JP2000008941A - Combustion state detection device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect a combustion state as well as fuel property in a short time in the area where the number of rotation of an engine just after starting is not stabilized, namely in an early stage after starting. SOLUTION: When a favorable combustion is compared with a rough combustion by a heavy quality fuel, a rapid increase in rotation speed is seen in either case, in the term from a start up to a complete explosion but at the dropping area of rotation speed thereafter, the rotation change rate in the rough combustion case is a vary bigger value than that of the favorable combustion. The increase of a rotation required time, namely the drop of the rotation speed between the last ignition cycle and a present ignition cycle is detected and the rotation change rate is found out. When this rotation change rate exceeds a judging base value, by judging that the combustion is deteriorated due to the heavy quality of a fuel property, the combustion state is detected immediately in the area just after starting, while removing the rapid increase area of rotation speed at the starting time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an apparatus for detecting a state of combustion in an internal combustion engine.

[0002]

2. Description of the Related Art Generally, when starting an internal combustion engine,
Because the intake air volume is small and the intake pipe pressure is unstable,
The amount of intake air cannot be accurately measured or estimated. Therefore, when starting, regardless of the amount of intake air,
The fuel injection amount is calculated based on the engine cooling water temperature. The fuel injection amount at the start is increased on the low temperature side because the fuel adhering to the wall surface is less likely to evaporate as the engine cools.

However, the amount of fuel adhering to the wall surface differs depending on the properties of the fuel even at the same engine coolant temperature. That is, in the case of a heavy fuel having poor volatility, it is difficult to vaporize, and therefore, it is easily attached to the wall surface. On the other hand, in the case of light fuel with good volatility, it is easy to vaporize,
Therefore, it does not easily adhere to the wall surface. Therefore, when starting the engine, it is preferable to perform fuel injection control that reflects fuel properties.

[0004] The simplest method for detecting the fuel property is to directly detect the fuel in the fuel tank, but such a direct method is not practical. for that reason,
For example, as disclosed in Japanese Patent Application Laid-Open No. 8-284708, there is known an apparatus for detecting a combustion state and, consequently, a fuel property based on engine speed fluctuations.

[0005]

In the above-mentioned prior art apparatus, detection of rotation fluctuation, that is, combustion state, is started after a predetermined time elapses after the engine starts and the engine rotation reaches a stable state, that is, an idling steady state. ing. However, the difference in the combustion state due to the fuel property appears remarkably immediately after starting, whereas the conventional method has a problem that it takes too much time to detect the fuel, and the correction of the fuel injection amount is delayed.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide an internal combustion system capable of detecting a combustion state in an early stage, that is, in a region in which engine rotation is not stable immediately after starting. An object of the present invention is to provide a combustion state detecting device for an engine.

[0007]

According to the present invention, a change rate of the engine speed for each ignition cycle when the engine speed is decreasing is calculated from the time when the engine is started. A combustion state of the internal combustion engine, comprising: a fluctuation rate calculating means to be started; and a combustion state determining means for determining that combustion has deteriorated when the fluctuation rate calculated by the fluctuation rate calculating means exceeds a predetermined determination reference value. A detection device is provided.

According to the present invention, when the combustion state determining means determines that the combustion has deteriorated, it is determined that the fuel property is heavy.

Further, according to the present invention, the determination reference value is changed according to the throttle opening and the elapsed time after starting.

[0010]

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

FIG. 1 is an overall schematic diagram of an electronically controlled internal combustion engine provided with a combustion state detecting device according to one embodiment of the present invention. The internal combustion engine 1 is an in-line 4-cylinder 4-stroke cycle reciprocating gasoline engine mounted on a vehicle. Institution 1
A cylinder block 2 and a cylinder head 3 are provided. In the cylinder block 2, four cylinders 4 extending in the vertical direction are arranged in parallel in the thickness direction of the paper.
The piston 5 is accommodated therein so as to be able to reciprocate. Each piston 5 is connected to a common crankshaft 7 via a connecting rod 6. The reciprocating motion of each piston 5 is converted into a rotational motion of a crankshaft 7 via a connecting rod 6.

