Electromechanically actuated steering vane for marine vessel

A steering assist system for a marine vessel includes a steering vane extending into water in the vicinity of a steering device for the vessel and that is pivotable about an at least generally vertical axis by an electromechanical drive unit. The drive unit is energized by an actuator assembly in response to the imposition of external forces on the steering system. The actuator assembly includes an actuator that is movable in response to the imposition of external forces in the steering system and a switch that is selectively engageable by the actuator arm to energize the drive unit to drive the steering vane to pivot. The actuator assembly may comprise a biasing assembly that resists movement of the actuator creating a force threshold that must be overcome to engage the switch. The biasing assembly may take the form of one or more springs, preferably having a settable preset.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to marine steering systems and, more particularly, relates to a method and apparatus for controlling operation of a steering vane or tab that counteracts externally imposed steering torques imposed on the outboard engine or other steering device of a vessel.

2. Discussion of the Related Art

Marine steering systems sometimes employ a moveable steering vane or tab that moves so as to counteract external forces imposed on the steering device of the vessel, reducing or negating the need for the operator to impose steering forces to counteract these forces. These devices most typically are used in conjunction with outboard engines, in which case the engine itself is the steering device and is steered by pivoting about a vertical axis. In this case, the steering vane typically is disposed within the slip stream of the propeller of the outboard engine to channel the water in the strip stream in a manner that opposes external forces imposed on the engine during operation. Publications describing these systems often refer to the actuated vane or tab as a trim tab. However, such a reference is not technically accurate when referring to tabs that pivot about a vertical axis because trim tabs most typically pivot about a horizontal axis to adjust the fore-to-aft orientation or “trim” of a boat. Accordingly, this document utilizes the term “steering vane” or “steering tab” to refer to a structure that pivots about an at least generally vertical axis or otherwise moves at least generally from side to side to counteract externally forces imposed externally on a rudder, outboard engine, or other steered device during operation.

Most steering vanes employed to date are operated mechanically and passively, such as by using the combination of a push pull cable and a passive hydraulic cylinder. One such vane is disclosed in U.S. Pat. No. 4,482,331, the subject matter of which is hereby incorporated by reference. Another example is disclosed in U.S. Pat. No. 4,349,341 (the '341 patent) to Morgan et al., the subject matter of which is also incorporated by reference. The '341 patent discloses the use of a control lever pivotally mounted to the steering control element of the boat. Movement of the lever in one direction or the other by the steering control element generates tensile forces in an appropriate control cable to pivot a steering vane.

One shortfall of the system disclosed in the '341 patent is the inclusion of a lost motion linkage between the steering arm and the control rod of the steering mechanism of a boat. The necessity of a lost motion linkage creates a lag in steering response, which can affect the handling of a boat. Another disadvantage of this type of system is that the lost motion linkage potentially allows the propulsion unit to be steered by external forces such as waves or current, which will cause course deviations. Passive systems also necessarily have limited effectiveness at counteracting forces imposed on the steering device.

Computer based actuator systems have been developed to in an attempt to address at least some the disadvantages of passive mechanical based systems. For instance, U.S. Pat. No. 4,787,867 (the '867 patent) to Takeuchi et al., discloses a steering vane or tab that is supported on the propulsion unit of a marine engine and that can be pivoted in a direction opposite to the operator's steering direction so as to create a hydrodynamic force to assist in the steering of a vessel immediately upon the detection of a given steering import force. The steering vane position, however, is determined by a computer system using a selected one of plurality of pre-mapped positions. Such a system is at the mercy of the accuracy of the pre-mapped positions and on the operator's ability to select the appropriate map. Furthermore, a computerized system of this type must be customized to particular boat characteristics such as engine and propeller characteristics, trim settings, and overall boat designs. Such a system therefore is relatively expensive and difficult to implement. It also cannot be used, without modification, on a variety of different vessels or retrofitted onto an existing vessel.

It thus would be desirable, in a marine steering system, to automatically actuate a powered steering vane to actively reduce or counteract the external forces imposed on the steering system of a boat or other marine vessel during operation.

It would also be desirable to provide a marine steering system which lacks a substantial lost motion connection in the actuating system for the steering vane or tab thereof and which, therefore, does not induce a lag to an operator-initiated steering command response.

It is yet further desirable to provide a steering vane actuator assembly that is versatile so as to be capable of being attached to or retrofitted on a variety of boats without reconfiguration.

