U.S. patent application number 09/732854 was filed with the patent office on 2002-06-13 for method for generating additional engine loads during start-up.
Invention is credited to Curtis, Eric Warren, Dai, Wengang, Gale, Allan Roy, Russ, Stephen George, Tabaczynski, Rodney John, Trigui, Nizar.
Application Number | 20020069639 09/732854 |
Document ID | / |
Family ID | 24945201 |
Filed Date | 2002-06-13 |
United States Patent
Application |
20020069639 |
Kind Code |
A1 |
Gale, Allan Roy ; et
al. |
June 13, 2002 |
METHOD FOR GENERATING ADDITIONAL ENGINE LOADS DURING START-UP
Abstract
A method and system for generating auxiliary load during
start-up and warm-up of a spark ignition engine operating with a
high load, cold start and spark retard and enleanment (HL-CSSRE)
methodology to achieve rapid light-off. The method and system of
the present invention uses existing vehicle systems (20) to couple
an auxiliary load to the engine for a predetermined period of time
during engine start-up and warm-up.
Inventors: |
Gale, Allan Roy; (Livonia,
MI) ; Curtis, Eric Warren; (Milan, MI) ;
Trigui, Nizar; (Ann Arbor, MI) ; Tabaczynski, Rodney
John; (Northville, MI) ; Russ, Stephen George;
(Canton, MI) ; Dai, Wengang; (Canton, MI) |
Correspondence
Address: |
John A. Artz
Artz & Artz PLC
28333 Telegraph Road, Suite 250
Southfield
MI
48034
US
|
Family ID: |
24945201 |
Appl. No.: |
09/732854 |
Filed: |
December 8, 2000 |
Current U.S.
Class: |
60/284 ; 60/274;
60/285 |
Current CPC
Class: |
F01N 3/2013 20130101;
Y02A 50/20 20180101; Y02A 50/2322 20180101; Y02T 10/12 20130101;
Y02T 10/26 20130101; F02D 41/0255 20130101; F02D 2041/026
20130101 |
Class at
Publication: |
60/284 ; 60/285;
60/274 |
International
Class: |
F01N 003/00 |
Claims
What is claimed is:
1. A method of operating an engine at high loads during start-up
and warm-up conditions to achieve rapid catalyst light-off, the
engine having a cold start spark retard and enleanment methodology
and a predetermined load upon start-up, said method comprising the
steps of: detecting an actual engine load during start-up;
determining an auxiliary load to be generated to raise said actual
engine load to said predetermined load; and coupling an auxiliary
load to the engine for a predetermined period of time during engine
start up and warm-up; whereby said auxiliary load on the engine is
additive to the actual engine load achieving the predetermined load
during start-up for rapid catalyst light-off.
2. The method as claimed in claim 1 wherein said step of coupling
an auxiliary load to the engine further comprises coupling an
auxiliary load to the engine to operate the engine at approximately
1200 RPM, 2 bar BMEP, and an air/fuel ratio of 15.
3. The method as claimed in claim 1 wherein the vehicle has an air
conditioner compressor and said step of coupling an auxiliary load
further comprises the step of activating the compressor for the
predetermined period of time during engine startup.
4. The method as claimed in claim 1 wherein the vehicle has a
starter/alternator and said step of coupling an auxiliary load
further comprises the step of over exciting the starter/alternator
during engine start-up.
5. A system for achieving rapid light-off in a catalytic converter
operating in conjunction with a spark ignition engine having a cold
start and spark retard and enleanment methodology, said system
comprising: an existing vehicle system for generating an auxiliary
engine load; and a controller for monitoring an engine load and
coupling said auxiliary engine load to said engine for a
predetermined period of time during engine start up when said
engine load is less than a predetermined load to achieve at least
said predetermined load for rapid catalyst light-off.
6. The system as claimed in claim 5 wherein said existing vehicle
system for generating an auxiliary load further comprises an air
conditioning compressor.
7. The system as claimed in claim 6 wherein said air conditioning
compressor generates a load whereby the engine operates at
approximately 1200 RPM, 2 bar BMEP, an air/fuel ratio of 15 with
moderately retarded spark timing for a predetermined period of
time.
8. The system as claimed in claim 7 wherein said predetermined
period of time is on the order of twenty seconds.
9. The system as claimed in claim 5 wherein said existing vehicle
system for generating an auxiliary load further comprises a
starter/alternator.
10. The system as claimed in claim 9 wherein said
starter/alternator generates a load whereby the engine operates at
approximately 1200 RPM, 2 bar BMEP, an air/fuel ratio of 15 with
moderately retarded spark timing for a predetermined period of
time.
11. The system as claimed in claim 10 wherein said predetermined
period of time is on the order of twenty seconds.
12. A method of operating an engine having a predetermined load
comprising the steps of: initiating the operation of the engine
during a cold start under a cold start spark retard enleanment
process by leaning an air/fuel ratio to the engines and retarding a
spark timing of the engine; detecting the actual engine load during
start-up; determining an auxiliary load to be generated to raise
said actual engine load to said predetermined load; and coupling an
auxiliary load to the engine for a predetermined period of time
during the cold start; whereby said auxiliary load on the engine is
additive to the actual engine load achieving the predetermined load
during cold start for rapid catalyst light-off.
