power tools

Abstract

We provide power tools that can output high torque and be made compact. [Solution] The power tool 10 is equipped with an electric motor 1 and does not have a reduction mechanism. The electric motor 1 is an inner rotor type electric motor in which a rotor 5 is positioned in the center of a cylindrical stator 2. The rotor 5 has a rotor core 6, a plurality of magnets 7, and a rotating shaft 51 held inside the rotor core 6. The plurality of magnets 7 are arranged in a spoke-like manner inside the rotor core 6 with the center of the rotating shaft 51 as the center.

Description

Technical Field

[0001] The present disclosure relates to power tools. More specifically, the present disclosure relates to power tools that include an electric motor and do not include a speed reduction mechanism.

Background Art

[0002] Conventionally, when powering tools, power tools that do not include a speed reduction mechanism are known for the purpose of reducing the reaction force generated during impact (see, for example, Patent Document 1). The power tool disclosed in Patent Document 1 transmits the rotation of the output part of an electric motor to an impact generating part, and generates a strong torque on the main shaft by the impact force generated in the impact generating part. The electric motor is an outer rotor type electric motor.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] An outer rotor type electric motor has a large inertia and can obtain a high torque. However, there is a problem that the inertia tends to become unnecessarily large and the size of the rotor becomes large.

[0005] An object of the present disclosure is to provide a power tool that can output a high torque and can be miniaturized.

Means for Solving the Problems

[0006] An electric tool according to one aspect of the present disclosure comprises an electric motor and does not have a reduction mechanism. The electric motor is an inner-rotor type electric motor in which a rotor is positioned in the center of a cylindrical stator. The rotor has a rotor core, a plurality of magnets, and a rotating shaft held inside the rotor core. The plurality of magnets are arranged in a spoke-like manner inside the rotor core with respect to the center of the rotating shaft. [Effects of the Invention]

[0007] This disclosure makes it possible to provide power tools that can output high torque and be made smaller. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a block diagram showing a schematic configuration of a power tool according to an embodiment of the present disclosure. [Figure 2] Figure 2 is a side view of the same power tool. [Figure 3] Figure 3 is a perspective view of the motor of the same power tool. [Figure 4] Figure 4 is a perspective view of the stator core of the motor shown above. [Figure 5] Figure 5 is a plan view of the rotor of the motor shown above. [Figure 6] Figure 6 is a plan view of the rotor of the motor according to the comparative example above. [Modes for carrying out the invention]

[0009] The power tools according to the embodiments will be described in detail below with reference to the drawings. However, the figures described in the following embodiments are schematic diagrams, and the dimensional ratios of the sizes of each component do not necessarily reflect the actual dimensional ratios. Furthermore, the configurations described in the following embodiments are merely examples of the present disclosure. The present disclosure is not limited to the following embodiments, and various modifications are possible depending on the design, etc., as long as the effects of the present disclosure can be achieved.

[0010] (1)Power tools As shown in Figure 1, the power tool 10 according to this embodiment includes a motor 1. Furthermore, as shown in Figure 1, the power tool 10 also includes a power supply unit 101, an impact mechanism 102, an output shaft 103, a motor control unit 104, a cutting tool 105, and an operating unit 106. The power tool 10 is a tool that drives the cutting tool 105 with the driving force of the electric motor 1. Hereinafter, for convenience, the electric motor may be simply referred to as "motor".

[0011] Motor 1 is a drive source that drives the cutting tool 105. Motor 1 is, for example, a brushless motor.

[0012] The power supply unit 101 is a DC power supply that supplies current to drive the motor 1. The power supply unit 101 includes one or more secondary batteries. The power tool 10 is a portable power tool.

[0013] The impact mechanism 102 applies a striking impact to the output shaft 103 using the rotational power of the motor 1. Since the power tool 10 of this embodiment does not have a reduction mechanism, the rotational power of the motor 1 is transmitted directly to the impact mechanism 102 without going through a reduction mechanism. The impact mechanism 102 generates an impact force by converting the rotational power of the motor 1, which is received via the rotation shaft 51 of the motor 1, into pulsed torque. The impact mechanism 102 includes, as an example, a drive shaft, a hammer, and an anvil. When the rotational force from the motor 1 is transmitted to the drive shaft, the hammer fitted to the drive shaft rotates, and the hammer and anvil collide. The anvil, struck by the hammer, rotates, and a striking impact is applied to the output shaft 103, which is integrally provided with the anvil.

