Electronic control device and combustion state detection system

Abstract

The electronic control device of the present application calculates the rotational speed or rotation time of a certain angle of the crankshaft based on the change in the detection signal of the sensor of the crankshaft. When the combustion cylinder is switched, the information of the rotational speed or rotation time of at least 2 combustion cycles is obtained, and the combustion phase is calculated based on the rotational speed or rotation time. Thus, the combustion state of the internal combustion engine can be detected with high precision using the sensor that measures the rotation of the crankshaft.

Description

TECHNICAL FIELD

[0001] The present application relates to an electronic control device and a combustion state detection system. BACKGROUND

[0002] In an internal combustion engine, high efficient operation is achieved by appropriately controlling air intake, fuel injection, EGR (Exhaust Gas Recirculation), ignition, and the like in accordance with a combustion state. In order to achieve high efficient operation, detection of the combustion state is important.

[0003] As a method of detecting the combustion state of an internal combustion engine, the following three methods are known.

[0004] (1) A method of measuring pressure caused by generation of heat in a combustion cylinder using an in-cylinder pressure sensor, and detecting the combustion state based on the pressure

[0005] (2) A method of measuring ion current, and detecting generation of ions caused by combustion based on the same

[0006] (3) A method of measuring rotation of a crankshaft caused by generation of heat in a combustion cylinder using a crank angle sensor, and detecting the combustion state based on the rotation time

[0007] Here, in the method of (1), an in-cylinder pressure sensor is required to be added, and in the method of (2), a modification of an ignition circuit is required in order to measure ion current, whereas the method using the crank angle sensor of (3) can use an existing crank angle sensor, and detection of the combustion state can be achieved by addition of software.

[0008] In Patent Literature 1, a control device of an engine that detects a combustion state using a crank angle sensor is described.

[0009] That is, Patent Literature 1 describes an angular velocity detection section that calculates an angular velocity of rotation of a crankshaft, an angular acceleration calculation section that calculates an angular acceleration from the angular velocity, and a combustion control section that controls combustion in a cylinder based on a change in the angular acceleration.

[0010] Here, the angular velocity detected by the angular velocity detection section is detected based on a division angle set to the crank angle of the crankshaft. Further, the angular acceleration calculated by the angular acceleration calculation section is calculated from the angular velocities corresponding to two division angles obtained in time series by the angular velocity detection section.

[0011] In the technology described in Patent Literature 1, when the angular velocity is detected by the angular velocity detection section, there are a plurality of division angle patterns in which the boundary positions of adjacent division angles are different from each other, and a process of calculating the angular velocity based on each of the plurality of division angle patterns is performed.

[0012] PRIOR ART DOCUMENT

[0013] Patent Literature

[0014] Patent Literature 1: Japanese Patent Laid-Open No. 2017-106360 SUMMARY

[0015] PROBLEMS TO BE SOLVED BY THE INVENTION

[0016] In the technology described in Patent Literature 1, when calculating the angular acceleration, the angular acceleration is calculated from the angular velocities corresponding to the two divided angles, and thus the calculation accuracy of the angular velocity is sometimes deteriorated by noise such as road surface vibration sound. In addition, the resolution at the time of control is determined by the resolution of the crank angle sensor, and thus there is a problem that the control ability becomes insufficient in highly combustion control such as EGR control.

[0017] Therefore, an electronic control device and a combustion state detection system that can accurately detect the combustion state of an internal combustion engine are desired.

[0018] MEANS OF SOLVING THE PROBLEM

[0019] The present application includes a plurality of methods for solving the above problems, and if one of them is exemplified, it is an electronic control device that detects the combustion state of an internal combustion engine based on a crank angle sensor signal that measures the rotation of a crankshaft of the internal combustion engine.

[0020] The electronic control device includes a crank angle synchronization processing section that detects a change in the crank angle sensor signal and calculates the rotational speed or the rotation time of a certain angle of the crankshaft based on the change in the sensor signal, and a time synchronization processing section that receives information on the rotational speed or the rotation time of at least two combustion cycles from the crank angle synchronization processing section when the combustion cylinder of the internal combustion engine is switched, and calculates the combustion phase based on the received rotational speed or rotation time.

[0021] Further, the electronic control device includes a crank angle synchronization processing section that detects a change in the crank angle sensor signal and calculates a rotational speed or a rotation time of a certain angle of the crankshaft on the basis of the change in the sensor signal, and a time synchronization processing section that receives information of the rotational speed or the rotation time of at least two combustion cycles from the crank angle synchronization processing section at the time when the combustion cylinder of the internal combustion engine is switched, interpolates the sensor signal itself for a timing at which the sensor signal is received and interpolates zero for a timing at which the sensor signal is not received with respect to the received information of the rotational speed or the rotation time of the sensor signal, thereby performing up-sampling of the sensor signal, and calculates a combustion torque by performing a filter processing of gain being proportional to frequency up to a prescribed frequency and the gain being attenuated above the prescribed frequency with respect to the result of the up-sampling, and searches for a peak value of the calculated combustion torque to calculate a combustion phase of the internal combustion engine.

[0022] Effects of Invention

[0023] According to the present application, the detection resolution of the combustion phase is improved, and a high-precision combustion phase that is not affected by noise can be detected. Therefore, according to the present application, for example, high-EGR control to obtain EGR until just before combustion becomes unstable can be performed, and an effect of contributing to improvement in fuel consumption rate of the internal combustion engine is obtained.

