JP2018123769A - Control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device for an internal combustion engine, for improving the determination accuracy of knocking, improving responsiveness to the knocking to be dissolved, and reliably dissolving the knocking.SOLUTION: A control device 3 includes a washer sensor 32 contacting a cylinder 11 at its outside so as to detect a combustion pressure in a combustion chamber 12 of the cylinder 11 of an internal combustion engine 1 for outputting a pressure signal according to the combustion pressure, and a crank angle acquisition part 43 for acquiring a crank angle, whereby the internal combustion engine 1 can be controlled in response to the occurrence of knocking in the combustion chamber 12. The control device 3 further includes an angle-pressure signal calculation part 44 for calculating an angle-pressure signal associating the pressure signal with a detection value θ for the crank angle, a knocking strength estimation part 46 using a rotation-pressure signal for calculating an estimation value K for knocking strength in the cylinder 11, and a knocking determination part 47 using the estimation value K for the knocking strength for determining whether the knocking occurs or not in the cylinder 11.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an internal combustion engine control device configured to be able to control an internal combustion engine in response to occurrence of knocking.

  In an internal combustion engine such as a reciprocating engine, knocking occurs due to a shock wave or the like generated in a cylinder, and there is a risk that piston knock-in, damage, etc. may occur due to knocking. Therefore, when knocking occurs, the control device for the internal combustion engine detects this, and immediately after the detection, controls the internal combustion engine so as to cancel the knocking. In order to solve this problem, it is required to improve the knocking determination accuracy.

  Therefore, as an example of a control device for an internal combustion engine, in order to improve the determination accuracy of knocking, DFT (Discrete Fourier Transform), STFT (Short-Time Fourier Transform, short time) is used as a detection signal detected by a knock sensor. The vibration waveform is acquired by applying (Fourier transform) etc., and the average value of the acquired multiple vibration waveforms is calculated, and the knock determination threshold is set using the peak value of the waveform obtained by subtracting the average value from the vibration waveform A technique for determining whether or not knocking has occurred in the internal combustion engine by comparing the peak value with a knock determination threshold value has been proposed. (For example, see Patent Document 1.)

JP 2014-34888 A

  However, in the example of the control device, since processing such as DFT and STFT is performed, the calculation load is high. In addition, since the knock determination threshold is calculated using the average value of the vibration waveform in a plurality of cycles and the knock determination threshold is continuously updated, the calculation load is further increased for setting the knock determination threshold. . Therefore, a lot of time is required for such processing and setting, and as a result, a lot of time is required for the determination of knocking. Therefore, there is a possibility that sufficient responsiveness for eliminating knocking cannot be secured.

  Therefore, in a control device for an internal combustion engine, it is desired to ensure knocking determination accuracy, improve responsiveness to eliminate knocking, and reliably eliminate knocking.

  In order to solve the problem, according to the control device for an internal combustion engine according to an aspect of the present invention, the cylinder is brought into contact with the cylinder from outside so as to be able to detect the combustion pressure in the combustion chamber of the cylinder in the internal combustion engine, and A washer-type pressure sensor configured to output a pressure signal according to the combustion pressure; and a crank angle acquisition unit configured to acquire a crank angle of a crankshaft of the internal combustion engine. An internal combustion engine control device configured to be capable of controlling an engine in response to occurrence of knocking in the cylinder, the angle configured to calculate an angle-pressure signal in which the pressure signal is associated with the crank angle A pressure signal calculation unit, a knocking strength estimation unit configured to calculate an estimated value of knocking strength in the cylinder using the rotation-pressure signal, and the knocking strength Based on the estimate, and a composed knock determination unit to determine whether or not knocking has occurred in said cylinder.

  According to the control apparatus for an internal combustion engine according to one aspect of the present invention, knocking determination accuracy can be improved, responsiveness for eliminating knocking can be improved, and knocking can be reliably eliminated. Can do.

It is a mimetic diagram showing a control system containing a control device of a gasoline direct-injection engine concerning an embodiment of the present invention. It is the A section enlarged view of FIG. It is a block diagram of the control apparatus which concerns on embodiment of this invention. In the embodiment of the present invention, it is a figure showing typically a typical angle-pressure signal obtained in one cylinder of a gasoline direct injection engine. (A) is a figure which shows roughly the in-cylinder angle-pressure signal obtained using an in-cylinder pressure sensor, (b) is a high-pass filter process with respect to the in-cylinder angle-pressure signal of (a). FIG. 6 is a diagram schematically showing a filter angle-pressure signal obtained by applying, and (c) is an absolute angle-pressure obtained by converting the filter angle-pressure signal of (b) to an absolute value. It is a figure which shows a signal roughly. It is a figure which shows roughly the in-cylinder angle-pressure signal obtained using an in-cylinder pressure sensor over a combustion process from a compression process. It is a figure which shows roughly the angle-pressure signal obtained using a washer sensor over a combustion process from a compression process. It is a figure which shows the relationship between the estimated value of knocking intensity | strength in an embodiment of this invention, and an auditory intensity level. It is a flowchart for demonstrating the control method which concerns on embodiment of this invention. 6 is a correlation diagram between the maximum change rate of Example 1 and the in-cylinder maximum change rate of Comparative Example 1. FIG. FIG. 6 is a correlation diagram between knocking strength and in-cylinder maximum change rate in Comparative Example 1.

