Power tool

Abstract

The electric power tool of the present application has a motor, an eccentric shaft, a motion conversion mechanism, and a balancer, wherein the motor has a rotating shaft; the eccentric shaft extends from one end of the rotating shaft and rotates around a center axis of rotation at a position radially offset from the center axis of rotation; the motion conversion mechanism converts one cycle of rotational motion of the eccentric shaft into oscillating motion that reciprocates the tip tool once; and the balancer rotates together with the rotating shaft. When viewed along the center axis of rotation, the center of gravity of the balancer is located on the opposite side of the center axis of the eccentric shaft, i.e., the eccentric axis, from an imaginary vertical line that intersects perpendicularly with a first imaginary straight line passing through the eccentric axis and the center axis of rotation and that passes through the center axis of rotation, and a second imaginary straight line passing through the center axis of rotation and the center of gravity of the balancer is inclined at an inclination angle greater than 0° and less than 90° in the direction opposite to the direction of rotation of the rotating shaft. Accordingly, vibration of the electric power tool can be suppressed.

Description

TECHNICAL FIELD

[0001] The present application relates to a power tool. BACKGROUND

[0002] A power tool is known in which a tip tool is swung by a motor to process a workpiece. For example, a power tool is disclosed in Patent Literature 1 below, in which an eccentric shaft is connected to an output shaft of a motor in a manner eccentric to the output shaft of the motor, and the tip tool is swung by an eccentric rotation of the eccentric shaft. In the power tool of Patent Literature 1, a balancer for adjusting the position of the center of gravity is attached to the output shaft of the motor to reduce the vibration of the power tool during driving due to the centrifugal force generated in the eccentric rotation of the eccentric shaft.

[0003] [Related Art Literature]

[0004] [Patent Literature]

[0005] Patent Literature 1: Japanese Patent Application Publication No. 2015-229223 SUMMARY

[0006] [Problems to be Solved by the Invention]

[0007] However, the inventors of the present application have found that even when a balancer is used as in Patent Literature 1, when the tip tool, which is swung by being driven, comes into contact with the workpiece, a resistance acting in a direction to suppress the swing of the tip tool is generated between the workpiece and the tip tool, and due to the action of this resistance, the vibration of the power tool sometimes becomes large. Thus, in the power tool in which the tip tool is swung, there is still room for improvement in suppressing the vibration of the power tool generated in the process of processing the workpiece.

[0008] [Means for Solving the Problems]

[0009] One aspect of the present application provides an electric power tool that processes a workpiece by driving a tip tool to oscillate. The electric power tool of this aspect has a motor, an eccentric shaft, a motion conversion mechanism, and a balancer. The motor has a rotating shaft that is rotationally driven in one direction. The eccentric shaft extends from one end of the rotating shaft and is configured to perform rotational motion centered on a rotational center axis at a position that is offset in a radial direction from the rotational center axis of the rotating shaft, where the radial direction is orthogonal to the rotational center axis. The motion conversion mechanism connects the tip tool and the eccentric shaft and is configured to convert one cycle of rotational motion of the eccentric shaft into oscillation motion that reciprocates the tip tool once. The balancer is disposed on the outer periphery of the rotating shaft and is configured to rotate together with the rotating shaft. When viewed along the rotational center axis, the center of gravity of the balancer is located in a region on the opposite side of an eccentric axis from an imaginary perpendicular line, where the eccentric axis is the center axis of the eccentric shaft, the imaginary perpendicular line perpendicularly intersects a first imaginary straight line that passes through the eccentric axis and the rotational center axis, and passes through the rotational center axis. When viewed along the rotational center axis, a second imaginary straight line that passes through the rotational center axis and the center of gravity of the balancer is inclined at an inclination angle greater than 0° and less than 90° in a direction opposite to the direction of rotation of the rotating shaft with respect to the first imaginary straight line.

[0010] According to the electric power tool of this aspect, the centrifugal force generated in conjunction with the rotational motion of the balancer is generated in a direction that counteracts the resistance that increases in synchronization with the period in which the tip tool oscillates and contacts the workpiece. Thus, it is possible to suppress an increase in vibration of the electric power tool due to the resistance generated between the tip tool and the workpiece during processing of the workpiece. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 is a cross-sectional view of the electric power tool taken through a cross-sectional plane that passes through the rotational center axis RX and the drive axis DX.

[0012] Figure 2 is a partial cross-sectional view of the tip region 2 shown in Figure 1 extracted.

[0013] Figure 3 is a partial cross-sectional view of the electric power tool taken along a cross-section indicated by 3-3 in Figure 2 extracted.

[0014] Figure 4 is a perspective view of the balancer.

[0015] Figure 5 is a perspective exploded view of the connecting arm of the rotational drive mechanism and the motion conversion mechanism.

[0016] Figure 6 is a perspective view of the connecting arm of the rotational drive mechanism and the motion conversion mechanism.

[0017] Figure 7 is a schematic view when a balancer mounted to a rotation shaft is viewed along a rotation center axis RX.

[0018] Figure 8 is a first schematic view showing a case where a tip tool is swung by rotation of a rotation shaft.

[0019] Figure 9 is a second schematic view showing a case where a tip tool is swung by rotation of a rotation shaft.

[0020] Figure 10 is a third schematic view showing a case where a tip tool is swung by rotation of a rotation shaft.

[0021] Figure 11 is a fourth schematic view showing a case where a tip tool is swung by rotation of a rotation shaft.

[0022] [Legend]

[0023] 10: power tool; 11: housing; 20: power supply portion; 22: power supply cord; 25: control circuit; 27: operation portion; 28: speed change operation portion; 30: rotation driving mechanism; 31: motor; 32: rotation shaft; 32s: notch wall surface; 33: rotor; 34: stator; 36: fan; 37: front side bearing portion; 38: rear side bearing portion; 40: eccentric shaft; 45: balancer; 50: motion conversion mechanism; 52: bearing; 53: connecting arm; 54: ring-shaped portion; 55: pair of arm portions; 60: main shaft; 62: tool mounting portion; 63: lower end opening; 65: protrusion portion; 66: clamping member; 67: coil spring; 68: operation lever; 70: main shaft holding mechanism; 73: first bearing portion; 75: elastic member; 76: second bearing portion; 80: base portion; 81: through-hole; 82: outer edge portion; 83: convex portion; 84: rounded portion; 85: notch portion; 86: washer; 87: snap ring; 100: tip tool; 102: through-hole; 103: fitting hole; 110: fastening shaft; 112: head portion; CF: arrow indicating direction of action of centrifugal force; CG: center of gravity; DX: driving axis; EF: centrifugal force of eccentric shaft; EX: eccentric axis; GA: region; Ll: first imaginary straight line; L2: second imaginary straight line; OD: swinging direction; RD: rotation direction; RE, REa: arrow indicating direction of action of resistance; RX: rotation center axis; SA: swinging range; VL: imaginary vertical line. DETAILED DESCRIPTION

[0024] In one or more embodiments of the present application, the balancer of the power tool can have a shape that is asymmetric with respect to the first imaginary straight line when viewed along the rotation center axis. According to the power tool of this structure, the center of gravity of the balancer can be more easily set at a position where the second imaginary straight line is inclined with respect to the first imaginary straight line.

