Patent Publication Number: US-2023150104-A1

Title: Power tool

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of priority to Japanese Patent Application No. 2021-187288, filed on Nov. 17, 2021, the entire contents of which are hereby incorporated by reference. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a power tool including a hammer drill. 
     2. Description of the Background 
     A known hammer drill includes an electric motor as described in Japanese Patent No. 6309881. 
     BRIEF SUMMARY 
     Known hammer drills may generate noise from electromagnetic interference (EMI) caused by, for example, commutation in electric motors. 
     Thus, techniques for reducing noise generation in a power tool are awaited. 
     A first aspect of the present disclosure provides a power tool, including: 
     a housing; 
     a field fixed to the housing, the field including a field coil; 
     an armature rotatable relative to the field, the armature including a commutator; 
     a brush configured to come in contact with the commutator; and 
     a choke coil configured to electrically connect the field coil and the brush, 
     A second aspect of the present disclosure provides a power tool, including: 
     a housing; 
     a field fixed to the housing, the field including a field coil; 
     an armature rotatable relative to the field, the armature including a commutator; 
     two brushes configured to come in contact with the commutator; and 
     a brush holder unit holding the two brushes, the brush holder unit including
         a stationary housing,   two contact rails held by the stationary housing and electrically connectable to the field coil,   a movable housing holding the two brushes and movable relative to the stationary housing,   two first terminals held by the movable housing, each of the two first terminals being configured to come in contact with either of the two contact rails in response to movement of the movable housing,   two second terminals held by the movable housing, each of the two second terminals being electrically connectable to a corresponding brush of the two brushes, and   a choke coil located between at least one of the two first terminals and at least one of the two second terminals.       

     The power tool according to the above aspects of the present disclosure is less likely to generate noise. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a left side view of a hammer drill according to one or more embodiments of the present disclosure. 
         FIG.  2    is a view of a rear part of  FIG.  1    without a cover. 
         FIG.  3    is a longitudinal central sectional view of  FIG.  2   . 
         FIG.  4    is a partially exploded perspective view of  FIG.  2   . 
         FIG.  5    is a perspective view including a cross section taken along line A-A in  FIG.  3   . 
         FIG.  6    is a perspective view including a cross section taken along line B-B in  FIG.  3   . 
         FIG.  7    is an exploded perspective view of a brush holder unit (BHU) in  FIG.  2    as viewed from the rear. 
         FIG.  8    is an exploded perspective view of the BHU in  FIG.  2    as viewed from the front. 
         FIG.  9    is a partially enlarged perspective view of a stationary housing in the BHU in  FIG.  7   , the front end of a terminal portion of a contact rail, and the front end of a lead wire terminal. 
         FIG.  10    is an exploded perspective view of brush connection terminal units in the BHU in  FIG.  7   . 
         FIG.  11    is a perspective view of the brush connection terminal units and the contact rails in the BHU in  FIG.  7   . 
         FIG.  12    is a cross-sectional view taken along line C-C in  FIG.  11   . 
         FIG.  13    is a cross-sectional view taken along line D-D in  FIG.  12   . 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments and modifications of the present disclosure will now be described with reference to the drawings as appropriate. 
     The directional terms such as front, rear, up, down, right, and left in the embodiments and the modifications are defined for ease of explanation, and may be changed depending on, for example, the operating situations or the status of a movable member. 
     The present disclosure is not limited to the embodiments and the modifications described below 
       FIG.  1    is a left side view of a hammer drill  1  as an example of a power tool (striking tool) according to one or more embodiments of the present disclosure.  FIG.  2    is a view of a rear part of  FIG.  1    without a cover.  FIG.  3    is a longitudinal central sectional view of  FIG.  2   .  FIG.  4    is a partially exploded perspective view of  FIG.  2   .  FIG.  5    is a perspective view including a cross section taken along line A-A in  FIG.  3   .  FIG.  6    is a perspective view including a cross section taken along line B-B in  FIG.  3   . 
     The hammer drill  1  includes a housing  2 , a power unit  4 , a trigger unit  5 , a power cable  6 , an intermediate portion  7 , an output unit  8 , and an auxiliary handle  10 . 
     The power unit  4  has its axis in the front-rear direction. The output unit  8  has its axis in the front-rear direction. 
     The housing  2  holds the components directly or indirectly. 
     The housing  2  includes a gear housing  20 , a motor housing  22 , and an outer housing  24 . 
     The gear housing  20  is cylindrical. The gear housing  20  extends in the front-rear direction. 
     The gear housing  20  holds the intermediate portion  7 . 
     The gear housing  20  includes multiple outlets  20 V. The outlets  20 V are located in a lower left portion and a lower right portion of the gear housing  20 . 
     The motor housing  22  is cylindrical. The motor housing  22  extends in the front-rear direction. The motor housing  22  includes a middle motor housing  22 C as its middle portion. The motor housing  22  includes a front motor housing  22 F as its front portion. The motor housing  22  includes a rear motor housing  22 B as its rear portion. 
