WO2019100752A1 - 电动工具 - Google Patents

电动工具 Download PDF

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Publication number
WO2019100752A1
WO2019100752A1 PCT/CN2018/098569 CN2018098569W WO2019100752A1 WO 2019100752 A1 WO2019100752 A1 WO 2019100752A1 CN 2018098569 W CN2018098569 W CN 2018098569W WO 2019100752 A1 WO2019100752 A1 WO 2019100752A1
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WO
WIPO (PCT)
Prior art keywords
capacitor
control unit
brushless motor
power
circuit
Prior art date
Application number
PCT/CN2018/098569
Other languages
English (en)
French (fr)
Inventor
王宏伟
陈伟鹏
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
Priority claimed from CN201810665144.7A external-priority patent/CN109842282B/zh
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 EP18880376.1A priority Critical patent/EP3687057B1/en
Publication of WO2019100752A1 publication Critical patent/WO2019100752A1/zh
Priority to US16/855,234 priority patent/US10898985B2/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

Definitions

  • the present disclosure relates to the field of power tools, and in particular to a control circuit for a power tool.
  • the existing power tools In order to meet the demand for stable output performance, the existing power tools often adopt a large-capacitance design scheme, resulting in a large size of the power tool, which is not convenient to carry and operate.
  • U.S. Patent Application No. US 20170110935 A1 discloses a capacitor circuit which determines whether a DC bus voltage collected by a sampling circuit reaches a threshold value by a comparator, and then discharges the capacitor through transistor control when the threshold value is reached, but is not powered. The charging process is controlled at the time. Since the power supply voltage cannot reach the comparator threshold at the moment of power-on, it is still charged at a high current during power-on. At the moment of power-on, the power supply voltage is directly applied across the capacitor, causing the capacitor to generate an instantaneous current that will bring power to the power supply. Shock. The instantaneous high current impact will form an electric spark on the power supply side, which brings certain safety hazards.
  • a power tool includes: a housing; a brushless motor housed in the housing, the brushless motor including a stator and a rotor; a motor shaft driven by the rotor; and a tool accessory shaft for supporting and driving the tool
  • An accessory device for connecting the motor shaft to the tool accessory shaft; a driving circuit for outputting a switching signal to drive the rotor of the brushless motor; and a control unit that outputs a driving signal to control the driving circuit; a DC unit that supplies power to the brushless motor, the driving circuit, and the control unit; and a capacitor circuit that is connected in parallel between the positive and negative terminals of the DC unit.
  • the capacitor circuit includes a capacitor C and a power switch tube Q, and the capacitor C and the power switch tube Q are connected in series; the control unit is also electrically connected to the power switch tube Q, and the control unit is configured A PWM duty cycle signal is output to control the power switch Q to be turned on and off.
  • control unit is configured to output a PWM duty cycle signal to turn on the power switch tube Q when the rotation speed of the brushless motor reaches a first speed.
  • the capacitor circuit is in a charged state.
  • control unit is configured to output a PWM duty cycle signal to turn off the power switch tube Q when the rotation speed of the brushless motor reaches a second rotation speed
  • the capacitor circuit is placed in a discharged state, wherein the first rotational speed is less than the second rotational speed.
  • the duty ratio of the PWM duty signal is gradually decreased, so that the capacitor circuit is in a state of slow discharge.
  • the present disclosure also provides another power tool including: a motor including a stator and a rotor; a transmission operatively coupled to the rotor, outputting power to drive the tool attachment; and a drive circuit for outputting the switch
  • the signal is driven to drive the rotor of the motor; the control unit outputs an output signal to control the driving circuit; the rectifier module is configured to convert the alternating current into direct current to supply power to the motor, the driving circuit and the control unit; and the capacitor circuit is connected Between the rectifier module and the drive circuit.
  • the capacitor circuit includes a capacitor C and a power switch tube Q, and the capacitor C and the power switch tube Q are connected in series; the control unit is also electrically connected to the power switch tube Q, and the control unit is configured A PWM duty cycle signal is output to control the power switch Q to be turned on and off.
  • the power tool as described above, wherein, when the power switch tube Q is turned off, the duty ratio of the PWM duty signal is gradually decreased.
  • the control unit is configured to output a PWM duty cycle signal according to a characteristic parameter related to the rotational speed of the motor to control the power switch tube Q to be turned on and off.
  • a characteristic parameter related to the rotational speed of the motor to control the power switch tube Q to be turned on and off.
  • the rotational speed of the brushless motor reaches the first rotational speed, outputting a PWM duty cycle signal to turn on the switching element to bring the capacitive circuit into a charging state; and the rotational speed of the brushless motor reaches a second state
  • the PWM duty cycle signal is output to cause the switching element to be turned off to cause the capacitive circuit to be in a discharged state, wherein the first rotational speed is less than the second rotational speed.
  • the present disclosure also provides yet another power tool comprising: a brushless motor including a stator and a rotor; a transmission operatively coupled to the rotor, outputting power to drive the tool attachment; and a drive circuit for Outputting a switch signal to drive the rotor of the brushless motor; a control unit for outputting a drive signal to control the drive circuit; a DC unit for supplying power to the brushless motor, the drive circuit, and the control unit; and a capacitor circuit connected in parallel Between the positive and negative electrodes of the DC unit.
  • the capacitor circuit includes a capacitor C and a switching element, the capacitor C and the switching element are connected in series; the control unit is further electrically connected to the switching element, and the control unit is configured to output a PWM duty cycle signal
  • the switching element is controlled to be turned on and off.
  • control unit is configured to: the control unit is configured to output a PWM duty cycle signal according to a characteristic parameter related to a rotational speed of the brushless motor to control the switching element Turning on and off, when the rotation speed of the brushless motor reaches the first rotation speed, outputting a PWM duty ratio signal to turn on the switching element to make the capacitor circuit be in a charging state.
  • control unit is configured to: when the rotation speed of the brushless motor reaches the first rotation speed, output a PWM duty ratio signal to turn on the switching element, so as to enable The capacitor circuit is in a charging state; when the rotation speed of the brushless motor reaches the second rotation speed, the PWM duty ratio signal is output to turn off the switching element to cause the capacitor circuit to be discharged; the first rotation speed is less than The second rotational speed.
  • the power tool as described above, wherein the DC unit comprises a rectifier module, at least for accessing an alternating current, and the rectifier module is configured to convert the alternating current into direct current.
  • the DC unit comprises a rectifier module, at least for accessing an alternating current
  • the rectifier module is configured to convert the alternating current into direct current.
  • the capacitor circuit is connected in parallel between the rectifier module and the driving circuit.
  • the power tool as described above, wherein the switching element comprises a power switch tube Q.
  • the duty ratio of the PWM duty cycle signal output by the control unit is gradually decreased, so that the capacitor circuit is in a discharging or slow discharging state.
  • the present disclosure also provides a power tool including: a housing; a brushless motor housed in the housing, the brushless motor including a stator and a rotor; a motor shaft driven by the rotor; and a tool accessory shaft for Supporting and driving a tool attachment; a transmission device for connecting the motor shaft to the tool accessory shaft; a driving circuit for outputting a switching signal to drive the rotor of the brushless motor; a control unit, an output driving signal control station a driving circuit; a DC unit for supplying power to the brushless motor, the driving circuit, and the control unit; and a capacitor circuit connected in parallel between the positive and negative terminals of the DC unit; wherein the capacitor circuit includes a capacitor C and a power switch tube Q, the capacitor C and the power switch tube Q are connected in series; the control unit is further electrically connected to the power switch tube Q, and the control unit is configured to output PWM duty according to the speed of the brushless motor The ratio signal is used to control the power switch tube Q to be turned on and off.
  • control unit is configured to output a PWM duty cycle signal to turn on the power switch tube Q when the speed of the brushless motor reaches a first speed
  • the capacitor circuit is placed in a charged state.
  • control unit is configured to output a PWM duty cycle signal to turn off the power switch tube Q when the rotation speed of the brushless motor reaches a second rotation speed
  • the capacitor circuit is placed in a discharged state, wherein the first rotational speed is less than the second rotational speed.
  • the power tool as described above, wherein, when the power switch tube Q is turned off, the duty ratio of the PWM duty signal is gradually decreased.
  • the present disclosure also provides a power tool comprising: an electric machine including a stator and a rotor; a transmission device operatively coupled to the rotor, outputting power to drive the tool attachment; and a drive circuit for outputting the switch signal Driving a rotor of the motor; a control unit that outputs a drive signal to control the drive circuit; a rectifier module for converting alternating current into direct current to supply power to the motor, the drive circuit, and the control unit; and a capacitor circuit coupled to the Between the rectifier module and the driving circuit; wherein the capacitor circuit comprises a capacitor C and a power switch tube Q, the capacitor C and the power switch tube Q are connected in series; the control unit is further connected to the power switch tube The Q is electrically connected, and the control unit is configured to output a PWM duty cycle signal according to a characteristic parameter related to the rotational speed of the motor to control the power switch tube Q to be turned on and off.
  • the power tool as described above, wherein, when the power switch tube Q is turned off, the duty ratio of the PWM duty signal is gradually decreased.
  • control unit is configured to output a PWM duty cycle signal according to a characteristic parameter related to the rotational speed of the motor to control the power switch tube Q to be turned on and off.
  • the PWM duty cycle signal is output to turn the switching element on, so that the capacitive circuit is in a charged state.
  • the present disclosure also provides a power tool comprising: a brushless motor including a stator and a rotor; a transmission device operatively coupled to the rotor, outputting power to drive the tool attachment; and a drive circuit for outputting the switch a signal for driving the rotor of the brushless motor; a control unit for outputting a driving signal to control the driving circuit; a DC unit for supplying power to the brushless motor, the driving circuit, and the control unit; and a capacitor circuit connected in parallel Between the positive and negative electrodes of the DC unit; wherein the capacitor circuit comprises a capacitor C and a switching element, the capacitor C and the switching element are connected in series; the control unit is also electrically connected to the switching element, the control unit It is arranged to output a PWM duty cycle signal according to a characteristic parameter related to the rotational speed of the brushless motor to control the switching element to be turned on and off.
  • control unit is configured to output a PWM duty cycle signal according to a characteristic parameter related to a rotational speed of the brushless motor to control the switching element to be turned on and off,
  • the PWM duty cycle signal is output to turn on the switching element to bring the capacitive circuit into a charged state.
  • control unit is configured to: when the rotation speed of the brushless motor reaches the first rotation speed, output a PWM duty ratio signal to turn on the switching element, so that The capacitor circuit is in a charging state; when the rotation speed of the brushless motor reaches the second rotation speed, the PWM duty signal is output to turn off the switching element to cause the capacitor circuit to be discharged; the first rotation speed Less than the second rotational speed.
  • the power tool as described above, wherein the DC unit comprises a rectifier module, at least for accessing an alternating current, and the rectifier module is configured to convert the alternating current into direct current.
  • the DC unit comprises a rectifier module, at least for accessing an alternating current
  • the rectifier module is configured to convert the alternating current into direct current.
  • the power tool as described above, wherein the capacitor circuit is connected between the rectifier module and the driving circuit.
  • the present disclosure also provides an angle grinder comprising: a housing; a brushless motor housed in the housing, the brushless motor including a stator and a rotor; a motor shaft driven by the rotor; and a tool accessory shaft for Supporting and driving a sanding disc; a transmission device for connecting the motor shaft to the tool accessory shaft; a driving circuit for outputting a switching signal to drive the rotor of the brushless motor; a control unit, an output driving signal control station a driving circuit; a DC unit for supplying power to the brushless motor, the driving circuit, and the control unit; and a capacitor circuit connected in parallel between the positive and negative terminals of the DC unit; wherein the capacitor circuit includes a capacitor C and a power switch tube Q, the capacitor C and the power switch tube Q are connected in series, and the ratio of the capacitance of the capacitor to the rated power of the brushless motor is 20 uF / kW ⁇ 80 uF / kW; the control unit is also The power switch tube Q is electrical
  • the angle grinder is as described above, wherein the control unit is configured to output a PWM duty cycle signal to turn on the power switch tube Q when the rotation speed of the brushless motor reaches a first speed
  • the capacitor circuit is placed in a charged state.
  • the angle grinder is as described above, wherein the control unit is configured to output a PWM duty cycle signal to turn off the power switch tube Q when the rotation speed of the brushless motor reaches a second rotation speed
  • the capacitor circuit is placed in a discharged state, wherein the first rotational speed is less than the second rotational speed.
  • the angular grinder as described above, wherein the duty cycle of the PWM duty cycle signal is gradually decreased when the power switch tube Q is turned off.
  • the present disclosure also provides an angle grinder comprising: a motor including a stator and a rotor; a transmission operatively coupled to the rotor, outputting power to drive the sanding disc; and a drive circuit for outputting the switching signal Driving a rotor of the motor; a control unit that outputs a drive signal to control the drive circuit; a rectifier module for converting alternating current into direct current to supply power to the motor, the drive circuit, and the control unit; and a capacitor circuit coupled to the Between the rectifier module and the driving circuit; wherein the capacitor circuit comprises a capacitor C and a power switch tube Q, the capacitor C and the power switch tube Q are connected in series, and the capacitance of the capacitor is related to the motor The ratio of rated power is 80 uF/kW or more; the control unit is further electrically connected to the power switch tube Q, and the control unit is configured to output a PWM duty cycle signal to control the power switch tube Q to be turned on and Shut down.
  • the angular grinder as described above, wherein the duty cycle of the PWM duty cycle signal is gradually decreased when the power switch tube Q is turned off.
  • the angle grinder as described above, wherein the control unit is configured to output a PWM duty cycle signal according to a characteristic parameter related to the rotational speed of the motor to control the power switch tube Q to be turned on and off.
  • the PWM duty cycle signal is output to turn the switching element on, so that the capacitive circuit is in a charged state.
  • the present disclosure also provides a power tool comprising: a brushless motor including a stator and a rotor; a transmission device operatively coupled to the rotor, outputting power to drive the tool attachment; and a drive circuit for outputting the switch a signal for driving the rotor of the brushless motor; a control unit for outputting a driving signal to control the driving circuit; a DC unit for supplying power to the brushless motor, the driving circuit, and the control unit; and a capacitor circuit connected in parallel Between the positive and negative electrodes of the DC unit; wherein the capacitor circuit includes a capacitor C and a switching element, the capacitor C and the switching element are connected in series, and a ratio of a capacitance of the capacitor to a rated power of the brushless motor is 80 uF / kW or more; the control unit is also electrically connected to the switching element, the control unit is arranged to output a PWM duty cycle signal to control the switching element to be turned on and off.
  • control unit is configured to output a PWM duty cycle signal according to a characteristic parameter related to a rotational speed of the brushless motor to control the switching element to be turned on and off,
  • the PWM duty cycle signal is output to turn on the switching element to bring the capacitive circuit into a charged state.
  • control unit is configured to: when the rotation speed of the brushless motor reaches the first rotation speed, output a PWM duty ratio signal to turn on the switching element, so that The capacitor circuit is in a charging state; when the rotation speed of the brushless motor reaches the second rotation speed, the PWM duty signal is output to turn off the switching element to cause the capacitor circuit to be discharged; the first rotation speed Less than the second rotational speed.
  • the power tool as described above, wherein the DC unit comprises a rectifier module, at least for accessing an alternating current, and the rectifier module is configured to convert the alternating current into direct current.
  • the DC unit comprises a rectifier module, at least for accessing an alternating current
  • the rectifier module is configured to convert the alternating current into direct current.
  • the power tool as described above, wherein the capacitor circuit is connected between the rectifier module and the driving circuit.
