Power tool

Abstract

A power tool includes an electric motor having a first stator winding, a second stator winding, a third stator winding, a first phase, a second phase, and a third phase; and a plurality of switches for selectively coupling the first stator winding, the second stator winding, and the third stator winding in a first configuration or a second configuration, where the plurality of switches includes: a first switch between the second stator winding and the first stator winding; a second switch between the first phase and the first stator winding; a third switch between the second stator winding and the second phase; a fourth switch between the third phase and the third stator winding; and the fifth switch is arranged between the third phase winding and the first phase winding.

Description

[0001] This application is a divisional application of a Chinese utility model patent application filed by the same applicant, with the application number 202290000362.9, the filing date of March 25, 2022, and the title "Power Tool Including Configurable Motor Stator Windings".

[0002] Cross - reference to related applications

[0003] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 166,452, filed on March 26, 2021, the entire content of which is hereby incorporated by reference. Technical field

[0004] The embodiments described herein provide a power tool including a configurable motor stator winding. Background art

[0005] The switching electronic device for converting between a delta configuration and a Y - configuration is likely to fail, causing the motor to fail to start or operate properly. The present utility model configures the controller to detect the failure. If the conversion between the delta configuration and the Y - configuration fails, the motor can be placed in a "limp mode", which holds the motor in a single configuration. Summary of the utility model

[0006] The power tool described herein includes: an electric motor having a rotor and a stator, the stator including a plurality of phase windings; a plurality of switches for selectively setting the configuration of the plurality of phase windings; and a controller connected to the plurality of switches, the controller being configured to: detect a failure to change the plurality of phase windings between configurations, and in response to the failure, lock the plurality of phase windings in a first configuration.

[0007] In some aspects, the controller is configured to detect the failure to change the plurality of phase windings between a delta configuration and a Y - configuration.

[0008] In some aspects, the controller is configured to detect the failure to change the plurality of phase windings between a series configuration and a parallel configuration.

[0009] In some aspects, the plurality of switches include at least eight switches.

[0010] In some aspects, the controller is configured to detect the failure to change the plurality of phase windings between configurations based on whether the gate driver power rail voltage is above a threshold voltage.

[0011] In some aspects, the controller is configured to detect the failure to change the plurality of phase windings between configurations based on the torque of the motor.

[0012] In some aspects, the controller is configured to detect the fault and change the plurality of phase windings between configurations based on the current of the motor.

[0013] In some aspects, the controller is further configured to: test for the fault during startup of the power tool to change the plurality of phase windings between configurations.

[0014] In some aspects, the power tool further includes: a Hall effect sensor configured to sense the position of the rotor, and wherein the controller is configured to detect the fault and change the plurality of phase windings between configurations based on the rotational position of the rotor indicated by the Hall effect sensor.

[0015] In some aspects, the controller is configured to detect the fault and change the plurality of phase windings between configurations based on an increase in transient current spikes.

[0016] In some aspects, the controller is further configured to: monitor the condition of the electric motor; and based on the condition, unlock the plurality of phase windings by controlling the plurality of switches to convert the configuration of the phase windings from the first configuration to a second configuration.

[0017] The power tool described herein includes: an electric motor having a stator including a plurality of stator poles, each stator pole having a plurality of phase windings; a plurality of switches for selectively setting the configuration of the plurality of phase windings to one of a first configuration and a second configuration; and a controller connected to the plurality of switches, the controller being configured to: detect a fault to change the plurality of phase windings from the first configuration to the second configuration, and in response to the fault, lock the plurality of phase windings in the first configuration.

[0018] In some aspects, the first configuration is a delta configuration and the second configuration is a Y configuration.

[0019] In some aspects, the first configuration is a series configuration and the second configuration is a parallel configuration.

[0020] In some aspects, the controller is configured to detect the fault and change the plurality of phase windings from the first configuration to the second configuration based on whether the gate driver power rail voltage is above a threshold voltage.

[0021] In some aspects, the controller is configured to detect the fault and change the plurality of phase windings from the first configuration to the second configuration based on the torque of the motor.

[0022] In some aspects, the controller is configured to detect the fault and change the plurality of phase windings from the first configuration to the second configuration based on the current of the motor.

[0023] In some aspects, the controller is further configured to test the fault during startup of the power tool to change the plurality of phase windings from the first configuration to the second configuration.

[0024] In some aspects, the power tool further includes a Hall effect sensor configured to sense the position of the rotor, and wherein the controller is configured to detect the fault and change the plurality of phase windings from the first configuration to the second configuration based on the rotational position of the rotor indicated by the Hall effect sensor.

[0025] In some aspects, the controller is further configured to monitor the condition of the electric motor and, based on the condition, unlock the plurality of phase windings by controlling the plurality of switches to convert the configuration of the phase windings from the first configuration to the second configuration.

[0026] Before explaining any embodiments in detail, it should be understood that the embodiments are not limited in their application to the configuration details and component arrangements set forth in the following description or shown in the drawings. The embodiments can be practiced or implemented in various ways. Further, it is to be understood that the language and terminology used herein are for the purpose of description and should not be regarded as limiting. The use of "including", "comprising", or "having" and their variants is intended to cover the items listed thereafter and their equivalents, as well as additional items. Unless otherwise stated or limited, the terms "mounted", "connected", "supported", and "coupled", and their variants are used broadly and cover both direct and indirect mounting, connection, support, and coupling.

[0027] In addition, it should be understood that embodiments can include hardware, software, and electronic components or modules, and for purposes of discussion, these components or modules may be shown and described as if most components were implemented only in hardware. However, one of ordinary skill in the art will recognize that, in at least one embodiment, the electronic aspects can be implemented in software (e.g., stored on a non-transitory computer-readable medium) executable by one or more processing units such as a microprocessor and / or an application specific integrated circuit ("ASIC"). Thus, it should be noted that embodiments can be implemented using multiple hardware- and software-based devices and multiple different structural components. For example, "servers", "computing devices", "controllers", "processors", etc. described in the specification can include one or more processing units, one or more computer-readable medium modules, one or more input / output interfaces, and different connectors connecting the components (e.g., a system bus).

[0028] Relative terms used in connection with a quantity or condition, such as "about", "approximately", "substantially", etc., will be understood by one of ordinary skill in the art to include the recited value and to have the meaning ascribed by the context (e.g., the term includes at least the degree of error associated with the measurement accuracy, tolerances associated with a particular value [e.g., manufacturing, assembly, use, etc.], etc.). Such terms should also be considered to disclose a range defined by the absolute values of the two endpoints. For example, the expression "about 2 to about 4" also discloses the range "2 to 4". Relative terms can refer to plus or minus a percentage of the indicated value (e.g., 1%, 5%, 10%, or more).

[0029] It should be understood that although some of the figures show hardware and software located within a particular device, these depictions are for illustrative purposes only. The functions described herein as being performed by one component can be performed by multiple components in a distributed manner. Similarly, the functions performed by multiple components can be combined and performed by a single component. In some embodiments, the components shown can be combined or divided into separate software, firmware, and / or hardware. For example, the logic and processing can be distributed among multiple electronic processors rather than being located within and performed by a single electronic processor. Regardless of how the hardware and software components are combined or divided, the hardware and software components can be located on the same computing device or can be distributed among different computing devices connected by one or more networks or other suitable communication links. Similarly, a component described as performing a particular function can also perform additional functions not described herein. For example, a device or structure "configured" in a certain way is at least configured in that way, but can also be configured in ways not explicitly listed.

[0030] Other aspects of these embodiments will become apparent by considering the detailed description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Shows a power tool according to an embodiment described herein.

[0032] Figure 2 Shows a block diagram of a controller for a Figure 1 power tool according to an embodiment described herein.

[0033] Figure 3A , Figure 3B and Figure 3C shows the independent rotor and internal bearings of a brushless DC motor included in a Figure 1 power tool.

