Electromagnetic welding method for molded parts and heat sink used in said method

Abstract

We provide a heat sink with a measurement function for use in electromagnetic welding of molded parts. [Solution] This heat sink contains a material with a thermal conductivity of more than 25 W / (m·K) according to ASTM C1113 at 25°C, and further comprises a machined cavity and a sensing device housed within the cavity for measuring the temperature at a location within the cavity, with a dimensional gap between the sensing device and the cavity wall. This heat sink is advantageously used in methods and apparatus for joining molded parts by electromagnetic welding. This heat sink with measuring function, which is in direct contact with the external surface of the molded part, cools the external surface of the molded part and improves the control of the welding temperature during welding.

Description

[Technical Field]

[0001] The present invention relates to a heat sink for use in an electromagnetic welding method for molded parts. The present invention also relates to an electromagnetic welding method for molded parts using the heat sink of the present invention. Furthermore, the present invention relates to an electromagnetic welding apparatus for molded parts comprising the heat sink of the present invention. [Background Art]

[0002] Several techniques exist for joining molded parts such as fiber-reinforced thermoplastic or thermosetting composite material parts. Conventionally, mechanical fastening and adhesive bonding have been used for this purpose. However, mechanical fastening requires high-cost hole positioning, drilling, shim adjustment, and fastener installation, and may cause delamination of fiber-reinforced composite material parts. Adhesive bonding requires complex surface pretreatment that may involve chemicals.

[0003] Electromagnetic welding (also called induction welding) may eliminate the need for using separate fasteners, and provides the possibility of joining contact surfaces of molded composite material parts at a relatively high speed with little or no pretreatment. In electromagnetic welding, an electromagnetic field is generated in one or more induction-sensitive components of the molded part to heat the heat-fusible bonding material of the molded part above its melting point. Heating is performed by an induction coil that induces eddy currents in an induction-sensitive component of the molded part (e.g., conductive carbon fibers disposed within the molded part). Examples of the bonding material include a thermoplastic resin of one or more parts to be joined, or a separately applied thermoplastic resin. The contact surfaces of the molded parts are joined to each other by the molten bonding material. By compressing the molded parts and then cooling them, a fusion-bonded joint or welded joint is formed.

[0004] Electromagnetic welding of molded parts may include spot welding, in which a discontinuous weld is formed at a welding point using a fixed inductor that generates an electromagnetic field under alternating voltage. The method and heat sink of the present invention may also relate to a continuous welding method. In such electromagnetic welding, an induction coil is moved along a welding line of the molded part.

[0005] Electromagnetic welding is an effective method for joining the surfaces of molded parts, but the inductor (or induction coil) tends to generate heat not only at the weld interface but throughout the entire molded part. Therefore, temperature control during induction welding remains a challenging process.

[0006] Extensive preliminary experiments and precise tests have been proposed to determine the temperature of the weld joint. However, even with such procedures, there is no guarantee that the heating behavior of the molded part material in the induction welding process can be accurately predicted. It is believed that the manufacturing tolerances of the molded part to be welded, the variation in molded part material between lots, and environmental factors can all affect the final quality of the weld. To solve this problem, a robust in-situ process control mechanism may be necessary to achieve high-quality welds in each welding step. Such an effective process control system may be able to control the weld interface temperature within a processing window. However, this seems to be possible only by acquiring temperature data at the weld interface during the induction welding process. In practice, such a method of directly measuring the temperature at the weld interface can be achieved by placing thermocouples (TCs) at the weld interface, or, less accurately, on the top and bottom surfaces of the molded part to be welded. However, this method is invasive, and the thermocouples are embedded as part of the weld structure, making it useful only for preliminary heating experiments.

[0007] European Patent Application Publication No. 3772403 proposes arranging a linear optical fiber sensor along a composite material component consisting of a matrix of fiber-reinforced thermoplastic resin, and measuring temperature through the linear optical fiber sensor. Since the linear optical fiber sensor is arranged on the composite material component, a heat sink cannot be used in this method because providing a heat sink would destroy the linear optical fiber sensor, which would negatively affect the weld quality. European Patent Application Publication No. 3772403 further discloses a method using a heat sink. In such embodiments, the sensor may be embedded in the heat sink or positioned at the left and right ends of the heat sink, the left and right ends of the weld interface, or below the molded part. The sensor may consist of a thermocouple, an electromagnetic field (EMF) sensor, or an infrared (IR) sensor for measuring temperature. European Patent Application Publication No. 3772403 does not disclose how the sensor is related to the heat sink, but the expression "embedded" suggests that the sensor is firmly fixed to the body of the heat sink. According to the drawings, the sensor appears to be bonded to the heat sink.

[0008] Conventional technologies propose the use of heat sinks with measurement functions, but known heat sinks with measurement functions have several drawbacks. Temperature measurements may be affected by the electromagnetic field during induction welding. Furthermore, if one of the sensors malfunctions, the entire heat sink must be replaced.

[0009] Therefore, there is a need for electromagnetic welding systems and methods for molded parts that can better control the temperature generated at the welding interface between molded parts. Another objective is to perform reliable, fixed-point temperature measurements near the welding interface without using invasive methods, by placing a sensing device such as a thermocouple inside a heat sink and managing the wiring of the sensing device to prevent interference with the welding process.

[0010] Furthermore, U.S. Patent Application Publication 2017 / 0305071 discloses an electric heating device for sealing polymer films. This device comprises a sealing section equipped with a heater and an aluminum support section for supporting the heater. The support section can dissipate heat from the heater to the outside, but aluminum strongly interferes with electromagnetic fields and therefore cannot be used as a heat sink for electromagnetic welding. The support section further includes a temperature sensor housed in a housing section located inside the support section. [Prior art documents] [Patent Documents]

[0011] [Patent Document 1] European Patent Application Publication No. 3772403 [Patent Document 2] U.S. Patent Application Publication No. 2017 / 0305071 [Overview of the project] [Problems that the invention aims to solve]

[0012] An object of the present invention is to provide an improved heat sink for use in electromagnetic welding methods for molded parts, which overcomes at least some of the shortcomings of known heat sinks. Another object of the present invention is to provide an improved method and apparatus for joining molded parts by electromagnetic welding. [Means for solving the problem]

[0013] For this purpose, the present invention provides a heat sink as described in claim 1. According to the present invention, a heat sink with a measuring function for use in electromagnetic welding of molded parts is provided, the heat sink comprising a material having a thermal conductivity of more than 25 W / (m·K) according to ASTM C1113 at 25°C, the heat sink comprising a machined cavity and a sensing device housed therein for measuring the temperature at a location within the cavity, further comprising a dimensional gap between the sensing device and the wall of the cavity.

[0014] This dimensional gap allowed the detection device housed within the machined cavity to deform virtually freely. In other words, it could deform substantially independently of the deformation of the heat sink itself caused by applied pressure, temperature fluctuations, etc.

[0015] The heat sink of the present invention enables rapid, efficient, and high-quality welded joints between molded parts without the risk of overheating. This is achieved by measuring the temperature of one or more sensors housed in one or more machined cavities within the heat sink, and by providing a dimensional clearance between the sensing device and the cavity wall.

[0016] In another aspect of the present invention, a method is provided for joining the surface of a first molded part to the surface of a second molded part by electromagnetic welding, the method comprising the following steps: • Prepare first and second molded parts including a heat-meltable bonding material and an induction-sensitive component. • Applying pressure to the surfaces to be connected by bringing the surfaces to be connected into contact with each other and bringing the pressure surface of the pressurizing body into contact with the molded part. - Using an inductor that moves in the welding direction, an electromagnetic field is generated at least on the surface of the molded parts to be joined, thereby heating an inductively sensitive component and causing the bonding material at the welding interface to thermally melt. - To cool the outer surface of the first molded part by providing the heat sink with measurement function described in the claim, in direct contact with the outer surface of the first molded part, and optionally such that the arrangement of the detection device (thermocouple and / or fiber Bragg grating sensor) extends substantially parallel to the welding direction. • Measure the temperature using a detection device and calculate the temperature of the welding interface based on that measurement. • Controlling welding parameters to control the temperature of the welding interface, and - Joining molded parts under pressure using molten, heat-meltable bonding material. Includes.

[0017] Controlling the welding parameters comprises controlling one or more welding parameters.

[0018] In yet another aspect, there is provided an apparatus for joining a surface of a first molded part and a surface of a second molded part along a welding direction by temperature-controlled electromagnetic welding, wherein the first and second molded parts comprise a heat-fusible bonding material and an induction-sensitive component, and the apparatus comprises: · an inductor provided for generating an electromagnetic field along the welding direction at least on the surfaces to be connected of the molded parts, whereby the induction-sensitive component is heated to thermally melt the bonding material at the welding interface; · the heat sink with a measurement function according to claim 1, wherein the heat sink is arranged along the welding direction, provided such that an outer surface thereof abuts against one of the molded parts, and is disposed between the inductor and the molded part; · a pressing member provided for pressing the surfaces to be connected; · a control device configured to measure the temperature in the heat sink by a detection device, calculate the temperature of the welding interface based thereon, and control the welding parameters; comprising the foregoing components.

[0019] Detailed description of the invention The present invention outlined above will be further described in detail below.

[0020] In a first aspect of the present invention, there is provided a heat sink with a measurement function for use in electromagnetic welding of molded parts. The heat sink comprises a material having a thermal conductivity of more than 25 W / (m·K) according to ASTM C1113 at 25°C. Suitable heat sink materials include those comprising reinforcing fibers embedded in a matrix material, preferably substantially all the reinforcing fibers are oriented unidirectionally in an in-plane fiber direction. The reinforcing fibers in the heat sink may comprise carbon fibers having a thermal conductivity in the range of 100 to 1000 W / (m·K) at room temperature and an electrical resistivity in the range of 0.5 to 10 μΩ·m at room temperature. The reinforcing fibers in the heat sink have a thermal conductivity in the range of 0.1 to 20 W / (m·K) at room temperature and an electrical resistivity at room temperature of 1×10 10 ~1×10 13 glass fibers in the range of Ω·m may be included. Combinations of carbon fibers and glass fibers are also possible. Such reinforcing fibers are commercially available. In the case of a composite heat sink, the matrix material of the heat sink may generally comprise a heat-resistant material having a glass transition temperature Tg of more than 350°C, optionally a thermosetting resin. Such matrix materials are also commercially available.

[0021] Other suitable heat sink materials may include ceramic materials, which are preferred as described hereinafter.

[0022] According to the present invention, the heat sink comprises at least one machined cavity and at least one sensing device accommodated in the cavity for measuring temperature at a position within the cavity. Furthermore, a dimensional gap exists between the sensing device and the wall of the cavity.

[0023] This heat sink is used for electromagnetic welding of molded parts and allows for the removal of excess heat from the external surface of the molded part when the heat sink is in direct contact with the external surface. This concentrates heating on the surface to be joined (weld interface) rather than other parts of the molded part, and further prevents overheating of other parts of the molded part. A suitable heat sink is planar in that its thickness is less than its planar dimensions. The planar dimensions of the heat sink are usually large enough to cover at least the area where welding is required, as defined by the weld line and weld width. One external surface of the heat sink is positioned to contact one side of the molded part, while the opposite external surface is positioned not to contact the other side of the molded part.