[0024] The technical problems, structures, and effects other than the above are further clarified by the following embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 is a structural diagram showing an example of the internal combustion engine to which the electronic control device according to one embodiment of the present application is applied.

[0026] Figure 2 is a characteristic diagram showing an example of a change in heat generation caused by a change in the EGR rate of the internal combustion engine.

[0027] Figure 3 is a structural diagram showing an example of a connecting rod structure from a piston to a crankshaft.

[0028] FIG. 4 is a characteristic diagram showing an example of a frequency characteristic of a differential filter for calculating a combustion torque according to a rotational angular velocity, according to one embodiment of the present application.

[0029] Figure 5 is a characteristic diagram showing a result after Fourier transform of the rotational speed, according to one embodiment of the present application.

[0030] Figure 6 is a graph showing a relationship between the rotational speed and the combustion torque, according to one embodiment of the present application.

[0031] Figure 7 is an explanatory diagram showing a relationship among a crank angle sensor signal interval, a combustion torque resolution, and a combustion cycle.

[0032] Figure 8 is a characteristic diagram showing an example of a periodicity of a rotation speed / rotation time of a crankshaft and a combustion torque.

[0033] Figure 9 is a block diagram showing a configuration example of a combustion state detection device according to an embodiment of the present application.

[0034] FIG. 10 is an explanatory diagram showing an example of a state after up-sampling of a rotation speed.

[0035] Figure 11 is a characteristic diagram showing a characteristic of a filter of comb Figure 4C

[0036] Figure 12 is a characteristic diagram showing an example of a relationship among an EGR rate, a fuel consumption rate, and a combustion phase.

[0037] Figure 13 is a block diagram showing a configuration example of EGR rate control in an electronic control device according to an embodiment of the present application.

[0038] Figure 14 is a characteristic diagram showing an example of a relationship among an ignition timing, an exhaust heat, and a combustion phase. DETAILED DESCRIPTION

[0039] Hereinafter, an electronic control device according to an embodiment of the present application (hereinafter, referred to as "the present example") will be described with reference to the drawings.

[0040] [Structure of Internal Combustion Engine]

[0041] Figure 1 A structure of an internal combustion engine 99 controlled by the electronic control device of the present example is shown.

[0042] The internal combustion engine 99 includes an air flow sensor 1 that measures an intake air amount, a compressor 2 that supercharges intake air, an intercooler 3 that cools the supercharged intake air, and a throttle valve 4 that adjusts an air amount drawn into a cylinder 5. In the vicinity of the throttle valve 4, a throttle sensor 19 for detecting an opening degree of the throttle valve 4 is provided.

[0043] ​​Further, the internal combustion engine 99 includes a spark plug 6 that supplies ignition energy to each cylinder 5, a fuel injection device 9 that injects fuel into each cylinder 5, and a piston 10 that compresses a mixture of fuel and air flowing into the cylinder 5. Further, the internal combustion engine 99 includes an intake valve 7 that adjusts the intake of the mixture into the cylinder 5, and an exhaust valve 8 that discharges burned exhaust gas. In addition, Figure 1 In the present embodiment, the cylinder 5 is illustrated as one cylinder for simplicity of explanation, but in fact, the cylinder 5 has a plurality of cylinders.

[0044] Further, the internal combustion engine 99 includes a crank angle sensor 11 that detects a signal of a signal rotor attached to the crank shaft, and a water temperature sensor 12 that measures the temperature of the cooling water. Further, the internal combustion engine 99 includes a turbine 13 that transmits the kinetic energy of the exhaust gas to the compressor 2 via a shaft, and a three-way catalyst 14 that purifies harmful substances in the exhaust gas. Then, in the vicinity of the three-way catalyst 14, an A / F sensor 15 that detects the oxygen concentration contained in the exhaust gas is attached.

[0045] Further, the internal combustion engine 99 includes an EGR passage pipe 16 that returns the exhaust gas (EGR gas) from the downstream of the three-way catalyst 14 to the upstream of the compressor 2, an EGR cooler 17 that cools the EGR gas, and an EGR valve 18 that adjusts the flow rate of the EGR gas passing through the EGR passage pipe 16. Then, in the vicinity of the EGR valve 18, a differential pressure sensor 21 that detects the differential pressure before and after the EGR valve 18 is attached. Here, the differential pressure before and after the EGR valve 18 is the difference between the pressure on the upstream side of the EGR valve 18 and the pressure on the downstream side in the EGR passage pipe 16.

[0046] In the internal combustion engine 99 having the above-described structure, the fuel injection device 9 injects fuel into air taken into the cylinder 5 via the intake valve 7 to generate a mixture. The generated mixture explodes at a prescribed ignition timing by a spark generated by the spark plug 6, and a driving force is generated by the combustion pressure pushing the piston 10. The burned exhaust gas is sent to the three-way catalyst 14 via the exhaust pipe, and harmful substances are purified by the three-way catalyst 14.

[0047] A part of the exhaust gas purified by the three-way catalyst 14 is not discharged to the outside, but flows into the EGR passage pipe 116, and is used as EGR gas. The EGR gas passes through the EGR cooler 17 and the EGR valve 18, and merges with the intake air on the upstream side of the compressor 2. Thereafter, the mixture of the EGR gas and the intake air flows into the cylinder 5 after passing through the intercooler 3 and the throttle valve 4.

