JP5263216B2 - Air flow measurement device - Google Patents

Description

The present invention relates to an air flow rate measuring device that is disposed in an intake passage to an engine and measures a flow rate of air that is sucked into the engine (hereinafter sometimes referred to as air flow rate).
In the following description, regarding the flow in the intake passage, the direction from the air cleaner (upstream) to the engine (downstream) is referred to as the forward direction, and the direction from the engine (downstream) to the air cleaner (upstream) is referred to as the reverse direction.

  Conventionally, for example, when measuring the flow rate of air sucked into an engine, the mass flow rate can be directly measured as an air flow rate, so that an output value corresponding to the mass flow rate is generated by generating a heat transfer phenomenon with the air. The generated thermal sensor is widely used. This thermal sensor has a heating element that applies heat to the air. For example, the temperature difference between the temperature of the air that is not thermally affected by the heating element and the temperature of the heating element becomes a predetermined numerical value. In addition, the heat generation of the heating element is controlled.

  As a result, as shown in FIG. 7B, the correlation between the amount of heat given to the air from the heating element and the air flow rate becomes convex upward when the heat amount is taken as the vertical axis and the air flow rate as the horizontal axis. That is, although the amount of heat increases as the air flow rate increases, the rate of increase of the heat amount relative to the air flow rate decreases as the air flow rate increases. The thermal sensor generates an output value corresponding to the mass flow rate according to the amount of heat given from the heating element to the air by the control based on the convex correlation.

  Here, in the air flow in the intake passage, pulsation is generated by opening and closing the valve of the engine, the forward and reverse flows are alternately repeated, and the output value of the thermal sensor repeatedly increases and decreases according to the pulsation. As a result, the measured value by the thermal sensor is inevitably lower than the true value due to the fact that the correlation between the heat quantity and the air flow rate is convex upward. Therefore, in order to increase the output value of the thermal sensor and bring the measurement value closer to the true value, as shown in FIG. An air flow rate measuring device 100 in which a thermal sensor 102 is arranged in the flow path 101 is widely adopted.

  That is, assuming that the flow path length when the air flow straight through the intake path without being taken into the internal flow path 101 is L1, and the flow path length of the internal flow path 101 is L2, the air flow rate measuring device 100 is an internal part that bypasses the linear flow. By forming the flow path 101 and disposing the thermal sensor 102 in the internal flow path 101, a correction function for increasing the output value according to L2 / L1 is provided. According to this correction function, the output value can be increased as L2 / L1 is increased. Therefore, by setting L2 / L1 to a desired value, it is possible to eliminate the decrease in the measured value caused by pulsation. .

  By the way, in such an air flow rate measuring apparatus 100, it is necessary to return the air which flowed through the internal flow path 101 to the intake passage, and various patterns are considered for the discharge port 103 for returning the air to the intake passage. . For example, according to Patent Document 1, the surface direction of the discharge port is parallel to the flow direction of the intake passage, and the outflow direction of air from the discharge port is orthogonal to the flow direction of the intake passage. According to Patent Document 2, the surface direction of the discharge port is perpendicular to the flow direction of the intake passage, and the discharge port opens toward the downstream side of the intake passage. And the outflow direction of the air from the discharge port substantially coincides with the flow direction of the intake passage.

  However, there are merits and demerits in the way of providing these discharge ports, and there are various problems. That is, according to Patent Document 1, since the surface direction of the discharge port is parallel to the flow direction of the intake passage, even if a reverse flow occurs outside the apparatus due to pulsation, air flowing in the reverse direction is discharged from the discharge port. It is difficult to flow in toward the internal flow path, and a decrease in output value due to pulsation is suppressed. However, if the air that flows in the forward direction outside the device drifts to the discharge port, the drifted air easily flows from the discharge port into the internal flow path, preventing the release of air from the discharge port. The output value will fluctuate.

  According to Patent Document 2, since the discharge port opens toward the downstream side of the intake passage, even if the air flowing in the forward direction drifts, the discharge of air from the discharge port is almost affected. Absent. However, since air flowing in the reverse direction easily flows from the discharge port, it is extremely difficult to avoid a decrease in measured value due to pulsation.

  Further, as described above, the conventional air flow rate measuring apparatus 100 has a correction function corresponding to L2 / L1 in order to improve the measurement value. However, the range of increase in the measurement value by this correction function depends on L2 / L1. It is almost constant. On the other hand, the amount of decrease in the measured value due to pulsation varies variously depending on the true value of the air flow rate and the frequency of pulsation (engine speed). For this reason, even if L2 / L1 is set so that the measured value substantially matches the true value at the air flow rate in the specific range and the engine speed in the specific range, the air flow rate and the engine speed greatly deviate from the specific ranges. In this case, there is a high possibility that the correction for the decrease in the measured value will be excessively small or excessive.

