JP4957594B2 - Noise reduction device for internal combustion engine - Google Patents

Description

  The present invention relates to an apparatus for reducing noise in an internal combustion engine.

  In a multi-cylinder internal combustion engine, torque fluctuations occur due to variations in the combustion state in each cylinder, and the internal combustion engine itself vibrates due to the torque fluctuations, generating noise (hereinafter referred to as “engine vibration system noise”). There is.

In Patent Document 1, the ignition timing of a cylinder to be controlled is controlled based on the engine rotation speed average value calculated from the engine rotation speed of each cylinder and the engine rotation speed of the cylinder to be controlled, and torque fluctuation is determined. An internal combustion engine that reduces and suppresses engine vibration noise is disclosed.
JP 2007-9835 A

  By the way, in the internal combustion engine described above, when the exhaust valve is opened during the exhaust stroke, the exhaust in the combustion chamber is discharged to the exhaust passage through the exhaust port. Since this exhaust gas is high pressure, it is rapidly discharged from the combustion chamber to the exhaust port immediately after the exhaust valve is opened. Thus, when exhaust is discharged from the combustion chamber, exhaust discharge noise is generated. Further, when the high-pressure exhaust discharged from each cylinder flows into the exhaust passage, the exhaust passage is vibrated and vibrated, and vibration noise is generated. Therefore, in the internal combustion engine, noise caused by high-pressure exhaust (hereinafter referred to as “exhaust system noise”) is generated in addition to engine vibration system noise.

  The internal combustion engine described in Patent Document 1 can suppress engine vibration system noise, but cannot improve exhaust system noise.

  Accordingly, the present invention has been made paying attention to such problems, and an object thereof is to provide a vibration reduction device for an internal combustion engine that can reduce exhaust system noise.

  The present invention solves the above problems by the following means. In addition, in order to make an understanding easy, although the code | symbol corresponding to embodiment of this invention is attached | subjected, it is not limited to this.

The present invention relates to a vibration reducing device for an internal combustion engine (100) provided with a variable valve gear (83) capable of changing the valve timing of an exhaust valve (8), the combustion chamber (6) of the internal combustion engine (100). Vibration reduction means (40) for reducing noise caused by exhaust discharged from the engine, and the vibration reduction means (40) controls the variable valve device (83) when the vibration reduction condition is satisfied, Valve timing setting means (S107) for setting the valve opening timing so that the exhaust valve (8) opens at a position closer to the bottom dead center of the piston than during normal operation, and the exhaust valve (8) opens and exhausts. The exhaust discharge pressure calculating means (S105) for calculating the exhaust discharge pressure when the exhaust gas is discharged to the intake port (3), and the vibration reduction condition is satisfied when the exhaust discharge pressure calculated value (S105) exceeds a predetermined pressure value Judgment to judge Characterized in that it comprises a means (S106), the.

  According to the present invention, the valve opening timing of the exhaust valve is set near the piston bottom dead center as compared with the normal operation by the variable valve operating device, so that the cylinder pressure when the exhaust valve opens can be reduced. Thereby, the exhaust discharge pressure can be reduced, and the exhaust system noise of the internal combustion engine can be suppressed.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic configuration diagram of an internal combustion engine 100.

  The internal combustion engine 100 is a port injection type in-line four-cylinder internal combustion engine that injects fuel into an intake port. The internal combustion engine 100 forms an intake port 2 and an exhaust port 3 in the cylinder head 1. The intake port 2 and the exhaust port 3 communicate with a combustion chamber 6 separated by the cylinder head 1, the cylinder 4 and the piston 5.

  An intake manifold 21 is connected to the intake port 2. An intake passage 22 is connected to the intake manifold 21. The intake air flowing through the intake passage 22 is distributed to each cylinder of the internal combustion engine 100 via the intake manifold 21.

  An air flow meter 23, a throttle valve 24, and a surge tank 25 are sequentially arranged in the intake passage 22 from the upstream side.

  The air flow meter 23 is a hot-wire air flow meter, and detects the amount of intake air taken into the internal combustion engine 100.

  The throttle valve 24 is installed in the intake passage 22 on the downstream side of the air flow meter 23. The throttle valve 24 adjusts the amount of intake air introduced into the combustion chamber 6 by changing the intake flow area of the intake passage 22.

  The surge tank 25 is installed in the intake passage 22 on the downstream side of the throttle valve 24. The surge tank 25 temporarily stores intake air flowing from the upstream side and suppresses intake pulsation.

