Note: Descriptions are shown in the official language in which they were submitted.
--- 2017690
POWER STEERING SYSTEM OF THE OUTBOARD MOTOR
BACKGROUND OF THE INVENTION
The present invention relates to a power steer-
ing system of the outboard motor particularly having an
improved power unit for applying a steering assist force
to a manual steering system, and for suitably controlling
the steering assist force.
A conventional manually operative steering
system of an outboard motor provides such a problem as
that the steering load increases, which may results in
the difficulty of the steering operation, in accordance
with navigation conditions, such as wind or wave
condition, hull speed, trim angle of the outboard motor
body and the like conditions.
In order to obviate the problem encountered to
the conventional manual steering system, a hydraulic
power steering system has been proposed.
A proposed hydraulic power steering system is
generally composed of the manual power steering system
and a power unit equipped with a hydraulic pump for
generating a steerng assist force. The power unit applies
the steering assist force to the manual power steering
system.
However, the hydraulic power steering system
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27860-6
~- 201 76qO
described above utilizes a power source of the outboard motor
itself as a power source of the hydraulic pump. Accordingly,
the steering assist force generated by the hydraulic pump is
changed in response to the rotations per minute of the engine,
i.e. engine speed, mounted on the outboard motor, which may not
be suitably controlled according to the navigation conditions.
SUMMARY OF THE INVENTION
An object of this invention is to substantially
eliminate the defects or drawbacks of the conventional
technology and to provide a power steering system of the out-
board motor capable of easily and suitably steering a outboard
motor body by a little steering load free from the changes of
the navigation conditions.
Another object of this invention is to provide a
power steering system of the outboard motor capable of reducing
an occupied space of the power steering system required in the
hull to thereby apply to a small sized hull.
These and other objects can be achieved according to
the present invention, in one aspect, by providing a power
steering system for an outboard motor, for steering an outboard
motor body of said outboard motor which is disposed outside of
a rear portion of a hull of a watercraft and which is
provided with an engine and a propeller driven by means of
said engine, comprising: a manual steering system mounted upon
said hull for operating a steering element in order to manually
steer said outboard motor body; a power unit operatively
connected to said manual steering system and including an
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20176qO 27860-6
electric motor for applying a steering assist force to said
manual steering system; a sensor means provided with a steering
torque sensor for detecting steering torque applied to said
steering element of said manual steering system during
operation thereof, an engine speed sensor for detecting engine
speed, and a steering angle sensor for detecting a steering
angle and a steering direction of said outboard motor body when
steered by said manual steering system; and a control means
operatively connected to said sensor means for controlling said
electric motor of said power unit by determining said steering
assist force in response to said steering torque detected by
said steering torque sensor and adjusting said determined
steering assist force in response to said engine speed and
said steering angle respectively detected by means of said
engine speed sensor and said steering angle sensor.
In preferred embodiments of the one aspect of the
present invention, the sensor means operatively connected to
the control means is provided with a steering torque sensor for
detecting steering torque during operation of the manual steer-
ing system and engine speed sensor for detecting engine speedand a steering sensor for detecting steering angle and steering
direction of the outboard motor body steered by the manual
steering system.
The control means controls the electric motor of the
power unit so as to determine the power assist force in response
to the steering torque detected by the steering torque sensor
and then to convert the determined force in response to the
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engine speed and the steering angle respectively detected by
the engine speed sensor and the steering angle sensor.
The sensor means comprises a thrust sensor
operatively connected to the control means for detecting thrust
force generated by the propeller of the outboard motor.
The control means controls the electric motor of the
power unit so as to generate the steering assist force in
proportion to the thrust force detected by the thrust sensor.
The outboard motor is provided with a power trim-tilt
system for automatically trimming and tilting the outboard
motor body and the thrust sensor directly detects pressure of
a pressure oil operating the power trim-tilt system to
indirectly detect the thrust generated by the propeller.
