DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0042] Now, a heat sink-equipped cooling apparatus according to the present invention will be described with reference to the accompanying drawings.

[0043] Referring first to FIGS. 1 to 5 , a first embodiment of a heat sink-equipped cooling apparatus according to the present invention is illustrated. A heat sink-equipped cooling apparatus of the illustrated embodiment, as shown in FIG. 1 , generally includes a heat sink 1 and a cooling fan 3 .

[0044] The heat sink 1 includes a base plate 5 having a front surface 5 a and a rear surface 5 b with which a heat source is contacted, as well as a radiation fin unit 7 . The base plate 5 may be made of a metal material such as, for example, aluminum alloy or copper alloy or a plate-like structure exhibiting an internal heat pipe function. Alternatively, it may be made of a non-metal material such as a carbon sheet or the like. The base plate 5 is formed at each of four corners thereof with a through-hole 8 .

[0045] The radiation fin unit 7 , as shown in FIG. 2 , includes a plurality of radiation fins 9 arranged in a manner to surround a virtual central line CL defined so as to extend in a direction perpendicular to the front surface 5 a of the base plate 5 while aligning the central line CL with a center of arrangement of the radiation fins 9 . In the illustrated embodiment, in order to specify a configuration of the radiation fins 9 and a posture of the radiation fins 9 with respect to the base plate 5 , a plurality of virtual vertical planes P are supposed which are defined so as to extend in both a radial direction from the central line CL and a vertical direction perpendicular to the front surface 5 a of the base plate 5 and be spaced from each other at equal intervals in a circumferential direction of a virtual circle C defined about the central line CL, as shown in FIG. 2 . The plural radiation fins 9 are arranged so as to surround the central line CL while aligning it with the center of arrangement of the radiation fins 9 . The plural radiation fins 9 , as shown in FIG. 6 , each include a lower edge 9 a positioned on a side of the base plate, an upper edge 9 b positioned opposite to the lower edge 9 a , and a radiation surface 9 c positioned between the lower edge 9 a and the upper edge 9 b . The radiation fins 9 each are fixedly mounted on the front surface of the base plate 5 so as to be positioned on an intersection line between the virtual vertical plane P corresponding to each of the lower edges 9 a and each of the radiation fin mounting sections 11 contacted with the front surface 5 a of the base plate 5 . In the illustrated embodiment, the radiation fins 9 each are formed by bending of a metal plate as described below, resulting in being made of two plates 10 . The radiation fins 9 each are arranged inclinedly or while being kept inclined so that an angle (inclination angle) θ between the radiation surface 9 c of the radiation fin 9 and the virtual vertical plane P is less than 45 degrees. More specifically, the plural radiation fins 9 each are inclined in the same direction with respect to the virtual vertical plane P corresponding thereto or toward one side in the circumferential direction of the virtual circle C. The inclination angle θ is preferably set to be less than 45 degrees and more than 15 degree. The angle set within such a range permits the number of radiation fins 9 arranged to be increased to a degree sufficient to permit the cooling apparatus of the illustrated embodiment to exhibit satisfactory cooling performance. Alternatively, inclination of the radiation fins 9 may be defined by means of an angle λ between each of the radiation fins 9 and each of the radiation fin mounting sections 11 . The angle λ is preferably set to be more than 45 degrees and less than 85 degrees (45°<λ<85°). Such an angular range reduces a pressure loss of air flow, to thereby increase a velocity of air flow occurring between the radiation fins 9 as compared with the case of λ=90°. This permits the amount of air discharged from the cooling apparatus to be increased, so that it may be increased in cooling efficiency. An optimum value of each of the angles θ and λ may be determined depending on a direction of rotation of an impeller of the cooling fan 3 and a rotational speed thereof, an angle of blades of the impeller, and an area of the radiation fins opposite to the blades. Also, a direction in which the radiation fins 9 are inclined may be opposite to that shown in FIG. 6 , as shown in FIG. 7 .

[0046] When a total radiation area of the radiation fins 9 is indicated at F and an area of the front surface 5 a of the base plate 5 is indicated at S, the radiation fin unit 7 is preferably constructed so that a ratio C=F/S is more than 10 and less than 40 (10<C<40). However, such conditions are not necessarily required in the present invention.

