Patent Description:
This disclosure relates to a power tool, such as an impact driver or impact wrench, and a compact motor assembly for use in a power tool, such as a low-profile and compact outer-rotor brushless motor assembly.

Conventional brushless direct-current (BLDC) motors are provided with a permanent magnet rotor supported within a stator. The stator includes a ring-shaped stator core, a series of stator teeth that extend radially inwardly from the stator core, and a series of stator windings wound in various patterns on the stator teeth. The rotor includes a rotor core that supports a number of magnets and is mounted on a rotor shaft. The shaft is supported relative to the stator via one or more bearings.

Another type of BLDC motor, referred to as an outer-rotor or external rotor motor, is provided with the rotor on the outside of the stator. In an outer-rotor motor, the rotor magnets are provided on an outer cup that is rotatable around a stator core. The outer cup includes a plate on one side of the stator that is secured to a rotor shaft. <CIT> provides an example of an outer-rotor motor in a nailer, where the outer rotor includes an integrated flywheel for driving a driver of the nailer. <CIT> provides an example of an outer-rotor motor in a circular saw. <CIT> discloses a drivetrain for a motor vehicle with an outer-rotor motor. Outer-rotor motors provides some performance advantages over comparable inner-rotor motors. Namely, since an outer rotor is by necessity larger than an inner rotor, it creates higher inertia and reduces the torque ripple effect and lower vibration. An outer rotor also provides higher magnetic flux and is also capable of producing more torque than a comparable inner rotor motor.

Power tools such as impact drivers and impact wrenches may be used for driving threaded fasteners into workpieces. Such power tools may lack sufficient power to drive a threaded fastener into a workpiece or may be too large in length or girth to fit into a desired location. In such power tools, it is desirable to reduce the girth and/or length of the tool, including the motor assembly and related components, without sacrifice power performance.

According to an example, a power tool is provided including a tool housing, a brushless direct-current (BLDC) motor disposed in the tool housing, and a transmission. The motor includes a stator including a stator core having an aperture extending therethrough and stator windings, a rotor including a cylindrical rotor core supporting at least one permanent magnet around an outer surface of the stator core, a rotor shaft rotatably coupled to the rotor, and a stator mount including a radial member disposed proximate a front end of the stator and an axial member secured to the stator. The transmission is secured to the tool housing and includes an input member coupled to and configured to be rotatably driven by rotation of the rotor shaft, and an output member configured to be driven by rotation of the input member. The radial member of the stator mount is secured to the transmission to support the stator at least radially within the rotor.

According to the invention, power tools according to claims <NUM> and <NUM> are provided.

In an embodiment, the rotor includes a rear wall proximate a rear end of the stator that is mounted on the rotor shaft, and the rotor shaft extends through the aperture of the stator to be coupled to the input member of the transmission.

In an embodiment, the axial member of the stator mount comprises a cylindrical portion onto which the stator core is securely mounted, and the rotor shaft extends through the cylindrical portion.

In an embodiment, the motor further includes at least one motor bearing having an inner race mounted on the rotor shaft and an outer race secured within the cylindrical portion. In an embodiment, the motor bearing is radially aligned with the stator core. In an embodiment, the motor bearing is radially oriented along a radial plane located between the stator core and the radial member of the stator mount.

In an embodiment, the transmission includes a transmission housing having a generally cylindrical body, and a planetary gear set including a pinion or a sun gear rotatably driven by the rotor shaft, a carrier, at least one planet gear rotatably mounted to the carrier and meshed with the pinion or the sun gear, and a ring gear supported by the transmission housing and meshed with the at least one planet gear.

In an embodiment, the transmission comprises a rear wall located at a rear end of the transmission housing, and the radial member of the stator mount is at least radially secured to the rear wall.

In an embodiment, the rear wall of the transmission includes a recessed surface formed by an annular peripheral body sized to form-fittingly receive the radial member of the stator mount therein.

In an embodiment, the radial member of the stator mount is rotationally secured to the rear wall of the transmission via at least one notch and indentation arrangement.

In an embodiment, the tool housing includes a radial wall projecting radially between the motor and the transmission assembly and engaging a rear surface of the radial member of the stator mount to axially hold the radial member in engagement with the rear wall of the transmission assembly.

In an embodiment, a carrier bearing is provided to support the carrier relative to the rear wall of the transmission.

In an embodiment, the rear wall of the transmission includes an annular center body forming a bearing holder for the carrier bearing, and the radial member of the stator mount includes an intermediary cylindrical portion forming a center recessed portion that receives the annular center body.

In an embodiment, a radial plane of the radial member of the stator mount intersects a portion of the carrier bearing.

In an embodiment, the rear wall of the transmission includes an annular body projecting towards the motor, and the tool includes a lock ring configured to axially hold the radial member of the stator mount in engagement with a rear surface of the annular body. In an embodiment, the lock ring includes a main portion having a threaded inner surface that is fastened onto a threaded outer surface of the annular body of the transmission, and a radial portion that engages and forces a rear surface of the radial member of the stator mount against the annular body of the transmission.

In an embodiment, the radial member of the stator mount includes tabs extending therefrom that engage the transmission housing to secure the stator mount at least radially to the transmission. In an embodiment, a rear end of the transmission housing defines an opening through which the ring gear is received.

In an embodiment, an interior of the transmission housing includes recessed surfaces near the rear end, and the tabs of the radial member extend axially through the opening in engagement with the recessed surfaces to affix the stator mount at least radially to the rear end of the transmission.

In an embodiment, the rear end of the transmission housing includes notches, and the tabs of the radial member extend radially in engagement with the notches to affix the stator mount at least rotationally to the rear end of the transmission.

In an embodiment, the radial member of the stator mount and the transmission housing mated together cooperate to substantially seal the transmission.

In an embodiment, the transmission includes of outer protrusions on the outer surface of the transmission housing configured to engage a portion of the tool housing to rotationally fix the transmission.

In an embodiment, the tool housing includes a radial wall projecting radially between the motor and the transmission assembly and engaging a rear surface of the radial member of the stator mount to axially hold the radial member to the transmission housing.

In an embodiment, a distance between a front end of the motor and a rear end of the transmission is at smaller than or equal to <NUM>. In an embodiment, the motor has an outer diameter than is smaller than or equal to approximately <NUM> and produces a maximum power output of at least <NUM> watts from a 20V max power tool battery pack.

According to another aspect of the invention, a power tool is provided including a tool housing, a brushless direct-current (BLDC) motor disposed in the tool housing, a stator mount assembly, and a transmission. The motor includes a stator including a stator core having an aperture extending therethrough and stator windings, a rotor including a cylindrical rotor core supporting at least one permanent magnet around an outer surface of the stator core, and a rotor shaft rotatably coupled to the rotor. The stator mount assembly includes a stator mount including an axial member secured to the stator, and an integrated mounting member including a radial member secured to the stator mount, a ring gear mount extending from the radial member away from the motor, and a ring gear supported by the ring gear mount. The transmission is secured to the tool housing, and it includes a transmission housing having a generally cylindrical body, and a planetary gear set including a carrier and at least one planet gear rotatably mounted to the carrier. The ring gear meshes with the at least one planet gear.

In an embodiment, the axial member of the stator mount includes a cylindrical portion onto which the stator core is securely mounted, and the rotor shaft extends through the cylindrical portion.

In an embodiment, at least one motor bearing is provided including an inner race mounted on the rotor shaft and an outer race secured within the cylindrical portion.

In an embodiment, the motor bearing is radially aligned with the stator core.

In an embodiment, the stator mount includes at least one radial arm, and the radial member of the integrated mounting member is molded around the radial arm to secure the integrated mounting member to the stator mount.

In an embodiment, the stator mount includes at least one protrusion that is received into a peripheral opening of the integrated mounting member to secure the integrated mounting member at least rotationally to the stator mount.

In an embodiment, a carrier bearing is provided to support the carrier relative to the stator mount assembly.

In an embodiment, the stator mount includes a frontal annular body forming a bearing holder for the carrier bearing to radially align the carrier bearing with the radial member of the integrated mounting member.

In an embodiment, the ring gear mount is discretely coupled to the transmission housing.

In an embodiment, the transmission housing overlaps at least the ring gear mount of the integrated mounting member.

In an embodiment, an O-ring is disposed between the integrated mounting member and the transmission housing to substantially seal the transmission.

In an embodiment, the power tool includes a nosecone mounted on the tool housing to provide an output member configured to be rotatably driven by a cam shaft coupled to the carrier, wherein the transmission housing is integrally formed with the nosecone and extends rearwardly therefrom inside the tool housing.

In an embodiment, the transmission housing is integrally coupled to the ring gear mount.

According to another aspect of the invention, a power tool is provided including a tool housing, a brushless direct-current (BLDC) motor disposed in the tool housing, and a stator mount assembly. The motor includes a stator including a stator core having an aperture extending therethrough and stator windings, a rotor including a cylindrical rotor core supporting at least one permanent magnet around an outer surface of the stator core, and a rotor shaft rotatably coupled to the rotor. The stator mount assembly includes a stator mount including an axial member secured to the stator, and an integrated mounting member including a radial member secured to the stator mount and a transmission housing having a generally cylindrical body integrally extending from the radial member away from the motor. The transmission housing is secured to the tool housing and houses components of a transmission, and the components of the transmission include a carrier, at least one planet gear rotatably mounted to the carrier, and a ring gear supported by the transmission housing and meshed with the planet gear(s).

