JPH07151584A - Suction wall face temperature inferring device and fuel injection amount control device of internal combustion engine - Google Patents

Abstract

PURPOSE:To provide a suction wall face temperature inferring device which can infer the port wall temperature accurately in all the operating conditions of an engine. CONSTITUTION:A TW sensor to detect the cooling water temperature of an engine, and a TA sensor to detect the suction air temperature of a suction pipe are provided, and by making the engine rotation frequency NE of the suction pipe of the engine, and the suction air flow rate X0 found by the suction pipe negative pressure PB, as the main factors, the inner division ratio at the middle part of an object wall temperature TCobj calculated as the middle temperature between the corrected suction temperature TA' which the primary advance correction is carried out, and the engine water temperature TW, is decided. Furthermore, the EGR reflux rate Kx is added to decide the inner division ratio, so as to infer the port wall temperature TC.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intake wall surface temperature estimating device for an internal combustion engine for estimating the wall surface temperature of an intake port of the internal combustion engine, and a fuel injection amount control device using the same.

[0002]

Most of fuel injected from a fuel injection valve is directly supplied to a combustion chamber of an internal combustion engine.
A part of it temporarily adheres to the wall surface of the intake port (in manifold port). The amount of fuel adhering to this wall surface and the amount of carry-away fuel that is sucked into the combustion chamber due to its evaporation etc. are predicted, and the fuel injection amount is determined in consideration of these predicted amounts (fuel transport delay correction). The fuel injection amount control device has been already known.

In this type of fuel injection amount control device,
Since the amount of adhered fuel depends not only on the negative pressure of the intake port and the engine speed but also on the temperature of the intake port wall surface (port wall temperature), the fuel transport delay correction is performed by taking this port wall temperature into consideration. Is being considered. In that case, a method of estimating the port wall temperature by calculation without using a wall temperature sensor that directly detects the port wall temperature due to problems such as an increase in cost due to an increase in the number of parts is disclosed in, for example, Japanese Patent Publication No.
No. 4 (first conventional example) and JP-A-1-305142 (second conventional example).

In the first conventional example, the port wall temperature is calculated from the temperature of the engine cooling water and the accumulated engine speed from the engine start. Then, the basic fuel injection amount is obtained from the engine speed and the intake air amount, and the basic fuel injection amount is further smoothed to obtain a desired smoothing function value. After that, the deviation between the basic fuel injection amount and the smoothing function value is calculated, the increase / decrease correction amount of the adhesion is determined based on this deviation and the predicted port wall temperature, and the basic fuel injection is set to the determined increase / decrease correction amount. The fuel injection amount is obtained by adding the amount.

In the second conventional example, the delay time constant of the equilibrium wall temperature which is the equilibrium temperature of the fuel adhering portion and the port wall temperature is obtained from the intake pipe negative pressure and the engine speed, and this equilibrium wall temperature is calculated. The instantaneous wall temperature is corrected by the cooling water temperature and the intake air temperature, and the predicted port wall temperature is calculated by performing the first-order lag processing on the instantaneous wall temperature with the delay time constant to correct the fuel injection amount. There is.

[0006]

However, neither of the above-mentioned first and second conventional examples accurately captures the characteristics of the port wall temperature, and the port wall temperature is accurate in all operating conditions of the engine. From the point of view of estimating the temperature, it was still not sufficiently satisfactory. Therefore, in the case of estimating the port wall temperature and correcting the fuel transportation delay, there is a problem that the fuel transportation delay cannot be accurately corrected.

In view of the above conventional problems, a first object of the present invention is to provide an intake wall surface temperature estimating device for an internal combustion engine, which can accurately estimate the port wall temperature in all operating conditions of the engine. It is in.

A second object of the present invention is to provide a fuel injection amount control device capable of performing accurate fuel transport delay correction by using the port wall temperature estimated by the intake wall temperature estimation device. The purpose is to

[0009]

In order to achieve the first object, the first invention is to detect a cooling water temperature of an internal combustion engine and an intake air temperature in an intake passage of the engine. Wall surface temperature estimating means for estimating the wall surface temperature of the intake passage to which the injected fuel adheres as an intermediate temperature between the cooling water temperature and the intake air temperature based on the intake air temperature sensor and the outputs of the water temperature sensor and the intake air temperature sensor. The invention provides an intake wall surface temperature estimation device for an internal combustion engine, which comprises:

Preferably, the wall surface temperature estimating means internally divides the intermediate temperature between the cooling water temperature and the intake air temperature at a predetermined intermediate ratio set according to the intake air amount of the engine, and divides the internal temperature by a predetermined value. The wall temperature of the intake passage is estimated based on the result.

Preferably, the wall surface temperature estimating means estimates an intermediate temperature between the cooling water temperature and the intake air temperature as a wall surface temperature in a steady operation state of the engine, and with respect to the wall surface temperature in the steady operation state. It is configured to perform a delay process to estimate the wall surface temperature in the transient operation state of the engine.

[0012] Preferably, the output value of the intake air temperature sensor is corrected by the amount of change in the output value.

Preferably, an exhaust gas recirculation means for recirculating the exhaust gas of the engine into the intake passage is provided, and the intermediate ratio is set according to the exhaust gas recirculation ratio of the exhaust gas recirculation device.

In order to achieve the above-mentioned second object, a second invention is to calculate a parameter representing a fuel transport characteristic in an intake passage of an internal combustion engine according to an operating state of the engine,
Fuel injection amount control means for determining a fuel injection amount to be injected into the intake passage according to the calculated parameter, and a wall temperature of the intake passage estimated by the intake wall temperature estimating device of the first aspect of the invention. According to another aspect of the present invention, there is provided a fuel injection amount control device for an internal combustion engine, comprising: a parameter correction unit that corrects a parameter representing the fuel transportation characteristic.

[0015]

According to the structure of the first aspect of the present invention, since the wall surface temperature in the intake passage is estimated as the temperature intermediate between the cooling water temperature and the intake air temperature, the characteristics of the wall temperature in the intake passage can be accurately grasped. To be Further, the intermediate temperature between the cooling water temperature and the intake air temperature is internally divided at a predetermined intermediate ratio set according to the intake air amount of the engine, and the wall surface temperature of the intake passage is estimated based on the internal division result. Therefore, an accurate port wall temperature can be estimated in all operating conditions of the engine.

According to the structure of the second invention, the wall surface temperature in the intake passage estimated by the intake wall surface temperature estimating device of the first invention is used, and the parameter representing the fuel transport characteristic is corrected accordingly. , Accurate fuel transportation delay correction can be performed.

[0017]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is an overall configuration diagram showing an embodiment of a fuel injection control device for an internal combustion engine including an intake wall surface temperature estimation device according to the present invention.

In the figure, reference numeral 1 denotes, for example, an in-line 4-cylinder internal combustion engine. A throttle body 3 is provided in the middle of an intake pipe 2 connected to an intake port 2A of the engine 1.
A throttle valve 3'is arranged inside thereof. Also,
A throttle valve opening (θTH) sensor 4 is connected to the throttle valve 3 ′, which outputs an electric signal corresponding to the opening of the throttle valve 3 ′ and supplies it to an electronic control unit (hereinafter referred to as ECU) 5. To do.

A fuel injection valve (injector) 6 is provided for each cylinder between the engine 1 and the throttle valve 3'and slightly upstream of an intake valve (not shown) in the intake pipe 2.
Each of the fuel injection valves 6 is connected to a fuel pump 8 via a fuel supply pipe 7 and electrically connected to the ECU 5,
A valve opening time of fuel injection is controlled by a signal from the ECU 5.

