JPS6113125A - Knocking detector for internal-combustion engine - Google Patents

Abstract

PURPOSE:To detect knocking at a high accuracy about individual cylinders by a method wherein signals from a knocking sensor are inputted into a processing circuit by the cylinders and cylinder-wire noise levels are prepared to compare knockings at each cylinder. CONSTITUTION:For example, respective knocking sensors 10 are provided at parts of a 6-cylinder engine to send signals to a multiplexer 20. Then, vibration thereof is converted into a voltage signal with a charge amplifier 21, allowed to pass with a band-pass filter 22 in the frequency band only peculiar to the knocking and rectified with a full-wave rectification circuit 23 to be inputted into an integrator 24. In a cylinder-wise discrimination means 25, cylinders in the combustion process are discriminated to generate cylinder-wise noise level signals, which are inputted into an interface 26. Then, the cylinder-wise knocking signals from the integrator 24 are compared with the cylinder-wise noise level signals through the interface 26 to identify knockings. Thus, knockings of respective cylinders can be detected accurately regardless of difference in mechanical noise among the cylinders.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a knocking detection device for an internal combustion engine having a plurality of cylinders, and particularly to a knocking detection device for an internal combustion engine having a plurality of cylinders. The present invention relates to a knocking detection device suitable for use in a knocking control device that controls knocking within a predetermined range.

[Prior Art J] In general, the knocking phenomenon in an internal combustion engine refers to abnormal combustion due to early ignition of unburned air-fuel mixture in the cylinder, and as a result, the knocking phenomenon is determined by the dimensions of the cylinder (particularly its bore diameter and combustion scum temperature). It appears as a damped vibration of the pressure inside the cylinder (in-cylinder pressure), which has a natural frequency of 194. This natural frequency is approximately 5 to 6 kHz or more, and 5 This pressure vibration is caused by the cylinder wall, cylinder block, etc. The unpleasant high-frequency sound that travels through the air and reaches the human auditory sense is called a knocking sound.

Then, when the load exceeds a certain value and the ignition timing is too advanced, a strong knocking phenomenon occurs. Such knocking causes unpleasant noise, and severe knocking causes strong air column vibrations inside the cylinder, which may generate abnormally high temperatures locally within the cylinder and damage the engine.

However, 7-ys) The knocking phenomenon itself does not have a negative effect on the engine, and even if knocking occurs by advancing the engine timing, the engine's combustion efficiency will increase and the vehicle will be improved. From the viewpoint of improving fuel efficiency, allowing a moderate amount of knocking is suitable for obtaining an operating state with optimal engine efficiency.

Therefore, in order to increase the operating efficiency of the engine and suppress the knocking noise level to a predetermined value or less, it is necessary to control the knocking intensity to suit various operating conditions. .

There are various knocking control devices for achieving this purpose, such as those described in Japanese Patent Application Laid-Open No. 56-13242.3, Japanese Patent Publication No. 58-1374.9, etc. being developed.

In order to perform such knocking control,
It is necessary to accurately detect the occurrence of knocking, and a conventional knocking detection device for this purpose has been constructed, for example, as shown in FIG. 9.

To explain this simply, one knocking sensor 1 is attached to each cylinder (6 cylinders in this example) of the internal combustion engine, and this detection signal is sent to the multiplexer 2.
one of them is selected and only the detection signal from the knocking sensor 1 closest to the cylinder in the combustion stroke is sequentially output.

The switching timing of the multiplexer 2 is controlled by a switching control signal generated by a switching control signal generating section B in accordance with the rotation angle of the crankshaft.

The detection signal output from the multiplexer 2 is input to a band pass filter 4, which passes only signal components in a predetermined frequency band specific to knocking.

This signal is input to the noise level generation section 5, first rectified by the full wave rectifier tJ86, then averaged by the averaging circuit 7 with a predetermined time constant, and the amplifier 8 adjusts the level to make the noise level ( Create a slice file.

Then, the output of the band pass filter 4 is compared with this noise level by the comparator S, and the output of the band pass filter 4 is
It is determined that there is knocking when the output is greater.

[Problem to be solved by the invention J However, in such a conventional knocking detection device, although the degree of mechanical noise (valve seating sound, piston hitting sound, etc.) differs from cylinder to cylinder, Since the noise level, which is the slice level for detecting knocking, is an averaged common level, there is a problem if there is a considerable variation in knocking detection accuracy between cylinders.

It is an object of the present invention to solve these problems and to perform knocking detection with less variation in detection accuracy between cylinders.

