This application is a national phase of International Application No. PCT/EP2017/055272 filed Mar. 7, 2017 and published in the English language, which is hereby incorporated herein by reference in its entirety.
The present invention relates to a power transmission device and method for an outboard motor. More specifically the present invention relates to a power transmission device comprising a drive shaft, an endless loop flexible drive coupling and a propeller shaft, wherein the endless loop flexible drive coupling operatively connects said drive shaft to said propeller shaft for transferring output power from the drive shaft to the propeller shaft. The present invention also relates to an outboard motor having an engine and such a power transmission device.
Outboard motors are self-contained propulsion and steering devices for watercrafts, such as boats, and are arranged to be fastened to the outside of a transom of a boat. One type of such watercrafts is boats that are designed to plane during operation, wherein the propeller shaft is arranged substantially horizontally and below a hull of the watercraft during operation. The present invention also relates to a watercraft with such an outboard motor.
Outboard motors are common for propulsion of watercrafts, such as boats. They have a powerhead with an engine, a midsection and a lower unit with a propeller connected to a propeller shaft. A power transmission device is arranged for transferring output power from the engine to the propeller shaft. Further, a mounting bracket for mounting to the transom of the boat is common. A plurality of outboard motors for boats are disclosed in the prior art. One type of such prior art outboard motors comprises an engine having a horizontal crankshaft for output torque from the engine. According to the prior art torque is transferred from the crankshaft to a propeller shaft through pinions, a gearbox, chains, a belt or similar.
However, it is desirable to improve output torque, efficiency, speed, acceleration and/or fuel consumption of such outboard motors.
Hence, one problem of such prior art outboard motors is that the efficiency is low.
One object of the present invention is to provide an efficient and reliable power transmission for an outboard motor. Further, an outboard motor comprising the power transmission device according to the invention can operate in an efficient manner to obtain straight tracking, faster acceleration and a favorable fuel to power ratio.
The present invention relates to a power transmission device for an outboard motor, comprising a drive shaft, an endless loop flexible drive coupling and a propeller shaft, wherein the endless loop flexible drive coupling operatively connects said drive shaft to said propeller shaft for transferring output power from the drive shaft to the propeller shaft, characterised in that the device comprises a first drive shaft, a second drive shaft, a first endless loop flexible drive coupling, a second endless loop flexible drive coupling, a first propeller shaft and a second propeller shaft, wherein the first propeller shaft is connected to the first drive shaft through the first endless loop flexible drive coupling to rotate the first propeller shaft in a first direction, and wherein the second propeller shaft is connected to the second drive shaft through the second endless loop flexible drive coupling to rotate the second propeller shaft in a second direction opposite to the first direction. The present invention is also related to an outboard motor having such a power transmission device, an engine and first and second propellers. Hence, the present invention results in efficient power transmission for an outboard motor and dual counter-rotating propellers of said outboard motor. The structure of the power transmission device, including the first and second endless loop flexible drive couplings, such as toothed belts, and the counter-rotating first and second propeller shafts result in the possibility of high torque power transfer and favorable grip in the water by means of the first and second propellers of the outboard motor, which also improves acceleration. Further, the outboard motor results in straight tracking of a watercraft and reduces lateral forces also when a plurality of outboard motors are used on a single watercraft. The present invention results in the possibility to efficiently transfer torque from high power diesel engines, such as engines developing up to 100, 200, 500, 1000 or more horsepowers, wherein 1 horsepower (hp) corresponds to approximately 0.74 kW. The disclosed power transmission device can allow for fully scalable torque transfer capability without affecting hydrodynamics. Further, the belt drive of the disclosed outboard motor result in a simple and reliable power transmission with few parts, resulting in an outboard motor with simplified maintenance.
The propeller shafts can be concentric. Further, the second drive shaft can be arranged in parallel to the first drive shaft. The second drive shaft can be arranged concentric to the first drive shaft or can be displaced vertically to the first drive shaft. The first and second drive shafts can be arranged in a common vertical plane. Hence, the first and second belts can be parallel and generally arranged in a common vertical plane when the outboard motor is mounted on the watercraft, which results in efficient hydrodynamics and efficient power transfer.
