U.S. patent application number 10/754382 was filed with the patent office on 2004-08-19 for method and system for controlling an internal combustion engine having a brake booster.
Invention is credited to Borrmann, Dirk, Brett, Steve, Eves, Brian, Grieser, Klemens.
Application Number | 20040159095 10/754382 |
Document ID | / |
Family ID | 32524228 |
Filed Date | 2004-08-19 |
United States Patent
Application |
20040159095 |
Kind Code |
A1 |
Grieser, Klemens ; et
al. |
August 19, 2004 |
Method and system for controlling an internal combustion engine
having a brake booster
Abstract
The invention relates to a method and system for controlling an
internal combustion engine (9) in a motor vehicle having a brake
booster (1), a low pressure chamber (2) of the brake booster being
connected to the intake manifold (8) of the internal combustion
engine (9). To ensure that the brake booster (1) functions during a
forced warm up of a catalytic converter, the pressure in the brake
booster (1) is monitored by pressure sensors (7a, 7b). If too high
a pressure is detected, the internal combustion engine (9) is
actuated by an engine control system (10) to decrease intake
manifold (8) pressure, for example, by increasing the engine speed
after startup. Spark retard, a measure for warming up a catalytic
converter, is temporarily reduced or eliminated, if increasing
engine speed is insufficient to reduce pressure.
Inventors: |
Grieser, Klemens;
(Langenfeld, DE) ; Brett, Steve; (Southminster,
GB) ; Eves, Brian; (Basildon, GB) ; Borrmann,
Dirk; (Huerth, DE) |
Correspondence
Address: |
FORD GLOBAL TECHNOLOGIES, LLC.
SUITE 600 - PARKLANE TOWERS EAST
ONE PARKLANE BLVD.
DEARBORN
MI
48126
US
|
Family ID: |
32524228 |
Appl. No.: |
10/754382 |
Filed: |
January 9, 2004 |
Current U.S.
Class: |
60/284 |
Current CPC
Class: |
F02D 37/02 20130101;
Y02A 50/20 20180101; F02D 31/003 20130101; Y02T 10/26 20130101;
Y02T 10/42 20130101; Y02T 10/40 20130101; F02D 41/064 20130101;
B60T 13/46 20130101; F01N 2430/00 20130101; F02D 41/0255 20130101;
Y02A 50/2322 20180101; F02D 2250/41 20130101; F02D 41/0002
20130101; Y02T 10/12 20130101; F01N 3/2006 20130101 |
Class at
Publication: |
060/284 |
International
Class: |
F01N 003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 9, 2003 |
EP |
03100027.6 |
Claims
We claim:
1. A method for controlling an internal combustion engine to
maintain pressure in a brake booster during warmup of an exhaust
gas treatment device coupled to the internal combustion engine, the
brake booster being coupled to an intake of the internal combustion
engine and being actuated by a reduced pressure in the intake,
comprising: monitoring pressure in the brake booster; and
decreasing pressure in the engine intake when said pressure in the
brake booster is greater than a threshold pressure.
2. The method of claim 1 wherein said threshold pressure is a
pressure above which an operational capability of the brake booster
is less than a desired operational capability.
3. The method of claim 1 wherein said monitoring comprises
measuring a pressure in a low pressure side of the brake
booster.
4. The method of claim 1 wherein monitoring comprises measuring a
pressure difference between a high pressure and a low pressure side
of the brake booster.
5. The method of claim 1, further comprising: Increasing engine
speed after startup of the engine to ensure a sufficient partial
vacuum in the engine intake.
6. The method of claim 5 wherein said increase is based on
providing a desired functional capability of the brake booster.
7. The method of claim 1, further comprising: reducing an amount of
spark retard to bring said brake booster pressure below said
threshold wherein said spark retard is employed to warmup the
exhaust gas treatment device.
8. The method of claim 5, further comprising: reducing an amount of
spark retard to bring said brake booster pressure below said
threshold when said increasing of engine speed is insufficient to
bring about the brake booster vacuum below said threshold.
9. An engine control system for the internal combustion engine of a
motor vehicle having an exhaust gas treatment arrangement coupled
to the engine, a brake booster actuated by a vacuum being coupled
to the intake of the internal combustion engine, comprising: a
control system which monitors pressure in the brake booster and
decreases pressure in the engine intake when said pressure in the
brake booster is greater than a threshold pressure
10. The system of claim 9, further comprising: a pressure sensor on
a low pressure side of the brake booster.
11. The system of claim 9, further comprising: a differential
pressure sensor between low and high pressure sides of the brake
booster.
12. The system of claim 9 wherein said control system causes engine
speed to increase when said pressure is greater than a threshold
pressure.
13. The system of claim 9 wherein said control system advances
spark timing when said pressure is greater than a threshold
pressure.
14. The system of claim 12, wherein said control system advances
spark timing when said engine speed increase is insufficient to
cause said intake pressure to exceed said threshold pressure.
