power tools

Abstract

The purpose of this disclosure is to improve the torque-corresponding control accuracy of power tools. The power tool (1) includes a holding section (11), a motor (15), a transmission mechanism (3), a torque detection section, a clutch mechanism (C1), and a control section. The holding section (11) is configured to hold the front end tool (12). The transmission mechanism (3) transmits the torque of the motor (15) to the holding section (11). The torque detection section detects the torque transmitted from the motor (15) to the holding section (11). The clutch mechanism (C1) can switch between a transmission state where the torque of the motor (15) is transmitted to the holding section (11) and a blocking state where the torque of the motor (15) is not transmitted to the holding section (11). When a predetermined condition related to the torque detected by the torque detection section is met, the control section switches the clutch mechanism (C1) from the transmission state to the blocking state.

Description

Technical Field

[0001] This disclosure relates generally to power tools, and more specifically to power tools including a clutch mechanism. Background Technology

[0002] Patent Document 1 discloses an electric rotary tool (electric tool). The electric tool includes a motor unit (motor) and a control circuit for controlling the motor unit. The control circuit calculates the tightening torque based on the drive current for the motor unit detected by a current detection means or the number of revolutions of the motor unit detected by a revolution detection means. When the tightening torque calculated thereby is equal to or greater than a preset tightening torque, the control circuit stops the operation of the motor unit.

[0003] In the power tool of Patent Document 1, the motor requires some time to stop rotating due to its inertial force. Therefore, the power tool can tighten fastening components such as screws, bolts, or nuts with a tightening torque greater than a preset tightening torque.

[0004] Existing technical documents

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2009-202317 Summary of the Invention

[0007] The purpose of this disclosure is to control power tools more precisely according to the corresponding torque (tightening torque).

[0008] An electric tool according to one aspect of this disclosure includes a holding unit, a motor, a transmission mechanism, a torque detection unit, a clutch mechanism, and a control unit. The holding unit holds a front-end tool thereon. The transmission mechanism transmits the torque from the motor to the holding unit. The torque detection unit detects the torque transmitted from the motor to the holding unit. The clutch mechanism can switch from a transmission state where the motor's torque is transmitted to the holding unit to a blocking state where the motor's torque is not transmitted to the holding unit, and vice versa. When a predetermined condition related to the torque detected by the torque detection unit is met, the control unit switches the clutch mechanism from the transmission state to the blocking state. Attached Figure Description

[0009] [ Figure 1 ] Figure 1 This is a schematic cross-sectional view of a power tool according to an exemplary embodiment.

[0010] [ Figure 2 ] Figure 2 This is the circuit diagram of the aforementioned power tool.

[0011] [ Figure 3 ] Figure 3This is a cross-sectional view of the clutch mechanism included in the aforementioned power tool and shown in a transmission state.

[0012] [ Figure 4 ] Figure 4 This is a cross-sectional view of the clutch mechanism included in the aforementioned power tool and shown in a stopped state.

[0013] [ Figure 5 ] Figure 5 This is a side view of the first rotating part of the aforementioned power tool. Detailed Implementation

[0014] The power tool according to an exemplary embodiment will now be described with reference to the accompanying drawings. Note that the embodiment described below is merely one exemplary embodiment among the various embodiments of this disclosure and should not be construed as limiting. Rather, the exemplary embodiment can be readily modified in various ways, depending on design choices or any other factors, without departing from the scope of this disclosure. The drawings referred to in the following description of the embodiments are schematic representations. Therefore, the scale of the dimensions (including thickness) of the various components illustrated in the drawings does not always reflect their actual size scale.

[0015] (Implementation Method)

[0016] (summary)

[0017] like Figure 1 and Figure 2 As shown, the power tool 1 according to this embodiment includes a holding part 11, a motor 15, a transmission mechanism 3, a torque detection unit 6, a clutch mechanism C1, and a control unit 49. The holding part 11 is configured to hold the front tool 12 thereon. The transmission mechanism 3 transmits the torque of the motor 15 to the holding part 11. The torque detection unit 6 detects the torque transmitted from the motor 15 to the holding part 11. The clutch mechanism C1 can switch from a transmission state where the torque of the motor 15 is transmitted to the holding part 11 to a blocking state where the torque of the motor 15 is not transmitted to the holding part 11, and vice versa. When a predetermined condition related to the torque detected by the torque detection unit 6 is met, the control unit 49 switches the clutch mechanism C1 from the transmission state to the blocking state. In this embodiment, the predetermined condition includes a condition where the torque detected by the torque detection unit 6 is greater than a threshold.

[0018] According to this embodiment, the control unit 49 switches the clutch mechanism C1 from the transmission state to the blocking state based on the torque detected by the torque detection unit 6. In other words, the clutch mechanism C1 is switched from the transmission state to the blocking state by electronic control executed by the control unit 49.

[0019] In parallel with the control clutch mechanism C1 switching from the transmission state to the blocking state, the control motor 15 stops rotating. However, due to inertial energy, the motor 15 continues to rotate for a period of time. In the blocking state, the motor 15 is disconnected from the holding part 11 and the front tool 12 held by the holding part 11, thereby suppressing the possibility that the holding part 11 and the front tool 12 will continue to rotate due to the inertial energy of the motor 15.

[0020] A clutch mechanism that switches from a transmitting state to a blocking state using the mechanical action of torque (rather than electronic control) is called a "mechanical clutch". According to a mechanical clutch, if the torque is greater than a threshold, the clutch switches from a transmitting state to a blocking state. However, according to a mechanical clutch, if the torque is much greater than the threshold, the clutch can reliably switch to a blocking state, but it may fail to switch to a blocking state at the instant the torque just reaches the threshold.

[0021] Conversely, according to this embodiment, the power tool 1 electronically switches the clutch mechanism C1 to the disengaged state based on the torque detected by the torque detection unit 6, thereby allowing the clutch mechanism C1 to switch to the disengaged state quickly. Switching the clutch mechanism C1 to the disengaged state suppresses the rotation of the retaining part 11 and the front tool 12. It can be seen that the power tool 1 according to this embodiment improves the accuracy of rotation control of the retaining part 11 and the front tool 12 corresponding to the torque. This reduces the possibility that fastening members such as screws, bolts, or nuts will be tightened with excessive torque.

