Improved stern drive systems and methods

Abstract

A method of controlling an electric motor coupled to a stern drive includes receiving a boat speed; receiving a motor drive speed command; causing a motor shaft to spin at a rotational speed based on the motor drive speed command; determining a theoretical boat speed based at least in part on the motor drive speed; determining a slip of the boat based at least in part on the boat speed and the theoretical boat speed; determining if the slip is near or below zero; and based on determining if the slip is near or below zero, reducing a torque setting of the motor.

Description

IMPROVED STERN DRIVE SYSTEMS AND METHODSCROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority under 35 U.S.C. § 119(e) and 37 C.F.R. § 1.78 to provisional application no. 63 / 631,599 filed on April 9, 2024, titled “IMPROVED STERN DRIVE” which is hereby incorporated by reference herein in its entirety.GOVERNMENT LICENSE RIGHTS

[0002] This invention was made with State of California support under California Energy Commission grant number PIR-20-003. The Energy Commission has certain rights to this invention.BACKGROUND

[0003] Stern drives are a type of system used for propelling watercraft of all sizes. Stern drives, also known as inboard-outboard drives, are propulsion systems commonly used in marine vessels. These drives are located at the stern of the boat and include a gearbox and an engine mounted inboard, with an adjustable drive unit that extends outside the hull. The drive unit, which includes a propeller, is capable of both vertical and horizontal movement, providing the vessel with enhanced maneuverability and efficiency. The integration of stern drives enables optimal power transfer from the engine to the propeller, resulting in improved performance and control of the watercraft.

[0004] A stern drive is typically mounted at the aft, or stern, of a watercraft. A stern drive usually has an input shaft turned by an internal combustion engine, and an output shaft that turns a propeller or screw. Stern drives usually include a system of complicated mechanical linkages including gears, universal joints, bearings, belts, clutches, drive shafts, and transmissions. The tolerance of these parts stack together creating a wide degree of movement and forces at the stern drive input shaft. Mechanical internal combustion engines have multiple bearings within them to handle the range of forces and tolerances within the engine, and a robust main rear seal bearing where the engine shaft is output from the engine. When connected to a stern drive, the overall robustness in mechanical design of this engine shaft is able to handle the significant additional forces from the stern drive shaft.

[0005] Internal combustion engine shafts turn only in one direction, so to move in reverse, a transmission is installed between the engine and the drive output shaft within the stern drive. The transmission adds complexity, cost, weight, size, and maintenance to the overall system.

[0006] In addition, a traditional stern drive has a mechanical freewheeling action, in case the propeller revolution speed (e.g., revolutions per minute or RPM) is higher than the corresponding engine RPM due to water flow. This freewheeling action results in the stern drive only accepting power input in a single direction (e.g., only clockwise or only counterclockwise depending on the configuration.) If the engine input rotation rate drops below the corresponding output rotation rate of the propeller, the propeller will continue to rotate at a rate of speed based on the flow of water relative to the propeller, having a “windmill” effect on the propeller. This freewheeling action may help the watercraft maintain directional stability, such as at high speeds after throttle reduction or engine failure. The freewheeling action helps to maintain non-turbulent water flow across the stern drive allowing for positive rudder control and stability in the case of sudden throttle reduction or engine failure.

[0007] Due to air pollution regulations and customer preference, many watercraft are being electrified. Electric motors do not have the robust bearings and seals that internal combustion engines have and cannot accommodate the forces imparted by traditional stern drive technology. Electric motors often have only a few moving parts (e.g., the rotor and bearings) and as a result can be manufactured with very high tolerances, which enables high reliability and efficiency. In addition, an electric motor’s rotating shaft can tolerate little allowable movement because the clearances between the rotor and stator are minimized. This means that the bearings that support the shaft in an electric motor must be more precise compared to an internal combustion engine, which inherently reduces the robustness of electric motors, relatively, in tolerating large forces. Therefore, the bearing system in an electric motor cannot tolerate the same level of forces and movement from a connected system, such as a stern drive, that a combustion engine can. The consequence of connecting an electric motor to a stern drive in the same way that is done with combustion engines, would be damage to the electric motor, the stern drive, or both. Today there does not exist a way to directly connect today’s stern drives with today’s electric motors. Therefore, electric motors cannot simply be coupled to existing-technology stern drives. Furthermore, electric motors can easily be reversed in rotation direction by changing the electrical signals fed to the motor. Existing stern drives cannot take advantage of this feature and must still carry an un-necessary transmission, thereby increasingcost, weight, and reducing reliability. Improved stern drives are desired that can couple to electric motors to support the electrification of watercraft.BRIEF SUMMARY

[0008] In one embodiment, a method of controlling a motor coupled to a stern drive includes: receiving a boat speed; receiving a motor drive speed command; causing a motor shaft to spin at a motor drive speed based on the motor drive speed command; determining a theoretical boat speed based at least in part on the motor drive speed; determining a slip of the boat based at least in part on the boat speed and the theoretical boat speed; determining if the slip is near or below zero; and based on determining if the slip is near or below zero, reducing a torque setting of the motor.

[0009] Optionally, in some embodiments, determining the theoretical boat speed includes using a propeller pitch and drive gear ratio.

[0010] Optionally, in some embodiments, the method further includes adjusting the motor drive speed command based on a user input.

[0011] Optionally, in some embodiments, the slip is determined as a percentage difference between the theoretical boat speed and actual boat speed.

[0012] Optionally, in some embodiments, reducing a torque setting involves maintaining a constant revolution speed of the motor shaft.

[0013] Optionally, in some embodiments, the method is executed as part of a closed loop control system.

