Information
-
Patent Grant
-
6332444
-
Patent Number
6,332,444
-
Date Filed
Friday, September 1, 200023 years ago
-
Date Issued
Tuesday, December 25, 200122 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
- Birch, Stewart Kolasch & Birch, LLP
-
CPC
-
US Classifications
Field of Search
US
- 123 196 R
- 123 198 R
- 123 198 C
-
International Classifications
-
Abstract
A power unit includes an engine portion and a transmission portion. The bottom portion of a crankcase of the power unit is formed into a shape, in which the right and left sides thereof are tilted downwardly toward a central portion. A main shaft, a counter shaft, and an output shaft of a transmission chamber are disposed one above the other on a right side of a crankshaft. An oil tank is disposed on a right side of the transmission. A bulkhead divides the transmission chamber from the oil tank. The oil tank is formed into an approximately crescent shape with its lower end extending under the output shaft. A suction port of a feed pump is provided in the lowest portion of the crescent shaped oil tank. An oil inlet is provided directly over the oil tank. An overflow hole for allowing oil to overflow into a transmission chamber is provided in the bulkhead. An oil pump is provided in the crank case on the left side of the crank shaft. A scavenging pump pumps up oil from an oil sump located at the lowest portion of the bottom of the crank case. A drain hole, provided in a lower portion of the crank case, communicates to both the oil tank and the transmission chamber. The drain hole is plugged with a drain bolt.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a dry sump type lubricating device for an internal combustion engine.
2. Description of the Relevant Art
In accordance with the background art, a dry sump structure includes an oil tank separated from an engine. Oil, having been used for lubrication, is collected on a bottom of a case of the engine, and is pumped up by a scavenging pump to be returned again to the oil tank. The bottom of the case is partially recessed, at the sacrifice of the height of the engine, so that oil can be collected in the recessed bottom, and pumped up therefrom by the scavenging pump.
For example, Japanese Patent Laid-open No. Hei 4-298618 discloses a dry sump type lubricating device in which an oil tank is provided under a clutch in a crank case. Japanese Utility Model Publication No. Sho 56-54321 discloses a dry sump type lubricating device in which an oil pan is provided as an oil sump on the bottom of a crank case.
In the above-described background art, the lowest portion of the case must be further recessed for ensuring the pumping performance of the scavenging pump. Further, the pumping must be performed from the lower portion of the recess. This arrangement results in an overall height increase of the engine. Also, since the background art's lubricating devices use an oil pan, the number of parts is increased, and the weight and cost of the engine are increased. Further, a portion of the feed pump and scavenge pump are located on a tank side of the case, thereby enlarging the size of the case on the tank side and complicating the layout of the engine.
SUMMARY OF THE INVENTION
It is an object of the present invention to solve one or more of the drawbacks associated with the background art.
These and other objects are accomplished by an internal combustion engine comprising: a crankcase; an oil tank formed inside said crankcase; an oil pump including a feed pump and a scavenge pump, said feed pump for supplying lubricating oil inside said oil tank to respective components of the internal combustion engine, and said scavenge pump for returning lubricating oil that has accumulated in a bottom of said crankcase to said oil tank; a crankshaft disposed in said crankcase; a transmission chamber disposed in said crankcase to one side of said crankshaft; and a transmission including a main shaft, a counter shaft, and an output shaft disposed in said transmission chamber, wherein said oil tank is disposed on a side of said transmission chamber opposite said crankshaft, and wherein said oil tank has an approximately crescent shaped cross section, with a lower end of said cross section extending under at least one of said main shaft, said counter shaft, and said output shaft.
Further, these and other objects are accomplished by a combination comprising: a vehicle; and an internal combustion engine including: a crankcase; an oil tank formed inside said crankcase; an oil pump including a feed pump and a scavenge pump, said feed pump for supplying lubricating oil inside said oil tank to respective components of the internal combustion engine, and said scavenge pump for returning lubricating oil that has accumulated in a bottom of said crankcase to said oil tank; a crankshaft disposed in said crankcase, with said crankshaft extending in a direction parallel to a direction of travel of said vehicle; a transmission chamber disposed in said crankcase to one side of said crankshaft; and a transmission including a main shaft, a counter shaft, and an output shaft disposed in said transmission chamber, wherein said oil tank is disposed on a side of said transmission chamber opposite said crankshaft, and wherein said oil tank has an approximately crescent shaped cross section, with a lower end of said cross section extending under at least one of said main shaft, said counter shaft and said output shaft.
Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitative of the present invention, and wherein:
FIG. 1
is a front view illustrating an arrangement of respective shafts in a crankcase, in accordance with the present invention;
FIG. 2
is a side view of an ATV including a power unit, in accordance with the present invention;
FIG. 3
is a partial cross sectional view of the power unit of
FIG. 2
;
FIG. 4
is a diagram illustrating a flow of oil through a lubrication system, in accordance with the present invention;
FIG. 5
is a cross sectional view illustrating an oil pump of the lubricating system;
FIG. 6
is a front view illustrating a front case cover;
FIG. 7
is a front view of a front case of a crankcase;
FIG. 8
is a front view of the front case of the crankcase, with a starting clutch removed;
FIG. 9
is a rear view of the front case illustrating a joining surface of the front case for mating to a rear case; and
FIG. 10
is a cross sectional view taken in a longitudinal direction of the crankcase illustrating an oil sump pump of the oil pump.
DETAILED DESCRIPTION OF THE INVENTION
A description will now be given of an embodiment of the present invention applied to a four-wheeled buggy or all-terrain vehicle (ATV). As illustrated in
FIG. 2
, the four-wheeled buggy is provided with a pair of left and right front wheels
2
and a pair of left and right rear wheels
3
, taken in a longitudinal direction of the vehicle frame
1
. A power unit
4
, comprising an engine and a transmission
44
, is supported in a central portion of the vehicle frame
1
. The power unit
4
has a transverse structure, wherein a crankshaft
5
extends in the longitudinal direction of the vehicle.
The four-wheeled buggy is a four-wheel drive type. An output shaft
6
is provided parallel to the crankshaft
5
and below the power unit
4
. The front wheels
2
are driven via a front wheel propeller shaft
7
connected to the output shaft
6
. The rear wheels
3
are driven via a rear wheel propeller shaft
8
connected to the output shaft
6
.
A front side of a crankcase
10
, constituting the power unit
4
, is covered by a front case cover
11
. A rear side is covered by a rear case cover
12
. These case covers
11
,
12
house the power unit
4
.
The crankcase
10
is also longitudinally partitioned into a front case
10
a
and a rear case
10
b.
A cylinder block
13
, a cylinder head
14
and a cylinder head cover
15
are attached to an upper part of the crankcase
10
. A carburetor
16
is connected to an intake port of the cylinder head
14
. An air cleaner
17
is connected to a rear side of the carburetor
16
. An exhaust pipe
18
is connected to an exhaust port of the cylinder head
14
.
An oil cooler
20
is arranged in front of the power unit
4
with a cooling surface facing toward the traveling direction of the ATV The oil cooler
20
receives oil from the crankcase
10
via a feed side hose
21
, and returns oil to the crankcase via a return side hose
22
. An oil pump
62
, in the crankcase
10
, facilitates the circulation of oil. The ATV also includes a cooling fan
23
, a handlebar
24
, a fuel tank
25
, and a saddle type seat
26
.
FIG. 3
is a cross sectional view of a transmission mechanism portion of the power unit
4
. As set forth above, the front side of the crankcase
10
is covered by a front case cover
11
, while the rear side is covered by the rear case cover
12
. The crankcase
10
, and the front and rear covers
11
,
12
constitute the power unit case. Also, the cylinder block
13
, the cylinder head
14
and the cylinder head cover
15
are attached to an upper part of the crankcase
10
.
The crankcase
10
is made up of two longitudinally divided sections, namely the front case
10
a
and the rear case
10
b.
The crankshaft
5
is fitted between the front case
10
a
and the rear case
10
b.
A starting clutch
40
, such as a well-known centrifugal clutch mechanism, is provided on one end of the crankshaft
5
. An AC generator (ACG)
41
is provided on the other end of the crankshaft
5
. The cross sectional view of
FIG. 3
also illustrates a connecting rod
42
and a piston
43
.
