Airflow detection device, airflow detection method, program, and storage medium

Abstract

The present invention provides a better airflow detection device, a better airflow detection method, a program that causes a computer to execute the better airflow detection method, and a storage medium that stores the program that causes a computer to execute the better airflow detection method. [Solution] The airflow detection device 10 includes a signal acquisition unit 16 that acquires a sampling value output from an airflow meter 26 installed in the intake piping of an internal combustion engine, an airflow waveform acquisition unit 18 that acquires an airflow waveform indicating the airflow in the intake piping based on the detected airflow calculated from the sampling value acquired by the signal acquisition unit, an approximate waveform calculation unit 20 that calculates an approximate waveform which is a sine wave that approximates a partial waveform which is a part of the airflow waveform, and an airflow calculation unit 24 that calculates the airflow based on the approximate waveform.

Description

Technical Field

[0001] The present disclosure relates to an air flow rate detection device, an air flow rate detection method, a program, and a storage medium.

Background Art

[0002] Japanese Unexamined Patent Application Publication No. 2002-295292 discloses a fuel injection control device. The fuel injection control device can accurately measure the flow rate average value of a pulsating flow including a reverse flow by adding the difference in pulsation errors at different times in the forward and reverse directions of a thermal flow sensor to the reverse direction table value.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Conventionally, efforts aimed at mitigating or reducing the impact of climate change have continued, and research and development on exhaust gas purification devices have been conducted towards this realization.

[0005] By the way, in an exhaust gas purification device, a better air flow rate detection device, a better air flow rate detection method, a program for causing a computer to execute a better air flow rate detection method, and a storage medium storing a program for causing a computer to execute a better air flow rate detection method are eagerly awaited. The present disclosure aims to achieve the provision of a better air flow rate detection device, a better air flow rate detection method, a program for causing a computer to execute a better air flow rate detection method, and a storage medium storing a program for causing a computer to execute a better air flow rate detection method. And, by extension, it contributes to mitigating or reducing the impact of climate change.

Means for Solving the Problems

[0006] A first aspect of the present disclosure is an airflow detection device comprising: a signal acquisition unit that acquires a sampled value output from an airflow meter provided in the intake piping of an internal combustion engine; an airflow waveform acquisition unit that acquires an airflow waveform indicating the airflow rate in the intake piping based on the detected airflow rate converted from the sampled value acquired by the signal acquisition unit; an approximate waveform calculation unit that calculates an approximate waveform which is a sine wave that approximates a partial waveform which is a part of the airflow waveform; and an airflow calculation unit that calculates the airflow rate based on the approximate waveform.

[0007] A second aspect of the present disclosure is an airflow detection method comprising: a signal acquisition step of acquiring a sampling value output from an airflow meter provided in the intake piping of an internal combustion engine using a signal acquisition unit; an airflow waveform acquisition step of acquiring an airflow waveform indicating the airflow in the intake piping using an airflow waveform acquisition unit based on the detected airflow rate converted from the sampling value acquired by the signal acquisition unit; an approximate waveform calculation step of calculating an approximate waveform which is a sine wave approximating a partial waveform which is a part of the airflow waveform using an approximate waveform calculation unit; and an airflow calculation step of calculating the airflow rate using an airflow calculation unit based on the approximate waveform.

[0008] A third aspect of this disclosure is a program that causes a computer to execute the air flow detection method according to the second aspect.

[0009] A fourth aspect of this disclosure is a computer-readable, non-transient storage medium storing a program according to the third aspect. [Effects of the Invention]

[0010] According to this disclosure, it is possible to provide a better airflow detection device, a better airflow detection method, a program that causes a computer to execute the better airflow detection method, and a storage medium that stores the program that causes a computer to execute the better airflow detection method. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a block diagram showing the configuration of an air flow detection device in one embodiment. [Figure 2] Figure 2 illustrates a method for calculating airflow rate in one embodiment. [Figure 3] Figure 3 is a graph showing the relationship between the actual airflow rate and the sampled value detected by the airflow meter in one embodiment. [Figure 4] Figure 4 shows the airflow waveform and approximate waveform in one embodiment. [Figure 5] Figure 5 illustrates a method for acquiring airflow waveforms in one embodiment. [Figure 6] Figure 6 illustrates a method for determining the local maximum in one embodiment. [Figure 7] Figure 7 illustrates a method for determining a local maximum in one embodiment. [Figure 8] Figure 8 illustrates a method for determining a local maximum in one embodiment. [Figure 9] Figure 9 is a flowchart showing the processing flow in airflow rate calculation control in one embodiment. [Modes for carrying out the invention]

