Patent Description:
Typical brushless direct current electric motors are electrically coupled to a printed circuit board, which includes field effect transistors (FETs) that power the electric motor. As the FETs power the electric motor, the FETs generate heat, which could increase the temperature of the printed circuit board or other components of the electric motor.

<CIT> relates to an electrical machine. There is disclosed an electric motor <NUM> comprising a stator <NUM> positioned between a first end shield <NUM> and a second end shield <NUM>. The electric motor <NUM> further comprises a printed circuit board <NUM> upon which electrical components <NUM> are mounted.

<CIT> relates to a control unit-integrated rotary electric machine (<NUM>). According to the abstract of this document, there is disclosed a rotary electric machine (<NUM>) and a control unit (<NUM>). Electronic components (33b) are installed in the controller (<NUM>) on a second surface (33d) of a circuit board device (<NUM>). A housing (<NUM>) receives the circuit board device (<NUM>). The controller (<NUM>) includes a sealing resin body (<NUM>) and a heat releasing plate (<NUM>). The sealing resin body (<NUM>) is placed in an interior of the housing (<NUM>) and seals the circuit board device (<NUM>). The heat releasing plate (<NUM>) is made of metal and placed in the Z direction on the side of the second surface (33d) of the circuit board device (<NUM>). The heat release plate (<NUM>) is thermally connected to at least one of the electronic components (33b) installed on the second surface (33d). The heat releasing plate (<NUM>) is firmly bonded to the sealing resin body (<NUM>) due to a bonding property of the sealing resin body (<NUM>).

<CIT> relates to a high power brushless motor. According to the abstract of this document, there is provided a power tool including a tool housing; at least one battery receptacle accommodated on the tool housing, the battery receptacle being adapted to receive a battery pack (<NUM>) having a maximum voltage of at least <NUM> volts; and a brushless DC (BLDC) motor (<NUM>) disposed within the tool housing, the motor including a stator assembly and a rotor assembly rotatably disposed within the stator assembly. A motor control and power module (<NUM>) is disposed in close proximity to the motor (<NUM>), including a power switch circuit electrically coupled to the motor and a first controller configured to control a switching operation of the power switch circuit for supply of power from the battery pack (<NUM>) to the motor. A battery management control module (<NUM>) is disposed in close proximity to the battery receptacle, including a second controller distinct from the first controller, the second controller configured to manage an operation of the battery pack (<NUM>).

<CIT> relates to an electronic control device. According to the abstract of this document, there is provided an electronic control device for controlling an electric actuator, including an air passage within a casing that is fixable to an actuator housing of the electric actuator. A circuit board is accommodated in the casing. A projecting portion is formed in the casing, on which a region of the circuit board in which the heat generating part is installed is seated. A vent hole extends through the casing to communicate to an outside of the casing. A communication hole extends through the casing to communicate to an inside of the actuator housing. The air passage allows air to flow between the vent hole and the communication hole when the electric actuator is driven in a state that the casing is fixed to the actuator housing.

<CIT> relates to an electrical machine and method of assembling the same. According to an abstract of this document, there is provided a housing for enclosing electronics of a motor having an axis of rotation. The housing includes an end cap having an outer surface and an inner surface. A control board is coupled to the inner surface, wherein the printed circuit board includes a first side, a second side and an edge located between the first side and the second side. The housing further includes a first circuit coupled to the first side which includes a plurality of first electrical components. Each first electrical component includes a tab extending beyond the edge. A second circuit is coupled to the second side and a fastener assembly is coupled to the tab and the inner surface.

In one aspect, there is provided a power tool includes a housing and an electric motor assembly supported in the housing. The electric motor assembly according to claim <NUM> includes a stator core and a circuit board proximate an end of the stator core. The circuit board includes a heat-generating component facing away from the stator core. The electric motor assembly also includes an end cap coupled to the stator core and in thermal contact with the heat-generating component as a heat sink to remove thermal energy from the heat-generating component.

In another aspect, there is provided an electric motor assembly includes a stator core and a circuit board proximate an end of the stator core. The circuit board includes a heat-generating component facing away from the stator core. The electric motor assembly also includes an end cap coupled to the stator core and in thermal contact with the heat-generating component as a heat sink to remove thermal energy from the heat-generating component.

The circuit board being positioned between the end cap and the end of the stator core. The end cap includes a protrusion extending from an inner surface of the end cap. The protrusion being in thermal contact with the heat-generating component.

