Electric power tool, electric power tool system, control method, and program

Abstract

The purpose of the present disclosure is to accurately determine whether there is a malfunction in screw fastening in an electric power tool that performs an impact operation. An electric power tool (10) comprises: a motor; a hammer; an anvil; an output shaft; an impact detection unit (112); a motor control unit (115); and a storage unit (117). Upon receiving a predetermined command from an external device (50a), the motor control unit (115) fastens a screw by means of a preset control of the motor. The motor control unit (115) executes a determination process for determining whether there is a malfunction in screw fastening, on the basis of the relationship between the rotational angle of the motor and the detection result from the impact detection unit (112) of whether there is an impact operation. The preset control includes stopping the motor when it is determined, as a result of the determination process, that there is a malfunction in screw fastening.

Description

Power tool, power tool system, control method and program

[0001] The present disclosure generally relates to a power tool, a power tool system, a control method, and a program. More specifically, the present disclosure relates to a power tool with an impact action, a power tool system including the power tool, a control method for a power tool with an impact action, and a program for executing the control method.

[0002] The automatic screw tightening device (power tool) described in Patent Document 1 includes a driver tool that engages with a screw, a reciprocating means, and a control means. The reciprocating means supports the driver tool so that it can be moved back and forth. The control means compares the movement distance of the driver tool with a preset distance to determine whether screw tightening is being performed normally, and if an abnormality is determined, the control means halts screw tightening.

[0003] However, when the configuration of the automatic screw tightening device described in Patent Document 1 is applied to a power tool that performs an impact operation, it may be difficult to determine whether or not there is an abnormality in the screw tightening.

[0004] JP 2013-031888 A

[0005] The present disclosure aims to provide a power tool, a power tool system, a control method, and a program that can accurately determine whether or not there is an abnormality in screw tightening in a power tool that performs an impact operation.

[0006] A power tool according to one aspect of the present disclosure is a power tool for tightening a screw. The power tool includes a motor, a hammer, an anvil, an output shaft, an impact detection unit, a motor control unit, and a memory unit. The hammer rotates by receiving power from the motor. The anvil rotates by receiving an impact force from the hammer in the direction of rotation of the hammer. The output shaft is configured to hold a tool tip that transmits torque to the screw and rotates together with the anvil. The impact detection unit detects whether or not an impact operation occurs, which is the operation of the hammer applying the impact force to the anvil. The motor control unit controls the operation of the motor based on a command from an external device outside the power tool. The memory unit stores information for the motor control unit to perform predetermined control of the motor. When the motor control unit receives a predetermined command from the external device, it tightens the screw by controlling the motor by the predetermined control. The motor control unit executes a determination process to determine whether or not there is an abnormality in the screw tightening based on the relationship between the rotation angle of the motor and the detection result of the impact detection unit indicating the presence or absence of the impact motion. The predetermined control includes stopping the motor when it is determined as a result of the determination process that there is an abnormality in the screw tightening.

[0007] A power tool system according to one aspect of the present disclosure includes the power tool and a robot arm, the robot arm holding the power tool and controlling the position and attitude of the power tool.

[0008] According to another aspect of the present disclosure, there is provided a power tool system including the power tool described above and a robot, the robot being the external device that issues commands to the motor control unit, the robot including a robot arm that holds the power tool and controls the position and attitude of the power tool.

[0009] A control method according to one aspect of the present disclosure is a control method for a power tool for tightening a screw. The power tool includes a motor, a hammer, an anvil, an output shaft, and an impact detection unit. The hammer rotates by receiving power from the motor. The anvil rotates by receiving an impact force from the hammer in the rotational direction of the hammer. The output shaft is configured to hold a tool bit that transmits torque to the screw and rotates together with the anvil. The impact detection unit detects whether or not an impact motion occurs, which is the action of the hammer applying the impact force to the anvil. The control method is executed by a computer system. When a predetermined command is received from an external device outside the power tool, the control method includes: tightening the screw by a predetermined control of the motor; and executing a determination process to determine whether or not an abnormality exists in the screw tightening process based on the relationship between the rotation angle of the motor and the detection result of the impact detection unit indicating the presence or absence of the impact motion. The predetermined control includes stopping the motor if the determination process determines that an abnormality exists in the screw tightening process.

[0010] A program according to one aspect of the present disclosure is a program for causing one or more processors of the computer system to execute the control method.

[0011] Fig. 1 is a block diagram of a power tool system according to one embodiment. Fig. 2 is a perspective view of the main components of the power tool system. Fig. 3 is a front view showing the power tool system in operation. Fig. 4 is a schematic diagram showing the internal structure of a power tool in the power tool system. Fig. 5 is an explanatory diagram showing an example of the operation of the power tool system. Figs. 6A to 6F are schematic diagrams showing a screw tightening operation using the power tool system.

[0012] (Embodiments) The following describes a power tool 10, a power tool system 100, a control method, and a program according to embodiments, using the drawings. However, the following embodiment is merely one of various embodiments of the present disclosure. The following embodiment can be modified in various ways depending on the design, etc., as long as the object of the present disclosure can be achieved. Furthermore, each diagram described in the following embodiments is a schematic diagram, and the ratios of the sizes and thicknesses of the components in the diagrams do not necessarily reflect the actual dimensional ratios.

