JP7312515B2 - Heat dissipation material - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat dissipating member attached around a heat source to radiate the heat of the heat source to the outside.

As demand for improved quietness in vehicle interiors increases, measures are being taken to reduce noise generated from driving devices such as engines and motors and power transmission devices such as transmissions. In recent years, electric vehicles (EVs) and hybrid electric vehicles (HEVs) have been promoted, so the drive noise of electric powertrains including inverters, motors, gearboxes, etc. is also targeted for reduction. As a measure against noise, for example, a soundproof material made of foam such as polyurethane foam is used. However, the foam has a small thermal conductivity because it has a large number of cells (bubbles) inside. For this reason, if it is placed around a noise source that generates heat, it may accumulate heat and cause problems. Therefore, from the viewpoint of improving the heat dissipation property of soundproofing materials using foams, Patent Documents 1 and 2, for example, disclose soundproofing materials in which magnetic fillers are contained in foams. In the soundproofing materials described in Patent Documents 1 and 2, magnetic fillers with high thermal conductivity are oriented in the thickness direction of the soundproofing material. Therefore, not only can noise be reduced, but heat generated by the noise source can be quickly released via the oriented magnetic filler.

JP 2015-069012 A JP 2017-181970 A JP 2017-69278 A

In the case of sound insulation materials using polymers such as foams, rigid cover members are sometimes used to attach them to noise sources and the like. For example, as shown in FIG. 1 of Patent Document 1, FIG. 7 of Patent Document 2, and the like, the cover member is arranged so as to cover the outside of the soundproof material. Further, in order to protect the soundproof material from sand and pebbles that are thrown up while the vehicle is running, the outside of the soundproof material may be covered with a hard cover member. However, when the soundproofing material is covered with the cover member, the heat resistance increases by the amount of the cover member.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a heat dissipating member that satisfies mounting properties and durability without impairing heat dissipating properties.

In order to solve the above problems, the heat dissipation member of the present invention includes a heat dissipation layer having a polymer and a protective layer laminated on the heat dissipation layer, the heat dissipation layer is arranged in contact with a mating member, the thermal conductivity in the lamination direction is 0.3 W/mK or more and 3.0 W/mK or less, and the thermal resistance of the protective layer calculated by the following formula (I) is 2.0× 10 ⁻⁶ m ² K/W or more and 1.5× 10 ⁻² m ² K/ W or less.
Thermal resistance of protective layer = L/k (I)
[L: thickness of protective layer in lamination direction (m), k: thermal conductivity in lamination direction of protective layer (W/mK)]

The heat dissipating member of the present invention comprises a heat dissipating layer and a protective layer. The "laminating direction" in the present invention is the overlapping direction of the heat dissipation layer and the protective layer. The heat-dissipating layer is arranged in contact with a mating member to be heat-dissipated. The heat dissipation layer has a thermal conductivity of 0.3 W/mK or more and 3.0 W/mK or less in the lamination direction, and the heat dissipation layer has a heat dissipation effect of dissipating the heat of the mating member to the outside by thermal conduction. In addition, the heat dissipation layer contains a polymer and has a soundproof effect of absorbing and shielding the sound radiated from the mating member.

A protective layer is laminated on the heat dissipation layer. That is, the surface of the heat-dissipating layer opposite to the mating member is covered with a protective layer (not necessarily covering the entire surface of the heat-dissipating layer, but including covering a portion of the surface of the heat-dissipating layer). By arranging the protective layer, the heat dissipation layer can be protected from the outside, and the heat dissipation member can be easily attached to a mating member or the like. Here, the thermal resistance of the protective layer in the stacking direction is as small as 2.0× 10 ⁻⁶ m ² K/W or more and 1.5× 10 ⁻² m ² K/W or less. For this reason, even if it is covered with a protective layer, the heat dissipation of the heat dissipation layer is less likely to be hindered. In addition, by laminating two layers having different natural frequencies, namely, a heat dissipation layer and a protective layer, there is a possibility that the damping property will be improved and the soundproofing property will be improved.

Thus, according to the heat dissipating member of the present invention, it is possible to improve the mountability and durability without impairing the heat dissipating properties of the heat dissipating layer.

As a heat-dissipating sheet member, for example, Patent Document 3 discloses a foamed composite sheet comprising a rubber-based foamed sheet containing a thermally conductive filler and a metal-based thin film disposed on one surface of the rubber-based foamed sheet. In Patent Document 3, a metal-based thin film is formed on one surface of a rubber-based foam sheet in order to impart electrical conductivity and electromagnetic wave shielding properties in addition to heat dissipation (paragraph [0006]). In addition, in paragraph [0018] of Patent Document 3, it is stated that "in the foamed composite sheet, the metal-based thin film conducts heat along the surface direction of the foamed sheet, so local overheating due to the heat source can be easily dispersed." Thus, Patent Document 3 does not pay attention to the heat conduction in the lamination direction (thickness direction of the foam sheet), and does not consider the thermal resistance of the metal-based thin film in the same direction. In addition, since the metal-based thin film is formed by sputtering or vapor deposition (paragraph [0032]), its thickness is extremely thin. Therefore, in Patent Document 3, there is no concept of protecting the rubber-based foam sheet with a metal-based thin film or facilitating attachment thereof.

