Electric work machines

Abstract

To suppress generation of noise caused by resonance of a stator at lower cost.SOLUTION: A circular saw includes a motor housing 6 having a cylindrical part 6C and a bottom part 6M, a brushless motor having a stator 20 having a first contact surface 58F and a rotor rotating inside the stator 20, a resin-made buffle plate 25, and an output shaft 31. The stator 20 has a cylindrical stator core 50 having a ring-shaped second contact surface 50S facing the first contact surface 58F, and a plurality of coils 56 wound around the stator core 50, and is held on the motor housing 6 in a state where the first contact surface 58F is brought into contact with the bottom part 6M. A projection 25S of the buffle plate 25 is brought into contact with the second contact surface 50S of the stator 50 over the whole circumference, and is fixed to the motor housing 6 with three or more screws 68.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to electric tools such as circular saws, grinders, hammer drills, and large impact wrenches, gardening tools such as lawnmowers, air compressors for air tools, and electric work tools such as transport vehicles. To the equipment Regarding. [Background technology]

[0002] As described in Japanese Patent Laid-Open Publication No. 2020-185652 (Patent Document 1), a hammer drill using a brushless motor as a drive source is known. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-185652 Summary of the Invention [Problem to be solved by the invention]

[0004] In electric power tools such as hammer drills, there is a need for a technology that can reduce noise caused by stator resonance at lower cost. [Means for solving the problem]

[0005] This specification discloses an electric power tool. The electric power tool may have a motor housing having a cylindrical portion and a bottom portion. The electric power tool may have a brushless motor including a stator having a first contact surface and a rotor rotating inside the stator. The circular saw or grinder may have a cylindrical member made of resin. The circular saw or grinder may have an output portion. The stator may have a cylindrical stator core having a ring-shaped second contact surface facing the first contact surface. The stator may have a plurality of coils wound around the stator core. The stator may be held in the motor housing with the first contact surface in contact with the bottom portion of the motor housing. The rotor may have a rotor shaft rotatably supported by the motor housing. The rotor may have a rotor core fixed to the rotor shaft. The rotor may have a permanent magnet supported by the rotor core. The cylindrical member may be in contact with the second contact surface of the stator core over the entire circumference. The cylindrical member may be fixed to the motor housing with three or more screws.

[0006] This specification also discloses a method for manufacturing an electric power tool. This method may be a method for manufacturing a second electric power tool of a different type from a first electric power tool in which a stator in a brushless motor is fixed with a first number of screws. In the method for manufacturing an electric power tool, the stator may be fixed with a second number of screws that is different from the first number. [Effects of the Invention]

[0007] Electrical work of the present disclosure To the equipment This makes it possible to suppress noise caused by resonance of the stator at lower cost. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a left side view of a circular saw according to a first embodiment of the present disclosure. [Figure 2] 2 is a longitudinal cross-sectional view taken at the center positions of the rotor shaft and the output shaft in FIG. 1 (the boundary being an imaginary plane passing through the center in the left-right direction of the gear associated with the output shaft). FIG. [Figure 3] FIG. 2 is a right side view of the motor housing with the stator and baffle plate in FIG. 1. [Figure 4] FIG. 4 is a partially exploded perspective view of FIG. 3. [Figure 5] FIG. 4 is an exploded perspective view of the screws, the baffle plate, the first insulator, and the stator core in FIG. 3. [Figure 6] FIG. 4 is a cross-sectional view taken along line AA in FIG. [Figure 7] FIG. 10 is a right side view of the motor housing with the stator and baffle plate attached when there are five screws for attaching the baffle plate. [Figure 8] FIG. 8 is a partially exploded perspective view of FIG. [Figure 9] FIG. 8 is an exploded perspective view of the screws, the baffle plate, the first insulator, and the stator core in FIG. 7. [Figure 10] FIG. 8 is a cross-sectional view taken along line BB in FIG. 7. [Figure 11] FIG. 4 is a left side view of a grinder according to a second embodiment of the present disclosure. [Figure 12] FIG. 12 is a central longitudinal cross-sectional view of FIG. [Figure 13] FIG. 12 is an enlarged front view of FIG. [Figure 14] FIG. 13 is a perspective view of the brushless motor, the baffle plate, and the fan in FIG. 12. [Figure 15] FIG. 13 is a partially exploded perspective view of the brushless motor, the motor housing, the screws, and the baffle plate in FIG. 12. [Figure 16] FIG. 13 is a perspective view of the baffle plate in FIG. 12. DETAILED DESCRIPTION OF THE INVENTION

[0009] The circular saw or grinder according to the present disclosure may have a motor housing having a cylindrical portion and a bottom portion. The circular saw or grinder may have a brushless motor including a stator having a first contact surface and a rotor rotating inside the stator. The circular saw or grinder may have a cylindrical member made of resin. The circular saw or grinder may have an output portion. The stator may have a cylindrical stator core having a ring-shaped second contact surface facing the first contact surface. The stator may have multiple coils wound around the stator core. The stator may be held in the motor housing with the first contact surface in contact with the bottom of the motor housing. The rotor may have a rotor shaft rotatably supported in the motor housing. The rotor may have a rotor core fixed to the rotor shaft. The rotor may have a permanent magnet supported by the rotor core. The cylindrical member may contact the second contact surface of the stator core over the entire circumference. The cylindrical member may be fixed to the motor housing with three or more screws, which reduces noise caused by resonance of the stator at lower cost. The screw may be located at a position other than the bottom of the circular saw or grinder when it is in its normal position. In this case, the bottom of the circular saw or grinder can be made more compact. The cylindrical member may have a plurality of protrusions. Each of the protrusions may contact the second contact surface of the stator core. In this case, components and parts of the stator other than the stator core are disposed between the protrusions, thereby making the stator more compact. The cylindrical member may have screw holes through which the screws pass. A portion of each screw hole of the cylindrical member may contact the second contact surface of the stator core. In this case, the screw holes serve both to fasten the screws and to hold the stator core, making the cylindrical member and, in turn, the grinder more compact. The bottom may have ventilation holes, which allows for a more efficient cooling structure for the brushless motor. The bottom may hold a bearing that supports the rotor shaft, making the circular saw / grinding tool more compact. The stator may have a terminal unit connected to each coil. The terminal unit may have a first contact surface. In this case, a coil connection mechanism can be provided more efficiently. The outer diameter of the stator core may be equal to or greater than the axial length of the stator core, in which case noise generation is more effectively suppressed. The circular saw or grinder may be provided with a fan rotated by a rotor. The cylindrical member may be a baffle plate that straightens the airflow from the fan. In this case, the fan and stator retainer can be provided more efficiently. The stator core may be formed by stacking ring-shaped steel plates. In this case, the number of steel plates stacked in the stator core is adjustable, and the stator core can be provided more efficiently. The rotor core may be formed by stacking ring-shaped steel plates. In this case, the number of steel plates stacked in the rotor core is adjustable, and the rotor core can be provided more efficiently.

[0010] The manufacturing method for a circular saw or grinder according to the present disclosure may be a method for manufacturing a second circular saw or grinder of a different type from a first circular saw or grinder in which the stator of the brushless motor is fixed with a first number of screws. The manufacturing method for a circular saw or grinder may be a method for fixing the same stator as the first circular saw or grinder with a second number of screws different from the first number. In this case, noise caused by resonance of the stator can be suppressed at lower cost. The stator may have a cylindrical stator core, in which case the stator can be mounted more efficiently. The stator core may be formed by stacking ring-shaped steel plates. In this case, the number of steel plates stacked in the stator core is adjustable, and the stator core can be provided more efficiently. The stator may be fixed via a pressing member, in which case the stator is pressed more uniformly. The stator may be cylindrical. A rotor may be provided radially inward of the stator. A circular saw or grinder may be provided with a fan rotated by the rotor. The retaining member may be a baffle plate that straightens the airflow from the fan. In this case, the rotor, fan, and stator retaining member can be provided more efficiently.

