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Claims  |
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I claim:
1. In an excess air rate control apparatus for an engine which is mounted
in a vehicle and which includes a suction passage and an exhaust gas
recirculation system for recirculating part of exhaust gas into the
suction passage, the excess air rate control apparatus controlling, in
accordance with operating conditions of the engine, an excess air rate of
an air-fuel mixture which is supplied to the engine while the exhaust gas
recirculation system is operating, the excess air rate control apparatus
comprising:
excess air rate estimating means for estimating the excess air rate of the
air-fuel mixture supplied to the engine;
target excess air rate setting means for setting a target excess air rate
of the air-fuel mixture supplied to the engine;
valve opening degree setting means for setting a target valve opening
degree for the exhaust gas recirculation system such as to remove a
deviation between the excess air rate estimated by said excess air rate
estimating means and the target excess air rate set by said target excess
air rate setting means; and
an operation control device for controlling operation of the exhaust gas
recirculation system in accordance with the target valve opening degree
set by said valve opening degree setting means,
said valve opening degree setting means setting the target valve opening
degree at least by proportional-plus-integral control such that an
integral term for the proportional-plus-integral control is not integrated
when an absolute value of the deviation between the estimated excess air
rate and the set target excess air rate is larger than a predetermined
value.
2. An excess air rate control apparatus for an engine according to claim 1,
which comprises fuel supply quantity detecting means for detecting a
quantity of fuel supply to the engine and engine rotation speed detecting
means for detecting a rotation speed of the engine;
wherein said target excess air rate setting means sets the target excess
air rate in accordance with the engine rotation speed detected by said
engine rotation speed detecting means and the fuel supply quantity set by
said fuel supply quantity setting means.
3. In an excess air rate control apparatus for an engine which is mounted
in a vehicle and which includes a suction passage, an exhaust passage, a
turbo charger for supercharging the engine with intake by driving a
turbine by means of exhaust gas of the engine, and an exhaust gas
recirculation system for recirculating part of the exhaust gas, taken out
of the exhaust passage on an upstream side of the turbo charger, into the
suction passage, the excess air rate control apparatus controlling, in
accordance with operating conditions of the engine, an excess air rate of
that air-fuel mixture which is supplied to the engine while the exhaust
gas recirculation system is operating, the excess air rate control
apparatus comprising:
intake pressure detecting means for detecting an intake pressure of the
engine;
exhaust pressure detecting means for detecting an exhaust pressure of the
engine;
exhaust gas recirculation quantity estimating means for estimating a
quantity of recirculation of the exhaust gas by the exhaust gas
recirculation system in accordance with the intake pressure detected by
said intake pressure detecting means and the exhaust pressure detected by
said exhaust pressure detecting means;
total intake quantity detecting means for detecting a total intake quantity
of the engine, including the quantity of the exhaust gas recirculated by
the exhaust gas recirculation system;
equivalent intake air quantity estimating means for estimating an
equivalent intake air quantity of the engine;
fuel supply quantity setting means for setting a quantity of fuel supply to
the engine in accordance with a depression amount of an accelerator pedal
of the vehicle;
fuel supply means for supplying a fuel to the engine in accordance with the
fuel supply quantity set by said fuel supply quantity setting means;
excess air rate estimating means for estimating the excess air rate for the
engine in accordance with the fuel supply quantity set by said fuel supply
quantity setting means and the equivalent intake air quantity estimated by
said equivalent intake air quantity estimating means;
storage means for storing the excess air rate estimated by said excess air
rate estimating means;
target excess air rate setting means for setting a target excess air rate
of the air-fuel mixture supplied to the engine;
valve opening degree setting means for setting a target valve opening
degree of the exhaust gas recirculation system in accordance with the
excess air rate estimated by said excess air rate estimating means and the
target excess air rate set by said target excess air rate setting means;
and
operation control means for controlling operation of the exhaust gas
recirculation system in accordance with the target valve opening degree
set by said valve opening degree setting means,
said equivalent intake air quantity estimating means for estimating the
equivalent intake air quantity in accordance with the total intake
quantity detected by said total intake quantity detecting means, the
excess air rate stored in said storage means and estimated for a last
cycle but a predetermined number of cycles, and the exhaust gas
recirculation quantity estimated by said exhaust gas recirculation
quantity estimating means.
4. An excess air rate control apparatus for an engine according to claim 3,
wherein said fuel supply means injects the fuel directly into a combustion
chamber of the engine.