[0013] (1) Overview Fig. 1 is a schematic block diagram of a power tool system 100 including a power tool 10 according to the present embodiment. Fig. 2 is an external perspective view showing an installation state of a robot 50 holding the power tool 10. Fig. 3 is a front view showing the power tool 10 performing a screw tightening operation. Fig. 4 is a schematic diagram showing the internal structure of the power tool 10.

[0014] The power tool 10 is used to tighten a screw B1. The power tool 10 includes a motor M1, a hammer 74, an anvil 75, an output shaft 22, an impact detection unit 112, a motor control unit 115, and a memory unit 117. The hammer 74 receives power from the motor M1 and rotates. The anvil 75 receives an impact force from the hammer 74 in the rotational direction of the hammer 74 and rotates. The output shaft 22 is configured to hold a tool bit 23 that transmits torque to the screw B1 and rotates together with the anvil 75. The impact detection unit 112 detects whether or not an impact operation, which is an operation in which the hammer 74 applies an impact force to the anvil 75, has occurred. The motor control unit 115 controls the operation of the motor M1 based on a command from an external device 50a external to the power tool 10. The memory unit 117 stores information used by the motor control unit 115 to perform predetermined control of the motor M1. When the motor control unit 115 receives a predetermined command from the external device 50a, it tightens the screw B1 by controlling the motor M1 in a predetermined manner. The motor control unit 115 executes a determination process to determine whether or not there is an abnormality in the screw tightening based on the relationship between the rotation angle of the motor M1 and the detection result of the impact detection unit 112, which indicates whether or not there is an impact operation. Here, the rotation angle may be a set value or a measured value. The predetermined control includes stopping the motor M1 when it is determined as a result of the determination process that there is an abnormality in the screw tightening.

[0015] According to the above configuration, the power tool 10 that performs impact operation can accurately determine whether or not there is an abnormality in screw tightening, and if there is an abnormality, the motor M1 can be stopped, thereby improving the accuracy of response to abnormalities.

[0016] Here, as a comparative example to be compared with the power tool 10 of this embodiment, a power tool that determines whether or not there is an abnormality in screw tightening based on the characteristics of the current flowing through the motor M1 during impact operation is assumed. If an abnormality such as galling (seizure) or oblique tightening occurs in the screw B1, the screw B1 becomes difficult to move. In this case, the characteristics of the current flowing through the motor M1 during impact operation may be similar to the characteristics when the screw B1 is properly seated and difficult to move. Therefore, with the power tool of the comparative example, it may be difficult to accurately determine whether or not there is an abnormality in screw tightening.

[0017] In contrast, in the power tool 10 of this embodiment, the motor control unit 115 determines whether or not there is an abnormality in the screw tightening based on the relationship between the rotation angle of the motor M1 and the detection result of the impact detection unit 112 as to whether or not there is an impact operation, so that the presence or absence of an abnormality in the screw tightening can be determined with high accuracy.

[0018] The power tool system 100 of this embodiment also includes the power tool 10 and a robot 50. The robot 50 is an external device 50a that issues commands to the motor control unit 115. The robot 50 includes a robot arm 51. The robot arm 51 holds the power tool 10 and controls the position and posture of the power tool 10. Therefore, the power tool system 100 can automatically perform screw tightening work and accurately determine whether or not there is an abnormality in the screw tightening.

[0019] The control method of this embodiment is a control method for a power tool 10 for tightening a screw B1. The power tool 10 includes a motor M1, a hammer 74, an anvil 75, an output shaft 22, and an impact detection unit 112. The hammer 74 receives power from the motor M1 and rotates. The anvil 75 receives an impact force from the hammer 74 in the rotational direction of the hammer 74 and rotates. The output shaft 22 is configured to hold a tool bit 23 that transmits torque to the screw B1 and rotates together with the anvil 75. The impact detection unit 112 detects whether or not an impact operation, which is an operation in which the hammer 74 applies an impact force to the anvil 75, has occurred. The control method is executed by a computer system. The control method includes, upon receiving a predetermined command from an external device 50a external to the power tool 10, tightening the screw B1 by a predetermined control of the motor M1, and executing a determination process to determine whether or not there is an abnormality in the screw tightening based on the relationship between the rotation angle of the motor M1 and the detection result of the impact detection unit 112 as to whether or not there is an impact operation. The predetermined control includes stopping the motor M1 when it is determined as a result of the determination process that there is an abnormality in the screw tightening.

[0020] The control method can be realized by a program. The program of this embodiment is a program for causing one or more processors of a computer system to execute the control method. The program may be recorded on a non-transitory recording medium readable by the computer system.

[0021] (2) Details The power tool 10 and the power tool system 100 according to this embodiment will be described in detail below with reference to the drawings.

[0022] (2.1) Configuration As described above, the power tool system 100 includes the power tool 10 and the robot 50. As shown in FIG. 1 , the power tool system 100 of this embodiment further includes a receiver 30, a centralized control unit 40, and a control device 60.

[0023] Here, the robot 50 is, for example, an industrial robot installed in a factory. The power tool 10 is a tool held by a robot arm 51 (see FIG. 2 ) of the robot 50 and is therefore a so-called end effector. The power tool 10 is a tool used for screw tightening, for example, to tighten a screw B1 (fastening member) such as a bolt or nut on a work object. Because the power tool 10 is held by the articulated robot arm 51, it can tighten a screw on the work object from any direction.

