JPH0326780B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ignition/misfire determination device for an internal combustion engine, which is used to detect the ignition limit of an internal combustion engine.

[Conventional technology]

If there is a means to detect the ignition limit of an internal combustion engine,
Useful for air-fuel ratio control, EGR control, ignition timing control, etc. In an internal combustion engine, if the air-fuel mixture can be controlled at the ideal air-fuel ratio, which achieves complete combustion just before a misfire occurs and HC increases, the harmful components CO and HC in the exhaust gas will be at their lowest, and _NOx will generally be at their highest. This is not only advantageous in terms of exhaust gas countermeasures since the air-fuel ratio is reduced compared to the vicinity of the stoichiometric air-fuel ratio used, but also has the lowest fuel consumption rate and is economically advantageous.

Conventional methods for determining ignition and misfire include a conventional pressure detector that detects the absolute pressure or negative pressure within one cylinder of an internal combustion engine (for example, when a piezoelectric element is used, its output is integrated by a charge amplifier; Alternatively, if a strain gauge is used, the bridge output is used as is), and a period T _n exceeding the output value of the pressure detector at a predetermined crank angle position before top dead center in the compression stroke of this cylinder is provided.
Ignition and misfire were determined by measuring and comparing with T _F during the relevant period at the time of misfire (see:
(Japanese Patent Application Laid-open No. 114838/1983).

[Problem to be solved by the invention]

However, recently, differential output type pressure detectors have been used that use piezoelectric elements with good responsiveness as they are without a charge amplifier. In other words, since the output of the differential output type pressure sensor corresponds to the differential component of the output of the above-mentioned normal type pressure sensor, the change period is 2.
It will be doubled. Therefore, if the above-mentioned ignition/misfire discrimination method is applied to a differential output type pressure detector, the measurement period will be approximately halved, and as a result, ignition,
There was a problem that the accuracy of misfire detection decreased.

Therefore, an object of the present invention is to improve the accuracy of determining ignition and misfire when using a differential output type pressure detector.

[Means to solve the problem]

Means for achieving the above-mentioned object is an internal combustion engine equipped with a differential output type pressure detector for detecting a change in combustion pressure in a predetermined cylinder, and a timing generating means is configured to detect a change in combustion pressure in a predetermined cylinder before top dead center in the compression stroke of the cylinder. A crank angle timing signal indicating a predetermined crank angle is generated, the counter means starts measuring the crank angle based on the crank angle timing signal, and the inverted value of the differential output type pressure detector at the predetermined crank angle is detected by the differential output type pressure sensor. Crank angle measurement is stopped when the output of the device exceeds. On the other hand, the value of the counter means at the time of misfire of the engine is set in the constant setting means. As a result, the comparison means compares the value of the counter means and the value of the constant setting means, thereby
Ignition or misfire of the engine is determined depending on the magnitude of the value of the counter means and the value of the constant setting means.

[Effect]

According to the above-mentioned means, the measurement period of the counter means is longer despite the use of a differential output type pressure detector, and the accuracy of determining ignition and misfire is reduced due to the use of a pressure detector with quick response. will improve.

〔Example〕

An ignition and misfire detection device for an internal combustion engine as an embodiment of the present invention is shown in FIG. The ignition and misfire detection device for an internal combustion engine shown in FIG. Includes 5.

An example of the pressure detector 1 in the device shown in FIG.
As shown in the figure.

A pressure receiving plug 103 serving as a pressure medium is inserted between the piezoelectric element 101 and the diaphragm 102.
Reference numeral 104 denotes an output electrode, which is connected to a terminal 106 of a connector 105 with a lead wire 107. 108 is a grounding electrode, and the pressure receiving plug 103
and the housing 1 via the diaphragm 102
Grounded at 09. Insulators 110 and 111 insulate the piezoelectric element 101 from the sensor body 112. Similarly, 113 is an insulator and an output electrode 104
is insulated from the sensor body 112.