[0047] Now, manufacturing of the radiation fin unit 7 constructed as described above will be described. First, a thin metal plate 13 of an elongated shape which has a thickness of, for example, 1 mm or less is prepared as shown in FIG. 2 . Then, trough lines 14 a and 15 b and crest lines 15 are described on the plate 13 . Thereafter, as shown in FIG. 5 , the plate 13 is subjected to repeated bending along the trough lines 14 a and 14 b and crest lines 15 and then both ends of the plate 13 are joined to each other, leading to completion of the radiation fin unit 7 of an annular configuration as shown in FIG. 2 . The trough lines 14 a and 14 b in each pair shown in FIG. 3 are arranged so as to directly intersect each other on the plate 13 . Alternatively, as shown in FIG. 4 , the trough lines 14 a and 14 b may be arranged so as to intersect each other on virtual extension lines thereof extending to an exterior of the plate 15 . In the radiation fin unit thus completed, the two trough lines 14 a and 14 b positioned on each of both sides of each of the crest lines 15 cooperate with each other to define each of the lower edges of the radiation fin 9 .

[0048] In each of FIGS. 3 and 4 , the trough lines 14 a and 14 b are arranged so as to define an angle θ′ therebetween while being kept from being parallel to each other. The above-described inclination angle θ or λ of each of the radiation fins 9 is determined depending on the angle θ′.

[0049] Joining between the base plate 5 and the radiation fin unit 7 is desirably carried out using a thermal conductive adhesion or by soldering, brazing, welding, ultrasonic welding or the like, because it is required to efficiently transmit heat from the base plate 5 to the radiation fin unit 7 .

[0050] Returning to FIG. 1 , the cooling fan 3 includes the impeller briefly described above which is designated at reference numeral 16 . The impeller 16 includes the plural blades briefly described above which are designated at reference numeral 17 and is rotated by a motor 19 . The motor 19 includes a housing supported on a casing 21 through a plurality of webs (not shown). The casing 21 includes a lower surface, which is integrally provided on each of four corners thereof with a pillar 23 . The four pillars 23 each are formed on a lower end thereof with a threaded hole, in which a threaded portion of a screw inserted via a through-hole 8 formed via each of four corners of the base plate 5 from the rear surface 5 b of the base plate 5 to the front surface 5 a thereof is threadedly fitted. The cooling fan 3 is fixed on the base plate 5 by means of the screws (not shown) inserted via the through-holes 8 while keeping the pillars 23 abutted against the front surface 5 a of the base plate 5 . This permits the radiation fin unit 7 and cooling fan 3 to be arranged in positional relationship which permits each of the blades 17 of the cooling fan 3 and the upper edge 9 a of each of the radiation fins 9 to be opposite to each other. Each of the blades 17 and the upper edge 9 a of each of the radiation fins 9 are so positioned that a gap therebetween is set to be within a range of, for example, between about 5 mm and about 10 mm. In the illustrated embodiment, the blades 17 of the cooling fan 3 are arranged at an angle which permits air to be blown against the radiation fins 9 of the radiation fin unit 7 .

[0051] Then, air which has been thus blown against the radiation fin unit 7 from the cooling fan 3 is permitted to enter a gap between each adjacent two radiation fins 9 through an opening defined between the upper edges 9 a of each adjacent two radiation fins 9 and then be radially outwardly discharged from the radiation fin unit 7 through the gap.

[0052] When the impeller 16 of the cooling fan 3 , as shown in FIG. 8 , is rotated in a right-hand direction in FIG. 8 , air sucked from an upper portion of the blades 17 is permitted to have a component in the direction of rotation of the impeller 16 , to thereby be discharged in directions of arrows indicated at reference numeral 25 , resulting in pressure loss of the air being reduced. Such a reduction in pressure loss permits the fins to be arranged at significantly increased density, to thereby further enhance cooling efficiency of the radiation fin unit 7 .