[0024] According to the present invention, a heat sink with a measuring function comprises a machined cavity and a sensing device housed inside the cavity for measuring the temperature at a location within the cavity. This is in contrast to a method in which the sensing device is embedded in the heat sink, because the sensing device is not firmly fixed to the body of the heat sink material. Instead, as described in the claims, a dimensional gap exists between the sensing device and the wall of the cavity. This dimensional gap is obtained by machining the cavity to a dimension slightly larger than the external dimensions of the sensing device, such as a thermocouple or an optical fiber sensor. In the circumferential direction of an elongated sensing device, this gap may extend around the entire circumference or be partial. An example of the latter is when a sensing device in the shape of an optical fiber or thermocouple wire is inserted into the machined cavity and rests on the bottom surface of the cavity due to gravity. In this case, the dimensional gap extends around the entire circumference of the sensing device, except for the contact surface with the bottom surface of the cavity. The dimensional gap may be left unfilled, in which case the gap forms an air gap, or more generally, a gas gap. Such unfilled dimensional gaps are preferably used when the detection device is an optical fiber sensor. In other embodiments, such as when a thermocouple is used as the detection device, the dimensional gaps may be filled at least partially with a filler material different from the heat sink material. In particular, a filler material with lower rigidity than the heat sink material (e.g., 1%, 5%, 10%, 15-20% or less), such as a potting compound, may be used. In embodiments where an optical fiber sensor is used as the detection device, the dimensional gaps are filled at least partially with a liquid or gel-like material, thereby substantially maintaining mechanical decoupling between the optical fiber sensor and the heat sink in which it is placed. This prevents deformation of the detection device that is substantially dependent on the deformation of the heat sink itself. In other words, deformation of the detection device and the heat sink (e.g., thermal expansion or deformation under applied pressure) is substantially isolated.In this context, the expression "substantially isolated" may mean that the deformation of the sensing device, which is directly affected by the deformation of the heatsink, is less than 10% of the deformation of the sensing device caused by the rise or fall in temperature.

[0025] It should be noted that the lateral dimensions of the detection device include the protective cover or sheath of the device. In this case, the gap extends between the outer surface of such cover or sheath and the wall of the cavity.

[0026] In one embodiment of the present invention, a heat sink with a measurement function is provided. The material of this heat sink has a thermal conductivity of 0.1 to 250 W / (m·K) at 25°C according to ASTM C1113, more preferably 25 to 250 W / (m·K), even more preferably 50 to 250 W / (m·K), and most preferably 80 to 250 W / (m·K).

[0027] As a suitable embodiment, a heat sink with a measurement function is provided, wherein the heat sink material comprises a ceramic substantially composed of nitrides. Such a material is an excellent heat sink material because it can remove excess heat from the external surface of a molded part during induction welding.

[0028] However, a drawback of ceramic materials is their tendency to become brittle, especially in ceramics with the highest thermal conductivity. It has been found that heat sink materials substantially composed of nitride composites, and more preferably substantially composed of boron nitride and aluminum nitride composites, offer a desirable combination of machinability and high thermal conductivity. Therefore, these materials are particularly suitable in the present invention because they can form machined cavities with high precision and reduce the risk of breakage (instantaneous or delayed).

[0029] Examples of ceramic materials include oxides such as alumina, beryllia, ceria, and zirconia, or non-oxides such as carbides, borides, nitrides, and silicides, or composite materials consisting of particle-reinforced, fiber-reinforced, and / or combinations of oxides and non-oxides, referred to herein as ceramic materials. Ceramics can be processed into heat sinks according to known processes. For example, one method involves "shaping" powder into a desired form and then sintering it to form a solid. Molding techniques include molding, casting, injection molding, and dry pressing. Processing methods include mixing ceramic powders and hot-pressing them to form the shape of a heat sink. It is also possible to mix ceramic powders with an organic matrix such as a thermosetting resin. The weight fraction of powders in such composite materials can be adjusted to obtain a desired thermal conductivity.

[0030] In the classification of preferred ceramic materials, a heat sink with a measurement function is provided, wherein the hardness of the ceramic material is 15-75 HR[A], more preferably 25-50 HR[A], and even more preferably 30-40 HR[A], according to ISO 6508.

[0031] According to the present invention, one or more cavities in the heat sink are machined. This means that at least one cavity is formed by removing a portion of the heat sink material body after the body has been formed. In other words, machining refers to a removal process in which excess material is removed from the heat sink using a tool. The machined cavities can be formed using any suitable tool appropriate for the purpose of forming the cavities. Suitable machining may include, but is not limited to, machine tools commonly used in punching, boring, drilling, turning, milling, etc. Machining may also include the use of non-mechanical tools commonly used in chemical, electrochemical, laser beam, abrasive water jet, ultrasonic machining, etc.

[0032] The cross-section of at least one cavity may be circular or non-circular. The at least one cavity extends over a certain distance along its longitudinal direction and preferably has an elongated shape in which the ratio of its longitudinal dimension to its cross-sectional dimension is greater than 1, more preferably greater than 2, 3, 4, or 5. The at least one cavity may also extend from one side of the heat sink to the other, in which case the ratio of the longitudinal dimension to the cross-sectional dimension of the at least one cavity may be relatively large, such as up to 20, 50, 100, or more.

[0033] A heat sink with a measuring function according to yet another embodiment is characterized in that the machined cavity is substantially cylindrical and has a diameter of 0.5 to 2.5 mm, more preferably 0.5 to 2.0 mm, and even more preferably 0.5 to 1.5 mm. Heat sinks according to these embodiments have been demonstrated to exhibit higher resistance to the pressures typically applied in induction welding of molded parts, even after multiple uses, compared to heat sinks with larger cavities. Furthermore, the dimensions of these embodiments have been demonstrated not to significantly affect the heat dissipation characteristics of the heat sink, particularly when the dimensional gap is an air gap.

[0034] Further embodiments with improved performance relate to a heat sink with a measuring function in which the tolerance for cross-sectional dimensions, such as the diameter of at least one cavity, is not zero but is at most 0.5 mm, more preferably at most 0.25 mm, and even more preferably at most 0.2 mm. This relatively narrow tolerance improves the smoothness of the wall surface of at least one cavity, which is beneficial in reducing friction between the outer surface of a sensing device provided in at least one cavity and the wall of the cavity.

[0035] The positioning of the sensing device, housed in at least one cavity, can be selected according to the specific shape of the heatsink and / or molded part. According to one embodiment, a heatsink with a measuring function is provided. This heatsink has a predetermined thickness, and the minimum distance between the machined cavity and the outer surface of the heatsink intended to contact any of the molded parts is at most half the thickness of the heatsink, preferably at most one-third the thickness of the heatsink, and more preferably one-quarter the thickness of the heatsink. Another preferred minimum distance between the machined cavity and the outer surface of the heatsink intended to contact any of the molded parts is 0.25 to 1.5 mm, more preferably 0.25 to 1 mm, and even more preferably 0.25 to 0.75 mm. Preferably, the cavity or group of cavities does not extend to the outer surface of the heatsink, as such a cavity or group of cavities may leave marks on the contact surface of the molded part, which is undesirable.

[0036] The heat sink with measurement function according to the present invention can accommodate all types of detection devices. A suitable embodiment is a heat sink with measurement function in which the detection device includes a thermocouple, an optical fiber sensor (preferably a fiber Bragg grating sensor), or a combination of both.

[0037] Depending on the type of detection device selected, it is reasonable to select the location of the cavity or group of cavities. In an embodiment of the present invention, a heat sink with a measurement function is provided, wherein the detection device is a thermocouple, and the machined cavity extends from the outer surface of the heat sink at an angle other than zero, preferably substantially perpendicular to the outer surface, intended not to come into contact with either of the molded parts.

[0038] In a preferred embodiment, the distance between the bottom surface of the machined cavity and the outer surface of the heatsink intended to contact one of the molded parts is at most half the thickness of the heatsink, preferably at most one-third the thickness of the heatsink, and more preferably one-quarter the thickness of the heatsink. Another preferred distance between the bottom surface of the machined cavity and the outer surface of the heatsink intended to contact one of the molded parts is 0.25 to 1.5 mm, more preferably 0.25 to 1 mm, and even more preferably 0.25 to 0.75 mm. Preferably, the cavity or group of cavities does not extend to the outer surface of the heatsink, as such a cavity or group of cavities may leave marks on the contact surface of the molded part, which is undesirable.

[0039] The heat sink according to the present invention comprises one or more sensing devices housed in one or more machined cavities. Naturally, the sensing devices need to be connected to auxiliary equipment such as a power supply, a computer, and measuring devices such as voltmeters and ammeters. In some embodiments, the sensing devices extend from one end of the heat sink to the other, and the connection between the sensing devices and the auxiliary equipment may be located at the end of the heat sink or further outside the heat sink. In other embodiments, for example, when a thermocouple is used as the sensing device, the sensing devices may extend only inside the heat sink. In such embodiments, appropriate wiring must be installed within the contour of the heat sink to connect the sensing devices and the auxiliary equipment. Therefore, in a given embodiment, the heat sink with measuring function comprises machined wiring slots for housing the wiring. The wiring slots extend between the cavity and the end of the heat sink, allowing the sensing devices housed in the cavity to be connected to auxiliary equipment located outside the heat sink.

[0040] According to another embodiment, a heat sink with a measuring function is provided, further comprising two machined wiring slots for each machined cavity, the wiring slots positioned on the outer surface of the heat sink intended not to come into contact with either of the molded parts, each machined wiring slot extending from the machined cavity to the end of the heat sink with a measuring function, and the wiring slots not intersect with each other. This embodiment has been found to be used preferably in combination with thermocouples and to significantly reduce interference between the applied electromagnetic field during induction welding and temperature measurement by the sensing device. In a more preferred heat sink with a measuring function, the width of the machined wiring slots is 0.5 to 2 mm, more preferably 0.5 to 1 mm, and even more preferably 0.5 to 0.75 mm, and the depth is 0.5 to 2 mm, more preferably 0.5 to 1 mm, and even more preferably 0.5 to 0.75 mm.

[0041] In yet another embodiment, a measuring heatsink is proposed in which the sensing device is a fiber Bragg grating (FBG) sensor, and the machined cavity extends from one end of the heatsink toward another end of the heatsink, substantially parallel to the outer surface of the heatsink intended to contact one of the molded parts. This other end may be the end that contacts the end of the heatsink where the machined cavity begins, or it may be the end opposite to the end of the heatsink where the machined cavity begins.

[0042] Fiber Bragg grating (FBG) sensors, well known to those skilled in the art, are a type of distributed Bragg reflector constructed within an optical fiber that reflects light of specific wavelengths and transmits all other wavelengths. This is achieved by causing a periodic change in the refractive index of the optical fiber core, thereby forming a number of sensing elements. FBG sensors have been found to be advantageously usable in induction welding. In fact, when an inductively sensitive component (e.g., carbon fiber) in a molded part is heated, the heat is dissipated to a heat sink with measuring capabilities and a fiber Bragg grating (FBG) sensor located in a machined cavity within the heat sink. When an optical fiber is heated, the fiber expands, and the refractive index of the optical fiber core also changes, causing a shift in the Bragg wavelength. The higher the temperature, the greater the expansion of the optical fiber and the greater the wavelength shift. This increase in wavelength shift is first detected by the sensing element closest to the inductor, and then by another sensing element located further downstream in the welding direction.

