US20150042204A1 - Brush assembly for an electric motor - Google Patents
Brush assembly for an electric motor Download PDFInfo
- Publication number
- US20150042204A1 US20150042204A1 US14/453,785 US201414453785A US2015042204A1 US 20150042204 A1 US20150042204 A1 US 20150042204A1 US 201414453785 A US201414453785 A US 201414453785A US 2015042204 A1 US2015042204 A1 US 2015042204A1
- Authority
- US
- United States
- Prior art keywords
- brush
- electric motor
- holders
- card mount
- commutator
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
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Classifications
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K7/00—Arrangements for handling mechanical energy structurally associated with dynamo-electric machines, e.g. structural association with mechanical driving motors or auxiliary dynamo-electric machines
- H02K7/14—Structural association with mechanical loads, e.g. with hand-held machine tools or fans
- H02K7/145—Hand-held machine tool
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01R—ELECTRICALLY-CONDUCTIVE CONNECTIONS; STRUCTURAL ASSOCIATIONS OF A PLURALITY OF MUTUALLY-INSULATED ELECTRICAL CONNECTING ELEMENTS; COUPLING DEVICES; CURRENT COLLECTORS
- H01R39/00—Rotary current collectors, distributors or interrupters
- H01R39/02—Details for dynamo electric machines
- H01R39/38—Brush holders
- H01R39/381—Brush holders characterised by the application of pressure to brush
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01R—ELECTRICALLY-CONDUCTIVE CONNECTIONS; STRUCTURAL ASSOCIATIONS OF A PLURALITY OF MUTUALLY-INSULATED ELECTRICAL CONNECTING ELEMENTS; COUPLING DEVICES; CURRENT COLLECTORS
- H01R39/00—Rotary current collectors, distributors or interrupters
- H01R39/02—Details for dynamo electric machines
- H01R39/38—Brush holders
- H01R39/385—Means for mechanical fixation of the brush holder
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K13/00—Structural associations of current collectors with motors or generators, e.g. brush mounting plates or connections to windings; Disposition of current collectors in motors or generators; Arrangements for improving commutation
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K13/00—Structural associations of current collectors with motors or generators, e.g. brush mounting plates or connections to windings; Disposition of current collectors in motors or generators; Arrangements for improving commutation
- H02K13/10—Arrangements of brushes or commutators specially adapted for improving commutation
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K3/00—Details of windings
- H02K3/32—Windings characterised by the shape, form or construction of the insulation
- H02K3/38—Windings characterised by the shape, form or construction of the insulation around winding heads, equalising connectors, or connections thereto
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K3/00—Details of windings
- H02K3/46—Fastening of windings on the stator or rotor structure
- H02K3/52—Fastening salient pole windings or connections thereto
- H02K3/527—Fastening salient pole windings or connections thereto applicable to rotors only
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K5/00—Casings; Enclosures; Supports
- H02K5/04—Casings or enclosures characterised by the shape, form or construction thereof
- H02K5/14—Means for supporting or protecting brushes or brush holders
- H02K5/143—Means for supporting or protecting brushes or brush holders for cooperation with commutators
- H02K5/148—Slidably supported brushes
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K7/00—Arrangements for handling mechanical energy structurally associated with dynamo-electric machines, e.g. structural association with mechanical driving motors or auxiliary dynamo-electric machines
- H02K7/08—Structural association with bearings
- H02K7/085—Structural association with bearings radially supporting the rotary shaft at only one end of the rotor
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K9/00—Arrangements for cooling or ventilating
- H02K9/02—Arrangements for cooling or ventilating by ambient air flowing through the machine
- H02K9/04—Arrangements for cooling or ventilating by ambient air flowing through the machine having means for generating a flow of cooling medium
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K9/00—Arrangements for cooling or ventilating
- H02K9/02—Arrangements for cooling or ventilating by ambient air flowing through the machine
- H02K9/04—Arrangements for cooling or ventilating by ambient air flowing through the machine having means for generating a flow of cooling medium
- H02K9/06—Arrangements for cooling or ventilating by ambient air flowing through the machine having means for generating a flow of cooling medium with fans or impellers driven by the machine shaft
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K9/00—Arrangements for cooling or ventilating
- H02K9/28—Cooling of commutators, slip-rings or brushes e.g. by ventilating
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K5/00—Casings; Enclosures; Supports
- H02K5/04—Casings or enclosures characterised by the shape, form or construction thereof
- H02K5/18—Casings or enclosures characterised by the shape, form or construction thereof with ribs or fins for improving heat transfer
Definitions
- the present disclosure relates to a brush assembly for electric motors, and more particularly to a brush assembly for motors used in electric power tools.
- Known portable power tools typically have an electric motor received within a tool housing.
- One common type of electric motor used in power tools has a rotor, a stator, and brushes.
- the rotor includes a rotor shaft, laminations mounted on the rotor shaft, armature windings wound in slots in the lamination stack, and a commutator mounted on the rotor shaft and electrically connected to the armature windings.
- the stator may have field windings wound in laminations, or may have permanent magnets.
- the brushes are mounted in brush housings, often known as brush boxes or brush holders, in sliding electrical contact with the commutator. Electric current is supplied from a power source through the brushes to the commutator, and from the commutator to the armature windings.
- the brushes and brush holders are typically part of a brush assembly(ies).
- the brush holders and brushes are disposed diametrically opposite to each other with the commutator disposed therebetween.
- the brush assembly(ies) includes springs that urge the brushes against the commutator.
- Exemplary brush assemblies may utilize two or four brushes around the commutator.
- Conventional brush holder designs often include a brush card mount that is made of a plastic material and the brush holders mounted on a top surface of the brush card mount.
- the brush holders are typically formed by stamping and folding a metal sheet formed to encase the four sides of the brush. While this process is easy to use, the outer surface area provided by the brush holder is often too small to efficiently transfer heat away from the brushes.
- Some other conventional designs include brush holders which do not fully encase the brush, with open channels for air circulation between the brush holder and the brush. Such designs, however, expose the brushes to debris from the air flow without the desired increased cooling effect.
- an electric motor including: a stator, an armature rotatably received within the stator and having an armature shaft on which a commutator is mounted, and a brush assembly.
- the brush assembly defines a first surface facing the stator and a second surface opposite the first surface.
- the brush assembly includes a brush card mount, brushes in sliding contact with the commutator to supply electric current to the commutator, and thermally-conductive brush holders disposed on the second surface of the brush assembly to house the brushes and secured to the brush card mount.
- each brush holder includes projections formed along a length of an outer surface of the brush holder to increase a total surface area of the brush holder and transfer heat away from the brush holder.
- each of the brush holders includes a base portion securely attached to the brush card mount and disposed to house a bottom surface of the brush, and a main body attached to the base portion to house side surfaces and a top surface of the brush.
- the projections are disposed on at least one of a top surface and/or side surfaces of the main body. In an embodiment, at least six projections are provided.
- the brush card mount includes openings and the brush holders are partially disposed within the openings.
- the openings extend to an outer periphery of the brush assembly.
- the brush holders are slidingly received within the openings from the periphery of the brush assembly in a radial direction.
- the base portions of the brush holders are securely disposed within the openings.
- the brush car mount includes separate planar pieces separated by the plurality of openings and the base portions of the brush holders are slidingly received within the openings and supported by the separate planar pieces of the brush card mount.
- each brush holder includes grooves on both sides thereon and the planar pieces include side guides on both sides thereon arranged to mate with the grooves of the brush holder as the brush holder is received inside the opening of the brush card mount.
- the grooves of the brush holder are formed between two adjacent projections and press-fitted onto the guides of the planar pieces.
- the base portions of the brush holders are exposed on the first surface of the brush assembly to transfer heat away from the brushes through the first surface of the brush assembly.
- the main body and the base portion of the brush holders are integrally formed as a single piece.
- the projections are substantially perpendicular to the main body.
- four brush holders are disposed equidistantly around a periphery of the brush card mount.
- a power tool including a housing and an electric motor disposed in the housing.
- the electric motor includes a stator, an armature rotatably received within the stator and having an armature shaft on which a commutator is mounted, and a brush assembly.
- the brush assembly defines a first surface facing the stator and a second surface opposite the first surface.
- the brush assembly includes a brush card mount, brushes in sliding contact with the commutator to supply electric current to the commutator, and thermally-conductive brush holders disposed on the second surface of the brush assembly to house the brushes and secured to the brush card mount.
- each brush holder includes projections formed along a length of an outer surface of the brush holder to increase a total surface area of the brush holder and transfer heat away from the brush holder.
- the above-described embodiments substantially improve heat transfer from the brushes and brush holders by increasing the total surface area of the brush holders. This arrangement thus improves heat transfer from the brushes through the brush holders.
- FIGS. 1A and 1B depict perspective side views of a four-pole brush assembly (also referred to herein as brush card) 100 , according to an embodiment
- FIGS. 2 and 3 respectively depict top and bottom views of the four-pole brush card 100 , according to an embodiment
- FIG. 4 depicts a perspective expanded view of brush card 100 , according to an embodiment
- FIG. 5 depicts a zoomed-in view of the bridge portion 112 showing the channels 124 a and 124 b and the vertical drop 128 within the channel 124 b , according to an embodiment
- FIG. 6A depicts a rear perspective view of the brush card mount 102 prior to the bearing 136 being inserted and heat-staked, according to an embodiment
- FIG. 6B depicts a rear perspective view of the brush card mount 102 after the bearing 136 is inserted into the bearing pocket 126 and heat-staked, according to an embodiment
- FIG. 7A depicts a front perspective view of a four-pole brush card 200 , according to an alternative embodiment
- FIG. 7B depicts a rear perspective view of the brush card mount 202 of the brush card 200 , according to an embodiment
- FIG. 7C depicts a perspective view of the brush card mount 202 , according to an embodiment
- FIG. 8 depicts a rear perspective view of a conventional brush assembly 300 including a brush card mount 302 , brush holders 304 , and brushes 306 , according to an embodiment
- FIGS. 9A-9C depict various expanded and assembled views of a brush holder 104 and a brush card mount 102 , according to an embodiment
- FIG. 10 depicts a zoomed-in perspective view of the top surface of the brush card 100 showing the upwardly-projecting legs 158 crimped over the top surface of the brush card mount 102 within recessed pockets 172 , according to an embodiment
- FIGS. 11A through 11D depict various views of the brush holder 104 , including the base piece 150 and the main piece 160 crimped together, according to an embodiment
- FIG. 12 provides a rear perspective view of the brush card 100 and a cut-off portion of a motor fan 502 , according to an embodiment
- FIG. 13A depicts a perspective view of a brush card 400 having a modified (extruded) brush holder 404 design, according to an alternative embodiment
- FIG. 13B depicts a perspective view of the brush card 400 without the brush holders 404 , according to an embodiment
- FIGS. 14A and 14B depict perspective and cross-sectional views of the brush holder 404 , according to an embodiment
- FIG. 15 depicts a partial cross-sectional view of a power tool 500 including a motor assembly 510 having a brush assembly 100 , a stator 512 , a rotor 514 , and a fan 502 , according to an embodiment;
- FIGS. 16A-16C depict various perspective and side views of the fan 502 , according to an embodiment
- FIG. 17 depicts a zoomed-in view of the fan 502 inside the tool housing 508 , according to an embodiment
- FIG. 18 depicts a cross-sectional view of a tool housing 508 including the brush card 100 , without the motor 510 and the fan 502 , according to an embodiment
- FIG. 19 depicts the fan 502 mounted on a fully wound and molded rotor 514 , according to an embodiment
- FIG. 20 depicts a perspective view of the same fan 502 and rotor 514 without the windings 552 , according to an embodiment
- FIGS. 21A-21C depict perspective views of a rotor end insulator 560 , according to an embodiment
- FIG. 22 depicts a spring 110 used in the brush card 100 , according to an embodiment
- FIG. 23 depicts a partial perspective view of the brush card 100 with the spring 110 inserted on the post 108 and engaging the brush 106 , according to an embodiment
- FIG. 24 depicts a rear view of the brush card 100 showing the first leg 604 of the spring 110 inside the pocket 614 , according to an embodiment
- FIG. 25 depicts a brush 106 inside the brush holder 104 , according to an embodiment.