In an embodiment, the rotor comprises a rear wall proximate a rear end of the stator that is mounted on the rotor shaft, and the rotor shaft extends through the aperture of the stator to be coupled to the input member of the transmission.

In an embodiment, at least one motor bearing is provided including an inner race mounted on the rotor shaft and an outer race secured within the cylindrical portion. In an embodiment, motor bearing is radially aligned with the stator core.

In an embodiment, the stator mount includes at least one radial arm, and wherein the radial member of the integrated mounting member is molded around the radial arm to secure the integrated mounting member to the stator mount.

In an embodiment, the power tool further includes a nosecone mounted on the tool housing to provide an output member, where a front portion of the transmission housing extends out of the tool housing and is received within the nosecone.

In an embodiment, an O-ring is disposed between the front portion of the transmission housing and the nosecone to substantially seal the transmission assembly.

In an embodiment, a nosecone mounted on the tool housing to provide an output member configured to be rotatably driven by a cam shaft coupled to the carrier, where the transmission housing is integrally formed with the nosecone and extends rearwardly therefrom inside the tool housing.

In an embodiment, the transmission housing includes at least one inner rim that engages an axial end of the ring gear to secure the ring gear within the transmission housing.

In an embodiment, the transmission includes outer protrusions on the outer surface of the transmission housing configured to engage a portion of the tool housing to rotationally fix the transmission.

In an embodiment, a distance between a front end of the motor and a rear end of the transmission is at most <NUM>. In an embodiment, the motor has an outer diameter than is smaller than or equal to approximately <NUM> and produces a maximum power output of at least <NUM> watts from a 20V max power tool battery pack.

According to an example, a brushless direct-current (BLDC) motor is provided including: a stator including a stator core having an aperture extending therethrough and a series of stator windings; and a rotor including a rotor core having a substantially cylindrical body, permanent magnets secured to an inner surface of the rotor core, a rotor shaft extending through the stator, and an overmold structure. The overmold structure includes: a radially body extending adjacent an axial end of the stator and coupled to the rotor shaft via a bushing, and a peripheral body formed around an outer surface and axial end surfaces of the rotor core and structurally securing the permanent magnets to the inner surface of the rotor core.

In an embodiment, the rotor core includes teeth axially projecting from at least one of its axial end surfaces, and the overmold structure is formed in engagement with the teeth to rotationally fix the rotor core relative thereto.

In an embodiment, the radial body of the overmold structure includes blades that form a fan for generating an airflow through the motor.

In an embodiment, the rotor core includes a continuous wire rod wound in a shape of a tubular body.

In an embodiment, the wire rod is welded in the shape of the tubular body.

In an embodiment, the wire rod is held in the shape of the tubular body via the overmold structure.

According to an example, a brushless direct-current (BLDC) motor is provided including: a stator including a stator core having an aperture extending therethrough and a series of stator windings; and a rotor including permanent magnets, a rotor shaft extending through the stator, and an overmold structure. The overmold structure includes: a radially body extending adjacent an axial end of the stator and coupled to the rotor shaft via a bushing, and a substantially cylindrical body formed to secure the plurality of permanent magnets. At least the substantially cylindrical body of the overmold structure is formed via a metal injection molding process to increase a magnetic flux of the rotor.

In an embodiment, the motor includes no solid core flux ring.

In an embodiment, the radial body of the overmold structure includes blades that form a fan configured to generate an airflow through the motor.

According to an example, a brushless direct-current (BLDC) motor is provided including: a rotor comprising a rotor core, permanent magnets secured to the rotor core, and a rotor shaft; a stator including a stator core having an inner annular body though which the rotor shaft extends and stator teeth extending radially outwardly from the inner annular body, stator windings wound around the stator teeth, an insulating body electrically insulating the stator windings from the stator core, and stator terminals mounted to the insulating body and electrically coupled to the stator windings; and a positional sensor board mounted to the insulating body and including at least one positional sensor configured to magnetically sense the permanent magnets. The positional sensor board is C-shaped including two ends defining a gap in between, and the stator terminals are located within the gap so as to radially intersect a radial plane of the positional sensor board.

In an embodiment, the positional sensor board includes an outer diameter than is greater than an outer diameter of the stator.

In an embodiment, the positional sensor board includes an inner diameter than is greater than an inner diameter of the inner annular body.

In an embodiment, the insulating body includes axial posts that support the positional sensor board.

In an embodiment, the stator terminals are aligned with three of the stator teeth.

In an embodiment, the gap occupies an angular distance of approximately <NUM> to <NUM> degrees.

Additional features and advantages of various embodiments will be set forth, in part, in the description that follows, and will, in part, be apparent from the description, or may be learned by the practice of various embodiments. The objectives and other advantages of various embodiments will be realized and attained by means of the elements and combinations particularly pointed out in the description herein.

The drawings described herein are for illustration purposes only and are not intended to limit the scope of this disclosure in any way.

Throughout this specification and figures like reference numbers identify like elements.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are intended to provide an explanation of various embodiments of the present teachings.

<FIG> depicts a side view of a power tool <NUM>, in this example an impact tool, according to a non-claimed embodiment. <FIG> depicts a partial cross-sectional view of the exemplary impact tool <NUM> according to a non-claimed embodiment. <FIG> depicts an exploded view of an impact mechanism of the exemplary impact tool <NUM> according to a non-claimed embodiment.

In a non-claimed embodiment, the exemplary impact tool <NUM> includes a housing <NUM> having a motor housing portion <NUM> including two clamshells that come together to house a motor <NUM> rotatably driving a rotor shaft <NUM> and a nosecone <NUM> coupled to the motor housing portion <NUM> that houses an impact mechanism <NUM>. A transmission assembly <NUM> is disposed between the motor <NUM> and the impact mechanism <NUM> that cooperates with the impact mechanism <NUM> to selectively impart rotary motion and/or a rotary impact motion to an output spindle <NUM>. Where the tool is an impact wrench, as shown in this example, a socket drive <NUM> is formed at the end of the output spindle <NUM> designed to drive a socket wrench (not shown). Alternatively, where the power tool is an impact driver, a bit holder may be coupled to the end of the output spindle. Details regarding exemplary tool holders are set forth in<CIT>.

The power tool further includes a handle <NUM> that extends transverse to the housing <NUM> and accommodates a trigger switch <NUM>, a control and/or power module (not shown) that includes control electronics and switching components for driving the motor <NUM>, and a battery receptacle <NUM> that receives a removeable power tool battery pack for supplying electric power to the motor <NUM>. The handle <NUM> has a proximal portion coupled to the housing <NUM> and a distal portion coupled to the battery receptacle <NUM>. The motor <NUM> may be powered by an electrical power source, such as a DC power source or battery (not shown), that is coupled to the battery receptacle <NUM>, or by an AC power source. The trigger <NUM> is coupled to the handle <NUM> adjacent the housing <NUM>. The trigger <NUM> connects the electrical power source to the motor <NUM> via the control and/or power module, which controls power delivery to the motor <NUM>.

In a non-claimed embodiment, the transmission assembly <NUM> may comprise a planetary transmission and may include, among other features, a pinion or sun gear <NUM> that is coupled to an end of the rotor shaft <NUM> of the motor <NUM> and that extends along a tool axis X. One or more planet gears <NUM> surround and have teeth that mesh with the teeth on the sun gear <NUM>. An outer ring gear <NUM> is rotationally fixed to the housing <NUM> and centered on the tool axis X with internal teeth meshing with the teeth on the planet gears <NUM>. A cam carrier <NUM> includes a pair of carrier plates 22A, 22B that support the planet gears <NUM> with pins <NUM> so that the planet gears <NUM> can rotate about the pins <NUM>. The cam carrier <NUM> further includes a rearward protrusion <NUM> that extends axially rearward from the rear carrier plate 22A along the axis X and a cam shaft <NUM> that extends axially forward from the front carrier plate 22B along the axis X.

When the motor <NUM> is energized, the rotor shaft <NUM> and the sun gear <NUM> rotate about the axis X. Rotation of the sun gear <NUM> causes the planet gears <NUM> to orbit the sun gear <NUM> about the axis X, which in turn causes the cam carrier <NUM> to rotate about the axis X at a reduced speed relative to the rotational speed of the rotor shaft <NUM>. In the illustrated embodiment, only a single planetary stage is shown. It should be understood that the transmission may include multiple planetary stages that may provide for multiple speed reductions, and that each stage can be selectively actuated to provide for multiple different output speeds of the planet carrier. Further, the transmission may include a different type of gear system such as a parallel axis transmission or a spur gear transmission.

