JPS635169A - Knocking control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To improve the response characteristic to a transient condition, by updating a reference level in accordance with a level of a knocking detector signal while detecting an acceleration condition by a movement of the reference level and automatically changing the updated amount of said reference level. CONSTITUTION:A knocking signal passes through a filter means, which allows only the component of a knocking frequency to pass through, and a number of pulses, output when the knocking signal exceeds a reference level, are counted. And a control device, which updates the reference level in accordance with the above counted value while discriminates the presence of knocking, controls a knocking control factor from the result. While the control device, which counts by a counter means how many times the reference level is continuously corrected to an increase side, discriminates an engine to be in an acceleration condition when the above counted value increases to a predetermined value or more, and the control device, which immediately increases a correction amount of the reference level by a reference level increasing means, performs the control so as to obtain the adequate reference level even in the time of acceleration.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention is applied to a knocking control device for an internal combustion engine, particularly an electronic ignition timing control device for engines such as automobiles, which accurately detects knocking occurring in the engine and adjusts the ignition timing. The present invention relates to a knocking control device for controlling.

[Conventional technology]

Conventional knocking control devices (for example, Japanese Patent Application Laid-Open No. 58-15
5283), as shown in FIG. 9, a knocking detector 1 detects vibrations caused by knocking of an internal combustion engine, and only the knocking frequency component (for example, 8 KHz) of the detection signal of this knocking detector 1 is detected. A filter circuit 2 for passing the detection signal, an average value output circuit 3-1 for outputting the average value of the detection signal that has passed through the filter circuit 2, a judgment level generation circuit 3-2 for creating a knocking judgment level based on the value, and the above-mentioned It is comprised of a comparison circuit 4 that compares the detection signal with a knocking determination level to determine whether or not there is knocking. Each of these circuits is composed of analog elements such as linear ICs, and knocking is detected using an analog method.

[Problem that the invention seeks to solve]

For this reason, although the circuit configuration is complicated, the control content is limited to a specific range, and it is difficult to apply it to complex control such as controlling the knocking judgment signal depending on the operating state such as the rotation speed. As a result, it has been difficult to accurately determine knocking.

By the way, as is already known, the above problem is
The problem can be solved to some extent by using a digital knocking detection device whose components are an A-D converter that converts an analog signal into a digital signal and a microcomputer. However, in such a system, in order to faithfully convert the detection signal of the knocking detector into an A-to-digital converter, an extremely high-speed A-to-D converter that can trace the waveform of the knocking detection signal in detail is required. Such an A-D converter is expensive, and there is a problem in that the cost of the device increases.

Furthermore, instead of tracing the waveform of the knocking detection signal, a method can be considered in which each peak value of the knocking detection signal is sampled and held and then A-D conversion is performed. It becomes necessary to add additional means, which inevitably complicates the configuration.

Also, in the digital system using a microcomputer, the knock judgment level necessary to detect knocking is created by multiplying the average value of the knocking detector signal by a predetermined value, as in the analog circuit. For this reason, during a transient state of the engine, the tracking of the judgment level is poor, and it may be incorrectly determined that knocking has occurred even though no knocking has occurred, or immediately after the transient state ends, , there is a problem that the determination level is set high due to the influence of the transient state, and even if knocking occurs, it cannot be detected. To address this problem, there are other methods that provide a means to detect acceleration and make the judgment level appropriate (for example, Japanese Patent Application Laid-Open No. 57-32065), but adding the acceleration detection means increases the cost. The problem is that it becomes large.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a knocking control device that has a much simpler configuration than conventional techniques of this type, facilitates the creation of judgment levels, and has excellent responsiveness in transient conditions. .

[Means for solving problems]

In order to achieve the above object, the present invention provides knocking control for an internal combustion engine that detects knocking in an internal combustion engine and corrects the values of knocking control factors such as ignition timing according to the knocking detection state, as shown in FIG. The device includes filter means for passing only the knocking frequency component of the knocking detection signal from the knocking detector; the knocking detection signal that has passed through the filtering means is applied to one input thereof, and a reference level is applied to the other input. A comparison means is provided with a signal representing the reference level, and pulses output from the comparison means are inputted and counted, and according to the counting result, a signal representing the reference level is set to approximately the center of the knocking detection signal. a control means for determining knocking based on the counting result and correcting the value of the knocking control factor according to the determination result; and counting how many times the reference level is consecutively corrected to the increasing side. The present invention provides a knocking control device for an internal combustion engine, comprising: a counter means for increasing the correction amount of the reference level when the counted value of the counter means exceeds a predetermined value.

