Electric work machine and method for manufacturing same

Abstract

The invention provides an electric working machine with a brushless motor. The brushless motor has a rotor and a stator. The rotor has a plurality of permanent magnets. The plurality of permanent magnets are arranged such that the same poles face each other in the circumferential direction of the rotor core, thereby forming a plurality of magnetic poles on the outer circumference of the rotor core in the circumferential direction thereof. The plurality of magnetic poles have 4m (m is a natural number) magnetic poles, and the stator has 3m slots. The rotor rotates at an electrical frequency of 1333 Hz or more. Therefore, the electric working machine provided with the brushless motor capable of realizing high-speed rotation and high output while suppressing large-scale is provided.

Description

Technical Field

[0001] This invention relates to an electric work machine with a brushless motor. Background Technology

[0002] Patent Document 1 discloses an electronic rectifier motor with a rotor of the permanent magnet type. The rotor has multiple slots, in which multiple permanent magnets are disposed respectively. Existing technical documents Patent documents

[0003] Patent Document 1: International Publication No. 2008 / 104156 Summary of the Invention [The technical problem that the invention aims to solve]

[0004] In recent years, brushless motors have been used as the power source for power work machines (such as power tools, gardening power tools, etc.). In order to improve the operability and / or functionality of power work machines, it is desirable to install (equip) small brushless motors that can be driven at high speeds and with high output.

[0005] Therefore, one objective of the present invention is to provide an electric work machine equipped with a brushless motor, wherein the brushless motor can achieve high-speed rotation and high output while suppressing large size. [Technical solutions used to solve technical problems]

[0006] In this invention, the terms "first," "second," etc., are merely used to distinguish structural elements from each other, and are not intended to limit the order or number of structural elements. Therefore, the first structural element can be referred to as the second structural element, and the second structural element can also be referred to as the first structural element. Alternatively, a first structural element may be present without a second structural element, and similarly, a second structural element may be present without a first structural element.

[0007] One aspect of the present invention provides an electric work machine having a brushless motor and a power transmission unit. The power transmission unit is configured to (i) mount a driven device or detachably mount a driven device, and is configured to (ii) transmit the rotation of the brushless motor to the driven device to drive the driven device.

[0008] A brushless motor has a rotor and a stator. The rotor has a rotor core and a plurality of permanent magnets. The plurality of permanent magnets are configured to (i) be separated from each other along the circumference of the rotor core and to (ii) be opposite each other with the same poles along the circumference, thereby forming a plurality of magnetic poles along the circumference.

[0009] The stator has multiple coils and multiple slots in which the multiple coils are respectively configured. The plurality of magnetic poles has 4m poles (m is a natural number). The plurality of slots has 3m slots. The rotor is configured to rotate at an electrical frequency of 1333Hz or higher. "m" can be, for example, a natural number (integer) in the range of 1 to 8, or, for example, in the range of 1 to 6, or, for example, in the range of 2 to 4.

[0010] This configuration of the electric work machine enables the brushless motor to be driven at high speed and high output while suppressing the large size of the brushless motor. As a structure that helps to achieve the above effect, at least the following configurations can be cited: (i) the ratio of the number of permanent magnets to the number of slots is 4:3, and / or (ii) multiple permanent magnets are circumferentially opposite each other with the same poles.

[0011] Another aspect of the present invention provides a method for manufacturing an electric work machine, comprising the following steps: Prepare a rotor with 4m (m is a natural number) magnetic poles, wherein the rotor has a plurality of permanent magnets, the plurality of permanent magnets being configured such that the same poles face each other along the direction of rotation of the rotor; Prepare a stator with 3m slots; A brushless motor is installed on the electric work machine, wherein the brushless motor includes the rotor and the stator and is configured to rotate at an electrical frequency of 1333 Hz or higher.

[0012] This method can achieve the same effect as the electric work machine mentioned above. Furthermore, in electric work machines equipped with brushless motors, a higher power density of the brushless motor is desirable. Higher power density allows for smaller and lighter brushless motors.

[0013] Therefore, another aspect of the present invention aims to provide an electric work machine equipped with a brushless motor that increases power density while suppressing large size. Specifically, another aspect of the present invention provides an electric work machine. This electric work machine has a brushless motor and a power transmission unit, wherein... The power transmission unit is configured to (i) mount a driven device or detachably mount the driven device, and is configured to (ii) transmit the rotation of the brushless motor to the driven device to drive the driven device. The brushless motor has a stator and a rotor. The stator has multiple coils; The rotor has a rotor core and multiple permanent magnets. The brushless electrical mechanism satisfies the following equation (1).

[0014] [Mathematical Formula 1]

[0015] In the above formula (1), R is the inter-line resistance value [mΩ] of the brushless motor based on the plurality of coils. Vin is the rated voltage value [V] of the brushless motor. Ne is the rotational speed [krpm] of the brushless motor when the effective induced voltage value is equal to the rated voltage value, wherein the effective induced voltage value represents the magnitude of the induced voltage generated by the plurality of coils. Vol is the volume of the stator [mm] 3 ].

[0016] This type of electric work machine can drive a brushless motor with high output density while suppressing the increase in the size of the brushless motor. Attached Figure Description

[0017] Figure 1 This is a perspective view of the electric work machine in the exemplary first embodiment. Figure 2 This is a first perspective view of the motor inside the electric work machine according to the first embodiment. Figure 3 This is a first exploded perspective view of the motor according to the first embodiment, corresponding to the first perspective view. Figure 4 This is a second perspective view of the motor according to the first embodiment. Figure 5 This is a second exploded perspective view of the motor according to the first embodiment, corresponding to the second perspective view. Figure 6 yes Figure 2 VI-VI cross-sectional view of the motor. Figure 7 This is a first perspective exploded view of the rotor according to the first embodiment. Figure 8 This is a second exploded perspective view of the rotor according to the first embodiment. Figure 9 This is a top view of the rotor core of the first embodiment. Figure 10 This is a top view of the rotor according to the first embodiment. Figure 11 This is a perspective view of the rotor of the first embodiment, omitting the resin section. Figure 12 This is a side view of the rotor of the first embodiment, omitting the resin section. Figure 13 This is an explanatory diagram of the rotor core lamination process. Figure 14 This is an explanatory diagram related to the minimum width of the connection part of the rotor core. Figure 15This is an explanatory diagram showing the electrical structure of the electric work machine according to the first embodiment. Figure 16 This is an explanatory diagram related to induced voltage. Figure 17 This is an explanatory diagram showing the characteristics of the motor according to the first embodiment. Figure 18 This is an explanatory diagram showing the difference in size between the motor of the first embodiment and the conventional motor. Figure 19 This is a top view of the rotor according to the second embodiment. Figure 20 This is a side view of the rotor in the second embodiment, omitting the resin section. Figure 21 This is a top view of the rotor according to the third embodiment. Figure 22 This is a perspective view of the stator and rotor of the motor according to the fourth embodiment. Explanation of reference numerals in the attached figures 1: Electric work machine; 3: Battery pack; 6: Battery mounting section; 7: Second power transmission section; 11, 250: Motor; 12: First power transmission section; 13: Controller; 15: Driven device; 20, 251: Stator; 21: Stator core; 25, 255: Coil; 26, 256: Slot; 31: First power terminal; 32: Second power terminal; 33: Third power terminal; 40, 260, 500: Rotor; 41, 150 261, 510: Rotor core; 41A, 150A, 510A: Core annular portion; 41B, 150B, 510B: Magnet support portion; 41C, 150C, 510C: Connecting portion; 42, 70, 141, 262: Permanent magnet; 45: Protrusion; 46: Recess; 141A: First part magnet; 141B: Second part magnet; 400: Core plate; 400A: First surface; 400B: Second surface. Detailed Implementation

[0018] [1. Overview of Implementation Methods] One embodiment may provide an electric work machine having at least one of the following features. Feature 1: Brushless motor. Feature 2: Power transmission unit. Feature 3: The power transmission unit is configured to have a driven device mounted on it or to have a driven device detachably mounted on it. Feature 4: The power transmission unit is configured to transmit the rotation of the brushless motor to the driven device to drive the driven device. Feature 5: Brushless motors have a rotor. Feature 6: The rotor has a rotor core. Feature 7: The rotor has multiple permanent magnets. Feature 8: The plurality of permanent magnets are at least partially located within the rotor core. The plurality of permanent magnets may be at least partially located on the rotor core. The plurality of permanent magnets may also be at least partially embedded in the rotor core. Feature 9: The plurality of permanent magnets are separated from each other along the circumference of the rotor core. The circumference of the rotor core may also be referred to as the rotation direction of the rotor core, the rotation direction of the rotor, the circumference of the rotor, or the rotation direction of the brushless motor. Feature 10: The plurality of permanent magnets are configured such that their same poles face each other along the circumferential direction of the rotor core. • Feature 11: The plurality of permanent magnets form a plurality of magnetic poles along the circumference of the rotor core. The plurality of magnetic poles can be formed at least by feature 10 described above. Feature 12: Brushless motors have a stator. Feature 13: The stator has multiple coils. Feature 14: The stator has multiple slots. Feature 15: The plurality of slots are respectively configured with the plurality of coils. Feature 16: The plurality of magnetic poles has 4m magnetic poles (m is a natural number). 4m refers to the product of 4 and m. Having 4m magnetic poles is synonymous with having 4m permanent magnets. Feature 17: The plurality of slots has 3m slots. 3m refers to the product of 3 and m. Having 3m slots can also be described as the plurality of coils having 3m coils. Feature 18: The rotor is configured to rotate at an electrical frequency of 1333 Hz or higher. The electrical frequency can also be defined as the product of the rotor's rotational speed per second (in other words, the rotational speed of the rotor core or the brushless motor) and the number of pole pairs. The number of pole pairs is half the number of the plurality of magnetic poles.

[0019] Among electric work machines with at least features 1 to 7 and 9 to 18, it is possible to drive a brushless motor with high speed and high output while suppressing the enlargement of the brushless motor. The statement that the plurality of magnetic poles has 4m magnetic poles means that the plurality of magnetic poles has exactly 4m magnetic poles, excluding cases with more than 4m magnetic poles.

[0020] Similarly, the statement that the plurality of slots has 3m slots means that the plurality of slots has exactly 3m slots, excluding cases with more than 3m slots.

