JPH0731098B2 - Air-fuel ratio controller for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention detects combustion fluctuations of an internal combustion engine according to torque fluctuations and rotational speed fluctuations, and controls the air-fuel ratio.

[Conventional technology and problems]

There is a system that detects the combustion fluctuation of the internal combustion engine according to the torque fluctuation and controls the air-fuel ratio. That is, since the combustion fluctuation increases as the air-fuel mixture becomes thinner, the air-fuel ratio is controlled so that the air-fuel mixture becomes as thin as possible within the limit of the allowable combustion fluctuation.
As a simple system for detecting combustion fluctuations, there is a method of detecting fluctuations in the rotational speed of the combustion engine. For example, JP-A-59-
See 201936. However, in a system that detects combustion fluctuations according to the number of revolutions, changes in the engine revolutions are affected by changes in the road surface. That is, when traveling on a rough road, the engine speed fluctuates regardless of the presence or absence of combustion fluctuation. In other words, this means that combustion fluctuations cannot be detected on a rough road.

Another method of detecting combustion fluctuation is by detecting combustion pressure. That is, the combustion pressure sensor is arranged in the combustion chamber of the internal combustion engine, the effective compression area (so-called torque) in the combustion stroke is known from the combustion pressure, and the combustion fluctuation is known from the fluctuation. In this method, it is necessary to install a combustion pressure sensor in each cylinder in order to know the combustion fluctuation of each cylinder, and there is a problem that the system becomes expensive. For example,
See JP-A-60-249647.

An object of the present invention is to make it possible to know the torque fluctuation without being affected by the road surface and at a low cost.

[Means for solving problems]

According to the present invention, as shown in FIG. 1, the combustion pressure detection means 2 arranged in a part of the cylinders 1a of the internal combustion engine, and the torque fluctuation of that cylinder from the combustion pressure signal from the combustion pressure detection means 2 Torque fluctuation calculation means 3, means 4 for detecting the rotation speed of the combustion engine, means 5 for calculating the fluctuation of the rotation speed for each cylinder, and torque fluctuation calculated by the torque fluctuation calculation means is a predetermined value. When it is larger, or when the torque fluctuation calculated by the torque fluctuation calculating means 3 is not larger than a predetermined value, but the rotation speed fluctuations of other cylinders in which the combustion pressure detecting means 2 is not installed are larger than the predetermined value,
A fuel amount increasing means 6 for increasing the amount of fuel introduced into the internal combustion engine from the combustion supply means 1b on the assumption that there is combustion fluctuation, and a torque fluctuation calculated by the torque fluctuation fluctuation calculating means 3 not exceeding a predetermined value and combustion pressure detection. When the fluctuations in the rotational speed of the other cylinders in which the means 2 is not installed are not larger than the predetermined value,
There is provided an air-fuel ratio control device for an internal combustion engine, which comprises fuel reducing means 7 for reducing the amount of fuel introduced into the internal combustion engine from the fuel supply means 1b on the assumption that there is no combustion fluctuation.

[Work]

The torque fluctuation calculating means 3 calculates the torque fluctuation of the cylinder from the combustion pressure signal from the combustion pressure detecting means 2, and the rotation fluctuation calculating means 5 calculates the fluctuation of the rotation speed of the internal combustion engine detected by the rotation speed detecting means 4 for each cylinder. Is calculated. Fuel increase means 6
Means when the torque fluctuation calculated by the torque fluctuation calculating means 3 is larger than a predetermined value, or when the torque fluctuation calculating means 3
Even if the torque fluctuation calculated by the above is not larger than the predetermined value, if the rotation speed fluctuation detected by the rotation speed detecting means 4 in the other cylinders in which the combustion pressure detecting means 2 is not installed is larger than the predetermined value, the combustion fluctuation is If so, the amount of fuel introduced into the internal combustion engine from the fuel supply means 1b is increased. When the torque fluctuation calculated by the torque fluctuation fluctuation calculating means 3 is not larger than a predetermined value and the rotation speed fluctuations of other cylinders in which the combustion pressure detecting means 2 is not installed are not larger than the predetermined value, the fuel reducing means 7 burns the fuel. Assuming that there is no change, the amount of fuel introduced into the internal combustion engine from the fuel supply means 1b is reduced.

