JPH02259444A - Knock detector of multicylinder type engine - Google Patents

Abstract

PURPOSE:To enhance detection accuracy by arranging a plurality of knock sensors and selecting the optimum knock sensor at every cylinder. CONSTITUTION:A cylinder discrimination means 31 discriminates the cylinder of a combustion process on the basis of the signal from a crank position sensor 18 to output the discrimination signal to a knock sensor selection means 33. In this means 33, a knock discrimination table TBKN is referred to with respect to the discriminated cylinder and a knock sensor 7 or 8 corresponding thereto is selected. An A/D conversion means 30 converts the signal to the sensor 7 or 8 selected by the means 33 to a digital signal to output the same to a knock judge means 34. In the means 34, the output signals of the sensors 7, 8 are averaged and the averaged signal is compared with a predetermined comparing reference level and, when the averaged signal is larger than said level, the generation of knock is judged to output a knock signal. Further, a table alteration judge means 35 judges whether the alteration of the knock sensors is necessary when trouble is generated in the sensors 7, 8 or the cylinder allotment thereof is altered and gives instructions to a rewriting means 36 if necessary to make it possible to enhance knock detection accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a knock detection device for a multi-cylinder engine having a plurality of knock sensors.

[Prior art and problems to be solved by the invention] Generally,
In gasoline engines, increasing the compression ratio to improve thermal efficiency is limited by the octane number of gasoline, and knocking becomes a problem, especially in modern supercharged engines.

This knocking is closely related to ignition timing; advancing the ignition timing increases the maximum combustion pressure, making knocking more likely to occur. On the other hand, since the ignition timing (MBT) that brings out the maximum torque of the engine exists near the knock limit, the output performance of the engine can be greatly improved by advancing the ignition timing to the knock region limit.

For this reason, recently, knock sensors have been installed to detect knocking, thereby increasing the ignition timing ff and I at the knock limit.
t till became possible, and the output performance of the engine could be greatly improved.

Normally, in a multi-cylinder engine, the above-mentioned knock sensor is constructed by installing knock sensors having a number of MW or less in the cylinder block between the cylinders, as disclosed in Japanese Patent Laid-Open No. 58-165573, for example, to reduce the combustion pressure of the air-fuel mixture. Many of these systems detect cylinder knocking by detecting the vibration of the cylinder block caused by the cylinder block.

However, since the knock sensor used for each cylinder is specified in advance, the state of transmission of vibration to the cylinder block varies depending on the operating condition, and the detection sensitivity of the knock sensor for some cylinders decreases, resulting in poor controllability. may worsen.

Therefore, in such cases, to improve detection accuracy,
It is necessary to change the knock sensor that detects knocking in the relevant cylinder.

Furthermore, if the knock sensor used for each cylinder is specified in advance, if a failure occurs in a part of the knock sensor, knock detection for the corresponding cylinder will become impossible.

[Objective of the Invention] The present invention has been made in view of the above circumstances, and improves the accuracy of knock detection by selecting an optimal knock sensor from a plurality of knock sensors for each cylinder of a multi-cylinder engine. It is an object of the present invention to provide a knock detection device for a multi-cylinder engine that can detect knocking in each cylinder even if some knock sensors fail.

[Means and effects for solving the problems] A knock detection device for a multi-cylinder engine according to the present invention includes a knock detection table that stores the correspondence between a plurality of knock sensors and corresponding cylinders in which knocking is detected, and knock sensor selection means that refers to a table and selects a knock sensor corresponding to each cylinder from the plurality of knock sensors; and table change determination means for determining whether or not to change the table.

That is, the knock sensor selection means selects a knock sensor corresponding to each cylinder from the knock detection table, and detects whether or not knocking has occurred in each cylinder.

Further, the table change determination means determines whether or not to change the knock sensor selected by the knock sensor selection means according to conditions, and when changing the knock sensor corresponding to a specific cylinder, or when changing the knock sensor selected by the knock sensor selection means, When it is determined that the knock sensor needs to be changed, such as when a part of the knock sensor is out of order, the correspondence between the knock sensor and each cylinder in the knock detection table is rewritten, and the knock sensor selected by the knock sensor selection means is changed. Be changed.

[Embodiments of the invention] Hereinafter, the present invention will be described in detail with reference to the drawings.

The drawings show an embodiment of the present invention, in which Fig. 1 is a functional block diagram of a knock detection device, Fig. 2 is a layout diagram of a knock sensor with respect to the engine, Fig. 3 is a circuit configuration diagram, and Fig. 4 is a knock detection table. FIG. 5 is a flowchart showing a knock detection procedure, and FIG. 6 is a flowchart showing a knock detection table rewriting procedure.

