VALVETRAIN OIL CONTROL SYSTEM AND OIL CONTROL VALVE
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of U.S. Provisional Application
61/082,575, filed July 22, 2008, which is hereby incorporated by reference in its entirety.
TECHNICAL FIELD
The present invention relates to p oil control system for a valvetrain, and
more specifically, to an arrangement and method for reducing oil consumption by the
valvetrain.
BACKGROUND OF THE INVENTION
A hydraulic control system for an engine supplies oil to various engine
components and may also include oil control valves to control oil under pressure that may
be used to, for example, switch latch pins in switching lifters, switching rocker arms, and
switching lash adjusters in engine valvetrain systems. Valve actuation systems include,
but are not limited to, valve deactivation and variable valve lift systems.
Valve lifters are engine components that transfer cam motion which
controls the opening and closing of exhaust and intake valves in an engine. Lash
adjusters and rocker arms may also be used to change lift profiles on exhaust and intake
valves in an engine. In addition to varying valve lift, variable valve actuation systems
may selectively activate or deactivate the engine valve. The engine valves are
deactivated or locked out to disable operation of some cylinders in an engine when power
demands on an engine are reduced. By deactivating cylinders, fuel efficiency of an
engine may be improved.
Engine oil control valves must operate with minimum response times to
maximize engine efficiency and increase engine durability. Latch pin switching response
times include latch pin activation response times and deactivation response times. In
variable valve actuation systems, the limited time window for valve actuation is critical
and must be minimized. Additionally, as the flow rate and pressures within the system
changes due to temperature and engine speed to actuate the valves, the oil flow rate to all
the system components is similarly affected.
SUMMARY OF THE INVENTION
A hydraulic control system is provided for reducing oil consumption of an
engine valvetrain. The hydraulic control system includes an oil reservoir and an oil pump
fluidly connected to the oil reservoir to pump oil from the reservoir to at least one engine
component.
An oil control valve is fluidly connected to the oil reservoir i*nd the uij
pump includes a housing defining a first chamber, a second chamber and a third chamber.
A wall of the housing is located between the first and the second chamber. The wall
defines an orifice having an angled edge to form a valve seat. A diaphragm is mounted to
the housing and forms a wall between the second chamber and the third chamber. A
poppet is mounted on the diaphragm. The poppet extends through the orifice and is
moveable relative to the valve seat based upon a change in pressures within the first
chamber, the second chamber, and the third chamber. Additionally, a solenoid valve
selectively fluidly connects the first chamber to the third chamber.
A method of controlling oil flow within a valvetrain includes pumping
fluid from a fluid reservoir to a control valve and varying the flow rate through the
control valve such that fluid enters the control valve at a first pressure and flows from the
control valve at a second pressure. The fluid from the control valve is directed to at least
one engine component of the valvetrain. The engine component is fluidly actuated from
a first position to a second position based upon the second pressure from the control
valve.
Varying the flow rate through the control valve includes increasing the
flow rate through the control valve to increase the second pressure to a first level which
actuates the engine component to the first position. After the engine component is
actuated, the flow rate through the control valve is maintained such that the second
pressure is at a second level which is less than the first level and sufficient to maintain the
engine component in the first position. To actuate the engine component to the second
position, the flow rate through the control valve is then decreased to decrease the second
pressure to a third level. The fluid flow rate through the control valve is then maintained
such that the second pressure is at a fourth level that is less than the second level and
sufficient to maintain the at least one engine component in the second position.
The above features and advantages and other features and advantages of
the present invention are readily apparent from the following detailed description of the
best modes for carrying out the invention when taken in connection with the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGURE 1 is a schematic illustration of a hydraulic control system;
FIGURE 2 is plot of pressure within the supply and control galleries
versus time for the hydraulic control system in Fig. 1;
FIGURE 3 is a schematic cross-sectional illustration of a variable flow
valve for use with the hydraulic control system of Figs 1 and 2.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to Fig. 1, wherein like reference numbers refer to the same or
similar components throughout the several views, a hydraulic control system 10 is
illustrated. The hydraulic control system 10 includes an oil reservoir 12 and an oil pump
14. The oil pump 14 pumps oil from the oil reservoir 12 to various engine components 16.
The engine components 16 includes at least one engine component 16A which includes a
latch pin 18 for actuation of the at least one engine component 16A between an engaged
and disengaged position. The at least one engine component 16A could be a lash adjuster.
a valve lifter, or a rocker arm. Although the embodiment described below is with reference
to one latch pin 18, multiple latch pins 18 may be actuated at one time. The engine
components 16 also include other valve-train components such as bearings.