[0025] In one or more embodiments of the present application, the balancer of the power tool can have a base portion and a protruding portion, wherein the base portion is penetrated by the rotation axis in the thickness direction, and the protruding portion protrudes from a side surface of the base portion in the direction along the rotation center axis. According to the power tool of this structure, the weight of the balancer can be increased by an amount corresponding to the protruding portion, and thus the centrifugal force for canceling the resistance generated between the tip tool and the workpiece can be further increased. Therefore, the vibration of the power tool due to the resistance generated between the tip tool and the workpiece during the machining of the workpiece can be more effectively suppressed from becoming large. In addition, according to the power tool of this structure, since the weight of the balancer can be increased by providing the protruding portion, the weight of the balancer can be increased even without increasing the radial dimension of the balancer. Furthermore, according to the power tool of this structure, the space of the side surface of the base portion of the balancer can be effectively used as a configuration region of the protruding portion, and thus a dead angle can be suppressed from being generated in the power tool.

[0026] In one or more embodiments of the present application, the protruding portion can be provided at an outer edge portion of the base portion that is farthest from the rotation center axis in the radial direction, or at a position of the base portion that is farther from the rotation center axis than the outer edge portion (a position closer to the rotation center axis and the outer edge portion among the outer edge portions). According to the power tool of this structure, since the center of gravity of the balancer can be easily set at a position farther from the rotation center axis, the centrifugal force generated by the rotational movement of the balancer can be more easily increased. Therefore, the vibration of the power tool during the machining of the workpiece can be more effectively suppressed from becoming large.

[0027] In one or more embodiments of the present application, the inclination angle of the second imaginary straight line with respect to the first imaginary straight line can be greater than 10 degrees and less than 60 degrees. According to the power tool of this structure, the period in which the resistance generated between the tip tool and the workpiece during the machining of the workpiece becomes large and the period in which the centrifugal force generated by the rotation of the balancer in the direction of canceling the resistance becomes large can be made closer. Therefore, the vibration of the power tool during the machining of the workpiece can be more effectively suppressed from becoming large.

[0028] In one or more embodiments of the present application, the power tool can further have a housing. The housing can house the motor, the eccentric shaft, the motion conversion mechanism, and the balancer. The motion conversion mechanism can have a main shaft and a connecting arm. The main shaft can be configured to have a tool mounting portion at an end portion where the tip tool is mounted, and to swing the tip tool by reciprocating rotation in the circumferential direction. The connecting arm can be configured to have one end fixed to the main shaft and the other end connected to the eccentric shaft, and to reciprocate rotation in the circumferential direction about the main shaft as a fulcrum by the rotational motion of the eccentric shaft. The main shaft can be supported so as to be able to reciprocate rotation in the circumferential direction by a first bearing portion and a second bearing portion, wherein the first bearing portion is provided inside the housing, and the second bearing portion is provided inside the housing between the first bearing portion and the tool mounting portion. The first bearing portion can be held to the housing by an elastic member. According to the power tool of this structure, since the vibration of the main shaft due to the swinging of the tip tool can be absorbed by the elastic member, the vibration transmitted to the housing via the main shaft can be suppressed. Therefore, the vibration of the power tool during processing of the workpiece can be further suppressed from becoming large.

[0029] In one or more embodiments of the present application, the second bearing portion can be configured by a ball bearing. According to the power tool of this structure, the main shaft is easily moved about the balls of the second bearing portion as rolling elements. Therefore, the vibration of the main shaft due to the swinging of the tip tool can be easily absorbed by the elastic member holding the first bearing portion, and thus the vibration due to the swinging of the tip tool can be further suppressed from being transmitted to the housing.

[0030] In one or more embodiments of the present application, the motor can be disposed in a posture in which the center axis of rotation intersects with the axis that becomes the fulcrum of the swinging of the tip tool. According to the power tool of this structure, the motor can be disposed in a manner such that the rotational axis of the motor is in a transverse posture with respect to the axis that becomes the fulcrum of the swinging of the tip tool.

[0031] Hereinafter, representative and non-limiting embodiments of the present application will be specifically described with reference to the drawings.

[0032] Referring to Figures 1-3 , the general structure of the power tool 10 of the present embodiment will be described. The power tool 10 is an example of a power-driven work tool that processes a workpiece not shown by driving the tip tool 100 to swing. As shown in Figure 1 , the power tool 10 has an elongated shape, and a tip tool 100 is mounted at one end in the length direction thereof. The tip tool 100 can be detached and replaced with respect to the power tool 10. As shown in Figure 1 and Figure 2 , the tip tool 100 is mounted to the lower end portion of the main shaft 60 described later, and as shown in Figure 3As shown, the power tool 10 swings the tip tool 100 about the spindle 60 as a fulcrum.

[0033] The power tool 10 is also called a so-called multi-purpose tool. In the power tool 10, a plurality of tip tools 100 are prepared, and a user can select an arbitrary tip tool 100 according to a kind of processing to be performed on a workpiece and install it in the power tool 10. As the tip tool 100, for example, there are tools in which a tip portion or an outer peripheral portion comes into contact with a workpiece to perform processing, such as a blade, a scraper, a polishing pad, and the like. As the processing performed on the workpiece using these tip tools 100, for example, there are cutting, peeling, polishing, and the like.

[0034] In Figures 1-3 , a state in which a long blade in which a cutting tooth is formed at a tip portion is installed as an example of a tip tool 100 used mainly for cutting processing in the power tool 10 is exemplified. In each of the drawings referred to in the following description, a blade is also illustrated as an example of the tip tool 100, but the tip tool 100 installed in the power tool 10 is not limited to the blade.

[0035] Hereinafter, in addition to Figures 1-3 , the structure of the power tool 10 will be described in detail with reference to other drawings in order.

