JP3334633B2 - Device for detecting combustion noise of internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion noise detecting device for an internal combustion engine which detects combustion noise in each cylinder of the internal combustion engine.

[0002]

2. Description of the Related Art In an internal combustion engine, for example, a diesel engine, a diesel knock in which combustion noise increases due to a sudden increase in combustion pressure due to ignition delay during combustion occurs. Also,
In a gasoline engine or the like, a similar increase in combustion noise occurs due to pre-ignition of the air-fuel mixture or unstable combustion. In order to prevent such an increase in the combustion noise of the internal combustion engine, a combustion noise detection device for detecting the actual combustion noise of the engine is provided, and the combustion noise is reduced when the combustion noise tends to increase. Suppression control devices are known.

An example of this type of control device is disclosed in Japanese Patent Application Laid-Open No. Sho 62-291452. In the device disclosed in the publication, a knock sensor is arranged in an engine block of a diesel engine, and a signal from the sensor is input to an arithmetic unit via a gate circuit and a peak hold circuit. That is, the device of the above publication inputs a combustion sound (vibration) signal continuously output from the knock sensor to the arithmetic unit in synchronization with a period in which combustion occurs in each cylinder by a gate circuit,
A peak hold circuit detects a combustion noise peak value for each cylinder. The apparatus disclosed in this publication increases or decreases the pilot fuel injection amount of each cylinder so that the combustion noise peak value of each cylinder detected as described above is minimized.

[0004]

When performing control for suppressing combustion noise, it is necessary to accurately detect noise and vibration caused by combustion in each cylinder. That is, since the internal combustion engine generates various vibration noises during operation, in order to perform accurate combustion noise suppression control, these noises are eliminated and only the vibration noise generated during the combustion period of each cylinder is eliminated. It is necessary to extract accurately. JP-A-62-2914 mentioned above
In the device disclosed in Japanese Patent Laid-Open No. 52, the gate of the gate circuit is opened for a period corresponding to the knock output region from the top dead center of each cylinder, and the input signal is processed by the peak hold circuit to obtain the combustion noise peak value.

However, the apparatus disclosed in the above publication has a problem that noise and vibration generated by combustion of each cylinder cannot be accurately detected. For example, in a diesel engine that performs pilot fuel injection, two-stage combustion is performed in each cylinder by combustion of the pilot injection fuel and combustion of the main injection fuel, but the combustion noise of the pilot injection fuel is reduced to suppress combustion noise. It is necessary to detect only the combustion noise of the main injection fuel by excluding it. Further, the combustion timing of the main injection fuel changes according to various conditions. Further, before and after the combustion period, mechanical vibration sounds such as opening and closing of a valve are generated.

In the device disclosed in the above-mentioned publication, the period during which the gate of the gate circuit is open, that is, the start timing and the end timing of the input operation of the signal to the peak hold circuit are determined by a certain crank angle (for example, top dead center of each cylinder). Is fixed to a period during which knock may occur), but as described above, the combustion period of the main injected fuel varies depending on the fuel injection timing, ignition delay time, and the like. The injection timing does not exactly match the period during which the gate of the gate circuit is open. For this reason, the apparatus disclosed in the above publication cannot detect the combustion noise to be detected originally, or may detect a vibration noise other than the combustion noise to be detected, and thus cannot accurately detect the combustion noise.

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a combustion noise detection device for an internal combustion engine that can accurately detect combustion noise.

[0008]

According to the first aspect of the present invention, there is provided a sensor for continuously detecting a combustion noise generated by an internal combustion engine, and a sensor for detecting a combustion noise in each cylinder of the internal combustion engine during a combustion period. In a combustion noise detection device for an internal combustion engine, comprising a calculation means for inputting a signal and performing a predetermined calculation,
The calculating means determines the input start time of the signal from the sensor, the fuel injection timing to each cylinder, the fuel ignition delay time, the combustion sound detection delay time of the sensor, and the signal input operation delay to the calculating means. An apparatus for detecting combustion noise of an internal combustion engine, which is set based on a time and a detection delay time of an input signal of a calculation means, is provided.