5. An excess air rate control apparatus for an engine according to claim 3,
wherein the engine is a diesel engine.
6. An excess air rate control apparatus for an engine according to claim 3,
wherein said valve opening degree setting means sets the target valve
opening degree such as to remove a deviation between the excess air rate
estimated by said excess air rate estimating means and the target excess
air rate set by said target excess air rate setting means.
7. An excess air rate control apparatus for an engine according to claim 6,
which comprises engine rotation speed detecting means for detecting a
rotation speed of the engine, and wherein said target excess air rate
setting means sets the target excess air rate in accordance with the
engine rotation speed detected by said engine rotation speed detecting
means and the fuel supply quantity set by said fuel supply quantity
setting means.
8. An excess air rate control apparatus for an engine according to claim 3,
which comprises fuel supply quantity correcting means for correcting the
fuel supply quantity set by said fuel supply quantity setting means, in
accordance with a result of comparison between the excess air rate
estimated by said excess air rate estimating means and a predetermined
excess air rate;
wherein said fuel supply means supplies the fuel to the engine in
accordance with the fuel supply quantity corrected by said fuel supply
quantity correcting means.
9. An excess air rate control apparatus for an engine according to claim 8,
wherein said fuel supply quantity correcting means corrects the fuel
supply quantity set by said fuel supply quantity setting means so that the
excess air rate estimated by said excess air rate estimating means
approaches the predetermined excess air rate.
10. An excess air rate control apparatus for an engine according to claim
8, wherein said fuel supply quantity correcting means reduces the fuel
supply quantity set by said fuel supply quantity setting means when the
excess air rate estimated by said excess air rate estimating means is not
higher than the predetermined excess air rate.
11. An excess air rate control apparatus for an engine according to claim
8, wherein said fuel supply quantity correcting means corrects the fuel
supply quantity in accordance with a value obtained by multiplying the
fuel supply quantity, which was set by the fuel supply quantity setting
means, by the estimated excess air rate, and then dividing an obtained
product by said predetermined excess air rate, when the excess air rate
estimated by said excess air rate estimating means is not higher than the
predetermined excess air rate.
12. An excess air rate control apparatus for an engine according to claim
3, which comprises decision means for determining whether or not the
excess air rate estimated by said excess air rate estimating means is
within a predetermined allowable range;
wherein said operation control means actuates the exhaust gas recirculation
system in a closing direction when said decision means concludes that the
estimated excess air rate is out of the allowable range.
13. An excess air rate control apparatus for an engine according to claim
12, wherein said fuel supply means includes restraining means for
restraining an increase of the fuel supply quantity without regard to the
depression amount of the accelerator pedal when said decision means
concludes that the estimated excess air rate is out of the allowable
range.
14. An excess air rate control apparatus for an engine according to claim
13, wherein said storage means stores the fuel supply quantity set for a
preceding cycle by said fuel supply quantity setting means; and
wherein said restraining means keeps the fuel supply quantity at the
preceding value stored in said storage means.
15. An excess air rate control apparatus for an engine according to claim
13, wherein said restraining means releases the fuel supply quantity from
the restraint after passage of a predetermined period since a start of the
actuation of the exhaust gas recirculation system in the closing
direction.
16. An excess air rate control apparatus for an engine according to claim
13, wherein said restraining means releases the fuel supply quantity from
the restraint when said decision means concludes that the estimated excess
air rate is restored to the allowable range.
17. In an excess air rate detecting apparatus for an engine which is
mounted in a vehicle and which includes a suction passage and an exhaust
gas recirculation system for recirculating part of exhaust gas into the
suction passage, the excess air rate detecting apparatus repeatedly
detecting, in accordance with operating conditions of the engine, an
excess air rate of that air-fuel mixture which is supplied to the engine
while the exhaust gas recirculation system is operating, the excess air
rate detecting apparatus comprising:
intake pressure detecting means for detecting an intake pressure of the
engine;
exhaust gas recirculation quantity estimating means for estimating a
quantity of recirculation of the exhaust gas by the exhaust gas
recirculation system in accordance with at least the intake pressure
detected by said intake pressure detecting means;
equivalent intake air quantity estimating means for estimating an
equivalent intake air quantity of the engine;
fuel supply quantity setting means for setting a quantity of fuel supply to
the engine;
excess air rate estimating means for estimating the excess air rate for the
engine in accordance with the fuel supply quantity set by said fuel supply
quantity setting means and the equivalent intake air quantity estimated by
said equivalent intake air quantity estimating means; and
storage means for storing the excess air rate estimated by said excess air
rate estimating means,
said equivalent intake air quantity estimating means estimating the
quantity of recirculation of the exhaust gas in accordance with at least
the exhaust gas recirculation quantity estimated by said exhaust gas
recirculation quantity estimating means and the excess air rate stored in
said storage means and estimated for a last cycle but a predetermined
number of cycles.
