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, <CIT>).

A further cooling structure is known from <CIT> forming the basis for the preamble of claim <NUM>. A similar cooling structure is described in <CIT>. <CIT> discloses a cooling structure comprising a metal section which has one surface opposite to a heat source and another surface facing not in a direction toward the heat source and a heat-conductive resin section which is formed to protrude from the other surface in an outward direction but not toward the heat source and integrally molded with the metal section.

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.

However, a resin cooling means, which is inferior in thermal conductivity to a metal heat sink, has room for improvement in cooling efficiency.

An aspect of the present invention has been made in view of the above conventional circumstances, and an object of the present invention is to provide a cooling structure made of resin and having excellent cooling efficiency.

A cooling structure of the present invention comprises the features of claim <NUM>.

The present invention can provide a cooling structure made of resin and having excellent cooling efficiency.

A cooling structure according to the present invention includes a flow path configuration member made of resin and forming a flow path through which a refrigerant flows, a heat diffuser having a plate shape, including a metal, and being embedded in the flow path configuration member or joined to the flow path configuration member, and one or more cooling fins extending from the heat diffuser into the flow path and having a surface made of resin. The cooling structure according to the invention includes the heat diffuser having a plate shape and including metal, and the cooling fin extending from the heat diffuser into the flow path and having a surface made of resin. Thus, heat received by the heat diffuser having excellent thermal conductivity is diffused in a plane direction of the heat diffuser having a plate shape, and the heat diffused in a wide range is dissipated from the surface of the cooling fin having excellent heat dissipation. As a result, the cooling structure according to the invention has more excellent cooling efficiency than a resin cooling means made of a resin member having a plate shape and a resin cooling fin extending from the resin member into a flow path.

Hereinafter, the cooling structure of the invention 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.

A cooling structure <NUM> illustrated in <FIG> includes a flow path configuration member <NUM> that is made of resin and forms a flow path <NUM> through which a refrigerant flows. The flow path may have a substantially rectangular cross section as illustrated in <FIG>, or may have a circular cross section, an elliptical cross section, a polygonal cross section other than a rectangular cross section, or the like.

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>.

On the upper inner wall <NUM> side, a plurality of cylindrical cooling fins <NUM> extends from a plate-shaped metal heat diffuser <NUM> to inside of the flow path <NUM>. The cooling fins <NUM> are made of resin similarly to the flow path <NUM>. In <FIG>, a part of each cooling fin <NUM> is indicated by imaginary lines.

On a side opposite to a side on which the cooling fins <NUM> of the heat diffuser <NUM> extend, the bus bar <NUM> as a cooling target cooled by transferring heat to the heat diffuser <NUM> is fixed by a bolt <NUM> and a nut <NUM>. The nut <NUM> includes a nut body <NUM> and the heat diffuser <NUM> provided on a side opposite to a side into which the bolt <NUM> of the nut body <NUM> is inserted. The heat diffuser <NUM> has a rectangular 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 the side 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 is not limited to be embedded in the flow path configuration member, and may be joined to the flow path configuration member, for example, may be joined to an outer wall of the flow path configuration member without being in contact with the flow path. For example, the heat diffuser may be joined to the flow path configuration member by a resin metal joining technique by laser roughening.

All of the plurality of cooling fins <NUM> extend from the heat diffuser <NUM> into the flow path <NUM>. As a result, the heat diffused in a plane direction by the heat diffuser <NUM> is easily dissipated by the cooling fins <NUM>.

<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 dotted 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. The heat diffuser <NUM> has a main surface that faces the flow path <NUM>.

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 rectangular 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> via the flow path configuration member <NUM>. The heat reaching the root of the cooling fins <NUM> moves from the root of the cooling fins <NUM> toward the inside of the flow path <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> do not reach the lower inner wall <NUM> from the upper inner wall <NUM>, and distal ends of the cooling fins <NUM> are located in the flow path <NUM>. The distal ends of the cooling fins <NUM> may be in contact with the lower inner wall <NUM> in terms of increasing the amount of refrigerant in contact with the cooling fins <NUM> to enhance the cooling efficiency of the cooling structure <NUM>. In addition, in a case in which the distal ends of the cooling fins <NUM> are in contact with the lower inner wall <NUM>, for example, 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 region of the flow path <NUM> where the cooling fins <NUM> are provided is observed from upstream in a direction in which the refrigerant flows, an area (area ratio A) 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, and still more preferably <NUM>%, 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.

