U.S. patent application number 12/144635 was filed with the patent office on 2009-01-15 for lubrication system for four-stroke engine.
Invention is credited to Szu Liang Lin.
Application Number | 20090014246 12/144635 |
Document ID | / |
Family ID | 40252068 |
Filed Date | 2009-01-15 |
United States Patent
Application |
20090014246 |
Kind Code |
A1 |
Lin; Szu Liang |
January 15, 2009 |
Lubrication system for four-stroke engine
Abstract
A lubrication system for a small lightweight four-stroke engine
is disclosed. The lubrication system, provided with a weight at one
end of a flexible oil tube inserted into an oil reservoir, is
capable of providing a sufficient lubrication to components of the
engine which may operate in a horizontal posture, a vertical
posture, or any posture therebetween.
Inventors: |
Lin; Szu Liang; (Taichung,
TW) |
Correspondence
Address: |
SAM CHEN
7F-1, 293, ROOSEVELT ROAD, SEC 3
TAIPEI
TW
|
Family ID: |
40252068 |
Appl. No.: |
12/144635 |
Filed: |
June 24, 2008 |
Current U.S.
Class: |
184/6.5 ;
123/196R |
Current CPC
Class: |
F01M 11/064 20130101;
F01M 1/04 20130101; F01M 2001/126 20130101; F01M 13/00
20130101 |
Class at
Publication: |
184/6.5 ;
123/196.R |
International
Class: |
F01M 1/04 20060101
F01M001/04 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 14, 2007 |
TW |
096125988 |
Claims
1. A single-cylinder, four-stroke cycle, spark ignition internal
combustion engine for mounting on a power tool comprising: a
cylinder (81); a piston (15) slidably disposed in the cylinder
(81); a crankcase (10) disposed below the cylinder (81); an oil
reservoir (30) disposed below the crankcase (10); a cam actuation
section (40) comprising a lower camshaft case (41), an upper space
(431), a plurality of pushing rods (43) passing through the upper
space (431), a plurality of passageways (432) disposed on the top
of the camshaft case (41) with the pushing rods (43) passing
through, a camshaft (44) with a cam (441) and a reduction gear
(442), a camshaft follower (45) engaged with the camshaft (44), a
lower gear (46) secured to the crankshaft (13) and being in mesh
with the reduction gear (442), and a gaseous oil tube (42)
extending to a position above the oil level of the oil reservoir
(30); an upper rocker arm case (50) disposed above the cam
actuation section (40) and being in fluid communication therewith,
the rocker arm case (50) comprising a rocker arm (511) and a valve
(512) on the top of the cylinder (81) wherein the rocker arm (511)
is adapted to operate by actuating the camshaft follower (45) and
the pushing rods (43) by rotating the cam (441); a check valve case
(20) disposed below the crankcase (10) and being in fluid
communication with the crankcase (10) and the oil reservoir (30),
the check valve case (20) having an oil mist return tube (22)
extending into the oil reservoir (30), and a check valve (21); a
first branch tube (60) being in fluid communication with the check
valve case (20) and the gaseous oil tube (42), the first branch
tube (60) having a diameter larger than that of the oil mist return
tube (22); a first venturi (61) disposed in the gaseous oil tube
(42) externally of the oil reservoir (30); a second branch tube
(70) interconnecting the crankcase (10) and the cam actuation
section (40) and being in fluid communication therewith; a second
venturi (71) disposed in the second branch tube (70); a flexible
oil tube (73) having a weight (731) at one end immersed in the oil
reservoir (30); a tubing member (72) connected to the flexible oil
tube (73); a crankshaft (13) rotatably disposed in the crankcase
(10); a connecting rod (14) interconnecting the crankshaft (13) and
the piston (15); an oil return section (83) disposed on the top of
the rocker arm case (50), the oil return section (83) comprising a
plurality of oil return reservoirs (831) being in fluid
communication with each other, and a plurality of channels (832)
interconnecting the oil return section (83) and the rocker arm case
(50); an oil return line (84) interconnecting the oil return
section (83) and the crankcase (10); and a liquid oil and gaseous
oil separation chamber (85) disposed between the oil return section
(83) and the rocker arm case (50), the liquid oil and gaseous oil
separation chamber (85) being in fluid communication with the