A combustion chamber 8 is provided between the cylinder block 2 and the cylinder head 3 above each piston 5. The cylinder head 3 is provided with an intake port 9 and an exhaust port 10 for communicating both outer surfaces thereof with the respective combustion chambers 8. In order to open and close these ports 9 and 10, an intake valve 11 and an exhaust valve 12 are supported on the cylinder head 3 so as to be able to reciprocate substantially vertically. In the cylinder head 3,
Above the valves 11 and 12, an intake camshaft 13 and an exhaust camshaft 14 are rotatably provided, respectively. Cams 15 and 16 for driving the valves 11 and 12 are attached to the camshafts 13 and 14, respectively. Timing pulleys 17 and 1 provided at ends of camshafts 13 and 14, respectively.
8 is connected to a timing pulley 19 provided at an end of the crankshaft 7 by a timing belt 20.

The intake port 9 is connected to an intake passage 30 having an air cleaner 31, a throttle valve 32, a surge tank 33, an intake manifold 34 and the like. Air (outside air) outside the engine 1 is supplied to the intake passage 3 toward the combustion chamber 8.
0 sequentially passes through the respective parts 31, 32, 33 and 34. The throttle valve 32 is rotatably provided in the intake passage 30 by a shaft 32a. The shaft 32a is connected to an accelerator pedal (not shown) in the driver's seat via a wire or the like, and rotates integrally with the throttle valve 32 in conjunction with the depression operation of the accelerator pedal by the driver. The amount of air flowing through the intake passage 30 is determined according to the inclination angle of the throttle valve 32 at this time. In addition, the idle adjustment passage 3 that bypasses the throttle valve 32
5 is provided with an idle rotation speed control valve (ISCV) 36 for adjusting the air flow during idling.
An injector 40 that injects fuel toward each intake port 9 is attached to the intake manifold 34. Fuel is stored in a fuel tank 41, is pumped up by a fuel pump 42, and is supplied to an injector 40 through a fuel pipe 43. And the injector 40
An air-fuel mixture composed of fuel injected from the air and air flowing through the intake passage 30 is introduced into the combustion chamber 8 via the intake valve 11.

An ignition plug 50 is attached to the cylinder head 3 to ignite the mixture. At the time of ignition, the igniter 51 that has received the ignition signal controls the supply and cutoff of the primary current of the ignition coil 52, and the secondary current is supplied to the ignition plug 5 via the ignition distributor 53.
0 is supplied.

The burned air-fuel mixture is guided to an exhaust port 10 via an exhaust valve 12 as exhaust gas. The exhaust port 10 has an exhaust manifold 61 and a catalytic converter 62.
The exhaust passage 60 provided with the above is connected. HC (hydrocarbon), which is an incomplete combustion component, is supplied to the catalytic converter 62.
And a three-way catalyst that simultaneously promotes the oxidation of CO (carbon monoxide) and the reduction of NO _x (nitrogen oxide) generated by the reaction of nitrogen in the air with unburned oxygen. . The exhaust gas thus purified in the catalytic converter 62 is discharged into the atmosphere.

The engine 1 is provided with various sensors. A water temperature sensor 74 for detecting the temperature of the cooling water of the engine 1 is attached to the cylinder block 2. An air flow meter 70 for detecting an intake air flow rate is attached to the intake passage 30. An intake air temperature sensor 73 for detecting the temperature of the intake air is attached near the air cleaner 31 in the intake passage 30.
In the intake passage 30, near the throttle valve 32, a throttle opening sensor 72 for detecting a rotation angle of the shaft (throttle opening) is provided. When the throttle valve 32 is in the fully closed state, the idle switch 82 is turned on, and the throttle fully closed signal output from the idle switch 82 becomes active. An intake pressure sensor 71 for detecting the pressure inside the surge tank 33 is provided.
Is installed. Catalytic converter 6 in exhaust passage 60
An O ₂ sensor 75 that detects whether the air-fuel ratio of the exhaust gas is rich or lean with respect to the stoichiometric air-fuel ratio
Is installed.

