JPS6347910B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION 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.

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 region (A) of Figure 1 (misfire
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 the ideal air-fuel ratio immediately before a 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 zirconia oxidized air-fuel ratio detector detects the air-fuel ratio near the stoichiometric air-fuel ratio (the air-fuel ratio in Figure 1).
14.5 to 15.0), and the ideal air-fuel ratio cannot be detected.

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 state immediately before a misfire (partial combustion) is 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 the state immediately before misfire (partial combustion).

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

FIG. 2 shows cylinder pressure waveforms in different combustion states under the same internal combustion engine conditions.

In FIG. 2, the maximum value P ₁ max of combustion pressure when complete combustion occurs is greater than the maximum value P ₂ max of combustion pressure when partial combustion occurs immediately before misfire. Therefore, find the maximum value Pimax of combustion pressure during each combustion and calculate the maximum value.
The purpose is to detect by comparing Pimax with a predetermined value and determining whether it is partial combustion or complete combustion.

FIG. 3 shows an example in which the value of Pimax differs even in the same complete combustion state depending on the operating condition of the internal combustion engine.

In Figure 3, if a predetermined value (K constant) is determined to suit high-load combustion, P ₂ max is smaller than the predetermined value (K) even though complete combustion occurs under light loads, so It is judged to be a partial combustion. In order to eliminate this kind of contradiction, the in-cylinder pressure PiθA at a fixed angle (θA) before the maximum ignition advance (only the compression stroke is being performed) is determined as an initial condition, and Pimax is divided by this PiθA. Then, by comparing this ratio with a predetermined value α (constant), it becomes possible to always determine whether partial combustion or complete combustion immediately before a misfire occurs at a constant level, regardless of the load, as shown in FIG.

The purpose of the present invention is to obtain the maximum combustion pressure during each combustion.
At the same time as determining Pimax, determine the cylinder pressure PiθA at a fixed advance angle θA before the maximum ignition advance angle, and determine whether the ratio of the two (Pimax/PiθA) is greater than or equal to a predetermined value α. The point is that the ignition limit is always detected regardless of the operating conditions of the internal combustion engine such as the load by determining whether it is complete combustion or partial combustion immediately before misfire.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The ignition limit detection device for an internal combustion engine according to the present invention will be described in detail below according to embodiments.

FIG. 4 shows a block diagram of the present invention, in which numeral 1 indicates an angular position detection device for detecting two angles during the entire stroke of each cylinder of a four-stroke internal combustion engine;
2 is a fixed angle calculation circuit that calculates a fixed angle θA based on the angular position detection signal of the angular position detection device 1;
4 is an ignition detection circuit that detects complete combustion or partial combustion immediately before misfire, and 4 is a pressure detector that detects the pressure inside the cylinder of the internal combustion engine.

Next, detailed circuits of the ignition limit detection device for an internal combustion engine according to the present invention will be explained with reference to FIGS. 5 to 9.

FIG. 5 shows the detailed circuit of the fixed angle calculation circuit.
A reference potential Vref is created by resistors 220, 221 and a capacitor 222, and is supplied to operational amplifiers 28, 213, which will be described below, via resistors 27, 212, respectively.

Then, the fixed angle calculation circuit 2 further performs NOT
Circuit 215, charging control circuit 21, discharge control circuit 2
2. Analog switches 23, 24, 29 that are turned on by a "1" level signal, charging resistor 25, discharging resistor 26, resistors 27, 212 connected to reference potential Vref, input resistor 211, It is composed of operational amplifiers 28 and 213, a capacitor 210, and an AND circuit 214. and resistor 25,
26, 27, a capacitor 210, and an operational amplifier 28 constitute a Miller integration circuit, and when the input voltage is lower than the reference voltage Vref, the capacitor 21
When 0 is charged and higher than Vref, capacitor 21
0 is discharged. Further, the resistors 211 and 212 and the operational amplifier 213 constitute a comparison circuit. Further, it is preferable that the analog switches 23, 24, and 29 be constructed of field effect transistors. Sho 10
is a key switch, 11 is a battery that provides power,
KS is a power supply terminal connected to a power supply 11 via a key switch 10.

