Brushless motor, electric working machine, and brushless motor manufacturing method

Abstract

To suppress deterioration in the performance of a brushless motor.SOLUTION: A brushless motor includes a rotor that rotates around a rotating shaft, and a stator with coils arranged around the rotor. The rotor includes a rotor core and a rotor shaft placed in the shaft hole of the rotor core, and the rotor shaft includes a small diameter press-fit portion that is press-fitted into the shaft hole with a first press-fit allowance, and a large-diameter press-fit portion that is placed at a different position from the small-diameter press-fit portion in the front-rear direction parallel to the rotation axis, and is press-fitted into the shaft hole with a second press-fit allowance that is larger than the first press-fit allowance.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The technology disclosed in this specification relates to a brushless motor, a power tool, and a method for manufacturing a brushless motor.

Background Art

[0002] In the technical field related to brushless motors, a motor as disclosed in Patent Document 1 is known. In Patent Document 1, an armature shaft having linear protrusions is press-fitted into a rotor core as a press-fitting cost.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the prior art, the rotor shaft (armature shaft) may bend in creating the linear protrusions. Also, in the case of the method of press-fitting the linear protrusions into the rotor core, the central axis of the rotor core and the central axis of the rotor shaft may be displaced. If the rotor shaft bends or the central axis of the rotor core and the central axis of the rotor shaft are displaced, the rotational balance of the rotor deteriorates. When the rotational balance of the rotor deteriorates, the performance of the brushless motor decreases. For example, in a brushed motor, since the rotational speed is low and the lock torque is small, even linear protrusions were sufficient. In a brushless motor with a high rotational speed and a large lock torque, it is necessary to increase the rotational fixing force between the rotor core and the rotor shaft. With a single-stage press-fitting, there is a possibility that the rotational fixing force is insufficient.

[0005] The technology disclosed in this specification aims to suppress a decrease in the performance of a brushless motor.

Means for Solving the Problems

[0006] This specification discloses a brushless motor. The brushless motor may include a rotor that rotates about a rotation axis and a stator having coils arranged around the rotor. The rotor may include a rotor core and a rotor shaft arranged in a shaft hole of the rotor core. The rotor shaft may include a small-diameter press-fit portion that is press-fitted into the shaft hole with a first press-fit allowance and a large-diameter press-fit portion that is positioned differently from the small-diameter press-fit portion in the front-rear direction parallel to the rotation axis and is press-fitted into the shaft hole with a second press-fit allowance greater than the first press-fit allowance. [Effects of the Invention]

[0007] The technology disclosed herein suppresses the degradation of performance in brushless motors. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a front perspective view showing an electric work machine according to an embodiment. [Figure 2] Figure 2 is a cross-sectional view showing an electric work machine according to an embodiment. [Figure 3] Figure 3 is a front perspective view showing a rotor according to an embodiment. [Figure 4] Figure 4 is a rear perspective view showing a rotor according to an embodiment. [Figure 5] Figure 5 is a side view showing a rotor according to an embodiment. [Figure 6] Figure 6 is a cross-sectional view showing a rotor according to an embodiment. [Figure 7] Figure 7 is an exploded perspective view from the front showing a rotor according to an embodiment. [Figure 8] Figure 8 is an exploded rear perspective view showing a rotor according to an embodiment. [Figure 9] Figure 9 is a rear perspective view showing the rotor shaft according to the embodiment. [Figure 10] Figure 10 is a side view showing a rotor shaft according to an embodiment. [Figure 11] Figure 11 is a schematic diagram showing a rotor shaft to be polished. [Figure 12] Figure 12 is a rear perspective view showing the rotor shaft being press-fitted into the shaft hole of the rotor core according to the embodiment. [Figure 13] Figure 13 is a rear perspective view showing the rotor shaft inserted into the shaft hole according to the embodiment. [Figure 14] Figure 14 is a side view showing a rotor shaft inserted into a shaft hole according to an embodiment. [Figure 15] Figure 15 is a schematic cross-sectional view illustrating the operation of inserting the rotor shaft into the shaft hole according to the embodiment. [Figure 16] Figure 16 is a schematic cross-sectional view illustrating the operation of inserting the rotor shaft into the shaft hole according to the embodiment. [Figure 17] Figure 17 is a schematic cross-sectional view illustrating the operation of inserting the rotor shaft into the shaft hole according to the embodiment. [Figure 18] Figure 18 is a schematic cross-sectional view illustrating the operation of inserting the rotor shaft into the shaft hole according to the embodiment. [Figure 19] Figure 19 is a schematic cross-sectional view showing a rotor shaft inserted into a shaft hole according to the embodiment. [Modes for carrying out the invention]

[0009] In one or more embodiments, the brushless motor may include a rotor that rotates about a rotation axis, and a stator having coils arranged around the rotor. The rotor may include a rotor core and a rotor shaft positioned in a shaft hole of the rotor core. The rotor shaft may include a small-diameter press-fit portion that is press-fitted into the shaft hole with a first press-fit allowance, and a large-diameter press-fit portion that is positioned differently from the small-diameter press-fit portion in a longitudinal direction parallel to the rotation axis, and is press-fitted into the shaft hole with a second press-fit allowance greater than the first press-fit allowance.

[0010] In the above configuration, the rotor core and the rotor shaft are fixed by press-fitting the small-diameter press-fitting portion and the large-diameter press-fitting portion into the shaft hole of the rotor core, respectively. In the creation of the small-diameter press-fitting portion and the large-diameter press-fitting portion, the rotor shaft is prevented from bending. Also, by surface press-fitting between the outer peripheral surface of the small-diameter press-fitting portion and the outer peripheral surface of the large-diameter press-fitting portion and the inner peripheral surface of the shaft hole, the misalignment between the central axis of the rotor core and the central axis of the rotor shaft is suppressed. Therefore, the deterioration of the rotational balance of the rotor is suppressed. Also, by surface press-fitting between the outer peripheral surface of the small-diameter press-fitting portion and the outer peripheral surface of the large-diameter press-fitting portion and the inner peripheral surface of the shaft hole, the rotor core and the rotor shaft are firmly fixed. Therefore, the relative rotation between the rotor core and the rotor shaft and the relative movement between the rotor core and the rotor shaft in the axial direction are suppressed. Therefore, the deterioration of the performance of the brushless motor is suppressed.

[0011] In one or more embodiments, in a cross-section orthogonal to the rotation axis, the outer shape of each of the small-diameter press-fitting portion and the large-diameter press-fitting portion may be circular.

[0012] In the above configuration, the deterioration of the rotational balance of the rotor is suppressed.

[0013] In one or more embodiments, the small-diameter press-fitting portion may be disposed behind the large-diameter press-fitting portion. The rotor shaft may have a small-diameter press-fitting guide portion whose diameter decreases rearward from the rear end portion of the small-diameter press-fitting portion.

[0014] In the above configuration, the small-diameter press-fitting guide portion makes it easier to press-fit the small-diameter press-fitting portion into the shaft hole. Also, since the small-diameter press-fitting guide portion suppresses the occurrence of excessive stress concentration in the rotor core when the small-diameter press-fitting portion is press-fitted into the shaft hole, damage to the rotor core is suppressed.

[0015] In one or more embodiments, the rotor shaft may be disposed between the small-diameter press-fitting portion and the large-diameter press-fitting portion in the front-rear direction and may have a large-diameter press-fitting guide portion whose diameter decreases rearward from the rear end portion of the large-diameter press-fitting portion.

[0016] In the above configuration, the large-diameter press-fit guide makes it easier to press-fit the large-diameter press-fit part into the shaft hole. Furthermore, the large-diameter press-fit guide suppresses excessive stress concentration in the rotor core when the large-diameter press-fit part is pressed into the shaft hole, thereby suppressing damage to the rotor core.

[0017] In one or more embodiments, the rotor shaft is positioned between a small-diameter press-fit portion and a large-diameter press-fit guide portion in the front-rear direction, and may have a relief portion with a diameter smaller than the diameter of the small-diameter press-fit portion.

