Patent Publication Number: US-2019189370-A1

Title: Electric power tool

Description:
BACKGROUND 
     Technical Field 
     The present invention relates to an electric power tool provided with a trigger switch. 
     Related Art 
     Patent Document 1 discloses a trigger switch used for an electric power tool. The trigger switch includes a cover and a case in which a switch mechanism is incorporated, and an operation unit that can be operated by a user with a finger and transmits an operational motion to the switch mechanism. 
     Patent Document 1: Japanese Unexamined Patent Publication No. 2010-192452 
     SUMMARY OF THE INVENTION 
     In the trigger switch, a switch mechanism is used to improve vibration resistance, the switch mechanism having a structure in which two movable contacts are simultaneously press-fit to two fixed contacts while resisting the urging force of springs. However, due to the recent increase in capacity and power of electric power tools, there have been more cases where such a switch mechanism cannot sufficiently prevent the occurrence of chattering. 
     One or more embodiments of the present invention provides an electric power tool capable of improving vibration resistance. 
     An electric power tool according to one aspect of the present invention includes: a tool housing; and a trigger switch fixed inside the tool housing. The tool housing internally has a trigger switch fixing unit that comes into contact with the trigger switch, and the trigger switch fixing unit is provided with a vibration damping elastic body interposed between the trigger switch fixing unit and the trigger switch. 
     According to the electric power tool according to one or more embodiments of the present invention, the trigger switch fixing unit in contact with the trigger switch is provided with the vibration damping elastic body interposed between the trigger switch fixing unit and the trigger switch, thereby enabling improvement in vibration resistance. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an electric power tool according to one embodiment of the present invention. 
         FIG. 2  is a side view of the electric power tool in  FIG. 1  with a part of a tool housing removed. 
         FIG. 3  is a sectional view taken along line III-III in  FIG. 2 . 
         FIG. 4  is a sectional view taken along line IV-IV in  FIG. 2 . 
         FIG. 5  is a front view of a right housing of the electric power tool in  FIG. 1 . 
         FIG. 6  is a perspective view of a trigger switch of the electric power tool in  FIG. 1 . 
         FIG. 7  is a perspective view of the trigger switch in  FIG. 6  as seen from a different direction from  FIG. 6 . 
         FIG. 8  is a schematic diagram illustrating a returned state of the trigger switch in  FIG. 6  with a part of a switch housing removed. 
         FIG. 9  is a schematic diagram illustrating an operating state of the trigger switch in  FIG. 6  with a part of the switch housing removed. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, terms (e.g., terms including “upper”, “lower”, “right”, “left”, “side”, and “end”) indicating specific directions or positions are used as necessary, but the use of these terms is for facilitating understanding of the invention with reference to the drawings, and the technical scope of the present invention is not limited by the meaning of these terms. The following description is merely exemplary in nature and is not intended to limit the present invention, its application, or its usage. Further, the drawings are schematic, and ratios of dimensions and the like do not necessarily agree with actual ones. In embodiments of the invention, numerous specific details are set forth in order to provide a more thorough understanding of the invention. However, it will be apparent to one of ordinary skill in the art that the invention may be practiced without these specific details. In other instances, well-known features have not been described in detail to avoid obscuring the invention. 
     As illustrated in  FIG. 1 , an electric power tool  1  according to one embodiment of the present invention includes a tool housing  10  made of resin and a trigger switch  20  fixed in the tool housing  10 . In  FIGS. 1 to 4 , components constituting the electric power tool  1  other than the trigger switch  20  are omitted. 
     As illustrated in  FIG. 1 , the tool housing  10  is made up of a right housing  11  and a left housing  12  joined to the right housing  11 . The right housing  11  and the left housing  12  are provided symmetrically with respect to a joining surface ( FIG. 2  only shows a joining surface  111  of the right housing  11 ). As illustrated in  FIG. 2 , the tool housing  10  includes a drive mechanism holder  13 , a trigger switch holder  14 , and a battery holder  15 . Note that  FIG. 2  illustrates the electric power tool  1  with the left housing  12  removed. 
     A drive mechanism part (not illustrated) such as a motor, electrically connected to the trigger switch  20 , is accommodated inside the drive mechanism holder  13 . The trigger switch holder  14  extends downward from substantially the center in the horizontal direction of the drive mechanism holder  13  in  FIG. 2 , and the trigger switch  20  is accommodated inside the trigger switch holder  14 . The outer surface of the trigger switch holder  14  constitutes a grip part  141  gripped by a user. The battery holder  15  is connected to the lower end of the trigger switch holder  14 , and a battery (not illustrated) electrically connected to the trigger switch  20  is accommodated inside the battery holder  15 . 
