JP2005128038A - Air flow rate measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat element type air flow rate measuring device reducing dirt, deterioration along with the time, and breakage of a flow rate measuring element due to dust and droplets in intake air. <P>SOLUTION: In this air flow rate measuring device, the flow passage shape of an auxiliary passage, in which the air flow rate measuring element is installed, is defined. Without using any new production method or the like, the heat element type air flow rate measuring device can be provided at a low cost. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an air flow rate measuring device for measuring the amount of air, and more particularly to a heating resistor type air flow rate measuring device whose main purpose is to measure the air flow rate taken into an internal combustion engine.

  There are several known structures for protecting the flow rate measuring element from dust that has entered the intake passage and preventing deterioration over time due to contamination. (1) Japanese Patent Application Laid-Open No. 11-248505 is a structure that traps dust that has entered the outer circumferential wall of the sub-passage bent portion by tackiness, but after the trapped dust has completely covered the adhesive material surface There is no effect, only a short-term effect is seen, and long-term use as an automotive flow meter is not considered at all. In addition, there is a problem that there is no effect on moisture and the like. (2) Japanese Patent Application No. 54-128927 has a structure that prevents dust from entering the sub-passage by adopting a static-pressure sub-passage that does not apply the dynamic pressure of the air flowing through the intake passage to the sub-passage entrance. However, in this structure, there is a drawback that the air flow rate itself flowing into the sub passage is extremely reduced, and it is difficult to measure a stable air flow rate. (3) German publication DE-19816154-A1 divides the inside of the auxiliary passage into two passages and arranges the flow rate measuring element in the first auxiliary passage. Dust that has entered the sub-passage is separated into a second sub-passage that opens in the velocity vector direction. There is a fear that the second sub-passage that is not installed is provided, a sufficiently stable air flow cannot be obtained in the first sub-passage, and the flow rate measurement accuracy is greatly deteriorated.

  The heating resistor type air flow measuring device according to the present invention is mainly installed in an intake passage of an internal combustion engine for automobiles. A filter element for cleaning the inflow air is installed in this intake passage, but its cleaning effect is not 100%. Dust or liquid contained in the intake air passes through the filter element and the heating resistor type air flow rate It may reach the intake passage where the measuring device is installed. In addition, there are cases in which poor filter elements other than genuine products are used in the market. In this case, the possibility that foreign matter such as dust will enter further increases. When dust contained in the intake air adheres to the flow measuring element of the heating resistor type air flow measuring device, there is a problem that the heat radiation characteristic of the flow measuring element changes and the output characteristic changes. Further, the flow measuring element itself may be damaged depending on the structure of the element and the particle size and speed of the incoming dust. In addition, when a liquid such as water adheres to the measuring element, there is a problem that deterioration due to rapid temperature change of the element and damage due to abnormal output or thermal stress due to instantaneous change in heat dissipation occur.

  The above-described problems are solved by the invention described in the claims. For example, it is possible to separate dust or droplets contained in the air that causes damage such as fouling deterioration, aging, damage, etc. to the flow measurement element by its own inertial force, and the flow measurement element Adopting a sub-passage shape that can maintain a sufficient air flow at the site where it is installed.

  First, the air flow in the sub-passage configured in a spiral shape flows along the shape of the passage, whereas particles such as dust contained in the air are as much as possible due to their own weight and inertial force due to the inflow velocity. Because it tries to go straight, it collides with the spiral passage outer peripheral wall. Thereafter, since the inertial force acts as a centrifugal force, foreign matter such as dust advances along the outer wall of the sub-passage, and does not pass through the flow rate measuring element portion disposed in the vicinity of the center of the sub-passage. Even in this case, since the inertial force of the air itself is very small compared to dust or the like, a sufficient flow rate necessary for stable measurement can be obtained even near the center of the sub-passage and near the inner peripheral wall. In addition, by providing a certain slope at the joint between the outer peripheral wall of the spiral passage and the side wall constituting the passage, it is also possible to guide the reflection direction when dust collides with the inclined wall to the outer periphery of the passage. This structure further increases the dust separation effect.

