JP2012189484A - Air flow rate measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an air flow rate measuring device capable of presenting highly accurate output characteristics even in a high flow rate area in engine pulsation.SOLUTION: A bypass channel 7 is formed to improve response delay of a flow rate sensor 4 in engine pulsation and a sub-bypass channel 9 in the bypass channel 7 includes projected walls 11, 12 forming barrier means only on the downstream side of an arrangement position of the flow rate sensor 4. Thereby, air collides with the projected walls 11, 12 especially in a high flow rate area and inertial force is weakened, so that excessive correction of output characteristics to the rich side can be prevented. Since the projected walls 11, 12 are located on the downstream side of the flow rate sensor 4, disturbance of airflow due to the projected walls 11, 12 is not influenced on the flow rate sensor 4 and the detection accuracy of the flow rate sensor 4 is not detracted.

Description

  The present invention is mounted on a vehicle such as an automobile and measures the flow rate of air flowing through an intake duct in order to measure the amount of air (intake) taken into an internal combustion engine (hereinafter referred to as an engine). The present invention relates to an air flow measuring device.

(Conventional technology)
Conventionally, this type of air flow measurement device has been put to practical use in various configurations and systems. However, due to the demand for higher accuracy in flow measurement associated with higher performance of the engine, particularly during engine pulsation. As a result of efforts to improve the response delay of the flow sensor, a so-called bypass system in which a bypass flow path for bypassing the air flow is provided and the flow sensor is disposed in the bypass flow path is now common. As shown in the pulsation characteristic (error) of FIG. 4, this method causes a lean error as indicated by a dotted line due to a response delay of the flow rate sensor when the engine pulsates when there is no bypass flow path (no bypass). . For this reason, the inertia of the air flowing through the bypass flow path is used as a method of returning the lean error to the steady-state reference (thin solid line) (correcting to the rich side).

Such a bypass system has also evolved, and as a bypass channel, a combination of a main channel and a sub channel is usually adopted. The typical air flow rate measuring device will be outlined with reference to FIG. 5 and FIG.
FIG. 5 shows an air flow rate measuring device known as Patent Document 1. In FIG.
This air flow rate measuring apparatus has a sensor body 110 disposed in an intake duct 100 that forms an air passage to the engine, and a part of the air A flowing through the intake duct 100 is taken into the sensor body 110. A bypass channel 120 is formed. The bypass passage 120 includes a linear main bypass passage 120a and a sub bypass passage 120b that forms a flow C of air that takes in a part of the air B flowing through the main bypass passage 120a and further bypasses it. It is configured. The sub-bypass channel 120b has a substantially inverted U shape having a channel length longer than that of the main bypass channel 120a, and the intake air amount is measured near the center of the sub-bypass channel 120b. A flow sensor 130 is disposed.

FIG. 6 is an air flow rate measuring apparatus known as Patent Document 2, and particularly shows another form of the bypass flow path 120 provided in the sensor body 110.
In the air flow rate measuring device of FIG. 6A, the entire bypass flow path 120 is configured as a spiral flow path, and the main bypass flow path 120a having the first opening D as an outlet and the second opening E as an outlet. A sub-bypass channel 120b, and a flow sensor 130 is disposed in the sub-bypass channel 120b.
The air flow rate measuring device of FIG. 6B includes a linear main bypass channel 120a having a first opening D as an outlet and a substantially J-shaped sub bypass channel 120b having a second opening E as an outlet. The flow sensor 130 is disposed in the sub-bypass channel 120b.

(Problems of conventional technology)
Such an air flow rate measuring device can form a bypass air flow (air flow B, C) that is not easily affected by the pulsation of the engine with respect to the main air flow A flowing through the intake duct 100. Although the response delay can be improved, as shown by the thick solid line (with bypass) in FIG. 4, there is a problem that a so-called rich error occurs in which the characteristic shifts to the rich side as the flow rate increases.

JP 2008-309623 A JP 2005-128038 A

  The present inventor has conducted various experiments and researches to find out such a problem. If the inertia effect of the bypass air flow becomes too large in a high flow rate region where the flow rate is large, an overcorrection phenomenon occurs. It turned out to be.

