Patent ID: 12237739

Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways.

DETAILED DESCRIPTION

FIG.1illustrates a simplified block diagram of a power tool100. The power tool100includes a power source105, field effect transistors (FETs)110, a brushless electric motor115, Hall-effect sensors120, a motor controller125, user input130, and other components135(such as current/voltage sensors, work lights (LEDs), etc.). The power source105provides DC power to the various components of the power tool100and may be a power tool battery pack that is rechargeable (e.g., a Lithium-ion battery pack). In some instances, the power source105may receive AC power (e.g., 120V/60 HZ) from a tool plug that is coupled to a standard wall outlet. The AC power may then be converted into DC power and provided to the components of the power tool100. The power source105provides operating power to the motor115through the FETs110(e.g., an inverter bridge).

The Hall-effect sensors120output motor feedback information, such as an indication (e.g., a pulse) when the Hall-effect sensors detect a pole of a magnet attached to a rotating shaft150of the motor115. Based on the motor feedback information from the Hall-effect sensors120, the motor controller125may determine the rotational position, velocity, and/or acceleration of the shaft150. The motor controller125also receives control signals from the user input130. The user input130may include, for example, a trigger switch, a forward/reverse selector switch, a mode selector switch, etc. In response to the motor feedback information and user control signals, the motor controller125transmits control signals to the FETs110to drive the motor115. By selectively activating the FETs110, power from the power source105is selectively applied to opposed coils of the motor115to cause rotation of a shaft150. Although not shown, the motor controller125and other components135of the power tool100may also be electrically connected to the power source105to receive operating power from the power source105.

With reference toFIGS.2A to3, a motor assembly140is shown including a motor housing145, the motor115positioned within the motor housing145, and a PCB assembly155coupled to an end of the motor housing145opposite the end from which the shaft150protrudes. The PCB assembly155is fastened to the motor housing145by fasteners170(FIG.3) equally spaced about the periphery of the motor housing145. The PCB assembly155includes a heat sink160, a power PCB165disposed on a rear side of the heat sink160, and a position sensor PCB355disposed on an opposite side of the heat sink160. The power PCB165includes the FETs110and a connection terminal that is connected to the power source105and the Hall-effect sensors120. In the illustrated embodiment, the power PCB165is coupled to the heat sink160by fasteners167. In some embodiments, rather than being attached to the motor housing145, the power PCB165may be located on a casting elsewhere within the power tool100. For example, the power PCB165may be located in a handle portion of the power tool housing or adjacent the motor assembly140in a motor housing portion of the power tool.

With reference toFIG.7, the motor115includes a rotor175from which the shaft150extends and a stator180(FIG.4) surrounding the rotor175. The stator180includes individual stator laminations185that are stacked together to form a stator core235. The stator180includes radially outward-extending ribs190on the outer surface of the stator core235that extend the entire length of the stator core235. Adjacent ribs190define a concave channel295through which the fasteners170extend. In addition, the stator180also includes recesses195, the purpose of which is described below, that extend parallel with the ribs190and that are rotationally offset from the ribs190. With reference toFIG.8, each stator lamination185includes a rim210having multiple radially outward-extending protrusions that collectively define the ribs190when the laminations185are stacked, and recesses195defined on the outer surface of the rim210. The stator180also includes inwardly extending stator teeth215and slots220defined between each pair of adjacent stator teeth215. An insulating member225(FIG.7) is provided in the slots220to insulate the stator teeth215from coil windings (not shown).

With reference toFIG.4, the motor115also includes a permanent ring magnet305mounted on the rear of the rotor shaft150. The ring magnet305is affixed to the rotor shaft150and co-rotates with the rotor shaft150, emanating a rotating magnetic field that is detectable by the Hall-effect sensors120. The ring magnet305is rotationally aligned with the magnets of the rotor175.

The stator180includes a front end cap200adjacent a front end of the stator core235and a rear end cap205adjacent a rear end of the stator core235. With reference toFIGS.9-14, the front end cap200and the rear end cap205each include rim portions240and end cap teeth245extending radially inward from the rim portions240. The end cap teeth245include projections250that prevent the respective coil windings from slipping off the stator teeth215and the end cap teeth245. Each of the front end cap200and the rear end cap205additionally includes tabs255extending transversely from the rim portions240, with each tab255including a radially inward extending projection260(FIG.12) that is received in a respective recesses195of the stator core235to rotationally align the front end cap200and the rear end cap205relative to the stator core235. The front end cap200includes concave recesses265(FIGS.9and10) that are aligned with the channels295in the stator core235through which the fastener170extend. The rear end cap205includes recessed portions270(FIGS.11and12) that receive respective poles330(FIG.17) of the motor housing145to rotationally align the rear end cap205relative to the stator core235.