In another aspect of the present invention, there is
provided a power steering system for an outboard motor having
an outboard motor body and means for mounting the motor body on
a transom having a front surface defining the rear of a water-
craft hull interior space, the outboard motor being provided
with an engine and a propeller driven by means of said
engine, said steering system comprising: a manual steering
system mounted upon said hull for operating a steering element
in order to manually steer said outboard motor body; and a
power unit operatively connected to said manual steering system
and including an electric motor for applying a steering assist
force to said manual steering system, and transmission means
for transmitting power generated by said electric motor to said
manual steering system, said electric motor being within a
201 7690 27860-6
._
motor box means located outside of said hull interior space
and said outboard motor body and to the rear of the transom
front surface when the motor body is mounted on the transom,
and said transmission means being disposed within a trans-
mission box means which is also located outside of said hull
interior space and said outboard motor body and to the rear of
the transom front surface when the motor body is mounted on
the transom.
In preferred embodiments, the transmission means is
accommodated in a transmission box means located outside the
hull. The hull is provided with a transom at the rear portion
thereof and the transmission means comprises reduction gears,
a rack and a pinion, the reduction gears being accommodated
in a gear box located outside the hull, the rack and pinion
being accGmmodated in a rack box located above a surface of
the transom.
According to the present invention of the characters
and structures described above, there is provided a power
steering system for an outboard motor, for steering an outboard
motor body of said outboard motor which is disposed outside of
a rear portion of a hull of a watercraft and which is provided
with an engine and a propeller driven by means of said engine,
comprising: a manual steering system mounted upon said hull
for operating a steering element in order to manually steer
said outboard motor body; a power unit operatively connected to
said manual steering system and including an electric motor for
applying a steering assist force to said manual steering
201 76~0 27860-6
system; a sensor means provided with a thrust sensor for
detecting a thrust force generated by means of said propeller
of said outboard motor; and control means operatively connected
to said sensor means for controlling said electric motor of
said power unit by determining said steering assist force in
proportion to said thrust force detected by means of said
thrust sensor.
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In addition, the control means sets the
steering asist force to be proportional to the thrust
force generated by the propepper of the outboard motor
and affecting the steering load, so that the steering
asist force can be controlled so as to correspond to the
fluctuation of the steering load. Thus, the power
steering system can easily and suitably steer the
outboard motor body by a little load free from the
navigation conditions, thereby improving the steering
feeling.
Furthermore, according to the present
invention, the power steering system camprises the motor
box in which the electric motor of the power unit is
accommoated and the transmission box in which the
transmission means for transmitting the steering asist
force generated by the electric motor to the manual
steering system is accommodated. The motor box and the
transmission box are located outside the rear portion of
the hull at which the outboard motor is disposed, thereby
reducing the location space of the power steering system
required in the hull and, hence, the power steering
system can be applied to a small sized craft to improve
the usage thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
2 ~ 9 0
For a better understanding of the present
invention and to show how the same is carried out,
reference is now made to, by way of preferred
embodiments, to the accompanying drawings, in which:
Fig. 1 is a block diagram mainly representing a
controller of a power steering system of an outboard
motor of the first embodiment according to the present
invention;
Fig. 2 is a side view of the outboard motor to
which a power steering system provided with the
controller shown in Fig. 1 is applied;
Fig. 3 is a front view of the power steering
system of the first embodiment;
Fig. 4 is a longitudinal sectional view of the
power steering system shown in Fig. 3;
Fig. 5 is an enlarged perspective view of a
portion enclosed by V shown in Fig. 4;
Fig. 6 is an illustration representing an
arrangement of a steering angle sensor shown in Fig. 4;
Fig. 7 is a sectional view representing a geer
tooth of a pinion shown in Fig. 6;
Fig. 8 is a flowchart representing control
condition of the controller shown in Fig. l;
Fig. 9 is a graph representing the relationship
between the steering torque and the current value
- 2 ~ Q
supplied to a motor, which is memorized in a ROM shown in
Fig. l;