The present invention has been made in view of the above investigation results, and the object of the present invention is to provide barrier means for slowing the inertial effect of the bypass air flow in a high flow rate region where the flow rate is high, and from a low flow rate. An object of the present invention is to provide an air flow rate measuring device that exhibits highly accurate output characteristics in a wide flow rate range up to a high flow rate.
It is another object of the present invention to provide an air flow rate measuring device that does not impair the detection accuracy of the flow rate sensor due to the barrier means.

[Means of Claim 1]
According to the air flow rate measuring apparatus employing the means of claim 1, the flow rate sensor is disposed in the bypass flow path that takes in a part of the air flowing inside the duct, and the flow rate is measured in the bypass flow path. Barrier means for causing air flowing in the flow path to collide only in the flow path located downstream from the sensor installation position and changing the flow resistance between the upstream side and the downstream side of the flow rate sensor is provided. It is characterized by that.

As a result, as the flow rate becomes higher, the air flowing through the bypass channel collides with the barrier means and its inertial force is weakened (slows down), which can cancel out the rich error in the high flow rate range. High-accuracy output characteristics can be obtained in a wide range of flow rates from low to high flow rates.
Further, since the barrier means is disposed only on the downstream side of the flow sensor, the disturbance of the air flow generated by the barrier means does not directly affect the flow sensor, and the detection accuracy of the flow sensor is not impaired.

[Means of claim 2]
According to the air flow rate measuring apparatus employing the means of claim 2, the bypass flow path is composed of a main bypass flow path and a sub bypass flow path that takes in a part of the air flowing through the main bypass flow path. The flow sensor is disposed in the sub-bypass channel and measures the flow rate of air flowing through the sub-bypass channel.
With such a configuration, the bypass flow path in which the flow sensor is disposed can be made longer and a stable measurement air flow can be secured, so that the output characteristic accuracy of the flow sensor can be further improved.

[Means of claim 3]
According to the air flow rate measuring apparatus employing the means of claim 3, the barrier means changes the flow path resistance according to the flow rate of the air passing through the flow sensor, and the flow path resistance increases as the flow rate increases. It is characterized by.
With such a configuration, the inertial effect of the air flow in the high flow rate region can be efficiently blunted.

[Means of claim 4]
According to the air flow rate measuring apparatus employing the means of claim 4, the barrier means is constituted by a protruding wall protruding so as to reduce a part of the flow cross section of the bypass flow path from the inner wall surface of the bypass flow path. It is characterized by.
[Means of claim 5]
According to the air flow rate measuring apparatus employing the means of claim 5, the protruding wall is provided at a position where the inertial force of the air flowing through the bypass flow path becomes large.
According to the configuration of the means of claims 4 and 5, the effect of the means of claim 1 can be obtained with a simple configuration.

[Means of claim 6]
According to the air flow rate measuring apparatus employing the means of claim 6, the barrier means is configured as a projection group in which the projection wall is composed of a plurality of projections, and the projection group is configured such that the projections are mutually connected along the bypass channel. It is characterized by being arranged in a zigzag shape so as not to face each other.
According to such a configuration, the bypass flow path downstream of the flow sensor can be made substantially zigzag to efficiently increase the flow path resistance, thereby further improving accuracy.

[Means of Claim 7]
According to the air flow rate measuring apparatus employing the means of claim 7, the barrier means is constituted by an annular throttle protruding so as to reduce the flow cross section of the bypass flow channel over the entire circumference from the inner wall surface of the bypass flow channel. It is characterized by that.
With this configuration, the same effect as that of the first aspect can be obtained.

[Means of Claim 8]
According to the air flow rate measuring apparatus employing the means of claim 8, the barrier means is formed by forming the inner wall surface of the bypass flow path in a zigzag shape along the bypass flow path. .
With this configuration, the same effect as that of the means of the sixth aspect can be obtained.

[Means of Claim 9]
According to the air flow rate measuring apparatus employing the means of claim 9, the body member forming the bypass flow path is formed of resin, and the barrier means is integrally formed with the body member. .
Thereby, a special man-hour is not required for providing the barrier means, and an inexpensive air flow measuring device can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS It shows typically the air flow rate measuring apparatus of Example 1 of this invention, (a) Longitudinal sectional view, (b) The expanded sectional view of the X section. The external appearance of a single air flow rate measuring device is shown, (a) a front view seen from the upstream side, (b) a side view, (c) a rear view seen from the downstream side (Example 1). It is a graph with which it uses for characteristic description of an air flow measuring device. It is a graph with which it uses for problem description of an air flow rate measuring apparatus. It is sectional drawing of the air flow rate measuring apparatus which concerns on a prior art. (A), (b) It is sectional drawing which shows the other form of the air flow rate measuring apparatus based on a prior art.

