Patent Publication Number: US-2023147745-A1

Title: Motor controller for a tool

Description:
TECHNICAL FIELD OF THE INVENTION 
     The present invention relates generally to a motor controller for a power tool. 
     BACKGROUND OF THE INVENTION 
     Power tools, such as, for example, drills, screwdrivers, impact drivers, grinders, ratchet, cutters, polishers, etc., commonly include a motor powered by a rechargeable power source, such as a battery, for example. In these conventional tools, the motor is often a brushless DC electric motor (BLDC) controlled via commutation. BLDC motor commutation is typically implemented using a motor controller that includes a microcontroller or microprocessor device disposed on a printed circuit board (PCB). 
     Many different techniques of commutation of three-phase brushless direct current (BLDC) motors are currently used. Typically, commutation is controlled based on a position of a rotor of the motor. The position of the rotor is detected by position sensors, such as, for example, Hall-effect sensors. The microcontroller or microprocessor device then controls high and low side switches, such as, for example metal-oxide semiconductor field-effect transistors (MOSFETs), of respective phases of the motor in a particular sequence to control the motor according to a commutation scheme, such as, for example, a six-step commutation. For example, in a three-phase brushless DC motor, three position sensors are located 60 or 120 degrees apart and have six transition points (i.e., three sensors each actuating between high and low in response to the position of the rotor). 
     Conventional power tools use a single motor controller PCB that includes the microcontroller, switches, sensors, etc. Thus, these conventional motor controller PCBs are relatively large and require the tool housing to have sufficient room to enclose the motor controller PCB. These conventional power tools also include one or more heat sinks to dissipate heat from the motor controller PCBs, which further enlarges the space required to house these components and requires additional assembly. 
     SUMMARY OF THE INVENTION 
     The present invention relates broadly to a motor controller for a BLDC motor. The motor controller includes a control board and a power board. The power and control boards are coupled to a motor end cap and are thereby part of the motor. The power board is disposed on and coupled to an internal side or first side of the motor end cap. A thermal conductive pad is disposed between the power board and the motor end cap. The control board is disposed on and coupled to an external side or second opposing side of the motor end cap. The motor end cap is used as a heat sink to dissipate heat created by the power and control boards, thereby eliminating the need for a separate heat sink. The present invention results in less components and simpler manufacturing, compared to current designs, and is able to be used in more compact items, such as power tools. 
     In an embodiment, the present invention broadly comprises a power tool. The tool includes a motor disposed in the housing and adapted to receive power from a power source. The electric motor includes an end cap having opposing first and second surfaces, a power board coupled to the first surface and including opposing first and second sides, position sensors disposed on the first side, and switching elements disposed on the second side, and a control board coupled to the second surface and including a processor. 
     In another embodiment, the present invention broadly comprises a motor controller for a motor having an end cap. The motor controller including a power board adapted to couple with a first surface of the end cap and including opposing first and second sides and a control board adapted to couple to a second surface of the end cap and including a processor. The power board including position sensors disposed on the first side and switching elements disposed on the second side. 
     In another embodiment, the present invention broadly comprises a motor adapted to be powered by a power source. The motor including an end cap having opposing first and second surfaces, a power board coupled to the first surface and including opposing first and second sides, position sensors disposed on the first side, and switching elements disposed on the second side, and a control board coupled to the second surface and including a processor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For the purpose of facilitating an understanding of the subject matter sought to be protected, there are illustrated in the accompanying drawings embodiments thereof, from an inspection of which, when considered in connection with the following description, the subject matter sought to be protected, its construction and operation, and many of its advantages should be readily understood and appreciated. 
         FIG.  1    is a perspective view of an exemplar tool incorporating an embodiment of the present invention. 
         FIG.  2    is a cross-sectional view of the exemplar tool of  FIG.  1   . 
         FIG.  3    is a cross-sectional view of an exemplar motor of the tool of  FIG.  1   . 
         FIG.  4    is a perspective, exploded view of the motor of  FIG.  3   . 
         FIG.  5    is a side view of an exemplar power board of the motor of  FIG.  3   . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     While the present invention is susceptible of embodiments in many different forms, there is shown in the drawings, and will herein be described in detail, embodiments of the invention, including a preferred embodiment, with the understanding that the present disclosure is to be considered as an exemplification of the principles of the present invention and is not intended to limit the broad aspect of the invention to any one or more embodiments illustrated herein. As used herein, the term “present invention” is not intended to limit the scope of the claimed invention, but is instead used to discuss exemplary embodiments of the invention for explanatory purposes only. 
     The present invention relates broadly to a motor controller for a BLDC motor, such as that used with a power tool. The motor controller includes a control board and a power board. The power and control boards are coupled to a motor end cap. The power board is disposed on and coupled to an internal side or first side of the motor end cap. A thermal conductive pad is disposed between the power board and the motor end cap. The control board is disposed on and coupled to an external side or second opposing side of the motor end cap. The motor end cap is used as a heat sink to dissipate heat created during use of the motor and control boards, thereby eliminating the need for a separate heat sink. The present invention results in less components and simpler manufacturing, compared to current designs, and is able to be used in more compact power tools. 
