JP2002097979A - Control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device of an internal combustion engine capable of precisely executing control according to the detected value of the internal pressure in the combustion chamber of the internal combustion engine with a small quantity of operation. SOLUTION: The parameter PRX of the combustion condition is calculated by deducing '1' from the pressure ratio P3/P2 of the internal pressure P2 in the combustion chamber detected at 60 degrees before the top dead center in the compression process to the internal pressure P3 in the combustion chamber detected at 60 degrees after the top dead center in the expansion process. A target value PRCMD of the parameter of the combustion condition is calculated based on the engine operation condition (S12), and a corrected value KP of the air/fuel ratio is calculated so that the absolute value of the deviation DP between the target value PRCMD and the parameter PRX of the combustion condition is smaller than a prescribed deviation ΔDP (almost 0) (S13-S18). A basic fuel quantity TIM is corrected based on the corrected value KP of the air/fuel ratio and the time of fuel injection TOUT is calculated (S19).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an internal combustion engine, and more particularly to a control device for detecting a pressure in a combustion chamber of an engine and controlling a fuel supply amount or the like based on the detected pressure in the combustion chamber.

[0002]

2. Description of the Related Art The pressure in a combustion chamber of an internal combustion engine is detected by using a pressure sensor, and the net average effective pressure P is determined from the detected pressure value.
Japanese Patent Laid-Open Publication No. Hei.
It is disclosed in JP-A-1-173535.

According to the technique disclosed in this publication, the net average effective pressure Pme is calculated based on the detected value of the pressure in the combustion chamber, and is compared with a threshold value a set according to the engine speed. When Pme ≧ a, the air-fuel ratio is gradually made lean, and when Pme <a, the air-fuel ratio is gradually made rich.

[0004]

However, in the above-mentioned conventional method, the net average effective pressure Pm indicating the work load of the engine is not sufficient.
In order to calculate e, it is necessary to detect the pressure in the combustion chamber for each cycle at a relatively small crank angle interval and perform an integration operation at a high speed. Therefore, the C / A of the A / D converter and the control device
There is a problem in that the cost of the PU increases, or the calculation load on the CPU increases, which may hinder other controls.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and a control apparatus for an internal combustion engine capable of accurately performing control in accordance with a detected value of a pressure in a combustion chamber of an engine with a small amount of calculation. The purpose is to provide.

[0006]

According to one aspect of the present invention, there is provided a pressure detecting means for detecting a pressure in a combustion chamber of an internal combustion engine, and an angle detecting means for detecting a crankshaft rotation angle of the engine. A first combustion chamber pressure during a compression stroke of the engine, the expansion stroke of the first combustion chamber, wherein a pressure of the first combustion chamber is increased during a compression stroke of the engine. Pressure ratio calculating means for calculating a pressure ratio with the pressure of the second combustion chamber in the inside, target pressure ratio calculating means for calculating a target pressure ratio according to the rotation speed and load of the engine, and wherein the pressure ratio is the target pressure. Fuel supply control means for controlling the amount of fuel supplied to the engine so as to match the pressure ratio.

According to this configuration, the pressure ratio between the pressure in the first combustion chamber during the compression stroke of the engine and the pressure in the second combustion chamber during the expansion stroke is calculated, and the pressure ratio is determined according to the engine speed and load. A target pressure ratio is calculated, and the amount of fuel supplied to the engine is controlled such that the pressure ratio matches the target pressure ratio. A parameter (pressure ratio -1) obtained by subtracting "1" from the ratio of the second combustion chamber pressure to the first combustion chamber pressure (second combustion chamber pressure / first combustion chamber pressure) is as follows: The pressure ratio is a parameter substantially proportional to the calorific value per unit weight due to combustion, and the pressure ratio itself can also be used as an index indicating the calorific value due to combustion.
Therefore, by controlling the fuel supply amount so that the pressure ratio matches the target pressure ratio set according to the engine operating state, it is possible to perform accurate fuel supply amount control with a small calculation amount. Such control of the fuel supply amount according to the pressure ratio is particularly effective during the period immediately after the start of the engine until the air-fuel ratio sensor is activated.

