JP2003232256A - Knocking determining device and engine provided therewith - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide knocking determining technology for permitting easy and highly precise determination of knocking in an engine 100. <P>SOLUTION: This knocking determining device comprises a detecting means 30 for detecting the condition of knocking in the engine 100 and a determining means 52 for determining the knocking in accordance with the frequency of knocking values regarding the sizes of the output of the detecting means 30, which are within a preset range where the occurrence of the knocking is predicted. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine knocking determination technique, and more particularly to a knocking determination technique of a premixed compression ignition engine.

[0002]

2. Description of the Related Art The above-mentioned premixed compression self-ignition engine was devised for the purpose of preventing the particulates of fuel injection diesel. Instead of injecting fuel to burn, pre-mixture is mainly filled in the combustion chamber in advance, the pre-mixture filled in the combustion chamber is compressed and ignited in the compression stroke, and then burned in the expansion stroke. Then, the exhaust gas of the combustion chamber is discharged to the exhaust passage in the exhaust stroke, the efficiency can be improved by increasing the compression ratio, and the fuel can be burned in a lean state to reduce NOx. In particular, when the fuel is an engine of gas fuel such as natural gas city gas, it is difficult to inject the gas fuel at a high pressure by configuring it as a diesel engine. It is easier to ignite the mixture by compression ignition.

Such a premixed compression ignition engine is
As described above, the premixed mixture enclosed in the combustion chamber is compressed and self-ignited for combustion.Therefore, the combustion system of the premixed mixture in the combustion chamber is a so-called multipoint where the premixed mixture self-ignites at many points. It is said to be due to self-ignition, and in such a premixed compression self-ignition engine, knocking such as rattling of the piston, crankshaft, etc. may occur due to premature self-ignition of the premixed air.

On the other hand, conventionally, a spark ignition type engine is provided with a knock sensor or the like configured to output a voltage signal according to the acceleration of vibration in the resonance frequency range of the cylinder block, and the knock sensor or the like outputs the signal. When the generated voltage signal becomes equal to or higher than a predetermined threshold value at which knocking is predicted to occur, it is determined that knocking has occurred, and knocking avoidance operations such as delaying the ignition timing are performed to suppress knocking. Was being done.

Also in the premixed compression self-ignition engine, such a knock sensor or the like is provided, and when the occurrence of knocking is judged by the output signal of the knock sensor or the like, various operating conditions are adjusted to adjust the mixture. It may be configured to suppress premature self-ignition and avoid knocking.

[0006]

However, since the premixed compression ignition engine ignites the premixed mixture enclosed in the combustion chamber by compression ignition, for example, if the intake temperature and intake pressure are too high, knocking occurs, When the intake pressure and intake temperature are too low, the premixture does not self-ignite, but a misfire occurs.Therefore, the range of operating conditions such as intake temperature and intake pressure that can maintain a stable combustion state is different from that of other engines. Very small compared to.

In the premixed compression self-ignition engine, when it is erroneously determined that knocking has occurred even though knocking does not actually occur, and various operating conditions are adjusted so as to avoid knocking, There is a possibility that the operating condition may deviate from the range where stable operation is possible, the operating state may become unstable, or the operation may be stopped due to misfire or the like. Therefore, there is a demand for a technique capable of detecting and determining knocking with high accuracy in a premixed compression self-ignition engine.

Therefore, in view of the above-mentioned circumstances, an object of the present invention is to provide a knocking determination technique capable of determining knocking of a premixed compression self-ignition engine particularly easily and with high accuracy.

[0009]

A first characteristic configuration of a knocking determination device according to the present invention for achieving this object relates to knocking of an engine, as described in claim 1 of the appended claims. Detection means for detecting the state, and a knock value related to the magnitude of the output of the detection means,
And a determination unit that determines the knocking based on a frequency within a predetermined set range in which the knocking is predicted to occur.