[0022] The clutch mechanism C1 according to this embodiment includes an electromagnet 91, and switches between a transmission state and a blocking state by changing the energization state of the electromagnet 91. However, the clutch mechanism C1 does not necessarily have this configuration including an electromagnet 91. Alternatively, the clutch mechanism C1 may also be a mechanical clutch used with an actuator. In this case, the actuator can drive the mechanical clutch under the electronic control of the control unit 49 to switch the mechanical clutch from the transmission state to the blocking state. The power tool 1 may also include such an actuator. The actuator may include, for example, a cylinder that extends and retracts under the control of the control unit 49.

[0023] (detail)

[0024] (1) Overall Structure

[0025] The construction of the power tool 1 will now be described in more detail. In the following description of the embodiment, the direction along which the motor 15 and the transmission mechanism 3 are arranged side by side is defined as the "left-right direction," with the transmission mechanism 3 considered to be located to the right of the motor 15 and the motor 15 considered to be located to the left of the transmission mechanism 3. Note that these definitions should not be interpreted as specifying the direction in which the power tool 1 should be used.

[0026] Power tool 1 can be used as, for example, an electric screwdriver, drill, drill-screwdriver, or wrench. Alternatively, power tool 1 can also be used as, for example, an electric saw, planer, grinder, hole saw, or grinder. In the following description of exemplary embodiments, the use of power tool 1 as a screwdriver for tightening fastening components such as screws, bolts, or nuts will be described as a typical example.

[0027] like Figure 1 As shown, the power tool 1 includes a housing 2, a motor 15, a power supply unit B1, an operating component 16, a power control block 4, a drive circuit unit 5, a clutch mechanism C1, a transmission mechanism 3, a chuck 10, and a front-end tool 12.

[0028] (2) Shell

[0029] The housing 2 includes a main body 21, a gripping part 22, and an attachment part 23. The main body 21 has a cylindrical shape. The gripping part 22 protrudes from the side of the main body 21. The gripping part 22 also has a cylindrical shape. The attachment part 23 is provided at the end of the gripping part 22. In other words, the main body 21 and the attachment part 23 are connected to each other via the gripping part 22. The power supply unit B1 is detachably attached to the attachment part 23.

[0030] The drive circuit section 5, motor 15, clutch mechanism C1, and transmission mechanism 3 are housed in the main body 21. The grip section 22 holds the operating member 16. The power control block 4 is housed in the attachment section 23.

[0031] (3) Chuck

[0032] like Figure 1 As shown, the chuck 10 includes an outer mounting part 101 and a retaining part 11.

[0033] The outer part 101 has a cylindrical shape. The outer part 101 is attached to the front end of the main body 21. The retaining part 11 is arranged inside the outer part 101. The outer part 101 rotatably holds the retaining part 11.

[0034] The retaining part 11 has a cylindrical shape. The retaining part 11 is mounted on the output shaft of the transmission mechanism 3. The retaining part 11 rotates using torque transmitted from the motor 15 via the transmission mechanism 3. The front-end tool 12 is detachably attached to the retaining part 11. The front-end tool 12 rotates together with the retaining part 11. The power tool 1 rotates the front-end tool 12 by rotating the retaining part 11 using the torque of the motor 15.

[0035] (4) Front-end tools

[0036] For example, the front-end tool 12 (also called a "bit") can be, for example, a screwdriver bit or a drill bit. One of various types of front-end tools 12 is selected according to the intended use and attached to the retaining part 11 for that intended purpose.

[0037] In this embodiment, the front-end tool 12 can be replaced for its intended use. However, the front-end tool 12 does not necessarily have to be replaceable. Alternatively, for example, the power tool 1 could be a power tool system designed to allow only the use of a specific type of front-end tool 12.

[0038] (5) Transmission mechanism

[0039] like Figure 1 As shown, the transmission mechanism 3 is disposed between the holding part 11 and the motor 15. The transmission mechanism 3 includes multiple gears. The transmission mechanism 3 transmits the torque of the motor 15 to the holding part 11. More specifically, the transmission mechanism 3 receives the torque of the motor 15 and transmits it to the holding part 11. The transmission mechanism 3 reduces the rotational speed of the motor 15. More specifically, the transmission mechanism 3 reduces the rotational speed of the motor 15 at a predetermined reduction ratio and outputs rotational force at the thus reduced rotational speed. That is, the rotational speed of the output shaft of the transmission mechanism 3 is lower than the rotational speed of the input shaft.

[0040] The transmission mechanism 3 includes multiple gears, including gear 31. Gear 31 meshes with gear 83 (described later) provided for clutch mechanism C1. In this way, the transmission mechanism 3 receives torque from clutch mechanism C1.

[0041] (6) Motor

[0042] Motor 15 can be, for example, a brushless motor. Specifically, motor 15 according to this embodiment is a synchronous motor. More specifically, motor 15 can be a permanent magnet synchronous motor (PMSM). Figure 2 As shown, the motor 15 includes a rotor 13 with permanent magnets 131 and a stator 14 with motor coils 141. The rotor 13 also includes a rotating shaft 132 for outputting torque (see reference). Figure 1 Due to the electromagnetic interaction between the motor coil 141 and the permanent magnet 131, the rotor 13 rotates relative to the stator 14.

[0043] (7) Clutch mechanism

[0044] like Figure 1 As shown, the clutch mechanism C1 is disposed between the holding part 11 and the motor 15. More specifically, the clutch mechanism C1 is disposed between the motor 15 and the transmission mechanism 3. When the clutch mechanism C1 is in the transmission state, it transmits the torque of the motor 15 to the transmission mechanism 3. As a result, the torque of the motor 15 is transmitted to the holding part 11 via the clutch mechanism C1 and the transmission mechanism 3. On the other hand, when the clutch mechanism C1 is in the disengaged state, it does not transmit the torque of the motor 15 to the transmission mechanism 3. As a result, the torque of the motor 15 is not transmitted to the holding part 11.

[0045] Clutch mechanism C1 includes a first rotating part 71, a second rotating part 81, and at least one (e.g., in...) Figure 1 (Two connecting parts 9 are shown in the example shown). The first rotating part 71 rotates with the motor 15. The holding part 11 is directly or indirectly connected to the second rotating part 81. In this embodiment, the holding part 11 is indirectly connected to the second rotating part 81 via the transmission mechanism 3.

[0046] The clutch mechanism C1 is in a transmission state where the first rotating part 71 and the second rotating part 81 are connected to each other via at least one connecting part 9 so that the torque of the first rotating part 71 is transmitted to the second rotating part 81. The clutch mechanism C1 is in a disengagement state where the first rotating part 71 and the second rotating part 81 are separated from each other so that the torque of the first rotating part 71 is not transmitted to the second rotating part 81.

[0047] like Figure 3 and Figure 4 As shown, the clutch mechanism C1 also includes a stator 70, a first bearing 72, and a second bearing 82.