[0012] To improve fuel combustion efficiency, in gasoline vehicles, the amount of fuel injected is determined according to the airflow rate in the intake piping of the internal combustion engine, so that the weight ratio of air to fuel in the air-fuel mixture supplied to the engine is the stoichiometric ratio (λ=1) or a predetermined air-fuel ratio. Therefore, it is necessary to determine the airflow rate with high precision using an airflow detection device.

[0013] An air flow meter is provided in the intake pipe of an internal combustion engine. The air flow meter outputs sampling values. The magnitude of the sampling values changes according to the air flow rate in the intake pipe. The sampling values are converted into an air flow rate. Hereinafter, the air flow rate converted from the sampling values may be referred to as the detected air flow rate.

[0014] Since each cylinder of the internal combustion engine intermittently inhales air by opening and closing the intake valve, pulsation occurs in the intake pipe. Therefore, when the detected air flow rates are arranged in the order in which the sampling values are acquired, a waveform close to a sine wave can be obtained. This waveform indicates the change over time of the air flow rate in the intake pipe. Hereinafter, the waveform indicating the change over time of the air flow rate in the intake pipe obtained based on the sampling values will be referred to as the air flow rate waveform.

[0015] In the air flow rate detection device, the average of the detected air flow rates indicated by each of a plurality of points on the air flow rate waveform for one cycle is calculated as the air flow rate.

[0016] However, due to the structure of the air flow meter, the sensitivity of the air flow meter to the air flow rate is relatively low in a region where the actual air flow rate in the intake pipe is relatively small. In particular, the convex part under the air flow rate waveform may be greatly disturbed. The accuracy of the air flow rate calculated based on the disturbed air flow rate waveform is relatively low, and an appropriate fuel injection amount cannot be determined with respect to the actual air flow rate. As a result, there is a problem that the combustion efficiency of the fuel is suppressed and the fuel consumption deteriorates. [[ID=*13]]

[0017] In the present disclosure, it is possible to suppress a decrease in the accuracy of the air flow rate calculated in a region where the air flow rate is relatively small.

[0018] A control device for an internal combustion engine, a control method for an internal combustion engine, a program, and a storage medium according to an embodiment will be described below with reference to the drawings.

[0019] A program (computer program, computer software) according to an embodiment may also be referred to as a computer program product. A computer program product is not limited to a computer program stored in a storage medium, but also includes a computer program transmitted, distributed, or downloaded via the Internet or the like.

[0020] 〔One Embodiment〕 [Configuration of Airflow Detection Device] FIG. 1 is a block diagram showing the configuration of an airflow detection device 10 in one embodiment. The airflow detection device 10 detects the flow rate of air flowing through the intake pipe of an internal combustion engine.

[0021] The airflow detection device 10 includes an arithmetic unit 12 and a storage unit 14. The arithmetic unit 12 is, for example, a processor such as a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit). The arithmetic unit 12 includes a signal acquisition unit 16, an airflow waveform acquisition unit 18, an approximate waveform calculation unit 20, an airflow determination unit 22, and an airflow calculation unit 24. The signal acquisition unit 16, the airflow waveform acquisition unit 18, the approximate waveform calculation unit 20, the airflow determination unit 22, and the airflow calculation unit 24 are realized by a program stored in the storage unit 14 being executed in the arithmetic unit 12. At least a part of the signal acquisition unit 16, the airflow waveform acquisition unit 18, the approximate waveform calculation unit 20, the airflow determination unit 22, and the airflow calculation unit 24 may be realized by an integrated circuit such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field-Programmable Gate Array). At least a part of the signal acquisition unit 16, the airflow waveform acquisition unit 18, the approximate waveform calculation unit 20, the airflow determination unit 22, and the airflow calculation unit 24 may be realized by an electronic circuit including discrete devices.

