Rotary tool driven by brushless motor

Abstract

To provide a rotary tool driven by a brushless motor with which constant torque tightening work for screws or the like can always be performed properly and efficiently, in which overall downsizing and improved torque control precision enhancement can easily be achieved, and with which it is possible to eliminate occurrences of switch contact-induced sparking and wear and of the damage imparted to the peripheral electronic equipment and electronic circuitry as occurred in drive switches or torque detection mechanisms that use a conventional mechanical switch mechanism, so that the constituting parts are able to have a reduced size and an extended life. First Hall elements 31 a and 31 b for respectively detecting operations of the respective lever operation mechanism 20 and push operation mechanism 18 , both being the drive switch, are provided, and a second Hall element 32 for detecting clutch actions is also provided; and a control means 50 is configured so that a DC brushless motor 12 is rotationally driven based on an operation signal provided by the first Hall elements 31 a and 31 b and is stopped based on an action signal provided by the second Hall element 32.

1 : A rotary tool driven by a brushless motor comprising: a DC brushless motor for rotationally driving a rotary bit, a torque setting clutch mechanism provided in a shaft-coupling portion for coupling said rotary bit and an output shaft of said brushless motor, a drive switch for drive-controlling a drive control circuit of said brushless motor, and a control means configured so as to rotationally drive said brushless motor by an operation of said drive switch and so as to stop a rotational drive of said brushless motor by detecting clutch action of said clutch mechanism, wherein:
 first Hall elements for respectively detecting a lever operation and a push operation are respectively provided for a lever operation mechanism and a push operation mechanism both being said drive switch for said brushless motor, and a second Hall element detecting a clutch action is provided for said clutch mechanism; and   said control means is configured so that, based on a drive switch operation signal provided by one of said first Hall elements, said drive control circuit of said brushless motor is drive-controlled so as to rotationally drive said brushless motor and so that, based on a clutch mechanism action signal provided by said second Hall element, said drive control circuit of said brushless motor is stop-controlled so as to stop the rotational drive of said brushless motor.   
   
   
       2 : The rotary tool driven by a brushless motor according to  claim 1 , wherein
 a forward/reverse switching operation mechanism performing forward/reverse switching operations for said brushless motor is further provided, and a third Hall element detecting forward/reverse switching operations of said forward/reverse switching operation mechanism is further provided; and wherein   based on a forward/reverse switching operation signal provided by said third Hall element, said brushless motor is rotated forward or rotated in reverse through said control means.   
   
   
       3 : The rotary tool driven by a brushless motor according to  claim 1 , wherein said brushless motor drive control circuit is comprised of: an AC/DC conversion means connected to a commercial power source for obtaining a power supply voltage for driving said brushless motor, an inverter circuit comprising a semiconductor bridge configuration that converts said power supply voltage into a brushless motor drive voltage, a drive circuit for ON/OFF-controlling a semiconductor that comprises said bridge configuration of said inverter circuit, and a position detection circuit for detecting a position of a rotor with respect to magnetizing windings in said brushless motor; and wherein said control means outputs to said drive circuit a control signal which is for switching a current supplied to said magnetizing windings by a position detection signal detected by said position detection circuit. 
   
   
       4 : The rotary tool driven by a brushless motor according to  claim 1 , wherein setting is effected so that when stop-control of said drive control circuit of said brushless motor is performed by said control means, a drive power for said brushless motor is interrupted based on said clutch mechanism action signal provided by said second Hall element, and said semiconductor that comprises said bridge configuration of said inverter circuit provided in said drive control circuit of said brushless motor is control-operated so as to short-circuit said magnetizing windings of said brushless motor, thus braking said rotor of said brushless motor. 
   
   
       5 : The rotary tool driven by a brushless motor according to  claim 1 , wherein setting is effected so that, when a lever operation or push operation of said lever operation mechanism or push operation mechanism, both being said brushless motor drive switch, is suspended, said semiconductor that comprises said bridge configuration of said inverter circuit provided in said drive control circuit of said brushless motor is control-operated so as to short-circuit said magnetizing windings of said brushless motor, thus braking said rotor of said brushless motor and stopping said brushless motor. 
   
   
       6 : A rotary tool driven by a brushless motor comprising: a DC brushless motor for rotationally driving a rotary bit, a load current detection means for detecting a load current of said brushless motor, a drive switch for drive-controlling a drive control circuit of said brushless motor, and a control means configured so as to rotationally drive said brushless motor by an operation of said drive switch and so as to stop a rotational drive of said brushless motor when a load current detected by said load current detection means exceeds a predetermined set value, wherein:
 first Hall elements for respectively detecting a lever operation and a push operation are respectively provided for a lever operation mechanism and a push operation mechanism both being said drive switch for said brushless motor; and   said control means is configured so that, based on a drive switch operation signal provided by one of said respective first Hall elements, said drive control circuit of said brushless motor is drive-controlled so as to rotationally drive said brushless motor and so that, when a load current detected by said load current detection means exceeds a set value, said drive control circuit of said brushless motor is stop-controlled so as to stop the rotational drive of said brushless motor.   
   
   
       7 : The rotary tool driven by a brushless motor according to  claim 6 , wherein a forward/reverse switching operation mechanism performing forward/reverse switching operations for said brushless motor is further provided, and a third Hall element detecting forward/reverse switching operations of said forward/reverse switching operation mechanism is further provided; and wherein based on a forward/reverse switching operation signal provided by said third Hall element, said brushless motor is rotated forward or rotated in reverse through said control means. 
   
   
       8 : The rotary tool driven by a brushless motor according to  claim 6 , wherein said brushless motor drive control circuit is comprised of: an AC/DC conversion means connected to a commercial power source for obtaining a power supply voltage for driving said brushless motor, an inverter circuit comprising a semiconductor bridge configuration that converts said power supply voltage into a brushless motor drive voltage, a drive circuit for ON/OFF-controlling a semiconductor that comprises said bridge configuration of said inverter circuit, and a position detection circuit for detecting a position of a rotor with respect to magnetizing windings in said brushless motor; and wherein said control means outputs to said drive circuit a control signal which is for switching a current supplied to said magnetizing windings by a position detection signal detected by said position detection circuit. 
   
   
       9 : The rotary tool driven by a brushless motor according to  claim 6 , wherein setting is effected so that when stop-control of said drive control circuit of said brushless motor is performed by said control means, a drive power for said brushless motor is interrupted if a load current that is detected by said load current detection means exceeds a set value, and said semiconductor that comprises said bridge configuration of said inverter circuit provided in said drive control circuit of said brushless motor is control-operated so as to short-circuit said magnetizing windings of said brushless motor, thus braking said rotor of said brushless motor. 
   
   
       10 : The rotary tool driven by a brushless motor according to  claim 6 , wherein setting is effected so that when a lever operation or push operation of said lever operation mechanism or push operation mechanism, both being said brushless motor drive switch, is suspended, said semiconductor that comprises said bridge configuration of said inverter circuit provided in said drive control circuit of said brushless motor is control-operated so as to short-circuit said magnetizing windings of said brushless motor, thus braking said rotor of said brushless motor and stopping said brushless motor.