[0018] In the above configuration, when the outer surface of the small-diameter press-fit portion is polished with a grinding wheel, the relief portion prevents the grinding wheel from interfering with the large-diameter press-fit portion, allowing the outer surface of the small-diameter press-fit portion to be polished with the grinding wheel.

[0019] In one or more embodiments, the dimensions of the small-diameter press-fit portion may be smaller than the dimensions of the large-diameter press-fit portion in the front-to-back direction.

[0020] In the above configuration, when the small-diameter press-fit section is pressed into the shaft hole first, and then the large-diameter press-fit section is pressed into the shaft hole, it is easier to press the rotor shaft into the shaft hole. Also, since the large-diameter press-fit section is longer than the small-diameter press-fit section, the rotor core and rotor shaft are firmly fixed together.

[0021] In one or more embodiments, the small-diameter press-fit portion may be positioned behind the large-diameter press-fit portion. The rear end of the small-diameter press-fit portion may be positioned in front of the rear end of the rotor core. The front end of the large-diameter press-fit portion may be positioned in front of the front end of the rotor core.

[0022] In the above configuration, the small-diameter press-fit section is not positioned behind the rear end of the rotor core, making it easier to press-fit a sleeve onto a rotor shaft behind the rotor core, for example. Also, since the large-diameter press-fit section is positioned in front of the front end of the rotor core, the contact area between the outer surface of the large-diameter press-fit section and the inner surface of the shaft hole is increased. This firmly fixes the rotor core and the rotor shaft together.

[0023] In one or more embodiments, the electric work machine may include the brushless motor described above and a tool holder on which a tool tip is attached and which is driven by the rotational force of the brushless motor.

[0024] In the above configuration, deterioration of the rotor's rotational balance is suppressed, thus reducing vibration and noise from the electric work implement during operations using the electric work implement.

[0025] In one or more embodiments, the electric work machine may include a gear provided at one end of the rotor shaft, a fan inserted into the rotor shaft from the one end side of the rotor shaft, a first bearing inserted into the rotor shaft from the one end side of the rotor shaft, a rotor core press-fitted into the rotor shaft from the other end side of the rotor shaft, and a second bearing inserted into the rotor shaft from the other end side of the rotor shaft.

[0026] With the above configuration, electric work machines can be manufactured efficiently.

[0027] In one or more embodiments, a method for manufacturing a brushless motor comprising a rotor that rotates about a rotation axis and a stator having coils arranged around the rotor may include press-fitting a rotor shaft into a shaft hole of a rotor core extending in a longitudinal direction parallel to the rotation axis, the rotor shaft having a small-diameter press-fit portion that is press-fitted into the shaft hole with a first press-fit allowance, and a large-diameter press-fit portion that is positioned differently from the small-diameter press-fit portion in the longitudinal direction parallel to the rotation axis and is press-fitted into the shaft hole with a second press-fit allowance greater than the first press-fit allowance.

[0028] In the above configuration, the rotor core and rotor shaft are fixed together by press-fitting the small-diameter and large-diameter press-fitting sections into the shaft hole of the rotor core. During the creation of the small-diameter and large-diameter press-fitting sections, bending of the rotor shaft is suppressed. Furthermore, surface press-fitting, where the outer surfaces of the small-diameter and large-diameter press-fitting sections are in close contact with the inner surface of the shaft hole, suppresses misalignment between the central axis of the rotor core and the central axis of the rotor shaft. Therefore, deterioration of the rotor's rotational balance is suppressed. Additionally, surface press-fitting between the outer surfaces of the small-diameter and large-diameter press-fitting sections and the inner surface of the shaft hole firmly fixes the rotor core and rotor shaft. Therefore, relative rotation between the rotor core and rotor shaft, or relative axial movement between the rotor core and rotor shaft, is suppressed. Consequently, a decrease in the performance of the brushless motor is suppressed.

[0029] In one or more embodiments, the small-diameter press-fit portion may be pressed into the shaft hole first, and then the large-diameter press-fit portion may be pressed into the shaft hole.

[0030] In the above configuration, both the small-diameter press-fit section and the large-diameter press-fit section are properly pressed into the shaft hole. If the large-diameter press-fit section is pressed into the shaft hole before the small-diameter press-fit section, the rotor core will plastically deform so that the inner diameter of the shaft hole expands to match the diameter of the large-diameter press-fit section, and only then will the small-diameter press-fit section be inserted into the shaft hole. In other words, the inner diameter of the shaft hole, which has been expanded to match the diameter of the large-diameter press-fit section, may be larger than the outer diameter of the small-diameter press-fit section, so the small-diameter press-fit section may not be properly pressed into the shaft hole. By pressing the small-diameter press-fit section into the shaft hole before the large-diameter press-fit section, even if the inner diameter of the shaft hole expands to match the diameter of the small-diameter press-fit section, the expanded inner diameter of the shaft hole will be smaller than the outer diameter of the large-diameter press-fit section, so the large-diameter press-fit section will be properly pressed into the shaft hole.

[0031] In one or more embodiments, the small-diameter press-fit portion may be positioned behind the large-diameter press-fit portion. The rotor shaft may be provided with a small-diameter press-fit guide portion whose diameter decreases towards the rear from the rear end of the small-diameter press-fit portion. The small-diameter press-fit guide portion may be inserted into the shaft hole, and then the small-diameter press-fit portion may be press-fitted into the shaft hole.

[0032] In the above configuration, the small-diameter press-fit guide makes it easier to press-fit the small-diameter press-fit part into the shaft hole. Furthermore, the small-diameter press-fit guide suppresses excessive stress concentration in the rotor core when the small-diameter press-fit part is pressed into the shaft hole, thereby suppressing damage to the rotor core.

[0033] In one or more embodiments, a large-diameter press-fit guide portion may be provided on the rotor shaft between the small-diameter press-fit portion and the large-diameter press-fit portion in the front-rear direction, with the diameter decreasing towards the rear from the rear end of the large-diameter press-fit portion. The large-diameter press-fit guide portion may be inserted into the shaft hole, and then the large-diameter press-fit portion may be press-fitted into the shaft hole.

[0034] In the above configuration, the large-diameter press-fit guide makes it easier to press-fit the large-diameter press-fit part into the shaft hole. Furthermore, the large-diameter press-fit guide suppresses excessive stress concentration in the rotor core when the large-diameter press-fit part is pressed into the shaft hole, thereby suppressing damage to the rotor core.

[0035] In one or more embodiments, the dimensions of the small-diameter press-fit portion may be smaller than the dimensions of the large-diameter press-fit portion in the front-to-back direction.

[0036] In the above configuration, when the small-diameter press-fit section is pressed into the shaft hole first, and then the large-diameter press-fit section is pressed into the shaft hole, it is easier to press the rotor shaft into the shaft hole. Also, since the large-diameter press-fit section is longer than the small-diameter press-fit section, the rotor core and rotor shaft are firmly fixed together.

[0037] In one or more embodiments, the outer surfaces of the small-diameter press-fit portion and the large-diameter press-fit portion may be polished so that, in a cross section perpendicular to the axis of rotation, the outer shapes of the small-diameter press-fit portion and the large-diameter press-fit portion are circular.

[0038] In the above configuration, polishing is used as the processing method for the small-diameter and large-diameter press-fit sections, which suppresses bending of the rotor shaft. Therefore, deterioration of the rotor's rotational balance is suppressed.

[0039] In one or more embodiments, a relief portion with a diameter smaller than the diameter of the small-diameter press-fit portion may be provided between the small-diameter press-fit portion and the large-diameter press-fit portion in the front-rear direction, and then the outer surface of the small-diameter press-fit portion may be polished.

[0040] In the above configuration, when the outer surface of the small-diameter press-fit portion is polished with a grinding wheel, the relief portion prevents the grinding wheel from interfering with the large-diameter press-fit portion, allowing the outer surface of the small-diameter press-fit portion to be polished with the grinding wheel.

[0041] The embodiments will be described below with reference to the drawings. In the embodiments, the positional relationships of each part will be described using the terms left, right, front, rear, top, and bottom. These terms indicate the relative position or direction with respect to the center of the electric work machine 1. The electric work machine 1 has a motor 6 as its power source.