〔Example〕

In FIG. 2, 10 is a main body of a 4-cylinder internal combustion engine, 11 is a combustion chamber of each cylinder, 12 is an intake pipe, 14 is a throttle valve, and 16 is an exhaust pipe. An injector 18 is installed in a branch pipe portion of the intake pipe 12 to each cylinder. The present invention is not limited to the fuel injection method. 20 is a distributor. The distributor 20 includes a distribution shaft 20a, and the toothed members 24 and 26 for detecting the rotation speed are fixed on the distribution shaft 20a. A magnetic sensor 28, 30 such as a Hall element is opposed to these toothed members 24, 26.
Is installed and a pulse signal is generated according to the rotation of the crankshaft connected to the distribution shaft 20a. First magnetic sensor 28
Is for confirming the reference position, and generates a pulse signal for each rotation of the crankshaft by 720 degrees (that is, one engine cycle). The second magnetic sensor 30 is for measuring the engine speed, for example, generates a pulse signal for every 30 degrees of rotation of the crankshaft, and as is well known, the engine speed is determined by the time interval between adjacent 30 ° CA signals. You can know.

The intake pipe pressure sensor 32 is installed in the intake pipe 12, and it is possible to know the intake pipe pressure which is the load equivalent value of the internal combustion engine.

According to the present invention, the combustion pressure sensor 34 is installed in a part of the four cylinders of the internal combustion engine, in the embodiment, the combustion chamber 11 of the first cylinder. The combustion pressure sensor 34 is configured as a piezoelectric type, for example. The effective compression work (indicated torque) during the compression stroke can be known from the combustion pressure.

The control circuit 40 is configured as a microcomputer system, and is for executing the air-fuel ratio control according to the present invention. The control circuit 40 has a micro processing unit (MPU) 42, a memory 44, an input port 46, an output port 48, and a bus 50 connecting these as basic components. The input port 46 is for each sensor 2 described above.
It is connected to 8,30,32,34 and the operating condition signal is input. The output port 48 is connected to the fuel injector 18 of each cylinder,
A fuel injection signal is applied.

The operation of the control circuit 40 will be described below with reference to the flowcharts of FIGS. FIG. 3 is a rotational speed measurement routine, which is used to know the rotational speed fluctuation of each cylinder. This routine is executed every time the pulse signal from the second magnetic sensor 30 comes at intervals of 30 ° CA. In step 60, counter C
Is incremented. In step 62, it is determined whether or not the position is the reference position based on the presence or absence of the pulse signal from the first magnetic sensor 28. If it is the reference position, the routine proceeds to step 64, where the counter C is cleared. As shown in (a) of FIG. 7, the counter value monotonically increases, but the increment timing is every 30 ° CA and is cleared every 720 ° CA. In step 66, it is judged whether or not it is the timing for measuring the minimum rotation speed of the first cylinder. As shown in FIG. 7B, the engine speed pulsates between the lowest and the highest. The lowest rotation speed is near the top dead center of compression, and the highest rotation speed is near the exhaust valve opening start point around 120 ° CA. The difference between the minimum and maximum rotational speeds is the contribution of that cylinder in the rotational fluctuation. The firing order as four-cylinder engine the first cylinder - the third cylinder - fourth cylinder - if the second cylinder, successively minimum rotation _{NE 1 a, NE 3 a,} NE 4 a, NE 2 a, the maximum rotational speed NE ₁ b, NE ₃ b, NE ₄ b, NE ₂
Since b appears in sequence, measure these and calculate their difference HNE
By calculating ₁ , HNE ₃ , HNE ₄ , and HNE ₂ , the combustion fluctuation amount of each cylinder can be known.

If the measurement timing of the minimum rotation NE ₁ a of the first cylinder is set in step 66 (this can be known by the number of the 30 ° CA counter), the process proceeds to step 68, and as is known by the interval of the 30 ° CA pulse. The calculated rotational speed NE is entered in NE ₁ a.
If No in Step 66, proceed to Step 70 and set the maximum speed.
It is determined whether it is the NE ₁ b measurement timing. If Yes, the routine proceeds to step 72, where the rotational speed NE is entered in NE ₁ b. Step 74 shows the measurement processing of the minimum rotation speed NE ₂ a and the maximum rotation speed NE ₂ b of the second cylinder, which can be executed similarly to steps 66-68-70-72. Step 76 shows the measurement processing of the minimum speed NE ₃ a and the maximum speed NE ₃ b of the third cylinder.
Reference numeral 78 denotes a measurement process of the minimum rotation speed NE ₄ a and the maximum rotation speed NE ₄ b of the fourth cylinder, which can be similarly executed.

FIG. 4 shows a torque fluctuation determination routine. This routine is executed every crank angle after the end of the combustion stroke of the first cylinder in which the combustion pressure sensor 34 is installed, for example, every 90 degrees after the compression top dead center. In step 80, the indicated torque equivalent value T is calculated from the pressures P ₁ , P ₂ , P ₃ , P _{4 at} a plurality of points in the combustion stroke. That is,
The pressure in the combustion chamber changes near the compression top dead center as shown in FIG. The effective compression pressure of the piston, that is, the indicated torque can be known from the area drawn by this pressure change characteristic. In this example, instead of measuring the area, pressures P ₁ , P ₂ ,
A convenient method of detecting a value, which should be called an equivalent value of the indicated torque, from P ₃ and P ₄ by a predetermined calculation formula is adopted. Of course, the indicated torque itself may be calculated.

