Microcontroller for and a method of controlling operation of the safety clutch of a hand-held electric power tool

• US 20020053892A1
• Filed: 08/21/2001
• Published: 05/09/2002
• Est. Priority Date: 08/24/2000
• Status: Active Grant

• Current Assignee: Hilti Aktiengesellschaft (Hilti Martin Family Trust)
• Original Assignee: Hilti Aktiengesellschaft (Hilti Martin Family Trust)
• Inventors: Schaer, Roland, Boni, Hans
• Granted Patent: US 6,700,341 B2
• Time in Patent Office: Days
• US Class Current: 318/432
• CPC Class Codes: B25F 5/00 Details or components of portable power-driven tools not particularly related to the operations performed and not otherwise provided for
• CPC Class Codes: Y10S 388/937 Hand tool

Abstract

A microcontroller for controlling operation of a safety clutch of a handheld electrical power tool and which is arranged in a force transmitting chain of the tool, with the microcontroller including a unit (2,5,4;8) for processing at least one parameter of the power tool and for outputting a resulting parameter in form of a calculated torque (M¹), and a control unit (7) for comparing an actually measured torque (M) with the calculated torque (M¹), and for outputting a control signal (θ) when a difference between the actually measured and calculated torques exceeds a predetermined threshold.

Claims

1. A microcontroller for controlling operation of a safety clutch of a hand-held electrical power tool and which is arranged in a force transmitting chain of the tool, the microcontroller comprising means (2,5,4;

8) for processing at least one parameter of the power tool and for outputting a resulting parameter in form of a calculated torque (M¹); and

a control unit (7) for comparing an actually measured torque (M), which is inputted in the control unit (7) as a first input parameter, with the calculated torque (M¹), which is inputted into the control unit (7) as a second input parameter, and for outputting a control signal (θ

) when a difference between the actually measured and calculated torques exceeds a predetermined threshold.

2. A microcontroller according to claim 1, wherein the processing means comprises a first calculation unit (2) for transforming an input current (I) of a power tool electromotor, which is inputted in the first calculation unit (2) as an input parameter, over a motor diagram (3), into the calculated torque (M¹) and a control unit (7) for comparing an actually measured torque, which is inputted into the control unit (7) as a first input parameter, with the calculated torque (M), at an output thereof.

3. A microcontroller according to claim 2, wherein the processing means comprises a second calculation unit (5) for transforming a measured rotational speed (n) of the power tool electromotor, which is inputted in the second calculation unit as an input parameter, over a friction diagram, into a friction torque at a second calculation unit output.

4. A microcontroller according to claim 3, wherein the processing means further comprises a summation point (4) having input means connected with the outputs of the first and second calculation units (2,5) and output means for outputting a calculated torque (M¹) obtained by summation of input torques inputted from the first and second calculation units (2,5).

5. A microcontroller according to claim 1, wherein the processing means comprises a filter unit (8) for converting the actually measured torque (M), which is inputted therein, into the calculated torque (M¹).

8. A method according to claim 5, further comprising the step of additionary comparing the actually measured torque with a fixed threshold.

6. A method of controlling operation of an electrically controlled safety clutch of a hand-held electrical power tool and arranged in a force transmitting chain of the tool, the method comprising the steps of one of transforming an input current (I) of a tool electromotor, by using a motor diagram (3) locally into a calculated torque (M¹) and transforming an electrically filtered actually measured torque (M) into a locally calculated torque (M¹);

comparing a difference (Δ

) between the actually measured torque (M) and the calculated torque (M¹) with a predetermined threshold value; and

outputting a control signal (θ

) for actuating the safety clutch in response to the difference (Δ

) between the actually measured and calculated torques (M, M¹) exceeding the predetermined threshold value.

7. A method according to claim 6, further comprising the step of using the control signal (θ

) for actuating an electric motor brake.