The impact mechanism <NUM> includes the cam shaft <NUM>, a generally cylindrical hammer <NUM> received over the cam shaft <NUM>, and an anvil <NUM> fixedly coupled to the output spindle <NUM>. The hammer <NUM> has two lugs <NUM> configured to engage two radial projections <NUM> on the anvil <NUM> in a rotating direction. Formed on an outer surface of the cam shaft <NUM> is a pair of rear-facing V-shaped cam grooves <NUM> with their open ends facing toward transmission assembly <NUM>. A corresponding pair of forward-facing V-shaped cam grooves (not shown) is formed on an interior surface of the hammer <NUM> with their open ends facing toward the output spindle <NUM>. Balls <NUM> are received in and rides along each of the cam grooves <NUM> to movably couple the hammer <NUM> to the cam shaft <NUM>. A compression spring <NUM> is received in a cylindrical recess in the hammer <NUM> and abuts a forward face of the front carrier plate 22B. The spring <NUM> biases the hammer <NUM> toward the anvil <NUM> so that the so hammer lugs <NUM> engage the corresponding anvil projections <NUM>.

At low torque levels, the impact mechanism <NUM> transmits torque from the transmission assembly <NUM> to the output spindle <NUM> in a rotary mode. In the rotary mode, the compression spring <NUM> maintains the hammer <NUM> in a forward position so that the hammer lugs <NUM> continuously engage the anvil projections <NUM>. This causes the cam shaft <NUM>, the hammer <NUM>, the anvil <NUM>, and the output spindle <NUM> to rotate together as a unit about the axis X. As torque increases, the impact mechanism <NUM> may transition to transmitting torque to the output spindle <NUM> in an impact mode. In the impact mode, the hammer <NUM> moves axially rearwardly against the force of the spring <NUM>, decoupling the hammer lugs <NUM> from the anvil projections <NUM>. The anvil <NUM> continues to spin freely on about the axis X without being driven by the motor <NUM> and the transmission assembly <NUM>, so that the anvil <NUM> coasts to a slower speed. Meanwhile, the hammer <NUM> continues to be driven at a higher speed by the motor <NUM> and transmission assembly <NUM>, while the hammer <NUM> moves axially rearwardly relative to the anvil <NUM> by the movement of the balls <NUM> in the V-shaped cam grooves <NUM>. When the balls <NUM> reach their rearmost position in the V-shaped cam grooves <NUM>, the spring <NUM> drives the hammer <NUM> axially forward with a rotational speed that exceeds the rotational speed of the anvil <NUM>. This causes the hammer lugs <NUM> to rotationally strike the anvil projections <NUM>, imparting a rotational impact to the output spindle <NUM>.

In a non-claimed embodiment, the motor <NUM> is a brushless direct-current (BLDC) motor that includes an inner rotor <NUM> having surface-mount magnets <NUM> on a rotor core <NUM> and a stator assembly <NUM> located around the rotor <NUM>. The stator assembly <NUM> includes a stator core <NUM> having a series of teeth <NUM> projecting radially inwardly from the stator core <NUM>, and a series of conductive windings <NUM> wound around the stator teeth <NUM> to define three phases connected in a wye or a delta configuration. As the phases of the stator assembly <NUM> are sequentially energized, they interact with the rotor magnets <NUM> to cause rotation of the rotor <NUM> relative to the stator assembly <NUM>.

In a non-claimed embodiment, the rotor core <NUM> is mounted on the rotor shaft <NUM> and supports a series of rotor magnet <NUM>. The rotor core <NUM> may be made of a solid core piece of metal or lamination stack that includes a series of parallel laminations. In an embodiment, the rotor magnet <NUM> is a ring surface-mounted on the outer surface of the rotor core <NUM> and magnetized in a series of poles, e.g., four poles having a S-N-S-N orientation. Alternatively, rotor magnet <NUM> may be provided as a series of discrete magnet segments that may be pre-magnetized prior to assembly. The outer surface of the rotor core <NUM> may be shaped for proper retention of the magnet segments. In yet another embodiment, the rotor magnets <NUM> may be fully or partially embedded within the rotor core <NUM>.

In a non-claimed embodiment, a fan <NUM> is mounted on the rotor shaft <NUM> behind the motor <NUM>. In an embodiment, a rear tool cap <NUM> is mounted to the end of the housing <NUM> to contain the end of the motor <NUM>. The rear tool cap <NUM> may be provided integrally with the housing <NUM> or as a separate piece. In an embodiment, the fan <NUM> is positioned between the motor <NUM> and the rear tool cap <NUM>. The fan <NUM> generates airflow through the motor <NUM> and (preferably) the transmission assembly <NUM> to cool the components.

In a non-claimed embodiment, a rear motor bearing <NUM> that supports the rotor shaft <NUM> is supported by a wall or retention rib of the tool housing <NUM>. In an embodiment, a support plate <NUM> supports a front motor bearing <NUM> that in turn supports the rotor shaft <NUM>. The support plate <NUM> includes a cylindrical portion <NUM> that receives the outer race of the front motor bearing <NUM> and a radial portion <NUM> that extends radially from the cylindrical portion <NUM> and includes radial ends supported by the tool housing <NUM>. The stator assembly <NUM> is also supported by the tool housing <NUM>, thus being axially and radially secure with respect to the support plate <NUM>. In this manner, the support plate <NUM> axially and radially supports the rotor <NUM> within the stator assembly <NUM>. In an embodiment, the support plate <NUM> and the stator assembly <NUM> may be independently supported by the tool housing <NUM>. In another embodiment, the support plate may be formed integrally as a part of two clamshells that form the tool housing <NUM>. Alternatively, the support plate <NUM> may be piloted to and retained by the stator assembly <NUM> directly and independently of the tool housing <NUM>.

In a non-claimed embodiment, the support plate <NUM> also has a front lip that supports a component of the transmission assembly <NUM>, such as supporting the ring gear <NUM>, to inhibit axially and rotational movement of the ring gear <NUM> relative to the housing <NUM>. In addition, the support plate <NUM> supports a cam carrier bearing <NUM> that supports the cam carrier <NUM> relative to the support plate <NUM>, and therefore relative to the motor <NUM> and the tool housing <NUM>. The cam carrier bearing <NUM> is nested within the support plate <NUM> adjacent the motor <NUM>. Specifically, the support plate <NUM> is positioned between the motor <NUM> and transmission assembly <NUM> and provides support for the front motor bearing <NUM> on one side and for the cam carrier bearing <NUM> on the other side. In an embodiment, the support plate <NUM> includes a recessed portion <NUM> that includes a larger diameter than the cylindrical portion <NUM> and is sized to receive the cam carrier bearing <NUM> therein. The cam carrier bearing <NUM> is thus located axially forward of the entire motor <NUM>.

In a non-claimed embodiment, motor <NUM> has a total length from the rearmost part of the motor (e.g., the fan <NUM>) to the frontmost part of the motor (e.g., front of the windings <NUM>) of approximately <NUM> to <NUM> and a diameter defined by the outer surface of the stator core <NUM> of approximately <NUM> to <NUM> (e.g., approximately <NUM>). In an embodiment, a distance L1 between a front of the motor, in this example defined by the forwardmost part of the windings <NUM>, to the rear of the cam carrier <NUM>, is approximately <NUM>. Thus, the power tool <NUM> has a total length of approximately <NUM> to <NUM>. In an embodiment, the motor <NUM> produces a maximum power output of at least <NUM> watts.

According to the invention, various examples of an outer-rotor BLDC motor is provided as a substitute for the above-described inner-rotor BLDC motor <NUM>, as described herein with reference to <FIG>. The outer-rotor motor may be configured to include many of the size and power limitations described above with reference to <FIG>, but it includes an exterior rotor that surrounds an interior stator. Outer-rotor motors typically have a higher inertia than comparable inner-rotor motors due to the greater size of the rotor assembly, which dampen torque ripple and provide a more stable operation even at low speed. Further, outer-rotor motors, due to the larger area of magnetic flux, are typically capable of providing higher torque than comparably sized inner-rotor motors. In an embodiment, the outer-rotor motors described herein produce more power than the inner-rotor motor described above, without adding to the overall size or length of the tool. In fact, embodiments of the outer-rotor motor described herein reduce the overall length of the motor and the power tool.

<FIG> depicts a perspective view of an outer-rotor BLDC motor <NUM>, according to a first embodiment of the invention. <FIG> depicts a partial exploded view of the power tool <NUM> including the outer-rotor BLDC motor <NUM> and a transmission assembly <NUM>, according to an embodiment. <FIG> depicts a partially cross-sectional view of the power tool <NUM> including the outer-rotor BLDC motor <NUM>, according to an embodiment. <FIG> depicts an exploded view of the outer-rotor BLDC motor <NUM>, according to an embodiment.

In an embodiment, power tool <NUM> includes many of the same features as power tool <NUM> described above, including but not limited to, a power tool housing <NUM> including two clamshells that come together to house the motor <NUM>, and a nosecone <NUM> that houses an impact mechanism (not shown). The transmission assembly <NUM> is disposed between the motor <NUM> and the impact mechanism and cooperates with the impact mechanism to selectively impart rotary motion and/or a rotary impact motion to an output spindle. In an embodiment, tool housing <NUM> and transmission assembly <NUM> respectively include many of the same features of tool housing and transmission assembly previously discussed, with some differences discussed below in detail. To the extent that these or other power tool components include identical or similar features as described above, the same reference numerals are used.