[0042] In this embodiment, the direction parallel to the rotation axis AX of the motor 6 is appropriately referred to as the axial direction, the direction that circles around the rotation axis AX is appropriately referred to as the circumferential direction or rotational direction, and the radial direction of the rotation axis AX is appropriately referred to as the radial direction.

[0043] In this embodiment, the rotation axis AX extends in the front-rear direction. The axial direction parallel to the rotation axis AX is the front-rear direction. Furthermore, in the radial direction, the position close to or approaching the rotation axis AX is appropriately referred to as the radially inward direction, and the position far from or away from the rotation axis AX is appropriately referred to as the radially outward direction.

[0044] [Electric work equipment] Figure 1 is a front perspective view showing the electric work machine 1 according to an embodiment. Figure 2 is a cross-sectional view showing the electric work machine 1 according to an embodiment. In this embodiment, the electric work machine 1 is a reciprocating saw, which is a type of power tool.

[0045] The electric work implement 1 comprises a rear housing 2, a front housing 3, a battery mounting section 4, a controller 5, a motor 6, a fan 7, a crank mechanism 8, a slider 9, a blade holder 10, and a guide shoe 11.

[0046] The rear housing 2 is made of synthetic resin. The rear housing 2 includes the left housing 2L and the right housing 2R, which is positioned to the right of the left housing 2L. The left housing 2L and the right housing 2R constitute a pair of split housings. The rear housing 2 is composed of a pair of split housings. The left housing 2L and the right housing 2R are fastened together by a number of screws 2S.

[0047] The rear housing 2 includes a motor housing 12, a handle 13, and a battery holder 14. The motor housing 12 houses the motor 6. The handle 13 is held by the operator. The battery holder 14 holds the battery pack 22. The handle 13 is loop-shaped. The motor housing 12 is located in front of the handle 13. The battery holder 14 is located below the handle 13.

[0048] A trigger lever 15 is located on the handle 13. The trigger lever 15 is operated by the operator to start the motor 6. By operating the trigger lever 15, the motor 6 is switched between running and stopping. A lock-off button 16 is provided on the top of the handle 13. The lock-off button 16 is slidable in the left and right directions. By operating the lock-off button 16, the lock on the trigger lever 15 is released. A window 17 indicating the position of the lock-off button 16 is provided on the top surface of the handle 13. A first air intake port 18 is provided at the rear of the motor housing 12. A second air intake port 19 is provided on the battery holder 14.

[0049] A cylindrical hook receiver 20 is provided on the right side of the motor housing 12. A hanging hook 21 is attached to the hook receiver 20.

[0050] The front housing 3 is positioned in front of the rear housing 2. The front housing 3 is cylindrical. The rear end of the front housing 3 is fixed to the front end of the rear housing 2. The front housing 3 houses the crank mechanism 8 and the slider 9.

[0051] The battery mounting section 4 is located below the battery holding section 14. The battery pack 22 is mounted in the battery mounting section 4. The battery pack 22 is the power source for the electric work machine 1. The battery pack 22 is detachable from the battery mounting section 4. The battery pack 22 is mounted in the battery mounting section 4 by being inserted into the battery mounting section 4 from the front of the battery holding section 14. The battery pack 22 is removed from the battery mounting section 4 by being pulled forward from the battery mounting section 4. The battery pack 22 includes a secondary battery. In one embodiment, the battery pack 22 includes a rechargeable lithium-ion battery. By being mounted in the battery mounting section 4, the battery pack 22 can supply power to the electric work machine 1. The motor 6 is driven based on the power supplied from the battery pack 22.

[0052] The controller 5 controls at least the motor 6. The controller 5 has a circuit board and a plurality of electronic components mounted on the circuit board. Examples of electronic components include a microcomputer and a switching element. The controller 5 is housed in the controller case 23 and then housed in the battery holder 14.

[0053] Motor 6 is the power source of the electric work machine 1. Motor 6 is an electric motor. Motor 6 is an inner rotor type brushless motor. Motor 6 has a stator 24 and a rotor 25. The stator 24 is arranged around the rotor 25. The rotor 25 rotates relative to the stator 24. The rotor 25 rotates around the rotation axis AX. The rotation axis AX extends in the front-rear direction.

[0054] The stator 24 includes a cylindrical stator core 26, a rear insulator 27 fixed to the rear of the stator core 26, a front insulator 28 fixed to the front of the stator core 26, a plurality of coils 29 wound around the teeth of the stator core 26 via the rear insulator 27 and the front insulator 28, and a busbar 30 that short-circuits the plurality of coils 29.

[0055] The rotor 25 includes a rotor core 31, permanent magnets 32, and a rotor shaft 33. A sleeve 51 is fixed to the rear of the rotor shaft 33. A sleeve 52 is fixed to the front of the rotor shaft 33. A sensor board 34 is attached to the rear insulator 27 to detect the rotation of the rotor 25 by detecting the position of the permanent magnets 32.

[0056] At least a portion of the motor 6 is housed in the motor case 35. The crankcase 36 is positioned in front of the motor case 35. The crank mechanism 8 and slider 9 are housed in the crankcase 36.

[0057] The stator 24 is positioned inside the motor case 35. The stator 24 is fixed to the motor case 35. The motor case 35 is fixed to the motor housing 12.

[0058] The rear end of the rotor shaft 33 is rotatably supported by a rotor bearing 37. The front end of the rotor shaft 33 is rotatably supported by a rotor bearing 38. The rotor bearing 37 is held in the motor case 35. The rotor bearing 38 is held in the crankcase 36.

[0059] The fan 7 is fixed to the front of the rotor shaft 33. The fan 7 is fixed to the rotor shaft 33 between the stator core 26 and the rotor bearing 38. When the rotor shaft 33 rotates, the fan 7 rotates. The rotation of the fan 7 generates airflow around the motor 6. The motor 6 is cooled by the airflow generated by the rotation of the fan 7.

[0060] A retaining plate 39 is positioned at the rear end of the crankcase 36. The retaining plate 39 is fixed to the rear end of the crankcase 36 by screws 40. The retaining plate 39 contacts the rear end of the outer ring of the rotor bearing 38. The retaining plate 39 prevents the rotor bearing 38 from coming out of the crankcase 36 to the rear.

[0061] A pinion gear 41 is provided at the front end of the rotor shaft 33. In the longitudinal direction, the rotor bearing 38 is positioned between the pinion gear 41 and the fan 7. The pinion gear 41 is located inside the crankcase 36. The rotor shaft 33 is coupled to the crank mechanism 8 via the pinion gear 41.

[0062] The crank mechanism 8 converts the rotational motion of the rotor 25 into reciprocating motion in the forward and backward direction. The crank mechanism 8 includes a bevel gear 42 to which a pinion gear 41 is coupled, an eccentric pin 43 provided at an eccentric position of the bevel gear 42, and a connecting rod 45 that connects the eccentric pin 43 to a connecting pin 44 provided at the rear end of the slider 9.

[0063] The slider 9 is moved in the forward and backward direction by the crank mechanism 8. The slider 9 is guided in the forward and backward direction by the holder 46 and the slider guide 47.

[0064] The blade holder 10 is connected to the front end of the slider 9. The blade holder 10 is moved in the forward and backward direction together with the slider 9 by the crank mechanism 8. The blade holder 10 is driven by the rotational force of the motor 6 transmitted via the crank mechanism 8. The blade holder 10 holds a blade, which is a type of cutting tool. The blade holder 10 functions as a cutting tool holder to which the cutting tool is mounted.

[0065] The guide shoe 11 is located on the underside of the slider 9. The guide shoe 11 includes a slide bar 48 that is slidable in the front-rear direction, and a shoe 49 fixed to the front end of the slide bar 48 into which the blade mounted on the blade holder 10 is inserted.

[0066] When the trigger lever 15 is operated, the motor 6 is driven by power supplied from the battery pack 22. As the rotor 25 rotates around the rotation axis AX, the pinion gear 41 located at the front end of the rotor shaft 33 rotates. As the pinion gear 41 rotates, the bevel gear 42 coupled to the pinion gear 41 rotates. As the bevel gear 42 rotates, the eccentric pin 43 moves eccentrically with respect to the rotation axis of the bevel gear 42, causing the slider 9 to reciprocate in the front-rear direction via the connecting rod 45. As the slider 9 reciprocates in the front-rear direction, the blade mounted on the blade holder 10 reciprocates in the front-rear direction. The reciprocating motion of the blade in the front-rear direction cuts the object to be cut.