According to the second aspect of the present invention, the arithmetic means determines the input start time of the signal from the sensor as input start time = injection timing- (ignition delay time + sensor combustion sound detection delay time + calculation means (1) input signal detection delay time−input operation delay time to signal calculation means).
The combustion noise detection device for an internal combustion engine according to (1) is provided. That is, in the first and second aspects of the present invention, the input start timing of the signal from the sensor is determined based on the fuel injection timing to each cylinder. Originally, the timing at which the detection of the combustion noise should start should coincide with the timing at which combustion actually occurs in the cylinder. However, in an actual engine, the timing at which combustion occurs varies depending on the fuel injection timing and the ignition delay time of the injected fuel. In addition, a certain delay time occurs before the combustion noise actually generated by the combustion is converted into a sensor output signal and processed in a form that can be calculated by the calculation means. According to the first and second aspects of the present invention, the actual combustion start timing for each cylinder is set based on the fuel injection timing and the ignition delay time, and further, the sensor signal to the arithmetic means is calculated by taking into account the actually generated signal delay time. Since the input start time is set, the arithmetic means can start arithmetic processing from a sensor signal that accurately corresponds to the combustion start time of each cylinder. Therefore, noise is not erroneously detected, and accurate combustion noise detection is performed.

According to a third aspect of the present invention, the arithmetic means sets the end time of the input from the sensor as a time when a predetermined input period has elapsed from the input start time. Item 3. A combustion noise detection device for an internal combustion engine according to item 2 is provided. That is, in the invention of claim 3, the input operation end timing from the sensor is determined according to claim 1 or 2.
Is a time when a predetermined input period has elapsed from the input operation start time determined by the above. In the internal combustion engine, mechanical vibration noise other than combustion noise is generated, and vibration due to opening and closing of the intake and exhaust valves of each cylinder occurs at a time relatively close to the combustion period of each cylinder. On the other hand, the combustion noise that is actually desired to be detected by the sensor is a combustion noise near the time when the combustion pressure immediately after the start of combustion reaches a peak. Therefore, in order to accurately detect the combustion noise without being affected by noise, it is preferable to input the sensor output near the combustion pressure peak and to shorten the input period as much as possible. According to the third aspect, since the sensor signal input timing at the start of combustion of each cylinder is accurately set according to the first or second aspect, the sensor signal input period accurately corresponds to the period during which the combustion pressure reaches a peak, and The input period can be set short. For this reason, noise is not erroneously detected, and more accurate combustion noise detection is performed.

According to the fourth aspect of the present invention, the arithmetic means includes a gate circuit for interrupting the input of a signal from the sensor, and a processing circuit for applying a predetermined process to the input signal before performing the arithmetic operation. Wherein the sensor combustion sound detection delay time is a time from when a combustion sound is generated in each cylinder to when the sensor outputs a signal corresponding to the combustion sound, and the input signal detection delay time of the calculation means is 4. The apparatus according to claim 3, wherein the signal processing delay time of the processing circuit is a signal processing delay time, and the input operation delay time to the arithmetic means is an operation delay time of the gate circuit.

That is, according to the invention of claim 4, the input operation start timing of the sensor signal is determined based on the fuel injection timing.
It is determined in consideration of the ignition delay time, the time from when the combustion noise is generated to when the sensor outputs a signal, the signal processing delay time of the calculation means, and the operation delay time of the gate circuit. Thus, the combustion noise detection device including the gate circuit and the signal preprocessing circuit in the arithmetic means can accurately detect the combustion noise.

[0013]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a diagram showing a schematic configuration of an embodiment when the present invention is applied to an automobile diesel engine. In FIG. 1, reference numeral 1 denotes an internal combustion engine (in this embodiment, a four-cylinder four-cycle diesel engine having four cylinders # 1 to # 4);
The fuel injection valves 3 for directly injecting fuel into the cylinders 1 to 4 indicate a common accumulator (common rail) to which the fuel injection valves 10a to 10d are connected. Common rail 3
Stores the pressurized fuel supplied from the high-pressure fuel injection pump 5, and stores the stored high-pressure fuel in each of the fuel injection valves 10a to 10d.
It has a function to distribute to d.