[0021] Therefore, brushless motors with m=2, for example, have 8 poles and 6 slots, but not those with more than 9 poles and more than 7 slots. The plurality of permanent magnets may also have 4m permanent magnets.

[0022] The plurality of permanent magnets can also be divided into multiple parts. For example, the plurality of permanent magnets can be divided radially, or axially. Radial is the direction perpendicular to the rotor's axis of rotation (in other words, the axis of rotation of the rotor core). Axial is the direction along the rotor's axis of rotation (i.e., parallel to the axis of rotation).

[0023] Electric work machines can also have a controller (or control circuit). The controller can also be configured to supply power to the brushless motor, causing the brushless motor to rotate at an electrical frequency of 1333Hz. For example, the rated electrical frequency of the brushless motor can be above 1333Hz, and the electrical frequency at which the brushless motor rotates at its maximum speed when the electric work machine is used can be above 1333Hz.

[0024] In addition to any of the features 1 to 18 described above, or in lieu of the features described above, a certain embodiment may also have at least any of the following features. Feature 19: The rotor core has multiple core plates. Feature 20: Each of the multiple iron core plates contains a plate-shaped soft magnetic material. Feature 21: Multiple core plates are stacked along the rotor's rotation axis. Feature 22: The thickness of each of the multiple core plates is greater than 0 mm and less than 0.35 mm in the direction along the rotation axis.

[0025] In electric work machines having at least features 1 to 22, losses generated in the rotor core (e.g., losses due to eddy currents) are reduced. Accordingly, the speed and / or output of the brushless motor can be further increased. Furthermore, speed refers to the rotational speed per unit time (e.g., 1 minute or 1 second). Speed ​​can also be referred to as rotational velocity.

[0026] In addition to at least one of the features 1 to 22 described above, or in lieu of the features described above, a certain embodiment may also have the following features. Feature 23: The thickness of each of the plurality of core plates is less than 0.30 mm.

[0027] In an electric work machine having at least features 1 to 23, compared to the case where the thickness of each of the plurality of core plates is greater than 0.30 mm, the speed and / or output of the brushless motor can be further increased.

[0028] In addition to at least one of the features 1 to 23 described above, or in lieu of the features described above, a certain embodiment may also have the following features. Feature 24: The thickness of each of the plurality of core plates is less than 0.25 mm. In electric work machines having at least features 1 to 24, compared to cases where the thickness of each of the plurality of core plates is greater than 0.25 mm, the speed and / or output of the brushless motor can be further increased.

[0029] Furthermore, the thickness of each of the plurality of core plates can be less than 0.23 mm or less than 0.20 mm. Additionally, the thickness of each of the plurality of core plates can be greater than 0 mm or greater than a specified lower limit thickness. The lower limit thickness is greater than 0 mm. However, it is not limited to this; for example, the lower limit of the core plate thickness can be 0.05 mm or 0.10 mm.

[0030] In addition to at least any one of the features 1 to 24 described above, or in lieu of the features described above, a certain embodiment may also have at least any one of the following features. Feature 25: Each of the multiple core plates has a first surface. Feature 26: The first surface is provided with a protrusion. Feature 27: Each of the multiple core plates has a second surface. Feature 28: On the second surface, a recess is provided at a position on the second surface that overlaps with the protrusion in the axial direction. Feature 29: The multiple core plates are stacked by embedding the protrusion of one of two opposing core plates into the recess of the other.

[0031] In electric operating machines having at least features 1 to 22 and 25 to 29, the quality and reliability of the rotor core can be improved. Specifically, during the manufacturing process of the rotor core, the multiple core plates can be stacked stably and with high precision.

[0032] The recess and protrusion can also be configured such that the protrusion does not detach from (or is difficult to detach from) the recess by bearing pressure (and / or friction) from the protrusion embedded in the recess. The protrusion can also be fastened to the recess by embedding itself in it. More specifically, the protrusion and / or recess can also receive pressure by embedding the protrusion into the recess, thereby undergoing mechanical deformation. This mechanical deformation can also fasten the protrusion to the recess.

[0033] In addition to at least any one of the features 1 to 29 described above, or in lieu of the features described above, a certain embodiment may also have at least any one of the following features. Feature 30: The rotor core has multiple holes. Feature 31: The plurality of holes are arranged separately from each other in the circumferential direction. Feature 32: Each of the plurality of holes is inserted into a corresponding permanent magnet among the plurality of permanent magnets.

[0034] In an electric work machine having at least features 1 to 18 and 30 to 32, the plurality of permanent magnets can be stably and efficiently fixed to the rotor core. Furthermore, the plurality of holes can be partially or completely axially penetrated.

[0035] In addition to at least any one of the features 1 to 32 described above, or in lieu of the features described above, a certain embodiment may also have at least any one of the following features. Feature 33: The rotor core has a cylindrical core ring. Feature 34: The rotor core has multiple magnet supports. Feature 35: The plurality of magnet supports are arranged separately from each other in the circumferential direction. Feature 36: Between two adjacent magnet supports in the circumferential direction, there is a corresponding hole among the plurality of holes. Feature 37: The rotor core has multiple connecting parts. Feature 38: The plurality of connecting portions are respectively provided corresponding to the plurality of magnet supports. Feature 39: The plurality of connecting parts connect the corresponding magnet support parts to the iron core ring part. Feature 40: The width of the smallest portion of each of the plurality of connecting parts is 0.4mm to 0.6mm. The width is the length in a direction orthogonal to both the axial and radial directions.

[0036] In an electric work machine having at least features 1 to 18 and 30 to 40, it is possible to maintain the strength of the rotor core appropriately while reducing magnetic flux short circuits (specifically, magnetic flux short circuits via the aforementioned multiple connections) within the rotor core.

[0037] In addition to at least any one of the features 1 to 40 described above, or in lieu of the features described above, a certain embodiment may also have at least any one of the following features. Feature 41: The rotor core has multiple openings. Feature 42: The plurality of openings are arranged circumferentially separated from each other on the outer peripheral surface of the rotor core. Feature 43: The plurality of openings are respectively connected to a corresponding hole in the plurality of holes, thereby the plurality of holes are exposed radially from the rotor core.

[0038] For example, suppose that the plurality of openings are not provided, but a portion of the rotor core still exists in the region corresponding to the openings (hereinafter, the region corresponding to the openings). In this case, a portion of the magnetic flux from the plurality of permanent magnets is short-circuited through the region corresponding to the openings, and thus, this portion of the magnetic flux may no longer be effectively used for the motor output.

[0039] In contrast, by setting the multiple openings, the magnetic reluctance of the region corresponding to the opening becomes higher, and the short circuit of magnetic flux through the region corresponding to the opening is reduced. Therefore, in electric work machines having at least features 1–18, 30–32, and 41–43, it is possible to reduce magnetic reluctance based on the rotor core and to effectively utilize the magnetic flux from the plurality of permanent magnets through the motor output. Accordingly, the possibility of high rotational efficiency and / or high output of the motor is further increased.

[0040] In addition to at least any one of the features 1 to 43 described above, or in lieu of the features described above, a certain embodiment may also have the following features. Feature 44: The brushless electrical mechanism is such that it satisfies the following formula (1).

[0041] [Mathematical Formula 2]

[0042] In the above formula (1), R is the inter-line resistance value [mΩ] of the brushless motor based on the plurality of coils. Vin is the rated voltage value [V] of the brushless motor. Ne is the speed [krpm] of the brushless motor when the effective induced voltage value is equal to the rated voltage value, where the effective induced voltage value represents the magnitude of the induced voltage generated by the plurality of coils. Vol is the volume of the stator [mm] 3 ].

[0043] The effective induced voltage value can be, for example, the effective value of the induced voltage generated by any one of the plurality of coils, or the average of the absolute values ​​of the induced voltage. Alternatively, the effective induced voltage can also be, for example, the average of the induced voltages generated in any one of the coils within a predetermined electrical angle range. The predetermined electrical angle range is a range of defined angles (e.g., 60 degrees) centered on the electrical angle where the induced voltage reaches its maximum value. For example, if the induced voltage reaches its maximum value at an electrical angle of 90 degrees, the electrical angle range could be, for example, 60 degrees to 120 degrees.

[0044] In electric work machines with at least features 1 to 18 and 44, it is possible to drive a brushless motor with high output density while suppressing the enlargement of the brushless motor. In addition to feature 44, embodiments having feature 44 may also have any of features 1 to 43 described above. For example, a certain embodiment may also have features 1, 5 to 7, 12, 13, and 44. This embodiment is referred to as a specific combination. Even in an electric work machine having this specific combination, it is possible to drive the brushless motor with high output density while suppressing the increase in the size of the brushless motor.

[0045] The specific combination described above may also have one or more other features. For example, the specific combination described above may also have at least one of (i) features 9-11, (ii) feature 16, (iii) feature 17 and (iv) feature 18.

[0046] In the case where the above-mentioned combination of features also includes features 9 to 11, in this type of electric work machine, more magnetic flux can be generated by the rotor, thereby enabling high rotational speed and / or high output of the brushless motor.

[0047] When the above-mentioned combination of features also includes features 9 to 11, 16, and 17, in this type of electric work machine, it is possible to achieve the desired speed, desired output, and / or desired power density while miniaturizing the brushless motor.

[0048] When the above-mentioned combination of features also includes features 9 to 11 and 16 to 18, this type of electric work machine enables a small brushless motor to rotate at high speed, thereby improving the workability of the electric work machine.

[0049] In addition to at least any one of the features 1 to 44 described above, or in lieu of the features described above, a certain embodiment may also have at least any one of the following features. Feature 45: The brushless motor has 3 terminals. Feature 46: The three terminals are configured to be electrically connected to the plurality of coils and to supply power to the plurality of coils.

[0050] In a certain embodiment with features 44 to 46, R in the above formula (1) can be the resistance value between any two of the three terminals. This resistance value can also be called the line-to-line resistance value or the motor resistance value. In addition, in this case, the effective induced voltage value of Ne in the above formula (1) can be the effective value or the average value of the induced voltage generated between any two of the three terminals, or it can be the average value of the induced voltage generated between any two terminals within the above electrical angle range.

[0051] The electric work machine may also have a power generation circuit (or drive circuit or controller) for generating electricity. The electricity may also be in the form of three-phase electricity. In this case, the three terminals may be configured to (i) be electrically connected to the power generation circuit, (ii) receive electricity from the power generation circuit, and (iii) supply the received electricity to the plurality of coils.

