Impact tool, control method, and program

Abstract

To suppress the decrease in calculation accuracy related to motor speed calculations. [Solution] The impact tool 1 comprises a motor 2, a striking rotation mechanism A1, a Hall sensor B1, a calculation unit 73, a monitoring unit 74, and a correction unit 75. The motor 2 is capable of forward and reverse rotation. The striking rotation mechanism A1 performs a striking action using rotational inertia force. The calculation unit 73 calculates the speed of the motor 2 using a first bit pattern based on the electrical signal from the Hall sensor B1. The monitoring unit 74 determines whether the first bit pattern deviates from a second bit pattern defined for reference. If the correction unit 75 determines that the first bit pattern deviates from the second bit pattern, it corrects the outlier value of the first bit pattern. If the calculation unit 73 determines that the first bit pattern deviates from the second bit pattern, it calculates the speed of the motor 2 based on the correction by the correction unit 75.

Description

Technical Field

[0001] The present disclosure generally relates to impact tools, control methods, and programs. More specifically, the present disclosure relates to an impact tool including a motor capable of forward and reverse rotation, a control method, and a program.

Background Art

[0002] Patent Document 1 discloses an impact tool for performing fastening work by impact. The impact tool includes a motor, a hammer that is rotated around a rotation axis by the motor and is movable in an axial direction in which the rotation axis extends, and an anvil that is disposed axially with respect to the hammer and has a protrusion that protrudes in the opposite axial direction and can abut against the hammer in the rotation direction of the hammer. The impact tool also includes a biasing member that biases the hammer toward the anvil, and a control unit that controls the motor so that the hammer that rotates in the forward rotation direction and collides with the protrusion maintains engagement with the protrusion and the hammer rotates in the reverse rotation direction after the hammer collides with the protrusion. Further, three rotation position detection elements (Hall elements) are provided behind the motor of this impact tool. The rotation position detection elements are provided at positions facing the permanent magnet of the rotor in order to detect the position of the rotor of the motor.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in an impact tool, the motor may reverse due to the recoil during impact, and the signal pattern of the electrical signal received from the Hall sensor (rotation position detection element) may be disturbed. In that case, the speed calculation (calculation of the speed response value) of the motor in the arithmetic unit of the impact tool may not be correctly performed.

[0005] This disclosure is made in view of the above circumstances and aims to provide an impact tool, a control method, and a program that suppress the decrease in calculation accuracy related to motor speed calculation. [Means for solving the problem]

[0006] An impact tool according to one aspect of the present disclosure comprises a motor, an impact rotation mechanism, a Hall sensor, a calculation unit, a monitoring unit, and a correction unit. The motor has a rotor and is capable of forward and reverse rotation. The impact rotation mechanism receives rotational force from the motor and performs an impact operation by rotational inertia force while repeatedly rotating forward and in reverse. The Hall sensor outputs an electrical signal corresponding to the rotational position of the rotor. The calculation unit calculates the speed of the motor using a first bit pattern based on the electrical signal. The monitoring unit monitors changes in the first bit pattern and determines whether the first bit pattern deviates from a second bit pattern defined for reference. If the monitoring unit determines that the first bit pattern deviates from the second bit pattern, the correction unit corrects the outlier value of the first bit pattern. If the monitoring unit determines that the first bit pattern deviates from the second bit pattern, the calculation unit calculates the speed of the motor based on the correction by the correction unit.

[0007] A control method according to one aspect of the present disclosure is a control method performed by one or more processors in an impact tool. The impact tool comprises a motor, a striking rotation mechanism, and a Hall sensor. The motor has a rotor and is capable of forward and reverse rotation. The striking rotation mechanism receives rotational force from the motor and performs a striking operation by rotational inertia force while repeatedly rotating forward and in reverse. The Hall sensor outputs an electrical signal corresponding to the rotational position of the rotor. The control method includes a calculation step, a monitoring step, and a correction step. In the calculation step, the speed of the motor is calculated using a first bit pattern based on the electrical signal. In the monitoring step, changes in the first bit pattern are monitored and it is determined whether the first bit pattern deviates from a second bit pattern defined for reference. In the correction step, if it is determined in the monitoring step that the first bit pattern deviates from the second bit pattern, the outlier value of the first bit pattern is corrected. In the calculation step, if the monitoring step determines that the first bit pattern deviates from the second bit pattern, the motor speed is calculated based on the correction performed in the correction step.

[0008] A program according to one aspect of this disclosure is a program that causes one or more processors to execute the control method described above. [Effects of the Invention]

[0009] According to this disclosure, there is an advantage in that it is possible to suppress the decrease in calculation accuracy related to motor speed calculation. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a block diagram showing the configuration of an impact tool according to one embodiment. [Figure 2] Figure 2 is a characteristic diagram showing the speed command value and speed response value for the impact tool of the comparative example. [Figure 3]Figure 3 is a waveform diagram of the voltage signals output from the three Hall elements of the Hall sensor in the impact tool according to one embodiment of the above. [Figure 4] Figure 4 is a characteristic diagram showing the speed command value and speed response value in an impact tool according to one embodiment of the above. [Figure 5] Figure 5 is a flowchart illustrating the operation of an impact tool according to one embodiment described above. [Figure 6] Figure 6 is a side view of an impact tool according to one embodiment of the above. [Figure 7] Figure 7 is a side cross-sectional view of the main part of an impact tool according to one embodiment of the above. [Figure 8] Figure 8 is a cross-sectional view corresponding to line III-III in Figure 7. [Figure 9] Figure 9 is a rear view of the planetary gear mechanism of an impact tool according to one embodiment of the above. [Figure 10] Figure 10 is a rear view of the planetary gear mechanism of an impact tool according to one embodiment of the above, and represents a point in time later than that shown in Figure 9. [Figure 11] Figure 11 is a rear view of the planetary gear mechanism of an impact tool according to one embodiment of the above, and represents a point in time later than that shown in Figure 10. [Figure 12] Figure 12 is an exploded perspective view of the main part of an impact tool according to one embodiment of the above, viewed from the front. [Figure 13] Figure 13 is an exploded perspective view of the main part of an impact tool according to one embodiment of the above, viewed from the rear. [Figure 14] Figure 14 is a timing chart showing the tightening operation of the workpiece in an impact tool according to one embodiment of the above. [Figure 15] Figure 15 is a block diagram showing the configuration of an impact tool according to Modification Example 1. [Figure 16] Figure 16 shows the waveform diagrams of the U-phase, V-phase, and W-phase electrical signals and the motor recognition position in the impact tool according to the modified example 1 described above. [Figure 17]FIG. 17 is a conceptual diagram for explaining the relationship between the current position and the next position of the motor recognized by the control unit in the impact tool according to the above-described Modification 1. [Figure 18] FIG. 18 is a conceptual diagram for explaining the correction process executed when the motor reverses in the control unit of the impact tool according to the above-described Modification 1.

Mode for Carrying Out the Invention

[0011] (Embodiment) (1) Overview Hereinafter, an impact tool, a control method, and a program according to an embodiment and a modification will be described with reference to the drawings. Note that the following embodiment and modification are merely one of various embodiments of the present disclosure. Further, the following embodiment and modification can be variously changed according to design and the like as long as the object of the present disclosure can be achieved. Also, the configurations of the following modifications can be appropriately combined with the following embodiment or other modifications. In addition, the drawings described in the present disclosure are schematic diagrams, and the ratios of the sizes and thicknesses of the respective components in the drawings do not necessarily reflect the actual dimensional ratios.

[0012] The arrows indicating the respective directions in the drawings are merely examples and are not intended to define the directions when using the impact tool. Also, the arrows indicating the respective directions in the drawings are merely shown for the purpose of explanation and do not have an entity.

[0013] As used in the present disclosure, “orthogonal (perpendicular)” means not only a state in which the angle between two objects is exactly 90 degrees, but also a state in which the two objects intersect within a certain range of difference. That is, the angle between the two orthogonal objects falls within a certain range of difference (for example, 10 degrees or less) with respect to 90 degrees. That is, “orthogonal” as used in the present disclosure includes a case where the angle formed by the two objects is 80 degrees or more and 100 degrees or less.

[0014] An impact tool 1 according to one embodiment (see Figures 1, 6, and 7) comprises a motor 2 (see Figures 1 and 7), an impact rotation mechanism A1 (see Figure 1), and a Hall sensor B1 (see Figures 1 and 7). The impact tool 1 also comprises a calculation unit 73, a monitoring unit 74, and a correction unit 75, as shown in Figure 1.

[0015] Motor 2 has a rotor 2A (see Figure 1). Motor 2 is capable of forward and reverse rotation. The striking rotation mechanism A1 receives rotational force from motor 2 and performs a striking action by rotational inertia while repeatedly rotating forward and reverse. In the following example, the striking rotation mechanism A1 is configured with a planetary gear mechanism 4 (see Figures 7 to 13).

[0016] Hall sensor B1 outputs an electrical signal corresponding to the rotational position of rotor 2A. Calculation unit 73 calculates the speed of motor 2 using a first bit pattern based on the electrical signal. Monitoring unit 74 monitors changes in the first bit pattern and determines whether the first bit pattern deviates from a second bit pattern defined for reference. Correction unit 75 corrects the outlier value of the first bit pattern if monitoring unit 74 determines that the first bit pattern deviates from the second bit pattern. Calculation unit 73 calculates the speed of motor 2 based on the correction by correction unit 75 if monitoring unit 74 determines that the first bit pattern deviates from the second bit pattern.

[0017] According to the configuration of the impact tool 1 in the above-described embodiment, if the monitoring unit 74 determines that the first bit pattern deviates from the second bit pattern (defined for reference), the correction unit 75 corrects the outlier value of the first bit pattern. The calculation unit 73 calculates the speed (speed response value) of the motor 2 based on the correction by the correction unit 75. Therefore, even if the motor 2 reverses direction due to the recoil during impact and the first bit pattern based on the electrical signal received from the Hall sensor B1 is disrupted, the possibility that the speed response value calculation will not be performed correctly can be reduced. As a result, the impact tool 1 has the advantage of suppressing a decrease in the calculation accuracy related to the calculation of the motor 2's speed.

[0018] Furthermore, the control method according to one embodiment is a control method executed by one or more processors in the impact tool 1 described above. The control method includes a calculation step, a monitoring step, and a correction step. In the calculation step, the speed of the motor 2 is calculated using a first bit pattern based on an electrical signal. In the monitoring step, changes in the first bit pattern are monitored, and it is determined whether or not the first bit pattern deviates from a second bit pattern defined for reference. In the correction step, if it is determined in the monitoring step that the first bit pattern deviates from the second bit pattern, the outlier value of the first bit pattern is corrected. In the calculation step, if it is determined in the monitoring step that the first bit pattern deviates from the second bit pattern, the speed of the motor 2 is calculated based on the correction made in the correction step. The control method according to one embodiment described above also has the advantage of suppressing a decrease in calculation accuracy related to the calculation of the speed of the motor 2.

[0019] The above control method is used on a computer system (impact tool 1). In other words, the above control method can also be implemented as a computer program. A program according to one embodiment is a program that causes one or more processors to execute the above control method. The program may be recorded on a computer-readable non-temporary recording medium. A computer program product according to one embodiment includes a computer program that, when executed by one or more processors, realizes the steps of the above control method.

[0020] (2) Configuration of impact tools (2.1) Overall structure The overall configuration of the impact tool 1 according to this embodiment will be described in detail below with reference to the drawings.

[0021] The impact tool 1 is, for example, a portable power tool. As shown in Figure 7, the impact tool 1 comprises a motor 2, an inertia body 3, a striking rotation mechanism A1 (see Figure 1), an output shaft 5, a housing 10 (see Figure 6), a battery pack 11 (see Figure 6), and a fan 8.

