U.S. patent application number 10/622428 was filed with the patent office on 2004-07-15 for ship's steering unit whose angular position is servo-controlled by an electric motor.
This patent application is currently assigned to ALSTOM. Invention is credited to Moneuse, Nicolas.
Application Number | 20040134403 10/622428 |
Document ID | / |
Family ID | 29797664 |
Filed Date | 2004-07-15 |
United States Patent
Application |
20040134403 |
Kind Code |
A1 |
Moneuse, Nicolas |
July 15, 2004 |
Ship's steering unit whose angular position is servo-controlled by
an electric motor
Abstract
The ship's steering unit comprises a mounting which is part of
the structure of the ship, and in which a rudder is pivotally
mounted, the angular positioning of said rudder being
servo-controlled by a motor. The motor is an electric motor
comprising a stator rigidly fixed to said mounting, and a rotor
rigidly fixed to said rudder. The steering motor is powered at
variable frequency and at variable voltage, and it transmits the
torque necessary for servo-controlling the rudder
electromagnetically, i.e. without physical contact, thereby
eliminating problems of wear. In addition, the steering unit is
simplified by reducing the number of items of equipment making up
said unit, thereby making it easier to install on board and
contributing to making it more reliable.
Inventors: |
Moneuse, Nicolas; (La Baule
Escoublac, FR) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W.
SUITE 800
WASHINGTON
DC
20037
US
|
Assignee: |
ALSTOM
|
Family ID: |
29797664 |
Appl. No.: |
10/622428 |
Filed: |
July 21, 2003 |
Current U.S.
Class: |
114/162 |
Current CPC
Class: |
B63H 25/26 20130101;
B63H 25/14 20130101 |
Class at
Publication: |
114/162 |
International
Class: |
B63H 025/06 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 25, 2002 |
FR |
0209438 |
Claims
What is claimed is.
1/ A ship's steering unit comprising a mounting which is part of
the structure of the ship, and in which a rudder is pivotally
mounted, the angular positioning of said rudder being
servo-controlled by a motor comprising a stator rigidly fixed to
the mounting, and a rotor rigidly fixed to said rudder, wherein
said rudder is held in position by controlling the power supply to
the motor.
2/ A ship's steering unit according to claim 1, in which the motor
is an asynchronous motor which is powered by a power converter
controlled so as to hold said rudder in position.
3/ A steering unit according to claim 1, in which said rudder
includes a steering cone pivotally mounted in said mounting, and in
which said electric motor is mounted inside said steering cone.
4/ A steering unit according to claim 1, in which said rudder
includes an underwater portion in the form of a rudder blade.
5/ A steering unit according to claim 1, in which said rudder
includes an underwater portion in the form of a pod enclosing a
propulsion motor for propelling said ship.
6/ A steering unit according to claim 2, in which said electric
motor is cooled by the ventilation system of said propulsion
motor.
7/ A steering unit according to claim 2, in which the stator has a
plurality of electrical windings, each of which is powered by an
independent power converter.
Description
[0001] The invention relates to a ship's steering unit comprising a
mounting which is part of the structure of the ship, and in which a
rudder is pivotally mounted, the angular positioning of said rudder
being servo-controlled by a motor. The invention applies more
particularly to a large ship such as a cruise liner in which the
servo-controlling of the position of the rudder is assisted by
machinery.
BACKGROUND OF THE INVENTION
[0002] Conventionally, the rudder is constrained to move with at
least two hydraulic motors that are fed with oil under pressure by
a hydraulic power unit. The hydraulic power unit itself has two
electric motors powered by an electricity network to provide
redundancy in servo-controlling the rudder. More particularly, the
top portion of the rudder, which is mounted to turn about a
vertical axis, is provided with a toothed ring situated in a
horizontal plane, and each hydraulic motor has an outlet gear
meshed with said ring to transmit servo-control torque to the
rudder. That solution makes it necessary to implement one or more
hydraulic power units associated with high-pressure pipes that take
up a large volume and require specific maintenance.
[0003] In a more recent development, the ring is moved by means of
electric motors, which makes it possible to omit the hydraulic
power unit. In view of the power required to move the rudder, that
solution results in increasing the number of electric motors, and
in equipping each of them with a gearbox, so as to guarantee that
sufficiently high torque is transmitted. That configuration suffers
from the drawback of being less compact due to the need to have a
larger number of motors equipped with gearboxes, and it requires
regular maintenance of said gearboxes in order to keep them in
satisfactory working order.
OBJECTS AND SUMMARY OF THE INVENTION
[0004] An object of the invention is to remedy those drawbacks by
providing an electrically servo-controlled steering unit that is
compact, and that requires only a minimal amount of
maintenance.
[0005] To this end, the invention provides a ship's steering unit
comprising a mounting which is part of the structure of the ship,
and in which a rudder is pivotally mounted, the angular positioning
of said rudder being servo-controlled by a motor, wherein said
motor is an electric motor comprising a stator rigidly fixed to
said mounting, and a rotor rigidly fixed to said rudder. This
motor, which is a steering motor, transmits the torque necessary
for servo-controlling the rudder electromagnetically, i.e. without
physical contact, which eliminates problems of wear. A fixed
position is thus held by means of a power supply adapted to the
type of electric motor in use. In the case of a synchronous motor,
blocking in position is performed by injecting direct current (DC)
into the rotor/stator windings. In contrast, in the case of an
asynchronous motor, blocking in position is performed by adjusting
the power supply frequency to match the rotor slip frequency, i.e.
by adjusting it to the same frequency, in such a manner as to zero
the mechanical speed of the rotor. This configuration simplifies
the steering unit by reducing the number of items of equipment that
make up said unit, thereby making it easier to install on board and
contributing to making it more reliable.