[0048] The internal combustion engine 99 forms a mixture by controlling the intake air amount, the EGR amount, and the fuel injection amount, and makes the mixture burn by ignition, and generates heat energy. The heat energy drives the piston, and rotates the crank shaft via the connecting rod mechanism. The rotation of the crank shaft becomes a propulsive force of the vehicle body by the transmission.

[0049] [Requirements for improving the combustion stability of internal combustion engines]

[0050] Increasing the EGR level reduces pumping losses in the internal combustion engine 99, thus improving efficiency. On the other hand, increasing the EGR level slows down the combustion rate in the internal combustion engine 99, and combustion soon becomes unstable.

[0051] Figure 2 This illustrates an example of how changes in the EGR rate of an internal combustion engine can lead to changes in heat generation.

[0052] Figure 2 The upper part compares the heat generation in cases (a), (b), and (c) where the EGR is three. Figure 2 The vertical axis at the top represents the amount of heat generated by combustion, and the horizontal axis represents time.

[0053] also, Figure 2 The middle section shows the combustion torque (vertical axis) for three cases (a), (b), and (c). Figure 2 The lower part shows the crankshaft speed (vertical axis) for three cases (a), (b), and (c), with the horizontal axis representing time for each case.

[0054] According to EGR from lowest to highest, Figure 2 The three cases shown above are (a) < (b) < (c). For example... Figure 2 As shown in the upper part, if EGR increases, the rate of heat generation decreases. Then, as... Figure 2 As shown in the middle, if heat generation is delayed, the peak value of the combustion torque is also delayed accordingly. Furthermore, as... Figure 2 As shown in the lower part, if the torque of the combustion peak is delayed, the rotation of the crankshaft is also delayed.

[0055] This rate of heat generation caused by the change in EGR rate (to) Figure 2 The change in heat generation rate (obtained by differentiating the heat generated in the upper part over time) can be detected, for example, by observing changes in cylinder pressure using an in-cylinder pressure sensor. Using an in-cylinder pressure sensor to detect the heat generation rate, if the heat generation rate is slower than a certain threshold, the EGR rate is increased, thereby ensuring combustion stability.

[0056] However, in-cylinder pressure sensors are relatively expensive. Therefore, in this example, combustion speed is detected based on the engine speed measured by the crank angle sensor.

[0057] In-cylinder pressure P, combustion torque τ comb The following relationships exist between the internal combustion engine speed ω and the speed ω: [Mathematical Formula 1] and [Mathematical Formula 2].

[0058] [Mathematical Expression 1]

[0059]

[0060] [Mathematical Expression 2]

[0061]

[0062] In [Mathematical Formula 1], the angles α and β, and the length R are as follows: Figure 3 As shown in the diagram of an internal combustion engine. That is, as... Figure 3 As shown, angle α represents the angle between connecting rod 32 and central shaft o, and angle β represents the angle between crank arm 31 and central shaft o. Furthermore, length R is the length of crank arm 31, and cylinder pressure is expressed as P. comb The cross-sectional area of ​​the cylinder is represented by A. cyl .

[0063] If the heat generated by combustion is generated prematurely, the cylinder pressure P comb The peak occurs earlier, such as Figure 2 As shown in the middle section, the peak value of the combustion torque also occurs earlier. The combustion torque is obtained by differentiating the rotational speed, i.e., by multiplying the rotational acceleration by the inertia of the rotating system. Therefore, by searching for the peak value of the differential of the rotational speed ω, the peak value of heat generation can be inferred.

[0064] Furthermore, when the rotational speed ω is obtained from the crank angle sensor, the accuracy of the speed measurement is determined by the resolution of the crank angle sensor. For example, if the crank angle sensor outputs a pulse every 10° of rotation, this is insufficient compared to the 1° resolution desired for combustion phase control. Moreover, even if the discretely obtained speed ω is differentiated, the torque cannot be smoothly calculated.

[0065] Therefore, in this example, the following process is performed: the rotational speed ω is approximated using trigonometric functions, and the approximated function is differentiated to differentiate the rotational speed ω at a 10° pitch, so as to obtain the combustion torque at a 1° pitch.

[0066] Here, we consider using a filter to perform differentiation operations.

[0067] First, as shown in [Mathematical Formula 3] below, the filter that differentiates ω is set as g(t).

[0068] [Mathematical Expression 3]

[0069]

[0070] If we perform a Fourier transform on both sides of [Mathematical Equation 3], it becomes [Mathematical Equation 4] as follows. In [Mathematical Equation 4], j is the imaginary unit, f is the frequency, Ω is the Fourier transform of ω, and G is the Fourier transform of the filter g.

[0071] [Equation 4]

[0072]

[0073] Thus, the Fourier transform G of the filter g having the differentiation characteristic is set as [Equation 5].

[0074] [Equation 5]

[0075]

[0076] Thus, the frequency-gain characteristic of the Fourier transform G of the filter g having the differentiation characteristic is shown in FIG. 6, where the vertical axis is the gain |G| and the horizontal axis is the frequency f. Thus, the frequency f is proportional to the gain |G|, but noise is present in the actual signal, so it is necessary to cut it off. Figure 4A Figure 4A Figure 4B Figure 4C Thus, in the case of the present example, as shown in FIG. 7, a filter that attenuates the gain at a frequency larger than the prescribed frequency fo is used. Here, the prescribed frequency at which the gain is attenuated is set by experimentally investigating the combustion torque and the rotational speed.

