Information
-
Patent Grant
-
6782855
-
Patent Number
6,782,855
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Date Filed
Wednesday, May 14, 200321 years ago
-
Date Issued
Tuesday, August 31, 200419 years ago
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Inventors
-
Original Assignees
-
Examiners
- Denion; Thomas
- Riddle; Kyle M.
Agents
-
CPC
-
US Classifications
Field of Search
US
- 123 9061
- 123 198 F
- 123 9016
- 123 9031
- 123 196 CP
- 123 196 M
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International Classifications
-
Abstract
An engine valve train has oil flow to valve actuating components cut off or restricted when the valves are closed, to reduce parasitic losses. In an exemplary embodiment, a pushrod has a pivotable connection with a valve actuating rocker arm through which internal oil passages conduct oil for lubricating the rocker arm. The passages are aligned during valve actuation but become misaligned when the valve is closed. Misalignment of the passages at the sliding connection reduces the amount of oil flow through the connection to improve engine efficiency. When applied to cylinder deactivation engines, oil flow to rocker arms of deactivated valves is completely cut off, or reduced, further reducing parasitic losses.
Description
TECHNICAL FIELD
This invention relates to engine valve trains and lubrication systems.
BACKGROUND OF THE INVENTION
It is known in the art to lubricate the components of engine valve trains to control wear of the relatively moving parts. Commonly, pressure lubrication is utilized, although some systems rely on oil spray or mist. It is also known to use pressurized lubricant to operate control devices, such as switching lifters for valve deactivation and cam phasers for varying valve timing. These devices may require increasing lubricant flow or maintaining prescribed oil pressure to assure their proper operation. However, it is desired to limit requirements for increased oil flow and pressure to avoid parasitic losses in the lubricant system that reduce overall engine efficiency.
SUMMARY OF THE INVENTION
The present invention provides a modified valve train for an internal combustion engine which improves engine efficiency by selectively reducing the flow of lubricating oil to the nonmoving parts of the valve train during cylinder deactivation.
Definitions: As used in the following summary, description, claims and abstract, the term pivot and its related terms, such as pivoting, pivotally, pivotable, etc. are intended to refer exclusively to oscillating motion of a member, such as a rocker arm, or a joint, such as a push rod to rocker arm connection as shown in the drawings illustrating the present invention and as these terms are commonly used in reference to such valve train components. Where a rotational joint or motion is intended, the term rotate and variations thereof are utilized to distinguish from oscillatory pivoting motion as referred to above.
Under normal operating conditions, oil is pumped through the engine to provide lubrication for all of the moving components of the valve train. Cylinder deactivation may be accomplished by switching valve lifters which are operated to selectively stop actuation of the intake and exhaust valves of the deactivated cylinders. This invention stems from the recognition that stopping or reducing lubrication to the nonmoving components in the valve train during cylinder deactivation can reduce parasitic losses from excess lubricant flow while continuing to provide necessary lubrication to the valve train when the cylinders are again activated.
In a preferred embodiment, the valves are actuated by cam following switching lifters connected through hollow pushrods with rocker arms that actuate the valves. Oil from the lifters is delivered through a pivotable connection between the pushrods and the rocker arms. Openings in the connection are misaligned when the valves are closed to limit or cut off oil flow. Opening of the valves aligns the openings to provide oil flow to the rocker arms when the valves are opening and closing.
Cutting off or limiting oil flow to the rocker arms when the valves are closed significantly reduces parasitic oil flow in the lubrication system and thereby increases engine efficiency. The arrangement not only limits oil flow to the rocker arms of deactivated cylinders but also limits (or cuts off) oil flow to the rocker arms of active cylinders when their valves are closed, allowing full lubrication flow only when the valve are being opened and closed. Thus, the invention can be used to increase lubrication system efficiency in engines without cylinder deactivation as well as in those having this feature.
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 cross-sectional view of a valve train assembly according to the present invention showing the valve in the closed position.
FIG. 2
is a cross-sectional view of the valve train of
FIG. 1
showing the valve in the open position.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to
FIGS. 1 and 2
of the drawings in detail, numeral
10
generally shows a valve train including a rotatable camshaft
12
, engaging a reciprocable cam follower
14
, a pushrod
15
and a rocker arm
16
, pivotally actuatable by the cam follower
14
and pushrod
15
to actuate a valve
18
. The valve
18
may be either an intake or exhaust valve. The cam follower shown is a switching valve lifter which is operable to deactivate valve actuation in response to an oil pressure signal, as is known in the art.
The camshaft
12
includes a base circle
20
and a lobe
22
extending from the base circle
20
. As the cam
12
rotates, the lobe
22
lifts the cam follower
14
inside a guide
24
of a lifter gallery
25
. Reciprocation of the cam follower
14
reciprocates the pushrod
15
. The pushrod
15
has a spherical connection
28
with the cam follower
14
and the rocker arm
16
as well as a pivotable connection with the rocker arm. As the pushrod
15
reciprocates, the rocker arm
16
pivots about a rocker shaft
30
. As the rocker arm
16
pivots, the valve
18
engaged by the arm
16
opens and closes.
