Patent Description:
International Patent Application Publication No. <CIT>, discloses a marine steering system comprising a propulsion unit including a tilt tube, a support rod received by the tilt tube, a tiller, and an electric actuator for imparting steering movement to the propulsion unit. The electric actuator includes a housing and an output shaft reciprocatingly received by the housing. The output shaft is partially threaded and has smooth surfaces. There is a motor disposed within the housing. The motor includes a stator and a rotor. Rotation of the rotor causes the output shaft to translate axially relative to the rotor and causes the output shaft to reciprocate relative to the housing. A pivot plate is pivotably connected to the tiller of the propulsion unit. The pivot plate rotationally constrains the housing of the electric actuator to provide reaction torque for rotation of the rotor. There are support arms which connect respective ends of the output shaft to the support rod of the propulsion unit. The support arms provide rotational constraint to the output shaft and the support arms inhibit axial movement of the output shaft relative to the marine vessel while the housing of the electric actuator reciprocates linearly along the output shaft. <CIT> discloses a remote, electrical steering system for marine vehicles including an electrical motor (<NUM>) operable by a control and power circuit to rotate a drive screw (<NUM>) having a screw connection to a nut (<NUM>) in a drive tube (<NUM>) for moving the drive tube (<NUM>) in translation to cause steering movement of motor/rudder. <CIT> describes an electric type steering device for outboard motors that can include a steering wheel, connecting members for connecting outboard motors together, and a plurality of steering motors for steering a plurality of outboard motors.

It is an object of the present invention as claimed to provide an electric actuator and, in particular, an electric actuator for a marine steering system.

There is accordingly provided an electric actuator for a marine steering system. The electric actuator comprises a housing and an output shaft reciprocatingly received by the housing. There is a rotor disposed within the housing. The rotor is coupled to the output shaft of the electric actuator. Rotation of the rotor causes the output shaft of the electric actuator to reciprocate relative to the housing. There is a motor disposed within the housing. The motor has an output shaft coupled to the rotor. A longitudinal axis of the output shaft of the motor is parallel with a longitudinal axis of the output shaft of the electric actuator. There is also a drive mechanism disposed within the housing. The drive mechanism couples the output shaft of electric actuator to the rotor. The drive mechanism is on a plane radial to a longitudinal axis of the output shaft of the motor.

The drive mechanism may be a tensioned drive mechanism. The drive mechanism may include a belt which couples the output shaft of the electric actuator to the rotor. The belt may be provided with a tensioner. The drive mechanism includes an idler gear which couples the output shaft of the electric actuator to the rotor. Wiring may be connected to the electric actuator along a longitudinal axis which is generally parallel to the longitudinal axis of the output shaft of the electric actuator.

The electric actuator includes a position sensor disposed on the rotor for sensing a position of the rotor. The position sensor may sense an actual steering position based on a position of the rotor. The position sensor may be a rotary position sensor. The position sensor may be a rotary position sensor that employs a gear reduction. The position sensor may be a rotary position sensor that employs a gear reduction so that a driven sensor gear never rotates more than one rotation.

The electric actuator may include a clutch directly coupled to the rotor. The clutch may function as a brake. The electric actuator may include a housing having a T-shaped profile with longitudinally extending arm portions.

There is also provided a steering system for a marine vessel. The steering system comprises a propulsion unit including a tilt tube, a support rod received by the tilt tube, a tiller, and an electric actuator. The electric actuator comprises a housing and an output shaft reciprocatingly received by the housing. There is a rotor disposed within the housing. The rotor is coupled to the output shaft of the electric actuator. Rotation of the rotor causing the output shaft of the electric actuator to reciprocate relative to the housing. There is a motor disposed within the housing. The motor has an output shaft coupled to the rotor. A longitudinal axis of the output shaft of the motor is parallel with a longitudinal axis of the output shaft of the electric actuator. There is also a drive mechanism disposed within the housing. The drive mechanism couples the output shaft of electric actuator to the rotor. The drive mechanism is on a plane radial to a longitudinal axis of the output shaft of the motor. There is a pivot plate is pivotably connected to the tiller of the propulsion unit. The pivot plate rotationally constrains the housing of the electric actuator to provide reaction torque for rotation of the rotor. Support arms connect respective ends of the output shaft to the support rod of the propulsion unit. The support arms provide rotational constraint to the output shaft and the support arms inhibiting axial movement of the output shaft relative to the marine vessel while the housing of the electric actuator reciprocates linearly along the output shaft. The motor of the electric actuator is disposed, relative to the marine vessel, in front of the output shaft of the electric actuator in the tilted down position and the tilted up position.