[0014] Optionally, in some embodiments, the method further includes recording historical data of boat speed and slip, wherein at least one of determining the theoretical boat speed or determining the slip is based, at least in part, on the historical data.

[0015] Optionally, in some embodiments, determining the slip includes comparing instantaneous and averaged speeds over a predetermined period of time.

[0016] Optionally, in some embodiments, the motor shaft is received in a coupler adapted to transmit torque from the motor shaft; a secondary shaft is in operational connection with the coupler; a bearing housing supports the secondary shaft via one or more bearings; and the secondary shaft is coupled to an output shaft configured to transmit torque to a stern drive that drives a propeller.

[0017] Optionally, in some embodiments, the motor includes an electric motor.

[0018] In one embodiment, a stern drive coupling system for use with an electric motor includes: a motor shaft; a coupler adapted to transmit torque from the motor shaft; a secondary shaft in operational connection with the coupler; a bearing housing supporting the secondary shaft via at least one bearing; and an output shaft configured to transmit torque to a stern drive.

[0019] Optionally, in some embodiments, the coupler includes an input receptacle and an output receptacle for mating with corresponding shafts.

[0020] Optionally, in some embodiments, the system further includes a spacer coupled to the bearing housing and the motor.

[0021] Optionally, in some embodiments, the at least one bearing includes a roller bearing configured for axial thrust absorption.

[0022] Optionally, in some embodiments, the secondary shaft includes a relief notch.

[0023] Optionally, in some embodiments, the system further includes a flexible coupling operatively connected to the secondary shaft and output shaft.

[0024] Optionally, in some embodiments, the flexible coupling compensates for angular or translational misalignment between shafts.

[0025] Optionally, in some embodiments, the bearing housing is integrally formed with a bell housing.

[0026] Optionally, in some embodiments, the bell housing is coupled to a transom of a boat.

[0027] In one embodiment, a method of controlling the stern drive system includes: receiving a boat speed; receiving a motor drive speed command; causing the motor shaft to spin at a motor drive speed based on the motor drive speed command; determining a theoretical boat speed based at least in part on the motor drive speed; determining a slip of the boat based at least in part on the boat speed and the theoretical boat speed; determining if the slip is near or below zero; and based on determining if the slip is near or below zero, reducing a torque setting of the motor.BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The figures herein may or may not be to scale. In particular, the schematic representations of FIG. 1 , FIG. IB, FIG. 2A, FIG. 2A, FIG. 5, and FIG. 6 are not to scale.

[0029] FIG. 1 is a schematic section view of an embodiment of a stern drive according to the present disclosure.

[0030] FIG. 2A is a schematic view the stern drive of FIG. 2A.

[0031] FIG. 2B is an isometric view of a bellhousing for mating to a stern drive.

[0032] FIG. 2C is a section view of an embodiment of an improved stern drive according to the present disclosure.

[0033] FIG. 3 is an isometric view of a motor mount of the stern drives disclosed herein.

[0034] FIG. 4 is an isometric view of a motor mount of the stern drives disclosed herein, with the motor being positioned.

[0035] FIG. 5 is a top, schematic view of an embodiment of a stern drive according to the present disclosure.

[0036] FIG. 6 is a top view of an embodiment of an embodiment of a stern drive according to the present disclosure.

[0037] FIG. 7 is an image of a motor for which the improved stern drives disclosed herein are adapted.

[0038] FIG. 8 is a flow chart of a method of controlling any stern drive disclosed herein.

[0039] FIG. 9 is a simplified block diagram of components of a computing system suitable for use with a stern drive disclosed herein.DETAILED DESCRIPTION

[0040] The improved stern drives disclosed allow the forward and reverse control of a watercraft to be provided by a prime mover (e.g., an electric motor) eliminating the need for a mechanical transmission. Furthermore, the improved stern drives disclosed enable electric motors to be used with watercraft.

[0041] As shown in FIG. 1 through FIG. 2C, the present disclosure and accompanying drawings and explanations describe methods and systems of connecting an electric motor to a stern drive in a way that protects the electric motor from excessive forces imparted by a stern drive. While the systems and methods disclosed are suitable for coupling an electric motor to a stern drive, they may also be used with any kind of rotational power generation device such as an internal combustion engine, external combustion engine (e.g., a Stirling engine), turbine, or the like. As such, where an electric motor is shown or described, it is envisioned that the electric motor may be replaced with any desired rotational power generation device, within the scope of this disclosure.

[0042] Also disclosed herein is an improved method of connecting an electric motor to a stern drive in a way that absorbs excess force while also preventing instability of imperfect balancing by reducing rotating mass and moment of inertia, and eliminating excess cushioning between components.

[0043] Also disclosed herein is an improved method of connecting an electric motor to a stern drive in a way that absorbs excess force by using a bearing in between, minimizing part count, reducing overall mass, and shortening the distance between the electric motor and the stern drive.

[0044] Also disclosed herein is an improved method of controlling the electric motor to enable freewheeling, thus eliminating the need for a transmission in the stern drive when connected to an electric motor.

[0045] Adaptable shaft attachments enable the connection between any stern drive and any electric motor, e.g., as shown in FIG. 1 to FIG. 2A.

[0046] In some embodiments, the disclosed solutions for connecting a stern drive to an electric motor may be integrated into a stern drive. In some embodiments, the connection solution may be coupled to an existing stern drive.

