JP6640706B2 - Thermal flow meter and method of manufacturing the same - Google Patents

Description

The present invention relates to a thermal flow meter for measuring a flow rate of intake air to an internal combustion engine of an automobile, and a method for manufacturing the same.

  As a device for measuring the mass flow rate of the gas to be measured flowing through the main passage, there is a thermal flow meter. As an example of the thermal flow meter, there is a technique described in Patent Document 1. As shown in FIG. 1 of Patent Document 1, a thermal flow meter is partially inserted into an intake pipe and installed.

  The shape of the connector flange portion (305) for transmitting the output signal of the thermal flow meter to the control unit (ECU) is parallel to the intake pipe insertion direction, as described in Patent Document 1. There are various shapes such as a structure that opens in a direction, and a shape that opens in a direction perpendicular to the intake pipe insertion direction and also in a direction perpendicular to the air flow direction as described in Patent Document 2. The reason for this is that the way of drawing out the connector wiring depends on the component mounting layout of the entire vehicle, and therefore, the opening direction of the connector flange is generally different for each vehicle-mounted manufacturer or for each applicable engine.

  In response to the request, there is a technique described in Patent Document 3, for example. According to Patent Document 3, a manufacturing method is proposed in which a main housing (housing) which greatly affects the flow characteristics of a thermal flow meter and a connector flange portion required for external signal transmission are separately molded and manufactured. ing. According to this manufacturing method, the mold of the main housing (housing) can be manufactured with one mold regardless of the opening direction of the connector flange portion, so that the flow characteristics of the thermal flow meter can be made close to the same specifications. Becomes

JP 2014-1993 JP 2015-17847 A JP 2013-104759 A

  In Patent Document 3, the joint between the primary resin part and the secondary resin part is located in a region in the direction outside the intake with respect to the installation surface where the thermal flow meter is installed in the intake duct. In this case, it is difficult to simultaneously improve the warp deformation of the resin at the connector flange portion and the warp deformation of the main housing (housing) in the primary molded product, and the warp deformation of the main housing (housing) occurs. It is feared that the detection accuracy of the flow rate characteristic is reduced due to the variation of the flange mounting surface.

  As a method for avoiding this, the above problem can be solved if the region constituted by the primary resin portion is only the main housing (housing) and the region constituted by the secondary resin portion is divided by the connector flange portion. However, in the above structure, the joint between the primary resin part and the secondary resin part is located on the intake side with respect to the intake duct mounting surface. As a problem in this case, insufficient bonding strength of the resin portion due to vibration may be considered. The connector flange side is fixed to the intake duct with screws, etc., so vibrations due to vehicle vibration and engine pulsation are small.However, the main housing (housing) has a cantilever structure that protrudes toward the intake side, so it is not The amount of vibration increases. For this reason, since a large stress is applied to the joint between the primary resin part and the secondary resin part due to the vibration of the main housing (housing), there is a problem that the strength near the resin joint must be secured.

  The present invention has been made in view of the above problems, and an object of the present invention is to prevent the detection accuracy of the flow rate characteristic from being reduced, in which a joining portion between a primary resin portion and a secondary resin portion is formed by an intake duct. An object of the present invention is to provide a structure capable of securing the strength of a main housing (housing) in the vicinity of a joint, even when the structure is located on the intake side with respect to a mounting surface.

  In order to solve the above-mentioned problem, the thermal type flow meter of the present invention has a first resin body having a sub passage groove and a second resin having a connector and a flange, wherein the first resin body is mechanically joined. And a cover that forms a sub-passage in which the sensor element is arranged in cooperation with the sub-passage groove, and a mechanical joint between the first resin body and the second resin body is , Is formed on the opposite side of the connector from the flange, the joint between the first resin body and the cover is on the opposite side of the flange than the mechanical joint, the second The joint between the resin body and the cover is closer to the flange than the mechanical joint.

  According to the present invention, warping deformation of the main housing (housing) occurs, or due to the flange mounting surface is varied, to suppress the detection accuracy of the flow characteristics from being reduced, the primary resin portion and Even when the joint of the secondary resin part is located on the intake side with respect to the intake duct mounting surface, the strength of the main housing (housing) near the joint can be ensured, It is possible to provide a high thermal flow meter.

