Control device for internal combustion engine

Abstract

To provide a control device that can easily or accurately improve combustion noise of an internal combustion engine.SOLUTION: A control device for an internal combustion engine performs control to reduce combustion noise associated with the combustion of an air-fuel mixture. The control device comprises: a parameter calculation unit 18A for calculating parameters that are determined by the maximum value of an in-cylinder pressure, which is the pressure in a combustion chamber, the maximum value of the rate of increase of the in-cylinder pressure, and the output rotation speed of the internal combustion engine; and a control command unit 18B for controlling at least one of the opening and closing timing of at least one of an intake valve and an exhaust valve, the amount of recirculated exhaust gas, and the ignition timing by a spark plug, so that the parameters become below a threshold value that is predetermined to limit combustion noise.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a device for controlling an internal combustion engine that outputs power by explosively burning a fuel-air mixture that is pressurized and compressed by a piston, and in particular to a device for performing control to suppress noise associated with combustion. [Background technology]

[0002] In vehicles equipped with this type of internal combustion engine (hereinafter referred to as the engine), it is known that noise caused by combustion (so-called combustion noise) affects ride comfort and discomfort. For example, Patent Documents 1 and 2 describe that the noise increases as the maximum combustion pressure and the combustion pressure rise rate increase. The device described in Patent Document 1 calculates a correction value so that the maximum in-cylinder pressure change rate matches a target maximum change rate, and corrects the fuel injection timing using that correction value to reduce combustion noise. Furthermore, the device described in Patent Document 2 aims to reduce noise in a frequency band (target frequency band) to which humans have high auditory sensitivity by calculating a target combustion period in which the target frequency band includes a groove frequency at which the frequency components of the in-cylinder pressure are minimized, and controls the engine's exhaust gas recirculation rate so that the engine's combustion period matches the target combustion period, i.e., so that the frequency components in the frequency band to which auditory sensitivity is high are minimized. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-9600 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-270460 Summary of the Invention [Problem to be solved by the invention]

[0004] The device described in Patent Document 1 controls the fuel injection timing to match the maximum rate of change of in-cylinder pressure with a target value, thereby reducing combustion noise. However, the impact on occupants, such as ride comfort and discomfort, is not limited to the volume of combustion noise (e.g., sound pressure). Therefore, as described in Patent Document 2, for example, there is sometimes no correlation between the maximum rate of increase of in-cylinder pressure and sound quality. Even if the maximum rate of increase of in-cylinder pressure is suppressed, sound quality may not improve. Therefore, the device described in Patent Document 2 controls the combustion period based on the engine's exhaust gas recirculation rate to reduce frequency components in the frequency range (2 kHz to 5 kHz) where human hearing sensitivity is high. That is, the device described in Patent Document 2 controls sound quality using the combustion period as a parameter. However, the relationship between the combustion period and sound quality was determined for a diesel engine, and it cannot necessarily be said to be versatile as a control parameter for reducing combustion noise. Furthermore, there is still room for improvement, as the labor required to determine this relationship is large.

[0005] The present invention has been made in light of the above circumstances, and has as its object to provide a control device that can easily or accurately improve combustion noise in an internal combustion engine. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, the present invention provides a control device for an internal combustion engine that performs control to reduce combustion noise associated with the combustion of a mixture of fuel and air, or a mixture obtained by recirculating a portion of the exhaust gas and mixing it, in a combustion chamber equipped with an intake valve and an exhaust valve, by pressurizing and compressing the mixture and igniting it with an ignition plug to cause explosive combustion, and that is characterized by comprising: a parameter calculation unit that calculates parameters determined by the maximum value of the in-cylinder pressure, which is the pressure of the combustion chamber, the maximum value of the rate of increase of the in-cylinder pressure, and the output speed of the internal combustion engine; and a control command unit that controls at least one of the opening and closing timing of at least one of the intake valve and the exhaust valve, the amount of recirculated exhaust gas, and the ignition timing by the spark plug, so that the parameters are below a predetermined threshold value to limit the combustion noise. [Effects of the Invention]

