JP2018100947A - Thermal flowmeter and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal flowmeter which can be manufactured easily, is highly reliable, and has a vibration resistance in an actual vehicle equipment environment when a main housing and a connector flange of the thermal flowmeter are manufactured separately.SOLUTION: The method for manufacturing a thermal flowmeter includes the step of performing attaching (depositing) so that the thermal flowmeter has a first region and a second region, the first region being a region in which a cover and a main housing formed by a primary formation step are connected to each other and the second region being a region in which the cover and a connector flange part formed by a secondary formation step are connected to each other.SELECTED DRAWING: Figure 4c

Description

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

  There is a thermal flow meter as a device for measuring the mass flow rate of the gas to be measured flowing through the main passage. 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 (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. This is because the method 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 portion is generally different for each vehicle 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) that 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, so the flow characteristics of the thermal flowmeter can be close to the same specifications. It becomes.

Japanese Unexamined Patent Publication No. 2014-1993 Japanese Unexamined Patent Publication No. 2015-17847 JP 2013-104759 A

  In Patent Document 3, the joint between the primary resin portion and the secondary resin portion is located in a region outside the intake air with respect to the installation surface on which the thermal flow meter is installed in the intake duct. In this case, in the primary molded product, it is difficult to improve the warpage deformation of the resin at the connector flange and the warpage deformation of the main housing (housing) at the same time, and warpage deformation of the main housing (housing) occurs. Or the flange mounting surface varies, there is a concern that the detection accuracy of the flow rate characteristic is lowered.

  As a method of 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 portion and the secondary resin portion 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 part due to vibration can be considered. Since the connector flange side is fixed to the intake duct with screws, etc., there is little vibration due to vehicle vibration or engine pulsation, but the main housing (housing) is a cantilever structure that protrudes toward the intake side, so compared to the flange part This increases the amount of vibration. For this reason, since a large stress is applied to the joint portion between the primary resin portion and the secondary resin portion due to the vibration of the main housing (housing), there is a problem that the strength near the resin joint portion must be ensured.

  The present invention has been made in view of the above problems, and its purpose is to prevent the detection accuracy of the flow rate characteristic from being lowered, so that the joint portion between the primary resin portion and the secondary resin portion is an intake duct. An object of the present invention is to provide a structure that can ensure the strength of a main housing (housing) in the vicinity of a joint even when the mounting surface is positioned on the intake side.

  In order to solve the above-described problems, a thermal flow meter of the present invention includes a first resin body having a sub-passage groove, and a second resin body mechanically joined to the first resin body and having a connector and a flange. A cover that forms a sub-passage in which a sensor element is arranged in cooperation with the sub-passage groove, and the mechanical joint between the first resin body and the second resin body is , Formed on the opposite side of the connector with respect to the flange, and the joint between the first resin body and the cover is on the opposite side of the flange from the mechanical joint, and the second The joint location between the resin body and the cover is closer to the flange than the mechanical joint location.

  According to the present invention, the primary resin portion and the main resin (housing) can be prevented from being warped and deformed, or the flange mounting surface varies, thereby preventing the flow rate characteristic detection accuracy from being lowered. Even when the joint of the secondary resin part is positioned on the intake side with respect to the intake duct mounting surface, the main housing (housing) strength in the vicinity of the joint can be secured, so reliability is ensured. A high thermal flow meter can be provided.

It is a figure which shows one Example which uses the thermal type flow meter which concerns on this invention for the internal combustion engine control system. It is a figure which shows one Example of the thermal type flow meter inserted and fixed to the intake duct of an internal combustion engine. It is a figure which shows the external appearance of a general thermal type flow meter. It is a figure which shows one Example of the circuit package of the thermal type flow meter which concerns on this invention. It is a figure which shows one Example of the primary molded product of the thermal type flow meter which concerns on this invention. It is a figure which shows one Example of the secondary molded product of the thermal type flow meter which concerns on this invention. It is a figure which shows one Example of the thermal type flow meter which concerns on this invention. It is a figure which shows one Example of the primary molded product of the thermal type flow meter which concerns on this invention. It is a figure which shows one Example of the secondary molded product of the thermal type flow meter which concerns on this invention. It is a figure which shows one Example of the manufacturing method of the thermal type flow meter which concerns on this invention.

