JP2004011569A - Knock control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve problems that occupants in a cabin feel disagreeable if knocking is excessive, and the fuel consumption or the output performance is degraded if knocking is excessively suppressed. <P>SOLUTION: A knock control means 22 performs trace knock control to advance the ignition timing as much as possible while suppressing excessive knocking based on the comparison of a detection signal of a knock sensor 10 with the knock determination level. A knock determination level setting means 14 sets the knock determination level based on the number of rotations. A changing means 18 changes the knock determination level based on the vehicle speed which is a parameter corresponding to the noise index in the cabin. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an improvement in a knock control device that suppresses knocking of an internal combustion engine.
[0002]
[Prior art]
A knock control device that suppresses knocking (also simply referred to as knock) of an internal combustion engine for a vehicle is disclosed in, for example, JP-A-2000-145530. This device detects knocking by comparing the output of a knock sensor with a knock determination level.When knocking is detected, the ignition timing is retarded to suppress the occurrence of knocking, and the ignition timing is reduced to the extent that weak knock occurs. Is gradually advanced, and a kind of feedback control of maintaining an optimal ignition timing is performed. Further, when a predetermined period elapses under the high-load operation condition, the knock determination level is modified to be low in order to suppress a local temperature rise due to the occurrence of knocking.
[0003]
[Problems to be solved by the invention]
Knocking is pressure vibration generated in the combustion chamber due to self-ignition of end gas in the cylinder, and as the name implies, is recognized by passengers in the vehicle cabin as an abnormal tapping sound like hitting a metal with a hammer. Excessive knocking causes discomfort to the occupant as noise, while excessive suppression of knocking accompanied by retardation of the ignition timing or the like causes a reduction in fuel consumption and engine output.
[0004]
Whether or not the knocking noise, that is, the knocking sound gives the occupant an unpleasant sensation, depends on the noise figure which is the degree of the noise in the vehicle interior other than the knocking sound. For example, a knock sound of the same level may cause discomfort to the occupant in a situation where the noise figure is low, while the knock sound may be inaudible to the occupant in a situation where the noise figure is high and may cause discomfort. There may not be. The present invention has been made on the basis of the unique viewpoint that the level of the knocking noise that is allowed varies depending on the noise index.
[0005]
[Means for Solving the Problems]
A knock control device for an internal combustion engine according to the present invention performs knock control for suppressing knock based on a detection signal of a knock detection unit and a knock determination level set based on an engine speed or the like. Typically, the ignition timing is feedback-controlled based on a comparison between a detection signal of the knock detection means and a knock determination level (intensity or frequency). Then, the knock determination level is changed based on the degree of noise in the vehicle interior that does not include the knock sound, that is, the noise index.
[0006]
【The invention's effect】
According to the present invention, by changing the knock determination level based on the noise index, it is possible to improve fuel efficiency and output performance without giving a passenger an unpleasant knock sound. That is, by allowing knocking as much as possible within a range that does not generate an unpleasant knocking sound, it is possible to sufficiently suppress a decrease in fuel efficiency and output performance due to suppression of knocking.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.
[0008]
FIG. 1 is a block diagram schematically showing a knock control device for an internal combustion engine according to the present invention. A knock sensor 10 is mounted on a cylinder block (not shown) of the internal combustion engine as knock detection means capable of detecting vibration in a combustion chamber that causes knock. The detection signal of the knock sensor 10 is output to an engine control unit 12 having a ROM, a RAM, a CPU, and an input / output interface. The engine control unit 12 has a function of storing and executing various means and flowcharts described below as programs.
[0009]
Knock determination level setting means 14 sets a knock determination level based on the engine speed. The engine speed described above is detected by, for example, a well-known crank angle sensor 16. The change means 18 changes the knock determination level based on the vehicle speed. The above-mentioned vehicle speed is detected by, for example, a well-known wheel rotation sensor 20 that detects a wheel speed.
