Impact tool, control method of impact tool, and program

Abstract

An object of the present application is to provide an impact tool capable of autonomously controlling a rotational speed of an output shaft according to a work condition. An impact tool (1) includes a motor (3), an impact mechanism, an output shaft, a control unit (7), and an angle lead measuring section (9A). The impact mechanism includes a hammer and an anvil. The anvil rotates upon receiving an impact force from the hammer. The angle lead measuring section (9A) measures an angle lead of the rotation of the anvil with respect to the rotation of the hammer. The control unit (7) changes a control mode for controlling the rotational speed of the output shaft from one mode to another mode among a plurality of modes according to the angle lead measured by the angle lead measuring section (9A).

Description

TECHNICAL FIELD

[0001] The present application generally relates to an impact tool, a control method for an impact tool, and a program. More particularly, the present application relates to an impact tool including an anvil that rotates upon receiving an impact force from a hammer, a control method for such an impact tool, and a program. BACKGROUND

[0002] Patent Literature 1 discloses an impact rotary tool (impact tool) including a motor, a hammer, an output shaft, an impact detector, and a setting input unit. The hammer is rotated by the motor. An impact is applied from the hammer to the output shaft so that a rotation force is applied to the output shaft. The impact detector detects the impact applied by the hammer upon finding that an impact determination value for use in the impact detection is greater than a threshold value. The output of the motor and the detection threshold value for use in the impact detector are switched according to a setting torque input through the setting input unit.

[0003] Sometimes, an operator who uses the impact tool of Patent Literature 1 needs to operate the impact tool according to a work condition to rotate the output shaft at an appropriate rotation speed. That is, the operator needs to have a skill to perform such a delicate operation.

[0004] PRIOR ART DOCUMENTS

[0005] PATENT LITERATURE

[0006] Patent Literature 1: Japanese Patent Application Publication No. 2009-083045 SUMMARY

[0007] In view of the above background, it is an object of the present application to provide an impact tool, a control method for an impact tool, and a program, all of which are configured or designed to autonomously control a rotation speed of an output shaft according to a work condition.

[0008] An impact tool according to an aspect of the present application includes a motor, an impact mechanism, an output shaft, a control unit, and an angle lead measuring section. The impact mechanism includes a hammer and an anvil. The hammer rotates using power supplied from the motor. The anvil rotates upon receiving an impact force from the hammer. The output shaft rotates together with the anvil. The control unit controls a rotation speed of the output shaft. The angle lead measuring section measures an angle lead of a rotation of the anvil with respect to a rotation of the hammer. The impact mechanism performs an impact operation in a case where a torque condition related to a magnitude of a torque applied to the output shaft is satisfied. The impact operation is an operation for applying the impact force from the hammer to the anvil. The control unit changes a control mode for controlling the rotation speed of the output shaft from one mode to another mode among a plurality of modes according to the angle lead measured by the angle lead measuring section.

[0009] According to another aspect of the present invention, a control method for an impact tool is provided. The impact tool includes a motor, an impact mechanism, and an output shaft. The impact mechanism includes a hammer and an anvil. The hammer rotates using power supplied from the motor. The anvil rotates upon receiving an impact force from the hammer. The output shaft rotates together with the anvil. The control method includes a control step and an angle lead measurement step. The control step controls the rotational speed of the output shaft. The angle lead measurement step measures the angle lead of the anvil's rotation relative to the hammer's rotation. The impact mechanism performs an impact operation while satisfying a torque condition related to the magnitude of the torque applied to the output shaft. The impact operation is an operation to apply the impact force from the hammer to the anvil. The control step changes the control mode for controlling the rotational speed of the output shaft from one of several modes to another based on the angle lead measured in the angle lead measurement step.

[0010] According to another aspect of the invention, the program is designed to cause one or more processors to perform the above-described control method. Attached Figure Description

[0011] Figure 1 This is a control block diagram of an impact tool according to a typical embodiment;

[0012] Figure 2 This is a 3D view of the impact tool;

[0013] Figure 3 This is a side cross-sectional view of the impact tool;

[0014] Figure 4 This is a three-dimensional view of the main parts of the impact tool;

[0015] Figure 5 This is a cross-sectional view of the screw to be tightened by the impact tool;

[0016] Figure 6 This illustrates how the control unit of the impact tool performs vector control;

[0017] Figure 7 This is a graph illustrating an exemplary operation of the impact tool;

[0018] Figure 8 A and Figure 8 Example B illustrates how the hammer and anvil of this impact tool operate;

[0019] Figure 9 A to Figure 9 F is a graph showing the angle lead measured by the impact tool;

[0020] Figure 10 This is a flowchart illustrating a method for controlling the impact tool; and

[0021] Figure 11 This is a graph illustrating an exemplary operation of the impact tool. Detailed Implementation

[0022] (Example)

[0023] Embodiments of the impact tool 1 will now be described with reference to the accompanying drawings. Note that the embodiments described below are merely typical examples among various embodiments of the invention and should not be construed as limiting. Rather, these typical embodiments can be readily modified in various ways, depending on design choices or any other factors, without departing from the scope of the invention. Furthermore, the figures referred to in the following description of the embodiments are schematic diagrams. That is, the aspect ratios (including thicknesses) of the various constituent elements shown in these figures do not always reflect the actual aspect ratios of these constituent elements.

[0024] (1) Overview

[0025] (1-1) Basic Structure

[0026] like Figures 1 to 4 As shown, the impact tool 1 according to a typical embodiment includes a motor 3, an impact mechanism 40, an output shaft 61, and a control unit 7. The impact mechanism 40 includes a hammer 42 and an anvil 45. The hammer 42 rotates using power supplied from the motor 3. The anvil 45 rotates when it receives an impact force from the hammer 42. The output shaft 61 rotates together with the anvil 45. The impact mechanism 40 performs an impact operation when a torque condition related to the magnitude of the torque applied to the output shaft 61 is met. The impact operation is the operation of applying an impact force from the hammer 42 to the anvil 45.

[0027] The impact tool 1 not only has this configuration, but also has a configuration that includes at least one of the first, second, and third features to be described below. More specifically, the impact tool 1 has a configuration that includes all of the first, second, and third features to be described below.

[0028] (1-2) First feature

[0029] The control unit 7 controls the rotational speed of the output shaft 61. The impact tool 1 also includes an angle lead measurement unit 9A (reference). Figure 1 The angle lead measuring unit 9A measures the angle of lead of the rotation of the anvil 45 relative to the rotation of the hammer 42. Based on the angle lead measured by the angle lead measuring unit 9A, the control unit 7 changes the control mode used to control the rotation speed of the output shaft 61 from one of the multiple modes to another.

[0030] This configuration, featuring the first characteristic, allows the impact tool 1 to autonomously control the rotational speed of the output shaft 61 according to the working conditions. For example, a small lead angle when using the impact tool 1 to tighten a screw corresponds to a state where the screw is tightened quite tightly by the impact tool 1. In this case, the control mode of the control unit 7 is the second control mode among several control modes (described later). In the second control mode, the control unit 7 reduces the load increase by reducing the rotational speed of the output shaft 61 (or stopping the rotation of the output shaft 61) according to the conditions to prevent excessive load from being applied to the output shaft 61 through tightening. This makes the operation using the impact tool 1 stable.

[0031] (1-3) Second feature

[0032] The control unit 7 controls the rotational speed of the output shaft 61. The impact tool 1 also includes a thrust detector 9B (reference). Figure 1 The thrust detector 9B detects the thrust F1 applied to the output shaft 61. As used herein, "thrust F1" refers to the force applied in a thrust direction defined for the output shaft 61. When a thrust condition related to the thrust F1 detected by the thrust detector 9B is met, the control unit 7 performs a limiting process. The limiting process includes at least one of reducing the rotational speed of the output shaft 61 and stopping the rotation of the output shaft 61.

[0033] This second feature allows the impact tool 1 to autonomously control the rotational speed of the output shaft 61 according to the operating conditions. For example, if the thrust F1 becomes too large, the impact tool 1 reduces the rotational speed of the output shaft 61 (or stops the rotation of the output shaft 61) by applying a limiting effect, thereby reducing the increase in thrust F1. This makes the operation using the impact tool 1 more stable.

[0034] (1-4) Third feature

[0035] The control unit 7 performs disengagement reduction control when a first predetermined condition is met, and stabilization control when a second predetermined condition is met. As used herein, "disengagement reduction control" refers to control for reducing the possibility of disengagement, which is the unintentional separation of the front-end tool 62 connected to the output shaft 61 from the screw 63, the object of work of the front-end tool 62, while the motor 3 is running. On the other hand, as used herein, stabilization control refers to control for reducing unstable behavior of the hammer 42.

[0036] The configuration with this third feature enables the impact tool 1 to perform autonomous control based on the working conditions. For example, if the screw 63 being worked on is a wood screw and there is a concern about it coming loose, the impact tool 1 can perform dislodgement reduction control. On the other hand, if the screw 63 being worked on is a bolt or hexagonal screw that is already relatively tightly tightened, and there is a concern that the hammer 42 may exhibit unstable behavior, the impact tool 1 can perform stabilization control. This makes the work using the impact tool 1 stable.

[0037] (2) Construction

[0038] Next, the impact tool 1 according to this embodiment will be described in detail. First, the structure of the impact tool 1 will be described.

[0039] In the following description, the orientation of the drive shaft 41 and output shaft 61 arranged side-by-side (to be explained later) will be defined as the "front-to-back direction," with output shaft 61 considered to be in front of drive shaft 41 and drive shaft 41 considered to be behind output shaft 61. Furthermore, in the following description, the orientation of the barrel 21 and grip 22 arranged one on top of the other (to be explained later) will be defined as the "up-down direction," with barrel 21 considered to be above grip 22 and grip 22 considered to be below barrel 21. Note that these definitions are merely examples and should not be construed as specifying the direction in which the impact tool 1 should be used.

[0040] The impact tool 1 according to this embodiment is a portable power tool. For example... Figure 2 and Figure 3 As shown, the impact tool 1 includes a housing 2, a motor 3, a transmission mechanism 4, an output shaft 61, an operating component 23, and a control unit 7.

[0041] The housing 2 houses the motor 3, the transmission mechanism 4, the control unit 7, and a portion of the output shaft 61. The housing 2 includes a cylindrical portion 21 and a gripping portion 22. The cylindrical portion 21 has a cylindrical shape. The gripping portion 22 protrudes from the cylindrical portion 21. More specifically, the gripping portion 22 protrudes from the side of the cylindrical portion 21.

[0042] The operating member 23 protrudes from the grip portion 22. The operating member 23 receives operating commands for controlling the rotation of the motor 3. Note that "rotation of the motor 3" as used herein refers to the rotation of the rotating shaft 311 of the motor 3. The ON / OFF state of the motor 3 can be switched by pulling the operating member 23. Furthermore, the rotation speed of the motor 3 can be adjusted by a manipulation variable indicating the depth to which the operating member 23 is pulled. Specifically, the larger the manipulation variable, the higher the rotation speed of the motor 3. The control unit 7 starts or stops rotating the motor 3 and controls the rotation speed of the motor 3 according to the manipulation variable indicating the depth to which the operating member 23 is pulled.

[0043] The front-end tool 62 is connected to the output shaft 61. More specifically, the front-end tool 62 can be attached to and removed from the output shaft 61. The output shaft 61 rotates together with the front-end tool 62 when receiving rotational power from the motor 3. The rotational speed of the motor 3 can also be controlled by operating the operating member 23.

[0044] In this embodiment, the front-end tool 62 is not a constituent element of the impact tool 1. However, this is merely an example and should not be construed as limiting. Alternatively, the impact tool 1 may include the front-end tool 62 as a constituent element.

[0045] The front-end tool 62 may be, for example, a screwdriver bit. More specifically, according to this embodiment, the front-end tool 62 is a plus screwdriver bit with the front end 620 formed in a + (plus sign) shape. The front-end tool 62 is fitted into the screw 63 (such as a bolt or "vis" screw) that is being worked on. Rotating the front-end tool 62 fitted into the screw 63 makes it possible to tighten or loosen the screw 63.

