WO2020001660A1 - 电动工具及其控制方法 - Google Patents

电动工具及其控制方法 Download PDF

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Publication number
WO2020001660A1
WO2020001660A1 PCT/CN2019/094242 CN2019094242W WO2020001660A1 WO 2020001660 A1 WO2020001660 A1 WO 2020001660A1 CN 2019094242 W CN2019094242 W CN 2019094242W WO 2020001660 A1 WO2020001660 A1 WO 2020001660A1
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WO
WIPO (PCT)
Prior art keywords
phase winding
power
rotor
voltage
power source
Prior art date
Application number
PCT/CN2019/094242
Other languages
English (en)
French (fr)
Inventor
李文成
王宏伟
徐谦
Original Assignee
南京德朔实业有限公司
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 南京德朔实业有限公司 filed Critical 南京德朔实业有限公司
Priority to EP19824959.1A priority Critical patent/EP3806316B1/en
Publication of WO2020001660A1 publication Critical patent/WO2020001660A1/zh
Priority to US17/135,579 priority patent/US11095238B2/en

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Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P6/00—Arrangements for controlling synchronous motors or other dynamo-electric motors using electronic commutation dependent on the rotor position; Electronic commutators therefor
    • H02P6/14—Electronic commutators
    • H02P6/15—Controlling commutation time
    • H02P6/153—Controlling commutation time wherein the commutation is advanced from position signals phase in function of the speed
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
    • B25B—TOOLS OR BENCH DEVICES NOT OTHERWISE PROVIDED FOR, FOR FASTENING, CONNECTING, DISENGAGING OR HOLDING
    • B25B23/00—Details of, or accessories for, spanners, wrenches, screwdrivers
    • B25B23/14—Arrangement of torque limiters or torque indicators in wrenches or screwdrivers
    • B25B23/147—Arrangement of torque limiters or torque indicators in wrenches or screwdrivers specially adapted for electrically operated wrenches or screwdrivers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B47/00—Drives or gearings; Equipment therefor
    • B24B47/10—Drives or gearings; Equipment therefor for rotating or reciprocating working-spindles carrying grinding wheels or workpieces
    • B24B47/12—Drives or gearings; Equipment therefor for rotating or reciprocating working-spindles carrying grinding wheels or workpieces by mechanical gearing or electric power
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
    • B25B—TOOLS OR BENCH DEVICES NOT OTHERWISE PROVIDED FOR, FOR FASTENING, CONNECTING, DISENGAGING OR HOLDING
    • B25B23/00—Details of, or accessories for, spanners, wrenches, screwdrivers
    • B25B23/14—Arrangement of torque limiters or torque indicators in wrenches or screwdrivers
    • B25B23/147—Arrangement of torque limiters or torque indicators in wrenches or screwdrivers specially adapted for electrically operated wrenches or screwdrivers
    • B25B23/1475—Arrangement of torque limiters or torque indicators in wrenches or screwdrivers specially adapted for electrically operated wrenches or screwdrivers for impact wrenches or screwdrivers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
    • B25F—COMBINATION OR MULTI-PURPOSE TOOLS NOT OTHERWISE PROVIDED FOR; DETAILS OR COMPONENTS OF PORTABLE POWER-DRIVEN TOOLS NOT PARTICULARLY RELATED TO THE OPERATIONS PERFORMED AND NOT OTHERWISE PROVIDED FOR
    • B25F5/00—Details or components of portable power-driven tools not particularly related to the operations performed and not otherwise provided for
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K3/00—Details of windings
    • H02K3/04—Windings characterised by the conductor shape, form or construction, e.g. with bar conductors
    • H02K3/28—Layout of windings or of connections between windings
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P6/00—Arrangements for controlling synchronous motors or other dynamo-electric motors using electronic commutation dependent on the rotor position; Electronic commutators therefor
    • H02P6/14—Electronic commutators
    • H02P6/16—Circuit arrangements for detecting position
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23B—TURNING; BORING
    • B23B2260/00—Details of constructional elements
    • B23B2260/024—Batteries
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23B—TURNING; BORING
    • B23B45/00—Hand-held or like portable drilling machines, e.g. drill guns; Equipment therefor
    • B23B45/02—Hand-held or like portable drilling machines, e.g. drill guns; Equipment therefor driven by electric power
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K7/00—Arrangements for handling mechanical energy structurally associated with dynamo-electric machines, e.g. structural association with mechanical driving motors or auxiliary dynamo-electric machines
    • H02K7/14—Structural association with mechanical loads, e.g. with hand-held machine tools or fans
    • H02K7/145—Hand-held machine tool
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P2203/00—Indexing scheme relating to controlling arrangements characterised by the means for detecting the position of the rotor
    • H02P2203/03—Determination of the rotor position, e.g. initial rotor position, during standstill or low speed operation

Definitions

  • the present application relates to a power tool, for example, to a power tool and a control method thereof.
  • the power tool includes a brushless motor and a functional accessory.
  • the rotation of the brushless motor drives the functional accessory to work to achieve the function of the functional accessory.
  • Brushless motors are generally composed of the motor itself and the corresponding drive circuit. Compared with brushed motors, brushless motors have lower operating noise and longer life. Generally speaking, according to whether there is a sensor that detects the position of the rotor, the brushless motor is divided into a brushless motor with a sensed control and a brushless motor with a senseless control. The setting of the position sensor and the coordination of the position sensor and the control method are important factors affecting the performance of the brushless motor.
  • Electric tools can be divided into AC electric tools and DC electric tools according to different power sources.
  • DC brushless power tools in general, the specifications of the power module to be adapted are different according to the output characteristics of the motor, especially for power tools using battery packs. In some cases, if the battery pack is powered by If the voltage is too low due to a long use time, the motor speed will drop and the output demand will not be met; or there is no suitable battery pack nearby and the power tool cannot complete the expected work.
  • the present application provides an electric tool and a control method thereof, which can be compatible with multi-voltage power supply and can meet output characteristic requirements.
  • An electric tool includes: a functional part configured to realize the function of the electric tool; a motor configured to drive the functional part; the motor includes a rotor, a first phase winding, a second phase winding, and a third phase winding
  • a driving circuit electrically connected to the first phase winding, a second phase winding, and a third phase winding, and configured to drive the motor to output power
  • a power module electrically connected to the driving circuit, configured to pass through The driving circuit supplies power to the first phase winding, the second phase winding, and the third phase winding; and a control module connected to the driving circuit and configured to output a control signal to control the driving circuit; the control module is configured When the voltage of the power module is less than or equal to a preset voltage threshold, the driving circuit is controlled according to the rotation position of the rotor of the motor so that the first phase winding, the second phase winding, and the third phase winding are simultaneously Connected to the power module.
  • An embodiment provides a method for controlling a power tool.
  • the power tool includes a motor including a rotor, a first-phase winding, a second-phase winding, and a third-phase winding; and a power module including a positive terminal of a power source. And the negative terminal of the power source, the power module is configured to generate a potential difference between the positive terminal of the power source and the negative terminal of the power source;
  • the control method includes: obtaining a voltage of the power module; and obtaining a rotation position of the rotor when the voltage of the power module is less than or equal to a preset voltage threshold, wherein when the rotor is rotated to a first preset When in the rotating position, the first-phase winding is electrically connected to the positive terminal of the power source, the second-phase winding is electrically connected to the negative terminal of the power source, and the third-phase winding is electrically connected to the positive terminal of the power source and One of the negative terminal of the power source; when the rotor rotates to a second preset rotation position, disconnect the third phase winding from the positive terminal of the power source and one of the negative terminal of the power source and It is electrically connected to the other of the positive terminal of the power source and the negative terminal of the power source.
  • An embodiment provides a method for controlling a power tool.
  • the power tool includes a motor including a rotor, a first-phase winding, a second-phase winding, and a third-phase winding; and a power module including a positive terminal of a power source. And the negative terminal of the power source, the power module generates a potential difference between the positive terminal of the power source and the negative terminal of the power source;
  • the control method includes:
  • FIG. 1 is a schematic structural diagram of a power tool according to an embodiment
  • FIG. 2 is a circuit block diagram of a motor driving system of the power tool shown in FIG. 1;
  • FIG. 3 is a circuit diagram of a driving circuit in the power tool
  • FIG. 4 is a schematic diagram of a correspondence relationship between a position sensor signal and a signal interval in a power tool
  • 6a, 6b, and 6c are graphs showing the corresponding relationship between the voltage of each phase and the rotor position of the brushless motor in different embodiments;
  • 7a is a corresponding relationship diagram of a control signal of a first phase winding A, a voltage of the first phase winding A, and a rotor position in a brushless motor in a related art electric tool;
  • 7b is a relationship diagram of an embodiment of a correspondence between a control signal of a first phase winding A of a brushless motor in a power tool, a voltage of the first phase winding A, and a rotor position;
  • 7c is a relationship diagram of another embodiment of the corresponding relationship between the control signal of the first phase winding A of the brushless motor in the electric tool, the voltage of the first phase winding A, and the rotor position;
  • FIG. 8 is a graph of an embodiment of the correspondence between the voltage of the first phase winding A of the brushless motor before and after the phase adjustment and the rotor position;
  • FIG. 10a, FIG. 10b and FIG. 10c are comparison graphs of the rotation speed of the power tool in the related art and the power tool in different embodiments of the present application;
  • FIG. 11 is a flowchart of a method for controlling a power tool according to an embodiment
  • FIG. 12 is a flowchart of another control method for a power tool according to an embodiment.
  • the power tool in this embodiment may be a handheld power tool, a garden tool, or a garden vehicle, such as a vehicle-type lawn mower, which is not limited herein.
  • the power tool 10 of this embodiment includes, but is not limited to, the following: power tools such as screwdrivers, electric drills, wrenches, and angle grinders that require speed adjustment; power tools such as sanders that may be used to grind workpieces; reciprocating saws, circular saws, Jigsaws and the like may be used to cut workpieces; electric hammers and the like may be used as power tools for impact.
  • These tools may also be garden tools, such as pruning machines, chainsaws, or vehicle lawn mowers; they may also be used for other purposes, such as mixers.
  • the electric power tool 10 includes a housing 11, a functional part 12, and a motor 34.
  • the casing 11 constitutes a main body portion of the power tool 10 and is provided to accommodate the motor 34.
  • One end of the housing 11 is also provided for installing a functional part 12.
  • the function part 12 is provided to realize the functions of the power tool 10, such as grinding and cutting.
  • the power tool 10 shown in FIG. 1 takes a handheld electric drill as an example, and the functional part 12 is a drill.
  • the function piece 12 is operatively connected to the motor 34, for example, to the motor 34 through a tool attachment shaft.
  • the motor 34 is configured to drive the functional component 12 so as to drive the functional component 12 to work and provide power to the functional component 12.
  • the motor 34 is a brushless motor.
  • the motor 34 includes a rotor and a first-phase winding group A, a second-phase winding B, and a third-phase winding C.
  • the motor 34 also includes a motor shaft and a stator, and the motor shaft is operatively connected to the functional component 12, for example, the motor shaft and the tool accessory shaft supporting the functional component are connected by a transmission device, and the driving force of the motor shaft is transmitted to the tool accessory shaft, thereby The functional part 12 mounted on the tool attachment shaft is operated.
  • the power module is configured to provide power to the power tool 10.
  • the power tool 10 is powered by a DC power source, and more specifically, the power tool 10 is powered by a battery pack 20.
  • the power tool 10 includes a receiving portion or a battery pack connection interface 16 configured to receive the battery pack 20, and the battery pack connection interface 16 is configured to accommodate battery packs 20 having different voltages or to connect battery packs 20 having different voltages.
  • the battery pack 20 includes a battery 22 and a case 21.
  • the battery 22 is housed in the case 21 and is configured to store energy and can be repeatedly charged and discharged.
  • the case 21 is provided to accommodate the battery 22 and other components in the battery pack 20, and the case is formed with a joint portion 23.
  • the battery pack 20 is suitable for the power tool 10 and can be used as a power source of the power tool 10.
  • the battery pack 20 further includes a plurality of electrode connection terminals, which at least electrically connect the battery 22 to an external circuit.
  • the power tool 10 can be powered by multiple battery packs 20 at the same time. In one embodiment, the power tool 10 can only be powered by one battery pack 20. The battery pack 20 used by the power tool 10 is not used here. The number is limited.
  • a motor driving system 30 of a power tool includes a power module 31, a control module 32, a driving circuit 33, and a motor 34.
  • the power module 31 provides power to the power tool 10.
  • the power module 31 includes a power source positive terminal 31a and a power source negative terminal 31b.
  • the power source positive terminal 31a is specifically the power source positive terminal of the power module 31, and the power source negative terminal 31b is specifically The negative terminal of the power source of the power module 31.
  • the power module 31 causes a potential difference between the positive terminal 31a of the electric power source and the negative terminal 31b of the electric power source.
  • the battery pack 20 is used as the power module 31.
  • the power module 31 may also be an AC power source and circuits such as rectification and filtering.
  • the power module 31 is electrically connected to the driving circuit 34, and supplies power to the motor 34 through the driving circuit. Referring to FIG. 3, the power module 31 supplies power to the first-phase winding A, the second-phase winding B, and the third-phase winding C of the motor 34 through the driving circuit 34.
  • the power tool 10 further includes a control module power supply circuit 37.
  • the control module power supply circuit 37 is electrically connected to the power module 31 and the control module 32.
  • the control module power supply circuit 37 will come from the power module 31.
  • the electrical energy is converted into electrical energy for use by the control module 32.
  • the control module 32 is electrically connected to the driving circuit 33 and configured to output a driving signal to control the driving circuit 33 to work.
  • the control module 32 uses a dedicated control core, for example, a micro-controller module (MCU, Microcontroller Unit).
  • the control chip 32 internally includes a power driving unit (not shown).
  • the power driving unit is used to improve the driving capability of the output signal of the control module 32.
  • the power driving unit may also be implemented by an external power driving unit.
  • the driving circuit 33 is connected to the motor 34 to drive the motor 34 to work.
  • the motor 34 may be a brushless motor or a brushed motor.
  • the following uses the motor 34 as an example to describe the solution of the present application.
  • the motor 34 includes a multi-phase winding.
  • the motor 34 includes a first phase winding A, a second phase winding B, and a third phase winding C.
  • the driving circuit 33 is electrically connected to The first-phase winding, the second-phase winding, and the third-phase winding of the motor 34 are configured to drive the motor 34 to output power.
  • the driving circuit 33 includes: a first driving terminal 33a, the first driving terminal 33a is used to be electrically connected to the positive power terminal 31a of the power module 31; and a second driving terminal 33b is configured to be electrically connected to the negative terminal 31b of the power of the power module 31.
  • the driving circuit 33 further includes a driving switch.
  • the driving switch includes a plurality of high-side switches and a plurality of low-side switches. The high-side ends of the high-side switches are respectively electrically connected to the first driving end 33a. The low-side terminals of the low-side switch are electrically connected to the second driving terminal 33b, respectively.
  • the power module 31 is electrically connected to the driving circuit 33 and is configured to supply power to the first phase winding A, the second phase winding B, and the third phase winding C of the motor through the driving circuit 33.
  • the driving switch includes a plurality of high-side switches and a plurality of low-side switches.
  • the plurality of high-side switches are the high-side switch Q1, the high-side switch Q3, and High-side switch Q5, multiple high-side switches have high-side and low-side, high-side switch Q1 has high-side Q1H and low-side Q1L, and high-side switch Q3 has high-side Q3H and low-side Q3L.
  • the high-side switch Q5 has a high-side terminal Q5H and a low-side terminal Q5L.
