JP3829930B2 - Air flow measurement device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an air flow rate measuring device for measuring the amount of intake air in an intake passage, and more particularly to an air flow rate measurement device having a bypass flow passage in the intake passage for allowing a part of the air flowing through the intake passage of an automobile engine to flow in.
[0002]
[Prior art]
As conventional techniques for improving the detection accuracy of an air flow rate measuring device, those disclosed in, for example, Japanese Patent Application Laid-Open No. 10-142020 and Japanese Patent Application Laid-Open No. 11-511262 are known. Those disclosed in these publications have a shape in which the cross section is two-dimensionally narrowed so that the side surface of the measurement channel is tapered in the axial direction when viewed from the flow direction, or upstream of the narrowest part of the measurement channel or measurement A detection element is arranged upstream of the outlet in the flow path. The measurement flow path in the flow direction is tapered to create a uniform parallel flow of intake air that is as obstructive as possible in the area where the detection element is present.
[0003]
[Problems to be solved by the invention]
However, in the technique disclosed in the above publication, since the measurement channel has a shape in which only the direction perpendicular to the flow direction of the intake air is throttled two-dimensionally, the fluctuation of the intake air on the throttled side can be reduced. The fluctuation of the intake air on the side that is not done cannot be suppressed. For this reason, there exists a subject that the effect with respect to detection accuracy is not enough.
[0004]
Further, in the above prior art, since the detection element is arranged at a position that can be seen from the inlet of the intake air, if foreign matter such as dust is mixed in the intake air, the foreign matter is reflected on the side surface (slope) of the diaphragm. In the worst case, there is a problem that the detection element may be broken by the reflected foreign matter.
The object of the present invention is to reduce the output fluctuation and the measurement error due to the disturbance of the flow of the intake air flowing into the measuring device by three-dimensionally restricting at least a part of the bypass flow path in view of the problems in the above prior art. An object of the present invention is to provide an air flow rate measuring device that can suppress and improve the measurement accuracy.
[0005]
Another object of the present invention is to prevent the detection element from being damaged by colliding with the detection element by forming an inflow port portion so that the detection element cannot be seen from the intake air inlet.
[0006]
[Means for Solving the Problems]
In order to solve the above problem, the means described in claim 1 can be employed.
According to this means, the cross-sectional area of the bypass flow path is the largest at the air inlet portion, and the cross section from the air inlet portion to the bypass flow passage to the detection element placement portion arranged in the downstream air passage Because of the three-dimensionally narrowed shape, the output fluctuation of the flow rate detection element due to the disturbance of the flow of intake air flowing into the air flow rate measuring device compared to the conventional bypass flow path narrowed only two-dimensionally Further, generation of measurement errors is suppressed, and as a result, measurement accuracy can be improved. Furthermore, by making the aperture height different depending on the location, such as the top and bottom of the detection element arrangement site, it can be used for control of a system that requires tuning of pulsation characteristics.
[0008]
Further, according to the means of claim 2, since the degree stop near the detection elements arranged site employs a shape that changes rapidly, can be used if turbulence upstream of the air flow is great.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. Throughout the drawings, the same reference numerals represent the same elements, and the same reference numerals with the alphabetic letters a, b, c, etc. represent similar elements.
FIG. 1 is a schematic sectional view of a part of an intake passage of an automobile engine according to an embodiment of the present invention. In the figure, 1 is a duct through which intake air passes, 2 is a bypass flow path provided in the duct 1 for measuring the amount of intake air, and 3 passes through the bypass flow path. 4 is a sensing unit of the sensor 3, 5 is a sensor support member, 6 is a circuit that processes the output of the sensor 3, and 7 is an air inlet to the bypass channel 2. According to the embodiment of the present invention, the inlet portion 7 is provided at a position where the sensor 3 cannot be seen from the inlet portion 7. Thereby, even if foreign substances are mixed in the air flowing in from the inlet portion 7, the probability that these foreign substances are reflected on the wall of the bypass flow path and collide with the sensor 3 can be reduced. The sensor 3 utilizes the resistance temperature characteristic of the heating resistor. The sensor 3 is attached to the sensor arrangement part of the sensor support member 5. The intake air flow rate measured by the sensor 3 is used in a system that controls the optimum air fuel consumption and ignition timing by the fuel injection control means.