[0043] The length of each sensing element within the optical fiber can be selected according to the requirements of each case. However, embodiments of heat sinks with measurement functions that include an FBG sensor having sensing elements with lengths of 1 to 25 mm, more preferably 1 to 15 mm, and even more preferably 1 to 5 mm have been shown to improve performance. Shorter lengths are also possible.

[0044] The lateral dimensions of at least one cavity and the optical fiber sensor can be selected within a predetermined range, for example, depending on the dimensions of the heat sink or molded part. Preferably, the at least one cavity should not be too large so as not to excessively reduce the strength of the heat sink. On the other hand, the at least one cavity should be large enough to accommodate the detection device by, for example, inserting it into the at least one cavity from the entrance side and pushing it through the cavity for a portion of its length. The detection device does not need to be inserted for the entire length of the cavity, but may be accommodated in only a portion of the cavity's length, for example, in a range of at least 50%, more preferably at least 75%, and even more preferably at least 90% of the cavity's length.

[0045] In a preferred embodiment of the heat sink with measurement function, the ratio of the lateral dimension of the optical fiber sensor to the lateral dimension of the machined cavity is between 1:2 and 1:50, more preferably between 1:4 and 1:20, and even more preferably between 1:5 and 1:10.

[0046] When using ceramic heat sink materials, particularly boron nitride / aluminum nitride composite materials, it has been found that the surface of molded parts that come into contact with the heat sink is prone to contamination with undesirable residues. In response to this, a heat sink with a measurement function according to one embodiment is proposed. In this heat sink, the outer surface of the heat sink intended to come into contact with any of the molded parts is coated with a heat-resistant polymer coating or film, preferably a polyimide film or polysilazane coating.

[0047] A heat sink with a measurement function may be continuous in that it extends as a single piece over most of the surface of the molded part to be welded. In another embodiment, a heat sink with a measurement function may be provided in which a plurality of heat sink tiles are arranged adjacent to each other in parallel, preferably provided within a holder plate. The heat sink tiles are available only in the form of small tiles, for example, 50 × 50 mm or 25 × 100 mm. In such embodiments, each heat sink tile is provided with a machined tile cavity, and the machined tile cavities of adjacent heat sink tiles are aligned to form a heat sink cavity, preferably extending from one end of the heat sink to the other. However, some tiles of the heat sink may not have machined cavities. This may occur, for example, at the ends of the heat sink as needed.

[0048] The heat sink can be milled in a later process to achieve even tighter final tolerances. When it is necessary to form a relatively long welding line, it is common to arrange a series of tiles on a so-called heat sink holder plate. However, in this case, heat transfer between the tiles is relatively poor, resulting in temperature differences along the welding line. Using the heat sink of the present invention, heat conduction can be made much more uniform.

[0049] The heatsink can be used as is or fixed to a heatsink support element such as a support plate. The support element is preferably made of a heat-resistant material similar to that used for the heatsink body, but it must not be conductive. If reinforcing fibers are used in the support element, they are non-conductive and therefore preferably include glass fibers. Another suitable material for the support element is mikanite, which is a sheet or molded material consisting of relatively thin flakes (or layers) of mica bonded together with a binder such as shellac, epoxy, alkyd, or silicone resin. Strips of mikanite can also be used to prevent the matrix material from being extruded from the molded part during induction heating. Such strips are usually placed on the side edges of the molded part.

[0050] To further enhance the beneficial effects of the heat sink of the present invention, a heat sink with a measurement function according to one embodiment further comprises means for actively cooling the heat sink with the measurement function. This makes it possible to control the temperature of the welding interface more effectively.

[0051] The heat sink of the present invention can be advantageously used in induction welding of molded parts. Accordingly, according to a second aspect, a method is provided for joining the surface of a first molded part and the surface of a second molded part by temperature-controlled electromagnetic welding, the method comprising the following steps: • Prepare first and second molded parts including a heat-meltable bonding material and an induction-sensitive component. • Applying pressure to the surfaces to be connected by bringing the surfaces to be connected into contact with each other and bringing the pressure surface of the pressurizing body into contact with the molded part. - Using an inductor that moves in the welding direction, an electromagnetic field is generated at least on the surface of the molded parts to be joined, thereby heating an inductively sensitive component and causing the bonding material at the welding interface to thermally melt. - To cool the outer surface of the first molded part by providing the heat sink with measurement function described in the claim, in direct contact with the outer surface of the first molded part, and optionally such that the arrangement of detection devices (such as thermocouples and / or fiber Bragg grating sensors) extends substantially parallel to the welding direction. • Measure the temperature using a detection device and calculate the temperature of the welding interface based on that measurement. • Controlling welding parameters to control the temperature of the welding interface, and - Joining molded parts under pressure using molten, heat-meltable bonding material. Includes.

[0052] The array of detection devices may extend along any direction. Preferably, the array of detection devices extends along the longitudinal direction of the heat sink, which may be parallel to the welding direction. In another preferred embodiment, the array of detection devices extends along the transverse direction of the heat sink, which may be in the welding width direction.

[0053] According to an embodiment of the present invention, a method for temperature-controlled electromagnetic welding is provided, where the welding parameters are the electromagnetic field intensity of the inductor, the flow rate of the coolant, or a combination thereof.

[0054] A particularly preferred embodiment according to a second aspect of the present invention provides a method for temperature-controlled electromagnetic welding. In this method, the sensing device includes an FBG sensor, and the temperature measurement includes measuring the optical wavelength shift of laser light propagating from the end of the FBG sensor to the sensing element, where the measured temperature is calculated based on the difference between the optical wavelength shift measured during welding and a reference optical wavelength shift measured before welding.

[0055] Needless to say, this method can be carried out using any device useful for its implementation. For example, a computer (or computer-readable medium) can be used that contains programmed instructions that, when executed by a processor, operate to carry out this method in a second aspect. Such a computer can also be used to store temperature and other data and to perform calculations such as estimating the temperature of a welding line or welding area based on data generated by sensing devices such as thermocouples, optical fibers, or a combination thereof.

[0056] A third aspect of the present invention relates to an apparatus for joining the surface of a first molded part and the surface of a second molded part along the welding direction by temperature-controlled electromagnetic welding, wherein the first and second molded parts include a heat-meltable bonding material and an inductively sensitive component, and the apparatus is An inductor provided on at least the surface to be joined of a molded part to generate an electromagnetic field along the welding direction, thereby heating an inductively sensitive component to thermally melt the bonding material at the welding interface, A heat sink with a measuring function as described in the claim, wherein the heat sink is arranged along the welding direction, its outer surface is in contact with either one of the molded parts, and the heat sink is positioned between the inductor and the molded part, • A pressurizing body provided for pressurizing the surface to be connected, A control device configured to measure the temperature inside the heat sink using at least one sensing device, calculate the temperature of the welding interface based on that temperature, and control the welding parameters, It is equipped with.

[0057] The first and / or second molded parts can be conveniently manufactured by a fiber-reinforced composite material comprising reinforcing fibers such as carbon fibers, graphite fibers, and / or glass fibers, and a matrix material in which the reinforcing fibers are embedded. The matrix material preferably comprises a thermoplastic polymer. Examples of matrix materials suitable for reinforcing fibers include, but are not limited to, polyamides, polyimides, polyethersulfones, polyaryletherketones (PAEKs) (e.g., low-melting-point polyaryletherketones (LM PAEK), polyetheretherketones (PEEK), and polyetherketoneketones (PEKK)), polyurethanes, polyphenylene sulfide (PPS), polyamide-imides, polycarbonates, polyphenylene oxide blends (PPOs), and mixtures and copolymers of one or more of the above polymers. Fiber-reinforced composite materials typically contain 25% to 60% fibers by volume.

[0058] The first and / or second molded parts may include, for example, fiber-reinforced composite layers in the form of a woven fabric. These layers preferably contain substantially continuous fibers (so-called UD materials) that extend mainly in one direction at angles of 0°, 90°, and / or 45° with respect to a reference direction. These layers are preferably arranged symmetrically with respect to the intermediate plane of the laminate. It is advantageous to use the fiber-reinforced composite layers in the form of a prepreg (pre-impregnated semi-finished product). Such "prepregs" generally exhibit good mechanical properties, in particular, because the fibers are pre-impregnated with a matrix polymer. Laminates of UD-reinforced fibers having a PPS and / or PAEK polymer matrix are particularly preferred. Toray TC1225 is an example of a very suitable PAEK polymer matrix.

[0059] The heat sink is positioned between the inductor and the pressure surface, preferably in direct contact with both. The heat sink material is configured to dissipate heat from the surroundings. The heat sink functions as a passive heat exchanger, transferring heat generated on the upper part of the molded component to the surrounding air or to a cooling means provided on or inside the inductor. It is also possible to provide a heat sink (second heat sink) in contact with the surface of the molded component opposite to the pressure surface facing the inductor. In this case, the heat sink is positioned between the opposite surface and a counter-pressure system, for example, made of an expandable rubber element. This configuration is particularly advantageous when the molded component facing away from the inductor is relatively thin. Such thin molded components are prone to melting.

[0060] The shape of the inductor (such as the cross-sectional shape) can, in principle, be selected as needed. For example, the cross-section can be triangular or circular. A useful embodiment is a device in which the inductor has a rectangular cross-section.

[0061] The three-dimensional shape of the inductor can also be selected as needed. This may be important in some embodiments described later, as the inductor may need to heat not only the molded part at the welding location but also other parts of the device. Therefore, in some embodiments, it may be necessary to extend the electromagnetic field.

[0062] The apparatus according to the present invention applies pressure to a molded part to be welded using a pressurizing body. Another embodiment of the apparatus includes passive or active counter-pressurizing means on the side of the molded part to be joined, opposite to the pressurizing surface.

[0063] In practical embodiments, the device is mounted as an end effector on the tip of a robotic arm or other tool. This allows for precise positioning of the inductor on the joined part in order to define and execute the welding path.

[0064] The appropriate power and frequency can be determined depending on the materials used, particularly the inductively sensitive component and the distance between the inductor and the component. The frequency, in particular, determines the penetrating force of the electromagnetic field. The power of the inductor determines the strength of the fluctuating electromagnetic field, and thereby the degree of heat generated within the inductively sensitive component.

[0065] The Foucault currents or eddy currents induced on the surface to be connected are limited by the shape of the molded part. Edges, corners, and holes in the molded part can affect the distribution of Foucault currents and, consequently, the amount of heat generated. Such disturbances in the electromagnetic field can result in parts that do not need to be heated during the welding process being heated. Conversely, areas that are difficult to heat may be created. These problems can be solved by repositioning the boundaries of the region where Foucault currents begin to be generated at a given location on the thermoplastic molded part. This preferred embodiment makes it possible to heat areas that were previously difficult to heat and prevents high temperatures in undesirable locations.

[0066] In the application of the method described in the claims of the present invention, the inductor is connected to an AC generator, which is electrically connected to the electrical connection means of the inductor. The usable frequency range is generally in the range of 0.1 to 10 MHz. Preferably, a frequency of 0.1 to 0.5 MHz is used, and more preferably, a frequency of 0.15 to 0.4 MHz is used. At such preferred frequencies, an optimal balance is obtained between the penetration force of the electromagnetic field and the heating rate.

