JPH0239729B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an ignition limit detection device for an internal combustion engine that detects the ignition limit of an internal combustion engine.

If there is a means for detecting the ignition limit of such an internal combustion engine, it is advantageous for air-fuel ratio control, EGR control, ignition timing control, etc.

(Prior art) As a conventional ignition limit detection device for an internal combustion engine,
For example, as in JP-A No. 53-129717, a value obtained by time-integrating the detected value of the cylinder internal pressure of an internal combustion engine from a predetermined angle before top dead center to top dead center and a predetermined angle from top dead center to after top dead center. Some systems detect a misfire state by detecting that the difference between the time-integrated value and the value that has been integrated over time has become less than a predetermined value.

However, in the above conventional technology, the time integral value changes greatly depending on the operating state (load state) of the internal combustion engine even in the same full fuel state, so the misfire state is determined by comparing the difference in the integral value with a predetermined value at a constant level. However, it is extremely difficult to accurately detect the ignition limit.

(Problems to be Solved by the Invention) The necessity of the ignition limit detection device will now be explained using air-fuel ratio control as an example.

Figure 1 shows the relationship between the air-fuel mixture supplied to the combustion chamber of an internal combustion engine, exhaust gas components, and fuel consumption rate _.
This is a graph representing HC and CO.

Near the ideal air-fuel ratio in area A in Figure 1 (misfire occurs)
Ideal air-fuel ratio for complete combustion just before HC increases)
If the air-fuel mixture of an internal combustion engine can be controlled, the harmful components CO and HC in exhaust gas will be at a minimum, and
Since _NOx is reduced compared to the vicinity of the stoichiometric air-fuel ratio which is generally most used, it is advantageous in purifying exhaust gas. Furthermore, the fuel consumption rate is also lowest near this ideal air-fuel ratio, which is economically advantageous.

Therefore, it is desirable to control the air-fuel mixture to near the ideal air-fuel ratio, which is advantageous for exhaust gas purification and economically advantageous, but in reality, in response to changes and fluctuations in the operating conditions of the internal combustion engine, the air-fuel mixture is always adjusted to the point just before a misfire. It is difficult to maintain the ideal air-fuel ratio, so in order to ensure that the air-fuel mixture ignites, it is used at a much richer air-fuel ratio than the ideal air-fuel ratio.

In order to solve this problem, a means is needed to detect misfire and the ideal air-fuel ratio just before the misfire occurs. As a conventional means for directly detecting the air-fuel ratio of an air-fuel mixture, there is an air-fuel ratio detector using a metal oxide semiconductor such as zirconia oxide. However, the oxidized zirconia air-fuel ratio detector can only detect the vicinity of the ideal air-fuel ratio (air-fuel ratio 14.5 to 15.0 in FIG. 1), and cannot detect the ideal air-fuel ratio.

Therefore, it is necessary to indirectly detect the ideal air-fuel ratio immediately before the misfire. As described above, the ideal air-fuel ratio is the air-fuel ratio at which complete combustion occurs immediately before a misfire, so a point slightly richer than the air-fuel ratio at which a misfire and a state immediately before a misfire (partial combustion) are detected is detected as the ideal air-fuel ratio.

That is, the ideal air-fuel ratio can be detected by a detector/ignition limit detector that detects misfire and the state immediately before misfire (partial combustion).

As seen in this air/fuel ratio example, an ignition limiter is useful.

FIG. 2 is a graph showing differences depending on the combustion state in the cylinder pressure waveform of a general internal combustion engine.

In Figure 2, when comparing the time during which the cylinder pressure of the internal combustion engine is above a certain pressure value P _B , the time for complete combustion T _F is greater than the time for misfire and partial combustion immediately before misfire T m and T ′ _F long. Therefore, by determining the time during which the cylinder pressure is above a certain pressure value P _B during each combustion and comparing this time with a predetermined value T _S , it is determined whether there is a misfire, partial combustion, or complete combustion. This allows the ignition limit to be detected.

If a certain pressure value P _B is a constant value, the combustion time may vary depending on the operating conditions of the internal combustion engine even in the same complete combustion state.
_TF is very different.

