Title of Invention

ALTERNATING-CURRENT GENERATOR

Abstract

57) Abstract;- An alternating-current generator having a heat sink with at least one of its heat sink fins provided with a push pad. A force is exerted onto the push pad when the heat sink is pushed out of its mold in its die-casting. This arrangement allows cooling air to flow longitudinally along the gaps between the fms without being blocked, and provides an improved cooling efficiency of the heat sink. PRICE: THIRTY RUPEES

Full Text

The present invention relates to an alternating-current generator for use in a vehicle or the like. Description of the Related Art Fig. 5 is a cross-sectional view showing generally a conventional alternating-current generator disclosed in Japanese Patent Laid-open No. 5-64450. Fig. 6A is a front view showing .the rectifier unit of the conventional alternating-current generator. Fig. 6B is a bottom view showing the rectifier unit of Fig. 6A. Fig. 7 shows two rectifier units stacked for the conventional alternating-current generator. A rotor 1 is made of magnetic poles 1a including N and S magnetic poles arranged circumferentially alternatingly, field windings lb for magnetizing the magnetic poles la, and a pair of fans 1c fixed to the magnetic poles la. The rotor 1 is supported by an axis of rotation 2 at both bearings 3 and 4. A pair of slip rings 5 attached onto the axis of rotation 2 are connected to the field windings 1. Brushes 6 that remain in sliding contact with the pair of slip rings 5 are supported by a brush holder 7. An armature 8 comprises armature cores 8a that face the rotor 1 with a small clearance therebetween and armature windings 8b that are configured in a three-phase star connection. Alternating current generated in the armature windings 8b is full-wave rectified by a rectifier unit 9. A pulley 10 is fixed to the axis of rotation 2 by a nut 11. The bearing 3 and one end of the armature 8 are supported by a front bracket 12. The bearing 4, the armature 8, the brush holder 7 and the rectifier unit 9 are supported by a rear bracket 13, A voltage adjuster 14 is accommodated in a recess portion disposed behind the brush holder 7. The front bracket 12 and the rear bracket 13 are connected each other by bolts 15. The field windings lb are electrically connected to the slip rings 5 via connection wires 16. The rectifier unit 9 is made of diodes 17 as a rectifier element and a heat sink 18 for absorbing heat emitted by the diodes 17. Lead wires 19 are attached to the diodes 17. The heat sink 18 has a plurality of equally spaced fins. Some fin gaps 24 are provided with push pads or knockout pin seatings 21. The fins 20 are tapered toward their edge to achieve an improved heat sink performance. The heat sink 18, when it is completed in its die-casting process, is pushed out of the mold by allowing knockout pins (not shown) to press the push pads 21. The lead wires 19 of the diodes 17 are connected to the armature windings 8b via connection wires 22. The connection wires 22 are connected to brushes 6 via AC-DC converter unit (not shown). In such an alternating-current generator, rotation of the rotor 1 generates alternating current in the armature windings 8b. Generated alternating current is fed via the connection wires 22 to the rectifier unit 9 to be rectified there. The AC-DC converter unit converts the rectified current to a direct current. The direct current is fed to the field windings lb via the brushes 6, the slip rings 5, the axis of rotation 2 and the connection wires 16. When the rectifier unit 9 performs rectification, the diodes 17 emit heat which is then transmitted to the heat sink 18. The heat sink 18 is cooled by cooling air which is ~ 4 m 2002 generated by the fans 1c when the rotor 1 rotates. Cooling air flows as shown by arrows in Fig. 5. As shown by the arrow F in Fig. 6B, cooling air flows longitudinally along gaps 23. The gaps 24 with the push pads 21 block air flow as shown by the arrow G. When the heat sink 18 cools in its die-casting process, it remains stuck to its mold. The die-cast sink 18 is pushed out of its mold, by allowing the knockout pins to press the push pads (hatched areas in Fig. 6B) . Since, in this step, a force is exerted on the push pads 21, the area of each push pads 21 is properly sized, and the push pads 21 are evenly distributed over the heat sink 18. Since the fins 20 are equally spaced, two heat sinks 18 may temporarily be stacked in handling for transportation as shown in Fig. 7. In the above-described conventional alternating-current generator, cooling efficiency of the heat sink is degraded, because the push pads 21 between fins 20 block cooling air. The heat sink 18, when die-cast, may occasionally be stacked on another heat sink 18 with the fins 18 of one heat sink 18 received in the gaps of the fins 18 of another heat sink 18. If a plating process is performed on the stacked heat sinks, plating takes place partially rather than uniformly. This may be a cause of uneven plating. SUMMARY OF THE INVENTION In view of the above problems, the present invention has been developed. It is an object of the present invention to provide an alternating-current generator wherein the heat sink of a rectifier element has an improved cooling efficiency and is free from uneven plating. ;. f, If :...;■ •■■; ■ ■> $% >>-!