JP6164019B2 - Air flow meter - Google Patents

Description

  The present invention is mounted on an internal combustion engine (hereinafter simply referred to as an engine) of a vehicle such as an automobile and measures an intake air amount (intake air flow rate) of the engine (hereinafter also referred to as a flow rate measuring device). About.

  Conventionally, various types of airflow meters of this type have been put to practical use. However, a housing that forms a bypass channel that takes in part of the air (intake air) flowing in the duct, and a bypass channel And a flow rate sensor for detecting the flow rate of the air flowing through the air.

  In addition, the air flow meter may have a complicated shape / structure such as a bypass flow path formed therein, and the production method of the housing is at least in consideration of manufacturing and assembly surfaces. The mainstream is an assembling method in which a housing is completed by making a split structure having two components and assembling and fixing the other component to one component.

  Air flow meters are installed in engines that are used in harsh operating environments, and have a mission to accurately detect the intake amount (air flow rate) of the engine that requires strict control performance. In the case of mass production by adopting the above assembly method, it is important to eliminate the influence on the accuracy due to the manufacturing variation of the component parts and to maintain the initial accuracy even for long-term use. .

Therefore, in a housing composed of at least two component members, high strength and high accuracy are required for an assembly fixing means for assembling and fixing one component member and the other component member. Various proposals have been made.
A typical example is a pin press-fit method as shown in Patent Document 1, for example.
In this pin press-fitting method, one component member is provided with a press-fit pin with a crushing margin, and the other component member is provided with a receiving hole corresponding to this press-fit pin, and the press-fit pin is press-fitted into the receiving hole. This component member is assembled and fixed to the other component member.
According to the pin press-fitting method of the above configuration, it is possible to absorb the manufacturing variation between the constituent members due to the crushing amount of the crushing allowance, and the initial use for long-term use by selecting the material and crushing allowance of the constituent member It is possible and accurate to maintain accuracy.

JP 2012-52974 A

  However, the pin press-fitting method with the above configuration does not cause any particular problem when only one assembly and fixing point is required, but it turns out that the two components cannot be assembled and fixed with high accuracy when there are a plurality of locations. did.

The present inventor conducted experiments and research in order to investigate the cause, and as a result, came up with the following idea.
That is, a crushing margin is formed on the outer periphery of the press-fit pin at an equal interval, for example, 180 degrees apart, and the press-fit pin is fitted in the receiving hole. Since it can be adjusted with one crushing allowance, there is no particular problem when the press-fit location is one location (a pair of pins and receiving holes), but when there are more than 2 press-fit locations (more than two pairs of pins and receiving holes) It is considered that even the mutual relationship between each pair could not be adjusted by the crushing allowance, and as a result, the two constituent members could not be assembled and fixed with high accuracy.

  In recent years, the operating environment of various devices mounted on engines has become increasingly severe, and this type of air flow meter has been strictly demanded without exception, and an air flow meter with exceptionally high strength and high accuracy has been eagerly desired. ing. Therefore, in the air flow meter, it is essential to ensure high accuracy while being assembled and fixed to the housing at a plurality of locations, and how to satisfy this is an immediate problem.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an air flow meter including a housing assembled and fixed at a plurality of locations and assembled with high strength and high accuracy. .

[Means of Claim 1]
In the invention according to claim 1, a housing that forms a bypass flow path that takes in part of the air flowing in the duct, a flow rate sensor that is disposed in the bypass flow path and detects an air flow rate flowing through the bypass flow path, and An air flow meter in which the housing has at least two constituent members, a first constituent member and a second constituent member, and the second constituent member is assembled and fixed to the first constituent member. ,
As means for assembling and fixing the first component member and the second component member,
And three pin portions which are protruded apart from each other in the first component, provided on the second component corresponds to the pin portion, three holes having a large consisting inner diameter than the outer diameter of the pin portion And an elastically deformable protrusion that is formed to protrude from the inner peripheral surface of the hole and reduces the inner diameter of the hole.
The projections are provided such that the tip is facing each other only in the inner peripheral surface side facing each other in the three holes, by press fitting the pin into the hole against the protrusion The first component member is assembled and fixed to the second component member.
In particular, to form a region surrounded by a triangle by connecting the centers by three pin portions or hole portions, regions the region S, the direction of more occurring reaction force to the protrusion when the press-fit pin portions into the hole When the direction P is called, the direction P is directed to the center of gravity of the region S, and is characterized by exhibiting a centering function structure.