  A fuel injection valve 26 is installed in the intake manifold 21 connected to the intake passage 22. The fuel injection valve 26 is provided for each cylinder of the internal combustion engine 100. The fuel injection valve 26 injects fuel corresponding to the operating state of the internal combustion engine toward the intake port 2 to form an air-fuel mixture.

  On the other hand, an exhaust passage 32 is connected to the exhaust port 3 via an exhaust manifold 31. The exhaust manifold 31 collects the exhaust discharged from each cylinder and flows it to the exhaust passage 32. The exhaust passage 32 is provided with a catalyst 33 for purifying exhaust gas. An air-fuel ratio sensor 34 is installed in the exhaust passage 32 upstream of the catalyst 33. The air-fuel ratio sensor 34 detects the exhaust air-fuel ratio of the exhaust flowing in the exhaust passage.

  The internal combustion engine 100 includes an intake valve 7 that opens and closes the intake port 2 and an exhaust valve 8 that opens and closes the exhaust port 3 in the cylinder head 1.

  The intake valve 7 is driven by an intake cam 72 formed on the intake camshaft 71. The exhaust valve 8 is driven by an exhaust cam 82 formed on the exhaust camshaft 81. The valve timing (opening / closing timing) of the exhaust valve 8 is adjusted by the variable valve operating device 83. This variable valve operating device 83 is a device that changes the relative phase angle of the exhaust camshaft 81 with respect to the crankshaft by hydraulic control.

  When the intake valve 7 opens the intake port 2, the air-fuel mixture formed in the intake port is introduced into the combustion chamber 6. The introduced air-fuel mixture is ignited by an ignition plug 9 installed in the upper part of the combustion chamber and explosively burns. Thereafter, when the exhaust valve 8 opens the exhaust port 3 in the exhaust stroke, the exhaust generated by the combustion is discharged from the combustion chamber 6 to the exhaust port 3. The exhaust gas is collected by the exhaust manifold 31 and flows into the exhaust passage 32, where it is purified by the catalyst 33 and discharged to the outside.

  The internal combustion engine 100 includes a controller 40 for controlling the variable valve operating device 83 in accordance with the operating state of the internal combustion engine. The controller 40 includes a microcomputer having a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), and an input / output interface (I / O interface).

  The controller 40 receives output signals from the air flow meter 23 and the air-fuel ratio sensor 34. The controller 40 includes a water temperature sensor 41 for detecting the cooling water temperature, a pressure sensor 42 for detecting the atmospheric pressure, an accelerator pedal sensor 43 for detecting the accelerator pedal depression amount, an intake air temperature sensor 44 for detecting the intake air temperature, An output signal such as a crank angle sensor 45 that outputs a reference crank position signal at the reference rotation position is input. The controller 40 adjusts the valve timing of the exhaust valve 8 by controlling the variable valve device 83 based on the detection signals from the various sensors described above.

  By the way, in the internal combustion engine of the conventional method described in Patent Document 1, there is a problem that exhaust system noise occurs due to high-pressure exhaust discharged from the internal combustion engine. The exhaust system noise becomes worse as the discharge pressure of the exhaust gas discharged from the combustion chamber to the exhaust port increases. Here, the exhaust discharge pressure correlates with the in-cylinder pressure at the time when the exhaust valve is opened.

  FIG. 2 is a diagram showing the relationship between the cylinder internal pressure and the exhaust discharge pressure.

  As shown in FIG. 2, the exhaust discharge pressure increases as the cylinder pressure increases when the exhaust valve is opened. Therefore, in order to suppress the exhaust system noise, it is necessary to reduce the exhaust discharge pressure by reducing the cylinder pressure when the exhaust valve is opened.

  Next, the cylinder pressure will be described with reference to FIG.

  FIG. 3 is a graph showing changes in the cylinder pressure when the ignition timing is advanced or retarded from the reference timing. In FIG. 3, the line C shows the in-cylinder pressure waveform when ignition is performed at the reference ignition timing. And when the ignition timing is controlled to the advance side in the order of line C → line B → line A, the ignition timing is controlled to the retard side in the order of line C → line D → line E → line F. Indicates.

  As shown by the lines A to F in FIG. 3, the cylinder pressure increases as the piston bottom dead center approaches the maximum volume in the cylinder as shown by the broken line region R, regardless of how the ignition timing is controlled. Will decline. Therefore, the closer the timing for opening the exhaust valve 8 is to the piston bottom dead center position, the lower the pressure in the cylinder when the exhaust valve is opened, and the lower the exhaust discharge pressure.