  • the present disclosure also provides an angle grinder comprising: a housing; a brushless motor housed in the housing, the brushless motor including a stator and a rotor; a motor shaft driven by the rotor; and a tool accessory shaft for Supporting and driving a sanding disc; a transmission device for connecting the motor shaft to the tool accessory shaft; a driving circuit for outputting a switching signal to drive the rotor of the brushless motor; a control unit, an output driving signal control station a driving circuit; a DC unit for supplying power to the brushless motor, the driving circuit, and the control unit; and a capacitor circuit connected in parallel between the positive and negative terminals of the DC unit; wherein the capacitor circuit includes a capacitor C and a power switch tube Q, the capacitor C and the power switch tube Q are connected in series; the control unit is further electrically connected to the power switch tube Q, and the control unit is configured to output PWM duty according to the speed of the brushless motor The ratio signal, when the rotation speed of the brushless motor reaches the first rotation
  • the angle grinder is as described above, wherein the control unit is configured to output a PWM duty cycle signal to turn off the power switch tube Q when the rotation speed of the brushless motor reaches a second rotation speed
  • the capacitor circuit is placed in a discharged state, wherein the first rotational speed is less than the second rotational speed.
  • the angle grinder is as described above, wherein the duty ratio of the PWM duty cycle signal is gradually increased when the power switch tube Q is turned on.
  • the angle grinder is as described above, wherein the capacitor C is an electrolytic capacitor, and a ratio of a capacitance of the electrolytic capacitor to a rated power of the brushless motor is 20 uF/kW to 80 uF/kW.
  • the present disclosure also provides an angle grinder comprising: a motor including a stator and a rotor; a transmission operatively coupled to the rotor, outputting power to drive the sanding disc; and a drive circuit for outputting the switching signal Driving a rotor of the motor; a control unit that outputs a drive signal to control the drive circuit; a rectifier module for converting alternating current into direct current to supply power to the motor, the drive circuit, and the control unit; and a capacitor circuit coupled to the Between the rectifier module and the driving circuit; wherein the capacitor circuit comprises a capacitor C and a power switch tube Q, the capacitor C and the power switch tube Q are connected in series; the control unit is further connected to the power switch tube Q is electrically connected, the control unit is configured to output a PWM duty cycle signal according to the rotation speed of the motor to control the power switch tube Q to be turned on, and when the rotation speed of the motor reaches the first rotation speed, the output PWM accounts for The space ratio signal is used to control the power switch tube Q
  • the angle grinder is as described above, wherein the duty ratio of the PWM duty cycle signal is gradually increased when the power switch tube Q is turned on.
  • the angle grinder is as described above, wherein the capacitor C is an electrolytic capacitor, and a ratio of a capacitance of the electrolytic capacitor to a rated power of the motor is 20 uF/kW to 80 uF/kW.
  • the present disclosure also provides a power tool comprising: a brushless motor including a stator and a rotor; a transmission device operatively coupled to the rotor, outputting power to drive the tool attachment; and a drive circuit for outputting the switch a signal for driving the rotor of the brushless motor; a control unit for outputting a driving signal to control the driving circuit; a DC unit for supplying power to the brushless motor, the driving circuit, and the control unit; and a capacitor circuit connected in parallel Between the positive and negative electrodes of the DC unit; wherein the capacitor circuit comprises a capacitor C and a switching element, the capacitor C and the switching element are connected in series; the control unit is also electrically connected to the switching element, the control unit Providing, according to the rotation speed of the brushless motor, outputting a PWM duty signal to control conduction of the switching element, and outputting a PWM duty signal to control the rotation when the rotation speed of the brushless motor reaches a first rotation speed The switching element is turned on to place the capacitor circuit in
  • control unit is configured to: when the rotation speed of the brushless motor reaches a first rotation speed, output a PWM duty cycle signal to turn on the switching element, so that The capacitor circuit is in a charging state; when the rotation speed of the brushless motor reaches the second rotation speed, the PWM duty cycle signal is output to turn off the switching element to cause the capacitor circuit to be discharged; the first rotation speed is less than Said second speed.
  • the power tool described above wherein the DC unit comprises a rectifier module, at least for accessing an alternating current, and the rectifier module is configured to convert the alternating current into direct current.
  • the capacitor circuit is connected between the rectifier module and the driving circuit.
  • the present disclosure also provides an angle grinder comprising: a housing; a brushless motor housed in the housing, the brushless motor including a stator and a rotor; a motor shaft driven by the rotor; and a tool accessory shaft for Supporting and driving a sanding disc; a transmission device for connecting the motor shaft to the tool accessory shaft; a driving circuit for outputting a switching signal to drive the rotor of the brushless motor; a control unit, an output driving signal control station a driving circuit; a DC unit for supplying power to the brushless motor, the driving circuit, and the control unit; and a capacitor circuit connected in parallel between the positive and negative terminals of the DC unit; wherein the capacitor circuit includes a capacitor C and a power switch tube Q, the capacitor C and the power switch tube Q are connected in series; the control unit is further electrically connected to the power switch tube Q, and the control unit is configured to output PWM duty according to the speed of the brushless motor a ratio signal, when the rotation speed of the brushless motor reaches the first
  • the angle grinder described above wherein the duty ratio of the PWM duty cycle signal is gradually increased when the power switch tube Q is turned on.
  • the angle grinder described above wherein, when the power switch tube Q is turned off, the duty ratio of the PWM duty cycle signal is gradually decreased.
  • the capacitor C is an electrolytic capacitor, and a ratio of a capacitance of the electrolytic capacitor to a rated power of the brushless motor is 20 uF/kW to 80 uF/kW.
  • the present disclosure also provides an angle grinder comprising: a motor including a stator and a rotor; a transmission operatively coupled to the rotor, outputting power to drive the sanding disc; and a drive circuit for outputting the switching signal Driving a rotor of the motor; a control unit that outputs a drive signal to control the drive circuit; a rectifier module for converting alternating current into direct current to supply power to the motor, the drive circuit, and the control unit; and a capacitor circuit coupled to the Between the rectifier module and the driving circuit; wherein the capacitor circuit comprises a capacitor C and a power switch tube Q, the capacitor C and the power switch tube Q are connected in series; the control unit is further connected to the power switch tube Q electrically connected, the control unit is configured to output a PWM duty cycle signal according to the rotation speed of the motor to control the power switch tube Q and turn off, and output PWM when the speed of the motor reaches the first speed a duty cycle signal turns on the switching element to bring the capacitor circuit into a charging state;
  • the angle grinder described above wherein, when the power switch tube Q is turned off, the duty ratio of the PWM duty cycle signal is gradually decreased.
  • the capacitor C is an electrolytic capacitor
  • a ratio of a capacitance of the electrolytic capacitor to a rated power of the motor is 20 uF/kW to 80 uF/kW.
  • the present disclosure also provides a power tool comprising: a brushless motor including a stator and a rotor; a transmission device operatively coupled to the rotor, outputting power to drive the tool attachment; and a drive circuit for outputting the switch a signal for driving the rotor of the brushless motor; a control unit for outputting a driving signal to control the driving circuit; a DC unit for supplying power to the brushless motor, the driving circuit, and the control unit; and a capacitor circuit connected in parallel Between the positive and negative electrodes of the DC unit; wherein the capacitor circuit comprises a capacitor C and a switching element, the capacitor C and the switching element are connected in series; the control unit is also electrically connected to the switching element, the control unit Is configured to output a PWM duty cycle signal according to the rotation speed of the brushless motor to control the switching element to be turned on or off, and output a PWM duty cycle signal when the rotation speed of the brushless motor reaches a first rotation speed The switching element is turned on to make the capacitor circuit in a
  • control unit is configured to output a PWM duty cycle signal according to a speed of the brushless motor to control the switching element to be turned on and off, in the brushless motor
  • the PWM duty cycle signal is output to turn on the switching element to bring the capacitive circuit into a charged state.
  • the power tool described above wherein the DC unit comprises a rectifier module, at least for accessing an alternating current, and the rectifier module is configured to convert the alternating current into direct current.
  • the capacitor circuit is connected between the rectifier module and the driving circuit.
  • the present disclosure is advantageous in that the impact on the power side of the power tool can be buffered by controlling the charging or discharging process of the capacitor.
  • FIG. 1 is a schematic view of a mechanical structure of an angle grinder according to a first embodiment of the present disclosure.
  • FIG. 2 is a circuit block diagram of an angle grinder of a first embodiment provided by the present disclosure
  • Figure 3 is a circuit diagram of the capacitor circuit of Figure 2 in a charged state
  • FIG. 5 is a schematic diagram showing a current flow direction of a capacitor circuit in a discharge state in the first embodiment provided by the present disclosure
  • Figure 6 is a schematic view showing the mechanical structure of a power tool according to a second embodiment of the present disclosure.
  • FIG. 7 is a circuit diagram of a capacitor circuit in a discharged state in a second embodiment provided by the present disclosure.
  • Figure 9 is one of the PWM control signal curves of the motor speed and the controller output to the power switch tube during the loading process of the power tool;
  • Figure 10 is the second curve of the PWM control signal of the motor speed and the controller output to the power switch tube during the loading process
  • Figure 11 is a schematic view showing the mechanical structure of an electric drill of a third embodiment provided by the present disclosure.
  • Figure 12 is a flow chart of a control method for an electric drill
  • Figure 13 is a flow chart of another control method for an electric drill
  • Figure 14 is a schematic view showing the mechanical structure of a polishing machine of a fourth embodiment provided by the present disclosure.
  • the angle grinder 100 mainly includes a sanding disc 110, a housing 120, a power module 10, a rectifying module 20, a capacitor circuit 30, a driving circuit 40, a brushless motor 50, and a controller 60.
  • the sanding disc 110 is mounted at one end of the housing 120 for driving, for example, a sanding or cutting function, driven by the brushless motor 50.
  • the power module 10 is used to access the power required for the power tool to operate.
  • the power source of the embodiment may be selected as an AC power source.
  • the power module 10 includes an AC plug to access AC power of 120V or 220V.
  • the AC plug is located at the other end of the housing.
  • the rectifier module 20 constitutes an angularly grounded DC unit that is configured to receive alternating current from the power module 10 and to output a DC bus voltage, that is, to convert the alternating current input by the power module 10 into a pulsating direct current output.
  • the rectifier module 20 is electrically connected to the power module 10 .
  • the rectifier module 20 includes a rectifier bridge composed of four diodes D1, D2, D3, and D4 that convert the alternating current into a pulsating direct current output in the same direction by the unidirectional conductivity of the diode and the tube voltage drop.
  • the capacitor circuit 30 is connected in parallel to the DC bus of the angle grinder, that is, parallel between the positive and negative terminals of the DC unit in the angle grind circuit. Specifically, the capacitor circuit 30 can be connected in parallel between the rectifier module 20 and the drive circuit 40. In one embodiment, the capacitor circuit 30 includes an electrolytic capacitor C and a power switch tube Q in series with the electrolytic capacitor C.
  • the pulsating direct current outputted by the rectifier module 20 is converted into a smooth direct current output by the electrolytic capacitor C to reduce harmonic interference in the pulsating direct current.
  • the ratio of the ratio of the electrolytic capacitor C to the rated power of the brushless motor can be selected from 20uF/kW to 80uF/kW.
  • the capacitor circuit 30 can reduce the size of the power tool and make the structure more compact while meeting the speed requirement of the power tool.
  • the drive circuit 40 is electrically coupled to the stator windings A, B, C of the brushless motor 50 and is used to transfer direct current from the rectifier module 20 to the stator windings A, B, C to drive the brushless motor 50.
  • the driving circuit 40 includes a plurality of switching elements Q1, Q2, Q3, Q4, Q5, and Q6. Each gate terminal of the switching element is electrically connected to the controller 60 for A control signal from controller 60 is received. Each drain or source of the switching element is connected to the stator windings A, B, C of the brushless motor 50.
  • the brushless motor 50 is a three-phase brushless motor, and a triangular or star connection is adopted between the three-phase stator windings A, B, and C.
  • the switching elements Q1-Q6 receive control signals from the controller 60 to change respective conduction states, thereby changing the current applied by the power module 10 to the stator windings A, B, C of the brushless motor 50.
  • the driving circuit 40 has a plurality of driving states. In one driving state, the stator winding of the motor generates a magnetic field, and the controller 60 outputs a corresponding PWM control signal to the driving according to the rotor position or the back electromotive force of the motor.
  • the switching elements in circuit 40 are such that drive circuit 40 switches the drive state such that the stator windings produce a varying magnetic field to drive the rotor to rotate, thereby effecting rotation or commutation of brushless motor 50. It should be noted that any other circuit and control mode capable of driving the rotation or commutation of the brushless motor 50 can be used in the present disclosure.
  • the present disclosure does not make the circuit structure of the drive circuit 40 and the control of the drive circuit 40 by the controller 60. limit.
  • the voltage on the DC bus on the angle grinder changes sharply at the moment of power-on.
  • a drastically varying voltage will produce a large instantaneous current peak under the action of electrolytic capacitor C.
  • This current fluctuation will have a greater impact on the power supply side, which may easily cause safety hazards such as electric sparks.
  • Current spikes also tend to trip the power supply and reduce capacitor life.
  • the power tools in this power supply mode tend to have a large operating power.
  • the ripple current flowing through the electrolytic capacitor C becomes large, and the electrolytic capacitor C repeatedly charges and discharges, thereby increasing the amount of heat, which poses a potential hazard to the safety of the power tool.
  • the ripple current flowing through the electrolytic capacitor C becomes larger than that under light load (below 1000 W), and it is usually necessary to select a larger electrolytic capacitor. To meet circuit safety requirements.
  • the charging and discharging process of the electrolytic capacitor C can be controlled by a control unit constituted by the controller.
  • the control unit limits the charging and discharging time of the electrolytic capacitor C, thereby limiting the charging and discharging power of the electrolytic capacitor C, thereby achieving the same smoothing filtering effect by the electrolytic capacitor C having a smaller capacitance value, thereby avoiding the occurrence of current spikes on the power supply.
  • the tripping threat is used to solve the problem of power-on ignition on the circuit. At the same time, because the current spike is contained, the impact on the life of the capacitor can be avoided, thereby extending the life of the whole machine.
  • FIG. 3 is a circuit diagram of the capacitor circuit 30 in a charged state.
  • the capacitor circuit 30 includes an electrolytic capacitor C and a power switch tube Q connected in series with the electrolytic capacitor C.
  • the electrolytic capacitor C is connected in parallel with the power switch tube Q on the DC bus of the power tool.
  • one pole of the capacitor C is connected to the high voltage output terminal HV+
  • the other pole of the capacitor C is connected to the first pole a of the power switch tube Q
  • the second pole b of the switch transistor Q is connected to the low voltage output terminal.
  • the third pole Vc of the power switch tube Q is connected to the controller.
  • the power switch tube Q can be an IGBT transistor (Insulated Gate Bipolar Transistor), the base of the transistor is controlled by a controller, the emitter is grounded, and the collector is connected to the electrolysis. The negative pole of the capacitor. When the transistor is in the switching state, it is controlled by the controller to switch between the on and off states to charge and discharge the electrolytic capacitor. Similar functions can be achieved by those skilled in the art through FETs.
  • IGBT transistor Insulated Gate Bipolar Transistor
  • the power switch tube Q' is selected as a field effect transistor in this embodiment.
  • the drain d of the FET is similar to the first pole a of the power switch Q' in the above embodiment, and is connected to a high voltage, that is, connected to the high voltage output terminal HV+; the source s of the FET is analogous to the power in the above embodiment.
  • the second pole b of the switch transistor Q' is connected to a low voltage, and is connected to one pole of the capacitor C' in the embodiment; the gate g of the field effect transistor is analogous to the third of the power switch transistor Q' in the above embodiment.
  • the pole Vc is connected to the controller; the cathode of the capacitor C' is connected to the low voltage output or to the ground.
  • the function implemented by the power switch tube Q is a control switch, and a hardware circuit component having a switching function such as a MOSFET, an IGBT, a thyristor, or the like, that is, a switching element, can be utilized. to fulfill.
