U.S. patent application number 09/726567 was filed with the patent office on 2001-06-07 for flywheel structure of outboard motor.
Invention is credited to Morikami, Tadaaki.
Application Number | 20010003080 09/726567 |
Document ID | / |
Family ID | 18375593 |
Filed Date | 2001-06-07 |
United States Patent
Application |
20010003080 |
Kind Code |
A1 |
Morikami, Tadaaki |
June 7, 2001 |
Flywheel structure of outboard motor
Abstract
An outboard motor has an engine in which a crankshaft is
disposed perpendicularly, a flywheel is disposed to an upper end
portion of the crankshaft to be rotatable in unison with the
crankshaft and the flywheel is provided with a detecting member a
motion of which is detected by a sensor means for detecting a
detecting number of revolution and a revolution angle of the
crankshaft. The detecting member is disposed in an axial direction
of the crankshaft.
Inventors: |
Morikami, Tadaaki;
(Hamamatsu-Shi, JP) |
Correspondence
Address: |
OBLON SPIVAK MCCLELLAND MAIER & NEUSTADT PC
FOURTH FLOOR
1755 JEFFERSON DAVIS HIGHWAY
ARLINGTON
VA
22202
US
|
Family ID: |
18375593 |
Appl. No.: |
09/726567 |
Filed: |
December 1, 2000 |
Current U.S.
Class: |
440/53 |
Current CPC
Class: |
F01P 5/04 20130101; F02B
61/045 20130101; F16F 15/30 20130101; F01P 2050/12 20130101 |
Class at
Publication: |
440/53 |
International
Class: |
B63H 005/125 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 3, 1999 |
JP |
PH11-345289 |
Claims
What is claimed is
1. A flywheel structure of an outboard motor in which a crankshaft
is disposed perpendicularly in an engine of an outboard motor in an
state installed to a hull, a flywheel is disposed to an upper end
portion of the crankshaft to be rotatable in unison with the
crankshaft and the flywheel is provided with a detecting member a
motion of which is detected by a sensor means to thereby detect the
number of revolution and a revolution angle of the crankshaft,
wherein said detecting member is disposed in an axial direction of
the crankshaft.
2. A flywheel structure of an outboard motor according to claim 1,
wherein said detecting member is arranged on a lower surface of the
flywheel along a circumferential direction thereof, said detecting
member is formed, at an outer end thereof, with a centrifugal
fan-shaped portion for discharging an air inside the detecting
member to an outside thereof when the flywheel is rotated.
3. A flywheel structure of an outboard motor according to claim 1,
wherein said flywheel is provided at, an outer peripheral edge
portion thereof, with a ring gear for starting an engine, said
detecting member and said sensor means are disposed inside of an
outer diameter of said ring gear in a plan view.
4. A flywheel structure of an outboard motor according to claim 1,
wherein three or more numbers of said detecting members are
arranged on the lower surface of the flywheel at an equal distance
from one another in the circumferential direction thereof and a
notch is formed to each of the detecting members by removing a
portion thereof.
5. A flywheel structure of an outboard motor according to claim 1,
wherein said flywheel is provided, at an upper surface thereof,
with a fan member for introducing an air outside the flywheel into
the flywheel.
6. A flywheel structure of an outboard motor according to claim 1,
wherein a size K of said detecting member in a diametrical
direction thereof is set to be equal to or greater than a size S of
said detecting member in the circumferential direction thereof.
7. A flywheel structure of an outboard motor according to claim 1,
wherein said detecting member is a trigger pole projecting downward
towards the engine and the sensor mean s comprises a pulser coil
disposed to the engine.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a flywheel structure of an
outboard motor.
[0002] In an engine of, for example, an outboard motor, an ignition
plug generates spark to ignite air-fuel mixture in a cylinder to
burn the mixture. This combustion in the engine is closely related
to the ignition timing of the ignition plug, and in order to burn
the mixture efficiently, it is necessary to appropriately set the
ignition timing.
[0003] In the engine, a speed of a piston is increased as the
engine revolution number is increased, and thus, it is common to
set the ignition timing faster as the engine revolution number is
increased.
[0004] An apparatus for automatically advancing the ignition timing
in accordance with increase in the engine revolution number is
called an automatic (spark) advance system (automatic timer).