[0022] The impact rotation mechanism A1 receives rotational force from the motor 2 and performs an impact action by rotational inertia while repeatedly rotating in forward and reverse directions. In this embodiment, the impact rotation mechanism A1 is composed of a planetary gear mechanism 4 (see Figure 7). In other words, the impact tool 1 is equipped with the planetary gear mechanism 4 that constitutes the impact rotation mechanism A1. Note that it is not essential for the impact tool 1 to be equipped with a battery pack 11.

[0023] Furthermore, as shown in Figure 1, the impact tool 1 further includes a memory unit 6, a control unit 7, a trigger switch 12 (see also Figure 6), a torque sensor 14, and a Hall sensor B1.

[0024] In the following description, the direction from the motor shaft 21 of motor 2 toward the output shaft 5 is defined as the forward direction, and the direction from the output shaft 5 toward the motor shaft 21 is defined as the rear direction. In the following description, the forward and rear directions may be collectively referred to as the "front-rear direction." In this embodiment, the rotation axis Ax1 of the output shaft 5 (see Figure 7) is aligned with the front-rear direction. In the following description, the direction from the grip portion 102 of housing 10 (see Figure 6) toward the body portion 101 of housing 10 (see Figure 6) is defined as the upward direction, and the direction from the body portion 101 toward the grip portion 102 is defined as the downward direction. In the following description, the upward and downward directions may be collectively referred to as the "up-down direction."

[0025] As shown in Figure 6, the housing 10 has a body portion 101, a grip portion 102, and a mounting portion 103. The body portion 101 houses the motor 2, the inertia body 3, and the planetary gear mechanism 4, etc. The grip portion 102 protrudes downward from the body portion 101. In this embodiment, the grip portion 102 is formed in a cylindrical shape with an open top and bottom. The mounting portion 103 is provided at the tip (lower end) of the grip portion 102. In other words, the body portion 101 and the mounting portion 103 are connected by the grip portion 102. The mounting portion 103 is configured so that the battery pack 11 can be detachably attached.

[0026] The battery pack 11 is a power source that supplies current to drive the motor 2. The battery pack 11 comprises a battery pack formed by connecting multiple secondary batteries (for example, lithium-ion batteries or all-solid-state batteries, etc.) in series, and a case that houses the battery pack.

[0027] Motor 2 is, for example, a brushless motor. Motor 2 comprises, for example, a rotor 2A (see Figure 1) having a motor shaft 21 (see Figure 7), and a stator 2B (see Figure 1) positioned opposite the rotor 2A. Motor 2 is capable of forward and reverse rotation. Motor 2 is, for example, a three-phase (AC) motor. The rotor 2A has permanent magnets including multiple sets of N and S poles. The rotor 2A rotates by sequentially switching the current flowing through the three-phase stator windings of U, V, and W connected in a star configuration in the stator 2B. Motor 2 converts the power supplied from the battery pack 11 into rotational driving force (torque) for the motor shaft 21. Motor 2 rotates a transmission body (motor shaft 21) that transmits torque to other components. The front end of the motor shaft 21 is fitted into an insertion hole 4410 (see Figure 13) of the planetary carrier 44.

[0028] The motor shaft 21 is supported in the housing 10 in a rotatable manner. More specifically, the motor shaft 21 is supported in the housing 10 via a bearing 15 (see Figure 7). The bearing 15 is, for example, a ball bearing.

[0029] The inertial body 3 is positioned between the motor 2 and the planetary gear mechanism 4. More specifically, the inertial body 3 is positioned in front of the motor 2 and behind the planetary gear mechanism 4. Furthermore, the inertial body 3 is positioned between the motor 2 and the multiple planetary gears 42. It is also positioned between the motor 2 and the internal gear 43. The inertial body 3 is mechanically connected to the motor shaft 21 and rotates together with the motor shaft 21. The inertial body 3 is a so-called flywheel and increases the inertial torque of the motor 2 (motor shaft 21). The shape of the inertial body 3 is disc-shaped. The thickness direction of the inertial body 3 is aligned with the front-to-back direction.

[0030] The planetary gear mechanism 4 constituting the striking rotation mechanism A1 includes a sun gear 41, a plurality of planetary gears 42 (five in the example of Figure 8), an internal gear 43, and a planetary carrier 44, as shown in Figures 8, 12, and 13. A detailed explanation of the planetary gear mechanism 4 will be given later, but the plurality of planetary gears 42 are arranged around the sun gear 41 and mesh with the sun gear 41. The planetary carrier 44 supports the plurality of planetary gears 42 so that they can rotate. The planetary carrier 44 rotates around the sun gear 41. The internal gear 43 is arranged to surround the plurality of planetary gears 42 and meshes with the plurality of planetary gears 42. The internal gear 43 is held in a rotatable state. The planetary carrier 44 is fixed to the transmission body (motor shaft 21) and rotates in accordance with the rotation of the transmission body. The internal gear 43 has a first engagement portion 432. The planetary carrier 44 has a second engagement portion 442. The first engaging portion 432 of the internal gear 43 and the second engaging portion 442 of the planetary carrier 44 are relatively movable along the rotational direction of the transmission body (motor shaft 21) and come into contact in accordance with the rotation of the internal gear 43.

[0031] A cutting tool is attached to the output shaft 5. The cutting tool may be, for example, a screwdriver bit, a socket bit, or a drill bit. Screwdriver bits and socket bits are used to tighten or loosen fastening members such as bolts. Drill bits are used to drill holes in materials such as wood or metal. The appropriate cutting tool from the various types is attached to the output shaft 5 according to its intended use. The rotation of the sun gear 41 is then transmitted to the output shaft 5. As a result, the cutting tool rotates integrally with the output shaft 5. Note that the cutting tool may also be attached to the output shaft 5 via an adapter.

[0032] The trigger switch 12 protrudes from the grip portion 102. The trigger switch 12 is an operating part that receives input for controlling the rotation of the motor 2. By pulling the trigger switch 12, the motor 2 can be switched on or off. Furthermore, the rotation speed of the motor 2 can be adjusted by the amount the trigger switch 12 is pulled. The greater the amount of pull, the faster the rotation speed of the motor 2.

[0033] The torque sensor 14 is, for example, a magnetostrictive torque sensor capable of detecting torsional strain. The torque sensor 14 is positioned in a location where it can detect torsional strain on the output shaft 5. The torque sensor 14 detects the change in magnetic permeability corresponding to the strain on the shaft caused by the torque applied to the output shaft 5 using a coil installed in the non-rotating part, and outputs a voltage signal proportional to the strain to the torque detection unit 71. The torque sensor 14 may also be a strain gauge type torque sensor.

[0034] The memory unit 6 includes, for example, ROM (Read Only Memory), RAM (Random Access Memory), or EEPROM (Electrically Erasable Programmable Read Only Memory). The memory unit 6 stores the control program executed by the control unit 7. The memory unit 6 also stores the tightening torque setting value (set torque), etc. In this disclosure, "tightening torque" refers to the torque applied to the workpiece, and is a concept that includes the torque applied to the tip tool, output shaft 5, or motor shaft 21 during the operation of the impact tool 1.

[0035] The control unit 7 includes a computer system having one or more processors and memory. At least some of the functions of the control unit 7 are realized by the computer system's processor executing a program recorded in the computer system's memory. The program may be recorded in memory, provided via a telecommunication line such as the Internet, or provided on a non-temporary recording medium such as a memory card.

[0036] As shown in Figure 1, the control unit 7 includes a torque detection unit 71, a drive control unit 72, a calculation unit 73, a monitoring unit 74, and a correction unit 75. Note that the torque detection unit 71, drive control unit 72, calculation unit 73, monitoring unit 74, and correction unit 75 do not necessarily represent actual physical configurations, but rather represent functions realized by the control unit 7.

[0037] The torque detection unit 71 detects the tightening torque of the output shaft 5 based on the voltage signal output from the torque sensor 14.

[0038] The drive control unit 72 controls the motor 2. The drive control unit 72 controls the motor 2, for example, using vector control. In vector control, the drive control unit 72 decomposes the motor current, which is the current supplied to the motor 2, into a torque current (q-axis current) that generates torque and an excitation current (d-axis current) that generates magnetic flux, and controls each current component independently. Note that the method by which the drive control unit 72 controls the motor 2 is not limited to vector control, and may use a control method other than vector control.

[0039] The drive control unit 72 controls the motor 2 so that the tightening torque measured by the torque detection unit 71 reaches a set torque that is stored in the memory unit 6 beforehand. When the tightening torque measured by the torque detection unit 71 exceeds the set torque, the drive control unit 72 controls the motor 2 to stop the rotation of the motor shaft 21.

[0040] When the operator pulls the trigger switch 12, the drive control unit 72 controls the motor 2 to rotate the motor shaft 21 in a first direction DR1 (see Figure 8; hereafter, the first direction DR1 is considered the forward direction) as an example. After the tightening torque increases and the integrated rotation of the internal gear 43 and the output shaft 5 stops, the drive control unit 72 controls the motor 2 to rotate the motor shaft 21 in a second direction opposite to the first direction DR1 (i.e., the opposite direction to forward rotation) for a predetermined time or by a predetermined angle. After rotating the motor shaft 21 in the second direction for a predetermined time or by a predetermined angle, the drive control unit 72 controls the motor 2 to rotate the motor shaft 21 back in the first direction DR1. The drive control unit 72 repeats this series of controls until the tightening torque measured by the torque detection unit 71 is equal to or greater than the set torque. In the example shown in Figure 8, the first direction DR1 is clockwise when viewed from the rear, and the second direction is counterclockwise when viewed from the rear. However, the first direction DR1 may be counterclockwise when viewed from the rear, and the second direction may be clockwise when viewed from the rear.

[0041] Incidentally, the drive control unit 72 adjusts the rotational speed of the motor 2 (also simply called the "speed" of the motor 2) according to the amount of pull of the trigger switch 12. The drive control unit 72 increases the speed of the motor 2 in accordance with the increase in the amount of pull of the trigger switch 12. The memory unit 6 stores in advance setting information that associates the amount of pull of the trigger switch 12 with the target rotational speed of the motor 2 (also simply called the "target speed" or "speed command value" of the motor 2). The drive control unit 72 refers to the above setting information to set the target speed of the motor 2 corresponding to the amount of pull of the trigger switch 12, and controls the motor 2 so that the actual speed (response value) of the motor 2 follows the target speed.

[0042] The fan 8 (see Figure 7) is positioned between the motor 2 and the planetary gear mechanism 4. More specifically, the fan 8 is positioned in front of the motor 2 and behind the inertial body 3. The fan 8 is mechanically connected to the motor shaft 21 and rotates together with the motor shaft 21. The fan 8, like the inertial body 3, increases the inertial torque of the motor 2 (motor shaft 21).

[0043] The Hall sensor B1 outputs an electrical signal corresponding to the rotational position of the rotor 2A. As shown in Figure 7, the Hall sensor B1 is located, for example, behind the motor 2. The Hall sensor B1 includes three Hall elements (rotational position detection elements) that output the U-phase electrical signal Sg1, the V-phase electrical signal Sg2, and the W-phase electrical signal Sg3 (see Figure 3), respectively, corresponding to the three-phase motor 2. Hereinafter, the Hall element that outputs the U-phase electrical signal Sg1 is sometimes referred to as the first Hall element B11, the Hall element that outputs the V-phase electrical signal Sg2 is sometimes referred to as the second Hall element B12, and the Hall element that outputs the W-phase electrical signal Sg3 is sometimes referred to as the third Hall element B13 (see Figure 1). The first to third Hall elements B11 to B13 are mounted on a printed circuit board located behind the motor 2. This printed circuit board is formed in a roughly donut shape with thickness in the front-to-back direction. The first to third Hall elements B11 to B13 are arranged on the roughly donut-shaped printed circuit board at intervals along its circumferential direction, facing the rotor 2A. The first to third Hall elements B11 to B13 are positioned to detect changes in the magnetic field of the rotor 2A, which rotates due to the currents flowing through the three phase stator windings of the stator 2B. This printed circuit board is electrically connected to the control unit 7, and the U-phase electrical signal Sg1, V-phase electrical signal Sg2, and W-phase electrical signal Sg3 output from the first to third Hall elements B11 to B13, respectively, are transmitted to the control unit 7. The electrical signals Sg1 to Sg3 are, for example, voltage signals.