JP 2007-327790 A Japanese Patent No. 4169802

  The present invention has been made in order to solve the above-described problems, and an object of the present invention is to reduce the influence of air pulsation and air drift in an air flow rate measuring apparatus that measures the flow rate of air sucked into an engine. To provide a structure.

[Means of Claim 1]
The air flow rate measuring device according to claim 1 is arranged in the intake passage to the engine, takes in part of the air flowing in the forward direction from the upstream to the downstream through the intake passage, and transfers heat between the taken-in air. This is to measure the flow rate of air taken into the engine by generating a phenomenon.
In addition, the air flow rate measuring device opens toward the upstream side of the intake passage, and causes a heat transfer phenomenon between the intake port that takes in a part of the air flowing in the forward direction in the intake passage and the air that is taken in from the intake port. It has an internal flow path for accommodating the sensor to be generated, and a discharge opening that opens toward the downstream side of the intake passage and returns air taken in from the intake opening and passing through the sensor to the intake passage.

Further, regarding the air flow direction in the internal flow path, if the suction port is the upstream end and the discharge port is the downstream end, the internal flow path downstream of the sensor has a bend, and the flow path forms the bend The wall is provided with a slit that connects the internal flow path and the intake path. When air flows in the reverse direction from the downstream toward the upstream in the intake path, a part of the air flows into the internal flow path from the discharge port, and the air flowing in from the discharge port returns to the intake path from the slit.
Further, the downstream end of the bend is a discharge port, and the slit extends downstream from the upstream end of the bend in the flow path wall that defines the outermost periphery of the swirling flow generated by the bend among the flow path walls that form the bend. It is provided as follows.

First, according to this air flow rate measuring device, since the discharge port opens toward the downstream side of the intake passage, even if the air flowing in the forward direction in the intake passage drifts, the release of air from the discharge port Is hardly affected. In addition, the air flowing in the reverse direction in the intake passage easily flows in from the discharge port and flows in the reverse direction upstream in the internal flow path, but returns to the intake passage from the slit before reaching the sensor. For this reason, since the influence which an air pulsation has on the output value of a sensor can be reduced, the fall of a measured value can be suppressed.
As described above, in the air flow rate measuring device, it is possible to provide a structure that is not easily affected by air pulsation or air drift.

[Means of claim 2 ]
According to the air flow rate measuring device of the second aspect , the discharge port and the slit are provided so that their longitudinal directions substantially coincide with each other, and the longitudinal length of the slit is the longitudinal direction of the discharge port. 1/3 or more of the length.
As a result, more air flowing in from the discharge port can be returned from the slit to the intake passage, so that the influence of air pulsation on the output value of the sensor can be further reduced to suppress a decrease in the measured value.

[Means of claim 3 ]
According to the air flow rate measuring device of the third aspect , the slit has a width of 2 mm or less in the direction perpendicular to the longitudinal direction.
Thereby, the situation where the air which flows through the sensor in the forward direction returns from the slit to the intake passage without reaching the discharge port can be suppressed. For this reason, it can suppress that L2 / L1 fluctuates by providing a slit.

  Further, if the width in the direction perpendicular to the longitudinal direction of the slit is too large, there is a possibility that air flowing in the reverse direction cannot be sufficiently released from the slit due to the influence of the drift in the intake passage. Therefore, by setting the above width to 2 mm or less to suppress the influence of drift, air can be sufficiently released from the slit.

It is sectional drawing which shows the inside of an air flow measuring device (Example). (A) is sectional drawing which shows L2 / L1 of an air flow rate measuring apparatus, (b) is a correlation diagram which shows the correlation with an air flow rate and calorie | heat amount (Example). It is a side view of an air flow rate measuring apparatus (Example). It is a rear view of an air flow measuring device (example). It is a front view of an air flow rate measuring apparatus (Example). It is a bottom view of an air flow measuring device (example). (A) is sectional drawing which shows the inside of an air flow rate measuring apparatus, (b) is a correlation diagram which shows the correlation with an air flow rate and calorie | heat amount (conventional example).