[0036] Here, for convenience of explanation, as directions related to the power tool 10, three directions that are orthogonal to each other, that is, a "front-rear direction", an "up-down direction", and a "left-right direction" are defined as follows. In each of the drawings referred to in the following description, Figure 1 , the direction along the length direction of the power tool 10 is defined as the "front-rear direction". In the front-rear direction of the power tool 10, the one end side on which the tip tool 100 is installed is defined as the "front side", and the other end side opposite thereto is defined as the "rear side". In each of the drawings referred to in the following description, Figure 1 and Figure 2 , the direction along the center axis DX of the spindle 60 on which the tip tool 100 is installed is defined as the "up-down direction". In the spindle 60, the one end side on which the tip tool 100 is installed is defined as the "lower side", and the other end side opposite thereto is defined as the "upper side". In each of the drawings referred to in the following description, Figure 3 , the direction orthogonal to the above-described front-rear direction and up-down direction is defined as the "left-right direction". Arrows indicating the front-rear direction, the up-down direction, and the left-right direction are also appropriately illustrated in each of the drawings referred to in the following description in a manner corresponding to Figures 1-3 .

[0037] With reference to Figure 1The electric power supply portion 20 is provided at the rear end portion of the housing 11. The electric power supply portion 20 has a function as a power supply portion of the electric power tool 10. In the present embodiment, the electric power supply portion 20 is connected with a power supply cord 22 extending from the rear end portion of the housing 11, and supplies electric power inputted from an external power supply through the power supply cord 22 to the rotary drive mechanism 30. In other embodiments, the electric power tool 10 can be configured so that a chargeable battery can be attached to and detached from the housing 11, and the electric power supply portion 20 is configured to supply electric power of the battery to the rotary drive mechanism 30.

[0038] The electric power supply portion 20 is provided at the rear end portion of the housing 11. The electric power supply portion 20 has a function as a power supply portion of the electric power tool 10. In the present embodiment, the electric power supply portion 20 is connected with a power supply cord 22 extending from the rear end portion of the housing 11, and supplies electric power inputted from an external power supply through the power supply cord 22 to the rotary drive mechanism 30. In other embodiments, the electric power tool 10 can be configured so that a chargeable battery can be attached to and detached from the housing 11, and the electric power supply portion 20 is configured to supply electric power of the battery to the rotary drive mechanism 30.

[0039] The electric power supply portion 20 has a control circuit 25 configured to control electric power supplied to the rotary drive mechanism 30. The control circuit 25 functions as a controller that controls driving of the electric power tool 10. The control circuit 25 controls start / stop of electric power supply to the rotary drive mechanism 30 in accordance with on / off operation of a slide-type operation portion 27 provided on the upper surface of the housing 11 by a user. In addition, the control circuit 25 controls the rotation speed of a motor 31 of the rotary drive mechanism 30 by controlling electric power supplied to the motor 31. In the electric power tool 10, a dial-type speed change operation portion 28 operated by a user is provided at the lower end of the rear end portion of the housing 11. The control circuit 25 changes electric power supplied to the motor 31 in accordance with the rotation angle of the speed change operation portion 28, and controls the rotation speed of the motor 31. In the electric power tool 10, the speed of oscillation of the tip tool 100 is changed in accordance with the rotation speed of the motor 31.

[0040] The rotary drive mechanism 30 has the motor 31, an eccentric shaft 40, and a balancer 45. The motor 31 corresponds to a driving power source of the electric power tool 10, and is driven by electric power supplied from the electric power supply portion 20. In the present embodiment, a commutator motor is employed as the motor 31. In other embodiments, a brushless DC motor can be employed as the motor 31. The motor 31 has a rotation shaft 32 corresponding to an output shaft that outputs a rotary driving force, a rotor 33 fixed around the rotation shaft 32, and a stator 34 disposed so as to surround the rotor 33.

[0041] The rotary shaft 32 is composed of a cylindrical member made of metal. The rotary shaft 32 is disposed in the substantially central portion of the housing 11 in the front-rear direction. The top end portion and the rear end portion of the rotary shaft 32 extend from the stator 34. The rotary shaft 32 is driven to rotate within the stator 34 together with the rotor 33 by electromagnetic force. The rotational center axis RX of the rotary shaft 32 coincides with the central axis of the rotary shaft 32. In the power tool 10, only the rotary shaft 32 is driven to rotate in a predetermined direction. On the rotary shaft 32, a fan 36 is provided in front of the stator 34, which rotates together with the rotary shaft 32 to generate an airflow for heat dissipation.

[0042] The rotary shaft 32 is rotatably supported by a front bearing portion 37 and a rear bearing portion 38 fixed to predetermined positions within the housing 11. The front bearing portion 37 and the rear bearing portion 38 are composed of, for example, ball bearings. The front bearing portion 37 supports the top end portion of the rotary shaft 32 extending forward from the stator 34. The front bearing portion 37 is provided at a position further forward than the fan 36. The rear bearing portion 38 supports the rear end portion of the rotary shaft 32 extending rearward from the stator 34.

[0043] Referring to Figure 2 and Figure 3 The eccentric shaft 40 is composed of a substantially cylindrical member made of metal having a smaller diameter than the rotary shaft 32. The eccentric shaft 40 is connected to the rotary shaft 32 as one body and extends forward from the top end, which is one end of the rotary shaft 32, at a position radially offset from the rotational center axis RX. The "radial direction" refers to a direction orthogonal to the rotational center axis RX. Hereinafter, the central axis of the eccentric shaft 40 will also be referred to as the "eccentric axis EX". The eccentric axis EX is substantially parallel to the rotational center axis RX. In addition, in the Figure 3 , the rotational center axis RX and the eccentric axis EX overlap in the up-down direction. The eccentric shaft 40 is driven to rotate by the rotation of the rotary shaft 32 by the motor 31 at a position radially offset from the rotational center axis RX to perform a rotational motion about the rotational center axis RX. As will be described later, in the power tool 10, the top tool 100 is swung by this eccentric rotational motion of the eccentric shaft 40.

[0044] The balancer 45 is a counterweight provided on the outer periphery of the rotary shaft 32 and rotates together with the rotary shaft 32. The balancer 45 is fixed to the rotary shaft 32 between the eccentric shaft 40 and the front bearing portion 37. The center of gravity of the balancer 45 is set at a position radially offset from the center of rotation axis RX. The center of gravity of the balancer 45 is adjusted so that centrifugal force is generated in a direction to cancel the centrifugal force generated by the eccentric rotation of the eccentric shaft 40, by the rotation of the balancer 45 when the motor 31 is driven. In addition, the center of gravity of the balancer 45 is adjusted so that centrifugal force is generated in a direction to reduce the resistance generated between the tip tool 100 and the workpiece when the power tool 10 is machining the workpiece, by the rotation of the balancer 45 when the motor 31 is driven. The shape of the balancer 45, the center of gravity, and the effects obtained by the center of gravity will be described later in detail.

