CA1266903A - Control system for internal combustion engines - Google Patents
Control system for internal combustion enginesInfo
- Publication number
- CA1266903A CA1266903A CA000533068A CA533068A CA1266903A CA 1266903 A CA1266903 A CA 1266903A CA 000533068 A CA000533068 A CA 000533068A CA 533068 A CA533068 A CA 533068A CA 1266903 A CA1266903 A CA 1266903A
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- Prior art keywords
- fuel
- air
- amount
- engine
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Abstract
Abstract:
In a control system for an internal combustion engine, the amount of fuel is determined on the basis of the depression of an accelerator pedal, and the amount of air is determined on the basis of the amount of fuel, while the changing amounts of the fuel and air are corrected by the changing rate of the depression of the accelerator pedal. The result is a system that affords improved acceleration characteristics without increasing the noxious components in the exhaust gas.
In a control system for an internal combustion engine, the amount of fuel is determined on the basis of the depression of an accelerator pedal, and the amount of air is determined on the basis of the amount of fuel, while the changing amounts of the fuel and air are corrected by the changing rate of the depression of the accelerator pedal. The result is a system that affords improved acceleration characteristics without increasing the noxious components in the exhaust gas.
Description
i6~
A control system for internal combustion engines .... . _ The present invention relates to a control system for an internal combustion engine, particularly of the type used in an automobile.
Desirable attributes of an automotive engine are a reduced fuel consumption and improved acceleration.
As a way of satisfying these demands, there has been known in the art a system for supplying an internal combustion engine with a lean air/fuel mixture, as 10 disclosed in Japanese Patent Laid-Open No. 59-224499 (1984).
However, -this approach is accompanied by the problem that a sufficient acceleration cannot be attained, because of the leanness of the mixture.
In order to eliminate this lack of good acceler-ation, on the other hand, it is effective to prepare a rich mixture and supply it to the engine during acceler-ation. However, there then arises the second problem that the engine torque will suddenly change, causing a deterioration in drivability, when the mixture makes a transition from rich to lean, or vice versa.
In order to eliminate such a sudden change of the torque, it is conceivable to have a gradual trans-ition of the richness of the mixture~ However, there exists between the lean mixture zone and the rich mixture zone a region, i.e. about 15 to 18 in air/fuel ratio, : , :
.:' ' ~ ' .,: -: ~ . .. .
where nitrogen oxides (NOX) are generated to a maximum extent, which adversely affects the noxious components in the exhaust gas.
It is, therefore, an object of -the present in~
vention to provide a control system for an internal combustion engine, that can ensure a sufficient acceler-ation without increasing the noxious components in exhaust gas.
The present invention is characterized in that the uniformity of the engine torque is enhanced by controlling the operation of an actuator for driving the throttle valve in accordance with the depression rate of the accelerator pedal.
In the drawings:
Fig. l is a schematic diagram showing the overall construction of a control system according to an embodiment of the present invention;
Fig. 2 is a schematic diagram showing the detailed construction of a throttle valve actuator;
Fig. 3 is a block diagram explaining the basic concept of control according to the embodiment of the present invention;
Fig. 4 is a block diagram showing an example of a detailed construction of a control unit used in the control system of the embodiment;
E'ig. 5 is a flow chart showing schematically the main routine of the control;
Figs. 6 and 7 are diagrams showing the relations for obtaining the corrected accelerator pedal position from actual accelerator pedal position signals;
Fig. 8 is a detailed flow chart showing step 170 in the control routine of Fig. 5;
Fig. 9 is a diagram showing the relation between the correc-ted accelerator pedal posi-tion signal and -the amount of fuel injection Ti;
. -~ ;
. . .
Fi~. 10 is a diagram showing the relation between the en~ine cooling water temperature and its correction coefficient KTW;
Fig. 11 is a table showing a correction coefEicient K~ obtained by an air/fuel ratio sensor;
Fig. 12 is a table showing a correction coefficient KMR for set-ting the air/fuel ratio according to the operational condition of the engine;
Fig. 13 is a diagram showing the relation between the air temperature upstream of a throttle valve and a correction coefficient KA;
Fig. 1~ is a diagram showing the relations for determining the openi.ng of the throttle valve from the ratio of Ti x KA/KMR and the number of revolutions of the engine;
Fig. 15 is a diagram showing the relations for determining an ignition timing BTDC from the amount of fuel injection and the number of revolutions of the engine;
Fig. 16 is a detailed flow chart showing step 280 in the control routine of Fig. 5;
Fig. 17 is a flow chart showing a modification of step 280 as shown in Fig. 16;
Fig. 18 is a flow chart of the control, which is added to the main control routine of Fig. 5, when a suction pressure sensor is used to improve the metering accuracy of the air flow rate;
Fig. 19 is a table of a correction coefficient K~ of the opening of the throttle valve;
Fig. 20 is a f].ow chart showing a modifica-tion of Fig. 18 when an air flow sensor is used in place of the suction pressure sensor to lmprove the metering accuracy of the air flow rate; and Figs. 21 and 22 are diagrams respectively explaining the effects of the present invention in comparison with those of the prior art.
Fig. 1 is a schematic diagram showing the overall construction of one embodiment of the present invention.
Here is shown in section one cylinder of a multi-cylinder engine. The reciprocal movements of a piston 102 in the cylinder 101 are converted into revolutions of a crankshaft 103 and outputted as driving power.
In accordance with the movements of the piston 102, on the other hand, an intake valve 104 and an exhaust valve 105 are opened or closed. In synchronism with opening of the intake valve 104, fuel is injected into an intake pipe 107 by an injection valve or injector 109.
The fuel thus injected is mixed with the suction air to fill the inside of the cylinder, i.e., the combustion chamber 108 and is compressed by the piston 102. Then, the air-fuel mixture is ignited by a spark plug 106.
Exhaust gas is discharged into an exhaust pipe 110 when the exhaust valve 105 is opened. There is disposed at the collector portion o~ an exhaust mani~old an air/fuel (A/F) ratio sensor 124 for detecting the ratio of the air to the fuel in the mixture sucked into the engine, in terms of the concentration of excess oxygen contained in the exhaust gas.
Downstream of an air cleaner 121, on the other hand, there are arranged: a suction air temperature sensor 102 (such as a thermocouple or a resistance bulb) for detecting the suction air temperature; an air flow sensor 119 for detecting the flow rate of the suction air; and an opening sensor 118 for detecting the opening of a throttle valve 116. There are also arranged: an accelerator pedal position sensor 113 for detecting the accelerator pedal position; a water temperature sensor 123 for detecting the tempera-ture of the engine cooling water or cylinder wall; and a crank angle sensor 111 for detecting the angle of the crankshaft 103.
: ' .
: ` ..
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- 5 - ~ 3i 3 All the signals detected by these sensors are inputted to and processed by a control unit 112 having a built-in computer, so that signals representing the in~ection valve opening time, the ignition timing and the throttle valve opening are produced and fed to the in-jector 109, the plug 106 and a throttle valve actuator 114.
The amount Qa of the air sucked into the engine can be calculated by not only the output signal of the air flow sensor 119 bu-t also the output signal of a pressure sensor 115 disposed midway of the intake pipe 107 and the number of revolutions of the engine, i.e., the output signal of the crank angle sensor 111.
In the vicinity of the intake valve 104 of the intake pipe 107, on the other hand, there i5 buried into an inner wall of the intake pipe 107 a flush-type heating resistor 132 which can have its calorific value controlled from the outside. The current to be applied to the heating resistor 132 is controlled by a heater driver 131 connected to the control unit 112, by which it is controlled in accordance with the respective output signals of the above-specified sensors, such that it is fed with a larger current when the engine is started, but has its current flow decreased gradually after the engine has been warme~
up. Reference numeral 122 denotes a battery.
Fuel is supplied to the injector 109 from a fuel reservoir 125 by way of a strainer 126, a pump 127, a regulator 128 and a fuel pipe 129 with its pressure controlled at a predetermined value.
Fig. 2 is a diagram showing the detailed con-struction of the throttle valve actuator 114. The necessary opening of the throttle valve 116 is determined by the arithmetic operation (which will be described hereinafter) of the control unit 112. In accordance with the throttle valve opening determined, a step motor driver 142 generates a signal for determining the direction, angle and velocity of the rotation of a step motor 143.
-- 6 - ~ 9~?~
In response to this signal, the step motor 1~3 is rotated -to t~lrn the throttle valve llG to a predetermined openiny through a reduction gear 1~4.
A potentiometer 145 is provided to measure the actual opening of the throttle valve 116 and is used to provide a feedback loop to ensure that the opening is the one de-termined by the control unit 112. More specific-ally, the voltage level of the potentiometer 145 is intro-duced to the control unit 112 when the current to be fed to the step motor 143 is at zero, i.e., when the throttle valve 116 is fully closed, and the throttle valve opening is measured by using that voltage level as a reference.
Thus, the dispersion of the resistances and adjustments of the individual potentiometers can be automatically corrected by the control unit 112.
