JPH02210228A - Internal heat engine knock detection device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a knock detection device for an internal combustion engine, and more specifically, the present invention relates to a knock detection device for an internal combustion engine, and more specifically, a knock sensor output is smoothed by a time constant depending on the engine rotation speed to obtain a noise level. The present invention relates to a knock detection device for an internal combustion engine that corrects a noise level according to the transient state when a transient state of engine operation is detected, thereby avoiding a delay in noise level calculation.

(Prior Art) In conventional knock detection technology, the output of a knock sensor is rectified, the rectified value is smoothed with a predetermined time constant, and a background value (hereinafter referred to as "noise level") is obtained.
Next, the noise level is amplified to obtain a knock determination level, which is compared with the sensor output to determine whether knock has occurred. An example thereof is the technique described in Japanese Patent Publication No. 56-636.

As described above, since the knock determination level is determined based on the noise level, it is necessary to appropriately determine the knock determination level in order to accurately detect a knock. in particular,
It is desirable to set the knock determination level at an appropriate position between the sensor output during normal combustion and the sensor output during abnormal combustion (when knock occurs). Thus, the knock sensor output fluctuates depending on the operating state of the engine, and fluctuates within a predetermined fluctuation range, for example, as the engine speed increases or decreases, or even in a steady state. Therefore, if the noise level is immediately determined in response to the noise level, the fluctuation range of the knock determination level calculated from the noise level becomes large, and it may become difficult to accurately detect the occurrence of knock.

From this point of view, a technology has recently been proposed in which the knock sensor output is smoothed for each ignition using a smoothing coefficient that is set to increase when the engine rotates at high speeds, thereby making the fluctuation range of the knock judgment level uniform. An example of this is JP-A-60-1237.
The technique described in Japanese Patent No. 46 can be mentioned.

(Problem to be Solved by the Invention) Therefore, when the engine is operating in a steady state, it is possible to appropriately obtain a desired knock determination level using the conventional technique, but when the engine is operating in a transient state, especially when the engine is operating in a transient state, When the engine speed changes rapidly due to a snap action such as sudden depression of the accelerator pedal, there is an inconvenience that the annealing time constant set in the steady state causes a delay in response. That is, as shown in Fig. 8, the calculated noise level is lower than the knock sensor actual level (true noise level) due to a response delay, and as a result, the knock judgment level is also low (so that it is actually Falsely detects that a knock has occurred even though there is no knock,
This had the drawback of adding meaningless retardation correction to the ignition timing.

Therefore, the present invention eliminates the above-mentioned drawbacks of the prior art, detects a transient state and appropriately corrects the noise level calculation value, eliminates the noise level calculation delay, and accurately calculates the knock judgment level. An object of the present invention is to provide a knock detection device for an internal combustion engine that can detect the occurrence of knock without error.

(Means for Solving the Problems) In order to achieve the above object, the invention as set forth in claim 1 provides a knock sensor 1 which is provided at an appropriate position of an engine and detects vibrations of the engine, as shown in FIG. , rotation speed detection means 2, which is provided near the rotating part of the engine and detects the rotation speed of the engine.
, a noise level calculation means 3 which receives the outputs of the rotational speed detection means and the knock sensor and calculates the noise level by smoothing the knock sensor output using a time constant set according to the engine rotational speed; a knock determination level calculation means 4 which inputs the output of the means and calculates a knock determination level from the noise level; and a knock determination which inputs and compares the outputs of the knock determination level calculation means and the knock sensor to determine the presence or absence of knock occurrence. In the internal combustion engine knock detection device comprising means 5, transient state detection means 6 is provided at an appropriate position of the engine and detects a transient state of engine operation.
The noise level calculation means inputs the output of the transient state detection means, and when a transient state is detected, calculates a correction value to be set according to the transient state, and uses the calculated correction value. It was configured to correct the noise level calculation value.

(Function) Since the transient state of engine operation is detected and the noise level calculation value is corrected according to the transient state, there is no delay in the noise level calculation even during the transient state, so the noise level is accurately calculated and the knock The determination level can be determined, and the presence or absence of knocking can be detected with high accuracy.

(Example) The present invention will be described in detail below. FIG. 2 is a schematic diagram showing the entire knock detection device for an internal combustion engine according to the present invention, including an ignition timing control device.