  Further, when dust discharge holes are provided in the direction of the tangential line of the bottom of the sub-passage configured in a spiral shape, dust collected near the outer peripheral wall of the sub-passage is effectively removed from the sub-passage by the effect of the dust inertia. Can be discharged.

  As another structure using the inertia force of dust, a fixed angle is provided on the projected bottom wall surface of the sub-passage entrance, and a dust discharge hole is provided at the bottom of the bottom wall surface having the angle. The dust flowing into the auxiliary passage goes straight by the inertial force due to its own weight and speed, and collides with the wall surface having an angle at the bottom of the auxiliary passage. At this time, the dust is reflected in the direction of the dust discharge hole depending on the angle of the wall surface and is discharged out of the auxiliary passage.

  Further, in all the configurations of the sub passages in the present invention, the flow rate measuring element itself is arranged at a position where it cannot be viewed directly from the inlet portion of the sub passage. According to this structure, the dust that has entered the sub-passage does not collide with the flow rate measuring element at the speed at the time of entry, but the kinetic energy possessed by itself collides with the wall surface of the sub-passage once or several times. Decrease. Therefore, even if the condition that the gas-liquid or gas-solid separation action using the inertial force, which is the original effect intended by the present invention, does not work properly occurs, The kinetic energy is remarkably reduced when reaching the value, and the possibility that the flow measuring element is damaged due to dust collision can be remarkably reduced.

  Furthermore, since the effect according to the present invention is achieved only by the shape of the sub-passage, the effect over time does not decrease, and the same effect can be continuously obtained.

  According to the present embodiment, without improving the flow rate measuring element of the heating resistor type air flow measuring device, it is possible to effectively prevent deterioration over time due to adhesion of foreign matter to the flow rate measuring element semipermanently only by the passage structure. In addition, it is possible to effectively prevent the flow rate measuring element from being damaged due to the collision of a foreign object. In addition, according to this structure, the object can be achieved at a cost equivalent to that of the conventional structure without changing the manufacturing method of the conventional heating resistor type air flow measuring device.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 is a longitudinal sectional view of a heating resistor type air flow measuring device showing an embodiment of the present invention. A module housing 2 of a heating resistor type air flow meter is attached to an intake passage 1 of an automobile internal combustion engine via a module flange 2. A sub-passage 7 is formed at the tip of the module housing 2, and the flow rate measuring element 3 is installed inside the sub-passage 7. The flow rate measuring element 3 (here, the heating resistor) is electrically connected to an electronic circuit 4 installed inside the module housing 2, and the electronic circuit 4 is further electrically connected to the outside via a connector 6. The sub-passage 7 includes a sub-passage inlet portion 9 that opens perpendicularly to the air flow that flows through the intake passage 1 and a sub-passage exit portion 10 that opens in the sub-passage side wall surface 72 in parallel with the air flow that flows through the intake passage 1. Have. Further, the sub-passage 7 bypasses 180 ° with a continuous curved surface at the bottom, and the flow rate measuring element 3 is installed on the downstream side of the sub-passage part of the sub-passage 7, that is, on the side where the sub-passage outlet 10 is formed. ing. According to this structure, the foreign matter such as dust that has entered the sub-passage 7 follows the outermost peripheral portion of the detour portion in the sub-passage bottom detour portion 8 due to its own speed and mass inertial force. Therefore, the air is discharged again from the sub-passage outlet 10 to the intake passage 1 without colliding with the flow rate measuring element 3 installed near the center of the sub-passage 7.