[0047] Together, the disclosed stern drives and connection solutions enable the immediate deployment of electric boats using conventional stern drives as well as the elimination of transmissions within the stern drive. Benefits of the disclosed technology include reduced cost, improved reliability, lower use of fossil fuels, and lower air pollution. The product can be used by motor manufacturers as add-on options making the motor installable to any stern drive; by stern drive manufacturers to likewise make a stern drive adaptable to any electric motor; and by boat original equipment manufacturers, repair facilities, and do-it-yourselfers to enable the connection between separate stern drive and electric motors for newly built or refitted units. The methods and systems disclosed herein can also be incorporated directly into the electric motor to enable integration with any stern drive, or into the stern drive to enable integration with any electric motor.

[0048] With specific reference to FIG. 1, a stern drive coupling system 100 is disclosed. The stern drive coupling system 100 is shown within the hull 104 of a boat 102. The stern drive 300 is mounted at the transom 106 of the boat 102. The stern drive coupling system 100 is adapted to couple a motor 700 with a stern drive 300. The stern drive coupling system 100 enables torque and rotation from the motor 700 to be transmitted to the stern drive 300 and ultimatelyto the water via one or more propellers 314. As such the stern drive coupling system 100 is suitable for use in repowering a boat with an electric motor, replacing an existing combustion engine, but retaining the stern drive 300.

[0049] The motor 700 includes a motor shaft 704 that spins relative to the main body 702 of the motor 700. See, e.g., FIG. 7. The motor shaft 704 is coupled to the rotor (not shown) of the motor that spins about a rotation axis 142 as a result of applied electromagnetic fields in motor 700. The motor shaft 704 may be directly coupled to the rotor, or may be coupled via a gearbox or internal transmission in, or coupled to, the motor 700. The motor shaft 704 may include a functional surface that enables the motor shaft 704 to transmit torque to one or more other components of the stern drive coupling system 100. For example, the motor shaft 704 may include a spline 140. Various shafts disclosed herein include various torque transmission features or surfaces such as splines, key and keyways, interference fits, etc., which may be used interchangeably as desired.

[0050] The stern drive coupling system 100 includes a coupler 108. The coupler 108 has a main body 112. The main body 112 may be symmetrical about the rotation axis 142, for example to help keep the stern drive coupling system 100 balanced as the motor 700 spins about the rotation axis 142. The main body 112 includes an input receptacle 110 and an output receptacle 114. The input receptacle 110 is adapted to receive the motor shaft 704. The input receptacle 110 may have a corresponding torque transmission feature to the motor shaft 704 (e.g., a spline 140). Thus, the motor shaft 704 may be received in the input receptacle 110 such that the respective torque transmission features mate to efficiently transmit torque from the motor 700 to the coupler 108.

[0051] The output receptacle 114 is adapted to receive a secondary shaft 116 of the stern drive coupling system 100. The output receptacle 114 and secondary shaft 116 may include complementary torque transmission features such as splines, keys, etc.

[0052] In some embodiments, the coupler 108 may simply adapt incompatible interfaces of the motor shaft 704 and the secondary shaft 116. In some embodiments, the coupler 108 may provide for some amount of angular or translational misalignment between the motor shaft 704 and the secondary shaft 116.

[0053] The secondary shaft 116 is formed of an elongate body 118 with a first portion 120 disposed opposite a second portion 122 along the rotation axis 142. The first portion 120 may be received in the output receptacle 114 of the coupler 108, as described. The second portion122 may include a receptacle 138. The receptacle 138 is adapted to receive a portion of an output shaft 128 of the stern drive coupling system 100. The elongate body 118 may be supported by one or more bearings 124 received and supported in a bearing housing 126. The bearings 124 may be radial roller bearings, cylindrical roller bearings, tapered roller bearings, spherical roller bearings, four-point contact roller bearings, needle roller bearings, ball-bearing hybrid roller bearings, or combinations of these. The elongate body 118 may be supported on an inner race of the bearings 124. The outer race of the bearings 124 may be supported by the bearing housing 126. In the embodiment shown, three bearings 124 are used. However, in other embodiments more or fewer bearings may be used. The bearings 124 may tolerate a certain amount of slippage of the secondary shaft 116 along the rotation axis 142. Similarly, the bearings 124 may tolerate a certain amount of angular misalignment of the secondary shaft 116 with the rotation axis 142. One or more of the bearings 124 may be thrust bearings that transmit thrust generated the propeller 314 to the hull 104 of the boat.

[0054] The bearing housing 126 may be coupled to, or integrally formed with, a spacer 136. The spacer 136 may be coupled to the first housing 132 and to the motor 700. A second housing 134 may at least partially surround a portion of the second portion 122 of the secondary shaft 116. The second housing 134 may help protect the moving portions of the stern drive coupling system 100.

[0055] The output shaft 128 is receivable in the receptacle 138 of the secondary shaft 116. As with other shafts of the stern drive coupling system 100, the output shaft 128 may include a spline 140 or other torque transmission feature that couples the output shaft 128 to the second portion 122 of the secondary shaft 116. The output shaft 128 transmits torque to the internal components of the stern drive 300 to cause the 300 to spin the

[0056] In operation, the motor 700 generates torque that causes the motor shaft 704 to spin about the rotation axis 142. This spinning causes each of the coupler 108, the secondary shaft 116, and the output shaft 128 to also spin about the rotation axis 142. Portions of the bearings 124 (e.g., the inner races and rolling elements) may also spin about the rotation axis 142. The spinning components are indicated in FIG. 1 with bold lines. The transmitted toque received by the stern drive 300 causes the propeller 314 to spin to propel the boat 102. The boat 102 may be steered by the rudder 316.