     Referring to  FIGS.  1 - 5   , an exemplary tool  100  incorporating an embodiment of the present invention, such as, for example, a drill is depicted. However, it will be appreciated that the present invention is not limited as such and can be implemented in not only other power tools, such as, for example, impact wrenches, power screwdrivers, power ratchets, impact drivers, etc., but in other devices that include an electric motor (for example, a kitchen appliance). In an embodiment, the tool  100  includes a housing  102  assembled from first and second clamshell housing portions that are coupled together to cooperatively form the housing  102  in a well-known manner. The housing  102  includes a handle portion  104  that is adapted to be gripped by a user. The housing encloses a motor  106 , gear assembly  142 , and other additional components for operation of the tool  100 . The tool  100  includes an output drive  108  coupled or engaged with the gear assembly  142 , and the gear assembly  142  is adapted to receive and transfer torque from the motor  106  to the output drive  108 . The output drive  108  is adapted to couple with a suitable tool, such as a socket, tool bit, or the like, for interfacing with a fastener or the like, to which torque is to be applied, all in a known manner. 
     A trigger  110  for controlling operation of the motor  106  is disposed on the handle portion  104 . Depression of the trigger  110  causes power to be delivered to the motor  106 , and hence rotation of the motor  106  selectively in either one of first and second rotational output directions (e.g., clockwise and counterclockwise), thereby selectively driving the output drive  108  in either one of first and second directions via the gear assembly  142 . The trigger  110  can be biased such that a user can depress the trigger  110  inwardly, relative to the tool  100 , which is detected by a trigger switch  114 , using known methods, to cause the motor  106  to operate, and release the trigger  110 , where the biased nature of the trigger  110  causes the trigger  110  to bias outwardly, relative to the tool  100 , which is detected by the trigger switch  114 , to cease operation of the motor  106 . The trigger switch  114  is disposed in the handle portion  104 . 
     In an embodiment, the trigger  110  can be a position sensitive trigger or variable speed trigger that also operates the motor  106  at varying speeds. For example, the further the trigger  110  is depressed, the faster the motor  106  operates. The rotational output direction of the motor  106 , and, consequently, the output drive  108 , is selectively controlled by a direction selector  116  in a known manner. The direction selector  116  can be, for example, a lever or knob. 
     In an embodiment, the tool  100  is powered by a battery (not shown), which may be removably coupled at a battery interface  112  of the handle portion  104 . In an embodiment, the battery can be rechargeable. However, the present invention is not limited to battery powered tools and can be implemented in tools receiving power from other power sources, such as, for example, external power via a cord. 
     Referring to  FIGS.  3 - 5   , the motor  106  includes first  120  and second  122  end caps, a stator  124 , a rotor  126 , and a motor controller including power  128  and control  130  boards. The first  120  and second  122  end caps are adapted to be coupled to opposing ends of the stator  124 , thereby enclosing the rotor  126  and power board  128 . The first end cap  120  is disposed between the stator  124  and the gear assembly  142  and/or faces in a direction of the gear assembly  142  when the first end cap  120  is coupled to the stator  124 . The second end cap  122  includes first  132  (also referred to as an internal surface) and second  134  (also referred to as an external surface) surfaces, wherein the first surface  132  faces an interior of the motor  106 , and the second surface  134  is on an exterior of the motor  106 . In an embodiment, the second end cap  122  is composed of a metal material, such as, for example, one or more of aluminum, magnesium, and carbon steel. The second end cap  122  thus functions as a structural support for the stator  124  and the rotor  126  while also functioning as a heat sink to reduce the temperatures of the power  128  and control  130  boards. In an embodiment, the motor  106  is a brushless DC electric motor (BLDC) that is controlled via commutation. 
     The rotor  126  includes an output shaft  144  that extends through an opening  158  in the first end cap  120  and is adapted to engage the gear assembly  142 . In an embodiment, the opening  158  of the first end cap  120  includes a first bearing (not shown) that the output shaft  144  extends through to facilitate rotation of the output shaft  144  with respect to the first end cap  120 . In an embodiment, the second end cap  122  includes an opening  150  having a second bearing  156  that receives a rear portion  148  of the rotor  126  to facilitate rotation of the rotor  126  with respect to the second end cap  122 . 
     The gear assembly  142  receives torque from the output shaft  144  and transfers torque from the output shaft  144  to the output drive  108 . The rotor  126  can also include rotor vanes or fins  146  that act as a heat exchanger and/or facilitate air flow through the motor  106  for cooling the motor  106 . As illustrated, the rotor vanes or fins  146  are enclosed by the first end cap  120  when the first end cap  120  is coupled to the stator  124 . 