[0046] Screw 63 includes a head 64 and a threaded portion 65. The head 64 has a disc-shaped shape. The threaded portion 65 protrudes from the head 64. The head 64 has a plus (+) screw hole 640 (reference). Figure 5 As used herein, the expression "the front end tool 62 and the screw 63 are engaged with each other" means that at least a portion of the front end 620 of the front end tool 62 is inserted into the screw hole 640 of the screw 63. On the other hand, the phenomenon of the front end tool 62 and the screw 63 disengaging from each other (i.e., disengagement) refers herein to the front end 620 of the front end tool 62 disengaging from the screw hole 640 while the motor 3 is running (i.e., rotating).

[0047] A rechargeable battery pack is removably attached to the impact tool 1. The impact tool 1 is powered by the battery pack. That is, the battery pack is the power source for supplying current to drive the motor 3. In this embodiment, the battery pack is not a constituent element of the impact tool 1. This is merely an example and should not be construed as limiting. Alternatively, the impact tool 1 may include a battery pack as a constituent element. The battery pack includes an assembled battery formed by connecting multiple secondary batteries (such as lithium-ion batteries) in series and a housing containing the assembled battery.

[0048] Motor 3 may be, for example, a brushless motor. Specifically, according to this embodiment, motor 3 is a synchronous motor. More specifically, motor 3 may be a permanent magnet synchronous motor (PMSM). Motor 3 includes: a rotor 31 having a rotating shaft 311 and a permanent magnet 312; and a stator 32 having a coil 321. The rotor 31 rotates relative to the stator 32 through electromagnetic interaction between the permanent magnet 312 and the coil 321.

[0049] Furthermore, motor 3 is a servo motor. The torque and rotational speed of motor 3 are varied under the control of control unit 7 (which is a servo driver). More specifically, control unit 7 controls the operation of motor 3 through feedback control to bring the torque and rotational speed of motor 3 closer to target values. For example, control unit 7 can perform vector control. Vector control is a motor control method in which the current supplied to motor 3 is decomposed into a current component that generates torque (rotational force) and a current component that generates magnetic flux, and these current components are controlled independently of each other.

[0050] The transmission mechanism 4 includes an impact mechanism 40. According to this embodiment, the impact tool 1 is an electric impact screwdriver used to tighten screws while performing an impact operation using the impact mechanism 40. During the impact operation, the impact mechanism 40 generates an impact force based on power supplied from the motor 3 and applies this impact force to the front tool 62.

[0051] The transmission mechanism 4 includes not only the impact mechanism 40 but also the planetary gear mechanism 48. The impact mechanism 40 includes a drive shaft 41, a hammer 42, a return spring 43, an anvil 45, and two steel balls 49. The rotational force of the rotating shaft 311 of the motor 3 is transmitted to the drive shaft 41 via the planetary gear mechanism 48. The transmission mechanism 4 transmits the torque of the motor 3 to the output shaft 61 via the drive shaft 41. The drive shaft 41 is inserted between the motor 3 and the output shaft 61.

[0052] The control unit 7 can change the rotational speed of the output shaft 61 by changing at least one of the rotational speed of the motor 3 and the gear ratio of the planetary gear mechanism 48. For example, the control unit 7 can change the rotational speed of the motor 3 by changing the power supplied to the motor 3. Alternatively, for example, the control unit 7 can also change the gear by driving an actuator and thereby causing one of the gears in the planetary gear mechanism 48 to slide. When the gear changes, the gear ratio of the planetary gear mechanism 48 changes. In this embodiment, the control unit 7 controls the change of the rotational speed of the motor 3 without controlling the gear ratio of the planetary gear mechanism 48.

[0053] The hammer 42 moves relative to the anvil 45 and applies an impact force to the anvil 45 when it receives power from the motor 3. Figure 3 and Figure 4As shown, the hammer 42 includes a hammer body 420 and two protrusions 425. The two protrusions 425 protrude from the surface of the hammer body 420 facing the output shaft 61. The hammer body 420 has a through hole 421 through which the drive shaft 41 passes.

[0054] The hammer body 420 has two grooves 423 on its inner circumferential surface of the through hole 421. The drive shaft 41 has two grooves 413 on its outer circumferential surface. The two grooves 413 are connected to each other. Two steel balls 49 are held between the two grooves 423 and the two grooves 413. The two grooves 423, the two grooves 413, and the two steel balls 49 together form a cam mechanism. The cam mechanism allows the hammer 42 to move and rotate relative to the drive shaft 41 along the axis of the drive shaft 41 while the two steel balls 49 are rolling. The hammer 42 rotates relative to the drive shaft 41 as it moves along the axis of the drive shaft 41 toward or away from the output shaft 61.

[0055] The anvil 45 is integrally formed with the output shaft 61. The anvil 45 rotates together with the output shaft 61. The anvil 45 includes an anvil body 450 and two claws 455. The anvil body 450 has an annular shape. The two claws 455 protrude from the anvil body 450 along the radius of the anvil body 450. The anvil 45 faces the hammer body 420 along the axial direction of the drive shaft 41.

[0056] Furthermore, when the impact mechanism 40 is not performing an impact operation, the hammer 42 and the anvil 45, along with the two protrusions 425 of the hammer 42 that are in contact with the two claws 455 of the anvil 45 in the direction of rotation of the drive shaft 41, rotate together. Therefore, at this time, the drive shaft 41, the hammer 42, the anvil 45, and the output shaft 61 rotate together with each other.

[0057] A return spring 43 is inserted between the hammer 42 and the planetary gear mechanism 48. According to this embodiment, the return spring 43 is a conical helical spring. The impact mechanism 40 also includes a plurality of (e.g., in) spaces inserted between the hammer 42 and the return spring 43. Figure 3 (Two steel balls 50 and a ring 51 are shown in the example.) This allows the hammer 42 to rotate relative to the return spring 43. The hammer 42 receives a biasing force applied along the axis of the drive shaft 41 toward the output shaft 61 from the return spring 43.

[0058] In the following description, the movement of hammer 42 along the axis of drive shaft 41 toward output shaft 61 will be referred to as "forward movement of hammer 42". Furthermore, in the following description, the movement of hammer 42 along the axis of drive shaft 41 away from output shaft 61 will be referred to as "reverse movement of hammer 42". Furthermore, in the following description, the movement of hammer 42 within its movable range to the position furthest from anvil 45 will be referred to as "maximum retraction". In this embodiment, the unstable behavior of hammer 42 to be reduced by stabilization control is the behavior of hammer 42 moving away from anvil 45 by a predetermined distance or further (i.e., retraction behavior). More specifically, the unstable behavior of hammer 42 to be reduced by stabilization control is maximum retraction as a retraction behavior. For example, maximum retraction may occur when the magnitude of the load applied to output shaft 61 increases sharply.

[0059] The impact mechanism 40 begins its impact operation when a torque condition (hereinafter referred to as "load torque") related to the magnitude of the torque applied to the output shaft 61 is met. As used herein, "impact operation" refers to the operation of applying an impact force from the hammer 42 to the anvil 45. In this embodiment, the torque condition is that the load torque is equal to or greater than a predetermined value. Specifically, as the load torque increases, the proportion of the force component having the direction of retraction of the hammer 42 increases relative to the force generated between the hammer 42 and the anvil 45. When the load torque increases to a predetermined value or greater, the hammer 42 retracts while compressing the return spring 43. Additionally, as the hammer 42 retracts, the hammer 42 rotates while the two protrusions 425 of the hammer 42 are passing over the two claw portions 455 of the anvil 45. Then, the hammer 42 advances upon receiving a restoring force from the return spring 43. Then, when the drive shaft 41 has rotated approximately half a turn, the two protrusions 425 of the hammer 42 collide with the respective side surfaces 4550 of the two claw portions 455 of the anvil 45. In this impact mechanism 40, each time the drive shaft 41 rotates approximately half a turn, the two protrusions 425 of the hammer 42 collide with the two claws 455 of the anvil 45. That is, each time the drive shaft 41 rotates approximately half a turn, the hammer 42 applies an impact force (rotational impact force) to the anvil 45.

[0060] As can be seen, in this impact mechanism 40, the collision between the hammer 42 and the anvil 45 occurs repeatedly. The torque generated by these collisions allows the screw 63 to be tightened more securely than in the case where no collision occurs between the hammer 42 and the anvil 45.

[0061] As described above, a "disengagement" phenomenon sometimes occurs in the impact tool 1. A first exemplary mechanism causing this disengagement will be explained. For example, when the motor 3's rotational speed is unstable during the impact operation of the impact mechanism 40, the hammer 42 may advance to its front end within its movable range, sometimes resulting in a momentary increase in the thrust applied from the front tool 62 to the screw 63. Subsequently, the reaction force of the screw 63 towards the front tool 62 may cause the front tool 62 to disengage from the screw 63, resulting in the disengagement phenomenon. In other words, the recoil of the front tool 62 from the screw 63 may force the front tool 62 to disengage from the screw 63, resulting in the disengagement phenomenon.

[0062] Next, a second exemplary mechanism for the dislodgement phenomenon caused by the impact tool 1 will be described. The screw hole 640 of the screw 63 (reference) Figure 5 The screw 63 has a tapered surface 641. When a force is applied from the tip tool 62 to the tapered surface 641 in a direction intersecting the axis of the screw 63, the tip tool 62 may disengage from the screw hole 640 along the tapered surface 641 (i.e., disengagement may occur). For example, if the tip tool 62 is oriented at an angle relative to the screw 63, the force component in the direction intersecting the axis of the screw 63 becomes relatively large relative to the force applied from the tip tool 62 to the tapered surface 641, thereby increasing the likelihood of disengagement occurring through this second exemplary mechanism.

[0063] Furthermore, the higher the rotational speed of the motor 3, the more likely the force applied from the front tool 62 to the tapered surface 641 is to increase, thereby increasing the possibility of disengagement caused by the second exemplary mechanism. Additionally, if the operator is applying sufficient thrust along the axis of the screw 63 to press the front tool 62 against the screw 63, the possibility of disengagement caused by either the first or second exemplary mechanism is small. However, if the thrust is insufficient, disengagement may sometimes occur.

[0064] like Figure 3 As shown, the impact tool 1 also includes a retaining base 11, a housing component 12, a drive circuit 81, a fan 14, a cover 15, a bearing 16, and another bearing 17. All these components are housed within the housing 2.

[0065] The retaining base 11 has a bottomed cylindrical shape. The retaining base 11 holds the planetary gear mechanism 48 inside. That is, the retaining base 11 rotatably holds the gears of the planetary gear mechanism 48. Additionally, the retaining base 11 also holds the bearing 17. The bearing 17 held by the retaining base 11 and the bearing 16 held by the cover 15 rotatably hold the rotating shaft 311 of the motor 3. That is, the retaining base 11 rotatably holds the rotating shaft 311 via the bearing 17. The rotating shaft 311 of the motor 3 is inserted into a through hole provided through the bottom surface of the retaining base 11 and connected to the planetary gear mechanism 48.

[0066] The housing member 12 has a cylindrical shape. The diameter of the housing member 12 decreases as the distance to its front end decreases. The housing member 12 houses the transmission mechanism 4 within itself. The retaining base 11 is arranged to close the opening at one end (i.e., the rear end in this case) of the housing member 12.

[0067] The drive circuit 81 is located behind the motor 3. The drive circuit 81 includes a substrate 810 and multiple power components, which may be, for example, field-effect transistors (FETs).

[0068] The control unit 7 controls the motor 3 via the drive circuit 81. That is, the control unit 7 controls the power supplied to the motor 3 via the multiple FETs of the drive circuit 81 by turning multiple FETs on and off.

[0069] Fan 14 is connected to the rotating shaft 311 of motor 3. Fan 14 is positioned between motor 3 and retaining base 11. Fan 14 generates a forward flow of air. This allows fan 14 to cool the internal space of housing 2.

[0070] Cover 15 is positioned behind drive circuit 81. Cover 15 covers drive circuit 81.

[0071] (3) Control Unit

[0072] The control unit 7 includes a computer system comprising one or more processors and memory. At least a portion of the functions of the control unit 7 are performed by causing one or more processors of the computer system to execute a program stored in the computer system's memory. This program may be stored in memory. The program may also be downloaded via a long-distance telecommunications line such as the Internet, or distributed after being stored on a non-transitory storage medium such as a memory card.