Figure 6 shows the charging control circuit 2 of the fixed angle calculation circuit 2.
1. Discharge control circuit 22 and angular position detection circuit 1
Show details. FIG. 7 shows a time chart explaining the operation of the apparatus of the present invention. The charging control circuit 21 is composed of resistors 211 and 212, and a constant voltage lower than the reference potential Vref is taken out from the output terminal A by resistance division.

The discharge control circuit 22 also includes resistors 221 and 22.
2, and a constant potential that is always higher than the reference potential Vref is taken out to the output terminal B by resistance division. Then, the fixed angle calculation circuit 2 determines a fixed angle θA that is a constant angle based on the crank angle.

Next, in the angular position detector 1, a rotor 110 has one protrusion 111 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. It is. Reference numerals 12 and 13 refer to first and second parts arranged at a predetermined angle in the circumferential direction of the rotor 110.
The electromagnetic pickup is opposed to the protrusion of the rotor 110. 16 and 17 are each electromagnetic pick-up 1
Transistors 2 and 13 are connected, and 14 and 15 are resistors. 18 and 19 are NAND circuits forming a flip-flop circuit, one input of which is connected to the collector of transistor 16, and the other input connected to the collector of transistor 17.
The rotor 110 rotates once in the direction of the arrow for every two revolutions of the crankshaft, and when each protrusion of the rotor 110 crosses the electromagnetic pick-ups 12, 13, each of the electromagnetic pick-ups 12, 13 dips into the negative direction as shown in FIGS. 7a and 7b. Generates a signal as shown. Therefore, each electromagnetic pickup 12, 13 detects the angular position M ₁ M ₂ in FIG. When a negative signal is generated in each electromagnetic pickup 12, 13, each transistor 16, 17 becomes conductive, and due to the conduction of each transistor 16, 17, a flip-flop circuit consisting of NAND circuits 18, 19 is activated. An output as shown in FIG. 7c is generated at one output terminal 1a of this flip-flop circuit.

FIG. 8 shows a detailed diagram of the ignition detection circuit 3 and pressure detector 4. The pressure detector 4 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.

The ignition detection circuit 3 uses a maximum pressure value detection circuit 33 that detects the maximum pressure value Pimax and a fixed angle pressure value detection circuit 32 that detects the pressure value PiθA at a fixed angle θA, so that the obtained Pimax/PiθA is a predetermined value. α
A determination circuit 34 that determines whether the
Detects whether complete combustion or partial combustion immediately before misfire occurs.