[0010]
Knock control means 22 performs knock control for suppressing occurrence of excessive knock based on the detection signal of knock sensor 10 and the knock determination level for each cylinder specified by the cylinder determination signal. Typically, when a detection signal of knock sensor 10 exceeds a knock determination level (at least one of intensity and frequency) in a knock detection section between knock detection start timing and knock detection end timing, a predetermined knock delay is set. If the detection signal of the knock sensor 10 does not exceed the knock determination level, the ignition timing is gradually advanced until a slight knock is generated, and the ignition timing is gradually advanced to the optimum level. A kind of feedback control (trace knock control) of maintaining a proper ignition timing is performed.
[0011]
FIG. 2 is a flowchart schematically showing the process of setting and changing the knock determination level by knock determination level setting means 14 and changing means 18.
[0012]
In S (step) 1, it is determined whether the vehicle speed VSP detected by the wheel rotation sensor 20 is equal to or higher than a predetermined vehicle speed noise threshold VSPksl. When the vehicle speed VSP is equal to or higher than the threshold value VSPks, the process proceeds from S1 to S2, where the engine speed Ne is used to look up a high vehicle speed knock determination strength threshold value rotation speed table KSLhi () to obtain a high vehicle speed knock. A determination strength threshold value (first threshold value) KSLlow (Ne) is calculated and set as a knock determination strength threshold value KSL. When the vehicle speed VSP is lower than the threshold value VSPksl, the process proceeds from S1 to S3, where the low vehicle speed knock determination strength threshold rotational speed table KSLlow () is looked up from the engine speed Ne to determine the low vehicle speed knock determination. An intensity threshold value (second threshold value) KSLhi (Ne) is calculated and set as a knock determination level, that is, a knock determination intensity threshold value KSL. The above S1 corresponds to the changing means 18, and S2 and S3 correspond to the knock determination level setting means 14.
[0013]
As shown in FIG. 3, the high vehicle speed knock determination strength threshold value table KSLhi () is set to a higher level than the low vehicle speed knock determination strength threshold value table KSLlow (). As shown in FIG. 4, the knock determination strength threshold may be a knock strength or a knock frequency. In any case, the high vehicle speed knock determination strength threshold value KSLhi (Ne) is set to a higher level than the low vehicle speed knock determination strength threshold value KSLlow (Ne). Therefore, stronger knocking is allowed at a high vehicle speed than at a low vehicle speed. In addition, as shown in FIG. 5, the knock retard amount at the time of high vehicle speed is suppressed to be lower than the knock retard amount at the time of low vehicle speed.
[0014]
Referring to the time chart of FIG. 6, as the vehicle speed increases, the noise in the vehicle interior also increases. When the vehicle speed VSP reaches the predetermined threshold value VSPksl, the knock determination strength threshold value (knock determination level) KSL is changed from the low vehicle speed knock determination strength threshold value KSLlow (Ne) to the high vehicle speed as described above. It is changed to the hour knock determination intensity threshold value KSLhi (Ne) to increase the level and to suppress the knock retard amount to a low value. These changes are reflected in the above-described trace knock control (feedback control of the ignition timing), and the ignition timing is relatively advanced. Therefore, the ignition timing approaches the advance limit MBT, the fuel consumption rate is reduced, the shaft torque is increased, and the fuel consumption and output performance are improved. By increasing the knock determination strength threshold value KSL, the knock sound increases, but when the vehicle speed corresponding to the noise index in the vehicle compartment is equal to or higher than the threshold value VSPksl, the noise in the vehicle compartment is originally large. The sound does not cause discomfort to the occupants. That is, the knock sound level (S / N) is maintained at a value lower than a predetermined knock sound level allowable upper limit that does not cause discomfort to the passengers in the vehicle compartment.