[0052] In addition to at least any one of the features 1 to 46 described above, or in lieu of the features described above, a certain embodiment may also have the following features. Feature 47: The stator has a cylindrical stator core.

[0053] In a certain embodiment with features 44 and 47, Vol in the above formula (1) can be the volume of the stator core. Specifically, Vol can be the product of the area of ​​the end circle of the core and the length of the core. The end circle of the core is a circle with the outer diameter of the stator core as its diameter. The length of the core is the axial length of the stator core.

[0054] In addition to at least any one of the features 1 to 47 described above, or in lieu of the features described above, a certain embodiment may also have at least any one of the following features. Feature 48: The plurality of magnetic poles has 8 magnetic poles. Feature 49: The plurality of slots has 6 slots.

[0055] In other words, features 48 and 49 mentioned above correspond to m=2 in features 16 and 17 mentioned above. In electric work machines with at least features 1 to 18, 48, and 49, it is possible to maintain the cost, size (and / or weight), speed, and output of the brushless motor at the desired overall level.

[0056] In addition to at least any one of the features 1 to 49 described above, or in lieu of the features described above, a certain embodiment may also have the following features. Feature 50: The brushless motor rotates at speeds of 20,000 rpm or higher.

[0057] An electric workpiece can also be configured to control a brushless motor, causing the brushless motor to rotate at a speed of 20,000 rpm or higher. For example, the rated speed of the brushless motor can be 20,000 rpm or higher, and the maximum speed of the brushless motor when using the electric workpiece can be 20,000 rpm or higher. In electric workpieces having at least features 1 to 18, 50, the operability of the electric workpiece can be improved.

[0058] In addition to any of the features 1 to 50 described above, or in lieu of the features described above, a certain embodiment may also have the following features. Feature 51: The plurality of permanent magnets extend radially along the rotor core.

[0059] The radial length of each of the plurality of permanent magnets may be longer than its circumferential length. The plurality of permanent magnets may also each have a plate-like shape, with the plate surface parallel to both the axial direction and the radial direction.

[0060] In an electric work machine having at least features 1 to 18, 51, a greater amount of magnetic flux can be generated through the plurality of permanent magnets (in other words, through the plurality of magnetic poles), thereby enabling the brushless motor to rotate at higher speeds and / or output higher.

[0061] In addition to at least any one of the features 1 to 51 described above, or in lieu of the features described above, a certain embodiment may also have at least any one of the following features. Feature 52: The plurality of permanent magnets respectively include a first part magnet and a second part magnet. Feature 53: The first and second magnets are separated from each other circumferentially. Feature 54: The first and second magnets are configured such that their opposite poles face each other circumferentially.

[0062] In an electric work machine having at least features 1 to 18 and 52 to 54, the magnetic flux generated by the plurality of permanent magnets can be increased. More specifically, the first and / or second part magnets can be arranged (extended) in a direction inclined relative to the radial direction. Accordingly, the surface area of ​​the plurality of permanent magnets (specifically, the surface area of ​​the magnetic poles) can be increased, and correspondingly, the miniaturization of the brushless motor can be achieved.

[0063] In addition to at least any one of the features 1 to 54 described above, or in lieu of the features described above, a certain embodiment may also have at least any one of the following features. Feature 55: The control unit is configured for user control of the electric work machine. Feature 56: Battery mounting section, configured to detachably mount a battery pack including the battery.

[0064] Among electric work machines having at least features 1 to 18, 55, and 56, it is possible to provide a handheld and battery-powered electric work machine that can achieve small size, high rotation and / or high output.

[0065] One embodiment may also provide a method for manufacturing an electric work machine having at least one of the following features: Feature 57: A rotor with 4m magnetic poles (m is a natural number) is prepared. The rotor may also have multiple permanent magnets. The multiple permanent magnets may also be configured such that the same poles face each other along the direction of rotation of the rotor. Feature 58: Prepare a stator with 3m slots. • Feature 59: A brushless motor is installed on an electric work machine. The brushless motor is composed of a rotor, including feature 57 and a stator, and rotates at an electrical frequency of 1333 Hz or higher.

[0066] According to the method with features 57 to 59, it is possible to drive a brushless motor with high speed and high output while suppressing the large size of the brushless motor. The examples of the aforementioned electric work machines include various types of equipment configured for use on construction, manufacturing, horticulture, civil engineering, and other work sites, specifically including: power tools for stonemasonry, metalworking, and woodworking; power tools for horticulture; power tools for improving the work site environment; fan vests; fan jackets; hand-pushed trolleys; electric-assisted bicycles; air pumps, etc.

[0067] Examples of the aforementioned power tools include: electric chainsaws, electric hand saws, electric blowers, electric hammers, electric hammer drills, electric drills, electric screwdrivers, electric wrenches, electric impact screwdrivers, electric impact wrenches, electric grinders, electric circular saws, electric reciprocating saws, electric jigsaws, electric cutting machines, electric planers, electric nail guns (including nail guns), electric hedge trimmers, electric lawn mowers, electric lawn trimmers, electric brush cutters, electric cleaners, electric sprayers, electric spreaders, electric dust collectors, electric trowels, electric vibrators, electric tampers, electric compactors, electric pumps, electric pile drivers, electric concrete saws, electric levelers, electric cutting saws, etc.

[0068] The above-described example of an electric work platform can be configured as a battery-powered device. Specifically, the above-described example of an electric work platform can have a built-in battery or can be configured to have a removable battery pack. The battery pack houses the batteries.

[0069] In one embodiment, features 1 to 59 described above can be combined arbitrarily. In one embodiment, any of the features 1 to 59 described above may be deleted. [2. Some exemplary implementations] [2-1. First Embodiment] Below, some exemplary embodiments are described. These exemplary embodiments provide an electric work machine 1 in the form of an electric impact screwdriver. However, this electric work machine 1 is merely an example, and the present invention is applicable to all forms of electric work machines.

[0070] In the following descriptions or accompanying drawings, for ease of explanation, such as Figure 1As shown, directions such as "up," "down," "forward," "backward," "left," and "right" are specified. However, these directions are merely for ease of understanding the structure of the electric work machine 1 and are not intended to limit the orientation of the electric work machine 1. The electric work machine 1 can face any direction. <2-1-1. Overall Structure of Electric Work Machine> like Figure 1 As shown, the electric work machine 1 has a work machine body 2. The work machine body 2 has a housing 4. The housing 4 houses a brushless motor (hereinafter referred to as "motor") 11.

[0071] The first power transmission unit 12 is housed inside the outer casing 4. The first power transmission unit 12 is located in front of the motor 11 and is mechanically connected to the motor 11. A second power transmission unit 7 is provided at the front end of the outer casing 4. The second power transmission unit 7 is mechanically connected to the first power transmission unit 12. The second power transmission unit 7 can also be referred to as a clamping sleeve.

[0072] The second power transmission unit 7 is detachably mounted with the driven tool 15. In this first embodiment, the driven tool 15 may be in the form of various tool heads. Examples of various tool heads include screwdriver heads, socket drill bits, and drill bits.

[0073] The first power transmission unit 12 transmits the rotation of the motor 11 to the second power transmission unit 7. Therefore, when the motor 11 rotates, the second power transmission unit 7 rotates together with the driven tool 15 mounted on the second power transmission unit 7. Additionally, the first power transmission unit 12 includes a striking mechanism (not shown). When the load applied by the second power transmission unit 7 exceeds a predetermined level, the striking mechanism intermittently applies a striking force in the direction of rotation to the second power transmission unit 7. The load is applied in the opposite direction to the rotation of the second power transmission unit 7. This striking mechanism achieves the characteristic function of an impact screwdriver.

[0074] The main body 2 of the power machine has a handle 5 extending downward from the outer casing 4. The handle 5 is held by the user of the electric power machine 1. The main body 2 of the work machine has a trigger 8. The trigger 8 is located on the upper front side of the handle 5. The trigger 8 is operated by the user from the initial position (e.g., pulled). When the trigger 8 is in the initial position, the motor 11 is in a stopped state. When the trigger 8 is moved from the initial position, the motor 11 rotates.

[0075] The main body 2 of the work machine has a battery mounting section 6. The battery mounting section 6 is located at the lower end of the handle 5. The battery mounting section 6 detachably mounts the battery pack 3. Figure 1 This indicates that the battery pack 3 is installed in the battery mounting section 6. The battery pack 3 has a battery 3A.

[0076] The main body 2 of the work machine has an operation panel 9 on the upper surface of the battery mounting section 6. The operation panel 9 is for user operation. The user can specify the operating mode of the motor 11 through the operation panel 9.

[0077] The controller 13 is housed below the handle 5 and above the battery mounting section 6 in the main body 2 of the work machine. When the battery pack 3 is installed in the battery mounting section 6, the battery 3A is electrically connected to the controller 13. The controller 13 receives power from the battery 3A and operates based on the battery power. When the trigger 8 is manually operated, the controller 13 converts the battery power into motor drive power and supplies it to the motor 11. The motor 11 rotates upon receiving the motor drive power. The motor drive power is in the form of three-phase electricity. The controller 13 controls the motor drive power according to the amount of movement of the trigger 8 and the set operating mode, thereby controlling the rotation of the motor 11. 2-1-2. Overall Structure of the Motor like Figures 2-6 As shown, the motor 11 has a stator 20 and a rotor 40. The motor 11 in this embodiment is an internal rotor type motor.

[0078] The motor 11 in this embodiment is a three-phase brushless motor having 4m poles (m is a natural number) and 3m slots. As an example of this combination of pole number (i.e., magnetic pole number) and slot number, an 8-pole, 6-slot brushless motor is shown in this embodiment.

[0079] The stator 20 has a generally circular shape. The rotor 40 is rotatably disposed on the inner circumference of the stator 20. Here, "axial," "radial," and "circumferential" are defined. The axial direction is parallel to the rotation axis AX of the motor 11 and faces forward. The radial direction extends from the rotation axis AX perpendicularly to it. The circumferential direction is, for example, a direction that circles the rotation axis AX in a clockwise direction. <2-1-2a. Stator> The stator 20 has a stator core 21. The stator core 21 is formed of electromagnetic steel. The stator core 21 includes multiple electromagnetic steel plates stacked along the axial direction.

