JPH03246346A - Combustion condition detector for internal combustion engine - Google Patents

Abstract

PURPOSE:To educe a combustion information by a simple method, by detecting the revolution velocity of an internal combustion engine, and at the same time seeking a revolution velocity correction quantity against this revolution velocity, and deciding an internal combustion engine combustion condition from a correc tion revolution velocity obtained from the revolution velocity correction quantity. CONSTITUTION:An angle counter 15 is reset at a predetermined timing, and a signal 5a outputted at every fixed crank angle is calculated, and a crank angle theta is calculated by means of a means 16 from this calculated value 13, and a timer signal 14 whose purpose is to detect a revolution velocity by means of a fixed crank angle position and width, is outputted. And a signal from a clock 18 is counted by means of a counter 19 only while the timer signal 14 is being outputted, and a revolution velocity omega is made to be calculated 20 from this count value. Also, a predetermined table value h(theta) is searched 17 on the basis of the crank angle theta, and a revolution velocity correction quan tity omegac and a correction revolution velocity omegag are calculated 21 from the above respective values omegag, theta, and a combustion condition is decided 22 from respective values omegag, theta.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a device for detecting the combustion state of an internal combustion engine based on its rotational speed.

[Conventional technology]

Conventional devices determine the combustion state based on the difference in rotational speed at two points within one ignition cycle, as described in Japanese Patent Laid-Open No. 58-51243. Also, JP-A-62-22812
There is also a method as described in No. 8 that determines the combustion state based on the difference in the square of the rotational speed.

[Problem to be solved by the invention]

The above-mentioned conventional technology assumes that rotational speed fluctuations occur only due to energy due to combustion, and does not take into account rotational speed fluctuations that occur due to reciprocating inertia of pistons and the like. For this reason, there is a problem that the error becomes large especially when the engine rotates at high speed, resulting in erroneous combustion state determination.

SUMMARY OF THE INVENTION An object of the present invention is to provide an information processing procedure for accurately detecting a combustion state from rotational speed fluctuations, and an apparatus for realizing the same.

[Means to solve the problem]

In order to achieve the above object, speed fluctuations due to reciprocating inertia and the like are corrected from the rotational speed, so that only the fluctuations caused by combustion energy can be obtained.

[Effect]

Rotational speed fluctuations during the ignition cycle of an internal combustion engine.

One is due to fluctuations in torque generated by combustion.

Furthermore, in an internal combustion engine having a piston that reciprocates, as most current automobile internal combustion engines do, the inertia of this reciprocating movement causes torque fluctuations, resulting in rotational speed fluctuations. Torque fluctuations also occur due to the valve train that moves the intake and exhaust valves. Torque fluctuations also occur due to the compressor of the air conditioner, but short-term fluctuations such as rotational speed fluctuations during the ignition cycle can be ignored, except for step-like fluctuations caused by, for example, 0N10FF.

In other words, in order to detect the combustion state, the rotational speed fluctuation is measured, and if only the rotational speed fluctuation due to combustion is extracted, excluding the reciprocating inertia, valve mechanism, etc., the subsequent processing can be done as in the above-mentioned known example. You should do it. In the present invention, it is possible to accurately and easily correct the rotational speed variation due to the reciprocating inertia etc. from the crank angle and rotational speed.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a drawing showing an embodiment of the present invention.

A magnetic pickup 5 facing the gears of a ring gear 4 fixed to the crankshaft 7 of the internal combustion engine 1 generates as many pulse signals as the gears of the ring gear 4 per revolution of the crankshaft 7. Further, the ring gear 4 has a protrusion 4a.
One pulse signal is output per rotation from the magnetic pickup 6 facing the protrusion 4a. Furthermore, from the cam angle sensor 3 attached to the camshaft 2,
One pulse signal is output for every two rotations of the crankshaft 7. These signals are input to the arithmetic circuit 8, and the rotational speed and crank angle are calculated and measured.

In this embodiment, the ring gear is used to detect the rotational speed, but there are also other methods, such as attaching another sensor to the crankshaft.

FIG. 2 is a diagram showing the configuration of the arithmetic circuit 3. The output 3a of the cam angle sensor 3, the output 5a of the magnetic pink-up 5, the output 6a of the magnetic pickup 6, and the outputs of an air flow rate sensor, a water temperature sensor, etc. (not shown) are input. Based on this input information, ignition, fuel, etc. are controlled by a program stored in the ROMII.

