JPH0522065B2 - - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for measuring output fluctuations of an internal combustion engine.

Prior Art In recent years, efforts have been made to optimally adjust the ignition timing and air-fuel ratio of engines as a measure to prevent exhaust pollution and save energy. Conventional methods for measuring output fluctuations include JP-A-51-104106 (``Method and device for measuring non-quietness of internal combustion engines'' by Robert Botsch), JP-A-53 -65531 (“Method and device for controlling the operation of an internal combustion engine in the limit range of lean mixture operation” by Robert Botsch), JP-A-57
-106834 (“Method for detecting torque fluctuations in internal combustion engines” Toyota Motor Corporation) is known. In both of these conventional methods, the time required for one rotation of the crankshaft is
Ti is measured in time series, and each rotation number, that is,
This method attempts to find fluctuations in the internal combustion engine by successively comparing the average number of revolutions per revolution.

Generally, when a vehicle is traveling at a constant speed and the road surface condition is changing, the rotational speed waveform measured at 30° intervals is shown in FIG. In Figure 1, the horizontal axis represents time and the vertical axis represents the number of revolutions N, where (1) is the tabletop, (2)
represents the case of a paved road, and (3) represents the case of a rough road.
One revolution corresponds to 360℃A. Air fuel ratio A/F is
14.5. As shown in Figure 1, even though the vehicle is traveling at a constant speed, the rotational speed varies greatly due to unevenness of the road surface, and from this result, the average rotational speed measured for each crankshaft rotation is the same as that of the engine. In addition to output fluctuations, it is also greatly affected by engine load fluctuations caused by uneven road surfaces, and it is difficult to accurately detect output fluctuations using methods that measure rotational fluctuations, or output fluctuations, from the number of rotations per crankshaft rotation. There was a problem with gender.

OBJECTS OF THE INVENTION An object of the present invention is to improve the accuracy of detecting output fluctuations of an internal combustion engine based on the concept of correcting the value of output fluctuations of an internal combustion engine calculated from internal combustion engine characteristic values using the envelope of the internal combustion engine characteristic values. It's about improving.

Composition of the Invention In the present invention, when measuring the output fluctuation of an internal combustion engine based on a periodic pulsating signal change in any one of engine speed, torque, and cylinder pressure that appears in each explosion stroke of the internal combustion engine, Sequentially detecting any one signal value of the periodic pulsating engine speed, torque, and cylinder pressure in a predetermined cylinder of the internal combustion engine at two different predetermined rotation angle positions in the internal combustion engine; Calculate the amount of change in any one of the periodic pulsating signals that appears in the explosion stroke of the cylinder based on the difference in values, and further calculate the amount of change in any one of the periodic pulsating signals from the amount of change. Which one of these corresponds to
The above amount of change is corrected by subtracting the amount of change obtained from the signal value in the relevant explosion stroke of the relevant cylinder and the signal value in the successive explosion stroke for the relevant cylinder. There is provided a method for measuring output fluctuations in an internal combustion engine, characterized in that the output fluctuations of the internal combustion engine are measured by calculating changes in the corrected amount of change in the subsequent explosion stroke.

The present invention is based on the following analysis performed by the present inventor.

The change over time in the rotational speed of a 4-cycle, 4-cylinder engine is as shown in FIG. In FIG. 2, the horizontal axis represents time and the vertical axis represents rotational speed.
S (TDC) represents the top dead center signal. Each cylinder repeats the explosion stroke in the order of 1st, _3rd , 4th, and _2nd , and in _FIG . N ₃ and N ₄ represent the rotational speed changes during the explosion stroke of the second, third, and fourth cylinders, respectively.

If we observe changes in engine speed from a microscopic perspective, we can see that engine speed changes consist of relatively long-period changes in engine speed caused by accelerator operation and the above-mentioned load fluctuations, and short-period pulsations that occur during the explosion stroke of each cylinder. rotational speed changes are superimposed. Similarly, pulsating changes appear in engine torque or cylinder pressure.

