Patent Publication Number: US-2022234161-A1

Title: Rotary tool

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of priority to Japanese Patent Application No. 2021-009038, filed on Jan. 22, 2021, the entire contents of which are hereby incorporated by reference. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a rotary tool, such as a grinder or a polisher. 
     2. Description of the Background 
     A rotary tool (e.g., a grinder) that rotates a tip tool (e.g., a grinding disc) is described in, for example, Japanese Unexamined Patent Application Publication No. 2019-51582 (Patent Literature 1). The rotary tool includes a housing. The housing includes a cylindrical motor housing accommodating a motor and extending in the front-rear direction, a gear housing including a spindle as a final output shaft at the front of the motor housing, and a handle housing accommodating a switch and other components at the rear of the motor housing. 
     The housing accommodates a controller for controlling, for example, the drive of the motor. In the rotary tool described in Patent Literature 1, the controller is divided into two, or upper and lower controllers, located above and below a commutator for a rotor in the motor housing. This structure allows efficient use of the space in the motor housing. 
     BRIEF SUMMARY 
     The controller is connected to electrical components of the rotary tool, such as sensors and lamps. Such components including sensors and lamps located away from the controller may use many wires drawn from the controller. This causes complicated wiring, involving more laborious assembly and a higher possibility of wire breakage. 
     One or more aspects of the present disclosure are directed to a rotary tool including simple wiring from a controller. 
     A first aspect of the present disclosure provides a rotary tool, including: 
     a housing; 
     a motor accommodated in the housing; 
     a final output shaft accommodated in the housing and configured to receive a tip tool, the final output shaft being rotatable by the motor being driven; and 
     a plurality of controllers accommodated in the housing, the plurality of controllers including at least a first controller receiving an electrical component of the rotary tool on an outer surface of the first controller, the electrical component being configured to perform an electrical operation. 
     The electrical component refers to either or both of an information input unit, such as a sensor or an operation unit, electrically connected to the controller to obtain information used by the controller to control the rotary tool, and an information output unit, such as a light emitter or an indicator, electrically connected to the controller to cause the controller to provide information used to operate the rotary tool. 
     The rotary tool according to the above aspect of the present disclosure includes simple wiring from the controller. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view of a grinder. 
         FIG. 2  is a longitudinal central sectional view of the grinder. 
         FIG. 3  is a plan view taken along line A-A in  FIG. 2 . 
         FIG. 4  is an enlarged cross-sectional view taken along line B-B in  FIG. 2 . 
         FIG. 5A  is a top perspective view of a first controller. 
         FIG. 5B  is a bottom perspective view of the first controller. 
         FIG. 6A  is a top perspective view of a second controller. 
         FIG. 6B  is a bottom perspective view of the second controller. 
         FIG. 7  is an enlarged cross-sectional view taken along line C-C in  FIG. 2 . 
         FIG. 8  is a perspective view of the grinder with a cover attached to a handle housing. 
         FIG. 9  is an exploded perspective view of the handle housing and the cover. 
         FIG. 10  is an enlarged cross-sectional view of the grinder in  FIG. 8  showing screw bosses. 
     
    
    
     DETAILED DESCRIPTION 
     An embodiment of the present disclosure will now be described with reference to the drawings. 
       FIG. 1  is a perspective view of a grinder as an example rotary tool.  FIG. 2  is a longitudinal central sectional view of the grinder.  FIG. 3  is a cross-sectional view taken along line A-A in  FIG. 2 . 
     A grinder  1  includes a housing  2  including a gear housing  3 , a motor housing  4 , and a handle housing  5  in this order from the front. 
     The gear housing  3  includes a spindle  6 . The spindle  6  is rotatably supported on an upper bearing  7  and a lower bearing  9  with its axis vertically extending. The upper bearing  7  is held in the gear housing  3 . The lower bearing  9  is held on a retainer  8  attached to the bottom of the gear housing  3 . 
     A bevel gear  10  is located on an upper portion of the spindle  6 . The spindle  6  has a lower end protruding downward from the retainer  8  to receive a grinding disc  13  with an inner flange  11  and an outer flange  12 . 
