Power tool

Abstract

The present application provides an electric power tool capable of improving a motor cooling structure in an electric power tool provided with a brushless electric motor. The electric power tool is provided with: a brushless electric motor having a rotor, a stator, and a motor shaft; a first bearing located on a first side opposite the rotor and the stator in a direction in which the motor shaft extends, i.e., an axial direction, and supporting the motor shaft so as to be rotatable; a second bearing located on a second side opposite the first side in the axial direction, and supporting the motor shaft so as to be rotatable; a housing having at least one air inlet on the first side and at least one air outlet on the second side, and housing the brushless electric motor; and a bracket supporting the first bearing. The bracket has at least one air passage groove that defines a direction of motor cooling air flowing into the housing from the at least one air inlet so as to be directed toward the brushless electric motor.

Description

Technical Field

[0001] This invention relates to a power tool. Background Technology

[0002] As a type of power tool, screwdrivers equipped with brushless electric motors are well-known (e.g., Japanese Patent Application Publication No. 2024-175645). Because such screwdrivers have high torque, the brushless electric motor generates a significant amount of heat. Therefore, this screwdriver includes a structure for cooling the brushless electric motor. Specifically, the housing includes an air inlet located on one side relative to the brushless electric motor and an exhaust outlet located on the other side. Air flowing into the housing from the air inlet is expelled through the brushless electric motor and discharged from the exhaust outlet by a fan fixed to the motor shaft. This airflow cools the brushless electric motor. Summary of the Invention

[0003] The cooling structures of brushless electric motors in conventional screwdrivers are not yet optimal and still have room for improvement. For example, conventional screwdrivers often feature inefficient airflow paths due to prioritizing compactness and other design considerations. Inefficient airflow paths increase pressure loss, leading to reduced airflow and consequently lower cooling efficiency. This problem is not limited to screwdrivers but exists in various power tools equipped with brushless electric motors and their corresponding motor cooling structures. Therefore, improvements to the motor cooling structures of power tools with brushless electric motors are anticipated.

[0004] This specification discloses an electric tool. The electric tool may include: a brushless electric motor having a rotor, a stator, and a motor shaft; a first bearing located on a first side relative to the rotor and stator in the axial direction of the motor shaft, supporting the motor shaft for rotation; a second bearing located on a second side opposite to the first side in the axial direction, also supporting the motor shaft for rotation; a housing housing the brushless electric motor; and a bracket supporting the first bearing. The housing may have at least one air inlet on the first side and at least one exhaust outlet on the second side. The bracket may have at least one air duct that directs the direction of motor cooling air flowing into the housing from the at least one air inlet toward the brushless electric motor.

[0005] According to this power tool, the bracket required to support the first bearing has at least one air passage slot that directs the direction of the motor cooling air toward the brushless electric motor. Therefore, without introducing additional components, an air passage with an effective path for motor cooling air from at least one air inlet toward the brushless electric motor can be established. Thus, pressure loss in the air passage can be reduced, and the brushless electric motor can be effectively cooled.

[0006] This specification also discloses an electric tool. The electric tool may include a brushless electric motor. The brushless electric motor may have: a rotor, a stator having a plurality of teeth with coils wound around it, and a motor shaft having a rotation axis. The electric tool may further include: a first bearing located on a first side relative to the rotor and stator in the direction extending along the rotation axis, i.e., the axial direction, and supporting the motor shaft for rotation; a second bearing located on a second side opposite to the first side in the axial direction, and supporting the motor shaft for rotation; a housing that houses the brushless electric motor; and a heat sink. The housing may have: at least one air inlet located on the first side and at least one exhaust outlet located on the second side. The heat sink may be configured in the airflow path of the motor cooling air flowing into the housing from at least one air inlet and exiting from at least one exhaust outlet, and is in contact with the coils wound around the plurality of teeth.

[0007] According to this power tool, the brushless electric motor can be effectively cooled by a radiator configured in the airflow path of the motor cooling system. Furthermore, since the heat generated by the brushless electric motor is mainly produced by the coil wound around multiple teeth, the cooling efficiency can be further improved by having the radiator contact the coil.

[0008] This specification also discloses an electric tool. The electric tool may include a brushless electric motor. The brushless electric motor may include: a rotor, a stator having multiple teeth with coils wound around them, and a motor shaft having a rotation axis. The electric tool may further include: a first bearing located on a first side relative to the rotor and stator in the direction extending from the rotation axis (i.e., the axial direction), supporting the motor shaft for rotation; a second bearing located on a second side opposite to the first side in the axial direction, supporting the motor shaft for rotation; a housing that houses the electric motor; and a heat sink. The housing may have: at least one air inlet located on the first side and at least one exhaust outlet located on the second side. The heat sink may be configured in the airflow path of motor cooling air flowing from at least one air inlet into the motor housing and exiting from at least one exhaust outlet, and may contact the brushless electric motor. The heat sink may have multiple heat sink fins. The multiple spaces between the heat sinks can also serve as air ducts to direct the motor cooling air from the air inlet to the brushless motor, or to direct the motor cooling air from the brushless motor to the exhaust port.

