Flow rate measurement system

Abstract

A flow rate measuring system that outputs a measured value (Q) representing a magnitude of a flow rate and a flow direction of a fluid flowing through a specific main passage (50) in which backflow may occur, the flow rate measuring system comprising: a housing (45) comprising a bypass passage (49) that receives a portion of the fluid flowing through the main passage and directs the portion of the fluid back into the main passage, the housing being disposed in the main passage; a detection unit (46) arranged in the bypass passage and outputting a detection value (QA) corresponding to a magnitude of a flow rate and a flow direction of the fluid flowing through the bypass passage; and a calculation unit (47) which performs an arithmetic operation using the detection value to output the measured value, wherein the calculation unit calculates the measured value by compensating for a delay in the change in the flow rate in the bypass passage with respect to the change in the flow rate in the main passage as required, the calculation unit performs an arithmetic operation required for the compensation using at least one of loss coefficients (Cs, Cb) of the main passage or the bypass passage and selectively uses one of at least two calculation methods depending on whether a magnitude of the loss coefficient is small or a magnitude of the loss coefficient is large, and the calculation unit comprises a determination unit (S301) that determines whether the flow direction in the main passage and / or the bypass passage has changed, uses a large-side calculation method related to the calculation of the loss coefficient having a numerical value if the determination unit determines that the flow direction has changed, and uses a small-side calculation method related to the calculation of the loss coefficient having a numerical value if the determination unit determines that the flow direction has not changed, wherein the numerical value of the large-side calculation method is much larger than the numerical value calculated by a map or mathematical expression of the small-side calculation method.

Description

Technical area

[0001] The present disclosure relates to a flow rate measuring system for outputting a measured value indicative of a magnitude of a flow rate and a flow direction of a fluid flowing through a predetermined main passage, and more particularly, to an apparatus for measuring a flow rate of intake air drawn into an internal combustion engine. General state of the art

[0002] To date, a flow rate measuring system as described above comprises a housing, a detection unit and a calculation unit.

[0003] In other words, the housing has a bypass passage for receiving a portion of a fluid flowing through a main passage and returning the portion of the fluid to the main passage, and is disposed in the main passage. The detection unit is disposed in the bypass passage and outputs a detection value corresponding to a magnitude of a flow rate of the fluid flowing through the bypass passage and a direction of the fluid flow. Further, the calculation unit performs an arithmetic operation to output a measured value using the detection value.

[0004] For example, when the flow rate measurement system is applied to measuring the intake air flow rate of an internal combustion engine for a vehicle, the functions of the housing and the detection unit are provided in an air flow meter with a known structure. The function of the calculation unit is provided in an electronic control unit (ECU) for controlling an operating state of the internal combustion engine.

[0005] Since it is known that a change in the flow rate in the bypass passage lags behind a change in the flow rate in the main passage, the calculation unit in the flow rate measurement system described above has a function for compensating for the above delay (for example, refer to Patent Literature 1). In other words, since the detection value by the detection unit lags behind an actual flow rate at the same time in the main passage, the calculation unit compensates for the delay of the detection value as a calculation to output the measured value.

[0006] Incidentally, in the calculation for the delay compensation, equations of motion of the fluid in the main passage and the bypass passage are used, and the equations of motion include the respective loss coefficients of the main passage and the bypass passage.

[0007] However, when the flow direction is switched from forward to reverse or from reverse to forward, the flow is disturbed and the loss increases rapidly. Therefore, there is a possibility that the accuracy of the measured value at the time of the flow direction change may be reduced. State of the art literaturePatent literature

[0008] Patent literature 1: JP 4 072 860 B2

[0009] US 5 817 932 A discloses the following: An intake air flow measuring device for an internal combustion engine has a thermal type air flow meter, a response delay correcting unit of the thermal type air flow meter, and a unit for detecting the direction of intake air flow, such that an amount of reverse air flow is detected by the response delay correcting unit and the air flow direction unit, and a true amount of intake air flow is calculated from the output of the thermal type air flow meter and the amount of reverse air flow.

[0010] JP 2000 - 320 391 A discloses the following: A model for compensating the response delay in bypass-type thermal air flow meters is used to compensate for the response delay in a thermal air flow meter at the outlet or to calculate a true bypass flow. A fluid motion model for simulating the relationship between a bypass flow and a main flow is then used to process the true bypass flow or to calculate a main flow. The pulse waveform of the main flow has a discrete normal and counterflow peak.At prescribed time intervals, the maximum and minimum values ​​of the last section of the main flow impulse curve corresponding to a given crank angle are recorded, distinguishing between peaks and troughs. The largest maximum value of all peaks is determined as the normal flow component, and those lying between the normal flow component are determined as the counterflow component. The main flow is then compensated for the counterflow components, and the true intake air flow is determined. Summary of the invention

[0011] It is an object of the present disclosure to prevent a decrease in measurement accuracy when a flow direction is changed in a flow rate measuring system that measures a flow rate in a main passage in which backflow may occur.

[0012] The object is achieved by a flow rate measuring system having the features of claim 1 and by a flow rate measuring system having the features of claim 3. Further advantageous embodiments and further developments are the subject of the subsequent claims.

[0013] A flow rate measuring system according to the present disclosure outputs a measured value representing a magnitude of a flow rate and a flow direction of a fluid flowing through a specific main passage in which backflow may occur, and includes a housing, a detection unit, and a calculation unit.

[0014] The housing includes a bypass passage that receives a portion of the fluid flowing through the main passage and guides the portion of the fluid back into the main passage, with the housing disposed in the main passage. The detection unit is disposed in the bypass passage and outputs a detection value corresponding to a magnitude, a flow rate, and a flow direction of the fluid flowing through the bypass passage. The calculation unit performs an arithmetic operation using the detection value to output the measured value.