[0022] The storage unit 14 is a computer-readable, non-transient, tangible storage medium. The storage unit 14 is composed of volatile memory (not shown) and non-volatile memory (not shown). The volatile memory is, for example, RAM (Random Access Memory). The non-volatile memory is, for example, ROM (Read Only Memory), flash memory, etc. Data is stored in the volatile memory, for example. Programs, tables, maps, etc. are stored in the non-volatile memory, for example. At least a portion of the storage unit 14 may be provided in the processor, integrated circuit, etc., as described above. At least a portion of the storage unit 14 may be mounted on equipment connected to the air flow detection device 10 by a network.

[0023] The signal acquisition unit 16 acquires the sampled value output from the airflow meter 26. The airflow meter 26 is installed in the intake piping of an internal combustion engine. The sampled value output from the airflow meter 26 changes according to the airflow rate in the intake piping. The airflow meter 26 is equipped with a sensing element. The sensing element is provided with a thermosensitive resistance element, which is heated to a constant temperature by a heater. When the thermosensitive resistance element is exposed to the flowing air, its resistance changes, and the voltage output by the sensing element changes. The greater the airflow rate, the greater the voltage change, so the voltage output from the sensing element can be converted to airflow rate.

[0024] If the airflow meter 26 is analog, the voltage output by the sensing element is output directly as the sampled value. If the airflow meter 26 is digital, the frequency obtained by digitally converting the voltage output by the sensing element is output as the sampled value. In one embodiment, an example using a digital airflow meter 26 is shown, but an analog airflow meter 26 may also be used. The detected airflow rate, converted from the voltage or frequency within the airflow meter 26, may also be output from the airflow meter 26.

[0025] The airflow waveform acquisition unit 18 acquires the airflow waveform based on sampling values ​​sequentially acquired by the signal acquisition unit 16. The airflow waveform acquisition unit 18 further includes a data selection unit 28 and a determination unit 30. The data selection unit 28 and the determination unit 30 will be described in detail later. The approximate waveform calculation unit 20 calculates an approximate waveform that approximates a partial waveform which is a part of the airflow waveform. The airflow determination unit 22 determines whether the airflow calculated by the airflow calculation unit 24 (described later) is equal to or greater than a predetermined flow rate. The airflow calculation unit 24 calculates the airflow based on the airflow waveform or the approximate waveform.

[0026] [Method for calculating airflow rate] Figure 2 illustrates a method for calculating airflow rate in one embodiment. The graph in Figure 2 shows the relationship between the detected airflow rate and the rotation angle of the crankshaft of a four-cylinder internal combustion engine.

[0027] For every two rotations (720°) of the crankshaft of an internal combustion engine, each cylinder repeats the intake stroke, compression stroke, expansion stroke, and exhaust stroke. In the case of a four-cylinder gasoline engine, when the crankshaft rotates 180°, the intake stroke occurs in the first cylinder, the compression stroke in the second cylinder, the expansion stroke in the third cylinder, and the exhaust stroke in the fourth cylinder. Therefore, as shown in Figure 2, the airflow waveform is close to a sine wave with a wavelength of 180°. The wavelength of the airflow waveform in a three-cylinder internal combustion engine, or the wavelength of the airflow waveform in a six-cylinder internal combustion engine, is different from the wavelength of the airflow waveform in a four-cylinder internal combustion engine.

[0028] The airflow rate calculation unit 24 calculates the average of the detected airflow rates indicated by each of the six points on the airflow rate waveform at 30° intervals of the crankshaft rotation angle, and uses this average as the airflow rate.

[0029] [Method for obtaining airflow rate and method for calculating approximate waveform] Figure 3 is a graph showing the relationship between the actual airflow rate and the sampled value output from the airflow meter 26 in one embodiment.

