Air flow rate measuring device and air flow rate measuring method

Abstract

This air flow rate measuring device comprises: an air flow rate detection device that detects the air flow rate of an air flow moving inside a pipe, and generates an input signal corresponding to the air flow rate; and a computation unit that determines whether the air flow is a laminar flow or a turbulent flow, on the basis of the input signal, and outputs, as an output signal corresponding to the air flow rate, results from a computation using the results output from a proportional computation performed on the input signal when the air flow was determined to be a laminar flow, or results from a computation using the results output from a square-sum computation performed on the input signal when the air flow was determined to be a turbulent flow.

Description

[Technical field]

[0001] The present invention relates to an air flow rate measuring device and an air flow rate measuring method. [Background technology]

[0002] Conventionally, air flow measuring devices have been used to measure the flow rate of air moving inside a pipe. The air flow measuring device is a device for measuring the air flow rate, which is an index for improving the fuel efficiency of an engine. For this reason, the air flow measuring device is installed, for example, in the intake pipe of an automobile engine. The air in the intake pipe is drawn into the cylinder during the intake stroke. After that, it goes through the combustion stroke, expansion stroke, and exhaust stroke, and then the intake stroke is performed again.

[0003] Incidentally, it is known that improving engine fuel efficiency causes pulsation in the air flow inside the intake pipe. The principle behind this is briefly explained. When a piston moves inside a cylinder, the air flow speed inside the intake pipe changes in accordance with the piston movement. This change in air flow speed is called pulsation. When pulsation occurs inside the intake pipe, it affects the air flow measured by the air flow measuring device, causing an error (called "pulsation error") in the average air flow (average flow rate). The pulsation error represents the difference between the average air flow measured by the air flow measuring device and the true average air flow rate. The pulsation amplitude rate is an index that represents the magnitude of pulsation as the ratio of pulsation amplitude to average flow rate. In general, as the pulsation amplitude rate increases, the pulsation error increases.

[0004] For example, when a throttle valve provided in an intake pipe is closed and the air in the intake pipe becomes difficult to flow, energy loss occurs, resulting in poor fuel economy. However, if the throttle valve is closed, even if pulsation occurs in the engine, the pulsation is unlikely to affect the intake pipe. On the other hand, to improve fuel economy, the throttle valve is opened. If the throttle valve is open, the pulsation generated by the engine is more likely to affect the air in the intake pipe, and the pulsation error in the air flow rate is more likely to have an effect.

[0005] One example of a method for reducing pulsation error is the technology described in Patent Document 1. Patent Document 1 describes a technology for determining the air flow rate flowing through an intake pipe from the air flow rate in a bypass passage measured by an air flow rate detection element. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2018-205134 A Summary of the Invention [Problem to be solved by the invention]

[0007] Here, the installation location of the conventional air flow measuring device described in Patent Document 1 will be described. Fig. 1 is a diagram showing an example of an installation location of an air flow detection device. A conventional air flow detection device 100 will be described in Fig. 1, but an air flow detection device 2 according to an embodiment described later will also be installed in the same manner as the air flow detection device 100.

[0008] Air taken into the engine moves through the intake pipe 16 from left to right in FIG. 1. A secondary passage 17 is provided in part of the intake pipe 16 to branch off the air. The part of the intake pipe 16 where the secondary passage 17 is provided is called the main passage 18 through which most of the air in the intake pipe 16 flows. An air flow detection device 100 is provided in the secondary passage 17 to detect the air flow rate in the secondary passage 17. The air flow detection device 100 outputs a detection signal when it detects air flowing through the secondary passage 17. An electronic control device (not shown) determines the air flow rate Q2 of the air flowing through the secondary passage 17 based on the detection signal output by the air flow detection device 100. The electronic control device then determines the air flow rate Q1 of the main passage 18 by numerical calculation from the air flow rate Q2 of the secondary passage 17.

[0009] Arranging the air flow detection device 100 in the sub-passage 17 is useful for preventing the air flow detection device 100 from being soiled or exposed to water. However, the passage diameter of the sub-passage 17 is smaller than the passage diameter of the main passage 18. In general, the air flow passing through a passage is laminar when the flow velocity is low, and becomes turbulent when the flow velocity is high. Also, the smaller the passage diameter, the higher the flow velocity when the laminar flow changes to turbulent flow. For this reason, when the flow rate Q1 of the main passage 18 is gradually increased, the flow in the main passage 18 becomes turbulent at an early stage, but the flow in the sub-passage 17 remains laminar. Also, the formula for calculating pressure loss differs between laminar flow and turbulent flow.

