JP2012196735A - Cutting tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the size of a tool body in a motor machine length direction, in order to solve the following problems of a mobile circular saw that moves along the upper surface of a cutting material: rotation output of an electric motor as a drive source is output to a rotating cutter by reducing speed using a gear meshing type speed-reducing mechanism or the like, so that it is difficult to reduce the size of the tool body in the machine length direction of the electric motor.SOLUTION: This cutting tool employs a direct-drive system in which a rotating cutter 12 is directly attached to an output shaft 11d of an electric motor 11 as a drive source. A tool body 10 can be made shorter in the motor axis J direction by a length equivalent to a conventional deceleration mechanism. The barycentric position and handle part thereof can be brought close to the rotating cutter 12, and thereby operability and handleability of the cutting tool 1 can be improved.

Description

  The present invention relates to a cutting tool that is a hand-held cutting tool called, for example, a portable marnoko, and performs a cutting process by a user moving it on a cutting material.

This type of cutting tool includes a base that comes into contact with the upper surface of the cutting material, and a tool main body supported on the upper surface of the base. The tool main body includes a circular rotary blade (saw blade) that is rotated by an electric motor. The lower edge side of the rotary blade is protruded to the lower surface side of the base, and the protruding portion is cut into the cutting material for cutting.
In general, the tool body has a configuration in which the rotational output of the electric motor is decelerated through a gear train for reduction and is output to a spindle to which a rotary blade is attached. A technique relating to such a gear reduction type maroon saw is disclosed in Patent Document 1 below. As disclosed in this document, in this type of cutting tool, the electric motor is oriented in the direction of projecting to the side with the motor axis orthogonal to the traveling direction of the rotary blade attached to the spindle (cutting traveling direction). Equipped.

JP 2010-194697 A

Thus, conventionally, since the rotation output of the electric motor is decelerated by the gear meshing reduction gear and output to the spindle, the motor axial direction (motor length direction) is equivalent to the reduction gear. The dimensions (side protruding dimensions with respect to the cutting progress direction) are increased, making it difficult to achieve compactness in the same direction.
The present invention has been made in view of such a problem, and an object thereof is to make the tool body compact in the motor axial direction.

The above problems are solved by the following invention.
1st invention is provided with the base contact | abutted to a cutting material, and the tool main body supported by the upper part of the base, and a tool main body is a cutting tool provided with the electric motor which rotates a rotary blade, The output shaft of an electric motor This is a direct-drive cutting tool with a rotary blade attached directly to the tool.
According to the first invention, since it is a direct drive system (direct connection drive system), a reduction gear such as a gear train can be omitted to make the motor axial direction compact. By reducing the size of the tool body in the motor axis direction, the center of gravity position of the cutting tool in the motor axis direction can be set to a position closer to the rotary blade, and the electric motor is usually adjusted to the position of the center of gravity. The handle portion provided in can also be provided at a position closer to the rotary blade. For this reason, the operability of the cutting tool at the time of cutting work can be improved, and the weight balance in the motor axis direction can be balanced and carried easily, so that the workability (operability) and handling of the cutting tool are possible. (Portability) can be improved.
In addition, since the rotary blade is directly attached to the output shaft of the electric motor by the direct drive method, the rotational speed of the rotary blade and the rotational speed of the electric motor are the same. For this reason, since the rotation speed of the electric motor matches the appropriate rotation speed of the rotary blade, it can be rotated at a low speed of, for example, about 5,000 to 6,000 rotations per minute, thereby mainly cooling the electric motor. It is possible to reduce the noise or vibration of the fan's wind noise, and it is possible to reduce the noise and vibration of the cutting tool.
2nd invention is a cutting tool whose electric motor is a brushless motor in 1st invention. According to the second aspect of the present invention, the maintainability of the electric motor can be improved, and the operation control such as the rotation speed can be easily performed.
A third invention is the cutting tool according to the second invention, wherein the electric motor is an outer rotor type brushless motor. According to the third aspect of the invention, since the outer rotor type brushless motor is provided as the drive source, the electric motor is maintained while maintaining its output and size compared to the case where the inner rotor type brushless motor is used as the drive source. It is possible to increase the low-speed rotation and torque of the motor, thereby reducing wind noise and vibration of the motor itself.
4th invention is the cutting tool in which rotation speed of the said electric motor was set so that the circumferential speed of a rotary blade might be 35-60 m / s in 1st invention.
According to the fourth aspect of the present invention, the electric motor can be rotated at a low speed based on an appropriate peripheral speed of the rotary blade by the direct drive method, and thereby the wind noise and vibration of the motor itself can be reduced.
A fifth invention is a cutting tool according to the fourth invention, wherein the diameter of the rotary blade is 185 mm to 190 mm, and the rotational speed of the electric motor is set to 5,000 to 6,000 revolutions per minute.
According to the fifth aspect, since the rotary blade is directly attached to the output shaft of the electric motor by the direct drive method, the rotational speed of the rotary blade matches the rotational speed of the electric motor. For this reason, it is possible to rotate the electric motor at a low speed of about 5,000 to 6,000 revolutions per minute using a rotary blade having a diameter of 185 mm to 190 mm, thereby quieting the wind noise of the cooling fan mainly of the electric motor. Or vibration can be reduced, and as a result, noise reduction and vibration reduction of the cutting tool can be realized.