[0080] The stator core 21 has a back core 211. The back core 211 has a cylindrical shape. The central axis of the back core 211 is aligned with the axis of rotation AX. like Figure 3 , Figure 5As shown, the stator core 21 has a plurality of core teeth 212. The plurality of core teeth 212 protrude from the inner circumferential surface of the back core 211 in a direction opposite to the radial direction (i.e., towards the rotation axis AX). The plurality of core teeth 212 are arranged at equal intervals between each other along the circumferential direction. The plurality of core teeth 212 are integrally formed with the back core 211. In this embodiment, the plurality of core teeth 212 has six core teeth 212.

[0081] like Figures 2-6 As shown, the stator 20 has an insulator 22. More specifically, the insulator 22 in this embodiment has a first insulator 23 and a second insulator 24, but this is only one example. The first insulator 23 and the second insulator 24 have a generally annular or generally cylindrical shape. The first insulator 23 and the second insulator 24 are electrically insulating components, for example, made of synthetic resin.

[0082] The first insulator 23 is fixed to the stator core 21 on the front side, covering the front surface of the stator core 21. The second insulator 24 is fixed to the stator core 21 on the rear side, covering the rear surface of the stator core 21. The first insulator 23 and the second insulator 24 may also be integrally formed with the stator core 21.

[0083] like Figure 3 , Figure 5 , Figure 6 As shown, the first insulator 23 has a plurality of first teeth 231. The plurality of first teeth 231 protrude from the inner circumferential surface of the annular (or cylindrical) component of the first insulator 23 in a direction opposite to the radial direction (i.e., towards the axis of rotation AX). In this embodiment, there are six first teeth 231. The plurality of first teeth 231 respectively cover the front side surface of a corresponding core tooth among the plurality of core teeth 212.

[0084] The second insulator 24 has a plurality of second teeth 241. The plurality of second teeth 241 protrude from the inner circumferential surface of the annular (or cylindrical) component of the second insulator 24 in a direction opposite to the radial direction (i.e., towards the axis of rotation AX). In this embodiment, there are six second teeth 241. The plurality of second teeth 241 respectively cover the rear side surface of a corresponding core tooth 212 among the plurality of core teeth 212.

[0085] A stator tooth is formed by one core tooth 212 from a plurality of core tooth portions 212, one first tooth 231 from a plurality of first tooth portions 231 corresponding to the core tooth 212, and one second tooth 241 from a plurality of second tooth portions 241 corresponding to the core tooth 212. That is, the stator 20 of this embodiment has 6 stator teeth.

[0086] The stator 20 has 3m slots 26 (m is a natural number). As an example, the stator 20 of this embodiment has 6 stator teeth. Therefore, the stator 20 of this embodiment has 6 slots 26. That is, in this embodiment, m = 2. The 6 slots 26 correspond to the space between 2 adjacent stator teeth.

[0087] like Figures 2-6 As shown, the stator 20 has a plurality of coils 25. In this embodiment, the plurality of coils 25 has six coils 25. The six coils 25 are respectively disposed in one corresponding stator tooth of the six stator teeth. That is, the six coils 25 are respectively disposed in a predetermined space including two slots 26 on both ends of the stator tooth while being wound around the corresponding stator tooth. The aforementioned motor drive power is supplied to the six coils 25. As will be referred to later Figure 15 As explained, the six coils 25 are electrically connected to each other in a prescribed wiring configuration. <2-1-2b. Rotor> like Figure 2 , Figure 3 , Figure 5 , Figure 6 As shown, the rotor 40 has a rotor core 41 and a plurality of permanent magnets 42.

[0088] like Figure 3 , Figure 5 As shown, the rotor core 41 has a central hole 410 extending axially. A rotor shaft 50 is inserted into and fixed within the central hole 410. The rotor core 41 has an outer peripheral surface 413. Notches are formed at equal intervals along the circumferential direction on the outer peripheral surface 413. These notched portions, along with the multiple openings 423 and holes 420 described later (see reference...). Figure 7 )correspond.

[0089] A plurality of permanent magnets 42 are at least partially disposed within the rotor core 41. In the following description, when simply referred to as "permanent magnet 42", it refers to each or any one of the plurality of permanent magnets 42. Similarly, when simply referred to as "opening 423", it refers to each or any one of the plurality of openings 423, and when simply referred to as "hole 420", it refers to each or any one of the plurality of holes 420.

[0090] In this embodiment, the permanent magnet 42 is in the form of a sintered magnet. A plurality of permanent magnets 42 are arranged at equal intervals along the circumferential direction on the rotor core 41. The plurality of permanent magnets 42 are respectively disposed at the aforementioned portions forming notches on the outer peripheral surface 413 of the rotor core 41.

[0091] like Figure 3 , Figure 5 , Figure 6As shown, the rotor 40 has a resin section 43. The resin section 43 integrally fixes a plurality of permanent magnets 42 to the rotor core 41. In this embodiment, the rotor core 41 and the plurality of permanent magnets 42 are integrally formed by the resin section 43.

[0092] The resin section 43 has an end face fixing portion 430. The end face fixing portion 430 covers the stator core 21 and a plurality of permanent magnets 42 from its rear side. Figure 5 , Figure 6 As shown, in this embodiment, the end face fixing portion 430 covers a plurality of permanent magnets 42 from its rear side. That is, the portion of the plurality of permanent magnets 42 that protrudes from the end face (second end face 412 described later) of the rotor core 41 is at least partially (completely) covered by the end face fixing portion 430.

[0093] In addition, such as Figure 5 As shown, the end face fixing part 430 covers most of the second end face 412 of the rotor core 41. On the other hand, such as Figure 3 As shown, the front end face of the rotor core 41 (the first end face 411 described later) and the front surface of the plurality of permanent magnets 42 are not covered by the resin part 43, but are exposed to the front.

[0094] like Figure 5 As shown, the end face fixing part 430 has a central hole 435. The central axis of the central hole 435 coincides with the rotation axis AX. The inner diameter of the central hole 435 of the end face fixing part 430 is larger than the inner diameter of the central hole 410 of the rotor core 41, but this is just one example.

[0095] like Figure 3 , Figure 5 , Figure 6 As shown, the resin portion 43 has a plurality of peripheral fixing portions 433. The resin portion 43 has a plurality of first fixing portions 431 (see reference). Figure 7 ), but Figures 2-6 Reference numerals are omitted from the drawings. The resin portion 43 has a plurality of second fixing portions 432 (see reference numerals). Figure 7 ), but Figures 2-6 Reference numerals are omitted from the accompanying drawings. Multiple peripheral fixing parts 433 cover the aforementioned multiple notched portions (i.e. multiple openings 423) on the outer peripheral surface 413 of the rotor core 41.

[0096] like Figures 2-6As shown, the motor 11 has the aforementioned rotor shaft 50. The rotor shaft 50 is fixed to the rotor core 41 (and even the rotor 40) with its shaft inserted through the central hole 410 of the rotor core 41. The rotor shaft 50 can also be fixed to the rotor core 41, for example, by pressing it into the rotor core 41. The central axis of the rotor shaft 50 coincides with the rotation axis AX. Therefore, the rotor 40 and the rotor shaft 50 rotate about the rotation axis AX. <2-1-2c. Sensor substrate> like Figure 2 , Figure 3 , Figure 5 , Figure 6 As shown, the motor 11 has a sensor substrate 60. Figure 5 As shown, the sensor substrate 60 has three magnetic sensors 61, 62, and 63. The three magnetic sensors 61, 62, and 63 respectively output position signals corresponding to the rotational position of the rotor 40.

[0097] like Figure 2 , Figure 3 , Figure 5 , Figure 6 As shown, the motor 11 has a wire assembly 65 that is electrically connected to the sensor substrate 60. In this embodiment, the wire assembly 65 has five wires. The wire assembly 65 is electrically connected to the controller 13.

[0098] The controller 13 supplies power to the three magnetic sensors 61, 62, and 63 via the wire group 65. The three magnetic sensors 61, 62, and 63 receive power and then operate. The position signals output by the three magnetic sensors 61, 62, and 63 are input to the controller 13 via the wire group 65. <2-1-2d. Power Terminals> like Figures 3-6 As shown, the motor 11 has a first power terminal 31, a second power terminal 32, and a third power terminal 33. The first to third power terminals 31 to 33 are electrically connected to six coils 25. The first to third power terminals 31 to 33 are also electrically connected to a controller 13, receiving the aforementioned motor drive power from the controller 13. The motor drive power is supplied to the stator 20 (specifically, to the six coils 25) via the first to third power terminals 31 to 33. <2-1-2e. Electrical Structure of Electric Working Machines> based on Figures 1-6 and mainly refer to Figure 15 To illustrate the general electrical structure of the electric work machine 1.

[0099] The controller 13 receives battery power from the battery pack 3. The controller 13 may include, for example, control circuitry, power supply circuitry, and drive circuitry, none of which are shown in the figure. The drive circuit receives power from the battery. The drive circuit is, for example, a three-phase full-bridge circuit. That is, the drive circuit has six semiconductor switching elements. Each of the six semiconductor switching elements is individually controlled according to control commands from the control circuit. The drive circuit, according to the control commands from the control circuit, converts the battery power into the aforementioned motor drive power (three-phase power) and supplies it to the motor 11. Accordingly, motor drive power is input to the first to third power terminals 31 to 33 of the motor 11, driving the motor 11.

[0100] The control circuit has a microcomputer. The control circuit is configured to execute various programs. By executing these programs, the electric work machine 1 performs various functions. Among the functions implemented by the control circuit is the function of controlling the drive circuit.

[0101] Additionally, three position signals from the sensor substrate 60 are input to the control circuit. The control circuit detects the rotational position (i.e., electrical angle) of the rotor 40 based on these three position signals. The control circuit generates control commands based on the detected rotational position and other drive information, and outputs them to the drive circuit. Accordingly, motor drive power corresponding to the rotational position of the rotor 40 is supplied to the motor 11. The drive information includes, for example, the operation amount of the trigger 8.

[0102] The control circuit of this embodiment is configured to rotate the motor 11 at an electrical frequency of 1333 Hz or higher. The electrical frequency is the product of the rotor speed 40 per unit time and the number of pole pairs. Specifically, in this embodiment, it is the product of the rotor speed 40 per second and the number of pole pairs. The number of pole pairs is half the number of poles.

