FIELD OF THE INVENTION

The present invention relates to monitoring the number of impacts delivered by a power tool.

SUMMARY

In some embodiments, a power tool is able to achieve consistent number of impacts in an effort to generate a consistent torque output over repeated trials of the same application. The power tool closely approximates the behavior of torque-specific impact drivers and wrenches without requiring the use of a torque transducer.

By monitoring a combination of several motor parameters, the impact detection algorithm is able to limit the tool's impacts to a consistent number regardless of motor speed or battery charge.

In one embodiment, the invention provides a power tool including a housing, an anvil supported by the housing, a motor positioned within the housing and configured to drive the anvil, and a hammer mechanically coupled to the motor. The hammer is configured to deliver a plurality of impacts to the anvil. The power tool also includes a motor control unit electrically coupled to the motor and to the hammer. The motor control unit is configured to determine a motor characteristic indicative of a speed of the motor. When the motor characteristic indicates that the speed of the motor is below a speed threshold, the motor control unit employs an acceleration-based technique to detect a first impact based on a change in motor acceleration and generate a first impact indication in response to detecting the first impact. When the motor characteristic indicates that the speed is above the speed threshold, the motor control unit employs a time-based technique to detect a second impact based on an elapsed time and generates a second impact indication in response to detecting the second impact.

In one embodiment, the invention provides a method of detecting an impact of a power tool including driving, by a motor, a hammer of the power tool to deliver impacts to an anvil of the power tool. The method further includes determining a motor characteristic indicative of a speed of the motor. When the motor characteristic indicates that the speed of the motor is below a speed threshold, the method includes employing an acceleration-based technique to detect a first impact based on a change in motor acceleration and generating a first impact indication in response to detecting the first impact. When the motor characteristic indicates that the speed is above the speed threshold, the method includes employing a time-based technique to detect a second impact based on an elapsed time and generating a second impact indication in response to detecting the second impact.

In one embodiment, the invention provides a method of detecting an impact of a power tool including driving, by a motor, a hammer of the power tool to deliver impacts to an anvil of the power tool and determining a motor characteristic indicative of a speed of the motor. The method further includes setting an acceleration threshold based on the motor characteristic and detecting an impact based on a change in motor acceleration exceeding the acceleration threshold. The method also includes generating an impact indication in response to detecting the impact.

In one embodiment, the invention provides a power tool including a housing, an anvil supported by the housing, a motor positioned within the housing and configured to drive the anvil, and a hammer mechanically coupled to the motor. The hammer is configured to deliver a plurality of impacts to the anvil. The power tool also includes a motor control unit electrically coupled to the motor and to the hammer. The motor control unit is configured to determine a desired number of delivered impacts to the anvil, determine a motor speed at which the motor drives the anvil, monitor the number of delivered impacts to the anvil according to one selected from a group consisting of an acceleration-based algorithm and a time-based algorithm based on the motor speed, and control the motor based on the number of delivered impacts to the anvil.

In another embodiment the invention provides a power tool including a housing, an anvil supported by the housing, a motor positioned within the housing and configured to drive the anvil, and a hammer mechanically coupled to the motor. The hammer is configured to deliver a plurality of impacts to the anvil. The power tool also includes a motor control unit electrically coupled to the motor and to the hammer. The motor control unit is configured to determine a desired number of delivered impacts to the anvil, receive signals from sensors, the signals indicative of a parameter of motor motion, and calculate, from the received signals, a motor acceleration. The motor control unit is also configured to monitor changes in motor acceleration, determine whether a change in motor acceleration exceeds a variable acceleration threshold, and detect that an impact is delivered when the motor acceleration exceeds the variable acceleration threshold.

Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings.