FIG. 3 shows the piston 9 for one cylinder of the internal combustion engine 1. Connecting rod 10 and crank part 7a of crankshaft 7
(hereinafter referred to as crank angle θ).

The torque tg generated by the pressure P in the combustion chamber 12 transmitted from the cylinder to the crankshaft 7 in this figure is a function of the pressure P and the crank angle θ, and can be defined by the following equation.

1g(θ)=p-A-sin(φ10)/cosφ・
(1) Here, A is the pressure-receiving area of the upper surface of the piston 9, φ indicates the angle of the illustrated portion, and the following relationship holds true.

sinφ=-sinθ=Ksinθ
=-(2) Here, R is the radius of rotation of the crank pin 7b, and L is the distance between the axes of the connecting rod 10. K hani=
Define R/L.

Similarly, the torque 11 generated by the inertia of reciprocating parts such as the piston 9 and a part of the connecting rod 10 is calculated by the crank angle θ.
is a function of rotation speed ω, and can be defined by the following equation.

...(3) Here, M is the mass of the reciprocating part.

Therefore, the torque t generated from one cylinder is expressed by the following equation.

t=tf+tl...(
4) Here, for the case of a 4-cylinder engine, the subscript j (j=
1+..., 4) to represent the j-th cylinder, the following equation holds true.

Here, it is defined as follows.

(5) The formula is as follows.

T '' Tz+T t (7) Here, if the rotational speed of the crankshaft 7 is ω, the following relationship holds true.

here, Ward 1 is the load from the clutch side in Figure 1 It is torque.

■ is the habit of rotation system such as crankshaft 7. It's a sexual moment.

(8).

From equation (7) Here ω.

is defined by the following equation.

(6).

Using equation (3), it can be approximated as shown in the following equation.

...(11) Then, The following formula is found.

ωC″: ωh(θ) ...(13) Also (9).

The following equation is obtained from equation (10).

Also.

is defined by the following equation.

ωg=　ω　-ωC ...(15) The following equation can be found from equations (14) and (15).

Here, when looking at short-period events such as fluctuations in each ignition cycle, Tm is constant (as for the stepwise fluctuations in load torque caused by the air conditioner compressor, etc., as mentioned above, for example, when the state of the air conditioner SW changes, the combustion This can be easily realized by simply canceling the status determination.) Therefore, by using ωg, it is possible to obtain information only about Tt, that is, the combustion state. ω1 is ω from the product ωC of ω and h(θ), which is a function of the crank angle θ.
It is obtained by setting g=ω−ωC.

Furthermore, h(θ) is a periodic function of θ, which is 360° or 72
If 0° is determined in advance, there is no need to calculate h(θ) every time ωC is calculated.

Note that equation (12) may be replaced by the following equation.

ωC#ω・h(θ) ...(13'
) where ω is the average value of a particular section within the ignition cycle, and is ω/ω valve 1.

The method for correcting reciprocating inertia has been described above. Normally, the influence of this reciprocating inertia is large.

This correction alone is often sufficient. For example, if you want to correct a valve mechanism (not shown)... (12'
) hz (θ) = Torque generated by the valve mechanism at crank angle θ ... (17) (+)c = (+3"hi (θ) + hz (O)
- If you do as in (18), the following steps may be the same. In this way, in general, if hx(θ) is determined as the correction coefficient for the variation due to inertial force, and bz(θ) is determined as the correction coefficient for variation due to the elastic force 1 of the spring, etc., then ωC can be further calculated using equation (18). ωg can be determined using equation (15), and combustion state information can be obtained.

FIG. 4 is a block diagram of this embodiment, and FIG. 5 is a diagram showing the timing of each signal. As mentioned above, 3a is the output of the cam angle sensor 3, which is output once every two rotations of the crankshaft 7. Similarly, 6a is the output after passing through a waveform shaping circuit (not shown) of the magnetic pickup 6, which is output once per revolution of the crankshaft 7, and is matched to, for example, the TDC of the first cylinder. 5a is an output after passing through a waveform shaping circuit (not shown) of the magnetic pickup 5, and is output at every fixed crank angle in correspondence with the teeth of the ring gear 4. Waveform 13 is angle counter 15
It is reset by the AND signal of 3a and 6a, and shows the value obtained by counting the number of pulses of 5a.