Fig. 10 is a graph representing the relation-
ship between the engine speed, the steering angle and the
current value to the motor, which are memorized in RAM
shown in Fig. l;
Fig. llA is a plan view representing the
arrangement of a detecting gear of one modification of
the first emboeiment;
Fig. llB is an enlarged sectional view of the
portion enclosed by XIB shown in Fig. llA;
Fig. 12 is a block diagram mainly representing
a controller of a power steering system of the second
embodiment according to the present invention;
Fig. 13 is a perspective view of the power
steering system including the controller shown in Fig. 12;
Fig. 14 is a front view of the power steering
system of the second embodiment shown in Fig. 12;
Fig. 15 is a longitudinal sectional view of the
power steering system shown in Fig. 14;
Fig. 16 is a front view of a power trim-tilt
system accommodated in the outboard motor body shown in
Fig. 14;
Fig. 17 is a side view of the power trim-tilt
system shown in Fig. 16;
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Fig. 18 is a front view of a thrust sensor of
the power trim-tilt system shown in Figs. 12 and 16;
Fig. 19 is a schematic sectional view of the
power trim-tilt system shown in Figs. 16 and 17;
Fig. 20 is a graph generally representing the
relationship between the engine speed and the thrust
force generated by a propeller;
Fig. 21 is a partial perspective view of the
power steering system of the third embodiment according
to the present invention;
Fig. 22 is a longitudinal sectional view
partially representing the power steering system shown in
Fig. 21;
Fig. 23 is a side view of the outboard motor
including the power steering system shown in Figs. 21 and
22;
Fig. 24 is a perspective view of a conventional
manual steering system; and
Fig. 25 is a side view representing the tilt-up
and tilt-down conditions of the outboard motor body
shown in Fig. 24.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In advance of the detailed description of
preferred embodiments of the present invention, the
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conventional art will be described hereunder with
reference to Figs. 24 and 25.
Referring to Fig. 24 showing a steering system
of an outboard motor operative manually, when an operator
handles a steering wheel 2 equipped at a driving portion
in a hull 1, a gear in a gear box 4 is rotated through a
steering shaft 3. In response to the rotation of the
gear, an inner cable 6 of a steering cable 5 is recipro-
cated axially forwardly or backwardly (push-pull motion).
The steering cable 5 comprises an outer cable 7 and the
inner cable 6 coaxially located therein.
The front end of the inner cable 6 slightly
extends beyond the front end of the outer cable 7 and is
connected to one end of a drag link 9 of a link mechanism
8. The drag link 9 has an L-shaped structure and has the
other end connected to one end of a steering bracket lO
to be rotatable. The other end of the steering bracket 10
is secured to a body 12 of the outboard motor 11.
As shown in Fig. 25, the outboard motor body 12
comprises a drive shaft housing 13 including a drive
shaft, not shown. The outboard motor body 12 is supported
by a swivel bracket 14 through a pilot shaft, not shown,
secured to the drive shaft housing 13 to be horizontally
rotatable or steerable around the pilot shaft. The swivel
bracket 14 is supported to be rotatable i.e. tiltable, in
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a vertical direction by a clamp bracket shaft 15 horizon-
tally mounted between a lateral pair of clamp brackets
16 and 16, by which a transom la of the hull 1 is held to
thereby secure the outboard motor body 12 to the hull 1.
According to the structure described above, the outboard
motor body 12 is horizontally bilaterally swung about the
pilot shaft by the push-pull motion of the inner cable 6
of the steering cable 5 through the link mechanism 8, thus
the outboard motor body 12 being steered.
However, with respect to the manual steering
system of the conventional type described above, the
maneuvaring of the outboard motor 11 may involve much
labour by the increasing of the steering load applied
during the steering operation due to the navigation
conditions, such as wind or wave condition, hull speed,
trim angle of the outboard motor 11.
In order to obviate the defect of the conven-
tional manual steering system and, hence, to reduce the
steering load, a conventional technology provides a
hydraulic power steering system of the outboard motor.
However, the hydraulic power steering system of prior art
utilizes a power source of the outboard motor itself as a
power source for driving a hydraulic pump. Accordingly,
an steering assist force generated by the hydraulic pump
is changed in response to rotations per minute of the
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drive shaft and may not be suitably controlled in accor-
dance with the navigation conditions.
A power steering system according to the present
invention conceived for substantially eliminating the
defects or drawbacks encountered to the prior art des-
cribed above will be described hereunder with reference
to Figs. 1 to 23.