  • the high-side terminal Q1H of the high-side switch Q1, the high-side terminal Q3H of the high-side switch Q3, and the high-side terminal Q5H of the high-side switch Q5 are all connected to the first driving terminal 33a of the driving circuit 33, respectively.
  • the plurality of low-side switches are the low-side switch Q2, the low-side switch Q4, and the low-side switch Q6 in FIG. 3.
  • the plurality of low-side switches also have high-side switches. End and low side end.
  • the low-side switch Q2 has a high-side Q2H and a low-side Q2L
  • the low-side switch Q4 has a high-side Q4H and a low-side Q4L
  • the low-side switch Q6 has a high-side Q6H and a low-side Q6L.
  • the low-side terminal Q2L of the low-side switch Q2, the low-side terminal Q4L of the low-side switch Q4, and the low-side terminal Q6L of the low-side switch Q6 are connected to the second driving terminal 33b of the driving circuit 33, respectively.
  • the low-side Q1L of the high-side switch Q1 is connected to the high-side Q2H of the low-side switch Q3, the low-side Q3L of the high-side switch Q3 is connected to the high-side Q4H of the low-side switch Q4, and the low-side of the high-side switch Q5
  • the terminal Q5L is connected to the high-side terminal Q6H of the low-side switch Q6.
  • the low-side terminal Q1L of the high-side switch Q1 and the high-side terminal Q2H of the low-side switch Q2 are both connected to the first phase winding A.
  • the ground-side terminal Q3L of the high-side switch Q3 and the high-side of the low-side switch Q4 are high.
  • the side terminal Q4H is connected to the second phase winding B, and the ground side terminal Q5L of the high-side switch Q51 and the high-side terminal Q6H of the low-side switch Q6 are connected to the third-phase winding C.
  • the three-phase winding of the motor 34 passes the above-mentioned multiple high-side switches (high-side switch Q1, high-side switch Q3, and high-side switch Q5) and multiple low-side switches (low-side switch Q2, low-side switch Q4, and low-side switch Q5). ) Is connected to the power module 31.
  • the high-side switch and the low-side switch may be a semiconductor device, for example, a metal oxide semiconductor field effect transistor (MOSFET) or an insulated gate bipolar transistor (IGBT).
  • MOSFET metal oxide semiconductor field effect transistor
  • IGBT insulated gate bipolar transistor
  • Each high-side switch and low-side switch have a parasitic diode in parallel.
  • AH, AL, BH, BL, CH, CL are the control terminals of high-side switch Q1, low-side switch Q2, high-side switch Q3, low-side switch Q4, high-side switch Q5, and low-side switch Q6, respectively.
  • the control terminals AH, AL, BH, BL, CH, CL of the driving switch are electrically connected to the control module 32 respectively.
  • the high-side switches Q1-Q6 change the conduction state according to the control signal output by the control module 32, thereby changing the power module. 31 State of voltage applied to the windings of the brushless motor 11.
  • the high-side switch Q1 is set to turn on or cut off the electrical connection between the first-phase winding A and the positive terminal 31a of the power supply module 31, and the high-side switch Q3 is set to turn on or cut off the second-phase winding B. Electrical connection to the positive terminal 31a of the power module 31.
  • the high-side switch Q5 is set to turn on or off the electrical connection between the third phase winding C and the positive terminal 31a of the power of the power module 31.
  • the low-side switch Q2 is set to conduct.
  • the first phase winding A is electrically connected to or disconnected from the power source negative terminal 31b of the power module 31.
  • the low-side switch Q4 is set to turn on or off the second phase winding B and electrically connected to the power source negative terminal 31b of the power module 31.
  • the low-side switch Q6 is configured to turn on or cut off the electrical connection between the third-phase winding C and the negative power terminal 31b of the power module 31.
  • the power tool 10 further includes a rotor position acquisition module 35, which is connected to the motor 34 and the control module 32 and configured to acquire the position of the rotor in the motor 34.
  • the rotor position acquisition module 35 When the rotor rotates to a preset range, the rotor position acquisition module 35 is in a signal state, and when the rotor rotates out of the preset range, the rotor position acquisition module 35 switches to another signal state.
  • the rotor position acquisition module 35 includes a position sensor 351 (eg, a Hall sensor).
  • the rotor position acquiring module 35 does not include a position sensor 351, but determines the rotor position by using a back-EMF signal to perform commutation.
  • the rotor position acquiring module 35 includes a position sensor 351, and the position sensors 351 are three Hall sensors. As shown in FIG. 2, three Hall sensors are provided along the circumferential direction of the rotor of the motor 34, and the position information of the rotor detected by the Hall sensors is input to the rotor position acquisition module 35.
  • the rotor position acquiring module 35 converts the inputted rotor position into a rotor position information which can be communicated with the control module 32 through logic processing and inputs the rotor position information to the control module 32.
  • the signal of the Hall sensor changes, and the output signal of the rotor position acquisition module 35 also changes accordingly.
  • the output signal of the rotor position acquisition module 35 is defined as 1, and when the rotor turns out of the preset range, the output signal of the rotor position acquisition module 35 is defined as 0.
  • the three Hall sensors will generate a position signal including six signal combinations so that the rotor position acquisition module 35 outputs a position signal including one of the six signal combinations. If arranged in the order in which the Hall sensors are placed, six different signal combinations 100, 110, 010, 011, 001, and 101 appear. In this way, the rotor position acquisition module 35 can output one of the above six position signals, and the position of the rotor can be obtained according to the position detection signal output by the rotor position acquisition module 35.
  • a motor 34 having three-phase windings it has six driving states in one energizing cycle corresponding to the output signals generated by the above scheme. Therefore, when the output signal of the rotor position acquisition module 35 changes, the motor 34 can be Perform a commutation.
  • the driving circuit 33 In order to rotate the motor 34, the driving circuit 33 has multiple driving states. In one driving state, the stator winding of the motor 34 generates a magnetic field.
  • the control module 32 controls the driving circuit 33 to switch the driving state to rotate the magnetic field generated by the winding to drive the rotor to rotate. , And then drive the motor 34.
  • the driving circuit 33 has at least six driving states.
  • the driving state corresponding to the driving state of the driving state is shown below.
  • the driving state is AB It means that in this state, the first phase winding A and the second phase winding B are turned on, which is called AB phase conduction; if the control module 32 controls the driving circuit 33 to connect the first phase winding A to the power source 31 of the power supply module 31, Extreme terminal 31b and the second phase winding B connected to the first power terminal 31b of the power module 31, then the driving state is represented by BA.
  • the BA phase is turned on, and its current direction is opposite to that of AB.
  • the drive mode indicated in this way is also applicable to the triangular connection scheme of the winding.
  • the switching of the driving state may be simply referred to as a commutation operation of the motor 34. Obviously, each time the rotor rotates through an electrical angle of 60 °, the motor 34 is commutated once, and the interval from one commutation to the next commutation of the motor 34 is defined as a commutation interval.
  • FIG. 5 is a related art brushless motor control method.
  • the control module 32 controls the driving circuit 33 so that the driving circuit 33 sequentially outputs AB, AC, BC, BA, CA, CB six driving states.
  • the three Hall sensors detect the position of the rotor.
  • the rotor position acquisition module 35 receives the detection signals from the three Hall sensors and sends the processed signals to the control module 32.
  • the control module 32 obtains the received rotor position according to the received rotor position.
  • the output signal of the module 35 controls the driving circuit 33 and causes the driving circuit to sequentially output six driving states of AB, AC, BC, BA, CA, and CB when driving.
  • Ha, Hb, and Hc are the output signals of the rotor position acquisition module 35, which correspond to the detection signals of the three Hall sensors; PWMa, PWMb, and PWMc are a series of duty cycles sent by the control module 32 to the drive switch.
  • the pulse signal with constant ratio; Ua, Ub, Uc are the voltages between the first phase winding A, the second phase winding B, the third phase winding C and the neutral point O.
  • PWMa is a pulse signal sent by the control module 32 to the control terminal AH of the high-side switch Q1 and the control terminal AL of the low-side switch Q2 to conduct the first phase winding A and the positive terminal 31a or the negative terminal 31b of the power source. Electrical connection.
  • the control terminal AH of the high-side switch Q1 receives the pulse signal, and the high-side switch Q1 conducts the electrical connection between the first-phase winding A and the positive terminal 31a of the power source with a preset duty ratio;
  • the low-side switch Q2 conducts the electrical connection between the first-phase winding A and the negative terminal 31b of the power supply with a preset duty ratio.
  • PWMb is the pulse signal sent by the control module 32 to the control terminal BH of the high-side switch Q3 and the control terminal BL of the low-side switch Q4.
  • the control terminal BH of the high-side switch Q3 receives Pulse signal
  • the high-side switch Q3 conducts the electrical connection between the second phase winding B and the positive terminal 31a of the power source with a preset duty ratio.
  • the control terminal BL of the low-side switch Q4 receives With a pulse signal
  • the low-side switch Q4 conducts the electrical connection between the second-phase winding B and the power-source negative terminal 31a of the power-source negative terminal 31b with a preset duty ratio.
  • PWMc is a pulse signal sent from the control module 32 to the control terminal CH of the high-side switch Q5 and the control terminal CL of the low-side switch Q6.
  • the control terminal CH of the high-side switch Q5 receives the pulse signal.
  • the high-side switch Q5 conducts the electrical connection between the third-phase winding C and the positive terminal 31a of the power source with a preset duty ratio.
  • the control terminal CL of the low-side switch Q6 receives a pulse signal.
  • the low-side switch Q6 conducts the electrical connection between the third-phase winding C and the negative terminal 31 b of the power source with a preset duty ratio.
  • control module 32 detects a change in the signal of the rotor position acquisition module 35, that is, the output control driving circuit 33 switches the driving state.
  • the continuous conduction time of each phase winding (that is, the time during which the control module 32 controls the drive circuit 33 to continuously conduct the windings to be electrically connected to the power module 31) is 120 °,
  • the voltage of each phase winding varies discontinuously.
  • the back-EMF increases as the motor speed increases.
  • the back-EMF may be higher than the maximum voltage that the power module 31 and the drive circuit 33 can supply.
  • the power module 31 and the drive circuit 33 cannot supply more energy to overcome the increased back-EMF, and the motor winding cannot When enough current is obtained to overcome the stall torque, the increase in motor speed will stagnate. however.
  • the voltage of the power module 31 is low, the rotation speed and power of the motor 34 are reduced, and the output demand of the power tool cannot be met.
  • the excitation of the rotor can be controlled by controlling the phase angle of the phase current. Relative to the increased phase current of the back-EMF, the magnetic flux generated by the permanent magnet is reduced, which in turn leads to a decrease in the back-EMF that the permanent magnet can generate.
  • the physical position of the Hall sensor can be set a certain angle ahead of the ideal position. For example, when setting the Hall sensor, make the Hall sensor advance the electrical angle of these positions within the range of 20 ° to 40 °, or say, advance the physical angle of these positions within the range of 20 ° / P to 40 ° / P, where P is the motor Number of pole pairs of the rotor of 34.
  • P is the motor Number of pole pairs of the rotor of 34.
  • the motor 34 is in a heavy load state, the armature response of the motor causes the position of the Hall sensor to be advanced by a small angle, or even lag behind the rotor magnetic field, and the speed-up effect cannot be achieved.
  • the rotation speed and power of the motor 34 will be reduced, and the output demand of the electric tool 10 cannot be met.
  • the battery pack 20 that supplies power is used for a long time and the voltage is low, then the battery pack 20 with the lower voltage is used.
  • the power tool 10 When the power tool 10 is connected, it will cause the speed and power of the motor 34 to drop, which cannot meet the output requirements of the power tool 10; or because there is no high-voltage battery pack 20 nearby to adapt the power tool 10, only a lower-voltage battery pack is available When the power tool 10 is ready for connection, the power tool 10 cannot complete the expected work due to the decrease in the speed and power of the motor 34.
  • This embodiment provides a power tool compatible with multi-voltage power supply and a control method of the power tool, so that the power tool 10 can be compatible with a multi-voltage power supply module and can meet output characteristic requirements.
  • control module 32 module is configured to: when the voltage of the power module 31 is less than a preset voltage threshold, control the driving circuit 33 according to the rotation position of the rotor of the motor 34 so that the motor 34 The first-phase winding A, the second-phase winding B, and the third-phase winding C are simultaneously connected to the power module 31.
  • the power tool 10 includes a voltage detection module 38 configured to detect a voltage of the power module 31; the voltage detection module 38 is connected to the control module 32, and the control module 32 can determine whether the voltage of the power module 31 is less than the preset voltage threshold according to a detection signal of the voltage detection module 38.
  • the power tool 10 includes a current detection module 36 configured to detect a current of the motor 34; the current detection module 36 is connected to the control module 32, and the control module 32 Whether the voltage of the power module 31 is less than the preset voltage threshold can be determined according to a detection signal of the current detection module 36.
  • control module 32 may further determine whether the voltage of the power module 31 is less than or equal to a preset voltage threshold by using a motor speed detected by a rotor speed detection module (not shown). In one embodiment, when the rotation speed of the motor 34 is less than a preset threshold, the control module 32 determines that the voltage of the power module 31 is less than or equal to a preset voltage threshold. In other embodiments, the control module 32 may further determine whether the voltage of the power module 31 is less than or equal to a preset voltage threshold by using the back electromotive force of the winding of the motor 34 detected by the back electromotive force measurement module (not shown). When the back electromotive force of the motor 34 meets a preset condition, the control module 32 determines that the voltage of the power module 31 is less than or equal to a preset voltage threshold.
  • the preset voltage threshold is 0.4-0.8 times the rated voltage of the power tool.
  • the pre-voltage threshold is set to 0.5-0.75 times the rated voltage of the power tool, that is, if the voltage of the power module 31 is less than 0.5-0.75 times the rated voltage of the power tool 10
  • the control module 32 determines that the power module 31 is a low-voltage power source. At this time, the control module 32 controls the driving circuit 33 according to the rotation position of the rotor of the motor 34 so that the first phase winding A, the second phase winding B, and The third phase winding C is connected to the power module 31 at the same time.
  • the control module 32 determines that the power module 31 is a low-voltage power supply. At this time, the control module 32 controls the driving circuit 33 according to the rotation position of the rotor of the motor 34 so that the first phase winding A, the second phase winding B, and the third phase winding C are connected to the power module 31 at the same time.
  • the control module 31 still adopts the control method in the related technology (FIG. 5).
  • control module 32 selects different control methods according to the voltage of the power module 31 in different ranges, and controls the driving circuit 33 to make the first phase winding A and the second phase winding B when the power module 31 is a low voltage power source. And the third phase winding C are connected to the power module 31 at the same time.
  • the power tool uses the low-voltage power module 31 with a voltage lower than a preset voltage threshold, it can also output a voltage close to the preset voltage.
  • the motor speed and power of the threshold high-voltage power module 31 is a voltage close to the preset voltage.
  • the control module 32 is configured to control the driving circuit 33 to make the first phase winding A and the second phase winding B according to the position of the rotor.
  • the third phase winding C is connected to the power module 31 at the same time.
  • the voltage of the power module 31 is greater than or equal to 0.2 times the rated voltage of the power tool 10. In one embodiment, the voltage of the power module 31 is greater than or equal to 0.3 times the rated voltage of the power tool 10. To avoid damage to the battery pack when it is used at a lower voltage, and to avoid the battery pack voltage being too low to meet the output requirements of the power tool.
  • the driving circuit 33 when the rotor rotates to the first preset rotation position, the driving circuit 33 is controlled so that: the first phase winding is electrically connected to the positive terminal 31a of the power source, and the second phase winding is electrically connected. Connected to the power supply negative terminal 31b, the third phase winding is electrically connected to one of the power supply positive terminal 31a and the power supply negative terminal 31b; when the rotor is rotated to a second preset rotation position, control The driving circuit 33 disconnects the third phase winding from one of the power source positive terminal 31a and the power source negative terminal 31b and is electrically connected to the power source positive terminal 31a and the power source negative terminal. 31b another. It should be noted that the first phase winding, the second phase winding, and the third phase winding are not limited to a one-to-one correspondence with the first phase winding A, the second phase winding B, and the third phase winding C.