[0045] Referring to Figure 2 and Figure 3 The motion conversion mechanism 50 is configured to connect the tip tool 100 and the eccentric shaft 40 and convert the one-cycle rotation of the eccentric shaft 40 into the oscillation of the tip tool 100 once. The motion conversion mechanism 50 has a bearing 52, a connecting arm 53, and a main shaft 60.

[0046] The bearing 52 is installed around the outer periphery of the eccentric shaft 40 as a medium to connect the eccentric shaft 40 and the connecting arm 53. The bearing 52 is configured by, for example, a ball bearing. By providing the bearing 52, the friction generated between the eccentric shaft 40 and the connecting arm 53 when the eccentric shaft 40 performs eccentric rotation is reduced. In the present embodiment, the outer peripheral surface of the bearing 52 is curved in a spherical shape so that the central portion of the bearing 52 in the direction along the center axis protrudes to the outside in the radial direction orthogonal to the center axis. The bearing having such a curved outer peripheral surface is also called a sphere bearing.

[0047] Referring to Figure 3 The connecting arm 53 has a structure in which one end is fixed to the main shaft 60 and the other end is connected to the eccentric shaft 40, and is configured to perform reciprocating rotation around the main shaft 60 as a fulcrum by the rotation of the eccentric shaft 40. The connecting arm 53 has a ring-shaped portion 54 located in the front and a pair of arm portions 55 provided behind the ring-shaped portion 54. In the connecting arm 53, the ring-shaped portion 54 corresponds to the above-described "one end", and the pair of arm portions 55 corresponds to the above-described "the other end". As shown in Figure 2 and Figure 3 The main shaft 60 is inserted through the through hole in the center of the ring-shaped portion 54, and the main body portion of the main shaft 60 is configured by a cylindrical metal member. The ring-shaped portion 54 is fixed to the outer periphery of the upper end portion of the main shaft 60. As shown in Figure 3As shown, a pair of arm portions 55 are arranged in the left-right direction and extend rearward from the rear end portions of the ring-shaped portion 54. In the present embodiment, each arm portion 55 has a quadrangular prism shape. The connecting arm 53 is connected to the eccentric shaft 40 by sandwiching the above-mentioned bearing 52 mounted to the eccentric shaft 40 in the left-right direction by the pair of arm portions 55. The pair of arm portions 55 are in a state of merely contacting the left and right side surfaces of the bearing 52, and are not fixed by engagement or the like. The mechanism by which the connecting arm 53 is reciprocally pivoted about the main shaft 60 by the rotational movement of the eccentric shaft 40 will be described later.

[0048] Referring to Figure 2 The lower end portion of the main shaft 60 extends out of the housing 11, and a tool mounting portion 62 provided at the lower end of the main shaft 60 is located outside the housing 11. The main shaft 60 holds the tip tool 100 at the tool mounting portion 62, and functions as a pivot point for the oscillating movement of the tip tool 100.

[0049] The main shaft 60 is held by the main shaft holding mechanism 70 at the tip portion of the power tool 10 in a posture in which the central axis DX of the main shaft 60 intersects the rotational center axis RX. In the present embodiment, the central axis DX of the main shaft 60 is substantially orthogonal to the rotational center axis RX. The main shaft holding mechanism 70 holds the main shaft 60 so as to be pivotable about the central axis DX. The tip tool 100 mounted on the tool mounting portion 62 is oscillated by the reciprocating pivoting of the main shaft 60 about the central axis DX. The central axis DX of the main shaft 60 is also referred to as a "drive axis DX".

[0050] As described above, in the power tool 10, the rotational center axis RX intersects the drive axis DX, which corresponds to the axis that becomes the pivot point for oscillating the tip tool 100. Accordingly, the motor 31 can be disposed in a posture in which the rotational shaft 32 of the motor 31 intersects the drive axis DX. By disposing the motor 31 in such a posture, the internal space of the central portion of the housing 11, which functions as the above-mentioned gripping portion, can be used as the accommodation portion of the motor 31 in a rational and efficient manner.

[0051] The tip tool 100 is mounted in the tool mounting portion 62 of the main shaft 60 in the following manner. The tool mounting portion 62 has a lower end opening 63 that is opened at the lower end of the main shaft 60 and communicates with the internal space of the main shaft 60, and a plurality of protrusion portions 65 that are provided around the lower end opening 63 and protrude downward. A fastening shaft 110 is used to fix the tip tool 100 to the tool mounting portion 62. The fastening shaft 110 is inserted into the internal space of the main shaft 60 through the lower end opening 63 of the tool mounting portion 62. The fastening shaft 110 is fixed to the main shaft 60 in a state in which the upper end thereof is clamped by a clamping member 66 inside the main shaft 60, by an upward force from a coil spring 67.

[0052] A through-hole 102 for inserting the fastening shaft 110 and a fitting hole 103 for fitting with the above-mentioned protruding portion 65 of the tool mounting portion 62 are provided at the base end portion of the tip tool 100. In addition, a head portion 112 which is partially enlarged in diameter and extends to the side is provided at the lower end of the fastening shaft 110. When the fastening shaft 110 is inserted into the inside of the main shaft 60 via the through-hole 102 of the tip tool 100 and is fixed, the peripheral portion of the through-hole 102 of the tip tool 100 is sandwiched between the head portion 112 of the fastening shaft 110 and the lower end surface of the main shaft 60. Accordingly, the tip tool 100 is prevented from falling downward from the main shaft 60.

[0053] Furthermore, although detailed description is omitted, in the power tool 10, by causing the operation lever 68 arranged along the top end surface of the housing 11 to be pulled up in the forward direction, the spiral spring 67 inside the main shaft 60 is elastically deformed in the direction of contraction. Accordingly, the fixed state of the fastening shaft 110 based on the force of the spiral spring 67 is released, so that the fastening shaft 110 and the tip tool 100 can be detached from the main shaft 60. In addition, as the fixing method of the fastening shaft 110 to the main shaft 60, for example, a screw fastening type, a clamping type different from the present embodiment, or any other fixing method can be adopted. Figure 1 and Figure 2 By rotating the operation lever 68 arranged along the top end surface of the housing 11 in the housing 11 shown in Figs. 1 and 2 in a manner of being pulled up in the forward direction, the spiral spring 67 inside the main shaft 60 can be elastically deformed in the direction of contraction. Accordingly, the fixed state of the fastening shaft 110 based on the force of the spiral spring 67 is released, so that the fastening shaft 110 and the tip tool 100 can be detached from the main shaft 60. In addition, as the fixing method of the fastening shaft 110 to the main shaft 60, for example, a screw fastening type, a clamping type different from the present embodiment, or any other fixing method can be adopted.