[0048] The stator portion 70 is fixed to the housing 2. The stator portion 70 has a cylindrical shape. The first bearing 72 is fixed to the inner surface of the stator portion 70.

[0049] The first rotating part 71 is held by the first bearing 72. This allows the first rotating part 71 to rotate freely relative to the stator part 70. The first rotating part 71 is connected to the rotating shaft 132 of the motor 15. This causes the first rotating part 71 to rotate as the motor 15 rotates. The rotating shaft 132 is configured to coincide with the central axis of the first rotating part 71.

[0050] The first rotating part 71 includes a cylindrical member 711 and a opposing member 712. The cylindrical member 711 has a cylindrical shape. The opposing member 712 is connected to the front end of the cylindrical member 711. The opposing member 712 has a disc-shaped shape. The opposing member 712 faces the second rotating part 81. The opposing member 712 has a plurality of (e.g., on its surface facing the second rotating part 81) Figure 3 The example shown in the illustration has two first recesses 713.

[0051] The second rotating part 81 is arranged to the right of the first rotating part 71. The second rotating part 81 is disposed between the first rotating part 71 and the transmission mechanism 3. The first rotating part 71 is disposed between the motor 15 and the second rotating part 81.

[0052] The second rotating part 81 has a disk shape. The second rotating part 81 has multiple (e.g., on its surface facing the first rotating part 71) a plurality of... Figure 3 The example shown has two second recesses 813.

[0053] The second bearing 82 is fixed to the second rotating part 81. The second bearing 82 holds the rotating shaft 132 of the motor 15. When the clutch mechanism C1 is in the disengaged state, the rotating shaft 132 rotates relative to the second rotating part 81. On the other hand, when the clutch mechanism C1 is in the engaged state, the second rotating part 81 rotates at the same number of revolutions as the rotating shaft 132.

[0054] The clutch mechanism C1 also includes a gear 83. The gear 83 is integrally formed with the second rotating part 81. The gear 83 is disposed on the opposite surface of the second rotating part 81 to the first rotating part 71. The gear 83 and the gear 31 of the transmission mechanism 3 (see reference) Figure 1 The two parts engage, thereby transmitting the torque of the second rotating part 81 to the transmission mechanism 3.

[0055] The first rotating part 71 and the second rotating part 81 face each other. Specifically, the first rotating part 71 and the second rotating part 81 face each other with a narrow gap between them. Alternatively, the first rotating part 71 and the second rotating part 81 may contact each other in at least some areas. Optionally, the power tool 1 may also include a spacer. In this case, the spacer may be fixed to the first rotating part 71 or the second rotating part 81 and sandwiched between the first rotating part 71 and the second rotating part 81.

[0056] The rotating shaft 132 of the motor 15 can be used as the input shaft of the clutch mechanism C1. That is, the rotating shaft 132 not only serves as a component of the motor 15, but also as a component of the clutch mechanism C1. The rotating shaft 132 transmits the torque of the motor 15 to the first rotating part 71.

[0057] Gear 83 serves as the output shaft of clutch mechanism C1. Gear 83 transmits the rotational force of the second rotating part 81 to the holding part 11. More specifically, gear 83 transmits the rotational force of the second rotating part 81 to the holding part 11 via transmission mechanism 3.

[0058] Gear 83 (output shaft) is coaxially configured with rotating shaft 132 (input shaft). This suppresses axial misalignment between the input and output shafts.

[0059] The plurality of first recesses 713 provided for the first rotating part 71 correspond one-to-one with the plurality of second recesses 813 provided for the second rotating part 81. When the clutch mechanism C1 is in the transmission state, the corresponding first recesses 713 and second recesses 813 face each other.

[0060] Each of the plurality of connecting parts 9 includes an electromagnet 91 and a permanent magnet block 92. The electromagnet 91 includes magnetic poles 911 and coils 912. The permanent magnet block 92 includes a permanent magnet 921 and an elastic member 922.

[0061] In other words, the connecting part 9 includes an electromagnet 91 and a permanent magnet 921, and the electromagnet 91 includes magnetic poles 911. The magnetic poles 911 are made of a magnetic material such as iron (e.g., electromagnetic soft iron). The permanent magnet 921 faces the magnetic poles 911.

[0062] Magnetic pole 911 is held by the first rotating part 71. Permanent magnet 921 is held by the second rotating part 81. Control part 49 (see reference) Figure 2 The clutch mechanism C1 can be switched from the transmission state to the blocking state by changing the energization state of the electromagnet 91, and vice versa. That is, the electromagnetic force acting between the magnetic pole 911 and the permanent magnet 921 changes according to the energization state of the coil 912 of the electromagnet 91, and the clutch mechanism C1 switches between the transmission state and the blocking state accordingly.

[0063] More specifically, when the control unit 49 executes control to make the intensity of the current supplied to the coil 912 equal to or greater than a predetermined intensity, an electromagnetic repulsive force is generated between the magnetic pole 911 and the permanent magnet 921, thereby creating a blocking state in which the first rotating part 71 and the second rotating part 81 are separated from each other. In other words, the control unit 49 switches the clutch mechanism C1 from the transmission state to the blocking state by generating an electromagnetic repulsive force between the magnetic pole 911 and the permanent magnet 921.

[0064] On the other hand, when the control unit 49 keeps the coil 912 unenergized, or if the intensity of the current supplied to the coil 912 is less than a predetermined intensity, the electromagnetic repulsion force is relatively small. Thus, the torque maintaining the first rotating part 71 is transmitted to the second rotating part 81.

[0065] It can be seen that when the electromagnet 91 (coil 912) is energized with a current of equal or greater intensity than a predetermined intensity, the clutch mechanism C1 enters the blocking state. When the electromagnet 91 (coil 912) is not energized, or if the electromagnet 91 (coil 912) is energized with a current of less than a predetermined intensity, the clutch mechanism C1 enters the transmitting state.

[0066] The multiple magnetic poles 911 of the multiple electromagnets 91 correspond one-to-one with the multiple first recesses 713 of the first rotating part 71. Each magnetic pole 911 is inserted into a corresponding first recess 713. The multiple coils 912 of the multiple electromagnets 91 are fixed to the stator part 70. The multiple coils 912 are arranged on the left side of the area where the multiple electromagnets 91 are arranged.