^« j* To achieve the above object, the alternating-current generator according to the present invention comprises rectifier elements and a heat sink which is molded to accommodate the rectifier elements and which has a plurality of fins, at least one of which is provided with a push pad, whereby a force is applied onto the push pad when the heat sink is pushed out of its mold. The alternating-current generator according to the present invention comprises rectifier elements and a heat sink which is molded to accommodate the rectifier elements and which has a plurality of fins, at least one of which is provided with a push pad, said at least one of the fins provided with the push pad having a width wider than the gap between fins, said fins provided with the push pads are disposed between the rectifier elements, whereby a force is applied onto the push pad when the heat sink is pushed out of its mold. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a cross-sectional view showing a first embodiment of the alternating-current generator of the present invention. Fig. 2 is a perspective view showing the rectifier unit and its associated components of the generator of Fig. 1 . Fig. 3A is a front view showing the rectifier unit of Fig. 2. Fig. 3B is a bottom view of the rectifier unit of Fig. 3A. Fig. 4 is a front view showing the rectifier as a second embodiment of the present invention. Fig. 5 is a cross-sectional view showing an example of ;*^p^'^o* tne conventional alternating-current generator. Fig. 6A is a front view showing the rectifier of the conventional alternating-current generator. Fig. 6B is a bottom view showing the rectifier of Fig. 6A. Fig. 7 is an explanatory view showing the state in which the two rectifier units for the conventional generator are stacked. DETAILED DESCRIPTION. OF THE PREFERRED EMBODIMENTS Embodiment 1 Fig. 1 is the cross-sectional view showing the alternating-current generator of the first embodiment of the present invention. Fig. 2 is the perspective view showing the rectifier unit and its associated components of the alternating-current generator of Fig. 1. FIG 3A is the front view showing the rectifier unit of Fig. 2. Fig. 3B is the bottom view of the rectifier unit of Fig. 2A. As shown, a heat sink 18 is provided with standard fins 20 and a plurality of push-pad fins 31 against which knockout pins are pressed. The push-pad fins 31 have a flat end portion 32 so that they are effectively pressed by the knockout pins. The fins 20 and the push-pad fins 31 in the center portion N of the heat sink 18 are low-profiled so that the their ends are kept cleared of a rear bracket 13. To allow the push-pad fins 31 to be pressed by the knockout pins, the mold should have holes corresponding to the knockout pins. In the course of die-casting, the push-pad fins 31 can protrude, and thus, the push-pad fins 31 are set shorter than the fins 20 in height. In such an alternating-current generator, cooling air is allowed to pass longitudinally along gaps between the " ♦ ^P^ 200i push-pad fins 3 1 and the fins 20 and gaps between the fins 20 as shown by arrows H and J in Fig. 3B. This arrangement offers an improved cooling efficiency of the heat sink 18. Since the push-pad fins or knockout pin seatings 31 are designed to be simple, specifically, rectangular in shape, they are easy to manufacture. Since each push-pad fin 31 that has a cooling efficiency lower than that the fin 20 is disposed in the middle between two neighboring diodes 17, each push-pad fin 31 is the most spaced apart from the diodes 17. Each diode 17 is thus less subject to heat buildup. Embodiment 2 Fig. 4 is a front view showing the rectifier unit of the second embodiment of the present invention. As shown, gaps between the fins 20 and the push-pad fins 31 are uneven, and the push-pad fins 31 have,different widths. Unequally spaced fins prevent one heat sink from being stacked on another with the fins of one heat sink received in the gaps of the fins of another heat sink. No uneven plating thus takes place. By making the width of the push-pad fins 31 wider than each gap between the fins 20, the push-pad fins 31 is prevented from being received in any of the gaps between the fins of another heat sink 18. This prevents the heat sink 18 from being stacked in a manner that fins are mutually engaged, and no uneven plating is thus prevented. In the above embodiments, diodes as the rectifier element are used. Alternatively, thyristors may be employed. Preferably, the heat sink is constructed of a high thermal conductivity material. WE CLAIM: 1. An alternating-current generator comprising at least one rectifier element and a heat sink which is molded to accommodate the rectifier elements and which has a plurality of fins, at least one of which is provided with a push pad, whereby a force is applied onto the push pad when the heat sink is pushed out of its mold. 2. The alternating-current generator according to claim 1, wherein each of said fins provided with the push pads is of a rectangular parallelopiped configuration. 3. The alternating-current generator according to claim 1, wherein at least one of said fins provided with the push pads has a width wider than a width of a gap between the fins. 4. The alternating-current generator according to claim 1, wherein the gaps between neighboring fins are uneven. 5. An alternating-current generator substantially as herein described with reference to figures 1 to 4 of the accompanying drawings.

Documents:

0632-mas-95 abstract.jpg

0632-mas-95 abstract.pdf

0632-mas-95 claims.pdf

0632-mas-95 correspondence-others.pdf

0632-mas-95 description (complete).pdf

0632-mas-95 drawings.pdf

0632-mas-95 form-1.pdf

0632-mas-95 form-26.pdf

0632-mas-95 form-4.pdf