- FIGS. 1A and 1B depict perspective side views of a four-pole brush assembly (also referred to herein as brush card) 100 , according to an embodiment of the invention.
- FIGS. 2 and 3 respectively depict top and bottom views of the four-pole brush card 100 , according to an embodiment.
- brush card 100 includes a brush card mount 102 and four brush holders 104 .
- the brush card mount 102 has a substantially circular circumference and the four brush holders 104 are arranged equidistantly on four sides of the brush card mount 102 .
- Each brush holder 104 accommodates a brush 106 therein.
- the brushes 106 housed in brush holders 104 facing each other are electrically connected to one another, as discussed below.
- each brush holder 104 Both ends of each brush holder 104 are open to allow radial movement of the brush 106 towards and away from a center of the brush card 100 .
- the brush card mount 102 includes upright posts 108 in close proximity to the brush holders 104 . Each post 108 is arranged to hold a wound portion of a spring 110 .
- Each spring 110 includes an extended arm that engages a back surface of brush 106 inside the brush holder 104 to bias the brush 106 towards the center of the brush card 100 .
- brush card mount 102 includes a planar portion, to which brush holders 104 are secured.
- a middle section of the planar portion includes an opening that receives a motor commutator (not shown).
- the brush card mount 102 also includes a bridge portion 112 arranged above the commutator opening (and the commutator) and connected to the planar portion via four bridge legs 114 a , 114 b , 116 a , and 116 b .
- Bridge legs 114 a , 114 b , 116 a , and 116 b extend longitudinally (i.e., in the direction of the motor, at a substantially right angle with respect to the plane of the brush card mount 102 ) from the planar portion to the bridge portion 112 .
- Radially formed between bridge legs 114 a , 114 b , 116 a , and 116 b are gaps that allow for the radial movement of brushes 106 .
- bridge leg 114 a and 114 b form walls that extend radially from the bridge portion 112 to (or near) outer edges of the brush card mount 102 .
- the bridge legs 116 a and 116 b similarly extend towards (or near) outer edges of the brush card mount 102 .
- This arrangement strengthens support for the bridge portion 112 .
- bridge leg 114 a mechanically supports and electrically isolates two terminals 118 a and 118 b provided on both sides of its outward-extending wall. Terminals 118 a and 118 b are connected to metal routings 120 a and 120 b , which extend over the bridge portion 112 to bridge leg 114 b .
- Metal routings 120 a and 120 b connect the brushes 106 facing each other to one of the terminals 118 a and 118 b . Specifically, ends of metal routings 120 a and 120 b are connected via wires 122 to either corresponding brush holders 104 or brushes 106 via wires 120 . In an embodiment, metal routings 120 a , 120 b are routed around a shaft bearing pocket 126 , which holds a shaft bearing 136 , as discussed below in detail. In an embodiment, metal routing 120 a crosses over routing 120 b to allow for opposite brushes 106 /brush holders 104 to be connected to the same terminal 118 a or 118 b.
- FIG. 4 depicts a perspective expanded view of brush card 100 , according to an embodiment.
- brush card mount 102 is depicted separately from the rest of the brush card 100 components.
- bridge portion 112 of the brush card mount 102 includes channels 124 a , 124 b that accommodate metal routings 120 a , 120 b .
- Each of the channels 124 a , 124 b in this embodiment extends from leg 114 a to leg 114 b , around shaft bearing pocket 126 .
- Metal routings 120 a , 120 b include vertically-extending teethed ends 132 a , 132 b on both ends, arranged to get pushed into slots 134 of bridge legs 114 a , 114 b during the assembly process.
- Terminals 118 a and 118 b integrally extend from the routings 120 a and 120 b above the teethed ends 132 a and 132 b on the two sides of leg 114 a .
- Channel 124 b includes a recessed portion 128 that penetrates into bridge portion 112 between the shaft bearing pocket 126 and the bridge leg 114 b .
- recessed portion 128 is substantially vertical.
- the channel 124 b extends out through the bridge portion 112 from the end of the recessed portion 128 along a lower plane.
- the recessed portion 128 intersects a portion of channel 124 a.
- Metal routing 120 b includes a penetrating portion 130 that is received inside the recessed portion 128 of channel 124 b .
- the penetrating portion 130 is substantially vertical. This allows routing 120 a to cross over metal routing 120 b as it extends through channel 124 a to bridge leg 114 b . This arrangement creates a gap between the metal routings 120 a and 120 b that, in an embodiment, is 1-3 mm. This gap is sufficient to prevent an electrical shortage.
- FIG. 5 depicts a zoomed-in view of the bridge portion 112 showing the channels 124 a and 124 b and the recessed portion 128 within the channel 124 b , in an embodiment.
- FIGS. 6A-7C Another aspect of the invention is discussed herein with reference to FIGS. 6A-7C .
- FIG. 6A depicts a rear perspective view of the brush card mount 102 prior to the bearing 136 being inserted and heat-staked.
- the brush card mount 102 includes a plastic ring 138 around the back side of the pocket 126 .
- plastic ring 138 slightly projects from a rear surface of the bridge portion 112 .
- FIG. 6B depicts a rear perspective view of the brush card mount 102 after the bearing 136 is inserted into the bearing pocket 126 and heat-staked.
- the plastic ring 138 is heated to deform around the circumference of the rear surface of the shaft bearing 136 .
- the plastic ring 138 in this manner folds inwardly to contain the bearing 136 . This secures the bearing 136 inside the pocket 126 .
- the remaining components of the brush card 100 are assembled on the brush card mount 102 after the heat-staking is completed. Once brush card 100 is fully assembled, the bearing 136 is press-fitted onto the motor shaft (not shown) during motor assembly.
- FIG. 7A depicts a front perspective view of a four-pole brush card 200 , according to an alternative embodiment of the invention.
- FIG. 7B depicts a rear perspective view of the brush card mount 202 of the brush card 200 , according to an embodiment.
- FIG. 7C depicts a perspective view of the brush card mount 202 , according to an embodiment.
- the top of the bridge portion 212 does not include an opening as in the previous embodiment.
- pocket 226 of the brush card mount 202 is not open-ended. Instead, pocket 226 encloses the top end of the shaft bearing 236 .
- Metal routings 220 a , 220 b extend in parallel over the bridge portion 212 .
- the pocket 226 includes one or more pins 228 inserted through two through-holes that extend into the pocket 226 within the bridge portion 212 .
- the through-holes are positioned to place a portion of the pins 226 inside the pocket 226 , as shown in FIG. 7B .
- the shaft bearing 236 includes a groove 238 formed on its outer surface.
- the groove 238 has the same width as the pins 226 .
- the shaft bearing 236 is first placed inside the pocket 226 and the pins 228 are then inserted through the grooves 238 .
- the pins 228 securely hold the shaft bearing 236 inside the pocket 226 .
- any retention mechanism e.g., an E-clip, a C-clip, a single piece U-shaped retainer, a split ring, etc., may be used to retain the shaft bearing 236 .
- FIG. 8 depicts a rear perspective view of a conventional brush assembly 300 including a brush card mount 302 , brush holders 304 , and brushes 306 .
- Brush holders 304 are mounted on a top surface of the brush card mount 302 .
- Brush holders 304 include legs 308 that penetrate through openings, or around the edges of the brush card mount 302 and crimp on the rear side of the brush card mount 302 .
- Brush holders 304 may be provided as single piece or multi-piece units.
- the brush card 300 is arranged around a motor commutator, with the rear surface of the brush card 300 facing the motor stator and fan.
- the top surface of the brush card 300 i.e., where the brush holders 304 are located
- Brush holders 304 generate a substantial amount of heat resulting from the electrical current passing through the brushes 306 .
- Air flows around the brush holders 304 , through the opening in the brush card 300 and around the outer circumference of the brush card 300 , into the fan. While the air flow cools the brush holders 304 to some degree, the cooling effect of the air flow in this conventional design is not sufficient in many power tool designs, in particular in high power applications. What is needed is a more effective cooling mechanism for the brush assembly.
- a new brush holder/brush card design is provided.
- brush card mount 102 includes four openings 140 for receiving the brush holders 104 through its rear surface. This results in brush holders 104 occupying a large portion of the surface area of the rear surface of the brush card 100 adjacent the motor fan.
- brush holders 104 act as heat sinks to transfer heat away from the brush card 100 . This design significantly improves heat transfer as compared to the conventional design discussed above.
- each opening 140 of the brush card mount 102 is defined by two recessed surfaces 142 of the brush card mount 102 on its sides and a boundary portion 144 of the brush card mount 102 on its radial end.
- the recessed surfaces 142 each include two slots 146 .
- the brush holders 104 each include a base piece 150 and a main piece 160 , according to an embodiment.
- the base piece 150 in this embodiment includes a flat portion 152 and two side portions 156 .
- Flat portion 152 includes two rectangular slots 154 .
- Side portions 156 each include two upwardly-projecting legs 158 .
- the main piece 160 in an embodiment, includes a brush-holder portion 162 that is shaped to contain two side surfaces and a top surface of the brush 106 . Extending from side ends the brush-holder portion 162 are two flat portions 166 that extend parallel with the rear surface of the brush card mount 102 . The flat portions 166 each include two slots 168 that correspond to and receive upwardly-projecting legs 158 of the base piece 150 . In addition, the brush-holder portion 162 includes two downward protrusions 164 that correspond to and are received inside rectangular slots 154 of the base piece 150 .
- the side surfaces of the brush-holder portion 162 include openings 170 that is open-ended on a distal end of the brush holder 104 and extends radially to accommodate the back and forth movement of the spring 110 and the wires 122 .
- FIGS. 9B and 9C depict steps of assembling the brush holder 104 into the brush card mount 102 , according to an embodiment of the invention.
- the main piece 160 of the brush holder 104 is inserted into the opening 140 of the brush card mount 102 .
- the top surfaces of the flat portions 166 mate with the recessed surfaces 142 of the bush card 102 around the opening 140 .
- the brush holder portion 162 penetrates through the opening 140 and projects above the top surface of the brush card mount 102 .
- Slots 168 of the main piece 160 in this position are aligned with slots 146 of the recessed surfaces 142 .
- upwardly-projecting legs 158 of the base piece 150 are inserted through the aligned slots 168 of the main piece 160 and slots 146 of the recessed surfaces 142 .
- Downward protrusions 164 are received inside the rectangular slots 154 as the base piece 150 comes in contact with the main piece 160 .
- Side portions 156 of the base piece 150 mate with the back surfaces of the flat portions 166 of the main piece 160 .
- the upwardly-projecting legs 158 are crimped as discussed below.
- the flat portion 152 of the base piece 150 together with the brush holder portion 162 , form a rectangular box for holding the brush 106 .
- FIG. 10 depicts a zoomed-in perspective view of the top surface of the brush card 100 showing the upwardly-projecting legs 158 crimped over the top surface of the brush card mount 102 within recessed pockets 172 .
- Recessed pockets 172 each include two slanted surfaces (see FIG. 4 ) between the slots 146 . Crimped portions of the upwardly-projecting legs 158 rest on these slanted surfaces once they are crimped.
- top surface of the boundary portion 144 of the brush card mount 102 is recessed to accommodate insertion of the brush 106 inside the brush holder 104 once the brush holder 104 assembly is complete. It is further noted that openings 170 of the brush holder 104 are arranged to accommodate the back and forth movement of the spring 110 and the wires 122 along with the brush 106 .