13. The method as claimed in claim 12 further comprising an air
conditioner compressor in operable association with said engine and
said step of coupling said auxiliary load to the engine further
comprises the step of activating said air conditioner compressor
for said predetermined period of time during engine start-up.
14. The method as claimed in claim 12 further comprising a
starter/alternator in operable association with said engine and
said step of coupling said auxiliary load to the engine further
comprises the step of activating said starter/alternator for said
predetermined period of time during engine start-up.
15. The method as claimed in claim 12 wherein said step of coupling
an auxiliary load to the engine further comprises coupling an
auxiliary load to the engine to operate the engine at approximately
1200 RPM, 2 bar BMEP, and an air/fuel ratio of 15.
Description
TECHNICAL FIELD
[0001] The present invention relates generally to controlling the
exhaust temperature of spark ignition engines operating with a cold
start and spark retard and enleanment methodology and more
particularly, to a method for generating additional engine load
using existing vehicle systems during periods of engine cold-start
and warm-up.
BACKGROUND OF THE INVENTION
[0002] Stringent standards have been placed on emissions for
internal combustion engines for cars, trucks and other vehicles to
control the amount of hydrocarbons (HC), carbon monoxide (CO), and
nitrogen oxides (NO.sub.x) that are released into the atmosphere.
However, increasingly more stringent emissions standards are being
placed on vehicles, and still further emissions reductions for
engine operation are being implemented.
[0003] A considerable amount of total emissions occur during engine
warm-up. During this time period, the emissions-reducing catalysts
located in the catalytic converters are largely ineffective due to
the fact that they have not reached a temperature at which
significant catalytic activity can be maintained, also known as
light-off. Thus attempts have been made to decrease emissions
during engine warm-up by decreasing the time it takes to raise the
exhaust temperature to light-off.
[0004] Cold start spark retard and enleanment (CSSRE) is a process
used to decrease cold-start emissions. With CSSRE, hydrocarbons are
oxidized prior to exiting the exhaust system and the catalyst is
rapidly heated by high exhaust temperatures. During a cold start
with CSSRE, engines operate at 1200 RPM, 1 bar brake mean effective
pressure (BMEP), slightly lean air/fuel ratios and heavily retarded
spark timing. While CSSRE enables engines to meet stringent
emissions standards, it subjects the engine to extremely retarded
spark timing and lean operating conditions, thereby increasing
cycle-to-cycle variations, which adversely affects the engine's
stability and increases the requirements for the fuel delivery
systems and engine controls for air/fuel mixtures and spark
timing.
[0005] There is a need for fast and robust catalyst light-off
during engine cold-start and warm-up periods in order to speed-up
catalyst light-off and meet stringent emissions standards.
Therefore there is a need for improved CSSRE methods that improve
engine performance and reduce emissions.
SUMMARY OF THE INVENTION
[0006] It is an object of the present invention to introduce an
auxiliary load on an engine operating with CSSRE during periods of
engine idle to produce higher exhaust gas temperatures for rapid
catalyst light-off.
[0007] In carrying out the above objects and other objects and
features of the present invention, a system and method is provided
for increasing the load of an engine during idle conditions in
order to speed-up catalyst light-off for a high load cold start and
spark retard and enleanment methodology. The engine is operating
with a CSSRE method.
[0008] It is preferred to operate the engine while additional
auxiliary loads are placed on it. According to the present
invention, additional loads are generated by existing systems on
the vehicle. For example, in one embodiment a compressor generates
the additional loads in the air-conditioning system. In the
alternative, the additional loads may be generated by a
starter/alternator. The present invention is advantageous in that
it provides a high-load CSSRE method, which functions without
additional hardware components, complexity or cost. The present
invention requires some software changes in order to control an
electronic engine control module.
[0009] Other objects and advantages of the present invention will
become apparent upon reading the following detailed description and
appended claims, and upon reference to the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] For a more complete understanding of this invention,
reference should now be had to the embodiments illustrated in
greater detail in the accompanying drawings and described below by
way of examples of the invention. In the drawings:
[0011] FIG. 1 is a graph depicting the engine stability and exhaust
port heat flux for various engine loads;
[0012] FIG. 2 is a diagram of one embodiment of the system of the
present invention which generates additional loads using an
air-conditioning compressor;
[0013] FIG. 3 is a diagram of another embodiment of the system of
the present invention, which generates additional loads using a
starter/alternator; and
[0014] FIG. 4 is a flowchart of the high load CSSRE method of the
present invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0015] Cold start spark retard and enleanment (CSSRE) is a process
used to decrease cold-start emissions. An engine operating at
stoichiometry does not rapidly heat the catalyst and therefore more
emissions are generated. With CSSRE, hydrocarbons are oxidized
prior to exiting the exhaust system and the catalyst is more
rapidly heated by high exhaust temperatures. During a cold start
with CSSRE engines operate at approximately 1200 RPM, 1 bar brake
mean effective pressure (BMEP), slightly lean air/fuel ratios and
heavily retarded spark timing. Idle speed may also be changed in
the CSSRE method. However, due to the extremely retarded spark
timing and lean operating conditions, CSSRE causes increased
cycle-to-cycle variations and increases the requirements for the
fuel delivery systems and engine controls for air/fuel mixtures and
spark timing.