FIG. 1 is a diagram showing an embodiment in which a thermal flow meter according to the present invention is used in an internal combustion engine control system. FIG. 2 is a view showing an embodiment of a thermal flow meter inserted and fixed in an intake duct of an internal combustion engine. It is a figure showing appearance of a general thermal type flow meter. It is a figure showing one example of a circuit package of a thermal type flow meter concerning the present invention. It is a figure showing an example of the primary cast of a thermal type flow meter concerning the present invention. FIG. 3 is a view showing one embodiment of a secondary molded product of the thermal flow meter according to the present invention. It is a figure showing one example of a thermal type flow meter concerning the present invention. It is a figure showing an example of the primary cast of a thermal type flow meter concerning the present invention. FIG. 3 is a view showing one embodiment of a secondary molded product of the thermal flow meter according to the present invention. It is a figure showing one example of a manufacturing method of a thermal type flow meter concerning the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  First Embodiment A first embodiment of the present invention will be described with reference to FIGS. 4A to 4D.

  As shown in FIG. 4A, the circuit package 330 includes a detection element 320 for detecting an air flow rate, a driving circuit for processing a signal of the detection element 320, and a lead frame 325. The air flow detecting element 320 is configured such that a region including a flow rate detecting portion is partially exposed from the resin forming the circuit package. The circuit package 330 is manufactured by mounting a detection element 320 for detecting an air flow rate and a drive circuit chip on a lead frame 325 and sealing (molding) with a package resin.

  In the description of the present embodiment, the support member on which the detection element 320 for detecting the air flow rate is mounted is a circuit package 330, but a commonly used circuit board such as a printed board or a ceramic board may be used. Use is possible as well.

  Next, as shown in FIG. 4b, a main housing 303 which is a first resin body that supports the circuit package 330 on which a detection element 320 for detecting an air flow rate is mounted is subjected to a primary molding step (first step). (One resin molding step). The main housing 303 also has a role of configuring the bypass passage 360.

  In the primary molding process, an example is shown in which a connector terminal 305 for electrical connection between a thermal flow type and an external medium and a circuit package 330 are manufactured by insert molding. After the main housing is formed in the primary molding step, a support member (a circuit package 330, a printed circuit board, a ceramic substrate, or the like) that supports the flow rate detection unit may be held by an adhesive or the like.

  The main housing 303 is formed with a part of a bypass passage 360 for taking in a part of the airflow flowing through the intake duct and introducing the airflow into the detection element 320. The bypass passage 360 cannot function as a bypass passage unless four sides are formed along the passage direction with respect to the intake port. Therefore, in the primary molding step, a groove (or hole) for forming the bypass passage 360 is formed in the main housing 303. This satisfies the requirement that the mold must be opened in at least one side direction in order to allow the mold to open and close when considered from the mold molding method.

  As shown in the side view, the main housing 303 manufactured in the primary molding step does not have the connector flange portion, and therefore has a shape elongated in the intake duct insertion direction as a whole structure. Therefore, the entire structure of the main housing 303 has a simple shape as compared with FIG. 3 in which the connector flange portion is formed in the primary molding step. That is, since the resin does not flow in the flange spreading direction, it is easy to make the resin flow uniform. In the present embodiment, the resin flow directions during molding can be easily uniformed, and the warpage of the main housing 303 during molding can be easily controlled.

  Thereafter, as shown in FIG. 4c, in a secondary molding step (second resin molding step), a connector flange portion 301 as a second resin body is manufactured. At this time, the main housing 303 is mechanically joined by being inserted into the connector flange portion 301.

  Although an insert has been described as an example of the mechanical connection between the main housing 303 as the first resin body and the connector flange portion 301 as the second resin body, it may be fixed by snap fitting. .

  The laser welded portion 306a of the main housing 303 and the laser welded portion 306b of the connector flange portion 301 are arranged in respective regions so as to sandwich the resin interface 302. Thereby, the main housing 303 and the cover 370 can be laser-welded, and the connector flange portion 301 and the cover 370 can be laser-welded.