[0011] A circular saw or grinder according to the present disclosure may include a brushless motor having a stator and a rotor disposed inside the stator, and a motor housing having a cylindrical portion for accommodating the stator and a bottom portion. The circular saw or grinder may include three or more screws. The stator may include a stator core, an insulator supported by the stator core, and a coil supported by the insulator. The rotor may include a rotor core and a permanent magnet supported by the rotor core. The maximum rotation speed of the rotor may be 14,600 RPM or more. Each screw may fix the stator to the motor housing. The maximum rotation speed may be the same during operation and during non-operation. The maximum rotation speed may be different between a maximum rotation speed during operation and a maximum rotation speed during non-operation, and the maximum rotation speed during operation may be higher than the maximum rotation speed during non-operation. In this case, noise caused by stator resonance is effectively suppressed at a lower cost. A circular saw or grinder according to the present disclosure may include a brushless motor having a stator and a rotor disposed inside the stator, and a motor housing having a cylindrical portion for accommodating the stator and a bottom portion. The circular saw or grinder may include three or more screws. The stator may include a stator core, an insulator supported by the stator core, and a coil supported by the insulator. The rotor may include a rotor core and a permanent magnet supported by the rotor core. The rotor may have a maximum rotation speed during operation (R) and a maximum rotation speed during non-operation (Rr), which may be different from or equal to each other. The maximum rotation speed during operation (R) and the maximum rotation speed during non-operation (Rr) may have a relationship expressed as "(r / R)≦0.12." Each screw may fix the stator to the motor housing. In this case, noise caused by stator resonance is effectively suppressed at a lower cost.

[0012] Hereinafter, embodiments of the present disclosure and modifications thereof will be described with reference to the accompanying drawings, but the present disclosure is not limited to these embodiments and modifications. The front, back, top, bottom, left and right directions in the embodiments and modified examples are defined for the convenience of explanation, and may change depending on at least one of the work situation and the movement of parts.

[0013] [First form] Fig. 1 is a left side view of a circular saw 1, which is an example of a handheld cutting machine among power tools belonging to the electric power equipment, according to a first embodiment of the present disclosure. Fig. 2 is a vertical cross-sectional view of the circular saw 1 at the center positions of the rotor shaft 22 and the output shaft 31 (bounded by an imaginary plane passing through the center of the gear 35 in the left-right direction). The circular saw 1 comprises a flat base 2 and a housing 3 disposed above the base 2. A "circular saw," also known as a circular saw or a circular saw, is a tool that rotates a circular saw blade. Note that a cutter, which is a tool that rotates a round grinding stone (diamond wheel), has a structure similar to that of the circular saw 1. The housing 3 indirectly supports a saw blade 4 as an end tool. The housing 3 holds a brushless motor 5 that rotates the saw blade 4. The housing 3 includes a motor housing 6, a main body housing 7, and a gear housing 8. The motor housing 6 is made of resin and has a tubular portion 6C and a box portion 6X. The tubular portion 6C is cylindrical with a bottom and has a bottom 6M. The bottom 6M is the left end portion of the motor housing 6. The motor housing 6 holds the brushless motor 5 in the tubular portion 6C. The bottom 6M of the tubular portion 6C has multiple air intake holes 6N formed therein as ventilation holes. The box portion 6X is a box-like shape with a bottom and an open lid that is open to the right, and is located above the tubular portion 6C. The bottom 6M may be separate from the tubular portion 6C. The ventilation holes may also be exhaust holes. The main body housing 7 is made of resin. The main body housing 7 is split into left and right halves that are joined together by multiple left and right screws 7a. The upper part of the main body housing 7 forms a grip part 9 shaped like the upper half of a loop. The motor housing 6 is connected to the left front portion of the main body housing 7 by a plurality of left-right screws 6a. The motor housing 6 has screw holes 6H corresponding to the screws 6a. The left part of the gear housing 8 is connected to the lower right part of the main body housing 7. The right part of the gear housing 8 serves as a blade case 10. The blade case 10 covers the upper part of the saw blade 4.

[0014] The grip portion 9 holds a switch (not shown) with a trigger 12 protruding downward. A lock-off lever 13 extending in the left-right direction passes through above the trigger 12. The lock-off lever 13 locks the trigger 12 from being pulled in when it is not pressed to the right or left. When the trigger 12 is operated upward with the lock-off lever 13 pressed, the switch turns on. When the upward operation of the trigger 12 is released, the switch turns off and the lock-off lever 13 returns to its normal state. A battery mounting section 15 is formed in the left rear portion of the main body housing 7. The battery mounting section 15 is disposed behind the motor housing 6. One or two batteries 16 are mounted in the battery mounting section 15 as a power source. Each battery 16 has a battery button 16A. Each battery 16 is mounted by sliding it from the left side to the right side of the battery mounting section 15. A mounted battery 16 is removed by sliding it to the left while operating the battery button 16A. The maximum number of batteries 16 that can be mounted in the battery mounting section 15 may be one or three or more. At least one of the batteries 16 may be mounted in a manner other than sliding. Instead of the battery 16 and the battery mounting section 15, a power cord that can be connected to an AC power source (commercial power source) may be provided.

[0015] The brushless motor 5 has a stator 20 and a rotor 21. The stator 20 is held in the cylindrical portion 6C of the motor housing 6. The rotor 21 is disposed on the inner circumferential side of the stator 20. The brushless motor 5 is an inner rotor type. The rotor 21 has a rotor shaft 22, a rotor core 59, a plurality of permanent magnets for sensors (not shown), and a plurality (four) of permanent magnets 60. The rotor shaft 22 extends in the left-right direction. The rotor 21 is rotatable about the rotor shaft 22. The rotor shaft 22 is the rotating shaft of the brushless motor 5. A pinion portion 22A is formed at the tip of the rotor shaft 22.

[0016] A fan 24 is fixed integrally to the rotor shaft 22. The fan 24 is a centrifugal fan. The fan 24 generates a flow of cooling air (wind). The fan 24 is disposed between the stator 20 and the pinion portion 22A in the left-right direction. The fan 24 may be another type of fan, such as an axial flow fan.

[0017] A baffle plate 25 is provided on the left side of the fan 24 as a cylindrical member and a retaining member. The baffle plate 25 is made of resin. The baffle plate 25 is fixed to the motor housing 6. The baffle plate 25 and the fan 24 are disposed between the motor housing 6 and the gear housing 8 in the left-right direction. The baffle plate 25 has a dish portion 25A, an extension portion 25B, and a cylindrical portion 25C. The dish portion 25A is dish-shaped and is adjacent to the fan 24. The dish portion 25A adjusts the direction of the airflow from the fan 24. The dish portion 25A straightens the airflow from the fan 24. A hole 25J is formed in the center of the dish portion 25A. The rotor shaft 22 passes through the hole 25J. The pinion portion 22A is housed within the gear housing 8. The extension portion 25B extends upward from the top of the dish portion 25A in a continuous manner with the dish portion 25A. A protrusion 25P is formed at the upper end of the extension portion 25B, protruding rightward relative to the adjacent portion. The cylindrical portion 25C is disposed on the left side of the dish portion 25A. The cylindrical portion 25C protrudes cylindrically from the left surface of the dish portion 25A. The cylindrical portion 25C has a plurality of protrusions 25S. Each protrusion 25S is disposed at the left end of the baffle plate 25. Each protrusion 25S protrudes leftward relative to the adjacent portion. Each protrusion 25S presses the stator 20 inside the motor housing 6 leftward. The stator 20 is sandwiched between the baffle plate 25 and the bottom 6M of the motor housing 6. The brushless motor 5 (stator 20), motor housing 6, and baffle plate 25 will be described in detail later.