[0009] According to this power tool, a radiator configured in the airflow path for motor cooling can effectively cool a brushless electric motor. Furthermore, since the multiple spaces between the radiator's multiple fins function as airflow paths that direct cooling air from the air inlet to the brushless electric motor, or from the brushless electric motor to the exhaust port, the cooling air can be effectively guided in the desired direction. Therefore, pressure loss in the airflow path can be reduced, and the brushless electric motor can be effectively cooled. Attached Figure Description

[0010] Figure 1 This is a perspective view of the screwdriver according to the first embodiment.

[0011] Figure 2 This is a right view of a screwdriver.

[0012] Figure 3 This is the left view of a screwdriver.

[0013] Figure 4 This is a longitudinal sectional view of a screwdriver.

[0014] Figure 5 yes Figure 4 A magnified view of a portion of the image.

[0015] Figure 6 It is along Figure 3 A partial sectional view of line A-A.

[0016] Figure 7 This is the front view of the motor; the insulators have been removed.

[0017] Figure 8 This is a 3D diagram of the support frame.

[0018] Figure 9 This is a partially enlarged left view of the screwdriver according to the second embodiment, with a portion of the outer casing removed.

[0019] Figure 10 This is a perspective view showing the installation state of the heat sink according to the second embodiment.

[0020] Figure 11 This is a partial longitudinal sectional view of the screwdriver according to the second embodiment.

[0021] Figure 12 It is along Figure 3 A partial sectional view of line B-B.

[0022] Figure 13 It is a 3D view of the radiator.

[0023] Figure 14 This is the left view of the radiator.

[0024] Figure 15 This is a 3D diagram of the motor stator.

[0025] Explanation of reference numerals in the attached figures

[0026] 10…Screwdriver; 20…Main housing; 21…Holding housing; 22…Battery holder; 22a…Battery assembly; 23…Chuck; 23a…Claw; 24…Reduction mechanism; 25…Vibration mechanism; 26…Spindle; 27…Trigger; 28…Battery; 29…Controller; 30…Motor; 31…Motor shaft; 32…Rotor; 33…Rotor core; 34…Magnet; 35…Stator; 36…Yoke; 37…Gear; 38…Coil; 39…Slot; 40…Air inlet; 41…Exhaust outlet; 42…Motor cooling fan; 43…Air duct; 50…First bearing; 51…Second bearing; 52…Front insulator; 53…Rear insulator; 60…Bracket; 61…Frustum conical section; 62…Gear holder; 63… Bearing support; 64… Screw boss; 65… Air duct groove; 66, 67… Side wall; 110… Screw drill; 135… Stator; 136… Magnetic yoke; 137… Tooth; 137a… Through hole; 137b… Positioning component; 137c… Screw boss; 143… Air duct; 152… Front insulator; 152a… Screw boss; 152b… Positioning part; 160… Bracket; 170… Radiator; 171… Base; 171a… Conical section; 171b… Cylindrical section; 172… Heat sink; 173… Mounting ring; 174… First mounting part; 175… Second mounting part; 176… End part; 177… First space; 178, 178a… Second space; 179a, 179b… Screw; AX1… Rotation axis. Detailed Implementation

[0027] Hereinafter, with reference to the accompanying drawings, representative and non-limiting examples of the present invention will be described in detail. This detailed description is merely intended to show those skilled in the art the details of preferred examples for carrying out the present invention and is not intended to limit the scope of the present invention. Furthermore, in order to provide further improved apparatus, methods of manufacturing thereof, and methods of use, the additional features and inventions disclosed below can be used separately from or together with other features and inventions.

[0028] Furthermore, the features or combinations of processes disclosed in the following detailed description are not, in the broadest sense, necessary for carrying out the invention, and are described merely to illustrate representative examples of the invention. Moreover, in providing additional and useful embodiments of the invention, the various features of the above and following representative examples, as well as the various features of the independent and dependent claims, are not necessarily required to be combined as in the examples described herein, or in the order listed.

[0029] All features set forth in this specification and / or claims are limitations imposed on the implementation and / or the features set forth in the claims, as a limitation of the disclosure made at the time of filing and on the specific matters set forth in the claims, and are intended to be disclosed separately and independently of each other. Furthermore, descriptions relating to all numerical ranges and groups or categories are limitations imposed on the disclosure made at the time of filing and on the specific matters set forth in the claims, and are intended to disclose their intermediate configurations.

[0030] In one or more embodiments, at least one air duct can be located in the axial direction at a position corresponding to at least one air inlet. According to this configuration, since at least one air inlet and at least one air duct are connected in the axial direction with the shortest path, the path of the motor cooling air from at least one air inlet to the brushless electric motor is more efficient in the axial direction, and the brushless electric motor can be cooled more effectively.

[0031] In one or more embodiments, at least one air duct can be located in the circumferential direction of the motor shaft, corresponding to at least one air inlet. According to this configuration, since at least one air inlet and at least one air duct are connected in the circumferential direction by the shortest path, the path of the motor cooling air from at least one air inlet to the brushless motor is more efficient in the circumferential direction, enabling more effective cooling of the brushless motor.

[0032] In one or more embodiments, at least one air inlet may have multiple air inlets. At least one air duct may have multiple air ducts located at multiple positions corresponding to the multiple air inlets. According to this configuration, motor cooling air can be effectively directed from all air inlets through the multiple air ducts to the brushless electric motor.

