Exhaust device of internal combustion engine

Abstract

To suppress generation of energization sound due to the drive of an exhaust pipe valve.SOLUTION: An exhaust system of an internal combustion engine 10 includes an exhaust pipe valve 34 that is driven by a motor 34m to switch an exhaust passage. The exhaust system includes a control device 100 that performs pulse width modulation control of the motor 34m. When a background noise inside a vehicle 500 in which the internal combustion engine 10 is mounted is low, the control device 100 executes processing to control the drive of the motor 34m so that an operating speed when opening and closing the exhaust pipe valve 34 is faster than when the background noise is high.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an exhaust system for an internal combustion engine. [Background technology]

[0002] The internal combustion engine described in Patent Document 1 is provided with an exhaust pipe valve that switches the exhaust path. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2022-135762 A Summary of the Invention [Problem to be solved by the invention]

[0004] When the exhaust valve is driven by a motor, it is possible to control the motor by pulse width modulation. However, when such pulse width modulation control is performed, there is a risk that electrical noise will be generated when the exhaust valve is driven. [Means for solving the problem]

[0005] The exhaust system for an internal combustion engine that solves the above problem is an exhaust system for an internal combustion engine that includes an exhaust pipe valve that is driven by a motor to switch exhaust paths. The exhaust system includes a control unit that performs pulse width modulation control of the motor. When background noise inside a vehicle equipped with the internal combustion engine is low, the control unit executes a process for controlling the drive of the motor so that the operating speed when opening and closing the exhaust pipe valve is faster than when the background noise is high.

[0006] An exhaust system for an internal combustion engine that solves the above problems is an exhaust system for an internal combustion engine that includes an exhaust pipe valve that is driven by a motor to switch exhaust paths. The exhaust system includes a control unit that performs pulse width modulation control of the motor. When performing a butting control to completely close the exhaust pipe valve, the control unit performs sweep control to gradually change the operating speed of the motor. The control unit then performs processing to prohibit the execution of the butting control when background noise inside the vehicle equipped with the internal combustion engine is low, and to permit the execution of the butting control when the background noise is high. Effect of the Invention

[0007] This exhaust system for an internal combustion engine can suppress the generation of electrical noise that accompanies the driving of the exhaust pipe valve. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing a configuration of a vehicle according to an embodiment. [Diagram 2] 4 is a flowchart showing a procedure of a process executed by the control device of the embodiment. [Diagram 3] 4 is a flowchart showing a procedure of a process executed by the control device of the embodiment. [Figure 4] 10 is a flowchart showing a procedure of a process executed by a control device in a modified example of the embodiment. [Diagram 5] 10 is a flowchart showing a procedure of a process executed by a control device in a modified example of the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment will be described with reference to the drawings. <Vehicle configuration> As shown in FIG. 1, a vehicle 500 is equipped with an internal combustion engine 10 as a prime mover.

[0010] A silencer 30 is connected to the exhaust passage 12 of the internal combustion engine 10 . The muffler 30 is connected to three exhaust pipes, namely, a first exhaust pipe 31, a second exhaust pipe 32, and a third exhaust pipe 33, which discharge exhaust gas inside the muffler 30 to the outside.

[0011] The third exhaust pipe 33 is provided with an exhaust pipe valve 34, in which a valve 34v is driven by a motor 34m to switch the exhaust path. The drive of the motor 34m is controlled by pulse width modulation control, or so-called PWM control. When the exhaust pipe valve 34 is closed, the exhaust gas in the muffler 30 is discharged from the first exhaust pipe 31 and the second exhaust pipe 32. When the exhaust pipe valve 34 is open, the exhaust gas in the muffler 30 is discharged from the first exhaust pipe 31, the second exhaust pipe 32, and the third exhaust pipe 33.

[0012] The vehicle 500 includes a control device 100 as a control unit. The control device 100 includes a CPU 110 and a memory 120 in which control programs and data are stored. Various controls are performed by the CPU 110 executing the programs stored in the memory 120. Although not shown, the control device 100 is composed of multiple control units.