[0014] The output shaft 103 is a part that is driven (e.g., rotated) by the driving force output from the impact mechanism 102. A tip tool 105 is attached to the output shaft 103. The tip tool 105 is, for example, a driver, a socket, or a drill. Among various tip tools 105, a tip tool 105 corresponding to the application is attached to the chuck 12 and used (see FIG. 2). Note that the chuck 12 is fixed to the output shaft 103 and is a part to which the tip tool 105 is detachably attached.

[0015] The operation unit 106 is, for example, a trigger volume that receives an operation for controlling the rotation of the motor 1. The operator can switch the on / off of the motor 1 by operating the trigger volume. Also, the operator can adjust the rotation speed of the output shaft 103, that is, the rotation speed of the motor 1, by the amount of operation of pulling in the trigger volume. The motor control unit 104 rotates or stops the motor 1 and controls the rotation speed of the motor 1 according to the operation input to the trigger volume. In this power tool 10, the rotation speed of the tip tool 105 is controlled by controlling the rotation speed of the motor 1 by operating the trigger volume.

[0016] As shown in FIG. 1, the power tool 10 according to the embodiment includes a motor 1 but does not include a speed reduction mechanism that reduces the rotation of the rotation shaft 51 of the motor 1 and transmits it to the output shaft 103. Thereby, the reaction force generated when the impact mechanism 102 applies an impact shock to the output shaft 103 by the rotational power of the motor 1 can be reduced. Moreover, since the power tool 10 according to the embodiment does not include a speed reduction mechanism, it can be made smaller and lighter than a power tool having a speed reduction mechanism. Note that the "speed reduction mechanism" referred to in the present disclosure means a mechanical device having a mechanism such as a gear, reducing the rotation speed of a motor, and obtaining high torque. Typically, the speed reduction mechanism outputs torque proportional to the speed reduction ratio (tooth number ratio or pulley ratio).

[0017] Further, the power tool 10 according to the embodiment further includes a main body case 11 (see FIG. 2). The main body case 11 houses the motor 1, the impact mechanism 102, the output shaft 103, and the motor control unit 104. The main body case 11 has a housing portion 11A, a grip portion 11B, and a mounting portion 11C (see FIG. 2). The shape of the housing portion 11A is a hollow cylindrical shape. The housing portion 11A houses the motor 1, a part of the output shaft 103, the impact mechanism 102, and the like. The grip portion 11B protrudes in one direction (downward in FIG. 2) from the outer peripheral surface of the housing portion 11A. The grip portion 11B is formed in a hollow cylindrical shape having the above-mentioned one direction as the longitudinal direction. An operator can hold the grip portion 11B and perform operations such as screwing. An operation unit 106 for receiving the operator's operation is arranged on the grip portion 11B. The internal space of the grip portion 11B is connected to the internal space of the housing portion 11A. The first end in the longitudinal direction of the grip portion 11B is connected to the housing portion 11A, and the second end in the longitudinal direction of the grip portion 11B is connected to the mounting portion 11C. A battery pack as the power supply unit 101 is detachably attached to the mounting portion 11C. The power tool 10 operates using the battery pack as a power source. That is, the battery pack is a power source that supplies a current for driving the motor 1. The battery pack is not a component of the power tool 10. However, the power tool 10 may include a battery pack.

[0018] (2) Motor (2-1) Overview Hereinafter, the configuration of the motor 1 included in the power tool 10 according to the embodiment will be described with reference to the drawings.

[0019] The motor 1 is an inner rotor type electric motor in which a rotor 5 is arranged at the center of a cylindrical stator 2 (see FIG. 3 and the like). The rotor 5 has a rotor core 6, a plurality of magnets 7, and a rotating shaft 51 held inside the rotor core 6 (see FIGS. 3 and 5 and the like). The plurality of magnets 7 are arranged in a spoke shape (radially) inside the rotor core 6 around the center C1 of the rotating shaft 51 of the rotor core 6 (see FIG. 5 and the like).

[0020] As shown in Figure 1, the power tool 10 according to this embodiment does not have a reduction gear mechanism. Therefore, although the reaction force generated when the impact mechanism 102 applies a striking impact to the output shaft 103 by the rotational power of the motor 1 can be reduced, it cannot generate sufficient torque.