[0034] Figure 3D shows the outer stator of a brushless DC motor included in a Figure 1 power tool.

[0035] Figure 4 Shows a motor stator including a plurality of field windings.

[0036] Figure 5A Shows a motor stator delta connection configuration.

[0037] Figure 5B Shows a motor stator Y connection configuration.

[0038] Figure 6 Shows the torque-speed curves of motors in Y connection configuration and delta connection configuration.

[0039] Figure 7 Shows the torque-current curves of motors in Y connection configuration and delta connection configuration.

[0040] Figure 8 Shows a circuit for configuring a motor into a Y configuration or a delta configuration.

[0041] Figure 9A Shows a technique for configuring a motor into a delta configuration.

[0042] Figure 9B Shows a technique for configuring a motor into a Y configuration.

[0043] Figure 10A Is a process for changing the motor configuration according to an embodiment described herein.

[0044] Figure 10B Is a process for changing the motor configuration according to an embodiment described herein.

[0045] Figure 10C Is a process for changing the motor configuration according to an embodiment described herein.

[0046] Figure 11 Shows a circuit for configuring a motor in a Y configuration or a delta configuration.

[0047] Figure 12A Shows a technique for configuring a motor in a delta configuration.

[0048] Figure 12B Shows a technique for configuring a motor in a Y configuration.

[0049] Figure 13A Is a process for changing the motor configuration according to the embodiments described herein.

[0050] Figure 13B Is a process for changing the motor configuration according to the embodiments described herein.

[0051] Figure 13C Is a process for changing the motor configuration according to the embodiments described herein.

[0052] Figure 14A Shows the torque-speed curve of a delta-Y motor configuration.

[0053] Figure 14B Shows the torque-speed curve of a delta-Y motor configuration.

[0054] Figure 14C Shows the torque-speed curve of a delta-Y motor configuration.

[0055] Figure 15 Shows the delta-Y motor configuration and the torque-speed curve for switching between the delta configuration and the Y configuration.

[0056] Figure 16 Shows the delta-Y motor configuration and the torque-speed curve for switching between the delta configuration and the Y configuration.

[0057] Figure 17 Shows the torque-power curve of a delta-Y motor configuration.

[0058] Figure 18A Shows the motor stator poles in a parallel configuration.

[0059] Figure 18B Shows the motor stator poles in a series configuration.

[0060] Figure 19 Shows a circuit for switching the motor stator poles between a series configuration and a parallel configuration.

[0061] Figure 20 Shows the torque-speed curves of the stator windings in a parallel connection configuration and a series connection configuration.

[0062] Figure 21 Shows the torque-current curves of the stator windings in parallel connection configuration and series connection configuration.

[0063] Figure 22A Is a process for changing the motor configuration according to the embodiments described herein.

[0064] Figure 22B Is a process for changing the motor configuration according to the embodiments described herein.

[0065] Figure 22C Is a process for changing the motor configuration according to the embodiments described herein.

[0066] Figure 23 Shows a switching circuit for configuring a motor according to the embodiments described herein.

[0067] Figure 24 Shows a bootstrap charge pump circuit and a gate driver for driving the Figure 23 switching circuit.

[0068] Figure 25 Shows an outer rotor electric motor according to the embodiments described herein.

[0069] Figure 26 Shows an Figure 25 outer rotor electric motor according to the embodiments described herein in a cross-sectional view. Detailed Description

[0070] Figure 1 Shows an example power tool 100 according to some embodiments. The power tool 100 includes a housing 105, a battery pack interface 110, a driver 115 (e.g., a chuck or a drill holder), a motor housing 120, a trigger 125, and a handle 130. The motor housing 120 houses a motor 275 (see Figure 2 ). A longitudinal axis 135 extends from the driver 115 through the rear of the motor housing 120. In operation, the driver 115 rotates about the longitudinal axis 135. The longitudinal axis 135 can be substantially perpendicular to the handle 130. Although Figure 1Illustrated is a particular power tool 100 with a rotational output, but it will be envisioned that the motor configuration control described herein can be used with a variety of types of power tools, such as drills, drivers, electric screwdrivers, electric ratchets, grinders, right-angle drills, rotary hammers, pipe threading machines, reciprocating saws, chain saws, crimping machines, pole saws, circular saws, cut-off saws, die grinders, table saws, vacuum cleaners, routers, augers, tillers, string trimmers, all-terrain vehicles, lawn mowers, material handling carts, nibblers, cable pullers / feeders, hydraulic pumps, PEX expanders, electric belt cranes, dust collectors, two-stage hydraulic tools, or another type of tool.

[0071] Shown in Figure 2 is a controller 200 for the power tool 100. The controller 200 is electrically and / or communicatively coupled to various modules or components of the power tool 100. For example, the illustrated controller 200 is coupled to an indicator or user interface 245, one or more sensors 250 (e.g., speed sensors, voltage sensors, temperature sensors, accelerometers, proximity sensors, Hall effect sensors, force or grip pressure sensors, etc.), a trigger 125 (connected via a trigger switch 255), a power switch network 260, and a power input unit 265. In some embodiments, the power tool 100 alternatively or additionally includes a heat accumulator, and the controller 200 can use the heat accumulator to determine (e.g., calculate, estimate, etc.) the temperature of the motor 275. In some embodiments, the heat accumulator can be used to determine (e.g., calculate, estimate, etc.) the temperature of other components of the power tool 100, such as terminals, bulk capacitors, and any other heat-sensitive components of the power tool 100.

[0072] The controller 200 includes a plurality of electrical and electronic components that provide power, operation control, and protection to components and modules within the controller 200 and / or the power tool 100. For example, the controller 200 includes, among other things, a processing unit 205 (e.g., a microprocessor, an electronic processor, an electronic controller, a microcontroller, or another suitable programmable device), a memory 225, an input unit 230, and an output unit 235. The processing unit 205 includes, among other things, a control unit 210, an arithmetic logic unit ("ALU") 215, and a plurality of registers 220 (in Figure 2shown as a set of registers), and implemented using known computer architectures (e.g., a modified Harvard architecture, von Neumann architecture, etc.). The processing unit 205, the memory 225, the input unit 230, and the output unit 235, as well as various modules connected to the controller 200, are connected via one or more control and / or data buses (e.g., the common bus 240). For illustrative purposes, the control and / or data bus is generally shown in Figure 2 It is known to those skilled in the art to use one or more control and / or data buses for the interconnection and communication between various modules and components in view of the embodiments described herein.

[0073] The memory 225 is a non-transitory computer-readable medium and includes, for example, a program storage area and a data storage area. The program storage area and the data storage area can include a combination of different types of memories, such as ROM, RAM (e.g., DRAM, SDRAM, etc.), EEPROM, flash memory, hard disk, SD card, or other suitable magnetic memory devices, optical memory devices, physical memory devices, or electronic memory devices. The processing unit 205 is connected to the memory 225 and executes software instructions that can be stored in the RAM of the memory 225 (e.g., during execution), the ROM of the memory 225 (e.g., on a generally permanent basis), or another non-transitory computer-readable medium such as another memory or disk. The software included in the implementation of the power tool 100 can be stored in the memory 225 of the controller 200. The software includes, for example, firmware, one or more application programs, program data, filters, rules, one or more program modules, and other executable instructions. The controller 200 is configured to obtain and in particular execute instructions related to the control processes and methods described herein from the memory 225. In other embodiments, the controller 200 includes additional, fewer, or different components.