[0015] The calculation unit calculates the measured value by compensating for a delay in the flow rate change in the bypass passage with respect to the flow rate change in the main passage, as needed. Further, the calculation unit performs an arithmetic operation required for the compensation using at least one of the loss coefficients of the main passage or the bypass passage, and selectively uses one of at least two calculation methods depending on whether a magnitude of the loss coefficient is small or a magnitude of the loss coefficient is large.

[0016] In addition, the calculation unit includes a determination unit that determines whether the flow direction in the main passage and / or the bypass passage has changed or not, uses a large side calculation method related to the calculation of the loss coefficient if the determination unit determines that the flow direction has changed, and uses a small side calculation method related to the calculation of the loss coefficient if the determination unit determines that the flow direction has not changed.

[0017] Therefore, even if the flow loss increases rapidly with a change in flow direction, delay compensation can be performed with high accuracy by calculating the loss coefficient using a large-scale calculation method. Therefore, the deterioration of measurement accuracy during flow direction switching can be reduced in the flow rate measurement system. Short description of the figures

[0018] The above and other objects, features, and advantages of the present disclosure will become more apparent from the following detailed description with reference to the accompanying drawings. In the drawings: Fig. 1 a configuration diagram of an entire control system of an internal combustion engine, Fig. 2 is a cross-sectional view showing a configuration of an air flow meter, Fig. 3 a block diagram showing a calculation unit, Fig. 4 a flowchart showing the processing of a main routine, Fig. 5 is a flowchart showing the processing of a first subroutine, Fig. 6 is a flowchart showing the processing of a second subroutine, and Fig. 7 is a block diagram showing a heat radiation reference unit. Embodiments for carrying out the invention

[0019] Embodiments for carrying out the present disclosure will be described below using examples. It should be noted that the examples disclose concrete examples, and it should be understood that the present disclosure is not limited to the examples. (Embodiment)

[0020] The configuration of a flow rate measuring system 1 according to an embodiment will be described with reference to the figures. The flow rate measuring system 1 may be abbreviated as the measuring system 1. In the present embodiment, the measuring system 1 is used to measure the intake air flow rate of an internal combustion engine for a vehicle. The internal combustion engine is sometimes abbreviated as an engine 2.

[0021] Therefore, a schematic configuration of the entire control system of the engine 2 is described above with reference to Fig. 1 described.

[0022] The control system of the engine 2 includes an electronic control unit (ECU) 3 for controlling an operating state of the engine 2.

[0023] In the engine 2, an air flow meter 5 for detecting a flow rate of intake air is provided at an upstream portion of an intake pipe 4. A throttle valve 8, whose opening degree is adjusted by a throttle actuator 7 such as a DC motor, is provided on a downstream side of the air flow meter 5. The throttle opening of the throttle valve 8 (throttle opening degree) is detected by a throttle opening sensor 9 integrally provided with the throttle actuator 7. A surge tank 10 is provided downstream of the throttle valve 8, and an intake manifold 11 leading to an intake port of each cylinder is attached to the surge tank 10.

[0024] The intake port and an exhaust port of the engine 2 are provided with an intake valve and an exhaust valve, respectively (both are not shown). The engine 2 is provided with a fuel injection valve 12 and a spark plug 13 for each cylinder.

[0025] An exhaust manifold 15 is connected to an exhaust port of the engine 2, and an exhaust pipe 16 is connected to a collecting portion of the exhaust manifold 15. The exhaust pipe 16 is provided with a catalyst 17 for purifying harmful components in the exhaust gas. Note: An air-fuel ratio sensor 18 for detecting an air-fuel ratio of an air-fuel mixture in the exhaust gas as a detection target is provided on an upstream side of the catalyst 17.

[0026] A turbocharger 20 is provided between the intake pipe 4 and the exhaust pipe 16. The turbocharger 20 includes an intake compressor 21 disposed upstream of the throttle valve 8 in the intake pipe 4, an exhaust turbine 22 disposed upstream of the catalyst 17 in the exhaust pipe 16, and a rotating shaft 23 connecting the intake compressor 21 and the exhaust turbine 22. When the exhaust turbine 22 is rotated by the exhaust gas flowing through the exhaust pipe 16, the intake compressor 21 is rotated along with the rotation of the exhaust turbine 22, and the intake air is compressed and supercharged by a compression force generated by the rotation of the intake compressor 21.

[0027] The intake pipe 4 is provided with an intercooler 24 as a heat exchanger for cooling the supercharged intake air on the downstream side of the throttle valve 8. The intake air is cooled by the intercooler 24, thereby preventing a decrease in air charging efficiency. The intercooler 24 is, for example, a water-cooled type, and is arranged in a path deviating from a cooling water path of the engine 2. In the embodiment, the intercooler 24 is provided integrally with the surge tank 10.

[0028] The upstream and downstream sides of the exhaust turbine 22 communicate via an exhaust bypass passage 26, and a wastegate valve 27 is provided in the exhaust bypass passage 26 for opening and closing the exhaust bypass passage 26. The wastegate valve 27 may be referred to as a WGV 27. The amount of exhaust gas supplied to the exhaust turbine 22 increases or decreases according to the opening or closing of the WGV 27 to adjust the rotational speeds of the exhaust turbine 22 and the intake compressor 21.