The sensor subassembly is assembled using the following steps. From the bottom of the sensor body 112, an insulator 110, an electrode 104, a piezoelectric body 101, a pressure receiving plug 1
03 and an insulator 111, and a metal protrusion ring 114 and a spacer 1 on the outer periphery of the pressure receiving plug 103.
The piezoelectric element 101 and the pressure receiving plug 103 are fixed to the sensor body by caulking the caulking portion 116 of the sensor body through the screws 15. On the other hand, an insulator 113 is inserted from the upper part of the sensor body 112, and a spacer 117 is press-fitted to form a sensor subassembly. Note that a preload is applied to the piezoelectric element 101 due to the springiness of the metal hollow ring 114.

The sensor subassembly is press-fitted into the inner wall of the housing 109, and the diaphragm 102 is welded to a protrusion 1031 at the tip of the pressure receiving plug and a protrusion 1091 at the tip of the housing 109.

The connector 105 is connected to the caulking portion 1 of the housing 109 via a spacer 118 and an O-ring 119.
By caulking 092, it is fixed to the housing 109.

Pressure detectors use piezoelectric elements, so
A signal S(1) representing pressure change per time, ie, dp/dt, is output.

The timing detection device 2 includes a reference signal and angle signal generation device 21, an angle signal waveform shaping circuit 22,
It has a reference signal waveform shaping circuit 23 and a timing calculation circuit 24.

The ignition/misfire determination device 3 includes a sample hold circuit 31, an inverting amplifier circuit 32, and an analog comparison circuit 3.
3, counter circuit 34, digital comparison circuit 35,
and a digital constant setting circuit 36.

The fuel injection pump 5 has injection nozzles 61, 62, 6
3,64.

Details of the angle signal waveform shaping circuit 22 and reference signal waveform shaping circuit 23 of the timing detection device 2 are shown in FIG. 3A. 211 is a combination of a rotor having a plurality of protrusions on the outer periphery and a rotor having one protrusion on the outer periphery, and rotates once for every two revolutions of the crankshaft.

Reference numerals 212 and 213 designate electromagnetic pickups that are opposed to the respective protrusions of the rotor 211.
221, 231 are transistors, 222, 232
is resistance. 223 and 233 are logic circuits, one shot multivibrator, and 224 and 234 are drivers.

One-shot multivibrator 223, 23
Transistors 221 and 23 are connected to the trigger terminal 3.
1 collectors are connected.

When the rotor 211 rotates and each protrusion crosses the electromagnetic pickups 212, 213, the electromagnetic pickups 212, 213 sometimes drop to a negative voltage, and at this moment, the transistors 221, 23
1 becomes conductive, and transistors 221 and 23
The one-shot multivibrators 223 and 233 are triggered by the falling edge of 1, respectively.

One-shot multivibrator 223, 23
3 outputs a low level signal for a time determined by the time constant of the resistor and capacitor, and the inverting driver 224,
234 into a high level signal.

As described above, both the angle signal waveform shaping circuit 22 and the reference signal waveform shaping circuit 23 send out signals S224 and S234 with a frequency proportional to the rotational speed and a constant pulse width, but the angle signal S224 is
As shown in FIG.
720° CA), and the reference signal S234 consists of one pulse per revolution (720° CA), as shown in FIG.
One protrusion is provided on the rotor so that it occurs slightly before the top dead center TDC of the intake stroke.

Timing calculation circuit 2 of timing detection device 2
4 details are shown in FIG. 3B. The timing calculation circuit 24 is composed of preset input (jam input) down counters 241 and 242 and a logic circuit flip-flop 243. down counter 24
Each of the 1,242 preset inputs has a register 241.
A and 242a are connected, and the values of these registers can be rewritten by a writing means (not shown).