[0024] The power tool 10, the robot 50, the receiver 30, the centralized control unit 40, and the control device 60 included in the power tool system 100 will be described in detail below with reference to the drawings.

[0025] (2.1.1) Robot The robot 50 is, for example, an industrial robot that performs a screw tightening operation to tighten a screw B1 into a workpiece W1 that is the work target (see FIG. 2).

[0026] As shown in FIG. 2, the robot 50 is installed on a workbench 500, and performs a screw tightening operation on a workpiece W1 placed on the upper surface of the workbench 500. The robot 50 has an articulated robot arm 51. The robot arm 51 has, for example, six degrees of freedom. The robot arm 51 has six arms 511 to 516, which are rotatably connected via joints. Motors are incorporated in the joints, and the arms 511 to 516 are configured to rotate individually by rotating the motors.

[0027] As shown in FIG. 1 , the robot 50 includes a control unit 52 , a communication unit 53 , a posture detection unit 54 , a load detection unit 55 , an arm drive unit 56 , and an operation unit 57 .

[0028] The control unit 52 performs overall control of the robot 50. The control unit 52 is mainly composed of a computer system having one or more processors and a memory. The functions of the control unit 52 are realized by the processor of the computer system executing a program recorded in the memory of the computer system. The program may be recorded in the memory, or may be provided via a telecommunications line such as the Internet, or may be recorded on a non-transitory recording medium such as a memory card and provided.

[0029] The communication unit 53 can communicate with the second communication unit 16 of the power tool 10 via wired communication or wireless communication.

[0030] The attitude detection unit 54 includes, for example, a plurality of rotary encoders that detect the rotation angles of the arms 511 to 516 of the robot arm 51, and a plurality of angular velocity sensors that detect the angular velocities of the arms 511 to 516. The attitude detection unit 54 detects the position, orientation, etc. of the arm 516 at the tip based on the detection results of the plurality of rotary encoders and the detection results of the plurality of angular velocity sensors, for example.

[0031] The load detection unit 55 includes, for example, a force sensor attached to the tip arm 516 and detects the magnitude of the load applied to the tip arm 516 or the impact force applied to the tip arm 516 .

[0032] The arm driving unit 56 includes a plurality of motors that rotate the arms 511 to 516, respectively, and a plurality of driver circuits that drive the plurality of motors, respectively. The arm driving unit 56 rotates the plurality of motors based on a control command input from the control unit 52, thereby moving the arm 516 at the tip to a position specified by the control command.

[0033] The operation unit 57 includes an interface device such as an operation button or a touch panel provided on the robot 50. The operation unit 57 receives operation information input by the user and outputs it to the control unit 52. The control unit 52 outputs a command to the power tool 10 via the communication unit 53 in accordance with the operation information.

[0034] (2.1.2) Control Device The control device 60 controls the operation of the robot 50. The control device 60 is installed, for example, in a factory where the robot 50 to be controlled is installed.

[0035] As shown in FIG. 1, the control device 60 includes a control unit 61, a communication unit 62, and a storage unit 63.

[0036] The communication unit 62 can communicate with the communication unit 53 of the robot 50 and the communication unit 42 of the centralized control unit 40 via wired communication or wireless communication.

[0037] The memory unit 63 stores information such as the work position where the robot 50 performs work on the work object and posture information related to the posture of the robot arm 51 at the work position. The posture information related to the posture of the robot arm 51 includes, for example, information such as the position and orientation of the arm 516 to which the power tool 10 is attached. If there are multiple work positions for the workpiece W1 where the robot 50 performs work, the memory unit 63 stores posture information related to the posture of the robot arm 51 at each of the multiple work positions. Furthermore, if the robot 50 performs work on multiple types of workpieces W1, posture information related to the posture of the robot arm 51 may be stored for each of the multiple types of workpieces W1.

[0038] The control unit 61 controls the operation of the robot 50 to cause the power tool 10 held by the robot 50 to perform work on a work object. Based on the work position and the posture information of the robot arm 51 at the work position stored in the memory unit 63, the control unit 61 moves the power tool 10 to the work position and causes the power tool 10 to perform work on the work object.

[0039] 1, the power tool 10 includes a processing unit 11, an inclination sensor 12, a torque sensor 13, a tool driving unit 14, a first communication unit 15, a second communication unit 16, a notification unit 17, a power supply unit 18, and a current sensor 19. The tool driving unit 14 includes a motor M1 (see FIG. 4).

[0040] The power tool 10 includes a tool body 21 that houses a processing unit 11, an inclination sensor 12, a torque sensor 13, a tool drive unit 14, a first communication unit 15, a second communication unit 16, a notification unit 17, a power supply unit 18, a current sensor 19, etc. The tool body 21 has a shape of an elongated rectangular tube. The tool body 21 is attached to an arm 516 at the tip of a robot arm 51 of a robot 50. An output shaft 22 protrudes from one end face in the longitudinal direction of the tool body 21. The output shaft 22 is held in a rotatable state relative to the tool body 21.

[0041] The first communication unit 15 is capable of communicating with the first communication unit 32 of the receiver 30 via a wireless communication system.

[0042] The second communication unit 16 is capable of communicating with the communication unit 53 of the robot 50 via wired communication or wireless communication.

