U.S. patent application number 12/334386 was filed with the patent office on 2010-06-17 for crankcase breech detection for boosted engines.
This patent application is currently assigned to FORD GLOBAL TECHNOLOGIES, LLC. Invention is credited to Ross Dykstra Pursifull, Joseph Norman Ulrey.
Application Number | 20100147270 12/334386 |
Document ID | / |
Family ID | 42239052 |
Filed Date | 2010-06-17 |
United States Patent
Application |
20100147270 |
Kind Code |
A1 |
Pursifull; Ross Dykstra ; et
al. |
June 17, 2010 |
CRANKCASE BREECH DETECTION FOR BOOSTED ENGINES
Abstract
Methods for indicating whether a crankcase of an engine is
breeched are provided. One example method comprises restricting a
communication of the crankcase with atmosphere, acting to increase
or decrease a crankcase pressure, and indicating whether the
crankcase is breeched based on the crankcase pressure. Another
example method comprises sensing a crankcase pressure component,
and indicating whether the crankcase is breeched based on the
crankcase pressure component, the crankcase communicating with
atmosphere via a conduit, a restrictedness of the conduit
responsive to one or more of a crankcase pressure and a signal from
an electronic control unit of the motor vehicle. Still other
examples provide more particular methods for indicating whether the
crankcase is breeched, and example configurations that enable the
various methods.
Inventors: |
Pursifull; Ross Dykstra;
(Dearborn, MI) ; Ulrey; Joseph Norman; (Dearborn,
MI) |
Correspondence
Address: |
ALLEMAN HALL MCCOY RUSSELL & TUTTLE, LLP
806 S.W. BROADWAY, SUITE 600
PORTLAND
OR
97205
US
|
Assignee: |
FORD GLOBAL TECHNOLOGIES,
LLC
Dearborn
MI
|
Family ID: |
42239052 |
Appl. No.: |
12/334386 |
Filed: |
December 12, 2008 |
Current U.S.
Class: |
123/521 |
Current CPC
Class: |
F01M 13/00 20130101;
F01M 13/028 20130101; F01M 1/18 20130101; F01M 2013/0083 20130101;
F01M 13/0011 20130101; F02B 33/00 20130101; F01M 1/16 20130101;
F01M 2013/0038 20130101; F01M 2013/0077 20130101 |
Class at
Publication: |
123/521 |
International
Class: |
F01M 13/00 20060101
F01M013/00 |
Claims
1. A method for indicating whether a crankcase of an engine is
breeched, the method comprising: restricting a communication of the
crankcase with atmosphere; acting to increase or decrease a
crankcase pressure; and indicating whether the crankcase is
breeched based on the crankcase pressure.
2. The method of claim 1, further comprising sensing the crankcase
pressure via a sensor coupled to the crankcase.
3. The method of claim 1, wherein restricting a communication of
the crankcase with atmosphere comprises closing one or more
electronically actuable valves.
4. The method of claim 1, wherein acting to increase or decrease a
crankcase pressure comprises selectably coupling the crankcase to a
source of pressure.
5. The method of claim 1, wherein acting to increase or decrease a
crankcase pressure comprises selectably coupling the crankcase to a
source of vacuum.
6. The method of claim 1, wherein the engine includes a PCV system,
and where acting to increase or decrease a crankcase pressure
includes influencing the PCV system to cause a net flow of gas into
or out of the crankcase.
7. The method of claim 1, wherein indicating whether the crankcase
is breeched based on the crankcase pressure comprises indicating
the crankcase breeched if, on acting to increase or decrease a
crankcase pressure, the crankcase pressure fails to respond as
expected.
8. The method of claim 1, wherein indicating whether the crankcase
is breeched based on the crankcase pressure comprises indicating
that an oil fill cap or dipstick is unseated.
9. The method of claim 1, wherein indicating whether the crankcase
is breeched based on the crankcase pressure comprises indicating
that a sealing element fluidically coupled to the crankcase is
leaking.
10. A method for indicating whether a crankcase of an engine is
breeched, the engine operatively coupled to an electronic control
unit, the method comprising: sensing a crankcase pressure
component; indicating whether the crankcase is breeched based on
the crankcase pressure component, the crankcase communicating with
atmosphere via a conduit, a restrictedness of the conduit
responsive to one or more of a crankcase pressure and a signal from
the electronic control unit.
11. The method of claim 10, further comprising acting to delay a
depletion of lubricant from the crankcase if the crankcase is
indicated breeched.
12. The method of claim 11, wherein acting to delay a depletion of
lubricant from the crankcase includes one or more of reducing an
intake of air into the engine and adding lubricant to the
crankcase.
13. The method of claim 10, wherein the crankcase pressure
component is derived from the crankcase pressure by low-pass
filtering.
14. The method of claim 10, wherein the crankcase pressure
component is an alternating component of the crankcase pressure,
and the crankcase is indicated breeched if an amplitude of the
crankcase pressure component is below a threshold.