- FIGS. 11A through 11D depict various views of the brush holder 104 , including the base piece 150 and the main piece 160 crimped together.
- the brush card mount 102 is not shown in these figures. However, as discussed above, in the fully-assembled brush card 100 , areas of the brush card mount 102 between recessed surfaces 142 and recessed pockets 172 are sandwiched between the crimp portions of the upwardly-projected legs 158 and the top surfaces of the flat portions 166 of the brush holders 104 .
- the brush holder design of the invention discussed herein provides several advantages.
- the two-piece assembly of the brush holders into the brush card mount is relatively easy.
- the metallic base pieces 150 of the brush holders 104 are exposed in close proximity to the motor fan.
- the brush holders 104 thus act as heat sink to transfer heat away from the brush holders 104 and brushes 106 .
- This arrangement substantially improved overall heat transfer from the brush card 100 .
- FIG. 12 provides a rear perspective view of the brush card 100 and a cut-off portion of a motor fan 502 , according to an embodiment of the invention.
- the brush holders 104 occupy at least 40% of the total surface area of the rear surface of the brush card 100 .
- the brush holders 104 take up at least 45% of the total area of the surface area of the rear surface of the brush card 100 .
- the brush holders 104 take up at least 50% of the total area of the surface area of the rear surface of the brush card 100 .
- the rear surface of the brush card 100 acts as a baffle for the fan 502 .
- FIG. 13A depicts a perspective view of a brush card 400 , according to this embodiment.
- the brush card 400 includes a brush card mount 402 and brush holders 404 .
- brush card mount 402 has a substantially circular periphery and the four brush holders 404 are arranged equidistantly around the periphery of the brush card mount 402 .
- the brush holders 404 facing each other are electrically connected to one another.
- Each brush holder 404 houses a brush 406 therein. Both ends of each brush holder 404 are open to allow radial movement of the bush towards a center of the brush card 400 .
- the brush card mount 402 includes posts 408 in close proximity to the brush holders 404 .
- the posts 408 accommodate springs 410 , each of which includes an extended arm that engages a back portion of a corresponding brush 406 to bias the brush 406 towards the center of the brush card 400 .
- Metal routings 420 a , 420 b are disposed on (over or within) bridge portion 412 to connect brushes 406 that are arranged opposite each other. As in the previously-described embodiments, metal routings 420 a , 420 b cross over each other within bridge portion 412 . Terminals 418 a , 418 b are disposed at the ends of the metal routings 420 a , 420 b.
- FIG. 13B depicts a perspective view of the brush card 400 without the brush holders 404 .
- bridge portion 412 includes channels 424 a , 424 b formed therein for placement of metal routings 420 a , 420 b .
- a planar portion of the brush card mount 402 includes four separate planar pieces 411 connected together via legs 414 of bridge portion 412 .
- the planar pieces 411 in this embodiment are not connected to one another along the main plane of the brush card mount 400 . Instead, planar openings 416 between the planar pieces 414 receive the brush holders 404 in a radial direction.
- Planar pieces 411 include side guides 415 arranged to be received in corresponding grooves of the brush holders 404 , as discussed below.
- planar openings 416 may be open-ended on the outer end for receiving the brush holders 404 , but close ended on the inner end to mechanically join the planar pieces 411 to one another.
- planar openings 416 may be open-ended on the inner end for receiving the brush holders 404 , but close ended on the outer end to mechanically join the planar pieces 411 to one another. Placing a ring on either the inner or outer circumferences of the planar pieces 411 to connect the planar pieces 411 together provides mechanical support for the brush card 400 and enhances the moldability of the planar pieces 411 during the manufacturing process.
- FIGS. 14A and 14B depict perspective and cross-sectional views of the brush holder 404 , according to an embodiment.
- Brush holder 404 in this embodiment includes a main body 450 and a base portion 452 formed together integrally as one piece.
- the main body 450 includes openings 470 for facilitating the back and forth movement of the springs 410 and the wires 422 .
- the main body 450 includes side projections 454 , which together with ends of the base portion 454 form grooves 462 .
- Grooves 462 receive side guides 415 of the brush card mount 402 as the brush holders 404 slides into planar openings 416 .
- the grooves 462 are press-fitted onto the guides 415 .
- an adhesive is used to secure the guides 415 inside the grooves 462 .
- a lower surface of the base portion 452 acts as a heat sink to carry heat away from the brush card 400 , including the brush holder 404 and the brushes 406 , similarly to the previous embodiment.
- the brush holder 404 includes projections 456 , 458 projecting from the main body 450 .
- four side projections 456 and two top projections 458 are provided. Projections 456 and 458 increase the total surface area of the brush holder 404 , thereby improving heat transfer away from the brush holder 404 .
- projections 456 , 458 shown in FIGS. 14A and 14B are used with a single-piece brush holder design, the same projections may be incorporated into the two-piece design of FIGS. 9A-12 to improve heat transfer.
- FIG. 15 depicts a partial cross-sectional view of a power tool 500 , according to an embodiment.
- the power tool 100 in this embodiment includes the brush card 100 , including the brush card mount 102 and the brush holders 104 , disposed at one end of the housing.
- Motor 510 in this embodiment includes a motor stator (i.e., can) 512 , a rotor 514 , and a commutator 516 rotatatably coupled to the rotor 514 .
- the commutator 516 is disposed inside the brush card 100 between the four brushes 106 .
- the fan 502 is also rotatably attached to the rotor 514 .
- the operation of the motor 510 and its components is beyond the scope of this disclosure and is not discussed in further detail, but reference is made to U.S. Pat. No. 7,126,242 issued Oct. 24, 2006, which is incorporated by reference in its entirety, as an example of an electric motor.
- FIGS. 16A-16C depict various perspective and side views of the fan 502 , according to an embodiment.
- FIG. 17 depicts a zoomed-in view of the fan 502 inside the tool housing 508 .
- fan 502 includes a plurality of blades 504 arranged between a first inner ring 520 and a second outer ring 522 .
- the inner ring 520 is arranged to mate with the rotor 514 , while the second ring 522 is disposed in the proximity of the brush card 100 , as shown in FIG. 15 .
- Each fan blade 504 includes an inner edge 524 that extends from a first end 520 a of the inner ring 520 towards the rear surface of the brush card 100 .
- the inner edge 524 is inclined towards the armature 516 and the rotor 514 (i.e., at an angle to the longitudinal axis of the motor 510 ), though the inner edge 524 may be parallel to the tool housing in an alternative embodiment.
- Each fan blade 504 also includes an outer edge 526 that extends from the outer ring 522 towards the stator 512 substantially in parallel with the longitudinal axis of the motor 510 .
- a first side edge 528 extends from a second end 520 b of the inner ring 520 to the end of the outer edge 526 .
- the first side edge 528 in an embodiment, is arranged at an angle away from the stator 512 in the direction of the end of the outer edge 526 .
- a second side edge 530 extends from the outer ring 522 to the end of the inner edge 524 , substantially parallel to the rear surface of the brush card 100 .
- the second side edge 530 may be inclined slightly towards the brush card 100 as it meets the inner edge 524 .
- the outer surface of the inner ring 522 includes a slanted surface 532 that is arranged at an angle away from the brush card 100 in the direction of the outer edge 526 . In an embodiment, this slanted surface 532 may be arranged at at least a 45 degree angle with respect to the rear surface of the brush card 100 . This arrangement helps reduce the length of the outer edge 526 of each blade 504 even further for more effective air flow generation.
- FIG. 18 depicts a cross-sectional view of a tool housing 508 including the brush card 100 , without the motor 510 and the fan 502 .
- air inlets 542 and 544 are provided in the rear and center portion of the power tool housing 508 .
- the fan 502 rotates, it generates an air flow from front inlets 542 through the motor 510 , in particular in the area between the stator 512 and the rotor 514 , in an axial direction to cool the motor 510 .
- the air is then redirected in a radial direction out of the power tool 500 through air vents 540 disposed in the tool housing 508 adjacent the fan 502 .
- the fan generates an air flow from rear inlets 544 through the brush card 100 , particularly around the brush holders 104 , and through the area between brush holders 104 and the commutator 516 , in an axial direction to cool the brush card 100 .
- This air is also redirected in a radial direction out of the power tool 500 through the same air vents 540 .
- the rear surface of the brush card 100 i.e., brush card mount 102 together with the brush holders 104 ) forms a baffle to contain the air flow inside the fan 502 and out of the vents 540 .
- the end surface 513 of the stator 512 facing the fan 502 forms a second baffle for the fan 502 .
- the angled surface of the first side edge 528 creates a gap between the stator 512 end surface baffle and the fan 502 .
- the angled surface of the outer ring 522 creates a gap between the brush card 100 baffle and the fan 502 .
- These gaps may adversely affect air flow through the fan 502 .
- two ribs 534 and 536 corresponding to the slanted surface 532 of the outer ring 522 and the first side edge 528 , respectively, are provided in the tool housing 508 .
- the first rib 534 includes a sloped surface disposed in close proximity to and in parallel with the slanted surface 532 of the outer ring 522 .
- the second rib 536 includes a sloped surface in close proximity to and in parallel with the first side edge 528 of the fan 501 .
- Both ribs 534 and 536 also include surfaces that are in contact with the rear surface of the brush card 100 (including a portion of the brush holders 104 and the brush card mount 102 ) and the end surface 513 of the stator 512 , respectively.
- the ribs 534 and 536 are both ring-shaped and extend around the two housing halves to fully close the gaps between the housing 508 and the fan 502 created by the angled surfaces of the outer ring 522 and the first side edge 528 .
- a combination of the rear surface of the brush card 100 (including the brush card mount 102 and the brush holders 104 ), and the sloped surface of the first rib 534 , forms the first baffle for the fan 502 .
- a combination of the end surface 513 of the stator 512 and the sloped surface of the second rib 536 forms the second baffle for the fan 502 .
- the ribs 534 and 536 provide alignment features for placement of the brush card 100 and the stator 512 within the power tool housing 508 .
- FIGS. 19-21C Another aspect of the invention is disclosed herein with reference to FIGS. 19-21C , and with continued reference to FIGS. 16A-16C .
- FIG. 19 depicts the fan 502 mounted on a fully wound and molded rotor 514 .
- the rotor 514 includes a lamination stack 550 , windings 552 , and end insulators 560 .
- End insulators 560 are disposed at the ends of the lamination stack 550 prior to the lamination stack 550 being wound.
- End insulators 560 provide insulation between the rotor windings and the rotor lamination stack 550 and protect the wires from being cut during the winding process.
- FIG. 20 depicts a perspective view of the same fan 502 and rotor 514 without the windings 552 .
- the fan 502 in order to property attach the fan 502 to the rotor 514 , the fan 502 is provided with a plurality of tongues 580 , as shown in FIGS. 16A , 16 C, 19 and 20 .
- Tongues 580 in an embodiment project in the direction of the rotor 514 from the inner ring 520 of the fan 502 .
- tongues 580 may be 2-6 mm in length.
- tongues 580 may be disposed equidistantly around the periphery of the inner ring 510 .
- the number of tongues 580 may correspond to the number of slots in the lamination stack 550 , although a lesser number of tongues 580 may be provided.
- end insulator 560 facing the fan 502 is provided with a plurality of notches 562 arranged to receive the tongues 580 of the fan 502 , as discussed below in detail.
- FIGS. 21A-21C depict perspective views of a rotor end insulator 560 , according to an embodiment of the invention.
- End insulator 560 is pre-molded to include a base portion 564 shaped to match a cross-sectional profile of the lamination stack 550 .
- the base portion 564 includes radially-extending slots 566 formed between teeth 558 of the base portion 564 .
- the slots 566 and teeth 568 respectively correspond to the slots and teeth of the lamination stack 550 .
- the teeth 568 extend outwardly along the circumference of the base portion 564 to partially close the outer end of the slots 566 .