The transmission
44
may be constructed as a well-known constant-mesh transmission. The transmission
44
includes a main shaft
45
and a counter shaft
46
arranged parallel to the crankshaft
5
. A speed change clutch, or centrifugal clutch,
47
is provided on one end of the main shaft
45
. The speed change clutch
47
selectively couples and disconnects a drive force of the crankshaft
5
to the main shaft
45
. A plurality of constant mesh transmission gear trains
48
are provided between the main shaft
45
and the counter shaft
46
. The gear trains
48
are used to selectively change a rotation speed at which the counter shaft
46
is driven by the main shaft
45
. Rotation of the counter shaft
46
is output from a final drive gear
49
, provided on one end of the counter shaft
46
, to a final driven gear
50
on the output shaft
6
.
FIG. 1
is a schematic diagram illustrating the layout of each shaft in the rear case
10
b.
FIG. 1
depicts the parting plane of the rear case
10
b
and the front case
10
a,
seen from a front side of the vehicle. The transmission
44
is arranged on the right side of the crankshaft
5
. An oil tank
51
is provided on an end of the transmission
44
, to the right of the transmission
44
. The oil tank
51
is formed between the front case cover
11
and the front case
10
a,
and between the front case
10
a
and the rear case
10
b.
The oil tank
531
is partitioned from a transmission chamber
52
, housing the transmission
44
, by a partitioning wall or bulkhead
53
.
The bulkhead
53
starts from an upper end of the rear case
10
b,
extends along the right side of the transmission
44
, and reaches to a bottom portion
54
of the rear case
10
b.
A lower end of the bulkhead
53
extends below the output shaft
6
. The oil tank
51
is longer in the vertical direction, and as a result, the oil tank
51
is formed into a substantially crescent shape, when viewed from the front (as illustrated in FIG.
1
).
Each of the front case
10
a
and the rear case
10
b
of the crankcase
10
has the same contour or outline shape, in the plane of FIG.
1
. The bottom section
54
slopes towards the center, via a left sloping surface
54
c
on the left side and a right sloping surface
54
a
on the right side, becoming narrower towards the center, with a central portion being the lowest point. A lower end of the bulkhead
53
is connected to a connection point between the right sloping section
54
a
and a central section
54
b,
forming the bottom of the oil tank
51
. The connection point of the three wall sections is punched out towards the bulkhead
53
, so that a drain hole
55
communicates with both the oil tank
51
and the transmission chamber
52
. A drain bolt
56
is fitted into this drain hole
55
. An oil inlet
57
is provided in an upper part of the oil tank
51
.
A cam shaft
58
and a balancer shaft
59
are arranged parallel with each other. The cam shaft
58
and the balancer shaft
59
are located on the left side of the crankshaft
5
. In other words, the cam shaft
58
and the balancer shaft
59
are located on a side opposite to the transmission
44
relative to the crankshaft
5
. The camshaft
58
is driven by the crankshaft
5
, via a cam chain
60
. The balancer shaft
59
is also driven by the crankshaft
5
, so that a balancer
61
, on the balancer shaft
59
, rotates in synchronism with the crankshaft
5
. The balancer shaft
59
is linked to the oil pump
62
at its front end, and drives the oil pump
62
.
Referring to
FIG. 4
, the oil pump
62
includes a feed pump
63
and a scavenge pump
64
. The feed pump
63
and the scavenge pump
64
have respective rotors on the same drive shaft, and are preferably integrally formed. The feed pump
63
sucks oil from the oil tank
51
and supplies the oil, through an oil filter
65
, to respective lubrication sections of the engine. The scavenge pump
64
draws oil from an oil sump
66
, which is formed, for instance, at the central section
54
b
of the bottom section
54
, sends the oil to the oil cooler
20
. After the oil passes through the oil cooler
20
, the oil is returned to the oil tank
51
. A relief valve
67
is provided inside the discharge passageway of the feed pump
63
. If the discharge pressure of the feed pump
63
exceeds a specified pressure, an escape is opened to the discharge passageway of the scavenge pump
64
.