[0029] The upstream and downstream sides of the intake compressor 21 communicate with each other via an intake bypass passage 28, and an air bypass valve 29 is provided in the intake bypass passage 28 for opening and closing the intake bypass passage 28. The air bypass valve 29 may be referred to as an ABV 29. The ABV 29 is opened to release excessive pressure between the turbocharger 20 and the throttle valve 8, thereby preventing turbo surging.

[0030] The engine 2 is equipped with an EGR device 31 that recirculates a portion of the exhaust gas to the intake pipe 4. The EGR device 31 includes an EGR line or pipe 32 connecting the intake pipe 4 and the exhaust pipe 16, an electromagnetically driven EGR valve 33 for adjusting the flow rate of the exhaust gas flowing through the EGR pipe 32, and an EGR cooler 34 as a heat exchanger for cooling the exhaust gas. The EGR cooler 34 is, for example, a water-cooled type and is located in a cooling water path of the engine 2.

[0031] The EGR pipe 32 connects the downstream side of the exhaust turbine 22 and the catalyst 17 in the exhaust pipe 16 and the upstream side of the intake compressor 21 in the intake pipe 4. For this reason, the EGR device 31 is a so-called low-pressure cycle exhaust gas recirculation system.

[0032] The control system of the engine 2 includes various sensors such as a crank angle sensor 36 for outputting a crank angle signal at every predetermined crank angle of the engine 2, a water temperature sensor 37 for detecting a coolant water temperature of the engine 2, an intake air temperature sensor 38 for detecting a temperature of the intake air, a humidity sensor 39 for detecting a humidity of an outside air, an outside air temperature sensor 40 for detecting an outside air temperature, and an atmospheric pressure sensor 41 for detecting an atmospheric pressure.

[0033] The ECU 3 is mainly configured by a microcomputer 43 including CPUs, ROMs, RAMs, and the like, as known, and executes various control programs stored in the ROM to perform various controls of the engine 2. In other words, the microcomputer 43 controls the operation of the throttle valve 8, the fuel injection valve 12, the spark plug 13, the EGR valve 33, the WGV 27, the ABV 29, and the like based on the detection values ​​input from the various sensors.

[0034] The measuring system 1 is then described in detail.

[0035] The flow rate measuring system 1 includes a housing 45 and a detection unit 46 which configure the air flow meter 5, and a calculation unit 47 which corresponds to part of the functions of the ECU 3.

[0036] First, the housing 45 and the detection unit 46 are assembled using the Fig. 2 shown air flow meter 5 is described.

[0037] The housing 45 has a bypass passage 49 for receiving a portion of the fluid flowing in the intake pipe 4 and returning the portion of the fluid to the intake pipe 4, and is arranged in the intake pipe 4. The fluid passage in the intake pipe 4 may be referred to as a main passage 50. In this example, the bypass passage 49 has a first passage portion 51 extending straight substantially parallel to the flow of the main passage 50, and a second passage portion 52 branching off from the first passage portion 51 and swirling the flow direction in the housing 45. An outlet 51g of the first passage portion 51 and outlets 52g of the second passage portion 52 are provided separately. In the present embodiment, the bypass passage 49 may be referred to as a housing passage.

[0038] The second passage section 52 is provided so that the flow direction is rotated by 360°, and it further branches into two sections to accommodate the first passage section 51 on the upstream side of the branching position therebetween. For this reason, there are two outlets 52g, and the two outlets 52g are both open to the downstream side.

[0039] An inlet 49i of the bypass passage 49 is provided so as to open toward the upstream side in the housing 45. In addition, the outlet 51g is located downstream of the inlet 49i and the two outlets 52g, and both outlets 52g are located between the inlet 49i and the outlet 51g along the flow direction.

[0040] With the configuration described above, in the bypass passage 49, dust or the like contained in the fluid directly migrates through the first passage portion 51 and returns to the main passage 50 from the outlet 51g, and the fluid with reduced dust or the like passes through the second passage portion 52.

[0041] The detection unit 46 is provided, for example, as an arrangement that accommodates a sensitive unit 54 and a processing unit 55 as follows.

[0042] The sensitive unit 54 is a section for outputting a signal corresponding to the magnitude of the flow rate of the fluid flowing through the second passage portion 52 and the flow direction of the fluid, and has, for example, a known structure. In other words, the sensitive unit 54 is a thermal flow rate sensor having a known structure including a heat-generating resistor element for increasing or decreasing the amount of heat generated by energization, and a plurality of temperature-measuring resistor elements arranged on the upstream and downstream sides of the heat-generating resistor in the flow direction in the second passage portion 52, on a substrate surface.

[0043] Furthermore, the sensitive unit 54 is arranged to protrude from the second passage portion 52, and the heat generating resistor element and the temperature measuring resistor are exposed to the flow of the second passage portion 52, and a temperature difference is generated between the temperature measuring resistor elements provided on the upstream side and the downstream side by heat radiation from the heat generating resistors to the fluid.

[0044] Subsequently, the energization or excitation of the heat generation resistor is controlled so that the heat generation amount generated by the heat generation resistor element increases or decreases according to the increase or decrease of the flow rate in the bypass passage 49, the temperature of the heat generation resistor is kept constant by the energization control, the temperature difference between the temperature measuring resistor elements on the upstream side and the downstream side is varied according to the increase or decrease of the flow rate, and a signal corresponding to the flow rate is output.

[0045] The processing unit 55 controls the energization of the heat generating resistance element, performs a predetermined conversion process on the signal output of the sensitive unit 54, and outputs the converted signal to the ECU 3 as a detection value QA through the detection unit 46.

[0046] With the configuration described above, the detection unit 46 generates the detection value QA according to the flow rate and the flow direction of the fluid flowing through the second passage portion 52, and outputs the detection value QA to the ECU 3.

