Information
-
Patent Grant
-
6561315
-
Patent Number
6,561,315
-
Date Filed
Tuesday, May 22, 200123 years ago
-
Date Issued
Tuesday, May 13, 200321 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
-
CPC
-
US Classifications
Field of Search
US
- 184 114
- 184 111
- 184 112
- 184 131
- 074 579 R
- 074 587
- 074 579 E
- 074 605
- 123 196 R
- 123 196 M
- 123 1903
-
International Classifications
-
Abstract
A scraper is provided in a large end portion of a connecting rod in an inclined type of overhead camshaft engine to lubricate a timing system by dipping a lubricating oil stored in a lower portion of a crank case up. The scraper includes a bottom wall and a side wall set up on the bottom wall, and have a substantially L-shaped cross-section. An angle between the bottom wall and the side wall is set in a range of 60° to 90°. Thus, the droplets of the oil can be splashed to the side direction of scraper also in three-dimensional inclined direction, so that oil can be securely supplied to and lubricate the timing system which is offset from the scraper in a longitudinal direction of the crankshaft.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a lubricating system for an overhead camshaft engine (hereinafter referred to simply as “OHC engine”), in particular, to an effective technique applied to the OHC type of general-purpose engine, a cylinder axis of which is located with an inclination with respect to the gravitational direction.
In the prior art, an overhead valve (hereinafter referred to simply as “OHV”) and OHC type of general-purpose engines have been widely used as power sources for mowers, power sprayers, power generators, etc. For example, Japanese Patent Application Laid-open Publication No. Hei. 10-280932 discloses an engine of the OHV type, a cylinder axis of which is inclined in order to realize a compact size of the system. Further, Japanese Patent Application Laid-open Publication No. Hei. 8-177441 discloses an engine of the OHC type, an oil dipper of which rotates together with a crankshaft to improve a lubricating performance for a valve-operating system.
In such a general-purpose engine, a so-called splash method has been widely employed as a lubricating method of such a valve-operating system as chains, sprockets, and cams for reducing cost and size. In this splash method, an oil pump is not used, but is used the oil dipper in order to pick up a lubricating oil in an oil pan, so that splashes of the oil lubricates the system. As the oil dipper, while a paddle type is disclosed in the Publication No. Hei. 10-280932, a water mill wheel type is disclosed in the Publication No. Hei. 8-177441.
However, there was a problem of resulting in a cost up by increasing the number of components and in a complicated structure in the case of the lubricating system as described in the Publication No. Hei. 8-177441 since the oil dipper is disposed on an axis different from that of a crankshaft. In addition, there was also a problem of causing not only a large stirring resistance to become a rotational load, but also a raised oil temperature since the water mill wheel dips the lubricating oil up from the oil pan. Furthermore, there was a disadvantage that the height of the engine is increased by the height of the oil dipper.
On the other hand, the system of the Publication No. Hei. 10-280932 dips the oil up by means of the dipper mounted on a large end portion of a connecting rod, thereby lubricating the valve-operating system without increasing the number of components. In addition, this system can cause less stirring resistance, resulting in less raised oil temperature, since the paddle type of dipper moves as cutting the oil. Although, however, such a dipper can splash the oil along the circumference direction of the connecting rod, the dipper can not splash it toward a side of the connecting rod. Therefore, the valve-operating system of OHC engine can not be well lubricated by such a dipper since the valve-operating system deviates from the connecting rod in the longitudinal direction of the crankshaft.
Namely, in the OHV engine as described in the Publication No. Hei. 10-280932, the valve-operating system can be well lubricated by the paddle type of dipper since a valve-operating cam can be disposed in the vicinity of the oil dipper. In the OHC engine, however, a timing valve-operating member such as a chain or a cogged belt is offset from the connecting rod, so that the oil can not be splashed to the place of the chain by the dipper of the paddle type.
SUMMARY OF THE INVENTION
An object of the present invention is to securely supply a lubricating oil to a timing system without increasing the number of components in an OHC general-purpose engine.
