Drill with solid state speed control and method of operating

• US 20070160353A1
• Filed: 11/03/2006
• Published: 07/12/2007
• Est. Priority Date: 11/04/2005
• Status: Active Grant

• Current Assignee: Credo Technology Corporation, Robert Bosch GmbH
• Original Assignee: Credo Technology Corporation, Robert Bosch GmbH
• Inventors: Pozgay, David, DeCicco, John, Kovarik, Illya
• Granted Patent: US 7,487,844 B2
• Time in Patent Office: Days
• US Class Current: 388/811
• CPC Class Codes: B25B 21/00 Portable power-driven screw or nut setting or loosening tools; details or components, e.g. casings, bodies, of portable power-driven tools not particularly related to the operation performed B25F5/00; for mounting or dismounting wheels B60B29/006; Attachments for drilling apparatus serving the same purpose machines B23P19/06
• CPC Class Codes: B25B 23/14 Arrangement of torque limiters or torque indicators in wrenches or screwdrivers couplings for transmitting rotation or clutches F16D; devices for measuring torque per se G01L
• CPC Class Codes: B25F 5/02 Construction of casings, bodies or handles B25F5/006, B25F5/008 take precedence
• CPC Class Codes: H01H 9/061 enclosing a continuously variable impedance
• CPC Class Codes: H02P 7/29 using pulse modulation
• CPC Class Codes: Y10S 388/937 Hand tool

Abstract

A power tool includes solid-state motor control. The tool includes a solid state variable speed control signal generator for generating a variable speed control signal, a microcontroller for generating a pulse width modulated (PWM) signal corresponding to the variable speed control signal, a driver circuit for generating H-bridge driving signals corresponding to the PWM signal, and an H-bridge circuit for selectively coupling a motor to a power source in accordance with the H-bridge driving signals.

Claims

1. A hand power tool having solid state motor control comprising:

a solid state variable speed control signal generator for generating a variable speed control signal;

a microcontroller for generating a pulse width modulated (PWM) signal corresponding to the variable speed control signal;

a driver circuit for generating H-bridge driving signals corresponding to the PWM signal; and

an H-bridge circuit for selectively coupling a motor to a power source in accordance with the H-bridge driving signals.

2. The tool of claim 1, the solid state variable speed control signal generator comprising:

an optical speed control switch.

3. The tool of claim 2, the optical speed control switch comprising:

a moveable member having a reflective surface and the moveable member traversing a distance between a stop position and a full speed position;

a biasing member operatively coupled to the moveable member to bias the moveable member toward the stop position;

an optical signal generator for generating an optical signal, the optical signal generator being oriented so that the optical signal is directed toward the reflective surface of the moveable member; and

a speed control signal generator for generating a variable speed control signal that corresponds to a reflection of the generated optical signal reflected by the reflective surface of the moveable member.

4. The tool of claim 1, the solid state variable speed control signal generator comprising:

a pressure transducer for generating a variable speed control signal that corresponds to a pressure applied to the pressure transducer.

5. The tool of claim 1, the solid state variable speed control signal generator comprising:

a capacitive sensor for generating a variable speed control signal that corresponds to an electrical capacitance that is generated by proximity of a moveable member to the capacitive sensor.

6. The tool of claim 1, the solid state variable speed control signal generator comprising:

an inductive sensor for generating a variable speed control signal that corresponds to an electrical inductance that is generated by proximity of a moveable member to the inductive sensor.

7. The tool of claim 1 further comprising:

a clutch circuit for generating a motor torque signal;

the microcontroller generating a dynamic braking signal in response to the motor torque signal being equal to or greater than a torque limit signal; and

the driver circuit generating dynamic braking signals for the H-bridge circuit corresponding to the dynamic braking signal.

8. The tool of claim 7, the clutch circuit further comprising:

a torque limit signal generator for generating the torque limit signal; and

a motor torque signal generator for generating the motor torque signal that corresponds to a motor current.

9. The tool of claim 7, the microcontroller generating a dynamic braking signal having a rectangular waveform.

10. The tool of claim 9, the microcontroller generating a rectangular waveform having an off-state of at least about 200 μ

seconds for the dynamic braking signal.

11. The tool of claim 9, the rectangular waveform having a frequency of about 30 Hz.

12. The tool of claim 7, the microcontroller being coupled to a motor direction control signal;

and

the microcontroller inverting the motor direction control signal and coupling the inverted motor direction control signal to the driver circuit so that the driver circuit reverses a battery polarity coupled to the motor after the off-state of the dynamic braking signal.

13. A method of operating a hand power tool comprising:

generating a variable speed control signal with a solid state switch that corresponds to a selected speed for a motor;

generating a pulse width modulated (PWM) signal corresponding to the variable speed control signal;

generating H-bridge driving signals for an H-bridge circuit in correspondence with the PWM signal; and

selectively coupling a motor to a power source using the H-bridge circuit in accordance with the H-bridge driving signals.

14. The method of claim 13, the variable speed control signal generation including:

generating the variable speed control signal in correspondence with a reflected optical signal.

15. The method of claim 14, the variable speed control signal generation including:

traversing a moveable member having a reflective surface through a distance between a stop position and a full speed position;

biasing the moveable member toward the stop position; and

directing an optical signal toward the reflective surface of the moveable member to generate the reflected optical signal.

16. The method of claim 13 further comprising:

generating a dynamic braking signal in response to a motor torque signal being equal to or greater than a torque limit signal; and

generating H-bridge driving signals for the H-bridge circuit that correspond to the dynamic braking signal.

17. The method of claim 16, the dynamic braking signal generation including:

generating a rectangular waveform.

18. The method of claim 17, the rectangular waveform generation including:

generating a rectangular waveform having an off-state of at least about 200 μ

seconds.

19. The method of claim 16 further comprising:

inverting a motor direction control signal; and

reversing a polarity of a battery coupled to the motor in response to the inverted motor direction control signal during an off-state of the rectangular waveform.

20. The method of claim 16 further comprising:

inverting a motor direction control signal; and

disabling the dynamic brake signal generation in response to the motor direction control signal being inverted.