1 is an overall front view of a cutting tool according to a first embodiment of the present invention. The white arrow in the figure indicates the direction in which cutting proceeds. 1 is an overall plan view of a cutting tool according to a first embodiment of the present invention. The white arrow in the figure indicates the direction in which cutting proceeds. It is the (III)-(III) arrow directional view of FIG. 1, Comprising: It is a longitudinal cross-sectional view of the cutting tool which concerns on 1st Embodiment of this invention. In this figure, an outer rotor type brushless motor is shown as a drive source. It is the whole rear view which looked at the cutting tool which concerns on 1st Embodiment of this invention from the arrow (IV) direction in FIG. The white arrow in the figure indicates the direction in which cutting proceeds. It is a longitudinal cross-sectional view of the cutting tool which concerns on 2nd Embodiment of this invention. In this figure, an outer rotor type brushless motor is shown as a drive source. 3 is different from FIG. 3 in that a cooling fan is provided on the front side. It is a longitudinal cross-sectional view of the cutting tool which concerns on 3rd Embodiment of this invention. In this figure, an inner rotor type brushless motor is shown as a drive source. It is a longitudinal cross-sectional view of the cutting tool which concerns on 4th Embodiment of this invention. In this figure, an inner rotor type brush motor is shown as a drive source.

Next, an embodiment of the present invention will be described with reference to FIGS. 1-3 has shown the cutting tool 1 of 1st Embodiment. The cutting tool 1 is a so-called portable marnoko, and includes a flat plate-like base 2 that is brought into contact with the upper surface of the cutting material W, and a tool body 10 supported on the upper portion of the base 2.
The tool body 10 includes an electric motor 11 as a drive source and a circular rotary blade 12 attached directly to the output shaft 11d of the electric motor 11. In the present embodiment, a speed reduction mechanism such as a gear train for reducing the rotational output of the electric motor 11 is omitted.
The lower side of the rotary blade 12 protrudes from the lower surface of the base 2, and the protruding portion is cut into the cutting material W to be cut. In each figure, the rotary blade 12 is cut into the cutting material by moving the cutting tool 1 in the cutting progress direction indicated by the white arrow. In the following description, with respect to the longitudinal direction of the member or configuration, the cutting progress direction is defined as the front side or the front portion, and the opposite side is defined as the rear side or the rear portion. However, regarding the electric motor 11, the rotating blade 12 side is the front side or the front part in the motor axis J direction, and the opposite side is the back side or the rear part.
As shown in FIG. 3, the electric motor 11 is a brushless motor, which is a so-called outer rotor type electric motor. Generally, this outer rotor type brushless motor has a rotor (rotor) configured to include a permanent magnet (magnet) including N poles and S poles on the outside of the motor, and includes a three-phase stator winding. The structure which has a stator inside a motor is provided. On the other hand, a normal inner rotor type brushless motor in which a stator is disposed on the outer peripheral side of a rotor (rotor) has a rotor (magnet) including an N pole and an S pole. And a stator having a three-phase stator winding on the outside of the motor.

