Flowmeter, and physical quantity measuring device

A flowmeter is configured to measure a flow rate of a gas flowing through a main passage. The flowmeter includes a housing and a flow rate detector. The housing is made of a resin and includes a bypass passage branched off from the main passage. The flow rate detector is disposed in the bypass passage and transmits detection signals in accordance with the flow rate of the gas flowing through the main passage. The housing includes a non-insulation portion including graphite.

TECHNICAL FIELD

The present disclosure relates to a flowmeter, a physical quantity measuring device, and a method for manufacturing the physical quantity measuring device.

BACKGROUND

A flowmeter includes a housing that defines a bypass passage branched off from a main passage and a flow rate detector disposed in the bypass passage. The flow rate detector measures a flow rate of a fluid flowing through the main passage. An antistatic agent is added to resin material of the housing to restrict foreign matter wafting in the bypass passage from charging.

SUMMARY

A flowmeter is configured to measure a flow rate of a gas flowing thorough a main passage. The flowmeter includes a housing and a flow rate detector. The housing is made of a resin and includes a bypass passage branched off from the main passage. The flow rate detector is disposed in the bypass passage and transmits detection signals in accordance with the flow rate of the gas flowing through the main passage. The housing includes a non-insulation portion including graphite.

A physical quantity measuring device is configured to measure a physical quantity of a fluid. The physical quantity measuring device includes a housing, a physical quantity detector, and an electrical conductive portion. The housing includes at least a resin and defines a measuring passage through which the fluid flows. The physical quantity detector is configured to transmit detection signals in accordance with the physical quantity of the fluid flowing through the measuring passage. The electrical conductive portion is disposed on at least either one of an outer surface and an inner surface of the housing, contains a carbonized material to have an electric conductivity, and discharges an electric charge to a ground.

A method for manufacturing a physical quantity measuring device includes a preparing step and a heating step. The preparing step includes preparing a housing and a physical quantity detector. The housing defines a measuring passage through which a fluid flows and includes at least a resin. The physical quantity detector transmits detection signals in accordance with a physical quantity of the fluid flowing through the measuring passage. The heating step includes heating at least one of an outer surface and an inner surface of the housing to form an electrical conductive portion on the at least one of the outer surface and the inner surface such that an electric charge is discharged to a ground. The electric conductive portion contains a carbonized material to have an electrical conductivity.

DESCRIPTION OF EMBODIMENTS

A flowmeter includes a housing that defines a bypass passage branched off from a main passage and a flow rate detector disposed in the bypass passage. The flow rate detector measures a flow rate of a fluid flowing through the main passage. When such flowmeter is used and foreign matters such as dusts wafting in the bypass passage are charged, the foreign matters may adhere to the flow rate detector. This may cause a difference of value detected by the flow rate detector.

An antistatic agent is added to resin material of the housing to restrict the foreign matter wafting in the bypass passage from charging.

However, when the housing contains the antistatic agent, an amount of resin used for the housing is decreased by an amount of the antistatic agent, which reduces a moldability of the housing.

The present disclosure is considered regarding above subjects and it is objective of the present disclosure to provide a flowmeter and a physical quantity measuring device that prevent a deviation in characteristic while keeping a moldability, and a method for manufacturing the physical quantity measuring device.

The flowmeter of the present disclosure includes a housing and a flow rate detector. The housing is made of a resin and includes a bypass passage branched off from a main passage. The flow rate detector is disposed in the bypass passage. The housing includes a non-insulation portion containing a graphite.

Since the housing includes the non-insulation portion containing the graphite, a charge of foreign matters such as dusts can be removed when the foreign matters get in contact with the housing. The non-insulation portion may be formed on a position with which the foreign matters are in contact or a position with which the foreign matters are not in contact. No matter where the non-insulation portion is located, the housing is polarized by including a portion having a non-insulation property. Thus, the foreign matters are restricted from adhering to the flow rate detector. Additionally, it is unnecessary to add antistatic agent to the resin of the housing. Thus, a moldability and a durability of the housing can avoid decreasing and a deviation in characteristic of the flowmeter can be reduced.

Preferably, the non-insulation portion is formed by converting a surface layer of a resin member with an electromagnetic wave and making the surface layer electric conductive. A part of the molecular structure of the resin member is converted into a graphite by irradiating the housing with the electromagnetic wave. Thus, the housing has an antistatic property. The housing is converted with energy of the electromagnetic wave as described above, thus only a desired portion of the housing can be converted. Therefore, the flowmeter is superior in processability.

The physical quantity measuring device of the present disclosure is a device configured to measure a physical quantity of a fluid. The physical quantity measuring device includes a housing, a physical quantity detector, and an electric conductive portion. The housing includes at least a resin and defines a measuring passage through which the fluid flows. The physical quantity detector is configured to transmit detection signals in accordance with the physical quantity of the fluid flowing through the measuring passage. The electric conductive portion is disposed on at least one of an outer surface and an inner surface of the housing, contains a carbonized material to have an electric conductivity, and discharge an electric charge to a ground.

A method for manufacturing the physical quantity measuring device of the present disclosure includes a preparing step and a heating step. The preparing step includes preparing a housing and a physical quantity detector. The housing defines a measuring passage through which a fluid flows and contains at least a resin. The physical quantity detector transmits detection signals in accordance with a physical quantity of the fluid flowing through the measuring passage. The heating step includes heating at least one of an outer surface and an inner surface of the housing to form an electric conductive portion on the at least one of the outer surface and the inner surface such that an electric charge is discharged to a ground. The electric conductive portion contains a carbonized material to have an electrical conductivity.

The electric conductive portion can remove the electric charge of foreign matters such as dusts that are in contact with the housing. Thus, a deviation in characteristics of the flowmeter can be reduced. Additionally, it is unnecessary to add an antistatic agent to a material of the housing, which causes an amount ratio of the resin in the housing to decrease. Therefore, the resin is kept sufficient and a moldability of the housing is restricted from impairing.

Various embodiments will be described with reference to the drawings. In the embodiments, substantially the same components are denoted by the same reference numerals and descriptions thereof are omitted.

First Embodiment

An air flowmeter14inFIG.1is disposed, for example, in a vehicle. The air flowmeter14is provided in an intake passage12as a main passage and measures physical quantities such as flow rate, temperature, humidity, and pressure of an intake air supplied into an internal combustion engine. The air flowmeter14is a physical quantity measuring device configured to measure a physical quantity of a fluid and corresponds to a flowmeter that measures an intake air as a gas.

The air flowmeter14is disposed at a position downstream of an air cleaner (not shown) and upstream of a throttle valve (not shown) in the intake passage12. In this case, in the intake passage12, the air cleaner is located at an upstream side of the air flowmeter14and a combustion chamber is located at a downstream side of the air flowmeter14.

The air flowmeter14shown inFIGS.1and2is detachably attached to an intake pipe12adefining the intake passage12. The air flowmeter14is inserted into an airflow insertion hole12bpassing through a cylindrical wall of the intake pipe12aand at least a part of the air flowmeter14is located in the intake passage12. The intake pipe12aincludes a pipe flange12chaving a circular annular shape and extends radially outward from the airflow insertion hole12band a pipe made of synthetic resin or the like. Hereinafter, a longitudinal direction of the intake passage12(i.e., a flow direction of the intake air in the intake passage12) is referred to as a flow direction.

As shown inFIGS.1to6, the air flowmeter14includes a housing21, a flow rate detector22, and an intake air temperature sensor23. The housing21includes at least a resin. Specifically, the housing21contains a base polymer and fillers that have a higher strength than the base polymer. The base polymer is made of a resin and has an insulation property. The fillers are a reinforcing member to reinforce the housing21. Since the housing21of the air flowmeter14is attached to the intake pipe12a, the flow rate detector22is able to receive the intake air flowing through the intake passage12.

The housing21includes a bypass housing24, a ring holder25, a flange27, a connector28, a root29a, and a protecting protrusion29b. An O-ring26is attached to the ring holder25. The ring holder25is a portion fit into the airflow insertion hole12bthrough the O-ring26. InFIG.6, an illustration of the O-ring26is omitted.

The bypass housing24protrudes from the ring holder25toward the intake passage12. Hereinafter, an end of the bypass housing24facing the ring holder25is referred to as a housing base end and the other end of the bypass housing24facing away from the ring holder25is referred to as a housing tip end.

The flange27is disposed outside of the intake pipe12arelative to the ring holder25(i.e., outside of the intake passage12). The flange27covers the airflow insertion hole12bfrom an outside of the intake pipe12a. The flange27defines multiple screw holes42and the housing21is fixed to a boss12dof the intake pipe12awith the screw holes42.

The connector28surrounds multiple connector terminals28aand corresponds to a terminal protector configured to protect the connector terminals28a. One of the multiple connector terminals28ais a ground terminal and connected to an external ground45.

The root29aprotrudes from the ring holder25toward a center of the intake passage12. The root29ais distanced sideward from the bypass housing24to avoid a heat of the bypass housing24that is temperature-increased by receiving heat from an internal combustion engine.

The intake air temperature sensor23includes a thermosensitive element23athat detects a temperature of the intake air, a pair of lead wire23bextending from the thermosensitive element23a, and a pair of intake air temperature terminal23cconnected to the pair of lead wire23b. The pair of intake air temperature terminal23cextends from the root29a. The thermosensitive element23abridges over the pair of intake air temperature terminal23cwith the pair of lead wire23b. The pair of lead wire23band the pair of intake air temperature terminal23care both electrically conductive. The pair of intake air temperature terminal23care electrically connected to the connector terminals28ain the connector28. The intake air temperature sensor23transmits detection signals in accordance with a temperature of the intake air sensed by the thermosensitive element23a.

The protecting protrusion29bprotrudes sideward from the bypass housing24and is located between the housing tip end and the intake air temperature sensor23. A dimension of the protecting protrusion29bfrom the bypass housing24in a protruding direction of the protecting protrusion29bis greater than a distance between the bypass housing24and the intake air temperature sensor23. The protecting protrusion29brestricts the intake air temperature sensor23from getting in contact with the intake pipe12awhen the air flowmeter14is attached to the intake pipe12a. Thus, the intake air temperature sensor23is restricted from being damaged.

As shown inFIG.6, the bypass housing24defines a bypass passage30through which a part of the intake air flowing through the intake passage12flows. The bypass passage30includes a flow passage31and a measuring passage32. Both of the flow passage31and the measuring passage32are inner space defined by the bypass housing24.

The flow passage31passes through the tip end of the bypass housing24in the flow direction. The flow passage31defines an inlet opening33athat is an upstream end of the flow passage31and an outlet opening33bthat is a downstream end of the flow passage31. The measuring passage32is a passage branched off from a middle part of the flow passage31and defines measuring outlet openings33cthat are downstream ends of the measuring passage32. The measuring outlet openings33care defined respectively one by one at both side surfaces of the bypass housing24.

The flow passage31is tilted such that a rear portion47of the flow passage31is located closer to the housing base end in a direction to the outlet opening33b. The rear portion47is configured to be narrowed toward the outlet opening33b. The measuring passage32defines a measuring inlet opening34that is an upstream end of the measuring passage32. The measuring inlet opening34is a boundary between the flow passage31and the measuring passage32.

As shown inFIG.1, when the outlet opening33bis viewed from a position upstream of the outlet opening33bin the flow direction, the measuring inlet opening34is hidden behind the housing base end side of the flow passage31. Thus, the measuring inlet opening34cannot be seen from the upstream side of the outlet opening33b. As a result, even if foreign matters such as sand and dusts flow into the flow passage31together with the intake air, the foreign matters are likely to flow straight through the flow passage31and out of the flow passage31through the outlet opening33b. Thus, foreign matters are less likely to reach the flow rate detector22.

As shown inFIGS.6and7, the measuring passage32has a folded shape that is folded back at an intermediate position of the measuring passage32. The measuring passage32includes a detection passage32awhere the flow rate detector22is disposed, an introduction passage32bthrough which the intake air is introduced into the detection passage32a, and a discharge passage32cthrough which the intake air from the detection passage32aflows. The introduction passage32bextends from the boundary34toward the housing base end. The discharge passage32cextends from the measuring outlet openings33ctoward the housing base end.

The detection passage32ais disposed closer to the housing base end than the introduction passage32band the discharge passage32c. The detection passage32afluidly connects between a downstream end of the introduction passage32band an upstream end of the discharge passage32cwith bridged between the introduction passage32band the discharge passage32c.

The intake air flows through the detection passage32ain a direction opposite to the flow direction in the intake passage12and the flow passage31. In the measuring passage32, the intake air flowing from the flow passage31flows toward the housing base end and then makes a U-turn toward the housing tip end through the detection passage32a. This U-turn shape makes it difficult for the foreign matters such as sand and dusts to reach the flow rate detector22even if the foreign matters flow into the air flowmeter14.

