JP2008068385A - Electric tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric tool in which vibration due to driving of a striker is reduced without increasing the size and deteriorating workability.
SOLUTION: A motor 21 having an output shaft 22, a crank 45 connected to the output shaft 22, and a piston 40 reciprocating by the rotational motion of the crank 45 are converted into reciprocating motion. The motion conversion mechanism 36 and a casing part that accommodates at least a part of the motor 21 and the motion conversion mechanism 36 are provided. A ball balancer 47 having a balancer body 47A having a central axis and a plurality of balls 47C incorporated in the internal space of the balancer body 47A and adjusting the balance of the motion conversion mechanism 36 by the movement of the plurality of balls 47C is provided. A power tool 1 is provided.
[Selection] Figure 1

Description

  The present invention relates to a power tool, and particularly to a power tool having a vibration damping mechanism.

  Conventionally, an electric tool having a vibration damping mechanism has been proposed, and an impact tool having a vibration damping mechanism will be described as an example. In an impact tool comprising a casing comprising a handle part, a motor housing, and a gear housing connected to each other, an electric motor is accommodated in the motor housing, and the gear housing includes a motion conversion housing, a vibration control housing, and an impact housing. ing. A motion conversion mechanism for converting the rotational motion of the electric motor into reciprocating motion is provided in the motion conversion housing. A cylinder extending in a direction orthogonal to the rotation axis of the electric motor is provided in the striking housing. A tool holding portion is provided on the tip side of the cylinder, and the tip tool is detachably attached.

  Further, the cylinder is provided with a piston slidably on its inner periphery. The piston reciprocates along the inner circumference of the cylinder by the motion conversion mechanism. A striker is slidably provided on the inner periphery of the cylinder at the tip side in the cylinder. An air chamber is defined in the cylinder and between the piston and the striker. On the tip side of the striker, an intermediate element is provided in the cylinder so as to be slidable in the front-rear direction. The above-described tip tool is located on the tip side of the meson.

  The vibration damping housing is provided on the side of the impact housing and communicates with the impact housing through an air passage. A space defined by the vibration control housing, the counterweight, the striking housing, the cylinder, and the piston is configured to be a sealed space. A counterweight capable of reciprocating in parallel with the reciprocating direction of the piston and two springs provided at both ends of the counterweight are disposed in the vibration damping housing.

  The rotational driving force of the electric motor is transmitted to the motion conversion mechanism, and the piston reciprocates in the cylinder by the motion conversion mechanism. Due to the reciprocating motion of the piston, the pressure of the air in the air chamber repeatedly rises and falls, giving a striking force to the striker. The striking element moves forward and collides with the rear end of the intermediate element, and the striking force is transmitted to the tip tool via the intermediate element. Thereby, a work material is crushed.

Further, when the piston moves to the front end side during the operation of the electric power tool, the counter weight moves to the rear end side. Conversely, when the piston moves to the rear end side, the counterweight moves to the front end side. In this way, the counterweight is configured to reciprocate in conjunction with the reciprocating motion of the piston (see, for example, Patent Document 1).
JP 2004-299036 A

  However, the power tool generally requires a large number of parts including a cylinder with an expensive machining cost, resulting in an expensive device. In addition, when the damping housing is provided on the side of the impact housing, it is necessary to provide it on both sides of the power tool in order to cancel out the rotational moment that is one of the causes of vibration, which further increases the number of parts. Will be invited. Furthermore, by providing the damping housing above and on the side of the impact housing, the size of the electric tool is increased. Further, the increase in size on the upper side and the side reduces the visibility of the tip tool portion, and improves workability. It was causing a decline.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an electric tool that can effectively reduce vibration caused by driving of a striker at a low cost without causing an increase in size and without deteriorating workability. And

  In order to achieve the above object, the present invention provides a motor having an output shaft that rotates, a rotating portion connected to the output shaft, and a reciprocating portion that reciprocates by the rotating motion of the rotating portion. A reciprocating motion conversion unit that converts the rotational motion of the reciprocating motion into a reciprocating motion, and a casing unit that houses at least a part of the motor and the reciprocating motion converting unit. A space is defined in the reciprocating motion converting unit. Provided is an electric tool provided with a ball balancer that is formed and has a cylindrical portion having a central axis parallel to the rotation axis of the rotating portion and a plurality of balls built in the internal space of the cylindrical portion. .

