JPS5814976B2 - Method and device for measuring the indicated average effective pressure fluctuation rate of an engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for measuring the indicated mean effective pressure fluctuation rate of an engine.

The performance value of an engine is mainly evaluated based on two characteristics: indicated mean effective pressure and fuel consumption rate. In particular, fluctuations in indicated mean effective pressure are extremely important factors, such as causing abnormal engine vibration when the vehicle is actually running. It is believed that.

When the indicated average effective pressure fluctuates, this output fluctuation causes a resonance effect at the natural frequency of the drive system, causing a so-called surge phenomenon in which the vehicle vibrates in the longitudinal direction when the vehicle is running.

This surge phenomenon must be eliminated because it significantly deteriorates the driving characteristics of the vehicle, and also has an adverse mechanical effect on various parts of the engine itself and impairs the feeling of the vehicle driver.

Many of these phenomena are caused by large rotational differentials and torque fluctuations of the engine, and are based on fluctuations in indicated mean effective pressure caused by combustion in the cylinders.

Fluctuations in the indicated mean effective pressure have caused a particularly serious problem in recent vehicles with exhaust gas cleaning measures.

In other words, treatment devices such as lean burn devices, EGR devices, and ignition timing control devices are installed as exhaust gas purification measures, but these devices also cause fluctuations in the combustion state of the engine, so the indicated mean effective pressure This has become a major factor in increasing the fluctuations in

However, the surge phenomenon has been measured by detecting torque fluctuations, rotational fluctuations, and vehicle acceleration.

However, the surge phenomenon may be caused not only by the engine itself but also by the drive system such as the clutch and transmission.

Also, regarding the engine itself, it is not possible to determine whether the original cylinder is the cause of the problem.

Therefore, this detection requires detecting fluctuations in the indicated mean effective pressure of each cylinder.

Therefore, it is necessary to reliably measure the rate of change in the engine's indicated mean effective pressure and take prompt countermeasures.

However, the indicated mean effective pressure is defined by the amount of work per cycle relative to the stroke volume of the engine, and it has been extremely difficult to accurately measure this variation.

Although there are several conventional means for measuring indicated mean effective pressure, none of them are fully satisfactory.

The first conventional device measures and stores the internal pressure of the engine for each rotation angle of the crankshaft based on the engine's acupressure diagram, and performs arithmetic processing on this. It was necessary and could only be used for special research purposes.

Therefore, it has been impossible to mount such a device on a vehicle and control the combustion conditions of the vehicle in response to fluctuations in the indicated mean effective pressure.

The second conventional device is a device that continuously measures acupressure diagrams and detects combustion fluctuations based on fluctuations in the time width of an output signal set at a specific trigger level.
It is stated in No. 9.

However, with this conventional device, it was impossible to accurately measure the rate of variation in the indicated mean effective pressure.

As a conventional third device, a device is known that measures engine output with a torque meter and shows combustion fluctuations by the average fluctuation width in a specific frequency range, but this conventional device only measures the total fluctuation width of all cylinders. The measured fluctuation rate is extremely different from the actual fluctuation rate, as it includes torsional vibration of the drive system.

Furthermore, as a fourth conventional device, there is a device that detects engine vibrations using an accelerometer to indicate fluctuations.

However, like the third conventional device described above, this device also has the drawback that good accuracy cannot be expected.

The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to provide a method and method for measuring the rate of change in indicated mean effective pressure, which can measure the rate of change in indicated mean effective pressure with extremely high precision and a simple configuration. The goal is to provide equipment.

To achieve the above object, the present invention takes advantage of the fact that the rate of variation in the indicated mean effective pressure of the engine closely matches the instantaneous variation in cylinder internal pressure at a particular crank angle.

As is well known, the indicated mean effective pressure Pi of the engine is expressed by the following formula, and from this, the standard deviation σPi and fluctuation rate ΔPi are also determined by the following formulas.

Here, vh is the stroke volume P is the cylinder internal pressure, and the crank angle θ (compression top dead center is 00)
The volumetric differential dV with respect to dV is determined as follows.

Here V.

is the combustion chamber volume at top dead center, D is the cylinder bore diameter, r is the crank radius, λ is the ratio of the connecting rod length l to the crank radius: l/
r.