The electric motor assembly further comprises a thermal pad positioned between the protrusion and the heat-generating component. The protrusion being in direct contact with the thermal pad. The thermal pad being in direct contact with the heat-generating component.

The end cap may include a radially extending aperture. The protrusion may be at least partially disposed in the radially extending aperture.

The end cap may include an end wall from which the protrusion extends, and a circumferential side wall at least partially defining the radially extending aperture.

The radially extending aperture may be a first radially extending aperture. The end cap may include a second radially extending aperture through which the circuit board extends.

The circuit board may include an electrical terminal disposed on a portion of the circuit board extending through the second radially extending aperture in the end cap. The electrical terminal is configured to provide power to the heat-generating component.

The end cap may include a plurality of cooling fins extending from the end wall in an opposite direction as the protrusion.

The cooling fins may be oriented in a radial direction relative to a central axis of the stator core.

The electric motor assembly may further include a fan that induces an airflow through the radially extending aperture to cool the protrusion and the heat-generating component.

The protrusion may be a first protrusion and the heat-generating component may be a first heat-generating component. The circuit board may include a second heat-generating component facing away from the stator core. The end cap may include a second protrusion extending from the inner surface of the end cap in thermal contact with the second heat-generating component.

The circuit board may include a third heat-generating component facing away from the stator core. The end cap may include a third protrusion extending from the inner surface of the end cap in thermal contact with the third heat-generating component.

The first, second, and third heat-generating components may be field effect transistors.

The electric motor assembly may further include a rotor disposed within the stator core. A first end of the rotor may be rotatably supported by the end cap.

The end cap may be a first end cap. The electric motor assembly may further include a second end cap coupled to an end of the stator core opposite the circuit board. A second end of the rotor may be rotatably supported by the second end cap.

It will be appreciated that, where appropriate, any of the optional features discussed above in relation to one aspect of the invention may be applied to another aspect of the invention.

<FIG> illustrates a power tool <NUM> (e.g., a router operable to cut into a workpiece) that includes a housing <NUM> and a brushless direct current (DC) electric motor assembly <NUM> supported in the housing <NUM>. The motor assembly <NUM> is electrically coupled to a rechargeable battery pack <NUM>, which is selectively coupled to the housing <NUM>. Using power from the battery pack <NUM>, a motor controller <NUM> (e.g., one or more microprocessors connected to one or more printed circuit boards) operates the motor assembly <NUM> to drive a drive mechanism <NUM> about a rotational axis <NUM> in response to an actuator <NUM> (e.g., a trigger button) of the power tool <NUM> being depressed. The illustrated drive mechanism <NUM> is a chuck that selectively couples a tool bit (e.g., a twist drill bit, a router bit, etc.) to the power tool <NUM> for the motor assembly <NUM> to drive the tool bit about the rotational axis <NUM>. In other embodiments, the power tool <NUM> can be a reciprocating saw, a rotary saw, a hammer drill, a grinder, a nailer, a sander, a shear, or the like with the particular power tool including an appropriate drive mechanism in order to carry out the specific function of the power tool. In addition, the illustrated battery pack <NUM> is a lithium-ion battery pack, but in other embodiments, the battery pack <NUM> can be a lead-acid, nickel-cadmium, nickel-metal hydride, etc. battery pack.

With reference to <FIG> and <FIG>, the illustrated motor assembly <NUM> includes a rotor <NUM> having magnets (not shown) fixed to an output shaft <NUM> that is coupled to the drive mechanism <NUM>, a stator core <NUM> having a central cavity <NUM> that receives the rotor <NUM> about the rotational axis <NUM>, a front end cap <NUM> coupled to a front end <NUM> of the stator core <NUM>, a rear end cap <NUM> coupled to a rear end <NUM> of the stator core <NUM>, and a printed circuit board <NUM> (PCB) positioned between the stator core <NUM> and the rear end cap <NUM>. A front portion of the output shaft <NUM> is rotatably supported by a first bearing <NUM>, which is seated within a front bearing housing <NUM> of the front end cap <NUM>. Likewise, a rear portion of the output shaft <NUM> is rotatably supported by a second bearing <NUM>, which is seated within a rear bearing housing <NUM> of the rear end cap <NUM>, so that the output shaft <NUM> is rotatably supported by the front and rear end caps <NUM>, <NUM> about the rotational axis <NUM>. In one embodiment, the second bearing <NUM> can be press fit into the rear bearing housing <NUM>. Once the motor assembly <NUM> is assembled, the front end cap <NUM> and the rear end cap <NUM> are fixed to the stator core <NUM> by fasteners <NUM> extending through mounting apertures <NUM> formed in a circumferential sidewall <NUM> of each of the front and rear end caps <NUM>, <NUM>. Specifically, by tightening the fasteners <NUM>, the front and rear end caps <NUM>, <NUM> apply a clamping force to the stator core <NUM>, thereby fixing the stator core <NUM> to the front and rear end caps <NUM>, <NUM>. In the illustrated embodiment, the mounting apertures <NUM> formed in the front end cap <NUM> are threaded to receive the threaded ends of the respective fasteners <NUM>, whereby the mounting apertures <NUM> in the rear end cap <NUM> are unthreaded.

