Nov 22, 1982 ... Honda Motor Co., Ltd., Tokyo,. Japan. [21] Appl. No. ..... absolute pressure; an
exhaust gas recirculation passage ..... gas recirculation valve)>
United States Patent [191
[11]
4,454,853
Hasegawa
[45]
Jun. 19, 1984
[54] ELECTRONIC FUEL INJECTION CONTROL
4,399,799 8/1983 Romblom et a1. ................ ..123/s71
SYSTEM FOR INTERNAL COMBUSTION
4,409,943 10/1933‘ Hasegawa etal. ................ .. 123/571
ENGINES HAVING EXHAUST GAS
FOREIGN PATENT DOCUMENTS
RECIRCULATION DEVICES
17421
[7 5] Inventor: Shumpei Hasegawa, Niiza, Japan [73] Assignee: Honda Motor Co., Ltd., Tokyo, Japan
[30]
Nov. 22, 1982
3/1979 Japan .................. ..
5/1979 United Kingdom .............. ..123/571
ABSTRACT
Japan .............................. .. 56-186632
An electronic fuel injection control system for an inter nal combustion engine includes means for controlling
Int. Cl.3 ...................... .. F02M 25/06; F02B 3/08;
the exhaust gas recirculation valve by using a plurality of different sets of predetermined valve opening com
F02D 17/00 [52]
123/571
2006988
[57]
Foreign Application Priority Data
Nov. 20, 1981 [JP]
[51]
123/571
3343:;
Primary Examiner—Wendell E. Burns Attomey, Agent. or Firm—Arthur L. Lessler
[21] Appl. No.: 443,563 [22] Filed:
2/1979 Japan ................................. ..123/s71
20203 2/1979 Japan
US. Cl. .................................. .. 123/571; 123/489;
mand values which are functions of ambient atmo
123/480; 123/491; 364/431.06; 364/431.04
spheric pressure and other parameters of operating
[58] Field of Search ............. .. 123/571, 480, 489, 491;
condition of the engine, and are set such that the ex haust gas recirculating rate can be maintained constant
364/431.06, 431.04
[56]
irrespective of changes in the atmospheric pressure, by
References Cited
the use of these command values, and means for cor
U.S. PATENT DOCUMENTS 4,165,722
8/1979 Aoyama ............................ .. 123/571
recting the injection period for fuel being supplied to the engine in dependence upon ambient atmospheric
4,181,944
1/ 1980
Yamauchi et al. . . . . .
. . . .. 123/571
pressure and intake pipe absolute pressure, whereby the
4,347,570
8/1982 .Akiyama et al. . . . . . . .
. . . .. 123/571
air/fuel ratio of the mixture is maintained at an optimum
4,369,752
l/ 1983 Ito et a1. .................... .. 123/568
4,375,800
3/1983
4,380,989
4/1983
Otsuka et a1. . . . . . . _Otsuka et a1.
. ........ .
4,388,909 6/1983 Ogasawara et a1. 4,399,791
. . . ..
123/571
. . . ..
123/571
value against changes in the ambientatmospheric pres sure even when the exhaust gas recirculation is effected.
123/571 X
7 Claims, 16 Drawing Figures
8/1983 Kobayashi et al. ........... .. 123/571 X
INTBBVAL COMBUSTION BVGNE
U.S. Patent
Jun. 19, 1984
Sheet 1 of 13
4,454,853
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US. Patent
Jun. 19, 1984
I Sheet 2 of 13
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Jun. 19, 1984
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US. Patent
Jun. 19, 1984
Sheet 5 of 13
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US. Patent
Jun. 19, 1984
Sheet 6 of 13
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Jun. 19, 1984
Sheet 7 of 13
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4,454,853
1
2
OBJECT AND SUMMARY OF THE INVENTION It is the object of the invention to provide an elec tronic fuel injection control system for an internal com
ELECTRONIC FUEL INJECTION CONTROL SYSTEM FOR INTERNAL COMBUSTION ENGINES HAVING EXHAUST GAS RECIRCULATION DEVICES
bustion engine, which is adapted to correct the air/fuel ratio of an air/fuel mixture being supplied to the engine
BACKGROUND OF THE INVENTION
during exhaust gas recirculating operation, in depen
This invention relates to control of the air/fuel ratio . of an air/fuel mixture being supplied to an internal com bustion engine, and more particularly to an electronic
intake pipe absolute pressure, so as to always control the air/fuel ratio to a desired value during exhaust gas
fuel injection control system which is adapted to cor rect the air/fuel ratio in dependence upon atmospheric pressure and intake pipe absolute pressure so as to main tain the air/fuel ratio at an optimum value during ex
haust gas recirculating operation.