It is.

As is clear from the above equation, the volumetric differential dV in equation (1) is a value determined only by the crank angle, and the cycle-to-cycle fluctuation is zero.

Therefore, it is understood that the fluctuation of the indicated average effective pressure Pi is a weighted average obtained by multiplying the fluctuation of the pressure P by the weight of the volumetric differential dV.

In addition, the fluctuation in pressure P is not a value determined independently at each crank angle, but is a continuous change determined by the heat release rate in the cylinder, so the indicated average is effective for internal pressure fluctuation at a specific crank angle where the volumetric differential dV is largest. It can represent fluctuations in pressure Pi.

The present invention has been made with attention to this point, and is characterized in that the rate of variation in the indicated mean effective pressure Pi is measured based on the variation in piston internal pressure at a specific crank angle.

According to the above formula, the crank angle at which the volumetric differential dV is maximum is determined only by the ratio λ of the connecting rod length l to the crank radius, and the value of λ is approximately constant in engines that are generally in practical use. , in practice (3
, s).

Figure 1 shows the characteristics of the volumetric differential dV with respect to the crank angle on the horizontal axis, and it is understood that the crank angle at which the volumetric differential dV takes the maximum value is 75 degrees after compression top dead center in the expansion stroke. Ru.

In other words, the crank angle at which the volumetric differential dV becomes the maximum value is the angle at which the piston speed becomes the maximum.

FIG. 2 shows the experimental results of the fluctuation rate ΔP of the internal pressure at a crank angle of 75 degrees with respect to the indicated mean effective pressure ΔPi, and it is understood that there is an extremely good correlation.

When actually detecting the internal pressure fluctuation rate, there is a risk that a fluctuation rate larger than the actual internal pressure fluctuation rate will be detected due to electrical noise, air column vibration of the acupressure needle, etc. Preferably, the variation is measured.

For this purpose, it is preferable to measure by giving an appropriate width to a specific crank angle.

FIG. 3 shows the relationship between the indicated average effective pressure fluctuation rate and the internal pressure fluctuation rate in the range of 10 degrees before and after the crank angle of 75 degrees, that is, the crank angle range of 65 degrees to 85 degrees.
Similar to FIG. 2, this shows that there is a good correlation.

On the other hand, the maximum internal pressure (internal combustion maximum pressure Pmax
) is shown in FIG. 4 at a crank angle of 20 degrees to 40 degrees (early stage of the expansion stroke), where the desired correlation cannot be obtained at this crank angle.

Furthermore, FIG. 5 shows the characteristics in the crank angle range of 100 degrees to 120 degrees, which is just before the exhaust valve opens (at the end of the expansion stroke), and it is understood that there is no correlation even at this time.

As is clear from the above experimental results, in the present invention, if the fluctuation rate of the cylinder internal pressure within a certain crank angle range is measured, the indicated mean effective pressure can be measured due to the remarkable correspondence with the indicated mean effective pressure of the engine. It is possible to know the volatility itself.

It is understood that this specific crank angle is in an expansion stroke that is later than the ignition timing.

From the above explanation, the correlation between the indicated average effective pressure variation rate and the internal pressure variation rate at a specific crank angle has been elucidated mainly by the volumetric differential dV, but this can also be explained from the perspective of engine torque (work). It is possible to do so.

That is, FIG. 9 shows the piston crank mechanism in the expansion stroke, where the explosion pressure in the cylinder 200 rises and pushes the piston 202 downward, and this force is transmitted to the crankshaft 206 via the connecting rod 204. There is.

FIG. 9 shows a state where the crank angle is 75 degrees during the expansion stroke, and it is understood that the angle between the connecting rod 204 and the crankshaft 206 is 90 degrees.

Therefore, at this time, the force pushing down the piston 202 is efficiently transmitted to the crankshaft 206. From this, it can be understood that the cylinder internal pressure at a specific crank angle can represent the overall indicated average effective pressure fluctuation rate. be done.

FIG. 6 shows a block diagram of a measuring device according to the invention.

The cylinder internal pressure is detected by a pressure detector 10 inserted into the cylinder.
is converted into an electrical signal by

The output of the pressure detector 10 passes through a filter 12 to remove noise components, and is supplied to a gate circuit 14.