A branch pipe 11 is provided on the downstream side of the intake pipe 2, and an intake pipe negative pressure sensor (P
B) The sensor 12 is attached. The PB sensor 1
Reference numeral 2 is electrically connected to the ECU 5, and the intake pipe negative pressure PB in the intake pipe 2 is converted into an electric signal by the PB sensor 12 and supplied to the ECU 5. An intake air temperature (TA) sensor 13 for detecting the intake air temperature TA is mounted on the pipe wall of the intake pipe 2 on the downstream side of the intake pipe 2, and detection signals of these sensors are supplied to the ECU 5. Further, an engine water temperature (TW) sensor 14 including a thermistor or the like is provided on the cylinder peripheral wall filled with the cooling water of the cylinder block of the engine 1.
The engine cooling water temperature TW detected by the TW sensor 14 is converted into an electric signal and supplied to the ECU 5.

A crank angle (CRK) sensor 15 and a cylinder discrimination (CYL) sensor 16 are mounted around the cam shaft or crank shaft (not shown) of the engine 1. The CRK sensor 15 generates a pulse (hereinafter referred to as a CRK pulse) at a predetermined crank angle position with a constant crank angle cycle (for example, 30 ° cycle) shorter than 1/2 rotation (180 °) of the crankshaft of the engine 1. To do. The CRK pulse is supplied to the ECU 5, and the CRK pulse is supplied.
A TDC pulse is output based on the pulse. That is,
The TDC pulse represents the reference crank angle position of each cylinder, and is generated every 180 ° rotation of the crankshaft.

Further, the ECU 5 calculates the CRME value by measuring the time interval at which the CRK pulse is generated, and further, the CRME value is calculated.
The ME value is added over the TDC pulse generation time interval to calculate the ME value, and the engine speed NE that is the reciprocal of the ME value is calculated. The CYL sensor 16 generates a pulse (hereinafter referred to as a CYL pulse) at a predetermined crank angle position (for example, 10 ° BTDC) before the TDC pulse generation position corresponding to the start of the intake stroke of a specific cylinder.

Further, the ECU 5 sets the crank angle stage (hereinafter, simply referred to as a stage) corresponding to the CRK pulse detected immediately after the generation of the TDC pulse as the # 0 stage. The stage advances one by one for each CRK pulse detected thereafter. For example, in a four-cylinder engine that generates a CRK pulse with a cycle of 30 °, stages # 0 to # 5 are set.

The spark plug 1 of each cylinder of the engine 1
The ECU 7 is electrically connected to the ECU 5, and the ECU 5 controls the ignition timing.

An O 2 sensor 22 as an exhaust gas concentration sensor is mounted in the middle of the exhaust pipe 21, detects the oxygen concentration in the exhaust gas, and outputs a signal corresponding to the detected value.
Supply to CU5. A three-way catalyst 23, which is an exhaust gas purification device, is provided downstream of the O2 sensor 22 in the exhaust pipe 21, and the three-way catalyst 23 allows HC and C in the exhaust gas to be discharged.
Purification of harmful components such as O and NOx is performed.

Next, the exhaust gas recirculation mechanism (EGR) will be described.

An exhaust gas recirculation passage 25 is provided between the intake pipe 2 and the exhaust pipe 21 in a bypass shape. The exhaust gas recirculation path 2
One end of the reference numeral 5 is connected to the exhaust pipe 21 upstream of the O2 sensor 22, and the other end thereof is connected to the intake pipe 2.

An exhaust gas recirculation amount control valve (hereinafter referred to as an EGR valve) 26 is provided in the exhaust gas recirculation passage 25. The EGR valve 26 includes a valve chamber 27 and a diaphragm chamber 28.
A casing 29, a wedge-shaped valve body 30 located in the valve chamber 27 and movably arranged in the vertical direction so that the exhaust gas recirculation passage 25 can be opened and closed, and a valve shaft 31.
A diaphragm 32 connected to the valve body 20 via
And a spring 33 for urging the diaphragm 32 in the valve closing direction.
It consists of and. Further, the diaphragm chamber 28 is
The atmospheric pressure chamber 3 defined on the lower side via the diaphragm 32
4 and a negative pressure chamber 35 defined on the upper side.

The atmosphere chamber 34 is communicated with the atmosphere through the vent 34a, while the negative pressure chamber 35 is connected to the negative pressure communication passage 36. That is, the negative pressure communication passage 36 is connected to the intake pipe 2
The intake pipe negative pressure PB in the intake pipe 2 is introduced into the negative pressure chamber 35 through the negative pressure communication passage 36. Further, an atmosphere communication passage 37 is connected in the middle of the negative pressure communication passage 36, and a pressure adjusting valve 38 is interposed in the middle of the atmosphere communication passage 37. The pressure adjusting valve 38 is a normally closed electromagnetic valve, and the atmospheric pressure or the negative pressure is the pressure adjusting valve 3
8 is selectively supplied into the negative pressure chamber 35 of the diaphragm chamber 28, and the negative pressure chamber 35 generates a predetermined control pressure.

Further, the EGR valve 26 is provided with a valve opening (lift) sensor 39, and the lift sensor 3
Reference numeral 9 detects the operating position (valve lift amount) of the valve element 30 of the EGR valve 26, and supplies the detection signal to the ECU 5. The EGR control is performed after the engine is warmed up (for example,
This is executed when the engine cooling water temperature TW is equal to or higher than a predetermined temperature.

The ECU 5 shapes the input signal waveforms from the various sensors described above to correct the voltage level to a predetermined level,
An input circuit 5a having a function of converting an analog signal value into a digital signal value and a central processing unit (hereinafter referred to as "CP").
U ”), a storage means 5c for storing a calculation program executed by the CPU, a calculation result, etc., and an output circuit 5d for supplying a drive signal to the fuel injection valve 6, the fuel pump 8, the spark plug 17 and the like. Is equipped with.

Further, the ECU 5 estimates the wall temperature of the intake port to which the injected fuel adheres (hereinafter referred to as port wall temperature) in order to perform the fuel transport delay correction, and based on this, various parameters relating to the fuel transport delay correction. To set. Further, based on the various engine parameter signals described above, O
Various engine operating states such as a feedback (O2 feedback) control operating region and an open loop control operating region according to the oxygen concentration in the exhaust gas detected by the two-sensor 22 are determined.

In the present embodiment, the intake air temperature sensor 13 is mounted on the downstream pipe wall of the intake pipe 2, but the mounting location of the intake air temperature sensor is not limited to this. It may be on the upstream side of the throttle valve 3 '. However, it is necessary to change the intermediate ratio coefficient X0, which will be described later, according to the installation location of the intake air temperature sensor.

The fuel transportation delay correction will be described below.

Before explaining a concrete example of the fuel transportation delay correction, first, the principle of the fuel transportation delay correction will be described with reference to FIGS.

FIG. 2 is a conceptual diagram showing the relationship between the fuel injection amount Tout and the required fuel amount Tcyl.

Tout in the figure is the amount of injected fuel injected from the fuel injection valve 6 to the intake pipe 2 in a certain cycle, and of this injected fuel amount Tout, the amount corresponding to (A × Tout) is the intake port. It is directly supplied to the cylinder without adhering to the wall surface of 2A, and the remaining amount is taken in as the adhering increment amount Fwin in the wall surface adhering fuel amount Fw adhering to the wall surface by the previous cycle. Here, A is a direct ratio, which represents a ratio of fuel to be directly sucked into a cylinder during a cycle of fuel injected during a certain engine operating cycle.
It is given by 0 <A <1.

Then, the above-mentioned (A × Tout) and the adhesion reduction amount Fwu carried away from the wall surface adhesion fuel amount Fw.
The value obtained by adding t is the required fuel amount Tcyl actually supplied into the cylinder.

Next, a first method for correcting the fuel transportation delay will be described.

