Inverter and manufacturing method therefor

Abstract

The present application relates to an inverter and a manufacturing method therefor. The inverter comprises a shell, and a circuit unit, a plastic frame and a bus which are accommodated in the shell, wherein the circuit unit is configured to convert a direct current inputted from a direct-current power supply into an alternating current and output same by means of the bus; the plastic frame is configured to retain and package the circuit unit and partially clad the bus, and is formed in a transfer molding mode along with the preformed bus; and the bus is made of a graphene polymer alloy, which is formed by means of adding graphene and other additives to a polymer matrix. The present application can significantly reduce the risk of producing cracks between a plastic frame and a bus under thermal cycling or temperature changes, and has the advantages of high reliability, low costs, simple and convenient implementation, etc.

Description

Inverter and manufacturing method thereof Technical Field

[0001] The present application relates to an inverter (especially an inverter using a new busbar material) and a manufacturing method thereof. Background Art

[0002] As is well known, an inverter refers to a power electronic device that converts direct current (DC) into alternating current (AC), and is widely used in fuel cell systems, vehicles, mobile devices, and other fields. For example, an inverter can be used in a new energy vehicle (NEV) such as an electric vehicle as a key component. In addition, in conventional power distribution, a busbar (also called a bus or busbar) is usually in the form of a metal strip or metal bar (which is made of, for example, copper, aluminum, etc.), which can be set in a switch cabinet, a distribution board, a bus duct, etc., for local high-current power distribution.

[0003] As a traditional structure, the inverter generally includes a housing, a circuit unit housed within the housing, a plastic frame, and busbars. The circuit unit is used to convert direct current (DC) input from a DC power supply into alternating current (AC) and output it via the busbars (e.g., to an AC motor). The plastic frame is used to hold and encapsulate the circuit unit and partially cover the busbars. The plastic frame, together with the preformed busbars, is formed through transfer molding. As known to those skilled in the art, transfer molding is a thermosetting plastic molding method in which the molding compound is typically first heated to soften, then injected into a heated mold cavity through a pouring port using plunger pressure. The mold cavity is then pressurized and deformed to form the molded compound, which is then heat-cured (crosslinking reaction of the molding compound in the mold cavity) and subsequently demolded. The finished plastic frame can be adhered to a cooler (e.g., an aluminum cooler) using an adhesive, for example, and then housed in the housing and secured, for example, with screws.

[0004] Currently, the busbars in the above-mentioned conventional inverters are typically made of copper, which has a significantly different coefficient of thermal expansion (CTE) from the plastic frame due to the different material (or material type). The thermal expansion coefficient refers to the expansion and contraction of an object due to temperature changes. Due to the difference in thermal expansion coefficients, stress may be generated in the joint between the copper busbar and the plastic frame, thereby potentially reducing the mechanical strength and sealing between the copper busbar and the plastic frame. In addition, with temperature changes or thermal cycles during transfer molding, the mismatch in the thermal expansion coefficients between the copper busbar and the plastic molding material can easily lead to risks such as cracks forming between the finished plastic frame and the busbar.

[0005] Therefore, it is necessary to improve the existing inverter to overcome the deficiencies or defects in the above-mentioned known technologies.

[0006] Summary of the Invention

[0007] In view of the above background, the purpose of the present application is to provide an improved inverter and a manufacturing method thereof, which can at least partially overcome or even completely eliminate the problems or defects existing in the above-mentioned known technologies.

[0008] To this end, according to one aspect of the present application, an inverter is provided, comprising:

[0009] a housing; and

[0010] A circuit unit, a plastic frame, and a busbar are housed in the housing. The circuit unit is used to convert direct current input from a DC power supply into alternating current and output the alternating current through the busbar. The plastic frame is used to hold and encapsulate the circuit unit and partially cover the busbar. The plastic frame is formed together with the preformed busbar by transfer molding.

[0011] The busbar is made of a graphene polymer alloy, which is formed by adding graphene and other necessary additives into a polymer matrix.

[0012] According to a feasible implementation manner, the graphene polymer alloy has a thermal conductivity or thermal expansion coefficient as close as possible to that of the plastic frame.

[0013] According to a feasible embodiment, the graphene polymer alloy contains 40-80% of polymer matrix and 3-5% of graphene in weight percentage.

[0014] According to a feasible embodiment, the other additives include a dispersant, and the dispersant includes spherical graphite and wood fiber.