[0047] Subsequently, the calculation unit 47 is described as a part of the functions of the ECU 3 with reference to a block diagram in Fig. 3. The calculation unit 47 performs an arithmetic operation to output a measured value Q as a numerical value for use in various controls using the detection value QA output from the air flow meter 5.

[0048] In this example, in the flow rate measuring system 1, the change in the flow rate in the bypass passage 49 lags behind the change in the flow rate in the main passage 50. Therefore, the calculation unit 47 has a function for compensating for such a lag. In other words, since the detection value QA by the detection unit 46 lags behind the actual flow rate in the main passage at the same time, the calculation unit 47 compensates for the delay in the detection value QA as a calculation to output the measured value Q.

[0049] In other words, the calculation unit 47 calculates the measured value Q by compensating for the fact that the change in flow rate in the bypass passage 49 is delayed behind the change in flow rate in the main passage 50, as needed.

[0050] In the above compensation, the calculation unit 47 performs the following arithmetic operation to calculate the measured value Q. In other words, at a pressure in the intake pipe 4 (i.e., the pressure in the main passage 50), future compensation values ​​(P0 to P2) for the delay and a future delay value estimated from the detection value QA of the present flow rate are calculated. The future delay value may be referred to as a delay value P3.

[0051] Subsequently, the compensation values ​​(P0 to P2) are added to the delay value (P3) to calculate a value of a future pressure without a delay in the main passage 50. A numerical value of a future flow rate without a delay in the main passage 50 is calculated according to a predicted value P, and the numerical value is output as the measured value Q. The value of the future pressure can be referred to as the predicted value P.

[0052] In the process of calculating the compensation values ​​(P0 to P2), the calculation unit 47 calculates both the loss coefficients Cs and Cb of the main passage 50 and the bypass passage 49 for use. Then, in calculating the loss coefficient Cs, two calculation methods are selectively used when the size of the loss coefficient Cs is small and when the size is large, and in calculating the loss coefficient Cb, two calculation methods are selectively used when the size of the loss coefficient Cb is small and when the size is large. In the present embodiment, the calculation of the loss coefficient Cs includes a large-side calculation and a small-side calculation. In this case, the large-side calculation corresponds to a calculation when the size of the loss coefficient Cs is too small, and the small-side calculation corresponds to a calculation when the size of the loss coefficient Cs is too large.In the present embodiment, the calculation of the loss coefficient Cb includes a large side calculation and a small side calculation. In this case, the large side calculation corresponds to a calculation when the size of the loss coefficient Cb is too small, and the small side calculation corresponds to a calculation when the size of the loss coefficient Cb is too large. In the present embodiment, the large side calculation may be referred to as a large side calculation method, and the small side calculation may be referred to as a small side calculation method.

[0053] Further, the calculation unit 47 has a determination unit for determining whether or not the flow direction in the main passage 50 and / or the bypass passage 49 has changed, and when the determination unit determines that the flow direction has changed, the large side calculation method is used for each of the loss coefficients Cs and Cb, and when the determination unit determines that the flow direction has not changed, the small side calculation method is used for each of the loss coefficients Cs and Cb.

[0054] In the following, the delay compensation by the calculation unit 47 is described with reference to the Fig. 3 to 7 are described in detail.

[0055] First, Fig. 3 P0, P1, P2, and P3 represent numerical values ​​of pressures in the main passage 50, and P0 is a future value calculated based on the operating state of the motor 2 and used to calculate the compensation values ​​(P0 to P2). P0 can be referred to as a dummy prediction value P0. P2 is a future deceleration value calculated based on the operating state of the motor 2 and used to calculate the compensation values ​​(P0 to P2). P2 can be referred to as a dummy deceleration value P2. P1 is a current value calculated based on the operating state of the motor 2 and used to calculate the dummy deceleration value P2. P1 can be referred to as a dummy estimate value P1.

[0056] Furthermore, QA0, QA1, and QA2 represent numerical values ​​of the flow rate in the main passage 50, and QA0 is a future value calculated based on the operating state of the engine 2 and used to calculate the dummy prediction value P0. The QA0 can be referred to as a dummy prediction value QA0.

[0057] QA2 is a future deceleration value calculated based on the operating state of motor 2 and used to calculate the dummy deceleration value P2. QA2 can be referred to as a dummy deceleration value QA2. QA1 corresponds to a present value calculated based on the operating state of motor 2 and used to calculate the dummy estimate value P1. QA1 can be referred to as a dummy estimate value QA1.

[0058] Furthermore, TA and TA0 represent numerical values ​​of the throttle opening degree, TA is a value detected by the throttle opening degree sensor 9, and TA0 is a future value calculated based on the detection value TA. In this case, TA can be referred to as the detection value TA, and TA0 can be referred to as the predicted value TA0. NE corresponds to the rotational speed of the engine 2, which is calculated based on a crank angle signal output from the crank angle sensor 36, and VT corresponds to a valve timing set by the ECU 3. NE and VT can be referred to as a rotational speed NE and a valve timing VT, respectively.

[0059] The function of the calculation unit 47 is described in detail below.

[0060] The calculation unit 47 includes a calculation system 470 for calculating the dummy prediction value P0 based on the operating state of the engine 2, a calculation system 471 for calculating the dummy estimation value P1 based on the operating state of the engine 2, a calculation system 472 for calculating the dummy deceleration value P2 using the dummy estimation value P1, and a calculation system 473 for calculating the deceleration value P3 according to the detection value QA of the current flow rate.

[0061] The calculation system 470 includes a prediction unit 470T, a prediction unit 470Q and a prediction unit 470P.

