Electric working machine

An electric working machine may include: a support rod constituted of metal; a tool disposed at a front end of the support rod; a motor configured to drive the tool; a control unit disposed at a rear end of the support rod and configured to control the motor; and a heat transfer structure configured to transfer heat from the control unit to the support rod.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Japanese Patent Application No. 2019-017382, filed on Feb. 1, 2019, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The technique disclosed herein relates to an electric working machine.

BACKGROUND

International Publication No. WO2013/062457 describes an electric working machine that is provided with a support rod, a tool disposed at a front end of the support rod, a motor configured to drive the tool, and a control unit disposed at a rear end of the support rod and configured to control the motor.

SUMMARY

In the electric working machine described above, increasing the output of the motor results in an increase in an amount of heat generated by the control unit correspondingly, as a result of which the control unit may have a high temperature. If the control unit becomes too hot, malfunctions may occur in the control unit. The disclosure herein provides a technique capable of improving cooling performance for a control unit that controls a motor in an electric working machine.

The disclosure herein discloses an electric working machine. The electric working machine may include a support rod constituted of metal, a tool disposed at a front end of the support rod, a motor configured to drive the tool, a control unit disposed at a rear end of the support rod and configured to control the motor, and a heat transfer structure configured to transfer heat of the control unit to the support rod.

According to the above configuration, the heat of the control unit is transferred to the support rod by the heat transfer structure. As such, the support rod can function as a heat dissipator that dissipates the heat of the control unit. Cooling performance for the control unit can thereby be improved.

DETAILED DESCRIPTION

In one or more embodiments, an electric working machine may include a support rod constituted of metal; a tool disposed at a front end of the support rod; a motor configured to drive the tool; a control unit disposed at a rear end of the support rod and configured to control the motor; and a heat transfer structure configured to transfer heat of the control unit to the support rod.

According to the above configuration, the heat of the control unit is transferred to the support rod by the heat transfer structure. As such, the support rod can function as a heat dissipator that dissipates the heat of the control unit. The cooling performance for the control unit can thereby be improved.

In one or more embodiments, the electric working machine may further comprise a fan driven by the motor. Cooling air generated by the fan may flow inside of the support rod.

According to the above configuration, the support rod is cooled by the cooling air flowing inside the support rod. Therefore, an amount of heat dissipated from the control unit via the support rod can be increased. The cooling performance for the control unit can be further improved.

In one or more embodiments, the electric working machine may further comprise a housing that accommodates the control unit. A section of the housing in which the control unit is accommodated may be sealed.

According to the above configuration, even when water or dust enters the inside of the housing, the water or dust can be prevented from reaching the control unit.

In one or more embodiments, the electric working machine may further comprise a grip housing constituted of resin. The grip housing may be mounted on the support rod and is configured to be grasped by a user.

In the configuration where the heat of the control unit is transferred to the support rod by the heat transfer structure, the support rod may have a high temperature. Even when the support rod has a high temperature, the grip housing constituted of resin does not have a temperature as high as the support rod. According to the above configuration, even when the support rod is at a high temperature, the user can handle the electric working machine by holding the grip housing without directly holding the support rod at a high temperature.

Embodiments

Hereinafter, a pole saw2, which is an example of electric working machine, will be described with reference to the drawings. The pole saw2shown inFIG.1is an electric working machine for horticulture, and is used for pruning high branches and the like. The pole saw2includes a support rod4, a front end unit6provided at a front end4aof the support rod4, a rear end unit8provided at a rear end4bof the support rod4, and a grip unit10provided near the rear end4bof the support rod4. The support rod4is a hollow metallic member having a round pipe shape and extends linearly from the front end4ato the rear end4b.

As shown inFIG.2, the front end unit6includes a front end housing12, a motor14, a fan16, a sprocket18, a guide bar20, an oil pump (not shown), an oil tank22, and a sprocket cover24. The front end housing12is a member constituted of resin. The motor14, the fan16, and the oil pump are accommodated in the front end housing12. The motor14is an outer rotor-type brushless DC motor that includes a stator28around which a coil26is wound and a rotor30disposed on outer side relative to the stator28. A position of the stator28is fixed relative to the front end housing12. The rotor30is fixed to a drive shaft32via the fan16. The drive shaft32extends in a right-left direction (vertical direction inFIG.2) and is held rotatably with respect to the front end housing12. A left end of the drive shaft32is positioned outside of the front end housing12. The sprocket18is fixed to the left end of the drive shaft32. When the rotor30is rotated by the driving of the motor14, the fan16, the drive shaft32, and the sprocket18are also rotated integrally. As shown inFIG.1, the guide bar20is a member having an elongated plate shape. A longitudinal direction of the guide bar20is along a front-rear direction, and a lateral direction thereof is along an up-down direction. As shown inFIG.2, the guide bar20is attached to a left surface of the front end housing12. A saw chain34(shown inFIG.1) is hung around the sprocket18and the guide bar20. When the sprocket18rotates, the saw chain34moves along a periphery of the guide bar20, by which an object to be cut is cut. The sprocket cover24is attached to the left surface of the front end housing12so as to cover the sprocket18and a rear end of the guide bar20. The oil pump supplies lubricating oil stored in the oil tank22to the saw chain34in conjunction with the rotation of the drive shaft32. The oil tank22is attached to a front surface of the front end housing12.

