JPH05302542A - Method of setting basic fuel injection volume for engine - Google Patents

Abstract

PURPOSE:To set a basic fuel injection volume with a high transient responsive ness by calculating an intake air volume at least from a transient compensating coefficient and an intake air pipe pressure which are calculated during steady state operation, when an engine falls in a transient operation condition. CONSTITUTION:During computation of the width of a fuel injection pulse by an ECU 51, at first whether the present operating condition is in a transient operation or not is determined in accordance with variations in intake air volume and engine rotational speed. During steady state operation, a transient compensating coefficient is calculated from an intake air volume, an intake air pipe pressure and an engine rotational speed. Meanwhile, a transient intake air volume is calculated from a newest transient compensating coefficient, engine rotational speed and intake air pipe pressure. During steady state operation and transient operation, a basic fuel injection volume is calculated from intake air volumes and engine rotational speeds which are obtained respectively both operations, and is compensated with the use of an air-fuel ratio feed-back compensating coefficient, various increment range compensating coefficients so as to obtain a final fuel injection volume in order to control the drive of an injector 23.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a basic fuel injection amount setting method for an engine which estimates the intake air amount during a transition and sets the basic fuel injection amount.

[0002]

2. Description of the Related Art Generally, in the case of controlling an object to be controlled such as a fuel injection amount and an ignition timing based on an intake air amount, an intake air amount detecting means (thermal type air flow) arranged upstream of the throttle valve is used. Meter).

By the way, the intake air amount detected by the intake air amount detecting means is determined by the intake air passing through a chamber volume (total volume of the throttle chamber, air chamber, intake manifold, etc.) from the downstream side of the throttle valve to the intake valve. Therefore, it always has a certain response delay.

However, this response delay is not a problem because the amount of intake air varies little during steady operation, but during transients such as acceleration / deceleration, the cylinder volume is actually affected by the intake air being filled into the cylinder. There is a difference between the supplied intake air amount and the measured intake air amount.

For example, in Japanese Patent Laid-Open No. 60-101240, an intake air amount sensor is arranged upstream of the throttle valve, and an intake pipe pressure sensor is arranged downstream of the throttle valve. A transient correction coefficient is set from the detected intake pipe negative pressure and engine speed by referring to a map, etc., and the basic fuel injection amount set based on the intake air amount and engine speed is corrected with this transient correction coefficient. A technique for compensating the response delay of the intake air amount sensor is disclosed.

On the other hand, in Japanese Patent Laid-Open No. 2-5746, the intake air amount detected by an intake air amount sensor, the rate of change of the intake air amount, and the intake air amount supplied to the cylinder based on the engine speed and the like. Is disclosed and a basic fuel injection amount is calculated from the estimated value and the engine speed.

[0007]

In an engine equipped with a supercharger, the structure of the intake system is complicated, and
Since the intake air is cooled by the intercooler and then sent to each cylinder under pressure, it is difficult to accurately predict the amount of intake air to be supplied to the cylinder as in a naturally aspirated engine. It is difficult to properly set the basic fuel injection amount at the time of transition because the density of the intake air that has been changed changes, and the controllability of the fuel injection amount, ignition timing, etc. set based on this basic fuel injection amount is impaired. Come.
As a result, the driving feeling during the transition is poor, which causes deterioration of exhaust emission.

On the other hand, as shown in the above-mentioned prior art, in the one in which the transient correction coefficient is mapped, the memory capacity of the control device is increased, and moreover, a large number of man-hours are required for creating the map. There is a problem that causes an increase in cost.

The present invention has been made in view of the above circumstances, and it is possible to determine the intake air amount during a transition with good responsiveness not only in a naturally aspirated engine but also in a supercharged engine. An object of the present invention is to provide a basic fuel injection amount setting method for an engine, which can properly set the basic fuel injection amount based on the air amount.