According to a second aspect of the present invention, there is provided a control apparatus for an internal combustion engine, comprising: a pressure detecting means for detecting a pressure in a combustion chamber of the internal combustion engine; and an angle detecting means for detecting a crankshaft rotation angle of the engine. Pressure ratio calculating means for calculating a pressure ratio between a first combustion chamber pressure during a compression stroke of the engine and a second combustion chamber pressure during an expansion stroke, such that the pressure ratio matches a predetermined pressure ratio. Ignition timing control means for controlling the ignition timing of the engine.

According to this configuration, the pressure ratio between the pressure in the first combustion chamber during the compression stroke of the engine and the pressure in the second combustion chamber during the expansion stroke is calculated, and the pressure ratio matches the predetermined pressure ratio. Thus, the ignition timing of the engine is controlled.
By setting the predetermined pressure ratio to, for example, an intermediate value between the pressure ratio at the time of normal combustion and the pressure ratio at the time of misfire occurrence, it is possible to retard the ignition timing to near the misfire limit.
Particularly, immediately after the start of the engine, by performing such ignition timing control, it is possible to promote the temperature rise of the catalyst provided in the engine exhaust system.

According to a third aspect of the present invention, there is provided a pressure detecting means for detecting a pressure in a combustion chamber of an internal combustion engine, an angle detecting means for detecting a crankshaft rotation angle of the engine, and an exhaust of the engine to an intake system. In a control device for an internal combustion engine having a recirculating exhaust gas recirculation mechanism, a pressure ratio calculation for calculating a pressure ratio between a first combustion chamber pressure during a compression stroke of the engine and a second combustion chamber pressure during an expansion stroke of the engine. Means, and an exhaust gas recirculation amount control means for controlling an exhaust gas recirculation amount by the exhaust gas recirculation mechanism such that the pressure ratio matches a predetermined pressure ratio.

According to this structure, the pressure ratio between the pressure in the first combustion chamber during the compression stroke of the engine and the pressure in the second combustion chamber during the expansion stroke is calculated, and the pressure ratio matches the predetermined pressure ratio. The exhaust gas recirculation amount is controlled in such a manner. By setting the predetermined pressure ratio to, for example, an intermediate value between the pressure ratio at the time of normal combustion and the pressure ratio at the time of misfire occurrence, it becomes possible to increase the amount of exhaust gas recirculation to near the misfire limit, thereby improving exhaust characteristics and Fuel efficiency can be improved.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing the configuration of an internal combustion engine (hereinafter simply referred to as “engine”) and a control device thereof according to an embodiment of the present invention. For example, a four-cylinder engine 1
In the middle of the intake pipe 2, a throttle valve 3 is arranged.
A throttle valve opening (THA) sensor 4 is connected to the throttle valve 3 and outputs an electric signal corresponding to the opening of the throttle valve 3 to output an electronic control unit for engine control (hereinafter referred to as “ECU”) 5. To supply.

A fuel injection valve 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, and each injection valve is connected to a fuel pump (not shown). The ECU 5 is electrically connected to the ECU 5 and controls a valve opening time of the fuel injection valve 6 based on a signal from the ECU 5.

On the other hand, immediately downstream of the throttle valve 3, an intake pipe absolute pressure (PBA) sensor 7 for detecting the pressure in the intake pipe is provided, and the absolute pressure signal converted into an electric signal by the absolute pressure sensor 7 is provided. Is supplied to the ECU 5. Further, an intake air temperature (TA) sensor 8 is mounted downstream thereof, detects the intake air temperature TA, outputs a corresponding electric signal, and supplies the electric signal to the ECU 5.

