Patent Description:
A vehicle equipped with a motor, such as a hybrid car or an electric car is equipped with a driving means that drives the motor. The driving means includes electronic components such as a power module including a plurality of power semiconductors such as an insulated gate bipolar transistor (IGBT), and a capacitor, and a bus bar electrically joining these electronic components.

When the motor is driven, a large current may flow through the power semiconductor, the capacitor, and the bus bar joining these electronic components. In this case, the driving means generates heat due to switching loss, resistance loss, or the like, and therefore needs to be cooled efficiently.

As a cooling means for cooling the driving means, a heat sink including a metal such as aluminum or copper is used because of its high thermal conductivity (see, for example, Patent Literature <NUM>).

Patent Literature <NUM>: Japanese Patent Application Laid-Open (<CIT>.

However, in order to manufacture a metal heat sink, it is necessary to perform complicated manufacturing processes such as extrusion molding, skiving, and caulking. Thus, the metal heat sink tends to be expensive.

In addition, many man-hours may be required to incorporate a metal heat sink into a cooling target such as a driving means. Therefore, there is a demand for a resin cooling means that is easy to process and easy to incorporate into a driving means or the like.

On the other hand, the resin cooling means, which generally has lower strength than the metal heat sink, is required to have high strength.

An aspect of the present disclosure has been made in view of the above conventional circumstances, and an object of the present disclosure is to provide a cooling structure made of resin and having excellent cooling efficiency and high strength. <CIT> discloses features falling under the preamble of claim <NUM>.

An aspect of the present disclosure can provide a cooling structure made of resin and having excellent cooling efficiency and high strength.

A cooling structure according to the disclosure includes a flow path configuration member made of resin and forming a flow path through which a refrigerant flows; and a cooling fin extending from an inner wall of the flow path toward an inside of the flow path, having a distal end that is in contact with the inner wall, and having a surface made of resin. The cooling structure according to the disclosure has excellent cooling efficiency and high strength.

Hereinafter, the cooling structure of the disclosure will be described with reference to the drawings. Note that sizes of members in the drawings are conceptual, and a relative relationship between the sizes of the members is not limited to the relationship disclosed herein. In addition, members having substantially the same functions are denoted by the same reference signs throughout the drawings, and redundant description may be omitted.

<FIG> is a sectional view illustrating a main part of a cooling structure <NUM> according to a first embodiment.

In the cooling structure <NUM>, the cooling fin is provided in a region where the inner wall of the flow path has a substantially rectangular shape when a cross section of the flow path orthogonal to a direction in which the refrigerant flows is observed. The cooling fin extends from one inner wall toward another inner wall of a pair of opposing inner walls of the inner wall having a substantially rectangular shape, and the cooling fin is in contact with the other inner wall.

Note that, in the disclosure, a sectional shape of the flow path at a portion of the cooling structure in which the cooling fin is provided is not limited, and may be a substantially rectangular shape, or may be a shape other than a substantially rectangular shape, such as a circular shape, an elliptical shape, or a polygonal shape other than a rectangular shape.

Further, in the disclosure, the sectional shape of the flow path other than the portion of the cooling structure in which the cooling fin is provided is not limited.

The cooling structure <NUM> illustrated in <FIG> includes a flow path configuration member <NUM> made of resin and forming a flow path <NUM> that circulates a refrigerant and has a substantially rectangular cross section. The flow path <NUM> is surrounded by an upper inner wall <NUM> corresponding to an inner wall of one of a pair of opposing inner walls, a lower inner wall <NUM> corresponding to an inner wall of the other one of the pair of opposing inner walls, and a side inner wall <NUM> and a side inner wall <NUM> that connect the upper inner wall <NUM> and the lower inner wall <NUM>.

Cooling fins <NUM> having a cylindrical shape and being in contact with a lower inner wall <NUM> extend from an upper inner wall <NUM> toward the lower inner wall <NUM>. Similarly to the flow path configuration member <NUM>, the cooling fins <NUM> is made of resin. In <FIG>, a part of each cooling fin <NUM> is indicated by dotted lines.