The measuring outlet openings33cfluidly connect the discharge passage32cto the intake passage12. Total opening area of the two measuring outlet openings33care substantially the same with an area of the discharge passage32c.

The flow rate detector22is a physical quantity detector that transmits detection signals in accordance with physical quantities of a fluid flowing through the measuring passage32. In the first embodiment, the flow rate detector22transmits detection signals in accordance with a flow rate of the intake air flowing through the detection passage32a.

As shown inFIGS.6to8, the flow rate detector22includes a detection board22aas a circuit board and a detection element22bmounted on the detection board22a. The detection board22aforms an outer frame of the flow rate detector22and the detection element22bis disposed at a center of a board surface of the detection board22a. The detection board22ais electrically connected to the connector terminals28a. The detection element22bincludes a temperature detector and a heat generator such as a heating resistor, and the flow rate detector22transmits detection signals in accordance with a change in a temperature along with a generation of heat in the detection element22b.

Some large temperature change is needed in the detection element22bof the temperature detector in accordance with the flow rate of the intake air detector to maintain a detection accuracy of the flow rate detector22properly. In addition, in order to increase the temperature change, it is preferable that a flow velocity of a fluid flowing to the detection element22bbe large to some extent. This is to restrict temperature change in the detection element22bcaused by natural convection from influencing on the temperature change of the detection element22bcaused by the flow velocity of the fluid. The temperature change due to the natural convection is changed depending on an angle at which the detection element22bis installed and causes an error in the detection signals of the temperature change of the fluid. By increasing the flow velocity of the fluid flowing to the detection element22b, the influence of natural convection caused by the angle at which the detection element22band the air flowmeter14are installed can be reduced and detection of the fluid can be performed appropriately.

The air flowmeter14has a sensor sub-assembly configured by including the chip-type flow rate detector22. The sensor sub-assembly is referred to as a sensor SA50.

The sensor SA50includes a circuit housing51, a relay portion52, a sensing portion53, and lead terminals54. The relay portion52is disposed between the circuit housing51and the sensing portion53. The lead terminals54have electric conductivity and extend from the circuit housing51away from the sensing portion53.

As shown inFIGS.6,7, and9, the sensor SA50is located in the housing21such that the sensing portion53is located in the detection passage32a. The sensing portion53is located in a middle part of the detection passage32a. The sensing portion53separates the middle part of the detection passage32ain a width direction of the detection passage32a. The detection passage32aincludes a detection throttle portion59at a position of an inner circumferential surface of the detection passage32athat faces the flow rate detector22. The detection throttle portion59is formed by reducing a passage area of the position.

In the detection passage32a, a distance between a sensing supporter57and the detection throttle portion59gradually decreases toward the flow rate detector22. In this configuration, when the intake air flowing into the detection passage32afrom the introduction passage32bflows through a gap between the sensing supporter57and the detection throttle portion59, a flow velocity of the intake air is likely to increase as approaching to the detection element22bof the flow rate detector22. In this case, the detection element22breceives the intake air at an appropriate flow velocity, thereby improving detection accuracy of the flow rate detector22.

As shown inFIGS.8and10, the sensor SA50includes a molding76forming an outer frame of the sensor SA50. The molding76is made of a resin such as a mold resin. The molding76fixes and protects the flow rate detector22, a circuit chip81, and the like.

As shown inFIGS.2and10, the lead terminals54of the sensor SA50are electrically connected to the connector terminals28athrough a terminal unit85. The lead terminals54and the connector terminals28aare respectively arranged at predetermined intervals.

The terminal unit85includes multiple bridge terminals86and terminal fixing portions87that fix the bridge terminals86. Each of the bridge terminals86has electric conductivity and is an elongated member extending in a U shape as a whole. The bridge terminals86are connected to both the connector terminals28aand the lead terminals54by welding and the like. The terminal fixing portions87are made of material having electric insulating property and connect middle parts of the bridge terminals86.

Signals from the thermosensitive element23ais transmitted to the connector28through an intake air temperature terminal23c, the bridge terminals86, the lead terminals54, the circuit chip81in the molding76, the lead terminals54, the bridge terminals86, and the connector terminals28ain this order.

In the sensor SA50, flow rate signals in accordance with a flow rate of the intake air flowing through the measuring passage32is transmitted to the circuit chip81from the flow rate detector22and treated by the circuit chip81. Thereby, a flow rate of the intake air flowing through the intake passage12is calculated. The flow rate calculated by the circuit chip81is transmitted to an external ECU by transmitting signals through the lead terminals54and the connector terminals28a. As described above, the air flowmeter14detects a flow rate of the intake air flowing through the intake passage12with the flow rate detector22.

A decrease of the detection accuracy of the air flowmeter14will be described. The decrease is caused when foreign matters adhere to the flow rate detector22. In the first embodiment, foreign matters are restricted from reaching the flow rate detector22because of a position of the measuring inlet opening34and a shape of the measuring passage32as described above. However, it is impossible to completely prevent foreign matters from reaching the flow rate detector22. Additionally, when foreign matters are charged, the foreign matters may adhere to the flow rate detector22and cause a deviation in characteristic of the air flowmeter14.

As for the deviation in the characteristic, to restrict foreign matters from being charged, an antistatic agent may be mixed into the resin of the housing. However, in the housing containing the antistatic agent, an amount of resin for the housing is reduced by an additive amount of the antistatic agent. Therefore, the moldability of the housing may decrease. Additionally, an amount of glass fiber is also reduced by the additive amount of the antistatic agents, thus a strength of the housing may decrease. A decrease in strength causes a decrease in durability. That is, the decrease of the moldability and the durability of the housing caused by adding the antistatic agent into the resin has been a subject.

Hereinafter, a configuration to restrict a deviation in characteristic of the air flowmeter14while avoiding decreasing the moldability and durability of the housing21will be described.

As shown inFIG.11, the housing21has a non-insulation portion90containing graphite. Specifically, the non-insulation portion90is formed on the inner surface of the housing21, specifically an inner wall24aof the bypass housing24that defines the bypass passage30. A hatched portion inFIG.11is the inner wall24aon which the non-insulation portion90is formed. The non-insulation portion90contains carbonized materials that are aggregates of graphite to have an electric conductivity. The non-insulation portion90is a conductive portion that discharges electric charges to the ground45. The non-insulation portion90is a portion irradiated with electromagnetic waves (i.e., an irradiated portion with electromagnetic waves).

A surface specific resistance of the non-insulation portion90is equal to or less than 1012Ω/square. When the surface specific resistance are divided into ranges as shown in (1) to (4), the non-insulation portion90in the first embodiment belongs to the range (4). The non-insulation portion90may belong to the range (2) or (3).

(1) Insulation range: equal to or more than 1013Ω/sq.

(4) Semi-conductive to conductive range: equal to or less than 107Ω/sq.

A method for forming the non-insulation portion90will be described together with a manufacturing procedure of the housing21. As shown inFIGS.6and10, the bypass housing24, the ring holder25, the root29a, and the protecting protrusion29bform a housing body91. The flange27and the connector28form an outside main passage housing92that is outside of the main passage.

A method for manufacturing the air flowmeter14includes a preparing step and a heating step. In the preparing step, the housing body91and the flow rate detector22are prepared. First, the housing body91is molded as shown inFIG.13in a state in which the housing body91is divided into two parts at the center position in the width direction when viewed in the flow direction. That is, the housing body91is molded in a state that is divided along a dividing surface shown by a chain double-dashed line inFIG.12. In the heating step, as shown inFIG.14, the housing body91is fixed to a jig48of a laser processing machine46, and the laser processing machine46heats the inner wall24aof the housing body91such that the non-insulation portion90is provided on the inner wall24a. That is, a surface layer of the inner wall24ato define the bypass passage30is irradiated with laser to locally heat-treat the surface layer. At this time, heat of 2000° C. or higher is applied to the surface layer to cause cleavage of bonds of the polymer that is a material of the housing body91. As a result, the constituent elements other than carbon are released as decomposition gas such as carbon dioxide, carbon monoxide, nitrogen and hydrogen. Thus, a portion of the surface layer irradiated with laser is carbonized. Then, the portion is partially converted into a graphite in which six-membered rings of carbon atoms (i.e., benzene rings) are connected each other in a plane. Therefore, the non-insulation portion90as a carbonized portion containing graphite is formed on the surface layer and conductivity is imparted to the non-insulation portion90. The two-divided resin member having the non-insulation portion90formed as described above are integrated with each other by welding or the like as shown inFIG.15. A laser is used as an electromagnetic wave, but the present disclosure is not limited to this. Other methods such as a plasma treatment, a high-pressure steam irradiation, an electron beam irradiation, and a heating using Joule heat may be used. The most suitable method can be selected depending on the processability of the resin member.

After the sensor SA50is mounted on the housing body91as shown inFIG.16, the lead terminals54of the sensor SA50and the terminal unit85are electrically connected through the connector terminals28aas shown inFIG.17. Then, as shown inFIG.10, the outside main passage housing92is secondarily molded to completely form the housing21.

A thermoplastic resin such as PBT (polybutylene terephthalate) or PPS (Polyphenylene Sulfide Resin) may be used as the resin for the housing21. The thermoplastic resin generally has a lower melting point than thermosetting resins and is superior in processability for imparting a graphite structure. However, the resin of the housing21is not limited to the thermoplastic resin and may be a thermosetting resin. In short, the resin may be any resin that has a benzene ring and has an electric conductivity by cutting the covalent bond of the benzene ring and releasing a restraint of free electrons.

As described above, in the first embodiment, the air flowmeter14includes the housing21and the flow rate detector22. The housing21is made of resin and has the bypass passage30branched off from the intake passage12. The flow rate detector22is disposed in the bypass passage30. The housing21has the non-insulation portion90containing graphite.

Since the housing21includes the non-insulation portion90containing graphite as described above, it is possible to remove the charge of foreign matters such as dusts that get in contact with the housing21. As a result, the foreign matters are restricted from adhering to the flow rate detector22. It is not necessary to add an antistatic agent to the resin of the housing21. Therefore, it is possible to restrict a deviation in characteristic of the air flowmeter14while avoiding decreasing the moldability and durability of the housing21.

In the first embodiment, the non-insulation portion90is the irradiated portion with electromagnetic waves. That is, the non-insulation portion90is formed by modifying the surface layer of the resin member with electromagnetic waves to make the surface layer conductive. An antistatic property is imparted to the housing21by converting a part of the molecular structure of the resin member into graphite by irradiating with electromagnetic waves. Since the part of the housing21is modified with the energy of the electromagnetic wave, only a desired portion can be processed and the workability improved.

No matter whether a target area has a plane surface or curved surface, no matter whether the target area is whole of the portions or a part of the portions or multiple areas of the portions, processing into graphite with the electromagnetic wave can be performed. In addition, the processing is completed in a few seconds to a few tens of seconds, thereby improving the processability. When the target is on surface layer, the processing can be performed for the target in any one of a component state, a finished product state (i.e., assembly completed state), and a post-processing state. Thus, the processing does not select steps, which improves the processability. Additionally, in the case that the target is a resin molded product, a moldability of the resin is not affected by the processing because the target can be processed after molding. Since the electric conductivity is secured when a depth of a layer processed with the laser is equal to or greater than 0.1 mm, the processing can be performed within a range of product dimensional tolerance. Therefore, the static elimination effect can be expected without changing physical properties such as product strength.

In the first embodiment, the electromagnetic wave is laser. The laser has a high energy density among electromagnetic waves, so that the resin member can be converted conductive in a short time.

In the first embodiment, the housing21includes the bypass housing24that is disposed in the intake passage12and defines the bypass passage30. The non-insulation portion90is formed on the bypass housing24. A part of the bypass housing24has an electric conductivity, so that other parts are polarized (i.e., an electric charge is transferred to the other parts). As a result, foreign matters are restricted from adhering to the flow rate detector22.

In the first embodiment, the non-insulation portion90is formed on the inner wall of the bypass housing24that defines the bypass passage30. Therefore, the electric charge of foreign matters flowing through the bypass passage30can be effectively removed. The polarization effect, which is obtained when charges in molecules of the resin are unevenly distributed, further restricts foreign matters from adhering to the flow rate detector22.

In the first embodiment, the surface specific resistance of the non-insulation portion90is equal to or less than 1012Ω/square. The non-insulation portion90belongs to any ranges of the antistatic range, the non-charged range, and the semi-conductive to conductive range, thereby removing an electric charge of the foreign matters.

In the first embodiment, the air flowmeter14includes the housing21, the physical quantity detector22, and the non-insulation portion90. The housing21defines the measuring passage32through which the fluid flows and contains at least resin. The physical quantity detector22transmits detection signals in accordance with physical quantity of the fluid flowing through the measuring passage32. The non-insulation portion90is formed on the inner wall24aof the housing21, contains carbonized materials to have an electric conductivity, and discharges electric charges to the ground45.