  FIG. 2 is a longitudinal sectional view of a sub passage structure showing an embodiment of the present invention. The sub-passage 7 having the flow rate measuring element 3 therein is detoured in a spiral shape with a continuous curved surface. The flow rate measuring element 3 is installed at a substantially central portion of the sub-passage 7 in the vicinity of the sub-passage that is detoured by about 180 °, the sub-passage inlet portion 9 is perpendicular to the air flow flowing through the intake passage, and the sub-passage outlet portion 10 is the sub-passage portion 10. The passage 7 is open to the side wall surface of the sub passage at the tip which is detoured by about 360 °. According to this structure, foreign matter such as dust entering the sub-passage 7 travels along the outer peripheral wall portion of the sub-passage 7 due to its own speed and mass inertial force. Without colliding with the flow rate measuring element 3 installed in the vicinity of the center, the air is again discharged from the auxiliary passage outlet 10 to the intake passage 1. Furthermore, according to this structure, the bypass of the sub-passage 7 is continuously formed, so that it is possible to effectively suppress the generation of separation vortices generated downstream of the inner peripheral portion of the passage bending portion, and there is little stable noise. It is possible to obtain the output of the heating resistor type air flow rate measuring device. Furthermore, in this structure, it is possible to change the position of the sub-passage outlet portion 10 without changing the size of the entire sub-passage, thereby changing the relative distance between the sub-passage inlet portion 9 and the sub-passage outlet portion 10. I can do it. The relative distance between the inlet and outlet of the auxiliary passage is an important factor that determines the inertia effect of the entire auxiliary passage, and this can be changed freely, so that the heating resistor type of the pulsating flow generated in the intake passage of the internal combustion engine for automobiles It is possible to adjust the degree of influence on the air flow rate measuring device.

  FIG. 3 shows an embodiment of the cross-sectional shape of the sub-passage 7 shown in FIGS. FIG. 3A does not particularly consider the shape. In this case, the foreign matter that has entered the sub-passage 7 collides with the sub-passage outer peripheral wall surface 71 almost perpendicularly. There is a possibility of reflection toward the center of the sub-passage. In actuality, while repeating this reflection and collision, it gradually flows along the outer peripheral wall surface of the sub-passage, but in FIGS. 3-2 to 3-4, the shape of the outer peripheral wall surface of the sub-passage is taken into consideration. Is effectively guided to the outermost periphery of the sub-passage. 3-2, the sub-passage outer peripheral wall surface 71 has a semicircular shape. 3C is a chamfer on one side of the joint between the sub-passage outer peripheral wall surface 71 and the sub-passage side wall surface 72, and FIG. 3-4 is a chamfer on both sides of the joint portion between the sub-passage outer peripheral wall surface 71 and the sub-passage side wall surface 72. Is provided. In any structure, foreign matter such as dust that collides with the outer peripheral wall surface 71 of the sub-path is reflected toward the outermost peripheral part of the sub-passage depending on the angle formed by the wall surface, and the foreign substances are more effectively collected on the outermost peripheral part of the sub-passage. It becomes possible.

  4 is a longitudinal sectional view of an embodiment in which the sub-passage structure shown in FIG. 2 is partially changed. With respect to FIG. 2, vent holes 11 having an area of ½ or less of the opening area of the sub-passage outlet 10 are provided on the side wall surface of the sub-passage in the downstream side of the air flow in the sub-passage of the flow measuring element 3 Yes. According to this structure, it is possible to effectively adjust the inertia effect of the sub-passage 7, and the influence of the pulsating flow generated in the intake passage of the automobile internal combustion engine on the heating resistor type air flow rate measuring device. The degree can be adjusted. Further, the spiral sub-passage structure has a drawback that water tends to be accumulated in the sub-passage 7 in the still air state, but the water that has entered the sub-passage through the vent holes 11 is effective even in the still air state. The auxiliary passage 7 is discharged to the outside.

  5 and 6 are longitudinal sectional views of an embodiment in which a part of the passage structure shown in FIGS. 1 and 2 is modified. In any example, a vent hole having a height of about 1 mm is provided in the tangential direction of curvature from the outer peripheral wall surface at the most downstream portion of the sub-passage 7 with respect to the airflow flowing in the intake passage. According to the present embodiment, the foreign matter such as dust collected on the outer peripheral wall portion by the bypass structure of the sub passage 7 is effectively discharged from the vent hole to the intake passage 1 and the portion where the flow rate measuring element 3 is installed. It is possible to further suppress the change of the flow rate measuring element with time, the occurrence of breakage, and the like without reaching the point. In this structure, the ratio of the cross-sectional area of the sub-passage 7 to the cross-sectional area of the vent hole 11 is 10: 1 or less, so that the foreign matter can be effectively discharged without substantially impairing the performance of the sub-passage 7. is there. Furthermore, this vent can also eliminate the disadvantage that water or the like tends to accumulate in the sub-passage 7 in a still air state.