The gate circuit 14 opens the gate in a specific crank angle range, and an internal pressure signal is output from the gate circuit 14.

A slit ring 1 having a crank angle detector fixed to a crankshaft 16 for detecting a specific crank angle range.
8 and an optical detection means 20.

The crank angle signal detected by the optical detection means 20 is converted into a pulse having a predetermined pulse width by the waveform shaping circuit 22 and is supplied to the gate terminal of the gate circuit 14.

FIG. 7 shows the relationship between the engine acupressure diagram and the gate signal pulse.

In the embodiment shown in FIG. 7, the position of the crank angle is 75 degrees and
-360) degree and gate circuit 14 at two points at -1285 degree.
is understood to open.

The pressure signal at -285 degrees is a suction stroke in which the pressure is maintained at approximately the same value each cycle and is not useful in the present invention for determining the indicated mean effective pressure.

However, in the illustrated embodiment, this -28
By using the internal pressure at 5 degrees as the reference zero voltage, the means of use can be made extremely simple, such as eliminating the need to calibrate the pressure detector 1.0, which is useful for obtaining a measuring device with a simple configuration. .

In FIG. 7, the internal pressure at -285 degrees is shown as Po, and the internal pressure at 75 degrees is shown as Pn.

Therefore, when calculating the fluctuation rate, if you calculate it using (Pn-Po), you can easily calculate the correct fluctuation rate without requiring calibration of the pressure detector or the signal conversion circuit described later. be.

In order to obtain such a reference zero position signal at -285 degrees, in a four-stroke engine, a single slit ring 18a may be provided in the slit ring 18 as shown in FIG.

In a two-stroke engine, this can be achieved by appropriately setting the number of slits to two.

When the gate circuit 14 opens, the cylinder internal pressure P at this time.

and Pn are supplied to an amplifier 24 to give an appropriate amplification factor.

An integrator 26 is connected to the amplifier 24, and the integrator 26 integrates the internal pressure signal obtained by integrating the amplified internal pressure signal during the gate open period.

This analog amount is then converted into a digital signal by the AD converter 28.

The amplifier 24 is provided with an adjustment resistor 30 for zero point setting and an adjustment resistor 32 for span adjustment, and receives a signal P supplied from the gate circuit 14.

The amplification factor of the amplifier 24 is adjusted so that Pn becomes zero of the AD converter 28 and Pn becomes a sufficiently large value that does not exceed the full scale of the AD converter 28.

As a result, the AD converter 28 adjusts the cylinder internal pressure (Pn
-Po) can be converted into a digital signal proportional to

The conversion characteristics of the AD converter 28 are displayed via the monitor circuit 34 on indicators 36 and 38 consisting of light emitting diodes and the like.

The display 36 is P.

The indicator 38 lights up when the value of Pn is less than zero, and the indicator 38 lights up when the value of Pn exceeds the scale. In either case, it means that the amplifier 24 is maladjusted.

The integrator 26 has a time determined by its integration time constant, and the amplifier 24
By making the integration time constant correspond to the engine speed, it is possible to obtain the correct cylinder internal pressure at a specific crank angle without being affected by engine air column vibration or noise. .

That is, the engine speed signal obtained from the primary signal of the distributor is supplied to a waveform shaping circuit 42 via a terminal 40, and is then supplied to a waveform shaping circuit 42 via an integral time constant generating circuit 44 that outputs an integral time constant that is inversely proportional to the engine speed. is applied to an integrator 26.

As a result, when the engine speed is high, the output of the amplifier 24 is sent to the AD converter 28 with a short integration time, and when the engine speed is low, the output is sent to the AD converter 28 with a long integration time. .

Therefore, in this embodiment, it is understood that the opening time of the gate circuit 14 does not directly determine the integration time of the internal pressure, but that the integration time is determined by the integration time constant of the circuit 44.

As described above, the AD converter 28 has the engine 1
Schilling internal pressure at a specific crank angle in a cycle is integrated and averaged into a digital signal, and this digital value is temporarily stored in the buffer circuit 46.

