps. The reference numeral  62  designates the transmission brake. The electronic monitoring device is designated by the reference numeral  80  and is, as can be seen in  FIG. 1 , in connection both with the system load limiter  70  and with the drive unit  10 . The drive unit  10  consists of hydraulic motors with adjustable displacement volume or brushless direct current motors. 
     Alternatively to the arrangement shown in  FIG. 1 , provision can furthermore be made for the sensor unit to be arranged in the first load station  60  (seen from the rear of the airplane). The load of the first station  60  is measured and an indication of an overload is reported to the electronic monitoring device  80 . In an embodiment of the invention of this kind, the further steps preferably take place in accordance with the procedure which is described pertaining to  FIG. 1 . The sensor unit which measures the load of the first station  60  is preferably the system load limiter shown in  FIG. 2   a . Generally, other sensor units can also be used. 
     The system load limiter  70  is a mechanically actuated electrical overload sensor. 
     If a system seizure occurs, the load is determined by the system load limiter  70  or a sensor unit. The load is compared with a threshold value. If the result of this comparison is that the actual value of the load lies above the threshold value, the electronic monitoring device  80  emits a corresponding signal to regulate the motors of the drive unit  10  down, as is indicated in  FIG. 1 . The comparison between the actual value of the load and the threshold value can take place in the system load limiter  70  or a sensor unit or also in the electronic monitoring device  80 , which comprises an electronic regulator. As a result of the high-dynamic drives of the drive unit  10 , the drive power can be reduced very rapidly, whereby the load in the transmission can be reduced, and it and the components contained in it can be designed with a correspondingly lighter weight. A mechanism which is in connection with the system load limiter  70  and which conducts the overload into the airplane structure, however, do not necessarily have to be provided. 
     Furthermore, the system load limiter  70  has a spring biased ball ramp mechanism which is deflected when the load exceeds the permitted amount in the case of a system seizure. Details of this are shown in  FIG. 2 , which in  FIG. 2   a  shows a schematic illustration of the ball ramp mechanism. The response point and the characteristic curve of the ball ramp mechanism are reproduced in  FIG. 2   b , and the load characteristic curve in the drive chain in the event of a system seizure is reproduced in  FIG. 2   c . As can be seen from  FIG. 2   b , the ball ramp mechanism is deflected by an amount Δx when the load of the transmission exceeds the value T 1o . This deflection can be detected by a suitable sensor, for example by a proximity switch, and transmitted to the electronic monitoring device  80 . The threshold value of the deflection of the ball ramp mechanism is designated in  FIG. 2   b  by the symbol Δx m . If this threshold value is reached, the electronic monitoring device  80  emits signals to the drive unit  10  which lead to a rapid reduction of the drive torque. 
     A positive side effect of the ball ramp mechanism consists of the fact that the load no longer rises as steeply when the mechanism responds (load of the transmission≧T 1o ), as can be seen from  FIG. 2   c . Time is thus gained for the electronic monitoring. 
       FIG. 3  shows a schematic illustration of the electronic monitoring device  80 , which has an electronic regulator. As can be seen from  FIG. 2 , the path distance signal Δx is detected by a sensor unit and transmitted to the electronic monitoring device  80 . It is polled here whether the path distance signal exceeds the threshold value Δx m . If this is the case, the electronic monitoring device emits the following commands or signals to the drive unit: 
     The motor torque is switched to 100% in the opposite direction; if the speed of rotation of the motor is 0, this value is maintained; furthermore, the brake receives the command: “apply”. 
     On reception of a load which exceeds the threshold value, an electrical signal is thus fed in to the drive system, which has the result that the drive energy is very rapidly reduced through reverse operation of the drive unit and the system is held at a low load level. 
     In summary, the following advantages can be achieved with the present invention. A substantial load reduction and thus a weight reduction are achieved. An indication and reporting back of overloads as a result of system seizures is possible. This indication can be integrated into various system components which are already present. A delay in the load rise on overloads can be achieved by a corresponding constructional design of the mechanism for the indication. Furthermore, a digital monitoring concept can be provided which is in connection with the overload sensor as well as with the drive unit. A reduction of the overload can be achieved particularly rapidly by an actively regulated reduction of the output torque by “trimming”. Furthermore, the function of the system can be tested without further ado. 
     In addition to the already named load and weight reduction, the aeronautical high-lift system in accordance with the invention has the advantage of a high reliability and is simple to test in order to ensure a correct functioning over its entire lifetime. 
     The overload safety device in accordance with the invention can be tested relatively simply. The test function described in the following is carried out on the ground and can take place in conjunction with the testing of the transmission brake which is done from time to time. For this purpose, one of the two transmission brakes (right or left wing) is arrested. Then the drive unit is operated against the brake at low speed of rotation and at a specific drive torque. The drive torque conforms to the response behavior of the ball ramp mechanism and must be so large that the deflection Δx m  is reached with certainty. When the drive unit comes to a standstill as a result of the applied transmission brake, an indication with respect to the deflection Δx m  must occur. 
     If it does not occur, a faulty overload safety device must be assumed. The procedure is repeated for a second wing half after successful completion for a wing half.