  FIG. 7 is a longitudinal sectional view of a sub passage structure showing an embodiment of the present invention. The sub-passage 7 includes a sub-passage inlet portion 9 that opens perpendicularly to the air flow that flows through the intake passage 1 and a sub-passage exit portion 10 that opens in the sub-passage side wall surface 72 in parallel with the air flow that flows through the intake passage 1. Have. Further, the sub-passage 7 bypasses 180 ° at the bottom, and the flow rate measuring element 3 is installed downstream of the sub-passage 7, that is, on the side where the sub-passage outlet 10 is formed. Further, a first vertical passage bottom inclined surface 12 having a certain angle is formed on the projection surface from the sub-passage inlet portion 9 at the bottom of the sub-passage 7, and a vent hole 11 is formed at the tip of the inclined surface 12. It is formed. According to this structure, foreign matter such as dust that has entered the auxiliary passage 7 collides with the inclined surface 12 at the bottom of the first longitudinal passage, trying to go straight through the bypass portion at the bottom of the auxiliary passage due to its own speed and weight. At this time, foreign matter such as dust is reflected in the direction of the vent hole 11 by the velocity vector direction and the angle of the inclined surface, and is discharged out of the sub-passage 7.

  FIG. 8 shows an embodiment in which the shape of the inclined surface of the bottom of the first vertical passage is devised in order to reduce the height dimension of the sub passage 7 with respect to the embodiment of FIG. This is the same as the embodiment.

  9 and 10 show an embodiment in which the configuration of the second lateral passage 76 is changed with respect to the embodiment of FIG. 7, and the effect and action on the foreign matter entering the sub passage 7 is the same as that of the embodiment of FIG. is there. FIG. 11 is an example of a CAE calculation result performed to confirm the effect of the present invention. The solid line shows the passage wall surface, and the dotted line shows the locus of dust in the air. It is confirmed that the dust that has entered from the sub-passage inlet 9 gradually progresses along the sub-passage outer peripheral wall 71 while repeatedly colliding and reflecting on the sub-passage outer peripheral wall 71. In addition, the particle | grains which cross a wall are particles which exited the exit (inlet).

  FIG. 12 is an example of CAE calculation results performed to confirm the effect of the present invention. The solid line shows the passage wall surface, and the dotted line shows the locus of dust in the air. Dust that has entered from the sub-passage entrance 9 proceeds linearly and collides with the inclined surface 12 at the bottom of the first vertical passage. Thereafter, it can be confirmed that the dust is reflected in the direction of the vent hole 11 depending on the angle of the inclined surface and is discharged out of the sub-passage 7.

BRIEF DESCRIPTION OF THE DRAWINGS The longitudinal cross-sectional view of the heating resistor type | formula air flow measuring device which shows one Example of this invention. The longitudinal cross-sectional view of the subchannel | path structure which shows one Example of this invention. FIG. 3 is an example of a cross-sectional shape of a sub passage with respect to FIGS. The longitudinal cross-sectional view of one Example which changed a part of sub-passage structure shown in FIG. The longitudinal cross-sectional view of one Example which changed a part of channel structure shown in FIG.1 and FIG.2. The longitudinal cross-sectional view of one Example which changed a part of channel structure shown in FIG.1 and FIG.2. It is a longitudinal cross-sectional view of the subchannel structure which shows one Example of this invention. The longitudinal cross-sectional view of one Example which changed the shape of the 1st vertical path bottom inclined surface with respect to the Example of FIG. The longitudinal cross-sectional view of one Example which changed the structure of the 2nd vertical passage with respect to the Example of FIG. The longitudinal cross-sectional view of one Example which changed the structure of the 2nd vertical passage with respect to the Example of FIG. An example of the CAE calculation result implemented in order to confirm the effect of this invention. An example of the CAE calculation result implemented in order to confirm the effect of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Intake passage of internal combustion engine, 2 ... Module housing, 3 ... Flow measuring element, 4 ... Electronic circuit, 5 ... Module flange, 6 ... Connector, 7 ... Subpassage, 8 ... Subpassage bottom part detour part, 9 ... Sub Passage entrance part, 10 ... sub-passage exit part, 11 ... ventilation hole, 12 ... first vertical passage bottom inclined surface,
71 ... Sub-passage outer peripheral wall surface, 72 ... Sub-passage side wall surface, 73 ... First longitudinal passage, 74 ... Second longitudinal passage,
75: first lateral passage, 76: second lateral passage.