  • the following description is made by taking the first phase winding, the second phase winding, and the third phase winding corresponding to the first phase winding A, the second phase winding B, and the third phase winding C as examples.
  • control module 31 as a controller of the three different embodiments controls the driving circuit 33 according to the rotation position of the rotor so that the first phase winding A and the second phase winding B
  • the third phase winding C is connected to the power module 31 at the same time.
  • control module 32 is configured to:
  • the zero position is used as the first preset rotation position.
  • the control module 32 controls the driving circuit 33 so that the first phase winding (first Phase winding A) is electrically connected to the positive power terminal 31a of the power module 31, and at the same time, a second phase winding (second phase winding B) is electrically connected to the negative terminal 31b of the power supply, so that the third phase winding (first The three-phase winding C) is electrically connected to one of the power source positive terminal 31a and the power source negative terminal 31b.
  • the third phase winding when the rotor is rotated to the first preset rotation position (zero position), the third phase winding (third phase winding C) is electrically connected to the positive pole of the power source. 31a.
  • the control module 32 controls the driving circuit 33 so that the third-phase winding (third-phase winding C) moves from the positive terminal 31a of the power source to the One of the power source negative terminal 31b is electrically disconnected and electrically connected to the other of the power source positive terminal 31a and the power source negative terminal 31b.
  • the third-phase winding (third-phase winding C) is electrically disconnected from the positive terminal 31a of the power source. And it is electrically connected to the power source negative terminal 31b.
  • the control module 32 controls the driving circuit 33 so that the first-phase winding (first-phase winding A) is moved from the positive terminal 31a of the power source. Disconnect and electrically connect to the negative terminal 31b of the power source or disconnect the second phase winding (second phase winding B) from the negative terminal 31 of the power source and electrically connect to the positive terminal 31a of the power source .
  • first-phase winding first-phase winding A
  • second phase winding second phase winding
  • the control module 32 controls the driving circuit 33 to make the second phase winding (
  • the second phase winding B) is electrically disconnected from the negative terminal 31 of the power source and is electrically connected to the positive terminal 31a of the power source.
  • the control module 32 controls the driving circuit 33 so that the third phase winding (third The voltage of the phase winding C) changes at least in part with the change of the rotation position of the rotor at a preset change rate.
  • the change rate in this embodiment refers to the speed of the change.
  • the control module 32 controls the driving circuit 33 so that the driving circuit 33
  • the rate of change of the voltage (Uc) of the third-phase winding (third-phase winding C) remains the same, but the magnitude of the voltage (Uc) of the third-phase winding (third-phase winding C) changes and rotates from the first preset
  • the positive maximum value of the position (zero position) gradually decreases to a zero value of the second preset rotation position (L1) according to a preset change rate.
  • the control module 32 controls the driving circuit 33 so that the voltage (Uc) of the third-phase winding (third-phase winding C) changes at a changing rate following a change in the rotational position of the rotor.
  • the control module 32 controls the driving circuit 33 to make the The voltage (Uc) of the third-phase winding (the third-phase winding C) changes at a decreasing rate following the change in the rotational position of the rotor.
  • the rate of change of the voltage (Uc) of the third-phase winding (third-phase winding C) gradually decreases, and the magnitude gradually decreases from the positive maximum value of the first preset rotation position (zero position) to the second preset rotation Zero value for position (L1).
  • the control module 32 controls the driving circuit 33 to make the The voltage (Uc) of the third-phase winding (third-phase winding C) changes at a gradually increasing rate following a change in the rotation position of the rotor.
  • the rate of change of the voltage (Uc) of the third-phase winding (third-phase winding C) gradually increases, and the magnitude gradually decreases from the positive maximum value of the first preset rotation position (zero position) to the second preset rotation Zero value for position (L1).
  • control module 32 controls the driving circuit 33 to be implemented as follows:
  • the control module 32 controls the driving circuit 33 so that The voltage (Uc) of the third-phase winding (third-phase winding C) changes at a preset change rate following a change in the rotational position of the rotor, and remains unchanged after reaching the maximum negative voltage.
  • the voltage (Uc) is changed until the rotor rotates to the third preset rotation position (L2).
  • the preset duration is a time during which the rotor is rotated by 30 ° electrical angle.
  • the control module 32 controls the driving circuit 33 so that the voltage (Uc) of the third-phase winding (third-phase winding C) changes at least in part with one of a gradually increasing change rate and a gradually decreasing change rate following a change in the rotation position of the rotor ;
  • the control module 32 controls the driving circuit 33 so that the third phase winding (third The voltage (Uc) of the phase winding C) changes at least in part with a gradually increasing rate of change and a decreasing rate of change following the change in the rotational position of the rotor.
  • the control module 32 controls the driving circuit 33 so that the third phase winding (third The voltage (Uc) of phase winding C) changes at a decreasing rate following the change of the rotation position of the rotor; when the rotor is located between the second preset rotation position (L1) and the third preset rotation position (L2) Over time, the control module 32 controls the driving circuit 33 so that the voltage (Uc) of the third-phase winding (the third-phase winding C) first follows the changing position of the rotor at a gradually increasing rate.
  • the control module 32 controls the driving circuit 33 so that the third phase winding (winding C The voltage (Uc) of) changes at a gradually increasing rate following the change of the rotation position of the rotor; when the rotor is located between the second preset rotation position (L1) and the third preset rotation position (L2), The control module 32 controls the driving circuit 33 so that the voltage (Uc) of the third-phase winding (the third-phase winding C) changes at a decreasing rate following a change in the rotational position of the rotor.
  • the rate of change of the voltage (Uc) of the third phase winding (third phase winding C) gradually decreases, and the magnitude gradually increases from the zero value of the second preset rotation position (L1) until it reaches a negative maximum value. After the voltage (Uc) of the three-phase winding (third-phase winding C) reaches a negative maximum value, it remains unchanged until the rotor rotates to a third preset rotation position (L2).
  • the control module 32 controls the driving circuit 33 to make the third phase winding ( At least part of the voltage (Uc) of the third phase winding C) remains unchanged.
  • the above-mentioned embodiment is only one position interval in one cycle. In other position intervals of one cycle, the control mode of the control module 32 is similar to the above-mentioned embodiment.
  • the implementation of the first phase winding, the second phase winding, and the third phase winding does not correspond to the first phase winding A, the second phase winding B, and the third phase winding C, and the rotor position is in another position interval within the above period. The method is described as an example.
  • the control module 32 controls the driving circuit 33 so that the first phase winding (first phase winding A) Is electrically connected to the positive terminal 31a of the power supply module 31, and at the same time, the second phase winding (third phase winding C) is electrically connected to the negative terminal 31b of the power supply, so that the third phase winding (second phase winding B) ) Is electrically connected to one of the power source positive terminal 31a and the power source negative terminal 31b.
  • the control module 32 controls the driving circuit 33 to electrically connect the third phase winding (second phase winding B) to the Power source negative terminal 31b.
  • the control module 32 controls the driving circuit 33 so that the third-phase winding (second-phase winding B) moves from the positive terminal 31a and the negative terminal 31b of the power source. One of them is electrically disconnected and electrically connected to the other of the power source positive terminal 31a and the power source negative terminal 31b.
  • the control module 32 controls the driving circuit 33 to make the third phase winding (second The phase winding B) is electrically disconnected from the negative terminal 31b of the power source and is electrically connected to the positive terminal 31a of the power source.
  • the control module 32 controls the driving circuit 33 to disconnect the first-phase winding (first-phase winding A) from the positive terminal 31a of the power source. Electrically and electrically connected to the negative terminal 31b of the power source or disconnecting the second phase winding (third phase winding C) from the negative terminal 31b of the power source and electrically connected to the positive terminal 31a of the power source.
  • first-phase winding first-phase winding A
  • second phase winding third phase winding C
  • the control module 32 controls the driving circuit 33 to make the first phase winding (first phase winding A)
  • the electrical connection is disconnected from the power source positive terminal 31a and is electrically connected to the power source negative terminal 31b.
  • the control module 32 controls the driving circuit 33 so that the third phase winding (second phase The voltage (Ub) of the winding B) changes at least in part with the change of the rotation position of the rotor at a preset change rate.
  • the control module 32 controls the driving circuit 33 so that the first The voltage (Ub) of the three-phase winding (second phase winding B) first maintains the negative maximum value unchanged for a preset period of time, and then gradually decreases from the negative maximum value to zero until the rotor rotates to the third preset rotation. It becomes zero at the position (L3).
  • the preset duration is a time during which the rotor rotates through an electrical angle of 30 °.
  • the control module 32 controls the driving circuit 33 so that the first The voltage (Ub) of the three-phase winding (winding B) first maintains the negative maximum value for a preset period of time, and then changes at a decreasing rate following the change in the rotational position of the rotor.
  • the rate of change of the voltage (Ub) of the second phase winding B) gradually decreases to a zero value of the second preset rotation position (L2).
  • the preset duration is a time during which the rotor rotates through an electrical angle of 15 °.
  • the control module 32 controls the driving circuit 33 so that the first The voltage (Ub) of the three-phase winding (second phase winding B) changes at a gradually increasing rate following a change in the rotation position of the rotor.
  • the rate of change of the voltage Uc of the third-phase winding (third-phase winding C) gradually increases, and the magnitude gradually decreases from the positive maximum value of the first preset rotation position (zero position) to the second preset rotation position ( L1).
  • control module 32 controls the driving circuit 33 to be implemented as follows:
  • the control module 32 controls the driving circuit 33 so that The voltage (Ub) of the third-phase winding (second-phase winding B) starts from the zero value of the second preset rotation position (L2), and first follows the rotor at a preset change rate within a preset duration.
  • the rotation position changes until it reaches the maximum forward voltage and remains unchanged until the rotor rotates to the third preset rotation position (L3).
  • the preset duration is a time during which the rotor rotates through an electrical angle of 30 °.
  • the control module 32 controls the driving circuit 33 so that the voltage (Ub) of the third phase winding (second phase winding B) changes at least in part with one of a gradually increasing rate of change and a decreasing rate of change following the change in the rotational position of the rotor ;
  • the control module 32 controls the driving circuit 33 so that the third phase winding (second phase winding The voltage (Ub) of B) changes at least in part with a gradually increasing rate and a decreasing rate of change following the change in the rotational position of the rotor.
  • the control module 32 controls the driving circuit 33 to make the third phase winding (
  • the voltage (Ub) of the second-phase winding B) first changes with the rotor's rotational position at a gradually increasing rate within a preset period of time until the positive maximum value is reached in the third-phase winding (second-phase winding).
  • the preset time is the time for the rotor to rotate through 45 ° electrical angle.
  • the control module 32 controls the driving circuit 33 to make the third phase
  • the voltage (Ub) of the winding (second phase winding B) changes with a decreasing rate of change within a preset period of time and follows the change in the rotational position of the rotor until it reaches a positive maximum value and remains unchanged until the rotor rotates to
  • the voltage (Ub) of the third phase winding (second phase winding B) gradually increases from the zero value of the second preset rotation position (L2) to the maximum forward voltage,
  • the preset duration is a time during which the rotor rotates through an electrical angle of 30 °.
  • the control module 32 controls the driving circuit 33 to make the third phase winding ( At least part of the voltage (Ub) of the second phase winding B) remains unchanged.
  • This embodiment also provides a method for controlling a power tool. As shown in FIG. 11, the method is a method for controlling the driving circuit 33 by the control module 32 of this embodiment, and includes the following steps:
  • the above embodiment is only a position interval in one cycle.
  • the control module 32 controls the driving circuit 32 according to the rotation position of the rotor of the motor 34 so that the first The one-phase winding, the second-phase winding, and the third-phase winding are connected to the power module 31 at the same time.
  • control method of another form of electric tool is that the control module 32 controls the driving circuit 32 so that the first phase winding
  • a method for simultaneously connecting the second phase winding and the third phase winding to the power module 31 includes the following steps:
  • the voltage of the power module is obtained, and when the voltage of the power module is less than or equal to a preset voltage threshold, the first phase winding A, the second phase winding B, and the third phase winding B are simultaneously connected to all the The power source positive terminal 31a or the power source negative terminal 31b is described.
  • the rotation position of the rotor is obtained.
  • the first one of the first-phase winding A, the second-phase winding B, and the third-phase winding C is positively driven from the power source.
  • the extreme terminal 31 or the negative electrode terminal 31b of the power supply is disconnected and connected to the other of the positive electrode terminal 31a and the negative electrode terminal 31b of the power supply; when the rotor is rotated to the second preset position, the first phase winding A and the second phase winding B.
  • the second one of the third phase winding C is disconnected from the power positive terminal 31a or the power negative terminal 31b and connected to the other of the power positive terminal 31a and the power negative terminal 31b; when the rotor rotates to the third preset position When disconnecting the third of the first phase winding A, the second phase winding B, and the third phase winding C from the power source positive terminal 31a or the power source positive terminal 31a and connecting to the power source positive terminal 31a and the power source The other of the negative terminal 31b.
  • control module 32 controls each of the phases of the windings and the power supply module by controlling the driving circuit 33 during one period of the rotor rotation (the rotor rotates through 360 ° electrical angle)
  • the specific steps of the electrical connection control method of 31 are as follows:
  • the first phase winding A and the third phase winding C are connected to the power source positive terminal 31a, and the second phase winding B is connected to the power source positive terminal 31a.
  • the continuous conduction time or continuous conduction angle of each phase winding is increased to 180 °, which improves the motor output performance, so that the power tool 10 can reach even if the low-voltage power module 31 is used below a preset voltage threshold. Or basically reach the output speed and power of the power tool using the power module 31 that is higher than the preset voltage threshold.
  • control mode of the control module 32 for controlling the electrical connection between each phase winding and the power supply module 31 is only for one cycle of the rotor rotation, which is not limited herein.
  • control module 32 outputs the PWM signal to the driving circuit 33 to realize that the first phase winding A, the second phase winding B, and the third phase winding C are connected to the power module 31 at the same time.
  • the driving circuit 33 includes a driving switch, and the driving switch can conduct the electrical connection between the third-phase winding and the power module with a preset duty ratio under the control of the control module 32.
  • the control module 31 controls the driving switch to turn on the third-phase winding (the first-phase winding) in the above-mentioned embodiment with a duty ratio that is at least partially changed.
  • A, one of the second phase winding B and the third phase winding C) are electrically connected to the power module 31.
  • the above-mentioned duty ratio can be obtained by looking up a table, or by calculating.
  • the changing duty cycle includes a duty cycle with a constant rate of change and a duty cycle with a changing rate of change.
  • the first phase winding A is taken as an example to illustrate that during one period of the rotor rotation (that is, the rotor rotates through 360 ° electrical angle), the control module 32 controls the driving circuit 33 so that the three-phase winding is connected to the power module 31 at the same time At this time, the control module 32 outputs a PWM signal to the driving circuit 33 to control the control mode of each phase winding.
  • the control module 32 controls the driving circuit 33 to work as follows:
  • the control module 32 controls the high-side switch Q1 in the driving circuit 33 to first conduct the first-phase winding A and the power supply positive with a preset duty ratio.
  • the control module 32 controls the high-side switch Q1 to conduct the first-phase winding with a gradually increasing duty cycle.
  • the electrical connection between the first phase winding A and the positive terminal 31a of the power supply is conducted with a certain duty ratio.