It is a top view of the heat radiating member of 1st embodiment. FIG. 2 is a cross-sectional view taken along the line II-II of FIG. 1; 3 is an enlarged view of a dashed-dotted line frame III in FIG. 2; FIG. It is a partial cross-sectional enlarged view of the heat radiating member of 2nd embodiment. 1 is a schematic cross-sectional view of an experimental device used in a heat radiation experiment; FIG. It is a graph plotting the temperature difference against the thermal resistance of the protective layer (thermal conductivity of the heat dissipation layer: 0.78 W/mK). It is the graph which plotted the temperature difference with respect to the area magnification of a protective layer (Thermal conductivity of a thermal radiation layer: 0.78 W/mK). It is a graph plotting the temperature difference against the thermal conductivity of the heat dissipation layer (protective layer: made of aluminum) It is a graph plotting the temperature difference against the thermal conductivity of the heat dissipation layer (protective layer: made of nylon 66 resin containing 30% by mass of glass fiber, made of polyurethane resin)

Embodiments of the heat radiating member of the present invention will be described below.

<First Embodiment>
[composition]
First, the structure of the heat radiating member of this embodiment will be described. FIG. 1 shows a top view of the heat radiating member of this embodiment. FIG. 2 shows a sectional view taken along the line II-II of FIG. FIG. 3 shows an enlarged view of the dashed-dotted line frame III in FIG. For convenience of explanation, hatching of the motor and the clip member is omitted in FIG. 1 to 3, the direction in which the two layers forming the heat dissipation member are laminated is defined as the vertical direction.

As shown in FIG. 1, the heat radiating member 1 has a square plate shape. As shown in FIGS. 1 and 2, the heat radiating member 1 is attached by a clip member 90 to the surface of the motor 9 which is the noise source. The motor 9 is included in the concept of "mating member" in the present invention.

As shown in FIGS. 2 and 3 , the heat dissipation member 1 has a heat dissipation layer 20 and a protective layer 30 . The heat dissipation layer 20 is arranged in contact with the motor 9 . The maximum thickness of the heat dissipation layer 20 is 4.5 mm. The heat dissipation layer 20 has a base material made of polyurethane foam and composite particles obtained by combining stainless steel particles with graphite particles. The composite particles are oriented so as to be continuous in the thickness direction (stacking direction, vertical direction) of the heat dissipation layer 20 . The thermal conductivity of the heat dissipation layer 20 in the stacking direction (vertical direction) is 0.78 W/mK. Polyurethane foam is included in the concept of the polymer constituting the heat-dissipating layer in the present invention. Composite particles are included in the concept of the magnetic filler that constitutes the heat dissipation layer in the present invention.

The protective layer 30 is laminated above the heat dissipation layer 20 . The protective layer 30 consists of an embossed aluminum plate. The vertical cross section of the protective layer 30 has an uneven shape. The thermal conductivity of the protective layer 30 in the stacking direction (vertical direction) is 240 W/mK. Of the two surfaces in the stacking direction (vertical direction) of the protective layer 30 , one surface on the heat dissipation layer 20 side is a back surface 31 and one surface on the opposite side to the heat dissipation layer 20 is a front surface 32 . In this case, the back surface 31 is an uneven surface having a plurality of convex portions protruding downward (toward the heat dissipation layer 20) with respect to the flat plate, and the front surface 32 is an uneven surface having a plurality of concave portions recessed downward from the flat plate. As shown in FIG. 1, the opening of the concave portion of the protective layer 30 has a circular shape when viewed from above. As shown in FIG. 3, the thickness t of the protective layer 30 is 0.5 mm, the height d of the unevenness is 1.3 mm, and the diameter φ of the recess is 3.2 mm. Both the back surface 31 and the front surface 32 are alumite treated and are black in color. The area of the surface 32 is 1.15 times the projected area of the protective layer 30 in the stacking direction (surface area when the protective layer 30 is regarded as a flat plate). The thermal resistance of the protective layer 30 calculated by the above formula (I) is 2.08× 10 ⁻⁶ m ² K/W.

[Production method]
Next, a method for manufacturing the heat radiating member of this embodiment will be described. The heat radiating member 1 is manufactured by an integral molding method. First, a raw material for a heat-dissipating layer is prepared by mixing a foamed urethane resin raw material, composite particles, a foaming agent, a catalyst, and the like. Next, an aluminum plate (embossed and black anodized) prepared in advance for the protective layer 30 is placed in the mold with the surface 32 facing the mold surface, and the mold is clamped. Then, the raw material for the heat dissipation layer is injected into the cavity of the molding die, and integrally molded while applying a magnetic field in the thickness direction of the cavity. Thus, the heat dissipation member 1 in which the heat dissipation layer 20 and the protective layer 30 (aluminum plate) are integrated is manufactured.