(Structure) Reference numeral 1 in FIG. 2 indicates the engine body, and the figure indicates a horizontally opposed six-cylinder engine. The cylinder block 2 of this engine body 1 is arranged on both sides (R) 1. with the crankshaft 1a as the center. It is divided into two banks (LH). A combustion chamber 5 is formed in a portion surrounded by each piston 3 fitted into each cylinder #1 to #6 provided in the RH bank and LH bank of the cylinder block 2 and the cylinder heads 4a and 4b.
A to 5f are formed, and spark plugs 6 whose ignition portions are exposed at the combustion points 5a to 5f are attached to the cylinder heads 4a and 4b corresponding to the cylinders #1 to #6.

In addition, the cylinder block 2 of the RH bank has #5
A knock sensor 7 is fixedly installed at the position of cylinder #3 near the cylinder, and the cylinder block 2 of the LH bank is equipped with a knock sensor 7.
A knock sensor 8 is fixedly installed at the position of the #4 cylinder near the #2 cylinder.

, the knock sensor 7.8 detects the vibration of the cylinder block 2 due to knocking and outputs a signal.Normally, the knock sensor 7 detects the vibration of the cylinder block 2 due to knocking and outputs a signal. #3. ．． #5
Vibrations due to cylinder knocking are detected, and the knock sensor 8 detects vibrations caused by cylinder knocking. Detects imaging due to knocking of #6 cylinder.

Reference numeral 10 denotes a control device, which receives signals from various sensors, calculates ignition timing, outputs an ignition signal to the ignition coil 9, and causes the ignition plug 6 to spark. Furthermore, the output signal from the knock sensor 7.8 is taken in to control the ignition timing to avoid occurrence of knocking.

(Circuit configuration) The control device 10 includes a CPU 11, a ROM 12, an RA
M13, a backup RAM 14, an analog/digital (A/D) converter 15, and an input/output (Ilo>interface 16) are connected to each other via a path line 17.

Knock sensors 7.8 are connected to the A/D converter 15 through amplifiers 7a and 8a, respectively, and output ends KOUT of the knock sensors 7.8 are connected through buffers 7b and 8b, respectively. has been done.

The above-mentioned knock sensor 7.8 is a resonant type knock sensor, which is composed of, for example, a vibrator having approximately the same frequency as the knock sensing and a piezoelectric element that detects the vibration pressure of this vibrator and converts it into an electric signal. Detects vibrations transmitted to the cylinder block due to combustion pressure waves during the engine's explosion stroke,
The presence or absence of knock is determined based on the magnitude of the amplitude of the captured waveform.

Further, the potential of the output terminal 1<OUT of the knock sensor 7.8 is the same as that of the buffers 7b, 8b and the A/D converter 15.
The data is taken into the CPU 11 via the CPU 11, and the presence or absence of a failure is determined.

In other words, the output terminal KOtlT of the above-mentioned knock sensor 7.8
The potential of is the resistance R2 from the power supply VCC and its internal resistance R
1, normally V CCX
R2/R1, but for example, if the above-mentioned knock sensor 7.8 fails and short-circuits, its output terminal K
The potential of OUT becomes the ground level.

Further, if the knock sensor 7.8 fails and becomes an oven, the potential of its output terminal K0tlT becomes VCC.

Therefore, with respect to the voltage Kv of the output terminal KO1l of the knock sensor 7.8, the voltage between the normal level V CCx R2/R1 and the earth level, and the normal level V CCX R
2/R1 and the power supply voltage VCC level, a failure determination voltage VF1. VF2, and these fault-specific constant voltages ffVF1. VF2 and the above output terminal Kou■) electric f
By comparing the fKV with the above knock sensor 7.8
It can be determined whether or not it is normal.

Incidentally, failure detection of the knock sensor +j7.8 may be performed by comparing the voltage KV of the output terminal KOUT with a reference voltage set in advance using, for example, a comparator.

Further, various sensors such as a crank position sensor 18 connected to the crankshaft 1a are connected to the input port of the I10 interface 16, while
10 Interface 16 output port has drive circuit 1
The ignition coil 9 is connected via 6a.

The ROM 12 contains a control program, various fixed data for control, and a knock detection table T BK to be described later.
The knock detection table TBKN is transferred from the ROM 12 to the RAM 13 when the system is initialized, and thereafter the knock detection table TBKN on the RAM 13 is referred to as appropriate, and , to be rewritten and used according to conditions.

In addition, the backup RAM 14 stores trouble data when an abnormality occurs, such as when the knock sensor 7.8 breaks down, so the data is stored even when a key switch (not shown) is turned off. It has become so.