[0010] However, in the conventional technology disclosed in Patent Document 1, the entire flow rate range was calculated using a turbulent flow calculation formula. Therefore, when calculating the air flow rate Q1 in the main passage 18 by numerical calculation from the air flow rate Q2 in the sub-passage 17, the pulsation error of the air flow rate was large, especially in the low flow rate range (for example, low pulsation amplitude rate (0 to 100%)). In other words, to calculate the air flow rate Q1 in the main passage 18 by numerical calculation from the air flow rate Q2 in the sub-passage 17, it is necessary to use different calculation formulas for laminar flow and turbulent flow, but the above conventional technology did not take this into consideration.

[0011] The present invention has been made in view of the above circumstances, and has an object to reduce the pulsation error of the air flow rate in the low flow rate region. [Means for solving the problem]

[0012] The air flow measuring device of the present invention comprises an air flow detection device that detects the air flow rate of an air flow moving within a pipe and generates an input signal corresponding to the air flow rate, and a calculation unit that determines whether the air flow is laminar or turbulent based on the input signal, and outputs, as an output signal corresponding to the air flow rate, the result of a calculation using the output result of a proportional calculation performed on the input signal when the air flow is determined to be laminar, or the result of a calculation using the output result of a square calculation performed on the input signal when the air flow is determined to be turbulent. Effect of the Invention

[0013] According to the present invention, it is possible to obtain an air flow rate while reducing pulsation errors in the low flow rate region. [Brief description of the drawings]

[0014] [Figure 1] FIG. 2 is a diagram showing an example of an installation location of an air flow detection device. [Diagram 2] 1 is a diagram showing an example of the configuration of an air flow measuring device according to a first embodiment of the present invention; [Diagram 3] 3 is a diagram illustrating an example of the internal configuration of a laminar flow / turbulent flow determining unit according to the first embodiment of the present invention; FIG. [Figure 4] FIG. 4 is a diagram showing an example of an output characteristic of a first input signal calculation unit with respect to an output signal of the air flow rate detection device according to the first embodiment of the present invention. [Diagram 5] FIG. 4 is a diagram showing an example of an output characteristic of a second input signal calculation unit with respect to an output signal of the air flow rate detection device according to the first embodiment of the present invention. [Figure 6] FIG. 4 is a diagram showing an example of an output characteristic of a switching unit with respect to an output signal of the air flow rate detection device according to the first embodiment of the present invention. [Figure 7] 1 is a block diagram showing an example of a hardware configuration of a computer according to a first embodiment of the present invention. [Figure 8] FIG. 11 is a block diagram showing an example of the configuration of a laminar flow / turbulent flow determining unit according to a second embodiment of the present invention. [Figure 9] FIG. 13 is a block diagram showing an example of the configuration of a laminar flow / turbulent flow determining unit according to a third embodiment of the present invention. [Figure 10] FIG. 13 is a block diagram showing an example of the configuration of a laminar flow / turbulent flow determining unit according to a fourth embodiment of the present invention. [Figure 11] FIG. 13 is a block diagram showing an example of the configuration of a laminar flow / turbulent flow determining unit according to a fifth embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. In this specification and the drawings, components having substantially the same functions or configurations are designated by the same reference numerals, and redundant description will be omitted.

[0016] [First embodiment] First, a configuration example of an air flow measuring device according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 6. FIG. FIG. 1 is a diagram showing an example of an installation location of an air flow detection device according to the first embodiment. FIG. 2 is a diagram showing an example of the configuration of an air flow measurement device 1 according to the first embodiment. FIG. 3 is a diagram showing an example of the configuration of a laminar flow / turbulent flow determination unit 5 shown in FIG. 2. FIG. 4 is a diagram showing an example of the input / output characteristics of a first input signal calculation unit 6 shown in FIG. 2. FIG. 5 is a diagram showing an example of the input / output characteristics of a second input signal calculation unit 7 shown in FIG. 2. FIG. 6 is a diagram showing an example of the output of a switching unit 8 shown in FIG. 2.

[0017] As shown in FIG. 2, the air flow measuring device 1 according to this embodiment includes a calculation unit 3 in addition to the air flow detection device 2 shown in FIG. The air flow detection device (air flow detection device 2) detects an air flow rate Q2 of air moving inside a pipe (e.g., inside the sub-passage 17) shown in Fig. 1 that is the measurement target of the air flow measurement device 1, and generates an input signal Qsen corresponding to the air flow rate Q2. The input signal Qsen is input to the calculation unit 3 as a signal according to the air flow rate Q2 in the sub-passage 17.

[0018] The calculation unit 3 performs a predetermined calculation process on the input signal Qsen input from the air flow rate detection device 2, and outputs an output signal Qout according to the air flow rate. Here, the calculation unit (calculation unit 3) judges whether the air flow is laminar or turbulent based on the input signal Qsen, and outputs the result of calculation using the output result of proportional calculation on the input signal Qsen when the air flow is judged to be laminar, or the result of calculation using the output result of square calculation on the input signal Qsen when the air flow is judged to be turbulent, as an output signal Qout according to the air flow rate. This calculation unit 3 includes a third input signal calculation unit 4, a laminar / turbulent flow judgment unit 5, a first input signal calculation unit 6, a second input signal calculation unit 7, a switching unit 8, a subtraction unit 10, an integration unit 11, an output signal calculation unit 9, and an addition unit 12. Each functional unit of the calculation unit 3 shown in FIG. 2 is assigned with a calculation formula and a value for each term used in equation (5) described later.