[Effect]
Next, the effect of the heat radiating member of this embodiment will be described. In the heat dissipating member 1, the heat dissipating layer 20 has a base material made of polyurethane foam and composite particles oriented in the stacking direction. By arranging the heat dissipation layer 20 in contact with the motor 9 , the heat of the motor 9 is radiated through the composite particles in the heat dissipation layer 20 , and the radiation sound is absorbed and shielded by the heat dissipation layer 20 . A protective layer 30 is laminated on the upper surface (outside) of the heat dissipation layer 20 . As a result, the heat dissipation layer 20 can be protected from the outside, and the heat dissipation member 1 can be easily attached to the motor 9 using the clip member 90 .

The protective layer 30 has a large thermal conductivity and a small thermal resistance. Therefore, the protective layer 30 is less likely to impede the heat dissipation of the heat dissipation layer 20 . The protective layer 30 is made of an aluminum plate, and the rear surface 31 and the front surface 32 are black anodized. This increases the emissivity of the protective layer 30, which is advantageous for improving heat dissipation. Moreover, the surface 32 has a plurality of recesses, the area of which is 1.15 times that of the protective layer 30 formed in a flat plate shape. Since the heat transfer area is large, the heat dissipation of the protective layer 30 becomes higher. On the other hand, the rear surface 31 has a plurality of protrusions protruding toward the heat dissipation layer 20 side. As a result, the contact area with the heat dissipation layer 20 is increased, which facilitates heat conduction and is advantageous for improving heat dissipation, and also improves the adhesiveness between the heat dissipation layer 20 and the protective layer 30 .

The heat radiating member 1 is manufactured by an integral molding method. Therefore, compared to the case where the heat dissipation layer 20 and the protective layer 30 are adhered with an adhesive or the like, the thermal resistance between the two layers is reduced, which is advantageous for improving heat dissipation. As described above, according to the heat dissipation member 1 , the mountability and durability can be improved without impairing the heat dissipation properties of the heat dissipation layer 20 .

<Second embodiment>
[composition]
First, the structure of the heat radiating member of this embodiment will be described. The difference between the configuration of the heat dissipating member of this embodiment and the heat dissipating member of the first embodiment is two points: the shape of the protective layer is different, and the heat conductive filler is arranged. Here, the differences will be mainly described. FIG. 4 shows a partially enlarged cross-sectional view of the heat radiating member of this embodiment. For convenience of explanation, the thermally conductive filler is exaggerated in FIG. FIG. 4 corresponds to FIG. 3 described above (enlarged view of dashed-dotted line frame III in FIG. 2). In FIG. 4, the same members as in FIG. 3 are denoted by the same reference numerals. As shown in FIG. 4 , the heat dissipation member 1 has a heat dissipation layer 20 , a protective layer 33 and thermally conductive fillers 40 .

The protective layer 33 is laminated above the heat dissipation layer 20 . The material of the protective layer 33 is the same as that of the protective layer 30 of the first embodiment. That is, the protective layer 33 is made of an embossed aluminum plate, and both the rear surface 34 and the front surface 35 are anodized and exhibit black color. The vertical cross section of the protective layer 33 has an uneven shape. The thermal conductivity of the protective layer 33 in the stacking direction (vertical direction) is 240 W/mK. The back surface 34 is an uneven surface having a plurality of recesses recessed upward with respect to the flat plate. The surface 35 is an uneven surface having a plurality of projections that protrude upward with respect to the flat plate. When the protective layer 33 is viewed from above, the opening of the recess has a diamond shape. The thickness t of the protective layer 33 is 0.5 mm, and the unevenness height d is 1.3 mm. The area of the surface 35 is 1.08 times the projected area of the protective layer 33 in the stacking direction (surface area when the protective layer 35 is regarded as a flat plate). The thermal resistance of the protective layer 33 calculated by the above formula (I) is 2.08× 10 ⁻⁶ m ² K/W, which is the same as that of the protective layer 30 of the first embodiment.

The thermally conductive filler 40 is arranged in a recess on the back surface 34 side of the protective layer 33 . In the recess, thermally conductive filler 40 is interposed between heat dissipation layer 20 and protective layer 33 . Thermally conductive filler 40 is aluminum hydroxide particles.

[Production method]
Next, a method for manufacturing the heat radiating member of this embodiment will be described. The heat dissipating member of this embodiment is also manufactured by the integral molding method, like the heat dissipating member of the first embodiment. First, a raw material for a heat-dissipating layer is prepared by mixing a foamed urethane resin raw material, composite particles, a foaming agent, a catalyst, and the like. Next, an aluminum plate (embossed and black alumite treated) prepared in advance for the protective layer 33 is placed in the mold so that the surface 35 faces the mold surface. Subsequently, a thermally conductive filler 40 is arranged in the concave portion of the rear surface 34 of the aluminum plate. After the mold is clamped, the raw material for the heat dissipation layer is injected into the cavity of the mold, and integrally molded while applying a magnetic field in the thickness direction of the cavity. In this way, a heat dissipating member is manufactured in which the heat dissipating layer 20 and the protective layer 33 (aluminum plate) are integrated and the heat conductive filler 40 is interposed between the two layers.