The first method is to reduce the adhesion amount Fwout.
Is assumed to follow the adhesion increase amount Fwin with a predetermined time delay, this is expressed as, for example, a first-order delay model, and the degree of delay of the adhesion decrease amount Fwout is expressed using a delay coefficient (time constant) T. .

As described above, the required fuel amount Tcyl is Tcyl = A · Tout + Fwout (1), so the fuel injection amount Tout is

[0043]

[Equation 1] Becomes Further, the adhesion increment Fwin is Fwin = (1-A) Tout (3).

Since the adhesion decrease amount Fwout is a first-order lag of the adhesion increase amount Fwin, when discretized with n,

[0045]

[Equation 2] Becomes

Here, T is a time constant, and the adhesion reduction amount F
At the rising change of wout, the total amount of change is 6
The time required to reach 3.2% is set according to the operating state of the engine, as will be described later.

According to the above equation (4), the present adhesion decrease amount Fwoutn is the adhesion increase amount Fw with respect to the previous value.
Value obtained by subtracting the adhesion reduction amount Fwout from in (deviation)
The value multiplied by 1 / T will increase. In other words, if the same calculation is performed for each cycle, the deviation will be 1
Adhesion decrease amount Fwout in increments of / T times is adhesion increment amount Fwin
Will approach you.

For example, assuming that the direct ratio A is constant when the fuel injection amount Tout is increased stepwise,
As shown in FIG. 3, the adhesion increment amount Fwin also increases stepwise. On the other hand, the adhesion decrease amount Fwout slowly responds based on the time constant T and approaches the adhesion increase amount Fwin.

Then, the fuel injection amount Tout can be obtained from the above equations (2), (3), and (4).

4 is a diagram modeling the first method (hereinafter referred to as AT method) for correcting the fuel transportation delay.

In the figure, the injection fuel amount Toutn injected from the fuel injection valve 6 in a predetermined cycle n is calculated by the multiplication unit 5
1 is multiplied by A (direct rate), while the multiplication unit 52 calculates (1-
A) Doubled. The output of the multiplication unit 51 is (An × Toutn
), Which is supplied to the addition unit 53 and added to the present adhesion reduction amount Fwoutn to obtain the present required fuel amount Tc.
It becomes yln.

On the other hand, the output of the multiplication unit 52 is the adhesion increment amount Fwinn at this time, and Fwin corresponding to the above equation (3).
n = (1-An) * Toutn. This is further multiplied by 1 / T in the multiplication unit 54, supplied to the addition unit 55, and added to the output of the multiplication unit 56. The output of the multiplication unit 56 is (1-1 / Tn) times the adhesion reduction amount Fwoutn, and thus becomes (1-1 / Tn) · Fwoutn.

Further, since the adhesion reduction amount Fwoutn supplied to the addition unit 53 is the output of the cycle delay unit 57 which delays the input by one cycle (1 TDC), the one input to this cycle delay unit 57 is the next time. Adhesion reduction amount Fw
outn + 1.

Therefore, the output of the addition unit 55, that is, the adhesion reduction amount Fwoutn + 1 input to the cycle delay unit 57.
Is

[0055]

[Equation 3] However, Fwinn = (1−An) × Toutn, which corresponds to the equation (4).

Next, a second method for correcting the fuel transportation delay will be described.

The second method is disclosed in, for example, Japanese Patent Laid-Open No. 58-8.
No. 238 (Japanese Patent Publication No. 3-59255), etc., and in addition to the above direct ratio A, of fuel (Fw) that has adhered to the port wall surface up to the previous time, due to evaporation etc. during this cycle. The carry-out rate B (0 <B <1), which is the ratio of the fuel sucked into the combustion chamber, is used. (A x
Tout) is the amount directly supplied to the cylinder without adhering to the port wall surface, and ((1-A) × Tout) is the adhering increment amount Fwin, which is the same as the above-mentioned AT method, but The reduction amount (carry-out amount) Fwout is a method that is considered to be (B × Fw) of the wall surface-attached fuel amount Fw at the start of this cycle.

As shown in the above equation (1), the required fuel amount T
cyl becomes Tcyl = A · Tout + Fwout. Here, Fwout = B × Fw Fwin = (1−A) Tout, and the wall surface adhered fuel amount Fwn at this time is the adhered increment amount Fwin and the adhered decrease amount Fwout with respect to the wall surface adhered fuel amount Fwn−1 up to the previous time. Since it increases or decreases by the deviation of, Fwn = Fwn-1 +
Fwin-Fwout = Fwn-1 + (1-A) Tout
-B * Fwn-1 = (1-A) Tout + (1-B) * F
wn-1 (6)

From the equation (1), the fuel injection amount To
ut is

[0060]

[Equation 4] Therefore, the fuel injection amount Tout can be obtained from the above equations (6) and (7).

5 is a diagram modeling the above-described second method (hereinafter referred to as AB method) of fuel transportation delay correction.

In the figure, the injected fuel amount Toutn injected from the fuel injection valve 6 in a certain cycle n is calculated by the multiplication unit 61.
Is multiplied by A (direct rate) while the multiplication unit 62 calculates (1-A)
Doubled. The output of the multiplication unit 61 becomes (An × Toutn), and this is supplied to the addition unit 63 and is added to the present adhesion reduction amount Fwoutn which is the output of the multiplication unit 64 that multiplies the input by the carry-out rate B. This required fuel amount T
It becomes cyln.

As described above, A. In the B method, the current adhesion reduction amount Fwoutn, which is the output of the multiplication unit 64, is considered to be (B × Fwn) of the wall surface adhesion fuel amount Fwn at the start of the current cycle accumulated up to the previous time.
The wall surface adhering fuel amount Fwn at the start of the current cycle is supplied to the input of the multiplication unit 64. Then, the wall-surface-attached fuel amount Fwn is multiplied by (1-B) in the multiplication unit 65 and supplied to the addition unit 66.

On the other hand, the output of the multiplication unit 62 is the adhesion increment amount Fw.
in which Fwinn = (1
-An) x Toutn. This is the addition unit 6
6 and is the output of the multiplication unit 65 (1-B)
× Fwn is added. Further, the amount of fuel adhered to the wall surface Fwn at the start of this cycle, which is an input to the multipliers 64 and 65,
Is the output of the cycle delay unit 66 that delays the input by one cycle (1 TDC), so that the input to this cycle delay unit 66 is the wall surface adhered fuel amount Fwn + 1 at the start of the next cycle, that is, the current cycle end. It is the amount of fuel adhering to the wall surface at that time.

That is, from the wall surface adhered fuel amount Fwn at the start of this cycle accumulated up to the previous time, (B · Fwo
utn) is the output of the multiplication unit 64 and is carried away, and is the amount that remains without being carried away (1-B) · F
woutn is added by the addition unit 66 to the present adhesion increment amount Fwinn output from the multiplication unit 62.

Therefore, the amount of fuel adhering to the wall surface Fwn + 1 at the start of the next cycle, which is the output of the adder 66, is Fwn + 1 = Fwinn + (1-Bn) Fwn = (1-An) * Toutn + (1- Bn) Fwn = Fwn + (1-An) .times.Toutn-Bn.Fwn (8) In the concrete examples described later, A. The T method shall be used.

Next, the principle of fuel transportation delay correction in consideration of unburned fuel (unburned HC) will be described.

As described above, the injected fuel injected from the fuel injection valve 6 may flow directly into the cylinder, or may flow into the cylinder after once adhering to the wall surface of the intake port 2A. Finally, all the injected fuel is supplied to the cylinder.