Since, rnoreover, the step motor 143 is a motor that will turn one step when it receives one pulse, as will be described hereinafter, the throttle valve opening can be determined without the potentiometer 145, if the number of pulses applied to the step motor 143 is integrated from the instant when the current fed to the step motor 143 is at the zero level.
Although not shown, moreover, there is provided a tension return spring that will urge the throttle valve 116 in the closing direction, so that the throttle valve 116 is closed by such spring if the current supply to the step motor 143 is interrupted in an abnormal operation.
The concept of a control system will next be described with reference to the block diagram of Fig. 3.
In accordance with an accelerator pedal position signal ~A, a changing rate signal d~A/dt thereof with respect to time, an engine number-of-revolution (per unit time) signal N and a transmission position signal S, the opening t~ Ti of the fuel injector 109 is determined by the control unit 112 and is set in an output circuit 117. That opening time Ti is determined by the following formula:
Ti = f(OA, d~A/dt, N, Sj.
. :
. , , :
: .... :
.
... .
Th~ opening time Ti is subjected to a feedback control by the signal of the A/F ratio sensor 124, which is denoted by K~.
On the other hand, the -throttle valve opening ~T
is determined by the control unit 112 in accordance with the opening time Ti of the injector ].09, the signal N
and an air temperature signal TA, and is set in an output circuit 133.
The throttle valve opening ~T is determined by ~he following formula:
~T = f (Ti, N, Ta).
This throttle valve opening ~T is subjected to a feedback control with the signal coming from the potentio-meter 145. This feedback signal is denoted by K9.
Next, an example of a detailed construction of the control system will be described with reference to Fig. 4.
With a microprocessor (CPU) 134, there is connected through a bus a timer 135, an interruption controller 136, a number-of-revolution counter 137, a digital input port 138, an analog input port 139, a RAM 140, a ROM 141, and the output circuits 117 and 133. The signals of the A/F ratio sensor 124 and the accelerator pedal position sensor 113 are introduced in-to the analog input port 139 If necessary, the signals of the air flow meter 119, the water temperature sensor 123 and the throttle valve opening sensor 118 are also introduced .into the analog input por-t 139.
The signal of a transmission position sensor 151 is inputted i.nto the digital input port 138. If an ignition switch IG is turned on, the electric power is supplied rom the battery 122 to the control unit 112.
Incidenta].ly, the RAM 140 is always supplied with power.
When the ignition switch IG is turned on, the control of the main routine shown in Fig. 5 is s-tarted .. ~
.. : . ;. ' ~., '.. .
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by executing a program that is stored in advance in the ROM 141. The main output signals of the control unit 112 are the signals of the fuel injection valve opening time, the ignition timing, the throttle valve opening and so on.
Next, the content of the main routine of Fig. 5 will be described with reference to Figs. 6 to 20. If the main routine is started, the initialization is conducted. Then, at step 160, the accelerator pedal position ~A, the transmission position S and the engine number-of-revolution N are read. At step 170, as a pre-processing for determining the basic amoun~ of fuel injection Ti, the corrected accelerator pedal position ~C2 is obtained by retrieving the relation provided therefor in advance on the basis of 0A.
When a driver desires to accelerate quickly or to decelera~e an automobile, he rapidly depresses or releases the accelerator pedal. The accelerator pedal position signal ~A is read into the control unit 112, in which the changing rate Q~A (i.e., d~A/dt) thereof for a predetermined time (e.g., 40 to 60 ms) is obtained.
In accordance with the absolute value ¦~A¦ of the changing rate Q~A, one of curves MODl, MOD2 and MOD3 shown in Fig. 6 is selected. For example:
MODl for 0 < ¦Q~A¦ < C1;
MOD2 for Cl < ¦Q~A¦ < C2; and MOD3 for C2 < ¦QQA¦ .
Cl and C2 are constants arbitrarily set in accordance with the required style of driving, i.e.
sporty driving or an economic one. Cl and C2 for sporty driving are selected with smaller values than those for economic driving.
Subsequently, a primary corrected accelerator _ 9 _ ~ ~ 6~g3(~
pedal position ~Cl is obtained by retrieving the selected one of the three curves on the basis of the actual accelerator pedal position ~A. By the use of Fig. 7, moreover, the primary corrected position ~Cl is converted into a secondary one ~C2 in accordance with the transmission gear position S.
This is to change the fuel increasing rate with respect to the amount of depression of the accelerator pedal in accordance with the transmission position, so that the changing rate (or acceleration) of the auto-mobile speed with respect to the amount of depression of the accelerator pedal may be substantially identical over the low to high gear positions of the transmission.
More specifically, when the transmission is in the 4th position, the torque to be transmitted to the wheels is lower than that in the 1st position, so the acceleration becomes lower. In the case of the ~th position, there-fore, the increasing rate of the fuel with respect to the accelerator pedal position is enlarged.
Details of the step 170 described above are shown in Fig. 8~ More specifically, the changing rate of the accelerator pedal position is calculated at step 300. At steps 301 and 303, it is judged which one of the modes MODl, MOD2 and MOD3 the changing rate is 25 located in. At steps 302, 30~ and 305, the primary corrected accelerator pedal position 0Cl is retrieved in accordance with each of the modes MODl to MOD3. Next, at steps 306, 308 and 310, it is judged what the trans-mission gear position is. At steps 307, 309, 311 and 312, the secondary corrected accelerator pedal position ~C2 is retrieved.
According to this processing of Fig. 8, the accelerator pedal position is corrected on the basis of the mode MODl to MOD3, which are different depending upon the changing rate of the accelerator pedal, so that ..~ .
~:
30~
the acceleration can be improved whatever the trarlsmisslon gear position.
Reverting to Fig. 5, at step 180, the basic amoun-t of fuel injection Ti is retrieved. Here, the amount Ti of the fuel to be injected auring one suction stroke is retrieve~ on the basis of the secondary corrected accelerator pedal position ~C2, by the use of Fig. 9.
Next, at step 190, a correction coefficient is retrieved from the relation between the cooling water temperature and the correction coefficient characteristics shown in ~ig. 10.
The correction of the output of the A/F ratio sensor 124 at and after the step 200 will now be described.
At step 200, an A/F ratio signal V is read from the A/F ratio sensor 124 disposed in the exhaust pipe 110. Then, at step 210, an A/F ratio reference VR
determined in advance is selected in accordance with the running state. At step 220, the set A/F ratio reference VR is compared with the A/F ratio signal V. Next, the correction coefficient K~ is calculated at step 230 in accordance with a formula described thereat and is stored in the RAM 140 at step 240. Here, the coefficient K~ is one for integration control.
Incidentally, the RAM 140 has a table of the coefficient K~, in which the number of revolutions of the engine N and the basic amount of fuel injection Ti are respectively shown on the abscissa and ordinate in Fig. 11. This table is renewed each time a new value of the coefficient K~ is obtained at step 230. As a result, the content of the table is gradually made appropriate by the learning effect. The table thus renewed will not have its content erased, even if the key switch IG of the engine is -turned oEf, because the RAM
140 is always supplied with electric power.
Next, at step 250, the correction coefficient . .
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6~
K~ is retrieved on the basis of the basic amount of fuel injection Ti and the number of revolutions ~ in the table of Fi~. 11, and the amoun-t of fuel injection Tinj is obtained by the following formula:
Tinj = Ti x COEFF x K~ ...................... (1), wherein the following coefficients are used solely, or in combination, as the "COEFF":
KAS: coefficient for increment of fuel after start;
KAI: coefficient for increment of fuel after idle;
TADD: coefficient for acceleration increment;
and KDEC: correction coefficient of deceleration.
Next, at step 260, an A/F ratio correction coefficient KMR is retrieved. Fig. 12 is a table of the correction coefficient KMR for setting the optimum A/F
ratio in each operational state of the engine.
The region where the value of the basic amount of fuel injection Ti is high corresponds to the so called "power region", in which the depression of the accelerator pedal is large to provide a rich mixture to increase the engine output. For a high speed region, a rich mixture i5 prepared to prevent seizure of the engine. In another running region, i.e. a partial load region, on the other hand, a lean mixture is prepared to reduce the fuel consumption rate. The correction the coefficient KMR is retrieved from -the basic amount of fuel injection Ti and the number of revolutions N by use of the table above.
At step 270, the signal of the suction air temperature sensor 120 disposed upstream of the throttle valve 116 is read to retrieve a correc-tion coefficien-t KA by the use of the relation shown in Fig. 13 and to calculate the value of Ti x KA/KMR.
