JPH06101518A - Combustion control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To improve quality of air-fuel ratio, thereby stabilize combustion condition, and widen a lean-burn range in a lean-burn system. CONSTITUTION:A combustion condition detecting means detects a combustion condition of an internal combustion engine. A combustion condition judging means judges whether or nor the combustion condition is within an allowable range based on roughness of the internal combustion engine, receiving an output from the combustion condition detecting means. Quality of air-fuel ratio is managed so as to keep a satisfactory condition according to the judgment of the combustion condition judging means by means of an air-fuel ratio quality managing means. It is thus possible to obtain stability without affecting fuel consumption performance and exhaust gas performance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion control device for an internal combustion engine which employs a lean burn system.

[0002]

2. Description of the Related Art Air-fuel ratio, fuel consumption rate, surge torque in a typical lean burn engine
FIG. 13 shows the relationship between (magnitude of combustion fluctuation) and exhaust gas performance (NO _x purification rate). As can be seen from FIG. 13, by increasing the air-fuel ratio, that is, by leaning the air-fuel mixture, NO
_X is greatly reduced and fuel consumption is improved by around 10%. But,
If it is made leaner, the fuel consumption is improved, but combustion becomes unstable, surge torque (combustion fluctuation) increases, and smooth rotational motility deteriorates. Therefore, in the lean burn system, it is common knowledge to set the air-fuel ratio immediately before the surge torque deteriorates.

However, there is a problem that the set air-fuel ratio becomes larger than the set air-fuel ratio due to variations in the performance of the components such as the fuel injection valve, the air flow sensor, the air-fuel ratio sensor, etc. and the deterioration over time, which impairs drivability. It was Therefore, the combustion fluctuation amount is detected, and the air-fuel ratio feedback means controls the air-fuel ratio to the rich side when the fluctuation amount is larger than a predetermined value, and controls the air-fuel ratio to the lean side when the fluctuation amount is smaller than the predetermined value. What is done is disclosed in, for example, JP-A-60-13938.

[0004]

However, in the prior art as described above, since the air-fuel ratio feedback means controls the air-fuel ratio to the rich side in order to reduce the fluctuation of combustion, the fuel consumption and exhaust gas performance are impaired. However, there is a problem that the lean operation range cannot be expanded because the control is performed only on the air-fuel ratio.

The present invention has been made in view of the above problems, and an object thereof is to improve the quality of the air-fuel mixture to stabilize the fluctuation of combustion and expand the lean burn region. A combustion control device for an internal combustion engine is provided. Here, a good mixture quality is
(i) A good mixture of fuel and air in the cylinder,
And (ii) the distribution of the air-fuel mixture in the cylinder is good.

[0006]

In order to achieve the above object, the combustion control system for an internal combustion engine according to the present invention basically detects the roughness of the internal combustion engine in a lean burn system, and The feature is that the quality of the air-fuel mixture is controlled accordingly. Then, as a more specific example, the combustion state detecting means for detecting the combustion state of the internal combustion engine and the combustion state within the allowable range depending on the roughness of the internal combustion engine receiving the output from the combustion state detecting means. And a combustion state determining means for determining whether or not the mixture is present, and a mixture quality control means for controlling the quality of the mixture to a good state according to the determination result of the combustion state determining means. Can be mentioned.

As means for controlling the quality of the air-fuel mixture, the control amount detecting means for controlling various combustion states and the optimum control amounts for the respective actuators are in order from the one having the largest deviation. It is characterized by comprising a priority determining means of a controlled variable operation actuator for determining a priority as a controlled object, a controlled variable changing means for changing a controlled amount of the actuator, and a combustion state evaluating means for changing the controlled amount. And the ones mentioned.

Further, at least one of the ignition timing, the intake air amount, the fuel flow rate, the fuel particle size, the fuel injection timing, the swirl control valve opening degree, and the EGR amount is controlled by the air-fuel mixture quality control means. There is a feature.

[0009]

When the combustion state of the internal combustion engine is detected by the combustion state detection means at a predetermined lean air-fuel ratio and the signal is input and the combustion state determination means determines that the combustion state is outside the allowable range, the mixing is performed. The air quality control means selects the actuator that most effectively improves the air-fuel mixture quality according to the operating state at each time, and the combustion state is allowed while controlling the amount of control to the actuator while monitoring the trend of the combustion state. It is changed so that it falls within the range.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A combustion control system according to an embodiment of the present invention will be described in detail below with reference to the illustrated embodiment. First,
The overall configuration of the combustion control device for an internal combustion engine according to the present invention will be described. FIG. 1 is an overall system diagram when a combustion control device for an internal combustion engine according to the present invention is used in a 4-cylinder engine, and FIG. 2 is an example of a block diagram showing its input / output specifications.

