JP2001032744A - Knocking determining device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To precisely determine knocking regardless of driving region, by extracting knocking information by a cylinder internal pressure, detecting load information of an internal combustion engine from one of the cylinder internal pressure and pressure inside an intake pipe, and determining knocking based on a compared result of the knocking information with the load information. SOLUTION: An extracting means 2a extracts knocking information from a detection signal of a cylinder internal pressure of a cylinder internal pressure detecting means 4. A load detecting means 2b detects load information of an internal combustion engine from one of the cylinder internal pressure detected by the cylinder internal pressure detecting means 4 and pressure inside an intake pipe. A knocking detection means 2c determines knocking based on a comparison result between the knocking information and the load information. Since the knocking is determined by the comparison result between the knocking information and the load information, the load information of the internal combustion engine is properly reflected on the determination of the knocking. Accordingly, when a load condition of the internal combustion engine changes, the knocking is properly determined while the change being reflected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a knocking determination device for an internal combustion engine which determines the occurrence of knocking based on the pressure in a cylinder of the internal combustion engine.

[0002]

2. Description of the Related Art In general, in an engine as an internal combustion engine, ignition timing control is performed at an optimum ignition timing that ensures both high output and avoidance of knocking. When it is determined that knocking actually occurs, the ignition timing is retarded to suppress knocking. As such a conventional knocking determination device, for example, Japanese Unexamined Patent Publication No.
What is described in 16030 gazette is known. This knocking determination device includes four in-cylinder pressure sensors that respectively detect pressures in four cylinders of an engine (hereinafter, referred to as “in-cylinder pressures”), and four knocking information that respectively extract knocking information from detection signals of the four in-cylinder pressure sensors. And a signal processing circuit that determines knocking in each cylinder. Specifically, each cylinder pressure sensor detects two predetermined crank angles in the compression stroke (for example, 300 °, 360 ° from the top dead center at the start of the intake stroke).
゜), the in-cylinder pressure values PL and PU are detected, and the difference P
D (= PL-PU) is stored in the RAM. Each signal processing circuit includes a band-pass filter (hereinafter, referred to as “BPF”), a rectifier circuit, and an integrating circuit.
F filters the detection signal of the in-cylinder pressure sensor between two predetermined crank angles (for example, 360 ° to 480 °) in the combustion stroke, and makes it a knocking signal as knocking information. This knocking signal is rectified by a rectifier circuit, further integrated by an integrating circuit, and stored in the RAM as an integrated value N1. When the ratio N1 / PD calculated from the N1 and PD values in the RAM is larger than a predetermined value, it is determined that knocking has occurred in this cylinder. That is, knocking is determined by determining the ratio N1 / PD of the integrated value N1 of the knocking signal and the in-cylinder pressure difference PD for each cylinder, and comparing this with a predetermined value.

[0003]

As described above, in the conventional knocking determination device, the ratio N1 / PD of the in-cylinder pressure difference PD and the integrated value N1 of the knocking signal is simply compared with a predetermined value. Knocking is determined. However, the actual occurrence of knocking changes as the intake air amount changes due to a change in the load state of the engine. Further, for example, when the engine speed is high, the vibration level of the cylinder increases, and the amplitude level of the knocking signal when knocking actually occurs tends to increase. On the other hand, in the conventional knocking determination device, knocking is determined by comparing the ratio N1 / PD with a predetermined value regardless of a change in the load state of the engine. Therefore, knocking can be appropriately determined. The operating range is limited, and there is a problem that knocking cannot be accurately determined in an operating region other than the operating region.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and has as its object to provide a knocking determination device for an internal combustion engine that can accurately determine knocking regardless of an operation range.

