JP6973228B2 - Internal combustion engine knocking determination device - Google Patents

Description

The present invention relates to a knocking determination device for an internal combustion engine.

In a spark ignition type internal combustion engine (engine), in the combustion stroke, the air-fuel mixture in the cylinder is ignited and burned by the spark from the spark plug, but the pressure in the cylinder is abnormally high during the flame propagation after ignition. In this case, a knocking phenomenon may occur in which the unburned portion of the air-fuel mixture self-ignites before the flame propagation is completed. Then, in a situation where this knocking phenomenon occurs, the occupant may feel uncomfortable or the engine may be adversely affected.

Therefore, conventionally, a knock control system (KCS) has been proposed, which is a control for eliminating knocking by retarding the ignition timing of the spark plug when knocking occurs and realizing optimum torque and fuel consumption.

In the knock control system, the presence or absence of knocking is determined by comparing the vibration level (vibration value) detected by the knock sensor attached to the cylinder block with the knocking determination level. When the vibration level is equal to or higher than the knocking determination level, it is determined that knocking has occurred, and when the vibration level is lower than the knocking determination level, it is determined that there is no knocking (noise less than knocking).

This knocking determination level is calculated by multiplying the background level (BGL), which represents the vibration intensity in a steady state where knocking does not occur, by a predetermined coefficient. This background level is updated by smoothing the vibration level only when the vibration level detected by the knock sensor is determined to be no knocking (noise less than knocking) (Equation (3) described later). By using the smoothing calculation, it is possible to absorb the variation in the machine difference and the change in the vibration level due to the deterioration over time, and it is possible to make an accurate judgment.

However, the follow-up delay occurs when the annealing calculation is used. Therefore, during transient operation, the background level tracking delay due to the smoothing calculation reduces the knock detection accuracy. FIG. 8 is a diagram for explaining a background level calculation image at the time of follow-up delay. The solid line 81 shows the time change of the vibration level detected by the knock sensor, and the solid line 82 shows the time change of the background level. As shown in region 83, during transient operation (acceleration in FIG. 8), the calculation for raising the knocking determination level to an appropriate level is delayed due to the follow-up delay of the background level by the smoothing calculation. Therefore, even though knocking does not actually occur, the vibration level detected by the knock sensor becomes equal to or higher than the knocking determination level, and it may be erroneously determined that the possibility of knocking is high. If it is determined that knocking is caused by an erroneous determination, the background level is not updated, so that the erroneous determination is further continued (region 84). As described above, there is a problem that the follow-up delay due to the smoothing calculation lowers the knock detection accuracy during the transient operation.

In order to reduce the delay in calculating the knocking determination level during transient operation, in Patent Document 1, when it is determined that the engine is in a transient operation state, a correction value is added or subtracted to the determination level, and the correction value is large. The value is changed according to the size of the calculated value of the degree of knocking.

The applicant recognizes the documents described below, including the above-mentioned documents, as related to the present invention.

Japanese Unexamined Patent Publication No. 8-151950 Japanese Unexamined Patent Publication No. 2004-101626 Japanese Unexamined Patent Publication No. 2000-205906 Japanese Unexamined Patent Publication No. 2008-261299

However, in the knocking control device of Patent Document 1, since the knocking occurrence degree is used to calculate the magnitude of the correction value, the knocking determination level cannot be calculated until knocking occurs several times, and the knocking determination is made. There is room for shorter level calculation delays.

The present invention has been made to solve the above-mentioned problems, and it is possible to improve the responsiveness of the background level and realize high knocking determination accuracy even when the operating conditions are suddenly changed. Knocking determination of the internal combustion engine. The purpose is to provide the device.

The present invention is a knocking determination device for an internal combustion engine in order to achieve the above object.
Vibration intensity detecting means for detecting the vibration level of an internal combustion engine,
A reference background level storage means in which the reference background level representing the vibration intensity in a steady state where knocking does not occur is stored in advance for each operating condition, and
For each control cycle, the reference background level according to the current operating conditions is acquired from the reference background level storage means, and the current background level is calculated based on the reference background level and the previous feedback value. , A level calculation means for calculating the knocking judgment level, which is a judgment criterion for the presence or absence of knocking based on the background level of this time,
When the vibration level detected by the vibration intensity detecting means is less than the knocking determination level under the current operating conditions, the feedback value updating means for updating the feedback value based on the value obtained by annealing the vibration level. , Is provided.