That is, according to the first characteristic configuration of the knocking determination device according to the present invention, in order to detect knocking in the engine, the state related to knocking such as the vibration state of the cylinder block or the pressure fluctuation state of the combustion chamber is detected. Knocking is determined using the output signal of the detection means for detection, and the determination means determines that the knock value related to the magnitude of the output of the detection means is within a predetermined set range in which it is predicted that knocking has occurred. It is possible to determine the frequency at which the knock value falls within the set range instead of determining knocking at the time when the knocking occurs, and determine knocking at the time when the frequency becomes equal to or higher than a predetermined frequency. By determining knocking by such a determination means, even if the knock value falls within the set range due to factors other than knocking, knocking does not actually occur, but knocking actually occurs. It is possible to determine that knocking has occurred and improve the knocking determination accuracy only when the knocking occurs continuously or intermittently occurs a plurality of times.

Therefore, it is possible to realize a knocking determination device which can determine knocking easily and with high accuracy. By performing an engine knocking avoidance operation based on the determination result of such a knocking determination device, knocking can be detected. It is possible to prevent an erroneous determination and prevent an unstable driving state and an operation stop due to a knocking avoidance operation at the time of erroneous knocking determination.

The predetermined setting range in which knocking is predicted to occur is a predetermined threshold value in which knocking is predicted to occur when the knock value tends to increase due to knocking. The above range is shown, and conversely, when the knock value tends to decrease due to the occurrence of knocking, the range below a predetermined threshold value at which knocking is predicted to occur is shown.

According to the second characteristic constitution, as described in claim 2 of the scope of the claims, in addition to the first characteristic constitution, the engine compresses the air-fuel mixture enclosed in the combustion chamber. It is a premixed compression self-ignition engine that self-ignites.

In the premixed compression self-ignition engine, unlike the spark ignition type engine, the combustion system of the premixed air in the combustion chamber is based on multipoint self-ignition, so that when knocking occurs and when it does not occur. In some cases, the difference in the vibration state and the pressure fluctuation state of the combustion chamber is small, and the reliability of the output of the detection means may be reduced. However, according to the knocking determination device of the present characteristic configuration, it is possible to determine with high accuracy even with such knocking of the premixed compression self-ignition engine, and in the premixed compression self-ignition engine, the operating state becomes unstable due to an erroneous determination. It is possible to satisfactorily prevent the operation stop due to the ignition and misfire.

The third characteristic configuration is, in addition to the first or second characteristic configuration, as described in claim 3 of the scope of claims, the detecting means determines the vibration state of the engine. It is a knock sensor for detecting.

As the detection means for detecting the state related to the engine knocking, the knock sensor as described above,
There is a pressure sensor or the like for detecting the pressure fluctuation state of the combustion chamber.
The former knock sensor is cheaper than a relatively expensive pressure sensor, but in terms of knocking detection accuracy,
It may be inferior to directly detecting the pressure fluctuation state of the combustion chamber with the pressure sensor. However, the knocking determination device having the present characteristic configuration can determine knocking with high accuracy even by using such an inexpensive knock sensor.

According to the fourth characteristic constitution, as described in claim 4 of the scope of claims, in addition to any one of the first to third characteristic constitutions, To obtain the extreme value of the output of the detection means as the knock value,
The number of times that the knock value is within the predetermined setting range within a predetermined determination period is obtained as the number of detections, the ratio of the number of detections to the number of cycles within the determination period is obtained as the frequency, and the frequency is a predetermined frequency. In the above case, it is determined that the knocking has occurred.

That is, according to the knocking determination device having the present characteristic configuration, the knocking determination is performed by the determination means.
Using the output signal that is continuously or relatively shortly input from the detection means and that changes depending on the vibration state of the engine and the pressure fluctuation state of the combustion chamber, knocking determination can be easily performed as in the present characteristic configuration. . Further, it is appropriate that the above-mentioned determination period is a period of about 2 to 30 cycles, preferably about 5 to 15 cycles. Further, when there is a high possibility of knocking that can be recognized from the past knocking occurrence rate and operating conditions, when the above-mentioned determination period is set short or the determination period is set to one cycle, knocking occurs. If the probability of occurrence of knocking is low, on the contrary, if the probability of occurrence of knocking is low, the determination period is extended to improve the accuracy of knocking determination, and the operating state becomes unstable due to erroneous knocking determination. Operation stop can be prevented.

A characteristic structure of an engine according to the present invention for achieving this object is a knocking having any one of the above-mentioned first to fourth characteristic structures as described in claim 5 of the appended claims. In addition to the determination device, a knocking avoiding means for performing a knocking avoiding operation based on the determination result of the knocking determination device is provided.