[0005]

In order to achieve this object, a knocking determination device 1 for an internal combustion engine (for example, an engine 3 in the embodiment (hereinafter, the same applies in this embodiment)) according to the first aspect of the present invention includes a knocking determination device 1 in the cylinder 3a. Knock detection is performed based on an in-cylinder pressure detecting means (in-cylinder pressure sensor 4) for detecting an in-cylinder pressure P which is a pressure, and a detection signal (in-cylinder pressure signal PCL) of the in-cylinder pressure P detected by the in-cylinder pressure detecting means (in-cylinder pressure sensor 4). Extraction means 2a (ECU2, steps 5 to 6) for extracting knocking information (maximum value bpfPMAX) representing the situation of the above, and the in-cylinder pressure P detected by the in-cylinder pressure detection means (in-cylinder pressure sensor 4) and the pressure in the intake pipe (intake Load information (maximum value PCLMA) of the internal combustion engine (engine 3) is obtained from one of the pipe absolute pressures PBA).
X) to detect the knocking information (maximum value bpfPMAX) extracted by the extraction means 2a (ECU2, steps 5 to 6) and the load detection means 2b (ECU2, step 6). Based on the comparison result with the detected load information (maximum value PCLMAX),
Knocking determination means 2c (ECU) for determining knocking
2, steps 7 to 8).

According to the knocking determination apparatus for an internal combustion engine, the extracting means extracts knocking information from the detection signal of the in-cylinder pressure of the in-cylinder pressure detecting means. In addition, the load detecting means includes:
Load information of the internal combustion engine is detected from one of the in-cylinder pressure and the pressure in the intake pipe detected by the in-cylinder pressure detecting means. further,
The knocking determination means determines knocking based on a comparison result between the knocking information and the load information. As described above, according to the comparison result between the knocking information and the load information,
Since knocking is determined, the load information of the internal combustion engine can be appropriately reflected in the knocking determination unlike the related art. Therefore, even when the load state of the internal combustion engine changes, knocking can be appropriately determined while reflecting the change, and knocking can be accurately determined regardless of the operation range.

In the above, the knocking determination means 2c
It is preferable that the determination of knocking by the (ECU 2) is executed in accordance with the rotation speed (engine speed NE) of the internal combustion engine (engine 3).

According to the knocking determination apparatus for an internal combustion engine, in addition to the load information detected from one of the in-cylinder pressure and the pressure in the intake pipe, it further responds to the rotation speed of the internal combustion engine, which is one of the load information of the internal combustion engine. Since the knocking is determined as described above, the load information of the internal combustion engine can be more appropriately reflected in the knocking determination. Therefore, knocking can be determined with higher accuracy.

In the above description, knocking information (maximum value bpfPMAX) and load information (maximum value PCLM)
AX) is preferably an average value (average value bpfPMAX (AVE), average value PCLMAX (AVE)) of a plurality of information values respectively obtained in a plurality of combustion cycles of the internal combustion engine (engine 3). .

According to this knocking determination apparatus for an internal combustion engine, an average value in a plurality of combustion cycles is used as knocking information and / or a detection signal of the load detection means. It is possible to reduce the influence of variations and temporary fluctuations between a plurality of combustion cycles. As a result, knocking can be more accurately determined.

[0011]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an internal combustion engine knock determination apparatus according to a first embodiment of the present invention. FIG. 1 shows a schematic configuration of an engine 3 as an internal combustion engine to which the knocking determination device 1 of the present invention is applied. As shown in FIG. 1, the knocking determination device 1 includes an ECU 2. The ECU 2 controls the ignition timing of the engine 3 according to a detection signal input from each of the sensors described later, and also as described later. A knocking determination process is performed.

The engine 3 is an in-line four-cylinder type, and an in-cylinder pressure sensor 4 as an in-cylinder pressure detecting means and a spark plug 5 are attached to a cylinder head 3b of each cylinder 3a. The in-cylinder pressure sensor 4 is of a piezoelectric element type integrated with the ignition plug 5 and is fixed to the cylinder head 3b together with the ignition plug 5. The in-cylinder pressure sensor 4 detects a pressure P in the cylinder 3a (hereinafter, referred to as “cylinder pressure P”).
, The in-cylinder pressure sensor 4 itself is bent together with the spark plug 5 to detect the in-cylinder pressure P as a voltage value (V), and the detection signal is used as an in-cylinder pressure signal PCL by the ECU.
Send to 2. On the other hand, the ignition plug 5 receives a high-voltage ignition signal from the ECU 2 via the ignition coil 6 (see FIG. 3A).
Is discharged, and the mixture in the combustion chamber is burned by discharging.