[0021] Therefore, as shown in Figure 5, the motor 1 of the power tool 10 according to this embodiment has multiple magnets 7 arranged in a spoke-like manner inside the rotor core 6, centered on the rotation axis 51 C1 of the rotor core 6. As a result, adjacent magnets 7 repel each other, which increases the torque of the motor 1 and enables the power tool 10 to output high torque.

[0022] Furthermore, the inner rotor type motor 1 has superior responsiveness (controllability) compared to the outer rotor type motor, allowing for fine adjustment of the output of the power tool 10 (the rotational speed of the output shaft 103).

[0023] Furthermore, in the inner rotor type motor 1, the outer stator core 20 is cylindrical in shape and surrounds the inner rotor core 6 (see Figure 3, etc.). Therefore, due to its structure, air can easily pass through the interior, making it easy to ensure cooling performance with a simple configuration such as a fan. In contrast, in the outer rotor type electric motor, the outer rotor core is generally cylindrical with a bottom, covering the inner stator core. Therefore, heat tends to build up inside, requiring a special mechanism to ensure cooling performance. Thus, the inner rotor type motor 1 has superior cooling performance compared to the outer rotor type motor, enabling continuous use of the power tool 10. Since the power tool 10 according to this embodiment does not require a special mechanism to ensure cooling performance, it is possible to make the power tool 10 smaller and lighter.

[0024] Furthermore, as described above, the power tool 10 according to this embodiment does not have a reduction mechanism, which makes it possible to make the power tool 10 smaller and lighter.

[0025] Therefore, according to this embodiment, it is possible to provide an electric power tool 10 that can output high torque and be made smaller.

[0026] (2-2) Details The motor 1 of the power tool 10 according to this embodiment will be described in detail below with reference to Figures 3 to 6 and other figures.

[0027] As shown in Figure 3, motor 1 comprises a stator 2 and a rotor 5. Motor 1 is an inner-rotor type electric motor in which the rotor 5 is positioned in the center of a cylindrical stator 2 (see Figure 3, etc.).

[0028] (2-2-1) Stator As shown in Figure 3, the stator 2 has a stator core 20 and a plurality (nine in Figure 3) of coils 23. More specifically, as shown in Figure 4, the stator core 20 has an outer cylinder portion 22 and a plurality (nine in Figure 3) of teeth 4.

[0029] The outer cylinder portion 22 is configured in a substantially cylindrical shape. Each of the multiple teeth 4 is provided at equal intervals on the inner surface of the outer cylinder portion 22. Each of the multiple teeth 4 protrudes radially inward from the inner surface of the outer cylinder portion 22 (see Figure 4). More specifically, each of the multiple teeth 4 includes a body portion and a tip portion. Coil winding frames 8 are arranged on the upper and lower surfaces in the axial direction of the outer cylinder portion 22 and the multiple teeth 4 of the stator core 20 (see Figure 3). A coil 23 is wound around the body portion of the tooth 4 via the coil winding frames 8. The tip portion of the tooth 4 extends from the tip-side portion of the body portion of the tooth 4 in a direction intersecting the protruding direction of the body portion. The tip portion of the tooth 4 is provided as a retainer to prevent the coil 23 from falling out of the tooth 4. A rotor 5 is arranged inside each of the multiple teeth 4.

[0030] (2-2-2) Rotor The rotor 5 rotates relative to the stator 2. That is, the magnetic flux generated from the multiple coils 23 wound around the stator core 20 generates an electromagnetic force that rotates the rotor 5. The motor 1 transmits the rotational force (driving force) of the rotor 5 from the rotating shaft 51 to the impact mechanism 102 (see Figure 1).

[0031] The rotor 5 comprises a cylindrical rotor core 6, a plurality of magnets 7 (12 in Figures 3 and 5), and a rotating shaft 51 held inside the rotor core 6. As shown in Figure 5, the plurality of magnets 7 are arranged in a spoke-like (radial) pattern inside the rotor core 6, centered on the center C1 of the rotating shaft 51 of the rotor core 6.