- the slots 566 of the base portion 564 have walls 570 projecting perpendicularly to the base portion 564 (in the longitudinal direction of the motor) on one side.
- the walls 570 are arranged to form-fittingly protrude into the slots of the lamination stack 550 to insulate the lamination stack teeth.
- the walls 570 may be, for example, 4 to 12 mm in depth.
- the base portion 564 includes a through-hole 572 at its center portion for accommodating the rotor shaft.
- two end insulators 560 are form-fittingly mounted on the ends of the lamination stack 550 .
- the thickness of the walls 570 ensures that no contact is made between the coil and the lamination stack 560 .
- the outer surface of the base portion 564 has a slanted profile near the outer ends of the teeth 568 that forces the coils to be packed tightly into the lamination stack slots.
- notches 562 are arranged at the outer ends of the teeth 568 on the periphery of the end insulator 560 to receive the tongues 580 of the fan 502 .
- the notches 562 extend longitudinally through the entire length of the teeth 568 . This arrangement allows the tongues 580 of the fan 502 to make direct contact with the end of the lamination stack 550 . This embodiment reduces the tolerances associated with the motor over a comparable design in which the fan 502 is mounted on the end insulator 560 .
- tongues 580 are mounted directly on the lamination stack 550 , calculating the total tolerances for the fan 502 needs only take into account the tolerance levels of the fan 502 and the lamination stack 550 , and not the tolerance levels of the end insulator 560 , which is made of plastic and has a relatively large tolerance. It is noted that tongues 580 may be secured within the notches 562 form-fittingly, or via heat-taking, welding, adhesive-bonding, etc.
- the fan 502 may be further provided with one or more additional tongues 582 arranged on opposite ends of the inner ring 520 .
- tongues 582 are longer than tongues 580 and are arranged to be received between two adjacent teeth of the lamination stack 550 .
- Long tongues 582 are provided to ensure that tongues 580 are placed inside the notches 562 , and not between the adjacent teeth of the lamination stack 550 , during assembly.
- FIG. 22 depicts a spring 110 , according to an embodiment.
- Spring 110 includes a wound portion 602 , a first leg 604 , and a second leg 606 that is longer than the first leg 604 and includes a hook 608 at its distal end.
- FIG. 23 depicts a partial perspective view of the brush card 100 , according to an embodiment.
- the wound portion 602 of the spring 110 is arranged around the post 108 of the brush card mount 102 .
- the hook 608 of the second leg 606 engages the back of the brush 106 .
- the first leg 604 of the spring 110 engages a pocket 614 of the brush card mount 102 .
- pockets 614 for each spring 110 are formed within end portions of the bridge legs 116 a , 116 b on both sides (e.g., close to the periphery of the brush card mount 102 ). The position of the first leg 604 within the pocket 614 allows the torsion spring 110 to be loaded as it engages the back of the brush 106 .
- the first leg 604 is placed within the pocket 614 as the wound portion 602 is pushed down the post 108 .
- the second leg 606 which at this point rests on top of the brush holder 104 , is then pulled to engage the back of the brush 106 (or an end portion 620 of the brush holder 104 ).
- the problem with this assembly process is that it is difficult to engage and move the second leg 606 after the wound portion 602 has been pushed down the post 108 . This process is time consuming and burdensome.
- the end of the bridge legs 116 a , 116 b are each provided with an arcuate surface 612 , as shown in FIG. 23 .
- Arcuate surface 612 is located above the pockets 614 .
- a sloped surface 610 is provided extending from the top of the bridge leg 116 a or 116 b to the top of the arcuate surface 612 .
- the first leg 604 at this point is placed on the sloped surface 610 or the arcuate surface 612 .
- the hook 608 remains within the recess 622 .
- the end of the first leg 604 slides down the sloped surface 610 over the arcuate surface 612 , and along the arcuate surface 612 until it snaps into the pocket 614 .
- the first leg 604 moves down the arcuate surface 612 it loads the torsion spring 110 , so the spring 110 will be loaded even after the first leg 604 snaps into the pocket 614 .
- FIG. 24 depicts a rear view of the brush card 100 showing the first leg 604 of the spring 110 inside the pocket 614 , according to an embodiment.
- the pockets 614 for adjacent springs 110 are located under the arcuate surface 612 , forming a mushroom-shaped cross-sectional profile.
- the arcuate surface 612 may be shaped as a half-circle above the pockets 614 , although a cam surface may be utilized to optimize the movement of the first leg 604 into the pocket 614 .
- FIG. 25 Another aspect of the invention is described herein with reference to FIG. 25 .
- brush 106 is shown inside the brush holder 104 .
- the hook 608 of the spring 110 engages the recess 622 of the end portion 620 of the brush holder during the assembly process.
- the hook 608 and the second leg 606 are pulled down to engage the rear surface of the brush 106 .
- the rear surface of the brush 106 includes two humped surfaces 624 and 626 and a groove 628 therebetween.
- the rear surface of the brush 106 is designed and arranged such that, after the motor is assembled and the commutator is placed inside the brush card 100 , a portion of the humped surface 624 is aligned with a lower end of the recess 622 .
- the recess 622 includes a slanted lower end 622 a which, as viewed from the side, ends in alignment with (or slightly above) the humped surface 624 .
- the second leg 606 of the spring 110 is simply pushed down. As the second leg 606 is pushed down, the hook 608 (or the second leg 606 ) slides down the slanted lower end 622 of the recess, onto and over the humped surface 624 , and into the groove 628 .
- This design substantially eases the assembly process.
- each the humped surfaces 624 may be semi-circular shaped, although a cam surface may be utilized to optimize the movement of the hook 608 over the humped surface 624 . It is also noted that two humped surfaces are shown in this embodiment to ease the assembly process, but the brush 106 may include a single humped surface above the groove 628 .
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Dc Machiner (AREA)
- Motor Or Generator Current Collectors (AREA)
- Motor Or Generator Cooling System (AREA)
- Iron Core Of Rotating Electric Machines (AREA)
Abstract
An electric motor is provided including: a stator, an armature rotatably received within the stator and having an armature shaft on which a commutator is mounted, and a brush assembly. The brush assembly defines a first surface facing the stator and a second surface opposite the first surface. The brush assembly includes a brush card mount, brushes in sliding contact with the commutator to supply electric current to the commutator, and thermally-conductive brush holders disposed on the second surface of the brush assembly to house the brushes and secured to the brush card mount. Each brush holder includes projections formed along a length of an outer surface of the brush holder to increase a total surface area of the brush holder and transfer heat away from the brush holder.
Description
- This utility application claims the benefit of U.S. Provisional Application No. 61/864,264 filed Aug. 9, 2013, and U.S. Provisional Application No. 61/932,932 filed Jan. 29, 2014, contents of both of which are incorporated herein by reference in their entirety.
- The present disclosure relates to a brush assembly for electric motors, and more particularly to a brush assembly for motors used in electric power tools.
- The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
- Known portable power tools typically have an electric motor received within a tool housing. One common type of electric motor used in power tools has a rotor, a stator, and brushes. The rotor includes a rotor shaft, laminations mounted on the rotor shaft, armature windings wound in slots in the lamination stack, and a commutator mounted on the rotor shaft and electrically connected to the armature windings. The stator may have field windings wound in laminations, or may have permanent magnets. The brushes are mounted in brush housings, often known as brush boxes or brush holders, in sliding electrical contact with the commutator. Electric current is supplied from a power source through the brushes to the commutator, and from the commutator to the armature windings.
- The brushes and brush holders are typically part of a brush assembly(ies). The brush holders and brushes are disposed diametrically opposite to each other with the commutator disposed therebetween. The brush assembly(ies) includes springs that urge the brushes against the commutator. Exemplary brush assemblies may utilize two or four brushes around the commutator.
- Generally, in brush assemblies, transmission of electric current across the sliding interface between the brushes and the motor commutator generates a considerable amount of heat. This heat is often associated with the material used in the brushes. Such materials have relatively higher electrical resistance in order to enhance desirable brush properties such as low friction coefficient and high durability. The heat is also generated from the electrical arcing that occurs when electrical switching occurs as the commutator and brushes rotate with respect to each other. It is desirable for this heat to be transferred away from the brushes and dissipated, for example by impinging air flow.
- Conventional brush holder designs often include a brush card mount that is made of a plastic material and the brush holders mounted on a top surface of the brush card mount. The brush holders are typically formed by stamping and folding a metal sheet formed to encase the four sides of the brush. While this process is easy to use, the outer surface area provided by the brush holder is often too small to efficiently transfer heat away from the brushes. Some other conventional designs include brush holders which do not fully encase the brush, with open channels for air circulation between the brush holder and the brush. Such designs, however, expose the brushes to debris from the air flow without the desired increased cooling effect.
- What is needed is a brush assembly design that enables more efficient heat transfer from the brushes through the brush holders.
- According to an embodiment of the invention, an electric motor is provided including: a stator, an armature rotatably received within the stator and having an armature shaft on which a commutator is mounted, and a brush assembly. In an embodiment, the brush assembly defines a first surface facing the stator and a second surface opposite the first surface. In an embodiment, the brush assembly includes a brush card mount, brushes in sliding contact with the commutator to supply electric current to the commutator, and thermally-conductive brush holders disposed on the second surface of the brush assembly to house the brushes and secured to the brush card mount. In an embodiment, each brush holder includes projections formed along a length of an outer surface of the brush holder to increase a total surface area of the brush holder and transfer heat away from the brush holder.
- In an embodiment, each of the brush holders includes a base portion securely attached to the brush card mount and disposed to house a bottom surface of the brush, and a main body attached to the base portion to house side surfaces and a top surface of the brush.
- In an embodiment, the projections are disposed on at least one of a top surface and/or side surfaces of the main body. In an embodiment, at least six projections are provided.
- In an embodiment, the brush card mount includes openings and the brush holders are partially disposed within the openings. In an embodiment, the openings extend to an outer periphery of the brush assembly. In an embodiment, the brush holders are slidingly received within the openings from the periphery of the brush assembly in a radial direction. In an embodiment, the base portions of the brush holders are securely disposed within the openings.
- In an embodiment, the brush car mount includes separate planar pieces separated by the plurality of openings and the base portions of the brush holders are slidingly received within the openings and supported by the separate planar pieces of the brush card mount. In an embodiment, each brush holder includes grooves on both sides thereon and the planar pieces include side guides on both sides thereon arranged to mate with the grooves of the brush holder as the brush holder is received inside the opening of the brush card mount. In an embodiment, the grooves of the brush holder are formed between two adjacent projections and press-fitted onto the guides of the planar pieces.
- In an embodiment, the base portions of the brush holders are exposed on the first surface of the brush assembly to transfer heat away from the brushes through the first surface of the brush assembly.
- In an embodiment, the main body and the base portion of the brush holders are integrally formed as a single piece.
- In an embodiment, the projections are substantially perpendicular to the main body.
- In an embodiment, four brush holders are disposed equidistantly around a periphery of the brush card mount.
- According to an embodiment of the invention, a power tool is provided including a housing and an electric motor disposed in the housing. In an embodiment, the electric motor includes a stator, an armature rotatably received within the stator and having an armature shaft on which a commutator is mounted, and a brush assembly. In an embodiment, the brush assembly defines a first surface facing the stator and a second surface opposite the first surface. In an embodiment, the brush assembly includes a brush card mount, brushes in sliding contact with the commutator to supply electric current to the commutator, and thermally-conductive brush holders disposed on the second surface of the brush assembly to house the brushes and secured to the brush card mount. In an embodiment, each brush holder includes projections formed along a length of an outer surface of the brush holder to increase a total surface area of the brush holder and transfer heat away from the brush holder.
- The above-described embodiments substantially improve heat transfer from the brushes and brush holders by increasing the total surface area of the brush holders. This arrangement thus improves heat transfer from the brushes through the brush holders.