The second drive shaft can be connected to the first drive shaft through gears for efficient power transfer and for rotating the second drive shaft in the opposite direction. Alternatively, the first and second drive shafts can be connected to the engine crankshaft through a gearbox, wherein the second drive shaft can be rotated in the opposite direction and the rotational direction of both the first and second drive shafts can be reversed to drive the first and second drive shafts in reverse by engine power. Hence, a reliable and efficient power transfer is provided, and according to one embodiment also reversibly for efficient backwards travel of the watercraft or reduction of forward speed.
Disclosed is also a method for power transmission of an outboard motor, comprising the steps of
a) transferring rotational power from an engine crankshaft to a first drive shaft,
b) transferring rotational power from the crankshaft to a second drive shaft,
c) rotating the first drive shaft in a first direction and the second drive shaft in a second direction opposite to the first direction,
d) transferring the rotational power from the first drive shaft to a first propeller shaft through a first endless loop flexible drive coupling,
e) transferring the rotational power from the second drive shaft to a second propeller shaft, arranged concentric with the first propeller shaft, through a second endless loop flexible drive coupling, and thereby rotate the first and second propeller shafts in opposite directions.
Further characteristics and advantages of the present invention will become apparent from the description of the embodiments below, the appended drawings and the dependent claims.
The invention will now be described in more detail with the aid of exemplary embodiments and with reference to the accompanying drawings, in which
With reference to
With reference also to
For example, the outboard motor 10 comprises conventional fastening means for fastening the outboard motor 10 to the stern of the hull 12, such as the transom 13. The fastening means is, for example, arranged as a conventional mounting bracket 22. For example, the mounting bracket 22 comprises or is provided with a trim/tilt system, such as a hydraulic or electric trim/tilt system. For example, the trim/tilt system is conventional. Hence, the outboard motor 10 comprises a laterally extending trim axis, such as a horizontal trim axis. The outboard motor 10 comprises a steering axis 23, such as a vertical or substantially vertical steering axis (depending on trim). The entire outboard motor 10, except for the mounting bracket 22, is turned around the steering axis 23 for steering the watercraft 11. Hence, the power head 15, the midsection 16 and the lower unit 17 are pivotable around the steering axis 23. For example, the power head 15, the midsection 16 and the lower unit 17 are arranged in fixed positions in relation to each other and are turned as one unit around the steering axis 23.
With reference to
The engine 24 comprises a crankshaft 25 for output power in the form of rotational power, also called torque herein. For example, the engine 24 is an internal combustion engine, such as a diesel engine. The outboard motor 10 of the present invention can handle a variety of output powers and can be arranged smaller or bigger as desired. However, the outboard motor 10 according to the described structure can handle high torque and still be hydrodynamic and efficient for use as an outboard motor 10. For example, the engine 24 is a high power engine able to develop at least 73.5 kW (100 horsepower, hp). For example, the engine 24 is a 100-1000 horsepower (hp) engine, such as a 200-500 hp engine. For example, the crankshaft 25 is horizontal or substantially horizontal when the outboard motor 10 is operated for propelling the watercraft. For example, the engine 24 is an automotive engine industrially produced, such as mass produced in series of at least thousands, for propelling an automobile, such as a car or a truck, and then adapted to marine applications. For example, the engine has a plurality of cylinders, such as 4, 6 or 8 cylinders. For example, the engine 24 is capable of outputting power at levels of 200 hp or 500 hp or above. For example, the engine 24 is turbocharged, intercooled and/or has a closed cooling system, optionally with electric starting. The engine 24 is mounted on an engine support structure 26. For example, the engine support structure 26 defines the top of the midsection 16.
According to one embodiment the engine 24 comprises a flywheel (not illustrated). As a general principle engines of this type comprises a flywheel. The flywheel is, e.g. mounted on the crankshaft 25. For example, the flywheel is arranged on an aft side of the engine 24. Alternatively, the flywheel is arranged on a forward side of the engine 24. According to one embodiment, the flywheel is provided with a vibration damper, such as a torsion oscillation damper, to reduce torsional vibrations in the structure. The vibration damper is, e.g. mounted on the flywheel.