[0018] An output shaft 31 serving as an output section is provided to the right front of the rotor shaft 22. The output shaft 31 extends in the left-right direction. A right section of the output shaft 31 is supported by a bearing 32. The bearing 32 is held by a bearing retainer 33. The bearing retainer 33 has a cylindrical section. The bearing 32 is disposed within the cylindrical section of the bearing retainer 33. A left end section of the output shaft 31 is supported by a bearing (not shown) held in the gear housing 8. A gear 35 is fixed integrally to the left portion of the output shaft 31. The gear 35 is in mesh with a pinion portion 22A of the rotor shaft 22. The pinion portion 22A has a smaller diameter than the gear 35. The number of teeth of the pinion portion 22A is fewer than the number of teeth of the gear 35. The pinion portion 22A is disposed rearward and downward of the uppermost portion of the gear 35. A ring 36 is provided on the left side of the bearing 32. The ring 36 is held by a bearing retainer 33. The ring 36 bears the thrust load of the bearing 32.

[0019] A saw blade 4 is fixed to the right end of the output shaft 31. The saw blade 4 is sandwiched between an outer flange 42 and an inner flange 43 and fixed by screwing a bolt 44 extending in the left-right direction into the axis of the output shaft 31 from the right. The output shaft 31, the outer flange 42, the inner flange 43, and the bolt 44 form a tool holder. A safety cover 45 is disposed within the gear housing 8. In a normal state, the safety cover 45 covers the underside of the saw blade 4. The safety cover 45 is rotatably attached to the gear housing 8. The safety cover 45 is biased to rotate toward its normal position.

[0020] An example of the operation of such a circular saw 1 will now be described. The user makes the following preparations: the safety cover 45 is rotated from its normal position to a position where it is housed in the blade case portion 10 of the gear housing 8, and the charged battery 16 is attached to the battery attachment portion 15. When the user pulls the trigger 12 upward, the switch is turned on, the brushless motor 5 is driven, and the rotor 21 rotates. The rotation of the rotor 21 rotates the rotor shaft 22, which in turn rotates the output shaft 31 at a reduced speed via the pinion portion 22A and the gear 35. This causes the saw blade 4 attached to the output shaft 31 to rotate, thereby enabling the circular saw 1 to cut a workpiece. In addition, as the fan 24 rotates in conjunction with the rotation of the rotor shaft 22, the cooling air drawn in through the intake hole 6N passes through the brushless motor 5 to cool it, and is then sent by the baffle plate 25 to the main housing 7 side and the gear housing 8 side.

[0021] The brushless motor 5 (stator 20), the motor housing 6, and the baffle plate 25 will be described in detail below. Fig. 3 is a right side view of the motor housing 6 with the stator 20 and the baffle plate 25 attached. Fig. 4 is a partially exploded perspective view of Fig. 3. Fig. 5 is an exploded perspective view of the screws 68, the baffle plate 25, the first insulator 51, and the stator core 50. Fig. 6 is a cross-sectional view taken along line AA in Fig. 3.

[0022] The stator 20 of the brushless motor 5 has a stator core 50, a first insulator 51, a plurality (six) of second insulators 52, a third insulator 53, a plurality (six) of coils 56, a sensor board 57, and a terminal unit 58.

[0023] The stator core 50 is made by laminating multiple ring-shaped steel plates. The stator core 50 has a cylindrical stator core body 50A and multiple teeth 50B. Each tooth 50B protrudes radially inward from the inner surface of the stator core body 50A. The second contact surface 50S is located on the right surface of the stator core 50. The second contact surface 50S is ring-shaped.

[0024] The first insulator 51 is an insulating member and is in contact with the stator core 50 on the right side. Each second insulator 52 is an insulating member and is disposed between adjacent teeth 50B in the circumferential direction. The third insulator 53 is an insulating member and is in contact with the stator core 50 on the left side. Each coil 56 is wound around the corresponding tooth 50B via the first insulator 51, the second insulator 52, and the third insulator 53. The number of each coil 56 is called the number of slots. At least one of the first insulator 51 and the third insulator 53 and the second insulator 52 may be formed integrally.

[0025] The sensor board 57 is ring-shaped and fixed to the left end of the stator core body 50A. The sensor board 57 is adjacent to the left side of the third insulator 53. The sensor board 57 is equipped with multiple (two) rotation detection elements (not shown). Each rotation detection element detects the position of a sensor permanent magnet and outputs a rotation detection signal. The sensor permanent magnets are provided in the rotor core 59. The rotor core 59 is cylindrical. The rotor core 59 is formed by laminating ring-shaped steel plates. The rotor core 59 is arranged around the rotor shaft 22. The rotor core 59 is fixed integrally to the rotor shaft 22. The rotor core 59 supports a plurality of (four) plate-shaped permanent magnets 60 (see FIG. 2). The permanent magnets 60 are positioned on four side surfaces of an imaginary rectangular parallelepiped. The imaginary rectangular parallelepiped extends in the left-right direction and is concentric with the rotor shaft 22. The terminal unit 58 is ring-shaped. The terminal unit 58 is fixed to the left end of the stator core main body 50A. The terminal unit 58 is arranged radially outward of the sensor board 57. The terminal unit 58 electrically connects each coil 56 in a predetermined manner. The terminal unit 58 has multiple (six) fusing terminals 58A. Each fusing terminal 58A is connected to a crossover wire between the corresponding coils 56. The left surface of the terminal unit 58 is a first contact surface 58F facing the second contact surface 50S. The first contact surface 58F contacts the bottom 6M of the motor housing 6.

[0026] A controller 62 is held in the box portion 6X of the motor housing 6. The right portion of the controller 62 protrudes rightward from the right end of the box portion 6X. The right portion of the controller 62 is held by the protruding portion 25P of the baffle plate 25. An electrolytic capacitor 63 is disposed above the controller 62. The electrolytic capacitor 63 is held in the main body housing 7. The electrolytic capacitor 63 is a smoothing capacitor. The controller 62 has a control circuit board 64. The control circuit board 64 is equipped with a microcomputer, a diode, a switching element, etc. The control circuit board 64 is also electrically connected to the electrolytic capacitor 63 via lead wires (not shown). The control circuit board 64 has a rectifier circuit and an inverter circuit. The control circuit board 64 is also electrically connected to the sensor board 57 via lead wires (not shown). The microcomputer on the control circuit board 64 obtains the rotation state of the rotor 21 by receiving a rotation detection signal indicating the position of the sensor permanent magnet of the rotor 21, which is output from the rotation detection element on the sensor board 57. The microcomputer on the control circuit board 64 also controls the on / off of each switching element in accordance with the obtained rotation state, and causes current to flow sequentially through each coil 56 of the stator 20, thereby rotating the rotor 21. The current to each coil 56 is rectified by the controller 62. The magnetic field generated in each coil 56 acts on the permanent magnet 60 of the rotor 21.