[0010]

A basic fuel injection amount setting method for an engine according to the present invention comprises a procedure for determining whether the engine is in a steady operation or a transient operation, and when it is determined that the engine is in a steady operation, at least an intake air passing through an air cleaner is used. The procedure for calculating the transient correction coefficient based on the air amount and the intake pipe pressure on the downstream side of the throttle valve, and when it is determined that the transient operation is performed, the transient intake air amount is calculated based on at least the transient correction factor and the intake pipe pressure. A procedure for calculating and setting a basic fuel injection amount based on at least the intake air amount during steady operation, and a procedure for setting the basic fuel injection amount based on at least the transient intake air amount during transient operation It is a thing.

[0011]

[Operation] According to the present invention, the transient correction coefficient is constantly calculated from at least the intake air amount and the intake pipe pressure during steady operation, and at the time of transient operation, the latest transient correction coefficient calculated at least during steady operation is used. Since the transient intake air amount is calculated from the intake pipe pressure, the basic fuel injection amount can be set with good transient response from the transient intake air amount.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention, FIG. 1 is a flow chart showing a fuel injection amount setting routine, FIG. 2 is a flow chart showing an intake pipe pressure / atmospheric pressure detection routine,
3 is an overall schematic diagram of the engine control system, and FIG. 4 is a circuit diagram of the control device.

In FIG. 3, reference numeral 1 is an engine body,
In the figure, a horizontally opposed four cylinder engine is shown. An intake port 2a is formed in the cylinder head 2 of the engine body 1. An intake manifold 3 is connected to the intake port 2a, and a throttle passage 5 is connected to an upstream side of the intake manifold 3 via an air chamber 4. An air cleaner 7 is attached to the upstream side of the throttle passage 5 via an intake pipe 6, and the air cleaner 7 is in communication with an air intake chamber 8 which is an intake port for intake air.

An exhaust pipe 10 is connected to the exhaust port 2b via an exhaust manifold 9, and a catalytic converter 11 is connected to the exhaust pipe 10 to be connected to a muffler 12. On the other hand, a throttle valve 5a is provided in the throttle passage 5, and an intercooler 13 is provided in the intake pipe 6 immediately upstream of the throttle passage 5.
Further, a resonator chamber 14 is provided downstream of the air cleaner 7 in the intake pipe 6.

Further, an idle speed control valve (IS) is provided in a bypass passage 15 which connects the resonator chamber 14 and the intake manifold 3 and bypasses the upstream side and the downstream side of the throttle valve 5a.
CV) 16 is interposed. Furthermore, this ISCV1
A check valve 17, which is opened immediately when the intake pressure is a negative pressure, and which is closed when the intake pressure becomes a positive pressure by being supercharged by a turbocharger 18 which will be described later, is provided on the downstream side of 6. ..

Reference numeral 18 is a turbocharger as a supercharger, and a turbine wheel 18a of the turbocharger 18 is housed in a turbine housing 18b interposed in the exhaust pipe 10, while the turbine wheel 1 is provided.
A compressor wheel 18d, which is connected to 8a via a turbine shaft 18c, is housed in a compressor housing 18e provided on the intake pipe 6 downstream of the resonator chamber 14.

A wastegate valve 19 is provided at the inlet of the turbine housing 18b, and a wastegate valve actuating actuator 20 is connected to the wastegate valve 19. The waste gate valve actuating actuator 20 is partitioned into two chambers by a diaphragm, one of which forms a pressure chamber which is inserted into the waste gate valve controlling duty solenoid valve 21, and the other of which is used to close the waste gate valve 19 in the closing direction. It forms a spring chamber that houses the spring that biases it.

The wastegate valve controlling duty solenoid valve 21 is provided in a passage connecting the resonator chamber 14 and the intake pipe 6 downstream of the compressor housing 18e, and a control unit (ECU) described later. According to the duty ratio of the control signal output from 51, the pressure on the resonator chamber 14 side and the pressure on the downstream side of the compressor housing 18e are adjusted and supplied to the pressure chamber of the waste gate valve operating actuator 20. The waste gate valve actuating actuator 20 is operated to adjust the exhaust gas relief by the waste gate valve 19 to control the supercharging pressure by the turbocharger 18.

An absolute pressure sensor 22 is connected to the intake manifold 3 via a passage 22a, and an intake pipe pressure for selectively connecting the absolute pressure sensor 22 to the intake manifold 3 or the atmosphere to the passage 22a. / Atmospheric pressure switching solenoid valve 22b is interposed.