The electric actuator may be disposed under an engine pan of the propulsion unit and above a splashwell of the marine vessel in the tilted down position and the tilted up position. The housing of the electric actuator may be pivotable when the propulsion unit is pivotable. The housing may have a T-shaped profile with longitudinally extending arm portions, wherein one of the longitudinal extending arm portions overlaps a respective one of the support arms when the electric actuator strokes to a hard over position.

The invention will be more readily understood from the following description of the embodiments thereof given, by way of example only, with reference to the accompanying drawings, in which:.

Referring to the drawings and first to <FIG>, there is shown a marine vessel <NUM> which is provided with a plurality of propulsion units which, in this example, are in the form of two outboard engines, namely, a port engine <NUM> and a starboard engine <NUM>. However, in other examples, the propulsion units may be any number or form of propulsion units. The marine vessel <NUM> is also provided with a control station <NUM> that supports a steering wheel <NUM> mounted on a helm <NUM>, a control head <NUM>, and a joystick <NUM>. The control station <NUM> is conventional and allows the port engine <NUM> and the starboard engine <NUM> to be steered using either the steering wheel <NUM> and the helm <NUM> or the joystick <NUM> as disclosed in <CIT> which is incorporated herein by reference. The control station <NUM> further includes a first display interface <NUM> and a second display interface <NUM>. In this example, the first display interface is a SIMRAD® display interface which displays navigational information and the second display interface is a BEP® display which displays onboard system information.

The port engine <NUM> of the marine vessel <NUM> is shown in greater detail in <FIG>. The port engine <NUM> is provided with an electric actuator <NUM>. The electric actuator <NUM> generally comprises a housing <NUM> with an output shaft <NUM> reciprocatingly received therein and spaced-apart housing arms <NUM> and <NUM> which extend radially outward of the housing <NUM>. A pivot plate <NUM> can be coupled to each of the housing arms <NUM> and <NUM> by respective pivot pins <NUM> and <NUM>. The pivot plate <NUM> extends between the housing arms <NUM> and <NUM>. The pivot plate <NUM> can pivot about the pivot pins <NUM> and <NUM>. A steering member or tiller <NUM> of the port engine <NUM> can be pivotably coupled to the pivot plate <NUM> by a tiller pin <NUM>. There are support arms <NUM> and <NUM> which connect respective ends of the output shaft <NUM> of the electric actuator <NUM> to a support rod <NUM> and a tilt tube <NUM> of the port engine <NUM>. The support arms <NUM> and <NUM> inhibit axial and rotational movement of the output shaft <NUM> of the electric actuator <NUM> relative to the marine vessel <NUM> while the housing <NUM> of the electric actuator <NUM> reciprocates along the output shaft <NUM> and linearly relative to the marine vessel <NUM>. This relative linear movement of the housing <NUM> causes the tiller <NUM> of the port engine <NUM> to pivot and thereby cause the port engine to be steered in a conventional manner. It will be understood by a person skilled in the art that the starboard engine <NUM> has a substantially identical structure and functions in a substantially similar manner. The starboard engine is accordingly not described in detail herein.

The electric actuator <NUM> is shown in greater detail in <FIG>. The housing <NUM> of the electric actuator <NUM> has a T-shaped profile with longitudinally extending arm portions <NUM> and <NUM>. The longitudinally extending arm portions <NUM> and <NUM> of the housing <NUM> extend longitudinally overlapping the support arms <NUM> and <NUM> when the electric actuator <NUM> strokes to hard over positions, as shown in <FIG>, for the longitudinally extending arm portion <NUM> and the support arm <NUM>. Wiring <NUM> is connected to the housing <NUM> of the electric actuator <NUM> at the longitudinally extending arm portion <NUM> along a longitudinal axis <NUM> which is generally parallel to a longitudinal axis <NUM> of the output shaft <NUM> of the electric actuator <NUM>. This may offer advantages in clearance.