In accordance with the control program stored in the ROM 12, the CPU 1i controls the ignition timing based on signals from various sensors such as the crank position sensor 18,
Based on the signal from the crank position sensor 18, an ignition signal is output from the output port of the I10 interface 16 to the drive circuit 16a at a predetermined timing.

Then, the ignition coil 9 is turned ON and the ignition plug 6 of the corresponding cylinder is sparked. As a result, the imaging by the combustion pressure wave is transmitted from the corresponding cylinder to the cylinder block 2, and the CPU 11 refers to the knock detection table TBKN configured in the RAM 13 to detect the knock sensor 7.8 corresponding to the corresponding cylinder. A knock sensor is selected and a channel select signal is output to the A/D converter 15, as well as an A/D conversion start signal. Thereby, the signal from the knock sensor 7 or the knock sensor 8 is taken in, and it is determined whether or not a knock has occurred. As a result, if knocking is detected, the ignition timing of the relevant cylinder is immediately delayed to avoid knocking.

(Functional configuration) The knock detection function in the control device 10 includes a Δ/D conversion means 30, a cylinder discrimination means 31, an engine rotation speed calculation means 32, a knock sensor selection means 33, a knock detection table TBKN, a knock determination means 34, a table It is realized by comprising a change determination means 35 and a rewriting means 36.

The A/D conversion means 30 selects the knock sensor 7 or the knock sensor 8 selected by the knock sensor selection means 33.
A signal is taken in from the corresponding channel, A/D converted, and outputted to the knock determination means 34.

The cylinder discrimination means 31 discriminates the cylinder in the combustion stroke based on a cylinder signal outputted from the crank position sensor 18, for example, at each compression top dead center of each cylinder, and outputs it to the knock sensor selection means 33.

The engine rotation speed calculating means 32 calculates the engine rotation speed N based on the weight position signal from the crank position sensor 18.
Calculate.

In the knock sensor selection means 33, the cylinder discrimination means 31
For the cylinder in the combustion stroke determined in , the knock sensor corresponding to the cylinder is identified from the knock sensors 7 to 8 by referring to the knock sensor detection table TBKN.

That is, as shown in FIG. 4, the knock detection table T
8 and N store the correspondence relationships of knock sensors 7.8 used corresponding to cylinders #1 to #6 in order from the top address AD2 to the last address ^07 of the table,
By reading the content of the address corresponding to the cylinder discriminated by the cylinder discriminating means 31, a sensor to be used for knock detection of that cylinder is selected from the knock sensors 7.8.

The knock determination means 34 averages the output signal of the knock sensor 7.8 which has been A/D converted by the A/D conversion means 30, and compares it with a predetermined comparison reference level. , determines that a knock has occurred and outputs a knock signal.

In the table change determination means 35, the knock sensor 7.
If a failure occurs in the knock sensor 8, or the knock sensor 7
．． When determining whether or not to change the knock sensor selected by the knock sensor selection means 33 according to conditions, such as when changing the assignment of 8 cylinders, and changing the knock sensor for the corresponding cylinder that detects knocking, Rewriting means 3
6 to rewrite.

That is, for example, the A/D conversion means 30
The voltage KV of 01JT is applied to the output terminal of the converted knock sensor 7.8 as a failure determination voltage VF1. Compared with F2, if the knock sensor 7 is determined to be malfunctioning, the rewriting means 3
6, the knock detection table TBKN is rewritten, and knock detection is performed for all cylinders #1 to #6 using the knock sensor 8.

Further, for example, the engine speed N calculated by the engine speed calculation means 32 is compared with a predetermined engine speed NO, and it is determined that the engine speed N is shifted from a low speed range to a high speed range when N≧NO. When it is determined that each cylinder of the knock detection table TBKN and the knock sensor 7.
The correspondence relationship with cylinder #1.8 is determined by the knock sensor 8. #2.
Detects knocking in cylinder #4 and uses knock sensor 7 to detect knocking in cylinder #3.
．． Switching is performed to detect knocking in #5 and #6.

As a result, even if a failure occurs in any of the above-mentioned knock sensors 7.8, knock detection for each cylinder can be performed without any problem, and the knock detection for each cylinder and knock sensor Since the correspondence relationship can be changed, the accuracy of knock detection can be improved.

(Knock Detection Procedure) Next, the knock detection procedure according to the above configuration will be explained according to the flowchart of FIG. 5.

First, when a key switch (not shown) is turned on in step 5101 in FIG.
The knock detection table TBKN of No. 3 is initialized.

Next, in step 8102, an interrupt is permitted, and the process proceeds to step 5103, where a predetermined task is executed until an interrupt occurs.

Next, when an interrupt occurs due to a signal from the crank position sensor 18, the cylinder in the combustion stroke is determined based on the cylinder signal from the crank position sensor 18 in step 5111 of FIG. move on.