[Effect]

As a result, the counter means counts how many times the reference level has been continuously corrected to the increasing side, and when the count value of the counter means exceeds a predetermined value, it is determined that the acceleration state is present, and the reference level increasing means This immediately increases the reference level correction amount so that an appropriate reference level can be obtained even during acceleration.

〔Example〕

Next, in order to clarify the specific structure and operation of the knocking control device according to the present invention, embodiments shown in the drawings will be described. In Fig. 2, 1 is a knocking detector that detects vibration noise caused by engine knocking, 2 is a filter circuit that passes only a predetermined frequency component of the detection signal of the knocking detector 1, and 5 is a filter circuit that transmits the detection signal and micro This is a comparator that compares the digital signal from the computer 6 with the output signal of the resistor ladder 7 which is D/A converted.

The aforementioned microcomputer 6 counts the determination pulses from the comparator 5, and according to the counting results, sends a signal to the resistance ladder 7 and also sends a signal to the ignition control device 8 including the igniter. It is equipped with a central processing unit (CPU), a storage device (ROM, RAM), an input/output device (I10), etc.

Filter circuit 2 is composed of a capacitor and a resistor,
The detection signal from the knocking detector 1 is passed through the filter circuit 2 to remove high-frequency and low-frequency noise components, and only engine knocking components with a frequency of about 8 KHz are passed.

The microcomputer 6 includes a well-known oscillation circuit 6-2, a power-on/reset circuit 6-3, and a power supply circuit (not shown) as peripheral circuits, and determines the reference position of the engine by using an ignition signal ( Reference position waveform shaping signal) Ne
is received at the iRQ terminal, which is an interrupt terminal, and this signal is subjected to retardation correction according to the determination pulse count result, and is outputted from the RO terminal, which is an output terminal, to the ignition control device 8 as a calculated ignition timing signal (igt).

On the other hand, the microcomputer 6 receives the output from the comparator 5 that compares the knocking detection signal that has passed through the filter circuit 2 with the output of the resistor ladder 7 that converts the digital signal (8 bits) from the microcomputer from D to A. The results of this comparison are counted and processed by the central processing unit.

Next, the operation of this embodiment will be explained with reference to FIGS. 3 to 5. For example, the reference position signal indicating the most advanced angle position, which is determined according to the engine rotation speed and load and is shown as waveform a in FIG. The waveform shaping signal Ne is inputted to the iRQ terminal of the microcomputer 6, and operational calculations are performed. The knocking detection signal having the waveform C includes abnormal combustion noise that occurs in the section τ of the waveform d, that is, around 10° C. to 90′ cA after top dead center (ATDC) with respect to the reference position waveform shaping signal Ne.

In FIG. 4 (1) to (4), the section τ of the waveform d,
That is, for the knocking detection signal (waveform C) between ATDC 10'CA and 90''cA, the DA conversion value e is set as a reference level which is approximately the median value of the knocking detection signal.
are outputted from the microcomputer via the resistor ladder 7, and compared with each other by the comparator 5, and a determination pulse of waveform f is output.

In this way, D-
Increase or decrease the A conversion value. Here, a method of increasing or decreasing the reference level according to the pulse count value will be explained using the flowchart of FIG. The increase/decrease of the reference level is performed by the calculation of the microcomputer 6.

In FIG. 5, in step 501, it is determined whether or not it is a knock determination section, and if it is outside the determination section, the process branches to NO and returns. If it is within the determination interval, the process branches to YES and the reference level V is output in step 502. The reference level VLh output here is the reference level VLh calculated at the end of the pre-ignition determination period for the same cylinder, which is stored and output. The reference level VLk is 5■13b
It is expressed as a value divided by it (256), and the minimum unit is LSB
=19.5mV. This value is the knocking detector 1
It is determined by the size of the signal output from the device, and depending on the situation, it is necessary to change the dynamic range or resolution. In this embodiment, a value obtained by dividing the above-mentioned dynamic range 5■ by 8 biL (256) was used as the optimum value.

After outputting the reference level vtt+ in step 502, it is checked in step 503 whether or not there is a pulse output from the comparator 5. If there is no output, the process branches to No, and in step 505 it is checked whether or not the determination period has ended. It is determined, and if the determination period continues, the process branches to No and returns to step 503 again. In step 503, if it is determined that there is a pulse, the process branches to YES, in step 504 the pulse counter is incremented by 1, and in step 5
Proceeds to 05, and if the judgment section continues, returns to 50
Branch to 3.

Steps 503 to 505 are continued as long as the determination interval continues, and all the pulse numbers generated in the determination interval are counted.

If it is determined in step 505 that the determination interval has ended, Y
The process branches to ES and proceeds to step 506.