The method for manufacturing the air flowmeter14includes the preparing step and the heating step. The preparing step includes preparing the housing21and the physical quantity detector22. The housing21defines the measuring passage32through which the fluid flows and contains at least resin. The physical quantity detector22transmits detection signals in accordance with the physical quantity of the fluid flowing through the measuring passage32. The heating step includes heating the inner wall24aof the housing21to form the non-insulation portion90that contains carbonized material to have electric conductivity and that discharges the electric charge to the ground45.

The non-insulation portion90can remove the electric charge of foreign matters such as dusts in contact with the housing21. Thus, the deviation in characteristic of the air flowmeter14is suppressed. In addition, it is unnecessary to add an antistatic agent to the material of the housing21, which reduces the amount ratio of the material in the housing21. Therefore, the processability of the housing is restricted from decreasing due to a low ratio of the material. In addition, the amount ratio of the grass fiber is not decreased, which is also caused by adding the antistatic agent to the material, so that the strength of the housing21is restricted from decreasing due to a low ratio of the glass fiber.

A difference of the resin moldability and durability between a comparative example in which the antistatic agent is added to the resin of the housing and the first embodiment in which the non-insulation portion90containing graphite is provided after molding the housing21will be described.

In the comparative example shown inFIG.34, electric conductivity is secured by an antistatic agent62such as metal and carbon, which also improves a thermal conductivity. As a result, the resin is cooled faster in molding and a fluidity of the resin is decreased. Thus, resin moldability of a housing61is likely to decrease. For example, if a temperature of the resin in molding is not set to be a maximum temperature for a resin degradation, a part of the housing61may be missed. In addition, a resin69may not be sufficiently crystallized due to a rapid cooling, which causes unstable size, strength, and a durability of the product. Further, since the antistatic agent62is added, it is needed to reduce an additive amount of glass fibers63and glass particles64to the resin69to secure the fluidity of the resin69. As a result, a strength and a dimensional stability of the housing61are also decreased. InFIG.34, hatching of the housing61is partially omitted for descriptive purposes.

In contrast, in the first embodiment inFIG.18, it is unnecessary to add the antistatic agents to the material of the housing21, thereby slowing a cooling rate in molding and keeping the fluidity of the material compared to that in the comparative example. Thus, a resin moldability of the housing21is restricted from decreasing. Graphitization by laser processing does not affect the resin moldability of the housing21because it is a process after molding the resin. Since the antistatic agent is not added and the fluidity is not decreased, it is not necessary to reduce an additive amount of the glass fibers73and the glass particles74. As a result, a strength and a dimensional stability of the housing21are restricted from decreasing. InFIG.18, hatching of the housing21is partially omitted for descriptive purposes.

Second Embodiment

In the second embodiment, as shown inFIGS.19and20, the non-insulation portion90is formed on an outer surface of the housing21, specifically, on an outer wall24bof the bypass housing24. A hatched portion inFIGS.19and20is a part of the outer wall24bon which the non-insulation portion90is formed.

In the preparing step of the method for manufacturing the air flowmeter14, the assembled air flowmeter14as shown inFIG.21is prepared. The air flowmeter14prepared here may be unused or used one. In the heating step, as shown inFIG.22, the air flowmeter14is fixed to the jig48, and the outer wall24bof the bypass housing24is heated using the laser processing machine46so that the non-insulation portion90is formed on the outer wall24b.

As described above, the non-insulation portion90may be formed on the outer wall24bof the bypass housing24. Also in this case, the foreign matters are restricted from adhering to the flow rate detector22due to the polarization effect. The non-insulation portion90can be formed even after assembling components into the air flowmeter14.

Third Embodiment

In the third embodiment, as shown inFIG.23, the non-insulation portion90is formed on the outer surface of the housing21, specifically, on an outer wall92aof the outside main passage housing92. The hatched portion inFIG.23is a portion of the outer wall92aon which the non-insulation portion90is formed. The non-insulation portion90may be formed on the outer wall92aof the outside main passage housing92as such. Also in this case, the foreign matters are restricted from adhering to the flow rate detector22due to the polarization effect. The non-insulation portion90can be formed even after assembling components into the air flowmeter14. Even if change in size occurs at a portion of the outside main passage housing92due to the processing for conductivity (i.e., heating with laser irradiation), the portion that is dimensionally changed is located outside of the bypass passage30(seeFIG.6). Therefore, flow rate measurement is not affected. In addition, the foreign matters are restricted from adhering to the connector28, thereby restricting a short circuit.

Fourth Embodiment

In a fourth embodiment, as shown inFIG.24, the non-insulation portion90is formed on the molding76as a sensor holder holding the flow rate detector22. The hatched portion inFIG.24is a portion of an outer wall on which the non-insulation portion90is formed. As described above, the non-insulation portion90may be formed on the molding76. Also in this case, the foreign matters are restricted from adhering to the flow rate detector22due to the polarization effect. Since especially a region near the flow rate detector22is made electrically conductive, polarization effect of the flow rate detector22is further increased and the foreign matters are further restricted from adhering to the flow rate detector22.

Fifth Embodiment

In a fifth embodiment, as shown inFIGS.25and26, the non-insulation portion90is formed on the outer surface of the housing21, specifically, on the root29a. The hatched portion inFIGS.25and26is a part of the outer wall29chaving the non-insulation portion90. The non-insulation portion90may be formed on the outer wall29cof the root29aas described above. Also in this case, the foreign matters are restricted from adhering to the flow rate detector22due to the polarization effect.

The non-insulation portion90includes a carbonized portion, which is generated through laser irradiation, at a contact boundary between the root29aand the intake air temperature terminal23chaving the GND potential. As a result, the non-insulation portion90is connected to the contact interface at a constant potential, i.e., the GND potential. Thus, by forming a path for electric charge, the electric charge of foreign matters can be removed effectively. In addition, the electric potential can be easily taken from the terminal of the intake air temperature sensor23. The non-insulation portion90may be connected to a constant potential such as a power supply potential other than GND potential. Also in this case, the same advantages can be obtained.

Sixth Embodiment

In a sixth embodiment, as shown inFIG.27, the outer wall of the housing body91has a contact portion93that is contact with the connector terminals28ahaving the GND potential. The non-insulation portion90is formed on the contact portion93. The non-insulation portion90is formed by being irradiated with laser before the connector terminals28aare attached as shown inFIG.28. As a result, the non-insulation portion90is connected to a constant potential, i.e., the GND potential. Thus, by forming a path for the electric charge, the electric charge of foreign matters can be effectively removed. The electric potential can be easily taken from the connector terminals28a.

Seventh Embodiment

In a seventh embodiment, as shown inFIG.29, the non-insulation portion90is formed on the outer surface of the housing21, specifically, on the outer wall24bof the bypass housing24. The hatched portion inFIG.10is a portion of the outer wall24bon which the non-insulation portion90is formed. The non-insulation portion90extends toward one terminal, which is connected to the ground45, of the pair of intake air temperature terminal23cprotruding from the outer surface of the housing21. The one terminal is referred to as a ground connecting portion71.

Specifically, as shown inFIGS.6and29, the non-insulation portion90is formed on a part of the outer wall24bof the bypass housing24that is outside of the measuring passage32. That is, the non-insulation portion90is located at a portion of the outer wall24bcorresponding to an inner wall defining the measuring passage32. The non-insulation portion90is located at a portion of the outer wall24bof the bypass housing24that corresponds to the flow passage31, the introduction passage32b, and the inlet opening of the detection passage32a. The non-insulation portion90extends from a position of the outer wall24bcorresponding to the flow passage31to a position of the outer wall24bnear the ground connecting portion71.

The ground connecting portion71is located on one side portion of the outer wall24bof the bypass housing24. The non-insulation portion90is located only on the one side portion of the bypass housing24. Hereinafter, forming the non-insulation portion90will be referred to as graphitization.

As shown inFIGS.30and31, the optimum configuration for graphitization is a configuration in which at least glass fibers73are added to a polymer72of PBT resin, the polymer72is carbonized by being treated at high temperature (e.g., irradiated with a laser) to generate graphite75, and the graphite75is mechanically fixed by the glass fibers73and glass particles74. The glass fibers73and the glass particles74are not burned and remain as they are even after being treated at high temperature. The electric conductivity of the non-insulation portion90can be improved by setting a thickness d of the graphitization layer to a value equal to or higher than 0.1 mm relative to a plate thickness t, of 0.5 to 2.0 mm, of a passage forming portion of the bypass housing24.

As shown inFIG.29, in case that charged dusts causing electrification flows in the airflow direction, it is safe and effective to remove the charge of the dusts at the flow passage31that is an inlet portion located in a position farthest from the flow rate detector22. Therefore, it is the most appropriate to graphitize the portion of the outer wall24bof the bypass housing24that corresponds to the flow passage31. When the outer surface corresponding to the flow passage31and the outer surface located near the ground connecting portion71are connected to the non-insulation portion90, static electricity can be released to the ground45. Even if the non-insulation portion90and the ground connecting portion71are not connected to each other, the same effect can be obtained if a distance therebetween is kept in a distance that allows the electricity to be released with an insulating breakdown (e.g., 0.5 to 2.0 mm).

A difference of an antistatic mechanism between a comparative example in which antistatic agent is added to a resin member of the housing and a seventh embodiment in which the non-insulation portion90containing graphite is located on the outer surface of the housing21will be described.

At first, the comparative example will be described. In the comparative example, as shown inFIG.35, multiple negative charges77are gathered at a conductive portion62X that is closer to an outer surface61aof the housing61. Thus, multiple positive foreign matters Fp are adhered to the outer surface61aof the housing61by being electrically attracted to the negative charges77. In this case, the larger the number of the negative charges77gathered at the conductive portion62X is, the higher the potential of the conductive portion62X in the negative direction is. That is, the housing61is negatively charged with static electricity and the conductive portion62X is included in a skin layer of the housing61. When a voltage due to this potential becomes high to some extent in the housing61, a discharge Ed occurs between the conductive portion62X and a conductive portion62Y near the conductive portion62X.

When the discharge Ed occurs between the conductive portion62X and the conductive portion62Y, an insulating breakdown occurs at a position of an insulation portion66between the conductive portion62X and the conductive portion62Y. The negative charges77of the conductive portion62X are transferred to the conductive portion62Y. Such discharges and insulating breakdowns occur at multiple portions in a path between the conductive portion62X and a ground terminal67. As a result, the negative charges77remained in the conductive portion62X can be discharged to the ground45through the multiple conductive portions62X and the ground terminal67. As described above, when the negative charges77that electrically attract the multiple positive foreign matters Fp are discharged from the conductive portion62X, the positive foreign matters Fp are likely to depart from the outer surface61aof the housing61. Thus, the housing61is restricted from being negatively charged and from generating negative charges77again due to the positive foreign matters Fp in contact with the outer surface61a.

Next, the seventh embodiment will be described. In the seventh embodiment, as shown inFIG.32, a base material resin is polarized by multiple positive foreign matters Fp, and the negative charges77are gathered on the inner wall24aof the bypass housing24. The large amount of the positive foreign matters Fp are electrically attracted to the inner wall24a. In this case, the larger the number of the negative charges77are located on the inner wall24a, the more negatively the inner wall24ais charged. When a potential of the inner wall24abecomes high to some extent, a discharge Ed due to an insulating breakdown occurs between the inner wall24aand the graphite in the outer wall24bthat is a conductive layer (i.e., the non-insulation portion90). This phenomenon is likely to occur at the graphite layer that is generated in a resin product having a plate thickness of 0.5 to 2.0 mm and that has a state static electricity of negative charge equal to or less than −1 kV, which attracts dusts having positive charges.

When the discharge Ed occurs, due to an insulating breakdown, between the inner wall24aand the non-insulation portion90of the outer wall24bthat is a conductive layer, the negative charges77of the inner wall24atransfer to the non-insulation portion90of the outer wall24b. Such discharges and insulating breakdowns occur at multiple portions, thus the negative charges77remained in the inner wall24acan be released to the ground45through the non-insulation portion90and the connector terminals28a(i.e., the ground terminal). As described above, when the negative charges77that electrically attract the multiple foreign matters Fp are released from the inner wall24a, the multiple foreign matters Fp are likely to depart from a surface of the inner wall24a. Thus, the inner wall24ais restricted from being negatively charged and from generating negative charges77again due to the positive foreign matters Fp in contact with the inner wall24a. The non-insulation portion90of the outer wall24bis graphite of the conductive layer, thus the foreign matters Fp are less likely to be electrically attracted to the outer wall24b.