[0067] [Rotor] Figure 3 is a front perspective view showing the rotor 25 according to the embodiment. Figure 4 is a rear perspective view showing the rotor 25 according to the embodiment. Figure 5 is a side view showing the rotor 25 according to the embodiment. Figure 6 is a cross-sectional view showing the rotor 25 according to the embodiment. Figure 7 is an exploded front perspective view showing the rotor 25 according to the embodiment. Figure 8 is an exploded rear perspective view showing the rotor 25 according to the embodiment.

[0068] The rotor 25 includes a rotor core 31, a permanent magnet 32, and a rotor shaft 33.

[0069] The rotor core 31 is substantially cylindrical. The rotor core 31 includes a plurality of steel plates stacked on top of each other. The plurality of steel plates are fixed to each other by crimping. The rotor core 31 is provided with crimped portions 31C formed by the crimping process. The rotor core 31 has a shaft hole 60 extending in the front-rear direction and a plurality of magnet holes 31A extending in the front-rear direction. At least a portion of the rotor shaft 33 is located inside the shaft hole 60. The permanent magnets 32 are located inside the magnet holes 31A.

[0070] The shaft hole 60 is formed to penetrate the front and rear end faces of the rotor core 31. In a cross-section perpendicular to the rotation axis AX, the shaft hole 60 is circular. The inner diameter of the shaft hole 60 is constant in the front-rear direction. In a cross-section perpendicular to the rotation axis AX, the shaft hole 60 is located at the center of the rotor core 31.

[0071] The magnet holes 31A are formed to penetrate the front and rear end faces of the rotor core 31. In a cross-section perpendicular to the rotation axis AX, the magnet holes 31A are substantially rectangular. The magnet holes 31A are located radially outward from the shaft hole 60. Multiple magnet holes 31A are formed in the circumferential direction. In one embodiment, four magnet holes 31A are formed at equal intervals in the circumferential direction. Permanent magnets 32 are placed in each of the multiple magnet holes 31A.

[0072] A gap 31B is formed between the surface of the permanent magnet 32 ​​placed in the magnet hole 31A and at least a portion of the inner surface of the magnet hole 31A. One gap 31B is provided on each of the circumferential sides of the permanent magnet 32 ​​placed in the magnet hole 31A. Synthetic resin is filled into the gap 31B. A portion of the synthetic resin forms a sleeve 52 on the front end surface of the rotor core 31. The sleeve 52 is connected to the front end surface of the rotor core 31.

[0073] The sleeve 51 is fixed to the rotor shaft 33 behind the rear end face of the rotor core 31. The fan 7 is fixed to the rotor shaft 33 in front of the sleeve 52.

[0074] Sleeves 51 and 52 are provided to correct the rotational balance of the rotor 25. Sleeve 51 is made of brass. Sleeve 52 is made of synthetic resin. Both sleeves 51 and 52 may be made of synthetic resin or of a metal such as brass. The rotational balance of the rotor 25 is corrected by machining at least one of sleeves 51 and 52. At least one of sleeves 51 and 52 improves the static and dynamic balance of the rotor 25. One or both of sleeves 51 and 52 may be fixed to the rotor shaft 33.

[0075] [Rotor shaft] Figure 9 is a rear perspective view showing the rotor shaft 33 according to the embodiment. Figure 10 is a side view showing the rotor shaft 33 according to the embodiment. The rotor shaft 33 is elongated in the front-rear direction. The rotor shaft 33 is made of a metal such as iron or steel. In a cross-section perpendicular to the rotation axis AX, the outer shape of the rotor shaft 33 is circular.

[0076] The rotor shaft 33 includes a pinion gear 41 provided at the front end of the rotor shaft 33, a bearing retaining portion 71 provided on the rear side of the pinion gear 41, a relief portion 72 provided on the rear side of the bearing retaining portion 71, a fan press-fitting guide portion 73 provided on the rear side of the relief portion 72, a fan press-fitting portion 74 provided on the rear side of the fan press-fitting guide portion 73, and a relief portion 75 provided on the rear side of the fan press-fitting portion 74.

[0077] Furthermore, the rotor shaft 33 has a first intermediate portion 76 provided on the rear side of the relief portion 75, a groove portion 77 provided on the rear side of the first intermediate portion 76, and a second intermediate portion 78 provided on the rear side of the groove portion 77.

[0078] Furthermore, the rotor shaft 33 has a large-diameter press-fit portion 79 provided on the rear side of the second intermediate portion 78, a large-diameter press-fit guide portion 80 provided on the rear side of the large-diameter press-fit portion 79, a relief portion 81 provided on the rear side of the large-diameter press-fit guide portion 80, a small-diameter press-fit portion 82 provided on the rear side of the relief portion 81, a small-diameter press-fit guide portion 83 provided on the rear side of the small-diameter press-fit portion 82, and a relief portion 84 provided on the rear side of the small-diameter press-fit guide portion 83.

[0079] Furthermore, the rotor shaft 33 includes a sleeve press-fit portion 85 provided behind the relief portion 84, a sleeve press-fit guide portion 86 provided behind the sleeve press-fit portion 85, a relief portion 87 provided behind the sleeve press-fit guide portion 86, and a bearing retaining portion 88 provided behind the relief portion 87. The bearing retaining portion 88 is provided at the rear end of the rotor shaft 33.

[0080] The small-diameter press-fit portion 82 and the large-diameter press-fit portion 79 are each press-fitted into the shaft hole 60 of the rotor core 31. In the front-rear direction, the large-diameter press-fit portion 79 is positioned differently from the small-diameter press-fit portion 82. In this embodiment, the small-diameter press-fit portion 82 is positioned further rearward than the large-diameter press-fit portion 79. In a cross-section perpendicular to the rotation axis AX, the outer shapes of the small-diameter press-fit portion 82 and the large-diameter press-fit portion 79 are circular. The diameter Ds2 of the small-diameter press-fit portion 82 and the diameter Ds1 of the large-diameter press-fit portion 79 are each larger than the inner diameter Dc of the shaft hole 60. The diameter Ds2 of the small-diameter press-fit portion 82 is smaller than the diameter Ds1 of the large-diameter press-fit portion 79. In the front-rear direction, the diameter Ds2 of the small-diameter press-fit portion 82 is constant. In the front-rear direction, the diameter Ds1 of the large-diameter press-fit portion 79 is constant. The small-diameter press-fit portion 82 is press-fitted into the shaft hole 60 with a first press-fit allowance. The large-diameter press-fit portion 79 is press-fitted into the shaft hole 60 with a second press-fit allowance that is larger than the first press-fit allowance.

[0081] The first press-fit allowance refers to the difference between the inner diameter Dc of the shaft hole 60 and the diameter Ds2 of the small-diameter press-fit portion 82. The second press-fit allowance refers to the difference between the inner diameter Dc of the shaft hole 60 and the diameter Ds1 of the large-diameter press-fit portion 79.

[0082] In the front-to-back direction, the dimension L2 of the small-diameter press-fit portion 82 is smaller than the dimension L1 of the large-diameter press-fit portion 79. In other words, the large-diameter press-fit portion 79 is longer than the small-diameter press-fit portion 82.

[0083] The small-diameter press-fit guide portion 83 is adjacent to the rear end of the small-diameter press-fit portion 82. The small-diameter press-fit guide portion 83 is tapered, with its diameter decreasing towards the rear from the rear end of the small-diameter press-fit portion 82.

[0084] The large-diameter press-fit guide section 80 is positioned between the small-diameter press-fit section 82 and the large-diameter press-fit section 79 in the front-rear direction. The large-diameter press-fit guide section 80 is adjacent to the rear end of the large-diameter press-fit section 79. The large-diameter press-fit guide section 80 is tapered, with its diameter decreasing towards the rear from the rear end of the large-diameter press-fit section 79.