According to the present invention having the above-described configuration, the protrusions in the three holes cooperate with each other to exhibit a centering function for the three pin portions. Can be absorbed, and the second component member can be assembled and fixed to the first component member with high accuracy. Therefore, an air flow meter provided with a housing assembled with high strength and high accuracy can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partially exploded perspective view showing an overall configuration of an air flow meter to which the present invention is applied (Example 1). It is typical sectional drawing with which it uses for function description of the said air flow meter (Example 1). (A), (b) is explanatory drawing with which it uses for description of the assembly fixing means which makes the principal part of this invention in the said air flow meter (Example 1). (A), (b) is explanatory drawing for demonstrating the relationship between the 1st structural member and the 2nd structural member in the said assembly fixing means (Example 1). (Example 1) which is a principal part expanded sectional view of the said assembly fixing means. (A), (b) shows another embodiment of an assembly fixing means, and is explanatory drawing for demonstrating the relationship between a 1st structural member and a 2nd structural member (Example 2). (A)-(d) is explanatory drawing for demonstrating the embodiment example only of the hole part in an assembly | attachment fixing means (modification). (A)-(c) is explanatory drawing for demonstrating the embodiment example of the press-fit part in an assembly | attachment fixing means (modification).

  Hereinafter, the best mode for carrying out the present invention will be described in detail according to embodiments (including modifications) shown in the drawings.

In this embodiment, as a typical example of an air flow meter to which the present invention is applied, a flow rate measuring device mounted on an automobile engine for measuring an intake air amount (intake air flow rate) of the engine is illustrated. First, the basic configuration of the air flow meter will be outlined, and then the features and basic functions of the present invention will be described for each embodiment, centering on the first and second embodiments and the modifications shown as typical embodiments of the present invention. Will be described sequentially, and finally, the effects of each feature point of the present invention will be summarized.
In the first and second embodiments and the modified examples, the same or equivalent parts are denoted by the same reference numerals, and redundant description is omitted.

[Example 1]
The overall configuration of the air flow meter AF will be described with reference to FIGS. 1 and 2.

[Basic configuration of air flow meter AF]
The air flow meter AF as a whole has a T-shaped appearance in which a flat detection portion K hangs down from a rectangular parallelepiped mounting portion J as shown in FIG. A detection unit K is inserted and disposed therein, and the intake air amount (intake air flow rate) is measured while being exposed to the air flow (intake air flow, hereinafter referred to as main flow X) flowing through the intake passage. A housing 1 having an internal structure as shown in FIG. 2 and forming the outline of the detection unit K, a flow rate sensor 2 disposed in the housing 1, a control circuit unit 3 built in the mounting unit J, etc. Is the main component.

[Basic configuration of housing 1]
The housing 1 is assembled and fixed to a housing main body (first constituent member) 11 that internally forms a bypass flow path 4 and a dust discharge flow path 5, and outer surfaces (both side surfaces) facing the housing main body 11. The plate-like cover (second component member) 12 has a split structure, and each component member 11 and 12 is made of a resin molded product and assembled by an assembly fixing means 50 described later. .
In the present embodiment, the housing main body 11 itself has a split structure formed by joining (welding) two members 11a and 11b.

  The housing main body 11 opens toward the upstream side of the main flow X, and the suction port 6 that takes in a part of the intake air, and opens toward the downstream side of the main flow X, and the first and second exhausts the taken-in air. 2 outlets 7 and 8. The suction port 6 and the first discharge port 7 are each provided so as to be opposed to each other, whereas the second discharge port 8 has two, and the housing body 11 faces the outer side surface ( Provided on both side surfaces). A bypass channel 4 is connected to the suction port 6.

  The bypass flow path 4 includes three flow paths, that is, a suction flow path 41, a discharge flow path 42, and a circulation flow path 43. The suction channel 41 opens to the suction port 6 at the inlet side to form the upstream end of the bypass channel 4, and the discharge channel 42 bypasses the outlet side from the second discharge port 8. A downstream end of the flow path 4 is formed. The circulation channel 43 connects the suction channel 41 and the discharge channel 42.

