Motor

The present invention relates to marine outboard motors. More specifically, the present invention relates to an outboard motor mountable to a transom of a boat, either as main motor or as auxiliary drive.

Outboard motors are a common type of marine propulsion system that comprise a motor engine, thrust-generator and steering mechanics in a self-contained unit that is mountable to a watercraft transom and removable for transport, storage and maintenance. Outboard motors can be of a single-person lift design of a few kg for small boats, or can be considerably larger, e.g. in the region of 100 kg or more.

Conventional outboard motors allow steering by way of their body being mounted in a laterally pivotable manner, providing a steering axis. Turning the body of the motor using a tiller or a steering system results in rotation of the thrust generator (e.g. a propeller) with the motor body about the steering axis.

More recently, outboard motors have been developed that allow a lower leg of the motor body to be rotated relative to the main outboard body. However, complexity, weight and sometimes relatively poor hydrodynamic shaping of such motors affect their popularity and wider adoption.

The present invention seeks to provide an improved outboard motor design alleviating at least some of the aforementioned disadvantages.

In accordance with a first aspect of the present invention, there is provided an outboard propulsion unit as defined in claim. The outboard propulsion unit is mountable on a watercraft structure, and comprises a main body and a propulsion leg carrying a thrust generator, the main body for mounting to a watercraft structure, the propulsion leg being rotatable relative to the main body for steering when submerged, wherein the propulsion unit comprises a helical actuator coupled with the propulsion leg and controllable to cause rotation of the propulsion leg relative to the main body.

The propulsion unit may be a boat motor. It will be understood that an outboard propulsion unit is mountable to a structure of watercraft such as a boat, typically via a transom bracket to a transom. The invention relates to boat motors of the type comprising a main body that comprises an (in use) lower leg, constituting a propulsion leg, rotatable relative to the main body, i.e. relative to a head or cowl of the motor and/or relative to a mid-section of the motor. In this manner, the main body does not need to be pivoted for steering.

The outboard propulsion unit typically comprises, or is connectable to, a transom bracket whereby it is pivotable via a trim axis between a deployed position in which the propulsion leg is submerged in water, and a non-use position in which it is generally horizontal, extending at an angle of around 70 to 90 degrees, for installation, removal and/or maintenance. In a deployed position, the unit may be fixed at one of different trim angles relative to the watercraft structure.

The lower leg carries a thrust generator such as a propeller. In accordance with an aspect of the invention, the propulsion unit comprises a helical actuator to control the degree of rotation of the propulsion leg relative to the main body.

In some embodiments, the helical actuator has a holding torque larger than a propulsion torque of the thrust generator.

The helical actuator may have a holding torque that is understood as the torque resisting rotation, e.g. in response to torque/rotation of the propulsion leg. The thrust generator may be a propeller that may be operated at an operating torque or maximum torque. A larger holding torque allows the propulsion leg to be held in a more stable manner. The holding torque may be at least 2×, 3×, 5× or 10× of the thrust generator torque. To provide illustrative example values, a boat motor may provide a drive torque of about 120 Nm. The helical actuator may have a holding torque of 5000 Nm. In the example, the actuator holding torque is about 40× the motor torque, i.e. at least a level of magnitude larger than the thrust generator torque. Thereby it can be avoided that the motor drive can affect steering of the lower leg.

In some embodiments, the helical actuator is controlled by a hydraulic system.

The helical actuator may be of a design comprising a hydraulic chamber arrangement to move a collar or helical gear, translating axial movement into a shaft rotation, to effect rotation of the propulsion leg. It is believed that hydraulic operation provides for stronger torque during steering, which may allow a more reliable and/or faster motor movement in strong currents or turbulent conditions.

In some embodiments, the helical actuator is configured to control rotation of the propulsion leg relative to the main body within a range of no less than 170 degrees.

In some embodiments, the helical actuator is configured to control rotation of the propulsion leg relative to the main body within a range of no less than 180 degrees.

The range may be limited to no less than 160, 170, 180, or 190 degrees.

In some embodiments, the helical actuator is configured to control rotation of the propulsion leg relative to the main body within a range of no more than 220 degrees.

The range may be limited to no more than 220, 210, 200, 190 or 180 degrees.

It was an appreciation underlying the invention that the use of a helical actuator provides an inherent range limitation e.g. to allow the rotation of a propulsion leg to be determined by lateral limits, e.g. +/−90 degrees (to amount to 180 degrees range). This avoids the need for additional range limitation systems.

The range limitation may allow an outboard propulsion unit to be mounted closer to the watercraft structure, or higher than might otherwise be desirable, while reducing a risk of damage.

In some embodiments, the main body comprises a motor arranged to drive the thrust generator via a drive shaft extending from the main body to the propulsion leg.

Preferably, the motor engine is mounted in the upper region of the main body, in the cowl or mid section region, to drive a propeller of the thrust generator via a drive shaft.