However, there is unburned fuel that does not burn in the cylinder. For example, some of the fuel supplied into the cylinder does not atomize (liquid particles), and some adheres to the inner wall surface of the cylinder or the gap between the pistons. It often occurs after fail cut after starting. If this unburned HC component is discharged to the exhaust system as it is, the air-fuel ratio (A / F) in the cylinder will not be stable at the target value. As a result, engine startability, drivability, and exhaust gas properties deteriorate.

Therefore, in order to stabilize the air-fuel ratio (A / F) in the cylinder, it is not enough to perform the above-described fuel transportation delay correction, and the fuel transportation delay correction ( It is necessary to perform unburned HC correction).

First, the first method of correcting the unburned HC will be described with reference to FIG.

In this first method, as shown in FIG. 6A, the fuel injection amount Tout injected from the fuel injection valve 6
Of these, A (direct rate) x Tout and C (unburned rate) x T
Out directly flows into the cylinder, and the remaining adhesion increment amount Fwin is taken into the wall surface adhesion fuel amount Fw. Then, A × Tout and the adhered decrease amount Fwout carried away from the wall surface adhered fuel amount Fw are the required fuel amount Tcyl, which is the fuel amount that contributes to combustion in the cylinder, and C (unburned rate) × Tout does not contribute to combustion. It is a fuel component, that is, an unburned HC component.

The first method can be expressed by a mathematical expression as follows.

The required fuel amount Tcyl is Tcyl = A.Tout + Fwout, and the adhesion increment Fwin is Fwin = (1-AC) Tout.

This method is described in the above A. When applied to the T method, the required fuel amount Tcyl is Tcyl = A · Tout + Fwout, and the present adhesion reduction amount Fwoutn is

[0076]

[Equation 5] Becomes

In addition, A. When applied to the B system, the required fuel amount Tcyl is Tcyl = A.Tout + B.Fw, and the wall surface adhered fuel amount Fw is Fwn = Fwn-1 + (1-A-C) Tout-B.Fw. Becomes

Next, a second method of unburned HC correction will be described with reference to FIG.
An explanation will be given using (b).

In the first method, the unburned HC component is considered to exist in the fuel injection amount Tout injected from the fuel injection valve 6, which directly flows into the cylinder. In the method of 2, the amount of fuel F adhering to the wall surface
Adhesion reduction amount Fw that is carried away from w and flows into the cylinder
It is considered that there is an unburned HC component in out.

That is, as shown in FIG. 6B, of the fuel injection amount Tout injected from the fuel injection valve 6, A
(Direct rate) × Tout directly flows into the cylinder, and the remaining adhesion increment amount Fwin is taken into the wall surface adhesion fuel amount Fw. Then, of the adhesion reduction amount Fwout that is carried away from the wall surface adhesion fuel amount Fw, C × Fwout is defined as the unburned HC.
As components, the remaining (1-C) × Fwout and A × Tou
t is a fuel amount that contributes to combustion in the cylinder as the required fuel amount Tcyl.

The second method is expressed by the following equation.

Since the required fuel amount Tcyl is Tcyl = A.Tout + (1-C) Fwout, the fuel injection amount Tout is

[0083]

[Equation 6] Becomes

This method is described in the above A. When applied to the T method, the adhesion reduction amount Fwout is

[0085]

[Equation 7] Becomes

In addition, A. In the case of applying to the B method, the adhesion reduction amount Fwout is Fwout = B · Fw, so the wall surface adhesion fuel amount Fw this time is Fwn = Fwn−1 + (1-A) Tout−B · Fw. .

Next, the fuel transportation delay correction in consideration of the O2 feedback control (air-fuel ratio correction coefficient KO2) will be described. In this O2 feedback control, the air-fuel ratio correction coefficient KO2 is calculated according to the output of the air-fuel ratio sensor provided on the upstream side of the catalyst purification device interposed in the exhaust passage of the engine, and the fuel injection amount Tout is calculated based on this KO2 value. Is to determine.

The air-fuel ratio of the air-fuel mixture does not always become the target air-fuel ratio simply by performing the above-described fuel transportation delay correction. For example, the characteristics of the fuel injection valve 6 are different, or the fuel pump 8
If the reference pressure of the pressure regulator is deviated, even if the injection pulse width is the same, the fuel injection amount To
There is an error in ut. Similarly, even if the intake pipe absolute pressure PBA and the engine speed NE are the same due to the difference in the engine, if the engine charging efficiency (air amount) is different, the engine speed NE and the intake pipe negative pressure PB are different. The basic Ti map set based on
An error occurs in the fuel injection amount Tout.

Therefore, in order to correct the error in the fuel injection amount Tout due to the error on the side of the fuel injection valve or the individual difference of the engine, the fuel transportation delay correction is performed in consideration of the air-fuel ratio correction coefficient KO2 including these correction terms. A method of performing has been proposed in the past.

The first method is disclosed in Japanese Patent Laid-Open No. 58-8238.
Japanese Patent Publication No. 3-59255 discloses a fuel injection amount Tout obtained by multiplying the required injection amount Tcyl by a KO2 value as shown in the following equation.

[0091]

[Equation 8] The second method is disclosed in Japanese Patent Application Laid-Open No. 61-126337, and the fuel injection amount Tout is obtained by multiplying the Tout value after adhesion correction by the KO2 value as shown in the following equation.

[0092]

[Equation 9] However, the above-mentioned first and second methods have the following problems.

Regarding the error correction of the fuel injection valve, in the characteristics of the fuel injection valve 6 shown in FIG. 7, the physical quantity of fuel (g) is not corrected and the characteristics of the injection valve (K and T in FIG. 7) are corrected.
Only iVB) should be corrected. In addition, T in FIG.
iVB is a dead time for battery voltage correction.

More specifically, for example, the required fuel amount of the engine is 10 g, and in the conventional fuel injection valve, in order to inject 10 g, it was sufficient to output an injection pulse having a pulse width of 20 ms. 2 instead of the fuel injection valve
When the injection pulse of 2 ms is output to try to match the required fuel amount of 10 g, the injection pulse width is 20 ms.
However, the physical fuel amount (g) is 10
It remains g.

As described above, in correcting the error on the fuel injection valve side, it is not necessary to correct the physical fuel amount (g).
It is sufficient to correct only the injection pulse width. If the fuel injection valve is changed to a small one as in the above example, KO2
As a result, the value increases correspondingly, and the injection pulse width also increases, but the physical fuel amount (g) flowing into the cylinder does not change. Therefore, it is not necessary to correct the adhesion reduction amount Fwout as the amount of fuel flowing into the cylinder so as to increase in accordance with the increase in the KO2 value.

However, in the above first method, apparently T
Since the fuel amount [g] of cyl × KO2 is corrected as if it had flowed into the cylinder, when the fuel injection valve is changed to one with a small bore diameter as in the above example, the fuel increased by correction with the KO2 value The injection amount Tout (10% increase in the above example) is
Since the carry-out fuel amount Fwout appears after a certain time, the carry-out fuel amount Fwout also increases by 10%.
In this way, there is a problem that the carry-out fuel amount Fwout, which may not be corrected in the error correction on the fuel injection valve side, changes following the change in the KO2 value, and the fuel transportation delay correction is not accurately performed. It was

Even in the second method, apparently, the amount of fuel [g] doubled by KO2 is corrected as if it was injected, so that the fuel injection corrected by the KO2 value is performed as in the first method. Fuel amount Fwout taken away following the amount Tout
Is changed and the fuel transportation delay is not corrected accurately.