The engine 24 can be a marinized automotive engine that provided quietness, effectiveness and high torque. For example, the engine has been redesigned to arrange all serve points on the front of the engine so that maintenance and service can be performed on the water, e.g. by a person standing on the boat. The engine can be a proven robust diesel engine mounted horizontally and marinized with a closed circuit coolant system. E.g. the engine 24 allows for high power alternator and cabin heat. E.g. the engine is a turbo charged diesel engine with high pressure direct fuel injection. E.g. the engine 24 has been converted for marine application by using separate systems for seawater, heat exchangers, intercooler and oil cooler and functionality that ensures that the engine, electrical system, fuel system and air intake will withstand marine conditions. For example, all service points are located at the front of the engine for easy access so service and service part replacement can be made directly from the boat by the users.
In the embodiment of
For example, the first and second belts 28a, 28b are arranged in parallel or substantially in parallel. In the illustrated embodiment the first and second belts 28a, 28b extend along the midsection 16 and into the lower unit 17, wherein the first and second belts 28a, 28b extend vertically or substantially vertically when the outboard motor 10 is operated (depending on trim) to transfer power in the same direction. The belts 28a, 28b connect the drive shafts 27a, 27b and the propeller shafts 29a, 29b and transfers rotational power from the drive shafts 27a, 27b to the propeller shafts 29a, 29b. In the embodiment of
The first and second propeller shafts 29a, 29b are arranged in the form of dual propeller shafts. For example, the first and second propeller shafts 29a, 29b are concentric and arranged to rotate in opposite directions to rotate the first and second propellers 19a, 19b in opposite directions. In the embodiment of
For example, the propeller shafts 29a, 29b, the drive shafts 27a, 27b and the crankshaft 25 are arranged in parallel or substantially in parallel. For example, the propeller shafts 29a, 29b, the drive shafts 27a, 27b and the crankshaft 25 are arranged in a common plane, such as a common vertical plane when the outboard motor 10 is mounted on the watercraft 11. For example, the crankshaft 25, the drive shafts 27a, 27b and the propeller shafts 29a, 29b are arranged horizontally or substantially horizontally when the outboard motor 10 is in a non-tilted operational position for propelling the watercraft 11 and the trim is neutral.
In the illustrated embodiment the first drive shaft 27a is connected to the crankshaft 25 through a power transfer device 32. The power transfer device 32 is arranged for transferring rotational power from the crankshaft 25 to the first drive shaft 27a. Hence, the power transfer device 32 connects the crankshaft 25 with the first drive shaft 27a for transferring the output power from the crankshaft 25 to the first drive shaft 27a. The power transfer device 32 extends substantially perpendicular to the crankshaft 25 and is arranged for transferring rotational power in a direction substantially perpendicular to the crankshaft 25 and the first drive shaft 27a for transferring the rotational power from the crankshaft 25 to the first drive shaft 27a being arranged in parallel to and below the crankshaft 25. For example, the power transfer device 32 comprises an endless loop flexible drive coupling, such as a toothed belt 33 connecting the crankshaft 25 and the first drive shaft 27a. The crankshaft 25 and the first drive shaft 27a extend from a first side of the power transfer device 32. For example, one end of the crankshaft 25 and one end of the first drive shaft 27a are connected to the power transfer device 32. For example, the crankshaft 25 projects from an engine interior and away from the stern.