Description
FIELD OF INVENTION
[0001] The invention relates to a method for controlling an
internal combustion engine, in particular an internal combustion
engine with direct injection and spark ignition, during warmup of
an exhaust gas treatment device connected to the internal
combustion engine.
[0002] Furthermore, the invention relates to an engine control
system for an internal combustion engine which is designed to carry
out such a method, and a brake booster which can be used within the
scope of the method.
BACKGROUND OF THE INVENTION
[0003] Brake boosters reduce the force which is applied by the
driver to brake a motor vehicle. An embodiment of a brake booster
has a movable working piston between a low pressure chamber and a
high pressure chamber. A pressure difference between the chambers
exerts a force on the piston to aid braking. The vacuum for the low
pressure chamber is usually generated by coupling to the intake
manifold of the internal combustion engine, while ambient pressure
is applied to the high pressure chamber. The brake booster
therefore relies on sufficient vacuum in the intake manifold.
[0004] Furthermore, it is known that engines with direct injection
and spark ignition (DISI) permit considerably faster warm up, and
thus activation of a catalytic converter arranged in the exhaust
gas path, in comparison with port fuel injected engines with
injection in the intake port. The control strategy commonly used
retards spark timing to maximize the flow of heat into the exhaust
gas. To maintain the desired engine speed, the throttle valve of
the internal combustion engine is opened further to supply a larger
quantity of air to the engine. This can lead to anabsolute pressure
in the intake manifold reaching approximately 80 kPa, is a low
vacuum.). The pressure difference between ambient pressure
(approximately 100 kPa at sea level) on the high pressure side and
a low vacuum, e.g., 80 kPa does not ensure reliable function of the
vacuum brake booster.
SUMMARY OF THE INVENTION
[0005] A method for controlling an internal combustion engine to
maintain pressure in a brake booster during warmup of an exhaust
gas treatment device coupled to the internal combustion engine is
disclosed. The brake booster is coupled to an intake of the
internal combustion engine and actuated by a reduced pressure in
the intake The method includes monitoring pressure in the brake
booster and decreasing pressure in the engine intake when the
pressure in the brake booster is greater than a threshold
pressure.
[0006] The threshold pressure is a pressure above which an
operational capability of the brake booster is less than
desired.
[0007] The method further includes reducing an amount of spark
retard to bring brake booster pressure below the threshold. The
method further includes increasing engine rotational speed to bring
brake booster pressure below the threshold.
[0008] An advantage of the present invention is that brake booster
operation is ensured. Furthermore, warmup of the catalytic
converter is resumed as soon after startup as possible.
[0009] A further advantage is that brake booster vacuum is
maintained via increasing engine speed and/or advancing spark
advance timing, both measures being readily controlled by the
engine control system.
BRIEF DESCRIPTION OF DRAWINGS
[0010] The invention is explained in more detail below with the aid
of drawings by way of example. In the drawings:
[0011] FIG. 1 is a schematic view of the components for carrying
out a method according to the invention;
[0012] FIG. 2 is a schematic flowchart of a control strategy
according to an aspect of the present invention;
[0013] FIG. 3 is a time line of various engine parameters showing
operation according to the present invention.
DETAILED DESCRIPTION
[0014] The internal combustion engine 9 illustrated in FIG. 1 is
preferably a petrol engine with direct injection and spark
ignition. The internal combustion engine 9 is supplied with air via
an intake manifold 8. Exhaust gases leave the internal combustion
engine 9 via an exhaust gas manifold and an exhaust gas pipe with a
catalytic converter (not shown) disposed therein. Operation of
engine 9 is controlled by an engine controller 10 which may be
implemented, for example, as a microprocessor and receives various
items of sensory information of the motor vehicle and of engine 9,
and outputs control signals to engine 9 and other components of the
motor vehicle.
[0015] Furthermore, FIG. 1 is a schematic illustration of a brake
booster 1. The brake booster 1 contains a working piston 4 which is
movably arranged between a low pressure chamber 2 and a high
pressure chamber 3. The working piston 4 is connected to the brake
pedal 6 via a piston rod. Due to a vacuum in the low pressure
chamber 2 and a comparatively higher pressure in the high pressure
chamber 3, a force is exterted on piston 4 which generates the
braking pressure. The vacuum in the low pressure chamber 2 is
generally obtained from the intake manifold 8 of the internal
combustion engine 9 via a one-way valve 5, while the high pressure
in the high pressure chamber 2 typically corresponds to ambient
pressure.
[0016] Reliable function of the brake booster 1 requires a
sufficient difference in pressure across the working piston 4,
which in turn requires sufficient vacuum in the intake manifold 8.