-
FIGS. 1A and 1B depict perspective side views of a four-pole brush assembly (also referred to herein as brush card) 100, according to an embodiment; -
FIGS. 2 and 3 respectively depict top and bottom views of the four-pole brush card 100, according to an embodiment; -
FIG. 4 depicts a perspective expanded view ofbrush card 100, according to an embodiment; -
FIG. 5 depicts a zoomed-in view of thebridge portion 112 showing thechannels vertical drop 128 within thechannel 124 b, according to an embodiment; -
FIG. 6A depicts a rear perspective view of thebrush card mount 102 prior to the bearing 136 being inserted and heat-staked, according to an embodiment; -
FIG. 6B depicts a rear perspective view of thebrush card mount 102 after thebearing 136 is inserted into thebearing pocket 126 and heat-staked, according to an embodiment; -
FIG. 7A depicts a front perspective view of a four-pole brush card 200, according to an alternative embodiment; -
FIG. 7B depicts a rear perspective view of thebrush card mount 202 of thebrush card 200, according to an embodiment; -
FIG. 7C depicts a perspective view of thebrush card mount 202, according to an embodiment; -
FIG. 8 depicts a rear perspective view of aconventional brush assembly 300 including abrush card mount 302,brush holders 304, and brushes 306, according to an embodiment; -
FIGS. 9A-9C depict various expanded and assembled views of abrush holder 104 and abrush card mount 102, according to an embodiment; -
FIG. 10 depicts a zoomed-in perspective view of the top surface of thebrush card 100 showing the upwardly-projectinglegs 158 crimped over the top surface of thebrush card mount 102 within recessedpockets 172, according to an embodiment; -
FIGS. 11A through 11D depict various views of thebrush holder 104, including thebase piece 150 and themain piece 160 crimped together, according to an embodiment; -
FIG. 12 provides a rear perspective view of thebrush card 100 and a cut-off portion of amotor fan 502, according to an embodiment; -
FIG. 13A depicts a perspective view of abrush card 400 having a modified (extruded)brush holder 404 design, according to an alternative embodiment; -
FIG. 13B depicts a perspective view of thebrush card 400 without thebrush holders 404, according to an embodiment; -
FIGS. 14A and 14B depict perspective and cross-sectional views of thebrush holder 404, according to an embodiment; -
FIG. 15 depicts a partial cross-sectional view of apower tool 500 including amotor assembly 510 having abrush assembly 100, astator 512, arotor 514, and afan 502, according to an embodiment; -
FIGS. 16A-16C depict various perspective and side views of thefan 502, according to an embodiment; -
FIG. 17 depicts a zoomed-in view of thefan 502 inside thetool housing 508, according to an embodiment; -
FIG. 18 depicts a cross-sectional view of atool housing 508 including thebrush card 100, without themotor 510 and thefan 502, according to an embodiment; -
FIG. 19 depicts thefan 502 mounted on a fully wound and moldedrotor 514, according to an embodiment; -
FIG. 20 depicts a perspective view of thesame fan 502 androtor 514 without thewindings 552, according to an embodiment; -
FIGS. 21A-21C depict perspective views of arotor end insulator 560, according to an embodiment; -
FIG. 22 depicts aspring 110 used in thebrush card 100, according to an embodiment; -
FIG. 23 depicts a partial perspective view of thebrush card 100 with thespring 110 inserted on thepost 108 and engaging thebrush 106, according to an embodiment; -
FIG. 24 depicts a rear view of thebrush card 100 showing thefirst leg 604 of thespring 110 inside thepocket 614, according to an embodiment; and -
FIG. 25 depicts abrush 106 inside thebrush holder 104, according to an embodiment. - Reference will now be made in detail to various aspects and embodiments of the invention, examples of which are illustrated in the accompanying drawings.
- Four-Pole Brush Card with Bridge Connector
- A first aspect of the invention is discussed herein.
FIGS. 1A and 1B depict perspective side views of a four-pole brush assembly (also referred to herein as brush card) 100, according to an embodiment of the invention.FIGS. 2 and 3 respectively depict top and bottom views of the four-pole brush card 100, according to an embodiment. In this embodiment,brush card 100 includes abrush card mount 102 and fourbrush holders 104. Thebrush card mount 102 has a substantially circular circumference and the fourbrush holders 104 are arranged equidistantly on four sides of thebrush card mount 102. Eachbrush holder 104 accommodates abrush 106 therein. Thebrushes 106 housed inbrush holders 104 facing each other are electrically connected to one another, as discussed below. Both ends of eachbrush holder 104 are open to allow radial movement of thebrush 106 towards and away from a center of thebrush card 100. Thebrush card mount 102 includesupright posts 108 in close proximity to thebrush holders 104. Eachpost 108 is arranged to hold a wound portion of aspring 110. Eachspring 110 includes an extended arm that engages a back surface ofbrush 106 inside thebrush holder 104 to bias thebrush 106 towards the center of thebrush card 100. - According to an embodiment,
brush card mount 102 includes a planar portion, to whichbrush holders 104 are secured. A middle section of the planar portion includes an opening that receives a motor commutator (not shown). Thebrush card mount 102 also includes abridge portion 112 arranged above the commutator opening (and the commutator) and connected to the planar portion via fourbridge legs Bridge legs bridge portion 112. Radially formed betweenbridge legs brushes 106. - According to an embodiment,
bridge leg bridge portion 112 to (or near) outer edges of thebrush card mount 102. In an embodiment, thebridge legs brush card mount 102. This arrangement strengthens support for thebridge portion 112. In addition,bridge leg 114 a mechanically supports and electrically isolates twoterminals Terminals metal routings bridge portion 112 to bridgeleg 114 b. Metal routings 120 a and 120 b connect thebrushes 106 facing each other to one of theterminals metal routings wires 122 to eithercorresponding brush holders 104 or brushes 106 via wires 120. In an embodiment,metal routings shaft bearing pocket 126, which holds ashaft bearing 136, as discussed below in detail. In an embodiment,metal routing 120 a crosses overrouting 120 b to allow foropposite brushes 106/brush holders 104 to be connected to thesame terminal -
FIG. 4 depicts a perspective expanded view ofbrush card 100, according to an embodiment. In this figure,brush card mount 102 is depicted separately from the rest of thebrush card 100 components. In an embodiment,bridge portion 112 of thebrush card mount 102 includeschannels metal routings channels leg 114 a toleg 114 b, aroundshaft bearing pocket 126. Metal routings 120 a, 120 b include vertically-extending teethed ends 132 a, 132 b on both ends, arranged to get pushed into slots 134 ofbridge legs metal routings bridge portion 112.Terminals routings leg 114 a.Channel 124 b includes a recessedportion 128 that penetrates intobridge portion 112 between theshaft bearing pocket 126 and thebridge leg 114 b. In an embodiment, recessedportion 128 is substantially vertical. Thechannel 124 b extends out through thebridge portion 112 from the end of the recessedportion 128 along a lower plane. The recessedportion 128 intersects a portion ofchannel 124 a. -
Metal routing 120 b includes a penetratingportion 130 that is received inside the recessedportion 128 ofchannel 124 b. In an embodiment, the penetratingportion 130 is substantially vertical. This allows routing 120 a to cross overmetal routing 120 b as it extends throughchannel 124 a to bridgeleg 114 b. This arrangement creates a gap between themetal routings -
FIG. 5 depicts a zoomed-in view of thebridge portion 112 showing thechannels portion 128 within thechannel 124 b, in an embodiment. - Another aspect of the invention is discussed herein with reference to
FIGS. 6A-7C . - According to an embodiment, as shown in
FIG. 1A throughFIG. 3 andFIGS. 6A and 6B , motor shaft bearing 136 is secured inside theshaft bearing pocket 126 via heat staking.FIG. 6A depicts a rear perspective view of thebrush card mount 102 prior to thebearing 136 being inserted and heat-staked. As shown in this figure, thebrush card mount 102 includes aplastic ring 138 around the back side of thepocket 126. In an embodiment,plastic ring 138 slightly projects from a rear surface of thebridge portion 112.FIG. 6B depicts a rear perspective view of thebrush card mount 102 after thebearing 136 is inserted into thebearing pocket 126 and heat-staked. In this embodiment, after the shaft bearing 136 is inserted into thepocket 126, theplastic ring 138 is heated to deform around the circumference of the rear surface of theshaft bearing 136. Theplastic ring 138 in this manner folds inwardly to contain thebearing 136. This secures the bearing 136 inside thepocket 126. According to an embodiment, the remaining components of thebrush card 100 are assembled on thebrush card mount 102 after the heat-staking is completed. Oncebrush card 100 is fully assembled, thebearing 136 is press-fitted onto the motor shaft (not shown) during motor assembly. -
FIG. 7A depicts a front perspective view of a four-pole brush card 200, according to an alternative embodiment of the invention.FIG. 7B depicts a rear perspective view of thebrush card mount 202 of thebrush card 200, according to an embodiment.FIG. 7C depicts a perspective view of thebrush card mount 202, according to an embodiment. As shown in these figures, the top of thebridge portion 212 does not include an opening as in the previous embodiment. In other words,pocket 226 of thebrush card mount 202 is not open-ended. Instead,pocket 226 encloses the top end of theshaft bearing 236. Metal routings 220 a, 220 b extend in parallel over thebridge portion 212. Thepocket 226 includes one ormore pins 228 inserted through two through-holes that extend into thepocket 226 within thebridge portion 212. The through-holes are positioned to place a portion of thepins 226 inside thepocket 226, as shown inFIG. 7B . Theshaft bearing 236 includes agroove 238 formed on its outer surface. Thegroove 238 has the same width as thepins 226. As the shaft bearing 236 is forced inside thepocket 226, it slides past thepins 228 until thepins 228 are locked inside thegroove 238. In an alternative embodiment, the shaft bearing 236 is first placed inside thepocket 226 and thepins 228 are then inserted through thegrooves 238. Thepins 228 securely hold the shaft bearing 236 inside thepocket 226. - In an alternative embodiment, instead of using two
pins 226 as shown herein, any retention mechanism, e.g., an E-clip, a C-clip, a single piece U-shaped retainer, a split ring, etc., may be used to retain theshaft bearing 236. - Another aspect of the invention is discussed herein with reference to
FIGS. 8-14B .FIG. 8 depicts a rear perspective view of aconventional brush assembly 300 including abrush card mount 302,brush holders 304, and brushes 306.Brush holders 304 are mounted on a top surface of thebrush card mount 302.Brush holders 304 includelegs 308 that penetrate through openings, or around the edges of thebrush card mount 302 and crimp on the rear side of thebrush card mount 302.Brush holders 304 may be provided as single piece or multi-piece units. - In four-pole motor platforms, particularly in the context of power tool designs, the
brush card 300 is arranged around a motor commutator, with the rear surface of thebrush card 300 facing the motor stator and fan. The top surface of the brush card 300 (i.e., where thebrush holders 304 are located) is arranged and at end of the power tool in the proximity of air inlets.Brush holders 304 generate a substantial amount of heat resulting from the electrical current passing through thebrushes 306. As the fan spins, air is sucked through the air inlets. Air flows around thebrush holders 304, through the opening in thebrush card 300 and around the outer circumference of thebrush card 300, into the fan. While the air flow cools thebrush holders 304 to some degree, the cooling effect of the air flow in this conventional design is not sufficient in many power tool designs, in particular in high power applications. What is needed is a more effective cooling mechanism for the brush assembly. - According to an embodiment of the invention, as shown in
FIGS. 9A-9C , a new brush holder/brush card design is provided. In an embodiment,brush card mount 102 includes fouropenings 140 for receiving thebrush holders 104 through its rear surface. This results inbrush holders 104 occupying a large portion of the surface area of the rear surface of thebrush card 100 adjacent the motor fan. Thus, in an embodiment,brush holders 104 act as heat sinks to transfer heat away from thebrush card 100. This design significantly improves heat transfer as compared to the conventional design discussed above. - According to an embodiment, each opening 140 of the
brush card mount 102, as viewed from the rear surface of thebrush holder 104, is defined by two recessedsurfaces 142 of thebrush card mount 102 on its sides and aboundary portion 144 of thebrush card mount 102 on its radial end. The recessed surfaces 142 each include twoslots 146. - As shown in the expanded view of