Here, when the size of the motor including the rotor and the stator is the same, when comparing the outer rotor type brushless motor and the inner rotor type brushless motor, the magnet attached to the outer rotor has a larger surface area than the inner rotor. Therefore, the outer rotor type brushless motor can take a larger torque. This makes it possible to reduce the size of the outer rotor type brushless motor compared to the inner rotor type without increasing the torque (while maintaining the same torque). In this case, it is possible to achieve a low rotation and high torque as compared with the inner rotor type.
The electric motor 11 includes a rotor 11c that is rotatably supported on the outer peripheral side of a stator 11b fixed in a motor case 11a. An output shaft 11d is attached to the rotor 11c. The output shaft 11d is rotatably supported via bearings 11f and 11g. The rear side bearing 11f is attached to the rear part of the motor case 11a, and the front side bearing 11g is attached to a motor mounting base part 14b provided on the back side of the blade case 14.
A cooling fan 11e for cooling the motor is attached to the rear portion of the output shaft 11d. A number of exhaust holes (wind windows) 11h to 11h are provided around the cooling fan 11e and in the rear part of the motor case 11a. On the other hand, as shown in FIG. 2, intake holes 14c to 14c are provided on the rear surface of the motor mounting base portion 14b. When the cooling fan 11e is rotated by starting the electric motor 11, outside air is introduced from the intake holes 14c to 14c. The introduced outside air (cooling air) flows toward the rear side of the motor by the wind force, and the electric motor 11 is cooled. The cooling air flowed to the rear side of the motor is exhausted to the outside through the exhaust holes 11h to 11h.
The length (machine length L0) of the electric motor 11 in the axis J direction (left-right direction in FIG. 3) is as short as an inner rotor type brushless motor.

The distal end side of the output shaft 11d of the electric motor 11 protrudes from the motor case 11a and enters the blade case 14. The rotary blade 12 is directly attached to the tip of the output shaft 11d protruding into the blade case 14. The rotary blade 12 is firmly attached to the tip of the output shaft 11d while being sandwiched between the receiving flange 26 and the presser flange 27.
For this reason, the cutting tool 1 of this embodiment is a direct drive type cutting tool, and the rotary blade 12 rotates integrally with the output shaft 11 d at the same rotational speed as the electric motor 11. In this embodiment, the rotation speed Rm of the electric motor 11 is set to about 6,000 rotations per minute. For this reason, the rotation speed Rc of the rotary blade 12 is set to about 6,000 rotations per minute that is the same as the rotation speed Rm of the electric motor 11 (Rm = Rc = about 6,000 rotations per minute).
As shown in FIG. 1, the rotary blade 12 rotates counterclockwise as viewed from the front. On the front side of the blade case 14, the rotation direction of the rotary blade 12 is indicated by an arrow 14a.
The number of rotations of the rotary blade 12 is appropriately set according to the diameter, the material of the cutting material W, and the like. For example, the rotational speed of the rotary blade 12 having a diameter of about 185 mm to 190 mm is set to about 5,000 to 6,000 revolutions per minute when the cutting material W is wood, and the cutting material W is a metal material. In some cases, it is preferable to set the speed to about 3,000 to 4,000 revolutions per minute. In addition, the rotational speed of the rotary blade 12 having a diameter of about 110 mm to 125 mm is preferably set to about 7,000 to 9,000 revolutions per minute when the cutting material W is wood. Further, the rotational speed of the rotary blade 12 having a diameter of about 210 mm to 235 mm is preferably set to about 3,500 to 4,500 revolutions per minute when the cutting material W is wood.

The tool body 10 is supported on the upper surface side of the base 2 via the front tilting support shaft 15 so as to be tiltable up and down. By changing the vertical tilt position of the tool body 10 with respect to the base 2, the projecting dimension of the rotary blade 12 to the lower surface side of the base 2 can be changed, whereby the cutting depth of the rotary blade 12 with respect to the cutting material W can be changed. Can be adjusted. As shown in FIG. 2, the rear side of the tool body 10 is supported by the base 2 via a curved guide member 3 called a depth guide that is attached to the upper portion of the base 2 in an upright state. By tightening the fixing screw 4 inserted through the guide hole 3a of the guide member 3 to the back side of the blade case 14, the tilting position of the tool body 10 with respect to the base 2 is fixed. The fixing screw 4 can be tightened by rotating the operation lever 5 attached to the front end of the back surface in the tightening direction. When the operation lever 5 is rotated to loosen the fixing screw 4, the tool body 10 can be tilted up and down with respect to the base 2, whereby the cutting depth of the rotary blade 12 can be changed.
The lower half of the rotary blade 12 protruding to the lower surface side of the base 2 is covered by the movable cover 16. The movable cover 16 is supported by the blade case 14 so as to be rotatable around the rotary blade 12. As shown in FIG. 1, the tip of the movable cover 16 is brought into contact with the cutting material W, and in this contacted state, the cutting tool 1 is moved in the cutting progress direction indicated by a white arrow in the drawing to rotate the rotary blade 12. Is cut into the cutting material W, so that the movable cover 16 is relatively opened in the clockwise direction in the drawing and gradually opened. A handle 17 is attached to the rear portion of the movable cover 16. The user can grip the handle 17 and rotate the movable cover 16 in the opening direction, thereby facilitating work such as replacement of the rotary blade 12.