  The best mode for carrying out the present invention will be described in detail with reference to the following examples.

[Example 1]
[Configuration of Example 1]
This embodiment will be described with reference to FIGS. FIG. 1 is a cross-sectional view for explaining the overall configuration of the air flow rate measuring device, and FIG. 2 is a single view for explaining the external appearance of the air flow rate measuring device shown in FIG.

  The air flow rate measuring apparatus 1 according to the present embodiment measures, for example, the intake air (intake) amount of an engine, and is connected to an air cleaner (not shown) as shown in FIG. Is detachably attached to the air intake duct 2 that forms, for example, by a plug-in method.

The air flow rate measuring device 1 is modularized so that the sensor body 3, the flow rate sensor 4, the circuit module 5 and the like are main components and can be handled as a whole. The sensor body 3 is inserted into the intake duct 2 through the attachment hole 2 a provided in the intake duct 2 so as to cross the main flow path 6.
The sensor body 3 is for forming a bypass flow path 7 that bypasses the main flow path 6, and has a cylindrical body 3 a having a warhead shape and a rectangular parallelepiped box shape provided integrally with the cylindrical body 3 a. It is comprised with the body 3b.
The cylindrical body 3a is formed with a main bypass passage 8 that takes in part of the air A flowing from the left side to the right side of the main duct 6 of the intake duct 2 to form an air flow B, and the box-type body 3b. Are formed with a sub-bypass channel 9 that takes in part of the air B flowing through the main bypass channel 8 and forms an air flow C. Hereinafter, the air flows A, B, and C are referred to as a main flow A and bypass flows B and C, respectively.

The main bypass channel 8 includes an inlet 8a that opens at the center of the front end (left end in FIG. 1) of the cylindrical body 3a and an outlet 8b that opens at the center of the rear end (right end of FIG. 1) of the cylindrical body 3a. And is linearly formed from the inlet 8a to the outlet 8b. Therefore, the bypass flow B flowing through the main bypass flow path 8 is in a bypass flow parallel to the main flow A.
Further, on the outlet 8b side of the main bypass channel 8, a tapered throttle portion 10 is provided that gradually decreases the channel cross-sectional area of the main bypass channel 8 toward the outlet 8b.

  The sub-bypass channel 9 includes an inlet 9a branched from the main bypass channel 8 on the upstream side of the throttle portion 10 of the main bypass channel 8, and an outlet 9b formed in an annular shape around the outlet 8b of the main bypass channel 8. And a U-turn portion 9c in which the air flow direction changes 180 degrees (U-turn) is provided between the inlet 9a and the outlet 9b. The sub-bypass channel 9 has a channel length longer than the channel length of the main bypass channel 8.

  The flow sensor 4 cooperates with the circuit module 5 to measure the air flow rate of the bypass flow C flowing through the sub bypass flow path 9 and output it as an electrical signal (for example, a voltage signal). It is used for practical use. The flow sensor 4 has, for example, a flow rate measuring element having a chip sensor structure composed of a heating element and a temperature sensitive element formed of a thin film resistor on the surface of a semiconductor substrate, and these elements are connected to the circuit module 5. It becomes the composition which is done.

  The flow sensor 4 is disposed at a predetermined position downstream of the inlet 9 a of the sub bypass flow path 9. The flow sensor 4 of the present embodiment is disposed at the approximate center of the U-turn portion 9c of the sub-bypass passage 9, but is disposed in the straight pipe portion 9d upstream of the U-turn portion 9c and downstream of the inlet 9a. May be.

  The circuit module 5 is provided integrally with the sensor body 3 and is disposed outside the mounting hole 2 a of the intake duct 2. The circuit module 5 is connected to a well-known ECU (electronic control unit) (not shown), and the ECU measures the intake air amount of the engine.