  A control system including an internal combustion engine control apparatus according to an embodiment of the present invention will be described below. As a preferred example, the internal combustion engine controlled by the control device according to the present embodiment is a naturally aspirated gasoline direct injection engine mounted on an automobile. The internal combustion engine may be a spark ignition type reciprocating engine. For example, the reciprocating engine may be a PFI (Port Fuel Injection) type gasoline engine, an NVO (Negative Valve Overlap) type or a port injection. It may be an HCCI engine, a diesel engine, or a CNG (Compressed Natural Gas) engine of the type.

  The reciprocating engine is particularly preferably a 4-stroke type. However, the reciprocating engine may be of a two-stroke type. In particular, the reciprocating engine preferably has a plurality of cylinders. However, the reciprocating engine can be of a single cylinder. The internal combustion engine may be mounted on a vehicle other than an automobile. For example, the internal combustion engine may be mounted on a motorcycle. The internal combustion engine may also be an internal combustion engine for power generation, a general-purpose engine mounted on various work machines, an inboard motor, an outboard motor, an inboard / outboard motor, or the like.

[Outline of control system]
First, an outline of the control system will be described. As shown in FIG. 1, the control system according to the present embodiment controls a gasoline direct injection engine (hereinafter simply referred to as “engine”) 1, an accelerator pedal 2 configured as an accelerator operation unit of an automobile, and the engine 1. And a control device 3 configured to be possible. The engine 1 has a plurality of cylinders 11, and FIG. 1 schematically shows a cross section of one of the plurality of cylinders 11 in the engine 1.

  The accelerator operation unit may be other than the accelerator pedal. In particular, in the case of a motorcycle, the accelerator operation unit may be an accelerator grip. The control device 3 includes an ECU (Engine Control Unit) 31 configured as a control unit used for controlling the engine 1 and a washer-type pressure sensor (hereinafter referred to as a “washer sensor”) 32 attached to each cylinder 11. Have.

  The ECU 31 is preferably configured to include an electronic component such as a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and a flash memory, and an electric circuit in which such an electronic component is arranged. . The washer sensor 32 has a piezoelectric element (not shown), and the washer sensor 32 is formed in a substantially ring shape as shown in cross section in FIG. The washer sensor 32 is attached to each cylinder 11 in contact with the cylinder 11 from the outside so that the combustion pressure in the combustion chamber 12 of each cylinder 11 can be detected. The washer sensor 32 only needs to be attached to at least one of the plurality of cylinders 11. In particular, the washer sensor 32 is preferably attached to all of the plurality of cylinders 11.

  Such a control system and its control device 3 can improve the knocking determination accuracy and the responsiveness to the knocking, and use the combustion pressure detected by the washer sensor 32 so that the knocking can be reliably eliminated. 11 is configured to detect the occurrence of knocking. Further, the control system and its control device 3 are configured to be able to control the engine 1 so that knocking can be eliminated.

[About engine details]
Here, the details of the engine 1 will be described with reference to FIG. The plurality of cylinders 11 of the engine 1 are defined by cylinder blocks 13. The engine 1 includes a piston 14 configured to reciprocate in each cylinder 11 in the axial direction thereof. A cylinder head 15 is disposed on the top side of each cylinder 11. The combustion chamber 12 is surrounded by the cylinder 11, the piston 14, and the cylinder head 15.

  A crankcase 16 is disposed on the bottom side of the cylinder 11 with respect to the cylinder block 13, and a crankshaft 17 is disposed in the crankcase 16. The piston 14 in each cylinder 11 is connected to a crankshaft 17 via a connecting rod 18. The reciprocating motion of the piston 14 is converted into the rotational motion of the crankshaft 17.

  A spark plug 19 configured to enable spark discharge in the combustion chamber 12 is attached to the cylinder head 15. An intake port 20 and an exhaust port 21 are connected to the cylinder head 15. The intake port 20 has an intake opening 20 a that opens toward the combustion chamber 12 at a connection portion with the cylinder head 15, and the exhaust port 21 faces the combustion chamber 12 at a connection portion with the cylinder head 15. The exhaust opening 21a is open. The intake port 20 defines a path for sending air to the combustion chamber 12, and the exhaust port 21 defines a path for sending exhaust gas generated after combustion in the combustion chamber 12 toward a catalyst (not shown). Yes. However, the present invention is not limited to this, and in the case of a PFI engine, the intake port may define a path for sending a premixed gas containing fuel and air to the combustion chamber. Further, the intake opening 20 a can be opened and closed by an intake valve 22, and the exhaust opening 21 a can be opened and closed by an exhaust valve 23.

  A throttle valve 24 is arranged on the upstream side of the air flow with respect to the intake port 20, and the throttle valve 24 is configured to be able to adjust the flow rate of air sent from the intake port 20 to the combustion chamber 12. Yes. A direct injection injector 25 is also attached to the cylinder head 15, and the direct injection injector 25 is configured to inject fuel directly into the combustion chamber 12.

  In the engine 1, an air-fuel mixture can be generated in the combustion chamber 12 by the air sent from the intake port 20 and the fuel injected from the direct injection injector 25. The engine 1 is configured to generate a flame kernel for combustion by generating a spark discharge in the combustion chamber 12 using the spark plug 19.

