Patent Publication Number: US-10322518-B2

Title: Chainsaw

Description:
BACKGROUND 
     1. Field 
     The present invention relates to a chainsaw for cutting wood such as timber or lumber by a saw chain which is endlessly moved along an outer periphery of a guide bar under driving of an electric motor. 
     2. Description of the Related Art 
     JP 2015-044293A discloses a chainsaw for cutting wood such as timber or lumber. This chainsaw comprises a body casing, an electric motor housed in the body casing, a guide bar provided on a front region of a lateral wall of the body casing, and a saw chain wound around an outer periphery of the guide bar. Further, a rear handle is formed integrally with a rear portion of the body casing, and a front handle is fixed to a front portion of the body casing, wherein each of the rear and front handles has a grip to be gripped by a user or worker. In the above chainsaw, when a worker grips the rear handle and the front handle, for example, by his/her right hand and left hand, respectively, and manipulates an operating lever provided in the rear handle, by the right hand, the electric motor is driven, and thus the saw chain is endlessly moved along the outer periphery of the guide bar. Then, the worker can press, against wood such as timber or lumber, the saw chain being endlessly moved along the outer periphery of the guide bar, to cut the wood by the saw chain. 
     SUMMARY 
     The chainsaw disclosed in JP 2015-044293A is a type of chainsaw employing an inner rotor-type electric motor with brush as a driving source. On the other hand, another type of chainsaw employing an outer rotor-type brushless electric motor as a driving source to promote reductions in size and weight is being developed. In a chainsaw employing a brushless electric motor, during control of current to be supplied to a stator coil of the electric motor, a control unit for driving the electric motor receives a large load and generates a large amount of heat. Thus, there is a need to adequately cool the control unit. Therefore, with a view to adequately cooling the control unit, the chainsaw is constructed such that a cooling fan is provided on a rotary shaft rotatable along with driving of the electric motor, and an air inlet is formed in a body casing to allow outside air to be introduced into the body casing therethrough during rotation of the cooling fan, to thereby cool the control unit. However, there is a risk that wood chips produced during cutting of wood, dusts or water droplets, enter from the air inlet formed in the body casing, into the body casing, and adhere around the control unit. An aspect of the present invention addresses a technical problem of introducing outside air into a body casing by rotation of a cooling fan to adequately cool a control unit provided inside the body casing, while making it less likely that wood chips, dusts or water droplets enter the body casing. 
     In order to solve the above technical problem, an aspect of the present invention provides a chainsaw which comprises: an electric motor provided inside a body casing; a guide bar provided in a front portion of the body casing in such a manner as to protrude forwardly; a saw chain provided around an outer periphery of the guide bar in an endlessly movable manner, and configured to be endlessly moved along the outer periphery of the guide bar under driving of the electric motor; a handle attached to the body casing, and configured to be gripped by a worker; a control unit provided inside the body casing, and configured to control driving of the electric motor; an air inlet for allowing outside air to be introduced into the body casing therethrough; and a cooling fan attached to a rotary shaft rotatable along with the driving of the electric motor, and configured to cool the control unit by outside air introduced from outside the body casing, wherein the handle comprises a base portion through which the handle is attached to the body casing, and a grip formed to extend from the base portion in such a manner as to be grippable by a worker; the air inlet is formed in a counter wall of the body casing opposed to the base portion; and the base portion is attached to the counter wall of the body casing to cover the air inlet in an air introduceable state. 
     In the chainsaw of the present invention having the above feature, the handle comprises a base portion through which the handle is attached to the body casing, and a grip formed to extend from the base portion in such a manner as to be grippable by a worker, and the air inlet is formed in a counter wall of the body casing opposed to the base portion, wherein the base portion is attached to the counter wall of the body casing to cover the air inlet in an air introduceable state. This makes it less likely that wood chips, dusts or water droplets enter from the air inlet into the body casing, so that the inside of the body casing of the chain saw becomes less likely to be contaminated by wood chips, dusts or the like. 