     The retainer  8  includes a wheel cover  14  to cover a rear half of the grinding disc  13 . The gear housing  3  has multiple outlets  15  in the front surface. 
     The motor housing  4  accommodates a motor  16 . The motor housing  4  is cylindrical and extends in the front-rear direction. The motor  16  includes a stator  17  and a rotor  18 . The motor  16  is accommodated with the rotor  18  having an output shaft  19  extending frontward. The output shaft  19  extends through a partition  20  between the motor housing  4  and the gear housing  3  and is supported on a bearing  21  held in the gear housing  3 . The output shaft  19  has a front end protruding into the gear housing  3  and receiving a bevel gear  22 . The bevel gear  22  meshes with the bevel gear  10  on the spindle  6 . A centrifugal fan  23  is fixed to the output shaft  19  rearward from the bearing  21 . A baffle plate  24  is held rearward from the centrifugal fan  23  in the motor housing  4 . 
     A commutator  25  is located at the rear of the rotor  18 . A pair of carbon brushes  26  are held on the left and right of the commutator  25  in the motor housing  4 . The carbon brushes  26  come in contact with the commutator  25 . Brush caps  27  are located on the left and right of the carbon brushes  26 . The brush caps  27  are fastened to the left and right surfaces of the motor housing  4  with screws. The brush caps  27  are detachable for, for example, replacing the carbon brushes  26 . 
     The shaft in the motor housing  4  has a rear portion supporting a bearing holder  28 . The bearing holder  28  holds a bearing  29  to support the rear end of the output shaft  19 . As shown in  FIG. 4 , a disc  30  is fixed to the output shaft  19  in front of the bearing  29 . The disc  30  is coaxial with and perpendicular to the output shaft  19 . The disc  30  includes eight permanent magnets  31  on the circumference at circumferentially equal intervals. 
     A first controller  35  is located at the rear of the rotor  18  above the commutator  25 . A second controller  36  is located at the rear of the rotor  18  below the commutator  25 . 
     The upper first controller  35  mainly forms a control unit. As also shown in  FIGS. 5A and 5B , the first controller  35  includes a resin case  37  rectangular as viewed from above. The case  37  accommodates a circuit board  38  ( FIGS. 2 and 4 ) receiving electronic components (e.g., a microcomputer  39 ) and having its surface molded. The first controller  35  has an upper surface with two LEDs  40 A and  40 B protruding at the front. The LEDs  40 A and  40 B are green and red and laterally arranged on the circuit board  38 . The first controller  35  has a lower surface receiving a pickup coil  41  at the center. 
     The lower second controller  36  mainly forms a power supply. As shown in  FIGS. 6A and 6B , the second controller  36  includes an aluminum case  42  square as viewed from above. The case  42  accommodates a circuit board  43  ( FIGS. 2 and 4 ) receiving heat-generating components such as triacs and field-effect transistors (FETs). The case  42  has upper, front, rear, left, and right surfaces with multiple projections  44 . The projections  44  serve as a heat dissipator. 
     The first controller  35  and the second controller  36  have substantially the same length in the front-rear direction. The second controller  36  has a slightly smaller width than the first controller  35  in the lateral direction. 
     The first controller  35  is held on an upper holder  45  located above the rotor  18  in the motor housing  4 . The second controller  36  is held on a lower holder  46  located below the rotor  18  in the motor housing  4 . 
     The upper holder  45  includes a pair of left and right upper sidewalls  47 . The upper sidewalls  47  extend downward from the upper inner surface of the motor housing  4 . The upper sidewalls  47  have upper fitting grooves  48  on their surfaces facing each other. The first controller  35  has left and right portions fitted in the upper fitting grooves  48 . The upper fitting grooves  48  extend in the front-rear direction. 
     A receiving wall  49  is between the lower ends of the upper sidewalls  47 . The receiving wall  49  supports the lower surface of the first controller  35 . The receiving wall  49  has a cutout  50  at the center to avoid interference with the pickup coil  41 . The cutout  50  extends frontward from the rear end of the receiving wall  49 . An upper front wall  51  is between the front ends of the upper sidewalls  47 . The upper front wall  51  is a grid in contact with the front surface of the first controller  35 . The upper front wall  51  has multiple through-holes  52 . 