[0073] like Figure 1 As shown, the control unit 7 includes a command value generator 71, a speed controller 72, a current controller 73, a first coordinate transformer 74, a second coordinate transformer 75, a flux controller 76, an estimator 77, and an impact detector 78. Note that these components do not necessarily have a substantial configuration, but merely represent the various functions to be performed by the control unit 7. Therefore, these components of the control unit 7 are free to use the various values ​​generated within the control unit 7.

[0074] In addition, the impact tool 1 also includes a drive circuit 81, a current measuring unit 82, a voltage measuring unit 83, and a motor rotation measuring unit 84.

[0075] The control unit 7 controls the operation of the motor 3. More specifically, the control unit 7 is used in conjunction with the drive circuit 81 that supplies current to the motor 3, and performs feedback control to control the operation of the motor 3. The control unit 7 performs vector control to independently control the excitation current (d-axis current) and torque current (q-axis current) to be supplied to the motor 3.

[0076] The current measurement unit 82 includes multiple (e.g., in) Figure 1 The system consists of two current sensors CT1 and CT2, and a second coordinate transformer 75. That is, the second coordinate transformer 75 serves not only as a component of the current measurement unit 82, but also as a component of the control unit 7. The current measurement unit 82 measures the excitation current (d-axis current measurement value id1) and torque current (q-axis current measurement value iq1) supplied to the motor 3. In other words, the current measurement values ​​id1 and iq1 are obtained by transforming the two-phase currents measured by the two current sensors CT1 and CT2 using the second coordinate transformer 75.

[0077] Multiple current sensors CT1 and CT2 each include, for example, a Hall element or a shunt resistor element. The multiple current sensors CT1 and CT2 measure the current supplied from the battery pack to the motor 3 via the drive circuit 81. In this embodiment, three-phase current (i.e., U-phase current, V-phase current, and W-phase current) is supplied to the motor 3. The multiple current sensors CT1 and CT2 measure the current in at least two phases. Figure 1 In the middle, the current sensor CT1 measures the U-phase current and outputs the current measurement value i. u 1. And the current sensor CT2 measures the V-phase current to output the current measurement value i. v 1.

[0078] The motor rotation measurement unit 84 includes, for example, a rotation sensor. The rotation sensor may be, for example, a magnetic rotation sensor for detecting the rotation angle using a Hall element or a photoelectric rotation sensor for detecting the rotation angle using light. The rotation sensor detects the rotation angle θ1 of the motor 3 (rotor 31).

[0079] The second coordinate transformer 75, based on the rotation angle θ1 of the motor 3 measured by the motor rotation measurement unit 84, converts the current measurement value i measured by multiple current sensors CT1 and CT2. u 1. i v 1. A coordinate transformation is performed to calculate the current measurement values ​​id1 and iq1. That is, the second coordinate transformer 75 calculates the current measurement values ​​iq1 and iq1 based on the current measurement values ​​iq1 in phases U and V. u 1. i v1. Calculate the W-phase current and transform the current measurements in the three phases (i.e., U-phase, V-phase, and W-phase) into current measurements id1 corresponding to the magnetic field component (d-axis current) and iq1 corresponding to the torque component (q-axis current).

[0080] Voltage measuring unit 83 measures the voltage applied to motor 3. For example, voltage measuring unit 83 measures the voltage applied between the U-phase winding and the V-phase winding of motor 3. Although in Figure 1 The system provides only one voltage measurement unit 83, but may alternatively provide multiple voltage measurement units 83. The single or multiple voltage measurement units 83 can measure at least one voltage selected from the group consisting of: a voltage applied between the U-phase winding and the V-phase winding; a voltage applied between the V-phase winding and the W-phase winding; and a voltage applied between the W-phase winding and the U-phase winding.

[0081] The estimator 77 performs time differentiation on the rotation angle θ1 of the motor 3 measured by the motor rotation measurement unit 84 to calculate the angular velocity ω1 of the motor 3 (i.e., the angular velocity of the rotor 31).

[0082] Command value generator 71 generates a command value cω1 for the angular velocity of motor 3. For example, command value generator 71 receives a command value cω0 from operating member 23, which represents the depth to which operating member 23 is pulled. Command value generator 71 generates a command value cω1 corresponding to command value cω0. That is, as the manipulated variable increases, command value generator 71 correspondingly increases the command value cω1 for the angular velocity.

[0083] The command value generator 71 includes a determination unit 710. The determination unit 710 obtains information from the impact detector 78, the angle advance measurement unit 9A, and the thrust detector 9B, and makes a predetermined determination based on this information. The command value generator 71 generates a command value cω1 based on the command value cω0 obtained from the operating member 23 and the determination made by the determination unit 710. The content of the determination made by the determination unit 710 will be described later in the "(6) Exemplary Operation" section.

[0084] The speed controller 72 generates a command value ciq1 based on the difference between the command value cω1 generated by the command value generator 71 and the angular velocity ω1 calculated by the estimator 77. The command value ciq1 specifies the magnitude of the torque current (q-axis current) of the motor 3. That is, the control unit 7 controls the operation of the motor 3 to make the torque current (q-axis current) supplied to the coil 321 of the motor 3 closer to the command value ciq1 (target value). The speed controller 72 determines the command value ciq1 so that the difference between the command value cω1 and the angular velocity ω1 is less than a predetermined value.

[0085] The flux controller 76 generates a command value cid1 based on the angular velocity ω1 calculated by the estimator 77 and the current measurement value iq1 (q-axis current). The command value cid1 specifies the magnitude of the excitation current (d-axis current) of the motor 3. In other words, the control unit 7 controls the operation of the motor 3 to make the excitation current (d-axis current) supplied to the coil 321 of the motor 3 closer to the command value cid1 (target value).

[0086] The command value cid1 generated by the flux controller 76 can be, for example, a command value that sets the magnitude of the excitation current to zero. In this embodiment, the flux controller 76 always generates a command value cid1 that sets the magnitude of the excitation current to zero. Alternatively, the flux controller 76 may also generate a command value cid1 that sets the magnitude of the excitation current to a value greater than or less than zero, as needed. When the command value cid1 of the excitation current becomes less than zero, a negative excitation current (i.e., a field weakening current) flows through the motor 3, thereby weakening the flux used to drive the rotor 31.

[0087] The current controller 73 generates a command value cvd1 based on the difference between the command value cid1 generated by the flux controller 76 and the current measurement value id1 calculated by the second coordinate transformer 75. The command value cvd1 specifies the magnitude of the excitation voltage (d-axis voltage) of the motor 3. The current controller 73 determines the command value cvd1 to reduce the difference between the command value cid1 and the current measurement value id1. The current controller 73 determines the command value cvd1 so that the difference between the command value cid1 and the current measurement value id1 is less than a predetermined value.

[0088] Furthermore, the current controller 73 generates a command value cvq1 based on the difference between the command value ciq1 generated by the speed controller 72 and the current measurement value iq1 calculated by the second coordinate transformation unit 75. The command value cvq1 specifies the magnitude of the torque voltage (q-axis voltage) of the motor 3. The current controller 73 generates the command value cvq1 to reduce the difference between the command value ciq1 and the current measurement value iq1. The current controller 73 generates the command value cvq1 so that the difference between the command value ciq1 and the current measurement value iq1 is less than a predetermined value.

[0089] The first coordinate transformer 74 performs coordinate transformation on the command values ​​cvd1 and cvq1 based on the rotation angle θ1 of the motor 3 measured by the motor rotation measurement unit 84, in order to calculate the command value cv. u 1. CV v 1. CV w 1. Specifically, the first coordinate transformer 74 transforms the command value cvd1 for the magnetic field component (d-axis voltage) and the command value cvq1 for the torque component (q-axis voltage) into command values ​​cv corresponding to the three-phase voltages. u 1. CVv 1. CV w 1. Specifically, the command value cv u 1 corresponds to the U-phase voltage, command value cv v 1 corresponds to phase V voltage, and the command value cv w 1 corresponds to the W-phase voltage.

[0090] The drive circuit 81 will be related to the command value cv u 1. CV v 1. CV w The corresponding three-phase voltages are supplied to the motor 3. The drive circuit 81 controls the power supplied to the motor 3 by performing pulse width modulation (PWM) control.

[0091] Motor 3 is driven by electricity (three-phase voltage) supplied from drive circuit 81, thereby generating rotational driving force.

[0092] As a result, the control unit 7 controls the excitation current so that the excitation current (d-axis current) flowing through the coil 321 of the motor 3 has a magnitude corresponding to the command value cid1 generated by the flux controller 76. In addition, the control unit 7 also controls the angular velocity of the motor 3 so that the angular velocity of the motor 3 becomes the angular velocity corresponding to the command value cω1 generated by the command value generator 71.

[0093] Impact detector 78 detects that the current measurement value id1 is equal to or less than the predetermined value Th5 (reference). Figure 7 When impact is detected, impact mechanism 40 is performing an impact operation. Then, impact detector 78 sends a signal b1 indicating whether an impact operation is in progress to command value generator 71.

[0094] (4) Details of vector control

[0095] Next, the vector control performed by control unit 7 will be explained in more detail. Figure 6 The analysis model for vector control is shown. Figure 6 The diagram shows the U-axis, V-axis, and W-axis, which serve as the fixed axes of the armature windings for phases U, V, and W, respectively. According to vector control, a rotational coordinate system is considered, rotating at the same speed as the magnetic flux generated by the permanent magnet 312 mounted on the rotor 31 of the motor 3. In this rotational coordinate system, the direction of the magnetic flux actually generated by the permanent magnet 312 is defined by the d-axis, and the coordinate axis corresponding to the control of the motor 3 by the control unit 7 and corresponding to the d-axis is defined by the γ-axis. The q-axis is set at a phase that leads the d-axis by an electrical angle of 90 degrees. The δ-axis is set at a phase that leads the γ-axis by an electrical angle of 90 degrees.

[0096] The dq axis has rotated, and its rotational speed is specified by ω. The γδ axis has also rotated, and its rotational speed is specified by ω. eThis indicates. Note that... Figure 6 ω in e and Figure 1 The ω1 shown corresponds to this. Furthermore, in the dq axis, the d-axis angle (phase) seen from the fixed axis of the U-phase armature winding is specified by θ. Similarly, in the γδ axis, the γ-axis angle (phase) seen from the fixed axis of the U-phase armature winding is specified by θ. e Specify. Note that... Figure 6 θ e and Figure 1 The θ1 shown corresponds to this. From θ and θ e The specified angle is an electrical angle and is commonly referred to as the "rotor position" or "pole position". It is determined by ω and ωpole. e The specified rotational speed is an angular velocity expressed in electrical degrees.

[0097] If θ and θ e If they are consistent, then the d-axis and q-axis are consistent with the γ-axis and δ-axis, respectively. Essentially, control unit 7 performs vector control, making θ and θ0 consistent. e They are consistent with each other. Therefore, when the command value cid1 of the d-axis current is 0, as the load applied to motor 3 increases or decreases, control unit 7 performs control to compensate for the resulting changes in θ and θ'. e The difference between the two currents results in the d-axis current measurement value id1 having either a positive or negative value. Specifically, immediately after the load applied to motor 3 decreases, the d-axis current measurement value id1 has a positive value. At the instant the load applied to motor 3 increases, the current measurement value id1 has a negative value.

[0098] During the period when the impact mechanism 40 is performing an impact operation, the load applied to the motor 3 changes more significantly compared to the period when the impact mechanism 40 is not performing an impact operation. Therefore, as Figure 7 As shown, during the time period when the impact mechanism 40 is performing the impact operation (i.e., during the predetermined time period from time point t3), the excitation current (with the current measurement value id1 of the d-axis current) oscillates.

[0099] (5) Angle advance measurement unit and thrust detector

[0100] (5-1) Structure

[0101] like Figure 1 As shown, the impact tool 1 includes an angle lead measurement unit 9A. Additionally, the impact tool 1 includes a thrust detector 9B. At least a portion of the components of the angle lead measurement unit 9A also serve as at least a portion of the components of the thrust detector 9B.