In order to achieve the above mentioned object, there is provided a lubricating system of an overhead camshaft engine having a valve-operating cam provided on a cylinder head of the engine and driven in synchronization with a crankshaft via a timing system which comprises a scraper provided on a large end portion of a connecting rod of the engine in order to pick up a lubricating oil stored in a lower portion of a crankcase of the engine so as to lubricate the timing system. The scraper includes a bottom wall extending in a radial direction of the crankshaft and a side wall erected from the bottom wall.
According to the present invention, droplets of the oil can be splashed in the three-dimensional inclined direction, i.e., to the side direction of the scraper. Therefore, the droplets of the oil can be supplied to the timing system offsetted to the scraper in a longitudinal direction of the crankshaft. Thus, the timing system of the OHC engine can be securely lubricated without increasing the number of the components even though being offsetted from the scraper,
In this case, the engine may be an inclined type of OHC engine which has a cylinder axis, inclined with respect to the gravitational direction. In addition, an angle formed between the bottom wall and the side wall may be appropriately set within a range of 60° to 90°.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other objects and advantages of the present invention will become clearly understood from the following description with reference to the accompanying drawings, wherein:
FIG. 1
is a diagram illustrating a structure of an OHC engine using a lubricating system according to one embodiment of the present invention;
FIG. 2
is an explanatory cross-sectional view of a timing system of the engine of
FIG. 1
along a direction of a cylinder axis;
FIGS. 3
a
and
3
b
are diagrams illustrating the structure of a connecting rod including a scraper, which illustrate a front view and a side view of the scraper, respectively; and
FIG. 4
is a perspective view of the scraper.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
An embodiment of the present invention will now be described in detail with reference to the drawings.
FIG. 1
is a diagram illustrating a structure of an OHC engine using a lubricating system of a valve-operating device in one embodiment of the present invention.
FIG. 2
is an explanatory cross-sectional view of the engine of
FIG. 1
taken along the cylinder axis direction.
The engine of
FIG. 1
is a single-cylinder 4-cycle gasoline engine, and is a so-called “inclined type of OHC engine” in which the cylinder axis CL is inclined by an angle θ with respect to the gravitational direction (see FIG.
2
). In this engine, an engine body
1
includes a cylinder block
2
and a crank case
3
which are integrally formed therein. The engine body
1
is made of iron or a light metal alloy such as an aluminum alloy. A cylinder head
4
made of an aluminum alloy is attached to an upper portion of the cylinder block
2
. A rocker cover
5
made of a sheet metal or a synthetic resin is mounted on a top of the cylinder head
4
.
The crank case
3
has a large opening at the right side thereof in
FIG. 1
, thereby providing a main bearing case attachment surface
6
. A main bearing case
7
made of an aluminum alloy is attached to the main bearing case attachment surface
6
. Thus, a crank chamber
8
is provided in the crank case
3
, and an oil pan
10
is provided under the crank chamber
8
for storing a lubricating oil (hereinafter referred to simply as “oil”)
9
.
A main bearing
11
a
is press-fitted into the main bearing case
7
, and one end of a crankshaft
12
is supported by the main bearing
11
a
. An oil seal
13
a
is press-fitted on the outer side of the main bearing
11
a.
A main bearing
11
b
is press-fitted into a wall surface
14
opposite to the main bearing case attachment surface
6
of the crank case
3
. The other end side of the crankshaft
12
is supported by the main bearing
11
b
. Similarly, an oil seal
13
b
is provided on the outer side of the main bearing
11
b
. The oil seals
13
a
and
13
b
prevent the oil
9
stored in the oil pan
10
from leaking out of the crank case
3
along the crankshaft
12
.
A flywheel
15
and a cooling fan
16
are attached to an end portion of the crankshaft
12
that extends out of the crank case
3
through the wall surface
14
. The cooling fan
16
is provided outside the crank case
3
and within a casing
57
, and rotates together with the crankshaft
12
so as to induce a cooling air from an outside of the casing
57
. The engine body
1
, the cylinder head
4
, etc. are cooled by the induced cooling air. Moreover, a recoil device
17
is provided on the outer side of the casing
57
. By pulling a recoil lever
17
a
by hand, the crankshaft
12
is rotated to start the engine.