FIG. 9A , the brush holders 104 (only one of which is shown herein) each include abase piece 150 and amain piece 160, according to an embodiment. Thebase piece 150 in this embodiment includes aflat portion 152 and twoside portions 156.Flat portion 152 includes tworectangular slots 154.Side portions 156 each include two upwardly-projectinglegs 158. - The
main piece 160, in an embodiment, includes a brush-holder portion 162 that is shaped to contain two side surfaces and a top surface of thebrush 106. Extending from side ends the brush-holder portion 162 are twoflat portions 166 that extend parallel with the rear surface of thebrush card mount 102. Theflat portions 166 each include twoslots 168 that correspond to and receive upwardly-projectinglegs 158 of thebase piece 150. In addition, the brush-holder portion 162 includes twodownward protrusions 164 that correspond to and are received insiderectangular slots 154 of thebase piece 150. The side surfaces of the brush-holder portion 162, in an embodiment, includeopenings 170 that is open-ended on a distal end of thebrush holder 104 and extends radially to accommodate the back and forth movement of thespring 110 and thewires 122. -
FIGS. 9B and 9C depict steps of assembling thebrush holder 104 into thebrush card mount 102, according to an embodiment of the invention. As shown inFIG. 9B , themain piece 160 of thebrush holder 104 is inserted into theopening 140 of thebrush card mount 102. The top surfaces of theflat portions 166 mate with the recessedsurfaces 142 of thebush card 102 around theopening 140. Thebrush holder portion 162 penetrates through theopening 140 and projects above the top surface of thebrush card mount 102.Slots 168 of themain piece 160 in this position are aligned withslots 146 of the recessed surfaces 142. - Next, as shown in
FIG. 9C , upwardly-projectinglegs 158 of thebase piece 150 are inserted through the alignedslots 168 of themain piece 160 andslots 146 of the recessed surfaces 142.Downward protrusions 164 are received inside therectangular slots 154 as thebase piece 150 comes in contact with themain piece 160.Side portions 156 of thebase piece 150 mate with the back surfaces of theflat portions 166 of themain piece 160. Once this step is complete, the upwardly-projectinglegs 158 are crimped as discussed below. Theflat portion 152 of thebase piece 150, together with thebrush holder portion 162, form a rectangular box for holding thebrush 106. -
FIG. 10 depicts a zoomed-in perspective view of the top surface of thebrush card 100 showing the upwardly-projectinglegs 158 crimped over the top surface of thebrush card mount 102 within recessed pockets 172. Recessedpockets 172 each include two slanted surfaces (seeFIG. 4 ) between theslots 146. Crimped portions of the upwardly-projectinglegs 158 rest on these slanted surfaces once they are crimped. - It is noted with reference to
FIG. 10 that the top surface of theboundary portion 144 of thebrush card mount 102 is recessed to accommodate insertion of thebrush 106 inside thebrush holder 104 once thebrush holder 104 assembly is complete. It is further noted thatopenings 170 of thebrush holder 104 are arranged to accommodate the back and forth movement of thespring 110 and thewires 122 along with thebrush 106. -
FIGS. 11A through 11D depict various views of thebrush holder 104, including thebase piece 150 and themain piece 160 crimped together. Thebrush card mount 102 is not shown in these figures. However, as discussed above, in the fully-assembledbrush card 100, areas of thebrush card mount 102 between recessedsurfaces 142 and recessedpockets 172 are sandwiched between the crimp portions of the upwardly-projectedlegs 158 and the top surfaces of theflat portions 166 of thebrush holders 104. - The brush holder design of the invention discussed herein provides several advantages. The two-piece assembly of the brush holders into the brush card mount is relatively easy. Furthermore, since the brush holders are inserted through a rear surface of the brush card mount, the
metallic base pieces 150 of thebrush holders 104 are exposed in close proximity to the motor fan. Thebrush holders 104 thus act as heat sink to transfer heat away from thebrush holders 104 and brushes 106. This arrangement substantially improved overall heat transfer from thebrush card 100. -
FIG. 12 provides a rear perspective view of thebrush card 100 and a cut-off portion of amotor fan 502, according to an embodiment of the invention. As shown herein, in an embodiment, thebrush holders 104 occupy at least 40% of the total surface area of the rear surface of thebrush card 100. Preferably, thebrush holders 104 take up at least 45% of the total area of the surface area of the rear surface of thebrush card 100. More preferably, thebrush holders 104 take up at least 50% of the total area of the surface area of the rear surface of thebrush card 100. Furthermore, in an embodiment of the invention as discussed in detail below, the rear surface of the brush card 100 (including thebrush card mount 102 and brush holders 104) acts as a baffle for thefan 502. As themotor fan 502, including themotor blades 504, spins, air is sucked through air vents disposed across the top surface of thebrush card 100, through and around thebrush card 100, into the fan 605. The air is then expelled radially between thefan 502 and thebrush card 100 through air outlets disposed in alignment with thefan 502. The generated air flow thus makes substantial contact with the rear surface of thebrush holders 104, which act as heat sinks for therespective brush holders 104 and brushes 106, allowing them to cool down. This design substantially improves heat control over the conventional design ofFIG. 8 discussed above. - Brush Holder with Extruded Heat Sink
- An alternative brush holder design is discussed herein with reference to
FIGS. 13A-14B , according to an embodiment of the invention.FIG. 13A depicts a perspective view of abrush card 400, according to this embodiment. Thebrush card 400 includes abrush card mount 402 andbrush holders 404. As in the previous embodiment,brush card mount 402 has a substantially circular periphery and the fourbrush holders 404 are arranged equidistantly around the periphery of thebrush card mount 402. Thebrush holders 404 facing each other are electrically connected to one another. Eachbrush holder 404 houses abrush 406 therein. Both ends of eachbrush holder 404 are open to allow radial movement of the bush towards a center of thebrush card 400. Thebrush card mount 402 includesposts 408 in close proximity to thebrush holders 404. Theposts 408 accommodatesprings 410, each of which includes an extended arm that engages a back portion of acorresponding brush 406 to bias thebrush 406 towards the center of thebrush card 400. Metal routings 420 a, 420 b are disposed on (over or within)bridge portion 412 to connectbrushes 406 that are arranged opposite each other. As in the previously-described embodiments,metal routings bridge portion 412.Terminals metal routings -
FIG. 13B depicts a perspective view of thebrush card 400 without thebrush holders 404. According to an embodiment, similarly to the previous embodiments,bridge portion 412 includeschannels metal routings FIGS. 9A-12 , a planar portion of thebrush card mount 402 includes four separateplanar pieces 411 connected together vialegs 414 ofbridge portion 412. In other words, unlike the previous embodiment whereboundary portions 144 of thebrush card mount 102 defineopenings 140 for receiving thebrush holder 104, theplanar pieces 411 in this embodiment are not connected to one another along the main plane of thebrush card mount 400. Instead,planar openings 416 between theplanar pieces 414 receive thebrush holders 404 in a radial direction.Planar pieces 411 include side guides 415 arranged to be received in corresponding grooves of thebrush holders 404, as discussed below. - In an alternative embodiment,
planar openings 416 may be open-ended on the outer end for receiving thebrush holders 404, but close ended on the inner end to mechanically join theplanar pieces 411 to one another. In yet another embodiment,planar openings 416 may be open-ended on the inner end for receiving thebrush holders 404, but close ended on the outer end to mechanically join theplanar pieces 411 to one another. Placing a ring on either the inner or outer circumferences of theplanar pieces 411 to connect theplanar pieces 411 together provides mechanical support for thebrush card 400 and enhances the moldability of theplanar pieces 411 during the manufacturing process. -
FIGS. 14A and 14B depict perspective and cross-sectional views of thebrush holder 404, according to an embodiment.Brush holder 404 in this embodiment includes amain body 450 and abase portion 452 formed together integrally as one piece. Themain body 450 includesopenings 470 for facilitating the back and forth movement of thesprings 410 and thewires 422. Themain body 450 includesside projections 454, which together with ends of thebase portion 454form grooves 462.Grooves 462 receive side guides 415 of thebrush card mount 402 as thebrush holders 404 slides intoplanar openings 416. In an embodiment, thegrooves 462 are press-fitted onto theguides 415. In an alternative embodiment, an adhesive is used to secure theguides 415 inside thegrooves 462. - According to an embodiment, once the
brush holders 404 are fitted between theplanar pieces 411, a lower surface of thebase portion 452 acts as a heat sink to carry heat away from thebrush card 400, including thebrush holder 404 and thebrushes 406, similarly to the previous embodiment. Additionally, in an embodiment, thebrush holder 404 includesprojections main body 450. In an exemplary embodiment shown herein, fourside projections 456 and twotop projections 458 are provided.Projections brush holder 404, thereby improving heat transfer away from thebrush holder 404. - It must be noted that while
projections FIGS. 14A and 14B are used with a single-piece brush holder design, the same projections may be incorporated into the two-piece design ofFIGS. 9A-12 to improve heat transfer. - Another aspect of the invention is discussed herein with reference to
FIGS. 15-17 .FIG. 15 depicts a partial cross-sectional view of apower tool 500, according to an embodiment. In this embodiment, one half of thepower tool housing 508 is shown for illustration purposes, though it is understood that the second half of the power tool housing includes more or less the same or similar features. Thepower tool 100 in this embodiment includes thebrush card 100, including thebrush card mount 102 and thebrush holders 104, disposed at one end of the housing.Motor 510 in this embodiment includes a motor stator (i.e., can) 512, arotor 514, and acommutator 516 rotatatably coupled to therotor 514. Thecommutator 516, only a portion of which is visible in this figure, is disposed inside thebrush card 100 between the four brushes 106. Thefan 502 is also rotatably attached to therotor 514. The operation of themotor 510 and its components is beyond the scope of this disclosure and is not discussed in further detail, but reference is made to U.S. Pat. No. 7,126,242 issued Oct. 24, 2006, which is incorporated by reference in its entirety, as an example of an electric motor. -
FIGS. 16A-16C depict various perspective and side views of thefan 502, according to an embodiment.FIG. 17 depicts a zoomed-in view of thefan 502 inside thetool housing 508. As shown in these figures,fan 502 includes a plurality ofblades 504 arranged between a firstinner ring 520 and a secondouter ring 522. Theinner ring 520 is arranged to mate with therotor 514, while thesecond ring 522 is disposed in the proximity of thebrush card 100, as shown inFIG. 15 . Eachfan blade 504 includes aninner edge 524 that extends from afirst end 520 a of theinner ring 520 towards the rear surface of thebrush card 100. In an embodiment, theinner edge 524 is inclined towards thearmature 516 and the rotor 514 (i.e., at an angle to the longitudinal axis of the motor 510), though theinner edge 524 may be parallel to the tool housing in an alternative embodiment. Eachfan blade 504 also includes anouter edge 526 that extends from theouter ring 522 towards thestator 512 substantially in parallel with the longitudinal axis of themotor 510. Afirst side edge 528 extends from asecond end 520 b of theinner ring 520 to the end of theouter edge 526. Thefirst side edge 528, in an embodiment, is arranged at an angle away from thestator 512 in the direction of the end of theouter edge 526. Asecond side edge 530 extends from theouter ring 522 to the end of theinner edge 524, substantially parallel to the rear surface of thebrush card 100. In an alternative embodiment, however, thesecond side edge 530 may be inclined slightly towards thebrush card 100 as it meets theinner edge 524. - Since the