On the intake side of the air cleaner 1 to the engine, an air flow sensor 2 for detecting the mass (flow rate) of the intake air filtered by the air cleaner 1 into the engine is provided. This intake air volume is ECM (Electronic Con
ISC controlled by control signal 204 from control module 27
(Idle Speed Control) Determined by the opening of the valve 10 and the opening of the slot valve, and the control signals are E as the signal value 107 of the throttle sensor 3 and the signal value 102 of the idle switch.
Output to CM27. An intake air temperature sensor 30 that detects the intake air temperature is provided in the intake pipe, and the detected value 110 is output to the ECM 27.

At the engine inlet of the intake pipe, a swirl control controlled by a control signal 208 of ECM27
A valve (hereinafter referred to as SCV) 20 is provided, and in the swirl control valve 20, intake air is formed into an air flow (swirl) that forms a lateral vortex and is sucked into the cylinder. This swirl amount is determined by the opening degree of the swirl control valve 20. That is, SCV is 2
It is attached to one side of the divided intake pipe, and SCV opens in the high speed rotation range to send more air into the cylinder. On the other hand, in the low speed rotation range where the intake air amount is small,
By closing the SCV, the intake speed is increased and the swirl generated in the combustion chamber is strengthened, and this air flow mixes with the fuel injected from the injector 4,
Make a rich mixture and swirl center (spark plug 5
It is designed to create a spark that is easy to ignite.

An injector 4 for injecting fuel is provided near the engine inlet of the intake pipe, and a fuel pump 11 for discharging the injection supply fuel to the injector 4 is installed in a fuel tank (not shown). Further, the injector 4 and the fuel pump 11 are connected by a pipe, and a fuel property sensor 12 is provided at an intermediate portion of the pipe. On the other hand, the injector 4 has an air cut valve 6
, And the air cut valve 6 is connected to the solenoid 9. The air sent from the air cut valve 6 collides with the fuel to promote atomization of the fuel.

The amount of air to the air cut valve 6 is ECM27.
Is determined by the solenoid valve 9 by a control signal 206 from On the other hand, the fuel injection amount 201 is the value 10 detected by the water temperature sensor 31 that detects the cooling water temperature of the engine.
5, the value 100 detected by the air flow sensor 2, the value 101 detected by the crank angle sensor 32, the value 111 detected by the fuel property sensor 12, and the like are calculated and determined by the ECM 27.

A spark plug 5 is provided above the cylinder, and the spark plug 5 guides the high-voltage electric energy generated in the ignition coil by the control unit 202 from the ECM 27 to ignite the air-fuel mixture sucked into the cylinder. It is designed to explode, burn, and be discharged through an exhaust valve. A knock sensor 29 is provided in the cylinder block of the engine. During ignition, the knock sensor 29 detects knocking due to abnormal combustion and outputs a detected amount 108 to the ECM 27. The burned mixture becomes exhaust gas and is discharged.

EGR (Exhaust Gas Recirculation) valve 7 and E controlled by control signal 209 of ECM 27
A communication passage communicating from the exhaust manifold to the intake manifold is provided via the GR control valve 8, whereby a part of the exhaust gas discharged is recirculated to the intake pipe, and the exhaust gas which is an inert gas is mixed with the intake mixed gas. Nitrogen oxides sucked into the cylinder and generated during high temperature combustion are suppressed. The pressure sensor 28 detects the pressure in the intake pipe for controlling the EGR amount, and the detected value 109 is output to the ECM 27.

An O ₂ sensor 1 is provided upstream of the manifold catalyst 17.
9 is attached, and the O ₂ sensor 19 detects the combustion state and the catalyst state occurring in the cylinder from the O ₂ concentration contained in the exhaust gas. The number of O ₂ sensors is one or more, and an A / F sensor can be substituted. O ₂ sensor 19
When is activated, feedback control is performed based on the detected value 104.