[0032] Here, the shape of the rotor core 6 when viewed from the axial direction of the rotation axis 51 is circular, and the center C1 of the rotor core 6 corresponds to the center of this circle. The shape of each magnet 7 is a rectangular parallelepiped. When viewed from the axial direction of the rotation axis 51 of the rotor core 6, the shape of each magnet 7 is rectangular (see Figure 5). Each magnet 7 is magnetized in the shorter direction of the rectangle. Each magnet 7 is arranged with the same poles facing each other relative to adjacent magnets 7. In other words, each magnet 7 is arranged so that adjacent magnets 7 face each other and repel each other. When multiple magnets 7 are arranged in a spoke-like manner around the center C1 of the rotor core 6, it means that when viewed from the axial direction of the rotor core 6, the longer direction of the rectangle of each magnet 7 is aligned with the radial direction of the rotor core 6, and the multiple magnets 7 are arranged in the rotational direction of the rotor core 6. Note that arranging multiple magnets 7 radially as shown in Figure 5 will also be referred to as "spoke arrangement" below.

[0033] (2-2-3) Shape of the magnet In the motor 1 according to this embodiment, the optimal shape of the magnet 7 in the spoke arrangement is defined in order to obtain a high torque output. More specifically, when the length of the long side of the magnet 7 is Ln and the length of the short side of the magnet 7 is Lm, equation (1) holds for the division value A obtained by dividing the length of the long side Ln of the magnet 7 by the length of the short side Lm of the magnet 7. The division value A is the ratio of the length of the long side to the length of the short side of the magnet 7. The division value A can also be described as the aspect ratio of the magnet 7.

[0034] 1 <A≦10···(1) In other words, the division value A obtained by dividing the length Ln of the longer side of magnet 7 by the length Lm of the shorter side of magnet 7 is greater than 1 and less than or equal to 10.

[0035] In a spoke-arranged motor 1, the torque of the motor 1 can be increased because adjacent magnets 7 repel each other by facing each other. In a spoke arrangement, as shown in Figure 5, by making the shape of each magnet 7 rectangular when viewed from the axial direction of the rotation axis 51 of the rotor core 6 (that is, the division value A in equation (1) is greater than 1), the longer sides of adjacent magnets 7 are more likely to face each other.

[0036] In equation (1), the larger the division value A, the more magnets 7 can be arranged in the direction of rotation of the rotor core 6, and the greater the torque of the motor 1. In a spoke arrangement, the maximum value of the length Ln of the long side of the magnet 7 is Rr-Rs, where Rr is the outer radius of the rotor core 6 and Rs is the inner radius of the rotor core 6. Therefore, if the length Ln of the long side of the magnet 7 is close to its maximum value (Rr-Rs), increasing the division value A further would make the length Lm of the short side of the magnet 7 too small, which is impractical. For this reason, considering manufacturing limitations, the maximum value of the division value A in equation (1) is set to 10.

[0037] (2-2-4) Number of magnets (number of poles) In the motor 1 according to this embodiment, the optimal number of magnets 7 in the spoke arrangement is determined in order to obtain a high torque output. The number of magnets 7 is also referred to as the number of poles of the motor 1. As shown in Figure 4, in the rotor core 6, a plurality of magnets 7 (12 in this embodiment) are arranged at equal intervals in the rotational direction of the rotor core 6. Among the plurality of magnets 7, the number of poles of the motor 1 is determined by the angle θ formed in the longitudinal direction between adjacent magnets 7. In Figure 4, the angle θ formed in the longitudinal direction between adjacent magnets 7 is 30 degrees, and the number of poles of the motor 1 is 12.

[0038] The spoke-arranged motor 1 performs by the mutual repulsion of adjacent magnets 7. By arranging multiple magnets 7 at equal intervals in the rotational direction of the rotor core 6 and setting the angle θ to 45° or less (motor 1 having 8 or more poles), it is possible to increase the torque. This makes it possible to miniaturize the power tool 10.

[0039] In this embodiment, it is desirable that the motor 1 has a high torque output, but it must be within a range suitable for the output of the power tool 10. The maximum number of poles for the optimal motor 1 in the power tool 10 is, for example, 14. Therefore, the optimal number of poles for the motor 1 in the power tool 10 are 8, 12, and 14.

[0040] Furthermore, since multiple magnets 7 are arranged in a spoke-like fashion around the center C1 of the rotor core 6's rotation axis 51, there is an advantage in that the diameter (outer diameter Rr) of the rotor 5 can be easily shortened. In particular, when the number of magnets 7 is relatively large, there is an advantage in that the diameter (outer diameter Rr) of the rotor 5 can be easily shortened while maintaining the longitudinal length of each magnet 7.