In <FIG>, a ratio (area ratio B) of a total sectional area of cooling fins <NUM> extending from the heat diffuser <NUM> into the flow path <NUM> in a direction parallel to the main surface of the heat diffuser <NUM> to an area of the main surface of heat diffuser <NUM> is preferably <NUM>% or more, and more preferably <NUM>% or more in terms of improving the cooling efficiency. In terms of resistance in the flow path <NUM>, the area ratio B is preferably <NUM>% or less, and more preferably <NUM>% or less.

In <FIG>, the heat diffuser <NUM> has a rectangular plate shape, but is not limited to a rectangle, and may be a circle, an ellipse, a polygon other than a rectangle, or the like.

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 may have a metal rod-shaped core material of a surface of which is covered with resin. 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.

The number of cooling fins <NUM> extending from the heat diffuser <NUM> into the flow path <NUM> may be one or two or more.

For example, as illustrated in <FIG>, the cooling fins <NUM> may be disposed at a position away from the heat diffuser <NUM>.

In a modification of the cooling structure according to the invention, a metal layer is provided on at least a part of the outer wall of the flow path configuration member, a power semiconductor, a capacitor, or the like as the cooling target is preferably disposed on the outer wall of the flow path configuration member, and the metal layer is provided such that at least a part of the cooling target is in contact with the metal layer. Since the metal layer is provided such that at least a part of the cooling target is in contact with the metal layer, the heat generated in the cooling target moves to the refrigerant flowing through the flow path via the metal layer, and thus the cooling target can be efficiently cooled.

Hereinafter, the modification of the cooling structure according to the invention will be described with reference to <FIG> is a sectional view illustrating a main part of the modification of the cooling structure. <FIG> illustrates a cross section of a cooling structure <NUM>, parallel to a direction in which the refrigerant flows through the flow path <NUM>. In <FIG>, the description of the cooling fins 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 electronic 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 metal layer <NUM> at 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 invention 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 <NUM>.

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

The types of the resins configuring the flow path configuration member <NUM> and the cooling fin <NUM> 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 resins, 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 <NUM> and the resin configuring the cooling fin <NUM> may be the same or different.

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

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

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

In the cooling structure <NUM>, in terms of the heat diffusibility of the heat diffuser <NUM> in the plane direction and heat dissipation of the cooling fin <NUM>, the metal configuring the heat diffuser <NUM> 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 <NUM> 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 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 of the cooling target.

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 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 <NUM> may include a temperature sensor that measures temperature of the refrigerant, and may include a temperature sensor downstream of the region in which the cooling fin <NUM> extends in the flow path <NUM>. In addition, the amount of the refrigerant may be adjusted in accordance with the temperature of the temperature sensor, or a controller may be provided that adjusts the amount of refrigerant in accordance with the temperature of the temperature sensor.

The cooling structure according to the invention 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 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> (length), an inner diameter of <NUM> (width) × <NUM> (length), and a length of <NUM> was formed with use of a PPS resin. A zinc layer <NUM> 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 zinc 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 zinc layer <NUM> was effective for cooling the cooling target.

Claim 1:
A cooling structure (<NUM>, <NUM>), comprising:
a flow path configuration member (<NUM>) made of resin and forming a flow path (<NUM>) through which a refrigerant flows; and
a bus bar (<NUM>), characterized in that the cooling structure (<NUM>, <NUM>) further comprises
a heat diffuser (<NUM>) having a plate shape, including a metal, and being embedded in the flow path configuration member (<NUM>) or joined to an outer wall of the flow path configuration member (<NUM>) without being in contact with the flow path (<NUM>);
one or more cooling fins (<NUM>) extending from the heat diffuser (<NUM>) into the flow path (<NUM>) and having a surface made of resin; and in that
the bus bar (<NUM>), which is cooled by transferring heat to the heat diffuser (<NUM>), is fixed by a bolt (<NUM>) and a nut (<NUM>) on a side opposite to a side from which the one or more cooling fins (<NUM>) of the heat diffuser (<NUM>) extend.