As described above, in the seventh embodiment, the outer wall24bof the housing21includes the non-insulation portion90that contains the carbonized material to have conductivity and that discharges the electric charge to the ground45. In the heating step, the outer wall24bof the housing21is heated such that the non-insulation portion90is formed on the outer wall24bof the housing21and the electric charge can be released from the non-insulation portion90to the ground45. Therefore, similarly to the first embodiment, it is possible to suppress the characteristic deviation and the deterioration of the moldability of the housing21.

In the seventh embodiment, the non-insulation portion90is formed on the outer wall24bof the bypass housing24that is outside of the measuring passage32. Thus, the foreign matters flowing through the measuring passage32is likely to be discharged. In addition, it is unnecessary to form the non-insulation portion90on the inner wall of the housing21, thus the non-insulation portion90can be formed after components of the air flowmeter14are assembled into the air flowmeter14.

In the seventh embodiment, the non-insulation portion90extends toward the ground connecting portion71that is connected to the ground45, so that electric charges can be released to the ground45through the ground connecting portion71. In the heating step, the outer surface of the housing21is heated such that the non-insulation portion90extends toward the ground connecting portion71that is connected to the ground45to release electric charges from the non-insulation portion90to the ground45through the ground connecting portion71. The ground connecting portion71is used to release the electric charges, thus a ground line exclusive for the non-insulation portion90is not needed.

In the seventh embodiment, the pair of intake air temperature terminal23cprotruding from the outer surface of the housing21is disposed. One of the intake air temperature terminals23cis the ground connecting portion71. In the preparing step, the pair of intake air temperature terminal23cprotruding from the outer surface of the housing21are prepared. In the heating, the outer surface of the housing21is heated such that the non-insulation portion90extends toward the ground connecting portion71that is the one of the intake air temperature terminals23c. The intake air temperature terminal23cis used to discharge the electric charge.

In the seventh embodiment, the ground connecting portion71is located on one side portion of the outer wall24bof the bypass housing24. The non-insulation portion90is located on the one side portion of the bypass housing24. As a result, it is not necessary to turn over the bypass housing24when forming the non-insulation portion90, so that the number of steps for forming the non-insulation portion90can be reduced.

The non-insulation portion90as described in the first to seventh embodiments includes a carbonized portion115which will be described in eighth to seventeenth embodiments. A resin member110in the eighth to seventeenth embodiment corresponds to the housing21in the first to seventh embodiments.

Eighth Embodiment

A resin member in the eighth embodiment is described inFIGS.36and37. The resin member110is made of resin that has a base polymer having insulation property as a main component and fillers. As shown inFIG.38, an oriented layer112is located near a surface111of the resin member110. The oriented layer112includes many fillers113that are oriented in a direction parallel to the surface111(hereinafter, referred to as a surface direction) and a base polymer114filled among the fillers113.

As shown inFIG.39, the oriented layer112includes the carbonized portion115containing graphite that is a carbonized material of the base polymer114to have electric conductivity and thermal conductivity. The graphite has carbon atoms that are bonded with each other as shown inFIG.43. In the graphite, one electron of the four outer shell electrons of each of the carbon atoms is free to transfer. Thus, the carbonized portion115is electrically conductive.

A thickness of a portion of the resin member110in which the carbonized portion115is formed is equal to or larger than 300 μm. As shown inFIG.36, in the eighth embodiment, the resin member110includes multiple carbonized portions115extending straight, which forms a conductive pattern. The conductive pattern is used as a static electricity removing circuit in an electronic device such as an air flowmeter and a rotation angle sensor. When the carbonized portion115is used as the static electricity removing circuit, a volume resistivity of the generated carbonized material is at least equal to or less than 1.0×10−3Ωm, preferably equal to or less than 1.0×10−4Ωm, more preferably equal to or less than 1.0×10−5Ωm. The carbonized portion115may configure other pattern such as a lattice. A shape of the carbonized portion115is not limited to a pattern and may be a film. The carbonized portion115may be used as a wiring circuit, an electromagnetic shield, an antistatic portion, or a heat-dissipating member other than the static electricity removing circuit.

Next, a method for manufacturing the resin member110will be described. The method for manufacturing the resin member110includes a molding step P1and a carbonization step P2as shown inFIG.40.

In the molding step P1, as shown inFIG.41, a resin material including the fillers113and the base polymer114having insulation property are melted at a predetermined plasticizing temperature. Then, the melting resin116is injected at high speed into a mold190having a predetermined shape. The melting resin116is cooled and solidified while being applied pressure. In this process, a shear stress is applied to a boundary between a surface of the mold190and a surface of the melting resin116or between a resin material stuck on the surface of the mold190by being deprived of heat by the mold190when injected and the melting resin116that still has fluidity around a center of the thickness. As a result, the fillers113are preferentially oriented in the surface direction rather than a surface normal direction and the base polymer114extends straight between the fillers113to form the oriented layer112in a vicinity of a surface of a molding117.

The fillers113relax a heating rate at which the carbonized portion115(seeFIG.39) is formed and restricts, with an anchor effect, the carbonized material from scattering even if the resin material is carbonized at a high temperature. Thus, detail conductive patterns can be accurately formed even under a temperature condition at which the carbonized material would severely scatter and it would be difficult to form detail conductive patterns if a natural resin member without fillers were used.

Not to restrict conduction between the carbonized materials on the conductive pattern, it is preferable that the fillers113are oriented in the surface direction.

Comparing a condition in which the resin member contains about 40 wt % of glass fibers as the fillers113to a condition in which the resin member does not contain the fillers113, conductivity of the conductive pattern generated by laser irradiation is significantly better in the former condition. Comparing a condition in which the resin member contains about 40 wt % of the glass fibers as the fillers113to a condition in which the resin member contains about 15 wt % of the glass fibers, conductivity of the conductive pattern generated by laser irradiation is better in the former condition. Comparing a condition in which a portion in which the fillers113are oriented is carbonized by laser irradiation to a condition in which a portion in which the fillers113are not oriented is carbonized by laser irradiation, the conductivity of the conductive pattern is significantly better in the former condition.

A method for producing the molding117may be an injection molding, transfer molding, an extrusion molding, and a compression molding. The injection molding is preferable because applied shear stress is large and the oriented layer112in which the fillers113are more oriented can be obtained.

As shown inFIGS.41and42, in the oriented layer112, the fillers113and molecular chains118are oriented in the surface direction and the base polymer114extends straight and fills around the fillers113. As a result, the carbonized material generated when being carbonized is oriented in the surface direction and likely to be an extending layer, thereby improving the electric conductivity and thermal conductivity in the surface direction. Shear stress is also applied to the base polymer114in the surface direction, thus the molecular chains118are oriented. As a result, an a-b surface (seeFIG.43) of the graphite forming the carbonized material is likely to be oriented in the surface direction. Therefore, the electrical conductivity and thermal conductivity in the surface direction are improved. The effects described above are particularly effective when selecting, as the base polymer114, a thermoplastic resin that is mainly composed of a chain polymer.

In a method for producing the molding117, it is preferable that shear stress be applied to a surface of a portion to be carbonized in molding and the fillers113and the molecular chains118be oriented. It is preferable to avoid forming a weld line or a final filling portion at the portion to be carbonized and to avoid a position, a shape, and a condition of a gate that may cause jetting. A mold surface may perform a motion that increases shear stress such as sliding and rotating to improve an orientation degree of the fillers113and the molecular chains in the molding step. The method for producing the molding117is not limited to an injection molding while the oriented layer112is formed in a vicinity of the surface of the molding117.

It is preferable that the base polymer114be a material having a high carbon content and a carbon cyclic structure similar to the a-b surface of the graphite at a point that the base polymer114is carbonized in the following carbonization step P2to form a graphite like structure. For example, the base polymer114may be a condensation aromatic polymer composed at least of one polymer selected from polyacrylonitrile, polyacryl/styrene, polyarylate, polyimide, polyamide-imide, polyimide, polyether ether ketone, polyether ketone, polyetherimide, polyether nitrile, polyethersulfone, polyoxybenzylmethyleneglycolanhydride, polyoxybenzoyl polyester, polysulfone, polycarbonate, polystyrene, polyphenylenesulfide, poly(p-xylene), polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyphenylene ether, liquid crystal polymer, bisphenol A copolymer, bisphenol F copolymer. The aromatic polymer is preferable at a point that the aromatic polymer contains, in a main chain, six membered ring of carbon (i.e., benzene ring) that is a basic structure of the graphite. However, it is not particularly limited to this. It is more preferable that the base polymer114has a self-extinguish property to prevent excessive combustion when being carbonized and to be locally carbonized.

It is preferable that the fillers113be superior in both strength and heat resistance and have a shape having a high aspect ratio to slow the heating rate and to restrict the carbonized material from scattering. The heating rate can be slowed down by decreasing a temperature of a spot processed with laser beam to reduce decomposition gas that is generated by rapidly increasing a temperature through a heat treatment in the following carbonization step P2. The carbonized material is restricted from scattering due to the decomposition gas by the fillers113serving as an anchor. That is, it is preferable that the fillers113have fiber shapes that are less likely to be combusted than the base polymer114, for example, inorganic fibrous substance. Specifically, the fillers113are preferably glass fibers due to the low cost in addition to the above. When the glass fibers are used, the glass is melt and solidified through the heat treatment. Thus, it is expected that a fixability of the carbonized material be improved. The fillers113may contain a flame-retardant material to impart self-extinguishing property for preventing excessive combustion in the carbonization and for locally performing the carbonization.

The additive amount of the glass fibers is preferably an amount in which the electrical conductivity and thermal conductivity are maximized. If the additive amount of the glass fibers is too small, the glass fiber cannot sufficiently fix the carbonized material with the anchoring effect. As a result, the carbonized material is more likely to be scattered by the decomposition gas that is rapidly generated through heating and carbonization. This may decrease electric conductivity and thermal conductivity. If the additive amount of the glass fibers is too large, an amount of the polymer is relatively decreased and a density of the carbonized material is decreased, which decreases electric conductivity and heat conductivity. Based on this, if the base polymer114is a polymer naturally having density of around 1.3 to 1.4 g/cm2such as polyphenylenesulfide, polybutylene terephthalate, polyether ether ketone, polyoxybenzylmethyleneglycolanhydrite, and the like, as a weight ratio of the glass fibers to the entire member, a weight ratio of the fillers113to the resin member110as a whole falls within 30 wt % to 66 wt %, preferably 30 wt % to 40 wt %, more preferably 40 wt %.

A material configuring the fillers113may be aramid fiber, asbestos fiber, gypsum fiber, carbon fiber, silica fiber, silica-alumina fiber, alumina fiber, zirconia fiber, silicon nitride fiber, silicon fiber, potassium titanate fiber, and inorganic fibrous substances such as metallic fibrous substances of stainless steel, aluminum, titanium, copper, and brass, other than the glass fiber.

Examples of a granular filler include silica, quartz powder, glass beads, milled glass fiber, glass balloon, glass powder, calcium silicate, aluminum silicate, kaolin, talc, clay, diatomaceous earth, silicates such as wollastonite, and metal oxide such as iron oxide, titanium oxide, zinc oxide, antimony trioxide, and alumina, metal carbonates such as calcium carbonate and magnesium carbonate, metal sulfates such as calcium sulfate and barium sulfate, other ferrites, silicon carbide, silicon nitride, boron nitride, various metal powders and the like. Examples of a plate-shaped filler include mica, glass flakes, various metal foils and the like. However, the fillers113are not limited to this while the fillers113can fix the carbonized material and form the oriented layer.

By adding the fillers113superior in electric conductivity or thermal conductivity, the electric conductivity and the thermal conductivity of the molding117can be increased by carbonizing the base polymer114even if the molding117before the carbonization already has the electric conductivity or thermal conductivity.

As shown inFIG.44, in the carbonization step P2, the oriented layer112located in a vicinity of the surface of the molding117is heated at at least 1000° C. by, for example, irradiating the vicinity of the surface with laser beam to cleavage bonds of the material polymer. As a result, constituent elements other than carbon are released as decomposition gas such as carbon dioxide, carbon oxide, nitrogen, and hydrogen. More preferably, the molding117is heated at equal to or more than 2000° C. to convert a part of the molding117to the graphite that six membered rings of carbon are connected and extend in a plane surface. As a result, the carbonized portion115including the graphite is locally generated in a surface of the oriented layer112. The carbonized portion115gives electric conductivity or thermal conductivity. It is preferable that carbonization treatment is performed in inert gas to restrict carbon components from decreasing. Examples of the inert gas include argon, helium, and the like.

