JP2857689B2 - Apparatus for estimating temperature of intake wall surface of internal combustion engine and control apparatus for fuel injection amount - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Most of fuel injected from a fuel injection valve is directly supplied to a combustion chamber of an internal combustion engine.
Part of it once adheres to the wall surface of the intake port (in manifold port). The amount of fuel adhering to the wall surface and the amount of carry-out fuel drawn into the combustion chamber due to evaporation and the like are predicted, and the fuel injection amount is determined in consideration of these predicted amounts (fuel transport delay correction). A fuel injection amount control device has been already known.

In this type of fuel injection amount control device,
Since the amount of deposited 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 above-described fuel transport delay correction is performed in consideration of the port wall temperature. Is considered. In this case, a method of estimating the port wall temperature by calculation without directly using the wall temperature sensor for directly detecting the port wall temperature due to a problem such as a cost increase due to an increase in the number of parts is disclosed in, for example, Japanese Patent Publication No. 60-5097.
No. 4 (first conventional example) and JP-A-1-305142 (second conventional example).

In the first conventional example, the port wall temperature is calculated based on the temperature of the cooling water of the engine, the accumulation of the engine speed since the engine was started, and the like. Then, a basic fuel injection amount is determined from the engine speed and the intake air amount, and the basic fuel injection amount is smoothed to obtain a desired smoothing function value. Thereafter, a deviation between the basic fuel injection amount and the smoothing function value is calculated, and an increase / decrease correction amount of adhesion is determined based on the deviation and the predicted port wall temperature. The fuel injection amount is determined by adding the amount.

In a second conventional example, an equilibrium wall temperature, which is an equilibrium state temperature of a fuel attachment portion, and a delay time constant of a port wall temperature are obtained from an intake pipe negative pressure and an engine speed. The instantaneous wall temperature is corrected by the cooling water temperature and the intake air temperature, and the instantaneous wall temperature is subjected to a first-order lag process with the delay time constant to obtain a predicted port wall temperature, and the fuel injection amount is corrected. I have.

[0006]

However, none of the first and second prior arts accurately captures the characteristics of the port wall temperature, and does not accurately determine the port wall temperature in all operating states of the engine. From the perspective of estimating temperature, it was not yet satisfactory. Therefore, when the fuel transport delay is corrected by estimating the port wall temperature, there is a problem that the fuel transport delay cannot be accurately corrected.

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

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

[0009]

According to a first aspect of the present invention, a water temperature sensor for detecting a temperature of a cooling water of an internal combustion engine and a temperature of an intake air in an intake passage of the engine are provided. Wall temperature estimation means for estimating, based on the output of the intake air temperature sensor and the water temperature sensor and the intake air temperature sensor, the wall 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. And a device for estimating an intake wall temperature of an internal combustion engine.

Preferably, the wall surface temperature estimating means internally divides an intermediate temperature between the cooling water temperature and the intake air temperature at a predetermined intermediate ratio set according to an intake air amount of the engine, and 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 calculates a temperature of the wall surface temperature in the steady operation state. The delay processing is performed to estimate the wall surface temperature in the transient operation state of the engine.

Preferably, the output value of the intake air temperature sensor is corrected based on the amount of change in the output value.

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

According to a second aspect of the present invention, a parameter representing a fuel transport characteristic in an intake passage of an internal combustion engine is calculated according to an operating state of the engine.
A fuel injection amount control means for determining a fuel injection amount to be injected into the intake passage according to the calculated parameter; A fuel injection amount control device for an internal combustion engine, comprising: a parameter correction unit that corrects a parameter representing the fuel transport characteristic in response to the parameter.

[0015]

According to the structure of the first aspect, the wall surface temperature in the intake passage is estimated as an intermediate temperature between the cooling water temperature and the intake air temperature, so that the characteristics of the wall surface temperature in the intake passage can be accurately grasped. Can be Further, an intermediate temperature between the cooling water temperature and the intake air temperature is internally divided at a predetermined intermediate ratio set according to an intake air amount of the engine, and a 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 states of the engine.

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

[0017]

Embodiments of the present invention will be described below 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 temperature estimation device according to the present invention.

In FIG. 1, reference numeral 1 denotes, for example, an in-line four-cylinder internal combustion engine, and a throttle body 3 is provided in the middle of an intake pipe 2 connected to an intake port 2A of the engine 1.
The inside thereof is provided with a throttle valve 3 '. Also,
A throttle valve opening (θTH) sensor 4 is connected to the throttle valve 3 ′, and 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. I 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) of the intake pipe 2.
Each fuel injection valve 6 is connected to a fuel pump 8 via a fuel supply pipe 7 and electrically connected to the ECU 5.
The 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 a negative pressure sensor (P
B) The sensor 12 is attached. The PB sensor 1
2 is electrically connected to the ECU 5, and the negative pressure PB in the intake pipe 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 an intake air temperature TA is mounted on a pipe wall of the intake pipe 2 on the downstream side of the intake pipe 2, and detection signals from these sensors are supplied to the ECU 5. Further, an engine water temperature (TW) sensor 14 such as a thermistor is provided on a cylinder peripheral wall of the cylinder block of the engine 1 which is filled with cooling water.
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 a camshaft or a crankshaft (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, a 30 ° cycle) shorter than 回 転 rotation (180 °) of the crankshaft of the engine 1. I do. The CRK pulse is supplied to the ECU 5, and the CRK pulse
A TDC pulse is output based on the pulse. That is,
The TDC pulse represents a reference crank angle position of each cylinder and is generated every time the crankshaft rotates 180 °.