     The outer housing  24  includes a rear portion being an outer wall of a handle  26 . The handle  26  extends vertically. A lateral direction is substantially orthogonal to the front-rear direction and the vertical direction, 
     The outer housing  24  includes left and right halves. The left half of the outer housing  24  includes multiple screw bosses  27 . The screw bosses  27  receive screws that join the left and right halves of the outer housing  24  together. 
     The outer housing  24  includes multiple inlets  24 A. The inlets  24 A are located in the lower left and the lower right of a middle portion of the outer housing  24  in the front-rear direction. 
     The middle motor housing  22 C is vertically and laterally smaller than the front motor housing  22 F. 
     The rear motor housing  22 B is vertically and laterally smaller than the middle motor housing  22 C. 
     The middle motor housing  22 C and the rear motor housing  22 B hold the power unit  4 . 
     An upper portion of the outer housing  24  is located outside the middle motor housing  22 C and the rear motor housing  22 B. 
     A flexible member  28  is located between the front end of the outer housing  24  and the rear end of the front motor housing  22 F. The flexible member  28  is elastic. The flexible member  28  is a bellows. 
     The outer housing  24  is movable in the front-rear direction relative to the motor housing  22 . As the outer housing  24  moves, the flexible member  28  expands or contracts. 
     The outer housing  24  is located behind the motor housing  22  with the flexible member  28  being in an equilibrium length or a length close to an equilibrium length (normal state). The outer housing  24  moves forward relative to the motor housing  22  (forward state) from the normal state. 
     The flexible member  28  located between the motor housing  22  and the outer housing  24  reduces vibration generated in the power unit  4 , the intermediate portion  7 , the output unit  8 , and another portion. 
     The outer housing  24  has a slot  24 S in its upper surface. The slot  24 S extends laterally. 
     The outer housing  24  includes an outer rib  24 B on its inner surface. The outer rib  24 B protrudes inward from the surrounding portion. The outer rib  24 B is located in the right half of the outer housing  24  and above the handle  26 . The outer rib  24 B extends in the front-rear and lateral directions. The outer rib  24 B may be located in another portion, for example, at the upper end of the handle  26  or in the left half of the outer housing  24 . 
     The outer housing  24  includes a center rib  24 J on its inner surface ( FIG.  5   ). The center rib  24 J protrudes inward from the surrounding portion. The center rib  24 J is located in the left half of the outer housing  24  and above the handle  26 . The center rib  24 J extends in the front-rear and lateral directions. The center rib  24 J is located on the left of the outer rib  24 B. The center rib  24 J and the outer rib  24 B face each other. The center rib  24 J may be located in another portion, for example, at the upper end of the handle  26 , in a portion that does not face the outer rib  24 B, or in the right half of the outer housing  24 . 
     The power unit  4  includes a motor  29 , multiple (two) brushes  30 , a brush holder unit (BHU)  31 , and a fan  32 . 
     The motor  29  is an electric motor. 
     The motor  29  includes a field  33  (stator) and an armature  34  (rotor). 
     The field  33  includes afield core  35  and multiple field coils  36 . The field core  35  is cylindrical. The field core  35  is fixed to the housing  2 . The field core  35  includes, on its inner surface, multiple projections around which the field coils  36  are wound. 
     The armature  34  includes a motor shaft  40 , an armature core  42 , multiple armature coils  44 , and a commutator  45 . The motor shaft  40  extends in the front-rear direction. The motor shaft  40  includes a pinion gear  40 G at its front end ( FIG.  1   ). The armature core  42  is fixed to a middle portion of the motor shaft  40  in the front-rear direction. The armature core  42  has multiple slots. The armature coils  44  are wound through the corresponding slots in the armature core  42 . The commutator  45  is cylindrical. The commutator  45  includes multiple conductive portions. The conductive portions are aligned in the circumferential direction of the motor shaft  40 . The armature coils  44  are electrically connected to the conductive portions in a predetermined manner. 
     The motor shaft  40  has its rear end rotatably supported in a rear bearing  46 . The rear bearing  46  is held in the rear end of the rear motor housing  22 B. The commutator  45  is located between the rear bearing  46  and the armature core  42 . The rear motor housing  22 B has a left opening  22 L in a portion on the left of the commutator  45 . The rear motor housing  22 B has a right opening  22 R in a portion on the right of the commutator  45 . 
     The motor shaft  40  has its front end rotatably supported in a front bearing (not shown). The front bearing is held in the rear end of the gear housing  20 . 
     The motor shaft  40  is rotatable on its central axis. 
     The brushes  30  are formed from carbon. 
     The BHU  31  is located radially outward from the rear motor housing  22 B. The BHU  31  is annular or cylindrical. The BHU  31  holds the brushes  30 . This structure allows the BHU  31  to be positioned more efficiently relative to the motor  29 . 
     The fan  32  is integrally attached to the outer circumference of the motor shaft  40 . 
     The fan  32  is a centrifugal fan. 
     The fan  32  is located between the pinion gear  40 G and the armature  34 . The fan  32  is located in the front motor housing  22 F. 