A secondary air pump 13 for supplying secondary air is provided downstream of the EGR intake position.
The secondary air amount is VC by the control signal 207 from ECM27.
It is controlled by the cut solenoid valve 16 and adjusted by the air cut valve 14. The check valve 15 prevents the backflow of the exhaust gas, and the drive of the secondary air pump 13 is output by the control signal 205 from the ECM 27. The exhaust gas mixed with the secondary air is reduced in hydrocarbons and carbon monoxide due to the thermal reactor effect.

Further, downstream of the manifold catalyst 17,
Three-way catalyst or NO _X catalyst or a main catalyst composed of the two, is provided. 3, 4, and 5 show the configuration of the present invention. 3 is an overall configuration diagram showing an embodiment of a combustion control device according to the present invention, FIG. 4 is a detailed diagram of a mixture quality control means, and FIG. 5 is a detailed diagram of a combustion state detection means and a combustion state determination means. .

In FIG. 3, in the basic control, the air amount changes according to the amount of depression of the accelerator, and the electronically controlled fuel injection device detects the air amount and injects the fuel amount corresponding to the air amount. Thus, the torque control is performed by controlling the air amount in this way.
In this way, the exhaust gas discharged from the engine is feedback-controlled so that the exhaust gas has a predetermined air-fuel ratio by the air-fuel ratio detecting means such as the A / F sensor and the O ₂ sensor.

Rotational fluctuations from the engine are detected by a combustion state detecting means including, for example, an in-cylinder pressure sensor, a knock sensor, or a crank angle sensor, and the detection signal is used to determine the degree of roughness of the internal combustion engine. Input to the means to determine whether the combustion state is as expected. Then, according to the result of the combustion state determination means, if the combustion state is bad, the optimum actuator for effectively improving the quality of the air-fuel mixture is selected, and the actuator is monitored while monitoring the trend of the combustion state. The quality of the air-fuel mixture is controlled by the air-fuel mixture quality control means for changing the control amount of. Control targets for managing this air-fuel mixture include ignition timing, intake air amount, fuel flow rate, fuel particle size (assist air amount), injection timing, SCV opening, and EGR amount. In addition, the assist air means air for blowing the air to the injector so as to make the fuel injected from the injector finer.

FIG. 4 shows details of the air-fuel mixture quality control means shown in FIG. Control quantity detection means for various actuators that influence the quality of the air-fuel mixture, priority control means for the control quantity operation actuator to improve the quality of the air-fuel mixture effectively according to the operating state at that time, optimal control quantity It is composed of a storage unit, a control amount changing unit, and a combustion state evaluation unit for control change for evaluating how the combustion state changes as a result of changing the control amount.

The control amount detecting means for the various actuators is a valve for controlling the assist air amount, or an SCV.
It detects the control amount of various actuators such as valves that control valves and EGR valves. Next, the priority determination means of the control amount operation actuator reads the deviation from the optimum control amount that each actuator should have, which is output from the optimum control amount storage means of various actuators, and the deviation from the largest one is in order. Control in the optimal direction.

Subsequently, the control amount changing means is used to change various actuators, and the combustion state evaluating means for changing the control amount changes the control amount, while considering how the combustion state changes. To change. FIG. 5 shows details of the combustion state detection means and the combustion state determination means of FIG.

In FIG. 5, when the combustion state (combustion pressure of each cylinder) is detected by the in-cylinder pressure sensor, peak values appear in the order of 1, 3, 4, 2, 1 ... For four cylinders.
As the air-fuel ratio is increased (lean combustion of the air-fuel mixture), the combustion state deteriorates, so the peak value changes. This signal is taken in by the waveform processing means and integrated to calculate the work of intake, compression, explosion and exhaust of each cylinder. Next, the analog output circuit outputs a rectangular wave, the combustion state processing means obtains the indicated mean effective pressure for each cylinder, and the magnitude of the combustion fluctuation is calculated. Then, the combustion state determination means looks at the calculation result, and it is determined that the combustion state is bad if it touches the allowable value or more and that the combustion state is good if it is less than the allowable value.

FIG. 6 shows an embodiment of the present invention in which the swirl control valve is controlled to improve the quality of the air-fuel mixture. In FIG. 6, the intake air amount Qa and the engine speed Ne are set to λ = 1.4 (lean burn region), and
Input into the map of the basic fuel injection amount Tp at λ = 1.0 (theoretical air-fuel ratio), and from the output and the air-fuel ratio A / F signal,
Air-fuel ratio feedback control is performed by PI (proportional + integral) control and PID (proportional + integral + derivative) control, respectively. Next, based on the λ = 1.0 / 1.4 switching map, Qa
/ Ne (corresponding to the basic fuel injection amount Tp) and the relationship between Ne and the current region on the map are determined, whereby λ =
The basic fuel injection amount Tp corresponding to 1.0 or 1.4 is switched, and the air intake amount Qψ signal for that is input to the engine. The intake air amount Qa during acceleration or deceleration
A transient compensation block is provided for compensating for the delay or lead of. For example, during acceleration, a delay such as a detection delay or a capture delay occurs, but this transient compensation compensates for the delay.