A handle portion 30 is provided on the upper portion of the electric motor 11. As shown in FIG. 4, the handle portion 30 has a triangular loop shape extending from the upper portion of the electric motor 11 to the rear portion, and a standing portion 31 that rises upward from the upper portion of the electric motor 11, and an upper portion of the standing portion 31. A main grip portion 32 extending in a downward direction from the rear, and a coupling portion 33 for coupling the rear portion of the main grip portion 32 to the rear portion of the electric motor 11. The main grip portion 32 is a portion that the user grips with one hand, and a trigger type switch lever 35 that is pulled by the fingertip of the hand gripped by the user is disposed on the lower surface side thereof. A front grip part 34 that is held by the user with the other hand is provided on the upper part of the standing part 31 so as to protrude forward.
A battery mounting base portion 36 is provided at the rear portion of the main grip portion 32. The battery pack B is mounted on the battery mounting base 36. The battery pack B can be slid upward to be removed from the battery mounting pedestal 36, and conversely slid downward to be attached to the battery mounting pedestal 36. The removed battery pack B can be used repeatedly by charging with a separately prepared charger. The electric motor 11 is activated using the battery pack B as a power source.
A lock lever 37 for locking the rotation of the output shaft 11 d is provided at the front portion of the electric motor 11. When the lock lever 37 is moved in the longitudinal direction, the rotation of the output shaft 11d is locked, and the operation of exchanging the rotary blade 12 is facilitated.

According to the first embodiment configured as described above, since the direct drive system (direct drive system) in which the rotary blade 12 is directly attached to the output shaft 11d of the electric motor 11 is provided, the conventional gear meshing system, etc. The tool body 10 can be made compact in the direction of the motor axis J by the amount corresponding to the speed reduction mechanism.
By downsizing the tool body 10 in the motor axis J direction, the center of gravity of the tool body 10 and thus the cutting tool 1 in the motor axis J direction can be brought closer to the rotary blade 12 side, and the handle portion 30 can be made more flexible. It can be arranged at a position close to the rotary blade 12 side, thereby improving the operability of the cutting tool at the time of cutting work and being easily carried with a weight balance in the motor axial direction. Therefore, workability (operability) and handling (portability) of the cutting tool can be improved.
Further, since the outer motor type brushless motor is used for the electric motor 11, the machine length L 0 of the electric motor 11 itself can be reduced. In this respect as well, the center of gravity position of the cutting tool 1 in the motor axis J direction can be reduced. And the position of the handle | steering-wheel part 30 can be set to the position which was made to approach the rotary blade 12 side, and, thereby, the workability | operativity (operability) and the handleability (portability) of the said cutting tool 1 can be improved.
Furthermore, since the rotary blade 12 is directly attached to the output shaft 11d of the electric motor 11 by the direct drive method, the rotational speed Rc of the rotary blade 12 and the rotational speed Rm of the electric motor 11 are the same. For this reason, since the rotation speed Rm of the electric motor 11 coincides with the appropriate rotation speed Rc of the rotary blade 12, for example, a configuration in which deceleration is performed using a normal reduction gear train at approximately 6,000 rotations per minute (deceleration drive). Can be rotated at a significantly lower speed than that of the system), thereby reducing the wind noise and vibration of the cooling fan 11e of the electric motor 11, and thus reducing the noise and vibration of the cutting tool 1. Can be realized.
In addition, since the brushless type electric motor 11 is used, the maintainability of the electric motor 11 and thus the cutting tool 1 can be improved, and the operation control such as the rotation speed of the electric motor 11 is easier than the brush type. Will be able to do.
Further, since the outer rotor type brushless motor is provided as the electric motor 11, the electric motor 11 can be rotated at a lower speed and increased in torque while maintaining its output and size as compared with the case of using the inner rotor type brushless motor. Thus, it is possible to achieve both the motor power up and the reduction of wind noise and vibration of the electric motor 11 itself.