The engine water temperature (TW) sensor 9 mounted on the main body of the engine 1 is composed of a thermistor or the like, detects the engine water temperature (cooling water temperature) TW, outputs a corresponding temperature signal, and supplies it to the ECU 5. The ECU 5 includes the engine 1
A crank angle position sensor 10 as angle detecting means for detecting a rotation angle of a crankshaft (not shown) is connected, and a signal corresponding to the rotation angle of the crankshaft is output from the ECU 5.
Supplied to The crank angle position sensor 10 outputs a signal pulse (hereinafter referred to as a “CYL signal pulse”) at a predetermined crank angle position of a specific cylinder of the engine 1, and a top dead center (TDC) at the start of an intake stroke of each cylinder. )
A TDC sensor that outputs a TDC signal pulse at a crank angle position earlier than a predetermined crank angle (every 180 degrees of a crank angle in a four-cylinder engine) and one pulse at a constant crank angle cycle (for example, a 30-degree cycle) shorter than the TDC signal pulse ( CRK that generates a “CRK signal pulse”)
A CYL signal pulse, a TDC signal pulse and a CRK signal pulse are supplied to the ECU 5. These signal pulses correspond to the sample timing of the pressure in the combustion chamber of the engine 1 (hereinafter referred to as “in-cylinder pressure”), the fuel injection timing,
It is used to control various timings such as ignition timing and to detect the engine speed (engine speed) NE.

In the exhaust pipe 12, NOx, HC,
A three-way catalyst 16 for purifying CO is provided.
An oxygen concentration sensor (hereinafter, referred to as “LAF sensor”) 14 as an air-fuel ratio sensor is mounted at an upstream position of the sensor 6. The LAF sensor 14 outputs an electric signal of a level substantially proportional to the oxygen concentration (air-fuel ratio) in the exhaust gas,
5

An exhaust gas recirculation passage 21 is provided between the intake pipe 2 downstream of the throttle valve 3 and the exhaust pipe 12 upstream of the three-way catalyst 16. An exhaust gas recirculation valve that controls the amount of exhaust gas recirculation (hereinafter referred to as an “EGR valve”)
22) are provided. The EGR valve 22 is an electromagnetic valve having a solenoid, and its valve opening is controlled by the ECU 5. The EGR valve 22 is provided with a lift sensor 23 for detecting the valve opening (valve lift amount) LACT, and the detection signal is supplied to the ECU 5. The exhaust gas recirculation passage 21 and the EGR valve 22 constitute an exhaust gas recirculation mechanism.

The ECU 5 has an input circuit having a function of shaping input signal waveforms from various sensors, correcting a voltage level to a predetermined level, converting an analog signal value into a digital signal value, and the like, a central processing unit (hereinafter referred to as a central processing unit). A CPU that stores various arithmetic programs executed by the CPU, arithmetic results, and the like, an output circuit that supplies a drive signal to the fuel injection valve 6 and the like.

The ECU 5 determines the engine operating state based on various engine parameter signals, and sets EG which is set according to the engine speed NE and the intake pipe absolute pressure PBA.
The valve opening command value LCMD of the R valve 22 and the lift sensor 23
The control signal is supplied to the solenoid of the EGR valve 22 so as to make the deviation from the actual valve opening LACT detected by the control routine to zero. Further, the ECU 5 calculates the fuel injection time TOUT as the valve opening time of the fuel injection valve 6 according to the engine operating state, and controls the fuel supply amount so as to obtain an optimum air-fuel ratio according to the engine operating state.

As shown in FIG. 2, each cylinder (#
Cylinders 1 to 4) are provided with in-cylinder pressure sensors 31 to 34 as pressure detecting means for detecting the pressure in the combustion chamber, respectively, and output signals of these sensors are output to a multiplexer 35 via a charge amplifier (not shown). Is supplied to the A / D converter 36 via the. Multiplexer 35
Switches the output signals of the in-cylinder pressure sensors 31 to 34 every 180 degrees of the crank angle, and supplies the signals indicating the in-cylinder pressure in the compression stroke and the expansion stroke of each cylinder to the A / D converter 36. The A / D converter 36 samples the input signal at a predetermined timing, converts the sampled value into a digital signal, and supplies the digital signal to the ECU 5.

FIG. 3 is a graph showing the transition of the in-cylinder pressure PCYL. The solid line L1 shows the characteristic during normal combustion, and the broken line L2 shows the characteristic during misfire. In the present embodiment, the in-cylinder pressure PCYL is sampled at a crank angle position of 60 degrees before the top dead center and at a crank angle position of 60 degrees after the top dead center, and the detected pressures are P2 and P3. Then, a parameter obtained by subtracting "1" from the pressure ratio PR = P3 / P2 of the detected pressure P3 to the detected pressure P2 is adopted as a combustion state parameter PRX (= PR-1) indicating the combustion state of the engine 1. .