[0043] The processing unit 11 is mainly composed of a computer system having one or more processors and a memory. The functions of the processing unit 11 are realized by the processor of the computer system executing a program recorded in the memory of the computer system. The program may be recorded in the memory, or may be provided via a telecommunications line such as the Internet, or may be recorded on a non-transitory recording medium such as a memory card and provided.

[0044] The processing unit 11 has the functions of a direction detection unit 111, an impact detection unit 112, a notification unit 113, a torque calculation unit 114, a motor control unit 115, and a current detection unit 116. Note that the direction detection unit 111, the impact detection unit 112, the torque calculation unit 114, the motor control unit 115, and the current detection unit 116 merely indicate functions realized by the processing unit 11, and do not necessarily indicate actual configurations.

[0045] The processing unit 11 also includes a storage unit 117. The storage unit 117 includes the memory of the computer system.

[0046] The tilt sensor 12 includes, for example, a three-axis acceleration sensor housed inside the tool body 21. The tilt sensor 12 detects the gravitational acceleration acting on the tool body 21, thereby being able to detect the tilt angle of the tool body 21 with respect to the direction of gravity.

[0047] For example, when the robot arm 51 moves and the output shaft 22 moves to a working position, the direction detection unit 111 detects the orientation of the output shaft 22 based on the detection result of the tilt sensor 12 .

[0048] The current sensor 19 outputs a detection signal corresponding to the magnitude of the current flowing through the motor M1. The current detection unit 116 detects (measures) the current flowing through the motor M1 based on the detection signal output from the current sensor 19.

[0049] The impact detection unit 112 detects whether or not an impact motion has occurred based on the current detected by the current detection unit 116. For example, the impact detection unit 112 determines that an impact motion has occurred when the current detected by the current detection unit 116 changes from a state below a threshold to a state above the threshold. Then, for example, the impact detection unit 112 determines that an impact motion has not occurred when the state in which the current detected by the current detection unit 116 remains below the threshold for a predetermined period of time or longer.

[0050] The motor control unit 115 determines a command rotation speed based on the information stored in the storage unit 117, and outputs a control command including information indicating the command rotation speed to the tool driving unit 14. The tool driving unit 14 controls the motor M1 so that the rotation speed of the motor M1 approaches the command rotation speed.

[0051] More specifically, information indicating the change in the command rotation speed in response to the elapsed time since the motor M1 started to rotate is stored in the storage unit 117. Fig. 5 shows an example of the change in the command rotation speed over time stored in the storage unit 117. The rotation speed of the motor M1 is controlled in accordance with this information.

[0052] The motor control unit 115 also executes a determination process to determine whether or not there is an abnormality in the screw tightening. If the motor control unit 115 determines as a result of the determination process that there is an abnormality in the screw tightening, it stops the motor M1.

[0053] The notification unit 113 performs processing to notify the result of the determination processing of the motor control unit 115. The notification unit 113 outputs a notification command according to the result of the determination processing to the notification unit 17, causing the notification unit 17 to perform a notification operation.

[0054] The alarm unit 17 performs an alarm operation using sound or light in response to an alarm command from the notification unit 113. The alarm unit 17 includes, for example, a buzzer 171 housed inside the tool body 21 and an indicator light 172 arranged visibly on the surface of the tool body 21. The indicator light 172 includes, for example, an LED capable of emitting light in two colors, red and green. The notification unit 113 changes the type of sound emitted by the buzzer 171 and the light color of the indicator light 172 depending on whether there is an abnormality in the screw tightening or not.

[0055] For example, if there is no abnormality in the screw tightening, the notification unit 113 does not make the buzzer 171 emit a sound, but if there is an abnormality in the screw tightening, the notification unit 113 makes the buzzer 171 emit a sound. In this way, in this embodiment, the notification unit 113 notifies the operator of the result of the determination process by sound, and the operator can grasp the result of the determination process by hearing it.

[0056] Furthermore, the notification unit 113, for example, lights the indicator light 172 in green if there is no abnormality in the screw tightening, and lights the indicator light 172 in red if there is an abnormality in the screw tightening. In this way, the notification unit 113 notifies the operator of the result of the determination process with light, allowing the operator to visually grasp the result of the determination process.

[0057] The torque sensor 13 detects the torque applied to the output shaft 22 when the power tool 10 performs a screw tightening operation on the screw B1, for example.

[0058] The torque calculation unit 114 calculates the tightening torque of the screw B1 by the tool bit 23 based on the detection result of the torque sensor 13 .

[0059] The power supply unit 18 receives power from an external power supply 90 such as a commercial AC power supply and generates an operating voltage for the power tool 10 .

[0060] The tool driving unit 14 includes a motor M1 (see FIG. 4) housed in the tool body 21, a drive circuit that drives the motor M1, and a transmission mechanism 70 (see FIG. 4) that transmits the rotational force of the motor M1 to the output shaft 22. The tool driving unit 14 rotates the motor M1 in response to a control command from the motor control unit 115, thereby rotating the tool tip 23 attached to the output shaft 22.

[0061] The transmission mechanism 70 will be described with reference to Figure 4. The transmission mechanism 70 transmits the rotational power of the motor M1 to the output shaft 22 to rotate the output shaft 22. In this embodiment, the side of the motor M1 on which the output shaft 22 is located is defined as the front, and the side of the output shaft 22 on which the motor M1 is located is defined as the rear. However, these definitions are not intended to limit the direction in which the power tool 10 is used.