In step 5112, the cylinder number determined in step 5111 is stored in address RAH1 of the RAM 13, and the interrupt routine returns to the main routine.

Then, the ignition timing is calculated in CPtJll based on the signal from the crank position sensor 18, and the ignition signal is changed to I.
10 interface 16, an A/D conversion interrupt as shown in FIG.
The contents of A old, that is, the cylinder number of the combustion stroke are read out.

Next, the process advances to step 5122, where the cylinder number stored in the address RAHI is decremented by 1, the start address AD2 of N is added to the knock detection table TB, and the knock detection table T corresponding to the cylinder in the combustion stroke is added. B
The corresponding address AD of KN is calculated.

Next, when the process advances to step 5123, the data at address A[) is read from the knock detection table T■N, the corresponding sensor is selected from knock sensors 7.8, and step 5
Proceed to 124.

In step 5124, the A/D converter 1 is connected to the knock sensor 7 or 8 selected in step 5123.
In addition to outputting the channel select signal to 5, the A/
A D conversion start signal is output, and the process proceeds to step 5125.

Then, in step 5125, the signal from the knock sensor 7 or 8 is A/D converted and taken into the CPU 11, and in step 312, it is determined whether or not the A/D conversion for a predetermined period has been completed. If the A/D conversion has not been completed, the process returns to step 5125 to continue the A/D conversion and complete the A/D conversion.
When the conversion is finished, end the interrupt.

According to the above procedure, the presence or absence of knock occurrence is determined based on the signal from the knock sensor 7 or 8 taken into the CPU 11. For example, if it is determined that knock occurrence has occurred, the ignition timing is immediately retarded. .

(Procedure for rewriting the knock detection table) Next, the procedure for rewriting the knock detection table TBKH will be explained in accordance with the flowchart in FIG. do.

After completing the A/D conversion of the knock sensor 7 signal, step 5
At 201, the voltage KV at the output terminal K out of the knock sensor 7
is compared with the failure judgment voltage VF1, and if KV<VN, the process proceeds to step 5203, and if KV≧VF1, the process proceeds to step 5202, where the voltage KV is compared to the failure judgment voltage VF2.
Compare with.

In step 5202, if the voltage KV is KV≦VF2, the routine is terminated, and if KV>VF2, the routine proceeds to step 5203.

On the other hand, if the voltage KV at the output terminal Kout of the knock sensor 7 is KV<VFl in step 5201, or if KV>VF2 in step 8202, then in step 3203 the knock sensor 7 After making a determination, the trouble data is stored in the backup RAM 14 and the process proceeds to step 5204.

In step 5204, knock detection table T BKN
The correspondence relationship between each cylinder and the knock sensor 7.8 stored in address D7 is rewritten to addresses AD2 to D7, the knock sensor 8 is changed to be used for all cylinders, and the routine is ended.

[Effects of the Invention] As explained above, according to the present invention, the correspondence between cylinders that detect knocking and knock sensors is stored in a knock detection table, and the knock sensor selection means refers to the knock detection table to select a plurality of knock detection tables. Select the knock sensor corresponding to each cylinder from among the knock sensors. When the table change determination means determines that the knock sensor should be changed, the knock detection table is rewritten and the knock sensor selected by the knock sensor selection means is changed, so that some of the knock sensors may be malfunctioning. Even if a knock occurs, it is possible to detect knock by backing up with another normal knock sensor, and it is also possible to select the optimal knock sensor for the relevant cylinder depending on the operating condition, improving the accuracy of knock detection. Qin has excellent effects such as being able to do so.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention; FIG. 1 is a functional block diagram of a knock detection device, FIG. 2 is a layout diagram of a knock sensor with respect to an engine, FIG. 3 is a circuit configuration diagram, and FIG. 4 is a knock detection table. FIG. 5 is a flowchart showing a knock detection procedure, and FIG. 6 is a flowchart showing a knock detection table rewriting procedure. DESCRIPTION OF SYMBOLS 1... Engine body, 7.8... Knock sensor, 33... Knock sensor selection means, 35... Table change determination means, 7' BKN... Knock detection table. Figure Figure Figure

Claims (1)

[Scope of Claims] A knock detection table that stores a correspondence relationship between a plurality of knock sensors and corresponding cylinders in which knocking is detected; and a knock sensor corresponding to each cylinder from among the plurality of knock sensors by referring to the knock detection table. knock sensor selection means for selecting a knock sensor; and table change determination means for rewriting the correspondence of the knock detection table and determining whether or not to change the knock sensor selected by the knock sensor selection means. Knock detection device for multi-cylinder engines.