Various modifications can be made to the first embodiment described above. For example, when the diameter of the rotary blade is 185 mm to 190 mm, the rotary blade is rotated at an appropriate rotation speed Rc by setting the rotation speed Rm of the electric motor in the range of 5,000 to 6,000 rotations per minute. be able to.
In addition, as described above, the appropriate rotation speed Rc (= rotation speed Rm of the electric motor) of the rotary blade differs depending on factors such as the diameter of the rotary blade and the material of the cutting material. With the drive system, the tool body 10 can be made compact in the motor axis J direction, and the rotational speed Rm of the electric motor can be significantly reduced as compared with the prior art. Or vibration can be reduced, and as a result, the cutting tool 1 can be reduced in noise and vibration.
Furthermore, in the first embodiment, the outer rotor type electric motor 11 provided with the cooling fan 11e at the rear part of the output shaft 11d as illustrated in FIG. 3 is illustrated, but the cooling fan 41 is connected to the output shaft 42 as illustrated in FIG. It is good also as a structure using the outer-rotor type electric motor 40 with which the front part is equipped. In the electric motor 40 according to the second embodiment, the orientation of the rotor 43 and the position of the cooling fan 41 are different from those of the electric motor 11 of the first embodiment. The direct drive method in which the rotary blade 12 is directly attached to the output shaft 42 of the electric motor 40 is the same as in the first embodiment. The same members and configurations as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.
In the case of the second embodiment, the rotor 43 is supported in the direction reversed in the front-rear direction from the first embodiment with respect to the direction in the motor axis J direction. For this reason, the bottom 43a of the rotor 43 is located on the front side, and the opening side is on the rear side. A cooling fan 41 is attached to the output shaft 42 along the bottom 43a located on the front side. The rotor 43 and the cooling fan 41 are fixed to the output shaft 42 and rotate integrally with the output shaft 42, respectively. A plurality of ventilation holes 43 b to 43 b are provided in the bottom 43 a of the rotor 43.
In the electric motor 40 according to the second embodiment, outside air is sucked from an intake hole provided in the rear part of the motor case 44, and the rotor 43, the stator 45, etc. are cooled by the sucked outside air (cooling air), and thereafter Outside air is exhausted from an exhaust hole provided in the front portion of the motor case 44. The intake holes and the exhaust holes are not shown.
In the case of the second embodiment, since the cooling fan 41 is arranged at the front part of the electric motor 40, it further rotates than the first embodiment in which the position of the center of gravity of the electric motor 40 in the motor axis J direction is arranged on the rear side. It can be set at a position close to the blade 12. By setting the position of the center of gravity of the electric motor 40 in the motor axis J direction to a position close to the rotary blade 12, the operability and workability of the cutting tool 1 in the cutting work can be improved. By being positioned below 30, the weight balance at the time of carrying can be taken, and the handling property and portability of the cutting tool 1 can be further improved.

As described above, the configuration using the outer rotor type brushless motor (electric motors 11 and 40) as the drive source has been exemplified, but the direct drive exemplified when the inner rotor type brushless motor or the inner rotor type brush motor is used as the drive source. Similar effects can be obtained by applying the method.
FIG. 6 shows a cutting tool 1 according to a third embodiment including an inner rotor type brushless motor as a drive source (electric motor 50). For members or configurations that do not require modification, the same reference numerals are used and the description thereof is omitted. The electric motor 50 has a configuration in which a rotor 53 is rotatably supported on an inner peripheral side of an annular stator 52 fixed in a motor case 51. The output shaft 54 that supports the rotor 53 is supported by the motor case 51 via bearings 55 and 56 so as to be rotatable about the axis J. A cooling fan 57 is attached on the output shaft 54 on the front side of the rotor 53. The front side of the output shaft 54 protrudes into the blade case 14. The circular rotary blade 12 is directly attached to the tip of the output shaft 54 protruding from the blade case 14.
As described above, according to the third embodiment using an inner rotor type brushless motor as a drive source, a direct drive system in which the rotary blade 12 is directly attached to the output shaft 54 of the electric motor 50 is used. The speed reduction mechanism is omitted. For this reason, since the tool body 10 can be made compact in the motor axis J direction by a dimension corresponding to the speed reduction mechanism, the position of the center of gravity and the position of the handle portion 30 in the same direction are closer to the rotary blade 12 side. Thus, the operability, workability, or handleability of the cutting tool 1 can be improved.