[0041] In contrast, Figure 6 is a plan view of the rotor 5P of the motor according to the comparative example. The size of the rotor 5P of the comparative example in Figure 6 is the same as the size of the rotor 5 of the embodiment in Figure 5. That is, the inner diameter Rs and outer diameter Rr of the rotor 5P of the comparative example are the same as the inner diameter Rs and outer diameter Rr of the rotor 5 of the embodiment in Figure 5. The size of the magnet 7 is also the same.

[0042] In the comparative example rotor 5P shown in Figure 6, multiple magnets 7 (six in Figure 6) are arranged in a polygonal (hexagonal) shape around the center C2 of the rotor core 6P. Hereafter, as shown in Figure 6, when the longitudinal direction of the rectangle of each magnet 7 is aligned with the rotation direction of the rotor core 6P when viewed from the axial direction of the rotor core 6P, this arrangement will also be referred to as "flat arrangement". In the flat arrangement, if the diameter (outer diameter Rr) of the rotor core 6P is constant, the more magnets 7 there are, the shorter the longitudinal length Ln of the rectangle of the magnet 7 needs to be. Also, if the longitudinal length Ln of the rectangle of the magnet 7 is constant, the more magnets 7 there are, the longer the diameter (outer diameter Rr) of the rotor core 6P needs to be. In this case, the longer the diameter (outer diameter Rr) of the rotor core 6P, the greater the moment force required when the rotor core 6P starts rotating and when it stops rotating. Furthermore, increasing the diameter (outer diameter Rr) of the rotor core 6P and thus the distance between the multiple magnets 7 and the center C2 increases, which in turn increases the centrifugal force acting on the multiple magnets 7. This increases the likelihood that the rotor core 6P will deform due to the forces from the multiple magnets 7. Therefore, increasing the diameter (outer diameter Rr) of the rotor core 6P may not be desirable in some cases.

[0043] On the other hand, in the rotor 5 of the embodiment, when the number of magnets 7 is relatively large, it is possible to suppress the increase in the diameter (outer diameter Rr) of the rotor core 6 compared to the rotor core 6P of the comparative example. That is, by narrowing the spacing between multiple magnets 7 in the rotational direction of the rotor core 6 as the number of magnets 7 increases, multiple magnets 7 can be arranged in a spoke-like manner around the center C1 of the rotor core 6. This makes it possible to arrange multiple magnets 7 while suppressing an increase in the diameter (outer diameter Rr) of the rotor core 6.

[0044] In other words, the rotor 5 of this embodiment may have six or more magnets 7. This makes it possible to increase the torque of the motor 1 while suppressing an increase in the diameter of the rotor core 6.

[0045] (2-2-5) Dimensions of the rotor core In the motor 1 according to this embodiment, the optimal dimensions of the rotor core 6 are defined in order to obtain a high torque output. More specifically, as shown in Figure 5, when the outer radius of the rotor core 6 is Rr and the inner radius of the rotor core 6 is Rs, equation (2) holds true for the dimensions of the rotor core 6. 1 <Rr / Rs<A···(2) In other words, the value obtained by dividing the outer radius Rr of the rotor core 6 by the inner radius Rs of the rotor core 6 is greater than 1 and less than the division value A.

[0046] The torque T of motor 1, when the stator size is constant, is proportional to the product of the number of poles P of magnet 7 and the magnetic flux M of magnet 7, as shown in equation (3). T ∝ P × M ···(3) Furthermore, the magnetic flux M of the magnet is proportional to the area of ​​the magnet 7, as shown in equation (4). Here, the area of ​​the magnet 7 is the product of the length of the longer side of the magnet 7, Ln, and the length of the shorter side of the magnet 7, Lm. M ∝ Ln × Lm···(4) From equations (3) and (4), the torque T of motor 1 is proportional to the product of the number P of magnets 7 and the area of ​​magnets 7.