  In particular, in one combustion cycle of the engine 1 that is a four-stroke system, the combustion stroke ST1, the exhaust stroke ST2, the intake stroke ST3, and the compression stroke ST4 are performed in this order. In one combustion cycle, the crankshaft 17 rotates twice. Therefore, in one combustion cycle, the crank angle of the crankshaft 17 changes in principle by 720 °. Basically, in each of the combustion stroke ST1, the exhaust stroke ST2, the intake stroke ST3, and the compression stroke ST4, The crank angle of the crankshaft 17 changes in principle by 180 °.

[Details of control device]
Next, details of the control device 3 will be described. In particular, as shown in FIG. 2, the washer sensor 32 is clamped between the cylinder head 15 and the spark plug 19. Therefore, when vibration is generated due to combustion in the combustion chamber 12, the tightening load of the washer sensor 32 is changed in the compression direction or the relaxation direction by the vibration, and the surface potential of the piezoelectric element is changed by the change of the tightening load. Change. The washer sensor 32 outputs a charge signal (hereinafter referred to as “pressure signal”) corresponding to a change in the surface potential of the piezoelectric element. However, the present invention is not limited to this, and the washer sensor may be clamped between the cylinder head and a member other than the spark plug as long as the combustion pressure in the combustion chamber of the cylinder can be detected. The washer sensor 32 can generate a pressure signal according to the combustion pressure in the combustion chamber 12.

  As shown in FIG. 1, the control device 3 also includes a crank angle sensor 33 configured as a crank angle detector that can detect the crank angle of the crankshaft 17. The crank angle sensor 33 can also detect the rotational speed of the crankshaft 17, that is, the rotational speed of the engine 1. The crank angle sensor 33 is particularly preferably configured to be able to detect the rotation angle and rotation speed of a timing rotor (not shown) attached to the crankshaft 17 in a non-contact manner and arranged around the timing rotor. .

  Further, the control device 3 is configured as a throttle opening degree sensor 34 configured as a throttle opening degree detection unit capable of detecting the opening degree of the throttle valve 24 and an accelerator operation amount detection unit capable of detecting an operation amount of the accelerator pedal 2. The accelerator sensor 35 is provided. The control device 3 also includes an intake pressure sensor 36 configured as an intake pressure detection unit capable of detecting the pressure of air in the intake port 20, an oxygen concentration in the exhaust gas sent from the combustion chamber 12 to the exhaust port 21, and It has a LAF sensor (Linear Air-Fuel ratio sensor) 37 configured as an air-fuel ratio detection unit capable of detecting the air-fuel ratio of the air-fuel mixture in the combustion chamber 12 based on the unburned gas concentration. The intake pressure sensor 36 is disposed on the intake port 20 between the intake valve 22 and the throttle valve 24. The LAF sensor 37 is disposed on the exhaust port 21.

[Details of ECU]
Details of the ECU 31 of the control device 3 will be described with reference to FIG. Since the pressure signal sent from the washer sensor 32 is weak, the ECU 31 has a pressure signal amplifier 41 configured to receive this pressure signal and amplify the pressure signal. The pressure signal amplifying unit 41 is electrically connected to the washer sensor 32.

  The ECU 31 includes a pressure signal acquisition unit 42 configured to be able to acquire a pressure signal amplified by the pressure signal amplification unit 41, and a crank configured to acquire a crank angle detection value θ sent from the crank angle sensor 33. And a corner acquisition unit 43. The ECU 31 is also configured to calculate an angle-pressure signal in which the pressure signal acquired by the pressure signal acquisition unit 42 is associated with the crank angle detection value θ acquired by the crank angle acquisition unit 43. A calculation unit 44 is included.

  The angle-pressure signal calculation unit 44 preferably calculates the angle-pressure signal within the range of the detected value θ of the crank angle corresponding to the state where both the intake valve 22 and the exhaust valve 23 are closed. Typically, both the intake valve 22 and the exhaust valve 23 are closed between the intake bottom dead center and the exhaust bottom dead center. Further, it is preferable that the angle-pressure signal calculation unit 44 calculates the angle-pressure signal in the range of the detected value θ of the crank angle calculated from the ignition start timing of the spark plug 19, and in particular, the angle-pressure signal calculation unit 44 More preferably, the angle-pressure signal is calculated in the range of the detected value θ of the crank angle corresponding to the period from the ignition start timing to the combustion end timing. More preferably, the angle-pressure signal calculation unit 44 calculates the angle-pressure signal in the period from the ignition start timing to the maximum peak of the angle-pressure signal that appears first thereafter.

  Here, an outline of a typical angle-pressure signal is shown in FIG. In FIG. 4, the horizontal axis θ represents the detected value θ (°) of the crank angle, the vertical axis I represents the intensity I (V) of the angle-pressure signal, and the solid line L1 represents the angle-pressure signal. In the cylinder 11, the combustion stroke ST1 is performed when the crank angle detection value θ is basically in the range of 0 ° to 180 °, and the crank angle detection value θ is basically 180 ° to 360 °. The exhaust stroke ST2 is performed when it is within the range, the intake stroke ST3 is performed when the crank angle detection value θ is basically in the range of 360 ° to 540 °, and the crank angle detection value θ is principally The compression stroke ST4 is performed when the angle is in the range of 540 ° to 720 °. In this case, a state in which the detected value θ of the crank angle is in principle 180 ° corresponds to the exhaust bottom dead center, and a state in which the detected value θ of the crank angle is in principle 540 ° corresponds to the intake bottom dead center. . Such an angle-pressure signal has a pulse waveform protruding in a period from the compression stroke ST4 to the combustion stroke ST1. Such a pulse waveform reaches a maximum peak in the combustion stroke ST1.