[0007] The parameters used to control combustion noise in this invention are determined by the maximum value of in-cylinder pressure (the pressure in the combustion chamber), the maximum rate of increase of in-cylinder pressure, and the output rotational speed of the internal combustion engine, so that their detection and calculation can be easily performed using equipment normally used to control internal combustion engines. Threshold values ​​for these parameters are predetermined to limit combustion noise to a low level, and therefore combustion noise can be reduced by controlling the operating state of the internal combustion engine - specifically, at least one of the opening and closing timing of at least one of the intake valve and exhaust valve, the amount of exhaust gas recirculation, and the ignition timing of the spark plug - so that the parameters are equal to or below the threshold values. Moreover, the control results for noise over a wide frequency band coincide with sensory evaluations, making it possible to effectively suppress combustion noise. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram illustrating a configuration of an engine according to an embodiment of the present invention. [Figure 2] FIG. 2 is a block diagram illustrating the functional configuration of a controller. [Figure 3]FIG. 4 is a block diagram for explaining a control procedure when controlling ignition timing with reference to parameters in an embodiment of the present invention. [Figure 4] FIG. 3 is a block diagram for explaining a control procedure when an EGR amount is controlled by also referring to parameters in an embodiment of the present invention. [Figure 5] FIG. 4 is a block diagram for explaining a control procedure when controlling a VVT displacement angle by also referring to parameters in an embodiment of the present invention. [Figure 6] 10 is a graph showing the maximum combustion pressure rise rate in each operating state of an engine in a comparative example and the results of each sensory evaluation, where (A) shows the result before control for reducing combustion noise was performed, and (B) shows the result after control for reducing combustion noise based on the maximum combustion pressure rise rate was performed. [Figure 7] 1 is a graph showing the parameters of the present invention and the results of the respective sensory evaluations in each operating state of the engine in the examples, where (A) shows the results before control for reducing combustion noise was performed, and (B) shows the results after control for reducing combustion noise based on the parameters was performed. [Figure 8] 10 is a graph showing the measurement results of the sound pressure level of each frequency before and after control for reducing combustion noise based on the parameters of the present invention is executed. DETAILED DESCRIPTION OF THE INVENTION

[0009] Next, an embodiment of the present invention will be described with reference to the accompanying drawings. Note that the embodiment described below is merely an example of how the present invention can be implemented, and is not intended to limit the present invention.

[0010] The internal combustion engine (hereinafter referred to as the engine) that is the subject of this invention is similar to conventional engines installed in automobiles as a driving force source, an example of which is shown schematically in FIG. 1. The engine 1 shown here is a so-called reciprocating engine, in which a piston 3 that moves back and forth in the axial direction is disposed inside a cylinder 2, and a combustion chamber 4 is formed on the top side of the piston 3. The combustion chamber 4 is provided with an intake port that is opened and closed by an intake valve 5, and an exhaust port that is opened and closed by an exhaust valve 6. The opening and closing timing of these valves 5, 6 is configured to be adjusted by a variable valve timing mechanism (VVT) 7. Therefore, the timing at which each valve 5, 6 is open (the amount of overlap) can be controlled.

[0011] An intake pipe 8 such as an intake manifold is connected to the intake port, and an electronic throttle valve 9 is provided in the intake pipe 8 to control the amount of intake air. The electronic throttle valve 9 is configured so that its opening is controlled based on the depression amount of an accelerator pedal (not shown), the idling speed, etc. An exhaust pipe 10 such as an exhaust manifold is connected to the exhaust port. To perform exhaust gas recirculation (EGR), an exhaust gas recirculation passage 11 is provided to connect the exhaust port and the intake port, or the exhaust pipe 10 and the intake pipe 8, and an EGR valve 12 is provided in the exhaust gas recirculation passage 11 to control the amount of exhaust gas recirculated (EGR amount).

[0012] Furthermore, an injector 13 that injects fuel and an ignition plug (spark plug) 14 are provided in the combustion chamber 4. The injector 13 injects high-pressure fuel supplied from a common rail (not shown) at a timing corresponding to a predetermined crank angle, and is configured so that the injection amount can be adjusted. The spark plug 14 is a well-known device that generates a spark to ignite the air-fuel mixture, and is configured so that the ignition timing (crank angle) can be appropriately controlled.

[0013] A pressure sensor 15 is provided to detect the pressure inside the combustion chamber 4, and the maximum combustion pressure value and the rate of increase of the combustion pressure are detected by this pressure sensor 15. Also, a rotation speed sensor 17 is provided to detect the output rotation speed of the engine 1 (for example, the rotation speed of the crankshaft 16).

[0014] When a mixture of air and fuel is pressurized and compressed to combust explosively in the combustion chamber 4, the pressure inside the combustion chamber 4 (in-cylinder pressure) increases instantaneously, generating combustion noise. A controller 18 is provided to perform control to suppress this combustion noise or the combustion noise heard by vehicle occupants. The controller 18 is an electronic control device primarily composed of a computer equipped with a processing element (CPU), memory elements (RAM, ROM), and various interfaces, and is configured to perform calculations according to a pre-prepared program using pre-stored data and data input from the outside, and to output the results of the calculations as control signals.

[0015] Examples of the input data include the pressure (in-cylinder pressure) P inside the combustion chamber 4 detected by the pressure sensor 15, the engine speed N detected by the speed sensor 17, and the rotation angle θ of the crankshaft 16. The pre-stored data includes threshold values ​​for parameters calculated based on the in-cylinder pressure P, its rate of increase, and the engine speed N. The output control signals include a signal indicating the ignition timing, a signal indicating the EGR amount, and a signal indicating the VVT ​​displacement angle or overlap amount, which are the timing for opening and closing the valves 5 and 6.