In this embodiment, the high-pressure fuel injection pump 5
Is a pump of a plunger type having a discharge amount adjusting mechanism, for example, and boosts fuel supplied from a fuel tank (not shown) to a predetermined pressure and supplies the fuel to the common rail 3. The amount of fuel pressure fed from the pump 5 to the common rail 3 is feedback-controlled by the ECU 20 so that the common rail 3 pressure becomes the target pressure.

In FIG. 1, reference numeral 20 denotes an electronic control unit (ECU) for controlling the engine. The ECU 20 is configured as a digital computer having a known configuration in which a read-only memory (ROM), a random access memory (RAM), a microprocessor (CPU), and an input / output port are connected by a bidirectional bus. The ECU 20 performs basic control of the engine such as fuel injection control for controlling the valve opening operation of the fuel injection valves 10a to 10d, such as the valve opening timing and time, to control the injection timing and injection amount of the main fuel injection.

In order to perform these controls, in the present embodiment, the common rail 3 is provided with a fuel pressure sensor 31 for detecting the fuel pressure in the common rail, and is provided near the accelerator pedal (not shown) of the engine 1. An accelerator opening sensor 21 for detecting an accelerator opening (a driver's accelerator pedal depression amount) is provided. A cooling water temperature sensor 23 for detecting a cooling water temperature is provided in the engine cooling water jacket.
Is provided. Further, reference numeral 25 in FIG. 1 denotes a crank angle sensor for detecting the rotational phase of the crank shaft. In the present embodiment, the crank angle sensor is arranged near the camshaft of the engine 1 and outputs a reference pulse every 720 degrees as a crank rotation angle (not shown).
And a crank rotation angle sensor which is arranged near the crankshaft of the engine 1 and generates a crank angle pulse at every predetermined crank rotation angle (for example, every 15 degrees).

In this embodiment, a combustion noise sensor 15 for detecting the combustion noise of the engine 1 is provided. As the combustion noise sensor, in the present embodiment, a frequency (for example, 1) specific to diesel knock in the vibration of the cylinder block of the engine 1 is used.
A knock sensor (vibration sensor) adjusted so as to detect the amplitude of a vibration component of 3 kHz) is used. In addition to the knock sensor described above, a sensor that detects engine noise by arranging an acoustic sensor or the like adjusted to detect sound pressure at a frequency specific to diesel knock in the engine room can be used as the combustion noise sensor. It is.

Fuel pressure sensor 31, accelerator opening sensor 2
1. An analog output signal from the cooling water temperature sensor 23 is supplied to an input port of the ECU 20 via an AD converter (not shown). The pulse signal from the crank angle sensor 25 is directly input to the input port of the ECU 20. ECU 20
Calculates the crankshaft rotation speed based on the crank angle pulse interval input from the crank angle sensor 25, and calculates the phase of the crankshaft from the number of crank angle pulses after the input of the reference pulse. The output of the combustion sound sensor 15 is
The ECU 2 is connected via a filter circuit 17, a gate circuit 18, a peak hold circuit 19, and an AD converter (not shown).
0 is supplied to the input port. The ECU 20 outputs a gate open signal to the gate circuit 18 for a predetermined period from the timing calculated from the fuel injection timing of each cylinder by a method described later. While the gate open signal is input to the gate circuit 18, the signal of the sensor 15 from which the knock-specific frequency component (for example, 1 to 3 kHz) is extracted by the filter circuit 17 is supplied from the gate circuit 18 to the peak hold circuit 19. You. The peak hold circuit 19 stores a sensor signal peak value during a signal input period from the sensor 15 and supplies the signal of the peak value to an input port of the ECU 20 via an AD converter (not shown). The filter circuit 1
The gate circuit 18, the gate circuit 18, and the peak hold circuit 19 may have a known configuration, and a detailed description thereof will be omitted.