15. The method of claim 14, wherein the sensing the crankcase
pressure component comprises synchronizing a sampling of the
crankcase pressure to an operational state of the engine.
16. The method of claim 10, further comprising restricting a
communication of the crankcase with atmosphere.
17. The method of claim 16, further comprising restricting a
communication of the crankcase with an intake of the engine.
18. The method of claim 16, further comprising acting to increase
the crankcase pressure and indicating the crankcase breeched if the
crankcase pressure component stays below a threshold.
19. The method of claim 16, further comprising acting to decrease
the crankcase pressure and indicating the crankcase breeched if the
crankcase pressure component stays above a threshold.
20. The method of claim 10, further comprising: coupling the
crankcase to a pressure or vacuum source; isolating the crankcase
from the pressure or vacuum source; indicating the crankcase
breeched based on a rate of approach of the crankcase pressure
component to atmospheric pressure.
21. An engine system having a crankcase and configured to indicate
whether the crankcase is breeched, the engine system comprising: a
sensor having an output responsive to a crankcase pressure; an
electronic control unit configured to sample the output and to
indicate whether the crankcase is breeched based on the output, the
crankcase communicating with atmosphere via a breather conduit, a
restrictedness of the breather conduit responsive to one or more of
the crankcase pressure and a signal from the electronic control
unit.
22. The engine system of claim 21, further comprising a check valve
disposed in the breather conduit, wherein the output includes an
alternating output, and the electronic control unit is further
configured to indicate the crankcase breeched if the alternating
output more closely matches an output expected for a breeched
crankcase than an output expected for an unbreeched crankcase.
23. The engine system of claim 21, further comprising an
electronically actuable PCV valve operatively coupled to the
electronic control unit, wherein the electronic control unit is
further configured to open the electronically actuable PCV valve
wide at idle and to indicate the crankcase breeched if the output
fail to indicate an expected level of vacuum in the crankcase.
24. The engine system of claim 21, further comprising an
electronically actuable check valve disposed in the breather
conduit, wherein the electronic control unit is further configured
to admit a flow of air through the electronically actuable check
valve and to indicate the crankcase breeched if the output fail to
indicate an expected level of vacuum in the crankcase.
25. The engine system of claim 21, further comprising an
electronically actuable check valve disposed in the breather
conduit, wherein the electronic control unit is further configured
to admit a flow of crankcase head gas through the electronically
actuable check valve and to indicate the crankcase breeched if the
output fail to indicate an expected level of pressure.
26. The engine system of claim 21, further comprising an
electronically actuable normally open valve disposed in the
breather conduit and operatively coupled to the electronic control
unit, wherein the electronic control unit is further configured to
indicate the crankcase breeched if the output fail to indicate one
or more of an expected level of pressure during push-over and an
expected level of vacuum during clean-air purge.
27. The engine system of claim 21, further comprising a first
electronically actuable normally open valve disposed in the
breather conduit and a second electronically actuable normally open
valve disposed in a PCV inlet conduit of the engine, wherein the
electronic control unit is further configured to close the first
and second normally open valves and to indicate the crankcase
breeched if the output fail to indicate an expected level of
pressure when the first and second normally open valves are
closed.
28. The engine system of claim 21, further comprising an
electronically actuable pressure or vacuum port coupled to the
crankcase, wherein the electronic control unit is further
configured to actuate the electronically actuable pressure or
vacuum port and to indicate the crankcase breeched if the output
fail to indicate an expected level of pressure or vacuum when the
electronically actuable pressure or vacuum port is actuated.
29. The engine system of claim 21, further comprising an intake
throttle and an electronically actuable PCV by-pass valve
configured to couple the crankcase to an intake of the engine,
wherein the electronic control unit is further configured to open
the electronically actuable PCV by-pass valve and to indicate the
crankcase breeched if the output fail to indicate an expected level
of vacuum in the crankcase while cranking the engine with the
electronically actuable PCV by-pass valve open and the intake
throttle closed.
Description
TECHNICAL FIELD
[0001] The present application relates to the field of
motor-vehicle engine systems and more particularly to maintenance
of engine lubricant in turbocharged or supercharged motor-vehicle
engine systems.
BACKGROUND AND SUMMARY
[0002] Relative to a naturally aspirated engine of similar output
power, a turbocharged or supercharged engine may exhibit a
prolonged duty cycle and increased blow-by (i.e., pressurized
combustion gas entering the crankcase via the piston rings).
Therefore, specialized engine components and/or configurations may
be provided for proper maintenance of the engine lubricant. For
example, a positive crankcase ventilation (PCV) system of a
turbocharged or supercharged engine may include one or more
enhanced air/lubricant separators to limit loss of engine lubricant
to the intake during high-load operation.