According to the present invention, it is possible to select a reference background level according to the current operating condition for each control cycle from the reference background level previously adapted for each operating condition. Therefore, the transient followability is high and erroneous determination can be reduced. Further, since noise less than knocking is less likely to be erroneously determined as knocking, the feedback value can be appropriately updated by smoothing calculation even during transient operation. The reference background level is corrected by this feedback value, and it is possible to absorb vibration changes due to machine error variations and aging deterioration. As described above, according to the present invention, it is possible to improve the responsiveness of the background level and realize high knocking determination accuracy even when the operating conditions are suddenly changed.

It is a figure for demonstrating the system structure of Embodiment 1 of this invention. FIG. 5 is a flowchart of a processing routine executed by the ECU 40 in order to realize the knocking determination device according to the first embodiment. It is a figure which shows the background level calculation image of the knocking determination apparatus at the time of a transient operation. It is a figure for demonstrating the variation due to the engine machine difference. It is a flowchart of the knocking determination routine in the conventional method. It is a graph which shows the verification result of the conventional method. It is a graph which shows the detection result of this method. It is a figure for demonstrating the background level calculation image at the time of a follow-up delay.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The elements common to each figure are designated by the same reference numerals, and duplicate description will be omitted.

Embodiment 1.
(System configuration)
FIG. 1 is a diagram for explaining the system configuration of the first embodiment of the present invention. The system shown in FIG. 1 includes a spark-ignition type internal combustion engine (as an example, a gasoline engine) 10. A piston 12 is provided in the cylinder of the internal combustion engine 10. A combustion chamber 14 is formed on the top side of the piston 12 in the cylinder. An intake passage 16 and an exhaust passage 18 communicate with the combustion chamber 14.

The intake port of the intake passage 16 is provided with an intake valve 20 that opens and closes the intake port. The exhaust port of the exhaust passage 18 is provided with an exhaust valve 22 that opens and closes the exhaust port. The intake passage 16 is provided with an electronically controlled throttle valve 24. The internal combustion engine 10 includes a fuel injection valve (for example, a direct injection fuel injection valve) 26 for supplying fuel into the combustion chamber 14, and an ignition device (only an ignition plug) for igniting the air-fuel mixture. ) 28 are provided respectively.

Further, in the system of the present embodiment, as a control device for controlling the internal combustion engine 10, an electronic control unit (ECU) 40 having a processor and a memory, and a drive circuit (not shown) for driving various actuators described below are provided. I have.

The actuator to which the ECU 40 transmits an operation signal includes various actuators for controlling engine operation such as the throttle valve 24, the fuel injection valve 26, and the ignition device 28 described above.

The sensor to which the ECU 40 receives the signal includes various sensors such as a knock sensor 30, a crank angle sensor 42, and an airflow sensor 44. The knock sensor 30 is attached to the cylinder block and outputs a signal according to the vibration level (vibration intensity) of the cylinder block. The crank angle sensor 42 is arranged in the vicinity of the crank shaft (not shown) and outputs a signal for each predetermined crank angle. The air flow sensor 44 is arranged near the inlet of the intake air passage 16 and outputs a signal according to the amount of intake air.

The ECU 40 controls the operating state of the internal combustion engine 10 by driving various actuators according to a predetermined program based on various sensor outputs. For example, the crank angle and the engine rotation speed (engine rotation speed) NE are calculated based on the output of the crank angle sensor 42, and the intake air amount is calculated based on the output of the air flow sensor 44. Further, the engine load factor KL is calculated based on the intake air amount, the engine rotation speed, and the like. Then, the fuel injection timing and the ignition timing are determined based on the crank angle, and when these timings arrive, the fuel injection valve 26 and the ignition device 28 are driven.

Further, the ECU 40 performs knocking control together with the above-mentioned actuators and sensors. In the knocking control, the presence / absence of knocking is determined based on the vibration level detected by the knock sensor 30, and when knocking occurs, the ignition timing of the ignition device 28 is retarded to eliminate knocking, and when knocking does not occur, the ignition device 28 The ignition timing is advanced to achieve optimum torque and fuel efficiency.

The ECU 40 has a function as a knocking determination device in order to determine whether or not knocking has occurred during knocking control. The knocking determination device according to the present embodiment will be described with reference to FIGS. 2 to 4.