[0057] FIG. 2A shows a stern drive coupling system 200. Like the stern drive coupling system 100, the stern drive coupling system 200. The stern drive coupling system 200 is shown withinthe hull 104 of a boat 102. The stern drive coupling system 100 is adapted to couple the motor 700 with a stern drive 300. The stern drive coupling system 200 enables torque and rotation from the motor 700 to be transmitted to the stern drive 300 and ultimately to the water via one or more propellers 314. As such the stern drive coupling system 200 is suitable for use in repowering a boat with an electric motor, replacing an existing combustion engine, but retaining the stern drive 300.[00581 Like the stern drive coupling system 100, the stern drive coupling system 200 includes a coupler 108 that couples the motor shaft 704 to a secondary shaft 216. The embodiment of the coupler 108 in the stern drive coupling system 200 includes a spline 140 at an input receptacle 110 and a key in the output receptacle 114. The secondary shaft 216 of the stern drive coupling system 200 includes an elongate body 218 with a first portion 220 and a second portion 222 disposed opposite the first portion 120 along the elongate body 218. The second portion 222 includes a spline 140. Like the secondary shaft 116, the secondary shaft 216 is supported by one or more bearings 124 as previously described.

[0059] The second portion 222 of the secondary shaft 216 couples the secondary shaft 216 to a backing plate 212 and to a flexible coupling 224. The backing plate 212 includes a receptacle 238 that receives the second portion 222 of the secondary shaft 216. The backing plate 212 is coupled to, or integrally formed with, the flexible coupling 224. The flexible coupling 224 includes an input portion 226 that couples to and interfaces with the backing plate 212. The flexible coupling 224 includes a mid-portion 228 coupled to the input portion 226. The mid portion 228 may be formed of an elastomeric or flexible material. For example, the elastomeric material may be a thermoplastic, thermoset, etc. In specific examples, the elastomeric material may be nitrile rubber (NBR), polybutadiene (BR), polyisoprene (NR), styrene-butadiene rubber (SBR), ethylene propylene rubber (EPR), fluoroelastomers (FKM), silicone rubber. In some embodiments, the mid portion 228 may include reinforcing material included with the elastomeric material, such as reinforcing filaments. The filaments may be made of metal (e.g., steel), aramid, glass, carbon fiber, or other materials.

[0060] The receptacle 238 may be a solid body through which the rotation axis 142 passes (e.g., as shown in FIG. 2C) or may be formed of a thin membrane that revolves around the rotation axis 142. The flexible coupling 224 includes an output portion 230 that couples to the output shaft 128. The output portion 230 may include a spline 140 complementary to a spline 140 formed in the elongate body 130.

[0061] The mid portion 228 of the flexible coupling 224 provides for misalignment of the secondary shaft 216 and the output shaft 128. For example, the elastomeric material of the mid portion 228 may flex or bend to accommodate either or both of angular or translational misalignments between the secondary shaft 116 and the output shaft 128.

[0062] The mid portion 228 may also provide some amount of shock absorption for sudden forces imparted to the stern drive coupling system 200. For example, if the propeller 314 were to strike a solid object, such as a rock, a sudden force may be imparted to the drive train. The mid portion 228 may absorb a portion of that shock to protect the balance of the stern drive coupling system 200 from damage caused by the shock.

[0063] The mid portion 228 may be particularly advantageous in the event of a crash stop, where the direction of the propeller and motor are suddenly reversed to halt the movement of the boat 102 as quickly as possible. Such events can induce large stresses in the stern drive coupling system. If an electric motor 700 were simply coupled to an existing stern drive, the forces induced would likely damage the electric motor. Thus, the stern drive coupling systems disclosed herein enable the electrification of watercraft with the accompanying benefits of low noise and air quality emissions compared to internal combustion engine. The stern drive coupling systems disclosed herein may also reduce noise emissions of the boat 102 in addition to that effected by the use of the electric motor 700, which may be advantageous for security or military operations where low noise signature is a tactical advantage. For example, the mid portion 228 may absorb vibrations from the propeller 314 and reduce the propagation of such vibrations through the hull and into the environment, thereby enabling lower noise operation compared to a boat 102 without the flexible coupling 224.

[0064] As with the stern drive coupling system 100, the torque transmitted from the motor 700 to the stern drive 300 via the stern drive coupling system 200 causes the propeller 314 to spin and thus to propel the boat 102.

[0065] With reference to FIG. 2B, an isometric view of an embodiment of the stern drive coupling system 200 is shown. In particular, the bell housing 210 of the stern drive coupling system 200 is shown. As shown for example in FIG. 2B, a bellhousing is a mechanical interface between a prime mover (such as an electrical motor) and a load that provides a transfer of torque between the two. Commonly the prime mover is an engine or motor and the load may be an input shaft of the stern drive. Bolt patterns refer to the arrangement of the bolts on thebellhousing and motor. A bolt pattern may determine the alignment of the shaft between the motor and load.

[0066] With reference to FIG. 2C, a cross section view of the stern drive coupling system 200 is shown, taken along line 2D-2D of FIG. 2C. As shown for example in FIG. 2C, the stern drive coupling system 200 includes a coupler 108 that connects the motor shaft 704 to the secondary shaft 216. As described herein, the coupler 108 may adapt incompatible mechanical interfaces of the motor shaft 704 and the output receptacle 206. The coupler 108 may also provide for some amount of angular or translational misalignment between the motor shaft 704 and the secondary shaft 216.

