HYBRID PROPULSION SYSTEM OF A HELICOPTER

Abstract

A hybrid propulsion system with controllers and a drive shaft of a helicopter with a main rotor connected to a gearbox which can keep a flight attitude set by a pilot stable. It includes a pilot controller, a combustion engine and an electric motor, both of which act directly on the drive shaft. The VM is connected to a VM controller, and the EM is connected to an EM controller. One torque sensor and one tachometer are each arranged on the drive shaft, wherein during operation both the VM controller and the EM controller are able to receive values for the current speed and the current torque. Specified values for speed and torque, in which the VM can attain its optimum efficiency, are stored in memory and can be retrieved by the EM controller, wherein the first value can also be retrieved by the VM controller.

Claims

1-9. (canceled)

10. A Hybrid propulsion system with controllers and a drive shaft of a helicopter, with a main rotor which is connected to a gearbox and is able to keep a flight attitude set by a pilot stable, comprising: a pilot controller, a combustion engine (VM) and an electric motor (EM), both of which act directly on the drive shaft, wherein the VM is connected to a VM controller which is able to adjust a supply of fuel from a fuel tank to the VM in order to provide a desired propulsive power at the drive shaft; and wherein the EM is connected to an EM controller, which is able to operate the EM by discharging a battery or charge the battery by an application of a mechanical power on the EM, whereby the drive shaft would be either accelerated or decelerated respectively, wherein one or more torque sensors and tachometers are each arranged on the drive shaft, and both the VM controller and the EM controller are able to maintain values for both a current speed and a current torque during operation, wherein specified values for the speed and the torque, in which the VM is able to attain its optimum efficiency, are stored in memory and are retrievable by the EM controller, a first value also being retrievable by the VM controller, and that the VM controller is able to reach a preset speed at the drive shaft at any time and maintain it autarchically by adapting an output of the VM in order to keep any flight attitude set by the pilot controller stable, wherein the EM controller is additionally able to accelerate or decelerate the drive shaft by engaging the EM, whereby the VM controller is able to adapt the output at the VM automatically based on the current speed in order to reach or maintain a preset speed at the drive shaft, and wherein a first directive is stored in the EM controller to continuously exert an accelerating or braking force of such kind from the EM on the drive shaft, thereby causing the VM, when it has reached or maintains the optimal speed at the drive shaft, to automatically generate the torque at the drive shaft, at which it attains an optimum engine output.

11. The hybrid propulsion system according to claim 10, wherein the EM is arranged between the VM and the gearbox of the main rotor.

12. The hybrid propulsion system according to claim 10, wherein a direct data signal line is set up between the pilot controller and the VM controller for take-off and landing of the helicopter.

13. The hybrid propulsion system according to claim 10, wherein a fuel level meter is also arranged on the fuel tank and a charge state indicator is arranged on the battery, and both are able to transmit their measurement data while the EM controller is in operation.

14. The hybrid propulsion system according to claim 13, wherein a calculation unit for calculating energies that are still available and if necessary for calculating a second directive which differs from the first directive for protecting the battery from overcharging and undercharging, economising on fuel and/or temporarily operating the VM at lower power to reduce emissions.

15. A method for operating a hybrid propulsion system for a drive shaft of a helicopter for guaranteeing a flight attitude set by the pilot using a hybrid propulsion system with controllers according to claim 1 wherein current speed and torque values at the drive shaft are measured continuously and transmitted to both the EM controller and the VM controller, specified values for speed and torque are stored in memory, wherein both values can be retrieved by the EM controller and at least the speed can be retrieved by the VM controller, wherein said controllers continuously calculate deviations of the measured values from the preset values, as soon as a pilot generates a changeable request for power at the drive shaft via the pilot controller to reach a desired flight attitude, a change in the speed at the drive shaft is also caused, the VM controller changes the output at the VM on the basis of a deviation between the current speed and the preset speed slowly in such a way that the preset speed is attained, the EM controller changes the output at the EM in accordance with its first directive in response to a difference between the current values for speed and/or torque and the corresponding preset values more quickly than the VM, in such manner that the VM, when it has adjusted its output to the preset speed with a time lag, exerts the preset torque in which it attains optimal efficiency, whereby either the battery is charged by the mechanical power at the EM or the EM is operated by the charge in the battery, and when the EM controller is deactivated, the VM controller automatically provides requisite propulsive power via VM based on the adjustment of the speed to the preset value and thus guarantees a stable flight attitude.

