Engine control unit

Abstract

To solve a piston striking sound problem while suppressing the lowering of engine heat efficiency.SOLUTION: An engine control device has a vibration sensor that detects engine vibrations, and a control system that controls an EGR device and an ignition device. As an EGR control map used for controlling the EGR device, there is a second EGR map in which an EGR rate higher than that of the first EGR map is set. As an ignition control map used for controlling the ignition device, there is a second ignition map in which an ignition timing is set to an advance side compared with the first ignition map. The control system performs band pass filter processing on a vibration signal outputted from the vibration sensor, thereby extracting a signal component in a frequency band relating to piston striking sound. The control system, if the size of the signal component exceeds a threshold value, switches the EGR control map to the second EGR map, and switches the ignition control map to the second ignition map.SELECTED DRAWING: Figure 8

Description

Technical Field

[0001] The present invention relates to an engine control device that controls an EGR device and an ignition device.

Background Art

[0002] In an engine that reciprocates a piston in a cylinder, there is a risk that piston slap noise due to the so-called piston rocking motion may occur. To suppress this piston slap noise, control devices have been proposed that depressurize the crank chamber or prohibit warm-up promotion control (see Patent Documents 1 and 2). Also, control devices that retard the ignition timing have been proposed to suppress engine knocking (see Patent Documents 3 and 4).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, as one of the factors causing piston slap noise, an excessive increase in the combustion speed during the expansion stroke is considered. Therefore, it is also conceivable to retard the ignition timing to reduce the combustion speed, suppress the rocking motion, and reduce the piston slap noise. However, retarding the ignition timing is a factor that reduces engine thermal efficiency. Therefore, it is required to eliminate piston slap noise while suppressing a decrease in engine thermal efficiency.

[0005] The objective of this invention is to eliminate piston knocking noise while suppressing a decrease in engine thermal efficiency. [Means for solving the problem]

[0006] An engine control device according to one embodiment controls an EGR device that supplies exhaust gas from the exhaust system to the intake system and an ignition device that ignites the air-fuel mixture in the combustion chamber, and comprises a vibration sensor attached to the engine body for detecting engine vibrations, and a processor and memory that are communicated with each other, and a control system for controlling the EGR device and the ignition device, wherein the EGR control map used to control the EGR device includes a first EGR map in which the EGR rate is set for each engine operating point, and a second EGR map in which a higher EGR rate than the first EGR map is set. The control system includes, as an ignition control map used to control the ignition device, a first ignition map in which the ignition timing is set for each engine operating point, and a second ignition map in which the ignition timing is set to be more advanced than that of the first ignition map. The control system extracts signal components in the frequency band related to piston knocking by applying a bandpass filter to the vibration signal output from the vibration sensor, and when the magnitude of the signal components exceeds a threshold, it switches the EGR control map from the first EGR map to the second EGR map and switches the ignition control map from the first ignition map to the second ignition map. [Effects of the Invention]

[0007] According to one aspect of the present invention, a signal component in the frequency band related to piston knocking is extracted, and if the magnitude of the signal component exceeds a threshold, the EGR control map is switched from the first EGR map to the second EGR map, and the ignition control map is switched from the first ignition map to the second ignition map. This makes it possible to eliminate piston knocking while suppressing a decrease in engine thermal efficiency. [Brief explanation of the drawing]

[0008] [Figure 1]This figure shows an example of a vehicle equipped with an engine control device, which is one embodiment of the present invention. [Figure 2] This diagram shows an example of an engine controlled by an engine control device. [Figure 3] This diagram shows an example of the configuration of an engine control system. [Figure 4] This diagram shows an example of the basic structure of an electronic control unit. [Figure 5] This flowchart shows an example of the procedure for implementing impact noise suppression control. [Figure 6] This figure shows an example of a vibration signal detected by a vibration sensor. [Figure 7] This figure shows an example of signal components extracted by bandpass filtering. [Figure 8] This figure shows an example of the changes in combustion velocity and combustion phase of the fuel-air mixture during impact noise suppression control. [Modes for carrying out the invention]

[0009] Embodiments of the present invention will be described in detail below with reference to the drawings. In the following description, identical or substantially identical components and elements will be denoted by the same reference numerals, and repeated descriptions will be omitted.

[0010] [vehicle] Figure 1 shows an example of a vehicle 11 equipped with an engine control device 10, which is one embodiment of the present invention. As shown in Figure 1, the vehicle 11 is equipped with a power unit 14 consisting of an engine 12 and a transmission 13. The output shaft 15 of the power unit 14 is connected to the rear wheels 18 via a propeller shaft 16 and a differential mechanism 17. The power unit 14 shown is a power unit for rear-wheel drive, but is not limited to this, and may also be a power unit for front-wheel drive or all-wheel drive.

