JPH07293305A - Control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To properly control the distribution ratio of the amount of fuel which is supplied from a plurality of intake ports of a cylinder in an internal combustion engine, and stabilize fuel condition while maintaining good operational property. CONSTITUTION:In the lean burn operating range of an engine, upper and lower limit values (S), (T) are decided (Step S5 to Step S7) so as to restrict a coefficient (X), an operating side distribution ratio (the distribution ratio on an operating intake valve side when two intake valves are set to the low speed valve timing of one valve operation/one valve rest) (B), and the control range of the distribution ratio (B) according to the state of operation (engine rotational speed and the absolute pressure in the air intake pipe. When combustion condition is not deteriorated, the distribution ratio (B) is gradually increased in the control range, and on the other hand, the distribution ratio (B) is reduced in the control range, when combustion condition is deteriorated.

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 which has a plurality of intake valves for each cylinder.

[0002]

2. Description of the Related Art A plurality of (for example, two) intake valves are provided for each cylinder, and a valve drive mechanism is provided for stopping the drive of one intake valve when the engine is running at low speed to generate swirl in the cylinder. In a conventional engine, a control device that can change the distribution ratio of the fuel amount supplied to each cylinder from each of the plurality of intake valves and controls the distribution ratio according to the number of driven intake valves is conventionally known. (JP-A-3-1305)
No. 73).

[0003]

However, in the above conventional control device, when the combustion state of the engine is deteriorated, the air-fuel ratio is made rich to stabilize the combustion, so that the opening degree of the throttle valve is increased. Even if it is constant, there is a problem that the engine output fluctuates with a change in the air-fuel ratio, which deteriorates drivability.

The present invention has been made in view of this point, and an internal combustion engine capable of stabilizing the combustion state while appropriately controlling the distribution ratio of the fuel amount and maintaining good drivability. An object is to provide a control device.

[0005]

To achieve the above object, the present invention provides an operating condition detecting means for detecting an operating condition of an internal combustion engine in which a plurality of intake valves are provided for each cylinder, and the plurality of intake valves. In the control device for the internal combustion engine, the control unit for the internal combustion engine comprises: a fuel distribution ratio changing unit that changes a distribution ratio of the amount of fuel flowing into the cylinder from each of the cylinders; and a combustion state detecting unit that detects a combustion state of each cylinder. A fuel distribution ratio control means for controlling the distribution ratio according to the combustion state is provided.

Further, it is desirable to further provide a timing control means for controlling at least one of fuel injection timing and ignition timing according to the detected combustion state.

[0007]

The distribution ratio of the amount of fuel flowing into the cylinder from the plurality of intake valves is controlled according to the detected engine combustion state.

At least one of fuel injection timing and ignition timing is controlled according to the detected engine combustion state.

[0009]

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

FIG. 1 is an overall configuration diagram of an internal combustion engine (hereinafter simply referred to as "engine") and a control system therefor according to one embodiment of the present invention. This engine is equipped with an exhaust gas recirculation mechanism, and an intake valve and The valve operating characteristic of the exhaust valve (hereinafter referred to as "valve timing") is switchable.

In the figure, in the engine 1, the valve timings of the intake valve and the exhaust valve can be switched between two stages, a high-speed valve timing suitable for a high-speed rotation region of the engine and a low-speed valve timing suitable for a low-speed rotation region. It has a valve timing switching mechanism 40. The valve timing switching in this embodiment also includes switching of the valve lift amount. Further, each cylinder of the engine 1 is provided with a pair of intake valves and exhaust valves, and in the present embodiment, the lift amount of one intake valve is set to almost 0 when the low speed valve timing is selected. That is, in the low speed rotation region of the engine 1, one intake valve is stopped and only the other intake valve is operated.

A throttle valve 3 is provided in the intake pipe 2 of the engine 1. A throttle valve opening degree (θTH) sensor 4 is connected to the throttle valve 3 and outputs an electric signal according to the opening degree of the throttle valve 3 to output an electronic control unit for engine control (hereinafter referred to as “ECU”) 5 Supply to.

A pair of fuel injection valves 6 (6a, 6b) is provided for each cylinder between the engine 1 and the throttle valve 3 and slightly upstream of the intake valve of the intake pipe 2, and each injection valve is The ECU 5 is connected to a fuel pump (not shown).
The fuel injection timing and the fuel injection time (valve opening time) are controlled by a signal from the ECU 5.

