Brush holder assembly

Abstract: A regulator and brush holder assembly having a regulator assembly (14) attachable to an alternator adjacent to the alternator's slip rings (48,50) and a housing (12) attached to the regulator assembly. The housing (12) has a brush holder portion and a regulator compartment (62) enclosing the regulator circuit (104) of the regulator assembly (14). The brush holder portion has a pair of spatially separated brush holder compartments (20,24) and a pigtail chamber (36) associated with each brush holder. The associated brush holder compartments (20,24) and the associated pigtail chambers (36) have an open end and a closed end and are connected by a slot (40). Brush terminals are attached to the housing and extend into the open end of the pigtail chambers (36). A carbon brush (22,26) is slidably received in each brush holder cavity and its pigtail connection (32) is connected to the associated brush terminal through the slot (40). A coil spring (46) engages the internal end of each carbon brush (22,26) and produces force urging the carbon brushes (22,26) away from the closed end of the brush holding compartment (20,24) into sliding contact with the slip rings (48,50).

Description: This invention relates to an alternator for generating electrical power and in particular to a regulator and brush holder assembly attachable to the alternator frame which controls the output voltage of the alternator. Alternators are commonly used as a source of electrical power in automotive vehicles, boats, aircraft, and various other applications. One of the problems associated with these alternators is the contamination of the carbon brushes which slidingly contact the slip ring of the alternator. In most applications, these brushes are exposed to water, salt, and other contaminants within the engine compartment of the vehicle. Another problem is that helical springs are used to bias the carbon brushes in sliding contact with the alternator slip rings. The force produced by these helical springs is variable as a function of their extension. As a result, the force produced by the helical springs on a new carbon brush is greater than necessary to ensure that after wear of the brush and the extension of the helical spring, the force remains sufficient to maintain the brushes in contact with the slip rings. This excessive force increases the wear on the carbon brushes and reduces their life expectancy. Another problem faced with existing alternator brush holders is during assembly in which the pigtail connection from the brush to an electrical terminal has to be threaded through a small hole. This is a time consuming assembly task. Additionally, the small hole through which the pigtail is inserted needs to be sealed with an epoxy to inhibit contamination by water, salt and other undesirable elements. The brush holder device taught by Nimura in U.S. Patent No. 4,404,487 is representative of brush holders currently in use. This brush holder device has helical springs biasing the carbon brushes in sliding contact with the slip rings of the alternator and the connector pigtails are inserted into a hole provided in the terminal plate and soldered thereto. Koster, in German patents DE 3627529 and DE 3726894 discloses a brush holder where the pigtail is attached to a terminal at the front of the holder. Like Nimura, the brush holder disclosed by Koster has a helical spring biassing the carbon brush against the slip rings. US Patent 3 454 803 discloses a brush holder for slidably supporting a brush and includes a tubular cartridge having a brush receiving channel open at one end. A ribbon-like rolled, constant-pressure spring has one end secured within the channel and the other end engages the brush within the channel. As the brush wears, the spring will roll into a coil bearing on the brush. The present invention now provides a brush assembly comprising: a housing having a pair of spatially separated brush holding compartments, a pigtail chamber adjacent to and associated with each of said brush holding compartments, an electrical brush terminal associated with each pigtail chamber and attached to said housing, a carbon brush slidably received in each of said brush holder compartments, each carbon brush having a pigtail lead extending to said brush terminal, and a coil spring disposed in each of the brush holding compartments, the coil spring engaging the end of the carbon brush to produce a force urging the carbon brush toward an open end of the brush holding compartment, the housing being a moulded plastic housing in which each brush holding compartment is connected to the associated pigtail chamber through a slot between the brush holding compartment and the pigtail chamber, each of said brush holding compartments and said pigtail chambers having a closed end and an open end, said open ends of said brush holding compartments and said pigtail chambers facing in the same direction, each brush terminal extending into the open end of the associated pigtail chamber and the pigtail lead of each carbon brush extending through the connecting slot and into the associated pigtail chamber and being connected to the associated brush terminal at the open