[0033] In one or more embodiments, the stator may have multiple teeth with coils wound around them. At least one air passage slot may also define the direction of the motor cooling air so that it passes through the gaps between the multiple teeth with coils wound around them. With this configuration, the motor cooling air comes into contact with the coils, which are the heat-generating parts, thus effectively cooling the brushless electric motor.

[0034] In one or more embodiments, at least one air passage slot may have an air passage width that narrows from the upstream side of the motor cooling air toward the downstream side. According to this configuration, when the gap between the multiple teeth is smaller than the air inlet, the motor cooling air can be effectively directed to the gap between the multiple teeth.

[0035] In one or more embodiments, the power tool may include a heat sink disposed in the airflow path for motor cooling and in contact with a coil wound around multiple teeth. According to this configuration, the heat sink can effectively cool the brushless electric motor. Furthermore, since the heat generated by the brushless electric motor is mainly generated in the coil wound around multiple teeth, the cooling efficiency can be further improved by the heat sink contacting the coil.

[0036] In one or more embodiments, the heat sink may include multiple heat sink fins that contact a coil wound around multiple teeth. According to this configuration, cooling efficiency can be further improved by using multiple heat sink fins.

[0037] In one or more embodiments, multiple heat sinks can be configured to extend radially relative to the axis of rotation. The spaces between the multiple heat sinks can function as airflow paths that guide motor cooling air radially along the axis of rotation. According to this configuration, improved cooling efficiency based on multiple heat sinks can be achieved, and motor cooling air can be guided radially along an effective path through the multiple heat sinks.

[0038] In one or more embodiments, the multiple spaces may include: a first space where the circumferential spacing between two adjacent heat sinks along the circumferential axis is a first distance, and a second space where the circumferential spacing between two adjacent heat sinks along the circumferential axis is a second distance greater than the first distance. The second space may be located at least in the circumferential direction at a position corresponding to the gap between the multiple teeth on which the coil is wound. According to this configuration, since the second space through which the motor cooling air most easily passes is located at a position corresponding to the gap between the multiple teeth, more motor cooling air can come into contact with the coil, which is the heat-generating part, thereby further and more effectively cooling the brushless electric motor.

[0039] In one or more embodiments, each of the multiple heat sinks may have an end portion, the end portion having a shape suitable for a coil wound on multiple teeth. According to this configuration, since the contact area between the multiple heat sinks and the coil is increased, the brushless electric motor can be cooled more effectively by the multiple heat sinks.

[0040] In one or more embodiments, the heat sink can be located in the axial direction corresponding to at least one air inlet. According to this configuration, the relatively cool motor cooling air from the brushless electric motor comes into contact with the heat sink. Therefore, the cooling efficiency based on the heat sink can be improved.

[0041] In one or more embodiments, the power tool may include an insulator in which a coil wound with multiple teeth is surrounded radially outward along the circumferential direction. The radiator can be fixed to the insulator with screws. According to this configuration, the radiator can be installed with a simple setup.

[0042] Hereinafter, with reference to the accompanying drawings, the screwdriver 10 according to the first embodiment will be further described in detail as a representative and non-limiting example of a "power tool" of the present invention. Figures 1-4 As shown, the screwdriver 10 includes: a main housing 20, a holding housing 21, a battery holding unit 22, and a chuck 23.

[0043] like Figure 4 as well as Figure 5 As shown, the main housing 20 has a cylindrical shape and houses a brushless electric motor (hereinafter referred to as the motor) 30, a reduction mechanism 24, a vibration mechanism 25, and a main shaft 26. The motor 30 includes a motor shaft 31 with a rotation axis AX1. The direction in which the rotation axis AX1 extends is consistent with the length direction of the main housing. In the following description, the direction in which the rotation axis AX1 extends (the direction in which the motor shaft 31 extends) is referred to as the axial direction. Furthermore, the direction orthogonal to the axial direction is referred to as the radial direction. Additionally, the direction around the rotation axis AX1 is referred to as the circumferential direction.

[0044] The spindle 26 is coaxial with the motor shaft 31. The spindle 26 is operatively connected to the motor shaft 31 via a reduction gear 24 and a vibration mechanism 25. The chuck 23 has a cylindrical shape and a jaw 23a at its front end for holding a front-end tool. The chuck 23 is operatively connected to the front end of the spindle 26 (the end opposite to the motor 30) on the opposite side of the jaw 23a. When the motor 30 is driven, rotational driving force is transmitted to the chuck 23 via the reduction gear 24 and the spindle 26, and rotational force is provided to the front-end tool held on the chuck 23. The screwdriver 10 can operate in a vibration mode and a non-vibration mode. When the vibration mode is selected, the vibration mechanism 25 causes the jaw 23a to vibrate in the axial direction. This mechanical configuration of the screwdriver 10 is known, therefore, its detailed description is omitted here.

[0045] like Figures 1-4As shown, the grip housing 21 extends in an elongated shape in a direction intersecting (more specifically, approximately orthogonal) the rotation axis AX1. The grip housing 21 is the part for the user to hold when using the screwdriver 10. One end of the grip housing 21 is connected to the main housing 20, and the other end is connected to the battery holder 22. A trigger 27 for starting and stopping the motor 30 is provided at one end of the grip housing 21.