[0077] Thus, in the case of the present example, as shown in FIG. 7, a filter that attenuates the gain at a frequency larger than the prescribed frequency fo is used. Here, the prescribed frequency at which the gain is attenuated is set by experimentally investigating the combustion torque and the rotational speed. Figure 4B

[0078] is the result of the Fourier transform of the rotational speed. Figure 5 The horizontal axis of FIG. 8 indicates the frequency, and the vertical axis indicates the frequency intensity in linear proportion. As shown in FIG. 8, the frequency components of the rotational speed are the combustion frequency > 2 times the combustion frequency > 3 times the combustion frequency > 4 times the combustion frequency, and the larger the frequency, the more it attenuates. Also, the component of 5 times the combustion frequency is shown to be almost the same as the level of the noise. Thus, if the frequency fo at which the gain is attenuated is set to be 4 times the combustion frequency or less, it is sufficient to reproduce the combustion torque. Even if it is set to a higher frequency, only noise can be picked up, so by setting it to a value of 4 times or less, the precision can be improved. Figure 5 Figure 5 In FIG. 9, the rotational speeds Sll, S12, S13, S14 (solid line) and the combustion torques Pll, P12, P13, P14 (dotted line) are shown when the frequency fo at which the gain is attenuated is set to the combustion frequency (uppermost), 2 times the combustion frequency (2nd from the top), 3 times the combustion frequency (3rd from the top), and 4 times the combustion frequency (lowermost). In each graph, the horizontal axis is the crank angle, and the vertical axis is the rotational speed, and the position Px of the combustion peak of the combustion torque Pll, P12, P13, P14 is shown in the graph. Also, in the four graphs, a line Pa that compares the positions Px of the combustion peaks is shown at the same position.

[0079] Figure 6 In FIG. 9, the rotational speeds Sll, S12, S13, S14 (solid line) and the combustion torques Pll, P12, P13, P14 (dotted line) are shown when the frequency fo at which the gain is attenuated is set to the combustion frequency (uppermost), 2 times the combustion frequency (2nd from the top), 3 times the combustion frequency (3rd from the top), and 4 times the combustion frequency (lowermost). In each graph, the horizontal axis is the crank angle, and the vertical axis is the rotational speed, and the position Px of the combustion peak of the combustion torque Pll, P12, P13, P14 is shown in the graph. Also, in the four graphs, a line Pa that compares the positions Px of the combustion peaks is shown at the same position. ​​​​

[0080] like Figure 6 As shown at the top, it can be seen that if the frequency f0 that causes gain attenuation is set as the combustion frequency, the combustion torque P11 cannot be properly reproduced, especially the position of its peak value Px cannot be fully reproduced. On the other hand, as Figure 6 As shown in Parts 2, 3, and the bottom section, if the combustion frequency is set to 2, 3, and 4 times, the combustion torques P12, P13, and P14 are appropriately reproduced, especially the position of their peak value Px, which is reproduced in accordance with the line Pa. Furthermore, the position of the peak value Px is almost identical in the cases of 2 to 4 times.

[0081] Therefore, as Figure 4C As shown, the frequency at which the gain is attenuated is preferably set at the combustion frequency f. comb The frequency range is approximately 2 to 4 times that of the previous frequency. Additionally, the combustion frequency f... comb It is the combustion cycle θ comb The reciprocal of the combustion period θ comb The interval between combustion occurrences is 720° / cylinder. Therefore, by setting the frequency f0 that attenuates the gain, it is possible to balance the accuracy of combustion torque reproduction with robustness against noise.

[0082] Therefore, as Figure 4B As shown, the following filter can be prepared: the gain is proportional to the frequency f up to the specified frequency f0, and the gain is attenuated at frequencies higher than the specified frequency f0.

[0083] Such filters can be designed using inverse Fourier transform, window function methods, etc. The differential of the filter g and ω designed in this way can be calculated using [Mathematical Equation 6] and [Mathematical Equation 7]. Here, N is the spacing θ of the crank angle sensor. sen The desired combustion torque resolution θ est The ratio of ω N The resolution θ is obtained from the crank angle sensor. sen The rotational angular velocity, ω, is the combustion torque resolution θ. est The rotational angular velocity, L is the length of the filter, i.e., the combustion period θ comb With combustion torque resolution θ est The ratio.

[0084] [Mathematical Expression 6]

[0085]

[0086] [Mathematical Expression 7]

[0087]

[0088] In addition, Figure 7 Summary of θsen θ est θ comb The relationship between N and L.

[0089] like Figure 7 As shown, the crank angle sensor signals CS1, CS2, CS3, CS4, ... are spaced at intervals θ. sen We obtain the interval θ sen The desired combustion torque resolution θ est The ratio (θ) sen / θ est The value is N. Furthermore, the combustion cycle θ comb / Combustion torque resolution θ est The ratio (θ) comb / θ est ) is L.

[0090] Combustion occurs at regular intervals; therefore, the combustion torque and crank speed are periodic. This period is called the combustion period θ. comb =720° / number of cylinders.

[0091] Figure 4B The text describes how the filter attenuation frequency f0, which smooths the rotational speed, is preferably 2 to 4 times the combustion frequency. The combustion frequency f... comb It is the combustion cycle θ comb The reciprocal, in Figure 4C In the example shown, the combustion frequency f is set. comb 2 times (f) comb ×2) and combustion frequency f comb 4 times (f comb Between (×4).