Referring to the figure, reference numeral 1O indicates a multi-cylinder internal combustion engine for a vehicle, which includes four cylinders or the like. The internal combustion engine 10 is equipped with an intake air passage 12, and air flowing from an air cleaner 14 is introduced into a ten-cylinder combustion chamber 20 through an intake manifold 18 while its flow rate is adjusted by a throttle valve 16.

A pipe 24 is connected to the intake air passage 12 at an appropriate position downstream of the throttle valve 16 to branch off, and near the end of the branch passage there is an intake air passage that measures the pressure of the intake air in absolute value to detect the engine load. A pressure sensor 26 is provided.

Further, a water temperature sensor 30 is provided near the cooling water passage 28 of the internal combustion engine 10 to detect the temperature of the engine cooling water, and an intake air temperature sensor 32 is provided at an appropriate position downstream of the throttle valve 16 in the intake air passage 12. It is installed to detect the temperature of the air that the engine takes in. Further, the throttle valve 16 is provided with a throttle position sensor 34, which is the above-mentioned transient state detection means for detecting the opening degree of the valve.

Further, a distributor 36 is located near the internal combustion engine 10.
The above-mentioned magnet is provided inside the magnet, which rotates in synchronization with the rotation of a crankshaft (not shown), which rotates as the piston moves up and down, and a rotating body arranged opposite to the magnet. A crank angle sensor 40 serving as rotation speed detection means is housed, and outputs a pulse signal at every predetermined crank angle. Furthermore, the above-mentioned piezoelectric knock sensor 1 is installed at an appropriate position on the cylinder block 42 of the internal combustion engine 10 to detect vibrations caused by knocks generated from the combustion chamber 20.
will be provided. A sensor 26 such as the above-mentioned intake pressure sensor,
The outputs of 30, 32, 34, 40°1 are output from the control unit 5.
Sent to 0.

FIG. 3 shows the details of the control unit 50, and will be explained according to the figure. After the analog output of the intake pressure sensor 26, etc. is input to the level conversion circuit 52 in the control unit and converted to a predetermined level, It is manually operated by a microcomputer 54. The intelligence microcomputer includes an A/Di conversion circuit 54a, l1054b, and a CPU5.
4c, ROM54, dSRAM54e, and a counter and timer for calculation (the counter and timer are not shown), and the level conversion circuit output is output from the CPU5.
After being converted into a digital value in the A/D conversion circuit 54a according to the command 4c, it is temporarily stored in the RAM 54e. Further, the output of the crank angle sensor 40 is sent to a waveform shaping circuit 56.
After being shaped into a waveform at , it is input into the microcomputer via l1054b.

Furthermore, the output of the knock sensor 1 described above is controlled by a control unit) 5.
After being sent out to 0, it is input to the knock detection circuit 60.

The knock detection circuit 60 includes a filter means 60a, a comparator means 60b, and a D/A conversion means 60c,
Filter means 60a is connected to a non-inverting input terminal of comparator means 60b, and its inverting input terminal is connected to D/
A conversion means 60c is connected. Further, the comparator means 60b is connected to the microcomputer 54, and the microcomputer 54 is connected to the D/A conversion means 6.
Connected to 0c. In addition, when a resonance type sensor that generates an output by resonating at a frequency based on knock is used as the knock sensor 1 described above, the filter means 60a becomes unnecessary as shown by the imaginary line.

In this knock detection circuit 60, the sensor output is sent to the microcomputer 5 in the comparator means 60b.
The noise level is calculated and knock is determined by comparing it with the reference value set by the microcomputer 54, and to explain this point with reference to the timing chart of FIG. In an angular range (for example, ATDC 120 to 140 degrees), a noise level VNOISE, which is a background value of engine vibration, is output as a comparison reference value to the D/A converter 60c.

This angular range is shown as "noise gate" in FIG. The output value is converted into an analog value by the D/A conversion means 60C, and compared with the sensor output level by the comparator means 60b. The micro combinator 54 changes this noise level based on the comparison result. The noise level is set to be approximately near the peak value of the sensor output level.

Further, the microcomputer 54 calculates a predetermined coefficient GAMP (depending on the operating state) based on the noise level VNOISE in an appropriate rank angle range (ATDCIO to 50 degrees) including the fuel state shown as "knock gate" in FIG. A knock determination level is calculated by multiplying the knock determination level by an appropriately set value), and the calculated knock determination level is output to the comparator means 60b via the D/A conversion means 60c.