[0067] Multiple permanent magnet blocks 92 correspond one-to-one with multiple second recesses 813 of the second rotating part 81. The permanent magnet 921 and elastic member 922 of each permanent magnet block 92 are inserted into a corresponding second recess 813. The permanent magnet 921 has a cylindrical shape. The second rotating part 81 has a shaft portion 84, each shaft portion 84 protruding from the bottom surface of a corresponding second recess 813 and inserted into a corresponding permanent magnet 921. The permanent magnet 921 is movable along the shaft portion 84.

[0068] An elastic member 922 is arranged on the right side of the permanent magnet 921. The elastic member 922 is positioned between the bottom of the second recess 813 and the permanent magnet 921. The elastic member 922 is a compression spring. More specifically, the elastic member 922 can be a compression coil spring. The elastic member 922 is configured to surround the shaft portion 84. The elastic member 922 applies a leftward force to the permanent magnet 921. That is, the elastic member 922 applies a force toward the permanent magnet 921 towards the first rotating portion 71.

[0069] Multiple connecting parts 9 are configured to surround at least one of the rotating shaft 132 (input shaft) and gear 83 (output shaft). Figure 5 The diagram illustrates the first rotating section 71 as viewed from the right. Multiple magnetic poles 911 of the multiple connecting sections 9 are arranged in a circular shape to surround the rotating shaft 132. Similarly, multiple coils 912 (see reference) Figure 3 The connecting parts 9 are also configured in a circular shape to surround the rotating shaft 132. Note that if multiple connecting parts 9 surround at least one of the rotating shaft 132 (input shaft) and the gear 83 (output shaft), the number of connecting parts 9 provided can be equal to or greater than 3.

[0070] Multiple permanent magnet blocks 92 are also arranged in a circular shape to surround the rotation shaft 132. In addition, when viewed in the left-right direction, the multiple permanent magnet blocks 92 are arranged in a circular shape to surround the gear 83.

[0071] Next, we will explain how the clutch mechanism C1 operates.

[0072] When coil 912 is not energized or is energized with a current less than a predetermined intensity, clutch mechanism C1 maintains the transmission state. When clutch mechanism C1 is in the transmission state, such as... Figure 3As shown, a permanent magnet 921 is inserted into the first recess 713 of the first rotating part 71. At this time, each permanent magnet 921 is in contact with a corresponding magnetic pole 911. More specifically, the permanent magnet 921 is sandwiched between the magnetic pole 911 and a corresponding elastic member 922. The elastic energy applied by the elastic member 922 holds the permanent magnet 921 in the same position. In each of the plurality of connecting parts 9, the permanent magnet 921 is inserted into the first recess 713 so that the first rotating part 71 and the second rotating part 81 are connected to each other. Thus, when the clutch mechanism C1 is in the transmission state, the first rotating part 71 and the second rotating part 81 rotate at the same number of revolutions.

[0073] In this way, the permanent magnet 921 is fitted into the first recess 713. That is, the clutch mechanism C1 has a fitting structure formed by the first recess 713 and the permanent magnet 921. When the clutch mechanism C1 is in the transmission state, the fitting structure connects the first rotating part 71 and the second rotating part 81 to each other through fitting.

[0074] When the clutch mechanism C1 is in the transmission state, if a current with an intensity equal to or greater than a predetermined intensity flows through the coil 912, an electromagnetic repulsive force is generated between the magnetic pole 911 and the permanent magnet 921, causing the permanent magnet 921 to move to the right. That is, the permanent magnet 921 disengages from the magnetic pole 911 when the elastic member 922 is compressed, thus... Figure 4 The first recess 713 of the first rotating part 71 is removed. More specifically, the permanent magnet 921 retracts into the second recess 813 of the second rotating part 81. In each connecting part 9, removing the permanent magnet 921 from the first recess 713 disengages the first rotating part 71 and the second rotating part 81 from each other. That is, the clutch mechanism C1 becomes blocked.

[0075] When the clutch mechanism C1 is in the disengaged state, only the first rotating part 71 rotates, while the second rotating part 81 does not rotate, along with the rotation of the rotating shaft 132 of the motor 15. Furthermore, the holding part 11 and the front tool 12, which are connected to the second rotating part 81 via the transmission mechanism 3, also do not rotate. More specifically, when the clutch mechanism C1 switches from the transmission state to the disengaged state, the second rotating part 81, the multiple gears of the transmission mechanism 3, the holding part 11, and the front tool 12 continue to rotate for a period of time due to inertial energy, but will immediately stop rotating when the inertial energy is exhausted.

[0076] As can be seen from the foregoing description, each of the plurality of connecting parts 9 also includes an elastic member 922 that stores elastic energy when the electromagnet 91 is energized. That is, the permanent magnet 921 compresses the elastic member 922, causing the elastic member 922 to store elastic energy. The elastic energy of the elastic member 922 switches the clutch mechanism C1 to a transmission state or a blocking state. In this embodiment, the elastic energy of the elastic member 922 switches the clutch mechanism C1 from the blocking state to the transmission state. That is, by adjusting the rotation angles of the first rotating part 71 and the second rotating part 81 so that each permanent magnet 921 faces the magnetic pole 911, the permanent magnet 921 moves due to the elastic energy of the elastic member 922 and inserts into the first recess 713. This means that the clutch mechanism C1 has switched from the blocking state to the transmission state.

[0077] Alternatively, the rotation angle of the first rotating part 71 and the second rotating part 81 can be adjusted by, for example, by allowing a user to operate an operating part connected to the first rotating part 71 or the second rotating part 81. Alternatively, the rotation angle can be adjusted by allowing a user to actuate a drive mechanism that uses a power source such as electricity to rotate the first rotating part 71 or the second rotating part 81. In this case, the rotation speed of the first rotating part 71 or the second rotating part 81 driven by the drive mechanism is lower than the rotation speed of the motor 15.

[0078] (8) Power Supply Section

[0079] Figure 1 The power supply unit B1 shown supplies current to the motor 15, electromagnet 91, and power control block 4, for example. For example, the power supply unit B1 can be a battery pack. The power supply unit B1 may include, for example, a single secondary battery or multiple secondary batteries.

[0080] (9) Operating components

[0081] The operating member 16 receives the operation to control the rotation of the motor 15. The motor 15 can be selectively actuated (connected or disconnected) by pulling the operating member 16. Furthermore, the rotational speed of the motor 15 can be adjusted based on the manipulation variable of pulling the operating member 16 (i.e., based on the depth to which the operating member 16 is pulled). Consequently, the rotational speed of the holding section 11 can be adjusted based on the manipulation variable of pulling the operating member 16. The larger this manipulation variable, the higher the rotational speed of the motor 15. The power control block 4 starts or stops the rotation of the motor 15 based on the manipulation variable of pulling the operating member 16, and controls the rotational speed of the motor 15.

