Internal-combustion engines – Poppet valve operating mechanism – Camshaft drive means
Reexamination Certificate
2000-09-01
2002-07-30
Walberg, Teresa (Department: 3742)
Internal-combustion engines
Poppet valve operating mechanism
Camshaft drive means
C123S1950HC, C123S1950HC, C440S012610
Reexamination Certificate
active
06425360
ABSTRACT:
RELATED APPLICATIONS
This application is based on Japanese Patent Application No. 11-249317, filed Sep. 2, 1999, the entire contents of which is hereby expressly incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to valve driving arrangements for outboard motors. More specifically, the present invention relates to an improved compact arrangement of valve driving components.
2. Related Art
Outboard motors are used to power watercraft to the water. The outboard motors are mounted to the transom or rear portion of the watercraft and provide a forward or reverse thrust. Because the outboard motor extends upward above a portion of the watercraft, the outboard is exposed to passing air streams caused by the movement through the water. Accordingly, the outboard motor can be a source of wind resistance or drag during movement through the water. This wind resistance results in decreased watercraft speeds or increased loading on the outboard motor.
Accordingly, it is desired to decrease the size of the exposed portion of the outboard motor. In some configurations, the outboard motors is decreased in a lateral direction while in other arrangements the engine is decreased in a vertical direction. By designing a more compact engine, the overall dimensions of the outer cowling, which surrounds the engine, can be decreased.
With reference now to
FIG. 1
, a typical outboard motor
10
is illustrated therein. In an effort to decrease the lateral dimension of the outboard motor
10
, a pair of cylinder banks
11
have been designed with cylinders
12
that are offset from one cylinder bank to the other. In particular, the engine generally comprises a V-type configuration having a first bank of cylinders
12
and a second bank of cylinders
12
. The first bank of cylinders comprises a plurality of cylinders
12
having a corresponding plurality of central axes A that extend through the cylinder bores while the second bank of cylinders is similarly comprised. As will be appreciated, one bank of cylinders is offset by approximately half of the diameter of cylinder bores in the other bank. Such a configuration allows the cylinder and the lateral dimension of the cylinder block to be decreased. This configuration, however, has ordinarily resulted in an increased height to the outboard motor due to an increased vertical dimension required to accommodate a cam shaft drive arrangement
14
.
The cam shaft drive arrangement
14
typically uses rotational motion from the crankshaft to drive the intake cam shaft
15
and the exhaust cam shaft
16
. The intake cam shaft
15
powers the intake valves while the exhaust cam shaft
16
powers the exhaust valves. Generally, as shown in
FIG. 1
, power is taken from the crankshaft into one of the intake cam shafts
15
or one of the exhaust cam shafts
16
. The power taken from the crankshaft into one of the cam shafts
15
,
16
is then transferred to the other of the paired cam shafts
15
,
16
. For instance, in the illustrated arrangement, power is taken from the crankshaft and transferred to the intake cam shaft
15
of the left cylinder bank and the exhaust cam shaft
16
of the right cylinder bank. The rotational motion then is transferred from the exhaust cam shaft
16
of the right cylinder bank to the intake cam shaft
15
of the right cylinder bank through a drive pulley
17
and a driven pulley
18
that are connected with a flexible transmitter
19
, such as a belt. Similarly, power is transferred from the exhaust cam shaft
16
of the left cylinder bank to the intake cam shaft
15
of the left cylinder bank through a drive pulley
17
and a driven pulley
18
that are connected with a flexible transmitter
19
.
This arrangement, however, results in the undesirable increase in the vertical dimension of the engine. As illustrated in
FIG. 1
, the length of the cam shafts
15
,
16
in the left cylinder bank must be increased to place the input pulley
13
at an appropriate location relative to the input pulley
13
of the cam shafts
15
,
16
of the right cylinder bank. Elongating the cam shafts results in the undesirable increase in the vertical dimension of the outboard motor. In addition, increasing the length of the cam shafts
15
,
16
increases the weight of the engine due to the excess material of the cam shaft extension. Furthermore, the strength of the elongated cam shafts must be increased to withstand the loading on the increased length of the cam shaft.
SUMMARY OF THE INVENTION
Accordingly, a more compact cam shaft drive arrangement is desired. Such an arrangement desirably should decrease the overall length of at least one set of cam shafts. The cam shaft drive arrangement preferably takes advantage of an offset cylinder configuration.
One aspect of the present invention involves an engine for use in an outboard motor. The engine comprises a pair of cylinder banks. A first set of cylinder bores is disposed in a first cylinder bank of the pair of cylinder banks. A second set of cylinder bores is disposed in a second cylinder bank of the pair of cylinder banks. A first plane is defined through central axes of the first set of cylinder bores and a second plane is defined through central axes of the second set of cylinder bores. The first plane and the second plane intersect at an angle. The engine has a first end surface. A crankshaft has a power take off end that extends through the first end surface. The first set of cylinder bores has a first end cylinder bore and the second set of cylinder bores has a second end cylinder bore. The first end cylinder bore is positioned closer to the first end surface than the second end cylinder bore. A first intake cam shaft and a first exhaust cam shaft are associated with the first cylinder bank and a second intake cam shaft and a second exhaust cam shaft are associated with the second cylinder bank. Power from the crankshaft drives the first intake cam shaft, the first exhaust cam shaft, the second intake cam shaft and the second exhaust cam shaft. The first intake cam shaft and the first exhaust cam shaft are joined by a first drive connection and the second intake cam shaft and the second exhaust cam shaft are joined by a second drive connection. The second drive connection is positioned at an end of the second intake cam shaft and the second exhaust cam shaft that is closest to the first end surface and the first drive connection is positioned at an end of the first intake cam shaft and the first exhaust cam shaft that is farthest from the first end surface.
Another aspect of the present invention involves an engine comprising a crankshaft and a cylinder block that comprises a first cylinder bank and a second cylinder bank. The cylinder block has a first end and an opposing second end. The crankshaft has a power take off end that extends through the first end of the cylinder block. The engine comprises a first set of cam shafts that are associated with the first cylinder bank and a second set of cam shafts that are associated with the second cylinder bank. The first set of cam shafts are coupled for rotation proximate the first end of the cylinder block and the second set of cam shafts are coupled for rotation proximate the second end of the cylinder block.
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Dahbour Fadi H.
Knobbe Martens Olson & Bear LLP
Sanshin Kogyo Kabushiki Kaisha
Walberg Teresa
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