In step 506, it is determined whether or not a pulse has occurred even once within the determination interval. If a pulse has not occurred even once, the process branches to No and proceeds to step 510.

In step 510, the reference level is set to ΔV(19,5
mV), and the process moves to step 511. In step 511, the value of the up counter that counts how many times the reference level V has increased continuously is cleared. After that, the process moves to step 512.

If at least one pulse is counted within the determination interval in step 506, the process branches to YES and proceeds to step 507. In step 507, it is determined whether to increase or hold the reference level VLh based on the number of pulses generated within the determination interval. In this embodiment, if a pulse occurs only once within the determination interval, it is held.

Therefore, in the case of hold, the reference level Vth is not updated, and the process proceeds to step 511, where the reference level V up counter is cleared. If the number of pulses generated within the determination interval is 2 or more, it is necessary to increase the reference level Vt'h, so the process moves to step 508. Step 5
In 08, the reference level V is increased by ΔV (19.5 mV). Thereafter, in step 509, the Vth up counter is incremented by one.

Between these steps 506 to 511, the reference level Vth
is updated, and the reference level VLh can obtain a level corresponding to the magnitude of the output signal of the knock detector 1.

As mentioned above, when the number of pulses in the judgment interval is "0", the reference level is decreased by Δ■, when the number of pulses is "1", it is held, and when the number of pulses is 2 or more, it is decreased by Δ■. By increasing the reference level by 1, the level of the reference level can take the median value when statistically looking at the magnitude of the signal output of the knock detector 1. This median value is defined as
The value is such that 50% of the signal output exists at the top and 50% at the bottom.

In step 512, it is determined how many times the reference level V- has increased consecutively, and when the reference level V- has increased a predetermined number of times (16 times in this embodiment) or more, in step 513, the reference level V- is increased again by ΔV.

As a result, when the reference level (I) continuously increases, the amount of increase can be doubled, and the followability of the reference level (I) can be improved. Figure 6 shows the movement during acceleration when the Mt43 level V is operated in this way. After a predetermined number of consecutive increases, the rate of increase doubles, as shown in Figure 6 (
It is possible to follow the output signal of the knocking detector 1 which rises secondarily as shown in bl.

Steps 514 to 516 are a routine for determining the presence or absence of knocking, and the determination is made based on the number of pulses generated within the determination period. Since the number of pulses when knocking occurs is proportional to the duration of the output signal of the knocking detector 1, the number of pulses generated is greater than normal. Therefore, it is possible to determine that knocking has occurred when more pulses than a predetermined value N are generated. In this embodiment, the predetermined value N is set to "18", but this value needs to be set for each engine model.

Therefore, if the number of pulses generated within the determination interval in step 514 is greater than the predetermined value N, the process moves to step 515,
Cent the knock flag. If the number of pulses is smaller than the predetermined value N, the process moves to step 516 and the knock flag is cleared. The amount of retardation of ignition timing is controlled according to this knock flag.

Next, the calculation of the amount of retardation of the ignition timing will be explained using the flowchart shown in FIG. In step 701, it is checked whether the knock flag is set, and if it is set, that is, a knock has occurred, the process branches to step 702.

In step 702, the advance angle timer ADT, which counts time to determine the timing to decrease the retard amount and advance the angle at regular intervals after the occurrence of knocking, is cleared. This advance angle timer starts counting again after being cleared.

Thereafter, the process moves to step 703, and a retard amount is calculated. That is, the retard amount ΔθR per knock is added to the total retard amount θR. Therefore, the ignition timing is retarded by θR from the basic advance angle.

In step 704, the total retardation amount θR and the maximum retardation amount θRma
If θR is larger, the process branches to step 705. The maximum retard amount is set in consideration of the exhaust temperature rise when retarding and seasonal changes in the knock limit.
- Generally around 10'CA. In step 705, the total retard amount θR is reset to the maximum retard amount and the process returns.

Next, if the knock flag is not set in step 701, the process branches to step 706^.

In step 706, it is determined whether the value of the advance angle timer ADT has reached the advance angle set time AT, and the value of the advance angle timer AD
If T is smaller than the set time AT, the process branches to NO and returns.

Further, if the advance angle timer ADT is larger than the set time AT, the advance angle timer is cleared 0. For example, assuming that a set time (for example, 0° 4 seconds) has passed since the last ignition when knock occurred, the ignition timing is advanced. Therefore, the process branches to step 707.

In step 707, the advance angle timer is cleared and step 7
Move to 08. In step 708, the advance angle amount ΔθA (for example, 0.25° C.A) for each set time is subtracted from the total retard amount. Therefore, the ignition timing for the next ignition is ΔθA
is advanced and ignites.