In the air-fuel ratio control using the air-fuel ratio sensor, the air-fuel ratio correction coefficient KO2 based on the output of the air-fuel ratio sensor.
Changes the fuel injection amount Tout. Therefore, the air-fuel ratio correction coefficient KO2 is a feedback control amount that increases and decreases in a certain cycle. On the other hand, in the fuel transport delay correction, the fuel injection amount Tout is determined in the cycle of the fuel transport delay of the change of the fuel injection amount Tout → the change of the wall surface adhered fuel amount Fw → the change of the adhered decrease amount Fwout. Then, the adhesion reduction amount Fwout changes with a certain period due to this cycle of fuel transportation delay. When the cycle of changing the KO2 value and the cycle of changing the adhesion reduction amount Fwout are synchronized with each other, the fuel transportation delay correction works for overcorrection, KO2 hunting occurs, and the fuel injection amount Tout is not properly determined. There was a problem of falling.

For example, in the steady operation state (during a cruise), the negative pressure in the intake pipe and the engine speed are constant, so that the direct a and the carry-out rate b do not change, and the required fuel amount Tcyl also becomes constant. Even in such a case, in the first and second methods, when the air-fuel ratio of the air-fuel mixture deviates from the target value and the KO2 value changes, the fuel injection amount Tout is changed.
Changes, the amount of change in the fuel injection amount Tout is fed back and returned with a delay. By this, K
When the O2 value change cycle and the adhesion decrease amount Fwout change cycle are synchronized, KO2 hunting occurs around the theoretical air-fuel ratio.

In consideration of such a point, in the present embodiment, K
Introducing the adhered carry-out amount correction coefficient f (KO2), which is set smaller as the O2 value increases, and for the first method,

[0101]

[Equation 10] And for the second method above,

[0102]

[Equation 11] Correct as follows.

Here, the adhered and removed amount correction coefficient f (KO
2) is specifically f (KO2) = 1 + α (1-KO2) (11) or

[0104]

[Equation 12] Can be expressed as

In the above equation (11), as shown in FIG. 8 (a), it becomes 1 when KO2 = 1.0, and the slope changes depending on the magnitude of the value α for setting the adhered carry-away amount correction coefficient, It becomes a straight line having a downward sloping tendency with respect to KO2.
In the above equation (12), as shown in FIG.

Further, the fuel transportation delay correction coefficient α is set to be large when the direct ratio A is small, such as when the engine water temperature is low. That is, since the direct ratio A becomes smaller as the engine water temperature becomes lower, the adhesion reduction amount Fw that flows into the cylinder from the wall surface adhesion fuel amount Fw than the fuel amount AxTout that directly flows into the cylinder.
out is considerably larger, and the degree of influence (ratio) of the adhesion reduction amount Fwout in the fuel injection amount Tout is larger. As a result, the degree of KO2 hunting described above increases. Therefore, when the direct ratio A is small, the fuel transportation delay correction coefficient α is set to a large value to strengthen the correction degree.

Next, the intake wall temperature estimation method will be described.

FIG. 9 is a block diagram showing the structure of the intake wall surface temperature estimating device of the present invention.

This intake wall temperature estimating device uses the EGR recirculation rate, the intake pipe negative pressure PB, the engine speed NE, the engine water temperature TW, and the intake temperature TA as input parameters, and estimates the port wall temperature TC from these parameters. To do.

The intake air temperature TA is supplied to the intake air temperature correction processing 71, and the means 71 corrects the response delay of the detection value of the TA sensor 13. The response delay of the TA sensor 13 is TA
This occurs because the output value of the TA sensor 13 cannot quickly react to a rapid change in intake air temperature due to the heat capacity of the sensor 13 itself.

In consideration of such characteristics, the following equation (13)
Thus, the response delay of the TA sensor 13 is corrected.

TA ′ = TAn−1 + K × (TAn−TAn−1) (13) That is, with respect to the deviation between the current output value TAn of the TA sensor 13 and the previous output value TAn−1, a predetermined value is set. The correction coefficient K is multiplied, and the value obtained by adding the previous output value TAn-1 to the result is the corrected intake air temperature TA '.

Then, the target wall temperature estimation processing 72 is performed based on the corrected intake air temperature TA 'and the engine water temperature TW. That is, the target wall temperature estimation processing 72 calculates the target wall temperature TCobj as the intermediate temperature between the corrected intake air temperature TA ′ and the engine water temperature TW by the following equation (14), and the intermediate (interior) ratio is the midpoint coefficient. Determine using X.

TCobj = X.TA '+ (1-X) TW (14) Here, the midpoint coefficient X is the intake air flow rate [l / min] obtained from the intake pipe negative pressure PB and the engine speed NE. ] As a main element and the EGR recirculation rate is added to calculate as shown in the following expression (15) (midpoint coefficient calculation processing 73).

X = X0 × Kx (15) Note that X0 is an intermediate ratio coefficient determined by searching an NE-PB map (not shown) given by the engine speed NE and the intake pipe negative pressure PB, and 0 <X0 <1 is set. Further, Kx is an intermediate ratio correction coefficient determined by searching a Kx table (not shown) given by the lift amount LACT of EGR.

The midpoint coefficient X thus obtained is
There is a tendency as shown in FIG. 10 with respect to the intake pipe negative pressure PB and the engine speed.

The above-mentioned intermediate ratio is determined mainly with the intake air flow rate obtained from the intake pipe negative pressure PB and the engine speed NE. This point will be described.

For example, the intake air amount per unit time increases as the intake pipe negative pressure PB and the engine speed NE are higher, that is, when the engine is under higher load and higher speed, so that the engine is cooled and the port The wall temperature decreases and approaches the intake temperature. On the contrary, since the intake air amount per unit time decreases as the load or rotation of the engine decreases, the port wall temperature rises to the vicinity of the engine water temperature TW under the influence of heat generation of the engine.

In the present embodiment, in consideration of such characteristics of the port wall temperature, the intake air flow rate X0 is used as a main element and calculated as an intermediate temperature between the corrected intake air temperature TA 'and the engine water temperature TW. Since the middle internal ratio of the target wall temperature TCobj is determined, the target wall temperature TCobj can be accurately obtained.

Further, in determining the above-mentioned intermediate internal division ratio, E
The reason why the GR recirculation rate Kx is added is that the temperature on the exhaust side is higher than that on the intake side, so the port wall temperature rises as the EGR recirculation rate increases. In the present embodiment, in consideration of this point, the internal division ratio is determined so that the higher the EGR recirculation rate Kx, the higher the EGR recirculation rate Kx, so the target wall temperature TCobj can be more accurately determined.

In addition, during a transition of the engine operating state, a response delay may occur in the actual port wall temperature TC.

FIG. 11 is a diagram showing the response delay of the port wall temperature TC during transition, in which the throttle valve 3'is fully opened → fully closed →
Port wall temperature TC, engine water temperature TW when fully opened,
And the transition of the intake air temperature TA. The port wall temperature TC and the intake air temperature TA are measured by using sensors with no response delay.

In the figure, if the throttle valve 3'is fully opened when the engine is in the warm-up completion state (engine water temperature TW is 80 ° C or higher), a large amount of outside air (about -10 ° C) flows in. Therefore, the port wall temperature TC is low (2 to 3
℃). After that, when the throttle valve 3'is fully closed, the port wall temperature T is affected by the heat generation of the engine.
C greatly rises. The rising tendency of the port wall temperature TC at this time does not immediately rise due to the heat capacity of the intake port 2A, but rises with a certain time delay tD from the time when the throttle valve 3 ′ is fully closed, and reaches a stable value (30 ° C.). degree)
Reach

That is, when the example of FIG. 11 is applied to the intake wall surface temperature estimating apparatus of the present embodiment, the target wall temperature TCobj is basically the engine water temperature TW and the corrected intake temperature TA 'as described above. Is decided. The engine water temperature TW and the corrected intake air temperature TA ′ are stationary, and the intermediate ratio between them changes mainly with the intake pipe negative pressure PB and the engine speed NE. Therefore, during the transition from the fully open state to the fully closed state of the throttle valve 3 ', the intake pipe negative pressure PB is rapidly reduced and the target wall temperature TCobj is set to the high temperature side. At this time, in consideration of the response delay (time delay tD), the target wall temperature TCobj is subjected to the first-order delay processing 74 to calculate the final predicted port wall temperature TC.