[0015] According to a feasible implementation manner, in terms of weight percentage, the content of the spherical graphite is 10-50%, and the content of the wood fiber is 3-5%.

[0016] According to a possible embodiment, the polymer matrix is ​​composed of phenolic resin or epoxy resin, and the plastic frame is made of the same material as the polymer matrix.

[0017] According to a feasible implementation manner, the plastic frame is a gel frame.

[0018] According to another aspect of the present application, a method for manufacturing the inverter as described above is provided, comprising the following steps:

[0019] Providing a busbar, wherein the busbar is made of a graphene polymer alloy, wherein the graphene polymer alloy is formed by adding graphene and other necessary additives into a polymer matrix;

[0020] forming a plastic frame together with the busbar by transfer molding, wherein the plastic frame is used to hold and encapsulate the circuit unit in the inverter and partially cover the busbar;

[0021] The plastic frame with the circuit unit and the busbar is accommodated and fixed in the housing.

[0022] According to a feasible embodiment, during the preparation of the busbar, the polymer matrix, the graphene and the other additives in powder form are pressed into shape at a temperature of 150-160° C. and a pressure of 200 MPa.

[0023] According to a feasible implementation method, during the transfer molding process, the molding material forming the plastic frame is preheated at a temperature of 140°C for a certain period of time to soften and pour; then the molding material injected into the mold cavity is maintained at a temperature of 175°C and a certain pressure for a certain period of time to perform transfer molding; and then the molded molding material is maintained at a temperature of 180°C for a certain period of time to perform solidification.

[0024] According to the present application, a busbar made of a graphene polymer alloy with excellent electrical conductivity and thermal conductivity is used to replace the metal (usually copper) busbar in the existing inverter. While being able to meet the desired requirements for electrical conductivity, etc., the graphene polymer alloy can have a thermal conductivity or thermal expansion coefficient similar or close to that of the plastic frame (the two are made of similar materials), thereby significantly reducing the risk of cracks between the plastic frame and the busbar under thermal cycles or temperature changes, and reliably ensuring the mechanical strength and sealing between the plastic frame and the busbar.

[0025] As can be seen from the above description, the present application mainly aims to improve the busbar part in the existing inverter. It can effectively overcome the deficiencies or defects in the existing technology while keeping the overall structure of the existing inverter basically unchanged, and has the advantages of high reliability, low cost, light weight, and simple and convenient implementation. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The features, advantages and other aspects of the present application will be more clearly understood through the following more detailed description of the present application given with reference to the accompanying drawings and in combination with exemplary embodiments. In the accompanying drawings:

[0027] FIG1 shows a schematic structural diagram of a plastic frame and a busbar portion of an inverter according to an exemplary embodiment of the present application.

[0028] FIG2 shows a general flow chart of a method for manufacturing an inverter according to an exemplary embodiment of the present application. DETAILED DESCRIPTION

[0029] The following describes in detail specific embodiments of the present application, including further details, with reference to the accompanying drawings. It should be understood that the embodiments and related descriptions provided herein are to be construed as illustrative only and do not constitute limitations on the present application. Furthermore, it should be understood that the sizes and positions of components in the accompanying drawings are not strictly drawn to scale, and that the sizes and proportional relationships of the components should not be construed as limitations on the present application.

[0030] In addition, it should be noted that, for the sake of simplicity and to facilitate understanding of the main improvements or key points of this application, the description and drawings of this application focus on describing or illustrating the content related to the improvements or improved parts of this application, while omitting or simplifying the content of other parts. As the specific structure, operating principle, dimensional design and other details of these omitted parts are known technologies in the art and can be appropriately selected by those skilled in the art based on existing knowledge in the art and specific applications, they will not be described in detail here, nor will they be illustrated in detail.

[0031] First, as mentioned above, the busbars in conventional inverters are typically made of a metal such as copper, which has a significantly different thermal conductivity or thermal expansion coefficient from the plastic frame used with the busbars in the inverter. This difference in thermal conductivity or thermal expansion coefficient can easily cause stress between the copper busbars and the plastic frame, potentially reducing the mechanical strength and seal between the two, and posing the risk of cracks, for example, between the plastic frame and the busbars.

[0032] It is precisely on the basis of fully recognizing the problems or defects existing in the above-mentioned traditional existing technologies that the inventors of this application have proposed a new technical solution, which can reliably and conveniently achieve its intended purpose in a low-cost manner without making significant changes to the existing structure of the existing inverter (it mainly improves or optimizes the busbar part) and effectively overcome the problems or defects in the above-mentioned existing technologies.

