U.S. patent application number 10/278416 was filed with the patent office on 2004-04-29 for variable lift electromechanical valve actuator.
Invention is credited to Alexander, James, Chung, Ha T., Norton, John D..
Application Number | 20040079306 10/278416 |
Document ID | / |
Family ID | 29401139 |
Filed Date | 2004-04-29 |
United States Patent
Application |
20040079306 |
Kind Code |
A1 |
Norton, John D. ; et
al. |
April 29, 2004 |
Variable lift electromechanical valve actuator
Abstract
A variable lift electromechanical valve actuator for use with an
internal combustion engine. The electromechanical valve includes a
first electromagnet, a second electromagnet, and a hydraulic
lifting mechanism. The upper electromagnet is fixedly mounted to a
housing while the lower electromagnet slides in conjunction with
the hydraulic lifting mechanism. Multiple valve lifts are provided
for by the movement of the lower electromagnetic electromagnet.
Variable valve lift allows for more efficient operation of the
engine and reduced power consumption, noise, vibration, and wear
concerns.
Inventors: |
Norton, John D.; (Ann Arbor,
MI) ; Alexander, James; (Canton, MI) ; Chung,
Ha T.; (Canton, MI) |
Correspondence
Address: |
Dickinson Wright PLLC
Suite 800
1901 L. Street NW
Washington
DC
20036
US
|
Family ID: |
29401139 |
Appl. No.: |
10/278416 |
Filed: |
October 23, 2002 |
Current U.S.
Class: |
123/90.11 |
Current CPC
Class: |
F01L 2009/2126 20210101;
F01L 9/20 20210101 |
Class at
Publication: |
123/090.11 |
International
Class: |
F01L 009/04 |
Claims
What is claimed is:
1. An electromechanical valve comprising: a first electromagnet; a
second electromagnet spaced from said first electromagnet; and a
hydraulic lifting mechanism coupled to one of said first and second
electromagnets to change the spacing between said first
electromagnet and said second electromagnet.
2. The electromechanical valve of claim 1 further comprising a
housing and wherein said hydraulic lifting mechanism further
includes a hydraulic slide moveable relative to said housing, said
first electromagnet being fixed to said housing and said second
electromagnet being fixed to said hydraulic slid.
3. The electromechanical valve of claim 2 wherein said hydraulic
slide and said housing define a pressure chamber, said pressure
chamber containing fluid that exerts a pressure on said hydraulic
slide, said hydraulic slide being moveable in response to said
pressure.
4. The electromechanical valve of claim 2 wherein said first
electromagnet is positioned vertically above said second
electromagnet.
5. The electromechanical valve of claim 2 further including a pin
attaching said first electromagnet to said housing and a passageway
defined in said hydraulic slide, said pin passing through said
passageway.
6. The electromechanical valve of claim 1 further including a first
spring positioned between said first electromagnet and said
hydraulic lifting mechanism.
7. The electromechanical valve of claim 1 further comprising a
second spring and a cylinder head, said second spring being located
between said cylinder head and said lower electromagnet.
8. The electromechanical valve of claim 1 further including an
armature having a neutral position, said first spring and said
second spring exerting a first pressure and a second pressure on
said armature in said neutral position, said first pressure and
said second pressure approximately centering said armature between
said first electromagnet and said second electromagnet at said
neutral position.
9. An electromechanical valve for an internal combustion engine
comprising: an upper electromagnet; a lower electromagnet spaced
from said upper electromagnet, a hydraulic slide coupled to said
lower electromagnet to change the spacing between said lower
electromagnet and said upper electromagnet.
10. The electromechanical valve of claim 9 further including an
actuator stem, said upper and lower electromagnet surrounding a
portion of said actuator stem.
11. The electromechanical valve of claim 10 further including an
armature attached to said actuator stem, said armature being
located between said upper electromagnet and said lower
electromagnet.
12. The electromechanical valve of claim 9 further including a
housing defining a defining a fluid chamber containing a fluid that
exerts a pressure on said slide, said slide moving relative to said
housing in response to said pressure.