     The trigger unit  5  includes a trigger switch  50  and a trigger  52 . 
     The trigger  52  is attached to a plunger for switching the trigger switch  50 . 
     The trigger switch  50  is located in the handle  26 . 
     The trigger  52  has a front portion exposed from a front middle portion of the outer housing  24  in the vertical direction. When a user operates the trigger  52  backward, the trigger switch  50  switches its state. 
     The trigger  52  includes an upper-trigger projection  52 P at its top. The upper-trigger projection  52 P protrudes upward from the surrounding portion. 
     The power cable  6  is electrically connected to the trigger switch  50  and the motor  29 . 
     The intermediate portion  7  includes a power transmission  60  and a striking assembly  62  ( FIG.  1   ). 
     The power transmission  60  includes a countershaft  64  and a cylinder  66 . The countershaft  64  extends in the front-rear direction. The countershaft  64  has its rear end meshing with the pinion gear  40 G on the motor shaft  40 . The countershaft  64  is rotatable on its central axis. The cylinder  66  is cylindrical. The cylinder  66  has, at its rear end, an outer surface meshing with the front end of the countershaft  64 . The cylinder  66  is rotatable on its central axis. 
     The striking assembly  62  includes a swing shaft  70  and a striking unit  72 . The swing shaft  70  is connected to the countershaft  64 . The swing shaft  70  is located radially outward from the countershaft  64 . The swing shaft  70  extends upward from the countershaft  64 . When the countershaft  64  rotates, the swing shaft  70  swings with its upper end moving back and forth. The striking unit  72  includes a piston, a striker, and an air chamber between the piston and the striker. The striking unit  72  extends in the front-rear direction. The striking unit  72  includes a rear portion located in the cylinder  66 . The striking unit  72  is connected to the distal end of the swing shaft  70 . The striking unit  72  is movable in the front-rear direction when the swing shaft  70  swings. 
     The output unit  8  includes a tip tool holder  78  ( FIG.  1   ). The tip tool holder  78  is cylindrical. The tip tool holder  78  can hold a tip tool such as a drill bit. The tip tool holder  78  is located in front of the cylinder  66  and is connected to the cylinder  66 . The central axis of the tip tool holder  78  is aligned with the central axis of the cylinder  66 . The tip tool holder  78  is integral with the cylinder  66  and is rotatable on its central axis. 
     The striking unit  72  has its front end adjacent to or received in the rear end of the tip tool holder  78 , and can strike the tip tool in the tip tool holder  78 . 
     The power transmission  60  rotates the cylinder  66 . The rotation is transmitted to the tip tool through the tip tool holder  78 . 
     The auxiliary handle  10  is attached to the outer surface of the gear housing  20 . The auxiliary handle  10  is detachable. 
       FIGS.  7  and  8    are exploded perspective views of the BHU  31 . 
     The BHU  31  includes a stationary housing  80 , multiple (two) contact rails  82 , a movable housing  84 , multiple (two) leaf springs  85  being elastic members, multiple (two) brush connection terminal units  86 , multiple (two) brush holders  88 , and multiple (two) lead wires  89 . 
     The stationary housing  80  includes a stationary housing body  80 M, a rail retainer  80 R, multiple (two) protrusions  80 C, and multiple (four) terminal retainers  80 T. 
     The stationary housing body  80 M is annular. 
     The rail retainer  80 R is at the rear of the stationary housing body  80 M and is recessed frontward. The rail retainer  80 R is annular. 
     The protrusions  80 C protrude rearward from the rear end face of the stationary housing body  80 M. 
     The terminal retainers  80 T protrude frontward from the front of the stationary housing body  80 M. Each terminal retainer  80 T includes a hole  80 H and a rectangular portion  80 B. The hole  80 H extends in the front-rear direction. The rectangular portion  80 B is located at the front end of the terminal retainer  80 T. The rectangular portion  80 B is open at its front and radially inward portion. The rectangular portion  80 B has four surfaces, or a rear surface, an upper surface, a lower surface, and a radially outward surface. The rectangular portion SOB communicates with the hole  80 H on its rear surface. One or more surfaces of the rectangular portion  80 B may be eliminated. 
     The stationary housing  80  is attached to the outer surface of the rear end of the middle motor housing  22 C. The stationary housing body  80 M is located behind the rear end face of the middle motor housing  22 C. The terminal retainers  80 T are each located outward from the upper right, the lower right, the upper left, and the lower left of the rear of the middle motor housing  22 C. 
     The contact rails  82  are formed from metal (brass). The contact rails  82  are thus resistant to at least one of friction or heat. Each contact rail  82  includes a rail portion  82 R and a terminal portion  82 T. Hereafter, the contact rail  82  located above may he referred to as an upper contact rail  82 U, and the contact rail  82  located below may be referred to as a lower contact rail  82 D. 
     The rail portions  82 R are arc-shaped and semicircular. The rail portions  82 R are plates. The rail portions  82 R extend in the circumferential and front-rear directions. Each rail portion  82 R includes a first arch  82 F at its first end. Each rail portion  82 R includes a second arch  82 S at its second end. The first arch  82 F has a smaller radius of curvature than the other portion of the rail portion  82 R. The first arch  82 F extends radially more outward than the other portion of the rail portion  82 R. The second arch  82 S has the same structure as the first arch  82 F. 