18. An excess air rate detecting apparatus for an engine according to claim
17, wherein said excess air rate estimating means estimates the excess air
rate with every stroke of the engine.
19. An excess air rate detecting apparatus for an engine according to claim
17, wherein the engine is a diesel engine.
20. An excess air rate detecting apparatus for an engine according to claim
17, which comprises total intake quantity detecting means for computing a
total intake quantity, including the quantity of the exhaust gas
recirculated by the exhaust gas recirculation system, in accordance with
the intake pressure detected by said intake pressure detecting means;
wherein said equivalent intake air quantity estimating means estimates an
equivalent intake air quantity in accordance with the computed total
intake quantity, the excess air rate stored in said storage means and
estimated for the last cycle but the predetermined number of cycles, and
the exhaust gas recirculation quantity estimated by said exhaust gas
recirculation quantity estimating means.
21. An excess air rate detecting apparatus for an engine according to claim
20, wherein said equivalent intake air quantity estimating means estimates
the equivalent intake air quantity by dividing the exhaust gas
recirculation quantity by the excess air rate, the exhaust gas
recirculation quantity being estimated by said exhaust gas recirculation
quantity estimating means and the excess air rate being stored in said
storage means and estimated for the last cycle but the predetermined
number of cycles, thereby obtaining a quantity of consumed air unconcerned
in combustion, out of the exhaust gas recirculated in the exhaust gas
recirculation system, and by subtracting the obtained consumed air
quantity from the computed total intake quantity.
22. An excess air rate detecting apparatus for an engine according to claim
17, which comprises exhaust pressure detecting means for detecting an
exhaust pressure of the engine; and
wherein said exhaust gas recirculation quantity estimating means estimates
the quantity of recirculation of the exhaust gas in accordance with the
intake pressure detected by said intake pressure detecting means and the
exhaust pressure detected by said exhaust pressure detecting means.
23. An excess air rate detecting apparatus for an engine according to claim
22, which comprises valve opening degree detecting means for detecting a
valve opening degree of the exhaust gas recirculation system; and
wherein said exhaust gas recirculation quantity estimating means estimates
the quantity of recirculation of the exhaust gas further in accordance
with the valve opening degree detected by said valve opening degree
detecting means.
24. An excess air rate detecting apparatus for an engine according to claim
23, which comprises engine rotation speed detecting means for detecting a
rotation speed of the engine;
wherein said exhaust gas recirculation quantity estimating means obtains an
orifice factor in accordance with a difference between the exhaust
pressure detected by said exhaust pressure detecting means and the intake
pressure detected by said intake pressure detecting means, obtains a
recirculated exhaust gas temperature coefficient in accordance with the
engine rotation speed detected by said engine rotation speed detecting
means and the fuel supply quantity set by said fuel supply quantity
setting means, and estimates the quantity of recirculation of the exhaust
gas in accordance with the valve opening degree detected by said valve
opening degree detecting means, the obtained orifice factor, and the
obtained recirculated exhaust gas temperature coefficient.
25. An excess air rate detecting apparatus for an engine according to claim
22, wherein the engine is provided with a turbo charger for supercharging
the engine with intake by driving a turbine by means of the exhaust gas,
and said exhaust pressure detecting means detects the exhaust pressure on
an upstream side of the turbine.