In an embodiment, as shown in these figures, the outer rotor-rotor BLDC motor <NUM> includes an internal stator assembly <NUM> received within an external rotor assembly <NUM>.

In an embodiment, stator assembly <NUM> includes a stator core (also referred to as stator lamination stack) <NUM> formed by a series of steel laminations. The stator lamination stack <NUM> is mounted on and structurally supported via a stator mount <NUM>, described below. The stator lamination stack <NUM> supports a series of stator windings (not shown). In an exemplary embodiment, the stator windings are wound in three phases, which, when respectively energized by a control module, cause rotation of the rotor assembly <NUM>. For a discussion of structural details of the stator assembly <NUM>, reference is made to <CIT>.

In an embodiment, the stator mount <NUM> includes an elongated cylindrical portion <NUM> sized to be received securely within a central aperture of the stator lamination stack <NUM>. In an embodiment, the stator lamination stack <NUM> may be press-fitted over the cylindrical portion <NUM> of the stator mount <NUM>. In an embodiment, stator mount <NUM> further includes a radial member <NUM> at an end of the cylindrical portion <NUM> outside the body of the stator lamination stack <NUM>. The radial member <NUM> of the stator mount, as described below in detail, engages the transmission assembly <NUM> and (in an embodiment) a portion of the tool housing <NUM> to structurally pilot and support the stator assembly <NUM>.

In an embodiment, a positional sensor board <NUM> is mounted on an end of the stator lamination stack <NUM>, between the stator lamination stack <NUM> and the radial member <NUM> of the stator mount <NUM>. In an embodiment, the positional sensor board <NUM> includes a series of Hall sensors positioned for sensing a rotary position of the rotor assembly <NUM>. Signals indicative of the rotary position of the rotor assembly <NUM> are provided by the Hall sensors to the control module.

In an embodiment, rotor assembly <NUM> includes a cylindrical rotor core <NUM> formed around the stator assembly <NUM>, and a series of permanent magnets <NUM> secured to the inner surface of the rotor core <NUM> facing the stator assembly <NUM> with a small airgap therebetween. As will be described later, the magnets <NUM> are held relative to the rotor core <NUM> via an overmold structure <NUM>. As the stator windings are energized in a controlled pattern, they magnetically interact with permanent magnets <NUM>, thus causing the rotation of the rotor assembly <NUM>.

In an embodiment, the rotor assembly <NUM> further includes a radial body <NUM> peripherally connected (either integrally or discretely) to a rear end of the rotor core <NUM>. In an embodiment, the radial body <NUM> includes a series of openings adjacent the rotor core <NUM>, which form a series of blades <NUM> extending radially therebetween. The blades <NUM> form a fan adjacent the rotor core <NUM> that generates an airflow with the rotation of the rotor assembly <NUM> for colling the stator and rotor components. In an embodiment, the radial body <NUM> is centrally mounted on a rotor shaft <NUM> via a bushing <NUM>. The rotation of the rotor assembly <NUM> is transferred via the radial body <NUM> an the bushing <NUM> to cause rotation of the rotor shaft <NUM>. In an embodiment, pinion <NUM> is mounted on a front end of the rotor shaft <NUM>, or integrally formed at the front end of the rotor shaft <NUM>, for coupling the rotor shaft <NUM> to transmission assembly <NUM>.

In an embodiment, at least a front motor bearing <NUM> and a rear motor bearing <NUM> are mounted on the rotor shaft <NUM> and received within the cylindrical portion <NUM> of the stator mount <NUM>. In an embodiment, rear motor bearing <NUM> is fully contained within an envelope defined by the radial ends of the stator core <NUM>, whereas the front motor bearing <NUM> is disposed outside the envelope. In an embodiment, the rear motor bearing <NUM> abuts against the bushing <NUM>. In an embodiment, the front motor bearing <NUM> is radially inward of the positional sensor board <NUM> such that a radial plane of the positional sensor board <NUM> intersects the front motor bearing <NUM>. In an embodiment, a spacer <NUM> is disposed between the bearings <NUM> and <NUM>. In an embodiment, the bearings <NUM> and <NUM> structurally support the rotor shaft <NUM> while allowing its free rotation within the stator assembly <NUM>. The bearings <NUM> and <NUM> consequently structurally support the.

In an embodiment, transmission assembly <NUM> includes a transmission housing <NUM> that is substantially cylindrical and houses the cam carrier <NUM> and associated components, and a rear wall <NUM>. The radial member <NUM> of the stator mount <NUM> is in contact with a rear surface of the rear wall <NUM> of the transmission assembly <NUM>. In an embodiment, radial member <NUM> includes a center recessed portion <NUM> formed by an intermediary cylindrical portion <NUM> having a larger diameter than the cylindrical portion <NUM> and a smaller diameter than the outer periphery of the radial member <NUM>. The center recessed portion <NUM> and the intermediary cylindrical portion <NUM> cooperatively form a cavity facing the transmission assembly <NUM>. In an embodiment, the rear surface of the rear wall <NUM> of the transmission assembly <NUM> includes an annular center body <NUM> arranged to be form-fittingly received within the cavity. Further, in an embodiment, the outer periphery of the radial member <NUM> is radially constrained within an annular peripheral body <NUM> of the transmission assembly <NUM>. In an embodiment, the rear wall <NUM> of the transmission assembly <NUM> is recessed relative to the annular peripheral body <NUM> and the annular center body <NUM>, forming a cavity sized to receive the radial member <NUM> of the stator mount <NUM>. This arrangement provides a support structure that pilots and radially supports the stator mount <NUM> directly to the transmission assembly <NUM> and thus relative to the power tool housing <NUM>.

Further, in an embodiment, the outer periphery of the radial member <NUM> of the stator mount <NUM> includes a series of notches <NUM> formed therein in a radially-inward direction at predetermined locations. the rear surface of the rear wall <NUM> of the transmission assembly <NUM> includes a series of peripheral indentations <NUM> that project axially in the direction of the motor <NUM>. The indentations <NUM> correspondingly engage the notches <NUM> of the radial member <NUM> to rotationally fix the stator mount <NUM> to the transmission assembly <NUM> and thus relative to the power tool housing <NUM>.

In an embodiment, radial member <NUM> is axially constrained and is in direct contact with the rear wall <NUM> of the transmission assembly <NUM>, and the center recessed portion <NUM> is axially constrained and is in contact with the cylindrical portion <NUM> of the transmission assembly <NUM>. Further, in an embodiment, a radial wall <NUM> of the tool housing <NUM> projects radially between the motor <NUM> and the transmission assembly <NUM> around the annual center body <NUM> of the transmission assembly <NUM>. In an embodiment, the radial member <NUM> of the stator mount <NUM> is disposed forward of the radial wall <NUM> and the rest of the motor assembly <NUM> is provided rearward of the radial wall <NUM>. As such, the radial member <NUM> is axially clamped by the rear wall <NUM> of the transmission assembly <NUM> on one side and by the radial wall <NUM> of the power tool housing <NUM> on the other side. This arrangement ensures that the stator mount <NUM> is axially fixed relative to the transmission assembly <NUM> and the power tool housing <NUM>. In an embodiment, the intermediary cylindrical portion <NUM> of the radial member <NUM> is received through a center opening of the radial wall <NUM> such that a radial plane of the radial wall <NUM> intersects the intermediary cylindrical portion <NUM>.

In an embodiment, the cam carrier bearing <NUM> of the transmission assembly <NUM> is supported by at least a portion of the annular center body <NUM>. In an embodiment, the radial plane of the radial member <NUM> of the stator mount <NUM> intersects a portion of the cam carrier bearing <NUM>.

In an embodiment, a rear end cap <NUM> is mounted on the rear end of the power tool housing <NUM> behind the motor <NUM>. In an embodiment, the rear end cap <NUM> captures the rear surface of the radial body <NUM> and the fan blades <NUM> of the rotor assembly <NUM>, thus providing a baffle for the fan blades <NUM> to radially expel the air away from the motor <NUM>. In an embodiment, the rear end cap <NUM> includes one or more radial openings <NUM> that allow the air to be radially expelled from the power tool <NUM>. In an embodiment, since both bearings <NUM> and <NUM> are contained within the stator mount <NUM>, the rear end cap <NUM> need not support a bearing of the rotor shaft <NUM> or make contact with any part of the motor <NUM>. In other words, the entirety of the motor <NUM> is piloted and structurally supported by the transmission assembly <NUM>, alone or in combination with the radial wall <NUM> of the tool housing <NUM>. No part of the motor <NUM> is supported or in contact with the rear end cap <NUM> or the part of the tool housing <NUM> surrounding the motor <NUM>. In an embodiment, a gap between the rear end cap <NUM> and the fan blades <NUM> is approximately <NUM> to <NUM>.

The embodiment described above provides a compact yet high power outer-rotor motor <NUM> having a small axial length suitable for many power tool applications such as drills, impact drivers, impact wrenches, etc. The stator assembly <NUM> of this embodiment is designed to be fully supported only on one side of the motor <NUM> by the transmission assembly <NUM> in cooperation with the radial wall <NUM> of the tool housing <NUM>. Further, the rotor assembly <NUM> is merely supported by bearings provided within the stator mount <NUM>, without any further support needed on the power tool end cap <NUM>.