In step 82, the torque fluctuation ΔT is calculated from the difference between the torque average value T _AVE and T. In step 84, the torque fluctuation Δ
It is determined whether or not _{T is} larger than an allowable limit value K _T (PM, N) determined by the intake pipe pressure PM and the engine speed N. ΔT
> K _T (PM, N) when recognizes that there is a torque variation, the process proceeds to step 86, the torque fluctuation flag Xderuta _T is set.
_{ΔT ≦ K T (PM, N} ) When is recognized as the torque fluctuation-free, the process proceeds to step 88, the torque fluctuation flag Xderuta _T is reset. In step 90, the average torque value T _AVE is calculated by T _AVE = (7 × T _AVE + T) / 8. That is, T _AVE is calculated as a _smoothed average value in which the average value up to that point is weighted 7 and the current torque value is weighted by 1.

In step 92 the rotational speed deviation of the first cylinder is calculated by _{HNE 1 = NE 1 a-NE} 1 b. See FIG. 7 (b). In step 94, the rotational speed fluctuation of the first cylinder is calculated by ΔNE ₁ = HNE _AVE −HNE ₁ . Here, HNE _AVE is the average value of the rotational speed deviation. In step 96, the rotational speed deviation of the first cylinder ΔNE ₁
Is larger than the allowable limit value K _N (PM, N) determined by the intake pipe pressure PM and the engine speed N. ΔNE ₁ ＞ K
_N (PM, N) recognizes that there is the engine speed fluctuation when, the process proceeds to step 98, the engine speed fluctuation flag Xderuta _N1 of the cylinder is set. _{ΔNE 1 ≦ K N (PM,} N) recognizes that there is no rotational speed change when the proceeds to step 100, the engine speed fluctuation flag Xderuta _N1 of the cylinder is reset.

Step 102 represents the process of the engine speed fluctuation flag Xderuta _N2 of the second cylinder, is treated as in Step 92-94-96-98-100, if present rotational speed fluctuation of the second cylinder, flag Xderuta
_N2 is set, the flag Xderuta _N2 is reset if there is rotational fluctuation. 104 is the rotation speed fluctuation flag XΔ _N3 of the third cylinder
Setting process, step 106 represents the rotation speed fluctuation flag Xderuta _N4 of the fourth cylinder, set or reset of the flag is performed by the same process as steps 92-100.

In step 108, the average value HNE
_AVE Is calculated by This formula has the meaning of a weighted average value obtained by weighting the average value up to that point with a weight of 4 and the fluctuation of the actual number of revolutions of the current cycle by a weight of 4.

FIG. 5 shows a fuel injection amount calculation routine. This routine can be located in the middle of the main routine. In step 120, the engine speed NE is input, and in step 1
In step 22, the intake pipe pressure PM is input, in step 124, the basic fuel injection amount TP is calculated from the engine speed NE and the intake pipe pressure PM, and in step 126, various correction coefficients K for the fuel injection amount are calculated. At 128, the final fuel injection amount TAU is calculated by TAU = TP × K × KAF. Here, KAF is a correction coefficient of the fuel injection amount due to the torque fluctuation and the rotational speed fluctuation according to the present invention. A known fuel injection routine (not shown) is executed at each fuel injection timing of each cylinder so that the fuel injection amount calculated in this way is injected from the injector.

FIG. 6 shows a routine for calculating the correction coefficient KAF of the fuel injection amount based on the torque fluctuation and the rotational speed fluctuation. This routine is 7
After completion of the combustion variation determination routine executed every 60 ° CA,
That is, it can be performed after the execution of step 108 in FIG. In step 130 it is determined whether the torque fluctuation flag XΔ _{T =} 0. When the XΔ _{T =} 1 is recognized that there is torque fluctuation, the correction coefficient KAF proceeds to step 131 is incremented by [Delta] K. That is, the magnitude of the torque fluctuation of the air-fuel ratio and the quality of the fuel consumption rate are related as shown in FIG.
The permissible limit of torque fluctuation (K _T in step 84 in Fig. 4) corresponds to the upper solid line. When the torque fluctuation exceeds this limit, the correction coefficient increases and the fuel injection amount increases. And the air-fuel ratio is returned to the rich side. As a result, the air-fuel ratio is controlled to the lean side as much as possible within the allowable limit of torque fluctuation.