[0012]
It is desirable that the air flow in the vicinity of the sensing unit 4 is a uniform parallel flow with as little interference as possible. In order to realize this, in the embodiment of the present invention, as described below, at least a part of the cross-section of the bypass channel is three-dimensionally narrowed.
FIG. 2 is a perspective view seen from the air inlet of the conventional bypass passage 2x. As shown in the drawing, conventionally, the throttle portions 21 and 22 are provided only on the side walls corresponding to the upper and lower positions with respect to the sensor support member 5 in the bypass flow path 2x.
[0013]
FIG. 3 is a perspective view seen from the upstream side opening of the bypass flow path according to the embodiment of the present invention. As shown in the figure, in the present embodiment, in addition to the throttle portions 21 ′ and 22 ′ on the side wall of the bypass flow path at the upper and lower positions of the sensor support member 5, the bypass at the left and right positions of the sensor support member 4. The throttle portions 31 and 32 were also provided on the side wall of the flow path.
In the example shown in FIGS. 2 and 3, the cross-sectional shape of the bypass channel is rectangular. In the following, the right and left directions of the rectangle shown in the figure are referred to as the vertical direction of the sensor or the direction parallel to the vertical direction of the sensor. Further, the inlet side of the bypass channel is upstream of the air flow, and the opposite side is downstream of the air flow. Various examples of the shape of the aperture of the aperture can be considered according to the specifications of the sensor.
[0014]
Various examples in the embodiment of the present invention will be described with reference to FIG. However, in the example after FIG. 4, the inflow port portion 7 is illustrated so as to be disposed at a position where the sensor 3 can be seen, but in reality, the sensor 1 cannot be seen as shown in FIG. It is desirable to arrange it at a position.
A first example of the present invention will be described with reference to FIGS.
[0015]
FIG. 4A is a cross-sectional view taken along line AA in FIG. As can be seen from the drawing, the inner wall of the bypass channel 2a is thinned on the vertical wall of the sensor 3 on the inlet 7 side (the lower side in FIG. 4A) and the flow of the sensor support member. The throttle portions 21a and 22a having an air flow rate that is gradually increased in the downstream direction opposite to the inlet portion 7 are provided.
[0016]
(B) of FIG. 4 is the figure which looked at the terminal surface which cut the bypass flow path of FIG. 3 by the BB line from the direction of the arrow shown. As can be seen from FIG. 5, among the inner walls of the bypass channel 2a, the sensor 3 is thinned on the wall in the left and right direction of the sensor 3 on the inlet 7 side (left side in FIG. 4B). The throttle portions 31a and 32a having an air flow rate that is gradually increased toward the side opposite to the inflow port portion 7 are provided.
[0017]
More specifically, in the example of FIG. 4, the throttle portions 21 a, 22 a, 31 a, and 32 a do not reduce the cross-sectional area from the position of the inlet port 7, but the throttle start position is upstream of the sensor support member 5. The diaphragm end position coincides with the position of the downstream end portion of the sensor support member 5. In addition, the shape of the restricting portion at the restricting end portion is a shape that prevents the backflow of air from entering the upstream side (a shape in which the restricting amount suddenly becomes zero). Thereby, when the sensor 3 is a backflow undetectable sensor, the air flow rate measuring device according to this embodiment can be used.
[0018]
FIG. 5 is an exploded perspective view for easy understanding of the bypass flow path shown in FIG. In the figure, shaded portions are pasted together to form a bypass channel. As can be seen from the figure, the cross section of the bypass channel is three-dimensionally restricted. In the following example, although an exploded perspective view is omitted for the sake of simplicity, an exploded perspective view similar to FIG. 5 is conceivable.
[0019]
FIG. 6 is a diagram for explaining a second example of the embodiment of the present invention. FIG. 6A is a cross-sectional view of the bypass channel of FIG. Sectional drawing of the bypass flow path by the 2nd example of embodiment of this invention, (B) is embodiment of this invention which looked at the cross section which cut the bypass flow path of FIG. It is sectional drawing of the bypass flow path by the 2nd example. The difference from the example of FIG. 4 is that in the example of FIG. 6, the throttle portions 21 b, 22 b, 31 b, and 32 b start the throttle from the position of the inflow port portion 7. Other configurations are the same as those in FIG. As in this example, depending on the specifications of the sensor, the detection accuracy may be improved by setting the throttle start position from the position of the inlet portion 7.