[0092] Figure 8 The upper part shows the change in crank speed S21. Figure 8 The lower part shows the change in combustion torque S22. Each vertical axis represents the crank speed and the value of combustion torque, and the horizontal axis is time.

[0093] like Figure 8 As shown, the combustion torque S22 and crank speed S21 have a variation according to θ in each combustion cycle. comb And the periodicity of change.

[0094] As shown in [Mathematical Formula 8], if according to this combustion cycle θ comb By determining the filter length L, noise generated on the crank angle sensor signal can be effectively removed. This is because the signal repeats during the combustion cycle.

[0095] [Mathematical Expression 8]

[0096]

[0097] [Structure of combustion state detection device]

[0098] Next, the structure of the combustion state detection system that filters the rotational speed calculated from the crank angle sensor in the process so far to calculate the combustion torque and detects the combustion peak will be described.

[0099] Figure 9 The structure of the combustion state detection device 100 of the combustion state detection system to which the present example is applied will be described.

[0100] The combustion state detection device 100 includes a crank angle synchronous processing section 110 and a time synchronous processing section 120.

[0101] The detection of the combustion state of the internal combustion engine is synchronized with the input of the crank angle sensor detection signal, and if all the processes are concentrated in one processing section, the load is concentrated and it is not preferable. Therefore, as shown in Figure 9 it is preferable that the functions are shared by the crank angle synchronous processing section 110 and the time synchronous processing section 120 to perform the processes.

[0102] The crank angle synchronous processing section 110 performs a process of calculating the rotational speed from the acquisition of the crank angle sensor detection signal. Then, the crank angle synchronous processing section 110 transmits the information of the rotational speed of at least two combustion cycles to the time synchronous processing section 120 that is activated at a certain time interval (for example, every 10 ms).

[0103] The time synchronous processing section 120 performs a process of estimating the combustion torque from the received rotational speed of two combustion cycles and detecting the peak of the combustion torque as the combustion phase.

[0104] Hereinafter, when the structure shown in Figure 9 is described, the detection signal of the crank angle sensor 11 is a signal that repeats conduction and non-conduction in synchronization with the concave-convex of the teeth installed on the crankshaft, and is a pulse signal that falls when the crankshaft rotates a certain angle, for example, 10°, each time.

[0105] The falling detection section 111 of the crank angle synchronous processing section 110 detects the timing of the falling of the detection signal of the crank angle sensor 11.

[0106] The rotational speed calculation section 112 calculates the time from the timing of the falling detected by the falling detection section 111 to the timing of the next falling, and calculates the crank rotational speed by taking the reciprocal of the calculated time or dividing the interval of the teeth installed on the crankshaft by the calculated time.

[0107] The time synchronous processing section 120 is activated at a certain time interval of 10 ms or the like, and if the switching of the combustion cylinder is detected from the cylinder discrimination signal, the rotational speed of the past two combustion cycles is received from the crank angle synchronous processing section 110.

[0108] The pitch θ of the upsampling unit 121 to the crank angle sensor 11 sen The signal with an angular resolution of (e.g., 10°) is upsampled to increase the sampling rate to the detection resolution θ. est (e.g., 1°).

[0109] Figure 10A and Figure 10B The processing in the upsampling unit 121 is shown. Here, the received rotational speed is set as ω. N ( Figure 10A The vertical axis), the increased rotational speed after resolution is set as ω( Figure 10B (the vertical axis). As shown in [Mathematical Expression 9] below, for Figure 10A The data S31 shown is set as follows, outside of the falling timing (m≠0): Figure 10B The data S32 after being processed by inserting "0" can improve the angular resolution of the rotational speed.

[0110] [Mathematical Expression 9]

[0111]

[0112] Filtering unit 122 according to Figure 4B As shown, the gain is proportional to the frequency up to the specified frequency f0, and the gain decreases if the frequency is exceeded. The upsampled rotational speed ω is filtered and the combustion torque is calculated.

[0113] By processing in this way, it is possible to... Figure 8 The upper part shows a coarser resolution rotation speed to estimate... Figure 8 The lower part shows high-resolution and smooth combustion torque.

[0114] Upsampled ω as Figure 10B As shown, the period θ sen The weight is quite noticeable. That is, as... Figure 10A As shown, compared with direct rotational speed ω N Compared to the upsampled data S31, the upsampled combustion torque resolution θ est The data S32's ω is as follows Figure 10B As shown, only the period θ of the sensor signal is related. sen The synchronous component is quite prominent.

[0115] Figure 11 This shows that the horizontal axis focuses on the combustion frequency f. comb The reciprocal θ comb To rewrite Figure 4C The characteristics of the filter after characteristic S41. Figure 11 The vertical axis represents gain, and the horizontal axis represents frequency. The sampling period θ of the rotational speed ω.sen Considering a typical crankshaft with a tooth spacing of 10°, if we consider a 4-cylinder internal combustion engine, it becomes as shown in [Mathematical Formula 10] below.

[0116] [Mathematical Expression 10]

[0117]

[0118] The sampling period θ of the rotational speed sen This falls within the region of filter gain attenuation. Therefore, as illustrated in Figure 10, by upsampling to smooth out the components of the prominent sampling period, the combustion torque synchronized with the combustion cycle can be smoothly determined.