     The upper contact rail  82 U includes the first arch  82 F on its left end and the second arch  82 S on its right end. The lower contact rail  82 D includes the first arch  82 F on its right end and the second arch  82 S on its left end. The second arch  82 S may be different from the first arch  82 F. At least one of the first arch  82 F or the second arch  82 S may be eliminated. 
     The terminal portion  82 T is a folded plate. The terminal portion  82 T is continuous with an intermediate portion of the rail portion  82 R. The terminal portion  82 T intersects with the rail portion  82 R. 
     As shown in  FIG.  9   , with the terminal portion  82 T placed in the hole  80 H in the corresponding terminal retainer  80 T, each contact rail  82  is held by the stationary housing  80 . Each terminal portion  82 T has its front end reaching the corresponding rectangular portion  80 B. The front edge of the terminal portion  82 T is located rearward from the front edge of the rectangular portion  80 B. In other words, the front end of each terminal portion  82 T does not protrude from the corresponding rectangular portion  80 B, and is located rearward from the front edge of the corresponding rectangular portion  80 B. The rail portions  82 R are located in the rail retainer  80 R. 
     The front end of each terminal portion  82 T is protected with the corresponding rectangular portion  80 B. The front end of each terminal portion  82 T is in contact with and is electrically connected to a terminal (not shown) in the corresponding field coil  36 . The field coils  36  each include terminals held by a terminal plate (not shown). 
     The stationary housing  80  and the contact rails  82  are placed close to the terminal plate, and are attached in the frontward direction to the terminal plate. The rectangular portions  80 B first come in contact with the terminal plate and are guided on the terminal plate. The front ends of the terminal portions  82 T then come in contact with the corresponding terminals on the terminal plate. Thus, the terminal portions  82 T are reliably in contact with the terminals in the field coils  36 . 
     The movable housing  84  includes a movable housing body  84 M, multiple (two) brush holder receivers  84 H, multiple (two) terminal holes  84 P, multiple (two) slits  84 S, a lever  84 V a rib  84 B, a projection  84 J, and a groove  84 R. 
     The movable housing body  84 M is annular or cylindrical, 
     The brush holder receivers  84 H are recessed frontward from the rear end face of the movable housing body  84 M. 
     The movable housing body  84 M has two arc-shaped rear end faces separated by the brush holder receivers  84 H. The rear end faces of the movable housing body  84 M and the radially inward surface of the movable housing body  84 M are connected with rear surfaces, or slopes  84 C. The slopes  84 C are flat or continuously curved surfaces. The slopes  84 C are increasingly closer to each other toward the front. In other words, the slopes  84 C are tapered with a space between them being smaller toward the front (tapered frontward). The slopes  84 C define a bowl shape. 
     The terminal holes  84 P are in the corresponding slopes  84 C. The terminal holes  84 P are adjacent to the corresponding brush holder receivers  84 H. 
     The slits  84 S are arc-shaped. The slits  84 S are open in the corresponding slopes  84 C. 
     The lever  84 V protrudes radially outward from an upper portion of the circumferential surface of the movable housing body  84 M. 
     The rib  84 B protrudes radially outward from the lower rear end face of the movable housing body  84 M. The rib  84 B extends circumferentially. The rib  84 B is adjacent to the right brush holder receiver  84 H. The rib  84 B in the present embodiment is adjacent to the right end of the outer rib  24 B. The rib  84 B in the present embodiment is located behind the right of the outer rib  24 B. 
     The projection  84 J protrudes downward from the lower circumferential surface of the movable housing body  84 M. The projection  84 H is located opposite to the lever  84 V across the central axis of the movable housing body  84 M as viewed from the rear. The projection  84 J is adjacent to the rib  84 B. The projection  84 J is located frontward from the left of the rib  84 B. 
     The groove  84 R is recessed annularly at the front of the movable housing body  84 M. 
     The movable housing  84  is connected to the stationary housing  80  in a rotatable manner. 
     The groove  84 R receives the rail retainer  80 R and the rail portions  82 R. 
     The slits  84 S receive the corresponding protrusions  80 C. 
     The lever  84 V includes an upper portion protruding from the upper surface of the outer housing  24 . The lever  84 V is received in the slot  24 S in the outer housing  24 . 
     The user laterally operates the upper portion of the lever  84 V to rotate the movable housing  84  relative to the stationary housing  80 . The movable housing  84  is rotatable from a first position (the position shown in the figures) at which the lever  84 V is at the right end of the slot  24 S to a second position at which the lever  84 V is at the left end of the slot  24 S. 
     The movable housing  84  may move relative to the stationary housing  80  in a manner other than rotation. For example, the movable housing  84  may move reciprocally by sliding linearly relative to the stationary housing  80 . 
     The leaf springs  85  are formed from metal (stainless steel). The leaf springs  85  are plates. The leaf springs  85  extend in the front-rear direction. 