[0015]
As described above, in the present embodiment, the knocking determination level is changed according to the vehicle speed which is a parameter corresponding to the noise index in the vehicle compartment. Specifically, when the vehicle speed is high and the noise is high, the knock determination strength threshold value KSL is increased, and knocking is positively allowed within a range that does not cause discomfort to the passenger, and excessive knocking is suppressed. The reduction in fuel consumption and output caused by the
[0016]
When a human distinguishes an arbitrary sound (S) under a certain noise (N), the human has sensitivity represented by S / N. For example, if N is large while S is constant, the S becomes difficult to hear. Assuming that the knock sound is S and the noise other than the knock sound is N, if the S / N is equal to or lower than a predetermined level, even if the knock sound S is large, the passenger does not feel uncomfortable. Since the noise N changes due to various factors, it is difficult to accurately change and control the noise, even if soundproofing can be performed. Therefore, in this embodiment, by changing and controlling the knock sound S, the S / N, The knocking sound level is kept lower than a predetermined allowable upper limit (see FIG. 6).
[0017]
The vehicle speed is substantially proportional to the road surface and road noise of tires, vibration, wind noise, and the like, and is closely related to the noise index in the vehicle compartment. Specifically, as shown in FIG. 7, the noise index increases as the vehicle speed increases. Further, the vehicle is generally equipped with a wheel rotation sensor 20 for detecting the vehicle speed (wheel speed), for displaying the vehicle speed on a speed meter, for use in ABS control, and the like. Therefore, by using the vehicle speed as a noise index parameter, it is possible to relatively accurately change the knock determination strength threshold value KSL, and it is necessary to add a sensor for newly detecting the noise index parameter. There is no cost advantage.
[0018]
Noise figure does not depend only on vehicle speed, but also on road surface conditions. Therefore, when only the vehicle speed is given as a parameter of the noise index as in the above-described embodiment, even if the knock determination level KSL is excessively finely changed and controlled according to the vehicle speed, there is not much effect. In the above embodiment, a simple configuration is employed in which the noise determination level is switched between KSLhi (Ne) and KSLlow (Ne) at the vehicle speed noise threshold VSPksl corresponding to the inflection point of the noise level. However, even with this, the above-described effects can be sufficiently obtained.
[0019]
As described above, the present invention has been described based on the specific embodiments. However, the present invention is not limited to the above embodiments, and includes various modifications and changes without departing from the gist of the present invention. . For example, when the noise index parameter can be detected with high accuracy, the knock determination level may be changed and controlled steplessly (continuously) according to the parameter. The knock control means 22 may be configured to temporarily increase the fuel injection amount when knocking is detected and reduce the temperature in the combustion chamber to suppress knocking.
[Brief description of the drawings]
FIG. 1 is a block diagram schematically showing a knock control device for an internal combustion engine according to one embodiment of the present invention.
FIG. 2 is a flowchart schematically showing a process of setting a knock determination level according to the embodiment.
FIG. 3 is a characteristic diagram showing a difference between knock determination levels at a low vehicle speed and at a high vehicle speed.
FIG. 4 is a characteristic diagram showing a relationship between knock intensity and knock frequency at low vehicle speed and at high vehicle speed.
FIG. 5 is a characteristic diagram showing a difference in knock retard amount between a low vehicle speed and a high vehicle speed.
FIG. 6 is a time chart illustrating the operation of the present embodiment.
FIG. 7 is a characteristic diagram showing a relationship between a vehicle speed and a noise index in a vehicle cabin.
[Explanation of symbols]
10 Knock sensor 14 Knock determination level setting means 18 Changing means 20 Vehicle speed sensor 22 Knock control means

Claims (3)

Knock determination level setting means for setting a knock determination level based on at least the engine speed,
Knock detection means,
Knock control means for suppressing knocking based on a detection signal of the knock detection means and a knock determination level,
Changing means for changing the knock determination level based on a parameter corresponding to a vehicle interior noise index;
A knock control device for an internal combustion engine having the same. A parameter corresponding to the noise index in the vehicle compartment is a vehicle speed,
2. The knock control device for an internal combustion engine according to claim 1, wherein the changing means increases the knock determination level when the vehicle speed is high, and lowers the knock determination level when the vehicle speed is low. The changing means sets the knock determination level to a first threshold when the vehicle speed is equal to or higher than a predetermined vehicle speed noise threshold, and sets the knock determination level to a second threshold when the vehicle speed is lower than the vehicle speed noise threshold. The knock control device for an internal combustion engine according to claim 2, wherein the threshold value is set to:

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