     Preferably, in the chainsaw of the present invention, the control unit provided inside the body casing is disposed between the air inlet and the cooling fan. According to this feature, it becomes possible to efficiently cool the control unit. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a chainsaw according to one embodiment of the present invention; 
         FIG. 2  is a side view of the chainsaw in  FIG. 1 ; 
         FIG. 3  is a side view of the chainsaw in  FIG. 1 , wherein respective right halves of a body casing and a handle are removed to bring insides thereof into view; and 
         FIG. 4  is a perspective view of the chainsaw in  FIG. 1 , wherein the body casing and the handle are disassembled from each other. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     With reference to the drawings, a chainsaw of the present invention will now be described based on one exemplary embodiment thereof. As depicted in  FIGS. 1 and 2 , a chainsaw  10  according to this embodiment comprises a body casing  11  which houses an electric motor  21  and others, and a handle  30  attached to a rear portion of the body casing  11 . The electric motor  21  is provided inside the body casing  11  at a position forward of an intermediate portion of the body casing  11  in a forward/rearward direction. The electric motor  21  comprises a rotary shaft  21   a  which is rotatable along with driving of the electric motor  21  and is disposed to protrude outwardly from an intermediate region of a right lateral wall of the body casing  11 . The electric motor  21  is an outer rotor-type brushless electric motor configured such that a current to be supplied to an inner stator coil is controlled by an aftermentioned control unit  27 , so as to controllably rotate the rotary shaft  21   a  coupled to an outer rotor. 
     In the outside of the body casing  11 , a sprocket  22  is fixed to the rotary shaft  21   a  of the electric motor  21 . That is, the sprocket  22  is configured to be rotated under driving of the electric motor  21 . A guide bar  23  is fixed to a front region of the right lateral wall of the body casing  11  at a position forward of the sprocket  22 , in such a manner as to protrude forwardly, and a saw chain  24  is provided in a tensioned state between the sprocket  22  and an outer periphery of the guide bar  23  in an endlessly movable manner. A sprocket cover  25  is provided on the front region of the right lateral wall of the body casing  11 , to cover the rotary shaft  21   a  of the electric motor  21 , the sprocket  22 , and a base end of the guide bar  23 . 
     As depicted in  FIGS. 1 to 2 , a battery pack  26  is detachably provided on the rear portion of the body casing  11 . In this embodiment, a pair of right and left battery packs  26  are provided, respectively, on right and left opposite sides of the rear portion of the body casing  11 . The battery packs  26  are operable to feed electric power to the electric motor  21  to thereby drive the electric motor  21 . As depicted in  FIG. 3 , a control unit  27  is provided inside and on a lower rearward side of the body casing  11 . The control unit  27  is operable to control driving of the electric motor  21 . Specifically, the control unit  27  comprises a drive circuit (not depicted) for driving the electric motor  21  as a brushless motor. The drive circuit is operable to control a current to be supplied to the stator coil of the electric motor  21  to controllably rotate the rotor of the electric motor  21 . 
     Within the body casing  11 , a cooling fan  28  is fixed to the rotary shaft  21   a  of the electric motor  21 , and an air inlet  11   a  ( 11   a   1 ,  11   a   2 ) is formed in each of a rear wall and rear regions of right and left lateral walls of the body casing  11  to introduce outside air therethrough by the rotation of the cooling fan  28 . The cooling fan  28  is operable to suck and move air in the body casing  11  toward the rotary shaft  21   a , and more specifically to cause outside air introduced from the air inlet  11   a  into the body casing  11  to be passed along the electric motor  21  and the control unit  27  to thereby cool the electric motor  21  and the control unit  27 . The air inlet  11   a   1  in the rear wall of the body casing  11  is formed to have a total opening area greater than that of the air inlet  11   a   2  in the rear regions of the lateral walls, so that outside air is mainly introduced from the air inlet  11   a   1  of the rear wall into the body casing  11 . 
     As depicted in  FIGS. 1 and 2 , the handle  30  is configured to be gripped by a worker during use of the chainsaw  10 . The handle  30  is prepared separately (as a separate component) from the body casing  11 , and then attached to the body casing  11  in an anti-vibration manner. The handle  30  comprises a base portion  31  through which the handle  30  is attached to the rear portion of the body casing  11 , a rear grip  32   a  of a rear handle portion  32  extending from the base portion  31 , and a front grip  33   a  of a front handle portion  33  extending from the base portion  31 . The base portion  31  has an approximately L shape in side view, and attached to cover the rear wall and a rear region of a bottom wall of the body casing  11  serving as a mounting surface, through a gap C therebetween. The air inlet  11   a  formed in the rear wall of the body casing  11  is covered by the base portion  31  through the gap C. Thus, outside air can be introduced into the body casing  11  through the gap C between the body casing  11  and the base portion  31 , and the air inlet  11   a . An anti-vibration member comprised of a coil spring  34  or a rubber member  35  is interposed between the base portion  31  and the body casing  11 , to thereby make it less likely that vibration generated in the body casing  11  is transmitted to the handle  30 . 