26. An excess air rate detecting apparatus for an engine according to claim
25, which comprises engine rotation speed detecting means for detecting a
rotation speed of the engine and total intake quantity detecting means for
computing a total intake quantity, including a quantity of the exhaust gas
recirculated by the exhaust gas recirculation system, in accordance with
the intake pressure detected by said intake pressure detecting means;
wherein said storage means stores the exhaust gas recirculation quantity
estimated by said exhaust gas recirculation quantity estimating means, the
total intake quantity computed by said total intake quantity detecting
means, and the exhaust pressure detected by said exhaust pressure
detecting means; and
wherein said exhaust pressure detecting means obtains a steady-state value
of the exhaust pressure on the upstream side of the turbine in accordance
with the engine rotation speed detected by said engine rotation speed
detecting means and the fuel supply quantity set by said fuel supply
quantity setting means, obtains a turbine acceleration pressure in
accordance with the obtained steady-state exhaust pressure value, the
exhaust gas recirculation quantity and the total intake quantity, the
exhaust gas recirculation quantity and the total intake quantity being
individually stored in said storage means for the last cycle but the
predetermined number of cycles, obtains a turbine load from the obtained
turbine acceleration pressure and the obtained steady-state exhaust
pressure value, and obtains a present value of the exhaust pressure in
accordance with a preceding value of the exhaust pressure stored in said
storage means and the obtained turbine acceleration value and the obtained
turbine load.
27. An excess air rate detecting apparatus for an engine according to claim
17, which comprises an airflow sensor provided on an upstream side of a
position where the exhaust gas is supplied into the suction passage by the
exhaust gas recirculation system, the airflow sensor detects a quantity of
intake air flowing in the suction passage;
wherein said exhaust gas recirculation quantity estimating means estimates
the exhaust gas recirculation quantity in accordance with the intake
pressure detected by said intake pressure detecting means and the intake
air quantity detected by said airflow sensor.
28. An excess air rate detecting apparatus for an engine according to claim
27, which comprises total intake quantity detecting means for computing a
total intake quantity, including the quantity of the exhaust gas
recirculated by the exhaust gas recirculation system, in accordance with
the intake pressure detected by said intake pressure detecting means;
wherein said exhaust gas recirculation quantity estimating means estimates
the exhaust gas recirculation quantity by subtracting the intake air
quantity detected by said airflow sensor from the intake quantity computed
by said total intake quantity detecting means.
29. An excess air rate detecting apparatus for an engine according to claim
27, wherein said equivalent intake air quantity estimating means estimates
an equivalent intake air quantity in accordance with the intake air
quantity detected by said airflow sensor, the excess air rate stored in
said storage means and estimated for the last cycle but the predetermined
number of cycles, and the exhaust gas recirculation quantity estimated by
said exhaust gas recirculation quantity estimating means.
30. An excess air rate detecting apparatus for an engine according to claim
27, which comprises in-cylinder intake air quantity estimating means for
estimating a quantity of intake air actually sucked into a cylinder in
accordance with the intake air quantity detected by said airflow sensor
and a delay in transportation time;
wherein said exhaust gas recirculation quantity estimating means estimates
the exhaust gas recirculation quantity in accordance with the actual
in-cylinder intake air quantity estimated by said in-cylinder intake air
quantity estimating means.
31. An excess air rate detecting apparatus for an engine according to claim
30, wherein said storage means stores the in-cylinder intake air quantity
estimated by said in-cylinder intake air quantity estimating means; and
wherein said in-cylinder intake air quantity estimating means estimates the
actual in-cylinder intake air quantity in accordance with a preceding
value of the in-cylinder intake air quantity stored in said storage means
and a present value of the intake air quantity detected by said airflow
sensor.
32. An excess air rate detecting apparatus for an engine according to claim
30, wherein said equivalent intake air quantity estimating means computes
a residual air quantity in accordance with the excess air rate and the
exhaust gas recirculation quantity, the excess air rate being stored in
said storage means and estimated for the last cycle but the predetermined
number of cycles and the exhaust gas recirculation quantity being
estimated by said exhaust gas recirculation quantity estimating means, and
wherein said equivalent intake air quantity estimating means estimates the
equivalent intake air quantity by adding the computed residual air
quantity to the actual in-cylinder intake air quantity estimated by said
in-cylinder intake air quantity estimating means. |
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Claims |
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Description |
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TECHNICAL FIELD
The present invention relates to an excess air rate detecting apparatus and
an excess air rate control apparatus for an engine, used in a fuel supply
system or exhaust emission control device of an automotive diesel engine
and the like.
BACKGROUND ART
Principal harmful exhaust components emitted from of a diesel engine
include NOx that is produced by combustion at high temperature, besides
black smoke, unburned HC, etc., which are attributable to uneven
distribution of a fuel injected into a cylinder or some other causes. A
reduction catalyst, such as the one used in a gasoline engine, cannot be
used as NOx reducing means for the diesel engine, since it contains extra
oxygen, so that retardation of fuel injection timing (timing retardation)
and water jet are being investigated. However, the former entails lowering
of outputs or worsening of fuel efficiency, inevitably causing increase of
CO and HC. The latter involves problems of installation of a water jet
system and water tank, inclusion of water in lubricating oil, etc.