inner edge 524 of the blades covers less air that theouter edge 526 of the blades as thefan 502 spins,inner edge 524 generates lower air velocity near the center of the fan. In order to generate equal air velocity throughout thefan 502, it is desirable for theinner edge 524 to be longer than theouter edge 526. The embodiment of the invention discussed above ensures that the lengthinner edge 524 of eachblade 504 is greater than the length of theouter edge 526. According to a further embodiment of the invention, the outer surface of theinner ring 522 includes aslanted surface 532 that is arranged at an angle away from thebrush card 100 in the direction of theouter edge 526. In an embodiment, thisslanted surface 532 may be arranged at at least a 45 degree angle with respect to the rear surface of thebrush card 100. This arrangement helps reduce the length of theouter edge 526 of eachblade 504 even further for more effective air flow generation. -
FIG. 18 depicts a cross-sectional view of atool housing 508 including thebrush card 100, without themotor 510 and thefan 502. According to an embodiment of the invention,air inlets power tool housing 508. As thefan 502 rotates, it generates an air flow fromfront inlets 542 through themotor 510, in particular in the area between thestator 512 and therotor 514, in an axial direction to cool themotor 510. The air is then redirected in a radial direction out of thepower tool 500 throughair vents 540 disposed in thetool housing 508 adjacent thefan 502. Similarly, the fan generates an air flow fromrear inlets 544 through thebrush card 100, particularly around thebrush holders 104, and through the area betweenbrush holders 104 and thecommutator 516, in an axial direction to cool thebrush card 100. This air is also redirected in a radial direction out of thepower tool 500 through the same air vents 540. The rear surface of the brush card 100 (i.e.,brush card mount 102 together with the brush holders 104) forms a baffle to contain the air flow inside thefan 502 and out of thevents 540. Similarly, the end surface 513 of thestator 512 facing thefan 502 forms a second baffle for thefan 502. These baffles ensure that the air is property redirected through thevents 540. - The angled surface of the
first side edge 528 creates a gap between thestator 512 end surface baffle and thefan 502. Similarly, the angled surface of theouter ring 522 creates a gap between thebrush card 100 baffle and thefan 502. These gaps may adversely affect air flow through thefan 502. In order to prevent such an adverse affect, according to an embodiment of the invention, tworibs surface 532 of theouter ring 522 and thefirst side edge 528, respectively, are provided in thetool housing 508. In an embodiment, thefirst rib 534 includes a sloped surface disposed in close proximity to and in parallel with theslanted surface 532 of theouter ring 522. Similarly, thesecond rib 536 includes a sloped surface in close proximity to and in parallel with thefirst side edge 528 of the fan 501. Bothribs brush holders 104 and the brush card mount 102) and the end surface 513 of thestator 512, respectively. Theribs housing 508 and thefan 502 created by the angled surfaces of theouter ring 522 and thefirst side edge 528. In this embodiment, a combination of the rear surface of the brush card 100 (including thebrush card mount 102 and the brush holders 104), and the sloped surface of thefirst rib 534, forms the first baffle for thefan 502. Similarly, a combination of the end surface 513 of thestator 512 and the sloped surface of thesecond rib 536 forms the second baffle for thefan 502. Additionally, in an embodiment, theribs brush card 100 and thestator 512 within thepower tool housing 508. - Another aspect of the invention is disclosed herein with reference to
FIGS. 19-21C , and with continued reference toFIGS. 16A-16C . -
FIG. 19 depicts thefan 502 mounted on a fully wound and moldedrotor 514. In this figure, therotor 514 includes alamination stack 550,windings 552, and endinsulators 560.End insulators 560 are disposed at the ends of thelamination stack 550 prior to thelamination stack 550 being wound.End insulators 560 provide insulation between the rotor windings and therotor lamination stack 550 and protect the wires from being cut during the winding process.FIG. 20 depicts a perspective view of thesame fan 502 androtor 514 without thewindings 552. - According to an embodiment of the invention, in order to property attach the
fan 502 to therotor 514, thefan 502 is provided with a plurality oftongues 580, as shown inFIGS. 16A , 16C, 19 and 20.Tongues 580 in an embodiment project in the direction of therotor 514 from theinner ring 520 of thefan 502. In an embodiment,tongues 580 may be 2-6 mm in length. In an embodiment,tongues 580 may be disposed equidistantly around the periphery of theinner ring 510. The number oftongues 580 may correspond to the number of slots in thelamination stack 550, although a lesser number oftongues 580 may be provided. According to an embodiment of the invention,end insulator 560 facing thefan 502 is provided with a plurality ofnotches 562 arranged to receive thetongues 580 of thefan 502, as discussed below in detail. -
FIGS. 21A-21C depict perspective views of arotor end insulator 560, according to an embodiment of the invention.End insulator 560 is pre-molded to include abase portion 564 shaped to match a cross-sectional profile of thelamination stack 550. Thebase portion 564 includes radially-extendingslots 566 formed between teeth 558 of thebase portion 564. Theslots 566 andteeth 568 respectively correspond to the slots and teeth of thelamination stack 550. At the periphery of thebase portion 564, theteeth 568 extend outwardly along the circumference of thebase portion 564 to partially close the outer end of theslots 566. Theslots 566 of thebase portion 564 havewalls 570 projecting perpendicularly to the base portion 564 (in the longitudinal direction of the motor) on one side. Thewalls 570 are arranged to form-fittingly protrude into the slots of thelamination stack 550 to insulate the lamination stack teeth. Thewalls 570 may be, for example, 4 to 12 mm in depth. - The
base portion 564 includes a through-hole 572 at its center portion for accommodating the rotor shaft. On the side of thebase portion 564 opposite where thewalls 570 are arranged, is anannular ring 574 fitted over the rotor shaft. - In an embodiment, two
end insulators 560 are form-fittingly mounted on the ends of thelamination stack 550. In an embodiment, there may be a gap of, for example, 2 to 10 mm between the ends of theinner walls 570 of the twoend insulators 560 within thelamination stack 550 slots. As the coils are wound into the lamination stack slots over theend insulators 560, the thickness of thewalls 570 ensures that no contact is made between the coil and thelamination stack 560. Furthermore, the outer surface of thebase portion 564 has a slanted profile near the outer ends of theteeth 568 that forces the coils to be packed tightly into the lamination stack slots. - According to an embodiment of the invention, as mentioned above,
notches 562 are arranged at the outer ends of theteeth 568 on the periphery of theend insulator 560 to receive thetongues 580 of thefan 502. Thenotches 562 extend longitudinally through the entire length of theteeth 568. This arrangement allows thetongues 580 of thefan 502 to make direct contact with the end of thelamination stack 550. This embodiment reduces the tolerances associated with the motor over a comparable design in which thefan 502 is mounted on theend insulator 560. Specifically, since thetongues 580 are mounted directly on thelamination stack 550, calculating the total tolerances for thefan 502 needs only take into account the tolerance levels of thefan 502 and thelamination stack 550, and not the tolerance levels of theend insulator 560, which is made of plastic and has a relatively large tolerance. It is noted thattongues 580 may be secured within thenotches 562 form-fittingly, or via heat-taking, welding, adhesive-bonding, etc. - According to an embodiment of the invention, with reference to
FIGS. 16A-16C , 19 and 20, thefan 502 may be further provided with one or moreadditional tongues 582 arranged on opposite ends of theinner ring 520. In an embodiment,tongues 582 are longer thantongues 580 and are arranged to be received between two adjacent teeth of thelamination stack 550.Long tongues 582 are provided to ensure thattongues 580 are placed inside thenotches 562, and not between the adjacent teeth of thelamination stack 550, during assembly. - Another aspect of the invention is discussed herein with reference to
FIGS. 22-24 .FIG. 22 depicts aspring 110, according to an embodiment.Spring 110 includes awound portion 602, afirst leg 604, and asecond leg 606 that is longer than thefirst leg 604 and includes ahook 608 at its distal end. -
FIG. 23 depicts a partial perspective view of thebrush card 100, according to an embodiment. In this embodiment, thewound portion 602 of thespring 110 is arranged around thepost 108 of thebrush card mount 102. Thehook 608 of thesecond leg 606 engages the back of thebrush 106. Thefirst leg 604 of thespring 110 engages apocket 614 of thebrush card mount 102. In an embodiment, pockets 614 for eachspring 110 are formed within end portions of thebridge legs first leg 604 within thepocket 614 allows thetorsion spring 110 to be loaded as it engages the back of thebrush 106. - During the assembly process, in one embodiment, the
first leg 604 is placed within thepocket 614 as thewound portion 602 is pushed down thepost 108. Thesecond leg 606, which at this point rests on top of thebrush holder 104, is then pulled to engage the back of the brush 106 (or anend portion 620 of the brush holder 104). The problem with this assembly process, however, is that it is difficult to engage and move thesecond leg 606 after thewound portion 602 has been pushed down thepost 108. This process is time consuming and burdensome. - According to an embodiment of the invention, in order to ease the assembly process of the
springs 110, the end of thebridge legs arcuate surface 612, as shown inFIG. 23 .Arcuate surface 612 is located above thepockets 614. Asloped surface 610 is provided extending from the top of thebridge leg arcuate surface 612. During the assembly process, after thewound portion 602 is placed on thepost 108 but before it is pushed down, thehook 608 of thesecond leg 606 of thespring 110 is placed within arecess 622 of theend portion 620 of thebrush holder 104. Thefirst leg 604 at this point is placed on thesloped surface 610 or thearcuate surface 612. As theround portion 602 of thespring 110 is pushed down, thehook 608 remains within therecess 622. Meanwhile, the end of thefirst leg 604 slides down the slopedsurface 610 over thearcuate surface 612, and along thearcuate surface 612 until it snaps into thepocket 614. As thefirst leg 604 moves down thearcuate surface 612 it loads thetorsion spring 110, so thespring 110 will be loaded even after thefirst leg 604 snaps into thepocket 614. -
FIG. 24 depicts a rear view of thebrush card 100 showing thefirst leg 604 of thespring 110 inside thepocket 614, according to an embodiment. As seen herein, thepockets 614 foradjacent springs 110 are located under thearcuate surface 612, forming a mushroom-shaped cross-sectional profile. Thearcuate surface 612 may be shaped as a half-circle above thepockets 614, although a cam surface may be utilized to optimize the movement of thefirst leg 604 into thepocket 614. - Another aspect of the invention is described herein with reference to
FIG. 25 . In this figure,brush 106 is shown inside thebrush holder 104. As discussed above, thehook 608 of thespring 110 engages therecess 622 of theend portion 620 of the brush holder during the assembly process. Once the motor is fully assembled and the commutator is placed inside thebrush card 100, thehook 608 and thesecond leg 606 are pulled down to engage the rear surface of thebrush 106. - According to an embodiment of the invention, in order to ease the above-described step, the rear surface of the
brush 106 includes twohumped surfaces groove 628 therebetween. The rear surface of thebrush 106 is designed and arranged such that, after the motor is assembled and the commutator is placed inside thebrush card 100, a portion of thehumped surface 624 is aligned with a lower end of therecess 622. Specifically, therecess 622 includes a slantedlower end 622 a which, as viewed from the side, ends in alignment with (or slightly above) thehumped surface 624. Using this arrangement, instead of having to pull thehook 608 out of therecess 622 and push it down inside thegroove 628, thesecond leg 606 of thespring 110 is simply pushed down. As thesecond leg 606 is pushed down, the hook 608 (or the second leg 606) slides down the slantedlower end 622 of the recess, onto and over thehumped surface 624, and into thegroove 628. This design substantially eases the assembly process. - In this embodiment, each the
humped surfaces 624 may be semi-circular shaped, although a cam surface may be utilized to optimize the movement of thehook 608 over thehumped surface 624. It is also noted that two humped surfaces are shown in this embodiment to ease the assembly process, but thebrush 106 may include a single humped surface above thegroove 628. - The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the scope of the invention.