Referring to 1 to 10 representing first embodi-
ment according to the present invention, Fig. 3 shows a
front view of a power steering system 20 of one embodiment
of the present invention. Referring to Fig. 3, the power
steering system 20 comprises a manual steering system 21
and a power unit 22 and the manual steering system 21 is
of the type substantially the same as that shown in Figs.
24 and 25, so that the like reference numerals are added
to elements or members corresponding to those shown in
Figs. 24 and 25 and the details thereof are now omitted
herein.
The power unit 22 acts to apply a steering
assist force directed to the same direction as the manual
steering force of the manual steering system 21 to an
input end of the link mechanism 8 to thereby reduce the
steering load. The power unit 22 comprises a motor box 23
in which a motor, not shown, is accommodated, a gear box
24 in which a reduction gear is accommodated and a sensor
201~
box 25 in which a torque sensor, not shown, is
incorporated.
As shown in Fig. 4, the motor box 23 and the
gear box 24 are integrally coupled with a rack box 27 in
which a rack 26 is accommodated and the integral
structure is secured to an upper portion of the swivel
bracket 14 of the outboard motor 11 by means of bolts.
The sensor box 25 is secured to one of the
paired clamp brackets 16 through a support arm 28 and
slidably accomodates a sensor rod, not shown, therein.
The sensor rod has one end secured to a terminal end of
the outer cable 107 by a stationary arm 28a. The other
end of the sensor rod is operatively connected to a
potentiometer, not shown, accomodated in the sensor box
25. The potentiometer and the sensor rod described above
constitute a steering torque sensor 32 as shown in Fig. 1.
When the inner cable 6 is pushed or pulled
with respect to the outer cable 7 by the manual operation
of the steering wheel 2, the reaction force applied to
the outer cable 7 by the push or pull motion of the inner
cable 6, i.e. the steering load, is transmitted to the
sensor rod through the stationary arm 28a. The displace-
ment of the sensor rod is detected by the potentiometer
in the sensor box 25 and a signal, i.e. steering torque
signal, representing the displacement detected by the
2 Q ~
potentiometer is transmitted to a controller 29 described
later herein.
As shown in Fig. 3, the rack box 27 has axial
ends to which shrinkable cylindrical bellows 31 and 31
are coaxially secured and the rack 26 is liquid-tightly
accommodated in the rack box 27 in an axially
reciprocating manner. The rack 26 has one axial end
(right end as viewed in Fig. 4) secured to a stay 26a
and, as shown in Fig. 5, the stay 26a is connected to a
bent end 9a of the drag link 9 in a direction normal
thereto by means of a washer 33 and a nut 34. The rack 27
is engaged with a pinion 30 at an intermediate portion
thereof, which is fixed to a pinion shaft 30a. The pinion
shaft 30a is operatively connected to the motor shaft 37
of the motor 38, shown in Fig. 1, through a reduction
gears 35 and 36 which are in the form of bevel gears and
engaged with each other. Accordingly, when the motor 38
is driven, the pinion 30 is rotated through the reduction
gears 35 and 36 to thereby move the rack 26 in the
linear direction thereof, whereby the rotating power of
the motor 38 is transmitted to the link mechanism 8 as
the steering assist force for reducing the steering load
to thereby easily steer the outboard motor body 12.
Referring to Fig. 1, an engine speed sensor 39
detects the rotations per minute of the engine (i.e.
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engine speed), not shown, mounted in the outboard motor
body 12 and transmits a signal representing the engine
speed, i.e. engine speed signal, to the controller 29.
A steering angle sensor 40 is utilized a non-
contact electromagnetic sensor and arranged in opposing
state to the pinion 30 as shown in Fig. 6. When an
operator handles the steering wheel 2 to move the inner
cable 6 of the steering cable 5 and to rotate the pinion
30 through the stay 26a and rack 26, the steering angle
sensor 40 counts the numbers of gear teeth 41 of the
pinion 30 to thereby detect the steering angle of the
outboard motor body 12. Referring to Fig. 7, each of the
gear teeth 41 of the pinion 30 has a top land 42 on which
a cutout portion 43 is formed so as not to damage to the
strength of the pinion 30. The cutout portion 43 is
formed to be in such asymmetrical manner as that the
position of the cutout portion 43 is set with distances L
and M respectively from bilateral ends of the top land
42. Accordingly, when the steering angle sensor 40
detects this asymmetrical cutout portion 43, detected
voltage waveforms of the gear teeth 41 of the pinion 30
are asymmetrical, thus detecting a direction of rotation
of the pinion 30, i.e. a steering direction of the
outboard motor body 12. The steering angle sensor 40
transmits signals representing these steering angle
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and steering direction described above as steering
angle-direction signals to the controller 29.