In the first-order delay processing 74, the following equation (16)
The predicted port wall temperature TCn from the current value to the previous value TC
It is calculated in the middle of n-1 and the target wall temperature TCobj.

TCn = β × TCn−1 + (1−β) × TCobj (16) However, the moderation time constant considering the response delay of β: TC Next, a specific example of the fuel transportation delay correction of the present embodiment. A general processing flow will be described with reference to FIGS.

FIG. 12 is a flow chart showing a concrete processing routine of the TDC processing executed in synchronization with the TDC signal pulse.

First, in step S51, it is determined whether or not the engine is in the starting mode, and the answer is affirmative (YE
S), the process proceeds to step S52. Step S
In 52, the basic injection amount TiCR at the time of starting is set to the engine water temperature T
In step S53, which is obtained from W, the required fuel amount TcylCR at the time of starting is calculated by the following equation (17) based on this basic injection amount TiCR.

TcylCR = TiCR × KNE × KPACR (17) Here, TiCR is a function of water temperature KNE is a function of engine speed KPACR is an atmospheric pressure correction term at the time of starting Further, in step S54, a direct rate is calculated by a subroutine described later. Various parameters such as A, delay time constant T, and starting unburned rate C1 are obtained, and in step S55,
The fuel injection time Tout for determining the injection stage at the time of starting is calculated by the following equation (18).

[0130]

[Equation 13] However, TiVB is a dead time for battery voltage correction In step S56, the injection stage is determined by the following equation (19) based on the fuel injection time Tout for determining the injection stage.

[0131]

[Equation 14] However, CRME: average CRK interval [ms].

When the engine is in the post-start mode and the answer to the step S51 is negative (NO), the process proceeds to step S57, the map value Ti of the basic fuel injection amount is searched, and in the following step S58, the following equation (20) The required fuel amount Tcyl is calculated by the equation).

Tcyl = Ti × KTOTAL (20) However, Ti: map value of basic fuel injection amount KTOTAL: a multiplication correction term excluding KO2. Here, the correction term KTOTAL is KTOTAL = KLAM x KTA x KPA (21) where KLAM is the target air-fuel ratio multiplication correction term KTA is the intake air temperature correction term KPA is the atmospheric pressure correction term, and the target air-fuel ratio is also the correction term. The multiplication correction term KLAM is KLAM = KWOT * KTW * KEGR * KAST (22) where KWOT: high load increase KTW: low water temperature increase KEGR: EGR correction term KAST: increase after start. Further, in step S59, various parameters such as the predicted port wall temperature TC, the direct rate A, the delay time constant T, and the post-starting unburned rate C2 are obtained by a subroutine described later, and in the subsequent step S60, the following equation (23) is used for starting. The fuel injection time Tout for determining the subsequent injection stage is calculated.

[0134]

[Equation 15] Then, in step S61, as in step S56, the injection stage is determined and the present routine is ended.

In the calculation of Tout for determining the injection stage, which is executed in steps S55 and S60, the adhesion reduction amount Fwout uses a common value (final calculation value) in each cylinder to simplify the processing. To do.

FIG. 13 is a flow chart showing a concrete processing routine of the CRK processing performed in synchronization with the CRK signal pulse.

First, in step S71, it is determined whether or not the crank interruption this time is the injection stage. If the answer is negative (NO), this routine is ended. When the crank interruption this time is the injection stage and the answer is affirmative (YES), the process proceeds to step S72,
Determine if the engine is in start mode. When the answer is affirmative (YES), the fuel injection amount Tout for the starting mode is calculated for each cylinder by the following equation (24) (step S73).

[0138]

[Equation 16] Here, TcylCR (i) is calculated by the above equation (17). It should be noted that i (= 1 to 4) means that it corresponds to the first to fourth cylinders.

Further, the present adhesion reduction amount Fwoutn (i)
Is calculated for each cylinder by the following expression (25) (step S74).

[0140]

[Equation 17] Here, the amount of adhered fuel Fwinn (i) at this time is Fwinn (i) = (1−A−C1) × (Toutn (i) −TiVB) (26).

After the fuel injection amount Tout and the adhesion reduction amount Fwout (i) are calculated in this way, step S7
The routine proceeds to step 5, fuel injection is executed, and this routine ends.

Since the initial injection at the time of starting in this starting mode is performed without the adhering fuel amount Fwin before the injection, the adhering decrease amount Fwout becomes zero. Therefore, the adhesion reduction amount Fwoutn (i) indicates the adhesion reduction amount when the fuel is injected from the second time.

On the other hand, if the answer to step S72 is negative (NO) after the start mode, step S7
6, the fuel injection amount Tout after the start mode is calculated for each cylinder by the following equation (27).

[0144]

[Equation 18] At this time, Tcyl (i) is calculated by the above equation (20) as in step S58. Furthermore, step S
In 77, as in step S74, the adhesion reduction amount Fw
outn (i) is calculated for each cylinder by the above equation (25),
The adhered fuel amount Fwinn (i) at this time is similarly expressed by the above equation (2)
Calculated according to 6). After that, fuel injection is executed (step S78), and this routine ends.

FIG. 14 is a flow chart showing the processing routine of the B / G processing executed during the period other than the TDC processing and CRK processing.

First, in step S81, the above T
The fuel transport delay correction coefficient α is searched and determined using the W-α table, and further, in the next step S82, the dead time TiVB for battery voltage correction is determined, and this routine ends.

Next, in steps S54 and S5 of FIG.
FIG. 1 shows the calculation method of various parameters executed in FIG.
This will be described with reference to FIGS.

FIG. 15 is a flow chart showing a concrete processing procedure of the calculation processing of the predicted port wall temperature TC.

First, in step S101, it is determined whether or not the engine operating state is the starting mode. If the answer is affirmative (YES) at the time of starting, the engine water temperature TW at this time is used as the predicted port wall. The temperature TC is set (step S102), and this routine ends.

On the other hand, if the answer to step S101 is negative (NO) after the start mode, the NE-
The intermediate ratio coefficient X0 is searched from the PB map (step S
103), and subsequently, the intermediate ratio coefficient X0 is corrected by the EGR recirculation rate by the equation (15) to calculate the midpoint coefficient X (step S104).

Further, in step S105, the target wall temperature TCobj is calculated by the above equation (14), and in step S106 the final predicted port wall temperature TC is obtained by the above equation (16), and this routine is ended. .

According to this embodiment, the intermediate temperature between the corrected intake air temperature TA 'and the engine water temperature TW is internally divided by an intermediate (internal division) ratio according to the intake air amount and the EGR recirculation rate.
The target wall temperature TCobj calculated by accurately grasping the characteristics of the port wall temperature is calculated as the port wall temperature in the steady state, and the target wall temperature TCobj is subjected to the first-order lag processing 74 and the port wall at the transition time is calculated. Since the temperature is calculated, the port wall temperature can be estimated more accurately in all operating conditions of the engine. Then, by using the predicted port wall temperature accurately estimated in this way, the parameters for the fuel transportation delay correction (in the present embodiment, the above-mentioned direct rate A and time constant T) are calculated, so that the engine 1 The fuel transportation delay correction can be performed with high accuracy in all operating conditions.

FIG. 16 is a flow chart showing the calculation process of the direct ratio A used for the fuel transportation delay correction.

First, in step S111, it is determined whether or not the operating state of the engine is in the starting mode. When the answer is affirmative (YES), the direct ratio A is set to a larger value as the engine water temperature TW increases. TW
-A table (not shown) is searched, the direct rate A is determined according to the engine water temperature TW at that time, and this routine is ended (step S112).

