Information
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Patent Grant
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6505589
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Patent Number
6,505,589
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Date Filed
Friday, February 1, 200222 years ago
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Date Issued
Tuesday, January 14, 200321 years ago
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Inventors
-
Original Assignees
-
Examiners
Agents
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CPC
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US Classifications
Field of Search
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International Classifications
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Abstract
A valve train layout for an overhead valve engine uses a single camshaft actuating two inlet valves and a single exhaust valve. The two inlet valves are preferably aligned on an inner side of a cylinder with the exhaust valve on an outer side. The inlet valves are preferably actuated by a cam follower and single push rod driving a rocker arm with dual arms and separate lash adjusters actuating the inlet valves. The exhaust valve is preferably actuated by a cam follower with a lash adjuster driving a single push rod operating a primary rocker arm that drives a secondary push rod pivoting an exhaust rocker arm to actuate the exhaust valve. In one embodiment, the primary rocker arm for the exhaust valve pivots on a common axis with the intake rocker arm. In an alternative embodiment, the primary rocker arm pivots on a canted pivot axis.
Description
TECHNICAL FIELD
This invention relates to valve trains for overhead valve engines and, in particular, to efficient valve trains for engines having three valves per cylinder.
BACKGROUND OF THE INVENTION
Internal combustion engines have been provided with numerous types of valve configurations, commonly including two, three or four valves. The valves are configured to obtain desirable gas flow, compression and combustion results while providing simplicity of the valve train to the extent possible for the particular engine arrangement. The most simple valve arrangements have generally involved a single intake valve and a single exhaust valve actuated by an overhead valve train including a single camshaft with cam followers and push rods actuating rocker arms of an overhead valve train. For obtaining higher engine outputs, valve configurations with four valves per cylinder have become common, utilizing dual intake valves on one side of the cylinder, usually the inside and dual exhaust valves on the other, outside, of the cylinder. Such valve configurations are more commonly actuated by multiple overhead camshafts directly driving the valves, or by a single overhead camshaft per cylinder bank driving some of the valves directly and others through finger followers or other rocker mechanisms.
An alternative valve configuration utilizes three valves per cylinder, generally including dual intake valves disposed along an inner side of the cylinder and a single exhaust valve located toward an outer side of the cylinder. Valves of this type may be actuated by overhead camshafts. Alternatively, a single camshaft per engine may connect through cam followers and push rods with rocker arms which actuate the various valves. The valve trains for such cylinder configurations vary in complexity and efficiency as do the valve arrangements themselves, and the relative placement of an igniter such as a spark plug and, if used, a fuel injector for the cylinder.
SUMMARY OF THE INVENTION
The present invention provides a valve train layout for an overhead valve (OHV) engine which uses a single camshaft in the cylinder block. A combustion chamber is provided for each cylinder which utilizes two inlet valves and a single exhaust valve. The two inlet valves may, as desired, be of equal or differing diameters. They are longitudinally aligned on the inner side of the cylinder (or combustion chamber) and are symmetrically located on opposite sides of a lateral plane through the cylinder axis and extending normal to the axis of the engine crankshaft and camshaft.
The single exhaust valve may be located either on the lateral plane or asymmetric to one side of the plane, depending on the requirements of the combustion system. Preferably, the exhaust valve is displaced to one side of the lateral plane and along the outer side of the cylinder and is inclined at a compound angle relative to the lower face of the cylinder head and the associated mounting deck of the engine cylinder block.
The inlet valves are preferably actuated by a cam follower and single push rod driving a rocker arm with dual arms carrying separate lash adjusters for actuating the two inlet valves. The exhaust valve is preferably actuated by a cam follower with a lash adjuster driving a single push rod operating a primary, or slave, rocker arm which in turn drives a secondary push rod actuating an exhaust rocker arm that opens the exhaust valve. Conventional springs are provided to close the valves and maintain the cam followers in contact with their cams.
In one embodiment, the primary or slave rocker arm for the exhaust valve is pivotable on a common axis with the intake rocker arm. In an alternative embodiment, the primary or slave rocker arm is pivotable on a canted pivot axis. In each case, a secondary push rod drives an exhaust rocker arm pivotable on a canted axis to engage the exhaust valve while pivoting in a plane common to the valve axis. In either embodiment, the camshaft may if desired be controlled by a cam phaser for varying valve timing.
Both embodiments for an overhead valve engine provide improved inlet port flow for better specific power output and dynamic range through the use of the two inlet valves. Improved exhaust port flow is obtained due to the compound angle of the exhaust valve. Better catalytic converter performance is obtained due to the reduced heat loss compared to a system with two or more exhaust valves. The compound angle of the exhaust valve also permits a larger exhaust valve for a given cylinder bore size. The space occupied by of the upper portion of the engine is reduced significantly over a multi-valve engine with overhead camshafts.