  • the duty ratio may be gradually increased or decreased with the rotation position of the rotor according to a constant rate of change, or may be gradually increased or decreased with the rotation position of the rotor according to the changed rate of change.
  • the change of the duty cycle, the preset rotation position is different, the preset duty cycle, etc. need to be set according to the application situation and specific conditions of the power tool to match the application characteristics of different power tools .
  • the control module 32 controls the high-side switch Q1 and the low-side switch Q2 during one period of the rotor rotation as follows:
  • the control module 32 controls the high-side switch Q1 to preset
  • the duty cycle (for example, 80%) conducts the electrical connection between the first-phase winding A and the positive terminal 31a of the power source; when the rotor rotates at an angular position L11 of 45 °, the control module 32 controls the proportion of the high-side switch Q1 to be turned on.
  • the decreasing rate of the air-to-air ratio gradually decreases; when the rotor rotates to an angular position L12 of 90 °, the duty cycle is reduced to 0%, and the control module 32 controls the duty cycle of the low-side switch Q2 to be turned on.
  • the control module 32 controls the low-side switch Q2 to be turned on
  • the duty cycle of the constant duty cycle remains unchanged; when the rotor rotates to an angular position L14 of 225 °, the control module 32 controls the duty cycle that the low-side switch Q2 is turned on to gradually decrease at a decreasing rate of change ;
  • the duty cycle is reduced to 0%, and the control module 3 2
  • the duty cycle that controls the high-side switch Q1 to turn on gradually increases with a gradually increasing rate of change; when the rotor rotates to an angular position L16 of 315 °, the duty cycle increases to a preset duty cycle (80% ),
  • the control module 32 controls the duty ratio that the high-side switch Q1 is turned on to keep the preset duty ratio unchanged.
  • the control module 32 controls the high-side switch Q1 and the low-side switch Q2 during one period of the rotor rotation as follows:
  • the control module 32 controls the high-side switch Q1 to preset
  • the duty cycle (for example, 100%) turns on the electrical connection between the first-phase winding A and the positive terminal 31a of the power source; when the rotor rotates to an angular position L21 of 60 °, the control module 32 controls the high-side switch Q1 to be turned on.
  • the duty cycle is gradually reduced at a gradually increasing rate of change; when the rotor is rotated to an angular position L22 of 90 °, the duty cycle is reduced to 0%, and the control module 32 controls the duty cycle that the low-side switch Q2 is turned on to The gradually smaller rate of change gradually increases; when the rotor rotates to an angular position L23 of 120 °, the duty cycle increases to a preset duty cycle, and the control module 32 controls the duty cycle of the low-side switch Q2 to remain on The preset duty ratio does not change; when the rotor rotates to an angular position L24 of 240 °, the control module 32 controls the duty ratio at which the low-side switch Q2 is turned on to gradually decrease at a gradually increasing rate; when the rotor rotates to When the angular position L25 is 270 °, the duty cycle is reduced to 0%, and the control module 32 controls the high The duty cycle when the side switch Q1 is turned on gradually increases at a decreasing rate of change; when the rotor rotate
  • Figure 6a shows the control method in the related art.
  • the continuous conduction current angle of the first phase winding A is 120 °
  • Figure 6b and Figure 6c is two implementations of the control method of this embodiment.
  • the first phase winding A is continuously turned on for 180 ° during one period of rotor rotation.
  • the continuous conduction time of each drive switch is an angle of 180 °, so that the continuous conduction time of each phase winding is increased to 180 ° angle.
  • the above electric tool and its control method improve the efficiency of the motor. It should be noted that the above-mentioned embodiment is only a description of the control method in one cycle of the rotor rotation, and is not limited herein.
  • control module 32 further includes a timing unit, a computing unit configured to process data, and a storage unit configured to store.
  • the calculation unit is configured to calculate a rotor position (that is, an angle through which the rotor rotates) according to a position signal sent by the rotor position acquisition module 35.
  • the storage unit stores the rotor position (that is, the angle through which the rotor is turned), and the above-mentioned control module 32 controls the duty cycle at which each drive switch in the drive circuit 33 is turned on, and establishes the duty cycle at which each drive switch is turned on and the rotor position Correspondence table.
  • the corresponding control signal is output, so that each drive switch works according to the corresponding on-duty ratio, so that the voltage of the three-phase winding can be changed with the rotation position of the rotor according to a preset change rule.
  • the calculation unit is configured to calculate a rotation position of the rotor (that is, an angle through which the rotor rotates) according to a position signal sent by the rotor position acquisition module 35.
  • the storage unit stores the rotational position of the rotor and the duty ratio at which the control module 32 controls each drive switch in the drive circuit 33 to establish a corresponding functional relationship between the duty ratio at which each drive switch is turned on and the rotor position.
  • the calculation unit is further configured to calculate the duty cycle that each drive switch should be turned on next time according to the calculated functional position of the rotor and the corresponding functional relationship between the on-duty of each drive switch and the rotation position of the rotor. ratio.
  • the timing unit records a time when the rotor rotates, and establishes a correspondence table between time data and angle data. Assuming that the time when the rotor rotates through ⁇ angle is t, the next rotation position of the rotor can be determined according to the time when the rotor rotates.
  • the preset duration in the foregoing embodiment may be implemented according to the timing time of the timing unit.
  • all preset positions in the control method can be moved forward or backward simultaneously.
  • the high-side switch Q1 of the control module 32 is changed from the originally preset duty cycle to a gradually reduced duty cycle.
  • the first preset position in FIG. 8 is moved forward or backward simultaneously.
  • the 7c can be moved forward by an angle of ⁇ (for example, 15 °), so that when the rotor is turned to the first preset position (60 ° - ⁇ , for example, 35 °)
  • the high-side switch Q1 of the control module 32 changes from the originally preset duty cycle to a gradually decreasing duty cycle.
  • the second preset position, the third preset position, the fourth preset position, the fifth preset position, and the sixth preset position all need to be moved forward by an angle of ⁇ at the same time.
  • the ⁇ angle is set according to the specific application to obtain better motor output characteristics.
  • the angle ⁇ ranges from -60 ° to + 10 °, where "-" indicates that all preset positions are moved forward simultaneously, for example, "-60 °” indicates that all preset positions are moved forward by 60 ° simultaneously; "+” Means that all preset positions are moved backward at the same time. For example, “+ 10 °” means that all preset positions are moved backward by 10 ° at the same time.