     A plurality of trigger switch fixing units  16  for fixing the trigger switch  20  are provided at the end in the trigger switch holder  14  on the drive mechanism holder  13  side. As illustrated in  FIGS. 3 to 5 , each trigger switch fixing unit  16  is in contact with a corner of a rectangular box-shaped switch housing  21  of a trigger switch  20  to be described later to fix the trigger switch  20  in the tool housing  10 . 
     In each trigger switch fixing unit  16 , there is provided a vibration damping elastic body  26  interposed between the trigger switch  20  and the tool housing  10  and disposed so as to prevent the tool housing  10  and the trigger switch  20  from coming into direct contact with each other. Each vibration damping elastic body  26  is, for example, an elastomer with a thickness of 1 mm, and as illustrated in  FIG. 5 , on the surfaces in three directions in contact with the switch housing  21 , each vibration damping elastic body  26  is provided integrally with the trigger switch fixing unit  16  by two-color formation. Each vibration damping elastic body  26  absorbs vibration generated by rotation of the motor of the electric power tool  1  or the like and transmitted to the tool housing  10 , to suppress vibration propagated from the three directions to the trigger switch  20 . 
     As illustrated in  FIG. 6 , the trigger switch  20  includes a switch housing  21  made of resin and a trigger  22  as an example of an operation unit. Inside the switch housing  21 , as illustrated in  FIGS. 8 and 9 , a holder  25  is provided, and a fixed contact  23  and a movable contact  24  are provided in the holder  25 . Note that  FIGS. 8 and 9  schematically illustrate the trigger switch  20  in a state where a second housing  212  to be described later has been removed. 
     As illustrated in  FIGS. 6 and 7 , the switch housing  21  is made up of a first housing  211  having an opening  214  (illustrated in  FIGS. 8 and 9 ) on one surface, and a second housing  212  joined in the width direction of the first housing  211  (i.e., the Y direction in  FIG. 5 ) and closing the opening  214 . A part of the joining surface of the first housing  211  and the second housing  212  is covered with the sub second housing  213 . 
     Each of the first housing  211  and the second housing  212  has a rectangular box shape and is provided symmetrically with respect to mutual joining surfaces. A trigger  22  is disposed on the right side of the first housing  211  and the second housing  212  in the short direction (i.e., the X direction in  FIG. 6 ). As illustrated in  FIG. 7 , the sub second housing  213  has a substantially plate shape and is attached to the left-side surface in the short direction of the first housing  211  and the second housing  212  (i.e., on the surface farther from the trigger  22 ). 
     Each of the eight corners of the outer surface of the switch housing  21  has a tool housing fixing unit  261  that comes into contact with the tool housing  10  and is fixed to the tool housing when fixed in the tool housing  10 . 
     As illustrated in  FIGS. 6 and 7 , the trigger  22  includes an operation body  221  operated by the user with the finger, and an operation shaft  222  extending from the surface of the operation body  221 , facing the switch housing  21 , toward the switch housing  21  to the inside of the switch housing  21 . The trigger  22  is provided outside the switch housing  21  and is connected to the switch housing  21  so as to be approachable to and separable from the switch housing  21 . 
     The operation body  221  has a curved surface on the surface opposite to the surface on which the operation shaft  222  is provided (i.e., the right-side surface in the X direction in  FIG. 5 ), so that the operation body  221  can be easily operated with the user&#39;s finger. 
     As illustrated in  FIGS. 8 and 9 , one end of the operation shaft  222  in the longitudinal direction (i.e., the right-side end in the X direction in  FIGS. 8 and 9 ) is positioned outside the switch housing  21  and connected to the operation body  221 , whereas the other end of the operation shaft  222  in the longitudinal direction (i.e., the left-side end in the X direction in  FIGS. 8 and 9 ) is positioned in the holder  25  of the switch housing  21  and is movably connected to the switch housing  21 . On the left side of the operation shaft  222  in the longitudinal direction, a return spring  27  is disposed in a state where the operation shaft  222  can be urged toward the right in the longitudinal direction. 
     The operation shaft  222  is provided with a plunger  28  that extends downward from the operation shaft  222  in the holder  25  (i.e., downward in the Z direction in  FIGS. 8 and 9 ). In conjunction with the movement of the trigger  22 , the tip of the plunger  28  (i.e., the lower end in the Z direction in  FIGS. 8 and 9 ) is disposed so as to be able to come into contact with a movable contact piece  241  to be described later. 