[0102] The angle lead measuring unit 9A measures the angle of rotation of the anvil 45 relative to the rotation of the hammer 42. The thrust detector 9B detects the thrust F1 applied to the output shaft 61. As used herein, "thrust F1" refers to the force applied in a direction aligned with the thrust direction defined for the output shaft 61. More specifically, thrust F1 is the force applied from the output shaft 61 to the front tool 62 or the reaction force applied from the front tool 62 to the output shaft 61.

[0103] The angle lead measurement unit 9A and the thrust detector 9B each include a computer system containing one or more processors and memory. At least a portion of the functions of the angle lead measurement unit 9A and the thrust detector 9B are performed by having one or more processors of the computer system execute a program stored in the computer system's memory. This program can be stored in memory. The program can also be downloaded via a long-distance telecommunications line such as the Internet, or distributed after being stored on a non-transitory storage medium such as a memory card.

[0104] The angle lead measurement unit 9A includes an impact interval measurement unit 91, a hammer rotation measurement unit 92, and a calculation unit 93. The thrust detector 9B includes an impact interval measurement unit 91, a hammer rotation measurement unit 92, and a processor 94. Note that these components do not necessarily have a substantial configuration, but only indicate the functions to be performed by the angle lead measurement unit 9A and the thrust detector 9B.

[0105] The angle lead measurement unit 9A and the thrust detector 9B also include a current measurement unit 82. Note that in Figure 1 In this example, the current measurement unit 82 is shown outside the angle lead measurement unit 9A and the thrust detector 9B.

[0106] The impact interval measuring unit 91 measures the impact interval of the hammer 42. As used herein, the impact interval of the hammer 42 (hereinafter referred to as "impact interval") refers to the time interval during which the hammer 42 applies an impact force to the anvil 45. The hammer rotation measuring unit 92 measures the rotational speed of the hammer 42. The calculation unit 93 calculates the angular lead of the rotation of the anvil 45 relative to the rotation of the hammer 42 based on the impact interval measured by the impact interval measuring unit 91 and the rotational speed of the hammer 42 measured by the hammer rotation measuring unit 92.

[0107] (5-2) Impact Interval Measurement Unit

[0108] As described above, the current measuring unit 82 measures the excitation current flowing through the motor 3. The impact interval measuring unit 91 measures the impact interval based on the current measurement value id1 of the excitation current measured by the current measuring unit 82. This allows for accurate measurement of the impact interval.

[0109] More specifically, the excitation current (current measurement value id1) measured by the current measurement unit 82 of the impact interval measurement unit 91 becomes equal to or less than the predetermined value Th5 (reference). Figure 7 The time interval is defined as the impact interval. That is, each time the impact mechanism 40 performs an impact operation and the hammer 42 collides with the anvil 45, the load applied to the motor 3 changes. This change itself manifests as a change in the excitation current. This allows the impact interval measuring unit 91 to measure the impact interval based on the excitation current. The predetermined value Th5 is negative.

[0110] For example, the current measurement value id1 of the excitation current can be as follows: Figure 7 The changes are shown. At time point t3, the impact mechanism 40 begins the impact operation, causing the current measurement value id1 to oscillate. Then, starting from time point t4, each time the current measurement value id1 reaches a trough in its waveform, the current measurement value id1 becomes equal to or less than a predetermined value Th5. This allows the impact interval measuring unit 91 to measure the impact interval. Optionally, the impact interval measuring unit 91 can also be used as an impact detector 78.

[0111] (5-3) Hammer rotation measuring section

[0112] Hammer rotation measuring unit 92 from estimator 77 (reference) Figure 1 The angular velocity ω1 of motor 3 (i.e., the rotational speed of motor 3) is obtained. The hammer rotation measuring unit 92 measures the rotational speed of hammer 42 based on the angular velocity ω1. More specifically, the hammer rotation measuring unit 92 calculates the angular velocity (rotational speed) of hammer 42 by dividing the angular velocity ω1 by the gear ratio of planetary gear mechanism 48.

[0113] Optionally, the hammer rotation measuring unit 92 may include, for example, a rotation sensor, and the rotation speed of the hammer 42 can be measured by differentiating the rotation angle of the hammer 42 detected by the rotation sensor. That is, the hammer rotation measuring unit 92 can directly measure the rotation speed of the hammer 42, rather than indirectly measuring the rotation speed of the hammer 42 based on the rotation speed of the motor 3.

[0114] (5-4) Calculation Department

[0115] Next, refer to Figure 8 A and Figure 8 The principle of the calculation unit 93 calculating the angle advance will be explained by B. In the following description, the two protrusions 425 of the hammer 42 will be referred to as "protrusion 425A" and "protrusion 425B" respectively to distinguish the two protrusions 425 from each other. In addition, the two claws 455 of the anvil 45 will be referred to as "claws 455A" and "claws 455B" respectively to distinguish the two claws 455 from each other.

[0116] Hammer 42 edge Figure 8 A and Figure 8 Rotate clockwise in B. As hammer 42 rotates, as... Figure 8 As shown in Figure A, protrusion 425A collides with claw 455A and protrusion 425B collides with claw 455B. This causes the anvil 45 to rotate in the same direction as the hammer 42.

[0117] After each protrusion 425 collides with one of the claws 455, the hammer 42 retracts so that protrusions 425A and 425B pass over claws 455A and 455B respectively. Then, the hammer 42 rotates at least 180 degrees. Then, as... Figure 8 As shown in Figure B, protrusion 425A collides with claw 455B and protrusion 425B collides with claw 455A. The following interval corresponds to the impact interval, which is the interval between the two protrusions 425 of the hammer 42 at... Figure 8 The point in time at which the two claws 455 of the anvil 45 collided at position A is the same as the point at which the protrusion 425 and the claw 455 collide. Figure 8 The interval between the time points when the points at position B collide with each other.

[0118] In this case, the leading angle of rotation of the anvil 45 is represented by the rotation angle α1 of the anvil 45. The rotation angle α1 is the rotation angle of the anvil 45 during the interval between the time when the protrusion 425 collides with the claw 455 once and the time when the protrusion 425 next collides with the claw 455. Figure 8 In B, Figure 8 The positions of the two protrusions 425 and the two claws 455 at the time point shown in Figure A are vaguely indicated by a double-dot chain. (As shown...) Figure 8 As shown in B, during the interval between the point at which protrusion 425A collides with claw 455A and the point at which protrusion 425A collides with claw 455B (i.e., during the impact interval), anvil 45 rotates by a rotation angle α1. In other words, during the interval between the point at which protrusion 425B collides with claw 455B and the point at which protrusion 425B collides with claw 455A, anvil 45 rotates by a rotation angle α1.

[0119] The calculation unit 93 calculates the rotation angle α1 (angle leading) using the following formula (1):

[0120] α1=Δt×β1–γ1 (1)

[0121] Wherein: the rotation angle α1 is in degrees, Δt is the impact interval (in seconds) measured by the impact interval measuring unit 91, β1 is the rotation speed of the hammer 42 (in degrees / second), and γ1 is a number representing the interval between a protrusion 425 and another protrusion 425 adjacent to it in the rotation direction of the hammer 42, expressed in degrees. If, as in this embodiment, multiple protrusions 425 are arranged at regular intervals, then γ1 = 360 / (number of protrusions 425). That is, in this embodiment, γ1 = 180.

[0122] like Figure 9 As shown in B, the hammer 42 rotates Δt×β1 degrees during the impact interval. The protrusions 425 are arranged at intervals of γ1 degrees. Therefore, if the anvil 45 is fixed, Δt×β1=γ1 will be satisfied. However, in reality, the anvil 45 rotates by a rotation angle α1 [degrees] during the impact interval, thus satisfying Δt×β1=γ1+α1. That is, the relationship expressed by equation (1) is satisfied.

[0123] There is a correlation between angular lead (rotation angle α1) and the tightness of the tightening using the impact tool 1. As used herein, "tightness of tightening" is a concept encompassing both the tightness to which the screw 63 is tightened and the tightness to which the screw 63 is loosened. In other words, "tightness of tightening" is the magnitude of the torque required to tighten or loosen the screw 63. Various types of screws 63 are provided, and the angular lead (rotation angle α1) is measured when tightening each of these screws 63. Figure 9 A to Figure 9 The results are shown in F.

[0124] exist Figure 9 A to Figure 9 In F, the vertical axis indicates the rotation angle α1 and the horizontal axis indicates time. The type of screw 63 used is... Figure 9 A to Figure 9 D contains wood screws and Figure 9 E and Figure 9 The F in the designation is a hexagonal bolt. The dimensions of screw 63 are as follows. Specifically, in... Figure 9 In component B, screw 63 has a diameter of 5.2 mm and a length of 120 mm. Figure 9 In C, screw 63 has a diameter of 4.5 mm and a length of 90 mm. Figure 9 In part D, screw 63 has a diameter of 4.2 mm and a length of 75 mm. Furthermore, Figure 9 The screw 63 in E conforms to the JIS standard M16 for hex bolts. Figure 9 The screw 63 in F conforms to the JIS standard M10 for hex bolts.

[0125] Screw 63 is screwed into an object to be fastened, such as a piece of wood or a metal plate. When the rotation angle α1 is first measured, screw 63 is not yet firmly fixed to the object, so the resistance hindering the rotation of the anvil 45, which is being struck by hammer 42, is relatively low. As a result, the rotation angle α1 has a relatively large value. However, as time progresses, screw 63 becomes increasingly firmly fixed to the object, leading to an increase in resistance and a corresponding decrease in the rotation angle α1.

[0126] exist Figure 9 A to Figure 9 In Figure F, the time period for the rotation angle α1 is plotted as corresponding to the time elapsed from the start of the impact operation by the impact mechanism 40 until the end of the impact operation (hereinafter referred to as the "impact time period"). Furthermore, in each of these figures, the rotation angle α1 varies within a range equal to or greater than a predetermined value approximately throughout the entire impact time period. Specifically, the rotation angle α1 in... Figure 9 A varies within a range equal to or greater than approximately 20 degrees. Figure 9 Within B, the temperature varies within a range equal to or greater than approximately 25 degrees. Figure 9 The value of C varies within a range equal to or greater than approximately 30 degrees. Figure 9 D varies within a range equal to or greater than approximately 35 degrees, and... Figure 9 E and Figure 9 The value of F varies within a range equal to or greater than approximately 0 degrees.

[0127] Generally, bolts tighten more than wood screws. Furthermore, the larger the diameter of screw 63, the tighter it is tightened. Additionally, the longer the screw 63, the tighter it is tightened. Figure 9 A to Figure 9 As can be seen from F, the tighter the given screw 63 is tightened, the smaller its angle lead (rotation angle α1) tends to be.

[0128] In view of this trend, the determination unit 710 of the command value generator 71 is configured to determine that the smaller the angle advance (rotation angle α1), the tighter the given screw 63 should be tightened. More specifically, the determination unit 710 classifies the tightness of the tightening into multiple (e.g., two in this example) levels based on the magnitude of the rotation angle α1. Specifically, when the rotation angle α1 is found to be greater than a first threshold Th1 (refer to...), the determination unit 710 further classifies the tightness of the tightening into multiple (e.g., two in this example) levels. Figure 10 When the rotation angle α1 is found to be equal to or less than the first threshold Th1, the determination unit 710 determines that the tightness of the fastening should be relatively low. On the other hand, when the rotation angle α1 is found to be equal to or less than the first threshold Th1, the determination unit 710 determines that the tightness of the fastening should be relatively high. The first threshold Th1 may be, for example, 15 degrees.

[0129] According to this embodiment, the impact tool 1 measures the angle lead and controls the motor 3 based on this measured angle lead. This makes measurement easier compared to determining the tightness of the fastening by measuring the tightness of the screw 63 and the object to be fastened, and then controlling the motor 3 based on the tightness of the fastening. Furthermore, the angle lead is closely related to the tightness of the fastening, thereby enabling significantly more accurate control of the motor 3. For example, by referencing the angle lead, it is possible to control the motor 3 while taking into account the influence of the various shapes of the screw 63, the pre-drilled hole, and the screw hole 640 as factors affecting the tightness of the fastening.

[0130] (5-5) Processor

[0131] The processor 94 of the thrust detector 9B determines the thrust F1 based on the rotational speed (angular velocity) of the hammer 42 measured by the hammer rotation measuring unit 92. As used herein, the thrust F1 refers to the force applied to the output shaft 61, and more specifically, the force applied in a direction aligned with the thrust direction (front-back direction) defined for the output shaft 61.