[0103] In this embodiment, the motor 11 has 8 poles, and therefore 4 pole pairs. Therefore, in this embodiment, rotating the motor 11 at an electrical frequency of 1333Hz or higher is synonymous with rotating the motor 11 at a speed of 20000rpm or higher.

[0104] In this embodiment, for example, the rated electrical frequency of motor 11 can be set to 1333Hz or higher. Alternatively, the electrical frequency at which motor 11 rotates at its maximum speed when using the electric work machine 1 can also be 1333Hz or higher. In other words, the rated speed of motor 11 can be set to 20,000 rpm or higher, and the maximum speed when using the electric work machine 1 can be 20,000 rpm or higher. The control circuit can also be configured such that, for example, when trigger 8 is operated, motor 11 is controlled (direct control drive circuit) to rotate at an electrical frequency of 1333Hz or higher, normally or during periods when the amount of operation of trigger 8 is greater than or equal to a predetermined amount.

[0105] The six coils 25 of the motor 11 can be divided into a first-phase coil group, a second-phase coil group, and a third-phase coil group. For example... Figure 15 (and Figure 3 , Figure 5 As shown, the first phase coil group includes a pair of first phase coils 25U1 and 25U2 connected in parallel. The second phase coil group includes a pair of second phase coils 25V1 and 25V2 connected in parallel. The third phase coil group includes a pair of third phase coils 25W1 and 25W2 connected in parallel. Furthermore, the first, second, and third phase coil groups are delta-connected to each other.

[0106] From another perspective, it can be said that motor 11 has two delta-connected groups. The first delta-connected group includes the first-phase coil 25U1, the second-phase coil 25V1, and the third-phase coil 25W1, which are delta-connected to each other. The second delta-connected group includes the first-phase coil 25U2, the second-phase coil 25V2, and the third-phase coil 25W2, which are delta-connected to each other. The first and second delta-connected groups are connected in parallel.

[0107] Furthermore, the first terminal of each of the first-phase coils 25U1 and 25U2 and the second terminal of each of the second-phase coils 25V1 and 25V2 are connected to the first power terminal 31. The first terminal of each of the second-phase coils 25V1 and 25V2 and the second terminal of each of the third-phase coils 25W1 and 25W2 are connected to the second power terminal 32. The first terminal of each of the third-phase coils 25W1 and 25W2 and the second terminal of each of the first-phase coils 25U1 and 25U2 are connected to the third power terminal 33.

[0108] Furthermore, the multiple (six in this embodiment) coils 25 in the motor 11 can be connected arbitrarily. For example, a pair of first-phase coils 25U1 and 25U2 in the first-phase coil group can be connected in series with each other. The same applies to the second and third coil groups.

[0109] Additionally, the first phase coil 25U1, the second phase coil 25V1, and the third phase coil 25W1 can be connected in a star configuration, for example. The same applies to the other first phase coil 25U2, the second phase coil 25V2, and the third phase coil 25W2. <2-1-2f. Fan> like Figures 2-6 As shown, the motor 11 has a fan 55. The fan 55 is fixed to the rear end of the rotor shaft 50. The fan 55 rotates together with the rotor 40, thereby generating airflow. This airflow cools the motor 11. <2-1-3. Detailed Structure of the Rotor> Reference Figures 7-14 A more detailed description of the structure of rotor 40 is provided.

[0110] As described above, the rotor 40 has a rotor core 41, a plurality of permanent magnets 42 and a resin section 43. In this embodiment, the rotor 40 is configured to have 4m magnetic poles along its outer periphery. As described above, in this embodiment, m = 2. Therefore, as Figure 10 As shown, the rotor 40 of this embodiment has 8 magnetic poles along its outer periphery.

[0111] In order to enable the rotor 40 to have 8 magnetic poles, the plurality of permanent magnets 42 in this embodiment have 4m permanent magnets 42, that is, 8 permanent magnets 42. The resin portion 43 contains resin. The resin portion 43 may also contain materials other than resin. In this embodiment, the resin portion 43 is entirely made of resin. The resin portion 43 of this embodiment contains a thermosetting resin. In this embodiment, the resin portion 43 is entirely made of a thermosetting resin. Examples of thermosetting resins include unsaturated polyester, phenolic resin, urea-formaldehyde resin, melamine resin, and / or epoxy resin.

[0112] The permanent magnet 42 has a generally cuboid shape. The permanent magnet 42 extends radially. That is, in this embodiment, a plurality of permanent magnets 42 are arranged in a spoke-like (in other words, radial) configuration.

[0113] like Figure 7 , Figure 8 , Figure 11 As shown, the permanent magnet 42 has a first surface 42a, a second surface 42b, and a third surface 42c that are intersected (orthogonal in this embodiment) with the axial direction. The first surface 42a is a surface facing forward, the second surface 42b is a surface facing backward, and the third surface 42c is a surface facing radially.

[0114] And, as Figure 10 As shown, multiple permanent magnets 42 are arranged circumferentially with their same poles facing each other. Additionally, in Figure 10 In the diagram, the letter "S" inside a solid circle indicates that the area is the S pole, and the letter "N" inside a solid circle indicates that the area is the N pole. The N and S poles of a permanent magnet 42 are arranged circumferentially.

[0115] Therefore, on the outer peripheral surface 413 of the rotor core 41, N-pole and S-pole magnetic poles are alternately generated circumferentially. For example, the outer peripheral surface 413 between two permanent magnets 42 with their N poles facing each other is energized as an N-pole. Additionally, in Figure 10 In the diagram, the letter "S" within the dashed circle represents the S pole, and the letter "N" within the dashed circle represents the N pole. The rotor 40 of this embodiment has 4 N poles and 4 S poles, for a total of 8 poles as described above.

[0116] like Figures 7-11 As shown, the rotor core 41 has the aforementioned center hole 410. (As...) Figure 7 , Figure 8 , Figure 11 , Figure 12 As shown, the rotor core 41 has a first end face 411, a second end face 412, and the aforementioned outer peripheral surface 413. Furthermore, although reference numerals are omitted, Figure 9 , Figure 10 A first end face 411 is also shown. The first end face 411 corresponds to the front end face of one of the two end faces of the rotor core 41 that intersect (orthogonal in this embodiment) the axial direction. The second end face 412 corresponds to the rear end face of the aforementioned two end faces of the rotor core 41.

[0117] like Figures 7-9 , Figure 14 As shown, the rotor core 41 has a plurality of holes 420. The plurality of holes 420 are arranged circumferentially separated from each other (equally spaced in this embodiment). The plurality of holes 420 in this embodiment has eight holes 420. A plurality of permanent magnets 42 are respectively inserted into the plurality of holes 420.

[0118] Figures 10-12 And the aforementioned Figures 2-6 This indicates that multiple permanent magnets 42 are inserted into multiple holes 420. In this embodiment, at least a portion (all of it in this embodiment) of the first surface 42a of the permanent magnet 42 and at least a portion (all of it in this embodiment) of the first end face 411 of the rotor core 41 are located on the same plane. On the other hand, as Figure 11 , Figure 12 As shown, the second surface 42b of the permanent magnet 42 protrudes rearward from the second end face 412 of the rotor core 41.

[0119] like Figures 7-11 , Figure 14 As shown, the rotor core 41 has a plurality of openings 423. The plurality of openings 423 are arranged separately from each other in the circumferential direction on the outer peripheral surface 413 of the rotor core 41. That is, as described above, the outer peripheral surface 413 of the rotor core 41 has notches formed at predetermined intervals in the circumferential direction, and the portions forming the notches correspond to the plurality of openings 423.

[0120] Multiple openings 423 are respectively connected to a corresponding hole 420 among multiple holes 420. Therefore, each hole 420 is exposed radially through its corresponding opening 423. Therefore, if the opening 423 is not blocked, the permanent magnet 42 of the insertion hole 420 is exposed radially through the opening 423. However, in this embodiment, as referred to above... Figure 3 , Figure 5 As stated above, and also as Figure 10 As shown, multiple openings 423 are blocked by resin portions 43 (more specifically, by multiple peripheral fixing portions 433).

[0121] like Figure 7 , Figure 9 , Figure 10 , Figure 14 As shown, the orifice 420 has at least one gating channel. The at least one gating channel is filled with molten resin during the formation of the resin portion 43. In this embodiment, the orifice 420 includes a first gating channel 421 and a second gating channel 422. The first gating channel 421 and the second gating channel 422 are respectively formed between the inner circumferential surface of the orifice 42 and the permanent magnet 42 inserted into the orifice 420, forming an axially penetrating space.

[0122] In addition, opening 423 also functions as a gating system. That is, during the formation of resin portion 43, resin is also filled into opening 423, thereby blocking opening 423 as described above. In the bore 420, resin is filled into at least the first gating 421, the second gating 422, and the opening 423 and cured. This resin adheres tightly to and bonds to the inner circumferential surface of the bore 420 and the permanent magnet 42. Accordingly, the permanent magnet 42 is bonded to the inner circumferential surface of the bore 420 by the resin. In addition, most of the side of the permanent magnet 42 opposite to the inner circumferential surface of the bore 420 is in contact with the inner circumferential surface of the bore 420 and bears pressure from the inner circumferential surface. Therefore, even without the resin portion 43, the permanent magnet 42 is fixed to the bore 420 by the pressure it receives from the bore 420 and / or by contact friction with the inner circumferential surface of the bore 420. Thus, the permanent magnet 42 is more firmly and integrally fixed to the bore 420 by the resin portion 43, and thus integrally and firmly fixed to the rotor core 41.

[0123] As in Figure 9 , Figure 14 As illustrated with reference numerals in the accompanying drawings, the rotor core 41 has a plurality of first limiting portions 416 and a plurality of second limiting portions 417. Each of the plurality of first limiting portions 416 is paired with a corresponding second limiting portion 417. The pair of first limiting portions 416 and second limiting portions 417 forms an opening 423.

[0124] Specially by Figure 9 , Figure 10 It can be clearly seen that a pair of first limiting parts 416 and second limiting parts 417 are radially opposite to the permanent magnet 42 inserted into the corresponding hole 420. Accordingly, the permanent magnet 42 is limited to move radially from the hole 420 (and thus disengage from the rotor core 41).

[0125] like Figure 12As shown in the enlarged view, the rotor core 41 is constructed by stacking multiple core plates 400 axially. The core plates 400 have a plate-like shape. The core plates 400 contain a soft magnetic material. In this embodiment, the core plate 400 is an electromagnet plate containing electromagnetism (or made of electromagnetism).