     As illustrated in  FIGS. 8 and 9 , the fixed contact  23  is attached to a fixed-contact-side terminal  231  fixed to the left end of a wall  215  on the lower side of the switch housing  21  (Le., the lower side in the Z direction in  FIGS. 8 and 9 ). The movable contact  24  is attached to a movable contact piece  241  turnably supported by a support  242  provided at a substantially center in the X direction of the bottom surface in the holder  25 . The movable contact  24  faces the fixed contact  23  and is disposed so as to be capable of coming into contact with and separating from the fixed contact  23 . The movable contact piece  241  extends in the short direction of the switch housing  21  (i.e., the X direction in  FIGS. 8 and 9 ) in the holder  25 , and the movable contact  24  is attached to the left-side end in the short direction. The right-side end in the short direction of the movable contact piece  241  is in contact with a movable-contact-side terminal  243  fixed to the right end of the lower wall  215  of the switch housing  21 . 
     Next, the operation of the electric power tool  1  will be described with reference to  FIGS. 8 and 9 . 
     Note that  FIG. 8  illustrates the trigger switch  20  in a returned state where the fixed contact  23  and the movable contact  24  are separated. Further,  FIG. 9  illustrates the trigger switch  20  in an operating state where the fixed contact  23  and the movable contact  24  are in contact with each other. 
     When the trigger switch  20  is in a returned state illustrated in  FIG. 8 , the end of the movable contact piece  241 , at which the movable contact  24  is provided, is separated from the lower wall  215  of the switch housing  21  more than the end in contact with the movable-contact-side terminal  243 , thereby separating movable contact  24  from the fixed contact  23 . At this time, no power is being supplied from the battery to the motor, and the motor is stopped. 
     When the operation body  221  of the trigger  22  of the trigger switch  20  in the returned state is operated with the finger to bring the trigger  22  close to the switch housing  21 , the plunger  28  moves to the left side in the X direction in conjunction with the movement of the trigger  22 . As a result, the plunger  28  comes into contact with the movable contact piece  241  on the side closer to the movable contact  24  than the support  242  of the movable contact piece  241 , and turns the movable contact piece  241  counterclockwise. As a result, the end of the movable contact piece  241 , at which the movable contact  24  is provided, approaches the lower wall  215  of the switch housing  21 , and the movable contact  24  comes into contact with the fixed contact  23 , whereby the operating state becomes the one illustrated in  FIG. 9 . As a result, power is supplied from the battery to the motor, and the motor is activated. 
     When the finger is released from the operation body  221  of the trigger  22  of the trigger switch  20  in the operating state, the operation shaft  222  is urged to the right side in the X direction by the return spring  27 , and the trigger  22  is separated from the switch housing  21 . In conjunction with the movement of the trigger  22 , the plunger  28  moves to the right in the X direction to turn the movable contact piece  241  clockwise. As a result, the end of the movable contact piece  241 , at which the movable contact  24  is provided, is separated from the lower wall  215  of the switch housing  21 , and the movable contact  24  is separated from the fixed contact  23  to come into the returned state illustrated in  FIG. 8 . As a result, the supply of electric power from the battery to the motor is stopped, and the motor is stopped. 
     In the electric power tool  1 , the trigger switch fixing unit  16  for fixing the trigger switch  20  inside the tool housing  10  is provided with the vibration damping elastic body  26  that is interposed between the trigger switch  20  and the trigger switch fixing unit  16 . Therefore, vibration generated by the rotation of the motor of the electric power tool  1  or the like is absorbed by the vibration damping elastic body  26  to suppress propagation of the vibration to the trigger switch  20 , thereby enabling improvement in vibration resistance. It is thereby possible to prevent occurrence of chattering without increasing the contact pressure of the movable contact  24  with respect to the fixed contact  23 . That is, it is possible to simultaneously achieve prevention of occurrence of chattering and reduction in wear between the fixed contact  23  and the movable contact  24 . 
     Further, since the vibration damping elastic body  26  is an elastomer, it is possible to easily obtain the vibration damping elastic body  26  having elasticity according to the design. 
     In addition, the vibration damping elastic body  26  may have a single layer structure constituted by one elastic layer, or may have a laminated structure constituted by a plurality of elastic layers. The plurality of elastic layers constituting the laminated structure may have the same rigidity or may have different rigidities. For example, by forming the vibration damping elastic body  26  into a laminated structure with different rigid elastic layers combined, it is possible to deal with vibrations having different frequencies, amplitude, or the like, and improve the vibration damping force of the vibration damping elastic body  26 . 
     In addition, the vibration damping elastic body  26  may be provided such that an area in a plan view along the direction orthogonal to the contact/separation direction (i.e., the Z direction in  FIGS. 7 and 8 ) in which the movable contact  24  contacts and separates from the fixed contact  23  (i.e., a plan view seen from the Z direction in  FIGS. 7 and 8 ) is larger than an area in a plan view along the contact/separation direction (i.e., a plan view seen from the X direction in  FIGS. 7 and 8 ). Hence it is possible to more greatly damp the vibration in the contact/separation direction than the direction intersecting the contact/separation direction, and more reliably prevent occurrence of chattering. 
