JP6085145B2 - Gas flow measuring device - Google Patents

Description

  The present invention relates to a gas flow rate measuring device.

  Generally, in an engine such as a diesel engine, a part of exhaust gas is extracted from the exhaust side and returned to the intake side, and combustion of fuel in the combustion chamber is suppressed by the exhaust gas returned to the intake side to lower the combustion temperature. Thus, so-called exhaust gas recirculation (EGR) is performed to reduce the generation of NOx.

  In order to realize further lower emission of the engine, precise control of the EGR is necessary, but in order to precisely control the EGR, a technique for measuring the EGR gas flow rate with high response and high accuracy. Development is essential.

  Conventionally, as an apparatus for measuring a gas flow rate, for example, an apparatus for calculating a flow rate from a differential pressure measurement before and after an orifice provided in the middle of a gas flow path is known.

  Patent Documents 1 and 2 include, for example, general technical standards related to an apparatus that calculates a flow rate from differential pressure measurement before and after an orifice.

JP 2010-266208 A JP 2008-224466 A

  However, when an orifice is installed in the EGR pipe for recirculating the exhaust gas, for example, when the EGR gas flow rate is small as in the low speed and low load operation, the differential pressure ΔP at the upstream and downstream positions of the orifice is small. As shown in FIG. 5, the error [%] between the actual flow rate and the calculated flow rate becomes large, and the calculated flow rate accuracy becomes extremely low.

  On the other hand, when the orifice is narrowed to ensure accuracy and the differential pressure ΔP is increased, the differential pressure ΔP is significantly increased when the EGR gas flow rate is large as in high speed and high load operation. The pressure loss (pumping loss) of EGR gas in the EGR pipe is increased, and the fuel consumption is greatly deteriorated.

  That is, it has been impossible to achieve both the accuracy of the calculated flow rate and the suppression of the pressure loss over the operation range where the EGR gas flow rate is low to the high operation range.

  On the other hand, the restrictive flow meter disclosed in Patent Document 1 is capable of measuring a small flow rate with high accuracy and measuring a large flow rate with low loss. In addition to the deterioration of the spring member that presses the movable orifice against the fixed orifice when exposed to an atmosphere containing acid and water due to high-temperature exhaust gas, the spring member resists pulsation of exhaust gas associated with engine operation. Since it becomes very difficult to maintain the passage area of the EGR gas at a desired value, it becomes difficult to measure the EGR gas flow rate with high accuracy and high response over a long period of time.

  In addition, the flowmeter having a variable cross-sectional area orifice disclosed in Patent Document 2 has a triangular cross-sectional shape of the orifice channel, and a square plate is slid in the height direction of the triangle with respect to the triangular orifice channel. Since the cross-sectional area of the orifice channel is variable by arranging it freely, when the flowmeter is used for measuring the EGR gas flow rate, the rectangular plate and the actuator for sliding the plate are located outside the pipe. It will be difficult to secure the installation space.

  In recent years, the amount of working gas that each cylinder can inhale per unit time is calculated based on the temperature and pressure in the intake manifold and the engine speed, and the amount of fresh air flowing through the intake pipe per unit time is calculated. A method for actually measuring and subtracting the fresh air amount from the working gas amount to obtain an exhaust gas recirculation amount (EGR gas flow rate) has also been proposed. This method uses a special sensor for directly measuring the EGR gas flow rate. Although it is excellent in that it does not need to be newly added, it is only an estimate of the EGR gas flow rate by calculation, so it is also very important to develop a device that directly measures the EGR gas flow rate. .

  The present invention has been made in view of the above-described conventional problems. The gas flow rate is highly responsive and highly accurate and the pressure loss of the gas flow passage is suppressed over the operation range where the gas flow rate is low to the high operation range. An object of the present invention is to provide a gas flow rate measuring device capable of measuring.