The ECU 5 calculates the CRME value by measuring the time interval of the occurrence of the CRK pulse.
The ME value is calculated by adding the ME value over the TDC pulse generation time interval, and the engine speed NE, which 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 suction stroke of a specific cylinder.

Further, the ECU 5 sets a 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. Thereafter, the stage moves up by one for each CRK pulse detected. For example, in a four-cylinder engine that generates a CRK pulse having a cycle of 30 °, stages # 0 to # 5 are set.

The ignition plug 1 for each cylinder of the engine 1
Reference numeral 7 is electrically connected to the ECU 5, and the ignition timing is controlled by the ECU 5.

An O2 sensor 22 as an exhaust gas concentration sensor is mounted in the exhaust pipe 21. The O2 sensor 22 detects the oxygen concentration in the exhaust gas and outputs a signal corresponding to the detected value.
Supply to CU5. Downstream of the O2 sensor 22 in the exhaust pipe 21, a three-way catalyst 23, which is an exhaust gas purification device, is interposed.
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
5 has one end connected to the exhaust pipe 21 upstream of the O2 sensor 22 and the other end connected to the intake pipe 2.

An exhaust gas recirculation amount control valve (hereinafter, referred to as an EGR valve) 26 is interposed in the exhaust gas recirculation passage 25. The EGR valve 26 includes a valve chamber 27 and a diaphragm chamber 28.
A wedge-shaped valve body 30 disposed 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.
Diaphragm 32 connected to the valve body 20 through
And a spring 33 for urging the diaphragm 32 in the valve closing direction.
It is composed of In addition, the diaphragm chamber 28
Atmospheric pressure chamber 3 defined on the lower side via diaphragm 32
4 and a negative pressure chamber 35 defined on the upper side.

The atmosphere chamber 34 is communicated with the atmosphere through a vent 34a, while the negative pressure chamber 35 is connected to a negative pressure communication passage 36. That is, the negative pressure communication passage 36 is
The negative pressure PB in the intake pipe 2 in the intake pipe 2 is introduced into the negative pressure chamber 35 through the negative pressure communication passage 36. An atmosphere communication passage 37 is connected in the middle of the negative pressure communication passage 36, and a pressure regulating valve 38 is provided in the middle of the atmosphere communication passage 37. The pressure regulating valve 38 is a normally closed solenoid valve, and the atmospheric pressure or the negative pressure is applied to the pressure regulating valve 3.
The pressure is selectively supplied into the negative pressure chamber 35 of the diaphragm chamber 28 via the negative pressure chamber 8, 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.
9 detects the operating position (valve lift amount) of the valve body 30 of the EGR valve 26 and supplies a 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 to a digital signal value and the like, and a central processing circuit (hereinafter referred to as "CP
U "), a storage means 5c for storing a calculation program executed by the CPU, a calculation result, and the like, and an output circuit 5d for supplying drive signals to the fuel injection valve 6, the fuel pump 8, the ignition plug 17, and the like. It has.

Further, the ECU 5 estimates the wall temperature of the intake port to which the injected fuel adheres (hereinafter referred to as the 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. Set. Further, based on the various engine parameter signals described above, O
Various engine operation states such as a feedback (O2 feedback) control operation area and an open loop control operation area corresponding to the oxygen concentration in the exhaust gas detected by the two sensors 22 are determined.

In this embodiment, the case where the intake air temperature sensor 13 is mounted on the pipe wall on the downstream side of the intake pipe 2 is shown. However, the mounting place 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 an intermediate ratio coefficient X0, which will be described later, according to the mounting location of the intake air temperature sensor.

Hereinafter, the fuel transport delay correction will be described.

Before describing a specific embodiment relating to fuel transport delay correction, the principle of fuel transport delay correction will first 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.

In the drawing, Tout is the amount of fuel injected from the fuel injection valve 6 to the intake pipe 2 in a certain cycle. Of the amount of fuel Tout, the amount corresponding to (A × Tout) is the intake port. The fuel is supplied directly to the cylinder without adhering to the wall of 2A, and the remaining amount is taken in as the adhesion increment Fwin in the amount of fuel Fw adhering to the wall by the previous cycle. Here, A is a direct rate, which indicates a proportion of fuel injected during a certain engine operation cycle to be directly taken into the cylinder during the cycle.
0 <A <1.

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

Next, a first method of correcting fuel transport delay will be described.