FIG. 3 is a graph showing differences in cylinder pressure waveforms of a general internal combustion engine depending on load conditions.

In Fig. 3, if the pressure value P _B is determined to match the high load, the time T _2f for complete combustion under light load is:
Not only the predetermined value Ts of high load but also the time of misfire Tm
It becomes shorter. That is, under light loads, it was determined that there was partial combustion just before a misfire or a misfire despite complete combustion. Therefore, in order to eliminate this problem, the pressure value _Pi (-θ A ) at the first angular position (-θ _A ) before the mixture explodes is determined, and this pressure value Pi (-θ _A ) By measuring the time of the cylinder pressure above, the combustion time Ti _F , which is not affected by the load, can be determined as shown in Fig. 3. In addition, the first angle position (+θ _A ) at the symmetrical position across the top dead center
When the required time is determined from the angular position (-θ _A ), the determined time becomes the time Tm in the case of a misfire, as can be seen from FIG. In other words, the misfire time Tm (time required for angular position (-θ _A ) and (+θ _A )) is:
It is determined as constant regardless of the load. Therefore, the predetermined value Ts, which is the standard for comparison of the combustion time _TiF mentioned above, is
Since Tm×α can be determined as a constant value regardless of the load, it is possible to always determine whether complete combustion has occurred at a constant level regardless of the load. In the case of a complete misfire, the pressure waveform shown in FIG. 3 is symmetrical around the crank angle around top dead center. Therefore, the present invention defines the misfire time as follows.

That is, the crank angle -θ _A before the crank angle at which the pressure waveform becomes larger than the compression pressure when combustion starts due to ignition is specified, and the time from the crank angle -θ _A to the crank angle +θ _A is defined.

At this time, as is clear from FIG. 3, the misfire time T ₂ m under light load and the misfire time T _1n under high load are the same. Considering the safety factor, set the misfire time Ts to α (α＞
1) Multiply the combustion time during actual combustion to the value P ₁ (-θ ₄ ) at crank angle -θ _A ; P 2 (-θ 4 ); at high load, P ₂ (-θ ₄ ); time T during light load. _1F ;
At high load, T _2F ; At light load, T _1F /Ts, T _2F /
If it is determined that ignition occurs when the value of Ts is greater than or equal to a predetermined value, and misfire occurs when the value of Ts is less than or equal to the predetermined value, ignition or misfire can be determined regardless of the load.

In addition, crank angle - θ _A to crank angle + θ _A
Although it is not possible to actually measure the time until _the
Calculate by doubling the time until the center).
That is, the ignition limit can be known regardless of operating conditions such as load.

The object of the present invention is to determine the cylinder pressure value _P (- θ _A ), and the time during which the cylinder pressure exceeds P (-θ _A ) is determined as the combustion time T _F. At the same time, if a misfire occurs in this state, P (-θ _A )
The operating condition of the internal combustion engine, such as the load, is determined by determining whether the ratio of these two times (T _F /Tm) is greater than or equal to a predetermined value α. The point is that the ignition limit is always detected regardless of the situation. That is, if the ratio T _F /Tm is greater than or equal to a predetermined value α, it is determined that there is ignition, and conversely, if it is less than or equal to the predetermined value α, it is determined that there is a misfire.

(Means and effects for solving the problems) The present invention is characterized by the configuration of an ignition limit detection device for an internal combustion engine, which adopts and combines the following technical means in order to achieve the above object. .

(a) A pressure detector that detects the cylinder pressure of the internal combustion engine; (b) An angular position detection device that detects the first angular position of the internal combustion engine during the compression stroke; (c) A cylinder pressure that exceeds the pressure value at the first angular position Combustion time measurement circuit that measures a certain time T _F ; D. Measures the time required from a first angular position to a second angular position that is symmetrical to this first angular position across the top dead center of the internal combustion engine. By doing so, if the internal combustion engine misfires under the same conditions, the first
A misfire time calculation circuit that calculates the time Tm at which the pressure at the angular position is equal to or higher; and a determination circuit that compares and determines the ratio T _F /Tm of both times with a predetermined value α.

