JP6312192B2 - Pitot tube air flow meter for exhaust gas recirculation system - Google Patents

Description

  The present invention relates to an air flow meter, and more particularly to an air flow meter that improves the reliability of an air flow meter that measures the flow rate of exhaust gas recirculated in an exhaust gas recirculation device.

Conventionally, in an operation control device for an internal combustion engine, as a sensor for measuring the flow rate of intake air of the internal combustion engine, for example, a so-called wire type or a thin film type is used. Is well known (see, for example, Patent Document 1).
By the way, some internal combustion engines have a configuration in which an exhaust gas recirculation device is provided from the viewpoint of improving emission characteristics. However, such an exhaust gas recirculation device is also re-used for more stable operation control. It may be necessary to measure the flow rate of the exhaust being circulated.

JP 2008-69690 A (page 5-12, FIG. 1 to FIG. 12)

However, the air in the so-called EGR pipe communicating with the intake pipe and the exhaust pipe contains a large amount of dissolved water droplets such as solid dust and nitrogen oxides. Therefore, when using the above-described conventional sensor, these dust etc. In addition to the problem that the sensor sensitivity is likely to be reduced due to a large amount of deposits and adsorption, there is a problem that it is difficult to perform stable and reliable measurement with a conventional sensor because intense pulsation occurs in the EGR pipe.
Furthermore, since the EGR pipe is very thin compared to the suction pipe and the like, and it is difficult to provide a conventional sensor directly in the EGR pipe, it is necessary to provide a new structure for mounting, which increases the complexity of the device, There is also the problem of incurring pricing.

  The present invention has been made in view of the above circumstances, and provides a pitot tube type air flow meter for an exhaust gas recirculation device that enables stable and reliable flow rate measurement in an EGR tube.

In order to achieve the above object of the present invention, a pitot tube type air flow meter for an exhaust gas recirculation device according to the present invention comprises:
A Pitot tube type air flow meter for measuring the flow rate of exhaust gas circulated in an exhaust gas recirculation device of an internal combustion engine,
It has a static pressure pipe for measuring static pressure and two dynamic pressure pipes for measuring dynamic pressure connected to the static pressure pipe, and the two dynamic pressure pipes have an opening direction of 180 positioned in the fluid. Based on a differential pressure generated between the static pressure tube and one of the two dynamic pressure tubes, and a differential pressure generated between the static pressure tube and the other of the two dynamic pressure tubes. Ri greens and enables measuring the flow rate of the circulation allowed is the exhaust gas,
The dynamic pressure pipe, the introduction portion which is arranged parallel to the flow of exhaust gas, shall comprise a body portion intersecting at an acute angle with the inlet portion.

  According to the present invention, the air flow meter is configured using a pitot tube, and the dust can be prevented from entering into the deep portion of the pitot tube, unlike the conventional case, without causing a decrease in measurement sensitivity due to dust, In addition, there is an effect that stable and reliable measurement is possible even in a place with pulsation.

It is a block diagram which shows the structural example of the principal part of the engine system in which the pitot tube type | formula airflow meter for exhaust-gas recirculation apparatuses in embodiment of this invention is used. It is a block diagram which shows the 1st structural example of the pitot tube type air flow meter for exhaust-gas recirculation apparatuses in embodiment of this invention. FIG. 5 is an enlarged longitudinal sectional view of an introduction portion of a dynamic pressure pipe in a second configuration example of a pitot tube type air flow meter for an exhaust gas recirculation device in an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 3.
The members and arrangements described below do not limit the present invention and can be variously modified within the scope of the gist of the present invention.
First, an engine system in which a pitot tube type air flow meter for an exhaust gas recirculation apparatus according to an embodiment of the present invention is used will be described with reference to FIG.
An engine 1 as an internal combustion engine is, for example, a diesel engine. FIG. 1 shows a configuration example of a main part of an engine system that uses a diesel engine and includes an exhaust gas recirculation device.
An intake pipe 2 for taking in air necessary for fuel combustion is connected to the intake manifold 4a of the engine 1, and an exhaust pipe 3 for exhausting exhaust gas is connected to the exhaust manifold 4b. Yes.

A communication path (EGR pipe) 5 that communicates the intake pipe 2 and the exhaust pipe 3 is provided at an appropriate position of the intake pipe 2 and the exhaust pipe 3. The exhaust gas recirculation device pitot tube type air flow meter 20, the EGR actuator 6 and the EGR cooler 7 are arranged in this order.
The exhaust gas recirculation device pitot tube type air flow meter 20 detects the flow rate of exhaust gas recirculated to the intake pipe 2 and has a configuration to be described later, and the detection result is sent to an electronic control unit ("ECU" in FIG. ”) 15) and can be output.
The EGR actuator 6 is for adjusting the communication state of the communication path 5 according to the operation control by the electronic control unit 15, in other words, the recirculation amount of the exhaust gas.
The EGR cooler 7 cools the passing exhaust gas.