On the other hand, when the answer to step S111 is negative (NO) after the start mode, the routine proceeds to step S113, where the flag FEGRAB indicating "1" indicating that the EGR is operating is "1". It is determined whether or not there is. When the answer is affirmative (YES), the process proceeds to step S114, the basic direct rate A0 for the EGR region is searched using the NE-PB map for EGR (not shown), and the process proceeds to step S115. Further, when the EGR is not operating and the answer in step S113 is negative (NO), the NE-PB map for normal (not shown)
Is used to search for the basic direct ratio A0 for the normal area (step S116), and the process proceeds to step S115.

In step S115, a KA map using the predicted port wall temperature TC and the engine speed NE calculated in the calculation process of the predicted port wall temperature TC shown in FIG. 15 (FIG. 1).
The direct rate correction coefficient KA is retrieved from 7), and the subsequent step S
At 117, the direct rate A is calculated from the following equation (28).

A = A0 × KA (28) The KA map is 0 <KA as shown in FIG.
When <1, the larger the predicted port wall temperature TC, the larger the value (1 when the port wall temperature TC is 80 ° C.) is set.

Further, in step S118, the direct ratio A
Of the lower limit value ALMTL0, and the subsequent step S119.
~ In S122, a limit check of the direct rate A is performed,
That is, the lower limit value ALMTL0 and the upper limit value ALM are added to the direct rate A.
TH is set (ALMTL0 ≦ A ≦ ALMTH), and this routine ends. The direct ratio A calculated in this way shows a tendency as shown in FIG.

FIG. 19 is a flow chart showing the calculation process of the delay time constant T used for the fuel transportation delay correction.

First, in step S131, it is determined whether or not the operating state of the engine is the start mode. If the answer is affirmative (YES), the TW-T table (not shown) is searched to determine the engine water temperature at that time. The delay time constant T is determined according to TW, and this routine is ended (step S
132). In the TW-T table, 1 / T is set to a larger value as the engine water temperature TW increases.

On the other hand, if the answer to step S131 is negative (NO) after the start mode, the routine proceeds to step S133, where it is judged if the flag FEGRAB is "1". When the answer is affirmative (YES), the process proceeds to step S134 and the NE-P for EGR is used.
1 / T for EGR region using B map (not shown)
0 (however, T0: basic delay time constant) is searched, and step S
Proceed to 135.

When the EGR is not in operation and the answer to step S133 is negative (NO), 1 / T0 for the normal area (however, T0 is used for the normal area) by using the NE-PB map for normal (not shown). : Basic delay time constant) is searched (step S136), and the process proceeds to step S135.

In step S135, the direct rate correction coefficient KT is retrieved from the KT map using the predicted port wall temperature TC calculated in the calculation process of the predicted port wall temperature TC shown in FIG. 15 and the engine speed NE, and the following step In S137, the delay time constant 1 / T is calculated by the following equation (29).

[0164]

[Formula 19] The KT map is 0 <KT as shown in FIG.
When <1, the larger the predicted port wall temperature TC, the larger the value (1 when the port wall temperature TC is 80 ° C.) is set.

In the following steps S138 to S141, 1
/ T limit check. That is, the lower limit value T to 1 / T
Set LMTL and upper limit value TLMTH (TLMTL ≤ 1
/ T ≦ TLMTH), and this routine ends.

The value of 1 / T calculated in this way is shown in FIG.
Shows a tendency as shown in.

FIG. 21 is a flow chart showing the calculation processing of the unburned rate C described above, and FIG. 22 is a time chart showing the concept of the calculation processing of the unburned rate C.

First, in step S151, it is determined whether or not the engine is in the starting mode, and the answer is affirmative (YE
If S), the process proceeds to step S152, and it is determined whether the fuel injected from the fuel injection valve 6 is the first fuel injected after the start of the engine start. When the answer is affirmative (YES), the process proceeds to step S153, and the starting unburned rate C1 is set as the initial value of the unburned rate C by the TW not shown.
The C1 table (which is set to a smaller value as the engine water temperature TW increases) is searched and determined (time t1 in FIG. 22).

Further, in a succeeding step S154, the starting unburned rate change amount ΔC1 is searched and determined by a TW-ΔC1 table (not shown) (which is set to a larger value as the engine water temperature TW is higher). Then, step S15
In step 5, the unburnt rate C changing counter NITDC is set to a predetermined value 0, and this routine ends.

When the injection is the second and subsequent injections in the starting mode and the answer to step S152 is negative (NO), the routine proceeds to step S156, and the counter NITDC is set.
It is determined whether the value of is greater than or equal to the predetermined value NTDC. At first, the answer is negative (NO), so step S15
When the value of the counter NITDC is incremented and reaches the predetermined value NTDC, the answer in step S156 becomes affirmative (YES).

Then, in step S158, the counter NITDC is set to a predetermined value 0 again, and then in step S158.
At 159, the start unburned rate change amount ΔC1 is subtracted from the present unburned rate C1n. Then, when the subtracted result becomes smaller than the predetermined value 0 (step S
160), in step S161, the starting unburned rate C1n of this time
Is determined to be the predetermined value 0, and this routine is finished.

When the engine shifts after the start mode and the answer to step S151 becomes negative (NO), the process proceeds to step S162, and it is determined whether the previous time was the start mode. Since the answer is affirmative (YES) at first, the process proceeds to step S163, and the unburned rate C2 after starting is again set as the initial value of the unburned rate C in the TW-C2 table showing the same tendency as the TW-C1 table. It is determined by searching (time t2 in FIG. 22).

Further, in a succeeding step S164, the unburnt rate change amount ΔC2 is searched and determined by a TW-ΔC2 table (not shown) showing the same tendency as the TW-ΔC1 table, and this routine is ended.

Then, when the previous time is not the start mode,
The answer to step S162 is negative (NO), and the process proceeds to step S165. In step S165, it is determined whether or not the previous time was the fail cut time, and if the answer is affirmative (YES), it means that the transition from the fail cut time to the fuel injection time occurs, and the air-fuel ratio changes abruptly. ,
It is determined that a part of the first fuel after the resumption of injection may not be burned, and the routine is ended after the processing of steps S163 and S164 so as to set the unburned rate C to the initial value again.

When the answer to step S165 is negative (NO), the routine proceeds to step S166, where the intake pipe negative pressure PB is reached.
It is determined whether or not the amount of change ΔPB of A is larger than a predetermined value ΔPBG, and even if the answer is affirmative (YES), the air-fuel ratio becomes unstable, so the unburned rate C should be set to the initial value. After the processing of steps S163 and S164, this routine ends.

Subsequent steps S167 to S1
At 72, the same processing as the processing at steps S156 to S161 is performed. However, the starting unburned rate C1 is replaced with the unburned rate after starting C2, and the starting unburned rate change ΔC1 is replaced with the unburned rate change ΔC2.

As the various parameters relating to the fuel transport delay correction, the above-described calculation process of the direct rate A, the delay time constant T, and the unburned rate C used in this embodiment has been described. TW not shown
The α table (which is set to a smaller value as the engine water temperature TW is higher) is searched and determined.

Next, in the fuel transportation delay correction executed as described above, at the time of initial injection at the start, in the start mode,
And, each fuel transportation delay correction after the start mode is modeled and described.

FIG. 23 is a block diagram modeling the fuel transport delay correction at the simultaneous injection (first injection at the start) executed in the engine start mode, in the case where the required fuel amount TcylCR at the start is determined. Fuel injection amount Tou
The calculation process of t is shown.