[0044] The calculation unit 73, monitoring unit 74, and correction unit 75 of the control unit 7 will be explained later in the section "(2.4) Bit Pattern Monitoring and Correction Processing".

[0045] (2.2) Detailed configuration of planetary gear mechanism As shown in Figures 8, 12, and 13, the planetary gear mechanism 4 constituting the striking rotation mechanism A1 comprises a shaft holding member 40, a sun gear 41, a plurality of planetary gears 42 (five in the example of Figure 8), an internal gear 43, and a planetary carrier 44.

[0046] The sun gear 41 is an external gear. The sun gear 41 has a main body portion 410 and a protruding portion 412.

[0047] The main body portion 410 is formed in a cylindrical shape with its axial direction aligned with the front-rear direction, and multiple teeth are provided on the outer circumferential surface of the main body portion 410. The main body portion 410 may also be formed in an annular shape with its axial direction (thickness direction) aligned with the front-rear direction.

[0048] The projection 412 protrudes forward from the front end (front surface) of the main body 410. The projection 412 is triangular prism-shaped. When viewed from the front or back, the projection 412 is formed in a triangular shape with rounded vertices. The outer shape of the projection 412 and the edge of the recess 50 (see Figure 13) of the output shaft 5 are roughly the same in shape and size. The projection 412 is fitted into the recess 50 of the output shaft 5. When the projection 412 is fitted into the recess 50 of the output shaft 5, the output shaft 5 and the sun gear 41 rotate as a single unit.

[0049] Multiple planetary gears 42 are arranged around the sun gear 41. The multiple planetary gears 42 are arranged at equal intervals on a circle centered on the central axis of the sun gear 41. The planetary gears 42 are external gears. Each of the multiple planetary gears 42 meshes with the sun gear 41 and the internal gear 43. The planetary gears 42 have through holes 422 (see Figure 8) that pass through the planetary gears 42 in the front-to-back direction. Viewed from the front-to-back direction, the through holes 422 are formed in the center of the planetary gears 42 and are circular holes. A cylindrical or cylindrical shaft 421, whose axial direction is aligned in the front-to-back direction, passes through the through holes 422. The planetary gears 42 are rotatable around the shaft 421. In other words, the planetary gears 42 are capable of rotating around the shaft 421. The shaft 421 of the planetary gear 42 may be passed through the through hole 422 via a bearing.

[0050] The shaft 421 of the planetary gear 42 is supported by the shaft holding member 40 and the planetary carrier 44. More specifically, the first end (front end) of the shaft 421 of the planetary gear 42 is inserted into a through hole 401 formed in the shaft holding member 40. The second end (rear end) of the shaft 421 of the planetary gear 42 is inserted into a through hole 4411 of the planetary carrier 44.

[0051] The shaft holding member 40 is a member that supports the shafts 421 of multiple planetary gears 42. The shaft holding member 40 is formed in an annular shape. The shaft holding member 40 is positioned such that, when viewed from the front-rear direction, the central axis of the shaft holding member 40 and the central axis of the sun gear 41 are concentric.

[0052] The shaft holding member 40 has multiple (five in the example in Figure 13) through holes 401 formed therein. The multiple through holes 401 are arranged at equal intervals on the circumference of a circle centered on the central axis of the sun gear 41. The multiple through holes 401 penetrate the shaft holding member 40 along the front-rear direction. The front end of the shaft 421 of the planetary gear 42 is inserted into each of the multiple through holes 401.

[0053] The shaft holder member 40 is supported by the internal gear 43 in a rotatable manner. More specifically, the shaft holder member 40 is supported by the internal gear 43 via a bearing 17. The bearing 17 is, for example, a ball bearing.

[0054] The planetary carrier 44 is a member that supports the shafts 421 of multiple planetary gears 42. The planetary carrier 44 has a carrier portion 441 and multiple (two in Figure 13) second engaging portions 442.

[0055] The carrier section 441 is formed in a disc shape with its thickness aligned with the front-to-back direction. The planetary carrier 44 is positioned such that, when viewed from the front-to-back direction, the central axis of the planetary carrier 44 and the central axis of the sun gear 41 are concentric.

[0056] An insertion hole 4410 is formed in the center of the carrier section 441. The front end of the motor shaft 21 is inserted into the insertion hole 4410. This fits the motor shaft 21 and the planetary carrier 44 together.

[0057] The carrier portion 441 has multiple (five in the example in Figure 13) through holes 4411. The multiple through holes 4411 are arranged at equal intervals on the circumference of a circle centered on the central axis of the sun gear 41. The multiple through holes 4411 penetrate the carrier portion 441 along the front-rear direction. The rear end of the shaft 421 of the planetary gear 42 is inserted into each of the multiple through holes 4411. In this way, the carrier portion 441 is connected to each of the shafts 421 of the multiple planetary gears 42.

[0058] The two second engaging portions 442 protrude from the carrier portion 441 along a direction perpendicular to the rotation axis Ax1 of the output shaft 5. More specifically, the two second engaging portions 442 protrude outward from the outer edge of the disc-shaped carrier portion 441 along the radial direction of the carrier portion 441. The two second engaging portions 442 protrude away from each other. The second engaging portions 442 protrude from a portion of the side surface of the carrier portion 441 and are formed in a rectangular parallelepiped shape.

[0059] The internal gear 43 is arranged around a plurality of planetary gears 42. The internal gear 43 meshes with the plurality of planetary gears 42. The internal gear 43 is supported by the housing 10 in a rotatable state. More specifically, in this embodiment, the internal gear 43 is supported by the housing 10 via a plurality of bearings 13 (two in Figure 7) arranged in the front-to-back direction. The bearings 13 are, for example, ball bearings. The internal gear 43 may be supported by the housing 10 via one or three or more bearings 13.

[0060] The internal gear 43 has a main body portion 431 and a plurality of (two in the example in Figure 13) first engaging portions 432.

[0061] The main body 431 is formed in a cylindrical shape with its axial direction aligned with the front-rear direction, and multiple teeth are provided on the inner circumferential surface of the main body 431. The number of teeth on the main body 431 is greater than the number of teeth on the sun gear 41. The main body 431 is positioned such that, when viewed from the front-rear direction, the central axis of the main body 431 and the central axis of the sun gear 41 are concentric. The main body 431 may also be formed in an annular shape with its axial direction (thickness direction) aligned with the front-rear direction.

[0062] Multiple first engaging portions 432 protrude rearward from the rear end (rear surface) of the main body portion 431. In other words, the multiple first engaging portions 432 protrude from the main body portion 431 along the rotation axis Ax1 of the output shaft 5. The first engaging portions 432 protrude from a part of the annular rear end of the main body portion 431 and are formed in a rectangular parallelepiped shape that is curved according to the curvature of the rear end of the main body portion 431. The two first engaging portions 432 in this embodiment are arranged to face each other in a direction perpendicular to the front-rear direction. More specifically, the two first engaging portions 432 face each other so as to straddle the rotation axis Ax1 of the output shaft 5.

[0063] In this embodiment, the first engaging portion 432 and the second engaging portion 442 protrude in directions perpendicular to each other. Therefore, compared to the case where both the first engaging portion 432 and the second engaging portion 442 protrude in the front-rear direction, the impact tool 1 can be made more compact in the front-rear direction.

[0064] The output shaft 5 is positioned in front of the planetary gear mechanism 4. The output shaft 5 rotates around the rotation axis Ax1 in accordance with the rotation of the sun gear 41. The rotation axis Ax1 of the output shaft 5 is also the rotation axis of the motor shaft 21, the sun gear 41, the internal gear 43, and the planetary carrier 44.

[0065] The output shaft 5 has a recess 50. The recess 50 is formed at the rear end of the output shaft 5. The edge of the recess 50 is triangular with a rounded vertex. The projection 412 of the sun gear 41 is fitted into the recess 50.

[0066] A cutting tool is attached to the front end of the output shaft 5. The output shaft 5 is supported in the housing 10 in a rotatable manner. More specifically, the output shaft 5 is supported in the housing 10 via a number of bearings 16 (two in Figure 7) arranged in the front-to-back direction. The bearings 16 are, for example, ball bearings. The output shaft 5 may be supported in the housing 10 via one or more than three bearings 16.

[0067] Here, assuming that the tip tool is attached to the output shaft 5 and the tip tool is set on the workpiece, such as a screw or bolt, that is, that the tip tool and the workpiece are in contact, we will briefly explain the operation of the impact rotation mechanism A1 (planetary gear mechanism 4). Furthermore, assuming that the transmission body (motor shaft 21) is rotating in the first direction DR1 in Figure 8, we will explain the general operation of the impact tool 1.

[0068] As shown in Figure 8, the rotation of the motor 2 is transmitted to the planetary carrier 44 via the transmission body, causing the planetary carrier 44 to rotate in the first direction DR1.

[0069] Since the tip tool attached to the output shaft 5 is in contact with the workpiece, a force is applied to the output shaft 5 that suppresses rotation. Consequently, the rotation of the sun gear 41, which transmits rotation to the output shaft 5, is suppressed. In other words, when the motor 2 first starts to rotate, the sun gear 41 is stopped in the planetary gear mechanism 4, while the planetary gears 42, internal gears 43, and planetary carriers 44 are able to rotate.

[0070] When the planetary carrier 44 rotates in the first direction DR1, as shown in Figure 8, the multiple planetary gears 42 supported by the planetary carrier 44 rotate in the first direction DR1 while revolving in the first direction DR1. The internal gear 43 also rotates in the first direction DR1. More specifically, the rotation of the planetary carrier 44 is accelerated to become the rotation of the internal gear 43.

[0071] The rotational speed of the internal gear 43 is the value obtained by multiplying the rotational speed of the planetary carrier 44 by the gear ratio obtained by [Equation 1] below. [Mathematics 1] (Z a + Z c ) / Z c Here, Z a This is the number of teeth on the sun gear 41, Z c This is the number of teeth on internal gear 43. The number of teeth on internal gear 43 is greater than the number of teeth on sun gear 41.

[0072] Since the internal gear 43 rotates faster than the planetary carrier 44, after some time has passed with the motor shaft 21 rotating, the first engaging portion 432 of the internal gear 43 comes into contact with the second engaging portion 442 of the planetary carrier 44, as shown in Figure 11. As a result, the planetary carrier 44 is pushed by the first engaging portion 432 of the internal gear 43 at the second engaging portion 442 and rotates in the first direction DR1 at the same speed as the internal gear 43. Also, if the force rotating the sun gear 41 exceeds the force suppressing the rotation of the output shaft 5, the sun gear 41 rotates in the first direction DR1 to cancel out the speed difference between the internal gear 43 and the planetary carrier 44.

[0073] Thus, when the tip tool is in contact with the workpiece, and the first engaging portion 432 of the internal gear 43 is in contact with the second engaging portion 442 of the planetary carrier 44, the sun gear 41, the internal gear 43, and the planetary carrier 44 rotate in the same direction as the rotation direction (first direction DR1) of the transmission body (motor shaft 21).

[0074] As the sun gear 41 rotates, rotation is transmitted from the sun gear 41 to the output shaft 5, causing the tip tool to rotate together with the output shaft 5. Therefore, the operator can perform work on the workpiece using the tip tool. The work is, for example, tightening screws or other fasteners.

