Patent Application
20050127763
The present invention relates to the field of bridge rectifiers used in alternators, and more particularly, this invention relates to the field of bridge rectifiers having positive and negative heat sinks, cooling fins and diodes for rectifying current produced by an alternator stator coil.
Charging system (CS) alternators are used in large numbers of vehicles and have numerical designations denoting the outside diameter in millimeters of the stator coil. For example, a CS-144 alternator has a stator outside diameter of about 144 millimeters. This CS number can be used to compare relative size and amperes output of different alternators. The CS-144 type alternator, for example, is typically a large case alternator that fits many large or heavy duty General Motors vehicles and Hummers. The CS-144 alternator can come in different output levels, for example, 190 amps and 210 amps. This alternator usually includes rotor windings forming a rotor coil and mounted on a rotor shaft, a stator coil, double sealed ball bearings, contoured rotor segments, an internal fan, long life brushes, high temperature insulation, and a high capacity and rugged bridge rectifier mounted adjacent a rear cover of the alternator body. A fan is mounted next to a pulley in the front section of the alternator and draws air through rear air vents in a rear cover and through front air vents for cooling the alternator components. An internal fan is typically mounted on a rotor shaft and also draws air through a slip ring and frame assembly to aid in cooling the rectifier bridge, any regulator device positioned in the alternator body and the rear bearing. The air is expelled through air vents at the “pulley” or front end.
Many of these types of alternators use a high capacity and rugged bridge rectifier having positive and negative heat sinks that are spaced adjacent to each other and forming a gap therebetween. Button diodes are soldered on respective sides of the heat sink facing each other. Insulating spaces having terminals of a terminal assembly and/or lead frame are positioned between the positive and negative heat sinks and interconnect the button diodes to complete the rectifier circuit.
Although the CS-144 alternators and their bridge rectifiers as described usually form a robust alternator, the button diodes sometimes fail when a shear force such as created by excessive vehicle or other vibration, is applied to any solder joint securing the button diodes to the sides of the heat sink. Even without any added shear force applied to a solder joint, the joint could fail because of excess heat.
Some prior bridge rectifiers for CS-144 and similar alternators have used press fitted diodes in their designs, but the configuration of the cooling fins on the heat sinks, the location of the press fitted diodes relative to the overall configuration of the heat sinks, or the generally small configuration of the cooling fins have not been advantageous. Overheating has sometimes occurred because of inadequate heat sink cooling.
It is therefore an object of the present invention to provide a charging system alternator that overcomes the disadvantages of prior art alternators as described above.
It is yet another object of the present invention to provide a charging system alternator for a CS-144 or similar alternator that incorporates a bridge rectifier that can withstand heat, provide adequate cooling, and have extended diode life.
In accordance with the present invention, a charging system alternator includes an alternator body and a rotor coil mounted for rotation within the alternator body. Stator windings are supported in the housing and produce an electrical output as the rotor coil is rotated. A bridge rectifier is positioned within the alternator body and has an input connected to the stator winding for receiving and rectifying the electrical output from the stator windings.
A positive heat sink and negative heat sink are spaced from each other and form a gap therebetween. Each heat sink includes a side configured to face an opposing side of the other respective heat sink. An opposite cooling side of each heat sink includes cooling fins. A plurality of diodes are positioned at each positive and negative heat sink. A terminal assembly interconnects respective pairs of negative and positive diodes. At least one pair of interconnected negative and positive diodes are positioned offset from each other at an angle to provide a maximum surface area for the cooling fins.
In one aspect of the present invention, the diodes comprise press fitted diodes. In yet another aspect of the present invention, depressions can be formed within the positive and negative heat sinks at their top surface in which the diodes are received. These depressions can be plated. Also, metallic slugs can be received within the positive and negative heat sinks and each receive a respective positive or negative diode.
In one aspect of the present invention, the stator windings have an outside diameter of about 144 millimeters, corresponding to a CS-144 series alternator. The positive and negative heat sinks can be formed from an extruded metal material, such as aluminum. The alternator body typically includes a rear cover having air vents to allow maximum air flow through the cooling fins. The diodes typically include terminals, engaged by the terminal assembly. A lead frame can be positioned on a side opposite the terminal assembly and fasteners extend between the heat sinks and connect the terminal assembly and lead frame to each other.
Other objects, features and advantages of the present invention will become apparent from the detailed description of the invention which follows, when considered in light of the accompanying drawings in which:
The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout, and prime notation is used to indicate similar elements in alternative embodiments.
The present invention advantageously provides a bridge rectifier for use in a charging system alternator such as a high capacity and robust CS-144 alternator used for heavy duty applications. The alternator includes an alternator body, a rotor coil mounted for rotation within the alternator body and stator windings supported in the housing for producing an electrical output as the rotor coil is rotated. In accordance with the present invention, the bridge rectifier is designed with inserted or press fitted diodes at the top surface of the heat sinks. No button diodes are soldered on the heat sink sides. At least one pair of negative and positive diodes are positioned offset to each to provide a maximum surface area for the cooling fins. The bridge rectifier is positioned within the alternator and has an input connected to the stator windings for receiving and rectifying an electrical output from the stator windings.