[0030] As mentioned above, due to the structure of the airflow meter 26, its sensitivity to airflow is relatively low in regions where the airflow rate is relatively small. As shown in Figure 3, in regions where the airflow rate is greater than the minimum guaranteed flow rate, the relationship between the actual airflow rate and the sampled value changes linearly. On the other hand, in regions where the airflow rate is less than or equal to the minimum guaranteed flow rate, the relationship between the actual airflow rate and the sampled value changes non-linearly. The minimum guaranteed flow rate is the lowest value of airflow at which the detection accuracy of the airflow meter 26 is guaranteed. The minimum guaranteed flow rate is set based on the detection performance, detection characteristics, etc., of the airflow meter 26.

[0031] Figure 4 shows the airflow waveform and approximate waveform in one embodiment. The airflow waveform shown in Figure 4 is a waveform calculated based on the detected airflow rate converted from sampled values ​​obtained when the actual airflow rate in the intake piping is relatively small. In particular, the airflow waveform shown in Figure 4 is greatly distorted in the downward-convex portion, which is the part of the airflow waveform where the detected airflow rate is small. With an airflow waveform as distorted as shown in Figure 4, it is not possible to determine the airflow rate with high accuracy.

[0032] Therefore, in a region where the airflow rate is relatively small, the airflow rate calculation unit 24 calculates the airflow rate based on an approximate waveform. The approximate waveform is a sine wave that approximates a partial waveform, which is a part of the airflow rate waveform. The partial waveform includes at least an upward-convex portion, which is the portion of the airflow rate waveform where the detected airflow rate is large. The partial waveform excludes the portion of the airflow rate waveform that is below a predetermined flow rate threshold. In other words, the partial waveform includes at least a portion of the airflow rate waveform that is greater than the flow rate threshold. The flow rate threshold indicates the value of the minimum guaranteed flow rate mentioned above. The flow rate threshold may be different from the value of the minimum guaranteed flow rate.

[0033] The method for acquiring the airflow waveform is described below. Figure 5 is a diagram illustrating the method for acquiring the airflow waveform in one embodiment.

[0034] The signal acquisition unit 16 acquires a sampled value from the airflow meter 26, for example, every 6° of crankshaft rotation. The timing at which the signal acquisition unit 16 acquires the sampled value does not have to be every 6° of crankshaft rotation. The signal acquisition unit 16 may acquire a sampled value from the airflow meter 26 at predetermined time intervals.

[0035] The airflow waveform acquisition unit 18 acquires the airflow waveform by sequentially storing the detected airflow values, converted from the sampling values ​​sequentially acquired by the signal acquisition unit 16, into the elements of array A. The number of elements in array A is, for example, 30, and array A consists of elements A0 to A29. The airflow waveform consists of a sequence of detected airflow values ​​composed of 30 detected airflow values ​​corresponding to the sampling values ​​sequentially acquired by the signal acquisition unit 16. The sequence of detected airflow values ​​composed of 30 detected airflow values ​​represents the airflow waveform for a crankshaft rotation angle of 180°. The sequence of detected airflow values ​​may consist of a number of detected airflow values ​​different from 30.

[0036] Furthermore, the airflow waveform acquisition unit 18 determines the maximum point of the airflow waveform. Figure 6 is a diagram illustrating the method for determining the maximum point in one embodiment. The notation "A0(f0)" in Figure 6 indicates, for example, that the detected airflow stored in element A0 is "f0".

[0037] First, the data selection unit 28 of the airflow waveform acquisition unit 18 selects from the detected airflow sequence multiple detected airflows whose magnitudes belong to the upper predetermined percentage. If the detected airflow sequence consists of 30 detected airflows and the predetermined percentage is 25%, then the top 7 detected airflows are selected. In the example shown in Figure 6, the detected airflows of elements A4 to A10 of array A are selected.

[0038] Next, the determination unit 30 of the airflow waveform acquisition unit 18 determines the maximum point of the airflow waveform based on the multiple detected airflow rates selected by the data selection unit 28. The determination unit 30 determines the maximum point based on the detected airflow rate corresponding to the timing midway between the earliest and last acquisition timings among the acquisition timings corresponding to each of the multiple detected airflow rates selected by the data selection unit 28.