[0075] The sun gear 41 and the output shaft 5 rotate due to the rotational energy (inertial torque) of the rotating body just before the first engaging portion 432 contacts the second engaging portion 442. The rotating body includes the internal gear 43, the planetary carrier 44, and the inertial body 3 (see Figure 7). Compared to simply transmitting the rotational energy of the motor 2 to the output shaft 5, the rotational speed of the output shaft 5 increases instantaneously when the first engaging portion 432 contacts the second engaging portion 442 (see timings T7 and T9 in Figure 14). In other words, a large rotational torque is generated. Therefore, a large rotational torque can be applied to the workpiece, similar to how the impact mechanism of a conventional impact tool applies a striking impact to the output shaft. Thus, tightening work on the workpiece can be performed with a large rotational torque. In this way, the impact tool 1 of this embodiment can rotate the output shaft 5 by the inertial torque of the rotating body.

[0076] Furthermore, the relative speed (speed difference) between the first engaging portion 432 of the internal gear 43 and the second engaging portion 442 of the planetary carrier 44 is slower than the rotational speed of the transmission body (motor shaft 21). Therefore, the sound generated when the first engaging portion 432 of the internal gear 43 and the second engaging portion 442 of the planetary carrier 44 come into contact is far quieter than the sound generated when the impact mechanism of a conventional impact tool applies a striking impact to the output shaft. Thus, noise can be suppressed compared to when a large torque is applied to the output shaft by the impact mechanism.

[0077] Furthermore, the impact generated when the first engaging portion 432 of the internal gear 43 and the second engaging portion 442 of the planetary carrier 44 come into contact is far smaller than the impact generated when the impact mechanism of a conventional impact tool applies a striking impact to the output shaft. In other words, the impact tool 1 of this embodiment has a longer lifespan compared to conventional impact tools because wear on the output shaft 5 (or anvil) and the like is suppressed.

[0078] Furthermore, in conventional impact tools, the internal gear of the planetary gear mechanism is generally fixed to the housing so that it does not rotate. Therefore, in conventional impact tools, when performing tightening work, the reaction force is transmitted from the internal gear to the housing, and thus transmitted to the operator. On the other hand, according to the impact tool 1 of this embodiment, the internal gear 43 of the planetary gear mechanism 4 is held in a rotatable state relative to the housing 10 (see Figure 7), so when performing tightening work, the reaction force is less likely to be transmitted from the internal gear 43 to the housing 10. In other words, according to the impact tool 1 of this embodiment, the reaction force transmitted to the operator when performing work can be reduced.

[0079] Furthermore, in conventional impact tools, after the hammer portion of the impact mechanism collides with the anvil, the hammer portion vibrates along the axial direction of the motor shaft due to elastic force in order to release the engagement (contact) with the anvil, causing the entire impact tool to vibrate along the axial direction of the motor shaft. However, in the impact tool 1 of this embodiment, the internal gear 43 does not move along the axial direction of the motor shaft 21 (axial movement is restricted), so vibration of the entire impact tool 1 along the axial direction of the motor shaft 21 is suppressed.

[0080] (2.3) Tightening operation of impact tools Next, the details of the tightening operation of the impact tool 1 in this embodiment will be explained with reference to Figures 8 to 11 and Figure 14 (timing chart). The tightening operation of the impact tool 1 will be explained assuming that the tip tool is attached to the output shaft 5 and that the tip tool is set on a workpiece such as a screw or bolt, that is, that the tip tool and the workpiece are in contact. Furthermore, the tightening operation of the impact tool 1 will be explained assuming that the transmission body (motor shaft 21) is rotating in the first direction DR1 in Figure 8. Since the planetary carrier 44 is connected to the shaft holding member 40 (see Figure 8) via the shaft 421 of the planetary gear 42, the planetary carrier 44 rotates together with the shaft holding member 40.

[0081] For example, at timing T0 in Figure 14, the operator pulls the trigger switch 12 to its maximum while the tip of the cutting tool is in contact with the workpiece, such as a screw. Here, at timing T0, it is assumed that, as shown in Figure 9 or Figure 10, the second engaging portion 442 of the planetary carrier 44 is separated by a certain distance or more in the rotational direction of the internal gear 43 (first direction DR1) relative to the first engaging portion 432 of the internal gear 43. In other words, it is assumed that the internal gear 43 is rotatable relative to the planetary carrier 44 in the first direction DR1 until the first engaging portion 432 and the second engaging portion 442 come into contact.

[0082] When the trigger switch 12 is pulled, the drive control unit 72 rotates the motor shaft 21 in the first direction DR1 (forward direction). In the following description, it is assumed that the operator maintains the trigger switch 12 pulled to its maximum position until the tightening operation of the workpiece is completed (until timing T10 in Figure 14). Note that the trigger switch 12 may also perform an alternate operation, where it remains pulled to its maximum position even when not being operated by the operator.

[0083] When the motor shaft 21 rotates, the planetary carrier 44 fixed to the motor shaft 21 also rotates integrally with the motor shaft 21. In other words, as shown in Figures 8 and 9, the planetary carrier 44 rotates in the first direction DR1 at the same rotational speed (rpm) as the motor shaft 21. To put it another way, the multiple planetary gears 42 revolve in the first direction DR1 at the same rotational speed (rpm) as the motor shaft 21. More specifically, the multiple planetary gears 42 revolve in the first direction DR1 while rotating on their own axis in the first direction DR1.

[0084] Furthermore, the internal gear 43, which meshes with multiple planetary gears 42, rotates in the first direction DR1 as the multiple planetary gears 42 rotate.

[0085] Here, the sun gear 41 is connected to the output shaft 5. Since the tip tool attached to the output shaft 5 is in contact with the workpiece, a force is applied to the output shaft 5 that suppresses rotation. In other words, the rotation of the sun gear 41, which transmits rotation to the output shaft 5, is suppressed. To put it another way, when the motor 2 first starts to rotate, in the planetary gear mechanism 4, the sun gear 41 is stationary, while the planetary gears 42, internal gear 43, and planetary carrier 44 are rotatable. More specifically, the sun gear 41 receives a force from multiple planetary gears 42 that tries to rotate the sun gear 41 in the second direction, but the sun gear 41 does not rotate before the first engaging part 432 engages with the second engaging part 442. Therefore, with the sun gear 41 fixed, the internal gear 43 and planetary carrier 44 rotate in the first direction DR1. The rotational speed of the internal gear 43 is faster than the rotational speed of the planetary carrier 44.

[0086] Figure 9 shows the state just before the motor shaft 21 begins to rotate. Figure 10 shows the state after some time has passed since the motor shaft 21 began to rotate in the first direction DR1. Figure 11 shows the state after the motor shaft 21 has continued to rotate in the first direction DR1 from the state shown in Figure 10.

[0087] As shown in Figures 10 and 11, as the internal gear 43 rotates in the first direction DR1 relative to the planetary carrier 44, the first engaging portion 432 of the internal gear 43 approaches the second engaging portion 442 which is further along in the direction of rotation. Then, for example, at timing T1 in Figure 14, as shown in Figure 11, the side surface of the first engaging portion 432 of the internal gear 43 comes into contact with the side surface of the second engaging portion 442 of the planetary carrier 44. In other words, the first engaging portion 432 of the internal gear 43 engages with the second engaging portion 442 of the planetary carrier 44. During the period between timing T0 and timing T1, the rotational speed of the motor shaft 21 exceeds a certain speed, so the inertial torque of the motor shaft 21 rises above a certain value. In the following explanation, the period during which the rotational speed of the motor shaft 21 increases in the first direction DR1 is called the charge period. The charge period is the period during which the inertial torque of the motor shaft 21 increases.

[0088] When each side of the multiple first engaging parts 432 engages with each side of the multiple second engaging parts 442, the planetary carrier 44 is accelerated in the first direction DR1 by the force applied from the multiple first engaging parts 432 to the multiple second engaging parts 442. This increases the force that rotates the sun gear 41 in the first direction DR1. Therefore, the sun gear 41 and the output shaft 5 connected to the sun gear 41 rotate in the first direction DR1. As the output shaft 5 rotates, the workpiece is tightened.

[0089] More specifically, when the planetary carrier 44 is accelerated in the first direction DR1 by the force applied from the multiple first engagement parts 432 to the multiple second engagement parts 442, each of the multiple planetary gears 42 experiences a force acting on it that causes it to rotate in the second direction (opposite to the first direction DR1) as a reaction force from the sun gear 41. On the other hand, each of the multiple planetary gears 42 also experiences a force acting on it that causes it to rotate in the first direction DR1, due to the force from the motor shaft 21 causing the planetary carrier 44 to rotate in the first direction DR1. Since both the force causing rotation in the first direction DR1 and the force causing rotation in the second direction are generated by the rotation of the planetary carrier 44 in the first direction DR1, the force causing rotation in the first direction DR1 and the force causing rotation in the second direction are in opposition to each other. Therefore, each of the multiple planetary gears 42 stops rotating around the shaft 421. As a result, the sun gear 41 rotates at the same speed and in the same direction as the internal gear 43.

[0090] Therefore, when the first engaging part 432 and the second engaging part 442 engage, the planetary carrier 44, the internal gear 43, the multiple planetary gears 42, and the sun gear 41 stop rotating relative to each other. In other words, the engagement of the first engaging part 432 and the second engaging part 442 fixes the planetary carrier 44, the internal gear 43, the multiple planetary gears 42, the sun gear 41, and the output shaft 5 to each other. Once the planetary carrier 44, the internal gear 43, the multiple planetary gears 42, the sun gear 41, and the output shaft 5 are fixed to each other, the planetary carrier 44, the internal gear 43, the multiple planetary gears 42, the sun gear 41, and the output shaft 5 rotate together in the first direction DR1 around the rotation axis Ax1. Therefore, at the timing T1 when the first engaging portion 432 and the second engaging portion 442 engage, the rotational speed of the output shaft 5 becomes the same as the rotational speed of the motor shaft 21.

[0091] In other words, the internal gear 43 rotates in the same direction as the transmission body (motor shaft 21) when the tip tool is in contact with the workpiece and the first engaging portion 432 of the internal gear 43 is not in contact with the second engaging portion 442 of the planetary carrier 44. The internal gear 43 and the output shaft 5 rotate integrally with the transmission body when the tip tool is in contact with the workpiece and the first engaging portion 432 of the internal gear 43 is in contact with the second engaging portion 442 of the planetary carrier 44.

[0092] At timing T2 in Figure 14, the workpiece is seated. Here, "seating" means that, if the workpiece is a screw or bolt, the head seating surface of the workpiece comes into contact with the mating member. If the workpiece is a nut, it means that the head seating surface of the workpiece comes into contact with the mating member. When the workpiece is seated, the tip tool rotates against the frictional force generated between the workpiece and the mating member, causing the tightening torque to increase rapidly.

[0093] In this embodiment, the drive control unit 72 stops supplying power to the motor 2 according to the magnitude or increase in the tightening torque detected by the torque detection unit 71.

[0094] The drive control unit 72 stops supplying power to the motor 2 at the timing (for example, timing T2) when the torque detection unit 71 detects that the workpiece has seated on the mating member. The torque detection unit 71 is configured to detect the seating of the workpiece when the increase in tightening torque per unit time exceeds a specified value, etc.

[0095] Furthermore, the drive control unit 72 stops supplying power to the motor 2 when the magnitude of the tightening torque detected by the torque detection unit 71 exceeds a specified value (for example, at timings T7 and T9).

[0096] After the power supply to motor 2 is cut off, the output shaft 5 and the tip tool attached to the output shaft 5 continue to rotate due to the inertial torque accumulated in the inertial body 3, etc., and tighten the workpiece. This reduces the reaction force that the operator receives from the impact tool 1 after the workpiece is seated. In detail, when power is not supplied to motor 2, no electromagnetic interaction occurs between the rotor 2A and the stator 2B of motor 2. Therefore, the reaction force transmitted from the output shaft 5 to the rotor 2A is not transmitted to the stator 2B, and the reaction force that the operator receives from the impact tool 1 is reduced.