[0011] [engine] Figure 2 shows an example of an engine 12 controlled by an engine control device 10. As shown in Figure 2, the engine 12 has a cylinder block 20 and a cylinder head 21 attached thereto. The cylinder block 20 rotatably supports a crankshaft 22 and houses a piston 23 connected to the crankshaft 22 so as to be reciprocating. The cylinder head 21 is connected to an intake system 25 that guides intake air toward an intake port 24 and an exhaust system 27 that guides exhaust gas from an exhaust port 26. The cylinder head 21 is also fitted with an injector 29 that injects fuel into a combustion chamber 28. Furthermore, the cylinder head 21 is fitted with an ignition device 30 consisting of an igniter and a spark plug, etc., to ignite the air-fuel mixture in the combustion chamber 28.

[0012] The intake system 25 connected to the cylinder head 21 consists of an air cleaner box 31, a throttle valve 32, an intake manifold 33, and intake pipes 34 and 35 connecting these components. The exhaust system 27 connected to the cylinder head 21 consists of an exhaust manifold 36, a catalytic converter 37, a muffler 38, and exhaust pipes 39 and 40 connecting these components. Intake air taken into the air cleaner box 31 is supplied to the intake manifold 33 via the throttle valve 32, and from the intake manifold 33 through the intake port 24 to the combustion chamber 28. Exhaust gas discharged from the combustion chamber 28 is then released to the outside via the exhaust manifold 36, catalytic converter 37, and muffler 38.

[0013] Furthermore, the engine 12 is equipped with an EGR device 50 that supplies a portion of the exhaust gas from the exhaust system 27 to the intake system 25. In the following description, the exhaust gas supplied from the exhaust system 27 to the intake system 25 will be referred to as EGR gas. EGR stands for "Exhaust Gas Recirculation".

[0014] The EGR device 50 includes an EGR upstream pipe 51 connected to the exhaust pipe 39 of the exhaust system 27, an EGR downstream pipe 52 connected to the intake manifold 33 of the intake system 25, and an EGR valve 53 provided between the EGR upstream pipe 51 and the EGR downstream pipe 52. Further, an EGR cooler 54 for cooling the EGR gas is provided in the EGR upstream pipe 51, and an EGR pressure sensor 55 for detecting the pressure of the EGR gas is provided. The supply of the EGR gas from the exhaust system 27 to the intake system 25 is controlled by the EGR valve 53 provided with a solenoid not shown. That is, when the solenoid is controlled to open the EGR valve 53, as indicated by the arrow Ge, the EGR gas is supplied from the exhaust system 27 to the intake system 25 through the EGR upstream pipe 51 and the EGR downstream pipe 52. On the other hand, when the solenoid is controlled to close the EGR valve 53, the supply of the EGR gas from the exhaust system 27 to the intake system 25 is stopped because the connection between the EGR upstream pipe 51 and the EGR downstream pipe 52 is blocked.

[0015] [Control System] FIG. 3 is a diagram showing a configuration example of the engine control device 10. As shown in FIG. 3, a control system 61 including an electronic control unit 60 is provided in the engine control device 10 to control the EGR device 50, the ignition device 30, etc. The electronic control unit 60 has a throttle control unit 62 for controlling the opening degree of the throttle valve 32, an injector control unit 63 for controlling the fuel injection amount of the injector 29, an ignition control unit 64 for controlling the ignition timing of the air-fuel mixture by the ignition device 30, and an EGR control unit 65 for controlling the opening degree of the EGR valve 53 constituting the EGR device 50.

[0016] As sensors connected to the electronic control unit 60, there are a vehicle speed sensor 66 that detects the vehicle speed which is the running speed of the vehicle 11, an accelerator sensor 67 that detects the operation status of the accelerator pedal, and a brake sensor 68 that detects the operation status of the brake pedal. Further, as sensors connected to the electronic control unit 60, there are an engine speed sensor 69 that detects the engine speed which is the rotational speed of the crankshaft 22, an air flow sensor 70 that detects the flow rate of the intake air flowing through the intake system 25, i.e., the intake air amount, an intake pressure sensor 71 that detects the pressure in the intake manifold 33, and an EGR pressure sensor 55 that detects the pressure in the EGR upstream pipe 51, etc. Furthermore, a vibration sensor 72 attached to the cylinder block (engine body) 20 is connected to the electronic control unit 60, and a start switch 73 operated by the driver when starting the control system 61 is connected thereto.