[0046] For ease of explanation, the direction extending from the rotation axis AX1 is defined as the front-rear direction of the screwdriver 10. Within the front-rear direction, the side where the chuck 23 is located is defined as the front side of the screwdriver 10, and the opposite side is defined as the rear side of the screwdriver 10. Furthermore, the direction orthogonal to the rotation axis AX1 and approximately parallel to the extending direction of the holding housing 21 is defined as the vertical direction of the screwdriver 10. Within the vertical direction, the side where the main housing 20 is located is defined as the upper side of the screwdriver 10, and the side where the battery holder 22 is located is defined as the lower side of the screwdriver 10. Additionally, the direction orthogonal to both the front-rear and vertical directions is defined as the left-right direction of the screwdriver 10. Within the left-right direction, the right side when viewed from the rear is defined as the right side of the screwdriver 10, and the opposite side is defined as the left side of the screwdriver 10.

[0047] like Figures 1-4 As shown, the battery holding section 22 includes a battery mounting section 22a, which is configured to detachably assemble the battery 28, which serves as the power source for the screwdriver 10. The battery mounting section 22a includes electrical terminals as an interface for electrical connection with the battery 28, and guide rails as an interface for mechanical connection with the battery 28.

[0048] like Figure 5 as well as Figure 7 As shown, motor 30 is an internal rotor type brushless motor, which, in addition to a motor shaft 31, also includes a rotor 32 and a stator 35. The rotor 32 includes a rotor core 33 and four magnets 34. In this embodiment, the rotor 32 has four poles, but the number of poles can be arbitrarily set. Figure 7 As shown, the stator 35 includes an annular magnetic yoke 36 and six teeth 37 extending radially inward from the magnetic yoke 36. A slot 39 is formed between two adjacent teeth 37. In this embodiment, the number of slots 39 is six, but the number of slots can be arbitrarily set. A coil 38 is wound around the teeth 37 such that it passes through the slots 39.

[0049] like Figure 5As shown, the front insulator 52 surrounds the portion of the coil 38 wound around the tooth 37 in the front direction along the radial outer side of the coil 38. The rear insulator 53 surrounds the portion of the coil 38 wound around the tooth 37 in the rear direction along the radial outer side of the coil 38.

[0050] like Figure 4 As shown, a controller 29 is housed in the battery holding section 22. The controller 29 includes a processor and a memory, and controls the overall operation of the screwdriver 10. Furthermore, the controller 29 includes a switching circuit (inverter circuit) with switching elements such as transistors and FETs, and controls the operation of the motor 30 via PWM control. In this embodiment, the motor 30 is a so-called sensorless brushless motor. That is, the motor 30 does not have a sensor board equipped with a sensor (e.g., a Hall effect IC) for detecting the rotational angular position of the rotor 32. Therefore, the controller 29 acquires the voltage values ​​of the wiring for each phase of the three-phase power supply to the motor 30, performs prescribed signal processing based on the acquired voltage values ​​for each phase, and outputs a position detection signal. Moreover, the controller 29 detects the rotational angular position of the motor 30 based on the position detection signal for each phase.

[0051] like Figure 5 As shown, the motor shaft 31 is supported for rotation by a first bearing 50 and a second bearing 51 that are separated in the front-rear direction. The first bearing 50 is located at the front side relative to the rotor 32 and the stator 35, and the second bearing 51 is located at the rear side relative to the rotor 32 and the stator 35.

[0052] like Figure 5 As shown, a motor cooling fan 42 is mounted around the motor shaft 31. The motor cooling fan 42 is located between the rotor 32 and the second bearing 51 in the front-rear direction. The motor cooling fan 42 generates motor cooling air to cool the motor 30. In this embodiment, the motor cooling fan 42 is a so-called radial fan, which guides the motor cooling air drawn from the front of the motor 30 radially outward.

[0053] like Figures 1-3 As shown, the main housing 20 includes an air inlet 40 and an exhaust outlet 41 for motor cooling air. In this embodiment, four air inlets 40 and eight exhaust outlets 41 are formed on the left and right sides of the main housing 20, respectively. However, the number of air inlets 40 and exhaust outlets 41 is not particularly limited and can be any number, including one or more. Figure 6As shown, in this embodiment, the eight air inlets 40 are positioned approximately at the same location in the longitudinal direction, and are located at the front relative to the rotor 32 and stator 35. The sixteen exhaust ports 41 are positioned approximately at the same location in the longitudinal direction, and are located at the rear relative to the rotor 32 and stator 35.

[0054] like Figure 5 As shown, a portion of the reduction mechanism 24 and the first bearing 50 are supported by the bracket 60. Figure 8 As shown, the support 60 is a cylindrical component coaxially arranged with the rotation axis AX1. The support 60 includes a truncated cone cylindrical portion 61 and a gear retaining portion 62. The truncated cone cylindrical portion 61 is located at the rear of the support 60 and has a generally truncated cone shape with its outer diameter decreasing towards the rear. Inside the truncated cone cylindrical portion 61 is a bearing support portion 63 that supports the first bearing 50. The gear retaining portion 62 is located at the front of the support 60 and extends forward in a cylindrical shape. A portion of the reduction mechanism 24 is supported inside the gear retaining portion 62.