[0097] As the tightening torque increases, the inertial torque of the motor shaft 21 is consumed, and the rotation of the motor shaft 21 and the output shaft 5 stops at timing T3. In this embodiment, the drive control unit 72 controls the motor 2 at timing T4, which is after timing T3 when the rotation of the motor shaft 21 and the output shaft 5 stops, to rotate the motor shaft 21 in the second direction (reverse direction) for a predetermined time or by a predetermined angle.

[0098] When the motor shaft 21 rotates, the planetary carrier 44 also rotates integrally with the motor shaft 21. In other words, the planetary carrier 44 rotates in the second direction at the same rotational speed (rpm) as the motor shaft 21.

[0099] Since the tip tool attached to the output shaft 5 is in contact with the workpiece, a force is applied to the output shaft 5 that suppresses rotation. In other words, the rotation of the sun gear 41 connected to the output shaft 5 is suppressed.

[0100] Therefore, when the motor shaft 21 rotates in the second direction, each of the planetary carrier 44, the multiple planetary gears 42, and the internal gear 43 rotates in the opposite direction (second direction) to when the motor shaft 21 rotates in the first direction DR1 (as in Figure 8). Since the rotational speed of the internal gear 43 is faster than the rotational speed of the planetary carrier 44, the first engaging portion 432 of the internal gear 43 and the second engaging portion 442 of the planetary carrier 44, which were in contact, move apart. The predetermined time for the motor shaft 21 to rotate in the second direction is the time during which the first engaging portion 432, which is moving apart from the second engaging portion 442, does not come into contact with any other second engaging portion 442. The predetermined angle (predetermined number of rotations) is the angle (amount of rotation) during which the first engaging portion 432, which is moving apart from the second engaging portion 442, does not come into contact with any other second engaging portion 442 until the motor shaft 21 has rotated by a predetermined angle (predetermined number of rotations).

[0101] The drive control unit 72 controls the motor 2 to stop the rotation of the motor shaft 21 at timing T5, which is either a predetermined time after timing T4 or when the motor shaft 21 has rotated by a predetermined angle.

[0102] At timing T6, after the drive control unit 72 has controlled the motor 2 to stop the rotation of the motor shaft 21, it controls the motor 2 to rotate the motor shaft 21 again in the first direction DR1. When the motor shaft 21 rotates in the first direction DR1, the internal gear 43 rotates in the first direction DR1 faster than the planetary carrier 44, similar to the period between timing T0 and timing T1.

[0103] In other words, the drive control unit 72 controls the motor 2 to rotate the motor shaft 21 in the second direction, thereby securing a charging period to increase the inertial torque again, and allowing the workpiece to be tightened again with the inertial torque.

[0104] The drive control unit 72 repeats the control performed from timing T0 to timing T5 from timing T6 until the tightening torque exceeds the set torque. In the example in Figure 14, timings T7 and T8 in the second control correspond to timings T2 and T3 in the first control, and timings T9 and T10 in the third control correspond to timings T2 and T3 in the first control. Since the workpiece is already seated in the first control, there is no period in the second and subsequent controls that corresponds to the period from timing T1 to timing T2 in the first control.

[0105] In the example in Figure 14, the first period from timing T2 to timing T3 is longer than the second period from timing T7 to timing T8. The second period is longer than the third period from timing T9 to timing T10. The peak value of the tightening torque in the first period is smaller than the peak value of the tightening torque in the second period. Also, the peak value of the tightening torque in the second period is smaller than the peak value of the tightening torque in the third period. Furthermore, the integrated value of the tightening torque in the first period is equal to the integrated value of the tightening torque in the second period and the integrated value of the tightening torque in the third period.

[0106] As described above, the impact tool 1 has three operating states when the motor 2 is in operation: a first operating state, a second operating state, and a third operating state. The first operating state is the state in which the motor shaft 21 rotates in the first direction DR1 and the output shaft 5 does not rotate (is stopped), as shown in Figure 14 during the period from timing T0 to timing T1. The second operating state is the state in which the motor shaft 21, the internal gear 43, the planetary carrier 44, and the output shaft 5 rotate together in the first direction DR1, as shown in Figure 14 during the period from timing T1 to timing T2. The third operating state is the state in which the motor shaft 21 rotates in the second direction and the internal gear 43 rotates in the second direction relative to the planetary carrier 44, as shown in Figure 14 during the period between timing T4 and timing T5. During the tightening operation using the impact tool 1 of this embodiment, the operating state of the impact tool 1 transitions from a first operating state to a second operating state, from the second operating state to a third operating state, and from the third operating state to a first operating state.

[0107] (2.4) Bit pattern monitoring and correction processing As described above, the control unit 7 of this embodiment includes a calculation unit 73, a monitoring unit 74, and a correction unit 75.

[0108] The arithmetic unit 73 performs calculation processing and calculates the speed of the motor 2 using a first bit pattern based on the electrical signal from the Hall sensor B1. Here, the arithmetic unit 73 calculates the speed (rotational speed), i.e., the speed response value, of the motor 2 using the first bit pattern (changes) based on the electrical signals Sg1 to Sg3 from the first to third Hall elements B11 to B13.

[0109] Figure 3 shows the waveforms of the electrical signals Sg1, Sg2, and Sg3, which are voltage signals output from the first Hall element B11, the second Hall element B12, and the third Hall element B13, respectively.

[0110] Each of the electrical signals Sg1, Sg2, and Sg3 is a square wave signal that changes in high / low level depending on the position of the rotating rotor 2A (the position of the north and south poles of the permanent magnet).

[0111] In this embodiment, it is assumed that the changing value of the first bit pattern (hereinafter also referred to as the "current value") can take values ​​from "0" to "5". The current value of the first bit pattern is calculated by the combination of High / Low levels of the electrical signals Sg1 to Sg3 output from the first to third Hall elements B11 to B13, respectively, when the motor 2 is actually rotating.

[0112] For example, the current value of the first bit pattern is calculated by (1) below. {(U)+(V*2)+(W*4)-1}=[0~5]···(1) For the U-phase electrical signal Sg1, if it is at a high level, U=1 is substituted into equation (1), and if it is at a low level, U=0 is substituted into equation (1). Similarly, for the V-phase electrical signal Sg2, if it is at a high level, V=1 is substituted into equation (1), and if it is at a low level, V=0 is substituted into equation (1). For the W-phase electrical signal Sg3, if it is at a high level, W=1 is substituted into equation (1), and if it is at a low level, W=0 is substituted into equation (1). It is not possible for all electrical signals Sg1 to Sg3 to be at a high or low level simultaneously; one or two of the electrical signals Sg1 to Sg3 will always be at a high level. Therefore, the solution (current value) to equation (1) will be one of the values ​​from "0" to "5".

[0113] Thus, the value of the first bit pattern (current value) is calculated based on three electrical signals Sg1 to Sg3 from the three Hall elements B11 to B13.

[0114] While motor 2 is operating, the current value of the first bit pattern changes in a basically regular manner, unless there are problems described later (for example, 3→4→0→2→1→5→3→4→0→2→1→5→3...). This "3→4→0→2→1→5→3" corresponds to the change pattern of one cycle, i.e., the change pattern of 360 degrees (one rotation) of electrical angle, which is the change pattern of switching the switch that applies voltage to the three-phase stator windings in stator 2B. Unless there are problems described later, the calculation unit 73 calculates the speed (rotational speed) of motor 2 based on the time it takes for the first bit pattern to change, for example, from "3" to "4" (hereinafter, the time required for the change of the first bit pattern will be called the calculation period, or simply the period).

[0115] However, for example, when the impact tool 1 is operating while the motor 2 is rotating in the forward direction, there is a problem that at the moment the impact rotation mechanism A1 makes a strike, that is, at the moment the first engaging portion 432 of the internal gear 43 in the planetary gear mechanism 4 comes into contact with the second engaging portion 442 of the planetary carrier 44, the motor 2 may unintentionally reverse direction instantaneously due to the recoil from the impact. Similarly, even when the impact tool 1 is operating while the motor 2 is rotating in the reverse direction, the motor 2 may unintentionally reverse direction instantaneously (in the forward direction) due to the recoil from the impact.

[0116] As a result, the electrical signal from the Hall sensor B1 may become distorted, and the first bit pattern, which should normally change regularly, may also become distorted.

[0117] In the multiple locations C11 enclosed by the ellipse in Figure 3, the motor 2 momentarily reverses direction due to the rebound during impact, causing signals that were showing a high level to momentarily drop to a low level, and signals that were showing a low level to momentarily rise to a high level.

[0118] Therefore, the first bit pattern change can momentarily deviate from the rule "3→4→0→2→1→5→3→..." and change to something like "3→4→0→2→1→2→1→5→3→...". In other words, the change from "1→2" is an impossible change pattern.

[0119] To solve this problem, in this embodiment, the monitoring unit 74 performs a monitoring process to monitor changes in the first bit pattern and determines whether the first bit pattern deviates from the second bit pattern defined for reference. The "second bit pattern defined for reference" here refers to, for example, the assumed correct rule pattern "3→4→0→2→1→5→3→..." as described above. Information on the second bit pattern is stored in advance in, for example, the storage unit 6.

[0120] In this embodiment, if the monitoring unit 74 determines that the first bit pattern deviates from the second bit pattern (for example, if it detects a change from "1" to "2"), the correction unit 75 executes a correction process to correct the outlier value in the first bit pattern. The outlier value here is, for example, "2" in the case of a change from "1" to "2".

[0121] For example, the correction unit 75 performs a correction by replacing an outlier (e.g., "2") with a value prior to the outlier (hereinafter also referred to as the past value). For example, if the outlier is "2", the past value is one of the values ​​prior to "2", such as "3→4→0→2→1". However, if, for example, "2" is replaced with "3", the outlier may continue to be replaced with "3" for a while until the change in the first bit pattern returns to the original correct rule "3→4". During that time, the calculation period used for speed calculation will be extended. Therefore, it is preferable that the past value is "1", which is the value immediately preceding "2". In other words, it is preferable for the correction unit 75 to perform a correction by replacing the outlier with the value immediately preceding the outlier. By replacing the outlier with the value immediately preceding it, the extension of the calculation period used for speed calculation can be suppressed.

[0122] In this manner, if the monitoring unit 74 determines that the first bit pattern deviates from the second bit pattern, the control unit 7 waits until the outlier is replaced with a past value by the correction unit 75, thereby returning to the original correct bit pattern (rule).

[0123] In this embodiment, if the monitoring unit 74 determines that the first bit pattern deviates from the second bit pattern, the calculation unit 73 calculates the speed of the motor 2 in the calculation process based on the correction by the correction unit 75. Then, the drive control unit 72 of the control unit 7 controls the motor 2 so that its speed follows the target speed, based on the calculation result of the calculation unit 73.

[0124] Figure 2 is a characteristic diagram showing an example of the changes in the speed command value E1 and speed response value F1 in an impact tool (hereinafter referred to as a comparative example) that does not have the functions of the monitoring unit 74 and the correction unit 75 in this embodiment, or the functions of the calculation unit 73 corresponding to the monitoring unit 74 and the correction unit 75. In Figure 2, the horizontal axis is time [msec] and the vertical axis is the rotational speed [rpm] of the motor 2 (rotational speed).

[0125] On the other hand, Figure 4 is a characteristic diagram showing an example of the changes in the speed command value E2 and speed response value F2 in an impact tool 1 having the functions of the monitoring unit 74 and the correction unit 75 in this embodiment, as well as the functions of the calculation unit 73 corresponding to the monitoring unit 74 and the correction unit 75. In Figure 4, as in Figure 2, the horizontal axis is time [msec] and the vertical axis is the rotational speed [rpm] (rotational speed) of the motor 2.