[0062] The transmission mechanism 70 includes a transmission 71 , a drive shaft 72 , a spring 73 , a hammer 74 , and an anvil 75 .

[0063] The transmission 71 includes, for example, a planetary gear mechanism and is interposed between the motor M1 and the drive shaft 72. The transmission 71 reduces the rotational power of the motor M1 at a predetermined reduction ratio and outputs the reduced power as rotation of the drive shaft 72.

[0064] The hammer 74 is attached to the drive shaft 72 via a cam mechanism. The anvil 75 rotates upon receiving a rotational force from the hammer 74. The spring 73 is a compression coil spring. The spring 73 pushes the hammer 74 toward the anvil 75 (forward). The anvil 75 is formed integrally with the output shaft 22. Note that the anvil 75 may be formed separately from the output shaft 22 and fixed to the output shaft 22.

[0065] When a load (torque) greater than a predetermined magnitude is not applied to the output shaft 22, the drive shaft 72 and hammer 74, which are connected by a cam mechanism, rotate together, and further the hammer 74 and anvil 75 rotate together, causing the output shaft 22, which is formed integrally with the anvil 75, to rotate. On the other hand, when a load greater than a predetermined magnitude is applied to the output shaft 22, the hammer 74 moves backward against the spring 73 while being restricted by the cam mechanism (i.e., moves away from the anvil 75). At the point when the connection between the hammer 74 and the anvil 75 is released, the hammer 74 moves forward while rotating, applying a rotational impact force to the anvil 75 and rotating the output shaft 22. In this way, an impact operation in which the hammer 74 and the anvil 75 collide and transmit an impact force is repeated.

[0066] 3, a holder 24 is attached to the output shaft 22, and a tool bit 23 is attached to the holder 24 via a coil spring 25. The tool bit 23 is a socket attached to the outer edge of the screw B1.

[0067] (2.1.4) Receiver The receiver 30 is installed in a location where it can wirelessly communicate with the first communication unit 15 of the power tool 10. The receiver 30 relays communication between the power tool 10 and the centralized control unit 40.

[0068] The receiver 30 includes a control unit 31 , a first communication unit 32 , and a second communication unit 33 .

[0069] The first communication unit 32 is capable of communicating with the first communication unit 15 of the power tool 10 via wireless communication.

[0070] The second communication unit 33 is capable of communicating with the communication unit 42 of the centralized control unit 40 via a network NT such as the Internet or a LAN.

[0071] The control unit 31 mainly comprises a computer system having one or more processors and a memory. The functions of the control unit 31 are realized by the processor of the computer system executing a program recorded in the memory of the computer system. The program may be recorded in the memory, or may be provided via a telecommunications line such as the Internet, or may be recorded on a non-transitory recording medium such as a memory card and provided.

[0072] When the first communication unit 32 receives a signal from the power tool 10, the control unit 31 causes the second communication unit 33 to transmit the signal from the power tool 10 to the centralized management unit 40. When the second communication unit 33 receives a signal from the centralized management unit 40, the control unit 31 causes the first communication unit 32 to transmit the signal from the centralized management unit 40 to the power tool 10.

[0073] (2.1.5) Centralized Control Unit The centralized control unit 40 manages the power tool 10. Here, managing the power tool 10 includes at least one of managing the work content of the work using the power tool 10 and managing the operating status of the power tool 10. Managing the work content includes at least one of setting a tightening torque value for the power tool 10 and acquiring work result information related to the work results of the work performed by the power tool 10 on the work object (e.g., the actual tightening torque value, the rotation speed during the screw tightening work, and whether or not there is an abnormality in the screw tightening). Managing the operating status of the power tool 10 also includes at least one of measuring the operating time of the power tool 10, notifying the power tool 10 when maintenance is required, and accumulating error signals output by the power tool 10 to notify of an abnormality.

[0074] As shown in FIG. 1, the centralized management unit 40 includes a control unit 41, a communication unit 42, and a storage unit 43.

[0075] The communication unit 42 is configured to be able to communicate with the second communication unit 33 of the receiver 30 and the communication unit 62 of the control device 60 via wired communication or wireless communication.

[0076] The storage unit 43 includes an internal memory such as a random access memory (RAM), a read-only memory (ROM), or an electrically erasable programmable read-only memory (EEPROM), and an external storage device such as a hard disk drive or an SSD. The storage unit 43 stores setting information such as a tightening torque setting value to be set in the power tool 10, work result information obtained from the power tool 10, error signals obtained from the power tool 10, etc.

[0077] The control unit 41 mainly comprises a computer system having one or more processors and a memory. The functions of the control unit 41 are realized by the processor of the computer system executing a program recorded in the memory of the computer system. The program may be recorded in the memory, or may be provided via a telecommunications line such as the Internet, or may be recorded on a non-transitory recording medium such as a memory card and provided.

[0078] The control unit 41 causes the communication unit 42 to transmit the setting information stored in the storage unit 43 to the power tool 10 via the receiver 30, and sets the setting information in the power tool 10. When the communication unit 42 receives work result information from the power tool 10, the control unit 41 causes the storage unit 43 to store the work result information received by the communication unit 42.

[0079] (2.2) Screw Tightening Abnormalities Here, first, an example of the structure of the screw B1 will be described, and then various examples of screw tightening abnormalities will be described.

