JPS62248852A - Combustion controller for internal combustion engine - Google Patents

Abstract

PURPOSE:To protect an engine by properly averting preignition and abnormal knocking by cutting the fuel supply into the cylinder in abnormal ignition on the basis of the signal of a cylinder internal-pressure sensor. CONSTITUTION:In an injection timing calculating circuit 34, the injection timing is calculated from the engine revolution speed and the intake air quantity, and the feed signals Si1-Si4 having the injection pulse corresponding to the injection timing are outputted into the injectors 36a-36b of the cylinders through a fuel-cut controlling circuit 35. When a knocking judging circuit 26 judges the generation of the abnormal combustion on the basis of the electric charge signals S1-S4 supplied from the cylinder internal-pressure sensors 1a-1d, an anom aly judging signal Sn0 is outputted into the fuel-cut controlling circuit 35. When the anomaly judging signal Sn0 is input, output of the feed signals Si1-Si4 into the injector 36a-36d of the cylinder in which abnormal combustion is generated is suspended.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a combustion control device that cuts off fuel during abnormal combustion in order to prevent damage to an internal combustion engine of an automobile or the like.
.

(Prior art) In general, abnormal combustion is combustion in which unburned air-fuel mixture or deposits spontaneously ignite or ignite on the surface, without fire propagation starting from an ignition spark. When abnormal combustion occurs, a sudden pressure rise and a knocking sound occur. This often results in not only energy loss but also burnout of pistons, valves, etc.

Therefore, in order to suppress the occurrence of knocking, which is one of the modes of such abnormal combustion, and realize smooth combustion, conventional methods such as those described in Japanese Patent Application Laid-open No. 59-1982 have been proposed. There is an apparatus described in Japanese Patent No. 39973.

In this device, the maximum value of the knock sensor output in a predetermined period after ignition is detected via an amplifier circuit, an integrating circuit, a peak hold circuit, etc., while the average value of the sensor output is determined, and from this average value, a comparison reference value is determined. Calculate. Then, by comparing this maximum value with the comparison reference value, it is determined whether knocking has occurred, and the ignition timing is advanced as much as possible according to the determination result, and if non-king occurs, the ignition timing is delayed to prevent knocking. control and improves drivability.

(Problems to be Solved by the Invention) However, in such conventional combustion control devices for internal combustion engines, the control specifications were only to retard the ignition timing to avoid knocking. There were some problems.

In other words, if preignition (surface ignition) due to deposits or abnormal non-king caused by it occurs, retarding the ignition timing alone will not adequately suppress the above phenomenon, and therefore the plug will melt. This may lead to engine damage such as damage or seizure of the piston, so improvements are desirable in terms of engine protection.

(Purpose of the Invention) Therefore, the present invention detects the occurrence of pre-ignition or abnormal non-king from the signal of the cylinder internal pressure sensor, and when it occurs, cants the fuel supply to the relevant cylinder. The purpose is to protect the engine by appropriately avoiding pre-ignition and abnormal knocking, which are difficult to suppress.

(Means for Solving the Problems) In order to achieve the above object, the combustion control device for an internal combustion engine according to the present invention has pressure detection means a for detecting the combustion pressure of the engine, as shown in FIG. and an operating state detecting means for detecting the operating state of the engine, an abnormality determining means C for determining whether combustion in the engine is abnormal based on the output of the pressure detecting means a, and a combustion supplying means based on the operating state. A supply amount calculation unit 19d calculates the amount and outputs a supply signal, and stops outputting the supply signal when combustion in the engine is determined to be abnormal; and a fuel supply means e for supplying.

(Function) In the present invention, the occurrence of pre-ignition or abnormal non-king is detected based on the output of the cylinder internal pressure sensor, and when such abnormal combustion occurs, the fuel supply to that cylinder is reduced. Therefore, the above phenomenon, which is difficult to suppress only by retarding the ignition timing, is appropriately avoided, and the engine is protected.

('Example) Hereinafter, the present invention will be explained based on the drawings.

2 to 4 are diagrams showing a first embodiment of the present invention.

