JP2021017844A - Intake air flow rate measurement device - Google Patents

Abstract

To reduce errors of detection values of an intake air flow rate sensor.SOLUTION: An intake air flow rate measurement device includes: an intake air flow rate sensor 13 provided at the upstream side of a compressor 14C of a turbocharger 14 on an intake passage 3 of an internal combustion engine 1 including the turbocharger; and a correction unit 100 which is configured to correct detection values of the intake air flow rate sensor based on a rotation speed of the turbocharger.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to an intake air flow rate measuring device, and more particularly to an apparatus for measuring an intake air flow rate of an internal combustion engine.

It is known that an intake flow rate sensor is provided in the intake passage of the internal combustion engine in order to measure the flow rate of the intake air of the internal combustion engine. Further, the internal combustion engine includes a turbocharged internal combustion engine equipped with a turbocharger, and in this case, a compressor for compressing the intake air is provided in the intake passage. Generally, the intake flow rate sensor is provided on the upstream side of the compressor in the intake passage.

JP-A-59-87235

As a result of diligent research by the present inventor, it has been confirmed that a remarkable error occurs in the detected value of the intake flow rate sensor in the low flow rate region where the intake flow rate is small. The present inventor has also newly found that the magnitude of this error correlates with the rotation speed of the turbocharger.

Therefore, the present disclosure was devised based on this new finding, and an object of the present disclosure is to provide an intake flow rate measuring device capable of suitably reducing an error of a detection value of an intake flow rate sensor.

According to one aspect of the present disclosure
In the intake passage of an internal combustion engine equipped with a turbocharger, an intake flow rate sensor provided on the upstream side of the compressor of the turbocharger and
A correction unit configured to correct the detection value of the intake flow rate sensor based on the rotation speed of the turbocharger, and a correction unit.
An intake flow rate measuring device is provided.

Preferably, the correction unit corrects so that the detection value becomes smaller as the rotation speed of the turbocharger becomes lower.

Preferably, the correction unit corrects when the operating state of the internal combustion engine is in a predetermined operating region located in a region on the low rotation side and the high load side.

According to the present disclosure, the error of the detection value of the intake flow rate sensor can be suitably reduced.

It is a schematic diagram which shows the structure of the Embodiment of this disclosure. It is a graph which shows the error of the detection value of the intake flow rate sensor. It is a map showing the relationship between the turbo rotation speed and the correction coefficient. It is a map of the engine operation area including the correction area. It is a flowchart of the intake flow rate measurement routine.

Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. It should be noted that the present disclosure is not limited to the following embodiments.

FIG. 1 is a schematic view showing the configuration of the present embodiment. The internal combustion engine (also referred to as an engine) 1 is a multi-cylinder engine mounted on a vehicle (not shown). In the present embodiment, the vehicle is a large vehicle such as a truck, and the engine 1 as a vehicle power source mounted on the large vehicle is a diesel engine. However, the type, type, use, and the like of the vehicle and the internal combustion engine are not particularly limited. For example, the vehicle may be a small vehicle such as a passenger car, and the engine 1 may be a gasoline engine.

The engine may be mounted on a moving body other than a vehicle, for example, a ship, a construction machine, or an industrial machine. Further, the engine does not have to be mounted on a moving body, and may be a stationary engine.

The engine 1 includes an engine main body 2, an intake passage 3 and an exhaust passage 4 connected to the engine main body 2, and a turbocharger 14. The engine body 2 includes structural parts such as a cylinder head, a cylinder block, and a crankcase, and movable parts such as a piston, a crankshaft, and a valve housed therein.

The intake passage 3 is mainly defined by an intake manifold 10 connected to the engine body 2 (particularly a cylinder head) and an intake pipe 11 connected to the upstream end of the intake manifold 10. The intake manifold 10 distributes and supplies the intake air sent from the intake pipe 11 to the intake ports of each cylinder. The intake pipe 11 is provided with an air cleaner 12, an intake flow rate sensor 13, a turbocharger 14 compressor 14C, and an intercooler 15 in this order from the upstream side. The intake air flow rate sensor 13 is a sensor for detecting the intake air flow rate, that is, the amount of intake air per unit time, and is also called a mass air flow (MAF (Mass Air Flow)) sensor or the like. The intake air flow rate sensor 13 outputs an electric signal having a value corresponding to the flow rate of the intake air passing therethrough.