     The leaf springs  85  are engageable with multiple receiving portions (not shown) arranged in an arc in the movable housing  84 . The leaf springs  85  sequentially engage with the corresponding receiving portions, thus allowing the movable housing  84  rotating relative to the stationary housing  80  to click. 
       FIG.  10    is an exploded perspective view of the brush connection terminal units  86 .  FIG.  11    is a perspective view of the brush connection terminal units  86  and the contact rails  82 .  FIG.  12    is a cross-sectional view taken alone line C-C in  FIG.  11   .  FIG.  13    is a cross-sectional view taken along line D-D in  FIG.  12   . 
     Each brush connection terminal unit  86  includes a case  90  as a terminal holder, a first terminal  92 , a second terminal  94 , and a choke coil  96 . 
     The cases  90  are each formed from a synthetic resin. Each case  90  is a curved plate extending in the circumferential and front-rear directions. The case  90  includes a terminal retainer  90 T and a recess  90 V. 
     The terminal retainer  90 T has a hole  90 H in the radial direction. 
     The recess  90 V is located on a curved inner surface and is adjacent to the terminal retainer  90 T. The recess  90 V is recessed radially outward from other portion of the inner curved surface. 
     The first terminal  92  is held in a portion in front of the hole  90 H in the terminal retainer  90 T. The first terminal  92  is formed from metal. The first terminal  92  protrudes frontward from the terminal retainer  90 T. 
     The first terminal  92  has a front portion exposed from the case  90 . The front portion of the first terminal  92  includes a base  92 B, a turned portion  92 T, a distal end  92 E, a curved portion  92 C, multiple (two) first guides  92 F, and multiple (two) second guides  92 S. 
     The base  92 B extends in the front-rear direction. The base  92 B has its front end connected to the turned portion  92 T. 
     The turned portion  92 T is U-shaped as viewed from the above. 
     The distal end  92 E extends in the front-rear direction. The distal end  92 E has its front end connected to the turned portion  92 T. The distal end  92 E and the base  92 B extend vertically and are parallel to each other. The distance between the distal end  92 E and the base  92 B is about the same as the distance by which the first arch  82 F and the second arch  82 S of the rail portions  82 R extend more outward. 
     The curved portion  92 C is connected to the rear end of the distal end  92 E. The curved portion  92 C bends toward the rear end of the base  92 B. The curved portion  92 C may be eliminated. 
     Each brush connection terminal unit  86  includes two first guides  92 F. One first guide  92 F is located at the base  92 B and is closer to a circumferentially middle portion of the brush connection terminal unit  86 . The other first guide  92 F is located at the distal end  92 E and is closer to the circumferentially middle portion of the brush connection terminal unit  86 . The first guides  92 F each protrude circumferentially from the base  92 B or the distal end  92 E. The first guides  92 F are increasingly spaced apart from each other as they are more away from the base  92 B and the distal end  92 E. The first guides  92 F extend outward. 
     Each brush connection terminal unit  86  includes two second guides  92 S. One second guide  92 S is located at the base  92 B and is closer to a circumferentially end portion of the brush connection terminal unit  86 . The other second guide  92 S is located at the distal end  92 E and is closer to the circumferentially end portion of the brush connection terminal unit  86 . The second guides  92 S each protrude circuinferentially from the base  92 B or the distal end  92 E. The second guides  92 S are increasingly spaced apart from each other as they are more away from the base  92 B and the distal end  92 E. The second guides  92 S extend outward. This structure allows the first terminals  92  to receive the corresponding contact rails  82  more smoothly. 
     The second terminal  94  is held in a front portion of the hole  90 U in the terminal retainer  90 T. The second terminal  94  is formed from metal. The second terminal  94  protrudes rearward from the terminal retainer  90 T. 
     The second terminal  94  includes a rear portion exposed from the case  90 . 
     Each choke coil  96  includes a core  96 C and a wire  96 L. 
     The core  96 C is formed from ferrite (a ceramic material including iron oxide). The core  96 C extends circumferentially. 
     The wire  96 L is wound around the core  96 C. 
     Each choke coil  96  includes a first coil terminal  96 F and a second coil terminal  96 S. The first coil terminal  96 F is electrically connected to the first terminal  92  by soldering or another method. The second coil terminal  96 S is electrically connected to the second terminal  94  by soldering or another method. 
     The choke coils  96  are received in the corresponding recesses  90 V. The cases  90  thus serve as containers for the corresponding choke coils  96  and are each installed in a smaller space. 
     The choke coil  96  may be connected to a single pair of the first terminal  92  and the second terminal  94 . The choke coils  96  may be located in other portions between the field coils  36  and the brushes  30 . The choke coils  96  may be, for example, located on contact rails  82 . 
     The first terminal  92  and the second terminal  94  are basically an integral terminal as in  FIG.  10    with a connection portion  92 L indicated by the dotted line. The first terminal  92 , the second terminal  94 , and the case  90  are integral with one another. The connection portion  92 L is received in the hole  90 H and is exposed from the case  90 . 