[0019] The third input signal calculation unit (third input signal calculation unit 4) performs a predetermined calculation on the input signal Qsen of the air flow detection device 2. For example, the third input signal calculation unit 4 performs a calculation to multiply the air flow rate Q2 represented by the input signal Qsen by a value obtained by dividing the passage length L2 of the sub passage 17 by the passage length L1 of the main passage 18.

[0020] The laminar / turbulent flow determination unit (laminar / turbulent flow determination unit 5) determines whether the airflow flowing around the airflow detection device 2 is laminar or turbulent based on the input signal Qsen of the airflow detection device 2. The laminar / turbulent flow determination unit 5 according to the first embodiment determines whether the airflow is laminar or turbulent by comparing a reference value with the absolute value of the airflow rate Q2.

[0021] The first input signal calculation unit (first input signal calculation unit 6) performs a squaring operation on the input signal Qsen of the air flow rate detection device 2. Through the squaring operation, an output result P2 of the turbulence is obtained for the air flow rate Q2. The second input signal calculation section (second input signal calculation section 7) performs proportional calculation on the input signal Qsen of the air flow detection device 2. By the proportional calculation, an output result P2 of laminar flow is obtained with respect to the air flow rate Q2.

[0022] The switching unit (switching unit 8) switches between the output result of the first input signal calculation unit (first input signal calculation unit 6) and the output result of the second input signal calculation unit (second input signal calculation unit 7) based on the judgment result of the laminar turbulence judgment unit (laminar turbulence judgment unit 5), and outputs the switched output result P2 to the subtraction unit 10. The output signal calculation unit (output signal calculation unit 9) performs a squaring operation on the output signal Qout from the addition unit 12 and outputs an output result P1 to the subtraction unit .

[0023] The subtraction unit (subtraction unit 10) determines the difference between the output result P2 of the first input signal calculation unit (first input signal calculation unit 6) or the output result P2 of the second input signal calculation unit (second input signal calculation unit 7), which is switched by the switching unit 8 (switching unit 8), and the output result P1 of the output signal calculation unit (output signal calculation unit 9). The integrating section (integrating section 11) integrates the difference obtained by the subtracting section (subtracting section 10) and outputs the integration result. The adder unit (adder unit 12) adds the output result of the third input signal calculation unit (third input signal calculation unit 4) and the integration result of the integrator unit (integrator unit 11) to output an output signal Qout of the calculation unit (calculation unit 3).

[0024] Next, the configuration of the laminar / turbulent flow determining unit 5 will be described with reference to FIG. FIG. 3 is a diagram showing an example of the internal configuration of the laminar flow / turbulent flow determining unit 5. As shown in FIG.

[0025] The laminar / turbulent flow determination unit (laminar / turbulent flow determination unit 5) determines whether the airflow is laminar or turbulent based on the instantaneous value of the input signal Qsen. For this purpose, the laminar / turbulent flow determination unit 5 includes an absolute value detection circuit 13, a reference value generation circuit 14, and a comparison unit 15.

[0026] The absolute value detection circuit 13 determines the absolute value of the input signal Qsen of the air flow detection device 2 . The reference value generating circuit 14 generates a reference value. The comparator 15 compares the output of the absolute value detection circuit 13 with the output of the reference value generation circuit 14 . That is, the laminar / turbulent flow determination unit 5 obtains the absolute value of the instantaneous value of the input signal Qsen of the air flow detection device 2 by the absolute value detection circuit 13. Then, the laminar / turbulent flow determination unit 5 outputs the determination result to the switching unit 8 that the flow is turbulent if the absolute value is greater than the output (reference value) of the reference value generation circuit 14, and that the flow is laminar if the absolute value is equal to or less than the output of the reference value generation circuit 14.

[0027] Next, an example of the operation of the first input signal calculation section 6 shown in FIG. 2 will be described with reference to FIG. Fig. 4 is a diagram showing an example of the output characteristics of the first input signal calculation unit 6 with respect to the input signal Qsen of the air flow detection device 2. The horizontal axis of the graph shown in Fig. 4 represents the value of the input signal Qsen of the air flow detection device 2, and the vertical axis represents the output result P2 of the first input signal calculation unit 6.