[0006] In a preferred embodiment of the invention, the rudder
includes a steering cone pivotally mounted in said mounting, and
the electric motor is mounted inside said steering cone. The
steering unit of the invention is thus made even more compact. The
rudder includes an underwater portion that may be in the form of a
rudder blade, or else in the form of a pod enclosing a propulsion
motor for propelling said ship. When it is in the form of an
underwater pod enclosing a propulsion motor that is cooled by a
ventilation system, the steering motor may be cooled by diverting
some of the ventilation provided for the propulsion motor. It is
thus not necessary to implement additional ventilation means
dedicated specially to cooling the steering motor.
[0007] In a preferred embodiment of the invention, the stator has a
plurality of electrical windings, each of which is powered by an
independent source of electricity. The electricity sources may be
dedicated power converters, thereby providing redundancy in the
servo-control function, so as to guarantee that the steering unit
of the invention operates reliably.
BRIEF DESCRIPTION OF THE DRAWING
[0008] The invention is described in more detail below with
reference to the accompanying drawing which shows an embodiment of
the invention by way of non-limiting example.
[0009] The sole FIGURE is a section view of a steering unit of the
invention.
MORE DETAILED DESCRIPTION
[0010] In the sole FIGURE, a ship's steering unit comprises a
rudder 1 pivotally mounted in a mounting 2 that is secured to or
integral with the structure of the ship. In this example, the
rudder 1 is provided with a steering cone 1' connected to the
mounting 2 via a rotary mechanical coupling 3 enabling the rudder
to turn about a vertical axis AX along which it extends. The
steering cone 1' passes through the structure of the ship in
watertight manner to hold an underwater portion 1" which is shown
in part only. The underwater portion 1" is fixed rigidly to the
steering cone 1' and it forms the active portion of the rudder 1 to
steer the ship on a certain heading depending on its position about
the axis AX. The angular position of the rudder 1 about the axis AX
is controlled by servo-controlling the angular position of the
steering cone which is situated inside the ship.
[0011] In the example shown in the FIGURE, the diameter of the
steering cone 1' decreases from top to bottom, and it extends down
into the mounting which forms a substantially complementary conical
well. The rotary coupling 3 is situated in a horizontal plane at
the top portion of the steering cone 1' that corresponds to the
largest-diameter portion of the cone. A circular gasket 4 surrounds
the small-diameter bottom portion of the steering cone to provide
sealing between it and the bottom portion of the mounting 2, which
is also of small diameter. In prior art steering units, a ring
provided with inwardly-facing teeth is generally mounted inside the
top portion of the cone, so that hydraulic or electric motors
having their outlet gears meshed with said inwardly-facing teeth
are capable of turning the rudder about the axis AX.
[0012] In the invention, such a drive system using a toothed ring
constrained to rotate with motors is replaced by a single
large-diameter "steering" motor mainly comprising a rotor 5 rigidly
fixed to the rudder 1, co-operating with a stator 6 which is
rigidly fixed to the mounting 2. The rotor 5 and the stator 6 are
chosen to be of large diameter to facilitate transmitting large
torque. Such a steering motor may be designed such that it
surrounds the steering cone 1', or else it may be mounted inside
the steering cone so as to make the steering unit more compact, the
choice being governed by dimensioning constraints corresponding in
particular to the power the motor needs to deploy in order to
achieve servo-control.
[0013] In the example given in the sole FIGURE, the motor is
mounted inside the top portion of the steering cone 1'. The rotor
5, which defines a substantially toroidal shape, is positioned in a
horizontal plane while being fixed to the inside surface of the
steering cone 1. It co-operates with the stator 6 which is also
substantially toroidal in shape but which is of smaller diameter,
and which is mounted inside the rotor 5 in the same horizontal
plane as said rotor. More particularly, the stator 5 extends down
into the steering cone 1' while being held at its top portion by a
large-diameter circular cap 7 covering the steering cone and fixed
rigidly to the mounting 2. In the example shown in the sole FIGURE,
the stator comprises windings 5' electrically powered by a power
converter 8 such as a variable-voltage and variable-frequency
converter connected to an electrical power supply network of the
ship. In this example, the rotor 6 is passive and mainly comprises
squirrel cages 6' disposed around its outer periphery to co-operate
with the stator to form an asynchronous motor. Implementing such an
asynchronous motor offers the particular advantage of making it
easier to block the rudder in position by adjusting the power
supply to the motor to match rotor slip in such a manner as to zero
the mechanical speed of said rotor.
[0014] This configuration consisting in mounting the windings on
the stator rather than mounting them on the rotor is advantageous
when implementing a plurality of windings each of which is powered
by a respective dedicated power converter. The quantity of wiring
is increased, but said wiring is connected to the stator, which is
stationary, and said wiring is therefore easier to install.
Implementing a plurality of separately-powered windings also
provides redundancy in the position servo-control function, thereby
improving the operating reliability of the steering unit of the
invention.
[0015] The underwater portion 1" of the rudder 1 of the invention
may be a rudder blade, or else it may be a pod enclosing an
electric motor for propelling the ship. When it is a pod 1"
enclosing a propulsion motor, the propulsion motor is generally
cooled by a ventilation system causing air to flow through the pod.
The flow of air is taken into the top portion of the steering unit
via a circular opening 7' provided in the cap 7, as indicated by
the arrow R in the FIGURE. In the invention, the flow of air is
also used to cool the steering motor, so that it is not necessary
to provide additional means dedicated to cooling the motor for
angularly positioning the steering unit.
[0016] The invention is not restricted to the above-described
embodiment in which the steering unit includes a conical coupling,
but rather it is also applicable to other types of mechanical
coupling between the rudder and the mounting.
* * * * *