[0085] The relief portion 81 is positioned between the small-diameter press-fit portion 82 and the large-diameter press-fit guide portion 80 in the front-rear direction. The relief portion 81 is adjacent to the rear end of the large-diameter press-fit guide portion 80 and adjacent to the front end of the small-diameter press-fit portion 82. The diameter of the relief portion 81 is smaller than the diameter Ds2 of the small-diameter press-fit portion 82.

[0086] In a cross-section perpendicular to the rotation axis AX, the outer surfaces of the small-diameter press-fit portion 82 and the large-diameter press-fit portion 79 are polished so that their respective outer shapes become circular.

[0087] The diameter Db1 of the bearing holder 71 is smaller than the diameter Df of the fan press-fit portion 74. The diameter Ds1 of the large-diameter press-fit portion 79 is smaller than the diameter Db1 of the bearing holder 71. The diameter Di of the sleeve press-fit portion 85 is smaller than the diameter Ds2 of the small-diameter press-fit portion 82. The diameter Db2 of the bearing holder 88 is smaller than the diameter Di of the sleeve press-fit portion 85. In other words, in this embodiment, the relationship [Df>Db1>Ds1>Ds2>Di>Db2] holds true. With this relationship in place, the rotor shaft 33 is press-fitted into the rotor core 31 from the front of the rotor core 31, the fan 7 is inserted into the rotor shaft 33 from the front of the rotor shaft 33, and then the rotor bearing 38 is inserted into the rotor shaft 33 from the front of the rotor shaft 33. After the sleeve 51 is inserted into the rotor shaft 33 from the rear of the rotor shaft 33, the rotor bearing 37 is inserted into the rotor shaft 33 from the rear of the rotor shaft 33.

[0088] Figure 11 is a schematic diagram showing a rotor shaft 33 to be polished. The rotor shaft 33 is formed by cutting a metal base member, for example, on a lathe. After the rotor shaft 33's approximate shape is determined by cutting, it is finished by polishing. As shown in Figure 11, for example, when polishing a small-diameter press-fit portion 82, a grinding wheel 100 is applied to the outer circumferential surface of the small-diameter press-fit portion 82. The outer circumferential surface of the small-diameter press-fit portion 82 is polished with the grinding wheel 100.

[0089] Before grinding, a relief section 81 is provided by cutting. The relief section 81 is provided between the small-diameter press-fit section 82 and the large-diameter press-fit section 79 in the front-rear direction. The diameter of the relief section 81 is smaller than the diameter of the small-diameter press-fit section 82. After the relief section 81 is provided by cutting, the outer surface of the small-diameter press-fit section 82 is ground with a grinding wheel 100. If the relief section 81 is not provided, when the outer surface of the small-diameter press-fit section 82 is ground with the grinding wheel 100, there is a possibility that the grinding wheel 100 will interfere with the large-diameter press-fit section 79. If interference between the grinding wheel 100 and the large-diameter press-fit section 79 is suppressed, there is a possibility that an unprocessed portion 101 will remain at the front end of the small-diameter press-fit section 82, as shown in Figure 11. The relief portion 81 prevents the grinding wheel 100 from interfering with the large-diameter press-fit portion 79, while the outer surface of the small-diameter press-fit portion 82 is polished by the grinding wheel 100.

[0090] The bearing retainer portion 71 is held by the rotor bearing 38. The outer circumferential surface of the bearing retainer portion 71 is polished. The relief portion 72 is adjacent to the rear end of the bearing retainer portion 71. The relief portion 72 is adjacent to the front end of the fan press-fit guide portion 73. The diameter of the fan press-fit guide portion 73 is larger than the diameter of the bearing retainer portion 71. The diameter of the relief portion 72 is smaller than the diameter of the bearing retainer portion 71. When the outer circumferential surface of the bearing retainer portion 71 is polished with the grinding wheel 100, the relief portion 72 prevents the grinding wheel 100 from interfering with the fan press-fit guide portion 73.

[0091] The fan press-fit portion 74 is press-fitted into the fan 7. The outer surface of the fan press-fit portion 74 is polished. The fan press-fit guide portion 73 is adjacent to the front end of the fan press-fit portion 74. The fan press-fit guide portion 73 is tapered, with its diameter decreasing towards the front of the fan press-fit portion 74.

[0092] The relief portion 75 is adjacent to the rear end of the fan press-fit portion 74. The diameter of the fan press-fit portion 74 is larger than the diameter Ds1 of the large-diameter press-fit portion 79. The diameter of the relief portion 75 is smaller than the diameter of the large-diameter press-fit portion 79. When the outer surface of the large-diameter press-fit portion 79 is polished with the grinding wheel 100, the relief portion 75 prevents the grinding wheel 100 from interfering with the fan press-fit portion 74.

[0093] The first intermediate section 76 and the second intermediate section 78 are positioned between the fan press-fit section 74 and the large-diameter press-fit section 79 in the front-rear direction. In this embodiment, the outer circumferential surfaces of the first intermediate section 76 and the second intermediate section 78 are not polished. The groove 77 is positioned between the first intermediate section 76 and the second intermediate section 78 in the front-rear direction.

[0094] The sleeve press-fit portion 85 is press-fitted into the sleeve 51. The outer surface of the sleeve press-fit portion 85 is polished. The sleeve press-fit guide portion 86 is adjacent to the rear end of the sleeve press-fit portion 85.

[0095] The relief portion 84 is adjacent to the rear end of the small-diameter press-fit guide portion 83. The relief portion 84 is adjacent to the front end of the sleeve press-fit portion 85. The diameter of the small-diameter press-fit guide portion 83 is larger than the diameter of the sleeve press-fit portion 85. The diameter of the relief portion 84 is smaller than the diameter of the sleeve press-fit portion 85. When the outer circumferential surface of the sleeve press-fit portion 85 is polished with the grinding wheel 100, the relief portion 84 prevents the grinding wheel 100 from interfering with the small-diameter press-fit guide portion 83.

[0096] The bearing retainer portion 88 is held by the rotor bearing 37. The outer circumferential surface of the bearing retainer portion 88 is polished. The relief portion 87 is adjacent to the rear end of the sleeve press-fit guide portion 86. The relief portion 87 is adjacent to the front end of the bearing retainer portion 88. The diameter of the sleeve press-fit guide portion 86 is larger than the diameter of the bearing retainer portion 88. The diameter of the relief portion 87 is smaller than the diameter of the bearing retainer portion 88. When the outer circumferential surface of the bearing retainer portion 88 is polished with the grinding wheel 100, the relief portion 87 prevents the grinding wheel 100 from interfering with the sleeve press-fit guide portion 86.

[0097] [Manufacturing method] Figure 12 is a rear perspective view showing a rotor shaft 33 being press-fitted into a shaft hole 60 of a rotor core 31 according to the embodiment. Figure 13 is a rear perspective view showing a rotor shaft 33 inserted into a shaft hole 60 according to the embodiment. Figure 14 is a side view showing a rotor shaft 33 inserted into a shaft hole 60 according to the embodiment. In Figures 13 and 14, the rotor core 31 is shown by dashed lines. Figures 15, 16, 17, and 18 are schematic cross-sectional views illustrating the operation of inserting a rotor shaft 33 into a shaft hole 60 according to the embodiment. Figure 19 is a schematic cross-sectional view showing a rotor shaft 33 inserted into a shaft hole 60 according to the embodiment.

[0098] As shown in Figure 12, in this embodiment, the rotor shaft 33 is press-fitted into the shaft hole 60 from the front of the rotor core 31. The rotor shaft 33 is inserted into the shaft hole 60 from the rear end of the rotor shaft 33. The press-fitting direction of the rotor shaft 33 is determined such that the small-diameter press-fitting portion 82 is press-fitted into the shaft hole 60 first, followed by the large-diameter press-fitting portion 79.