[0028] When the input signal Qsen of the air flow detection device 2 is positive, the first input signal calculation unit 6 outputs the result of a simple squaring operation on the input signal Qsen. On the other hand, when the input signal Qsen is negative, the first input signal calculation unit 6 performs a squaring operation on the input signal Qsen. Then, the first input signal calculation unit 6 outputs the result of converting the sign of the input signal Qsen to negative. When the input signal Qsen is negative, this indicates that air is flowing backward inside the pipe. For example, when the pulsation amplitude rate increases, the air flowing through the intake pipe 16 begins to flow backward. Through this process, the first input signal calculation unit 6 generates the output signal shown in FIG. 4.

[0029] Next, an example of the operation of the second input signal calculation unit 7 shown in FIG. 2 will be described with reference to FIG. Fig. 5 is a diagram showing an example of the output characteristics of the second input signal calculation unit 7 with respect to the input signal Qsen of the air flow detection device 2. The horizontal axis of the graph shown in Fig. 5 represents the value of the input signal Qsen of the air flow detection device 2, and the vertical axis represents the output result P2 of the second input signal calculation unit 7.

[0030] The second input signal calculation unit 7 outputs the result of proportional calculation of the input signal Qsen of the air flow detection device 2. Through such processing, the second input signal calculation unit 7 generates the output signal shown in FIG.

[0031] Next, an example of the operation of the switching unit 8 shown in FIG. 2 will be described with reference to FIG. Fig. 6 is a diagram showing an example of the output characteristics of the switching unit 8 with respect to the input signal Qsen of the air flow detection device 2. The horizontal axis of the graph shown in Fig. 6 represents the value of the input signal Qsen of the air flow detection device 2, and the vertical axis represents the output result P2 of the switching unit 8.

[0032] The switching unit 8 switches between the output of the first input signal calculation unit 6 and the output of the second input signal calculation unit 7 according to the instantaneous value of the output of the laminar / turbulent flow determination unit 5. The laminar / turbulent flow determination unit 5 determines that the airflow is turbulent if the absolute value of the instantaneous value of the input signal Qsen of the air flow detection device 2 is greater than the output of the reference value generation circuit 14, and outputs a determination result that the airflow is laminar if the absolute value of the instantaneous value of the input signal Qsen is equal to or less than the output of the reference value generation circuit 14. Then, the switching unit 8 outputs the output result of the first input signal calculation unit 6 when a determination result that the airflow is turbulent is input. On the other hand, the switching unit 8 outputs the output result of the second input signal calculation unit 7 when a determination result that the airflow is laminar is input.

[0033] 6 shows examples of transition points (1) and (2) used when determining whether a flow is turbulent or laminar by the switching unit 8. The transition points (1) and (2) are points at which the determination result of laminar flow or turbulent flow is switched, and correspond to values ​​generated as reference values ​​by the reference value generating circuit 14 shown in FIG.

[0034] For example, if the intake pipe 16 has a symmetrical shape with respect to the installation position of the air flow detection device 2, the transition points (1) and (2) are set at positions equidistant in the positive and negative directions from "0" of the input signal Qsen of the air flow detection device 2. In other words, the transition points (1) and (2) are values ​​output from the reference value generating circuit 14 as reference values.

[0035] 6, the output of the switching unit 8 becomes the output of the second input signal calculation unit 7 (output proportional to the input signal Qsen of the air flow detection device 2) when the absolute value of the instantaneous value of the input signal Qsen of the air flow detection device 2 is smaller than the output of the reference value generation circuit 14. On the other hand, the output of the switching unit 8 becomes the output of the first input signal calculation unit 6 (output obtained by squaring the input signal Qsen of the air flow detection device 2) when the absolute value of the instantaneous value of the input signal Qsen of the air flow detection device 2 is greater than the output of the reference value generation circuit 14. In FIG. 6, the determination result (laminar flow or turbulent flow), which is the output of the switching unit 8, is shown based on the transition points (1) and (2).

[0036] If the intake pipe 16 has an asymmetric shape, the value of the transition point changes depending on whether the airflow is forward or reverse. For example, if the intake pipe 16 is narrowed, expanded, or bent, the intake pipe 16 is likely to have an asymmetric shape. In this case, two comparison units 15 may be provided in accordance with each transition point, and the two comparison units 15 may determine whether the flow is laminar or turbulent depending on each transition point.

[0037] Next, an example of the arrangement of the air flow measuring device 1 in an intake pipe 16 will be described with reference to Fig. 1. An air flow Q flows into the intake pipe 16, which is provided with a main passage 18 and a sub-passage 17, and the air flow detection device 2 is installed in the sub-passage 17.

[0038] Next, an example of the operation of the air flow measuring device 1 will be described. As shown in Fig. 1, the air flow with an air flow rate Q flowing through the intake pipe 16 is divided into the main passage 18 and the sub passage 17. If the flow rate in the main passage 18 is Q1 and the flow rate in the sub passage 17 is Q2, the pressure difference Δp between the upstream surface A and the downstream surface B of the main passage 18 is expressed as follows from the Navier-Stokes equations.