[0119] In other words, as an upsampling process, the received speed or rotation time information is processed as follows: for timings where a sensor signal is received, the sensor signal itself is interpolated; for timings where no sensor signal is received, zero is used for interpolation. Then, the upsampled result is filtered to calculate the combustion torque by applying a gain proportional to the frequency up to a specified frequency and a gain attenuation above the specified frequency. The peak value of the calculated combustion torque is then searched to calculate the combustion phase of the internal combustion engine, thus smoothly determining the combustion torque synchronized with the combustion cycle.

[0120] The combustion torque output by the filter processing unit 122 repeats in each combustion cycle; therefore, the peak search unit 123 searches for the peak value in each combustion cycle. Then, the peak search unit 123 sets the angle of the peak value as the combustion phase. The combustion phase information searched by the peak search unit 123 is sent to the EGR control unit of the electronic control device. Furthermore, later... Figure 13 The structure of EGR control is explained in the text.

[0121] like Figure 8 As shown in the lower part, the combustion torque in each combustion cycle θ comb Therefore, since the combustion cycle length is repeated, it is preferable to search for the combustion peak based on the combustion torque. Furthermore, when calculating the combustion torque, it is preferable to perform periodic filtering utilizing the combustion torque and crankshaft speed. The period of the combustion torque and crankshaft speed is the combustion cycle θ. comb Therefore, it is preferable to set the length of the filter when calculating the combustion torque to the combustion period θ. comb .

[0122] Therefore, the combustion peak value is searched from the combustion torque of one combustion cycle, and each sample value of the combustion torque is calculated based on the crankshaft speed of one combustion cycle. Based on this, the combustion peak value of each combustion cycle is calculated based on the crankshaft speed of two combustion cycles.

[0123] Therefore, if the information transmitted from the crank angle synchronous processing section 110 that calculates the rotational speed or the rotational time to the time synchronous processing section 120 that calculates the combustion torque and searches for the peak value thereof is set to the crankshaft rotational speed for 2 combustion cycles or the crankshaft rotational time for 2 combustion cycles, the combustion peak value can be searched with good predictability.

[0124] Further, consider the case where the time synchronous processing section is activated at 10 ms intervals. In the case where the 4-cylinder internal combustion engine is operated at 3000 rpm, the time for the internal combustion engine to rotate once is 20 ms, and the time corresponding to the combustion cycle of 180° is 10 ms. Therefore, in all the time synchronous processing activated at 10 ms intervals, the combustion peak value corresponding to all the combustion cycles is found by calculating the combustion peak value through the estimation of the torque.

[0125] In the case where the rotational speed of the internal combustion engine is less than 3000 rpm, the time corresponding to the combustion cycle is longer than 10 ms, and therefore, the combustion torque estimation and the combustion peak value search are not required in all the time synchronous processing activated at 10 ms intervals. Therefore, if it is decided that the combustion torque estimation and the combustion peak value search are performed in the time synchronous processing immediately after the combustion cylinder is switched, the search of the combustion peak value can be prevented from being repeated.

[0126] Further, if the rotational speed of the internal combustion engine exceeds 3000 rpm, the time corresponding to the combustion cycle is shorter than 10 ms, and therefore, the time synchronous processing needs to be activated at a time interval shorter than 10 ms. If the number of cylinders of the internal combustion engine is denoted as C, and the rotational speed of the internal combustion engine is denoted as Neng [rpm], the activation interval Tjob of the time synchronous processing is given by [Mathematical Expression 11].

[0127] [Mathematical Expression 11]

[0128]

[0129] With the combustion state detection device 100 of this structure, the estimation of the combustion torque with high resolution and high accuracy can be performed, and high-accuracy combustion phase detection can be performed based thereon.

[0130] [Example of Calculation Using Rotational Time]

[0131] Even if the time required for rotation calculation processing is performed, Figure 9 The positive and negative sign changed value of the amplitude of the combustion torque can be obtained by the rotational speed calculation section 112 shown, and the position of the combustion shift does not change.

[0132] That is, if T is divided into the average value To and the AC component T dev = T - To, the crankshaft rotation θ sen The relationship between the time T required and the angular velocity becomes as shown in [Mathematical Expression 12].

[0133] [Math. 12]

[0134]

[0135] Therefore, if the rotational speed ω is divided into an average value ω0and an AC component ω dev = ω - ω0, it becomes as shown in [Math. 13].

[0136] [Math. 13]

[0137]

[0138] The filter g is a filter that extracts the AC component, and therefore in Figure 9 In the example of the filter processing section 122 that filters the rotational speed or the time required for rotation, only the proportional coefficient is changed, and the position of the peak of the filtered result is the same.

[0139] Therefore, even if the rotational speed calculation section 112 of Figure 9 is replaced with a rotation time calculation section (time required for rotation calculation section), the value after the positive and negative sign of the amplitude of the combustion torque changes, and the position of the combustion peak does not change.

[0140] [Structure of controlling EGR rate]

[0141] Next, the structure of the electronic control device that controls the EGR rate based on the combustion phase obtained by the combustion state detection device of the present example will be described.

[0142] Figure 12 The relationship between the EGR rate and the combustion phase and the fuel consumption rate is shown. Figure 12 The upper portion of Figure 12 The lower portion of Figure 12 The two lines shown in the upper portion of

[0143] As shown in the lower portion of Figure 12 If the EGR rate is increased, the fuel consumption rate characteristic S53 is improved due to the reduction in pumping loss, as shown in the lower portion of Figure 12 On the other hand, as shown in the upper portion of Figure 12 shows the case where the combustion becomes unstable when the EGR rate is large.