[0047] First, from equations (3) and (4), we obtain the torque T for the comparative example of a rotor core 6P with a horizontal arrangement (see Figure 6). s This is expressed by equation (5). T s = (Maximum number of magnet poles) × (Area of ​​the magnet) = (Circumference of rotor outer diameter Rr / Length of the longer side of the magnet) × (Area of ​​the magnet) =(2π×Rr / Ln)×(Ln×Lm) (5) Next, from equations (3) and (4), the torque T for the rotor core 6 with the spoke arrangement of the embodiment (see Figure 5) is obtained. I This is expressed by equation (6). T I = (Maximum number of magnet poles) × (Area of ​​the magnet) = (Circumference of the inner diameter of the rotor / Length of the shorter side of the magnet) × (Area of ​​the magnet) =(2π×Rs / Lm)×(Ln×Lm) (6) Here, the torque T of the embodiment I However, the comparative example's torque T s Considering the case where it is greater than, we can derive the condition of equation (2) above from equations (5) and (6). 1 <Rr / Rs<A···(2) This makes it possible to increase the torque of motor 1 compared to a flat-arranged motor, provided that the dimensions of the rotor core 6 satisfy the conditions of equation (2).

[0048] (3) Operation Description When an operator performing a tightening operation using the power tool 10 pulls in the operating section 106 of the power tool 10, the motor control unit 104 controls the rotational speed of the motor 1 according to the amount the operating section 106 is pulled in (see Figures 1 and 2). When the rotating shaft 51 of the motor 1 rotates, the impact mechanism 102 applies an impact to the output shaft 103 using the rotational power of the motor 1. Since the power tool 10 in this embodiment does not have a reduction mechanism, the rotational power of the motor 1 is transmitted directly to the impact mechanism 102 without going through a reduction mechanism. This makes it possible to realize a high-torque power tool 10, and the tip tool 105 held on the output shaft 103 is used to tighten or loosen fastening members.

[0049] (4) Effects As shown in Figure 1, the power tool 10 according to this embodiment is equipped with a motor 1 and does not have a reduction mechanism, so the reaction force generated when the impact mechanism 102 applies a striking impact to the output shaft 103 by the rotational power of the motor 1 can be reduced. Moreover, since the power tool 10 according to this embodiment does not have a reduction mechanism, it can be made smaller and lighter compared to power tools that have a reduction mechanism.

[0050] Furthermore, as shown in Figure 5, the motor 1 of this embodiment has multiple magnets 7 arranged in a spoke-like pattern. As adjacent magnets 7 repel each other, the torque of the motor 1 can be increased. This allows the power tool 10 to output high torque.

[0051] Furthermore, since the power tool 10 of this embodiment employs an inner-rotor type motor 1, which has superior responsiveness compared to an outer-rotor type motor, it becomes possible to finely adjust the output of the power tool 10. Due to its structure, the inner-rotor type motor 1 allows air to pass through easily inside. As a result, it has good cooling performance, making it possible to use the power tool 10 continuously. Since no special cooling mechanism is required to ensure cooling performance, the power tool 10 can be made smaller and lighter.

[0052] Therefore, according to this embodiment, it is possible to provide an electric power tool 10 that can output high torque and be made smaller.

[0053] As shown in Figure 5, the power tool 10 according to this embodiment has a rectangular magnet 7 when viewed from the axial direction of the rotation axis 51 of the rotor core 6. The division value A obtained by dividing the length Ln of the long side of the magnet 7 by the length Lm of the short side of the magnet 7 is greater than 1 and less than or equal to 10. By making the shape of the magnet 7 rectangular, the long sides of adjacent magnets 7 are more likely to face each other. This makes it possible to increase the number of magnets 7 arranged on the rotor core 6 and increase the torque of the motor 1.

[0054] Furthermore, in the electric tool 10 according to this embodiment, the value obtained by dividing the outer radius Rr of the rotor core 6 by the inner radius Rs of the rotor core 6 is greater than 1 and less than the above division value. This makes it possible to increase the torque of the motor 1 compared to a motor (see Figure 6) in which the longitudinal direction of each magnet 7 is arranged along the rotation direction of the rotor core. This makes it possible to miniaturize the electric tool 10.

[0055] Furthermore, in the electric tool 10 according to this embodiment, as shown in Figure 5, the multiple magnets 7 are arranged at equal intervals in the rotational direction of the rotor core 6, and the number of poles of the motor 1 is determined by the angle θ formed in the longitudinal direction between adjacent magnets 7. By having adjacent magnets 7 arranged at equal intervals face each other and repel each other, it becomes possible to increase the torque of the motor 1.