Extending directions of a plurality of the cooling fins <NUM> are substantially parallel to each other. Since the extending directions of the plurality of cooling fins <NUM> are substantially parallel, when the flow path configuration member <NUM> including the cooling fins <NUM> is manufactured with use of a mold, the cooling fins <NUM> can be easily pulled out from the mold. It is therefore easy to manufacture the flow path configuration member <NUM> including the cooling fin <NUM> with use of a mold.

A bus bar <NUM> as a cooling target is fixed to a root of the cooling fins <NUM> with a bolt <NUM> and a nut <NUM>. The nut <NUM> includes a nut body <NUM> and the heat diffuser <NUM> provided on a side of the nut body <NUM> opposite to a side into which the bolt <NUM> is inserted. The heat diffuser <NUM> has a quadrangular plate shape and is integrated with the nut body <NUM>.

The bus bar <NUM> is connected to electronic components (not illustrated) such as a power semiconductor and a capacitor.

The entire heat diffuser <NUM> of the nut <NUM> and a part of the nut body <NUM> opposite to the side where the bolt <NUM> is inserted are embedded in the flow path configuration member <NUM>. The heat diffuser <NUM> is not limited to be embedded in the flow path configuration member <NUM>, and may be joined to the flow path configuration member <NUM>, for example, may be joined to an outer wall of the flow path configuration member <NUM>. For example, the heat diffuser <NUM> may be joined to the flow path configuration member <NUM> by a resin metal joining technique by laser roughening.

<FIG> is a diagram of a region in which the cooling fins <NUM> is provided in the cooling structure <NUM> illustrated in <FIG>, as viewed from an insertion direction of the bolt <NUM>. In order to facilitate understanding of a positional relationship between the cooling fins <NUM> and the heat diffuser <NUM>, the bus bar <NUM> and the like are omitted in <FIG>. In order to facilitate understanding of the positional relationship between the cooling fins <NUM> and the heat diffuser <NUM>, the heat diffuser <NUM> is indicated by a two-dot chain line. <FIG> is a sectional view taken along line AA illustrated in <FIG>.

As illustrated in <FIG>, the number of cooling fins <NUM> is seven, and the cooling fins <NUM> are provided in a range where the heat diffuser <NUM> is disposed.

Here, when a current flows through the bus bar <NUM>, the bus bar <NUM> itself generates heat due to a resistance loss. The bus bar <NUM> is connected to the electronic components (not illustrated), and heat generated from the electronic components by energization is diffused through the bus bar <NUM>. The bus bar <NUM> is therefore likely to have high temperature.

The heat generated from the bus bar <NUM> itself and the heat diffused through the bus bar <NUM> are transferred to a portion integrated with the nut body of the heat diffuser <NUM> via the bolt <NUM> and the nut body <NUM>. Since the heat diffuser <NUM> has a quadrangular plate shape, the heat transferred to the heat diffuser <NUM> is diffused in the plane direction of the heat diffuser <NUM> and can be diffused in a wide range.

The heat diffuser <NUM> is disposed at a root of the cooling fins <NUM>, and the heat diffused to the heat diffuser <NUM> reaches the root of the cooling fins <NUM>. The heat reaching the root of the cooling fins <NUM> moves from the root of the cooling fins <NUM> toward the lower inner wall <NUM> through the cooling fins <NUM>. At this time, the heat is transferred from the cooling fins <NUM> to the refrigerant by the refrigerant flowing through the flow path <NUM>. The cooling target such as the bus bar <NUM> is cooled in this way.