     The rear handle portion  32  is formed to have a rearwardly-closed approximately-C shape, and integrated with a rear end of the base portion  31 . The rear grip  32   a  is formed in an upper region of the rear handle portion  32  in such a manner as to be grippable by a worker, and provided with a trigger lever  36  configured to be swingably manipulated to trigger driving of the electric motor  21 . The base portion  31  is provided with a switch unit  37  operable to output an operating signal to the control unit  27  in response to a swinging manipulation of the trigger lever  36 . The switch unit  37  is electrically connected to the control unit  27 . The front handle portion  33  is formed in an upwardly-closed, upside-down approximately-U shape, and fixed to the base portion  31 . The front grip  33   a  is formed in an upper region of the front handle portion  33  in such a manner as to be grippable by a worker. 
     When the chainsaw  10  constructed as above is used in wood cutting work, a worker grips the front grip  33   a  of the front handle portion  33  and the rear grip  32   a  of the rear handle portion  32 , for example, by his/her left hand and right hand, respectively, and pulls the forefinger of the right hand toward the rear grip  32   a  to swingingly move the trigger lever  36 . In response to the manipulation of the trigger lever  36 , the switch unit  37  outputs an operating signal to the control unit  27 , and thus the electric motor  21  is driven based on control of the control unit  27 . The saw chain  24  is endlessly moved along the outer periphery of the guide bar  23  by the sprocket  22  being rotated under driving of the electric motor  21 . Then, the worker manipulates the handle portions  32 ,  33  to press, against an outer periphery of lumber such as a log, the saw chain  24  being endlessly moved along the outer periphery of the guide bar  23 , to thereby cut the lumber such as a log. During this work, around the chainsaw  10 , wood chips will fly apart from the lumber cut by the saw chain  24  being endlessly moved. 
     The chainsaw  10  according to this embodiment employs an outer rotor-type brushless electric motor  21  as a driving source to promote reductions in size and weight. As a result of employing the brushless electric motor  21 , the control unit  27  for controlling driving of the electric motor  21  receives a large load and generates a large amount of heat, because it operates to control a current to be supplied to the stator coil of the electric motor  21  based on the built-in drive circuit. Therefore, in the chainsaw  10  according to this embodiment, the cooling fan  28  is provided on the rotary shaft  21   a  of the electric motor  21 , to cause outside air to be sucked mainly from the air inlets  11   a   1 ,  11   a   2  formed in the rear wall and the rear regions of the lateral walls of the body casing  11  and then passed along the control unit  27  to thereby cool the control unit  27 . In particular, the control unit  27  provided inside the body casing  11  is disposed between the air inlet  11   a  and the cooling fan  28 , so that it becomes possible to effectively cool the control unit  27 . 
     In the chainsaw  10  according to this embodiment, the handle  30  prepared separately from the body casing  11  is attached to the body casing  11 . More specifically, the handle  30  comprises the base portion  31  through which the handle  30  is attached to the body casing  11 , the rear grip  32   a  of the rear handle portion  32  extending from the base portion  31  in such a manner as to be grippable by a worker, and the front grip  33   a  of the front handle portion  33  extending from the base portion  31  in such a manner as to be grippable by the worker. In the chainsaw  10  according to this embodiment, the air inlet  11   a   1  is formed in the rear wall (counter wall) of the body casing  11  opposed to the base portion  31 , and the base portion  31  is attached to the rear wall of the body casing  11  through the gap C to cover the air inlet  11   a   1  in an air introduceable (suctionable) state. This makes it less likely that wood chips flying apart around the chainsaw  10 , dusts or water droplets enter from the air inlet  11   a   1  into the body casing  11 , so that the inside of the body casing  11  of the chain saw  10  becomes less likely to be contaminated by wood chips, dusts or the like. 
     Although the chainsaw according to the above embodiment is a so-called “rear-handle chainsaw” comprising a rear handle and a front handle (also called “side handle”), the present invention is not limited to the rear-handle chainsaw, but may be applied to a so-called “top-handle chainsaw” comprising a top handle provided at a top of a body casing, and a front handle (also called “side handle”).