[0074] Controller 200 drives motor 275 to rotate driver 115 in response to actuation of trigger 125 by a user. Driver 115 may be coupled to motor 275 via an output shaft. Pressing trigger 125 actuates trigger switch 255, which outputs a signal to controller 200 to drive motor 275 and thus drive driver 115. In some embodiments, controller 200 controls power switch network 260 (e.g., FET switch bridge) to drive motor 275. For example, power switch network 260 may include a plurality of high-side switch elements (e.g., FETs) and a plurality of low-side switch elements. Controller 200 may control each FET of the plurality of high-side switch elements and the plurality of low-side switch elements to drive each phase of motor 275. When trigger 125 is released, controller 200 may apply a braking force to motor 275. For example, power switch network 260 may be controlled to decelerate motor 275 more quickly. In some embodiments, phase advance and field weakening techniques are implemented to control the conduction angle for driving motor 275 (e.g., based on motor speed). In some embodiments, the no-load speed of motor 275 is limited to a predetermined maximum value. In some embodiments, power tool 100 does not include a transmission gearbox. Instead, the output of power tool 100 is directly driven by the motor (e.g., single-speed power tool).

[0075] Indicator 245 is also connected to controller 200 and receives control signals from controller 200 to turn on and off or otherwise convey information based on different states of power tool 100. Indicator 245 includes, for example, one or more light-emitting diodes (LEDs), a display screen, etc. Indicator 245 may be configured to display the condition of power tool 100 or information associated with the power tool. For example, indicator 245 may display information related to the charge state of battery pack 150 (such as charge capacity or state of charge). Indicator 245 may also display information related to a fault condition or other abnormality of power tool 100. As a supplement or alternative to visual indicators, indicator 245 may also include a speaker or a tactile feedback mechanism to convey information to the user via auditory or tactile output. In some embodiments, indicator 245 displays information related to the configuration of motor 275. For example, one or more LEDs are activated based on the delta configuration or wye configuration of motor 275.

[0076] The battery pack interface 110 is connected to the controller 200 and is configured to couple with the battery pack 150. The battery pack interface 110 includes a combination of mechanical components (e.g., a battery pack receiving portion) and electrical components that are configured and operable to engage the power tool 100 with the battery pack 150 (e.g., mechanically, electrically, and communicatively connect). The battery pack interface 110 is coupled to the power input unit 265. The battery pack interface 110 transfers power received from the battery pack 150 to the power input unit 265. The power input unit 265 includes active and / or passive components (e.g., a buck controller, a voltage converter, a rectifier, a filter, etc.) to condition or control the power received through the battery pack interface 110 and provided to the controller 200. In some embodiments, the battery pack interface 110 is also coupled to the power switch network 260. The operation of the power switch network 260 controlled by the controller 200 determines how power is supplied to the motor 275.

[0077] Figures 3A to 3C The motor 275 or various parts thereof are shown. The motor 275 is a brushless direct current (“BLDC”) motor. As Figures 3A to 3C shown, the motor 275 includes features that enable a reduction in the axial length, which allows for a smaller tool housing and / or additional space for other components within the tool housing. The motor 275 includes a rotor 300, a front bearing 305, a rear bearing 310 (collectively referred to as bearings 305, 310), a position sensor board assembly 315 within the stator housing of the motor 275, and a shaft 330. The stator housing is the space between the ends of the stator coil 320 along the length of the rotor axis 325. Recessing the rotor 300, bearings 305, 310, and the position sensor board assembly 315 within the stator housing allows for a more compact motor 275 in the axial direction. In this document, the axial direction refers to the direction extending along the length of the shaft 330 of the motor 275 (i.e., along the central axis), while the radial direction refers to the direction extending radially from the length of the shaft 330 (i.e., the central axis). The rotor 300 is shown as being entirely within the stator housing. In some embodiments, the bearings 305, 310, and the position sensor board assembly 315 are also entirely within the stator housing. In some embodiments, the position sensor board assembly 315 is entirely within the stator housing, but one or both of the bearings 305, 310 are partially within the stator housing and partially outside the stator housing. In some embodiments, the bearings 305, 310 are entirely within the stator housing, but the position sensor board assembly 315 is partially within the stator housing and partially outside the stator housing. In some embodiments, the position sensor board assembly 315 and one bearing (e.g., the front bearing 305 or the rear bearing 310) are entirely within the stator housing, while the other bearing (e.g., the other of the front bearing 305 or the rear bearing 310) is partially within the stator housing and partially outside the stator housing.

[0078] The position sensor board assembly 315 includes a Hall effect sensor (or other position sensor) to detect one or more of the rotational position, speed, and acceleration of the motor 275. In some embodiments, sensorless motor control is employed and a Hall effect sensor is not required. The position sensor board assembly 315 is electrically coupled to a control PCB within the power tool 100 having the controller 200. The position sensor board assembly 315 includes a through hole that receives the motor shaft / spindle 330 and one motor bearing (e.g., the front bearing 305). By recessing the position sensor board assembly 315 within the stator housing, the rotor magnet 335 is closer to the Hall sensor, which improves the detection of the rotor position without axially extending the rotor magnet 335 and / or the rotor 300.

[0079] The motor 275 includes a rotor 300 having a rotor magnet 335 (e.g., a permanent magnet) and an outer stator 340 having coil windings that are selectively energized to drive the rotor 300. Refer Figure 3D , the outer stator 340 includes a stator frame 345 having a first stator end cap 350 located on the front side of the stator 340 and a second stator end cap 355 located on the rear side of the stator 340. The first stator end cap 350 and the second stator end cap 355 may be integrally formed as a single piece (i.e., the stator frame 345), or alternatively, may be two separate pieces that together form the stator frame 345. The stator frame 345 may be formed by an injection molding process, e.g., by injecting a resin material into a mold that includes a stator lamination stack. Thus, the stator frame 345 may be a monolithic structure formed of hardened resin. The stator 340 includes a plurality of stator laminations. The stator laminations and the stator frame 345 include teeth 360 around which the coils are wound. At the inner radial end of the stator 340, there is a gap 365 between each stator tooth 360.

[0080] Figure 4 A motor stator 340 including a plurality of stator poles is shown. These stator poles are typically identified with markings of U, V, and W or alternatively A, B, and C for the stator phases. Each phase of the stator 340 includes two phase windings. Specifically, phase U includes a first phase winding 400 and a second phase winding 405. Phase V includes a first phase winding 410 and a second phase winding 415. Phase W includes a first phase winding 420 and a second phase winding 425. Although the stator 340 is Figure 4is shown as including three phases, each phase including two phase windings, but in some embodiments, stator 340 includes more than three phases or less than three phases. For example, stator 340 may include a single phase, two phases, four phases, five phases, six to ten phases, or more than ten phases (e.g., ten to twenty phases). Additionally, in some embodiments, each phase includes more than two phase windings. For example, each phase may include three, four, five, six, seven, eight, nine, ten, or more than ten (e.g., ten to twenty) phase windings. In embodiments where the motor stator 340 includes two stator poles, and each phase of stator 340 may include one phase winding.

[0081] The phase windings of stator 340 may be connected in various motor configurations. Figure 5A and Figure 5B Shows two possible motor configurations of stator 340. Figure 5A Shows the delta configuration 500 of stator 340. In the delta configuration, phase windings 400, 405 are connected to each of phase windings 410, 415 and phase windings 420, 425. Phase windings 410, 415 are connected to each of phase windings 400, 405 and phase windings 420, 425. Phase windings 420, 425 are connected to each of phase windings 400, 405 and phase windings 410, 415. Figure 5A Shows the Y - configuration 505 of stator 340. In the Y - connection, phase windings 400, 405, phase windings 410, 415, and phase windings 420, 425 are all connected to a common point 510. The advantages of the delta connection and the Y - connection, as well as the techniques for transitioning from one configuration to the other, will be described in more detail below. Depending on the desired output characteristics of the power tool 100, the motor 275 may initially operate in a delta configuration or a Y - configuration.