In the cooling structure <NUM>, the cooling fins <NUM> extends from the upper inner wall <NUM> toward the lower inner wall <NUM>, and the cooling fins <NUM> are in contact with the lower inner wall <NUM>. For example, when the cooling fins <NUM> do not reach the lower inner wall <NUM>, the refrigerant flowing between the distal ends of the cooling fins <NUM> and the lower inner wall <NUM> passes without contacting the cooling fin <NUM>. The refrigerant passing without contacting the cooling fins <NUM> does not contribute to cooling of the cooling fins <NUM>. As compared with a case in which the distal ends of the cooling fins <NUM> are not in contact with the lower inner wall <NUM>, an amount of the refrigerant not in contact with the cooling fins <NUM> can be reduced in the cooling structure <NUM>. Thus, the cooling efficiency of the cooling structure <NUM> is high. In addition, since the cooling fins <NUM> are in contact with the lower inner wall <NUM>, particularly, when a load is applied from the upper inner wall <NUM> toward the lower inner wall <NUM> (or from the lower inner wall <NUM> toward the upper inner wall <NUM>), a strength of the cooling structure <NUM> can be increased.

In <FIG>, when the portion of the flow path <NUM> in which the cooling fins <NUM> are provided is observed from a direction in which the refrigerant flows, an area of the observed part of the cooling fins <NUM> in an area of the flow path <NUM> is preferably <NUM>% or more, more preferably <NUM>% or more, in terms of improving the cooling efficiency.

In <FIG>, a minimum distance h from a surface of the heat diffuser <NUM> on a side of the flow path <NUM> to the inner wall of the flow path configuration member <NUM> is preferably <NUM> or more in terms of insulating properties, and more preferably <NUM> or more and still more preferably <NUM> or more in terms of moldability. The minimum distance h is preferably <NUM> or less in terms of the cooling efficiency.

At least a surface of the cooling fins <NUM> needs to be made of resin, and the entire cooling fins <NUM> may be made of resin, or the cooling fins <NUM> may have a metal rod-shaped core material. When the cooling fin <NUM> includes a rod-shaped core material, an entire surface of the metal core material is preferably covered with resin in terms of suppressing corrosion and the like. One end of the core material may be connected to the heat diffuser <NUM> in terms of improving the cooling efficiency.

In <FIG>, the distal ends of the cooling fins <NUM> have a flat shape orthogonal to an extending direction of the cooling fins <NUM>, but a shape of the distal ends of the cooling fins <NUM> is not limited, and may be hemispherical, conical, pyramidal, or the like.

Examples of the cooling target include electronic components such as a power semiconductor and a capacitor in addition to the bus bar <NUM>. In a case in which the cooling target is an electronic component, the cooling fins may be provided at a portion where the electronic component is disposed in the cooling structure.

A positional relationship between the cooling fins <NUM> and the heat diffuser <NUM> in the cooling structure <NUM> is not limited.

For example, as shown in <FIG>, the cooling fins <NUM> may be disposed along a direction orthogonal to a direction in which the refrigerant flows in the flow path <NUM>. The cooling fins <NUM> may be disposed at a position away from a region in which the heat diffuser <NUM> is disposed.

<FIG> is an end view illustrating a main part of a cooling structure <NUM> according to a second embodiment.

In the cooling structure <NUM> illustrated in <FIG>, a recess <NUM> having a concave shape is provided in a portion of the lower inner wall <NUM> in contact with each cooling fin <NUM>. The distal end of each cooling fin <NUM> is fitted in the recess <NUM>. The distal end of each cooling fin <NUM> is fitted in the recess <NUM>, and this increases a strength of the cooling fins <NUM> when a load is applied to the cooling fins <NUM> in the direction in which the refrigerant flows. Therefore, a flow rate of the refrigerant can be increased, and the cooling efficiency can be further improved.

In <FIG>, the distal end of each cooling fin <NUM> has a flat shape orthogonal to the extending direction of the cooling fins <NUM>, and a bottom surface of the recess <NUM> is parallel to the lower inner wall <NUM>. For example, in a case in which the distal end of each cooling fin <NUM> has a hemispherical shape, the recess <NUM> may have a concave shape having a radius of curvature larger than a radius of curvature of the distal end of each cooling fin <NUM>.