The comparator means 60b compares the sensor output level with the knock determination level, and determines that a knock has occurred when the sensor output exceeds the knock determination level. Note that the calculation of the noise level and the knock judgment level in this knock detection method is performed in the microcomputer 54 using a software method, but it may also be detected in an analog manner using a hardware circuit (or Various methods may be used to generate the level, such as using an average value of sensor outputs.

As is well known, in the microcomputer, the CPU 54c calculates the engine speed from the output of the crank angle sensor 40, determines the engine load state from the output of the intake pressure sensor 26, and searches for a basic ignition timing map stored in the ROM 54d. In addition to calculating the basic ignition timing, the basic ignition timing is corrected from other operating parameters such as water temperature and intake air temperature. Furthermore, the final ignition timing is calculated by correcting the advance/retard angle, and an ignition command is sent to the ignition device 70 consisting of an igniter etc. via the output circuit 68.
The spark plug 72 of a predetermined cylinder is ignited via the distributor 36 to ignite the air-fuel mixture in the combustion chamber 20.

Next, the operation of this detection device will be explained with reference to the flow chart in FIG. Incidentally, the program shown in FIG. 5 is started by interruption in the microcomputer at every predetermined crank angle.

First, in S10, the throttle valve opening degree θ detected this time
THn and engine speed Ne are read, and in S12, the throttle change amount ΔθTH is calculated from the currently detected throttle valve opening θTHn and the previously detected throttle valve opening θTHn-1, and in S14, it is compared with a predetermined throttle change amount ΔθTHREF. do. That is, a transient state of engine operation is detected based on whether the amount of change in throttle valve opening per unit time exceeds a predetermined value.

If it is determined in step 314 that the amount of throttle change does not exceed the predetermined value and therefore the engine is not in a transient state, it is assumed that the engine is in a steady state of operation, and the process proceeds to step 516, where the smoothing coefficient described above is determined. Search according to the engine speed at which NIS was detected. FIG. 6 shows the characteristics of this smoothing coefficient. As shown in the figure, the characteristic value is set to increase in proportion to the engine speed, and the characteristic value is stored in the ROM 54d of the microcomputer so as to be searchable according to the engine speed.

Here, referring again to FIGS. 3 and 4, the method of calculating the noise level (the method of smoothing the knock sensor output) in this embodiment will be explained in detail.
The current comparison reference value (this comparison reference value is the result of comparison with the knock sensor output compared during the previous noise gate) is sent from the microcomputer 54 to the zero comparator means 60b via the D/A conversion means 60c. The noise level VNOISEn-1 calculated based on the noise level VNOISEn-1) is sent out and compared with the sensor output in the current noise gate. When the sensor output exceeds the comparison reference value, a pulse (hereinafter referred to as a "noise pulse") is output. In the microcomputer, the CPU 54c inputs the output of the comparator means and determines whether the noise pulse is a predetermined value or not. The comparison reference value is increased or decreased to match the frequency, and the value thus determined is set as the current noise level VNOISEn. Since the sensor output value fluctuates due to increases and decreases in engine speed, etc.,
The noise level also needs to be updated accordingly.

Specifically, the noise level is updated as follows: ■ When noise pulses exceed a predetermined value (e.g., 3 or more) VNOISEn= VNOISEn-IX (1+
)2 Old S ■When no noise pulse occurs at all VNOISEn= VNOISEn-I X (1)
2N+3 ■When the noise pulse exceeds zero and is less than the predetermined value (e.g., 1 to 2) V N0ISEn = V N0ISEn-1, and when the noise pulse exceeds the predetermined value, the sensor output is larger. 1/2 the previous value V N0ISEn-1 as
) The seta value increased by I+s is set as the current value VNOISEn, and when it does not occur at all, a value decreased by the same amount is set as the current value, and when there are 1 or 2 noise pulses, it is not updated. In this way, the noise level is always located near the peak value of the sensor output during the noise gate. Therefore, the noise level is the raw coefficient (power) NI
The amount of fluctuation is determined by S, but as mentioned above, the sensor output itself increases or decreases depending on the engine speed, so by changing the smoothing coefficient NIS depending on the engine speed, the fluctuation width becomes approximately equal. (In addition, the smoothing coefficient NIS
may be appropriately different in the increasing direction and decreasing direction). It goes without saying that the reason why a dead zone is provided so that updating is not performed when the number of noise pulses is one or two is to ensure stability of control.

Returning to the flow chart in FIG. 5 again, 316
~323, the latest noise level VNOISEn is calculated as described above (corrected) according to the frequency of noise pulses.