  • the power switch tube Q realizes its own on or off under the control of the controller 60, and then controls the empty discharge branch of the electrolytic capacitor C where it is located, thereby controlling the charge and discharge time or the charge and discharge power of the electrolytic capacitor C.
  • the power switch tube Q can be turned on or off by a software program written into the controller 60.
  • the controller 60 can also implement the control of the power switch tube Q in a hardware output manner by designing a related control circuit, which is not limited in this disclosure.
  • the controller 60 is configured to send a PWM duty cycle signal to the power switch tube Q when the angle grinder plug is powered up to control the power switch tube Q to be periodically turned on.
  • the capacitor circuit is in a charging state during the on period of the power switch transistor Q.
  • the controller controls the power switch tube Q to be turned on, the capacitor circuit is in a charging state; when the controller controls the power switch tube Q to be turned off, the capacitor circuit is not in a charging state.
  • the controller controls the power switch tube Q to be turned off, the fluctuation condition of the ripple current of the capacitor circuit by the DC bus is correspondingly in a charging or discharging state.
  • the controller 60 may be further configured to turn on or gradually turn on the power switch Q when the rotational speed of the brushless motor 50 reaches the first rotational speed to bring the capacitive circuit 30 into a charged state.
  • FIG. 3 a circuit diagram in which the capacitor circuit 30 is in a charged state. The power tool is connected to the alternating current.
  • the controller 60 outputs a PWM control signal to the power switch tube Q to turn on or gradually increase the conduction time of the power switch tube Q.
  • the flow through the electrolytic capacitor C flows in the direction indicated by the arrow 11 to constitute a current loop, and the capacitor circuit 30 is in a charged state.
  • the controller 60 outputs a corresponding control signal to the drive circuit 40 to cause the drive circuit 40 to drive the brushless motor 50 to operate.
  • the first rotational speed can be set to zero.
  • the electrolytic capacitor C is electrically connected to the rectifier module 20 by turning on the power switch tube Q, and the voltage waveform is ensured while providing the necessary starting torque for the power tool. Smoothing, so that the motor can have a more stable output performance.
  • the controller 60 can also be arranged to turn off the power switch tube Q to bring the capacitor circuit 30 into a discharged state when the rotational speed of the brushless motor 50 reaches the second rotational speed.
  • FIG. 5 a circuit diagram in which the capacitor circuit 30 is in a discharged state.
  • the controller 60 outputs a second control signal to the power switch tube Q to turn off the power switch tube Q.
  • the current is from the positive pole of the electrolytic capacitor C as indicated by the arrow 12
  • the direction sequentially flows through the switching element, the stator windings A, B, C and the diode back to the negative pole of the electrolytic capacitor C, and the capacitor circuit 30 is in a discharged state.
  • the capacitor circuit 30 is not connected to the rectifier circuit by opening the power switch tube Q, thereby reducing the heat loss of the electrolytic capacitor C, prolonging the life of the capacitor circuit 30, and improving the electric power. The reliability of the tool.
  • the rotation speed detection of the brushless motor 50 can be detected by a separate rotation speed detecting module, or can be obtained by detecting or calculating by a detecting unit integrated in the controller 60. Any solution capable of obtaining the rotational speed of the brushless motor 50 can be used in the present disclosure, and is not limited thereto.
  • the first rotation speed n1 is zero
  • the second rotation speed n2 ranges from 30%n0 ⁇ n2 ⁇ 70%n0, wherein n0 is the gear rotation speed of the electric tool.
  • the power tool with speed regulation usually has a gear speed switch of multiple gear positions. When the speed control switch is located at different gear positions, the motor correspondingly outputs different gear speeds, that is, the gear speed mentioned here.
  • the controller may be further configured to control the turn-off of the power switch tube Q according to the temperature of the power switch tube or the capacitor C.
  • the above control of the capacitor circuit is equally applicable to a DC powered power tool. Taking the hand-held circular saw shown in FIG. 6 as an example, other DC-powered power tools are similar.
  • a bottom plate 20 for contacting with a workpiece including: a casing 21 on which the casing is mounted; a blade cover 213, the saw blade cover and the same
  • the casing shaft 22 is configured to support the rotation of the saw blade in the saw blade cover to realize the cutting operation of the workpiece;
  • the motor 23 is disposed in the casing, including the stator and the rotor; a motor shaft 231 driven by a rotor of the motor; a transmission device 24 for connecting the motor shaft and the saw blade shaft to conduct rotational motion of the motor shaft to the saw blade
  • the shaft drives the saw blade to operate.
  • the transmission may specifically include a speed reduction mechanism such as a worm gear and a worm that mesh with each other, or a reduction gear box.
  • the worm gear or reduction gearbox may include a gear structure with different gear ratios, or a timing belt transmission structure configured with different timing of the synchronous wheel.
  • the motor can be selected as a brushless motor.
  • the operation of the hand-held circular saw described above also relies on the electronic components mounted on the PCB circuit board, which are housed in the casing 21 and are not exposed to the viewing angle shown in FIG.
  • the PCB circuit board body includes the following circuit hardware: a power supply module 200, a motor sampling module R, a controller 260, a drive circuit 240, and a capacitor circuit 230 similar to the previous embodiment.
  • the circular saw here uses a battery pack to form a power module.
  • the capacitor circuit 230 is connected in parallel to the DC bus, that is, parallel between the positive and negative terminals of the DC unit in the circular saw circuit, that is, in parallel with the positive and negative poles of the DC power supply in a state in which a DC power supply such as a battery pack is supplied.
  • the capacitor circuit 30 can be selectively connected in parallel between the operation switch SW and the drive circuit 240.
  • the battery pack ignition is similar to the process of the alternating current power-on of the previous embodiment.
  • the battery pack When the battery pack is installed, that is, when the DC power module is powered on, the voltage on the DC bus of the power tool changes drastically at the moment of power-on. A drastically varying voltage will produce a large instantaneous current peak under the action of electrolytic capacitor C. This current fluctuation will be on the power supply side, and in this embodiment, it specifically refers to a large impact on the battery pack. It is easy to cause safety hazards such as electric sparks between the battery pack pole pieces.
  • FIG. 8 is a PWM control signal curve of the motor speed and the controller 260 output to the power switch tube Q during the power-on startup.
  • the abscissa indicates time
  • the ordinate indicates the motor speed and the PWM control signal of the power switch Q gate.
  • the controller 260 can output a fully-on PWM control signal to the power switch gate to turn the power switch Q all-on. At this time, the rotation speed of the motor gradually rises. When the rotation speed is greater than or equal to the second rotation speed n2, the controller 60 outputs a control signal to the power switch tube Q gate to turn off the power switch tube Q.
  • one of the PWM control signal curves of the motor speed and the controller 260 output to the power switch tube Q during the running load of the power tool.
  • the speed of the motor gradually decreases as the torque increases.
  • the controller 260 outputs a control signal to the power switch tube Q gate to turn on the power switch tube Q.
  • the capacitor circuit 230 is in a charging state, and the electric energy stored in the electrolytic capacitor C is stably loaded to the motor side, and the power supply voltage of the motor is gradually increased, thereby ensuring stable output performance of the motor.
  • the third rotation speed n3 ranges from 80% n0 ⁇ n3 ⁇ 100% n0.
  • the power tool can also be controlled by charging or discharging the electrolytic capacitor C by means of "soft opening” or “soft switching".
  • Soft-on” or “soft-off” is specifically to increase or decrease the turn-on or turn-off of the electrolytic capacitor C by gradually increasing the duty ratio or gradually decreasing the duty ratio by controlling the duty ratio of the PWM control signal.
  • the time of the branch that is, the charge capacity or the discharge amount of the electrolytic capacitor C is controlled by the duty ratio, so that the electrolytic capacitor C is slowly charged or slowly discharged.
  • the electrolytic capacitor C can be slowly charged or discharged to reduce the impact of the charging and discharging processes on the entire circuit.
  • the power tool is suddenly changed or vibrated due to the impact of the capacitor charging and discharging current on the circuit. It can improve the user's operating feel and ensure that the power output of the power tool is free from sudden changes and is safer.
  • FIG. 10 it is one of the PWM control signal curves of the brushless motor speed and the controller output to the power switch tube Q.
  • the abscissa indicates time
  • the ordinate indicates the rotational speed of the brushless motor and the PWM control signal of the power switch tube gate (ie, the third pole).
  • the controller 260 outputs a PWM control signal whose duty cycle is gradually reduced to the power switch tube gate to modulate the power switch tube to achieve soft turn-off;
  • the load torque is increased, the rotation speed is decreased.
  • the controller 60 When the rotation speed is less than or equal to the third rotation speed n3, the controller 60 outputs a PWM control signal whose duty ratio is gradually increased to the power switch tube gate to modulate the power switch tube to realize soft turn-on.
  • the third rotation speed value n3 ranges from 80% n0 ⁇ n3 ⁇ 100% n0. Thereby, the loss and temperature of the power switch tube can be reduced.
  • the above charging and discharging control for the electrolytic capacitor can also be applied to a larger capacitor, for example, the electrolytic capacitor C and the rated power of the brushless motor can be selected.
  • the ratio is greater than 80uF/kW.
  • the mechanical structure specifically includes: a housing 301, an output member 302, a motor 303, a transmission assembly 304, and a PCB (Printed Circuit Board). Circuit board) circuit board 305, power supply device 306.
  • the housing 301 is used to accommodate the motor 303, the transmission assembly 304, the PCB circuit board 305, etc., and one end of the housing 301 is also used to mount the output member 302.
  • the motor 303, the PCB circuit board 305, and the power supply device 306 are blocked by the housing 301 and are not directly exposed to the viewing angle of Fig. 11.
  • the housing 301 may further include a main body housing portion 311 and a head housing portion 312, wherein the main housing portion 311 may be used to accommodate the motor 303, the transmission assembly 304, the PCB circuit board 305, and the head housing.
  • Portion 312 can be coupled to output 302.
  • the main body casing portion 311 may be symmetrically disposed with respect to the tangential plane of the structure shown in Fig. 11, and on both sides of the tangential plane, the main casing portion 311 may include a left casing portion and a right casing portion which are symmetrical to each other, respectively.
  • the output member 302 is for outputting power.
  • the output member 302 can be specifically selected as a collet capable of gripping the drill bit.
  • the motor 303, the transmission assembly 304 and the PCB circuit board 305 are all disposed in the housing 301.
  • the power supply device 306 is used to supply power to the electronic devices inside the electric drill.
  • the PCB circuit board 305 is used to control the operation of the motor 303, and the motor 303 is used to drive the transmission assembly.
  • the transmission assembly 304 is configured to transmit the power output by the motor 303 to the output member 302, thereby driving the output member 302 to output power.
  • the PCB circuit board 305 can be similarly referred to the above embodiment, and includes the following circuit hardware: a power control module, a control unit, a driving circuit, and a motor sampling module.
  • the power control module, the control unit, the drive circuit, and the motor sampling module are all enclosed by the housing 301.
  • the power supply device 306 of the handheld electric drill shown in FIG. 2 can be selected as a battery pack or an AC power source, wherein the battery pack can be assembled by a group of battery units.
  • the battery cells can be connected in series to form a single power supply branch to form a 1P battery pack.
  • the output voltage of the battery pack is changed by a specific power control module, such as a DC-DC module, and the power supply voltage suitable for the control unit, the drive circuit, the motor, and the like is output.
  • a specific power control module such as a DC-DC module
  • the DC-DC module is a mature circuit structure and can be selected according to the specific parameter requirements of the power tool.
  • the power supply device 306 can also be selected as an AC power source, and converts the input AC power through the corresponding power control module, and can also supply power to the power supply device detection module, the control unit, the drive circuit, the optimal duty cycle storage device, the motor, and the like.
  • the circuit structure of the above electric drill is similar to the circuit structure of the angle grinder or the circular saw in the above embodiment, and will not be described herein.
  • the control unit can specifically control the operation of the electric drill by the following step flow.
  • a control method for use in a power tool such as an electric drill includes the following steps:
  • step S102 If it is determined that the power tool is powered on, then go to step S103, otherwise return to S101;
  • the second condition includes but is not limited to: whether the characteristic parameter related to the rotational speed of the brushless motor is satisfied, the power switch tube Q Or whether the temperature of the capacitor C reaches the threshold H, whether the modulation power switch tube Q reaches the preset time T, and the like.
  • the characteristic parameter related to the rotational speed of the brushless motor may include the rotational speed of the motor in the electric tool, for example, whether the rotational speed of the motor in the electric tool reaches the second rotational speed n2, and may also include the motor in the electric tool. Speed related current, voltage or rotor position signal.
  • gradually turning on means gradually increasing the on-time of the power switch tube Q by gradually increasing the duty ratio of the PWM control signal outputted to the power switch tube Q until the power switch tube Q is fully turned on; gradually turning off It means that the duty ratio of the PWM control signal outputted to the power switch tube Q is gradually reduced, and the on-time of the power switch tube Q is gradually reduced until the power switch tube Q is completely turned off.
  • step S102 the motor corresponds to the first rotational speed, and the first rotational speed may be zero.
  • step S103 can also be divided into two sub-steps, when the power tool is powered on, the power switch tube Q is turned on at a gradually increasing duty ratio, and after the power-on preset time or the motor reaches a certain preset speed, Then, the power switch tube Q is fully turned on.
  • control method for use in a power tool such as an electric drill shown in FIG. 13, the control method includes the following steps:
  • the speed n of the motor can be detected by the speed detection module built into the power tool.
  • the rotation speed detecting module may select a position sensor for detecting the rotor of the motor, such as a Hall element, a carbon brush, a commutator, etc.; and may also select a current and/or voltage sampling element disposed on the phase line and/or the bus of the motor, For example, the sampling resistor R is matched with the corresponding motor position calculation module to realize the detection of the motor speed.
  • step S202 Determine whether the rotation speed n of the brushless motor is greater than or equal to the first rotation speed n1; if yes, go to step S203; otherwise, go to step S201.
  • the controller outputs a first control signal for turning on the power switch tube to the power switch tube when the rotation speed of the brushless motor is greater than or equal to the first rotation speed n1, so that the power switch tube is turned on.
  • the first control signal is a first PWM signal.
  • the duty cycle of the first PWM signal is gradually increased.
  • the controller outputs a second control signal for turning on the power switch tube to the power switch tube when the rotation speed of the brushless motor is greater than or equal to the second rotation speed n2, so that the power switch tube is turned off.
  • the second control signal is a second PWM signal.
  • the duty cycle of the second PWM signal is gradually reduced.
  • step S206 It is judged whether the rotation speed of the brushless motor reaches the gear rotation speed n0, and if yes, the process goes to step S207; otherwise, the process goes to step S205.
  • the controller When the speed of the brushless motor is the gear speed, the controller outputs a control signal for softly turning off the power switch tube to the power switch tube, so that the power switch tube is softly turned off.
  • step S208 Determine whether the rotation speed of the brushless motor is less than or equal to the third rotation speed, and if yes, go to step S209; otherwise, go to step S207.
  • the controller When the speed of the brushless motor is less than or equal to the third speed, the controller outputs a control signal for soft-conducting the power switch tube to the power switch tube, so that the power switch tube is soft-conducted.
  • the first rotation speed n1 ranges from 0 ⁇ n1 ⁇ n2
  • the second rotation speed n2 ranges from 30%n0 ⁇ n2 ⁇ 70%n0
  • n0 is the gear speed of the electric tool
  • the third rotation speed The value range of n3 is 80% n0 ⁇ n3 ⁇ 100% n0.
  • the electric tool in the present disclosure may also be a power tool with a speed control function such as an electric drill, an electric hammer, an electric circular saw and a marble machine, which solves the impact of the power-on process on the power supply side, and avoids power-on and sparking. Avoid sudden changes in motor speed during operation and maintain a good operating feel of the power tool.
  • a speed control function such as an electric drill, an electric hammer, an electric circular saw and a marble machine
  • the housing 41 is for housing various components within the polishing machine 400.