[0126] like Figure 13 As shown, the core plate 400 has a first surface 400A and a second surface 400B. In this embodiment, the thickness Dt of the core plate 400 is greater than 0 mm and less than 0.35 mm. Furthermore, the thickness Dt is the axial length of the core plate 400.

[0127] The thickness Dt can be any value within the range of greater than 0 mm and less than 0.35 mm. For example, the thickness Dt can be greater than 0.30 mm and less than 0.35 mm. Or, the thickness Dt can be greater than 0.25 mm and less than 0.30 mm. Or, the thickness Dt can be less than 0.25 mm. Specifically, the thickness Dt can be greater than 0.23 mm and less than 0.25 mm. Or, the thickness Dt can be greater than 0.20 mm and less than 0.23 mm. Or, the thickness Dt can be less than 0.20 mm. The thickness Dt can be greater than 0.05 mm or greater than 0.10 mm.

[0128] A protrusion 45 is formed on the first surface 400A. A recess 46 is formed on the second surface 400B. Figure 7 , Figure 9 , Figure 10 , Figure 12 , Figure 14 The diagram also shows the protrusion 45. Figure 8 , Figure 11 The illustration of the recessed portion 46 is omitted.

[0129] The recess 46 is provided on the second surface 400B at a position where it overlaps with the protrusion 45 in the axial direction. In the process of stacking multiple core plates 400, a recess 46 of one of two opposing core plates 400 is inserted into a protrusion 45 of the other. Accordingly, as Figure 13 As shown, a rotor core 41 (i.e., laminations) is formed by multiple core plates 400 that are tightly stacked together in the axial direction.

[0130] When the protrusion 45 is embedded in the recess 46, the protrusion 45 cannot be dislodged from the recess 46 (or is difficult to dislodged) due to the pressure (and / or friction) of the interaction between the protrusion 45 and the recess 46.

[0131] In this embodiment, when the protrusion 45 is inserted into the recess 46, the protrusion 45 and / or the recess 46 are mechanically deformed (elastic or plastic) by the pressure exerted during insertion. Through this mechanical deformation, the protrusion 45 is secured to the recess 46.

[0132] As in Figure 9 , Figure 10 , Figure 12 , Figure 14 As shown with the reference numerals in the accompanying drawings, the rotor core 41 can be mainly divided into three regions: the annular portion 41A, the multiple magnet support portions 41B, and the multiple connecting portions 41C.

[0133] The annular portion 41A of the core is a cylindrical region in the center of the rotor core 41. Multiple magnet supports 41B are arranged radially outside the annular portion 41A of the core, circumferentially separated from each other. The rotor core 41 of this embodiment has eight magnet supports 41B. The space between two adjacent magnet supports 41B in the circumferential direction corresponds to one of the multiple holes 420.

[0134] Multiple connecting portions 41C connect multiple magnet support portions 41B to the annular portion 41A of the iron core, respectively. That is, the rotor iron core 41 of this embodiment has eight connecting portions 41C. Figure 14 The minimum width Wt shown is the width of the smallest portion of the connecting part 41C. The width of the connecting part 41C is its length in a direction orthogonal to both the axial and radial directions.

[0135] In this embodiment, the minimum width Wt is 0.4 mm to 0.6 mm. The smaller the minimum width Wt, the greater the magnetic reluctance of the connection portion 41C, and the less magnetic flux that short-circuits the connection portion 41C. The less magnetic flux that short-circuits the connection portion 41C, the more effectively the magnetic flux of the permanent magnet 42 can be used for the rotation of the motor 11. Therefore, from the viewpoint of reducing the magnetic flux that short-circuits the connection portion 41C, the smaller the minimum width Wt, the better.

[0136] On the other hand, the smaller the minimum width Wt, the weaker the force connecting the magnet support 41B to the core ring 41A. From the viewpoint that the permanent magnet 42 is stably fixed to the rotor core 41 by stably fixing the magnet support 41B to the core ring 41A, the larger the minimum width Wt, the better.

[0137] Thus, a balance is achieved between reducing the short circuit in magnetic flux and ensuring the stable fixation of the magnet support portion 41B. Therefore, in this embodiment, by setting the minimum width Wt to ​​0.4 mm to 0.6 mm, both the reduction of the short circuit in magnetic flux and the stable fixation of the magnet support portion 41B can be achieved.

[0138] Multiple core plates 400 correspond to a portion of the core annular portion 41A, a portion of each of the multiple magnet support portions 41B, and a portion of each of the multiple connecting portions 41C. The core annular portion 41A, the multiple magnet support portions 41B, and the multiple connecting portions 41C are formed by stacking the multiple core plates 400.

[0139] like Figure 7 , Figure 8 , Figure 10 As shown, the resin portion 43 includes the aforementioned end face fixing portion 430, the aforementioned first fixing portion 431, the aforementioned second fixing portion 432, and the aforementioned outer peripheral fixing portion 433. The first fixing portion 431 is formed by curing resin filled into the first gating channel 421. The second fixing portion 432 is formed by curing resin filled into the second gating channel 422. The outer peripheral fixing portion 433 is formed by curing resin filled into the opening 423.

[0140] The rotor 40 can be integrally formed in any manner. For example, the rotor 40 can be integrally formed by insert molding. Specifically, the rotor 40 can be integrally formed as described below. That is, firstly, a rotor core 41 and a plurality of permanent magnets 42 are arranged in a mold. Then, the plurality of permanent magnets 42 are respectively inserted into a plurality of holes 420 in the rotor core 41. Furthermore, the aforementioned plurality of gating channels are present in each hole 420 at this time.

[0141] Next, resin is injected into the mold. Accordingly, resin is filled into the resin filling space within the mold, which includes the aforementioned multiple runners. Then, the filled resin is allowed to cure, after which the mold is removed.

[0142] Accordingly, a rotor 40 is obtained in which the rotor core 41 and multiple permanent magnets 42 are integrated through a resin section 43. Furthermore, as a result of this integral molding, an end face fixing portion 430, a plurality of first fixing portions 431, a plurality of second fixing portions 432, and a plurality of peripheral fixing portions 433 are integrally formed in the resin portion 43. In other words, the plurality of permanent magnets 42 are integrally fixed to the rotor core 41 through the resin portion 43.

[0143] The structural elements (multiple first fixing portions 431, multiple second fixing portions 432, multiple peripheral fixing portions 433, and end face fixing portions 430) included in the resin section 43 are integrally formed by a one-piece molding method. That is, the multiple first fixing portions 431 are formed by curing resin filling multiple first runners 421. The multiple second fixing portions 432 are formed by curing resin filling multiple second runners 422. The multiple peripheral fixing portions 433 are formed by curing resin filling multiple openings 423.

[0144] In addition, such as Figure 12 As shown, the outer diameter of the rotor core 41 is D1, and the thickness of the rotor core 41 is H1. These outer diameter D1 and thickness H1 are again referred to in the second embodiment described later. <2-1-4. Characteristics of Electric Motors> As described above, the motor 11 of this embodiment has various features, but the motor 11 also has the features described below.

[0145] That is, the motor 11 in this embodiment is configured to satisfy the following formula (1).

[0146] [Mathematical Formula 3]

[0147] In equation (1) above, R is the line-to-line resistance value of motor 11 [mΩ]. The line-to-line resistance value is the magnitude of the line-to-line resistance of motor 11. The line-to-line resistance is also called motor resistance. Specifically, the line-to-line resistance refers to the resistance between two terminals of the first to third power terminals 31 to 33. In this embodiment, the line-to-line resistance values ​​between the first power terminal 31 and the second power terminal 32, between the second power terminal 32 and the third power terminal 33, and between the third power terminal 33 and the first power terminal 31 are all equal. R can be a pre-set design line-to-line resistance value.

[0148] In equation (1) above, Vin is the rated voltage value [V] of motor 11. In this embodiment, the rated voltage value of motor 11 is equal to the rated voltage value of battery 3A. The rated voltage value of battery 3A in this embodiment is 36 [V], but this is just one example. Therefore, in this embodiment, Vin is 36 [V].

[0149] In equation (1) above, Ne is the rotational speed [krpm] of motor 11 when the effective induced voltage value E[V] becomes equal to the rated voltage value of motor 11. The effective induced voltage E will be described in detail later. In equation (1) above, Vol is the volume of stator 20 [mm²]. 3 More specifically, in this embodiment, Vol represents the volume of the stator core 21. In this embodiment, the volume of the stator core 21 is the area of ​​the end circle of the core [mm²]. 2 The product of the core length (mm) and the core end circle. The core end circle is the outer diameter Ld of the stator core 21 (refer to...). Figure 6 The circle has a diameter of 21. The core length is the axial length Ls of the stator core 21 (refer to...). Figure 6 Additionally, such as Figure 2 , Figure 3 As shown, protruding components are discretely formed circumferentially on the outer peripheral surface of the back core 211, but due to... Figure 6It can be seen that the outer diameter Ld is the outer diameter of the back core 211 excluding the protruding component. The relationship between Ls and Ld can be, for example, 2·Ls≦Ld, 3·Ls≦Ld, 4·Ls≦Ld, or 10·Ls≦Ld.

[0150] The effective induced voltage value E will be explained in detail. First, the induced voltage will be explained. It is generally known that when a rotor with a permanent magnet rotates, an induced voltage is generated in the coils on the stator side.

[0151] Even in the motor 11 of this embodiment, when the rotor 40 rotates, induced voltages are generated in each of the six coils 25, thereby... Figure 16 As illustrated, an induced voltage is generated between two terminals of the first to third power terminals 31 to 33.

[0152] Here, as Figure 16 As illustrated in the example, a defined electrical angle range (90 degrees between UV) encompassing the electrical angle with the highest induced voltage is defined as a defined interval. In this embodiment, the angle width of the defined interval is 60 degrees. However, the angle width can also be a value other than 60 degrees. For example, the angle width can be suitably selected within a range of 40 degrees to 90 degrees.

[0153] In this embodiment, the average value of the induced voltage within the specified range is taken as the effective induced voltage value E. As shown in equations (2) and (3) below, the left side of equation (1) is defined as the first characteristic value fa, and the right side of equation (1) is defined as the second characteristic value fb.