The support rod4is fixed to the front end housing12with the front end4ainserted in a cylindrical portion12aof the front end housing12. An internal space of the support rod4communicates with an internal space of the front end housing12. Motor power lines (not shown) that supply power to the coil26of the motor14extend from the internal space of the front end housing12, through the internal space of the support rod4, to the rear end unit8. A discharge port12bis provided near the fan16of the front end housing12. When the fan16rotates, air is sucked from the internal space of the support rod4into the internal space of the front end housing12. The sucked air passes through the motor14to cool the motor14and then is discharged from the internal space of the front end housing12to outside of the front end housing12through the discharge port12b.

As shown inFIG.3, the grip unit10includes a grip housing40, a trigger42, a lock-off lever44, an operation panel46, and a display panel48. The grip housing40is a member that is constituted of resin and is formed in a shape that covers an outer surface of the support rod4. The support rod4is fixed to the grip housing40in a state of penetrating the grip housing40. A rear portion of the grip housing40has a shape that expands rearward.

The trigger42is provided on a lower surface of the grip housing40. The trigger42is operated to drive the motor14of the front end unit6. In a state where the trigger42is not pushed in, supply of electric power to the motor14is cut off. In a state where the trigger42is pushed in, electric power is supplied to the motor14. A trigger switch (not shown) configured to detect the push operation on the trigger42is accommodated in the grip housing40. The lock-off lever44is provided on an upper surface of the grip housing40. The lock-off lever44is a lever configured to restrict the push operation on the trigger42and release the restriction. In a state where the lock-off lever44is not pushed in, the push operation on the trigger42is restricted. In a state where the lock-off lever44is pushed in, the restriction of the push operation on the trigger42is released. The user can drive the motor14by grasping the grip housing40while pushing in the lock-off lever44with his/her palm of one hand and pushing in the trigger42with the finger of the hand.

The operation panel46and the display panel48are provided on the upper surface of the grip housing40on a front side relative to the lock-off lever44. The operation panel46is provided with an operation button46athat is for controlling the driving of the motor14of the front end unit6. An operation circuit board (not shown) that is configured to detect an operation on the operation button46ais accommodated in the grip housing40. By operating the operation button46a, the user can switch the driving and stopping of the motor14, switch the rotation directions of the motor14, and change the rotation speed of the motor14. A display lamp48aconfigured to display the operating state of the pole saw2is mounted on the display panel48. A display circuit board (not shown) that is configured to control the operation of the display lamp48ais accommodated in the grip housing40. A signal line (not shown) extending from each of the trigger switch, the operation circuit board, and the display circuit board passes through a space between the support rod4and the grip housing40, and extends up to the rear end unit8.

As shown inFIGS.3and4, the rear end unit8includes a rear end housing50, battery packs52, a battery cover54, a coupling member56, a support member58, a control circuit board60, and a heat transfer member62. The rear end housing50is a member constituted of resin. A front end of the rear end housing50is connected to a rear end of the grip housing40. The battery packs52include a plurality of rechargeable battery cells (not shown). The battery cells are, for example, lithium ion battery cells. As shown inFIG.3, the battery packs52are detachably attached to a rear surface of the rear end housing50. The battery packs52are attached to and detached from the rear end housing50by being slid in the right-left direction with respect to the rear end housing50. The battery cover54is attached to the rear end housing50so as to cover a lower surface of the battery packs52.

As shown inFIG.4, the coupling member56is fixed to the rear end housing50via the support member58. The coupling member56is a member constituted of metal. The coupling member56is provided with a through hole56athat has a substantially round columnar shape extending along the front-rear direction. The support rod4is fixed to the coupling member56with its rear end4binserted into the through hole56aof the coupling member56. The support member58is a member constituted of metal. The support member58is provided with a through hole58athat has a substantially round columnar shape extending along the front-rear direction. The coupling member56is fixed to the support member58with the through hole56acommunicating with the through hole58a. In a state where the rear end unit8and the grip unit10are mounted on the support rod4, the coupling member56is disposed inside the grip housing40of the grip unit10.

The control circuit board60is configured to control the driving of the motor14in response to operations on the operation panel46and the trigger42. The control circuit board60includes a plurality of switching elements (not shown) for controlling electric power supplied to the motor14. The control circuit board60further controls display on the display panel48. The control circuit board60is disposed inside the rear end housing50on a rear side relative to the support member58. The control circuit board60is disposed along the up-down direction and the right-left direction. In other words, the control circuit board60is disposed such that its normal direction is along the front-rear direction. The heat transfer member62is interposed between the support member58and the control circuit board60. The heat transfer member62is a member constituted of metal. The motor power lines, which extend from the front end unit6through the internal space of the support rod4, pass through the through hole56aof the coupling member56and the through hole58aof the support member58and are connected to the control circuit board60. The through hole58aof the support member58is provided with a grommet64through which the motor power lines pass. The signal lines, which extend from the grip unit10through the space between the support rod4and the grip housing40, pass through a space between the coupling member56and the grip housing40, pass through a space between the support member58and the rear end housing50, and are connected to the control circuit board60. The space between the support member58and the rear end housing50is provided with a grommet66through which the signal lines from the trigger switch, the operation circuit board, and the display circuit board pass. A space of the rear end housing50in which the control circuit board60is accommodated is sealed by the grommets64and66.