[0067] As shown for example in FIG. 2C, the secondary shaft 216 in this embodiment includes a number of features enabling it to integrate with the balance of the stern drive coupling system 200. Starting at the first portion 220, the secondary shaft 216 includes a key way suitable to receive a key 208 as disclosed herein. The secondary shaft 216 includes a first shoulder 240 that steps the diameter of the 216 from the portion received in the output receptacle 206 of the coupler 108. This relatively thicker portion of the secondary shaft 216 helps stiffen the secondary shaft 216 to applied torques. Continuing toward the second portion 222, the secondary shaft 216 includes a second shoulder 242 that further steps up the diameter of the secondary shaft 216 from the first shoulder 240. The second shoulder 242 adapts the secondary shaft 216 to an appropriate diameter of the inner races of the bearings 124, forming a bearing surface 244. The bearing surface 244 may be subjected to special surface roughness treatments to enable smooth interfacing with the bearings 124. The portion of the secondary shaft 216 received in the bearing housing 126 includes the fastener 214. Continuing toward the second portion 222, the secondary shaft 216 may include a relief notch 246 that effectively steps the diameter of the secondary shaft 216 to a size suitable to be received in the receptacle 238 formed in the backing plate 212 (e.g., as shown in FIG. 2A). A relief notch 246 may also provide for shock absorption or may act as a mechanical fuse, rupturing before other more expensive components of the stern drive coupling system in the event of the application of an above-design load. In the example shown in FIG. 2C, the embodiment of the secondary shaft 216 shown includes a flange 248. The flange 248 includes a plurality of apertures formed therein that accept fasteners 214 to couple the secondary shaft 216 to the backing plate 212. An advantage of the 216 shown in FIG. 2C may be reduced parts count, easier alignment and harmonic balancing, by forming more features into the secondary shaft 216 compared to thatshown in FIG. 2A. The backing plate 212 may be coupled to the first portion 220 by any desired method, including fasteners, integral forming of the portions, adhesives, etc.

[0068] In the embodiment shown in FIG. 2C, the first housing 132 includes opposing flange portions 234 at opposite ends of a spool portion 236. The spool portion 236 is smaller in dimension than the opposing flange portions 234. This structure helps save weight, packaging volume and cost compared to having the first housing 132 have a uniform diameter.

[0069] As shown for example in FIG. 3, the disclosed stern drive coupling systems include a bell housing 210 to a stern drive 300 connection including two mounting locations, near to the horizontal plane of the output shaft 128. The connection may provide for a small amount of vertical movement while canceling out lateral movements. The connection transmits torque between the motor 700 and the stern drive 300. The connection may be provided by a stern end mount 302. The stern end mount 302 in the example shown includes a main body 304 that runs predominantly athwartships. The main body 304 may include bosses 308 at opposing end portions 306 of the main body 304. The bosses 308 may extend toward the bow of the boat 102 from the main body 304. The bosses 308 may include one or more apertures 310 formed therein or therethrough that provide mounting locations for the bell housing 210, and thus the stern drive coupling system. The stern end mount 302 may be coupled to a stern drive input housing 312 of the stern drive 300 by any desired method including welding, fasteners, adhesives, or integral forming therewith.

[0070] The stern drive 300 includes a hull 104, a stern end mount 302, a main body 304, an end portion 306, a boss 308, an aperture 310, a stern drive input housing 312, and a mounting point 318.

[0071] FIG. 4 and illustrate motor mounts for an improved stern drive as disclosed herein, for example for use with the motor of FIG. 7. Any stern drive coupling system disclosed herein may include a bow end mount 400. The bow end mount 400 is suitable for coupling the end of the motor 700 oriented toward the bow of the boat 102.

[0072] The bow end mount 400 includes a main body 402. The main body 402 may be substantially planar. The main body 402 includes a central aperture 404 that exposes the end of the motor 700 when the bow end mount 400 is coupled to the motor 700. The main body 402 includes a plurality of mounting apertures 408 formed therein or therethrough. The mounting apertures 408 may be arrayed around the periphery of the central aperture 404 and may be evenly or unevenly spaced as adapted for a given motor 700. Fasteners (not shown) such asbolts or screws may be received in the mounting apertures 408 to couple the bow end mount 400 to the motor 700.

[0073] The bow end mount 400 may include one or more wings 406 extending from the planar main body 402. In some embodiments, the wing 406 extend normal to the plane of the main body 402. In other embodiments, the wings 406 extend at an angle other than perpendicular to the plane of the main body 402. The wings 406 may be disposed at respective 3 o'clock and 9 o'clock positions about the main body 402. In other embodiments, the wings 406 may be disposed at other positions, as desired or as needed to couple to a desired motor 700. The wings 406 enable the bow end mount 400 to couple the motor 700 to one or more mounting points 318 on the hull 104 of the boat 102. Thus, the bow end mount 400 enables coupling the stern drive coupling system to the boat 102.

[0074] FIG. 5 shows an embodiment of a stern drive coupling system 500. The stern drive coupling system 500 include a motor 700 which may be coupled to the hull 104 of the boat 102 as disclosed herein, e.g., at one or more mounting points 318 using an appropriate stern end mount 302 and bow end mount 400.

[0075] In the embodiment of FIG. 5, the stern drive coupling system 500 may include a shaft (such as a cardan assembly 502) that couples an output of an electric motor to a flange. A cardan assembly 502 includes at least one universal joint 504, and may include a second universal joint 506 to enable smooth and continuous rotation of two shafts (e.g., the secondary shaft 508, and an output shaft 510). The secondary shaft 508 and output shaft 510 may be as described with respect to the secondary shaft 116, the secondary shaft 216 and respectively to the output shaft 128 disclosed herein. Each of the universal joint 504 and universal joint 506 include a pin joint 512 and joint 514 disposed at an angle with respect to one another (typically 90°).

[0076] In some embodiments, the output shaft 510 and the secondary shaft 508 may be disposed at an angle with respect to each other, while transmitting power or motion. The stern drive coupling system 500 designed to compensate for slight misalignment between the secondary shaft 508 and the output shaft 510, providing a flexible and forgiving connection therebetween.

