U.S. patent application number 10/943532 was filed with the patent office on 2006-03-16 for fuel vapor detection system for vehicles.
Invention is credited to Jae Chung, David Waskiewicz, Marsha Wendel.
Application Number | 20060053868 10/943532 |
Document ID | / |
Family ID | 34984250 |
Filed Date | 2006-03-16 |
United States Patent
Application |
20060053868 |
Kind Code |
A1 |
Chung; Jae ; et al. |
March 16, 2006 |
Fuel vapor detection system for vehicles
Abstract
An electric motor or generator is used to spin the vehicle's
internal combustion engine while the engine is not running, in
order to draw a vacuum within the vapor control system. Vacuum
bleed off is then monitored to determine if an unacceptable
condition in the control system may exist. The evaporative fuel
emissions test may be conducted either while the vehicle is at rest
or while under way in an electric drive mode of operation.
Inventors: |
Chung; Jae; (Novi, MI)
; Wendel; Marsha; (New Boston, MI) ; Waskiewicz;
David; (Hamburg, MI) |
Correspondence
Address: |
TUNG & ASSOCIATES
838 WEST LONG LAKE, SUITE 120
BLOOMFIELD HILLS
MI
48302
US
|
Family ID: |
34984250 |
Appl. No.: |
10/943532 |
Filed: |
September 16, 2004 |
Current U.S.
Class: |
73/49.7 |
Current CPC
Class: |
F02N 11/04 20130101;
Y02T 10/623 20130101; B60W 20/00 20130101; B60K 6/44 20130101; F02M
25/0827 20130101; Y02T 10/6286 20130101; Y02T 10/62 20130101; B60W
10/08 20130101; F02D 29/02 20130101; B60W 10/06 20130101 |
Class at
Publication: |
073/049.7 |
International
Class: |
G01M 3/04 20060101
G01M003/04 |
Claims
1. A method of detecting evaporative fuel emissions in a fuel vapor
emission control system of an internal combustion engine driven
vehicle while the engine is not running, comprising the steps of:
opening a fuel vapor management valve connecting the engine with
the control system; rotating the engine to reduce the fuel vapor
pressure in the control system; and measuring the vapor pressure in
the control system, a change in pressure being related to possible
fuel vapor evaporative fuel emissions in the control system.
2. The method of claim 1 further comprising the steps, prior to
said opening step, of: closing a first valve for controlling the
escape of fuel vapor from the control system to the atmosphere; and
closing a throttle on the engine to prevent air from entering into
the engine through the throttle.
3. The method of claim 2 further comprising the step, inbetween
said rotating step and said measuring step, of: closing the vapor
management valve.
4. The method of claim 2, wherein the step of closing the throttle
comprises closing a throttle plate controlling the flow of air into
engine.
5. The method of claim 1, wherein the step of rotating the engine
comprises powering the engine using an electric drive motor.
6. The method of claim 1, wherein the rotating step is continued
for a preselected length of time.
7. The method of claim 6, wherein the step of measuring the vapor
pressure is performed continuously during the preselected length of
time.
8. The method of claim 6, further comprising the step of closing a
vapor management after the preselected time period.
9. The method of claim 1, wherein the rotating step is continued
for a preselected length of time, and the method further comprises
closing a vapor management valve when the measured vapor pressure
is below a preselected pressure.
10. The method of claim 1, wherein the rotating step comprises
powering the engine with an electrical generator operated as an
electric motor.
11. The method of claim 1, wherein the method further comprises
ending rotation of the engine after the vapor pressure has been
measured for a preselected length of time.
12. The method of claim 11, wherein the method further comprises
monitoring the vapor pressure after the engine rotation of the
engine has ended.
13. A method of detecting a evaporative fuel emissions in an
evaporative vapor control system for a vehicle having a fuel tank,
a vent valve controlling the flow of fuel vapor to a vent, an
internal combustion engine having an intake manifold and a throttle
valve for controlling the flow of air into the intake manifold, and
a vapor management valve for controlling the flow of fuel vapor
between the control system and the engine, comprising the steps of:
closing the vent valve; closing the throttle valve to prevent air
from being drawn into the engine; opening the vapor management
valve to place the intake manifold in fluid communication with the
control system; rotating the engine using an auxiliary power source
to produce a partial vacuum in the control system; closing the
vapor management valve; and, measuring changes the vapor pressure
within the control system, changes in the vapor pressure indicating
a possible evaporative fuel emissions in the control system.
14. The method of claim 13, wherein closing the throttle valve
comprises closing a throttle plate controlling air flow into he
intake manifold.
15. The method of claim 13, wherein rotating the engine is
performed by using an electrical generator as the auxiliary power
source.
16. The method of 13, wherein the rotating step is continued until
the vapor pressure within the control system is reduced to a
preselected pressure value.