[0056] Furthermore, in the electric tool 10 according to this embodiment, by specifying the angle between adjacent magnets 7 in the longitudinal direction to be 45 degrees or less, the number of poles of the motor 1 can be determined to be 8 or more. This makes it possible to increase the torque of the motor 1 compared to the case where the number of magnets 7 is less than 8. This makes it possible to miniaturize the electric tool 10.

[0057] Furthermore, in the electric tool 10 according to this embodiment, the rotor 5 has six or more magnets 7. This makes it possible to increase the torque of the motor 1 compared to the case where the number of magnets 7 is less than six. This makes it possible to miniaturize the electric tool 10.

[0058] Furthermore, as shown in Figures 1 and 2, the power tool 10 according to this embodiment further includes a power supply unit 101 (battery pack) containing one or more secondary batteries. This makes it possible to realize a portable power tool 10.

[0059] Furthermore, as shown in Figure 1, the power tool 10 according to this embodiment is further equipped with an impact mechanism 102, which reduces the reaction force generated when the impact mechanism 102 applies a striking impact to the output shaft 103 by the rotational power of the motor 1.

[0060] (5) Variant The above embodiments are merely one of many embodiments of this disclosure. The above embodiments can be modified in various ways depending on the design, etc., as long as the objectives of this disclosure are achieved. The following lists some modifications of the above embodiments. The modifications described below can be combined and applied as appropriate.

[0061] As shown in Figure 1, the power tool 10 according to the above embodiment is equipped with an impact mechanism 102, but the impact mechanism 102 is not an essential component of the power tool 10. In other words, in the power tool 10, the rotating shaft 51 of the motor 1 may be directly connected to the output shaft 103 of the power tool 10. In the modified power tool, the impact mechanism 102 is not provided, so it can be made smaller and lighter compared to the power tool 10 of the more advanced embodiment.

[0062] In the above embodiment, where "greater than" is used in the comparison of two values, it may also be used as "greater than or equal to". In other words, whether or not the case where the two values ​​are equal is included in the comparison of two values ​​can be arbitrarily changed depending on the setting of the reference value, etc., so there is no technical difference between "greater than" and "greater than or equal to". Similarly, where "less than or equal to" is used, it may also be used as "less than".

[0063] (summary) Based on the embodiments described above, the following aspects are disclosed.

[0064] The power tool (10) of the first embodiment includes an electric motor (1) and does not have a reduction mechanism. The electric motor (1) is an inner rotor type electric motor in which a rotor (5) is positioned in the center of a cylindrical stator (2). The rotor (5) has a rotor core (6), a plurality of magnets (7), and a rotating shaft (51) held inside the rotor core (6). The plurality of magnets (7) are arranged in a spoke-like manner inside the rotor core (6) with the center of the rotating shaft (51) as the center.

[0065] In this embodiment, the power tool (10) is equipped with a motor (1) and does not have a reduction mechanism, making it possible to reduce the reaction force generated during operation. Moreover, since the power tool (10) does not have a reduction mechanism, it is possible to make it smaller and lighter compared to power tools that have a reduction mechanism. Furthermore, in the motor (1), multiple magnets (7) are arranged in a spoke-like manner around the center (C1) of the rotation axis (51) of the rotor core (6), so that adjacent magnets (7) face each other and repel each other, making it possible to increase the torque of the motor (1). The power tool (10) can output high torque. In addition, the drive source of the power tool (10) is an inner rotor type electric motor, which has superior responsiveness compared to an outer rotor type electric motor. This makes it possible to finely adjust the output of the power tool (10). Furthermore, due to its structure, the inner rotor type electric motor (1) allows air to pass through easily inside. Therefore, it has good cooling performance, making it possible to use the power tool (10) continuously. Since a special cooling mechanism is not required to ensure cooling performance, the power tool (10) can be made smaller and lighter. Therefore, it becomes possible to provide a power tool (10) that can output high torque and be made smaller.

[0066] In the second embodiment of the power tool (10), the magnet (7) is rectangular when viewed from the axial direction of the rotating shaft (51) in the first embodiment. The division value obtained by dividing the length of the long side of the magnet (7) by the length of the short side of the magnet (7) is greater than 1 and less than or equal to 10.

[0067] According to this embodiment, by making the shape of the magnet (7) rectangular, the longer sides of adjacent magnets (7) are more likely to face each other. This makes it possible to increase the number of magnets (7) arranged on the rotor core (6) and increase the torque of the electric motor (1).