[0062] The prediction unit 470T calculates the prediction value TA0, which corresponds to a numerical value in the future at the throttle opening degree, using the detection value TA. In this example, the future numerical value is a numerical value after a predetermined time has elapsed from the present, and corresponds, for example, to a numerical value at the time the intake valve of the engine 2 closes. Therefore, the prediction unit 470T calculates the prediction value TA0 according to the detection value TA based on the rotational speed NE and the valve timing VT of the engine 2.

[0063] The prediction unit 470Q calculates a dummy prediction value QA0 of the flow rate in the main passage 50. When calculating the dummy prediction value QA0, the prediction unit 470Q uses the prediction value TA0 of the throttle opening degree, the rotational speed NE of the engine 2, the valve timing VT, the predicted dummy value P0 of the pressure of the main passage 50, and the like. The dummy prediction value P0 is calculated by the prediction unit 470P described below.

[0064] The prediction unit 470P calculates a dummy prediction value P0 of the pressure of the main passage 50. When calculating the dummy prediction value P0, the prediction unit 470P uses the dummy prediction value QA0 of the flow rate in the main passage 50.

[0065] The calculation system 471 includes an estimation unit 471Q and an estimation unit 471P.

[0066] The estimation unit 471Q calculates the dummy estimated value QA1 of the flow rate in the main passage 50. In calculating the dummy estimated value QA1, the estimation unit 471Q uses the detection value TA of the throttle opening degree, the rotational speed NE of the engine 2, the valve timing VT, the dummy estimated value P1 of the pressure of the main passage 50, and the like. The dummy estimated value P1 is calculated by the estimation unit 471P to be described below.

[0067] The estimation unit 471P calculates the dummy estimate P1 of the pressure of the main passage 50. When calculating the dummy estimate P1, the estimation unit 471P uses the dummy estimate QA1 of the flow rate in the main passage 50.

[0068] The calculation system 472 includes a prediction unit 472Q and a prediction unit 472P.

[0069] The prediction unit 472Q calculates the dummy delay value QA2 of the flow rate in the main passage 50. Then, when calculating the dummy delay value QA2, the prediction unit 472Q calculates the dummy delay value QA2 using a bypass reference unit 57 and a heat radiation reference unit 58, which will be described later. The dummy estimated value P1 is used to calculate the dummy delay value QA2.

[0070] The prediction unit 472P calculates the dummy delay value P2 of the pressure of the main passage 50. When calculating the dummy delay value P2, the prediction unit 472P uses the dummy delay value QA2 of the flow rate in the main passage 50.

[0071] The calculation system 473 includes a prediction unit 473P.

[0072] The prediction unit 473P calculates a delay value P3 of the pressure of the main passage 50. In calculating the delay value P3, the prediction unit 473P uses the detection value QA of the air flow meter 5.

[0073] The delay value P3 and the dummy delay value P2 have the same response behavior.

[0074] Subsequently, the dummy delay value P2 calculated by the calculation systems 471 and 472 is subtracted from the dummy prediction value P0 calculated by the calculation system 470 to calculate future compensation values ​​(P0 to P2) for the delay, and the future compensation values ​​(P0 to P2) are added to the future delay value P3 calculated by the calculation system 473.

[0075] Consequently, the prediction value P is calculated without any delay, and the prediction value P is applied to a predetermined map or the like to calculate the measured value Q of the flow rate without any delay.

[0076] Next, the bypass reference unit 57 and the heat radiation reference unit 58 included in the prediction unit 472Q will be described in detail.

[0077] According to the structure in which the thermal-type flow rate sensor such as the air flow meter 5 is housed in the bypass passage 49, the change in the flow rate in the bypass passage 49 lags behind the change in the flow rate in the main passage 50. Moreover, the heat radiation from the heat-generating resistance element to the fluid is delayed by the heat capacity of the assembly or the like constituting the detection unit 46.

[0078] Due to these two main delay factors, the detection value QA detected by the air flow meter 5 is delayed behind the actual flow rate at the same time in the main passage 50.

[0079] Therefore, in order to compensate for the delay in the detection value QA due to the passage of the fluid through the bypass passage 49, the bypass reference unit 57 is provided in the prediction unit 472Q. In this case, the delay in the detection value QA can be referred to as a delay caused by bypassing. Furthermore, in order to compensate for a delay in the detection value QA due to a delay in heat radiation from the heat-generating resistance element to the fluid, the heat radiation reference unit 58 is provided in the prediction unit 472Q. In this case, the delay in the detection value QA can be referred to as a delay caused by heat radiation.

[0080] The following describes the functions of the bypass reference unit 57 and the heat radiation reference unit 58 based on the main routine, the first subroutine and the second subroutine described in the Fig. 4, Fig. 5 and Fig. 6. The first subroutine corresponds to a step of the main routine, and the second subroutine corresponds to a step of the first subroutine. The main routine is executed in a predetermined cycle during the operation of the engine 2.

[0081] According to the main routine, first, at S101, the dummy estimated value QA1 of the flow rate output by the estimation unit 471Q of the calculation system 471 is read. Then, at S102, it is determined whether the flow state is a transient state or not. The above determination can be made, for example, by comparing the dummy estimated value QA1(i-1) read in a previous main routine process with a dummy estimated value QA1(i) read in the current main routine process. If it is determined that the current state corresponds to the transient state (YES), the process then proceeds to S103, and if it is determined that the current state does not correspond to the transient state (i.e., the steady state) (NO), the process proceeds to S105.

[0082] Subsequently, at S103, it is determined whether the flow rate is in a low flow rate region or not, or whether the amount of change in the flow rate is large or not, according to the dummy estimation value QA1.