  • the power tool 10 that requires power from the battery pack 20 with a high voltage (rated voltage) can be connected to a low voltage (rated Voltage) battery pack 20 can also meet the output characteristics requirements; on the other hand, the performance of the power tool 10 connected to the low voltage battery pack 20 is close to the power tool 10 connected to the high voltage battery pack 20, so that The output performance of the power tool 10 connected to the low-voltage battery pack 20 is improved. That is, when the power tool 10 is connected to the battery pack 20 of the first voltage, the motor 34 outputs the first output power and the first rotation speed.
  • the motor 34 outputs at least one of a second speed close to the first speed and a second power close to the first output power.
  • the second voltage and the first voltage are batteries.
  • the rated voltage of the bag, and the second voltage is less than the first voltage. That is to say, by using the above method, the output rotational speed and output power of the motor of the power tool 10 are increased.
  • the above solution achieves speed increase by increasing the continuous conduction time or continuous conduction electrical angle of each phase winding, increasing the motor speed of the power tool, and making the performance of the low-voltage power tool close to that of the high-voltage power tool.
  • high-voltage power tools can also meet the output characteristics requirements when they are powered by low-voltage power modules.
  • low-voltage power modules can be used as backup power modules for high-voltage power tools, that is, the same voltage can be used.
  • Power modules for example, battery packs
  • Power modules are applied to power tools with different output requirements, thereby increasing the utilization rate of power modules; in addition, by improving the output performance of power tools, the same power tool can be adapted to power modules with different voltages, And according to the use occasions and needs of different electric tools, different motor characteristic curves can be configured to improve the working efficiency and effect of electric tools.
  • FIG. 9 is an output characteristic curve of a power tool with a rated voltage of 48V, where a curve is the output characteristic curve (speed-torque relationship diagram) of the power tool when the power tool is powered by a low voltage battery pack (24V), and the c curve It is the output characteristic curve (speed-torque relationship diagram) of a power tool powered by a high voltage battery pack (48V), and the b curve is the power tool when the above control method is adopted when the power tool is powered by a low voltage battery pack (24V).
  • the output characteristic curve (speed-torque relationship diagram) of the b curve approximates the c curve. Therefore, by adopting the above-mentioned control method, when a high-voltage power supply power tool is powered by a low-voltage power supply, its output characteristics are similar to those of a high-voltage power supply, which can meet the demand.
  • Figures 10a, 10b, and 10c are comparison graphs of the speed of different types of electric motors, where the abscissa is the torque T, the unit is N.mm, the ordinate is the speed n, the unit is rpm, and the dashed line indicates the speed of the relevant power tool
  • the change curve of n with torque T, the solid line represents the change curve of the rotation speed n of torque of the electric tool using the above scheme. It can be seen from Figs. 10a, 10b, and 10c that the power tool adopting the above scheme has a higher rotation speed than the power tool in the related art under heavy load. At the same time, using the above scheme, different motor output characteristic curves can be configured.
  • the electric tool shown in FIG. 10b may be an impact drill with a rotation speed and an impact frequency. After adopting the above scheme, corresponding the rotation speed to an appropriate impact frequency can effectively improve the impact efficiency and impact performance of the whole machine.
  • the electric tool shown in Figure 10c can be a snowplow. After the above solution is adopted, a constant low speed can be used when there is less snow and light load to save energy and increase battery life. As the amount of snow throws increases, the load When increasing, increase the speed of the motor to speed up the snow throwing speed and avoid snow accumulation in the machine cavity.
  • the power tool provided in this embodiment improves the compatibility of multi-voltage power supply, so that the power tool can adapt to different power supply voltages and can meet the output characteristic requirements.
  • Power tools are not limited to the above devices. Hair dryers, impact drills, snowplows, electric circular saws, jigsaws, miter saws, reciprocating saws, angle grinders, cutters, and lawn mowers can be used with brushless motors The above scheme.

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Abstract

一种电动工具，包括：功能件,设置为实现所述电动工具的功能；电机，设置为驱动所述功能件；所述电机包括转子、第一相绕组、第二相绕组和第三相绕组；驱动电路，电连接至所述第一相绕组、第二相绕组和第三相绕组，并设置为驱动所述电机以输出动力；电源模块，电连接至所述驱动电路，设置为通过所述驱动电路为所述第一相绕组、第二相绕组和第三相绕组供电；及控制模块，与所述驱动电路连接，设置为输出控制信号控制所述驱动电路；所述控制模块被配置为：在所述电源模块的电压小于等于预设电压阈值时，根据所述电机的转子的转动位置控制所述驱动电路以使所述第一相绕组、第二相绕组和第三相绕组同时连接至所述电源模块。

Description

电动工具及其控制方法
本申请要求申请日为2018年6月29日、申请号为201810699098.2的中国专利申请的优先权，该申请的全部内容通过引用结合在本申请中。
技术领域
本申请涉及电动工具，例如涉及一种电动工具及其控制方法。
背景技术
电动工具包括无刷电机和功能附件，通过无刷电机的转动带动功能附件工作以实现功能附件的功能。
无刷电机一般由电机本身和相应的驱动电路组成，相比于有刷电机，无刷电机运转噪音低且寿命更长。一般而言，按照是否具有检测转子位置的传感器来区分，无刷电机分为有感控制的无刷电机和无感控制的无刷电机。位置传感器的设置及位置传感器与控制方法的配合是影响无刷电机性能的重要因素。
电动工具按照电源不同可分为交流电动工具和直流电动工具。对于直流无刷电动工具而言，一般来说，根据电机的输出特性不同，需要适配的电源模块的规格不同，尤其是对于使用电池包的电动工具，在一些情况下，若供电的电池包因使用时间较长致使电压过低，会导致电机转速下降，不能满足输出需求；或者附近没有适配的电池包而使电动工具无法完成预期工作。
发明内容
本申请提供了一种电动工具及其控制方法，能够兼容多电压供电且能满足输出特性需求。
一种电动工具，包括：功能件,设置为实现所述电动工具的功能；电机，设置为驱动所述功能件；所述电机包括转子、第一相绕组、第二相绕组和第三相绕组；驱动电路，电连接至所述第一相绕组、第二相绕组和第三相绕组，并设置为驱动所述电机以输出动力；电源模块，电连接至所述驱动电路，设置为通过所述驱动电路为所述第一相绕组、第二相绕组和第三相绕组供电；及控制模块，与所述驱动电路连接，设置为输出控制信号控制所述驱动电路；所述控制模块被配置为：在所述电源模块的电压小于等于预设电压阈值时，根据所述 电机的转子的转动位置控制所述驱动电路以使所述第一相绕组、第二相绕组和第三相绕组同时连接至所述电源模块。
一实施例提供了一种电动工具的控制方法，所述电动工具包括：电机，所述电机包括转子、第一相绕组、第二相绕组和第三相绕组；及电源模块，包括电源正极端和电源负极端，所述电源模块设置为使所述电源正极端和电源负极端之间产生电势差；
所述控制方法包括：获取所述电源模块的电压；及在所述电源模块的电压小于等于预设电压阈值时，获取所述转子的转动位置，其中，当所述转子转动至第一预设转动位置时，将所述第一相绕组电连接至所述电源正极端，所述第二相绕组电连接至所述电源负极端，所述第三相绕组电连接至所述电源正极端和所述电源负极端中的一个；当所述转子转动至第二预设转动位置时，将所述第三相绕组从所述电源正极端和所述电源负极端中的一个断开电连接并电连接至所述电源正极端和所述电源负极端中的另一个。
一实施例提供了一种电动工具的控制方法，所述电动工具包括：电机，所述电机包括转子、第一相绕组、第二相绕组和第三相绕组；及电源模块，包括电源正极端和电源负极端，所述电源模块使所述电源正极端和电源负极端之间产生电势差；
所述控制方法包括：
获取所述电源模块的电压；
在所述电源模块的电压小于等于预设电压阈值时，将所述第一相绕组、第二相绕组及第三相绕组同时连接至所述电源正极端或电源负极端；及
获取所述转子的转动位置，其中，在所述转子转动至一个预设位置时，使所述第一相绕组、第二相绕组及第三相绕组中的一个从所述电源正极端或电源负极端断开并连接至所述电源正极端和电源负极端中的另一个。
附图说明
图1是一实施例提供的电动工具的结构示意图；
图2是图1所示的电动工具的电机驱动系统的电路框图；
图3是电动工具中的驱动电路的电路图；
图4是电动工具中位置传感器信号与信号区间的对应关系示意图；
图5是相关技术中的电动工具中无刷电机的控制方法；
图6a、图6b、图6c是不同实施例的无刷电机的每相电压与转子位置的对应关系的曲线图；
图7a是相关技术中的电动工具中无刷电机的第一相绕组A的控制信号、第一相绕组A的电压与转子位置的对应关系图；
图7b是电动工具中无刷电机的第一相绕组A的控制信号、第一相绕组A的电压与转子位置的对应关系的一个实施例的关系图；
图7c是电动工具中无刷电机的第一相绕组A的控制信号、第一相绕组A的电压与转子位置的对应关系的另一个实施例的关系图；
图8是相位调节前后无刷电机的第一相绕组A的电压与转子位置对应关系的一个实施例的曲线图；
图9是额定电压为48V的电动工具在使用不同电压的电池包时的输出特性曲线；
图10a、图10b及图10c是相关技术中的电动工具与本申请的不同实施例的电动工具的转速对比曲线图；
图11为一实施例提供的电动工具的控制方法的流程图；
图12为一实施例提供的电动工具的另一种控制方法的流程图。
具体实施方式
本实施例的电动工具可以为手持式电动工具、花园类工具或花园类车辆，如车辆型割草机，在此并非有所限制。本实施例的电动工具10包括但不限于以下内容：螺丝批、电钻、扳手及角磨等需要调速的电动工具，砂光机等可能用来打磨工件的电动工具，往复锯、圆锯、曲线锯等可能用来切割工件；电锤等可能用来做冲击使用的电动工具。这些工具也可能是园林类工具，比如修枝机、链锯或车辆型割草机；另外这些工具也可能作为其它用途，比如搅拌机。
参照图1，电动工具10包括：壳体11、功能件12及电机34。壳体11构成电动工具10的主体部分，设置为容纳电机34。壳体11的一端还设置为安装功能件12。
功能件12设置为实现电动工具10的功能，例如打磨及切削等。图1所示的电动工具10以手持式电钻为例，功能件12为钻头。功能件12可操作地与电机34连接，例如，通过工具附件轴与电机34连接。
电机34，设置为驱动功能件12，从而带动功能件12工作，为功能件12提供动力。参照图3，电机34为无刷电机，具体而言，电机34包括转子以及第一相绕 组A、第二相绕组B和第三相绕组C。电机34还包括电机轴及定子，电机轴可操作地与功能件12连接，例如，通过传动装置连接电机轴以及支撑功能件的工具附件轴，将电机轴的驱动力传递至工具附件轴，从而使安装在工具附件轴上的功能件12工作。
电源模块设置为为电动工具10提供电能。在本实施例中，电动工具10使用直流电源供电，更具体地，电动工具10使用电池包20供电。电动工具10包括设置为容纳电池包20的容纳部或电池包连接界面16，电池包连接界面16设置为容纳具不同电压的电池包20，或设置为连接具不同电压的电池包20。电池包20包括电池22和壳体21。电池22容纳在壳体21中，设置为存储能量，能被反复充放电。壳体21设置为容纳电池包20中的电池22以及其他部件，并且壳体形成有结合部23。在本实施例中，所述的电池包20适用于电动工具10，可以作为电动工具10的动力源使用。电池包20还包括多个电极连接端子，它们至少使电池22与外部的电路构成电性连接。
在一实施例中，电动工具10可同时使用多个电池包20供电，在一实施例中，电动工具10仅可使用一个电池包20供电，在此并不对电动工具10所使用的电池包20的数量加以限制。