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

As described above, the required fuel amount Tcyl is as follows: Tcyl = A · Tout + Fwout (1)

[0043]

(Equation 1) Becomes In addition, the adhesion increment Fwin is as follows: Fwin = (1−A) Tout (3)

Since the adhesion decrease amount Fwout is a first-order delay of the adhesion increment amount Fwin, discretization by n gives

[0045]

(Equation 2) Becomes

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

According to the above equation (4), the current adhesion decrease amount Fwoutn is different from the previous value by the adhesion increment amount Fw.
The value (deviation) obtained by subtracting the adhesion reduction amount Fwout from in.
Is increased by 1 / T. That is, if the same calculation is performed for each cycle, 1
The amount of adhesion decrease Fwout is incremented by an amount equal to / T times.
Will be approaching.

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

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

FIG. 4 is a diagram in which the first method (hereinafter referred to as the AT method) of the fuel transport delay correction is modeled.

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

On the other hand, the output of the multiplying section 52 is the current adhesion increment Fwinn, which is equivalent to the above equation (3).
n = (1-An) .times.Toutn. This is further multiplied by 1 / T in the multiplier 54 and supplied to the adder 55, where it is added to the output of the multiplier 56. The output of the multiplication unit 56 is (1-1 / Tn) .Fwoutn because the output of the multiplication unit 56 is multiplied by (1-1 / Tn).

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

Therefore, the output of the adder 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 is equivalent to the above equation (4).

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

This second method is described in, for example,
No. 238 (Japanese Patent Publication No. 3-59255) and the like. In addition to the direct rate A, the fuel (Fw) that has adhered to the port wall surface up to the last time is subject to evaporation during the current cycle. The removal rate B (0 <B <1), which is the proportion of fuel sucked into the combustion chamber, is used. (A ×
Tout) is the amount supplied directly to the cylinder without adhering to the port wall surface, and ((1−A) × Tout) is the adhesion increment Fwin in the same manner as in the above-mentioned AT method. The reduction amount (removed amount) Fwout is a method that is considered to be (B × Fw) in the wall-surface-adhered fuel amount Fw at the start of the current cycle.

As shown in the above equation (1), the required fuel amount T
cyl is Tcyl = A · Tout + Fwout. Here, Fwout = B × Fw Fwin = (1−A) Tout, and the current wall-adhered fuel amount Fwn is larger than the previous wall-adhered fuel amount Fwn−1 by the adhesion increment Fwin and the adhesion reduction amount Fwout. Fwn = Fwn-1 +
Fwin−Fwout = Fwn−1 + (1-A) Tout
−B × Fwn−1 = (1−A) Tout + (1−B) × F
wn-1 (6)

From the above 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).

FIG. 5 is a diagram in which the above-mentioned second method (hereinafter referred to as AB method) of fuel transport delay correction is modeled.

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

As described above, A.I. In the B method, the current adhesion decrease amount Fwoutn, which is the output of the multiplying unit 64, is considered to be (B × Fwn) of the wall-adhered fuel amount Fwn accumulated up to the previous time at the start of the current cycle.
The input of the multiplier 64 is supplied with the fuel amount Fwn deposited on the wall surface at the start of the current cycle. The multiplied portion 65 multiplies the amount of fuel Fwn deposited on the wall surface by (1-B) and supplies the multiplied portion to the adding portion 66.

On the other hand, the output of the multiplying unit 62 is the adhesion increment Fw.
in and Fwinn = (1) corresponding to the above equation (3).
−An) × Toutn. This is further the addition unit 6
6 and is the output of the multiplier 65 (1-B).
× Fwn. Further, the fuel amount Fwn attached to the wall surface at the start of the current cycle, which is an input of the multiplying units 64 and 65
Is the output of the cycle delay unit 66 that delays the input by one cycle (1 TDC), and the input to the cycle delay unit 66 is the wall-adhered fuel amount Fwn + 1 at the start of the next cycle, that is, the current cycle end. It is the amount of fuel on the wall at the time.

That is, based on the fuel amount Fwn deposited on the wall surface at the start of the current cycle accumulated up to the previous time, (B · Fwo
utn) is output as the output of the multiplying unit 64 and is carried away, and is the remaining amount without being carried away (1-B) · F.
woutn is added by the adder 66 to the current adhesion increment Fwinn, which is the output of the multiplier 62.

Accordingly, the fuel amount Fwn + 1 on the wall surface at the start of the next cycle, which is the output of the adder 66, is as follows: Fwn + 1 = Fwinn + (1-Bn) Fwn = (1-An) × Toutn + (1- Bn) Fwn = Fwn + (1−An) × Toutn−Bn · Fwn (8) In a specific embodiment described later, A.I. It is assumed that the T method is used.

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

As described above, the fuel injected from the fuel injection valve 6 directly flows into the cylinder, and the fuel injected into the cylinder once passes through the process of attaching 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, of the fuel supplied into the cylinder, there are fuels that do not atomize (liquid droplets) or fuels that adhere to the inner wall surface of the cylinder or gaps between the pistons. It often occurs after a fail cut after starting. If this unburned HC component is directly discharged to the exhaust system, the air-fuel ratio (A / F) in the cylinder will not be stabilized at the target value. As a result, the startability, drivability and exhaust gas properties of the engine deteriorate.