[0013] A crank angle sensor 70 that detects the rotation angle of a crankshaft included in the internal combustion engine 10, and a vehicle speed sensor 76 that detects the vehicle speed SP of the vehicle 500 are connected to the control device 100. An ignition switch 77 is also connected to the control device 100. The control device 100 calculates the engine rotation speed NE based on the output signal Scr of the crank angle sensor 70.

[0014] The control device 100 also controls the opening and closing drive of the exhaust pipe valve 34 by implementing pulse width modulation control of the motor 34m via an appropriate driver. The exhaust passage 12, the muffler 30, the first exhaust pipe 31, the second exhaust pipe 32, the third exhaust pipe 33, the exhaust pipe valve 34, and the control device 100 that controls the exhaust pipe valve 34 constitute an exhaust system for the internal combustion engine 10.

[0015] <Exhaust valve opening / closing control> The control device 100 performs opening and closing control of the exhaust pipe valve 34, for example, as follows. First, when the ignition switch 77 is turned off, the control device 100 drives the exhaust pipe valve 34 to open. This drive to open the valve 34v of the exhaust pipe valve 34 is intended to prevent freezing, for example.

[0016] In addition, after the ignition switch 77 is turned on to start the internal combustion engine 10, when the internal combustion engine 10 enters an idling operation state, the control device 100 drives the exhaust pipe valve 34 to close in order to reduce exhaust noise.

[0017] Furthermore, when the vehicle 500 is accelerating while traveling, the control device 100 drives the exhaust pipe valve 34 to open in order to increase the exhaust sound and create a sporty feel for the vehicle 500. Then, when the acceleration of the vehicle 500 subsides, the control device 100 drives the exhaust pipe valve 34 to close in order to reduce the exhaust sound.

[0018] Furthermore, when a specific condition is met when closing the exhaust pipe valve 34, the control device 100 executes butting control. The butting control is a control for completely closing the exhaust pipe valve 34, that is, for driving the exhaust pipe valve 34 to close so that the valve 34v of the exhaust pipe valve 34 hits the valve seat of the valve 34v. By executing this butting control, for example, fluttering of the valve 34v is suppressed. When executing the butting control, the control device 100 executes sweep control for gradually changing the operating speed of the motor 34m immediately before the valve 34v of the exhaust pipe valve 34 is seated. The sweep control is executed in order to suppress the generation of valve seating noise due to the execution of the butting control.

[0019] Incidentally, when the motor 34m of the exhaust pipe valve 34 is controlled by pulse width modulation, an energization sound may be generated when the exhaust pipe valve 34 is driven. This is believed to be due to the following reasons. That is, when the exhaust pipe valve 34 is driven to open from a closed state to an open state, when the exhaust pipe valve 34 is driven to close from an open state to a closed state, or when the above-mentioned sweep control is performed, the command duty ratio input to the motor 34m changes. When the command duty ratio is changed, coil whine is likely to occur from the winding of the motor 34m. When such coil whine occurs, the vibration caused by the coil whine resonates with the components of the exhaust pipe valve 34, and the vibration becomes audible to the vehicle occupants as an energization sound.

[0020] In this embodiment, when the ignition switch 77 is turned off, the exhaust pipe valve 34 is driven to open. If the driver of the vehicle hears the energization sound associated with the exhaust pipe valve 34 being driven to open even though the ignition switch 77 is turned off, the driver of the vehicle may feel uncomfortable. Also, in this embodiment, when the internal combustion engine 10 enters an idle operating state, the exhaust pipe valve 34 is driven to close. In this way, the driver of the vehicle may feel uncomfortable if the driver hears the energization sound associated with the exhaust pipe valve 34 being driven to close even though the driver of the vehicle is not operating the vehicle.

[0021] Therefore, in this embodiment, the control device 100 executes the process described below to suppress the generation of energization noise accompanying the driving of the exhaust pipe valve . <Changing the operating speed of the exhaust valve> 2 shows the procedure of the process executed by the control device 100 to suppress the generation of the above-mentioned energization sound. This process is executed when the exhaust pipe valve 34 is requested to be opened or when the exhaust pipe valve 34 is requested to be closed. In the following, the step number of each process is represented by a number preceded by "S."