[0067] The method of using the heat sink described in the claims according to the present invention can join first and second molded parts of any shape. For example, the first molded part may include an aircraft skin, and the second molded part may include a reinforcing member for supporting the skin. Other examples include aircraft window frames, fuel tank covers, and components of wind turbines.

[0068] Embodiments of the present invention will be described with reference to the following drawings, but are not limited thereto. [Brief explanation of the drawing]

[0069] [Figure 1] A schematic perspective view shows a welding system that can be used in the method according to an embodiment of the present invention. [Figure 2] A schematic cross-sectional view of one step of an induction welding method according to an embodiment of the present invention is shown. [Figure 3A] A schematic perspective top view of a heat sink tile according to an embodiment of the present invention is shown. [Figure 3B] A schematic perspective top view of a heat sink tile according to another embodiment of the present invention is shown. [Figure 3C] Figure 3A shows a cross-sectional view of the heat sink tile and a schematic diagram of the steps of the induction welding method according to an embodiment of the present invention. [Figure 3D] Figure 3C shows a schematic, detailed cross-sectional view of the cavity in the heat sink tile. [Figure 4] A schematic plan view of a heat sink comprising a plurality of heat sink tiles arranged adjacently within a holder plate, according to another embodiment of the present invention, is shown. [Figure 5] This graph shows the temperature detected by a thermocouple during induction welding according to an embodiment of the present invention. [Figure 6A] A schematic perspective top view of a heat sink tile according to an embodiment of the present invention is shown. [Figure 6B] Figure 6A schematically shows a perspective top view of the heat sink tile, cut along a plane extending in the welding direction, exposing the cavity and optical fiber housed within. [Figure 6C] Figure 6A shows a cross-sectional view of the heat sink tile and a schematic diagram of the steps of the induction welding method according to an embodiment of the present invention. [Figure 7] Figure 6A schematically shows a plan view of a heat sink in which a plurality of heat sink tiles, as shown in Figure 6A, are arranged adjacently within a holder plate, cut along a plane extending in the welding direction, and the cavities and optical fibers housed therein are exposed. [Figure 8]A schematic perspective top view of a heat sink tile according to yet another embodiment of the present invention is shown. [Figure 9] An embodiment of the present invention shows a device for holding a heat sink or heat sink tile during machining of a cavity. [Figure 10] This shows a setup with a measurement function for a molded part according to an embodiment of the present invention. [Figure 11] This graph shows the temperature detected by a thermocouple and a fiber Bragg grating sensor during induction welding according to an embodiment of the present invention. [Figure 12] A flowchart of induction welding according to an embodiment of the present invention is shown. [Figure 13] Several assembly structures of a heat sink tile and holder plate according to an embodiment of the present invention are schematically shown. [Figure 14] Several assembly structures of a heat sink tile and holder plate according to an embodiment of the present invention are schematically shown. [Figure 15] Several assembly structures of a heat sink tile and holder plate according to an embodiment of the present invention are schematically shown. [Figure 16] Several assembly structures of a heat sink tile and holder plate according to an embodiment of the present invention are schematically shown. [Modes for carrying out the invention]

[0070] Description of Exemplary Embodiments Figure 1 shows a welding system 5 equipped with a device 1 that can be used in a method according to an embodiment of the present invention. The device 1 functions as an end effector for a robot arm 50, which is part of an industrial 6-axis robot 51. It should be noted that the robot arm 50 is not essential to the present invention, and other means of movement for the device 1, such as a static actuator, may also be envisioned. The robot 51 is programmed to move the robot arm 50 and the end effector device 1 along a path toward the assembly of molded parts (2, 3) to be welded, or at locations where spot welding is required. An inductor 11 (see Figure 2) incorporated in the device 1 is connected to and operates in conjunction with an AC generator 52 located on the robot 51 to generate an electromagnetic field. However, the AC generator 52 may be located elsewhere. In the illustrated embodiment, the opposing pressurizing means 4 is provided on the side of the molded parts (2, 3) to be joined, opposite to the side toward the assembly (2, 3) toward the robot arm 50. This opposing pressurizing means 4 may be configured as a solid, or it may be operable in the sense that it can be pressed against the side surface of the molded parts (2, 3) to be joined, for example, when configured as an expandable bellows.

[0071] As shown in detail in Figure 2, a suitable system for joining the surfaces of molded parts (2, 3) by electromagnetic welding comprises a pressurizing body 10. This pressurizing body 10 may be a solid block of a high-temperature nonmetallic material, or it may be composed of other forms as long as it can apply pressure to the substrate. The pressurizing body 10 in Figure 2 has two sides (101a, 101b) in addition to the pressurizing surface 100, and a top surface 102 facing the pressurizing surface 100. As shown in the figure, the pressurizing body 10 further has a central pocket 103 from which an inductor 11 can move along the welding path. The pressurizing body 10 works in cooperation with the opposing pressurizing means 4 to pressurize the assembly of molded parts (2, 3) during induction welding.

[0072] As shown in Figure 2, the inductor 11 is positioned in the central pocket 103 of the pressurizer 10 so that it can be brought as close as possible to the outer surface 21 of the molded part 2. The inductor 11 is moved by the robot arm 50 while maintaining a small distance from the outer surface 21, and during movement, it generates an electromagnetic field 12 at least at the contact surfaces (20, 30) of the molded parts (2, 3) to be welded. In the illustrated embodiment, the inductor 11 has a cylindrical cross-section and further includes a linear segment configured to generate a substantially cylindrical electromagnetic field at least a portion of the contact surfaces (20, 30) to be connected of the molded parts (2, 3). In this way, the electromagnetic field can be concentrated so as not to spread too far beyond the welding location. The linear segment shown in Figure 2 extends substantially parallel to the pressurizing surface 100 of the pressurizer 10. One or more inductors may be used.

[0073] A shield 13 may be provided around at least a portion of the inductor 11. This shield is configured to prevent overheating and / or to concentrate the electromagnetic field to achieve deeper fusion. For this purpose, it is made from a suitable insulating material such as Fluxtrol®.

[0074] The apparatus 10 of the present invention further comprises a heat sink 6 provided between the inductor 11 and the outer surface 21 of the first molded part 2, and between the pressure surface 100 and the outer surface 21 of the first molded part 2. The heat sink 6 is usually a separate body and is positioned to be in direct contact with the pressure surface 100 and the outer surface 21. The heat sink 6 can be embodied as a plate-like structure extending along the weld line with a length covering at least the weld length and a width 106 covering at least the weld width. As schematically shown in Figure 2, the heat sink 6 is provided with at least one cavity 70 capable of housing a sensing device such as a thermocouple or an optical fiber, as will be described later.

[0075] The heat sink 6 is made from a material having the thermal conductivity described in the claim. Its rigidity and / or hardness may be selected so that one or more cavities do not substantially deform even when subjected to repeated pressures of, for example, 7-8 bar at high temperatures of 500°C or higher, which are typically used in induction welding. A very suitable material is a boron nitride / aluminum nitride (BN / AlN) composite material, such as Aremcolox 502-1820, available from Aremco. The thermal conductivity of this material is approximately 85 W / (m·K).

[0076] In the first step (Figure 2), the apparatus 1 is positioned near the first molded part 2 and the second molded part 3, which need to be joined by electromagnetic welding. The molded parts (2, 3) are assembled and positioned between the pressurizing body 10 and the opposing pressurizing means 4. As shown in the figure, a heat sink 6 is positioned on top of the assembly of molded parts (2, 3). The molded parts (2, 3) include a heat-meltable bonding material and an inductively sensitive component that is heated under the influence of an electromagnetic field generated by the inductor 11. Therefore, the molded parts (2, 3) can be manufactured from a thermoplastic polymer reinforced with carbon fibers. In this case, the carbon fibers may function as the inductively sensitive component, and the thermoplastic polymer may function as the heat-meltable bonding material. The first molded part 2 may represent the outer skin of an aircraft, while the second molded part 3 has a folded edge and may represent, for example, a reinforcing material. Naturally, both molded parts (2, 3) may have any other arbitrary shape, such as being curved.

[0077] A further step involves moving the inductor 11 along the welding path while generating an electromagnetic field at least at the contact surfaces (20, 30) of the molded parts (2, 3) to be joined. This heats the carbon fibers within the molded parts (2, 3), thereby heating, and possibly melting, the thermoplastic polymer in volume 12 that covers a portion of the contact surfaces (20, 30) of both molded parts (2, 3). The temperature within volume 12 may not be uniform throughout, with only the central portion of the volume being above the melting point of the thermoplastic polymer. Naturally, the temperature of volume 12 is highest when the inductor 11 is directly above it. Downstream of the inductor 11 along the welding path, the temperature within volume 12 located upstream of the inductor decreases, causing the thermoplastic polymer to solidify. A heat sink 13 provided on one of the two molded parts (20, 30) plays an important role in concentrating heat in the necessary areas (around the welding path) and dissipating heat from unwanted areas. For this reason, a cylindrical electromagnetic field is preferred. The assembled molded parts (2, 3) are heated to a temperature high enough to melt the thermoplastic polymer, causing the two molded parts (2, 3) to fuse together, at least in the region along the weld path. During and / or optionally immediately thereafter, it is preferable to press the contact surfaces (20, 30) against each other using the pressurizer 10 and the opposing pressurizer 4 to achieve the joint between the molded parts (2, 3). The joined assembly (2, 3) can then be removed from the welding system.

[0078] In one embodiment used for spot welding, the pressurizing body 10 may be incorporated into the apparatus 1, and the heat sink 6 may also be associated with the apparatus 1.

[0079] Figure 3A shows a heat sink tile 7 with a measurement function according to an embodiment of the present invention. As will be further detailed in the description of Figure 4, a heat sink 6 can be formed by arranging a plurality of such heat sink tiles 7 with measurement functions in a holder. The heat sink 6 is used in a method of joining two molded parts (2, 3) by electromagnetic welding, as described above. Each heat sink tile with measurement function 7 is surrounded by a surface 701 provided to contact a pressurizing body 10 (see Figure 2) and a surface 702 provided on the opposite side of surface 701 to contact the upper surface 21 of the molded part 2 (see Figure 2). Surface 702 may include a high-temperature polymer coating or film to prevent discoloration of the molded part and / or to extend the service life of the heat sink tile with measurement function. This polymer coating or film is preferably a polyamide film or a polysilazane coating. Furthermore, the heat sink tile 7 with measuring function has two side edges (703, 704) extending substantially parallel to the welding direction 40, and two edges (705, 706) extending substantially parallel to the welding width direction 41 perpendicular to the welding direction 40. To form the heat sink 6, multiple heat sink tiles 7 with measuring function are arranged so as to be in contact with each other along their edges (705, 706). In this way, an elongated heat sink 6 with measuring function is formed that extends along the welding path in the welding direction 40.

[0080] In one embodiment of the present invention shown in Figures 3A and 3C, the heat sink tile 7 with measuring function comprises one or more machined cavities 70 extending from and substantially perpendicular to the surface 701, as is evident from Figure 3C. As is evident from Figure 3D, the machined cavities 70 are provided for housing a sensing device, typically a thermocouple 8, for measuring the temperature at a location within the cavities 70.