At step 280, the opening of the throttle valve lL6 and the iynition timing are retrieved. At first, the opening ~T of the throttle valve 116 is retrieved on the basis of the value of Ti x KA/KMR and the number of revolutions N of the engine, by using the relation of Fig. 14. This relation is so set that ~he amount of suction air Qa/N per one suction stroke of the engine satisfies the following formula (2):
10 Qa/N = Kq x Ti/KMR ...................... .(2) wherein Kq: a constant.
On the other hand, the amount of fuel injection Qf/N during the engine suction stroke is expressed by the following formula (3):
15 Qf/N = K10 x Tinj ....................... (3) wherein K10: a constant.
As a result, the set A/F ratio is expressed from formulas (2) and (3) by the following formula (4):
(A/F)A = Kll x Ti/(KMR x Tinj) .......... (4) Incidentally, for an A/F ratio range of 15 to 18, the concentration of NOX as noxious exhaust components rises to a high value, as is well known in the art. In order to reduce the emission of NOX, there-fore, the set A/F ratio has to avoid the range of 15 to 18.
The detail of step 280 is shown in Fig. 16. At step 400, the set A/F ratio (A/F)A is calculated by use of formula (4). If this (A/F)A is within the range of 15 to 18, namely, if it is judyed at step 401 that 15 < (A/F)A < 18, the emission of NOX increases, as has been described above. At steps 405 and 406, the value KMR is detected for (A/F)A = 15 or (A~F)A = 18 by use of formula (4) to prepare a rich mixture. More , :. .
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specifically, the amount of air is reducecl while the amount of fuel is left as it is, so that the A/F ratio of high NO~ emission may be avoided.
A new throttle valve opening ~T is then obtained by use of the newly retrieved KMR from the value of Ti x KA/KMR and the revolutions N in view of the relations of Fig. 14. Thus, the emission of NOX can be reduced.
Returning to Fig. 5, at step 290, the opening signal aT of the throttle valve 116 thus obtained is sent to the throttle valve actuator 114. The difference A~T between the set throttle valve opening ~T and the present throttle valve opening detected by the po-tentio-meter 145 is obtained to control the throttle valve 116.
Incidentally, if the step motor 143 is used as the throttle valve actuator 114, the number of pulses corresponding to the difference ~T is given to the step motor 143. If it is necessary to set the throttle valve opening highly accurately, moreover, the actual throttle valve opening is measured by the potentiometer 145 to provide a feedback loop to set the throttle valve opening ~T.
The ignition timing is obtained by an inter-polation from the relation between the number of revolu-tions N of the engine and the basic amoun-t offuel injection Ti, which is shown by using the ignition timing BTDC as a parameter.
Incidentally, the aforementioned relations~and tables of Figs. 6 to 10 and Figs. 12 to 15 are stored in advance in the ROM 141 of the control unit 112.
In the lean mixture combustion system of the prior art, the accelerator and the -throttle valve are mechanically connected through a link or the like, so that the throttle valve has its opening increased to increase the amount of suction air with the increase in the depression amount OA, as shown in Fig. 22c. In the vicinity of the maximum depression aA of the accelerator 3~
pedal, on the other hand, a high engine output is required, so that: there is nothing for it to do but enrich the mixture. As a result, the characteristics of the A/F
ratio for the depression amount ~A of the accelerator pedal are expressed by the curve shown in Fig. 22d.
Accordingly, the characteristics of the opening time of the fuel injector 109, i.e., the amount of fuel for the depression ~A of the accelerator pedal are expressed by the curve shown in Flg. 22a, and the engine torque is expressed by the curve shown in Fig. 22b, because it is in proportion to the amount of fuel. More specifically, the torque is characterized in that its increment is low for the range of a smaller depression ~A of the accelerator pedal, but suddenly becomes high in the vicinity of the maximum depression. With these characteristics, however, the torque is so small as to make the driver experience a lack of acceleration in the lower range of the depression ~A of the accelerator pedal.
On the other hand, the characteristics of the 20 A/F ratio are expressed by the curve shown in Fig. 22d, such that the A/F ratio continuously changes from a lean mixture to a rich mixture in the range oE a large depression ~A of the accelerator pedal. This raises the defect that much NOX is emitted, because the A/F ratio 25 range of 15 to 18 is passed with the increase in depression ~A of the accelerator pedal.
According to the control shown in the flow chart of Fig. 5, on the contrary, the amount of fuel can be characterized to be generally proportional to the 30 depression ~A of the accelerator pedal, as shown in Fig.
21a. As a result, the control of Fig. 5 has the advantage that the torque is uniformly increased with the depression ~A of the accelerator pedal, as shown in Fig. 21b, so that the acceleration is smooth from a small depression to a 35 larger one.
': , ' Since, moreover, the amount of suction air to the englne can be freely set by the throttle valve actuator 114, the A/F ratio can be characterized, as shown ln Fig.
21d, if the amount of suction air is set as shown in Fig.
21c. As a result, the operation can be conducted without any increase in NOX emissions from a small depression to a large one, by skipping over the A/F ratio range of 15 to 1~.
In other words, the amount of suction air can be set freely in accordance with the command of the control unit 112 by adopting the throttle valve actuator 114, so that the torque to be produced ~y the engine and the A/F
ratio of the fuel mixture can be controlled independently of each other. As a result, there can be attained the effect that the countermeasures against noxious exhaust emission can be simplified, the acceleration performance and the fuel economy being caused to be compatible by making the amount of fuel injection proportional to the depression ~A of the accelerator pedal.
Incidentally, if the A/F ratio is controlled to vary at steps 405, 406 and 403 of Fig. 16, the torque fluctuates a little. In this case, however, these torque fluctuations can be suppressed, if the ignition timing is corrected at steps 407 and 408, as shown in Fig. 17. More specifically, the torque fluctuations are suppressed by retarding the ignition timing for the lower A/F ratio and advancing it for the higher A/F ratio.
Fig. 1~ shows another example in which a correction is made by the intake pressure.
Generally speaking, the amount of air Qa/N to be sucked into the cylinder for one revolution of the engine is expressed by the following formula (5) if a suc-tion pressure Pm is used:
Qa/N = K2 x Pm x r~ x KAIR ................. (5) wherein:
- 16 ~ 6~3Ct~
K2 : a constan-t;
~ : a suction efficiency; and KAIR: a correction coefficient of suction air temperature.
The pressure of suc~ion air Pm for giving the amount of suction air for a set A/F' ratio is given by the following formula (6) with the basic amount of fuel injection Ti and the correction coefficient KMR of A/F
ratio depending upon the engine operatlonal condition:
10 Pm = K3 x Ti/ (n x KAIR x KMR) ............ (6) wherein K3: a constant.
Therefore, if the opening of the throttle valve 116 is subjected to the feedback loop control, while the aetual suetion air pressure is being measured by the suetion air pressure sensor 115, the set suetion air pressure of formula (6) may be attained, and a hi~hly aeeurate control of the amount of suetion ean be realized.
New steps will now be described with referenee to the flow ehart of Fig. 18. At step 500, the set pressure of suetion air Pm is calculated by the use of formula (6). At step 501, the aetual pressure of suetion air Pmr is read by the use of the suetion air pressure sensor 115.
At step 502, the throttle valve opening eorreetion eoefficient K~ is ealeulated by use of the following formula (7) from the set suetion air pressure Pm calculated at step 500 and -the actual suction air pressure Pmr, and is stored in the RAM 1~0 of the control unit 112:
K~ = K4(Pm ~ Pmr) ~ K5 J (Pm -Pmr)dt....... (7) wherein:
K4: a constant of proportion; and K5: an integration constant.
At step 504, the correction coefficient K~ of , . .. .
' ' ~ : ' '' ':''" ', the throttle valve openin~ is retrieved in the t~ble shown in Fig. 19. Fig. 19 tabulates the correction coefficient K~ for the basic amount of fuel injection Ti retrieved at step 180 (Fig. 5) and -the number of revolution N of the engine.
At step 505, a corrected opening ~T' is calculated from the following formula (8):
9T' = K0 x ~T ..................... (8), wherein:
K0: a correction coefficient of throttle valve opening; and ~T: a set opening of throttle valve.
Fig. 20 shows a modification of E'ig. 18, in which the air Elow sensor 119 is used in place of the suction air pressure sensor 115 of Fig. 18. From the basic amount of fuel injection Ti and the correction coefficient of the A/F ratio KMR depending upon the engine operational condition, the amount of suction air Qa for the set A/F
ratio is given by the following formula (9):
Qa = K6 x Ti x N/KMR .............. (9) wherein K6: a constant.
Therefore, the opening of the throttle valve lL6 is subjected to a closed loop control, while the actual air flow rate is being metered by the air fLow sensor 119, so that -the suction air amount Qa may be the set one given by formuLa (9). New steps will now be described with reference to the flow chart of Fig. 20.
At step 600, the air fLow rate Qa is caLcuLated by the use of formuLa (9) from the Ti of step L80 and ICMR of step 2L0. The value thus calculated is designated at Qa. At step 601, the ac-tual air fLow rate is read by the use of the air flow sensor 119.
At step 602, the throttle valve correction coefficient K~ is calcuIated by the use of -the following '; ' ~
formula (10) from the set air flow rate Qar. At step 603, the value K~ is stored in the RAM 140:
K0 = K7(Qa - Qar) + K8 ~ (Qa - Qar)dt...... (10) wherein:
S K7: a constant of proportion; and K8: an integration constant.
This value KO is similar to that of Fig. 19 and steps 604 and 605 are also similar to the steps 504 and 505.