<FIG> is an end view illustrating a main part of a cooling structure <NUM> according to a third embodiment.

In the cooling structure <NUM> according to the third embodiment, the cooling fins are provided in a region where the inner wall of the flow path has a circular shape when a cross section orthogonal to the direction in which the refrigerant flows in the flow path is observed. The cooling fins extend from the circular inner wall toward the inside of the flow path, and the distal ends of the cooling fins are in contact with the inner wall.

The cooling structure <NUM> illustrated in <FIG> includes a flow path configuration member <NUM> made of resin and forming a flow path <NUM> that circulates a refrigerant and has a circular cross section.

The cooling fins <NUM> extend from an upper part of a cylindrical inner wall <NUM> constituting the flow path <NUM> in the drawing toward the inside of the flow path <NUM>, and the distal ends of the cooling fins <NUM> are in contact with a lower part of the inner wall <NUM> in the drawing.

A bus bar <NUM> as a cooling target is fixed to a root of the cooling fins <NUM> with a bolt <NUM> and a nut <NUM>. The nut <NUM> includes a nut body <NUM> and a heat diffuser <NUM> provided on a side of the nut body <NUM> opposite to a side into which the bolt <NUM> is inserted. Unlike the heat diffuser <NUM> illustrated in <FIG>, the heat diffuser <NUM> is curved along the shape of the cylindrical inner wall <NUM> and is integrated with the nut body <NUM>.

<FIG> is a sectional view illustrating a main part of a cooling structure <NUM> according to a fourth embodiment. <FIG> illustrates a cross section of a cooling structure <NUM>, parallel to a direction in which the refrigerant flows through the flow path configuration member <NUM>. In <FIG>, the description of the cooling fin is omitted.

In the cooling structure <NUM> illustrated in <FIG>, a power semiconductor <NUM> as a cooling target is in contact with the flow path configuration member <NUM> with the metal layer <NUM> provided on the outer wall of the flow path configuration member <NUM> interposed therebetween. A bus bar <NUM> is connected to the power semiconductor <NUM> to ensure conduction with other power semiconductors (not illustrated), other electric components, and the like. The cooling fins (not illustrated) extend from the upper inner wall <NUM> toward the lower inner wall <NUM> at a portion where the flow path configuration member <NUM> is in contact with the power semiconductor <NUM>. That is, the power semiconductor <NUM> is disposed at the root of the cooling fins (not illustrated).

Heat generated from the power semiconductor <NUM> reaches the outer wall of the flow path configuration member <NUM> via the metal layer <NUM>, and further, the heat reaching the root of the cooling fins (not illustrated) moves from the root of the cooling fins toward the lower inner wall <NUM> through the cooling fins. At this time, the heat is transferred from the cooling fins to the refrigerant by the refrigerant flowing through the flow path <NUM>. Since the power semiconductor <NUM> is in contact with the flow path configuration member <NUM> with the metal layer <NUM> interposed therebetween, the heat generated from the power semiconductor <NUM> is likely to efficiently move to the cooling fins, and the cooling efficiency is improved.

In addition, the metal layer <NUM> can shield a magnetic field in a low frequency range (in particular, a radio band) generated from the power semiconductor <NUM>. It is therefore effective to provide the metal layer <NUM> on the outer wall of the flow path configuration member <NUM> in terms of magnetic field shielding. The metal layer <NUM> only has to be provided on at least a part of the outer wall of the flow path configuration member <NUM>. Note that, the metal layer <NUM>, which is conductive, does not have to be provided at a portion where insulating properties are required. In addition, the metal layer <NUM> may be formed on the outer wall of the flow path configuration member <NUM>, and the portion where insulating properties are required may be covered with a resin layer.