[0126] The speed command value E1 is an example of a command value determined according to the amount of retraction of the trigger switch of the comparative example, and the speed response value F1 is an example of a result calculated by the calculation unit of the comparative example. In contrast, the speed command value E2 is an example of a command value determined according to the amount of retraction of the trigger switch 12 of the impact tool 1, and the speed response value F2 is an example of a result calculated by the calculation unit 73 of the impact tool 1.

[0127] In the comparative example, due to the disruption of the electrical signal from the Hall sensor caused by the motor momentarily reversing due to the rebound during impact, there is a relatively long period of time during which the calculation unit fails to calculate the speed response value F1 and the rotation speed (rotational velocity) is 0 (zero) (see Figure 2).

[0128] On the other hand, in the impact tool 1, even if the electrical signal from the Hall sensor B1 is disturbed due to the problem of motor 2 momentarily reversing due to the rebound during impact, the speed of motor 2 is calculated using a calculation cycle based on the correction by the correction unit 75. Therefore, there is no long period of time when the rotational speed is 0 as shown in Figure 2, and the calculation of the speed response value F2 is performed appropriately (see Figure 4).

[0129] (2.5) Operations related to monitoring and correction processes The following describes the sequence of operations related to the monitoring and compensation processes in the impact tool 1 with reference to Figure 5. The flowchart shown in Figure 5 is merely one example of the operation flow for the impact tool 1, and the order of operations may be changed as appropriate, or operations may be added or omitted as appropriate.

[0130] When the control unit 7 starts driving the motor 2, the monitoring unit 74 monitors for changes in the first bit pattern (execution of monitoring process). The control unit 7 determines whether or not the first bit pattern (value) based on the electrical signals Sg1, Sg2, and Sg3 has changed (step ST1). If the control unit 7 determines that the first bit pattern has changed (step ST1: Yes), it proceeds to step ST2. On the other hand, if the control unit 7 determines that the first bit pattern has not changed (step ST1: No), it counts up the calculation cycle (step ST3) and returns to step ST1. In other words, the control unit 7 continues to count up the calculation cycle until the first bit pattern changes.

[0131] Next, in step ST2, the control unit 7 (monitoring unit 74) determines whether the first bit pattern has changed a predetermined number of times or more (after the motor 2 starts driving). In the example in Figure 5, the predetermined number is set to 5 times, but it is not limited to 5 times. If the control unit 7 determines that the first bit pattern has changed a predetermined number of times (5 times) or more (step ST2: Yes), it proceeds to step ST4, which determines whether the first bit pattern is different from the second bit pattern.

[0132] On the other hand, if the control unit 7 determines that the first bit pattern has changed less than a predetermined number of times (5 times) (step ST2: No), it saves the bit pattern (value) at the next time the first bit pattern changes (step ST5). In other words, in step ST5, the control unit 7 refers to the second bit pattern "3→4→0→2→1→5→3→..." in the memory unit 6 and saves the value that is expected to change from the current value of the first bit pattern next time (saves the expected value). For example, if the current value after the change is "4" in steps ST1 and ST2, the control unit 7 refers to the second bit pattern and saves "0" as the expected value, which is expected to be the change from "4" at the next time the first bit pattern changes. Then, after step ST5, the control unit 7 resets the operation cycle count (step ST6) and returns to step ST1.

[0133] In short, in this embodiment, the monitoring unit 74 starts determining whether the first bit pattern deviates from the second bit pattern (step ST4) after the motor 2 has started and the first bit pattern has changed a predetermined number of times or more. By not proceeding to step ST4 until the first bit pattern has changed a predetermined number of times or more after the motor 2 has started, the possibility that unstable changes in the first bit pattern immediately after the motor 2 has started will also be subject to determination by the monitoring unit 74 can be reduced. Once the first bit pattern has changed a predetermined number of times or more after the motor 2 has started, step ST2 is always determined to be "Yes" thereafter.

[0134] Next, in step ST4, the control unit 7 uses the monitoring unit 74 to determine whether the current bit pattern is the expected bit pattern, that is, whether the first bit pattern deviates from the second bit pattern. If the current bit pattern is the expected bit pattern (step ST4: Yes, the first bit pattern is not deviating from the second bit pattern), the control unit 7 saves the pattern for the next change (step ST7). In other words, in step ST7, similar to step ST5, the control unit 7 refers to the second bit pattern and saves the value that is expected to change from the current value of the first bit pattern to the expected value. For example, if the current value of the first bit pattern is "0" and the saved expected value is also "0", the control unit 7 determines that the current bit pattern is the expected bit pattern. Then, the control unit 7 refers to the second bit pattern and saves "2", which is expected to be the change from the current value "0" when the first bit pattern changes next, as the expected value.

[0135] Then, after step ST7, the control unit 7 saves the calculation period that was being counted at that point (for example, the time from when it changed to "4" to when it changed to the expected "0") (step ST8), and the calculation unit 73 uses this calculation period for speed calculation. The control unit 7 also resets the calculation period count (step ST9), returns the process to step ST1, and waits again for the first bit pattern to change.

[0136] On the other hand, if the current bit pattern is not the expected bit pattern (step ST4: No, if the first bit pattern is different from the second bit pattern), the control unit 7 counts up the calculation cycle (step ST10). Furthermore, the control unit 7 uses the correction unit 75 to rewrite the first bit pattern (its current value) to a past value (step ST11, execution of correction process). For example, if the current value of the first bit pattern is "2" and the stored expected value is "5", the control unit 7 determines that the current bit pattern is not the expected bit pattern. The correction unit 75 corrects the current value "2" by replacing it with the past value "1" which is the value immediately preceding the current value "2". After replacing the current value with the past value, the control unit 7 returns to step ST1 and waits again for a change in the first bit pattern.

[0137] In short, in the example above, since "5" follows "1", the control unit 7 stores "5" as the expected value and waits for a change in the first bit pattern. It continues to replace the first bit pattern with the past value "1" until the current value matches the expected value "5". By performing this replacement with the past value once or multiple times, the control unit 7 restores the first bit pattern, which had deviated, to its original correct pattern (rule). As can be seen from the flowchart in Figure 5, if the current bit pattern ≠ the expected bit pattern, the count-up of the calculation period will continue until the current bit pattern = the expected bit pattern. In other words, the calculation period will be extended by the amount of the correction.

[0138] As described above, with the impact tool 1 according to this embodiment, if the monitoring unit 74 determines that the first bit pattern deviates from the second bit pattern, the correction unit 75 corrects the deviation value of the first bit pattern to a past value. As a result, the first bit pattern that had deviated is returned to its original correct pattern (rule). Then, the calculation unit 73 calculates the speed (speed response value) of the motor 2 based on the calculation cycle at the time when the correction unit 75 corrected the pattern.

[0139] Therefore, even if the motor 2 reverses direction due to the recoil during impact, and the first bit pattern based on the electrical signal received from the Hall sensor B1 is disrupted, the possibility that the calculation of the speed response value will not be performed correctly can be reduced. As a result, the impact tool 1 can suppress the decrease in calculation accuracy related to the speed calculation of the motor 2.

[0140] (3) Variant The following lists modifications of the above embodiment. In the description of the following modifications, elements similar to those in the above embodiment may be given the same reference numerals and their descriptions may be omitted as appropriate.

[0141] (3.1) Variation 1 The impact tool 1 according to Modification 1 will be described below with reference to Figures 15 to 18.

[0142] In the above embodiment, even if the motor 2 momentarily reverses direction due to the rebound during impact, the speed of the motor 2 is calculated using the calculation cycle based on the correction by the correction unit 75. Therefore, the calculation of the speed response value F2 is performed appropriately.

[0143] Incidentally, the problem of motor 2 momentarily reversing direction due to the recoil during impact can affect the drive control of motor 2 in the drive control unit 72, potentially causing a control error. Generally, when an impact tool is operating while maintaining forward rotation of the motor, the motor drive control is programmed to execute processing based on the assumption of forward rotation. Similarly, when an impact tool is operating while maintaining reverse rotation of the motor, the motor drive control is programmed to execute processing based on the assumption of reverse rotation. Therefore, if the above problem occurs while the impact tool is operating while maintaining forward (or reverse) rotation of the motor, it can potentially cause a control error.

[0144] The impact tool 1 according to Modification 1 differs from the above embodiment in that it further includes a determination unit 76 and an energization position correction unit 77 (see Figure 15) in order to suppress the occurrence of the above control errors.

[0145] More specifically, the impact tool 1 according to Modification 1 comprises a motor 2, an impact rotation mechanism A1, a memory unit 6, a control unit 7, a trigger switch 12 (see also Figure 6), a torque sensor 14, a Hall sensor B1, and an encoder D1, as shown in Figure 15. The impact tool 1 according to Modification 1 further comprises an inertia body 3 (see Figure 7), an output shaft 5 (see Figure 7), a housing 10 (see Figure 6), a battery pack 11 (see Figure 6), and a fan 8 (see Figure 7). Note that the configuration of Modification 1 other than the control unit 7 and encoder D1 is generally the same as in the above embodiment, so a detailed explanation is omitted.

[0146] As shown in Figure 15, the control unit 7 according to Modified Example 1 includes a torque detection unit 71, a drive control unit 72, a calculation unit 73, a monitoring unit 74, a correction unit 75, a judgment unit 76, and an energized position correction unit 77. The torque detection unit 71, drive control unit 72, calculation unit 73, monitoring unit 74, correction unit 75, judgment unit 76, and energized position correction unit 77 do not necessarily represent actual physical configurations, but rather represent functions realized by the control unit 7.

[0147] The following describes the drive control unit 72, the determination unit 76, and the energized position correction unit 77 in the control unit 7 according to Modification 1.

[0148] The drive control unit 72, upon interruption occurring in response to a change in the value of the first bit pattern, determines which of the U-phase, V-phase, and W-phase circuits will be energized to supply the drive current for the motor 2, and controls the motor 2 based on the energized position. In other words, an "interrupt" from the Hall sensor B1 to the drive control unit 72 occurs when a change in the signal level of any of the electrical signals Sg1, Sg2, and Sg3 (see Figure 16) of the U-phase, V-phase, and W-phase output from the first to third Hall elements B11 to B13 occurs. Here, "change in signal level" means, for example, a change in voltage level from a High level to a Low level, or from a Low level to a High level. The drive control unit 72 switches the energized position at the timing when the "interrupt" occurs. The drive control unit 72 determines the energized position according to the (software) recognized position (for example, a value from "1" to "6") described later, upon interruption.

[0149] Figure 16 shows an example of the rectangular wave signal waveforms of the electrical signals Sg1, Sg2, and Sg3 output from the three Hall elements B11 to B13 of the Hall sensor B1 while the impact tool 1 according to Modification 1 is operating while maintaining forward rotation. In Figure 16, for convenience, the labels t1 to t10 are only given to some of the time points among the multiple time points in which "interrupts" occur. The signal level (voltage level) of any of the electrical signals Sg1, Sg2, and Sg3 of the U-phase, V-phase, and W-phase changes from a high level to a low level, or from a low level to a high level, at each time point t1, t2, ..., in accordance with the rotation of the motor 2 (occurrence of an interrupt).

[0150] Figure 16 also shows an example of a rectangular wave signal waveform of the electrical signal Sg4 (e.g., a voltage signal) that indicates the (soft) recognized position of the motor 2 recognized by the control unit 7, overlaid on the waveform diagrams of the electrical signals Sg1, Sg2, and Sg3 of the U-phase, V-phase, and W-phase. Since there are a total of 6 patterns of combinations of High level / Low level for the electrical signals Sg1, Sg2, and Sg3 of the U-phase, V-phase, and W-phase, it is assumed here, as an example, that the control unit 7 manages the (recognized) position of the motor 2 using values ​​from "1" to "6" corresponding to each of the 6 patterns. In other words, in Modification 1, it is assumed that the value of the first bit pattern is a value from "1" to "6". However, the value of the first bit pattern may also be a value from "0" to "5" using equation (1) of the above embodiment.