-
- 100 Brush card (or brush assembly)
- 102 Brush card mount
- 104 Brush holder
- 106 Brush
- 108 Post
- 110 Spring
- 112 Bridge portion
- 114 a,b Bridge legs
- 116 a,b Bridge legs
- 118 a,b Terminals
- 120 a,b Metal routings
- 122 Wire
- 124 a,b Channels
- 126 Shaft bearing pocket
- 128 Recessed portion
- 130 Penetrating portion
- 132 a,b Teethed ends
- 134 Slot
- 136 Shaft bearing
- 138 Plastic ring
- 140 Opening
- 142 Recessed surface
- 144 Boundary portion
- 146 Slot
- 150 Base piece
- 152 Flat portion
- 154 Rectangular slot
- 156 Side portion
- 158 Upwardly-projecting leg
- 160 Main piece
- 162 Brush holder portion
- 164 Downward protrusion
- 166 Flat portion
- 168 Slot
- 170 Opening
- 172 Recessed pocket
- 200 Brush card (or brush assembly)
- 202 Brush card mount
- 204 Brush holder
- 206 Brush
- 212 Bridge portion
- 220 a,b Metal routings
- 226 Pocket
- 228 Pin
- 236 Bearing
- 238 Groove
- 300 Conventional brush assembly
- 302 Brush card mount
- 304 brush holder
- 306 Spring
- 308 Legs
- 400 Brush card (or brush assembly)
- 402 Brush card mount
- 404 Brush holder
- 406 Brush
- 408 Post
- 410 Spring
- 411 Planar piece
- 412 Bridge portion
- 414 Bridge Leg
- 415 Side guide
- 416 Planar opening
- 418 a,b Terminals
- 420 a,b Metal routings
- 422 Wire
- 424 a,b Channels
- 450 Main body
- 452 Base portion
- 454 Projection
- 456 Side projection
- 458 Top projection
- 470 Opening
- 500 Power tool
- 502 Fan
- 504 Fan blades
- 508 Tool housing
- 510 Motor
- 512 Stator
- 513 Rear surface
- 514 Rotor
- 516 Commutator
- 520 Inner ring
- 522 Outer ring
- 524 Inner edge
- 526 Outer edge
- 528 First side edge
- 530 Second side edge
- 532 Slanted surface
- 534 First rib
- 536 Second rib
- 540 Vent
- 542 Front inlet
- 544 Rear inlet
- 550 Rotor lamination stack
- 552 Windings
- 560 End insulator
- 562 Notch
- 564 Base portion
- 566 Slot
- 568 Teeth
- 570 Wall
- 572 Through-hole
- 574 Annular ring
- 580 Tongue
- 582 Long tongue
- 602 Wound portion
- 604 First leg
- 606 Second leg
- 608 Hook
- 610 Sloped surface
- 612 Arcuate surface
- 614 Pocket
- 620 End portion
- 622 Recess
- 624 First harped surface
- 626 Second harped surface
- 628 Grove
Claims (20)
1. An electric motor comprising:
a stator;
an armature rotatably received within the stator, the armature having an armature shaft on which a commutator is mounted; and
a brush assembly disposed around the commutator and defining a first surface facing the stator and a second surface opposite the first surface, the brush assembly comprising:
a brush card mount;
a plurality of brushes in sliding contact with the commutator to supply electric current to the commutator; and
a plurality of thermally-conductive brush holders disposed on the second surface of the brush assembly to house the plurality of brushes and secured to the brush card mount, each brush holder including a plurality of projections formed along a length of an outer surface of the brush holder to increase a total surface area of the brush holder and transfer heat away from the brush holder.
2. The electric motor of claim 1 , wherein each of the plurality of brush holders includes a base portion securely attached to the brush card mount and disposed to house a bottom surface of the brush, and a main body attached to the base portion to house side surfaces and a top surface of the brush.
3. The electric motor of claim 2 , wherein the projections are disposed on at least one of a top surface and/or side surfaces of the main body.
4. The electric motor of claim 2 , wherein the plurality of projections comprises at least six projections.
5. The electric motor of claim 2 , wherein the brush card mount includes a plurality of openings and the brush holders are partially disposed within the plurality of openings.
6. The electric motor of claim 5 , wherein the plurality of openings extend to an outer periphery of the brush assembly.
7. The electric motor of claim 6 , wherein the plurality of brush holders are slidingly received within the plurality of openings from the periphery of the brush assembly in a radial direction.
8. The electric motor of claim 6 , wherein the base portions of the brush holders are securely disposed within the plurality of openings.
9. The electric motor of claim 6 , wherein the brush card mount comprises separate planar pieces separated by the plurality of openings and the base portions of the brush holders are slidingly received within the openings and supported by the separate planar pieces of the brush card mount.
10. The electric motor of claim 6 , wherein each brush holder includes grooves on both sides thereon and the planar pieces comprise side guides on both sides thereon arranged to mate with the grooves of the brush holder as the brush holder is received inside the opening of the brush card mount.
11. The electric motor of claim 10 , wherein the grooves of the brush holder are formed between two adjacent projections and press-fitted onto the guides of the planar pieces.
12. The electric motor of claim 6 , wherein the base portions of the brush holders are exposed on the first surface of the brush assembly to transfer heat away from the brushes through the first surface of the brush assembly.
13. The electric motor of claim 2 , wherein the main body and the base portion of the brush holders are integrally formed as a single piece.
14. The electric motor of claim 2 , wherein the plurality of projections are substantially perpendicular to the main body.
15. The electric motor of claim 1 , wherein the plurality of brush holders comprises four brush holders disposed equidistantly around a periphery of the brush card mount.
16. A power tool comprising:
a housing; and
an electric motor including a stator; an armature rotatably received within the stator, the armature having an armature shaft on which a commutator is mounted; and a brush assembly disposed around the commutator and defining a first surface facing the stator and a second surface opposite the first surface,
the brush assembly comprising:
a brush card mount;
a plurality of brushes in sliding contact with the commutator to supply electric current to the commutator; and
a plurality of thermally-conductive brush holders disposed on the second surface of the brush assembly to house the plurality of brushes and secured to the brush card mount, each brush holder including a plurality of projections formed along a length of an outer surface of the brush holder to increase a total surface area of the brush holder and transfer heat away from the brush holder.
17. The power tool of claim 16 , wherein each of the plurality of brush holders includes a base portion securely attached to the brush card mount and disposed to house a bottom surface of the brush, and a main body attached to the base portion to house side surfaces and a top surface of the brush.
18. The power tool of claim 17 , wherein the projections are disposed on at least one of a top surface and/or side surfaces of the main body.
19. The power tool of claim 17 , wherein the brush card mount includes a plurality of openings and the brush holders are partially disposed within the plurality of openings.
20. The power tool of claim 17 , wherein the main body and the base portion of the brush holders are integrally formed as a single piece.
Priority Applications (1)
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US14/453,785 US20150042204A1 (en) | 2013-08-09 | 2014-08-07 | Brush assembly for an electric motor |
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US201361864264P | 2013-08-09 | 2013-08-09 | |
US201461932932P | 2014-01-29 | 2014-01-29 | |
US14/453,785 US20150042204A1 (en) | 2013-08-09 | 2014-08-07 | Brush assembly for an electric motor |
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US20150042204A1 true US20150042204A1 (en) | 2015-02-12 |
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US14/453,706 Active 2036-12-04 US10003238B2 (en) | 2013-08-09 | 2014-08-07 | Brush assembly with bridge and leg portions with metal routing |
US14/453,863 Active 2036-09-14 US9923429B2 (en) | 2013-08-09 | 2014-08-07 | Power tool having improved motor fan assembly |
US14/453,873 Abandoned US20150076936A1 (en) | 2013-08-09 | 2014-08-07 | Brush assembly having improved brush profile for an electric motor |
US14/453,755 Abandoned US20150042189A1 (en) | 2013-08-09 | 2014-08-07 | Brush assembly for an electric motor |
US14/453,785 Abandoned US20150042204A1 (en) | 2013-08-09 | 2014-08-07 | Brush assembly for an electric motor |
US14/453,766 Active 2037-08-15 US10181767B2 (en) | 2013-08-09 | 2014-08-07 | Brush assembly with brush card mount with brush holders having base and main portion pieces |
US14/453,793 Abandoned US20150194859A1 (en) | 2013-08-09 | 2014-08-07 | Power tool having improved motor fan assembly |
US16/204,451 Active US10734864B2 (en) | 2013-08-09 | 2018-11-29 | Brush assembly having multi-piece brush holders for an electric motor, brush holder main piece with flat portions between base piece and brush card mount |
Family Applications Before (4)
Application Number | Title | Priority Date | Filing Date |
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US14/453,706 Active 2036-12-04 US10003238B2 (en) | 2013-08-09 | 2014-08-07 | Brush assembly with bridge and leg portions with metal routing |
US14/453,863 Active 2036-09-14 US9923429B2 (en) | 2013-08-09 | 2014-08-07 | Power tool having improved motor fan assembly |
US14/453,873 Abandoned US20150076936A1 (en) | 2013-08-09 | 2014-08-07 | Brush assembly having improved brush profile for an electric motor |
US14/453,755 Abandoned US20150042189A1 (en) | 2013-08-09 | 2014-08-07 | Brush assembly for an electric motor |
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US14/453,766 Active 2037-08-15 US10181767B2 (en) | 2013-08-09 | 2014-08-07 | Brush assembly with brush card mount with brush holders having base and main portion pieces |
US14/453,793 Abandoned US20150194859A1 (en) | 2013-08-09 | 2014-08-07 | Power tool having improved motor fan assembly |
US16/204,451 Active US10734864B2 (en) | 2013-08-09 | 2018-11-29 | Brush assembly having multi-piece brush holders for an electric motor, brush holder main piece with flat portions between base piece and brush card mount |
Country Status (2)
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EP (7) | EP2835892B1 (en) |
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- 2014-08-08 EP EP14180413.8A patent/EP2835898A3/en not_active Withdrawn
- 2014-08-08 EP EP14180385.8A patent/EP2835893B1/en active Active
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Also Published As
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EP2835898A3 (en) | 2016-01-27 |
EP2835897B1 (en) | 2019-09-25 |
US20190097498A1 (en) | 2019-03-28 |
US10003238B2 (en) | 2018-06-19 |
US10181767B2 (en) | 2019-01-15 |
EP2835894A2 (en) | 2015-02-11 |
EP2835893B1 (en) | 2020-07-01 |
EP2835897A2 (en) | 2015-02-11 |
US20150042202A1 (en) | 2015-02-12 |
EP2835893A2 (en) | 2015-02-11 |
US20150042214A1 (en) | 2015-02-12 |
EP2835892A2 (en) | 2015-02-11 |
EP2835897A3 (en) | 2015-12-16 |
EP2835894B1 (en) | 2017-06-21 |
EP2835894A3 (en) | 2016-05-04 |
EP2835891A3 (en) | 2016-01-27 |
EP2835898A2 (en) | 2015-02-11 |
EP2835891A2 (en) | 2015-02-11 |
US20150042189A1 (en) | 2015-02-12 |
US10734864B2 (en) | 2020-08-04 |
EP2835896B1 (en) | 2019-03-06 |
US20150194859A1 (en) | 2015-07-09 |
EP2835896A3 (en) | 2016-01-27 |
US9923429B2 (en) | 2018-03-20 |
US20150042203A1 (en) | 2015-02-12 |
US20150076936A1 (en) | 2015-03-19 |
EP2835893A3 (en) | 2016-05-04 |
EP2835892A3 (en) | 2016-01-27 |
EP2835892B1 (en) | 2018-12-26 |
EP2835896A2 (en) | 2015-02-11 |
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