The present invention provides an orifice fixing plate disposed in the middle of the gas flow passage and having a fixed passage hole,
A gas is disposed between the orifice fixing plate and the fixed passage hole in the middle of the gas flow passage so as to be rotatable about the axis of the gas flow passage and adjacent to the orifice fixed plate in the gas flow direction. An orifice movable plate having a rotation passage hole for changing the passage area of
A drive mechanism for rotating the orifice movable plate;
A differential pressure gauge for measuring a differential pressure at upstream and downstream positions of the orifice fixed plate and the orifice movable plate;
A controller for calculating a gas flow rate based on the differential pressure measured by the differential pressure gauge ,
The orifice fixed plate and the orifice movable plate are disposed in an EGR pipe as the gas flow passage so as to be applied to an EGR gas flow rate measurement of an engine in which exhaust gas recirculation is performed, and an EGR gas flow rate based on an operating state of the engine is set. The present invention relates to a gas flow rate measuring apparatus configured to output a drive signal for increasing or decreasing the passage area corresponding to an increase / decrease setting from the controller to a drive mechanism .

Further, the fixed passage hole of the orifice fixing plate is an ellipse having a major axis 2a _S and a minor axis 2b _S , and the rotational passage hole of the orifice movable plate is an ellipse having a major axis 2a _M and a minor axis 2b _M ,
2a _S > 2b _M
2b _S <2a _M
age,
When the cross-sectional area of the EGR pipe is A, the area A _S = π · a _S · b _{S of} the orifice fixing plate and the area A _M = π · of the rotation passage hole of the orifice movable plate a _M · b _M 0.3A <A _S <0.7A
0.3A _<A M _<0.7A
It is preferable that

According to the gas flow rate measuring device of the present invention, over the large operation range from the EGR gas flow rate is small operation range, that the EGR gas flow rate can be measured with and suppress the pressure loss of the gas flow path with high response and high-precision An excellent effect can be achieved.

It is a sectional side view which shows the Example of the gas flow measuring device of this invention. It is a front view which shows the orifice fixed plate and orifice movable plate in the Example of the gas flow measuring device of this invention. It is a front view which shows the state which rotated the orifice movable plate by the required angle with respect to the orifice fixed plate in the Example of the gas flow measuring device of this invention, Comprising: (a) is a rotation angle of 0 degree, (b) FIG. 4 is a diagram showing a case where the rotation angle is 30 °, (c) a case where the rotation angle is 60 °, and (d) a case where the rotation angle is 90 °. It is a schematic diagram which shows the modification of the drive mechanism of the orifice movable plate in the Example of the gas flow measuring device of this invention. It is a diagram which shows the relationship between differential pressure | voltage and calculation flow volume precision.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

1 to 3 is an embodiment of a gas flow rate measuring device of the present invention, the EGR pipe 1 midway as a gas flow passage, with the fixed passage hole H _S is disposed an orifice fixing plate S drilled The orifice movable plate M is arranged so as to be adjacent to the orifice fixed plate S on the upstream side in the gas flow direction so that the drive mechanism 2 can rotate about the axis O of the EGR pipe 1 as the gas flow passage. and setting, in the orifice movable plate M, drilled the turning passage hole H _M for changing the passage area of the EGR gas between the fixed passage hole H _S along with its rotation, the orifice fixing plate S and The differential pressure ΔP at the upstream / downstream position of the orifice movable plate M is measured by the differential pressure gauge 3, and the EGR gas flow rate is calculated by the controller 4 based on the differential pressure ΔP measured by the differential pressure gauge 3.

  In the case of the present embodiment, the drive mechanism 2 incorporates a ring gear 5 having internal teeth at the peripheral portion of the orifice movable plate M on the surface facing the orifice fixed plate S. A pinion 8 that is rotationally driven via a speed reducer 7 by an actuator 6 such as a motor is engaged.

  In the case of an automobile, the controller 4 is called an engine control computer (ECU: Electronic Control Unit). For example, the controller 4 sets a low EGR gas flow rate during low-speed and low-load operation and sets a large EGR gas flow rate during high-speed and high-load operation. Since it is programmed in advance, a drive signal 9 for increasing / decreasing the passage area corresponding to the increase / decrease setting of the EGR gas flow rate based on the operating state of the engine is output to the actuator 6 of the drive mechanism 2. is there.

Fixed passage hole H _S of the orifice fixing plate S, as shown in FIG. 2, the oval short diameter 2b _S in major axis 2a _S, turning passage hole H _M of the orifice movable plate M is short in major axis 2a _M It is an ellipse with a diameter of 2b _M ,
2a _S > 2b _M
2b _S <2a _M
It is as.