[0003] The prolonged duty cycle and increased blow-by in a
turbocharged or supercharged engine may cause engine lubricant to
aspirated rapidly through any breech of the crankcase--through an
uncapped lubricant filling port or unseated dipstick, for example.
In some cases, an unacceptable loss of engine lubricant may occur
in just a few hours of high-load operation when a dipstick is left
unseated. If the loss of engine lubricant goes undetected,
significant engine damage may result.
[0004] The inventors herein have recognized the disadvantages noted
above and have provided a series of approaches to address them. One
embodiment provides a method for indicating whether a crankcase of
an engine is breeched, the engine having a crankcase ventilation
system (positive, road draft, or foul air). This example method
comprises restricting a communication of the crankcase with
atmosphere, acting to increase or decrease a crankcase pressure,
and indicating whether the crankcase is breeched based on the
crankcase pressure. Another example method comprises sensing a
crankcase pressure component, and indicating whether the crankcase
is breeched based on the crankcase pressure component, the
crankcase communicating with atmosphere via a conduit, a
restrictedness of the conduit responsive to one or more of a
crankcase pressure and a signal from an electronic control unit of
the motor vehicle. Still other embodiments provide more particular
methods for indicating whether the crankcase is breeched, and
example configurations that enable the various methods. The
approaches described herein provide reliable detection of a
breeched crankcase in boosted engines, thereby avoiding excessive
lubricant loss and prolonging engine life.
[0005] It will be understood that the summary above is provided to
introduce in simplified form a selection of concepts that are
further described in the Detailed Description. It is not meant to
identify key or essential features of the claimed subject matter,
the scope of which is defined by the claims that follow the
Detailed Description. Further, the claimed subject matter is not
limited to implementations that solve any disadvantages noted above
or in any part of this disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 shows an example turbocharged engine in accordance
with the present disclosure.
[0007] FIG. 2 shows various example flow-control components of an
example turbocharged engine, in accordance with the present
disclosure.
[0008] FIG. 3 shows a first example method for determining when a
crankcase of a turbocharged engine is breeched, in accordance with
the present disclosure.
[0009] FIG. 4 shows a second example method for determining when a
crankcase of a turbocharged engine is breeched, in accordance with
the present disclosure.
[0010] FIG. 5 shows a third example method for determining when a
crankcase of a turbocharged engine is breeched, in accordance with
the present disclosure.
DETAILED DESCRIPTION
[0011] FIG. 1 shows example engine 10 in schematic detail. The
drawing schematically shows a V-type engine, but other
configurations are contemplated as well. The engine includes
crankcase 12, which contains crankcase head gas and engine
lubricant. In some embodiments, the crankcase may include one or
more access ports for checking and/or correcting the level of the
engine lubricant. FIG. 1 shows access port 14, which is isolated
from the atmosphere via closure 16. The closure may be a cap, e.g.,
a screw cap or snap cap. In some embodiments, the closure may
include a dipstick for checking the level of the engine lubricant.
In these and other embodiments, the closure may include a
pressure-relief valve configured to discharge crankcase head gas to
the atmosphere when the pressure of the crankcase head gas exceeds
a threshold.
[0012] FIG. 1 shows cylinder 18 coupled to intake valve 20 and to
exhaust valve 22; both valves are disposed below right valve cover
24. Internal lubricant separator 26 is also disposed below the
right valve cover, and external lubricant separator 28 is disposed
above the right valve cover.
[0013] FIG. 1 shows a piston within cylinder 18, and piston rings
19 configured to isolate the combustion gasses inside cylinder from
crankcase 12. Nevertheless, combustion gasses may `blow by` the
piston rings at some rate, and accumulate in the crankcase.
Therefore, a crankcase ventilation system (e.g., a PCV system) is
provided. Thus, PCV valve 30 is shown in FIG. 1, coupled to the
external lubricant separator and configured to admit crankcase head
gas to intake manifold 32 via PCV-inlet tube 34.
[0014] Intake manifold 32 may communicate with a plurality of
cylinders equivalent to cylinder 18 via a plurality of intake
valves. For ease of illustration, however, only one other cylinder
is shown in FIG. 1; left valve cover 38 is shown disposed over the
other cylinder. As shown in the drawing, the left and right valve
covers may be disposed over cylinders on substantially opposite
sides of engine 10.
[0015] In FIG. 1, intake manifold 32 is shown coupled to the
high-pressure side of turbocharger 38, which draws intake air from
air cleaner 40. Breather tube 42 couples left valve cover 36 to the
low-pressure side of the turbocharger. In other embodiments, the
breather tube may be coupled to an outlet of the air cleaner, to
another air cleaner, etc. As shown in the drawing, breather tube 42
and PCV valve 30 may communicate with substantially opposite sides
of crankcase 12.