The spark plug 16 of each cylinder of the engine 1 is connected to the ECU via a drive circuit 17 and a distributor 18.
5 is electrically connected, and the ignition timing θIG is controlled by the ECU 5. An ion current sensor 19 for detecting an ion current flowing between the electrodes of the ignition plug 16 at the time of ignition is provided in the middle of a connecting line connecting the distributor 18 and the ignition plug 16, and the detection signal is E
Supplied to CU5.

On the other hand, an intake pipe absolute pressure (PBA) sensor 7 is provided immediately downstream of the throttle valve 3, and the absolute pressure signal converted into an electric signal by the absolute pressure sensor 7 is supplied to the ECU 5. . Further, an intake air temperature (TA) sensor 8 is attached downstream thereof, detects the intake air temperature TA, outputs a corresponding electric signal, and supplies it 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 1 has an engine 1
, A cylinder discrimination sensor (hereinafter referred to as “CYL sensor”) that outputs a signal pulse (hereinafter referred to as “CYL signal pulse”) at a predetermined crank angle position of each cylinder, and a top dead center (TDC) at the start of the intake stroke of each cylinder. ), A TDC signal pulse is generated at a crank angle position before a predetermined crank angle (in a 4-cylinder engine, every 180 ° crank angle).
A sensor 11 and a crank angle sensor 12 that generates one pulse (hereinafter referred to as “CRK signal pulse”) at a constant crank angle cycle shorter than the cycle of the TDC signal pulse are electrically connected to each other, and a CYL signal pulse and a TDC signal are provided. The pulse and the CRK signal pulse are sent to the ECU 2. The output signal pulses of these three sensors 10, 11, 12 are used for various timing controls such as fuel injection timing and ignition timing, and detection of engine speed.

The three-way catalyst 15 is arranged in the exhaust pipe 14 of the engine 1 and purifies components such as HC, CO, NOx in the exhaust gas. An oxygen concentration sensor 13 as an exhaust gas concentration detector is mounted upstream of the three-way catalyst 15 in the exhaust pipe 14, detects the oxygen concentration in the exhaust gas, and outputs a signal according to the detected value to output the ECU 5 Supply to. The oxygen concentration sensor 13 is a linear type that outputs a signal proportional to the oxygen concentration.

Further, the valve timing switching mechanism 40
Has an electromagnetic valve for controlling switching of valve timing. The electromagnetic valve is connected to the ECU 5, and its opening / closing operation is controlled by the ECU 5. The solenoid valve switches the hydraulic pressure of the valve timing switching mechanism 40 between high and low, and the valve timing is switched between a high speed valve timing and a low speed valve timing according to the high / low of the hydraulic pressure. Next, the exhaust gas recirculation mechanism 20 will be described.

The exhaust gas recirculation passage 21 of this mechanism 20 has one end 2
1a communicates with the exhaust pipe 13 upstream of the three-way catalyst 14, and the other end 21b communicates with the intake pipe 2 downstream of the throttle valve 3.
An exhaust gas recirculation valve 22 for controlling the amount of exhaust gas recirculation and a volume chamber 21C are provided in the middle of the exhaust gas recirculation passage 21. The exhaust gas recirculation valve 22 is a solenoid valve having a solenoid 22a, which is connected to the ECU 5,
The valve opening is configured to be linearly changed by a control signal from the ECU 5. The exhaust gas recirculation valve 22 has a lift sensor 23 that detects the valve opening degree.
Is provided, and the detection signal thereof is supplied to the ECU 5.

The ECU 5 determines the engine operating state based on the engine parameter signals from the above-mentioned various sensors, and the valve opening degree of the exhaust gas recirculation valve 22 set according to the intake pipe absolute pressure PBA and the engine speed NE. Command value LCMD
And exhaust gas recirculation valve 22 detected by the lift sensor 23
The control signal is supplied to the solenoid 22a so as to make the deviation from the actual valve opening value LACT of 0.

The ECU 5 shapes input signal waveforms from various sensors, corrects the voltage level to a predetermined level, converts an analog signal value into a digital signal value, and the like, a central processing circuit (hereinafter referred to as a central processing unit). "CPU") 5b, various calculation programs executed by the CPU 5b, storage means 5c for storing the calculation results, an output circuit 5d for supplying a drive signal to the fuel injection valve 6, and the like.