     The lower holder  46  includes a pair of left and right lower sidewalls  55 . The lower sidewalls  55  extend upward from the lower inner surface of the motor housing  4 . The lower sidewalls  55  have lower fitting grooves  56  on their surfaces facing each other. The second controller  36  has left and right portions fitted in the lower fitting grooves  56 . The lower fitting grooves  56  extend in the front-rear direction. A protective wall  57  is between the upper ends of the lower sidewalls  55 . The protective wall  57  covers the top of the second controller  36 . A lower front wall  58  is between the front ends of the lower sidewalls  55 . The lower front wall  58  is a grid in contact with the front surface of the second controller  36 . The lower front wall  58  has multiple through-holes  59 . 
     The first controller  35  and the second controller  36  respectively held on the upper holder  45  and the lower holder  46 , above and below the output shaft  19 , extend in the front-rear direction along the output shaft  19  at symmetric positions with respect to a point. 
     The pickup coil  41  on the first controller  35  is near the top of the disc  30  on the output shaft  19  to detect the magnetic field of the permanent magnets  31 . The LEDs  40 A and  40 B are near the upper inner surface of the motor housing  4 . A lens  60  is located on the motor housing  4  above the LEDs  40 A and  40 B. The lens  60  is insert molded onto the motor housing  4 . The lens  60  guides light from the LEDs  40 A and  40 B outside the motor housing  4 . 
     The handle housing  5  includes a pair of half housings  5   a  and  5   b.  The half housings  5   a  and  5   b  are fastened together laterally with screws with a rear end portion  65  of the motor housing  4  in between. The handle housing  5  includes a handle  66  at the rear end. The handle  66  extends rearward. A strip of anti-vibration rubber  67  is wound between the rear end portion  65  of the motor housing  4  and the handle housing  5 . The anti-vibration rubber  67  allows the handle housing  5  to be elastically joined to the motor housing  4 . 
     The handle housing  5  is rotatable about the rear end portion  65 . The handle housing  5  has a lower surface with a lock button  68 . The lock button  68  is pivotable about a lower screw boss  69 . The lower screw boss  69  is one of upper and lower screw bosses  69  joining the handle housing  5 . In the normal state, the lock button  68  being urged by a coil spring  70  has a front end pressing the rear end portion  65 . Multiple engagement portions  71  are circumferentially arranged on the circumference of the rear end portion  65 . The lock button  68  having the front end engaged with any of the engagement portions  71  prevents the handle housing  5  from rotating. With the rear end pushed toward the handle housing  5 , the lock button  68  is disengaged at its front end and thus permits rotation of the handle housing  5 . 
     The handle  66  holds a switch  72  inside. The switch  72  extends in the front-rear direction with a plunger  73  protruding downward. The handle  66  includes a switch lever  74  at the bottom. The switch lever  74  has a front end vertically pivotable about its rear end. Urged by a coil spring  75 , the switch lever  74  is pivoted to a lower position. The switch lever  74  pivoted to the lower position causes the switch  72  to be off. The switch lever  74  is pushed upward with the hand gripping the handle  66  to push the plunger  73  that turns on the switch  72 . 
     The switch lever  74  includes a lock lever  76  at the front end. The lock lever  76  is rotatable forward and backward. The lock lever  76  is rotatable to a position selected from an unlocking position, a neutral position, and a locking position. At the unlocking position, the lock lever  76  restricts the switch lever  74  from being pushed. At the neutral position, the lock lever  76  permits the switch lever  74  to be pushed. At the locking position, the lock lever  76  maintains the switch lever  74  in the pushed state. 
     The handle  66  is connected to a power cable  77  at the rear end. As shown in  FIGS. 1 and 7 , the handle housing  5  has multiple inlet ports  78  in the left and right surfaces frontward from the handle  66 . The inlet ports  78  are slits extending in the front-rear direction. The multiple inlet ports  78  are arranged at predetermined intervals in the circumferential direction of the handle housing  5 . 
