U.S. patent application number 11/075129 was filed with the patent office on 2005-09-15 for steering assist system for boat.
Invention is credited to Mizutani, Makoto.
Application Number | 20050199169 11/075129 |
Document ID | / |
Family ID | 34918269 |
Filed Date | 2005-09-15 |
United States Patent
Application |
20050199169 |
Kind Code |
A1 |
Mizutani, Makoto |
September 15, 2005 |
Steering assist system for boat
Abstract
A steering system can be provided for a boat. Such a boat can
include a rudder device using an electric actuator to allow a
rudder to rotate about a rotational shaft, and a steering wheel 7
for operation by an operator. The steering system can include a
steering wheel displacement sensor for detecting the displacement
of the steering wheel and a controller for calculating the
rotational displacement of the rudder device corresponding to the
detected steering wheel displacement and sending an actuation
signal to the electric actuator based on the calculated rotational
displacement, in which the controller receives a signal indicating
an engine speed for producing a propulsive force in the boat, and
changes, in accordance with the engine speed, the ratio of the
rotational displacement of the rudder relative to the steering
wheel displacement.
Inventors: |
Mizutani, Makoto;
(Shizuoka-ken, JP) |
Correspondence
Address: |
KNOBBE MARTENS OLSON & BEAR LLP
2040 MAIN STREET
FOURTEENTH FLOOR
IRVINE
CA
92614
US
|
Family ID: |
34918269 |
Appl. No.: |
11/075129 |
Filed: |
March 8, 2005 |
Current U.S.
Class: |
114/144RE ;
440/62 |
Current CPC
Class: |
B63H 21/265
20130101 |
Class at
Publication: |
114/144.0RE ;
440/062 |
International
Class: |
B63H 005/125; B63H
020/08; B63H 025/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 9, 2004 |
JP |
2004-065701 |
Claims
What is claimed is:
1. A steering system for a boat comprising an engine configured to
provide propulsion for the hull and a rudder device including an
electric actuator to rotate a rudder about a rotational shaft, a
steering wheel configured to be operated by an operator of the
boat, a steering wheel displacement sensor configured to detect the
displacement of the steering wheel, and a controller configured to
calculate the rotational displacement of the rudder device
corresponding to the detected steering wheel displacement and to
send an actuation signal to the electric actuator based on the
calculated rotational displacement, the controller being further
configured to receive a signal indicating a speed of the engine,
and to change, in accordance with the engine speed, a ratio of the
rotational displacement of the rudder relative to the steering
wheel displacement.
2. The steering system according to claim 1, wherein the ratio is
varied in stages in accordance with the preset ranges of the speed
of the engine.
3. The steering system according to claim 1, wherein the engine is
mounted in an outboard motor.
4. The steering system according to claim 1 additionally comprising
a load sensor configured to detect loads applied to the rudder and
a reaction torque motor configured to apply a torque to the
steering wheel, the controller being configured to apply a torque
to the steering wheel based on loads detected by the load
sensor.
5. The steering system according to claim 1, wherein the ratio is
changed proportional to changes in the speed of the engine.
6. The steering system according to claim 1, wherein a value of the
ratio is changed incrementally with incremental changes in the
speed of the engine.
7. A steering system for a boat comprising an engine configured to
provide propulsion for the hull and a rudder device including an
electric actuator to rotate a rudder about a rotational shaft, a
steering wheel configured to be operated by an operator of the
boat, a steering wheel displacement sensor configured to detect the
displacement of the steering wheel, and means for changing a ratio
of the rotational displacement of the rudder relative to the
steering wheel displacement in accordance with the engine
speed.
8. The steering system according to claim 7 additionally comprising
means for detecting loads applied to the rudder and means for
applying torque to the steering wheel based on the loads detected
by the means for detecting loads.
Description
PRIORITY INFORMATION
[0001] This application is based on and claims priority under 35
U.S.C. .sctn.119 to Japanese Patent Application No. 2004-065701,
filed on Mar. 9, 2004, the entire contents of which is hereby
expressly incorporated by reference herein.
BACKGROUND OF THE INVENTIONS
[0002] 1. Field of the Inventions
[0003] The present inventions relate to an electric steering system
for a small boat, and in particular, to steering systems that
provide variable steering response.
[0004] 2. Description of the Related Art
[0005] Japanese Patent Publication JP-B-Hei 6-33077 discloses a
steering system for a small boat having a boat speed sensor, which
is designed to change the ratio of the displacement of a rudder
device relative to steering wheel angle depending on the boat
speed. This system generates proportionally larger rudder
displacements at low boat speeds by raising the steering angle to
the steering wheel turning angle ratio. Similarly, the system
generates proportionally smaller rudder displacements at higher
boat speeds by decreasing the steering angle to steering wheel
angle ratio, thereby providing speed dependant steering
response.
[0006] However, unlike ground vehicles, a boat speed (velocity
relative to the water in which the boat operates) is influenced by
tide flows, waves and/or winds. Thus, it is difficult to realize a
highly accurate control if boat operations are controlled based on
the boat speed. In addition, boat speed sensors are expensive, can
become clogged and thus inoperable, and installation thereof on a
boat makes the wiring layout and control mechanism more
complicated.