Further, an injector 23 is provided immediately upstream of each intake port 2a of each cylinder of the intake manifold 3.
An ignition plug 24 whose tip is exposed to the combustion chamber is attached to each cylinder of the cylinder head 2, and an igniter 31 is connected to the ignition plug 24.

In the injector 23, the fuel tank 3
Fuel is pressure-fed from an in-tank type fuel pump 33 provided inside 2 through a fuel filter 34, and the pressure is regulated by a pressure regulator 35.

An intake air amount sensor (a thermal air flow meter in the figure) 41 is provided in the intake pipe 6 immediately downstream of the air cleaner 7, and a throttle opening sensor integrated with the throttle valve 5a is provided. 42 are arranged in series. Further, a knock sensor 43 is attached to the cylinder block 1a of the engine body 1, and a cooling water temperature sensor 45 is exposed to a cooling water passage 44 communicating between the left and right banks of the cylinder block 1a, so that the exhaust pipe 10 is exhausted. O2 in the manifold 9
The sensor 46 is exposed.

A crank rotor 25 is rotatably mounted on a crank shaft 1b supported by the cylinder block 1a, and a crank angle sensor 26 including an electromagnetic pickup is provided on the outer periphery of the crank rotor 25. Further, a cam rotor 27 connected to the cam shaft 1c of the engine body 1 is provided with a cam angle sensor 28 for discriminating a cylinder, which is composed of an electromagnetic pickup or the like.
Incidentally, the crank angle sensor 26 and the cam angle sensor 2
8 is not limited to a magnetic sensor such as an electromagnetic pickup, but may be an optical sensor or the like.

A plurality of protrusions (or slits) are formed at predetermined intervals on the outer periphery of the crank rotor 25, and the number of engine revolutions N from the time when these protrusions (or slits) pass over the crank angle sensor 26. And the projections (or slits) serve as reference crank angles when setting fuel injection timing and ignition timing.

On the other hand, on the outer circumference of the cam rotor 27, a protrusion (or slit) for cylinder discrimination is formed.

(Circuit Configuration of Control Device) In FIG. 4, reference numeral 51 is a control device (ECU) composed of a microcomputer or the like, and a constant voltage circuit 53 is built in the ECU 51, and each part from the constant voltage circuit 53. The stabilizing voltage is supplied to the backup RAM 61 and the backup voltage is always applied to the backup RAM 61. The constant voltage circuit 53 is connected to the battery 55 via a relay contact of the ECU relay 54, and the relay coil of the ECU relay 54 is connected to the battery 5 via the key switch 56.
Connected to 5. Further, the fuel pump 33 is connected to the battery 55 via a relay contact of the fuel pump relay 57.
Are connected.

CPU 58, R constituting the ECU 51
OM59, RAM60, backup RAM61, I /
The O interfaces 64 are connected to each other via a bus line 65.

The sensors 41, 26, 28, 42, 45, 4 are connected to the input ports of the I / O interface 64.
6, 22, 43, and the vehicle speed sensor 47 are connected,
Further, the battery 55 is connected and the battery voltage is monitored.

An igniter 31 is connected to the output port of the I / O interface 64, and further,
Via the drive circuit 66b, the ISCV 16, the injector 23, the relay coil of the fuel pump relay 57, and
Wastegate valve control duty solenoid valve 21,
An intake pipe pressure / atmospheric pressure switching solenoid valve 22b is connected.

The ECU 51 calculates the fuel injection pulse width, the ignition timing, etc. based on the output signals from the sensors.

The air-fuel ratio control and ignition timing control in the ECU 51 are executed by the CPU 58 in accordance with a control program stored in the ROM 59. That is,
The CPU 58 calculates the intake air amount from the output signal of the intake air amount sensor 41, and calculates the RAM 60 and the backup RA.
Based on the various data stored in M61, the fuel injection amount corresponding to the intake air amount is calculated, and the ignition timing is calculated.