17. A method of claim 13, wherein the rotating step is continued
for a presented length of time.
18. The method of claim 13, wherein the method further comprises
stopping rotation of the engine and the measuring step is performed
after the rotating step has stopped.
19. A method of detecting a evaporative fuel emissions in a fuel
vapor emission control system of a hybrid powered vehicle having an
internal combustion engine and an electric drive motor, comprising
the steps of: determining if the internal combustion engine is
running; if the internal combustion engine is determined not to be
running, closing the emission control system; opening a fuel vapor
management valve connecting the engine with the emission control
system; rotating the engine to reduce the fuel vapor pressure
within emission control system; closing the fuel vapor management
valve; and measuring the vapor pressure in the emission control
system, a change in the vapor pressure indicating a possible fuel
vapor evaporative fuel emissions in the emission control
system.
20. The method of claim 19, wherein closing the emission control
system comprises closing a valve connecting the emission control
system with the atmosphere.
21. The method of claim 20, wherein closing the emission control
system further comprises closing an engine throttle valve to
prevent the flow of air into the engine.
22. The method of claim 19, wherein closing the emission control
system comprises closing an engine throttle valve to prevent the
flow of air into the engine.
23. The method of claim 19, wherein rotating the engine comprises
driving the engine with the electric motor.
24. The method of claim 19, wherein rotating the engine comprises
driving the engine with an electric generator.
25. The method of claim 19, wherein rotating the engine is
performed for a preselected length of time.
26. The method of claim 19, wherein rotating the engine is
performed until the vapor pressure in the emission control system
is reduced to a preselected pressure level.
27. The method of claim 25, wherein the step of measuring the vapor
pressure level is performed after the vapor pressure has been
reduced to at least the preselected pressure level.
Description
FIELD OF THE INVENTION
[0001] This invention generally relates to emission control systems
for vehicles, and deals more particularly with a method of
detecting evaporative fuel emissions for a vehicle.
BACKGROUND OF THE INVENTION
[0002] Evaporative emission control systems are well known in
internal combustion engine powered motor vehicles to prevent
evaporative fuel, i.e., fuel vapor, from being emitted from the
fuel tank into the atmosphere. These control systems typically
include several primary components that control evaporative
emission operations: vapor control valves, vapor management valves
and a carbon canister for absorbing the vapors.
[0003] From time to time, fuel vapors may be vented improperly,
resulting in reduced engine performance and the possibility of
vapor emissions into the atmosphere. A variety of on-board
diagnostic systems have been devised for detecting such emissions
in the evaporative emission control system so that appropriate
corrective measures may be taken.
[0004] Conventional emissions control may include: (1) an intake
manifold of an engine connecting to a vapor control system in order
to draw a vacuum on the control system, (2) sealing the vapor
control system and/or, (3) bleeding-off and monitoring the
resulting vacuum in the control system. With vehicles powered only
by an internal combustion engine, these steps can only be performed
while the engine is running. Coordinating the requirements of the
engine control system and the evaporative emission control system
test procedure places constraints on both systems.
[0005] These problems are exacerbated in hybrid powered vehicles
using both an internal combustion engine and an electric drive
motor. Hybrid powered vehicles, when operating in an internal
combustion (IC) mode, tend to run at relatively wide-open throttle
for substantial periods in order to maximize operating efficiency.
At open or near wide-open throttle, however, intake manifold
pressure is lower, limiting the engine's ability to draw a vacuum
in the evaporative emission control system to facilitate emissions
detection.
[0006] Accordingly, a need exists in the art for a method of
emissions detection that can be performed effectively while the
engine is not running. The present invention is intended to satisfy
that need.
SUMMARY OF THE INVENTION
[0007] A method is provided for detecting fuel vapor emissions from
an internal combustion engine driven vehicle while the engine is
not running. A detection test can be performed while the vehicle is
not operating, or while the vehicle is powered by an alternative
drive source such as an electric motor in combination with a
battery fuel cell or other electric power source. In accordance
with one embodiment of the present method, the method
advantageously uses an onboard electric machine operated in a motor
mode, to spin the non-running IC engine in order to draw a vacuum
on the vapor emission control system, which is then monitored to
diagnose proper operation of the vehicle emissions control
system.
[0008] In accordance with a first embodiment of the invention, a
method is provided of detecting a fuel vapor emissions of an
internal combustion, while the engine is not running. The method
includes closing a first valve used for controlling the escape of
fuel vapor emissions from the system, closing a throttle to prevent
air from entering the engine through the throttle, opening a fuel
vapor management valve to connect the engine with the control
system, rotating the engine to reduce the fuel vapor pressure in
the control system, then closing the vapor management valve and
measuring the vapor pressure in the control system, a change in the
system pressure indicating a possible unacceptable condition in the
control system. The throttle is closed by moving a throttle plate
to a closed position blocking airflow into the intake manifold of
the engine. Rotation of the engine is performed using either an
electric drive motor or an onboard generator operated as a drive
motor. The detection method may be used in hybrid powered vehicles
in which the electric drive motor or generator is employed as the
power source to spin the IC engine during the evaporative fuel
emissions test.