[0154] [Mathematical Formula 4]

[0155] Figure 17 The example shows the first characteristic value fa and the second characteristic value fb for each of the 13 motors. The 13 motors are: 4 first-proposal motors, 4 second-proposal motors, 1 conventional motor, 2 second conventional motors, 3 conventional motors, and 4 conventional motors. The parameters of each motor are shown in Table 1 below. Table 1 In Table 1, “1st PM” represents “Proposal 1 motor”, “2nd PM” represents “Proposal 2 motor”, “1st C.M.” represents “1st conventional motor”, “2nd CM” represents “2nd conventional motor”, “3rd CM” represents “3rd conventional motor”, and “4th CM” represents “4th conventional motor”. “Ke” represents the induced voltage constant, which will be described later.

[0156] Both the first and second proposed motors correspond to the motor 11 of this first embodiment. That is, both the first and second proposed motors have at least the features described in (a) to (c) below. (a) It has 8 (or 4m) magnetic poles and 6 (or 3m) slots. (b) The thickness Dt of the core plate 400 is less than 0.35 mm. (c) It is configured to rotate at an electrical frequency of 1333 Hz or higher.

[0157] Furthermore, the difference between the first and second proposed motors lies at least in the width of the permanent magnets. Specifically, the width of the permanent magnet 42 in the second proposed motor is smaller than the width of the permanent magnet 42 in the first proposed motor. Here, the width, like the aforementioned minimum width Wt, refers to the length in a direction orthogonal to both the axial and radial directions.

[0158] On the other hand, conventional motors 1 through 4 do not possess at least feature (a) of the above (a) through (c). Specifically, conventional motors 1 through 4 are all 4-pole, 6-slot types. Regarding (b) above, the thickness Dt of the proposed motor 1 is 0.25 mm. The thickness Dt of the other 9 types of motors is 0.35 mm. The rated voltage of conventional motors 3 and 4 is 18 V, and the rated voltage of the other 11 types of motors is 36 V.

[0159] Furthermore, the length and / or number of turns of each coil varies with volume Vol. Therefore, the inter-wire resistance R may also vary with volume Vol. Additionally, the magnetic characteristics (e.g., reluctance) of the stator and rotor also vary with volume Vol. Therefore, the aforementioned rotational speed Ne may also vary with volume Vol. Therefore, the first characteristic value fa also varies with volume Vol.

[0160] The first characteristic value, fa, is an indicator of the motor's power density. The higher the line resistance R, the lower the motor's power. Therefore, it can be said that the smaller the first characteristic value fa, the higher the power density. The second characteristic value, fb, is an indicator (in other words, a threshold) used to evaluate the first characteristic value fa. In a motor with a given volume Vol, if the first characteristic value fa is smaller than the second characteristic value, the motor's power density can be said to be high. If the first characteristic value is larger than the second characteristic value, the motor's power density can be said to be low.

[0161] Depend on Figure 17It is clear that the first characteristic value fa of the first proposed motor and the first characteristic value fa of the second proposed motor are smaller than the second characteristic value fb. That is, both the first proposed motor and the second proposed motor satisfy the above equation (1). The motor 11 that satisfies the above equation (1) can suppress the increase in size while achieving the desired power density.

[0162] On the other hand, the first characteristic value fa of the first to fourth conventional motors is larger than the second characteristic value fb. That is, none of the first to fourth conventional motors satisfy the above equation (1). Therefore, under the premise of the same volume Vol, the power density of the first to fourth conventional motors is smaller than that of the first proposed motor and the second proposed motor. <2-1-5. Technical Effects of the First Embodiment> According to the first embodiment described above, the following technical effects are achieved.

[0163] The motor 11 has features (a) to (c) described in items 2-1-4, thereby having a high power density. Therefore, it is possible to drive the motor 11 at high speed and with high output while suppressing the increase in the size of the motor 11. In addition, such an effect can be obtained even without feature (b).

[0164] Regarding the dimensions of motor 11, use Figure 18 Further explanation is provided. Figure 18 This section presents a comparison of the mass and volume of a conventional motor and a proposed motor. Specifically, Figure 18 The examples illustrate the mass ratio and volume ratio of the conventional motor and the proposed motor. The mass ratio of the conventional motor is the ratio of its mass to a reference mass. The reference mass is the mass of the conventional motor. The volume ratio of the conventional motor is the ratio of its volume to a reference volume. The reference volume is the volume of the conventional motor. Therefore, both the mass ratio and volume ratio of the conventional motor are 100%. The mass ratio of the proposed motor is the ratio of its mass to a reference mass. The volume ratio of the proposed motor is the ratio of its volume to a reference volume. Furthermore, the volume referred to here, like the volume Vol mentioned above, refers to the volume of the stator.

[0165] Both the conventional motor and the proposed motor have the same induced voltage constant Ke and the same line-to-line resistance value R. That is, the conventional motor and the proposed motor have the same level of output capability. The induced voltage constant Ke represents the ratio of the induced voltage value to the rotational speed. In this embodiment, the induced voltage constant Ke is defined by the following equation (4).

[0166] [Mathematical Formula 5]

[0167] In equation (4) above, E is the effective induced voltage [V]. Na [krpm] is the rotational speed at which the effective induced voltage E is generated. That is, the induced voltage constant Ke is defined according to the effective induced voltage E generated when rotating at a speed Na.

[0168] As mentioned above, the conventional motor and the proposed motor have the same induced voltage constant Ke and line-to-line resistance R. However, the conventional motor and the proposed motor differ in the following aspects. The proposed motor has the features described in (a) to (c) above. Specifically, the proposed motor has 8 magnetic poles and 6 slots. In addition, the outer diameter of the proposed motor (i.e., the outer diameter of the stator) is 50 mm.

[0169] On the other hand, conventional motors do not possess the features described in (a) to (c) above. Specifically, conventional motors have 4 magnetic poles and 6 slots. Furthermore, the outer diameter of a conventional motor is 52 mm.

[0170] Depend on Figure 18 It is clear that the proposed motor is smaller in both mass and size than the conventional motor. In other words, to achieve the same performance as the proposed motor, the conventional motor would need to be larger and heavier compared to the proposed motor.

[0171] The core plate 400 of this first embodiment has a thickness Dt of 0.35 mm. As described above, this thickness Dt can be less than 0.30 mm or less, or less than 0.25 mm. Since the rotor core 41 is formed from such a thin core plate 400, losses in the motor 11 (e.g., eddy current losses) can be suppressed. Accordingly, higher speeds and / or higher outputs can be achieved while suppressing larger size.

[0172] Additionally, as referenced Figure 13 As explained, the core plate 400 of this embodiment has a thickness Dt of 0.35 mm or less. Therefore, compared with the case where the thickness Dt is greater than 0.35 mm, the losses generated by the rotor core 41 (e.g., losses due to eddy currents) are reduced. Accordingly, it is possible to further increase the speed and / or output of the motor 11 while suppressing the increase in the size of the motor 11.

[0173] Additionally, as referenced Figure 13 As explained, the core plate 400 has a protrusion 45 and a recess 46. Furthermore, in the stacking process of multiple core plates 400, the recess 46 of one of two opposing core plates 400 is inserted into the protrusion 45 of the other. Then, through this insertion, the protrusion 45 is secured to the recess 46. Therefore, in the stacking process, multiple core plates 400 can be stacked stably and with high precision. Accordingly, a high-quality rotor core 41 can be provided, and consequently, a high-quality motor 11 can be provided.

[0174] Additionally, as referenced Figure 14 As explained, the minimum width Wt of the connecting portion 41C in the rotor core 41 is 0.4 mm to 0.6 mm. Therefore, both the reduction of magnetic flux short circuits and the stable fixation of the magnet support portion 41B are taken into account. [2-2. Second Implementation] The second embodiment illustrates another form of the rotor. For example... Figure 19 and Figure 20 As shown, the basic structure of the rotor 500 in the second embodiment is the same as that of the rotor 40 in the first embodiment.

[0175] That is, the rotor 500 has a rotor core 510 and a plurality of permanent magnets 70. The rotor core 510 has an annular portion 510A, a plurality of magnet support portions 510B, and a plurality of connecting portions 510C. Similar to the first embodiment, the plurality of permanent magnets 70 are arranged such that they are opposite each other with the same poles in the circumferential direction. Similar to the first embodiment, the rotor 500 is configured to have, for example, eight magnetic poles. Therefore, the rotor core 510 has eight permanent magnets 70, eight magnet support portions 510B, and eight connecting portions 510C.

[0176] Furthermore, similar to the first embodiment, the rotor core 510 has a plurality of holes 520. A plurality of permanent magnets 70 are inserted into each of these plurality of holes 520. Furthermore, similar to the first embodiment, the rotor core 510 and the plurality of permanent magnets 70 are integrally formed by the resin portion. Similar to the resin portion 43 of the first embodiment, the resin portion has a plurality of first fixing portions 531, a plurality of second fixing portions 532, a plurality of peripheral fixing portions 533, and an end face fixing portion (not shown).

[0177] The main difference between this rotor 500 and the rotor 40 of the first embodiment lies in the thickness of the rotor core 510 and the width of the permanent magnet 70. like Figure 20 As shown, the outer diameter of the rotor core 510 is the same as that of the rotor core 41 in the first embodiment, which is D1.

[0178] On the other hand, the thickness of the rotor core 510 is H2. H2 is larger than the thickness H1 in the first embodiment. Furthermore, the width of the permanent magnet 70 is smaller than the width of the permanent magnet 42 in the first embodiment. That is, when the radial dimension of the rotor core is constant, the greater the thickness of the rotor core, the smaller the width of the permanent magnet. Furthermore, for the sake of simplicity, Figure 20 The resin section is omitted from the diagram. Here, the widths of the permanent magnets 42 and 70 are measured in directions orthogonal to both the axial and radial sides of the rotors 40 and 500.

[0179] As the thickness of the rotor core increases, the magnetic force generated by the permanent magnets increases, which may lead to noise due to stator resonance. Therefore, by appropriately reducing the width of the permanent magnets when increasing the thickness of the rotor core, it is possible to ensure the desired speed and / or the desired motor output while suppressing noise caused by stator resonance. [2-3. Third Implementation] The third embodiment illustrates another form of permanent magnet. For example... Figure 21 As shown, the multiple sets of permanent magnets 141 in the third embodiment include a first part magnet 141A and a second part magnet 141B.