In an embodiment, motor <NUM> has a total length from the rearmost part of the motor (e.g., the radial body <NUM>) to the frontmost part of the motor (e.g., front of the windings <NUM>) of approximately <NUM> to <NUM> and a diameter as defined by the outer surface of the rotor assembly <NUM> of approximately of approximately <NUM> to <NUM> (e.g., approximately <NUM>). In an embodiment, a distance L2 between a front of the motor, in this example defined by the forwardmost part of the windings (not shown) and/or the frontmost part of the positional sensor board <NUM>, to the rear of the cam carrier <NUM>, is at smaller than or equal to <NUM>, preferably smaller than or equal to approximately <NUM>. Thus, the power tool <NUM> has a total length of approximately <NUM> to <NUM>, preferably smaller than or equal to <NUM>, even more preferably smaller than or equal to approximately <NUM>. In an embodiment, the motor <NUM> produces a maximum power output of at least <NUM> watts from a 20V max power tool battery pack.

A further and/or alternative embodiment of the invention is described with reference to <FIG>.

<FIG> depicts a perspective view of an outer-rotor BLDC motor <NUM>, according to a second embodiment of the invention. <FIG> depicts a partial exploded view of a power tool <NUM> including the outer-rotor BLDC motor <NUM> and a transmission assembly <NUM>, according to an embodiment. <FIG> depicts a partially cross-sectional view of the power tool <NUM> including the outer-rotor BLDC motor <NUM>, according to an embodiment. <FIG> depicts an exploded view of the outer-rotor BLDC motor <NUM>, according to an embodiment.

In an embodiment, power tool <NUM> includes many of the same features as power tools <NUM> and/or <NUM> described above, including but not limited to, a power tool housing <NUM> including two clamshells that come together to house the motor <NUM>, and a nosecone <NUM> that houses an impact mechanism (not shown). The transmission assembly <NUM> is disposed between the motor <NUM> and the impact mechanism and cooperates with the impact mechanism to selectively impart rotary motion and/or a rotary impact motion to an output spindle. In an embodiment, transmission assembly <NUM> includes a transmission housing <NUM> that is substantially cylindrical and houses the cam carrier <NUM> and associated components, and a rear wall <NUM>. In an embodiment, tool housing <NUM> and transmission assembly <NUM> respectively include many of the same features of tool housing and transmission assembly previously discussed, with some differences discussed below in detail. To the extent that these or other power tool components include identical or similar features as described above, the same reference numerals are used.

In an embodiment, the motor <NUM> includes many of the same features as motor <NUM> described above, and to the same extent that identical or similar features are incorporated in motor <NUM>, the same reference numerals are used. In an embodiment, motor <NUM> includes a modified stator mount <NUM> design. The rear wall <NUM> of the transmission assembly <NUM> also includes a modified design for retention of the stator mount <NUM>. In an embodiment, a lock ring <NUM> is utilized to secure the stator mount <NUM> to the transmission assembly <NUM>. These features are described here in detail.

In an embodiment, the stator mount <NUM> includes an elongated cylindrical portion <NUM> sized to be received securely within a central aperture of the stator lamination stack <NUM>. In an embodiment, the stator lamination stack <NUM> may be press-fitted over the cylindrical portion <NUM> of the stator mount <NUM>. In an embodiment, stator mount <NUM> further includes a radial member <NUM> at an end of the cylindrical portion <NUM> outside the body of the stator lamination stack <NUM>. In an embodiment, radial member <NUM> is formed as an outward projecting rim from the end of the cylindrical portion <NUM>. In an embodiment, notches <NUM> are formed at predetermined locations in the peripheral edge of the radial member <NUM>.

In an embodiment, the rear wall <NUM> of the transmission assembly <NUM> is integrally formed with an annular body <NUM> projecting in the direction of the motor <NUM>. In an embodiment, the annular body <NUM> forms a bearing holder facing the cam carrier <NUM> that securely receives the cam carrier bearing <NUM> therein and thus pilots and supports the cam carrier <NUM> relative to the transmission assembly <NUM>. In an embodiment, annular body <NUM> includes a diameter that is smaller than the outer diameter of transmission assembly <NUM>, but greater than the outer diameter of the radial member <NUM> of the stator mount <NUM>. In an embodiment, the outer surface of the annular body <NUM> is threaded. A rear surface <NUM> of the annular body <NUM> opposite the cam carrier bearing <NUM> is slightly recessed relative to the rear end of its outer surface and sized to receive and engage the radial member <NUM> of the stator mount <NUM>. This arrangement ensures that the stator mount <NUM> is radially fixed relative to the transmission assembly <NUM> and thus radially piloted to the power tool housing <NUM>. In an embodiment, the rear surface <NUM> of the annular body <NUM> includes one or more projecting indentations <NUM> arranged to engage the notches <NUM> of the stator mount <NUM>. Engagement of the indentations <NUM> and the notches <NUM> rotationally fixes the stator mount <NUM> to the transmission assembly <NUM> and the power tool housing <NUM>.

In an embodiment, lock ring <NUM> includes a nut-shaped main portion <NUM> having a threaded inner surface and a radial portion <NUM>. The nut-shaped main portion <NUM> is sized to be fastened onto the annular body <NUM>. The radial portion <NUM> includes an inner opening having a slightly larger inner diameter than the outer diameter of the cylindrical portion <NUM> of the stator mount <NUM>. The cylindrical portion <NUM> is received through the inner opening of the radial portion <NUM>, and the radial portion <NUM> clamps the radial member <NUM> of the stator mount <NUM> against the rear surface <NUM> of the annular body <NUM> of the transmission assembly <NUM> when the lock ring <NUM> is fastened onto the annular body <NUM>. This arrangement ensures that the stator mount <NUM> is axially fixed and structurally secured to the transmission assembly <NUM> and the power tool housing <NUM>.

In an embodiment, lock ring <NUM> is slid over the cylindrical portion <NUM>, thus capturing the radial member <NUM> of the stator mount <NUM>, before the stator assembly <NUM> is tightly mounted on the cylindrical portion <NUM>. In an embodiment, the lock ring <NUM> and the annular body <NUM> are both partially received within the center opening formed by the radial wall <NUM> of the tool housing <NUM>.

In an embodiment, the cam carrier bearing <NUM> of the transmission assembly <NUM> is supported by at least a portion of the annular body <NUM>. In an embodiment, a radial plane that intersects a front portion of the lock ring <NUM> also radially intersects a portion of the cam carrier bearing <NUM>.

With this arrangement, like the previous embodiment, the stator assembly <NUM> is fully supported only on one side of the motor <NUM> by the transmission assembly <NUM>. Unlike the previous embodiment, however, the radial wall <NUM> of the power tool housing <NUM> is not relied on to axially fix the stator mount <NUM> to the transmission assembly <NUM>. Rather, the lock ring <NUM> is configured to fully fix and support the stator mount <NUM> to the transmission assembly <NUM> independently of the power tool housing <NUM>.

<FIG> depicts a perspective view of an outer-rotor BLDC motor <NUM>, according to a third embodiment of the invention. <FIG> depicts a perspective view of a transmission assembly <NUM> configured for coupling with the motor <NUM>, according to an embodiment. <FIG> depicts a partial cross-sectional view of the power tool <NUM> including the motor <NUM> and the transmission assembly <NUM>, according to an embodiment.

In an embodiment, power tool <NUM> includes many of the same features as the various power tools described above, including but not limited to, a power tool housing <NUM> including two clamshells that come together to house the motor <NUM>, and a nosecone <NUM> that houses an impact mechanism (not shown). The transmission assembly <NUM> is disposed between the motor <NUM> and the impact mechanism and cooperates with the impact mechanism to selectively impart rotary motion and/or a rotary impact motion to an output spindle. In an embodiment, tool housing <NUM> and transmission assembly <NUM> respectively include many of the same features of tool housing and transmission assembly previously discussed, with some differences discussed below in detail. To the extent that these or other power tool components include identical or similar features as described above, the same reference numerals are used.

In an embodiment, motor <NUM> includes many of the same features as motors <NUM>-<NUM> described above, and to the same extent that identical or similar features are incorporated in motor <NUM>, the same reference numerals are used. In an embodiment, motor <NUM> includes a positional sensor board <NUM> which, similarly to positional sensor board <NUM> described above, senses a rotational position of the rotor. The motor <NUM> further includes a modified stator mount <NUM> design and the transmission assembly <NUM> also includes a corresponding modified design for coupling with and retention of the stator mount <NUM>. Specifically, in an embodiment, stator mount <NUM> includes a series of axial and radial tabs <NUM> and <NUM> that extend peripherally from a radial member <NUM> of the stator mount <NUM> and are coupled to a rear end of a transmission housing <NUM> of the transmission assembly <NUM> having a substantially cylindrical body to radially and rotationally fix the stator mount <NUM> to the transmission assembly <NUM>. These features are described here in detail.