[0082] (10) Drive circuit section

[0083] like Figure 1As shown, the drive circuit section 5 is arranged adjacent to the motor 15. The drive circuit section 5 supplies power to the motor 15 under the control of the power control block 4. The drive circuit section 5 includes an inverter circuit section 51 (see reference 51). Figure 2 The inverter circuit section 51 converts the power supplied from the power supply section B1 into power with the desired voltage, and supplies the converted power to the motor 15.

[0084] (11) Motor rotation measuring unit

[0085] The power tool 1 also includes a motor rotation measuring unit 27 (see reference). Figure 2 The motor rotation measuring unit 27 measures the rotation angle of the motor 15 (rotor 13). For example, a photoelectric encoder or a magnetic encoder can be used as the motor rotation measuring unit 27.

[0086] (12) Power control block

[0087] like Figure 2 As shown, the power control block 4 is used in conjunction with the inverter circuit section 51 and controls the operation of the motor 15 through feedback control.

[0088] The power control block 4 includes a computer system comprising one or more processors and memory. At least some functions of the power control block 4 are performed by causing the processors of the computer system to execute programs stored in the memory of the computer system. The programs can be stored in memory. The programs can also be downloaded via telecommunications lines such as the Internet, or provided after being stored on a non-transitory storage medium such as a memory card.

[0089] The power control block 4 includes an instruction value generation unit 41, a speed control unit 42, a current control unit 43, a first coordinate transformer 44, a second coordinate transformer 45, a flux control unit 46, an estimation unit 47, a control unit 49, and a calculation unit 63. Note that these constituent elements of the power control block 4 merely represent the functions to be performed by the power control block 4 and do not always have a physical structure.

[0090] Power tool 1 also includes multiple (e.g., in) Figure 2 The illustrated example shows two current sensors 61 and 62. Each of the multiple current sensors 61 and 62 includes, for example, a Hall element current sensor or a shunt resistor element. The multiple current sensors 61 and 62 measure current from the power supply unit B1 (see reference). Figure 1 The current is supplied to the motor 15 via the inverter circuit section 51. In this embodiment, three-phase current (i.e., U-phase current, V-phase current, and W-phase current) is supplied to the motor 15. Multiple current sensors 61 and 62 measure the current of at least two phases. Figure 2 In the middle, current sensor 61 measures the U-phase current to output the current measurement value i.u 1. And the current sensor 62 measures the V-phase current to output the current measurement value i. v 1.

[0091] The estimation unit 47 obtains the time derivative of the rotation angle θ1 of the motor 15 measured by the motor rotation measurement unit 27, and calculates the angular velocity ω1 of the motor 15.

[0092] The torque detection unit 6 includes a current measurement unit 60 and a calculation unit 63. The current measurement unit 60 consists of two current sensors 61 and 62 and a second coordinate transformer 45. The current measurement unit 60 acquires the d-axis current (excitation current) and the q-axis current (torque current), both of which are supplied to the motor 15. That is, the current measurement value id1 of the d-axis current and the current measurement value iq1 of the q-axis current are calculated by transforming the two-phase currents measured by the two current sensors 61 and 62 using the second coordinate transformer 45.

[0093] The second coordinate transformer 45 uses the rotation angle θ1 of the motor 15 measured by the motor rotation measuring unit 27 to measure the current values ​​i measured by multiple current sensors 61 and 62. u 1. i v 1. Perform coordinate transformation to calculate the current measurement values ​​id1 and iq1. That is, the second coordinate transformer 45 will transform the current measurement values ​​i corresponding to the two-phase currents. u 1. i v 1 is transformed into the current measurement value id1 corresponding to the magnetic field component (d-axis current) and the current measurement value iq1 corresponding to the torque component (q-axis current).

[0094] The calculation unit 63 calculates the torque to be transmitted from the motor 15 to the holding unit 11 based on the torque current (current measurement value iq1) measured by the current measurement unit 60. The calculation unit 63 calculates the torque to be transmitted from the motor 15 to the holding unit 11 by, for example, multiplying the current measurement value iq1, which represents the torque current, by a predetermined constant.

[0095] As used herein, the torque to be transmitted from the motor 15 to the holding part 11 may be the torque of the motor 15, the torque of the holding part 11, or the torque of a component (which may be the clutch mechanism C1 or the transmission mechanism 3) used to transmit the torque of the motor 15 to the holding part 11.

[0096] Control unit 49 switches the coil 912 of electromagnet 91 (see reference) Figure 1 The energized state of the clutch mechanism C1 allows the control unit 49 to switch the clutch mechanism C1 from the transmission state to the blocking state.

[0097] When a predetermined condition related to the torque detected by the torque detection unit 6 (hereinafter referred to as "detected torque") is met, the control unit 49 switches the clutch mechanism C1 from the transmission state to the blocking state. Additionally, when a predetermined condition is met, the control unit 49 stops the motor 15 from rotating. The predetermined condition may include a condition where the detected torque is greater than a threshold value.

[0098] The predetermined condition can be, for example, the detected torque being greater than a threshold. Alternatively, the predetermined condition can also be, for example, the detected torque remaining greater than a threshold for at least a predetermined time. Still alternatively, the torque detection unit 6 can detect torque at predetermined time intervals, and the predetermined condition can also be, for example, the number of times the detected torque is greater than the threshold being at least a predetermined number.

[0099] When the clutch mechanism C1 is in the disengaged state and the motor 15 is rotating, the control unit 49 does not perform control to switch the clutch mechanism C1 from the disengaged state to the transmission state. That is, even after the clutch mechanism C1 has been disengaged, the control unit 49 maintains a current in the coil 912 with an intensity equal to or greater than a predetermined intensity. This allows the disengaged state to be maintained and prevents the front tool 12 from rotating until the motor 15 stops rotating.

[0100] The command value generation unit 41 generates a command value cω1 for the angular velocity of the motor 15. The command value generation unit 41 receives, for example, a command value cω0 from the operating member 16 corresponding to the operation of pulling the operating member 16. The command value generation unit 41 generates a command value cω1 corresponding to the command value cω0. That is, as the operated variable increases, the command value generation unit 41 correspondingly increases the command value cω1 for the angular velocity.

[0101] The speed control unit 42 generates a command value ciq1 based on the difference between the command value cω1 generated by the command value generation unit 41 and the angular velocity ω1 calculated by the estimation unit 47. The command value ciq1 is a command value that specifies the intensity of the torque current (q-axis current) of the motor 15. The power control block 4 executes control to make the torque current (q-axis current) to be supplied to the motor coil 141 closer to the command value ciq1. The speed control unit 42 determines the command value ciq1 in a manner that makes the difference between the command value cω1 and the angular velocity ω1 less than a predetermined value.