During assembly of the stator180, stator windings are wound around the stator teeth215and the end cap teeth245. The stator windings are guided between adjacent stator teeth215by wire guiding tabs230on the rear end cap205(FIG.13). The stator180also includes coil contact plates275a,275b, and275c(also referred interchangeably herein as coil contact plates275) that short-circuit diagonally opposite pairs of coil windings (FIGS.14-15). With reference toFIGS.14and15, the coil contact plates275are generally semi-circular in shape and staggered to avoid contact between adjacent coil contact plates275. In particular, the first coil contact plate275ais positioned radially inward of the second coil contact plate275b, and the first coil contact plate275ais positioned radially outward of the third coil contact plate275c. Each of the coil contact plates275includes a first terminal280and a second terminal285diagonally opposite the first terminal280. Stator windings are connected to hooks290on the respective terminals280,285. With reference toFIG.2A, the first terminals280extend through the heat sink160and are electrically connected to the power PCB165, while the second terminals285do not protrude through the heat sink160. Particularly, the terminals280of the coil contact plates275a,275b,275care connected, respectively, to the U, V, W phases of the inverter bridge (i.e., FETs110). The first and second terminals280,285and the hooks290protrude from the guiding tabs230. In some embodiments, where the power PCB165is located elsewhere within the power tool100as described above, the coil contact plates275may be connected to the power PCB165by lead wires. Lead wires may be connected to the first terminals280(e.g., to holes in the first terminals280) and routed to the power PCB165within the power tool housing.

With continued reference toFIGS.14and15, a plurality of spacers293are coupled to the coil contact plates275. At least some of the spacers293are positioned between adjacent coil contact plates275in order to create and maintain an insulating gap (e.g., a space) between the adjacent coil contact plates275. In some embodiments, the plurality of spacers293are equally spaced circumferentially around the coil contact plates275. The spacers293are pre-molded onto the coil contact plates275before the coil contact plates275are overmolded as discussed in further detail below. In particular, each of the spacers293are molded on one of the coil contact plates275. In the illustrated embodiment, the spacers293include a first spacer positioned between the first and second adjacent coil contact plates275a,275b, and a second spacer293positioned between the adjacent first and third coil contact plates275a,275c. As such, insulating gaps are created between the adjacent coil contact plates275.

The pre-molded spacers293prevent internal shorts between coil contact plates275and portions of the coil contact plates275being exposed. In other words, the relative spacing between adjacent coil contact plates275may be difficult to adequately control during an injection molding process, and the coil contact plates275may deform during the molding process from the injection pressure. This deformation of the coil contact plates275can cause internal shorts or exposure. By adding the pre-molding spacers293, deformation of the coil contact plates275while being overmolded is prevented.

With reference toFIGS.13and14, the coil contact plates275and the spacers283are overmolded in the rear end cap205. In some embodiments, the front end cap200and the rear end cap205may be manufactured separately from the stator core235, positioned relative to the stator core235using the tabs255and the recesses195, and then retained to the stator core by the coil windings. In such an embodiment, the coil contact plates275may be overmolded by the rear end cap205using, for example, an insert molding process. In other embodiments, the stator core235and the coil contact plates275may be insert molded together, for example, using an injection molding process. In such an embodiment, the mold material defining each of the end caps200,205may also overlie one or multiple of the laminations185in the front and the rear of the stator core235. In both embodiments, because the coil contact plates275are molded within the rear end cap205, separate means of attaching the coil contact plates275to the end cap205is unnecessary. Also, the entire circumferential length of the coil contact plates275is insulated within the non-conductive mold material comprising the rear end cap205, thereby reducing the likelihood of corrosion of the coil contact plates275if the motor115is exposed to wet or damp environments.

With reference toFIGS.16-18, a rear end cap205′ according to another embodiment includes features similar to the rear end cap205identified with the same references numerals appended with an (′). In particular, the rear end cap205′ includes three coil contact plates275a′,275b′, and275c′. In this embodiment, there are no spacers (similar to spacers293) included.

With reference toFIG.15A, another embodiment of a rear end cap205″, which may be used in place of the end cap205ofFIG.13, is shown with like reference numerals with two appended prime markers (″) being associated with like components in the end cap205. In the rear end cap205″ ofFIG.15A, the coil contact plates275″ are first positioned in a pre-molded annular carrier294prior to being positioned in a mold for applying an outer resin layer296to the pre-assembled carrier294and coil contact plates275″.

The carrier294includes a single circumferential groove297defined in a side of the end cap205″ facing the stator core235in which the coil contact plates275″ are positioned (FIG.15B). A plurality of ribs298are located in the groove297for maintaining an air gap between adjacent coil contact plates275″, thereby preventing relative movement between the plates275″ during an injection molding process to apply the resin layer296that might otherwise cause two adjacent plates275″ to come into contact and short.

With reference toFIGS.19-22, the motor housing145includes a cylindrical portion310that houses the motor115. Mounting bosses320are provided along the cylindrical portion310through which the fasteners170extend to interconnect the PCB assembly155to the motor housing145. The motor housing145also includes a hub portion340coaxial with the cylindrical portion310and axially spaced from the cylindrical portion310, posts330extending axially from a rear end of the cylindrical portion310, and radially extending spokes335interconnecting the hub portion340to the posts330. With reference toFIG.20, the cylindrical portion310of the motor housing145also includes radially inward-extending ribs315extending the entire length of the cylindrical portion310, with each pair of adjacent ribs315defining a channel325therebetween. When the motor115is inserted into the motor housing145, the adjacent ribs190on the motor115are slidably received within the respective channels325defined in the cylindrical portion310, thereby rotationally orienting the motor115relative to the motor housing145.