[0054] Referring to Figure 3 , the mechanism of the oscillating motion of the tip tool 100 by the eccentric rotation of the eccentric shaft 40 will be described. In the eccentric rotation of the eccentric shaft 40, the eccentric shaft 40 reciprocates in the left-right direction with respect to the rotation center axis RX. By the reciprocating movement of the eccentric shaft 40 in the left-right direction, the pair of arm portions 55 of the connecting arm 53 rotates in the left-right direction, so that the main shaft 60 of the embedded ring-shaped portion 54 reciprocates in the circumferential direction around the drive axis DX. Accordingly, the tip tool 100 fixed to the tool mounting portion 62 at the lower end of the main shaft 60 oscillates around the drive axis DX with the drive axis DX as a fulcrum. The angle of the oscillation of the tip tool 100 with the drive axis DX as a fulcrum is, for example, about 1 to 5°.

[0055] Referring to Figure 2 , the main shaft holding mechanism 70 is provided in the top end portion of the housing 11 to hold the main shaft 60 in a state of being able to rotate in the circumferential direction with the drive axis DX as the center. The main shaft holding mechanism 70 has a first bearing portion 73, an elastic member 75, and a second bearing portion 76.

[0056] The first bearing portion 73 is provided at the upper end portion of the main shaft 60 and supports the main shaft 60 so as to be rotatable in the circumferential direction. The first bearing portion 73 is constituted by, for example, a ball bearing. An elastic member 75 is arranged on the outer periphery of the first bearing portion 73, and the first bearing portion 73 is held to the case 11 by the elastic member 75. The vibration of the main shaft 60 due to the swing of the tip tool 100 during the driving of the power tool 10 is absorbed by the elastic member 75, and thus the vibration due to the swing of the tip tool 100 can be suppressed from being transmitted to the case 11 through the main shaft 60.

[0057] The second bearing portion 76 is fixed to the case 11 between the first bearing portion 73 and the tool mounting portion 62 and supports the main shaft 60 so as to be rotatable in the circumferential direction. The second bearing portion 76 is provided at a position lower than the connecting arm 53. The second bearing portion 76 supports the vicinity of the central portion of the main shaft 60 in the vertical direction.

[0058] In the present embodiment, the second bearing portion 76 is constituted by a ball bearing. In the ball bearing, balls as rolling elements are in point contact with an inner ring and an outer ring. Since the main shaft 60 is fixed to the inner ring of the second bearing portion 76, the main shaft 60 is virtually in a state of being supported by the balls as rolling elements in point contact at the second bearing portion 76. In contrast, in the case where the second bearing portion 76 is constituted by a roller bearing such as a needle bearing instead of a ball bearing, since the rolling elements are rollers, the main shaft 60 is in a state of being supported by the rollers in line contact. In the state where the main shaft 60 is supported by the rolling elements of the second bearing portion 76 in point contact, the main shaft 60 is more likely to move with respect to the case 11 with the rolling elements of the second bearing portion 76 as a fulcrum than in the state where the main shaft 60 is supported by the rolling elements of the second bearing portion 76 in line contact. Therefore, by constituting the second bearing portion 76 by a ball bearing, the vibration of the main shaft 60 due to the swing of the tip tool 100 can be easily absorbed by the elastic member 75 arranged between the first bearing portion 73 and the case 11. Therefore, the vibration due to the swing of the tip tool 100 can be further suppressed from being transmitted to the case 11.

[0059] With reference to Figure 4 , Figure 5 , Figure 6 , Figure 7 , Figures 8-11 , the shape and the position of the center of gravity of the balancer 45 will be described in detail.

[0060] With reference to Figure 4The balancer 45 has a base 80. A through hole 81, serving as a through-hole, is formed on the base 80, through which the rotating shaft 32 passes. In this embodiment, the balancer 45 is constructed of a plate-like metal component, and the base 80 is flat. The base 80 has a generally fan-shaped shape when viewed along its thickness direction. The rotating shaft 32 passes through the base 80 along its thickness direction via the through hole 81.

[0061] A protrusion 83 is provided on the balancer 45, protruding from the side surface of the base 80 in a direction along the rotation center axis RX. In this specification, the side surface of the base 80 refers to at least one of a pair of surfaces of the base 80 facing the direction along the rotation center axis RX. In this embodiment, the protrusion 83 is provided on the outer edge portion 82 of the arc forming the base 80. The protrusion 83 extends in an arc shape along the outer edge portion 82 and has a portion that extends radially outward beyond the outer edge portion 82. Furthermore, in this embodiment, the protrusion 83 protrudes forward. In other embodiments, the protrusion 83 may protrude rearward, and the protrusion 83 may have both a forward-protruding protrusion and a rearward-protruding protrusion.

[0062] In the balancer 45, the corner between the two straight sides of the fan-shaped base 80 is rounded to form a rounded corner 84. The angle of the rounded corner 84, corresponding to the central angle of the fan shape, is approximately 80° to 110°. The through hole 81 is located at a distance from the outer edge 82 forming the arc that is greater than the distance from the rounded corner 84 (closer to both the outer edge 82 and the rounded corner 84). The opening cross-section of the through hole 81 has a roughly D-shaped shape formed by cutting off a portion of a circle, and a planar notch 85 is formed on the inner circumferential surface of the through hole 81.

[0063] Reference Figure 5 and Figure 6 When assembling the power tool 10, after installing the front bearing portion 37 on the rotating shaft 32, the balancer 45 is installed. (As follows) Figure 5 As shown, a notched wall 32s is provided at the top end of the rotating shaft 32. The notched wall 32s is formed by cutting a portion of the cylindrical side surface into a planar shape so that the top end engages with the through hole 81 of the balancer 45. The engagement between the notch 85 of the through hole 81 and the notched wall 32s of the rotating shaft 32 defines the mounting angle of the balancer 45 in the direction about the rotation center axis RX. The position of the center of gravity of the balancer 45 relative to the eccentric axis EX of the eccentric shaft 40 is defined as described later.