[0102] The flux control unit 46 generates a command value cid1 based on the angular velocity ω1 calculated by the estimation unit 47 and the current measurement value iq1. The command value cid1 is a command value that specifies the intensity of the excitation current (d-axis current) of the motor 15. That is, the power control block 4 controls the operation of the motor 15 so that the excitation current (d-axis current) to be supplied to the motor coil 141 is closer to the command value cid1.

[0103] In this embodiment, the command value cid1 generated by the flux control unit 46 may be, for example, a command value that sets the intensity of the excitation current to zero. The flux control unit 46 may generate the command value cid1 to constantly set the intensity of the excitation current to zero, or it may generate the command value cid1 as needed to set the intensity of the excitation current to a value greater than or less than zero. When the command value cid1 of the excitation current is less than zero, a negative excitation current (i.e., a flux weakening current) flows through the motor 15, thereby weakening the flux driving the rotor 13.

[0104] The current control unit 43 generates a command value cvd1 based on the difference between the command value cid1 generated by the flux control unit 46 and the current measurement value id1 calculated by the second coordinate transformer 45. The command value cvd1 is a command value that specifies the intensity of the d-axis voltage of the motor 15. The current control unit 43 determines the command value cvd1 in a manner that makes the difference between the command value cid1 and the current measurement value id1 less than a predetermined value.

[0105] Furthermore, the current control unit 43 generates a command value cvq1 based on the difference between the command value ciq1 generated by the speed control unit 42 and the current measurement value iq1 calculated by the second coordinate transformer 45. The command value cvq1 is a command value specifying the intensity of the q-axis voltage of the motor 15. The current control unit 43 generates the command value cvq1 in a manner that makes the difference between the command value ciq1 and the current measurement value iq1 less than a predetermined value.

[0106] The first coordinate transformer 44 performs coordinate transformation on the command values ​​cvd1 and cvq1 based on the rotation angle θ1 of the motor 15 measured by the motor rotation measuring unit 27, in order to calculate the command value cv u 1. CV v 1. CV w 1. Specifically, the first coordinate transformer 44 transforms the command value cvd1 for the magnetic field component (d-axis voltage) and the command value cvq1 for the torque component (q-axis voltage) into command values ​​cv corresponding to the three-phase voltages. u 1. CV v 1. CV w 1. Instruction value cv u 1 corresponds to the U-phase voltage, command value cv v 1 corresponds to phase V voltage, and the command value cv w 1 corresponds to the W-phase voltage.

[0107] Inverter circuit section 51 will correspond to the command value cv respectively u 1. CV v 1. CV w The three-phase voltage of 1 is supplied to the motor 15. The inverter circuit section 51 controls the power to be supplied to the motor 15, for example, by performing pulse width modulation (PWM) control.

[0108] Torque is generated by driving the motor 15 with the power (three-phase voltage) supplied from the inverter circuit section 51.

[0109] As a result, the power control block 4 controls the excitation current flowing through the motor coil 141, so that the excitation current has an intensity corresponding to the command value cid1 generated by the flux control unit 46. In addition, the power control block 4 also controls the angular velocity of the motor 15, so that the angular velocity of the motor 15 becomes the angular velocity corresponding to the command value cω1 generated by the command value generation unit 41.

[0110] The power to be supplied to motor 15 is controlled by power control block 4 using vector control. Vector control is a motor control technique that decomposes the current to be supplied to motor coil 141 into a current component that generates magnetic flux (excitation current) and a current component that generates torque (torque current), and these current components are controlled independently of each other.

[0111] The current measurement value iq1 used for torque current is used to perform vector control and calculate the torque to be transmitted from motor 15 to holding part 11. This allows a portion of the circuit used for performing vector control and a portion of the circuit used for calculating torque to be shared. This helps to reduce the area and size of the circuit set up for power tool 1 and reduce the cost required for the circuit.

[0112] (Variations on the implementation method)

[0113] Next, variations of exemplary embodiments will be listed one by one. Note that the variations described below can be used in combination as appropriate.

[0114] The front-end tool 12 need not be one of the constituent components of the power tool 1.

[0115] The power supply unit B1 need not be one of the constituent components of the power tool 1.

[0116] The elastic member 922 can also be a tension spring (e.g., a tension coil spring). In this case, the control unit 49 maintains the clutch mechanism C1 in the transmission state by generating an electromagnetic attraction between the magnetic pole 911 and the permanent magnet 921. When the control unit 49 reduces or removes the electromagnetic attraction, the elastic energy of the tension spring causes the permanent magnet 921 to move out of the first recess 713, thereby switching the clutch mechanism C1 from the transmission state to the disengagement state.

[0117] In the exemplary embodiment described above, the first rotating part 71 and the second rotating part 81 are connected to each other and rotate at the same number of revolutions by inserting the permanent magnet 921 into the first recess 713 of the first rotating part 71. However, the permanent magnet 921 need not be inserted into the first recess 713. Alternatively, the first rotating part 71 and the second rotating part 81 may also be connected to each other simply by magnetic attraction acting between the permanent magnet 921 and the magnetic pole 911.

[0118] The holding part 11 can be integrally formed with a part of the transmission mechanism 3.

[0119] The first rotating part 71 can be an integral part of the rotor 13 of the motor 15.

[0120] In the exemplary embodiments described above, the fitting structure for connecting the first rotating part 71 and the second rotating part 81 to each other by fitting is formed by a first recess 713 and a permanent magnet 921. However, this is merely an example and should not be construed as limiting. According to a first alternative example, the fitting structure may also be formed by a recess (first recess 713 or other recesses) provided for the first rotating part 71 and a protrusion provided for the second rotating part 81. According to a second alternative example, the fitting structure may also be formed by a recess (second recess 813 or other recesses) provided for the second rotating part 81 and a protrusion provided for the first rotating part 71. According to the first or second alternative example, the recess and the protrusion only need to fit together by changing the relative positions of the first rotating part 71 and the second rotating part 81 using the electromagnetic force acting between the electromagnet 91 and the permanent magnet 921.

[0121] The clutch mechanism C1 need not be configured as described in the exemplary embodiment. Alternatively, the clutch mechanism C1 may be configured, for example, between the transmission mechanism 3 and the holding part 11.

[0122] The torque detection unit 6 can be a torque sensor. For example, a resistance strain sensor or a magnetostrictive strain sensor can be used as the torque sensor.