When the output S234 of the reference signal waveform shaping circuit 23 is supplied to the set inputs of the down counters 241 and 242, the values N _a and N _b set in the registers 241 a and 242 a are applied to the down counters 241 and 2 respectively.
42. In this state, down counter 2
When the output S224 of the angle signal waveform shaping circuit 22 is supplied to the clock inputs 41 and 242, the down counters 241 and 242 use this signal clock S2.
Count down to 24. here,
If N _a <N _b is set, the value of the down counter 241 becomes 0 and its Z/D (zero detection) terminal becomes high level (“1”) as shown in FIG. So, at this moment, flipflop 2
43 is set. Next, as shown in FIG. 5, the value of the down counter 242 becomes 0 and its Z/D terminal becomes high level ("1"), and at this moment, the flip-flop 243 is reset. Here, the set period of the flip-flop 243 depends on the difference N _b -N _a between the register values, and defines the sample/hold period of the sample hold circuit 30. Note that this sample/hold period is set to a period sufficient for the analog comparison circuit 33 in FIG. 1 to operate.

The configuration of the sample hold circuit 31, inverting amplifier circuit 32, and analog comparison circuit 33 of the ignition/misfire determination device 3 shown in FIG. 1 is shown in FIG. 4A. Figure 4A
In the sample and hold circuit 31, the output S1 of the differential output type pressure detector 1 shown in FIG. As a result, the output S31 of the sample hold circuit 31 becomes as shown in FIG. This output S
31 by an inverting amplifier circuit 32, as shown in FIG. 5, an inverted output S32 of the output S31 is obtained. This output S32 and the output S1 of the differential output type pressure detector 1 are compared by the analog comparison circuit 33. As a result, as shown in FIG. 5, the output S33 of the comparison circuit 33 becomes high level when the output S1 becomes larger than the output S32. Note that MF in FIG. 5 represents a misfire state, and F represents an ignition state.

The configuration of the counter circuit 34, digital comparison circuit 35, and digital constant setting circuit 36 of the ignition/misfire determination device 3 shown in FIG. 1 is shown in FIG. 4B.

In FIG. 4B, the counter circuit 34 has three terminals CLK, STRT, and STR, and these terminals have the following functions.

CLK: Clock to be counted STRT: Starts clock CLK counting at the rising edge of the signal applied to this terminal STR: Ends clock CLK counting at the rising edge of the signal applied to this terminal Therefore, with the rise of the output S243 of the timing detection device 2 at time t ₁ (t ₁ ') in FIG. 5, counting is started using the output S224 of the timing detection device 2 as a clock. Next, the time shown in Figure 5
Output S of the analog comparator circuit 33 at t ₂ (t ₂ ′)
33 rises, the counter circuit 34 stops counting.

This counter output S34 (=T ₁ ) is compared with a preset output S36 (=T ₂ ) of the digital constant setting circuit 36 by a digital comparison circuit 35. In the case of ignition, T ₁ >T ₂ and the output of the digital comparison circuit 35 becomes high level. Conversely, in the case of misfire, T ₁ <T ₂ and the output of the digital comparison circuit 35 becomes low level.

The above operations are performed for each rotation, and are reset for each rotation.

In this way, in the device shown in FIG. 1, the output of the differential output type pressure detector 1 and the timing detection device 2
Signal processing is performed in the ignition/misfire determination device 3 based on the calculation output of the counter output.
A digital comparison circuit 35 compares T ₁ with the output of a digital constant setting circuit 36 in which a constant T ₂ corresponding to the number of counters in case of misfire is set in advance to determine whether ignition or misfire occurs.

Further, an optimal injection timing is calculated in an injection timing calculation circuit 4 based on the output of the ignition/misfire determination device 3 and other information such as the rotation speed and crank angle, and the fuel injection pump 5 is controlled.

Figure 1 shows the principle of determining ignition and misfire of the device in Figure 6A.
This will be explained with reference to the characteristic diagram of B.

FIG. 6A shows the integrated output IP of the pressure detector 1, and therefore corresponds to the waveform when the above-mentioned normal pressure detector is used as the pressure detector. Here, IP1 is the IP at complete ignition (proper injection timing).
2 corresponds to just before a misfire, and IP3 corresponds to a complete misfire. FIG. 6B shows the output P of the pressure detector corresponding to each state in FIG. 6A, where P1 corresponds to complete ignition, P2 corresponds to just before a misfire, and P3 corresponds to a complete misfire.

