Power tool having improved motor fan assembly
A power tool is provided including an electric motor and a tool housing arranged to house the motor. The electric motor includes a stator, an armature rotatably with respect to the stator and having an armature shaft, and a fan rotatably attached to the armature adjacent the stator. The fan includes blades each having an angled side edge such that a longitudinal length of each blade is smaller at an outer periphery of the fan than at an inner edge of the fan blade near the armature shaft. The tool housing includes an annular rib disposed around a periphery of the housing in close proximity to the fan. The annular rib has an angled surface substantially parallel to the angled side edges of the fan blades to contain airflow generated by the fan in a centrifugal direction of the power tool radially from the armature shaft.
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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.
LIST OF REFERENCES
- 100 Brush card (or brush assembly)
- 102 Brush card mount
- 104 Brush holder
- 106 Brush
- 108 Post
- 110 Spring
- 112 Bridge portion
- 114a,b Bridge legs
- 116a,b Bridge legs
- 118a,b Terminals
- 120a,b Metal routings
- 122 Wire
- 124a,b Channels
- 126 Shaft bearing pocket
- 128 Recessed portion
- 130 Penetrating portion
- 132a,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
- 220a,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
- 418a,b Terminals
- 420a,b Metal routings
- 422 Wire
- 424a,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
The present disclosure relates to a electric motors, and more particularly to a housing/fan assembly for power tools having electric motors.
BACKGROUNDThe 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, electric motors include a fan attached to the armature. The fan rotates along with the armature to cool the motor stator, armature, and commutator. The fan generally includes a plurality of fan blades that dispel air centrifugally, thus generating air flow through the stator, armature, and the commutator.
Conventional fans include rectangular blades. It has been shown, however, that fan blades are most effective when a product of fan blade speed through the air and the contact area of the blade with air is held constant across the entire area of the fan blade. Alternative fan blade geometries have been proposed for this reason, but such designs encounter other challenges of their own. One challenge is that modifications to fan blade geometries increases gaps surrounding the fan, e.g., between the fan and the stator assembly, which allow warm air to escape. To overcome this challenge, some designs utilize additional fan baffles or other components, which add costs associated with parts and assembly. What is needed is a power tool and fan assembly design utilizing effective fan blade geometry without added costs and assembly components.
SUMMARYAccording to an embodiment of the invention, a power tool is provided including an electric motor and a tool housing arranged to house the motor. The electric motor includes a stator; an armature rotatably with respect to the stator and having an armature shaft; and a fan rotatably attached to the armature adjacent the stator. The fan includes blades each having an angled side edge such that a longitudinal length of each blade is smaller at an outer periphery of the fan than at an inner edge of the fan blade near the armature shaft. In an embodiment, the tool housing includes an annular rib disposed around a periphery of the housing in close proximity to the fan. The annular rib has an angled surface substantially parallel to the angled side edges of the fan blades to contain airflow generated by the fan in a centrifugal direction of the power tool in a radial direction away from the shaft.
According to an embodiment, the tool housing includes two housing halves configured to mate together around the electric motor to form the annular rib. In an embodiment, the annular rib is disposed between the stator and the fan. In an embodiment, the annular rib has a second surface opposite the angled surface that is substantially parallel to an end surface of the stator. In an embodiment, second surface of the annular rib is in contact with at least a portion of the end surface of the stator near the outer periphery of the stator.
In an embodiment, the electric motor further includes a brush assembly disposed around the commutator and having a first surface facing the fan and a second surface opposite the first surface. The brush assembly includes a brush card mount, and brushes arranged on the first surface of the brush assembly in sliding contact with the commutator to supply electric current to the commutator.
In an embodiment, the annular rib is disposed between the first surface of the brush assembly and the fan. In an embodiment, the annular rib has a second surface opposite the angled surface that is substantially parallel to the first surface of the brush assembly. In an embodiment, the second surface of the annular rib is in contact with an outer periphery of the first surface of the brush assembly, and the angled surface of the annular rib together with the first surface of the brush assembly form a baffle for the fan to redirect airflow generated by the fan in a centrifugal direction. In an embodiment, the first surface of the brush assembly further includes brush holders having base portions that are exposed on the first surface of the brush assembly to transfer heat away from the brushes to the air flow generated by the fan.
In an embodiment, the fan includes an annular ring mounted on the armature. In an embodiment, the annular ring includes tongues mounted on the armature. In an embodiment, the fan includes an annular ring arranged to radially retain the plurality of blades. In an embodiment, the annular ring is formed on the angled side edge of the blades and includes a corresponding angled surface.