Next, the combustion fluctuation of the engine is detected by the roughness detecting means. The roughness state is detected by the roughness detecting means by directly detecting the combustion state with a cylinder pressure sensor or a knock sensor. Whether the detected value of the surge torque by the roughness detecting means is 0.1 kg · m or less is determined by the next combustion state determining means. Surge torque is 0.1kg ・ m
In the above case, the vehicle is fluctuated in the front-rear direction and the driver feels uncomfortable. Therefore, the opening degree of the SCV is corrected by the air-fuel mixture quality control means so that the surge torque becomes smaller. In other words, the duty that is the basis of SCV is determined by inputting the intake air amount Qa and the engine speed Ne, and the SCV is determined according to the current state from the relationship between the duty and the surge torque and the swirl strength.
It is output so as to perform the correction control of.

The effects of swirl control and engine characteristics will be described with reference to FIGS. FIG. 7 shows the effect of swirl control. Opening the swirl control valve (SCV) indicates no swirl in each cylinder, and closing the SCV indicates swirl. It can be seen that when the SCV is closed, that is, swirl is applied, the point where the surge torque (combustion fluctuation) deteriorates moves to the lean side of the air-fuel ratio. FIG. 8 shows the relationship between the swirl control valve opening, the surge torque, and the fuel consumption rate. As can be seen from FIG. 8, at the SCV opening where the surge torque is the minimum, the fuel consumption rate is also the minimum. By the way, since the engine is a pump, if you throttle the swirl control valve to apply swirl,
It becomes resistance and the inside of the cylinder becomes negative pressure. As a result, extra work is forced on the piston, which causes pumping loss and deteriorates fuel efficiency. In this way, if you swirl too much, pumping loss will increase,
The SCV opening is set on the opening side of the SCV with respect to the minimum point of the surge torque.

FIG. 9 shows that when the combustion fluctuation is small at a predetermined air-fuel ratio, the air-fuel ratio is further shifted to the lean side,
It shows an example of expanding the lean burn region. The entire system circuit shown in FIG. 9 is provided in parallel with the system circuit of FIG. 6 in the air-fuel mixture quality control means shown in FIG. In the example shown below, the basic configuration is shown in FIG.
Since it is almost the same as that shown in FIG. 3, only the differences will be mainly described below.

In this embodiment, when the surge torque detection value by the roughness detecting means is 0.1 kg · m or less, the lean burn region (λ = λ) is corrected by correcting the target λ to the lean side of the predetermined λ. (Lean from 1.0) is expanded. FIG. 10 shows an embodiment in which a plurality of swirl control valves and EGR amounts are controlled in order to improve the quality of the air-fuel mixture.

In the present embodiment, as in the example shown in FIG. 6, basic duties such as SCV, EGR, air assist, etc. are determined in advance by inputting the intake air amount Qa and the engine speed Ne. , Surge torque and swirl strength, Surge torque and EGR amount, Surge torque and air assist amount are output to perform correction control of SCV, EGR amount, and air assist amount according to the current state. It is a thing. Figure 11 shows E
FIG. 12 shows the relationship between the GR amount and the surge torque, and FIG. 12 shows the relationship between the air assist amount (spray particle size) and the surge torque.

In FIG. 11, the surge torque deteriorates as the EGR amount increases. Usually EGR
The amount is set to the maximum amount at which the surge torque does not exceed 0.1 kg ・ m. In FIG. 12, when the air assist amount is increased, the spray particle size becomes finer accordingly, and the surge torque also decreases. However, if the particle size is made too small, the combustion speed decreases and the combustion state becomes unstable, so the surge torque deteriorates.