[0132] The processor 94 determines the thrust F1 through calculation. The thrust F1 is given by the following equation (2):

[0133] F1 = Fth + Ffloat (2)

[0134] Wherein: Fth is the force component in the propulsion direction of the impact force applied from the hammer 42 to the anvil 45, and Ffloat is the load applied in the propulsion direction and caused by the torsional torque of the front tool 62.

[0135] Fth and Ffloat are represented by the following equations (3) and (4), respectively:

[0136] Fth=Aω ds (3)

[0137]

[0138] Where: ω ds The angular velocity of the hammer 42 is measured by the hammer rotation measuring unit 92, and The angle formed between the direction of propulsion and the outer surface of the front tool 62 (reference) Figure 5 ).

[0139] "A" is a coefficient calculated based on a first parameter that contributes to the impact torque generated by the impact mechanism 40. Examples of the first parameter include parameters that depend on the shape of the components of the impact mechanism 40 (such as the moment of inertia of the hammer 42 and the spring constant of the return spring 43) and the impact angle defined by the hammer 42 relative to the anvil 45. The coefficient "A" can be obtained, for example, through experiments using an actual impact tool 1.

[0140] "B" is also a coefficient calculated based on a second parameter that contributes to the impact torque generated by the impact mechanism 40. Examples of the second parameter include parameters that depend on the shape of the components of the impact mechanism 40, such as the moment of inertia of the hammer 42, the spring constant of the return spring 43, the moment of inertia of the output shaft 61, and the outer diameter of the output shaft 61. The coefficient "B" can be obtained, for example, through calculation.

[0141] Note that equations (3) and (4) are approximate expressions. Furthermore, equations (2), (3), and (4) are merely exemplary formulas for determining the thrust F1. Alternatively, the thrust F1 can be determined by any other formula. Alternatively, the thrust F1 can also be determined based on the impact interval measured by the impact interval measuring unit 91.

[0142] (6) Exemplary Operation

[0143] (6-1) Operating Procedures

[0144] Control unit 7 controls motor 3 when changing the control mode from one of multiple modes to another. Examples of multiple modes include a first control mode, a second control mode, and a normal mode. In normal mode, control unit 7 controls the motor 3 according to the already adjusted operating member 23 (reference). Figure 2 The control unit 7 controls the motor 3 based on the details of the operation performed on the operating member 23 and the thrust F1 detected by the thrust detector 9B. In the second control mode, the control unit 7 controls the motor 3 based on the details of the operation performed on the operating member 23 and the current measurement value id1 of the excitation current.

[0145] Figure 10 An exemplary operating flow of the impact tool 1 according to this embodiment is shown. First, the impact detector 78 attempts to detect an impact operation that may be being performed by the impact mechanism 40 (step ST1). If the impact detector 78 does not detect an impact operation (i.e., unless the impact mechanism 40 is performing any impact operation), the answer to the query in step ST1 is "no", and the control unit 7 controls the motor 3 in normal mode (step ST2). Afterwards, the control unit 7 returns to the determination step ST1.

[0146] On the other hand, if the impact detector 78 detects any impact operation (i.e., if the impact mechanism 40 is performing an impact operation), the answer to the query in step ST1 is "yes". In this case, the command value generator 71 (refer to...) Figure 1 The determination unit 710 compares the angle advance (rotation angle α1) measured by the angle advance measurement unit 9A with the first threshold Th1 (step ST3). The state where the angle advance is greater than the first threshold Th1 corresponds to the state where the screw 63 has been relatively loosely tightened (i.e., the load is relatively light). When the control unit 7 detects that the angle advance is greater than the first threshold Th1 (if the answer in step ST3 is "yes"), it changes the control mode to the first control mode (step ST4).

[0147] In the first control mode, the control unit 7 compares the thrust F1 measured by the thrust detector 9B with the third threshold Th3 (step ST5). If the thrust F1 is found to be greater than the third threshold Th3 (if the answer in step ST5 is "yes"), the control unit 7 reduces the rotational speed of the motor 3 or stops its rotation (step ST6). That is, the command value generator 71 of the control unit 7 reduces the command value cω1 of the angular velocity of the motor 3. Afterwards, the control unit 7 returns to the decision step ST1.

[0148] In the first control mode, if the thrust F1 is equal to or less than the third threshold Th3 (if the answer in step ST5 is "No"), then the control of motor 3 by control unit 7 can be the same as in the normal mode. Afterwards, control unit 7 returns to the decision step ST1.

[0149] If the angle advance becomes equal to or less than the first threshold Th1 in step ST3 (if the answer in step ST3 is "No"), the determination unit 710 compares the angle advance (rotation angle α1) measured by the angle advance measurement unit 9A with the second threshold Th2 (step ST7). The state where the angle advance is equal to or less than the second threshold Th2 corresponds to the state where the screw 63 has been relatively tightened (i.e., the load is relatively heavy). When the control unit 7 detects that the angle advance is equal to or less than the second threshold Th2 (if the answer in step ST7 is "Yes"), it changes the control mode to the second control mode (step ST8).

[0150] For example, the second threshold Th2 can be equal to the first threshold Th1. In this case, if the answer in step ST3 is "no", then step ST8 is performed without skipping step ST7.

[0151] In the second control mode, the control unit 7 compares the measured current value id1 of the excitation current with the fourth threshold Th4 (step ST9). The fourth threshold Th4 is negative. When the measured current value id1 is found to be less than the fourth threshold Th4 (if the answer in step ST9 is "yes"), the control unit 7 reduces the rotational speed of the motor 3 or stops its rotation (step ST6). That is, the command value generator 71 of the control unit 7 reduces the command value cω1 of the angular velocity of the motor 3. Afterwards, the control unit 7 returns to the decision step ST1.

[0152] In the second control mode, if the current measurement value id1 is equal to or greater than the fourth threshold Th4 (if the answer in step ST9 is "No"), then the control of motor 3 by control unit 7 can be the same as in the normal mode. Afterwards, control unit 7 returns to the decision step ST1.

[0153] If the angle advance becomes greater than the second threshold Th2 in step ST7 (if the answer in step ST7 is "no"), then control unit 7 controls motor 3 in normal mode (in step ST2). After that, control unit 7 returns to decision step ST1.

[0154] Control unit 7 changes the control mode based on angular advance (rotation angle α1) throughout the entire interval from the time the impact detector 78 detects the impact operation to the time the motor 3 stops running. On the other hand, control unit 7 controls motor 3 in normal mode during the interval from the time the motor 3 starts running to the time the impact detector 78 detects the impact operation.

[0155] Notice, Figure 10 The flowchart shown only illustrates an exemplary operation of the impact tool 1. Therefore, Figure 10 The processing steps shown can be performed in different orders as appropriate. Additional processing steps can be added as needed, or they can be omitted as appropriate. Figure 10 Any of the processing steps shown in the processing steps.

[0156] (6-2) Restriction Processing

[0157] The limiting process is defined herein as a process that includes at least one of the following: reducing the rotational speed of the output shaft 61 to a lower value than in the normal mode; or stopping the rotation of the output shaft 61. The first and second control modes described above correspond to the deceleration mode in which the limiting process is performed based on conditions (i.e., the process in step ST6). In other words, the multiple modes of the control unit 7 include a normal mode that allows the output shaft 61 to rotate and a deceleration mode in which the limiting process is performed based on conditions.

[0158] Furthermore, in the first control mode, a limiting process is applied when the thrust F1 exceeds the third threshold Th3. This control in the first control mode corresponds to the ejection reduction control. The ejection reduction control is a control designed to reduce the likelihood of ejection. The ejection reduction control will be explained in detail in the following section, “(7) Ejection Reduction Control”.

[0159] Furthermore, in the second control mode, a limiting process is performed when the measured current value id1 of the excitation current is less than the fourth threshold Th4. This control in the second control mode corresponds to the stabilization control. The stabilization control is used to reduce the unstable behavior (maximum retreat) of the hammer 42. The stabilization control will be explained in detail later in the section "(8) Stabilization Control".

[0160] Table 1 below summarizes the correspondence between the magnitude of the angle advance (rotation angle α1), the tightness of the fastening, the control mode of control unit 7, and the control details:

[0161] [Table 1]

[0162] Angle lead Fastening tightness Control mode Control Control parameter Large Low First control mode Exit reduction Thrust Small High Second control mode Stabilization Excitation current

[0163] (6-3) First and Second Conditions

[0164] As described above, the control unit 7 performs disengagement reduction control when a first predetermined condition is met, and performs stabilization control when a second predetermined condition is met. At least one of the first and second conditions is a condition related to the angle lead measured by the angle lead measurement unit 9A.

[0165] More specifically, the first condition is that the impact detector 78 detects an impact operation and the angle lead (rotation angle α1) is greater than the first threshold Th1. That is, the first condition includes the condition that the angle lead is greater than the first threshold Th1. If the first condition is met, the control mode of the control unit 7 changes to the first control mode and performs disengagement reduction control.

[0166] On the other hand, the second condition is that the impact detector 78 detects an impact operation, the angle advance (rotation angle α1) is equal to or less than the first threshold Th1, and the angle advance (rotation angle α1) is equal to or less than the second threshold Th2. That is, the second condition includes the condition that the angle advance is equal to or less than the second threshold Th2. If the second condition is met, the control mode of the control unit 7 changes to the second control mode and stabilization control is performed.

[0167] During the entire interval from the time the impact detector 78 detects the impact operation to the time the motor 3 stops running, the control unit 7 determines whether the first condition and the second condition are met. If the first condition is met, the control unit 7 performs disengagement reduction control; if the second condition is met, it performs stabilization control.

[0168] (6-4) Thrust Condition

[0169] Furthermore, when the thrust condition is met, the control unit 7 performs a limiting process. As used herein, the thrust condition is a condition related to the thrust F1 detected by the thrust detector 9B. In this embodiment, the thrust condition includes the condition that the thrust F1 is greater than a third threshold Th3 (thrust threshold) (as opposed to...). Figure 10 (This corresponds to the case where the answer in step ST5 is "no"). The limiting process includes at least one of reducing the rotational speed of the output shaft 61 and stopping the rotation of the output shaft 61.

[0170] Control unit 7 determines whether the thrust condition is met within the entire interval from the time the impact detector 78 detects the impact operation to the time the motor 3 stops running. If the thrust condition is met, control unit 7 performs a limiting process.

[0171] More specifically, when both the angle advance condition related to the angle advance measured by the angle advance measurement unit 9A and the thrust condition are met, the control unit 7 performs a restriction process. The angle advance condition includes the condition that the angle advance (rotation angle α1) is greater than the angle advance threshold (first threshold Th1) (corresponding to the case where the answer in step ST3 is "yes").

[0172] (7) Exhaustion Reduction Control

[0173] Next, refer to Figure 7 The following describes an exemplary operation in the case of disengagement reduction control. In the foregoing description, it is assumed that the command value generator 71 generates a command value cω1 for the angular velocity of the motor 3. In the following description, it is assumed that the command value generator 71 generates a command value for the rotational speed of the motor 3.

[0174] At time t1, the operator manipulates the operating component 23 to start the motor 3. At the time the motor 3 starts running, the impact mechanism 40 is not performing an impact operation. At this time, the upper limit of the rotational speed of the motor 3 is set to the first setting value Th6. The command value generator 71 sets the command value of the rotational speed of the motor 3 to a value equal to or less than the upper limit value. That is, when the operating component 23 is pulled to its maximum depth, the command value of the rotational speed of the motor 3 becomes equal to the upper limit value. Figure 7 In the middle, the rotational speed of motor 3 reaches the upper limit value (first setting value Th6) at time point t2.

[0175] The control unit 7 controls the rotation speed of the output shaft 61 to be equal to or less than the upper limit of the rotation speed of the output shaft 61 by controlling the rotation speed of the motor 3 to be equal to or less than the upper limit of the rotation speed of the motor 3.