Therefore, in order to stabilize the air-fuel ratio (A / F) in the cylinder, it is not sufficient to simply perform the fuel transport delay correction described above. 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 the first method, as shown in FIG. 6A, the fuel injection amount Tout injected from the fuel injection valve 6
Of these, A (direct rate) × Tout and C (unburned rate) × T
The out flow directly into the cylinder, and the remaining adhesion increment Fwin is taken into the fuel adhesion Fw on the wall surface. Then, A × Tout and the adhesion reduction amount Fwout taken away from the wall-adhered fuel amount Fw are used as the required fuel amount Tcyl as fuel for contributing to combustion in the cylinder, and C (unburned rate) × Tout does not contribute to combustion. The fuel component, that is, the unburned HC component.

The first method is expressed by the following equation.

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

This method is described in A. When applied to the T method, the required fuel amount Tcyl becomes Tcyl = A · Tout + Fwout, and the amount of adhesion decrease Fwoutn this time is:

[0076]

(Equation 5) Becomes

A. When applied to the B method, the required fuel amount Tcyl is Tcyl = A · Tout + B · Fw, and the fuel amount Fw on the wall surface at this time is Fwn = Fwn−1 + (1−A−C) Tout−B · Fw. Becomes

FIG. 6 shows a second method of correcting unburned HC.
This will be described with reference to FIG.

In the first method, the fuel injection amount Tout injected from the fuel injection valve 6 is considered to include the unburned HC component in the one directly flowing into the cylinder. In the second method, the amount of fuel F on the wall is
fw, which is removed from w and flows into the cylinder
It is considered that unburned HC components exist 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 amount of deposition Fwin is taken into the amount of fuel Fw deposited on the wall surface. Then, of the adhesion reduction amount Fwout taken away from the wall surface adhesion fuel amount Fw, C × Fwout is changed to the unburned HC.
And the remaining (1-C) × Fwout and A × Tou
t is the required fuel amount Tcyl, which is the amount of fuel that contributes to combustion in the cylinder.

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 A. When applied to the T method, the adhesion reduction amount Fwout is

[0085]

(Equation 7) Becomes

A. In the case where the method is applied to the B method, the adhesion decrease amount Fwout is Fwout = B · Fw, and therefore, the fuel amount Fw on the wall surface at this time is Fwn = Fwn−1 + (1−A) Tout−B · Fw. .

Next, a description will be given of fuel transport delay correction in consideration of O2 feedback control (air-fuel ratio correction coefficient KO2). In this O2 feedback control, an air-fuel ratio correction coefficient KO2 is calculated in accordance with an output of an air-fuel ratio sensor provided on the upstream side of a catalyst purification device interposed in an exhaust passage of an engine, and a fuel injection amount Tout is calculated based on the KO2 value. Is determined.

The air-fuel ratio of the air-fuel mixture does not always reach the target air-fuel ratio simply by performing the fuel transport delay correction described above. 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 shifted, the fuel injection amount To
ut has an error. Similarly, even if the intake pipe absolute pressure PBA and the engine speed NE are the same and the filling efficiency (air amount) of the engine is different due to individual differences in the engine, if the engine speed NE and the intake pipe negative pressure PB are different. The basic Ti map set based on is different,
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 fuel injection valve side or the individual difference of the engine, the fuel transport delay correction is performed by taking into account the air-fuel ratio correction coefficient KO2 including these correction terms. Conventionally, a method for performing the above has been proposed.

The first method is disclosed in Japanese Patent Application Laid-Open No. 58-8238.
In this publication, the fuel injection amount Tout is obtained by multiplying the required injection amount Tcyl by the KO2 value as shown in the following equation.

[0091]

(Equation 8) A second method is disclosed in Japanese Patent Application Laid-Open No. S61-126337, in which the fuel injection amount Tout is obtained by multiplying the KO2 value by the Tout value after the adhesion correction as shown in the following equation.

[0092]

(Equation 9) However, the first and second methods have the following problems.

Regarding the correction of the error of the fuel injection valve, in the characteristics of the fuel injection valve 6 shown in FIG. 7, the physical fuel amount (g) is not corrected, and the characteristics of the injection valve (K and T in FIG. 7) are not corrected.
iVB) only. Note that T in FIG.
iVB is an invalid time for battery voltage correction.

More specifically, for example, the required fuel amount of the engine is 10 g, and it has been sufficient for the conventional fuel injection valve to output an injection pulse having a pulse width of 20 ms in order to inject 10 g. 2 in place of the fuel injection valve
In the case where an injection pulse of 2 ms is output to match the required fuel amount of 10 g, the injection pulse width is 20 ms.
To 22ms, but the physical fuel quantity (g) is 10
g.

As described above, it is not necessary to correct the physical fuel amount (g) in the error correction on the fuel injection valve side.
It is sufficient to correct only the injection pulse width. When the fuel injection valve is changed to one having a small diameter as in the above example, KO2
As a result, 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 as the KO2 value increases.