With continued reference to <FIG> and <FIG>, the motor assembly <NUM> also includes a fan <NUM> fixed to the output shaft <NUM> and positioned between the front end <NUM> of the stator core <NUM> and the first bearing <NUM>. The illustrated fan <NUM> is at least partially received within the front end cap <NUM> and includes cooling blades <NUM> extending toward the stator core <NUM> that radially align with airflow apertures <NUM> formed through the circumferential sidewall <NUM> of the front end cap <NUM> (<FIG>).

As best shown in <FIG>, the rear end cap <NUM> includes an end wall <NUM> from which the circumferential sidewall <NUM> of the rear end cap <NUM> extends. The rear end cap <NUM> also includes protrusions <NUM> (<FIG>) extending from an inner surface <NUM> of the end wall <NUM> toward the PCB <NUM>. Each protrusion <NUM> is positioned adjacent a radially extending aperture <NUM> in the rear end cap <NUM>, with each radially extending aperture <NUM> at least partially defined by the circumferential sidewall <NUM> of the rear end cap <NUM>. In particular, each radially extending aperture <NUM> is defined by a portion of the circumferential sidewall <NUM> as well as a portion of the end wall <NUM> with at least a portion of each protrusion <NUM> being disposed in one radially extending aperture <NUM>. In the illustrated embodiment, the rear end cap <NUM> includes three protrusions <NUM> equally spaced <NUM> degrees about the rotational axis <NUM>. In other embodiments, the rear end cap <NUM> can include more or fewer than three protrusions <NUM> that are equally spaced or non-equally spaced about the rotational axis <NUM>.

With reference to <FIG>, the PCB <NUM>, which is electrically coupled to the controller <NUM>, includes a side <NUM> that interfaces with the rear end cap <NUM>. In particular, the side <NUM> includes mounting apertures <NUM>, each of which receives a post <NUM> extending from the end wall <NUM> of the rear end cap <NUM> (<FIG>) to attach the PCB <NUM> to the rear end cap <NUM>. With reference to <FIG>, the PCB <NUM> includes heat-generating components (e.g., metal-oxide semiconductor FETs <NUM> and current sense resistors <NUM>), a thermistor <NUM>, and other electrical components (e.g., capacitors, diodes, voltage sensors, etc.) extending from the side <NUM> of the PCB <NUM>. As such, the heat-generating components face away from the stator core <NUM> and toward the rear end cap <NUM>. In the illustrated embodiment, the PCB <NUM> includes three pairs <NUM> of FETs <NUM> spaced about the rotational axis <NUM> in the same manner as the protrusions <NUM> of the rear end cap <NUM> (i.e., equally spaced <NUM> degrees about the rotational axis <NUM>). As a result, the respective protrusions <NUM> are in thermal contact with the pairs <NUM> of FETs <NUM> when the PCB <NUM> is attached to the posts <NUM> as described above. In particular, each protrusion <NUM> includes an end surface <NUM> (<FIG>) that is in direct contact with one side of a thermal pad <NUM> (e.g., a highly thermal conductive member such as copper, aluminum, etc.) and another side of the thermal pad <NUM> is in direct contact with a pair <NUM> of FETs <NUM> (<FIG>) and additional heat-generating components on the PCB <NUM> (e.g., a current sense resistor <NUM>). In other embodiments, the thermal pads <NUM> can be omitted such that the heat sink protrusions <NUM> directly contact the FETs <NUM> and the current sense resistor(s) <NUM>. In further embodiments, the PCB <NUM> can include more or fewer than three pairs <NUM>, and/or a different number of FETs <NUM> (and current sense resistors <NUM>) can be associated with each pair <NUM>. In yet further embodiments, the heat sink protrusions <NUM> and/or the thermal pads <NUM> can directly contact heat-generating components of the PCB <NUM> other than the FETs <NUM> and the current sense resistors <NUM>. In addition, the PCB <NUM> includes a projection <NUM> that extends through one of the radially extending apertures <NUM> (<FIG>). Electrical terminals <NUM> are positioned on the PCB projection <NUM>, outside the rear end cap <NUM>, for connection with electrical wires (not shown) connected at their opposite ends to the battery pack <NUM>. In other embodiments, the PCB projection <NUM> can be omitted such that the electrical terminals <NUM> are positioned inside the rear end cap <NUM>.