[0082] Figure 6 Shows a chart 600 of the torque - speed curves of a motor in delta configuration and a motor in Y - configuration. Compared to the motor in Y - configuration, the torque - speed curve 605 of the motor in delta configuration shows higher output speed values (in revolutions per minute ("RPM")) in low - torque or no - torque situations. However, compared to the motor in Y - configuration, the motor in delta configuration produces less output torque at low speeds. Conversely, compared to the motor in delta configuration, the torque - speed curve 610 of the motor in Y - configuration shows lower output speeds (in RPM) in low - torque or no - torque situations. However, compared to the motor in delta configuration, the motor in Y - configuration produces greater torque at low speeds.

[0083] Figure 7Chart 700 shows the torque-current curves of a motor in delta configuration and a motor in wye configuration. The torque-current curve 705 of the motor in delta configuration indicates that the motor in delta configuration generally draws higher current compared to the torque-current curve 710 of the motor in wye configuration. When the motor stalls, this difference in source current is the result of the motor resistance increasing by approximately three times (3x) in the wye configuration compared to the delta configuration. Despite the 3x change in motor resistance, when switching from the delta configuration to the wye configuration, the overall system resistance only increases by approximately 33%. Additionally, the motor in wye configuration has a larger back electromotive force (BEMF) and RPM compared to the motor in delta configuration, thus reducing the current.

[0084] Since the motors in delta configuration and wye configuration have different operating properties or characteristics, it would be advantageous to be able to switch between the motor in delta configuration and the motor in wye configuration to take advantage of the benefits of each motor configuration. Specifically, it would be advantageous to be able to utilize the increased speed of the delta configuration and the increased torque (and reduced current) of the wye configuration.

[0085] Figure 8 Shows a circuit 800 for switching between the delta configuration and the wye configuration of a motor. In Figure 8 the circuit shown, in addition to phases A, B, and C, a fourth phase D is included in circuit 800. For example, an additional pair of phase switches can be added to the power switch network 260. Thus, the power switch network 260 can include eight switches (e.g., two switches per phase of motor 275) instead of having a total of six switches (e.g., MOSFETs) in the power switch network 260. However, since motor 275 only includes three pairs of phase windings in stator 340, only three of the four motor phases are effectively used at a given time. Which phases are effective depends on the selected configuration of stator 340.

[0086] As Figure 8As shown, circuit 800 further includes a first switching point 805, a second switching point 810, and a third switching point 815. The first switching point 805 is between phase A and phase D, the second switching point 810 is between phase C and the third switching point 815, and the third switching point 815 is between phase B and the second switching point 810. In some embodiments, each switching point includes a switch (e.g., FET, MOSFET, solid state relay, etc.). In other embodiments, each switching point includes more than one switch (e.g., two back-to-back switches [common source or common drain] to create a four-quadrant switching implementation). Thus, in some embodiments, circuit 800 includes a total of eight additional switches compared to a conventional three-phase DC motor that is permanently configured in a delta configuration or a Y configuration. The switches at switching points 805, 810, 815 are selectively controlled by controller 200 to configure stator 340 in a delta configuration or a Y configuration.

[0087] Figure 9A shows stator 340 in Figure 8 the delta configuration of a four-phase circuit of. In the delta configuration, the first switching point 805 and the second switching point 810 are configured to be closed (i.e., in a conducting state), and the third switching point 815 is configured to be open (i.e., in a non-conducting state). Also as Figure 9A shown, stator 340 uses an additional fourth phase D instead of the conventional phase A. Thus, phase windings 410, 415 include the first switching point 805 (and associated switch) and phase windings 420, 425 include the second switching point 810 (and associated switch).

[0088] Figure 9B shows stator 340 in Figure 8 the Y configuration of a four-phase circuit of. In the Y configuration, the first switching point 805 and the second switching point 810 are configured to be open (i.e., in a non-conducting state), and the third switching point 815 is configured to be closed (i.e., in a conducting state). Also as Figure 9B shown, stator 340 uses an additional fourth phase D instead of the conventional phase B. Thus, phase windings 420, 425 include the third switching point 815 (and associated switch).

[0089] Figure 10A is for switching between the delta configuration of circuit 900 and the Y configuration of circuit 905 Figure 8The general process 1000 of the circuit 800, and vice versa. At step 1005, the controller 200 operates the power tool 100 such that the stator 340 of the motor 275 is in the first motor configuration. The operation of the power tool 100 generally refers to the rotation of the motor 275 to produce a rotational output of the shaft 330. Then, the rotational movement of the shaft 330 is used to produce a desired output operation, which varies depending on the type of the power tool 100 (e.g., rotational output, reciprocating output, pulling output, etc.). At step 1010, the controller 200 receives a signal to change the configuration of the motor 275. In some embodiments, the signal is provided by the user through the user interface 245. For example, the user can select or adjust the transition point based on a particular application (e.g., wood, metal, embedded nails, etc.). In other embodiments, the signal is generated internally by the controller 200 based on the conditions of the power tool 100 and / or the motor 275. For example, the controller 200 can be based on the speed of the motor, the torque of the motor, the current of the motor, the load point of the motor, the field weakening conduction angle of the motor (e.g., the amount of field weakening for maintaining the current speed), the type of the battery pack connected to the power tool (e.g., based on the capacity of the battery pack), the state of charge of the battery pack (e.g., for optimizing runtime performance), the battery pack impedance (e.g., based on the voltage and current measurements of the battery pack), the grip strength above a grip strength threshold, whether there is one hand on the power tool 100, whether there are two hands on the power tool 100 (e.g., the main handle and a fixed or detachable side handle), the temperature above or below a temperature threshold (e.g., the motor temperature), the age of the battery pack (e.g., the number of charge / discharge cycles, the manufacturing date, the battery pack identification, the battery pack model, etc.) or any combination thereof (e.g., multiple factors) to generate a signal to change the motor configuration or the transition point. In some embodiments, the controller 200 can generate a signal to change the motor configuration or the transition point based on whether the gate drive refresh ("GDR") is active. GDR is a forced pulse width modulation ("PWM") signal designed to keep the gate driver power rail voltage above the off voltage (see Figure 24in the gate drive circuit 2400). For example, when GDR is active, the configuration of the motor 275 can be switched from a delta configuration to a Y configuration, and when GDR is inactive, it can be switched from a Y configuration to a delta configuration. In high-load applications where the gate driver would degrade the PWM signal and the performance of the motor 275, switching the motor configuration to avoid GDR will allow the power tool 100 to operate the motor 275 at full power. After the controller 200 determines to change the motor configuration, the motor control switching points 805, 810, 815 are used to switch the motor from a delta configuration to a Y configuration or from a Y configuration to a delta configuration (step 1015). In some embodiments, before changing the motor configuration to a delta configuration or a Y configuration, the motor 275 is allowed to coast (e.g., all switches in the switch network 260 are turned on) for a predetermined amount of time (e.g., 600 µs). The controller 200 then operates the power tool 100 and the motor 275 with the modified motor configuration (step 1020).

[0090] Figure 10B is for switching Figure 8 the circuit 800 from the delta configuration of the circuit 900 to the Y configuration of the circuit 905 in the process 1025. At step 1030, the controller 200 operates the power tool 100 with the stator 340 in the delta configuration. In the delta configuration, the first switching point 805 is turned on, the second switching point 810 is turned on, and the third switching point 815 is turned off (step 1035). When the controller 200 switches from the delta configuration to the Y configuration, the first switching point 805 is turned off, the second switching point 810 is turned off, and the third switching point 815 is turned on (step 1040). The stator 340 is now in the Y configuration, and the first switching point 805 is turned off, the second switching point 810 is turned off, and the third switching point 815 is turned on (step 1045). The controller 200 then operates the power tool 100 and the motor 275 with the Y configuration (step 1050).