[Effect]
Next, the effect of the heat radiating member of this embodiment will be described. The heat dissipating member of this embodiment has the same effect as the heat dissipating member of the first embodiment with respect to the portions having the same configuration. According to the heat dissipating member of this embodiment, the heat conductive filler 40 is interposed between the heat dissipating layer 20 and the protective layer 33 . By interposing the thermally conductive filler, the amount of heat transferred between the heat dissipation layer 20 and the protective layer 33 is increased, and the heat dissipation can be improved. In addition, since the protective layer 33 has an uneven shape, it is easy for air to be involved during integral molding, and voids (bubbles) are likely to be formed in the concave portions. If voids are present in the concave portion, they become heat resistance and impede heat dissipation. In this regard, according to the manufacturing method of the present embodiment, the thermally conductive filler is placed in the concave portion of the protective layer 33 and integrally molded. Thereby, generation of voids can be suppressed.

<Other embodiments>
The embodiments of the heat radiating member of the present invention have been described above. However, the embodiments are not particularly limited to the above forms. It is also possible to implement in various modified forms and improved forms that can be made by those skilled in the art.

In the above-described embodiment, the heat dissipating member has a square shape. The heat dissipating member may cover a part of the mating member, or may cover the entire mating member. Examples of mating members include vehicle parts such as electric powertrain inverters, motors, and gearboxes, engine cylinder heads, and cylinder head covers, as well as electronic parts such as semiconductor elements, electric pumps, and electric compressors.

The heat dissipation layer only needs to contain a polymer, and does not necessarily contain a magnetic filler (composite particles) as in the above embodiment. The polymer may be foam or solid. In the former case, foamed resins or foamed elastomers such as polyurethane foams, polyethylene foams and polypropylene foams can be used. In the latter case, cross-linked rubbers such as urethane rubber, silicone rubber, fluororubber, acrylic rubber and acrylonitrile-butadiene rubber, and various thermoplastic elastomers such as styrene, olefin, vinyl chloride, polyester, polyurethane and polyamide can be used.

When a magnetic filler is added to a polymer and the magnetic filler is oriented in the stacking direction, the heat of the mating member is quickly released via the magnetic filler that is continuous in the stacking direction. Therefore, incorporating a magnetic filler into a polymer is effective in improving heat dissipation. As the magnetic filler, for example, particles of ferromagnetic materials such as iron, nickel, cobalt, gadolinium and stainless steel, antiferromagnetic materials such as MnO, Cr ₂ O ₃ , FeCl ₂ and MnAs, and alloys using these may be used. Among them, stainless steel particles, copper-iron alloy particles, and the like are suitable because of their high thermal conductivity and excellent workability as a filler. From the viewpoint of improving heat dissipation, composite particles in which magnetic particles are attached to the surface of thermally conductive particles having high thermal conductivity may be used as in the above embodiment. Carbon materials such as graphite, expanded graphite, and carbon fiber are suitable as the material of the thermally conductive particles. Particles suitable for magnetic filler may be used as the magnetic particles.

The thermal conductivity of the heat dissipation layer in the stacking direction is 0.3 W/mK or more and 3.0 W/mK or less. When it is 0.7 W/mK or more, the heat dissipation is improved, which is preferable. The thickness of the heat dissipation layer is not particularly limited. The thickness of the heat dissipation layer is desirably 2 mm or more and 10 mm or less from the viewpoints of reducing thermal resistance, facilitating molding, and having appropriate strength and excellent handleability.

The material of the protective layer is not particularly limited. Examples include metals, resins, elastomers, and the like. Metals have the advantage of relatively high thermal conductivity. Resins and elastomers have the advantage that their surfaces can be made uneven and can be easily formed into thin films. Examples of metals include aluminum, aluminum alloys, copper, and stainless steel; examples of resins include polyurethane resins, polyamide (PA) resins such as nylon 66, ABS resins, and polypropylene (PP) resins; examples of elastomers include urethane rubber, silicone rubber, and various thermoplastic elastomers. Also, materials in which various reinforcing materials such as glass fibers are blended with these, or composite materials of these and other materials may be used.

Depending on the application, the surface of the protective layer (the surface opposite to the heat-dissipating layer) may be surface-treated. For example, when forming the protective layer from aluminum or an aluminum alloy, the surface is preferably treated with black alumite. The alumite treatment improves the corrosion resistance and wear resistance, and by making the surface black, the emissivity increases and the heat dissipation can be improved.