  The ball is made of a magnetic material, generates a magnetic force to the ball and moves the ball, and controls the magnetic force generated by the magnetic force generator connected to the magnetic force generator. It is preferable to further comprise a control device.

  Moreover, it is preferable that this magnetic force generator is arrange | positioned in the position which opposes at least one part of this cylindrical part in this casing part.

  The magnetic force generator is preferably disposed on the ball balancer.

  The reciprocating motion converting unit includes a hollow cylinder, a piston slidably provided on the inner periphery of the cylinder, a motion converting unit that converts the rotational driving force of the motor into a reciprocating motion of the piston, And a striking element driven by the reciprocating motion of the piston.

  According to the first aspect of the present invention, the power tool has a cylinder centering on an axis parallel to the rotation axis of the rotary motion in the reciprocating motion conversion unit, and a plurality of balls are built in the cylinder, and balance is achieved by movement of the balls. The ball balancer to be adjusted is installed. Therefore, the movement of the ball in the direction to reduce the periodic vibration generated by the reciprocating motion of the reciprocating motion converting portion reduces the vibration due to the reciprocating motion of the reciprocating motion converting portion and improves the operability of the electric tool. Can do.

  According to a second aspect of the present invention, the power tool includes a magnetic force generator, the magnetic force generator includes a control device that controls generation and stop of the magnetic force, and the ball is a magnetic material. Thereby, the movement of the ball can be promoted by generating a magnetic force in accordance with the timing of the reciprocating motion of the reciprocating motion conversion unit. Therefore, the vibration due to the reciprocating motion of the reciprocating motion converting portion can be more reliably reduced. In particular, as described in claim 3, by providing the magnetic force generation device at a position facing at least a part of the cylindrical portion, the position of the ball can be easily controlled, and the reciprocating motion converting portion is reciprocated. Periodic vibration generated by movement can be reduced more effectively. Further, as described in claim 4, even when the magnetic force generator is disposed on the ball balancer, the position of the ball can be easily controlled, and the period generated by the reciprocating motion of the motion converting unit. Vibration can be reduced more effectively.

  According to the electric tool of claim 5, the reciprocating motion conversion unit includes a cylinder and a piston slidably provided on the inner periphery of the cylinder, and a motion converting unit that converts the rotational driving force of the electric motor into the reciprocating motion of the piston. And a striker driven by a reciprocating motion of the piston. Therefore, it is possible to reduce the periodic vibration generated in the electric tool in which the tool main body reciprocally vibrates due to the reciprocating motion of a member having a certain mass such as a striker.

  1st Embodiment which applied the electric tool of this invention to the impact tool is described based on FIG.1 and FIG.2. FIG. 1 is a cross-sectional view of a first embodiment in which the electric tool of the present invention is applied to an impact tool. In the following description, the left side in FIG. 1 is the front end side of the impact tool 1 and the right side is the rear end side of the impact tool 1. The impact tool 1 includes a casing including a handle portion 10, a motor housing 20, and a gear housing 30 that are connected to each other.

  A power cable 11 is attached to the handle portion 10 and a switch mechanism 12 is built therein. A trigger 13 that can be operated by a user is mechanically connected to the switch mechanism 12. The switch mechanism 12 can switch between connection and disconnection of an electric motor 21 and an external power source, which will be described later, by connecting the power cable 11 to an external power source (not shown) and operating the trigger 13. . The handle portion 10 also has a grip portion 14 that is gripped when the user uses the impact tool 1.

  The motor housing 20 is provided at the lower end on the front end side of the handle portion 10. An electric motor 21 is accommodated in the motor housing 20. The electric motor 21 includes an output shaft portion 22 that outputs the rotational driving force. A pinion gear 23 is provided at the tip of the output shaft portion 22 and is located in the gear housing 30. A rotation control device 24 for controlling the rotation speed of the electric motor 21 is disposed in the motor housing 20 on the rear end side of the electric motor 21.

  The gear housing 30 includes a motion conversion housing 31 and a striking housing 32. The motion conversion housing 31 is located on the upper portion of the motor housing 20, and the rear end thereof is connected to the handle portion 10. The striking housing 32 is located on the front side of the motion conversion housing 31 above the motor housing 20.

  A crankshaft portion 33 extending in parallel with the output shaft portion 22 is rotatably supported in the motion conversion housing 31 on the rear end side of the pinion gear 23. A first gear 35 that meshes with the pinion gear 23 is coaxially fixed to the lower end of the crankshaft portion 33. The crankshaft 33 is provided with a motion conversion mechanism 36.