[0151] For example, the relationship between the values ​​"1" to "6" and the High / Low levels of the U-phase, V-phase, and W-phase electrical signals Sg1, Sg2, and Sg3 is as shown in Table 1 below. That is, for example, a value of "5" indicates that the U-phase electrical signal Sg1 is at a High level, the V-phase electrical signal Sg2 is at a Low level, and the W-phase electrical signal Sg3 is at a High level. The energization position is determined according to the values ​​"1" to "6" (i.e., the High / Low level patterns of the U-phase, V-phase, and W-phase electrical signals Sg1, Sg2, and Sg3).

[0152] [Table 1]

[0153] As shown in Figure 16, the signal level (e.g., voltage level) of the electrical signal Sg4 indicating the recognized position of motor 2 changes in six steps according to a value from "1" to "6". As shown in Figure 16, when the impact tool 1 is operating while maintaining forward rotation and motor 2 is rotating in the forward direction, the position of motor 2 is expected to change periodically in the order of "5" → "4" → "6" → "2" → "3" → "1" → "5".... In the modified example 1, the memory unit 6 has in advance stored information on the normal change pattern ("5" → "4" → "6" → "2" → "3" → "1" → "5"...) when the impact tool 1 is operating while maintaining forward rotation, and the drive control unit 72 uses this change pattern information to determine the energized position during forward rotation. Although a detailed explanation is omitted here, the memory unit 6 also stores information on the normal change pattern while the impact tool 1 is operating in reverse, and the drive control unit 72 uses this change pattern information to determine the energized position during reverse operation.

[0154] In short, the drive control unit 72 does not determine the energized position from a value (actual value) that is one of "1" to "6" based on the change in the signal levels of the actual electrical signals Sg1, Sg2, and Sg3. Rather, each time an "interrupt" occurs, it compares the actual value with information about a (known) change pattern that is likely to change periodically in the order of "5" → "4" → "6" → "2" → "3" → "1" → "5"... and if they match, it determines the energized position from the matching value. In other words, the drive control unit 72 monitors the change in the signal levels of the actual electrical signals Sg1, Sg2, and Sg3 in order to know the timing of the "interrupt" (the timing of switching the energized position) and to determine the energized position by comparing the actual value with information about the (known) change pattern.

[0155] In Figure 16, the recognized position of the motor 2, as recognized by the control unit 7 based on the change pattern information stored in the memory unit 6, and the actual motor position are illustrated with values ​​from "1" to "6" on top of the waveform diagram of the electrical signal Sg4.

[0156] The following provides a detailed explanation of "recognition position" and "motor position."

[0157] Figure 17 shows the relationship between the current position and the next position of motor 2, which is recognized as the "recognized position" by the control unit 7 based on the information of the normal change pattern described above, when, for example, the impact tool 1 is operating while maintaining forward rotation. For example, if the current position of motor 2 is "2" when an interrupt occurs at a certain point in time, the control unit 7 has pre-recorded that the position (next position) when the next interrupt occurs will be "3" based on the information of the normal change pattern described above, as shown in Figure 17. Similarly, the control unit 7 has pre-recorded that if the current position is "3", the next position is "1", if the current position is "1", the next position is "5", if the current position is "5", the next position is "4", if the current position is "4", the next position is "6", if the current position is "6", the next position is "2", and so on, in preparation for the occurrence of the next interrupt.

[0158] The motor position values ​​"1" to "6" shown in Figure 16 are actual values ​​based on the signal levels of the electrical signals Sg1, Sg2, and Sg3. On the other hand, the electrical signal Sg4 and the recognized position values ​​"1" to "6" shown in Figure 16 are not actual values ​​based on the signal levels of the electrical signals Sg1, Sg2, and Sg3, but rather signals and values ​​corresponding to the position of motor 2 recognized by the control unit 7 based on the information of the normal change pattern described above.

[0159] Incidentally, in the example shown in Figure 16, at time t7, an interrupt occurs in which motor 2 momentarily reverses direction due to the rebound from the impact, causing the signal level of the V-phase electrical signal Sg2 to change from a low level to a high level (hereinafter also referred to as a "reversal interrupt"). As a result, at time t7, the actual motor position changes from "1" to "3", which differs from the position recognized by the control unit 7 (i.e., the recognition that the recognized position changes from "1" to "5").

[0160] In Modification 1, the control unit 7 performs a correction process to correct the energized position so that it is easy to return to control of forward rotation even if it momentarily reverses direction while maintaining forward rotation, and so that it is easy to return to control of reverse rotation even if it momentarily reverses direction (in the forward direction) while maintaining reverse rotation. This correction process will be described in detail below.

[0161] First, it is necessary to determine whether the interrupt that occurred is an interrupt during forward rotation or reverse rotation. Therefore, the determination unit 76 determines whether the motor 2 is rotating in the forward or reverse direction at an earlier timing than the interrupt occurs. For example, the determination unit 76 monitors the count value of encoder D1 at a shorter period than the period during which an interrupt may occur, and determines whether the motor 2 is rotating in the forward or reverse direction at an earlier timing than the interrupt occurs.

[0162] Encoder D1 is, for example, optical or magnetic. Encoder D1 is attached to motor 2 and detects the rotation angle and direction of movement (direction of rotation) of motor 2. Encoder D1 is connected to control unit 7 in a communicative manner and outputs an electrical signal to control unit 7 corresponding to the rotation angle and direction of rotation of motor 2. In particular, encoder D1 outputs a count value to control unit 7 that indicates whether the rotation direction of motor 2 is forward or reverse. The count value output from encoder D1 increases (count up) if motor 2 is rotating in the forward direction and decreases (count down) if motor 2 is rotating in the reverse direction. In other words, if the difference between the current count value and the previous count value (count difference) is positive, motor 2 is rotating in the forward direction, and if it is negative, motor 2 is rotating in the reverse direction. The determination unit 76 determines whether motor 2 is rotating in the forward or reverse direction from the count difference of encoder D1.

[0163] If the impact tool 1 is operating while maintaining forward rotation, the judgment unit 76 determines that the motor 2 is rotating in reverse, or if the impact tool 1 is operating while maintaining reverse rotation, the judgment unit 76 determines that the motor 2 is rotating in forward rotation, and the energized position correction unit 77 determines that the interrupt is a reverse interrupt and corrects the energized position. If the judgment unit 76 determines that the motor 2 is rotating in forward rotation (as in forward rotation operation), or if the judgment unit 76 determines that the motor 2 is rotating in reverse (as in reverse rotation operation), the energized position correction unit 77 determines that the interrupt is a normal interrupt. If it is a normal interrupt, the drive control unit 72 compares the actual value of the motor position (one of the values ​​from "1" to "6") with the value of the recognized position (one of the values ​​from "1" to "6") which has been recorded in advance based on the above change pattern information. If they match, the energized position is determined and switched according to the value of the recognized position. If they do not match, for example, the energized position may be determined according to the value of the recognized position without correcting the energized position or considering the actual value of the motor position.

[0164] For example, Figure 18 shows an example of correction when correcting the energized position while the impact tool 1 is operating while maintaining forward rotation. Figure 18 shows the recognized position (labeled "soft recognized position" in Figure 18) and motor position at times t3 to t10 in Figure 16. As described above, at time t7, while the impact tool 1 is operating while maintaining forward rotation, the motor 2 momentarily reverses direction due to the recoil during impact, causing the actual motor position to change from "1" to "3" and a reverse interrupt to occur. In the example in Figure 18, the judgment unit 76 determines that the rotation of motor 2 is reversed (contrary to the forward rotation) at an earlier timing than this "reverse interrupt". The energized position correction unit 77, according to the judgment result of the judgment unit 76, replaces (corrects) the recognized position corresponding to the occurrence of the next interrupt after the reverse interrupt (i.e., time t8) with a recognized position earlier than recognized position "5" (here, "2" as an example). In other words, the energized position correction unit 77 moves the energized position (energized location) at the time of the next interrupt following the reverse interrupt to an energized position corresponding to a recognition position before the recognition position "5" (here, "2" as an example). In the example in Figure 18, the reason for moving back three positions from the recognition position "5" to "2" is as follows: That is, while the actual motor position returns from "1" to "3" due to the reverse rotation during impact, the recognition position changes from "1" to "5" according to the change pattern information assuming forward rotation. At this stage, a difference of two positions occurs between the actual motor position and the recognition position. Then, at the timing of the next interrupt (time t8) while motor 2 is reversing, the energized position is actually switched, resulting in a total positional change of three positions, which in Figure 18 is three positions back from "5" to the position "2". In short, the energized position correction unit 77 corrects (determines) the position of motor 2 (i.e., the energized position) according to the difference in position between the actual motor position and the recognized position when a reverse interrupt occurs.

[0165] At time t7, the actual motor position is "3," but the drive control unit 72, as planned, determines the energized position based on the recognized position "5," which was previously recorded as the "next position" at the previous time t6, and performs drive control of the motor 2 based on that energized position.

[0166] In the example shown in Figure 18, the energized position correction unit 77 corrects the recognized position from "4" to "2" at time t8, and at time t9, the next time after t8, it corrects the recognized position from "6" to "3" according to the information of a normal change pattern ("2" → "3"). The energized position correction unit 77 similarly corrects the recognized position from time t10 onwards. The drive control unit 72 applies the energized position corrected by the energized position correction unit 77 when the next interrupt following the reverse interrupt occurs to control the drive of the motor 2.

[0167] According to the configuration of Modified Example 1, even if the motor 2 reverses direction due to the rebound during impact, the occurrence of control errors can be suppressed.

[0168] In this explanation, the correction process was described using the example of a case where the rotation of motor 2 momentarily reverses due to the recoil from impact while impact tool 1 is operating in the forward direction. However, even if the rotation of motor 2 momentarily reverses (to the forward direction) due to the recoil from impact while impact tool 1 is operating in the reverse direction, the same correction process is performed to suppress the occurrence of control errors.

[0169] (3.2) Other variations Functions similar to those of the impact tool 1 according to the above embodiment may be realized by a control method, a computer program, or a non-temporary recording medium on which a computer program is stored.

[0170] The impact tool 1 in this disclosure includes a computer system. The computer system mainly consists of a processor and memory as hardware. The function of the impact tool 1 in this disclosure is realized by the processor executing a program recorded in the memory of the computer system. The program may be pre-recorded in the memory of the computer system, provided via a telecommunication line, or provided on a non-temporary recording medium such as a memory card, optical disk, or hard disk drive that can be read by the computer system. The processor of the computer system consists of one or more electronic circuits including semiconductor integrated circuits (ICs) or large-scale integrated circuits (LSIs). The integrated circuits such as ICs or LSIs referred to here are named differently depending on the degree of integration, and include integrated circuits called system LSIs, VLSIs (Very Large Scale Integration), or ULSIs (Ultra Large Scale Integration). Furthermore, FPGAs (Field-Programmable Gate Arrays) that are programmed after the manufacture of the LSI, or logic devices that allow for the reconfiguration of junction relationships or circuit compartments within the LSI, can also be used as processors. Multiple electronic circuits may be aggregated on a single chip or distributed across multiple chips. Multiple chips may be integrated into a single device or distributed across multiple devices. The computer system referred to here includes a microcontroller having one or more processors and one or more memories. Therefore, the microcontroller also consists of one or more electronic circuits, including semiconductor integrated circuits or large-scale integrated circuits.