With reference to
In the embodiment of
With reference to
According to one embodiment the outboard motor 10 also comprises a clutch 41, such as a hydraulic clutch, e.g. having a clutch housing with clutch discs connected to a hydraulic pump for the clutch 41. The clutch 41 is for example arranged as a dog clutch, automotive clutch or any other conventional or special type of clutch. For example, the clutch 41 is an automotive clutch industrially mass produced for automobiles, such as cars or trucks. For example, the gearbox and the clutch 41 are an electro-hydraulically operated system with two multi-plate clutch packages that allows for high torque and power transfer in both clockwise and counter-clockwise rotational directions. For example, the outboard motor 10 comprises Low Speed Control (LSC) that enables unprecedented control while mooring and low speed travel. LSC incorporates an electro-hydraulically operated clutch for smooth shifting between neutral, forward and reverse. LSC features sensor controlled propeller speed allowing for seamless control from zero to maximum rpm. According to one embodiment the gearbox is provided with a trolling function, wherein the clutch 41 is arranged to be able to slip so as to gradually reduce the rotational speed of the propellers 19a, 19b down to zero when the gearbox is in forward gears 39a, 39b or reverse gears 40a, 40b. For example, the clutch 41 comprises lamellas or a plate which can be slipped in both forward and reverse direction. For example, the clutch 41 comprises a plurality of individually lamellas which can be slipped. For example, the gearbox also comprises a neutral gear. For example, the gearbox is operable in forward, neutral and reverse gears. For example, the outboard motor 10 is arranged with the gearbox so that the output power is reversible, such as fully reversible, wherein the propellers 19a, 19b can be driven in a forward mode as well as a reverse mode by the engine 24. Hence, the rotational power from the engine 24 can be transferred to the propeller shafts 27a, 27b in either rotational direction for full engine power forward or full engine power in reverse. For example, the transmission drive shaft 38 is arranged in parallel to the crankshaft 25 and the propeller shafts 27a, 27b. For example, the transmission drive shaft 38 is arranged below the crankshaft 25. For example, the gearbox is arranged below the powerhead 15 and below the engine 24. Further, the gearbox is arranged above the waterline when the outboard motor 10 is propelling the watercraft 11.
For example, the first belt 28a and the second belt 28b are at least partially immersed in oil, wherein said oil is engaging said belts 28a, 28b. According to the illustrated embodiment the outboard motor 10 comprises a fence 42 arranged between the first belt 28a and the second belt 28b to reduce turbulence effects by the oil on the belts 28a, 28b during operation. The fence 42 extends along the belts 28a, 28b. For example, the fence 42 is arranged between the belts 28a, 28b in the lower unit 17, such as from a position above the propeller shafts 29a, 29b and towards the drive shafts 27a, 27b. For example, the fence 41 extends between the propeller shafts 29a, 29b and the second drive shaft 27b.
In the illustrated embodiment, the crankshaft 25 is arranged at the aft side of the engine 24, wherein the power transfer device 32 is connected to the aft side of the engine 24. In the embodiment of
The outboard motor 10 comprises a drive housing 43 for receiving the power transmission device including the drive shafts 27a, 27b, the belts 28a, 28b and the propeller shafts 29a, 29b and optionally also the gearbox. The outboard motor 10 also comprises the engine housing 16 for receiving the engine 24. The drive housing 43 provides functions of structural support, spacing and enclosing for the power transmission device and also supports the propellers 19a, 19b through the propeller shafts 29a, 29b being supported by the drive housing 43. For example, the drive housing 43 extends from the engine support structure 26 to the skeg 20. The drive housing 43 is connected to a structure for pinching legs of the first belt 28a together and for pinching legs of the second belt 28b together to reduce the cross-section of the outboard motor 10 below the water line 14 to reduce drag. For example, said structure comprises curved surfaces bending the path of travel of the belt legs of the power transmission device together. Further, according to one embodiment of the present invention the drive housing 43 is formed for containing oil for the power transmission device. Hence, the power transmission device is running in a partially oil filled housing. According to one embodiment of the invention the drive housing 43 is formed with a water inlet or a water pickup for cooling. The drive housing 43 is, for example, formed in a composite material or any other suitable material. According to one embodiment the gearbox, the drive shafts 27a, 27b and the belts 28a, 28b are positioned in the drive housing 43. The propeller shafts 29a, 29b are positioned partially in the drive housing 43, wherein outer portions thereof project out from the drive housing 43 for carrying the propellers 19a, 19b.
According to one embodiment the drive housing 43 is provided with an exhaust outlet (not illustrated) for exhaust gases from the engine 24. For example, the exhaust outlet is arranged above the propellers 19a, 19b. Alternatively or in addition, the centers of the propellers 19a, 19b are arranged with an exhaust outlet for a part of the exhaust gases or for all of it.
With reference to
With reference to
Filing Document | Filing Date | Country | Kind |
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PCT/EP2017/055272 | 3/7/2017 | WO | 00 |
Publishing Document | Publishing Date | Country | Kind |
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WO2018/162039 | 9/13/2018 | WO | A |
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Entry |
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PCT International Search Report and Written Opinion for corresponding International Application No. PCT/EP2017/055272 dated Nov. 2, 2017. |
Number | Date | Country | |
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20210129965 A1 | May 2021 | US |