[0064] After the installation of the balancer 45, the bearing 52 is installed on the eccentric shaft 40 in front of the balancer 45 with the pad 86 interposed, with the eccentric shaft 40 being provided at the top end of the rotation shaft 32. A snap ring 87 for restricting the bearing 52 from falling off the eccentric shaft 40 is embedded in the top end outer periphery of the eccentric shaft 40. Then, the connecting arm 53 is installed in a manner that a pair of arm portions 55 sandwich the outer peripheral side surface of the bearing 52 installed on the eccentric shaft 40 in the left and right directions.

[0065] Referring to Figure 7 Here, a state when viewed along the rotation center axis RX is assumed. By the "when viewed along the rotation center axis RX", it means "when viewed from the front side or the rear side of the balancer 45". Figure 7 A state when viewed from the front side of the balancer 45 is shown. At this time, the balancer 45 has the center of gravity CG in the region GA on the side of the direction from the eccentric axis EX toward the rotation center axis RX than the rotation center axis RX. In other words, the center of gravity CG of the balancer 45 is located in the region GA on the side opposite to the eccentric axis EX with the imaginary perpendicular line VL being perpendicular to the 1st imaginary straight line L1 passing through the eccentric axis EX and the rotation center axis RX and passing through the rotation center axis RX. By having the center of gravity CG in this region GA, when the motor 31 is rotationally driven, a centrifugal force having a component in the direction opposite to the centrifugal force generated by the eccentric rotational movement of the eccentric shaft 40 can be generated by the rotational movement of the balancer 45. Accordingly, the vibration generated on the power tool 10 due to the effect of the centrifugal force generated by the rotational movement of the eccentric shaft 40 is suppressed.

[0066] Here, the 2nd imaginary straight line L2 passing through the rotation center axis RX and the center of gravity CG of the balancer 45 is inclined with respect to the 1st imaginary straight line L1. The 2nd imaginary straight line L2 is inclined with respect to the 1st imaginary straight line L1 in the direction opposite to the rotation direction RD of the rotation shaft 32 at an inclination angle θ greater than 0° and less than 90°. Accordingly, when the power tool 10 is driven to process the workpiece by the tip tool 100, the centrifugal force generated by the rotational movement of the balancer 45 can be generated in the direction to offset the resistance generated between the tip tool 100 and the workpiece in accordance with the period in which the resistance is increased.

[0067] Next, the effect of the centrifugal force generated by the rotational movement of the balancer 45 will be described in detail.

[0068] Referring to Figures 8-11 In Figures 8-11 , the case when the rotation shaft 32 is rotationally driven for one cycle and the tip tool 100 is reciprocally swung once is shown in order every 90° rotation angle of the rotation shaft 32. In Figures 8-11In each of the drawings, the balancer 45 mounted to the rotation shaft 32 is illustrated in the upper part of the paper when viewed from the front side along the rotation center axis RX, and the tip tool 100 is illustrated in the lower part of the paper when viewed from the upper side along the drive axis DX.

[0069] In Figures 8-11 the upper part of the paper, arrows indicating the up-down direction and the left-right direction are illustrated in correspondence with the configuration posture of the rotation shaft 32, the eccentric shaft 40, and the balancer 45 in the power tool 10. In addition, in Figures 8-11 the lower part of the paper of each of the drawings, a range in which the tip tool 100 swings during the driving of the power tool 10, that is, a swing range SA is illustrated by a double-dot chain line. Further, in Figures 8-11 of the drawings, in order to easily understand the situation in which the tip tool 100 swings, the angle at which the tip tool 100 swings with the drive axis DX as a fulcrum is intentionally illustrated extremely enlarged.

[0070] Figure 8 indicates a state in which the rotation center axis RX is located above the eccentric shaft axis EX, the eccentric shaft axis EX is located below the rotation center axis RX, and the rotation center axis RX and the eccentric shaft axis EX are located at a position in which they coincide in the up-down direction. At this time, the tip tool 100 is located at a central position of the swing range SA thereof. If the rotation shaft 32 is rotated by 90° from Figure 8 , the eccentric shaft axis EX is eccentrically rotated with the rotation center axis RX as a center and moves to a position in which it is aligned with the rotation center axis RX in the left-right direction, as illustrated in Figure 9 of the drawings. In Figure 9 , the eccentric shaft axis EX moves to the left side of the rotation center axis RX. Then, the tip tool 100 swings from the central position of the swing range SA illustrated in Figure 8 to an end of the swing range SA, which is on the left side of the paper in Figure 9 .

[0071] If the rotation shaft 32 is rotated by 90° from Figure 9 in the direction of rotation RD of the motor 31, the eccentric shaft axis EX is eccentrically rotated with the rotation center axis RX as a center and moves above the rotation center axis RX so as to coincide with the rotation center axis RX in the up-down direction, as illustrated in Figure 10 . Along therewith, the tip tool 100 rotates from the position illustrated in Figure 9 to the central position of the swing range SA. If the rotation shaft 32 is rotated by 90° from Figure 10 in the direction of rotation RD of the motor 31, the eccentric shaft axis EX is eccentrically rotated with the rotation center axis RX as a center and moves to a position in which it is aligned with the rotation center axis RX in the left-right direction, as illustrated in Figure 11 . In Figure 9The positions arranged on the opposite side. Figure 11 In the middle, the eccentric axis EX moves to the right of the rotation center axis RX. The top tool 100, centered on the drive axis DX, moves from... Figure 10 The central position of the swing range SA shown is towards the other end of the swing range SA. Figure 11 The right end of the paper within the swing range SA rotates. This process is repeated during the drive of motor 31. Figures 8-11 The movement.

[0072] Reference Figure 9 and Figure 11 .exist Figure 9 and Figure 11 In the state indicated by arrow CF, the centrifugal force generated by the rotational motion of the balancer 45 is generated in a manner that has a component in the direction that counteracts the centrifugal force EF generated by the eccentric rotational motion of the eccentric shaft 40. Therefore, during the operation of the power tool 10, the rotational motion of the balancer 45 suppresses the increase in vibration caused by the centrifugal force generated by the eccentric rotational motion of the eccentric shaft 40.