[0123] (Summarize)

[0124] The above exemplary embodiments and variations thereof are specific implementations of the following aspects of this disclosure.

[0125] The power tool (1) according to the first aspect includes a holding part (11), a motor (15), a transmission mechanism (3), a torque detection unit (6), a clutch mechanism (C1), and a control unit (49). The holding part (11) is configured to hold a front-end tool (12) thereon. The transmission mechanism (3) transmits the torque of the motor (15) to the holding part (11). The torque detection unit (6) detects the torque transmitted from the motor (15) to the holding part (11). The clutch mechanism (C1) can switch from a transmission state in which the torque of the motor (15) is transmitted to the holding part (11) to a blocking state in which the torque of the motor (15) is not transmitted to the holding part (11), and vice versa. The control unit (49) switches the clutch mechanism (C1) from the transmission state to the blocking state when a predetermined condition related to the torque detected by the torque detection unit (6) is met.

[0126] According to this configuration, the control unit (49) switches the clutch mechanism (C1) to the blocking state based on the torque detected by the torque detection unit (6). This improves the control accuracy corresponding to the torque compared to switching the clutch mechanism (C1) to the blocking state by mechanical action based on the torque rather than by electronic control of the control unit (49).

[0127] In the electric tool (1) according to the second aspect, which can be implemented in conjunction with the first aspect, the predetermined condition includes the condition that the torque detected by the torque detection unit (6) is greater than a threshold.

[0128] This design reduces the chance that fasteners will be tightened with excessive torque exceeding a threshold.

[0129] In the power tool (1) according to the third aspect, which can be implemented in conjunction with the first or second aspect, the torque detection unit (6) includes a current measuring unit (60) and a calculation unit (63). The current measuring unit (60) measures the torque current flowing through the motor (15). The calculation unit (63) calculates the torque transmitted from the motor (15) to the holding unit (11) based on the torque current measured by the current measuring unit (60).

[0130] This construction allows torque to be calculated based on torque current.

[0131] In the electric tool (1) according to the fourth aspect, which can be implemented in combination with any of the first to third aspects, the control unit (49) suspends the control of switching the clutch mechanism (C1) from the blocking state to the transmission state when the clutch mechanism (C1) is in the blocking state and the motor (15) is rotating.

[0132] This structure can prevent the front tool (12) from rotating by maintaining the blocking state until the motor (15) stops rotating.

[0133] In the power tool (1) according to the fifth aspect, which can be implemented in combination with any of the first to fourth aspects, the transmission mechanism (3) reduces the rotational speed of the motor (15). A clutch mechanism (C1) is disposed between the motor (15) and the transmission mechanism (3).

[0134] The transmission mechanism (3) reduces the rotational speed of the motor (15), so the torque of the motor (15) is less than the torque of the transmission mechanism (3). As a result, compared with the case where the clutch mechanism (C1) is arranged between the transmission mechanism (3) and the holding part (11), this configuration can reduce the load on the clutch mechanism (C1) when the clutch mechanism (C1) is in the transmission state.

[0135] In the electric tool (1) according to the sixth aspect, which can be implemented in combination with any of the first to fifth aspects, the clutch mechanism (C1) includes a first rotating part (71), a second rotating part (81), and at least one connecting part (9). The first rotating part (71) rotates with the rotation of the motor (15). The retaining part (11) is directly or indirectly connected to the second rotating part (81). The transmission state is a state in which the first rotating part (71) and the second rotating part (81) are connected to each other via at least one connecting part (9) such that the torque of the first rotating part (71) is transmitted to the second rotating part (81). The blocking state is a state in which the first rotating part (71) and the second rotating part (81) are separated from each other such that the torque of the first rotating part (71) is not transmitted to the second rotating part (81).

[0136] This configuration allows the clutch mechanism (C1) to selectively transmit or block torque.

[0137] In the power tool (1) according to the seventh aspect, which can be implemented in conjunction with the sixth aspect, at least one connecting part (9) includes: an electromagnet (91) having magnetic poles (911); and a permanent magnet (921) facing the magnetic poles (911). The magnetic poles (911) are held by a first rotating part (71). The permanent magnet (921) is held by a second rotating part (81). The control part (49) switches the clutch mechanism (C1) from a transmitting state to a blocking state and vice versa by changing the energization state of the electromagnet (91).

[0138] This configuration allows the clutch mechanism (C1) to be switched from the transmitting state to the blocking state and vice versa using electromagnetic force.

[0139] In the electric tool (1) according to the eighth aspect, which can be implemented in conjunction with the seventh aspect, the control unit (49) switches the clutch mechanism (C1) from the transmission state to the blocking state by generating an electromagnetic repulsion force between the magnetic pole (911) and the permanent magnet (921).

[0140] This configuration allows the clutch mechanism (C1) to quickly switch from the transmission state to the blocking state.

[0141] In the electric tool (1) according to the ninth aspect, which can be implemented in conjunction with the seventh or eighth aspect, the clutch mechanism (C1) becomes in a blocking state when the electromagnet (91) is energized with a current of equal or greater than a predetermined intensity, and the clutch mechanism (C1) becomes in a transmitting state when the electromagnet (91) is not energized or is energized with a current of less than a predetermined intensity.

[0142] This design can reduce power consumption during transmission.

[0143] In the electric tool (1) according to the tenth aspect, which can be implemented in conjunction with any of the seventh to ninth aspects, at least one connecting part (9) further includes an elastic member (922). The elastic member (922) stores elastic energy when the electromagnet (91) is energized. The elastic energy of the elastic member (922) causes the clutch mechanism (C1) to switch from one state selected from the transmission state and the blocking state to another state selected from the transmission state and the blocking state.

[0144] This configuration allows the use of elastic energy stored in the elastic member (922) to switch the clutch mechanism (C1) from the transmission state to the blocking state, and vice versa.

[0145] In the electric tool (1) according to the eleventh aspect, which can be implemented in conjunction with any of the sixth to tenth aspects, the clutch mechanism (C1) further includes an input shaft (rotary shaft 132) and an output shaft (gear 83). The input shaft transmits the torque of the motor (15) to the first rotating part (71). The output shaft is coaxially configured with the input shaft. The output shaft transmits the rotational force of the second rotating part (81) to the holding part (11).

[0146] According to this configuration, the input shaft and the output shaft are coaxially configured with each other, thereby suppressing axial offset of the input shaft and the output shaft.