However, in the 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 was changed to one having a small diameter as in the above example, the fuel increased by being corrected by the KO2 value. The injection amount Tout (10% increase in the above example)
Since it appears as the carry-out fuel amount Fwout with a certain delay, the carry-out fuel amount Fwout also increases by 10%.
As described above, the carry-out fuel amount Fwout, which does not need to be corrected in the error correction on the fuel injection valve side, changes following the change of the KO2 value, and there is a problem that the fuel transport delay correction is not accurately performed. Was.

In the second method, the fuel is apparently corrected so that the amount of fuel [g] multiplied by KO2 is injected. Therefore, similarly to the first method, the fuel injection corrected by the KO2 value is performed. The amount of fuel taken away Fwout following the amount Tout
Is changed, and the fuel transport delay correction is not accurately performed.

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 is used.
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 a fuel transport delay cycle in which a change in the fuel injection amount Tout → a change in the amount of fuel Fw deposited on the wall → a change in the amount of reduced fuel Fwout. Then, the adhesion reduction amount Fwout changes with a certain cycle due to the fuel transport delay cycle. When such a change cycle of the KO2 value is synchronized with a change cycle of the adhesion decrease amount Fwout, the fuel transport delay correction works 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 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 is also 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, the change in the fuel injection amount Tout is fed back and returned with a delay. This allows K
When the change cycle of the O2 value and the change cycle of the adhesion decrease amount Fwout are synchronized, KO2 hunting occurs around the stoichiometric air-fuel ratio.

In consideration of such points, in this embodiment, K
An adhesion removal amount correction coefficient f (KO2) which is set to be smaller as the O2 value becomes larger is introduced.

[0101]

(Equation 10) And, for the second method,

[0102]

[Equation 11] Correct as follows.

Here, the adhesion and removal 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 equation (11), as shown in FIG. 8A, the value becomes 1 when KO2 = 1.0, and the slope changes depending on the value α for setting the adhesion and removal amount correction coefficient. It becomes a straight line that has a downward tendency to KO2.
In the above equation (12), as shown in FIG.

The fuel transport delay correction coefficient α is set so as to increase when the direct rate A decreases, such as when the engine water temperature is low. That is, since the direct rate A decreases as the engine coolant temperature decreases, the amount of adhesion decrease Fw flowing into the cylinder from the amount of fuel Fw adhering to the wall surface becomes smaller than the amount of fuel Aw flowing directly into the cylinder A × Tout.
out becomes much larger, and the degree of influence (ratio) of the adhesion reduction amount Fwout in the fuel injection amount Tout becomes larger. As a result, the degree of KO2 hunting described above increases. Therefore, when the direct ratio A is small, the fuel transport delay correction coefficient α is set large to increase the degree of correction.

Next, a method of estimating the temperature of the intake wall surface will be described.

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

This intake wall temperature estimating apparatus uses the EGR recirculation rate, the intake pipe negative pressure PB, the engine speed NE, the engine coolant temperature TW, and the intake air temperature TA as input parameters, and estimates the port wall temperature TC from these parameters. Is what you do.

The intake air temperature TA is supplied to an intake air temperature correction process 71, which corrects a response delay of the detected 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 respond quickly to a rapid change in the intake air temperature due to the heat capacity of the sensor 13 itself.

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

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

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

TCobj = X · TA ′ + (1−X) TW (14) Here, the midpoint coefficient X is an intake air flow rate [l / min] obtained from the intake pipe negative pressure PB and the engine speed NE. ] As a main element, and taking into account the EGR recirculation rate, is calculated as shown in the following equation (15) (middle point coefficient calculation processing 73).

X = X0 × Kx (15) where 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. <X0 <1 is set. Kx is an intermediate ratio correction coefficient determined by searching a Kx table (not shown) given by the EGR lift amount LACT.

The midpoint coefficient X thus obtained is
The intake pipe negative pressure PB and the engine speed tend to be as shown in FIG.

The above-mentioned intermediate ratio is determined using the intake air flow rate obtained from the intake pipe negative pressure PB and the engine speed NE as a main factor. This will be described.

For example, when the intake pipe negative pressure PB and the engine speed NE are high, that is, when the engine is under high load and high speed, the amount of intake air per unit time increases. The wall temperature decreases and approaches the intake air temperature. Conversely, the lower the load or rotation of the engine, the smaller the amount of intake air per unit time. Therefore, the port wall temperature rises to near the engine water temperature TW under the influence of the heat generated by the engine.

In this embodiment, in consideration of such a characteristic 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 coolant 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, E is used to determine the above-mentioned intermediate internal ratio.
The reason why the GR recirculation rate Kx is considered is that the temperature on the exhaust side is higher than that on the intake side, so that the port wall temperature increases as the EGR recirculation rate increases. In this embodiment, in consideration of this point, the internal division ratio is determined so that the higher the EGR recirculation rate Kx, the higher the temperature becomes. Therefore, the target wall temperature TCobj can be obtained more accurately.

Further, in the transient state 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 the transition, in which the throttle valve 3 'is fully opened → fully closed →
When fully open, port wall temperature TC, engine coolant temperature TW,
And the transition of the intake air temperature TA. Note that the measurement of the port wall temperature TC and the intake air temperature TA are performed by using sensors having no response delay.