[Means for Solving the Problem 3] In order to solve the above-mentioned problems, the knocking detection device for an internal combustion engine according to the present invention, as shown in FIG. A knocking sensor 10 that is attached to a block or the like and detects combustion pressure or vibration, a signal processing circuit 11 that converts the output into a signal related to the knocking intensity, and a cylinder determining means 12 that determines which cylinder is in the combustion stroke. The knocking determination means 13 inputs the output signal from the signal processing circuit 11 and the determination result by the cylinder determination means 12 to determine knocking.

The knocking determination means 16 is connected to a cylinder-specific noise level creation section 14 that creates a cylinder-specific noise level based on the output signal of the signal processing circuit 11, and a cylinder-specific noise level creation section 14 that creates a cylinder-specific noise level based on the output signal of the signal processing circuit 11. The present invention is characterized by comprising a cylinder-by-cylinder knocking determination means 15 which determines knocking by cylinder by comparison.

[For production]

The knocking detection device for an internal combustion engine according to the present invention is
With the above configuration, a detection signal from the knocking sensor 10 is processed by the signal processing circuit 11 and converted into a signal related to the knocking intensity.

1. In the knocking determination means 13, a noise level for each cylinder is created according to the determination result by the cylinder determination means 12 based on the output signal from the signal processing circuit 11,
The noise level for each cylinder is compared with the output signal of the signal processing circuit 11 to determine knocking for each cylinder. .

Therefore, highly accurate knocking detection can be performed for each cylinder, and there is almost no variation in detection accuracy between cylinders.

[Embodiment J] Hereinafter, embodiments of the present invention will be described with reference to FIGS. 2 to 8 of the drawings.

FIG. 2 is a block diagram showing an embodiment of the present invention, and parts corresponding to those in FIG. 1 are given the same reference numerals.

In this embodiment, the present invention is applied to a six-cylinder engine, and a knocking sensor 10 is attached to the ignition plaque attachment portion of the cylinder head of each cylinder as shown in FIG.

FIG. 3(A) is a sectional view of the spark plug mounting portion of the cylinder head, and FIG. 3(B) is a plan view of only the knocking sensor 10.

The knocking sensor 10 is formed in the shape of a washer of a first spark plug 17 that is screwed onto the cylinder head 16, and the spark plug 17 is screwed into the outer recess of the cylinder eight 1-16; It is attached and fixed to Pak.

The knocking sensor 10 uses a combustion pressure sensor that converts combustion pressure in a cylinder into an electric charge using a piezoelectric element and outputs the electric charge.

Returning to FIG. 2, 20 is a multiplexer.

Switching control signal: The switching control signal created by the f1 configuration 60 controls the six knocking sensors 10 in a predetermined relationship with the rotation of the crankshaft by synchronizing it with the ignition timing, for example. One of the input signals (a signal from a knocking sensor attached to a cylinder undergoing a combustion stroke) is sequentially output.

11 is a signal processing circuit that converts the output of the knocking sensor 10 inputted via the multiplexer 20 into a signal indicating a physical quantity related to the knocking intensity; Bandpass filter 22. It is composed of an aftereffect rectifier circuit 2 and an integrator 24.

The charge amplifier 21 is for converting the output of the knocking sensor 10 into a voltage, and for example, as shown in FIG.
-D3r and operational amplifier 01).

A known charge-to-voltage conversion amplifier constructed by O20 is used.

The band pass filter 22 is a filter that passes only components of a predetermined knocking frequency band (for example, 6 kHz to 17 kl(z)) from the output signal of the charge amplifier 21.

The aftereffect rectifier circuit 23 is a circuit that performs aftereffect rectification on the signal that has passed through the pan 1-bass filter 21 and converts it into a voltage signal of either positive or negative polarity.

The integrator 24 controls a predetermined crank angle range in which knocking occurs (for example, from compression top dead center to 40 degrees after compression top dead center) based on a control signal from the integration interval control signal generation circuit 61.
This is a circuit that integrates the output signal from the full-wave rectifier circuit 26 in ``).

A crank angle sensor 32 measures the rotation angle of the crankshaft with reference to a specific position of a specific cylinder (for example, 70'' before compression-I-dead center of the first cylinder).

Reference numeral 25 denotes a microphone computer which serves as the cylinder discrimination means 12 and the knocking determination means 13 in FIG. an input/output interface 26 for outputting as
27 and.

A read-only memory (ROM) 2 that stores a control block and various constants used for calculations in the block.
8, and a random access memory (RAM) 29 that temporarily stores input data and the results of calculations by the CPU 27.