First, the configuration will be explained. In FIG. 2, reference numerals la to 1d are cylinder internal pressure sensors (pressure detection means), and the cylinder internal pressure sensors 1a to 1d convert the internal pressure of the cylinder 1 in each cylinder of a four-cylinder engine into an electric charge using a piezoelectric element. Output signals S, ~S4. As an example of the cylinder internal pressure sensor 1axld, the one in the first cylinder is specifically shown as shown in FIG. 3 (ta) to (C1).

In Fig. 3 ia), 2 indicates the cylinder head of the engine, and the ignition plug screw hole 3 formed in the cylinder head 2
A spark plug 4 is screwed into the ignition plug 4 . A cylinder internal pressure sensor la serving as a washer is sandwiched between the ignition plug 4 and the mounting seat surface 5 so that they are collinear. The cylinder internal pressure sensor la is shown in Figure 3 (
b), (As shown in C1, two piezoelectric elements 7 are placed on both sides of a ring-shaped center electrode 6, and an upper electrode 8 and a lower electrode 9 are laminated in order on the outside thereof, as shown in C1, These inner and outer circumferences are fixed together with an insulating mold member 10. Also, a lead wire 11 is connected from the center electrode 6.
is removed through the mold member IO.

Since the cylinder internal pressure sensor 1a is tightened as a washer for the ignition plug 4, when the combustion pressure in the cylinder acts on the ignition plug 4, the tightening force increases or decreases, and the electric charge generated by the piezoelectric element 7 increases. outputs an analog signal Sl having a voltage value corresponding to the cylinder internal pressure. Therefore, the combustion pressure of the engine can be extracted in a form that is easy to use as an electrical signal.

Again in FIG. 2, the outputs S1 to S4 of the cylinder internal pressure sensors 1a to ld are input to the knock vibration extraction means 20, and the knock vibration extraction means 20 is connected to a multiplexer (MP
X) 21, a switching signal generator 22, an input amplifier 23, and a bandpass filter (BPF) 24. The signals S, -S4 are input to the multiplexer 21, and the switching signal Sc is further input from the switching signal generator 22 to the multiplexer 21 at a predetermined timing.

The output signal of the crank angle sensor 25 is input to the switching signal generator 22, and the crank angle sensor 25 detects the crank angle of the engine and generates signals Ct, Ca, C, and C at every 720°, 180°, and 2°, respectively. Output. In addition, 720
The degree signal Ci is output at a timing of 90' before the compression top dead center of the first cylinder, and the 180 degree signal Ca is also output at a timing of 90 degrees before the compression top dead center of each cylinder.

The switching signal generator 22 generates the switching signal Sc in synchronization with the output timing of the 180° signal Ca, and the multiplexer 21 changes the output of the cylinder internal pressure sensors 1 a - 1 d every time this switching signal Sc is input. S+ -33
-34-3t and output to the input amplifier 23. The input amplifier 23 amplifies these signals and outputs them as a signal S to a band-pass filter (BPF) 24, and the band-pass filter 24 passes only the signal S6 in the frequency band corresponding to the knock vibration out of the signal S5. It is output to the determining means 26.

The knock determining means 26 is composed of a knocking measuring circuit 27 and a determining circuit 28, and the knocking measuring circuit 27 receives a set signal Ss and a reset signal Sr from a timing circuit 29 in addition to the signal S6.

Based on the signal CI XCa % Cz from the crank angle set 25, the timing circuit 29 outputs a set signal Ss and a reset signal Sr that are a single (H) pulse at the timing shown in Table 1 below.

(This page, blank spaces below) Table 1 In Table 1, BTDC represents the time before compression top dead center, and ATDC represents the time after compression top dead center. The crank angle sensor 25 and the timing circuit 29 constitute a period setting means 30 that sets a knocking detection period for each cylinder in the explosion stroke.

The knocking detection circuit 27 integrates the output signal S of the bandpass filter 24 when the set signal Ss is input, and stops the integration process when the reset signal Sr is input.

This integration processing is performed so that the output of signals Ss and 3r is before compression top dead center (
Since the knocking detection period is repeated before and after TDC), it is divided into an integral output N before and after the compression top dead center each time, and an integral output S after the compression top dead center, and the knocking measurement circuit 27 uses these integral outputs S. , N to the determination circuit 28. The determination circuit 28 determines the ratio S between the integral output S and the integral output N.
/N, and when the value of this ratio S/N is larger than a predetermined value SL, it is determined that it is a regular knock and the knock signal 'S
n is output to the ignition timing calculation circuit 31.