In step 132, it is determined whether or not the rotation speed fluctuation flag XΔ _N1 = 0 for the first cylinder in which the combustion pressure sensor 34 is installed. XΔ
When the _N1 = 1 means that the larger the engine speed fluctuation, inconsistent with the results of the torque fluctuation flag XΔ _{T =} 0, i.e. step 130 that there is no torque variation. That is, the rotation speed fluctuation is not caused by the engine combustion fluctuation, but can be regarded as being caused by the road surface condition such as running on a rough road. Figure 10 shows the relationship between the air-fuel ratio and the standard deviation of rotational speed fluctuations on rough roads and paved roads. In this case, step 134
Bypass the following: When XΔ _N1 = 0, the routine proceeds to step 134, and it is determined whether or not all the rotation speed fluctuation flags XΔ _N2 , XΔ _N3 , XΔ _N4 of the other cylinders in which the combustion pressure sensor 34 is not installed, that is, all cylinders 2-4. It is determined whether or not there is a fluctuation in the number of revolutions. When flag = 0 in all cylinders, the routine proceeds to step 136, where the correction coefficient KAF is decremented by ΔK. If even one flag = 1, it is considered that there is combustion fluctuation and the routine proceeds to step 131, where the fuel correction coefficient is incremented and the fuel injection amount is increased.

〔The invention's effect〕

According to the present invention, the combustion pressure is detected by the fuel pressure detection means (in-cylinder pressure sensor) installed in a part of the cylinders of the internal combustion engine, and when there is a large torque fluctuation grasped, there is a combustion fluctuation. As a result, the fuel supply amount is increased, and even if it is determined that the torque fluctuation is not greater than the combustion pressure detected by the combustion pressure detection means, if the rotation speed fluctuations of other cylinders are large, it is considered that there is a combustion fluctuation and the fuel supply If the torque fluctuation is not larger than the combustion pressure detected by the combustion pressure detection means and there is no fluctuation in the rotation speed, the fuel is reduced because it is determined that there is no combustion fluctuation. By only providing internal pressure sensors in some cylinders, it is possible to accurately detect combustion fluctuations in each cylinder by eliminating the effects of rotational fluctuations caused by factors other than combustion fluctuations. Never raising the rough road detection accuracy due to the influence of the road surface at the same time reducing the cost by saving the number of sensor, it is possible to obtain the excellent effect that.

[Brief description of drawings]

FIG. 1 is a diagram showing the configuration of the present invention. FIG. 2 is a diagram showing the configuration of an embodiment of the present invention. 3 to 6 are flowcharts for explaining the operation of the control circuit. FIG. 7 is a graph schematically illustrating fluctuations in the rotation speed of each cylinder over a series of time passages. FIG. 8 is a graph showing the relationship between the crank angle and the combustion pressure in the combustion stroke. FIG. 9 is a graph showing the relationship between crank angle, torque fluctuation, and fuel consumption rate. FIG. 10 is a graph showing the relationship between the air-fuel ratio and the standard deviation of the rotational speed fluctuation when traveling on a paved road and when traveling on a rough road. 10 …… Engine body 11 …… Combustion chamber 12 …… Intake pipe 18 …… Injector 28,30 …… Crank angle sensor 32 …… Intake pipe pressure sensor 34 …… Combustion pressure sensor 40 …… Control circuit 38 …… Cylinder Pressure sensor

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akio Yasuda 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation (56) References JP 61-55338 (JP, A) JP 62-118031 (JP, A)

Claims (1)

[Claims] 1. A combustion pressure detecting means installed in a part of cylinders of an internal combustion engine, a torque fluctuation calculating means for calculating a torque fluctuation of the cylinder from a combustion pressure signal from the combustion pressure detecting means, and an internal combustion engine A means for detecting the rotational speed, a means for calculating the fluctuation of the rotational speed for each cylinder, and a torque fluctuation calculated by the torque fluctuation calculating means when the torque fluctuation calculated by the torque fluctuation calculating means is larger than a predetermined value. Is greater than a predetermined value, if the rotation speed fluctuations of the other cylinders in which the combustion pressure detecting means is not installed are larger than the predetermined value, it is considered that there is combustion fluctuation and the fuel amount introduced into the internal combustion engine from the fuel supply means is determined. The number of revolutions of the other cylinder for which the fuel amount increasing means and the torque fluctuation calculated by the torque fluctuation calculating means are not larger than a predetermined value and the combustion pressure detecting means is not installed. When the dynamic is not greater than the predetermined value,
An air-fuel ratio control device for an internal combustion engine, comprising: a reduction means for reducing the amount of fuel introduced from the fuel supply means into the internal combustion engine on the assumption that there is no combustion fluctuation.