An intake pipe internal pressure sensor 8 is mounted downstream of the throttle valve 7a of the intake pipe 7 of the engine 3. The intake pipe internal pressure sensor 8 is a semiconductor pressure sensor that detects the intake pipe absolute pressure PBA (pressure in the intake pipe) in the intake pipe 7 and converts the detection signal into an EC.
Send to U2.

On the other hand, the crankshaft 3d of the engine 3
Has a magnet rotor (timing rotor) 9a
Is attached, and the magnet rotor 9a
The crank angle sensor 9 is formed together with the E (magnetic resistance element) pickup 9b. The crank angle sensor 9 is
With the rotation of the crankshaft 3d, both the CRK signal and the TDC signal, which are pulse signals, are output. CRK
The signal is a signal indicating the rotational angle position of the crankshaft 3d. One pulse is output for each 1 ° of the crank angle, and the ECU 2 obtains a measurement end timing and the like described later based on the CRK signal. The TDC signal is
This signal indicates that the piston 3c is at the top dead center position at the start of the intake stroke in each cylinder 3a, and four pulses are output each time the crankshaft 3d rotates twice. Further, the engine 3 is provided with a cylinder discrimination sensor (not shown).
Output to CU2. The ECU 2 uses the cylinder discrimination signal, the CRK signal, and the TDC signal to control each cylinder 3a.
Is determined at what crank angle position in which stroke.

The ECU 2 includes a microcomputer including a CPU, a RAM, a ROM, an I / O port, and the like;
And an input / output interface (both not shown). The detection signals from the above-described in-cylinder pressure sensor 4, intake pipe internal pressure sensor 8, and crank angle sensor 9 are input to a microcomputer after being subjected to A / D conversion, shaping, and the like by an input / output interface. The microcomputer executes ignition timing control based on these detection signals and control programs, tables and maps (not shown) stored in the ROM. Specifically, the start and end times of energization to the ignition plug 5 are calculated, and the ignition signal according to the calculation results is calculated as follows:
The signal is output to the ignition plug 5 via the input / output interface and the ignition coil 6. Thus, the ECU 2 controls the ignition timing of the ignition plug 5.

The ECU 2 executes the following knocking determination process based on the detection signals from the sensors, the control program, and the knocking determination table (see FIG. 4). In this knocking determination process, the ECU 2 constitutes an extraction unit 2a, a load detection unit 2b, and a knocking determination unit 2c (see FIG. 1), and the extraction unit 2a outputs the in-cylinder pressure signal P detected by the in-cylinder pressure sensor 4.
The knocking information is extracted from the CL and the load detecting means 2b
Detects load information of the engine 3 from the in-cylinder pressure signal PCL. Further, knocking determination means 2c determines knocking of engine 3 based on a comparison result between the knocking information and the load information. Then, in the knocking determination process,
When it is determined that knocking has occurred, the ignition timing is retarded by a conventionally known method so as to suppress knocking.

Next, the knocking determination process executed by the ECU 2 will be described with reference to FIG.
This will be specifically described with reference to FIG. FIG.
A configuration for processing the in-cylinder pressure signal PCL and the ignition signal when the knocking determination process is performed and a method of processing these signals are shown. A portion surrounded by a two-dot chain line in FIG. The content of the arithmetic processing is shown. FIG. 3 shows an example of a timing chart of (a) the ignition signal, (b) the in-cylinder pressure signal PCL, and (c) a BPF signal bpfP described later. In particular, FIG. The in-cylinder pressure signal PCL and the BPF signal bpfP indicate a state in which knocking has occurred, and both signals in a measurement section from time t5 to t6 indicate a state in which knocking has not occurred.