  The motion conversion mechanism 36 includes a counterweight 34, a crankpin 37, a connecting rod 38, a crank 45, a crankshaft 46, and a ball balancer 47.

  The counterweight 34 is fixed to the upper end of the crankshaft portion 33. The crank pin 37 has one end fixed to the end of the counterweight 34 and the other end fixed to the crank 45. The crankpin 37 is arranged so that the central axis from one end side to the other end side is parallel to the rotation axis of the crankshaft portion 33 and is different from the other axis. The connecting rod 38 is connected to the crank pin 37 at the rear end portion and connected to a piston pin 41 described later at the front end portion. The connecting rod 38 is rotatable around the central axis with respect to the crankpin 37 at this connection location. The crank 45 is connected to the crankshaft portion 33 via a crankpin 37. The crankshaft 46 is fixed to the crank 45, and extends upward from the crank 45 on the same axis as the crankshaft portion 33. The crankshaft 46 is rotatably supported by the motion conversion housing 31.

  The ball balancer 47 is fixed to the crankshaft 46. The ball balancer 47 includes a balancer body 47A, a balancer cover 47B, and a plurality of balls 47C. The balancer body 47A is configured in a cylindrical shape having a bottom wall, and the bottom wall is fixed to the crankshaft portion 33 so that the central axis of the cylinder is coaxial with the rotation axis of the crankshaft portion 33. ing. The ball 47C is built in the balancer body 47A and can freely move. The balancer cover 47B is disposed on the opposite bottom wall side of the balancer body 47A, and encloses the ball 47C in the balancer body 47A.

  A rotation transmission shaft portion 51 extending in parallel with the output shaft portion 22 is rotatably supported in the motion conversion housing 31. A second gear 52 that meshes with the pinion gear 23 is coaxially fixed to the lower end of the rotation transmission shaft portion 51. A first bevel gear 51 </ b> A is coaxially fixed to the upper end of the rotation transmission shaft portion 51.

  A cylinder 39 extending in a direction orthogonal to the output shaft portion 22 is provided in the impact housing 32. The central axis of the cylinder 39 and the rotation axis of the output shaft portion 22 are located on the same plane. The rear end portion of the cylinder 39 faces the electric motor 21. A piston 40 is provided in the cylinder 39 so as to be slidable on the inner periphery thereof.

  The piston 40 has a piston pin 41 at its rear end, and the tip of the connecting rod 38 is inserted into the piston pin 41. A striker 42 is provided on the tip side in the cylinder 39 so as to be slidable with the inner periphery of the cylinder 39. An air chamber 43 is defined in the cylinder 39 and between the piston 40 and the striker 42.

  A rotating cylinder 50 is rotatably supported in the impact housing 32 so as to cover the outer periphery of the cylinder 39. The rotary cylinder 50 extends to the front end side of the cylinder 39, and a tool holding portion 15 is provided at the front end portion thereof so as to be movable in the front-rear end direction, so that a front end tool (not shown) can be detachably attached. A spring 15 </ b> A is interposed between the tool holding portion 15 and the striking housing 32, and the tool holding portion 15 is biased toward the front end side with respect to the striking housing 32 by the spring 15 </ b> A. Therefore, when the tip tool not shown is pressed against the non-cutting material, the tool holding unit 15 and the striking housing 32 are configured to approach each other.

  A second bevel gear 50A that meshes with the first bevel gear 51A is provided at the rear end of the rotating cylinder 50. The central axis of the rotating cylinder 50 and the rotating shaft of the output shaft portion 22 are located on the same plane. Further, an intermediate element 44 is provided in the rotary cylinder 50 so as to be slidable in the front-rear direction on the tip side of the striker 42.

  Next, the operation of the impact tool 1 according to the first embodiment will be described. With the handle portion 10 held by hand, a tip tool (not shown) is pressed against a workpiece (not shown). Next, the trigger 13 is pulled, and electric power is supplied to the electric motor 21 to rotate. This rotational driving force is transmitted to the crankshaft 33 through the pinion gear 23 and the first gear 35. The rotation of the crankshaft 33 is converted into a reciprocating motion of the piston 40 in the cylinder 39 by the motion conversion mechanism 36. Due to the reciprocating motion of the piston 40, the pressure of the air in the air chamber 43 repeatedly rises and falls, giving a striking force to the striking element 42. The striking element 42 moves forward and collides with the rear end of the intermediate element 44, and the striking force is transmitted to the tip tool (not shown) via the intermediate element 44.