When the cross-sectional area of the EGR pipe 1 is A, the area A _S = π · a _S · b _S of the fixed passage hole H _S of the orifice fixing plate S and the rotation passage hole of the movable orifice plate M area _{a M = π · a M ·} b M of H _M, compared sectional area a, excessively increases too small pressure loss, because the pressure difference ΔP can not be secured and an excessively large,
0.3A <A _S <0.7A
0.3A _<A M _<0.7A
It is necessary to.

  This is a numerical value obtained from an experiment, and is a range necessary for ensuring both the accuracy of the calculated flow rate and the suppression of pressure loss.

  Next, the operation of the above embodiment will be described.

  For example, when the EGR gas flow rate is set to decrease during low-speed and low-load operation, a drive signal 9 for reducing the EGR gas passage area corresponding to the setting is sent from the controller 4 to the actuator 6 of the drive mechanism 2. As shown in FIG. 3D, the orifice movable plate M is rotated to a position of 90 °.

When the orifice movable plate M is rotated at the position of 90 °, rotation passing hole H _M orifice movable plate M with respect to the fixed passage hole H _S orifice fixing plate S is disposed at a right angle, the passage area of the EGR gas Since it is the most throttled and minimum state, even if the EGR gas flow rate is small as in the low speed and low load operation, the differential pressure at the upstream and downstream positions of the orifice fixed plate S and the orifice movable plate M arranged adjacent to each other. ΔP is secured, the differential pressure ΔP is measured by the differential pressure gauge 3, and the gas flow rate is calculated by the controller 4 based on the differential pressure ΔP measured by the differential pressure gauge 3. As a result, an error between the actual flow rate and the calculated flow rate is obtained. [%] Does not increase, and the calculated flow rate accuracy improves.

  In contrast, when the EGR gas flow rate is set to increase during high-speed and high-load operation, a drive signal 9 for increasing the passage area corresponding to the setting is sent from the controller 4 to the actuator 6 of the drive mechanism 2. As shown in FIG. 3A, the orifice movable plate M is rotated to a position of 0 °.

Wherein the orifice movable plate M is rotated at the position of 0 °, it is disposed relative to the fixed passage hole H _S orifice fixing plate S in the form of rotation passing hole H _M orifice movable plate M coincides completely, EGR gas Therefore, even if the EGR gas flow rate is large as in the high speed and high load operation, the differential pressure ΔP does not increase remarkably, and the pressure loss (pumping) of the EGR gas in the EGR pipe 1 does not occur. Loss) and fuel efficiency is improved.

  During operation between the low speed and low load operation and the high speed and high load operation, as shown in FIG. 3B, the orifice movable plate M is rotated to a position of 30 °, or as shown in FIG. By rotating the orifice movable plate M to a position of 60 °, or by rotating the orifice movable plate M to a position between them, the pressure loss of the EGR gas ( (Pumping loss) can be suppressed.

  Since the flow coefficient for calculating the EGR gas flow rate from the differential pressure ΔP changes due to the change in the passage area of the EGR gas accompanying the rotation of the orifice movable plate M, the flow coefficient is obtained in advance from experiments, What is necessary is just to input into the controller 4 beforehand.

  Further, in order to calculate the EGR gas flow rate, the differential pressure ΔP measured by the differential pressure gauge 3 is used. However, since the differential pressure gauge 3 can respond in several [ms], the EGR gas flow rate can also be calculated. High response is possible.

  On the other hand, in this embodiment, unlike the restrictive flow meter disclosed in Patent Document 1, since no spring member is used, the spring member is exposed to an atmosphere containing acid and water by high-temperature exhaust gas. In addition to the fact that the orifice movable plate M does not shake against the pulsation of exhaust gas accompanying the operation of the engine, it is easy to maintain the passage area of the EGR gas at a desired value. It becomes possible to measure the EGR gas flow rate accurately and with high response over a long period of time.