[0039] In the example shown in Figure 6, the detected airflow rate corresponding to the earliest timing is the detected airflow rate of element A4. The detected airflow rate corresponding to the last timing is the detected airflow rate of element A10. The detected airflow rate corresponding to the timing midway between the earliest and last timings is the detected airflow rate of element A7, which is located in the middle of the detected airflow rates of elements A4 to A10. In other words, element A7 is selected as the maximum point of the airflow waveform, and the detected airflow rate f7 of element A7 becomes the maximum value of the airflow waveform.

[0040] In the example shown in Figure 6, the number of selected detected airflow rates is odd, but it may also be even. For example, if the data selection unit 28 selects eight detected airflow rates from elements A4 to A11 of array A, the point between element A7 and element A8 may be determined as the local maximum. In that case, the average of the detected airflow rate f7 of element A7 and the detected airflow rate f8 of element A8 may be used as the local maximum value of the airflow waveform.

[0041] Figures 7 and 8 illustrate a method for determining a local maximum in one embodiment. As shown in Figure 7, the data selection unit 28 may select the leading and trailing portions of the detected airflow rate sequence. In the example shown in Figure 7, elements A0 to A3 (leading portion) and elements A27 to A29 (trailing portion) of array A, which is the detected airflow rate sequence, are selected by the data selection unit 28.

[0042] In this case, the determination unit 30 may determine the maximum point based on a plurality of detected airflow rates that have been rearranged by placing the leading portion after the trailing portion. In the example shown in Figure 8, elements A0 to A3 (leading portion) of array A are rearranged to elements A30 to A33, which are after elements A27 to A29 (trailing portion). The determination unit 30 determines the maximum value based on the air data values ​​of elements A27 to A33.

[0043] The method for calculating the approximate waveform is explained below using Figure 6. The approximate waveform is a sine wave that approximates a partial waveform, which is a part of the airflow waveform. In the example shown in Figure 6, the part corresponding to elements A0 to A16 of array A is the partial waveform.

[0044] Using the variables p, q, and the detected air flow rates of elements A0 to A16, we can formulate equations (1) to (17) as follows.

[0045] f7 = p + q ... (1) f6 = psin(π / 2 - π / 15) + q ... (2) f5 = psin(π / 2 - 2π / 15) + q ... (3) f4 = psin(π / 2 - 3π / 15) + q ... (4) f3 = psin(π / 2 - 4π / 15) + q ... (5) f2 = psin(π / 2 - 5π / 15) + q ... (6) f1 = psin(π / 2 - 6π / 15) + q ... (7) f0 = psin(π / 2 - 7π / 15) + q ... (8) f8 = psin(π / 2 + π / 15) + q ... (9) f9 = psin(π / 2 + 2π / 15) + q ... (10) f10=psin(π / 2+3π / 15)+q…(11) f11=psin(π / 2+4π / 15)+q…(12) f12=psin(π / 2+5π / 15)+q…(13) f13=psin(π / 2+6π / 15)+q…(14) f14=psin(π / 2+7π / 15)+q…(15) f15=psin(π / 2+8π / 15)+q...(16) f16=psin(π / 2+9π / 15)+q...(17)

[0046] Let (2)~represent(17) and let (1) represent q. On the p, write a row of (18) ~ 33 (33).

[0047] p=(f7-f6) / {1-sin(π / 2-π / 15)}...(18) p=(f7-f5) / {1-sin(π / 2-2π / 15)}...(19) p=(f7-f4) / {1-sin(π / 2-3π / 15)}...(20) p=(f7-f3) / {1-sin(π / 2-4π / 15)}...(21) p=(f7-f2) / {1-sin(π / 2-5π / 15)}...(22) p=(f7-f1) / {1-sin(π / 2-6π / 15)}...(23) p=(f7-f0) / {1-sin(π / 2-7π / 15)}...(24) p=(f7-f8) / {1-sin(π / 2+π / 15)}...(25) p=(f7-f9) / {1-sin(π / 2+2π / 15)}...(26) p=(f7-f10) / {1-sin(π / 2+3π / 15)}...(27) p=(f7-f11) / {1-sin(π / 2+4π / 15)}...(28) p=(f7-f12) / {1-sin(π / 2+5π / 15)}...(29) p=(f7-f13) / {1-sin(π / 2+6π / 15)}...(30) p=(f7-f14) / {1-sin(π / 2+7π / 15)}...(31) p=(f7-f15) / {1-sin(π / 2+8π / 15)}...(32) p=(f7-f16) / {1-sin(π / 2+9π / 15)}...(33)

[0048] The amplitude P of the approximation formula is the average of the variable p obtained from equations (18) to (33). The center of oscillation Q of the approximation formula can be found from equation (34).