[0055] like Figure 8 As shown, the bracket 60 also has four screw bosses 64. The screw bosses 64 are located near the four corners of the bracket 60 in the vertical and horizontal directions. The screw bosses 64 are used to mount the bracket 60 onto a gearbox that houses the reduction mechanism 24. The bracket 60 also has four air passage slots 65 adjacent to the four screw bosses 64. The air passage slots 65 are formed on the truncated cone portion 61 and have a shape formed by cutting grooves on the outer surface of the truncated cone portion 61. The air passage slots 65 extend from the radially outer edge of the truncated cone portion 61 to the radially inner edge. Figure 6 as well as Figure 8 As shown, the air duct 65 has a curved surface, which defines the direction of the motor cooling air flowing from the air inlet 40 into the main housing 20 so that it flows along the curved surface of the air duct 65 toward the motor 30.

[0056] Figure 6The diagram shows an airflow path 43 for motor cooling air, oriented by the airflow channel 65. Motor cooling air flowing into the main housing 20 from the air inlet 40 gradually changes its flow direction towards the rear along the curved surface of the airflow channel 65, passing through the motor 30 from the front to the rear, and then its flow direction is changed radially outward by the motor cooling fan 42 before being discharged from the exhaust port 41. With this configuration, since the existing components of the screwdriver 10, namely the bracket 60, have the airflow channel 65, the path efficiency of the airflow path 43 can be optimized without introducing additional components. In other words, the airflow path 43 can be made a smooth path that does not obstruct the flow of motor cooling air, and the path can be shortened. Therefore, the pressure loss of the airflow path 43 can be reduced, and the motor 30 can be effectively cooled.

[0057] like Figure 6 As shown, in this embodiment, the air duct 65 directs the direction of the motor cooling air so that it passes through the gap between adjacent teeth 37 on which the coil 38 is wound (in other words, the gap between two adjacent coils 38 with different phases in the slot 39). With this configuration, since the motor cooling air comes into contact with the coil 38, which is a heat-generating component, the motor 30 can be effectively cooled. Furthermore, as... Figure 8 As shown, the airflow channel 65 has an airflow width that narrows from the upstream side of the motor cooling air towards the downstream side. In this embodiment, the gap between the two coils through which the motor cooling air passes is smaller than the air inlet 40. The airflow channel 65, with such an airflow width, is located between the air inlet 40 and this gap, thereby allowing the flow path width from the air inlet 40 to this gap to change smoothly. In other words, the generation of turbulence can be suppressed, and the motor cooling air can be effectively guided towards the gap between the two coils.

[0058] like Figure 6 As shown, in this embodiment, the air duct 65 is located at a position corresponding to the air inlet 40 in the front-rear direction. "Located at a corresponding position" means that the air duct 65 and the air inlet 40 at least partially overlap when viewed in a direction orthogonal to the front-rear direction, or, although not overlapping, the air duct 65 and the air inlet 40 are adjacent in the front-rear direction. According to this configuration, since the air inlet 40 and the air duct 65 are connected by the shortest path in the axial direction, the path of the motor cooling air from the air inlet 40 to the motor 30 is more efficient in the axial direction, enabling more effective cooling of the motor 30.

[0059] Similarly, as Figure 6As shown, in this embodiment, the air duct 65 is located circumferentially opposite to the air inlet 40. Furthermore, although not shown in the figure, the air duct 65 is located circumferentially opposite to the two adjacent air inlets 40. With this configuration, since the air inlets 40 and the air duct 65 are connected circumferentially by the shortest path, the path of the motor cooling air from the air inlets 40 to the motor 30 is more efficient circumferentially, enabling more effective cooling of the motor 30.

[0060] like Figure 8 As shown, the support 60 further includes a pair of sidewalls 66 facing each other in the vertical direction and a pair of sidewalls 67 facing each other in the horizontal direction. The sidewalls 66 and 67 extend rearward from the frustum-shaped cylindrical portion 61. The pair of sidewalls 66 are located near the upper and lower edges of the frustum-shaped cylindrical portion 61, respectively. The pair of sidewalls 67 are located near the right and left edges of the frustum-shaped cylindrical portion 61, respectively.

[0061] Sidewalls 66 extend between the inner edge of the upstream side of the air passage 65 located on the right side in the left-right direction and the inner edge of the upstream side of the air passage 65 located on the left side in the left-right direction. Sidewalls 67 extend between the lower edge of the upstream side of the air passage 65 located on the upper side in the vertical direction and the upper edge of the upstream side of the air passage 65 located on the lower side in the vertical direction. That is, sidewalls 66 and 67 surround the portion circumferentially free from the portion where the air passage 65 is formed. As a result, sidewalls 66 and 67 can guide the motor cooling air flowing in from the air inlet 40 through the air passage 65 and toward the motor 30. Therefore, the generation of turbulence can be further suppressed, and the motor 30 can be cooled more effectively.

[0062] As described above, since the screwdriver 10 uses a sensorless brushless motor as the motor 30, there is no need for space to install a sensor substrate. Therefore, compared to a screwdriver with a sensor substrate, the cooling air path of the motor can be made more efficient through the air duct 65 without increasing the size of the device in the front-to-back direction, thereby improving the cooling efficiency of the motor 30.