The reason will be described below. The heat value Q due to the combustion of the engine 1 is given by the following equation (1). Here, ηh is the combustion efficiency, B is the supplied fuel amount, Hu is the low calorific value of the fuel, G is the operating gas weight, λ is the excess air ratio, Ga
th is the theoretical air weight.

The constant volume specific heat is Cv, and the pressure and temperature before and after combustion at the top dead center in the ideal cycle are P2 'and P2, respectively.
Assuming 3 ′, T2 ′ and T3 ′, the calorific value Q is given by the following equation (2). Q = G × Cv × (T3′−T2 ′) (2) Equation (2) can be modified as follows. Q = G × Cv × T2 ′ × (T3 ′ / T2′−1) = G × Cv × T2 ′ × (P3 ′ / P2′−1) = P2 ′ × V2 ′ × (P3 ′ / P2′−1) ) / (Κ-1) (3) where V2 ′ is the combustion chamber volume at the top dead center, and κ is the specific heat ratio of the air-fuel mixture. The specific heat ratio κ is defined as constant pressure specific heat Cp / constant volume specific heat Cv, and it has been experimentally confirmed that in an actual engine, κ is approximately constant at κ = 1.3.

From the equations (1) and (3), the calorific value q per unit weight is given by the following equation (4). q = ηh × Hu / (1 + λ × Gath) = (P2 ′ / G) × V2 ′ × (P3 ′ / P2′−1) / (κ−1) = R × T2 ′ × (P3 ′ / P2′− 1) / (κ−1) = R × T1 × ε ^(κ−1) × (P3 ′ / P2′−1) / (κ−1) Here, P3 ′ / P2 ′ is substantially equal to P3 / P2. Therefore, q ≒ R × T1 × ε ^(κ-1) × (P3 / P2-1) / (κ-1) (4) where R is the gas constant, ε is the compression ratio, and T1 is the start of the compression stroke. , And (P3 / P2-1) is a combustion state parameter PRX. As described above, the combustion state parameter PRX is an index corresponding to the calorific value q per unit weight (proportional to the calorific value q if the temperature T1 is constant), and is a parameter that accurately indicates the combustion state. I understand.

FIG. 4 is a diagram showing the relationship between the air-fuel ratio A / F and the combustion state parameter PRX. The solid line L3 indicates the theoretical characteristic, and the broken line L4 indicates the actual characteristic. The reason why L4 indicating actual characteristics is lower than L3 indicating theoretical characteristics, that is, the amount of generated heat is reduced is because heat is taken away by thermal dissociation which is a reaction opposite to the combustion reaction. As is clear from the broken line L4 in FIG. 4, PRX = 3.7 corresponds to the air-fuel ratio A / F = 12.5 to 14.0, and PRX = 3.7.
2.6 corresponds to the air-fuel ratio A / F = about 20.0. In the range where the air-fuel ratio is leaner than 14.0, the combustion state parameter PRX monotonously decreases as the air-fuel ratio increases. Therefore, instead of the LAF sensor output, the air-fuel ratio feedback control according to the combustion state parameter PRX is performed. It can be performed.

FIG. 5 shows the valve opening time (hereinafter referred to as "fuel injection time" or "fuel injection amount") TOU of the fuel injection valve 6.
5 is a flowchart of a process for calculating T, which is executed by the CPU of the ECU 5 in synchronization with generation of a TDC signal pulse. In the following description, (n), (n-1)
Are added to indicate the current value and the previous value, respectively. (N) indicating the current value is usually omitted, but is added when it is necessary to clarify the current value.

In step S11, the engine operation state,
Specifically, the engine speed NE and the absolute pressure PB in the intake pipe
A TI map is searched according to A, and a basic fuel amount TIM is calculated. The TI map indicates the engine speed NE on the map.
In the operating state corresponding to the intake pipe absolute pressure PBA, the air-fuel ratio of the air-fuel mixture supplied to the engine 1 is set to be substantially equal to the stoichiometric air-fuel ratio.