[0016] When engine 10 is moderately loaded, lightly loaded, or
idling, crankcase head gas is suctioned into intake manifold 32
through PCV valve 30. Fresh air from air cleaner 40 flows into the
crankcase via left valve cover 36. This condition, called
`clean-air purge,` occurs when the crankcase is at lower pressure
than the turbocharger inlet. However, when the crankcase is at
higher pressure than the turbocharger inlet, crankcase head gas
flows up breather tube 42 and enters the intake through the
turbocharger; this condition-called `push-over`-may occur when the
engine is more highly loaded.
[0017] Continuing in FIG. 1, engine 10 includes pressure sensor 44
configured to sense a pressure of the head gas in crankcase 12. The
pressure sensor may be configured to generate an output (e.g., an
output voltage) responsive to a pressure of the head gas. Although
the pressure sensor is shown coupled to access port 14 and disposed
between closure 16 and crankcase 12, it may be coupled to the
crankcase at various other locations instead. In some embodiments,
the pressure sensor may be configured to sense one or more
particular components of the crankcase pressure--a steady-state
pressure, a low-pass filtered pressure, one or more Fourier
components of the pressure, a component locked in phase with an
operating condition of the engine, etc. In other embodiments, the
pressure sensor may be a pressure-activated switch, for
example.
[0018] Pressure sensor 44 may be operatively coupled to controller
46, which may be any electronic control unit of the motor vehicle.
In some embodiments, the same conductors that supply a heating
current to PCV valve 30 may conduct the output voltage of the
pressure sensor back to the controller. Thus, existing conductors
may be used to provide operative coupling between the sensor and
the controller. Controller 46 may be operatively coupled to other
engine and/or motor-vehicle components as well-to switchable
pressure/vacuum sources, controllable valves, indicators, alarms,
and diagnostic systems, as examples. In the various embodiments
disclosed herein, the controller may be configured to sample an
output of the pressure sensor and to indicate whether the crankcase
is breeched based on the output. In some embodiments, the same
pressure sensor may be configured to report the pressure of the
crankcase head gas as well as the external barometric pressure, for
the controller may be configured to identify conditions where the
two pressures are equal or otherwise relatable to each other.
[0019] The embodiments illustrated in FIG. 1 enable various methods
to detect an unexpected breech of crankcase 12, which may occur,
for instance, if closure 16 is defective or is left open by
mistake. It will be understood, however, that a crankcase may be
breeched in various other ways as well-via a leaky sealing element
fluidically coupled to the crankcase (leaky piston rings, a leaky
PCV valve, for example). In general, unexpected communication
between a crankcase of an engine and the environment exterior the
crankcase may be identified to constitute a crankcase breech; it is
contemplated that crankcase breeches of various kinds may be
detected and indicated via the systems and methods described
herein, although with some variation depending on the type of
breech being monitored.
[0020] Some of the methods presently disclosed rely on one or more
dedicated flow-control components (valves, conduits, etc.) disposed
in the PCV system of engine 10, or elsewhere in the motor vehicle.
In some embodiments, the one or more flow-control components
located in breather tube 42 may present a restrictedness in the
breather tube that is responsive to the crankcase pressure and/or a
signal from the electronic control unit. For example, a check valve
located in the breather tube may present a restrictedness
responsive to a crankcase pressure, while a controllable valve
located in the breather tube may present a restrictedness
responsive to controller 46.
[0021] Various flow-control embodiments are described presently by
way of example, and some are illustrated schematically in FIG. 2.
It will be understood that not all of the components presently
described are necessary to enable crankcase breech detection in any
given engine system. The flow-control components to be included
will depend on the particular method or methods of breech detection
enacted by the system.
[0022] FIG. 1 shows breather valve 48 disposed in breather tube 42.
In a first flow control embodiment, the breather valve (shown also
in FIG. 2) includes two check valves (e.g., one-way
pressure-activated valves) disposed in parallel, with the inlet of
first check valve 50 coupled to left valve cover 36, and the inlet
of second check valve 52 coupled to the low-pressure side of
turbocharger 38. This orientation routes the breather flow through
a different check valve depending on whether the flow is towards
the left valve cover (during clean-air purge) or towards the air
cleaner (during push-over). One or both of the check valves may
present a small but significant restriction to the breather flow.
This aspect may be advantageous for detecting a breech of crankcase
12. For example, restricting the flow of air to the left valve
cover may cause the crankcase, if unbreeched, to develop a vacuum
during clean-air purge. Likewise, restricting the flow of crankcase
head gas to the turbocharger inlet may cause the crankcase to
develop a positive pressure during push-over. Moreover, a
restriction to breather flow in either direction will lessen the
degree to which fluctuations in the pressure of the crankcase head
gas are vented to the atmosphere, resulting in better accuracy for
methods that rely on sensing such fluctuations (vide infra).