That is, since the engine according to the present invention is provided with the knocking determination device having the above-mentioned first to fourth characteristic configurations, the function and effect described so far can be exerted and the knocking can be performed with high accuracy. Further, it is possible to make a determination, and further, by the knocking avoiding means, based on the determination result of such a highly accurate knocking determination device, for example, when it is determined that knocking has occurred, the spark ignition timing in the spark ignition type engine. In order to avoid knocking by delaying the engine, knocking avoidance operation is performed.On the other hand, in an engine such as a premixed compression ignition engine, the closing timing of the exhaust valve is adjusted to reduce the internal EGR amount to the combustion chamber and It is possible to perform a knocking avoidance operation that reduces pre-mixture pre-ignition by reducing the intake pressure and intake air pressure to avoid knocking. It is possible to maintain a stable operating condition.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a knocking determination device according to the present invention will be described with reference to the drawings. Figure 1
The premixed compression ignition engine 100 (an example of an engine) shown in FIG. 1 supplies fuel to the air compressed by the supercharger 18 and flowing through the intake passage 11 by the mixer 15 to form a mixture, and the premixed mixture formed. Air is sucked into the combustion chamber 7 formed in the cylinder 3 through the intake valve 1, and the premixed gas enclosed in the combustion chamber 7 is compressed to cause self-ignition combustion to push down the piston 4 to move the piston 4 Is output as the rotational power of the crankshaft 6 via the connecting rod 5. Further, the exhaust gas after combustion is discharged from the combustion chamber 7 to the exhaust passage 12 via the exhaust valve 2.

The mixer 15 is constructed so as to supply the fuel, which is natural gas, to the air supplied from the upstream side of the intake passage 11 while adjusting the flow rate. The ECU (engine control unit) 50 supplies the fuel in the mixer 15 with the fuel. Is adjusted so that the equivalence ratio of the premixed gas formed in the intake passage 11 can be controlled.

Further, in the premixed compression ignition engine 100, cooling water cooled by a cooling tower (not shown) and air flowing in the intake passage 11 are provided in the intake passage 11 on the downstream side of the supercharger 18. A cooler 16 that cools the compressed and heated air by exchanging heat is provided. Further, an adjustment valve 17 capable of adjusting the flow rate of the cooling water flowing through the cooler 16 is provided, and the ECU 50 adjusts the flow rate of the cooling water by the adjustment valve 17 to adjust the cooling amount of the intake passage 11 to the air. It is configured to be controllable.

The premixed compression self-ignition engine 100 is provided with a valve timing variable mechanism 20 capable of adjusting the opening / closing timing of the intake valve 1 and the exhaust valve 2, and the ECU 50 uses the crank angle sensor 23 to crank the crankshaft 6. With the angle detection, the opening / closing timing of the intake valve 1 and the exhaust valve 2 can be set to a predetermined timing with respect to the crank angle.

For example, the ECU 50 sets the closing timing of the exhaust valve 2 to a point advanced from the bottom dead center so that the combustion exhaust gas remains in the combustion chamber 7, and the remaining combustion exhaust gas is taken into the next intake air. It is possible to increase the initial temperature of the premixed gas and accelerate compression ignition of the premixed gas by performing so-called internal EGR in which the premixed air that is taken in during the stroke is mixed.
Further, the ECU 50 can adjust the amount of advance of the closing timing of the exhaust valve 2 to adjust the amount of combustion exhaust gas remaining in the combustion chamber 7, that is, the internal EGR amount.

Further, the premixed compression ignition engine 100
Is provided with a knock sensor 30 (an example of detection means) that detects a vibration state of the cylinder 3 due to knocking. The knock sensor 30 uses a voltage signal (DC signal) according to the vibration acceleration of the cylinder 3 at a predetermined resonance frequency.
0-5V) is output. The resonance frequency of the knock sensor 30 is set to 5 to 10 kHz.
Further, this resonance frequency is the same as the premixed compression ignition engine 1
00 is appropriately set according to the specification.

The ECU 50 receives the output signal of the crank angle sensor 23 and the output signal of the knock sensor 30, and functions as a determination means 51 for determining knocking based on the input signal. The knocking determination device according to the present invention is provided with the knock sensor 30 and the knock sensor E.
It is composed of the CU 50.