Referring to Fig. 1, the controller 29 is
composed of a central processing unit (CPU) 44, memories
provided with a read only memory (ROM) 45 and a random
access memory (RAM) 46 and a signal converter provided
with an analog-to-digital converter (A-D converter) 47
and a digital-to-analog converter (D-A converter) 48.
The ROM 45 has a data-table, as shown in Fig.
9, representing relationship between the steering torque
T and current value A supplied to the motor 30. The
steering assist force applied to the link mechanism 8
from the power unit 22 is determined in accordance with
the current value A supplied to the motor 30. Referring
to Fig. 8, CPU 44 reads the steering torque signal and
the engine speed signal from the steering torque sensor
32 and the engine speed sensor 39 respectively through
the A-D converter 47 in condition of switch ON, and then
determines the current value A supplied to the motor 38
for generating the steering assist force corresponding to
the steering torque T represented by the steering torque
signal with reference to the data-table memorized in the
ROM45.
The RAM 46 has a data-table, as shown in Fig.
10, representing the relationship between the steering
1 6
2~ 7~
angle ~ , the engine speed R and current values A' and A"
supplied to the motor 38. Referring to Fig. 8, the CPU
44 continually reads the steering angle ~ through the
A-D converter 47 during the operation of a shift device
accomodated in the outboard motor body 12. The CPU 44
then memorizes said steering angle ~ to the RAM 46 and
simultaneously calculates so as to adjust the current
value A determined by the data-table memorized in the
ROM 45.
Namely, the characteristics of the current
values A' and A" memorized in RAM 46, as shown in Fig.
10, are different in accordance with the engine speed R
even in the same steering angle ~ . The CPU 44 selects
one of these characteristics of the current values A' and
A" in accordance with the engine speed signal transmitted
from the engine speed sensor 39 and, for example, selects
a characteristic represented by a full line P as viewed
in Fig. 10 in a case where the enginespeed R is more
than 5500 r.p.m. This characteristic represented by the
full line P designates the supplying current value A
determined by the data-table as shown in Fig. 9 in a case
where the steering angle~ is less than steering anglea ( ~
< a ) , and designates the supplying current value A'
determined by a formula described such as
A' = A - X ( ~ - a )
2 ~ ~ 7 ~
in a case where the steering angle~ is more than a
steering angle a and less than a steering angle ~ ( a ~ ~
< ~; a < ~ ), thus reducing the steering assist force
settled by the supplying current value A'. The letter X
represents a gradient of the full line P as shown in
Fig. 10 in condition of a ~ ~ < ~ . The characteristic
represented by the full line P designates then a
supplying current value A" determined by a formula
described such as
A " = A - X ( ,~ -- a )
in a case where the steering angle~ is more than a
steering angle~ ( ~ 2 ~ ). As this supplying current
value A" is constant, the steering assist force settled
by the current value A" is also constant. Accordingly to
the manner described above, when the engine speed R is
high and the steering angle ~ is large, the controller
29 operates to reduce the current value supplied to the
motor 38, thus avoiding the turn-over, for example, of
the hull 1.
Referring to Fig. 1, the current value A, A' or
A" supplied to the motor 38 is transmitted to a driver 49
through the D-A converter 48, which amplifies the current
value from the controller 29 so as to drive the motor 38
and then flows the amplified current to the motor 38.
According to the described first embodiment,
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the controller 29 adjusts the supplying current value A
to the motor determined by the steering torque T from the
steering torque sensor 32 in accordance with the engine
speed R and the steering angle ~ respectively detected
by the engine speed sensor 39 and the steering angle
sensor 40. In a case where the engine speed R is high,
the controller 29 preferably supplies to the motor 38 the
current value less than the supplying current value A
determined by the steering torque T so as to reduce the
steering assist force, so that the steering assist force
can be suitably controlled in accordance with the
navigation conditions. Thus, the power steering system of
the outboard motor can easily and suitably steer the
outboard motor body with a little steering load.