This improved bridge rectifier of the present invention includes a positive heat sink and a negative heat sink spaced from each other and forming a gap therebetween. Each heat sink includes a side configured to face each other. An opposing cooling side includes cooling fins. A plurality of diodes are positioned at each positive and negative heat sink on a top surface and are preferably press fitted therein, but can be formed to be received in plated depressions on the top surface. A terminal assembly interconnects respective pairs of negative and positive diodes. At least one pair of interconnected negative and positive diodes are positioned offset from each other at an angle to provide a maximum surface area for the cooling fins.
The alternator 20, for example, the illustrated CS-144 alternator produced by General Motors, includes the alternator body 36 (also known as a housing) that defines an alternator enclosure or interior space. The alternator body 36 or housing includes a front end or drive end body section and a rear end or slip ring body section having the rear cover 34. The drive end body section and rear cover include the air vents 32, allowing air flow into the alternator interior space and out the drive end body section. This alternator can be provided with any suitable air flow path for cooling the alternator, however.
The alternator interior space or enclosure includes a rotor coil mounted on a rotatable drive shaft. The drive end or front body section typically includes a bearing well that receives a drive end bearing for rotatably supporting one end of the drive shaft of the rotor coil. The rear body section having the rear cover typically includes a bearing well that receives a slip ring end bearing for rotatably supporting the other end of the drive shaft of the rotor coil.
The alternator body has a first side, a second side, a top end, a bottom end, a predetermined length, a predetermined width, and a predetermined height. The predetermined length of the alternator body 36 extends generally between an outermost portion of the drive end or front body section and an outermost portion of the bearing well of the slip ring or rear body section. The predetermined width of the alternator body 36 extends generally between the first side and the second side. The predetermined height of the alternator body extends generally between the top end and the bottom end.
In an installed position, the alternator 20 is disposed in a predetermined alternator space within a vehicle. This alternator space has a predetermined length, a predetermined width and a predetermined height, which typically corresponds to the length, width, and height, respectively, of the alternator.
A stator coil surrounds the rotor coil and is positioned in the magnetic field generated by the rotor coil. The stator coil is formed as a plurality of stator windings wound about a stator lamination, typically in a three-phase configuration.
The rotor coil is rotated by the vehicle engine via the drive shaft of the rotor coil so that a current is induced in the stator windings. The alternator generates Alternating Current (AC) electricity. The electricity induced in the stator windings is typically three-phase electricity, although in some instances, single phase electricity can be produced.
A voltage regulator is provided in the alternator interior space of the alternator body and is electrically connected to the rotor coil via slip rings provided on the drive shaft of the rotor coil for controlling the intensity of the magnetic field generated by the rotor coil. The voltage output of the alternator is typically maintained within predefined limits.
The AC output signal induced in the stator coil is supplied to the bridge rectifier 22 via output leads, typically three, which are either connected to or formed integrally with the stator windings and which are electrically connected to the bridge rectifier. Because of the close dimensions of the alternator enclosure or interior, the bridge rectifier has a certain configuration in CS-144 alternators, such as shown in
The DC output signal is transmitted to a DC output port provided on the alternator. As will be understood by those skilled in the art, the particular implementation of the DC output port will vary among different makes and models of alternators. For example, the DC output port can be “B+post” or any other suitable DC output port.
Button diodes 56,57 are soldered on the facing diode receiving sides 44,46. A lead frame 58 is positioned on the bottom surface of each heat sink and includes terminal connectors 59 that extend upward and connect the three illustrated screw terminals 38, which can be connected to wires or other connectors and securely locked by fasteners such as nuts. Insulated spacers 60 are located between the diode receiving sides of the negative and positive heat sinks. The spacers 60 support the terminal connectors 59 and terminals 38. This type of prior art bridge rectifier can be formed in a robust design when adequately designed button diodes are used. Shear forces, however, such as created by vehicle vibration, can weaken the solder joint of the button diodes and cause early diode failure.
The positive and negative heat sinks 102,104 are preferably formed from an extruded metal such as aluminum and the cooling fins 120,121 could be formed by cutting with a saw blade or formed by other means. In one aspect of the present invention, the lead frame 130 and terminal assembly 132 are formed from an insulator material, such as vinyl. When the bridge rectifier shown in
The lead frame 130 shown in
Many modifications and other embodiments of the invention will come to the mind of one skilled in the art having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is understood that the invention is not to be limited to the specific embodiments disclosed, and that modifications and embodiments are intended to be included within the scope of the appended claims.