The distributor 53 incorporates two rotors that rotate in synchronization with the rotation of the crankshaft 7, and detects the reference angle of the crankshaft 7 based on the rotation of one of the rotors. (C
A) is provided with a crank reference position sensor 80 that generates a reference position detection pulse every 720 ° CA in terms of A), and detects a rotation speed of the crankshaft 7 based on the rotation of the other rotor. Crank angle sensor 81 that generates a rotation speed detection pulse for each CA
Is provided. The vehicle is provided with a vehicle speed sensor 83 that generates a number of output pulses per unit time in proportion to the rotation speed of the transmission output shaft, that is, the vehicle speed.

Engine electronic control unit (engine ECU) 90
Is a microcomputer system that executes fuel injection control, ignition timing control, idle speed control, and the like.
The ignition timing control is based on the engine speed obtained from the crank angle sensor 81 and signals from other sensors, comprehensively determines the state of the engine, determines the optimal ignition timing, and sends an ignition signal to the igniter 51. It is. The idle speed control detects an idle state based on a throttle fully-closed signal from an idle switch 82 and a vehicle speed signal from a vehicle speed sensor 83, and a water temperature sensor 74.
The actual engine speed is compared with the target engine speed determined by the engine cooling water temperature and the like, and the control amount is determined so as to reach the target engine speed according to the difference.
To maintain the optimum idle rotation speed by controlling the air amount.

The fuel injection control is basically based on the amount of intake air per one cycle of the engine, that is, the fuel injection amount that achieves a predetermined target air-fuel ratio, that is, the injector 40.
Is calculated, and the injector 40 is controlled to inject fuel when a predetermined crank angle is reached. The intake air amount per engine cycle is calculated from the intake air flow rate measured by the air flow meter 70 and the engine rotation speed obtained from the crank angle sensor 81, or the intake pipe obtained from the intake pressure sensor 71. Estimated by pressure and engine speed. In the calculation of the fuel injection amount, basic correction based on signals from sensors such as a throttle opening sensor 72, an intake air temperature sensor 73, and a water temperature sensor 74, an O ₂ sensor 75
The air-fuel ratio feedback correction based on the signal from

In particular, at the time of starting, as described above,
The fuel injection amount is calculated based on the engine cooling water temperature,
At that time, it is important to detect the combustion state and thus the fuel property at an early stage and reflect it in the control. Next, the combustion state detection processing according to the present invention will be described in detail.

In the present invention, in order to detect the combustion state,
The variation rate of the engine speed for each ignition cycle is calculated.
Specifically, in the present embodiment, first, for each cylinder, the crankshaft is moved from the compression top dead center to after the compression top dead center (ATD
C) Time T3 required to rotate to an angle position of 30 °
Calculate 0. In the case of a four-cylinder engine, the required rotation time T30 is calculated every 180 ° CA as shown in FIG. Incidentally, T30 _i represents the time required for the rotation about the latest ignition cylinders, T30 _i-1 represents the time required for the rotation about the ignition cycle preceding the ignition cylinder.

However, from the start to the complete explosion, a rapid increase in the rotational speed is observed regardless of the combustion state, which is not suitable for detecting the combustion state. The area that is decreasing, ie, T30 _i > T
The combustion state detection based on the rotation fluctuation is performed only in a region where 30 _i-1 is satisfied.

[0023] Then, T30 _i> T30 _{when i-1} is satisfied, rotational variation VRNEC in the current ignition cycle, VRNEC ← _{[(T30 i -T30 i-1)} / T30 i ] × 100 [%] becomes It is obtained by calculation. The rotation variation rate VRN calculated in consideration of the variation in the detection accuracy for each ignition.
It is preferable to perform a dulling process (so-called annealing process) on EC.

FIGS. 3A and 3B are time charts showing the behavior of the engine speed and the rate of change of the engine speed from the start of the engine start, where (A) shows good combustion, and (B) shows rough combustion with heavy fuel. The case of is shown. From the start to the complete explosion,
In both cases, a sharp increase in the rotation speed is observed, but in the region where the rotation speed thereafter decreases, the rotation fluctuation rate for rough combustion is much larger than the rotation fluctuation rate for good combustion. Take. Therefore, according to the present invention, when the rotation fluctuation rate exceeds a predetermined determination reference value, it is determined that combustion is deteriorating, and that the fuel property is determined to be heavy.