If it is determined in S14 that the engine is in a transient state, the process proceeds to S24, where a noise level correction value ΔVNOISE is searched in accordance with the throttle change amount ΔθTH. Figure 7 shows this correction characteristic, where the throttle change amount ΔθT
When H exceeds the predetermined value ΔθT)IREF and a transient state is determined, the correction value is set to increase according to the magnitude of the change, that is, the magnitude of the transient state.

Subsequently, in steps 326 to S31, the latest noise level V NOISEn is calculated by increasing or decreasing the frequency according to the frequency of noise pulses. In other words, when a noise pulse occurs, it means that it cannot follow the sensor output, so in step 328, VNOISEn-1 is multiplied by the smoothing coefficient, and then the noise level correction value ΔVNOISI! is added to correct the noise level itself. Note that when a noise pulse does not occur, there is no follow-up delay, so the arithmetic processing in S30 is the same as that in steady operation (S22).

In the above embodiment, when a transient state is detected, the noise level correction value ΔVNOISE set according to the transient state is added to the noise level update value obtained by multiplying by the smoothing coefficient NIS during steady operation. ! As a result, as shown by the broken line in FIG. 8, it is possible to follow the actual sensor level well. In the above-mentioned embodiment, the abnormal state of the engine was detected from the amount of throttle change, but the present invention is not limited to this, and the previous throttle valve opening θTH
The rate of change may be calculated from the ratio of n-1 and the current throttle valve opening θTHn, and the rate of change may be detected by comparing it with a predetermined value set appropriately, or the rate of change may be detected by calculating the rate of change from the ratio of n-1 and the current throttle valve opening θTHn. It may be detected from the amount of change.Also, in the above embodiment, the sluggish coefficient was changed from the engine speed, but it may be changed depending on the engine load condition, or even both the engine speed and the engine load condition. You can change it from

(Effects of the Invention) The knock detection device for an internal combustion engine according to the present invention is provided with a transient state detection means for detecting a transient state of engine operation, which is provided at an appropriate position of the engine, and the noise level calculation means is provided with a transient state detection means for detecting a transient state of engine operation. When a transient state is detected, a correction value to be set according to the transient state is calculated, and the noise level calculation value is corrected using the calculated correction value. The noise level can be calculated with good followability even during a transient period, and the knock determination level can be accurately calculated based on the noise level, so that the presence or absence of knock occurrence can be detected with high accuracy.

[Brief explanation of the drawing]

FIG. 1 is a diagram corresponding to claims of the present invention, FIG. 2 is a schematic diagram showing a knock detection device according to the present invention including an ignition timing control device, and FIG. 3 is a block diagram showing details of the control unit.
Fig. 4 is an explanatory timing chart showing the operation of the knock detection circuit therein, Fig. 5 is a flow chart showing the operation of the device, and Fig. 6 is the smoothing coefficient of the sensor output in the flow chart. FIG. 7 is an explanatory diagram showing the correction characteristics of the annealing time constant during transient operation, and FIG. FIG. 1... Knock sensor, 2... Rotation speed detection means (crank angle sensor 40), 3... Noise level calculation means (
knock detection circuit 60, microcomputer 54),
4...Knock judgment level calculation means (knock detection circuit 6
0, microcomputer 54), 5...knock determination means (knock detection circuit 60, microcomputer 54), 6... transient state detection means (throttle position sensor 34, microcomputer 54L), 50...
Control unit, 54... Microcomputer, 6
0...knock detection circuit

Claims (1)

[Scope of Claims] a. A knock sensor provided at an appropriate position on the engine to detect vibrations of the engine; b. A rotation speed detection means provided near a rotating part of the engine to detect the rotation speed of the engine; c. Noise level calculation means d, which inputs the outputs of the rotation speed detection means and the knock sensor and calculates the noise level by smoothing the knock sensor output using a time constant set according to the engine rotation speed; a knock determination level calculation means which inputs the output of the knock determination level calculation means and calculates a knock determination level from the noise level; A knock detection device for an internal combustion engine, comprising: f, a transient state detection means provided at an appropriate position of the engine to detect a transient state of engine operation; The internal combustion engine is characterized in that the output of the internal combustion engine is inputted, and when a transient state is detected, a correction value is calculated to be set according to the transient state, and the noise level calculation value is corrected with the calculated correction value. Engine knock detection device.