[0083] Accordingly, if it is determined that the flow rate is in the low flow rate region or the flow rate change amount is large (YES), it is determined that the delay caused by the bypass is becoming large, and the process proceeds to S104. If it is determined that the flow rate is not in the low flow rate region and the flow rate change amount is small (NO), the process proceeds to S105.

[0084] At S104 the Fig. The first subroutine shown in Figure 5 is executed.

[0085] S104 in the main routine, that is, all steps of the first subroutine, correspond to the bypass reference unit 57, and the dummy delay value QA11 of the flow rate in the main passage 50 is calculated according to the dummy estimated value QA1. In this example, the dummy delay value QA11 represents a numerical value of the flow rate in the main passage 50 and is a value delayed by an amount corresponding to a delay caused by bypassing behind the dummy estimated value QA1.

[0086] Each step of the first subroutine is described below.

[0087] First, at S201, a flow velocity Us of the main passage 50 is calculated by the following Expression 1 according to the dummy estimated value QA1, a density ρ of the fluid, and a flow channel cross-sectional area S of the flow passage. Us=QA1 / ρ / S

[0088] The flow channel cross-sectional area S corresponds to an area of ​​the cross section of the main passage 50 at the mounting position of the air flow meter 5, excluding a protrusion portion of the air flow meter 5.

[0089] The density ρ can be calculated based on the current fluid temperature and atmospheric pressure according to a predetermined map or mathematical expression. Furthermore, in a map or mathematical expression for obtaining the density ρ, the density ρ is set to be smaller as the fluid temperature is higher, and the air density ρ is set to be larger as the atmospheric pressure is higher.

[0090] Then at S202 the Fig. 6 is executed. The second subroutine corresponds to a routine for calculating the loss coefficients Cs and Cb used at the time of calculating the dummy delay values ​​QA11.

[0091] In the second subroutine, at S301, it is first determined whether the flow direction in the main passage 50 and / or the bypass passage 49 has changed or not. In other words, S301 serves as the determination unit described above. If it is determined that the flow direction has changed (YES), the process proceeds to S302, and both calculation methods of the loss coefficients Cs and Cb are set to the large-side calculation method. If it is determined that the flow direction has not changed (NO), the process proceeds to S303, and both calculation methods of the loss coefficients Cs and Cb are set to the small-side calculation method.

[0092] In other words, when the flow direction is switched from forward flow to reverse flow or from reverse flow to forward flow, the flow is disturbed and the loss increases rapidly. For this reason, there is a possibility that the accuracy of the measured value Q will be reduced at the time of the flow direction change. Therefore, when the flow direction changes, both calculation methods of the loss coefficients Cs and Cb are set to the large-side calculation method in response to the rapid increase in loss. If the flow direction has not been changed, both calculation methods of the loss coefficients Cs and Cb are set to the small-side calculation method.

[0093] In this example, at S301, when it is determined that the magnitude (absolute value) of the flow rate becomes smaller than a predetermined threshold, it is determined that the flow direction has changed. For example, the threshold is preferably 2 g / sec, and more preferably 0.5 g / sec.

[0094] In addition, various numerical values ​​related to the flow rate, such as the dummy prediction value QA0, the dummy estimate value QA1, the dummy delay value QA2, the dummy delay value QA11, and the detection value QA, can be used for the above determination.

[0095] For example, it may be determined that the flow direction has changed when it is determined that the dummy prediction value QA0 has become smaller than the threshold while the threshold of the dummy prediction value QA0 is set, or it may be determined that the flow direction has changed when it is determined that the dummy prediction value QA1 has become smaller than the threshold while the threshold of the dummy estimation value QA1 is set.

[0096] The values ​​of the dummy prediction value QA0, the dummy estimation value QA1, the dummy delay value QA2, and the dummy delay value QA11 are compared with the thresholds, whereby it can be determined whether the flow direction in the main passage 50 has changed or not. Furthermore, the numerical value of the detection value QA is compared with the threshold, whereby it can be determined whether the flow direction in the bypass passage 49 has changed or not.

[0097] Furthermore, in the small-side calculation method set at S303, for example, the loss coefficients Cs and Cb are calculated with the flow rate and a flow rate change rate as parameters according to a predetermined map or mathematical expression. In the large-side calculation method set at S302, for example, the loss coefficients Cs and Cb are set to fixed values, and the fixed values ​​are set as numerical values ​​that are much larger than the numerical values ​​calculated by the map or mathematical expression for calculating the small-side numerical values.

[0098] According to the map or mathematical expression for calculating the numerical value on the small side, the loss coefficients Cs and Cb are set to be smaller as the flow rate is larger and larger as the flow rate change is larger. The set value for the numerical value on the large side, the map, and the mathematical expression for calculating the numerical value on the small side are individually set for each of the loss coefficients Cs and Cb.

[0099] Then, the process returns to the first subroutine, and the flow velocity Ub of the bypass passage 49 is calculated at S203.

[0100] In this example, the flow velocity Ub can be expressed as the following mathematical expression 4 using the equations of motion of the fluid in the main passage 50 and the bypass passage 49 as shown in mathematical expressions 2 and 3. ΔPρ=LsdUsdt+Cs⋅Us2 ΔPρ=LbdUbdt+Cb⋅Ub2 Ub(i)=−Lbdt±(Lbdt)2+4⋅Cb{LbdtUb(i−1)+LsUs(i)−Us(i1)dt+Cs⋅Us(i)2}2⋅Cb

[0101] In mathematical expressions 2 to 4, ΔP corresponds to a pressure difference between the inlet 49i and the outlets 52g, Lb is a path length along the first and second passage sections 51, 52 from the inlet 49i to the outlets 52g, and Ls corresponds to a path length outside the housing 45 along the flow of the main passage 50 from the inlet to the outlets a and b. Furthermore, Us(i) corresponds to a current value of the flow velocity of the main passage 50, and Us(i-1) corresponds to a previous value of the flow velocity of the main passage 50. Ub(i) corresponds to a current value of the flow velocity of the bypass passage 49, and Ub(i-1) corresponds to a previous value of the flow velocity of the bypass passage 49.

