Patent Description:
<CIT>, discloses an electric actuator comprising a housing and an output shaft reciprocatingly received by the housing. There is a screw assembly disposed within the housing and coupled to the output shaft. The screw assembly includes a plurality of annular rollers and a central screw received by the annular rollers. The annular rollers are rotatable about the central screw. There is a motor which includes a stator and a rotor. The rotor has an inner bore which engages the annular rollers. Rotation of the rotor causes the central screw to translate axially relative to the rotor and the output shaft to reciprocate relative to the housing. <CIT> discloses a step actuator apparatus. <CIT> discloses a tubular drive apparatus including sensor elements.

It is an object of the present invention to provide an electric actuator for a marine steering system for steering a marine vessel.

There is accordingly provided an electric actuator for imparting steering movement to a propulsion unit of a marine vessel. The electric actuator includes a housing and an output shaft reciprocatingly received by the housing. There is a motor disposed within the housing. The motor has a rotor assembly and a stator. Rotation of the rotor assembly causes the output shaft to translate axially relative to the rotor assembly and causing the output shaft to reciprocate relative to the housing. There is a coupling assembly mounted to the housing. The coupling assembly couples the electric actuator to the propulsion unit of the marine vessel. There is a steering control unit mounted to the housing. The steering control unit drives the motor to cause the rotor assembly to rotate and the output shaft to reciprocate relative to the housing. There is a magnetic position target mounted on the coupling assembly. There is a position sensor mounted on the actuator. The position sensor senses a position of the electric actuator based on a position of the magnetic position target. The coupling assembly has a curved surface and the magnetic position target has a curved surface which is driven by the curved surface of the coupling assembly when the coupling assembly rotates.

The electric actuator may include an electrical connector which electrically connects the steering control unit to the stator. There may be an opening in the housing and the electrical connector may extend through the opening to electrically connect the steering control unit to the stator. An interior of the steering control unit may be sealed. The electrical connector may include a commutation sensor board which senses a position of the rotor assembly and a motor connection which provides power to the stator. The commutation sensor board may include three sets of sensors with each set of sensors having redundant and offset sensors. A first sensor of each set of sensors may be positioned for advanced timing of the stator in a first direction and a second sensor of each set of sensors may be positioned for advanced timing of the stator in a second direction. The first direction and the second direction may be opposite directions and may respectively correspond to opposite steering directions based on rotation of the rotor assembly.

The electric actuator may include a brake. The brake may include an electromagnetic circuit and a brake pad. The electromagnetic circuit may include a magnet and a coil assembly. The magnet may generate a magnetic field which pulls the brake pad to an engaged position. The brake pad may be actuated to a released position when the coil assembly is energized by an electric current. The brake pad may engage a first friction surface and a second friction surface. The first friction surface and the second friction surface may be annular and concentric. The coil assembly may be an annular coil assembly which is rotatable within the housing for alignment purposes. The brake may pad may be actuated to a released position when the coil assembly is energized by an electric current between a first threshold current and a second threshold current. There may be a magnetic retainer received within a body and there may be an air gap between the magnetic retainer and the body to set brake strength and current thresholds.

The electric actuator may include an end gland at each end of the housing. Each end gland may include an annular seal within a floating seal housing and each floating seal housing may be sealed by an O-ring. The floating seal housing may include a radial lip with a sharp edge which functions as a scraper to scrape debris from the output shaft. The floating seal housing may include a heel which is concentric with the output shaft and the heel moves radially with the output shaft as the heel is side loaded.

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:
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 four outboard engines, namely, a port engine <NUM>, a port center engine 14a, a starboard center engine 14b, and a starboard engine <NUM>. However, the propulsion units may be any number or form of propulsion units in other examples. 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>, the port center engine 14a, the starboard center engine 14b, 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 PCT International Application Publication Number <CIT>. 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 display interface which displays navigational information and the second display interface is a display interface which displays onboard system information.