As described above, in the present invention, an increase in the required rotation time between the previous ignition cycle and the current ignition cycle, that is, a decrease in the rotation speed is detected, and the rotation fluctuation rate is obtained. As shown, it is possible to immediately determine the combustion state in a region immediately after the start, that is, in a region where the engine rotational speed is decreasing and is not stable, while excluding a sudden increase in the rotational speed at the time of start as shown. Also,
Since the dimensionless parameter called the rotation fluctuation rate is used, it is not necessary to calculate a reference value for combustion determination according to the engine rotation speed or the like from the map. Note that even in a region such as indicated by R2 in FIG. 4 after the complete explosion and until the engine rotation speed is stabilized, a difference in behavior appears due to combustion, so that a combustion state is detected in that region. Further, similarly to the conventional device, the combustion state is detected even in the idling steady state.

Although the first object of the present invention is to detect the combustion state immediately after starting, according to the structure of the present invention, it is possible to detect cold hesitation. Hesitation is a response delay of the vehicle when the accelerator pedal is depressed, and generally refers to a temporary decrease in engine output that occurs during or shortly after the accelerator is depressed. That is, as shown in FIG. 5, when the throttle opening is increased by depressing the accelerator, the engine speed increases in a normal state, whereas the engine speed decreases when hesitation occurs. As a result, when hesitation occurs, the rotation fluctuation rate increases. Therefore, according to the present invention, cold hesitation, that is, deterioration of drivability during cold, is also detected as deterioration of the combustion state.

FIG. 6 is a flowchart of a combustion state detection routine executed by the ECU 90 to specifically realize the above-described combustion state detection processing according to the present invention. This routine is executed every ignition cycle, that is, every predetermined crank angle of a 180 ° CA cycle from the start. As the combustion state determination reference value applied to the rotation fluctuation rate, a value separately adapted for immediately after start-up, for idle steady state, and for cold hesitation is used, and the detection accuracy is improved. ing.

[0028] First, in step 102, the current, the cylinder in the ignition cycle, the crankshaft calculates the time T30 _i required to rotate from the compression top dead center to the angular position of 30 ° ATDC. Next, step 104
In compares the time required for the rotation T30 _i-1 which is calculated in the present calculated rotation required time T30 _i and the previous ignition cycle, step when the T30 _i> T30 _i-1 106
On the other hand, when T30 _i ≦ T30 _i−1 , this routine ends.

In step 106, as described above, V
RNEC ← [(T30 _i −T30 _i−1 ) / T30 _i ] ×
By the calculation of 100 [%], the rotation fluctuation rate VRNEC in the current cycle is obtained. Next, at step 108, VRNE ← VRNE * k + VRNE * (1-k)
By performing the above calculation, the rotation fluctuation rate VRNE after the averaging process is calculated. In this smoothing operation, a weight of 1-k is applied to the rotation fluctuation rate VRNE after the previous annealing processing, and a weight of k is applied to the rotation fluctuation rate VRNEC of the current cycle calculated this time to obtain a weighted average. , And set it as the new post-smoothing rotation fluctuation rate VRNE.
For example, 1/32 is adopted.

Next, at step 110, it is determined whether or not the engine is currently idling. If the engine is not idling, the routine proceeds to step 118, where the rotational fluctuation rate VRNE is determined.
Condition value (variable) JVR applied to combustion
The reference value JVRNE3 for cold hesitation set in advance is substituted for NE. More specifically, step 110 proceeds to step 118 for at least a predetermined time from the transition from the idle state to the non-idle state so that cold hesitation detection as shown in FIG. 5 is enabled. It is configured.

On the other hand, when it is determined in step 110 that the vehicle is in the idle state, the process proceeds to step 112, in which it is determined whether a predetermined time has elapsed from the start.
If the predetermined time has not elapsed, the routine proceeds to step 114, where the immediately after starting reference value JVRNE1 is adopted as the combustion state determination reference value JVRNE. Idle steady state reference value JVRN as determination reference value JVRNE
E2 is adopted.