On the other hand, an output port of the ECU 20 is connected to the high-pressure fuel injection pump 5 and the fuel injection valves 10a to 10d of the respective cylinders via a drive circuit (not shown). 18 is supplied with a gate open signal. In the present embodiment, EC
U20 performs pilot fuel injection before performing main fuel injection to each cylinder. Since the fuel injected by the pilot burns prior to the main injection, the temperature and pressure in the cylinder increase during the main injection, and the fuel becomes in a state suitable for combustion.
Therefore, the ignition delay of the fuel injected by the main injection is reduced, and the combustion noise is suppressed by executing the pilot injection. Incidentally, the combustion noise changes depending on the pilot fuel injection amount. Therefore, in the present embodiment, feedback control for detecting the combustion noise of each cylinder by the sensor 15 and increasing or decreasing the pilot fuel injection amount so as to minimize the combustion noise is performed. It is necessary to accurately detect the combustion noise of each cylinder.

Hereinafter, detection of combustion noise according to this embodiment will be described. FIG. 2 is a diagram illustrating the combustion noise detection timing by the sensor 15 of the present embodiment. Curve in Figure 2
(A) is the valve lift and curve of the fuel injection valve for each cylinder (B)
Represents the combustion pressure in the cylinder, and curve (C) represents the output waveform of the sensor 15. Curve (D) is the filter circuit 1
7 shows the output. Since a time delay occurs during the filtering process in the filter circuit 17, the output signal of the filter circuit 17 is delayed from the output signal of the sensor 15 by the time TED. This time TED acts as an input signal detection delay time of the ECU 20.

As described above, in this embodiment, the ECU 20
Performs two fuel injections from the fuel injection valve: pilot fuel injection and main fuel injection. In FIG. 2A, a valve lift P indicates a pilot injection operation, and M indicates a main injection operation. In the present embodiment, the crank angle AINJ from the top dead center (indicated by TDC in FIG. 2) of each cylinder at the start of the pilot injection is defined as the fuel injection timing. Since AINJ is represented by a crank angle before top dead center (BTDC), AINJ takes a larger positive value as the fuel injection timing advances.

As shown in FIG. 2B, when the main fuel injection is started after the end of the pilot fuel injection, the fuel injected by the main injection starts to burn, and the in-cylinder combustion pressure starts to rise. In the present embodiment, the time TBD (ms) from the pilot injection start time to the ignition (start of combustion) of the main injection fuel is defined as the fuel ignition delay time.

Therefore, the crank angle (BTDC) at which combustion starts to occur in the cylinder and combustion noise to be detected starts to be AI
NJ-aTBD. Here, a is the ignition delay time (m
s) is a coefficient for converting the crankshaft rotation angle, and a = (NE × 36) using the engine speed NE (rpm).
0) / (60 × 1000). Further, the combustion noise generated in the cylinder propagates through, for example, a cylinder block and reaches the sensor 15. In addition, when an acoustic sensor disposed in an engine room is used as a combustion noise sensor, it takes more time to propagate through the air from the cylinder block to the sensor before reaching the sensor. For this reason, a certain time delay occurs after the combustion noise is generated in the cylinder until the sensor 15 outputs a signal corresponding to the combustion noise. The time (ms) indicated by TSD in FIG. 2 is the time from when the combustion noise is generated in the cylinder to when the sensor outputs a signal corresponding to the combustion noise, that is, the combustion noise detection delay time of the sensor 15.

For this reason, the crank angle (B) at which the sensor 15 outputs a signal corresponding to the combustion sound at the start of combustion in the cylinder.
TDC) becomes AINJ- (aTBD + aTSD). Further, since the sensor output is input from the gate circuit 18 to the peak hold circuit 19 via the filter circuit 17, the sensor signal input to the peak hold circuit 19 is the input signal delay time TED (the delay time of the filter circuit 17) of the ECU 20 described above. ) Will be delayed. For this reason,
The crank angle (BTDC) at which the signal corresponding to the combustion sound at the start of combustion is actually input to the peak hold circuit 19 is
AINJ- (aTBD + aTSD + aTED).