Each of the port engine <NUM>, the port center engine 14a, the starboard center engine 14b, and the starboard engine <NUM> is provided with an electric actuator which steers each engine. <FIG> and <FIG> show an electric actuator <NUM> of the port engine <NUM>. It will be understood by a person skilled in the art that the electric actuators for the port center engine 14a, the starboard center engine 14b, and the starboard engine <NUM> are substantially identical in structure and function to the electric actuator <NUM> for the port engine <NUM>. The electric actuators for the port center engine 14a, the starboard center engine 14b, and the starboard engine <NUM> are accordingly not described in detail herein. The electric actuator <NUM> includes a housing <NUM> as well as an output shaft <NUM> which is reciprocatingly received by the housing <NUM>. It will be understood by a person skilled in the art that, when the electric actuator <NUM> is mounted on the port engine <NUM>, axial movement of the output shaft <NUM> is inhibited relative to the marine vessel <NUM> while the housing <NUM> reciprocates linearly along the output shaft <NUM> and relative to the marine vessel <NUM>. This relative linear movement of the housing <NUM> imparts a steering force to a tiller <NUM> of the port engine <NUM> and thereby causes the port engine <NUM> to be steering in a conventional manner.

There is a coupling assembly <NUM> mounted on the housing <NUM>. The coupling assembly <NUM> is a ball joint assembly, in this example, and allows the housing <NUM> to be coupled to the tiller <NUM> of the port engine <NUM>. There is also a steering control unit <NUM> mounted on the housing <NUM>. The steering control unit <NUM> is accordingly integral with the electric actuator <NUM> as opposed to being elsewhere on the marine vessel <NUM> as is conventional. There are inputs, for example input <NUM>, which allow the steering control unit <NUM> to be in communication with the control station of the marine vessel <NUM>. Making the steering control unit <NUM> integral with the electric actuator <NUM> simplifies wiring, by eliminating the need for a number of wires/harnesses required in conventional systems, and reduces voltage drop between the steering control unit and the actuator.

<FIG> is an exploded view of the electric actuator <NUM> and shows a cover <NUM> of the steering control unit <NUM> which covers electrical components within an interior <NUM> of the steering control unit <NUM> which is integral with the actuator housing <NUM> in this example. A gasket <NUM> is employed between the cover <NUM> and the interior <NUM> of the steering control unit <NUM> to seal the steering control unit <NUM> and the actuator housing <NUM>. The electric actuator <NUM> further includes the following general components, namely, a stator <NUM>, a rotor assembly <NUM>, and a brake <NUM> which are disposed within an interior <NUM> of the housing <NUM> as best shown in <FIG>. The housing <NUM> is sealed at opposite ends by an end gland <NUM> and an end gland <NUM>. The electrical components of the steering control unit <NUM> are generally separated from the components disposed within the housing <NUM>. However, with reference to <FIG>, an electrical connector <NUM> extends through an opening <NUM> in the housing <NUM> to electrically connect the stator <NUM> to the steering control unit <NUM>. A gasket <NUM> is employed about the electrical connector <NUM>.

The stator <NUM> includes a plurality of segments, for example segments 78a and 78b, which are arranged in a generally annular formation and, in this example, are initially retained in the generally annular formation by a retaining ring <NUM>. The segments 78a and 78b are received by the housing <NUM> and the retaining ring <NUM> is removed. The segments may then be retained in the generally annular formation in the housing <NUM> by potting about the stator with epoxy (not shown). The epoxy is sealed within the interior <NUM> of the housing <NUM> by the gasket <NUM>. The segments may initially be arranged in the generally annular formation with play to allow the stator <NUM> to adjust to different sized housings. Each of the segments has a separate electrical winding coil, for example, coils 82a and 82b which are shown respectively for segments 78a and 78b. This arrangement allows for reduced end turns. The stator <NUM> also includes a lead frame <NUM>, best shown in <FIG>, with a plurality of openings, for example openings 86a and 86b, through which respective coils 82a and 82b are crimped and wired to the steering control unit <NUM> by the electrical connector <NUM>. The lead frame <NUM> of the stator <NUM> also includes a portion <NUM> with a plurality of openings 90a, 90b, and 90c, shown in <FIG>, which receive respective fasteners 92a, 92b, and 92c to allow for alignment and connection of the stator <NUM> with the electrical connector <NUM>. The electrical connector <NUM> receives dowel pins 93a and 93b which allow for alignment of the stator <NUM> with the electrical connector <NUM>. The electrical connector <NUM> also receives a plurality of fasteners 94a, 94b, 94c and 94d which hold the electrical connector in place. This arrangement separates electrical components within the interior <NUM> of the steering control unit <NUM> from the components within the interior <NUM> of the housing <NUM>.