FIG. 5
is a cross section drawing illustrating the oil pump
62
. The feed pump
63
and the scavenge pump
64
are integrally formed with each other inside a common pump housing. A feed pump rotor
70
for the feed pump
63
and a scavenge pump rotor
71
for the scavenge pump
64
are arranged on a common drive shaft
68
, while being disposed on opposite sides of a dividing or partition wall
69
. The drive shaft
68
is arranged coaxially with the balancer shaft
59
. The drive shaft
68
is arranged to the front of the front case
10
a,
while the balancer shaft
59
is arranged between the front case
10
a
and the rear case
10
b.
The drive shaft
68
and the balancer shaft
59
are connected and rotate integrally.
In
FIG. 5
, a feed pump pipe
72
for the feed pump
63
is connected to an inlet
73
of the feed pump
63
. A scavenge pump discharge port
74
of the scavenge pump
64
leads to a discharge passageway
75
formed in the front case cover
11
. One end of the feed side hose
21
is connected to an outlet
76
of the discharge passageway
75
.
A balancer gear
78
is provided on the balancer shaft
59
. The balancer gear
78
meshes with a balancer drive gear
79
formed on the crankshaft
5
. A cam sprocket
80
is provided at one end of the cam shaft
58
. The cam sprocket
80
is driven by a drive sprocket provided on the crankshaft
5
, via the cam chain
60
. A cam
81
on the cam shaft
58
drives a valve mechanism on the cylinder head
14
side, via a push rod
82
.
FIG. 6
shows the front case cover
11
from the front.
FIG. 7
shows the front case
10
a
from the front with part of the front case cover
11
cut away.
FIG. 8
shows a front cover attaching surface of the front case
10
a
with the starting clutch
40
removed.
FIG. 9
shows a surface of the front case
10
a,
to which the rear case
10
b
would be attached.
In
FIGS. 6-9
, the bottom section
54
of the front case
10
a
has a shape becoming narrower towards the bottom. The feed pump
63
of the oil pump
62
draws up oil from an inlet
85
(
FIG. 9
) provided at a lower end of the oil tank
51
via the feed pump pipe
72
. The inlet
85
is formed at a lower end of the oil tank
51
wrapping around to the bottom of the output shaft
6
(FIG.
8
). The feed pump pipe
72
runs over the starting clutch
40
and leads to a rear side of the starting clutch
40
, and is piped to below the crankshaft
5
and the centrifugal clutch
47
.
The feed pump
63
discharges oil from a discharge passageway
86
(
FIG. 8
) to the oil filter
65
(FIG.
7
). The discharge outlet
87
of the oil filter
65
communicates with an oilway
88
facing towards the center of the crankshaft
5
formed in the front case cover
11
. A filter housing
84
is provided in an upper shoulder of the front case cover
11
. The oilway
88
is connected at the same time to an oilway
89
formed running through the center of the crankshaft
5
and to an oilway
90
formed running upwards above the front case cover
11
. The oilway
90
supplies oil to parts other than the crankshaft
5
, such as a valve mechanism and the transmission
44
.
The scavenge pump
64
draws up oil from an inlet
91
through a scavenge pump pipe
92
, using an oil sump
66
provided in the center section
54
b.
The scavenge pump pipe
92
runs diagonally along the direction of the sloping surface
54
c,
and has a middle section which is fastened to the front case
10
a
by a clip
93
.
As shown in
FIG. 6
, an oil outlet
76
from the scavenge pump
64
is provided at a central section in the vertical direction of a front left end of the front case cover
11
, at a position overlapping the oil pump
62
. A return port
94
, in communication with the return side hose
22
(
FIG. 2
) from the oil cooler
20
, is provided in the right upper section of the front case, at a position overlapping the oil tank
51
. Oil, returned from the oil cooler
20
, enters the return port
94
and passes into sections of the oil tank
51
between the front case cover
11
and the front case
10
a.
As shown in
FIG. 7
, a dividing or partition wall
95
is provided in the oil tank
51
for partitioning the inside of the oil tank
51
into a portion on the front case
10
a
side and a portion on the rear case
10
b
side. The partition wall
95
is provided with a rib
95
a,
and a communicating hole
96
communicated to the rear case
10
b
side. The communicating hole
96
is provided in the lower portion of the partition wall
95
at a position slightly elevated relative to the output shaft
6
.