Therefore, an exhaust gas recirculation (EGR) system, in which exhaust
gas, an inert material, is recirculated as an EGR gas to a combustion
chamber, is being put to practical use, since it has a relatively simple
construction and is less susceptible to the aforesaid harmful influences.
In an EGR system for a diesel engine, if the recirculation quantity
(hereinafter referred to as EGR quantity) of the EGR gas becomes
excessive, the delivery of smoke or HC suddenly increases as the excess
air rate lowers, and the fuel efficiency deteriorates. Besides, engine oil
is deteriorated by inclusion of free carbon or particulates, so that
lowering of the engine durability or the like occurs. In order to reduce
NOx while minimizing these troubles, therefore, it is advisable to use an
electronic control device for detecting the excess air rate to effect
feedback control of the EGR quantity or to keep the excess air rate within
an appropriate range even during transient operation or the like, to say
nothing of steady-state operation.
In general, methods for detecting the excess air rate include a method
using a CO.sub.2 analyzer and a method using a linear air-fuel ratio
sensor (hereinafter referred to as LAFS).
As is generally known, however, the CO.sub.2 analyzer is large-sized and
heavy in weight, so that it is not practical for vehicular use, although
it can be used for a bench test or the like. As known EGR apparatuses
equipped with the LAFS, on the other hand, there are ones described in
Jpn. Pat. Appln. KOKAI Publication Nos. 55-7964 and 63-201356. In the
former EGR apparatus, the LAFS is attached to an exhaust system, and an
EGR valve is actuated in its opening direction when the output current of
the LAFS is higher than a given threshold value, and in contrast with
this, in its closing direction when the output current is lower. In the
latter EGR apparatus, an EGR valve is actuated with reference to a control
map for the EGR quantity, while the EGR valve opening degree (control map)
is corrected by means of the LAFS that is attached to an exhaust system,
which control map is determined as a function of the lever opening degree
(accelerator opening degree) of a fuel injection pump and the engine
rotation speed.
Nevertheless, those EGR apparatuses equipped with the LAFS for the feedback
control of the EGR quantity have the following problems.
Since the LAFS is attached to the exhaust system, for example, a delay in
transfer is caused before the exhaust gas reaches the LAFS even though the
excess air rate actually changes. Since the LAFS is designed so as to
output a current corresponding to the excess air rate, based on the
principle of an oxygen concentration cell, and that the exhaust gas
reaches the elements through a protective tube, moreover, the response to
change of the excess air rate is low itself. At the time of acceleration
or deceleration such that the excess air rate suddenly changes, therefore,
a delay (normally tens of strokes) is caused before the LAFS detects the
change of the excess air rate, as shown in FIG. 1. FIG. 1 shows changes of
the excess air rate with time caused when the injection quantity is
suddenly increased, the full and tow dot chain lines representing an
actual excess air rate change and an excess air rate change detected by
the LAFS, respectively. Naturally, therefore, the control of the EGR
apparatus is subject to a delay, so that the delivery of NOx or black
smoke increases inevitably, posing a problem. In particular, immediately
after acceleration, when black smoke is originally liable to be
discharged, the delivery of black smoke is further increased by the
excessive EGR quantity.
In the case of a diesel engine, moreover, the exhaust gas contains free
carbon or particulates in abundance, so that the LAFS is soiled in a short
period of time and ceases to output the current corresponding to the
excess air rate. Accordingly, the accuracy of detection gradually
deteriorates, so that the EGR quantity cannot be controlled accurately.
Since the LAFS itself is an expensive component, moreover, the initial
cost is naturally high, and besides, routine inspections, replacement,
etc. entail a high running cost.
On the other hand, many diesel engines are furnished with a turbo charger,
in order to increase the output per stroke volume. The turbo charger,
which serves for supercharge utilizing exhaust gas energy (exhaust
pressure), comprises a turbine attached to an exhaust manifold or the like
and a compressor coaxial therewith and arranged in a suction system. As is
generally known, the work load or supercharge pressure of the turbo
charger depends on the exhaust pressure, and becomes lower in a low-load
low-speed engine operation mode and higher in a high-load high-speed
engine operation mode. Also, the turbo charger is subject to a natural
response delay (turbo lag), since it takes some time for the exhaust
pressure to increase, due to a delay in transfer or the like, even though
the quantity of fuel supply is increased by a driver's accelerator
operation, and the inertias of the turbine and the compressor prevent an
immediate triggering of their rotation.