     The motor housing  4  and the handle housing  5  accommodate a brake assembly  80 . The brake assembly  80  includes a brake  81  and a link unit  82 . The brake  81  is located rearward from the rotor  18  in the motor housing  4 . The link unit  82  is between the brake  81  and the switch lever  74 . The link unit  82  links the operations of the switch lever  74  and the brake  81  with each other. 
     The brake  81  includes a base  83 , a brake plate  84 , a brake shoe  85 , a shoe holder  86 , a cap  87 , and two coil springs  88 . 
     The base  83  is coaxial with the output shaft  19 . The base  83  is a bottomed cylinder that is open frontward. The base  83  includes four protruding pieces  89  protruding outward. The four protruding pieces  89  are arranged circumferentially evenly on the circumferential surface of the base  83 . 
     As shown in  FIG. 3 , the two (left and right) protruding pieces  89  are fastened to the left and right elongated pieces  90  with screws from behind. The elongated pieces  90  hold the bearing holder  28  in the motor housing  4 . As shown in  FIG. 2 , the two (upper and lower) protruding pieces  89  each have a boss  91  protruding frontward and integral with the corresponding protruding piece  89 . Each boss  91  receives a cylindrical rubber pin  92 . Each rubber pin  92  protrudes frontward from the corresponding boss  91  and is in contact with the rear surface of the corresponding one of the upper first controller  35  and the lower second controller  36 . The rubber pins  92  press the first controller  35  and the second controller  36  against the upper front wall  51  and the lower front wall  58  to reduce rattle. 
     The brake plate  84  is a metal disc located in the base  83 . The brake plate  84  is integral with a cylinder  93  extending frontward from the front surface of the brake plate  84  at the center. A connecting shaft  94  is located coaxially with and at the rear end of the output shaft  19 . The connecting shaft  94  penetrates the bearing holder  28  and protrudes rearward. The cylinder  93  is fitted around the connecting shaft  94  to be rotatable together with the connecting shaft  94 . The brake plate  84  includes multiple fins  95  standing on its rear surface. The fins  95  extend radially and arranged at circumferentially equal intervals. 
     The brake shoe  85  is a disc having substantially the same diameter as the brake plate  84 . The brake shoe  85  applies a brake on the brake plate  84 . 
     The shoe holder  86  holds the brake shoe  85  inside and is integral with the brake shoe  85 . The shoe holder  86  is a bottomed cylinder that is open rearward. The shoe holder  86  is held in the base  83  in a manner movable forward and backward but is restricted from rotating. 
     The cap  87  closes the rear end of the shoe holder  86 . The cap  87  is movable forward and backward together with the shoe holder  86 . The cap  87  includes a rear cylinder  96  with a smaller diameter at the center. The rear cylinder  96  penetrates the rear end of the base  83  and protrudes rearward. The rear cylinder  96  has multiple openings  97  ( FIG. 10 ). 
     Each coil spring  88  is between the shoe holder  86  and the corresponding one of the left and right elongated pieces  90 . The coil springs  88  urge the shoe holder  86  rearward. The shoe holder  86  and the cap  87  are urged to a rearward position (braking position) to press the brake shoe  85  against the front surface of the brake plate  84 . A brake is thus applied on the output shaft  19  through the brake plate  84  and the connecting shaft  94  integral with the brake plate  84 . At the braking position, the rear cylinder  96  on the cap  87  protrudes rearward from the base  83 . 
     As shown in  FIGS. 2 and 3 , the link unit  82  includes a holder case  100 , a slider  101 , and a press lever  102 . 
     As also shown in  FIG. 7 , the holder case  100  is held in the handle housing  5 . The holder case  100  includes a pair of guide shafts  103  on the left and right. 
     The guide shafts  103  penetrate the slider  101  in the holder case  100 . The slider  101  is held in the holder case  100  in a manner movable vertically. A coil spring  104  is wound around each guide shaft  103  to urge the slider  101  downward to a lower limit position in the holder case  100 . The slider  101  includes a link piece  105  protruding rearward from the rear surface at its upper end. The link piece  105  protrudes rearward from the holder case  100 . The link piece  105  engages with the upper front end of the switch lever  74  pivoted to the lower position. The slider  101  has a curved guide surface  106  at the front. The guide surface  106  inclines downward as it extends frontward. 