[0073] Reference Figure 8 and Figure 10 During the machining of the workpiece using the power tool 10, the resistance generated between the tip tool 100 and the workpiece acts in the opposite direction to the swing direction OD of the tip tool 100, as indicated by arrow RE, and in the direction that hinders the eccentric rotational motion of the eccentric shaft 40, as indicated by arrow REa. This resistance is greatest when the tip tool 100 is located at the center of the swing range SA. As described above, in this embodiment, the center of gravity CG of the balancer 45 is located at a position where the second imaginary line L2 is tilted relative to the first imaginary line L1 in the opposite direction to the rotation direction RD of the rotation axis 32 at an angle θ greater than 0° and less than 90°. Because the center of gravity CG of the balancer 45 is located in such a position, Figure 8 , Figure 10 In the illustrated cycle, as indicated by arrow CF, the centrifugal force generated by the rotational motion of the balancer 45 is produced in a manner that includes a component in the direction that promotes the eccentric rotational motion of the eccentric shaft 40, i.e., in the direction that counteracts the aforementioned resistance acting on the eccentric shaft 40. Thus, according to the power tool 10, when machining a workpiece, it is possible to generate a centrifugal force due to the eccentric rotational motion of the balancer 45 in the direction that counteracts the resistance, coinciding with the cycle in which the resistance generated between the tip tool 100 and the workpiece increases. Therefore, during the machining of the workpiece, the increased vibration of the power tool 10 due to the resistance generated between the tip tool 100 and the workpiece is suppressed.

[0074] Here, as a first comparative example with respect to the structure of the present embodiment, a structure is assumed in which the center of gravity CG of the balancer 45 is located at a position in which the inclination angle θ of the second imaginary straight line L2 with respect to the first imaginary straight line Ll is 0°. In this case, the centrifugal force generated by the balancer 45 has almost no component in a direction for canceling the influence of the resistance generated between the tip tool 100 and the workpiece. Therefore, in the structure of this comparative example, the vibration generated during the machining of the workpiece is hardly reduced.

[0075] Further, as a second comparative example, a structure is assumed in which the center of gravity CG of the balancer 45 is located at a position in which the inclination angle θ is 90° or 270°. In this case, the centrifugal force generated by the center of gravity of the balancer 45 has almost no component in a direction acting on the centrifugal force generated by the eccentric shaft 40. Therefore, in the structure of this comparative example, the vibration when the tip tool 100 is not in contact with the workpiece can become large.

[0076] As a third comparative example, a structure is assumed in which the center of gravity CG of the balancer 45 is located at a position in which the inclination angle θ is larger than 90° and smaller than 270°. In this case, the centrifugal force generated by the balancer 45 has a component in a direction acting to make the influence of the centrifugal force generated by the eccentric rotation movement of the eccentric shaft 40 large. Therefore, in the structure of this comparative example, the vibration when the tip tool 100 is not in contact with the workpiece can become large.

[0077] As a fourth comparative example, a structure is assumed in which the center of gravity CG of the balancer 45 is located at a position in which the inclination angle θ is larger than 180° and smaller than 360°. In this case, the centrifugal force generated by the balancer 45 has a component in the same direction as the resistance generated between the tip tool 100 and the workpiece, hinders the swing of the tip tool 100, and the machining performance on the workpiece can be degraded.

[0078] By locating the center of gravity CG of the balancer 45 at a position in which the inclination angle θ is a value larger than 0° and smaller than 90° as in the present embodiment, as Figures 8-11 described above, it is possible to reduce both the vibration generated when the tip tool 100 is not in contact with the workpiece and the vibration generated when the tip tool 100 is in contact with the workpiece. Here, the inclination angle θ is preferably larger than 10° and smaller than 60°, and more preferably larger than 15° and smaller than 50°. By this, it is possible to more evenly obtain both the vibration suppression effect when the tip tool 100 is not in contact with the workpiece and the vibration suppression effect when the tip tool 100 is in contact with the workpiece. The inclination angle θ can be, for example, a value larger than 20° and smaller than 45°, or a value larger than 25° and smaller than 40°. The inclination angle θ can be appropriately determined in consideration of conditions such as the weight of the balancer 45, the position of the eccentric axis EX with respect to the rotation center axis RX, the range of the rotational speed of the motor 31, and the like.

[0079] With reference to Figure 7 In the present embodiment, the balancer 45 has a shape that is asymmetric with respect to the first imaginary straight line Ll when viewed along the rotation center axis RX. By such a shape, it is easy to position the center of gravity CG of the balancer 45 at a position offset from the first imaginary straight line Ll. Therefore, it is easy to adjust the center of gravity CG of the balancer 45 to a position at which the inclination angle Θ is a value greater than 0° and less than 90°. In addition, in the present embodiment, the balancer 45 has a shape in which the volumes of the portions included in the regions on both sides of the imaginary plane defined by the rotation center axis RX and the eccentric shaft axis EX are different. By this, it is easier to adjust the center of gravity CG of the balancer 45 to a position at which the inclination angle Θ is a value greater than 0° and less than 90°.

[0080] With reference to Figure 4 As described above, in the present embodiment, the balancer 45 has the protruding portion 83 that protrudes from the base portion 80 in the direction along the rotation center axis RX. According to this balancer 45, since the weight thereof is increased by an amount corresponding to the protruding portion 83, the centrifugal force generated by the rotational motion is greater than in the case where the protruding portion 83 is not provided. Therefore, it is possible to more effectively reduce the resistance generated between the tip tool 100 and the workpiece during the machining of the workpiece. In addition, since the weight of the balancer 45 can be increased by providing the protruding portion 83, it is also possible to increase the weight of the balancer 45 without increasing the radial dimension of the balancer 45. That is, by providing the protruding portion 83, it is possible to increase the weight of the balancer 45 without increasing the radial dimension of the balancer 45, and thus it is possible to avoid an increase in the size of the balancer 45 in the radial direction.

[0081] Further, when the balancer 45 of the present embodiment is used, the space in the housing 11 faced by the side surface of the base portion 80 of the balancer 45 can be used as a region in which the protruding portion 83 is disposed, in a reasonable and efficient manner. In the present embodiment, the protruding portion 83 protrudes from the side surface of the base portion 80 toward the direction in which the eccentric shaft 40 is located, and the outer peripheral space of the bearing 52 mounted to the eccentric shaft 40 does not become a dead space, and can be used as a region in which the protruding portion 83 is disposed, in a reasonable and efficient manner.