[0091] Figure 10C is for switching Figure 8Process 1055 in which circuit 800 switches from the Y-configuration of circuit 905 to the delta configuration of circuit 900. At step 1060, controller 200 operates power tool 100 with stator 340 in the Y-configuration. In the Y-configuration, first switch point 805 is open, second switch point 810 is open, and third switch point 815 is closed (step 1065). When controller 200 switches from the Y-configuration to the delta configuration, first switching point 805 closes, second switching point 810 closes, and third switching point 815 opens (step 1070). Stator 340 is now in the delta configuration, and first switch point 805 is closed, second switch point 810 is closed, third switch point 815 is open (step 1075). Controller 200 then operates power tool 100 and motor 275 in the delta configuration (step 1080).

[0092] Figure 11 Shows another circuit 1100 for switching between the delta and Y-configurations of a motor. In Figure 11 the circuit shown, power tool 100 includes phases A, B, and C (but not including Figure 8 phase D, the fourth phase included in circuit 800). As Figure 11 shown, circuit 1100 further includes a first switch point 1105, a second switch point 1110, a third switch point 1115, a fourth switch point 1120, and a fifth switch point 1125. First switch point 1105 is between phase windings 410, 415 and phase windings 400, 405. Second switch point 1110 is between phase windings 400, 405 and phase windings 410, 415. Third switch point 1115 is between phase windings 410, 415 and phase B. Fourth switch point 1120 is between phase C and phase windings 420, 425. Fifth switch point 1125 is between phase windings 420, 425 and phase windings 400, 405. In some embodiments, each switch point includes a switch (e.g., a FET, MOSFET, solid state relay, etc.). In other embodiments, each switch point includes more than one switch (e.g., two back-to-back switches to create a four quadrant switch implementation). Thus, in some embodiments, circuit 1100 includes a total of ten additional switches (e.g., MOSFETs) compared to a traditional three-phase DC motor that is permanently configured as either a delta or Y-configuration. In some embodiments, five additional switches (e.g., relays) are used. The switches at switch points 1105, 1110, 1115, 1120, 1125 are selectively controlled by controller 200 to configure stator 340 as either a delta or Y-configuration. Compared to traditional delta-Y switching configurations, circuit 1100 uses fewer switches and keeps the neutral line attached to one of the three phases when not in the Y-configuration. Traditionally, the neutral line would be floating when not in the Y-configuration.

[0093] Figure 12A shows circuit 1200 in the delta configuration of circuit 1100 of Figure 11 In the delta configuration, the first switching point 1105 and the fifth switching point 1125 are configured to be open (i.e., non-conductive state), and the second switching point 1110, the third switching point 1115, and the fourth switching point 1120 are configured to be closed (i.e., conductive state). Thus, phase windings 400, 405 include the second switching point 1110 (and associated switch), phase windings 410, 415 include the third switching point 1115 (and associated switch), and phase windings 420, 425 include the fourth switching point 1120 (and associated switch).

[0094] Figure 12B shows stator 340 in Figure 11 the Y configuration of circuit 1100 of

[0095] Figure 13A is for switching between the delta configuration of circuit 1200 and the Y configuration of circuit 1205 Figure 11General process 1300 of circuit 1100, and vice versa. At step 1305, the controller 200 operates the power tool 100 such that the stator 340 of the motor 275 is in a first motor configuration. The operation of the power tool 100 generally refers to the rotation of the motor 275 to generate a rotational output of the shaft 330. Then, the rotational movement of the shaft 330 is used to generate a desired output operation, which varies depending on the type of the power tool 100 (e.g., rotational output, reciprocating output, pulling output, etc.). At step 1310, the controller 200 receives a signal to change the configuration of the motor 275. In some embodiments, the signal is provided by the user through the user interface 245. For example, the user can select or adjust the switching point based on a specific application (e.g., wood, metal, embedded nails, etc.). In other embodiments, the signal is internally generated by the controller 200 based on the conditions of the power tool 100 and / or the motor 275. For example, the controller 200 can generate a signal to change the motor configuration based on the speed of the motor, the torque of the motor, the current of the motor, the load point of the motor, the field weakening conduction angle of the motor, the type of the battery pack connected to the power tool (e.g., based on the capacity of the battery pack), the state of charge of the battery pack (e.g., for optimizing the runtime performance), the grip strength above or equal to the grip strength threshold, the temperature above or below or equal to the temperature threshold (e.g., motor temperature), etc. After the controller 200 determines to change the motor configuration, the motor control switching points 1105, 1110, 1115, 1120, 1125 are switched to switch the motor from the delta configuration to the Y configuration or from the Y configuration to the delta configuration (step 1315). In some embodiments, before changing the motor configuration to the delta configuration or the Y configuration, the motor 275 is allowed to coast (e.g., all switches in the switching network 260 are opened, one phase is fixed, etc.) for a predetermined amount of time (e.g., 600 µs). The controller 200 then operates the power tool 100 and the motor 275 with the modified motor configuration (step 1320).

[0096] Figure 13B is for converting Figure 11The process 1325 in which the circuit 1100 of [the device] switches from the delta configuration of the circuit 1200 to the wye configuration of the circuit 1205. At step 1330, the controller 200 operates the power tool 100 with the stator 340 in the delta configuration. In the delta configuration, the first switch point 1105 is off, the second switch point 1110 is on, the third switch point 1115 is on, the fourth switch point 1120 is on, and the fifth switch point 1125 is off (step 1335). When the controller 200 switches from the delta configuration to the wye configuration, the first switching point 1105 is on, the second switching point 1110 is off, the third switching point 1115 is off, the fourth switching point 1120 is off, and the fifth switching point 1125 is on (step 1340). The stator 340 is now in the wye configuration, and the first switch point 1105 is on, the second switch point 1110 is off, the third switch point 1115 is off, the fourth switch point 1120 is off, and the fifth switch point 1125 is on (step 1345). The controller 200 then operates the power tool 100 and the motor 275 in the wye configuration (step 1350).

[0097] Figure 13C is for switching Figure 11 the circuit 1100 of [the device] from the wye configuration of the circuit 1205 to the delta configuration of the circuit 1200 in the process 1355. At step 1360, the controller 200 operates the power tool 100 with the stator 340 in the wye configuration. In the wye configuration, the first switch point 1105 is on, the second switch point 1110 is off, the third switch point 1115 is off, the fourth switch point 1120 is off, and the fifth switch point 1125 is on (step 1365). When the controller 200 switches from the wye configuration to the delta configuration, the first switching point 1105 is off, the second switching point 1110 is on, the third switching point 1115 is on, the fourth switching point 1120 is on, and the fifth switching point 1125 is off (step 1370). The stator 340 is now in the delta configuration, and the first switch point 1105 is off, the second switch point 1110 is on, the third switch point 1115 is on, the fourth switch point 1120 is on, and the fifth switch point 1125 is off (step 1375). The controller 200 then operates the power tool 100 and the motor 275 in the delta configuration (step 1380).

[0098] The power tool 100 is configured to control its operation using the various motor configuration switching circuits described herein, where the motor 275 and the stator 340 are configured in a delta configuration or a wye configuration. However, the point at which the controller 200 switches from the delta configuration to the wye configuration or from the wye configuration to the DELA configuration is selected based on various factors. For example, the point at which the motor 275 switches configurations depends on the specific type of performance desired for the motor 275. Figure 14A 、Figure 14B and Figure 14C shows various torque-speed curves of the motor 275. Figure 14A 、 Figure 14B and Figure 14C The torque-speed curves shown in have varying output characteristics, and each curve is shown relative to the standard motor output (i.e., the output of a motor that does not switch between a delta configuration and a Y configuration). The torque-speed curves can be modified based on, for example, the gear ratio used to reduce the output speed of the motor 275. Figure 14A shows the torque-speed curve 1400 optimized for increasing torque. Figure 14B shows the torque-speed curve 1405 optimized for increasing speed. Figure 14C shows the torque-speed curve 1410 balanced between increased speed and increased torque.