The thermal resistance of the protective layer calculated by the above formula (I) [thermal resistance of protective layer=L/k] is 2.0× 10 ⁻⁶ m ² K/W or more and 1.5× 10 ⁻² m ² K/W or less. As shown in formula (I), the smaller the thickness of the protective layer, the smaller the thermal resistance, and the larger the thermal conductivity of the protective layer, the smaller the thermal resistance. Therefore, the material (thermal conductivity) and thickness of the protective layer should be determined so that the thermal resistance falls within the above range. For example, when forming the protective layer from a metal having a relatively high thermal conductivity of 200 W/mK or more, the thickness of the protective layer is desirably 0.3 mm or more and 2.0 mm or less. Conversely, when the protective layer is formed from a resin or elastomer having a relatively low thermal conductivity of less than 1.0 W/mK, the thickness of the protective layer is desirably 1.0 mm or more and 3.0 mm or less.

The shape of the protective layer is not particularly limited. As in the above embodiment, it may be uneven or flat with flat front and back surfaces. For example, of the two surfaces of the protective layer in the stacking direction, when one surface on the heat dissipation layer side is the back surface and one surface on the opposite side to the heat dissipation layer is the front surface, at least one of the back surface and the front surface is an uneven surface having at least one of concave portions and convex portions. Specific forms include (a) a form in which a plurality of recesses are arranged only on the front surface (rear surface is flat), (b) a form in which a plurality of protrusions are arranged only on the front surface (rear surface is flat), (c) a form in which a plurality of recesses are arranged only on the rear surface (surface is flat), (d) a form in which a plurality of protrusions are arranged only on the rear surface (surface is flat), (e) a form in which a plurality of recesses are arranged on the front surface and the rear surface, (f) a form in which a plurality of protrusions are arranged on the front surface and the rear surface, (g) a plurality of recesses on the front surface. , a form in which a plurality of protrusions are arranged on the back surface (for example, the first embodiment), and (h) a form in which a plurality of protrusions are arranged on the front surface and a plurality of recesses are arranged on the back surface (for example, the second embodiment).

The larger the surface area (surface area) exposed to the outside, the larger the heat transfer area. For this reason, in order to improve the heat dissipation property of the protective layer, it is desirable to increase the surface area by at least making the surface uneven. In this case, the surface area of the uneven surface is preferably 1.04 to 1.60 times the projected area of the protective layer in the lamination direction. If the surface area is less than 1.04 times, the effect of improving heat dissipation is small. Conversely, if the surface area exceeds 1.60 times, it becomes difficult to form uneven shapes by embossing. The "projected area of the protective layer in the stacking direction" is equal to the surface area when the surface of the protective layer is assumed to have no unevenness. Further, when a plurality of projections are arranged on the back surface of the protective layer, the contact area with the heat dissipation layer is increased, so the heat dissipation is enhanced and the adhesiveness between the heat dissipation layer and the protective layer is improved.

The configuration, shape, size, and the like of the recesses and protrusions are not particularly limited. As in the above embodiment, concave portions or convex portions may be interspersed in the surface direction, or grooves or ridges extending in a predetermined direction may be used. The cross-sectional shape is also not particularly limited and may be semicircular, semielliptical, triangular, square, rectangular, trapezoidal, or the like. For example, by applying embossing to the material forming the protective layer, various uneven patterns can be formed on the front and back surfaces.

If a plurality of concave portions are arranged on the back surface of the protective layer, voids (bubbles) may be formed when the protective layer and the heat dissipation layer are integrally molded. If voids are present in the concave portion, they become heat resistance and hinder heat dissipation. As a countermeasure for suppressing the generation of voids, it is preferable to dispose a thermally conductive filler in the concave portion on the back surface of the protective layer as in the second embodiment. By doing so, not only is the amount of air involved less and voids are less likely to be generated, but the thermally conductive filler interposed between the heat dissipation layer and the protective layer increases the amount of heat transferred between the two layers, improving heat dissipation. Particles having a thermal conductivity of 20 W/mK or more are preferably used as the thermally conductive filler. For example, aluminum hydroxide, magnesium oxide, boron nitride, graphite, expanded graphite, carbon materials such as carbon fiber, aluminum, magnesium, gold, silver, copper, alloys using these as base materials, and oxides thereof are suitable. The shape of the thermally conductive filler is not particularly limited and may be spherical, flaky, fibrous, columnar, or the like.

A method for manufacturing the heat dissipating member is not particularly limited. In addition to the integral molding method of the above embodiment, a protective layer may be adhered to the surface of the heat dissipation layer with an adhesive or the like. When the protective layer is made of a resin or an elastomer, the raw material for the protective layer is first injected into a mold and molded, and then the raw material for the heat dissipation layer is injected and molded while a magnetic field is applied. Alternatively, the raw material for the protective layer may be applied to the surface of the heat-dissipating layer by spraying or the like and dried. The latter coating method is suitable for forming a thin protective layer. Further, according to the coating method, by making the surface of the heat radiation layer uneven, the uneven protective layer can be easily formed. According to the integral molding method, two-step molding method, coating method, etc., the heat dissipation layer and the protective layer can be fixed without using an adhesive, so the thermal resistance between the two layers is reduced, which is advantageous for improving heat dissipation.

EXAMPLES Next, the present invention will be described more specifically with reference to examples.

<Production of samples>
[Protective layer made of aluminum]
Three kinds of protective layers with different surface areas were prepared, each made of an aluminum plate with black alumite treatment on both front and back surfaces.