FIG. 2 is a flowchart of a processing routine executed by the ECU 40 in order to realize the knocking determination device according to the present embodiment. This routine is repeatedly executed in a predetermined control cycle (for example, every cycle). For each control cycle, the knocking determination device acquires the engine rotation speed, engine load factor, and vibration level described above.

First, in step S100, the background level (BGL) of this time is calculated using the following equation (1).
This time BGL = expected term (map value for each operating condition x K) + previous F / B term ... (1)
The value of the prospective term is calculated by multiplying the value obtained from the map described below by the K value. The value (feedback value) of the previous F / B term is a value calculated by annealing the knock sensor detection value when there is no knocking (noise) up to the previous routine, and is an initial value (for example, 0) in the initial routine. There is (step S130 described later).

The prospective term of equation (1) will be described. The knocking determination device stores in advance a reference background level indicating the vibration intensity in a steady state in which knocking does not occur in the map according to each operating condition (determined by the engine rotation speed and the engine load factor).

FIG. 3 is a diagram showing a background level calculation image of the knocking determination device during transient operation. The solid line 31 indicates the reference background level acquired from the map according to the current operating conditions. At each control cycle, the reference background level that matches the current operating conditions is acquired from the map. In FIG. 3, a reference background level that changes linearly with acceleration is acquired. Since the acquisition of the map value does not depend on the smoothing calculation, there is no follow-up delay, and the erroneous determination described with reference to FIG. 8 described above is reduced.

In addition, the map value alone cannot absorb the variation in machine difference, deterioration over time, and the change in vibration level due to changes in the control state. It can also absorb vibration level changes due to machine error variations and aging deterioration.

Next, the coefficient K of the expected term in the equation (1) will be described. FIG. 4 is a diagram for explaining variations due to engine machine differences. Even in the engines A and B of the same type, there are variations in the vibration intensity with respect to the engine rotation speed. Therefore, there is concern about the influence of map deviation. As a result of the investigation, as shown in FIG. 4, there is an offset change in the engine machine difference, and the amount is learned. As a method, a correction is provided in which the map value is multiplied by K by comparing the stable vibration level states in which knocking does not occur during idling.

As described above, in step S100, the knocking determination device acquires the reference background level suitable for the current operating conditions from the map for each control cycle, and multiplies it by the coefficient K, which is the previous F. The background level of this time is calculated by adding the value of the / B term.

Returning to FIG. 2, the explanation will be continued. Next, in step S110, the knocking determination level, which is a criterion for determining whether or not knocking has occurred, is obtained by multiplying the current background level, which represents the vibration intensity in a steady state where knocking does not occur, calculated in step S100 by a predetermined coefficient. calculate.

Next, in step S120, the knocking determination device compares the vibration level detected by the knock sensor 30 with the knocking determination level to determine whether it is noise or knocking. When the vibration level is equal to or higher than the knocking determination level, it is determined to be knocking, and when it is lower than the knocking determination level, it is determined to be noise (no knocking). If it is determined to be noise, the process proceeds to step S130. On the other hand, if it is determined to be knocking, this routine is terminated. In this case, since the feedback value is not updated, the value of the F / B term of the equation (1) in this routine of the next control cycle is not changed.

If the vibration level detected by the knock sensor 30 under the current operating conditions is less than the knocking determination level, that is, if it is determined to be noise, the vibration level is smoothed and after the next control cycle. The value (feedback value) of the F / B term used in step S100 of the above is updated (step S130). The following equation (2) is used for the smoothing calculation of the F / B term, and the difference between the vibration level and the BGL is fed back this time in consideration of the machine difference variation and the like.
Update F / B term = (vibration value-BGL) x smoothing constant + previous F / B term ... (2)
Here, the smoothing constant is a conforming value. After that, the processing of this routine is terminated.