dence upon not only atmospheric pressure but also
recirculating operation, irrespective of changes in the atmospheric pressure, to thereby improve the fuel con
sumption, emission characteristics and driveability of the engine. 15
A fuel supply control system adapted for use with an internal combustion engine, particularly a gasoline en
is variable as a function of intake pipe absolute pressure as well as atmospheric pressure, and the atmospheric pressure-dependent air/fuel ratio correction can be
gine has been proposed e.g. by US. Ser. No. 348,648, ?led Dec. 12, 1981 and assigned to the same assignee as
the present application, which is adapted to determine 20 the valve opening period of a fuel injection device for control of the fuel injection quantity, i.e. the air/fuel ratio of an air/fuel mixture being supplied to the engine, by ?rst determining a basic value of the above valve 25 opening period as a function of engine rpm and intake pipe absolute pressure and then adding to and/or multi plying same by constants and/or coefficients being functions of engine rpm, intake pipe absolute pressure,
engine temperature, throttle valve opening, exhasut' gas
ingredient concentration (oxygen concentration), etc., by electronic computing means.
The present invention is based upon the recognitions that the quantity of air sucked into the engine cylinders
made during exhaust gas recirculating operation, by a correcting amount corresponding to that applied for such correction when the exhaust gas recirculating operation is not effected, if the exhaust gas recirculating rate is maintained constant irrespective of changes in the atmospheric pressure. The present invention provides an electronic fuel injection control system for use with an internal com
bustion engine, which comprises in combination: a ?rst sensor for detecting a value of engine rpm; a second 30 sensor for detecting a value of absolute pressure in an
intake passage of the engine at a location downstream of a throttle valve arranged in the intake passage; a third sensor for detecting a value of ambient atmospheric absolute pressure; an exhaust gas recirculation passage
On the other hand, during operation of an engine at a high altitude, etc., it is generally carried out to correct the fuel supply quantity for the engine, in response to 35 communicating the exhaust passage of the engine with changes in the atmospheric pressure, so as to obtain an
optimum air/fuel ratio best suited for the atmospheric pressure, for improvements in the fuel consumption, emission characteristics and driveability of the engine. For instance, in a fuel supply control system adapted for correction of the basic valve opening period of a fuel injection valve by means of a correction coef?cient as
mentioned above, an atmospheric pressure-dependent correction coefficient is provided as one of the afore
the intake passage of same at a location downstream of
the throttle valve; an exhaust gas recirculation valve arranged across the exhaust gas recirculation passage; and valve opening command means for determining a
desired value of the valve opening of the exhaust gas recirculation valve and generating a command signal indicative of the determined valve opening value. The valve opening command means including ?rst memory means stored a plurality of different sets of predeter
mentioned correction coef?cients, for correction of the 45 mined valve opening command values previously deter air/fuel ratio of the mixture. mined as a function of variables of engine rpm, absolute However, according to such conventional atmo pressure in the intake passage and atmospheric absolute
spheric pressure-dependent correction of the air/fuel ratio which is determined by intake pipe absolute pres
sure as noted above, the air/fuel ratio is corrected in
dependence upon the atmospheric pressure alone. That is, the correction amount is not based upon the actual
operating condition of the engine per se, making it dif? cult to perform the air/fuel ratio correction in a perfect manner.
pressure. The above different sets individually corre
spond to predetermined different values of one of the above variables. The above predetermined valve open ing command values in each of said different sets are functions of the other two variables. The system further comprises in combination with the above elements means responsive to output signals from the first, sec 55 ond and said third sensors to selectively read at least one
On the other hand, in an engine which is provided with an exhaust gas recirculating device for improve ment of the emission characteristics of the engine, abso lute pressure in the exhaust gas recirculating passage at a location upstream of the exhaust gas recirculation
valve, that is, back pressure in the exhaust pipe de creases with a decrease in the atmospheric pressure so that the exhaust gas recirculating rate decreases. As a
consequence, the air/fuel ratio, of the mixture becomes leaner. The degree of leaning of the air/fuel ratio is
larger during exhaust gas recirculating operation than
predetermined valve opening command value corre sponding to the output signals from a corresponding set of the above different sets of predetermined valve open ing command values; means responsive to the command signal indicative of the read predetermined valve open ing command value to control the valve opening of the exhaust gas recirculation valve; whereby a quantity of
exhaust gases being recirculated through the exhaust gas recirculation passage is maintained at a constant 65 value with respect to a total intake air quantity being
that when the exhaust gas recirculating operation is not
supplied to the engine through the intake passage, irre spective of changes in the ambient atmospheric pres
effected.