Next, to explain the operation of this embodiment, the 1° switching control signal generation unit 60 generates a reference cylinder signal (in this example, rises at 70'' before compression top dead center of the first cylinder) as shown in FIG. A short pulse signal) and the ignition signal shown in (b) are input, and a switching control signal is generated and input to the multiplexer 20 in synchronization with the ignition timing after the reference cylinder signal is input.

This switching control signal is transmitted from the first cylinder to the fifth cylinder according to the ignition order of the six-cylinder engine, as shown in FIGS. Third. 6th. Second. This is a signal that controls the multiplexer 20 to select the output signal of the knocking sensor 10 in the order of the 4th cylinder. This is the period during which the output of the knocking sensor is selected A'L.

The signal processing circuit 11 has the role of converting the output signal of the knocking sensor 10 selected and outputted by the multiplexer 20 into a signal indicating a physical quantity related to the knocking intensity. The waveforms are shown in (a) to (e) of the timing chart of FIG.

Further, in this embodiment, the integration interval by the integrator 24 is from compression top dead center to 40° (crank angle) after compression top dead center, and the integral interval control signal d, which becomes H' only in this interval, is It is created by the creation circuit 31 based on the signal from the rotation angle sensor 32.

Furthermore, in this embodiment, the integrator 24 has a function of holding the integrated value until the next integration is started, as shown in FIG. 6 (,e,).

The microphone computer 25 receives the output signal of the signal processing circuit 11 (integral output e of the integrating circuit 24) and the rotation angle sensor 62.
A signal f indicating the rotation angle of the crankshaft from the reference position of a specific cylinder is manually generated.

The block diagram shown in the flowchart of FIG. 7 performs cylinder discrimination, generation of cylinder-specific noise levels, and cylinder-specific knocking determination.

This brocrum is applied every 120" of crank angle for a 6-cylinder engine, or +8" of crank angle for a 4-cylinder engine.
It is executed in synchronization with the rotation of the engine, such as every 0".

Next, the program of FIG. 7 will be explained step by step. In step 1, the cylinder in the combustion stroke is determined based on the signal f from the rotation angle sensor 32.

3. It is determined that the contents to be processed in subsequent steps relate to the i-th cylinder. In step 2, the integral value output from the signal processing circuit 11 is converted into a signal 1.1 related to the knocking intensity. S).

In step 3, the noise level (NLi) of the i-th cylinder calculated up to the previous cycle is read from the RAM 2.

In step 4, the signal S read in step 2 and the noise level NLi read out in step 3 are compared, and S
>NLi, it is determined that there is knocking, and the process proceeds to step 5, where the judgment result is temporarily stored in the area (address) for storing the judgment result of the i-th cylinder in the RAM 2B, and then the process proceeds to step 6.

If S≦NLi, it is determined that there is no knocking and the process proceeds to step 6 without doing anything.

In step 6, a predetermined function 1, for example, the following equation, is used from the current noise level NLi and the signal S to determine knocking in the next cycle.

Calculation is performed to create a new noise level NLi for the No. 1 cylinder.

((NL i IX(n-1)/n+(S)X I/n
)
It is stored in M28 as a map.

Generally, as the engine speed increases, the vibration component of the engine itself increases, and the proportion of the vibration component due to knocking in the output of the vibration sensor becomes relatively small.

However, it is better to increase the value of K when the engine speed is low.

It is also better to set the value of n larger at low speeds.

This is because a larger proportion of knock vibration occurs at low rotation speeds than at high rotation speeds, compared to the normal non-knock vibration, and this is the comparison base 1 (1; value (N
This is to avoid having a large influence on ST,).

After all, in the quintic table, these constants are determined so that nl > n2 + Kl > K2. The current noise level NLi is also initially created only by the signal S, and then the weighted average calculation as described above is performed. The noise level NL is created by arithmetic processing from the output signal S of the signal processing circuit 11.

By the way, when creating this noise level, 1. If the signal S becomes large due to the occurrence of knocking, there is a possibility that the noise level becomes abnormally large and may interfere with subsequent knocking determination.

Therefore, in order to prevent this, as shown in the partial flowchart in Fig. 8, an upper limit (SMax) is set for the value of the signal S used to create the noise level, and S Max is set in step 7 after step 4 or 5. Make a judgment of S Max, and
exceeds SMax, in step 8 the value of S is set to SM
It is preferable to change the value to ax and use that value to perform the arithmetic processing for creating the noise level for each cylinder in step 6 of FIG.

Also, as another measure against abnormal increases in noise levels, when creating noise levels for each cylinder.