In step S12, the engine speed NE
And the PRCM shown in FIG. 6 according to the intake pipe absolute pressure PBA.
The D map is searched to calculate a target value PRCMD of the combustion state parameter PRX. The PRCMD map shows the target value P
The RCMD is set to a predetermined value PRCMD1 on the lean side (for example, 2.
6) and a region R2 for setting the target value PRCMD to a rich predetermined value PRCMD2 (for example, 3.7).

In step S13, the deviation DP (= P) between the detected combustion state parameter PRX and the target value PRCMD is determined.
RCMD-PRX), and then determines whether or not the absolute value of the deviation DP is smaller than a predetermined deviation ΔDP (for example, 0.1) (Step S14). As a result | DP | <
If ΔDP, the current value KP of the air-fuel ratio correction value KP
(N) is set to the previous value KP (n-1) (step S1).
8) Go to step S19.

When | DP | ≧ ΔDP in step S14, it is determined whether or not the deviation DP is a negative value (step S14).
15) When DP <0, the air-fuel ratio correction value KP (n) is calculated by the following equation (5), and when DP> 0, by the following equation (6) (steps S17 and S16),
Proceed to step S19. KP (n) = KP (n-1) -DKP (5) KP (n) = KP (n-1) + DKP (6) where DKP is a predetermined correction value set to a relatively small positive value. is there. By repeating the operation of equation (5),
The air-fuel ratio correction value KP gradually decreases, and the air-fuel ratio correction value KP gradually increases by repeating the calculation of Expression (6). Step S
In step 19, the fuel injection time TOUT is calculated by the following equation (7), and this processing ends. TOUT = TIM × KP (n) (7)

As described above, according to the processing of FIG. 5, the air-fuel ratio correction value KP is calculated so that the target value PRCMD set according to the engine operating state matches the combustion state parameter PRX. Is multiplied by the basic fuel amount TIM to calculate the fuel injection time TOUT. That is, the fuel supply amount is controlled so as to attain the target air-fuel ratio corresponding to the target value PRCMD. Therefore, the LAF sensor 14 is not activated immediately after the start or the LAF sensor 14
Even at the time of failure, the air-fuel ratio can be feedback-controlled to the target air-fuel ratio by the combustion state parameter PRS. Since the combustion state parameter PRX can be calculated with a smaller amount of calculation than the net average effective pressure Pme in the conventional method, accurate fuel supply control can be performed with a smaller amount of calculation.

FIG. 7 is a flowchart of a process for controlling the ignition timing according to the combustion state parameter PRX.
This processing is executed in synchronism with the generation of the TDC signal pulse.
Of the CPU. In step S21, the basic ignition timing IGB is calculated in accordance with the engine operating state, specifically, the engine speed NE and the intake pipe absolute pressure PBA. Then, it is determined whether the engine operating state is an operating state after a predetermined start. A determination is made (step S22). Here, the operation state after the predetermined start is immediately after the start of the engine 1 and the temperature TCAT of the three-way catalyst 16 is equal to the predetermined temperature (for example, 300 degrees).
℃) or less.

If the answer to step S22 is affirmative (YES), the combustion state parameter PRX is set to a predetermined value PRXT.
It is determined whether it is H or more (step S23). Predetermined value P
RXTH is a value between the combustion state parameter value at the time of misfire occurrence and the combustion state parameter value at the time of normal combustion, for example, 1
Is set to As a result of the determination in step S23, PRX ≧
If it is PRXTH, the ignition timing correction value DIG is calculated by the following equation (8) (step S24), and the process proceeds to step S30. DIG (n) = DIG (n-1) -DDIG (8) Here, DDIG is a predetermined correction value set to a relatively small positive value. The timing correction value DIG gradually decreases, that is, the correction amount increases in the retard direction.