Conventionally, a mechanical automatic advance system utilizing a
difference in centrifugal force caused by revolution of the engine
has been used in many cases. Recently, in order to set more
appropriate the ignition timing, there has been used an electronic
automatic advance system utilizing the revolution number and
revolution angle of the engine (crankshaft), opening degree of a
throttle and the like as parameters to set the ignition timing that
is more suitable for a driving state by means of a
microcomputer.
[0005] In the case of an engine mounted in the outboard motor, in
which a crankshaft is disposed perpendicularly, the revolution
number and a revolution angle of the crankshaft are obtained by
detecting, by using a detection sensor or the like, a motion of the
detection member such as a trigger pole or the like provided on a
flywheel provided on an upper end of the crankshaft so that they
are rotated in unison (e.g., see Japanese Patent Laid-open
Publication No. HEI 10-22026).
[0006] In a known structure, the trigger pole projects from an
outer peripheral surface of the flywheel diametrically outward of
the flywheel, and the detection sensor is disposed outside the
trigger pole.
[0007] When the crankshaft also functions as a driving shaft for a
camshaft, the detecting member is disposed below a drive pulley
around which a timing belt is wound or the detecting member is
disposed between the flywheel and the drive pulley.
[0008] The flywheel is provided with a magneto or a ring gear that
is operatively connected to a drive gear of a starter motor so as
to be rotatable in unison.
[0009] However, in the case of an engine in which a flywheel is
provided with a ring gear, if a trigger pole, as a detecting
member, projects from the outer peripheral surface of the flywheel,
the detection sensor and the ring gear disposed outside the trigger
pole may adversely interfere with each other. Therefore, the ring
gear must consequentially be disposed at a higher position. As a
result, a position of the center of gravity of the engine becomes
higher, vibration of the crankshaft is increased, and there is an
adverse possibility that durability of the crankshaft and its
bearing may be lowered.
[0010] Further, in the case of an engine in which the detecting
member is disposed below the drive pulley or between the flywheel
and the drive pulley, a special procedure may be necessary for
guiding the timing belt, or the diameter of the detecting member is
reduced and the precision of the position (angle) of the detecting
member is lowered. Furthermore, since the diameter of the detecting
member is reduced, the starting revolution number (controllable
revolution number) of the engine is increased, and the starting
performance is deteriorated.
[0011] In the case of an engine having a flywheel provided with a
magneto, the magneto and the engine are heated to increase a
temperature around the engine, which speeds up deterioration of an
electrical equipment disposed therearound. Further, a wire used for
a stator coil of the magneto must have high heat resistance, which
will increase costs.
SUMMARY OF THE INVENTION
[0012] The present invention has been accomplished in view of the
above-described circumstances, and it is an object of the present
invention to provide a flywheel structure of an outboard motor
capable of lowering the center of gravity of an engine and
enhancing the starting performance of the engine.
[0013] It is another object of the present invention to provide a
flywheel structure of an outboard motor capable of facilitating the
cooling operation around the flywheel.
[0014] These and other objects can be achieved according to the
present invention by providing a flywheel structure of an outboard
motor in which a crankshaft is disposed perpendicularly in an
engine, a flywheel is disposed to an upper end portion of the
crankshaft to be rotatable in unison with the crankshaft and the
flywheel is provided with a detecting member a motion of which is
detected by a sensor means to thereby detect the number of
revolution and a revolution angle of the crankshaft, wherein the
detecting member is disposed in an axial direction of the
crankshaft.
[0015] In a preferred embodiment, the detecting member is arranged
on a lower surface of the flywheel along a circumferential
direction thereof, the detecting member is formed, at an outer end
thereof, with a centrifugal fan-shaped portion for discharging an
air inside of the detecting member to an outside thereof when the
flywheel is rotated.
[0016] The flywheel is provided at, an outer peripheral edge
portion thereof, with a ring gear for starting an engine, the
detecting member and the sensor means are disposed inside of an
outer diameter of the ring gear in a plan view.
[0017] Three or more numbers of the detecting members are arranged
on the lower surface of the flywheel at an equal distance from one
another in the circumferential direction thereof, a notch is formed
to each of the detecting members by removing a portion thereof.
[0018] The flywheel is provided, at an upper surface thereof, with
a fan member for introducing an air outside the flywheel into the
flywheel.
[0019] The detecting member has a size K in a diametrical direction
thereof, which is set to be equal to or greater than a size S of
the detecting member in the circumferential direction thereof.