[0144] Therefore, in order to avoid the operation in this unstable region, as shown in [Math. 14], the detected combustion phase is compared with a limit combustion phase set in advance.

[0145] [Math. 14]

[0146] [Combustion phase detection value] > [Limit combustion phase]

[0147] When the relation of this [Math. 14] is satisfied, the electronic control device preferably performs control to decrease the EGR rate.

[0148] Alternatively, the deviation of the combustion phase is calculated, and it is determined whether the relation shown in [Math. 15] is satisfied.

[0149] [Math. 15]

[0150] [Deviation of combustion phase] > [Allowable value of combustion phase deviation]

[0151] When the relation of this [Math. 15] is satisfied, the electronic control device maximally increases the EGR rate by performing control to decrease the EGR rate, and can reduce the margin of the EGR rate control.

[0152] Figure 13 The electronic control device shown performs this processing.

[0153] That is, the electronic control device 200 is provided with a combustion state detection device 100 Figure 9 , and calculates the combustion phase based on the detection signal of the crank angle sensor 11. As already explained, the combustion state detection device 100 here is provided with a rotation required time calculation section instead of the rotation speed calculation section 112.

[0154] The information of the combustion phase calculated by the combustion state detection device 100 is supplied to the combustion phase determination section 201.

[0155] As explained in [Math. 14], the combustion phase determination section 201 compares the calculated combustion phase with the limit combustion phase. Further, as explained in [Math. 15], the combustion phase determination section 201 calculates the deviation of the combustion phase, and compares it with the allowable value of the combustion phase deviation to determine whether the combustion state is stable or unstable.

[0156] The EGR control section 202 calculates the set value of the opening degree of the EGR valve 18 so as to increase the EGR rate in the case where the determination result in this combustion phase determination section 201 is stable, and decrease the EGR rate in the case where it is unstable. This result is output to the EGR valve 18.

[0157] By thus performing feedback control of the EGR rate, it is possible to reduce individual differences in the internal combustion engine, deterioration, or to reduce the margin for estimating the accuracy of the differential pressure sensor 21 of the EGR valve 18, to increase the EGR rate to the limit, and to reduce the fuel consumption rate.

[0158] [Modified example]

[0159] The present application is not limited to the above-described embodiments, and various modified examples are also included.

[0160] For example, the combustion phase detected by the combustion state detection device 100 can be reflected not only in the EGR rate but also in air-fuel ratio control, ignition timing control, and the like.

[0161] That is, even if the horizontal axis of the upper and lower portions of Figure 12 is set to the air-fuel ratio instead of the EGR rate, it becomes a characteristic diagram of the same tendency.

[0162] In the case of performing air-fuel ratio control, it is possible to operate the internal combustion engine at an air-fuel ratio just before combustion becomes unstable by setting the threshold value of the combustion phase determination section 201 to correspond to the air-fuel ratio, replacing the EGR control section 202 with an air-fuel ratio control section, and controlling the fuel injection device 9 instead of the EGR valve 18. In this case, it is possible to reduce individual differences in the internal combustion engine, deterioration, or to reduce the margin for estimating the accuracy of the differential pressure sensor 21 of the EGR valve 18.

[0163] It is possible to increase the air-fuel ratio to the limit to reduce the fuel consumption rate. Furthermore, by increasing the air-fuel ratio to the limit in the inclined region, it is also possible to expect a reduction effect in NOx emissions. The reduction in NOx emissions is related to a reduction in the capacity of the exhaust catalyst, and thus also has the effect of reducing costs.

[0164] Furthermore, in addition to the EGR rate and the air-fuel ratio, it is also possible to consider controlling the ignition timing.

[0165] Ignition is generally efficient at an advance angle, and thus the ignition is advanced until knocking is detected by the knocking sensor. Advancing the ignition refers to advancing the ignition timing by a predetermined angle from the top dead center of the crank angle. Here, in order to advance heating of the air-fuel ratio sensor and the catalyst at the time of starting the internal combustion engine, if the ignition timing is intentionally delayed to reduce the efficiency of the internal combustion engine, control is also performed to increase the heat discharged to the exhaust gas accordingly.

[0166] Figure 14 The relationship between the ignition timing at this time and the combustion phase and the exhaust heat is shown. Figure 14 The vertical axis of the upper portion of Figure 14 The vertical axis of the lower portion of Figure 14The upper two lines indicate an upper limit characteristic S61 and a lower limit characteristic S62 of the combustion phase.

[0167] As Figure 14 the lower part as indicated by the characteristic S63, the later the ignition timing is delayed, the more the exhaust heat increases, but in conjunction therewith, the combustion phase is delayed as indicated by the upper part of Figure 14 , and the deviation of the combustion phase also becomes large.

[0168] Therefore, as in the case of controlling the EGR rate, the stability of combustion is determined based on the combustion phase or the deviation thereof, and if it is stable, the ignition timing is delayed, and if it is unstable, it is advanced, and by performing such control, it is possible to control the ignition timing so as to advance the heating.

[0169] In addition, the electronic control device 200 can control any one of the EGR valve opening degree, the throttle opening degree, the combustion injection amount, and the ignition timing of the internal combustion engine described above based on the combustion phase. Alternatively, a plurality of the EGR valve opening degree, the throttle opening degree, the combustion injection amount, and the ignition timing of the internal combustion engine can be controlled based on the combustion phase.