  Referring to FIG. 3 again, the ECU 31 is configured to apply a filter process for gradually decreasing a frequency component higher than a predetermined cutoff frequency to the angle-pressure signal sent from the angle-pressure signal calculation unit 44. 45 is preferred. The filter unit 45 is configured to perform low-pass filter processing or band-pass filter processing. The cut-off frequency may be set after confirming the frequency band of a noise signal caused by engine drive vibration or the like using a technique such as FFT (Fast Fourier Transform Analysis). For example, when it is confirmed that the frequency band of the noise signal is about 100 Hz to 500 Hz, the cutoff frequency may be set to about 100 Hz. However, the present invention is not limited to this, and the cutoff frequency may be other values as long as the noise signal can be removed and the angle-pressure signal resulting from the combustion in the combustion chamber can be extracted with high accuracy.

  The ECU 31 is configured to calculate an estimated value K of a knocking intensity (Knocking Intensity) in the cylinder 11 using an angle-pressure signal sent from the angle-pressure signal calculation unit 44 via the filter unit 45. Using the knocking strength estimation unit 46 and the knocking strength estimation value K calculated by the knocking strength estimation unit 46, a knocking determination unit 47 configured to determine whether knocking has occurred in the cylinder 11 or not. And have.

  In the present embodiment, the knocking intensity is the maximum amplitude value obtained by subjecting the angle-pressure signal (hereinafter referred to as “in-cylinder angle-pressure signal”) acquired by the in-cylinder pressure sensor to a high-pass filter process and converting it to an absolute value. Define as The in-cylinder pressure sensor is a pressure sensor configured to directly detect the combustion pressure in the combustion chamber. Such knocking strength can be obtained through a process as shown in FIGS. 5 (a) to 5 (c). 5 (a) to 5 (c), the horizontal axis θ represents the detected value θ (°) of the crank angle, and the vertical axis P represents the combustion pressure (hereinafter referred to as “cylinder”) obtained by the in-cylinder pressure sensor. The detected value P (bar) of “internal pressure” is shown.

  Specifically, a high-pass filter process is performed on the in-cylinder angle-pressure signal as shown by a solid line L2 in FIG. 5A, whereby a filter process is performed as shown by a solid line L3 in FIG. To obtain an angle-pressure signal subjected to. The in-cylinder angle-pressure signal that has been subjected to the filter processing is converted into an absolute value, thereby obtaining an in-cylinder angle-pressure signal that has been converted into an absolute value, as indicated by a solid line L4 in FIG. Further, as shown in FIG. 5C, the knocking strength is obtained from the maximum value Pm of the detected value P of the in-cylinder pressure based on the in-cylinder angle-pressure signal converted into an absolute value.

  The ECU 31 includes an ignition adjustment unit 48 configured to be able to adjust ignition by the ignition plug 19 in the combustion chamber 12. Further, with reference to FIG. 1, the ECU 31 sends a detected value of the rotational speed of the engine 1 sent from the crank angle sensor 33, a detected value of the throttle opening sent from the throttle opening sensor 34, and a sent value from the accelerator sensor 35. At least one of the required torque determined according to the detected value of the accelerator operation amount, the detected value of the air pressure sent from the intake pressure sensor 36, the detected value of the air-fuel ratio of the air-fuel mixture sent from the LAF sensor 37, etc. Based on this, the air flow rate, the air-fuel ratio of the air-fuel mixture, and the like are adjusted. The air flow rate can be adjusted by controlling the opening / closing timing of the intake valve 22, the opening degree of the throttle valve 24, and the like. The air-fuel ratio of the air-fuel mixture can be adjusted by controlling the fuel injection amount from the direct injection injector 25 and the like.

[Details of knocking strength estimation unit]
The details of the knocking strength estimation unit 46 of the ECU 31 will be described with reference to FIG. The knocking strength estimation unit 46 has a plurality of changes that are ratios of the strength I of the angle-pressure signal that changes in a certain section of the detected value θ of the crank angle in each combustion cycle in the combustion chamber 12 on the angle-pressure signal. A change rate calculation unit 51 configured to calculate a rate C (= dI / dθ) is included. The change rate calculation unit 51 can store the calculated change rate C. In addition, the constant interval of the detected value θ of the crank angle that determines the rate of change C may be determined according to the resolution of the digitized angle-pressure signal. For example, such a fixed section can be about 1 °. However, the present invention is not limited to this, and the constant interval of the detected value θ of the crank angle may be determined within a range of about 0.05 ° or more and about 5 ° or less.

  The knocking strength estimation unit 46 selects the maximum value (hereinafter referred to as “maximum change rate”) M from among the plurality of change rates C calculated by the change rate calculation unit 51 in each combustion cycle in the combustion chamber 12. The change rate selection unit 52 is configured. Specifically, the change rate selection unit 52 selects the maximum change rate M from the plurality of change rates C stored by the change rate calculation unit 51 in one combustion cycle. However, the present invention is not limited to this, and the change rate selection unit may select a change rate C other than the maximum change rate M as long as a value substantially equal to the maximum change rate M is obtained. For example, the change rate selection unit may select the nth largest one of the plurality of change rates C. Note that n is an integer of 2 or more, and in particular, n is preferably 2 or 3. Further, it is preferable that the change rate selection unit 52 can store the calculated maximum change rate M.