[0077] The universal joint 506 or the universal joint 504 may include a flange 516. The flange 516 may be coupled to the output shaft 510. The output shaft 510 may be rotatably supported by one or more bearings 124 coupled to a bearing holder 518. The bearings 124 may be spacedalong the output shaft 510 or may be disposed at respective opposite ends of the output shaft 510. The bearing holder 518 may be fixed to, or formed with, the transom 106. For example, the bearing holder 518 may be coupled to the transom 106 by one or more transom mounts 520. The output shaft 510 may be coupled to an input of a stern drive 300 as disclosed herein (e.g., via a torque transmission feature such as a spline 140, key 208, etc.)

[0078] FIG. 6 shows an embodiment of stern drive coupling system 600. In the embodiment of FIG. 6, the stern drive coupling system 600 includes a coupler 108 that transmits rotational energy from a motor 700 output (e.g., motor shaft 704) to a secondary shaft 216. The secondary shaft 216 may be rotationally coupled to a bearing housing 126 by one or more bearings 124. The bearing housing 126 may be coupled to the motor 700 by one or more first housing 132, spacer 136, and / or bell housings 210, as disclosed herein. The secondary shaft 216 may transmit rotational energy to a coupling, such as a flexible coupling 224. The flexible coupling 224 may be as described herein. The flexible coupling 224 may pass rotational energy from the secondary shaft 216 to the output shaft 128 and then to a stern drive 300 as disclosed herein. In the embodiment of the flexible coupling 224 shown in FIG. 6, the output portion 230 may be recessed into the mid portion 228, rather than disposed at a face of the mid portion 228 as in the embodiment shown in FIG. 2A. The bell housing 210 of the motor 700 may be coupled to the transom 106, such as via one or more transom mount 520.

[0079] As shown for example in FIG. 7, an example motor 700 for use with a stern drive coupling system disclosed herein, such as a stern drive coupling system 100, stern drive coupling system 200, stern drive coupling system 500, stern drive coupling system 600 that uses an SAE 3 bolt pattern is shown. The motor 700 is suitable for use with an improved stern drive as disclosed herein. Other motors 700 may be used as desired. One of the benefits of the disclosed improved stern drive systems includes the ability to adapt to a wide variety of motors, such as by providing suitable first housings 132, couplers 108, and / or other components.

[0080] FIG. 8 illustrates an example method 800 for controlling a motor for use with a stern drive disclosed herein. Although the example method 800 depicts a particular sequence of operations, the sequence may be altered without departing from the scope of the present disclosure. For example, some of the operations depicted may be performed in parallel or in a different sequence that does not materially affect the function of the method 800. In other examples, different components of an example device or system that implements the method 800 may perform functions at substantially the same time or in a specific sequence.

[0081] According to some examples, the method 800 includes receiving boat speed at operation 802. In some embodiments, of the operation 802, the boat speed may be measured by a speed sensor. According to some examples, the method 800 includes receiving boat speed at operation 802. To achieve freewheel-effect control with an electric motor 700, boat 102 speed may be considered as in input to an algorithm such as the method 800 that allows the electric motor 700 to freewheel. For example, a processing element 902 may receive a boat 102 speed from a sensor, or may calculate the boat speed from a variety of inputs. In some embodiments, the operation 802 the boat speed may be estimated based on the rotational speed of the propeller 314, the propeller 314 pitch, any gearing in the stern drive 300, and / or some estimate of the propeller slip.

[0082] According to some examples, the method 800 includes receiving a motor drive speed command at operation 804. For example, the processor may receive a motor drive speed input from an input such as a throttle. For example, the motor drive speed (e.g., revolutions per minute or RPM) may be measured by a tachometer or similar sensor. In some embodiments, the motor 700 speed may be estimated based on drive signals to the motor 700 or motor controller. In some embodiments, the operation 802 and the operation 804 may be executed simultaneously.

[0083] According to some examples, the method 800 includes setting motor speed (e.g., RPM) at operation 806. For example, control signals may be supplied to the motor 700 or a motor controller to cause a certain speed output from the motor 700. For example, the processing element 902 may receive the motor 700 drive speed command at operation 804 and set one or more electrical signals to cause the motor 700 to produce a certain level of revolution speed. In some examples, a motor drive may be received from a drive speed sensor such as a tachometer, or may calculate the motor speed from a variety of inputs. In some examples, the operation 804 and operation 806 may form a closed loop control such as a proportional-integral-derivative control.

[0084] According to some examples, the method 800 includes determining theoretical boat speed based on motor drive speed at operation 808. According to some examples, the method 800 includes determining theoretical boat speed based on motor drive speed (either commanded motor drive speed, actual motor speed, or both) at operation 808. In some examples, a theoretical boat speed may be based on a propeller (or screw) pitch. In one example, a deep-V speed boat with a Crouch’s constant of 180, drive gear ratio of 1.501: 1, a propeller pitch of24P, and a slip of 24%, while on a plane, may produce approximately 10 knots of boat speed for every 100 RPM of drive input. At 5000 drive RPM, the boat speed may be approximately 50 knots. In some embodiments, slip is determined as a percentage difference between the theoretical boat speed and actual boat speed.

[0085] According to some examples, the method 800 includes determining slip based on difference between actual boat speed and theoretical boat speed at operation 810. According to some examples, the method 800 includes operation 810 where a processing element 902 determines slip based on difference between actual boat 102 speed (e.g., as determined in 802) and theoretical boat 102 speed (e.g., as determined in 808). For example, the slip may be calculated as a difference between, ratio of, an actual boat 102 speed and a theoretical boat 102 speed. In some embodiments, the method 800 may include recording historical data of boat speed and slip (e.g., and storing the historical data in a memory component 908), and at least one of determining the theoretical boat speed or determining the slip is based, at least in part, on the historical data. In some embodiments, determining the slip includes comparing instantaneous and averaged speeds over a predetermined period of time.