When the conversion operation of the AD converter 28 is completed, the stored value of the buffer circuit 46 is transferred to the arithmetic circuit 5 by the signal 48.
0.

When the internal pressure measurement in the engine cycle is completed and the result is sent to the arithmetic circuit 50, the values stored in the AD converter 28 and the buffer circuit 46 are reset to zero.

In order to obtain the internal pressure fluctuation rate, the above measurements are repeated a predetermined number of measurements n, and the measured values are sequentially processed by the calculator 50.

The set value of the number setting device 52 is compared with the crank angle signal by a comparator 54.

The comparator 54 can be constructed from a well-known subtraction counter or the like.

When the comparator 54 counts a predetermined number of times, an end signal 55 is supplied to the calculation circuit 50, and the calculation ends.

Next, the arithmetic circuit 50 will be explained.

The signal of the buffer circuit 46 is applied to an adder 56, and together with an accumulator 58, ΣPn is calculated.

(Actually, it is the sum of (Pn-Po), but P.

Since it is set to O, it will be referred to as Pn below.

) The signal Pn of the buffer circuit 46 is further supplied to a multiplication/accumulation circuit consisting of a multiplier 60, an adder 62, and an accumulator 64 to calculate ΣPn'.

The aforementioned end signal 55 is supplied to the accumulators 58 and 64 to confirm that the predetermined number of times of calculating the fluctuation rate has been completed, and the outputs of the accumulators 58 and 64 are respectively supplied to the arithmetic unit 66.

A ROM (read only memory) 67 is connected to the arithmetic unit 66, and arithmetic processing is performed on both input signals according to the memory of the ROM 67.

This calculator 66 calculates the fluctuation rate and also calculates the exchange constant between the internal pressure fluctuation rate and the indicated mean effective pressure shown in FIG.

That is, the indicated average effective pressure fluctuation rate ΔPi is obtained by the following formula.

In the above equation, a and b are constant values determined from the characteristic diagram in Figure 2, and when the specific crank angle is set to 75 degrees, according to experiments, a = 0.88, b - - 2.03. be done.

The desired indicated mean effective pressure ΔPi is obtained through the above calculation steps, and this value is displayed on the display 68.

As explained above, according to the present invention, the rate of change in the indicated mean effective pressure of the engine can be obtained from the rate of change in internal pressure at a specific crank angle, and the rate of change in the indicated mean effective pressure of the engine can be obtained using a device that is extremely simplified compared to conventional measuring devices. It is possible to measure the rate of variation in accuracy.

This measured fluctuation rate is measured in each cylinder of a multi-cylinder engine, and by comparing these measurement results, it is possible to accurately diagnose engine characteristics, etc.
An extremely good measuring device can be provided in the engine production process or in the inspection and maintenance process.

The present invention further controls the combustion state of the engine based on the above fluctuation rate measurement results, and can reduce engine combustion fluctuations while the vehicle is running.By adopting this automatic control system, the running stability of the vehicle can be improved. And the driving operability can be greatly improved.

Furthermore, as a result of these, vibrations and surges applied to the engine are reduced, making it possible to improve the durability of the engine.

Especially for engines with exhaust gas purification measures,
It becomes possible to appropriately control these purifying devices from the fluctuation rate measurement values.

FIG. 8 schematically shows an engine equipped with exhaust gas purification measures.

An air-fuel mixture is supplied to the engine body 70 from an air cleaner 72 via a carburetor 74 and an intake manifold 76, and combustion exhaust gas is supplied to the exhaust manifold 7.
8 through a catalytic converter 79.

The negative pressure of the capretor 74 is passed through the three-way valve 80 to the advance angle device 8.
2, and the ignition timing of the distributor 84 is advanced.

In addition, the negative pressure of the capretor 74 is transferred to EGR via a three-way valve 85.
is supplied to the valve 86 and the exhaust manifold 78
A portion of the exhaust gas is returned to the intake manifold 76 via the EGR pulp 86.

Furthermore, three-way valves 88 and 90 are provided to release the primary-main system air bleed and the slow system air bleed of the carburetor 74 to the atmosphere.

Furthermore, secondary air from the secondary air injection pump 92 is supplied to the three-way valve 9.
4 directly after the exhaust valve.

