JP7024575B2 - Internal combustion engine knock detector - Google Patents

Description

The present invention relates to a knock detection device for an internal combustion engine.

Conventionally, as described in, for example, Japanese Patent Application Laid-Open No. 8-151950, there is known a technique of calculating a knock determination level based on a background value obtained by smoothing a detection value of a knock sensor. By comparing the calculated knock determination level with the detection value of the knock sensor, it is possible to determine the presence or absence of knock occurrence.

Japanese Unexamined Patent Publication No. 8-151950 Japanese Unexamined Patent Publication No. 2005-188297 Japanese Unexamined Patent Publication No. 2013-015105

When the detection value of the knock sensor is sufficiently large, the knock determination is correctly performed even with the above-mentioned conventional technique, so that the knock determination level is not updated. However, if there is an effect of a small knock that is difficult to determine as a knock immediately, or if there is an effect of mechanical peculiar noise such as valve seating, the knock determination level will gradually increase. If the knock determination level is not calculated correctly, the knock detection accuracy may decrease.

That is, what is desired to be adopted as the knock determination level is steady vibration having no peak associated with engine rotation and drive shaft rotation. On the other hand, small knocks and mechanically singular noises are noises with peak values. If noise having such a peak value is included in the background value, the background value becomes too large. As a result, there is a problem that the accurate calculation of the knock determination level is hindered and the knock detection accuracy is lowered.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a knock detection device for an internal combustion engine capable of suppressing a decrease in knock detection accuracy.

The knock detection device for an internal combustion engine according to the present invention is
The knock sensor installed in the internal combustion engine and
A control device that determines whether or not knock has occurred by comparing the detection value of the knock sensor with the knock determination level.
Equipped with
The control device is
A predetermined crank angle range as a range having a higher knock occurrence frequency than a predetermined standard is set as a predetermined crank angle range, and the first before the predetermined crank angle range predetermined so as to exclude the predetermined crank angle range. One detection section and a second detection section after the predetermined crank angle range are stored.
The vibration values in each of the first detection section and the second detection section are acquired based on the output of the knock sensor.
A relatively small vibration average value of the first vibration average value which is the average value of the vibration values of the first detection section and the second vibration average value which is the average value of the vibration values of the second detection section is set. selection,
It is constructed so as to set the knock determination level based on the relatively small vibration average value.

The effects of small knocking and mechanical singular noise rarely appear in both the first and second detection compartments. According to the present invention, an appropriate knock determination level can be set by using a relatively small vibration average value among the vibration average values of these two sections. Therefore, it is possible to suppress a decrease in knock detection accuracy.

It is a flowchart of the routine executed by the knock detection apparatus of the internal combustion engine which concerns on the comparative example with respect to embodiment. It is a figure for demonstrating operation of the knock detection apparatus of the internal combustion engine which concerns on the comparative example with respect to embodiment. It is a flowchart of the routine executed by the knock detection apparatus of the internal combustion engine which concerns on embodiment. It is a figure for demonstrating operation of the knock detection apparatus of the internal combustion engine which concerns on embodiment. It is a flowchart of the routine executed by the knock detection apparatus of the internal combustion engine which concerns on embodiment. It is a figure for demonstrating operation of the knock detection apparatus of the internal combustion engine which concerns on embodiment. It is a figure for demonstrating operation of the knock detection apparatus of the internal combustion engine which concerns on embodiment. It is a figure for demonstrating operation of the knock detection apparatus of the internal combustion engine which concerns on embodiment. It is a figure for demonstrating operation of the knock detection apparatus of the internal combustion engine which concerns on embodiment. It is a figure for demonstrating operation of the knock detection apparatus of the internal combustion engine which concerns on embodiment. It is a figure for demonstrating operation of the knock detection apparatus of the internal combustion engine which concerns on embodiment.