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

That is, the example of FIG. 11 described above is applied to the intake wall temperature estimating apparatus of the present embodiment. As described above, the target wall temperature TCobj is basically the engine water temperature TW and the corrected intake air temperature TA '. Is determined. The engine water temperature TW and the corrected intake air temperature TA 'are stationary, and the intermediate ratio between them varies with the intake pipe negative pressure PB and the engine speed NE as main elements. Accordingly, in the transition from when the throttle valve 3 'is fully opened to when it is fully closed, the intake pipe negative pressure PB is suddenly reduced, and the target wall temperature TCobj is set to a high temperature side. At this time, in consideration of the response delay (time delay tD), a first-order delay process 74 is performed on the target wall temperature TCobj to calculate a final predicted port wall temperature TC.

In the first order delay processing 74, the following equation (16) is used.
Of the predicted port wall temperature TCn to the previous value TC
It is determined at an intermediate point between n-1 and the target wall temperature TCobj.

TCn = β × TCn−1 + (1−β) × TCobj (16) where β is a smoothed time constant taking into account the response delay of TC. A typical processing flow will be described with reference to FIGS.

FIG. 12 is a flowchart showing a specific processing routine of the TDC processing executed in synchronization with the TDC signal pulse.

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

TcylCR = TiCR × KNE × KPACR (17) where 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. A, a delay time constant T, and various parameters such as a starting unburned rate C1 are obtained.
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 an invalid 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] Here, CRME: average CRK interval [ms].

When the engine is in the post-start mode and the answer to step S51 is negative (NO), the process proceeds to step S57, in which a map value Ti of the basic fuel injection amount is searched, and in step S58, the following equation (20) is obtained. The required fuel amount Tcyl is calculated by the equation (1).

Tcyl = Ti × KTOTAL (20) where Ti: map value of basic fuel injection amount KTOTAL: multiplication correction term excluding KO2 Here, the correction term KTOTAL is: KTOTAL = KLAM × KTA × KPA (21) where KLAM is a target air-fuel ratio multiplication correction term KTA: intake temperature correction term KPA: atmospheric pressure correction term, and the target air-fuel ratio is 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 a predicted port wall temperature TC, a direct rate A, a delay time constant T, and a post-start unburned rate C2 are obtained by a subroutine described later. In a subsequent step S60, starting is performed by the following equation (23). The fuel injection time Tout for determining the injection stage later is calculated.

[0134]

(Equation 15) In step S61, the injection stage is determined in the same manner as in step S56, and the routine ends.

In the calculation of the injection stage determination Tout executed in steps S55 and S60, the adhesion reduction amount Fwout uses a common value (final calculation value) for each cylinder, so that the processing is simplified. I do.

FIG. 13 is a flowchart showing a specific processing routine of the CRK processing performed in synchronization with the CRK signal pulse.

First, in a step S71, it is determined whether or not the present crank interruption is the injection stage, and if the answer is negative (NO), this routine is ended. When the present crank interruption is the injection stage and the answer is affirmative (YES), the process proceeds to step S72,
It is determined whether or not the engine is in the start mode. When the answer is affirmative (YES), the fuel injection amount Tout for the start 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 corresponding to the first to fourth cylinders.

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

[0140]

[Equation 17] Here, the attached fuel amount Fwinn (i) at this time is as follows: Fwinn (i) = (1−A−C1) × (Toutn (i) −TiVB) (26)

After calculating the fuel injection amount Tout and the adhesion reduction amount Fwout (i) in this manner, the process proceeds to step S7.
The routine proceeds to step 5, where fuel injection is executed, and this routine ends.

In the initial injection at the time of starting in the start mode, the amount of adhesion reduction Fwout is 0 since the injection is performed without the amount of attached fuel Fwin before the injection. Therefore, the above-mentioned adhesion reduction amount Fwoutn (i) indicates the adhesion reduction amount when the fuel is injected from the second time.

On the other hand, when the answer to step S72 is negative (NO) after the start mode, step S7 is executed.
Then, the program proceeds to S6, where 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. Further, step S
At 77, the adhesion reduction amount Fw is determined in the same manner as in step S74.
outn (i) is calculated for each cylinder by the above equation (25),
At this time, the attached fuel amount Fwinn (i) is similarly calculated by the above equation (2).
It is calculated by 6). Thereafter, fuel injection is performed (step S78), and this routine ends.

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

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

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

FIG. 15 is a flowchart showing a specific processing procedure for calculating the predicted port wall temperature TC.

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

On the other hand, if the answer to step S101 is negative (NO) after the start mode, the above NE-
Search the intermediate ratio coefficient X0 from the PB map (step S
103) Then, the intermediate ratio coefficient X0 is corrected by the EGR recirculation rate according to the above 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 terminated. .

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

FIG. 16 is a flowchart showing a process for calculating the direct ratio A used for fuel transport delay correction.