  Although laser welding is described as an example, bonding using an adhesive may be used. In this case, the laser welded part is replaced with the adhesive filling groove. The same applies to other joining methods.

  Thereafter, as shown in FIG. 4d, a cover 370 is attached to the front surface or the front and back surfaces of the main housing 303, and as shown in FIG. 4e, the cover 370 and the main housing 303, and the cover 370 and the connector flange portion. 301 is joined by laser welding.

  The bypass passage structure does not hold only with the groove (or hole) formed in the main housing 303, and the bypass passage is generally completed by assembling the cover and the main housing 303. Construct the passage 360.

  Here, the cover 370 having the role of constituting the bypass passage 360 is also used for joining the main housing 330 and the connector flange portion 301, so that the cover 370 can be manufactured at low cost without additional members and additional steps.

  In the case where the holes forming the bypass passage 360 are provided in the main housing 303, the covers 370 for forming the bypass passage 360 need to be provided on both the front side and the back side. However, when the groove that forms the bypass passage 360 is formed in the main housing 303, it is only necessary to close the opening side of the groove, so that the cover 360 can be configured by providing the cover 370 on the opening side.

  According to this embodiment, in addition to the mechanical connection between the main housing 303 and the connector flange portion 301, the main housing 303 as the first resin body and the connector as the second resin body are welded or bonded. The cover 370 joined to the flange portion 301 has a structure that bridges this mechanical connection, so that the strength of the flow meter as a whole is reinforced and the breakage is suppressed even in a vibration environment in actual vehicle mounting. It is possible to provide a highly reliable thermal flow meter.

  A second embodiment of the present invention will be described. The description of the same structure as in the first embodiment is omitted.

  In the second embodiment, an example in which the joining between the connector flange portion 301 and the cover 370 and the joining between the main housing 303 and the cover 370 are limited to laser welding. A general manufacturing method and problems of laser welding will be described. First, when performing laser welding, an object to be welded is sandwiched between laser-transparent flat plates made of glass or the like, and a laser is irradiated while being pressed under a certain load to perform welding. By this, when the cover resin is melted, it sinks by the load, so that a cavity is not formed in the welded resin portion and a welded surface having high bonding strength can be formed. In general, laser irradiation is performed not by simultaneous irradiation of the entire welded portion but by scanning. Further, it is desirable that the laser welding surface has the same plane without any step on the surface. When there is no step on the surface, a uniform welding interface is formed, and a welding surface with higher bonding strength can be formed.

  In the present embodiment, it is desirable from the viewpoint of laser welding that the surface heights of the laser welding portions 306a and 306b provided on the main housing 303 and the connector flange portion 301 are on the same plane. However, in the case where there is a step between the two welding surfaces in different regions, after the laser welding, the welding region sinks, so if the laser is irradiated from a region where the welding surface is high, the high region sinks by welding, The low welding surface and the cover can make stable contact.

  In other words, when there is a step on the welding surface, a gap may be generated between the cover and the welding surface, particularly when laser irradiation is performed from a welding portion where the welding surface is low during laser irradiation scanning, and the bonding strength of the welding surface is reduced. There is fear. Further, when the surface step portions are arranged adjacent to each other, the welding surfaces of the adjacent surface steps different from each other are simultaneously welded by laser irradiation, so that the step may not be absorbed by the welding sink and a gap may be generated. is there.

  However, in the manufacturing method shown in the present embodiment, in the secondary molding step of forming the connector flange portion 301, the main housing 303 is placed in a secondary mold and resin is poured. Here, when the main housing 303 is sandwiched by the mold, an arbitrary gap may be provided between the mold and the main housing 303 so as not to damage the main housing 303. In that case, the position of the main housing 303 may be shifted within the clearance during the secondary molding, whereby the surface height of the laser welded portions 306a and 306b is completely the same in the secondary molded product. It may happen that one of the welding surface heights of 306a and 306b is not flat, and one of the welding surface heights of 306a and 306b is high.