Base vibration calculation technique according to the embodiment and a knock detection device using the technique.
Prior to the description of the embodiment, a comparative example for making the effect of the embodiment easy to understand will be described. FIG. 1 is a flowchart of a routine executed by a knock detection device of an internal combustion engine according to a comparative example with respect to an embodiment. As shown in FIG. 1, in the comparative example, BGL is calculated from the vibration mean value in the gate (step S200).

Next, it is determined whether or not the variation of the obtained data is within 3σ (step S202). If it is within 3σ, the base vibration is calculated according to the following equation (1) (step S204).
Base vibration = previous base vibration- (BGL-previous base vibration) / NSM (smoothing value) ... (1)

FIG. 2 is a diagram for explaining the operation of the knock detection device of the internal combustion engine according to the comparative example with respect to the embodiment. Explaining the problem of the comparative example, in the logic of the comparative example, knock is detected by the relative strength based on the base vibration level.

As shown in FIG. 2, since the average value in the 0 to 90 ° CA section is used for the calculation of the base vibration, there are the following problems. First, since the base vibration increases due to a small knock of less than 3σ, there is a problem that the knock determination accuracy is lowered. Secondly, there is a problem that the base vibration increases due to the peculiar noise and the knock determination accuracy decreases. The peculiar noise is noise caused by sitting, an injector, a piston slap, or the like.

In order to solve the above-mentioned problem of deterioration in knock determination accuracy, according to the embodiment, a new and unique knock detection device having an improved method for calculating the base vibration level used in the knock determination is provided. According to the knock detection device according to the embodiment, the knock determination accuracy can be improved by accurately calculating the base vibration while suppressing the influence of knock and peculiar noise.

The internal combustion engine according to the embodiment includes an internal combustion engine main body in which a cylinder block, a piston, and the like are assembled, a knock sensor attached to the internal combustion engine main body, and an engine electronic control unit. The engine electronic control unit receives signals from various sensor devices including a knock sensor, performs arithmetic processing according to a program, and supplies control signals to various engine device actuators. The knock detection device of the internal combustion engine according to the embodiment is realized as one function of the engine electronic control unit. The detection result of the knock detection device is reflected in the ignition timing control for the spark plug of the internal combustion engine.

With reference to FIGS. 3 and 4, the differences between the embodiment and the comparative example of the calculation method of the base vibration will be described. As a first point different from the comparative example, in the embodiment, the knock generation position is not included in the calculation of the base vibration. The knock generation position is in the range of 20 to 70 ° CA.

FIG. 4 is a diagram for explaining the operation of the knock detection device of the internal combustion engine according to the embodiment. As shown in FIG. 4, only the first half and the second half sections of the knock gate are used for calculating the base vibration. This is different from using the vibration mean value over the entire range of 0 to 90 ° CA as shown in FIG. 2 in the comparative example.

In the embodiment, as an example, the first half of the knock gate may be in the range of 0 to 20 ° CA, and the second half of the knock gate may be in the range of 70 to 90 ° CA. The knock detection section is preset in the engine electronic control unit according to the embodiment. The knock detection section is set to exclude a predetermined crank angle range (that is, 20 to 70 ° CA). This predetermined crank angle range is a range set so as to have a knock occurrence frequency higher than a predetermined standard. The knock detection section according to the embodiment is a first detection section (that is, 0 to 20 ° CA) before the predetermined crank angle range and a second detection section (that is, 70 to 90 ° CA) after the predetermined crank angle range. Is.

As a second point different from the comparative example, in the embodiment, the smaller value of the average intensity in the first half of the gate and the average intensity in the second half of the gate is used for calculating the base vibration so as not to include the peculiar noise as much as possible. is doing. In the comparative example, such an appropriate selection of the average strength is not made.

FIG. 3 is a flowchart of a routine executed by the knock detection device of the internal combustion engine according to the embodiment. The processing of each step of this routine is performed by the engine electronic control unit. As shown in FIG. 3, the arithmetic process A for calculating the vibration mean value in the first half of the gate is executed (step S100). Next, the arithmetic process B for calculating the vibration mean value in the latter half of the gate is executed (step S102).