[0049] Q = f7 - P…(34)

[0050] Using the amplitude P and the center of vibration Q obtained as described above, the approximate waveform is given by equation (35). In equation (35), "F" is the approximate value of the airflow rate shown by the approximate waveform, "θ" is the rotation angle of the crankshaft, and "θ7" is the rotation angle of the crankshaft corresponding to the detected airflow rate f7 of element A7.

[0051] F=Asin{2(θ+θ7-π / 4)}+Q…(35)

[0052] In one embodiment, element A7 is selected as the maximum point of the airflow waveform. Therefore, in equation (35), the phase of the approximate waveform is defined using the crankshaft rotation angle θ7 corresponding to the detected airflow rate f7 of element A7. For example, if the area between element A7 and element A8 is selected as the maximum point of the airflow waveform, the phase of the approximate waveform may be defined using the median value (θ7+θ8) / 2 between the crankshaft rotation angle θ7 corresponding to the detected airflow rate f7 of element A7 and the crankshaft rotation angle θ8 corresponding to the detected airflow rate f8 of element A8.

[0053] If the airflow rate determination unit 22 determines that the airflow rate is equal to or greater than a predetermined rate, the airflow rate calculation unit 24 calculates the average of the detected airflow rates indicated by each of the six points on the airflow rate waveform at every 30° of crankshaft rotation angle as the airflow rate. If the airflow rate determination unit 22 determines that the airflow rate is less than a predetermined rate, the airflow rate calculation unit 24 calculates the average of the approximate airflow rates indicated by each of the six points on the approximate waveform at every 30° of crankshaft rotation angle as the airflow rate.

[0054] [Airflow calculation and control] Figure 9 is a flowchart showing the processing flow in airflow rate calculation control in one embodiment. The airflow rate calculation control is performed repeatedly at a predetermined cycle.

[0055] In step S1, the signal acquisition unit 16 acquires the sampled value output from the airflow meter 26. Then, the process proceeds to step S2.

[0056] In step S2, the airflow waveform acquisition unit 18 acquires an airflow waveform based on the detected airflow rate converted from the sampling values ​​sequentially acquired by the signal acquisition unit 16. Then, the process proceeds to step S3.

[0057] In step S3, the airflow rate determination unit 22 determines whether the airflow rate calculated by the airflow rate calculation unit 24 is equal to or greater than a predetermined rate. The airflow rate determination unit 22 makes this determination using the airflow rate calculated by the airflow rate calculation unit 24 during the previous airflow rate calculation control.

[0058] If the airflow rate calculated by the airflow rate calculation unit 24 is equal to or greater than a predetermined rate (step S3: YES), the process proceeds to step S4. In step S4, the airflow rate calculation unit 24 calculates the airflow rate based on the airflow rate waveform. After that, the airflow rate calculation control is terminated.

[0059] If the airflow rate calculated by the airflow rate calculation unit 24 is less than a predetermined rate (step S3: NO), the process proceeds to step S5. In step S5, the data selection unit 28 of the airflow rate waveform acquisition unit 18 selects from the detected airflow rate sequence multiple airflow rate data points whose detected airflow rate magnitudes belong to the upper predetermined proportion. After that, the process proceeds to step S6.

[0060] In step S6, the determination unit 30 of the airflow waveform acquisition unit 18 determines the maximum point of the airflow waveform based on the multiple detected airflow rates selected by the data selection unit 28. Then, the process proceeds to step S7.

[0061] In step S7, an approximate waveform is calculated that approximates a partial waveform, which is a part of the airflow waveform. Then, the process proceeds to step S8.

[0062] In step S8, the airflow rate calculation unit 24 calculates the airflow rate based on the approximate waveform. After that, the airflow rate calculation control is terminated.