[0099] After selecting the nature or characteristics of the desired torque-speed curve of the power tool 100, the point at which the motor 275 switches between the delta configuration and the Y configuration is selected. In some embodiments, the transition point or transition point for transitioning between the delta configuration and the Y configuration is selected as the point at or near the point where the delta motor configuration torque-speed curve intersects the Y motor configuration torque-speed curve (e.g., torque in N-M or In-lbs). However, when transitioning between the delta configuration and the Y configuration, the amount of current drawn from the power source (e.g., battery pack 150) of the power tool 100 may overload the power source. For example, a very high output current during the transition may last longer than the power source can tolerate. If this occurs, the power source will shut down or become inoperable. However, if the transition point for transitioning between the delta configuration and the Y configuration is selected as a lower torque point along the torque-speed curve (i.e., before the point where the delta torque-speed curve intersects the Y torque-speed curve), the amount of current drawn from the power source is lower. Therefore, the likelihood of damaging the power source or rendering it inoperable is reduced.

[0100] Figure 15Graph 1500 showing torque-speed curves, which includes triangular torque-speed curve 1505, Y-shaped torque-speed curve 1510, and conversion mode torque-speed curve 1515. In the conversion mode, the configuration of the motor is switched from a triangular configuration to a Y-shaped configuration, or from a Y-shaped configuration to a triangular configuration. Generally, the switch from a triangular configuration to a Y-shaped configuration occurs when the load increases or an increase in torque is desired. In some embodiments, the transition point is selected between 50% and 100% of the torque value at the intersection of the triangular torque-speed curve and the Y-shaped torque-speed curve. In some embodiments, the transition point is selected between 50% and 75% of the torque value at the intersection of the triangular torque-speed curve and the Y-shaped torque-speed curve. In some embodiments, the transition point is selected between 75% and 100% of the torque value at the intersection of the triangular torque-speed curve and the Y-shaped torque-speed curve. In some embodiments, the transition point is selected between 25% and 75% of the torque value at the intersection of the triangular torque-speed curve and the Y-shaped torque-speed curve.

[0101] In Figure 15 , the switch between the triangular configuration and the Y-shaped configuration occurs at approximately 0.7 N-M. In other embodiments, different transition point torques are selected. For Figure 15 embodiments, the transition points for the motor 275 to switch from a triangular configuration to a Y-shaped configuration or from a Y-shaped configuration to a triangular configuration are the same. In some embodiments, a speed / torque trade-off of approximately 1.73 ( ) is achieved (i.e., the torque increase or speed increase depending on the transition is 1.73 times that before the transition). Although the transition points for switching between the triangular configuration and the Y-shaped configuration are described relative to torque values, the transition points can be similarly described relative to speed values. In some embodiments, field weakening can be used to smooth and / or reduce the transition step 1520 when switching from a triangular configuration to a Y-shaped configuration.

[0102] The point at which the motor 275 transitions between the delta configuration and the wye configuration can also depend on the rotational position of the rotor 300 (e.g., detected by a Hall effect rotor position sensor). Tests have shown that the transient current spikes when switching between the delta configuration and the wye configuration depend largely on the rotational position of the rotor 300. Thus, in some embodiments, the motor 275 is only allowed to transition between the delta configuration and the wye configuration when the rotor 300 is in a specific rotational position. For example, a predetermined window is selected for transitioning between the delta configuration and the wye configuration. This window can correspond to a specific range of rotational positions of the rotor 300 (e.g., a 30° window, a 60° window, a 90° window, etc.). When the rotor 300 is within the transition window, the motor 275 is allowed to transition between the delta configuration and the wye configuration. When the rotor 300 is outside the transition window, the motor 275 is prevented from transitioning between the delta configuration and the wye configuration.

[0103] In some embodiments, the timing of the control switches to switch from the delta configuration to the wye configuration is also controlled by the controller 200 to reduce the transient current spikes experienced during the transition. For example, in some embodiments, the switches for the new stator configuration are closed (i.e., turned on) before the switches for the old stator configuration are opened (i.e., turned off). By closing the switches required to form the new stator configuration before opening the switches for the previous stator configuration, the transient current spikes are reduced. In some embodiments, improved braking of the motor 275 is also achieved by turning on all the switches for connecting the stator 340 in either the delta configuration or the wye configuration.

[0104] Figure 16 A graph 1600 showing torque-speed curves is presented, which includes a delta torque-speed curve 1505, a wye torque-speed curve 1510, and a transition mode torque-speed curve 1605. In the transition mode, the configuration of the motor is switched from the delta configuration to the wye configuration, or from the wye configuration to the delta configuration. However, the transition mode torque-speed curve 1605 introduces hysteresis during the transition between the delta configuration and the wye configuration. Specifically, the transition mode torque-speed curve includes two transition points. The first transition point 1610 corresponds to the transition from the delta configuration to the wye configuration. The second transition point 1615 corresponds to the transition from the wye configuration to the delta configuration. The first transition point 1610 corresponds to a higher torque value than the second transition point 1615. Thus, in the illustrated embodiment, the motor 275 transitions from the delta configuration to the wye configuration at a torque value higher than the torque value at which the motor 275 transitions from the wye configuration to the delta configuration. In other embodiments, the motor 275 transitions from the delta configuration to the wye configuration at a torque value lower than the torque value at which the motor 275 transitions from the wye configuration to the delta configuration.

[0105] Figure 17Shows one of the results of switching between a delta configuration and a Y configuration. Specifically, Figure 17 Shows graph 1700, which includes a standard motor torque-power curve 1705 and a delta-Y torque-power curve 1710. The switching point 1715 corresponds to the point at which the motor 275 switches between the delta configuration and the Y configuration. Due to the smooth transition between the delta configuration and the Y configuration, the output power of the power tool 100 is reduced by approximately 25% at the switching point 1715. However, when the output power is reduced, the power tool 100 experiences a flatter power curve over a wide range of torque values. In some embodiments, a PWM signal may not be used to control the motor 275. In such embodiments, when transitioning between the delta configuration and the Y configuration, a step function for both speed and power is implemented. In some embodiments, the power tool 100 operates at full power until the switching point, and a step function transition occurs. The abruptness of the transition is configured to warn the user that the transition is occurring and that an overload condition is approaching (e.g., for a chainsaw).

[0106] The switching electronics used to switch between the delta configuration and the Y configuration are subject to failure. If the switch between the delta configuration and the Y configuration fails, the motor 275 can be placed in a "limp mode" that holds the motor in a single configuration. For example, if the motor 275 fails to transition from the Y configuration to the delta configuration, the motor 275 remains in the Y configuration. Alternatively, if the motor 275 fails to transition from the delta configuration to the Y configuration, the motor 275 remains in the delta configuration. In some embodiments, the failure can also be tested at startup, and the power tool 100 can operate in limp mode from the start (e.g., without attempting to switch).

[0107] In addition to switching the motor 275 between the delta configuration and the Y configuration, the motor 275 can also be controlled to switch the stator phase windings between a parallel configuration and a series configuration. Figure 18A Shows a single stator motor phase 1800 that includes a first phase winding 1805 and a second phase winding 1810. In Figure 18A , the first phase winding 1805 and the second phase winding 1810 are connected in parallel with each other. Figure 18B Shows a single stator motor phase 1815 that includes a first phase winding 1805 and a second phase winding 1810. In Figure 18B , the first phase winding 1805 and the second phase winding 1810 are connected in series with each other.