Therefore, the crank angle (BTD) should be originally set for each cylinder.
If the gate open signal is output from the ECU 20 to the gate circuit 18 when C) becomes AINJ- (aTBD + aTSD + aTED), the combustion noise at the start of combustion of each cylinder should be detectable. However, the gate circuit 18 actually has an operation delay time TGD (ms) from the input of the gate open signal to the actual opening of the gate. The time TGD corresponds to a delay time of a signal input operation to the ECU 20. Therefore, in order to accurately detect the combustion noise at the start of combustion, it is actually necessary to output a gate open signal before time TGD before the crank angle of each cylinder becomes AINJ- (aTBD + aTSD + aTED).

That is, in order to accurately detect the combustion noise at the start of combustion in each cylinder, the signal input operation should be started (a gate open signal should be output).
P is ACOP = AINJ- (aTBD + aTSD + a
TED-aTGD). Further, as described above, the combustion noise that should be originally detected is the combustion noise near the time when the combustion pressure immediately after the start of combustion in each cylinder reaches a peak. Therefore, in the present embodiment, the constant crank angle AGTR
Only when the crankshaft rotates, the gate open signal is stopped to end the signal input operation. AG
TR corresponds to a signal input period.

Conventionally, when detecting combustion noise with the same configuration as in FIG. 1, the crank angle at which the input operation is started and the crank angle at which the input operation is ended are usually fixed. However, especially in the case of a diesel engine, the timing at which combustion starts in a cylinder greatly changes depending on the pilot fuel injection amount, the fuel injection timing, and the like. It is necessary to set a long input period so that the combustion noise can be detected even if the combustion start timing varies. If the input period is set to be long, vibration noises other than the combustion sound at the time when the combustion pressure immediately after the start of combustion reaches a peak in each cylinder that should be detected are detected, and the reliability of the detected combustion sound is reduced. Problems arise. In the present embodiment, since the input operation is started in correspondence with the combustion start timing in each cylinder exactly as described above, the input period AG
Even if TR is set short, it is possible to detect the combustion sound at the peak of the combustion pressure immediately after the start of combustion. Therefore, the reliability of the detected signal is greatly improved.

Next, the specific setting of the start and end times of the input operation will be described. As described above, in this embodiment, the input operation start timing (gate open signal output timing) A
GOP and input operation end timing (gate open signal stop timing) AGCP is: AGOP = AINJ− (aTBD + aTSD + aTED)
-ATGD) and AGCP = AGOP-AGTR. Hereinafter, the setting of each term in the above equation will be described.

Setting of Pilot Injection Timing AINJ In the present embodiment, pilot injection timing AINJ is determined by the following equation. Pilot injection timing = [Main injection timing] + [Basic interval] + [Water temperature correction amount] In the above equation, the main injection timing is the engine speed NE.
Is determined from a basic main injection timing map set in advance by an experiment based on and the main fuel injection amount. The main fuel injection amount is determined by the accelerator opening and the engine speed N.
Based on E, it is set from a main fuel injection amount map set in advance by an experiment.

The basic interval (interval between the pilot injection start timing and the main injection start timing) is set from a basic interval map prepared in advance based on the engine speed and the main fuel injection amount calculated as described above. Is done. The water temperature correction amount is set from a preset correction amount map based on the engine cooling water temperature.

That is, the ECU 20 calculates the engine speed calculated based on the output of the crank angle sensor 25, the accelerator opening input from the accelerator opening sensor 21, and the engine cooling water temperature input from the cooling water temperature sensor 23. Using the main injection amount map, the basic main injection timing map, the basic interval map, and the water temperature correction amount map stored in advance in the ROM of the ECU 20, the main injection timing, the basic interval, and the water temperature correction amount are set. The pilot injection timing AINJ is calculated.