[0081] Each machined cavity 70 is preferably substantially cylindrical, with a diameter 75 in the range of 0.5 to 2.5 mm, preferably 0.5 to 2.0 mm, and more preferably 0.5 to 1.5 mm. The diameter should be large enough to accommodate the sensing device, but ideally it should be as small as possible to maximize the amount of heat sink material that can absorb heat during welding. Preferably, the tolerance of the diameter 75 (or other lateral dimension) of each machined cavity 70 is not zero, but a maximum of 0.5 mm, more preferably a maximum of 0.25 mm, and even more preferably a maximum of 0.2 mm. Such tight tolerances reduce the risk of malfunction of the heat sink 6. Methods for achieving the desired tight tolerances can be described later with reference to Figure 9.

[0082] In the embodiments shown in Figures 3A and 3C, the machined cavities 70 are arranged along a virtual line 45 extending substantially parallel to the welding direction 40. This configuration allows for temperature measurement at three different locations along the welding path in the welding direction 40 for each heat sink tile 7. Furthermore, each heat sink tile with measurement capabilities 7 is provided with two machined wiring slots (73, 74) located within the surface 701 for each machined cavity 70. The machined wiring slot 73 extends from each machined cavity 70 to the edge 703 of the heat sink tile with measurement capabilities, while the machined wiring slot 74 extends from each machined cavity 70 to the edge 704 of the heat sink tile with measurement capabilities 7. The paths of the wiring slots (73, 74) from the machined cavities 70 to the edge 703 or edge 704 may be of any shape, as long as they do not intersect themselves or with other wiring slots (73, 74). Each path is preferably the shortest distance between the machined cavity 70 and the edge 703 or edge 704. The width of the machined wiring slot can be, for example, 0.5 to 2 mm, specifically 0.5 to 0.75 mm. The depth of the machined wiring slot can also be, for example, 0.5 to 2 mm, specifically 0.5 to 0.75 mm. The dimensions of the wiring slot are selected so that the wiring of the sensing device can be embedded within the wiring slot and substantially all of the wiring is located below the surface 701. This prevents compression of the wiring by the pressurizer 10 and prevents contact between the wiring and the device 1 during electromagnetic welding, thereby contributing to extending the service life of the sensing device and / or heat sink with measuring function. In other embodiments (see, for example, Figure 15), the wiring slot may instead be provided within the holder plate.

[0083] Figure 3B shows a heat sink 7 with a measurement function according to another embodiment of the present invention. This embodiment comprises a plurality of machined cavities 70 arranged on a straight line substantially parallel to the welding width direction 41 and substantially perpendicular to the welding direction 40. Furthermore, the heat sink 7 with a measurement function comprises two machined wiring slots (73, 74) on the surface 701 of the machined cavities 70 located substantially equidistant from the sides (703, 704), with one machined wiring slot 73 extending from the machined cavity 70 to the edge 703 and the other machined wiring slot 74 extending from the machined cavity 70 to the edge 704. For the machined cavity 70 closest to the edge 703, two wiring slots 73 are preferably provided, extending from the machined cavity 70 to the edge 703, while for the machined cavity 70 closest to the edge 704, two wiring slots 74 are preferably provided, extending from the machined cavity 70 to the edge 704. In other embodiments not shown, the wiring slots for machined cavities 70 closer to either the edge 703 or the edge 704 may also be arranged such that one wiring slot 73 extends from the machined cavity 70 to the edge 703 and the other wiring slot 74 extends from the machined cavity 70 to the edge 704. The paths that the wiring slots (73, 74) take from the machined cavity 70 to the edge 703 or edge 704 can be of any shape, as long as they do not intersect themselves or intersect with other wiring slots (73, 74). This path is preferably the shortest distance between the machined cavity 70 and the edge 703 or edge 704.

[0084] Figure 3C shows a cross-sectional view of one step of a welding method according to another embodiment of the present invention. The heat sink with measuring function comprises a heat sink tile 7 held in a heat sink holder plate (not shown). The heat sink tile 7 has a thickness of 707. A machined cavity 70 inside the heat sink tile 7 with measuring function extends substantially perpendicularly from a surface 701 that contacts a pressurizing body 10 (not shown). The minimum distance 708 between the machined cavity 70 and the surface 702 that contacts the surface 21 of the molded part 2 is at most half the thickness 707 of the heat sink tile 7. Preferably, the minimum distance 708 is 0.25 to 1.5 mm, more preferably 0.25 to 1 mm, and even more preferably 0.25 to 0.75 mm. The machined cavity 70 can house a sensing device (not shown), typically a thermocouple, for measuring the temperature at a location within the cavity. Figure 3C is a cross-sectional view of the heat sink 6 with measuring function through a vertical intermediate plane. Although the machined cavity 70 may appear to have an open front, in some embodiments it is surrounded by the material of the heat sink tile 7 with measuring function, such as a central cylindrical cavity provided in a solid block.

[0085] Figure 3D reproduces a portion of the cross-sectional view of Figure 3C, showing in detail the position of the sensing device inside the machined cavity 70. The thermocouple 8 is positioned inside the machined cavity 70 such that a dimensional gap 70a exists between the thermocouple 8 and the wall 70b of the cavity 70. The dimensional gap 70a may be an air gap, i.e., filled with (ambient) air. In other embodiments, the dimensional gap 70a may be filled with a material different from the material of the heat sink tile 7, such as a potting compound. Each thermocouple 8 includes dissimilar conductors (8a, 8b) that contact at a measuring contact 8c, as is well known to those skilled in the art. Each thermocouple 8 is connected to an electrical wiring system and a voltmeter (not shown), as is well known to those skilled in the art. By placing an insulating element, such as a polyimide film (not shown), between the conductors (8a, 8b) in the machined cavity 70, the risk of short circuits in the wiring can be eliminated.

[0086] Figure 4 schematically shows a heat sink 6 with a measurement function, comprising a plurality of heat sink tiles arranged adjacent to each other in parallel within a holder plate 80, according to an embodiment of the present invention. The heat sink 6 with a measurement function comprises heat sink tiles with a measurement function (7-1 to 7-5) and heat sink tiles without a measurement function (7'). In other embodiments, the heat sink with a measurement function may consist only of heat sink tiles with a measurement function. The holder plate 80 includes holder plate end brackets 81 that hold the heat sink tiles within the holder plate 80. Furthermore, the holder plate 80 has a groove (not shown) along its centerline. This groove is aligned with a central pocket 103 for receiving the apparatus 1 during electromagnetic welding, thereby allowing the pressurized surface 100 of the apparatus 1 to make direct contact with the surface of the heat sink tiles (7-1 to 7-5, 7').

[0087] The heat sink 6 with measuring function shown in Figure 4 comprises five heat sink tiles with measuring function (7-1 to 7-5) and 22 heat sink tiles without measuring function 7'. Each heat sink tile with measuring function (7-1 to 7-5) has a layout equivalent to that of the heat sink 7 in Figure 3A and contains three sets of thermocouples within three machined cavities 70. Each machined cavity 70 of the heat sink tiles with measuring function 7-1 to 7-5 can house a thermocouple for measuring the temperature at a specific location within the cavity. The machined cavities 70 of each heat sink tile with measuring function are arranged such that a parallel arrangement of heat sink tiles comprising multiple heat sink tiles forms an arrangement of at least one machined cavity 70 arranged in a straight line substantially parallel to the welding direction 40. The heat sink 6 with measuring function shown in Figure 4 comprises 15 machined cavities 70 arranged in a row parallel to the welding direction 40 along the centerline of the heat sink 6.

[0088] In other embodiments not shown, the heat sink tile with measuring function may have a layout as shown in Figure 3B, or any other layout that satisfies the requirements of the claims. In embodiments in which the heat sink 6 with measuring function comprises a heat sink tile having an arrangement equivalent to that of the heat sink tile 7 in Figure 3B, the machined cavities 70 are arranged on three straight lines parallel to the welding direction 40, one of which is located on the centerline of the heat sink 6 along the welding direction 40, and the other two are arranged equally spaced on either side of the centerline.

[0089] Each heat sink tile with measurement function (7-1 to 7-5) has two machined wiring slots 73 and 74 in each machined cavity 70, the machined wiring slot 73 extending from the machined cavity 70 to the edge 603 of the heat sink 6 with measurement function, and the machined wiring slot 74 extending from the machined cavity 70 to the edge 604 of the heat sink 6 with measurement function. The holder plate 80 has at least one wiring slot 83 on the side 603 of the heat sink 6 and at least one wiring slot 84 on the side 604, where the wiring slots (83, 84) extend from the edge 605 of the heat sink 6 with measurement function and terminate at the edge 606. Each machined wiring slot 73 of the heat sink tiles with measurement functions (7-1 to 7-5) terminates in a wiring slot 83 of the heat sink holder plate, and each machined wiring slot 74 of the heat sink tiles with measurement functions (7-1 to 7-5) terminates in a wiring slot 84 of the heat sink holder plate. The wiring slots (83, 84) of the holder plate can accommodate wiring extending from multiple heat sink tiles with measurement functions (7-1 to 7-5). The machined wiring slots (73, 74) of the heat sink tiles with measurement functions (7-1 to 7-5) may instead be provided within the holder plate 80.

[0090] Figure 4 is a schematic diagram of the heat sink 6 with measuring function, viewed from the surface that contacts the surface 21 of the molded part 2 (not shown). The machined cavities 70 and machined wiring slots 73, 74 are shown schematicly, but in embodiments they are housed within the heat sink tiles with measuring function (7-1 to 7-5). Similarly, the wiring slots 83 and 84 are shown schematicly, but in embodiments they are enclosed within the material of the holder plate 80. The heat sink 6 with measuring function in Figure 4 was used in an electromagnetic welding experiment. A thermocouple was placed in each machined cavity 70, and additional thermocouples were placed on and between the molded parts (20, 30). Specifically, five thermocouples were placed between the contact surfaces (20, 30) of the molded parts (2, 3), and one thermocouple was placed below each of the heat sink tiles 7-1 to 7-5 with measuring functions, along a line substantially perpendicular to the welding direction 40 and the welding width direction 41. Furthermore, four thermocouples were placed between the contact surface 21 of the molded part 2 and the heat sink 6 with measuring functions, and one thermocouple was placed below each of the heat sink tiles 7-2 to 7-5 with measuring functions, along a line substantially perpendicular to the welding direction 40 and the welding width direction 41. In this particular embodiment, due to the limitations of the experimental apparatus, no thermocouple was placed between the contact surface 21 of the molded part 2 and the heat sink 6 with measuring functions at a position below the heat sink tile 7-1 with measuring functions.

[0091] Figure 5 is a graph showing the temperature measured by a thermocouple during an electromagnetic welding experiment. The horizontal axis represents the elapsed time of the experiment (in seconds), and the vertical axis represents the measured temperature (°C). The temperature can be measured using any E-type thermocouple as long as there is a dimensional gap 70a between the thermocouple 8 and the wall 70b of the cavity 70, and the wiring is embedded in machined wiring slots 73 and 74, and substantially all of the wiring is positioned below the surface 701. In the experiment of this embodiment, Omega TT-E-40 thermocouple wire was used, and spot welding was performed for this experiment.