  In order to solve the above problem, in the present embodiment, as shown in FIG. 4C, the laser welding portion 306a on the housing 303 side and the laser welding portion 306b on the connector flange portion 301 side sandwich the resin interface 302. It is arranged in each area, and each welded part is arranged independently. With such an arrangement, the welding surfaces 306a and 306b having different surface heights are not adjacent to each other, so that a direct welding surface step does not occur. Further, one of the height of the welding surface 306a and the height of the welding surface 306b is previously set to be high, and the step between the two surfaces is set to be smaller than the depth of sinking by laser welding. Then, by performing laser irradiation and welding from the side where the laser welding surface is always higher during production, the decrease in the bonding strength of the welding surface can be prevented, and stable mass production can be achieved.

  Since the sinking amount due to laser welding is generally 0.1 mm or less, it is desirable that the preset welding surface step is set to less than 0.1 mm.

  In addition, when the Young's modulus of the resin material of the cover 370 is higher than the Young's modulus of the resin material of the main housing 303, the rigidity of the housing in the vicinity of the joint can be increased, and the reliability is further improved. Can be enhanced.

  In the description of the present embodiment, the embodiment in which the main housing 303 is formed in the primary molding process and the connector flange portion 301 is formed in the secondary molding process has been described. The effect is clear.

  In addition, although the laser welding is taken as an example of the bonding method in the present embodiment, a similar effect can be obtained by a method using an adhesive. However, in the laser welding method, since the cover 370, the main housing 303, and the resin melt with each other to form a bonding interface, the bonding strength and the strength of the housing near the bonding portion are higher than when a normal adhesive is used. Rigidity can be increased, and higher reliability can be expected.

  Next, a third embodiment will be described below.

  In FIG.5a, the circuit package 330 in which the detection element 320 for detecting the air flow rate is mounted as described above, and the connector terminal 305 for electrical connection between the thermal flow rate type and the external medium are insert-molded. The main housing 303 is formed in a primary molding process manufactured by the above method.

  In FIG. 5b, the connector flange portion 301 is manufactured in the secondary molding step as described above. Here, in FIG. 5B, the laser welded part 306a on the main housing 303 side and the laser welded part 306b on the connector flange part 301 side are arranged adjacent to each other and combined to form one laser welded part. With such a structure, at the time of laser welding, the resin in the resin interface portion 302 having the lowest bonding force can be melted and bonded to the cover, so that the strength of the bonded portion can be further improved. Become.

  Here, since this is a problem, it is important not to generate this surface step because it is the step between the adjacent surfaces described above.

  FIG. 6 (a) shows the manufacturing method. FIG. 6 (a) is a view showing the configuration of a molding die during secondary molding from a cross-sectional direction, in which there are a lower die 410 and an upper die 420, and the main casing 303 of the primary molded product is a die. Is set to "1". As described above, it is general to provide a small gap so as not to crush the insert product with a mold. Further, the upper mold 420 is provided with a movable type insert 430, and the insert 430 moves up and down in the drawing direction, and comes into contact with the laser welding surface 306a. As a movable system, a load control system using a spring 435 or the like is general. By controlling the load, the welding surface can be stably brought into close contact with the insertion piece without damaging the fragile 306a in shape. The reason that the entire upper mold is not movable is that the resin is injected into the mold with a very large pressure when the resin molding flows in.If there are many movable areas, the entire upper mold is fixed by the internal pressure of the resin. Can be difficult. Therefore, it is desirable that the area of the movable system section be as small as possible. According to the manufacturing method described above, the secondary molded product can be molded in a state where there is no step on each welding surface as shown in FIG. 6 (b).