As the temperature applied through the heat treatment increases, the resin material can be converted to high quality graphite that is superior in electric conductivity or thermal conductivity. Thus, the temperature applied through the heat treatment is preferably equal to or higher than 2000° C. so as to obtain carbonized material having good electric conductivity and thermal conductivity. Examples of the local heat treatment include laser beam irradiation, plasma treatment, high-pressure steam treatment, electron beam irradiation, and a heating using Joule heat. The heat treatment is preferably performed with the laser beam irradiation because the high temperature more than 2000° C. can be locally applied in a short time, which is economical.

A graphite film is generally produced by gradually heating in a furnace over a long time as disclosed in JP 2008-24571 A. Compared to this, the heating rate is higher when the laser beam irradiation is used. When the resin is irradiated with the laser beam to rapidly increase the temperature of the resin, carbonized material having electric conductivity and decomposition gas are generated. An impact generated when the decomposition gas is emitted is strong. Thus, the carbonized material may depart from the base material together with the decomposition gas. That is, the carbonized material scatters significantly when the decomposition gas is rapidly emitted. This causes the electric conductivity and thermal conductivity of the carbonized portion115to decrease. In particular, when a member having a thickness of at least 300 μm that is different from a thin member such as a film is carbonized, it is difficult to release the decomposition gas generated inside the member and the carbonized material is likely to scatter while destroying structures in a process in which the decomposition gas is released. This is a big cause to decrease the electric conductivity and the thermal conductivity.

In this embodiment, to restrict such phenomena, the fillers113are added to the resin material to some extent to slow the heating rate and anchor the carbonized material in the carbonization step. The main cause that the temperature increases with the laser irradiation is heat generated by absorbing laser light and a combustion heat generated when the base polymer114is carbonized. The latter influences more on the temperature increase. When the fillers113are added to the resin material to some extent, the amount of the base polymer114in the resin material is relatively decreased, thereby reducing the combustion heat and slowing the heating rate. The fillers113fixed to the base polymer114enter into or pass through the carbonized material to serve as like a wedge, which generates an anchor effect that the carbonized material and the base polymer114are restricted from being separated. The fillers113are fixed to a portion of the resin that is adjacent to the carbonized portion115and not to be carbonized or a portion of the resin that is located on a downstream side in the laser scanning direction and has not irradiated with laser yet. Thereby, the carbonized material anchored by the fillers113is restricted from falling off. This prevents the carbonized material from scattering and falling off, and improves the fixability.

In addition, by forming a layer in which the fillers113are oriented in the surface direction before the carbonization, a structure in which polymer filling among the fillers113is carbonized is also has a layer shape extending in the surface direction. This improves the electric conductivity and the thermal conductivity. In this embodiment, in the molding step P1, the polymer configuring the base polymer114is applied with shear stress when the polymer is melting and the polymer is oriented in the surface direction. Thus, it is likely to reduce an angle between the surface direction and the a-b surface of the graphite forming the carbonized material. This improves the electric conductivity and the thermal conductivity in the surface direction.

As for a method for irradiating with the laser beam, the oriented layer112before carbonization may be scanned once with a laser beam having a high energy density (i.e., laser intensity) to form a pattern as fine as possible in a short time. In contrast, to restrict the decomposition gas from rapidly generating and the carbonized material from scattering, a scanning may be performed in a two step such that the oriented layer112is irradiated with a laser beam having a relatively low energy density under a depressurized environment to form a structure containing carbon as a main component at a relatively gentle heating rate and then irradiated with a laser beam having a high energy density to increase the temperature and promote carbonization. The irradiation may be performed appropriately in multiple steps. After a conductive pattern is formed with a laser beam or during the formation of the conductive pattern, heating with Joule heat may be performed by applying voltage to promote the carbonization.

As for an orbit of the laser beam, a linear pattern is depicted by simply scanning with the laser beam. In this time, a part of the polymer evaporates and is removed in a vicinity of a focus of the laser beam to form recesses. As for other scanning method, an elaborate carbonized film can be formed in a wide area by scanning an arbitrary surface without gaps with the laser beam. Also in this case, the laser beam evaporates and removes a part of the polymer to form recesses along the orbit of the laser. Thus, a surface of the polymer becomes uneven. During the laser beam irradiation, the laser beam may move relative to the molding117, the molding117may move while fixing the laser, or the both may move.

Examples of the laser beam include CO2laser, YAG laser, YVO4laser or semiconductor laser (e.g., GaAs, GaAlAs, and GaInAs) that can locally apply a high temperature. When forming a fine pattern, a laser having a short wavelength such as YAG laser is preferable. When carbonizing in a wide area or deep area, a laser beam having a long wavelength such as CO2laser is preferable.

As for a condition of the laser beam, the laser beam having too high density is not preferable because a temperature at a spot becomes too high, a heating rate becomes too high, and the carbonized material scatters by rapidly generated decomposition gas. In contrast, the laser beam having too low energy density is not preferable because the temperature is not increased to be a temperature required for generating the graphite. However, the laser irradiation is not adjusted to prevent the fillers113from burning. Since the temperature of the laser spot becomes extremely high, the fillers113at the laser spot is melt or cut. However, the temperature of a part slightly offset from the laser spot (e.g., a bottom or a side surface of the recess) is relatively low, thus the fillers113are remained in the part. When irradiating with the general semiconductor laser from a focal length near the just focus, it is preferable that an output is 100 W and a scanning speed is around 50 mm/s. It is not preferably that the atmospheric pressure during the laser processing be too low because the density of the carbonized material becomes low. It is not preferably that the atmospheric pressure during the laser processing be too high because the decomposition gas is less likely to leave and the structure of the carbonized material is destroyed. Thus, the atmospheric pressure is preferably equal to or less than 3 MPa.

The stronger the laser strength is or the higher the atmospheric pressure during the laser processing is, the lower the volume resistivity of the carbonized portion115is. This is because a bonding structure of the base polymer114is prompted to be converted into a bonding structure of the graphite-based carbon by increasing the temperature of the processed portion.

Volume resistivity is an index of conductivity per unit volume. Therefore, in the carbonized portion115composed of the carbonized material and the fillers113, the larger the ratio of the carbonized material having conductivity contained per unit volume of the carbonized portion115, the lower the volume resistivity is. When the amount of the fillers113is too small, the carbonized material is scattered by the decomposition gas in the carbonization step P2. Therefore, the volume resistivity of the carbonized portion115can be lowered by decreasing the fillers113within a range that the fillers113can anchor the carbonized material with the anchor effect and by increasing the ratio of the formed carbonized material.

As described above, in the eighth embodiment, the fillers113oriented in the surface direction and the oriented layer112including the base polymer114filling among the fillers113are formed in the vicinity of the surface111of the resin member110. The oriented layer112includes the carbonized portion115containing graphite that is a carbonized material of the base polymer114to have both electrical conductivity and thermal conductivity.

Since the fillers113are oriented in the oriented layer112, the carbonized material generated when carbonizing the base polymer114filling among the fillers113is likely to form a layered structure oriented in the surface direction. The a-b surface of the graphite in the carbonized material is likely to be oriented in the surface direction. Thus, electric conductivity of the carbonized material in the surface direction is improved.

Since the oriented layer112includes the fillers113, the temperature of the heating spot is restricted from being too high and the heating rate is slowed down when the oriented layer112is locally heated for the carbonization. This restricts the decomposition gas from rapidly generating and the carbonized material from scattering. The fillers113serve as an anchor of the carbonized material or the base polymers114and restricts the carbonized material from scattering due to the generation of the decomposition gas. Thus, the fixability of the carbonized material and the conductivity are improved.

In the eighth embodiment, the thickness of a portion of the resin member110at which the carbonized portion115is formed is equal to or greater than 300 μm. Even if such relatively thick member is carbonized, the carbonized material is restricted from scattering by adding the fillers113to the resin member to some extent, slowing the heating rate, and anchoring the carbonized material during the carbonization.

In the eighth embodiment, the weight ratio of the fillers113to the resin member110is 40 wt %. According to this, the heating rate during the carbonization is slowed down and the carbonized material is effectively anchored to improve the conductivity of the carbonized portion115.

In the eighth embodiment, the fillers113are glass fibers. Therefore, the heating rate during the carbonization is slowed down and the carbonized material is effectively anchored to improve the conductivity of the carbonized portion115. In addition, it costs low. The carbonized material is fixed more tightly because the glass is melt and solidified through the heat treatment.

In the eighth embodiment, the method for manufacturing the resin member110includes the molding step P1and the carbonization step P2. The molding step P1includes melting the resin material, applying share stress to the molten resin material in a vicinity of the surface111of the resin member110, and solidifying the resin material to form, in the vicinity of the surface111, the oriented layer112that includes the fillers113oriented in the surface direction and the base polymer114filling among the fillers113. The carbonization step P2includes locally heating the oriented layer112, carbonizing the base polymer114in the oriented layer112to form the carbonized portion115containing the graphite to have both electric conductivity and thermal conductivity.

Since the fillers113are oriented in the surface direction in the oriented layer112in the molding step P1, the carbonized material generated in the base polymer114filling among the fillers113is likely to form a layered structure oriented in the surface direction. Additionally, the a-b surface of the graphite in the carbonized material is likely to be oriented in the surface direction. Thus, electric conductivity of the carbonized material in the surface direction is improved.

Since the oriented layer112includes the fillers113, the temperature of a heating portion is restricted from being too high and the heating rate is slowed down when the oriented layer112is locally heated for the carbonization in the carbonization step P2. Thus, the decomposition gas is restricted from rapidly generating and the carbonized material is restricted from scattering. The fillers113also serve as an anchor of the carbonized material or the base polymer114, thereby restricting the carbonized material from scattering due to the decomposition gas. Therefore, the fixability of the carbonized material and the conductivity is improved.

In the eighth embodiment, the oriented layer112is locally heated with the laser beam in the carbonization step P2. Thus, the high temperature more than 2000° C. can be locally applied to the oriented layer112in a short time. Thus, the conductive pattern can be formed in a short time at a low cost. When the laser beam is used and when a layout of the conductive pattern is changed, it is necessary to modify a software of the scanning program and it is not necessary to change a hardware. Therefore, the layout of the conductive pattern can be changed in a short time at low cost. For example, when using a press part, there is a disadvantage that it takes man-hours to attach and detach the mold.

In the eighth embodiment, the resin material is molded by injection molding in the molding step P1. Thereby, a relatively large shear stress can be applied to the melting resin near the surface111of the resin member110. Thus, the oriented layer112in which the fillers113are more strongly oriented can be formed.

Ninth Embodiment

In the ninth embodiment, as shown inFIGS.45and46, the resin member110is not a simple flat plate. The resin member110includes a first surface131, a second surface132, and a third surface133that cross with each other to form a step portion. The carbonized portion115is dimensionally formed from the first surface131to the second surface132and from the second surface132to the third surface133. A shape of a molding before the carbonization is preferably a shape such that share stress is applied on a surface in molding and molten resin can flow to orient the fillers and the molecular chains. Thus, a corner134between the first surface131and the second surface132and a corner135between the second surface132and the third surface133have relatively large R shape (i.e., round shape). A curvature radius of each of the corner134and the corner135is preferably as large as possible, and specifically, at least equal to or larger than 5 mm.

As shown inFIG.47, a surface layer of the resin member110(i.e., the oriented layer112) includes recesses141. The carbonized portions115are formed by carbonizing bottom wall portions142of the recesses141. Between the adjacent ones of the carbonized portions115, ribs143are formed to improve creepage insulation property. By carbonizing inner wall portions of the recesses141, the ribs143are disposed between the adjacent ones of the carbonized portions115and the creepage insulation property can be improved.

In the molding step P1of the manufacturing method in the ninth embodiment, the recesses141are formed in the oriented layer112of the molding117as shown inFIG.48. In the carbonization step P2, bottom wall portions142of the recesses141are carbonized by being irradiated with the laser beam. A width W1of each of the recesses141is larger than a converging diameter of the laser beam in the recesses141. As a result, the bottom wall portions142of the recesses141can be locally carbonized.

Tenth Embodiment

In a tenth embodiment, as shown inFIG.49, a bottom surface of each of the recesses141of the molding117has an R shape. This can improve an orientation degree of the fillers and the molecular chains in the bottom wall portions142of the recesses141.

Eleventh Embodiment

In an eleventh embodiment, as shown inFIG.50, the carbonized portion115is formed by carbonizing the bottom wall portions142and side wall portions144of the recesses145of the molding117. A width W2of each of the recesses145is at least less than a focusing diameter of the laser beam on the surface of the molding117(i.e., an opening of the recess145). When the carbonized portion115forms the wiring-shaped conductive pattern, it is preferable that a cross-sectional area of the carbonized portion115be increased in a thickness direction of the resin member110in order to improve the conductivity and to narrow distances between the conductive patterns. In the eleventh embodiment, the recesses145are formed in advance in the molding117before the molding117is carbonized and the side wall portions144are carbonized to increase the cross-sectional area of the carbonized portion115in a depth direction.