[0016] FIG. 1 illustrates the relationship 10 between the exhaust
port heat flux and engine stability for various engine loads. It is
clear that as the engine load increases from one bar 12, to one and
one-half bars 14, to two bars 16 and two and a half bars 18, the
exhaust port temperature rises at a faster rate.
[0017] Through testing and simulation it has been discovered that
operating spark ignition engines at high loads speeds up catalyst
light-off. Operating a spark ignition engine at high loads with
CSSRE raises the manifold pressure, which reduces residual gas in
the cylinder and increases the burn rate. As a result, the engine's
operation is more stable and the exhaust heat flux is drastically
increased (as shown in FIG. 1) due to higher exhaust temperatures
and higher mass flow rates.
[0018] Testing has shown that typical conditions for operating a
spark ignition engine with CSSRE according to the present invention
are to operate the engine at 1200 RPM, 2 bar BMEP, an air/fuel
ratio of 15 with moderately retarded spark timing during cold-start
and warm-up. This operation dramatically speeds up catalyst
light-off. The duration of high load CSSRE is less than thirty
seconds, and typically on the order of twenty seconds. In order to
operate the engine at 2 bar BMEP under idle conditions, additional
loads need to be placed on the engine for a predetermined amount of
time. The additional loads can be mechanical, such as an
air-conditioner compressor, or electrical, such as a
starter/alternator.
[0019] An engine system incorporating high load CSSRE according to
the present invention allows the use of CSSRE without extraordinary
requirements on the fuel preparation, combustion and control
systems. The engine's operation is improved due to lower cyclic
variations. Higher exhaust temperatures and exhaust gas energy are
obtained for enhanced post-combustion HC oxidation and faster
catalyst light-off. Further, as shown in FIG. 1, the exhaust heat
flux is increased with the same levels of engine cyclic variations
as a regular CSSRE.
[0020] According to the present invention the electronic engine
control (EEC) module has a modified control strategy in which an
existing vehicle system, such as an air-conditioner compressor or a
starter/alternator, is activated for a predetermined amount of time
during high load CSSRE. The air/fuel ratio is leaned and the spark
timing is retarded as in conventional CSSRE processes. The system
generates enough auxiliary load during this predetermined amount of
time, which is typically twenty seconds, to operate the engine at
the desired operating conditions and thereby speed up catalyst
light-off. Further, a system is used for generating the auxiliary
load that is already present on the vehicle, i.e. compressor or
starter/alternator, to generate the additional load does not add
cost to the vehicle.
[0021] FIG. 2 is a diagram of an air-conditioning system 20
including a compressor 22 which is typically controlled by two
switches 24, 26 and is connected in series with a battery 28. The
compressor 22 is activated when both the air conditioning
activation switch 24 and the temperature control switch 26 are
activated. Typically, the switches 24 and 26 are controlled by the
EEC and a climate control system (not shown). During start-up, both
switches 24 and 26 can be automatically closed to turn on the
air-conditioner compressor 22 for a predetermined amount of time
during engine start-up and warm-up thereby generating additional
load to the engine. The compressor provides the additional load to
the engine (not shown) necessary to speed-up catalyst
light-off.
[0022] It is also possible, in an alternative embodiment also shown
in FIG. 2, to have a separate switch 25 dedicated to engine
start-up that is closed during start-up to activate the compressor.
Switch 25 is activated by an EEC unit 27 during start-up in place
of the two switches 24 and 26 as described above.
[0023] Another embodiment 30 is shown in FIG. 3, where a
starter/alternator 36 is used to generate the additional load. A
load control switch 32 is located between the battery 28 and a
starter/alternator inverter 34. During start-up of the engine, the
load control switch 32 is activated, typically upon command from
the EEC 27, sending a command 35 to a starter/alternator inverter
34 to overexcite the starter/alternator 36, thereby generating
additional load to the engine (not shown).
[0024] FIG. 4 is a flowchart of the method 100 according to the
present invention. The vehicle's electronic engine control (EEC)
module will store a value that is representative of a predetermined
load that is required during start up of the engine having a CSSRE
methodology. The predetermined load will be applied to the engine
for a predetermined period of time during start up to achieve rapid
light-off.
[0025] Upon engine start up, the EEC will detect 102 the load that
is already existing on the engine. The existing load will be
compared to the predetermined load, or desired load, in order to
calculate 104 the auxiliary load that will be generated by another
system already existing on the vehicle, i.e. starter/alternator, or
air conditioning compressor. The EEC will command 106 the
generation of the auxiliary load by activating the load-generating
system for a predetermined period of time during engine start-up.
In this regard, the high-load CSSRE of the present invention is
implemented for a predetermined period of time, thereby achieving
rapid catalyst light-off.
[0026] The invention covers all alternatives, modifications, and
equivalents, as may be included within the spirit and scope of the
appended claims.
* * * * *