电动工具10的运行还依赖于电路系统。参照图2，在一实施例中，电动工具的电机驱动系统30包括：电源模块31、控制模块32、驱动电路33及电机34。电源模块31为电动工具10提供电能，如图3所示，电源模块31包括电源正极端31a和电源负极端31b，电源正极端31a具体为电源模块31的电源正极端，电源负极端31b具体为电源模块31的电源负极端，电源模块31使得电电源正极端31a和电源负极端31b之间产生电势差。在本实施方式中，使用电池包20作为电源模块31。在其他实施方式中，电源模块31还可以是交流电源以及整流、滤波等电路。电源模块31电连接至所述驱动电路34，通过所述驱动电路为所述电机34供电。参照图3，电源模块31通过驱动电路34为电机34的所述第一相绕组A、第二相绕组B和第三相绕组C供电。
在一实施例中，如图2所示，电动工具10还包括控制模块供电电路37，控制模块供电电路37与电源模块31和控制模块32电性连接，控制模块供电电路37将来自电源模块31的电能转换成供控制模块32使用的电能。控制模块32电连接至驱动电路33，用以输出驱动信号控制所述驱动电路33工作。在一些实施例中，控制模块32采用专用的控制芯，例如，微控制模块(MCU，Microcontroller Unit)。 控制芯片32内部包括功率驱动单元(未示出)，利用功率驱动单元提升控制模块32输出信号的驱动能力，所述功率驱动单元也可采用外置式的功率驱动单元实现。
驱动电路33与电机34连接，以驱动电机34工作.电机34可以是无刷电机，也可以是有刷电机，下面以电机34为例说明本申请的方案。参照图3，在一实施例中，电机34包括多相绕组，在一实施例中，电机34包括第一相绕组A、第二相绕组B和第三相绕组C，驱动电路33电连接至所述电机34的所述第一相绕组、第二相绕组和第三相绕组，驱动电路33设置为驱动所述电机34输出动力。驱动电路33包括：第一驱动端33a，第一驱动端33a用于与电源模块31的电源正极端31a电连接；第二驱动端33b，设置为与电源模块31的电源负极端31b电连接。驱动电路33还包括驱动开关，所述驱动开关包括：多个高侧开关及多个低侧开关，所述高侧开关的高侧端分别电性连接至所述第一驱动端33a；所述低侧开关的低侧端分别电性连接至所述第二驱动端33b。
电源模块31电连接至所述驱动电路33，设置为通过所述驱动电路33为所述电机的所述第一相绕组A、第二相绕组B和第三相绕组C供电。
在一实施例中，如图3所示，驱动开关包括多个高侧开关及多个低侧开关，所述的多个高侧开关为图3中的高侧开关Q1、高侧开关Q3及高侧开关Q5，多个高侧开关均具有高侧端和低侧端，高侧开关Q1具有高侧端Q1H和低侧端Q1L，高侧开关Q3具有高侧端Q3H和低侧端Q3L，高侧开关Q5具有高侧端Q5H和低侧端Q5L。高侧开关Q1的高侧端Q1H、高侧开关Q3的高侧端Q3H、高侧开关Q5的高侧端Q5H均分别连接至驱动电路33的第一驱动端33a。
在一实施例中，如图3所示，所述的多个低侧开关为图3中的低侧开关Q2、低侧开关Q4和低侧开关Q6，多个低侧开关也均具有高侧端和低侧端。低侧开关Q2具有高侧端Q2H和低侧端Q2L，低侧开关Q4具有高侧端Q4H和低侧端Q4L，低侧开关Q6具有高侧端Q6H和低侧端Q6L。低侧开关Q2的低侧端Q2L、低侧开关Q4的低侧端Q4L、低侧开关Q6的低侧端Q6L均分别连接至驱动电路33的第二驱动端33b。
上述高侧开关Q1的低侧端Q1L与低侧开关Q3的高侧端Q2H连接，高侧开关Q3的低侧端Q3L与低侧开关Q4的高侧端Q4H连接，高侧开关Q5的低侧端Q5L与低侧开关Q6的高侧端Q6H连接。
在一实施例中，高侧开关Q1的低侧端Q1L和低侧开关Q2的高侧端Q2H均连接至第一相绕组A，高侧开关Q3的地侧端Q3L和低侧开关Q4的高侧端Q4H均连接至第 二相绕组B，高侧开关Q51的地侧端Q5L和低侧开关Q6的高侧端Q6H均连接至第三相绕组C。电机34的三相绕组通过上述多个高侧开关(高侧开关Q1、高侧开关Q3及高侧开关Q5)和多个低侧开关(低侧开关Q2、低侧开关Q4及低侧开关Q5)组成的电桥与电源模块31相连接。上述高侧开关和低侧开关可以是半导体器件，例如，金属氧化物半导体场效应晶体管(MOSFET)或者绝缘栅双极型晶体管(IGBT)。每个高侧开关和低侧开关均并联有一个寄生二极管。AH、AL、BH、BL、CH、CL分别为高侧开关Q1、低侧开关Q2、高侧开关Q3、低侧开关Q4、高侧开关Q5、低侧开关Q6的控制端。
上述驱动开关的控制端AH、AL、BH、BL、CH、CL与分别与控制模块32电性连接，高侧开关Q1-Q6依据控制模块32输出的控制信号改变导通状态，从而改变电源模块31加载在无刷电机11的绕组上的电压状态。
在本实施方式中，高侧开关Q1设置为导通或切断第一相绕组A与电源模块31的电源正极端31a的电性连接,高侧开关Q3设置为导通或切断第二相绕组B与电源模块31的电源正极端31a的电性连接,高侧开关Q5设置为导通或切断第三相绕组C与电源模块31的电源正极端31a的电性连接，低侧开关Q2设置为导通或切断第一相绕组A与电源模块31的电源负极端31b的电性连接，低侧开关Q4设置为导通或切断第二相绕组B与电源模块31的电源负极端31b的电性连接,低侧开关Q6设置为导通或切断第三相绕组C与电源模块31的电源负极端31b的电性连接。当绕组连接至电源负极端31b时，绕组的电压表现为负电压，而当绕组连接至电源正极端31a时，绕组的电压表现为正电压。
在一实施例中，电动工具10还包括转子位置获取模块35，转子位置获取模块35与电机34和控制模块32连接，设置为获取电机34中的转子的位置。当转子转动至一个预设范围时，转子位置获取模块35处于一种信号状态，当转子转出预设范围时转子位置获取模块35切换至另一信号状态。在一些实施例中，转子位置获取模块35包括位置传感器351(例如，霍尔传感器)。在另一些实施例中，转子位置获取模块35不包括位置传感器351，而是通过反电动势信号判断转子位置进行换相。
在本实施例中，转子位置获取模块35包括位置传感器351，所述的位置传感器351为三个霍尔传感器。如图2所示，沿电机34的转子的圆周方向设置三个霍尔传感器，霍尔传感器检测的转子的位置信息输入至转子位置获取模块35。转子位置获取模块35将输入的转子的位置经逻辑处理转换为可与控制模块32通讯 的转子位置信息输入至控制模块32。当转子转入和转出预设范围时，霍尔传感器的信号发生改变，转子位置获取模块35的输出信号也随之改变。
转子转入预设范围时，转子位置获取模块35的输出信号定义为1，而转子转出预设范围时，转子位置获取模块35的输出信号定义为0。将三个霍尔传感器彼此相距物理角度120°。
参照图4，当转子转动时，三个霍尔传感器将会产生包括六种信号组合的位置信号使得转子位置获取模块35输出包括六种信号组合之一的位置信号。如果按霍尔传感器放置的顺序排列则出现六个不同的信号组合100、110、010、011、001及101。这样一来转子位置获取模块35就可输出上述六个位置信号之一，依据转子位置获取模块35输出的位置检测信号即可得知转子所处的位置。
对于具有三相绕组的电机34而言，其在一个通电周期内具有六个驱动状态与上述方案产生的输出信号相对应，因此在转子位置获取模块35的输出信号发生变化时，电机34即可执行一次换向。
为了使电机34转动，驱动电路33具有多个驱动状态，在一个驱动状态下电机34的定子绕组会产生一个磁场，控制模块32控制驱动电路33切换驱动状态使绕组产生的磁场转动以驱动转子转动，进而实现对电机34的驱动。
为了驱动电机34，驱动电路33至少具有六个驱动状态，为了方便说明，以下以驱动状态对应接通的接线端表示驱动状态。例如，如果控制模块32控制驱动电路33使第一相绕组A连接至电源模块31的电源正极端31a以及使第二相绕组B连接至电源模块31的电源负极端31b，则该驱动状态用AB表示，在该状态下，第一相绕组A和第二相绕组B导通，称为AB相导通；如果控制模块32控制驱动电路33使第一相绕组A连接至电源模块31的电源负极端31b以及使第二相绕组B连接至电源模块31的第一电源端31b，则该驱动状态用BA表示，在该状态下，第一相绕组A和第二相绕组B导通，称为BA相导通，其电流方向与AB时相反，这样表示的驱动方式同样适用于绕组的三角型连接方案。另外，驱动状态的切换也可简称为电机34的换向动作。显然，转子每转过60°电角度，电机34换向一次，定义电机34的一次换向至下一次换向的间隔为换向区间。
图5为相关技术的无刷电机控制方法，在一个周期内，无刷电机正常工作时，控制模块32控制驱动电路33使驱动电路33在驱动时依次输出AB、AC、BC、BA、CA、CB六个驱动状态。在一实施例中，三个霍尔传感器检测转子的位置，转子位置获取模块35接收三个霍尔传感器的检测信号并经过处理后发送给控制模块 32，控制模块32根据接收到的转子位置获取模块35的输出信号，控制驱动电路33并使驱动电路在驱动时依次输出AB、AC、BC、BA、CA及CB六个驱动状态。
如图5所示，Ha、Hb及Hc为转子位置获取模块35的输出信号，分别对应三个霍尔传感器的检测信号；PWMa、PWMb、PWMc为控制模块32发送给驱动开关的一系列占空比不变的脉冲信号；Ua、Ub、Uc为第一相绕组A、第二相绕组B、第三相绕组C与中性点O之间的电压。
其中，PWMa为控制模块32发送给高侧开关Q1的控制端AH和低侧开关Q2的控制端AL的脉冲信号，用以导通第一相绕组A与电源正极端31a或电源负极端31b的电性连接。当PWMa信号为正脉冲信号时，高侧开关Q1的控制端AH接收到脉冲信号，高侧开关Q1以预设的占空比导通第一相绕组A与电源正极端31a的电性连接；当PWMa信号为负脉冲信号时，低侧开关Q2以预设的占空比导通第一相绕组A与电源负极端31b的电性连接。同理，PWMb为控制模块32发送给高侧开关Q3的控制端BH和低侧开关Q4的控制端BL的脉冲信号，当PWMb信号为正脉冲信号时，高侧开关Q3的控制端BH接收到脉冲信号，高侧开关Q3以预设的占空比导通第二相绕组B与电源正极端31a的电性连接，当PWMb信号为负脉冲信号时，低侧开关Q4的控制端BL接收到脉冲信号，低侧开关Q4以预设的占空比导通第二相绕组B与电源负极端31a电源负极端31b的电性连接。PWMc为控制模块32发送给高侧开关Q5的控制端CH和低侧开关Q6的控制端CL的脉冲信号，当PWMc信号为正脉冲信号时，高侧开关Q5的控制端CH接收到脉冲信号，高侧开关Q5以预设的占空比导通第三相绕组C与电源正极端31a的电性连接，当PWMc信号为负脉冲信号时，低侧开关Q6的控制端CL接收到脉冲信号，低侧开关Q6以预设的占空比导通第三相绕组C与电源负极端31b的电性连接。当PWM信号的连续的多个脉冲信号之间的间隔时间或间隔的转子位置足够小时，在连续的脉冲信号区间驱动开关等效维持导通状态。
相关技术中的电动工具的无刷电机控制技术中，驱动状态与转子位置获取模块35的输出信号的对应关系如表1所示：
信号组合 驱动状态
101 AB
100 AC
110 BC
010 BA
011 CA
001 CB
表1
根据这样的对应关系，在控制模块32检测到转子位置获取模块35的信号变化即输出控制驱动电路33切换驱动状态。
参照图5中的(c)图，按照这样的方式，每相绕组的连续导电时间(即控制模块32控制驱动电路33连续导通绕组与电源模块31的电性连接的时间)为120°，每相绕组的电压不连续变化。
当电机转速增加时，反电动势随着电机速度的增加而增加。当电机转速接近额定转速时，反电动势可能高于电源模块31和驱动电路33能够供应的最大电压，电源模块31和驱动电路33无法供应更大的能量以克服增长的反电动势，电机绕组就无法获得足够的电流来克服阻转力矩，电机转速的增长也就停滞了。然而。尤其是，在电源模块31的电压较低的情况下，电机34转速和功率下降，更不能满足电动工具输出需求。
为了能够为克服在较高的电机速度上增加的反电动势，或者在达到电机34的最大输出转速但对电机34的转速需求持续增加时，可通过控制相电流的相位角来控制转子的励磁。相对于增加的反电动势超前的相电流，使得永磁体产生的磁通减少，进而导致永磁体能够产生的反电动势的减少。
然而当电机34处于重载状态时，定子绕组电流较大，将引起严重的电枢反应，导致相电流的相位超前角度减小甚至于滞后转子磁场，达不到提速效果。在实际在实际情况中，由于控制的延时性，当转子转动至需要切换驱动状态的位置时，往往来不及控制，这会影响无刷电机的性能的发挥。
为了尽可能消除延迟，使换相与转子位置能够对应，可以采用超前于转子的实际位置即开始进行换相的控制的方法。可通过对霍尔传感器的物理位置进行设置，将霍尔传感器的物理位置设置超前于理想位置一定角度。例如，设置霍尔传感器时使霍尔传感器超前这些位置电角度20°至40°的范围内，或者说，超前这些位置物理角度20°/P至40°/P的范围内，其中P为电机34的转子的极对数。但是，当电机34处于重载状态时，电机电枢反应导致霍尔传感器的位置超前角度变小，甚至滞后于转子磁场，达不到提速效果。
另外，当电源模块31较低时，会导致电机34转速和功率下降，不能满足电 动工具10的输出需求。例如，对于使用电池包20作为电源模块31的电动工具10而言，在一些情况下，若供电的电池包20因使用时间较长致使电压较低，此时将该电压较低的电池包20接入电动工具10时，会导致电机34转速和功率下降，不能满足电动工具10的输出需求；或者因附近没有具高电压的电池包20适配该电动工具10，只有较低电压的电池包20可供接入电动工具10时，因电机34转速和功率下降致使电动工具10无法完成预期工作。
本实施例提供了一种可以兼容多电压供电的电动工具以及电动工具的控制方法，使得电动工具10可以兼容多电压的电源模块且能满足输出特性要求。
在本申请中，控制模块32模块被配置为：在所述电源模块31的电压小于预设电压阈值时，根据所述电机34的转子的转动位置控制所述驱动电路33以使所述电机34的第一相绕组A、第二相绕组B和第三相绕组C同时连接至所述电源模块31。
在一些实施方式中，所述电动工具10包括电压检测模块38，电压检测模块38设置为检测所述电源模块31的电压；所述电压检测模块38与所述控制模块32连接，所述控制模块32能够根据所述电压检测模块38的检测信号判断所述电源模块31的电压是否小于所述预设电压阈值。
在一些实施方式中，所述电动工具10包括电流检测模块36，电流检测模块36设置为检测所述电机34的电流；所述电流检测模块36与所述控制模块32连接，所述控制模块32能够根据所述电流检测模块36的检测信号判断所述电源模块31的电压是否小于所述预设电压阈值。
在其他实施方式中，控制模块32还可以通过转子转速检测模块(未示出)检测到的电机转速来判断电源模块31的电压是否小于等于预设电压阈值。在一实施例中，在电机34的转速小于预设阈值时，控制模块32判断电源模块31的电压小于等于预设电压阈值。在其他实施方式中，控制模块32还可以通过反电动势测算模块(未示出)检测出的电机34的绕组的反电动势来判断电源模块31的电压是否小于等于预设电压阈值。在电机34的反电动势满足预设条件时，控制模块32判断电源模块31的电压小于等于预设电压阈值。
在一些实施方式中，所述预设电压阈值为所述电动工具的额定电压的0.4-0.8倍。在一实施例中，所述预电压设阈值为所述电动工具的额定电压的0.5-0.75倍，也即是说，若电源模块31的电压小于电动工具10的额定电压的0.5-0.75倍时，控制模块32判断电源模块31是低电压电源，此时控制模块32根 据所述电机34的转子的转动位置控制所述驱动电路33以使所述第一相绕组A、第二相绕组B和第三相绕组C同时连接至所述电源模块31。以额定电压为48V的直流供电的电动工具为例，当控制模块32获取的电源模块31的电压在24V-36V的范围内时，控制模块32判断电源模块31是低电压电源，此时控制模块32根据所述电机34的转子的转动位置控制所述驱动电路33以使所述第一相绕组A、第二相绕组B和第三相绕组C同时连接至所述电源模块31。而在电源模块31的电压大于所述预设电压阈值时，控制模块31仍然采用相关技术中的控制方式(图5)。也即是说，控制模块32根据电源模块31的电压处于不同范围时选择不同的控制方式，并且在电源模块31为低电压电源时控制驱动电路33使第一相绕组A、第二相绕组B和第三相绕组C同时连接至所述电源模块31，通过这样的方式使得电动工具使用电压低于预设电压阈值的低电压电源模块31时，也能够输出近似于使用电压高于预设电压阈值的高电压电源模块31的电机转速和功率。
在本实施例中，控制模块32在判断电源模块31的电压小于等于预设电压阈值后，控制模块32被配置为根据转子的位置控制驱动电路33使第一相绕组A、第二相绕组B和第三相绕组C同时连接至所述电源模块31。在一实施例中，所述电源模块31的电压大于等于电动工具10的额定电压的0.2倍，在一实施例中，所述电源模块31的电压大于等于电动工具10的额定电压的0.3倍，以避免电池包在较低电压情况下使用而遭到损坏，并且避免电池包电压过低而不能满足电动工具输出需求。
在一实施例中，在转子转动至第一预设转动位置时，控制所述驱动电路33以使：所述第一相绕组电连接至所述电源正极端31a、所述第二相绕组电连接至所述电源负极端31b、所述第三相绕组电连接至所述电源正极端31a和所述电源负极端31b中的一个；在所述转子转动至第二预设转动位置时，控制所述驱动电路33以使所述第三相绕组从所述电源正极端31a和所述电源负极端31b中的一个断开电连接并电连接至所述电源正极端31a和所述电源负极端31b中的另一个。需要说明的是，上述第一相绕组、第二相绕组以及第三相绕组与第一相绕组A、第二相绕组B和第三相绕组C并非仅限定为一一对应关系。
下面以第一相绕组、第二相绕组以及第三相绕组分别对应第一相绕组A、第二相绕组B和第三相绕组C为例进行说明。
参照图6a、图6b和图6c，作为三种不同的实施方式的控制方下控制模块31根据转子的转动位置控制所述驱动电路33以使所述第一相绕组A、第二相绕组B 和第三相绕组C同时连接至所述电源模块31。
在图6a、图6b和图6c所示的实施方式，在转子转过的其中一个周期内，控制模块32被配置为：
以零点位置作为第一预设转动位置，在所述转子转动至第一预设转动位置(零点位置)时，控制模块32控制所述驱动电路33以使：所述第一相绕组(第一相绕组A)电连接至所述电源模块31的电源正极端31a，同时使第二相绕组(第二相绕组B)电连接至所述电源负极端31b，使所述第三相绕组(第三相绕组C)电连接至所述电源正极端31a和所述电源负极端31b中的一个。在图6a、图6b和图6c所示的实施方式，在所述转子转动至第一预设转动位置(零点位置)时，第三相绕组(第三相绕组C)电连接至电源正极端31a。
当所述转子转动至第二预设转动位置(L1)时，控制模块32控制所述驱动电路33以使所述第三相绕组(第三相绕组C)从所述电源正极端31a和所述电源负极端31b中的一个断开电连接并电连接至所述电源正极端31a和所述电源负极端31b中的另一个。在图6a、图6b和图6c所示的实施方式，当转子转动至第二预设转动位置(L1)时，第三相绕组(第三相绕组C)与电源正极端31a断开电连接并且电连接至电源负极端31b。