[0099] As shown in Figure 15, the rear end of the rotor shaft 33 is inserted into the front end of the shaft hole 60. After the rear end of the rotor shaft 33 is inserted into the front end of the shaft hole 60, the rotor shaft 33 moves backward, causing the small-diameter press-fit guide portion 83 to be inserted into the shaft hole 60. The outer surface of the small-diameter press-fit guide portion 83 is tapered, with the diameter decreasing towards the rear from the rear end of the small-diameter press-fit portion 82, thus preventing the small-diameter press-fit portion 82 from getting caught at the rear end of the shaft hole 60. Furthermore, the small-diameter press-fit guide portion 83 allows the central axis of the rotor shaft 33 to be aligned with the central axis of the shaft hole 60 when the small-diameter press-fit portion 82 is press-fitted into the shaft hole 60.

[0100] After the small-diameter press-fit guide portion 83 is inserted into the shaft hole 60, as shown in Figure 16, the rotor shaft 33 moves further backward, initiating the press-fitting of the small-diameter press-fit portion 82 into the shaft hole 60. As shown in Figure 17, the rotor shaft 33 moves further backward, press-fitting the small-diameter press-fit portion 82 into the shaft hole 60.

[0101] After the small-diameter press-fit portion 82 is pressed into the shaft hole 60, the rotor shaft 33 moves further rearward, causing the large-diameter press-fit guide portion 80 to be inserted into the shaft hole 60. The outer surface of the large-diameter press-fit guide portion 80 is tapered, with the diameter decreasing towards the rear from the rear end of the large-diameter press-fit portion 79, thus preventing the large-diameter press-fit portion 79 from getting caught at the rear end of the shaft hole 60.

[0102] After the large-diameter press-fit guide portion 80 is inserted into the shaft hole 60, as shown in Figure 18, the rotor shaft 33 moves further backward, initiating the press-fitting of the large-diameter press-fit portion 79 into the shaft hole 60.

[0103] As the rotor shaft 33 moves further rearward, the small-diameter press-fit portion 82 and the large-diameter press-fit portion 79 are pressed into the shaft hole 60, as shown in Figures 13, 14, and 19. As shown in Figure 14, the rear end of the small-diameter press-fit portion 82 is positioned in front of the rear end of the rotor core 31. In the front-rear direction, the position of the rear end of the small-diameter press-fit portion 82 and the position of the rear end of the rotor core 31 may coincide. The front end of the large-diameter press-fit portion 79 is positioned in front of the front end of the rotor core 31.

[0104] The rotor shaft 33 is moved rearward relative to the rotor core 31 and pressed into the small-diameter press-fit section 82 and the large-diameter press-fit section 79 in the shaft hole 60. Then, the sleeve 51 is pressed into the sleeve press-fit section 85 from the rear of the rotor shaft 33. Since a sleeve press-fit guide section 86 is provided on the rear side of the sleeve press-fit section 85, the sleeve 51 is smoothly pressed into the sleeve press-fit section 85. The sleeve press-fit guide section 86 allows the central axis of the rotor shaft 33 and the central axis of the sleeve 51 to be aligned when the sleeve 51 is pressed into the rotor shaft 33. After the sleeve 51 is pressed into the sleeve press-fit section 85 from the rear of the rotor shaft 33, the rotor bearing 37 is inserted into the bearing holder section 88 from the rear of the rotor shaft 33.

[0105] The fan 7 is press-fitted into the fan press-fit section 74 from the front of the rotor shaft 33. Since a fan press-fit guide section 73 is provided on the front side of the fan press-fit section 74, the fan 7 is smoothly press-fitted into the fan press-fit section 74. After the fan 7 is press-fitted into the fan press-fit section 74 from the front of the rotor shaft 33, the rotor bearing 38 is inserted into the bearing holder section 71 from the front of the rotor shaft 33.

[0106] [effect] As described above, in this embodiment, the motor 6, which is a brushless motor, comprises a rotor 25 that rotates around a rotation axis AX, and a stator 24 that is arranged around the rotor 25 and has coils 29. The rotor 25 comprises a rotor core 31 and a rotor shaft 33 that is positioned in a shaft hole 60 of the rotor core 31. The rotor shaft 33 comprises a small-diameter press-fit portion 82 that is press-fitted into the shaft hole 60 with a first press-fit allowance, and a large-diameter press-fit portion 79 that is positioned differently from the small-diameter press-fit portion 82 in the front-rear direction parallel to the rotation axis AX, and is press-fitted into the shaft hole 60 with a second press-fit allowance greater than the first press-fit allowance.

[0107] In the above configuration, the rotor core 31 and the rotor shaft 33 are fixed together by press-fitting the small-diameter press-fit portion 82 and the large-diameter press-fit portion 79 into the shaft hole 60 of the rotor core 31. When manufacturing the small-diameter press-fit portion 82 and the large-diameter press-fit portion 79, bending of the rotor shaft 33 is suppressed. Furthermore, surface press-fitting, in which the outer circumferential surfaces of the small-diameter press-fit portion 82 and the large-diameter press-fit portion 79 are in close contact with the inner circumferential surface of the shaft hole 60, suppresses misalignment between the central axis of the rotor core 31 and the central axis of the rotor shaft 33. As a result, deterioration of the rotational balance of the rotor 25 is suppressed. In addition, the rotor core 31 and the rotor shaft 33 are firmly fixed together by surface press-fitting between the outer circumferential surfaces of the small-diameter press-fit portion 82 and the large-diameter press-fit portion 79 and the inner circumferential surface of the shaft hole 60. Therefore, relative rotation between the rotor core 31 and the rotor shaft 33, and relative movement between the rotor core 31 and the rotor shaft 33 in the axial direction are suppressed. Consequently, a decrease in the performance of the motor 6 is suppressed.

[0108] In this embodiment, in a cross-section perpendicular to the rotation axis AX, the outer shapes of the small-diameter press-fit portion 82 and the large-diameter press-fit portion 79 are circular.

[0109] In the above configuration, deterioration of the rotational balance of the rotor 25 is suppressed.

[0110] In this embodiment, the small-diameter press-fit portion 82 is positioned behind the large-diameter press-fit portion 79. The rotor shaft 33 has a small-diameter press-fit guide portion 83 whose diameter decreases towards the rear from the rear end of the small-diameter press-fit portion 82.

[0111] In the above configuration, the small-diameter press-fit guide portion 83 makes it easier to press-fit the small-diameter press-fit portion 82 into the shaft hole 60. Furthermore, the small-diameter press-fit guide portion 83 suppresses excessive stress concentration in the rotor core 31 when the small-diameter press-fit portion 82 is pressed into the shaft hole 60, thereby suppressing damage to the rotor core 31.

[0112] In this embodiment, the rotor shaft 33 is positioned between a small-diameter press-fit portion 82 and a large-diameter press-fit portion 79 in the front-rear direction, and has a large-diameter press-fit guide portion 80 whose diameter decreases towards the rear from the rear end of the large-diameter press-fit portion 79.

[0113] In the above configuration, the large-diameter press-fit guide portion 80 makes it easier to press-fit the large-diameter press-fit portion 79 into the shaft hole 60. Furthermore, the large-diameter press-fit guide portion 80 suppresses excessive stress concentration in the rotor core 31 when the large-diameter press-fit portion 79 is pressed into the shaft hole 60, thereby suppressing damage to the rotor core 31.

[0114] In this embodiment, the rotor shaft 33 is positioned between a small-diameter press-fit portion 82 and a large-diameter press-fit guide portion 80 in the front-rear direction, and has a relief portion 81 with a diameter smaller than the diameter of the small-diameter press-fit portion 82.

[0115] In the above configuration, when the outer surface of the small-diameter press-fit portion 82 is polished with a grinding wheel, the relief portion 81 prevents the grinding wheel from interfering with the large-diameter press-fit portion 79, while the outer surface of the small-diameter press-fit portion 82 is polished with the grinding wheel.

[0116] In this embodiment, the dimensions of the small-diameter press-fit portion 82 are smaller than the dimensions of the large-diameter press-fit portion 79 in the front-rear direction.

[0117] In the above configuration, when the small-diameter press-fit portion 82 is pressed into the shaft hole 60, and then the large-diameter press-fit portion 79 is pressed into the shaft hole 60, it is easier to press-fit the rotor shaft 33 into the shaft hole 60. Also, since the large-diameter press-fit portion 79 is longer than the small-diameter press-fit portion 82, the rotor core 31 and the rotor shaft 33 are firmly fixed together.