     When no choke coil  96  is to be used, a brush connection terminal unit  86  including the integral terminal is used. 
     When a choke coil  96  is to be used, the connection portion  92 L is partially or entirely removed by, for example, cutting to separate the first terminal  92  and the second terminal  94 . The first coil terminal  96 F in the choke coil  96  is then electrically connected to the first terminal  92 , and the second coil terminal  96 S is electrically connected to the second terminal  94 . 
     The integral terminal or the first terminal  92  and the second terminal  94  are integral with and firmly attached to the case  90 . The choke coil  96  may be used more easily by simply selecting either cutting or not cutting the connection portion  92 L. The first terminal  92  and the second terminal  94  integral with each other are thus easier to handle with. The first terminal  92  and the second terminal  94  connected together can be cut apart through the hole  90 U, thus simplifying the separation of the first terminal  92  and the second terminal  94 . 
     The first terminal  92  and the second terminal  94  may be basically separate from each other. The first terminal  92 , the second terminal  94 , and the case  90  may be formed in a manner other than being integral with one another. 
     The brush connection terminal units  86  are fixed in the groove  84 R on the movable housing  84 . 
     The brush connection terminal units  86  are located at positions corresponding to the spaces circumferentially between the rail portions  82 R of the contact rails  82 . 
     The second terminals  94  in the brush connection terminal units  86  are placed in the corresponding terminal holes  84 P in the movable housing  84 . 
     The brush holders  88  hold the corresponding brushes  30 . 
     Each brush holder  88  includes a brush case  100 , a spiral spring  102  being an elastic member, and a brush terminal  104 . 
     The brush cases  100  hold the corresponding brushes  30 . The brush cases  100  are held in the corresponding brush holder receivers  84 H. 
     The spiral springs  102  are held in the corresponding brush cases  100 . The spiral springs  102  push the corresponding brushes  30  radially inward. The brushes  30  come in contact with the commutator  45  on their radially inward surfaces. Each brush  30  extends through the left opening  22 L or the right opening  22 R. 
     The brush terminals  104  are electrically connected to the corresponding brushes  30 . Each brush terminal  104  is electrically connected to the corresponding second terminal  94 . 
     Each lead wire  89  includes a lead wire body  89 M and a lead wire terminal  89 T. The lead wire terminals  89 T are formed from metal and are folded plates. Each lead wire terminal  89 T is electrically connected to a conductive wire under a covering of the corresponding lead wire body  89 M. 
     As shown in  FIG.  9   , each lead wire terminal  89 T is placed in the hole  80 H in the corresponding terminal retainer  80 T and is held by the stationary housing  80 . The lead wire terminal  89 T has its front end reaching the corresponding rectangular portion  80 B. The front edge of the lead wire terminal  89 T is located rearward from the front edge of the rectangular portion  80 B. In other words, the front end of each lead wire terminal  89 T does not protrude from the corresponding rectangular portion  80 B, and is located rearward relative to the front edge of the corresponding rectangular portion  80 B. 
     The front end of each lead wire terminal  89 T is protected with the corresponding rectangular portion  80 B. 
     The front end of each lead wire terminal  89 T is in contact with and is electrically connected to a terminal in the corresponding field coil  36 . 
     When the stationary housing  80  and the contact rails  82  are attached to the terminal plate, the rectangular portions  80 B first come in contact with the terminal plate and are guided on the terminal plate. The front ends of the lead wire terminals  89 T then come in contact with the corresponding terminals on the terminal plate. The front ends of the lead wire terminals  89 T are thus reliably in contact with the terminals in the field coils  36 . 
     The lead wire bodies  89 M are electrically connected to the power cable  6  or the trigger switch  50 . 
     Each lead wire  89  may not be a component of the BHU  31 . 
     When the outer housing  24  is in the normal state and the trigger  52  is not operated rearward (no operation on the trigger  52 ) with the movable housing  84  at the first position (the position shown in the figures), the first terminal  92  in each brush connection terminal unit  86  is in contact with the first arch  82 F on the corresponding contact rail  82 . Each first arch  82 F is surrounded by the corresponding base  92 B, turned portion  92 T, distal end  92 E, and curved portion  82 C (the surrounding structure of the first terminal  92 ). 
     When the movable housing  84  is rotated to the second position, each first terminal  92  moves away from the corresponding first arch  82 F, moving closer to and coming in contact with the adjacent second arch  82 S. The second guides  92 S in each first terminal  92  receive the corresponding second arch  82 S in a wider space between them, and guide the second arch  82 S to between the base  92 B and the distal end  92 E. 
     When the movable housing  84  is at the second position, each first terminal  92  is in contact with the corresponding second arch  82 S. Each second arch  82 S is surrounded by the corresponding base  92 B, turned portion  92 T, distal end  92 E, and curved portion  82 C (the surrounding structure of the first terminal  92 ). 
     At least one of the surrounding structure of the first terminal  92 , the guidance with the second guides  92 S, or the formation of the second arches  82 S allows the first terminals  92  to be more reliably in contact with the corresponding contact rails  82 . This structure reduces chattering when the first terminals  92  receive the corresponding second arches  82 S. 