[0086] According to some examples, the method 800 includes slipping < 0 at operation 812. According to some examples, the method 800 includes determining if the slip is less than or near zero operation 812. If the slip is less than or near zero, the method 800 may proceed to operation 814. If the slip is not less than or near zero, the method 800 may return to operation 802.

[0087] According to some examples, the method 800 includes reducing motor 700 torque at operation 814. For example, the torque command provided to the motor 700 from the processor may be set such that the motor 700 produced low or no torque, thereby emulating the freewheeling effect of a traditional stern drive 300, but without the weight, bulk, and expense of a transmission. In some embodiments, reducing the torque setting involves maintaining a constant revolution speed of the motor shaft.

[0088] For example, as the commanded drive rotation is reduced below the corresponding boat 102 speed for a given propeller 314 rotation, commanded torque output from the motor 700 may be reduced (e.g., set to zero). As boat 102 speed decreases to a level below the commanded rotation, the normal torque characteristics based on the throttle mapping may be reintroduced. Electric motors can operate in forward or reverse direction. When integrated with an improved stern drive disclosed herein, an electric motor 700 eliminates the need for atransmission to change direction, providing advantages of lower cost, lower complexity, and higher reliability of the stern drive. Permanent-magnet, synchronous electric motors, a typical type for propulsion applications, will not freewheel unless specifically mapped out in a throttle control scheme such as method 800.

[0089] In some embodiments, a boat 102 executing the method 800 or using an improved stern drive, or any stern drive coupling system disclosed herein, may be operated autonomously or semi-autonomously. For example, the control system 900 (described with respect to FIG. 9) may be in communication with an external controller, such as in wireless communication. The control system 900 may receive and execute commands received from the external controller to operate the boat 102. For example, the control system 900 may steer the boat 102, control power levels, and / or rotation direction of the motor 700 and thus the propeller 314, alter the trim of the boat 102, execute the method 800, or perform other actions to operate the boat 102. In some embodiments, the control system 900 may receive human initiated commands via the external controller. In some examples, the control system 900 or external controller may execute an artificial intelligence algorithm that controls the boat 102, the improved stern drive, any stern drive coupling system, and / or executes the method 800 autonomously or semi- autonomously. The artificial intelligence algorithm may be trained by recording human-based operation of the boat 102, improved stern drive, or stern drive coupling system, and using such recorded operation to train the algorithm.

[0090] FIG. 9 is a simplified block diagram of components of a control system suitable to execute the method 800. For example, the processing element 902 and the memory component 908 may be located at one or in several computing systems 900. This disclosure contemplates any suitable number of such computing systems 900. For example, the control system may be a desktop computing system, a mainframe, a blade, a mesh of computing systems 900, a laptop or notebook computing system 900, a tablet computing system 900, an embedded computing system 900, a system-on-chip, a single-board computing system 900, a marine controller, a programmable logic controller, or a combination of two or more of these. Where appropriate, a computing system 900 may include one or more computing systems 900; be unitary or distributed; span multiple locations; span multiple machines; span multiple data centers; or reside in a cloud, which may include one or more cloud components in one or more networks. A computing system 900 may include one or more processing elements 902, an input / output I / O interface 904, one or more external devices 912, one or more memory components 608, anda network interface 910. Each of the various components may be in communication with one another through one or more buses or communication networks, such as wired or wireless networks. The components in FIG. 9 are exemplary only. In various examples, the computing system 900 may include additional components and / or functionality not shown in FIG. 9.

[0091] The processing element 902 may be any type of electronic device capable of processing, receiving, and / or transmitting instructions. For example, the processing element 902 may be a central processing unit, microprocessor, processor, or microcontroller.Additionally, it should be noted that some components of the computing system 900 may be controlled by a first processing element 902 and other components may be controlled by a second processing element 902, where the first and second processing elements may or may not be in communication with each other.

[0092] The I / O interface 904 allows a user to enter data in to computing system 900, as well as provides an input / output for the computing system 900 to communicate with other devices or services. The I / O interface 904 can include one or more input buttons, touch pads, touch screens, and so on. In some examples, the I / O interface 904 may include a throttle that a user may use to command the computing system to cause the motor to turn at a desired rotational speed (e.g., RPM).

[0093] The external device 912 are one or more devices that can be used to provide various inputs to the computing systems 600, e.g., mouse, microphone, keyboard, trackpad, sensing element (e.g., a thermistor, humidity sensor, light detector, etc. The external devices 912 may be local or remote and may vary as desired. In some examples, the external devices 912 may also include one or more additional sensors.

[0094] The memory components 908 are used by the computing system 900 to store instructions for the processing element 902 such as instructions to execute the method 800, a user interface, as well as store data, such as user preferences, alerts, etc. The memory components 908 may be, for example, magneto-optical storage, read-only memory, random access memory, erasable programmable memory, flash memory, or a combination of one or more types of memory components.

[0095] The network interface 910 provides communication to and from the computing system 900 to other devices. The network interface 910 includes one or more communication protocols, such as, but not limited to Wi-Fi, Ethernet, Bluetooth, National Marine Electronics Association (NMEA) 2000 network, etc. The network interface 910 may also include one ormore hardwired components, such as a Universal Serial Bus (USB) cable, or the like. The configuration of the network interface 910 depends on the types of communication desired and may be modified to communicate via Wi-Fi, Bluetooth, etc.