  Here, the in-cylinder change rate D, which is the ratio of the detected value P of the in-cylinder pressure that changes in a certain section of the detected value θ of the crank angle, is calculated, and as shown in FIG. Assuming that the maximum value (hereinafter referred to as “in-cylinder maximum change rate”) N of a plurality of in-cylinder change rates D calculated in the combustion cycle is calculated, as shown in FIGS. The rate M has a high correlation with the in-cylinder maximum change rate N. Furthermore, since the knocking strength has a high correlation with the in-cylinder maximum change rate N as described above, the maximum change rate M has a high correlation with the knocking strength. Specifically, the maximum change rate M and the in-cylinder maximum change rate N are within the range of the detected value θ of the crank angle from about 0 ° to 30 ° as shown in FIGS. The maximum change rate M and the maximum in-cylinder change rate N that can be obtained in the period from the ignition start timing to the angle-pressure signal and in-cylinder angle-maximum peak of the in-cylinder signal that appear first thereafter. Are highly correlated with each other.

  In FIG. 6, the horizontal axis θ represents the detected value θ (°) of the crank angle, the vertical axis P represents the detected value P (bar) of the in-cylinder pressure, and the solid line L5 represents the in-cylinder angle-pressure signal. The in-cylinder maximum change rate N is the in-cylinder angle-pressure signal in which the maximum change amount ΔP of the detected value P of the in-cylinder pressure is obtained in a certain section of the detected value θ of the crank angle indicated by Δθ. It is calculated in the area of In FIG. 7, the horizontal axis θ represents the detected value θ (°) of the crank angle, the vertical axis I represents the angle based on the washer sensor 32—the intensity I (V) of the pressure signal, and the solid line L6 represents the in-cylinder angle— The maximum change rate M indicates a pressure signal, and the maximum change rate ΔI of the intensity I of the angle-pressure signal is obtained in a certain section of the detected value θ of the crank angle indicated by Δθ. Calculated in the area.

  The knocking strength estimation unit 46 can calculate an estimated value K of the knocking strength from the maximum change rate M calculated by the change rate selection unit 52 based on such a high correlation between the maximum change rate M and the knocking strength. It has a configured strength estimated value calculation unit 53. The strength estimation value calculation unit 53 stores a knocking strength map in which the relationship between the maximum change rate M and the knocking strength is defined in advance, and the strength estimation value calculation unit 53 determines the maximum change based on the knocking strength map. It is preferable to calculate the estimated value K of the knocking strength from the rate M. The relationship between the maximum rate of change M and the knocking strength may be obtained in advance based on the results of experiments such as conformance tests according to operating conditions and numerical simulations.

  However, the present invention is not limited to this, and the strength estimation value calculation unit calculates the knocking strength estimated value K from the maximum rate of change M based on a formula that predefines the relationship between the maximum rate of change M and the knocking strength. It may be calculated. Further, the estimated strength value calculation unit may calculate the in-cylinder maximum change rate N from the maximum change rate M, and may further calculate the estimated value K of the knocking strength from the in-cylinder maximum change rate N. The relationship between the maximum change rate M and the in-cylinder maximum change rate N and the relationship between the knocking strength and the in-cylinder maximum change rate N are based on the results of experiments such as conformance tests and numerical simulations according to operating conditions. It is good to obtain in advance.

[Details of knock determination unit]
Details of the knock determination unit 47 of the ECU 31 will be described. As shown in FIG. 3, when the knocking strength estimation value K is smaller than the first knocking threshold value T1, the knocking determination unit 47 determines that knocking has not occurred, and the knocking strength estimation value K is A knocking occurrence determination unit 61 configured to determine that knocking has occurred when the knocking threshold value is equal to or greater than the first knocking threshold value T1 is provided. The knocking determination unit 47 also includes a knocking strength identification unit 62 configured to identify which of the plurality of strength levels corresponds to the knocking strength estimation value K calculated by the strength estimation value calculation unit 53. . The plurality of intensity levels may be set in advance by human hearing.

  In the present embodiment, as shown in FIG. 8, four intensity levels, that is, first to fourth intensity levels Lv1 to Lv4 are set. When five or more strength levels are set, the knocking strength determination accuracy described later can be further increased. In FIG. 8, the horizontal axis K represents the knocking strength estimation value K (bar), the vertical axis Lv represents the strength level, and the solid line L7 represents the correlation between the knocking strength estimation value K and the strength level. Indicates a linear function.

  As shown in FIG. 8, the first to fourth intensity levels Lv1 to Lv4 increase in this order. Specifically, the first strength level Lv1 corresponds to the range of the estimated value K of the knocking strength that is smaller than the first knocking threshold T1, and is evaluated as “no knocking”. The second intensity level Lv2 corresponds to the range of the estimated value K of the knocking intensity that is greater than or equal to the first knocking threshold T1 and smaller than the second knocking threshold T2, and is evaluated as “trace knocking”. The third intensity level Lv3 corresponds to the range of the estimated value K of the knocking intensity that is greater than or equal to the second knocking threshold T2 and smaller than the third knocking threshold T3, and is evaluated as “light knocking”. The fourth strength level Lv4 corresponds to the range of the knocking strength estimated value K that is equal to or greater than the third knocking threshold T3, and is evaluated as “heavy knocking”.