[0020]
FIG. 7 is a view for explaining a third example of the embodiment of the present invention. FIG. 7A is a cross-sectional view of the bypass flow path of FIG. Sectional drawing of the bypass flow path by the 3rd example of embodiment of this invention, (B) is embodiment of this invention which looked at the cross section which cut the bypass flow path of FIG. It is sectional drawing of the bypass flow path by the 3rd example. The difference from the example of FIG. 6 is that in the example of FIG. 7, the diaphragm by the diaphragm portions 31 c and 32 c in the left-right direction of the sensor 3 is started from the arrangement site of the sensor 3. Other configurations are the same as those in FIG. As a result, the cross section from the inlet 7 of the bypass flow path to the position immediately before the sensor 3 placement portion has a shape that is gradually narrowed two-dimensionally in a direction parallel to the direction in which the inflowing air flows. The cross section of only the peripheral portion has a shape that is gradually narrowed in three dimensions. By adopting this configuration according to the sensor specifications, it may be possible to suppress output fluctuations, measurement and error generation due to disturbance of the flow of intake air flowing into the air flow measurement device, and improve measurement accuracy. is there.
[0021]
FIG. 8 is a diagram for explaining a fourth example of the embodiment of the present invention. FIG. 8A is a cross-sectional view of the bypass channel of FIG. Sectional drawing of the bypass flow path by the 4th example of embodiment of this invention, (B) is embodiment of this invention which looked at the cross section which cut the bypass flow path of FIG. It is sectional drawing of the bypass flow path by the 4th example. The difference from the example of FIG. 4 is that in FIG. 8, the contours of the throttle portions 21d, 22d, 31d, and 32d along the direction of the air flow are changed in a curved line. Other configurations are the same as those in FIG. By adopting this configuration according to the sensor specifications, it may be possible to suppress output fluctuations, measurement and error generation due to disturbance of the flow of intake air flowing into the air flow measurement device, and improve measurement accuracy. is there.
[0022]
FIG. 9 is a cross-sectional view of the bypass flow path according to the fifth example of the embodiment of the present invention, in which a cross section of the bypass flow path of FIG. Since the cross-sectional view taken along the line BB can be inferred from the above example, the illustration is omitted. In this example, the contours of the throttle portions 21e and 22e along the air flow direction are curved in the same manner as in the example of FIG. 8, and further downstream from the position corresponding to the downstream end of the sensor support member 5. Then, the aperture is gradually reduced in a curved line. Other configurations are the same as those in FIG. This configuration makes it possible to rectify both forward and reverse flow, and as a result, it is possible to use a reverse flow detection type sensor.
[0023]
FIG. 10 is a cross-sectional view of the bypass flow path according to the sixth example of the embodiment of the present invention, in which a cross section of the bypass flow path of FIG. Since the cross-sectional view taken along the line BB can be inferred from the above example, the illustration is omitted. In this example, the contours of the throttle portions 21 f and 22 f along the air flow direction are curves that change rapidly in the vicinity of the sensor support member 5. In other words, the diaphragms 21f and 22f start to be throttled near the position corresponding to the upstream end of the sensor support member 5, the throttle amount becomes maximum near the sensor 3, and then the throttle amount decreases toward the downstream. The throttle amount is zero near the position corresponding to the downstream end of the sensor support member 5. By adopting such a configuration, even when the turbulence of the air flow in the upstream is large, it is possible to suppress output fluctuations, measurement, and generation of errors due to the turbulence, and to improve the measurement accuracy.
[0024]
FIG. 11 is a cross-sectional view of the bypass flow path according to the seventh example of the embodiment of the present invention, in which the cross section of the bypass flow path of FIG. Since the cross-sectional view taken along the line BB can be inferred from the above example, the illustration is omitted. In this example, the aperture height h1 of the aperture portion 21g and the aperture height h2 of the aperture portion 22g are different. The diaphragm heights of the diaphragm portions 31g and 32g (not shown) may be different. Thus, by making the aperture heights different, the pulsation characteristics can be tuned.