Although we have shown and described only some forms of apparatus embodying the invention, it is under-stood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of the invention.
' ': :
A control system for internal combustion engines .... . _ The present invention relates to a control system for an internal combustion engine, particularly of the type used in an automobile.
Desirable attributes of an automotive engine are a reduced fuel consumption and improved acceleration.
As a way of satisfying these demands, there has been known in the art a system for supplying an internal combustion engine with a lean air/fuel mixture, as 10 disclosed in Japanese Patent Laid-Open No. 59-224499 (1984).
However, -this approach is accompanied by the problem that a sufficient acceleration cannot be attained, because of the leanness of the mixture.
In order to eliminate this lack of good acceler-ation, on the other hand, it is effective to prepare a rich mixture and supply it to the engine during acceler-ation. However, there then arises the second problem that the engine torque will suddenly change, causing a deterioration in drivability, when the mixture makes a transition from rich to lean, or vice versa.
In order to eliminate such a sudden change of the torque, it is conceivable to have a gradual trans-ition of the richness of the mixture~ However, there exists between the lean mixture zone and the rich mixture zone a region, i.e. about 15 to 18 in air/fuel ratio, : , :
.:' ' ~ ' .,: -: ~ . .. .
where nitrogen oxides (NOX) are generated to a maximum extent, which adversely affects the noxious components in the exhaust gas.
It is, therefore, an object of -the present in~
vention to provide a control system for an internal combustion engine, that can ensure a sufficient acceler-ation without increasing the noxious components in exhaust gas.
The present invention is characterized in that the uniformity of the engine torque is enhanced by controlling the operation of an actuator for driving the throttle valve in accordance with the depression rate of the accelerator pedal.
In the drawings:
Fig. l is a schematic diagram showing the overall construction of a control system according to an embodiment of the present invention;
Fig. 2 is a schematic diagram showing the detailed construction of a throttle valve actuator;
Fig. 3 is a block diagram explaining the basic concept of control according to the embodiment of the present invention;
Fig. 4 is a block diagram showing an example of a detailed construction of a control unit used in the control system of the embodiment;
E'ig. 5 is a flow chart showing schematically the main routine of the control;
Figs. 6 and 7 are diagrams showing the relations for obtaining the corrected accelerator pedal position from actual accelerator pedal position signals;
Fig. 8 is a detailed flow chart showing step 170 in the control routine of Fig. 5;
Fig. 9 is a diagram showing the relation between the correc-ted accelerator pedal posi-tion signal and -the amount of fuel injection Ti;
. -~ ;
. . .
Fi~. 10 is a diagram showing the relation between the en~ine cooling water temperature and its correction coefficient KTW;
Fig. 11 is a table showing a correction coefEicient K~ obtained by an air/fuel ratio sensor;
Fig. 12 is a table showing a correction coefficient KMR for set-ting the air/fuel ratio according to the operational condition of the engine;
Fig. 13 is a diagram showing the relation between the air temperature upstream of a throttle valve and a correction coefficient KA;
Fig. 1~ is a diagram showing the relations for determining the openi.ng of the throttle valve from the ratio of Ti x KA/KMR and the number of revolutions of the engine;
Fig. 15 is a diagram showing the relations for determining an ignition timing BTDC from the amount of fuel injection and the number of revolutions of the engine;
Fig. 16 is a detailed flow chart showing step 280 in the control routine of Fig. 5;
Fig. 17 is a flow chart showing a modification of step 280 as shown in Fig. 16;
Fig. 18 is a flow chart of the control, which is added to the main control routine of Fig. 5, when a suction pressure sensor is used to improve the metering accuracy of the air flow rate;
Fig. 19 is a table of a correction coefficient K~ of the opening of the throttle valve;
Fig. 20 is a f].ow chart showing a modifica-tion of Fig. 18 when an air flow sensor is used in place of the suction pressure sensor to lmprove the metering accuracy of the air flow rate; and Figs. 21 and 22 are diagrams respectively explaining the effects of the present invention in comparison with those of the prior art.
Fig. 1 is a schematic diagram showing the overall construction of one embodiment of the present invention.
Here is shown in section one cylinder of a multi-cylinder engine. The reciprocal movements of a piston 102 in the cylinder 101 are converted into revolutions of a crankshaft 103 and outputted as driving power.
In accordance with the movements of the piston 102, on the other hand, an intake valve 104 and an exhaust valve 105 are opened or closed. In synchronism with opening of the intake valve 104, fuel is injected into an intake pipe 107 by an injection valve or injector 109.
The fuel thus injected is mixed with the suction air to fill the inside of the cylinder, i.e., the combustion chamber 108 and is compressed by the piston 102. Then, the air-fuel mixture is ignited by a spark plug 106.
Exhaust gas is discharged into an exhaust pipe 110 when the exhaust valve 105 is opened. There is disposed at the collector portion o~ an exhaust mani~old an air/fuel (A/F) ratio sensor 124 for detecting the ratio of the air to the fuel in the mixture sucked into the engine, in terms of the concentration of excess oxygen contained in the exhaust gas.
Downstream of an air cleaner 121, on the other hand, there are arranged: a suction air temperature sensor 102 (such as a thermocouple or a resistance bulb) for detecting the suction air temperature; an air flow sensor 119 for detecting the flow rate of the suction air; and an opening sensor 118 for detecting the opening of a throttle valve 116. There are also arranged: an accelerator pedal position sensor 113 for detecting the accelerator pedal position; a water temperature sensor 123 for detecting the tempera-ture of the engine cooling water or cylinder wall; and a crank angle sensor 111 for detecting the angle of the crankshaft 103.
: ' .
: ` ..
":"
. .
- 5 - ~ 3i 3 All the signals detected by these sensors are inputted to and processed by a control unit 112 having a built-in computer, so that signals representing the in~ection valve opening time, the ignition timing and the throttle valve opening are produced and fed to the in-jector 109, the plug 106 and a throttle valve actuator 114.
The amount Qa of the air sucked into the engine can be calculated by not only the output signal of the air flow sensor 119 bu-t also the output signal of a pressure sensor 115 disposed midway of the intake pipe 107 and the number of revolutions of the engine, i.e., the output signal of the crank angle sensor 111.
In the vicinity of the intake valve 104 of the intake pipe 107, on the other hand, there i5 buried into an inner wall of the intake pipe 107 a flush-type heating resistor 132 which can have its calorific value controlled from the outside. The current to be applied to the heating resistor 132 is controlled by a heater driver 131 connected to the control unit 112, by which it is controlled in accordance with the respective output signals of the above-specified sensors, such that it is fed with a larger current when the engine is started, but has its current flow decreased gradually after the engine has been warme~
up. Reference numeral 122 denotes a battery.
Fuel is supplied to the injector 109 from a fuel reservoir 125 by way of a strainer 126, a pump 127, a regulator 128 and a fuel pipe 129 with its pressure controlled at a predetermined value.
Fig. 2 is a diagram showing the detailed con-struction of the throttle valve actuator 114. The necessary opening of the throttle valve 116 is determined by the arithmetic operation (which will be described hereinafter) of the control unit 112. In accordance with the throttle valve opening determined, a step motor driver 142 generates a signal for determining the direction, angle and velocity of the rotation of a step motor 143.
-- 6 - ~ 9~?~
In response to this signal, the step motor 1~3 is rotated -to t~lrn the throttle valve llG to a predetermined openiny through a reduction gear 1~4.
A potentiometer 145 is provided to measure the actual opening of the throttle valve 116 and is used to provide a feedback loop to ensure that the opening is the one de-termined by the control unit 112. More specific-ally, the voltage level of the potentiometer 145 is intro-duced to the control unit 112 when the current to be fed to the step motor 143 is at zero, i.e., when the throttle valve 116 is fully closed, and the throttle valve opening is measured by using that voltage level as a reference.
Thus, the dispersion of the resistances and adjustments of the individual potentiometers can be automatically corrected by the control unit 112.
Since, rnoreover, the step motor 143 is a motor that will turn one step when it receives one pulse, as will be described hereinafter, the throttle valve opening can be determined without the potentiometer 145, if the number of pulses applied to the step motor 143 is integrated from the instant when the current fed to the step motor 143 is at the zero level.
Although not shown, moreover, there is provided a tension return spring that will urge the throttle valve 116 in the closing direction, so that the throttle valve 116 is closed by such spring if the current supply to the step motor 143 is interrupted in an abnormal operation.
The concept of a control system will next be described with reference to the block diagram of Fig. 3.
In accordance with an accelerator pedal position signal ~A, a changing rate signal d~A/dt thereof with respect to time, an engine number-of-revolution (per unit time) signal N and a transmission position signal S, the opening t~ Ti of the fuel injector 109 is determined by the control unit 112 and is set in an output circuit 117. That opening time Ti is determined by the following formula:
Ti = f(OA, d~A/dt, N, Sj.
. :
. , , :
: .... :
.
... .
Th~ opening time Ti is subjected to a feedback control by the signal of the A/F ratio sensor 124, which is denoted by K~.