125 ・ ・ ・ Mounting surface to intake duct
301 ・ ・ ・ Connector flange
302 ・ ・ ・ Bonding interface between main housing and connector flange
303 ・ ・ ・ Main housing
305 ・ ・ ・ Connector terminal
306a ・ ・ ・ Laser welding part on main housing 303 side
306b ・ ・ ・ Laser welded part on connector flange part 301 side
320 ・ ・ ・ Detector
330 ・ ・ ・ Circuit package
360 ・ ・ ・ Bypass passage
370 ・ ・ ・ Cover

Claims (15)

A first resin body having an auxiliary passage groove,
The first resin body is mechanically joined, a second resin body having a connector and a flange,
A cover forming a sub-passage in which the sensor element is arranged in cooperation with the sub-passage groove,
The mechanical joining portion between the first resin body and the second resin body is formed on the opposite side of the connector from the flange,
The joint between the first resin body and the cover is on the opposite side of the flange from the mechanical joint,
The joint between the cover and the second resin bodies, thermal flow meter is in said flange side than the mechanical junction point.   The thermal flow meter according to claim 1, wherein the first resin body is mechanically joined by being inserted into the second resin body. The thermal flowmeter according to claim 1, wherein the second resin body is mechanically joined by being inserted into the first resin body. The thermal flowmeter according to claim 1, wherein the first resin body and the second resin body are mechanically joined by a snap-fit structure.   At the boundary between the first resin body and the second resin body, a resin constituting the first resin body, a resin constituting the second resin body, and a resin constituting the cover The thermal flow meter according to any one of claims 1 to 3, wherein there is a region where are melted and fused with each other. A second cover forming a sub-passage in which the sensor element is arranged in cooperation with the sub-passage groove,
The joint between the first resin body and the second cover is on the opposite side of the flange than the mechanical joint,
The joint between the second resin member and the second cover, the thermal type flow meter according to any one of claims 1 to 4 than the mechanical junction portion in said flange side.   7. The heat according to claim 6, wherein the joint between the first resin body and the second cover and the joint between the second resin body and the second cover are in a bonded or welded state. Flow meter.   The joint portion between the first resin body and the cover and the joint portion between the second resin body and the cover are in a bonded or welded state. Thermal flow meter. Towards the cover, the thermal type flow meter according to any one of claims 1 to 6, wherein the Young's modulus is higher than the second resin member and the first resin body. A first resin molding step of forming a first resin body having a sub passage groove,
A second resin molding step of forming a second resin body having a connector and a flange,
At the time of the second resin molding step, the first resin body and the second resin body are mechanically joined by including a part of the first resin body on a side opposite to the connector from the flange. To
In the first resin molding step and the second resin molding step, a welding portion for laser welding a cover forming a sub-passage in cooperation with the sub-passage groove is formed in the first resin molding step, respectively. The first resin body, the second resin body formed in the second resin molding step,
A first resin body formed in the first resin molding step, and a laser welding step of laser welding the second resin body formed in the second resin molding step with the cover. Manufacturing method of flow meter. A first resin molding step of forming a first resin body having a sub passage groove,
A second resin molding step of forming a second resin body having a connector and a flange,
A snap fitting step of mechanically joining the first resin body and the second resin body by snap fitting by including a part of the first resin body on the opposite side of the connector from the flange; ,
In the first resin molding step and the second resin molding step, a welding portion for laser welding a cover forming a sub-passage in cooperation with the sub-passage groove is formed in the first resin molding step, respectively. The first resin body, the second resin body formed in the second resin molding step,
A first resin body formed in the first resin molding step, and a second resin body formed in the second resin molding step, a laser welding step of laser welding the cover with the cover, Manufacturing method of flow meter.   The thermal flowmeter according to claim 10, wherein, in the laser welding step, a second cover on which the same laser welding as the cover is performed is laser-welded also on a side opposite to a side on which the cover is formed. Manufacturing method.   The welded portion formed on the first resin body and the welded portion formed on the second resin body are provided with a difference in height thereof smaller than a depth sinked by laser welding. Item 12. The method for producing a thermal flow meter according to item 10 or 11.   The manufacturing of the thermal flow meter according to claim 10 or 11, wherein the welded portion formed on the first resin body and the welded portion formed on the second resin body are formed adjacent to each other. Method. The second tree butter molding process, the manufacturing method of the thermal type flow meter according to the interface portion of the welded portion formed by the adjacent to claim 14 which is formed by using a mold mechanism movable.

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