13. The electromechanical valve actuator of claim 12 further
including a hydraulic pump in fluid communication with said fluid
chamber, said hydraulic pump changing a fluid pressure in said
fluid chamber.
14. The electromechanical valve actuator of claim 12 further
including a cylinder head and valve stem having an open position
with a lift relative to said cylinder head, said lift being
proportional to said pressure.
15. An internal combustion engine having a variable lift
electromechanical valve comprising; an upper electromagnet; a lower
electromagnet spaced from said upper electromagnet; and a hydraulic
positioning means connected to said lower electromagnet to change
the spacing between said upper electromagnet and said lower
electromagnet.
16. The internal combustion engine of claim 15 wherein said
hydraulic positioning means includes a fluid chamber containing a
fluid that exerts a pressure on a hydraulic slide, said hydraulic
slide moving said lower electromagnet relative to said upper
electromagnet in response to said pressure.
17. The internal combustion engine of claim 17 wherein said fluid
exerts a first pressure and a second pressure, said first pressure
having a first spacing between said upper electromagnet and said
lower electromagnet, said second pressure having a second spacing
between said upper electromagnet and said lower electromagnet.
18. The internal combustion engine of claim 17 wherein if said
second pressure is greater than said first pressure then said
second spacing is greater than said first spacing.
19. The internal combustion engine of claim 17 wherein as said
pressure increases said space between said upper electromagnet and
said lower electromagnet increases.
20. The internal combustion engine of claim 19 further comprising
an upper spring and a lower spring, said upper spring and said
lower spring exerting a first spring pressure and a second spring
pressure, said first spring pressure and said second spring
pressure increasing as said pressure increases.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to electromechanical valve
actuators and more particularly to variable lift electromechanical
valves for internal combustion engines.
[0002] Engine valves control the flow in and out of the cylinders
in internal combustion engines. Engine valves are typically
controlled by camshafts that rotate, at a speed proportional to the
crankshaft causing the valves to open and close at specified
intervals. An example of a typical valve train includes a rotating
camshaft having elliptical lobes which contact tappets or lash
compensators on the valve. As the elliptical lobe presses against
the tappet, the valve is pushed open at determined intervals, and
as the elliptical lobes rotate away from the tappet, the valve is
closed by a spring. The opening and closing times of the valves are
determined by the geometry of the lobes, and the relative angular
position with respect to the crankshaft when the engine is
assembled. Manufacturers can adjust this timing by altering the
shape, size, and angular location of the elliptical lobes. However,
the timing as well as the torque curve is typically fixed at the
time the engine is assembled. The amount of valve lift is also
determined by the lobes on the camshaft and therefore determined
when the engine is assembled. The lack of variable valve timing and
variable valve lift reduces engine optimization and therefore may
reduce engine efficiency.
[0003] Another problem with conventional engines is that they
require a throttle body and the associated components. The throttle
body restricts air flow into the engine. One problem with using a
throttle body is that engine efficiency is reduced due to intake
restrictions. When air flows through the throttle body, an air
pressure drop occurs across the throttle plate. Therefore, when the
intake valve opens under throttled conditions, the piston pulls in
air of a lower pressure than the surrounding atmosphere, resulting
in engine inefficiencies. Manufacturers have strived to create true
throttless engine operation to increase engine efficiency as well
as allow for drive-by-wire systems.
[0004] To address problems associated with traditional valves
activated by camshafts, some manufacturers have attempted to
substitute electromechanical valve actuators (also known as
electromagnetic valve actuators) in place of camshafts. Generally,
these electromechanical actuators include upper and lower
electromagnets that are formed from lamination stacks and coiled
wire. The electromechanical valve actuators also include an
armature located between the electromagnets. The armature generally
forms a plane somewhat perpendicular to the valve stem and includes
an armature stem, that passes through both the upper and lower
electromagnets, in order to open or close a valve.