As described above, the engine shown in FIG. 8 is equipped with various exhaust gas purification devices, and by providing the indicated mean effective pressure fluctuation rate measuring device according to the present invention together with these devices, the fluctuation rate can be adjusted to a predetermined value or more. It is possible to suitably control the operation of each purification device when this is reached.

That is, a crank angle detection signal made up of the slit ring 1B provided on the crankshaft 16 and the optical detection means 20 is supplied to the fluctuation rate measuring device 96, and the engine body 70
Similarly, a signal from an internal pressure detector 10 provided in a cylinder head 98 and a signal from a distributor 84 are supplied to a measuring device 96.

The fluctuation rate measuring device has the configuration shown in FIG. 6, and it is understood from the above description that the indicated mean effective pressure fluctuation rate of the engine is calculated and measured.

This measurement result is then compared with a predetermined value by the comparator 100, and the comparison result is supplied to the control device 102,
The three-way valves 80, 8 are controlled by control signals from the control device 102.
5, 94 and two-way valves 88, 90 are controlled to control each purifying device so as to regulate the fluctuation rate within a predetermined range.

As explained above, according to the present invention, it is possible to accurately and easily measure the indicated mean effective pressure fluctuation rate of an engine, and it is possible to provide a device that is extremely useful as an engine characteristic diagnostic device. .

Furthermore, the measuring device according to the present invention can be installed in a vehicle, and has the great advantage of constantly monitoring the fluctuation rate and making it possible to optimally control the combustion state of the engine.

[Brief explanation of the drawing]

Figure 1 is a characteristic diagram showing the relationship between crank angle and volumetric differential.
FIG. 2 is a characteristic diagram showing the correlation between the indicated average effective pressure fluctuation rate and the internal pressure fluctuation rate at a specific crank angle, explaining the characteristics of the identification method according to the present invention, and FIG. 4 and 5 are characteristic diagrams at a specific crank angle. FIG. 6 is a block diagram showing a preferred embodiment of the measuring device according to the present invention. FIG. 7 is a diagram showing characteristics at other crank angles. FIG. 8 is a schematic configuration diagram showing a preferred embodiment of controlling an exhaust gas purification device using the measuring device according to the present invention, and FIG. FIG. 2 is a schematic diagram of a piston crank mechanism for explaining the present invention. 10...Pressure detector, 14...Gate circuit, 20...Crank angle detector, 26...
・Integrator, 28...AD converter, 50...
...Arithmetic circuit.

Claims (1)

[Scope of Claims] 1. A method for measuring the indicated mean effective pressure variation rate of an engine, which comprises calculating and measuring the indicated mean effective pressure variation rate of the engine by measuring fluctuations in cylinder internal pressure at a specific crank angle. 2. The method for measuring the indicated mean effective pressure fluctuation rate of an engine according to claim 1, characterized in that a specific crank angle is set in the expansion stroke following the ignition timing. 3. The method for measuring the indicated mean effective pressure fluctuation rate of an engine according to claim 1, characterized in that a specific crank angle is set in the vicinity where the volumetric differential dV is maximum. 4 A pressure detector that converts the cylinder internal pressure into an electrical signal and detects it, a gate circuit connected to the output side of the pressure detector, and a gate circuit that detects a specific crank angle range and opens the gate circuit only during that period (crank angle A detector, a processing circuit that converts the output signal of the gate circuit, a measurement number detection circuit for calculating the internal pressure fluctuation, and an arithmetic circuit that calculates the fluctuation rate from the output signals of the processing circuit and the measurement number detection circuit. An apparatus for measuring an indicated average effective pressure fluctuation rate of an engine, comprising the following: 5. An apparatus for measuring an indicated average effective pressure fluctuation rate of an engine according to claim 4, characterized in that the processing circuit includes an AD converter. 6. Claims 6. 4.5, the processing circuit includes an integral circuit that makes the integral time constant of the gate circuit output correspond to the engine rotational speed. 7 Claim 1.2 In .3, there is a small
1. A method for measuring an indicated average effective pressure fluctuation rate of an engine, characterized in that a fluctuation rate of cylinder internal pressure is detected as a signal for controlling two or more exhaust gas purification devices.