[0108] Figure 19A circuit 1900 is shown for converting stator motor phases between a parallel phase winding connection and a series phase winding connection. In the illustrated embodiment, a first phase winding 1805 and a second phase winding 1810 are connected between a motor tap of the V-U phase and a motor tap of the V-W phase. The circuit 1900 includes a first switching point 1905, a second switching point 1910, and a third switching point 1915. In some embodiments, each switching point includes a switch (e.g., a FET, MOSFET, solid state relay, etc.), for a total of nine switches (i.e., three per phase), for converting the stator motor phases between a parallel phase winding connection and a series phase winding connection. In other embodiments, each switching point includes more than one switch (e.g., two back-to-back switches to create a four-quadrant switching implementation). Thus, in some embodiments, the circuit 1900 includes a total of six additional switches per phase compared to a conventional motor phase that is permanently configured as either a parallel configuration or a series configuration. The switches at the switching points 1905, 1910, 1915 are selectively controlled by a controller 200 to configure the first phase winding 1805 and the second phase winding 1810 as either a parallel configuration or a series configuration. Thus, in some embodiments, a three-phase motor will include a total of eighteen additional switches, more than a conventional motor phase that is permanently configured as either a parallel configuration or a series configuration. In some embodiments, a speed / torque tradeoff of approximately 2.0 is achieved by switching between a series stator phase configuration and a parallel stator phase configuration.

[0109] Figure 20 A chart 2000 is shown of torque-speed curves for a stator winding in a parallel configuration and a stator winding in a series configuration. Compared to a motor in a series configuration, the torque-speed curve 2005 for the stator winding in a parallel configuration shows higher output speed values (in revolutions per minute (“RPM”)) in the case of low torque or no torque. However, compared to a stator winding in a series configuration, the stator winding in a parallel configuration produces less output torque at low speeds. Conversely, compared to a stator winding in a parallel configuration, the torque-speed curve 2010 for the stator winding in a series configuration shows lower output speeds (in RPM) in the case of low torque or no torque. However, compared to a stator winding in a parallel configuration, the stator winding in a series configuration produces more torque at low speeds.

[0110] Figure 21Graph 2100 shows torque-current curves for stator windings in parallel configuration and stator windings in series configuration. The torque-current curve 2105 for the motor in parallel configuration shows that the stator windings in parallel configuration generally draw higher currents compared to the torque-current curve 2110 for the stator windings in series configuration. This difference in source current is a result of the approximately fourfold (4x) increase in motor resistance for the series configuration compared to the parallel configuration. Although a 4x change in motor resistance occurs, the overall system resistance only increases by approximately 50% when switching from a parallel configuration to a series configuration.

[0111] Since stator windings in parallel configurations and stator windings in series configurations have different operating properties or characteristics, it would be advantageous to be able to switch between stator windings in parallel configurations and stator windings in series configurations to take advantage of the advantages of each motor configuration. Specifically, it would be advantageous to be able to take advantage of the increased speed of the parallel configuration and the increased torque of the series configuration.

[0112] Figure 22A It is used to switch between parallel configuration of motor phases and series configuration of motor phases. Figure 19 The general process 2200 of the circuit 1900 of the motor 275 is described in detail, and vice versa. At step 2205, the controller 200 operates the power tool 100 in a manner that the stator 340 of the motor 275 is in a first stator winding configuration. The operation of the power tool 100 generally refers to the rotation of the motor 275 to produce a rotational output of the shaft 330. The rotational motion of the shaft 330 is then used to produce a desired output operation, which varies depending on the type of power tool 100 (e.g., rotational output, reciprocating output, pulling output, etc.). At step 2210, the controller 200 receives a signal to change the configuration of the motor 275. In some embodiments, the signal is provided by a user through the user interface 245. In other embodiments, the signal is generated internally by the controller 200 based on the condition of the power tool 100 and / or the motor 275. For example, the controller 200 can generate a signal to change the motor configuration based on the speed of the motor, the torque of the motor, the current of the motor, the load of the motor, the field weakening conduction angle of the motor, etc. After the controller 200 determines that the motor configuration is to be changed, the motor controls the switching points 1905, 1910, 1915 to switch the stator windings from a parallel configuration to a series configuration or from a series configuration to a parallel configuration (step 2215). In some embodiments, the motor 275 is allowed to coast (e.g., all switches in the switch network 260 are turned on) for a predetermined amount of time (e.g., 600 μs) before the stator winding configuration is changed to a parallel configuration or a series configuration. The controller 200 then operates the power tool 100 and the motor 275 with the modified stator winding configuration (step 2220).

[0113] Figure 22B is used to Figure 19The process 2225 by which the circuit 1900 switches from a series configuration of stator phases to a parallel configuration of stator phases. At step 2230, the controller 200 operates the power tool 100 such that the windings of the stator 340 are in a series configuration. In the series configuration, the first switch point 1905 is open, the second switch point 1910 is closed, and the third switch point 1915 is open (step 2235). When the controller 200 switches from the series configuration to the parallel configuration, the first switching point 1905 closes, the second switching point 1910 opens, and the third switching point 1915 closes (step 2240). The windings of the stator 340 are now in a parallel configuration, and the first switch point 1905 is closed, the second switch point 1910 is open, and the third switch point 1915 is closed (step 2245). The controller 200 then operates the power tool 100 and the motor 275 such that the stator windings are in a parallel configuration (step 2250). Although the process 2225 is typically described with respect to a single stator phase of the motor 275, the same process can be performed for each stator phase (e.g., three phases) of the motor 275.

[0114] Figure 22C is for switching Figure 19 The process 2255 by which the circuit 1900 switches from a parallel configuration of stator phases to a series configuration of stator phases. At step 2260, the controller 200 operates the power tool 100 such that the windings of the stator 340 are in a parallel configuration. In the parallel configuration, the first switch point 1905 is closed, the second switch point 1910 is open, and the third switch point 1915 is closed (step 2265). When the controller 200 switches from the parallel configuration to the series configuration, the first switching point 1905 opens, the second switching point 1910 closes, and the third switching point 1915 opens (step 2270). The windings of the stator 340 are now in a series configuration, and the first switch point 1905 is open, the second switch point 1910 is closed, and the third switch point 1915 is open (step 2275). The controller 200 then operates the power tool 100 and the motor 275 such that the stator windings are in a series configuration (step 2280). Although the process 2255 is typically described with respect to a single stator phase of the motor 275, the same process can be performed for each stator phase (e.g., three phases) of the motor 275.

[0115] The controller 200 can control the configuration between the delta configuration and the Y configuration as well as between the series configuration and the parallel configuration. Thus, four possible torque-speed trade-offs can be achieved. The torque-speed trade-offs for the four possible motor configurations are provided in Table #1 below.

[0116]

[0117] As described above, the switch for controlling the conversion of the motor 275 between the delta configuration and the Y configuration of the stator 340 or between the stator windings in the parallel configuration and the series configuration of the stator windings can be configured as back-to-back switches sharing a common source or a common drain. Figure 23 The switching circuit 2300 showing such a switch configuration. In Figure 23 the illustrated embodiment, two back-to-back MOSFETs 2305, 2310 form a four-quadrant switch. In the switching circuit 2300, the resistors R7, R8 and the capacitors C7, C8 form a buffer circuit that reduces the transient voltage across the MOSFETs 2305, 2310. The Zener diode 2315 and the capacitor 2320 reduce the noise on the gate drive signals of the MOSFETs 2305, 2310.

[0118] Figure 24 The gate drive circuit 2400 for driving Figure 23 the MOSFETs 2305, 2310 is shown. The capacitor 2405 forms a bootstrap capacitor. The Zener diode 2410 clamps the voltage across the capacitor 2405 to a voltage (e.g., 20 V) that the integrated circuit 2415 can withstand. In the case of a large negative transient voltage, the diode (e.g., Schottky diode) 2420 on the power supply rail protects the gate driver from fusing. Specifically, in the case where a negative voltage appears on the pin Vb, the internal diode of the integrated circuit 2415 becomes forward-conducting from the ground to Vb. This internal diode cannot carry a large current and will fail due to a large negative transient voltage. The failure of the internal diode can be observed as a short circuit of Vb to Vs. By placing the diode 2420 at Vs instead of Vb, the transient voltage can be applied to the capacitor 2405 before the integrated circuit 2415 is at risk of failure. In some embodiments, a resistor can be connected between Figure 23 the MOSFETs 2305, 2310 and the Vs pin of the integrated circuit 2415 to reduce the transient potential of the gate driver.