[0171] It is not mandatory for the impact tool 1 to be equipped with a torque sensor 14. If the impact tool 1 is not equipped with a torque sensor 14, the torque detection unit 71 may detect, based on the rotational speed (revolutions per minute [rpm]) of the motor shaft 21, that the workpiece has seated on the mating member or that the tightening torque has exceeded a specified value. Alternatively, the torque detection unit 71 may determine the tightening torque based on the amount of rotation (rotation angle) of the motor shaft 21 from the timing when the torque detection unit 71 detects that the workpiece has seated on the mating member, or when the tightening torque detected by the torque detection unit 71 exceeds a specified value, until the motor shaft 21 stops. Furthermore, the torque detection unit 71 may determine the tightening torque by determining the inertial torque of the output shaft 5 of the motor shaft 21 based on the rotational speed of the motor shaft 21 and the mass of the inertial body 3, etc.

[0172] In the above embodiment, if the correction unit 75 determines that the first bit pattern deviates from the second bit pattern, it performs a correction as an example of outlier correction, which involves replacing the outlier with a value from the past (for example, the past value immediately preceding the outlier). However, the correction is not limited to replacing with a past value. For example, if the correction unit 75 determines that the first bit pattern deviates from the second bit pattern, it may always replace the outlier with a predetermined value. To explain with a specific example, the correction unit 75 may replace the outlier with the predetermined value "0" even if the first bit pattern changes from "1 to 2" and the outlier is "2", or even if the first bit pattern changes from "2 to 5" and the outlier is "5". Note that if it always replaces with a predetermined value (for example, "0"), the outlier may continue to be replaced with "0" for a while until the change in the first bit pattern returns to the correct rule "0 to 2".

[0173] In the above embodiment, the impact rotation mechanism A1 is composed of a planetary gear mechanism 4 (see Figures 7 to 13). However, it is not limited to this, and the impact rotation mechanism A1 may be an impact rotation mechanism including a hammer and anvil in a conventional impact tool, as described in Patent Document 1.

[0174] (summary) Based on the embodiments described above, the following aspects are disclosed.

[0175] The impact tool (1) according to the first embodiment comprises a motor (2), an impact rotation mechanism (A1), a Hall sensor (B1), a calculation unit (73), a monitoring unit (74), and a correction unit (75). The motor (2) has a rotor (2A) and is capable of forward and reverse rotation. The impact rotation mechanism (A1) receives rotational force from the motor (2) and performs an impact operation by rotational inertia force while repeatedly rotating forward and in reverse. The Hall sensor (B1) outputs an electrical signal corresponding to the rotational position of the rotor (2A). The calculation unit (73) calculates the speed of the motor (2) using a first bit pattern based on the electrical signal. The monitoring unit (74) monitors changes in the first bit pattern and determines whether the first bit pattern deviates from a second bit pattern defined for reference. If the monitoring unit (74) determines that the first bit pattern is different from the second bit pattern, the correction unit (75) corrects the outlier value of the first bit pattern. If the monitoring unit (74) determines that the first bit pattern is different from the second bit pattern, the calculation unit (73) calculates the speed of the motor (2) based on the correction by the correction unit (75).

[0176] According to the above embodiment, it is possible to suppress the decrease in calculation accuracy related to the speed calculation of the motor (2).

[0177] The impact tool (1) according to the second embodiment further comprises a drive control unit (72) that controls the motor (2) so that the speed of the motor (2) follows a target speed based on the calculation result of the calculation unit (73), in the first embodiment.

[0178] According to the above embodiment, the motor (2) becomes easier to control appropriately.

[0179] With respect to the impact tool (1) according to the third embodiment, in the first or second embodiment, the correction unit (75) performs a correction by replacing outliers with values ​​from a past period before the outliers.

[0180] According to the above embodiment, although the calculation period is extended until the first bit pattern becomes the correct pattern because it is replaced with a past value, it is easier to suppress the decrease in speed calculation accuracy.

[0181] With respect to the impact tool (1) according to the fourth embodiment, in the third embodiment, the correction unit (75) performs a correction by replacing the outlier with the value immediately preceding the outlier.

[0182] According to the above embodiment, the extension of the calculation period until the first bit pattern becomes the correct pattern can be further suppressed.

[0183] With respect to the impact tool (1) according to the fifth embodiment, in any one of the first to fourth embodiments, the monitoring unit (74) starts determining whether the first bit pattern deviates from the second bit pattern after the motor (2) has started and the first bit pattern has changed a predetermined number of times or more.

[0184] According to the above embodiment, the possibility that unstable changes in the first bit pattern immediately after starting the motor (2) may also be subject to judgment by the monitoring unit (74) can be reduced.

[0185] With respect to the impact tool (1) according to the sixth embodiment, in any one of the first to fifth embodiments, the motor (2) is a three-phase motor. The Hall sensor (B1) includes three Hall elements (B11, B12, B13) that output U-phase electrical signals, V-phase electrical signals, and W-phase electrical signals, respectively. The value of the first bit pattern is calculated based on the three electrical signals from the three Hall elements (B11, B12, B13).

[0186] According to the above embodiment, it is possible to suppress the decrease in calculation accuracy related to the speed calculation of a three-phase motor.

[0187] The impact tool (1) according to the seventh embodiment further comprises a drive control unit (72), a determination unit (76), and an energization position correction unit (77) in the sixth embodiment. The drive control unit (72), upon interruption occurring in response to a change in the value of the first bit pattern, determines which of the U-phase, V-phase, and W-phase circuits to energize the motor (2), and controls the motor (2) based on the energization position. The determination unit (76) determines whether the motor (2) is rotating in the forward or reverse direction at an earlier timing than the interrupt. The energization position correction unit (77), if the determination unit (76) determines that the motor (2) is rotating in the reverse direction while the impact tool (1) is operating while maintaining forward rotation, or if the determination unit (76) determines that the motor (2) is rotating in the forward direction while the impact tool (1) is operating while maintaining reverse rotation, determines that the interrupt is a reverse interrupt and corrects the energization position. The drive control unit (72) applies the energized position corrected by the energized position correction unit (77) when the next interrupt following the reverse interrupt occurs, and performs drive control of the motor (2).

[0188] According to the above embodiment, for example, even if the motor (2) reverses direction due to the rebound during impact, the occurrence of control errors can be suppressed.

[0189] In the impact tool (1) according to the eighth embodiment, in the seventh embodiment, the determination unit (76) determines whether the motor (2) is rotating in the forward or reverse direction from the count difference of the encoder (D1).

[0190] According to the above embodiment, the rotation direction of the motor (2) can be accurately determined with a simple configuration and at a timing earlier than that of an interrupt.

[0191] The control method according to the ninth aspect is a control method performed by one or more processors in an impact tool (1). The impact tool (1) includes a motor (2), a striking rotation mechanism (A1), and a Hall sensor (B1). The motor (2) has a rotor (2A) and is capable of forward and reverse rotation. The striking rotation mechanism (A1) receives rotational force from the motor (2) and performs a striking action by rotational inertia force while repeatedly rotating forward and in reverse. The Hall sensor (B1) outputs an electrical signal corresponding to the rotational position of the rotor (2A). The control method includes a calculation step, a monitoring step, and a correction step. In the calculation step, the speed of the motor (2) is calculated using a first bit pattern based on the electrical signal. In the monitoring step, changes in the first bit pattern are monitored and it is determined whether the first bit pattern deviates from a second bit pattern defined for reference. In the correction step, if the monitoring step determines that the first bit pattern deviates from the second bit pattern, the outlier value of the first bit pattern is corrected. In the calculation step, if the monitoring step determines that the first bit pattern deviates from the second bit pattern, the speed of motor (2) is calculated based on the correction made in the correction step.

[0192] According to the above embodiment, a control method is provided that can suppress a decrease in calculation accuracy related to the speed calculation of the motor (2).

[0193] The program according to the tenth embodiment is a program that causes one or more processors to execute the control method according to the ninth embodiment.

[0194] According to the above embodiment, a function can be provided that can suppress the decrease in calculation accuracy related to the speed calculation of the motor (2). [Explanation of symbols]

[0195] 1. Impact Tools 2 motors 2A Rotor 72 Drive Control Unit 73 Arithmetic section 74 Monitoring Department 75 Correction section 76 Judgment Department 77 Energization position correction section A1 Striking rotation mechanism B1 Hall sensor B11 First Hall element (Hall element) B12 Second Hall element (Hall element) B13 Third Hall element (Hall element) D1 encoder

Claims

1. A motor having a rotor and capable of forward and reverse rotation, A striking rotation mechanism that receives rotational force from the motor and performs a striking action by rotational inertia force while repeatedly rotating in the forward and reverse directions, A Hall sensor that outputs an electrical signal corresponding to the rotational position of the rotor, A calculation unit that calculates the speed of the motor using a first bit pattern based on the aforementioned electrical signal, A monitoring unit that monitors changes in the first bit pattern and determines whether the first bit pattern deviates from a second bit pattern defined for reference, If the monitoring unit determines that the first bit pattern deviates from the second bit pattern, a correction unit corrects the outlier value of the first bit pattern. Equipped with, If the monitoring unit determines that the first bit pattern deviates from the second bit pattern, the calculation unit calculates the speed of the motor based on the correction performed by the correction unit. Impact tools.

2. The system further includes a drive control unit that controls the motor so that its speed follows a target speed based on the calculation results of the calculation unit. The impact tool according to claim 1.

3. The correction unit performs a correction by replacing the outlier with a value from a previous period. The impact tool according to claim 1.

4. The correction unit performs a correction by replacing the outlier with the value immediately preceding the outlier. The impact tool according to claim 3.

5. The monitoring unit, after the motor has been started, begins to determine whether the first bit pattern has deviated from the second bit pattern after the first bit pattern has changed a predetermined number of times or more. The impact tool according to claim 1.

6. The motor is a three-phase motor, The Hall sensor includes three Hall elements that output the U-phase electrical signal, the V-phase electrical signal, and the W-phase electrical signal, respectively. The value of the first bit pattern is calculated based on the three electrical signals from the three Hall elements. The impact tool according to claim 1.

7. A drive control unit, which, in response to an interrupt occurring in accordance with a change in the value of the first bit pattern, determines which of the U-phase, V-phase, and W-phase circuits will be energized to supply the motor drive current, and controls the motor's operation based on the energized circuit position, A determination unit that determines whether the motor is rotating in the forward or reverse direction at an earlier timing than the aforementioned interrupt, The system further comprises: If the impact tool is operating while maintaining forward rotation, the determination unit determines that the motor is rotating in reverse, or if the impact tool is operating while maintaining reverse rotation, the determination unit determines that the motor is rotating in forward rotation, the interrupt is determined to be a reverse interrupt, and the energized position correction unit corrects the energized position; The drive control unit applies the energized position corrected by the energized position correction unit when the next interrupt following the reverse interrupt occurs, and performs drive control of the motor. The impact tool according to claim 6.

8. The determination unit determines whether the motor is rotating in the forward or reverse direction based on the count difference of the encoder. The impact tool according to claim 7.

9. A control method for an impact tool, which is performed by one or more processors, The impact tool comprises a motor having a rotor and capable of forward and reverse rotation, an impact rotation mechanism that receives rotational force from the motor and performs an impact operation by rotational inertia force while repeatedly rotating forward and reverse, and a Hall sensor that outputs an electrical signal corresponding to the rotational position of the rotor. A calculation step of calculating the speed of the motor using a first bit pattern based on the electrical signal, A monitoring step that monitors changes in the first bit pattern and determines whether the first bit pattern deviates from a second bit pattern defined for reference, If the monitoring step determines that the first bit pattern deviates from the second bit pattern, a correction step is performed to correct the outlier value of the first bit pattern. Includes, In the calculation step, if the monitoring step determines that the first bit pattern deviates from the second bit pattern, the motor speed is calculated based on the correction performed in the correction step. Control method.

10. A program for causing one or more processors to execute the control method described in claim 9.

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