The air flow measurement device of the embodiment is arranged in the intake passage to the engine, takes in a part of the air flowing in the forward direction from the upstream to the downstream of the intake passage, and generates a heat transfer phenomenon with the taken-in air. By doing so, the flow rate of air taken into the engine is measured.
In addition, the air flow rate measuring device opens toward the upstream side of the intake passage, and causes a heat transfer phenomenon between the intake port that takes in a part of the air flowing in the forward direction in the intake passage and the air that is taken in from the intake port. It has an internal flow path for accommodating the sensor to be generated, and a discharge opening that opens toward the downstream side of the intake passage and returns air taken in from the intake opening and passing through the sensor to the intake passage.

  Further, regarding the air flow direction in the internal flow path, if the suction port is the upstream end and the discharge port is the downstream end, the internal flow path downstream of the sensor has a bend, and the flow path forms the bend The wall is provided with a slit that connects the internal flow path and the intake path. When air flows in the reverse direction from the downstream toward the upstream in the intake path, a part of the air flows into the internal flow path from the discharge port, and the air flowing in from the discharge port returns to the intake path from the slit.

The downstream end of the bend is a discharge port, and the slit extends downstream from the upstream end of the bend in the flow path wall that defines the outermost periphery of the swirl flow generated by the bend among the flow path walls that form the bend. It is provided as follows.
The discharge port and the slit are provided so that their longitudinal directions substantially coincide with each other, and the length of the slit in the longitudinal direction is 1/3 or more of the length of the discharge port in the longitudinal direction.
Furthermore, the slit has a width of 2 mm or less in a direction perpendicular to the longitudinal direction.

[Configuration of Example]
The structure of the air flow rate measuring apparatus 1 of an Example is demonstrated using FIGS.
The air flow rate measuring device 1 is disposed so as to protrude into an intake passage to the engine and is used for measuring a flow rate of air taken into the engine.
In the following description, in the intake passage, the direction from the air cleaner (upstream) to the engine (downstream) is referred to as the forward direction, and the direction from the engine (downstream) to the air cleaner (upstream) is referred to as the reverse direction.

  The air flow rate measuring device 1 directly measures a mass flow rate as an air flow rate by taking a part of the air flowing in the forward direction in the intake passage and generating a heat transfer phenomenon with the taken air. To do.

  That is, the air flow rate measuring device 1 accommodates a thermal sensor (hereinafter abbreviated as a sensor) 2 and a sensor 2 that generate a heat transfer phenomenon with air to generate an output value corresponding to a mass flow rate. A housing 4 and a connector 4 for outputting an output value obtained from the sensor 2 to an electronic control unit (ECU: not shown) are provided. And ECU grasps | ascertains the flow volume of the air inhaled by an engine based on the output value obtained from the air flow measuring device 1, and performs various control processes, such as fuel injection control, based on the grasped air flow volume. .

  The sensor 2 has a heating element (not shown) that applies heat to the air. For example, the temperature difference between the temperature of the air that is not thermally influenced by the heating element and the temperature of the heating element is a predetermined numerical value. The heat generation of the heating element is controlled so that Thereby, the correlation between the amount of heat given to the air from the heating element and the air flow rate becomes convex upward when the heat amount is taken as the vertical axis and the air flow rate is taken as the horizontal axis (see FIG. 2B). That is, although the amount of heat increases as the air flow rate increases, the rate of increase of the heat amount relative to the air flow rate decreases as the air flow rate increases. The sensor 2 generates an output value corresponding to the mass flow rate in accordance with the amount of heat given from the heating element to the air by the control based on the convex correlation.

  The housing 3 opens, for example, toward the upstream side of the intake passage, and passes through the intake port 6 for taking in part of the air flowing in the forward direction of the intake passage, the air taken in from the intake port 6 and accommodates the sensor 2. And a discharge port 8 that opens toward the downstream side of the intake passage and returns the air taken in from the intake port 6 and passed through the sensor 2 to the intake passage. The sensor 2 generates a heat transfer phenomenon with the air taken in from the suction port 6 to generate an output value corresponding to the mass flow rate.

  In the following description, regarding the air flow direction in the internal flow path 7, the suction port 6 is the upstream end, the discharge port 8 is the downstream end, the flow direction from the suction port 6 toward the discharge port 8 is the forward direction, The flow direction from the outlet 8 toward the suction port 6 is the reverse direction.

  The internal flow path 7 contains, for example, a suction flow path 10 that is continuous downstream from the suction opening 6, a discharge flow path 11 that is continuous upstream from the discharge opening 8, and the sensor 2, and also discharges from the suction flow path 10. It has the circulation channel 12 which circulates so that the channel 11 may be connected.