In step 120 executed after step 114, 116 or 118, it is determined whether or not the post-annealing rotation fluctuation rate VRNE is larger than a combustion state determination reference value JVRNE. If VRNE> JVRNE, step 122 is executed. The combustion state is getting worse,
That is, after it is determined that the fuel property is heavy, this routine is terminated, while when VRNE ≦ JVRNE, this routine is terminated as it is.

After the combustion state and thus the fuel properties are determined, the map of the fuel injection amount, ignition timing, etc. may be switched according to the fuel properties, or the fuel injection quantity increase, ignition timing, etc., depending on the combustion state. May be implemented.
In particular, when the occurrence of hesitation during cold, that is, the deterioration of drivability is detected, it is preferable to change the fuel correction amount in the transient state in addition to the processing.

Although the embodiments of the present invention have been described above, the present invention is not limited to the embodiments, and various embodiments can be adopted. For example, in the present embodiment, the time required to rotate 30 ° from the compression top dead center to 30 ° ATDC is determined as the rotation required time for detecting the rotation fluctuation, but is not limited to this.

[0035]

As described above, according to the present invention,
After starting, it is possible to detect the combustion state early, and it is also possible to detect cold hesitation.

[Brief description of the drawings]

FIG. 1 is an overall schematic diagram of an electronically controlled internal combustion engine including a combustion state detection device according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining a required rotation time T30.

FIG. 3 is a time chart illustrating behaviors of an engine rotation speed and a rotation fluctuation rate from the start of a start, and
(A) shows the case of good combustion, and (B) shows the case of rough combustion with heavy fuel.

FIG. 4 is a diagram for explaining behaviors of an engine rotation speed and a rotation fluctuation rate.

FIG. 5 is a time chart showing behaviors of a throttle opening, an engine rotation speed, and a rotation fluctuation rate for explaining detection of cold hesitation.

FIG. 6 is a flowchart showing a processing procedure of a combustion state detection routine executed by the ECU.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... In-line 4-cylinder 4-stroke cycle reciprocating gasoline engine 2 ... Cylinder block 3 ... Cylinder head 4 ... Cylinder 5 ... Piston 6 ... Connecting rod 7 ... Crankshaft 8 ... Combustion chamber 9 ... Intake port 10 ... Exhaust port 11 ... Intake valve 12 ... Exhaust valve 13 ... Intake side camshaft 14 ... Exhaust side camshaft 15 ... Intake side cam 16 ... Exhaust side cam 17,18,19 ... Timing pulley 20 ... Timing belt 30 ... Intake passage 31 ... Air cleaner 32 ... Throttle valve 32a ... Throttle valve shaft 33 Surge tank 34 Intake manifold 35 Idle adjust passage 36 Idle speed control valve (ISCV) 40 Injector 41 Fuel tank 42 Fuel pump 43 Fuel pipe 50 Ignition plug 51 Ig Naita 52 ... ignition coil 53 ... ignition distributor 60 ... exhaust passage 61 ... exhaust manifold 62 ... catalytic converter 70 ... air flow meter 71 ... intake pressure sensor 72 ... Throttle opening sensor 73 ... intake air temperature sensor 74 ... water temperature sensor 75 ... O ₂ sensor 80: Crank reference position sensor 81: Crank angle sensor 82: Idle switch 83: Vehicle speed sensor 90: Engine ECU

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Kazuhisa Mogi 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation F-term (reference) 3G084 CA01 CA02 EA05 EA07 EA11 EB12 EB22 FA10 FA14 FA19 FA34 FA35 FA38

Claims (3)

[Claims] 1. A rate-of-change calculating means which starts calculating a rate of change of an engine speed for each ignition cycle from the time of engine start when the engine speed is decreasing; A combustion state detection device for an internal combustion engine, comprising: combustion state determination means for determining that combustion has deteriorated when a value exceeds a predetermined determination reference value. 2. The combustion state detection device for an internal combustion engine according to claim 1, wherein when the combustion state determination means determines that the combustion has deteriorated, it is determined that the fuel property is heavy. 3. The internal combustion engine combustion state detection device according to claim 1, wherein the determination reference value is changed according to a throttle opening and an elapsed time after starting.