In an embodiment, the tool housing comprises at least one air vent formed around the fan.
It is noted that while embodiments of this invention are described herein with reference to brushed motor having an armature and a commutator, the fan and housing assembly of this invention may also be used in any brushed or brushless motor. Within the scope of a brushless motor, the claimed “armature” may refer to a rotor having permanent magnets received inside a stator having field windings. Alternatively, the armature may be an outer rotor having permanent magnets disposed outside an inner stator with field windings.
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.
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.
According to an embodiment, 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 114a, 114b, 116a, and 116b. Bridge legs 114a, 114b, 116a, and 116b 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 114a, 114b, 116a, and 116b are gaps that allow for the radial movement of brushes 106.
According to an embodiment, bridge leg 114a and 114b form walls that extend radially from the bridge portion 112 to (or near) outer edges of the brush card mount 102. In an embodiment, the bridge legs 116a and 116b similarly extend towards (or near) outer edges of the brush card mount 102. This arrangement strengthens support for the bridge portion 112. In addition, bridge leg 114a mechanically supports and electrically isolates two terminals 118a and 118b provided on both sides of its outward-extending wall. Terminals 118a and 118b are connected to metal routings 120a and 120b, which extend over the bridge portion 112 to bridge leg 114b. Metal routings 120a and 120b connect the brushes 106 facing each other to one of the terminals 118a and 118b. Specifically, ends of metal routings 120a and 120b are connected via wires 122 to either corresponding brush holders 104 or brushes 106 via wires 120. In an embodiment, metal routings 120a, 120b are routed around a shaft bearing pocket 126, which holds a shaft bearing 136, as discussed below in detail. In an embodiment, metal routing 120a crosses over routing 120b to allow for opposite brushes 106/brush holders 104 to be connected to the same terminal 118a or 118b.
Metal routing 120b includes a penetrating portion 130 that is received inside the recessed portion 128 of channel 124b. In an embodiment, the penetrating portion 130 is substantially vertical. This allows routing 120a to cross over metal routing 120b as it extends through channel 124a to bridge leg 114b. This arrangement creates a gap between the metal routings 120a and 120b that, in an embodiment, is 1-3 mm. This gap is sufficient to prevent an electrical shortage.
Another aspect of the invention is discussed herein with reference to
According to an embodiment, as shown in
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 the shaft bearing 236.
Bottom-Mount Brush HolderAnother aspect of the invention is discussed herein with reference to
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 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) 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 the brushes 306. As the fan spins, air is sucked through the air inlets. 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.
According to an embodiment of the invention, as shown in
According to an embodiment, each opening 140 of the brush card mount 102, as viewed from the rear surface of the brush holder 104, 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.
As shown in the expanded view of
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, in an embodiment, 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.
Next, as shown in
It is noted with reference to
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 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.
Brush Holder with Extruded Heat Sink
An alternative brush holder design is discussed herein with reference to
In an alternative embodiment, 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. In yet another embodiment, 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.
According to an embodiment, once the brush holders 404 are fitted between the planar pieces 411, 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. Additionally, in an embodiment, the brush holder 404 includes projections 456, 458 projecting from the main body 450. In an exemplary embodiment shown herein, 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.
It must be noted that while projections 456, 458 shown in
Another aspect of the invention is discussed herein with reference to
Since the inner edge 524 of the blades covers less air that the outer edge 526 of the blades as the fan 502 spins, inner edge 524 generates lower air velocity near the center of the fan. In order to generate equal air velocity throughout the fan 502, it is desirable for the inner edge 524 to be longer than the outer edge 526. The embodiment of the invention discussed above ensures that the length inner edge 524 of each blade 504 is greater than the length of the outer edge 526. According to a further embodiment of the invention, 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.
The angled surface of the first side edge 528 creates a gap between the stator 512 end surface baffle and the fan 502. Similarly, 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. In order to prevent such an adverse affect, according to an embodiment of the invention, 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. In an embodiment, 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. Similarly, 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. In this embodiment, 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. Similarly, 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. Additionally, in an embodiment, 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.
Rotor End InsulatorAnother aspect of the invention is disclosed herein with reference to
According to an embodiment of the invention, 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
The base portion 564 includes a through-hole 572 at its center portion for accommodating the rotor shaft. On the side of the base portion 564 opposite where the walls 570 are arranged, is an annular ring 574 fitted over the rotor shaft.