Ignition delay time TBD The ignition delay time TBD is determined from an experimental map using the engine speed and the accelerator opening in the same manner as the main fuel injection amount. Sensor detection delay time TSD TSD is determined by experiments using an actual engine because it is determined by the arrangement of sensors. The TSD becomes a substantially constant value when the engine type and the sensor arrangement are the same.

The ECU input detection delay time TED and the input operation delay time TGD TED and TGD are characteristic values of a filter circuit and a gate circuit to be used, and thus are constant values if an actual filter circuit and a gate circuit are determined. Become. Input period AGTR As described above, the shorter the input period AGTR is set, the more the effect of noise is eliminated and the more accurate combustion noise detection becomes possible.
In practice, the AGTR is preferably set experimentally as short as possible within the range in which the combustion noise at the peak combustion pressure can be detected.

In this embodiment, the ECU 20 calculates the pilot injection timing AINJ and the ignition delay time TBD at each calculation timing of the fuel injection amount.
A time / crank angle conversion coefficient a is calculated based on the engine speed NE calculated from the five outputs. Then, based on the sensor detection delay time TSD, the input signal detection delay time TED, and the input operation delay time TGD, which are separately obtained in advance, a
TSD, aTED, and aTGD are calculated, an input operation start time AGOP is obtained from these, and an input operation end time AGCP is obtained from AGOP and a preset input period AGTR.
Is calculated.

Then, the ECU 20 outputs a gate open signal to the gate circuit 18 when the crank angle matches AGOP in each cylinder, and stops the gate open signal when the crank angle matches AGCP. Thereby, the peak value of the combustion noise is stored in the peak hold circuit 19 accurately.

[0036]

According to the invention described in each of the claims, it is possible to detect an accurate combustion noise by eliminating the influence of noise, so that the accuracy of the combustion noise suppression control based on the detected combustion noise is improved. It has a common effect of improving.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a schematic configuration of an embodiment when the present invention is applied to an automobile diesel engine.

FIG. 2 is a diagram illustrating combustion noise detection timing of the embodiment of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Diesel engine 3 ... Common rail 10a-10d ... Fuel injection valve 15 ... Combustion sound sensor 30 ... ECU

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-58-144652 (JP, A) JP-A-62-267546 (JP, A) JP-A-4-136485 (JP, A) JP-A 64-64 12243 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F02D 45/00 368 G01M 15/00

Claims (4)

(57) [Claims] 1. A sensor for continuously detecting a combustion noise generated by an internal combustion engine, and a calculation means for inputting a signal from the sensor during a combustion period in each cylinder of the internal combustion engine and performing a predetermined calculation. In the combustion noise detection device for an internal combustion engine, the calculation means determines a start time of inputting a signal from the sensor, a fuel injection timing to each cylinder, a fuel ignition delay time, and a combustion noise detection delay time of the sensor. A combustion noise detection device for an internal combustion engine, which is set based on the input operation delay time of the signal to the operation means and the detection delay time of the input signal of the operation means. 2. The arithmetic means calculates an input start time of a signal from the sensor as: input start time = injection timing− (ignition delay time + sensor combustion sound detection delay time + input signal detection delay time of calculation means−signal) The combustion noise detection device for an internal combustion engine according to claim 1, wherein the calculation is performed as an input operation delay time to an arithmetic unit. 3. The combustion of an internal combustion engine according to claim 1, wherein said calculating means sets an input end time from said sensor as a time when a predetermined input period has elapsed from said input start time. Sound detection device. 4. The sensor according to claim 1, further comprising a gate circuit for interrupting the input of a signal from the sensor, and a processing circuit for applying a predetermined process to the input signal before performing the arithmetic operation. The time is the time from when the combustion noise is generated in each cylinder to when the sensor outputs a signal corresponding to the combustion noise, and the input signal detection delay time of the arithmetic unit is the signal processing delay time of the processing circuit. The combustion noise detection device for an internal combustion engine according to claim 3, wherein the input operation delay time to the calculation means is an operation delay time of the gate circuit.