  • the housing 41 may include a handle portion 411 and a receiving portion 412.
  • the handle portion 411 is for holding by the user
  • the housing portion 412 is formed to accommodate the accommodation space of the respective components
  • the switch 42 is attachable to the handle portion 411.
  • the switch 42 can be, for example, a trigger for activating the polishing machine 400.
  • the housing portion 412 of the housing 41 houses the motor 43.
  • the motor 43 is used to convert energy provided by an energy source, such as an alternating current source, into a power output.
  • the motor 43 is connected to a motor shaft 431, and one end of the motor shaft 431 is connected to a transmission to output power.
  • the bottom plate 44 is used to mount sandpaper, the bottom plate is connected with a tool accessory shaft, and the tool accessory shaft is connected to the transmission. Under the action of the drive of the motor 43 and the motor shaft, the transmission and the tool accessory shaft, the bottom plate 44 is driven by the motor to be reciprocable or oscillating. When the bottom plate 44 is reciprocated or oscillated, the bottom plate 44 drives the sandpaper to continuously rub on the surface of the workpiece, thereby realizing the functions of grinding and polishing the workpiece.
  • the electronic component may include a power module mainly composed of a battery pack, and a capacitor circuit, a drive circuit connected in parallel to its output terminal, and a control unit.
  • the electronic component can include a rectifier module, a capacitor circuit, a drive circuit, and a control unit.
  • the control unit therein can control the capacitor C in the capacitor circuit to be charged or discharged accordingly with reference to the steps described in the third embodiment. Specifically, the control unit is turned on or off by controlling the power switch tube Q connected in series with the capacitor C, thereby controlling the capacitor C in the capacitor circuit to be charged or discharged accordingly. Specifically, the control unit can control the capacitor C to charge or discharge according to the output PWM signal of the duty ratio, and control the time or amount of charging or discharging of the capacitor C, thereby achieving slow charging or slow discharging of the capacitor.
  • the power-on state of the power tool is detected; when the power tool is powered on, the power switch tube Q is turned on or gradually turned on, and at this time, the capacitor circuit 30 is in a charging state; otherwise, it is continuously detected whether the power tool is powered on;
  • the power switch tube Q is turned off or gradually turned off, thereby causing the capacitor circuit 30 to be in a discharging state, or causing the capacitor circuit 30 to follow the ripple current of the DC bus.
  • the fluctuation is correspondingly in a charging or discharging state; if the second condition is not reached, the power switching tube Q is kept on or gradually turned on.
  • the second condition includes, but is not limited to, whether the rotation speed of the motor in the electric tool reaches the second rotation speed n2, whether the temperature of the power switch tube Q or the capacitor C reaches the threshold H, and whether the modulation power switch tube Q reaches the preset time T.
  • the speed of the motor can be obtained by sampling and calculating the operating current of the motor through the Hall element.
  • the rotation speed of the motor in the power tool reaches the second rotation speed n2
  • the second condition is reached.
  • the power switch tube Q is turned off or gradually turned off, thereby causing the capacitor circuit 30 to be in a discharged state, or causing the capacitor circuit 30 to be in a charged or discharged state corresponding to fluctuations in the ripple current of the DC bus.
  • the surface temperature of the capacitor C may be detected by a thermal element or the like. When the temperature of the capacitor C exceeds a preset threshold H, it is determined that the second condition is reached, and the power switch tube Q is turned off or gradually closed accordingly. Broken.
  • a timing interrupt in the control unit to record the time in the complex control (for example, in the speed regulation state or the PWM duty cycle modulation power switch tube Q), and judge that it is reached when a certain preset time T is exceeded.
  • the second condition causes the power switch tube Q to be turned off or gradually turned off accordingly.
  • the impact on the power source during the power-on process can be reduced, especially the instantaneous current peak at the moment of power-on.
  • the capacitor By controlling the capacitor to be slowly charged during power-on, the power tool and its power supply can be protected with a small capacitance, making the power tool structure more compact and reducing its circuit hardware cost.
  • the control capacitor can be slowly discharged, thereby reducing the impact of the capacitor charging and discharging process on the entire circuit.
  • the power tool's power is suddenly changed or vibrated due to the impact of the capacitor charging and discharging current on the circuit, thereby improving the user's operating feel and ensuring that the power output of the power tool is free from sudden changes and is safer.
  • the second condition herein is independent of the power up state or first speed of the electrician tool. That is, in an embodiment of the present disclosure, whether the power tool is powered on, or whether the power tool has the first rotational speed, the power switch can be correspondingly determined by determining whether the power tool reaches the second condition. Q is turned off or gradually turned off. For example, when the second condition is that the motor speed reaches the second speed, the determination of whether the motor reaches the second speed can be independently determined without considering whether the power tool is powered on or whether the first speed is met, and the control unit is The PWM duty cycle signal is output to control the switching element such as the power switch tube Q to be turned off or gradually turned off, so that the capacitor circuit is in a discharged state.
  • the present disclosure provides a power tool that can buffer the impact on the power side of the power tool by controlling the charging or discharging process of the capacitor, making the power tool compact and improving its safety performance.

Abstract

一种电动工具，包括直流单元、电机（50）、驱动电路（40）、电容电路（30）和控制单元，其中，电容电路（30）包括开关元件（Q1-Q6）和电容（C），控制单元驱动开关元件（Q1-Q6）以实现对电容（C）充电或放电的控制。电容电路（30）连接在直流单元与驱动电路（40）之间，可缓冲对电动工具电源侧的冲击，使电动工具结构紧凑，并提高其安全性能。

Description

电动工具 技术领域
本公开涉及电动工具技术领域，具体涉及一种电动工具的控制电路。
背景技术
现有的电动工具为满足输出性能稳定的需求，多采用大电容的设计方案，导致电动工具的尺寸较大，不便于携带和操作。
美国专利申请US 20170110935 A1公开有一种电容电路，该电路通过比较器判断采样电路采集的直流母线电压是否达到阈值，进而在达到阈值的状况下通过晶体管控制对上述电容进行放电，但未对上电时的充电过程进行控制。由于上电瞬间电源电压无法达到比较器阈值，因此上电时还是大电流充电，在上电瞬间，电源电压将直接加载在电容两端，使电容产生瞬时电流，该瞬时电流将对电源带来冲击。瞬间的大电流冲击会在电源侧形成电火花，带来一定的安全隐患。
为满足用户需求，需设计一种可缓冲对电动工具电源侧的冲击的电动工具。
发明内容
为解决现有技术的不足，本公开的目的在于提供一种结构紧凑且能满足安全性能要求的电动工具。
为了实现上述目标，本公开采用如下的技术方案：
一种电动工具，包括：壳体；无刷电机，容纳于所述壳体内，所述无刷电机包括定子和转子；电机轴，由所述转子驱动；工具附件轴，用于支持并驱动工具附件；传动装置，用于连接所述电机轴至所述工具附件轴；驱动电路，用于输出开关信号以驱动所述无刷电机的转子运转；控制单元，输出驱动信号控制所述驱动电路；直流单元，为所述无刷电机、驱动电路、控制单元供电；电容电路，并联于所述直流单元的正负极之间。其中，所述电容电路包括电容C和功率开关管Q，所述电容C和所述功率开关管Q串联连接；所述控制单元还 与所述功率开关管Q电性连接，所述控制单元设置为输出PWM占空比信号以控制所述功率开关管Q导通和关断。