Then, a drive pulse width signal corresponding to the fuel injection amount is output to the injector 23 of the corresponding cylinder at a predetermined timing via the drive circuit 66b to inject fuel, and at the predetermined timing, the igniter 31 is also used. To the ignition plug 24, and the ignition plug 24 of the corresponding cylinder is ignited.

As a result, the air-fuel mixture supplied to the corresponding cylinder explodes and burns, and the oxygen concentration in the exhaust gas is detected by the O2 sensor 46 facing the collecting portion of the exhaust manifold 9, and this detection signal is waveform-shaped. And then the CPU
At 58, it is compared with the slice level, and it is determined whether the air-fuel ratio state of the engine is on the rich side or the lean side with respect to the target air-fuel ratio, and feedback control is performed so that the air-fuel ratio becomes the target air-fuel ratio.

(Operation) Next, the fuel injection amount control (air-fuel ratio control) by the ECU 51 will be described with reference to FIGS.

The flowchart shown in FIG. 2 shows a routine for switching the detection target of the absolute pressure sensor 22 between the intake pipe pressure and the atmospheric pressure, which is executed every set time after the key switch 56 is turned on.

First, step (hereinafter abbreviated as "S") 10
1, the intake pipe pressure detection determination flag F1 is referred to, and F1 =
If 0, the process proceeds to S102, and if F1 = 1, the process proceeds to S103. This intake pipe pressure detection determination flag F1 indicates the previous detection target, F1 = 1 indicates that the atmospheric pressure PA was detected last time, F1 = 0 indicates that the intake pipe pressure PS was detected last time, It is set in S108 and cleared in S114.

In the following, the atmospheric pressure detection routine will be described first, and then the intake pipe pressure detection routine will be described.

When F1 = 0 (previously detected intake pipe pressure) is determined in S101 and the process proceeds to S102, the output value G1 from the output port of the I / O interface 64 for the intake pipe pressure / atmospheric pressure switching solenoid valve 22b is set to 1 As S1
Go to 04. When the output value G1 is set to 1, the coil of the intake pipe pressure / atmospheric pressure switching solenoid valve 22b is energized to open the atmosphere port and close the passage 22a communicating with the intake manifold 3, thereby making the absolute pressure sensor 2
Connect 2 and the atmospheric port.

Then, in S104, the elapsed time count value C1 after switching from the intake pipe pressure to the atmospheric pressure is incremented (C1 ←
After C1 +1), the process proceeds to S105, where the intake pipe pressure is →
The elapsed time after atmospheric pressure switching count value C1 is compared with the detection start set value CT1. If C1> CT1, the process proceeds to S106 to start atmospheric pressure detection, and if C1≤CT1, the process jumps to S109.

When it is judged that the switching delay time (CT1) has elapsed and the routine proceeds to S106, the output value P of the absolute pressure sensor 22 is stored as the atmospheric pressure PA in a predetermined address of the RAM 60 (PA ← P). (In this case, the atmospheric pressure PA may be sampled until the detection end set value CT2 is reached, and the average value thereof may be stored as the atmospheric pressure PA.) And S1
At 07, the above-mentioned intake pipe pressure → atmospheric pressure switching elapsed time count value C1 and the detection end set value CT2 (where CT2> CT1) are compared, and if C1> CT2, it is judged that detection is completed and the routine proceeds to S108, where the intake pipe The pressure detection determination flag F1 is set and S10
Proceed to 9. If C1 ≤ CT2, it is determined that detection is in progress, and S
Jump to 109.

The above S105, S107, or S1
When the process proceeds from S08 to S109, after resetting the elapsed time count value C2 after switching from atmospheric pressure to intake pipe pressure, the routine exits.

On the other hand, if it is determined in S101 that F1 = 1 (previous atmospheric pressure detection) and the routine proceeds to S103, the intake pipe pressure /
The output value G1 from the output port of the I / O interface 64 for the atmospheric pressure switching solenoid valve 22b is set to 0, and the process proceeds to S110. When the output value G1 is set to 0, the coil of the intake pipe pressure / atmospheric pressure switching solenoid valve 22b is de-energized, closing the atmospheric port and communicating with the intake manifold 3 and the absolute pressure sensor 22. And communicate with.