  The suction channel 41 is provided so as to extend linearly from the suction port 6 to the downstream side, and the air flow through the suction channel 41 is parallel to the main flow X. At the downstream end of the suction channel 41, in the vicinity of the connection portion with the circulation channel 43, a linear dust discharge channel for moving the dust contained in the air taken in from the suction port 6 straight and discharging it. 5 are connected. The dust discharge channel 5 has a truncated cone shape, and a downstream end (minimum diameter portion) of the dust discharge channel 5 opens to a first discharge port 7 that forms a dust discharge port. Therefore, it is possible to prevent dust from entering the circulation channel 43.

  The discharge flow channel 42 is connected to the downstream end of the circular flow channel 43 and is bent so as to turn at a substantially right angle from the downstream end of the circular flow channel 43, and the downstream end (exit side) branches into two. The second discharge ports 8 are opened.

  The circulation channel 43 connects the suction channel 41 and the discharge channel 42 in a substantially C shape, and circulates the air taken in from the suction port 6 toward the discharge channel 42 from the suction channel 41. In the circulation channel 43, the flow rate sensor 2 is disposed at a portion that flows in a direction opposite to the flow direction in the suction channel 41.

The flow sensor 2 outputs a signal (for example, a voltage signal) in accordance with the flow rate of air flowing through the bypass flow path 4 (particularly the circulation flow path 43), and a general sensor is adopted.
For example, a basic configuration in which a heating element and a temperature-sensitive element formed of a thin film resistor are provided on a membrane provided on a semiconductor substrate, and these elements are electrically connected to the control circuit unit 3. It is.

  The control circuit unit 3 is also general, a heating element control circuit for controlling the heating element to a set temperature, an output circuit for outputting a voltage according to the flow rate, and an amplification circuit for amplifying the output voltage of this output circuit Etc.

[Features of this embodiment]
The air flow meter AF that is the object of the present embodiment includes two constituent members of the housing 1, that is, a housing main body 11 that forms the first constituent member, and a second constituent member that is assembled and fixed to the housing main body 11. The pair of plate-like covers 12 has the following basic configuration.

In FIG. 1, a second discharge port 8 that forms the downstream end of the bypass flow path 4 is formed to bulge on the side surface of the housing body 11 that faces the housing body 11. A pair of rectifying plates 13 and 14 are provided so as to protrude from the side surface of the housing body 11 with the discharge port 8 being spaced apart from the direction perpendicular to the main flow X direction. Note that the pair of rectifying plates 13 and 14 have a throttle shape in which the interval between the rectifying plates 13 and 14 is narrower downstream of the discharge port 8 in the mainstream X direction.
On the other hand, the plate-like cover 12 has a simple rectangular shape in this embodiment, and functions as a lid that bridges the pair of rectifying plates 13 and 14 and covers the outside of the discharge port 8 and an air flow path. Is responsible.

Thus, as shown in FIG. 3A, the pair of rectifying plates 13, 14 causes the outer passage flow Y flowing along each side surface of the housing body 11 as a branch flow of the main flow X and the bypass passage flowing out from the discharge port 8. Stream Z merges while being squeezed. Thereby, a stable bypass passage flow Z, that is, a stable air flow passing through the circulation passage 43 can be generated, and the measurement accuracy can be improved.
Therefore, not only the high strength that naturally withstands vibration and the like, but also the above-mentioned outside passage also for the mounting and fixing means 50 for mounting and fixing the first structural member (housing body 11) and the second structural member (cover 12). High accuracy is required to contribute to the proper and smooth generation of the flow Y and the bypass flow Z.

  As shown in FIG. 1, the assembly fixing means 50 employed in the present invention is provided with “pins” (pin portions 51) on the housing body 11 side and “receiving holes” (hole portions 52) on the cover 12 side. The “pin” (pin portion 51) is press-fitted into the “receiving hole” (hole portion 52), and is basically a so-called pin press-fitting method. It is characterized by the arrangement relationship of the “receiving holes” (holes 52) and the internal structure on the “receiving holes” (holes 52) side. Hereinafter, an example thereof will be described with reference to FIGS.