In an embodiment, the stator mount <NUM> includes an elongated cylindrical portion <NUM> sized to be received securely within a central aperture of the stator lamination stack <NUM>. In an embodiment, the stator lamination stack <NUM> may be press-fitted over the cylindrical portion <NUM> of the stator mount <NUM>. In an embodiment, stator mount <NUM> further includes a radial member <NUM> at an end of the cylindrical portion <NUM> outside the body of the stator lamination stack <NUM>. In an embodiment, radial member <NUM> includes a stepped portion <NUM> that forms a bearing holder facing the cam carrier <NUM> for receiving the cam carrier bearing <NUM>. In an embodiment, the radial member <NUM> has an outer diameter that is slightly smaller than the outer diameter of the transmission housing <NUM> by approximately <NUM> to <NUM>. In an embodiment, the axial tabs <NUM> and radial tabs <NUM> (in this example four axial tabs <NUM> and four radial tabs <NUM> alternatively arranged) extend axially and radially outwardly, respectively, from the outer periphery of the radial member <NUM>. In an embodiment, an outer periphery formed by distal edges of the radial tabs <NUM> includes approximately the same diameter as the outer diameter of the transmission housing <NUM>.

In an embodiment, the transmission assembly <NUM> includes a front portion <NUM> that is at least partially received within the nosecone <NUM> and a rear portion <NUM> that is configured to receive and securely house a ring gear <NUM>. An inner annular projection <NUM> separating the front portion <NUM> and the rear <NUM> forms a radial wall against which the ring gear <NUM> abuts.

In an embodiment, the rear portion <NUM> of the transmission assembly <NUM> includes a series of first recessed surfaces <NUM> and a series of second recessed surfaces <NUM> alternatingly formed in its inner surface and extending axially from its rear surface. In an embodiment, the rear surface of the transmission housing <NUM> includes notches <NUM> aligned with the second recessed surfaces <NUM>. In an embodiment, the axial tabs <NUM> of the stator mount <NUM> are slip-fit along the first recessed surfaces <NUM> to secure the stator mount <NUM>, rotationally and radially, to the transmission assembly <NUM>. In an embodiment, the ring gear <NUM> includes a series of (in this example four) outer tabs <NUM> that are slidingly received in engagement with the second recessed surfaces <NUM> to secure the ring gear <NUM> within the rear portion <NUM> of the transmission assembly <NUM>. In an embodiment, radial tabs <NUM> of the stator mount <NUM> are received into the notches <NUM> of the transmission assembly <NUM> to provide additional rotational support for the stator mount <NUM> relative to the transmission assembly <NUM>. In an embodiment, the radial member <NUM>, with mated with the transmission housing <NUM> in this manner, substantially seals the transmission assembly <NUM>.

<FIG> depicts a partial exploded view of a power tool <NUM> including the motor <NUM> and the transmission assembly <NUM>, according to an embodiment. <FIG> depicts another partial exploded view of the power tool <NUM> prior to mounting of the motor <NUM> to the transmission assembly <NUM>, according to an embodiment. <FIG> depicts a partial perspective view of the power tool <NUM> with a housing half removed to show the motor <NUM> and the transmission assembly <NUM>, according to an embodiment. <FIG> depicts zoomed-in view of the transmission assembly <NUM> and the tool housing <NUM>, according to an embodiment.

During the assembly process, as seen in <FIG> and <FIG>, the front portion <NUM> of the transmission assembly <NUM> is mounted into the nosecone <NUM> and the rear portion <NUM> is positioned to house the cam carrier <NUM>, with the ring gear <NUM> being in radial alignment with the planet gears <NUM> of the cam carrier <NUM>. In an embodiment, an O-ring <NUM> is received between the front portion <NUM> and the nosecone <NUM> to radially secure the transmission assembly <NUM>. In an embodiment, the motor <NUM>, including the stator mount <NUM>, is mounted onto the transmission assembly <NUM>, with the axial tabs <NUM> fitted along the first recessed surfaces <NUM> and the radial tabs <NUM> received into the recessed regions <NUM> of the transmission assembly <NUM>.

In an embodiment, as shown in <FIG> and <FIG>, the entire assembly is then placed in the tool housing <NUM>. In an embodiment, the tool housing <NUM> includes a series of threaded openings <NUM> facing the nosecone <NUM>. A series of fasteners <NUM> are received into the threaded openings <NUM> to secure the nosecone <NUM> to the tool housing <NUM>. In an embodiment, the tool housing <NUM> includes annular rims <NUM> formed around the threaded openings <NUM>. In an embodiment, the front portion <NUM> of the transmission assembly <NUM> includes outer protrusions <NUM> having rounded outer edges. When fully assembled, the rounded edges of the outer protrusions <NUM> rest against the annular rims <NUM> of the tool housing <NUM> to rotational lock the transmission assembly <NUM> relative to the tool housing <NUM>. Further, the tool housing <NUM> includes a radial wall <NUM> that projects radially between the motor <NUM> and the transmission assembly <NUM> and engages the rear surface of the radial member <NUM> of the stator mount <NUM>. The radial wall <NUM> axially constrains the stator mount <NUM> against the transmission assembly <NUM>, and in turn, the transmission assembly <NUM> against the nosecone <NUM>. In this manner, the tool housing <NUM> cooperates with the nosecone <NUM> to rotationally and axially pilot and support the transmission assembly <NUM> and the stator mount <NUM>.

The above-described arrangement provides a structure whereby, like the previous embodiments, the stator assembly <NUM> is fully supported only on one side of the motor <NUM> by the transmission assembly <NUM>. However, unlike the previous embodiments, where the retention features of the stator mount are located between the transmission assembly and the stator assembly, the stator mount <NUM> of the above embodiment is locked into the transmission housing <NUM>. In other words, the retention features required for axial, rotational, and radial piloting and support of the stator mount <NUM> are located radially outwardly of the ring gear <NUM> and the cam carrier bearing <NUM>, and do not occupy the space between the stator mount <NUM> and the transmission assembly <NUM> along the axial direction. This arrangement thus reducing the axial length of the power tool <NUM>.

In an embodiment, a distance L3 between a front of the motor <NUM>, in this example defined by the forwardmost part of the windings (not shown) and/or the frontmost part of the positional sensor board <NUM>, to the rear of the cam carrier <NUM>, is smaller than or equal to approximately <NUM>, preferably smaller than or equal to approximately <NUM>. Thus, where the motor performance, diameter and length are the same as motor <NUM> described above, this arrangement allows the total length of the tool to be reduced by an additional <NUM>, preferably to a total length smaller than or equal to <NUM>, even more preferably smaller than or equal to approximately <NUM>.

<FIG> depicts a perspective view of an outer-rotor BLDC motor <NUM>, according to a fourth embodiment of the invention. <FIG> depicts a partial exploded view of a power tool <NUM> provided with the outer-rotor BLDC motor <NUM> and a transmission assembly <NUM>, according to an embodiment. <FIG> depicts a partially cross-sectional view of the power tool <NUM> including the outer-rotor BLDC motor <NUM> and the transmission assembly <NUM>, according to an embodiment. <FIG> depicts a partially exploded view of the outer-rotor BLDC motor <NUM>, according to an embodiment.

In an embodiment, power tool <NUM> includes many of the same features as the above-described power tools, including but not limited to, a power tool housing <NUM> including two clamshells that come together to house the motor <NUM>, and a nosecone <NUM> that houses an impact mechanism (not shown). The transmission assembly <NUM> is disposed between the motor <NUM> and the impact mechanism and cooperates with the impact mechanism to selectively impart rotary motion and/or a rotary impact motion to an output spindle. In an embodiment, tool housing <NUM> and transmission assembly <NUM> respectively include many of the same features of tool housing and transmission assembly previously discussed, with some differences discussed below in detail. To the extent that these or other power tool components include identical or similar features as described above, the same reference numerals are used.

In an embodiment, motor <NUM> includes many of the same features as the motors <NUM>-<NUM> described above, and to the extent that identical or similar features are incorporated in motor <NUM>, the same reference numerals are used. Similarly, the transmission assembly <NUM> includes many of the same features as transmission assemblies described above, and to the extent that identical or similar features are incorporated in, the same reference numerals are used. In an embodiment, unlike the previous embodiments, motor <NUM> includes a stator mount assembly <NUM> having an integrated mounting member <NUM> that supports the stator on one side and includes a ring gear mount <NUM> for supporting a ring gear <NUM> on the other side. Accordingly, in an embodiment, some components of the transmission assembly <NUM>, including the ring gear <NUM> and the associated planet gears of the cam carrier <NUM>, are at least partially nested within the integrated mounting member <NUM>. Integration of the ring gear mount <NUM> and the ring gear <NUM> to the motor assembly contributes to a reduction in axial length of the power tool <NUM>. Details of the stator mount assembly <NUM> and the transmission assembly <NUM> are discussed below.

In an embodiment, stator mount assembly <NUM> includes a stator mount <NUM>. Stator mount <NUM> includes an elongated cylindrical portion <NUM> sized to be received securely within a central aperture of the stator lamination stack <NUM>. In an embodiment, the stator lamination stack <NUM> may be press-fitted over the cylindrical portion <NUM> of the stator mount <NUM>. In an embodiment, stator mount <NUM> further includes a radial member <NUM> extending radially from an end of the cylindrical portion <NUM> outside the body of the stator lamination stack <NUM>. In an embodiment, an annular body extends from the radial member <NUM> opposite the cylindrical portion <NUM>, where the inner surface of the annular body <NUM> has a larger diameter than the inner diameter of the cylindrical portion <NUM>. In an embodiment, a series of radial arms <NUM> (in this example, three radial arms <NUM>) extend radially outwardly from the outer surface of the annular body <NUM>, each arm <NUM> forming an outer protrusion <NUM> that extends further out than the main body of the radial arm <NUM>.