  Therefore, in the internal combustion engine 100 of the present embodiment, the valve opening timing of the exhaust valve 8 is controlled by the variable valve device 83 so that the exhaust discharge pressure is reduced in the operation region where the exhaust system noise becomes significant, and the internal combustion engine 100 is controlled. Reduce exhaust system noise.

  Control executed by the controller 40 of the internal combustion engine 100 will be described with reference to FIGS.

  FIG. 4 is a flowchart showing a control routine executed by the controller 40. This control is performed when the internal combustion engine is started, and is performed at a constant cycle (for example, a cycle of 10 milliseconds) until the internal combustion engine is finished.

  In step S101, the controller 40 determines whether or not the internal combustion engine 100 is in a fast idle operation. During the first idle operation, the ignition timing is retarded in order to activate the catalyst 33 early. When the retard amount of the ignition timing increases, the amount of air necessary to maintain the idle rotation speed increases, so that the cylinder pressure when the exhaust valve is opened increases and the exhaust discharge pressure increases. Therefore, when the internal combustion engine 100 is in the fast idle operation, exhaust system noise may become a problem.

  Whether or not the first idle operation is being performed can be determined based on the intake air amount, the intake air temperature, the coolant temperature, the engine rotation speed, the atmospheric pressure, and the accelerator pedal depression amount.

  If the internal combustion engine 100 is not in the fast idle operation, the controller 40 determines that the exhaust system noise does not become a problem, and moves the process to step S102. On the other hand, when the internal combustion engine 100 is in the fast idle operation, the controller 40 determines that the exhaust system noise may be a problem, and moves the process to step S103.

  In step S102, the controller 40 maintains the valve timing of the exhaust valve 8 during normal operation, and ends the process.

  In step S103, the controller 40 calculates an in-cylinder pressure waveform Peng as shown in FIG. 3, and moves the process to step S104. The in-cylinder pressure waveform Peng can be calculated based on the intake air amount, the intake air temperature, the coolant temperature, the air-fuel ratio, the ignition timing, and the engine speed.

  In step S104, the controller 40 calculates the cylinder pressure Pevo when the exhaust valve is opened based on the calculated cylinder pressure waveform Peng and the exhaust valve opening timing, and the process proceeds to step S105.

  In step S105, the controller 40 determines the exhaust discharge pressure Pex when the exhaust is discharged to the exhaust port 3 based on the cylinder pressure Pevo when the exhaust valve is opened and the atmospheric pressure detected by the pressure sensor 42. The calculation is performed and the process proceeds to step S106.

In step S106, the controller 40 was calculated exhaust discharge pressure Pex is equal to or greater than the discharge pressure reference value P _0. That is, as shown in FIG. 5, it is determined whether or not the calculated exhaust discharge pressure Pex is larger than a discharge pressure reference value P ₀ determined according to the engine speed.

When the calculated exhaust discharge pressure Pex is smaller than the discharge pressure reference value P ₀ , the controller 40 determines that the exhaust system noise does not become a problem, and moves the process to step S102. On the other hand, when the calculated exhaust discharge pressure Pex is larger than the discharge pressure reference value P ₀ , the controller 40 determines that there is a possibility of exhaust system noise, and moves the process to step S107.

In step S107, the controller 40 controls the valve timing of the exhaust valve 8 based on the difference between the calculated exhaust discharge pressure Pex and the discharge pressure reference value P _0, the process ends. That is, as the difference between the calculated exhaust discharge pressure Pex and the discharge pressure reference value P ₀ becomes larger, the opening timing of the exhaust valve 8 is set closer to the bottom dead center of the piston, and the exhaust discharge pressure is set to the discharge pressure reference. Control is made to be smaller than the value P ₀ .

  The valve timing control of the exhaust valve 8 when the exhaust discharge pressure is reduced will be described with reference to FIG. FIG. 6 is a diagram showing valve timings of the intake valve 7 and the exhaust valve 8. FIG. 6A shows valve timings of the intake valve 7 and the exhaust valve 8 during normal operation in which exhaust system noise does not become a problem. FIG. 6B shows valve timings of the intake valve 7 and the exhaust valve 8 when the exhaust discharge pressure is reduced.