     When the outer housing  24  is in the normal state and the movable housing  84  is rotated from the second position to the first position, each first terminal  92  moves away from the corresponding second arch  82 S, moving closer to and coming in contact with the adjacent first arch  82 F. The first guides  92 F in each first terminal  92  receive the corresponding first arch  82 F in a wider space between them, and guide the first arch  82 F to between the base  92 B and the distal end  92 E. 
     At least one of the surrounding structure of the first terminal  92 , the guidance with the first guides  92 F, or the formation of the first arches  82 F allows the first terminals  92  to be more reliably in contact with the corresponding contact rails  82 . This structure reduces chattering when the first terminals  92  receive the corresponding first arches  82 F. 
     The rail portions  82 R of the contact rails  82  define a larger space radially inside when being placed in the circumferential direction and the front-rear direction (direction of the motor shaft  40 ) than when being placed in the circumferential direction and the vertical direction to have the same dimensions in the radial direction of the rail portions  82 R. 
     The larger space allows the space radially inside the BHU  31  to be larger accordingly. The blow from the fan  32  is then more easily guided into the motor  29 , allowing the motor  29  to be cooled more efficiently. 
     The larger space can also accommodate another structure. 
     For example, the annular or cylindrical BHU  31  with a larger space radially inside allows the rear motor housing  22 B to have a larger internal space accordingly. The internal space may accommodate a stronger holding structure for the rear bearing  46 . More specifically, another rib to hold the rear bearing  46  or more ribs may be included, or at least one of the ribs or the rear motor housing  22 B may be thicker. 
     In some embodiments, the rail portions  82 R are radially smaller to define a space radially inside that is as large as a space defined by rail portions  82 R extending in the circumferential and vertical directions. The structure may thus be smaller. 
     When the outer housing  24  is in the normal state and the movable housing  84  is being rotated to a position between the first position and the second position (a transitional position), the projection  84 J on the movable housing  84  is located behind the upper-trigger projection  52 P. This structure prevents the user from operating the trigger  52  rearward with the upper-tugger projection  52 P coming in contact with the projection  84 J. 
     When the outer housing  24  is in the normal state and the movable housing  84  is at the transitional position, the projection  84 J on the movable housing  84  is located in front of the center rib  24 J on the outer housing  24 . This structure prevents the outer housing  24  from moving forward with the center rib  24 J coming in contact with the projection  84 J. When the movable housing  84  is not at the transitional position, the projection  84 J is located above the center rib  24 J. This structure no longer prevents the outer housing  24  from moving forward and allows the outer housing  24  to move forward. 
     When the outer housing  24  is in the normal state or in the forward state and the movable housing  84  is at the first position with the trigger  52  operated rearward by the user, the projection  84 J is located on the left of the upper-trigger projection  52 P. This structure prevents the user from moving the movable housing  84  to the second position with the projection  84 J coming in contact with a left portion of the upper-trigger projection  52 P. 
     When the outer housing  24  is in the normal state or in the forward state and the movable housing  84  is at the second position with the trigger  52  operated rearward by the user, the projection  84 J is located on the right of the upper-trigger projection  52 P. This structure prevents the user from moving the movable housing  84  to the first position with the projection  84 J coining in contact with a right portion of the upper-trigger projection  52 P. 
     When the outer housing  24  moves from the normal state to the forward state with the movable housing  84  at the first position, the outer rib  24 B moves closer to the rib  84 B and is located on the right of the rib  84 B. This structure prevents a leftward operation on the lever  84 V and an operation to move the movable housing  84  to the second position, with the rib  84 B coming in contact with the outer rib  24 B. 
     When the outer housing  24  is in the normal state and the movable housing  84  is at the second position, the left end of the rib  84 B is located in an upper right position behind the outer rib  24 B. When the outer housing  24  further moves from the normal state to the forward state, the outer rib  24 B moves closer to the rib  84 B and is located at the lower left of the rib  84 B. This structure prevents a rightward operation on the lever  84 V and an operation to move the movable housing  84  to the first position, with the rib  84 B coming in contact with the outer rib  24 B. 
     The MU  31  includes the brushes  30  and the brush holders  88  arranged laterally. 
     The BHU  31  is vertically smaller than a BHU  31  with the brushes  30  and the brush holders  88  arranged vertically. The BHU  31  protrudes less in the downward direction. The trigger unit  5  can thus be located closer to the central axis (operational axis) of the output unit  8 , improving workability. 
     The BHU  31  protrudes less in the upward and downward directions. In this structure, the outer housing  24  and the BHU  31  held by the outer housing  24  can move by a larger distance in the front-rear direction than in a structure with vertically arranged brushes  30  and brush holders  88 . 
     An example operation of the hammer drill  1  according to the present embodiment will now be described. 
