Marine propulsion – Screw propeller – Shafting
Reexamination Certificate
2000-06-29
2003-04-15
Basinger, Sherman (Department: 3617)
Marine propulsion
Screw propeller
Shafting
C440S075000
Reexamination Certificate
active
06547613
ABSTRACT:
PRIORITY INFORMATION
This inventions based on and claims priority to Japanese Patent Application No. Hei 11-186192, filed Jun. 30, 1999, the entire contents of which is hereby expressly incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a marine drive transmission, and more particularly to an improved marine drive transmission that absorbs a shift shock.
2. Description of Related Art
A wide variety of marine propulsion units propel watercraft. For instance, outboard motors commonly power boats and other watercraft. Stern drive units, which include an inboard motor and an outboard drive, also are often used to power boats and watercraft.
A typical outboard motor includes a power head atop a drive unit. The power head includes an internal combustion engine having an output shaft extending generally vertically. A driveshaft housing depends from the power head and encloses a driveshaft that extends generally vertically from the output shaft. A lower unit further depends from the driveshaft housing. A propulsion shaft is provided therein and extends generally horizontally. The driveshaft and the propulsion shaft are coupled together within the lower unit so that the propulsion shaft extends normal to the driveshaft. A propulsion device, such as, for example, a propeller is affixed to an outer end of the propulsion shaft. A bevel gear transmission, for example, is provided between the driveshaft and the propulsion shaft and includes a forward, neutral, reverse shift mechanism for moving between forward, neutral and reverse positions. The engine powers the propeller through the driveshaft, bevel gear transmission and propulsion shaft. The propeller, thus, can propel the outboard motor and the associated watercraft in both forward and reverse directions, unless the shift mechanism is in the neutral position.
An outboard section of the stem drive unit has a construction similar to that of the outboard motor except that the engine is not positioned over the propulsion device. The engine is placed in the hull of the watercraft. A propulsion device of the stern drive unit, which typically is a propeller, is powered by the engine through the driveshaft and propulsion shaft combination (i.e., drive train arrangement) similar to that of the drive unit of the outboard motor.
Users continue to desire more powerful marine drives and prefer large propulsion units having engines which produce higher horsepower. An engine, for example, which operates on a four-stroke combustion principle and having multiple cylinders, can provide the desired increased horsepower.
However, when engaging these larger engines, the marine propulsion unit tends to jolt the occupants of the watercraft. The sudden movement gives the occupants an uncomfortable feeling. In other words, because the large-sized engine generates a relatively strong propulsive force, an uncomfortable shock is created by the abrupt change in direction of the propulsive force, particularly when the shift mechanism is shifted from the neutral position to the forward drive position or to the reverse drive position.
In order to address this problem, a shock absorbing device for the shift mechanism has been proposed in U.S. Pat. No. 4,747,796.
FIGS. 1 and 2
illustrate this type of coupling.
FIG. 1
is a cross-sectional, side elevational view of a transmission coupling
20
arranged to absorb the shock, and
FIG. 2
is a cross-sectional view of the coupling
20
taken along the line
2
—
2
of FIG.
1
.
With reference to these figures, a driveshaft
22
is divided into a drive section
24
and a driven section
26
and the coupling
20
joins these sections. The lower end of the drive section
24
has a depending socket
28
that defines an internal cavity
30
. An upper end portion
32
of the driven section
26
extends into the cavity
30
. Three blocks of elastic members
34
are interposed between the internal cavity
30
and the end portion
32
. As seen in
FIG. 2
, the socket
28
and its internal cavity
30
have a generally triangular configuration in section. The end portion
32
has a complementary triangular shape featuring three points
38
.
The coupling
20
provides vibration damping and force absorption under a low speed and low load condition. This damping is provided by the compressible elastic members
34
. When the driving load increases, the elastic members
34
are increasingly compressed and the points
38
of the projecting portion
32
directly contact the inner cavity
30
of the socket
28
. The torque of the drive section
24
is transmitted to the driven section
26
through this connection.
Because the transmission shift shock occurs under low speeds, the coupling
20
is quite useful for preventing the shock. However, another problem arises with this coupling
20
, namely, the driving force cannot be securely transferred from the drive section
24
to the driven section
26
when the driving load increases, because the driving force is conveyed to the inner cavity
30
by the contacts of the points
38
and these contacts are unreliable. Of course, the elastic members
34
also are involved in this force transferring mechanism; however, the elastic members
34
tend to slip within the cavity
30
and do not increase reliability.
SUMMARY OF THE INVENTION
Increasing the contact areas between the points
38
and the cavity
30
or using elastic members that have larger volumes could resolve the above-identified problems. Both of the improvements, however, would require enlarging the surrounding housing and would thereby interfere with the arrangement of other components disposed proximate the housing.
A need therefore exists for a marine drive transmission that can absorb a shock generated when a shift mechanism is operated. The transmission preferably has a compact structure comprising a coupling that can securely transmit the driving force from a drive section to a driven section after operation of the shift mechanism.
In accordance with one aspect of the present invention, a power transmission system for a marine propulsion unit is provided. The marine propulsion unit has a powering element and a propulsion device. The power transmission system comprises a first shaft driven by the powering element, and a second shaft driven by the first shaft and driving the propulsion device. The first and second shafts have a common axis. A coupling assembly is mounted on both the first and second shafts so as to couple the first and second shafts for rotation together. A damper is disposed next to the coupling assembly. The coupling assembly includes a pair. of coupling members. One of the coupling members is axially moveable along the common axis relative to the other coupling member to compress the damper at the moment the first shaft begins to drive the second shaft.
In accordance with another aspect of the present invention, a coupling for a power transmission is provided. The power transmission has a drive shaft and a driven shaft. The coupling comprises a first member. The first member is rotatable together with one of the drive shaft and the driven shaft and has at least one tooth extending axially. The coupling comprises also a second member. The second member is rotatable together with the other shaft and has at least one tooth extending axially to engage with the tooth of the first member. A damper is disposed next to the second member. Confinement members confine the first member, second member and the damper therebetween. The second member compresses the dampers when the drive shaft begins to rotate the driven shaft.
In accordance with a further aspect of the present invention, a marine drive comprises a shaft. The shaft includes a first section driven by a prime mover and a second section driven by the first section to drive a propulsion mechanism. A first coupling member is connected to one of the first and second sections by spline connection. A second coupling member is connected to the other section by spline connection. Both the first and second coupling
Onoue Akihiro
Yoshino Hisayoshi
Basinger Sherman
Knobbe Martens & Olson Bear LLP.
Sanshin Kogyo Kabushiki Kaisha
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