[0027] The stator 20 is inserted into the cylindrical portion 6C of the motor housing 6. The cylindrical portion 6C has multiple (three) screw boss portions 6B. The three screw boss portions 6B are located at the top, lower front, and lower rear of the cylindrical portion 6C. Therefore, the lower portion of the motor housing 6 is not protruded by the screw boss portions 6B and the screws 68 described below. In other words, the screw boss portions 6B and the screws 68 described below are located at a position other than the lower portion when the circular saw 1 is in its normal position. Therefore, the maximum thickness of the workpiece that can be cut by the saw blade 4 is increased. That is, unlike the circular saw 1 shown in FIG. 2 and other figures, if the screw boss portion 6B were located at the bottom of the tubular portion 6C, the tubular portion 6C would be located higher than the circular saw 1 shown in FIG. 2 to avoid interference between the screw boss portion 6B at the bottom and the base 2. As a result, the rotor shaft 22 of the brushless motor 5 located inside the tubular portion 6C would also be located higher than the circular saw 1 shown in FIG. 2. The output shaft 31 connected to the rotor shaft 22 and the saw blade 4 attached thereto would also be located higher than the circular saw 1 shown in FIG. 2. When the screw boss portion 6B is located at the bottom of the tubular portion 6C, the saw blade 4 is located higher, and thus its protrusion height (the vertical extent of protrusion) from the base 2 is reduced. Therefore, in this case, the maximum thickness of a workpiece that can be cut by the saw blade 4 is smaller than in the circular saw 1. In contrast, in the circular saw 1, the maximum thickness of a workpiece that can be cut by the saw blade 4 is greater. The baffle plate 25 has a plurality of (three) screw holes 25H on the periphery of the dish portion 25A. The arrangement of the screw holes 25H when viewed leftward from the right side of the baffle plate 25 matches the arrangement of the screw boss portions 6B of the motor housing 6. The first insulator 51 has a ring-shaped first insulator body 51A and multiple (six) first tooth covering portions 51B. The first insulator body 51A has multiple (six) recesses 51C that are recessed radially inward relative to adjacent portions. Each recess 51C is located between adjacent first tooth covering portions 51B in the circumferential direction.

[0028] The baffle plate 25 is screwed to the cylindrical portion 6C in a state of contact with the stator 20. That is, a plurality of screws 68 (three, a first number) are provided to pass through the screw boss portions 6B and the corresponding screw hole portions 25H. Each protrusion 25S of the baffle plate 25 is disposed radially outward of the corresponding recess 51C of the first insulator 51. Each protrusion 25S contacts the second contact surface 50S of the stator core main body 50A. The entire protrusion 25S contacts the entire circumference of the ring-shaped second contact surface 50S. Each protrusion 25S presses the stator core 50 to the left. The stator 20 is supported by the bottom 6M of the motor housing 6 at the first contact surface 58F. Note that the first contact surface, which is the surface at which the stator 20 is supported by the motor housing 6, may be provided in one or more other portions of the stator 20 instead of or together with the terminal unit 58. For example, the first contact surface may be provided on the stator core 50. The pressing force (load) of the baffle plate 25 against the stator core 50 by the three screws 68 increases monotonically with the number of screws 68.

[0029] The stator 20 resonates when the rotational frequency of the rotor 21 or its harmonic components (Hz, Hertz) matches the resonant frequency (Hz) of the stator 20. This resonance of the stator 20 generates a sound that is noticeable to the user of the circular saw 1. A circular mode exists as a vibration mode caused by resonance of the stator 20, mainly in the radial direction. Examples of vibration in the circular mode include elliptical deformation (second-order circular), triangular deformation (third-order circular), and rectangular deformation (fourth-order circular). Furthermore, when the thickness of the stator 20 (the size in the left-right direction in the first form) is smaller than a predetermined value, the stator 20 also deforms and vibrates in an axial direction. If a portion of the stator 20 that deforms in the axial direction during vibration receives an external load in the axial direction, the stator 20 is constrained in the axial direction. This increases the rigidity of the stator 20. This increases the resonant frequency of the stator 20 compared to when there is no load. Furthermore, when the magnitude of the load on the stator 20 increases, the rigidity of the stator 20 further increases. This further increases the resonant frequency of the stator 20. This means that the resonant frequency of the stator 20 changes as the magnitude of the load on the stator 20 changes. The resonant frequency of the stator 20 increases monotonically with the magnitude of the load on the stator 20. Here, the rotational frequency or its harmonic components of the rotor 21, and the resonant frequency of the stator 20 will be described in further detail. That is, for each rotation of the rotor 21, the stator 20 experiences changes in the magnetic field caused by the permanent magnets 60 a number of times equal to the number of permanent magnets 60 (four). The number of permanent magnets 60 is called the number of poles. Therefore, the stator 20 vibrates at a frequency obtained by multiplying the rotational frequency by the number of poles, that is, at the fourth-order harmonic component in the case of the brushless motor 5. Furthermore, the rotation speed of the rotor 21 is generally expressed in terms of RPM (rotations per minute) rather than rotation frequency (Hz). On the other hand, for people with normal hearing, sounds in the frequency range of 1600 Hz to 4000 Hz and adjacent ranges are noticeable. Of the above frequency ranges, sounds in the frequency range of 2000 Hz to 3150 Hz are particularly noticeable. Furthermore, the brushless motor 5 (rotor 21) of this embodiment can rotate at 30,000 RPM. Therefore, if the resonant frequency of stator 20 is 2000 Hz for rotor 21 rotating at 30,000 RPM (500 Hz), the vibration of 2000 Hz, calculated by multiplying the rotational frequency by the number of poles (4), will be amplified by the resonance, and the sound will be audible to the user. Also, unlike brushless motor 5, brushless motors with two poles or more are now available that can rotate at 80,000 RPM (approximately 1,333 Hz). In such brushless motors, if resonance of stator 20 occurs at the same frequency as the rotational frequency of rotor 21, sound belonging to the adjacent frequency range described above will be generated, even if it is the rotational frequency itself and not a harmonic component.

[0030] In the above-described circular saw 1 (first electric implement), vibration or noise above a predetermined level is not generated. If a different type of circular saw (second electric implement) having a different main rotation speed of the brushless motor 5 is designed or prototyped using the same brushless motor 5, and vibration or noise above a predetermined level is generated due to resonance of the stator 20, the vibration or noise in the second electric implement can be reduced by changing the resonant frequency of the stator 20. For example, if the main rotation speed of the circular saw 1 is 20,000 RPM, and a different type of circular saw having a main rotation speed of 36,000 RPM is designed or prototyped using the same brushless motor 5, and vibration or noise above a predetermined level is generated due to resonance of the stator 20, the vibration or noise in the second electric implement can be reduced by changing the resonant frequency of the stator 20. As described above, the resonant frequency of the stator 20 is changed by changing the axial load on the stator 20. In the first embodiment, the axial load on the stator 20 is changed by changing the number of screws 68 attached to the baffle plate 25 and the motor housing 6. The number of screws 68 is changed from three (first number) for the first electric power implement to five (second number) for the second electric power implement.

[0031] Fig. 7 is a right side view of the motor housing 106 with the stator 20 and baffle plate 125 of a circular saw (second electric power implement) when there are five screws 68. Fig. 8 is a partially exploded perspective view of Fig. 7. Fig. 9 is an exploded perspective view of the screws 68, the baffle plate 125, the first insulator 51, and the stator core 50. Fig. 10 is a cross-sectional view taken along line BB in Fig. 7. Hereinafter, the same members and parts as those in the case where there are three screws 68 will be denoted by the same reference numerals, and the description thereof will be omitted as appropriate.