[0080] As shown in Fig. 6A, the screw B1 includes a head B11 and a threaded portion B12. The head B11 has a disk-like shape. The threaded portion B12 has a cylindrical shape. The threaded portion B12 protrudes from the head B11. The diameter of the threaded portion B12 is smaller than the diameter of the head B11.

[0081] Galling (seizure) in which the threaded portion B12 welds to the inner surface of the threaded hole W10 in the workpiece W1 is an example of a screw tightening abnormality.

[0082] "Diagonal tightening," in which the screw B1 is screwed in at an angle, is an example of an abnormal screw tightening.

[0083] When the screw hole W10 has a bottom surface, bottoming out, in which the tip of the threaded portion B12 comes into contact with the bottom surface before the screw B1 is seated, is an example of a screw tightening abnormality.

[0084] An example of a screw tightening abnormality is when the diameter of the threaded portion B12 is excessively large compared to the diameter of the screw hole W10.

[0085] An example of a screw tightening abnormality is when the diameter of the threaded portion B12 is too small compared to the diameter of the screw hole W10.

[0086] An example of a screw tightening abnormality is when the inner diameter of the socket-shaped tool bit 23 is excessively large compared to the outer diameter of the head B11.

[0087] The fact that the pitch (the distance between the threads) of the threaded portion B12 does not correspond to the pitch of the screw hole W10 is an example of an abnormality in screw tightening.

[0088] The damage to the screw B1 is an example of an abnormality in screw tightening.

[0089] The absence of screw B1 (forgotten to set) is an example of an abnormality in screw tightening.

[0090] The absence of the workpiece W1 (forgetting to set it) is an example of a screw tightening abnormality.

[0091] (2.3) Description of Operation The operation of the power tool system 100 of this embodiment will be described with reference to Figures 5, 6A to 6F, etc. Note that while star-shaped marks are shown in Figures 6B and 6C, these marks merely indicate that an impact operation is being performed and do not represent an actually existing configuration.

[0092] As described above, when the motor control unit 115 receives a predetermined command from the external device 50a (robot 50), it tightens the screw B1 by performing predetermined control on the motor M1. More specifically, a signal including a first signal and a second signal is output from the external device 50a to the motor control unit 115.

[0093] The first signal is a signal that instructs whether to rotate or stop the motor M1. The first signal is a high-level signal or a low-level signal. If the first signal acquired from the external device 50a is a high-level signal, the motor control unit 115 rotates the motor M1. If the first signal acquired from the external device 50a is a low-level signal, the motor control unit 115 stops the motor M1.

[0094] The second signal is a signal that instructs whether to tighten or loosen the screw B1. The second signal is a high-level signal or a low-level signal. If the second signal acquired from the external device 50a is a high-level signal, the motor control unit 115 controls the motor M1 to tighten the screw B1. If the second signal acquired from the external device 50a is a low-level signal, the motor control unit 115 controls the motor M1 to loosen the screw B1.

[0095] The motor control unit 115 determines control based on a combination of the first signal and the second signal acquired from the external device 50a. When the first signal is a high-level signal and the second signal is a high-level signal, the motor control unit 115 performs predetermined control on the motor M1. When the first signal is a high-level signal and the second signal is a low-level signal, the motor control unit 115 causes the motor M1 to rotate in the reverse direction. When the first signal is a low-level signal, the motor control unit 115 stops the motor M1.

[0096] In this way, the signal output from the external device 50a to the motor control unit 115 is a simple signal, and the detailed control of the motor M1 is determined on the power tool 10 side.

[0097] The default control will be described below. The default control is control for tightening the screw B1. The motor control unit 115 also executes a determination process to determine whether or not there is an abnormality in the screw tightening, and if it determines as a result of the determination process that there is an abnormality in the screw tightening, it stops the motor M1. Figure 5 shows the change over time in the command rotation speed when it is not determined as a result of the determination process that there is an abnormality in the screw tightening.

[0098] The motor control unit 115 performs default control to cause the motor M1 to perform forward and reverse rotations. Forward rotation is rotation in the direction in which the screw B1 is tightened. Reverse rotation is rotation in the opposite direction to the forward rotation. In other words, reverse rotation is rotation in the direction in which the screw B1 is loosened (the opposite direction to the direction in which the screw B1 is tightened). If the screw B1 is a right-handed screw, forward rotation is clockwise rotation, and reverse rotation is counterclockwise rotation.

[0099] As shown in Figure 5, the default control can be expressed as a change in the commanded rotation speed over time. When the commanded rotation speed is a positive value, the motor M1 rotates forward, and when the commanded rotation speed is a negative value, the motor M1 rotates reverse. When the commanded rotation speed is 0, the motor M1 stops.

[0100] Periods T1, T2, ..., T8 are set in chronological order from earliest to latest. In each of periods T1 to T8, the command rotation speed is a positive or negative value. In addition, a brake period is set between periods. In the brake period, the command rotation speed is set to 0.

[0101] When the default control is started, the motor control unit 115 first causes the motor M1 to rotate in the reverse direction during the period T1 in order to reduce the possibility of the screw B1 being tightened at an angle. In other words, the motor control unit 115 sets the command rotation speed to a negative value during the period T1.

[0102] Next, motor control unit 115 sets the command speed to a positive value during period T2. Furthermore, motor control unit 115 sets the command speed to a positive value during period T3. The command speed during period T2 is smaller than the command speed during period T3, which causes motor M1 to soft start during period T2.