In some embodiments, the helical actuator is arranged coaxially with the drive shaft.

In some embodiments, the helical actuator is of annular configuration comprising an axial passage, the drive shaft extending through the axial passage.

By providing a helical actuator of annular design, the inventors found that the drive shaft may be located through the helical actuator and coaxially with the rotation axis of the propulsion leg. It will be appreciated that axial passage through the helical actuator must be sufficiently wide to allow operation of the drive shaft independently of the helical actuator. The coaxial arrangement allows for a compact design such that the vertical extension of either or both of the head region and mid section of the main body may be reduced. Likewise, a head region or cowl of the main body may be located so low that it is practically unitary with a mid section of the main body. In this manner, the motor may sit (in use) vertically above the helical actuator

In some embodiments, the helical actuator is located in the main body.

The helical actuator may be located in a mid section of the main body. The helical actuator may be located in a cowl region of the main body.

In some embodiments, the main body comprises a trim pivot located at a top end of the main body.

The compact arrangement allows a trim pivot point or axis to be at the cowl or head region of the propulsion unit. In this manner, the propulsion unit may be mounted to a watercraft structure at a conventional location (i.e., the upper edge or gunwale of the transom), but protrudes less high than is conventionally the case, such that only a small portion of the propulsion unit extends above the transom, or such that the entire propulsion unit remains below the transom edge in a deployed position. This reduces the silhouette of an outboard propulsion unit such that it is better suited (i.e., not in the way) for towing or water-skiing.

In some embodiments, the main body comprises a head and a transom attachment for mounting the main body aft of a plane of a transom, the main body comprising a pivot joint configured to allow the motor to be pivoted between a deployed position and a non-use position, wherein the pivot joint is located relative to the head such that the head is aft of the plane in the non-use position.

In some embodiments, the transom attachment is provided by a transom bracket integral with the main body.

The transom bracket may be an integral part of the outboard propulsion unit.

In some embodiments, the transom attachment is provided by a transom bracket assembly comprising a first bracket subassembly and a second bracket subassembly mountable to the first bracket subassembly, the first bracket subassembly being detachable from the second bracket subassembly for installation to a transom without the main body, the second bracket subassembly being part of or connected with the main body for mounting to the first bracket subassembly.

The transom bracket may be separable from the outboard propulsion unit in a manner allowing the transom bracket to be fixed to a transom without the propulsion unit. This facilities installation and removal of the propulsion unit main body. For instance, the transom bracket may remain installed on the watercraft structure if the propulsion unit needs to be taken away. The transom bracket may be attached or reconnected to the main body without requiring disassembly of the main body.

In some embodiments, the outboard propulsion unit is pivotable about a trim axis in the cowl region of the main body.

In some embodiments, the outboard propulsion unit is pivotable about a trim axis in the upper half of the cowl region.

In some embodiments, the outboard propulsion unit is pivotable about a trim axis at the top of the cowl region.

As will be understood, references to an upper half or top of a cowl region are references to an in-use vertical upper or top position.

Any one or more of the embodiments described herein may be combined with any one or more other embodiments described herein.

With reference to the figures, a boat(indicated only in part) constituting a watercraft comprises a transomconstituting a structure of the watercraft to which an outboard propulsion unit may be mounted.

The boat motorconstitutes an outboard propulsion unit and is mountable via a transom bracketto the transom. The boat motorcomprises a head regionor cowl, a mid section, and a lower legconstituting a propulsion leg. The head regionand the mid sectionmake up the main body of the boat motorand may be relatively compact (see also the comparison of).

The lower legcarries a propellerconstituting a thrust generator. It will be appreciated that the propelleris driven by a (horizontal) propeller drive shaft(illustrated schematically in) which in turn is driven by a (vertical) transmission drive shaftvia a motor(motorindicated schematically in). The transmission drive shaftmay be connected to the propeller drive shaftvia a bevel gear transmission. As will be appreciated, other transmission means such as a universal joint or other suitable transmission from a vertical drive shaft to a horizontal drive shaft may be used.

The motoris typically located in the head regionor mid section. In this embodiment, the motoris an electrical motor avoiding the need for a fuel tank, however the invention may be used with a combustion engine or other suitable drive. Power supply and control signals may be provided via wiring, or may be controlled by other suitable means. An energy source such as a battery (not shown) may be located in the boat. Alternatively or in addition, the battery or a tank, as may be applicable, may be part of the boat motor.

The lower legis rotatably mounted to the main body, in use rotatable about a vertical axis, such that rotation of the lower legchanges the orientation of the propellerfor steering.