[0032] The cylindrical portion 106C of the motor housing 106 has two screw bosses 106B in addition to the three screw bosses 6B. The front screw boss 106B is located between the upper screw boss 6B and the lower front screw boss 6B in the circumferential direction of the cylindrical portion 106C. The rear screw boss 106B is located between the upper screw boss 6B and the lower rear screw boss 6B in the circumferential direction of the cylindrical portion 106C. Therefore, the lower part of the motor housing 6 does not protrude due to the screw bosses 6B, 106B. In other words, the screw bosses 6B, 106B and the screw 68 are located at a position other than the lower part of the circular saw 1 in its normal position. Therefore, the maximum thickness of the workpiece that can be cut by the saw blade 4 is increased. The baffle plate 125 has two screw holes 125H in addition to the three screw holes 25H. When viewed from the right side to the left, the arrangement of the two screw holes 125H corresponds to the two screw bosses 106B.

[0033] The baffle plate 125 is screwed to the cylindrical portion 106C in a state of contact with the stator 20. That is, a total of five screws 68 are provided that pass through the screw boss portions 6B, 106B and the corresponding screw holes 25H, 125H. Each protrusion 25S of the baffle plate 125 is disposed radially outward of the corresponding recess 51C of the first insulator 51. Each protrusion 25S contacts the second contact surface 50S. The entire protrusion 25S contacts the entire circumference of the ring-shaped second contact surface 50S. Each protrusion 25S presses the stator core body 50A to the left. The stator 20 is supported by the bottom 6M of the motor housing 6 at the first contact surface 58F. The load of the baffle plate 125 on the stator core 50 due to the five screws 68 is greater than when there are three screws 68. Therefore, the resonance frequency of the stator 20 is higher than when there are three screws 68. Therefore, the vibration and noise caused by the three screws 68 are reduced by the stator 20 being pressed by the baffle plate 125 attached by the five screws 68.

[0034] Such reduction in vibration and noise can be achieved not by changing the type (specifications) of the brushless motor 5, but by changing the number of screws 68 attached to the baffle plates 25, 125 that press the stator 20. Therefore, when manufacturing a second electric power implement (a circular saw with five screws 68) using the stator 20 of the brushless motor 5 of the first electric power implement (a circular saw 1 with three screws 68), noise reduction can be easily achieved by changing the number of screws 68 used to secure the stator 20. Furthermore, the same type of brushless motor 5 can be used in various circular saws 1, including the first and second electric power implements, with vibration and noise suppressed simply by changing the number of screws 68 as appropriate. This reduces costs. Furthermore, such reduction in vibration and noise can be achieved not by changing the material (Young's modulus) of the baffle plates 25, 125, but by changing the number of screws 68 attached to the baffle plates 25, 125 that press the stator 20. This reduces the cost for suppressing the generation of vibration and noise.

[0035] In the first embodiment, as described above, the resonant frequency of the stator 20 can be changed by increasing the number of screws 68 to increase the load on the stator 20 and increase the rigidity of the stator 20. Therefore, the resonant frequency of the stator 20 can be changed more easily in a stator 20 with a relatively low rigidity than in a stator 20 with a sufficiently high rigidity to begin with. For example, when the condition of the following formula (1) is satisfied, the resonant frequency of the stator 20 can be changed more effectively. In formula (1), Φ is the outer diameter of the cylindrical stator core 50. Furthermore, T is the thickness of the stator core 50 (the size in the left-right direction in the first embodiment), i.e., the axial length of the stator core 50. Φ≧T (1) Furthermore, the smaller T is relative to Φ, the more effectively the resonant frequency of the stator 20 is changed.

[0036] The first embodiment is not limited to the above and the modified examples, and further modifications such as those described below can be made as appropriate. The number of screws 68 may be three or more, may be four, may be six or more, or may be two or less. In the motor housing 106 having a total of five screw boss portions 6B, 106B, the load on the stator 20 may be increased or decreased by inserting three, four, or five screws 68. The cylindrical portion 25C may be separated from the other portions of the baffle plates 25 and 125. The cylindrical member that holds the stator 20 may be something other than the baffle plate 25. When the same type of brushless motor 5 is used in a circular saw 1 (first electric implement) and a product (second electric implement) other than the circular saw 1, adjusting the number of screws 68 may suppress vibration and noise in the product other than the circular saw 1. When the same type of brushless motor 5 is used in a product (first electric implement) and a product (second electric implement) other than the circular saw 1, adjusting the number of screws 68 may suppress vibration and noise in the product (second electric implement) other than the circular saw 1.

[0037] The number of permanent magnets 60 (the number of poles of the rotor 21) or the number of coils 56 in the brushless motor 5 may be increased or decreased relative to the above. For example, the number of permanent magnets 60 may be six. The number of laminations in the stator core 50 can also be set as appropriate. The reduction mechanism from the rotor shaft 22 to the output shaft 31 in the circular saw 1 may be replaced with other reduction mechanisms such as a planetary gear reduction mechanism, or may be a combination of these. The circular saw 1 may be powered by a commercial power source by having a power cord instead of the battery mounting portion 15. In the brushless motor 5, at least one of the microcomputer and the switching element may be mounted on the sensor board 57. At least one of the materials of the various cases and housings may be changed to resin, metal, a composite thereof, etc. The metal may be an aluminum alloy, a magnesium alloy, or other metal. The classification of the housing 3 may be changed from that described above. In addition, at least one of the various members, the number of parts, whether or not they are installed, the material, arrangement, structure, and type may be changed as appropriate. Furthermore, the first embodiment or its modifications may be applied to other types of circular saws, such as those in which the saw blade 4 is arranged on the left side, other handheld cutting machines other than circular saws, or non-handheld cutting machines, or other power tools, or other power-driven work equipment, etc. For example, the first embodiment or its modifications are applied to high-power products, such as angle drills, hammers, hammer drills, reciprocating saws, or grinders among power tools, or chainsaws, hedge trimmers, blowers, lawn mowers, grass cutters, hedge trimmers, or cleaners among gardening tools, or air compressors for air-powered pneumatic tools. Electric equipment for operating work machines that perform work, such as air compressors for air tools, is included in the category of power-driven work equipment.

[0038] [Second form] Fig. 11 is a left side view of a grinder 201, which is an example of a power tool belonging to the category of electric power equipment, according to a second embodiment of the present disclosure. Fig. 12 is a central vertical cross-sectional view of the grinder 201. Fig. 13 is an enlarged front view of Fig. 12. Fig. 14 is a perspective view of a brushless motor 228, a baffle plate 285, and a fan 284 of the grinder 201. Fig. 15 is a partially exploded perspective view of the brushless motor 228, a motor housing 212, a screw 218, and a baffle plate 285 of the grinder 201. Fig. 16 is a perspective view of the baffle plate 285 of the grinder 201. The grinder 201 includes a main body 202 and an output mechanism 204 . The main body 202 extends in the front-rear direction. The output mechanism 204 is provided on the front side of the main body 202. The outer shell of the main body 202 and the output mechanism 204 forms a housing 206 .

[0039] The housing 206 includes a rear housing 210 , a motor housing 212 , a first bearing retainer 213 , a gear housing 214 , and a second bearing retainer 216 .

