JP7839062B2 - Engine control unit - Google Patents

Description

This invention relates to an engine control device for controlling an EGR device and an ignition device.

In engines where a piston reciprocates within a cylinder, there is a risk of piston knocking noise occurring due to the so-called piston slap motion. To suppress this piston knocking noise caused by piston slap, control devices have been proposed that reduce the pressure in the crankcase or disable warm-up acceleration control (see Patent Documents 1 and 2). Furthermore, to suppress engine knocking, control devices that retard the ignition timing have also been proposed (see Patent Documents 3 and 4).

Japanese Patent Publication No. 2010-174659 Japanese Patent Publication No. 2011-236783 JP-A-2-104971 Japanese Patent Publication No. 2012-193628

Incidentally, one possible cause of piston knocking is an excessive increase in combustion speed during the expansion stroke. Therefore, it is conceivable to reduce piston knocking by retarding the ignition timing to decrease the combustion speed and suppress the oscillation motion. However, retarding the ignition timing reduces engine thermal efficiency. Therefore, there is a need to eliminate piston knocking while suppressing the decrease in engine thermal efficiency.

The objective of this invention is to eliminate piston knocking noise while suppressing a decrease in engine thermal efficiency.

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 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 applies a bandpass filter to the vibration signal output from the vibration sensor to extract the signal component in the frequency band related to piston knocking. When the magnitude of the signal component exceeds a threshold, the system switches the EGR control map from the first EGR map to the second EGR map, and also switches the ignition control map from the first ignition map to the second ignition map.

According to one aspect of the present invention, the 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.

This figure shows an example of a vehicle equipped with an engine control device, which is one embodiment of the present invention. This diagram shows an example of an engine controlled by an engine control device. This diagram shows an example of the configuration of an engine control system. This diagram shows an example of the basic structure of an electronic control unit. This flowchart shows an example of the procedure for implementing impact noise suppression control. This figure shows an example of a vibration signal detected by a vibration sensor. This figure shows an example of signal components extracted by bandpass filtering. This figure shows an example of the changes in combustion velocity and combustion phase of the fuel-air mixture during impact noise suppression control.

The 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.

[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.

[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 able to reciprocate. 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.

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, also 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 then supplied from the intake manifold 33 to the combustion chamber 28 via the intake port 24. 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.

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."

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. The EGR upstream pipe 51 is also equipped with an EGR cooler 54 for cooling the EGR gas, and an EGR pressure sensor 55 for detecting the pressure of the EGR gas. The supply of EGR gas from the exhaust system 27 to the intake system 25 is controlled by an EGR valve 53 equipped with a solenoid (not shown). That is, when the solenoid is controlled and the EGR valve 53 is opened, EGR gas is supplied from the exhaust system 27 to the intake system 25 via the EGR upstream pipe 51 and the EGR downstream pipe 52, as indicated by the arrow Ge. On the other hand, when the solenoid is controlled and the EGR valve 53 is closed, the connection between the EGR upstream piping 51 and the EGR downstream piping 52 is blocked, thus stopping the supply of EGR gas from the exhaust system 27 to the intake system 25.

[Control System]
Figure 3 shows an example of the configuration of the engine control device 10. As shown in Figure 3, the engine control device 10 is equipped with a control system 61 consisting of an electronic control unit 60 to control the EGR device 50, the ignition device 30, etc. The electronic control unit 60 includes a throttle control unit 62 that controls the opening degree of the throttle valve 32, an injector control unit 63 that controls the fuel injection amount of the injector 29, an ignition control unit 64 that controls the ignition timing of the ignition device 30 to the air-fuel mixture, and an EGR control unit 65 that controls the opening degree of the EGR valve 53 that constitutes the EGR device 50.

The electronic control unit 60 is connected to a vehicle speed sensor 66 that detects the vehicle's speed, 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. Other sensors connected to the electronic control unit 60 include an engine speed sensor 69 that detects the engine speed, which is the rotational speed of the crankshaft 22, an airflow sensor 70 that detects the flow rate (i.e., intake air volume) of the intake air flowing through the intake system 25, 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 piping 51. Furthermore, the electronic control unit 60 is connected to a vibration sensor 72 attached to the cylinder block (engine body) 20, and to a start switch 73 that is operated by the driver when starting the control system 61.