With this count number 13, for example, the explosion TD of the first cylinder
The crank angle based on C can be detected.

The crank angle θ calculation and sampling timer section 16 calculates the crank angle θ from the above-mentioned count number, and further outputs a timer signal 14 for detecting the rotational speed at a constant crank angle position and width.

The counter 19 counts the signal from the clock 18 only while the timer signal 14 is being output. From this count value, the rotation speed calculation unit 20 calculates the rotation speed ω. Further, based on the crank angle 0, the h(θ) table search unit 17 searches for the table value h(θ). The table values may be stored in the ROM II as shown in FIG. Here, figure (a) is an example of using one type of h(θ) as in equation (13), and figure (b) is an example of using two types of h(θ) as in equation (18). This is an example of when to use it. In addition,
The h(θ) table may be stored in correspondence with the crank angle at which the rotational speed ω is detected. From ω and h(θ) obtained in the above manner, the ωC2ωg calculation unit 21 calculates ωg as described above. The combustion state determining section 21 determines the combustion state based on the crank angle θ corresponding to this ωg. As for the determination method, for example, time differentiation as shown in equation (16) or other known methods can be used.

FIG. 7 is an example of rotational speed data for a four-cylinder internal combustion engine. θ=0° corresponds to the explosion TDC of the first cylinder.

Further, the operating condition is high rotation where the influence of reciprocating inertia is large. As an example, the optimum within one ignition cycle,
ATDC90@, 180' to detect the minimum rotation speed
When detecting the rotation speed in ..., in the conventional case,
Maximum rotational speed = ω'H1 Minimum rotational speed = ω'L and the magnitude relationship may be reversed 0 Looking at ωg determined by the present invention, it accelerates from θ push O0, and reaches the maximum rotational speed at θ″: 90°. It is seen that the maximum rotational speed is reached again at θ phantom 180° at which the next ignition cycle begins, and combustion information can be extracted.In this case, the maximum and minimum rotational speeds are ωH9ωL, and there is no reversal.

〔Effect of the invention〕

According to the present invention, combustion information can be extracted from rotational speed data using a simple method. As a result, even if the combustion state determination method, which conventionally could only be determined at low rotation speeds, can be determined over the entire rotation speed range.

It also becomes possible to quantitatively detect the combustion state.

This improves the accuracy of combustion state determination, and if applied to, for example, lean burn, failure diagnosis, etc., it will also lead to reduction in fuel burn, exhaust gas purification, etc.

[Brief explanation of drawings]

FIG. 1 is a drawing showing an internal combustion engine equipped with an embodiment of the present invention, FIG. 2 is a drawing showing an example of the configuration of an arithmetic circuit, and FIG. 3 is a drawing showing the relationship between the piston, crankshaft, etc. of the internal combustion engine. FIG. 4 is a block diagram of the embodiment, FIG. 5 is a diagram showing the timing of various signals, FIG. 6 is a diagram explaining a coefficient table for correction, and FIG. 7 is a diagram for explaining the present invention in detail. 2 is a drawing showing an example of rotational speed data. DESCRIPTION OF SYMBOLS 1... Internal combustion engine, 4... Ring gear, 7... Crankshaft, 9... Piston, 17... h(0) Table search section, Fig. 4... Ring gear Fig. Figure 2

Claims (1)

[Scope of Claims] 1. Rotational speed detection means for detecting the rotational speed of an internal combustion engine, means for determining a rotational speed correction amount for this rotational speed, and rotational speed correction means for determining a corrected rotational speed from the rotational speed correction amount. A combustion state detection device for an internal combustion engine, comprising: and a combustion state determination means for determining the combustion state of the internal combustion engine based on the corrected rotational speed. 2. The combustion state detection device for an internal combustion engine according to claim 1, wherein the combustion state determining means determines a misfire state of the engine. 3. The rotational speed correction means includes a storage means for storing coefficients, and a rotational speed correction amount based on the coefficients stored in the storage means corresponding to the detected crank angle of the rotational speed and the rotational speed, and further corrects the rotational speed correction amount. A combustion state detection device for an internal combustion engine according to any one of claims 1 to 2, characterized in that it comprises a calculation means for calculating a rotational speed.