  The plurality of intensity levels can be preset as follows. That is, the tester calculates the knocking strength using the in-cylinder angle-pressure signal, and at the same time listens to the sound acquired by the microphone installed near the surface of the cylinder block 13. Further, the tester listens to the sound as described above, and listens to the vibration sound caused by the knocking, and divides the magnitude of the vibration sound into a plurality of intensity levels. Further, a correspondence relationship between knocking strength and a plurality of strength levels is determined. Note that the sound acquired by the microphone is emphasized in a frequency band (generally 5 kHz to 20 kHz) of vibration sound caused by knocking using an equalizer (an acoustic device that changes the frequency characteristics of the audio signal) or the like. Should be processed as follows.

[Details of ignition control unit]
The details of the ignition adjustment unit 48 of the ECU 31 will be described with reference to FIG. The ignition adjustment unit 48 ignites in the combustion chamber 12 of the cylinder 11 based on the detected value of the rotational speed of the engine 1 sent from the crank angle sensor 33 and the detected value of the throttle opening sent from the throttle opening sensor 34. A target ignition timing calculation unit 71 configured to calculate the timing of ignition by the plug 19 and the ignition timing of the ignition plug 19 according to the target value of the ignition timing calculated by the target ignition timing calculation unit 71 are controlled. An ignition control unit 72 configured as described above.

  The target ignition timing calculation unit 71 is electrically connected to the crank angle sensor 33 and the throttle opening sensor 34. It is preferable that the ignition timing map is stored in the target ignition timing calculation unit 71. Further, the target ignition timing calculation unit 71 performs ignition based on the detected values of the rotational speed of the engine 1 and the throttle opening based on the ignition timing map. It is preferable to calculate a target value for the time. Specifically, the target value of the ignition timing is preferably calculated using a correction coefficient corresponding to the detected value of the rotational speed of the engine 1 and the throttle opening on the ignition timing map. However, the present invention is not limited to this, and the target ignition timing calculation unit may calculate the target value of the ignition timing from the detected values of the engine speed and the throttle opening based on the calculation formula.

  Further, when the knocking occurrence determination unit 61 determines that knocking has occurred, the target ignition timing calculation unit 71 sets a retard amount (ignition delay angle) set in advance according to the intensity level identified by the knocking intensity identification unit 62. The target value of the ignition timing is corrected to be delayed based on the amount. In this case, it is preferable that the target ignition timing calculation unit 71 corrects the ignition timing map so as to delay the target value of the ignition timing in a part or the whole region of the ignition timing map. In particular, in the target ignition timing calculation unit 71, it is preferable that the predetermined ignition timing map is rewritten with an ignition timing map corrected in advance so as to delay the target value of the ignition timing.

[About control method]
With reference to FIG. 9, the control method of the engine 1 which concerns on this embodiment is demonstrated below. The ignition control unit 72 controls the spark plug 19 so as to perform ignition in the combustion chamber 12 of the cylinder 11 according to a predetermined target value of ignition timing (step S1). The pressure signal acquisition unit 42 acquires the pressure signal, and the crank angle acquisition unit 43 acquires the detected value θ of the crank angle (step S2). The angle-pressure signal calculation unit 44 calculates an angle-pressure signal in which the pressure signal is associated with the crank angle detection value θ (step S3). The filter unit 45 performs a filtering process for gradually decreasing the frequency component higher than the predetermined cutoff frequency with respect to the angle-pressure signal (step S4).

  The change rate calculation unit 51 has a plurality of ratios of the intensity I of the angle-pressure signal that changes in a certain section of the detected value θ of the crank angle in each combustion cycle in the combustion chamber 12 on the angle-pressure signal. The change rate C is calculated and stored (step S5). The change rate selection unit 52 selects the maximum change rate M of the plurality of change rates C in each combustion cycle (step S6). The strength estimated value calculation unit 53 calculates the knocking strength estimated value K based on the maximum rate of change M (step S7). The knocking occurrence determination unit 61 determines whether or not the knocking strength estimated value K is smaller than the first knocking threshold value T1 (step S8).

  When the knocking occurrence determination unit 61 determines that the knocking strength estimated value K is equal to or greater than the first knocking threshold value T1 (NO), it determines that knocking has occurred (step S9). In this case, the knocking strength identifying unit 62 identifies which of the second to fourth strength levels Lv2 to Lv4 corresponds to the knocking strength estimated value K (step S10). The ignition timing calculation unit 71 corrects the target value of the ignition timing to be delayed based on the retard amount set in advance according to one of the identified second to fourth intensity levels Lv2 to Lv4 (step) S11). The ignition control unit 72 controls the spark plug 19 so as to perform ignition in the combustion chamber 12 of the cylinder 11 in accordance with the corrected target value of the ignition timing (step S12). On the other hand, when the knocking occurrence determination unit 61 determines that the knocking strength estimated value K is smaller than the first knocking threshold value T1 (YES), it determines that knocking has not occurred (step S13). In this case, the current ignition timing is maintained (step 14).