In such an ignition detection circuit 3, 31 is a processing circuit that processes the signal of the pressure detector 4, and includes resistors 311, 312, 313, 315, 316,
317, 319 and operational amplifiers 314, 318. Note that the resistors 313 and 317 are connected to the reference potential Vref, and their output is
The result will be as shown in Figure 7g. Further, 35 is a monostable generating circuit that generates a monostable output (f) from a fixed angle θA as shown in FIG.
A monostable circuit consisting of a NAND circuit 354, a resistor 352, and a capacitor 353 generates a monostable output (f), and 36 is a NOT circuit 361, 365,
A monostable circuit consisting of a NAND circuit 364, a resistor 362, and a capacitor 363 generates the monostable output shown in FIG. 7d from the output 1-a of the angular position detection circuit 1. Further, 32 is an analog switch 321, a resistor 322, a capacitor 323 connected to the reference potential Vref, and an operational amplifier 324.
This is a hold circuit consisting of a fixed angle θA.
The value Pi of the pressure waveform at is held each time as shown in FIG. 7i, and constitutes a fixed angle pressure value detection circuit. 33 is an operational amplifier 33
1,337, diode 332, resistor 333,3
34, a transistor 335, and a capacitor 336. The peak detector circuit is a maximum pressure value detection circuit. Note that this circuit 33 is grounded to the reference potential Vref. The output signal g of the processing circuit 31 is input to the peak detector circuit, and the operational amplifier 331
and diode 332, the peak value of the input is detected and stored in capacitor 336 through resistor 333. On the other hand, the charge in the capacitor 336 is erased each time by the monostable output f through the resistor 334 and the transistor 335, and the voltage hollow circuit of the operational amplifier 337 takes out an output as shown in FIG. 7h. This output, that is, the maximum pressure value Pmax each time, is divided by resistors 338 and 339, and the output of the maximum pressure value detection circuit 33 is Pimax/α (α>
1). Also, 34 is a resistor 341, 342,
A comparison circuit consisting of an operational amplifier 343, an analog switch 344, a resistor 345, and a capacitor 3
46, a determination circuit made up of a hold circuit made up of an operational amplifier 347. When the output iPθA of the fixed angle pressure value detection circuit 32 and the output Pimax/α of the maximum pressure value detection circuit 53 are input, if Pimax/α is larger than PiθA, the output of the comparison circuit is "1" indicating complete combustion. This becomes a level output, which is taken out by the hold circuit as a monostable output d as shown in FIG. 8j. Further, when Pimax/α is smaller than PiθA, the output is at a level of “0” representing partial combustion just before a misfire, and is similarly taken out by the hold circuit. Next, the operation of the ignition limit detection device according to the present invention will be explained with reference to the time chart of FIG. 7 for the above-mentioned embodiment. In Figure 7, T is Top Dead Center
Center). The angular position detection device 1 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 output is "1" level between _M1 and _M2 , and "0" level is output between _M2 and _M1 .
It emits an output of one pulse per period per two rotations of the internal combustion engine. When the output of the angle detection device 1 reaches the "1" level, the analog switch 23 of the fixed angle calculation circuit 2 is turned on. At this time, NOT
Since the output of the circuit 215 is at the "0" level, the analog switch 24 is turned off, and the AND
Since the output signal of the circuit 214 is at the "0" level and the analog switch 29 for resetting the capacitor is off, the capacitor 210 is charged by the charging control circuit 21 from the reference potential vref from the time point _M1 as shown in FIG. 7e. It will be done. However, charging control circuit 2
Since the output voltage A of No. 1 is constant, the charging current is constant. This charging of the capacitor 210 causes the output of the operational amplifier 28 to become higher than the reference potential Vref, so that the output of the comparison circuit becomes 0 level.

Next, when the signal at the output terminal 1a of the angular position detection device 1 becomes 0 level at the time _M2 , the analog switch 23 is turned off and at the same time the analog switch 24 is turned on, so that the capacitor 210 is connected to the discharge control circuit 22. A discharge is started as shown in FIG. 7e by a constant discharge current due to a constant potential (B).
Then, when the discharge of the capacitor 210 is completed, the output of the operational amplifier 28 becomes lower than the reference potential Vref, so the output of the comparator circuit is inverted and becomes the "1" level, and the output of the AND circuit 214 becomes "1". level, so analog switch 29
is turned on, and the output of the operational amplifier 28 is as shown in FIG.
It is kept constant at the reference potential Vref as shown in .

In this way, since the output potentials A and B of the charging and discharging control circuits 21 and 22 are constant, both the charging current and the discharging current are constant, so there is always a constant voltage at the output terminal 2a regardless of the engine speed. Fixed angle position θA
A fixed angular position signal is generated at.

In addition, the ignition detection circuit 3 generates monostable outputs d and f shown in FIG. 7, and the rotational angle pressure value detection circuit 32 detects PiθA at each fixed angle θA during the compression stroke using the monostable output f. The pressure is then held until the next θA, and the determination circuit 34 compares this PiθA with Pimax/α detected by the maximum pressure value detection circuit 33.
The result is held at the monostable output d from M ₁ to the next M ₁ . Therefore, when Pimax/α is larger than PiθA, that is, when Pimax/PiθA is larger than the predetermined value α, the output is “1” indicating complete combustion, and when Pimax/α is smaller than PiθA, that is, when Pimax/PiθA is larger than the predetermined value α,
When Pimax/PiθA is smaller than the predetermined value α, an output of “0” is shown, indicating partial combustion immediately before a misfire.
In this way, by calculating Pimax and PiθA and comparing the value of Pimax/PiθA, which is obtained by dividing both with the predetermined value α, it is possible to detect partial combustion immediately before a misfire, that is, to determine the ignition limit. can be detected. Note that the output of the determination circuit 34 is input to a control device or a display device (not shown).

