# US 10,770,993 B2 · Power tool

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- Number: US 10,770,993 B2
- Document ID: US10770993B2
- Status: Granted
- Kind: B2
- Application number: 16/368,227
- Filed: 2019-03-28
- Published: 2019-10-31
- Granted: 2020-09-08
- Earliest claimed: 2018-04-28
- Assignees: Nanjing Chervon Industry Co., Ltd.
- Applicants: Nanjing Chervon Industry Co., Ltd.
- Inventors: Weipeng Chen; Dezhong Yang; Wencheng Li
- Web page: https://patentgrep.com/patent/US10770993B2

## CPC

- H02P 6/08: Arrangements for controlling the speed or torque of a single motor (H02P6/10, H02P6/28 take precedence)
- H02P 27/085: {wherein the PWM mode is adapted on the running conditions of the motor, e.g. the switching frequency}
- B25F 5/00: Details or components of portable power-driven tools not particularly related to the operations performed and not otherwise provided for
- H02P 6/10: Arrangements for controlling torque ripple, e.g. providing reduced torque ripple
- H02P 23/0027: {using different modes of control depending on a parameter, e.g. the speed}
- H02P 23/0031: {implementing a off line learning phase to determine and store useful data for on-line control}
- H02P 29/02: Providing protection against overload without automatic interruption of supply (protection against faults of stepper motors H02P8/36)
- H02P 29/032: Preventing damage to the motor, e.g. setting individual current limits for different drive conditions
- H02P: CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- B25F: COMBINATION OR MULTI-PURPOSE TOOLS NOT OTHERWISE PROVIDED FOR; DETAILS OR COMPONENTS OF PORTABLE POWER-DRIVEN TOOLS NOT PARTICULARLY RELATED TO THE OPERATIONS PERFORMED AND NOT OTHERWISE PROVIDED FOR {(machines or arrangements of machines for performing specified combinations of different metal-working operations not covered by a single other subclass B23P23/00 and subgroups)}

## Abstract

A duty ratio under different working conditions is determined according to an analysis of a characteristic parameter x of a motor of a power tool and then a drive circuit is controlled with the duty ratio to drive the motor to operate. It is only needed to calculate the duty ratio without needing to make any variable to the circuit hardware or the mechanical structure of the power tool. That is, the duty ratio can be adjusted to achieve optimized control of the motor, thereby optimizing the working performance such as an output torque of the power tool.

## Claims

### Claim 1

A power tool, comprising:
a motor, comprising a stator and a rotor;
a transmission device, configured to connect the rotor to a tool accessory;
a drive circuit, configured to output a switch signal to drive the rotor of the motor to operate;
a control unit, configured to output a drive signal to control the drive circuit; and
a power supply device, configured to supply power to the motor, the drive circuit, and the control unit;
wherein the control unit is configured to determine a variable ΔPWM of a duty ratio according to a variable Δx of a characteristic parameter of the motor, wherein the variable ΔPWM of the duty ratio is obtained by a function f(Δx) and is within a range of 0.01 to 0.1, and according to the variable ΔPWM of the duty ratio, output the drive signal to the drive circuit to control the rotor of the motor to operate to output a driving force.

### Claim 2 (depends on 1)

The power tool of claim 1, further comprising a motor detection module configured to detect and obtain the characteristic parameter x of the motor; wherein the motor detection module is integrated into the control unit or disposed separated from the control unit.

### Claim 3 (depends on 1)

The power tool of claim 1, wherein the characteristic parameter x of the motor comprises at least one of a motor speed, a current, or an output torque.

### Claim 4 (depends on 1)

The power tool of claim 1, wherein the power supply device comprises a battery pack composed of a plurality of single battery cells connected in series.

### Claim 5 (depends on 1)

The power tool of claim 1, wherein the variable Δx of the characteristic parameter of the motor is a variable Δn of a motor speed.