Also, the S/N value is a predetermined value SL! (However, SL.

<St, set to *), it is determined that there is an abnormal knock and an abnormal combustion determination signal S1° is output to a fuel cut control circuit 35, which will be described later.

In the above, the knock vibration extracting means 20 and the knock determining means 26 constitute an abnormality determining means 37 as a whole.

The ignition timing calculation circuit 31 further includes a crank angle sensor 2.
A signal from an operating state detecting means 40 composed of a load sensor 5 and a load sensor 32 is input. The load sensor 32 detects an intake air amount Qa corresponding to a re-engine load using, for example, an air flow meter.

The ignition timing calculation circuit 31 calculates the engine speed N based on the output of the crank angle sensor 25, and also calculates the engine speed N and Q.
The basic ignition timing is calculated from a, and this is corrected depending on the presence or absence of the knock signal Sn to determine the final ignition timing. For example, when the knock signal Sn is input, the basic ignition timing is corrected to the retarded side so as to suppress non-king. The output of the ignition timing calculation circuit 31 is input to the ignition means 33, and the ignition means 33 generates a high voltage at a timing corresponding to the final ignition timing to ignite the air-fuel mixture.

On the other hand, 34 is an injection time calculation circuit, which calculates the engine rotation speed N based on the output of the crank angle sensor 25, and from this N and the detection output Qa of the load sensor 32, the injection time Tp (Tp=-Qa /N) and supply signal 3 having an injection pulse corresponding to this calculated value 'rp.
i1 to Si4 are output to the injectors (fuel supply means) 36a to 36d of each cylinder via the fuel power/nodule control circuit 35.

The fuel cut control circuit 35 further receives an abnormal combustion determination signal S, . . . from the abnormality determination means 37. is inputted (that is, inputted only at the time of abnormal combustion), and the abnormal combustion determination signal S□. is input, the supply signals Si, ~S are set so as to cut the supply of fuel to the corresponding cylinder.
t, the output to the corresponding injector 36a to 36d is stopped. The injectors 36a to 36d supply fuel to the engine based on supply signals St, to S14 from the injection time calculation circuit 34.

In the above, the injection time calculation circuit 34 and the fuel cut control circuit 35 constitute a supply amount calculation means 38.

Further, the abnormality determining means 37 and the supply amount calculating means 38 are constituted by a so-called control unit consisting of a microcomputer, an I10 port, and the like.

Next, the operation will be explained with reference to the timing chart shown in FIG.

The four cylinders repeat four cycles corresponding to the crank angles shown in FIG. 4 (ta), and the crank angle sensor 25 receives signals Ci and C shown in FIG.
A, C, are output. Now, focusing on the first cylinder, the cylinder pressure sensor 1a installed in the first cylinder produces a signal S that changes as shown in FIG. 4 (141).

In addition to the normal knock nk during the explosion stroke, this signal SL includes noise 1. due to intake valve seating vibration, which is mechanical noise. , + (hereinafter referred to as suction/closing noise) and noise e1 due to exhaust valve seating vibration (hereinafter referred to as exhaust/close noise) are superimposed. Such signal changes are the same for the other 2nd to 4th cylinders, as shown in Figure 4(f).
-(h) as signals 82-S, respectively. This is because in a high rotation range, vibrations due to the seating of the intake and exhaust valves become large, and the vibrations are also detected by the cylinder internal pressure sensor la.

Each cylinder repeatedly explodes in the order of 1st - 3rd - 4th -> 2nd cylinder, and in particular, the cylinder internal pressure sensor 1b and IC of the 2nd and 3rd cylinder are sandwiched between the adjacent 1st and 3rd cylinders on both sides.
It is greatly affected by the seating vibration of the intake and exhaust valves of the 4th cylinder. Therefore, adjacent cylinder intake/exhaust noise e□, 11 is likely to be superimposed on the signals S2, S even during the explosion stroke.

This intake/exhaust valve noise e0, 50 occurs regardless of the regular knock nk, so this should be properly determined and the regular knock n
, only need to be determined.・Signal S,
, S, are sequentially switched for each explosion stroke by the multiplexer 21 in accordance with the switching signal Sc shown in FIG. Furthermore, this signal S.

is output by the bandpass filter 24 as a signal S having only a portion of the frequency band □ corresponding to a predetermined non-king vibration, as shown in FIG. 4(G).