However, a sufficient vacuum in the intake manifold 8 is not
ensured when a cold start of the internal combustion engine 9
occurs in engines with direct injection and spark ignition.,
Typically, spark retard is used to achieve more rapid warming of
the catalytic converter. To ensure a sufficient engine speed of the
internal combustion engine 9, the throttle is opened and absolute
pressures in the intake manifold of 80 kPa result. However, 80 kPa
is not sufficient vacuum for reliably operating the brake booster
1.
[0017] According to the invention, the pressure state of the brake
booster 1 is therefore monitored. This is preferably carried out by
an absolute pressure sensor 7a which is arranged in the low
pressure chamber 2 to measure the pressure, pI, present there and
to communicate it to the engine controller 10. The engine
controller 10 can therefore detect an insufficient partial vacuum
and correspondingly actuate the internal combustion engine 9 in
such a way that the vacuum in the intake manifold 8 is sufficient.
If, for example, pressure, pI, in the low pressure chamber 2 lies
above a predefined absolute pressure of, for example, 60 kPa at sea
level at the start of the warming-up phase of the internal
combustion engine 9, the engine controller 10 can increase the
maximum engine speed after starting up occurs and before the idling
state to generate a lower absolute pressure in the intake manifold
8 after the initial overshooting of the engine speed, and to
achieve the desired vacuum in the brake booster 1. The degree of
overshooting of the engine speed preferably depends on the pressure
in the low pressure chamber 2 when engine 9 starts, i.e. the higher
the pI, the greater the overshoot of the engine speed, and vice
versa.
[0018] If the increase in the engine speed overshoot, at the
changeover into the idling mode, is unable to bring about a
sufficient vacuum in the brake booster 1, the strategy for more
rapidly warming up the catalytic converter is discontinued by the
engine controller 10 until the desired vacuum in the brake booster
1 is reached. This leads to a normal idling mode of engine 9 in
which the desired low absolute pressure in the intake manifold 8 of
40 kPa, for example, is brought about more quickly.
[0019] If the pressure state of the brake booster 1 is sensed only
by pressure sensor 7a in the low pressure chamber 2 the pressure of
the high pressure chamber 3 is presumed to be virtually constant,
i.e. average atmospheric pressure. To improve the precision of the
system and to ensure reliable functioning even at a high altitude
above sea level (i.e., at a relatively low ambient pressure), the
pressure in the high pressure chamber 3 is taken into account. This
can be carried out, as illustrated in FIG. 1, by a second pressure
sensor 7b arranged in the high pressure chamber 3, which
communicates the pressure to the engine controller 10.
Alternatively, the engine controller 10 can also measure the
ambient pressure as this variable is frequently already determined
for other purposes of engine control. Alternatively, the pressure
difference between the high pressure chamber 3 and the low pressure
chamber 2 can be sensed directly by a differential pressure sensor
(not shown, as ultimately only pressure difference is significant
for determining proper function of the brake booster 1.
[0020] FIG. 2 shows the sequence of a method according to the
invention in yet more detail. After the engine is started in step
12, it is checked in step 14, after the a certain delay (not shown)
by which time the pressure in the intake manifold is nearly steady
state, whether the pressure in the brake booster, p_brake, lies
below a predefined threshold value (for example 40 kPa absolute. If
this criterion is fulfilled, a normal idling mode with a desired
maximum engine speed of des_engine_speed is initiated, which
corresponds to a maximum engine speed nom_engine_speed (for example
1300 rpm), (step 16). Otherwise, after startup, the desired maximum
engine speed is increased in step 18 as follows:
des.sub.--engine.sub.--speed=nom.sub.--engine.sub.--speed+(speed.sub.--add-
*(p.sub.--brake/threshold-1))
[0021] The factor speed_add is a normalization factor, for example
200 rpm.
[0022] If the pressure in the brake booster exceeds a second
threshold (for example, 50 kPa absolute) in step 20, the forced
warm up for the exhaust gas treatment arrangement is reduced or
eliminated in step 22 until the corresponding second threshold
value has been reached. The sub-routine is then terminated.
[0023] FIG. 3 illustrates a timeline of engine parameters. This is
a NEDC test cycle at 20.degree. C., which is used to measure
pollutant emission over a predefined engine speed/load schedule.
Curve 30 shows the pressure profile in the intake manifold. In a
forced warm up of the catalytic converter, manifold vacuum reaches,
according to the prior art, 10 kPa, which is insufficient to
reliably operate a brake booster. Brake booster vacuum (32)
correspondingly remains low. When the brakes are not actuated,
brake booster vacuum assumes approximately the maximum intake
manifold vacuum due to the check valve present between the intake
manifold and the brake booster.
[0024] According to the invention, intake manifold vacuum is
reduced to approximately 60 kPa (34), several seconds after startup
as a result of diminishing or eliminating measures undertaken to
rapidly warm up the exhaust treatment device. Consequently, brake
booster vacuum is at a higher level 36, thereby ensuring reliable
operation of the brake booster (curves 34 and 36 at later times not
shown).
* * * * *