  In the above drawings, FIG. 3 is for explaining the entire assembly and fixing means 50. FIG. 3 (a) is a plan view showing the appearance of the assembly and fixing means 50, and FIG. 3 (b) is a diagram. 3A is a cross-sectional view taken along the line AA of FIG. 3, and FIG. 4 is an exploded view for explaining the assembly fixing means 50 divided into a first component member and a second component member, and FIG. FIG. 4B shows the housing main body 11 side forming the first constituent member. FIG. 4B shows the cover 12 side forming the two constituent members. FIG. 5 is an enlarged cross-sectional view of a portion B in FIG.

["Pin" side structure]
As shown in FIG. 4B, the housing main body 11 of the first component member has one on the rectifying plate 13 side and two on the rectifying plate 14 side with respect to the tips of the pair of rectifying plates 13 and 14. The three pin portions 51 are integrally formed.
Although each pin part 51 is exhibiting the mere cylindrical rod of the same diameter over the full length, these three pin parts 51 are spaced apart by the special arrangement | positioning relationship so that it may mention later.

[Structure on the "receiving hole" side]
As shown in FIG. 4A, the cover 12 of the second component member is provided with three hole portions 52 corresponding to the pin portions 51. Each hole 52 is formed as a through hole that completely penetrates the cover 12.
As shown in FIG. 5, the hole portion 52 forming the through hole has an inner peripheral surface with an inner diameter R2 larger than the outer diameter R1 of the pin portion 51, but from the inner peripheral surface of the hole portion 52. Two protrusions 53 are provided that protrude in the radial direction over the entire length in the axial direction and substantially reduce the inner diameter R2 of the hole 52.
The two protrusions 53 are provided such that the tips are opposed to each other within the range of only the inner peripheral surfaces facing each other in the three holes 52 (see FIG. 4A). The pin portion 51 can be pressed into the hole portion 52 against the projection portion 53.
In each protrusion 53, the tip portion that contributes to the reduction in diameter forms a crush margin that is elastically deformed (collapsed) when pressed.

Therefore, the cover 12 forming the second component can be assembled and fixed to the housing body 11 forming the first component by pressing the pin 51 into the hole 52 against the projection 53. .
In addition, the basic press-fitting structure by the pin portion 51, the hole portion 52, and the projection portion 53 can be constructed by appropriately selecting the projection height of the projection portion 53. For example, the diameter of the inscribed circle formed at the tips of the projections 53 of the three hole portions 52 is set to be smaller than the diameter of the circumscribed circle formed at the outer peripheral side of the three pin portions 51. However, it is a matter of course that the present invention is not limited to this.

[Relationship between the arrangement of “pins” and “receiving holes” and the internal structure of “receiving holes”]
This relationship forms the basis of the present invention together with the above basic press-fitting structure, and is based on the following concept .

Reaction force more occurring two protrusions 53 when the press-fitting area of the triangle formed when connecting the centers of the pin portion 51 and the hole 52 (the hatched portion) region S, the pin portion 51 into the hole 52 when calling the direction of the resultant force and the direction P, the direction P is set to direct the center of gravity Q of the region S. The center of gravity Q is an intersection where three lines intersect when three lines connecting the apex of the triangle ( the center of the pin portion 51 and the hole portion 52) and the midpoint of the facing sides are drawn. is there.

In this way, when all the pin portions 51 are press-fitted into the respective hole portions 52 by gathering all the reaction force directions P due to the projections 53 of the respective hole portions 52 to the center of gravity Q , the three hole portions 52 In the process in which each projection 53 receives the three pin portions 51 while elastically deforming the tip portion thereof, the pin 53 exhibits a kind of alignment function with respect to the three pin portions 51, so that the three pins The relative positions of the part 51 and the three hole parts 52 can be uniquely determined.

[Effect of this embodiment]
According to the present invention having this configuration (the present embodiment), the following operational effects can be obtained.
(1) Since the housing body 11 of the first component member and the cover 12 of the second component member are assembled and fixed by the assembly fixing means 50 at a plurality of locations (three locations), sufficient assembly strength is ensured. be able to.
(2) By specifying the relationship between the arrangement of the pin portion 51 and the hole portion 52 of each assembly fixing means 50 and the projection portion 53 provided in the hole portion 52, the projection portions 53 of the three hole portions 52 at the time of press-fitting. Cooperate with each other to exert a centering function for the three pin portions 51 so that the relative positions of the three pin portions 51 and the three hole portions 52 are uniquely determined. The manufacturing variation among the constituent members can be absorbed by the elastic deformation of the protrusion 53. Therefore, the housing main body 11 of the first component member and the cover 12 of the second component member can be assembled and fixed with high accuracy.
(3) Accordingly, it is possible to provide an air flow meter AF including the housing 1 assembled with high strength and high accuracy.