The exhaust passage 4 is mainly defined by an exhaust manifold 20 connected to the engine body 2 (particularly a cylinder head) and an exhaust pipe 21 connected to the downstream side of the exhaust manifold 20. The exhaust manifold 20 collects the exhaust gas sent from the exhaust port of each cylinder. A turbine 14T of a turbocharger 14 is provided between the exhaust pipe 21 or the exhaust manifold 20 and the exhaust pipe 21. An aftertreatment device (oxidation catalyst, filter for collecting particulate matter, selective reduction NOx catalyst, ammonia oxidation catalyst, etc.) (not shown) is provided in the exhaust passage 4 on the downstream side of the turbine 14T.

The vehicle is equipped with a control device for controlling the engine 1. The control device includes a control unit, a circuit element (circuitry), or an electronic control unit (referred to as an ECU (Electronic Control Unit)) 100 that forms a controller. The ECU 100 includes a CPU (Central Processing Unit) having a calculation function, ROM (Read Only Memory) and RAM (Random Access Memory) as storage media, an input / output port, and a storage device other than ROM and RAM. The ECU 100 is configured to control an injector (not shown) or the like that injects fuel into the cylinder.

The control device includes the following sensors in addition to the above-mentioned intake flow rate sensor 13. That is, an engine rotation sensor 40 for detecting the engine rotation speed, specifically, the engine rotation speed (rpm) per minute, and an accelerator opening sensor 41 for detecting the accelerator opening degree are provided. The engine rotation sensor 40 and the accelerator opening sensor 41 output electric signals having values corresponding to the engine speed and the accelerator opening, respectively.

Further, the turbocharger 14 is provided with a turbo rotation sensor 42 for detecting the rotation speed of the turbocharger 14, specifically, the turbo rotation speed (rpm) per unit time (minutes). The turbo rotation sensor 42 outputs an electric signal having a value corresponding to the turbo rotation speed. The output signals of these sensors are sent to the ECU 100. The turbo rotation speed is synonymous with the rotation speed of the turbine shaft.

The ECU 100 basically measures the intake air flow rate based on the value of the intake air flow rate detected by the intake air flow rate sensor 13, that is, the detected value. Therefore, the ECU 100 and the intake flow rate sensor 13 constitute the intake flow rate measuring device of the present embodiment. The measured intake flow rate value is used for various controls.

By the way, in the configuration of the present embodiment, it was confirmed that a remarkable error occurs in the detected value of the intake air flow rate sensor 13 in the low flow rate region where the intake air flow rate is small. FIG. 2 shows the situation, where the horizontal axis shows the turbo rotation speed Nt (rpm), the vertical axis shows the error Er (%) of the detection value of the intake flow sensor 13, and the broken line a shows the relationship between the turbo rotation speed Nt and the error Er. .. Since the intake flow rate tends to increase as the turbo rotation speed Nt increases, the turbo rotation speed Nt on the horizontal axis may be considered as the intake flow rate here for convenience.

As shown in the figure, a positive error Er occurs in the low flow rate region A where the turbo rotation speed Nt is Nt1 or less, and the absolute value of this error Er tends to increase as the intake flow rate decreases. In the illustrated example, the maximum value of the error Er corresponding to the minimum value Nt0 of the turbo rotation speed Nt is Er0. One of the reasons why such an error Er occurs is considered to be that the swirling flow generated by the rotation of the compressor 14C affects the detected value of the intake flow rate sensor 13. When the error Er is positive, it means that the intake air flow rate (detected value) detected by the intake air flow rate sensor 13 is larger than the true intake air flow rate (true value). The error Er is represented by a percentage value obtained by dividing the difference obtained by subtracting the true value from the detected value by the true value. In the region B where the turbo rotation speed Nt is larger than Nt1 (for convenience, it is referred to as a high flow rate region), the error Er hardly occurs and is zero.