Further, when the determination means 51 determines that knocking has occurred, the ECU 50 functions as knocking avoidance means 52 which executes at least one of the following knocking avoidance operations to avoid knocking. As such a knocking avoiding operation, the regulating valve 17 is adjusted to increase the flow rate of the cooling water supplied to the cooler 16 to lower the temperature (intake temperature) of the premixed air sucked into the combustion chamber 7, By delaying the timing of pre-mixture self-ignition, operation to avoid knocking due to pre-ignition,
The fuel supply amount in the mixer 15 is adjusted so that the combustion chamber 7
By reducing the equivalence ratio of the premixed air that is sucked into the air and reducing the combustion speed of the premixed air, an operation that avoids knocking by mitigating a sudden pressure increase, and a valve timing variable mechanism 20 is used. Internal EG by delaying the closing time of 2
By decreasing the R amount, the initial temperature of the premixed gas in the combustion chamber 7 is decreased to avoid knocking due to premature self-ignition. It should be noted that such knocking avoidance operation may be any operation that avoids knocking by adjusting other operating conditions such as lowering the intake pressure.

Next, the determination means 51 for determining knocking
The flow of the knocking determination process by the will be described based on FIG. First, the determination unit 51 sets the cycle number n assigned to each cycle to 1, resets the knocking occurrence flag Yn for identifying that knocking may have occurred in each cycle, and then, Knocking determination processing is started. The determination means 51 is
In one cycle from when the piston 4 is at the bottom dead center position to when it is at the next bottom dead center position (in the case of a four-cycle engine, this corresponds to two revolutions of the crankshaft 6).
The maximum value of the gain of the knock sensor 23, which is the vibration width of the voltage signal that fluctuates according to the vibration acceleration fluctuation of the cylinder 3 that is continuously input from the knock sensor 30, is obtained as the knock value (# 101), and the knock value is , A preset set value A (for example, A =) at which knocking is predicted to occur in the premixed compression ignition engine 100.
2.0 V) or more (an example of a predetermined setting range) is determined (# 102).

When the knock value is equal to or greater than the predetermined set value A, it is considered that knocking may have occurred in the cycle, and the knocking occurrence flag Yn is set to 1 (# 103), and conversely, When the knock value is less than the predetermined set value A, it is considered that knocking has not occurred in the cycle, the knocking occurrence flag Yn is set to 0 (# 107), and the cycle number n is incremented by 1. After that (# 108), the process returns to the above-mentioned step 101.

Next, when there is a possibility that knocking has occurred in the cycle as described above, as a frequency within the predetermined setting range in which it is predicted that knocking has occurred, B (for example, up to the present) , B = 2 to 30, preferably about 5 to 15) The ratio of the number of cycles in which the knocking may have occurred in the determination period corresponding to the cycle, that is, the knock value for the number B of cycles forming the determination period is The knocking occurrence flag Yk (k = n- (B-
The total of 1) to n) is obtained by dividing by B, and it is determined whether or not the ratio is a predetermined frequency value C (for example, C = about 0.3 to 0.8) or more (# 104).

Then, when the ratio of the number of detections when the knock value is equal to or more than the predetermined set value is less than the frequency value C, the cycle number n is incremented by 1 (# 108), and then the process returns to the above-mentioned step 101. .

On the contrary, when the ratio of the number of detections in which the knock value is equal to or greater than the predetermined set value is equal to or greater than the frequency value C, it is determined that knock has occurred (# 105), and the knock avoiding means 52 is activated. After performing the above-described knocking avoidance operation (# 106), the knocking determination process described so far is executed again.

By the knocking determination processing executed by the determining means 51, the maximum value of the gain of the knocking sensor 30 is sporadically caused by factors other than knocking.
Even when the so-called knock value exceeds a predetermined set value, it is not judged that knocking has occurred, but only if knocking occurs and the knocking occurs continuously or intermittently multiple times, knocking occurs. It is possible to determine that the engine has occurred, and it is possible to improve the knocking determination accuracy.