  The suction channel 10 is provided so as to extend linearly from the suction port 6 to the downstream side, and the flow in the suction channel 10 is parallel to the forward flow in the intake channel. A dust discharge flow path 13 is connected to the downstream end of the suction flow path 10 for moving the dust contained in the air taken in from the suction port 6 straight and discharging it. Further, a dust discharge port 14 is formed at the downstream end of the dust discharge channel 13, and the dust discharge channel 13 tapers toward the dust discharge port 14.

  For example, the circulation channel 12 is connected to the suction channel 10 and the discharge channel 11 in a substantially C shape, and circulates the air taken in from the suction port 6 toward the discharge channel 11 from the suction channel 10. . Further, the sensor 2 is accommodated in a portion of the circumferential flow channel 12 that flows in a direction opposite to the flow direction in the suction flow channel 10.

  Here, the circulation channel 12 is branched at a downstream end of the suction channel 10 so as to bend at a substantially right angle from a linear channel composed of the suction channel 10 and the dust discharge channel 13. That is, the suction channel 10 is branched into the circulation channel 12 and the dust discharge channel 13 at the downstream end, and the dust travels straight from the suction channel 10 to the dust discharge channel 13 due to the inertial force. The air is discharged from the outlet 14 to the intake passage, and the air flows from the intake passage 10 into the circulation passage 12 while changing the flow direction.

  The discharge flow channel 11 is connected to the downstream end of the circular flow channel 12 and is bent so as to turn the forward flow at the downstream end of the circular flow channel 12 at a substantially right angle, and the discharge port 8 is the downstream end of the bending. It is. Further, the discharge channel 11 is branched into two from the upstream end so as to straddle the suction channel 10, and the discharge ports 8 are formed at two positions on both sides of the suction channel 10 (FIGS. 1 and 2). FIG. 5 and FIG. 6). That is, the discharge channel 11 is branched into two so as to be mirror-symmetrical with the cut surface including the channel axis of the suction channel 10 and the circulation channel 12 as a symmetry plane (see FIGS. 4 to 6). Yes.

  As described above, the internal flow path 7 is provided so as to bypass the linear flow in the intake passage, and the air taken in from the suction port 6 can be used to bypass the linear flow in the intake passage. 2 (see FIG. 2).

  That is, assuming that the flow path length when the air flow path is not taken into the internal flow path 7 and goes straight through the intake path is L1, and the flow path length of the internal flow path 7 is L2, the air flow rate measuring device 1 is an internal part that bypasses the linear flow. By forming the flow path 7 and arranging the sensor 2 in the internal flow path 7, it has a correction function for increasing the output value according to L2 / L1. According to this correction function, the output value can be increased as L2 / L1 is increased.

Here, a portion of the housing 3 that forms the flow path wall outside the discharge flow path 11 is referred to as an outlet cover 15.
The outlet cover 15 is provided with a slit 17 perpendicular to the flow direction of the intake passage and the intake passage 10, and the slit 17 communicates the internal passage 7 and the intake passage (FIGS. 1 to 3). reference). When air flows through the intake passage in the reverse direction, a part of the air flows into the internal flow path 7 from the discharge port 8, and the air flowing in from the discharge port 8 returns from the slit 17 to the intake passage.

The slit 17 is provided so as to extend from the upstream end of the discharge flow channel 11 to the downstream side in the portion of the outlet cover 15 that defines the outermost periphery of the swirling flow generated in the discharge flow channel 11.
That is, the slit 17 is provided along the streamline A passing through the outermost periphery of the swirl circumference among the streamlines indicating the forward swirl flow generated in the discharge channel 11, and in the discharge channel 11 of the streamline A. It is provided so as to extend downstream from the upstream end along the streamline A.

Further, the discharge port 8 and the slit 17 are provided so that their longitudinal directions substantially coincide with each other (see FIGS. 1 to 3), and the length of the slit 17 in the longitudinal direction is the longitudinal direction of the discharge port 8. The length is 1/3 or more (see FIG. 3).
Further, the slit 17 has a width of 2 mm or less in a direction perpendicular to the longitudinal direction (see FIG. 3).

[Effects of Examples]
According to the air flow rate measuring device 1, the discharge port 8 opens toward the downstream side of the intake passage.
Thereby, even if the air flowing in the forward direction drifts in the intake passage, the release of air from the discharge port 8 is hardly affected.

  Further, the discharge flow channel 11 is connected to the downstream end of the circular flow channel 12 that accommodates the sensor 2, and is bent to turn the forward flow at the downstream end of the circular flow channel 12 at a substantially right angle. 11 is provided with a slit 17 that communicates the internal flow path 7 and the intake path. When air flows through the intake passage in the reverse direction, a part of the air flows into the internal flow path 7 from the discharge port 8, and the air flowing in from the discharge port 8 returns from the slit 17 to the intake passage.