First, as shown in FIG. 2, an ignition cycle is measured in step 1 (abbreviated as "S1" in the figure; the same applies hereinafter) from an ignition signal at the ignition signal interface 10 of the input / output interface. As shown in FIG. 3, the ignition cycle measures a time interval between the fall timing of the previous ignition signal (time t1 in FIG. 3) and the fall timing of the current ignition signal (time t4). It is required by things.

Next, based on the calculated ignition cycle, the engine 3
Is calculated (step 2). At the same time, from the falling timing of this ignition signal,
The current measurement start timing and measurement end timing are generated (steps 3 and 4). Step 3
Then, a predetermined time (for example, 1.5 msec) is set in a down-count type program timer, and this timer is started in synchronization with the falling timing of the current ignition signal (time t4). t5) is determined as the measurement start timing.

In step 4, an up-count type program counter is used to input C to the ECU 2 at the falling timing of the current ignition signal (time t4).
The timing at which the counting of the RK signals is started and a predetermined number of CRK signals are input (time t6) is set as the measurement end timing. Through the processing in steps 3 and 4 described above, measurement sections (sections from time t2 to t3 and sections from time t5 to t6) for sampling the in-cylinder pressure signal PCL and the BPF signal bpfP are obtained. Specifically, this measurement section is set to a predetermined section in the combustion stroke.

On the other hand, the in-cylinder pressure signal PCL input from the in-cylinder pressure sensor 4 to the ECU 2 is filtered by the analog filter 11 of the input / output interface so that only signals in the frequency band of 0 to 50 kHz are passed. The analog signal is converted into a digital signal by the / D converter 12.

Further, the digitally converted in-cylinder pressure signal PCL is processed by two different methods. First, in one processing method, filtering is performed by a digital band pass filter (hereinafter, referred to as “BPF”) processing by a program (step 5). Specifically, the BPF process is a process of sampling only a signal in a frequency band of 5 kHz to 50 kHz from the in-cylinder pressure signal PCL, and thereby, from the in-cylinder pressure signal PCL shown in FIG. )
The BPF signal bpfP shown in FIG. Thereafter, the maximum value bpf of the BPF signal bpfP is calculated by a maximum value calculation process.
PMAX (see FIG. 3C) is calculated as knocking information (step 6). This maximum value calculation process is performed in the B section in the measurement section determined in the processes of steps 3 and 4.
This is for calculating the maximum value bpfPMAX of the PF signal bpfP.

In the other processing method, the in-cylinder pressure signal PCL from the A / D converter 11 is sampled as it is without undergoing the BPF processing, and the in-cylinder pressure signal PCL in the measurement section is subjected to the maximum value calculation processing. Signal PCL
(See FIG. 3B) is calculated as the load information of the engine 3 (step 6).

Next, these maximum values bpfPMAX,
Statistical calculation processing is performed on PMAX (step 7).
Specifically, the maximum values bpfPMAX, PMAX obtained for each combustion cycle (ie, for one measurement section).
Are stored in the RAM, and when a predetermined number of combustion cycles (ie, a predetermined number of measurement sections) have elapsed, these average values bpfPMAX (AVE), PM
Find AX (AVE). At the same time, a peak value and a standard deviation are obtained.

Thereafter, these bpfPMAX (AV
E), knocking determination is performed using PMAX (AVE) (step 8). Specifically, the average value bpfPMA
Calculate knock intensity ratio RKN (%) obtained by converting the ratio of X (AVE) to average value PMAX (AVE) as a percentage ｛RKN = [bpfPMAX (AVE) / PMAX (A)
VE)] x 100 °. Then, using the calculated knock intensity ratio RKN and the engine speed NE at that time, a knocking determination is made by referring to a knocking determination table shown in FIG.

The knocking determination table shown in FIG. 4 has a determination value RKNREF of knock intensity ratio RKN on the vertical axis.
[%], And the horizontal axis represents the engine speed NE [rpm]. As shown in FIG.
F is set to increase as the engine speed NE increases. For example, if the engine speed NE is 1
It is set to 2.5% when the engine speed is 000 rpm or less, and is set to 25% when the engine speed NE is 6000 rpm or more. Between 1000 and 6000 rpm, the engine speed NE is set to increase as the engine speed NE increases. Have been. The reason that the determination value RKNREF is set in this manner is that the higher the engine speed NE, the higher the vibration level of the engine 3 itself, and the higher the vibration level when knocking actually occurs. is there.