(effect)
As described above, in the routine shown in FIG. 2, mapping and annealing processing are integrated. By using the map value, the reference background level suitable for the current operating conditions can be selected for each control cycle, and the knocking determination level can be made to follow the change of the vibration level without delay. Therefore, the transient followability is high, and knocking can be determined with high accuracy even during transient operation. As a result, it is possible to reduce the possibility that the vibration level that should be originally determined as noise is erroneously determined as knocking. If it is appropriately determined to be noise, the value of the F / B term in the equation (1) used in the next control cycle is also updated by the smooth calculation of the vibration level. In the formula (1), not only the above map value but also the vibration level change due to the machine error variation and the aging deterioration can be absorbed by adding the F / B term using the smoothing calculation. As described above, according to the knocking determination device of the present embodiment, it is possible to flexibly respond to changes in the vibration level even during transient operation, and it is possible to determine knocking with high accuracy.

(Verification results of the conventional method and this method)
Finally, the verification results of the conventional method (annealing) and the current method (fusion of map and annealing) will be explained.

The conventional method to be compared is as shown in the flowchart of FIG. Specifically, first, the background level of the previous routine is acquired (step S200), and the knocking determination level is calculated based on this (step S210). When the vibration level detected by the knock sensor is less than the knocking determination level, it is determined to be noise (step S220), and only when it is determined to be noise, the vibration level (vibration value) is smoothed to determine the background level. Update (step S230). The background level is annealed by the following equation (3).
BGL = (vibration value-previous BGL) x smoothing constant + previous BGL ... (3)
Here, the smoothing constant is a conforming value.

As described above, the conventional method to be compared is a method of updating the background level only when the vibration level is determined to be noise this time, and the difference between the previous BGL and the vibration level this time is learned by smoothing processing.

FIG. 6 is a graph showing the verification results of the conventional method. According to the conventional method, the calculation for raising the knocking determination level to an appropriate level is also delayed due to the follow-up delay of the background level by the smoothing calculation during the transient operation. Therefore, even though knocking has not actually occurred, the vibration level detected by the knock sensor is equal to or higher than the knocking determination level, and the knocking is erroneously determined. If it is determined that knocking is caused by an erroneous determination, the background level is not updated, so that the erroneous determination is continued for about 10 more ignitions. In this way, the erroneous determination that occurs after the sudden change in the operating conditions continues, and the knock detection accuracy is lowered.

On the other hand, FIG. 7 is a graph showing the detection result of this method. In the above-mentioned method, mapping and annealing are integrated. As a result, as described above, the improvement of transient followability by mapping and the absorption of changes such as machine error variation by annealing processing are compatible. In FIG. 7, compared to FIG. 6, there is no follow-up delay after a sudden change, and erroneous judgment is improved. Even during transient operation, it is possible to flexibly respond to changes in vibration level and to judge knocking with high accuracy. can do.

In the first embodiment described above, the memory of the ECU 40 corresponds to the "reference background level storage means" in the present invention, and the knock sensor 30 corresponds to the "vibration intensity detecting means" in the present invention.
Further, here, the ECU 40 executes the processes of steps S100 and S110 so that the "level calculation means" in the present invention executes the processes of steps S120 and S130 to execute the processes of the first invention. "Feedback value updating means" are realized respectively.

By the way, in the system of the first embodiment described above, the vibration level is detected by the knock sensor 30, but the vibration level equivalent value may be calculated from the detected value of the in-cylinder pressure sensor for detecting the in-cylinder pressure.

The engine to which the present invention is applied is not limited to the in-cylinder direct injection engine as in the above-described embodiment. The present invention can also be applied to a port injection type engine.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and can be variously modified and implemented without departing from the spirit of the present invention.

10 Internal combustion engine 12 Piston 14 Combustion chamber 16 Intake passage 20 Intake valve 22 Exhaust valve 24 Throttle valve 26 Fuel injection valve 28 Ignition device 30 Knock sensor 40 ECU
42 Crank angle sensor 44 Airflow sensor

Claims (1)

Vibration intensity detecting means for detecting the vibration level of an internal combustion engine,
A reference background level storage means that stores in advance a reference background level indicating the vibration intensity in a steady state where knocking does not occur for each operating condition, and
For each control cycle, the reference background level according to the current operating conditions is acquired from the reference background level storage means, and the current background level is calculated based on the reference background level and the previous feedback value. , A level calculation means for calculating the knocking judgment level, which is a judgment criterion for the presence or absence of knocking based on the background level of this time,
When the vibration level detected by the vibration intensity detecting means is less than the knocking determination level under the current operating conditions, the feedback value updating means for updating the feedback value based on the value obtained by annealing the vibration level. ,
A knocking determination device for an internal combustion engine.

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