[0039]

number

[0040] Here, the constants in equations (1) and (2) are defined as follows: ρ: Fluid density Δp: Pressure difference between surface A and surface B L1: Length of main aisle 18 L2: Length of secondary passage 17 C1: Loss coefficient of main passage 18 C2: Loss coefficient of sub-passage 17

[0041] Here, by substituting equation (2) into equation (1) to calculate the flow rate Q1, we obtain the following equation (3).

[0042]

number

[0043] Here, since Q=Q1+Q2, the air flow rate Q of the air flowing through the intake pipe 16 is expressed by the following equation (4).

[0044]

number

[0045] Here, if it can be assumed that the flow rate Q2 is sufficiently smaller than the flow rate Q1, the flow rate Q of the air flowing through the intake pipe 16 is expressed by the following equation (5).

[0046]

number

[0047] Since the air flow rate measured by the air flow measuring device 1 is the flow rate Q2 in the bypass passage 17, the air flow rate measuring device 1 can calculate the air flow rate Q from the flow rate Q2 at every moment by solving equation (5). This holds true even if the air flow rate Q flowing through the intake pipe 16 is in a pulsating state, and the air flow rate Q flowing through the intake pipe 16 can be calculated from the flow rate Q2 in the bypass passage 17 at every moment.

[0048] That is, the air flow measuring device 1 can accurately determine the flow rate Q through the intake pipe 16 without being affected by pulsation, regardless of the pulsation state of the flow rate Q through the intake pipe 16. In other words, pulsation errors caused by pulsation can be eliminated. Furthermore, the air flow measuring device 1 according to this embodiment can constantly determine the air flow rate Q through the intake pipe 16 from the flow rate Q2 in the bypass passage 17, even if the pulsation waveform is not a sine wave but a distorted waveform including harmonics, so that pulsation errors can be reduced.

[0049] In the above-mentioned Patent Document 1, the loss coefficient C1 of the main passage 18 and the loss coefficient C2 of the sub-passage 17 are considered to be fixed values. However, when the air flow is laminar, the loss coefficient is inversely proportional to the flow rate. In other words, the pressure difference Δp is proportional to the air flow rate. Since Patent Document 1 did not take this into consideration, the pulsation error increased at low flow rates.

[0050] In particular, since the passage width of the sub-passage 17 is narrower than that of the main passage 18, the transition from laminar flow to turbulent flow has a large effect on the sub-passage 17, which maintains a laminar flow state up to a higher flow rate. For this reason, in this embodiment, the configuration shown in Fig. 2 is adopted, which makes it possible to calculate equation (5) that takes into account the transition from laminar flow to turbulent flow when calculating the sub-passage 17 side. If the air flow measuring device 1 is in a high flow rate range where the flow rate Q2 of the sub-passage 17 becomes turbulent, the first term in the integral of equation (5) is changed to the output of the first input signal calculation unit 6.

[0051] On the other hand, in the low flow rate range where the flow rate Q2 in the secondary passage 17 becomes laminar (for example, the flow velocity during idling is 1 m / sec or less), the air flow measuring device 1 changes the first term in the integral of equation (5) to the output of the second input signal calculation unit 7. Therefore, even in the low flow rate range where the flow rate Q2 in the secondary passage 17 becomes laminar, the air flow measuring device 1 can obtain the air flow rate Q flowing through the intake pipe 16 from the flow rate Q2 in the secondary passage 17 with higher accuracy from moment to moment. Therefore, the air flow measuring device 1 can provide a pulsation error correction process that can reduce pulsation errors in the low flow rate range more than ever before.

[0052] <Computer hardware configuration> Next, the hardware configuration of the computer 30 constituting the air flow measuring device 1 will be described. Fig. 7 is a block diagram showing an example of a hardware configuration of calculator 30. Calculator 30 is an example of hardware used as a computer capable of operating as air flow measuring device 1 according to this embodiment. Air flow measuring device 1 according to this embodiment can realize an air flow measuring method in which each functional block shown in Fig. 2 cooperates with each other by causing calculator 30 (computer) to execute a program.

[0053] The computer 30 includes a central processing unit (CPU) 31, a read only memory (ROM) 32, and a random access memory (RAM) 33, each of which is connected to a bus . Furthermore, the computer 30 includes a non-volatile storage 35 and a network interface .

[0054] The CPU 31 reads out program code of software for implementing each function according to the present embodiment from the ROM 32, loads it into the RAM 33, and executes it. Variables, parameters, etc. generated during the arithmetic processing of the CPU 31 are temporarily written into the RAM 33, and these variables, parameters, etc. are read out by the CPU 31 as appropriate. However, an MPU (Micro Processing Unit) may be used instead of the CPU 31. Each function of the arithmetic unit 3 shown in FIG. 2 is implemented by a program executed by the CPU 31.