end of the pigtail chamber. The brush assembly may have the housing attached to a regulator assembly to form a combined brush and regulator assembly. The advantages of the brush holder assembly is that the ends of the brush holder compartments and the associated pigtail chambers opposite the slip rings are closed to prevent water, salt and other contaminants from the brushes, the pigtail connection and the electrical connection of the pigtail to the electrical terminal. Another advantage of the disclosed brush holder assembly is that the coil springs produce a uniform force on the carbon brushes eliminating excessive loads which reduce brush wear and results in increased durability and reliability. A still further advantage is the terminal to which the brush's pigtails are electrically connected is located adjacent to the open end of the brush holder compartment eliminating the need to thread the pigtail through a small hole during assembly and eliminating the need to seal the hole with an epoxy or other sealing material. The invention will now be described further, by way of example, with reference to the accompanying drawings, in which; Figure 1 is a top view of the regulator and brush holder assembly; Figure 2 is a side view of the regulator and brush holder assembly; Figure 3 is a top view of the moulded plastic housing showing the location of the internally moulded leads and terminals; Figure 4 is a side view of the regulator and brush holder showing the engagement of the carbon brushes with the alternator's slip rings; Figure 5 is a side view of the coil spring in its relaxed state; Figure 6 is a partial front view showing the relative locations of the carbon brushes and the terminals; and Figure 7 is a plan view of the regulator assembly. The details of the regulator and brush holder assembly are shown in Figures 1 through 4. The regulator and brush holder assembly 10 has a moulded plastic housing member 12 and a regulator assembly 14. The housing member 12 is attached to regulator assembly 14 by a set of posts 16 which pass through a corresponding set of apertures 102 provided through the metal base plate 18 of the regulator assembly 14. The heads of the posts 16 are swaged to secure the housing member 12 to the regulator assembly 14. The housing member 12 has a pair of side-by-side brush holder compartments 20 and 24 which house a pair of spatially separated carbon brushes 22 and 26. The internal ends 28 and 30 of the brush holder compartments 20 and 24, respectively, are closed and protect the brushes 22 and 26 and their associated braided copper wire pigtail shunts such as pigtail shunt 32 from exposure to water and salt. A corresponding pigtail shunt (not shown) is connected to the end of carbon brush 26. The pigtail shunt 32 passes through a slot 34 provided between the brush holder compartment 20 and a pigtail compartment 36 and has its end connected to a terminal 38 provided at the open end of the pigtail compartment 36. Like the brush compartment 20, the internal end of the shunt compartment 36 is closed to protect the pigtail shunt 32 and the terminal 38 from water and salt. In a like manner, the pigtail shunt 32 of carbon brush 26 passes through a slot 40 between the brush compartment 24 and an associated pigtail compartment 42 and is connected to a terminal 44 as shown in Figure 6. The carbon brushes 22 and 26 are biased by a coil spring, such as coil spring 46, into sliding contact with the slip rings 48 and 50, respectively, of an alternator (not shown) to which the regulator and brush holder assembly 10 is attached. Each of the coil springs 46 have a U-shaped catch 52 provided at one edge which engages a lip 54 provided adjacent the open end of the brush housing compartments 20 and 24 on the side opposite the associated pigtail compartments. The coiled face of the coil spring 46 engages the internal end of the carbon brushes 22 and 24 and produces a constant force such that the load on the brushes will be constant regardless of the extension of the coiled springs 46. The constant force produced by the coil springs 46 reduces wear of the carbon brushes and increases durability. A side view of the coil spring 46 in its relaxed state is shown in Figure 5. The moulded plastic housing 12 also incorporates shielded two-prong connector 56 having two male connector elements 58 and 60 through which electrical power from the battery and/or the alternator is delivered to the regulator assembly 14. As is known in the art, the regulator circuit mounted on the regulator assembly will regulate to the electrical power being supplied to the rotor of the alternator so as to maintain the output voltage of the alternator independent of the electrical load. The moulded plastic housing 12 also has a regulator compartment 62 which houses the electrical components of the regulator circuit mounted on the regulator assembly 18. The regulator compartment has a removable cover 63 which is removed to make the soldered electrical connections between the regulator circuit and the regulator circuit contacts 64, 70, 74, 80 and 84. After the electrical connections are made, the cover 63 is snapped in place enclosing the top of the regulator compartment 