Oil entering between the front case cover
11
and the front case
10
a
flows through the communicating hole
96
to the oil tank
51
formed between the front case
10
a
and the rear case
10
b.
During the flow of oil to the oil tank
51
, gas-liquid separation for the oil is promoted.
As shown in
FIG. 9
, a slot
97
is provided in an upper part of the bulkhead
53
, and communication is established between the oil tank
51
and the transmission chamber
52
. The height of the slot
97
is substantially the same as the height of the oil inlet
57
. The slot
97
acts as an overflow to the inside of the transmission chamber, if supply to the oil tank
51
fills up. A number of ribs
98
are formed in the surface of the partition wall
95
on the rear case
10
b
side.
FIG. 9
also illustrates a bearing hole
100
for the main shaft, a bearing hole
101
for the counter shaft, and a bearing bole
102
for the output shaft.
FIG. 10
illustrates the structure of the oil sump
66
. The oil sump
66
is formed in a section located at the juncture of the front case
10
a
and the central section
54
b
of the rear case
10
b.
A strainer
103
is contained in this space, with a rear portion of the strainer
103
supported by a wall section
104
of the rear case lob. A scavenge pump inlet passageway
105
communicates with the oil sump
66
in the front case
10
a.
A lower end of the scavenge pump pipe
92
is connected to a tip opening section of the inlet passageway
105
.
FIG. 10
also illustrates a shift drum
106
, a stopper arm
107
, a return spring
108
, a reverse switching shaft
109
, a stopper sensor arm
110
, and a stopper position detection switch
111
.
Next, operation of the present invention will be described. Oil, after lubrication, drops down to the bottom
54
of the crankcase
10
. Since the left and right of the crankcase
10
becomes narrower toward the bottom section
54
, the oil easily accumulates in the oil sump
66
of the central section
54
b,
which is the lowest part of the crankcase
10
. Oil accumulating in the oil sump
66
is drawn into the scavenge pump
64
housed inside the oil pump
62
via the scavenge pump pipe
92
. This oil is sent through a discharge outlet
74
, through a discharge outlet
75
, formed in the front case cover
11
, and through an outlet
76
to the sending side hose
21
. The sending side hose
21
sends the oil to the oil cooler
20
. Oil that has been cooled in the oil cooler
20
is returned to an upper section of the oil tank
51
, via the return side hose
22
and the return outlet
94
.
In this way, since the oil pump
62
and the oil tank
51
are provided on the left and right sides of the crankcase
10
, the outlet
76
and the return port
94
can be provided in the left and right surfaces of the upper portion of the front case cover
11
covering the front case
10
a.
Accordingly, the outlet
76
and the return port
94
can be separately connected nearly in straight lines to the inlet and outlet provided in the left and right surfaces of the oil cooler
20
using the feed side hose
21
and the return side hose
22
. As a result, the feed side hose
21
and the return side hose
22
can be made relatively short, and the piping layout can be simplified. This results in a reduction both in weight and cost, and also simplifies the assembly and maintenance procedures.
Furthermore, since the oil tank
51
and the oil pump
62
are arranged on the left and right sides of the crankshaft
5
, the left side (the side on which the oil tank
51
is provided) of the oil cooler
20
facing to the front case cover
11
may be taken as the outlet and connected to the return side hose
22
. The right side (the side on which the oil pump
62
is provided) of the oil cooler
20
may be taken as the inlet and connected to the feed side hose
21
. With this arrangement, the feed side hose
21
and the return side hose
22
can be separated from each other and can be laid out in nearly straight lines. As a result, feed side hose
21
and the return side hose
22
can be made relatively short and the piping layout is simplified.
Since the oil tank
51
is elongated in the vertical direction and has a substantially crescent shape, and also since the crankcase
10
becomes narrower towards the bottom, oil is efficiently sent in to the inlet
85
at the lowest point, the capacity of the oil tank
51
can be made as large as a half or more of the total capacity of the crankcase
10
, and the variation of the oil level is thus reduced. Since the oil tank
51
is provided in the crank case
10
, the center of gravity is lowered and the weight of the parts is more concentrated, so that a change in the center of gravity due to variations in the oil level is reduced.