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

  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 the air flow rate, a drive circuit for processing a signal of the detection element 320, and a lead frame 325. In the air flow rate detection element 320, a region including a portion for detecting the flow rate is partially exposed from the resin constituting the circuit package. The circuit package 330 is manufactured by mounting a detection element 320 for detecting the air flow rate and a drive circuit chip on a lead frame 325, and sealing (molding) with a package resin.

  As an explanation of the present embodiment, the support member on which the detection element 320 for detecting the air flow rate is mounted is the circuit package 330, but a circuit board generally used such as a printed board or a ceramic board may also be used. It can be used as well.

  Next, as shown in FIG. 4b, the main casing 303, which is the first resin body that supports the circuit package 330 on which the detection element 320 for detecting the 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 constituting a 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 insert molded. Note that after the main casing is formed in the primary molding step, a support member (circuit package 330, printed circuit board, ceramic substrate, or the like) that supports the flow rate detection unit may be held with an adhesive or the like.

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

  As shown in the side view, the main housing 303 manufactured in the primary molding process does not have a connector flange portion, and thus has an elongated shape 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 process. That is, since there is no resin flow in the flange spreading direction, it is easy to make the resin flow uniform. In the present embodiment shape, the resin flow direction at the time of molding can be easily aligned, and the warp of the main casing 303 at the time of molding can be easily controlled.

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

  In addition, although the insert has been described as an example of the mechanical coupling between the main housing 303 which is the first resin body and the connector flange portion 301 which is the second resin body, the insert may be fixed by a snap fit. .

  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 casing 303 and the cover 370 can be laser-welded, and the connector flange portion 301 and the cover 370 can be laser-welded.

  In addition, although laser welding is mentioned as an example, the adhesion | attachment by an adhesive agent may be sufficient. In this case, the laser welding portion is replaced with an adhesive filling groove. The same applies to other joining methods.

  Thereafter, as shown in FIG. 4d, the 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 is not established only by the groove (or hole) formed in the main housing 303, and in general, the bypass passage is completed by assembling the cover and the main housing 303. A passage 360 is formed.

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

  When a hole constituting the bypass passage 360 is provided in the main housing 303, the cover 370 for constituting the bypass passage 360 needs to be provided on both the front surface side and the back surface side. However, when the groove constituting 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 bypass 360 can be configured if the cover 370 is provided on the opening side.

  According to the present embodiment, in addition to the mechanical coupling portion between the main housing 303 and the connector flange portion 301, the main housing 303 which is the first resin body and the connector which is the second resin body by welding or adhesion. With the cover 370 joined to the flange part 301, the structure that bridges this mechanical coupling part, the strength of the flowmeter as a whole is reinforced, and the prevention of breakage is suppressed even in a vibration environment mounted on an actual vehicle. It is possible to provide a highly reliable thermal flow meter.

  A second embodiment of the present invention will be described. Note that a description of the same structure as in the first embodiment will be omitted.

  The second embodiment shows an example in which the joining of the connector flange portion 301 and the cover 370 and the joining of 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 laser welding is performed, a welding target is sandwiched between flat plates that can transmit laser, such as glass, and laser is irradiated in a state of being pressurized with a certain load to perform welding. Thereby, when the cover resin is melted, it is submerged by a load, so that a welded surface with high bonding strength can be formed without forming a cavity in the welded resin portion. In general, laser irradiation is performed not by irradiating the entire welded portion all at once but by scanning. Moreover, as a laser welding surface, it is desirable that the surface part does not have a level | step difference but is the same plane. When there is no step on the surface, a uniform weld interface is formed, and a weld 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 in the main housing 303 and the connector flange portion 301 are in the same plane. However, in the case where there are steps on the two welding surfaces in different areas, after laser welding, the welding area sinks, so if laser irradiation is performed from a high area of the welding surface, the high area sinks due to welding, A low welding surface and a cover can contact stably.