Hydraulic lash adjusters may be provided for all three valves in the engine layout although mechanical lash adjustment could be used if desired. With a camshaft phaser, the inlet and exhaust timing may be adjusted for better performance. A potential for reduced hydrocarbon emissions is possible due to reduced crevice volume associated with the single exhaust valve as opposed to dual exhaust valves in four-valve engines. The invention provides valve train driving inlet and exhaust valves on substantially different axes without using common rocker shafts that have longer, less desirable, rocker arm arrangements. Finally, a simple cam drive for a multi-valve engine cylinder concept is provided which allows improved cylinder head water jacket geometries and better cylinder head cooling performance.
These and other features and advantages of the invention will be more fully understood from the following description of certain specific embodiments of the invention taken together with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a plan view of a single cylinder bank of an engine showing a first embodiment of valve train according to the invention;
FIG. 2
is a transverse cross-sectional view of a portion of the engine of
FIG. 1
further illustrating the valve train embodiment;
FIG. 3
is a bottom view of the cylinder head of
FIG. 1
showing the internal combustion chamber arrangement and valve locations;
FIG. 4
is a view similar to
FIG. 2
showing an alternative embodiment of a valve train according to the invention; and
FIG. 5
is a view similar to
FIG. 1
showing the alternative embodiment of FIG.
4
.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring first to
FIGS. 1-3
of the drawing in detail, numeral generally indicates an internal combustion engine having a plurality of cylinders
12
, only one of which is shown. The cylinders
12
are conventionally arranged in cylinder banks
14
with the upper ends of the cylinders being closed by cylinder heads
16
.
The engine includes a cylinder block
18
supporting a crankshaft, not shown, which drives a camshaft
22
having a longitudinal axis extending parallel to the crankshaft axis, not shown. In a V-type engine, as shown, the camshaft
22
is located at the bottom of a V between the cylinder banks
14
.
FIGS. 1-3
illustrate the valve train arrangement in a single cylinder bank on one side of the engine and
FIG. 2
additionally illustrates a portion of the valve train for a cylinder on the opposite cylinder bank
14
of the engine.
The valve train components include the camshaft
22
having a plurality of inlet cams
26
. When rotated, each cam
26
reciprocates at least one inlet cam follower
28
connected with a push rod
30
. The push rod actuates an inlet rocker arm
32
that rocks on a pivot axis
34
parallel to the camshaft axis
24
. Rocker arm
32
includes a pair of actuating arms
36
each of which preferably carries a hydraulic lash adjuster
38
. The lash adjusters engage a pair of inlet valves
40
, each having a valve spring
42
for closing the respective valve and holding the cam follower
28
against the inlet cam
26
. The inlet valves
40
are longitudinally aligned on the inner side of the cylinder and its associated combustion chamber
44
and are symmetrically located on opposite sides of a central lateral plane
46
extending normal to the crankshaft and camshaft axes and passing through the central axis, not shown, of the cylinder.
The camshaft
22
also carries a plurality of exhaust cams
48
, only one of which is shown. Each exhaust cam actuates at least one cam follower
50
connecting with an exhaust push rod
52
for actuating a primary rocker arm or slave rocker arm
54
which in this embodiment is pivotable on the same pivot axis
34
as the inlet rocker arm
32
. The cam follower and push rod for the rocker arm
54
illustrated are hidden in the drawing but are identical to the cam follower
50
and push rod
52
shown for actuating an exhaust valve in the opposite cylinder bank. The exhaust cam follower
50
preferably includes an internal hydraulic lash adjuster for adjusting the lash in the exhaust valve train driven by the follower.
The primary rocker arm
54
in turn engages a secondary push rod
56
which extends laterally at a slight longitudinally inward angle to engagement with a secondary rocker arm
58
pivotable on a canted axis
60
. An actuating arm of rocker arm
58
directly engages the single exhaust valve
62
for its respective cylinder which includes a valve return spring
64
functioning as do the inlet valve springs to close the valve.
The exhaust valve may be located as desired on the outer side of the cylinder but as shown is desirably located asymmetrically longitudinally offset to one side of the cylinder, that is to one side of the central lateral plane
46
. The exhaust valve
62
is angled at a compound angle with its axis directed generally toward the axis of the cylinder to provide a minimum crevice volume within the cylinder. Preferably, the rocking plane of the secondary rocker arm
58
where it contacts the exhaust valve
62
lies coplanar with the axis of the exhaust valve.
Spaced longitudinally on the other end of the outside of the cylinder from the exhaust valve location is an igniter in the form of a spark plug
66
or similar device. A fuel injector
68
may also be located at a position inwardly adjacent to the spark plug when the engine is provided with direct cylinder injection. However, the same cylinder configuration absent the direct fuel injector may also be utilized for an engine having manifold injection of the fuel.