(1) The first protective layer has a square plate shape of 130 mm long, 130 mm wide and 0.5 mm thick. The front and back surfaces of the first protective layer are flat surfaces without unevenness. The surface area of the first protective layer is 1.69× 10 ⁻² m ² .

(2) The second protective layer has a square plate shape of the same size as the first protective layer, but differs in that the front and back surfaces are embossed. The second protective layer has the same size and shape as the protective layer of the second embodiment (see FIG. 4). That is, the back surface of the second protective layer is an uneven surface having a plurality of concave portions recessed upward with respect to the flat plate, and the front surface is an uneven surface having a plurality of convex portions protruding upward from the flat plate. The surface area of the second protective layer is 1.82× 10 ⁻² m ² . The area magnification of the surface of the second protective layer is 1.08 when the surface area of the flat plate-like first protective layer having no unevenness is taken as the reference (1.00).

(3) The third protective layer has a square plate shape of the same size as the first protective layer, but differs in that the front and back surfaces are embossed. The third protective layer has the same size and shape as the protective layer of the first embodiment (see FIG. 3). That is, the back surface of the third protective layer is an uneven surface having a plurality of protrusions projecting downward from the flat plate, and the front surface is an uneven surface having a plurality of recesses recessed downward from the flat plate. The surface area of the third protective layer is 1.95× 10 ⁻² m ² . The area magnification of the surface of the third protective layer is 1.15 when the surface area of the flat plate-like first protective layer having no unevenness is taken as the reference (1.00).

Each of the first to third protective layers has a projected area of 1.69× 10 ⁻² m ² , a thermal conductivity in the thickness direction of 240 W/mK, and a thermal resistance of 2.08× 10 ⁻⁶ m ² K/W.

[Protective layer made of nylon 66 resin containing 30% by mass of glass fiber]
Two types of protective layers having different heat resistances were produced from nylon 66 resin containing 30% by mass of glass fiber (hereinafter sometimes simply referred to as "made of nylon 66 resin"). The two types of protective layers produced had different thicknesses, but both had a square plate shape of 130 mm long and 130 mm wide. That is, the front and back surfaces of the two types of protective layers are flat surfaces without irregularities, and all have the same surface area (area magnification is 1.00). The surface area (projected area) of each protective layer is 1.69× 10 ⁻² m ² .

(1) The thickness of the first protective layer is 2.5 mm, the thermal conductivity in the thickness direction is 0.34 W/mK, and the thermal resistance is 7.35× 10 ⁻³ m ² K/W.

(2) The thickness of the second protective layer is 3.5 mm, the thermal conductivity in the thickness direction is 0.34 W/mK, and the thermal resistance is 1.03× 10 ⁻² m ² K/W.

[Protective layer made of polyurethane resin]
Two kinds of protective layers with different surface areas were manufactured from polyurethane resin.

(1) The first protective layer has a square plate shape of 130 mm long, 130 mm wide and 2.0 mm thick. The front and back surfaces of the first protective layer are flat surfaces without unevenness. The surface area of the first protective layer is 1.69× 10 ⁻² m ² .

(2) The second protective layer has a square flat plate shape of the same size as the first protective layer, but differs in that the front and back surfaces are uneven because it was molded using an uneven mold. The second protective layer has the same dimensions (only the thickness is different) and shape as those of the protective layer of the first embodiment (see FIG. 3). That is, the back surface of the second protective layer is an uneven surface having a plurality of protrusions projecting downward from the flat plate, and the front surface is an uneven surface having a plurality of recesses recessed downward from the flat plate. The thickness t in FIG. 3 is 2.0 mm, the unevenness height d is 1.3 mm, and the recess diameter φ is 3.2 mm. The surface area of the second protective layer is 1.95× 10 ⁻² m ² . The area magnification of the surface of the second protective layer is 1.15 when the surface area of the plate-like first protective layer having no unevenness is taken as the reference (1.00).

Each protective layer has a projected area of 1.69× 10 ⁻² m ² , a thermal conductivity in the thickness direction of 0.24 W/mK, and a thermal resistance of 8.33× 10 ⁻³ m ² K/W.

Table 1 summarizes the specifications of the protective layer.

[Heat dissipation material]
A heat dissipation member was manufactured by integrating a heat dissipation layer with each protective layer. Regarding the protective layer made of aluminum, after the protective layer was placed in the mold with the surface facing the mold surface and clamped, the raw material for the heat dissipation layer was injected into the cavity of the mold, and a magnetic field was applied in the thickness direction of the cavity. Regarding the protective layer made of nylon 66 resin containing 30% by mass of glass fiber and polyurethane resin, first, the raw material for the protective layer was injected into the cavity of the mold to mold the protective layer, and then the raw material for the heat dissipation layer was injected, and molding was performed while applying a magnetic field in the thickness direction of the cavity (two-step molding method). In this manner, a sheet-like heat-dissipating member was manufactured in which the heat-dissipating layer and the protective layer were laminated.