  As shown in FIG. 6 (A), during normal operation, the opening timing (EVO) of the exhaust valve 8 is between the stroke center position on the way of the piston 5 toward the bottom dead center and the piston bottom dead center position. Thus, it is set on the side closer to the stroke center position. The valve closing timing (EVC) of the exhaust valve 8 is set immediately after the top dead center of the piston. The valve opening timing (IVO) of the intake valve 7 is set after the exhaust valve is closed, and the valve closing timing (IVC) is between the stroke center position in the middle of the piston 5 toward the top dead center and the piston bottom dead center position. Thus, it is set on the side closer to the stroke center position.

  On the other hand, when reducing the exhaust discharge pressure, the valve timing of the exhaust valve 8 is changed by the variable valve device 83 without changing the valve timing of the intake valve 7 as it is during normal operation. That is, as shown in FIG. 6B, the valve opening timing (EVO) of the exhaust valve 8 is retarded to the piston bottom dead center side than during normal operation. By controlling the exhaust valve opening timing (EVO) in this way, the cylinder pressure when the exhaust valve 8 is opened can be reduced, and the exhaust discharge pressure can be reduced.

  Further, the variable valve device 83 of the internal combustion engine 100 is configured to retard the valve closing timing (EVC) by the same amount when the valve opening timing (EVO) of the exhaust valve 8 is retarded, as described above. When the valve opening timing (EVO) is retarded, the valve closing timing (EVC) is also retarded, and a valve overlap period in which both the intake valve 7 and the exhaust valve 8 are opened is set. When the valve overlap period is set in this way, part of the exhaust in the combustion chamber flows backward to the intake port side. The exhaust gas flowing backward is introduced again into the combustion chamber together with the air-fuel mixture in the intake port, and acts as so-called internal EGR gas. Therefore, when the exhaust discharge pressure is reduced, dilution combustion can be performed by the internal EGR, and the combustion speed in the combustion chamber can be suppressed.

  However, there is a problem that combustion stability deteriorates when the valve opening timing (EVO) of the exhaust valve 8 is increased and the valve overlap period is increased. Therefore, in the internal combustion engine 100, when the exhaust discharge pressure is reduced, the valve opening timing (EVO) of the exhaust valve 8 is set within a range in which the combustion stability does not deteriorate.

  The combustion stability is determined based on the engine rotational angular velocity fluctuation αN calculated from the detection value of the crank angle sensor 45. In the internal combustion engine 100, the valve overlap period is set based on the MAP shown in FIG. 7 so that the combustion stability does not deteriorate. That is, as shown in FIG. 7, the valve timing of the exhaust valve 8 is set so that the calculated engine rotational angular speed fluctuation αN does not exceed a threshold value determined from the engine rotational speed Ne and the intake charging efficiency ηc.

  As described above, in the internal combustion engine 100 of the present embodiment, the following effects can be obtained.

  In the internal combustion engine 100, at the time of the fast idle operation, the variable valve device 83 controls the opening timing of the exhaust valve 8 more retarded than the normal operation and sets it near the piston bottom dead center, so that the exhaust valve 8 opens. The pressure in the cylinder can be reduced. Thereby, the exhaust discharge pressure can be reduced, and the exhaust system noise of the internal combustion engine can be suppressed. During the first idle operation, the ignition timing is retarded to activate the catalyst 33 early, and the amount of air necessary to maintain the idle rotation speed increases, but the internal combustion engine 100 controls the ignition timing and the intake air amount. Instead, since the exhaust discharge pressure is reduced by controlling the opening timing of the exhaust valve 8, exhaust system noise can be suppressed without deteriorating exhaust performance or causing engine stall.

  Further, in the internal combustion engine 100, the opening timing of the exhaust valve 8 is retarded so that the exhaust discharge pressure is reduced when the calculated exhaust discharge pressure is larger than the discharge pressure reference value during the fast idle operation. Since the control is performed, it is possible to appropriately suppress the exhaust system noise as necessary.

  Further, in the internal combustion engine 100, since the valve overlap period is set by controlling the closing timing of the exhaust valve 8, it is possible to perform dilution combustion by the internal EGR and to suppress the combustion speed in the combustion chamber. . When the combustion speed is thus suppressed, the in-cylinder pressure fluctuation with respect to the unit crank angle is reduced, so that the internal combustion engine itself can be prevented from vibrating, and engine vibration noise can be reduced.

  Note that the present invention is not limited to the above-described embodiment, and it is obvious that various modifications can be made within the scope of the technical idea.