[0005] In operation, the electromagnets are selectively energized,
creating a magnetic force to draw the armature to the energized
electromagnet. The surface of the electromagnet which the armature
contacts may be referred to as a pole face. As the armature moves
back and forth in pole face to pole face operation, the valve is
opened and closed. Electromechanical valve actuators allow for
complete control of the timing of every valve. Electromechanical
valve actuators may also open more than one valve at the same time.
One problem with electromechanical actuated valves is that as the
distance between the armature and the magnetized electromagnet
decreases, the magnetic force exponentially increases. The increase
in magnetic force causes the armature to increase in velocity as it
approaches an energized electromagnet. The armature then impacts
the electromagnet, causing noise and vibration. Forceful contact
between the armature and electromagnet also may cause excessive
wear on the components of the electromechanical valve actuator and
other engine components.
[0006] Some manufacturers have shaped the power profile supplied to
the lamination stack in an effort to soften the impact, but this
may increase the time it takes the armature to travel from pole
face to pole face. An increase in time to travel from pole face to
pole face increases the transition times and may prevent the engine
from operating properly because the valve cannot open and close
fast enough.
[0007] At idle speeds, electromechanical valves may consume a
significant portion of power to overcome the springs in the system,
and move the armature from the pole face to pole face. Enough power
must be applied to the electromagnet to overcome any exhaust
pressure in the cylinder during the opening of an exhaust valve,
which creates a large draw on the electrical system of the engine
at idle speeds. The springs may be sized to accommodate desired
valve transition times as well as provide enough force to open
against any exhaust pressure. Another problem with
electromechanical valves is that they are not capable of operating
throttless in all engine conditions. For many electromechanical
valves, varying the valve timing still leaves large regions at mid
to high flow regimes where they are not able to operate. These
voids in operating conditions many times occur in the most
desirable operating regions of the engine. Yet another problem is
that electromechanical valves are not as efficient as they can be,
because the valve lift or how far the valves open can not be
changed. Valve lift is generally set by operating conditions that
demand maximum flow, which cause inefficient engine operation in
low flow conditions.
[0008] To solve some of the problems associated with
electromechanical valves, a few manufacturers have varied the lift
of the valves. Varying the lift of the valves may help increase the
efficiency of the engine by allowing the lift of the valve to match
the operating conditions. Reduced valve lift at idle conditions
also helps to reduce noise, vibration, power consumption, and wear
concerns.
[0009] A disadvantage some of these systems have is that the valve
has only two lift positions, a high and a low position. The
inability to adjust the lift throughout the range reduces the
optimization of engine operation associated with variable lift and
can prevent maximum engine efficiency from being obtained. Another
problem with some of these systems is that the spring bias may be
offset as the valve lift is changed which may cause the armature
plate, when at rest, such as when the valve actuator is unpowered
and no magnetic force is applied, to be off center between the
lamination stacks. During operation, this bias may cause the
armature to be more forcefully attracted to one pole face, causing
noise and vibration. This bias may also make it difficult to be
attracted to the other electromechanical plate, thereby requiring
additional power.
[0010] Another system addresses some of these problems by providing
a range of variable lifts. The problem with this variable valve
lift system is that it is difficult to accurately determine the
lift of the valve. The lash in the system may make it even more
difficult. Due to the type of and amount of moving parts, the
inaccuracy of the system only increases with use. Yet another
problem with this system is the increase in moving parts, including
the use of an additional motor may decrease the reliability of the
system over time.
SUMMARY OF THE INVENTION
[0011] The aforementioned problems are overcome in the present
invention where an electromechanical valve includes an actuator
that adjusts the lower magnet, varying the valve lift, along with
the armature spring seat, varying the bias and spring forces,
throughout a range of adjustment. More specifically, the present
invention includes a variable lift actuator in conjunction with an
electromechanical valve, providing variable valve lift while
centering the armature in all lift positions between the two
electromagnets and reducing the impact forces of the armature
against the electromagnets during pole face to pole face
operation.