[0017] Each control unit 62 - 65 of the electronic control unit 60 sets control targets for the throttle valve 32, the injector 29, the ignition device 30, and the EGR device 50 based on the output signals from the respective sensors. Then, each control unit 62 - 65 of the electronic control unit 60 outputs control signals set according to the respective control targets toward the throttle valve 32, the injector 29, the ignition device 30, and the EGR device 50. For example, the electronic control unit 60 sets a target ignition timing according to the operating point of the engine 12, and controls the ignition device 30 based on this target ignition timing. Also, the electronic control unit 60 sets a target EGR rate (mixing ratio of EGR gas to intake air) according to the operating point of the engine 12, and controls the opening degree of the EGR valve 53 based on this EGR rate.

[0018] Figure 4 shows an example of the basic structure of an electronic control unit 60. As shown in Figure 4, the electronic control unit 60 has a microcontroller 82 into which a processor 80 and main memory (memory) 81 are incorporated. A predetermined program is stored in the main memory 81, and the program is executed by the processor 80. The processor 80 and the main memory 81 are connected to each other so as to be able to communicate with each other. Note that the microcontroller 82 may incorporate multiple processors 80, and the microcontroller 82 may also incorporate multiple main memory 81.

[0019] The electronic control unit 60 also includes an input circuit 83, a drive circuit 84, a communication circuit 85, an external memory 86, and a power supply circuit 87. The input circuit 83 converts signals input from various sensors into signals that can be input to the microcontroller 82. The drive circuit 84 generates drive signals for the aforementioned ignition device 30, EGR device 50, etc., based on signals output from the microcontroller 82. The communication circuit 85 converts signals output from the microcontroller 82 into communication signals for other electronic control units, etc. The communication circuit 85 also converts communication signals received from other electronic control units, etc., into signals that can be input to the microcontroller 82. Furthermore, the power supply circuit 87 supplies a stable power supply voltage to the microcontroller 82, input circuit 83, drive circuit 84, communication circuit 85, and external memory 86, etc. The external memory 86, which consists of non-volatile memory, stores programs and various data.

[0020] [Sound suppression control] Incidentally, in the initial stages of the expansion stroke, when the fuel-air mixture is burned, a so-called oscillating motion occurs in the piston 23 inside the cylinder block 20, and there is a risk that the piston 23 may collide with the inner wall 20a of the cylinder. In other words, in the initial stages of the expansion stroke, there is a risk that the piston 23 may collide with the inner wall 20a of the cylinder, which may generate a collision sound, or piston knocking sound, due to so-called piston slap. To suppress the generation of this piston knocking sound, the control system 61 performs knocking sound suppression control, as will be described later.

[0021] Next, the execution status of the impact noise suppression control by the control system 61 will be explained. Figure 5 is a flowchart showing an example of the execution procedure for impact noise suppression control. Furthermore, each step of the impact noise suppression control shown in Figure 5 indicates the processing performed by the processor 80 that constitutes the control system 61. In addition, the impact noise suppression control shown in Figure 5 is a control that is executed by the control system 61 at predetermined intervals after the control system 61 is started up.

[0022] As shown in Figure 5, in step S10, the vibration signal output from the vibration sensor 72 is read into the control system 61, and in step S11, the control system 61 applies a bandpass filter to the vibration signal to extract signal components in the frequency band related to the piston striking sound from the vibration signal. When performing the bandpass filter to pass signal components in a specific frequency band, the bandpass filter may be performed by an analog circuit incorporated in the electronic control unit 60, or the bandpass filter may be performed by a program executed by the electronic control unit 60, for example, using a fast Fourier transform.

[0023] Figure 6 shows an example of a vibration signal detected by the vibration sensor 72, and Figure 7 shows an example of a signal component extracted by bandpass filtering. As shown in Figure 6, the vibration sensor 72, which detects engine vibration, outputs a voltage signal as a vibration signal obtained from the vibration of the cylinder block 20. The control system 61 applies bandpass filtering to the vibration signal output from the vibration sensor 72, thereby extracting the signal component in the frequency band related to piston knocking from the vibration signal, as shown in Figure 7. For example, the frequency band of engine vibration caused by the aforementioned piston knocking is the frequency band Fx between the lower frequency limit (e.g., 800 Hz) and the upper frequency limit (e.g., 1800 Hz). By applying the aforementioned bandpass filtering to the vibration signal, signal components other than the frequency band Fx are attenuated, and the signal component in the frequency band Fx is extracted. The amplitude of the vibration signal, which is the signal component in the frequency band Fx, that is, the amplitude of the vibration signal of the vibration sensor 72 after bandpass filtering, is defined as the knocking level LP. If the magnitude of this impact sound level LP exceeds a predetermined threshold L1, it is considered that a piston impact sound is being generated by piston slap.

