Planetary gear transmission systems or components – Nonplanetary variable speed or direction transmission... – Nonplanetary transmission is friction gearing
Patent
1996-12-09
2000-03-28
Marmor, Charles A
Planetary gear transmission systems or components
Nonplanetary variable speed or direction transmission...
Nonplanetary transmission is friction gearing
475214, B64C 2754
Patent
active
060424990
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to a power transmission device for a helicopter which device is capable of continuously varying a rotating speed of a main rotor over a wide range.
BACKGROUND OF THE INVENTION
Recently the demand for a commuter helicopter which lands and takes off in an urban heliport is increasing, and noise reduction is required for realizing such a commuter helicopter. One of effective countermeasures is to slow down the rotating speed of the main rotor.
FIG. 10 is a perspective view showing an example of a conventional power transmission mechanism for a helicopter. The main rotor is fixed on an extension of a main rotor shaft 14, and a tail rotor is fixed on an extension of a tail rotor shaft 18. Output shafts of a pair of engines 1, 2 rotate at 20,000 to 30,000 rpm, whose rotation speed is reduced to about 6,000 rpm by gear boxes 3, 4. The output shafts are coupled to spiral bevel gears 7, 8 through freewheel clutches 5, 6 and are further in mesh with one collector gear 13, thereby rotating and driving the main rotor shaft 14 at about 350 rpm. Relating to peripheral accessories, a lubricant pump is driven by spiral bevel gears 7, 8, and a hydraulic pump is driven through transmission shafts 9, 10, and a cooling fan is driven through a transmission shaft 11.
On the other hand, a gear 15 is in mesh with the collector gear 13 and coupled with three tail rotor shafts 16, 17 and 18 so as to divide the torque of the collector gear 13, thereby rotating and driving the tail rotor at about 2,200 rpm.
As other prior arts, Japanese Unexamined Patent Publications JP-A 4-287799(1992), JP-A 4-306196(1992), JP-A 5-139386(1993), and JP-A 5-149351(1993) are known.
In conventional helicopters, since revolution of the engines 1, 2 is slowed down at a fixed reduction ratio by different gear trains, the main rotor and tail rotor can rotate only at a constant number of rotations.
Accordingly, in order to decrease the rotating speed of the main rotor to reduce noises, it is necessary to decrease a number of revolutions per unit time of the engine. However, since a conventional engine is designed so as to attain its maximum performance at a predetermined number of revolutions of the engine, it is difficult to control the number of revolutions of the engine unrestrictedly, and the number of revolutions can be lowered by at most only about 3%. Additionally, it may be considered to control the number of revolutions of the engine by optimizing the fuel flow rate and ignition timing by electronic control of the engine, but because of other problems such as lowered efficiency, generation of resonance and limitation of allowable strength of transmission system, at the present the number of revolutions of the engine can be varied by only a small percent in practice. Besides, if the number of rotations of the main rotor is decreased to a large extent, the lift may drop, and the flight performance of the helicopter may be lowered.
It is hence a more practical manner to decrease the number of rotations of the main rotor over urban districts to reduce noises, and return the number of rotations of the main rotor to an optimum over rural districts so as to fly at its maximum performance. For example, it is reported that the equivalent weight noise level is lowered by 3 dB to 5 dB by decreasing the number of rotations of the main rotor or the wing end speed by 10%.
DISCLOSURE OF THE INVENTION
It is an object of the invention to provide a power transmission device for a helicopter, capable of continuously changing a rotating speed of a main rotor over a wide range (a variable range of 0% to 30%, if necessary, more than 30% is optionally designable), while a number of revolutions of an engine is kept constant.
The invention provides a power transmission device for a helicopter, the device comprising: change ratio, connected to an output shaft of an engine, mechanism, and drive and rotate a main rotor.
According to the invention, a number of rotations of the main rotor can be continuously decreased or incre
REFERENCES:
patent: 3574289 (1971-04-01), Scheiter
patent: 3748927 (1973-07-01), Hertzog et al.
patent: 3977632 (1976-08-01), Watson
patent: 4382188 (1983-05-01), Cronin
patent: 4768398 (1988-09-01), Greenwoood
patent: 4856371 (1989-08-01), Kemper
patent: 4856374 (1989-08-01), Kreuzer
patent: 4922788 (1990-05-01), Greenwood
patent: 5090951 (1992-02-01), Greenwood
patent: 5232414 (1993-08-01), Fellows et al.
patent: 5271295 (1993-12-01), Marnot
patent: 5782433 (1998-07-01), Goi et al.
Goi Tatsuhiko
Yamauchi Nobuyuki
Advanced Technology Institute of Commuter-Helicopter, Ltd.
Ho Ha
Marmor Charles A
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