UMH5]" Engagement and disengagement of the latch pin 18 within the at least one
engine component 16A is actuated by the hydraulic control system 10 as described below.
For example, the at least one engine component 16A is a lash adjuster that changes the lift
properties for engine intake and exhaust valves, as is known by those skilled in the art. Oil
from the oil pump 14 passes through a oil control valve assembly 20 to the engine
components 16 including the at least one engine component 16Abefore returning to the oil
reservoir 12.
The oil control valve assembly 20 includes a solenoid valve 22 and a
variable flow valve 24. The oil control valve assembly 20 varies the flow rate from an oil
supply gallery 26 to a control gallery 28 to vary pressure within the control gallery 28. The
variation in pressure within the control gallery 28 will engage or disengage the latch pin 18.
Oil flow from the control gallery 28 also flows to the other engine components 16 prior to
returning to the oil reservoir 12.
Referring to Figures 1 and 2, a method of operating the oil control system
10 is explained in further detail. Oil enters the variable flow valve 24 from the supply
gallery 26 at a first pressure Pi. Oil flow is directed through the variable flow valve 24 to
the control gallery 28 which is at a second pressure P2. The second pressure P2 of the
control gallery 28 is a sufficient pressure to lubricate the engine components 16. An
exemplary maintenance pressure for lubricating and assuring performance of the engine
components 16 is 5-12 psi within the control gallery 28. As oil enters the engine
components 16 at the P2, the variable flow valve 24 increases or decreases flow in an
effort to reach pressure balanced equilibrium within the variable flow valve 24.
The solenoid valve 22 includes an electro-magnetic coil 23. When the
electro-magnetic coil 23 for the solenoid valve 22 is energized, a bypass 30 to the solenoid
valve 22 is opened. Oil from the supply gallery 26 flows through the solenoid valve 22 to a
chamber 32 within the variable flow valve 24. The increased pressure within the chamber
32 significantly biases the pressure balanced equilibrium within the variable flow valve 24
and adjusts the variable flow valve 24 to increase the flow rate from the supply gallery 26,
to the control gallery 28. The sudden increase in flow rate into the control gallery 28
causes pressure within the control gallery 28 to increase, which results in sufficient
pressure to effect actuation of the latch pin 18. Actuation of the latch pin 18 moves the
latch pin 18 from a first position to a second position. In the embodiment shown the latch
pin 18 is a normally engaged pin and actuation of the latch pin 18 from the first position to
the second position moves the pin from an engaged position to a disengaged position. An
example of the latch pin 18 disengagement pressure Pdis for the embodiment shown is 15-
20 psi. This is illustrated by the dashed lines of Figure 2. Due to the sudden increase in
flow rate into the control gallery 28 from the supply gallery 26, the control gallery 28
pressure P2 will increase to a first level well past the latch pin 18 disengagement pressure
Pdis- The rate of the pressure increase within the control gallery 28 is illustrated by the
slope of P2 on Figure 2. The over-rise in pressure decreases the time taken for the control
gallery 28 to increase to the disengagement pressure Pdis- That is, the rate of pressure
increase (the slope of P2) is steeper, reaching the disengagement pressure Pdis sooner and
actuating the latch pin 18 more quickly. Thus, the travel time to actuate the latch pin 18 is
decreased.
Once the latch pin 18 is disengaged, the increased flow rate from the supply
gallery 26 to the control gallery 28 that maintains the higher pressure P2 in the control
gallery 28 is not necessary. This higher pressure increases the oil flow through the engine
components 16 and back to the reservoir 12, which decreases the engine efficiency.
However, the pressure P2 in the control gallery 28 must be maintained above an
engagement pressure Pdis for the latch pin 18 such that the normally engaged latch pin 18
is maintained in the second position, which in this embodiment is the disengaged position.
As the pressure P2 in the control gallery 28 increases, the variable flow valve 24 re-
establishes an equilibrium force between the spring 58 at a reduced load, the pressure in
chamber 32 against the diaphragm 52, and the pressure in chamber 24 against the
diaphragm 52. Pressure also acts on the poppet 50 from the first chamber 42 and the second
chamber 44. The flow rate from the supply gallery 26 to the control gallery 28 settles with
the control gallery pressure P2 at a second level. The flow rate is greater than the flow rate
when the solenoid valve 22 is off and the bypass 30 is closed. However, the variable flow
valve 24 also allows the flow rate to settle such that the pressure P2 in the control gallery 28
at the second level is only slightly above the pressure required to maintain the latch pin 18
in the second position. In the embodiment shown, the control gallery 28 is at a pressure of
approximately 30 psi and the pressure to maintain the second position for the latch pin 18 is
at 25 psi. The flow rate creating this pressure can be maintained until it is time to move the
pin 18 back to the first position, which is the engaged position in this embodiment. The
variable flow valve 24 allows the flow rate to the control gallery 28 to settle at a lower flow
rate, resulting in the lower pressure in the control gallery 28. Therefore, the oil flow
through all the engine components 16 is reduced, reducing oil consumption of the engine
components 16 after the latch pin 18 has been moved to the second position and prior to the
latch pin 18 being moved back to the first position.