可选的，如上所述的电动工具，所述控制单元设置为在所述无刷电机的转速达到第一转速时，输出PWM占空比信号使所述功率开关管Q导通，以使所述电容电路处于充电状态。
可选的，如上所述的电动工具，其中，所述控制单元设置为在所述无刷电机的转速达到第二转速时，输出PWM占空比信号使所述功率开关管Q关断，以使所述电容电路处于放电状态，其中所述第一转速小于所述第二转速。
可选的，如上所述的电动工具，在使所述功率开关管Q关断时，所述PWM占空比信号的占空比逐渐减小，以使所述电容电路处于缓慢放电的状态。
可选的，如上所述的电动工具，其中，所述电容C为电解电容，所述电解电容的容值与所述无刷电机的额定功率之比为20uF/kW～80uF/kW。
本公开还同时提供另一种电动工具，包括：电机，包括定子和转子；传动装置，所述传动装置可操作地与所述转子连接，输出动力以驱动工具附件；驱动电路，用于输出开关信号以驱动所述电机的转子运转；控制单元，输出驱动信号控制所述驱动电路；整流模块，用于将交流电转换为直流电，为所述电机、驱动电路、控制单元供电；电容电路，连接在所述整流模块与所述驱动电路之间。其中，所述电容电路包括电容C和功率开关管Q，所述电容C和所述功率开关管Q串联连接；所述控制单元还与所述功率开关管Q电性连接，所述控制单元设置为输出PWM占空比信号以控制所述功率开关管Q导通和关断。
可选的，如上所述的电动工具，其中，在使所述功率开关管Q关断时，所述PWM占空比信号的占空比逐渐减小。
可选的，如上所述的电动工具，其中，所述控制单元设置为依据与所述电机的与转速有关的特性参数输出PWM占空比信号以控制所述功率开关管Q导通和关断，在所述无刷电机的转速达到第一转速时，输出PWM占空比信号使所述开关元件导通，以使所述电容电路处于充电状态；在所述无刷电机的转速达到第二转速时，输出PWM占空比信号使所述开关元件关断，以使所述电容电路处于放电状态，其中所述第一转速小于所述第二转速。
可选的，如上所述的电动工具，其中，所述电容C为电解电容，所述电解电容的容值与所述电机的额定功率之比为20uF/kW～80uF/kW。
本公开还同时提供又一种电动工具，包括：无刷电机，包括定子和转子；传动装置，所述传动装置可操作地与所述转子连接，输出动力以驱动工具附件；驱动电路，用于输出开关信号以驱动所述无刷电机的转子运转；控制单元，用于输出驱动信号控制所述驱动电路；直流单元，为所述无刷电机、驱动电路、控制单元供电；电容电路，并联在所述直流单元的正负极之间。其中，所述电容电路包括电容C和开关元件，所述电容C和开关元件串联连接；所述控制单元还与所述开关元件电性连接，所述控制单元设置为输出PWM占空比信号以控制所述开关元件导通和关断。
可选的，如上所述的电动工具中，所述控制单元设置为：所述控制单元设置为依据与所述无刷电机的转速有关的特性参数输出PWM占空比信号以控制所述开关元件导通和关断，在所述无刷电机的转速达到第一转速时，输出PWM占空比信号使所述开关元件导通，以使所述电容电路处于充电状态。
可选的，如上所述的电动工具中，所述控制单元设置为：在所述无刷电机的转速达到第一转速时，输出PWM占空比信号使所述开关元件导通，以使所述电容电路处于充电状态；在所述无刷电机的转速达到第二转速时，输出PWM占空比信号使所述开关元件关断，以使所述电容电路处于放电；所述第一转速小于所述第二转速。
可选的，如上所述的电动工具，其中，所述直流单元包括整流模块，至少用于接入交流电，所述整流模块用于将所述交流电转换为直流电。
可选的，如上所述的电动工具中，所述电容电路并联于所述整流模块与所述驱动电路之间。
可选的，如上所述的电动工具，其中，所述开关元件包括功率开关管Q。
可选的，如上所述的电动工具，所述控制单元输出的所述PWM占空比信号的占空比逐渐减小，以使所述电容电路处于放电或缓慢放电状态。
本公开还提供一种电动工具，包括：壳体；无刷电机，容纳于所述壳体内，所述无刷电机包括定子和转子；电机轴，由所述转子驱动；工具附件轴，用于 支持并驱动工具附件；传动装置，用于连接所述电机轴至所述工具附件轴；驱动电路，用于输出开关信号以驱动所述无刷电机的转子运转；控制单元，输出驱动信号控制所述驱动电路；直流单元，为所述无刷电机、驱动电路、控制单元供电；电容电路，并联于所述直流单元的正负极之间；其中，所述电容电路包括电容C和功率开关管Q，所述电容C和所述功率开关管Q串联连接；所述控制单元还与所述功率开关管Q电性连接，所述控制单元设置为依据所述无刷电机的转速输出PWM占空比信号以控制所述功率开关管Q导通和关断。
可选的，如上所述的电动工具，其中，所述控制单元设置为在所述无刷电机的转速达到第一转速时，输出PWM占空比信号使所述功率开关管Q导通，以使所述电容电路处于充电状态。
可选的，如上所述的电动工具，其中，所述控制单元设置为在所述无刷电机的转速达到第二转速时，输出PWM占空比信号使所述功率开关管Q关断，以使所述电容电路处于放电状态，其中所述第一转速小于所述第二转速。
可选的，如上所述的电动工具，其中，在使所述功率开关管Q关断时，所述PWM占空比信号的占空比逐渐减小。
可选的，如上所述的电动工具，其中，所述电容C为电解电容，所述电解电容的容值与所述无刷电机的额定功率之比为20uF/kW～80uF/kW。
本公开还提供一种电动工具，包括：电机，包括定子和转子；传动装置，所述传动装置可操作地与所述转子连接，输出动力以驱动工具附件；驱动电路，用于输出开关信号以驱动所述电机的转子运转；控制单元，输出驱动信号控制所述驱动电路；整流模块，用于将交流电转换为直流电，为所述电机、驱动电路、控制单元供电；电容电路，连接在所述整流模块与所述驱动电路之间；其中，所述电容电路包括电容C和功率开关管Q，所述电容C和所述功率开关管Q串联连接；所述控制单元还与所述功率开关管Q电性连接，所述控制单元设置为依据与所述电机的与转速有关的特性参数输出PWM占空比信号以控制所述功率开关管Q导通和关断。
可选的，如上所述的电动工具，其中，在使所述功率开关管Q关断时，所述PWM占空比信号的占空比逐渐减小。
可选的，如上所述的电动工具，其中，所述控制单元设置为依据与所述电 机的与转速有关的特性参数输出PWM占空比信号以控制所述功率开关管Q导通和关断，在所述无刷电机的转速达到第一转速时，输出PWM占空比信号使所述开关元件导通，以使所述电容电路处于充电状态。
可选的，如上所述的电动工具，其中，所述电容C为电解电容，所述电解电容的容值与所述电机的额定功率之比为20uF/kW～80uF/kW。
本公开还提供一种电动工具，包括：无刷电机，包括定子和转子；传动装置，所述传动装置可操作地与所述转子连接，输出动力以驱动工具附件；驱动电路，用于输出开关信号以驱动所述无刷电机的转子运转；控制单元，用于输出驱动信号控制所述驱动电路；直流单元，为所述无刷电机、驱动电路、控制单元供电；电容电路，并联在所述直流单元的正负极之间；其中，所述电容电路包括电容C和开关元件，所述电容C和开关元件串联连接；所述控制单元还与所述开关元件电性连接，所述控制单元设置为依据与所述无刷电机的转速有关的特性参数输出PWM占空比信号以控制所述开关元件导通和关断。
可选的，如上所述的电动工具，其中，所述控制单元设置为依据与所述无刷电机的转速有关的特性参数输出PWM占空比信号以控制所述开关元件导通和关断，在所述无刷电机的转速达到第一转速时，输出PWM占空比信号使所述开关元件导通，以使所述电容电路处于充电状态。
可选的，如上所述的电动工具，其中，所述控制单元设置为：在所述无刷电机的转速达到第一转速时，输出PWM占空比信号使所述开关元件导通，以使所述电容电路处于充电状态；在所述无刷电机的转速达到第二转速时，输出PWM占空比信号使所述开关元件关断，以使所述电容电路处于放电；所述第一转速小于所述第二转速。
可选的，如上所述的电动工具，其中，所述直流单元包括整流模块，至少用于接入交流电，所述整流模块用于将所述交流电转换为直流电。
可选的，如上所述的电动工具，其中，所述电容电路连接在所述整流模块与所述驱动电路之间。
本公开还提供一种角磨，包括：壳体；无刷电机，容纳于所述壳体内，所述无刷电机包括定子和转子；电机轴，由所述转子驱动；工具附件轴，用于支持并驱动打磨盘；传动装置，用于连接所述电机轴至所述工具附件轴；驱动电 路，用于输出开关信号以驱动所述无刷电机的转子运转；控制单元，输出驱动信号控制所述驱动电路；直流单元，为所述无刷电机、驱动电路、控制单元供电；电容电路，并联于所述直流单元的正负极之间；其中，所述电容电路包括电容C和功率开关管Q，所述电容C和所述功率开关管Q串联连接，所述电容的容值与所述无刷电机的额定功率之比为20uF/kW～80uF/kW；所述控制单元还与所述功率开关管Q电性连接，所述控制单元设置为输出PWM占空比信号以控制所述功率开关管Q导通和关断。
可选的，如上所述的角磨，其中，所述控制单元设置为在所述无刷电机的转速达到第一转速时，输出PWM占空比信号使所述功率开关管Q导通，以使所述电容电路处于充电状态。
可选的，如上所述的角磨，其中，所述控制单元设置为在所述无刷电机的转速达到第二转速时，输出PWM占空比信号使所述功率开关管Q关断，以使所述电容电路处于放电状态，其中所述第一转速小于所述第二转速。
可选的，如上所述的角磨，其中，在使所述功率开关管Q关断时，所述PWM占空比信号的占空比逐渐减小。
本公开还提供一种角磨，包括：电机，包括定子和转子；传动装置，所述传动装置可操作地与所述转子连接，输出动力以驱动打磨盘；驱动电路，用于输出开关信号以驱动所述电机的转子运转；控制单元，输出驱动信号控制所述驱动电路；整流模块，用于将交流电转换为直流电，为所述电机、驱动电路、控制单元供电；电容电路，连接在所述整流模块与所述驱动电路之间；其中，所述电容电路包括电容C和功率开关管Q，所述电容C和所述功率开关管Q串联连接，所述电容的容值与所述电机的额定功率之比为80uF/kW或以上；所述控制单元还与所述功率开关管Q电性连接，所述控制单元设置为输出PWM占空比信号以控制所述功率开关管Q导通和关断。
可选的，如上所述的角磨，其中，在使所述功率开关管Q关断时，所述PWM占空比信号的占空比逐渐减小。
可选的，如上所述的角磨，其中，所述控制单元设置为依据与所述电机的与转速有关的特性参数输出PWM占空比信号以控制所述功率开关管Q导通和关断，在所述无刷电机的转速达到第一转速时，输出PWM占空比信号使所述开 关元件导通，以使所述电容电路处于充电状态。
本公开还提供一种电动工具，包括：无刷电机，包括定子和转子；传动装置，所述传动装置可操作地与所述转子连接，输出动力以驱动工具附件；驱动电路，用于输出开关信号以驱动所述无刷电机的转子运转；控制单元，用于输出驱动信号控制所述驱动电路；直流单元，为所述无刷电机、驱动电路、控制单元供电；电容电路，并联在所述直流单元的正负极之间；其中，所述电容电路包括电容C和开关元件，所述电容C和开关元件串联连接，所述电容的容值与所述无刷电机的额定功率之比为80uF/kW或以上；所述控制单元还与所述开关元件电性连接，所述控制单元设置为输出PWM占空比信号以控制所述开关元件导通和关断。
可选的，如上所述的电动工具，其中，所述控制单元设置为依据与所述无刷电机的转速有关的特性参数输出PWM占空比信号以控制所述开关元件导通和关断，在所述无刷电机的转速达到第一转速时，输出PWM占空比信号使所述开关元件导通，以使所述电容电路处于充电状态。
可选的，如上所述的电动工具，其中，所述控制单元设置为：在所述无刷电机的转速达到第一转速时，输出PWM占空比信号使所述开关元件导通，以使所述电容电路处于充电状态；在所述无刷电机的转速达到第二转速时，输出PWM占空比信号使所述开关元件关断，以使所述电容电路处于放电；所述第一转速小于所述第二转速。
可选的，如上所述的电动工具，其中，所述直流单元包括整流模块，至少用于接入交流电，所述整流模块用于将所述交流电转换为直流电。
可选的，如上所述的电动工具，其中，所述电容电路连接在所述整流模块与所述驱动电路之间。
本公开还提供一种角磨，包括：壳体；无刷电机，容纳于所述壳体内，所述无刷电机包括定子和转子；电机轴，由所述转子驱动；工具附件轴，用于支持并驱动打磨盘；传动装置，用于连接所述电机轴至所述工具附件轴；驱动电路，用于输出开关信号以驱动所述无刷电机的转子运转；控制单元，输出驱动信号控制所述驱动电路；直流单元，为所述无刷电机、驱动电路、控制单元供电；电容电路，并联于所述直流单元的正负极之间；其中，所述电容电路包括 电容C和功率开关管Q，所述电容C和所述功率开关管Q串联连接；所述控制单元还与所述功率开关管Q电性连接，所述控制单元设置为依据所述无刷电机的转速输出PWM占空比信号，在所述无刷电机的转速达到第一转速时，输出PWM占空比信号以控制所述功率开关管Q导通，以使所述电容电路处于充电状态。
可选的，如上所述的角磨，其中，所述控制单元设置为在所述无刷电机的转速达到第二转速时，输出PWM占空比信号使所述功率开关管Q关断，以使所述电容电路处于放电状态，其中所述第一转速小于所述第二转速。
可选的，如上所述的角磨，其中，在使所述功率开关管Q导通时，所述PWM占空比信号的占空比逐渐增加。
可选的，如上所述的角磨，其中，所述电容C为电解电容，所述电解电容的容值与所述无刷电机的额定功率之比为20uF/kW～80uF/kW。
本公开还提供一种角磨，包括：电机，包括定子和转子；传动装置，所述传动装置可操作地与所述转子连接，输出动力以驱动打磨盘；驱动电路，用于输出开关信号以驱动所述电机的转子运转；控制单元，输出驱动信号控制所述驱动电路；整流模块，用于将交流电转换为直流电，为所述电机、驱动电路、控制单元供电；电容电路，连接在所述整流模块与所述驱动电路之间；其中，所述电容电路包括电容C和功率开关管Q，所述电容C和所述功率开关管Q串联连接；所述控制单元还与所述功率开关管Q电性连接，所述控制单元设置为依据所述电机的转速，输出PWM占空比信号以控制所述功率开关管Q导通，在所述电机的转速达到第一转速时，输出PWM占空比信号以控制所述功率开关管Q导通，以使所述电容电路处于充电状态。
可选的，如上所述的角磨，其中，在使所述功率开关管Q导通时，所述PWM占空比信号的占空比逐渐增加。
可选的，如上所述的角磨，其中，所述电容C为电解电容，所述电解电容的容值与所述电机的额定功率之比为20uF/kW～80uF/kW。
本公开还提供一种电动工具，包括：无刷电机，包括定子和转子；传动装置，所述传动装置可操作地与所述转子连接，输出动力以驱动工具附件；驱动电路，用于输出开关信号以驱动所述无刷电机的转子运转；控制单元，用于输 出驱动信号控制所述驱动电路；直流单元，为所述无刷电机、驱动电路、控制单元供电；电容电路，并联在所述直流单元的正负极之间；其中，所述电容电路包括电容C和开关元件，所述电容C和开关元件串联连接；所述控制单元还与所述开关元件电性连接，所述控制单元设置为依据所述无刷电机的转速，输出PWM占空比信号以控制所述开关元件导通，在所述无刷电机的转速达到第一转速时，输出PWM占空比信号以控制所述开关元件导通，以使所述电容电路处于充电状态。
可选的，上述的电动工具，其中，所述控制单元设置为：在所述无刷电机的转速达到第一转速时，输出PWM占空比信号使所述开关元件导通，以使所述电容电路处于充电状态；在所述无刷电机的转速达到第二转速时，输出PWM占空比信号使所述开关元件关断，以使所述电容电路处于放电；所述第一转速小于所述第二转速。
可选的，上述的电动工具，其中，所述直流单元包括整流模块，至少用于接入交流电，所述整流模块用于将所述交流电转换为直流电。
可选的，上述的电动工具，其中，所述电容电路连接在所述整流模块与所述驱动电路之间。
本公开还提供一种角磨，包括：壳体；无刷电机，容纳于所述壳体内，所述无刷电机包括定子和转子；电机轴，由所述转子驱动；工具附件轴，用于支持并驱动打磨盘；传动装置，用于连接所述电机轴至所述工具附件轴；驱动电路，用于输出开关信号以驱动所述无刷电机的转子运转；控制单元，输出驱动信号控制所述驱动电路；直流单元，为所述无刷电机、驱动电路、控制单元供电；电容电路，并联于所述直流单元的正负极之间；其中，所述电容电路包括电容C和功率开关管Q，所述电容C和所述功率开关管Q串联连接；所述控制单元还与所述功率开关管Q电性连接，所述控制单元设置为依据所述无刷电机的转速输出PWM占空比信号，在所述无刷电机的转速达到第一转速时，输出PWM占空比信号以控制所述功率开关管Q导通，以使所述电容电路处于充电状态；在所述无刷电机的转速达到第二转速时，输出PWM占空比信号使所述功率开关管Q关断，以使所述电容电路处于放电状态，其中所述第一转速小于所述第二转速。
可选的，上述的角磨，其中，在使所述功率开关管Q导通时，所述PWM占空比信号的占空比逐渐增加。
可选的，上述的角磨，其中，在使所述功率开关管Q关断时，所述PWM占空比信号的占空比逐渐减小。
可选的，上述的角磨，其中，所述电容C为电解电容，所述电解电容的容值与所述无刷电机的额定功率之比为20uF/kW～80uF/kW。
本公开还提供一种角磨，包括：电机，包括定子和转子；传动装置，所述传动装置可操作地与所述转子连接，输出动力以驱动打磨盘；驱动电路，用于输出开关信号以驱动所述电机的转子运转；控制单元，输出驱动信号控制所述驱动电路；整流模块，用于将交流电转换为直流电，为所述电机、驱动电路、控制单元供电；电容电路，连接在所述整流模块与所述驱动电路之间；其中，所述电容电路包括电容C和功率开关管Q，所述电容C和所述功率开关管Q串联连接；所述控制单元还与所述功率开关管Q电性连接，所述控制单元设置为依据所述电机的转速，输出PWM占空比信号以控制所述功率开关管Q和关断，在所述电机的转速达到第一转速时，输出PWM占空比信号使所述开关元件导通，以使所述电容电路处于充电状态；在所述电机的转速达到第二转速时，输出PWM占空比信号使所述开关元件关断，以使所述电容电路处于放电状态；所述第二转速大于第一转速。