The CPU 5b determines various engine operating states such as a feedback control operating region to the stoichiometric air-fuel ratio by the oxygen concentration sensor 13 and an open loop control operating region based on the various engine parameter signals described above, and determines the engine operating state. Accordingly, according to the following equations (1) and (2), the fuel injection time Tout of the fuel injection valve 6 and the spark plug 16
Of the fuel amount to be injected from the two fuel injection valves 6a and 6b in accordance with the detected fuel state based on the output of the ignition current sensor 19. To calculate.

Tout = TI × KO2 × K1 + K2 (1) θIG = θIGMAP + θIGCR (2) where TI and θIGMAP are engine speed NE.
And the basic injection time and basic ignition timing set according to the intake pipe absolute pressure PBA, which are read from the TI map and the θIG map stored in advance in the storage means 5c.
In the present embodiment, these maps are the EGR on map used when the exhaust gas recirculation is executed (when the exhaust gas recirculation valve 22 is opened) and the EGR off map used when the exhaust gas recirculation is stopped (when the exhaust gas recirculation valve is closed). And are provided. Further, a map for high speed valve timing and a map for low speed valve timing are provided for each of EGR ON and EGR OFF, corresponding to the selected valve timing. Therefore, four types of TI maps and four types of θIG maps are provided.

KO2 is an air-fuel ratio correction coefficient which is set based on the output of the oxygen concentration sensor 13 during the air-fuel ratio feedback control, and is set to a predetermined value when the feedback control is not performed (during open loop control). It

Further, K1, K2 and θIGCR are other correction coefficients or variables calculated according to various engine operating parameter signals.

Two injection valves 6a and 6b are provided according to the fuel injection time Tout and the distribution rate calculated by the above equation (1).
The respective injection times Touta and Toutb are calculated.

The CPU 5b further controls the valve opening degree of the exhaust gas recirculation valve 22 and the valve timing switching control according to the engine operating condition.

The CPU 5b outputs signals for driving the solenoid valves of the fuel injection valves 6a and 6b, the spark plug 16, the exhaust gas recirculation valve 22 and the valve timing switching mechanism 40 based on the results calculated and determined as described above. Output through the circuit 5d.

In this embodiment, the ECU 5 constitutes part of the fuel distribution rate changing means, part of the combustion state detecting means, the fuel distribution rate control means and the timing control means.

FIG. 2 is a view showing a cross section of the main part of the engine 1. In the figure, the engine 1 includes a piston 53, a cylinder block 55 in which four cylinders 54 fitted with the piston 53 are arranged in parallel, and a cylinder block 5
5 and a cylinder head 56 coupled to the upper side of the cylinder 5. Further, the cylinder head 56 has a pair of intake ports 57a, 57b and a pair of exhaust ports 58a, 58b formed in a portion corresponding to the upper side of the piston 53, and the intake ports 57a, 58b are formed in the cylinder head 6. The exhaust port 58 is connected to an intake port (not shown) that opens on one side surface.
The a and 58b are connected to an exhaust port (not shown) that opens to the other side surface of the cylinder head 56.

A pair of intake valves 62a, 62b and exhaust valves 63a, 63b are inserted into the valve guides 60, 61 fixed to the cylinder head 56 so that the intake ports 57a, 57b and the exhaust ports 58a, 58b can be opened and closed. It is configured. Then, above the piston 53 and the intake port 57 and the exhaust port 58.
A combustion chamber 64 is formed by the portion surrounded by and.

In the following description, since the valve mechanism on the intake side and the valve mechanism on the exhaust side have almost the same structure, only the intake side will be described, and only the differences on the exhaust side will be described. To do.

That is, in FIG. 2, the intake valve 62 is
a and 62b of the flange portions 65a and 65b and the cylinder head 56
Valve springs 66a and 66b are provided between and, and the intake valves 62a and 62b are elastically urged upward (in the valve closing direction) in the figure by the valve springs 66a and 66b.

On the other hand, above the cylinder head 56, 1
A cam shaft 69 in which a pair of low speed cams 67a and 67b and a high speed cam 68 are fitted is rotatably arranged. The cam shaft 69 is connected to a crank shaft (not shown) via a timing belt (not shown).

The cams 67a, 67b, 68 and the intake valve 6
A valve mechanism 70 is interposed between the 2a and 62b.