In operation, the battery pack <NUM> provides DC power to the various electrical components of the PCB <NUM> by supplying an electrical current to the electrical terminals <NUM>. The controller <NUM> is configured to monitor the electrical current drawn by the motor assembly <NUM> using current sense resistors <NUM> on the PCB <NUM>. In addition, as the electrical current travels through the PCB <NUM>, the electrical current provides operating power to the FETs <NUM>. In particular, by selectively activating the FETs <NUM>, power from the battery pack <NUM> is selectively applied to the stator core <NUM> to cause rotation of the output shaft <NUM> about the rotational axis <NUM> to operate the drive mechanism <NUM>. As the electrical current passes through the FETs <NUM> and the current sense resistors <NUM>, the FETs <NUM> and the current sense resistors <NUM> generate heat (i.e., thermal energy), which if not dissipated, could otherwise decrease the performance of the motor assembly <NUM>. The rear end cap <NUM> functions as a heat sink for the PCB <NUM> to remove thermal energy from the FETs <NUM> and the current sense resistors <NUM>, and to direct the thermal energy away from the stator core <NUM> and the rotor <NUM>. In particular, the thermal energy generated by the FETs <NUM> and the current sense resistors <NUM> dissipates through the thermal pads <NUM>, the protrusions <NUM> and into the end wall <NUM>, ultimately to be dissipated by convection (at least partially) through cooling fins <NUM> extending from an outer surface <NUM> of the rear end cap <NUM>.

Moreover, as the battery pack <NUM> powers the motor assembly <NUM>, the fan <NUM> rotates about the rotational axis <NUM> to induce an airflow through the motor assembly <NUM>. In particular, as the output shaft <NUM> rotates, the airflow enters the motor assembly <NUM> through the radially extending apertures <NUM>, travels forwardly through the central cavity <NUM> between the stator core <NUM> and the rotor <NUM>, and exits the motor assembly <NUM> through the airflow apertures <NUM>. As the airflow moves through the radially extending apertures <NUM>, the airflow cools the heat sink protrusions <NUM>, the thermal pads <NUM>, the FETs <NUM>, and the current sense resistors <NUM> to also dissipate thermal energy away from the motor assembly <NUM>.

Claim 1:
An electric motor assembly (<NUM>) comprising:
a stator core (<NUM>);
a rotor (<NUM>) disposed within the stator core (<NUM>);
a circuit board (<NUM>) proximate an end of the stator core (<NUM>), the circuit board (<NUM>) including a heat-generating component (<NUM>, <NUM>) facing away from the stator core (<NUM>); and
an end cap (<NUM>) coupled to the stator core (<NUM>) and in thermal contact with the heat-generating component (<NUM>, <NUM>) as a heat sink to remove thermal energy from the heat-generating component (<NUM>, <NUM>), a first end of the rotor (<NUM>) being rotatably supported by the end cap (<NUM>);
wherein the circuit board (<NUM>) is positioned between the end cap (<NUM>) and the end of the stator core (<NUM>),
characterized in that
the end cap (<NUM>) includes a protrusion (<NUM>) extending from an inner surface (<NUM>) of the end wall (<NUM>) of the end cap (<NUM>) and toward the circuit board (<NUM>), and wherein the protrusion (<NUM>) is in thermal contact with the heat-generating component (<NUM>, <NUM>);
further comprising a thermal pad (<NUM>) positioned between the protrusion (<NUM>) and the heat-generating component (<NUM>, <NUM>), wherein the protrusion (<NUM>) is in direct contact with the thermal pad (<NUM>), and wherein the thermal pad (<NUM>) is in direct contact with the heat-generating component (<NUM>, <NUM>).