[0103] The motor control unit 115 sets the command rotation speed to a positive value during periods T4, T7, and T8, and sets the command rotation speed to a negative value during periods T5 and T6.

[0104] 6A to 6F show examples of the relationship between the screw B1 and the workpiece W1 during periods T3 to T8, respectively.

[0105] 6A, the power tool 10 temporarily tightens the screw B1. That is, the power tool 10 partially inserts the threaded portion B12 into the threaded hole W10 of the workpiece W1. For example, the motor control unit 115 rotates the motor M1 forward by a certain rotation angle.

[0106] 6B, the power tool 10 performs an impact operation to tighten the screw B1. For example, the motor control unit 115 rotates the motor M1 in the forward direction until the number of impact operations reaches a predetermined number.

[0107] During the period T5, the power tool 10 loosens the screw B1 as shown in Fig. 6C. For example, the motor control unit 115 rotates the motor M1 in the reverse direction by a certain rotation angle.

[0108] During a period T6, the power tool 10 further loosens the screw B1 as shown in Fig. 6D. For example, the motor control unit 115 rotates the motor M1 in the reverse direction by a certain rotation angle.

[0109] During the period T7, the power tool 10 temporarily tightens the screw B1 as shown in Fig. 6E. For example, the motor control unit 115 rotates the motor M1 forward by a certain rotation angle.

[0110] During period T8, the power tool 10 tightens the screw B1 as shown in FIG. 6F. For example, the motor control unit 115 rotates the motor M1 forward by a certain rotation angle. The screw tightening during period T8 is the final tightening (final tightening).

[0111] Thus, the default control includes a first control and a second control. In the first control, the motor M1 is caused to alternately perform a forward rotation operation in which it rotates in the direction in which the screw B1 is tightened, and a reverse rotation operation in which it rotates in the opposite direction to the forward rotation operation. In the second control, if it is determined as a result of the determination process that there is no abnormality in the screw tightening in the first control, the motor M1 is caused to perform a forward rotation operation to tighten the screw B1. The control in periods T3 to T7 is the first control, and the control in period T8 is the second control.

[0112] Here, "alternating forward and reverse rotation" may include at least one of a forward rotation followed by a reverse rotation, or a reverse rotation followed by a forward rotation. Therefore, when "alternating forward and reverse rotation" refers to alternating forward and reverse rotation, the number of forward rotations and the number of reverse rotations each may be at least one. Note that in the first control, it is preferable to have the motor M1 perform a forward rotation followed by a reverse rotation.

[0113] Furthermore, after the motor M1 rotates forward during period T4, the motor M1 rotates reversely during period T5. Thus, in the first control, when the motor M1 is rotating forward and the number of impact motions detected by the impact detection unit 112 exceeds the switching threshold, the motor control unit 115 causes the motor M1 to rotate reversely. The switching threshold is, for example, a value within the range of 100 to 200 times.

[0114] (2.4) Determination Process Next, the determination process during period T3 (determining whether or not there is a screw tightening abnormality) will be described. During period T3, only the portion near the tip of the threaded portion B12 is inserted into the screw hole W10 of the workpiece W1. Therefore, if there is no screw tightening abnormality, no impact motion will occur. Therefore, the motor control unit 115 determines that there is a screw tightening abnormality if the number of times that the impact detection unit 112 detects impact motions exceeds a predetermined number during the period from the start of period T3 until the rotation angle of the motor M1 reaches a certain rotation angle (until the end of period T3). In other words, when the motor M1 is rotating forward in the direction that tightens the screw B1 and the screw B1 is initially inserted into the screw hole W10, the motor control unit 115 determines that there is a screw tightening abnormality if the number of times that the impact detection unit 112 detects impact motions exceeds a predetermined number during the period from the start of period T3 until the rotation angle of the motor M1 reaches a certain rotation angle (period T3). Furthermore, if the number of times that the impact detection unit 112 detects impact motions during the period T3 is less than a predetermined number, the motor control unit 115 determines that there is no abnormality in the screw tightening. The predetermined number may be, for example, once, several times, or several tens of times.

[0115] Next, the judgment process for period T4 will be described. During period T4, if everything is normal, an impact operation is performed. Therefore, if the number of times that the impact detection unit 112 detects impact operations is less than a predetermined number from the start of period T4 until the rotation angle of the motor M1 reaches a certain rotation angle, the motor control unit 115 judges that there is an abnormality in the screw tightening. Furthermore, if the number of times that the impact detection unit 112 detects impact operations is equal to or greater than a predetermined number from the start of period T4 until the rotation angle of the motor M1 reaches a certain rotation angle, the motor control unit 115 judges that there is no abnormality in the screw tightening. The predetermined number may be, for example, one time, several times, or several tens of times.

[0116] The judgment process for period T5 will now be described. During period T5, if the screw B1 is normally loosened and the impact motion ceases after a certain period of time has elapsed. Therefore, if the number of times the impact detection unit 112 detects impact motions is less than a predetermined number during the period from the start of period T5 until the rotation angle of the motor M1 reaches a certain rotation angle, the motor control unit 115 determines that there is no abnormality in the screw tightening. In other words, after the motor M1 performs forward rotation, in the judgment process, if the number of times the impact detection unit 112 detects impact motions is less than a predetermined number during the period from the start of period T5 until the rotation angle of the motor M1 reaches a certain rotation angle during reverse rotation (period T5), the motor control unit 115 determines that there is an abnormality in the screw tightening. Furthermore, if the number of times the impact detection unit 112 detects impact motions during period T5 exceeds a predetermined number, the motor control unit 115 determines that there is an abnormality in the screw tightening. The predetermined number is, for example, several tens of times.