[0092] The temperature profiles measured by sets of three thermocouples housed within machined cavities in the heat sink tiles with measurement functions (7-1 to 7-5) are shown as groups of three dotted lines (92a to 92e). From left to right, the first three dotted lines 92a correspond to the temperatures measured by the three thermocouples inside the heat sink tile 7-1, the second three dotted lines 92b correspond to the temperatures measured by the three thermocouples inside the heat sink tile 7-2, and so on.

[0093] The dashed lines (91b~91e) represent the temperature profiles measured by thermocouples placed between the contact surface 21 of the molded part 2 and the heat sink 6 with measuring function. From left to right, the first dashed line 91b corresponds to the temperature measured by a thermocouple placed directly beneath the heat sink tile 7-2 with measuring function, the second dashed line 91c corresponds to the temperature measured by a thermocouple placed directly beneath the heat sink tile 7-3 with measuring function, and so on.

[0094] The dashed lines (90a to 90e) represent the temperature profiles measured by thermocouples placed between the contact surfaces (20, 30) of the molded parts (2, 3). From left to right, the first dashed line 90a corresponds to the temperature measured by a thermocouple placed under the heat sink tile 7-1 with measurement function, the second dashed line 90b corresponds to the temperature measured by a thermocouple placed under the heat sink tile 7-2 with measurement function, and so on.

[0095] During the experiment, apparatus 1 moves from left to right along the welding line in Figure 4. In Figure 4, this welding line is substantially parallel to the welding direction 40 along the centerline of the heat sink 6 with measuring function, and therefore passes substantially directly over each thermocouple. As the inductor 11 in apparatus 1 moves along the welding line, the electromagnetic field generated by the inductor 11 heats the inductively sensitive components in the molded parts (2, 3). As the inductor approaches the position of the heat sink tile 7-1 with measuring function, the inductively sensitive components near the thermocouple heat up, resulting in a temperature rise being measured by the thermocouple. This temperature rise is first detected by a thermocouple located in or beneath the heat sink tile 7-1 with measuring function, then by a thermocouple located in or beneath the heat sink tile 7-2 with measuring function, and so on. A slight time difference is observed between peaks 90a to 90e, 91b to 91e, and 92a to 92e, due to the time it takes for heat to propagate from the weld interface to the location of each sensing device. As the inductor passes the thermocouple's position and continues along the weld line, the magnetic field strength weakens, and the thermocouple measures the temperature decrease as the heat of the inductively sensitive component is gradually dissipated until it reaches equilibrium with the ambient temperature.

[0096] As can be seen in Figure 5, of the three locations where temperature is measured, the highest temperature (90a~90e) is measured by a thermocouple placed between the contact surfaces of the molded parts (20, 30), the second highest temperature (91b~91e) is measured by a thermocouple placed between the contact surface 21 of the molded part 2 and the heat sink 6 with measuring function, and the lowest temperature (92a~92e) is measured by a set of three thermocouples housed inside each heat sink tile with measuring function (7-1~7-5).

[0097] Thermocouples located inside or beneath the heat sink tiles 7-1 and 7-5 with measuring functions are located at or near the edges of the molded parts (20, 30) and are therefore affected by edge effects that cause the electromagnetic field to become non-uniform. As a result, less heat is induced in the inductively sensitive components, and the measured temperature is lower compared to the temperature measured by thermocouples located inside or beneath the heat sink tiles 7-2, 7-3, and 7-4 with measuring functions that are not affected by these edge effects.

[0098] A first correlation exists between the temperature measured by a thermocouple placed in a machined cavity of the heat sink and the temperature of the weld interface, and a second correlation exists between the electromagnetic field strength of the inductor 11 and the temperature of the weld interface. During electromagnetic welding, the temperature is measured by a thermocouple 8 placed in a machined cavity 70 of the heat sink 6, and the temperature of the weld interface is calculated using the first correlation. The second correlation is used to control the calculated temperature of the weld interface by adjusting the electromagnetic field strength of the inductor 11.

[0099] The first statistical correlation between interface temperature and heat sink temperature was performed by performing Pearson correlation analysis on the data using the Python module "scipy.stats.pearsonr". This is explained in more detail at https: / / docs.scipy.org / doc / scipy / reference / generated / scipy.stats.pearsonr.html, which is referenced in its entirety here. The Pearson correlation coefficient measures the linear relationship between two datasets. Like other correlation coefficients, this coefficient ranges from -1 to +1, with 0 meaning no correlation. A correlation coefficient of -1 or +1 indicates a perfectly linear relationship. A positive correlation means that both variables x and y increase, while a negative correlation means that y decreases as x increases.

[0100] As an example, the correlation was calculated between the temperature measurements of the central TC (curves 92a, 92b, 92c, 92d, and 92e) placed on each tile within a heat sink with measurement capabilities, and the temperature measurements of the TC at the weld interface (curves 90a, 90b, 90c, 90d, and 90e). Correlation analysis was performed between temperature measurements of TC placed at the same position along the welding direction (e.g., data 92a and 90a, 92b and 90b). The resulting correlation matrix is ​​shown in Table 1.

[0101] [Table 1] Table 1: Correlation between temperature measurements

[0102] These correlation coefficients demonstrate a good linear relationship between the central TC temperature measurements at each tile of the heat sink with measurement capabilities (curves 92a, 92b, 92c, 92d, 92e) and the actual temperature measurements of the TC at the weld interface (curves 90a, 90b, 90c, 90d, 90e).

[0103] Referring to Figure 6A, a heat sink tile with a measuring function 7 according to another embodiment of the present invention is shown. This heat sink tile with a measuring function 7 is used to connect two molded parts (not shown). The heat sink tile with a measuring function 7 has a surface 701 that contacts a pressurizing body 10 (see Figure 2) and a surface 702 that contacts the surface 21 of a molded part 2 (not shown) on the opposite side of surface 701. Furthermore, the heat sink tile with a measuring function 7 has two side edges (703, 704) extending substantially parallel to the welding direction 40 and two side edges (705, 706) extending substantially parallel to the welding width direction 41 perpendicular to the welding direction 40. To form a heat sink 6, a plurality of heat sink tiles with a measuring function 7 are arranged so as to be in contact with each other along their edges (705, 706). In this way, an elongated heat sink with a measuring function 6 is formed that extends along the welding path in the welding direction 40.

[0104] The heat sink tile with measurement function 7 includes a machined cavity 70 that extends from the edge 705 of the heat sink tile 7 substantially parallel to the surface 702 and toward the opposite edge 706 of the heat sink tile 7. An intermediate surface 400 parallel to directions 40 and 42 penetrates the heat sink tile with measurement function 7 and the machined cavity 70 contained within the heat sink tile 7. Figure 6B shows a cross-sectional view of the intermediate surface 400 that penetrates the heat sink tile with measurement function 7 of Figure 6A. The machined cavity 70 can house a sensing device for measuring the temperature at a location within the machined cavity 70, preferably an optical fiber sensor 8 as shown in Figure 6B. The optical fiber sensor is preferably a fiber Bragg grating sensor.

[0105] Note that in Figures 6A and 6B, the machined cavity 70 is shown extending from edges 705 and 706. In other embodiments not shown, the machined cavity may also extend from edge 705 or 706 toward the opposing edge without penetrating the opposing edge. In such embodiments, the fiber Bragg grating sensor 8 may be positioned inside the machined cavity 70 only from the edge of the heat sink tile 7 on which the machined cavity 70 extends.

[0106] The optical fiber sensor comprises a section (referred to here as the sensing element) that includes a fiber Bragg grating. The length of the sensing element is 1 to 25 mm, more preferably 1 to 10 mm, and even more preferably 1 to 5 mm. As is known to those skilled in the art, an optical interlogger can be used to irradiate an optical fiber sensor having a fiber Bragg grating with broadband light and measure the reflected Bragg wavelength. When the optical fiber sensor is heated, the fiber and the fiber Bragg grating contained within the fiber expand, which can change the refractive index of the optical fiber core. This expansion of the fiber and the change in refractive index, combined, result in a shift in the reflected Bragg wavelength, which can be measured by the optical interlogger. In embodiments of the present invention, an optical fiber sensor is used that includes a fiber Bragg grating in which each sensing element reflects light at a different Bragg wavelength. This makes it possible to measure the Bragg wavelength shift caused by temperature changes in each sensing element.

[0107] Figure 6C shows a cross-sectional view of one step of a welding method according to another embodiment of the present invention. The heat sink tile 7 with measuring function has a thickness of 707. The minimum distance 708 between the machined cavity 70 and the surface 702 that contacts the surface 21 of the molded part 2 is at most half the thickness 707 of the heat sink tile 7. The machined cavity 70 has a lateral dimension 75 and can accommodate a fiber Bragg grating sensor 8. The ratio of the lateral dimension 85 of the fiber Bragg grating sensor 8 to the lateral dimension 75 of the machined cavity 70 is between 1:2 and 1:50, more preferably between 1:4 and 1:20, and even more preferably between 1:5 and 1:10. The fiber optic sensor 8 is installed inside the machined cavity 70 such that there is a dimensional gap 70a between the thermocouple 8 and the wall 70b of the cavity 70. The dimensional gap 70a may be an air gap, i.e., filled with (ambient) air. The optical fiber cable 8 may be in localized contact with the wall 70b of the machined cavity 70. Due to the air gap 70a and the smoothness of the wall 70b, the optical fiber sensor can expand and contract freely with virtually no friction. Each optical fiber sensor 8 is connected to an interlogger (not shown), as is well known to those skilled in the art.

[0108] Figure 7 is a cross-sectional view of a heat sink 6 with measuring functions, in which 27 heat sink tiles 7 with measuring functions are arranged adjacent to each other in parallel within a holder plate 80, according to an embodiment of the present invention. The heat sink tiles are held in place within the holder plate 80 by end brackets (not shown) of the holder plate and by inclined edges 87 that cooperate with the inclined edges 703, 704 of each heat sink tile 7. Each heat sink tile with measuring functions 7 has a layout similar to the heat sink tile 7 in Figure 6A, and each heat sink tile is provided with a machined tile cavity 70 extending from edge 705 to edge 706. The heat sink tiles with measuring functions are arranged such that the edge 705 of one tile contacts the edge 706 of an adjacent tile, and the machined tile cavities 70 of adjacent heat sink tiles align to form a heat sink cavity 60. The heat sink cavity 60 preferably extends from one end of the heat sink to the other. As shown in Figure 7, the heat sink cavity 60 can house an optical fiber sensor 8 for measuring the temperature at a specific location within the cavity. The holder plate 80 has a groove 86 along its centerline, and the device 1 is positioned within this groove during electromagnetic welding. This allows the pressurized surface 100 of the device 1 to make direct contact with the surface 701 of each heat sink tile 7 within the heat sink 6.