As described above, it is assumed that the first half of the knock gate is in the range of 0 to 20 ° CA and the latter half of the knock gate is in the range of 70 to 90 ° CA. According to steps S100 and S102, the engine electronic control unit is in the first detection section (that is, 0 to 20 ° CA in the first half of the knock gate) and the second detection section (that is, 70 to 90 ° CA in the second half of the knock gate), respectively. It is built to get the vibration value.

Next, the smaller of the vibration mean values calculated by the above arithmetic processing A and the arithmetic processing B is substituted into the BGL (step S104). According to step S104, the engine electronic control unit has a first vibration average value which is an average value of vibration values in the first detection section, and a second vibration average value which is an average value of vibration values in the second detection section. Of these, a relatively small vibration mean value can be selectively used.

Next, the base vibration is calculated by the same calculation as in step S204 of FIG. 1 (step S106). According to step S106, the engine electronic control unit can set and update the knock determination level based on the relatively small vibration mean value selected in step S104.

The effects of small knocking and mechanical singular noise rarely appear in both the first and second detection compartments. Therefore, since an appropriate knock determination level can be set by using a relatively small vibration average value among these sections, it is possible to suppress a decrease in knock detection accuracy.

FIG. 5 is a flowchart of a routine executed by the knock detection device of the internal combustion engine according to the embodiment. The processing of each step of this routine is performed by the engine electronic control unit.

Explaining the existing knock determination flow shown in FIG. 5, first, the vibration mean value over the section of 0 to 90 ° CA is calculated (step S110). Next, the value obtained by dividing the vibration mean value calculated in step S110 by the value of the base vibration calculated in step S106 of FIG. 3 is calculated as the knock intensity (step S112).

Next, it is determined whether or not the knock strength exceeds a predetermined knock determination threshold value (step S114). If the knock intensity exceeds the knock determination threshold value, it is determined that knock has occurred (step S116). If the knock intensity does not exceed the knock determination threshold value, it is determined that knock has not occurred (step S118).

The base vibration may also be used in the frequency vibration section difference determination. According to the routine of FIG. 5, the engine electronic control unit can determine whether or not knock has occurred by comparing the detection value of the knock sensor with the knock determination level.

Other knock determination techniques according to the embodiment.
Here, a knock determination technique as a comparative example will be described. In the knock determination technique according to the comparative example, it is determined that knock has occurred when the vibration sections of the first frequency f1 to the fourth frequency f4 are applied to the following determination formulas. However, in this comparative example, it is permissible for two adjacent values to be exchanged before and after in the following equation (2).
f1 vibration section> f2 vibration section> f3 vibration section> f4 vibration section ... (2)

This means that the trends shown in FIG. 6 are true. However, from the first frequency f1 to the third frequency f3, the primary frequency in the lateral direction (near f1 to f2) of the knock combustion chamber and the primary frequency in the vertical direction (near f2 to f3) overlap, so that the first frequency f1 to f1 It has been found that there is no unique difference in the duration of the knock frequency at the third frequency f3. Incorporating the difference between the vibration sections of f1 to f3 may reduce the knock detection accuracy.

Further, even with noise, there is a cycle in which the f1 vibration section> the f4 vibration section depending on the variation position, and there is a case where the noise is erroneously determined as knock. If a simple comparison of f1 vibration section> f4 vibration section is adopted, the knock detection accuracy may decrease.

Therefore, in the embodiment, there is also provided a technique for improving the accuracy of separating knock and noise by using the frequency characteristic of knock. In the embodiment, knock detection is performed by using the vibration section difference of the knock vibration for each frequency. 6 and 7 are diagrams for explaining the operation of the knock detection device of the internal combustion engine according to the embodiment. 6 and 7 show vibration waveforms having a first frequency f1, a second frequency f2, a third frequency f3, and a fourth frequency f4, respectively. f1 to f4 are four different frequencies, and f1 <f2 <f3 <f4.