SUMMARY OF THE INVENTION

In accordance with a first aspect of the invention, a steering system for a marine vessel includes a steering vane that extends into the water in the vicinity of a steering device for the vessel. The steering vane preferably is pivotable about an at least generally vertical axis and is driven by an electromechanical drive unit. An electromechanical drive unit is energized by an actuator assembly in response to the imposition of external forces on the steering system. The actuator assembly includes an actuator that is movable in response to the imposition of external forces in the steering system and a switch that is selectively engageable by the actuator to energize the drive unit to drive the steering vane to pivot or otherwise move.

The actuator assembly preferably comprises a biasing assembly that resists movement of the actuator to create a force threshold that must be overcome to engage the switch. The biasing assembly may take the form of one or more springs, preferably having a settable preset.

The steering vane and its actuator assembly may be used with, along other things, either mechanically or hydraulically steered vessels. If used with a mechanically steered vessel, the actuator assembly preferably is actuated mechanically and may be employed within or at an end of a steering linkage connecting a push-pull cable or the like to a steering arm. For instance, the actuator could be a pivoting arm driven by the steering system.

If used with a hydraulically steered vessel, the actuator assembly preferably is actuated hydraulically and is fluidically coupled to a steering cylinder for the vessel. For instance, the actuator could be a lever arm responsive to movement of a hydraulically driven piston.

The invention additional relates to a method of automatically actuating an electromechanically driven steering vane of a marine vessel to counteract external forces imposed on the vessel's steering system during operation.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Electromechanically actuated steering vanes constructed in accordance with the present invention may be used on a variety of marine vessels powered by a variety of propulsion systems and steered by a variety of steering devices. For instance, they are usable with boats and other vessels having either an inboard engine or an outboard engine. They could also be used with vessels whose rudder or other steering device is either integrated with the engine, as is typically the cause with an outboard engine, or is separate from the engine. Hence, while embodiments of the invention will now be described primarily in conjunction with relatively small boasts powered and steered by outboard engines having integrated rudders, the invention is in no way limited to those embodiments.

Referring toFIG. 1, a boat20incorporating an electromechanically actuated steering vane constructed in accordance with a first preferred embodiment of the present invention is illustrated at least someone schematically. The boat20ofFIG. 1includes a hull22having a bow24, a stern26, and a transom28formed on the stern26of the hull22. The boat20also includes a helm assembly30and an outboard engine32mounted on the transom28. The engine32is pivotable about a generally vertical axis34under the application of steering forces transmitted from the helm assembly30via a steering arm36. The helm assembly30includes a steering wheel40and a flexible push-pull cable42that responds to steering wheel rotation. The push-pull cable42extends to the stern26of the boat20and is operatively connected to the steering arm36by a linkage assembly44. Referring toFIGS. 2 and 3, the linkage assembly44includes a first link46that may be formed from an end of the cable42and a second link48that is operatively connected to the first link46at one end thereof and to the steering arm36(via an adapter plate80of an actuator assembly70) at the other end thereof. The steering arm36is able to respond to the linear movement of the push-pull cable42to pivot the engine32about the axis34in the commanded direction to steer the boat20.

Referring particularly toFIGS. 2 and 3, a steering vane or tab60is mounted on the rear of the engine32and extends downwardly into the slipstream created by the engine's propeller50. The steering vane60is connected to an electromechanical drive unit62by a shaft64so as to be pivotal about an at least generally vertical axis. The drive unit62may be any electrically powered motor or other electromechanical drive capable of driving the steering vane60to pivot about shaft64. It preferably contains a permanent magnet DC motor. The drive unit62is electrically connected to an actuator assembly70by a wire or cable66. The actuator assembly70is, in turn, connected to a cable72leading to a main fuse box74of the boat20(FIG. 1). The actuator assembly70is responsive to the application of external forces to engine32to activate the drive unit62to drive the steering vane60to pivot about its vertical axis to counteract the external forces.

Referring now toFIGS. 4-6, the actuator assembly70includes an adapter plate80, an actuator arm82, and a switch assembly84. The actuator arm82is connected to the steering linkage assembly44and is mounted for limited movement with respect to the adapter plate80. The switch assembly84is responsive to that limited actuator arm movement to actuate the drive unit62.