[0176] At time t3, the load torque on the output shaft 61 becomes equal to or greater than the predetermined value Th8. Then, the impact mechanism 40 begins its impact operation. Afterward, the current measurement value id1 of the excitation current becomes equal to or less than the predetermined value Th5. At time t4, the impact detector 78 determines that the current measurement value id1 has become equal to or less than the predetermined value Th5, thereby detecting that the impact mechanism 40 is performing an impact operation.

[0177] From the time point t4 when the impact detector 78 detects the impact operation, the determination unit 710 compares the angle advance (rotation angle α1) measured by the angle advance measurement unit 9A with the first threshold Th1 and the second threshold Th2. Figure 10 (See steps ST3 and ST7). In this case, it is assumed that the rotation angle α1 is greater than the first threshold Th1, and the control mode of the control unit 7 changes to the first control mode. That is, the control unit 7 performs disengagement reduction control in the first control mode.

[0178] When the impact detector 78 detects an impact operation, the control unit 7 (command value generator 71) increases the upper limit of the rotational speed of the motor 3. Therefore, the control unit 7 (command value generator 71) increases the upper limit of the rotational speed of the output shaft 61. In this embodiment, if the control mode of the control unit 7 is the first control mode when the impact detector 78 detects an impact operation, the control unit 7 increases the upper limit of the rotational speed of the output shaft 61. On the other hand, if the control mode of the control unit 7 is the second control mode, the control unit 7 maintains the upper limit of the rotational speed of the output shaft 61. That is, the greater the angle lead, the more significantly the control unit 7 increases the upper limit of the rotational speed of the output shaft 61.

[0179] exist Figure 7 At time t4 when the impact detector 78 detects the impact operation, the upper limit of the rotational speed of motor 3 is increased to the second setting value Th7. The second setting value Th7 is greater than the first setting value Th6 at the time when motor 3 has already started running. If the operating member 23 is pulled deep enough after the upper limit of the rotational speed of motor 3 has been increased, then as... Figure 7 As shown in the time interval between t4 and t5, the rotational speed of motor 3 increases to a new upper limit value (second setting value Th7).

[0180] In the first control mode (disengagement reduction control), the determination unit 710 compares the thrust F1 detected by the thrust detector 9B with the third threshold Th3. More specifically, the determination unit 710 compares the thrust F1 with the third threshold Th3 at predetermined time intervals. At time point t6, the thrust F1 exceeds the third threshold Th3. Then, the control unit 7 (command value generator 71) reduces the rotational speed of the motor 3. More specifically, the control unit 7 (command value generator 71) lowers the upper limit of the rotational speed of the motor 3. Then, at least when the operating member 23 has been pulled in sufficiently, the rotational speed of the motor 3 decreases, and therefore the rotational speed of the output shaft 61 also decreases. That is, reducing the rotational speed includes not only directly reducing the rotational speed, but also reducing the upper limit of the rotational speed.

[0181] For example, each time the thrust F1 exceeds the third threshold Th3, the control unit 7 reduces the upper limit of the rotational speed of the motor 3. As another example, once the thrust F1 exceeds the third threshold Th3, the control unit 7 can gradually reduce the upper limit of the rotational speed of the motor 3. Furthermore, the control unit 7 can stop the motor 3 from operating, thereby stopping the rotation of the output shaft 61.

[0182] If the thrust F1, i.e., the force acting between the output shaft 61 and the front tool 62, is too large, disengagement may occur. Reducing the rotational speed of the motor 3 reduces the increase in thrust F1. For example, in normal mode, control to reduce the rotational speed of the motor 3 based on the thrust F1 is not performed. Therefore, in normal mode, such as Figure 7 As shown by the dashed line, the thrust F1 may exceed the threshold Th9 (where Th9 > Th3). In contrast, when the control unit 7 changes its control mode to the first control mode to reduce the rotational speed of the motor 3, the thrust F1 can be controlled to be at or below the threshold Th9. Reducing the increase in thrust F1 makes it possible to reduce the possibility of disengagement. That is, disengagement reduction control includes at least one of reducing the rotational speed of the output shaft 61 and stopping the rotation of the output shaft 61, such that the thrust F1 detected by the thrust detector 9B becomes equal to or less than a predetermined value (threshold Th9).

[0183] In addition, the disengagement reduction control also reduces the thrust F1, thereby reducing the possibility that the thrust F1 becomes so strong that it damages the head of the screw.

[0184] Optionally, during the disengagement reduction control, the control unit 7 can control the rotational speed of the output shaft 61 so that the thrust F1 detected by the thrust detector 9B becomes equal to a predetermined value or falls within a predetermined range. This enables stable operation. For example, the control unit 7 can control the rotational speed of the output shaft 61 so that the thrust F1 becomes equal to a third threshold Th3. If the thrust F1 deviates from the third threshold Th3, the control unit 7 can control the rotational speed of the output shaft 61 through feedback control so that the thrust F1 converges back towards the third threshold Th3.

[0185] Alternatively, the control unit 7 can also control the rotational speed of the output shaft 61 so that the thrust F1 falls within a predetermined range including the third threshold Th3. If the thrust F1 deviates from the predetermined range, the control unit 7 can control the rotational speed of the output shaft 61 through feedback control so that the thrust F1 returns to the predetermined range.

[0186] Optionally, if a predetermined condition is met in the first control mode, the control unit 7 can stop controlling the reduction of the upper limit of the rotational speed of the motor 3. In this case, it is assumed that the predetermined condition is that the difference between the upper limit of the rotational speed of the motor 3 and the first set value Th6 is equal to or less than a predetermined value. Figure 7 At time point t7, the difference between the upper limit of the rotational speed of motor 3 and the first set value Th6 becomes approximately zero and a predetermined condition is met. In response, control unit 7 stops controlling the reduction of the upper limit of the rotational speed of motor 3. Alternatively, when the predetermined condition is met, control unit 7 can change the control mode to normal mode.

[0187] Alternatively, the predetermined condition can also be the condition that screw 63 is in place. For example, in... Figure 7 As shown, screw 63 is considered in place when the load torque on output shaft 61 exceeds threshold Th10 (reference time point t7) or when the rate of increase of the load torque exceeds the threshold. Alternatively, screw 63 is considered in place when the load torque enters a predetermined range. The load torque can be measured, for example, by a torque sensor including a resistance strain sensor or a magnetostrictive strain sensor. Alternatively, screw 63 is considered in place when the measured value iq1 of the torque current enters a predetermined range.

[0188] (8) Stabilization control

[0189] Next, refer to Figure 11 This section describes an exemplary operation in the case of performing stabilization control to reduce the unstable behavior (maximum backward movement) of the hammer 42. In the foregoing description, it is assumed that the command value generator 71 generates a command value cω1 for the angular velocity of the motor 3. In the following description, it is assumed that the command value generator 71 generates a command value for the rotational speed of the motor 3.

[0190] At time t8, the operator operates the control component 23 to start the motor 3. At the time the motor 3 starts running, the impact mechanism 40 is not performing an impact operation. At this time, the upper limit of the rotational speed of the motor 3 is set to the first setting value Th6.

[0191] At time t9, the impact mechanism 40 begins the impact operation detected by the impact detector 78. Furthermore, in this example, it is assumed that the angular lead (rotation angle α1) is equal to or less than the second threshold Th2 (as opposed to...). Figure 10 (This corresponds to the case where the answer is "yes" in step ST7 shown), and the control mode of control unit 7 changes to the second control mode. That is, control unit 7 performs stabilization control in the second control mode.

[0192] As described above, even if the impact detector 78 detects an impact operation, but the control mode of the control unit 7 is the second control mode, the control unit 7 maintains the upper limit of the rotational speed of the output shaft 61. This reduces the increase in the rotational speed of the output shaft 61, thereby reducing the possibility of causing maximum backward movement.

[0193] At time t10, the rotational speed of motor 3 reaches its upper limit. That is, the rotational speed of output shaft 61 reaches its upper limit.

[0194] Subsequently, at time point t11, the measured current value id1 of the excitation current becomes less than the fourth threshold Th4. Then, the control unit 7 (command value generator 71) reduces the rotational speed of the motor 3. More specifically, the control unit 7 (command value generator 71) reduces the upper limit of the rotational speed of the motor 3. Then, at least until the operating member 23 has been pulled sufficiently deep, the rotational speed of the motor 3 decreases (refer to time point t12). This results in a decrease in the rotational speed of the output shaft 61.

[0195] For example, such as Figure 11 As shown, each time the current measurement value id1 becomes less than the fourth threshold Th4, the control unit 7 reduces the upper limit of the rotation speed of the motor 3. Figure 11 During the process, the current measurement value id1 becomes less than the fourth threshold Th4 at time points t11, t13, and t15. Each time the current measurement value id1 becomes less than the fourth threshold Th4, the control unit 7 reduces the upper limit of the rotation speed of the motor 3 by a predetermined amount Δn (reference time points t12, t14, and t16). The rotation speed is at... Figure 11 China and Belgium in Figure 7 The speed decreases more drastically in the middle. However, this is merely an example and should not be interpreted as limiting. Alternatively, the rotational speed in Figure 11 It can be compared toFigure 7 The decrease is more gradual.

[0196] As another example, once the current measurement value id1 becomes less than the fourth threshold Th4, the control unit 7 can gradually reduce the upper limit of the rotational speed of the motor 3 from that point onwards. Alternatively, the control unit 7 can stop running the motor 3, thereby stopping the rotation of the output shaft 61.

[0197] The greater the backward movement of hammer 42, the heavier the load applied to motor 3. This causes the current measurement value id1 to decrease in the negative direction. That is, as... Figure 11 As shown, if the current measurement value id1 is negative, the larger the absolute value of the current measurement value id1, the greater the backward movement of the hammer 42. As used herein, "backward movement of the hammer 42" refers to the amount of backward movement of the hammer 42 from a predetermined reference position within its movable range. The backward movement of the hammer 42 when the current measurement value id1 equals the fourth threshold Th4 corresponds to the threshold Th12. When the current measurement value id1 becomes less than the fourth threshold Th4, the rotational speed of the output shaft 61 (motor 3) decreases. This reduces the likelihood that the backward movement of the hammer 42 will reach the threshold Th13 (where Th13 > Th12).

[0198] When the backward movement of hammer 42 equals the threshold Th13, hammer 42 has moved backward to its maximum extent. According to the stabilization control, the rotational speed of output shaft 61 is reduced based on the current measurement value id1, thereby reducing the possibility of hammer 42 moving backward to its maximum extent.

[0199] It can be seen that the stabilization control can reduce the likelihood that the hammer 42 will move away from the anvil 45 by a predetermined distance or more (hereinafter referred to as "backward behavior"). According to this embodiment, the stabilization control reduces the likelihood of causing maximum backward movement as a form of backward behavior. That is, the stabilization control includes at least one of reducing the rotational speed of the output shaft 61 and stopping the rotation of the output shaft 61 to reduce the likelihood of causing maximum backward movement of the hammer 42.

[0200] Furthermore, the current measurement value id1 corresponds to the threshold Th11 when the backward movement of hammer 42 is equal to the threshold Th13. That is, the occurrence of maximum backward movement (backward behavior) means that the excitation current becomes equal to or less than the excitation current threshold (threshold Th11). Stabilization control includes at least one of reducing the rotational speed of output shaft 61 and stopping the rotation of output shaft 61 to reduce the possibility that the excitation current (current measurement value id1) measured by current measurement unit 82 becomes equal to or less than the excitation current threshold (threshold Th11).

[0201] (9) Advantages

[0202] As described above, in the impact tool 1, when the angle advance is relatively large (i.e., when the tightness is relatively low), the control unit 7 performs disengagement reduction control in the first control mode and reduces the rotational speed of the output shaft 61 according to the magnitude of the thrust F1. This makes it possible to reduce the possibility of disengagement.

[0203] On the other hand, when the angle lead (rotation angle α1) is relatively small (i.e., when the tightness is relatively high), the control unit 7 performs stabilization control in the second control mode and controls the rotation speed of the output shaft 61 according to the magnitude of the excitation current. This makes it possible to reduce the possibility of causing maximum backlash.

[0204] Therefore, this embodiment enables stable operation of tightening screws, for example, using the impact tool 1.