[0082] With reference to Figure 7In the present embodiment, the convex portion 83 is provided at the outer edge portion 82 that is farthest from the rotation center axis RX in the radial direction orthogonal to the rotation center axis RX. In the present embodiment, the outer edge portion 82 is a circular arc-shaped portion. According to the balancer 45 of the present embodiment, it is easy to increase the distance between the position of the center of gravity CG of the balancer 45 and the rotation center axis RX by the weight of the convex portion 83, and thus it is easy to increase the centrifugal force generated by the rotation of the balancer 45. Therefore, it is possible to more effectively suppress the vibration of the power tool 10 from becoming large during the machining of the workpiece. In addition, in other embodiments, the convex portion 83 can also not be provided at the outer edge portion 82, but can be provided at a position farther from the rotation center axis RX than the outer edge portion 82. With this structure, it is also possible to easily make the position of the center of gravity CG of the balancer 45 farther from the rotation center axis RX by the weight of the convex portion 83, and thus to easily increase the centrifugal force generated by the rotation of the balancer 45.

[0083] As described above, according to the power tool 10 of the present embodiment, the center of gravity CG of the balancer 45 is defined at a position at which the centrifugal force is generated in a direction that counteracts the influence of the resistance generated between the tip tool 100 and the workpiece during the machining of the workpiece. Therefore, during the machining of the workpiece, it is possible to suppress the vibration of the power tool 10 from becoming large due to the resistance generated between the tip tool 100 and the workpiece.

[0084] [Other Embodiments]

[0085] The technology of the present application is not limited to the structures of the above-described embodiments and the structures described as other embodiments in the above-described embodiments. The structures of the above-described embodiments can be changed, for example, as follows. The structures of the embodiments described below are positioned as one way of implementing the technology of the present application, as with the structures described in the above-described embodiments.

[0086] In the above-described embodiments, the balancer 45 can also not have a sector shape when viewed along the rotation center axis RX, and can have, for example, a perfect circular shape, an elliptical shape, or can have a substantially triangular shape. The balancer 45 can have a structure in which the position of the center of gravity CG is adjusted to a position at which the inclination angle θ between the first imaginary straight line L1 and the second imaginary straight line L2 is a value greater than 0° and less than 90°, as with the above-described embodiments. In addition, in the above-described embodiments, the balancer 45 can also be configured to have a spherical shape as a whole in a manner in which the thickness gradually increases toward the outer edge portion 82 on the circular arc, for example.

[0087] In the above-described embodiments, the motor 31 may, for example, also be arranged in a posture in which the rotation center axis RX is substantially parallel to the driving axis DX. In this case, the motor 31 can also be arranged above the main shaft 60. The motor 31 can also be arranged so that the rotation center axis RX is located at a position deviated from the driving axis DX. In the above-described embodiments, instead of the motor 31 being arranged in a posture in which the rotation center axis RX is substantially orthogonal to the driving axis DX, the motor 31 can also be arranged in a posture in which the rotation center axis RX is obliquely intersected with the driving axis DX.

Claims

1. A power tool that processes a workpiece by oscillating a driving tip tool, characterized by comprising: a motor; an eccentric shaft; a motion conversion mechanism; and a balancer, wherein the motor has a rotating shaft that rotates in one direction; the eccentric shaft extends from one end of the rotating shaft and is configured to perform a rotational motion centered on a rotating center axis at a position that is offset in a radial direction from the rotating center axis, the radial direction being orthogonal to the rotating center axis, by rotation of the rotating shaft; the motion conversion mechanism connects the eccentric shaft and the driving tip tool and is configured to convert one cycle of the rotational motion of the eccentric shaft into an oscillation motion that reciprocates the driving tip tool once; and the balancer is provided on an outer periphery of the rotating shaft and is configured to rotate together with the rotating shaft, a center of gravity of the balancer is located in a region on an opposite side of an eccentric axis from an imaginary vertical line when viewed along the rotating center axis, the eccentric axis being a center axis of the eccentric shaft, the imaginary vertical line being orthogonal to a first imaginary straight line that passes through the eccentric axis and the rotating center axis and that passes through the rotating center axis, and a second imaginary straight line that passes through the rotating center axis and the center of gravity of the balancer is inclined at an inclination angle that is greater than 0° and less than 90° with respect to the first imaginary straight line in a direction opposite to a direction of rotation of the rotating shaft.

2. The power tool according to claim 1, characterized in that the balancer has an asymmetric shape with respect to the first imaginary straight line when viewed along the rotating center axis.

3. The power tool according to claim 1, characterized in that the balancer has a base portion and a protruding portion, wherein the base portion is penetrated by the rotating shaft in a thickness direction; and the protruding portion protrudes from a side surface of the base portion in a direction along the rotating center axis.

4. The power tool according to claim 2, characterized in that the balancer has a base portion and a protruding portion, wherein the base portion is penetrated by the rotating shaft in a thickness direction; and the protruding portion protrudes from a side surface of the base portion in a direction along the rotating center axis.

5. The power tool according to claim 3, characterized in that the protruding portion is provided at an outer edge portion of the base portion that is farthest from the rotating center axis in the radial direction or at a position closer to the outer edge portion than the rotating center axis in the radial direction.

6. The power tool according to any one of claims 1 to 5, characterized in that the inclination angle is greater than 10° and less than 60°.

7. The power tool according to any one of claims 1 to 5, characterized by further comprising a housing that accommodates the motor, the eccentric shaft, the motion conversion mechanism, and the balancer, wherein the motion conversion mechanism has a main shaft and a connecting arm, the end portion of the main shaft is provided with a tool mounting portion for mounting the driving tip tool, and the main shaft is configured to oscillate the driving tip tool by reciprocating rotation in a circumferential direction. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ One end of the connecting arm is fixed to the main shaft and the other end is connected to the eccentric shaft, and the connecting arm is configured to perform reciprocating rotation about the main shaft as a fulcrum by the rotational movement of the eccentric shaft, The main shaft is supported by a first bearing portion and a second bearing portion in a manner that allows reciprocating rotation in the circumferential direction, wherein the first bearing portion is provided inside the housing, and the second bearing portion is provided inside the housing and is located between the first bearing portion and the tool mounting portion, The first bearing portion is held to the housing by an elastic member.

8. The power tool according to claim 7, wherein The second bearing portion is configured by a ball bearing.

9. The power tool according to any one of claims 1 to 5, wherein The motor is disposed in a posture in which the rotational center axis intersects with an axis that becomes a fulcrum for oscillating the tip tool.

10. The power tool according to claim 6, wherein The motor is disposed in a posture in which the rotational center axis intersects with an axis that becomes a fulcrum for oscillating the tip tool.

11. The power tool according to claim 7, wherein The motor is disposed in a posture in which the rotational center axis intersects with an axis that becomes a fulcrum for oscillating the tip tool.

12. The power tool according to claim 8, wherein The motor is disposed in a posture in which the rotational center axis intersects with an axis that becomes a fulcrum for oscillating the tip tool.

Images