[0055] The nonvolatile storage 35 may be, for example, a hard disk drive (HDD), a solid state drive (SSD), a flexible disk, an optical disk, a magneto-optical disk, a CD-ROM, a CD-R, a magnetic tape, or a nonvolatile memory. In addition to an operating system (OS) and various parameters, a program for making the computer 30 function is recorded in the nonvolatile storage 35. The ROM 32 and the nonvolatile storage 35 record programs and data necessary for the CPU 31 to operate, and are used as an example of a computer-readable non-transient storage medium that stores a program executed by the computer 30.

[0056] For example, a NIC (Network Interface Card) or the like is used for the network interface 36, and various data can be transmitted and received between devices via a LAN (Local Area Network), a dedicated line, etc. connected to a terminal of the NIC. For example, the output signal Qout is output through the network interface 36 to an external device (another electronic control device, etc.) connected to the air flow measuring device 1.

[0057] In the air flow measuring device 1 according to the first embodiment described above, the calculation unit 3 switches the output result taking into account the transition between laminar flow and turbulent flow, so that a result with reduced pulsation error can be obtained. Therefore, even in a low flow rate region, it is possible to obtain an accurate air flow measurement result with reduced pulsation error.

[0058] [Second embodiment] Next, an example of the configuration of an air flow measuring device according to a second embodiment of the present invention will be described with reference to FIG. FIG. 8 is a block diagram showing an example of the configuration of a laminar flow / turbulent flow determining unit 5A according to the second embodiment.

[0059] The air flow measuring device 1 according to the second embodiment is basically the same as the air flow measuring device 1 according to the first embodiment, but is different in that it includes a laminar turbulence determining unit 5A in which the configuration of the laminar turbulence determining unit 5 is changed as shown in FIG. 8. The laminar turbulence determining unit 5A according to the second embodiment has a function of determining whether the air flow is laminar or turbulent, basically in the same way as the laminar turbulence determining unit 5 according to the first embodiment. However, the laminar turbulence determining unit (laminar turbulence determining unit 5A) determines whether the air flow is laminar or turbulent based on the differential value of the input signal Qsen. Therefore, the laminar turbulence determining unit 5A is provided with a differentiation circuit 19 that differentiates the input signal Qsen, and a subtraction unit 20 (an example of a second subtraction unit) that determines the difference between the input signal Qsen and the output of the differentiation circuit 19.

[0060] The flow speed at which a laminar flow transitions to a turbulent flow depends on the flow speed in a steady flow; when the flow speed is low, the flow is laminar, and when the flow speed is high, the flow is turbulent. However, in an accelerating flow, the flow speed at which the laminar flow transitions to a turbulent flow increases as the acceleration increases, and in a decelerating flow, the flow speed at which the laminar flow transitions to a turbulent flow decreases as the acceleration increases. The air flow measuring device 1 according to the second embodiment handles a pulsating flow, and therefore repeats accelerating and decelerating flows.

[0061] To deal with this, in the second embodiment, a differentiation circuit 19 is provided to obtain the acceleration of the flow velocity, and a subtraction unit 20 is provided to obtain the difference between the input signal Qsen and the output value of the differentiation circuit 19. The greater the acceleration of the flow velocity, the greater the flow velocity subtracted from the input signal Qsen by the subtraction unit 20. Conversely, the smaller the acceleration of the flow velocity, the smaller the flow velocity subtracted from the input signal Qsen.

[0062] Therefore, by providing the subtraction unit 20, the laminar flow / turbulent flow determination unit 5A can more accurately determine the transition point between laminar flow and turbulent flow due to acceleration (see FIG. 6). The transition point is determined by the comparison unit 15 as in the first embodiment, but in this embodiment, the transition point is compensated for the change in acceleration. As a result, the air flow measuring device 1 according to the second embodiment can provide a pulsation error correction process that can reduce pulsation error in the low flow rate range more than ever before.

[0063] [Third embodiment] Next, an example of the configuration of an air flow measuring device according to a third embodiment of the present invention will be described with reference to FIG. FIG. 9 is a block diagram showing an example of the configuration of a laminar flow / turbulent flow determining unit 5B according to the third embodiment.

[0064] The air flow measuring device 1 according to the third embodiment is basically the same as the air flow measuring device 1 according to the first embodiment, but is different in that it includes a laminar turbulence determining unit 5B in which the configuration of the laminar turbulence determining unit 5 is changed as shown in FIG. 9. The laminar turbulence determining unit 5B according to the third embodiment has a function of determining whether the air flow is laminar or turbulent, basically in the same manner as the laminar turbulence determining unit 5 according to the first embodiment. However, the laminar turbulence determining unit (laminar turbulence determining unit 5B) determines whether the air flow is laminar or turbulent based on the average value of the input signal Qsen. Therefore, the laminar turbulence determining unit 5B is provided with an average value calculation circuit 21 that calculates the average value of the input signal Qsen, and an adder 22 that calculates the sum of the input signal Qsen and the output of the average value calculation circuit 21.