To reliably irradiate the corners of the recesses145with the laser beam and carbonize the recesses145, a slope eg of the side wall portion144of each of the recesses145is equal to or larger than the laser focusing angle θl. In the eleventh embodiment, the slope eg of each of the side wall portions144of the recesses145is approximately the same as the laser focusing angle θl from the viewpoint of narrowing the distance between the conductive patterns. As a result, the wall surfaces of the recesses145are entirely carbonized and the conductivity is improved. In contrast, in a comparative example inFIG.51in which side wall surfaces182of recesses181are not sloped, the laser beam cannot reach corners of the recesses181. Thus, the carbonized material may be separated and the conductivity may be decreased.

Twelfth Embodiment

In a twelfth embodiment, as shown inFIG.52, the recesses145are formed in recesses141. As a result, the creepage insulation property between the adjacent ones of the carbonized portions115can be improved similarly in the ninth embodiment, and the conductivity can be improved while narrowing the distances of the conductive patterns similarly in the eleventh embodiment.

Thirteenth Embodiment

In a thirteenth embodiment, as shown inFIG.53, recesses145are formed inside the recesses141as with in the twelfth embodiment. The difference from the twelfth embodiment is that the recesses145and the side wall portions144of the recesses141are continuously formed. The slope θg of the side wall portions144is set to a value larger than the focusing angle θl of the laser beam. A width of each of the recesses141is set to a value smaller than the focusing diameter of the laser beam at that height. As a result, concave portions including the recesses141and the recesses145include, in inner wall portions, carbonized portions to improve the cross-sectional area in the depth direction and not-carbonized portions to improve the creepage insulation property. As described above, the recesses141and the recesses145may be integrally formed.

Fourteenth Embodiment

In a fourteenth embodiment, as shown inFIG.54, the resin member110is a resin body containing a resin material and is used, for example, as a housing or cover of an electronic device such as an air flowmeter and a rotation angle sensor. The resin member110includes a base portion161and a carbonized portion115.

As shown inFIGS.54,55, and56, the base portion161has the base polymer114and fillers113. The base portion is formed of a resin material and having an insulation property. The fillers113has a strength higher than that of the base polymer114. The base polymer114constitutes a resin portion of the base portion161. The fillers113serve as a reinforcing member that strengthens the base portion161. The base portion161is reinforced by the fillers113mixed with the base polymer114.

The carbonized portion115is a conductive portion that is formed on an outer surface162of the base portion161and include carbonized material166(seeFIG.43) to have a conductivity. The multiple carbonized portions115extend linearly. The carbonized portions115are pattern portions arranged in a pattern and form a wiring pattern. This wiring pattern is a current-carrying portion used as a static electricity removing circuit in an electronic device such as an air flowmeter and a rotation angle sensor.

The carbonized material is a carbon having conductivity (i.e., a conductive carbon). The carbonized material is a conductive material, for example, carbon material such as graphite, carbon powder, carbon fiber, nanocarbon, graphene, or carbon micromaterial. Nanocarbons are, for example, carbon nanotubes, carbon nanofibers, and fullerenes.

As shown inFIGS.55and56, the resin member110includes a skin layer163extending along the outer surface162of the base portion161, and a core layer164provided inside the skin layer163. The skin layer163is a surface layer portion that forms the outer surface162of the base portion161. The skin layer163is also a solidified layer that is formed by the molten resin coming in contact with the inner surface of the mold and being solidified during the resin molding of the base portion161. The core layer164is a fluidized layer that is formed by the molten resin flowing inside of the solidified layer during the resin molding of the base portion161. The outer surface162of the base portion161is an outer surface of the skin layer163and also an outer surface of the resin member110. The outer surface162has a groove-shaped concave surface165that is recessed toward the core layer164. The carbonized portion115extends from the skin layer163toward the core layer164on the groove-shaped concave surface165. The carbonized portion115is formed by carbonizing at least a part of the skin layer163. As a material of the base polymer114which is a resin forming the skin layer163and the core layer164, a material containing at least a six-membered ring of carbon (i.e., a benzene ring) is used.

At least the core layer164among the skin layer163and the core layer164forms the base portion161. In the fourteenth embodiment, the carbonized portion115is located on the skin layer163that is apart from the core layer164. That is, the groove-shaped concave surface165does not reach the core layer164and the carbonized portion115is located adjacent to only the skin layer163.

Both the skin layer163and the core layer164form the base portion161.

As shown inFIGS.54,55, and56, in the skin layer163, more fillers113are oriented in a predetermined direction along the outer surface162of the base portion161than that in the core layer164. Hereinafter, the fillers113oriented in the predetermined direction is referred to as “oriented fillers113”. The carbonized portion115extends in a direction intersecting with the oriented fillers113. Particularly, in the fourteenth embodiment, the carbonized portion115extends in the direction orthogonal to the orientation fillers113.

As shown inFIG.57, a large number of carbonized material166is gathered to form the carbonized portion115. At least a part of the fillers113enters into the carbonized portion115and restricts the carbonized portion115from falling off from the base portion161. That is, the fillers113are a restriction member that restricts the carbonized material166from falling off from the carbonized portion115. As material of the fillers113, a fibrous material, a granular material, or a plate-shaped material can be used as described in the eighth embodiment. In the fourteenth embodiment, a fiber material such as flame-retardant fiber, glass fiber, and carbon fiber is used as the material of the fillers113, thereby forming a fiber portion. InFIG.57, illustration of hatching is omitted for descriptive purposes.

A part of the fillers113included in the base portion161protrudes from the groove-shaped concave surface165. The part of the fillers113has one end retained by the base portion161and the other end caught by the carbonized portion115, which strengthens a connection between the carbonized portion115and the base portion161. By using fiber material as the material of the fillers113, a length of the part of the fillers113caught in the carbonized portion115can be increased. In particular, the orientation fillers113intersect with an extending direction of the carbonized portions115. Thus, the oriented fillers113are likely to protrude from the groove-shaped concave surface165and easily caught by the carbonized portion115. In addition, a part of the oriented fillers113penetrates the carbonized material166of the carbonized portion115, which effectively restricts the carbonized material166from falling off.

The method for manufacturing the resin member110includes the preparing step P1and the carbonization step P2as shown inFIG.58. In the preparing step P1, as shown inFIGS.59and60, the base portion161reinforced with the fillers113mixed with the base polymer114is prepared. The preparing step P1includes preparing the base portion161that is molded similarly to the molding step P1in the eighth embodiment, but alternatively may include preparing the base portion161that has been already molded regardless of whether it is unused or used.

The carbonization step P2, as shown inFIGS.61and62, includes heating the base portion161prepared in the preparing step P1. The base portion161is heated such that the carbonized portion115is located on the outer surface162of the base portion161and at least a part of the fillers113enters into the carbonized portion115. The carbonized portion115of the base polymer114contains the carbonized material166to have conductivity and the entering fillers113restrict the carbonized portion115from falling off from the base portion161. In addition, the skin layer163is heated such that a part of the skin layer163is carbonized to form the carbonized portion115on a position distanced from the core layer164.

In the carbonization step P2, as shown inFIG.61, the skin layer163is heated such that carbonized portion115extends in a direction intersecting with the fillers113extending along the outer surface162of the base portion161on the skin layer163.

As described above, in the fourteenth embodiment, the resin member110includes the base portion161and the carbonized portion115. The base portion161includes the base polymer114and the fillers113. The base polymer114is formed of a resin material and has an insulation property. The fillers113have a strength higher than that of the base polymer114. The base polymer161is reinforced by the fillers113mixed with the base polymer114. The carbonized portion115is provided on the outer surface162of the base portion161and contains the carbonized material166to have an electrical conductivity. At least a part of the fillers113enters into the carbonized portion115and restricts the carbonized portion115from falling off from the base portion161.

The method for manufacturing the resin member110includes the preparing step P1of preparing the base portion161and the carbonization step P2. In the carbonization step P2, the base portion161is heated such that the carbonized portion115is located on the outer surface162of the base portion161and at least a part of the fillers113enters into the carbonized portion115.

The carbonized portion115contains the carbonized material166that is formed by carbonizing a part of the base polymer114to have electrical conductivity. The entering fillers113restrict the carbonized portion115from falling off from the base portion161.

According to the resin member110and the method for manufacturing the resin member110, the fillers113restrict the carbonized material166from falling off after the resin member110is molded. Therefore, it is possible to restrict the carbonized material166from falling off and the conductivity of the carbonized portion115from decreasing. In addition, when the carbonized portion115is formed by carbonizing the base polymer114through the heat treatment, the fillers113restrict the carbonized portion115from scattering along with a generation of the decomposition gas. Thus, it is possible to restrict a part of the carbonized portion115from scattering through the heating, which causes the conductivity of the carbonized portion115to decrease, and to restrict the carbonized portion115from being divided.

In the fourteenth embodiment, the resin member110includes the skin layer163extending along the outer surface162of the base portion161and the core layer164provided inside the skin layer163. At least the core layer164in the skin layer163and the core layer164forms the base portion161. The outer surface162of the base portion161has the groove-shaped concave surface165that is recessed toward the core layer164. The carbonized portion115is located on the groove-shaped concave surface165such that the carbonized portion115extends from the skin layer163toward the core layer164. In the preparing step P1, the base portion161having the skin layer163and the core layer164are prepared. In the carbonization step P2, the skin layer163is heated such that at least a part of the skin layer163is carbonized to form the carbonized portion115.

In the resin member110, the fillers113in the skin layer163whose orientations are aligned are more likely to restrict the carbonized portion115from falling off than the fillers113in the core layer164whose orientations are irregular. Therefore, according to the resin member110and the manufacturing method thereof described above, it is possible to further restrict the carbonized portion115from falling off from the core layer164.

The fillers113are likely to orient irregularly in the core layer154. Thus, in the configuration in which the carbonized portion115is located in the core layer164, it may be difficult for the fillers113to restrict the carbonized portion115from falling off from the core layer164.

In contrast, in the fourteenth embodiment, the carbonized portion115is located in the skin layer163at a position distanced from the core layer164. In the carbonization step P2, the skin layer163is heated such that the carbonized portion115is formed on a position distanced from the core layer164. According to the above-described resin member110and the manufacturing method thereof, since the carbonized portion115is not located in the core layer164, the carbonized portion115can be more effectively restricted from falling off from the core layer164.

If the fillers113are entirely included in the carbonized portion115, the fillers113may be separated from the base portion161together with the carbonized portion115.

In contrast, in the fourteenth embodiment, the carbonized portion115extends in the direction intersecting with the fillers113that extend along the outer surface162of the base portion161in the skin layer163. In the carbonization step P2, the skin layer163is heated such that the carbonized portion115extends in a direction intersecting with the fillers113that extend along the outer surface162of the base portion161in the skin layer163. When the carbonized portion115and the fillers113intersect with each other in this way, one end of the fillers113enters into the base portion161and the other end of the fillers113is stuck in the carbonized portion115. Therefore, the fillers113together with the carbonized portion115can be restricted from being separated from the base portion161.

In the fourteenth embodiment, the fillers113pass through the carbonized material166in the carbonized portion115. Thus, the fillers113can more reliably restrict the carbonized material166from falling off. When heating the base polymer114that has a polymer portion (i.e., a lump of polymer) through which the fillers113pass, the polymer portion is converted into the carbonized materials166in a state where the fillers113remain passing through the polymer portion. With this matter, the fillers113can restrict the carbonized materials from scattering when the base polymer114is combusted.

Fifteenth Embodiment

In a fifteenth embodiment, as shown inFIGS.63to65, the carbonized portion115extends in a direction parallel to the oriented fillers113. In the carbonization step P2(seeFIG.58), as shown inFIGS.66to67, the skin layer163is heated by scanning the skin layer163with the laser beam in the direction parallel to the oriented fillers113such that the carbonized portion115extends in the direction parallel to the oriented fillers113. That is, the scanning direction of the laser beam and the orientation direction of the oriented fillers113are parallel to each other.

As described above, an extending direction of the carbonized portion115and the orientation direction of the oriented fillers113do not necessary cross with each other. As shown inFIG.66, during the carbonization with the laser irradiation, the fillers113are fixed to a resin part that is located adjacent to the carbonized portion115and that is not to be carbonized, or a resin part that is located ahead of a position in the laser scanning direction on the laser orbit and that has not irradiated with the laser yet. Thus, the carbonized material caught by the fillers113is restricted from falling off. As a result, the carbonized material is restricted from scattering and falling off, thereby improving the fixability.