A raw material for a heat-dissipating layer was prepared as follows. First, polyether polyol, a cross-linking agent, water as a foaming agent, a catalyst, and a foam stabilizer were mixed to prepare a polyol raw material. Next, composite particles obtained by combining graphite particles with stainless steel particles and a plasticizer were added to the prepared polyol raw material and mixed to prepare a premix polyol. Subsequently, the premixed polyol and the polyisocyanate raw material were mixed to obtain a heat-dissipating layer raw material. For the protective layer, four types of heat dissipation layers having different thermal conductivities in the thickness direction (laminating direction) were appropriately combined. The thermal conductivity of the four heat dissipation layers is 0.1 W/mK, 0.3 W/mK, 0.78 W/mK and 3.0 W/mK. The thermal conductivity of the heat dissipation layer was adjusted by changing the blending amount of the composite particles.

<Heat dissipation experiment>
A heat dissipation experiment was conducted using the manufactured heat dissipation member. FIG. 5 shows a schematic cross-sectional view of the experimental apparatus. As shown in FIG. 5, the experimental apparatus 5 includes a support table 50, a rubber heater 51, a heating plate 52, and a thermocouple 53. The rubber heater 51 has a rectangular sheet shape and is horizontally arranged on the support base 50 . The rubber heater 51 is connected to a temperature controller (not shown) through wiring 510, and is supplied with a constant amount of heat of 0.2 W/ cm ² from the temperature controller. The heating plate 52 is made of aluminum and has a rectangular plate shape. The heating plate 52 is arranged on the upper surface of the rubber heater 51 . The thermocouple 53 is arranged at the center of the upper surface of the heating plate 52 . A thermocouple 53 measures the temperature of the upper surface of the heating plate 52 .

A heat dissipation experiment was conducted by placing the manufactured heat dissipating member 54 on the heating plate 52 with the protective layer facing up, and measuring changes in the upper surface temperature of the heating plate 52 with time. The heat dissipation experiment was conducted under forced convection conditions by blowing air from the side of the experimental device 5 . Then, the temperature when the change in temperature became almost constant was adopted as the final temperature. Similarly, the temperature of the upper surface of the heating plate 52 was measured without the heat radiating member 54, and the final temperature was obtained. The temperature difference was obtained by subtracting the final temperature without the heat radiating member 54 from the final temperature with the heat radiating member 54 . The smaller the temperature difference, the greater the heat dissipation effect of the heat dissipation member 54 .

<Experimental results>
[Relationship Between Thermal Resistance and Heat Dissipation of Protective Layer]
FIG. 6 shows a graph in which the temperature difference is plotted against the thermal resistance of the protective layer as experimental results of a heat dissipating member in which a heat dissipating layer having a thermal conductivity of 0.78 W/mK is combined with various protective layers. In FIG. 6, the plot with a thermal resistance of 2.08× 10 ⁻⁶ m ² K/W (near 0 m ² K/W) is the result of the “aluminum protective layer”, the plot of the thermal resistance of 8.33× 10 ⁻³ m ² K/W (0.00833 m ² K/W) is the result of the “polyurethane resin protective layer”, and the thermal resistance is 7.35× 10 ⁻³ m ² K/. The plot of W (0.00735 m ² K/W) is the result of "protective layer made of nylon 66 resin". 0.0103 m ² K/W

As shown in FIG. 6, it was confirmed that the smaller the thermal resistance of the protective layer, the smaller the temperature difference and the higher the heat dissipation. Moreover, when comparing the same thermal resistance, it was confirmed that the larger the area magnification of the protective layer, in other words, the larger the surface area, the smaller the temperature difference and the higher the heat dissipation.

[Relationship between Surface Area of Protective Layer and Heat Dissipation]
FIG. 7 shows a graph plotting the temperature difference against the area ratio of the protective layer as experimental results of a heat dissipating member in which a heat dissipating layer having a thermal conductivity of 0.78 W/mK is combined with various protective layers. In FIG. 7, the thermal resistance of the “aluminum” protective layer is 2.08× 10 ⁻⁶ m ² K/W, the thermal resistance of the “nylon 66 resin” protective layer is 7.35× 10 ⁻³ m ² K/W, and the thermal resistance of the “polyurethane resin” protective layer is 8.33× 10 ⁻³ m ² K/W. The thermal resistance of the protective layer shown in FIG. 7 decreases in the order of "made of polyurethane resin">"made of nylon 66 resin">"made of aluminum". As shown in FIG. 7, when comparing the same materials (those with the same thermal resistance), it was confirmed that the larger the area magnification of the protective layer, in other words, the larger the surface area, the smaller the temperature difference and the higher the heat dissipation. Moreover, when comparing the same area magnification, it was confirmed that the smaller the thermal resistance, the smaller the temperature difference and the higher the heat dissipation.