可选的，上述的角磨，其中，在使所述功率开关管Q关断时，所述PWM占空比信号的占空比逐渐减小。
可选的，上述的角磨，其中，所述电容C为电解电容，所述电解电容的容值与所述电机的额定功率之比为20uF/kW～80uF/kW。
本公开还提供一种电动工具，包括：无刷电机，包括定子和转子；传动装置，所述传动装置可操作地与所述转子连接，输出动力以驱动工具附件；驱动电路，用于输出开关信号以驱动所述无刷电机的转子运转；控制单元，用于输出驱动信号控制所述驱动电路；直流单元，为所述无刷电机、驱动电路、控制单元供电；电容电路，并联在所述直流单元的正负极之间；其中，所述电容电路包括电容C和开关元件，所述电容C和开关元件串联连接；所述控制单元还与所述开关元件电性连接，所述控制单元设置为依据所述无刷电机的转速，输 出PWM占空比信号以控制所述开关元件导通或关断，在所述无刷电机的转速达到第一转速时，输出PWM占空比信号使所述开关元件导通，以使所述电容电路处于充电状态；在所述无刷电机的转速达到第二转速时，输出PWM占空比信号使所述开关元件关断，以使所述电容电路处于放电状态；所述第一转速小于所述第二转速。
可选的，上述的电动工具，其中，所述控制单元设置为依据与所述无刷电机的转速输出PWM占空比信号以控制所述开关元件导通和关断，在所述无刷电机的转速达到第一转速时，输出PWM占空比信号使所述开关元件导通，以使所述电容电路处于充电状态。
可选的，上述的电动工具，其中，所述直流单元包括整流模块，至少用于接入交流电，所述整流模块用于将所述交流电转换为直流电。
可选的，上述的电动工具，其中，所述电容电路连接在所述整流模块与所述驱动电路之间。
本公开的有益之处在于可通过对电容充电或放电过程的控制，缓冲对电动工具电源侧的冲击。
附图说明
图1是本公开提供的第一实施例的一种角磨的机械结构示意图
图2是本公开提供的第一实施例的一种角磨的电路框图；
图3是图2中电容电路处于充电状态的电路图；
图4是另一种电容电路的电路图；
图5是本公开提供的第一实施例中电容电路处于放电状态的电流流向示意图；
图6本公开提供的第二实施例的一种电动工具的机械结构示意图；
图7本公开提供的第二实施例中电容电路处于放电状态的电路图；
图8是电动工具在上电启动过程中电机转速和控制器输出至功率开关管的PWM控制信号曲线；
图9是电动工具在加载过程中电机转速和控制器输出至功率开关管的PWM控制信号曲线之一；
图10是电动工具在加载过程中电机转速和控制器输出至功率开关管的PWM控制信号曲线之二；
图11本公开提供的第三实施例的一种电钻的机械结构示意图；
图12是用于电钻的一种控制方法的流程图；
图13是用于电钻的另一种控制方法的流程图；
图14本公开提供的第四实施例的一种抛光机的机械结构示意图。
具体实施方式
以下结合附图和具体实施例对本公开作具体的介绍。
在本公开的第一个实施例中，参考图1所示的角磨的机械结构以及图2所示的角磨的电路结构。角磨100主要包括：打磨盘110、壳体120、电源模块10、整流模块20、电容电路30、驱动电路40、无刷电机50和控制器60。
打磨盘110安装在壳体120的一端，在无刷电机50的带动下用于实现例如打磨或切割功能。
电源模块10用于接入电动工具工作所需的电源。作为具体实施方式的一种，本实施例的电源可选择为交流电源。电源模块10包括交流电插头，以接入120V或220V的交流市电。交流电插头位于壳体的另一端。
整流模块20构成角磨的直流单元，所述整流模块设置为接收来自电源模块10的交流电并用于输出直流母线电压，也即用于将电源模块10输入的交流电转化为脉动直流电输出。整流模块20与电源模块10电性连接。具体而言，整流模块20包括由四个二极管D1、D2、D3、D4组成的整流桥，利用二极管的单向导电性和管压降将交流电转换成同一方向的脉动直流电输出。
电容电路30并联于角磨的直流母线上，即并联在角磨电路中直流单元的正负极之间。具体，电容电路30可选择并联在整流模块20与驱动电路40之间。一种实施方式下，电容电路30包括电解电容C和与所述电解电容C串联的功率 开关管Q。
整流模块20输出的脉动直流电经电解电容C滤波转化为平滑直流电输出，以降低脉动直流电中的谐波干扰。其中，电解电容C与无刷电机的额定功率之比的取值范围可选用20uF/kW～80uF/kW。采用这一电容电路30在满足电动工具调速需求的同时能够减小电动工具尺寸，使其结构更为紧凑。
驱动电路40与无刷电机50的定子绕组A、B、C电性连接并用于将来自整流模块20的直流电传递至定子绕组A、B、C以驱动无刷电机50。作为实施例的一种，如图1所示，驱动电路40包括多个开关元件Q1、Q2、Q3、Q4、Q5、Q6，开关元件的每个栅极端与控制器60电性连接，用于接收来自控制器60的控制信号。开关元件的每个漏极或源极与无刷电机50的定子绕组A、B、C连接。作为具体实施例的一种，无刷电机50为三相无刷电机，三相定子绕组A、B、C之间采用三角形或星型连接。开关元件Q1-Q6接收来自控制器60的控制信号改变各自的导通状态，从而改变电源模块10加载在无刷电机50的定子绕组A、B、C上的电流。
为了使无刷电机50转动，驱动电路40具有多个驱动状态，在一个驱动状态下电机的定子绕组会产生一个磁场，控制器60依据电机的转子位置或反电动势输出相应的PWM控制信号至驱动电路40中的开关元件以使驱动电路40切换驱动状态，从而使定子绕组产生变化的磁场以驱动转子转动，进而实现无刷电机50的转动或换相。需要说明的是，其它任何能够驱动无刷电机50的转动或换相的电路和控制方式均可用于本公开，本公开对驱动电路40的电路结构和控制器60对驱动电路40的控制不做限制。
由于本实施例中电动工具的电源模块10接入交流市电，在上电瞬间，角磨直流母线上电压变化剧烈。剧烈变化的电压将在电解电容C作用下产生较大的瞬时电流峰值。这一电流波动将对电源侧带来较大冲击，极易引起电火花等安全隐患。电流尖峰还易使供电电源跳闸，减小电容寿命。
并且，这种供电方式下的电动工具往往具有较大的工作功率。电动工具在大功率工况下工作时，流经电解电容C的纹波电流变大，电解电容C反复充放电因而发热量增加，对电动工具的安全性造成潜在危害。例如，额定功率1200W的角磨，当工作功率达到1000W以上时，流经电解电容C的纹波电流会相比轻 载(1000W以下)时变大，此时通常需要通过选择更大的电解电容以满足电路安全要求。
本实施例可通过控制器所构成的控制单元控制所述电解电容C的充放电过程。具体，通过控制单元限制电解电容C的充、放电时间，进而限制电解电容C的充、放电电量，从而通过较小容值的电解电容C实现同样的平滑滤波效果，避免电流尖峰对供电电源产生的跳闸威胁，以此解决电路上电打火的问题。同时，由于电流尖峰被遏制，可避免其对电容寿命的影响，进而延长整机寿命。
具体的一种电容电路结构可参考图3所示。图3为电容电路30处于充电状态的电路图。电容电路30包括电解电容C和与电解电容C串联的功率开关管Q。电解电容C与功率开关管Q并联在电动工具的直流母线上。作为实施方式的一种，电容C的一极连接至高压输出端HV+，电容C的另一极连接至功率开关管Q的第一极a，开关管Q的第二极b连接至低压输出端或接地，功率开关管Q的第三极Vc与控制器连接。作为一种可行的实施方式，这里的功率开关管Q可选用IGBT晶体管(Insulated Gate Bipolar Transistor，绝缘栅双极型晶体管)，晶体管的基极由控制器控制，其发射极接地，集电极连接电解电容的负极。晶体管工作在开关状态下，由控制器控制其在导通与关断两种状态之间切换，对电解电容进行充放电。类似的功能，本领域技术人员同样可选择通过场效应管实现。
参考图4所示，作为实施方式的另一种，功率开关管Q’在这种实施方式下选择为场效应管。场效应管的漏极d类比于上述实施方式中功率开关管Q’的第一极a，连接高电压，即连接至高压输出端HV+；场效应管的源极s类比于上述实施方式中功率开关管Q’的第二极b，连接低电压，在本实施方式中对应连接至电容C’的一极；场效应管的栅极g类比于上述实施方式中功率开关管Q’的第三极Vc，与控制器连接；电容C’的负极连接至低压输出端或接地。
由上述实施方式，本领域技术人员可理解：所述的功率开关管Q实现的功能为一个控制开关，可利用例如MOSFET、IGBT、可控硅等具有开关作用的硬件电路元件，即开关元件，来实现。功率开关管Q在控制器60的控制下实现自身的导通或关断，进而对其所在的电解电容C的空放电支路进行控制，从而控制电解电容C的充放电时间或充放电电量。具体的，可通过写入进控制器60的 软件程序来控制功率开关管Q的导通或关断。需要说明的，控制器60也可以是通过设计相关的控制电路以硬件输出方式实现对功率开关管Q的控制，本公开对此不作限制。
控制器60设置为当角磨插插头上电时，所述控制器发送PWM占空比信号给功率开关管Q，以控制所述功率开关管Q周期性导通。在功率开关管Q的导通周期内，所述电容电路处于充电状态。通过控制所述PWM占空比信号的导通时间，即限制信号的占空比，可限制电容充电时间以及充电电量，实现电容的缓充电。通过对电容C缓慢充电，可减少交流电源侧或直流电源的瞬间电流对供电系统如插座的冲击，避免安全隐患发生。
具体，所述控制器控制功率开关管Q导通时，所述电容电路处于充电状态；当所述控制器控制功率开关管Q关断时，所述电容电路不处于充电状态。当所述控制器控制功率开关管Q关断时，电容电路由直流母线的纹波电流的波动状况相应处于充电或放电状态。
进一步，控制器60还可设置为在无刷电机50的转速达到第一转速时使功率开关管Q导通或逐渐导通以使电容电路30处于充电状态。参考图3所示，为电容电路30处于充电状态的电路图。电动工具接入交流电，在无刷电机50的转速达到第一转速时，控制器60输出PWM控制信号至功率开关管Q以使功率开关管Q导通或逐渐增加导通时间，此时，电流流经电解电容C再按箭头11所示方向流动以构成电流回路，电容电路30处于充电状态。控制器60输出相应的控制信号至驱动电路40以使驱动电路40驱动无刷电机50工作。作为实施方式的一种，第一转速可设置为零。
这样在无刷电机50的转速达到第一转速时，通过导通功率开关管Q使得电解电容C与整流模块20电性连接，在为电动工具提供了必须的启动转矩的同时保证了电压波形的平滑，从而使得电机能够具有较为稳定的输出性能。
控制器60还可设置为在无刷电机50的转速达到第二转速时使功率开关管Q关断以使电容电路30处于放电状态。参考图5所示，为电容电路30处于放电状态的电路图。在无刷电机50的转速达到第二转速时，控制器60输出第二控制信号至功率开关管Q以使功率开关管Q断开，此时，电流从电解电容C的正极沿箭头12所示方向依次流经开关元件、定子绕组A、B、C和二极管回到电 解电容C的负极，电容电路30处于放电状态。
这样在无刷电机50的转速达到第二转速时，通过断开功率开关管Q使得电容电路30不接入整流回路，降低了电解电容C的发热损耗，延长了电容电路30寿命，提高了电动工具的可靠性。
需要说明的是，无刷电机50的转速检测可以通过单独的转速检测模块来检测，也可以通过集成在控制器60中的检测单元经检测或计算获得。任何能够获取无刷电机50的转速的方案均可用于本公开，对此不作限制。
作为具体实施方式的一种，第一转速n1为零，第二转速n2的取值范围为30％n0≤n2≤70％n0，其中，n0为电动工具的档位转速。具有调速功能的电动工具通常具有多个档位的档位调速开关，调速开关位于不同的档位位置时，电机对应输出不同的档位转速，即这里所说的档位转速。
作为具体实施方式的另一种，控制器还可设置为依据功率开关管或电容C的温度来控制功率开关管Q的关断。
在本公开的第二个实施例中，上述对于电容电路的控制同样可应用于直流供电的电动工具中。具体以图6所示的手持式圆锯为例，其他直流供电的电动工具与之类似。
以图6所示的圆锯为例，包括有：底板20，用于与工件接触；机壳21，所述机壳安装在所述底板上；锯片罩213，所述锯片罩与所述机壳连接；锯片轴22，用于在所述锯片罩内支持锯片转动从而实现对工件进行切割作业；电机23，所述电机设置于所述机壳内，包括定子和转子；电机轴231，所述电机轴由所述电机的转子驱动；传动装置24，所述传动装置用于连接所述电机轴与所述锯片轴，将电机轴的旋转运动传导至所述锯片轴以驱动锯片运转。所述传动装置具体可包括减速机构，如，相互啮合的蜗轮和蜗杆，或减速箱。所述蜗轮蜗杆或减速箱可包括配有不同齿数比的齿轮结构，或配置不同同步轮半径的同步带传动结构。在本公开的一个较佳实施例中，所述电机可选择为无刷电机。
上述手持式圆锯的运转还需依赖安装于PCB电路板上的电子部件，PCB电路板容纳于机壳21内，未暴露于图6所示视角。参考图7所示，PCB电路板具 体包括如下的电路硬件：电源模块200、电机采样模块R、控制器260、驱动电路240以及类似上一实施例的电容电路230。这里的圆锯采用电池包构成电源模块。电容电路230并联于直流母线上，即并联在圆锯电路中直流单元的正负极之间，即在电池包等直流电源供电的状态下并联在直流电源的正负极之间。具体，电容电路30可选择并联在操作开关SW与驱动电路240之间。
电池包打火类似于上一实施例交流电上电的过程。由于电池包安装时，即直流的电源模块上电时，在上电瞬间，电动工具的直流母线上电压变化剧烈。剧烈变化的电压将在电解电容C作用下产生较大的瞬时电流峰值。这一电流波动将对电源侧，本实施例中，具体指对电池包，带来较大冲击。极易引起电池包极片之间出现电火花等安全隐患。
由此，类似上一实施例中对电解电容充、放电过程的控制，同样可应用于直流供电的电动工具中。参考图8所示，为电动工具在上电启动过程中电机转速和控制器260输出至功率开关管Q的PWM控制信号曲线。图中，横坐标表示时间，纵坐标分别表示电机的转速和功率开关管Q栅极接入的PWM控制信号。当电动工具接入电源上电时，控制器260输出占空比逐渐增大的PWM控制信号至功率开关管Q栅极以调制功率开关管Q。在此阶段，电机的转速接近为零，在调制功率开关管Q预设时间后，控制器260可输出全导通的PWM控制信号至功率开关栅极以使功率开关管Q全导通。此时电机的转速逐渐上升，当转速大于等于第二转速n2时，控制器60输出控制信号至功率开关管Q栅极使功率开关管Q关断。
参考图9所示，为电动工具在运行加载过程中电机转速和控制器260输出至功率开关管Q的PWM控制信号曲线之一。随着电动工具负载的增加，电机的转速随扭矩增加而逐渐下降。当转速小于等于第三转速n3时，控制器260输出控制信号至功率开关管Q栅极使功率开关管Q导通。电容电路230处于充电状态，电解电容C存储的电能稳定加载至电机侧，逐渐提高电机的供电电压，由此可保证电机输出性能的稳定。具体的，第三转速n3的取值范围为80％n0≤n3≤100％n0。
参考图10所示，为电动工具在上述的工作过程中，还可采用“软开通”或“软关断”的方式实现对上述电解电容C充、放电的控制。“软开通”或“软关 断”具体至，通过控制PWM控制信号的占空比，通过逐渐增加占空比或逐渐减小占空比而逐渐增加或减少开通或关断所述电解电容C支路的时间，即通过占空比控制电解电容C充电电量或放电电量，使电解电容C缓慢充电或缓慢放电。由此，可通过控制电解电容C缓慢充电或放电，减小其充、放电过程对电路整体的冲击。避免用户操作中，因电容充、放电电流对电路的冲击而感到电动工具转速突变或震动。可提升用户操作手感，并保证电动工具功率输出无突变，更为安全。
参考图10所示，为无刷电机转速和控制器输出至功率开关管Q的PWM控制信号曲线之一。图中，横坐标表示时间，纵坐标分别表示无刷电机的转速和功率开关管栅极(即第三极)接入的PWM控制信号。电动工具在工作过程中，在转速达到档位转速n0时，控制器260输出占空比逐渐减小的PWM控制信号至功率开关管栅极以调制功率开关管使其实现软关断；随着负载扭矩的增加，转速下降，在转速小于等于第三转速n3时，控制器60输出占空比逐渐增大的PWM控制信号至功率开关管栅极以调制功率开关管使其实现软开通。具体的，第三转速值n3的取值范围为80％n0≤n3≤100％n0。由此，可降低功率开关管的损耗和温度。
可选的，当应用于高压无刷的电动工具产品中时，上述对于电解电容的充、放电控制同样可应用于更大的电容，例如，可选择电解电容C与无刷电机的额定功率之比的取值范围大于80uF/kW。
在本公开的第三个实施例中，参考图11所提供的一种电钻，其机械结构具体包括：壳体301、输出件302、电机303、传动组件304、PCB(Printed Circuit Board，印制电路板)电路板305、供电装置306。其中，壳体301用于容纳电机303、传动组件304、PCB电路板305等，壳体301的一端还用于安装输出件302。图11所示视角下，电机303、PCB电路板305以及供电装置306由壳体301遮挡，未直接暴露于图11视角。在前后方向上，壳体301还可以包括主机壳体部分311和头部壳体部分312，其中主机壳体部分311可以用于容纳电机303、传动组件304、PCB电路板305，头部壳体部分312可以连接输出件302。在左右方向上，主机壳体部分311可以关于图11所示结构的切面对称设置，在 该切面的两侧，主机壳体部分311可以分别包括相互对称的左壳体部和右壳体部。输出件302用于输出动力，例如对于电钻而言，输出件302可具体选择为一个能夹持钻头的夹头。电机303、传动组件304以及PCB电路板305均设置在壳体301内，供电装置306用于为电钻内部各电子装置供电，PCB电路板305用于控制电机303运转，电机303用于驱动传动组件304，传动组件304用于将电机303输出的动力传递至输出件302，从而驱动输出件302输出动力。