The metal layer <NUM> is preferably provided, for example, on the outer wall of the flow path configuration member <NUM> opposite to a side on which the cooling target is disposed. Further, as shown in <FIG>, when the metal layer <NUM> is provided on a part of the outer wall of the flow path configuration member <NUM> on the side where the cooling target is disposed, a region <NUM> where the metal layer <NUM> is not provided may exist on the outer wall of the flow path configuration member <NUM> opposite to the side on which the cooling target is disposed. Further, a region where the metal layer <NUM> is not provided may exist on the outer wall opposite to a portion where the heat diffuser <NUM> in <FIG> is disposed.

A method of manufacturing the cooling structure according to the disclosure is not limited, and it is possible to adopt a usual method of molding a resin molded body such as an injection molding method, a die slide injection molding method, a blow molding method, a compression molding method, a transfer molding method, an extrusion molding method, or a cast molding method. Note that the die slide injection molding method is preferable because high positional accuracy may be required for manufacturing the cooling structure.

A portion of the nut embedded in the flow path configuration member may be separately manufactured by an insert molding method.

The types of the resins configuring the flow path configuration member and the cooling fin are not limited. Examples of the resin include a polyethylene-based resin, a polypropylene-based resin (PP), a composite polypropylene-based resin (PPC), a polyphenylene sulfide-based resin (PPS), a polyphthalamide-based resin (PPA), a polybutylene terephthalate-based resin (PBT), an epoxy-based resin, a phenol-based resin, polystyrene-based resin, a polyethylene terephthalate-based resin, a polyvinyl alcohol-based resin, a vinyl chloride-based resin, an ionomer-based resin, a polyamide-based resin, an acrylonitrile-butadiene-styrene copolymer resin (ABS), and a polycarbonate-based resin. The resins configuring the flow path configuration member and the resin configuring the cooling fin may be the same or different.

The resins configuring the flow path configuration member and the cooling fin may contain an inorganic filler. Examples of the inorganic filler include silica, alumina, zircon, magnesium oxide, calcium silicate, calcium carbonate, potassium titanate, silicon carbide, silicon nitride, boron nitride, beryllia, and zirconia. Furthermore, examples of the inorganic filler having a flame retardant effect include aluminum hydroxide and zinc borate.

The inorganic fillers included in the resins configuring the flow path configuration member and the cooling fin may be the same or different. One of the resins configuring the flow path configuration member or the resin configuring the cooling fin may include an inorganic filler, and the other does not have to include an inorganic filler.

Examples of the metal configuring the heat diffuser include metals such as aluminum, iron, copper, gold, silver, and stainless steel, and alloys thereof.

The heat diffuser may have a mesh shape, a punching metal, or the like in terms of suppressing a load on the cooling structure due to a difference in thermal expansion coefficient between the resins configuring the flow path configuration member and the cooling fin and the metal configuring the heat diffuser.

In the cooling structure, in terms of the heat diffusibility of the heat diffuser in the plane direction and heat dissipation of the cooling fin, the metal configuring the heat diffuser is preferably at least one selected from the group consisting of aluminum, iron, copper, gold, silver, and stainless steel, and the resin configuring the cooling fin is preferably at least one selected from the group consisting of a polyphenylene sulfide-based resin, a polyamide-based resin, a polyphthalamide-based resin, a polybutylene terephthalate-based resin, a phenol-based resin, and an epoxy-based resin. Preferable examples of the polyamide-based resin include nylon <NUM> and nylon <NUM>.

The type of the refrigerant flowing through the flow path is not limited. Examples of the refrigerant include a liquid such as water and an organic solvent, and a gas such as air. The water used as the refrigerant may include a component such as an antifreeze liquid.

The component configuring the metal layer <NUM> is not limited, and examples thereof include zinc, aluminum, a zinc-aluminum alloy, carbon steel, stainless steel, nickel, a nickel alloy, tin, copper, a copper alloy, silver, a silver alloy, gold, a gold alloy, and molybdenum. Among these components, silver and copper are preferable in terms of enhancing a magnetic field shielding effect. On the other hand, silver and gold are preferable in terms of the cooling efficiency.