[Characteristics of Example 1]
Thus, the sub-bypass channel 9 is provided with a pair of protruding walls 11 and 12 only on the downstream side of the position where the flow sensor 4 is disposed. The pair of projecting walls 11 and 12 form a barrier means for changing the flow resistance between the upstream side and the downstream side of the flow sensor 4 by colliding with the bypass flow C, and is also shown in FIG. The specific configuration is as follows.
That is, the projection walls 11 and 12 are each configured as a projection group including a plurality of (two in this embodiment) projections 11a, 11b, 12a, and 12b. The protrusions 11a, 11b, 12a, and 12b protrude in the sub-bypass channel 9 so as to partially reduce the flow cross section of the channel from the inner wall surface, and are provided in series at equal intervals along the bypass flow C. It has been. Also, the projections 11a and 11b of one projection wall 11 and the projections 12a and 12b of the other projection wall 12 are arranged in a zigzag shape so as not to face each other, and the zigzag flow channel undulates along the flow. 9e is formed.
The sensor body 3 is formed of an injection-molded product made of resin, and is manufactured by bonding a pair of half-divided products along the parting line (YY) in FIG. In this case, the protruding walls 11 and 12 are integrally formed when the sensor body 3 is formed.

[Operation and Effect of Example 1]
When the main flow A of air is generated inside the intake duct 2 by starting the engine, a part of the main flow A is taken into the bypass flow path 7 of the sensor body 3. The air taken into the bypass flow path 7 becomes a bypass flow B flowing through the main bypass flow path 8, and a part of the bypass flow B is taken into the sub bypass flow path 9. Thus, a stable air flow, that is, a bypass flow C can be formed in the sub-bypass channel 9, and the flow rate is detected by the flow rate sensor 4 disposed in the sub-bypass channel 9.

  Here, for example, when the intake air amount increases as in the case of high-speed operation of the engine, the air amount in each of the main flow A and the bypass flows B and C becomes a high flow rate, and the inertia of the bypass flow C in the sub-bypass channel 9. Since the force also increases rapidly, the flow rate sensor 4 is on the rich side as the flow rate increases, as shown by the one-dot chain line in FIG. The output characteristic that the fluctuation to

According to the present embodiment, since the sub-bypass channel 9 is provided with the protruding walls 11 and 12 on the downstream side of the flow sensor 4, the bypass flow C collides with the protruding walls 11 and 12, and the inertial force is generated. It will weaken (slow down).
It should be noted here that when the amount of air in the bypass flow C is relatively small (low flow rate), the air smoothly flows through the center of the sub-bypass channel 9 as shown by the arrow in FIG. 11 and 12 do not become a hindrance (flow path resistance). On the other hand, as the flow rate increases, air is drawn to the outside of the inner wall of the sub bypass flow path 9 (projection wall 11 side) as the flow rate increases. 12 indicates a larger flow path resistance as the flow rate increases. Thereby, the flow sensor 4 exhibits an output characteristic as shown by a thick solid line (the present invention) in FIG. 3, and obtains a characteristic with a small rich error along the steady-state reference (thin solid line) even in a high flow rate region. be able to. Thus, highly accurate output characteristics can be obtained in a wide flow range from low flow rate to high flow rate.

  In addition, since the projection walls 11 and 12 are provided downstream from the arrangement position of the flow sensor 4, the flow turbulence generated by the collision with the projection walls 11 and 12 does not directly hit the flow sensor 4. The detection accuracy of the flow sensor 4 is not impaired.

  In particular, the pair of protruding walls 11 and 12 of the sub-bypass channel 9 are displaced so that the protrusions 11a and 11b and the protrusions 12a and 12b do not face each other, as shown in FIG. The flow passage cross-sectional area of the sub-bypass passage 9 is not extremely narrowed, the flow passage resistance is small at a low flow rate, and the air flowing through the sub-bypass flow passage 9 along the zigzag flow passage 9e at a high flow rate Since it flows in a zigzag shape like ', the flow path resistance increases. Thus, the accuracy of the output characteristics of the flow rate sensor 4 can be further improved in a wide flow rate range from a low flow rate to a high flow rate.