According to the present invention, the oil recovery rate or ratio is high and there is no need to use a special oil pump because the scavenge pump
64
draws up oil from the oil sump
66
, which is located in the lowest part of the crankcase
10
wherein the crankcase becomes narrower towards the bottom. As a result, no special oil pan is required. Thus, ground clearance is increased, the overall height of the engine is reduced, and the oil passageways are shortened. Shortening the oil passageways shortens the time required to supply oil to portions of the engine to the lubricated.
According to the present invention, oil is returned from the oil cooler
20
to the return inlet
94
of the front case cover
11
provided on an upper part of the oil tank
51
. The oil exiting from the return inlet
94
collides with the partition wall
95
of the oil tank
51
. The oil then drops down downwardly and comes into contact with a number of the plurality of ribs
95
a.
This path of the oil exiting from the return inlet
94
causes air entrapped in the oil to be easily separated from the oil, thus facilitating gas-liquid separation of air within the oil. Moreover, movement of the oil through the communication hole
96
inside the oil tank
51
also promotes gas-liquid separation.
The plurality of ribs
95
a
and
98
not only serve to promote air-oil separation, the ribs
95
a
and
98
also act as structural reinforcement members. By reinforcing the walls of the oil tank
51
, resonance due to vibration of the walls of the oil tank
51
is reduced or prevented.
Due to the slot
97
, provided on an upper part of the bulkhead
53
, excess oil in the oil tank
51
overflows from the slot
97
to the transmission chamber
52
. If the width of the slot
97
is set so that the slot
97
covers the overall width of the gear train, the meshing sections and sliding sections of the gear train immediately below the slot
97
, as well as sliding grooves of a shift drum, are lubricated. Because the oil tank
51
is usually filled, the feed pump
63
stably supplies oil to necessary lubrication locations.
The oil inlet
57
is provided just above the oil tank
51
. When oil is added, excess oil overflows into the transmission chamber
52
through the cutout
97
. As a result, it is easy to maintain an oil level inside the oil tank
51
at a specified level at all times. The present invention does not have an independent oil tank. However, by providing the overflow slot
97
, it is possible to ensure the oil level using the same procedure as in a normal wet sump structure.
Since the bottom
54
and the bulkhead
53
are punched out so that the drain hole
55
communicates with both the oil tank
51
and the transmission chamber
52
, a single drain hole
55
can be commonly used. Therefore, the number of manufacturing steps is minimized and only a single drain bolt
56
is used, thus reducing the number of parts. When the oil is changed, used oil is taken out from the drain hole
55
and new oil is put in through the inlet
57
. The oil level is checked and confirmed using a level gauge.
Still further, a cam sprocket
80
of the cam shaft
58
and the oil pump
62
are respectively separately arranged behind and in front of the balance shaft
59
. As a result, there is no danger of the oil pump
62
interfering with a cam chain
60
for driving the cam sprocket
80
. Therefore, it is possible to increase the size of the oil pump
62
without increasing the size of the crankcase
10
.
Further, oil pipe clips are arranged inside the starting clutch
40
, and the cam chain
60
is arranged between a balancer gear
78
and the ACG
41
, which means that a space for housing the oil tank
51
can be maintained more to the outside than these internal components. In this way, it is possible to design a more compact engine by more efficient use of space and to have more flexibility in arranging auxiliary devices and in planning the engine structure. Further, since there is no need to provide an independent oil tank, the advantages of a conventional dry sump structure are maintained, while also enjoying the advantages of simplifying the lubrication system.
This above described arrangement structure of the oil tank, transmission and auxiliary devices can also be used in engines other than engines for use with an ATV, and with engines which do not have an output shaft. When no output shaft is employed, the space of the output shaft may be assigned to the oil tank. As a result, an overall height of the right side may be reduced lower than the crank shaft, and it is possible to further slope the cylinder block to the right side using that empty space. As a result, it is possible to provide an engine having a low center of gravity with a reduced overall height. Also, it is possible to vertically divide connecting sections of the piping for the oil pump
62
and the oil tank
51
, so that the scavenge pump
64
and the upper part of the oil tank
51
are connected, and the feed pump
63
and the lower part of the oil tank
51
are connected.