[0022] When this process starts, the control device 100 acquires the vehicle speed SP (S100). Next, the control device 100 judges whether the acquired vehicle speed SP is equal to or greater than a threshold value SPref (S110). The threshold value SPref is a predetermined minimum value of the vehicle speed SP at which the background noise inside the vehicle becomes large enough that the energization sound of the motor 34m described above cannot be heard by vehicle occupants. In other words, the threshold value SPref is a value for judging that the background noise inside the vehicle is large when the vehicle speed SP is equal to or greater than the threshold value SPref, and that the background noise inside the vehicle is small when the vehicle speed SP is less than the threshold value SPref.

[0023] When it is determined in the process of S110 that the vehicle speed SP is equal to or greater than the threshold value SPref (S110: YES), the control device 100 sets a first speed VS1 as a valve operating speed VS, which is an operating speed when opening and closing the exhaust pipe valve 34 (S120). The valve operating speed VS is, for example, the rotation angle per unit time of the motor 34m. The first speed VS1 is a speed slower than a second speed VS2 described later, and is a default value that takes into consideration the suppression of chattering when the valve 34v is closed and the suppression of wear of the moving parts that constitute the exhaust pipe valve 34.

[0024] On the other hand, when it is determined in the process of S110 that the vehicle speed SP is less than the threshold value SPref (S110: NO), the control device 100 sets the valve actuation speed VS to a second speed VS2 (S130). The second speed VS2 is faster than the first speed VS1, and is a default value for increasing the actuation speed of the exhaust pipe valve 34 while taking into consideration to some extent the suppression of chattering and wear of the moving parts.

[0025] After executing the process of S120 or the process of S130, the control device 100 then inputs a command duty ratio corresponding to the set valve actuation speed VS to the motor 34m to actuate the exhaust pipe valve 34 (140).

[0026] Then, when the process of S140 is completed, the control device 100 ends this process. <Whether or not exhaust valve bumping control can be performed> 3 shows another processing procedure executed by the control device 100 to suppress the generation of the above-mentioned power supply sound. Note that this processing is executed when the exhaust pipe valve 34 is requested to be driven to close.

[0027] When this process starts, the control device 100 acquires the vehicle speed SP (S200). Next, the control device 100 judges whether the acquired vehicle speed SP is equal to or greater than a threshold value SPref (S210). The threshold value SPref in the process of S210 is the same as the threshold value SPref in the process of S110 described above, but may be different as long as the loudness of the background noise in the vehicle can be appropriately judged.

[0028] When it is determined in the process of S210 that the vehicle speed SP is equal to or greater than the threshold value SPref (S210: YES), the control device 100 permits the execution of the above-mentioned butting control (S220).

[0029] On the other hand, when it is determined in the process of S210 that the vehicle speed SP is less than the threshold value SPref (S210: NO), the control device 100 prohibits the execution of the above-mentioned butting control (S230).

[0030] After the process of S120 or the process of S230 is executed, the control device 100 then drives the exhaust pipe valve 34 to close (240). If execution of the butting control is permitted when executing the process of S240, the exhaust pipe valve 34 is completely closed and the sweep control is executed. On the other hand, if execution of the butting control is prohibited when executing the process of S240, the exhaust pipe valve 34 is closed with the valve 34v slightly spaced from the valve seat and the sweep control is not executed.

[0031] Then, when the process of S240 is completed, the control device 100 ends this process. <Actions and Effects of the Present Embodiment> (1) The exhaust device of the internal combustion engine 10 includes an exhaust pipe valve 34 that is driven by a motor 34m to switch exhaust paths. The control device 100 performs pulse width modulation control on the motor 34m. The control device 100 then determines whether the background noise inside the vehicle is large based on the vehicle speed SP. When the background noise is small as a result of a negative determination in the processing of S110, the second speed VS2 is set as the valve operating speed VS. On the other hand, when the background noise is large as a result of a positive determination in the processing of S110, the first speed VS1 is set as the valve operating speed VS. Through this processing, when the background noise is small, processing is executed to control the driving of the motor 34m so that the valve operating speed VS is faster than when the background noise is large.