[0012] A hydraulic actuator is used to vary the lift of the valve,
allowing for maximum engine efficiency by allowing a range of flow
depending on the engine requirements, in addition to variable valve
timing. The present invention allows true throttless operation
through its entire engine speed and load ranges. The valve lift can
control the air flow, eliminating the need for a throttle body.
Variable valve lift and variable timing allow the engine to provide
optimum torque at all rpms, unlike some electromechanical valves,
which have gaps in the rpm power band where the engine can not
function properly without throttling. Another benefit of the
hydraulic actuator providing variable valve lift is that a
hydraulic pocket also provides a dampening means, which may reduce
impact noise and wear concerns. The present invention also allows
complete pole face to pole face movement of the armature no matter
what lift is being used. Complete pole face to pole face operation
also helps accurately determine the amount of valve lift. Variable
valve lift also reduces the spring force thereby reducing noise and
wear concerns, as well as reduces the power required to hold the
armature against either pole face, especially during engine
operation with reduced valve lift. Variable valve lift combined
with variable valve timing allows for efficient engine operation
and minimal energy consumption.
[0013] Further scope of applicability of the present invention will
become apparent from the following detailed description, claims,
and drawings. 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.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The present invention will become more fully understood from
the detailed description given below, the appended claims, and the
accompanying drawings in which:
[0015] FIG. 1 is a sectional view of an engine valve assembly with
the valve shown in the fully closed position with reduced lift;
[0016] FIG. 2 is a sectional view similar to FIG. 1 but with the
valve shown in its middle position with reduced lift;
[0017] FIG. 3 is a sectional view similar to FIG. 1 but with the
valve shown in the open position with reduced lift;
[0018] FIG. 4 is a sectional view similar to FIG. 1 but with the
valve being in the closed position with full lift;
[0019] FIG. 5 is a sectional view similar to FIG. 3 showing the
valve in a open position set in the mode for full lift; and
[0020] FIG. 6 is a block diagram of the engine valve assembly and
control system.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0021] FIG. 1 illustrates an electromechanical valve actuator
assembly 10 which is mounted on an internal combustion engine to
open and close the valves (e.g., intake or exhaust valves).
[0022] The electromechanical valve assembly 10 is generally mounted
on the cylinder head 12 of the internal combustion engine. While
the cylinder head 12 may be formed in a variety of shapes and
configurations, it typically includes a port 14, a valve seat 16,
and a valve guide 18. The port 14 may be an intake or an exhaust
port depending on the function of the valve.
[0023] The valve 20 includes a valve disc or head 22, a tapered
portion 24, and a valve stem 26. An upper spring retainer 32 and a
lower spring retainer 34 may also be included. The valve 20 and the
cylinder head 12 are formed and assembled as generally well known
in the art. The valve guide 18 receives the valve stem 26 and
aligns the valve 20 as it moves up and down so that a tight seal is
formed between the valve seat 16 and the tapered portion 24
surrounding the valve disc 22, when the valve 20 is in its closed
position, as may be seen in FIGS. 1 and 4.
[0024] The electromechanical valve actuator 10 generally includes a
housing 40 defining a cavity containing electromagnets 52 and 54,
an armature stem 60, an armature 70, and a hydraulic lift mechanism
80. The upper and lower electromagnets 52 and 54 move the armature
70 and attached armature stem 60 to drive the engine valve 20
between its open and closed positions.
[0025] The housing 40 may be formed in a variety of sizes and
shapes, which may be dictated by space constraints of the internal
combustion engine. The housing 40 provides structural rigidity and
attaches the electromechanical valve actuator 10 to a cylinder head
12 of an internal combustion engine. Of course, it should be
readily apparent to one skilled in the art that a variety of means
may be used to provide the structural rigidity or method of
attachment.