Further, the engine system is provided with a variable turbo 8 having a known and well-known configuration mainly including the variable turbine 9 and the compressor 10, and the compressor is obtained by the rotational force obtained by the variable turbine 9. 10 is rotated, and the compressed air is sent to the intake manifold 4a as intake air.
The variable turbine 9 is provided at an appropriate position downstream of the communication path 5 in the exhaust pipe 3, and the compressor 10 is provided at an appropriate position upstream of the communication path 5 in the intake pipe 2. It has become.
Further, the intake pipe 2 is provided with an intercooler 11 that cools intake air at an appropriate position between the communication passage 5 and the variable turbo 8 described above.

An intake throttle valve 12 for adjusting the amount of intake air is provided between the intercooler 11 and the communication path 5.
An air mass sensor 16 for detecting the intake air amount is provided at an appropriate position on the upstream side of the variable turbo 8 while an intake air temperature is detected at an appropriate position near the intake manifold 4a. An intake air temperature sensor 17 is provided.

  The electronic control unit 15 has a storage element (not shown) such as a RAM and a ROM, as well as a microcomputer having a known and well-known configuration, and energizes a fuel injection valve (not shown). A circuit (not shown) for driving and a circuit (not shown) for energizing and driving the EGR actuator 6, the intake throttle valve 12 and the like are configured as main components.

  The electronic control unit 15 receives various detection signals such as an engine speed, an accelerator opening, an outside air temperature, and an atmospheric pressure detected by various sensors (not shown), and an air mass sensor 16 and an intake air temperature sensor 17. The detection signal of the exhaust gas recirculation device and the detection signal of the Pitot tube type air flow meter 20 are input to be used for operation control of the engine 1, EGR control operation, and the like.

FIG. 2 shows a first configuration example of a pitot tube type air flow meter 20 for an exhaust gas recirculation apparatus according to an embodiment of the present invention. Hereinafter, the first configuration example will be described with reference to FIG. Will be described.
A pitot tube type air flow meter 20 for exhaust gas recirculation apparatus according to an embodiment of the present invention includes a static pressure tube 21 for measuring static pressure, two dynamic pressure tubes 22a and 22b for measuring dynamic pressure, and a differential pressure measuring device. The two differential pressure sensors 23a and 23b are configured.

The static pressure tube 21 is a conventional Pitot tube formed as a straight tube.
The dynamic pressure tubes 22a and 22b are roughly classified into an introduction portion 24a and a main body portion 24b, and a pitot tube having a bent portion 24c forming an acute angle θ is formed between the introduction portion 24a and the main body portion 24b.
The dynamic pressure tubes 22a and 22b are formed in a straight tube shape except for the bent portion 24c, and the other dynamic pressure tube 22a has an end opposite to the bent portion 24c of the main body portion 24b. The other dynamic pressure tube 22b is connected to the static pressure tube 21 through the differential pressure sensor 23b at the end opposite to the bent portion 24c of the main body portion 24b. It has become a thing.
Note that the differential pressure sensors 23a and 23b are not unique to the present invention, and have a configuration conventionally used.

The connection between the dynamic pressure tubes 22a and 22b and the static pressure tube 21 is such that the introduction portion 24a is positioned in a direction orthogonal to the static pressure tube 21, and the opening 25a of the introduction portion 24a of one dynamic pressure tube 22a and the other. The opening 25b of the dynamic pressure tube 22b faces the direction shifted by 180 degrees.
Therefore, the positional relationship between the arrangement of the one static pressure tube 21a and the differential pressure sensor 23a and the arrangement of the other static pressure tube 21b and the differential pressure sensor 23b is substantially line symmetrical about the static pressure tube 21.

In the pitot tube type air flow meter 20 for an exhaust gas recirculation device having such a configuration, a part where the differential pressure sensors 23 a and 23 b are provided is located outside the communication path 5, and the other part is located in the communication path 5. In this way, it is provided (see FIG. 2).
At this time, either one of the dynamic pressure tubes 22a and 22b, for example, the opening 25a of the introduction portion 24a of the dynamic pressure tube 22a is provided at a position facing the flow of gas or fluid (see thick line arrow in FIG. 2).
In this case, the opening 21a of the static pressure tube 21 is parallel to the flow of gas or liquid, and the openings 25a and 25b of the dynamic pressure tubes 22a and 22b are positioned in directions 90 degrees apart from each other (FIG. 2). reference).
The differential pressure sensors 23a and 23b are connected to the electronic control unit 15 as described above. In the electronic control unit 15, gas or fluid is generated based on output signals obtained by the differential pressure sensors 23a and 23b. Is calculated and calculated.