[0009] In accordance with a second embodiment of the invention, a
method is provided for detecting a evaporative fuel emissions in a
fuel vapor emission control system of a hybrid powered vehicle
having an internal combustion engine and an electric drive motor.
The method comprises the steps of determining if the IC engine is
running, closing the emission control system when the IC engine is
determined not to be running, opening a fuel vapor management valve
connecting the engine with the emission control system, rotating
the engine to reduce the fuel vapor pressure within the emission
control system, closing the fuel vapor management valve and then
measuring the vapor pressure in the control system to determine
whether a evaporative fuel emissions may be present.
[0010] These non-limiting features, as well as other advantages of
the present invention may be better understood by considering the
following details of a description of a preferred embodiment of the
present invention. In the course of this description, reference
will frequently be made to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a combined block and schematic diagram of a hybrid
powered vehicle provided with a fuel vapor emission control system;
and,
[0012] FIG. 2 is a flow diagram showing the steps of the method
forming the preferred embodiment of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0013] Referring first to FIG. 1, a vehicle is equipped with an
evaporative, fuel vapor emission control system, generally
indicated by the numeral 10. In the illustrated embodiment, the
vehicle is of the hybrid powered type, driven by an internal
combustion engine 38 and an electric motor 50 which drive one or
more traction wheels 44 through a set of gears 42. The electric
motor 50 is powered by energy stored in a battery 46 whose DC
output is converted to AC by an inverter 48. The electric motor 50
may be operated in a regenerative mode to generate electrical power
used for recharging battery 46. Additionally, an electrical
generator 40 also produces electrical energy and is driven either
directly by the engine 38 or through gear-set 42. Generator 40 may
also be operated as an electric motor capable of spinning
(cranking) the IC engine 38 through either a direct drive
connection or via the gear-set 42. The above mentioned drive
components are controlled by an electronic engine control (EEC) 34,
which also controls the operation of the emission control system
10.
[0014] The emission control system 10 includes a fuel tank 12
having its upper internal volume in communication with one or more
evaporative canisters 16 and the intake manifold 14 of engine 38.
The fuel tank 12 provides fuel to the engine 38 and typically
includes a vapor vent valve 18 as well as a rollover valve 20. The
fuel tank 12 may also include a vacuum relief valve 22, integral
with the fuel tank cap, for preventing excessive vacuum or pressure
from being applied to the fuel tank 12. The fuel tank 12 further
includes a pressure transducer 24 for monitoring fuel tank pressure
or vacuum and for providing a corresponding input signal to the EEC
34. The pressure transducer 24 may be installed directly into the
fuel tank 12 or remotely mounted and connected by a line to the
fuel tank 12.
[0015] Evaporation canister 16 is provided for trapping and
subsequently using fuel vapor dispelled from the fuel tank 12. The
evaporation canister 16 is connected to the atmosphere through a
canister vent valve (CVV) 26. A filter 28 may be provided between
the CVV 26 and the atmosphere for filtering the air pulled into the
evaporation canister 16. The CVV 26 may comprise a normally open
solenoid controlled by the EEC 34 via an electrical connection to
the CVV 26.
[0016] A vapor management valve (VMV) 30 is coupled between the
intake manifold 14 and a fuel tank 12 and the evaporation canister
16. The VMV 30 may comprise a normally closed vacuum operated
solenoid which is also energized by the EEC 34. When the VMV 30
opens, the vacuum of the intake manifold 14 draws fuel vapor from
the evaporation canister 16 for combustion in the cylinders of the
engine 38. When the EEC 34 de-energizes the VMV 30, fuel vapors are
stored in the evaporation canister 16.
[0017] The system 10 may further include a service port 32 coupled
between the VMV 30 and the fuel tank 12 and the evaporation
canister 16. The service port 32 aids an operator in performing
diagnostics on the emission control system 10 to identify
malfunctions.
[0018] In addition to controlling the CVV 26 and VMV 30, the EEC 34
also controls a throttle plate 36 forming part of a throttle body
(not shown) which in turn controls the flow of air into the intake
manifold 14.
[0019] The EEC 34 may perform a series of routine diagnostic tests
to determine whether the emission control system 10 is operating
properly, at any of various times when the vehicle is running.
These diagnostic tests may include gross evaporative fuel emissions
detection and small evaporative fuel emissions detection. In
accordance with the method of the present invention, however, a
diagnostic test to determine the possibility of a evaporative fuel
emissions in the control system 10 may be carried out while the
engine 38 is not running, as would be the case when the vehicle was
either being driven under the power of the electric motor 50 or
when the vehicle is stationary and the IC engine 38 is turned
off.