[0020] The detecting member is a trigger pole projecting downward
towards the engine and the sensor means comprises a pulser coil
disposed to the engine.
[0021] As explained hereinabove, according to the present
invention, in a flywheel structure of an outboard motor for
detecting, by using a sensor means, a motion of a detecting member
provided on a flywheel which is formed on an upper end of a
crankshaft so that the flywheel is rotated in unison with the
crankshaft, thereby detecting the number of revolution and a
revolution angle of the crankshaft, and the detecting member is
disposed in an axial direction of the crankshaft. Therefore, the
position of the ring gear can be set lower, and the position of the
center of gravity of the engine can be lowered.
[0022] The detecting member is disposed on a lower surface of the
flywheel in its circumferential direction, the detecting member is
formed at its outer end with a centrifugal fan-shaped portion for
discharging the air inside the detecting member to the outside of
the detecting member when the flywheel is rotated. Therefore, the
space surrounded by the flywheel and the engine can be cooled
efficiently with a simple structure.
[0023] Further, the flywheel is provided, at its outer peripheral
edge, with a ring gear for starting an engine, the detecting member
and the sensor means are disposed inside of an outer diameter of
the ring gear as viewed from above. Therefore, the layout can be
made compact.
[0024] Furthermore, the number of the detecting member is three or
more, which are disposed on the lower surface of the flywheel at at
equal distance from one another in its circumferential direction,
and a notch is formed on each of the detecting members by removing
a portion thereof. Therefore, wind noise generated by the detecting
means at a time when the flywheel is rotated can be reduced.
[0025] Furthermore, the flywheel is provided at its upper surface
with a fan structure for introducing air outside the flywheel into
the flywheel. Therefore, the space surrounded by the flywheel and
the engine can be cooled efficiently with a simple structure.
[0026] Further, a size of each of the detecting members in its
diametrical direction is set to be equal to or greater than a size
of the detecting member in its circumferential direction.
Therefore, cranking noise generated when the engine is started is
reduced.
[0027] The nature and further characteristic features of the
present invention will be made clear from the following
descriptions made with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] In the accompanying drawings:
[0029] FIG. 1 is a right side view of an outboard motor showing one
embodiment of a flywheel structure of the outboard motor according
to the present invention;
[0030] FIG. 2 is an enlarged right side view of an engine portion
of the outboard motor shown in FIG. 1;
[0031] FIG. 3 a plan (top) view of the engine shown in FIG. 2;
[0032] FIG. 4 is a plan (top) view of the engine in a state in
which a ring gear cover is detached;
[0033] FIG. 5 is a sectional view taken along a V-V line in FIG.
4;
[0034] FIG. 6 is a lower surface view of a flywheel; and
[0035] FIG. 7 is a sectional view taken along a VII-VII line in
FIG. 6.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0036] An embodiment of the present invention will be explained
based on the drawings below.
[0037] FIG. 1 is a right side view of an outboard motor to which
the present invention is applied. As shown in FIG. 1, the outboard
motor 1 is mounted to a transom 4a of a hull 4 through a bracket 3
mounted to an engine holder 2. An engine 5 is disposed on an upper
portion of the engine holder 2.
[0038] Further, it is to be noted that the terms "upper", "lower",
"right", "left" and the like mentioned herein are used in a state
of the outboard motor in the illustrated state or mounted to a hull
in a usable state.
[0039] A crankshaft 6 is vertically disposed in the engine 5 such
that the crankshaft 6 is directed substantially in a vertical
direction. A drive shaft housing 8 is disposed at a lower portion
of the engine holder 2 through an oil pan 7.
[0040] A drive shaft 9 connected to a lower end of the crankshaft 6
extends downward in the oil pan 7 and the drive shaft housing 8.
The drive shaft 9 drives a propeller 13 through a bevel gear 11 and
a propeller shaft 12 arranged in a gear case 10 disposed in a lower
portion of the drive shaft housing 8.
[0041] The engine 5 is covered with an engine cover 14. The engine
cover 14 can be divided into an upper cover 14a and a lower cover
14b. An upper portion of the engine 5 is covered with the upper
cover 14a. The engine holder 2, the oil pan 7 and a lower portion
of the engine 5 are covered with the lower cover 14b.