[0016] 2, the controller 18 has, as its functional configuration, a parameter calculation unit 18A and a control command unit 18B that calculates and outputs a control signal. The parameters calculated by the parameter calculation unit 18A are parameters based on the in-cylinder pressure P and the engine speed N, and are calculated by the following equations. (Pmax×dP / dθ) / N Here, Pmax is the maximum combustion pressure (kPa), and dP / dθ is the combustion pressure rise rate (kPa / deg).

[0017] The control command unit 18B calculates at least one of the ignition timing, the EGR amount, or the VVT ​​displacement angle at which the above parameters become smaller than a predetermined threshold value, and outputs the calculated value as a control command signal. Note that, since the manner in which combustion noise is transmitted (particularly the manner in which it is transmitted into the vehicle interior) differs depending on the displacement of the engine 1, the configuration of the accessories, or the configuration of the engine mount or engine compartment, the threshold value is determined in advance by experiments or simulations using an actual vehicle.

[0018] The control of ignition timing, EGR amount, or VVT displacement angle using the above parameters will be described. Ignition timing is usually controlled based on requirements such as maximizing combustion efficiency (output) and avoiding knocking. In addition, in this embodiment of the present invention, the final ignition timing is determined by referring to the ignition timing obtained based on the above parameters. This relationship is shown in FIG. 3. That is, the ignition timing is first determined by MBT (optimum ignition timing). Then, the ignition timing is determined based on the requirement to avoid knocking. In addition, the ignition timing at which the above parameters become smaller than predetermined threshold values ​​is determined. The minimum (Min) ignition timing of these three ignition timings is selected as the final ignition timing, and the timing of ignition by the spark plug 14 is controlled based on this.

[0019] The EGR amount is usually controlled within a range that satisfies requirements such as fuel economy and stable rotation. In this embodiment of the present invention, the final EGR amount is determined by referring to the EGR amount obtained based on the above parameters. This relationship is shown in FIG. 4. Specifically, the EGR amount is determined from the viewpoint of ensuring a predetermined negative pressure, improving fuel economy, improving rotational fluctuation, and maintaining the intake pipe temperature at a predetermined temperature. Additionally, the EGR amount is determined so that the above parameters are smaller than predetermined threshold values. The minimum (Min) EGR amount of these four EGR amounts is selected as the EGR amount to be executed, and this is used to control, for example, the opening of the EGR valve 12.

[0020] The overlap amount according to the VVT ​​displacement angle is usually controlled to a predetermined amount based on factors such as fuel economy, ensuring combustion without misfires, engine 1 rotation fluctuations, and maintaining wide-open throttle (WOT) performance. In this embodiment of the present invention, the final VVT displacement angle is determined by referencing the VVT ​​displacement angle obtained based on the above parameters. This relationship is shown in FIG. 5. That is, the VVT ​​displacement angle is determined based on the requirements of each factor, and the VVT ​​displacement angle at which the above parameters become smaller than predetermined threshold values ​​is also determined. The minimum (Min) VVT displacement angle of the VVT ​​displacement angles thus determined is then selected and used as the VVT ​​displacement angle to be executed. This is used to control, for example, the VVT ​​7 described above.

[0021] According to the control device of the embodiment of the present invention, the operating state of the engine 1 is controlled based on the above parameters, thereby improving the tone of the combustion noise and reducing the impact of the noise on passengers. In other words, noise control that reflects the average sensitivity of passengers in the above parameters becomes possible.

[0022] The effects obtained by the embodiment of the present invention will be explained using a comparative example and an example. First, as a comparative example, the engine 1 was operated in the six states shown in Table 1. [Table 1] The left column of Table 1 shows a number indicating the operating state, the column immediately to the right of which shows the engine speed (rpm), and the column immediately to the right of which shows the accelerator opening.

[0023] When no control was performed to reduce combustion noise, the maximum combustion pressure rise rate (dP / dθmax) for each operating state was as shown in Figure 6 (A). The sensory evaluation of the sound quality for each operating state is written below the number of each operating state. "○" indicates good, "△" indicates acceptable, and "×" indicates poor. Operating state "2" had the smallest maximum combustion pressure, but the sensory evaluation was "△." Furthermore, even though operating states "1" and "6" had similar maximum combustion pressures, the sensory evaluations were "×" and "○."