[Example 2]
Next, another embodiment (Example 2) of the present invention will be described with reference to FIG. In FIG. 6, (a) shows the cover 12 alone, while (b) shows the entire assembly fixing means 50.

  In the second embodiment, as the assembly fixing means 50, as in the first embodiment, the pair of rectifying plates 13 and 14 and the pair of plate-like covers (second component) 12 of the housing body (first component member) 11 are used. Are provided with three pin portions 51 and three hole portions 52, but one protrusion portion 53 protruding from each hole portion 52 of the cover 12 is formed.

Also in this embodiment, the relationship between the arrangement of the three pin portions 51 and the three hole portions 52 and the projections 53 protruding from the three hole portions 52 is described in detail in the first embodiment . It is set on the basis of the thinking person.

In other words, when calling the direction of more occurring reaction forces on the sole of the protrusion 53 of the hole 52 when the press-fitting pin 51 into the hole 52 and the direction P, the center of gravity G in all directions P is a region S Oriented Set to

  Thus, also in the present embodiment, since the protrusions 53 in the three hole portions 52 cooperate with each other to exhibit a kind of alignment function with respect to the three pin portions 51, the three pin portions The relative position of 51 and the three hole parts 52 can be defined uniquely, and the same effect as Example 1 can be obtained.

[Modification]
Although the present invention has been described in detail with reference to two embodiments, various modifications can be made without departing from the spirit of the present invention, and modifications thereof will be exemplified.

(2) In the first and second embodiments, the number of protrusions 53 of each hole 52 is two, but three or more may be provided. However, in order to project the protrusions 53 so that the tips of the holes 52 are opposed to each other, the inner peripheral surface of each hole 52 is limited to the inner peripheral surface side of the holes 52 facing each other. In addition, considering that the direction P of the reaction force by the projection 53 is focused on the center of gravity Q, the projectable range of the projection 53 is only on the inner peripheral surface side of the hole 52 facing each other. The angle range around the center of the hole 52 is preferably less than 180 degrees.

(3) In the present invention, in the assembly and fixing means 50, the protrusion 53 provided in the hole 52 is an essential component, and the arrangement (protrusion position) of the protrusion 53, the protrusion direction (direction of the tip), The tip shape can be selected as appropriate from various considerations from the required press-fit load, manufacturing surface, durability, and the like.
For example, a representative example of the tip shape of the protrusion 53 is shown in FIG. 7, and the advantages and disadvantages for each shape are outlined below.

FIG. 7A shows the tip of the projection 53 formed with an acute angle. The tip is easily damaged when pressed, and is difficult to manufacture.
-FIG.7 (b) is what rounded the front-end | tip, and can prevent the defect | deletion accident of a front-end | tip.
FIG. 7C shows the projection 53 itself formed in a trapezoidal shape, and FIG. 7D shows the projection 53 itself formed in a circular shape.
Although the shape of the protrusion 53 shown in FIGS. 7C and 7D cannot provide a large crushing margin, the contact area with the pin 51 can be increased to ensure a large press-fitting load.

(4) Various additional structures can be selected and employed for the press-fitting part (combination structure of the pin part 51 and the hole part 52) in the assembly fixing means 50. A typical structural example is shown in FIG. 8, and the characteristics of each structure are outlined below.

FIG. 8A shows that the tip of the pin portion 51 is formed in the reduced diameter truncated cone 51a and the inlet (insertion) side of the hole portion 52 is formed in the enlarged diameter conical recess 52a. The insertion with the part 52 can be performed quickly and smoothly, and the assembling property is improved.
FIG. 8 (b) shows that the exit (anti-insertion) side of the hole 52 is formed in the enlarged diameter conical recess 52b, and the shavings generated by partly cutting the projection 53 when the pin 51 is press-fitted. It can be stored in the recess 52b.
FIG. 8C is an example of a structure that is useful when the press-fitting portion between the pin portion 51 and the hole portion 52 is further caulked, and a concave groove 54 is formed so as to surround the hole portion 52 of the cover 12. Yes. In this way, since the hot melted part 51b of the pin part 51 can be accommodated in the concave groove 54, the generation of burrs can be prevented.