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

On the other hand, if the answer to step S111 is negative (NO) after the start-up mode, the routine proceeds to step S113, where the flag FEGRAB indicating "1" indicating that the EGR is operating is set to "1". It is determined whether or not there is. If the answer is affirmative (YES), the flow proceeds to step S114 to search for the basic direct ratio A0 for the EGR region using the NE-PB map (not shown) for the EGR, and then proceeds to step S115. When the EGR is not operating and the answer to step S113 is negative (NO), a normal NE-PB map (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, the KA map (FIG. 1) using the predicted port wall temperature TC and the engine speed NE calculated in the process of calculating the predicted port wall temperature TC in FIG.
7) directly retrieves the rate correction coefficient KA from the following step S
In step 117, the direct rate A is calculated from the following equation (28).

A = A0 × KA (28) In the KA map, as shown in FIG. 17, 0 <KA
In <1, the value is set to a larger value as the predicted port wall temperature TC increases (it becomes 1 when the port wall temperature TC is 80 ° C.).

Further, in step S118, the direct rate A
The lower limit value ALMTL0 is calculated, and the subsequent step S119
In S122, a limit check of the direct rate A is performed.
That is, the lower limit ALMTL0 and the upper limit 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 manner shows a tendency as shown in FIG.

FIG. 19 is a flowchart showing a process for calculating a delay time constant T used for fuel transport delay correction.

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

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

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

In step S135, a rate correction coefficient KT is directly searched from a KT map using the predicted port wall temperature TC calculated in the above-described calculation processing of the predicted port wall temperature TC and the engine speed NE. In S137, the delay time constant 1 / T is calculated by the following equation (29).

[0164]

[Equation 19] Note that the KT map has 0 <KT as shown in FIG.
In <1, the value is set to a larger value as the predicted port wall temperature TC increases (it becomes 1 when the port wall temperature TC is 80 ° C.).

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

1 / T calculated in this way is shown in FIG.
The tendency shown in FIG.

FIG. 21 is a flowchart showing the above-described process of calculating the unburned rate C. FIG. 22 is a time chart showing the concept of the process of calculating the unburned rate C.

First, in a step S151, it is determined whether or not the engine is in a start 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. When the answer is affirmative (YES), the process proceeds to step S153, and the starting unburned rate C1 is set as a TW (not shown) as an initial value of the unburned rate C.
A C1 table (set to a smaller value as the engine coolant temperature TW increases) is searched and determined (time t1 in FIG. 22).

Further, in the following step S154, the starting unburned rate change ΔC1 is retrieved and determined from a TW-ΔC1 table (not shown) (which is set to a larger value as the engine water temperature TW becomes higher). Then, step S15
In step 5, the unburned fuel ratio C change counter NITDC is set to a predetermined value 0, and the routine ends.

If the answer to step S152 is negative (NO) as the second or subsequent injection in the start mode, the flow advances to step S156 to execute the counter NITDC.
Is determined to be equal to or greater than a predetermined value NTDC. Initially, the answer is negative (NO), so step S15
Proceeding to 7, the value of the counter NITDC is incremented, and when it reaches the predetermined value NTDC, the answer in step S156 is affirmative (YES).

Then, in step S158, the counter NITDC is set again to a predetermined value 0, and then in step S158
In step 159, the start unburned rate change ΔC1 is subtracted from the current started unburned rate C1n. Then, when the result of the subtraction becomes smaller than the predetermined value 0 (step S
160), in step S161, the current unburned fuel ratio C1n
Is determined to be the predetermined value 0, and this routine ends.

When the engine shifts after the start mode and the answer in step S151 is negative (NO), the flow advances to step S162 to determine whether or not the previous time was in the start mode. At first, since the answer is affirmative (YES), the process proceeds to step S163, and as the initial value of the unburned rate C, the post-starting unburned rate C2 is again stored 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 the subsequent step S164, the unburned rate change ΔC2 is searched and determined in a TW-ΔC2 table (not shown) having the same tendency as the TW-ΔC1 table, and the routine is terminated.

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 time of the fail cut. If the answer is affirmative (YES), it means the transition from the time of the fail cut to the time of the fuel injection, and the air-fuel ratio changes rapidly. ,
It is determined that part of the first fuel after the restart of the injection may not be burned, and the routine ends after the processing of steps S163 and S164 in order to set the unburned rate C to the initial value again.

If the answer to step S165 is negative (NO), the process proceeds to step S166, where the intake pipe negative pressure PB
It is determined whether or not the change amount ΔPB is larger than a predetermined value ΔPBG. When the answer is affirmative (YES), the air-fuel ratio becomes unstable. After the processing in steps S163 and S164, this routine ends.

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

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

Next, in the fuel transport delay correction executed as described above, in the initial injection at start, in the start mode,
A description will be given by modeling each fuel transport delay correction after the start mode.

FIG. 23 is a block diagram modeling fuel transport delay correction at the time of simultaneous injection (first injection at start) executed in the engine start mode, in which the required fuel amount TcylCR at start is determined. Fuel injection amount To
This shows the calculation processing of t.