Moreover, the value △Nr (=Nm - Nn) calculated as the difference in the amount of pulsation change at a predetermined timing in successive explosion strokes of a predetermined cylinder using the above-mentioned pulsating rotation speed that appears in the explosion stroke of an internal combustion engine and the indicated mean effective pressure. The relationship with Pi is shown in Figures 3 and 4. Third
The figure shows the case when the rotation speed is 1000 rpm, and Figure 4 shows the case when the rotation speed is 1500 rpm. Figure 3,
In Figure 4, the average rotational speed (Nn) from 30℃A to 60℃A after TDC and the average rotational speed (Nm) from 90℃A to 120℃A after TDC during the explosion stroke of the first cylinder shown in Figure 2 are shown. ) is used.

In addition, the indicated mean effective pressure corresponding to the air-fuel ratio A/F
The relationship between the standard deviation σ(Pi) of Pi and the standard deviation σ(ΔNr) of the rotational speed variation ΔNr is shown in FIGS. 5 and 6. Figure 5 shows a rotation speed of 1000 rpm and a torque of 4.
This is the case of Kg・m.

As shown in FIGS. 3 to 6, the output of the internal combustion engine can be detected with high accuracy by using the pulsating rotational speed that appears during the explosion stroke of the internal combustion engine.

For example, in FIG. 7, which shows changes in the rotational speed N over time t, the rotational speed fluctuation of the first cylinder is expressed by the following equation.

△N=(N _1,3 −N _1,1 )−(N′ _1,3 −N′ _1,1 ) …(1) According to equation (1), each term in the bracket of equation (1) By determining the amount of pulsating rotational speed change that appears in the explosion stroke corresponding to , and successively comparing the amount of rotational speed change in successive explosion strokes in a given cylinder, combustion fluctuations can be detected almost unaffected by road surface conditions. It has become clear that it is possible to detect the rotation speed fluctuation caused by this.
However, if it is necessary to further improve the detection of ΔN, the variation due to the affected road surface condition, although slight, becomes a problem.

To explain this using Figure 7, (N _1,3 - N _1,1 ) in the first term of equation (1) includes the change in rotational speed due to combustion and the rotational speed due to road surface conditions shown by the broken line. The changes are combined. The amount of change in the rotational speed due to the road surface condition depends on the interval between N _1,1 and N _1,3 , so it only corresponds to the following equation.

K×△N ₁ = K (N _3,0 − N _1,0 ) …(2) Here, K is a value determined by the sample interval, and if the current temperature is 60℃, K is about 1/3 . This value K changes by changing the sample interval. Therefore, in order to further improve the detection accuracy of △N, (2)
The difference due to the road surface condition shown in the formula becomes an error.

The present invention attempts to solve the above problems by detecting the pulsating rotational speed change amount (N _1,3 −N _1,1 ) that appears in the engine's explosion stroke, and from which it is possible to determine the road surface condition. The change K(N _3,0 −
Specifically, by subtracting N _1,0 ), the rotational speed fluctuation ΔN is detected using the following equation.

△N={(N _1,3 −N _1,1 )−K×(N _3,0 −N _1,0 )} −{(N′ _1,3 −N′ _1,1 )−K×(N ′ _3,0 −
N′ _1,0 )} …(3) This makes it possible to detect only rotational speed fluctuations caused by combustion fluctuations without being affected by road surface conditions.

Embodiment FIG. 8 shows an apparatus for performing a method for measuring output fluctuations in an internal combustion engine as an embodiment of the present invention. In FIG. 8, E is a 4-cycle, 4-cylinder engine whose output fluctuations are to be measured, and an angle signal plate 3 is attached to a pulley 2 located at the tip of the crankshaft 1.

The angle signal plate 3 is a disk made of magnetic material, and on its circumference there are
It has 12 teeth. Reference numeral 4 denotes an angle signal sensor provided so as to face the teeth of the signal plate 3, which outputs a pulse signal every time each tooth of the signal plate 3, which rotates integrally with the shaft 1, passes. Therefore, sensor 4
outputs 12 pulses per revolution of shaft 1. Further, the shaft 1 rotates twice during one cycle of the explosion stroke from the first cylinder to the fourth cylinder.

5 is a distributor, and 6 is a cylinder discrimination sensor built into the distributor 5, which outputs a pulse signal at the compression top dead center of the first cylinder. Reference numeral 7 denotes an output fluctuation calculation unit, into which pulse signals from the angle signal sensor 4 and cylinder discrimination sensor 6 are input.