FIG. 3 is a detailed view of the intake side valve operating mechanism (a view taken along the arrow (A-A) in FIG. 2), in which the high speed cam 68 and a pair of low speed cams are provided on the cam shaft 69 as described above. Cams 67a, 67
b and the cam shaft 69 are integrally fitted to the outside. Further, the rocker shaft 82 is disposed in parallel with the cam shaft 69, and a pair of drive rocker arms 83a and 83b and a free rocker arm 84 are pivotally supported on the rocker shaft 82. The cams 67a, 67b, 68 are capable of contacting the rocker arms 83a, 83b, 84, and the exhaust valves 63 are driven by the rotation of the cams 67a, 67b, 68.
Control the on-off valves a and 63b. Here, the low speed cam 6
The cam profile of one cam 67b of 7a and 67b is different from the cam profile of the other cam 67a,
The lift amount of the intake valve 63b is configured to be substantially zero.

However, the valve operating mechanism has a connection switching mechanism for switching the valve timing.

More specifically, as shown in FIG. 4, the connection switching mechanism 85 has a first switching pin 86 for connecting the first drive rocker arm 83a and the free rocker arm 84.
And the free rocker arm 84 and the second drive rocker arm 8
3b, a second switching pin 87, a restriction pin 88 for restricting the movement of the first and second switching pins 86, 87, and a resilient biasing force of these pins 86-88 toward the disconnection side. And a return spring 89 for

The first drive rocker arm 83a has a bottomed first open end on the free rocker arm 84 side.
Guide hole 90 is bored in parallel with the rocker shaft 82, and the first switching pin 86 is slidably fitted in the first guide hole 90, and the first switching pin 85 is connected to one end side of the first switching pin 85. First
A hydraulic chamber 91 is defined between the guide hole 90 and the closed end of the guide hole 90. Further, a passage 92 communicating with the hydraulic chamber 91 is provided through the first drive rocker arm 83a, and an oil supply passage 93 is provided on the rocker shaft 82. The oil supply passage 93 always communicates with the hydraulic chamber 91 via the passage 92 regardless of the swinging state of the first drive rocker arm 83a.

The free rocker arm 84 has a guide hole 94 facing the first guide hole 90.
A second switching pin 87, which is provided so as to extend between both side surfaces of the first and second ends and is capable of abutting against the first switching pin 86, is slidably fitted in the guide hole 94. .

The second drive rocker arm 83b has a second guide hole 95 penetrating in parallel with the rocker shaft 82 at a position facing the guide hole 94, and the other end of the second switching pin 87. A disc-shaped restricting pin 88 that abuts on is slidably fitted in the second guide hole 95. Further, a guide tube 96 is fitted to the other end of the second guide hole 95,
A shaft portion 97 slidably fitted in the guide cylinder 96 is provided on the restriction pin 98 so as to project. Further, the return spring 89 is contracted between the guide tube 96 and the restriction pin 88, and the return spring 89 elastically urges the pins 86 to 88 toward the hydraulic chamber 91 (disconnection).

In the connection switching mechanism 85 thus constructed, the hydraulic pressure in the hydraulic chamber 91 becomes higher, so that the first switching pin 86 slides toward the guide hole 94 (to the right in the figure). The second switching pin 87 has the second guide hole 9
Sliding to the 5 side (right side in the figure), each rocker arm 83
a, 83b, 84 are connected. Further, when the hydraulic pressure in the hydraulic chamber 91 becomes low, one end of the first switching pin 86 is on the side of the first guide hole 90 due to the elastic urging force of the return spring 89 toward the hydraulic chamber 91 side (left side in the drawing). The second switching pin 87 is accommodated in the guide hole 94 while being in contact with the portion, and the connected state of the rocker arms 83a, 83b, 84 is released.

The oil supply passage 93 in the rocker shaft 82 is also used.
Is connected to an oil pump 74 via a switching valve 72, and the switching operation of the switching valve 72 raises or lowers the hydraulic pressure in the oil supply passage 93, and thus the hydraulic pressure in the hydraulic chamber 91 of the connection switching mechanism 85. Can be switched. This switching valve 72 is a solenoid valve 71.
The switching operation of the switching valve 72 is performed by the ECU.
5 is controlled via a solenoid valve 71.

The intake side valve operating mechanism of the engine 1 configured as described above operates as follows.