[0063] The screwdriver 110 of the second embodiment will now be described. Regarding the screwdriver 110, a portion of the configuration for cooling the motor 30 differs from that of the first embodiment. Referring hereafter... Figures 9-15 This section only describes the differences from the first embodiment. In the drawings of the second embodiment, the same components as in the first embodiment are given the same reference numerals as in the first embodiment. For example... Figure 9As shown, the screwdriver 110 includes a heat sink 170. Furthermore, instead of the bracket 60, stator 35, and front insulator 52 of the first embodiment, the screwdriver 110 includes a bracket 160, stator 135, and front insulator 152. The bracket 160, like in the first embodiment, supports a portion of the reduction mechanism 24 and the first bearing 50. Since the bracket 160 has a shape common to conventional screwdrivers that lacks the air passage 65, its detailed description is omitted here.

[0064] like Figure 15 As shown, the stator 135 includes an annular magnetic yoke 136 and six teeth 137. Each tooth 137 has a through hole 137a extending in the front-rear direction. The through hole 137a is an elongated hole with the radial direction as its length. Positioning members 137b, having a size and shape suitable for the through holes 137a, are inserted into the through holes 137a in a fitted state. Each positioning member 137b has a screw boss 137c extending in the front-rear direction. The screw boss 137c protrudes forward from the front edge of the magnetic yoke 136. As will be described in detail later, the positioning members 137b are used to position the relative positions of the motor 30 and the radiator 170.

[0065] like Figure 9 as well as Figure 11 As shown, the heat sink 170 is located between the bracket 160 and the stator 135 in the front-to-back direction. The space for the heat sink 170 is equivalent to the space for arranging the sensor substrate in the case that the screwdriver 10 is equipped with a sensor substrate.

[0066] like Figure 9 , 10 As shown in Figures 13 and 14, the radiator 170 includes a base 171, a plurality of heat sinks 172, and a mounting ring 173. The base 171 is a cylindrical portion located at the front of the radiator 170, comprising a conical cylindrical portion 171a and a cylindrical portion 171b. The conical cylindrical portion 171a has a shape in which its outer and inner diameters gradually decrease from the front to the rear. The cylindrical portion 171b extends cylindrically from the rear edge of the conical cylindrical portion 171a toward the rear. The plurality of heat sinks 172 are arranged to extend radially relative to the rotation axis AX1. The heat sinks 172 extend from the cylindrical portion 171b to the radially outer edge of the conical cylindrical portion 171a.

[0067] like Figure 13As shown, the circumferential separation distance of the multiple heat sinks 172 is not constant. Therefore, the multiple spaces formed between the multiple heat sinks 172 (multiple spaces circumferentially separated by the multiple heat sinks 172) include: a first space 177 with a relatively small spacing between two adjacent heat sinks 172, and a second space 178 with a relatively large spacing between two adjacent heat sinks 172. For example... Figure 14 As shown, the heat sinks 172 have different heights (widths in the front-to-back direction).

[0068] like Figure 13 as well as Figure 14 As shown, the mounting ring 173 has an annular shape and is connected to the radially outer side of a plurality of heat sinks 172. The mounting ring 173 is integrated with the plurality of heat sinks 172, for example, by welding. Figure 14 As shown, the mounting ring 173 connects to the plurality of heat sinks 172 near the end 176 of the heat sink 172 with the shortest height among the plurality of heat sinks 172. Figure 13 As shown, the mounting ring 173 includes a plurality of first mounting portions 174 and a plurality of second mounting portions 175. The first mounting portions 174 and the second mounting portions 175 are each a portion protruding radially outward and have through holes extending in the front-rear direction. The first mounting portions 174 and the second mounting portions 175 are arranged equally in the circumferential direction.

[0069] The radiator 170 is mounted on the front insulator 152 using a simple configuration utilizing the mounting ring 173. Specifically, as... Figure 9 , 10 As shown in Figure 12, screws 179a are inserted into the first mounting portions 174 of the mounting ring 173 and the screw bosses 152a of the front insulator 152 for tightening, thereby mounting the radiator 170 onto the front insulator 152. At this time, the screw bosses 137c of the stator 135 are respectively inserted into the positioning portions 152b of the front insulator 152. The positioning portions 152b are shaped with through holes or notches suitable for the shape of the screw bosses 137c. Screws 179b are inserted into the second mounting portions 175 of the mounting ring 173 and the screw bosses 137c of the stator 135 for tightening, thereby fixing the radiator 170 onto the stator 135. With this configuration, the radiator 170 is positioned relative to the stator 135. In particular, the relative rotational angle position of the radiator 170 relative to the stator 135 is positioned. In the state where the radiator 170 is installed, as Figure 12 As shown, the heat sink 172 is in contact with the coil 38 wound on the teeth 137 of the stator 135.

[0070] like Figure 12As shown, the radiator 170 is disposed on the airflow path 143 for motor cooling air, wherein the motor cooling air flows into the main housing 20 from the air inlet 40 and is discharged from the exhaust port 41. The motor cooling air flowing into the main housing 20 from the air inlet 40 passes through the space between the multiple heat sinks 172, namely the first space 177 and the second space 178, and flows radially inward. The flow direction is changed by the cylindrical portion toward the axial direction, passing through the motor 30 from the front to the rear, and the flow direction is changed by the motor cooling fan 42 toward the radial outward, and is discharged from the exhaust port 41.

[0071] Because the radiator 170 is in contact with the coil 38, heat exchange can be effectively carried out between the radiator 170 and the motor cooling air, thereby effectively cooling the motor 30. In particular, since the heat generated by the motor 30 is mainly generated in the coil 38, the contact between the radiator 170 and the coil 38 can further improve the cooling efficiency. Moreover, the radiator 170 having multiple heat sinks 172 can further improve the cooling efficiency.