The set value A is appropriately set based on the maximum value of the gain of the knocking sensor 30 when knocking of the premixed compression self-ignition engine 100 does not occur, and the cycle number B of the determination period is set. It is preferable that the frequency value C and the frequency value C are appropriately set based on the knocking detection accuracy of the knocking sensor 30. In addition, the cycle number B of the determination period is set to a small number, for example, 1 when there is a high possibility of knocking occurrence that can be recognized from operating conditions such as a past knocking occurrence rate, engine load, or engine speed. , If the knocking delay occurs as short as possible, on the contrary, if the possibility of knocking is low, set it to a large value to improve the accuracy of knocking judgment and Instability and outages can also be prevented.

Further, in the above embodiment, the premixed compression self-ignition engine in which it is difficult to accurately determine knocking is provided with the knocking sensor 30 and the ECU 50 which constitute the knocking determination device according to the present invention. However, it goes without saying that the knocking determination device according to the present invention can be provided in a spark ignition type engine or another engine.

In the above-described embodiment, as the detecting means, instead of the knock sensor 30, a pressure sensor, which is expensive but can detect the pressure fluctuation state of the combustion chamber 7 as a state related to engine knocking, may be provided. However, when the pressure sensor is provided, the determination unit 51 uses the combustion chamber 7
With the number of cycles in which the pressure is equal to or higher than a predetermined set value (an example of a set range) as the number of detections, the occurrence of knocking can be determined from the ratio of the number of detections within the determination period.

The detecting means may be arranged to detect an instantaneous load reduction of the crankshaft 6 as a state relating to knocking. When detecting the load reduction in this way, the determining means 51 The number of cycles in which the load becomes equal to or lower than a predetermined set value (an example of a set range) is set as the number of detections, and the occurrence of knocking can be determined from the ratio of the number of detections in the determination period.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram illustrating an embodiment of the present invention.

FIG. 2 is a flowchart showing a knocking determination processing flow.

[Explanation of symbols]

1 intake valve 2 exhaust valve 3 cylinders 4 pistons 5 connecting rod 6 crankshaft 7 Combustion chamber 11 Intake passage 12 exhaust path 15 Fuel nozzle 16 Cooler 17 on-off valve 18 supercharger 20 Valve timing variable mechanism 30 Knocking sensor (detection means) 50 ECU 51 determination means 52 Knocking Avoidance Means 100 premixed compression ignition engine

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) // F02D 13/02 F02D 13/02 H (72) Inventor Koji Moriya 4 Hiranocho, Chuo-ku, Osaka-shi, Osaka In 1-2, Osaka Gas Co., Ltd. (72) Inventor, Masashi Nishigaki, 4-1-2, Hirano-cho, Chuo-ku, Osaka City, Osaka Prefecture In-house, Osaka Gas Co., Ltd. (72) Yuki Sato, Hirano, Chuo-ku, Osaka-shi, Osaka 4-1-2 Machi, Osaka Gas Co., Ltd. F term (reference) 3G084 AA01 BA13 BA23 BA30 DA13 DA27 DA38 EA05 EA07 EA11 EC01 EC04 FA00 FA25 3G092 AA00 AA02 BB01 DA02 DA08 EA01 EA09 EA17 FA16 FB06 HC05B22 JA02 JA02 20G02J0220G02X02 LA00 MA11 MA19 NA08 NA09 NE01 NE19 NE23 PC08Z PE00Z

Claims (5)

[Claims] 1. A detection unit that detects a state related to engine knocking, and a knock value related to the magnitude of the output of the detection unit based on a frequency within a predetermined setting range in which the knocking is predicted to occur. A knocking determination device, comprising: determination means for determining knocking. 2. The knocking determination device according to claim 1, wherein the engine is a premixed compression self-ignition engine that compresses the air-fuel mixture enclosed in the combustion chamber to self-ignite. 3. The knocking determination device according to claim 1, wherein the detection means is a knock sensor that detects a vibration state of the engine. 4. The determination means obtains the extreme value of the output of the detection means as the knock value for each cycle, and detects the number of times that the knock value falls within the predetermined setting range within a predetermined determination period. 4. The method according to claim 1, wherein the knocking frequency is determined as the number of times, the ratio of the number of detection times to the number of cycles in the determination period is determined as the frequency, and the knocking is determined to occur when the frequency is equal to or higher than a predetermined frequency. The knocking determination device according to item 1. 5. An engine comprising the knocking determination device according to claim 1, and a knocking avoidance means for performing a knocking avoidance operation based on a determination result of the knocking determination device.