When the valve opening command signal is output from the ECU 5 to the solenoid valve 71, the solenoid valve 71 is opened, the switching valve 72 is opened, and the oil pressure in the oil supply passage 93 is increased. As a result, the connection switching mechanism 85 operates and each rocker arm 8
3a, 83b, 84 are in the connected state, and the high speed cam 68
As a result, the rocker arms 83a, 83b, 84 operate integrally (FIG. 3 shows this state), and the pair of intake valves 62a, 62b cause the valve opening period and the high-speed valve timing with a relatively large lift amount. Open and close with.

On the other hand, when the ECU 5 outputs a valve closing command signal to the electromagnetic valve 71, the electromagnetic valve 71 and the switching valve 72 are closed, and the oil pressure in the oil supply passage 93 is lowered. as a result,
The connection switching mechanism operates reversely to the above, and each rocker arm 8
The connection state of 3a, 83b, 84 is released (FIG. 4 shows this state), the corresponding rocker arms 83a, 83b are actuated by the low speed cams 67a, 67b, respectively.
One intake valve 62a operates at the low valve timing with the valve opening period and the lift amount relatively small, and the other intake valve 6a
2b is almost dormant. In this way, when the low speed valve timing is selected, a swirl is generated in the cylinder by stopping the valve so that good combustion can be obtained even with an air-fuel ratio leaner than the theoretical air-fuel ratio. The almost idle state is a state in which fuel is operating with a slight lift amount to prevent the fuel from accumulating in the vicinity of the intake valve 67b.

In the exhaust side valve operating mechanism, the cam profiles of the pair of low speed cams have the same shape.
When the low speed valve timing is selected, a pair of exhaust valves 63a,
63b operates at a low valve timing with the valve opening period and the lift amount relatively small. The other points are the same as those of the intake valve side valve operating mechanism.

Next, the arrangement of the pair of fuel injection valves 6a and 6b will be described with reference to FIGS. FIG. 7 shows C- of FIG.
It is a C line arrow line view.

As is clear from these figures, the fuel injection valves 6a and 6b are provided slightly upstream of the intake ports 57a and 57b, respectively, at positions facing them, and the injection valves 6a and 6b are Intake ports 57 facing each other
It is arranged so as to inject fuel toward a and 57b.

FIG. 7 shows the fuel injection valve 6 when the air-fuel ratio A / F is constant (however, leaner than the stoichiometric air-fuel ratio).
It is a figure which shows the relationship between the fuel distribution rate of a and 6b, and the fluctuation rate of NOx generation amount and Pmi (illustrated average effective cylinder pressure).
Here, the distribution ratio of the injection valve 6a facing the intake valve 62a that operates when the low speed valve timing is selected is defined as the operation-side distribution ratio B. Therefore, the distribution ratio of the injection valve 6b is (1-
B).

As is clear from this figure, the control range (B
= 60% to 85%), if the distribution rate B is decreased, the Pmi fluctuation rate is decreased. That is, the combustion state in the cylinder is improved. Moreover, within this range, NOx
The increase in emissions is slight. Focusing on this point, the present invention controls the fuel state by changing the distribution ratio B while keeping the air-fuel ratio A / F constant.

The control method of the distribution ratio B will be described below with reference to FIG.

FIG. 8 is a fuel supply control (lean burn control) in which the air-fuel ratio on the lean side of the theoretical air-fuel ratio is used as the target air-fuel ratio.
6 is a flowchart showing a procedure of fuel distribution rate control of the fuel injection valves 6a and 6b in the case of performing.

In step S1 of the figure, the operating state is confirmed. Here, in particular, the engine speed NE, the intake pipe absolute pressure PBA, and the air-fuel ratio A / F detected by the O ₂ sensor 13 are read. Next, it is determined whether or not the A / F value matches the target value (step S2), and if they do not match, the TI value is corrected using the above equation (1) to determine the A / F value. Control to match the target value is performed (step S3).

When the air-fuel ratio A / F matches the target value, it is judged whether the engine 1 is in the lean burn operation region (step S4). If it is not in the lean burn operation region, this processing is immediately performed. To finish. When in the lean burn operation region, the coefficient X is read from the map set according to the engine speed NE and the intake pipe absolute pressure PBA (step S5). This coefficient X is NE value and PBA
It is set to a predetermined value (for example, 1.02) larger than 1 according to the value, and is used for calculating the operating side distribution ratio B in step S11 or step S13 described later.