Fig. llA shows a fragmentary plan view of one
modification according to the first embodiment. In this
first modification, the pinion 30 and a detecting gear 50
is coaxially located to the pinion shaft 30a, and the
detecting gear 50 has gear teeth 41 provided with the
cutout portion 43 as shown in Fig. 7 so as to detect the
direction of rotation of the pinion 30 or has gear teeth
51, as shown in Fig. llB, respectively provided with
larger cutout portions 52 so as to detect the same. The
shapes of the teeth of the detecting gear 50 provided
with the cutout portion 43 or 52 is detected by the
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2 ~ ~L rl ~ ~ ~
steering angle sensor 40. According to this modification,
these cutout portions 43 and 52 are larglycut regardless
of the strength of the pinion 30, thus correctly
detecting the steering direction of the outboard motor
body 12 by means of a voltage wave of the detecting gear
50.
In another modification of the first
embodiment, the steering sensor 40 may be arranged to
directly detect the rotation of the motor 38 so as to
detect the steering direction of the outboard motor body
12.
Referring to Figs. 12 to 20 representing the
second embodiment according to the present invention,
Fig. 13 shows a perspective view of a power steering
system 60 of the second embodiment of the present
invention, in which like reference numerals are added to
portions or members corresponding to those used for the
first embodiment shown in Figs. 1 to 10 and detailed
description thereof is now omitted herein.
In the second embodiment, the power steering
system 60 is applied to the outboard motor 11 in which a
power trim-tilt system 62 is accommodated, as shown in
Figs. 16 and 17, and comprises the manual steering system
21 and a power unit 61.
The power unit 61 comprises a thrust sensor 63
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as shown in Figs. 12, 16 and 18, the motor box 23, as
shown in Figs. 13 to 15, in which a motor 38 for
generating the steering assist force is accommodated, the
gear box 24 in which the reduction gears 35 and 36 for
transmitting a turning force are accommodated and the
rack box 27 in which the rack 26 and pinion 30 for
transmitting the turning force from the gears 35 and 36
to the drag link 9 of the link mechanism 8 through the
stay 26a are incorporated.
The thrust sensor 63, as described later in
detail, detects a thrust of a propeller 64, as shown in
Fig. 2, of the outboard motor 11 and transmits a thrust
signal representing said thrust to controller 65 as shown
in Figs. 12 and 13.
Referring to Fig. 12, the controller 65 is
composed of an arithmetic unit 66, an output unit 67 for
a torque control signal and a motor control unit 68, and
the arithmetic unit 66 calculates and determines the
steering assist force in proportion, for example, to said
thrust represented by said thrust signal and transmits an
assist force control signal representing the steering
assist force to the motor control unit 68 through the
output unit 67 as output end. The motor control unit 68
manipulates, and preferably amplifies the assist force
contrl signal and transmits the amplified signal to the
2 ~ Q
motor 38. Thus it is that the controller 65 controls the
rotation of the motor 38 to generate the suitable
steering assist force.
Namely, the steering load applied to the steer-
ing wheel 2 during the steering operation is generally
affected at the thrust force generated by the propeller
64 and the force applied to the outboard motor body 12 in
the rectangular direction of the axis of the propeller 64
or the moment around the pirot shaft, not shown, applied
to the outboard motor body 12. The applied force and the
moment respectively described above are proportional to
the thrust force generated by the propeller 64.
Accordingly, the controller 65 controls the steering
assist force generated by the motor 38 to be in
proportional to the thrust force of propeller 64, thus
suiting the steering assist force to fluctuation of the
steering load, whereby the steering feeling can be
improved.
Referring to Fig. 20, in a sliding or running
craft such as a motor boat, the thrust force generated by
the propeller 64 during the engine operation is maximum
before the sliding of the craft and is constant during
the sliding manner of the craft. In this case, the
controller 65 controls the steering assist force
generated by the motor 38 to rapidly increase before the
2 ~
sliding of the craft and to be constant during the
sliding of the craft in response to the thrust force
generated by the propeller 64 described above.