  Further, the rotational driving force of the electric motor 21 is transmitted to the pinion gear 23, the second gear 52, and the rotation transmission shaft portion 51. The rotation of the rotation transmission shaft portion 51 is transmitted to the rotation cylinder 50 via the first bevel gear 51A and the second bevel gear 50A, and the rotation cylinder 50 rotates. A rotational force is applied to the tip tool by the rotation of the rotary cylinder 50. By this rotational force and the above-described impact force, a rotational force and impact force are imparted to the tip tool (not shown), and the work material is crushed.

  Next, the behavior of the ball balancer 47 during operation of the impact tool 1 according to Embodiment 1 will be described with reference to FIG. FIG. 2 is a schematic diagram for explaining the operation of the first embodiment in which the electric tool of the present invention is applied to a striking tool, and is a view of the striking tool 1 of FIG. 1 as viewed from above. Here, in order to make the operation easy to understand, each part has a simple shape, each support portion is omitted, and the operation is exaggerated. Further, the center line in FIG. 2 indicates the position of the center axis of the crankshaft portion 33.

  FIG. 2A shows a state where the counterweight 34 is at the bottom dead center, which is an initial state. In this initial state, the striker 42 is moving from the bottom dead center side to the top dead center side. FIG. 2B shows a state in which the counterweight 34 is rotated 90 degrees from the bottom dead center, and the piston 40 moves to the tip side, and the pressure in the air chamber 43 becomes maximum. As the pressure in the air chamber 43 increases, the striker 42 starts to move toward the tip side. At this time, the reaction force to the piston 40 becomes maximum, and this tries to move the impact tool 1 itself to the rear end side via the connecting rod 38 and the crankshaft portion 33. Since the ball balancer 47 also moves toward the rear end side simultaneously with the impact tool 1, this corresponds to the fact that the radius of the balancer body 47A extends toward the rear end side of the impact tool 1, and the ball 47C starts moving toward the rear end side due to centrifugal force. To do. Accordingly, as shown in FIG. 2C, the striker 42 and the ball 47C move in opposite phases. Thereafter, the ball 47C descends as the impact tool 1 descends, and returns to the initial state as shown in FIG. As described above, when the striker 42 and the ball 47C move in substantially opposite phases, vibration due to the reciprocating motion of the striker can be reduced.

  Further, since the striker 42 does not reciprocate during no-load operation, no load is generated due to the reciprocation. At this time, since the ball 47C moves to a position where the unbalance of the rotating parts of the motion conversion mechanism 36 such as the counterweight 34, the crank 45, or the ball balancer 47 is corrected, vibration during no-load operation can be reduced. is there.

  In the first embodiment, it is possible to reduce a constant period of vibration caused by the reciprocating motion during the actual load operation of the impact tool 1, and also reduce vibration due to unbalance of the rotating parts during the no load operation. it can.

  Next, a second embodiment in which the electric tool of the present invention is applied to an impact tool will be described with reference to FIGS. FIG. 3 is a cross-sectional view of a second embodiment in which the electric tool of the present invention is applied to an impact tool. In addition, about the same member as 1st embodiment, the same number is attached | subjected and description is abbreviate | omitted and only a different part is demonstrated.

  In the impact tool 2, the ball 47C is made of a magnetic material. An electromagnet 53 is disposed in the motion conversion housing 31 so as to face the balancer body 47 on the rear end side of the balancer body 47A. A magnetic force control device 54 that controls the magnetic force is connected to the electromagnet 53, and the magnetic force control device 54 is connected to the switch mechanism 12.

  A gap sensor 56 is connected to the magnetic force control device 54 by a lead wire (not shown). The gap sensor 56 is disposed in the motion converting housing 31 at a position facing the counterweight 34 at the substantially rear end portion. As shown in FIG. 4A, the counter weight 34 is about ¼ of the outer peripheral portion thereof, specifically, a position facing the gap sensor 56 of the counter weight 34 (C ) Is provided from the position where the piston 40 is at the bottom dead center to the position when the piston 40 is moved to the substantially central portion between the top dead center and the bottom dead center in FIG. ing. Therefore, the voltage is output from the gap sensor 56 only while facing the protrusion 34A shown in FIGS. 4C and 4D, and at the position shown in FIGS. 4A and 4B, the gap sensor 56 is output. Does not output voltage.