In the following step S6, the engine speed N
The operating side distribution ratio B is read from the map set in accordance with E and the intake pipe absolute pressure PBA, and in step S7,
Similarly, the upper limit S and the lower limit T of the distribution ratio B are set to the NE value and the P
Read from the map set according to the BA value. Here, the upper and lower limit values S and T are the steps S11 and S13 described later.
The upper and lower limits of the range (corresponding to the “control range” in FIG. 7) in which the distribution ratio B in FIG.

In step S8, it is determined whether or not the combustion state of the cylinder to which fuel is to be injected has deteriorated. This determination is performed, for example, by determining whether the combustion roughness value RN calculated based on the detection value of the ion current sensor 19 is smaller than a predetermined value as described later.

When the combustion state has not deteriorated, it is determined whether the distribution ratio B read in step S6 is smaller than the upper limit S read in step S7 (step S1).
0) and B <S are satisfied, the distribution ratio B is corrected by the following equation (step S13). B = B × X Since X> 1.0 as described above, the B value is gradually increased by this correction. When the combustion state has not deteriorated, the operating side distribution ratio B is gradually increased.

On the other hand, when B ≧ S is satisfied in step S10, the B value read in step S6 is set as the distribution rate B (step S12).

When it is determined in step S8 that the combustion state has deteriorated, it is determined whether the distribution ratio B is larger than the lower limit value T (step S9). When B> T is satisfied, the distribution ratio B is corrected by the following equation (step S11).

B = B / (nX) Here, n is a predetermined integer of 2 or more. By this correction, the B value is greatly reduced, and the deteriorated combustion state is immediately improved.

On the other hand, when B≤T is satisfied in step S9, the process proceeds to step S12.

After execution of steps S11 to S13, the map is updated with the latest distribution ratio B (step S14), and this processing ends. By this updating process, the map of the distribution ratio B is constantly updated to the latest value, so that the distribution ratio B is controlled so as to gradually increase by repeatedly executing, for example, step S13 in almost the same operating condition. It

As described above, according to the method of FIG. 8, since the operating side distribution ratio B of the fuel injection amount is controlled according to the combustion state of the engine, the air-fuel ratio A / F is changed to control the combustion state. It is possible to stabilize the combustion state without causing a torque fluctuation and a large increase in the NOx emission amount unlike the conventional method.

FIG. 9 shows the air-fuel ratio A / F (lean side from the theoretical air-fuel ratio) and BMEP (net mean effective pressure) representing the engine output (FIG. 9A), Pmi fluctuation rate (FIG. 9B).
And a NOx emission amount ((c) in the same figure). In these figures, a solid line, a broken line, and a dashed-dotted line correspond to small, medium, and large engine loads (outputs), respectively. See a)).

Referring to these figures, if the air-fuel ratio A / F is changed in the rich direction, the Pmi fluctuation rate decreases and the combustion state of the engine improves, but at the same time the BMEP increases and the drivability is impaired. It can be seen that the NOx emission amount increases. According to this embodiment, the combustion state is improved by changing the fuel distribution ratio while keeping the air-fuel ratio A / F constant, and it is possible to avoid the above-mentioned inconvenience caused by changing the air-fuel ratio.

Next, a method of calculating the combustion roughness value RN based on the detection value of the ion current sensor 19 will be described with reference to FIGS.

FIG. 10 shows a drive circuit 17 for the spark plug 16.
3 is a diagram showing the configuration of an ion current sensor 19;

In the figure, the power supply terminal T1 to which the power supply voltage VB is supplied has a primary coil 172a and a secondary coil 1
72b is connected to the ignition coil 172.
The primary coil 172a and the secondary coil 172b are connected to each other at one end thereof, the other end of the primary coil 172a is connected to the collector of the transistor 173, the base of the transistor 173 is connected to the ECU 5, and its emitter is grounded. ing. At the base of the transistor 172,
The ignition command signal A is supplied from the ECU 5. The other end of the secondary coil 172b is connected to the center electrode 16a of the spark plug 16 via a diode 174, and the ground electrode 16b of the spark plug 16 is grounded.

The center electrode 16a of the spark plug 16 is grounded via the diode 191, the resistor 192 and the power supply circuit 193, and the voltage sensor 194 for detecting the voltage across the resistor 192 is connected to the center electrode 16a. Power supply circuit 193
Is connected to the ECU 5 and supplies a predetermined voltage near the ignition timing in each cycle of the engine to the spark plug 1.
6 to the center electrode 16a. The diode 191, the power supply circuit 193, the resistor 192, and the voltage sensor 194 constitute an ion current sensor 19 that detects an ion current flowing between the electrodes of the spark plug 16, and a detection signal of the voltage sensor 194 is supplied to the ECU 5.