[Relationship Between Thermal Conductivity and Heat Dissipation of Heat Dissipating Layer]
(1) Combination with aluminum protective layer As an experimental result of a heat dissipating member in which a heat dissipating layer having a thermal conductivity of 0.30 W / mK and 0.78 W / mK is combined with an aluminum protective layer, Fig. 8 shows a graph plotting the temperature difference against the thermal conductivity of the heat dissipating layer. In this experiment, the case where the temperature difference was 15° C. or less was evaluated as “good heat dissipation”. In FIG. 8, the thick dotted line indicates a temperature difference of 15° C., which serves as a reference for determining the quality of heat dissipation.

As shown in FIG. 8, regardless of whether the thermal conductivity of the heat dissipation layer was 0.30 W/mK or 0.78 W/mK, the temperature difference was less than 15°C (more precisely, 5°C or less), and the heat dissipation property of the heat dissipation member was good. It was also confirmed that the higher the thermal conductivity, the smaller the temperature difference and the better the heat dissipation. In addition, when comparing the heat-dissipating layers with the same thermal conductivity, it was confirmed that the larger the area magnification of the protective layer, in other words, the larger the surface area, the smaller the temperature difference and the higher the heat-dissipating property.

(2) Combination with a resin-made protective layer A graph showing the temperature difference plotted against the thermal conductivity of the heat-dissipating layer is shown in FIG. As in FIG. 8, in FIG. 9, the thick dotted line indicates a temperature difference of 15° C., which is a reference for the quality of heat dissipation.

As shown in FIG. 9, when the thermal conductivity of the heat dissipation layer was 0.10 W/mK, the temperature difference exceeded 15° C., resulting in poor heat dissipation of the heat dissipation member. On the other hand, when a heat-dissipating layer having a thermal conductivity of 0.30 W/mK or more was used, the temperature difference was less than 15° C., indicating that the heat-dissipating member had good heat-dissipating properties. Moreover, when the thermal conductivity was 0.78 W/mK and 3.00 W/mK, the temperature difference was 5° C. or less, and the heat dissipation was further improved.

<Summary>
From the above results, it was confirmed that the heat dissipation member of the present invention, in which the heat dissipation layer has a thermal conductivity of 0.3 W/mK or more and 3.0 W/mK or less and the protective layer has a thermal resistance of 2.0× 10 ⁻⁶ m ² K/W or more and 1.5× 10 ⁻² m ² K/W or less, has excellent heat dissipation properties.

The heat dissipation member of the present invention is suitable for applications that require heat dissipation, such as inverters, motors, and gearboxes for electric power trains, vehicle parts such as engine cylinder heads and cylinder head covers, electronic parts such as semiconductor devices, electric pumps, and electric compressors.

1: heat dissipation member, 20: heat dissipation layer, 30: protective layer, 31: back surface, 32: front surface, 33: protective layer, 34: back surface, 35: front surface, 40: thermal conductive filler, 5: experimental apparatus, 50: support base, 51: rubber heater, 52: heating plate, 53: thermocouple, 54: heat dissipation member, 510: wiring, 9: motor (mating member), 90: clip member.

Claims (7)

A heat dissipation layer having a base material made of a foam and magnetic fillers oriented so as to be continuous in the lamination direction in the base material ;
A protective layer laminated on the heat dissipation layer,
The heat dissipation layer is arranged in contact with the mating member, and has a thermal conductivity in the lamination direction of 0.3 W/mK or more and 3.0 W/mK or less,
A heat dissipating member, wherein the thermal resistance of the protective layer calculated by the following formula (I) is 2.0× 10 ⁻⁶ m ² K/W or more and 1.5× 10 ⁻² m ² K/W or less.
Thermal resistance of protective layer = L/k (I)
[L: thickness of protective layer in lamination direction (m), k: thermal conductivity in lamination direction of protective layer (W/mK)] 2. The heat dissipating member according to claim 1, wherein, of the two surfaces in the stacking direction of the protective layer, when one surface on the heat dissipation layer side is the back surface and one surface on the opposite side of the heat dissipation layer is the front surface, at least one of the back surface and the front surface is an uneven surface having at least one of concave portions and convex portions. The heat dissipation member according to claim 2, wherein the protective layer is made of an aluminum plate having the uneven surface on at least one of the back surface and the front surface, the uneven surface is formed by embossing, and the surface area of the uneven surface is 1.04 to 1.60 times the projected area of the protective layer in the stacking direction . 4. The heat dissipating member according to claim 2, wherein the surface of the protective layer is the uneven surface having a plurality of recesses. 5. The heat dissipating member according to claim 2, wherein the back surface of the protective layer is the uneven surface having a plurality of protrusions projecting toward the heat dissipating layer. 3. The heat dissipating member according to claim 1, wherein the protective layer comprises one or more selected from resins and elastomers. Of the two surfaces in the stacking direction of the protective layer, when one surface on the side of the heat dissipation layer is the back surface and one surface on the opposite side of the heat dissipation layer is the front surface, the back surface is an uneven surface having a plurality of recesses,
7. The heat dissipating member according to any one of claims 1 to 3, or claim 6, wherein a thermally conductive filler having a thermal conductivity of 20 W/mK or more is disposed in the recess.

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