Although the above-mentioned embodiment is a detector that detects the ignition limit of only one cylinder, it can be similarly performed with multiple cylinders.

FIG. 9 shows another embodiment 110' of rotor 110.

To explain using a four-cylinder example in FIG.
0', 2 cycles per 2 revolutions of the internal combustion engine 2
It is configured to emit a rectangular pulse.

FIG. 10 shows a detailed diagram of the pressure detector 4 and the processing circuit 31.

In FIG. 10, a resistor 311 is connected to each detector 41, 42, 4 so that the processing circuit 31 has an addition function.
4 resistors 3111, 3112 every 3,44,
Similar measurements can be made by providing 3113 and 3114 and connecting them to the operational amplifier 314 for addition. Even if the pressure for four cylinders were simply added, the change in pressure during the intake stroke and exhaust stroke was small, so other cylinders did not have a large effect and there was no problem.

Furthermore, in the embodiment described above, the fixed angle θA was detected using the two electromagnetic pickups 12 and 13 and the capacitor 210, and the charge/discharge calculation was performed.
Of the three electromagnetic peak ups, 13 (M ₂ in Figure 7)
The electromagnetic pickup may be shifted to directly detect θA.

Further, although the angular position detection device 1 described above uses an electromagnetic pickup to detect the angular position, a photoelectric type or a point type can be used for detection as well.

As described above, according to the device of the present invention, the pressure ratio between the maximum pressure value Pmax in the cylinder of the internal combustion engine and the pressure PθA at the fixed angle θA before the mixture explodes is equal to or greater than the predetermined value α. , or less, it is possible to detect partial combustion immediately before a misfire at a constant level regardless of the operating status of the internal combustion engine. That is, there is an excellent effect that the ignition limit can always be detected at a constant level.

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.

Further, in this embodiment, the circuit is constructed using an analog circuit, but it goes without saying that the ignition limit can be detected in the same manner even if the circuit is constructed digitally.

[Brief explanation of drawings]

Figure 1 is a graph showing the relationship between the air-fuel ratio, exhaust gas components, 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, and Figure 3 4 is a graph showing differences in cylinder pressure waveforms depending on load conditions in a general internal combustion engine; FIG. 4 is a block diagram showing an embodiment of the device of the present invention; FIGS. 5, 6, 8, and 9. 1 and 10 respectively show an example of a detailed circuit of the device of the present invention, and FIG. 7 shows a time chart for explaining the operation of the device of the present invention. 1...Angle position detection device, 2...Fixed angle calculation circuit, 3...Ignition detection circuit, 4...Pressure detector,
10... Key switch, 12, 13... Electromagnetic pickup, 21... Charge control circuit, 22... Discharge control circuit, 23, 24, 29... Analog switch, 32... Fixed angle pressure value detection circuit, 33...
Maximum pressure value detection circuit, 34...determination circuit, 11
0,110'...Rotor.

Claims (1)

[Claims] 1 A pressure detector that detects the cylinder pressure of an internal combustion engine, a maximum pressure value detection circuit that is connected to the pressure detector and that detects the maximum pressure value of the cylinder pressure, and a pressure detector that is connected to the maximum pressure value detection circuit and that A fixed angle pressure value detection circuit that detects the pressure in the cylinder at a predetermined internal combustion engine angular position before the air-fuel mixture in the cylinder explodes, and the pressure detected by the maximum pressure value detection circuit and the fixed angle pressure value detection circuit. An ignition limit detection device for an internal combustion engine, comprising a determination circuit that compares a ratio of values with a predetermined value to detect an ignition limit.