16. The method according to claim 15, using a hybrid propulsion system wherein the EM controller determines an amount of energy still available on the basis of a measurement data from a fuel level meter of the fuel tank and/or a charge state indicator of the battery, and consequently, behaves according to a second directive with differs from an instruction of the first directive, in order to selectively charge or discharge the battery, to protect the battery, to save fuel or to temporarily operate the VM at lower power, in order to reduce emissions.

17. The method according to claim 15, wherein during a take-off and landing phases only the EM is operated, in order to reduce noise and exhaust emissions in a landing area.

18. The method according to claim 15, wherein during operation the EM controller increases the output at the EM if speed is too low (DZ<DZ.sub.0) and/or torque is too high (DM>DM.sub.0), and vice versa.

19. The method according to claim 16, wherein during a take-off and landing phases only the EM is operated, in order to reduce noise and exhaust emissions in a landing area.

20. The method according to claim 16, wherein during operation the EM controller increases the output at the EM if speed is too low (DZ<DZ.sub.0) and/or torque is too high (DM>DM.sub.0), and vice versa.

21. The method according to claim 17, wherein during operation the EM controller increases the output at the EM if speed is too low (DZ<DZ.sub.0) and/or torque is too high (DM>DM.sub.0), and vice versa.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In the following text, the invention will be described in greater detail with reference to the drawing. In the drawing:

[0037] FIG. 1 is a schematic representation of a hybrid propulsion system according to the invention;

[0038] FIG. 2 is a graph describing the distribution of loads in various flight attitude, such as climbing, level flight and descent.

DETAILED DESCRIPTION

[0039] FIG. 1 represents a hybrid propulsion system 4 according to the invention in greater detail than is necessary for a simple description of the invention. It shows a partial area of a helicopter with a drivetrain 3, a gearbox with main rotor 1, as well as a tail rotor 2, which is not significant for the object of the invention. A combustion engine (VM) 6 and an electric motor (EM) 10 are arranged in parallel on the drivetrain 3, wherein the EM 10 is preferably arranged between the VM 6 and the gearbox of the main rotor 1. Other configurations are also possible.

[0040] A pilot controller 5 is responsible for receiving the control commands of a pilot for trimming the main rotor blades, as a result of which the engine output to be set is calculated indirectly as the required speed DZ.sub.0 at the drive shaft 3. A data signal line 19 from the pilot controller to the VM controller 7 which is optional for the flight mode according to the invention may be used for take-off and landing manoeuvres.

[0041] The VM 6 is connected to a fuel tank 8, which is connected to the VM controller 7, which can adjust the supply of fuel from the fuel tank 8 to the VM 6 to provide the required propulsive output at the drive shaft 3. The EM 10 is also connected to a battery 14, preferably via a power converter 12 and via a charging unit 13, which may be equipped with current peak buffering. The EM 10 may be operated by the charge in the battery 14, or the battery 14 may be charged by the mechanical power at the EM 10, with the result that the drive shaft 3 is either accelerated or decelerated in each case. An EM controller 11 is connected to the EM 10 at least indirectly, via a power converter 12 for example, and can adjust it to deliver a required accelerating or decelerating force at the drive shaft 3.

[0042] In addition, a fuel level meter 9 may be arranged on the fuel tank 8 and a charge state indicator 15 on the battery 14, both of which can transmit their measurement data during operation to a calculation unit 16.

[0043] At least one torque sensor 17 and one tachometer 18 each are arranged on the drive shaft 3. During operation, the VM controller 7 and the EM controller 11 each receive data from at least one torque sensor 17 and one tachometer 18.

[0044] The calculation unit 16 is connected to the EM controller 11 and to the VM controller 7. It is used to calculate the energies that are still available, the torque required at the drive shaft 3 and/or to manage the EM controller 11. It includes a data memory 20, in which the values of a preset speed DZ.sub.0 and a preset torque DM.sub.0 are stored, wherein based on these values an optimum power coupling of the VM 6 is achieved, the efficiency of the VM being greatest at these values.

[0045] In operation, it is the EM controller 11 which initiates the distribution of loads to the VM 6 and the EM 10. This is represented schematically in FIG. 2.

[0046] The dashed plot in the top diagram represents the flight attitude as a function of time, as requested in each case by the pilot controller 5, in particular altitude H. In this context, altitude “0” is understood to be the ground. The solid line represents the effective altitude H, which is slightly delayed. In the first phase (I) the helicopter climbs steadily until it has reached the desired altitude H.sub.1. In the second phase (II) it continues flying level at this altitude, and in the third phase (III) it descends again. There is a period between each flight phase before the newly specified target is reached.