[0023] In a second flow-control embodiment, breather valve 48
includes two opposing check valves as in the first flow-control
embodiment. In addition, an electronically actuable PCV valve 54 is
used in place of PCV valve 30. The electronically actuable PCV
valve is operatively coupled to controller 46 and may be triggered
by the controller to open wide at idle (contrary to the usual
operation of a PCV valve). By opening wide at idle, the
electronically actuable PCV valve may draw a large flow, causing
crankcase 12, if unbreeched, to develop a vacuum. If the crankcase
fail to develop an expected level of vacuum under such conditions,
a breech of the crankcase may be indicated.
[0024] In a third flow-control embodiment, breather valve 48
includes two opposing check valves as in the first flow-control
embodiment. But here, the first check valve 50 is replaced by
electronically actuable check valve 56. Coupled to controller 46,
the electronically actuable check valve may be normally open to
flow in the indicated direction; closing it cuts off a supply of
air to left valve cover 36, which may cause the crankcase, if
unbreeched, to develop a vacuum during clean-air purge. If the
crankcase fail to develop an expected level vacuum under such
conditions, a breech of the crankcase may be indicated.
[0025] In a fourth flow-control embodiment-the converse of the
third embodiment-breather valve 48 includes two opposing check
valves as in the first flow-control embodiment. But here, second
check valve 52 is replaced by electronically actuable check valve
56. Closing this valve cuts off the flow of crankcase head gas to
the inlet of turbocharger 38, which may cause the crankcase, if
unbreeched, to develop a positive pressure during push-over
conditions. If the crankcase fail to develop an expected positive
pressure under such conditions, a breech of the crankcase may be
indicated.
[0026] In a fifth flow-control embodiment, breather valve 48
includes two opposing check valves, as in the first flow-control
embodiment. But here, first check valve 50 is coupled to pulsation
sensor 58. The pulsation sensor is operatively coupled to
controller 46, which is configured to correlate the amplitude of
the pulsation with the integrity of crankcase 12, viz., a pulsation
of lower amplitude than expected may indicate that the crankcase is
breeched.
[0027] In a sixth flow-control embodiment, breather valve 48
includes an electronically actuable, normally-open valve 60
disposed between left valve cover 36 and the low-pressure side of
turbocharger 38. The normally open valve may operatively coupled to
controller 46 and configured to close in response to a signal from
the controller. Closure of the valve during clean air flow may
cause vacuum to develop in the crankcase, if the crankcase is
unbreeched. Closure of the valve during push-over conditions may
cause pressure to develop in the crankcase if the crankcase is
unbreeched. If the crankcase fail to develop the expected level of
vacuum or pressure, a breech of the crankcase may be indicated.
[0028] In a seventh flow-control embodiment, breather valve 48
includes one electronically actuable, normally open valve 60, as
described in the previous embodiment. In addition, a second
electronically actuable, normally open valve 60' is provided in
PCV-inlet tube 34. During normal operation of the vehicle, both
valves may remain open to permit the PCV system to function
normally. Pursuant to a signal from controller 46, however, the
valves may close to temporarily isolate crankcase 12 from the PCV
system of engine 10. If the isolated crankcase is unbreeched, the
pressure within it may increase due to blow-by, heating from the
engine, etc. If the pressure in the crankcase fail to increase as
expected, a breech of the crankcase may be indicated.
[0029] Returning now to FIG. 1, an eighth flow-control embodiment
is illustrated, wherein one or more access ports of crankcase 12
(the same or different than those referred to above) may couple the
crankcase to switchable pressure/vacuum port 64. The switchable
pressure/vacuum port may comprise a controllable pump, or in other
embodiments, a controllable valve via which access port 14 may be
switchably linked to a source of pressure or vacuum. The source of
pressure or vacuum may be actively driven by engine 10; it may be a
turbocharger or intake manifold of the engine, for example. In
other embodiments, the source of pressure or vacuum may derive from
a changing temperature in one or more motor-vehicle cavities. In
one embodiment, the switchable pressure/vacuum port may communicate
with an engine-off natural vacuum (EONV) source; it may be
operable, therefore, even when the engine is turned off.
[0030] Switchable pressure/vacuum port 64 may be operatively
coupled to controller 46, and used in a closed-loop manner to
actively regulate the pressure of the crankcase head gas. In this
example, an inability of the controller to regulate to the desired
pressure, or an unexpected change in the control input needed to
provide the regulation, may indicate a breech of crankcase 12.
[0031] In another example, switchable pressure/vacuum port 64 may
be configured to provide an initial level of vacuum or
pressurization in crankcase 12 by initially coupling the crankcase
to a pressure or vacuum source. The switchable pressure/vacuum port
may then be switched off, isolating the crankcase from the pressure
or vacuum source and allowing the initial level to approach
atmospheric pressure. Controller 46 may be configured to monitor an
output of pressure sensor 44 during the approach and to correlate
crankcase integrity with some property of the approach, e.g., a
decay time constant or similar metric.
[0032] Continuing in FIG. 1, a ninth flow-control embodiment is
illustrated, wherein one or more access ports of crankcase 12 (the
same or different than those referred to above) may provide
auxiliary coupling to intake manifold 32 via PCV-bypass valve 66.