     The press lever  102  has a lower end supported on a connecting pin  107  in a manner pivotable forward and backward. The connecting pin  107  extends laterally. The press lever  102  includes a roller  108  at the upper rear end. The roller  108  is in contact with the guide surface  106  of the slider  101 . The press lever  102  includes a pressing portion  109  protruding frontward at the upper front end. The pressing portion  109  comes in contact with the center of the rear cylinder  96  on the cap  87 . 
     In the grinder  1 , the switch lever  74  is pushed with the lock lever  76  coming off the unlocking position. The switch lever  74  then pushes, with its front end, the link piece  105 , which then pushes the slider  101  in the link unit  82  upward along the guide shafts  103  against the urging force from the coil springs  104 . The roller  108  on the press lever  102  then rolls forward relative to the guide surface  106  of the slider  101 . The press lever  102  then pivots forward to cause the pressing portion  109  to press the cap  87  and the shoe holder  86  forward against the urging force from the coil springs  88 . The brake shoe  85  then moves forward, together with the shoe holder  86 , to be separate from the brake plate  84  (brake release position). This releases the brake on the output shaft  19  through the connecting shaft  94 . 
     The pushed switch lever  74  also pushes the plunger  73  to turn on the switch  72 . This starts power supply to the motor  16  to cause the output shaft  19  to rotate together with the rotor  18  with the brake released. The rotation is transmitted to the spindle  6  through the bevel gears  22  and  10 , causing the grinding disc  13  to rotate. 
     While the motor  16  is being driven, the pickup coil  41  on the lower surface of the first controller  35  detects the rotation of the disc  30  (the rotation of the output shaft  19 ). The first controller  35  performs constant-speed rotation control on the motor  16  based on the detected rotational speed. The first controller  35  also monitors the rotational speed and the motor current to detect an overload. 
     In a normal operation, the green LED  40 A alone is lit on the upper surface of the first controller  35 . The green light through the lens  60  allows the operator to learn that the tool is normal. 
     In response to an abnormality, such as a power shutdown during use in the locked state followed by the restoration of power, the red LED  40 B flashes on the upper surface of the first controller  35  without the motor  16  being driven. The red light through the lens  60  allows the operator to learn that the tool is abnormal and is not in a condition for use. 
     The output shaft  19  rotates to rotate the centrifugal fan  23 , which draws outside air into the handle housing  5  through the inlet ports  78 . The drawn air passes through the openings  97  in the cap  87  on the base  83  and outside the base  83  to enter the motor housing  4 . The air passing inside and outside the base  83  passes outside the bearing holder  28  and between the stator  17  and the rotor  18  to cool the motor  16 . 
     The air passes around the first and second controllers  35  and  36  as it passes through the upper holder  45  and the lower holder  46  outside the bearing holder  28 . This cools the first and second controllers  35  and  36 . After cooling the first and second controllers  35  and  36 , the air passes through the through-holes  52  in the upper front wall  51  and the through-holes  59  in the lower front wall  58  to reach the motor  16 . 
     The air then flows through the baffle plate  24  and through-holes (not shown) in the partition  20  to enter the gear housing  3  and is then discharged through the outlet  15 . 
     The brake plate  84  includes the fins  95  radially extending on the rear surface. The brake plate  84  thus serves as a centrifugal fan rotating to generate airflow. This allows more effective cooling for the brake  81  in cooperation with the air passing inside the base  83 . 
     The switch lever  74  released from being pushed releases the plunger  73  from being pushed to turn off the switch  72 . The release also causes the slider  101  to slide to the lower limit position under the urging force from the coil spring  104 . This causes the roller  108  to move upward relative to the guide surface  106  to reduce the pressing force on the cap  87  from the press lever  102 . Urged by the coil springs  88 , the shoe holder  86  and the cap  87  return to the rearward position (braking position) to cause the brake shoe  85  to come in contact with the brake plate  84 . A brake is thus applied to the output shaft  19  through the brake plate  84  and the connecting shaft  94 . The braking force is transmitted to the spindle  6  to immediately stop the grinding disc  13 . 