当所述转子转动至第三预设转动位置(L2)时，所述控制模块32控制所述驱动电路33以使所述第一相绕组(第一相绕组A)从所述电源正极端31a断开电连接并电连接至所述电源负极端31b或使所述第二相绕组(第二相绕组B)从所述电源负极端31断开电连接并电连接至所述电源正极端31a。在图6a、图6b和图6c所示的实施方式，当转子转动至第三预设转动位置(L2)时，所述控制模块32控制所述驱动电路33以使所述第二相绕组(第二相绕组B)从所述电源负极端31断开电连接并电连接至所述电源正极端31a。
在所述转子位于第一预设转动位置(零点位置)和第二预设转动位置(L1)之间，所述控制模块32控制所述驱动电路33以使所述第三相绕组(第三相绕组C)的电压至少部分以预设的变化率跟随所述转子的转动位置变化而变化。需要说明的是，本实施例中的变化率指的是变化的快慢程度。
图6a所示的实施方式中，在转子位于第一预设转动位置(零点位置)和第二预设转动位置(L1)之间，所述控制模块32控制所述驱动电路33以使所述第三相绕组(第三相绕组C)的电压(Uc)的变化率保持不变，但第三相绕组(第三相绕组C)的电压(Uc)大小发生变化，从第一预设转动位置(零点位置)正 向最大值按照预设的变化率逐渐减小到第二预设转动位置(L1)的零值。
参照图6b和图6c所示的实施方式中，在转子位于第一预设转动位置(零点位置)和第二预设转动位置(L1)之间时，所述控制模块32控制所述驱动电路33以使所述第三相绕组(第三相绕组C)的电压(Uc)以变化的变化率跟随所述转子的转动位置变化而变化。
如图6b所示，在所述转子位于第一预设转动位置(零点位置)和第二预设转动位置(L1)之间时，所述控制模块32控制所述驱动电路33以使所述第三相绕组(第三相绕组C)的电压(Uc)以逐渐减小的变化率跟随所述转子的转动位置变化而变化。第三相绕组(第三相绕组C)的电压(Uc)的变化率逐渐减小，且大小从第一预设转动位置(零点位置)的正向最大值逐渐减小到第二预设转动位置(L1)的零值。
如图6c所示，在所述转子位于第一预设转动位置(零点位置)和第二预设转动位置(L1)之间时，所述控制模块32控制所述驱动电路33以使所述第三相绕组(第三相绕组C)的电压(Uc)以逐渐增大的变化率跟随所述转子的转动位置变化而变化。第三相绕组(第三相绕组C)的电压(Uc)的变化率逐渐增大，且大小从第一预设转动位置(零点位置)的正向最大值逐渐减小到第二预设转动位置(L1)的零值。
在所述转子位于第二预设转动位置(L1)和第三预设转动位置(L2)之间时，所述控制模块32控制所述驱动电路33按照如下方式实施：
图6a所示的实施方式中，在所述转子位于第二预设转动位置(L1)和第三预设转动位置(L2)之间时，所述控制模块32控制所述驱动电路33以使所述第三相绕组(第三相绕组C)的电压(Uc)先在预设时长内以预设的变化率跟随所述转子的转动位置变化而变化，当达到最大负向电压后保持不变的电压(Uc)直至转子转动至第三预设转动位置(L2)。在本实施方式中，所述预设时长为转子转动30°电角度的时间。
在图6a和6b所示的实施方式中，在所述转子位于第一预设转动位置(L1)和第二预设转动位置(L2)之间时，所述控制模块32控制所述驱动电路33以使所述第三相绕组(第三相绕组C)的电压(Uc)至少部分以逐渐增大的变化率和逐渐减小的变化率中的一个跟随所述转子的转动位置变化而变化；而在转子位于第二预设转动位置(L1)和第三预设转动位置(L2)之间时，所述控制模块32控制所述驱动电路33以使所述第三相绕组(第三相绕组C)的电压(Uc)至少 部分以逐渐增大的变化率和逐渐减小的变化率中的另一个跟随所述转子的转动位置变化而变化。
如图6b所示，在转子位于第一预设转动位置(L1)和第二预设转动位置(L2)之间时，控制模块32控制所述驱动电路33以使第三相绕组(第三相绕组C)的电压(Uc)以逐渐减小的变化率跟随所述转子的转动位置变化而变化；当转子位于第二预设转动位置(L1)和第三预设转动位置(L2)之间时，所述控制模块32控制所述驱动电路33以使所述第三相绕组(第三相绕组C)的电压(Uc)先以逐渐增大的变化率跟随所述转子的转动位置变化而变化，第三相绕组(第三相绕组C)的电压(Uc)的变化率逐渐增大，第三相绕组(第三相绕组C)的电压(Uc)的大小从第二预设转动位置(L1)的零值逐渐增大到负向最大值，当第三相绕组(第三相绕组C)的电压(Uc)达到负向最大值后保持不变直至所述转子转动至第三预设转动位置(L2)。
如图6c所示，在转子位于第一预设转动位置(L1)和第二预设转动位置(L2)之间时，控制模块32控制所述驱动电路33以使第三相绕组(绕组C)的电压(Uc)以逐渐增大的变化率跟随所述转子的转动位置变化而变化；当转子位于第二预设转动位置(L1)和第三预设转动位置(L2)之间时，所述控制模块32控制所述驱动电路33以使所述第三相绕组(第三相绕组C)的电压(Uc)先以逐渐减小的变化率跟随所述转子的转动位置变化而变化，第三相绕组(第三相绕组C)的电压(Uc)的变化率逐渐减小，且大小从第二预设转动位置(L1)的零值逐渐增大直至达到负向最大值，当第三相绕组(第三相绕组C)的电压(Uc)达到负向最大值后保持不变直至所述转子转动至第三预设转动位置(L2)。
换句话说，当转子位于第二预设转动位置(L1)和第三预设转动位置(L2)之间时，所述控制模块32控制所述驱动电路33以使所述第三相绕组(第三相绕组C)的电压(Uc)的至少部分保持不变。
上述实施方式仅是一个周期内的一个位置区间，在一个周期的其他位置区间，控制模块32的控制方式与上述实施方式类似。下面以第一相绕组、第二相绕组以及第三相绕组与第一相绕组A、第二相绕组B和第三相绕组C不对应，转子位置在上述周期内的另一个位置区间的实施方式为例进行说明。
以L1作为第一预设转动位置，在转子转动至第一预设转动位置(L1)时，控制模块32控制所述驱动电路33以使：所述第一相绕组(第一相绕组A)电连接至所述电源模块31的电源正极端31a，同时使第二相绕组(第三相绕组C)电连 接至所述电源负极端31b，使所述第三相绕组(第二相绕组B)电连接至所述电源正极端31a和所述电源负极端31b中的一个。图6a、图6b及图6c中，当转子转动至第一预设转动位置(L1)，控制模块32控制驱动电路33使所述第三相绕组(第二相绕组B)电连接至所述电源负极端31b。
当转子在转子转动至第二预设转动位置(L2)，控制模块32控制所述驱动电路33以使所述第三相绕组(第二相绕组B)从电源正极端31a和电源负极端31b中的一个断开电连接并电连接至所述电源正极端31a和所述电源负极端31b中的另一个。在图6a、图6b和图6c所示的实施方式，当转子转动至第二预设转动位置(L2)时，控制模块32控制所述驱动电路33以使所述第三相绕组(第二相绕组B)与电源负极端31b断开电连接并且电连接至电源正极端31a。
当转子转动至第三预设转动位置(L3)时，所述控制模块32控制所述驱动电路33以使所述第一相绕组(第一相绕组A)从所述电源正极端31a断开电连接并电连接至所述电源负极端31b或使所述第二相绕组(第三相绕组C)从所述电源负极端31b断开电连接并电连接至所述电源正极端31a。在图6a、图6b和图6c所示的实施方式，当转子转动至第三预设转动位置(L3)时，控制模块32控制驱动电路33以使第一相绕组(第一相绕组A)从所述电源正极端31a断开电连接并电连接至所述电源负极端31b。
在所述转子位于第一预设转动位置(L1)和第二预设转动位置(L2)之间，所述控制模块32控制所述驱动电路33以使所述第三相绕组(第二相绕组B)的电压(Ub)至少部分以预设的变化率跟随所述转子的转动位置变化而变化。
图6a所示的实施方式中，在转子位于第一预设转动位置(L1)和第二预设转动位置(L2)之间，所述控制模块32控制所述驱动电路33以使所述第三相绕组(第二相绕组B)的电压(Ub)先在预设时长内保持负向最大值不变，再从负向最大值逐渐减小到零，直至转子转动至第三预设转动位置(L3)时变为零。在本实施方式中，所述的预设时长为转子转过30°电角度的时间。
如图6b所示，在所述转子位于第一预设转动位置(L1)和第二预设转动位置(L2)之间时，所述控制模块32控制所述驱动电路33以使所述第三相绕组(绕组B)的电压(Ub)先在预设时长内保持负向最大值不变，再以逐渐减小的变化率跟随所述转子的转动位置变化而变化，第三相绕组(第二相绕组B)的电压(Ub)的变化率逐渐减小到第二预设转动位置(L2)的零值。在一实施例中，所述的预设时长为转子转过15°电角度的时间。
如图6c所示，在所述转子位于第一预设转动位置(L1)和第二预设转动位置(L2)之间时，所述控制模块32控制所述驱动电路33以使所述第三相绕组(第二相绕组B)的电压(Ub)以逐渐增大的变化率跟随所述转子的转动位置变化而变化。第三相绕组(第三相绕组C)的电压Uc的变化率逐渐增大，且大小从第一预设转动位置(零点位置)的正向最大值逐渐减小到第二预设转动位置(L1)的零值。
在所述转子位于第二预设转动位置(L2)和第三预设转动位置(L3)之间时，所述控制模块32控制所述驱动电路33按照如下方式实施：
图6a所示的实施方式中，在所述转子位于第二预设转动位置(L2)和第三预设转动位置(L3)之间时，所述控制模块32控制所述驱动电路33以使所述第三相绕组(第二相绕组B)的电压(Ub)从第二预设转动位置(L2)的零值开始，先在预设时长内以预设的变化率跟随所述转子的转动位置变化而变化直至到达最大正向电压后保持不变，直至转子转动至第三预设转动位置(L3)。在一实施例中，所述预设时长为转子转过30°电角度的时间。
在图6a和6b所示的实施方式中，在所述转子位于第一预设转动位置(L1)和第二预设转动位置(L2)之间时，所述控制模块32控制所述驱动电路33以使所述第三相绕组(第二相绕组B)的电压(Ub)至少部分以逐渐增大的变化率和逐渐减小的变化率中的一个跟随所述转子的转动位置变化而变化；在转子位于第二预设转动位置(L2)和第三预设转动位置(L3)间时，所述控制模块32控制所述驱动电路33以使所述第三相绕组(第二相绕组B)的电压(Ub)至少部分以逐渐增大的变化率和逐渐减小的变化率中的另一个跟随所述转子的转动位置变化而变化。
如图6b所示，当转子位于第二预设转动位置(L2)和第三预设转动位置(L3)时，所述控制模块32控制所述驱动电路33以使所述第三相绕组(第二相绕组B)的电压(Ub)先在预设时长内以逐渐增大的变化率跟随所述转子的转动位置变化而变化直至达到正向最大值后第三相绕组(第二相绕组B)的电压(Ub)保持不变，第三相绕组(第二相绕组B)的电压(Ub)从第二预设转动位置(L2)的零值逐渐增大至正向最大值，且保持该正向最大值不变直至所述转子转动至第三预设转动位置(L3)。在一实施例中，所述预设时长为转子转过45°电角度的时间。
如图6c所示，当转子位于第二预设转动位置(L2)和第三预设转动位置(L3) 之间时，所述控制模块32控制所述驱动电路33以使所述第三相绕组(第二相绕组B)的电压(Ub)先在预设时长内以逐渐减小的变化率跟随所述转子的转动位置变化而变化直至达到正向最大值后保持不变至转子转动至第三预设转动位置(L3)，第三相绕组(第二相绕组B)的电压(Ub)从第二预设转动位置(L2)的零值开始逐渐增大至最大正向电压后，当第三相绕组(第二相绕组B)的电压(Ub)达到最大正向电压后保持不变直至转子转动至第三预设转动位置(L3)。在一实施例中，所述的预设时长为转子转过30°电角度的时间。
换句话说，当转子位于第二预设转动位置(L2)和第三预设转动位置(L3)之间时，所述控制模块32控制所述驱动电路33以使所述第三相绕组(第二相绕组B)的电压(Ub)的至少部分保持不变。
本实施例还提供了一种电动工具的控制方法，如图11所示，所述方法为本实施例的控制模块32控制驱动电路33的控制方法，包括以下步骤：
S10'中，获取所述电源模块31的电压。
S20'中，在所述电源模块31的电压小于等于预设电压阈值时，将第一相绕组A、第二相绕组B、第三相绕组B同时连接至所述电源正极端31a或电源负极端31b。
S30'中，获取转子的转动位置，其中，在所述转子转动至一个预设位置时，使所述第一相绕组、第二相绕组及第三相绕组中的一个从所述电源正极或电源负极断开并连接至所述电源正极端和电源负极端中的另一个。
上述实施方式仅是一个周期内的一个位置区间，在转子转动的一个周期内，即转子转过360°电角度，控制模块32根据电机34的转子的转动位置控制所述驱动电路32以使第一相绕组、第二相绕组和第三相绕组同时连接至电源模块31。
一实施例提供的另一种形式的电动工具的控制方法，如图12所示，该控制方法为控制模块32根据电机34的转子的转动位置控制所述驱动电路32以使第一相绕组、第二相绕组和第三相绕组同时连接至电源模块31的方法，包括以下步骤：
S10中，获取所述电源模块的电压，其中，在所述电源模块的电压小于等于预设电压阈值时，将第一相绕组A、第二相绕组B、第三相绕组B同时连接至所述电源正极端31a或电源负极端31b。
S20中，获取转子的转动位置，其中，当转子转动至第一预设位置时，将第一相绕组A、第二相绕组B、第三相绕组C中的第一个从所述电源正极端31或电源 负极端31b断开并连接至电源正极端31a和电源负极端31b中的另一个；当转子转动至第二预设位置时，将所述第一相绕组A、第二相绕组B、第三相绕组C中的第二个从电源正极端31a或电源负极端31b断开并连接至电源正极端31a和电源负极端31b中的另一个；当转子转动至第三预设位置时，将第一相绕组A、第二相绕组B、第三相绕组C中的第三个从电源正极端31a或电源正极端31a电源负极端31b断开并连接至电源正极端31a和电源负极端31b中的另一个。
参照图6a、图6b和图6c所示的实施方式中，在转子转过的其中一个周期内(转子转过360°电角度)，控制模块32通过控制驱动电路33使每相绕组与电源模块31的电性连接的控制方法的具体步骤如下：
S100中，将第一相绕组A和第三相绕组C连接至电源正极端31a，将第二相绕组B连接至电源正极端31a电源负极端31b。
S200中，当转子转动至第一预设位置(L1)时，将第三相绕组C从电源正极端31a断开，并将其连接至电源负极端31b。
S300中，当转子转动至第二预设位置(L2)时，将第二相绕组B从电源负极端31b断开，并将其连接至电源正极端31a。
S400中，当转子转动至第三预设位置(L3)时，将第一相绕组A从电源正极端31a断开，并将其连接至电源负极端31b。
S500中，当转子转动至第四预设位置(L4)时，将第三相绕组C从电源负极端31b断开，并将其连接至电源正极端31a。
S600中，当转子转动至第五预设位置(L5)时，将第二相绕组B从电源正极端31a断开，并将其连接至电源负极端31b。
S700中，当转子转动至第六预设位置(L6)时，将第一相绕组A从电源负极端31b断开，并将其连接至电源正极端31a。
将相关技术的电动工具中无刷电机采用的控制方法和上述改进的控制方法进行对比，驱动状态与转子位置获取模块35的输出信号的对应关系对比如表2所示：
Figure PCTCN2019094242-appb-000001
Figure PCTCN2019094242-appb-000002
表2
表2中，“-”表示在一个换向区间内，每相绕组由连接电源正极端31a趋向于连接至电源负极端31b，“+”表示在一个换向区间内，每相绕组由连接电源负极端31b趋向于连接至电源正极端31a。例如，“ABC-”，表示控制模块32控制驱动电路33使第一相绕组A连接至电源正极端31a、第二相绕组B连接至电源负极端31b、第三相绕组C连接至电源正极端31a，在转子转动至下一个预设位置时，使第三相绕组C从电源正极端31a断开并连接至电源负极端31b。“BAC+”表示控制模块32控制驱动电路33使第二相绕组B连接至电源正极端31a、第一相绕组A连接至电源负极端31b、第三相绕组C连接至电源负极端31b，在转子转动至下一个预设位置时，使第三相绕组C从电源负极端31b断开并连接至电源正极端31a。
按照上述方式，每相绕组的连续导电时间或连续导通电角度增加至180°，提高了电机输出性能，使得电动工具10即使使用低于预设电压阈值的低电压的电源模块31也能够达到或基本达到使用高于预设电压阈值的电源模块31的电动工具的输出转速和功率。
需要说明的是，上述控制模块32控制每相绕组与电源模块31的电性连接的控制方式仅仅是针对转子转过的其中一个周期而言，在此并非限制。
上述实施方式中，控制模块32通过输出PWM信号至驱动电路33来实现第一相绕组A、第二相绕组B及第三相绕组C同时连接至电源模块31。
驱动电路33包括驱动开关，所述驱动开关能在所述控制模块32的控制下以预设的占空比导通所述第三相绕组与所述电源模块的电性连接。
在转子位于第一预设转动位置和第二预设转动位置之间时，控制模块31控制驱动开关以至少部分变化的占空比导通上述实施方式中的第三相绕组(第一相绕组A、第二相绕组B和第三相绕组C中的一个)与电源模块31的电性连接。上述占空比可以通过查表的方式获得，也可以通过计算的方式获得。这里变化的占空比包括变化率不变的占空比和变化率变化的占空比。
下面以第一相绕组A为例，说明在转子转过的其中一个周期内(即转子转过360°电角度)，控制模块32通过控制驱动电路33以使三相绕组同时连接至电源 模块31时，控制模块32输出PWM信号至驱动电路33以控制每相绕组的控制方式。
参照图7b和图7c，控制模块32控制驱动电路33按如下方式工作：控制模块32控制驱动电路33中的高侧开关Q1先以预设的占空比导通第一相绕组A与电源正极端31a的电性连接；在转子转动到第一预设转动位置(L11、L21)时，控制模块32控制高侧开关Q1以逐渐减小的占空比导通第一相绕组A与电源正极端31a的电性连接；在转子转动到第二预设转动位置(L12、L22)时，占空比减小到零，控制模块32控制低侧开关Q2以逐渐增大的占空比导通第一相绕组A与电源负极端31b的电性连接；在转子转动到第三预设转动位置(L13、L23)时，占空比逐渐增大到预设的占空比，控制模块32控制低侧开关Q2以预设的占空比导通第一相绕组A和电源负极端31b的电性连接；在转子转动到第四预设转动位置(L14、L24)时，控制模块32控制低侧开关Q2以逐渐减小的占空比导通第一相绕组A和电源负极端31b的电性连接；在转子转动到第五预设转动位置(L15、L25)时，占空比逐渐减小到零，控制模块32控制高侧开关Q1以逐渐增大的占空比导通第一相绕组A和电源正极端31a的电性连接；在转子转动到第六预设转动位置(L16、L26)时，占空比逐渐增大到预设的占空比，控制模块32控制高侧开关Q1以一定的占空比导通第一相绕组A和电源正极端31a的电性连接。
上述控制方法中，占空比可以是按照不变的变化率随转子的转动位置逐渐变大或逐渐减小，也可以按照变化的变化率随转子的转动位置逐渐变大或逐渐减小。
在实际情况中，占空比的变化、预设的转动位置不同、预设的占空比等均需要根据电动工具的应用场合及具体工况来设定，以匹配不同的电动工具的应用特性。