Then, the process proceeds to S110, in which the elapsed time count value C2 and the detection start set value CS after switching from atmospheric pressure to intake pipe pressure are set.
1 is compared, and if C2> CS1, the process proceeds to S112 to detect the intake pipe pressure, and if C2≤CS1, the process jumps to S115.

When it is judged that the switching delay time (CS1) has elapsed and the routine proceeds to S112, the output value P of the absolute pressure sensor 22
Is stored in the RAM 60 at a predetermined address as the intake pipe pressure PS (PS ← P). (In this case, intake pipe pressure PS
May be sampled until the detection end set value CS2 is reached, and the average value thereof may be stored as the intake pipe pressure PS. ) Then, in step S113, the elapsed time count value C2 after the switching from the atmospheric pressure to the intake pipe pressure and the detection end set value CS2 (however, CS
2> CS1), and when C2> CS2, it is determined that the detection is completed and the routine proceeds to S114, where the intake pipe pressure detection discrimination flag F1 is cleared and the routine proceeds to S115. If C2≤CS2, it is determined that detection is in progress, and the process jumps to S115. The above S111,
When the process proceeds from S113 or S114 to S115,
After resetting the elapsed time count value C1 after switching from the intake pipe pressure to the atmospheric pressure (C1 ← 0), the routine exits.

The intake pipe pressure detection determination flag F1
, The initial value of each elapsed time count value C1, C2 is 0
Is. Further, the atmospheric pressure PA and the intake pipe pressure PS are, for example, the fuel injection amount T in the following fuel injection amount setting routine.
Used as a parameter when setting i.

When the key switch 56 is turned on, the fuel injection amount setting routine shown in FIG. 1 is executed every set time together with the intake pipe pressure / atmospheric pressure detection routine.

First, in step S201, it is determined whether the present operating state is a transient operation (acceleration / deceleration) based on the amount of change (change speed) of the intake air amount Q, the engine speed N, the throttle opening θTH, etc. The process proceeds to S202, and in the case of transient operation S
Go to 203.

When it is judged to be a steady operation and the routine proceeds to S202, the measured intake air amount QS calculated from the output voltage of the intake air amount sensor 41 and the intake pipe pressure / atmospheric pressure detection routine are set and stored in a predetermined address of the RAM 60. Intake pipe pressure P
Based on S and the engine speed N calculated from the pulse interval from the crank angle sensor 26, a transient correction coefficient KP
Is calculated from the following formula.

KP = QS / (N.multidot.PS) During steady operation, the intake air amount QS measured by the intake air amount sensor 41 and the intake air amount passing through the downstream chamber of the throttle valve 5a are substantially equal to each other. The measured intake air amount QS can be expressed by the product of the volumetric flow rate Vae of the chamber downstream of the throttle valve 5a and the air specific gravity ε.

QS = Vae × ε (1) This volume flow rate Vae is Vae = N × η × V (2) η: Volume efficiency with respect to chamber internal pressure and temperature downstream of the throttle valve V: Engine It can be calculated from the total displacement, and the air specific gravity ε can be calculated from ε = PS / (R · T) (3) R: gas constant T: temperature in the chamber downstream of the throttle valve. .. Therefore, the measured intake air amount QS is given by the above equations (2) and (3) as follows: QS = N × η × V × PS / (R · T) (4)

By the way, the total displacement V is constant for each engine, and in a short time, the volume efficiency η, the gas constant R,
If the chamber temperature T is considered to be constant, then η × V / (R · T) = CONST (5), and if this is KP, then the above equation (4) is KP = QS / (N · PS) (6), the amount of air passing through the chamber downstream of the throttle valve from the transient correction coefficient KP, the engine speed N, and the intake pipe pressure PS, that is, the amount of intake air supplied to the combustion chamber of each cylinder (this Can be estimated as Qe).

Then, in S204, the intake air amount sensor 41
The intake air amount Q stored in the RAM 60 is updated with the measured intake air amount QS detected in step (Q ← QS), and S206
Go to.

On the other hand, if it is judged at S201 that the engine is in a transient state and the routine proceeds to S203, the transient intake air amount Qe is calculated from the following equation based on the latest transient correction coefficient KP, engine speed N and intake pipe pressure PS calculated at S202. To calculate.