Sixteenth Embodiment

In a sixteenth embodiment, as shown inFIG.68, the outer surface162of the base portion161of the resin member110has a first surface170as a “first outer surface” and a second surface171as a “second outer surface” extending in a direction crossing with the first surface170and a chamfered surface173as a “chamfered outer surface” formed by chamfering a portion where the first surface170and the second surface171cross with each other (i.e., a corner portion). The outer surface162also has a third surface172as a “first outer surface” extending in a direction crossing with the second surface171and a chamfered surface174as a “chamfered outer surface” formed by chamfering a portion at which the third surface172and the second surface171cross with each other (i.e., a corner portion).

The carbonized portion115includes a first carbonized portion175located on the first surface170, a second carbonized portion176located on the second surface171, and a connecting carbonized portion178located on the chamfered surface173. The connecting carbonized portion178connects the first carbonized portion175to the second carbonized portion176. The carbonized portion115also has a third carbonized portion177located on the third surface172and a connecting carbonized portion179located on the chamfered surface174. The connecting carbonized portion179connects the second carbonized portion176to the third carbonized portion177.

In a comparative example, two surfaces cross with each other and a corner portion of the two surfaces are directly connected without being chamfered. In such comparative example, the fillers are less likely to exist at the corner portion and a ratio of the base polymer114becomes relatively high at the corner portion. As a result, a heating rate in the laser irradiation becomes too high at the corner portion and decomposition gas are rapidly generated, which causes the carbonized material to scatter. Thereby, the carbonized material at the corner portion may be electrically disconnected. In addition, if the resin member is slightly deformed and stress is concentrated on the corner portion, the carbonized portions located on the two surfaces are physically separated with each other and the carbonized portion at the corner portion may be broken.

In contrast, in the sixteenth embodiment, the corner portion between the first surface170and the second surface171is chamfered and the chamfered surface173includes the connecting carbonized portion178. The corner portion between the second surface171and the third surface172is chamfered and the chamfered surface174includes the connecting carbonized portion179. As a result, the connecting carbonized portions178and179can restrict electric disconnection at a boundary between the first carbonized portion175and the second carbonized portion176and a boundary between the second carbonized portion176and the third carbonized portion177.

As shown inFIG.69, the method for manufacturing the resin member10includes a preparing step P1, a chamfering step P2, and a carbonization step P3. In the preparing step P1, as shown inFIG.70, a base portion161having three surfaces crossing with each other (i.e., the first surface170, the second surface171, and the third surface172) are prepared. The chamfered surface174has been formed at a portion at which the third surface172and the second surface171cross with each other. In contrast, a portion at which the first surface170and the second surface171cross with each other is sharp without being chamfered (i.e., the sharp corner without being chambered).

In the chamfering step P2, as shown inFIG.71, the chamfered surface173is formed by chamfering a portion at which the first surface170and the second surface171cross with each other. The chamfering is performed by removing the sharp corner through the laser irradiation.

In the carbonization step P3, as shown inFIG.72, the base portion161is heated such that, as the carbonized portion115, the first carbonized portion175that is extending along the first surface170, the second carbonized portion176that is extending along the second surface171, and the connecting carbonized portion178that is extending along the chamfered surface173and that is connecting the first carbonized portion175to the second carbonized portion176is formed on the outer surface162of the base portion161. In addition, the base portion161is heated such that, as the carbonized portion115, the third carbonized portion177that is extending along the third surface172and the connecting carbonized portion179that is extending along the chamfered surface174and that is connecting the third carbonized portion177to the second carbonized portion176are formed on the outer surface162of the base portion161.

A manufacturing method in which the first carbonized portion175, the second carbonized portion176, and the third carbonized portion177are firstly formed and then the connecting carbonized portions178and179are formed will be described. In such manufacturing method, the first carbonized portion175and the second carbonized portion176may not be connected to each other through the connecting carbonized portion178and the second carbonized portion176and the third carbonized portion177may not be connected to each other through the connecting carbonized portion179at a time when the carbonized portion115is formed.

In contrast, in the sixteenth embodiment, in the carbonization step P3, the base portion161is continuously heated from the first surface170to the second surface171over the chamfered surface173such that the first carbonized portion175and the second carbonized portion176are connected to each other through the connecting carbonized portion178. The base portion161is continuously heated from the second surface171to the third surface172through the chamfered surface174such that the second carbonized portion176and the third carbonized portion177is connected to each other through the connecting carbonized portion179. Thus, at a time when the carbonized portion115has been formed, the first carbonized portion175and the second carbonized portion176are surely connected to the connecting carbonized portion178and the second carbonized portion176and the third carbonized portion177are surely connected to the connecting carbonized portion179.

Seventeenth Embodiment

In a seventeenth embodiment, as shown inFIGS.73and74, the carbonized portion115is formed into a lattice shape. The carbonized portion115may be located on an outer wall surface of the housing of an electronic device such as an air flowmeter and a rotation angle sensor and used as a static electricity removing circuit.

The outer surface162of the base portion161includes deformation marks185that extend along an outer peripheral part of the carbonized portion115. The deformation marks185are marks generated by deforming a part of the base portion161. In the seventeenth embodiment, the deformation marks185are melting and solidified marks generated by being melted and solidified. In other embodiment, the deformation marks185may be removal marks generated by laser processing, mechanical processing such as polishing, and dissolution processing with solution. When foreign matters generated when the carbonized portion115is formed are attached to the base portion161, the foreign matters can be removed from the base portion161in forming the deformation marks185. The deformation marks185can avoid deteriorating a design of the base portion161due to the foreign matters.

The deformation marks185include foamed portions186generated by foaming at least a part of the base portion161and multiple dotted recesses187located on the outer surface162of the base portion161. The foamed portions186and the dotted recesses187are deformation marks that can be generated by heating the base portion161.

As shown inFIG.75, the method for manufacturing the resin member10includes a preparing step P1, a carbonization step P2, and a deformation step P3. In the deformation step P3following the carbonization step P2, at least a part of the base portion161is deformed such that the deformation marks185extend along the peripheral part of the carbonized portion115on the outer surface162of the base portion161. In the deformation step P3, at least a part of the base portion161and at least a part of the carbonized portion115are heated such that the deformation marks185are formed on the outer surface162of the base portion161. The temperature of heating in the deformation step P3is lower than the heating temperature of the base portion161in the carbonization step P2.

When foreign matters generated through the heating in the carbonization step P2are remained attached to the outer surface162of the base portion161, the foreign matters may restrict the carbonized portion115from discharging.

In contrast, in the seventeenth embodiment, the foreign matters attached to the base portion161can be removed by burning the foreign matters or the like in the deformation step P3.

When the carbonized portion115include a portion attached to the base portion161with an unstable posture, the flowability of the electric charge in the carbonized portion115is changed by changing the posture of the portion. In this case, the electric conductivity of the carbonized portion115is changed in accordance with the posture of the portion, and thus the electric conductivity may be unstable.

In contrast, in the seventeenth embodiment, not only the base portion161but also a part of the carbonized portion115are removed when the deformation marks185are formed. In this time, a portion of the carbonized portion115having unstable posture is more likely to be removed than a portion of the carbonized portion115having a stable posture. That is, in the deformation step P3, not only the base portion161but also the carbonized portion115are heated, thereby removing the portion of the carbonized portion115having unstable posture through heating and combustion. Thus, the electric conductivity of the carbonized portion115is restricted from changing and can be stabilized.

In addition, by performing a trimming that removes a part of the carbonized portion115, a resistance value of the carbonized portion115can be adjusted to a predetermined value.

In the carbonization step P2, the carbonized portion115is formed by irradiating the base portion161with the electromagnetic wave such as laser beam and heating the base portion161. In the deformation step P3, the deformation marks185are formed by irradiating the base portion161with the electromagnetic wave at a lower intensity (i.e., a lower output), a higher scanning rate, and a lower frequency than those in the carbonization step P2.

As described above, both of the carbonized portion115and the deformation marks185are formed through the electromagnetic irradiation. Thus, a work load for forming the carbonized portion115and the deformation marks185can be reduced. For example, in a configuration in which the carbonization step P2and the deformation step P3are successively performed, it is needed to operate once a process in which the base portion161is placed relative to a device that is configured to transmit electromagnetic wave.

When laser is used to form the deformation marks185, the resin may be foamed and changed in color depending on an energy of the laser, which may be intentionally used as the design. When laser is used to form the deformation marks185, it is preferable to use a pulse laser because the pulse laser is appropriate for removal processing. By using the pulse laser, the dotted recesses187can be periodically formed.

Hereinafter, multiple practical examples will be described. These practical examples are examples in which a short time processing is performed using laser beam having a relatively high output in view of obtaining both of economic efficiency and conductivity. However, the present disclosure is not limited to this. In order to improve the conductivity, a long time processing may be performed using laser beam having a relatively low output. In this case, the heating rate becomes gentle and the conductivity is expected to be further improved.

In example 1, as shown inFIG.76, the molding117is configured with an insulation resin member having a volume resistivity equal to or greater than 1013 Ωm. The insulation resin member is generated by adding 40 wt % of glass fibers as fillers to a base polymer that contains polyphenylenesulfide as a main component. The oriented layer112is formed in a range of the depth equal to or greater than 0.3 mm from a surface of the molding117. The molding117has a flat plate shape having both width and depth of 80 mm and a thickness of 3 mm. The focusing distance of a semiconductor laser is adjusted to near the just focus relative to the surface of the molding117. As shown inFIGS.76and77, a predetermined portion of the oriented layer112on the surface of the molding117having a straight length of 40 mm is scanned with the semiconductor laser that has an oscillation wavelength of 940 nm and the focusing diameter of 0.6 mm at a rate of 50 mm/s with an output of 100 W under argon gas atmosphere having a pressure of 0.15 MPa. As a result, the part of the oriented layer112is carbonized.

As shown inFIGS.76and77, the temperature of the portion of the oriented layer112irradiated with the laser beam (hereinafter, referred to as a first region A1) is increased to the temperature from 2300° C. to 2500° C. and high-temperature decomposition gas is actively generated. In this case, the portion of the oriented layer112is expanded since the resin member is foamed, but the expanded portion is evaporated and removed with the laser beam. Thus, the recess is formed in the first region A1and the carbonized material in the recess has a porous structure.

Along with this, due to thermal conduction from the first region A1heated to the high temperature and high-temperature decomposition gas generated in the first region A1, a temperature of a peripheral part of the first region A1is increased to a temperature of 1800° C. to 2200° C. As a result, the peripheral part of the first region A1is carbonized to form a second region A2.

Since the second region A2is offset from the scanning orbit of the laser beam, the laser beam does not directly reach the second region A2. A portion that is carbonized by receiving a temperature of decomposition gas (hereinafter, referred to as a third region A3) is less likely to evaporate and be removed. Thus, the third region A3becomes a protrusion due to the foaming and volume expansion (seeFIG.78). In the third region A3, the fillers are oriented before the carbonization. Reflecting this orientation state, a carbonized structure was formed in a state where at least 10 layers extending in the surface direction were formed (seeFIG.79).

InFIG.80, a first layer121, a foamed second layer122, and a third layer123are observed. The first layer121is made of a resin material in which fillers113are oriented. The foamed second layer122is located on the first layer121. The third layer123is located on the foamed second layer122and has layered carbonized material as described above. In a range of 100 μm in a normal line direction of the third layer123, at least 10 layers of the carbonized material can be observed. At a lower part of the first region A1and the third region A3, the foamed second layer122at which the resin is foamed is located.

InFIG.80, a direction in which the fillers113are oriented is the same with a direction in which the carbonized material is formed, but it is necessary that the fillers113be oriented in a predetermined main direction of the surface of the resin member and the main direction may extend any direction on the surface of the resin member. For example, the fillers113may be oriented in a direction perpendicular to a plane of paper inFIG.80. An angle formed between the layer of the carbonized material and the surface of the resin member is defined by a position that is firstly carbonized and expanded depending on the scanning direction of the laser beam. The layer of the carbonized material is formed such that an upstream side of the carbonized material on the laser orbit in the laser scanning direction is located on an upper side of the surface (i.e., a far side from the surface) with a slight angle.

In example 1, the conductive pattern formed in the first region A1and the third region A3had a straight linear shape having a width of 0.9 mm, a depth of 0.12 mm, and a length of 40 mm. The depth is a depth of a carbonized portion from the surface of the resin member in the thickness direction. When a commercially available silver paste was applied and cured at both ends of the conductive pattern and the electric resistance value at the center of 20 mm was measured, the electric resistance value at the both ends was 97.1 Ω.

The conductive pattern formed in the first region A1and the third region A3was covered and fixed with a casting material made of epoxy resin. After it is confirmed that the electric resistance value of the whole did not change, cross-section polishing was performed to remove the carbonized material formed in the first region A1to form a sample. According to relations between the electric resistance value, length, and cross-sectional shape, the electric conductivity of the carbonized material formed in the first region A1and the electric conductivity of the carbonized material formed in the third region A3are compared to each other. As a result, the carbonized material formed in the first region A1has the electric conductivity that is three times or more than the electric conductivity of the carbonized material formed in the third region A3.