The PCV-bypass valve may be an electronically actuable, normally
open valve operatively coupled to controller 46. The controller may
be configured to open the PCV-bypass valve during engine cranking.
Under such conditions, with the intake throttle closed and the
crankcase isolated (as in the seventh flow-control embodiment, for
example), crankcase 12, if unbreeched, will develop a vacuum. If
the crankcase fail to develop an expected level of vacuum under
these conditions, a breech of the crankcase may be indicated.
[0033] In some embodiments, the same conductors that supply a
heating current to PCV valve 30 may carry the actuating signal from
controller 46 to one or more electronically controlled valves.
Thus, existing conductors may be used to provide operative coupling
between the sensor and the controller, and in some examples, a
multiplexing scheme may be used.
[0034] FIG. 3 illustrates a first example method 68 to detect a
breech of a crankcase in a motor vehicle. Though presently
described with continued reference to aspects of FIG. 1, method 68
may be enabled by various other configurations as well.
[0035] Method 68 begins at 70, where a pressure of the crankcase
head gas is sensed via a sensor and received at an electronic
control unit of the motor-vehicle. The sensor may be a crankcase
pressure sensor such as pressure sensor 44 or a pulsation sensor
such as pulsation sensor 58. At 72, it is determined whether
sufficient time has been provided for the electronic control unit
to determine whether the crankcase is breeched. If it is determined
that sufficient time has not been provided, then execution resumes
at 70, where pressure sensing continues. Otherwise, execution
proceeds to 74, where it is determined whether a pressure signature
received by the electronic control unit is consistent with the
crankcase being breeched.
[0036] When crankcase 12 is unbreeched, the pressure signature that
is received at the electronic control unit may comprise a train of
pulsations or oscillations that correlate with an operational state
of one or more cylinders of engine 10 and/or an operational state
of turbocharger 38. The train of pulsations or oscillations may be
separable from a substantially steady-state pressure of the
crankcase head gas via appropriate electronics, algorithms, etc.,
and may by expressible as an alternating component of the crankcase
head pressure superposed over the substantially steady-state
pressure. Further, in embodiments as illustrated in FIG. 1, wherein
breather valve 48 provides a restriction in breather tube 42, the
pressure signature of an unbreeched crankcase may retain a greater
amplitude, because of less facile venting to the atmosphere.
[0037] Therefore, in embodiments where a check valve is disposed in
the breather tube, and where the output of the sensor includes an
alternating output, the controller may be further configured to
indicate the crankcase breeched if the alternating output more
closely matches an output expected for a breeched crankcase than an
output expected for an unbreeched crankcase. In one particular
example, an amplitude of the alternating component of the crankcase
head pressure may be correlated to crankcase integrity. In this
example, the crankcase may be indicated breeched if the amplitude
of the alternating component drops below a threshold value.
Further, the threshold value may depend on an operating parameter
of the engine and/or the characteristics of one or more
flow-control elements provided in the PCV system.
[0038] In other examples, one or more sub-components of the
alternating component may be correlated to crankcase integrity-a
sub-component phase-locked to an operational state of a cylinder of
the engine, for example. An appropriately phase-locked component
may be provided in a variety of different ways, including, in one
example, by synchronizing a sampling of the crankcase head gas
pressure from the sensor to an operational state of cylinder
18.
[0039] If it is determined that the pressure signature is
consistent with the crankcase being breeched, then at 76, the
breech is indicated via the electronic control unit. A crankcase
breech may be indicated in various ways: by illuminating a
dashboard indicator, by sounding an alarm, by setting a dedicated
MIL flag or other diagnostic code in an on-board diagnostic system
of the motor vehicle, for example.
[0040] The pressure signature evaluated at 74 may admit of a more
detailed indication than whether or not the crankcase is breeched.
For example, the pressure signature may be used to detect whether
the crankcase has a relatively large breech, such as may be caused
by an oil cap being left off or a dipstick being unseated. In this
example, the pressure signature may not enable detection of a much
smaller breech, such as may be caused by leaky piston rings or a
leaky PCV valve, for example. In other examples, it may be possible
to detect both large and small breeches, and to discriminate
between them based on the pressure signature. Likewise, the rate of
change of a size of a detected breech may be indicative of a type
of breech. For example, an oil cap off condition may result in a
relatively rapid change in the detected breech, whereas degradation
of piston rings may results in a relatively slow, in comparison,
change in the detected breech. As such, the systems and methods
here may further discriminate in the type of breech based on such
information.