为控制所述电机303运转，参考图2，上述PCB电路板305具体可类似参考上述实施例，包括如下的电路硬件：电源控制模块、控制单元、驱动电路、电机采样模块。上述，电源控制模块、控制单元、驱动电路、电机采样模块均由壳体301封闭。
图2所示的手持式电钻的供电装置306具体可选择为电池包或交流电源，其中的电池包可由一组电池单元组合而成。例如，本实施例中可将电池单元串联成单一电源支路，形成1P电池包。电池包输出电压通过具体的电源控制模块，例如DC-DC模块进行电压变化，输出适合控制单元、驱动电路、电机等的供电电压，为其供电。本领域技术人员可理解，DC-DC模块为成熟的电路结构，可根据电动工具具体参数要求而相应选择。供电装置306也可选择为交流电源，通过相应的电源控制模块对输入交流电进行转化，同样可以为供电装置检测模块、控制单元、驱动电路、最佳占空比存储装置、电机等供电。
上述电钻的电路结构与上述实施例中角磨或圆锯的电路结构类似，在此不加赘述。其控制单元具体可通过如下的步骤流程控制所述电钻运转。
参考图12所示的一种用于例如电钻等电动工具中的控制方法，该控制方法包括如下步骤：
S101.检测电动工具上电状态；
S102.若判断电动工具上电则转至步骤S103，否则返回S101；
S103.使功率开关管Q导通或逐渐导通，此时电容电路30处于充电状态；
S104.判断是否到达第二条件；若是则转至步骤S105，否则返回S103；所述的第二条件包括但不限于：是否满足与所述无刷电机的转速有关的特性参数，功率开关管Q或电容C的温度是否达到阈值H，调制功率开关管Q是否达到预 设时间T，等。其中，与所述无刷电机的转速有关的特性参数可包括电动工具中的电机的转速，例如，电动工具中的电机的转速是否达到第二转速n2，还可包括与电动工具中的电机的转速相关的电流、电压或者转子位置信号。
S105.使功率开关管Q关断或逐渐关断；此时，使电容电路30处于放电状态，或使所述电容电路30随直流母线的纹波电流的波动而相应处于充电或放电状态。
其中，逐渐导通指通过逐渐增加输出至功率开关管Q的PWM控制信号的占空比，而逐渐增加功率开关管Q的导通时间，直至所述功率开关管Q完全导通；逐渐关断指逐渐减小输出至功率开关管Q的PWM控制信号的占空比，而逐渐减小功率开关管Q的导通时间，直至所述功率开关管Q完全关断。
步骤S102中，电机对应为第一转速，所述第一转速可为零。S103还可分为两个子步骤，在电动工具上电时使功率开关管Q以逐渐增大的占空比导通，待上电预设时间或电机达到某一较小的预设转速后，再使功率开关管Q全导通。
参考图13所示的另一种用于例如电钻等电动工具中的控制方法，该控制方法包括如下步骤：
S201.检测电机的转速n。通过电动工具中内置的转速检测模块可检测电机的转速n。其中，转速检测模块可选择为检测电机转子的位置传感器，如霍尔元件、碳刷、换向器等；还可选择为设置于电机相线和/或母线的电流和/或电压采样元件，例如采样电阻R，配合相应的电机位置计算模块，实现对电机转速的检测。
S202.判断无刷电机的转速n是否大于等于第一转速n1；若是则转至步骤S203；否则转至步骤S201。
S203.若无刷电机的转速n≥n1则使功率开关管导通。
控制器在无刷电机的转速大于等于第一转速n1时，输出使功率开关管导通的第一控制信号至功率开关管，以使功率开关管导通。具体的，第一控制信号为第一PWM信号。可选的所述第一PWM信号的占空比逐渐增大。
S204.判断无刷电机的转速n是否大于等于第二转速n2；若是则转至步骤S205；否则转至步骤S203。
S205.若无刷电机的转速n≥n2则使功率开关管关断。
控制器在无刷电机的转速大于等于第二转速n2时，输出使功率开关管导通的第二控制信号至功率开关管，以使功率开关管关断。具体的，第二控制信号为第二PWM信号。可选的所述第二PWM信号的占空比逐渐减小。
S206.判断无刷电机的转速是否达到档位转速n0，若是则转至步骤S207；否则转至步骤S205。
S207.若所述无刷电机的转速为档位转速，则使功率开关管软关断。
控制器在无刷电机的转速为档位转速时，输出使功率开关管软关断的控制信号至功率开关管，以使功率开关管软关断。
S208.判断无刷电机的转速是否小于等于第三转速，若是则转至步骤S209；否则转至步骤S207。
S209.若无刷电机的转速小于等于第三转速，则使功率开关管软导通。
控制器在无刷电机的转速小于等于第三转速时，输出使功率开关管软导通的控制信号至功率开关管，以使功率开关管软导通。
其中，第一转速n1的取值范围为0≤n1＜n2，第二转速n2的取值范围为30％n0≤n2≤70％n0，其中，n0为电动工具的档位转速，第三转速n3的取值范围为80％n0≤n3≤100％n0。
本公开中的电动工具也可以是电钻、电锤、电圆锯和云石机等带有调速功能的电动工具，解决其上电过程对电源侧的冲击，避免上电打火，还可避免操作中电机转速突变，保持电动工具良好的操作手感。
在本公开的第四个实施例中，参考图14所提供的打磨类工具，例如，抛光机。其机械结构具体包括：
壳体41，用于容纳抛光机400内的各部件。壳体41可以包括把手部411和容纳部412。把手部411用于供用户握持，容纳部412形成容纳各部件的容纳空间；开关42可以安装于把手部411上。用户在握持把手部411时，能够相对方便的触发开关42，开关42例如可以为用于启动抛光机400的扳机。
其中，壳体41的容纳部412容纳有电机43。电机43用于将能量源，例如交流电源提供的能量转换成动力输出。电机43连接有电机轴431，电机轴431的一端连接传动装置以输出动力。
底板44用于安装砂纸，底板连接有工具附件轴，工具附件轴与所述传动装置连接。在电机43的驱动以及电机轴、传动装置以及工具附件轴的作用下，底板44由电机驱动而能够做往复运动或者摆动。当底板44做往复运动或者摆动时，底板44带动砂纸，在工件的表面不断的摩擦，从而实现对工件的打磨和抛光等的功能。
上述打磨类工具同样可依赖如前述实施例中所公开的电子部件实现对电机的驱动与控制。例如，在直流供电的打磨类工具中，电子部件可包括主要由电池包构成的电源模块，以及并联于其输出端的电容电路、驱动电路，还包括控制单元。在交流供电的打磨类工具中，所述的电子部件可包括整流模块、电容电路、驱动电路和控制单元。
其中的控制单元可参考第三个实施例中所述的步骤控制电容电路中的电容C相应地进行充电或放电。具体，控制单元通过控制电容C所串联的功率开关管Q导通或断开，从而控制电容电路中的电容C相应地进行充电或放电。具体，所述控制单元可通过输出占空比变化的PWM信号控制电容C相应地进行充电或放电，控制电容C进行充电或放电的时间或电量，从而实现电容的缓充电或缓放电。
例如，首先检测电动工具上电状态；在电动工具上电时使功率开关管Q导通或逐渐导通，此时电容电路30处于充电状态；否则继续检测电动工具是否上电；
然后判断是否到达第二条件；若到达第二条件则使功率开关管Q关断或逐渐关断，以此使电容电路30处于放电状态，或使所述电容电路30随直流母线的纹波电流的波动而相应处于充电或放电状态；若未到达第二条件则继续保持使所述功率开关管Q导通或逐渐导通。
其中，第二条件包括但不限于：电动工具中的电机的转速是否达到第二转速n2，功率开关管Q或电容C的温度是否达到阈值H，调制功率开关管Q是否达到预设时间T。
例如，可选通过霍尔元件或对电机工作电流进行采样和计算，获得电机的转速，在电动工具中的电机的转速达到第二转速n2时，判断为达到所述第二条件，此时，使功率开关管Q关断或逐渐关断，以此使电容电路30处于放电状态，或使所述电容电路30随直流母线的纹波电流的波动而相应处于充电或放电状态。或者，还可以通过热敏元件等方式检测电容C的表面温度，在电容C的温度超过预设阈值H时，判断为达到所述第二条件，相应地使功率开关管Q关断或逐渐关断。或者，还可以在控制单元内增加计时中断，记录处于复杂控制(例如处于调速状态，或进行PWM占空比调制功率开关管Q)的时间，在超过某一预设时间T时判断为达到所述第二条件，相应地使功率开关管Q关断或逐渐关断。
由此，通过对电动工具上电状态的响应，可降低上电过程中对电源的冲击，尤其降低上电瞬间的瞬时电流峰值。通过控制电容在上电过程中缓慢充电，可以较小的电容实现对电动工具及其电源的保护，使得电动工具结构更为紧凑，同时降低其电路硬件成本。
通过第二条件的控制，可通过控制电容缓慢放电，实现减小电容充、放电过程对电路整体的冲击。避免用户操作中，因电容充、放电电流对电路的冲击而感到电动工具转速突变或震动，从而提升用户操作手感，并保证电动工具功率输出无突变，更为安全。
本领域技术人员应当理解，这里的第二条件与电工工具的上电状态或第一转速之间是相互独立的。即，在本公开的一种实施方式下，不论电动工具是否上电，或者，不论电动工具是否存在第一转速，均可通过对电动工具是否达到第二条件的判断而相应地使功率开关管Q关断或逐渐关断。例如，当所述第二条件为电机转速达到第二转速时，可独立通过对电机是否达到第二转速的判断，而无需考虑电动工具是否上电或者是否满足第一转速，而通过控制单元，输出PWM占空比信号以控制所述功率开关管Q等开关元件关断或逐渐关断，以使所述电容电路处于放电状态。
以上显示和描述了本公开的基本原理、主要特征和优点。本行业的技术人员应该了解，上述实施例不以任何形式限制本公开，凡采用等同替换或等效变换的方式所获得的技术方案，均落在本公开的保护范围内。
工业实用性
本公开提供了一种电动工具，通过对电容充电或放电过程的控制，可缓冲对电动工具电源侧的冲击，使电动工具结构紧凑，并提高其安全性能。

Claims (62)

  1. 一种电动工具，包括：
    壳体；
    无刷电机，容纳于所述壳体内，所述无刷电机包括定子和转子；
    电机轴，由所述转子驱动；
    工具附件轴，用于支持并驱动工具附件；
    传动装置，用于连接所述电机轴至所述工具附件轴；
    驱动电路，用于输出开关信号以驱动所述无刷电机的转子运转；
    控制单元，输出驱动信号控制所述驱动电路；
    直流单元，为所述无刷电机、驱动电路、控制单元供电；
    电容电路，并联于所述直流单元的正负极之间；
    其特征在于，所述电容电路包括电容C和功率开关管Q，所述电容C和所述功率开关管Q串联连接；
    所述控制单元还与所述功率开关管Q电性连接，所述控制单元设置为输出PWM占空比信号以控制所述功率开关管Q导通和关断。
  2. 如权利要求1所述的电动工具，其特征在于，所述控制单元设置为在所述无刷电机的转速达到第一转速时，输出PWM占空比信号使所述功率开关管Q导通，以使所述电容电路处于充电状态。
  3. 如权利要求2所述的电动工具，其特征在于，所述控制单元设置为在所述无刷电机的转速达到第二转速时，输出PWM占空比信号使所述功率开关管Q关断，以使所述电容电路处于放电状态，其中所述第一转速小于所述第二转速。
  4. 如权利要求3所述的电动工具，其特征在于，在使所述功率开关管Q关断时，所述PWM占空比信号的占空比逐渐减小。
  5. 如权利要求1所述的电动工具，其特征在于，所述电容C为电解电容，所述电解电容的容值与所述无刷电机的额定功率之比为20uF/kW～80uF/kW。
  6. 一种电动工具，包括：
    电机，包括定子和转子；
    传动装置，所述传动装置可操作地与所述转子连接，输出动力以驱动工具附件；
    驱动电路，用于输出开关信号以驱动所述电机的转子运转；
    控制单元，输出驱动信号控制所述驱动电路；
    整流模块，用于将交流电转换为直流电，为所述电机、驱动电路、控制单元供电；
    电容电路，连接在所述整流模块与所述驱动电路之间；
    其特征在于，所述电容电路包括电容C和功率开关管Q，所述电容C和所述功率开关管Q串联连接；
    所述控制单元还与所述功率开关管Q电性连接，所述控制单元设置为输出PWM占空比信号以控制所述功率开关管Q导通和关断。
  7. 如权利要求6所述的电动工具，其特征在于，在使所述功率开关管Q关断时，所述PWM占空比信号的占空比逐渐减小。
  8. 如权利要求7所述的电动工具，其特征在于，所述控制单元设置为依据与所述电机的与转速有关的特性参数输出PWM占空比信号以控制所述功率开关管Q导通和关断，在所述无刷电机的转速达到第一转速时，输出PWM占空比信号使所述开关元件导通，以使所述电容电路处于充电状态。
  9. 如权利要求6所述的电动工具，其特征在于，所述电容C为电解电容， 所述电解电容的容值与所述电机的额定功率之比为20uF/kW～80uF/kW。
  10. 一种电动工具，包括：
    无刷电机，包括定子和转子；
    传动装置，所述传动装置可操作地与所述转子连接，输出动力以驱动工具附件；
    驱动电路，用于输出开关信号以驱动所述无刷电机的转子运转；
    控制单元，用于输出驱动信号控制所述驱动电路；
    直流单元，为所述无刷电机、驱动电路、控制单元供电；
    电容电路，并联在所述直流单元的正负极之间；
    其特征在于，所述电容电路包括电容C和开关元件，所述电容C和开关元件串联连接；
    所述控制单元还与所述开关元件电性连接，所述控制单元设置为输出PWM占空比信号以控制所述开关元件导通和关断。
  11. 如权利要求10所述的电动工具，其特征在于，所述控制单元设置为依据与所述无刷电机的转速有关的特性参数输出PWM占空比信号以控制所述开关元件导通和关断，在所述无刷电机的转速达到第一转速时，输出PWM占空比信号使所述开关元件导通，以使所述电容电路处于充电状态。
  12. 如权利要求10所述的电动工具，其特征在于，所述控制单元设置为：
    在所述无刷电机的转速达到第一转速时，输出PWM占空比信号使所述开关元件导通，以使所述电容电路处于充电状态；
    在所述无刷电机的转速达到第二转速时，输出PWM占空比信号使所述开关元件关断，以使所述电容电路处于放电；
    所述第一转速小于所述第二转速。
  13. 如权利要求10所述的电动工具，其特征在于，所述直流单元包括整流模块，至少用于接入交流电，所述整流模块用于将所述交流电转换为直流电。
  14. 如权利要求13所述的电动工具，其特征在于，所述电容电路连接在所述整流模块与所述驱动电路之间。
  15. 一种电动工具，包括：
    壳体；
    无刷电机，容纳于所述壳体内，所述无刷电机包括定子和转子；
    电机轴，由所述转子驱动；
    工具附件轴，用于支持并驱动工具附件；
    传动装置，用于连接所述电机轴至所述工具附件轴；
    驱动电路，用于输出开关信号以驱动所述无刷电机的转子运转；
    控制单元，输出驱动信号控制所述驱动电路；
    直流单元，为所述无刷电机、驱动电路、控制单元供电；
    电容电路，并联于所述直流单元的正负极之间；
    其特征在于，所述电容电路包括电容C和功率开关管Q，所述电容C和所述功率开关管Q串联连接；
    所述控制单元还与所述功率开关管Q电性连接，所述控制单元设置为依据所述无刷电机的转速输出PWM占空比信号以控制所述功率开关管Q导通和关断。
  16. 如权利要求15所述的电动工具，其特征在于，所述控制单元设置为在所述无刷电机的转速达到第一转速时，输出PWM占空比信号使所述功率开关管 Q导通，以使所述电容电路处于充电状态。
  17. 如权利要求16所述的电动工具，其特征在于，所述控制单元设置为在所述无刷电机的转速达到第二转速时，输出PWM占空比信号使所述功率开关管Q关断，以使所述电容电路处于放电状态，其中所述第一转速小于所述第二转速。
  18. 如权利要求17所述的电动工具，其特征在于，在使所述功率开关管Q关断时，所述PWM占空比信号的占空比逐渐减小。
  19. 如权利要求15所述的电动工具，其特征在于，所述电容C为电解电容，所述电解电容的容值与所述无刷电机的额定功率之比为20uF/kW～80uF/kW。
  20. 一种电动工具，包括：
    电机，包括定子和转子；
    传动装置，所述传动装置可操作地与所述转子连接，输出动力以驱动工具附件；
    驱动电路，用于输出开关信号以驱动所述电机的转子运转；
    控制单元，输出驱动信号控制所述驱动电路；
    整流模块，用于将交流电转换为直流电，为所述电机、驱动电路、控制单元供电；
    电容电路，连接在所述整流模块与所述驱动电路之间；
    其特征在于，所述电容电路包括电容C和功率开关管Q，所述电容C和所述功率开关管Q串联连接；
    所述控制单元还与所述功率开关管Q电性连接，所述控制单元设置为依据与所述电机的与转速有关的特性参数输出PWM占空比信号以控制所述功率开 关管Q导通和关断。
  21. 如权利要求20所述的电动工具，其特征在于，在使所述功率开关管Q关断时，所述PWM占空比信号的占空比逐渐减小。
  22. 如权利要求21所述的电动工具，其特征在于，所述控制单元设置为依据与所述电机的与转速有关的特性参数输出PWM占空比信号以控制所述功率开关管Q导通和关断，在所述无刷电机的转速达到第一转速时，输出PWM占空比信号使所述开关元件导通，以使所述电容电路处于充电状态。