On the other hand, if the horizontal axis of FIG. 2 is interpreted as the turbo rotation speed Nt as shown in the figure, the present inventor newly finds that the error Er in the low flow rate region A has a correlation with the turbo rotation speed Nt as shown by the broken line a. Found in. Therefore, the intake air flow rate measuring device of the present embodiment corrects the detected value of the intake air flow rate by utilizing the relationship between the turbo rotation speed Nt and the error Er.

Specifically, as shown in FIG. 3, the relationship between the turbo rotation speed Nt and the correction coefficient K is defined in advance as shown by the solid line b, and is stored in the ECU 100 in the form of a map. Then, the ECU 100 calculates a correction coefficient K corresponding to the actual turbo rotation speed Nt detected by the turbo rotation sensor 42 from the map, and multiplies this correction coefficient K by the detection value of the intake flow sensor 13 to obtain the intake flow sensor. The detected value of 13 is corrected. Assuming that the detection value of the intake flow rate sensor 13 before correction (referred to as the detection value before correction) is Ga and the detection value of the intake flow rate sensor 13 after correction (referred to as the detection value after correction) is Ga', Ga'= K × Ga. expressed. The ECU 100 constitutes a correction unit as defined in the claims.

The solid line b has a shape in which the broken line a is turned upside down. The correction coefficient K = 1 corresponds to the error Er = 0. In the low flow rate region A, as the turbo rotation speed Nt becomes lower than Nt1, the correction coefficient K becomes smaller from 1. Therefore, the detected value of the intake flow rate sensor 13 is corrected so as to decrease as the turbo rotation speed Nt decreases. The correction coefficient K and the error Er at the same turbo rotation speed Nt have a relationship of K = (100-Er) / 100. For example, when the error Er0 is 10 (%) at the minimum value Nt0 of the turbo rotation speed Nt, the correction coefficient K0 is 0.9. On the other hand, in the high flow rate region B, K = 1 and no correction is substantially made.

In this way, by correcting the detection value of the intake flow rate sensor 13 using the preset relationship between the turbo rotation speed Nt and the correction coefficient K (solid line b), the detection value of the intake flow rate sensor 13 in the low flow rate region A can be obtained. The error can be suitably reduced.

By the way, according to the research results of the present inventor, it has been found that an error in the low flow rate region A occurs in a specific operating region of the engine. Therefore, in the present embodiment, the correction is performed only when the operating state of the engine is in such a specific operating region.

FIG. 4 shows a map that defines an operating area of the engine, and this map is stored in the ECU 100 in advance. In the map, the horizontal axis indicates the engine speed Ne, the vertical axis indicates the engine torque Trq, and the line c indicates the maximum torque curve. A predetermined operation area, that is, a correction area R for correction is defined in the map. The correction region R is set as a region located on the low rotation side and the high load side. Here, the region on the low rotation speed side means a region of 1/2 or less of the maximum engine speed, and the region on the high load side means a region of 1/2 or more of the maximum torque of the engine.

More specifically, the correction region R is set to a region near the maximum load that touches the maximum torque curve c. The correction region R is set to a region having a predetermined lower limit rotation speed Ne1 or more higher than the idle rotation speed and slightly lower than 1/2 of the maximum rotation speed Ne2 or less.

The correction area R described here is just an example, and the correction area R can be arbitrarily set based on the test results and the like.

The ECU 100 calculates the fuel injection amount from the injector according to a predetermined map based on the engine speed Ne and the accelerator opening Ac detected by the engine rotation sensor 40 and the accelerator opening sensor 41, respectively. Then, the ECU 100 calculates the engine torque Trq according to a predetermined map based on the engine speed Ne and the fuel injection amount. Further, the ECU 100 determines whether or not the engine operating state defined by the engine speed Ne and the engine torque Trq is within the correction region R of the map of FIG. If it is in the correction area R, the correction is executed, and if it is not in the correction area R, the correction is not executed.

As described above, since the correction is performed only when the engine operating state is within the correction region R, the correction can be performed with the minimum necessary frequency, and the calculation load of the ECU 100 can be suppressed.

Next, the intake flow rate measurement routine in the present embodiment will be described with reference to FIG. The illustrated routine is repeatedly executed by the ECU 100 every predetermined calculation cycle τ (for example, 10 msec).