Qe ← KP × NPS Then, in step S205, the intake air amount Q stored in the RAM 60 is updated by the transient intake air amount Qe (Q ← Qe
), And proceeds to S206.

In the supercharged engine, since the intake pipe 6 has a complicated shape and has a large capacity, the response delay of the intake air amount sensor 41 during transition becomes remarkable, and the transient correction coefficient KP calculated during steady operation is used. From the above, the transient intake air amount Qe is calculated based on the intake system model described above.

Then, when proceeding from S204 or S205 to S206, the basic fuel injection amount TP is calculated from the following equation based on the intake air amount Q and the engine speed N.

TP ← K × Q / N K: Injector characteristic correction constant After that, in S207, the air-fuel ratio feedback correction coefficient α for making the air-fuel ratio close to the target air-fuel ratio is set based on the output voltage of the O2 sensor 46, and the cooling water temperature TW, Throttle opening θTH
Based on, etc., set the correction coefficient COEF for each increase amount related to the cooling water temperature correction, the acceleration / deceleration correction, the full opening increase correction, etc.
The air-fuel ratio learning correction coefficient KBLRC is set by referring to the air-fuel ratio learning value map with interpolation calculation using the engine speed and basic fuel injection amount TP as parameters, and the altitude correction coefficient KA is set based on the atmospheric pressure PA, and the battery is also set. Based on the terminal voltage of 55, a voltage correction coefficient TS for interpolating the invalid injection time of the injector 23 is set.

Then, in S208, the basic fuel injection amount T
P is corrected by the air-fuel ratio feedback correction coefficient α, various increment correction coefficients COEF, air-fuel ratio learning correction coefficient KBLRC, and altitude correction coefficient KA, and the voltage correction coefficient TS
Then, the fuel injection amount Ti is set by correction. In addition,
This fuel injection amount Ti is calculated based on the following equation.

Ti ← TP × α × COEF × KBLRC × KA + TS After that, in S209, an injection time corresponding to the fuel injection amount Ti is set by a timer, and then the routine exits.

The injection time set by the timer is output as a drive signal to the injector 23 of the cylinder corresponding to the injection at a predetermined timing.

As described above, in this embodiment, the intake air amount during the transient is estimated from the intake system model formula based on the transient correction coefficient KP calculated during the steady operation. The intake air amount at this time can be set accurately.

Further, since the intake air amount during the transition is accurate, the basic fuel injection amount TP set based on this intake air amount, various correction terms using this basic fuel injection amount TP as the engine load, and the ignition timing Values and other control amounts become appropriate, and air-fuel ratio controllability and ignition timing controllability are improved.

[0064]

As described above, according to the present invention,
Since the intake air amount during transient is calculated from at least the transient correction coefficient calculated during steady state and the intake pipe pressure,
The basic fuel injection amount can be set with good transient response based on the intake air amount, and the controllability is improved.

Further, since the map of the basic fuel injection amount based on the intake pipe pressure is not required, the memory capacity of the control device and the matching man-hours can be reduced.

[Brief description of drawings]

FIG. 1 is a flowchart showing a fuel injection amount setting routine.

FIG. 2 is a flowchart showing an intake pipe pressure / atmospheric pressure detection routine.

FIG. 3 is an overall schematic diagram of an engine control system

FIG. 4 is a circuit diagram of a control device.

[Explanation of symbols]

 QS ... Intake air amount PS ... Intake pipe pressure KP ... Transient correction coefficient Qe ... Transient intake air amount TP ... Basic fuel injection amount

Claims (1)

[Claims] 1. A procedure for determining whether the engine is in steady operation or transient operation, and when it is determined to be steady operation, a transient correction coefficient is based on at least the intake air amount passing through the air cleaner and the intake pipe pressure on the downstream side of the throttle valve. To calculate the transient intake air amount based on at least the transient correction coefficient and the intake pipe pressure, and at the time of steady operation, at least based on the intake air amount. A basic fuel injection amount setting method for an engine, comprising: setting a fuel injection amount; and setting a basic fuel injection amount based on at least the transient intake air amount during transient operation.