In an embodiment, stator mount assembly <NUM> additionally includes the integrated mounting member <NUM>, which is designed to couple to and structurally support the stator mount <NUM> on one side and integrally support the ring gear <NUM> on the other side. In an embodiment, integrated mounting member <NUM> is a molded structure formed around the stator mount <NUM>.

In an embodiment, the integrated mounting member <NUM> includes a radial member <NUM> that radially occupies spaces between the arms <NUM> of the stator mount <NUM> and together with the arms <NUM> forms a radial partitioning wall separating the stator mount <NUM> from the transmission assembly <NUM>. An annular portion <NUM> of the integrated mounting member <NUM> extending rearward from the radial member <NUM> includes a first series of peripheral openings <NUM> through which the outer protrusions <NUM> of the radial arms <NUM> are radially received.

In an embodiment, the integrated mounting member <NUM> further includes the ring gear mount <NUM> having a generally cylindrical peripheral body for supporting the ring gear <NUM>. The ring gear <NUM>, which is conventionally provided in the transmission assembly separately from the motor, is incorporated into the integrated mounting member <NUM> and supported within the ring gear mount <NUM> adjacent the stator mount <NUM> opposite the radial partitioning wall. The ring gear mount <NUM> includes a series of second openings <NUM> that receive outer tabs <NUM> of the ring gear <NUM> to rotationally secure the ring gear <NUM>. The ring gear mount <NUM> further includes inner rims <NUM> and <NUM> that engage axial ends of the ring gear <NUM>. These features provide a structure whereby the integrated mounting member <NUM> axially, radially and rotationally constrains and affixes the ring gear <NUM> and the stator mount <NUM> relative to one another.

In an embodiment, the transmission assembly <NUM> includes a transmission housing <NUM> that is substantially cylindrical and extends integrally from the nosecone <NUM> with a rear end <NUM> thereof facing the motor <NUM>. The integrated mounting member <NUM> is form-fittingly received within the transmission housing <NUM> through rear end <NUM> thereof. A C-clip <NUM> is provided to axially stop a front end of the ring gear mount <NUM>. The C-clip <NUM> positions the radial partitioning wall (formed by the radial member <NUM> of the integrated mounting member <NUM> and the arms <NUM> of the stator mount <NUM>) adjacent the cam carrier <NUM> of the transmission assembly <NUM> and radially aligns the ring gear <NUM> with the planet gears of the cam carrier <NUM>. In an embodiment, the transmission housing <NUM> includes an annular groove to securely receive the C-clip <NUM>. The integrated mounting member <NUM> is further radially and axially secured to the transmission housing <NUM> of the transmission assembly <NUM> via an O-ring <NUM>. In an embodiment, the integrated mounting member <NUM> and transmission housing <NUM> are provided with corresponding annular grooves to receive the O-ring <NUM>. In an embodiment, the O-ring <NUM> cooperates with the integrated mounting member <NUM> to substantially seal the transmission assembly <NUM>.

In an embodiment, the rear end <NUM> includes a series of notches <NUM> that receive the outer protrusions <NUM> of the radial arms <NUM> of the stator mount <NUM>, thus rotationally affixing the stator mount assembly <NUM> to the transmission assembly <NUM>. Further, in an embodiment, once assembled inside the tool housing <NUM>, a rear surface of the radial partitioning wall (i.e., the radial member <NUM> and the arms <NUM>) rests against a radial wall <NUM> of the tool housing <NUM> to hold the ring gear mount <NUM> against the C-clip and thus axially secure the stator mount assembly <NUM> to the transmission assembly <NUM>. These features cooperate to constrain and affix the stator mount assembly <NUM> relative to the transmission assembly <NUM> and the tool housing <NUM> in axial, radial and rotational directions.

In an embodiment, an outer race of the cam carrier bearing <NUM> of the transmission assembly <NUM> is received and supported within the annular body <NUM> of the stator mount <NUM>. Accordingly, the cam carrier bearing <NUM> is piloted to and supported by the stator mount assembly <NUM>. In an embodiment, both the ring gear <NUM> and the cam carrier bearing <NUM> may be pre-assembled into the stator mount assembly <NUM> prior to assembly of the transmission assembly <NUM> and the moto <NUM> within the power tool <NUM>.

In an embodiment, integration of the ring gear <NUM> and the cam carrier bearing <NUM> into the stator mount assembly <NUM> provides a structure in which features required to structurally support the stator mount <NUM> are integrated radially outwardly of the ring gear <NUM> and the cam carrier bearing <NUM>, thus reducing the axial length of the power tool.

In an embodiment, a distance L4 between a front of the motor <NUM>, in this example defined by the forwardmost part of the windings (not shown) and/or the frontmost part of the positional sensor board <NUM>, to the rear of the cam carrier <NUM>, is smaller than or equal to approximately <NUM>, preferably smaller than or equal to approximately <NUM>. Thus, where the motor performance, diameter and length are the same as motor <NUM> described above, this arrangement allows the total length of the tool to be reduced by approximately an additional <NUM>, preferably to a total length smaller than or equal to approximately <NUM>, even more preferably smaller than or equal to approximately <NUM>.

<FIG> depicts a perspective view of an outer-rotor BLDC motor <NUM>, according to a fifth embodiment of the invention. <FIG> depicts a partially exploded view of the outer-rotor BLDC motor <NUM>, according to an embodiment. <FIG> depicts a partially cross-sectional view of the power tool <NUM> including the outer-rotor BLDC motor <NUM> and the transmission assembly <NUM>, according to an embodiment.

In an embodiment, power tool <NUM> includes many of the same features as the above-described power tools, including but not limited to, a power tool housing <NUM> including two clamshells that come together to house the motor <NUM>, and a nosecone <NUM> that houses an impact mechanism (not shown). Similarly, motor <NUM> includes many of the same features as the motor <NUM> described above. To the extent that these or other power tool components include identical or similar features as described above, the same reference numerals are used.

In this embodiment, like the previous embodiment, motor <NUM> includes a stator mount assembly <NUM> that integrally structurally supports the ring gear <NUM> and the stator mount <NUM>. Like the previous embodiment, the stator mount assembly <NUM> includes an integrated mounting member <NUM> that is coupled to the stator mount <NUM> on one side and includes a radial member <NUM> formed in contact with the stator mount <NUM>. Also, the stator mount assembly <NUM> includes a ring gear mount for supporting the ring gear <NUM>. The rotor assembly <NUM>, positional sensor board <NUM>, stator mount <NUM>, and ring gear <NUM>, among other features, remain substantially unchanged.

In this embodiment, however, the portion of the integrated mounting member <NUM> that forms the ring gear mount is elongated and forms a transmission housing <NUM> of the transmission assembly <NUM> that has a substantially cylindrical body and houses various transmission components such as the carrier, the transmission spring <NUM>, and the cam shaft <NUM>. Thus, unlike the previous embodiment, the housing of the transmission assembly <NUM> is not formed as a part of the nosecone <NUM>. Rather, the transmission housing <NUM> is integrally incorporated as a part of the stator mount assembly <NUM>. Integration of the transmission housing <NUM> into the stator mount assembly <NUM> reduces necessary components and provides a more robust and easier to manufacture design. Details of the integrated mounting member <NUM> are discussed below.

In an embodiment, the integrated mounting member <NUM> includes a molded structure formed around the stator mount <NUM> to radially, rotationally, and axially support the stator mount <NUM>. The integrated mounting member <NUM> includes many of the retention and support features described above, including the radial member <NUM> and openings <NUM>, details of which are not repeated here. The molded structure further includes inner rims <NUM> and <NUM> that engage axial ends of the ring gear <NUM> to form the ring gear mount within the transmission housing <NUM> adjacent the radial member <NUM>. The molded structure is formed in engagement with the outer tabs <NUM> of the ring gear <NUM> to rotationally, as well as axially and radially, support the ring gear <NUM>.

In an embodiment, the length of the transmission housing <NUM> is greater than a length of the motor <NUM>. In an embodiment, a front portion <NUM> of the transmission housing <NUM> extends beyond a front end of the tool housing <NUM> and a front end of the cam carrier <NUM>. The front portion <NUM> is at least partially received within the nosecone <NUM>. In an embodiment, an O-ring <NUM> is disposed between the front portion <NUM> of the transmission housing <NUM> and the nosecone <NUM> to substantially seal the transmission assembly <NUM>.

In an embodiment, the front portion <NUM> includes outer protrusions <NUM> having rounded outer edges. When fully assembled, the rounded edges of the outer protrusions <NUM> (similar to outer projections <NUM> described previously) engage the annular rims formed around threaded openings of the tool housing <NUM> to rotational lock the transmission assembly <NUM> relative to the tool housing <NUM>.