[0065] The flow velocity at which a steady flow transitions from laminar to turbulent flow depends on the flow velocity; when the flow velocity is low, the flow becomes laminar, and when the flow velocity is high, the flow becomes turbulent. However, in a pulsating flow, the average value of the flow velocity is easily affected. To address this, in the third embodiment, an average value calculation circuit 21 is provided to calculate the average value of the flow velocity, and an adder 22 is provided to add the input signal Qsen and the average value output by the average value calculation circuit 21. The larger the average value of the flow velocity, the larger the flow velocity added to the input signal Qsen by the adder 22. Conversely, the smaller the average value of the flow velocity, the smaller the flow velocity added to the input signal Qsen by the adder 22.

[0066] Therefore, by providing the adder 22, the laminar / turbulent flow determination unit 5B can more accurately determine the transition point between laminar flow and turbulent flow (see FIG. 6) based on the average flow velocity. The transition point is determined by the comparison unit 15, as in the first embodiment. As a result, the air flow measuring device 1 according to the third embodiment can provide a pulsation error correction process that can reduce pulsation errors in the low flow rate range more than ever before.

[0067] [Fourth embodiment] Next, an example of the configuration of an air flow measuring device according to a fourth embodiment of the present invention will be described with reference to FIG. FIG. 10 is a block diagram showing an example of the configuration of a laminar flow / turbulent flow determining unit 5C according to the fourth embodiment.

[0068] The air flow measuring device 1 according to the fourth embodiment is basically the same as the air flow measuring device 1 according to the first embodiment, but is different in that it includes a laminar turbulence determining unit 5C in which the configuration of the laminar turbulence determining unit 5 is changed as shown in FIG. 10. The laminar turbulence determining unit 5C according to the fourth embodiment has a function of determining whether the air flow is laminar or turbulent, basically in the same way as the laminar turbulence determining unit 5 according to the first embodiment. However, the laminar turbulence determining unit (laminar turbulence determining unit 5C) determines whether the air flow is laminar or turbulent based on the time function of the input signal Qsen. Therefore, a time function circuit 23 that delays the input signal Qsen is added to the laminar turbulence determining unit 5C.

[0069] The transition from laminar flow to turbulent flow, or from turbulent flow to laminar flow, does not occur immediately when a predetermined flow velocity is reached, but is delayed in time. To address this, in the fourth embodiment, a time function circuit 23 is provided to delay the input signal Qsen, thereby making it possible to more accurately determine the transition point between laminar flow and turbulent flow (see FIG. 6). Here, the time function is a function that delays the input signal Qsen, as described above. Since a growth time is required for an air flow to become a laminar flow, a process is performed to delay the signal by the growth time. As a result, the air flow measuring device 1 according to the fourth embodiment can provide a pulsation error correction process that can reduce the pulsation error in the low flow rate range more than in the past.

[0070] [Fifth embodiment] Next, an example of the configuration of an air flow measuring device according to a fifth embodiment of the present invention will be described with reference to FIG. FIG. 11 is a block diagram showing an example of the configuration of a laminar flow / turbulent flow determining unit 5D according to the fifth embodiment.

[0071] The air flow measuring device 1 according to the fifth embodiment is basically the same as the air flow measuring device 1 according to the first embodiment, but is different in that it includes a laminar turbulence determining unit 5D in which the configuration of the laminar turbulence determining unit 5 is changed as shown in FIG. 11. The laminar turbulence determining unit 5D according to the fifth embodiment has a function of determining whether the air flow is laminar or turbulent, basically in the same way as the laminar turbulence determining unit 5 according to the first embodiment. However, the laminar turbulence determining unit (laminar turbulence determining unit 5D) determines whether the air flow is laminar or turbulent based on the amount of noise in the input signal Qsen. Therefore, a noise amount detection circuit 24 that detects the amount of noise in the input signal Qsen is added to the laminar turbulence determining unit 5D.

[0072] The transition from laminar flow to turbulent flow is difficult to grasp accurately because it is affected by flow speed, acceleration, delay, etc. However, it is known that the turbulence of the air flow changes between laminar flow and turbulent flow. Such turbulence of the air flow is called "noise." In turbulent flow, vortices are generated in the flow path and the flow speed changes, so the noise is large. On the other hand, in laminar flow, there are no vortices and the flow speed does not change, so the noise is small. Therefore, the comparison unit 15 can determine the difference between laminar flow and turbulent flow by the noise level. Therefore, laminar flow and turbulent flow can be distinguished by detecting the noise level of the input signal Qsen of the air flow detection device 2. In the fifth embodiment, a noise level detection circuit 24 is provided to make it possible to obtain the transition between laminar flow and turbulent flow. As a result, the air flow measurement device 1 according to the fifth embodiment can provide a pulsation error correction process that can reduce the pulsation error in the low flow rate range more than before.