In the figure, the required fuel amount TcylCR is T
It is calculated by the above equation (17) during the DC processing. Then, in this initial injection at the time of starting, the adhesion reduction amount Fwout is set to 0.
In addition, the fuel injection amount Tout is calculated by the above equation (24) during the CRK process, and the adhesion reduction amount Fwoutn (i) shown in the figure indicates the adhesion reduction amount when the fuel is injected from the second time. . Furthermore, in this initial injection at the time of starting, as shown in FIG.
As shown in step S153 of No. 1, starting unburned rate C
1 is determined by the table search.

FIG. 24 is a block diagram modeling the fuel transportation delay correction in the start mode in which the simultaneous injection is changed to the sequential injection. When the required fuel amount TcylCR at the start is determined as in the simultaneous injection. The calculation processing of the fuel injection amount Tout is shown.

In the figure, the required fuel amount TcylCR is T
It is calculated by the above equation (17) during the DC processing. The fuel injection amount Tout and the adhesion reduction amount Fwout are CRK.
The current value Fwoutn (i) of the adhesion reduction amount calculated respectively by the above equations (24) and (25) at the time of processing is stored as the latest value of the adhesion reduction amount and used to determine the injection stage.

FIG. 25 is a block diagram modeling the correction of the fuel transportation delay after the start mode. The required fuel amount Tcy is shown in FIG.
It shows the calculation processing of the fuel injection amount Tout when 1 is determined.

The difference from the calculation processing in the starting mode shown in FIG. 24 is that the air-fuel ratio correction coefficient KO2 and the fuel transportation delay correction coefficient α related thereto are added as new parameters, and the starting unburned rate C1 is also added. Is the point where the unburned rate C2 was replaced after the start.

That is, in the figure, the required fuel amount Tc
yl is calculated by the above equation (20) during TDC processing,
The fuel injection amount Tout with respect to the required fuel amount Tcyl is calculated by the above equation (27). Also, the adhesion reduction amount F
wout is calculated by the above equation (25), and the current value Fwoutn (i) is stored as the latest value of the adhesion reduction amount, and is used to determine the injection stage.

[0186]

As described in detail above, according to the first aspect of the invention, a water temperature sensor for detecting the cooling water temperature of the internal combustion engine, an intake air temperature sensor for detecting the intake air temperature in the intake passage of the engine, Since a wall surface temperature estimating means for estimating the wall surface temperature of the intake passage to which the injected fuel adheres as an intermediate temperature between the cooling water temperature and the intake air temperature based on the outputs of the water temperature sensor and the intake air temperature sensor is provided. It is possible to accurately grasp the characteristics of the port wall temperature and estimate the accurate port wall temperature. Further, the intermediate temperature between the cooling water temperature and the intake air temperature is internally divided at a predetermined intermediate ratio set according to the intake air amount of the engine, and the wall surface temperature of the intake passage is estimated based on the internal division result. Therefore, an accurate port wall temperature can be estimated in all operating conditions of the engine.

According to the second aspect of the present invention, the parameter representing the fuel transport characteristic in the intake passage of the internal combustion engine is calculated according to the operating state of the engine, and the fuel is injected into the intake passage according to the calculated parameter. A fuel injection amount control means for determining a fuel injection amount, and a parameter correction means for correcting a parameter representing the fuel transport characteristic according to the wall temperature of the intake passage estimated by the intake wall temperature estimation device for the internal combustion engine. Since it is provided, accurate fuel transportation delay correction can be performed.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a fuel injection control device for an internal combustion engine.

FIG. 2 is a conceptual diagram showing a relationship between a fuel injection amount Tout and a required fuel amount Tcyl.

FIG. 3 is a diagram for explaining a delay time constant T.

FIG. 4A. It is the figure which modeled T system.

5: A. It is the figure which modeled the b system.

FIG. 6 is a diagram illustrating an unburned HC correction method.

FIG. 7 is a diagram showing injector characteristics.

FIG. 8 is a diagram showing a tendency of a fuel transportation delay correction coefficient α.

FIG. 9 is a block diagram showing a configuration of an intake wall surface temperature estimation device of the present invention.

FIG. 10 is a diagram showing a tendency of a midpoint coefficient X.

FIG. 11 is a diagram showing a response delay of the port wall temperature TC during transition.

FIG. 12 is a flowchart showing a processing routine of TDC processing.

FIG. 13 is a flowchart showing a processing routine of CRK processing.

FIG. 14 is a flowchart showing a processing routine of B / G processing.

FIG. 15 is a flowchart showing a process of calculating a predicted port wall temperature TC.

FIG. 16 is a flowchart showing a process of calculating a direct ratio A.

FIG. 17 is a diagram showing KA and KT maps.

FIG. 18 is a diagram showing a tendency of a direct ratio A.

FIG. 19 is a flowchart showing a calculation process of a delay time constant T.

FIG. 20 is a diagram showing a tendency of 1 / T.

FIG. 21 is a flowchart showing a process for calculating an unburned rate C.

FIG. 22 is a time chart showing the concept of the calculation process of the unburned rate C.

FIG. 23 is a block diagram modeling a fuel transportation delay correction at the time of initial injection at startup.

FIG. 24 is a block diagram modeling the fuel transportation delay correction in the start mode in which simultaneous injection is changed to sequential injection.

FIG. 25 is a block diagram modeling a fuel transportation delay correction after a start mode.

[Explanation of reference numerals] 1 internal combustion engine 2A intake port 5 ECU 6 fuel injection valve 12 PB sensor 13 TA sensor 14 TW sensor 15 CRK sensor 16 CYL sensor 26 EGR valve

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yukito Fujimoto 1-4-1 Chuo, Wako, Saitama Stock company Honda R & D Co., Ltd.

Claims (6)

[Claims] 1. A water temperature sensor for detecting a cooling water temperature of an internal combustion engine, an intake air temperature sensor for detecting an intake air temperature in an intake passage of an engine, and an injected fuel based on outputs of the water temperature sensor and the intake air temperature sensor. An intake wall surface temperature estimating device for an internal combustion engine, comprising: a wall surface temperature estimating means for estimating a wall surface temperature of the adhering intake passage as an intermediate temperature between the cooling water temperature and the intake air temperature. 2. The wall surface temperature estimating means internally divides the intermediate temperature between the cooling water temperature and the intake air temperature at a predetermined intermediate ratio set according to the intake air amount of the engine, and the internal division result is obtained. 2. The intake wall surface temperature estimating device for an internal combustion engine according to claim 1, wherein the wall surface temperature of the intake passage is estimated based on the above. 3. The wall surface temperature estimating means estimates an intermediate temperature between the cooling water temperature and the intake air temperature as a wall surface temperature in a steady operation state of the engine, and delays the wall surface temperature in the steady operation state. The intake wall surface temperature estimating apparatus for an internal combustion engine according to claim 1, wherein the intake wall surface temperature estimating apparatus is configured to perform a process to estimate a wall surface temperature in an engine transient operation state. 4. The intake wall temperature estimating apparatus for an internal combustion engine according to claim 1, wherein the output value of the intake air temperature sensor is corrected by the amount of change in the output value. 5. An exhaust gas recirculation means for recirculating exhaust gas of the engine into the intake passage, wherein the intermediate ratio is set in accordance with an exhaust gas recirculation rate of the exhaust gas recirculation device. Intake wall temperature estimation device for internal combustion engine. 6. A parameter representing a fuel transportation characteristic in an intake passage of an internal combustion engine is calculated according to an operating state of the engine, and a fuel injection amount injected into the intake passage is determined according to the calculated parameter. And a parameter correction means for correcting the parameter representing the fuel transport characteristic according to the wall temperature of the intake passage estimated by the intake wall temperature estimation device for the internal combustion engine. The fuel injection amount control device for an internal combustion engine according to any one of claims 1 to 5.