The above-described arrangement provides a structure whereby, like the previous embodiments, the stator assembly <NUM> is fully supported only on one side of the motor <NUM> by the transmission assembly <NUM>. However, unlike the previous embodiments, where the transmission assembly <NUM> is provided separately from the motor and as an integral part of the nosecone, in this embodiment, the transmission housing <NUM> is integrally incorporated into the integrated mounting member <NUM> and is therefore pre-assembled with the motor <NUM> prior to the full assembly into the power tool <NUM>. This arrangement provides a highly robust and reliable structure that is easy and efficient to manufacture.

Various aspects and embodiments of the rotor assembly <NUM> are described herein with reference to <FIG>.

<FIG> depicts an exploded perspective view of the rotor assembly <NUM>, according to an embodiment. <FIG> depicts a side cross-sectional view of the rotor assembly <NUM>, according to an embodiment. <FIG> depicts a partial perspective view of the rotor assembly <NUM>, according to an embodiment.

As shown in these figures, permanent magnets <NUM>, of which ten are provided in this example, are secured to the rotor core <NUM> via the overmold structure <NUM>. In an embodiment, the permanent magnets <NUM> are mounted to the inner surface of the rotor core <NUM> and secured via an injection-molding or over-molding process to form the overmold structure <NUM>. In an embodiment, the rotor core <NUM> includes a series of axially projecting teeth <NUM>. The overmold structure <NUM> is formed around the teeth <NUM> along with the rest of the rotor core <NUM>, ensuring that the rotor core <NUM> is rotationally fixed relative to the overmold structure <NUM>. The teeth <NUM> also allow the molding machine to secure the rotor core <NUM> during the molding process. As such, overmold structure <NUM>, when viewed in isolation, includes end slots <NUM> that contain the teeth <NUM> of the rotor core <NUM>, and inner magnet grooves <NUM> that capture the permanent magnets <NUM>. In an embodiment, permanent magnets <NUM> include chamfers that, when engaged by the overmold structure <NUM>, retain the permanent magnets <NUM> against the inner surface of the rotor core <NUM>.

<FIG> depict a perspective view of a rotor core <NUM>, according to an alternative and/or additional embodiment of the invention. <FIG> depicts a coil-shape continuous wire rod <NUM> used to form the rotor core <NUM>, according to an embodiment. <FIG> depicts an exploded view of the rotor assembly <NUM> utilizing the rotor core <NUM>, according to an embodiment.

In this embodiment, the rotor core <NUM>, which is the flux ring to which the magnets are mounted, is made of the coil-shaped continuous wire rod <NUM>. The wire rod <NUM> may be wound around a tubular body to form the coil-shaped pattern, then welded to form a solid flux ring body. Additionally, and/or alternatively, the wire rod <NUM> may be compressed and held together via the overmold structure <NUM>. The wire rod <NUM> is less expensive than a seamless tube.

<FIG> depicts a perspective view of the rotor assembly <NUM>, according to a further and/or alternative embodiment. In this embodiment, the rotor core is not formed separately from the overmold structure. Rather, the rotor assembly <NUM> includes a rotor core <NUM> formed using a metal injection molding (MIM) process. In this process, finely-powdered metal is mixed with a binding material and molded to the desired shape of the rotor core <NUM>. In an embodiment, the rotor core <NUM> is formed around the magnets <NUM> during the MIM process. The molded magnet core <NUM> increases the magnetic flux of the rotor assembly <NUM> similarly to a conventional rotor core made of a flux ring, but it is easier and less expensive to manufacture with a high dimensional accuracy.

<FIG> depicts a perspective view of a rotor core <NUM> for use in the rotor assembly <NUM>, according to a further and/or alternative embodiment. <FIG> depicts an explode view of the rotor core <NUM>, according to an embodiment.

In this embodiment, the rotor core <NUM> comprises a metal portion <NUM> and a molded portion <NUM>. The metal portion is made of stamped metal and includes a cylindrical body <NUM>, an inner cylindrical member <NUM> for securely receiving a rotor shaft (not shown), and a series of first radial arms <NUM> integrally attached and extending radially between the cylindrical body <NUM> and the inner cylindrical member <NUM>. The molded portion <NUM> is formed from resin or epoxy material via an insert-molding or injection-molding process around the metal portion <NUM>. The molded portion <NUM> includes a radial plate <NUM> having a first center opening and located along a first radial plane, and a series of second radial arms <NUM> that are attached to the radial plate <NUM> via a series of axial pins <NUM> and are formed along a second radial plane. When the molding process is completed, the radial plate <NUM> is located in contact with rear surfaces of the first radial arms <NUM>, and the second radial arms <NUM> are located in contact with front surfaces of the first radial arms <NUM>. In an embodiment, the first radial arms <NUM> may include a series of through-holes (not shown) through which the axial pins <NUM> extend between the radial plate <NUM> and the second radial arms <NUM>. It is noted, however, that the mold structure may wrap around the first radial arms <NUM> to connect the radial plate <NUM> to the second radial arms <NUM>. In an embodiment, the second radial arms <NUM> extend radially from a center ring <NUM> that is formed around the inner cylindrical member <NUM>. In an embodiment, the second radial arms <NUM> may be formed in the molding process in any desired fan blade contour designed to cooperate with the first radial arms <NUM> to optimize airflow generation.

<FIG> depicts a perspective exploded view of the stator assembly <NUM> and the positional sensor board <NUM>, according to an embodiment. <FIG> depicts a partial perspective view of the motor <NUM> including the positional sensor board <NUM>, according to an embodiment. In an embodiment, stator core <NUM> includes a center annular body <NUM> and a series of outwardly projecting teeth <NUM>. Stator windings (not shown) are wound around the stator teeth <NUM>. In an embodiment, a molded insulating body <NUM> formed around the stator core <NUM> to electrically insulate the stator teeth <NUM> from the windings. The insulating body <NUM> substantially covers both end surfaces of the stator core <NUM> and the inner surfaces of the stator teeth <NUM>. In an embodiment, the insulating body <NUM> further includes a series of first axial posts <NUM> that support the positional sensor board <NUM> at a set distance relative to the stator core <NUM>. In an embodiment, the insulating body <NUM> further includes a series of second axial posts <NUM> that support motor terminals <NUM>. In an embodiment, there are three second axial posts <NUM> are provided to support three motor terminals <NUM>. The three second axial posts <NUM> are aligned with three adjacent ones of the stator teeth <NUM>.

<FIG> depicts a zoomed-in view of one of the second axial posts <NUM> and a corresponding motor terminal <NUM>, according to an embodiment. In an embodiment, each terminal <NUM> includes a substantially planar body and a rear tab <NUM>. The insulating body <NUM> is molded to securely capture the rear tab <NUM> within the second axial post <NUM>.

In an embodiment, referring again to <FIG> and <FIG>, the positional sensor board <NUM> is substantially C-shaped with an outer diameter that is slightly greater than the outer diameter of the stator core <NUM> and an inner diameter than is greater than the diameter of the center annular body <NUM>. A series of positional sensors <NUM> are mounted on the positional sensor board <NUM> to sense a magnetic flux of the rotor. The positional sensor board <NUM> includes a series of openings <NUM> that receive the first axial posts <NUM> to secure the positional sensor board <NUM> to the insulating body <NUM>. Further, the ends of the positional sensor board <NUM> define a gap <NUM> that is aligned with the motor terminals <NUM>. In an embodiment, the gap <NUM> extends an angular distance of approximately <NUM> to <NUM> degrees. This structure allows motor terminals <NUM> to be received within the gap <NUM> and therefore be orientated radially in-line with the positional sensor board <NUM>.

Example embodiments have been provided so that this disclosure will be thorough, and to fully convey the scope to those who are skilled in the art.

Terms of degree such as "generally," "substantially," "approximately," and "about" may be used herein when describing the relative positions, sizes, dimensions, or values of various elements, components, regions, layers and/or sections. These terms mean that such relative positions, sizes, dimensions, or values are within the defined range or comparison (e.g., equal or close to equal) with sufficient precision as would be understood by one of ordinary skill in the art in the context of the various elements, components, regions, layers and/or sections being described.

Claim 1:
A power tool comprising:
a tool housing (<NUM>);
a brushless direct-current (BLDC) motor (<NUM>) disposed in the tool housing and including a stator (<NUM>) including a stator core having an aperture extending therethrough and a plurality of stator windings, a rotor (<NUM>) comprising a cylindrical rotor core (<NUM>) supporting at least one permanent magnet (<NUM>) around an outer surface of the stator core, and a rotor shaft (<NUM>) rotatably coupled to the rotor;
a stator mount assembly (<NUM>) comprising a stator mount (<NUM>) including an axial member (<NUM>) secured to the stator, and an integrated mounting member (<NUM>) including a radial member (<NUM>) secured to the stator mount,
characterized in that the power tool further comprises a ring gear mount (<NUM>) extending from the radial member away from the motor, and a ring gear (<NUM>) supported by the ring gear mount; and
a transmission (<NUM>) secured to the tool housing, the transmission including a transmission housing (<NUM>) having a generally cylindrical body, and a planetary gear set including a carrier and at least one planet gear rotatably mounted to the carrier, wherein the ring gear meshes with the at least one planet gear.