In FIG. 6B, a line corresponding to the sample-and-hold circuit output signal S31 and a line corresponding to the inverting amplifier circuit output signal S32 are each indicated by a chain line. The waveforms of the analog comparator output signals S33, MF' in the case immediately before a misfire and the comparator circuit output signals S33, F in the case of complete ignition are shown at the bottom of FIG. 6B.

That is, as shown in FIG. 6B, the outputs P1, P2, and P3 of the pressure detector 1 become the inverting amplifier circuit output signal S32 from the sample hold start time STRT.
Time to point STR exceeding level T ₁ , T ₂ , T ₃
is different. Therefore, if the time T ₂ for P2 is set as the judgment reference value in the digital constant setting circuit 36 described above, the time T ₁ for the complete ignition state P1 can be set as the judgment reference value.
Since T ₁ >T ₂ and time T ₃ for misfire state P3 satisfy T ₃ <T ₂ , these can be determined.

Furthermore, the measurement period (T ₁ , T ₃ ) is also relatively long;
The difference between these and the criterion value T ₂ is also large, so
The accuracy of determining ignition and misfire is high.

In carrying out the present invention, various modifications can be made in addition to the above-described embodiments. for example,
Although the above embodiments have been described for diesel engines, they are not limited thereto and can be applied to gasoline engines. When applied to gasoline engines, 4
and 5 are air-fuel ratio control sections, and 61 to 64 are injection extension sections.

〔Effect of the invention〕

As described above, according to the present invention, when a differential output type pressure detector is used, the accuracy of ignition and misfire determination can be improved.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an ignition/misfire determination device for an internal combustion engine as an embodiment of the present invention, FIG. 2 is a diagram showing the configuration of a differential output type pressure detector in the device shown in FIG. 1, and FIG. B is a diagram showing the configuration of the timing detection circuit in FIG. 1, and FIGS. 4A and B are the ignition circuit in FIG.
5 is a waveform diagram showing the signal waveforms of each part of the device shown in FIG. 1, and FIG.
FIG. 2 is a characteristic diagram for explaining the principle of determining ignition and misfire of the device. (Explanation of symbols), 1...Pressure detector, 2...Timing detection device, 21...Reference signal and angle signal generation device, 22...Angle signal waveform shaping circuit,
23...Reference signal waveform shaping circuit, 24...Timing calculation circuit, 3...Ignition and misfire determination device, 31
... Sample hold circuit, 32 ... Inverting amplifier circuit, 33 ... Analog comparison circuit, 34 ... Counter circuit, 35 ... Digital comparison circuit, 36 ... Digital constant setting circuit, 4 ... Injection timing calculation circuit,
5...Fuel injection pump, 61, 62, 63, 64
...Injection nozzle, E...Diesel engine.

Claims (1)

[Scope of Claims] 1. A differential output type pressure detector 1 that detects a change in combustion pressure in a predetermined cylinder of an internal combustion engine; and a crank angle timing signal that indicates a predetermined crank angle before top dead center in the compression stroke of the cylinder. S24
3, and a timing generating means 2 that starts measuring the crank angle according to the crank angle timing signal, and detects an inverted value of the differential output type pressure detector at the predetermined crank angle as an output of the differential output type pressure detector. a counter means 34 that stops measuring the crank angle when the crank angle is exceeded; a constant setting means 36 for setting a value of the counter means when the engine misfires; and a value of the counter means and a value of the constant setting means. an ignition/misfire determination device for an internal combustion engine, comprising a comparing means (35) for comparing the values of the counter means and the value of the constant setting means to determine whether the engine is ignition or misfire according to the magnitude of the value of the counter means and the value of the constant setting means. 2. The timing generating means includes: means 213, 23 for detecting a reference signal S231 indicating a reference crank angle position of the cylinder; and an angle signal S22 for each predetermined crank angle of the cylinder.
4. The ignition/misfire discriminating device for an internal combustion engine according to claim 1, further comprising: means 212, 22 for detecting the crank angle timing signal; and means 24 for generating the crank angle timing signal based on the reference signal and the angle signal.