[0033] More specifically, the inventors of this application noted that graphene, a single layer of carbon atoms arranged in a two-dimensional manner, is considered a "future material" due to its excellent electrical conductivity, impressive thermal conductivity, and good mechanical properties. In terms of thermal properties, graphene has a thermal conductivity (or thermal conductivity coefficient) of approximately 5200 W / mK, which is much higher than traditional metal materials such as copper and aluminum. In addition, graphene polymer alloy (GPA) is a composite material formed by adding graphene and other necessary additives to a polymer (usually epoxy resin, etc.), which is usually a thermosetting material.

[0034] The inventors of the present application realized that, compared with other conductive materials, the most significant feature of graphene as an additive is that a small amount of additives can greatly improve the electrical conductivity, and a small amount of additives is conducive to ensuring the original performance of the polymer. In this case, the composite material made based on graphene and polymer can not only improve the electrical conductivity of the material, but also give the material excellent mechanical properties and thermal conductivity. In other words, since graphene has a unique structure and excellent electrical conductivity, filling it into a polymer matrix to form a graphene polymer alloy can effectively improve the electrical conductivity of the polymer matrix, thereby expanding the application range of the polymer. In particular, since graphene polymer alloys generally have high thermal conductivity (which can, for example, even be higher than 10W / mK, which is comparable to cast aluminum) and low electrical resistance (for example, about 10 -4 Ω·m), so it is possible to be used as a busbar material in inverters to replace the current copper busbar.

[0035] Based on the above findings and understandings and through relevant research and experiments, the present application proposes a new inverter, which includes a housing and a circuit unit, a plastic frame and a busbar accommodated in the housing, wherein the circuit unit is used to convert direct current input from a DC power supply into alternating current and output it through the busbar, and the plastic frame is used to hold and encapsulate the circuit unit and partially cover the busbar. The plastic frame is formed together with the pre-formed busbar by transfer molding, wherein the busbar is made of a graphene polymer alloy, which is formed by adding graphene and other necessary additives to a polymer matrix.

[0036] More specifically, FIG1 shows a plastic frame and a busbar portion of an inverter according to an exemplary embodiment of the present application. From FIG1 , it is clear to see the plastic frame 1 according to the present application and the busbar 2 partially enclosed in the plastic frame 1 .

[0037] In FIG1 , three busbars (represented as U, V, and W) are shown, taking the output of three-phase AC power as an example. Each busbar 2 has a rectangular shape, as viewed in plan view in FIG1 , but the present application is obviously not limited thereto. Furthermore, as previously mentioned, according to embodiments of the present application, each busbar 2 can be made of a graphene polymer alloy.

[0038] As a non-limiting example, the graphene polymer alloy may comprise, by weight, 40-80% phenolic resin (as a polymer matrix), 3-5% graphene, and other necessary additives, such as an appropriate amount of a dispersant. The dispersant may comprise, by weight, 3-5% wood fiber and 10-50% spherical graphite, wherein the spherical graphite may also serve as a thermal conductor.

[0039] It should be noted that the specific composition and content of the graphene polymer alloy can be appropriately adjusted according to actual needs to meet different usage conditions or requirements. For example, the phenolic resin can be replaced by epoxy resin or other polymer materials. In addition, the plastic frame in the inverter can be a gel frame. Alternatively, preferably, the plastic frame can be made of the same material as the polymer matrix (such as phenolic resin, epoxy resin, etc.), and the various components and contents of the graphene polymer alloy used can be appropriately adjusted so that it has a thermal conductivity or thermal expansion coefficient as close as possible to that of the plastic frame.

[0040] The busbar (also referred to as a graphene polymer alloy busbar) according to an embodiment of the present application can be formed in the following manner. Specifically, during the busbar forming process, a powdered polymer matrix, graphene, and other additives can be pressed together at a high temperature of 150-160°C and a high pressure of 200 MPa. The busbar can then be directly formed or processed to a predetermined size and shape.

[0041] Aside from using a graphene polymer alloy to replace the metal (typically copper) busbars commonly used in the prior art, the manufacturing process (e.g., transfer molding) of the inverter according to the embodiments of the present application can be substantially the same as that of the prior art, i.e., the process parameters and the like of the prior art can be substantially adopted. As a non-limiting example, during the transfer molding process of the plastic frame of the inverter according to the embodiments of the present application, the preheating time of the molding material can be, for example, approximately 11 seconds, and the temperature can be, for example, approximately 140°C; the transfer molding can be performed within, for example, 120 seconds, and at, for example, approximately 175°C; and after molding, a curing process can be performed at, for example, approximately 180°C for approximately 5 hours.