[0118] In this embodiment, the small-diameter press-fit portion 82 is positioned behind the large-diameter press-fit portion 79. The rear end of the small-diameter press-fit portion 82 is positioned in front of the rear end of the rotor core 31. The front end of the large-diameter press-fit portion 79 is positioned in front of the front end of the rotor core 31.

[0119] In the above configuration, the small-diameter press-fit portion 82 is not positioned behind the rear end of the rotor core 31, so for example, when press-fitting the sleeve 51 onto the rotor shaft 33 behind the rotor core 31, it is easier to press-fit the sleeve 51. Also, since the large-diameter press-fit portion 79 is positioned in front of the front end of the rotor core 31, the contact area between the outer surface of the large-diameter press-fit portion 79 and the inner surface of the shaft hole 60 is increased. As a result, the rotor core 31 and the rotor shaft 33 are firmly fixed together.

[0120] In one embodiment, the electric work machine 1 comprises the motor 6 described above, and a blade holder 10, which is a tool holder that is mounted on a blade, a tool tip, and is driven by the rotational force of the motor 6.

[0121] In the above configuration, deterioration of the rotational balance of the rotor 25 is suppressed, so that when using the electric work implement 1, the generation of vibration or noise from the electric work implement 1 is suppressed.

[0122] In this embodiment, the electric work machine 1 includes a pinion gear 41 provided at the front end of the rotor shaft 33, a fan 7 inserted into the rotor shaft 33 from the front end side, a rotor bearing 38 which is a first bearing inserted into the rotor shaft 33 from the front end side after the fan 7 has been inserted into the rotor shaft 33, a rotor core 31 which is press-fitted into the rotor shaft 33 from the rear end side, and a rotor bearing 37 which is a second bearing inserted into the rotor shaft 33 from the rear end side after the fan 7 has been press-fitted into the rotor shaft 33 from the rear end side.

[0123] In the above configuration, the electric work machine 1 is manufactured efficiently.

[0124] In one embodiment, a method for manufacturing a motor 6 comprising a rotor 25 that rotates around a rotation axis AX and a stator 24 having coils 29 arranged around the rotor 25 includes press-fitting a rotor shaft 33 into a shaft hole 60 of a rotor core 31 extending in a front-rear direction parallel to the rotation axis AX. The rotor shaft 33 has a small-diameter press-fit portion 82 that is press-fitted into the shaft hole 60 with a first press-fit allowance, and a large-diameter press-fit portion 79 that is positioned differently from the small-diameter press-fit portion 82 in the front-rear direction parallel to the rotation axis AX and is press-fitted into the shaft hole 60 with a second press-fit allowance greater than the first press-fit allowance.

[0125] In the above configuration, the rotor core 31 and the rotor shaft 33 are fixed together by press-fitting the small-diameter press-fit portion 82 and the large-diameter press-fit portion 79 into the shaft hole 60 of the rotor core 31. When manufacturing the small-diameter press-fit portion 82 and the large-diameter press-fit portion 79, bending of the rotor shaft 33 is suppressed. Furthermore, surface press-fitting, in which the outer circumferential surfaces of the small-diameter press-fit portion 82 and the large-diameter press-fit portion 79 are in close contact with the inner circumferential surface of the shaft hole 60, suppresses misalignment between the central axis of the rotor core 31 and the central axis of the rotor shaft 33. As a result, deterioration of the rotational balance of the rotor 25 is suppressed. In addition, the rotor core 31 and the rotor shaft 33 are firmly fixed together by surface press-fitting between the outer circumferential surfaces of the small-diameter press-fit portion 82 and the large-diameter press-fit portion 79 and the inner circumferential surface of the shaft hole 60. Therefore, relative rotation between the rotor core 31 and the rotor shaft 33, and relative movement between the rotor core 31 and the rotor shaft 33 in the axial direction are suppressed. Consequently, a decrease in the performance of the motor 6 is suppressed.

[0126] In this embodiment, the small-diameter press-fit portion 82 is first pressed into the shaft hole 60, and then the large-diameter press-fit portion 79 is pressed into the shaft hole 60.

[0127] In the above configuration, the small-diameter press-fit portion 82 and the large-diameter press-fit portion 79 are each properly press-fitted into the shaft hole 60. If the large-diameter press-fit portion 79 is press-fitted into the shaft hole 60 before the small-diameter press-fit portion 82, the rotor core 31 will plastically deform so that the inner diameter of the shaft hole 60 expands to match the diameter of the large-diameter press-fit portion 79, and only then will the small-diameter press-fit portion 82 be inserted into the shaft hole 60. In other words, the inner diameter of the shaft hole 60, which has been expanded to match the diameter of the large-diameter press-fit portion 79, may be larger than the outer diameter of the small-diameter press-fit portion 82, so the small-diameter press-fit portion 82 may not be properly press-fitted into the shaft hole 60. Because the smaller diameter press-fit portion 82 is pressed into the shaft hole 60 before the larger diameter press-fit portion 79, even if the inner diameter of the shaft hole 60 is enlarged to match the diameter of the smaller diameter press-fit portion 82, the enlarged inner diameter of the shaft hole 60 is smaller than the outer diameter of the larger diameter press-fit portion 79, so the larger diameter press-fit portion 79 is properly pressed into the shaft hole 60.

[0128] In this embodiment, the small-diameter press-fit portion 82 is positioned behind the large-diameter press-fit portion 79. The rotor shaft 33 is provided with a small-diameter press-fit guide portion 83, the diameter of which decreases towards the rear from the rear end of the small-diameter press-fit portion 82. After inserting the small-diameter press-fit guide portion into the shaft hole 60, the small-diameter press-fit portion 82 is press-fitted into the shaft hole 60.

[0129] In the above configuration, the small-diameter press-fit guide portion 83 makes it easier to press-fit the small-diameter press-fit portion 82 into the shaft hole 60. Furthermore, the small-diameter press-fit guide portion 83 suppresses excessive stress concentration in the rotor core 31 when the small-diameter press-fit portion 82 is pressed into the shaft hole 60, thereby suppressing damage to the rotor core 31.

[0130] In this embodiment, a large-diameter press-fit guide portion 80 is provided on the rotor shaft 33 between the small-diameter press-fit portion 82 and the large-diameter press-fit portion 79 in the front-rear direction, with the diameter decreasing towards the rear from the rear end of the large-diameter press-fit portion 79. After inserting the large-diameter press-fit guide portion 80 into the shaft hole 60, the large-diameter press-fit portion 79 is press-fitted into the shaft hole 60.

[0131] In the above configuration, the large-diameter press-fit guide portion 80 makes it easier to press-fit the large-diameter press-fit portion 79 into the shaft hole 60. Furthermore, the large-diameter press-fit guide portion 80 suppresses excessive stress concentration in the rotor core 31 when the large-diameter press-fit portion 79 is pressed into the shaft hole 60, thereby suppressing damage to the rotor core 31.

[0132] In this embodiment, the dimensions of the small-diameter press-fit portion 82 are smaller than the dimensions of the large-diameter press-fit portion 79 in the front-rear direction.

[0133] In the above configuration, when the small-diameter press-fit portion 82 is pressed into the shaft hole 60, and then the large-diameter press-fit portion 79 is pressed into the shaft hole 60, it is easier to press-fit the rotor shaft 33 into the shaft hole 60. Also, since the large-diameter press-fit portion 79 is longer than the small-diameter press-fit portion 82, the rotor core 31 and the rotor shaft 33 are firmly fixed together.

[0134] In this embodiment, the outer surfaces of the small-diameter press-fit portion 82 and the large-diameter press-fit portion 79 are polished so that, in a cross-section perpendicular to the rotation axis AX, the outer shapes of the small-diameter press-fit portion 82 and the large-diameter press-fit portion 79 are circular.

[0135] In the above configuration, polishing is used as the processing method for the small-diameter press-fit section 82 and the large-diameter press-fit section 79, thereby suppressing bending of the rotor shaft 33. Consequently, deterioration of the rotational balance of the rotor 25 is suppressed.