[0047] The plots in the middle diagram schematically indicate the total load P.sub.H, i.e. the total torque at the main rotor (dashed line), the load P.sub.VM at the VM 6 (dot-dashed line) and the load P.sub.EM at the EM 10 (dotted line). The bottom diagram indicates the speed DZ.

[0048] After the take-off procedure, the VM 6 works at a constant, high level. In the first phase I, the EM 10 serves as an additional drive by delivering the torque DM.sub.0 as soon as the VM 6 has reached the preset optimal load P.sub.VM. It supports the VM (6) during phase I while climbing until the preset altitude H.sub.1 is reached, i.e. the pilot slightly flattens the angle of attack of the rotor blades. The take-off procedure can be performed according to instructions other than the first directive until the helicopter is safely airborne.

[0049] Flattening the rotor blades at the beginning of phase II causes the speed DZ to briefly increase slightly, as is shown in the bottom diagram. The EM 10 responds to this immediately, and lowers its output until the speed DZ matches the setpoint DZ.sub.0 again. The altitude now remains constant throughout the entire phase II. The VM 6 is slow and therefore does not respond to this brief change. In the example shown, the load on the EM 10 in phase II is negative, so it functions as a generator, returning the extra available energy from the excess output from the VM 6 to the battery 14. The VM 6 also does not change its load in phase II.

[0050] When preparing to descend, at the beginning of phase III, the pilot slightly flattens the rotor blades again, the speed DZ again increases briefly, the EM 10 again responds to this by reducing its output. This time, however, it adjusts to a speed DZ slightly higher than the preset value DZ.sub.0, according to a second directive. Now the energy at the EM 6 is recovered faster still, because the EM 10 continues to decelerate the drive shaft 3. Since the speed DZ is slightly elevated, the VM 6 now responds by reducing its output steadily. Meanwhile, the EM 10 maintains the elevated DZ, as is represented by the bottom plot in phase III: The solid line, representing the current speed DZ, is higher than the dashed line, which represents DZ.sub.0. While the current speed DZ is greater than the setpoint speed DZ.sub.0, the output at the VM 6 decreases, and the noise and exhaust emissions at the landing site are also reduced. This is achieved by the EM 10 steadily reducing its electrically generated power, accordingly it also reduces its decelerating effect.

[0051] According to the invention, the speed DZ of the drive shaft 3 is adjusted exclusively by the EM 10 in accordance with the first directive, such that it is maintained constant at DM.sub.0 at the preset speed DZ.sub.0 by the VM 6. According to the second directive, as shown in phase III the behaviour deviates from this in order to selectively reduce the load on the VM 6. Other reasons may result in the deviation from the first directive besides the reduction of emissions mentioned earlier. In particular, these are the deliberate charging and discharging of the battery 14 if its charge state requires such. The EM 10 may also be introduced as a booster to deliver increased power briefly, or to save fuel, at higher altitudes for example.

[0052] The second directive may be adjusted by noise regulations depending on overflight altitude and/or by prior definition of the planned flight path based on information about energy reserves, for example, if the EM controller 11 has information about the charging state of the battery 14 and the fuel remaining in the tank.

LIST OF REFERENCE SIGNS

[0053] 1 Gearbox with main rotor [0054] 2 Tail rotor [0055] 3 Drive shaft [0056] 4 Hybrid propulsion system [0057] 5 Pilot controller [0058] 6 Combustion engine (VM) [0059] 7 VM controller [0060] 8 Fuel tank [0061] 9 Fuel level meter [0062] 10 Electric motor (EM) [0063] 11 EM controller [0064] 12 Power converter [0065] 13 Charging unit [0066] 14 Battery [0067] 15 Charge state indicator [0068] 16 Calculation unit [0069] 17 Torque sensor [0070] 18 Tachometer [0071] 19 Data signal line [0072] 20 Data memory with value of optimum VM speed [0073] I First phase, climbing [0074] II Second phase, level flight [0075] III Third phase, descent [0076] t Time [0077] H Current altitude [0078] H.sub.1 Target altitude [0079] P Power (redundantly for torque) [0080] P.sub.H Total power [0081] P.sub.EM Output at the EM [0082] P.sub.VM Output at the VM [0083] DZ Speed at the drive shaft, measured [0084] DZ.sub.0 Optimum speed [0085] DM Torque at the drive shaft, measured [0086] DM.sub.0 Target torque