As shown in Figs. 16 and 17, the power
trim-tilt system 62 is composed of a pair of trim
cylinders 69a and 69b accommodated in the outboard motor
body 12, a tilt cylinder 70 arranged between the trim
cylinders 69a and 69b in the outboard motor body 12 and
an oil pump 71 located outside the outboard motor body
12. Referring to Fig. 19, the oil pump 71 supplies a
pressure oil to an inner upper chamber and an inner lower
chamber of the tilt cylinder 70 through a tilt-down tube
72 and a tilt-up tube 73 respectively to thereby slide a
piston rod 74 incorporated in the tilt cylinder 70
downwardly and upwardly, whereby the outboard motor body
12 can be automatically tilted down and tilted up
respectively. The oil pump 71 also supplies the pressure
oil to an inner upper chamber and an inner lower chamber
of trim cylinder 69a and 69b through a trim-down tube 75
and a trim-up tube 76 respectively to thereby slide
piston rods 77a and 77b respectively incorporated in the
trim cylinders 69a and 69b downwardly and upwardly. Thus,
the outboard motor body 12 can be automatically trimed
down and trimed up within the range of the tilt angle.
The trim-up tube 76 is interposed between an
2 3
2 Q ~ 4 ~
..
output end of the oil pump 71 and the inner lower
chambers of the trim cylinders 69a and 69b so as to
supply the pressure oil in the oil pump 71 into the inner
lower chambers. The thrust sensor 63 is arranged to the
trim-up tube 76 and, as shown in Fig. 18, composed of a
pressure sensor 78 and a sensor body 79 which is of a
liquid-tight hollow box structure and secured to the
trim-up tube 76. The pressure sensor 78 is accommodated
in the sensor body 79 and adapted to detect the pressure
of the pressure oil in the trim-up tube 76 and then
transmits an electric signal representing the detected
pressure to the arithmetic unit 66 of the controller 65
through a signal cable 80. The pressure oil in the
trim-up tube 76 applies to the outboard motor body 12 the
force which is substantially the same level as that of
the thrust force generated by the propeller 65 in a
direction opposite to the thrust force direction to
thereby hold the hull 1 in a predetermined navigation
state with the bow thereof lifted up. Accordingly, the
thrust force generated by the propeller 64 can be
indirectly detected by the thrustsensor 63 which directly
detects the pressure of the pressure oil in the trim-up
tube 76.
The arithmetic unit 66 of the controller 65, as
shown in Fig. 12, has a data-table representing the
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relative relationship between the pressure of the
pressure oil in the trim-up tube 76 and the thrust force
generated by the propeller 64 and the arithmetic unit 66
reads the thrust force corresponding to the detected
signal from the thrust sensor 63 according to the
data-table. The arithmetic unit 66, further, culculates
and determins the steering assist force proportional to
the thrust force read in the described manner and
transmits the assist force control signal representing
the steering assist force determined in the described
manner to the motor control unit 68 through the output
unit 67. The motor control unit 68 manipulates,
preferably amplifies the assist force control signal and
then transmits the amplified signal to the motor 38,
whereby the controller 65 enables the motor 38 to
generate the suitable steering assist force corresponding
to the fluctuation of the steering lood.
According to the described second embodiment,
the controller 65 enables the motor 38 to generate the
suitable steering assist force corresponding to the
fluctuation of the steering load which is generally
affected by the thrust force generated by the propeller
64 and the like force, thus reducing the steering load
applied to the steering wheel 2 and, hence, the steering
feeling can be improved by the suitable steering assist
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force corresponding to the fluctuation of the steering
load.
In addition, the thrust sensor 63 indirectly
detects the thrust force generated by the propeller 65 in
a manner of directly detecting the pressure of the
pressure oil in the trim-up tube 76 of the existing power
trim-tilt system 62, so that the thrust sensor 63 can be
made compact and simplified with reduced cost.
In the first modification of the second embodi-
ment, the thrust sensor 63 may be arranged to the tilt-up
tube 73 of the power trim-tilt system 62 to thereby
directly the pressure of the pressure oil in the tilt-up
tube 73, thus indirectly detecting the thrust force
generated by the propeller 64, because the pressure oil
is also supplied to the tilt cylinder 70 as well as the
trim cylinders 69a and 69b during the trim-up operation.