[0063] [Effects and Effects] In this disclosure, if the airflow rate calculated by the airflow rate calculation unit 24 is less than a predetermined flow rate, the airflow rate calculation unit 24 calculates the airflow rate based on an approximate waveform. The approximate waveform is a sine wave that approximates a partial waveform which is a part of the airflow rate waveform.

[0064] This makes it possible to suppress a decrease in the accuracy of the airflow rate calculated by the airflow rate calculation unit 24 in regions where the airflow rate in the intake piping is relatively small.

[0065] The following additional information is disclosed regarding the above embodiment.

[0066] (Note 1) The airflow detection device (10) of this disclosure includes: a signal acquisition unit (16) that acquires a sampled value output from an airflow meter (26) installed in the intake piping of an internal combustion engine; an airflow waveform acquisition unit (18) that acquires an airflow waveform indicating the airflow in the intake piping based on the detected airflow converted from the sampled value acquired by the signal acquisition unit; an approximate waveform calculation unit (20) that calculates an approximate waveform which is a sine wave that approximates a partial waveform which is a part of the airflow waveform; and an airflow calculation unit (24) that calculates the airflow based on the approximate waveform. This makes it possible to suppress a decrease in the accuracy of the airflow calculated by the airflow calculation unit in regions where the airflow in the intake piping is relatively small.

[0067] (Note 2) The airflow detection device described in Appendix 1 further includes an airflow determination unit (22) that determines whether the airflow is equal to or greater than a predetermined flow rate, and if the airflow determination unit determines that the airflow is equal to or greater than the predetermined flow rate, the airflow calculation unit calculates the airflow based on the airflow waveform, and if the airflow determination unit determines that the airflow is less than the predetermined flow rate, the airflow calculation unit calculates the airflow based on the approximate waveform.

[0068] (Note 3) In the airflow detection device described in Appendix 1, the partial waveform may include at least an upwardly convex portion of the airflow waveform that represents the larger airflow.

[0069] (Note 4) In the airflow detection device described in Appendix 3, the partial waveform may exclude the portion of the airflow waveform that is below a predetermined flow threshold.

[0070] (Note 5) In the airflow detection device described in Appendix 3 or 4, the airflow waveform consists of a sequence of detected airflows, each corresponding to a sampling value acquired by the signal acquisition unit. The airflow waveform acquisition unit includes a data selection unit (28) that selects from the sequence of detected airflows a plurality of detected airflows whose magnitudes belong to a predetermined upper proportion, and a determination unit (30) that determines the maximum point of the airflow waveform based on the plurality of detected airflows selected by the data selection unit. The approximate waveform calculation unit may calculate the approximate waveform using the maximum point determined by the determination unit.

[0071] (Note 6) In the airflow detection device described in Appendix 5, the determination unit may determine the maximum point based on the detected airflow that corresponds to a timing midway between the earliest and last acquisition timings among the acquisition timings corresponding to each of the plurality of detected airflows selected by the data selection unit.

[0072] (Note 7) In the airflow detection device described in Appendix 5, if the data selection unit selects the leading and trailing portions of the detected airflow sequence, the determination unit may determine the maximum point based on a plurality of detected airflows rearranged by placing the leading portion after the trailing portion.

[0073] (Note 8) The airflow detection method of this disclosure includes: a signal acquisition step of acquiring a sampled value output from an airflow meter provided in the intake piping of an internal combustion engine using a signal acquisition unit; an airflow waveform acquisition step of acquiring an airflow waveform indicating the airflow in the intake piping using an airflow waveform acquisition unit based on the detected airflow converted from the sampled value acquired by the signal acquisition unit; an approximate waveform calculation step of calculating an approximate waveform which is a sine wave that approximates a partial waveform which is a part of the airflow waveform using an approximate waveform calculation unit; and an airflow calculation step of calculating the airflow based on the approximate waveform using an airflow calculation unit.

[0074] (Note 9) The program disclosed herein causes a computer to execute the airflow detection method described in Appendix 8.

[0075] (Note 10) The computer-readable, non-transient storage medium of this disclosure stores the program described in Appendix 9.