The adapter plate80comprises rigid L-shaped plate that is bolted or otherwise attached to the steering arm36at its rear end and that has a slot86formed in its front end. The actuator arm82is centered in the slot86in the adapter plate80with a gap “G” formed on either side of the actuator arm82. The width of each gap G represents the maximum distance the actuator arm82can move relative to the adapter plate80. An actuator pin88extends vertically upwardly from a front end of the actuator arm82. The second end of second link48of the steering linkage44is pivotally connected to the actuator arm82near the rear end thereof via a bolt and bushing assembly89. The link48is stationary in a no-steer situation.

Still referring toFIGS. 4-6, the switch assembly84is maintained in a switch housing90that is mounted on the front end of the adapter plate80by bolts92. The switch housing90also is pivotally attached to the actuator arm82by a bolt and bushing assembly94extending through the actuator arm82between the bolt and bushing assembly89and the actuator pin88.

As can be seen inFIG. 5, the switch housing90houses two switches100aand100blocated on opposite sides of the actuator pin88. These switches100aand100bhave plungers that are in contact with the actuator pin88. Depression of one of the plungers will activate the corresponding switch100aor100bto activate the drive unit62to pivot the steering vane60in one direction or the other.

The switch housing90also contains a biasing assembly that resists pivoting movement of the actuator arm82relative to the adapter plate80, hence setting a resistance or force threshold that must be overcome to activate the drive unit62. The threshold preferably is between 5 and 10 lbs. In this embodiment, the biasing assembly takes the form of a spring assembly110mounted in a cross bore112in the switch housing90as best seen inFIG. 5. Spring assembly110includes two springs114aand114b, two inboard spring guides116a, and116b, and two outboard spring retainers118aand118b. Each spring114aor114babuts against an associated side of the actuator pin88via the associated spring guide116aor116b. The positions of the outboard spring retainers118aand118bwithin the bore112are adjustable using set screws120aand120b(FIG. 4), hence permitting the pretension on the springs114aand114bto be adjusted to adjust the reaction force threshold that must be applied on the actuator assembly70by the engine32to activate the drive unit62.

The switches100aand100bin this system preferably are wired in a way that, when they are not activated, the two wires leading from the switches are shorted together. This shorting generates an electromagnetic pulse in the motor of the drive unit62that acts as a brake to stop the motor immediately upon switch deactivation. This feature stops the steering vane60from continued movement after the drive unit62has been deenergized.

In use, the steering link48is stationary in a no-steer situation. If a reaction force, applied to the adapter plate80by the engine32and the steering arm36, is of sufficient magnitude to overcome the spring pressure of one the springs114aand114b, the actuator arm82will pivot relative to the adapter plate80and the switch housing90through a stroke determined by the width of the associated gap “G”. This pivoting will cause the actuator pin88to activate one of the switches100aor100b. The switch100aor100bwill energize the motor in the drive unit62, which will rotate the steering vane60in a direction to counter the force applied to the adapter plate80by the engine32. When the force applied to the adapter plate80becomes less than the spring-applied force, the actuator arm82will move back to its centered neutral position under the spring force. The switch100aor100bwill be deactivated, and the motor in the control until62will stop the movement of the steering vane60. At this time, the outboard engine32can be steered without further movement of the steering vane60if the external operating parameters remain beneath the threshold determined by the spring114aor114b. If the external operating parameters change and the load imposed on the adapter plate80becomes high enough to overcome the spring force keeping the actuator arm82centered within the slot86, the position of the steering vane60will again be adjusted to compensate for the change in the external operating parameters.

Referring now toFIGS. 7-11, a second embodiment of the invention is illustrated that differs from the first embodiment primarily in that the actuator assembly170is mounted within the steering linkage148rather than between the steering linkage and the engine steering arm36. The engine32, helm30, etc. are thus identical to the first embodiment. The actuator assembly170of this embodiment includes a stationary bracket180and a movable actuator arm182. Stationary bracket180is attached to the steering cable or link146by a bolt184. The actuator moveable arm182is free to pivot about bolt184. A link148is pivotally attached to the actuator arm182at one end thereof and to the steering arm of the engine at the other end thereof.

The actuator arm182is held in a center position with respect to the bracket180by a spring assembly which, like the spring assembly of the first embodiment, sets an initial or threshold force that the engine will have to apply to the actuator arm182before the steering vane60will be moved. As best seen inFIG. 11, the spring assembly includes a single spring214housed in a bore216. One end of spring214holds a spring guide218against one end of the bore216. A sleeve220is held in place on the other end of the bore216by a set screw222that sets the position of the sleeve220to determine the preset of the biasing force imposed by the spring214. The other end of the spring214forces a spring guide224against the end of the sleeve220.