[0032] In this way, when the background noise inside the vehicle is low and the vehicle occupants can easily hear the energization sound of the motor 34m, the operating speed when opening and closing the exhaust pipe valve 34 is fast. Therefore, the time during which the energization sound is generated is shorter than when the operating speed is slow. As a result, the generation of the energization sound associated with the drive of the exhaust pipe valve 34 can be suppressed.

[0033] (2) When the control device 100 performs the butting control to completely close the exhaust pipe valve 34, the control device 100 performs the sweep control to gradually change the operating speed of the motor 34m. The control device 100 then determines the level of background noise inside the vehicle based on the vehicle speed SP. When the background noise is low as a result of a negative determination in the processing of S210, the execution of the butting control is prohibited. On the other hand, when the background noise is high as a result of a positive determination in the processing of S210, the execution of the butting control is permitted. In this way, in a situation where the background noise inside the vehicle is low and the energization sound of the motor 34m is easily heard by the vehicle occupants, the execution of the butting control is prohibited and the sweep control is not performed. Therefore, the generation of the energization sound due to the execution of the sweep control is suppressed. Therefore, the frequency of the energization sound is reduced compared to the case where the butting control is always performed when the exhaust pipe valve 34 is closed. Therefore, the generation of the energization sound accompanying the drive of the exhaust pipe valve 34 can be suppressed.

[0034] (3) Even when the vehicle speed SP is less than the threshold value SPref and the background noise is small, the generation of the energization sound caused by the operation of the exhaust pipe valve 34 is suppressed. Therefore, the energization sound is suppressed from being heard when the ignition switch 77 is turned off as described above. Therefore, it is possible to suppress the driver from feeling uncomfortable when the ignition switch 77 is turned off.

[0035] (4) Even when the vehicle speed SP is less than the threshold value SPref and the background noise is small, the generation of the energization sound caused by the drive of the exhaust pipe valve 34 is suppressed. Therefore, the energization sound is suppressed from being heard when the vehicle is idling and the vehicle speed SP is low. Therefore, it is possible to suppress the driver from feeling uncomfortable when the vehicle is idling.

[0036] <Example of change> The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other to the extent that no technical contradiction occurs.

[0037] In the process of S110 shown in Fig. 2, the magnitude of the background noise is determined based on the vehicle speed SP. Alternatively, the magnitude of the background noise may be determined based on the engine rotation speed NE. Fig. 4 shows the procedure of the process executed by the control device 100 in this modified example. In Fig. 4, the same processes as those shown in Fig. 2 are denoted by the same step numbers.

[0038] When this process starts, the control device 100 acquires the engine speed NE (S300). Next, the control device 100 judges whether the acquired engine speed NE is equal to or greater than a threshold value NEref (S310). The threshold value NEref is the lowest engine speed NE at which the background noise inside the vehicle becomes large enough that the energization sound of the motor 34m described above cannot be heard by vehicle occupants, and is determined in advance. In other words, the threshold value NEref is a value for judging that the background noise inside the vehicle is large when the engine speed NE is equal to or greater than the threshold value NEref, and that the background noise inside the vehicle is small when the engine speed NE is less than the threshold value NEref.

[0039] In the process of S310, if it is determined that the engine speed NE is equal to or greater than the threshold value NEref (S310: YES), the control device 100 executes the above-described process of S120 and subsequent steps. On the other hand, in the process of S310, if it is determined that the engine speed NE is less than the threshold value NEref (S310: NO), the control device 100 executes the above-described process of S130 and subsequent steps.

[0040] Even in such a modified example, the same actions and effects as those of the above embodiment can be obtained. In the process of S210 shown in Fig. 3, the magnitude of the background noise is determined based on the vehicle speed SP. Alternatively, the magnitude of the background noise may be determined based on the engine rotation speed NE.