rocker arm case (50) and including a top porous plate (851) for
absorbing lubricating oil; wherein irrespective of the posture of
the internal combustion engine in response to moving the piston
(15) in a first direction to decrease the volume of the crankcase
(10), oil mist in the crankcase (10) enters the check valve case
(20) a first portion of the oil mist flows to the oil reservoir
(30) via the oil mist return tube (22), a second portion of the oil
mist being smaller than the first portion thereof in volume flows
to the first branch tube (60), liquid oil in the oil mist is formed
in the oil mist return tube (22) and flows into the oil reservoir
(30), gaseous oil in the oil mist is accumulated on the oil level
of the oil reservoir (30) and flows to the gaseous oil tube (42),
the oil mist also branches from the check valve case (20) to flow
to the first venturi (61) via the first branch tube (60), and the
oil mist is mixed with the gaseous oil from the gaseous oil tube
(42) at the first venturi (61) to form a nebulized mixture which is
sent to the cam actuation section (40) and the rocker arm case (50)
in sequence for lubrication; and wherein irrespective of the
posture of the internal combustion engine in response to moving the
piston (15) in a second direction to increase the volume of the
crankcase (10), excess oil mist and liquid oil in the crankcase
(40) are inhaled into the second branch tube (70), lubricating oil
in the oil reservoir (30) is sucked into the flexible oil tube (73)
and flows to the second branch tube (70) via the tubing member
(72), the lubricating oil is nebulized in the second venturi (71)
and flows to the crankcase (10), oil mist and liquid oil in the
rocker arm case (50) enter the oil return reservoirs (831) via the
channels (832), a portion of oil mist enters the liquid oil and
gaseous oil separation chamber (85) with liquid oil contained
therein being absorbed by the porous plate (851), the absorbed
liquid oil is sent to the oil return section (83) via the channels
(832), the oil mist and the liquid oil contained in the oil return
section (83) are inhaled into the oil return line (84) prior to
entering the crankcase (10), and the oil mist and the liquid oil in
the oil return line (84) and the second branch tube (70) flow from
the crankcase (10) to the check valve case (20).
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of Invention
[0002] The invention relates to four-stroke internal combustion
engine (ICE) and more particularly to an improved lubrication
system for a small lightweight four-stroke engine.
[0003] 2. Description of Related Art
[0004] Portable power tools such as lawn movers, line trimmers,
chain saws as mostly powered by two-stroke ICEs in earlier days.
Gradually, two-stroke engines are phased out due to heavy harmful
exhaust emissions (e.g., hydrocarbon (HC)). Nowadays, almost all
such portable power tools are powered by four-stroke ICEs.
[0005] Lubrication becomes a very serious problem since portable
power tools are required to operate in a wide range of orientations
(i.e., being tilted or even upside down). There have been numerous
suggestions in prior patents for solving this problem. For example,
U.S. Pat. No. 7,287,508 discloses an engine lubrication method
which is incorporated herein by reference. Thus, continuing
improvements in the exploitation of lubrication system for a small
lightweight four-stroke engine are constantly being sought.
SUMMARY OF THE INVENTION
[0006] It is therefore one object of the invention to provide a
lubrication system for a small lightweight four-stroke engine and
the lubrication system, provided with a weight at one end of a
flexible oil tube inserted into an oil reservoir, is capable of
providing a sufficient lubrication to the engine which may operate
in a horizontal posture, a vertical posture, or any posture
therebetween.
[0007] The above and other objects, features and advantages of the
invention will become apparent from the following detailed
description taken with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a longitudinal sectional view of a four-stroke
engine incorporating a lubrication system according to an
embodiment of the invention;
[0009] FIG. 2 is a sectional view taken along line A--A of FIG.