[0102] The mathematical expressions 2 and 3 are solved for the flow velocity Ub(i) to derive the mathematical expression 4.

[0103] Subsequently, at S204, a delayed flow velocity Usb is calculated. In this example, the delayed flow velocity Usb is delayed by an amount corresponding to the delay of the flow rate change of the bypass passage 49 behind the flow rate change of the main passage 50 behind the flow rate Us. The delayed flow velocity Usb is calculated according to the following mathematical expression 5, which is obtained under the assumption that the above equation of motion (Mathematical Expressions 2 and 3) also holds in a steady state (that is, under the assumption that a time-differentiated term is equal to 0). Usb=Ub×Cb / Cs

[0104] Then, at S205, the dummy deceleration value QA11 is calculated by the following mathematical expression 6 using the deceleration flow velocity Usb, the air density ρ and the flow channel cross-sectional area S. QA11=Usb⋅ρ⋅S

[0105] Subsequently, at S105, back in the main routine, the dummy delay value QA2 of the flow rate in the main passage 50 is calculated, in which a delay caused by heat radiation is added to the dummy delay value QA11. In other words, S105 serves as the heat radiation reference unit 58.

[0106] In the following, the heat radiation reference unit 58 is described with reference to Fig. 7 described.

[0107] The heat radiation reference unit 58 includes a total heat radiation amount calculation unit 60, a first-order delay processing unit 61, a time constant calculation unit 62, and the like.

[0108] The total heat radiation amount calculation unit 60 calculates a total heat radiation amount, or a total heat radiation amount that does not include a response delay, based on the heat capacity, mass, and the like of the device, and the like, based on the map, and the like, according to the dummy delay value QA11. In this case, a total amount of heat radiation may be referred to as the total heat radiation amount W.

[0109] The first-order delay processing unit 61 performs a first-order delay process on the total heat radiation amount W using a first-order delay time constant τ of the heat radiation system including the array, and calculates the heat radiation amount including the response delay. In this case, the amount of heat radiation can be referred to as a response heat radiation amount w.

[0110] The time constant calculation unit 62 calculates the time constant τ used in the first-order delay processing unit 61 using a map or the like according to the detection value QA by the air flow meter 5.

[0111] Then, the air flow rate corresponding to the response heat radiation amount w is calculated using the map or the like, and the calculated air flow rate is set as the dummy delay value QA2.

[0112] The processing at S105, that is, the heat radiation reference unit 58, is also executed when it is determined at S102 that the flow state corresponds to the steady state, and when it is determined at S103 that the flow rate is not in the low flow rate region and the flow rate change amount is small. In other words, the heat radiation reference unit 58 is executed when the bypass reference unit 57 is not executed (or when the dummy delay value QA11 is not calculated). In this case, the total heat radiation amount calculation unit 60 calculates the total heat radiation amount W using the dummy estimated value QA1.

[0113] According to the measurement system 1 of the embodiment, the ECU 3 calculates the measured value Q of the flow rate in the main passage 50 by compensating for a fact that the change in the flow rate in the bypass passage 49 lags behind the change in the flow rate in the main passage 50, as needed. In addition, the ECU 3 calculates the respective loss coefficients Cs and Cb of the main passage 50 and the bypass passage 49, and performs the necessary arithmetic operation for compensation using the calculated loss coefficients Cs and Cb. Then, in calculating the loss coefficient Cs, two calculation methods are selectively used when the magnitude of the loss coefficient Cs is small and when the magnitude is large, and in calculating the loss coefficient Cb, two calculation methods are selectively used when the magnitude of the loss coefficient Cb is small and when the magnitude is large.

[0114] Further, the ECU 3 has a determination unit for determining whether the direction of flow in the main passage 50 has changed or not, and the determination unit uses a large side calculation method for the loss coefficients Cs and Cb when it determines that the direction of flow has changed, and uses a small side calculation method when it determines that the direction of flow has not changed.

[0115] Therefore, even though the flow loss increases rapidly with a change in flow direction, delay compensation can be performed with high accuracy by calculating the loss coefficients Cs and Cb using a large-scale calculation method. Therefore, in the measuring system 1, the deterioration of measurement accuracy when the flow direction changes can be reduced.

[0116] In particular, when the surging of the turbo is eliminated by opening the valve of the ABV 29, there is no pulsation due to the surging, the intake pulsation due to the intake and exhaust becomes small, and the switching of the low flow rate and the flow direction occurs frequently.

[0117] For this reason, the effect of preventing the deterioration of the measurement accuracy is particularly significant when the surging of the turbo is eliminated by opening the ABV 29.

[0118] Furthermore, according to the measuring system 1, when the ECU 3 determines that the magnitude of the flow rate is smaller than a predetermined threshold, it is determined that the flow direction has changed.

[0119] This makes it easy to determine whether the flow direction has changed or not.

[0120] The present disclosure may be modified into various modifications without departing from the spirit of the present disclosure.

[0121] For example, according to the measurement system 1 of the embodiment, the ECU 3 determines that the flow direction has changed when it is determined that the magnitude of the flow rate has become smaller than a predetermined threshold, but the mode of the determination unit is not limited to the above example.