  23. 如权利要求20所述的电动工具，其特征在于，所述电容C为电解电容，所述电解电容的容值与所述电机的额定功率之比为20uF/kW～80uF/kW。
  24. 一种电动工具，包括：
    无刷电机，包括定子和转子；
    传动装置，所述传动装置可操作地与所述转子连接，输出动力以驱动工具附件；
    驱动电路，用于输出开关信号以驱动所述无刷电机的转子运转；
    控制单元，用于输出驱动信号控制所述驱动电路；
    直流单元，为所述无刷电机、驱动电路、控制单元供电；
    电容电路，并联在所述直流单元的正负极之间；
    其特征在于，所述电容电路包括电容C和开关元件，所述电容C和开关元件串联连接；
    所述控制单元还与所述开关元件电性连接，所述控制单元设置为依据与所述无刷电机的转速有关的特性参数输出PWM占空比信号以控制所述开关元件导通和关断。
  25. 如权利要求24所述的电动工具，其特征在于，所述控制单元设置为依据与所述无刷电机的转速有关的特性参数输出PWM占空比信号以控制所述开关元件导通和关断，在所述无刷电机的转速达到第一转速时，输出PWM占空比信号使所述开关元件导通，以使所述电容电路处于充电状态。
  26. 如权利要求24所述的电动工具，其特征在于，所述控制单元设置为：
    在所述无刷电机的转速达到第一转速时，输出PWM占空比信号使所述开关元件导通，以使所述电容电路处于充电状态；
    在所述无刷电机的转速达到第二转速时，输出PWM占空比信号使所述开关元件关断，以使所述电容电路处于放电；
    所述第一转速小于所述第二转速。
  27. 如权利要求24所述的电动工具，其特征在于，所述直流单元包括整流模块，至少用于接入交流电，所述整流模块用于将所述交流电转换为直流电。
  28. 如权利要求27所述的电动工具，其特征在于，所述电容电路连接在所述整流模块与所述驱动电路之间。
  29. 一种角磨，包括：
    壳体；
    无刷电机，容纳于所述壳体内，所述无刷电机包括定子和转子；
    电机轴，由所述转子驱动；
    工具附件轴，用于支持并驱动打磨盘；
    传动装置，用于连接所述电机轴至所述工具附件轴；
    驱动电路，用于输出开关信号以驱动所述无刷电机的转子运转；
    控制单元，输出驱动信号控制所述驱动电路；
    直流单元，为所述无刷电机、驱动电路、控制单元供电；
    电容电路，并联于所述直流单元的正负极之间；
    其特征在于，所述电容电路包括电容C和功率开关管Q，所述电容C和所述功率开关管Q串联连接，所述电容的容值与所述无刷电机的额定功率之比为20uF/kW～80uF/kW；
    所述控制单元还与所述功率开关管Q电性连接，所述控制单元设置为输出PWM占空比信号以控制所述功率开关管Q导通和关断。
  30. 如权利要求29所述的角磨，其特征在于，所述控制单元设置为在所述无刷电机的转速达到第一转速时，输出PWM占空比信号使所述功率开关管Q导通，以使所述电容电路处于充电状态。
  31. 如权利要求30所述的角磨，其特征在于，所述控制单元设置为在所述无刷电机的转速达到第二转速时，输出PWM占空比信号使所述功率开关管Q关断，以使所述电容电路处于放电状态，其中所述第一转速小于所述第二转速。
  32. 如权利要求31所述的角磨，其特征在于，在使所述功率开关管Q关断时，所述PWM占空比信号的占空比逐渐减小。
  33. 一种角磨，包括：
    电机，包括定子和转子；
    传动装置，所述传动装置可操作地与所述转子连接，输出动力以驱动打磨盘；
    驱动电路，用于输出开关信号以驱动所述电机的转子运转；
    控制单元，输出驱动信号控制所述驱动电路；
    整流模块，用于将交流电转换为直流电，为所述电机、驱动电路、控制单 元供电；
    电容电路，连接在所述整流模块与所述驱动电路之间；
    其特征在于，所述电容电路包括电容C和功率开关管Q，所述电容C和所述功率开关管Q串联连接，所述电容的容值与所述电机的额定功率之比为80uF/kW或以上；
    所述控制单元还与所述功率开关管Q电性连接，所述控制单元设置为输出PWM占空比信号以控制所述功率开关管Q导通和关断。
  34. 如权利要求33所述的角磨，其特征在于，在使所述功率开关管Q关断时，所述PWM占空比信号的占空比逐渐减小。
  35. 如权利要求34所述的角磨，其特征在于，所述控制单元设置为依据与所述电机的与转速有关的特性参数输出PWM占空比信号以控制所述功率开关管Q导通和关断，在所述无刷电机的转速达到第一转速时，输出PWM占空比信号使所述开关元件导通，以使所述电容电路处于充电状态。
  36. 一种电动工具，包括：
    无刷电机，包括定子和转子；
    传动装置，所述传动装置可操作地与所述转子连接，输出动力以驱动工具附件；
    驱动电路，用于输出开关信号以驱动所述无刷电机的转子运转；
    控制单元，用于输出驱动信号控制所述驱动电路；
    直流单元，为所述无刷电机、驱动电路、控制单元供电；
    电容电路，并联在所述直流单元的正负极之间；
    其特征在于，所述电容电路包括电容C和开关元件，所述电容C和开关元 件串联连接，所述电容的容值与所述无刷电机的额定功率之比为80uF/kW或以上；
    所述控制单元还与所述开关元件电性连接，所述控制单元设置为输出PWM占空比信号以控制所述开关元件导通和关断。
  37. 如权利要求36所述的电动工具，其特征在于，所述控制单元设置为依据与所述无刷电机的转速有关的特性参数输出PWM占空比信号以控制所述开关元件导通和关断，在所述无刷电机的转速达到第一转速时，输出PWM占空比信号使所述开关元件导通，以使所述电容电路处于充电状态。
  38. 如权利要求36所述的电动工具，其特征在于，所述控制单元设置为：
    在所述无刷电机的转速达到第一转速时，输出PWM占空比信号使所述开关元件导通，以使所述电容电路处于充电状态；
    在所述无刷电机的转速达到第二转速时，输出PWM占空比信号使所述开关元件关断，以使所述电容电路处于放电；
    所述第一转速小于所述第二转速。
  39. 如权利要求36所述的电动工具，其特征在于，所述直流单元包括整流模块，至少用于接入交流电，所述整流模块用于将所述交流电转换为直流电。
  40. 如权利要求39所述的电动工具，其特征在于，所述电容电路连接在所述整流模块与所述驱动电路之间。
  41. 一种角磨，包括：
    壳体；
    无刷电机，容纳于所述壳体内，所述无刷电机包括定子和转子；
    电机轴，由所述转子驱动；
    工具附件轴，用于支持并驱动打磨盘；
    传动装置，用于连接所述电机轴至所述工具附件轴；
    驱动电路，用于输出开关信号以驱动所述无刷电机的转子运转；
    控制单元，输出驱动信号控制所述驱动电路；
    直流单元，为所述无刷电机、驱动电路、控制单元供电；
    电容电路，并联于所述直流单元的正负极之间；
    其特征在于，所述电容电路包括电容C和功率开关管Q，所述电容C和所述功率开关管Q串联连接；
    所述控制单元还与所述功率开关管Q电性连接，所述控制单元设置为依据所述无刷电机的转速输出PWM占空比信号，在所述无刷电机的转速达到第一转速时，输出PWM占空比信号以控制所述功率开关管Q导通，以使所述电容电路处于充电状态。
  42. 如权利要求41所述的角磨，其特征在于，所述控制单元设置为在所述无刷电机的转速达到第二转速时，输出PWM占空比信号使所述功率开关管Q关断，以使所述电容电路处于放电状态，其中所述第一转速小于所述第二转速。
  43. 如权利要求41所述的角磨，其特征在于，在使所述功率开关管Q导通时，所述PWM占空比信号的占空比逐渐增加。
  44. 如权利要求41所述的角磨，其特征在于，所述电容C为电解电容，所述电解电容的容值与所述无刷电机的额定功率之比为20uF/kW～80uF/kW。
  45. 一种角磨，包括：
    电机，包括定子和转子；
    传动装置，所述传动装置可操作地与所述转子连接，输出动力以驱动打磨 盘；
    驱动电路，用于输出开关信号以驱动所述电机的转子运转；
    控制单元，输出驱动信号控制所述驱动电路；
    整流模块，用于将交流电转换为直流电，为所述电机、驱动电路、控制单元供电；
    电容电路，连接在所述整流模块与所述驱动电路之间；
    其特征在于，所述电容电路包括电容C和功率开关管Q，所述电容C和所述功率开关管Q串联连接；
    所述控制单元还与所述功率开关管Q电性连接，所述控制单元设置为依据所述电机的转速，输出PWM占空比信号以控制所述功率开关管Q导通，在所述电机的转速达到第一转速时，输出PWM占空比信号以控制所述功率开关管Q导通，以使所述电容电路处于充电状态。
  46. 如权利要求45所述的角磨，其特征在于，在使所述功率开关管Q导通时，所述PWM占空比信号的占空比逐渐增加。
  47. 如权利要求45所述的角磨，其特征在于，所述电容C为电解电容，所述电解电容的容值与所述电机的额定功率之比为20uF/kW～80uF/kW。
  48. 一种电动工具，包括：
    无刷电机，包括定子和转子；
    传动装置，所述传动装置可操作地与所述转子连接，输出动力以驱动工具附件；
    驱动电路，用于输出开关信号以驱动所述无刷电机的转子运转；
    控制单元，用于输出驱动信号控制所述驱动电路；
    直流单元，为所述无刷电机、驱动电路、控制单元供电；
    电容电路，并联在所述直流单元的正负极之间；
    其特征在于，所述电容电路包括电容C和开关元件，所述电容C和开关元件串联连接；
    所述控制单元还与所述开关元件电性连接，所述控制单元设置为依据所述无刷电机的转速，输出PWM占空比信号以控制所述开关元件导通，在所述无刷电机的转速达到第一转速时，输出PWM占空比信号以控制所述开关元件导通，以使所述电容电路处于充电状态。
  49. 如权利要求48所述的电动工具，其特征在于，所述控制单元设置为：
    在所述无刷电机的转速达到第一转速时，输出PWM占空比信号使所述开关元件导通，以使所述电容电路处于充电状态；
    在所述无刷电机的转速达到第二转速时，输出PWM占空比信号使所述开关元件关断，以使所述电容电路处于放电；
    所述第一转速小于所述第二转速。
  50. 如权利要求48所述的电动工具，其特征在于，所述直流单元包括整流模块，至少用于接入交流电，所述整流模块用于将所述交流电转换为直流电。
  51. 如权利要求50所述的电动工具，其特征在于，所述电容电路连接在所述整流模块与所述驱动电路之间。
  52. 一种角磨，包括：
    壳体；
    无刷电机，容纳于所述壳体内，所述无刷电机包括定子和转子；
    电机轴，由所述转子驱动；
    工具附件轴，用于支持并驱动打磨盘；
    传动装置，用于连接所述电机轴至所述工具附件轴；
    驱动电路，用于输出开关信号以驱动所述无刷电机的转子运转；
    控制单元，输出驱动信号控制所述驱动电路；
    直流单元，为所述无刷电机、驱动电路、控制单元供电；
    电容电路，并联于所述直流单元的正负极之间；
    其特征在于，所述电容电路包括电容C和功率开关管Q，所述电容C和所述功率开关管Q串联连接；
    所述控制单元还与所述功率开关管Q电性连接，所述控制单元设置为依据所述无刷电机的转速输出PWM占空比信号，在所述无刷电机的转速达到第一转速时，输出PWM占空比信号以控制所述功率开关管Q导通，以使所述电容电路处于充电状态；在所述无刷电机的转速达到第二转速时，输出PWM占空比信号使所述功率开关管Q关断，以使所述电容电路处于放电状态，其中所述第一转速小于所述第二转速。
  53. 如权利要求52所述的角磨，其特征在于，在使所述功率开关管Q导通时，所述PWM占空比信号的占空比逐渐增加。
  54. 如权利要求52所述的角磨，其特征在于，在使所述功率开关管Q关断时，所述PWM占空比信号的占空比逐渐减小。
  55. 如权利要求52所述的角磨，其特征在于，所述电容C为电解电容，所述电解电容的容值与所述无刷电机的额定功率之比为20uF/kW～80uF/kW。
  56. 一种角磨，包括：
    电机，包括定子和转子；
    传动装置，所述传动装置可操作地与所述转子连接，输出动力以驱动打磨盘；
    驱动电路，用于输出开关信号以驱动所述电机的转子运转；
    控制单元，输出驱动信号控制所述驱动电路；
    整流模块，用于将交流电转换为直流电，为所述电机、驱动电路、控制单元供电；
    电容电路，连接在所述整流模块与所述驱动电路之间；
    其特征在于，所述电容电路包括电容C和功率开关管Q，所述电容C和所述功率开关管Q串联连接；
    所述控制单元还与所述功率开关管Q电性连接，所述控制单元设置为依据所述电机的转速，输出PWM占空比信号以控制所述功率开关管Q和关断，在所述电机的转速达到第一转速时，输出PWM占空比信号使所述开关元件导通，以使所述电容电路处于充电状态；在所述电机的转速达到第二转速时，输出PWM占空比信号使所述开关元件关断，以使所述电容电路处于放电状态；所述第二转速大于第一转速。
  57. 如权利要求56所述的角磨，其特征在于，在使所述功率开关管Q关断时，所述PWM占空比信号的占空比逐渐减小。
  58. 如权利要求56所述的角磨，其特征在于，所述电容C为电解电容，所述电解电容的容值与所述电机的额定功率之比为20uF/kW～80uF/kW。
  59. 一种电动工具，包括：
    无刷电机，包括定子和转子；
    传动装置，所述传动装置可操作地与所述转子连接，输出动力以驱动工具 附件；
    驱动电路，用于输出开关信号以驱动所述无刷电机的转子运转；
    控制单元，用于输出驱动信号控制所述驱动电路；
    直流单元，为所述无刷电机、驱动电路、控制单元供电；
    电容电路，并联在所述直流单元的正负极之间；
    其特征在于，所述电容电路包括电容C和开关元件，所述电容C和开关元件串联连接；
    所述控制单元还与所述开关元件电性连接，所述控制单元设置为依据所述无刷电机的转速，输出PWM占空比信号以控制所述开关元件导通或关断，在所述无刷电机的转速达到第一转速时，输出PWM占空比信号使所述开关元件导通，以使所述电容电路处于充电状态；
    在所述无刷电机的转速达到第二转速时，输出PWM占空比信号使所述开关元件关断，以使所述电容电路处于放电状态；
    所述第一转速小于所述第二转速。
  60. 如权利要求59所述的电动工具，其特征在于，所述控制单元设置为依据与所述无刷电机的转速输出PWM占空比信号以控制所述开关元件导通和关断，在所述无刷电机的转速达到第一转速时，输出PWM占空比信号使所述开关元件导通，以使所述电容电路处于充电状态。
  61. 如权利要求59所述的电动工具，其特征在于，所述直流单元包括整流模块，至少用于接入交流电，所述整流模块用于将所述交流电转换为直流电。
  62. 如权利要求61所述的电动工具，其特征在于，所述电容电路连接在所述整流模块与所述驱动电路之间。
PCT/CN2018/098569 2017-11-24 2018-08-03 电动工具 WO2019100752A1 (zh)

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CN201810665144.7 2018-06-26
CN201810665467.6A CN109842325B (zh) 2017-11-24 2018-06-26 角磨及电动工具
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CN201810673985.2A CN109842326B (zh) 2017-11-24 2018-06-26 角磨及电动工具
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WO2016100891A1 (en) * 2014-12-19 2016-06-23 Black & Decker Inc. Power tool with electric motor and auxiliary switch path
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EP1174998A1 (en) * 2000-06-21 2002-01-23 MAGNETEK S.p.A. Brushless motor,method and circuit for its control
JP2003305667A (ja) * 2002-04-12 2003-10-28 Nidec Shibaura Corp 電動工具
WO2016100891A1 (en) * 2014-12-19 2016-06-23 Black & Decker Inc. Power tool with electric motor and auxiliary switch path
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