Furthermore, a second angular position symmetrical to the first angular position is determined by narrowing the top dead center of the internal combustion engine, and a time required between the first angular position and the second angular position is determined using a misfire time calculation circuit. .

With the above configuration, even if the cylinder pressure changes greatly depending on the operating state of the internal combustion engine, the present invention prevents a misfire from occurring during the time T _F when the cylinder pressure is higher than the pressure value at the first angular position during the compression stroke. The ratio T _F /
By comparing Tm with a predetermined value, the ignition limit can always be accurately detected regardless of operating conditions such as load.

(Example) The ignition limit detection device for an internal combustion engine according to the present invention will be described in detail below according to an example.

FIG. 4 is a block diagram showing an embodiment of the ignition limit detection device for an internal combustion engine according to the present invention.

In FIG. 4, 1 indicates two angular positions during the entire stroke of each cylinder of a four-cycle internal combustion engine, that is, the first angular position (-θ _A ) and top dead center TDC
This is an angular position detection device that detects a second angular position (+θ _A ) of a predetermined internal combustion engine that is located at a target position and is in the expansion stroke by narrowing the (Top Dead Center). 2
is an ignition detection circuit that detects whether the internal combustion engine has undergone complete combustion, misfire, or partial combustion immediately before misfire. Further, numeral 3 is a pressure detector that detects the pressure inside the cylinder of the internal combustion engine.

5 and 6 are detailed views of FIG. 4, and FIG. 7 is a time chart explaining the operation of the apparatus of the present invention.

First, one embodiment of the detailed circuit of the angular position detecting device 1 will be described with reference to FIG. In the angular position detector 1 shown in FIG. 5, a rotor 11 has one protrusion on its outer periphery, and is fixed to a distributor shaft (not shown) of an internal combustion engine, and rotates together with the distributor shaft. be. Reference numerals 12 and 13 denote first and second electromagnetic pick-ups, respectively, which are arranged at predetermined angles apart from each other in the circumferential direction of the rotor 11, and are opposed to the protrusions of the rotor 11. 16,1
7 is a transistor connected to each electromagnetic pickup 12, 13, and 14, 15 is a resistor. 1
8 and 19 constitute a flip-flop circuit with NAND circuits, one input of which is the collector of transistor 16, and the other input of which is the collector of transistor 17.
are connected to their respective collectors. and,
The rotor 11 rotates once in the direction of the arrow with two revolutions of the crankshaft.
As the rotor 11 rotates and each protrusion of the rotor 11 crosses the electromagnetic pickups 12, 13, each electromagnetic pickup 12, 13 generates a negative falling signal as shown in FIGS. 7a and 7b. Therefore, the electromagnetic pickups 12 and 13 detect the first angular position (-θ _A ) and the second angular position (+θ), respectively. And each electromagnetic pick-up 12,
When a negative signal occurs at 13, each transistor 1
6 and 17 become conductive, and due to the conduction of each transistor 16 and 17, NAND circuits 18 and 1
The flip-flop circuit consisting of 9 is activated, and an output as shown in FIG. 7c is generated at one output terminal 1a of this flip-flop circuit.

Next, the pressure detector 3 and the ignition detection circuit 2 will be explained with reference to FIG. First, the ignition detection circuit 2 determines the misfire time using the angular position detection signal from the angular position detection device 1.
A misfire time calculation circuit 23 that calculates Tm and a combustion time T _F at which the internal combustion engine cylinder pressure becomes equal to or higher than the pressure value P (-θ _A ) at a predetermined internal combustion engine angular position (-θ _A ) a combustion time measuring circuit 22 for determining the combustion time, and a determination circuit 2 for determining whether the ratio of the times (T _F /Tm) obtained by both circuits is larger or smaller than a predetermined value α.
Consists of 4. Furthermore, in the ignition detection circuit 2, a reference potential Vref is created by resistors 291, 292 and a capacitor 293, and is connected to an operational amplifier shown below via a resistor. Reference numeral 28 denotes a charging control circuit which allows a constant potential to be taken out to the output terminal A by resistance division using resistors 281 and 282. In addition, 100 is a key switch, 110 is a battery forming a DC power supply, and Ks is a key switch 1.
This is a power supply terminal connected to the power supply 110 via 00.