Further, in this embodiment, unlike the flowmeter equipped with a variable cross-sectional area orifice disclosed in Patent Document 2, turning passage hole H _M of the stationary passage holes H _S and orifice movable plate M orifice fixed plate S The orifice movable plate M is disposed outside the EGR pipe 1 because the passage area of the EGR gas is variable by arranging the orifice movable plate M so as to be rotatable with respect to the orifice fixed plate S. It is only necessary to arrange the actuator 6 of the drive mechanism 2 outside the EGR pipe 1 without projecting, and it is easy to secure an installation space.

  For example, when the EGR pipe 1 is thin and it is difficult to dispose the orifice fixed plate S and the orifice movable plate M therein, the casing having the orifice fixed plate S and the orifice movable plate M built therein. Of course, the EGR pipe 1 may be provided separately.

Further, the fixed passage hole H _S and the rotating passage hole H _M, although as the oval equal the same shape dimensions may be different elliptical dimensions, short, rotating the orifice movable plate M Thus, any shape other than a circle can be used as long as the EGR gas passage area can be changed.

  In this way, the EGR gas flow rate can be measured with high response and high accuracy while suppressing the pressure loss in the gas flow passage from the operation range where the EGR gas flow rate is low to the high operation range.

  FIG. 4 shows a modified example of the drive mechanism 2 for the orifice movable plate M in the embodiment of the gas flow rate measuring apparatus of the present invention. In the figure, the parts denoted by the same reference numerals as those in FIGS. The basic configuration is the same as that shown in FIGS. 1 to 3, but the arc-shaped groove 10 is formed in the orifice fixing plate S, and the pin 11 inserted into the arc-shaped groove 10 is movable through the orifice. The orifice movable plate M is rotated around the axis O of the EGR pipe 1 by protruding from the plate M and pushing and pulling the pin 11 by an actuator of the drive mechanism 2 (not shown). is there.

  When the drive mechanism 2 is configured as shown in FIG. 4, the amount of the actuator that pushes and pulls the pin 11 to the outside of the EGR pipe 1 is larger than that of the embodiment shown in FIG. 1 is the same as the embodiment shown in FIG. 1, and the EGR gas flow rate is highly responsive and the pressure loss of the gas flow passage from the operation range where the EGR gas flow rate is low to the high operation range. It can be measured while suppressing.

The gas flow rate measuring device of the present invention is not limited to the above-described embodiment, and various changes can be made without departing from the scope of the present invention.

1 EGR pipe (gas flow passage)
2 Drive mechanism 3 Differential pressure gauge 4 Controller 9 Drive signal S Orifice fixed plate H _S fixed passage hole M Orifice movable plate H _M rotation passage hole O Axis center

Claims (2)

An orifice fixing plate disposed in the middle of the gas flow path and having a fixed passage hole;
A gas is disposed between the orifice fixing plate and the fixed passage hole in the middle of the gas flow passage so as to be rotatable about the axis of the gas flow passage and adjacent to the orifice fixed plate in the gas flow direction. An orifice movable plate having a rotation passage hole for changing the passage area of
A drive mechanism for rotating the orifice movable plate;
A differential pressure gauge for measuring a differential pressure at upstream and downstream positions of the orifice fixed plate and the orifice movable plate;
A controller for calculating a gas flow rate based on the differential pressure measured by the differential pressure gauge ,
The orifice fixed plate and the orifice movable plate are disposed in an EGR pipe as the gas flow passage so as to be applied to an EGR gas flow rate measurement of an engine in which exhaust gas recirculation is performed, and an EGR gas flow rate based on an operating state of the engine is set. A gas flow rate measuring apparatus configured to output a drive signal for increasing / decreasing the passage area corresponding to an increase / decrease setting from the controller to a drive mechanism . The fixed passage hole of the orifice fixing plate is an ellipse having a major axis 2a _S and a minor axis 2b _S , and the rotary passage hole of the orifice movable plate is an ellipse having a major axis 2a _M and a minor axis 2b _M ,
2a _S > 2b _M
2b _S <2a _M
age,
When the cross-sectional area of the EGR pipe is A, the area A _S = π · a _S · b _{S of} the orifice fixing plate and the area A _M = π · of the rotation passage hole of the orifice movable plate a _M · b _M 0.3A <A _S <0.7A
0.3A _<A M _<0.7A
The gas flow rate measuring device according to claim 1 .

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