  By providing the exhaust gas recirculation device pitot tube type air flow meter 20 in the communication passage 5 as described above, the differential pressure corresponding to the flow rate of the exhaust gas passing through the communication passage 5 is caused by the differential pressure sensors 23a and 23b. In the obtained electronic control unit 15, the flow rate is calculated from a predetermined arithmetic expression based on the differential pressure obtained by the differential pressure sensors 23a and 23b.

  Here, in the embodiment of the present invention, since the bent portion 24c is formed so that the introduction portion 24a and the main body portion 24b form an acute angle θ, for example, one of the movements faces the flow direction. In the state where the opening 25a of the pressure tube 22a is positioned, the gas or fluid flows into the main body portion 24b through the introduction portion 24a, but even if there is foreign matter such as dust mixed in with the inflow of gas or fluid. Since the foreign matter collides with the inner wall of the bent portion 24c and stays in the vicinity thereof, the foreign matter hardly flows into the main body portion 24b, and the foreign matter flows into the main body portion 24b and causes an error in differential pressure measurement. Is avoided, and a highly reliable measurement result can be obtained as compared with the prior art.

  In particular, when measuring the flow rate of a vehicle that contains a large amount of water droplets, such as exhaust gas from a vehicle, the water droplets stay in the bent portion 24c as well as foreign matter, and the flow into the main body portion 24b can be avoided as much as possible. It is possible to measure the gas flow rate more accurately than in the past.

  It should be noted that the degree to which the acute angle θ formed by the bent portion 24c between the introduction portion 24a and the main body portion 24b depends on the thickness and length of the static pressure tube 21 and the dynamic pressure tubes 22a and 22b. It is preferable to set an appropriate value based on test results, simulation results, and the like in consideration of specific specifications of the Pitot tube type air flow meter for the exhaust gas recirculation device.

Next, a second configuration example will be described with reference to FIG.
The same components as those shown in FIG. 2 are denoted by the same reference numerals, detailed description thereof is omitted, and different points will be mainly described below.
In this second configuration example, the dynamic pressure tubes 22a and 22b are formed so that the introduction portion 24a and the main body portion 24b are substantially perpendicular to each other, and the passage 26 is provided in the middle of the passage 26 inside the introduction portion 24a. On the other hand, dust reservoirs 27 a and 27 b are recessed so as to sandwich the passage 26 in a direction substantially perpendicular to the passage.

By providing such dust reservoirs 27a and 27b in the middle of the passage 26, even if there is foreign matter mixed in with the inflow of fluid, most of the foreign matter stays in the dust reservoirs 27a and 27b, and the main body portion 24b. Therefore, it is avoided that water droplets or foreign matters flow into the main body 24b and cause an error in the differential pressure measurement, and a more reliable measurement result can be obtained than in the past. It will be.
The dust reservoirs 27a and 27b desirably have a cross section with respect to the passage 26, in other words, the size of the opening with respect to the passage 26 as large as possible in order to ensure the retention of foreign matter.
In the second configuration example, the dust reservoirs 27a and 27b are formed in a semi-elliptical spherical shape, but are not necessarily limited to such a shape. It may be spherical.

  The present invention is suitable for vehicles in which stable and reliable measurement of the exhaust gas recirculation amount in the exhaust gas recirculation device is desired.

20 ... Air flow meter 21 ... Static pressure tubes 22a, 22b ... Dynamic pressure tubes 23a, 23b ... Differential pressure sensor 24c ... Bending portions 27a, 27b ... Dust pool

Claims (2)

A Pitot tube type air flow meter for measuring the flow rate of exhaust gas circulated in an exhaust gas recirculation device of an internal combustion engine,
It has a static pressure pipe for measuring static pressure and two dynamic pressure pipes for measuring dynamic pressure connected to the static pressure pipe, and the two dynamic pressure pipes have an opening direction of 180 positioned in the fluid. Based on a differential pressure generated between the static pressure tube and one of the two dynamic pressure tubes, and a differential pressure generated between the static pressure tube and the other of the two dynamic pressure tubes. Ri greens and enables measuring the flow rate of the circulation allowed is the exhaust gas,
The dynamic pressure pipe, the introduction portion which is arranged parallel to the flow of the exhaust gas, the inlet portion and the body portion and the exhaust gas recirculation apparatus for the Pitot tube type air flow meter, characterized in Rukoto provided with intersecting at an acute angle.   2. A pitot tube type air flow meter for an exhaust gas recirculation device according to claim 1, wherein a dust reservoir is recessed in the vicinity of the opening of the dynamic pressure tube.

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