If PRX <PRXTH in step S23, misfire may occur if the ignition timing is further retarded. Therefore, the ignition timing correction value DI is calculated by the following equation (9).
G is corrected in the advance direction (step S25), and step S is performed.
Go to 30. DIG (n) = DIG (n-1) + DDIG (9) In step S30, the ignition timing feedback control flag FPFBIG indicated by "1" indicating that the ignition timing feedback control is being performed according to the combustion state parameter is set to "1".
Then, the ignition timing IG is calculated by adding the ignition timing correction value DIG (n) to the basic ignition timing IGB according to the following equation (10) (step S31). IG = IGB + DIG (n) (10)

On the other hand, if the answer to step S22 is negative (NO),
That is, when the engine operation state is not the operation state after the predetermined start, the ignition timing feedback control flag FPFBI
It is determined whether or not G is "1" (step S2).
6). If FPFBIG = 1 and it is immediately after the driving state has stopped after the predetermined start, step S27
Then, it is determined whether or not the ignition timing correction value DIG (n) is 0 or more. As a result, when DIG (n) <0, the correction value DIG is corrected in the increasing direction according to the equation (9) (step S29), and the process proceeds to step S30. By steps S27 and S29, the correction value DIG gradually increases until it reaches 0. When DIG ≧ 0, the process proceeds from step S27 to step S28, where the ignition timing correction value DI
G (n) and ignition timing feedback control flag FPF
The BIG is set to “0”, and the process proceeds to step S31. After the flag FPFBIG is set to "0", the process proceeds to step S2.
From 6 immediately proceed to step S28.

According to the processing of FIG. 7, immediately after the start of the engine 1 and in a state where the catalyst temperature is equal to or lower than the predetermined temperature, the feedback is performed so that the ignition timing IG is set to the most retarded side within a range where the misfire does not occur. Since the control is performed, the temperature rise of the three-way catalyst 16 can be promoted immediately after the engine is started. Note that the catalyst temperature TCAT is detected by a sensor, or is estimated according to the elapsed time after starting or the number of combustions.

FIG. 8 is a flowchart of a process for controlling the exhaust gas recirculation amount (EGR amount) according to the combustion state parameter PRX. This process is executed by the CPU of the ECU 5 in synchronization with the generation of the TDC signal pulse. . Step S41
Then, the engine operating state, specifically, the engine speed N
EGR amount LC according to E and intake pipe absolute pressure PBA
Calculate MDB. Since the EGR amount is proportional to the lift amount of the EGR valve 22, it is actually indicated by the EGR valve lift amount.

Next, it is determined whether or not the engine operation state is an EGR operation state where exhaust gas recirculation can be performed (step S42). Here, the EGR-enabled operating state includes, for example, the engine speed NE and the absolute pressure PB in the intake pipe.
A is within the range of predetermined upper and lower limits, and the engine coolant temperature T
This is an operation state in which W is equal to or higher than a predetermined temperature (eg, 55 ° C.).

If the answer to step S42 is affirmative (YES), the combustion state parameter PRX is set to a predetermined value PRXT.
It is determined whether it is H or more (step S43). Predetermined value P
RXTH is the same as the process in FIG. If the result of determination in step S43 is that PRX ≧ PRXTH, an EGR amount correction value DL is calculated by the following equation (11) (step S44), and the process proceeds to step S50. DL (n) = DL (n-1) + DDL (11) Here, DDL is a predetermined correction value set to a relatively small positive value, and the EGR amount is obtained by repeating the calculation of Expression (11). The correction value DL gradually increases, that is, the correction amount increases in a direction to increase the EGR amount.

If PRX <PRXTH in step S43, a misfire may occur if the EGR amount is further increased. Therefore, EGR is calculated by the following equation (12).
The amount correction value DL is corrected in the decreasing direction (step S45),
Proceed to step S50. DL (n) = DL (n-1) -DDL (12) In step S50, the EG corresponding to the combustion state parameter is determined.
E indicated by "1" indicating that feedback control of R amount is being performed.
The GR amount feedback control flag FPFBL is set to “1”, and then the basic EGR amount L is calculated by the following equation (13).
The EGR amount LCMD, that is, the valve opening command value of the EGR valve 22 is calculated by adding the EGR amount correction value DL (n) to the CMDB (step S51). LCMD = LCMDB + DL (n) (13)

On the other hand, if the answer to step S42 is negative (NO),
That is, when the engine operation state is not the EGR-enabled operation state, the EGR amount feedback control flag FPFBL
Is determined as "1" (step S46).
Then, when FPFBL = 1 and immediately after the EGR-enabled operation state is stopped, the process proceeds to step S47,
It is determined whether or not the EGR amount correction value DL (n) is 0 or less. As a result, when DL (n)> 0, the correction value DL is corrected in the decreasing direction by the equation (12) (step S49), and the process proceeds to step S50. By steps S47 and S49, the correction value DL gradually decreases until it reaches zero. When DL ≦ 0, the process proceeds from step SS47 to step S48, in which the EGR amount correction value DL (n) and the EGR amount feedback control flag FPFBL are set to “0”.
To step S51. After the flag FPFBL is set to “0”, the process immediately proceeds from step S46 to step S48.