[0041] At 78, a mitigating action is initiated by the electronic
control unit of the motor vehicle. The mitigating action may
include acting to delay a depletion of lubricant from the crankcase
if the crankcase is indicated breeched. In particular, the
mitigating action may include reducing an intake of air into the
engine, limiting a speed or torque of engine 10, limiting a fuel
injection amount supplied to the engine, limiting a throttle
opening, disabling turbocharger 38, and/or various other actions
intended to limit an aspiration of engine lubricant from breeched
crankcase 12. In some embodiments, the mitigating action taken at
78 may be one of a plurality of mitigating actions taken when a
crankcase breech is detected. In one example, the plurality of
mitigating actions may include adding lubricant to the
crankcase--pumping lubricant from an auxiliary reservoir and into
the crankcase, for example. After 78, or if it is determined that
the pressure signature is not consistent with the crankcase being
breeched, method 68 returns. For increased reliability of method
68, it may be advantageous to limit execution of the method to a
predetermined set of operating conditions of the engine, e.g.,
idle, a fixed range of engine speeds, etc.
[0042] FIG. 4 illustrates a second example method 80 to detect a
breech of a crankcase in a motor vehicle. Process steps in this and
subsequent embodiments that are substantially the same as described
in a previous embodiment are labeled in the same way, and are
described no further. It will be understood, however, that
equivalently labeled steps may differ to some degree in the
different embodiments of this disclosure. And, while presently
described with continued reference to aspects of FIG. 1, method 80
may be enabled by various other configurations as well.
[0043] Method 80 begins at 82, where an action is taken to increase
or decrease the crankcase pressure. The action may be taken in any
number of ways, depending on the particular configuration of the
engine and the motor vehicle in which the method is enacted. In
subsequent steps of the method, the crankcase may be indicated
breeched based if, on acting to increase or decrease a crankcase
pressure, the crankcase pressure fails to respond as expected.
[0044] In embodiments where the engine includes a PCV system,
acting to increase or decrease a crankcase pressure may include
influencing the PCV system to cause a net flow of gas into or out
of the crankcase. For example, in particular configurations where
breather valve 48 includes an electronically actuable check valve
or an electronically actuable normally open valve, pressure may be
applied by closing off the valve during push-over, or, vacuum may
be applied by closing off the valve during clean-air purge. Thus,
method 80 may include restricting a communication of the crankcase
with atmosphere by closing one or more electronically actuable
valves. In another embodiment, where the engine includes an
electronically actuable breather valve 48 and PCV-inlet valve 60',
pressure may be applied to the crankcase by closing both of these
valves. Thus, method 80 may further include restricting a
communication of the crankcase with an intake of the engine.
[0045] In other embodiments, where the engine includes an
electronically actuable PCV valve, vacuum may be applied by opening
wide the electronically actuable PCV valve during idle. In another
embodiment, where breather valve 48 is configured like an EGR
injector valve, vacuum may be applied to the crankcase by opening
the valve during high-flow conditions. In another embodiment, where
the engine includes a switchable pressure/vacuum source such as
switchable pressure/vacuum source 64, pressure or vacuum may be
applied by switching on the switchable pressure/vacuum source. In
this manner, acting to increase the crankcase pressure may comprise
selectably coupling the crankcase to a source of pressure, and,
acting to decrease the crankcase pressure may comprise selectably
coupling the crankcase to a source of vacuum. In still another
embodiment, where the engine includes a PCV by-pass valve 66,
vacuum may be applied by opening the PCV by-pass valve during
engine cranking, with the intake throttle closed and the crankcase
isolated (via electronically actuable valves in breather tube 42
and PCV-inlet tube 34, for example).
[0046] Method 80 then continues to 84, where it is determined
whether the time since acting to increase or decrease the crankcase
pressure exceeds a pre-determined build time. The build time may be
any suitable time interval over which the pressure of the crankcase
head gas would significantly change were the crankcase isolated
from the atmosphere and subject to the application of pressure or
vacuum. The build-time may be a function of various engine
parameters (displacement, for example), and on the manner of
application of pressure/vacuum. The build-time may be 2 seconds or
5 seconds, in some examples. If the build time has not been
exceeded, then the method loops back to 84; otherwise, the method
continues to 86.
[0047] At 86, a filtered pressure of the crankcase head gas is read
at the controller. In some embodiments, the controller may read a
filtered pressure from a pressure sensor, such as pressure sensor
44. The filtered pressure may be the substantially steady state
pressure referred to hereinabove. The filtered pressure may be the
result of low-pass filtering (analog filtering, digital filtering,
Fourier filtering, etc.) of the output voltage of the pressure
sensor. The filtering may be enacted at the pressure sensor, or in
other embodiments, at controller 46, to which the pressure sensor
is operatively coupled.
[0048] If the pressure of the crankcase head gas fails to increase
as expected when pressure is applied to the crankcase, or, fails to
decrease as expected when vacuum is applied to the crankcase, then
the crankcase may be indicated breeched. Therefore, at 88, it is
determined whether the filtered pressure traverses a pre-determined
threshold (exceeds the threshold in embodiments where a pressure is
applied to the crankcase, or drops below the threshold in
embodiments where a vacuum is applied to the crankcase). The
threshold may be a function of various engine parameters
(displacement, compression, coolant temperature, etc.). The
threshold may be 2 or 5 pounds per square inch, in some examples.