[0024] As shown in Figure 5, in step S12, the peak value LPp of the knocking sound level LP is detected, and in the following step S13, it is determined whether or not the peak value LPp of the knocking sound level LP exceeds a predetermined threshold L1. In order to prevent misjudgment of piston knocking sound generation, it is desirable that the peak value LPp of the knocking sound level LP be the average value of the peak value LPp detected multiple times. In the following step S13, if it is determined that the peak value LPp is less than or equal to the threshold L1, it is determined that the engine is operating in a state where piston knocking sound is sufficiently suppressed, and the process proceeds to step S14, where the target EGR rate, which is the control target for the EGR device 50, is determined based on the normal EGR map (first EGR map). In step S15, the target ignition timing, which is the control target for the ignition device 30, is determined based on the normal ignition map (first ignition map). On the other hand, if in step S13 it is determined that the peak value LPp exceeds the threshold L1, it is determined that the engine is operating in a condition where piston knocking is occurring, and the process proceeds to step S16, where the target EGR rate, which is the control target for the EGR device 50, is determined based on the corrected EGR map (second EGR map). Also, in step S17, the target ignition timing, which is the control target for the ignition device 30, is determined based on the corrected ignition map (second ignition map).

[0025] Here, the normal EGR map and the corrected EGR map are EGR control maps used to control the EGR device 50. In other words, the normal EGR map and the corrected EGR map are EGR control maps in which a target EGR rate is set for each engine operating point determined by the engine speed and intake air volume. Furthermore, at the same engine operating point, the EGR rate set in the corrected EGR map is higher than the EGR rate set in the normal EGR map. In other words, when the EGR device 50 is controlled using the corrected EGR map, the EGR device 50 is controlled to increase the EGR gas toward a higher EGR rate than when the EGR device 50 is controlled using the normal EGR map. Note that the corrected EGR map may have a higher EGR rate set than the normal EGR map at all engine operating points, or it may have a higher EGR rate set than the normal EGR map at at least some engine operating points.

[0026] Furthermore, the normal ignition map and the corrective ignition map are ignition control maps used to control the ignition device 30. In other words, the normal ignition map and the corrective ignition map are ignition control maps in which a target ignition timing is set for each engine operating point determined by the engine speed and intake air volume. Also, at the same engine operating point, the ignition timing set in the corrective ignition map is advanced compared to the ignition timing set in the normal ignition map. In other words, when the ignition device 30 is controlled using the corrective ignition map, the ignition device 30 is controlled to advance the ignition timing compared to when the ignition device 30 is controlled using the normal ignition map. Note that the corrective ignition map may have an ignition timing that is advanced compared to the normal ignition map at all engine operating points, or it may have an ignition timing that is advanced compared to the normal ignition map at least at some engine operating points.

[0027] As shown in Figure 5, in step S13, if it is determined that the peak value LPp of the knocking sound level LP exceeds the threshold L1, it is determined that the engine 12 is operating in a condition where piston knocking is occurring. When it is determined that piston knocking is occurring in this way, the process proceeds to step S16, where the EGR device 50 is controlled based on the corrected EGR map, and then to step S17, where the ignition device 30 is controlled based on the corrected ignition map. That is, when it is determined that the knocking sound level LP exceeds the threshold L1, the EGR control map is switched from the normal EGR map to the corrected EGR map, and the ignition control map is switched from the normal ignition map to the corrected ignition map. As a result, the EGR rate is increased and the ignition timing is controlled to the advance side, so that the combustion speed of the air-fuel mixture can be reduced while maintaining the combustion phase of the engine 12 within a specific range, thereby suppressing piston knocking while suppressing a decrease in engine thermal efficiency.

[0028] Here, Figure 8 shows an example of the transition of the combustion velocity and combustion phase of the fuel-air mixture in impact noise suppression control. The combustion phase Xa of the fuel-air mixture shown in Figure 8 refers to the crank rotation angle (CA50) when 50% of the supplied fuel in the combustion chamber 28 is burned. The situation where 50% of the supplied fuel is burned means that 50% of the mass of the supplied fuel is burned.