The electrical connector <NUM> is shown in greater detail in <FIG> and <FIG>. The electrical connector <NUM> has a commutation sensor board with sensors which, in this example, is a Hall Effect sensor board <NUM> with an array of Hall Effect sensors. There are three sets of Hall Effect sensors 98a, 98b, and 98c, in this example, because the electric actuator <NUM> has a three-phase electric motor. Alternating current fluctuates according to a curve from a positive to negative state over time. Each component of the three-phase current follows the same pattern but are spaced apart timewise. Each current phase uses all three sets of Hall Effect sensors. Each set of Hall Effect sensors 98a, 98b, and 98c is coupled to a respective one of Hall Effect sensor connections 100a, 100b and 100c. The electric connector <NUM> also has a plurality of motor connections 102a, 102b and 102c and corresponding motor pins 103a, 103b, and 103c as well as a plurality of brake connections 104a and 104b and corresponding brake pins 105a and 105b.

Referring now to <FIG>, an inner side <NUM> of the cover <NUM> of the steering control unit <NUM> is provided with a first connection <NUM> and a second connection <NUM>. The first connection <NUM> connects to the Hall Effect sensor connections 100a, 100b and 100c as well as the brake pins 105a and 105b. The second connection <NUM> connects to the motor connections 102a, 102b and 102c. The steering control unit <NUM> is thereby connected to the motor which includes the stator <NUM>, the rotor assembly <NUM>, and the Hall Effect sensor board <NUM>. The rotor assembly <NUM> is best shown in <FIG> and includes a first rotor member <NUM> having a magnet sleeve <NUM> provided with a plurality of slots (not shown) which receive a plurality of magnets, for example magnets 111a and 111b, which are adhered to the magnet sleeve <NUM> in a generally annular formation. There are also retaining rings 113a and 113b that provide backup retention of the magnets 111a and 111b. The magnet sleeve <NUM> is mounted on a second rotor member <NUM> with an internally threaded bore <NUM>. There is an angular contact bearing <NUM> that allows the rotor assembly <NUM> to rotate. There is also a lock washer <NUM> and a lock nut <NUM>.

The Hall Effect sensor board <NUM> senses the relative position of the magnets 111a and 111b and is timed to the stator <NUM>. The Hall Effect sensor board <NUM> is advanced timed in each direction. The stator <NUM> is accordingly powered by motor connections 102a, 102b and 102c such that the magnetic field generated is slightly in front of the rotational position of the magnets 111a and 111b and the magnetic field pulls the magnets 111a and 111b to rotate the rotor assembly <NUM>. Each set of Hall Effect sensors 98a, 98b, and 98c on the Hall Effect sensor board <NUM>, as called out for a first set of the Hall Effect sensors in <FIG>, has a first Hall Effect sensor 99a and a second redundant and offset Hall Effect sensor 99b. A first one of the Hall Effect sensors in each set of Hall Effect sensors 98a, 98b, and 98c is positioned for advanced timing in a first rotational direction and a second one of the Hall Effect sensors in each set of Hall Effect sensors 98a, 98b, and 98c is positioned for advanced timing in a second rotational direction. The first rotational direction and the second rotational direction are opposite and respectively correspond to opposite steering directions of the marine vessel <NUM> based on the rotation of the rotor assembly <NUM>. The use of two different Hall Effect sensors in each set of Hall Effect sensors 98a, 98b, and 98c allows each set of Hall Effect sensors 98a, 98b, and 98c to "soak up" manufacturing tolerances while allowing advanced timing for the first rotational direction and the second rotational direction. Furthermore, if one of the Hall Effect sensors in any set of Hall Effect sensors 98a, 98b, and 98c fails then the other one of the Hall Effect sensors may function as a failsafe.