[0026] In the illustrated embodiment, the upper electromagnet 52 is
fixed relative to the housing 40 such as by pins 42 while the lower
electromagnet 54 is mounted within the housing 40 so that it is
movable relative to the housing 40. Suitable electromagnets are
generally well known in the art and can have a variety of shapes
that may be formed from the individual plates of magnetically
conductive material to form a lamination stack. The electromagnets
52 and 54 may include a coil of wires 53 wound within the
lamination stack. The electromagnets 52 and 54 are connected to a
source of electrical current (not shown) which can be selectively
turned on and off independently by a controller such as an engine
management system 100 (FIG. 6). An energized electromagnet 52 or 54
provides magnetic force to attract the armature 70. It should
readily be recognized that a separate means may be used in place of
the housing 40 to hold the upper electromagnet 52 in place.
[0027] The armature 70 is mounted to move with the armature stem 60
and is located between the upper electromagnet 52 and the lower
electromagnet 54. In the illustrated embodiment, the surfaces of
the armature 70 facing the electromagnets 52 and 54 are
approximately the same size and shape as the surfaces of the
electromagnets 52 and 54 facing the armature 70. Of course, it
should be readily obvious to one skilled in the art that the sizes
and shapes of the armature 70 and of the electromagnets 50 may vary
between applications.
[0028] An armature spring 62 and a valve spring 64 operably engage
the valve to urge the valve toward its open or closed positions.
The armature spring 62 is mounted above the upper electromagnet 52
within the housing 40 to exert a biasing force urging the valve 20
toward its open position. In the illustrated embodiment, the
armature spring 62 is a compression spring and is located between
the armature spring retainer 32 and the hydraulic lift mechanism
80. The armature spring 62 may be any compression spring known in
the art for use with traditional valves or electromechanical
valves. The size, shape, and location of the armature spring 62 may
vary from application to application. A valve spring 64 is mounted,
in the illustrated embodiment, between the cylinder head 12 and the
valve spring retainer 34. The valve spring 64 is also a compression
spring as shown in the illustrated embodiment. Of course, it should
be readily recognized to one skilled in the art that other
placements of the springs 62 and 64 are possible and that certain
placements may also result in opening and closing of the valves
differently than shown in the illustrated embodiment.
[0029] The hydraulic lift mechanism 80 varies the amount of valve
lift and, in the illustrated embodiment, includes a hydraulic slide
82 and a hydraulic chamber 84. The hydraulic slide 82 is formed in
the illustrated embodiment in the shape of a sleeve having an upper
segment 72, a lower segment 74, and a passage 78 to accommodate the
upper electromagnet 52 and pins 42. The lower electromagnet 54 is
attached to move with the slide 82 by a variety of means such as a
compression fit, adhesive, bonding or pins. The hydraulic chamber
84 is defined in the illustrated embodiment at the upper end of the
housing 40 by the housing and the hydraulic slide 82. As the
pressure in the chamber 84 is varied, the slide 82 moves relative
to the housing 40. As the lower electromagnet 54 moves with the
slide 82 and the upper electromagnet 52 is fixed to the housing 40,
movement of the slide 82 changes the distance between the
electromagnets 52 and 54 and the length of the valve stroke.
[0030] In the illustrated embodiment, hydraulic fluid in the
hydraulic chamber 84, such as engine oil, is pressurized by the oil
pressure of the engine or an auxiliary pump. In some embodiments
the hydraulic lift mechanism 80 may include hydraulic lines 86,
hydraulic valves 88 and a pump 102. The hydraulic lines 86 provide
a fluid connection between the hydraulic chamber 84 and the pump
102. Hydraulic valves 88 may be situated between the hydraulic
chamber 84 and the pump 102 to control flow through the hydraulic
lines 86. The hydraulic valves 88 control the height of the
hydraulic slide 82 in conjunction with the forces from the springs
62 and 64. The hydraulic valve or valves 88 control the fluid
pressure in the hydraulic chamber 84. In the illustrated
embodiment, the hydraulic valve 88 is a spool valve. A spool valve
is used because it uses a series of hydraulic channels to maintain
a specified position regardless of the forces acting on the slide
82. The hydraulic valve 88 is controlled by the engine management
system 100. The engine management system 100 can easily control
valve lift through existing techniques of determining air flow
needed to the engine. Of course, the engine management system may
be programmed from lab tests or road tests of what valve lifts are
needed under specified engine operating conditions to maximize
efficiency. In the illustrated embodiment, the pump 102 is the
engine oil pump and engine oil is used as the hydraulic fluid. Of
course a separate pump as well as separate hydraulic fluid may be
used. A separate means for heating the fluid may also be included
(not shown).