As a result, air flowing in the reverse direction in the intake passage easily flows in from the discharge port 8 and flows in the reverse direction in the internal flow path 7, but returns to the intake passage from the slit 17 before reaching the sensor 2. For this reason, since the influence which an air pulsation exerts on the output value of the sensor 2 can be reduced, the fall of a measured value can be suppressed.
As described above, the air flow measuring device 1 can be provided with a structure that is not easily affected by air pulsation or air drift.

Further, the downstream end of the bend as the discharge flow path 11 is the discharge port 8, and the slit 17 is bent in the flow path wall defining the outermost periphery of the swirl flow generated by the bend among the flow path walls forming the bend. It is provided so that it may extend from the upstream end to the downstream side.
As a result, more air flowing in from the discharge port 8 can be returned from the slit 17 to the intake passage, so that the influence of air pulsation on the output value of the sensor 2 can be further reduced to suppress the decrease in the measured value. Can do.

Further, the discharge port 8 and the slit 17 are provided so that their longitudinal directions substantially coincide with each other, and the length of the slit 17 in the longitudinal direction is 1/3 or more of the length of the discharge port 8 in the longitudinal direction. It is.
As a result, more air flowing in from the discharge port 8 can be returned from the slit 17 to the intake passage, so that the influence of air pulsation on the output value of the sensor 2 can be further reduced to suppress the decrease in the measured value. Can do.

The slit 17 has a width of 2 mm or less in a direction perpendicular to the longitudinal direction.
Thereby, it is possible to suppress a situation in which the air flowing in the forward direction that has passed through the sensor 2 returns from the slit 17 to the intake passage without reaching the discharge port 8. For this reason, it can suppress that L2 / L1 fluctuates by providing the slit 17.

  Further, if the width of the slit 17 in the direction perpendicular to the longitudinal direction is too large, there is a possibility that air flowing in the opposite direction cannot be sufficiently released from the slit 17 due to the influence of the drift in the intake passage. Therefore, by setting the width in the direction perpendicular to the longitudinal direction of the slit 17 to 2 mm or less to suppress the influence of drift, air can be sufficiently released from the slit 17.

[Modification]
The aspect of the air flow rate measuring device 1 is not limited to the embodiment, and various modifications can be considered.
For example, according to the air flow rate measuring apparatus 1 of the embodiment, the discharge flow path 11 is formed only by a curve, and the downstream end of the curve is the discharge port 8, but linearly from the discharge port 8 to the upstream side. A continuous straight path may be provided as part of the discharge flow path 11 and a bend may be connected to the upstream end of the straight path.

DESCRIPTION OF SYMBOLS 1 Air flow measuring device 2 Sensor 6 Intake port 7 Internal flow path 8 Outlet port 17 Slit

Claims (3)

A part of the air flowing in the forward direction from upstream to downstream through the intake passage is taken in the intake passage to the engine, and a heat transfer phenomenon is generated between the intake air and the intake passage. In the air flow measurement device that measures the flow rate of air,
An intake port that opens toward the upstream side of the intake passage and takes in a part of the air flowing in the forward direction through the intake passage;
An internal flow path for accommodating a sensor that generates a heat transfer phenomenon with the air taken in from the suction port;
An opening that opens toward the downstream side of the intake passage, and that returns air that has been taken in from the intake port and passed through the sensor to the intake passage;
Regarding the air flow direction in the internal flow path, if the suction port is an upstream end and the discharge port is a downstream end,
A curve is formed in the internal flow path on the downstream side of the sensor,
The flow path wall that forms this bend is provided with a slit that communicates the internal flow path and the intake path,
When air flows in the reverse direction from the downstream toward the upstream through the intake path, a part of the air flows into the internal flow path from the discharge port, and the air flowing in from the discharge port passes through the slit to the intake air. to return to the road,
The downstream end of the bend is the outlet;
The slit is provided so as to extend from the upstream end to the downstream side of the bend in the flow path wall that defines the outermost periphery of the swirling flow generated by the bend among the flow path walls that form the bend. A characteristic air flow rate measuring device. The air flow rate measuring device according to claim 1,
The discharge port and the slit are provided so that their longitudinal directions substantially coincide with each other,
The length of the slit in the longitudinal direction is 1/3 or more of the length in the longitudinal direction of the discharge port . In the air flow rate measuring device according to claim 1 or 2,
The air flow measuring device according to claim 1, wherein the slit has a width of 2 mm or less in a direction perpendicular to the longitudinal direction .

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