[0109] Figure 8 shows a heat sink tile with measuring function 7 according to yet another embodiment of the present invention. Each heat sink tile with measuring function 7 is surrounded by a surface 701 configured to contact a pressurizing body 10 (see Figure 2) and a surface 702 located opposite the surface 701 and configured to contact the upper surface 21 of the molded part 2. Furthermore, the heat sink tile with measuring function 7 has two side edges (703, 704) extending substantially parallel to the welding direction 40 and two edges (705, 706) extending substantially parallel to the welding width direction 41 perpendicular to the welding direction 40. The heat sink tile with measuring function 7 shown in Figure 8 includes four machined cavities 70 extending from the surface 701 and substantially perpendicular to the surface 701. The machined cavities 70 are provided to house a sensing device, typically a thermocouple, for measuring the temperature at a location within the cavities 70. Furthermore, the heat sink tile with measuring function 7 has three machined cavities 70 extending substantially parallel to the surface 702 and toward the opposing edge 706 of the heat sink tile 7 from the edge 705 of the heat sink tile 7. To form the heat sink with measuring function 6, multiple heat sink tiles with measuring function 7 are arranged in contact with each other along their edges (705, 706). In this way, an elongated heat sink with measuring function 6 is formed that extends along the welding path in the welding direction 40. The heat sink tiles with measuring function are arranged such that a machined tile cavity 70 extending from the edge 705 of one heat sink aligns with a machined tile cavity 70 extending from the edge 706 of an adjacent heat sink, thereby forming a continuous heat sink cavity. This continuous heat sink cavity can house an optical fiber sensor for measuring the temperature at a specific location within the cavity. The combination of machined cavities extending from surface 702 and machined cavities extending from edges 705 and 706 enables temperature measurement using different types of sensing devices, allowing for more precise control of the temperature at the weld interface during electromagnetic welding. Other embodiments not shown may include combinations of machined cavities in other configurations, as long as the cavities do not intersect.

[0110] Figure 9 shows a device 120 for holding a heat sink during machining. The device 120 has a machined slot in the edge 121, the shape of which the machined slot can be any closed path, preferably a rectangular perimeter. A rubber seal 123 is embedded along the entire circumference of the slot, which extends from the edge 121 and forms a raised perimeter along a plane parallel to the plane of the edge 121. The dimensions of the slot are set so that when the heat sink is placed on the rubber seal 123, the heat sink substantially covers the rubber seal 123. Furthermore, the device 120 has at least one, preferably two, machined cavities 124 extending from the edge 121 to the edge 122 opposite to the edge 121. Each cavity 124 extends from a position on the edge 121 within the perimeter of the machined slot containing the rubber seal 123.

[0111] The apparatus 120 is used to hold the heat sink tile in place during the process of machining one or more cavities 70 and / or one or more wiring slots (73, 74) into the material of the heat sink tile. The process of machining cavities and / or slots in a heat sink tile includes the following steps: preparing the apparatus 120, the heat sink tile to be machined, and the tools for machining cavities and / or wiring slots in the heat sink tile; fixing the apparatus 120 in place relative to the machining tools; placing the heat sink tile on the rubber seal 123 of the apparatus 120 such that the heat sink tile substantially covers the periphery of the rubber seal 123; creating a partial vacuum between the heat sink tile and the apparatus 120 by connecting a vacuum pump to the cavity 124 at the edge 122; machining cavities and / or slots in the heat sink tile using the machining tools; removing the partial vacuum between the heat sink tile and the apparatus 120 by disconnecting the vacuum pump from the cavity 124; and removing the machined heat sink tile from the apparatus 120.

[0112] Figure 10 shows two opposing surfaces of molded part 2 to which thermocouples (8-1 to 8-16) are attached. The upper half of Figure 10 shows surface 20 of molded part 2 that is in contact with surface 30 of molded part 3. The lower half of Figure 10 shows surface 21 of molded part 2 that is in contact with heat sink 6. The thermocouples (8-1 to 8-16) are attached to molded part 2 using heat-resistant tape such as polyimide. Thermocouple 8-1 is positioned substantially opposite to 8-9 on molded part 2, thermocouple 8-2 is positioned substantially opposite to 8-10, and so on.

[0113] An electromagnetic welding experiment was conducted using a molded part with thermocouples attached and a heat sink 6 with a measurement function, as shown in Figure 7. An optical fiber sensor 8 consisting of four 1 cm long sensing elements was placed inside the heat sink cavity 60 of the heat sink 6 with a measurement function. At this time, the first sensing element was aligned with thermocouples 8-2 and 8-10, the second sensing element with thermocouples 8-4 and 8-12, the third sensing element with thermocouples 8-6 and 8-14, and the fourth sensing element with thermocouples 8-8 and 8-16.

[0114] Figure 11 is a graph showing the temperature measured by thermocouples and the wavelength shift measured by an optical fiber sensor during an electromagnetic welding experiment. The x-axis represents the elapsed time of the experiment (seconds). The y-axis on the left represents the temperature (°C) measured by thermocouples (8-2, 8-4, 8-6, 8-8, 8-10, 8-12, 8-14, and 8-16). The temperature can be measured with any E-type thermocouple as long as the wire fits within the machined cavity and wiring slot. In the experiment of this embodiment, Omega TT-E-40 thermocouple wire was used and spot-welded for this experiment.

[0115] The right y-axis represents the wavelength shift (nm) measured by the optical fiber sensor. The wavelength shift can be measured using any type of single-mode optical fiber with a fiber Bragg grating, as long as the ratio of the lateral dimension of the optical fiber 8 to the lateral dimension of the machined cavity 70 is between 1:2 and 1:50, more preferably between 1:4 and 1:20, and even more preferably between 1:5 and 1:10. In the experiment of this embodiment, a polyimide-coated SMF optical fiber was used, having a lateral dimension of 150 nm and four fiber Bragg grating sensing elements with a length of 10 mm. The lateral dimension of the heat sink cavity 60 in the heat sink 6 is 1 mm, resulting in a lateral dimension ratio of 1:6.7. Each sensing element of the fiber Bragg grating sensor 8 reflects light at a specific Bragg wavelength. Prior to the electromagnetic welding experiment, these specific Bragg wavelengths were measured as 1559 nm with the first sensor element, 1551 nm with the second sensor element, 1543 nm with the third sensor element, and 1535 nm with the fourth sensor element. The wavelengths were measured using a Luna / Micronoptics Hyperion si225 optical interlogger.

[0116] The dotted lines represent the wavelength shift profiles measured using the optical fiber sensor 8 located within the heat sink cavity 60 of the heat sink 6 with measurement function. From left to right, the first dotted line corresponds to the wavelength shift measured by the first sensing element, the second dotted line corresponds to the wavelength shift measured by the second sensing element, and so on.

[0117] The dashed lines represent the temperature profile measured using thermocouples placed between the contact surface 21 of the molded part 2 and the heat sink 6g with measurement function. From left to right, the first dashed line corresponds to the temperature measured by thermocouples 8-10, the second dashed line corresponds to the temperature measured by thermocouples 8-12, and so on.

[0118] The dashed lines represent the temperature profiles measured by thermocouples placed between the contact surfaces (20, 30) of the molded parts (2, 3). From left to right, the first dashed line corresponds to the temperature measured by thermocouple 8-2, the second dashed line corresponds to the temperature measured by thermocouple 8-4, and so on.

[0119] During the experiment, as shown in Figure 10, apparatus 1 moves from left to right. As the inductor approaches the thermocouple, the inductively sensitive components near the thermocouple are heated, resulting in a temperature increase being measured by the thermocouple. This temperature increase is first detected by thermocouple sets 8-2 and 8-10, then by sets 8-4 and 8-12, and so on. A slight time difference is observed between peaks 93a-93d and peaks 94a-94d, due to the time required for heat to transfer from the weld interface to the position of each detection device. As the inductor passes the thermocouple and continues to move along the weld line, the magnetic field strength weakens, and the heat from the inductively sensitive components is gradually dissipated until it reaches equilibrium with the ambient temperature, causing the thermocouple to measure the temperature decrease.

[0120] Simultaneously, when the inductively sensitive components within the molded part are heated, the heat is dissipated to the heat sink 6 with measurement function and the optical fiber sensor 8 located inside the heat sink cavity 60 of the heat sink 6. Heating of the optical fiber causes it to expand, and the refractive index of the optical fiber core may change, resulting in a Bragg wavelength shift. The higher the temperature, the greater the wavelength shift. This increase in wavelength shift is detected first by the first sensing element, then by the second sensing element, and so on. A slight time difference is observed between peaks 93a-93d, peaks 94a-94d, and peaks 95a-95d due to the time required for heat to propagate from the welding interface to the location of each sensing device. The peak width of the optical fiber sensor (95a-95d) can be narrowed by shortening the length of the sensor. As the inductor passes the position of the sensing element in the optical fiber sensor 8 and continues along the welding line, the magnetic field strength attenuates, the heat within the inductively sensitive component is gradually dissipated until it reaches equilibrium with the ambient temperature, the sensing element in the fiber Bragg grating sensor contracts to its length before welding, and the refractive index returns to its pre-welding state. As a result, the wavelength shift decreases as the specific Bragg wavelength returns to the specific Bragg wavelength measured before the electromagnetic welding experiment.

[0121] A first correlation exists between the wavelength shift measured by an optical fiber sensor 8 equipped with a fiber Bragg grating placed in the heat sink cavity 60 of the heat sink 6 with measurement function, and the temperature measured at the weld interface between the molded parts (2, 3). Furthermore, a second correlation exists between the electromagnetic field strength of the inductor 11 and the temperature at the weld interface. These correlations are obtained in the same manner as disclosed for the TC (thermocouple) described above. During electromagnetic welding, the wavelength shift is measured using an optical fiber sensor placed in the machined cavity of the heat sink, and the temperature at the weld interface is calculated using the first correlation. This calculated temperature at the weld interface is controlled by adjusting the electromagnetic field strength of the inductor 11 using the second correlation.

[0122] Figure 12 is a flowchart showing a method 900 for performing temperature-controlled electromagnetic welding of a first molded part and a second molded part according to one embodiment. In step 901, a first molded part and a second molded part are prepared, each consisting of a heat-meltable bonding material and an inductively sensitive component. The surfaces to be joined are brought into contact with each other, and pressure is applied by bringing the pressing surface of a pressurizing body into contact with the molded parts. In step 902, an inductor moving in the welding direction is used to generate an electromagnetic field at least on the surfaces to be joined of the molded parts, thereby heating the inductively sensitive component and causing the bonding material at the welding interface to melt. In step 903, the outer surface of the first molded part is cooled by directly contacting a heat sink with a measuring function to the outer surface of the first molded part. The heat sink with a measuring function includes an array of detection devices (thermocouples and / or optical fiber sensors with fiber Bragg gratings) extending substantially parallel to the welding direction. In step 904, the temperature is measured using the detection devices, and the temperature of the welding interface is calculated based on the temperature. In step 905, the temperature of the sensing device is measured, the temperature of the weld interface is calculated based on this, and the temperature of the weld interface is controlled by a controller configured to control the welding parameters. Examples of welding parameters for controlling the temperature of the weld interface include, but are not limited to, the electromagnetic field strength generated by the inductor 11, the distance between the inductor and the weld interface, the speed at which the inductor moves along the welding direction, and / or the flow rate of the coolant flowing through a heat sink equipped with active cooling.