As shown in FIG. 6, in the case of knocking, the vibration section is longer toward the lower frequency side. As shown in FIG. 7, in the case of noise, the length of the low frequency vibration section is equivalent to the length of the high frequency vibration section. The vibration section difference is calculated by comparing the waveforms of the first frequency f1 on the lowest frequency side and the fourth frequency f4 on the highest frequency side.

In the result of the above waveform comparison, when the vibration section difference is larger than the predetermined reference section difference, it is determined that knocking has occurred. When the condition of the knock determination equation (3) shown below is satisfied, it is considered that the knock has occurred. Q is a reference interval difference and is a predetermined constant.
f1 vibration section-f4 vibration section> Q (Unit: CA) ... (3)

FIG. 8 is a diagram for explaining the operation of the knock detection device of the internal combustion engine according to the embodiment. According to the characteristics of the knock shown in FIG. 8, the vibration section of the first frequency f1 is 40 ° CA, the vibration section of the fourth frequency f4 is 10 ° CA, and the vibration section difference is 30 ° CA. In this way, when knocking occurs, the vibration section difference becomes sufficiently large.

Further, according to the characteristics of the piston ring noise shown in FIG. 8, the vibration section of the first frequency f1 is 15 ° CA, the vibration section of the fourth frequency f4 is 15 ° CA, and the vibration section difference is 0 ° CA. Is. In this way, in the case of noise, the vibration section difference becomes sufficiently small. Therefore, in consideration of these tendencies, the value of the reference section difference Q can be determined so that knock and noise can be separated with sufficient accuracy, and can be used as the reference section difference Q determination threshold value.

9 to 11 are diagrams for explaining the operation of the knock detection device of the internal combustion engine according to the embodiment. As shown in FIG. 9, the vibration section may be calculated by specifying the waveform peak to the attenuation point. Specifically, the vibration section may be calculated using the damping determination level calculated using the following equation (4). k is a predetermined coefficient.
Attenuation judgment line = base vibration level x k ・ ・ ・ (4)

Here, the base vibration level calculated by the routine of FIG. 3 described above can be substituted into the above equation (4). That is, as the base vibration level of the equation (4), the value calculated in step S106 of FIG. 3 described above can be used.

As shown in FIG. 10, when the vibration waveform is, for example, a sampling waveform every 5 ° CA, the attenuation point may be complemented and calculated. The complementary point (x) may be obtained by the method shown in FIG. The complementary point Vp between the first detection value V1 and the second detection value V2 is calculated using the parameters a, b, and x.

As shown in FIG. 11, the parameter a is the difference between V1 and V2. As shown in FIG. 11, the parameter b is the difference between V1 and the attenuation determination line. The parameter x can be obtained from V1, V2, a, and b. Once the parameter x is known, the vibration section can be calculated by further adding x ° CA to the section length from the waveform peak crank angle to the crank angle of the first detection value V1.

Claims (1)

The knock sensor installed in the internal combustion engine and
A control device that determines whether or not knock has occurred by comparing the detection value of the knock sensor with the knock determination level.
Equipped with
The control device is
A predetermined crank angle range as a range having a higher knock occurrence frequency than a predetermined standard is set as a predetermined crank angle range, and the first before the predetermined crank angle range predetermined so as to exclude the predetermined crank angle range. One detection section and a second detection section after the predetermined crank angle range are stored.
The vibration values in each of the first detection section and the second detection section are acquired based on the output of the knock sensor.
A relatively small vibration average value of the first vibration average value which is the average value of the vibration values of the first detection section and the second vibration average value which is the average value of the vibration values of the second detection section is set. selection,
A knock detection device constructed to set the knock determination level based on the relatively small vibration mean value.

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