In the lubricating device of the present invention, an oil tank is formed having a sufficient capacity without enlarging the size of the power unit case by making effective use of a space not interfering with transmission members. Also, by the crescent shape of the oil tank, an oil suction port provided at the lowest portion of the crescent shaped oil tank certainly and efficiently supplies oil to the feed pump. Moreover, the shape of the oil tank reduces a variation in the oil level.
In the lubricating device of the present invention, the piping between the oil tank and the oil pump is substantially eliminated. Therefore, the weight and costs are reduced. Moreover, the time required to supply oil to portions of the engine are shortened. Additionally, since the weights of parts are concentrated and the center of gravity is lowered, it is possible to reduce a change in the center of gravity due to a variation in oil level.
In the lubricating device of the present invention, a drain hole for communicating with the oil tank and the transmission chamber is provided under the oil tank and the transmission chamber. With this configuration, the drain hole is shared between the oil tank and the transmission chamber. Therefore, the number of manufacturing steps and the number of parts are reduced.
In the lubricating device of the present invention, a cutout for overflow is provided in the bulkhead. With this configuration, even if oil is excessively poured into the oil tank, the excess oil is allowed to overflow into the transmission chamber.
The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.
Claims
- 1. An internal combustion engine comprising:a crankcase; an oil tank formed inside said crankcase; an oil pump including a feed pump and a scavenge pump, said feed pump for supplying lubricating oil inside said oil tank to respective components of the internal combustion engine, and said scavenge pump for returning lubricating oil that has accumulated in a bottom of said crankcase to said oil tank; a crankshaft disposed in said crankcase; a transmission chamber disposed in said crankcase to one side of said crankshaft; a transmission including a main shaft, a counter shaft, and an output shaft disposed in said transmission chamber, wherein said oil tank is disposed on a side of said transmission chamber opposite said crankshaft, and wherein said oil tank has an approximately crescent shaped cross section, with a lower end of said cross section extending under at least one of said main shaft, said counter shaft, and said output shaft; and a drain hole formed in said crankcase, said drain hole communicating with said oil tank and with said transmission chamber.
- 2. The engine according to claim 1, further comprising:a bulkhead partitioning said oil tank from said transmission chamber.
- 3. The engine according to claim 2, wherein said bulkhead extends from a top of said crankcase to said bottom of said crankcase.
- 4. The engine according to claim 3, further comprising:a cutout formed in an upper portion of said bulkhead for allowing, when said oil tank is filled with oil, excess oil to overflow into said transmission chamber.
- 5. The engine according to claim 4, wherein said cutout is elevated relative to said main shaft, said counter shaft and said output shaft of said transmission.
- 6. The engine according to claim 2, wherein said drain hole extends into a portion of said bulkhead.
- 7. The engine according to claim 6, wherein said drain hole is a threaded hole communicating with a lower portion of said oil tank and with a lower portion of said transmission chamber, and further comprising:a threaded drain bolt engaged within said threaded hole.
- 8. The engine according to claim 1, further comprising:an oil filling inlet located above said oil tank.
- 9. The engine according to claim 1, wherein said main shaft is elevated relative to said counter shaft and said counter shaft is elevated relative to said output shaft.
- 10. The engine according to claim 9 wherein said oil tank extends under said output shaft.
- 11. A combination comprising:a vehicle; and an internal combustion engine including: a crankcase; an oil tank formed inside said crankcase; an oil pump including a feed pump and a scavenge pump, said feed pump for supplying lubricating oil inside said oil tank to respective components of the internal combustion engine, and said scavenge pump for returning lubricating oil that has accumulated in a bottom of said crankcase to said oil tank; a crankshaft disposed in said crankcase, with said crankshaft extending in a direction parallel to a direction of travel of said vehicle; a transmission chamber disposed in said crankcase to one side of said crankshaft; a transmission including a main shaft, a counter shaft, and an output shaft disposed in said transmission chamber, wherein said oil tank is disposed on a side of said transmission chamber opposite said crankshaft, and wherein said oil tank has an approximately crescent shaped cross section, with a lower end of said cross section extending under at least one of said main shaft, said counter shaft and said output shaft; and a drain hole formed in said crankcase, said drain hole communicating with said oil tank and with said transmission chamber.