sure; means for determining a desired value of a basic
*
3
4,454,853
4
valve opening period for the fuel injection valve and generating a ?rst signal indicative of the determined desired valve opening period value, the basic valve opening period determining means including second
dependent correction coef?cient KPA for correction of the air/fuel ratio and the lift command for the exhaust gas recirculation valve; FIG. 11 is a timing chart showing the relationship
memory means storing a plurality of predetermined
between a pulse signal So inputted to the sequential clock generator in FIG. 10 and clock pulses generated
basic valve opening period values being functions of
therefrom;
engine rpm and absolute pressure in the intake passage, and means responsive to output signals from the ?rst
FIG. 12 is a view showing an intake pipe absolute pressure-engine rpm map for determining a basic valve
and second sensors to selectively read as a value of the
?rst signal a desired predetermined basic valve opening period from the second memory means, corresponding to the above output signals; means responsive to output
opening period Ti for the injectors;
signals from the second and third sensors to correct the
ues of the correction coef?cient KPA; FIG. 14 is a circuit diagram illustrating the interior construction of the EGR lift command value determin
FIG. 13 is a view showing an atmospheric pressure
intake pipe absolute pressure map for determining val
value of the ?rst signal and generating a second signal indicative of the corrected valve opening period value;
ing circuit in FIG. 10, according to another embodi
and means responsive to the second signal to drive the fuel injection valve to open for a period of time corre
ment of the invention; and FIG. 15 is a circuit diagram illustrating essential part of the EGR lift command value determining circuit determine a desired valve opening command value from 20 according to a still further embodiment of the invention. at least two read predetermined valve opening com DETAILED DESCRIPTION mand values and a detected atmospheric absolute pres The present invention will now be described in detail sure value, and also from a detected engine rpm value with reference to the drawings. and/or a detected intake pipe absolute pressure value, if FIG. 1 is a pressure volume diagram of an Otto cycle 25 required, by means of interpolation.
sponding to the second signal. Preferably, means is provided, which is operable to
The above and other objects, features and advantages
engine. 0—>1 designates an adiabatic compression step,
of the invention will be more apparent from the ensuing detailed description taken in connection with the ac
expansion step, and 3—>4—>5 an exhaust step, respec
1—>2 an isochoric combustion step, 2->3 an adiabatic
tively. According to the diagram, when the exhaust
companying drawings: BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a pressure volume diagram of an Otto cycle
30 valve is closed and simultaneously the intake valve is
opened at state point 5, the pressure in the engine cylin der instantaneously drops from a value corresponding
engine;
to exhaust pipe pressure Pr to a value corresponding to
intake pipe pressure PB (step 5—>6). In the diagram,
FIG. 2 is a view illustrating quantities of state of
6—>0 designates a suction step where the piston is
residual exhaust gas, fresh air, and a mixture thereof available, respectively, at state points 5, 6 and 0 in FIG.
moved from its top dead center to its bottom dead cen ter.
It will now be explained how the suction gas amount
FIG. 3 is a graph showing the relationship between exhaust gas recirculating quantity, total intake air quan tity and atmospheric pressure; FIG. 4 is a graph showing the relationship between exhaust gas recirculating quantity, total intake air quan tity and atmospheric pressure, which is required for maintaining the exhaust gas recirculating rate constant;
Ga is determined during the step 5—>6->0 where fresh air is sucked into the engine cylinder. In the explana tion, let it be assumed that ?rst, during the step 5-6 the residual gas in the engine cylinder is adiabatically ex panded back into the intake pipe, while simultaneously
reducing its own pressure from a value corresponding FIG. 5 is a block diagram illustrating the arrangement 45 to pressure Pr to a value corresponding to pressure PB, and during the following step 6—>0, the ?owing-back of a fuel injection control system according to the pres residual gas and fresh air are sucked into the cylinder, ent invention; while simultaneously exchanging heat with each other. FIG. 6 is a block diagram illustrating a whole pro
Further, the heat exchange between the cylinder wall gram for control of the valve opening periods TOUTM and TOUTS of the main injectors and the subinjector, 50 and the intake pipe wall, and the residual gas and fresh air is not taken into account in the assumption. Let it be which is incorporated in the electronic control unit also assumed as a second assumption that the residual (ECU) in FIG. 5; gas and fresh air behave as ideal ?uid and assume identi FIG. 7 is a timing chart showing the relationship cal values with each other with respect to gas constant
between a cylinder-discriminating signal and a TDC
signal inputted to the ECU, and driving signals for the main injectors and the subinjector, outputted from the
55
at constant volume Cv, and ratio of speci?c heat x. FIG. 2 shows the quantities of state of the residual gas, the fresh air and a mixture thereof, respectively, at
ECU; FIGS. 8A and 8B are a flow chart showing a main
state points 5, 6 and 0. The relationships between these quantities of state can be represented by the following equations. Symbols used in the equations are interpreted
program for control of the valve opening periods TOUTM and TOUTS; FIG. 9 is a view showing a plurality of intake pipe
absolute pressure-engine rpm maps for determining lift command values LMAPij for the exhaust gas recircula tion valve, individually applicable under different atmo
spheric pressure values; FIG. 10 is a block diagram illustrating the internal arrangement of the ECU in FIG. 5, including circuits for determining values of an atmospheric pressure
Ra, speci?c heat at constant pressure Cp, speci?c heat
as follows:
P =pressure (Kg/cmzabsJ,
T=temperature (°K.), 65
G=quantity of air (Kg), V=volume (m3), e=compression ratio of the engine, |