The signal S is integrated by the non-king measuring circuit 27 only during the knocking detection period set for each cylinder, but this knocking detection period is determined by the signals SS and Sr shown in FIG. As shown in Table 1, the output timing of the signals Ss and Sr is 90 degrees before and after compression top dead center for the first and fourth cylinders, and shorter than that for the second and third cylinders. It is 45 degrees before and after the point.

Therefore, the signal S6 is integrated twice with TDC as the boundary per cylinder, and the integrated outputs S and N are as shown in Fig. 4 (1).
) is shown.

Here, in the vibration component of the signal S1, a part nkslnl etc. that approximates a knocking vibration is likely to appear in the signal S, but the first
The cylinder intake/closing noise 10 does not appear in the integral output even if it appears in the signal S6 superimposed on the signal S2 because the non-king detection period of the second cylinder is 45 degrees before and after TDC.

Therefore, the knock signal Sn based on the S/N is as shown in FIG.
As shown in 0), this opening/closing noise i□ does not cause the pulse to rise and is not determined to be a normal knock. On the other hand, the vibration nh appears in the signal s6 and belongs to the period of 90° before and after TDC, which is the first cylinder knocking detection period, so the integral output S has a value larger than N. As a result, the SZN ratio becomes equal to or higher than the predetermined value SL, and as shown in FIG.
As shown in 01, the knock signal Sn generates an (H) pulse and is determined to be a normal knock. Therefore, the ignition timing is corrected to the retarded side, and non-king is suppressed.

In this way, even if the suction/closing noise 10 of the first cylinder is superimposed on the cylinder internal pressure sensor output S2 of the second cylinder, the knocking detection period of the second cylinder is limited to an area of 45° before and after TDC, so the suction/closing noise 11 can be eliminated to improve the detection accuracy of non-king. Note that this also applies to the exhaust/close noise e0 of the first cylinder, and even if this noise is superimposed on the output S2, it will be outside the non-king detection period of the second cylinder and will be reliably eliminated.

On the other hand, the injection time calculation circuit 34 calculates the injection time 'rp from the engine speed N and the intake air amount Qa, and furthermore, the supply signals St, ~Si4 having injection pulses corresponding to the injection time Tp are used for cut control. It is outputted via the circuit 35 to the injectors 36a to 36d of each cylinder. In this case, the knock determination means 26 determines that the S/N value is the predetermined value SL! When it is larger than that (that is, when abnormal combustion occurs), the abnormality determination signal S is sent to the fuel cut control circuit 35. is output. Then, when this abnormal combustion determination signal S7° is input, abnormal combustion has occurred in the supply signal Sl+"Si4 (that is, it is calculated and determined that the S/N value is larger than the predetermined value SL. ) Output to the cylinder's injector is stopped.

Therefore, it is possible to appropriately avoid abnormal combustion due to abnormal knocking, which is difficult to suppress only by retarding the ignition timing as in the past. As a result, engine damage such as plug volume or piezo seizure can be prevented, and the engine can be protected.

Further, in this embodiment, the fuel supply is cut for each cylinder, and the fuel supply is continued for normal cylinders. Therefore, it is possible to protect the engine by controlling the combustion state more precisely while preventing a decrease in engine output.

FIG. 5.6 is a diagram showing a second embodiment of the present invention. In explaining this embodiment, the same components as those in the first embodiment are given the same reference numerals, and the explanation thereof will be omitted.

In this embodiment, combustion abnormality is determined by specifically detecting pre-ignition.

In FIG. 5, la to 1d are cylinder internal pressure sensors, 21 is a multiplexer, 22 is a switching signal generator,
23 is an input amplifier, 25 is a crank angle sensor, and their configurations and functions are the same as in the first embodiment. The output signal S of the input amplifier 23 is input to the A/D converter 39, and the A/D converter 39 converts the output signal S into a digital signal and sends this digital conversion value to the preignition determination circuit 41. Output.

The pre-ignition determination circuit 41 differentiates the cylinder internal pressure after passing through the multiplexer 21, and compares this differential value with a predetermined slice level before compression top dead center. When this differential value is larger than a predetermined slice level, it is determined that pre-ignition has occurred, and an abnormal combustion determination signal S0 is output to the fuel cut control circuit 35.