In the arithmetic unit 7, 71A and 71B are waveform shaping circuits, 72 is a counting circuit, 73 is a reading circuit, 74 is a calculation circuit, and 75 is a D/A converter, and the calculation circuit 74 is of the form of a microcomputer. be able to.

The pulse signal from the angle signal sensor 4 is input to the calculation circuit 72 via the waveform shaping circuit 71A. A counting circuit 72 counts the period of the pulse signal. Since 12 pulse signals are output per crankshaft rotation, the period is the period in which shaft 1 rotates 30 degrees. The output of the counting circuit 72 is input to the calculation circuit 74.

On the other hand, the discrimination signal of the cylinder discrimination sensor 6 is passed through the waveform shaping circuit 71B and the reading circuit 73 to the calculation circuit 74.
is input. The engine speed or torque fluctuation calculated by the calculation circuit 74 is converted into an analog signal by a D/A converter 75, and sent to an air-fuel ratio control device or an ignition timing control device (not shown).

The content of the calculation of the rotational speed fluctuation performed by the calculation circuit 74 will be explained using the flowchart shown in FIG.
A commercially available microcomputer is used for the calculation circuit 74, and an interrupt signal is issued to the calculation circuit 74 every time the 30°A angle signal shown in FIG. 2 falls, and a flowchart is shown in FIG. The rotation speed fluctuation calculation program starts.

First, in step S101, the level of the cylinder discrimination signal is read into the memory A1, and in step S102, it is checked whether this is "0". "0"
If so, the position of the angle signal of the interrupt calculation is the TDC of the first cylinder, so the counter m is set to 0.
If yes, the counter m is incremented by 1 in step S103.

In step S105, the counter m is 0, 1, 3, 6,
It is checked whether it is any one of 7, 9, 12, 13, 15, 18, 19, and 21, and if it is YES, the process jumps to step S113 and the calculation ends. If YES, step S106 and subsequent steps are executed. Step S106 is 30℃
The period of the angle signal A is read from the counting circuit 72 and stored in the memory A2.

In step S107, the cycle data in the memory A2 is converted into a rotational speed by performing reciprocal calculation, and is stored in the memory A3. Here, K1 is a proportionality constant for the conversion. Step S108 stores the contents of memory A3 in memory N _n . Here, 12 memories N _n are prepared since m takes 12 values in step S105, and these are sequentially stored as rotation speed data N _1,0 , N 1,1 , N _1,1 , N _1,3 ,...
This corresponds to three pieces of data for each of the first to second cylinders, such as N _2,0 , N _2,1 , and N _2,3 .

In step S109, the counter m is 0, 6, 12, 18.
If it is NO, the process jumps to step S113 and the calculation ends. If YES, in step S110, a calculation corresponding to the above-mentioned equation (3) is performed to obtain the rotational speed variation ΔN _n .

Here, in the equation shown in step S110, when m=0, m-3=21, m-5=19, and m-6=18. Furthermore, as stated in the explanation of equation (3), the amount of change in rotational speed during combustion in each cylinder is calculated by (N _n-3 − _{N n-5} ), and further K×(N _n −N _{n -6} ), the amount of change in rotational speed due to changes in road surface conditions while the rotational speed changes is calculated and subtracted to remove the influence of changes in rotational speed due to changes in road surface conditions.

Step S111 outputs the rotational speed fluctuation ΔN _n obtained in step S110 to the D/A converter 75,
In step S112, memories N _n-3 , N _n-5 , and N _n-6 are stored in N' _n-3 , N' _n-5 , and N' _n-6, respectively, in preparation for the next calculation in step S110. Step S113 cancels this interrupt operation.

In this way, the device shown in Fig. 8 detects the pulsating rotation speed change that appears during the engine's explosion stroke, and subtracts the change due to the road surface condition from this, specifically, the above-mentioned (3). calculation of expressions,
This makes it possible to detect only rotational speed fluctuations caused by combustion fluctuations without being affected by road surface conditions.