     In the grinder  1  according to the embodiment, the controller is divided into the first controller  35  and the second controller  36 . The first controller  35  receives the LEDs  40 A and  40 B and the pickup coil  41  (electrical components of the grinder  1 ) on the upper and lower surfaces (part of the outer surface). The LEDs  40 A and  40 B and the pickup coil  41  perform their electrical operations on the upper and lower surfaces of the first controller  35 . 
     This structure uses fewer wires drawn from the first controller  35  that receives the electrical components, among the divided first and second controllers  35  and  36 , thus allowing simple wiring. This structure involves less laborious assembly and a lower possibility of wire breakage. 
     The electrical components include LEDs  40 A and  40 B (light emitters) that emit light outside the housing  2  to indicate the operating state of the grinder  1 . The light emitters are installable in a space-saving manner. 
     The lens  60  is insert molded (integrally molded) onto the housing  2  to guide light from the LEDs  40 A and  40 B outside. The lens  60  can thus be included without compromising sealing and insulation. The lens  60  can also reliably guide light from the LEDs  40 A and  40 B outside the housing  2 . 
     The LEDs  40 A and  40 B indicate whether the operating state of the grinder  1  is normal or abnormal. The light from the LEDs  40 A and  40 B allows the operator to easily learn whether the operating state of the tool is normal or abnormal. 
     The electrical components include the pickup coil  41  (rotational speed sensor) for the motor  16 . The rotational speed sensor  41  is installable in a space-saving manner. 
     The pickup coil  41  detects an overload on the motor  16 . The first controller  35  can thus use the pickup coil  41  to easily detect an overload on the motor  16 . 
     The pickup coil  41  performs constant-speed rotation control on the motor  16 . The first controller  35  can thus use the pickup coil  41  to easily perform constant-speed rotation control on the motor  16 . 
     The second controller  36 , different from the first controller  35  receiving the electrical components, receives the heat-generating components such as triacs and FETs in a concentrated manner. The first controller  35  is thus less susceptible to heat. The second controller  36  includes the aluminum case  42 . Thus, the second controller  36  receiving the heat-generating components in a concentrated manner can effectively dissipate heat. 
     The first and second controllers  35  and  36  are at symmetric positions with respect to a point, with the output shaft  19  of the motor  16  in between. The first and second controllers  35  and  36  can be effectively in the space around the output shaft  19 . 
     The first and second controllers  35  and  36  extend along the output shaft  19  and are located between the motor  16  and the inlet ports  78  (inlets) in the housing  2 . This structure allows effective cooling of the first and second controllers  35  and  36  using the cooling air for the motor  16 . 
     A modification will now be described. 
     As shown in  FIG. 8 , the handle housing  5  may include a pair of covers  115 A and  115 B on the left and right surfaces. The covers  115 A and  115 B prevent dust and other foreign matter from entering through the inlet ports  78 . As shown in  FIG. 9 , the covers  115 A and  115 B each include a frame  116  and a net  117 . The frames  116  are each slightly larger than the area of the inlet ports  78  in the corresponding side surface of the handle housing  5 . The frames  116  have curved surfaces along and in contact with the side surfaces of the handle housing  5 . The nets  117  are stretched within the frames  116 . 
     The left cover  115 A includes three fitting ribs  118  extending in the front-rear direction at the top, bottom, and an intermediate position on the frame  116 . The handle housing  5  has three fitting recesses  119  extending in the front-rear direction in an area other than the area of the inlet ports  78  in the left surface. Each fitting recess  119  receives the corresponding fitting rib  118 . 
     As shown in  FIG. 10 , the fitting ribs  118  are fitted in the fitting recesses  119 . This structure allows the cover  115 A to be attached to the left surface of the handle housing  5  without using screws or other parts. This structure also allows easy detachment of the cover  115 A. 
     The right cover  115 B includes two circular projections  120  projecting leftward at the top and bottom of the frame  116 . The frame  116  includes a fitting rib  118  between the circular projections  120 . The fitting rib  118  is similar to those on the cover  115 A. 