  In other words, when there is a step on the welding surface, laser irradiation from a welded portion with a low welding surface particularly during laser irradiation scanning may cause a gap between the cover and the welding surface, which reduces the bonding strength of the welding surface. There is a fear. In addition, when the surface stepped portions are arranged adjacent to each other, the welding surfaces having different surface steps adjacent to each other are welded simultaneously by the 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 process for forming the connector flange portion 301, the main housing 303 is installed in the secondary mold and the resin is poured into the mold. Here, there is a case where an arbitrary gap is provided between the mold and the main casing 303 so that the main casing 303 is not damaged when the main casing 303 is sandwiched between the molds. In that case, the position of the main housing 303 may be displaced within the clearance during the secondary molding, and as a result, the surface height of the laser welded portions 306a and 306b in the secondary molded product is completely the same. There may be a case where one of the welding surface heights of 306a and 306b is not flat and becomes high.

  In this embodiment, as shown in FIG. 4c, the laser welded portion 306a on the housing (housing) 303 side and the laser welded portion 306b on the connector flange portion 301 side sandwich the resin interface 302 in this embodiment. It arrange | positions in each area | region and it is set as the arrangement | positioning which each welding part became independent. 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 portion is not generated. Further, either the height of the welding surface 306a or the height of the welding surface 306b is set to be high in advance, and the level difference between the two surfaces should be smaller than the depth of sinking by laser welding. Thus, from the side where the laser welding surface is always high at the time of production, laser welding is performed to prevent the reduction of the bonding strength of the welding surface, and stable mass production is possible.

  In general, since the sinking amount by laser welding is 0.1 mm or less, it is desirable to set the welding surface step set in advance to be less than that.

  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 near the joint can be increased, and the reliability can be improved. Can be increased.

  In the description of the present embodiment, the main casing 303 is formed in the primary molding process, and the connector flange portion 301 is formed in the secondary molding process. It is clear that an effect can be obtained.

  In addition, although the laser welding is mentioned as an example for the bonding method in the present embodiment, the same effect can be obtained by a method using an adhesive. However, in the laser welding method, the cover 370, the main housing 303, and the resin are melted together to form a joint interface, so that the joint strength and the housing in the vicinity of the joint are used rather than using ordinary adhesives. Rigidity can be increased and higher reliability can be expected.

  Next, Example 3 will be described below.

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

  In FIG. 5b, the connector flange portion 301 is manufactured in the secondary molding process as described above. Here, in FIG. 5b, the laser welded portion 306a on the main housing 303 side and the laser welded portion 306b on the connector flange portion 301 side are arranged adjacent to each other to constitute one laser welded portion. With such a structure, at the time of laser welding, the resin at 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.

  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.

  The manufacturing method is shown in FIG. FIG. 6 (a) is a diagram showing the configuration of the molding die at the time of secondary molding from the cross-sectional direction. There are a lower die 410 and an upper die 420, and the main casing 303 of the primary molded product is the die. The state set to. As described above, basically, it is general to provide a minute gap so that the insert is not crushed by the mold. Further, the upper mold 420 is provided with a movable insertion piece 430. The insertion piece 430 is movable in the vertical direction in the drawing direction and is brought into contact with the laser welding surface 306a. As a movable method, a load control method using a spring 435 or the like is common. By controlling the load, the welding surface and the insert piece can be stably brought into close contact with each other without damaging the fragile 306a. The reason why the entire upper mold is not movable is that the resin is injected into the mold with a very large pressure at the time of resin molding inflow, so if there are many movable areas, the entire upper mold is fixed by the resin internal pressure. May be difficult. For this reason, it is desirable that the area of the movable part is as small as possible. By the above manufacturing method, the secondary molded product can be molded without any step on each welding surface as shown in FIG. 6 (b).