Each control unit 62-65 of the electronic control unit 60 sets control targets for the throttle valve 32, injector 29, ignition device 30, and EGR device 50 based on the output signals from each sensor. Then, each control unit 62-65 of the electronic control unit 60 outputs control signals set according to each control target to the throttle valve 32, injector 29, ignition device 30, and 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. Furthermore, the electronic control unit 60 sets a target EGR ratio (the 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 ratio.

Figure 4 shows an example of the basic structure of the electronic control unit 60. As shown in Figure 4, the electronic control unit 60 has a microcontroller 82 incorporating a processor 80 and a main memory (memory) 81. 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 for communication. Note that the microcontroller 82 may incorporate multiple processors 80, or multiple main memory 81.

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 from various sensors into signals that can be input to the microcontroller 82. The drive circuit 84 generates drive signals for the 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 voltage to the microcontroller 82, input circuit 83, drive circuit 84, communication circuit 85, and external memory 86, etc. The external memory 86, consisting of non-volatile memory, etc., stores programs and various data.

[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.

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 performed by the control system 61 at predetermined intervals after the control system 61 is activated.

As shown in Figure 5, in step S10, the vibration signal output from the vibration sensor 72 is read into the control system 61. In step S11, the control system 61 applies a bandpass filter to the vibration signal, extracting the signal component in the frequency band related to the piston striking sound. Note that 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.

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 that has been bandpass filtered, 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.

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. 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 values 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, the engine operation is such that 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). Furthermore, 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 indicates that piston knocking is occurring during engine operation. Therefore, 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). Furthermore, 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).

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. That is, when the EGR device 50 is controlled using the corrected EGR map, the EGR device 50 will be 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.

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 more advanced than the ignition timing set in the normal ignition map. That is, when the ignition device 30 is controlled using the corrective ignition map, the ignition device 30 is controlled to advance the ignition timing more than 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 more advanced than the normal ignition map at all engine operating points, or it may have an ignition timing that is more advanced than the normal ignition map at at least some engine operating points.

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 piston knocking is determined to be 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. This increases the EGR rate and controls the ignition timing to the advanced side, allowing the combustion speed of the air-fuel mixture to be reduced while maintaining the combustion phase of the engine 12 within a specific range. This suppresses piston knocking while suppressing a decrease in engine thermal efficiency.

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 represents the crank rotation angle (CA 50) 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.

As shown in Figure 8, when the engine 12 is operating at operating point P1 and 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 is reduced, and the combustion phase of the mixture can be controlled to the retarded side. Furthermore, when the engine 12 is operating at operating point P1 and it is determined from the vibration signal that piston knocking is occurring, the ignition timing is advanced by using a corrected ignition map. By controlling the ignition timing to the advanced side in this way, as indicated by arrow α2, the combustion phase of the air-fuel mixture can be controlled to the advanced side so that it maintains the initial specific range X1.

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 minimizing the decrease in engine thermal efficiency. Specifically, reducing the combustion speed suppresses piston knocking, and maintaining the combustion phase within the specific range X1 minimizes the decrease in engine thermal efficiency. Furthermore, the specific range X1 where 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 this specific range X1, it is possible to suppress the decrease in engine thermal efficiency even when reducing the combustion speed. From the perspective of improving engine thermal efficiency, it is desirable to maintain the combustion phase Xa when transitioning from operating point P1 to operating point P2.

Here, to reduce the combustion speed and suppress piston knocking, it is conceivable to control the ignition timing to the retarded side. However, if the ignition timing is retarded to suppress piston knocking, as shown by arrow β1 in Figure 8, both the ignition timing and the combustion phase are retarded, which may significantly reduce 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, the combustion speed can be reduced while maintaining the combustion phase within a specific range X1, thereby suppressing piston knocking while suppressing a decrease in engine thermal efficiency.

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. Furthermore, 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.

10 Engine control device 20 Cylinder block (engine body)
25 Intake system 27 Exhaust system 28 Combustion chamber 30 Ignition device 50 EGR device 61 Control system 72 Vibration sensor 80 Processor 81 Main memory (memory)
LP sound level (signal component)
L1 Threshold X1 Specific range Xa Combustion phase

Claims (3)

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. 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. 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.