The pressure detector 3 is a pressure sensor attached to a cylinder of an internal combustion engine, and its output potential increases as the pressure of the cylinder increases. This signal from the pressure detector 3 is processed by the processing circuit 21 of the ignition detection circuit 2. The signal processing circuit 21 includes resistors 211, 21
2, 213, 215, 216, 217, 219 and operational amplifiers 214, 218. Note that the resistors 213 and 217 are connected to the reference potential Vref. The output of the signal processing circuit 21 is the seventh
The result will be as shown in Figure f. 22 is a combustion time measuring circuit, and an analog switch 221 is turned on when it is set to "1".
A time measurement circuit consisting of a resistor 222, a capacitor 223, a transistor 224, operational amplifiers 225, 226, a flip-flop circuit 227, and an AND circuit 228, an analog switch 229 that turns on at "1", and resistors 2210, 2214, 2215,
It is composed of a time integration circuit consisting of a capacitor 2211, a transistor 2212, and an operational amplifier 2213. In addition, resistor 2210 and capacitor 221
1, the time constant of the integrating circuit is sufficiently large compared to the pulse width. 23 is a misfire time calculation circuit, which includes an analog switch 231 that turns on when "1" is set, and a resistor 23.
2. This is an integrating circuit consisting of a capacitor 233, a transistor 234, and an operational amplifier 235. Note that the time constant of the integrating circuit made up of the resistor 232 and the capacitor 233 is sufficiently large compared to the pulse width. 24
is a judgment circuit consisting of a comparison circuit consisting of resistors 241, 242 and an operational amplifier 243, an analog switch 244 that is turned on at “1”, a resistor 245, a capacitor 246, and an operational amplifier 247. Consists of a hold circuit.

25 is a monostable circuit, and a combustion time measuring circuit 22
When the output of the time measuring circuit (Fig. 7g) falls, a monostable output (Fig. 7i) is produced. Its composition is
It consists of NOT circuits 251, 252, 257, a NAND circuit 256, a resistor 253, and a capacitor 254. Similarly, 26 is a monostable circuit, and monostable circuit 25
When the output i falls, a monostable output (Fig. 7 j) is produced. Its configuration is NOT circuits 261, 262, 2
66, a NAND circuit 265, a resistor 263, and a capacitor 264. 27 is a monostable circuit that generates a monostable force as shown in FIG.
NOT circuits 271, 275, NAND circuit 274,
It consists of a resistor 272 and a capacitor 273.

Next, the operation of the embodiment of the present invention described above will be explained using the time chart shown in FIG.

The angular position detection device 1 shown in FIG. 5 emits a rectangular pulse in synchronization with the rotation of the crankshaft of an internal combustion engine (not shown), and its output terminal 1a
As shown in Fig. 7c, the first angular position (-
“1” between θ _A ) and the second angular position (+θ _A )
level, a “0” level output is generated between the second angular position (+θ _A ) and the first angular position (−θ _A ), and one pulse output is generated with two rotations of the internal combustion engine as one cycle. It is something to do.

Then, while the output level of the angular position detection device 1 is "1", the analog switch 231 of the misfire time calculation circuit 23 of the ignition detection circuit 2 is turned on, and is charged with a constant voltage by the output terminal A of the charging control circuit 28. Therefore, the charged voltage value Vm is held as an output representing the misfire time Tm until it is erased by the output of the monostable circuit 26. The appearance of the output is as shown in FIG. 7d.