[0020] The method of the present invention may be better understood
by referring now also to FIG. 2, which shows the flow chart of the
steps comprising the present method. The evaporative fuel emissions
detection method is started at 52 and responds to an initiating
signal produced by the EEC 34 or other on-board controller which
initiates periodic diagnostic tests. A determination is initially
made at 54 as to whether a evaporative fuel emissions test needs to
be performed based upon current vehicle operating conditions or
historical data. For example, pre-programmed instructions may
dictate that a evaporative fuel emissions test be performed within
ten minutes following turning on of the vehicle's ignition. If it
is confirmed that a evaporative fuel emissions test is to be
initiated, then the existence of a series of operating conditions
are confirmed at step 56. For example, before proceeding with the
evaporative fuel emissions test, it must be confirmed that the
pressure within the fuel tank 12 is within a prescribed range, that
there have been no sensor or actuator failures, that the tank 12
has not been recently refueled, that the engine controls are in a
closed loop mode and the vehicle is at idle conditions. Further it
is confirmed that the ambient air pressure is sufficiently high,
that ambient temperature is within a prescribed range, that the
cumulative engine run-time is low enough and that the level of the
fuel within tank 12 is within a certain range.
[0021] Once the conditions in step 56 have been confirmed, a
determination is made at step 58 of whether the IC engine 38 is
running. If the engine 38 is running, then the EEC 34 initiates a
conventional evaporative fuel emissions test of the control system
10. However, if the engine is determined not to be running at step
58, then the following steps of the method of the present invention
are carried out to perform evaporative fuel emissions testing.
[0022] First, at step 62 a determination is made as to whether the
battery 46 has a state of charge (SOC) within a prescribed range.
If the battery SOC is not within a prescribed range, the process
returns to step 54. However, if the battery SOC is within the
prescribed range, then the process proceeds to step 64 in which
both the CVV 26 and the throttle plate 36 are moved to their closed
positions. With both the CVV 26 and throttle plate 36 closed, the
emission control system 10 is effectively closed from the
atmosphere, since atmospheric air may not pass into the system
through the CVV 26 and fresh air may not pass into the intake
manifold 14.
[0023] Next, at step 66, the VMV 30 is opened, placing the engine
38 in fluid communication within the control system 10. Then, at
step 68, the generator 40 is operated as a motor to spin or "crank"
the engine 38, causing the engine's pistons to reciprocate which in
turn forces air out of the piston cylinders into an exhaust
manifold (not shown). Spinning of the engine 38 therefore reduces
the vapor pressure within intake manifold 14, and thus within the
lines and components comprising the emission control system 10. The
EEC 34 monitors the vapor pressure within the control system 10 and
when this pressure drops to a pre-selected level representing the
necessary vacuum required to perform the evaporative fuel emissions
detection, the EEC 34 commands the generator 40 to stop spinning
the engine 38. If, however, the requisite vacuum level is not
created within a pre-selected time period shown in step 72, the
evaporative fuel emissions detection method is terminated, and a
different protocol is followed, such as the performance of a
conventional, gross evaporative fuel emissions detection at step
74.
[0024] Assuming however that spinning of the engine 38 reduces the
vapor pressure in the control system 10 to the pre-selected level
within the prescribed time period, then the VMV 30 is closed at 76
and spinning of the engine 38 is terminated at step 78. At this
point, with the intake manifold 14 isolated from the remainder of
the control system, the EEC 34 monitors the rate of vacuum
bleed-off within the control system 10. The rate of vacuum
bleed-off, i.e. pressure drop in the control system is indicative
of a possible evaporative fuel emissions in the system. If the
pressure drop exceeds a pre-selected rate then a flag is issued
within the EEC 34 which records the possibility of a vapor
evaporative fuel emissions requiring corrective action.
[0025] From the foregoing, it can be seen that the method of the
present invention provides a very simple evaporative fuel emissions
detection method which uses the IC engine 38 to produce a vacuum
within the emission control system 10, then seals the control
system and subsequently monitors the ability of the system to
maintain this vacuum. When used in a hybrid vehicle, advantage can
be taken of the electric drive motor or generator to spin the IC
engine 38 to produce the vacuum while the engine is not running.
Although a generator 40 has been disclosed as being the motive
means for spinning the IC engine 38, the spinning could also be
produced by power from the electric motor 20 which is transmitted
as a torque through the gear-set 42 to the crankshaft of the IC
engine 38.
[0026] It is to be understood that the specific methods and
techniques which have been described are merely illustrative of one
application of the principles of the invention. Numerous
modifications may be made to the method and system as described
without departing from the true spirit and scope of the
invention.
* * * * *