[0025]
FIG. 12 is a cross-sectional view of the bypass flow path according to the eighth example of the embodiment of the present invention, in which a cross section of the bypass flow path of FIG. Since the cross-sectional view taken along the line BB can be inferred from the above example, the illustration is omitted. In this example, the contours of the throttle portions 21h and 22h on the upstream side are the same as those of any of those shown in FIGS. 4 to 10, but on the downstream side from the position corresponding to the sensor 3, the downstream side of the sensor support member 5 The diaphragm height is constant up to the position corresponding to the end. The throttle amount is gradually reduced further downstream from the position corresponding to the downstream end of the sensor support member 5. The diaphragm portions 31h and 32h (not shown) have the same contour as the diaphragm portions 21h and 22h. With this configuration, the cross-sectional area of the air circulation portion of the bypass flow path is constant in the vicinity of the sensor 3 and there is no increase in the cross-sectional area immediately downstream of the sensor. Measurement accuracy can be improved by suppressing the occurrence of measurement errors.
FIG. 13 is a diagram showing a cross section of a bypass flow path according to an example of the second embodiment of the present invention.
In this embodiment, the narrowed portion 22i in the bypass flow path 2i has a gentle shape in the upstream and downstream directions as in FIGS. 9 to FIG. 12 is different from the embodiment shown in FIGS. 9 to 12 in FIG. 13 in that a diaphragm portion is not provided in a direction perpendicular to the sensor 3 but only in a direction parallel to the left and right of the sensor 3. Is provided.
In FIG. 13, the height of the radial throttle of the bypass flow path 2i from the throttle start position S of the bypass flow path 2i to the highest position P of the throttle is set to h, and from the throttle start position S of the bypass flow path 2i. The length of the bypass flow path 2i (upstream throttle length) up to the highest throttle position P is L1, and the bypass flow from the highest throttle position P to the throttle end position E The length of the path 2i (the length of the downstream throttle) is L2. Further, the channel width of the bypass channel 2i is a.
FIG. 14 is a graph showing the relationship obtained by the experiment of h, L2 and pulsation noise amount. Above the pulsating noise amount indicated by the diagonal lines in the figure, it cannot be put into practical use as an air flow rate measuring device. As shown in the figure, when L2 / h is 1 or more, the pulsating noise is kept low below a value that can be put to practical use. Therefore, it is necessary to satisfy 1 ≦ L2 / h on the downstream side. Similarly, it is necessary to satisfy 1 ≦ L1 / h on the upstream side.
FIG. 15 is a graph showing the relationship obtained by experiments of a and h and detection accuracy. In the figure, below the detection accuracy indicated by hatching, it cannot be put to practical use as an air flow rate measuring device. As shown in the figure, it has been found that the detection accuracy is higher than a practical value when a / h is larger than 2.5 and 20 or smaller. Therefore, a relationship of 2.5 <a / h ≦ 20 is necessary.
FIG. 13 shows an example in which the upstream length L1 is asymmetric with respect to the longitudinal direction of the bypass flow path, which is shorter than the downstream length L2, but it is desirable that the upstream length L1 be symmetrical (L1 = L2).
FIG. 16 is a diagram showing a cross section of the bypass flow path according to the second example of the second embodiment of the present invention. In this example, the throttle portion 22j has a symmetric shape with respect to the longitudinal direction of the bypass flow path, and the cross section has a shape obtained by cutting a part of a sphere.
FIG. 17 is a view showing a cross section of the bypass flow path according to the third example of the second embodiment of the present invention. In this example, the narrowed portion 22k has a symmetrical shape and has a trapezoidal cross section.
FIG. 18 is a view showing a cross section of the bypass flow path according to the fourth example of the second embodiment of the present invention. In this example, the diaphragm portion 22l has a symmetrical shape and has a triangular cross section.
FIG. 19 is a diagram showing a cross section of the bypass flow path according to the fifth example of the second embodiment of the present invention. In this example, the diaphragm 22m has a symmetric shape, and has a substantially trapezoidal cross section with a longer upper side and curved sides than the example of FIG.
Since L1 = L2 = L in any of the aperture shapes shown in FIGS. 16 to 19, the following relationship 1 ≦ L / h
2.5 <a / h ≦ 20
It is desirable to satisfy.
20 is a cross-sectional view taken along line AA ′ of the bypass flow path shown in FIGS. 16 to 19.
As described above, according to the embodiment shown in FIG. 13 to FIG. 20, it is difficult for foreign matter to hit the sensor 3, and the probability that the sensor 3 is damaged even at a large flow rate is reduced.
Further, a parallel flow of the intake air can be created in the area where the sensor 3 is present, and the reverse flow can be well rectified, so that the air flow rate can be detected with high accuracy.