With reference to, the lower legmay be operated to rotate relative to the mid sectionand head portionover a range of (here:) 180°, between a port orientationP and a starboard orientationS, e.g. +/−90°. The angular range may depend on the type of helical actuator and coupling mechanism, and may be larger or smaller than +/−90° (180°). It will be appreciated that, in this manner, steering can be effected without having to pivot the entire boat motorabout a vertical shaft axis. The boat motormay therefore be mounted to the transomin a manner permitting pivoting about a horizontal pivot axisonly, i.e. about a trim axis. This allows for a more compact design of the propulsion unit and/or the transom bracket. It will be appreciated that the manner of control, motor installation and/or centre calibration may be carried out in a usual manner, and are not described in detail herein.

The boat motorcomprises a steering subunitin the form of a helical actuator. An exemplary helical actuator may be a Helac L Series Helical Actuator available from Parker Hannifin (Parker Hannifin Corporation, 225 Battersby Avenue, Enumclaw, WA 98022, United States, or Parker Sales Company, Tachbrook Park, Warwick CV34 6TU, United Kingdom). Other helical actuator designs may be used. In the embodiment depicted in the Figures, the helical actuatorcomprises a housing structure comprising an annular, axially extending chamber comprising, conceptually, a first (annular) hydraulic chamber endand a second (annular) hydraulic chamber endthat are separated by a collarsuch as a helical gear that is axially moveable relative to the housing structure of the helical actuator. The hydraulic chamber ends,can be pressurised by hydraulic fluid at appropriate pressure levels in a coordinated manner such that the hydraulic pressure acts on the collar, thereby causing axial movement in the manner of a piston. By control of the pressurisation of the hydraulic chamber either from the first hydraulic chamber endand/or the second hydraulic chamber end, movement of the collaris caused either towards the first hydraulic chamber end(in response to pressure from the second hydraulic chamber end) or towards the second hydraulic chamber end(in response to pressure from the first hydraulic chamber end).

Parts of the helical actuatorand the actuator housing comprise axially and/or helically extending guide elements such as ridges, teeth or splines and corresponding grooves or tracks to guide the axial movement of the collarrelative to the actuator housing. The collaris provided with helical gear teeththat are engaged with corresponding helical featuresof a drive cylinder. The helical gear teethcause rotation of the drive cylinderduring axial movement of the collar. As will be appreciated, the collarmay be of a design comprising inner and outer teeth or splines, e.g., two counter-rotating helical teeth arrangements on its inner and outer diameters for a compact design. However, other guide track arrangements may be used in some embodiments. The drive cylinderis mechanically coupled via a couplingwith the lower legsuch that hydraulic actuation of the helical actuatorresults in a corresponding rotation of the drive cylinder, and, therefore, of the lower leg.

The helical actuatoris driven by a hydraulic system (not illustrated in the Figures) and control logic that converts a steering command, rudder command or the like into a corresponding hydraulic pressurisation to effect rotation of the lower leg. It will also be understood that the hydraulic system comprises valve control and release mechanisms, for the adjustment, increase and reduction of pressure levels, that are not described in detail herein. In the present embodiment, the hydraulic system is a closed system, however other designs may be used in different embodiments. The use of a hydraulic system to drive the helical actuatorallows the lower legto be steered with relatively strong torque, and with relatively precise control over the angular steering position of the lower leg. Preferably, the helical actuator torque is larger than the motor torque. Through pressure applicable from the two hydraulic chamber endsand, the hydraulic actuatoris provided with a holding torque exceeding the motor torque. Thereby, operation, acceleration and deceleration of the propeller, or “prop torque”, that may otherwise act on the lower leg, has no practical effect on the angular orientation of the lower leg. As will be appreciated, the angular range of rotation may be determined by the relative axial travel range of the collarrelative to the drive cylinder. In addition, the steering system may comprise additional range limiters in mechanical or software form.

The helical driveis of annular configuration, wherein the collaris of ring form and the drive cylinderis provided by a tubular body, the components of the helical drivebeing arranged coaxially to provide an axial passage. The axial passageis dimensioned with a sufficiently wide diameter to allow the transmission drive shaftto extend through the passage. In this manner, the transmission drive shaftmay be operated without interfering with the operation of the helical actuator, taking into account tolerances and build-up of contaminants. This is facilitated by the use of a collarof annular form that is disposed to move axially along the drive shaft. As will be appreciated, appropriate selection of bearings and race tolerances allows the transmission drive shaftto be held in a relatively precise, predetermined position. The helical actuatorand the transmission drive shaftare disposed securely enough to allow independent operation of the steering and the thrust generation.

As the transmission drive shaftrotates independently of the lower leg, steering may result in a cumulative rotation of the transmission drive shaftand helical actuator. However, the effect of any cumulative rotation in typical use scenarios is practically irrelevant, because the output of the motoris typically a few 1000 rpm, whereas the lower legis rotated for practical purposes with less than 1 rpm. The coaxial arrangement of the mechanisms allows for a relatively compact motorin which the head regionand mid sectionare relatively short.