1;
[0010] FIG. 3 schematically depicts the check valve case in FIG.
1;
[0011] FIG. 4 shows lubricating oil flowing to the crankcase when
the piston moves upward;
[0012] FIG. 5 schematically shows the oil return section;
[0013] FIG. 6 schematically depicts the path of lubricating oil
flow when the piston moves downward;
[0014] FIG. 7 schematically depicts the path of lubricating oil
flow when the piston moves upward;
[0015] FIG. 8 schematically depicts the path of lubricating oil
flow when the piston moves upward when the engine is disposed
upright;
[0016] FIG. 9 schematically depicts the path of lubricating oil
flow when the piston moves upward when the engine is disposed
upside down; and
[0017] FIG. 10 schematically depicts the path of lubricating oil
flow when the piston moves downward with an overhead camshaft being
mounted in the engine according to another embodiment of the
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0018] Referring to FIGS. 1 to 9 a four-stroke internal combustion
engine (ICE) in accordance with a preferred embodiment of the
invention is shown. The engine is constructed as a lightweight
housing and comprises the following components. Each component is
discussed in detail below.
[0019] A crankcase 10 is provided. An oil reservoir 30 is provided.
A check valve case 20 is provided in fluid communication with both
the crankcase 10 and the oil reservoir 30. A first branch tube 60
is in fluid communication with both the check valve case 20 and a
gaseous oil tube 42 of a cam actuation section 40. A first venturi
61 is provided proximate a joining portion of the cam actuation
section 40 and the gaseous oil tube 42. Note that the number of the
first venturi 61 may be more than one depending on applications. A
second branch tube 70 is provided between the crankcase 10 and a
camshaft case 41 of the cam actuation section 40 and is in fluid
communication therewith. A second venturi 71 is provided in the
second branch tube 70. The second branch tube 70 has a flexible oil
tube 73 having a weight 731 at one end so that one end of the
flexible oil tube 73 may be always immersed in the oil reservoir
30, and a tubing member 72 connected to the flexible oil tube 73
and being in fluid communication therewith.
[0020] The crankcase 10 comprises a crank casing 11 formed with a
cylinder block 81 which has a cylinder bore (not numbered) with a
piston 15 slidably provided therein. A passage 12 is provided on
the bottom of the crankcase 10 and is in fluid communication with
the check valve case 20. A crankshaft 13, provided in the crankcase
10, has two sets of bearings 131 at both ends and an O-ring 132 at
one set of bearings 131. A connecting rod 14 is provided to
interconnect the crankshaft 13 and the piston 15.
[0021] The check valve case 20 is provided below the crankcase 10.
The check valve case 20 comprises an oil mist return tube 22
extending from the bottom into the oil reservoir 30 and a check
valve 21 having a deflector plate 211 with an elastic member 212
formed on the top surface of the deflector plate 211. Oil mist from
the crankcase 10 may deflect the deflector plate 211 to open the
check valve 21 when the piston 15 moves downward. Hence, oil mist
enters the check valve case 20. Finally, oil mist flows to the oil
reservoir 30 via the oil mist return tube 22. At the same time, a
small portion of oil mist enters the first branch tube 60 which is
in fluid communication with the check valve case 20 (see FIG. 3).
To the contrary, the deflector plate 211 returns to its original
position to block the check valve 21 when the piston 15 moves
upward. Hence, oil mist is prevented from returning from the oil
reservoir 30 to the crankcase 10.
[0022] The oil reservoir 30 is provided below the check valve case
20 and is in fluid communication with the check valve case 20 via
the oil mist return tube 22. Liquid lubricating oil is filled in
the oil reservoir 30. The oil reservoir 30 has a volume great
larger than that of the check valve case 20. Heavy liquid oil
particles in the oil mist may fall into the oil reservoir 30 and
light gaseous oil particles in the oil mist is accumulated on the
oil level of the oil reservoir 30. Further, gaseous oil may enter
the gaseous oil tube 42. An open end of the oil mist return tube 22
is provided above the center of the oil reservoir 30.