FIG. 7 shows a cutting tool 1 according to a fourth embodiment having an inner rotor type brush motor as a drive source (electric motor 60). In the fourth embodiment, members or configurations that do not need to be changed are denoted by the same reference numerals and description thereof is omitted. The electric motor 60 has a configuration in which a rotor 63 is rotatably supported on the inner peripheral side of an annular stator 62 fixed in a motor case 61. The output shaft 64 that supports the rotor 63 is supported by the motor case 61 via bearings 65 and 66 so as to be rotatable about the axis J. A cooling fan 67 is mounted on the output shaft 64 on the front side of the rotor 63. The front side of the output shaft 64 protrudes into the blade case 14. The circular rotary blade 12 is directly attached to the tip of the output shaft 64 protruding into the blade case 14.
A commutator 68 is attached to the rear side of the rotor 63 and to the rear portion of the output shaft 64. Carbon brushes 69 and 69 are slidably contacted with the commutator 68 from two opposite sides around the axis J. The carbon brushes 69 and 69 can be replaced by removing the cap 61a of the motor case 61.
As described above, the fourth embodiment using an inner rotor type brush motor as a drive source is also a direct drive system in which the rotary blade 12 is directly attached to the output shaft 64 of the electric motor 60, such as a conventional gear meshing system. The speed reduction mechanism is omitted. For this reason, since the tool body 10 can be made compact in the motor axis J direction by a dimension corresponding to the speed reduction mechanism, the position of the center of gravity and the position of the handle portion 30 in the same direction are closer to the rotary blade 12 side. Accordingly, the operability of the cutting tool 1 can be improved.
Moreover, in embodiment illustrated above, although the rotary blade 12 was directly attached to the output shaft 11d (42, 54, 64) of the electric motor 11 (40, 50, 60) as a direct drive system, it illustrated the structure. The direct drive system in FIG. 1 is intended not to intervene speed change means such as a reduction gear train, and even if it is a shaft (cutlery shaft) physically different from the output shaft of the electric motor, it is coaxial with the output shaft of the electric motor. A configuration in which a rotating blade is attached to the blade shaft rotating at the same rotational speed as a result of being integrated with respect to rotation is also included.

DESCRIPTION OF SYMBOLS 1 ... Cutting tool 2 ... Base 3 ... Guide member (depth guide), 3a ... Guide hole 4 ... Fixing screw 5 ... Operation lever 10 ... Tool body 11 ... Electric motor (outer rotor type)
DESCRIPTION OF SYMBOLS 11a ... Motor case, 11b ... Stator, 11c ... Rotor, 11d ... Output shaft 11e ... Cooling fan, 11f, 11g ... Bearing, 11h ... Exhaust hole J ... Motor axis line 12 ... Rotary blade 14 ... Blade case 14a ... Arrow, 14b ... Motor mounting base portion, 14c ... Intake hole 15 ... Tilt support shaft 16 ... Movable cover 17 ... Handle 30 ... Handle portion 31 ... Standing portion 32 ... Main grip portion 33 ... Coupling portion 34 ... Sub grip 35 ... Switch lever 36 ... Battery mounting base 37 ... Lock lever 40 ... Electric motor (second embodiment)
50. Electric motor (inner rotor type brushless motor)
60 ... Electric motor (inner rotor type brush motor)
69 ... Carbon brush B ... Battery pack L0 ... Motor machine length L1 ... Interval in the motor axis direction between the handle portion and the rotary blade

Claims (5)

A cutting tool including a base to be brought into contact with the cutting material and a tool main body supported on an upper portion of the base, the tool main body having an electric motor for rotating a rotary blade; and the rotation on the output shaft of the electric motor Direct drive type cutting tool with cutting tool attached directly. The cutting tool according to claim 1, wherein the electric motor is a brushless motor. The cutting tool according to claim 2, wherein the electric motor is an outer rotor type brushless motor. The cutting tool according to claim 1, wherein the rotational speed of the electric motor is set so that a peripheral speed of the rotary blade is 35 to 60 m / s. The cutting tool according to claim 4, wherein the diameter of the rotary blade is 185 mm to 190 mm, and the rotation speed of the electric motor is set to 5,000 to 6,000 rotations per minute.

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