In operation, rotation of the camshaft
24
during engine operation actuates the intake and exhaust valves in timed relation in accordance with predetermined valve lift diagrams. Actuation of the inlet cam follower
28
raises the push rod
30
, pivoting the rocker arm
32
and opening both inlet valves
40
at the same time to provide a maximum amount of intake air flow. The separate lash adjusters at the ends of the actuating arms
36
of the rocker arm are required to separately adjust the lash of the two individual valves when driven by a single cam follower and push rod. If desired, the intake valves could be of differing sizes and could be driven by separate rocker arms actuated by individual push rods and cam followers from separate inlet cams in order to obtain a desired pattern of air flow within the cylinder. The general locations of the inlet valves being more or less symmetrical on the inner sides of the cylinder could remain the same.
Rotation of the camshaft
24
actuating the exhaust cam follower
50
with its integral lash adjuster raises the push rod
52
to actuate the primary rocker arm
54
, secondary push rod
56
and secondary rocker arm
58
which opens the exhaust valve
62
. Upon further rotation, the exhaust valve
62
is closed by the valve spring
64
. Injection of fuel and ignition by the spark plug
66
will occur conventionally after compression of an air charge admitted through the intake valves with combustion and exhaust of the burned fuel-air charge following in conventional fashion.
FIGS. 4 and 5
illustrate an alternative embodiment similar to but modified from the embodiment of
FIGS. 1-3
and wherein like numerals indicate like parts. Thus, engine
70
of
FIGS. 4 and 5
includes a camshaft
22
and intake valve train like that of the first described embodiment. This alternative embodiment differs in that the slave rocker or primary exhaust rocker arm
72
is positioned on a canted axis
74
lying essentially parallel to the canted axis
60
of the secondary rocker arm
58
. The two rocker arms are connected by a secondary push rod
76
essentially as before. As a result of repositioning the primary rocker arm
72
, the exhaust primary push rod
52
and its connected follower
50
are also canted slightly from engagement of the follower with the exhaust cam
48
up to engagement of the push rod with the primary rocker arm
72
. The configuration of the exhaust valve
62
and its valve spring
64
and the position of the spark plug
66
and the fuel injector
68
, if used, are essentially the same as in the first described embodiment. Thus, the primary advantage of the second embodiment of
FIGS. 4 and 5
is a more direct application of forces between the primary and secondary rocker arms due to the slight canting of the exhaust follower and push rod and the provision of a canted rocker arm pivot for the primary rocker arm.
While the invention has been described by reference to certain preferred embodiments, it should be understood that numerous changes could be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the disclosed embodiments, but that it have the full scope permitted by the language of the following claims.
Claims
- 1. A valve train for a three-valve-per-cylinder engine, said valve train comprising:a single camshaft extending longitudinally along a cylinder bank of the engine, the camshaft including at least one inlet cam and one exhaust cam for each engine cylinder; at least one inlet cam follower engaging each of the inlet cams and an exhaust cam follower engaging each of the exhaust cams; an inlet pushrod connecting each inlet cam follower with an inlet rocker arm; a first exhaust pushrod connecting each exhaust cam follower with a first exhaust rocker arm; a second exhaust pushrod connecting each first exhaust rocker arm with a second exhaust rocker arm; and each inlet rocker arm operatively engaging at least one inlet valve for actuating the inlet valve and each second exhaust rocker arm operatively engaging at least one exhaust valve for actuating the exhaust valve.
- 2. A valve train as in claim 1 wherein each cylinder has dual inlet valves and a single exhaust valve.
- 3. A valve train as in claim 2 wherein said inlet valves are aligned longitudinally adjacent an inner side of the cylinder and the single exhaust valve is located adjacent an outer side of the cylinder.
- 4. A valve train as in claim 3 wherein said dual inlet valves are actuated by a single inlet rocker arm.
- 5. A valve train as in claim 4 wherein said second exhaust pushrod extends generally laterally across said cylinder between the first and second exhaust rocker arms to actuate said single exhaust valve.
- 6. A valve train as in claim 5 wherein said exhaust valve is offset longitudinally toward one side of the cylinder and an igniter is disposed longitudinally from the exhaust valve toward an opposite side of the cylinder.
- 7. A valve train as in claim 6 wherein a fuel injector is disposed adjacent the igniter in said opposite side of the cylinder.
- 8. A valve train as in claim 5 wherein said inlet rocker arm and said first exhaust rocker arm are pivotable on a common axis.
- 9. A valve train as in claim 5 wherein said inlet rocker arm and said first exhaust rocker arm are pivotable on non-parallel axes.
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Date |
Kind |
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Enomoto et al. |
May 1985 |
A |
4649874 |
Sonoda et al. |
Mar 1987 |
A |
5253620 |
Dohn et al. |
Oct 1993 |
A |
5398649 |
Shimamoto |
Mar 1995 |
A |
6205966 |
Breitenberger |
Mar 2001 |
B1 |