A cylinder bore
18
is provided in the cylinder block
2
. A piston
19
is fitted within the cylinder bore
18
so as to be slidable therein. An upper end of the cylinder bore
18
is closed by the cylinder head
4
, and an upper surface of the piston
19
and a bottom wall surface
20
of the cylinder head
4
form a combustion chamber
21
together. An intake valve
22
, an exhaust valve (not shown), an ignition plug (not shown), etc. are provided in the upper portion of the combustion chamber
21
.
A small end portion
25
of a connecting rod
24
is rotatably connected to the piston
19
via a piston pin
23
. A crank pin
27
of the crankshaft
12
is rotatably connected to a large end portion
26
of the connecting rod
24
. Thus, the crankshaft
12
is rotated along with the vertical reciprocation of the piston
19
.
On the other hand, a camshaft
28
is provided in the cylinder head
4
parallel to the crankshaft
12
on the cylinder axis CL. The camshaft
28
includes a valve-operating cam
29
and a sprocket
31
, which are integrally formed with each other. The valve-operating cam
29
is driven in synchronization with the crankshaft
12
by a timing system
30
.
A sprocket
32
is secured on the crankshaft
12
. Chain chambers
50
,
51
are provided in the cylinder block
2
and the cylinder head
4
, respectively, and the sprocket
31
and the sprocket
32
are connected to each other via a chain
33
provided in the chain chambers
50
and
51
. The sprockets
31
,
32
and the chain
33
form the timing system
30
together. The number of teeth of the sprocket
31
is twice as large as the number of teeth of the sprocket
32
, so that the valve-operating cam
29
undergoes one revolution per two revolutions of the crankshaft
12
. Also, an appropriate tension is applied to the chain
33
by a chain tensioner
55
.
The valve-operating cam
29
is provided with a cam surface
29
a
, and a slipper
35
formed at one end of a rocker arm
34
slidably contacts with the, cam surface
29
a
. The valve-operating cam
29
and the rocker arm
34
form a valve-operating device together. Two rocker arms
34
of a rocking type are provided respectively for intaking and exhausting air. Each of the rocker arms
34
is provided to rock about a rocker shaft
36
which is supported by a rocker support
59
. The other end of each rocker arm
34
is connected to a top end portion of the intake valve
22
or an exhaust valve (not shown) via an adjusting screw
56
. The intake valve
22
and the exhaust valve are each driven when the rocker arm
34
is rocked by the valve-operating cam
29
. The intake valve
22
and the exhaust valve are each biased by a valve spring
37
toward the closed position. Thus, the intake valve
22
is opened/closed by the rotation of the valve-operating cam
29
.
The timing system
30
is lubricated by a scraper
38
provided on a large end portion
26
of the connecting rod
24
.
FIGS. 3
a
and
3
b
are diagrams illustrating a structure of a connecting rod
24
including a scraper
38
, which illustrate a front view and a side view of the scraper
38
, respectively. Further,
FIG. 4
is a perspective view of the scraper
38
.
As illustrated in
FIG. 2
, the scraper
38
extends downward from a lower member
39
of the large end portion
26
, i.e., in a radial direction of the crankshaft
12
. The scraper
38
swings by the rotation of the crankshaft
12
through a path as indicated by a one-dotted-chain line in FIG.
2
. Thus, the oil
9
stored in the oil pan
10
is dipped and scraped up by the scraper
38
, and the oil
9
is splashed onto the chain
33
when the scraper
38
comes out of an oil surface
40
, thereby lubricating the timing system
30
.
The scraper
38
, having a generally L-shaped cross section, includes a bottom wall
41
and a side wall
42
extending upwardly on one lateral end of the bottom wall
41
as shown in FIG.
4
. In the present embodiment, the angle α formed by both the bottom wall
41
and the side wall
42
is set to be 90°. However, the angle therebetween is not limited to the right angle, but may be appropriately selected in the about range of 60° to 90°.