On the other hand, the injection time calculation circuit 34 calculates the injection time 'rp from the output signal of the crank angle sensor 25 and the detection means Qa of the load sensor in the same manner as in the first embodiment, and also calculates the injection time 'rp corresponding to this calculated value 'rp. Supply signal Si with pulses
1 to Si4 are output to each injector 36a to 36d via the fuel cut control circuit 35.

The fuel cut control circuit 35 is further configured to receive an abnormal combustion determination signal 5fip from the pre-ignition determination circuit 41 (in other words, it is input only when pre-ignition occurs), and an abnormal combustion determination signal S□. When this happens, the output of the corresponding injector among the supply signals St to S14 is stopped so as to cant the supply of fuel to the corresponding cylinder.

In the above, the multiplexer 21 and the switching signal generator 22
, input amplifier 23, A/D converter 39, and pre-ignition determination circuit 41 collectively constitute abnormality determination means 47, and injection time calculation circuit 34 and fuel cut control circuit constitute supply amount calculation means 48.

Next, the operation will be explained according to the timing chart shown in FIG. The gradient of the cylinder internal pressure at this time is larger than that during normal combustion, and
The maximum value of cylinder internal pressure also occurs at compression top dead center.

As shown by the broken line in FIG. 6 (Tk), the cylinder internal pressure after passing through the multiplexer 21 is differentiated by the pre-ignition determination circuit 41, and the differential value is compared with a predetermined slice level before compression top dead center. When this differential value is larger than a predetermined slice level (that is, when pre-ignition occurs), the fuel cant control diagram is as shown in FIG. 6 (1). 35, an abnormal combustion determination signal S0 is output. When this abnormal combustion determination signal S7 is input, the fuel cut control circuit 35 outputs the supply signal 5i from the injection time calculation circuit 34.
The output of the supply signal to the injectors 36a to 36d of the cylinder in which pre-ignition is occurring among l-8i4 is stopped. Therefore, in this embodiment, abnormal combustion called pre-ignition, which is particularly difficult to predict, can be appropriately avoided, and the engine can be protected as in the first embodiment.

(Effects) According to the present invention, when abnormal combustion such as abnormal knocking or pre-ignition occurs, the fuel supply to the relevant cylinder is cut, so abnormal combustion can be appropriately avoided and the plug can be prevented from melting. Engine damage such as piston seizure can be prevented, and the engine can be protected.

[Brief explanation of drawings]

Fig. 1 is a basic conceptual diagram of the present invention, Figs. 2 to 4 are diagrams showing a first embodiment of the invention, Fig. 2 is an overall configuration diagram thereof, and Fig. 3 (a) is a cylinder of the □. Figure 3 (bl is a cross-sectional view of the cylinder internal pressure sensor, Figure 3 (C1 is a plan view of the cylinder internal pressure sensor, and Figure 4 is a timing chart for explaining its operation) showing the installed state of the internal pressure sensor. ,
FIG. 5.6 is a diagram showing the second embodiment of the present invention, and the fifth embodiment is a diagram showing the second embodiment of the present invention.
The figure is an overall configuration diagram, and FIG. 6 is a timing chart for explaining its operation. 1a to 1d... Cylinder internal pressure sensor (pressure detection means), 36a to 36d... Injector (fuel supply means), 37.47... Abnormality determination means, 38.4
8...Supply amount calculation means, 40...Operating state detection means. Figure 1

Claims (2)

[Claims] (1) a) Pressure detection means for detecting the combustion pressure of the engine; b) Operating state detection means for detecting the operating state of the engine; and c) Based on the output of the pressure detection means, whether or not combustion of the engine is abnormal. d) Calculates the combustion supply amount based on the operating state and outputs a supply signal, and stops outputting the supply signal when it is determined that combustion in the engine is abnormal; A combustion control device for an internal combustion engine, comprising: a supply amount calculating means for supplying fuel to the engine based on the supply signal; and e) a fuel supply means for supplying fuel to the engine based on the supply signal. (2) The combustion control device for an internal combustion engine according to claim 1, wherein the abnormality determining means determines the combustion abnormality by detecting knocking or pre-ignition at a predetermined level or higher.