Raman spectroscopic analysis was performed on the third region A3and peaks at 1580 cm−1(G band) and 1360 cm−1(D band) were observed. As a result, the peak intensity ratio of the G band and the D band (I1580/I1360) was 1.61.

The produced carbonized material was oxidized in nitric acid having a concentration of 60% at room temperature for 5 minutes and the nitric acid was rinsed with distilled water. The obtained portion is sufficiently dried in a constant temperature bath at 50° C. The electric resistance was measured in the similar manner as described above to find that the electric conductivity was reduced by 30%.

In example 2, the molding was formed using an insulation resin material having a volume resistivity of 1013 Ωm or more in a similar manner in the example 1. The insulation material is configured with a base polymer containing a polyphenylenesulfide as a main component without including fillers. The carbonization is performed in the similar to that in example 1. In this case, the carbonized material was violently scattered and the carbonized material was not fixed. After that, the electrical resistance was measured in the similar manner to that in the example 1 to find that the electrical conductivity was at least equal to or greater than 50 MO. The electric resistance was measured multiple times with changing the output of the laser beam to 5 W, 10 W, 50 W, 100 W, 150 W, and 200 W, but the electric resistance was equal to or greater than 50 MΩ in all conditions.

A molding is formed using a conductive resin member having a volume resistivity of 10 Ωm in a similar manner to that in example 1. The conductive resin member is generated by adding 30 wt % of carbon fibers as the fillers to a base polymer containing polyphenylenesulfide as a main component. The carbonization is performed in a similar manner to that in example 1 and a conductive pattern similar to that in example 1 is formed. The electric resistance was measured in a similar manner to that in example 1 to find that the electric resistance was 21.8Ω. The volume resistivity of the conductive pattern was roughly estimated from the length, cross-sectional shape, and electric resistance value as 8.4×10−5Ωm.

The carbonized material is formed in the same manner as that in example 1 except for changing the pressure of the atmosphere during the laser beam irradiation to 0.001 MPa that is a decompression atmosphere. The temperature of the generated decomposition gas was rapidly decreased and the layers of the carbonized materials are rarely formed in the third region A3(seeFIG.81). The generated wiring pattern in this time has a straight linear shape having a width of 0.6 mm, a depth of 0.05 mm, and a length of 40 mm. The depth is a depth of a carbonized portion of the resin member from the surface of the resin member in the thickness direction. When a commercially available silver paste was applied and cured on both ends of the conductive pattern and the electric resistance value at the center of 20 mm was measured, the electric resistance value at both ends was 1124 Ω.

As shown inFIG.82, 50 lines of the carbonized portions each having a straight linear shape and a length of 40 mm were formed in the similar manner to that in the example 1. The 50 lines of the carbonized portions are formed by displacing the scanning orbit of the laser beam by 0.8 mm in a direction perpendicular to the surface direction each after forming one line of the carbonized portions. As a result, the carbonized portions were linearly and electrically connected to each other and a conductive pattern having a 40 mm square shape was formed. The electric conductivity of the carbonized material generated at this time was about the same as that of the carbonized material generated in example 1. The surface became uneven similarly to that in example 1.

The molding is formed in the similar manner to that in example 1 using an insulation resin material having a volume resistivity of equal to greater than 1013 Ωm. The insulation resin material is formed by adding total 66 wt % of fillers consisting of 33 wt % of glass fibers and 33 wt % of calcium carbide to the base polymer that contains polyphenylenesulfide as a main component. The carbonized treatment was performed in the similar manner to that in example 1 to form the wiring pattern similar to that in example 1. The electric resistance was measured in the same way in example 1 to find that the electric resistance was 1270 Ω.

The molding was formed in the similar manner to that in example 1 using an insulation resin material having a volume resistivity of equal to greater than 1013 Ωm. The insulation resin material is formed by adding 30 wt % of glass fibers as fillers to the base polymer that contains polyphenylenesulfide as a main component. The carbonization was performed in the similar manner to that in example 1 to form a wiring pattern similar to that in example 1. The electric resistance was measured in the same way in example 1 to find that the electric resistance was 139.3 Ω.

The molding was formed in the similar manner to that in example 1 using an insulation resin material having a volume resistivity that is equal to or greater than 1013 Ωm. The insulation resin material is formed by adding 45 wt % of glass fibers as the fillers to the base polymer that contains polyphenylenesulfide as a main component. The carbonization was performed in the similar way to that in example 1 to form a wiring pattern similar to that in example 1. The electric resistance was measured in the same way in example 1 to find that the electric resistance was 169.1 Ω.

The molding was formed with compression molding using an insulation resin material having a volume resistivity that is equal to or greater than 1013 Ωm. The insulation resin material is formed by adding total 50 wt % of fillers consisting of 35 wt % of glass fibers and 15 wt % of other inorganic fillers to the base polymer that contains phenol resin as a main component. The carbonization was performed in the similar manner to that in example 1 to form a pattern that has a width of 0.75 mm, a depth of 0.05 mm, and a length of 40 mm. The depth is a depth of a carbonized portion of the molding from the surface of the resin member in the thickness direction. The electric resistance was measured in a section of 20 mm in the same way in example 1 to find that the electric resistance was 171.2 Ω.

The molding was formed with injection molding using the same insulation resin material in example 9. The carbonization was performed in the similar manner to that in example 1 to form a wiring pattern similar to that in example 9. The electric resistance was measured in a section of 20 mm in the similar way to that in example 1 to find that the electric resistance was 133.3 Ω.

The carbonized material was formed in a same method in example 1 except for that the atmospheric pressure during the laser irradiation was 1.0 MPa (i.e., pressurized atmosphere). As a result, the electrical conductivity of the conductive pattern was improved by 30% compared to that in example 1.

The molding was formed in the similar manner to that in example 1 and wet polishing was performed from the surface of the molding by 1.5 mm in the thickness direction to remove the oriented layer. The obtained molding was sufficiently dried. The carbonized material was formed on the dried surface of the resin member in the similar way to that in eleventh example to form a conductive pattern similar to that in example 1. The electric resistance was measured in a section of 20 mm in the same way to that in example 1 to find that the electric resistance was 558 Ω.

As shown inFIG.83, the carbonized portion115as shown inFIG.84is formed by closely contacting the oriented layer112of the molding117, which was formed in the similar manner to that in example 1, with a metal member151made of iron, copper or brass, and by irradiating a contact boundary152between the oriented layer112and the metal member151with the laser beam under the same condition as that in example 1. Sufficient conduction was secured between the carbonized portion115and the metal member151.

As shown inFIG.85, the carbonized portion115as shown inFIG.86is formed by thinning a predetermined part of the molding117using the same insulation material as that in example 1 to a thickness of about 0.1 mm, closely contacting the thin part with the metal member151, and irradiating the thin part of the molding117with the laser beam toward the metal member151in the thickness direction under the same condition as that in example 1. The carbonized portion115corresponding to the predetermined portion having the thin portion is in contact with the metal member151in the thickness direction and sufficient conduction was secured between the carbonized portion115and the metal member151.

When the carbonized portion is formed at the contact boundary between the oriented layer of the molding and the metal member, the heat source for carbonizing the oriented layer may be obtained not only by heating the resin in the oriented layer but also by heating the metal member.

The metal member used in the above-described method is not limited, but particularly good connection and conduction can be obtained by selecting the metal with which carbon is likely to form a solid solution such as nickel, bismuth, and iron. Particularly, nickel is effective because by using nickel, a catalytic action works at the boundary and high quality graphite can be formed. The above-described method is also effective in the case that the metal such as iron forms the conductive material by reacting with carbon depending on the temperature and the supplied amount of the carbon. Further, these metal species may be attached to the surface of the metal member by plating and the like.

The carbonized materials formed in examples 1 to 14 were covered with a casting material made of epoxy resin. In this case, the electric conductivity of the carbonized materials were not changed and the resin members having good electric conductive pattern therein were obtained.

Other Embodiments

In other embodiments, a portion on which the non-insulation portion is formed is not limited to the surface of the housing and may be inside of the housing. For example, the portion may be a portion of the inner part of the housing that is hidden after welding.

In other embodiments, the ground connecting terminal is not limited to the intake air temperature terminal and may be other portion such as an intake pipe. In short, the ground connecting terminal is connected to the ground45and able to discharge the electric charge to the ground45.

In other embodiment, the graphitization processing through laser irradiation may be performed on a partial area or multiple areas. As shown inFIG.33, the non-insulation portion90may be formed more than one of parts of the outer wall24bof the bypass housing24that are a part A corresponding to the flow rate detector, a part B corresponding to the measuring outlet portion, a part C corresponding to the discharge passage, and a part D corresponding to flow passage. The non-insulation portion90may be formed on a part E of the outer wall92aof the outside main passage housing92.

In other embodiments, the carbonized portion is not limited to a pattern shape and may be formed in a film shape. In this case, a dense conductive film can be formed on the surface of the resin member as compared with a resin member in which conductive fillers are mixed and dispersed in a resin material to impart conductivity. Therefore, it is possible to impart a more excellent electromagnetic wave shielding property to the resin member. It is possible to improve both the electrical conductivity and thermal conductivity of a thick resin member having a thickness of more than 300 μm, and to improve the electromagnetic wave shielding property.

In other embodiments, the carbonized portion is not necessarily provided on a position separated from the core layer. That is, the carbonized portion may be provided so as to reach from the skin layer to the core layer. In the core layer, the orientations of the fillers are likely to be irregular, but the carbonized portion is restricted from falling off from the base portion because at least a part of the fillers enters into the carbonized portion.

In other embodiment, a carbonized portion may be formed in a planar shape in a range including the entire outer surface of the resin member, and the carbonized portion may be provided so as to reach from the skin layer to the core layer. In that case, the base portion is composed of only the core layer.

In other embodiment, the electrical resistance value may be adjusted by adjusting the additive amount of the fillers and the heating condition. The resultant with the electrical resistance adjusted may be used as a resistor or a heater inside an electric device.

In other embodiment, electroplating may be performed using, as an electrode, the carbonized material formed on the surface of the resin member to improve both the electrical conductivity and thermal conductivity. Additionally, an oxidizing treatment may be performed using an oxidant to improve the electrical conductivity.

In other embodiment, to form a complicated conductive pattern, the conductive pattern may be formed on any surface of the molding. For example, a through hole may be defined in the molding and conductive patterns may be formed on both side surfaces of the molding. Then, the conductive patterns on the both side surfaces may be electrically connected to each other by carbonizing an inside of the through hole or inserting a current-carrying member into the through hole.

In other embodiment, to form a more complicated crossover, the molding117molded as shown inFIG.87is prepared and carbonized portions115are formed on predetermined positions of the molding117in a similar way shown inFIG.88to form the resin member110. Then, as shown inFIG.89, multiple resin members110may be prepared and integrally molded by engagement of press-fitting or snap-fitting, adhesion, welding, insert molding, or the like. In order to restrict the carbonized material from falling off, as shown inFIG.90, a covering portion153for fixing the periphery of the carbonized material may be formed by insert molding, potting, application of a hardening material, other coating, or the like. At this time, some of the fillers pass through the carbonized material and are exposed to the outside of the resin members110. Therefore, the exposed portions of the fillers enter into the covering portion153, which is the secondary molding, to improve the adhesion between the resin members110and the covering portion153.

In other embodiment, in order to prevent the carbonized material from falling off, a part of the resin forming the molding may be heated and melted to seal the carbonized material. A laser beam may be used as the heat source at this time.

In other embodiment, a layer of a material (i.e., transmitting material) that transmits a laser beam is formed on the surface of the molding117before carbonization, and the molding117is irradiated with the laser beam through the transmitting material155as shown inFIG.91. Thereby, the carbonized portion115is formed between the molding117and the transmitting material155. At this time, for example, it is preferable to dispose a porous layer between the molding117and the transmitting material155or to form irregularities on the surface of the molding117or the transmitting material155so that a passage through which decomposition gas is released is defined.

In order to ensure conduction between the generated carbonized material and the other metal member, it is possible to contact simply the carbonized material with the metal member. However, in other embodiment, a conductive adhesive such as silver paste or carbon paste, melting metal such as solder, or the like may be disposed between the carbonized material and the metal member.

In other embodiment, processing such as deburring or printing of the resin member may be performed with a laser used in the carbonization step.

The present disclosure has been described based on the embodiments. However, the present disclosure is not limited to the embodiments and structures. The present disclosure also encompasses various modifications and variations within the scope of equivalents. Furthermore, various combination and formation, and other combination and formation including one, more than one or less than one element may be made in the present disclosure.