     As shown in  FIG. 10 , the handle housing  5  has circular recesses  122  above and below the area of the inlet ports  78  in the right surface. The circular recesses  122  receive screws  121 . The screws  121  are placed in the upper and lower screw bosses  69  on the half housing  5   a  to join the half housing  5   b  to the half housing  5   a.  The handle housing  5  has a fitting recess  119  between the circular recesses  122  in an area other than the area of the inlet ports  78  in the right surface. The fitting recess  119  receives the fitting rib  118 . 
     The circular projections  120  are placed in the circular recesses  122 , and the fitting rib  118  is fitted in the fitting recess  119 . This structure allows the cover  115 B to be attached to the right surface of the handle housing  5  without using screws or other parts. This structure also allows easy detachment of the cover  115 B. 
     In some embodiments, the handle housing may eliminate the fitting recesses. In this case, the fitting ribs on the left and right covers may be fitted in selected inlet ports aligning with the fitting ribs with optional screws. 
     The LEDs and the pickup coil may be located at any position on the first controller. The LEDs may be located on, for example, the rear, left, or right surface of the first controller. More LEDs or fewer LEDs than in the above embodiments may be used. Light emitters other than LEDs may be used. The lens may be other than an integrally molded lens. Similarly, the position of the pickup coil on the first controller may be modified as appropriate. 
     The second controller may include fins instead of projections to serve as the heat dissipator. A separate heat dissipator may be attached to the surface of the second controller. The heat dissipator may be eliminated. 
     The first and second controllers may have any size and shape other than those in the above embodiments. The first and second controllers each may have a rectangular shape elongated in the front-rear direction or a shape other than rectangular or square. The case may be eliminated. 
     The two controllers in the above embodiments are located above and below the output shaft. However, their positions may be modified. The two controllers may be located on the left and right of the output shaft. The two controllers may be aligned laterally or vertically instead of being located with the output shaft in between. 
     The controller may be divided into three or more controllers instead of two controllers. In this case, at least one controller may receive electrical components on the outer surface. For example, one of the three or more controllers may receive LEDs, and another controller may receive a pickup coil. 
     The rotational speed sensor may be used to prevent a kickback, or a phenomenon in which the tip tool hits a hard object and causes the tool body to bounce toward the operator. 
     The electrical components are not limited to the light emitters as an information output unit and the rotational speed sensor as an information input unit. For example, the information output unit on the outer surface of the controller may be an indicator for indicating the rotational speed of the motor or the remaining battery level. The information input unit on the outer surface of the controller may be a temperature sensor for detecting the temperature inside the housing, or may be an operation unit, such as a dial or a switch, operable to change the rotational speed of the motor. An accelerometer may also be used to prevent a kickback. The controller may receive either the information output unit or the information input unit. 
     For multiple electrical components, at least one electrical component may be located on the outer surface of the controller, and at least another electrical component may be located away from the controller and connected to the controller with a lead wire. This structure also uses fewer wires. 
     The rotary tool may include a housing without an anti-vibration member. 
     The brake assembly may have a structure modified as appropriate. The brake assembly may be located at the front of the output shaft instead of being located at the rear of the output shaft. The brake assembly may be eliminated. 
     The rotary tool may be powered by a battery pack. The rotary tool may include a brushless motor as the motor. 
     The rotary tool is not limited to a grinder but may be, for example, a polisher or a sander. 
     REFERENCE SIGNS LIST 
     
         
           1  grinder 
           2  housing 
           3  gear housing 
           4  motor housing 
           5  handle housing 
           6  spindle 
           13  grinding disc 
           16  motor 
           19  output shaft 
           25  commutator 
           28  bearing holder 
           30  disc 
           31  permanent magnet 
           35  first controller 
           36  second controller 
           37 ,  42  case 
           38 ,  43  circuit board 
           40 A,  40 B LED 
           41  pickup coil 
           45  upper holder 
           46  lower holder 
           60  lens 
           66  handle 
           72  switch 
           74  switch lever 
           78  inlet port 
           80  brake assembly 
           81  brake 
           82  link unit 
           83  base 
           84  brake plate 
           85  brake shoe 
           86  shoe holder 
           87  cap 
           94  connecting shaft 
           100  holder case 
           101  slider 
           102  press lever 
           115 A,  115 B cover