The time measuring circuit of the combustion time measuring circuit 22 turns on the analog switch 221 at the output e of the monostable circuit 27, that is, the angle of the angular position (-θ _A ), and first holds the cylinder pressure value P (-θ _A ). do. Then, the held P(-θ _A ) and the cylinder pressure P are compared by the arithmetic amplifier 226 . Furthermore, since the output e of the monostable circuit 27 is input as the clock signal c1 of the flip-flop circuit 227, the output Q of the flip-flop circuit 227 and the operational amplifier 22
The output of the AND circuit which inputs the output of 6 becomes "1" at the angular position (-θ _A ), and the cylinder pressure P
It becomes "0" at the point where becomes smaller than P(-θ _A ).
Therefore, the output of the time measuring circuit is detected as "1" when the cylinder pressure P is greater than P(-θ _A ) as shown in FIG. 7g. And the output g of this time measurement circuit
Analog switch 229 of the time integration circuit by
The output terminal A of the charging control circuit 28 charges the voltage at a constant voltage while the voltage is turned on and becomes "1". This charged voltage value V _F represents the combustion time T _F (the time during which the cylinder P is greater than P(-θ _A )) and is maintained as shown in FIG. 7h. At the output of the monostable circuit 26 in FIG. 7j, the cylinder pressure value P (-θ _A ) held in the time measurement circuit is erased, the flip-flop circuit is reset (R), and the time integration circuit is reset to the voltage value V _F will be deleted.

Then, the output Vm of the misfire time calculation circuit 23 and the output V _F /α of the combustion time calculation circuit 22 (here, α is a predetermined value determined by the dividing resistors 2214 and 2215 and indicates 1 or more) are calculated by the calculation width of the determination circuit 24. When V _F /α is larger than Vm,
The output of the monostable circuit 25 (FIG. 7i) is held at "1" indicating complete combustion. When V _F /α is smaller than Vm, the output of the monostable circuit 25 (FIG. 7i) is similarly held at "0", which indicates misfire and partial combustion immediately before misfire.

As described above, for each combustion, the time when the cylinder pressure P is greater than the cylinder pressure value P (-θ _A ) at the angular position (-θ _A ) of the internal combustion engine before the air-fuel mixture explodes and burns. In other words, the combustion time T _F can be determined as the voltage value V _F , and the time when the cylinder pressure P is greater than P (-θ _A ) when a misfire occurs under the same conditions, that is, the misfire time.
Since Tm can be calculated as the time required from the angular position (-θ _{A )} to the second angular position (+θ _A ), which is symmetrical to the first angular position (-θ A ) and the top dead center, The misfire time Tm can be determined as a voltage value Vm. This measured burn time
Represents the misfire time _Tm calculated by V representing T _F
By comparing Vm in the form of V _F /α and Vm, it is determined whether V _F /Vm is larger or smaller than a predetermined value α that is a reference for the combustion state.

That is, when it is larger than the predetermined value α, the output is “1” indicating complete combustion, and when it is smaller than the predetermined value α,
Output “0” indicating misfire and partial combustion immediately before misfire
shows. In this way, the misfire time for the combustion time T _F is
Find Tm and calculate the ratio T _F /Tm (=V _F /
By comparing Vm) with a predetermined value α, misfires and partial combustion immediately before a misfire can be detected stably regardless of the load or the like. That is, the ignition limit of the internal combustion engine can be detected. Although the above-described embodiment of the present invention is a detector for detecting the ignition limit of an internal combustion engine with only one cylinder, it can be similarly applied to an internal combustion engine with multiple cylinders.

FIG. 8 shows another embodiment of the rotor used in the present invention, and FIG. 9 shows a detailed diagram of the pressure detector 3 and the processing circuit 21.

To explain this using an example of a four-cylinder internal combustion engine in FIG. 8, four protrusions 11a, 11b, 1
1c and 11d are provided, and generate two rectangular pulses with two periods and two pulses per two revolutions of the internal combustion engine.

In FIG. 9, four resistors 2111, 2112, 2113, 2114 are installed for each detector 31, 32, 33, 34 so that the processing circuit 21 has an addition function.
A similar measurement can be made by connecting the arithmetic amplifier 214 and adding the signals. Even if the pressure for four cylinders is simply added, there is no problem since the pressure changes during the intake stroke and exhaust stroke are small, so other cylinders do not have a large influence.
Furthermore, in the embodiment of the present invention described above, the angular position (-
The misfire time _Tm was calculated by directly determining the angular position (θ A ) and the angular position (+θ _{A )} using an electromagnetic pickup, but it is also The misfire time Tm is determined. Therefore,
It is also possible to find the time between two easy-to-find angular positions of the internal combustion engine and multiply it by β to obtain the misfire time Tm.
Furthermore, it can also be easily determined in the form of misfire time Tm×predetermined value α.