SUMMARY OF THE INVENTION
[0007] An aspect of at least one of the embodiments disclosed
herein includes the realization that an electric steering system
for a small boat can constantly provide good steering performance
corresponding to the boat running speed without a boat speed
sensor, thereby reducing the cost and improving the reliability of
the system. For example, such a steering system can change, in
accordance with the boat running speed, the ratio of the rudder
steering angle or displacement relative to the steering wheel
turning angle.
[0008] Thus, in accordance with an embodiment, a steering system is
provided for a boat comprising an engine configured to provide
propulsion for the hull and a rudder device including an electric
actuator to rotate a rudder about a rotational shaft, a steering
wheel configured to be operated by an operator of the boat. The
steering system includes a steering wheel displacement sensor
configured to detect the displacement of the steering wheel, and a
controller configured to calculate the rotational displacement of
the rudder device corresponding to the detected steering wheel
displacement and to send an actuation signal to the electric
actuator based on the calculated rotational displacement. The
controller is also configured to receive a signal indicating a
speed of the engine, and to change, in accordance with the engine
speed, a ratio of the rotational displacement of the rudder
relative to the steering wheel displacement.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The above-mentioned and other features of the inventions
disclosed herein are described below with reference to the drawings
of the preferred embodiments. The illustrated embodiments are
intended to illustrate, but not to limit the inventions. The
drawings contain the following Figures:
[0010] FIG. 1 is a schematic top plan view of a watercraft having a
steering system in accordance with an embodiment.
[0011] FIG. 2 is a block diagram of an electric steering system
according to the embodiment of the present invention.
[0012] FIGS. 3(A) and 3(B) are explanatory graphs, showing examples
of preset steering angle relative to steering wheel turning
angle.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0013] FIG. 1 is a schematic top plan view of a small boat
including an outboard motor with which the present embodiments are
applicable. The embodiments disclosed herein are described in the
context of a marine propulsion system of a small boat because these
embodiments have particular utility in this context. However, the
embodiments and inventions herein can also be applied to other
marine vessels, such as personal watercraft and small jet boats, as
well as other vehicles.
[0014] An outboard motor 3 is mounted to a transom plate 2 of a
hull 1 through clamp brackets 4. The outboard motor 3 is rotatable
about a swivel shaft 6. A steering bracket 5 is fixed to an upper
end of the swivel shaft 6. A rudder device 15 is connected to an
end 5a of the steering bracket 5.
[0015] The rudder device 15 includes, for example, a DD (Direct
Drive) type electric motor including a motor body (not shown). The
motor body slides along a threaded shaft (not shown) that can be
oriented generally parallel to the transom plate 2. The steering
bracket 5 is connected to the motor body to allow the outboard
motor 3 to rotate about the swivel shaft 6 in conjunction with the
sliding motion of the motor body.
[0016] A steering wheel 7 is provided in the vicinity of an
operator's seat on the hull 1. A steering wheel control section 13
can be provided at the root or base of a steering column shaft 8 of
the steering wheel 7, however other locations can also be utilized.
A steering wheel displacement (e.g. operation angle) sensor 9 and a
reaction torque motor 11 are provided inside the steering wheel
control section 13. The steering wheel control section 13 can be
connected, via a signal cable 10, to a controller 12, which in turn
is connected to the rudder device 15.
[0017] The controller 12 can be configured to calculate a steering
angle based on a detection signal from the steering wheel operation
angle sensor 9. The calculated steering angle is sent to the rudder
device 15 as an electric command signal, to drive the rudder device
15 so as to allow the outboard motor 3 to rotate about the swivel
shaft 6 for boat steering.
[0018] A load sensor 16 (See FIG. 2) that can be provided in the
outboard motor 3 or the rudder device 15 itself, can be configured
to detect an external force F (See FIG. 2) exerted on the outboard
motor 3. The controller 12 can be configured to calculate a target
value of reaction torque to be exerted to the steering wheel 7 by
the reaction torque motor 11 based on the external force. The
controller 12 then drives the reaction torque motor 11 in
accordance with the target torque, thereby applying a reaction
force corresponding to the external force to the steering wheel
7.
[0019] FIG. 2 is a block diagram of a steering system according to
an embodiment of the present invention.
[0020] When an operator rotates the steering wheel 7, the rotated
angle is detected by the steering wheel operation angle sensor 9.
Based on the detection signal, a steering angle calculation circuit
21 of the controller (ECU) 12 calculates a steering angle as will
be described later, and converts it into an electrical current
value to drive the electric motor (not shown) of the rudder device
15. This allows the outboard motor 3 to swing about the swivel
shaft 6 (See FIG. 1), to change the direction of the boat.
[0021] While the outboard motor 3 rotates, an external resistance
(external force) F as a reaction force is applied to the outboard
motor 3. The load sensor 16 detects the external force F, and data
of which is sent to a reaction torque calculating circuit 17. Based
on the data for the detected external force, a target torque is
calculated and the reaction torque motor 11 is so driven as to
apply such target torque. This causes a reaction force
corresponding to the steering operation to be applied to the
steering wheel 7 so that the operator can steer the steering wheel
while feeling the reaction force in response to the steering wheel
operation.