[0040] The rear housing 210 , the motor housing 212 and the first bearing retainer 213 form the outer shell of the main body 202 . The rear housing 210 is split into left and right halves. The left and right halves of the rear housing 210 are joined together with a plurality of left-right screws 218. A left and right half-sized cover 220 is attached to the outer surface of the rear housing 210. The front half of each of the rear housing 210 and cover 220 is the portion that the user grips, i.e., the grip portion 217. The motor housing 212 is connected at its front side to the rear housing 210. The motor housing 212 is cylindrical and has a cylindrical portion throughout. The motor housing 212 has a bottom 212M. The bottom 212M has a plurality of holes 212N in the front-rear direction as ventilation holes. The first bearing retainer 213 is ring-shaped. The first bearing retainer 213 extends vertically and horizontally. The first bearing retainer 213 has a plurality of exhaust holes (not shown). Each exhaust hole is arc-shaped.

[0041] The gear housing 214 and the second bearing retainer 216 form the outer shell of the output mechanism portion 204 . The gear housing 214 is connected to the motor housing 212 at the front side via a first bearing retainer 213. The gear housing 214 and the first bearing retainer 213 are fastened together to the motor housing 212 with a plurality of (four) screws 222 extending in the front-to-rear direction. The gear housing 214 has a plurality of exhaust holes 215. The exhaust holes 215 are arranged above and below the rear part of the gear housing 214. Each exhaust hole 215 is connected to a corresponding exhaust hole in the first bearing retainer 213 via the inside of the rear end part of the gear housing 214. As shown in FIG. 15, the motor housing 212 has screw bosses 212G for each screw 222. The motor housing 212 also has a plurality (two) of raised portions 212U on its inner surface that protrude radially inward from other portions. The raised portions 212U are arranged above and below. A plurality (two on each side, for a total of four) of screw boss portions 212B are formed in the front of each raised portion 212U. Each screw boss portion 212B extends in the front-to-rear direction. Two screw boss portions 212B are arranged on the left and right of the upper raised portion 212U. Another two screw boss portions 212B are arranged on the left and right of the lower raised portion 212U. Unlike the circular saw 1, the grinder 201 is gripped by the outer periphery of the motor housing 212 by the user. Therefore, the outer diameter of the motor housing 212 of the grinder 201 may be as small as possible. And, unlike the circular saw 1, the arrangement of the screws 222 of the grinder 201 is arbitrary. Also, in the grinder 201, the screws 222 (screw bosses 212G) are arranged at the upper left, upper right, lower left, and lower right. Therefore, the upper, lower, left, and right portions of the motor housing 212 do not protrude due to the screws 222 (screw bosses 212G), making the grinder compact. The second bearing retainer 216 is held by the gear housing 214. The second bearing retainer 216 is disposed below the gear housing 214. The second bearing retainer 216 is fixed to the gear housing 214 by a plurality of (four) screws 226. Each screw 226 extends vertically. Each screw 226 is inserted from below the second bearing retainer 216.

[0042] The motor housing 212 holds an electric brushless motor 228 . Brushless motor 228 has a stator 230 and a rotor 231. Rotor 231 is disposed on the inner periphery side of stator 230. Brushless motor 228 is an inner rotor type.

[0043] The rotor 231 has a rotor shaft 232, a rotor core 233, a plurality of (four) permanent magnets 234, a plurality of (four) permanent magnets for sensors (not shown), and a sleeve 235. The number of poles of the brushless motor 228 (rotor 231) is four, the same as that of the brushless motor 5 of the circular saw 1.

[0044] The rotor shaft 232 extends in the front-rear direction. The rotor 231 is rotatable about the rotor shaft 232. The rotor shaft 232 is the rotation shaft of the brushless motor 228. A pinion gear 238 is held at the front end of the rotor shaft 232. The pinion gear 238 has a bevel gear shape. The rotor shaft 232 extends from inside the motor housing 212 to inside the gear housing 214. The rotor shaft 232 is rotatably supported by a front bearing 242 and a rear bearing 244. The front bearing 242 is held by a first bearing retainer 213. The rear bearing 244 is held by a bottom portion 212M of the motor housing 212.

[0045] The rotor core 233 is cylindrical. The rotor core 233 is disposed around the rotor shaft 232. The rotor core 233 is a rotor iron core. The rotor core 233 is formed by laminating ring-shaped steel plates. Each permanent magnet 234 is held inside the rotor core 233 . Each sensor permanent magnet is held inside the rotor core 233.

[0046] The sleeve 235 is ring-shaped and made of metal (brass). The sleeve 235 is disposed around the rotor shaft 232. The sleeve 235 is adjacent to the rotor core 233. The sleeve 235 covers a radially outer portion of the front plane of the rotor core 233. After the rotor 231 (and the fan 284 described below) is formed, a portion of the sleeve 235 is removed to adjust the rotational balance of the rotor 231. The sleeve 235 is made of brass, which is relatively soft, so this adjustment is easy to make. The sleeve 235 is fixed to the rotor core 233. The sleeve 235 covers the front end of each permanent magnet 234. The sleeve 235 may be made of resin.

[0047] The stator 230 includes a stator core 250, a first insulator 251, a plurality (six) of second insulators (not shown), a third insulator 253, a plurality (six) of coils 256, a sensor board 257, and a terminal unit 258. The stator 230 is held in the motor housing 212 . The outer diameter and number of slots of the stator 230 are the same as those of the stator 20 of the first embodiment.

[0048] That is, the stator core 250 is configured similarly to the stator core 50, and includes a stator core body 250A and a plurality of teeth 250B. The front surface of the stator core 250 is a second contact surface 250S. The second contact surface 250S is ring-shaped. The first insulator 251 has the same configuration as the first insulator 51. The first insulator 251 has a ring-shaped first insulator body 251A and multiple (six) first tooth covering portions 251B. The first insulator body 251A has multiple (six) recesses 251C recessed radially inward relative to adjacent portions. Each recess 251C is disposed between adjacent first tooth covering portions 251B in the circumferential direction. The second insulator 252 (not shown) is configured similarly to the second insulator 52 . The third insulator 253 is configured in the same manner as the third insulator 53 . Coil 256 is similar to coil 56 . At least one of the first insulator 251 and the third insulator 253 and the second insulator 252 may be formed integrally.

[0049] The sensor substrate 257 is configured similarly to the sensor substrate 57 . The terminal unit 258 is configured similarly to the terminal unit 58, and has a plurality of fusing terminals 258A (see FIG. 14). 258 The rear surface of the terminal unit 258 is a first contact surface 258F facing the second contact surface 250S. The first contact surface 258F comes into contact with the bottom 212M of the motor housing 212. The terminal unit 258 also has a connection portion 258B. A plurality of power supply leads (not shown) and a plurality of signal leads (not shown) are connected to the connection portion 258B. These leads pass through holes 212N in the motor housing 212. The terminal unit 58 of the first embodiment also has a connection portion similar to the connection portion 258B. The stator 230 is encased within the motor housing 212 .

[0050] A controller 262 is held at the rear of the rear housing 210. Except for its arrangement, the controller 262 is similar to the controller 62 of the first embodiment, and has a control circuit board 264. The controller 262 extends vertically and front-to-rear. The controller 262 is oriented with its front tilted downward. The control circuit board 264 is connected to the above-mentioned multiple power supply leads and multiple signal leads. The control circuit board 264 is electrically connected to the connection portion 258B.