First, in step S101, the ECU 100 determines whether or not the engine operating state is within the correction region R of the map of FIG. If it is not in the correction area R, the routine ends, and if it is in the correction area R, the process proceeds to step S102.

In step S102, the ECU 100 acquires the detection value Ga of the intake flow rate sensor 13 and the turbo rotation speed Nt detected by the turbo rotation sensor 42.

Next, in step S103, the ECU 100 calculates the value of the correction coefficient K corresponding to the turbo rotation speed Nt from the correction map (solid line b) of FIG.

Finally, in step S104, the ECU 100 corrects the detected value Ga by multiplying the detected value Ga of the intake flow rate sensor 13 by the correction coefficient K. In other words, the corrected detection value Ga'= K × Ga is calculated. As a result, the error of the detected value Ga can be suitably reduced, and the value of the intake air flow rate closer to the true value can be measured.

By the way, in the present embodiment, the detection value Ga of the intake flow rate sensor 13 is corrected based on the turbo rotation speed Nt, but separately, the detection value Ga is corrected based on the detection value Ga itself of the intake flow rate sensor 13. A comparative example is also conceivable. For example, it is conceivable to replace the horizontal axis of the map in FIG. 3 with the detection value Ga as shown in parentheses, obtain the correction coefficient K from the detection value Ga, and perform correction.

However, this comparative example has a drawback that the absolute value of the error Er becomes larger than that in the case of the turbo rotation speed Nt. The virtual line d in FIG. 3 schematically shows the error Er in the case of the comparative example. For example, at the minimum detected value Ga, the maximum value Er0d of the error of the comparative example is larger than the error Er0 of the present embodiment. Therefore, although not shown, the minimum value of the correction coefficient K is also smaller than K0.

Then, if the correction deviates due to variations in the engine operating state (when the calculated correction coefficient K deviates from an appropriate value), the deviation of the corrected detection value for the deviation becomes large, and the correction accuracy becomes large. Getting worse.

On the other hand, in the present embodiment, even if the correction is deviated, the influence of the deviation on the corrected detection value can be reduced. Therefore, the accuracy of correction can be improved.

Although the embodiments of the present disclosure have been described in detail above, various other embodiments and modifications of the present disclosure can be considered.

(1) For example, a function or the like may be used instead of the map. Maps, functions, etc. can be collectively referred to as relationships.

(2) The correction can be performed by a method other than multiplication of the correction coefficient K. For example, as shown by the broken line a in FIG. 2, a map that defines the relationship between the turbo rotation speed Nt and the error (absolute value in this case) is created and stored in advance, and the error corresponding to the actual turbo rotation speed Nt is calculated from the map. .. Then, this error may be subtracted from the detected value Ga of the intake flow rate sensor 13 to correct the detected value Ga.

(3) The turbo rotation speed Nt may be estimated based on other parameters such as temperature and pressure, and at this time, a characteristic map created and stored in advance may be used.

The embodiments of the present disclosure are not limited to the above-described embodiments, and all modifications, applications, and equivalents included in the ideas of the present disclosure defined by the scope of claims are included in the present disclosure. Therefore, this disclosure should not be construed in a limited way and can be applied to any other technique that belongs within the scope of the ideas of this disclosure.

1 Internal combustion engine (engine)
3 Intake passage 13 Intake flow sensor 14 Turbocharger 14C Compressor 100 Electronic control unit (ECU)

Claims (3)

In the intake passage of an internal combustion engine equipped with a turbocharger, an intake flow rate sensor provided on the upstream side of the compressor of the turbocharger and
A correction unit configured to correct the detection value of the intake flow rate sensor based on the rotation speed of the turbocharger, and a correction unit.
An intake flow rate measuring device comprising. The intake flow rate measuring device according to claim 1, wherein the correction unit corrects so that the detected value becomes smaller as the rotation speed of the turbocharger becomes lower. The intake flow rate measuring device according to claim 1 or 2, wherein the correction unit corrects when the operating state of the internal combustion engine is in a predetermined operating region located in a region on the low rotation side and a high load side.

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