[0170] Furthermore, the above-described embodiment examples are detailed descriptions made for the purpose of facilitating understanding of the present application, and are not limited to having all the structures described. For example, Figure 13 the electronic control device 200 described in Figure 9 , but the combustion state detection device (combustion state detection system) 100 can be configured by a device separate from the electronic control device 200.

[0171] Furthermore, Figure 9 , Figure 13 the structure of the device described in

[0172] In addition to the non-volatile memory such as an HDD, an SSD, and the like, information such as a program that realizes each function in this case can also be placed in a storage medium such as a memory, an IC card, an SD card, an optical disc, and the like.

[0173] Furthermore, in the case where a part or all of the device described in Figure 9 , Figure 13 is configured by hardware, it can be realized by hardware such as an FPGA (Field Programmable Gate Array), an ASIC (Application Specific Integrated Circuit), and the like.

[0174] Furthermore,Figure 9 , Figure 13 The block diagrams shown only illustrate control lines and information lines necessary for the explanation; however, not all control lines and information lines may be shown on the actual product. In fact, almost all structures can be considered interconnected.

[0175] In addition, for Figure 1 The structure of the internal combustion engine shown is also an example; the internal combustion engine to which this invention is applied is not limited to... Figure 1 The structure.

[0176] Label Explanation

[0177] 1. Air Flow Sensor

[0178] 2. Compressor

[0179] 3. Intercooler

[0180] 4. Throttling valve

[0181] 5 cylinders

[0182] 6. Spark plugs

[0183] 7. Intake valve

[0184] 8. Exhaust valve

[0185] 9. Fuel Injection Valve

[0186] 10 Pistons

[0187] 11 Crank Angle Sensor

[0188] 12 Water Temperature Sensor

[0189] 13 Turbo

[0190] 14 Three-way catalyst

[0191] 15. Air-fuel ratio sensor

[0192] 16 EGR flow tube

[0193] 17 EGR Cooler

[0194] 18 EGR valve

[0195] 19 Throttling Sensor

[0196] 21 Differential pressure sensor

[0197] 31 Crank arm

[0198] 32 Connecting rod

[0199] 100 Combustion Status Detection Device

[0200] 101 crank angle sensor

[0201] 110 crank angle synchronization processing section

[0202] 111 drop detection section

[0203] 112 rotation speed calculation section

[0204] 120 time synchronization processing section

[0205] 121 up-sampling section

[0206] 122 filter processing section

[0207] 123 peak search section

[0208] 200 electronic control device

[0209] 201 combustion phase determination section

[0210] 202 EGR control section

Claims

1. An electronic control device for detecting the combustion state of an internal combustion engine based on a sensor signal from a crank angle sensor that measures the rotation of the crankshaft of the internal combustion engine, and for controlling the internal combustion engine, the electronic control device being characterized in that it comprises: A crank angle synchronization processing unit calculates the rotational speed or rotation time of the crankshaft at a certain angle based on the changes in the sensor signal. as well as A time synchronization processing unit receives information on the engine speed or rotational time of at least two combustion cycles from the crank angle synchronization processing unit when the combustion cylinder of the internal combustion engine switches, and calculates the combustion phase based on the received engine speed or rotational time. The time synchronization processing unit uses a filter whose gain is proportional to the frequency up to a specified frequency and whose gain decreases above the specified frequency to filter the received speed or rotation time information to calculate the combustion torque, and searches for the peak value of the calculated combustion torque to calculate the combustion phase of the internal combustion engine.

2. The electronic control device as described in claim 1, characterized in that, The time synchronization processing unit upsamples the information on the rotational speed or rotational time of at least two combustion cycles received from the crank angle synchronization processing unit, and performs the filtering processing on the upsampled rotational time information.

3. The electronic control device as described in claim 2, characterized in that, As a form of upsampling, the time synchronization processing unit performs upsampling of the sensor signal by interpolating the received sensor signal timing with the received sensor signal timing and interpolating with zero for timing when no sensor signal is received. The upsampled results are filtered to calculate the combustion torque, where the gain is proportional to the frequency up to the specified frequency and decreases above the specified frequency. The peak value of the calculated combustion torque is then searched to calculate the combustion phase of the internal combustion engine.

4. The electronic control device as described in claim 2, characterized in that, The frequency at which the gain is attenuated in the filtering process is a frequency set in the range of 2 to 4 times the combustion frequency of the internal combustion engine.

5. The electronic control device as described in any one of claims 1 to 4, characterized in that, Based on the combustion phase calculated by the time synchronization processing unit, at least one of the following is controlled: EGR valve opening, throttle opening, combustion injection quantity, and ignition timing of the internal combustion engine.

6. A combustion state detection system, which detects the combustion state of an internal combustion engine based on a sensor signal from a crank angle sensor that measures the rotation of the crankshaft of the internal combustion engine, the combustion state detection system being characterized by comprising: A crank angle synchronization processing unit calculates the rotational speed or rotation time of the crankshaft at a certain angle based on the changes in the sensor signal. as well as A time synchronization processing unit receives information on the engine speed or rotational time of at least two combustion cycles from the crank angle synchronization processing unit when the combustion cylinder of the internal combustion engine switches, and calculates the combustion phase based on the received engine speed or rotational time. The time synchronization processing unit uses a filter whose gain is proportional to the frequency up to a specified frequency and whose gain decreases above the specified frequency to filter the received speed or rotation time information to calculate the combustion torque, and searches for the peak value of the calculated combustion torque to calculate the combustion phase of the internal combustion engine.

Images