[0051] A battery mounting portion 270 is formed at the rear end portion of the rear housing 210. A single battery 272 is mounted in the battery mounting portion 270 as a power source. The battery 272 has a battery button 272A. The battery 272 is attached by sliding downward from the top of the battery attachment section 270. When attached, the battery 272 is positioned with its front tilted downward. The attached battery 272 can be removed by operating the battery button 272A and sliding it upward. The battery 272 is electrically connected to the controller 262 via a terminal in the battery mounting section 270 . The number of batteries 272 that can be attached to the battery attachment section 270 may be two or more. The batteries 272 may be attached in a manner other than slide attachment. Furthermore, instead of the battery 272 and the battery attachment section 270, a power cord that can be connected to an AC power source (commercial power source) may be provided.

[0052] A switch 274 is held in the rear housing 210. The switch 274 is connected to the controller 262 by a switch lead wire (not shown). A switch lever 276 is disposed below the switch 274. The switch lever 276 is held by the rear housing 210. The rear end of the switch lever 276 is rotatably supported by the rear lower part of the rear housing 210. The downward rotational movement of the front end of the switch lever 276 is restricted by the front lower part of the rear housing 210. The switch lever 276 rotates upward around its rear end when the user pushes it upward (pulls it up with their fingers). The switch lever 276 that has moved upward pushes up the plunger of the switch 274, turning the switch 274 on.

[0053] The switch lever 276 has a locking portion 278. The locking portion 278 is a rod-shaped member. When the switch lever 276 is not operated (FIGS. 11 and 12), the locking portion 278 extends vertically and takes an upright position. The locking portion 278 is attached to the switch lever 276 so as to be rotatable in the left-right direction. A torsion spring (not shown) is connected to the locking portion 278. When not in operation, the upper end of the locking portion 278 abuts against a rib on the rear housing 210, thereby preventing the switch lever 276 from moving upward and preventing the switch 274 of the brushless motor 228 from being turned on. In contrast, when the user rotates the lower part of locking portion 278 against the biasing force of the torsion spring, locking portion 278 assumes a position extending in the front-to-rear direction and no longer prevents the upward movement of grip portion 217. Therefore, the operator can turn on switch 274 of brushless motor 228 by simply gripping grip portion 217.

[0054] Between the pinion gear 238 of the rotor shaft 232 and each coil 256, a fan 284 and a baffle plate 285 as a cylindrical member are provided. The fan 284 is an axial flow fan and is fixed to the rotor shaft 232. The baffle plate 285 has a dish portion 285A, a cylindrical portion 285C, and a plurality of (four) screw hole portions 285H. The dish portion 285A has holes 285J, similar to the baffle plate 25 of the first embodiment. The cylindrical portion 285C protrudes cylindrically from the rear surface of the dish portion 285A. The cylindrical portion 285C has a plurality of protrusions 285S. Each protrusion 285S is disposed at the rear end of the baffle plate 285. Each protrusion 285S protrudes rearward relative to the adjacent portion. Each screw hole 285H is arranged from the periphery of the dish portion 285A to the cylindrical portion 285C. The arrangement of the screw holes 285H when viewed from the front to the rear of the baffle plate 285 matches the arrangement of the screw boss portions 212B of the motor housing 212. In the front-to-rear direction, the position of the rear end of each screw hole 285H matches the position of the rear end of each protrusion 285S.

[0055] Baffle plate 285 is screwed to cylindrical motor housing 212 in contact with stator 230. That is, a plurality of (four) screws 288 are provided to pass through screw boss portions 212B and corresponding screw holes 285H. Each of the protrusions 285S of the baffle plate 285 is disposed radially outward of the first insulator 251. Each of the screw holes 285H is disposed radially outward of a corresponding recess 51C of the first insulator 251. The radially inner portions of each of the protrusions 285S and screw holes 285H contact the second contact surface 250S of the stator core main body 250A. The entire periphery of the protrusions 285S and the radially inner portions of each of the screw holes 285H contacts the ring-shaped second contact surface 50S. The radially inner portions of each of the protrusions 285S and screw holes 285H press the stator core 250 rearward. Each of the screw holes 285H serves both as a screw hole and a pressing function. The stator 230 is sandwiched between the baffle plate 285 and the bottom portion 212M of the motor housing 212. The stator 230 is supported by the bottom portion 212M of the motor housing 212 at the first contact surface 258F. The load of the baffle plate 285 on the stator core 250 due to the four screws 288 depends on the number of the screws 288.

[0056] The pinion gear 238 meshes with the bevel gear 290. The number of teeth of the pinion gear 238 is smaller than the number of teeth of the bevel gear 290. The bevel gear 290 is fixed to a spindle 292. The spindle 292 serving as the output unit is at an angle of approximately 90° to the rotor shaft 240. The spindle 292 extends vertically. The spindle 292 (the output shaft of the output mechanism unit 204) is at an angle of approximately 90° to the rotor shaft 240, and the grinder 201 is an angle tool (angle power tool). An upper portion of the spindle 292 is disposed within the gear housing 214. A central portion of the spindle 292 is disposed within the second bearing retainer 216. A lower portion of the spindle 292 is exposed from the second bearing retainer 216. The upper end of the spindle 292 is housed in a spindle upper bearing 294. The spindle upper bearing 294 is held in the gear housing 214. The center of the spindle 292 is housed in a spindle middle bearing 296. The spindle middle bearing 296 is fixed to the second bearing retainer 216. A disc-shaped grindstone 298 is attached to the lower end of the spindle 292. The grindstone 298 is an end tool. A wheel cover 299 is attached to the lower part of the second bearing retainer 216. The wheel cover 299 is arranged around the grindstone 298.

[0057] Such a grinder 201 operates, for example, as follows. That is, the user mounts the charged battery 272 in the battery mounting portion 270. Then, the user pushes the switch lever 276 upward while unlocking the locking portion 278. This turns on the switch 274 of the brushless motor 228. As a result, the control circuit board 264 controls the power to the stator 230, causing the rotor 321 to rotate. This causes the pinion gear 238 attached to the rotor shaft 322 to rotate. This causes the spindle 292 to rotate at a reduced speed via the bevel gear 290, causing the grinding wheel 298 attached to it to rotate. The user can grind the workpiece by bringing the rotating grinding wheel 298 into contact with the workpiece. When the user releases the switch lever 276, the switch lever 276 returns downward, and the switch 274 of the brushless motor 228 is turned off. This stops the rotation of the rotor shaft 240. This also stops the rotation of the bevel gear 290, the spindle 292, and the grindstone 298. The locking portion 278 returns to a position that locks the pushing operation of the switch lever 276 due to the torsion spring.

[0058] Furthermore, the rotation of the rotor shaft 240 rotates the fan 284, causing an airflow (wind) to flow to each exhaust hole of the first bearing retainer 213 and each exhaust hole 215 of the gear housing 214. This wind is rectified by the dish portion 285A of the baffle plate 285. This wind then cools the internal mechanisms of the grinder 201, such as the brushless motor 228 and the controller 262. The external intake portion of the grinder 201 for this wind is the portion of the rear housing 210 where the switch lever 276 is installed. At least a portion of this wind passes through the hole 212N of the motor housing 212. Therefore, the hole 212N serves as an air vent.