  However, the present invention is not limited to this, and in the control method of the present invention, the steps may be changed in accordance with the modified example of the control system.

  As described above, according to the control device 3 according to the present embodiment, the angle-pressure in which the pressure signal of the combustion pressure sent from the washer sensor 32 attached so as to come into contact with the cylinder 11 from the outside is associated with the crank angle of the crankshaft 17. Since the signal is used, it is not necessary to perform processing such as DFT and STFT for noise removal as in the in-cylinder angle-pressure signal, and the calculation load can be reduced. As a result, knocking determination time can be shortened, and responsiveness for eliminating knocking can be improved. Further, the knocking strength estimated value K in the cylinder 11 is calculated using the rotation-pressure signal, and it is determined whether knocking has occurred using the knocking strength estimated value K. Accuracy can be increased. As a result, knocking can be reliably eliminated. In addition, since the cost of the washer sensor 32 can be made lower than the cost of the in-cylinder pressure sensor, the manufacturing cost can be reduced. Further, since the washer sensor 32 is a washer mold and is attached so as to be in contact with the cylinder 11 from the outside, the attachment is easy. In particular, since the washer sensor 32 is tightened between the cylinder head 15 and the spark plug 19, the attachment becomes easier.

  According to the control device 3 according to the present embodiment, the pressure signal corresponding to the combustion pressure detected with the intake valve 22 and the exhaust valve 23 being closed is influenced by the vibration generated when the intake valve 22 and the exhaust valve 23 are seated. Therefore, the determination accuracy of combustion stability can be improved. Incidentally, since the pressure signal used for the calculation process is limited, the calculation load can be reduced.

  According to the control device 3 according to the present embodiment, the maximum change rate M of the plurality of change rates C, which is the ratio of the angle-pressure signal intensity I that changes in a certain section of the crank angle detection value θ, is determined by knocking. Has a high correlation with the knocking intensity generally used as an evaluation item, and whether knocking occurred based on the estimated value K of the knocking intensity calculated from the maximum rate of change M Since it is determined whether or not, knocking determination accuracy can be made extremely high. Note that the same effect can be obtained when a plurality of change rates C that are substantially equal to the maximum change rate M are used instead of the maximum change rate M.

  According to the control device 3 according to the present embodiment, the ignition timing is delayed when it is determined that knocking has occurred by the highly accurate determination of knocking as described above, so that knocking can be reliably eliminated.

  According to the control device 3 according to the present embodiment, the estimated value K of the knocking strength is divided into a plurality of preset strength levels, and the retard amount is changed according to any of these strength levels. The ignition timing can be corrected, and knocking can be reliably eliminated. Moreover, since the retard amount is set in advance, the calculation load for calculating the retard amount can be reduced. As a result, knocking determination time can be shortened, and responsiveness for eliminating knocking can be improved. In addition, a stable combustion state can be obtained by reliably eliminating knocking.

  Although the embodiment of the present invention has been described so far, the present invention is not limited to the above-described embodiment, and the present invention can be modified and changed based on its technical idea.

[Example 1]
Example 1 will be described. In Example 1, in addition to the washer sensor 32, the engine 1 of the above embodiment in which the cylinder pressure sensor was attached to the cylinder head 15 was used. In particular, the engine 1 is an in-line four-cylinder engine. Regarding the operating conditions of the engine 1, in order to intentionally generate knocking, the rotational speed of the engine 1 is set to 2000 rpm, the load of the engine 1 is set to the wide open throttle state (full load state), and the ignition timing crank The angle was 20.2 ° with respect to BTDC (Before Top Dead Center). The filter unit 45 performs low-pass filter processing, and the cutoff frequency of the low-pass filter processing is 100 Hz.

  Under such operating conditions, an angle-pressure signal is acquired by the washer sensor 32, an angle-pressure signal based on the pressure signal is calculated, and a maximum change rate between a plurality of change rates C from the angle-pressure signal. M was calculated. The angle-pressure signal is acquired during a period in which the crank angle is 20 ° with respect to BTDC and 30 ° with respect to ATDC (After Top Dead Center), and the maximum change rate M The fixed interval of the detected value θ of the crank angle used for the calculation of the angle was 0.1 °.

[Comparative Example 1]
Comparative Example 1 will be described. In Comparative Example 1, the same engine as in Example 1 was used. Further, in the first comparative example, under the same conditions as in the first embodiment, the pressure signal is obtained in the first embodiment, and at the same time, the in-cylinder pressure signal is obtained from the in-cylinder pressure sensor. The internal angle-pressure signal was calculated, and the in-cylinder maximum change rate N and knocking strength KI were calculated from the in-cylinder angle-pressure signal. The period during which the angle-pressure signal is acquired and the constant section of the crank angle detection value θ used for calculating the in-cylinder maximum change rate N are also the same as in the first embodiment.