Thus, the crankcase may be indicated breeched if the crankcase
pressure stays below a threshold, or in other examples, stays above
a threshold. However, if it is determined that the threshold has
been traversed in the expected manner, then the method returns;
otherwise, the method continues to 76, and then to 78.
[0049] In other embodiments fully consistent with this disclosure,
there may be a plurality of pressure thresholds that are traversed
depending on the nature of the crankcase breech. For example, there
may be a first threshold corresponding to a relatively large
crankcase breech, such as may result from an oil cap being left off
or a dipstick being left unseated. In this or other embodiments,
there may be a second threshold corresponding to a smaller
crankcase breech, such as may result from leaky piston rings or a
leaky PCV valve, for example. Accordingly, methods to detect
crankcase breech may comprise comparing an output of the pressure
sensor to one or more different thresholds and determining which,
if any, are traversed. In this manner, the method may indicate or
extrapolate the manner in which the crankcase is breeched.
[0050] It is further contemplated that the output of the pressure
sensor may be compared against the first threshold at one point in
the diagnostic procedure, and against the second threshold at
another point, later in the diagnostic procedure. Thus, a first
diagnosis may be applied according to the methods set forth above
to establish that the crankcase is not severely breeched (as a
result of an oil cap being left off, etc.). Then, if it is
determined that the crankcase is not severely breeched, action may
be taken to increase or decrease the crankcase pressure, and a
relatively smaller breech may be diagnosed by monitoring the
resulting pressure change, again as set forth above.
[0051] FIG. 5 illustrates a third example method 88 to detect a
breech of a crankcase in a motor vehicle. While presently described
with continued reference to aspects of FIG. 1, method 88 may be
enabled by various other configurations as well.
[0052] Method 88 begins at 90, where an initial level of pressure
or vacuum is established in the crankcase. The initial level of
pressure or vacuum may be established in a variety of different
ways, depending on the particular configuration of the engine and
the motor vehicle in which the method is enacted. The description
of process step 82 of method 80 gives examples of ways of applying
pressure or vacuum to the crankcase; an initial level of pressure
or vacuum may be established in the same manner. In some
embodiments, however, a closed loop procedure may be used, wherein
pressure or vacuum is applied to the extent necessary to elicit a
pre-determined response from the sensor. In this manner, the
initial level of pressure or vacuum may be established. After
establishing the initial level of pressure or vacuum, the
application of pressure or vacuum may be discontinued. In some
embodiments, the crankcase may be isolated from the source of the
pressure or vacuum, as with a controllable valve, when the
application of pressure or vacuum is discontinued.
[0053] In some embodiments, process step 90 may commence when the
motor vehicle is turned off. Such embodiments may be particularly
suited to the use of an EONV source to establish an initial level
of vacuum. In other embodiments, process step 90 may commence while
the engine is running and while the motor vehicle is in
operation.
[0054] At 92, an output of the pressure sensor is sampled by an
electronic control unit of the motor vehicle. In some embodiments,
the sampled output of the sensor may be recorded by the electronic
control unit at regularly spaced time intervals. In this manner, a
profile of the decay of initial level of pressure or vacuum may be
accumulated.
[0055] At 94, it is determined whether the time over which the
output of the pressure sensor has been sampled is sufficient to
allow the electronic control unit to assess crankcase integrity. If
it is determined that the sampling time is not yet sufficient, then
the method loops back to 92, where sampling is continued.
Otherwise, the method continues to 96.
[0056] At 96, the electronic control unit determines whether the
decay profile is consistent with the crankcase being breeched. If
it is determined that the decay profile is not consistent with the
crankcase being breeched, then the method returns. Otherwise, the
method continues to 76, and then to 78.
[0057] It will be understood that the example control and
estimation routines disclosed herein may be used with various
system configurations. These routines may represent one or more
different processing strategies such as event-driven,
interrupt-driven, multi-tasking, multi-threading, and the like. As
such, the disclosed process steps (operations, functions, and/or
acts) may represent code to be programmed into computer readable
storage medium in a control system. It will be understood that some
of the process steps described and/or illustrated herein may in
some embodiments be omitted without departing from the scope of
this disclosure. Likewise, the indicated sequence of the process
steps may not always be required to achieve the intended results,
but is provided for ease of illustration and description. One or
more of the illustrated actions, functions, or operations may be
performed repeatedly, depending on the particular strategy being
used.
[0058] Finally, it will be understood that the systems and methods
described herein are exemplary in nature, and that these specific
embodiments or examples are not to be considered in a limiting
sense, because numerous variations are contemplated. Accordingly,
the present disclosure includes all novel and non-obvious
combinations and sub-combinations of the various systems and
methods disclosed herein, as well as any and all equivalents
thereof.
* * * * *