[0123] Figure 13 shows yet another embodiment, which includes a heat sink tile 7 with a measurement function and a portion of a holder plate on which this heat sink tile can be fixed. In this embodiment, the holder plate 80 is provided with a recessed receiving portion 80a in the center, into which the heat sink tile 6 can be housed and fixed by means of adhesive or other appropriate means. This step is schematically indicated by arrow 55 and includes turning the heat sink tile 7 (shown upside down in the figure) over onto the holder plate 80. Note that the holder plate 80 typically extends longitudinally to accommodate multiple heat sink tiles 7, as shown in Figure 7. The illustrated portion of the holder plate 80 is provided with elliptical mounting holes 88. Furthermore, the portion of the holder plate 80 is provided with multiple cooling channels 89, such as four for a single heat sink tile 7, as shown in the figure. The ends of the cooling channels 89 are configured to be connected to hoses that carry a liquid coolant, such as water. In the illustrated embodiment, each cooling channel 89 of the holder plate 80 deviates from a straight path as it enters the receiving area 80a and moves closer to the mounted heat sink tile 7. This can be seen more clearly in Figure 14, which shows the cooling channel 89 in a cross-section. This bend or step occurs at the wall portion 89c. This step in the cooling channel 89 avoids interference with the groove 86 for the induction coil. The groove 86 is intended to minimize the coupling distance between the induction coil and the molded parts (2, 3) to be welded. The cooling channels 89a in the heat sink receiving area 80a of the holder plate 80 are "exposed" when the heat sink tile 7 is not housed in that area 80a. However, when the heat sink tile 7 is mounted on the plate holder 80, these channels 89a work in conjunction with the open cooling channels 89b provided on the heat sink tile 7 to form closed cooling channels 89. In addition, the heat sink tile 7 may have a portion of the cooling channel 89b machined into it so that the coolant can flow even closer to the surface 702, which is intended to come into contact with the molded parts (2, 3).

[0124] The holder plate 80 can be conveniently manufactured from, for example, a glass fiber epoxy composite material, but it can also be manufactured from other rigid solids that are transparent to magnetic fields, machinable, and impermeable to liquid coolants such as water. In embodiments where the material of the heat sink tile 7 is a ceramic such as boron nitride and the coolant is an aqueous solution or water, it is preferable to coat the cooling channels and / or isolate them from direct contact with the coolant in order to suppress or prevent oxidation.

[0125] Referring to Figure 14, the heat sink tile 7 fixed to the holder plate 80 is shown in a perspective view. As mentioned above, the holder plate 80 is shown in a cross-sectional view, with one of the cooling channels 89 exposed. The heat sink tile 7 has an FBG cavity 70 integrally formed by machining, extending parallel to the welding direction 40.

[0126] Figure 15 shows a cross-section of a heat sink tile 7 with a measurement function, in which TC cavities and wiring slots are integrally formed. In this embodiment, the integration with the TC may cause spatial interference with the cooling channel 89, so the path of the TC wiring slot has been redesigned. The heat sink tile 7 has three TCs along the welding width direction 41, but the number of TCs may be fewer or more. The TC wiring slots (73, 74) can accommodate multiple TC wirings. For example, a configuration with two wirings in wiring slot 73 and one wiring in wiring slot 74 located on the opposite side of the heat sink tile 7 is possible. However, other configurations are not excluded.

[0127] Referring to Figure 16, a cross-sectional view through groove 86 is shown of the assembly of the heat sink tile 7 and the holder plate 80 portion having the cooling channel 89 and TC cavity 70. Preferably, design aspects such as the depth of the FBG / TC measurement point, the size / location of the cooling channel 89, or the thickness of the heat sink in the cooling channel 89 are all selected according to specific requirements. For example, the TC measurement point should not be too close to the cooling channel 89 in order to concentrate temperature measurements on the heat sink surface rather than the coolant within the cooling channel 89. The closer the coolant is to the surface 702 that contacts the heated molded parts (2, 3), the greater the cooling effect may be. However, if the distance remaining between the cooling channel 89 and the heat sink tile surface is too small, the heat sink tile 7 may become too fragile and unable to withstand the required pressure.

[0128] The embodiments shown in Figures 13-16 feature a liquid cooling system integrated into a heat sink 6 with a measurement function. This allows the heat sink to cool more quickly between welding operations, thereby shortening the welding (production) cycle time. The cooling rate and cooling capacity of the heat sink 6 during the welding process can be adjusted according to the temperature requirements of the molded part being welded. The temperature and flow rate of the coolant can be controllable parameters depending on the values ​​measured by the sensing device during the welding process. Incorporating such controllable parameters opens up further possibilities for process control.

Claims

1. A heat sink with a measuring function for use in electromagnetic welding of molded parts, wherein the heat sink contains a material with a thermal conductivity of more than 0.1 W / (m·K) according to ASTM C1113 at 25°C, the heat sink has a machined cavity inside which a sensing device for measuring the temperature at a position within the cavity is housed, and further, a dimensional gap exists between the sensing device and the wall of the cavity, thereby substantially isolating the deformation of the sensing device from that of the heat sink.

2. The heat sink with measuring function according to claim 1, wherein the dimensional gap is not filled and forms an air layer, or the dimensional gap is at least partially filled with a filler material different from the heat sink material.

3. The heat sink with measuring function according to claim 1 or 2, wherein the material of the heat sink has a thermal conductivity of 0.1 to 250 W / (m·K) at 25°C based on ASTM C1113, more preferably 25 to 250 W / (m·K), even more preferably 50 to 250 W / (m·K), and most preferably 80 to 250 W / (m·K).

4. A heat sink with a measuring function according to any one of claims 1 to 3, wherein the material of the heat sink includes a ceramic substantially containing a nitride, preferably substantially containing a composite material of nitrides, and more preferably substantially containing a composite material of boron nitride and aluminum nitride.

5. Ceramic materials have a hardness of 15-75 HR according to ISO 6508. [A], more preferably 25 to 50 HR [A], more preferably 30 to 40 HR[A], the heat sink with measurement function according to claim 4.

6. The machined cavity is substantially cylindrical and has a diameter of 0.5 to 2.5 mm, more preferably 0.5 to 2.0 mm, and even more preferably 0.5 to 1.5 mm, according to any one of claims 1 to 5, a heat sink with a measuring function.

7. The heat sink with measuring function according to claim 6, wherein the tolerance of the diameter is not zero, but is a maximum of 0.5 mm, more preferably a maximum of 0.25 mm, and even more preferably a maximum of 0.2 mm.

8. The heat sink with measuring function according to any one of claims 1 to 7, wherein the heat sink has a predetermined thickness, and the minimum distance between the machined cavity and the outer surface of the heat sink intended to contact one of the molded parts is at most half the thickness of the heat sink, preferably 0.25 to 1.5 mm, more preferably 0.25 to 1 mm, and most preferably 0.25 to 0.75 mm.

9. The heat sink with measurement function according to any one of claims 1 to 8, wherein the detection device includes a thermocouple or an optical fiber sensor, preferably a fiber Bragg grating sensor, or a combination of both.

10. The heat sink with measuring function according to any one of claims 1 to 9, wherein the detection device is a thermocouple, and the machined cavity extends from an external surface of the heat sink that is intended not to come into contact with one of the molded parts, and is substantially perpendicular to the external surface.

11. The heat sink with measuring function according to claim 10, further comprising two machined wiring slots for each machined cavity, wherein the wiring slots are positioned on an external surface of the heat sink intended not to come into contact with one of the molded parts, each machined wiring slot extends from the machined cavity to the end of the heat sink with measuring function, and the wiring slots do not intersect with each other.

12. The heat sink with measuring function according to claim 11, wherein the width of the machined wiring slot is 0.5 to 2 mm, more preferably 0.5 to 1 mm, even more preferably 0.5 to 0.75 mm, and the depth is 0.5 to 2 mm, more preferably 0.5 to 1 mm, even more preferably 0.5 to 0.75 mm.

13. A heat sink with a measuring function according to any one of claims 1 to 9, wherein the detection device is an optical fiber sensor, and the machined cavity extends substantially parallel to the opposite end of the heat sink from one end of the heat sink to the outer surface of the heat sink intended to contact one of the molded parts.

14. The heat sink with measuring function according to claim 13, wherein the ratio of the lateral dimension of the optical fiber sensor to the lateral dimension of the machined cavity is between 1:2 and 1:50, more preferably between 1:4 and 1:20, and even more preferably between 1:5 and 1:

10.

15. The heat sink with measurement function according to claim 13 or 14, wherein the optical fiber sensor is a fiber Bragg grating sensor having a sensing element with a length of 1 to 25 mm, more preferably 1 to 15 mm, and even more preferably 1 to 5 mm.

16. A heat sink with a measuring function according to any one of claims 1 to 15, wherein a heat-resistant polymer coating or film, preferably a polyimide film or polysilazane coating, is provided on the outer surface of the heat sink intended to be in contact with one of the molded parts.

17. A heat sink with a measuring function according to any one of claims 1 to 16, comprising a plurality of heat sink tiles arranged adjacent to each other in parallel, preferably provided within a holder plate.

18. Each heat sink tile has a machined tile cavity, and the machined tile cavities of adjacent heat sink tiles are aligned with each other to form a heat sink cavity, which preferably extends from one end of the heat sink to the other, as described in claim 17.

19. The heat sink with a measurement function according to claim 17 or 18, further comprising means for actively cooling the heat sink with a measurement function.

20. A method for joining the surface of a first molded part and the surface of a second molded part by temperature-controlled electromagnetic welding, comprising the following steps: - Prepare first and second molded parts including a heat-meltable bonding material and an induction-sensitive component. - Applying pressure to the surfaces to be connected by bringing the surfaces to be connected into contact with each other and bringing the pressing surface of the pressurizing body into contact with the molded part. - Using an inductor that moves in the welding direction, an electromagnetic field is generated at least on the surface of the molded part to be connected, thereby heating the inductively sensitive component and causing the bonding material at the welding interface to melt. - To cool the outer surface of the first molded part by providing a heat sink with a measurement function according to any one of claims 1 to 19, in direct contact with the outer surface of the first molded part, and optionally such that the arrangement of detection devices (thermocouples and / or fiber Bragg grating sensors, etc.) extends substantially parallel to the welding direction. - Measure the temperature using the detection device and calculate the temperature of the welding interface based on that measurement. - Controlling the temperature of the welding interface by controlling the welding parameters, and - To join molded parts under pressure using molten, heat-meltable bonding material. A method that includes this.

21. The method according to claim 20, wherein the welding parameter is the electromagnetic field strength of the inductor, the flow rate of the coolant, or a combination thereof.

22. An apparatus for joining the surface of a first molded part and the surface of a second molded part along the welding direction by temperature-controlled electromagnetic welding, wherein the first and second molded parts include a heat-meltable bonding material and an inductively sensitive component, and the apparatus is - An inductor provided to generate an electromagnetic field along the welding direction at least on the surface of the molded part to be joined, thereby heating an inductively sensitive component to thermally melt the bonding material at the welding interface, A heat sink with a measurement function according to any one of claims 1 to 19, wherein the heat sink is arranged along the welding direction, its outer surface is provided to contact either one of the molded parts, and the heat sink is positioned between the inductor and the molded part, - A pressurizing body provided for pressurizing the surface to be connected, A control device configured to measure the temperature of the heat sink using at least one detection device, calculate the temperature of the welding interface based on that temperature, and control the welding parameters, A device equipped with the following features.

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