- 12. The combination according to claim 11, further comprising:a bulkhead partitioning said oil tank from said transmission chamber.
- 13. The combination according to claim 12, wherein said bulkhead extends from a top of said crankcase to said bottom of said crankcase.
- 14. The combination according to claim 13, further comprising:a cutout formed in an upper portion of said bulkhead for allowing, when said oil tank is filled with oil, excess oil to overflow into said transmission chamber.
- 15. The combination according to claim 14, wherein said cutout is elevated relative to said main shaft, said counter shaft and said output shaft of said transmission.
- 16. The combination according to claim 11, further comprising:an oil filling inlet located above said oil tank.
- 17. The combination according to claim 11, wherein said main shaft is elevated relative to said counter shaft and said counter shaft is elevated relative to said output shaft.
- 18. The combination according to claim 17, wherein said oil tank extends under said output shaft.
- 19. An internal combustion engine comprising:a crankcase; an oil tank formed inside said crankcase; an oil pump including a feed pump and a scavenge pump, said feed pump for supplying lubricating oil inside said oil tank to respective components of the internal combustion engine, and said scavenge pump for returning lubricating oil that has accumulated in a bottom of said crankcase to said oil tank; a crankshaft disposed in said crankcase; a transmission chamber disposed in said crankcase to one side of said crankshaft; a transmission including a main shaft, a counter shaft, and an output shaft disposed in said transmission chamber, wherein said oil tank is disposed on a side of said transmission chamber opposite said crankshaft, and wherein said oil tank has an approximately crescent shaped cross section, with a lower end of said cross section extending under at least one of said main shaft, said counter shaft, and said output shaft; a bulkhead partitioning said oil tank from said transmission chamber, wherein said bulkhead extends from a top of said crankcase to said bottom of said crankcase; and a cutout formed in an upper portion of said bulkhead for allowing, when said oil tank is filled with oil, excess oil to overflow into said transmission chamber.
- 20. The engine according to claim 19, wherein said cutout is elevated relative to said main shaft, said counter shaft and said output shaft of said transmission.
- 21. An internal combustion engine comprising:a crankcase; an oil tank formed inside said crankcase; an oil pump including a feed pump and a scavenge pump, said feed pump for supplying lubricating oil inside said oil tank to respective components of the internal combustion engine, and said scavenge pump for returning lubricating oil that has accumulated in a bottom of said crankcase to said oil tank; a crankshaft disposed in said crankcase; a transmission chamber disposed in said crankcase to one side of said crankshaft; and a transmission including a main shaft, a counter shaft, and an output shaft disposed in said transmission chamber, wherein said main shaft is elevated relative to said counter shaft and said counter shaft is elevated relative to said output shaft, wherein said oil tank is disposed on a side of said transmission chamber opposite said crankshaft, and wherein said oil tank has an approximately crescent shaped cross section, with a lower end of said cross section extending under said output shaft.
- 22. A combination comprising:a vehicle; and an internal combustion engine including: a crankcase; an oil tank formed inside said crankcase; an oil pump including a feed pump and a scavenge pump, said feed pump for supplying lubricating oil inside said oil tank to respective components of the internal combustion engine, and said scavenge pump for returning lubricating oil that has accumulated in a bottom of said crankcase to said oil tank; a crankshaft disposed in said crankcase, with said crankshaft extending in a direction parallel to a direction of travel of said vehicle; a transmission chamber disposed in said crankcase to one side of said crankshaft; and a transmission including a main shaft, a counter shaft, and an output shaft disposed in said transmission chamber, wherein said main shaft is elevated relative to said counter shaft and said counter shaft is elevated relative to said output shaft, wherein said oil tank is disposed on a side of said transmission chamber opposite said crankshaft, and wherein said oil tank has an approximately crescent shaped cross section, with a lower end of said cross section extending under said output shaft.
Priority Claims (1)
Number |
Date |
Country |
Kind |
11-250061 |
Sep 1999 |
JP |
|
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Date |
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5031591 |
Shinoda et al. |
Jul 1991 |
|
5887564 |
Kawamoto |
Mar 1999 |
|
6029638 |
Funai et al. |
Feb 2000 |
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