[0205] (10) Methods and procedures for controlling impact tools

[0206] For example, the functions of some of the constituent elements involved in controlling the impact tool 1 (such as the control unit 7, the angle advance measurement unit 9A, and the thrust detector 9B) can also be implemented as a method for controlling the impact tool 1, a (computer) program, or a non-temporary storage medium storing the program.

[0207] According to one aspect, the method for controlling the impact tool 1 includes a control step and an angle lead measurement step. The control step includes controlling the rotational speed of the output shaft 61. The angle lead measurement step includes measuring the angle lead of the rotation of the anvil 45 relative to the rotation of the hammer 42. The control step includes changing the control mode for controlling the rotational speed of the output shaft 61 from one of multiple modes to another based on the angle lead measured in the angle lead measurement step.

[0208] According to another aspect, a method for controlling an impact tool 1 includes a control step and a thrust detection step. The control step includes controlling the rotational speed of an output shaft 61. The thrust detection step includes detecting a thrust F1 applied to the output shaft 61. The thrust F1 is a force applied in a direction aligned with a thrust direction defined for the output shaft 61. The control step includes performing a limiting process when a thrust condition is met. The thrust condition is a condition related to the thrust F1 detected in the thrust detection step. The limiting process includes at least one of reducing the rotational speed of the output shaft 61 and stopping the rotation of the output shaft 61.

[0209] According to another aspect, a method for controlling the impact tool 1 includes control steps. The control steps include: performing a disengagement reduction control when a first predetermined condition is met, and performing a stabilization control when a second predetermined condition is met. The disengagement reduction control is a control used to reduce the possibility of disengagement. Disengagement refers to the unintentional separation between the front-end tool 62, connected to the output shaft 61, and the screw 63, which is the object of work of the front-end tool 62, while the motor 3 is running. The stabilization control is a control used to reduce the unstable behavior of the hammer 42.

[0210] According to another aspect of the program, it is designed to cause one or more processors to perform any of the control methods described above.

[0211] (First variation)

[0212] Next, the impact tool 1 according to the first modification will be described. In the following description, any constituent element of the first modification having the same function as the counterpart of the above embodiment will be indicated by the same reference numerals as the counterpart, and its description will be omitted here.

[0213] In this variation, the control unit 7 changes the control mode based on the angular advance during the interval of a predefined number of times (which may be two or more times) the hammer 42 strikes the anvil 45, to perform at least one of stabilization control and disengagement reduction control. That is, at least one of the first condition for initiating stabilization control and the second condition for initiating disengagement reduction control is a condition related to the angular advance during the interval of a predefined number of times (which may be two or more times) the hammer 42 strikes the anvil 45. This configuration reduces the possibility of control mode changes due to instantaneous changes in angular advance, thereby stabilizing the operation of the impact tool 1.

[0214] Alternatively, the first condition may be, for example, the following condition: each time the hammer 42 applies an impact force to the anvil 45, the angle leading (rotation angle α1) of the hammer 42 striking the anvil 45 within a predefined number of times is greater than a first threshold Th1. Alternatively, the first condition may also be, for example, the sum of the angle leading (rotation angle α1) of the hammer 42 striking the anvil 45 within a predefined number of times is greater than a predetermined threshold.

[0215] Alternatively, the second condition may be, for example, the following condition: each time the hammer 42 applies an impact force to the anvil 45, the angle leading (rotation angle α1) of the hammer 42 striking the anvil 45 within a predefined number of times is equal to or less than a second threshold Th2. Alternatively, the second condition may also be, for example, the sum of the angle leading (rotation angle α1) of the hammer 42 striking the anvil 45 within a predefined number of times is equal to or less than a predetermined threshold.

[0216] (Other variations of the typical embodiment)

[0217] Next, other variations of the typical embodiments will be listed one by one. Note that the variations described below can be appropriately combined. Alternatively, the variations described below can also be appropriately combined with the first variation described above.

[0218] The impact interval measuring unit 91 can measure the impact interval based on the voltage measured by the voltage measuring unit 83. That is, the impact interval measuring unit 91 can measure the impact interval based on the voltage change caused by the collision between the hammer 42 and the anvil 45.

[0219] In the above-described typical embodiment, the control unit 7 changes the upper limit value of the rotational speed of the output shaft 61 from one of several values ​​(i.e., a first setting value Th6 and a second setting value Th7) based on the magnitude of the angular lead. However, this is merely an example and should not be construed as limiting. Alternatively, the control unit 7 may also continuously change the upper limit value as the magnitude of the angular lead changes.

[0220] The angle lead measuring unit 9A does not need to measure the rotation angle α1 of the anvil 45 relative to the hammer 42 as the angle lead. Alternatively, the angle lead measuring unit 9A can also measure the distance traveled by the anvil 45 relative to the hammer 42 as the angle lead.

[0221] The control unit 7 can stop the rotation of the output shaft 61 by cutting off the transmission of rotational force from the motor 3 to the output shaft 61. For example, if the transmission mechanism 4 includes a clutch mechanism, the clutch mechanism can cut off the transmission of rotational force from the motor 3 to the output shaft 61. The clutch mechanism can be implemented, for example, as an electronic clutch.

[0222] In the above-described typical embodiment, the impact detector 78 detects that the impact mechanism 40 is performing an impact operation when it finds that the current measurement value id1 of the excitation current is equal to or less than a predetermined value Th5. Alternatively, the impact detector 78 may also detect that the impact mechanism 40 is performing an impact operation when it finds that the absolute value of the AC component of the current measurement value id1 of the excitation current is greater than a threshold.

[0223] The impact detector 78 can also detect that the impact mechanism 40 is performing an impact operation when the current measurement value id1 has become equal to or less than the predetermined value Th5 a predetermined number of times or more.

[0224] The impact detector 78 can detect impact operations based on the current measurement value iq1 of the torque current. That is, during an impact operation, the load torque of the output shaft 61 changes more significantly, thus... Figure 7As shown, this also causes the current measurement value iq1 to change more significantly. The impact detector 78 can detect an impact operation by sensing this change. The impact detector 78 can detect that the impact mechanism 40 is performing an impact operation when it finds that the current measurement value iq1 is greater than a threshold. Alternatively, the impact detector 78 can also detect that the impact mechanism 40 is performing an impact operation when it finds that the absolute value of the AC component of the current measurement value iq1 is greater than a threshold.

[0225] The impact detector 78 can also determine whether any impact operation is in progress based on the command value cid1 of the excitation current or the command value ciq1 of the torque current.

[0226] The impact detector 78 can be installed separately from the control unit 7. That is, the components of the control unit 7 that performs the function of controlling the rotation of the motor 3 and the components of the impact detector 78 that perform the function of determining whether the impact mechanism 40 is performing any impact operation can be installed separately from each other.

[0227] In the above-described typical embodiment, for example, the second threshold Th2 may be equal to the first threshold Th1. However, this is merely an example and should not be construed as limiting. Alternatively, the second threshold Th2 may be greater than or less than the first threshold Th1, either way being appropriate. In this case, when the control unit 7 detects that the angle lead is greater than the first threshold Th1, it changes the control mode to the first control mode and performs disengagement reduction control. Furthermore, when the control unit 7 detects that the angle lead is equal to or less than the second threshold Th2, it changes the control mode to the second control mode and performs stabilization control. Optionally, when the control unit 7 detects that the angle lead is greater than the first threshold Th1 and equal to or less than the second threshold Th2, it may perform both the control in the first control mode and the control in the second control mode.

[0228] Even if the angle advance is greater than the first threshold Th1, the control mode of the control unit 7 does not have to be the first control mode. For example, a fifth threshold greater than the first threshold Th1 can be preset. If the angle advance is greater than the first threshold Th1 and equal to or less than the fifth threshold, the control mode can be the first control mode. On the other hand, if the angle advance is greater than the fifth threshold, the control mode can be another mode (such as normal mode).

[0229] Even if the angle advance is equal to or less than the second threshold Th2, the control mode of the control unit 7 does not have to be the second control mode. For example, a sixth threshold less than the second threshold Th2 can be preset. If the angle advance is equal to or less than the second threshold Th2 and greater than the sixth threshold, the control mode can be the second control mode. On the other hand, if the angle advance is equal to or less than the sixth threshold, the control mode can be another mode (such as normal mode).

[0230] The thrust detector 9B is not always configured to detect thrust F1 based on the impact interval and the rotational speed of the hammer 42. Alternatively, the thrust detector 9B may also use a sensor to detect thrust F1. The sensor may be, for example, a pressure sensor such as a strain gauge attached to the output shaft 61.

[0231] The thrust threshold (third threshold) can vary depending on the rotational speed of motor 3.

[0232] The thrust condition can be that the thrust F1 falls within a certain range.

[0233] Optionally, the control mode of the control unit 7 can be fixed while the impact mechanism 40 is performing the impact operation. For example, once the impact mechanism 40 has started performing the impact operation, the control mode changes to the first control mode or the second control mode, and the control mode can be fixed until the impact operation ends.

[0234] When the impact mechanism 40 is performing an impact operation, the control mode of the control unit 7 can be changed as needed according to the change of the angle advance (rotation angle α1).

[0235] The unstable behavior of hammer 42 that needs to be reduced through stabilization control is not necessarily maximum retreat. Alternatively, unstable behavior could be, for example, a state where the contact point between the colliding hammer 42 and the anvil 45 falls outside a predetermined range.

[0236] Alternatively, unstable behavior could also be a state in which the protrusion 425 of the hammer 42 repeatedly collides with the claw 455 of the anvil 45 while the protrusion 425 is passing over the claw 455 once.

[0237] Alternatively, unstable behavior could also be, for example, the occurrence of an "upward sliding" operation. In this document, an "upward sliding" operation refers to an operation mode in which the protrusion 425 of the hammer 42 collides with one of the two claws 455 of the anvil 45, and then moves to slide along the side surface 4550 of the claw 455 (i.e., while maintaining contact with the side surface 4550), thereby passing over the claw 455.

[0238] Alternatively, unstable behavior could also be, for example, the state in which the hammer 42 moves forward to reach the front end of its movable range.

[0239] Alternatively, unstable behavior could also be, for example, the state in which the front surface of the protrusion 425 of the hammer 42 contacts the rear surface of the claw 455 of the anvil 45.

[0240] Alternatively, the output shaft 61 can be integrally formed with the front-end tool 62.

[0241] The front-end tool 62 is not necessarily a screwdriver drill bit. Alternatively, the front-end tool 62 can also be a drill bit used to make the impact tool 1 function as, for example, an electric drill, milling cutter, grinder, cleaner, jigsaw, or hole saw.

[0242] Control unit 7 does not necessarily perform vector control. Alternatively, any other scheme can be used to control motor 3.

[0243] In motor 3, which is a synchronous motor, the voltage between the windings of motor 3 changes periodically when the polarity of motor 3 changes, thereby causing motor 3 to rotate. Voltage measuring unit 83 measures the voltage applied to motor 3 (i.e., the voltage between its windings). Estimator 77 can measure the angular velocity ω1 of motor 3 based on the voltage measured by voltage measuring unit 83.

[0244] Optionally, the various types of thresholds available for use in the impact tool 1 can be varied, for example, according to the operator's operating commands.

[0245] Furthermore, in this invention, if one of two values ​​being compared is “equal to or greater than” the other, the phrase can encompass both the cases where the two values ​​are equal and the cases where one value is greater than the other. However, this should not be construed as limiting. Alternatively, the phrase “equal to or greater than” can also be a synonym for the phrase “greater than”, which only covers the cases where one value exceeds the other. That is, depending on the choice of the reference value or any preset value, whether or not the phrase “equal to or greater than” covers the cases where the two values ​​are equal is arbitrarily changeable. Therefore, from a technical point of view, there is no distinction between the phrase “equal to or greater than” and the phrase “greater than”. Similarly, the phrase “less than” can also be a synonym for the phrase “equal to or less than”.