[0059] When designing or prototyping a different type of grinder (second electric power tool) using the brushless motor 228 and motor housing 212 of the grinder 201 (first electric power tool) described above but with a different main rotation speed of the brushless motor 228, if vibration or noise of a predetermined level or more is observed due to resonance of the stator 20, the vibration or noise in the different type of grinder can be suppressed, for example, as follows: That is, the number of screws 288 fixing the baffle plate 285 to the motor housing 212 is reduced to three. Alternatively, a motor housing having five or more screw boss portions 212B is prepared, and the number of screws 288 fixing the baffle plate 285 is set to five or more. By changing the number of screws 288 in this way, the axial load on the stator 230 is changed, thereby changing the rigidity of the stator 230. Therefore, the resonance frequency of the stator 230 is changed, thereby reducing vibration or noise in other types of grinders.

[0060] Such reduction in vibration and noise can be achieved by changing the number of screws 288, rather than by changing the type of brushless motor 228. Therefore, the same type of brushless motor 228 can be used in various grinders with reduced vibration and noise generation, thereby reducing costs. Furthermore, such reduction in vibration and noise can be achieved by changing the number of screws 288, rather than by changing the material (Young's modulus) of the baffle plate 285. This reduces the cost for suppressing the generation of vibration and noise.

[0061] The second embodiment has the same modifications as the first embodiment, as appropriate.

[0062] [Brushless motor rotation speed, etc.] The brushless motors 5,228 of the first and second embodiments rotate at higher speeds than brushed motors. As mentioned above, the maximum rotation speed of the brushless motor 5,228 is 30,000 RPM. In such a high-speed brushless motor 5,228, there is a high possibility that resonance will occur. In the applicant's trials, the impact of resonance was greater in brushless motors with a maximum rotation speed of 14,600 RPM or more than in those with a maximum rotation speed of less than 14,600 RPM. Therefore, the usefulness of changing the resonance frequency using screws is greater in brushless motors with a maximum rotation speed of 14,600 RPM or more. Furthermore, in brushless motors with a maximum rotation speed of 25,000 RPM or more, the usefulness of changing the resonance frequency using screws is even greater. Furthermore, in brushless motors with a maximum rotation speed of 50,000 RPM or more, the usefulness of changing the resonance frequency using screws is even greater. In addition, in brushless motors with a maximum rotation speed of 80,000 RPM or more, the usefulness of changing the resonance frequency using screws is even greater.

[0063] [Software no-load availability, etc.] The circular saw 1 of the first embodiment and the grinder 201 of the second embodiment do not employ a so-called soft no-load. A soft no-load operation means that the motor is rotated at a speed (not exceeding the maximum non-working speed) when not in use (when unloaded) that is lower than the maximum working speed (maximum working speed) during use (when loaded). For example, in a hammer drill, if the motor is rotated at the same speed during use as when not in use, power consumption and vibration will be relatively high. Therefore, a soft no-load operation is performed in the hammer drill to reduce power consumption and vibration.

[0064] In electric power tools that use a soft no-load system, such as hammer drills, the operating noise generated during operation is relatively loud. Therefore, even if noise due to stator resonance occurs during operation, it is masked by the operating noise and is relatively unnoticeable to the user. Furthermore, when stator resonance occurs at the rotational speed during operation and the rotational speed during non-operation is significantly reduced by the soft no-load system compared to the rotational speed during operation, noise due to stator resonance during non-operation is unlikely to occur. For example, let R (RPM) be the (maximum) rotation speed during operation, r (RPM) be the range of rotation speed reduction during non-operation, and Rr be the (maximum) rotation speed during non-operation. In a hammer drill that generates noise due to stator resonance when R=18,000, the possibility of noise due to stator resonance occurring when r=5,000 is relatively low. Similarly, when R=18,000 and r=3,000, the possibility of noise due to stator resonance occurring during non-operation is low. On the other hand, when R=18,000 and r=2,000, the rotation speed during non-operation, Rr, is close to the rotation speed during operation, R, i.e., the change in Rr relative to R is small, so the possibility of noise due to stator resonance occurring during non-operation is high. The noise during non-operation is not masked by the operating noise and is therefore easily noticeable to the user.

[0065] In the applicant's trials, when the quotient of the reduced rotation speed range r divided by the rotation speed R during operation is 12% or less, that is, when the relationship (r / R)≦0.12 (Equation (1)) is satisfied, noise during non-operational periods can also be sufficiently reduced, and changing the resonance frequency by using screws becomes more useful. The smaller r / R is, the more useful changing the resonance frequency by using screws becomes. For example, when (r / R)×100=12, 10, 8, 6, 5, 4, and 2, the usefulness of changing the resonance frequency by using screws increases in that order. Of course, when (r / R)=0, i.e., when soft no-load is not performed and the rotation speed is the same during operation and when not in operation, changing the resonant frequency using a screw is quite useful. For example, in the circular saw 1 of the first embodiment and the grinder 201 of the second embodiment, which do not perform soft no-load, changing the resonant frequency using a screw is quite useful. Also, in other electric power tools, such as a blower, where the rotation speed is the same during operation when blowing air against an object and during non-operation when not blowing air against an object (the air continues to blow at the same strength as long as the power is on), changing the resonant frequency using a screw is quite useful. [Explanation of symbols]

[0066] 1··Circular saw (electric work equipment), 6,212··Motor housing, 6C,212C··Cylinder portion, 6M,212M··Bottom portion, 20,230··Stator, 21,231··Rotor, 22,232··Rotor shaft, 25, 125, 285··Baffle plate (cylindrical member, holding member), 25S, 285S··Convex portion, 31··Output shaft (output part), 50, 250··Stator core, 50S, 250S··Second contact surface, 56, 256··Coil, 58F, 258F··First contact surface, 59, 233··Rotor core, 60, 234··Permanent magnet, 68, 288··Screw, 201··Grinder (electric work equipment), 292··Spindle (output part).

Claims

1. a motor housing having a cylindrical portion and a bottom portion; a brushless motor including a stator having a first contact surface and a rotor rotating inside the stator; a fan rotated by the rotor; a resin baffle plate that rectifies the airflow from the fan; an output unit; It is equipped with the stator has a cylindrical stator core and a plurality of coils wound around the stator core, and is held by the motor housing with the first contact surface in contact with the bottom portion of the motor housing; the first contact surface is one end surface of the stator core or an end surface of a terminal unit provided on the end surface and connected to each of the coils, the stator core has, on the other end surface thereof, a ring-shaped second contact surface that extends in the same direction as the first contact surface, the rotor includes a rotor shaft rotatably supported by the motor housing, a rotor core fixed to the rotor shaft, and a permanent magnet supported by the rotor core; the baffle plate has a cylindrical portion that protrudes in a cylindrical shape, and is fixed to the motor housing with three or more screws; The cylindrical portion has a plurality of protrusions and three or more screw hole portions through which the screws are respectively passed, and a tip end of each of the protrusions and a tip end of each of the screw hole portions contact the second contact surface of the stator core over the entire circumference. An electric work device characterized by:

2. The screw is positioned at a position other than the bottom of the electric power tool when it is in its normal position.

2. The electric power tool according to claim 1.

3. The bottom has a vent hole 3. The electric power tool according to claim 1 or 2.

4. The bottom portion holds a bearing that supports the rotor shaft.

4. The electric power tool according to claim 1, wherein the electric power tool is a power tool.

5. The outer diameter of the stator core is equal to or greater than the axial length of the stator core.

5. The electric power tool according to claim 1, wherein the electric power tool is a power tool.

6. The stator core is formed by laminating ring-shaped steel plates.

6. The electric power tool according to claim 1, wherein the electric power tool is a power tool.

7. The rotor core is formed by laminating ring-shaped steel plates.

7. The electric power tool according to claim 1, wherein the electric power tool is a power tool.

Images