Next, the process moves to step 709, and in step 709, θR
Determine whether N has become 0, and if it is greater than 0, N
Branch to o and return. When it is determined that θR is smaller than O, the process branches to step 710, clears θR, and returns.

As explained above, by comparing the reference level V and the output signal of the knocking detector 1 and updating the reference level to be output next based on the number of pulses output at that time, the output signal of the knocking detector 1 can be improved. You can get the median value. Furthermore, it is possible to detect whether or not knocking has occurred based on the time during which the output signal of the knocking detector l exceeds this reference level (2), that is, the magnitude of the number of pulses. Further, in a situation where the knocking detection signal increases continuously, such as during acceleration, followability can be improved by increasing the update of the reference level VLk.

Therefore, since an appropriate reference level can always be obtained, knocking can be accurately determined.

Next, the general logic of this embodiment is shown in FIG.
0, the Ne signal (8-1) is counted down from its rise and fall (8-3).
), (8-2) are performed, and a calculation signal igt indicating the energization timing and ignition timing is retarded by a predetermined angle according to the amount of knocking.
(8-4) is obtained. Actual ignition is performed by this calculation signal igt. Further, a predetermined angle masking (8-6) is performed by a timer after ignition. During the masking period (8-6), the microcomputer 6 calculates the ignition timing and the like. After masking, the number of knock waveforms exceeding the reference level corresponding to the number of pulses during the first determination period (877), that is, the number of knock pulses KNP is obtained.

Thereafter, a knock determination is made as described above in accordance with the number of knock pulses KNP, a retard amount is determined, and the reference level is updated as described above (8-8).

Note that all operations are controlled by a timer (8-5) that is initialized at overflow.

〔Effect of the invention〕

As explained above, the present invention utilizes the fact that the peak value of the signal waveform output from the knocking detector, its duration, and the timing of occurrence carry the information necessary for knocking detection. Direct technology A-D
Without conversion, the number of pulses output when the knocking detector signal exceeds the reference level in a predetermined determination interval is counted using a comparison means, and the reference level is determined according to the counted value of the pulses. In addition to updating, it is also possible to determine the presence or absence of knocking, and by controlling the knocking control factors according to the knocking detection result, it is possible to control the knocking sound to a target level, which is an excellent effect.

In addition, during acceleration when the knocking detector signal increases continuously, the acceleration state is detected from the movement of the reference level, which is updated according to the magnitude of the knocking detector signal, and the update amount of the reference level is automatically changed. By doing so, it is possible to improve the followability of the reference level. Therefore, it is possible to determine the acceleration state without using any other means for detecting acceleration, and there is an excellent effect that the order for knocking can always be accurately detected.

[Brief explanation of the drawing]

Fig. 1 is a diagram corresponding to the claims of the present invention, Fig. 2 is an electric circuit diagram showing an embodiment of the device of the present invention, and Figs.
FIG. 5 is a signal waveform diagram of the main parts of the illustrated device; FIG. 5 is a flowchart showing reference level updating and knocking judgment calculation in the illustrated device;
b) is a graph showing the movement of the reference level during acceleration in the device shown in FIG. 2 and a graph showing the movement of the peak value of the signal output of the knocking detector, and FIG. 7 is a graph showing the determination result of knocking in the device shown in FIG. 8 is a timing chart for explaining the operation of the embodiment shown in FIG. 2, and FIG. 9 is a block diagram showing a conventional knocking detection method using analog technology. be. 1... Knocking detector, 2... Filter circuit, 5
... comparator, 6... microcomputer,
7... Resistance ladder, 8... Ignition control device.

Claims (1)

[Claims] A knocking control device for an internal combustion engine that detects knocking in an internal combustion engine and corrects values of knocking control factors such as ignition timing according to the knocking detection state, comprising: filter means for allowing only the knocking frequency component to pass therethrough; a comparison means having one input to which the knocking detection signal passed through the filter means is applied, and a signal representing a reference level being applied to the other input; and the comparison means. The number of pulses output from the knocking detection signal is inputted and counted, and the signal representing the reference level is increased or decreased according to the counting result so that it becomes approximately the median value of the knocking detection signal, and the knocking detection signal is determined based on the counting result. a control means for making a determination and correcting the value of the knocking control factor according to the determination result; a counter means for counting how many times the reference level has been consecutively corrected to the increasing side; and a count value of the counter means. 1. A knocking control device for an internal combustion engine, comprising: a reference level increasing means for increasing a correction amount of the reference level when the reference level exceeds a predetermined value.