[0031] In operation, the valves are opened and closed as is well
known in the art for electromechanical valves. While the system is
unpowered, the armature 70 is in a neutral position, approximately
centered between the upper and lower electromagnets 52 and 54 due
to the biasing of the springs 62 and 64. Upon start up, either the
upper or lower electromagnet 52 or 54 is energized, attracting the
armature 70, thereby opening or closing the valve 20. The power is
then switched between the electromagnets 52 and 54 causing the
armature 70 to travel pole face to pole face, opening and closing
the valve 20. As with most electromechanical valves, the timing of
the opening and closing may also be varied for more efficient
engine operation.
[0032] When the valve 20 is commanded to a full open or full closed
position, the armature 70 is attracted to an electromagnet pole
face. In order to hold the valve 20 closed enough current must be
delivered to the electromagnet pole face to produce a magnetic
force larger than the spring force which acts in the opposite
direction. The illustrated embodiment has the advantage that during
reduced lift operation the hydraulic slide moves resulting in a
lower spring force that the electromagnet must overcome. In other
words, during low lift operation, the spring force opposing the
electromagnet force is reduced. This results in less required
electromagnet force and therefore less power consumption by the
electromagnet when compared to a stationary full lift actuator.
[0033] The amount of valve lift during engine operation may be
changed by varying the pressure in the hydraulic chamber 84 and
therefore the position of the slide 82. A low pressure causes the
hydraulic slide 82 to be in a reduced lift position, as shown in
FIGS. 1-3. Valve spring 64 exerts pressure on the slide 82, causing
the slide to move upward during low pressure conditions such as at
low rpms. Of course, other means may be used to exert pressure on
the hydraulic slide 82 to move the slide 82 to a reduced lift
position such as an additional spring or an oil pocket. The reduced
valve lift allows for optimized throttless engine operation through
all ranges.
[0034] As the engine revolutions increase, more flow is needed to
and from the cylinders for the engine to operate efficiently and at
the desired power levels. Engine oil pressure increases as the
revolutions increase and pushes the hydraulic slide 82 downward to
a desired lift, as shown in FIGS. 4 and 5, at the maximum lift.
When the hydraulic slide 82 moves downward so does the lower
electromagnet 54, causing the armature to travel a greater distance
between the upper and lower electromagnets 52 and 54. It should
readily be seen that because the hydraulic slide 82 compresses or
relaxes spring 62, the armature 70, when at rest, is centered
between the upper and lower electromagnets 52 and 54, no matter
what lift is being provided.
[0035] To provide more precise control over the valve lift, the
hydraulic lifting mechanism 80 may use the hydraulic valves 88 and
separate oil pump 102. A separate hydraulic pump 102 also can be
helpful to provide full valve lift in any engine operating
conditions. For example, a separate pump 102 is useful at low rpms
where lots of torque is needed, such as pulling a heavy trailer, to
increase valve lift and allow more flow. The hydraulic valves 88
may reduce valve lift at higher rpm conditions where little power
is needed from the engine, for example, during operation at
constant speeds such as operation of a vehicle on the highway.
[0036] In operation, the above electromechanical valve also allows
for throttless operation. The variability of the valve lift and
timing allows the amount of air entering the cylinder to be
controlled without a throttle body or throttle plate. This allows
the piston to pull in atmospheric pressurized air, thereby
increasing engine efficiency.
[0037] The foregoing discussion discloses and describes an
exemplary embodiment of the present invention. One skilled in the
art will readily recognize from such discussion, and from the
accompanying drawings and claims that various changes,
modifications and variations can be made therein without departing
from the true spirit and fair scope of the invention as defined by
the following claims.
* * * * *