The most recent signal S value for each cylinder is manually taken as many times as the first set number (m values), and only the second set number (n values) of the smallest values are used. An abnormally large signal S at the time of occurrence of knocking may be excluded by performing arithmetic processing such as taking a weighted average.

In the above embodiment, a plurality of combustion pressure sensors were used as knocking sensors to detect the combustion pressure by being attached to the cylinder head of each cylinder, but the present invention is not limited to this. It may be one vibration sensor that detects knocking.

In short, any sensor that can be attached to the cylinder head, cylinder block, etc. of an internal combustion engine and detect its combustion pressure or vibration may be used.

In addition, in the signal processing circuit 11 of the above embodiment, an integral value of a predetermined frequency component of the knocking sensor output in a predetermined crank angle region is created, but the five knocking intensities, such as the peak value of a predetermined frequency component in a predetermined crank angle region, are Any signal indicating a related physical quantity may be created by other signal processing.

Furthermore, the function shown in step 6 of Figure 7 was used to create the noise level for each cylinder, but this is a type of weighted average and is intended to prevent sudden fluctuations in the noise level due to new signals. ,others.

Of course, other functions may be used as long as they represent a simple average equal noise level.

[Effects of the Invention j As described above, the knocking detection device for an internal combustion engine according to the present invention converts the output of the knocking sensor into a signal related to the knocking intensity using the signal processing circuit, and also determines which cylinder is in the combustion stroke. Then, a calculation is performed using a predetermined function from the output signal of the signal processing circuit to create a noise level for each cylinder, and the noise level for each cylinder is compared with the output signal of the signal processing path to calculate the noise level for each cylinder. Since knocking is determined, even if the mechanical noise is different for each cylinder, knocking can be determined by setting the optimum noise level for each cylinder.
There is almost no variation in detection accuracy between cylinders (1) Highly accurate knocking detection for each cylinder can be performed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the basic configuration of the second invention. FIG. 2 is a block diagram showing an embodiment of the invention. FIG. 3 is a cylinder showing an example of the state in which the knocking sensor is installed. A partial sectional view of the head and a plan view of only the knocking sensor. FIG. 4 is a circuit diagram showing an example of a charge amplifier, FIG. 5 is a timing chart showing the relationship between a reference cylinder signal, an ignition signal, and a switching control signal for each cylinder. A timing chart diagram showing waveforms of output signals and integral interval control signals of each part of the signal processing circuit 11, FIG. 7 is a CPU of the microcomputer 25 of FIG.
FIG. 8 is a flowchart showing an example of a knocking detection processing program to be executed; FIG. 8 is a flowchart showing the power of the additional processing portion; FIG. 9 is a block diagram showing an example of a conventional knocking detection device for an internal combustion engine. It is a diagram. 10・Knocking sensor 11・Signal processing time w1 12・Cylinder discrimination means 13・
Knocking determination means 14, noise level generation unit for each cylinder 15, knocking determination unit for each cylinder 25, microcomputer 30, switching control signal generation unit Otsu 1, integral interval control signal generation circuit 32, rotation angle sensor

Claims (1)

[Scope of Claims] 1. A knocking sensor that is attached to the cylinder head, cylinder block, etc. of an internal combustion engine and detects combustion pressure or vibration, and signal processing that converts the output of the knocking sensor into a signal related to the knocking intensity. a cylinder discriminating means for discriminating a cylinder in a combustion stroke; and a knocking determining means for determining knocking based on an output signal of the signal processing circuit and a determination result by the cylinder discriminating means; , a cylinder-by-cylinder noise level creation unit that creates a cylinder-by-cylinder noise level based on the output signal of the signal processing circuit; and a cylinder-by-cylinder noise level creation unit that performs knocking by cylinder-by-cylinder by comparing the cylinder-by-cylinder noise level with the output signal of the signal processing circuit. A knocking detection device for an internal combustion engine, comprising a cylinder-by-cylinder knocking determination section. 2. Claim No. 2, characterized in that, when the output signal of the signal processing circuit exceeds a preset upper limit value, the cylinder-specific noise level creation section creates a cylinder-specific noise level using the upper limit value. The knocking detection device for an internal combustion engine according to item 1. 3. The cylinder-specific noise level generation unit inputs the latest output signal of the signal processing circuit in a first setting number for each cylinder, and calculates the noise level in advance by using the second setting number of data from the smallest value among them. 2. The knocking detection device for an internal combustion engine according to claim 1, wherein a noise level for each cylinder is created by performing calculations using a predetermined function.