     In an embodiment, the power board  128  is coupled to the first surface  132  (also referred to as an internal surface) of the second end cap  122  using, for example, fasteners, adhesives, etc., thereby being disposed inside the motor  106 . The power board  128  may be a printed circuit board (PCB), and be electrically coupled to the stator  124 . In an embodiment, the power board may also have a cross-sectional shape that corresponds with a motor shape, such as for example, circular, square, rectangular, etc. 
     The power board  128  includes first and second opposing sides. The first side of the power board  128  faces in a direction towards the stator  124  (away from the first surface  132 ), and the second side faces in a direction towards the first surface  132  of second end cap  122 . The first side of the power board  128  includes one or more position sensors  138 , such as, for example, Hall-effect sensors, that detect a rotational position of a permanent magnet of the rotor  126  relative to the stator  124 . In an embodiment, the motor  106  is a three-phase BLDC motor, and the power board  128  includes three position sensors  138 . The second side of the power board  128  includes one or more switching elements  136  that are adapted to selectively provide power from the power source (e.g., a battery) to the stator  124 . The switching elements  136  include a high-side and low-side switching element. In an embodiment, the switching elements are metal-oxide semiconductor field-effect transistors (MOSFETs). In an embodiment, the motor  106  is a three-phase BLDC motor, and the power board  128  includes six switching elements  136  (e.g., a high and low side switching element for each phase). In an embodiment, the power board  128  includes an opening  152  adapted to allow the rear portion  148  of the rotor  126  to extend therethrough. 
     The control board  130  is coupled to the second surface  134  (also referred to as an external surface) of the second end cap  122  using, for example, fasteners, adhesives, etc. The control board  130  may be a printed circuit board (PCB), and be electrically coupled to one or more of the power source and the power board  128 . In an embodiment, the control board  130  includes an opening  154  adapted to allow the rear portion  148  of the rotor  126  to extend therethrough. In an embodiment, the control board  130  includes a processor, such as, for example, a microcontroller or microprocessor device, for processing data and computer-readable instructions, and a memory for storing data and instructions. The memory may include volatile random access memory (RAM), non-volatile read only memory (ROM), and/or other types of memory. A data storage component may also be included, for storing data and controller/processor-executable instructions (for example, instructions for the operation and functioning of the tool  100 ). The data storage component may include one-or-more types of non-volatile solid-state storage, such as flash memory, read-only memory (ROM), magnetoresistive RAM (MRAM), ferroelectric RAM (FRAM), phase-change memory, etc. 
     Computer instructions for operating the tool  100  and its various components may be executed by the control board  130 , using the memory as temporary “working” storage at runtime. The computer instructions may be stored in a non-transitory manner in non-volatile memory, storage, or an external device. Alternatively, some of the executable instructions may be embedded in hardware or firmware in addition to or instead of in software. 
     In operation, a position of the rotor  126  relative to the stator  124  can be determined using signals received from position sensors  138  using known methods. The switching elements  136  are selectively actuated to supply power from the power source (e.g., a battery) to the stator  124  to achieve a desired commutation based on a position of the rotor  126  relative to the stator  124 . By selectively actuating the switching elements  136 , the motor  106  is operated by sending a current signal through coils located on the stator  124 . The coils cause a magnetic force to be applied to the rotor  126 , which rotates the rotor  126  when current runs through the coils. The rotor  126  contains permanent magnets that interact with the magnetic forces created by windings of the stator  124 . By activating successive combinations of high-side and low-side switching elements in a particular order based on the position of the rotor  126 , thereby sending a particular order of current signals through the windings of the stator  124 , the stator  124  creates a rotating magnetic field that interacts with the rotor  126  causing it to rotate and generate torque. The torque can then be applied to the gear assembly  142  and output drive  108 . 
     A thermal interface material  140 , such as, for example, a thermally conductive pad or thermal paste, may also disposed between the power board  128  and the first surface  132  (internal surface) of the second end cap  122 . The thermal interface material  140  is adapted to assist in transferring heat away from the power board  128  and into the second endcap  122 , which functions as a heatsink to dissipate heat created during use of the power  128  and control  130   boards. In an embodiment, the thermal interface material  140  includes an opening  160  adapted to allow the rear portion  148  of the rotor  126  to extend therethrough. 
     As used herein, the term “coupled” can mean any physical, electrical, magnetic, or other connection, either direct or indirect, between two parties. The term “coupled” is not limited to a fixed direct coupling between two entities. 
     The matter set forth in the foregoing description and accompanying drawings is offered by way of illustration only and not as a limitation. While particular embodiments have been shown and described, it will be apparent to those skilled in the art that changes and modifications may be made without departing from the broader aspects of the inventors’ contribution. The actual scope of the protection sought is intended to be defined in the following claims when viewed in their proper perspective based on the prior art.