     When the user operates the trigger  52  rearward with the movable housing  84  at the first position, the trigger switch  50  is turned on. Power from the power cable  6  is supplied to the field coils  36  through the pair of lead wires  89 , the brushes  30 , the brush connection terminal units  86 , and the contact rails  82 . The field coils  36  are electrically connected to the corresponding brushes  30  through the brush connection terminal units  86  and the contact rails  82 . The armature  34  thus rotates in a first direction (forward rotation). The amount by which the armature  34  rotates corresponds to the amount of a rearward operation on the trigger  52 . The choke coils  96  in the brush connection terminal units  86  block higher-frequency components of power, reducing electromagnetic interference (EMI) generation. This reduces noise from the higher-frequency components. A rearward operation on the trigger  52  prevents the user from moving the movable housing  84  to the second position with the projection  84 J coming in contact with the left portion of the upper-trigger projection  52 R 
     A leftward operation on the lever  84 V without a rearward operation on the trigger  52  allows the user to switch the movable housing  84  from the first position to the second position. During the switching, a rearward operation on the trigger  52  is prevented by the upper-trigger projection  52 P coming in contact with the projection  84 J. During the switching, the outer housing  24  is less likely to move forward with the center rib  24 J coming in contact with the projection  84 J. 
     When the user operates the trigger  52  rearward with the movable housing  84  at the second position, the trigger switch  50  is turned on. The brush connection terminal units  86  are in contact with the contact rails  82  at different positions, and the brushes  30  come in contact with the commutator  45  in a relationship opposite to the relationship at the first position. Thus, power from the power cable  6  is supplied reversely to the field coils  36 . The field coils  36  are electrically connected to the corresponding brushes  30  through the brush connection terminal units  86  and the contact rails  82 . The armature  34  thus rotates in a second direction (reverse rotation). The amount by which the armature  34  rotates corresponds to the amount of a rearward operation on the trigger  52 . The choke coils  96  in the brush connection terminal units  86  block higher-frequency components of power, reducing EMI generation. This reduces noise from the higher-frequency components. The trigger  52  operated rearward prevents the user from moving the movable housing  84  to the first position, with the projection  84 J coming in contact with the right portion of the upper-trigger projection  52 P. 
     The armature  34  rotates to rotate the motor shaft  40 . The rotation of the motor shaft  40  is reduced and transferred through the power transmission  60  to the output unit  8  with a tip tool. The rotation of the motor shaft  40  is, through the striking assembly  62 , converted to a striking force to strike the tip tool as appropriate. 
     The output unit  8  rotates and also strikes as appropriate to process a workpiece (operation). 
     At least one of vibration or impact generated during processing is less with the outer housing  24  movable in the front-rear direction and the flexible member  28  located between the motor housing  22  and the outer housing  24 . 
     When the outer housing  24  is moved forward, an operation to rotate and move the movable housing  84  is prevented by the rib  84 B coming in contact with the outer rib  24 B. 
     When the motor shaft  40  rotates, the fan  32  rotates to draw air in through the inlets  24 A. The air is drawn to pass through the hammer drill  1 , or specifically through the inside and the outside of the motor  29  before flowing out through the outlets  20 V. Such flow of air (blow) cools the internal components of the hammer drill I including the motor  29 . 
     More specifically, the blow can be smoothly guided into the inside of the motor  29  with the slopes  84 C of the movable housing  84  that are flat or continuously curved and are tapered forward. 
     Air through the inlets  24 A partially flows through the left opening  22 L and the right opening  22 R into the motor housing  22 . 
     The present disclosure is not limited to the above embodiments and the modifications and may further include, for example, modifications described below as appropriate. 
     The structure of the housing may be modified variously. For example, the motor housing and the gear housing may be integral with each other, or at least either one of the housings may be further divided. 
     The power tool may include a battery mount and a battery mounted on the battery mount instead of the power cable  6  and may be powered by the battery. The striking assembly  62  may be eliminated. The numbers of at least coils or lead wires used herein may be increased or decreased. The numbers of screws and threaded holes may be increased or decreased. The protrusions and recesses may be located at different positions. The contact rails  82  may be formed from a material other than brass. At least any of the engaging portions, the connectors, the screwed portions, the retainers, and the attachment portions may be modified to a different structure or to a different type or to both a different structure and a different type. The number, arrangement, material, structure, or type of at least one of any components or portions may be modified as appropriate, and at least one of any components or portions may be eliminated as appropriate. 
     The present disclosure may be applicable to different types of hammer drills or other power tools, gardening tools, or electric work machines. 
     REFERENCE SIGNS LIST 
     
         
           1  hammer drill (power tool) 
           2  housing 
           22  motor housing 
           24  outer housing 
           28  flexible member 
           29  motor 
           30  brush 
           31  brush holder unit (BHU) 
           33  field 
           34  armature 
           36  field coil 
           45  commutator 
           80  stationary housing 
           80 B rectangular portion 
           82  contact rail 
           82 R rail portion 
           82 T terminal portion 
           84  movable housing 
           84 C slope (flat surface, continuously curved surface) 
           90  case (terminal holder) 
           90 V recess 
           92  first terminal 
           92 F first guide (guide) 
           92 S second guide (guide) 
           94  second terminal 
           96  choke coil