On the other hand, the -throttle valve opening ~T
is determined by the control unit 112 in accordance with the opening time Ti of the injector ].09, the signal N
and an air temperature signal TA, and is set in an output circuit 133.
The throttle valve opening ~T is determined by ~he following formula:
~T = f (Ti, N, Ta).
This throttle valve opening ~T is subjected to a feedback control with the signal coming from the potentio-meter 145. This feedback signal is denoted by K9.
Next, an example of a detailed construction of the control system will be described with reference to Fig. 4.
With a microprocessor (CPU) 134, there is connected through a bus a timer 135, an interruption controller 136, a number-of-revolution counter 137, a digital input port 138, an analog input port 139, a RAM 140, a ROM 141, and the output circuits 117 and 133. The signals of the A/F ratio sensor 124 and the accelerator pedal position sensor 113 are introduced in-to the analog input port 139 If necessary, the signals of the air flow meter 119, the water temperature sensor 123 and the throttle valve opening sensor 118 are also introduced .into the analog input por-t 139.
The signal of a transmission position sensor 151 is inputted i.nto the digital input port 138. If an ignition switch IG is turned on, the electric power is supplied rom the battery 122 to the control unit 112.
Incidenta].ly, the RAM 140 is always supplied with power.
When the ignition switch IG is turned on, the control of the main routine shown in Fig. 5 is s-tarted .. ~
.. : . ;. ' ~., '.. .
- 8 ~ 6C3~
by executing a program that is stored in advance in the ROM 141. The main output signals of the control unit 112 are the signals of the fuel injection valve opening time, the ignition timing, the throttle valve opening and so on.
Next, the content of the main routine of Fig. 5 will be described with reference to Figs. 6 to 20. If the main routine is started, the initialization is conducted. Then, at step 160, the accelerator pedal position ~A, the transmission position S and the engine number-of-revolution N are read. At step 170, as a pre-processing for determining the basic amoun~ of fuel injection Ti, the corrected accelerator pedal position ~C2 is obtained by retrieving the relation provided therefor in advance on the basis of 0A.
When a driver desires to accelerate quickly or to decelera~e an automobile, he rapidly depresses or releases the accelerator pedal. The accelerator pedal position signal ~A is read into the control unit 112, in which the changing rate Q~A (i.e., d~A/dt) thereof for a predetermined time (e.g., 40 to 60 ms) is obtained.
In accordance with the absolute value ¦~A¦ of the changing rate Q~A, one of curves MODl, MOD2 and MOD3 shown in Fig. 6 is selected. For example:
MODl for 0 < ¦Q~A¦ < C1;
MOD2 for Cl < ¦Q~A¦ < C2; and MOD3 for C2 < ¦QQA¦ .
Cl and C2 are constants arbitrarily set in accordance with the required style of driving, i.e.
sporty driving or an economic one. Cl and C2 for sporty driving are selected with smaller values than those for economic driving.
Subsequently, a primary corrected accelerator _ 9 _ ~ ~ 6~g3(~
pedal position ~Cl is obtained by retrieving the selected one of the three curves on the basis of the actual accelerator pedal position ~A. By the use of Fig. 7, moreover, the primary corrected position ~Cl is converted into a secondary one ~C2 in accordance with the transmission gear position S.
This is to change the fuel increasing rate with respect to the amount of depression of the accelerator pedal in accordance with the transmission position, so that the changing rate (or acceleration) of the auto-mobile speed with respect to the amount of depression of the accelerator pedal may be substantially identical over the low to high gear positions of the transmission.
More specifically, when the transmission is in the 4th position, the torque to be transmitted to the wheels is lower than that in the 1st position, so the acceleration becomes lower. In the case of the ~th position, there-fore, the increasing rate of the fuel with respect to the accelerator pedal position is enlarged.
Details of the step 170 described above are shown in Fig. 8~ More specifically, the changing rate of the accelerator pedal position is calculated at step 300. At steps 301 and 303, it is judged which one of the modes MODl, MOD2 and MOD3 the changing rate is 25 located in. At steps 302, 30~ and 305, the primary corrected accelerator pedal position 0Cl is retrieved in accordance with each of the modes MODl to MOD3. Next, at steps 306, 308 and 310, it is judged what the trans-mission gear position is. At steps 307, 309, 311 and 312, the secondary corrected accelerator pedal position ~C2 is retrieved.
According to this processing of Fig. 8, the accelerator pedal position is corrected on the basis of the mode MODl to MOD3, which are different depending upon the changing rate of the accelerator pedal, so that ..~ .
~:
30~
the acceleration can be improved whatever the trarlsmisslon gear position.
Reverting to Fig. 5, at step 180, the basic amoun-t of fuel injection Ti is retrieved. Here, the amount Ti of the fuel to be injected auring one suction stroke is retrieve~ on the basis of the secondary corrected accelerator pedal position ~C2, by the use of Fig. 9.
Next, at step 190, a correction coefficient is retrieved from the relation between the cooling water temperature and the correction coefficient characteristics shown in ~ig. 10.
The correction of the output of the A/F ratio sensor 124 at and after the step 200 will now be described.
At step 200, an A/F ratio signal V is read from the A/F ratio sensor 124 disposed in the exhaust pipe 110. Then, at step 210, an A/F ratio reference VR
determined in advance is selected in accordance with the running state. At step 220, the set A/F ratio reference VR is compared with the A/F ratio signal V. Next, the correction coefficient K~ is calculated at step 230 in accordance with a formula described thereat and is stored in the RAM 140 at step 240. Here, the coefficient K~ is one for integration control.
Incidentally, the RAM 140 has a table of the coefficient K~, in which the number of revolutions of the engine N and the basic amount of fuel injection Ti are respectively shown on the abscissa and ordinate in Fig. 11. This table is renewed each time a new value of the coefficient K~ is obtained at step 230. As a result, the content of the table is gradually made appropriate by the learning effect. The table thus renewed will not have its content erased, even if the key switch IG of the engine is -turned oEf, because the RAM
140 is always supplied with electric power.
Next, at step 250, the correction coefficient . .
.
.
. .
.
6~
K~ is retrieved on the basis of the basic amount of fuel injection Ti and the number of revolutions ~ in the table of Fi~. 11, and the amoun-t of fuel injection Tinj is obtained by the following formula:
Tinj = Ti x COEFF x K~ ...................... (1), wherein the following coefficients are used solely, or in combination, as the "COEFF":
KAS: coefficient for increment of fuel after start;
KAI: coefficient for increment of fuel after idle;
TADD: coefficient for acceleration increment;
and KDEC: correction coefficient of deceleration.
Next, at step 260, an A/F ratio correction coefficient KMR is retrieved. Fig. 12 is a table of the correction coefficient KMR for setting the optimum A/F
ratio in each operational state of the engine.
The region where the value of the basic amount of fuel injection Ti is high corresponds to the so called "power region", in which the depression of the accelerator pedal is large to provide a rich mixture to increase the engine output. For a high speed region, a rich mixture i5 prepared to prevent seizure of the engine. In another running region, i.e. a partial load region, on the other hand, a lean mixture is prepared to reduce the fuel consumption rate. The correction the coefficient KMR is retrieved from -the basic amount of fuel injection Ti and the number of revolutions N by use of the table above.
At step 270, the signal of the suction air temperature sensor 120 disposed upstream of the throttle valve 116 is read to retrieve a correc-tion coefficien-t KA by the use of the relation shown in Fig. 13 and to calculate the value of Ti x KA/KMR.
At step 280, the opening of the throttle valve lL6 and the iynition timing are retrieved. At first, the opening ~T of the throttle valve 116 is retrieved on the basis of the value of Ti x KA/KMR and the number of revolutions N of the engine, by using the relation of Fig. 14. This relation is so set that ~he amount of suction air Qa/N per one suction stroke of the engine satisfies the following formula (2):
10 Qa/N = Kq x Ti/KMR ...................... .(2) wherein Kq: a constant.
On the other hand, the amount of fuel injection Qf/N during the engine suction stroke is expressed by the following formula (3):
15 Qf/N = K10 x Tinj ....................... (3) wherein K10: a constant.
As a result, the set A/F ratio is expressed from formulas (2) and (3) by the following formula (4):
(A/F)A = Kll x Ti/(KMR x Tinj) .......... (4) Incidentally, for an A/F ratio range of 15 to 18, the concentration of NOX as noxious exhaust components rises to a high value, as is well known in the art. In order to reduce the emission of NOX, there-fore, the set A/F ratio has to avoid the range of 15 to 18.
The detail of step 280 is shown in Fig. 16. At step 400, the set A/F ratio (A/F)A is calculated by use of formula (4). If this (A/F)A is within the range of 15 to 18, namely, if it is judyed at step 401 that 15 < (A/F)A < 18, the emission of NOX increases, as has been described above. At steps 405 and 406, the value KMR is detected for (A/F)A = 15 or (A~F)A = 18 by use of formula (4) to prepare a rich mixture. More , :. .
.;
:~ .
