CN-115117853-B - Overcurrent protection for an electric motor

Abstract

Over-current protection for electric, motorized devices such as power tools, wherein the tool includes a tool housing, an output assembly, a trigger, an electrical safety device, a motor, an indicator, a controller, and a power source. An electrical safety device (e.g., a fuse) is provided in series with the power connection from the power source to the controller. When the trigger is actuated, the controller measures the current through the electrical safety device at time intervals. The controller determines the accumulated thermal energy through the electrical safety device and compares the accumulated thermal energy to a threshold. If the accumulated thermal energy exceeds the threshold, the controller stops or interrupts the supply of power from the power source to the motor, thereby shutting down the motor. The controller may also activate an indicator to indicate a fault to the user.

Inventors

• Michael. T. Raj
• Jason Genz
• Christopher S. Fox

Assignees

• 施耐宝公司

Dates

Publication Date

20260505

Application Date

20220322

Priority Date

20220314

Claims (20)

1. 1. A method of operating a power tool including a motor, an output assembly adapted to be driven by the motor, a power source adapted to supply power to the motor, and a controller operatively coupled to the motor and the power source, the method comprising: Determining an amount of accumulated thermal energy through an electrical safety device when power is supplied to the motor, wherein the electrical safety device is operably coupled in series with a power connection from the power source to the controller; comparing the amount of accumulated heat energy with a threshold limit value, and When the accumulated thermal energy reaches or exceeds the threshold limit, power supply to the motor is stopped.
2. 2. The method of claim 1, further comprising measuring the amount of current passing through the electrical safety device at predetermined time intervals, respectively.
3. 3. The method of claim 2, wherein determining the amount of accumulated thermal energy passing through the electrical safety device is based on an amount of current respectively passing through the electrical safety device at the predetermined time interval.
4. 4. The method of claim 2, further comprising filtering the amount of current through a filter of the power tool.
5. 5. The method of claim 4, wherein the filter is a high pass filter.
6. 6. The method of claim 1, further comprising filtering the amount of accumulated thermal energy through a filter of the power tool.
7. 7. The method of claim 6, wherein the filter is a high pass filter.
8. 8. The method of claim 1, further comprising allowing power to the motor when the amount of accumulated thermal energy is below the threshold limit.
9. 9. The method of claim 1, wherein the step of determining the amount of accumulated thermal energy passing through the electrical safety device begins when a trigger of the power tool is actuated.
10. 10. A power tool having a motor, a power source adapted to supply power to the motor, and an output assembly adapted to be driven by the motor, the power tool comprising; A controller operatively coupled to the motor and the power source, and An electrical safety device operably coupled in series with a power connection from the power source to the controller; wherein the controller is adapted to: Determining an amount of accumulated thermal energy passing through the electrical safety device when power is supplied to the motor; comparing the amount of accumulated heat energy with a threshold limit value, and When the amount of accumulated thermal energy reaches or exceeds the threshold limit, power supply to the motor is stopped.
11. 11. The power tool of claim 10, wherein the controller is further adapted to separately measure the amount of current through the electrical safety device at predetermined time intervals.
12. 12. The power tool of claim 11, wherein the controller is further adapted to determine the amount of accumulated thermal energy passing through the electrical safety device based on the respective amounts of current passing through the electrical safety device at the predetermined time interval.
13. 13. The power tool of claim 11, further comprising a filter adapted to filter the amount of current.
14. 14. The power tool of claim 13, wherein the filter is a high pass filter.
15. 15. The power tool of claim 10, further comprising a filter adapted to filter the amount of accumulated thermal energy.
16. 16. The power tool of claim 15, wherein the filter is a high pass filter.
17. 17. The power tool of claim 10, wherein the controller is further adapted to allow power to the motor when the amount of accumulated thermal energy is below the threshold limit.
18. 18. The power tool of claim 10, wherein the controller is further adapted to determine the amount of accumulated thermal energy passing through the electrical safety device when a trigger of the power tool is actuated.
19. 19. The power tool of claim 10, wherein the controller includes a data storage component adapted to store executable instructions.
20. 20. The power tool of claim 19, wherein the data storage component is a ferroelectric random access memory.