[0053] A heat sink which has dimensions of 50 mm×50 mm×15 mm, an angle λ of 55 degrees (angle θ of 45 degrees) and C of 17.4 was made of aluminum according to the above-described construction of the illustrated embodiment. Then, the heat sink thus manufactured was subjected to a test of cooling performance under the conditions that the impeller of the axial fan is set at a rotational speed of 4000 rpm and a heat source of 34 W in power is kept contacted with the rear surface of the base plate of the heat sink. As a result, it was confirmed that air is discharged at a flow velocity of 2.8 m/s from an outer periphery of the cooling fan unit of the heat sink and a temperature of the heat source is raised to a level of 42° C.

[0054] Also, a comparative test was carried out using a heat sink wherein an inclination angle θ of each of radiation fins is set to be 0 degree (λ=90°). As a result, the best cooling performance was obtained at λ=90°, C=8.2. At this time, a flow velocity of air discharged was 2.1 m/s and a temperature of a heat source was increased to a level of 48° C.

[0055] Referring now to FIGS. 9 to 16 , a second embodiment of a heat sink-equipped cooling apparatus according to the present invention is illustrated. In connection with the illustrated second embodiment, reference numerals correspond to those discussed in the first embodiment described above, except with an additional prefix of 100. The illustrated embodiment is essentially different in structure and manufacturing of a heat sink from the first embodiment described above. In the first embodiment, the radiation fin unit for the heat sink 1 is formed of a single thin metal plate by bending. On the contrary, in the illustrated embodiment, a radiation fin unit 107 includes a plurality of radiation fins 109 each formed of a flat metal plate made by punching. Then, the radiation fins 109 each are joined at a lower edge 109 b thereof ( FIG. 14 ) to a fin mounting metal plate 108 , resulting in the radiation fin unit 107 being manufactured.

[0056] Now, manufacturing of the radiation fin unit 107 will be described with reference to FIGS. 14 to 16 . The radiation fins 109 , as shown in FIG. 14 , each include in addition to the lower edge 109 b , an upper edge 109 a positioned opposite to the lower edge 109 b and a radiation surface 109 c positioned between the lower edge 109 b and the upper edge 109 a . The lower edge 109 b of each of the radiation fins 109 is integrally provided with a fit projection 109 d . The fin mounting metal plate 108 is formed into a disc-like shape and made so as to exhibit increased thermal conductivity. The fin mounting metal plate 108 , as shown in FIG. 15 , is formed with a plurality of slits S so as to radially extend from a central line CL and be spaced from each other at predetermined intervals in a circumferential direction of a virtual circle C. The slits S each are included in each of a plurality of virtual vertical planes P defined so as to extend in both a radial direction from the central line CL and a direction perpendicular to a surface of the fin mounting metal plate 108 and be spaced from each other at predetermined intervals in the circumferential direction of the virtual circle C. The slits S each are formed into a width larger than a thickness of the radiation fin 109 and formed into dimensions which permit each of the radiation fin 109 to be inclined at a predetermined angle θ in a circumferential direction of the virtual circle C while keeping each of the fit projections 109 d fitted in each of the slits S.

[0057] After the fit projection 109 d of each of the radiation fins 109 is fitted in the slit S, the radiation fin 109 is inclined toward one side in the circumferential direction of the virtual circle C (or in a counterclockwise direction in FIG. 15 ), so that the lower edge 109 b may be joined to the fin mounting metal plate 108 in a manner to be heat-transferable or in a manner to permit heat transfer to be carried out therebetween. Alternatively, the joining may be carried out by means of an adhesive increased in thermal conductivity or by soldering or the like. The radiation fins 109 may be joined to the fin mounting metal plate 108 in order. Alternatively, the joining may be executed by respectively fitting the fit projections 109 d of the radiation fins 109 in the slits S and concurrently inclining the radiation fins 109 as described above while previously applying a thermosetting adhesive to a surface of the fan mounting metal plate 108 , followed by curing of the adhesive. This results in the radiation fin unit 107 being readily manufactured at a reduced cost. The slits S highly facilitate positioning of the radiation fins 109 and joining of the radiation fins 109 to the fin mounting metal plate 108 .