- 13 ~ t ~ 3 ~ ~
specifically, the amount of air is reducecl while the amount of fuel is left as it is, so that the A/F ratio of high NO~ emission may be avoided.
A new throttle valve opening ~T is then obtained by use of the newly retrieved KMR from the value of Ti x KA/KMR and the revolutions N in view of the relations of Fig. 14. Thus, the emission of NOX can be reduced.
Returning to Fig. 5, at step 290, the opening signal aT of the throttle valve 116 thus obtained is sent to the throttle valve actuator 114. The difference A~T between the set throttle valve opening ~T and the present throttle valve opening detected by the po-tentio-meter 145 is obtained to control the throttle valve 116.
Incidentally, if the step motor 143 is used as the throttle valve actuator 114, the number of pulses corresponding to the difference ~T is given to the step motor 143. If it is necessary to set the throttle valve opening highly accurately, moreover, the actual throttle valve opening is measured by the potentiometer 145 to provide a feedback loop to set the throttle valve opening ~T.
The ignition timing is obtained by an inter-polation from the relation between the number of revolu-tions N of the engine and the basic amoun-t offuel injection Ti, which is shown by using the ignition timing BTDC as a parameter.
Incidentally, the aforementioned relations~and tables of Figs. 6 to 10 and Figs. 12 to 15 are stored in advance in the ROM 141 of the control unit 112.
In the lean mixture combustion system of the prior art, the accelerator and the -throttle valve are mechanically connected through a link or the like, so that the throttle valve has its opening increased to increase the amount of suction air with the increase in the depression amount OA, as shown in Fig. 22c. In the vicinity of the maximum depression aA of the accelerator 3~
pedal, on the other hand, a high engine output is required, so that: there is nothing for it to do but enrich the mixture. As a result, the characteristics of the A/F
ratio for the depression amount ~A of the accelerator pedal are expressed by the curve shown in Fig. 22d.
Accordingly, the characteristics of the opening time of the fuel injector 109, i.e., the amount of fuel for the depression ~A of the accelerator pedal are expressed by the curve shown in Flg. 22a, and the engine torque is expressed by the curve shown in Fig. 22b, because it is in proportion to the amount of fuel. More specifically, the torque is characterized in that its increment is low for the range of a smaller depression ~A of the accelerator pedal, but suddenly becomes high in the vicinity of the maximum depression. With these characteristics, however, the torque is so small as to make the driver experience a lack of acceleration in the lower range of the depression ~A of the accelerator pedal.
On the other hand, the characteristics of the 20 A/F ratio are expressed by the curve shown in Fig. 22d, such that the A/F ratio continuously changes from a lean mixture to a rich mixture in the range oE a large depression ~A of the accelerator pedal. This raises the defect that much NOX is emitted, because the A/F ratio 25 range of 15 to 18 is passed with the increase in depression ~A of the accelerator pedal.
According to the control shown in the flow chart of Fig. 5, on the contrary, the amount of fuel can be characterized to be generally proportional to the 30 depression ~A of the accelerator pedal, as shown in Fig.
21a. As a result, the control of Fig. 5 has the advantage that the torque is uniformly increased with the depression ~A of the accelerator pedal, as shown in Fig. 21b, so that the acceleration is smooth from a small depression to a 35 larger one.
': , ' Since, moreover, the amount of suction air to the englne can be freely set by the throttle valve actuator 114, the A/F ratio can be characterized, as shown ln Fig.
21d, if the amount of suction air is set as shown in Fig.
21c. As a result, the operation can be conducted without any increase in NOX emissions from a small depression to a large one, by skipping over the A/F ratio range of 15 to 1~.
In other words, the amount of suction air can be set freely in accordance with the command of the control unit 112 by adopting the throttle valve actuator 114, so that the torque to be produced ~y the engine and the A/F
ratio of the fuel mixture can be controlled independently of each other. As a result, there can be attained the effect that the countermeasures against noxious exhaust emission can be simplified, the acceleration performance and the fuel economy being caused to be compatible by making the amount of fuel injection proportional to the depression ~A of the accelerator pedal.
Incidentally, if the A/F ratio is controlled to vary at steps 405, 406 and 403 of Fig. 16, the torque fluctuates a little. In this case, however, these torque fluctuations can be suppressed, if the ignition timing is corrected at steps 407 and 408, as shown in Fig. 17. More specifically, the torque fluctuations are suppressed by retarding the ignition timing for the lower A/F ratio and advancing it for the higher A/F ratio.
Fig. 1~ shows another example in which a correction is made by the intake pressure.
Generally speaking, the amount of air Qa/N to be sucked into the cylinder for one revolution of the engine is expressed by the following formula (5) if a suc-tion pressure Pm is used:
Qa/N = K2 x Pm x r~ x KAIR ................. (5) wherein:
- 16 ~ 6~3Ct~
K2 : a constan-t;
~ : a suction efficiency; and KAIR: a correction coefficient of suction air temperature.
The pressure of suc~ion air Pm for giving the amount of suction air for a set A/F' ratio is given by the following formula (6) with the basic amount of fuel injection Ti and the correction coefficient KMR of A/F
ratio depending upon the engine operatlonal condition:
10 Pm = K3 x Ti/ (n x KAIR x KMR) ............ (6) wherein K3: a constant.
Therefore, if the opening of the throttle valve 116 is subjected to the feedback loop control, while the aetual suetion air pressure is being measured by the suetion air pressure sensor 115, the set suetion air pressure of formula (6) may be attained, and a hi~hly aeeurate control of the amount of suetion ean be realized.
New steps will now be described with referenee to the flow ehart of Fig. 18. At step 500, the set pressure of suetion air Pm is calculated by the use of formula (6). At step 501, the aetual pressure of suetion air Pmr is read by the use of the suetion air pressure sensor 115.
At step 502, the throttle valve opening eorreetion eoefficient K~ is ealeulated by use of the following formula (7) from the set suetion air pressure Pm calculated at step 500 and -the actual suction air pressure Pmr, and is stored in the RAM 1~0 of the control unit 112:
K~ = K4(Pm ~ Pmr) ~ K5 J (Pm -Pmr)dt....... (7) wherein:
K4: a constant of proportion; and K5: an integration constant.
At step 504, the correction coefficient K~ of , . .. .
' ' ~ : ' '' ':''" ', the throttle valve openin~ is retrieved in the t~ble shown in Fig. 19. Fig. 19 tabulates the correction coefficient K~ for the basic amount of fuel injection Ti retrieved at step 180 (Fig. 5) and -the number of revolution N of the engine.
At step 505, a corrected opening ~T' is calculated from the following formula (8):
9T' = K0 x ~T ..................... (8), wherein:
K0: a correction coefficient of throttle valve opening; and ~T: a set opening of throttle valve.
Fig. 20 shows a modification of E'ig. 18, in which the air Elow sensor 119 is used in place of the suction air pressure sensor 115 of Fig. 18. From the basic amount of fuel injection Ti and the correction coefficient of the A/F ratio KMR depending upon the engine operational condition, the amount of suction air Qa for the set A/F
ratio is given by the following formula (9):
Qa = K6 x Ti x N/KMR .............. (9) wherein K6: a constant.
Therefore, the opening of the throttle valve lL6 is subjected to a closed loop control, while the actual air flow rate is being metered by the air fLow sensor 119, so that -the suction air amount Qa may be the set one given by formuLa (9). New steps will now be described with reference to the flow chart of Fig. 20.
At step 600, the air fLow rate Qa is caLcuLated by the use of formuLa (9) from the Ti of step L80 and ICMR of step 2L0. The value thus calculated is designated at Qa. At step 601, the ac-tual air fLow rate is read by the use of the air flow sensor 119.
At step 602, the throttle valve correction coefficient K~ is calcuIated by the use of -the following '; ' ~
formula (10) from the set air flow rate Qar. At step 603, the value K~ is stored in the RAM 140:
K0 = K7(Qa - Qar) + K8 ~ (Qa - Qar)dt...... (10) wherein:
S K7: a constant of proportion; and K8: an integration constant.
This value KO is similar to that of Fig. 19 and steps 604 and 605 are also similar to the steps 504 and 505.
Although we have shown and described only some forms of apparatus embodying the invention, it is under-stood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of the invention.