[0119] The motor control and configuration techniques described herein can be applied to any of a variety of different applications to achieve the desired power tool output characteristics. For example, these techniques can be applied to a vacuum cleaner, and the configuration conversion point can be based on air pressure, motor speed, motor current, etc. When high suction is required, a configuration conversion (e.g., from delta to Y) can be performed to clear debris in the vacuum filter (e.g., high-power pulses of air flow or suction) to maximize the runtime, etc. When the vacuum tool or other power tool (e.g., belt sander) is unloaded or in the economy mode, a configuration conversion can also be performed to reduce the current consumption.

[0120] Motor control and configuration techniques can also be implemented in a stapler. For example, the startup of a stapler is a stall event. The motor can be configured in a Y configuration to reduce the current required to activate the firing mechanism. After the firing pin is released and the lifter rotates freely under no load, the motor can operate in a delta configuration to increase the reset speed on the stapler (e.g., increase the firing rate and reduce the firing time). In some embodiments, the configuration of the motor in the stapler is based on the temperature of the stapler or the environment of the stapler. In some embodiments, the configuration of the motor in the stapler is based on the size of the nails inserted into the stapler and / or the speed setting of the stapler. Similarly, a rivet tool can control the configuration of its motor based on whether stainless steel rivets or aluminum rivets are being used or the size of the rivets (e.g., 1 / 8-inch rivets vs. 1 / 4-inch rivets). For a tightening operation, the motor configuration can be selected based on the output size (e.g., drill bit size).

[0121] Motor control and configuration techniques can also be implemented in a saw. For example, for a table saw, the motor configuration can be selected based on the cutting depth. For depths greater than a predetermined value, the motor is switched to a Y configuration. Similarly, the motor configuration can be based on the material being cut. For materials that generate a relatively small load, such as drywall, a delta configuration can be used. For materials that generate a relatively high load, such as concrete or tile, a Y configuration can be used.

[0122] Figures 25 to 26 An external rotor electric motor 2500 for a power tool 100 is shown, which implements the motor switching circuit disclosed herein. Specifically, Figure 25 the profile of the external rotor motor 2500 is shown, and Figure 26Shows a cross-sectional view of an outer rotor electric motor 2500. The outer rotor electric motor 2500 includes a rotor 2502 having a hollow armature 2504 surrounding a stator 2506, and the stator 2506 is located at the center of the hollow armature 2504. The stator 2506 includes a lamination stack 2508 that is locked together by pin elements and forms stator teeth 2510. The stator teeth 2510 are wrapped by a stator winding 2512. The rotor 2502 includes an output shaft 2516 connected to the rotor 2502. The output shaft 2516 is configured to rotate with the rotor 2502. The rotor 2502 includes permanent magnets 2518 positioned around the rotation center 2520 of the output shaft 2516. The rotational radius 2522 of the stator 2506 can be derived from the rotation center 2520 of the output shaft 2516. Similar to the inner rotor electric motor 2500, the torque output of the outer rotor electric motor 2500 can be determined based on the rotational radius 2522 multiplied by a force vector 2524, which is generated by the electromagnetic force of the stator 2506 on the permanent magnets 2418 of the rotor 1252 during the operation of the outer rotor electric motor 2500. A fan 2526 is located at one end of the outer rotor motor 2500 to assist in cooling the outer rotor motor 2500 during operation. In some embodiments, the outer diameter of the rotor 2502 of the motor 2500 is approximately 25 mm. In other embodiments, the outer diameter of the rotor 2502 of the motor 2500 has a value between 15 mm and 36 mm. In some embodiments, the length of the stator 2506 is between approximately 35 mm and 60 mm.

[0123] Accordingly, the embodiments described herein particularly provide a motor switching circuit for switching between a triangular stator configuration and a Y-shaped stator configuration, as well as between a parallel stator winding configuration and a series stator winding configuration. Various features and advantages are set forth in the appended claims.

Claims

1. A power tool, characterized in that, The power tool includes: An electric motor having a rotor and a stator, the stator including a plurality of phase windings; A plurality of switches for selectively setting the configuration of the plurality of phase windings; and A controller connected to the plurality of switches, the controller being configured to: Detect a fault to change the plurality of phase windings between configurations, and In response to the fault, lock the plurality of phase windings in a first configuration.

2. The power tool according to claim 1, characterized in that, The controller is configured to detect the fault to change the plurality of phase windings between a delta configuration and a Y configuration.

3. The power tool according to claim 1, characterized in that, The controller is configured to detect the fault to change the plurality of phase windings between a series configuration and a parallel configuration.

4. The power tool according to claim 1, characterized in that, The plurality of switches includes at least eight switches.

5. The power tool according to claim 1, characterized in that, The controller is configured to detect the fault to change the plurality of phase windings between configurations based on whether a gate driver power rail voltage is above a threshold voltage.

6. The power tool according to claim 1, wherein The controller is configured to detect the fault to change the plurality of phase windings between configurations based on the torque of the motor.

7. The power tool according to claim 1, characterized in that, The controller is configured to detect the fault to change the plurality of phase windings between configurations based on the current of the motor.

8. The power tool according to claim 1, characterized in that, The controller is further configured to: Test for the fault during startup of the power tool to change the plurality of phase windings between configurations.

9. The power tool according to claim 1, characterized in that, Further includes: A Hall effect sensor configured to sense the position of the rotor, and wherein the controller is configured to detect the fault to change the plurality of phase windings between configurations based on the rotational position of the rotor indicated by the Hall effect sensor.

10. The power tool according to claim 1, characterized in that, The controller is configured to detect the fault to change the plurality of phase windings between configurations based on an increase in transient current spikes.

11. The power tool according to claim 1, characterized in that, The controller is further configured to: Monitor the condition of the electric motor; and Based on the condition, unlock the plurality of phase windings by controlling the plurality of switches to convert the configuration of the phase windings from the first configuration to a second configuration.

12. A power tool, characterized in that, The power tool includes: An electric motor having a stator, the stator including a plurality of stator poles, each stator pole having a plurality of phase windings; A plurality of switches for selectively setting the configuration of the plurality of phase windings to one of a first configuration and a second configuration; and A controller connected to the plurality of switches, the controller being configured to: Detect a fault to change the plurality of phase windings from the first configuration to the second configuration, and In response to the fault, lock the plurality of phase windings in the first configuration.

13. The power tool according to claim 12, wherein The first configuration is a delta configuration and the second configuration is a Y configuration.

14. The power tool according to claim 12, characterized in that, The first configuration is a series configuration and the second configuration is a parallel configuration.

15. The power tool according to claim 12, characterized in that, The controller is configured to detect the fault to change the plurality of phase windings from the first configuration to the second configuration based on whether a gate driver power rail voltage is above a threshold voltage.

16. The power tool according to claim 12, characterized in that, The controller is configured to detect the fault to change the plurality of phase windings from the first configuration to the second configuration based on the torque of the motor.

17. The power tool according to claim 12, characterized in that, The controller is configured to detect the fault and change the plurality of phase windings from the first configuration to the second configuration based on the current of the motor.

18. The power tool according to claim 12, characterized in that The controller is further configured to test the fault during startup of the power tool to change the plurality of phase windings from the first configuration to the second configuration.

19. The power tool according to claim 12, characterized in that, Further comprising: A Hall effect sensor configured to sense the position of the rotor, and wherein the controller is configured to detect the fault and change the plurality of phase windings from the first configuration to the second configuration based on the rotational position of the rotor indicated by the Hall effect sensor.

20. The power tool according to claim 12, characterized in that, The controller is further configured to: Monitor the condition of the electric motor; and Based on the condition, unlock the plurality of phase windings by controlling the plurality of switches to convert the configuration of the phase windings from the first configuration to the second configuration.

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