[0136] In this embodiment, a relief portion 81 with a diameter smaller than the diameter of the small-diameter press-fit portion 82 is provided between the small-diameter press-fit portion 82 and the large-diameter press-fit portion 79 in the front-rear direction, and then the outer surface of the small-diameter press-fit portion 82 is polished.

[0137] In the above configuration, when the outer surface of the small-diameter press-fit portion 82 is polished with a grinding wheel, the relief portion 81 prevents the grinding wheel from interfering with the large-diameter press-fit portion 79, while the outer surface of the small-diameter press-fit portion 82 is polished with the grinding wheel.

[0138] [Other embodiments] In the above-described embodiment, the electric work machine 1 is a reciprocating saw, which is a type of power tool. The power tool is not limited to a reciprocating saw. Examples of power tools include impact drivers, driver drills, rotary hammer driver drills, angle drills, screwdrivers, hammers, hammer drills, and circular saws.

[0139] In the embodiments described above, the electric work implement 1 may be an outdoor power equipment. Examples of outdoor power equipment include chainsaws, brush cutters, lawnmowers, hedge trimmers, and blowers. [Explanation of Symbols]

[0140] 1…Electric work implement, 2…Rear housing, 2L…Left housing, 2R…Right housing, 2S…Screw, 3…Front housing, 4…Battery mounting section, 5…Controller, 6…Motor, 7…Fan, 8…Crank mechanism, 9…Slider, 10…Blade holder, 11…Guide shoe, 12…Motor housing, 13…Handle section, 14…Battery holder, 15…Trigger lever, 16…Lock-off button, 17…Window, 18…First air intake, 19…Second 2 intake ports, 20...hook receiver, 21...hanging hook, 22...battery pack, 23...controller case, 24...stator, 25...rotor, 26...stator core, 27...rear insulator, 28...front insulator, 29...coil, 30...busbar, 31...rotor core, 31A...magnet hole, 31B...gap, 31C...crimped part, 32...permanent magnet, 33...rotor shaft, 34...sensor board, 35...motor case, 36...c Rank case, 37...Rotor bearing, 38...Rotor bearing, 39...Retaining plate, 40...Screw, 41...Pinion gear, 42...Bevel gear, 43...Eccentric pin, 44...Connecting pin, 45...Connecting rod, 46...Holder, 47...Slider guide, 48...Slide bar, 49...Shoe, 51...Sleeve, 52...Sleeve, 60...Shaft hole, 71...Bearing retaining part, 72...Relief part, 73...Fan press-fitting guide part, 74...Fan press Entry section, 75...Relief section, 76...First intermediate section, 77...Groove section, 78...Second intermediate section, 79...Large diameter press-fit section, 80...Large diameter press-fit guide section, 81...Relief section, 82...Small diameter press-fit section, 83...Small diameter press-fit guide section, 84...Relief section, 85...Sleeve press-fit section, 86...Sleeve press-fit guide section, 87...Relief section, 88...Bearing holding section, 100...Grinding wheel, 101...Unprocessed section, Dc...Inner diameter, Ds1...Diameter, Ds2...Diameter, L1...Dimension, L2...Dimension, AX...Rotation axis.

Claims

1. A rotor that rotates about a rotation axis, and A stator disposed around the rotor and having a coil, comprising: The rotor has a rotor core and a rotor shaft disposed in a shaft hole of the rotor core. The rotor shaft has a small-diameter press-fitting portion press-fitted into the shaft hole with a first press-fitting allowance, and a large-diameter press-fitting portion disposed at a position different from the small-diameter press-fitting portion in the front-rear direction parallel to the rotation axis and press-fitted into the shaft hole with a second press-fitting allowance larger than the first press-fitting allowance. A brushless motor.

2. In a cross section orthogonal to the rotation axis, the outer shapes of the small-diameter press-fitting portion and the large-diameter press-fitting portion are both circular. The brushless motor according to claim 1.

3. The small-diameter press-fitting portion is disposed rearward of the large-diameter press-fitting portion. The rotor shaft has a small-diameter press-fitting guide portion whose diameter decreases rearward from the rear end portion of the small-diameter press-fitting portion. The brushless motor according to claim 2.

4. The rotor shaft is disposed between the small-diameter press-fitting portion and the large-diameter press-fitting portion in the front-rear direction, and has a large-diameter press-fitting guide portion whose diameter decreases rearward from the rear end portion of the large-diameter press-fitting portion. The brushless motor according to claim 3.

5. The rotor shaft is disposed between the small-diameter press-fitting portion and the large-diameter press-fitting guide portion in the front-rear direction, and has a relief portion having a diameter smaller than that of the small-diameter press-fitting portion. The brushless motor according to claim 4.

6. In the front-rear direction, the dimension of the small-diameter press-fitting portion is smaller than the dimension of the large-diameter press-fitting portion. The brushless motor according to claim 2.

7. The small-diameter press-fitting portion is disposed rearward of the large-diameter press-fitting portion. The rear end portion of the small-diameter press-fitting portion is disposed forward of the rear end portion of the rotor core. The front end portion of the large-diameter press-fitting portion is disposed forward of the front end portion of the rotor core. The brushless motor according to claim 6.

8. The brushless motor according to claim 1, and A tip tool holding portion to which a tip tool is attached and which is driven by the rotational force of the brushless motor. An electric working machine.

9. A gear provided at one end portion of the rotor shaft, A fan inserted into the rotor shaft from one end portion side of the rotor shaft, A first bearing inserted into the rotor shaft from one end portion side of the rotor shaft, The rotor core press-fitted into the rotor shaft from the other end side of the rotor shaft, and a second bearing inserted into the rotor shaft from the other end side of the rotor shaft. The electric working machine according to claim 8.

10. A method for manufacturing a brushless motor including a rotor that rotates about a rotation axis and a stator that is disposed around the rotor and has coils, including press-fitting a rotor shaft having a small-diameter press-fitting portion press-fitted into a shaft hole of a rotor core extending in a front-rear direction parallel to the rotation axis with a first press-fitting allowance and a large-diameter press-fitting portion disposed at a position different from the small-diameter press-fitting portion in the front-rear direction parallel to the rotation axis and press-fitted into the shaft hole with a second press-fitting allowance larger than the first press-fitting allowance. A method for manufacturing a brushless motor.

11. After press-fitting the small-diameter press-fitting portion into the shaft hole, press-fitting the large-diameter press-fitting portion into the shaft hole. The method for manufacturing a brushless motor according to claim 10.

12. The small-diameter press-fitting portion is disposed rearward of the large-diameter press-fitting portion, a small-diameter press-fitting guide portion having a diameter that decreases rearward from the rear end portion of the small-diameter press-fitting portion is provided on the rotor shaft, and after inserting the small-diameter press-fitting guide portion into the shaft hole, press-fitting the small-diameter press-fitting portion into the shaft hole. The method for manufacturing a brushless motor according to claim 11.

13. A large-diameter press-fitting guide portion having a diameter that decreases rearward from the rear end portion of the large-diameter press-fitting portion is provided on the rotor shaft between the small-diameter press-fitting portion and the large-diameter press-fitting portion in the front-rear direction, and after inserting the large-diameter press-fitting guide portion into the shaft hole, press-fitting the large-diameter press-fitting portion into the shaft hole. The method for manufacturing a brushless motor according to claim 12.

14. In the front-rear direction, the dimension of the small-diameter press-fitting portion is smaller than the dimension of the large-diameter press-fitting portion. The method for manufacturing a brushless motor according to claim 11.

15. Polishing the outer peripheral surface of the small-diameter press-fitting portion and the outer peripheral surface of the large-diameter press-fitting portion so that the outer shape of each of the small-diameter press-fitting portion and the large-diameter press-fitting portion is circular in a cross section orthogonal to the rotation axis. The method for manufacturing a brushless motor according to claim 14.

16. After providing a relief portion having a diameter smaller than the diameter of the small-diameter press-fitting portion between the small-diameter press-fitting portion and the large-diameter press-fitting portion in the front-rear direction, polishing the outer peripheral surface of the small-diameter press-fitting portion. The manufacturing method of the brushless motor according to claim 15.

Images