[0246] Some constituent elements of the impact tool 1 according to the invention (such as the control unit 7, the angle lead measurement unit 9A, and the thrust detector 9B, etc.) each include a computer system. The computer system may include a processor and memory as its main hardware components. The function of these constituent elements of the impact tool 1 according to the invention can be performed by causing the processor to execute a program stored in the memory of the computer system. The program may be pre-stored in the memory of the computer system. Alternatively, the program may also be downloaded via a remote telecommunication line or distributed after being recorded on some non-transitory storage medium such as a memory card, optical disc, or hard disk drive (any of which is readable by the computer system). The processor of the computer system may consist of one or more electronic circuits including semiconductor integrated circuits (ICs) or large-scale integrated circuits (LSIs). As used herein, "integrated circuit" such as ICs or LSIs is referred to by different names depending on its degree of integration. Examples of integrated circuits include system LSIs, very large-scale integrated circuits (VLSIs), and ultra-large-scale integrated circuits (ULSIs). Alternatively, a field-programmable gate array (FPGA) that is programmed after the LSI is manufactured, or a reconfigurable logic device that allows reconfiguration of connections or circuit sections within the LSI, may also be used as the processor. These electronic circuits can be integrated together on a single chip or distributed across multiple chips, whichever is appropriate. These multiple chips can be aggregated together in a single device or distributed across multiple devices, without limitation. As used herein, a "computer system" includes a microcontroller comprising one or more processors and one or more memories. Therefore, a microcontroller can also be implemented as a single or multiple electronic circuits comprising semiconductor integrated circuits or large-scale integrated circuits.

[0247] Furthermore, at least some of the functions of the impact tool 1, which are distributed in multiple devices in the above-described typical embodiments, can also be integrated into a single device. For example, the functions of the control unit 7, the angle lead measurement unit 9A, and the thrust detector 9B can be integrated into a single device.

[0248] (Summary)

[0249] The above embodiments and their variations can be specific implementations of the following aspects of the present invention.

[0250] The impact tool (1) according to the first aspect includes a motor (3), an impact mechanism (40), an output shaft (61), a control unit (7), and an angle lead measuring unit (9A). The impact mechanism (40) includes a hammer (42) and an anvil (45). The hammer (42) rotates using power supplied from the motor (3). The anvil (45) rotates when it receives an impact force from the hammer (42). The output shaft (61) rotates together with the anvil (45). The control unit (7) controls the rotation speed of the output shaft (61). The angle lead measuring unit (9A) measures the angle lead (rotation angle α1) of the rotation of the anvil (45) relative to the rotation of the hammer (42). The impact mechanism (40) performs an impact operation when a torque condition related to the magnitude of the torque applied to the output shaft (61) is met. The impact operation is an operation for applying an impact force from the hammer (42) to the anvil (45). The control unit (7) changes the control mode for controlling the rotation speed of the output shaft (61) from one of the multiple modes to another based on the angle advance measured by the angle advance measuring unit (9A).

[0251] This configuration enables the impact tool (1) to autonomously control the rotation speed of the output shaft (61) according to the working conditions.

[0252] In the impact tool (1) according to the second aspect, which can be implemented in conjunction with the first aspect, the angle lead measuring unit (9A) includes an impact interval measuring unit (91), a hammer rotation measuring unit (92), and a calculation unit (93). The impact interval measuring unit (91) measures the impact interval, which is the time interval during which the hammer (42) applies an impact force to the anvil (45). The hammer rotation measuring unit (92) measures the rotation speed of the hammer (42). The calculation unit (93) calculates the angle lead based on the impact interval measured by the impact interval measuring unit (91) and the rotation speed of the hammer (42) measured by the hammer rotation measuring unit (92).

[0253] This configuration enables accurate estimation of the angle lead.

[0254] In the impact tool (1) according to the third aspect, which can be implemented in conjunction with the second aspect, the angle lead measurement unit (9A) further includes at least one of a current measurement unit (82) and a voltage measurement unit (83). The current measurement unit (82) measures the current flowing through the motor (3). The voltage measurement unit (83) measures the voltage applied to the motor (3). The impact interval measurement unit (91) measures the impact interval based on the current measured by the current measurement unit (82) or the voltage measured by the voltage measurement unit (83).

[0255] This configuration enables accurate estimation of impact intervals.

[0256] In the impact tool (1) according to the fourth aspect, which can be implemented in conjunction with the third aspect, the angle advance measurement unit (9A) includes a current measurement unit (82). The impact interval measurement unit (91) measures the time interval during which the excitation current measured by the current measurement unit (82) becomes equal to or less than a predetermined value (Th5).

[0257] This configuration enables accurate estimation of impact intervals.

[0258] In the impact tool (1) according to the fifth aspect, which can be implemented by combining any of the first to fourth aspects, multiple modes include a first control mode. When the control unit (7) detects that the angle advance is greater than a first threshold (Th1), it changes the control mode to the first control mode.

[0259] This configuration allows the control mode to be changed to the first control mode when appropriate.

[0260] In the impact tool (1) according to the sixth aspect, which can be implemented by combining any of the first to fifth aspects, multiple modes include a second control mode. The control unit (7) changes the control mode to the second control mode when it detects that the angle advance is equal to or less than the second threshold (Th2).

[0261] This configuration allows the control mode to be changed to a second control mode when appropriate.

[0262] In the impact tool (1) according to the seventh aspect, which can be implemented by combining any of the first to sixth aspects, multiple modes include: a normal mode in which the output shaft (61) is able to rotate; and a deceleration mode in which a limiting process is performed according to conditions. The limiting process includes at least one of reducing the rotational speed of the output shaft (61) to a lower speed than in the normal mode and stopping the rotation of the output shaft (61).

[0263] This configuration enables the impact tool (1) to operate stably.

[0264] In the impact tool (1) according to the eighth aspect, which can be implemented by combining any of the first to seventh aspects, the control unit (7) controls the rotational speed of the output shaft (61) to an upper limit value or less. The control unit (7) increases the upper limit value as the angle advance increases.

[0265] This configuration enables the impact tool (1) to operate stably.

[0266] The impact tool (1) according to the ninth aspect, which can be implemented in combination with any of the first to eighth aspects, also includes an impact detector (78). The impact detector (78) detects the impact operation performed by the impact mechanism (40). The control unit (7) changes the control mode based on the angle advance throughout the entire time period from the time when the impact detector (78) detects the impact operation to the time when the motor (3) stops running.

[0267] This configuration allows the control mode to be changed at appropriate time intervals.

[0268] Note that the constituent elements of the second to ninth aspects are not the basic constituent elements of the impact tool (1), but can be appropriately omitted.

[0269] The tenth aspect of the control method for controlling an impact tool (1) is a method for controlling an impact tool (1) including a motor (3), an impact mechanism (40), and an output shaft (61). The impact mechanism (40) includes a hammer (42) and an anvil (45). The hammer (42) rotates using power supplied from the motor (3). The anvil (45) rotates when it receives an impact force from the hammer (42). The output shaft (61) rotates together with the anvil (45). The control method includes a control step and an angle lead measurement step. The control step includes controlling the rotational speed of the output shaft (61). The angle lead measurement step includes measuring the angle lead of the rotation of the anvil (45) relative to the rotation of the hammer (42). The impact mechanism (40) performs an impact operation when a torque condition related to the magnitude of the torque applied to the output shaft (61) is met. The impact operation is an operation for applying an impact force from the hammer (42) to the anvil (45). The control steps include changing the control mode used to control the rotational speed of the output shaft (61) from one of multiple modes to another based on the angle advance measured in the angle advance measurement step.

[0270] This control method enables the impact tool (1) to autonomously control the rotation speed of the output shaft (61) according to the working conditions.

[0271] The procedure according to the eleventh aspect is designed to enable one or more processors to perform the control method according to the tenth aspect for controlling the impact tool (1).

[0272] The program enables the impact tool (1) to autonomously control the rotation speed of the output shaft (61) according to the working conditions.

[0273] Note that these are not the only aspects of the present invention. On the contrary, various structures (including variations) of the impact tool (1) according to the above-described typical embodiments can also be implemented as control methods or programs for controlling the impact tool (1).

[0274] Explanation of reference numerals in the attached figures

[0275] 1. Impact tools

[0276] 3 motors

[0277] 7 Control Unit

[0278] 9A Angle Lead Measurement Unit

[0279] 40 Impact Mechanism

[0280] 42 hammers

[0281] 45 Anvil

[0282] 78 Impact Detector

[0283] 61 Output shaft

[0284] 82 Current Measurement Unit

[0285] 83 Voltage Measurement Unit

[0286] 91 Impact Interval Measurement Unit

[0287] 92 Hammer Rotation Measuring Section

[0288] 93 Computing Department

[0289] Th1 First Threshold

[0290] Th2 second threshold

[0291] Th5 Pre-determined Value

[0292] α1 Rotation angle

Claims

1. An impact tool, comprising: motor; An impact mechanism comprising a hammer and an anvil, the hammer being configured to rotate using power supplied from the motor, and the anvil being configured to rotate upon receiving an impact force from the hammer. An output shaft is configured to rotate together with the anvil. A control unit configured to control the rotational speed of the output shaft; as well as An angle-leading measuring unit is configured to measure the angle leading the rotation of the anvil relative to the rotation of the hammer. The impact mechanism is configured to perform an impact operation to apply the impact force from the hammer to the anvil, provided that a torque condition related to the magnitude of the torque applied to the output shaft is met. The control unit is configured to change the control mode for controlling the rotational speed of the output shaft from one of multiple modes to another based on the angle advance measured by the angle advance measuring unit.

2. The impact tool according to claim 1, wherein, The angle leading measurement unit includes: An impact interval measuring unit is configured to measure the impact interval, which is the time interval during which the hammer applies the impact force to the anvil. A hammer rotation measuring unit, configured to measure the rotational speed of the hammer; and The calculation unit is configured to calculate the angular lead based on the impact interval measured by the impact interval measuring unit and the rotation speed of the hammer measured by the hammer rotation measuring unit.

3. The impact tool according to claim 2, wherein, The angle advance measurement unit further includes at least one of the following units: A current measuring unit configured to measure the current flowing through the motor; and A voltage measuring unit is configured to measure the voltage applied to the motor, and the impact interval measuring unit is configured to measure the impact interval based on the current measured by the current measuring unit or the voltage measured by the voltage measuring unit.

4. The impact tool according to claim 3, wherein, The angle lead measurement unit includes the current measurement unit, and The impact interval measuring unit is configured to measure the time interval during which the excitation current measured by the current measuring unit becomes equal to or less than a predetermined value as the impact interval.

5. The impact tool according to any one of claims 1 to 4, wherein, The multiple modes include a first control mode, and The control unit is configured to change the control mode to the first control mode if it is found that the angle is ahead by more than a first threshold.

6. The impact tool according to any one of claims 1 to 4, wherein, The multiple modes include a second control mode, and The control unit is configured to change the control mode to the second control mode if it is found that the angle is ahead of a second threshold.

7. The impact tool according to any one of claims 1 to 4, wherein, The multiple modes include: a normal mode, in which the output shaft can rotate; and a deceleration mode, in which restrictions are applied based on conditions; and The limiting process includes at least one of reducing the rotational speed of the output shaft to a lower speed than in the normal mode and stopping the rotation of the output shaft.

8. The impact tool according to any one of claims 1 to 4, wherein, The control unit is configured to control the rotational speed of the output shaft to an upper limit or less, and The control unit is configured to increase the upper limit value as the angle advances.

9. The impact tool according to any one of claims 1 to 4, further comprising an impact detector configured to detect the impact operation performed by the impact mechanism. in, The control unit is configured to change the control mode based on the angle advance throughout the entire time period from the time the impact detector detects the impact operation to the time the motor stops running.

10. A method for controlling an impact tool, the impact tool comprising: motor; An impact mechanism comprising a hammer and an anvil, the hammer being configured to rotate using power supplied from the motor, and the anvil being configured to rotate upon receiving an impact force from the hammer. as well as An output shaft, configured to rotate together with the anvil. The control method includes: Control steps are used to control the rotational speed of the output shaft; as well as The angle lead measurement step is used to measure the angle lead of the rotation of the anvil relative to the rotation of the hammer. The impact mechanism is configured to perform an impact operation to apply the impact force from the hammer to the anvil, provided that a torque condition related to the magnitude of the torque applied to the output shaft is met. The control step is used to change the control mode for controlling the rotational speed of the output shaft from one of multiple modes to another based on the angle advance measured in the angle advance measurement step.

11. A computer system-readable non-transitory storage medium storing a program designed to cause one or more processors of the computer system to perform the control method according to claim 10.

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