<FIG> shows a partly broken away view of the electric actuator <NUM>. A motor <NUM> of the electric actuator <NUM> is disposed such that an output shaft <NUM> of the motor <NUM> has a longitudinal axis <NUM> which is generally parallel to the longitudinal axis <NUM> of the output shaft <NUM> of the electric actuator <NUM>. The longitudinal axis <NUM> of the output shaft <NUM> of the electric actuator <NUM> and the longitudinal axis <NUM> of the output shaft <NUM> of the motor <NUM> are orthogonal to a longitudinal axis of the marine vessel <NUM>. In this example, the output shaft <NUM> of the motor <NUM> is coupled to a rotor <NUM> of the electric actuator <NUM> by a drive mechanism that includes a belt <NUM>, as best shown in <FIG>, in order to transmit rotational motion from the output shaft <NUM> of the motor <NUM> to a rotor <NUM> of the electric actuator <NUM>. In this example, the belt <NUM> is provided with a tensioner <NUM>. Use of the belt <NUM> to couple the output shaft <NUM> of the motor <NUM> to the rotor <NUM> of the electric actuator <NUM> may dampen out the load impulses from the port engine <NUM>. However, in other examples, the drive mechanism may employ other means such as an idler gear <NUM>, shown in <FIG>, to couple the output shaft <NUM> of the motor <NUM> to the rotor <NUM> of the electric actuator <NUM>. The drive mechanism is on a plane radial to the longitudinal axis <NUM> of the output shaft <NUM> of the electric actuator <NUM>.

Referring back to <FIG>, the electric actuator <NUM> also includes a position sensor <NUM> for sensing a position of the rotor <NUM> of the electric actuator <NUM>. An actual steering position is determined based on the position of the rotor <NUM>. The position sensor may be a rotary positions sensor, or a linear position sensor with a helical magnetic element, or any other suitable sensor. The position sensor <NUM> employs a gear reduction which, in this example, is a worm-like drive best shown in <FIG>. There is an outer threading <NUM> on the rotor <NUM> which engages a driven sensor gear <NUM>. There is a magnet <NUM> disposed on the end of a shaft <NUM> which extends axially from the driven sensor gear <NUM>. A position of the magnet is sensed by a non-contact position sensor element <NUM>. A controller <NUM>, disposed within the housing <NUM> of the electric actuator, reads the sensor element <NUM> as the actual steering position. The controller also reads a steering command from the steering wheel <NUM> and then drives the motor <NUM> based on a difference between the steering command and the actual steering position.

The rotor <NUM> also has inner threading <NUM> which is shown in <FIG>. The inner threading <NUM> of the rotor <NUM> engages a roller screw assembly <NUM>. The roller screw assembly is axially and rotationally inhibited by the support arms <NUM> and <NUM>. It is possible to remove a nut at the support arms, for example nut <NUM> shown in <FIG>, to manually reposition the housing. In this example, the lead of a roller screw assembly <NUM> of the electric actuator <NUM> is <NUM> inches, so for an <NUM> inch stroke, the rotor <NUM> of the electric actuator <NUM> turns approximately eighty times. A reduction gear of ><NUM>:<NUM> is accordingly employed so the driven sensor gear <NUM> never rotates more than one rotation. Disposing the position sensor <NUM> on the rotor <NUM> places the position sensor <NUM> closer to the output of the electric actuator <NUM> to avoid fault.

The electric actuator <NUM> also includes a clutch <NUM>, which may function as a brake, which is coaxial to the rotor <NUM> and shown in <FIG> and <FIG>. The clutch <NUM> is generally similar to the clutch disclosed in International Patent Application Publication No. <CIT> However, in this example, there is a flexure <NUM> directly coupled to the rotor <NUM> without a hub. The flexure <NUM> pulls back a brake pad <NUM> when the clutch <NUM> is released and the flexure <NUM> transmits torque from the rotor <NUM> when the clutch <NUM> is engaged. There is a bearing <NUM> which clamps the flexure <NUM> against a flange <NUM> on the rotor <NUM> of the electric actuator <NUM>. There is also a lock nut <NUM> which allows the clutch <NUM> to be manually released.