With reference toFIGS.19-22, the hub portion340defines a central aperture345into which a bearing300(FIG.5) for supporting a rear of the rotor shaft150is interference-fit and the ring magnet305(FIG.4) is received. In some embodiments, the motor housing145′ may include a recessed portion350′ (FIG.29) formed in the hub portion340′ and partially along one of the spokes335′ into which a position sensor PCB355′ is at least partially received. The recessed portion350′ allows the position sensor PCB355′ to be located in close proximity and in facing relationship with the ring magnet305′ for accurate readings by multiple Hall-effect sensors120′ on the position sensor PCB355′.

With reference toFIGS.23-26, the heat sink160is sandwiched between the power PCB165and the position sensor PCB355at the rear of the motor housing145. In the illustrated embodiment, the position sensor PCB355is coupled to the heat sink160by fasteners357. In the illustrated embodiment, there are three Hall-effect sensors120on the position sensor PCB355. Alternatively, there may be other numbers of Hall-effect sensors120(e.g., two, four, etc.). With reference toFIGS.27and28, the power PCB165includes a first, generally flat surface360facing the heat sink160and a second surface365opposite the first surface360. The FETs110and capacitors370associated with the power PCB165are positioned on the second surface365(FIG.28). The first surface360is held in contact with the heat sink160so that heat generated by the power PCB165is transferred by conduction to the heat sink160, where it is subsequently dissipated.

A connection terminal375connecting the FETs110to the power source105is also positioned on the second surface365. Connections between the FETs110, the capacitors370, and the connection terminal375may be routed on the first surface360or the second surface365, for example, by a wiring substrate (e.g., printed electrical traces on the power PCB165). The power PCB165also includes holes380through which the terminals280of the coil contact plates275protrude. The terminals280are connected to the U, V, and W terminals of the inverter bridge (i.e., FETs110), respectively, via printed electrical traces on the power PCB165. Accordingly, individual electrical wires are not required to electrically connect the FETs110to the coil contact plates275. Additionally, recesses385are provided on the outer circumference of the power PCB165through which the fasteners170extend.

With reference toFIG.25, the Hall-effect sensors120on the position sensor PCB355detect the rotating magnetic field emanated by the ring magnet305. A connection terminal390is provided at one end of the position sensor PCB355to connect with a mating connection terminal425on the first surface360of the power PCB165. In this manner, power is provided to the position sensor PCB355via the mating connection terminals390,425, and the motor information feedback from the Hall-effect sensors120is transmitted to the motor controller125via the power PCB165. The connection between the power PCB165and the position sensor PCB355is made around an outermost edge of the heat sink160. In some embodiments, the power PCB165and the position sensor PCB355may be combined on a single motor controller PCB (not shown). The motor controller PCB may include the Hall-effect sensors120on the side facing the ring magnet305and the FETs110on the side opposite the side with the Hall-effect sensors120.

With reference toFIG.26, the heat sink160includes holes405aligned with the respective holes380in the power PCB through which the terminals280pass and connect to the power PCB165as mentioned above. Recesses410are also provided on the outer circumference of the heat sink160through which the fasteners170extend. With reference toFIGS.23and24, a low-pressure molding400provided with the heat sink160supports the end of the position sensor PCB355proximate the connection terminals390against the heat sink160, while the position sensor PCB355is also fastened to the heat sink160(via fasteners357) to ensure that the position sensor PCB355remains in contact with the heat sink160and to reduce tolerance stack-up back to the ring magnet305. In other words, the molding400supports the connection terminal390on the position sensor PCB355and the mating connection terminal425on the power PCB165.

In the illustrated embodiment, the position sensor PCB355is received within a recess402formed in the heat sink160, and the low-pressure molding400encases the position sensor PCB355. The low-pressure molding400also insulates solder joints for power leads and a ribbon cable connector from contamination. In the illustrated embodiment, the low-pressure molding400extends to the holes405in the heat sink160to provide electrical insulation between terminals280and the heat sink160. In other words, the molding400electrically insulates the holes405in heat sink160. Specifically, the heat sink160includes a plurality of tracks403extending between the recess402and the holes405to form the molding400. The molding400covers the recess402, the tracks403, and the holes405. The heat sink160may also be hard-coat anodized or carbon coated to provide electrical isolation from the terminals280.

With reference toFIGS.29-32, a motor assembly140′ according to another embodiment, includes an alternative PCB assembly155′. The PCB assembly155′ includes features similar to the PCB assembly155identified with the same references numerals appended with an (′). The low-pressure molding400shown inFIG.30does not encase the position sensor PCB355, but rather encases only an end of the position sensor PCB355. In addition, the position PCB355is mounted to the heat sink160without any recess.

Various features of the invention are set forth in the following claims.