[0076] While this disclosure has been described in detail, it is not limited to the individual embodiments described above. These embodiments can be added, replaced, modified, partially deleted, etc., in any way that does not depart from the gist of this disclosure or from the intent of this disclosure derived from the claims and their equivalents. These embodiments can also be implemented in combination. For example, the order of operations and processes in the embodiments described above are given as examples only and are not limited thereto. The same applies when numerical values ​​or mathematical formulas are used in the description of the embodiments described above. [Explanation of symbols]

[0077] 10...Air flow detection device 16...Signal acquisition unit 18...Air flow rate waveform acquisition unit 20...Approximate waveform calculation unit 22...Air flow rate determination unit 24...Air flow rate calculation unit 26...Airflow meter 28...Data selection section 30…Judgment section

Claims

1. A signal acquisition unit that acquires sampled values ​​output from an airflow meter installed in the intake piping of an internal combustion engine, An airflow waveform acquisition unit acquires an airflow waveform indicating the airflow rate in the intake piping based on the detected airflow rate converted from the sampling value acquired by the signal acquisition unit, An approximate waveform calculation unit calculates an approximate waveform which is a sine wave that approximates a partial waveform which is a part of the airflow waveform, An airflow rate calculation unit that calculates the airflow rate based on the approximate waveform, An air flow detection device having the following features.

2. In the air flow detection device according to claim 1, The system further includes an airflow rate determination unit that determines whether or not the airflow rate is equal to or greater than a predetermined rate. If the airflow rate determination unit determines that the airflow rate is equal to or greater than the predetermined flow rate, the airflow rate calculation unit calculates the airflow rate based on the airflow rate waveform. If the airflow rate determination unit determines that the airflow rate is less than the predetermined flow rate, the airflow rate calculation unit calculates the airflow rate based on the approximate waveform, an airflow rate detection device.

3. In the air flow detection device according to claim 1, An airflow detection device wherein the partial waveform includes at least an upwardly convex portion of the airflow waveform that represents the side with a larger airflow rate.

4. In the air flow detection device according to claim 3, The aforementioned partial waveform is an airflow detection device that excludes the portion of the airflow waveform below a predetermined flow threshold.

5. In the air flow detection device according to claim 3 or 4, The airflow waveform consists of a sequence of detected airflows, which are composed of a plurality of detected airflows corresponding to the sampling values ​​acquired by the signal acquisition unit. The aforementioned airflow waveform acquisition unit is A data selection unit that selects from the detected airflow rate sequence a plurality of detected airflow rates whose magnitudes belong to the upper predetermined proportion, A determination unit that determines the maximum point of the airflow waveform based on a plurality of detected airflow rates selected by the data selection unit, Equipped with, The approximate waveform calculation unit calculates the approximate waveform using the maximum point determined by the determination unit, and is an air flow detection device.

6. In the air flow detection device according to claim 5, The determination unit determines the maximum point based on the detected air flow rate corresponding to an intermediate timing between the earliest and last acquisition timings among the acquisition timings corresponding to each of the plurality of detected air flow rates selected by the data selection unit, in an air flow rate detection device.

7. In the air flow detection device according to claim 5, An airflow detection device in which, when the leading and trailing portions of the detected airflow sequence are selected by the data selection unit, the determination unit determines the maximum point based on a plurality of detected airflows rearranged by placing the leading portion after the trailing portion.

8. A signal acquisition step involves acquiring a sampled value output from an airflow meter installed in the intake piping of an internal combustion engine using a signal acquisition unit, and An airflow waveform acquisition step is performed in which an airflow waveform acquisition unit acquires an airflow waveform indicating the airflow rate in the intake pipe based on the detected airflow rate converted from the sampling value acquired by the signal acquisition unit, An approximate waveform calculation step in which an approximate waveform calculation unit calculates an approximate waveform which is a sine wave that approximates a partial waveform which is a part of the airflow waveform, An airflow rate calculation step in which the airflow rate is calculated by the airflow rate calculation unit based on the approximate waveform, An air flow detection method having the following features.

9. A program that causes a computer to execute the airflow detection method described in claim 8.

10. A computer-readable, non-transient storage medium storing the program described in claim 9.

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