A method of forming the metal layer <NUM> is not limited, and examples thereof include electrolytic plating, electroless plating, vapor deposition, attachment of a metal plate, and metal spraying. The metal layer <NUM> is preferably a sprayed metal layer formed by a metal thermal spraying method in terms of formability, and is more preferably zinc in terms of workability.

A thickness of the metal layer <NUM> is not limited, and is preferably from <NUM> to <NUM>.

An average thickness of the metal layer <NUM> in contact with the power semiconductor <NUM> as the cooling target is preferably from <NUM> to <NUM>, and more preferably from <NUM> to <NUM> in terms of the cooling efficiency.

The average thickness of the metal layer <NUM> provided on the outer wall of the flow path configuration member <NUM> on the side opposite to the side where the cooling target is disposed is preferably from <NUM> to <NUM>, preferably from <NUM> to <NUM>, and more preferably from <NUM> to <NUM> in terms of magnetic field shielding.

The cooling structure according to the disclosure is effective for cooling electronic components such as a power module including a plurality of power semiconductors, and a capacitor, and a bus bar electrically joining these electronic components in a vehicle equipped with a motor such as a hybrid vehicle or an electric vehicle.

Hereinafter, magnetic field shielding performance and cooling performance of the metal layer are studied on the basis of an experimental example.

A PPS resin plate having a length of <NUM>, a width of <NUM>, and a thickness of <NUM> was prepared and used as a test piece <NUM>.

A metal layer (a zinc layer) having an average thickness of <NUM> was formed on one surface of the test piece <NUM> by a thermal spraying method. This was used as a test piece <NUM>.

An aluminum plate having a length of <NUM>, a width of <NUM>, and a thickness of <NUM> was used as a test piece <NUM>.

For the test piece <NUM>, the test piece <NUM>, and the test piece <NUM>, the magnetic field shielding performance was evaluated by an apparatus for evaluating a magnetic field shielding effect in a KEC method (from <NUM> to <NUM>) described below.

The obtained results are shown in <FIG>. As is clear from <FIG>, it can be seen that the test piece <NUM> and the test piece <NUM> show a more excellent magnetic field shielding effect than the test piece <NUM>.

A channel model <NUM> having a rectangular cross section with an outer diameter of <NUM> (width) × <NUM> (height), an inner diameter of <NUM> (width) × <NUM> (height), and a length of <NUM> was formed with use of a PPS resin. A metal layer <NUM> (a zinc layer) having an average thickness of <NUM> was formed on an upper surface of an outer wall of <NUM> × <NUM> of the channel model <NUM> by the thermal spraying method. This was defined as a channel model <NUM>.

On each of the outer wall of <NUM> × <NUM> of the channel model <NUM> and the surface on which the metal layer <NUM> of the water channel model <NUM> was formed, an iron block <NUM> having a size of <NUM> × <NUM> × <NUM> and heated to <NUM> was disposed as shown in <FIG>, and water at <NUM> was circulated in each channel model at a flow rate of <NUM>/min.

Temperature changes at a total of four points A to D shown in <FIG> were measured with a high-performance recorder GR-<NUM> manufactured by KEYENCE CORPORATION immediately after the iron block <NUM> was disposed. As a result, the temperature at each measurement point <NUM> minutes after the iron block <NUM> was disposed was as shown in Table <NUM> below, and it became clear that the metal layer <NUM> was effective for cooling the cooling target.

Claim 1:
A cooling structure, comprising:
a flow path configuration member (<NUM>) made of resin and forming a flow path (<NUM>) through which a refrigerant flows; and
a cooling fin (<NUM>) extending from an inner wall (<NUM>) of the flow path (<NUM>) toward an inside of the flow path (<NUM>), having a distal end that is in contact with the inner wall (<NUM>), and having a surface made of resin,
characterized by
further comprising a heat diffuser (<NUM>) disposed at a root of the cooling fin (<NUM>) and a nut body (<NUM>) connected to the heat diffuser (<NUM>).