[0072] Furthermore, according to the radiator 170, the multiple spaces between the multiple heat sinks 172, namely the first space 177 and the second space 178, function as part of the airflow path 143. This allows the motor cooling air to be effectively guided in the desired direction. Therefore, compared to a radiator 170 configured to obstruct the flow of motor cooling air, the pressure drop in the airflow path 143 can be reduced, and the motor 30 can be effectively cooled. Moreover, since the first space 177 and the second space 178 guide the motor cooling air radially, an improved cooling efficiency based on the multiple heat sinks 172 can be achieved, and the motor cooling air can be guided radially along an effective path through the multiple heat sinks 172.

[0073] Furthermore, the radiator 170 is positioned in the front-to-back direction corresponding to the air inlet 40. Thus, the relatively cool motor cooling air from the motor 30 comes into contact with the radiator 170. Therefore, the cooling efficiency based on the radiator 170 can be improved. Furthermore, as... Figure 12 As shown, the first space 177 and the second space 178, which function as airflow paths, are located in the front-to-back direction corresponding to the air inlet 40. Therefore, since the air inlet 40 and the first space 177 and the second space 178 are connected in the front-to-back direction with the shortest path, the path of the motor cooling air from the air inlet 40 to the motor 30 is more efficient in the front-to-back direction, and the motor 30 can be cooled more effectively.

[0074] Furthermore, according to radiator 170, such as Figures 12-14As shown, the end portion 176 of the heat sink 172 has a shape suitable for the coil 38. More specifically, the end portion 176 has a shape where the two edges in the radial direction protrude beyond the central portion and the central portion is concave, so as to adapt to the curved shape of the wound coil 38. According to this configuration, since the contact area between the multiple heat sinks 172 and the coil 38 is increased, the motor 30 can be cooled more effectively by means of the multiple heat sinks 172. In addition, as mentioned above, the heights of the multiple heat sinks 172 are different from each other in a way that adapts to the curved shape of the wound coil 38. Thus, as Figure 12 As shown, all heat sinks 172 can reliably contact the coil 38. This configuration increases the contact area between the multiple heat sinks 172 and the coil 38, thereby improving cooling efficiency. Furthermore, since the screwdriver 10 has a structure for positioning the relative rotational angle of the heat sink 170 relative to the stator 135, the end portion 176 can be more reliably fitted to the coil 38.

[0075] Furthermore, according to radiator 170, such as Figure 10 As shown, the second space 178, which is a larger space than the first space 177 (in other words, the second space 178 through which the motor cooling air passes most easily), is located in the circumferential direction at least at a position corresponding to the gap between the multiple teeth 137 on which the coil 38 is wound (in other words, the gap between two adjacent coils 38 with different phases in the slot 39). Figure 10 In this context, such a second space 178 is referred to as second space 178a. According to this configuration, more motor cooling air can come into contact with the coil 38, which is a heat-generating component, thereby further improving the cooling efficiency of the motor 30.

[0076] Furthermore, since the screwdriver 110 uses a sensorless brushless motor as the motor 30, there is no need for space to install a sensor substrate. By arranging the heat sink 170 in the space for the sensor substrate, the cooling efficiency of the motor 30 can be improved by the heat sink 170 without increasing the size of the device in the front-to-back direction, compared to a screwdriver with a sensor substrate.

[0077] While embodiments have been described above, these embodiments are provided for ease of understanding of the invention and are not intended to limit the invention. Modifications and improvements can be made to the invention without departing from its spirit, and the invention includes equivalent features. Furthermore, within the scope of solving at least a portion of the above-mentioned problems, or producing at least a portion of the effects, any combination or omission of the constituent elements described in the claims and specification is permitted.

[0078] Furthermore, the positional relationship between the air intake 40 and the exhaust port 41 in the front-rear direction can be reversed compared to the above-described embodiment. Specifically, the air intake 40 can be located at the rear relative to the motor 30, and the exhaust port 41 and the motor cooling fan 42 can be located at the front relative to the motor 30.

[0079] Alternatively, the radiator 170 can be positioned between the stator 135 and the motor cooling fan 42 in the front-to-back direction, or in any other way. When the radiator 170 is positioned behind the stator 135 and between the stator 135 and the motor cooling fan 42, the first space 177 and the second space 178 function as airflow paths that guide motor cooling air from the motor 30 toward the exhaust port 41.

[0080] Furthermore, in addition to contacting the coil 38, or alternatively, the heat sink 172 of the radiator 170 can also contact any part of the motor 30 (e.g., the stator 135). Moreover, for example, the radiator 170 can be modified to any shape and distribution as long as it is configured in the airflow path of the motor cooling air in a manner that contacts the motor 30.

[0081] Furthermore, the first and second embodiments can be combined. That is, the screwdriver can include a bracket 60 with an air passage 65 and a radiator 170. In this case, the radiator 170 can also be arranged in the front-to-back direction between the bracket 60 and the motor 30, changing its shape to not obstruct the flow of motor cooling air. Alternatively, in the screwdriver 10 according to the first embodiment, the radiator 170 can also be arranged between the motor 30 and the motor cooling fan 42.