The rotor assembly <NUM>, as shown in <FIG>, receives the output shaft <NUM> which is shown in greater detail in <FIG> and, in this example, the output shaft <NUM> includes a roller screw assembly <NUM>, a first shaft portion <NUM>, and a second shaft portion <NUM>. The roller screw assembly <NUM> has a central screw <NUM> and a plurality of rollers, for example, rollers 130a and 130b, which are able to rotate about the central screw in a planetary fashion but do not translate axially relative to the central screw <NUM>. The rollers 130a and 130b are aligned by annular end plates 131a and 131b. The roller screw assembly <NUM> is received by the internally threaded bore <NUM> of the rotor assembly <NUM> which is shown in <FIG>. Rotation of the rotor assembly <NUM> causes the output shaft <NUM>, as shown in <FIG> and <FIG>, to reciprocate relative to the housing <NUM>. When the electric actuator <NUM> is mounted on the port engine <NUM>, axial movement of the output shaft <NUM> is inhibited relative to the marine vessel <NUM> while the housing <NUM> reciprocates linearly along the output shaft <NUM> and relative to the marine vessel <NUM>. This relative linear movement of the housing <NUM> imparts a steering force to the tiller <NUM> of the port engine <NUM> and thereby causes the port engine <NUM> to be steered in a conventional manner. The output shaft <NUM> may also be rotated manually in an emergency by loosening a lock nut (not shown) which prevents rotation of the output shaft in normal operation.

The brake <NUM> of the electric actuator <NUM> is shown in greater detail in <FIG>. The brake <NUM> has an annular body <NUM> which houses an electromagnetic circuit <NUM>. The electromagnetic circuit <NUM> includes a magnet retainer <NUM>, a magnet holder <NUM> which holds a plurality of magnets, for example, permanent magnets 148a and 148b, and a brake coil assembly <NUM>. The magnet retainer <NUM> retains the magnets and magnetic field. The magnet retainer <NUM>, the magnet holder <NUM> and the permanent magnets 148a and 148b are shown in greater detail in <FIG>. In other examples, there may be an annular magnetic ring. Referring back to <FIG>, the brake <NUM> further includes a hub <NUM> which is pressfitted to a bearing <NUM>. The bearing <NUM> is loose-fitted to the annular body <NUM>. The bearing <NUM> holds the annular body <NUM> concentric to the hub <NUM>. This allows the brake assembly <NUM> to align the rotor member <NUM> to the housing <NUM>. The brake assembly <NUM> may be subassembled and tested as a module in production before integrating with the rotor member <NUM> and the housing <NUM>. A retaining ring <NUM> acts as a backup retention. The bearing <NUM> allows the hub <NUM> to rotate with the rotor assembly <NUM>. A plurality of flexures, for example arcuate flexures 158a, 158b, and 158c, are radially retained by and rotate with the hub <NUM>. There is an annular brake pad <NUM> disposed between the electromagnet circuit <NUM> and the hub <NUM>. The brake pad <NUM> is coupled to the hub <NUM> by the flexures 158a, 158b and 158c. The brake pad <NUM> therefore also rotates with the hub <NUM>. The hub <NUM>, the brake pad <NUM>, and the flexures 158a, 158b, and 158c are shown in greater detail in <FIG>.