[0029] As shown in Figure 8, when the engine 12 is running at operating point P1, if it is determined from the vibration signal that piston knocking is occurring, the EGR rate is increased by using a corrected EGR map to increase the EGR gas. By increasing the EGR gas in this way, as indicated by arrow α1, the combustion speed of the air-fuel mixture can be reduced and the combustion phase of the air-fuel mixture can be controlled to the retard side. Furthermore, when the engine 12 is running at operating point P1, if it is determined from the vibration signal that piston knocking is occurring, the ignition timing is controlled to the advance side by using a corrected ignition map. By controlling the ignition timing to the advance side in this way, as indicated by arrow α2, the combustion phase of the air-fuel mixture can be controlled to the advance side so that the combustion phase of the air-fuel mixture maintains the initial specific range X1.

[0030] In other words, by reducing the combustion speed while maintaining the combustion phase within a specific range X1, as the engine transitions from operating point P1 to operating point P2, piston knocking can be suppressed while suppressing a decrease in engine thermal efficiency. That is, piston knocking can be suppressed by reducing the combustion speed, and a decrease in engine thermal efficiency can be suppressed by maintaining the combustion phase within a specific range X1. Furthermore, the specific range X1 in which the combustion phase is maintained includes the combustion phase Xa when 50% of the fuel supplied to the combustion chamber 28 is burned. By maintaining the combustion phase within such a specific range X1, it is possible to suppress a decrease in engine thermal efficiency even when the combustion speed is reduced. From the viewpoint of improving engine thermal efficiency, it is desirable to maintain the combustion phase Xa when transitioning from operating point P1 to operating point P2.

[0031] In this case, one might consider controlling the ignition timing to the retarded side in order to reduce the combustion speed and suppress piston knocking. However, if the ignition timing is controlled to the retarded side in order to suppress piston knocking, as shown by arrow β1 in Figure 8, both the ignition timing and the combustion phase are controlled to the retarded side, which may significantly reduce the engine thermal efficiency. In contrast, in this embodiment, as shown by arrows α1 and α2, by increasing the EGR rate and advancing the ignition timing, it is possible to reduce the combustion speed while maintaining the combustion phase within a specific range X1, thereby suppressing piston knocking while suppressing a decrease in engine thermal efficiency.

[0032] The present invention is not limited to the embodiments described above, and it goes without saying that various modifications are possible without departing from the spirit of the invention. For example, in the above description, the control system 61 is configured by one electronic control unit 60, but it is not limited to this, and the control system 61 may be configured by multiple electronic control units connected to each other via a network. Also, as the vibration sensor 72 for detecting engine vibration, a knocking sensor incorporating a piezoelectric element can be used, but any vibration sensor capable of detecting acceleration may be used. Also, in the above description, the vibration sensor 72 is attached to the cylinder block 20, but it is not limited to this, and for example, the vibration sensor 72 may be attached to the cylinder head 21. [Explanation of Symbols]

[0033] 10 Engine control unit 20 Cylinder block (engine body) 25 Intake System 27 Exhaust System 28 Combustion chamber 30 Ignition devices 50 EGR devices 61 Control Systems 72 Vibration Sensor 80 processors 81 Main memory (memory) LP sound level (signal component) L1 threshold X1 Specific range Xa combustion phase

Claims

1. An engine control device that controls an EGR device that supplies exhaust gas from the exhaust system to the intake system, and an ignition device that ignites the air-fuel mixture in the combustion chamber, A vibration sensor is attached to the engine body to detect engine vibrations, A control system comprising a processor and memory connected to each other in a manner that enables communication between them, for controlling the EGR device and the ignition device, It has, The EGR control map used to control the EGR device includes a first EGR map in which the EGR rate is set for each engine operating point, and a second EGR map in which a higher EGR rate than that of the first EGR map is set. The ignition control maps used to control the ignition device include a first ignition map in which the ignition timing is set for each engine operating point, and a second ignition map in which the ignition timing is set to be more advanced than that of the first ignition map. The control system is By applying a bandpass filter to the vibration signal output from the vibration sensor, the signal components in the frequency band related to the piston striking sound are extracted. When the magnitude of the signal component exceeds a threshold, the EGR control map is switched from the first EGR map to the second EGR map, and the ignition control map is switched from the first ignition map to the second ignition map. Engine control device.

2. In the engine control device according to claim 1, By switching the EGR control map from the first EGR map to the second EGR map, and switching the ignition control map from the first ignition map to the second ignition map, the combustion speed of the air-fuel mixture is reduced while maintaining the combustion phase of the air-fuel mixture within a specific range. Engine control device.

3. In the engine control device according to claim 2, The aforementioned specific range includes the combustion phase when 50% of the fuel supplied to the combustion chamber is burned. Engine control device.

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