  In the present embodiment, exhaust system noise is reduced during the first idle operation when the internal combustion engine 100 is cold-started. However, the idle operation in which the auxiliary machine is driven by the internal combustion engine 100 such as during idle operation using an air conditioner. Sometimes exhaust system noise may be reduced. In this case, in step S101 of FIG. 4, it is configured to determine whether or not the idling operation in which the internal combustion engine 100 drives the auxiliary machine is in progress. In this way, the intake system vibration noise is suppressed during the idling operation of driving the auxiliary machine because the amount of air necessary for maintaining the idle rotation speed while driving the auxiliary machine increases and the exhaust discharge pressure increases. It is. It should be noted that exhaust system noise may be reduced when the operating state of the internal combustion engine 100 is in a partial load region even during idle operation where there is a load request.

  In the internal combustion engine 100 of the present embodiment, the variable valve operating device 83 is configured to control the valve opening timing and the valve closing timing of the exhaust valve 8 at the same time. However, the present invention is not limited to this, and the exhaust valve 8 is not limited thereto. The valve opening timing and the valve closing timing may be controlled independently by electromagnetic driving. In this case, it is possible to control only the valve opening timing of the exhaust valve 8 without setting the overlap period, and it is possible to reduce the exhaust system noise without considering the combustion stability.

It is a schematic block diagram of an internal combustion engine. It is a figure which shows the relationship between a cylinder internal pressure and exhaust discharge pressure. It is a figure which shows the change of the in-cylinder pressure when ignition timing is advanced or retarded from the reference timing. It is a flowchart which shows the control routine which a controller performs. It is a figure which shows the discharge pressure reference value defined according to an engine speed. It is a figure which shows the valve timing of an intake valve and an exhaust valve. It is a figure which shows the relationship between an engine rotational angular velocity fluctuation | variation, an engine rotational speed, and an intake charging efficiency.

Explanation of symbols

100 Internal combustion engine 3 Exhaust port 6 Combustion chamber 8 Exhaust valve 23 Air flow meter 31 Exhaust manifold 32 Exhaust passage 34 Air-fuel ratio sensor 40 Controller 41 Water temperature sensor 42 Pressure sensor 43 Accelerator pedal sensor 44 Intake temperature sensor 45 Crank angle sensor 83 Variable valve device Step S107 Valve timing setting means Steps S101 to S106 Condition determining means

Claims (8)

An internal combustion engine vibration reduction device including a variable valve device capable of changing a valve timing of an exhaust valve,
Comprising vibration reducing means for reducing noise caused by exhaust discharged from the combustion chamber of the internal combustion engine;
The vibration reducing means includes
Valve timing setting that controls the variable valve device to set the valve opening timing so that the exhaust valve opens at a position closer to the piston bottom dead center than during normal operation when vibration reduction conditions are met Means ,
An exhaust discharge pressure calculating means for calculating an exhaust discharge pressure when the exhaust valve is opened and the exhaust is discharged to the intake port;
Condition determination means for determining that the vibration reduction condition is satisfied when the exhaust discharge pressure calculation value exceeds a predetermined pressure value;
Vibration reduction apparatus of an internal combustion engine, characterized in that it comprises a. The condition determination means determines that the vibration reduction condition is satisfied when the internal combustion engine is in a fast idle operation and the exhaust discharge pressure calculation value exceeds a predetermined pressure value.
The vibration reduction device for an internal combustion engine according to claim 1 . The condition determination means determines that the vibration reduction condition is satisfied when the exhaust discharge pressure calculation value exceeds a predetermined pressure value during idle operation in which the auxiliary machine is driven by the internal combustion engine.
The vibration reduction device for an internal combustion engine according to claim 1 . The valve timing setting means, as the difference between the exhaust discharge pressure calculation value and the predetermined pressure value increases, the valve opening timing of the exhaust valve approaches the piston bottom dead center.
Vibration reduction apparatus of an internal combustion engine according to any one of claims 1 to 3, characterized in that. The predetermined pressure value is set according to the engine speed.
Vibration reduction apparatus of an internal combustion engine according to any one of claims 1 to 4, characterized in that. The valve timing setting means controls the opening timing of the exhaust valve to be retarded than during normal operation;
The vibration reduction device for an internal combustion engine according to any one of claims 2 to 5 , wherein the vibration reduction device is an internal combustion engine. The valve timing setting means controls the variable valve operating apparatus when a vibration reduction condition is satisfied, and sets a valve overlap period by changing a closing timing of the exhaust valve;
It vibration damping system for an internal combustion engine according to any one of claims 1 to 6, wherein. The valve overlap period is set based on engine rotational angular speed fluctuation.
8. The vibration reduction device for an internal combustion engine according to claim 7 , wherein:

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