[Modification]
As described above, the first embodiment has been described in detail, but the arrangement, shape, size, and number of the protruding walls 11 and 12 as the barrier means can be variously changed without departing from the spirit of the present invention.
For example, in the first embodiment, the pair of projecting walls 11 and 12 are provided. However, even if the projecting walls 11 are provided only at the position where the inertial force of the air flow increases, that is, along the bypass flow C, only on the outer flow path inner wall. good.
Further, the barrier means provided downstream of the flow sensor 4 in the sub-bypass channel 9 collides with the air flowing in the flow channel, and changes the flow channel resistance between the upstream side and the downstream side of the position where the flow sensor 4 is disposed. Instead of the projecting walls 11 and 12, it may be constituted by an annular throttle protruding from the inner wall surface of the sub-bypass channel 9 so as to reduce the flow cross section of the sub-bypass channel 9 over the entire circumference. Alternatively, the sub-bypass channel 9 itself may be configured as the zigzag channel 9e by forming the inner wall surface of the sub-bypass channel 9 in a zigzag shape along the direct channel.

  Moreover, as an application example to the air flow rate measuring device in which the bypass channel 7 is configured by a combination of the main bypass channel 8 and the sub-bypass channel 9, in addition to the type of the first embodiment, FIG. ), (B) can also be applied to the air flow measuring device having the bypass flow path 120. In this case, a barrier means such as a protruding wall is provided downstream of the flow sensor 130 in the sub bypass flow path 120b. Therefore, the same effect as in the first embodiment can be obtained.

  In the above-described example, the application example to the air flow rate measuring device including the main bypass channel and the sub-bypass channel as the bypass channel has been described in detail, but one bypass corresponding to only the main bypass channel is provided. It goes without saying that the present invention can be similarly applied to an air flow rate measuring apparatus having a flow path and a flow rate sensor disposed in the bypass flow path, by providing a barrier means downstream of the flow sensor location. Also, various types of configurations that are in practical use can be applied to the flow rate sensor.

1 Air flow measurement device 2 Air intake duct (duct)
3 Sensor body (body member)
4 Flow sensor 6 Main flow path 7 Bypass flow path 8 Main bypass flow path 9 Sub bypass flow path 11 Projection wall (barrier means)
11a, 11b Projection 12 Projection wall (barrier means)
12a, 12b Protrusion

Claims (9)

A bypass flow path for taking in part of the air flowing inside the duct;
An air flow rate measuring device having a flow rate sensor that is disposed in the bypass flow channel and measures a flow rate of air flowing through the bypass flow channel,
The bypass flow channel collides with air flowing in the flow channel only in the flow channel located downstream from the position where the flow sensor is disposed, and the flow resistance is increased between the upstream side and the downstream side of the flow rate sensor. An air flow rate measuring device comprising a barrier means for changing. In the air flow rate measuring device according to claim 1,
The bypass channel is composed of a main bypass channel and a sub-bypass channel that takes in part of the air flowing through the main bypass channel,
The flow rate sensor is disposed in the sub-bypass channel and measures the flow rate of air flowing through the sub-bypass channel. In the air flow rate measuring device according to claim 1 or 2,
The air flow measuring device according to claim 1, wherein the barrier means changes the flow path resistance according to the flow rate of air passing through the flow sensor, and the flow path resistance increases as the flow rate increases. In the air flow rate measuring device according to any one of claims 1 to 3,
The air flow measuring device according to claim 1, wherein the barrier means includes a protruding wall that protrudes from an inner wall surface of the bypass channel so as to reduce a part of a flow section of the bypass channel. In the air flow measuring device according to claim 4,
The air flow measuring device according to claim 1, wherein the protruding wall is provided at a position where an inertial force of the air flowing through the bypass flow path is increased. In the air flow measuring device according to claim 4,
The barrier means is configured as a projection group in which the projection wall includes a plurality of projections,
The air flow measuring device, wherein the protrusion group is arranged in a zigzag shape so that the protrusions do not face each other along the bypass flow path. In the air flow rate measuring device according to any one of claims 1 to 3,
The air flow measuring device according to claim 1, wherein the barrier means comprises an annular throttle projecting from the inner wall surface of the bypass channel so as to reduce the flow cross section of the bypass channel over the entire circumference. In the air flow rate measuring device according to any one of claims 1 to 3,
The said barrier means is comprised by forming the inner wall surface itself of the said bypass flow path in zigzag shape along the said bypass flow path, The air flow measuring device characterized by the above-mentioned. In the air flow rate measuring device according to any one of claims 1 to 8,
A body member forming the bypass flow path is formed of resin, and the barrier means is integrally formed with the body member.

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