In the second modification of the second
embodiment, the power trim-tilt system 62 is composed of
a single hydraulic cylinder for attaining both power trim
effect and power tilt effect. The thrust sensor may be
mounted to a tube through which the pressure oil is
supplied from the oil pump 71 to the inner chamber of the
hydraulic cylinder described above, thus indirectly
detecting the thrust force generated by the propeller 64.
Referring to Figs. 21 to 23 representing the
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third embodiment according to the present invention, Fig.
21 shows a partial perspective view of a power steering
system 90 of the third embodiment of the present invention,
in which like reference numerals are added to portions
or members corresponding to those used for the first
embodiment shown in Figs. l to 10 and detailed
description thereof is now omitted herein.
In the third embodiment, the power steering
system 90 comprises the manual steering system 21 and a
power unit 91. Referring to Figs. 21 and 22, the power
unit 91 is provided with a motor box 92 in which a motor
38 is accommodated, a gear box 93 in which the reduction
gears 35 and 36 are accommodated, a rack box 94 in which
a rack 97 and a pinion 96 are incorporated and a sensor
box 95 in which a potentiometer and a sensor rod
constituting the steering torque sensor 32 are accommo-
dated. The reduction gears 35 and 36, the rack 97 and the
pinion 96 are constructed as a transmission means for
transmitting the steering assist force generated by the
motor 38 to the link mechanism 8 of the manual steering
system 21. The motor box 92 and the gear box 93 are
located outside the transom la of the hull, and the rack
box 94 is disposed above, as viewed, an upper end surface
of the transom la in parallel relationship thereto. The
sensor box 95 is coaxially mounted to the outer periphery
of the inner cable 6 of the steering cable 5.
Namely, the motor box 92 is arranged outside
the transom in such a manner as that the longitudinal
direction of the motor box 92 corresponds to the upward
and downward direction as viewed, and the gear box 93 is
integrally secured to the upper, as viewed, portion of
the motor box 92. The reduction gear 35 secured to the
motor shaft, not shown, is substantially perpendicularly
engaged with the reduction gear 36 secured to the pinion
shaft 96a extending horizontally as viewed, whereby the
rotating force of the motor 38 changes to the horizontal
direction from the vertical direction as shown in Fig.
21.
The rack box 94 which accommodates a pinion
shaft 96a as well as the rack 97 and the pinion 96 is
mounted to one of the cramp brackets 16 in the coaxial
relationship with respect to the cramp bracket shaft 15
interposed between the cramp brackets 16 and 16. One of
the bellows 31 is attached to the rack box 94 and the
other thereof is attached to the end portion of the clamp
bracket shaft 15 in a manner of outwardly extending from
the other one of the clamp brackets 16. The rack 97 is
coaxially accommodated in the rack box 94 and the hollow
clamp bracket shaft 15 in an axially reciprocating
manner and both the axial end of the rack 97 is incorpo-
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rated in the bellows 31. The most outward end portion97a, i.e. the most rightward end as viewed in Fig. 22, of
the rack 97 extends outside bellow 31 and is perpend-
cularly connected to the stay 26a through a free joint
device 98 to thereby transmit the axial reciprocation of
the rack 97 to the outboard motor body 12 through the
link mechanism 8, whereby the outboard motor 12 can be
steered in the bilateral direction.
According to the third embodiment described
above, the motor box 92 and the gear box 93 are located
outside the transom la of the hull 1 and the rack box 97
is disposed above the transom la out of the steering
cable 5, so that the power unit 91 composed of the motor
box 92, the gear box 93, the rack box 94 and the like
member is not mounted inside the hull 1, thus preventing
the reduction of the space of the hull 1. Accordingly,
the power steering system 90 is applied to a small sized
craft, for example a small sized motor boat, which has no
sufficient space, thereby improving the utility of the
power steering system 90.
It is to be understood by persons skilled in
the art that the present invention is not limited to the
described embodiments and many other modifications and
changes may be made without departing from the spilit and
scope of the appended claims.
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