The specific knocking determination is performed by referring to the knocking determination table as described above and calculating the calculated knock intensity ratio RKN by a determination value RKNREF according to the engine speed NE at the time when the predetermined number of cycles have elapsed.
When the knock intensity ratio RKN is equal to or greater than the determination value RKNREF, it is determined that knocking has occurred. That is, if the knock intensity ratio RKN is in the area indicated by hatching in the figure, it is determined that knocking has occurred, and in this case, a knock flag is set. If knock intensity ratio RKN is smaller than determination value RKNREF, it is determined that knocking has not occurred, and no knock flag is set. Further, when the knock flag is set, the above-described ignition timing retard control is executed to suppress knocking.

As described in detail above, according to the knocking determination device 1 of the present embodiment, the maximum value b of the BPF signal bpfP, which is knocking information extracted from the in-cylinder pressure signal PCL,
The average value bpfPMAX (AVE) of pfPMAX and the maximum value P of the in-cylinder pressure signal PCL, which is load information of the engine 3,
Knocking is determined by further using the engine speed NE, which is one of the load information of the engine 3, in addition to the knock intensity ratio RKN, which is the ratio of the average value MAX to the average value PMAX (AVE). The load information of the engine 3 can be appropriately reflected in the knocking determination. Therefore, even when the load state of the engine 3 changes, knocking can be appropriately determined while reflecting the change, and knocking can be accurately determined regardless of the operation range. As described above, the maximum values bpfPMAX and PMAX of the BPF signal bpfP and the in-cylinder pressure signal PCL are determined in order to obtain the knock intensity ratio RKN.
As an average value bpf in a predetermined number of combustion cycles
Since PMAX (AVE) and PMAX (AVE) are used, it is possible to reduce the influence of these signals in a plurality of combustion cycles and temporary fluctuations when knocking is determined. As a result, knocking can be more accurately determined.

In the first embodiment described above,
Although the detection signal PCL of the in-cylinder pressure sensor 4 is used as the load information of the engine 3, instead of this, the intake pipe internal pressure sensor 8
May be used. The reason why the intake pipe absolute pressure PBA is used as the load information of the engine 3 is that it appropriately represents the load state of the engine 3. In this case, the maximum value PBAMAX of the intake pipe absolute pressure PBA in the measurement section is obtained, and the maximum value PBAMA obtained in the predetermined number of combustion cycles is obtained.
It is preferable to use the average value PBAMAX (AVE) of X as the load information, and the knocking information includes the BPF signal bpfP extracted from the in-cylinder pressure signal PCL as described above.
May be used. The maximum value PBAMAX of the intake pipe absolute pressure PBA is the maximum value PCL of the cylinder pressure signal PCL.
It shows a fixed ratio to MAX. Therefore, a conversion value obtained by multiplying the detected value of the intake pipe absolute pressure PBA by a conversion coefficient for converting the detected value into the cylinder pressure P is obtained, and the maximum value of this conversion value in a predetermined measurement section is calculated for each combustion cycle. The average value of the maximum values obtained in the number of combustion cycles may be used as the load information.

Further, the BPF signal bpfP and the in-cylinder pressure signal P for calculating the knock intensity ratio RKN to be compared with the determination value RKNREF in the knocking determination table of FIG.
As the maximum value of CL, the average value bpfPMAX (AV) of the maximum values of both signals obtained in a predetermined number of combustion cycles
E) and PMAX (AVE) were used, but instead of these, the maximum value b obtained in only one combustion cycle
pfPMAX or PMAX may be used.