62. The details of the regulator assembly are shown in Figure 7. Figure 3 shows leads embedded within the moulded plastic housing 12 which connect the male connector elements 58 and 60 to the regulator circuit and the carbon brushes 38 and 44. In Figure 3, the cover 63 is removed to show the internal structure of the regulator compartment 62. Male connector element 58 is connected to a regulator circuit contact 64 within the regulator compartment 62 via electrical lead 66 while male connector element 60 is connected to the brush terminal 44 via lead 68 and to a regulator circuit contact 70 within the regulator compartment 62 via lead 72. The brush terminal 38 is connected to the regulator circuit contact 74 via lead 76. The alternator sense contact 78, which senses the failure of the alternator to output electrical power, is connected to regulator circuit contact 80 via lead 82. A ground regulator circuit contact 84 is connected to a pair of ground terminals 86 and 88 by internal lead 90. The ground terminals 86 and 88 contact the base plate 18 when the housing member 12 is mounted to the regulator assembly 14. The holes 92 and 94 of the ground terminals 86 and 88 align with the mounting holes 96 and 98 provided in the base plate 18. The details of the regulator assembly are shown in Figure 7. The base plate 18 has three mounting holes 96, 98 and 100 by means of which the regulator and brush holder assembly 10 is attached to the alternator using threaded fasteners (not shown). The base plate 18 also has a plurality of through apertures 102 through which are received the posts 16 as previously described. A regulator circuit board 104 containing the regulator circuit is bonded to the base plate 18 such that the regulator circuit board 104 is received in the regulator compartment 62.

Claims: A brush assembly comprising: a housing (12) having a pair of spatially separated brush holding compartments (20,24), a pigtail chamber (36) adjacent to and associated with each of said brush holding compartments (20,24), an electrical brush terminal (38,44) associated with each pigtail chamber (36) and attached to said housing (12), a carbon brush (22,26) slidably received in each of said brush holder compartments (20,24), each carbon brush (22,26) having a pigtail lead (32) extending to said brush terminal (38,44), and a coil spring (46) disposed in each of the brush holding compartments, the coil spring (46) engaging the end of the carbon brush (22,26) to produce a force urging the carbon brush toward an open end of the brush holding compartment (20,24), characterised in that, the housing (12) is a moulded plastic housing in which each brush holding compartment (20,24) is connected to the associated pigtail chamber (36) through a slot (34) between the brush holding compartment and the pigtail chamber, each of said brush holding compartments (20,24) and said pigtail chambers (36) having a closed end and an open end, said open ends of said brush holding compartments (20,24) and said pigtail chambers (36) facing in the same direction, each brush terminal (38,44) extending into the open end of the associated pigtail chamber (36) and the pigtail lead (32) of each carbon brush (22,26) extending through the connecting slot (34) and into the associated pigtail chamber and being connected to the associated brush terminal (38,44) at the open end of the pigtail chamber (36). A brush assembly according to claim 1, wherein each coil spring (46) has a coiled portion at one end engaging the associated carbon brush (22,26) and a catch (52) at its opposite end engaging said housing (12) adjacent to the open end of the associated brush holder compartment (20,24). A brush assembly as claimed in claim 2, wherein the catch (52) of each spring (46) engages the housing (12) on the side of the brush holder compartment (20,24) opposite to the associated pigtail chamber (36). A regulator and brush assembly for an alternator having a rotor and two slip rings by means of which electrical power is supplied to said rotor, said regulator and brush assembly comprising a brush assembly as claimed in claim 1, 2 or 3 in combination with a regulator assembly (14) attachable to the alternator, the housing (12) of the brush assembly being attached to the regulator assembly (14) and having electrical leads (72,76) moulded therein connecting said brush terminals (38,44) to the regulator assembly (14). A regulator and brush assembly as claimed in claim 4, wherein said housing (12) further comprises a sense contact terminal (78) automatically connected to a sense output of the alternator when the regulator and brush assembly is mounted on the alternator and an electrical lead (82) moulded in the housing (12) connecting the sense contact terminal (78) to a contact (80) of the regulator assembly (14). A regulator and brush assembly as claimed in claim 5, further comprising an electrical connector for providing electrical power to said regulator assembly (14) from an external source.

Inventors: LAMB CHARLOTTE A, YOCKEY STEVEN J, LAMB, CHARLOTTE A., YOCKEY, STEVEN J.
Applicants: FORD MOTOR CO, FORD MOTOR COMPANY
Application year: 1993
Main classification: H01R39
IPC codes: H02K5, H02K19, H02K13