### Claim 6 (depends on 5)

The power tool of claim 5, wherein, when the variable Δn of the motor speed is within a range from 500 rpm to 1000 rpm, the corresponding variable ΔPWM of the duty ratio is within a range from 0.02 to 0.05 and, when the variable Δn of the motor speed is within a range of 1000 rpm to 1500 rpm, the corresponding variable ΔPWM of the duty ratio is within a range from 0.05 to 0.08.

### Claim 7

A power tool, comprising:
a motor, comprising a stator and a rotor;
a transmission device, configured to connect the rotor to a tool accessory;
a drive circuit, configured to output a switch signal to drive the rotor of the motor to operate;
a control unit, configured to output a drive signal to control the drive circuit; and
a battery pack, configured to supply power to the motor, the drive circuit and the control unit;
wherein the control unit is configured to determine a variable ΔPWM of a duty ratio according to a variable Δx of a characteristic parameter of the motor, wherein the variable ΔPWM of the duty ratio is obtained by a function f(Δx) and is within a range of 0.1 to 0.2, and to output the drive signal to the drive circuit according to the variable ΔPWM of the duty ratio, to control the rotor of the motor to operate to output a driving force.

### Claim 8 (depends on 7)

The power tool of claim 7, wherein the characteristic parameter x of the motor comprises at least one of a motor speed, a current, or an output torque.

### Claim 9 (depends on 7)

The power tool of claim 7, wherein the variable Δx of the characteristic parameter of the motor is a variable Δn of a motor speed.

### Claim 10 (depends on 9)

The power tool of claim 9, wherein, when the variable Δn of the motor speed is within a range from 500 rpm to 1000 rpm, the corresponding variable ΔPWM of the duty ratio is within a range from 0.02 to 0.05 and, when the variable Δn of the motor speed is within a range of 1000 rpm to 1500 rpm, the corresponding variable ΔPWM of the duty ratio is within a range from 0.05 to 0.08.

### Claim 11

A power tool, comprising:
a brushless motor, comprising a stator and a rotor;
a transmission device, configured to connect the rotor to a tool accessory;
a drive circuit, configured to output a switch signal to drive the rotor of the brushless motor to operate;
a control unit, configured to output a drive signal to control the drive circuit; and
a power supply device, configured to supply power to the brushless motor, the drive circuit, and the control unit;
wherein the control unit is configured to determine a variable ΔPWM of a duty ratio according to a variable Δx of a characteristic parameter of the brushless motor and a characteristic parameter V of the power supply device, wherein the variable ΔPWM of the duty ratio is obtained by a function f(Δx, V) and is within a range of 0.01 to 0.2, and to output the drive signal to the drive circuit according to the variable ΔPWM of the duty ratio, to control the rotor of the brushless motor to operate to output a driving force.

### Claim 12 (depends on 11)

The power tool of claim 11, wherein the control unit is configured to determine the variable ΔPWM of the duty ratio according to the variable Δx of the characteristic parameter of the brushless motor, a number of P of a battery pack and the characteristic parameter V of the power supply device, wherein the variable ΔPWM of the duty ratio is obtained by a function f(Δx, V, P) and is within a range from 0.01 to 0.1 or from 0.1 to 0.2; and to output the drive signal to the drive circuit according to the variable ΔPWM of the duty ratio, to output the driving force for controlling the rotor of the brushless motor to operate.

### Claim 13 (depends on 11)

The power tool of claim 11, wherein the power tool has a maximum output torque greater than or equal to 5N·m.

### Claim 14 (depends on 11)

The power tool of claim 11, wherein the variable Δx of the characteristic parameter of the motor is a variable Δn of a motor speed.

### Claim 15 (depends on 14)

The power tool of claim 14, wherein, when the variable Δn of the motor speed is within a range from 500 rpm to 1000 rpm, the corresponding variable ΔPWM of the duty ratio is within a range from 0.02 to 0.05 and, when the variable Δn of the motor speed is within a range of 1000 rpm to 1500 rpm, the corresponding variable ΔPWM of the duty ratio is within a range from 0.05 to 0.08.