Spark plug 1 according to a command from ECU 5
When 6 ignites the air-fuel mixture in the combustion chamber of the engine, the air-fuel mixture is sufficiently ionized if the combustion state is normal. Therefore, the center electrode 16a and the ground electrode 16 of the spark plug 16 are
A large ion current flows from the power supply circuit 193 between the points b and the voltage across the resistor 192 detected by the voltage sensor 194 increases. On the other hand, if the combustion state is bad due to misfire or the like, the air-fuel mixture is not sufficiently ionized, so that the ionic current flowing between the center electrode 16a and the ground electrode 16b of the spark plug 16 becomes small, and the voltage detected by the voltage sensor 194 becomes Get smaller. The voltage value detected by the voltage sensor 194 is detected a plurality of times corresponding to a plurality of crank angles near the ignition timing. In this way, the ionic current that changes depending on whether the combustion state of the air-fuel mixture is good or bad is detected by the voltage sensor 194 for each cycle, and the combustion roughness value RN described later is calculated based on this detected current value, and the combustion is performed. The state is determined.

FIG. 11 is a flow chart showing the procedure for calculating the combustion roughness value RN based on the detected current value.

First, in step S21, the engine speed NE and the intake pipe absolute pressure PBA, which are parameters indicating the operating state of the engine 1, are read. Next, step S
The coefficient K is calculated from the map using the NE value and the PBA value at 22.
(Θ) is read. As shown in FIG. 12, the current value I
C (θ) is a predetermined crank angle θ near the ignition timing
Corresponding to _{1 to} θ ₆ , a plurality of current values IC _{1 to} IC ₆ are detected, and the map of the coefficient K (θ) is also the crank angle θ ₁
It is set corresponding to each of ~ ₆ .

Then, in step S24, a plurality of current values IC _{1 to} IC corresponding to the crank angles θ _{1 to} θ ₆ are obtained.
₆ and a plurality of coefficients K ₁ to corresponding to the respective crank angles θ _{1 to} θ ₆
Based on K ₆ and the following equation (3), the indicated mean effective pressure Pm
The correlation value HPmi of i is calculated.

HPmi = K ₁ IC ₁ + K ₂ IC ₂ + ... + K ₆ IC ₆ (3) Subsequently, in step S 25, the correlation value HPmi for each cylinder and each cycle is stored, and in step S 26, the correlation value HPmi is stored. The combustion roughness value RN is calculated based on HPmi using, for example, the following equation (4).

Equation (4) is the correlation value HP in N cycles.
The standard deviation of mi is obtained as the combustion roughness value RN. Here, HPmiav is an average value of correlation values HPmi in N cycles.

[0077]

[Equation 1] Next, a method of controlling the ignition timing of the engine 1 according to the combustion roughness value RN calculated for each cylinder will be described based on the flowchart of FIG.

First, in step S35, the current value RN (n) of the combustion roughness value is compared with the previous value RN (n-1), and the answer is negative (NO) and the current value RN (n).
Is increasing from the previous time, that is, when the combustion state is deteriorating, the process proceeds to step S36. If the previous ignition timing is ahead of the reference ignition timing in step S36, the ignition timing is retarded in step S37, and conversely, the ignition timing is retarded in step S36, step S3.
8 to thereby advance the combustion roughness value RN (n).
Can be reduced to improve the combustion state.

On the other hand, the answer in step S35 is affirmative (YE
S), and if RN (n) of this time is smaller than that of the previous time, that is, if the combustion state is improving, the process proceeds to step S39. If RN (n) is equal to or less than the predetermined value in step S39, it is determined that a sufficiently good combustion state is obtained, and the ignition timing is fixed in step S40. If RN (n) is larger than the predetermined value in step S39 and the previous ignition timing is advanced in step S41, the ignition timing is further advanced in step S42, and conversely the step is performed. If retarded in S41, further retarded in step S43, whereby the combustion roughness value RN (n) can be reduced and the combustion state can be improved.

Further, it is desirable to control the fuel injection timing by the combustion injection valves 6a and 6b according to the combustion roughness value RN. For example, when the RN value tends to increase, the injection timing is controlled so as to gradually advance. . This can further stabilize the combustion state and improve drivability.

