Power tool and method for switching power tool control mode

By switching the motor control mode in the power tool, square wave control is adopted under light load and sine wave or saddle wave control is adopted under heavy load according to the motor load parameters, which solves the problem of low speed and efficiency of the power tool under heavy load and improves the overall performance of the motor.

CN113131831BActive Publication Date: 2025-09-16NANJING CHERVON IND
View PDF 2 Cites 0 Cited by

Patent Information

Application Number
CN202011262017.6
Authority / Receiving Office
CN · China
Patent Type
Patents(China)
Current Assignee / Owner
Priority Date
2020-08-10
Filing Date
2020-11-12
Publication Date
2025-09-16
Estimated Expiration
2040-11-12

AI Technical Summary

Technical Problem

Existing power tools use square wave control under heavy load conditions, resulting in low speed and efficiency, and the output characteristics need to be improved urgently.

Method used

The motor control module is used to switch the control mode under light load and heavy load conditions. Square wave control is used under light load, and sine wave or saddle wave control is used under heavy load. The switching timing is determined by detecting the load-related parameters of the motor such as current and speed, and the output of the PWM signal is suspended during the switching process to reduce oscillation.

Benefits of technology

The efficiency and output characteristics of the motor under light and heavy load conditions are improved, achieving better heavy-load performance.

✦ Generated by Eureka AI based on patent content.

Smart Images

  • Figure CN113131831B_ABST
    Figure CN113131831B_ABST
Patent Text Reader

Abstract

The present invention provides an electric tool, an electric tool control method, and a motor control mode switching method. The electric tool includes functional elements, a motor, a power supply module, a drive circuit, and a control module. The module is electrically connected to the drive circuit and is used to output a control signal to the drive circuit to control the drive circuit. The control module is configured to: when the electric tool is in a first operating stage, control the drive circuit in a first control mode so that the voltage of the motor changes in a square wave following the position of the rotor of the motor; when the electric tool is in a second operating stage, control the drive circuit in a second control mode so that the voltage of the motor changes in a sinusoidal wave or a saddle wave following the position of the rotor of the motor. The present invention can improve motor efficiency and effectively enhance performance.
Need to check novelty before this filing date? Find Prior Art

Claims

1. An electric tool comprising: functional elements; A motor, used to drive the functional element to rotate, the motor comprising a stator and a rotor; a power supply module, used to supply power to the motor; a drive circuit, electrically connected to the motor and the power supply module, for applying the voltage of the power supply module to the motor; A control module is electrically connected to the driving circuit and is used to output a control signal to the driving circuit to control the driving circuit. The control module is configured to: When the electric tool is in a first operating stage, controlling the drive circuit in a first control mode so that the voltage of the motor changes in a square wave pattern following the position of the rotor of the motor; When the electric tool is in the second operating stage, the drive circuit is controlled in a second control mode so that the voltage of the motor changes in a sinusoidal wave or a saddle wave pattern following the position of the rotor of the motor; When the speed of the motor is less than or equal to a first preset speed threshold and the current of the motor is greater than or equal to a first preset current threshold, it is determined that the power tool is in the second operation stage, and the control module switches from the first control mode to the second control mode.

2. The electric tool according to claim 1, wherein: The control module is configured to: It is determined whether the electric tool is in the first operating stage or the second operating stage according to the load-related parameters of the motor.

3. The electric tool according to claim 2, wherein: The load-related parameter of the motor includes at least one of the current of the motor, the speed of the motor, the torque of the motor, and the acceleration of the power tool.

4. The electric tool according to claim 3, wherein: The control module is configured to: When the speed of the motor is greater than or equal to a second preset speed threshold and the current of the motor is less than or equal to a second preset current threshold, it is determined that the power tool is in the first operation stage, and the control module switches from the second control mode to the first control mode; The second preset current threshold is smaller than the first preset current threshold, and the second preset speed threshold is larger than the first preset speed threshold.

5. The electric tool according to claim 4, wherein: The control module is configured to: In the first control mode, a first PWM control signal is output to the driving circuit; In the second control mode, outputting a second PWM control signal to the driving circuit; The duty cycle of the second PWM control signal changes as the position of the rotor of the motor changes.

6. The electric tool according to claim 5, wherein: The control module is configured to: performing a switching process before switching from the first control mode to the second control mode; During the switching process, outputting the first PWM control signal to the driving circuit is suspended to stop driving the motor.

7. The electric tool according to claim 6, wherein: The control module is configured to: The switching process is started at a preset position of the rotor.

8. The electric tool according to claim 6, wherein: A change in the rotation speed of the motor before and after the switching process is less than a preset threshold.

9. The electric tool according to claim 6, wherein: The control module is configured to: During the switching process, the initial duty cycle of the second PWM control signal after switching is obtained according to the duration of the switching process executed by the control module, the speed of the motor, the position of the rotor of the motor, and the bus current or bus voltage of the motor.

10. A method for switching a control mode of an electric tool, the control mode comprising: A first control mode is to output a first PWM control signal to drive the motor so that the input voltage of the motor changes in a square wave pattern following the rotor position of the motor; The second control mode outputs a second PWM control signal to drive the motor, so that the input voltage of the motor changes in a sinusoidal wave or a saddle wave following the rotor position of the motor; The method for switching the electric tool control mode of the motor from the first control mode to the second control mode includes: When the rotor of the motor is in a preset position: stopping driving the motor; Obtaining the bus voltage or bus current of the motor and the speed of the motor before switching; Calculating the motor speed and the rotor position after the preset time period based on the preset time period, the motor speed before switching, and the preset position of the rotor; The initial duty cycle of the second PWM control signal after switching is obtained by calculation or table lookup based on the calculated rotational speed and rotor position of the motor after the preset time period, and the bus voltage or bus current of the motor.

Citation Information

Patent Citations

  • Controller for brushless motors

    JP2008172948A

  • Electric power tool and control method therefor

    WO2019184975A1