Next, a description will be given of a knocking determination device 1 for an internal combustion engine according to a second embodiment of the present invention. The knocking determination device 1 of the present embodiment differs from that of the first embodiment only in that a charge amplifier (not shown) is used, and the other points are the same. Hereinafter, only different points will be described. As shown in FIG. 5, in the knocking determination device, the in-cylinder pressure signal P detected by the in-cylinder pressure sensor 4
The CL (see FIG. 5B) is input to the charge amplifier and amplified, and then the charge amplifier signal CPCL (see FIG. 5B).
(See (c)). Like the in-cylinder pressure signal PCL of the first embodiment, this charge amplifier signal CPCL is used as load information of the engine 3, and a BPF signal bpfCP (see FIG. 5D) obtained by subjecting this to the BPF signal is used as knocking information. Used. Then, the maximum value bpfCPM of the BPF signal bpfCP in the measurement section
AX and the maximum value CPMA of the charge amplifier signal CPCL
X is determined for a predetermined number of combustion cycles, and knocking determination is performed in the same manner as in the first embodiment described above, using the ratio of these average values (percent converted value) as the knock intensity ratio RKN. Thus, effects similar to those of the first embodiment can be obtained.

In this embodiment, the maximum value bpfC of the BPF signal is also used to calculate the knock intensity ratio RKN.
Instead of the ratio between the average value of PMAX and the average value of maximum value CPMAX of charge amplifier signal CPCL, maximum value bpfCPMAX and maximum value C in only one combustion cycle
The ratio of PMAX may be used.

[0033]

As described above, according to the knocking determination apparatus for an internal combustion engine of the present invention, knocking can be accurately determined regardless of the operating range.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an internal combustion engine to which a knocking determination device according to a first embodiment of the present invention is applied.

FIG. 2 is a diagram showing a configuration in which a knocking determination device performs knocking determination processing based on an in-cylinder pressure signal and an ignition signal, and a processing method thereof.

FIG. 3 is a timing chart showing an example of an ignition signal, an in-cylinder pressure signal, and a BPF signal.

FIG. 4 is a diagram showing an example of a knocking determination table used by a knocking determination device for knocking determination.

FIG. 5 is a timing chart showing an example of an ignition signal, an in-cylinder pressure signal, a charge amplifier signal, and a BPF signal in a knocking determination device according to a second embodiment of the present invention.

[Explanation of symbols]

Reference Signs List 1 knocking determination device 2 ECU (extraction means, load detection means, knocking determination means) 2a extraction means 2b load detection means 2c knocking determination means 3 engine (internal combustion engine) 3a cylinder 4 in-cylinder pressure sensor (in-cylinder pressure detection means) 8 in the intake pipe Pressure sensor bpfPMAX Maximum value of BPF signal (knocking information) bpfPMAX (AVE) Average value (average value of knocking information) NE Engine speed (speed of internal combustion engine) P In-cylinder pressure (in-cylinder pressure) PCL In-cylinder pressure signal ( PCLMAX Maximum value of cylinder pressure signal (load information) PCLMAX (AVE) Average value (average value of load information) PBA Absolute pressure in intake pipe (pressure in intake pipe) S5 to S6 Processing to extract knocking information S6 Processing for detecting load information S7 Processing for obtaining an average value of knocking information and load information S8 Processing for determining knocking

Claims (3)

[Claims] 1. An in-cylinder pressure detecting means for detecting an in-cylinder pressure which is a pressure in a cylinder, and an extracting means for extracting knocking information indicating a knocking situation from a detection signal of the in-cylinder pressure detected by the in-cylinder pressure detecting means. Load detection means for detecting load information of the internal combustion engine from one of the cylinder pressure and the pressure in the intake pipe detected by the cylinder pressure detection means; and the knocking information and the load detection means extracted by the extraction means. A knocking determination unit that determines knocking based on a comparison result with the load information detected by the knocking determination device. 2. The knocking determination device for an internal combustion engine according to claim 1, wherein the determination of the knocking by the knocking determination unit is performed in accordance with a rotation speed of the internal combustion engine. 3. The apparatus according to claim 1, wherein at least one of the knocking information and the load information is an average value of a plurality of information values respectively obtained in a plurality of combustion cycles of the internal combustion engine. An apparatus for determining knocking of an internal combustion engine according to claim 1.