When it is time to reengage the latch pin 18, the magnetic coil 23 for the
solenoid valve 22 is de-energized. The solenoid valve 22 switches to an exhaust position.
The bypass 30 from the supply gallery 26 to the chamber 32 is closed. However, the
chamber 32 is now opened through the solenoid valve 22 to the exhaust gallery 34. Oil
within the chamber 32 drains back to the oil reservoir 12. The sudden pressure loss within
the chamber 32 causes the force balance within the variable valve 24 to bias the poppet 50
toward the valve seat 46 shutting off the flow to second chamber 44 and control gallery 28.
Thus, the pressure within the control gallery 28 drops to a third level. Similar to when the
latch pin 18 is disengaged, the pressure change in the in the control gallery 28 is more than
what is needed to move the latch pin 18. Thus, the actuation time to re-engage the latch pin
18 is decreased. Additionally, because the variable flow valve 24 previously allowed the
pressure P2 within the control gallery 28 to remain only slightly above the disengagement
pressure Pdis of the pin 18, the engagement pressure Peng of the latch pin 18 is reached
quickly which also reduces the actuation time.
Once the latch pin 18 is engaged, the variable flow valve 24 re-establishes
an equilibrium force between the spring 58 at an increased load, the lower pressure in the
third chamber 32 acts against the diaphragm 52, and the pressure P2 in the second chamber
44 also acts against the diaphragm 52. Pressure is also acting on the poppet 50 from the
first chamber 42 and the second chamber 44. The flow rate settles at a fourth level that
maintains pressure sufficient to maintain engine performance and lubricate the engine
components 16. As mentioned above, in the embodiment illustrated in Figure 2, the flow
rate is such that the pressure P2 within the control gallery 28 is approximately 10 psi.
Although the above embodiment is described as having at least one engine
component 16A with a normally engaged latch pin 18 that may be disengaged with the oil
control valve 20, the at least one engine component 16A may alternately be a normally
disengaged pin 18 which is engaged with the oil control valve 20. One skilled in the art
would know the proper arrangement for the at least one engine component 16A and latch
pin 18 based upon the engine and oil control system 10 for which it is used.
Referring to Figure 3, an embodiment of a variable flow valve 24 is
illustrated. The variable flow valve includes a housing 40 defining a first chamber 42 and a
second chamber 44. An orifice 46 is defined by a wall 48 which divides the first chamber
42 from the second chamber 44. Oil enters the first chamber 42 from the supply gallery 26
at a first pressure Pi and flows through the orifice to the second chamber 44 which is at the
second pressure P2 and connected to the control gallery 28. In the embodiment shown, the
orifice 46 has an angled edge defined by the wall 48 which acts as a seat for a poppet 50.
Other arrangements for the orifice 46 to form a valve seat may also be utilized, such as the
wall 48, may be flat or otherwise shaped to form the valve seat. One skilled in the art
would know the proper arrangement for a valve seat given the variable flow valve 24
application and specifications.
The poppet 50 is mounted to a diaphragm 52. The diaphragm 52 is located
between the second chamber 44 and a third chamber 32. The diaphragm 52 seals the
second chamber 44 from the third chamber 32 and allows the poppet 50 to move along an
axis A. A damper 56 is located at an opposing end of the poppet 50 and dampens
oscillations of the poppet 50 that would occur as a result of the changes in the pressure
between the first chamber 42, the second chamber 44 and the third chamber 32. In the
embodiment shown the damper 56 is illustrated as a fluid damper 56. However, other types
of dampers may be utilized as is known to those skilled in the art. A spring 58 is located in
the third chamber 32 and biases the poppet 50 to a neutral open position as shown in Figure
3. The spring 58 acts upon a support 60 which is secured to and protects the diaphragm 52.
As described above, and with reference to Figures 1 and 2, fluid from the
supply gallery 26 enters the first chamber 42 and flows through the orifice 46 into the
second chamber 44, where it then exits the flow control valve 24 to the control gallery 28.