[0068] In the third embodiment of the power tool (10), in the second embodiment, the value obtained by dividing the outer radius (Rr) of the rotor core (6) by the inner radius (Rs) of the rotor core (6) is greater than 1 and less than the above division value.

[0069] According to this embodiment, the torque of the motor (1) can be increased compared to a motor in which the longitudinal direction of each magnet (7) is arranged along the rotation direction of the rotor core. This makes it possible to miniaturize the power tool (10).

[0070] In the fourth embodiment of the power tool (10), in any one of the first to third embodiments, the multiple magnets (7) are arranged at equal intervals in the rotational direction of the rotor core. The number of poles of the electric motor (1) is determined by the longitudinal angle between adjacent magnets (7) among the multiple magnets (7).

[0071] According to this embodiment, the torque of the motor (1) can be increased by having adjacent magnets (7) arranged at equal intervals repel each other.

[0072] In the fifth embodiment of the power tool (10), the angle is 45 degrees or less in the fourth embodiment.

[0073] According to this embodiment, by specifying the longitudinal angle between adjacent magnets (7) to be 45 degrees or less, the number of poles of the electric motor (1) can be determined to be 8 or more. This makes it possible to increase the torque of the electric motor (1) compared to the case where the number of magnets (7) is less than 8. This makes it possible to miniaturize the power tool (10).

[0074] The power tool (10) of the sixth embodiment, in any one of the first to fifth embodiments, has a rotor (5) which has six or more magnets (7).

[0075] According to this embodiment, the torque of the electric motor (1) can be increased compared to the case where the number of magnets (7) is less than six. This makes it possible to miniaturize the power tool (10).

[0076] The power tool (10) of the seventh embodiment further comprises a power supply unit (101) including one or more secondary batteries in any one of the first to sixth embodiments.

[0077] According to this embodiment, a portable power tool (10) can be realized by equipping a power supply unit (101) including a secondary battery in a power tool (10) that can output high torque.

[0078] The power tool (10) of the eighth embodiment further comprises an impact mechanism (102) that applies a striking impact to the output shaft (103) by the rotational power of the electric motor (1) in any one of the first to seventh embodiments.

[0079] According to this embodiment, in the power tool (10), the reaction force generated when the impact mechanism (102) applies a striking impact to the output shaft (103) by the rotational power of the motor (1) can be reduced.

[0080] The configurations relating to the second to eighth aspects are not essential to the power tool (10) and can be omitted as appropriate. [Explanation of Symbols]

[0081] 1 motor 2 staters 5 rotors 6 rotor cores 7 Magnets 10 Power tools 20 stator cores 51 Rotating shaft (motor) 101 Power supply section 102 Impact Mechanism 103 Output shaft 104 Motor Control Unit 105 Tip tools 106 Operation section Rs rotor inner radius Rr Rotor Outer Radius Lm is the length of the shorter side of the magnet. Ln: Length of the longer side of the magnet A Division value C1 Center of the rotation axis

Claims

1. A power tool equipped with an electric motor but without a reduction mechanism, The aforementioned electric motor is an inner-rotor type electric motor in which the rotor is positioned in the center of a cylindrical stator. The rotor is Rotor core and Multiple magnets, The rotor core has a rotating shaft held inside it, The plurality of magnets are arranged in a spoke-like manner inside the rotor core with respect to the center of the rotation axis. Power tools.

2. The magnet is rectangular when viewed from the axial direction of the rotation axis. The division value obtained by dividing the length of the longer side of the magnet by the length of the shorter side of the magnet is greater than 1 and less than or equal to 10. The power tool according to claim 1.

3. The value obtained by dividing the outer radius of the rotor core by the inner radius of the rotor core is greater than 1 and less than the division value. The power tool according to claim 2.

4. The plurality of magnets are arranged at equal intervals in the rotational direction of the rotor core, The number of poles of the electric motor is determined by the angle formed in the longitudinal direction between adjacent magnets among the plurality of magnets. The power tool according to claim 1.

5. The aforementioned angle is 45 degrees or less. The power tool according to claim 4.

6. The rotor has six or more of the magnets, The power tool according to claim 1.

7. The power supply unit further comprises one or more secondary batteries, The power tool according to claim 1.

8. The system further includes an impact mechanism that applies a striking shock to the output shaft using the rotational power of the aforementioned electric motor. The power tool according to any one of claims 1 to 7.

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