  The magnetic force control device 54 is also connected to the switch mechanism 12 with a lead wire (not shown) so that the current flowing through the switch mechanism 12 can be detected. By detecting this current, the magnetic force control device 54 detects whether the impact tool 2 is in an actual load state or an unloaded state.

  Next, regarding the operation of the second embodiment, differences from the first embodiment will be described with reference to FIGS. First, in the magnetic force control device 54, the current flowing through the switch mechanism 12 is detected to detect whether it is an actual load state or a no-load state. When the detection result is an actual load state, a magnetic force is generated in the electromagnet 53 according to the output voltage of the gap sensor 56. The protruding portion 34A of the counterweight 34 extends from the position where the striker 42 starts moving toward the tip side (FIG. 4C) to the position where the striker 42 collides with the intermediate element 44 (FIG. 4D). Therefore, the voltage is output from the gap sensor 56 only during this period. The magnetic force control device 54 causes the electromagnet 53 to generate a magnetic force only when there is an output voltage of the gap sensor 56. Thereby, the ball 47C is in a phase opposite to that of the striker 42, and vibration can be reduced.

  During no-load operation, the gap sensor 56 has no voltage output and does not generate a magnetic force. Therefore, as in the first embodiment, the ball 47C moves to a position where the unbalance of the rotating parts of the motion conversion mechanism 36 is corrected, and vibration occurs. Can be reduced.

  Next, a third embodiment in which the electric tool of the present invention is applied to an impact tool will be described with reference to FIGS. In addition, about the same member as 1st embodiment and 2nd embodiment, the same number is attached | subjected and description is abbreviate | omitted and only a different part is demonstrated.

  As shown in FIG. 5, the electromagnet 53 is fixed to the outer peripheral surface of the balancer body 47 </ b> A, and the balancer body 47 </ b> A is fixed to the crankshaft 46 so that the position of the electromagnet 53 is opposite to the crank 45. The balancer cover 47B is made of an insulating material, and as shown in FIG. 6, an inner ring 57 and an outer ring 58 made of a conductor are arranged on the upper surface thereof, and are fixed coaxially with the rotation axis of the ball balancer 47. Has been. One end of a coil (not shown) constituting the electromagnet 53 is connected to the inner ring 57 and the other end is connected to the outer ring 58.

  As shown in FIG. 5, an inner terminal 59 is provided at a position facing the inner ring 57 provided on the balancer cover 47 </ b> B in the motion conversion housing 31, and at a position facing the outer ring 58. Is provided with an external terminal 60. The inner terminal 59 and the outer terminal 60 are extended toward the inner ring 57 and the outer ring 58, respectively, and their extending direction tips are slidably contacted with the inner ring 57 and the outer ring 58, respectively. Yes.

  The inner terminal 59 and the outer terminal 60 are connected to the magnetic force control device 54 by conducting wires (not shown). Similarly to the second embodiment, the switch mechanism 12 is connected to the magnetic force control device 54 by a conducting wire (not shown), and the current flowing through the switch mechanism 12 can be detected. By detecting this current, it is detected whether the impact tool 3 is in an actual load state or an unloaded state. The magnetic force control device 54 detects the current flowing through the switch mechanism 12 to determine whether it is an actual load state or an unloaded state, and generates a magnetic force in the electromagnet 53 during the actual load operation, and does not generate a magnetic force during the no-load operation. It is set to.

  During actual load operation, a magnetic force is generated from the electromagnet 53 based on the current detected by the switch mechanism 12, so that the ball 47C is always concentrated at the position of the electromagnet 53 as shown in FIGS. 7 (A) to 7 (D). To do. Accordingly, as shown in FIGS. 7B to 7C, the ball 47C moves to the rear end side when the striker 42 moves to the front end side, so that the load by the striker 42 is reduced and vibration is generated. Can be reduced.

  In addition, since the electromagnet 53 does not generate a magnetic force during no-load operation, the ball 47 moves to a position for correcting the unbalance of the rotating parts of the motion conversion mechanism 36 as in the second embodiment, and during no-load operation. It is also possible to reduce the vibration. In particular, since the ball 47C moves to the opposite side of the electromagnet 53 so as to correct the unbalance caused by providing the electromagnet 53 in the balancer body 47A, unbalanced vibration due to the electromagnet 53 does not occur.

  The striking element 42 during the actual load operation is a periodic motion, and is pushed out when the piston 40 comes to a predetermined position. Therefore, the ball 47C is fixed so as to move in the opposite direction to the striking element 42, so that the reciprocating motion The load due to can be reduced, and vibration can be reduced. Further, during the no-load operation, the striker 42 does not reciprocate, so that the ball 47C can be moved freely to move to a position where the unbalance is canceled, and vibration can be reduced.