[0096] The display 906 provides a visual output for the computing system 900 and may be varied as needed based on the device. The display 906 may be configured to provide visual feedback to a and may include a liquid crystal display screen, light emitting diode screen, plasma screen, or the like. In some examples, the display 906 may be configured to act as an input element for a user through touch feedback or the like.

[0097] Any description of a particular component being part of a particular embodiment, is meant as illustrative only and should not be interpreted as being required to be used with a particular embodiment or requiring other elements as shown in the depicted embodiment.

[0098] All relative and directional references (including top, bottom, side, front, rear, and so forth) are given by way of example to aid the reader’s understanding of the examples described herein. They should not be read to be requirements or limitations, particularly as to the position, orientation, or use unless specifically set forth in the claims. Connection references (e.g., attached, coupled, connected, joined, and the like) are to be construed broadly and may include intermediate members between a connection of elements and relative movement between elements. As such, connection references do not necessarily infer that two elements are directly connected and in fixed relation to each other, unless specifically set forth in the claims.

[0099] The present disclosure teaches by way of example and not by limitation. Therefore, the matter contained in the above description or shown in the accompanying drawings should be interpreted as illustrative and not in a limiting sense. The following claims are intended to cover all generic and specific features described herein, as well as all statements of the scope of the present method and system, which, as a matter of language, might be said to fall there between.

[0100] Any description of a particular component being part of a particular embodiment, is meant as illustrative only and should not be interpreted as being required to be used with a particular embodiment or requiring other elements as shown in the depicted embodiment.

[0101] All relative and directional references (including top, bottom, side, front, rear, and so forth) are given by way of example to aid the reader’s understanding of the examples described herein. They should not be read to be requirements or limitations, particularly as to theposition, orientation, or use unless specifically set forth in the claims. Connection references (e.g., attached, coupled, connected, joined, and the like) are to be construed broadly and may include intermediate members between a connection of elements and relative movement between elements. As such, connection references do not necessarily infer that two elements are directly connected and in fixed relation to each other, unless specifically set forth in the claims.[01021 The present disclosure teaches by way of example and not by limitation. Therefore, the matter contained in the above description or shown in the accompanying drawings should be interpreted as illustrative and not in a limiting sense. The following claims are intended to cover all generic and specific features described herein, as well as all statements of the scope of the present method and system, which, as a matter of language, might be said to fall there between.

Claims

CLAIMSWhat is claimed is:

1. A method of controlling a motor coupled to a stern drive comprising: receiving a boat speed; receiving a motor drive speed command; causing a motor shaft to spin at a motor drive speed based on the motor drive speed command; determining a theoretical boat speed based at least in part on the motor drive speed; determining a slip of the boat based at least in part on the boat speed and the theoretical boat speed; determining if the slip is near or below zero; and based on determining if the slip is near or below zero, reducing a torque setting of the motor.

2. The method of claim 1, wherein determining the theoretical boat speed comprises using a propeller pitch and drive gear ratio.

3. The method of claim 1, further comprising adjusting the motor drive speed command based on a user input.

4. The method of claim 1, wherein the slip is determined as a percentage difference between the theoretical boat speed and actual boat speed.

5. The method of claim 1, wherein reducing a torque setting involves maintaining a constant revolution speed of the motor shaft.

6. The method of claim 1, wherein the method is executed as part of a closed loop control system.

7. The method of claim 1, further comprising recording historical data of boat speed and slip, wherein at least one of determining the theoretical boat speed or determining the slip is based, at least in part, on the historical data.

8. The method of claim 1, wherein determining the slip comprises comparing instantaneous and averaged speeds over a predetermined period of time.

9. The method of claim 1, wherein: the motor shaft is received in a coupler adapted to transmit torque from the motor shaft; a secondary shaft is in operational connection with the coupler; a bearing housing supports the secondary shaft via one or more bearings; and the secondary shaft is coupled to an output shaft configured to transmit torque to a stern drive that drives a propeller.

10. The method of claim 1, wherein the motor comprises an electric motor.

11. A stern drive coupling system for use with an electric motor comprising: a motor shaft; a coupler adapted to transmit torque from the motor shaft; a secondary shaft in operational connection with the coupler; a bearing housing supporting the secondary shaft via at least one bearing; and an output shaft configured to transmit torque to a stern drive.

12. The stern drive coupling system of claim 11, wherein the coupler comprises an input receptacle and an output receptacle for mating with corresponding shafts.

13. The stern drive coupling system of claim 11, further comprising a spacer coupled to the bearing housing and the motor.

14. The stern drive coupling system of claim 11, wherein the at least one bearing comprises a roller bearing configured for axial thrust absorption.

15. The stern drive coupling system of claim 11, wherein the secondary shaft includes a relief notch.

16. The stern drive coupling system of claim 11, further comprising a flexible coupling operatively connected to the secondary shaft and output shaft.

17. The stern drive coupling system of claim 16, wherein the flexible coupling compensates for angular or translational misalignment between shafts.

18. The stern drive coupling system of claim 11, wherein the bearing housing is integrally formed with a bell housing.

19. The stern drive coupling system of claim 18, wherein the bell housing is coupled to a transom of a boat.

20. A method of controlling the stern drive system of claim 11 comprising: receiving a boat speed; receiving a motor drive speed command; causing the motor shaft to spin at a motor drive speed based on the motor drive speed command; determining a theoretical boat speed based at least in part on the motor drive speed; determining a slip of the boat based at least in part on the boat speed and the theoretical boat speed; determining if the slip is near or below zero; and based on determining if the slip is near or below zero, reducing a torque setting of the motor.

Images