[0024] Next, the maximum rate of combustion pressure rise was reduced by controlling the ignition timing. The maximum rate of combustion pressure rise for each operating condition is shown in Figure 6(B). The results of the sensory evaluation are indicated by a circle, a triangle, or an x ​​below each operating condition number, similar to Figure 6(A). As shown in Figure 6(B), operating condition 3 had the smallest maximum rate of combustion pressure rise, earning a sensory evaluation of circle. Operating conditions 1 and 2, which had larger maximum rates of combustion pressure rise, also earned a sensory evaluation of triangle. However, operating conditions 4 through 6, despite their even larger maximum rates of combustion pressure rise, received a sensory evaluation of circle.

[0025] Therefore, it was found that the suppression control of combustion noise based on the maximum value of the combustion pressure rise rate did not match the control content and sensory evaluation (i.e., how the passengers felt). In other words, there is still room for improvement in the suppression control of combustion noise based on the maximum value of the combustion pressure rise rate.

[0026] On the other hand, in the embodiment of the present invention, the engine 1 was operated in the same six operating states as in the comparative example. The parameter ((Pmax×dP / dθ) / N) in each operating state when the combustion noise reduction control based on the above-mentioned parameters was not performed is shown in FIG. 7A. Note that FIG. 7A also shows the results of the sensory evaluation, as in FIG. 6. As shown in FIG. 7A, the parameter in operating state "6" was the smallest, and the sensory evaluation result was "○". This was followed by the parameter in operating state "2", which was small, and the sensory evaluation result was "△". The parameters in the other operating states were much larger than the parameter in operating state "2", and the sensory evaluation results for all of these were "×".

[0027] Next, the ignition timing was adjusted so that the parameter was smaller than a predetermined threshold, and the engine was operated. The maximum combustion pressure rise rate for each operating condition is shown in Figure 7(B). The results of the sensory evaluation are indicated by a "○", "△", or "×" below the number of each operating condition, as in Figure 6(A). As shown in Figure 7(B), the parameter was largest in operating condition "2", followed by operating condition "1", and the sensory evaluation results for all of these operating conditions were "△". In contrast, the parameters for operating conditions "3" through "6" were smaller than the parameters for operating conditions "1" and "2", and the sensory evaluation results for each operating condition were all "○".

[0028] These results confirmed that the magnitude of the above parameters employed in the present embodiment coincided with the results of the sensory evaluation of combustion noise. In other words, by controlling at least one of the ignition timing, EGR amount, and VVT displacement angle based on the values ​​of the above parameters to change the operating state or combustion state of the engine 1, it is possible to reduce combustion noise or the impact of combustion noise on passengers.

[0029] In addition, in an embodiment of the present invention, noise inside a vehicle was measured to confirm the effect of implementing control to reduce combustion noise based on the above parameters. The results are shown in Figure 8. Figure 8 shows the results of measuring sound pressure levels for each Octave (octave) / 3 frequency (Hz), with the hatched areas indicating the amount of reduction achieved when control to reduce combustion noise based on the above parameters was implemented. As can be seen from these measurement results, it was confirmed that noise in the mid-frequency band, mainly from about 250 Hz to 800 Hz, could be reduced.

[0030] Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and the vehicle to which the present invention is applied may be a hybrid vehicle (HEV, PHEV) equipped with another driving power source such as a motor in addition to an engine. In a hybrid vehicle, a change in driving power caused by a change in the operating state of the engine can be compensated for by another driving power source such as a motor, and a portion of the power output by the engine can be regenerated by the other driving power source such as a motor. Furthermore, the engine may be equipped with a supercharger, and a portion of the exhaust gas may be recirculated to the intake side via the supercharger. [Explanation of symbols]

[0031] 1 engine 2 cylinders 3 pistons 4 Combustion chamber 5 intake valve 6 Exhaust valve 7 Variable valve timing mechanism (VVT) 8 Intake pipe 9. Electronic Throttle Valve 10 Exhaust pipe 11 Exhaust gas recirculation circuit 12 valves 13 Injector 14 Spark plug 15 Pressure Sensor 16 crankshaft 17 Rotational speed sensor 18 Controller 18A Parameter calculation section 18B Control Command Unit

Claims

[Claim 1] A control device for an internal combustion engine, which performs control to reduce combustion noise accompanying the combustion of a mixture of fuel and air or a mixture of the fuel and air mixed by recirculating a portion of the exhaust gas in a combustion chamber equipped with an intake valve and an exhaust valve, by igniting the mixture by an ignition plug in a pressurized and compressed state, a parameter calculation unit that calculates a parameter determined by a maximum value of an in-cylinder pressure, which is the pressure of the combustion chamber, a maximum value of a rate of increase of the in-cylinder pressure, and an output rotation speed of the internal combustion engine; a control command unit that controls at least one of the opening / closing timing of at least one of the intake valve and the exhaust valve, the amount of recirculated exhaust gas, and the ignition timing of the spark plug so that the parameter is equal to or less than a predetermined threshold value that limits the combustion noise; A control device for an internal combustion engine, comprising:

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