[0041] Fig. 5 shows the procedure of the process executed by the control device 100 in this modified example. In Fig. 5, the same processes as those shown in Fig. 3 are denoted by the same step numbers. When this process starts, the control device 100 acquires the engine speed NE (S400).

[0042] Next, the control device 100 determines whether the acquired engine speed NE is equal to or greater than a threshold value NEref (S410). The threshold value NEref in the process of S410 is the same as the threshold value NEref in the process of S310 described above, but may be different as long as the loudness of the background noise in the vehicle can be appropriately determined.

[0043] In the process of S410, if it is determined that the engine speed NE is equal to or greater than the threshold value NEref (S410: YES), the control device 100 executes the above-mentioned processes from S220 onwards. On the other hand, in the process of S410, if it is determined that the engine speed NE is less than the threshold value NEref (S410: NO), the control device 100 executes the above-mentioned processes from S230 onwards.

[0044] Even in such a modified example, the same actions and effects as those of the above embodiment can be obtained. In the above embodiment, only one of the processing procedures shown in Fig. 2 and the processing procedures shown in Fig. 3 may be executed. Even in this case, the actions and effects according to the processing procedures executed can be obtained.

[0045] The number of exhaust pipes connected to the silencer 30 may be any number other than three, and may be any number more than one. In the above embodiment, the configuration of the vehicle 500 is not limited to the example of the above embodiment. For example, the vehicle may be equipped with an internal combustion engine 10 and an electric motor as a prime mover.

[0046] The control device 100 includes a CPU 110 and a memory 120, and executes software processing. However, this is merely an example. The control device 100 may include, for example, a dedicated hardware circuit (e.g., ASIC, etc.) that processes at least a part of the software processing executed in the above embodiment. That is, the control device 100 may have any of the following configurations (a) to (c). (a) A processing device that executes all of the above processing according to a program, and a program storage device such as a memory that stores the program. (b) A processing device and a program storage device that execute a part of the above processing according to a program, and a dedicated hardware circuit that executes the remaining processing. (c) A dedicated hardware circuit that executes all of the above processing. Here, the software circuit including the processing device and the program storage device, and the dedicated hardware circuit may be multiple. That is, the above processing may be executed by a processing circuit that includes at least one of one or more software circuits and one or more dedicated hardware circuits. The program storage device, i.e., the computer-readable medium, includes any available medium that can be accessed by a general-purpose or dedicated computer. [Explanation of symbols]

[0047] 10. Internal combustion engine 12...Exhaust passage 30...Silencer 31…First exhaust pipe 32…Second exhaust pipe 33…Third exhaust pipe 34…Exhaust pipe valve 34m…Motor 34v...valve 70...Crank angle sensor 76...Vehicle speed sensor 77…Ignition switch 100...Control device 110…CPU 120…Memory 500…Vehicle

Claims

1. An exhaust system for an internal combustion engine, comprising an exhaust pipe valve that is driven by a motor to switch an exhaust path, A control unit that performs pulse width modulation control of the motor, The control unit executes a process of controlling the drive of the motor so that, when background noise inside the vehicle equipped with the internal combustion engine is low, the operating speed when opening and closing the exhaust pipe valve is faster than when the background noise is high. Exhaust system for internal combustion engines.

2. An exhaust system for an internal combustion engine, comprising an exhaust pipe valve that is driven by a motor to switch an exhaust path, A control unit that performs pulse width modulation control of the motor, The control unit performs a sweep control to gradually change the operating speed of the motor when performing a butting control to completely close the exhaust pipe valve, and When background noise in the interior of the vehicle equipped with the internal combustion engine is low, the execution of the butting control is prohibited, whereas when the background noise is high, the execution of the butting control is permitted. Exhaust system for internal combustion engines.

3. The control unit determines the magnitude of the background noise based on a vehicle speed of the vehicle equipped with the internal combustion engine.

3. An exhaust system for an internal combustion engine according to claim 1 or 2.

4. The control unit determines the magnitude of the background noise based on an engine rotation speed of the internal combustion engine.

3. An exhaust system for an internal combustion engine according to claim 1 or 2.

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