<FIG> show the coil assembly <NUM> disposed in an annular space or annulus <NUM> between the body <NUM> and the magnet retainer <NUM>. The annulus <NUM> is larger in cross section than the coil assembly <NUM>. This allows the coil assembly <NUM> to move within the annulus <NUM> so that a connector <NUM> of the coil assembly <NUM> may be aligned with the electrical connector <NUM> to connect with the brake connections 104a and 104b, shown in <FIG>, during assembly of the electric actuator <NUM>. The movement of the coil assembly <NUM> within the annulus <NUM> may be rotary and/or radial movement. There is also an air gap <NUM> between the body <NUM> and the magnet retainer <NUM>.

The permanent magnets 148a and 148b generate magnetic fields which pull the brake pad <NUM> to an engaged position against a first friction surface <NUM> and a second friction surface <NUM>. In this example, the first friction surface <NUM> is a shoulder of the body <NUM> and the second friction surface <NUM> is an annular surface of the magnet retainer <NUM>. The brake torque, or friction between the brake pad <NUM> and the first friction surface <NUM> and the second friction surface <NUM>, is sufficient to prevent rotation of the hub <NUM> which is torsionally coupled to the rotor assembly <NUM>. The brake <NUM> is accordingly normally in an engaged position, as shown in <FIG>, until the coil assembly <NUM> is energized to actuate the brake pad <NUM> to a released position.

<FIG> show the brake <NUM> in the released position, when the coil assembly <NUM> is energized, and the coil assembly <NUM> generates a magnetic field which is sufficient to redirect the magnetic field generated by the permanent magnets 148a and 148b. This allows the flexures 158a, 158b, and 158c to bias the brake pad <NUM> away from the first friction surface <NUM> and the second friction surface <NUM> to the released position. There is a brake pad stop <NUM> which, in this example, is an annular lip of the hub <NUM> that restricts movement of the brake pad <NUM> away from the first friction surface <NUM> and the second friction surface <NUM> when the brake <NUM> is in the released position so the hub <NUM> can rotate freely. The brake pad stop <NUM> sets a maximum distance of the brake pad <NUM> from the first friction surface <NUM> and the second friction surface <NUM> when the brake <NUM> is in the released position. The maximum distance is set to allow the brake <NUM> to re-engage.

The coil assembly <NUM> is energized by receiving an electric current. However, in this example, the brake <NUM> is only actuated to the released position if a current supplied to the coil assembly <NUM> is between a first threshold current and a second threshold current. The first threshold current may be, for example, about <NUM> amps and the second threshold current may be about <NUM> amps, or the first threshold current may be about <NUM> amps and the second threshold current may be about <NUM> amps. This ensures consistent release of the brake <NUM> within the design limits of the current draw.

The air gap <NUM> between the body <NUM> and the magnet retainer <NUM> sets brake strength and current thresholds when the brake is in the released position. This minimizes the electric current required to move the brake to the released position while maintaining a desired minimum brake torque. The brake torque may be lower than an output torque of the motor of the electric actuator <NUM>. This allows the motor of the electric actuator <NUM> to override the brake <NUM> in the event of brake failure. The brake torque may be greater than a back driving torque. This allows the brake <NUM> to restrict movement of the output shaft <NUM> in the event of motor failure. This also allows the brake to restrict movement of an engine mounted on a marine vessel which is important during trailering of the marine vessel.

The brake <NUM> may also be provided with an H-bridge in the steering control unit for reversing the polarity of the voltage supplied to the coil assembly <NUM>. This increases the speed at which the brake <NUM> is actuated from the released position to the engaged position. This also increases the brake torque. There is an O-ring <NUM> which mates against the rotor assembly to provide rotational dampening. There is also a support ledge <NUM> on the body <NUM> of the brake <NUM> which minimizes thermal expansion of the brake <NUM>.