According to the processing of FIG.
When the vehicle is in a possible operation state, E
Since the feedback control is performed so that the GR amount is set to the maximum, the effect of the exhaust gas recirculation can be obtained to the maximum, and the exhaust characteristics and the fuel efficiency can be improved.

In this embodiment, the ECU 5 constitutes pressure ratio calculating means, target pressure ratio calculating means, fuel supply control means, ignition timing control means, and exhaust gas recirculation amount control means. More specifically, step S12 in FIG. 5 corresponds to target pressure ratio calculating means, steps S13 to S19 in FIG. 5 correspond to fuel supply control means, and the processing in FIG. 7 corresponds to ignition timing control means. The processing in FIG. 8 corresponds to the exhaust gas recirculation amount control means.

Note that the present invention is not limited to the above-described embodiment, and various modifications are possible. For example, in the embodiment described above, the pressure ratio PR (= P3 / P2) is set to “1”.
Is used for control, but the pressure ratio PR itself may be used.

The sampling of the in-cylinder pressure is performed at two timings centered on the top dead center, that is, SA before the top dead center during the compression stroke and SA after the top dead center during the expansion stroke (0 <SA <
(90 degrees), but it is also possible to use a detection pressure sampled at another timing. That is, for example, if the pressure value sampled at the timing of the SB degree before top dead center is P2B, the pressure value P2B can be converted into the pressure value P2 of the SA degree before top dead center by the following equation (14). P2 = P2B × (V2B / V2) ⁿ (14)

Here, V2 is the volume of the combustion chamber at SA degree before top dead center, V2B is the volume of the combustion chamber at SB degree before top dead center, and n is the polytropic index (about 1.3 to 1.4). Incidentally, it is possible in terms according to equation (6), the sample timing (SB degree) in the range of polytropic change, i.e. it is necessary to be within a range where the P × V ⁿ becomes substantially constant.

[0047]

As described above in detail, according to the first aspect of the present invention, the pressure ratio between the pressure in the first combustion chamber during the compression stroke of the engine and the pressure in the second combustion chamber during the expansion stroke. Is calculated, the target pressure ratio is calculated according to the engine speed and the load, and the amount of fuel supplied to the engine is controlled so that the pressure ratio matches the target pressure ratio. Thus, it is possible to control the fuel supply amount.

According to the second aspect of the present invention, the pressure ratio between the pressure in the first combustion chamber during the compression stroke of the engine and the pressure in the second combustion chamber during the expansion stroke is calculated, and the pressure ratio is calculated. The ignition timing of the engine is controlled to match the predetermined pressure ratio. By setting the predetermined pressure ratio to, for example, an intermediate value between the pressure ratio at the time of normal combustion and the pressure ratio at the time of misfire occurrence, it is possible to retard the ignition timing to near the misfire limit. Particularly, immediately after the start of the engine, by performing such ignition timing control, it is possible to promote the temperature rise of the catalyst provided in the engine exhaust system.

According to the third aspect of the present invention, the pressure ratio between the pressure in the first combustion chamber during the compression stroke of the engine and the pressure in the second combustion chamber during the expansion stroke is calculated, and the pressure ratio is calculated. The exhaust gas recirculation amount is controlled so as to match the predetermined pressure ratio. The predetermined pressure ratio, for example, the pressure ratio during normal combustion,
By setting the value to an intermediate value with the pressure ratio at the time of occurrence of misfire, it becomes possible to increase the exhaust gas recirculation amount to near the misfire limit, thereby improving exhaust characteristics and fuel efficiency.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an internal combustion engine and a control device thereof according to an embodiment of the present invention.