In the case where the EGR apparatus is attached to a turbo-charged diesel
engine, accelerative operation involves the following problems.
In the case of a diesel engine without a throttle valve, the quantity of
fuel injection into the combustion chamber is increased according to the
driver's stepping on the accelerator pedal, whereupon the operation mode
changes from steady-state over to acceleration. Unlike a gasoline engine
of the manifold-injection type or the like, to which an air-fuel mixture
of a predetermined air-fuel ratio is supplied, this engine is designed so
that the injection quantity increases irrespective of the quantity of
intake air, whereby the torque generated increases to effect acceleration.
Accordingly, the rate of excess air in the combustion chamber is set
according to the intake air quantity and the fuel injection quantity, and
substantially varies during the acceleration. Thus, the excess air rate is
instantaneously lowered as the injection quantity increases in a very
early stage of the acceleration. If the supercharge pressure provided by
the turbo charger rises as the exhaust pressure increases, however, the
excess air rate is suddenly enhanced with the increase of the intake. In
consideration of the entire period of the acceleration, therefore, the
increase of harmful exhaust components can be restricted to a negligible
degree.
In the turbo-charged engine equipped with the EGR apparatus, however, the
EGR gas is fetched from the exhaust system on the upstream side of the
turbine. When the EGR apparatus is actuated (EGR gas is recirculated),
therefore, a nonnegligible portion of the increased exhaust pressure
inevitably runs out into the suction system without driving the turbine.
As a result, the increasing rate of the supercharge pressure is lowered,
and the harmful exhaust components are increased on account of lowering of
the excess air rate. If the fuel injection quantity is restricted
unconditionally in order to prevent the excess air rate from lowering,
accelerating force is reduced, so that the drivability deteriorates.
DISCLOSURE OF THE INVENTION
An object of the present invention is to provide an excess air rate
detecting apparatus, for rapidly detecting the excess air rate of a diesel
engine or the like despite the use of a simple, low-cost apparatus
arrangement, and an excess air rate control apparatus based on the
principle thereof.
Another object of the present invention is to provide an excess air rate
control apparatus, which can reconcile the maintenance of accelerating
force and reduction of harmful exhaust gas components despite the use of a
simple, low-cost apparatus arrangement, and which is suited for use with
an engine furnished with a turbo charger.
According to the present invention, there is provided an excess air rate
detecting apparatus for an engine which is mounted in a vehicle and which
includes a suction passage and an exhaust gas recirculation system for
recirculating part of exhaust gas into the suction passage. In accordance
with operating conditions of the engine, the excess air rate detecting
apparatus repeatedly detects the excess air rate of that air-fuel mixture
which is supplied to the engine while the exhaust gas recirculation system
is operating.
The excess air rate detecting apparatus according to the present invention
comprises: intake pressure detecting means for detecting the intake
pressure of the engine; exhaust gas recirculation quantity estimating
means for estimating the quantity of recirculation of the exhaust gas by
the exhaust gas recirculation system in accordance with at least the
intake pressure detected by the intake pressure detecting means;
equivalent intake air quantity estimating means for estimating an
equivalent intake air quantity of the engine; fuel supply quantity
detecting means for detecting the quantity of fuel supply to the engine;
excess air rate estimating means for estimating the excess air rate for
the engine in accordance with the fuel supply quantity set by the fuel
supply quantity setting means and the equivalent intake air quantity
estimated by the equivalent intake air quantity estimating means; and
storage means for storing the excess air rate estimated by the excess air
rate estimating means. The equivalent intake air quantity estimating means
estimates, preferably with every stroke, the quantity of recirculation of
the exhaust gas in accordance with at least the exhaust gas recirculation
quantity, which was estimated by the exhaust gas recirculation quantity
estimating means, and the excess air rate, which was estimated during the
last cycle but a predetermined number of cycles and stored in the storage
means.
According to the excess air rate detecting apparatus arranged in this
manner, the excess air rate for a diesel engine or the like can be
detected accurately and rapidly without using an LAFS or the like, which
is poor in reliability and entails high cost. With use of this detecting
apparatus, the injection quantity and EGR quantity can be appropriately
controlled in order to reduce the delivery of NOX or black smoke.