The present invention is not limited to the above-described embodiment, but various modifications can be made. For example, instead of the ion current at the time of ignition, the secondary side voltage (ignition voltage) of the ignition coil may be detected, and the combustion state of the engine may be detected based on the period when the ignition voltage exceeds a predetermined voltage value. Good.

Further, one fuel injection valve may be used so that the injection direction can be changed, and the combustion distribution ratio for the two intake ports may be changed.

[0083]

As described in detail above, according to the present invention, the distribution ratio of the amount of fuel flowing into the cylinders from a plurality of intake valves is controlled in accordance with the detected engine combustion state. During control, it is possible to stabilize the combustion state while preventing torque fluctuation, and improve the drivability of the engine.

Further, since at least one of the combustion injection timing and the ignition timing is controlled according to the detected engine combustion state, it is possible to further improve the drivability.

[Brief description of drawings]

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

FIG. 2 is a sectional view of a main part of an internal combustion engine.

FIG. 3 is a view on arrow (A-A) in FIG.

FIG. 4 is a (BB) arrow view of FIG. 3;

FIG. 5 is a diagram showing an arrangement of fuel injection valves.

FIG. 6 is a view taken along the line (C-C) of FIG.

FIG. 7 is a diagram showing a relationship between a fuel distribution rate, a NOx generation amount, and a Pmi variation rate.

FIG. 8 is a flowchart showing a procedure of fuel distribution rate control.

FIG. 9: Air-fuel ratio (A / F) and net mean effective pressure (BME
It is a figure which shows the relationship between P), a Pmi fluctuation rate, and the NOx generation amount.

FIG. 10 is a diagram showing a configuration of an ignition plug drive circuit and an ion current sensor.

FIG. 11 is a flowchart showing a procedure for calculating a combustion roughness value.

FIG. 12 is a diagram showing a transition of an ion current value (IC).

[Explanation of symbols]

 1 Internal Combustion Engine 5 Electronic Control Unit (ECU) 6 Fuel Injection Valve 7 Intake Pipe Absolute Pressure Sensor 11 TDC Sensor 12 Crank Angle Sensor 16 Spark Plug 19 Ion Current Sensor 40 Valve Timing Switching Mechanism

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[Procedure amendment]

[Submission date] June 9, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Added

[Correction content]

[Brief description of drawings]

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

FIG. 2 is a sectional view of a main part of an internal combustion engine.

FIG. 3 is a view on arrow (A-A) in FIG.

FIG. 4 is a (BB) arrow view of FIG. 3;

FIG. 5 is a diagram showing an arrangement of fuel injection valves.

FIG. 6 is a view taken along the line (C-C) of FIG.

FIG. 7 is a diagram showing a relationship between a fuel distribution rate, a NOx generation amount, and a Pmi variation rate.

FIG. 8 is a flowchart showing a procedure of fuel distribution rate control.

FIG. 9: Air-fuel ratio (A / F) and net mean effective pressure (BME
It is a figure which shows the relationship between P), a Pmi fluctuation rate, and the NOx generation amount.

FIG. 10 is a diagram showing a configuration of an ignition plug drive circuit and an ion current sensor.

FIG. 11 is a flowchart showing a procedure for calculating a combustion roughness value.

FIG. 12 is a diagram showing a transition of an ion current value (IC).

FIG. 13 is a flowchart showing a procedure of ignition timing control.
is there.

[Description of Reference Signs] 1 internal combustion engine 5 electronic control unit (ECU) 6 fuel injection valve 7 intake pipe absolute pressure sensor 11 TDC sensor 12 crank angle sensor 16 ignition plug 19 ion current sensor 40 valve timing switching mechanism

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display location F02D 41/04 335 B 43/00 301 B J 45/00 368 Z F02M 69/00 360 G F02P 5 / 15

Claims (2)

[Claims] 1. An operating state detecting means for detecting an operating state of an internal combustion engine in which a plurality of intake valves are provided for each cylinder, and a distribution rate of the amount of fuel flowing into the cylinders from each of the plurality of intake valves. In a control device for an internal combustion engine, comprising: a fuel distribution rate changing means for changing the fuel consumption rate and a combustion state detecting means for detecting a combustion state for each cylinder, a fuel distribution system for controlling the distribution rate according to the detected combustion state. A control device for an internal combustion engine, characterized in that a rate control means is provided. 2. The timing control means for controlling at least one of fuel injection timing and ignition timing in accordance with the detected combustion state is further provided.
A control device for an internal combustion engine as described.