In the figure, the required fuel amount TcylCR is T
It is calculated by the above equation (17) during DC processing. In the first injection at the time of starting, the adhesion reduction amount Fwout is set to 0.
Then, the fuel injection amount Tout is calculated by the above equation (24) at the time of the CRK processing, 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. . Further, in this initial injection at the time of starting, FIG.
As shown in step S153 of FIG.
1 is determined by a table search.

FIG. 24 is a block diagram showing a model of the fuel transport delay correction in the start mode in which the simultaneous injection is shifted to the sequential injection. In the case where the required fuel amount TcylCR at the start is determined similarly to the simultaneous injection. 3 shows the calculation processing of the fuel injection amount Tout of FIG.

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

FIG. 25 is a block diagram modeling the fuel transport delay correction after the start mode, and shows the required fuel amount Tcy.
This shows the calculation processing of the fuel injection amount Tout when l is determined.

The difference from the calculation processing in the start mode shown in FIG. 24 is that the air-fuel ratio correction coefficient KO2 and the related fuel transport delay correction coefficient α are added as new parameters, and the start unburned rate C1 Is replaced by the post-start unburned rate C2.

That is, in the figure, the required fuel amount Tc
yl is calculated by the above equation (20) at the time of TDC processing,
The fuel injection amount Tout for the required fuel amount Tcyl is calculated by the above equation (27). In addition, the amount of decrease in adhesion 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 above in detail, according to the first aspect, 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 the engine, and A wall temperature estimating unit that estimates a 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 outputs of the water temperature sensor and the intake air temperature sensor. Thus, the characteristics of the port wall temperature can be accurately grasped, and the accurate port wall temperature can be estimated. Further, an intermediate temperature between the cooling water temperature and the intake air temperature is internally divided at a predetermined intermediate ratio set according to an intake air amount of the engine, and a 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 states of the engine.

According to the second aspect of the present invention, a parameter representing a 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. Fuel injection amount control means for determining a fuel injection amount to be determined, and parameter correction means for correcting a parameter representing the fuel transport characteristic in accordance with the wall surface temperature of the intake passage estimated by the intake wall temperature estimation device for the internal combustion engine. Since it is provided, accurate fuel transport delay correction can be performed.

[Brief description of the 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. It is the figure which modeled the T system.

FIG. It is the figure which modeled method b.

FIG. 6 is a diagram for explaining a method of correcting unburned HC.

FIG. 7 is a diagram showing injector characteristics.

FIG. 8 is a diagram showing a tendency of a fuel transport 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 a transition.

FIG. 12 is a flowchart illustrating a processing routine of a TDC process.

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

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

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

FIG. 16 is a flowchart illustrating a calculation process of a direct rate A.

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

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

FIG. 19 is a flowchart showing a process for calculating a delay time constant T.

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

FIG. 21 is a flowchart illustrating a calculation process of an unburned rate C.

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

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

FIG. 24 is a block diagram modeling fuel transport delay correction in a start mode in which simultaneous injection is sequentially shifted to injection;

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

[Explanation of symbols]

 Reference Signs List 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

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Yukito Fujimoto 1-4-1 Chuo, Wako-shi, Saitama Pref. Honda Technical Research Institute Co., Ltd. (56) References JP-A-58-8238 (JP, A) JP-A-57-24427 (JP, A) JP-A-3-111639 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01F 15/02 F02D 41/04 330 F02D 45/00 314

Claims (6)

(57) [Claims] 1. A water temperature sensor for detecting a cooling water temperature of an internal combustion engine; an intake temperature sensor for detecting an intake air temperature in an intake passage of the engine; and an injection fuel based on outputs of the water temperature sensor and the intake temperature sensor. An apparatus for estimating an intake wall surface temperature of an internal combustion engine, comprising: a wall surface temperature estimating unit for estimating a wall surface temperature of the intake passage adhering as an intermediate temperature between the cooling water temperature and the intake air temperature. 2. The wall temperature estimating means internally divides an intermediate temperature between the cooling water temperature and the intake air temperature at a predetermined intermediate ratio set according to an intake air amount of an engine, and calculates an internal division result. 2. A device for estimating an intake wall temperature of an internal combustion engine according to claim 1, wherein a wall surface temperature of said intake passage is estimated on the basis of: 3. The wall temperature estimating means estimates an intermediate temperature between the cooling water temperature and the intake air temperature as a wall temperature in a steady operation state of the engine, and delays the wall temperature in the steady operation state. 2. The apparatus for estimating an intake wall temperature of an internal combustion engine according to claim 1, wherein the processing is performed to estimate a wall temperature in a transient operation state of the engine. 4. The intake wall temperature estimation device for an internal combustion engine according to claim 1, wherein an output value of the intake temperature sensor is corrected based on a change amount of 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 according to an exhaust gas recirculation rate of the exhaust gas recirculation device. Estimation device for intake wall temperature of internal combustion engine. 6. A parameter representing a fuel transport characteristic in an intake passage of an internal combustion engine is calculated in accordance with an operation state of the engine, and a fuel injection amount injected into the intake passage is determined in accordance with the calculated parameter. Fuel injection amount control means, and parameter correction means for correcting a parameter representing the fuel transport characteristic according to the wall surface 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.