[0082] The above-described embodiments are not limited to vibratory impact drills, but are also applicable to various fastening tools such as impact drills without vibration functions. Furthermore, the above-described embodiments are not limited to fastening tools, but are also applicable to various power tools equipped with brushless electric motors and motor cooling structures.

[0083] Furthermore, the motor cooling configuration with the aforementioned bracket 60 or heat sink 170 can also be applied to power tools with a motor having a sensor substrate that detects the rotational angle position of the rotor.

Claims

1. A power tool, characterized in that, The power tool includes: A brushless electric motor has a rotor, a stator, and a motor shaft; The first bearing is located on the first side relative to the rotor and the stator in the direction in which the motor shaft extends, i.e., in the axial direction, and supports the motor shaft so that it can rotate. A second bearing, located on the second side opposite to the first side in the axial direction, supports the motor shaft so that it can rotate; The housing has at least one air inlet on the first side and at least one exhaust outlet on the second side, and houses the electric motor. as well as A bracket that supports the first bearing; The bracket has at least one air duct that directs the direction of motor cooling air flowing into the housing from the at least one air inlet toward the brushless electric motor.

2. The power tool according to claim 1, characterized in that, The at least one air duct is located in the axial direction at a position corresponding to the at least one air inlet.

3. The power tool according to claim 1 or 2, characterized in that, The at least one air duct is located in the circumferential direction of the motor shaft at a position corresponding to the at least one air inlet.

4. The power tool according to any one of claims 1 to 3, characterized in that, The at least one air inlet has multiple air inlets. The at least one air duct has multiple air ducts located at multiple positions corresponding to the multiple air inlets.

5. The power tool according to any one of claims 1 to 4, characterized in that, The stator has multiple teeth with coils wound around them. The at least one air duct defines the direction of the motor cooling air so that it passes through the gap between the plurality of teeth on which the coil is wound.

6. The power tool according to claim 5, characterized in that, The at least one air duct has an air duct width that narrows from the upstream side of the motor cooling air toward the downstream side.

7. The power tool according to any one of claims 1 to 6, characterized in that, The stator has multiple teeth with coils wound around them. The power tool includes a radiator disposed in the airflow path of the motor cooling air and in contact with the coil wound on the plurality of teeth.

8. A power tool, characterized in that, The power tool includes: A brushless electric motor has a rotor, a stator with multiple teeth wound with coils, and a motor shaft with a rotation axis. The first bearing is located on the first side relative to the rotor and the stator in the direction extending from the axis of rotation, i.e., the axial direction, and supports the motor shaft so that it can rotate. The second bearing is located on the second side opposite to the first side in the axial direction and supports the motor shaft so that it can rotate; The housing has at least one air inlet on the first side and at least one exhaust outlet on the second side, and houses the brushless electric motor. as well as A radiator is disposed in the airflow path of motor cooling air flowing into the housing from the at least one air inlet and being discharged from the at least one air outlet, and is in contact with the coil wound on the plurality of teeth.

9. A power tool, characterized in that, The power tool includes: A brushless electric motor has a rotor, a stator with multiple teeth wound with coils, and a motor shaft with a rotation axis. The first bearing is located on the first side relative to the rotor and the stator in the direction extending from the axis of rotation, i.e., the axial direction, and supports the motor shaft so that it can rotate. The second bearing is located on the second side opposite to the first side in the axial direction and supports the motor shaft so that it can rotate; The housing has at least one air inlet on the first side and at least one exhaust outlet on the second side, and houses the brushless electric motor. as well as A radiator is configured in the airflow path for motor cooling air flowing into the housing from the at least one air inlet and out from the at least one exhaust outlet, and is in contact with the brushless electric motor. The radiator has multiple heat sinks. The multiple spaces between the multiple heat sinks function as air paths to direct the motor cooling air from the at least one air inlet to the brushless electric motor, or to direct the motor cooling air from the brushless electric motor to the at least one exhaust port.

10. The power tool according to claim 8, characterized in that, The heat sink includes a plurality of heat sink fins that are in contact with the coil wound around the plurality of teeth.

11. The power tool according to claim 9 or 10, characterized in that, The plurality of heat sinks are configured to extend radially relative to the axis of rotation. The spaces between the multiple heat sinks function as airflow paths that guide the motor cooling air radially along the axis of rotation.

12. The power tool according to claim 11, characterized in that, The plurality of spaces include: a first space in which the circumferential spacing between two adjacent heat sinks in the circumferential direction along the axis of rotation is a first distance, and a second space in which the circumferential spacing between two adjacent heat sinks in the circumferential direction is a second distance greater than the first distance. The second space is located at least in the circumferential direction at a position corresponding to the gap between the plurality of teeth on which the coil is wound.

13. The power tool according to claim 10, or claim 11 or 12 which is dependent on claim 10, characterized in that, Each of the plurality of heat sinks has an end portion having a shape suitable for winding the coil around the plurality of teeth.

14. The power tool according to any one of claims 8 to 13, characterized in that, The radiator is located in the axial direction at a position corresponding to the at least one air inlet.

15. The power tool according to any one of claims 8 to 14, characterized in that, The power tool includes an insulator that surrounds the coil wound around the plurality of teeth in a circumferential direction on the radially outer side. The radiator is fixed to the insulator with screws.

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