When the electro-magnetic coil 23 for the solenoid valve 22 is energized the bypass 30 is
opened and fluid also flows from the supply gallery 26, through the first chamber 42, into
the bypass 30 and through the solenoid valve 22 to the third chamber 32. The pressure
within the third chamber 32 increases and the resulting pressure differential between the
second chamber 44 and the third chamber 32 results in unbalancing the force balance
equation and creating a biasing force at the diaphragm 52. Therefore, oil flowing into the
third chamber 32 forces the diaphragm to flex and moves the poppet 50 axially along the
axis A to open the orifice 46 to a greater extent and increase the flow rate from the first
chamber 42 to the second chamber 44. Thus, flow from the supply gallery 26 to the control
gallery 28 is increased when the solenoid valve 22 is activated. Additionally, because the
orifice 46 is larger in diameter than the valve seat (not shown) within the solenoid valve 22
a smaller magnetic coil 23 is sufficient to energize the solenoid valve 22. Thus, reducing
the amount of copper required by the magnetic coil 23, the current to the solenoid valve 22,
and the amount of oil pressure required to open the solenoid valve 22. Because the size of
the orifice 46 allows for increased flow rate of fluid to the control gallery 28 this also
increases the rate of latch pin 18 motion and increases the pressure rise (the slope of P2)
from PDis to Peng on the oil control system 10 over systems having smaller flow rates to the
control gallery 28.
After the initial flow of fluid into the third chamber 32, the force applied to
the diagram 52 will balance. The variable valve 24 will stabilize at a point that allows
increased flow from the first chamber 42 to the second chamber 44 than when the solenoid
valve 22 is not energized. The pressure increase in the point of equilibrium is based on the
force balance equation. The force balance equation is the force of spring 58 plus the force
on the area of the diaphragm 52 multiplied by the pressure within the third chamber 32
minus the force due to the area of the orifice 46 times the control gallery 28 pressure P2,
which is equal to the force due to the area of the orifice 46 times the supply gallery 26
pressure Pi plus force on the area of the diaphragm 52 times the control gallery 28 pressure
P2. This is represented by the following force balance equation:
F(spring 58)+F((area of diaphragm 52)*P(chamber 32)) - F((area of orifice 46)*P2)
= F((area of orifice 46)*Pi) + F((area of diaphragm 52)*P2)
When the solenoid valve is de-energized, the bypass 30 is fluidly
disconnected from the third chamber 32. The fluid within the third chamber 32 exits
through the exhaust gallery 34 (shown in Figure 1) to the oil reservoir 12. The flow of oil
out of the third chamber 32 decreases the pressure within the third chamber 32 and the
fluid pressure P2 within the second chamber 44 to cause the poppet 50 to move axially
along the axis A to reduce flow through orifice 46. Due to the extreme delta pressures on
both sides of the diaphragm 52 and unbalancing of the force balance equation, the poppet
will momentarily close the orifice 46. As the pressure P2 in the second chamber 44
drops, the poppet begins to reopen until the force balance equation come back to
equilibrium. The spring 58 prevents the fluid pressure Pi in the first chamber 42 from
keeping the orifice 46 closed. Fluid continues to flow from the first chamber 42 to the
second chamber 44, although at a reduced rate than before. The poppet 50 is again in the
position shown in Figure 3 which allows fluid to flow into the control gallery 28 at a
sufficient rate to maintain the minimal pressure P2 needed to lubricate the engine
components 16.
While the best modes for carrying out the invention have been described
in detail, those familiar with the art to which this invention relates will recognize various
alternative designs and embodiments for practicing the invention within the scope of the
appended claims.
WE CLAIM:
1. An oil control valve (20) comprising:
a housing (40) defining a first chamber (42), a second chamber (44) and a
third chamber (32);
a wall (48) of the housing (40) located between the first chamber(42) and
the second chamber (44), wherein the wall (48) defines an orifice (46);
a diaphragm (52) mounted to the housing (40) and forming a wall (48)
between the second chamber (44) and the third chamber (32);
a valve member (50) mounted on the diaphragm (52), wherein the valve
member (50) extends through the orifice (46) and is moveable relative to the orifice (46)
based upon a change in pressures within at least one of the first chamber (42), the second
chamber (44), and the third chamber (32); and
a solenoid valve (22) fluidly connected to the first chamber (42) and the
third chamber (32).
2. The oil control valve (20) of claim 1, wherein the wall (48) defines an
angled edge at the orifice (46), and wherein the angled edge forms a valve seat for the
valve member (50).
3. The oil control valve (20) of claim 2, wherein the valve member (50) is in
a first position relative to the valve seat when the solenoid valve (22) fluidly connects the
first chamber (42) to the third chamber (32) and in a second position relative to the valve
seat when the solenoid valve (22) fluidly disconnects the first chamber (42) from the third
chamber (32).