[0023] The cam actuation section 40 comprises a lower camshaft case
41 and an upper space 431 with two pushing rods 43 passing through.
Two passageways 432 are provided on the top of the camshaft case 41
with the pushing rods 43 passing through. In addition to the
pushing rods 43, a camshaft 44 and a camshaft follower 45 are
provided in the cam actuation section 40. The camshaft 44 comprises
a cam 441 and a reduction gear 442 coaxially formed therewith. The
camshaft 44 and the camshaft follower 45 are engaged. The reduction
gear 442 is in mesh with a lower gear 46 which is in turn formed
around the crankshaft 13. The cam actuation section 40 has a top
end in fluid communication with a rocker arm case 50 and a bottom
end provided with the gaseous oil tube 42. The gaseous oil tube 42
has a bottom end disposed above the oil level of the oil reservoir
30. Gaseous oil rather than liquid oil in the oil reservoir 30 may
flow to the cam actuation section 40 via the gaseous oil tube 42
when the piston 15 moves downward. Oil mist in the camshaft case 41
is directed along an inner wall 411 of the camshaft case 41 to the
passageways 432 and a second branch tube 701 when the reduction
gear 442 rotates.
[0024] The engine may be implemented as an overhead valve (OHV)
engine in the embodiment. Alternatively, the engine may be
implemented as an overhead camshaft (OHC) engine equipped with a
cam 443, upper and lower pulleys 444 in which one of the pulleys
444 is secured to the cam 443, and a belt 47 passing around the
pulleys 444 in another embodiment (see FIG. 10).
[0025] The rocker arm case 50 is provided in a cylinder head 80
which is affixed to the cylinder block 81. In the rocker arm case
50 a rocker arm mechanism 51 is provided. The rocker arm mechanism
51 comprises a rocker arm 511, a valve 512, and a compression
spring 513. The cam 441 may rotate to actuate the rocker arm
mechanism 51 via the camshaft follower 45 and the pushing rods
43.
[0026] A small portion of oil mist in the check valve case 20
enters the first venturi 61 via the first branch tube 60. Liquid
oil particles in the oil mist are absorbed and nebulized by the
first venturi 61. As an end, oil mist with a small amount of liquid
oil enters the camshaft case 41.
[0027] The second branch tube 70 has an inlet 701 provided in the
camshaft case 41 proximate the passageway 432. Excess oil mist in
the cam actuation section 40 may enter the crankcase 10 via the
second branch tube 70 when the piston 15 moves upward. As a result,
excess oil mist and liquid oil are prevented from remaining in the
cam actuation section 40 and the rocker arm case 50. This has the
benefit of reducing the consumption of lubricating oil.
[0028] The number of the second branch tube 70 may be more than one
depending on applications. Excess oil mist enters the second branch
tube 70 when the piston 15 moves upward. Also, lubricating oil in
the oil reservoir 30 flows to the second branch tube 70 via the
flexible oil tube 73 and the tubing member 72. Oil mist in the
second branch tube 70 and liquid oil in the tubing member 72 are
mixed with air in the second venturi 71. Further, the nebulized oil
mist enters the crankcase 10 when the piston 15 moves upward.
[0029] An oil return section 83 is provided on the top of the
cylinder head 80 and is separated from the rocker arm case 50
therebelow. The oil return section 83 comprises two oil return
reservoirs 831 being in fluid communication with each other, and a
plurality of channels 832 interconnecting the oil return section 83
and the rocker arm case 50. Excess oil mist and liquid oil may
enter at least one of the channels 832 irrespective of the posture
of the engine (i.e., horizontal posture, vertical posture, or any
posture therebetween). Therefore, the purpose of returning
lubricating oil in the rocker arm case 50 can be achieved.