125 ... Mounting surface to intake duct
301 ・ ・ ・ Connector flange
302 ... Joint interface between main housing and connector flange
303 ・ ・ ・ Main housing
305 ... Connector terminal
306a: Laser welding part on the main housing 303 side
306b ・ ・ ・ Laser weld on connector flange 301
320 ... Detection element
330 ・ ・ ・ Circuit package
360 ... Bypass passage
370 ... Cover

Claims (15)

A first resin body having a secondary passage groove;
A second resin body mechanically joined to the first resin body and having a connector and a flange;
A cover that forms a sub-passage in which the sensor element is arranged in cooperation with the sub-passage groove;
The mechanical joint 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 joining part of said 2nd resin body and said cover is a thermal flowmeter which exists in the said flange side rather than the said mechanical coupling | bond part.   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 flow meter according to claim 1, wherein the second resin is mechanically joined by being inserted into the first resin body.   The thermal flow meter according to claim 1, wherein the first resin and the second resin 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 the two melt and are melted together. A second cover forming a sub-passage in which the sensor element is arranged in cooperation with the sub-passage groove;
The joint location between the first resin body and the second cover is on the opposite side of the flange from the mechanical joint location,
The thermal flowmeter according to any one of claims 1 to 4, wherein a joint portion between the second resin body and the second cover is closer to the flange than the mechanical joint portion.   The heat according to claim 6, wherein the joint portion between the first resin body and the second cover and the joint portion between the second resin body and the second cover are in an adhered or welded state. Type flow meter.   The joining location of said 1st resin body and said cover, and the joining location of said 2nd resin body and said cover exist in the state which was adhere | attached or welded. Thermal flow meter.   The method for manufacturing a thermal flowmeter according to claim 1, wherein the cover has a higher Young's modulus than the first resin body and the second resin body. A first resin molding step for forming a first resin body having a sub-passage groove;
A second resin molding step for forming a second resin body having a connector and a flange,
In the second resin molding step, mechanically joining the first resin body and the second resin body by including a part of the housing on the opposite side of the connector from the flange,
In the first resin molding step and the second resin molding step, weld portions for laser welding the cover forming the sub passage in cooperation with the sub passage groove are formed in the first resin molding step, respectively. The first resin body, the second resin body formed in the second resin molding step,
A thermal process comprising: a first resin body formed in the first resin molding step; and a laser welding step for laser welding the second resin body formed in the second resin molding step to the cover. A manufacturing method of a flow meter. A first resin molding step for forming a first resin body having a sub-passage groove;
A second resin molding step for forming a second resin body having a connector and a flange;
A snap fit step of mechanically joining the first resin body and the second resin body by snap fit by including a part of the housing on the opposite side of the connector from the flange,
In the first resin molding step and the second resin molding step, weld portions for laser welding the cover forming the sub passage in cooperation with the sub passage groove are formed in the first resin molding step, respectively. The first resin body, the second resin body formed in the second resin molding step,
A thermal process comprising: a first resin body formed in the first resin molding step; and a laser welding step for laser welding the second resin body formed in the second resin molding step to the cover. A manufacturing method of a flow meter.   12. The thermal flow meter according to claim 10, wherein, in the laser welding step, a second cover that is laser-welded in the same manner as the cover is laser-welded on the side opposite to the side on which the cover is formed. Manufacturing method.   The welding part formed in said 1st resin body and the welding part formed in said 2nd resin body provide the difference smaller than the depth amount which sinks by laser welding to the height. Item 12. A method for producing a thermal flow meter according to Item 10 or 11.   The welded part formed on the first resin body and the welded part formed on the second resin body are formed adjacent to each other. Method.   The manufacturing method of the thermal type flow meter according to claim 14, wherein in the second resin molding step, the adjacent interface portion is formed by using a movable mold mechanism.

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