' ': :
Claims (26)
1. A control apparatus for an internal combustion engine, comprising:
an accelerator pedal position sensor for producing a signal representing a depression amount of an accelerator pedal;
a crank angle sensor for detecting a number of revolutions of the engine;
an air/fuel ratio sensor, disposed in an exhaust pipe, for detecting an air/fuel ratio of fuel mixture fed to the engine from the exhaust gas thereof;
a fuel injector for injecting fuel into the engine in response to a fuel control signal indicating an amount of fuel to be injected;
a throttle valve actuator for controlling the degree of opening of a throttle valve in response to a suction air control signal indicating an amount of air to be sucked into the engine; and a control unit, including a computer connected to receive output signals of said accelerator pedal position sensor, crank angle sensor and air/fuel ratio sensor, for executing a predetermined processing on the basis of the received output signals to produce the fuel control signal and the suction air control signal, wherein the predetermined processing executed by said control unit comprises at least the following steps:
a first step of reading the signals representing the depression amount (.THETA.A) of the accelerator pedal and the number (N) of revolutions of the engine into the computer;
a second step of obtaining a changing rate (.DELTA..THETA.A) of the depression amount signal (.THETA.A) read in said first step in relatin to time and producing a primary corrected depression amount signal (.THETA.Cl) by correcting the depression amount signal (.THETA.A) in accordance with the changing rate (.DELTA..THETA.A);
a third step of determining a basic amount (Ti) of fuel to be injected on the basis of the primary corrected depression amount signal (.THETA.Cl) obtained in said second step, a fourth step of correcting the basic amount (Ti) of fuel determined in said third step by using a first correction coefficient (K.alpha.) depending on the characteristics of said air/fuel ratio sensor to produce a fuel control signal (Tinj); and a fifth step of determining an amount (.THETA.T) of the suction air on the basis of the basic amount (Ti) of fuel determined in said third step and the detected number (N) of revolutions of the engine to produce a suction air control signal (.THETA.T).
an accelerator pedal position sensor for producing a signal representing a depression amount of an accelerator pedal;
a crank angle sensor for detecting a number of revolutions of the engine;
an air/fuel ratio sensor, disposed in an exhaust pipe, for detecting an air/fuel ratio of fuel mixture fed to the engine from the exhaust gas thereof;
a fuel injector for injecting fuel into the engine in response to a fuel control signal indicating an amount of fuel to be injected;
a throttle valve actuator for controlling the degree of opening of a throttle valve in response to a suction air control signal indicating an amount of air to be sucked into the engine; and a control unit, including a computer connected to receive output signals of said accelerator pedal position sensor, crank angle sensor and air/fuel ratio sensor, for executing a predetermined processing on the basis of the received output signals to produce the fuel control signal and the suction air control signal, wherein the predetermined processing executed by said control unit comprises at least the following steps:
a first step of reading the signals representing the depression amount (.THETA.A) of the accelerator pedal and the number (N) of revolutions of the engine into the computer;
a second step of obtaining a changing rate (.DELTA..THETA.A) of the depression amount signal (.THETA.A) read in said first step in relatin to time and producing a primary corrected depression amount signal (.THETA.Cl) by correcting the depression amount signal (.THETA.A) in accordance with the changing rate (.DELTA..THETA.A);
a third step of determining a basic amount (Ti) of fuel to be injected on the basis of the primary corrected depression amount signal (.THETA.Cl) obtained in said second step, a fourth step of correcting the basic amount (Ti) of fuel determined in said third step by using a first correction coefficient (K.alpha.) depending on the characteristics of said air/fuel ratio sensor to produce a fuel control signal (Tinj); and a fifth step of determining an amount (.THETA.T) of the suction air on the basis of the basic amount (Ti) of fuel determined in said third step and the detected number (N) of revolutions of the engine to produce a suction air control signal (.THETA.T).
2. A control apparatus according to claim 1, including a transmission position sensor for producing a signal (S) representative of a position of transmission gears, which is read into the computer in said first step;
and that, in said second step, the primary corrected depression amount (.THETA.Cl) is further corrected in response to the transmission position signal (S) to thereby produce a secondary corrected depression amount (.THETA.C2), according to which the basic amount (Ti) of fuel to be injected is determined in said third step.
and that, in said second step, the primary corrected depression amount (.THETA.Cl) is further corrected in response to the transmission position signal (S) to thereby produce a secondary corrected depression amount (.THETA.C2), according to which the basic amount (Ti) of fuel to be injected is determined in said third step.
3. A control apparatus according to claim 1, wherein the first correction coefficient (K.alpha.) used in said fourth step is retreived in a table provided within a storage of the computer on the basis of the basic amount (Ti) of fuel determined in said third step and the detected number (N) of revolutions of the engine.
4. A control apparatus according to claim 3, wherein the value of the first correction coefficient (K.alpha.) is calculated on the basis of an output signal of said air/fuel ratio sensor for every time of execution of the predetermined processing in the computer, and the table is renewed by the newly calculated value.
5. A control apparatus according to claim 1, wherein, in said fifth step, a second correction coefficient (KMR) for setting a reference ((A/F)A) of the air/fuel ratio suited to each operational state of the engine is determined on the basis of the basic amount (Ti) of fuel determined in said third step and the detected number (N) of revolutions of the engine, and the suction air control signal (.THETA.T) is determined on the basis of the basic amount (Ti) of fuel, which is corrected by the second correcting coefficient (KMR), and the detected number (N) of revolutions of the engine.
6. A control apparatus according to claim 5, wherein, in said fifth step, the temperature of the suction air is detected to determine a third correction coefficient (KA) based on the detected temperature, and the suction air control signal (.THETA.T) is determined on the basis of the basic amount (Ti) of fuel, which is corrected by the second correction coefficient (KMR) and the third correction coefficient (KA), and the detected number (N) of revolutions of the engine.
7. A control apparatus according to claim 5, wherein, when the set air/fuel ratio reference ((A/F)A) lies within a predetermined range, in which range the concentration of noxious components in the exhaust gas becomes high, the second correction coefficient (KMR) is determined at such a value that the air/fuel ratio reference ((A/F)A) has a value outside the predetermined range.
8. A control apparatus according to claim 7, wherein the predetermined range of the air/fuel ratio is from 15 to 18 and the second correction coefficient (KMR) is determined at a value at which the air/fuel ratio reference ((A/F)A) is either 15 or 18.
9. A control apparatus according to claim 8, wherein when the air/fuel ratio reference ((A/F)A) lies within the predetermined range and is close to 15, the suction air control signal (.THETA.T) is determined on the basis of an air/fuel ratio reference ((A/F)A) of 15 and the ignition timing is retarded by a constant time and thereafter returned gradually, whereas when the air/fuel ratio reference ((A/F)A) lies within the predetermined range and is close to 18, the suction air control signal (.THETA.T) is determined on the basis of an air/fuel ratio reference ((A/F)A) of 18 and the ignition timing is advanced by a constant time and thereafter returned gradually.
10. A control apparatus according to claim 1, wherein the predetermined processing executed by said control unit further comprises a step of determining an ignition timing on the basis of the basic amount (Ti) of fuel determined in said third step and the detected number (N) of revolutions of the engine.
11. A control system for an internal combustion engine of a vehicle having an accelerator pedal and a transmission, comprising:
(a) accelerator pedal depression amount detecting means for producing a pedal position signal indicating the depression amount of said accelerator pedal;
(b) number-of-revolution detection means for detecting the number of revolutions of the engine;
(c) air/fuel ratio detecting means disposed in an exhaust pipe for detecting an air/fuel ratio of fuel mixture from engine exhaust gas;
(d) accelerator pedal depression changing rate detecting means for producing a rate signal indicating the changing rate of the depression amount of the accelerator pedal;
(e) fuel injection amount determining means for determining a basic amount of fuel to be injected on the basis of said pedal position signal as corrected in accordance with said rate signal;
(f) fuel injection amount correcting means for producing a first output signal representing a corrected amount of fuel to be injected by correcting the basic amount of fuel to be injected in accordance with the air/fuel ratio detected by said air/fuel ratio detecting means;
(g) throttle valve opening determining means for producing a second output signal representing a desired degree of opening of a throttle valve on the basis of said basic amount of fuel to be injected, as corrected in accordance with the temperature of suction air and an operational state of the engine, and the detected number of revolutions of the engine;
(h) fuel injection means for injecting fuel on the basis of said first output signal from said fuel injection amount correcting means; and (i) throttle valve control means for controlling the throttle valve opening on the basis of said second output signal from said throttle valve opening determining means.
(a) accelerator pedal depression amount detecting means for producing a pedal position signal indicating the depression amount of said accelerator pedal;
(b) number-of-revolution detection means for detecting the number of revolutions of the engine;
(c) air/fuel ratio detecting means disposed in an exhaust pipe for detecting an air/fuel ratio of fuel mixture from engine exhaust gas;
(d) accelerator pedal depression changing rate detecting means for producing a rate signal indicating the changing rate of the depression amount of the accelerator pedal;
(e) fuel injection amount determining means for determining a basic amount of fuel to be injected on the basis of said pedal position signal as corrected in accordance with said rate signal;
(f) fuel injection amount correcting means for producing a first output signal representing a corrected amount of fuel to be injected by correcting the basic amount of fuel to be injected in accordance with the air/fuel ratio detected by said air/fuel ratio detecting means;
(g) throttle valve opening determining means for producing a second output signal representing a desired degree of opening of a throttle valve on the basis of said basic amount of fuel to be injected, as corrected in accordance with the temperature of suction air and an operational state of the engine, and the detected number of revolutions of the engine;
(h) fuel injection means for injecting fuel on the basis of said first output signal from said fuel injection amount correcting means; and (i) throttle valve control means for controlling the throttle valve opening on the basis of said second output signal from said throttle valve opening determining means.