As is clear from the above description, the air-fuel ratio 22
Driving in the lean burn area, the NO _X decreases,
And, while the fuel consumption also improves, the surge torque gradually deteriorates from this point (see Fig. 13). Nevertheless, in order to maintain the air-fuel ratio around this, a method of adjusting the fuel amount is also known, but in the present invention, swirling is applied, the EGR amount is changed, and the air assist amount is changed. By using a method such as changing the particle size of the spray, the combustion state is improved and the air-fuel ratio is maintained in the lean burn state.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments, and various design changes can be made without departing from the present invention described in the claims. It is possible to For example, in the embodiment according to the present invention, in order to detect the roughness state,
An example of a method for directly detecting the combustion state with an in-cylinder pressure sensor or knock sensor is shown, but other methods such as estimating from the fluctuation of the engine speed or changing the torque of the drive system propeller shaft, etc. The estimation method is also effective.

[0035]

According to the present invention, even if the combustion changes at a predetermined lean air-fuel ratio, the quality of the air-fuel mixture is improved to cope with it. Since it does not need to be changed, it is possible to stabilize without compromising fuel economy and exhaust gas performance.

Further, since the quality of the air-fuel mixture can be improved, there is an effect that the lean burn region can be expanded.

[Brief description of drawings]

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

FIG. 2 is a circuit block diagram of a control unit of FIG.

FIG. 3 is an overall configuration diagram showing an embodiment of a combustion control device according to the present invention.

FIG. 4 is a functional block diagram of the present invention in FIG.

5 is a functional block diagram of the present invention in FIG.

FIG. 6 is an explanatory diagram showing a configuration of an embodiment of a combustion control device according to the present invention.

FIG. 7 is a diagram showing an effect of swirl.

[Fig. 8] Swirl control opening, surge torque,
It is a figure which shows the relationship of a fuel consumption rate.

FIG. 9 is a diagram showing the configuration of another embodiment of the combustion control device according to the present invention.

FIG. 10 is a diagram showing the configuration of another embodiment of the combustion control device according to the present invention.

FIG. 11 is a diagram showing a relationship between an EGR amount and a surge torque.

FIG. 12 is a diagram showing a relationship between an air assist amount and a surge torque.

FIG. 13 is a diagram showing a relationship between an air-fuel ratio and various engine performances.

[Explanation of symbols]

1 Air Cleaner 2 Air Flow Sensor 3 Throttle Sensor 4 Injector 5 Spark Plug 6 Air Cut Valve 7 EGR Valve 8 EGR Control Valve 9 Solenoid Valve 10 ISC Valve 11 Fuel Pump 12 Fuel Property Sensor 13 Secondary Air Pump 14 Air Cut Valve 15 Check Valve 16 VC cut solenoid valve 18 Main catalyst 19 O ₂ sensor (A / F sensor) 20 Swirl control valve 27 ECM (control unit) 28 Intake pressure sensor 29 Knock sensor 30 Intake temperature sensor 31 Water temperature sensor 32 Crank angle sensor

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Internal reference number FI Technical display location F02D 45/00 301 G 7536-3G 330 7536-3G 368 S 7536-3G F02M 25/07 550 FR NF02P 5/15 D (72) Inventor Toshimichi Minowa 4026, Kuji-cho, Hitachi-shi, Ibaraki Prefecture Hitachi Research Laboratory, Hitachi Co., Ltd.

Claims (4)

[Claims] 1. A combustion control device for an internal combustion engine, comprising: detecting a roughness of an internal combustion engine in a lean burn system; and controlling a quality of an air-fuel mixture according to the result. 2. A combustion state detecting means for detecting a combustion state of the internal combustion engine and an output from the combustion state detecting means are used to determine whether or not the combustion state is within an allowable range based on the roughness of the internal combustion engine. A combustion control device for an internal combustion engine, comprising: a combustion state determining means for controlling the combustion state, and a mixture quality control means for controlling the quality of the mixture in a good state according to the determination result of the combustion state determining means. 3. The quality control means for the air-fuel mixture, in order from a control amount detection means for controlling various combustion states of the various actuators, and an optimal control amount which the actuator should have, respectively. It is characterized by comprising a priority determining means of a controlled variable operation actuator for determining a priority as a controlled object, a controlled variable changing means for changing a controlled amount of the actuator, and a combustion state evaluating means for changing the controlled amount. The combustion control device for an internal combustion engine according to claim 2. 4. The control target of the air-fuel mixture quality control means is ignition timing, intake air amount, fuel flow rate, fuel particle size, fuel injection timing, swirl control valve opening,
The combustion control device for an internal combustion engine according to claim 2, wherein at least one of the EGR amounts is used.