[0058] The thus-manufactured radiation fin unit 107 is joined to a front surface 105 a of a base plate 105 using a joint means increased in thermal conductivity. This results in providing a heat sink structure which is constructed so that the radiation fins 109 each may be fixed indirectly on the front surface 105 a of the base plate 105 while being positioned along an intersection line between the virtual vertical plane P corresponding to the lower edge 109 b of the radiation fin 109 and the front surface 105 a of the base plate 105 , and the radiation fins 109 each may be inclined in an identical direction with respect to the virtual vertical plane P (or toward one side in the circumferential direction of the virtual circle C) so as to form a predetermined inclination angle θ between the radiation surface 109 c of the radiation fin 109 and the virtual vertical plane P. In the illustrated embodiment, the base plate 105 and radiation fin unit 107 each may be formed of copper alloy.

[0059] As will be noted from FIG. 12 , the radiation fin unit 107 including the radiation fins 109 each having a main section formed into a rectangular shape permits a space SP of a substantially frust-conical shape to be formed in the radiation fin unit 107 while having a center positioned on or aligned with a central line of the radiation fin unit and being gradually reduced in diameter toward the base plate 105 .

[0060] The cooling fan 103 shown in FIGS. 9 to 11 includes a casing 121 integrally formed of a synthetic resin material. The casing 121 includes a casing body 121 b provided with an air duct 121 a in a manner to surround at least a part of a periphery of an impeller 116 , three webs 122 for supporting a housing of a motor 119 on the casing body 121 b , and four pillars 123 each mounted at one end thereof on the casing body 121 b and held at the other end thereof on the base plate 105 . The casing body 121 b is provided with a plurality of contact sections 124 which are contacted with an outer surface of the radiation fin unit 107 to prevent lateral movement of the casing 121 . The pillars 123 each are provided at the other end thereof with a hook acting as a held portion. Correspondingly, the base plate 105 is formed at each of four corners with a through-hole 108 acting as a holding portion in which the hook of each of the pillars 123 is held.

[0061] The illustrated embodiment is different in relationship between blades of the impeller and the radiation fins from the first embodiment described above. More specifically, in the illustrated embodiment, a plurality of blades 117 of the impeller 116 are arranged in the same direction as the radiation fins 109 . Also, the cooling fan 103 is operated to rotate the impeller 107 in a direction in which the radiation fins 109 are inclined. Such configuration permits the cooling apparatus of the illustrated embodiment to be increased in cooling performance as compared with the contrary case.

[0062] In the illustrated embodiment as well, the inclination angle θ of the radiation fins 109 and the like may be set as in the first embodiment described above.

[0063] In the illustrated embodiment, the radiation fins 109 are fixed on the fin mounting metal plate 108 . Alternatively, as shown in FIG. 17, a base plate 205 may be formed with a plurality of slits S. The slits S thus formed each have the fit projection 109 d of each of the radiation fins 109 to be fitted therein, to thereby construct the heat sink.

[0064] Also, the radiation fin unit may be configured as shown in FIG. 18 . In FIG. 18 , radiation fins 209 each are provided at a lower edge 209 b thereof with a flange 209 e for fixing. In this instance, a radiation surface 209 c and the flange 209 e may be so arranged that an angle therebetween is set to be 90°+θ. Such arrangement ensures that the inclination angle θ of the radiation fins 209 may be positively provided. The radiation fins 209 may be mounted on the fin mounting metal plate free from any slit. In addition, as shown in each of FIGS. 19 and 20 , the flange 209 e may be fixed directly on the front surface 105 a of the base plate 105 .

[0065] Further, a radiation fit unit may be constructed in such a manner as shown in FIGS. 21 and 22 . More specifically, radiation fins 309 constructed in a simplified manner each are joined directly to the main plate 105 .

[0066] As can be seen from the foregoing, the cooling apparatus of the present invention exhibits cooling performance at substantially the same level as an expensive cooling apparatus conventionally used without being increased in dimensions in a radial direction thereof and ensuring satisfactory durability of the motor.

[0067] While preferred embodiments of the invention have been described with a certain degree of particularity with reference to the drawings, obvious modifications and variations are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.