[0122] For example, it can be determined that the flow direction has changed when the sign of the numerical value of the flow rate changes from + to - or from - to +. Similarly, in this case, various numerical values ​​related to the flow rate, such as the dummy prediction value QA0, the dummy estimation value QA1, the dummy delay value QA2, the dummy delay value QA11, and the detection value QA, can be used as the numerical values ​​of the flow rate. Furthermore, a comparison between the current value and the previous value of these numerical values ​​can be used, or a comparison between the previous value and a value before the previous value can be used to determine whether the reference sign has changed or not.

[0123] Further, whether or not the flow direction has changed can be determined based on the rotational speed NE of the engine 2, the throttle opening degree, a negative pressure of the intake pipe 4, the rotational speed of the turbocharger 20, the operation of the ABV 29, and the like.

[0124] Furthermore, according to the measurement system 1 of the embodiment, the ECU 3 calculates the loss coefficients Cs and Cb through a predetermined map or mathematical expressions when it is determined that the flow direction has not changed. The ECU 3 sets predetermined values, which are much larger than the numerical values ​​calculated by the map or mathematical expressions, as the loss coefficients Cs and Cb when it is determined that the flow direction has changed, but the mode of the loss coefficients Cs and Cb is not limited to the above values.

[0125] For example, the loss coefficients Cs and Cb may be calculated by a predetermined map or a mathematical expression when it is determined that the flow direction is not changed, and the loss coefficients Cs and Cb may be calculated by multiplying a numerical value calculated by the map or the mathematical expression by a predetermined coefficient when it is determined that the flow direction has been changed.

[0126] Although the present disclosure has been described according to the examples, it should be understood that the disclosure is not limited to such examples or structures. The present disclosure encompasses various modifications and variations within the range of equivalence. Furthermore, various combinations and configurations, as well as further combinations and configurations including only one element, more or less, are within the spirit of the present disclosure.

Claims

[1] A flow rate measuring system that outputs a measured value (Q) representing a magnitude of a flow rate and a flow direction of a fluid flowing through a specific main passage (50) in which backflow may occur, the flow rate measuring system comprising: a housing (45) comprising a bypass passage (49) that receives a portion of the fluid flowing through the main passage and directs the portion of the fluid back into the main passage, the housing being disposed in the main passage; a detection unit (46) arranged in the bypass passage and outputting a detection value (QA) corresponding to a magnitude of a flow rate and a flow direction of the fluid flowing through the bypass passage; and a calculation unit (47) which performs an arithmetic operation using the detection value to output the measured value, wherein the calculation unit calculates the measured value by compensating for a delay in the change in the flow rate in the bypass passage with respect to the change in the flow rate in the main passage as required, the calculation unit performs an arithmetic operation required for the compensation using at least one of loss coefficients (Cs, Cb) of the main passage or the bypass passage and selectively uses one of at least two calculation methods depending on whether a magnitude of the loss coefficient is small or a magnitude of the loss coefficient is large, and the calculation unit comprises a determination unit (S301) that determines whether the flow direction in the main passage and / or the bypass passage has changed, uses a large-side calculation method related to the calculation of the loss coefficient having a numerical value if the determination unit determines that the flow direction has changed, and uses a small-side calculation method related to the calculation of the loss coefficient having a numerical value if the determination unit determines that the flow direction has not changed, wherein the numerical value of the large-side calculation method is much larger than the numerical value calculated by a map or mathematical expression of the small-side calculation method. [2] The flow rate measuring system according to claim 1, wherein the determining unit determines that the flow direction in the main passage and / or the bypass passage has changed when the magnitude of the flow rate in the main passage and / or the bypass passage is determined to be smaller than a predetermined threshold. [3] A flow rate measuring system which outputs a measured value (Q) indicative of a magnitude of a flow rate and a flow direction of a fluid flowing through a main passage (50), the flow rate measuring system comprising: a housing (45) comprising a bypass passage (49) that receives a portion of the fluid and returns the portion of the fluid to the main passage, the housing being disposed in the main passage; a detection unit (46) arranged in the bypass passage and outputting a detection value (QA) corresponding to a magnitude of a flow rate and a flow direction of the fluid flowing through the bypass passage; and a calculation unit (47) which calculates the measured value using the detection value, wherein the calculation unit calculates the measured value by compensating for a delay in the change in the flow rate of the fluid in the bypass passage with respect to the change in the flow rate of the fluid in the main passage, the calculation unit performs an arithmetic operation required for compensation using at least one of loss coefficients (Cs, Cb) of the main passage or the bypass passage and selectively uses one of a large side calculation or a small side calculation in calculating the loss coefficient, the calculation unit comprises a determination unit (S301) which determines whether the flow direction in the main passage and / or the bypass passage has changed, and the calculation unit uses the large side calculation for calculating the loss coefficient having a numerical value when the determination unit determines that the flow direction has changed, and uses the small side calculation for calculating the loss coefficient having a numerical value when the determination unit determines that the flow direction has not changed, where the numerical value of the large side calculation is much larger than the numerical value calculated by a map or mathematical expression of the small side calculation. [4] The flow rate measuring system according to claim 3, wherein the determining unit determines that the flow direction in the main passage and / or the bypass passage has changed when it is determined that the magnitude of the flow rate in the main passage and / or the bypass passage is smaller than a predetermined threshold. [5] The flow rate measuring system according to claim 3 or 4, wherein the determining unit determines that the flow directions in both the main passage and the bypass passage are not changed when it is determined that the magnitudes of the flow rates in both the main passage and the bypass passage are larger than a predetermined threshold.

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