[0073] [Variations] The air flow measuring device 1 according to each of the above-mentioned embodiments is configured by an electronic control device mounted on a vehicle or the like. The calculation unit 3 according to each of the embodiments may be one function of the electronic control device. This electronic control device may be used as a device capable of measuring the air flow rate in a pipe in which the air flow detection device 2 is installed, other than in a vehicle.

[0074] Incidentally, the present invention is not limited to the above-described embodiments, and it goes without saying that various other applications and modifications are possible without departing from the gist of the present invention as set forth in the claims. For example, each of the above-mentioned embodiments describes the configuration of the device in detail and specifically in order to explain the present invention in an easily understandable manner, and is not necessarily limited to having all of the configurations described. In addition, it is possible to replace a part of the configuration of the embodiment described here with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. In addition, it is also possible to add, delete, or replace a part of the configuration of each embodiment with another configuration. In addition, the control lines and information lines shown are those that are considered necessary for the explanation, and not all control lines and information lines in the product are necessarily shown. In reality, it can be considered that almost all components are connected to each other. [Explanation of symbols]

[0075] 1...air flow rate measuring device, 2...air flow rate detection device, 3...calculation section, 4...third input signal calculation section, 5, 5A to 5D...laminar flow / turbulent flow determination section, 6...first input signal calculation section, 7...second input signal calculation section, 8...switching section, 9...subtraction section, 10...integration section, 11...output signal calculation section, 12...addition section, 13...absolute value detection circuit, 14...reference value generation circuit, 15...comparator, 16...intake pipe, 17...secondary passage, 18...main passage

Claims

1. an air flow rate detector that detects an air flow rate of an air stream moving through the pipe and generates an input signal corresponding to the air flow rate; a calculation unit that determines whether the air flow is laminar or turbulent based on the input signal, and outputs, as an output signal corresponding to the air flow rate, a result of calculation using an output result of a proportional calculation performed on the input signal when the air flow is determined to be laminar, or a result of calculation using an output result of a square calculation performed on the input signal when the air flow is determined to be turbulent. Air flow measuring device.

2. The calculation unit is a first input signal calculation unit that performs a square operation on the input signal; A second input signal calculation unit that performs a proportional calculation on the input signal; a third input signal calculation unit that performs a calculation on the input signal based on a length of a pipe in which the air flow detection device is installed; a laminar / turbulent flow determination unit that determines whether the air flow is laminar or turbulent; a switching unit that switches between an output result of the first input signal calculation unit and an output result of the second input signal calculation unit based on a determination result of the laminar flow / turbulent flow determination unit; an output signal calculation unit that performs a square operation on the output signal; a subtraction unit that calculates a difference between an output result of the first input signal calculation unit or an output result of the second input signal calculation unit, which is switched by the switching unit, and an output result of the output signal calculation unit; an integration unit that integrates the difference and outputs the integration result; an adder that outputs the output signal obtained by adding the output result of the third input signal calculation unit and the integration result; 2. The air flow rate measuring device according to claim 1.

3. The laminar / turbulent flow determination unit determines whether the air flow is a laminar flow or a turbulent flow based on an instantaneous value of the input signal.

3. The air flow rate measuring device according to claim 2.

4. The laminar / turbulent flow determination unit determines whether the air flow is a laminar flow or a turbulent flow based on a differential value of the input signal.

3. The air flow rate measuring device according to claim 2.

5. The laminar / turbulent flow determination unit determines whether the air flow is a laminar flow or a turbulent flow based on an average value of the input signal.

3. The air flow rate measuring device according to claim 2.

6. The laminar / turbulent flow determination unit determines whether the air flow is laminar or turbulent based on a time function of the input signal.

3. The air flow rate measuring device according to claim 2.

7. The laminar / turbulent flow determination unit determines whether the air flow is a laminar flow or a turbulent flow based on an amount of noise in the input signal.

3. The air flow rate measuring device according to claim 2.

8. An air flow rate measuring method performed by an air flow rate measuring device including an air flow rate detection device that detects an air flow rate of an air flow moving through a pipe and a calculation unit, the air flow detection device detecting the air flow and generating an input signal corresponding to the air flow; The calculation unit determines whether the air flow is laminar or turbulent based on the input signal, and outputs, as an output signal corresponding to the air flow rate, a result of calculation using an output result of a proportional calculation performed on the input signal when the air flow is determined to be laminar, or a result of calculation using an output result of a square calculation performed on the input signal when the air flow is determined to be turbulent. Air flow measurement method.

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