FIG. 2 is a block diagram showing an arrangement of an in-cylinder pressure sensor and an output signal processing circuit thereof.

FIG. 3 is a graph showing a change characteristic of an in-cylinder pressure with respect to a rotation angle of a crankshaft.

FIG. 4 is a diagram showing a relationship between an air-fuel ratio and a combustion state parameter (PRX).

FIG. 5 is a flowchart of a process for calculating a fuel injection amount (TOUT).

FIG. 6 is a diagram showing a map used in the processing of FIG. 5;

FIG. 7 is a flowchart of a process for calculating an ignition timing (IG).

FIG. 8 is a flowchart of a process for calculating an exhaust gas recirculation amount (LCMD).

[Explanation of symbols]

Reference Signs List 1 internal combustion engine 5 electronic control unit (pressure ratio calculation means, target pressure ratio calculation means, fuel supply control means, ignition timing control means, exhaust gas recirculation amount control means) 6 fuel injection valve 7 intake pipe absolute pressure sensor (load detection means) DESCRIPTION OF SYMBOLS 10 Crank angle position sensor (angle detection means, rotation speed detection means) 31, 32, 33, 34 In-cylinder pressure sensor (pressure detection means) 21 Exhaust recirculation passage (exhaust recirculation mechanism) 22 Exhaust recirculation valve (exhaust recirculation mechanism)

 ──────────────────────────────────────────────────続 き Continued on front page F term (reference) 3G022 AA10 DA07 EA01 FA02 FA06 GA01 GA05 GA07 GA08 GA09 GA10 GA11 GA15 3G062 AA03 BA02 EA12 FA02 FA03 FA04 FA06 FA08 FA13 GA02 GA04 GA08 GA15 GA17 GA18 GA21 GA26 3G092 AA01 BA09 BA BB01 DC09 EA04 EA17 EC01 FA06 FA15 FA24 GA02 HA04Z HA05Z HA06Z HA11Z HB01X HC01Z HC09X HD02Z HD03Z HD05Z HE01Z HE03Z HE05Z HE08Z 3G301 HA01 HA13 JA00 JA02 JA18 JA21 KA05 LA01 LB02 MA01 MA11 NB03ZA01 PD02 PE01Z PE03Z PE05Z PE08Z PE09A

Claims (3)

[Claims] 1. A pressure detecting means for detecting a pressure in a combustion chamber of an internal combustion engine, an angle detecting means for detecting a crankshaft rotation angle of the engine, a rotational speed detecting means of the engine, and a load of the engine are detected. A control device for an internal combustion engine having a load detection unit that performs a first combustion chamber pressure during a compression stroke of the engine;
A pressure ratio calculating means for calculating a pressure ratio with the pressure in the second combustion chamber during an expansion stroke; a target pressure ratio calculating means for calculating a target pressure ratio according to a rotational speed and a load of the engine; A control device for controlling the amount of fuel supplied to the engine so as to match the target pressure ratio. 2. A control device for an internal combustion engine, comprising: a pressure detecting means for detecting a pressure in a combustion chamber of the internal combustion engine; and an angle detecting means for detecting a crankshaft rotation angle of the engine. A first combustion chamber pressure;
Pressure ratio calculating means for calculating a pressure ratio with the pressure in the second combustion chamber during the expansion stroke; and ignition timing control means for controlling the ignition timing of the engine so that the pressure ratio matches a predetermined pressure ratio. A control device for an internal combustion engine, comprising: A pressure detecting means for detecting a pressure in a combustion chamber of the internal combustion engine; an angle detecting means for detecting a crankshaft rotation angle of the engine; and an exhaust gas recirculation mechanism for recirculating exhaust gas of the engine to an intake system. A control apparatus for an internal combustion engine having a first combustion chamber pressure during a compression stroke of the engine;
Pressure ratio calculating means for calculating a pressure ratio with the pressure in the second combustion chamber during an expansion stroke; and exhaust gas recirculation amount control for controlling an exhaust gas recirculation amount by the exhaust gas recirculation mechanism so that the pressure ratio matches a predetermined pressure ratio. And a control device for an internal combustion engine.