In carrying out the present invention, various modifications can be made in addition to the above-described embodiments. For example, in the above-mentioned embodiment, the method of correcting the variation in rotational speed due to road surface conditions was based on the variation in rotational speed at the TDC position of each cylinder, that is, N _1,0 and N _3,0 in Fig. 7. However, it is also possible to correct this by, for example, the change in the average rotational speed in the combustion cycle of each cylinder, that is, the average value of N _1,0 to _{N 1,5} for the first cylinder in Fig. 7. can. In short, the present invention deals with the pulsating rotational speed movement having the slope shown by the broken line in FIG. It is sufficient to correct the change in rotational speed due to road surface conditions using the envelope curve of .

Further, in the above-mentioned embodiments, everything is taken as the amount of change in the number of revolutions, but it goes without saying that the same results can be obtained even if this is calculated from the slope of the change in the number of revolutions.

In addition, in the above-mentioned embodiment, the engine rotation speed was used as the detected value, but this can be calculated in exactly the same way using engine torque or cylinder pressure to measure engine output fluctuations. I can do it.

Effects of the Invention According to the present invention, a periodic pulsating signal value of any one of the engine speed, torque, and cylinder pressure in a predetermined cylinder of an internal combustion engine is determined at two predetermined different rotation angle positions in the internal combustion engine. Detect sequentially with
The amount of change in any one of the periodic pulsating signals that appears in the explosion stroke of the cylinder is calculated from the difference between these detected values, and further, the amount of change in any one of the periodic pulsating signals that appears in the explosion stroke of the cylinder is calculated from the amount of change. The amount of change is corrected by subtracting the amount of change found from the signal value in the relevant explosion stroke of the relevant cylinder for any one of the corresponding signals and the signal value in the successive explosion strokes. By calculating the above-mentioned corrected change in the amount of change in successive explosion strokes in the cylinder of the internal combustion engine, combustion fluctuations can be corrected without being affected by rotational speed fluctuations caused by changes in road surface conditions. It is possible to stably detect only the rotational speed fluctuations caused by the engine, and the accuracy of detecting the output fluctuations of the internal combustion engine is improved.

[Brief explanation of drawings]

Figure 1 is a characteristic diagram showing the internal combustion engine speed characteristics depending on the road surface condition, Figure 2 is a characteristic diagram showing the change over time in the rotation speed of a 4-cylinder internal combustion engine, and Figures 3 and 4 are both effective as indicated averages. Characteristic diagrams showing the relationship between pressure and rotation amount during explosion, Figures 5 and 6 are characteristic diagrams showing the relationship between air-fuel ratio, standard deviation of indicated average effective pressure, and standard deviation of rotational speed variation, and Figure 7 Figure 8 is a characteristic diagram showing changes in rotation speed over time, Figure 8 is a diagram showing a device for measuring output fluctuations in an internal combustion engine as an embodiment of the present invention, and Figure 9 is a flowchart of calculations in the device shown in Figure 8. It is a calculation flow chart showing. Explanation of symbols, 1... Crankshaft, 2... Pulley, 3... Magnetic disk, 4... Angle signal sensor, 5...
Distributor, 6... Cylinder discrimination sensor, 7...
Arithmetic unit, 71A, 71B...waveform shaping circuit,
72...Counting circuit, 73...Reading circuit, 74...Calculation circuit, 75...D/A converter, E...Engine.

Claims (1)

[Claims] 1. When measuring output fluctuations of an internal combustion engine based on periodic pulsating signal changes in any one of engine speed, torque, and cylinder pressure that appear in each explosion stroke of the internal combustion engine, Periodic and pulsating signal values of any one of engine speed, torque, and cylinder pressure are sequentially detected at two predetermined different rotation angle positions in the internal combustion engine, and the difference between these detected values is used to determine the Calculate the amount of change in any one of the periodic pulsating signals that appears in the explosion stroke of the cylinder, and further calculate the corresponding one of the one periodic pulsating signals from the amount of change. The amount of change is corrected by subtracting the amount of change obtained from the signal value in the relevant explosion stroke of the relevant cylinder and the signal value in the successive explosion strokes, and A method for measuring output fluctuations of an internal combustion engine, characterized in that the output fluctuations of the internal combustion engine are measured by calculating changes in the corrected amount of change during the explosion stroke.