Along with the rocking of the scraper
38
, the oil
9
is dipped and scraped up by the bottom wall
41
, and guided to the side wall
42
and splashed away from the side wall
42
as shown in FIG.
4
. Thus, the droplets of the oil
9
are splashed also in three-dimensionally inclined directions, i.e., in the lateral direction from the scraper
38
, thereby throwing some droplets of the oil
9
toward a root portion of the chain tensioner
55
. Some of the droplets hit the inner wall of the crank case
3
and are bounced back toward the chain
33
.
In this way, droplets of the oil
9
can be supplied to the chain
33
, which is offsetted toward the main bearing case
7
with respect to the scraper
38
, thereby ensuring to supply the oil
9
to the chain
33
. In such a way, the timing system
30
of the OHC engine can also be securely lubricated without increasing the number of components even though the timing system
30
of the OHC engine is located at a deviated position from the longitudinal direction of the crankshaft due to the structure thereof.
The oil
9
thus splashed onto the chain
33
is transferred toward the cylinder head
4
along with the movement of the chain
33
, thereby lubricating the, sprocket
31
also. Moreover, the sprocket
32
is also lubricated by the oil
9
attached on the chain
33
.
On the side of the cylinder head
4
, some of the oil
9
attached on the chain
33
is shaken off by a centrifugal force. As the chain
33
travels around the sprocket
31
, some of the oil
9
on the chain
33
is thrown off from the chain
33
toward the circumferential directions of the sprocket
31
to be separated from the chain
33
. In the illustrated engine, the rocker cover
5
is provided above the sprocket
31
, and those droplets of the oil
9
hit the ceiling surface
53
of the rocker cover
5
. The oil
9
attached onto the ceiling surface
53
runs down along the ceiling surface
53
back into the oil pan
10
via the chain chambers
51
and
50
.
In the present invention, an oil dripping portion
54
having a convex shape are provided on one part of the ceiling surface
53
of the rocker cover
5
as shown in
FIG. 1
, so that the oil
9
attached onto the ceiling surface
53
drips from the oil dripping portion
54
. This oil dripping portion
54
is positioned above a contacting portion between the valve-operating cam
29
and the slipper
35
, thereby lubricating the contacting portion by the oil
9
dropped therefrom.
In the cylinder head
4
, a gas-liquid separation chamber
43
is further provided separately from the chain chamber
51
. Another gas-liquid separation chamber
45
is provided in the rocker cover
5
and is communicated to the gas-liquid separation chamber
43
via a lead valve
44
. The gas-liquid separation chamber
45
is further connected to an air cleaner
47
via a blow-by passage
46
. The air cleaner
47
is further connected to an intake port
49
in the cylinder head
4
via a carburetor
48
.
The gas-liquid separation chambers
43
,
45
are provided for separating a mist of the oil
9
from a blow-by gas when the blow-by gas stored in the crank chamber
8
is recirculated to the air cleaner
47
. In the illustrated engine, the gas-liquid separation chamber
43
is opened to the chain chamber
50
, which is provided separately from the cylinder bore
18
. Specifically, a gas inlet
52
is provided at an upper end portion of the chain chamber
50
of the cylinder block
2
, and the blow-by gas, which has flowed into the chain chamber
50
, flows into the gas-liquid separation chamber
43
via the gas inlet
52
. As the blow-by gas flows through the gas-liquid separation.chamber
43
, the oil mist contained therein attaches to a wall surface of the gas-liquid separation chamber
43
, thereby separating the oil mist from the blow-by gas. The oil component, which has been separated in the gas-liquid separation chamber
43
, returns to the oil pan
10
via the wall surfaces of the gas-liquid separation chamber
43
and then the chain chamber
50
.
The blow-by gas, which has flowed into the rocker cover via the lead valve
44
, is subjected to a further oil mist separation process in the gas-liquid separation chamber
45
. Specifically, the oil mist contained in the blow-by gas, which has entered the gas-liquid separation chamber
45
, attaches to the wall surface of the gas-liquid separation chamber
45
, thereby achieving a further gas-liquid separation. Incidentally, an oil return hole (not shown) may be provided in the bottom surface of the rocker cover
5
, whereby the oil, which has attached to the wall surface of the gas-liquid separation chamber
45
, flows into the chain chambers
51
,
50
through the oil return hole and returns to the oil pan
10
via the wall surface of the chain chambers
51
,
50
.