In an embodiment, two end insulators 560 are form-fittingly mounted on the ends of the lamination stack 550. In an embodiment, there may be a gap of, for example, 2 to 10 mm between the ends of the inner walls 570 of the two end insulators 560 within the lamination stack 550 slots. As the coils are wound into the lamination stack slots over the end insulators 560, the thickness of the walls 570 ensures that no contact is made between the coil and the lamination stack 560. Furthermore, 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.
According to an embodiment of the invention, as mentioned above, 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. Specifically, since the 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.
According to an embodiment of the invention, with reference to
Another aspect of the invention is discussed herein with reference to
During the assembly process, in one embodiment, 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, however, 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.
According to an embodiment of the invention, in order to ease the assembly process of the springs 110, the end of the bridge legs 116a, 116b are each provided with an arcuate surface 612, as shown in
Another aspect of the invention is described herein with reference to
According to an embodiment of the invention, in order to ease the above-described step, 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. Specifically, the recess 622 includes a slanted lower end 622a which, as viewed from the side, ends in alignment with (or slightly above) the humped surface 624. Using this arrangement, instead of having to pull the hook 608 out of the recess 622 and push it down inside the groove 628, 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.
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 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.
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.
Claims
1. An power tool comprising:
- an electric motor having a stator; an armature rotatably with respect to the stator and having an armature shaft; and a fan rotatably attached to the armature adjacent the stator, the fan including a plurality of blades each having an angled side edge such that a longitudinal length of each blade is smaller at an outer periphery of the fan than at an inner edge of the fan blade near the armature shaft; and
- a tool housing arranged to house the electric motor, the housing including an annular rib disposed around a periphery of the housing in close proximity to the fan, the annular rib having an angled surface substantially parallel to the angled side edges of the fan blades to contain airflow generated by the fan in a centrifugal direction of the power tool radially from the armature shaft.
2. The power tool of claim 1, wherein the tool housing comprises two housing halves configured to mate together around the electric motor to form the annular rib.
3. The power tool of claim 1, wherein the annular rib is disposed between the stator and the fan.
4. The power tool of claim 3, wherein the annular rib has a second surface opposite the angled surface that is substantially parallel to an end surface of the stator.
5. The power tool of claim 4, wherein the second surface of the annular rib is in contact with at least a portion of the end surface of the stator near the outer periphery of the stator.
6. The power tool of claim 1, wherein the electric motor further comprises a brush assembly disposed around the commutator and having a first surface facing the fan and a second surface opposite the first surface, the brush assembly comprising: a brush card mount, and plurality of brushes arranged on the first surface of the brush assembly in sliding contact with the commutator to supply electric current to the commutator.
7. The power tool of claim 6, wherein the annular rib is disposed between the first surface of the brush assembly and the fan.
8. The power tool of claim 7, wherein the annular rib has a second surface opposite the angled surface that is substantially parallel to the first surface of the brush assembly.
9. The power tool of claim 8, wherein the second surface of the annular rib is in contact with an outer periphery of the first surface of the brush assembly, the angled surface of the annular rib together with the first surface of the brush assembly forming a baffle for the fan to redirect airflow generated by the fan in a centrifugal direction.
10. The power tool of claim 9, wherein the first surface of the brush assembly further includes a plurality of brush holders having base portions that are exposed on the first surface of the brush assembly to transfer heat away from the plurality of brushes to the air flow generated by the fan.
11. The power tool of claim 1, wherein the fan includes an annular ring mounted on the armature.
12. The power tool of claim 11, wherein the annular ring includes a plurality of tongues mounted on the armature.
13. The power tool of claim 1, wherein the fan includes an annular ring arranged to radially retain the plurality of blades.
14. The power tool of claim 13, wherein the annular ring is formed on the angled side edge of the plurality of blades and includes a corresponding angled surface.
15. The power tool of claim 1, wherein the tool housing comprises at least one air vent formed around the fan.
Type: Application
Filed: Aug 7, 2014
Publication Date: Jul 9, 2015
Applicant: BLACK & DECKER INC. (Newark, DE)
Inventors: Stephen P. Osborne (Pikesville, MD), Daniel F. Heck (Baltimore, MD), Colin M. Crosby (Baltimore, MD), Ryan F. Schroeder (Hampstead, MD), Barak N. Gohn (Shrewsbury, MD), William D. Spencer (Ellicott City, MD)
Application Number: 14/453,793