When the actuator arm182is moved in one direction or the other by forces imposed thereon by the engine32, the associated spring guide218or224will compress the spring214to generate a force tending to move the actuator arm182back to its center position.

Centering screws230and232also are housed in the bracket180. The screws230and232center the actuator arm182within the bracket180and create an equal gap “G” between each side of the actuator arm182and the bracket180. This gap defines the maximum movement that arm182can move with respect to the bracket180. Centering screws230and232are adjustable to come into contact with the spring guides218and224.

Referring especially toFIGS. 8 and 9, a pair of actuator pins240and242is mounted on the bracket180, and a switch244is mounted on the actuator arm182between the pins240and242. Movement of the actuator arm182in one direction or another will cause one of two plungers246and248on the switch244to engage an associated actuator pin240or242to activate the switch244and energize the drive unit62to drive the steering vane to move in one direction or the other.

The operation of the system is as follows. Under a no-steer condition, the steering cable146is stationary. When the engine32produces a force in one direction or the other, the cable146and link148will move actuator arm182in that direction. Movement of the actuator arm182causes one of the actuator pins240or242to be contacted with the plunger244or248of the switch244, activating the switch244and actuating the drive unit62to pivot the steering vane60(FIGS. 1 and 2) a direction to counteract the force produced by the engine32.

Turning now toFIGS. 12 and 13, another embodiment of the invention is illustrated that is applicable to a hydraulically steered system. The engine32, vane60, and drive unit62of this embodiment are identical to those of the first two embodiments. In this embodiment, the engine32is pivoted by a piston300that is movable axially within a cylinder302in either direction. Pressurized fluid flows to and from chambers304and306on opposed sides of the piston300via hydraulic lines308and310attached to the helm assembly (not shown). A link312is attached to opposed axial ends of the piston300, extends through opposed ends of the cylinder302, and is attached to the engine steering assembly370.

Still referring toFIG. 13, the actuator assembly includes a self contained unit370coupled to the steering cylinder302by hydraulic lines372and374teed to the lines308and310, respectively. The unit370includes a housing380having a bore382formed therein that is sealed at its opposed ends by end caps384,386. A piston380is disposed in the bore382between first and second chambers371and373, each of which opens into an associated one of the lines372,374. A rod390extends through the piston388and the end caps384and386, where it engages opposed lever arms392and394disposed adjacent opposite sides of housing380. Each lever arm392,394rotates about an associated pin396,398located behind piston390. The lever arms392and394are biased into a neutral position by a spring400mounted in a bore402formed into the housing380behind the pivot pins396,398. Each end of the spring400rests against a spring guide404,406. Each spring guide404,406rests against an adjustment screw408,410threaded through the associated lever arm392,394. The pretension of the spring400, and hence the force required to actuate the steering vane60, can be adjusted by rotating one or both of the threaded adjustment screws408and410. Switches412and414are mounted on the housing380behind the adjustment screws408and410. Each switch contains a plunger416,418that is engaged upon pivoting movement of the associated lever arm392,394to activate the associated switch and energize the drive unit62to pivot the steering vane60in the appropriate direction.

In operation, engine movement in response to external forces generates a force that is transmitted to the steering cylinder302by way of steering arm36. That force causes the piston300to move in one direction or the other relative to the cylinder302, causing hydraulic fluid to flow out of one of the chambers304or306and into the other306or304. This fluid flow will create a pressure differential between the chambers371and373on the opposed sides of the actuator assembly piston388, forcing the rod390towards one of the lever arms392or394. When the pivoting forces imposed on the relevant lever arm392or394by this pressure differential are high enough to overcome the biasing force of the spring400, the piston388and the rod390will move in one direction or the other, causing the associated lever arm392or394to depress the associated switch plunger416or418. This plunger depression will activate the associated switch412or414, energizing the drive unit62to move the steering vane60to counter the force created by engine32.

Many changes and modifications could be made to the invention without departing from the spirit thereof. For instance, the system need not be used with a traditional tiller-based steering system. For instance, the system ofFIGS. 12 and 13can be used with a tiller-based steering system having a hydraulic lock as disclosed and claimed in U.S. Pat. No. 7,325,507, the subject matter of which is hereby incorporated by reference. When the system is used with the hydraulic lock, a second set of switches is needed. These switches are activated by movement of the tiller handle, and they override switches412and414of the actuator assembly370.