As shown inFIG.3, an air supply port40ais provided in the rear portion of the grip housing40. As shown inFIG.4, a notch56bis provided in the coupling member56. Therefore, when air is sucked from the through hole56aof the coupling member56to the inside of the support rod4, air flows into the grip housing40through the air supply port40a, and air also flows into the through hole56aof the coupling member56from the outside of the coupling member56through the notch56b. That is, when the fan16of the front end unit6rotates in the pole saw2, air flows in from the outside of the grip unit10through the air supply port40a, the air which has flowed into the inside of the grip unit10flows into the support rod4through the notch56band the through hole56aof the coupling member56, the air which has flowed into the support rod4flows through the inside of the support rod4and flows into the front end housing12of the front end unit6, and the air which has flowed into the front end housing12flows through the motor14and then is discharged to the outside of the front end housing12through the discharge port12b.

When the motor14is driven in the pole saw2, the control circuit board60generates heat due to the operation of the switching elements. The heat generated by the control circuit board60is transferred to the support rod4via the heat transfer member62, the support member58, and the coupling member56. Further, the fan16rotates as the motor14is driven, and this generates the air flow from the air supply port40aof the grip unit10to the discharge port12bof the front end unit6. As a result, the coupling member56, the support rod4, and the motor14are cooled thereby. That is, in the pole saw2, the heat generated by the control circuit board60is transferred to the support rod4, and the support rod4is cooled by the cooling air generated by the fan16, as a result of which the control circuit board60can be cooled. In the pole saw2, the control circuit board60is disposed along the up-down direction and the right-left direction. With such a configuration, the heat of the control circuit board60can be easily transferred to the support rod4.

As described above, in one or more embodiments, the pole saw2(an example of electric working machine) includes the support rod4constituted of metal, the saw chain34(an example of tool) disposed at the front end4aof the support rod4, the motor14configured to drive the saw chain34, the control circuit board60(an example of control unit) disposed at the rear end4bof the support rod4and configured to control the motor14, and the coupling member56, the support member58, and the heat transfer member62(an example of heat transfer structure) configured to transfer the heat of the control circuit board60to the support rod4.

According to the above configuration, the heat of the control circuit board60is transferred to the support rod4by the coupling member56, the support member58, and the heat transfer member62. Thus, the support rod4can function as a heat dissipator that dissipates the heat of the control circuit board60. The cooling performance for the control circuit board60can be improved.

In one or more embodiments, the pole saw2further includes the fan16driven by the motor14. The cooling air generated by the fan16flows inside of the support rod4.

According to the above configuration, the support rod4is cooled by the cooling air flowing inside the support rod4. Therefore, an amount of heat dissipated from the control circuit board60via the support rod4can be further increased. The cooling performance for the control circuit board60can be further improved.

In one or more embodiments, the pole saw2further includes the rear end housing50(an example of housing) that accommodates the control circuit board60. The section of the rear end housing50in which the control circuit board60is accommodated is sealed.

According to the above configuration, even when water or dust enters inside of the rear end housing50, the water or dust can be prevented from reaching the control circuit board60.

In one or more embodiments, the pole saw2further includes the grip housing40constituted of resin. The grip housing40is mounted on the support rod4and is configured to be grasped by the user.

In the configuration where the heat of the control circuit board60is transferred to the support rod4by the coupling member56, the support member58, and the heat transfer member62, the support rod4may be at a high temperature. Even when the support rod4is at a high temperature, the grip housing40constituted of resin does not have a temperature as high as the support rod4. According to the above configuration, even when the support rod4is at a high temperature, the user can handle the pole saw2by grasping the grip housing40without directly grasping the support rod4at a high temperature.

In the embodiment described above, the motor14and the fan16are accommodated in the front end unit6, however, the motor14and the fan16may be accommodated in the rear end unit8. In this case, the drive shaft32of the motor14passes through the inside of the support rod4in place of the motor power lines, and a power transmission mechanism including bevel gears is disposed in the front end unit6, by which the sprocket18can be rotated by the motor14.

In the above embodiment, the motor14is a brushless DC motor, however, the motor14may be a DC motor with a brush or another type of motor.

In the above embodiment, electric power is supplied from the battery packs52to the pole saw2, however, electric power may be supplied to the pole saw2via a power cord (not shown) instead of the battery packs52.

In the above embodiment, the electric working machine is the pole saw2and the tool is the saw chain34, however, the electric working machine may be a brush cutter, a mower, a pole hedge trimmer, or the like, and the tool may be a rotary cutting blade, a hedge trimmer, a brush, a sweeper, a mop, or the like.