Claims (19)

A measuring element for measuring the air flow rate;
A sub-passage in which the measuring element is disposed and an outlet is opened parallel to the main air flow;
A housing in which the secondary passage is configured and disposed in the main air stream;
In the air flow measuring device with
An air flow rate measuring apparatus, wherein the inlet side sub-passage wall surface has a curvature more than the measuring element. In claim 1,
The air flow rate measuring device, wherein the outlet side sub-passage wall surface has a curvature more than the measuring element. In claim 2,
The air flow rate measuring device according to claim 1, wherein a curvature of the outlet side sub-passage wall surface is larger than a curvature of the inlet side sub-passage wall surface. In claim 1,
The sub-passage is configured in the housing so as to surround the outlet. A measuring element for measuring the air flow rate;
The measuring element is disposed, and a sub-passage having a bent portion;
A housing in which the secondary passage is configured and disposed in the main air stream;
In the air flow measuring device with
The bent portion is provided on the inlet side of the measuring element,
An air flow rate measuring device, wherein a hole communicating with the main air flow is provided in a wall surface on the inlet side sub-passage with respect to the measuring element. In claim 5,
The air flow rate measuring device according to claim 1, wherein the opening surface of the hole is provided on a wall surface of the sub-passage where the air flow entering the sub-passage from the inlet changes direction. In claim 6,
The air flow measuring device according to claim 1, wherein the opening surface of the hole is smaller on the main air flow side than on the sub passage side.   A sub-passage having a heating resistor (hereinafter referred to as a flow measurement element) attached to an intake passage of an internal combustion engine and having a function of detecting an air flow rate, and an electron electrically connected to the flow measurement element In the heating resistor type air flow measuring device provided with a circuit, the inlet portion of the auxiliary passage opens upstream of the intake passage, and the auxiliary passage is continuous at 180 ° or more at the most downstream portion with respect to the intake passage. Detouring by curvature, the flow measuring element is installed near the center of the sub-passage downstream of the bypass part of the sub-passage, and the sub-passage outlet is upstream of the intake passage of the flow measuring element and the axis of the intake passage A heating resistor type air flow rate measuring device, characterized by being open in the horizontal plane.   A heating resistor air having a sub-passage which is attached to an intake passage of an internal combustion engine and has a flow measuring element having a function of detecting an air flow rate, and an electronic circuit electrically connected to the flow measuring element. In the flow measuring device, the inlet portion of the auxiliary passage opens upstream of the intake passage, the auxiliary passage is detoured in a spiral shape from 270 ° to 360 ° due to continuous curvature, and the auxiliary flow passage is connected to the flow measuring element. It is installed in the vicinity of the central portion of the sub-passage, which is deviated by 180 ° from the inlet, and the sub-passage outlet is open at the tip of the sub-passage in the axis and horizontal plane of the intake passage. Resistor type air flow measuring device.   The heating resistor type air flow measuring device according to claim 8 or 9, wherein a chamfered inclined surface is provided at a joint portion on one side or both sides of a passage outer peripheral inner wall surface and a side wall surface forming a bypass portion of the sub-passage. A heating resistor type air flow rate measuring device characterized by.   The heating resistor type air flow measuring device according to claim 8 or 9, characterized in that the inner peripheral wall surface of the passage forming the bypass portion of the sub passage is U-shaped.   The heating resistor type air flow rate measuring device according to any one of claims 9, 10 and 11, wherein the side wall of the sub-passage and the downstream side of the flow rate measuring element with respect to the air flow in the sub-passage are disposed on one side or both sides. A heating resistor type air flow rate measuring device characterized in that a vent hole having an area of 1/2 or less with respect to the opening area of the auxiliary passage outlet is provided.   The heating resistor type air flow rate measuring device according to any one of claims 8 to 11, wherein the flow rate measuring element is located between a bypass portion of the auxiliary passage located at a most downstream portion with respect to an air flow of the intake passage and the flow rate measuring element. A heating resistor type air flow measuring device, characterized in that a vent hole with a height of about 1 mm is provided in the tangential direction from the outer peripheral wall portion of the auxiliary passage.   