The present invention has been specifically described above based on a particular embodiment thereof. It is understood, however, that the present invention is not limited to the above-described embodiment, but rather various modifications can be made thereto without departing from the scope and spirit of the present invention.
For example, the scraper
38
may have not only a generally L-shaped cross section as described in the above embodiment, but also one of an acute angle or an arcuated shape in which the bottom wall and the side wall are continuously formed.
Moreover, while the present invention is applied to an air-cooled engine with a single-cylinder, the present invention may alternatively be applied to an air-cooled engine with a multi-cylinder, or a liquid-cooled engine with a single- or multi-cylinder. In addition, although the cylinder block
2
and the crank case
3
are formed integrally with each other in the embodiment described above, they may alternatively be provided separately, and further the cylinder head
4
and the cylinder block
2
may be formed integrally with each other.
Furthermore, the timing system
30
is provided by using the sprockets
31
,
32
and the chain
33
in the embodiment described above, but the timing system
30
may alternatively be provided by using other driving members known in the art, such as a cogged pulley and a cogged belt, or a timing pulley and a timing belt. Moreover, in the present invention, the term “rotation” has a general concept including a circular motion in both directions, i.e., a clockwise direction and a counterclockwise direction, not a circular motion in only one direction.
According to the lubricating system for the OHC engine of the present invention, the scraper is provided on a large end portion of a connecting rod with a L-shaped cross-section constructed by a bottom wall and a side wall, thereby allowing the droplets of the oil to be splashed in three-dimensional inclined directions, i.e., the side direction also of the scraper. Therefore, the droplets of the oil can be attached to the timing system also which is located at the deviated portion from the scraper in the longitudinal direction of the crankshaft. That is, even in the case of the OHC engine, the timing system of which is offsetted from the scraper, it becomes possible to securely lubricate the timing system without adding components such as an oil dipper according to the present invention.
While there has been described what are at present considered to be preferred embodiments of the present invention, it will be understood that various modifications may be made thereto, and it is intended that the appended claims cover all such modifications as fall within the true spirit and scope of the invention.
Claims
- 1. A lubricating system of an overhead camshaft engine having a valve-operating cam provided on a cylinder head of the engine and driven in synchronization with a crankshaft via a timing system, the timing system being offset from a connecting rod in a direction of a crank shaft, comprising:a scraper provided on a large end portion of the connecting rod of the engine and including a bottom wall extending in a radial direction of the crankshaft and a side wall erected from the bottom wall on a side opposite to the timing system in order to pick up a lubricating oil stored in a lower portion of a crank case of the engine so as to lubricate said timing system.
- 2. The lubricating system of the overhead camshaft engine according to claim 1, wherein said engine is an inclined type of engine which has a cylinder axis inclined with respect to a gravitational direction.
- 3. The lubricating system of the overhead camshaft engine according to claim 1, wherein an angle formed between said bottom wall and said side wall is in a range of 60° to 90°.
- 4. The lubricating system of the overhead camshaft engine according to claim 2, wherein an angle formed between said bottom wall and said side wall is in a range of 60° to 90°.
- 5. The lubricating system of the overhead camshaft engine according to claim 1, wherein said scraper has an arc-shaped cross section in which the bottom wall and the side wall are continuously formed.
- 6. The lubricating system of the overhead camshaft engine according to claim 1, wherein said timing system comprises sprockets and a chain for carrying the lubricating oil to the valve-operating cam.
Priority Claims (1)
Number |
Date |
Country |
Kind |
2000-150850 |
May 2000 |
JP |
|
US Referenced Citations (13)
Foreign Referenced Citations (2)
Number |
Date |
Country |
8177441 |
Jul 1996 |
JP |
10280932 |
Oct 1998 |
JP |