[0180] In a set of permanent magnets 141, a first part magnet 141A and a second part magnet 141B are configured such that (i) they are separated from each other in the circumferential direction and (ii) their opposite poles are opposite to each other in the circumferential direction.

[0181] The rotor core 150 has an annular portion 150A, multiple magnet support portions 150B, and multiple connecting portions 150C. Similar to the first embodiment, the rotor core 150 is configured to have, for example, eight magnetic poles. Therefore, the rotor core 150 has eight sets of permanent magnets 141, eight magnet support portions 150B, and eight connecting portions 150C.

[0182] On the rotor core 150, a first hole 151 and a second hole 152 are provided for arranging the permanent magnet 141. The first part of the magnet 141A is inserted into the first hole 151, and the second part of the magnet 141B is inserted into the second hole 152.

[0183] The first magnet 141A and the second magnet 141B constituting a set of permanent magnets 141 are configured such that their cross-sections orthogonal to the axial direction have a generally V-shaped shape. That is, the first magnet 141A extends at a slight radial inclination, and the second magnet 141B also extends at a slight radial inclination. The first magnet 141A and the second magnet 141B may be inclined radially at an angle of, for example, less than 20 degrees, or less than 15 degrees, or less than 10 degrees.

[0184] A first gating system 151A is formed between the inner peripheral surface of the first hole 151 and the first partial magnet 141A, and a first fixing part 161 is filled in the first gating system 151A. A second gating system 152A is formed between the inner peripheral surface of the second hole 152 and the second partial magnet 141B, and a second fixing part 162 is filled in the second gating system 152A.

[0185] In addition, each opening of the rotor core 150 is covered by the outer peripheral fixing part 163. Similar to the first fixing part 431, the second fixing part 432 and the outer peripheral fixing part 433 in the first embodiment, the first fixing part 161, the second fixing part 162 and the outer peripheral fixing part 163 are also part of the resin part, and are formed when multiple sets of permanent magnets 141 are integrally molded with the rotor core 150 through the resin part. [2-4. Fourth Implementation] In the first embodiment, an 8-pole, 6-slot motor 11 is shown. However, the motor of the present invention can also take any form satisfying the combination of 4m poles and 3m slots. For example, it can be a 4-pole, 3-slot motor, a 12-pole, 9-slot motor, or a 16-pole, 12-slot motor.

[0186] Figure 22 Example of a 16-pole, 12-slot motor 250. Additionally, in Figure 22 The illustrations of several parts, such as the rotor shaft and the sensor substrate, are omitted in the text.

[0187] The motor 250 has a rotor 260 and a stator 251. The stator has 12 slots 256 and 12 coils 255. The 12 coils 255 can be divided into a first-phase coil group, a second-phase coil group, and a third-phase coil group. The first-phase coil group includes first-phase coils 255U1, 255U2, 255U3, and 255U4. These four coils can also be connected in parallel with each other, for example. The second-phase coil group includes second-phase coils 255V1, 255V2, 255V3, and 255V4. These four coils can also be connected in parallel with each other, for example. The third-phase coil group includes third-phase coils 255W1, 255W2, 255W3, and 255W4. These four coils can also be connected in parallel with each other, for example. Furthermore, the first-phase coil group, the second-phase coil group, and the third-phase coil group are connected in delta configuration, for example. Furthermore, similar to the first embodiment, the first phase coil group, the second phase coil group, and the third phase coil group are respectively connected to the first to third power terminals 31 to 33 (see reference). Figure 15 ).

[0188] The rotor 260 has a rotor core 261 and 16 permanent magnets 262. Similar to the first embodiment, the 16 permanent magnets 262 are configured such that they are circumferentially opposite each other with the same poles. [2-5. Other Implementation Methods] The above describes the embodiments of the present invention, but the present invention is not limited to the above embodiments and can be implemented in various ways.

[0189] (1) Figure 13 This example shows a protrusion 45 and a recess 46 in the core plate 400. However, the protrusion 45 and the recess 46 can each have any shape. In addition, the combination of protrusion 45 and recess 46 can be set at any position in a core plate 400, and any number of them can be set.

[0190] Alternatively, the two core plates 400 can be fixed to each other by a different method than the combination of the protrusion 45 and the recess 46. (-2) The electric work machine 1 in the first embodiment described above is in the form of an electric impact screwdriver. However, the electric work machine 1 may also be in a form different from an electric impact screwdriver. Specifically, the electric work machine 1 may be configured as any of the various devices used in the aforementioned construction, manufacturing, gardening, civil engineering and other work sites.

[0191] The electric work machine 1 can also be configured to replace the battery pack 3, or be able to receive AC power from an AC power source for driving, in addition to the battery pack 3. In addition, the present invention can also be applied to electric work machines whose driven devices are fixed in a non-removable (or difficult-to-remove) manner. [2-6. Supplement] Multiple functions implemented by one structural element in the above embodiments can be implemented by multiple structural elements, and a single function implemented by one structural element can also be implemented by multiple structural elements. Furthermore, multiple functions implemented by multiple structural elements can be implemented by one structural element, and a single function implemented by multiple structural elements can also be implemented by one structural element. Additionally, a portion of the structure in the above embodiments can be omitted. Furthermore, at least a portion of the structure in one of the above embodiments can be added to the structure of another of the above embodiments, or replaced by the structure of another of the above embodiments.

Claims

1. An electric working machine, having a brushless motor and a power transmission portion, characterized by the power transmission portion being configured (i) to have a driven device mounted thereon or to have the driven device removably mounted thereon, and being configured (ii) to transmit rotation of the brushless motor to the driven device to drive the driven device, the brushless motor having a rotor and a stator, wherein the rotor has a rotor core and a plurality of permanent magnets, the plurality of permanent magnets being configured (i) to be separated from each other along a circumferential direction of the rotor core and (ii) to be opposite to each other in the same polarity along the circumferential direction, whereby a plurality of magnetic poles are formed along the circumferential direction of the rotor core; the stator has a plurality of coils and a plurality of slots in which the plurality of coils are respectively arranged, the plurality of magnetic poles has 4m magnetic poles, where m is a natural number, the plurality of slots has 3m slots, the rotor is configured to rotate at an electric frequency of 1333 Hz or more.

2. The electric working machine according to claim 1, characterized by the rotor core has a plurality of core plates, the plurality of core plates (i) each containing a plate-shaped soft magnetic material and (ii) being stacked along a rotation axis of the rotor, each of the plurality of core plates has a thickness in a direction along the rotation axis that is greater than 0 mm and is 0.35 mm or less.

3. The electric working machine according to claim 2, characterized by the thickness of each of the plurality of core plates is 0.30 mm or less.

4. The electric working machine according to claim 3, characterized by the thickness of each of the plurality of core plates is 0.25 mm or less.

5. The electric working machine according to any one of claims 2 to 4, characterized by each of the plurality of core plates has a first surface and a second surface, wherein a protrusion is provided on the first surface; a recess is provided on the second surface at a position overlapping the protrusion in a direction along the rotation axis of the rotor, the plurality of core plates are stacked by fitting the recess of one of two core plates that are opposite to each other into the protrusion of the other.

6. The electric working machine according to any one of claims 1 to 5, characterized by the rotor core has a plurality of hole portions, the plurality of hole portions (i) being arranged separately from each other along the circumferential direction and (ii) being respectively inserted into a corresponding one of the plurality of permanent magnets.

7. The electric working machine according to claim 6, characterized by the rotor core has a core ring portion, a plurality of magnet support portions, and a plurality of connection portions, wherein the core ring portion has a cylindrical shape; the plurality of magnet support portions (i) are arranged separately from each other along the circumferential direction and (ii) have a corresponding one of the plurality of hole portions between two magnet support portions adjacent to each other along the circumferential direction; the plurality of connection portions are respectively provided corresponding to the plurality of magnet support portions to connect the corresponding magnet support portions to the core ring portion. A minimum width of each of the plurality of connection portions is 0.4 mm to 0.6 mm, the width being a length in a direction orthogonal to a rotational axis of the rotor and orthogonal to a radial direction of the rotor.

8. The electric power tool according to claim 6 or 7, characterized in that, The rotor core has a plurality of openings configured (i) to be arranged separately from each other in the circumferential direction on an outer circumferential surface of the rotor core and (ii) to be connected to a corresponding one of the plurality of hole portions, respectively, whereby the plurality of hole portions are exposed from the rotor core to a radial direction of the rotor core, respectively.

9. The electric power tool according to any one of claims 1 to 8, characterized in that, The brushless motor is configured to satisfy the following expression (1), In the following expression (1), R is an inter-winding resistance value [mΩ] of the brushless motor based on the plurality of coils, Vin is a rated voltage value [V] of the brushless motor, Ne is a rotational speed [krpm] of the brushless motor at which an effective induced voltage value is equal to the rated voltage value, the effective induced voltage value indicating a magnitude of induced voltages generated in the plurality of coils, Vol is the volume of the stator [mm 3 ] [mathematical formula 1] 10. The electric power tool according to any one of claims 1 to 9, characterized in that, The plurality of magnetic poles has eight magnetic poles, The plurality of slots has six slots.

11. The electric power tool according to any one of claims 1 to 10, characterized in that, The brushless motor is configured to rotate at a rotational speed of 20,000 rpm or more.

12. The electric power tool according to any one of claims 1 to 11, characterized in that, The plurality of permanent magnets respectively extend in a radial direction of the rotor core.

13. The electric power tool according to any one of claims 1 to 11, characterized in that, The plurality of permanent magnets respectively includes a first portion of magnets and a second portion of magnets, The first portion of magnets and the second portion of magnets are arranged (i) to be separate from each other in the circumferential direction and (ii) to be opposite to each other in the circumferential direction.

14. The electric power tool according to any one of claims 1 to 13, characterized in that, Further comprising a holding portion and / or a battery mounting portion, wherein The holding portion is configured to be held by a user of the electric power tool, The battery mounting portion is configured to detachably mount a battery pack including a battery.

15. A manufacturing method of an electric power tool, characterized by comprising the steps of: preparing a rotor having 4m magnetic poles, where m is a natural number, the rotor having a plurality of permanent magnets arranged to be opposite to each other in a same polarity in a rotational direction of the rotor; preparing a stator having 3m slots; mounting a brushless motor to the electric power tool, the brushless motor including the rotor and the stator and being configured to rotate at an electric frequency of 1,333 Hz or more. ​

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