Description

Overcurrent protection for an electric motor Cross Reference to Related Applications The present application claims the benefit of U.S. provisional patent application No. 63/164,860, filed 3/23, 2021, and U.S. patent application No. 17/694,242, filed 3/14, 2022, which are incorporated herein by reference in their entirety. Technical Field The present invention relates to electric motors and more particularly to over-current protection of electrical components used in the operation of electric motors. Background Power hand tools such as, for example, power ratchet wrenches, impact wrenches, and other drivers are commonly used in automotive, industrial, and household applications to install and remove threaded fasteners and apply torque and/or angular displacement to a workpiece such as, for example, a threaded fastener. Power hand tools typically include an output member, such as a drive flange or drive chuck, a trigger switch that is actuatable by a user, an electric motor housed in a housing, and other components, such as, for example, a switch, a Light Emitting Diode (LED), a controller, and a power source, such as a battery. Some power hand tools employ a fuse in series with a power connection from a power source to a controller in order to open the fuse in the event of a fault, such as a short circuit condition, for example, to protect electrical components, such as the controller, motor and/or trigger switch, from damage by excessive currents. However, fuses may be difficult to size properly (especially for high current tools) so that they can quickly open in the event of a fault, such as, for example, a short circuit condition, and also allow the tool to continue to operate during normal operation. This results in the fuse being used either too small or too large (i.e., the I 2 t rating of the fuse is too low or too high). The I 2 t ratings are provided in the data table by each fuse series. Undersized fuses can result in an interruption of operation that is not necessary for protection of the electrical components, while oversized fuses can result in a high current flow through the electrical components for a long period of time in the event of a failure, resulting in greater damage. Disclosure of Invention The present invention relates generally to over-current protection of electric motor apparatus, such as electric tools. The tool includes a tool housing, an output assembly (such as a ratchet head assembly) adapted to provide torque to a workpiece, a trigger switch, a motor housed in the housing, an indicator, a controller, and a power source. An electrical safety device, such as for example a fuse, is arranged in series with the power connection from the power source to the controller. When the trigger is actuated, the controller measures the current through the fuse at time intervals. The controller determines the accumulated thermal energy by repeatedly using the formula current x time (I 2 x t) at each time interval. The controller compares the accumulated thermal energy to a threshold. If the accumulated thermal energy exceeds the threshold, the controller stops or interrupts the supply of power from the power source to the motor, thereby shutting down the motor. The controller may also activate an indicator to indicate a fault to the user. The present invention utilizes a controller to limit thermal energy passing through an electrical safety device, such as, for example, a fuse, rather than relying solely on an appropriately sized electrical safety device to protect the electrical components of the tool in the event of a failure of the tool, such as, for example, a short circuit. The present invention prevents the electrical safety device from prematurely and/or unnecessarily blocking or interrupting the current from the power source while also allowing the electrical safety device to act quickly in the event of a malfunction. Furthermore, the present invention enables successful use of a somewhat smaller size conventional electrical safety device without having to upgrade to a larger electrical safety device having a higher rating (e.g., a higher I 2 t rating). Drawings In order to facilitate an understanding of the claimed subject matter, embodiments thereof are shown in the drawings. The claimed subject matter, its construction and operation, and many of its advantages should be readily understood and appreciated by reference to the embodiments when considered in connection with the following description. FIG. 1 is a perspective view of an exemplary tool incorporating one embodiment of the present invention. Fig. 2 and 3 are component block diagrams of electronic components of an exemplary tool incorporating embodiments of the present invention. FIG. 4 is a block diagram of a method of operation of an exemplary tool incorporating one embodiment of the invention. Detailed Description While this invention is susceptible of embodiment in many different forms, there is shown in the drawings