在一实施例中，参照图7b，在转子转过的其中一个周期内，控制模块32控制高侧开关Q1和低侧开关Q2按如下方式工作：控制模块32控制高侧开关Q1先以预设的占空比(例如，80％)导通第一相绕组A与电源正极端31a的电性连接；在转子转动45°的角度位置L11时，控制模块32控制高侧开关Q1导通的占空比以的逐渐减小的变化率逐渐减小；在转子转动到90°的角度位置L12时，占空比减小到0％，控制模块32控制低侧开关Q2导通的占空比的以逐渐增大的变化率逐渐增大；在转子转动到135°的角度位置L13时，占空比增大到预设的占空比(80％)，控制模块32控制低侧开关Q2导通的占空比保持预设的占空比不变；在转子转动到225°的角度位置L14时，控制模块32控制低侧开关Q2导通的占空比以逐渐减 小的变化率逐渐减小；在转子转动到270°的角度位置L15时，占空比减小到0％，控制模块32控制高侧开关Q1导通的占空比以逐渐增大的变化率逐渐增大；在转子转动到315°的角度位置L16时，占空比增大到预设的占空比(80％)，控制模块32控制高侧开关Q1导通的占空比保持预设的占空比不变。
在一实施例中，参照图7c，在转子转过的其中一个周期内，控制模块32控制高侧开关Q1和低侧开关Q2按如下方式工作：控制模块32控制高侧开关Q1先以预设的占空比(例如，100％)导通第一相绕组A与电源正极端31a的电性连接；在转子转动到60°的角度位置L21时，控制模块32控制高侧开关Q1导通的占空比以逐渐增大的变化率逐渐减小；在转子转动到90°的角度位置L22时，占空比减小到0％，控制模块32控制低侧开关Q2导通的占空比以逐渐较小的变化率逐渐增大；在转子转动到120°的角度位置L23时，占空比增大到预设的占空比，控制模块32控制低侧开关Q2导通的占空比保持预设的占空比不变；在转子转动到240°的角度位置L24时，控制模块32控制低侧开关Q2导通的占空比以逐渐增大的变化率逐渐减小；在转子转动到270°的角度位置L25时，占空比减小到0％，控制模块32控制高侧开关Q1导通的占空比以逐渐减小的变化率逐渐增大；在转子转动到300°的角度位置L26时，占空增大到预设占空比，控制模块32控制高侧开关Q1导通的占空比保持预设占空比不变。
图6a所示为相关技术中的控制方式，在转子转到的一个周期内，即转子转过360°电角度，第一相绕组A的连续导通电角度为120°，而图6b和图6c为本实施例的控制方式的两种实施方式，在本实施例中，在转子转动的一个周期内，使第一相绕组A的连续导通180°。按照这样的方式，在转子转过的一个周期内(即转子转过360°的角度)，每个驱动开关的连续导通时间为180°角度，从而每相绕组的连续导电时间增加到180°角度。相对于相关技术中的电动工具中每相绕组的连续导通时间120°，上述电动工具及其控制方法提高了电机效率。需要说明的是，上述实施例仅仅是转子转过的其中一个周期内的控制方法说明，在此并非限制。
在一实施例中，控制模块32还包括计时单元、设置为对数据处理的计算单元及设置为存储的储存单元。
在一个实施例中，计算单元设置为根据转子位置获取模块35的发送的位置信号，计算出转子位置(即转子转过的角度)。存储单元存储转子位置(即转子转过的角度)以及上述控制模块32控制驱动电路33中的每个驱动开关导通的占 空比，并建立每个驱动开关导通的占空比和转子位置的对应关系表。这样根据每个驱动开关导通的占空比和转子的转动位置对应关系的信息表，即可得到下一次转子的转动位置对应的每个驱动开关导通的占空比，控制模块32在下一次输出对应的控制信号，使得每个驱动开关按照对应的导通的占空比工作，这样便能使三相绕组的电压以预设的变化规律随转子的转动位置变化。
在一实施例中，计算单元设置为根据转子位置获取模块35的发送的位置信号，计算出转子的转动位置(即转子转过的角度)。存储单元存储转子的转动位置以及控制模块32控制驱动电路33中的每个驱动开关导通的占空比，并建立每个驱动开关导通的占空比和转子位置的对应的函数关系。计算单元还设置为根据计算得出的转子的转动位置以及每个驱动开关导通的占空比和转子的转动位置的对应的函数关系，来计算下一次每个驱动开关应该导通的占空比。
计时单元则记录一个转子转动的时间，并建立时间数据与角度数据的对应关系表，假设转子转过θ角度的时间为t，则可根据转子转动的时间确定转子的下一个转动位置。在上述实施方式中的预设时长，则可根据计时单元的计时时间来实现。
为了获得更好的电机输出特性，还可以通过调节每相绕组的电压的相位角来提速。
以第一相绕组A为例，参照图8说明调节每相绕组的电压的相位角的方法。在一实施例中，可以通过将上述控制方法中的所有预设位置同时前移或后移。例如，在图7c中在转子转到第一预设位置60°角度时，控制模块32高侧开关Q1从原先预设的占空比改变为逐渐减小的占空比，为了将相位角提前，在图8中，可以将图7c中的第一预设位置前移θ角度(例如，15°)，这样当转子转到第一预设位置(60°-θ，例如，35°)时，控制模块32高侧开关Q1从原先预设的占空比改变为逐渐减小的占空比。按照此方式，第二预设位置、第三预设位置、第四预设位置、第五预设位置及第六预设位置均需同时前移θ角度。
实际情况中，θ角度根据具体应用场合设定，以获得较佳的电机输出特性。在一个实施例中，θ角的范围为-60°至+10°，其中，“-”表示所有预设位置同时前移，例如“-60°”表示所有预设位置同时前移60°；“+”表示所有预设位置同时后移，例如“+10°”表示所有预设位置同时后移10°。
通过上述实施方式，对于使用电池包20作为电源模块31电源模块的电动工具10而言，一方面可使要求高电压(额定电压)的电池包20供电的电动工具10 在接入低电压(额定电压)的电池包20时也能满足输出特性需求；另一方面，使得接入低电压的电池包20的电动工具10的性能接近于接入高电压的电池包20的电动工具10，以此提高接入低电压的电池包20的电动工具10的输出性能。也就是说，当电动工具10接入第一电压的电池包20时，电机34输出第一输出功率和第一转速；采用本实施例中的电动工具及其控制方式后，当电动工具10接入第二电压的电池包20时，电机34输出与第一转速接近的第二转速和与第一输出功率接近的第二功率中的至少一个，所述的第二电压和第一电压为电池包的额定电压，且第二电压小于第一电压。也即是说，采用上述方法，提高了电动工具10的电机输出转速和输出功率。
上述方案通过增大每相绕组的连续导电时间或连续导通的电角度来实现提速，提升电动工具的电机转速，使低压供电的电动工具的性能接近于高压供电的电动工具。同时，高压供电的电动工具在使用低电压的电源模块供电时也能满足输出特性需求，这样可以将低电压的电源模块作为高电压供电的电动工具的后备电源模块使用，也就是可以将同一电压的电源模块(例如，电池包)应用于不同输出需求的电动工具，从而提高电源模块的使用率；另外，通过提高电动工具的输出性能，可以使同一种电动工具适配不同电压的电源模块，并可根据不同电动工具的使用场合和需求，配置不同的电机特性曲线，提高电动工具的工作效率和工作效果。
参照图9是额定电压为48V的电动工具的输出特性曲线，其中a曲线是该电动工具使用低电压电池包(24V)供电时电动工具的输出特性曲线(转速-转矩关系图)，c曲线是该电动工具使用高电压电池包供电(48V)的电动工具的输出特性曲线(转速-转矩关系图)，b曲线是在使用低电压电池包(24V)供电时采用上述控制方法时电动工具的输出特性曲线(转速-转矩关系图)，由图9可知，b曲线近似贴合c曲线。因此，采用上述控制方法，使得高电压电源供电的电动工具在使用低电压电源供电时，其输出特性近似于高电压电源供电时的输出特性，可以满足需求。
图10a、图10b和图10c为不同种类电动的转速对比曲线图，其中横坐标为转矩T，单位为N.mm，纵坐标为转速n，单位为rpm，虚线表示相关的电动工具的转速n随转矩T的变化曲线，实线表示采用上述方案的电动工具的转速n随转矩T的变化曲线。从图10a、10b及10c可以看出，采用上述方案的电动工具在重载时相比于相关技术中的电动工具具有较高的转速。同时，采用上述方案，可以配置 不同的电机输出特性曲线。图10a所示的电动工具可以是需要较大转速的吹风机，采用上述方案后，吹风机具有更高的转速、更大的风量以及更大推力，这样可以吹动更重的物体(例如，石子)。图10b所示的电动工具可以是转速与冲击频率有要求的冲击钻，采用上述方案后，将转速与合适的冲击频率对应，可有效提高整机的冲击效率以及冲击性能。图10c所示的电动工具可以是扫雪机，采用上述方案后，可以在雪少轻载时使用恒定较低的转速，以节约能源，增加续航时间，随着抛雪量的增加，即负载增加时，将电机转速提高，以加快抛雪速度，避免雪堆积在机器腔道内。
本实施例提供的电动工具通过提高多电压供电的兼容性，使电动工具能够适配不同的电源电压且能满足输出特性需求。
电动工具不限于上述装置，吹风机、冲击钻、扫雪机，电圆锯、曲线锯、斜锯、往复锯、角磨、切割机及割草机等利用无刷电机驱动的电动工具均可以采用上述方案。
需要说明的是，本申请不限于直流无刷电动工具，凡是采用上述控制方法的申请均落在本申请的范围内。

Claims (29)

  1. 一种电动工具，包括：
    功能件，设置为实现所述电动工具的功能；
    电机，设置为驱动所述功能件；所述电机包括转子、第一相绕组、第二相绕组和第三相绕组；
    驱动电路，电连接至所述第一相绕组、第二相绕组和第三相绕组，并设置为驱动所述电机以输出动力；
    电源模块，电连接至所述驱动电路，设置为通过所述驱动电路为所述第一相绕组、第二相绕组和第三相绕组供电；及
    控制模块，与所述驱动电路连接，设置为输出控制信号控制所述驱动电路；所述控制模块被配置为：在所述电源模块的电压小于等于预设电压阈值时，根据所述电机的转子的转动位置控制所述驱动电路以使所述第一相绕组、第二相绕组和第三相绕组同时连接至所述电源模块。
  2. 根据权利要求1所述的电动工具，其中，所述预设电压阈值为所述电动工具的额定电压的0.4-0.8倍。
  3. 根据权利要求1所述的电动工具，其中，所述电源模块的电压大于等于所述电动工具的额定电压的0.2倍。
  4. 根据权利要求1所述的电动工具，其中，所述电源模块包括电源正极端和电源负极端；所述电源模块设置为使所述电源正极端和电源负极端之间产生电势差；所述控制模块被配置为：在所述转子转动至第一预设转动位置时，控制所述驱动电路以使：所述第一相绕组电连接至所述电源正极端、所述第二相绕组电连接至所述电源负极端、所述第三相绕组电连接至所述电源正极端和所述电源负极端中的一个；
    所述控制模块还被配置为：在所述转子转动至第二预设转动位置时，控制所述驱动电路以使所述第三相绕组从所述电源正极端和所述电源负极端中的一个断开电连接并电连接至所述电源正极端和所述电源负极端中的另一个。
  5. 根据权利要求4所述的电动工具，其中，所述控制模块设置为在所述转子转动至第三预设转动位置时，控制所述驱动电路以使所述第一相绕组从所述电源正极端断开电连接并电连接至所述电源负极端或使所述第二相绕组从所述电源负极端断开电连接并电连接至所述电源正极端。
  6. 根据权利要求4所述的电动工具，其中，所述控制模块设置为在所述转子处于第一预设转动位置和第二预设转动位置之间，控制所述驱动电路以使所述 第三相绕组的电压至少部分以预设的变化率跟随所述转子的转动位置变化而变化。
  7. 根据权利要求4所述的电动工具，其中，所述控制模块设置为在所述转子位于第一预设转动位置和第二预设转动位置之间时，控制所述驱动电路以使所述第三相绕组的电压至少部分以变化的变化率跟随所述转子的转动位置变化而变化。
  8. 根据权利要求5所述的电动工具，其中，所述控制模块设置为在所述转子位于第二预设转动位置和第三预设转动位置之间时，控制所述驱动电路以使所述第三相绕组的电压的至少部分保持不变。
  9. 根据权利要求5所述的电动工具，其中，所述控制模块设置为在所述转子位于第一预设转动位置和第二预设转动位置之间时，控制所述驱动电路以使所述第三相绕组的电压至少部分以逐渐增大的变化率和逐渐减小的变化率中的一个跟随所述转子的转动位置变化而变化；
    所述控制模块设置为在所述转子位于第二预设转动位置和第三预设转动位置之间时，控制所述驱动电路以使所述第三相绕组的电压至少部分以逐渐增大的变化率和逐渐减小的变化率中的另一个跟随所述转子的转动位置变化而变化。
  10. 根据权利要求1所述的电动工具，其中，所述第一相绕组的电压、所述第二相绕组的电压、所述第三相绕组的电压互成120°相位角。
  11. 根据权利要求4所述的电动工具，其中，所述驱动电路包括驱动开关，所述驱动开关能在所述控制模块的控制下以预定的占空比导通所述第三相绕组与所述电源模块的电性连接；
    所述控制模块设置为在所述转子位于所述第一预设转动位置和所述第二预设转动位置之间时，控制所述驱动开关至少部分以变化的占空比导通所述第三相绕组与所述电源模块的电性连接。
  12. 根据权利要求11所述的电动工具，其中，所述控制模块还包括存储单元，所述存储单元设置为存储所述占空比和所述转子的转动位置的对应关系表。
  13. 根据权利要求11所述的电动工具，其中，所述控制模块还包括计算单元，所述计算单元设置为根据所述转子的转动位置计算得出所述占空比。
  14. 根据权利要求1所述的电动工具，其中，所述电动工具包括电压检测模块，所述电压检测模块设置为检测所述电源模块的电压；所述电压检测模块与所述控制模块连接，所述控制模块能够根据所述电压检测模块的检测信号判断 所述电源模块的电压是否小于所述预设电压阈值。
  15. 根据权利要求1所述的电动工具，其中，所述电动工具包括电流检测模块，所述电流检测模块设置为检测所述电机的电流；所述电流检测模块与所述控制模块连接，所述控制模块设置为根据所述电流检测模块的检测信号判断所述电源模块的电压是否小于所述预设电压阈值。
  16. 根据权利要求1所述的电动工具，其中，所述控制模块电连接至所述驱动电路并向所述驱动电路发送控制信号以使所述第一相绕组、第二相绕组及第三相绕组中的电压的相位角超前或滞后一个预设角度。
  17. 一种电动工具的控制方法，所述电动工具包括：电机，所述电机包括转子、第一相绕组、第二相绕组和第三相绕组；及
    电源模块，包括电源正极端和电源负极端，所述电源模块设置为使所述电源正极端和电源负极端之间产生电势差；
    所述控制方法包括：
    获取所述电源模块的电压；及
    在所述电源模块的电压小于等于预设电压阈值时，获取所述转子的转动位置，其中，当所述转子转动至第一预设转动位置时，将所述第一相绕组电连接至所述电源正极端，所述第二相绕组电连接至所述电源负极端，所述第三相绕组电连接至所述电源正极端和所述电源负极端中的一个；当所述转子转动至第二预设转动位置时，将所述第三相绕组从所述电源正极端和所述电源负极端中的一个断开电连接并电连接至所述电源正极端和所述电源负极端中的另一个。
  18. 根据权利要求17所述的电动工具的控制方法，还包括：在所述转子转动至第三预设转动位置时，将所述第一相绕组从所述电源正极端断开电连接并电连接至所述电源负极端或将所述第二相绕组从所述电源负极端断开电连接并电连接至所述电源正极端。
  19. 根据权利要求17所述的电动工具的控制方法，其中，所述预设电压阈值为所述电动工具的额定电压的0.4-0.8倍。
  20. 根据权利要求17所述的电动工具的控制方法，其中，所述电源模块的电压大于等于所述电动工具的额定电压的0.2倍。
  21. 根据权利要求17所述的电动工具的控制方法，其中，所述第一相绕组的电压、所述第二相绕组的电压及所述第三相绕组的电压互成120°相位角。
  22. 根据权利要求17所述的电动工具的控制方法，其中，在所述转子位于所 述第一预设转动位置和第二预设转动位置之间时，使所述第三相绕组的电压至少部分以预设的变化率跟随所述转子的转动位置变化而变化。
  23. 根据权利要求17所述的电动工具的控制方法，其中，在所述转子位于所述第一预设转动位置和第二预设转动位置之间时，使所述第三相绕组的电压至少部分以变化的变化率跟随所述转子的转动位置变化而变化。
  24. 根据权利要求18所述的电动工具的控制方法，其中，在所述转子位于第二预设转动位置和第三预设转动位置之间时，控制模块控制驱动电路以使所述第三相绕组的电压的至少部分保持不变。
  25. 根据权利要求18所述的电动工具的控制方法，其中，在所述转子位于第一预设转动位置和第二预设转动位置之间时，使所述第三相绕组的电压至少部分以逐渐增大的变化率和逐渐减小的变化率中的一个跟随所述转子的转动位置变化而变化；在所述转子位于第二预设转动位置和第三预设转动位置之间时，使所述第三相绕组的电压至少部分以逐渐增大的变化率和逐渐减小的变化率中的另一个跟随所述转子的转动位置变化而变化。
  26. 一种电动工具的控制方法，所述电动工具包括：
    电机，所述电机包括转子、第一相绕组、第二相绕组和第三相绕组；及
    电源模块，包括电源正极端和电源负极端，所述电源模块使所述电源正极端和电源负极端之间产生电势差；
    所述控制方法包括：
    获取所述电源模块的电压；
    在所述电源模块的电压小于等于预设电压阈值时，将所述第一相绕组、第二相绕组及第三相绕组同时连接至所述电源正极端或电源负极端；及
    获取所述转子的转动位置，其中，在所述转子转动至一个预设位置时，使所述第一相绕组、第二相绕组及第三相绕组中的一个从所述电源正极端或电源负极端断开并连接至所述电源正极端和电源负极端中的另一个。
  27. 根据权利要求26所述的电动工具的控制方法，其中，在所述转子转动至第一预设位置时，使所述第一相绕组、第二相绕组及第三相绕组中的一个从所述电源正极端或电源负极端断开并连接至所述电源正极端和电源负极端中的另一个；在所述转子转动至第二预设位置时，使所述第一相绕组、第二相绕组及第三相绕组中的另一个从所述电源正极端或电源负极端断开并连接至所述电源正极端和电源负极端中的另一个。
  28. 根据权利要求26所述的电动工具的控制方法，其中，在所述转子转动至第一预设位置时，使所述第一相绕组、第二相绕组及第三相绕组中的第一个从所述电源正极端或电源负极端断开并连接至所述电源正极端和电源负极端中的另一个；在所述转子转动至第二预设位置时，使所述第一相绕组、第二相绕组及第三相绕组中的第二个从所述电源正极端或电源负极端断开并连接至所述电源正极端和电源负极端中的另一个；在所述转子转动至第三预设位置时，使所述第一相绕组、第二相绕组及第三相绕组中的第三个从所述电源正极端或电源负极端断开并连接至所述电源正极端和电源负极端中的另一个。
  29. 根据权利要求26所述的电动工具的控制方法，其中，所述第一相绕组的电压、所述第二相绕组的电压及所述第三相绕组的电压互成120°相位角。
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EP3806316A1 (en) 2021-04-14
CN109873578A (zh) 2019-06-11
EP3806316A4 (en) 2021-07-28

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