Application of Push-Pull Control Slipping Clutch to the Marine Propulsion System
Yasuo YOSHIMURA*, Kazuyoshi MAEKAWA*
Shuiclli NAKAJIMA** and Kazuhiro OSAKA***
The use of an electronically controlled slipping clutch is gradually increasing for a marine propulsion system. This system can provide a continuous change of propeller revolution even in a lower revolution zone of prime mover. However, it hardy make the decelerating condition, because the slipping clutch itself can not make the negative torque.
In this paper, the authors have designed a push-pull control system using two slipping clutches in order to improve the above disadvantage of the conventional slipping clutch. For the evaluation of this system, the whole propulsion system including prime mover, clutches, propeller and ship are numerically simulated using the precise mathematical model described here. From several accelerating and decelerating simulations, the following results are pointed out.
1) FPP's revolution can be easily changed in the slipping zone by using this system, although the main engine is governed constant revolution.
2) Astern and ahead maneuvering is also performed by this system.
3) The mathematical model for this simulation including engine, clutch, propeller and ship is useful for the design and evaluation of the whole propulsion system.
As the result, this push-pull controlled slipping clutch system will be very useful for a marine propulsion system.
Key Words : slipping clutch. FPP, push-pull control, harbor maneuvering, astern maneuvering
When a ship proceeds into a harbor, a frequent ship-speed change is ordered. A CPP (Controllable Pitch Propeller) is conveniently used for this purpose because of the easily change of the engine output as well as its direction. However, CPP has some disadvantages in the cost of construction, efficiency of propulsion plant, cavitation and noise of propeller. While an FPP (Fixed Pitch Propeller) has not such problems but has not any other control device except the revolution of a prime mover. So, the following control devices of propeller revolution are required.
(1) Electric generator-motor system
(2) Reversible hydraulic converter coupling system
(3) Mechanical transmission system with conventional clutch and gear
(4) Slipping clutch system
The characteristics of these propulsion systems are listed in Table.1 comparing with the CPP system. As for the prime mover, uni-directional engines are used such as medium speed diesel and gas turbine. The electric generator-motor system is sometimes used for special ships. This system however becomes a large scale of plant and requires a significant cost of construction. The efficiency of power plant is not also good. The hydraulic transmission system has the similar tendencies. For the mechanical transmission system, the reduction gear ratio is usually fixed, so that the change of continuous propeller revolution is not obtained particularly under the idling range of prime mover.
The slipping clutch that is electronically controlled with a hydraulic power unit becomes one solution. It easily makes an arbitrary propeller revolution to the accelerating side. It well realizes the propeller revolution by means of adjusting the hydraulic pressure of the clutch disk. However, it can hardly make the decelerating condition, because the slipping clutch itself can not provide the negative torque induced by the propeller.
In this paper, the authors propose an idea of new control system of the slipping clutch in order to improve the decelerating condition as well as the propeller-reversing zone. In this system, two slipping clutches are installed in both forward and reverse revolution gears, then they are controlled continuously in order to get the ordered propeller revolution. This system is called here a "push-pull control slipping clutch system".
2. PUSH-PULL CONTROL SLIPPING CLUTCH SYSTEM
The slipping clutch produces a lower revolution than the direct connecting system so as to slip the clutch disk by means of adjusting the connecting pressure of the disk. The pressure is usually provided by a hydraulic oil system. The clutch disk is filled by lubricating oil to make easy control. The cooling system of the lubricating oil is also provided for absorbing the thermal energy by the friction. For the actual control of the shaft revolution, it is continuously picked up and the pressure of clutch disk is automatically adjusted in order to get the ordered revolution. This schematic diagram is shown in Fig.1
* Hokkaido University
3-1-1 Minato-cho. Hakodate, Hokkaido 041-861 1 JAPAN
FAX:+81-138-40-8520, E-mail: firstname.lastname@example.org
** Marine United Inc.
*** Sumitomo Heavy Industries, Ltd.