4. The oil control valve (20) of claim 2, wherein fluid within the first
chamber (42) is at a first pressure and fluid within the second chamber (44) is at a second
pressure, wherein the second pressure is lower that the first pressure and the pressure
differential between the first chamber (42) and the second chamber (44) biases the valve
member (50) in a first direction toward the valve seat.
5. The oil control valve (20) of claim 4, wherein the oil control valve (20)
further comprises a spring (58) located within the third chamber (32) to bias the valve
member (50) in a second direction away from the valve seat.
6. The oil control valve (20) of claim 4, wherein the second pressure is at a
first level when the solenoid valve (22) fluidly connects the first chamber (42) to the third
chamber (32) and at a second level, lower than the first level, when the solenoid valve
(22) fluidly disconnects the first chamber (42) from the third chamber (32).
7. The oil control valve (20) of claim 1, wherein the solenoid valve (22)
fluidly connects the third chamber (32) to an exhaust gallery when the first chamber (42)
is fluidly disconnected from the third chamber (32).
8. The oil control valve (20) of claim 1, wherein the valve member (50) is
connected to the housing (40) with a damper.
9. A method of controlling oil flow within a valvetrain comprising:
pumping fluid from a fluid reservoir (12) to a control valve (20);
varying the flow rate through the control valve (20) such that fluid enters the
control valve (20) at a first pressure and flows from the control valve (20) at a second
pressure;
directing fluid from the control valve (20) to at least one engine component (16A)
of the valvetrain, wherein the at least one engine component (16A) is fluidly actuated
from a first position to a second position based upon the second pressure; and
wherein varying the flow rate through the control valve (20) includes;
increasing the flow rate through the control valve (20) to increase the
second pressure to a first level to actuate the at least one engine component (16A)
to the first position;
maintaining the flow rate through the control valve (20) such that the
second pressure is at a second level which is less than the first level and sufficient
to maintain the at least one engine component (16A) in the first position;
decreasing the flow rate through the control valve (20) to decrease the
second pressure to a third level to actuate the at least one engine component (16 A)
to the second position; and
maintaining the flow rate through the control valve (20) such that the
second pressure is at a fourth level which is less than the second level but greater
than the fourth level and sufficient to maintain the at least one engine component
(16A) in the second position.
10. The method of claim 9, wherein varying the flow rate through the control
valve (20) further includes directing fluid within the control valve (20) from a first
chamber (42) at the first pressure to a second chamber (44) at the second pressure by
moving a valve member (50) relative to a valve seat located between the first chamber
(42) and the second chamber (44).
11. The method of claim 10, wherein varying the flow rate through the control
valve (20) further includes activating a solenoid valve (22) to fluidly connect the first
chamber (42) to a third chamber (32) to move the valve member (50) in a first direction
away from the valve seat to increase the second pressure to the first level and then
maintain the second pressure at the second level.
12. The method of claim 11, wherein varying the flow rate through the control
valve (20) further includes deactivating a solenoid valve (22) to fluidly disconnect the
first chamber (42) from the third chamber (32) to move the valve member (50) in a
second direction toward from the valve seat to decrease the second pressure to the third
level and then maintaining the second pressure at the fourth level.
13. The method of claim 10, further comprising damping vibrations of the
valve member (50) resulting from the changes in pressure between the first chamber (42)
and the second chamber (44).
14. The method of claim 9, wherein maintaining the flow rate through the
control valve (20) such that the second pressure is at a second level to maintain the at
least one engine component (16A) in the first position further includes maintaining a
normally engaged lash actuator in a disengaged position; and wherein maintaining the
flow rate through the control valve (20) such that the second pressure is at a fourth level
to maintain the at least one engine component in the second position further comprises
maintain the normally engaged lash actuator in an engaged position.

A hydraulic control system (10) is provided having an oil control valve (20) to
control oil flow within a valvetrain. The control valve (20) varies the flow rate to actuate
an engine component (16A) from a first position to a second position based upon the
pressure of fluid from the control valve (20). Varying the flow rate through the control
valve (20) includes increasing the flow rate through the control valve (20) to increase the
pressure to a first level to actuate the engine component (16A) to the first position. After
the engine component (16A) is actuated, the flow rate through the control valve (20) is
maintained at a level sufficient to maintain the engine component (16A) in the first
position. To actuate the engine component (16A) to the second position the flow rate
through the control valve (20) is then decreased. The fluid flow rate through the control
valve (20) is then maintained at a level sufficient to maintain the engine component
(16A) in the second position.