The electric actuator <NUM> has an envelope such that the motor <NUM> of the electric actuator <NUM> is disposed, relative to the marine vessel <NUM>, in front of the output shaft <NUM> of the electric actuator <NUM> in the tilted down position and the tilted up position, and all tilt positions therebetween, as shown in <FIG>. The motor <NUM> of the electric actuator <NUM> is also disposed under the port engine <NUM> and above a splashwell <NUM> of the marine vessel in the tilted down position and the tilted up position, and all tilt positions therebetween, as shown in <FIG>. The housing of the electric actuator is pivotable when the propulsion unit is pivotable.

Another actuator <NUM> is shown in <FIG> and <FIG>. The actuator <NUM> is generally similar to the actuator <NUM>, as shown in <FIG> and <FIG>, with the following notable exceptions. The actuator <NUM> shown in <FIG> and <FIG> is a mirror image of the actuator <NUM>, shown in <FIG> and <FIG>, with like parts given like reference numerals in the <NUM> series. Furthermore, the actuator <NUM> is provided with a brake <NUM> which is shown in <FIG> and <FIG>. The brake <NUM> includes a brake pad <NUM> secured to the rotor <NUM>. The brake pad <NUM> is generally annular and is circumambient to the rotor <NUM>. The brake pad <NUM> has a plurality of radial openings, for example, radial openings 304a and 304b.

The brake <NUM> is in an engaged position when a pin <NUM> engages one of said radial openings, for example, said radial opening 304a as shown in <FIG>. The brake <NUM> is provided with a solenoid <NUM> which, when de-energized and as shown in <FIG>, allows the brake to be in the engaged position with a pin <NUM> engaging one of said radial openings 304a. A biased slider <NUM> is coupled to the pin <NUM> and biases the pin <NUM> to engage one of said radial openings 304a. However, when the solenoid <NUM> is energized, the slider <NUM> is pushed away from the brake pad <NUM> and the pin <NUM> disengages from the brake pad <NUM>, as shown in <FIG>, when the brake is in the released position. Accordingly, when the electric actuator <NUM> is not powered the brake <NUM> is in the engaged position. This prevents the electric actuator <NUM> from being back driven. When the electric actuator is powered then the brake <NUM> is released to allow steering. The slider <NUM> allows for manual override by a user.

Claim 1:
An electric actuator (<NUM>, <NUM>) for a marine steering system, the electric actuator comprising:
a housing (<NUM>, <NUM>);
an output shaft (<NUM>, <NUM>) of the electric actuator reciprocatingly received by the housing;
a rotor (<NUM>, <NUM>) disposed within the housing and coupled to the output shaft of the electric actuator, rotation of the rotor causing the output shaft of the electric actuator to reciprocate relative to the housing;
a motor (<NUM>, <NUM>) disposed within the housing; and
a drive mechanism (<NUM>, <NUM>, <NUM>) disposed within the housing;
wherein the motor has an output shaft (<NUM>, <NUM>) coupled to the rotor, wherein a longitudinal axis (<NUM>) of the output shaft of the motor is parallel with a longitudinal axis (<NUM>) of the output shaft of the electric actuator; and
wherein the drive mechanism couples the output shaft of electric actuator to the rotor, wherein the drive mechanism is on a plane radial to the longitudinal axis of the output shaft of the motor, and
wherein an outer threading (<NUM>) on the rotor engages a driven sensor gear (<NUM>) of a position sensor (<NUM>, <NUM>) disposed on the rotor for sensing a position of the rotor, and wherein the electric actuator is characterised in that ends of the output shaft (<NUM>, <NUM>) are connectable to respective support arms (<NUM>, <NUM>, <NUM>, <NUM>) to connect the ends of the output shaft to a support rod (<NUM>, <NUM>) and a tilt tube (<NUM>) of a propulsion unit (<NUM>, <NUM>).