[0042] FIG. 2 is an enlarged right side view of a portion of the
engine 5 shown in FIG. 5. FIG. 3 is a plan (top) view of the engine
5. As shown in FIGS. 2 and 3, the engine 5 is, for example, a
water-cooled four-stroke-cycle four-cylinder engine and comprises a
crankcase 15, a cylinder block 16, a cylinder head 17 and the like
arranged in the longitudinal direction.
[0043] An electrical equipment 18, a discharge device 19, an intake
device 20 and the like are disposed around the engine 5. The intake
device 20 is unified and disposed from left side to a front portion
of the engine 5, the discharge device 19 is disposed on the right
side of the engine 5, and the electrical equipment 18 is
accommodated in an electrical equipment box 21 disposed on the
right side of the engine 5 like the discharge device 19. Each of
devices (which will be described later) above the engine 5 is
covered with a ring gear cover 22.
[0044] FIG. 4 is a plan (top) view of the engine 5 in which the
ring gear cover 22 is detached, and FIG. 5 is a sectional view
taken along a V-V line in FIG. 4. As shown in FIGS. 1 and 5, an
upper end of the crankshaft 6 projects upward of the engine 5. The
flywheel 23 is provided on the projected end to be rotatable with
the crankshaft 6 in unison.
[0045] Although it is not described in detail, an upper end of a
camshaft 24 for a valve moving mechanism provided in the cylinder
head 17 in parallel to the crankshaft 6 also projects upward over
the engine 5, and a driven pulley 25 is provided on the projected
end such that the driven pulley 25 can rotate with the camshaft 24
in unison. A timing belt 27 is wound up around between the driven
pulley 25 and a driving pulley 26 provided on the crankshaft 6, so
that the rotation of the crankshaft 6 is transmitted to the
camshaft 24.
[0046] The engine 5 is provided, at its front upper portion, with a
starter motor 28 for starting the engine 5. The flywheel 23 is
provided, at its outer peripheral edge, with a ring gear 29. A
drive gear 28a of the starter motor 28 and the ring gear 29 are
operatively connected to each other so that the rotation driving
force of the starter motor 28 is transmitted to the crankshaft
6.
[0047] The flywheel 23, the starter motor 28, the ring gear 29, the
driven pulley 25 and the timing belt 27 are covered with the ring
gear cover 22.
[0048] As shown in FIG. 5, a magneto 30 is disposed in the flywheel
23. A central portion of the flywheel 23 is formed into an
inverted-concave (gate) shape so as to cover the magneto 30 from
above. The magneto 30 comprises a stator coil 31 fixed on the side
of the engine 5, and a permanent magnet 32 disposed in the
inverted-concave portion 23a of the flywheel 23 opposed to the
stator coil 31. By rotating the flywheel 23, AC current is
generated in the stator coil 31.
[0049] FIG. 6 shows a lower surface of the flywheel 23. As shown in
FIGS. 5 and 6, trigger poles 33, as detecting members, are provided
outside of an outer diameter of a mounting boss 23b of the flywheel
23 and inside of an outer diameter of the ring gear 29. The trigger
poles 33 are disposed in an axial direction of the crankshaft 6 and
project downward (towards the engine 5) in the present embodiment.
A sensor means 34 (pulser coil), as a sensor means, is provided
inside the outer diameter of the ring gear 29 on the engine 5 as
viewed from above (i.e. in a plan view).
[0050] As shown in FIG. 6, the number of the trigger poles 33 is
three or more, and the trigger poles 33 are disposed in and along
the circumferential direction at an equal distance from one
another, and in the present embodiment, the trigger poles 33 are
arranged at 10.degree.(crank angle) from one another. A portion
(e.g., adjacent two) of the trigger pole 33 is removed, and a notch
35 having an angle of 30.degree. (crank angle) is formed. In the
present embodiment, a total 34 (thirty-four) triggers poles 33 are
provided.
[0051] A size K of each of the trigger poles 33 in its diametrical
direction is set to be equal to or greater than a size S of the
trigger pole 33 in its circumferential direction (K.gtoreq.S). A
centrifugal fan-shaped portion 36 is formed on an outer end of the
trigger pole 33 so that an air inside the trigger pole 33 to the
outside of the trigger pole 33 when the flywheel is rotated.
[0052] FIG. 7 is a sectional view taken along a VII-VII line in
FIG. 6. As shown in FIGS. 5 to 7, an upper surface of the
inverted-concave (gate-shape) portion 23a of the flywheel 23
covering the magneto 30 is provided with a fan structure 37 for
introducing air outside the gate-shaped portion 23a thereinto. The
ring gear cover 22 immediately above the fan structure 37 is formed
with an intake port 38. A side surface of the ring gear cover 22 is
formed with a discharge port 39.