[0022] The outboard motor 3 functions as a rudder when it rotates
about the swivel shaft. In this case, the steering angle
calculating circuit 21 calculates the displacement of the rudder or
the steering angle (e.g. rudder angle) .beta. based on the steering
wheel turning angle a detected by the steering wheel operation
angle sensor 9. At this time, the steering angle calculating
circuit 21 calculates .beta. such that the value .beta./a varies
with the engine speed N detected by the engine speed sensor 20. The
value .beta./a corresponding to the engine speed N can be stored in
a memory 22 as a preset map. On calculating .beta., the steering
angle calculating circuit 21 reads out the map of the value
.beta./a stored in the memory 22 to calculate the steering angle
.beta. based on the data of the turning angle a detected by the
steering wheel operation angle sensor 9.
[0023] FIGS. 3(A) and 3(B) are explanatory graphs, showing examples
of preset steering angle relative to steering wheel turning angle.
FIG. 3(A)(a) shows two preset gradient values of the steering angle
.beta. relative to the steering wheel turning angle a, that is, a
smaller preset value (a) and a larger preset value (b), between
which there are included additional preset gradient values
proportional to the engine speed N. In other words, as shown in
FIG. 3(A)(b), the value .beta./a is set to a larger value for use
in a lower speed range, smaller value for use in a higher speed
range, and set to vary more linearly with the engine speed N in a
middle speed range (an engine speed range between the lower and
higher engine speeds). Thus, in the middle speed rage, the value
.beta./a itself can change proportionally to the engine speed N. As
used herein, the tem "proportionally" is intended to include any
type of relationship, whether it is linear or non-linear. For
example, the term "proportional" encompasses relationships where
incremental increases in a engine speed N trigger incremental
increases (or decreases) in the value .beta./a.
[0024] FIG. 3(B)(a) shows three preset gradient values of the
steering angle .beta. relative to the steering wheel turning angle
a; a smaller preset value (a), a larger preset vale (b) and a
medium preset value (c). In other words, as shown in FIG. 3(B)(b),
the preset value .beta./a sequentially decreases in a stepped
manner in three stages, a low, medium and high speed range of the
engine speed N.
[0025] The preset value .beta./a relative to the engine speed N as
shown in FIGS. 3(A)(b) or 3(B)(b) is stored in the memory as a map,
and read out when the steering wheel is operated to calculate the
steering angle .beta. based on the steering wheel turning angle a
and engine speed N.
[0026] Boats troll at low speed in the port or on the sea for
fishing while generally cruising at high speed on the sea. Both
speeds approximately correspond to engine speed, when the boat has
reached a steady-state of operation, i.e., when the boat is no
longer accelerating or decelerating or decelerating speed with high
load variation. This is because most boats used a single-speed
reduction gear to drive a propeller or jet pump. Thus, the steering
system can simply use engine speed N as the basis for changing the
value .beta./a and still provide a response that is like the
response provided by systems that use boat speed (and a more
expensive and less reliable boat speed sensor).
[0027] Moreover, there is no need to connect the expensive boat
speed sensor to an engine controller, resulting in cost reduction
as well as simplified control mechanism, wiring layout and the
like. In some embodiments, if a boat sensor is used at all, it can
be directly connected to a gauge (not shown) near the steering
wheel 7, and thus does not affect the complexity of the controller
12 or wiring layout of the boat. In addition, a typical engine
control unit is provided with the engine speed sensor since it is
such is commonly used for fuel and ignition timing controls. Thus,
no additional sensor is required because the existing engine speed
sensor can be used with the present steering system.
[0028] In the embodiments where the engine speed is categorized
into stages, e.g. three speed ranges including low, middle and high
speed the steering control is more simple, and thus less expensive
to manufacture. Additionally, when in the low-speed range, steering
response is more nimble because the steering displacement relative
to the steering wheel operation angle is increased.
[0029] The present inventions can be effectively applied to a small
boat having an outboard motor or a stern drive, particularly to a
rudder device using an electric motor. However, although these
inventions have been disclosed in the context of certain preferred
embodiments and examples, it will be understood by those skilled in
the art that the present inventions extend beyond the specifically
disclosed embodiments to other alternative embodiments and/or uses
of the inventions and obvious modifications and equivalents
thereof. In addition, while several variations of the inventions
have been shown and described in detail, other modifications, which
are within the scope of these inventions, will be readily apparent
to those of skill in the art based upon this disclosure. It is also
contemplated that various combination or sub-combinations of the
specific features and aspects of the embodiments may be made and
still fall within the scope of the inventions. It should be
understood that various features and aspects of the disclosed
embodiments can be combined with or substituted for one another in
order to form varying modes of the disclosed inventions. Thus, it
is intended that the scope of at least some of the present
inventions herein disclosed should not be limited by the particular
disclosed embodiments described above.
* * * * *