  In such Example 1 and Comparative Example 1, the correlation between the maximum change rate M of Example 1 and the in-cylinder maximum change rate N of Comparative Example 1 was confirmed, and the knocking strength KI and the cylinder in Comparative Example 1 were further confirmed. The correlation with the maximum change rate N was confirmed. As a result, a correlation diagram between the maximum change rate M and the in-cylinder maximum change rate N as shown in FIG. 10 is obtained, and the correlation diagram between the knocking strength KI and the in-cylinder maximum change rate N as shown in FIG. Obtained. In FIG. 10, the horizontal axis N indicates the in-cylinder maximum change rate N (bar / °), and the vertical axis M indicates the maximum change rate M (V / °). In FIG. 11, the horizontal axis N indicates the maximum in-cylinder change rate N (bar / °), and the vertical axis KI indicates the knocking strength KI (bar). In addition, in each of the correlation diagrams of FIG. 10 and FIG. 11, data of a plurality of combustion cycles obtained by the present embodiment are plotted.

  As shown in FIG. 10, the correlation coefficient between the maximum change rate M of Example 1 and the in-cylinder maximum change rate N of Comparative Example 1 was 0.724, and the correlation coefficient R was 0.7 or more. . As shown in FIG. 11, the correlation coefficient R between the knocking strength KI and the in-cylinder maximum change rate N in Comparative Example 1 was 0.848, and the correlation coefficient R was 0.7 or more. Therefore, it was confirmed that the maximum change rate M and the in-cylinder maximum change rate N were highly correlated, and that the correlation between the knocking strength KI and the in-cylinder maximum change rate N was high. Based on these correlations, it was also confirmed that the correlation between the maximum change rate M and the knocking strength KI was high. According to this correlation, it was confirmed that the in-cylinder maximum change rate N can be estimated from the maximum change rate M, and that the knocking strength KI can be estimated from the in-cylinder maximum change rate N. When the first knocking threshold T1 is set as shown in FIG. 11, it is determined that knocking has not occurred in the combustion cycle of the data plotted in a range smaller than the knocking threshold T1, and knocking is performed. It was determined that knocking occurred in the combustion cycle of the data plotted in the range above the threshold value T1.

[Example 2]
A second embodiment of the present invention will be described. In this example, the engine 1 having the same configuration as that of the above embodiment was used, and the engine 1 was operated under the condition that the rotational speed was 2000 rpm and the load was fully opened. Furthermore, the retard amount when trace knocking occurs under such conditions is set to 1 °, the retard amount when light knocking occurs under the same conditions is set to 4 °, and heavy knocking is performed under the same conditions. When generated, the retard amount was set to 8 °. As a result, knocking could be eliminated in each of cases where trace knocking, light knocking, and heavy knocking occurred.

1 Gasoline direct injection engine (engine)
11 Cylinder 12 Combustion chamber 17 Crankshaft 19 Spark plug 22 Intake valve 23 Exhaust valve 3 Controller 32 Washer type pressure sensor (washer sensor)
43 Crank angle acquisition unit 44 Angle-pressure signal calculation unit 45 Filter unit 46 Knocking strength estimation unit 47 Knocking determination unit 48 Ignition adjustment unit 51 Change rate calculation unit 52 Change rate selection unit 53 Strength estimated value calculation unit 62 Knocking strength identification unit θ Crank angle detection value I Angle-pressure signal intensity C Change rate M Maximum value of multiple change rates (maximum change rate)
K knocking strength estimated values Lv1 to Lv4 1st to 4th strength levels

Claims (6)

A washer-type pressure sensor configured to come into contact with the cylinder from outside so as to be able to detect a combustion pressure in a combustion chamber of the cylinder in the internal combustion engine and to output a pressure signal in accordance with the combustion pressure;
A crank angle acquisition unit configured to acquire a crank angle of a crankshaft of the internal combustion engine,
A control device for an internal combustion engine configured to be able to control the internal combustion engine in response to occurrence of knocking in the cylinder,
An angle-pressure signal calculator configured to calculate an angle-pressure signal associated with the crank angle of the pressure signal;
A knocking strength estimator configured to calculate an estimated value of the knocking strength in the cylinder using the rotation-pressure signal;
A control device for an internal combustion engine, comprising: a knock determination unit configured to determine whether knocking has occurred in the cylinder based on the estimated value of the knocking strength.   2. The angle-pressure signal calculation unit is configured to calculate the angle-pressure signal within a range of the crank angle in a state where both an intake valve and an exhaust valve of the internal combustion engine are closed. Control device for internal combustion engine. The knocking strength estimation unit
Based on the angle-pressure signal, a plurality of change rates, which are ratios of the intensity of the angle-pressure signal that changes in a certain section of the crank angle, are calculated in each combustion cycle in the combustion chamber. A rate-of-change calculating unit,
A change rate selecting unit configured to select one selected change rate among the plurality of change rates in each combustion cycle in the combustion chamber;
The control apparatus for an internal combustion engine according to claim 1, further comprising: an intensity estimated value calculation unit configured to calculate an estimated value of the knocking intensity using the selection change rate.   The control device for an internal combustion engine according to claim 3, wherein the selection change rate is a maximum value of the plurality of change rates.   When the knocking determination unit determines that the knocking has occurred, the knocking determination unit further includes an ignition control unit configured to control a spark plug so as to delay the timing of ignition in the combustion chamber of the cylinder so as to eliminate the knocking. Item 5. The control device for an internal combustion engine according to any one of Items 1 to 4. The knock determination unit
A knocking strength identification unit configured to identify which of the plurality of preset strength levels corresponds to the estimated value of the knocking strength;
6. The control device for an internal combustion engine according to claim 5, wherein the ignition control unit is configured to delay the ignition timing based on a retard amount set in advance according to the identified intensity level.

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