The end gland <NUM> is shown in greater detail in <FIG>. The end gland <NUM> includes an annular body <NUM>. The annular body <NUM> receives a floating seal housing <NUM> and a bushing <NUM>. The bushing <NUM> is disposed between an inner seal <NUM> and an outer seal <NUM>. The inner seal <NUM> is provided with an inner seal energizer <NUM> and the outer seal <NUM> is provided with an outer seal energizer <NUM>. The outer seal <NUM> and the outer seal energizer <NUM> are received by a groove <NUM> in the seal housing <NUM>. There is a seal, in this example, an O-ring <NUM> disposed between the annular body <NUM> and the seal housing <NUM>. The O-ring <NUM> sits on a concave wall <NUM> of the seal housing <NUM>. This centers the O-ring <NUM> relative to the floating seal housing <NUM>. The seal housing <NUM> is provided with a first radial lip <NUM> and a second radial lip <NUM>. The first radial lip <NUM> is resilient and facilitates the installation of the seal housing <NUM> in the end gland <NUM>. The second radial lip <NUM> has a sharp edge which functions as a scraper for scraping debris from the output shaft <NUM> and also provides stability and output shaft tracking. The sealing housing <NUM> is also provided with a chamfer <NUM> which facilitates the installation of the O-ring <NUM>. A back wall <NUM> of the seal housing <NUM> is flush with the annular body <NUM> for stability. A back heel <NUM> of the seal housing <NUM> is concentric with the output shaft <NUM> and is formed of a rigid low wear material. The O-ring <NUM> allows the seal housing <NUM> to move radially when subjected to loads against the output shaft <NUM>. This reduces wear of the second radial lip <NUM> and back heel <NUM> of the seal housing <NUM>.

<FIG> shows the electric actuator <NUM> coupled to the tiller arm <NUM>. There is a magnetic position target <NUM> mounted on the coupling assembly <NUM> and absolute position sensors 212a and 212b mounted on the electric actuator <NUM> within the steering control unit <NUM>. The absolute position sensors 212a and 212b sense a steering position based on a position of the magnetic position target <NUM>. The steering position may be referred to as the steering angle. The steering control unit <NUM> and the absolute position sensors 212a and 212b move axially relative to the output shaft <NUM> when steering motion is imparted to the tiller arm <NUM>. The coupling assembly <NUM> and magnetic position target <NUM> rotate when steering motion is imparted to the tiller arm <NUM>. The coupling assembly <NUM> has a curved surface <NUM> which drives a curved surface <NUM> of the magnetic position target <NUM>. The curved surface <NUM> and the curved surface <NUM> allow a rotational degree of freedom in the direction of the output shaft <NUM> axis to handle potential rotational misalignment due to manufacturing tolerances and external loading.

Claim 1:
An electric actuator (<NUM>) for imparting steering movement to a propulsion unit of a marine vessel (<NUM>), the electric actuator (<NUM>) comprising:
a housing (<NUM>);
an output shaft (<NUM>) reciprocatingly received by the housing (<NUM>);
a motor disposed within the housing (<NUM>), the motor including a rotor assembly (<NUM>) and a stator (<NUM>), rotation of the rotor assembly (<NUM>) causing the output shaft (<NUM>) to translate axially relative to the rotor assembly (<NUM>) and causing the output shaft (<NUM>) to reciprocate relative to the housing (<NUM>);
a coupling assembly (<NUM>) mounted to the housing (<NUM>), the coupling assembly (<NUM>) coupling the electric actuator (<NUM>) to the propulsion unit of the marine vessel (<NUM>);
a steering control unit (<NUM>) mounted to the housing (<NUM>), the steering control unit (<NUM>) driving the motor in use to cause the rotor assembly (<NUM>) to rotate and cause the output shaft (<NUM>) to reciprocate relative to the housing (<NUM>);
a magnetic position target (<NUM>) mounted on the coupling assembly (<NUM>); and
a position sensor (212a, 212b) mounted on the actuator (<NUM>), the position sensor (212a, 212b) sensing, in use, a position of the electric actuator (<NUM>) based on a position of the magnetic position target (<NUM>);
wherein the coupling assembly (<NUM>) has a curved surface (<NUM>) and the magnetic position target (<NUM>) has a curved surface (<NUM>) which is driven by the curved surface (<NUM>) of the coupling assembly (<NUM>) when the coupling assembly (<NUM>) rotates.