[0147] In the electric tool (1) according to the twelfth aspect, which can be implemented in conjunction with the eleventh aspect, the clutch mechanism (C1) includes a plurality of coupling portions (9). The plurality of coupling portions (9) are configured to surround at least one of the input shaft and the output shaft.

[0148] According to this configuration, the multiple connecting parts (9) are arranged in a ring shape, thereby suppressing the bias of force when operating the clutch mechanism (C1). This reduces the possibility of the clutch mechanism (C1) tilting. It also reduces the possibility that the tilting of the clutch mechanism (C1) will cause the clutch mechanism (C1) to be difficult to operate normally.

[0149] In the electric tool (1) according to the thirteenth aspect, which can be implemented in conjunction with any of the sixth to twelfth aspects, the clutch mechanism (C1) has a mating structure (including a first recess 713 and a permanent magnet 921). The mating structure engages the first rotating part (71) and the second rotating part (81) in the transmission state.

[0150] This design makes the transmission state of the clutch mechanism (C1) relatively stable.

[0151] Note that the elements of the second to thirteenth aspects are not necessary components of the power tool (1), but can be appropriately omitted.

[0152] Explanation of reference numerals in the attached figures

[0153] 1 Power tools

[0154] 3. Transmission mechanism

[0155] 6 Torque Detection Unit

[0156] 9 Connecting parts

[0157] 11 Maintenance Department

[0158] 12 Front-end tools

[0159] 15 motors

[0160] 49 Control Department

[0161] 60 Current Measurement Section

[0162] 63 Computing Department

[0163] 71 First Rotating Part

[0164] 81 Second Rotating Part

[0165] 83 Gears

[0166] 91 Electromagnets

[0167] 132 Rotation axis

[0168] 713 First recess

[0169] 911 magnetic poles

[0170] 921 permanent magnet (interlocking structure)

[0171] 922 Elastic Component

[0172] C1 Clutch Mechanism

Claims

1. An electric tool, comprising: A retaining part, which is configured to hold the front-end tool on the retaining part; motor; A transmission mechanism configured to transmit the torque of the motor to the holding portion; A torque detection unit is configured to detect the torque transmitted from the motor to the holding unit; A clutch mechanism configured to switch from a transmission state in which the torque of the motor is transmitted to the holding part to a blocking state in which the torque of the motor is not transmitted to the holding part, and to switch from the blocking state to the transmission state. as well as The control unit is configured to switch the clutch mechanism from the transmission state to the blocking state when a predetermined condition related to the torque detected by the torque detection unit is met. The clutch mechanism includes: A plurality of first recesses are provided for a first rotating part that rotates as the motor operates; A plurality of magnetic poles corresponding one-to-one with the plurality of first recesses, each of the plurality of magnetic poles being inserted into a corresponding first recess among the first recesses; A plurality of second recesses are provided for the second rotating part that is directly or indirectly connected to the holding part. The plurality of second recesses correspond one-to-one with the plurality of first recesses. When the clutch mechanism is in the transmission state, a pair of corresponding first recesses and second recesses face each other. A plurality of permanent magnets corresponding one-to-one with the plurality of second recesses, each of the plurality of permanent magnets being inserted into a corresponding second recess; A plurality of elastic members corresponding one-to-one with the plurality of second recesses, each of the plurality of elastic members being arranged between the bottom surface of a corresponding second recess and a permanent magnet inserted into a corresponding second recess. Each of the plurality of permanent magnets engages with a corresponding first recess among the plurality of first recesses in the transmission state, and does not engage with a corresponding first recess among the plurality of first recesses in the blocking state.

2. The power tool according to claim 1, characterized in that, The predetermined conditions include the condition that the torque detected by the torque detection unit is greater than a threshold.

3. The power tool according to claim 1 or 2, characterized in that, The torque detection unit includes: A current measuring unit configured to measure the torque current flowing through the motor; and The calculation unit is configured to calculate the torque transmitted from the motor to the holding unit based on the torque current measured by the current measuring unit.

4. The power tool according to claim 1 or 2, characterized in that, The control unit is configured to suspend the control of switching the clutch mechanism from the blocking state to the transmission state when the clutch mechanism is in the blocking state and the motor is rotating.

5. The power tool according to claim 1 or 2, characterized in that, The transmission mechanism is configured to reduce the rotational speed of the motor, and The clutch mechanism is disposed between the motor and the transmission mechanism.

6. The power tool according to claim 1 or 2, characterized in that, The clutch mechanism includes: a first rotating part configured to rotate with the rotation of the motor; a second rotating part to which the retaining part is directly or indirectly connected; and at least one connecting part. The transmission state is a state in which the first rotating part and the second rotating part are connected to each other via the at least one connecting part, such that the torque of the first rotating part is transmitted to the second rotating part. The blocking state is a state in which the first rotating part and the second rotating part are separated from each other, so that the torque of the first rotating part is not transmitted to the second rotating part.

7. The power tool according to claim 6, characterized in that, The at least one connecting part includes: an electromagnet having magnetic poles; and a permanent magnet facing the magnetic poles. The magnetic poles are held by the first rotating part, and the permanent magnet is held by the second rotating part. The control unit is configured to switch the clutch mechanism from the transmission state to the blocking state or from the blocking state to the transmission state by changing the energization state of the electromagnet.

8. The power tool according to claim 7, characterized in that, The control unit is configured to switch the clutch mechanism from the transmission state to the blocking state by generating an electromagnetic repulsion force between the magnetic pole and the permanent magnet.

9. The power tool according to claim 7 or 8, characterized in that, The clutch mechanism is configured to enter the blocking state when the electromagnet is energized with a current of equal or greater than a predetermined intensity, and to enter the transmitting state when the electromagnet is not energized or is energized with a current of less than the predetermined intensity.

10. The power tool according to claim 7 or 8, characterized in that, The at least one connecting portion includes an elastic member configured to store elastic energy when the electromagnet is energized. The elastic energy of the elastic member causes the clutch mechanism to switch from one of the transmission state and the blocking state to another of the transmission state and the blocking state.

11. The power tool according to claim 6, characterized in that, The clutch mechanism further includes: An input shaft, configured to transmit the torque of the motor to the first rotating part; and An output shaft, which is coaxially configured with the input shaft and is constructed to transmit the rotational force of the second rotating part to the holding part.

12. The power tool according to claim 11, characterized in that, The clutch mechanism includes multiple connecting parts, and The plurality of said couplings are configured to surround at least one of the input shaft and the output shaft.

13. The power tool according to claim 6, characterized in that, The clutch mechanism has a meshing structure configured to connect the first rotating part and the second rotating part to each other by meshing in the transmission state.

Images