(5) In the above-described embodiment, the example in which the housing body 11 is the first constituent member and the cover 12 is the second constituent member as the at least two constituent members constituting the housing 1 has been described. When the housing main body 11 itself has a split structure constituted by two members 11a and 11b, the assembling and fixing means of the present invention is used as an assembling and fixing means for the two constituent members 11a and 11b. 50 can also be applied.

  The features and effects of the present invention that have been described in detail above will be summarized as follows according to each means described as a dependent claim in the scope of claims.

(Feature 1 = Means of Claim 2 )
The air flow meter according to claim 1 ,
The mutually facing inner peripheral surface side in the hole 52 is a range of less than 180 degrees in the angle range with the center of the hole 52 as the center, and a plurality of protrusions 53 are provided over the angle range. , the direction of the resultant force of more occurring reaction forces to the plurality of the protrusions 53 is characterized in that it coincides with the direction P.
According to the above means, in each hole 52, it is possible to provide a large number of protrusions 53 over a relatively wide range, and the degree of design freedom can be improved.

(Feature 2 = Means of Claim 3 )
In the air flow meter according to claim 1 or 2 ,
The protrusion 53 has a crush margin at the tip, and the protrusion 53 is crushed when the pin 51 is press-fitted into the hole 52.
According to the above means, the press-fit load can be appropriately selected depending on the size of the crushing allowance.

DESCRIPTION OF SYMBOLS 1 Housing 2 Flow sensor 4 Bypass flow path 11 Housing main body (1st structural member) 12 Cover (2nd structural member) 50 Assembly fixing means 51 Pin part 52 Hole part 53 Protrusion part AF Air flow meter D Duct R1 Outside of pin part Diameter R2 Inner diameter of hole S area Q Center of gravity P direction

Claims (3)

A housing (1) that forms a bypass channel (4) that takes in part of the air flowing in the duct (D), and the air that is disposed in the bypass channel (4) and flows through the bypass channel (4) A flow sensor (2) for detecting the flow rate,
The housing (1) has at least two constituent members, ie, a first constituent member (11) and a second constituent member (12), and both the constituent members (11, 12) are assembled and fixed. In the air flow meter (AF)
As means (50) for assembling and fixing the first component member (11) and the second component member (12),
Said three pin portions which are protruded apart from each other in the first component (11) and (51), provided in the corresponding to the pin portion (51) second component (12), wherein comprises three holes having a large becomes an inner diameter (R2) than the outer diameter (R1) of the pin portion (51) and (52),
On the inner peripheral surface of the hole (52), an elastically deformable protrusion (53) that reduces the inner diameter (R2) of the hole (52) is formed to protrude.
The protrusions (53) are provided such that the tips thereof are opposed to each other only on the inner peripheral surface sides facing each other in the three hole portions (52),
The first component member (11) and the second component member (12) are assembled by press-fitting the pin portion (51) against the projection portion (53) into the hole portion (52). Is to be fixed,
The positional relationship of the pin part (51), the hole part (52) and the protrusion part (53) is surrounded by a triangle connecting the centers of the three pin parts (51) or the hole part (52). when forming the region (S), referred to the direction (P) in the direction of more resulting reaction force said pin portion (51) on the projections (53) when press-fitted into the hole (52), the direction ( An air flow meter characterized in that P) exhibits a centering function structure by being directed to the center of gravity (Q) of the region (S) . The air flow meter according to claim 1,
The mutually facing inner peripheral surface side in the hole (52) is a range of less than 180 degrees in an angle range centered on the center of the hole (52),
A plurality of the protrusions (53) are provided over the angular range,
The direction of the resultant force of the reaction force generated by each of the plurality of protrusions (53) coincides with the direction P. The air flow meter according to claim 1 or 2,
The protrusion (53) has a crushing margin at the tip,
The air flow meter, wherein the projection (53) is crushed when the pin (51) is press-fitted into the hole (52) .