Preferably, the apparatus further comprises exhaust pressure detecting
means for detecting the exhaust pressure of the engine, and the exhaust
gas recirculation quantity estimating means estimates the quantity of
recirculation of the exhaust gas in accordance with the intake pressure
detected by the intake pressure detecting means and the exhaust pressure
detected by the exhaust pressure detecting means.
Preferably, moreover, the apparatus comprises valve opening degree
detecting means for detecting the valve opening degree of the exhaust gas
recirculation system, and the exhaust gas recirculation quantity
estimating means estimates the quantity of recirculation of the exhaust
gas further in accordance with the valve opening degree detected by the
valve opening degree detecting means.
Further preferably, the apparatus comprises engine rotation speed detecting
means for detecting the rotation speed of the engine, and the exhaust gas
recirculation quantity estimating means obtains an orifice factor in
accordance with the difference between the detected exhaust pressure and
the detected intake pressure, obtains a recirculated exhaust gas
temperature coefficient in accordance with the detected engine rotation
speed and the detected fuel supply quantity, and estimates the quantity of
recirculation of the exhaust gas in accordance with the detected valve
opening degree, the obtained orifice factor, and the obtained recirculated
exhaust gas temperature coefficient.
Thus, the apparatus according to the present invention need not be provided
with a flow sensor or the like for recirculated exhaust gas, so that its
costs and the number of its components can be restrained from increasing.
A preferred mode of the present invention is applied to an engine which is
provided with a turbo charger for supercharging the engine with intake by
driving a turbine by means of the exhaust gas, and the exhaust pressure
detecting means detects the exhaust pressure on the upstream side of the
turbine. According to this mode, the apparatus need not be provided with a
flow sensor or the like for detecting the quantity of recirculation of the
exhaust gas, so that its costs and the number of its components can be
restrained from increasing.
Preferably, the apparatus comprises engine rotation speed detecting means
for detecting the rotation speed of the engine and total intake quantity
detecting means for computing a total intake quantity, including the
quantity of the exhaust gas recirculated by the exhaust gas recirculation
system, in accordance with the detected intake pressure. The storage means
stores the exhaust gas recirculation quantity estimated by the exhaust gas
recirculation quantity estimating means, the total intake quantity
computed by the total intake quantity detecting means. The exhaust
pressure detected by the exhaust pressure detecting means, and the exhaust
pressure detecting means obtains a steady-state value of the exhaust
pressure on the upstream side of the turbine in accordance with the
detected engine rotation speed and the detected fuel supply quantity,
obtains a turbine acceleration pressure in accordance with the obtained
steady-state exhaust pressure value, the exhaust gas recirculation
quantity and total intake quantity, which quantities were individually
stored in the storage means for the last cycle but a predetermined number
of cycles, obtains a turbine load from the obtained turbine acceleration
pressure and the obtained steady-state exhaust pressure value, and obtains
the present value of the exhaust pressure in accordance with the preceding
value of the exhaust pressure stored in the storage means, the obtained
turbine acceleration pressure, and the obtained turbine load. This
preferred apparatus of the invention need not be provided with an exhaust
pressure sensor, so that its costs and the number of its components can be
restrained from increasing.
Another preferred apparatus according the present invention comprises total
intake quantity detecting means for computing a total intake quantity,
including the quantity of the exhaust gas recirculated by the exhaust gas
recirculation system, in accordance with the detected intake pressure, and
the equivalent intake air quantity estimating means estimates the
equivalent intake air quantity accurately and in a real-time fashion, in
accordance with the computed total intake quantity, the excess air rate,
which was estimated during the last cycle but the predetermined number of
cycles and stored in the storage means, and the estimated exhaust gas
recirculation quantity.
Preferably, the equivalent intake air quantity estimating means divides the
estimated exhaust gas recirculation quantity by the excess air rate, which
was estimated the predetermined number of cycles in advance of current
cycle, to obtain the quantity of consumed air, which is not contributory
to combustion, out of the exhaust gas recirculated in the exhaust gas
recirculation system, and subtracts the obtained consumed air quantity
from the computed total intake quantity, to estimate the equivalent intake
air quantity, thus estimating the equivalent intake air quantity
accurately and in a real-time fashion.
An apparatus according to still another preferred mode of the present
invention comprises an airflow sensor, which is provided on the upstream
side of the position where the exhaust gas is supplied into | | |