Further, in the above-mentioned angular position detection, the angular position is detected by an electromagnetic pickup, but it can be similarly detected by a photoelectric type or a point type.

Further, although the above-described embodiment of the present invention is constructed using an analog circuit, detection can be performed in the same manner even when constructed using a digital circuit.

(Effects of the Invention) As described above, according to the ignition limit detection device for an internal combustion engine according to the present invention, the angular position (-
By measuring the cylinder pressure value P (-θ _A ) of θ _A ), the time during which the cylinder pressure P exceeds this pressure value P (-θ _A ) can be measured as the combustion time T _F and under the same conditions. If a _{misfire occurs at} It can be calculated as the time required to reach the position symmetrical to _A ). Then, by detecting whether the ratio T _F /Tm between the obtained combustion time T _F and the misfire time Tm is larger or smaller than a predetermined value α that is a criterion for combustion, the operating status of the internal combustion engine can be adjusted. This has the excellent effect of being able to always detect the ignition limit at a constant level regardless of the situation.

Therefore, it is possible to detect a wide range of ignition limits caused by not only the above-mentioned air-fuel ratio but also the amount of exhaust gas recirculation, ignition timing, etc.

[Brief explanation of drawings]

Figure 1 is a graph showing the relationship between the air-fuel ratio, total exhaust gas, and fuel consumption rate in a general internal combustion engine. Figure 2 is a graph showing the difference in cylinder pressure waveforms depending on the combustion state of a general internal combustion engine. The figure is a graph showing the difference in the cylinder pressure waveform of a general internal combustion engine depending on the load condition, Figure 4 is a block diagram showing an embodiment of the device of the present invention, and Figures 5 and 6 are detailed views of Figure 4. , 7th
The figure is a time diagram for explaining the operation of the device of the present invention.
8 and 9 are diagrams showing other embodiments of the apparatus of the present invention. DESCRIPTION OF SYMBOLS 1... Angular position detection device, 2... Ignition detection circuit, 3... Pressure detector, 11... Rotor, 12,
13... Electromagnetic pick-up, 21... Processing circuit, 22... Combustion time measuring circuit, 23... Misfire time calculation circuit, 24... Judgment circuit, 25, 26, 2
7... Monostable circuit, 28... Charging control circuit.

Claims (1)

[Scope of Claims] 1. A pressure detector that detects the in-cylinder pressure of an internal combustion engine, an angular position detection device that detects a first angular position of the internal combustion engine during a compression stroke, and the first angular position. a combustion time measuring circuit for measuring a time T _F during which the cylinder pressure is greater than or equal to the pressure value;
By measuring the time required from the angular position to a second angular position that is symmetrical to this first angular position across the top dead center of the internal combustion engine, if a misfire occurs under the same conditions of the internal combustion engine, the first A misfire time calculation circuit calculates the time Tm during which the pressure at the angular position is equal to or greater than , and compares the ratio T _F /Tm of both times with a predetermined value α, and determines whether the ratio T _F /Tm is equal to or greater than the predetermined value α. An ignition limit detection device for an internal combustion engine, comprising: a determination circuit that determines that there is ignition if the value is equal to or less than the predetermined value α, and that it is a misfire. 2. The angle detection device also detects the second angular position, and the misfire time calculation circuit directly measures the time required between the first angular position and the second angular position. An ignition limit detection device for an internal combustion engine according to claim 1. 3. The angle detection device also detects the top dead center, and the misfire time calculation circuit measures the time required from the first angular position to the top dead center, and doubles this time to calculate the time from the first angular position to the top dead center. 2. The ignition limit detection device for an internal combustion engine according to claim 1, wherein the ignition limit detection device for an internal combustion engine indirectly measures the time required from an angular position to a second angular position.