     According to the design of the electric power tool  1  or the like, the trigger switch fixing unit  16  can be provided in an arbitrary shape, can be provided in an arbitrary number, and can be provided at an arbitrary position. 
     The trigger switch  20  is not limited to the above configuration, and any configuration can be adopted. For example, there may be used a trigger switch configured such that a microcomputer and a printed circuit are provided in the holder  25 , the printed circuit being mounted with a resistive body having a resistance value which fluctuates in conjunction with movement of a trigger (e.g., a resistance value decreases as the operating state becomes higher), and the microcomputer controls the rotation of the motor in accordance with the position of the trigger detected by a current flowing through the resistive body. 
     Various embodiments of the present invention have been described in detail with reference to the drawings, and lastly, various aspects of the present invention will be described. 
     An electric power tool of a first aspect of the present invention is provided with a tool housing; and a trigger switch fixed inside the tool housing. The tool housing internally has a trigger switch fixing unit configured to fix the trigger switch, and the trigger switch fixing unit is provided with a vibration damping elastic body interposed between the trigger switch fixing unit and the trigger switch. 
     According to the electric power tool of the first aspect, the trigger switch fixing unit configured to fix the trigger switch inside the tool housing is provided with the vibration damping elastic body interposed between the trigger switch and the trigger switch fixing unit. Therefore, the vibration generated by the rotation of the motor of the electric power tool or the like is absorbed by the vibration damping elastic body disposed between the tool housing and the trigger switch, and vibration propagated to the trigger switch via the tool housing is suppressed, thereby enabling improvement in vibration resistance. 
     In an electric power tool of a second aspect of the present invention, the vibration damping elastic body is provided integrally with the tool housing. 
     In an electric power tool of a third aspect of the present invention, the vibration damping elastic body has a laminated structure including a plurality of elastic layers. 
     According to the electric power tool of the third aspect, for example, by forming the vibration damping elastic body into a laminated structure with different rigid elastic layers combined, it is possible to deal with vibrations having different frequencies, amplitudes, or the like, and improve the vibration damping force of the vibration damping elastic body. 
     In an electric power tool of a fourth aspect of the present invention, the vibration damping elastic body is an elastomer. 
     According to the electric power tool of the fourth aspect, it is possible to easily obtain a vibration damping elastic body having elasticity according to the design. 
     In an electric power tool of a fifth aspect of the present invention, the trigger switch includes a switch housing fixed inside the tool housing and internally having a holder, an operation unit provided outside the switch housing and connected to the switch housing so as to be approachable to and separable from the switch housing, a fixed contact provided in the holder, and a movable contact provided so as to face the fixed contact in the holder and configured to come into contact with and separate from the fixed contact in conjunction with an approaching motion and a separating motion of the operation unit with respect to the switch housing. An area of the vibration damping elastic body in a plan view along a direction orthogonal to a contact/separation direction in which the movable contact comes into contact with and separates from the fixed contact is larger than an area of the vibration damping elastic body in a plan view along the contact/separation direction. 
     According to the electric power tool of the fifth aspect, among the vibrations propagating to the trigger switch via the tool housing, the vibration in the contact/separation direction can be more greatly damped than the direction intersecting the contact/separation direction, and the occurrence of chattering in the trigger switch can be prevented more reliably. 
     Note that by appropriately combining freely selected embodiments or modifications of the above variety of embodiments and modifications, it is possible to achieve the respective effects of those combined. While it is possible to combine embodiments, combine examples, or combine an embodiment and an example, it is also possible to combine features in different embodiments or examples. 
     The present invention has been fully described in connection with the preferred embodiments with reference to the accompanying drawings, but various modifications or corrections will be apparent to those skilled in the art. Such modifications or corrections are to be understood as being included in the scope of the present invention according to the appended claims so long as not deviating therefrom. 
     INDUSTRIAL APPLICABILITY 
     One or more embodiments of the present invention can be applied to an electric power tool of any configuration as long as it includes a tool housing and a trigger switch fixed inside the tool housing. 
     While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims. 
     DESCRIPTION OF SYMBOLS 
       1  electric power tool 
       10  tool housing 
       11  right housing 
       12  left housing 
       13  drive mechanism holder 
       1  trigger switch holder 
       141  grip part 
       15  battery holder 
       16  trigger switch fixing unit 
       20  trigger switch 
       21  switch housing 
       211  first housing 
       212  second housing 
       213  sub second housing 
       214  opening 
       215  wall 
       22  trigger 
       221  operation body 
       222  operation shaft 
       23  fixed contact 
       231  fixed contact side terminal 
       24  movable contact 
       241  movable touch piece 
       242  support 
       243  movable contact side terminal 
       25  holder 
       26  vibration damping elastic body 
       261  tool housing fixing unit 
       27  return spring 
       28  plunger