12. A control system according to claim 11, further comprising transmission position detecting means for detecting the operating position of said transmission, said fuel injection amount determining means being responsive to said transmission position detecting means for determining the basic amount of fuel to be injected on the basis of said pedal position signal, said rate signal and said transmission position signal.
13. A control system according to claim 11, wherein said fuel injection amount correcting means further corrects the basic amount of fuel to be injected in accordance with a correction coefficient which is determined by the detected engine number of revolutions and the basic amount of fuel to be injected.
14. A control system according to claim 11, further comprising ignition timing determining means for determining an ignition timing on the basis of the basic amount of fuel to be injected as determined by said fuel injection amount determining means and the detected number of revolutions of the engine.
15. A control system for an internal combustion engine, comprising:
(a) accelerator pedal detecting means for detecting the depression amount of an accelerator pedal and the rate of movement thereof;
(b) number-of-revolution detecting means for detecting the number of revolutions of the engine;
(c) air/fuel ratio detecting means disposed in an exhaust pipe for detecting an air/fuel ratio of fuel mixture from engine exhaust gas;
(d) fuel injection amount determining means for determining the basic amount of fuel to be injected on the basis of the depression amount and the rate of movement of said accelerator pedal detected by said accelerator pedal detecting means;
(e) NOx emission detecting means for producing an output signal indicating that the air/fuel ratio is within a range of 15 to 18;
(f) throttle valve opening determining means for producing an output signal representing a desired degree of opening of a throttle valve on the basis of the basic amount of fuel to be injected as determined by said fuel injection amount determining means and for causing the throttle valve to close in response to the output signal of said NOx emission detecting means;
(g) throttle valve control means for controlling the throttle valve opening on the basis of the output signal produced by said throttle valve opening determining means.
(a) accelerator pedal detecting means for detecting the depression amount of an accelerator pedal and the rate of movement thereof;
(b) number-of-revolution detecting means for detecting the number of revolutions of the engine;
(c) air/fuel ratio detecting means disposed in an exhaust pipe for detecting an air/fuel ratio of fuel mixture from engine exhaust gas;
(d) fuel injection amount determining means for determining the basic amount of fuel to be injected on the basis of the depression amount and the rate of movement of said accelerator pedal detected by said accelerator pedal detecting means;
(e) NOx emission detecting means for producing an output signal indicating that the air/fuel ratio is within a range of 15 to 18;
(f) throttle valve opening determining means for producing an output signal representing a desired degree of opening of a throttle valve on the basis of the basic amount of fuel to be injected as determined by said fuel injection amount determining means and for causing the throttle valve to close in response to the output signal of said NOx emission detecting means;
(g) throttle valve control means for controlling the throttle valve opening on the basis of the output signal produced by said throttle valve opening determining means.
16. A control system according to claim 15, further comprising suction air pressure detecting means for detecting the pressure of suction air; suction air pressure discriminating means for producing an output signal indicating whether or not the suction air pressure is at a set level; and throttle valve opening correcting means for correcting the output signal produced by said throttle valve opening determining means on the basis of the output signal produced by said suction air pressure discriminating means.
17. A control system according to claim 15, further comprising air amount detecting means for detecting the amount of suction air; air amount discriminating means for producing an output signal indicating whether or not the suction air amount is at a set value; and throttle valve opening correcting means for correcting the output signal produced by said throttle valve opening determining means on the basis of the output signal produced by said air amount discriminating means.
18. A control system for an internal combustion engine, comprising:
accelerator pedal position sensor means for producing a signal representing the depression amount of an accelerator pedal;
crank angle sensor means for detecting the number of revolutions of the engine;
air/fuel ratio sensor means, disposed in an exhaust pipe, for detecting an air/fuel ratio of a fuel mixture fed to the engine from the exhaust gas thereof;
fuel injector means for injecting fuel into the engine in accordance with a fuel control signal indicating the amount of fuel to be injected;
throttle valve actuator means for controlling the degree of opening of a throttle valve in accordance with a suction air control signal indicating the amount of air to be sucked into the engine; and control means including a computer connected to receive output signals of said accelerator pedal position sensor means, crank angle sensor means and air/fuel ratio sensor means, for processing those output signals to produce said fuel control signal and said suction air control signal, the processing of the output signals including at least the steps of:
producing a signal indicating a changing rate of the depression amount of the accelerator pedal in relation to time;
correcting the signal indicating the depression amount of the accelertor pedal on the basis of the changing rate thereof;
retrieving a value indicating a basic amount of the fuel to be injected from a table within a storage of said computer with a corrected value of the depression amount of the accelerator pedal;
correcting the basic amount of the fuel to be injected on the basis of the detected air/fuel ratio to produce said fuel control signal; and retrieving a value representing the amount of the suction air from a table within the storage of the computer on the basis of the fuel control signal and the detected number of revolutions of the engine to produce said suction air control signal.
accelerator pedal position sensor means for producing a signal representing the depression amount of an accelerator pedal;
crank angle sensor means for detecting the number of revolutions of the engine;
air/fuel ratio sensor means, disposed in an exhaust pipe, for detecting an air/fuel ratio of a fuel mixture fed to the engine from the exhaust gas thereof;
fuel injector means for injecting fuel into the engine in accordance with a fuel control signal indicating the amount of fuel to be injected;
throttle valve actuator means for controlling the degree of opening of a throttle valve in accordance with a suction air control signal indicating the amount of air to be sucked into the engine; and control means including a computer connected to receive output signals of said accelerator pedal position sensor means, crank angle sensor means and air/fuel ratio sensor means, for processing those output signals to produce said fuel control signal and said suction air control signal, the processing of the output signals including at least the steps of:
producing a signal indicating a changing rate of the depression amount of the accelerator pedal in relation to time;
correcting the signal indicating the depression amount of the accelertor pedal on the basis of the changing rate thereof;
retrieving a value indicating a basic amount of the fuel to be injected from a table within a storage of said computer with a corrected value of the depression amount of the accelerator pedal;
correcting the basic amount of the fuel to be injected on the basis of the detected air/fuel ratio to produce said fuel control signal; and retrieving a value representing the amount of the suction air from a table within the storage of the computer on the basis of the fuel control signal and the detected number of revolutions of the engine to produce said suction air control signal.
19. A control system according to claim 18, wherein there is further provided transmission position sensor means for detecting the position of transmission gears, and wherein the depression amount of the accelerator pedal, which is corrected on the basis of the changing rate thereof, is further corrected in response to the detected position of the transmission gears.
20. A control system according to clim 18, wherein correction of the basic amount of the fuel to be injected is carried out by a correction coefficient which is retrieved from said memory on the basis of the detected number of revolutions of the engine and the basic amount of the fuel to be injected.
21. A control system according to claim 18, wherein the suction air amount retrieving step further includes a step of detecting whether or not an air/fuel ratio falls into a range in which the concentration of noxious components in the exhaust gas becomes high, and the suction air control signal is set so as to maintain the air/fuel ratio outside said range.
22. A control system according to claim 21, wherein when the detected air/fuel ratio lies within the range of 15 to 18, the suction air control signal is determined on the basis of the air/fuel ratio of either 15 or 18.
23. A control system according to claim 18, wherein an ignition timing is determined on the basis of the basic amount of the fuel to be injected, which is corrected by a temperature of suction air and an operational state required of the engine, and the detected number of revolutions of the engine.
24. A control system according to claim 23, wherein the suction air amount retrieving step further includes a step of detecting whether or not the air/fuel ratio detected by said air/fuel ratio sensor means is within a range of 15 to 18, and the suction air control signal is set so as to maintain the air/fuel ratio outside said range.
25. A control system according to claim 24, wherein when the detected air/fuel ratio lies within the range of 15 to 18, the suction air control signal is determined on the basis of the air/fuel ratio of either 15 or 18.
26. A control system according to claim 24, wherein when the detected air/fuel ratio lies within said range and is close to 15, the suction air control signal is determined on the basis of the air/fuel ratio of 15 and the ignition timing is retarded for a constant time and thereafter returned gradually, whereas when the detected air/fuel ratio lies within said range and is close to 18, the suction air control signal is determined on the basis of the air/fuel ratio of 18 and the ignition timing is advanced for a constant time and thereafter returned gradually.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000533068A CA1266903A (en) | 1986-03-26 | 1987-03-26 | Control system for internal combustion engines |
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP61-65723(1986) | 1986-03-26 | ||
| JP61065723A JP2507315B2 (en) | 1986-03-26 | 1986-03-26 | Internal combustion engine controller |
| CA000533068A CA1266903A (en) | 1986-03-26 | 1987-03-26 | Control system for internal combustion engines |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1266903A true CA1266903A (en) | 1990-03-20 |
Family
ID=25671283
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000533068A Expired - Lifetime CA1266903A (en) | 1986-03-26 | 1987-03-26 | Control system for internal combustion engines |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1266903A (en) |
-
1987
- 1987-03-26 CA CA000533068A patent/CA1266903A/en not_active Expired - Lifetime
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