A sub-passage having a heating resistor (hereinafter referred to as a flow measurement element) attached to an intake passage of an internal combustion engine and having a function of detecting an air flow rate, and an electron electrically connected to the flow measurement element In the heating resistor type air flow measuring device comprising a circuit, the auxiliary passage has a first vertical passage that is horizontal in the axial direction of the intake passage and a first horizontal passage that is perpendicular to the axial direction of the intake passage, One end of the first vertical passage located upstream of the air flow in the intake passage opens in a plane perpendicular to the axial direction of the intake passage, and the other end of the first vertical passage is the first horizontal passage. Connected. A joint portion of the first vertical passage and the first horizontal passage, that is, a bottom surface of the first vertical passage is provided with a certain inclination from the first horizontal passage direction toward the downstream side with respect to the air flow direction of the intake passage. A heating resistor type air flow rate measuring device characterized in that a vent hole is provided at a portion where the tip of the inclined surface and the wall surface constituting the first vertical passage are joined.   The heating resistor type air flow rate measuring device according to claim 14, wherein an inclination angle of an inclined surface formed on a bottom surface of the first vertical passage is 45 ° ± 15 ° with respect to an axis of the intake passage. Heating resistor type air flow measuring device.   The heating resistor type air flow rate measuring device according to claim 14 or 15, wherein the inclined surface formed on the bottom surface of the first vertical passage is a projection surface of the first vertical passage opening surface with respect to the axial direction of the intake passage. Heating resistor type air flow rate measuring device characterized by being equal or higher.   The heating resistor type air flow rate measuring device according to any one of claims 14 to 16, wherein the auxiliary passage has a second longitudinal passage parallel to the axial direction of the intake passage and further including the flow rate measuring element therein. The first horizontal passage formed by a straight pipe or a curved pipe connects the first vertical passage and the second vertical passage at the most downstream portion of the first vertical passage and the second vertical passage with respect to the intake passage. A heating resistor type air flow rate measuring device, wherein the outlet of the secondary passage is opened on one side or both sides of a side wall constituting the secondary passage of the most upstream portion of the second longitudinal passage with respect to the intake passage.   The heating resistor type air flow rate measuring device according to any one of claims 14 to 16, wherein the auxiliary passage has a second longitudinal passage parallel to the axial direction of the intake passage and further including the flow rate measuring element therein. The first horizontal passage formed by a straight pipe or a curved pipe connects the most downstream portion of the first vertical passage with respect to the intake passage and the most upstream portion of the second vertical passage with respect to the intake passage, and A heating resistor type air flow rate measuring device characterized in that the outlet of the auxiliary passage is opened on one side or both sides of a side wall constituting the downstream passage of the longitudinal passage with respect to the intake passage.   The heating resistor type air flow rate measuring device according to any one of claims 14 to 16, wherein the sub passage is parallel to the axial direction of the intake passage and further includes the flow rate measuring element therein and the intake passage. The first horizontal passage formed by a straight pipe or a curved pipe is the most downstream portion of the first vertical passage with respect to the intake passage and the second vertical passage. The most upstream portion with respect to the intake passage is connected, the second lateral passage is connected to the most downstream portion with respect to the intake passage of the second longitudinal passage, and a side wall constituting a sub-passage at the other end of the second transverse passage is connected. A heating resistor type air flow rate measuring device characterized in that the outlet of the auxiliary passage opens on one side or both sides.

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