[0053] An operation of the present embodiment will be explained
hereunder.
[0054] When the engine 5 is started to rotate the crankshaft 6, the
flywheel 23 is also rotated. When the flywheel 23 is rotated and
each of the trigger poles 33 moves across above the detecting
sensor 34, an electric signal (sensor signal) is outputted to the
detecting sensor 34, and this electric signal is utilized for
detecting the ignition timing.
[0055] When the flywheel 23 rotates, the fan structure 37 provided
on the upper surface of the flywheel 23 introduces the outside air
from the intake port 38 on the upper surface of the ring gear cover
22 into the inverted-concave portion 23a of the flywheel 23,
thereby cooling the magneto 30 that is heated by power-generating
operation and the upper portion of the engine 5.
[0056] The centrifugal fan-shaped portion 36, for discharging the
air inside the trigger pole 33 to the outside of the trigger pole
33 when the flywheel 23 is rotated, is formed on the outer end of
the trigger pole 33. Therefore, the air cooling the magneto 30 and
the upper portion of the engine 5 is discharged from the discharge
port 39 formed in the side surface of the ring gear cover 22.
[0057] Air flow as shown with arrow in FIG. 5 is generated by the
fan structure 37 provided on the upper surface of the flywheel 23
and the centrifugal fan-shaped portion 36 provided on the outer end
of the trigger pole 33. This air flow is further facilitated by the
air discharged by the ring gear 29 so that space surrounded by the
flywheel 23, and the engine 5 is cooled efficiently.
[0058] Since the space is cooled efficiently, a temperature of the
stator coil 31 is prevented from increasing, the durability of the
stator coil 31 is enhanced, and costs required for a wire (not
shown) used for the stator coil 31 are reduced.
[0059] Conventionally, since the trigger pole projects on an outer
peripheral surface of the flywheel, the detection sensor and the
ring gear disposed outside the trigger pole may adversely interfere
with each other and thus, the ring gear must be disposed at a
higher position. However, in the present invention, the trigger
pole 33 provided on the lower surface of the flywheel 23 is
disposed in the axial direction of the crankshaft 6 so as to
project towards the engine 5 disposed below. Therefore, it is
possible to lower the position of the ring gear 29. As a result,
the position of the center of gravity of the engine 5 is lowered,
vibration of the crankshaft 6 is reduced, the stress applied to the
crankshaft 6 is reduced, and the durability of the crankshaft 6 and
its bearing, not shown, is enhanced.
[0060] The trigger pole 33 is provided outside the outer diameter
of the mounting boss 23b of the flywheel 23 and inside of the outer
diameter of the ring gear 29. Therefore, a positional (angle)
precision of the trigger pole 33 is enhanced, the angle speed is
increased and thus, a sensor signal is outputted correctly even in
a low revolution region of the engine 5, and the number of starting
revolution of the engine 5 (controllable revolution number) is
reduced, thus enhancing the starting performance of the engine
5.
[0061] Further, the size K of each of the detecting members 33 in
its diametrical direction is set to be equal to or greater than the
size S of the detecting member 33 in its circumferential direction
(K.gtoreq.S). Therefore, a time during which the trigger pole 33
and the detecting sensor 34 are opposed to each other is shortened,
and cranking noise (meshing noise) generated when the engine 5 is
started is reduced.
[0062] Further, since a portion of the trigger poles 33 which are
arranged at equal distances from each other in the circumferential
direction is removed so as to form the notch 35, wind noise
generated at a time when the trigger pole 33 functions as a
centrifugal fan is reduced.
[0063] Since the trigger pole 33 is provided inside the outer
diameter of the ring gear 29, an escape shape is unnecessary for
the ring gear cover 22, and the shape of the ring gear cover 22 is
simplified, and the entire structure can be made compact.
[0064] Further, since the trigger pole 33 is disposed in the axial
direction of the crankshaft 6, the detecting sensor 34 can also be
disposed in the axial direction of the crankshaft 6. As a result, a
position of the detecting sensor 34 can be lowered, and noise
caused through the vibration of the engine 5 and the like can be
suppressed from entering into the detecting sensor 34.
* * * * *