A series of oil passages
32
lubricate the assembly
10
. The interior of the cam follower
14
defines an oil passage
34
, which receives oil for operating the lash adjuster and valve deactivation functions of the switching valve lifter contained in the cam follower and also for lubricating the pushrods
15
and rocker arm
16
. The interior of the pushrod
15
defines an oil passage
36
which extends longitudinally through the pushrod
15
and conducts pressurized oil from the oil passage
34
of the cam follower
14
to an oil passage
38
in the rocker arm
16
, which lubricates the rocker arm pivot action on the rocker shaft
30
. A pivoting connection
40
, between the pushrod
15
and the rocker arm
16
, also creates a lubrication connection
42
, which controls oil flow from the oil passage
36
of the pushrod
15
to the oil passage
38
of the rocker arm
16
.
In accordance with the present invention, the lubrication connection
42
between the rocker arm
16
and the pushrod
15
is a pivotable connection. The connection
42
may resemble a ball and socket or any other type of pivotable connection. The lubrication connection
42
between the rocker arm
16
and the pushrod
15
regulates the amount of oil flow to the rocker arm
16
by varying alignment of the pushrod oil passage
36
with the rocker oil passage
38
at the lubrication connection
42
.
FIG. 1
shows complete misalignment of oil passages
36
,
38
when the rocker arm
16
is in the valve closed position. When oil passages
36
,
38
are completely misaligned, the flow of oil to the rocker arm
16
is cut off. The degree of misalignment in the closed position may be made less severe than shown in
FIG. 1
in order to maintain minimal oil flow through the valve train
10
.
FIG. 2
shows full alignment of oil passages
36
,
38
during the open valve position. The aligned oil passages
36
,
38
allow the maximum amount of oil to flow into rocker arm
16
.
In operation, the camshaft
12
rotates to actuate components of the valve train
10
. Rotation of the camshaft
12
causes the lobe
22
to contact the follower
14
. The lobe
22
lifts the follower
14
to the valve open position and then lowers the follower to the cam base circle
20
, causing the follower
14
to remain stationary until the lobe
22
reengages the follower
14
. The lifting motion of the cam follower
14
actuates the pushrod
15
which, in turn, pivots the rocker arm
16
and opens the valve.
In the valve closed position, oil passages
36
,
38
are partially or fully misaligned to reduce or cut off oil flow to the rocker arm
16
. As the rocker arm
16
is actuated to open the valve
18
, the connection
42
between oil passages
36
,
38
aligns, allowing oil to flow freely from the pushrod
15
into the rocker arm
16
. As the rocker arm
16
pivots back to the closed position, to close valve
18
, the connection
42
between oil passages
36
,
38
again becomes misaligned to cut off or reduce the flow of oil to the rocker arm
16
.
During engine operation on all cylinders, all of the valves operate during each cycle, allowing a consistent flow of oil through the assemblies of the valve train. The flow is shut off or restricted to each rocker arm when its valve is closed. Thus, oil flows to a rocker arm only (or primarily) when its valve is opening and closing. Accordingly, oil flow to each rocker arm is interrupted during each cycle when its valve is closed, but flow to the system should be continuous, since at least one valve will be opening or closing at all times. With this arrangement, total oil flow through the rocker arms will be reduced, compared to other systems, since little or no oil flows to any rocker arm during periods when its valve is closed. Therefore, a substantial reduction in the oil flow may be obtained while adequate oil is supplied during periods when the valve trains are moving and need lubrication.
Cylinder deactivation may be accomplished with a switching valve lifter, such as cam follower
14
, which can be activated or deactivated by an oil pressure signal. However, other forms of cylinder deactivation may be provided. During deactivation, oil flow to the deactivated valve train assemblies
10
is restricted or cut off, further reducing the amount of oil flowing to the inactive cylinders, and reducing total engine oil flow even further. Thus, oil pressure for other engine requirements may be maintained with a smaller oil pump and parasitic losses will be further reduced.
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 an internal combustion engine, the valve train comprising;a cam having a base circle and a lobe extending from the base circle; a cam follower engaging the cam for reciprocation in a guide; and a rocker arm operably engaged by the cam follower at a pivotable connection operative to pivot the rocker arm for opening and closing a valve; the pivotable connection including lubrication passages which are aligned for lubricant flow from the cam follower to the rocker arm when the rocker arm is pivoted in a valve opening direction, the passages being at least partially misaligned when the rocker arm is in a valve closed position for limiting lubricant flow to the rocker arm when the valve is closed; the cam follower being a switching hydraulic valve lifter capable of being deactivated so that the valve remains closed during engine operation and oil flow to the rocker arm in the valve closed position is at least substantially reduced.
- 2. A valve train as in claim 1 wherein a lubrication supply opening in a generally reciprocable component communicates with an inlet opening in the rocker arm, the communication being such that the openings are aligned during valve actuation and become misaligned when the valve is closed.
- 3. A valve train as in claim 1 wherein the pivotable connection is a spherical end and a socket.
- 4. A valve train as in claim 1 including a pushrod between the cam follower and the rocker arm wherein the pivotable connection is between the pushrod and the rocker arm.
- 5. A valve train as in claim 1 wherein misalignment of the passages in the pivotable connection stops the flow of lubrication to the rocker arm.
- 6. A valve train as in claim 1 wherein lubrication flow to the rocker arm is substantially cut off when the valve is closed.
US Referenced Citations (6)