[0030] One end of the oil return section 83 is provided with an oil
return line 84 which has one end in fluid communication with the
crankcase 10 so that the oil return section 83 can communicate with
the crankcase 10. Excess oil mist and liquid oil in the rocker arm
case 50 may return to the oil return section 83 via the channels
832. Next, the excess oil mist and liquid oil are inhaled into the
crankcase 10 via the oil return line 84.
[0031] A liquid oil and gaseous oil separation chamber 85 is
provided between the oil return section 83 and the rocker arm case
50. A porous plate 851 for absorbing lubricating oil is provided on
the top of the liquid oil and gaseous oil separation chamber 85. A
plurality of apertures 852 are provided on the bottom of the liquid
oil and gaseous oil separation chamber 85 and are in fluid
communication with the rocker arm case 50. Thus, excess oil mist
may enter the liquid oil and gaseous oil separation chamber 85 via
the apertures 852. Liquid oil particles in the oil mist are
absorbed by the porous plate 851. Next, the absorbed liquid oil is
inhaled into the oil return section 83 via the channels 832.
Finally, it is sent to the crankcase 10 via the oil return line 84.
Gaseous oil is separated by the liquid oil and gaseous oil
separation chamber 85 to form blow-by gas which is again sent to an
air filter (not shown) via a breather pipe 86. Clean air from the
air filter is inhaled into a combustion chamber 87 in an air intake
cycle of the engine (see FIG. 1). Also, a spark plug (not numbered)
is provided on the top edge of the combustion chamber 87.
[0032] As shown FIG. 6, volume of the crankcase 10 is decreased
when the piston 15 moves downward. And in turn, oil mist in the
crankcase 10 enters the check valve case 20. Diameter of the oil
mist return tube 22 is much larger than that of the first branch
tube 60. Hence, a large portion of oil mist flows toward the oil
reservoir 30 via the oil mist return tube 22 and only a small
portion thereof flows to the first branch tube 60. Liquid oil in
the oil mist is formed in the oil mist return tube 22 since the
flow speed in the oil mist return tube 22 decreases greatly. Hence,
the heavy liquid oil flows from the open end of the oil mist return
tube 22 into the oil reservoir 30. Also, light gaseous oil is
accumulated on the oil level of the oil reservoir 30 and is sent to
the gaseous oil tube 42. Also, oil mist may branch from the check
valve case 20 to flow to the first venturi 61 via the first branch
tube 60. Oil mist is then mixed with gaseous oil sent from the
gaseous oil tube 42 at the first venturi 61. The nebulized
lubricating oil mixture is sent to the cam actuation section 40 and
the rocker arm case 50 in sequence for lubrication.
[0033] As shown in FIGS. 7, 8, and 9, volume of the crankcase 10 is
increased when the piston 15 moves upward. And in turn, excess oil
mist and liquid oil in the crankcase 40 are inhaled into the second
branch tube 70. Also, lubricating oil in the oil reservoir 30 is
sucked into the flexible oil tube 73. And in turn, lubricating oil
flows to the second branch tube 70 via the tubing member 72 which
is connected to the flexible oil tube 73. Lubricating oil is
nebulized in the second venturi 71. The nebulized lubricating oil
is then sent to the crankcase 10. At the same time, oil mist and
liquid oil in the rocker arm case 50 may enter the oil return
reservoirs 831 via the channels 832. Further, a portion of oil mist
may enter the liquid oil and gaseous oil separation chamber 85 with
liquid oil contained therein being absorbed by the porous plate
851. And in turn, the absorbed liquid oil is sent to the oil return
section 83 via the channels 832. All oil mist and liquid oil
contained in the oil return section 83 will be inhaled into the oil
return line 84 prior to entering the crankcase 10.
[0034] Oil mist and liquid oil accumulated in the oil return line
84 and the second branch tube 70 will flow from the crankcase 10 to
the check valve case 20 when the piston 15 moves downward.
[0035] While the invention herein disclosed has been described by
means of specific embodiments, numerous modifications and
variations could be made thereto by those skilled in the art
without departing from the scope and spirit of the invention set
forth in the claims.
* * * * *