  The power tool of the present invention is effective for a power tool that generates periodic vibrations. In the above embodiment, the power tool is applied to a striking tool. For example, the power tool can be used for another power tool having a reciprocating mechanism such as a saver saw. You may apply.

  In the first to third embodiments, the ball balancer 47 is mounted on the crankshaft 46, but the same effect can be obtained by mounting it on the crankshaft portion 33. Further, the dimensions and materials of the balancer body 47A and the dimensions, materials and number of the balls 47 are appropriately selected according to the product so as to reduce the load fluctuation generated by the motion conversion mechanism 36. Further, in the second embodiment and the third embodiment, the magnetic load control device 54 detects the actual load state and the no-load state of the striking tool based on the current of the switch mechanism 12, but the present invention is not limited to this. For example, the actual load state and the no-load state of the impact tool may be detected by the magnetic force control device 54 based on the current flowing through the rotation control device 24.

  The present invention can be applied to any electric tool having a reciprocating mechanism such as an electric hammer driven by an electric motor.

Sectional drawing of the electric tool which concerns on 1st embodiment of this invention. The schematic diagram explaining operation | movement of the electric tool which concerns on 1st embodiment of this invention. Sectional drawing of the electric tool which concerns on 2nd embodiment of this invention. The schematic diagram explaining operation | movement of the electric tool which concerns on 2nd embodiment of this invention. Sectional drawing of the electric tool which concerns on 3rd embodiment of this invention. The partial detailed perspective view showing the balancer cover periphery of the electric tool which concerns on 3rd embodiment of this invention. The schematic diagram explaining operation | movement of the electric tool which concerns on 3rd embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 .... Impact tool 2 .... Impact tool 10 .. Handle part 11 .. Power supply cable 12 .. Switch mechanism 13 .. Trigger 14 .... Grip part 15 .... Tool holding part 15A ... Spring 20 ... Motor housing 21 · · Electric motor 22 · · Output shaft portion 23 · · Pinion gear 24 · · Rotation control device 30 · · Gear housing 31 · · Motion conversion housing 32 · · Stroke housing 33 · · Crankshaft portion 34 · · Counterweight 34A · · · Projection 35 ·· First gear 36 · · Motion conversion mechanism 37 · · Crank pin 38 · · Connecting rod 39 · · Cylinder 40 · · Piston 41 · · Piston pin 42 · · Stroke 43 · · Air chamber 44 · · Intermediate 45 ·· Crank 46 · · Crankshaft 47 · · Ball balancer 47A · · Balancer body 47B · · Balancer cover -47C · · Ball 50 · · Rotary cylinder 50A · · Second bevel gear 51 · · Transmission shaft 51A · · First bevel gear 52 · · Second gear 53 · · Electromagnet 54 · Magnetic control device 56 · Gap sensor 57 · · Inner ring 58 · · Outer ring 59 · · Inner terminal 60 · · Outer terminal

Claims (5)

A motor having an output shaft for rotational movement;
A reciprocating motion conversion unit that has a rotating part connected to the output shaft and a reciprocating part that reciprocates by the rotating motion of the rotating part, and converts the rotating motion of the output shaft into a reciprocating motion;
A casing portion that houses at least a part of the motor and the reciprocating motion conversion portion;
The reciprocating motion conversion unit has a space defined therein and a cylindrical part having a central axis parallel to the rotation axis of the rotating part, and a plurality of balls built in the internal space of the cylindrical part, A power balance is provided with a ball balancer. The ball is made of a magnetic material,
A magnetic force generator capable of generating a magnetic force on the ball and moving the ball;
The power tool according to claim 1, further comprising a control device that is connected to the magnetic force generation device and controls a magnetic force generated from the magnetic force generation device.   The power tool according to claim 2, wherein the magnetic force generator is disposed at a position facing at least a part of the cylindrical portion in the casing portion.   The power tool according to claim 2, wherein the magnetic force generator is disposed on the ball balancer.   The reciprocating motion converting unit includes a hollow cylinder, a piston slidably provided on the inner periphery of the cylinder, a motion converting unit that converts a rotational driving force of the motor into a reciprocating motion of the piston, An electric power tool according to any one of claims 1 to 4, further comprising an impactor driven by a reciprocating motion of a piston.

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