FIG. 21 is a graph showing experimental results on the relationship between the air flow velocity in the second embodiment and the presence or absence of breakage. As shown in the figure, according to the second embodiment of the present invention, it has been found that even if the flow velocity is larger than the conventional one, it is not damaged. In the figure, a cross indicates a case where the sensor is broken, and a circle indicates a case where the sensor is not broken. It cannot be put into practical use as an air flow rate measuring device below the flow velocity indicated by the oblique lines.
FIG. 22 is a graph of experimental results in which the relationship between the output flow rate converted value and the time in the second embodiment is compared between the actual air amount, the second embodiment of the present invention, and the conventional example. . As shown in the figure, it has been found that the value of the output flow conversion amount at the time of the reverse flow is closer to the actual air flow rate than the conventional value in the second embodiment of the present invention.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view of a part of an intake passage of an automobile engine according to an embodiment of the present invention.
FIG. 2 is a perspective view seen from an air inlet of a conventional bypass channel 2;
FIG. 3 is a perspective view seen from the air inlet of the bypass channel according to the embodiment of the present invention.
4A is a cross-sectional view of the bypass flow path of FIG. 3 cut along the line AA as viewed from the direction of the arrow, and FIG. 4B is a cross-section of the bypass flow path of FIG. 3 cut along the line BB. It is the figure which looked at the terminal surface from the direction of the illustrated arrow.
FIG. 5 is an exploded perspective view showing the bypass flow path shown in FIG. 4 so that it can be easily understood.
FIG. 6 is a diagram illustrating a second example of an embodiment of the present invention.
FIG. 7 is a diagram illustrating a third example of an embodiment of the present invention.
FIG. 8 is a diagram illustrating a fourth example of an embodiment of the present invention.
FIG. 9 is a diagram for explaining a fifth example of the embodiment of the present invention;
FIG. 10 is a diagram illustrating a sixth example of an embodiment of the present invention.
FIG. 11 is a diagram illustrating a seventh example of an embodiment of the present invention.
FIG. 12 is a diagram illustrating an eighth example of an embodiment of the present invention.
FIG. 13 is a diagram showing a cross section of a bypass flow path according to an example of a second embodiment of the present invention.
FIG. 14 is a graph showing a relationship obtained by experiments of h, L2, and pulsating noise amount.
FIG. 15 is a graph showing a relationship obtained by experiments of a and h and detection accuracy.
FIG. 16 is a view showing a cross section of a bypass flow path according to a second example of the second embodiment of the present invention;
FIG. 17 is a view showing a cross section of a bypass flow path according to a third example of the second embodiment of the present invention;
FIG. 18 is a diagram showing a cross section of a bypass flow path according to a fourth example of the second embodiment of the present invention;
FIG. 19 is a diagram showing a cross section of a bypass flow path according to a fifth example of the second embodiment of the present invention;
20 is a cross-sectional view taken along line AA ′ of the bypass channel shown in FIGS. 16 to 19; FIG.
FIG. 21 is a graph showing experimental results on the relationship between the air flow velocity and the presence or absence of breakage in the second embodiment.
FIG. 22 is a graph of experimental results in which the relationship between the output flow rate converted value and the time in the second embodiment is compared between the actual air amount, the second embodiment of the present invention, and a conventional example. .
[Explanation of symbols]
2a to 2j ... Bypass channel 3 ... Sensor (detection element)
4 ... Sensing part 5 ... Sensor support member 7 ... Inlet part 21a-21h, 22a-22m ... Restriction part 31a-31d, 32a-32d ... Restriction part h1, h2 ... Restriction height h ... Restriction in 2nd Embodiment The height L1 of the bypass channel from the throttle start position to the apex position of the throttle unit L2 The length of the bypass channel from the apex position of the throttle unit to the throttle end position a ... the channel width of the bypass channel

Claims (1)

In the air flow rate measuring device in which a flow rate detecting element for measuring the air flow rate is arranged inside the bypass passage for inflowing a part of the air flowing through the intake passage,
The cross-sectional area of the bypass channel is the largest at the air inlet to the bypass channel, and the cross-section from the inlet to the detection element arrangement site arranged in the downstream air passage is three-dimensional. Has a gradually narrowed shape,
An air flow rate measurement characterized in that the throttle shape of the cross-section of the bypass flow path around the detection element arrangement site is a shape in which the throttle height on one side wall of the bypass flow path is different from the throttle height on the other side wall. apparatus.

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