[0042] As a non-limiting example, FIG2 shows a general flow chart of a method for manufacturing an inverter according to an exemplary embodiment of the present application.

[0043] As shown in FIG2 , a method for manufacturing an inverter according to an embodiment of the present application may include the following steps:

[0044] Step S1: Start the inverter manufacturing process;

[0045] Step S2: providing a busbar, wherein the busbar is made of a graphene polymer alloy, and the graphene polymer alloy is formed by adding graphene and other necessary additives into a polymer matrix;

[0046] Step S3: forming a plastic frame together with the busbar by transfer molding, wherein the plastic frame is used to hold and encapsulate the circuit unit in the inverter and partially cover the busbar;

[0047] Step S4: accommodating and fixing the plastic frame with the circuit unit and the busbar in the housing;

[0048] Step S5: End the inverter manufacturing process.

[0049] By replacing the metal busbars typically used in existing technologies with busbars made of a graphene polymer alloy, this application enables the busbars, partially encased in a plastic frame, to have a thermal conductivity or coefficient of thermal expansion similar or close to that of the plastic frame. This significantly reduces the risk of cracking due to temperature fluctuations or thermal cycling during transfer molding or use, while reliably ensuring the mechanical strength and seal between the busbars and the plastic frame. Research, analysis, and experiments have confirmed that the inverter of this application can well meet its intended use requirements and achieve the desired results.

[0050] The inverter of the present application may be used in new energy vehicles (NEVs) such as electric vehicles, but is obviously not limited thereto.

[0051] The present application has been described in detail above with reference to specific embodiments. It is obvious that the above description and the embodiments shown in the accompanying drawings should be understood as illustrative only and not limiting of the present application. Those skilled in the art may make various modifications or variations without departing from the spirit of the present application, and such modifications or variations do not depart from the scope of the present application.

Claims

1. An inverter, comprising: case; as well as A circuit unit, a plastic frame and a busbar are contained in the housing, wherein the circuit unit is used to convert direct current input from a direct current power supply into alternating current and output the alternating current through the busbar, the plastic frame is used to hold and encapsulate the circuit unit and partially cover the busbar, and the plastic frame is formed together with the preformed busbar by transfer molding. The busbar is made of a graphene polymer alloy, which is formed by adding graphene and other necessary additives into a polymer matrix.

2. The inverter according to claim 1, wherein: The graphene polymer alloy has a thermal conductivity or a thermal expansion coefficient as close as possible to that of the plastic frame.

3. The inverter according to claim 1, wherein: In terms of weight percentage, the graphene polymer alloy contains 40-80% of a polymer matrix and 3-5% of graphene.

4. The inverter according to claim 3, wherein: The other additives include a dispersant including spherical graphite and wood fiber.

5. The inverter according to claim 4, wherein: In terms of weight percentage, the content of the spherical graphite is 10-50%, and the content of the wood fiber is 3-5%.

6. The inverter according to claim 1, wherein: The polymer matrix is ​​composed of phenolic resin or epoxy resin, and the plastic frame is made of the same material as the polymer matrix.

7. The inverter according to claim 1, wherein: The plastic frame is a gel frame.

8. A method for manufacturing an inverter according to any one of claims 1 to 7, comprising the following steps: A busbar is provided, wherein the busbar is made of a graphene polymer alloy. Gold is formed by adding graphene and other necessary additives to a polymer matrix; Forming a plastic frame together with the busbar by transfer molding, wherein the plastic frame is used to hold and encapsulate the circuit unit in the inverter and partially cover the busbar; The plastic frame with the circuit unit and the busbar is accommodated and fixed in the housing.

9. The method according to claim 8, wherein: During the preparation of the busbar, the polymer matrix, the graphene and the other additives in powder form are pressed into shape at a temperature of 150-160° C. and a pressure of 200 MPa.

10. The method according to claim 8, wherein: During the transfer molding process, the molding material forming the plastic frame is preheated at a temperature of 140°C for a certain period of time for softening and infusion; then the molding material injected into the mold cavity is maintained at a temperature of 175°C and a certain pressure for a certain period of time for transfer molding; then the molded molding material is maintained at a temperature of 180°C for a certain period of time for curing.

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