[0117] Furthermore, after determining that there is no abnormality in the screw tightening during the reverse rotation operation (period T5), the motor control unit 115 causes the motor M1 to perform a further reverse rotation operation by a predetermined rotation angle during period T6.

[0118] The judgment process for period T6 will be described. During period T6, the screw B1 is loose, so if this is normal, there will be no impact motion. Therefore, if the number of times that the impact detection unit 112 detects impact motions is equal to or greater than a predetermined number during the period from the start of period T6 until the rotation angle of the motor M1 reaches a certain rotation angle (period T6), the motor control unit 115 judges that there is an abnormality in the screw tightening. Furthermore, if the number of times that the impact detection unit 112 detects impact motions during period T6 is less than the predetermined number, the motor control unit 115 judges that there is no abnormality in the screw tightening. The predetermined number may be, for example, one time, several times, or several tens of times.

[0119] Next, another example of the determination process for period T6 will be described. During period T6, the motor control unit 115 detects the rotation angle of the motor M1 from the detection of an impact operation to the detection of the next impact operation. A situation in which the rotation angle of the motor M1 during this period is equal to or greater than a predetermined value corresponds to a situation in which the screw B1 has loosened. Therefore, if the rotation angle of the motor M1 during the period from the start of period T6 until the rotation angle of the motor M1 reaches a certain rotation angle, is equal to or greater than the predetermined value, the motor control unit 115 determines that there is no abnormality in the screw tightening. Furthermore, if the rotation angle of the motor M1 during the period from the start of period T6 until the rotation angle of the motor M1 reaches a certain rotation angle, is less than the predetermined value, the motor control unit 115 determines that there is an abnormality in the screw tightening.

[0120] The determination process for period T7 will now be described. Because the threaded portion B12 was passed through the threaded hole W10 during period T6, burrs and dirt on the threaded portion B12 and the threaded hole W10 were removed to a certain extent. Therefore, under normal circumstances, impact motion is unlikely to occur during period T7. Therefore, if the number of times the impact detection unit 112 detects impact motions exceeds a predetermined number during the period from the start of period T7 until the rotation angle of the motor M1 reaches a certain rotation angle, the motor control unit 115 determines that there is an abnormality in the screw tightening. In other words, after the motor M1 performs reverse rotation, in the determination process, if the number of times the impact detection unit 112 detects impact motions exceeds a predetermined number during the period from the start of period T7 until the rotation angle of the motor M1 reaches a certain rotation angle (period T7) while the motor M1 is rotating forward, the motor control unit 115 determines that there is an abnormality in the screw tightening. Furthermore, if the number of times the impact detection unit 112 detects impact motions is less than the predetermined number during period T7, the motor control unit 115 determines that there is no abnormality in the screw tightening. The predetermined number is, for example, once, several times, or several tens of times.

[0121] During period T8, there is no particular need for a determination process to determine whether or not there is an abnormality in the screw tightening. However, during period T8, the motor control unit 115 may stop the motor M1 when it is determined that the tightening torque calculated by the torque calculation unit 114 has reached or exceeded a predetermined torque. The torque calculation unit 114 may calculate the tightening torque based on the detection results of the torque sensor 13 as described above, or may calculate the tightening torque based on the number of times the impact motion was detected and the current of the motor M1 detected by the current detection unit 116.

[0122] Furthermore, as described above, when the first signal is a high-level signal and the second signal is a low-level signal, the motor control unit 115 causes the motor M1 to rotate in the reverse direction. In this case, no particular determination process is required.

[0123] (Modifications of the embodiment) Modifications of the embodiment are listed below. The following modifications may be realized in appropriate combination. Hereinafter, the configuration of the above-described embodiment will be referred to as the basic example. The same components as those in the basic example will be assigned the same reference numerals and descriptions thereof will be omitted.

[0124] (Modification 1) Modification 1 differs from the basic example in that the current of the motor M1 detected by the current detection unit 116 is also used in the determination process for determining whether or not there is an abnormality in screw tightening.

[0125] That is, in the judgment process of this variant example 1, if a provisional judgment is made in at least one of the first provisional judgment process and the second provisional judgment process that there is an abnormality in the screw tightening, the motor control unit 115 judges that there is an abnormality in the screw tightening.

[0126] In the first determination process, the presence or absence of an abnormality in screw tightening is provisionally determined based on the relationship between the rotation angle of the motor M1 and the detection result of the impact detection unit 112 as to whether or not an impact operation has occurred.

[0127] In the second determination process, a provisional determination is made as to whether or not there is an abnormality in the screw tightening based on the current detected by the current detection unit 116 .

[0128] As an example, the conditions for provisionally determining that there is an abnormality in screw tightening in the first determination process are the same as the conditions for determining that there is an abnormality in screw tightening in the determination process of the basic example.

[0129] Also, as an example, in the second determination process, if the current detected by the current detection unit 116 exceeds the current threshold, it is provisionally determined that there is an abnormality in the screw tightening. This makes it possible to determine that a state in which the load of the screw tightening is excessive is an abnormality.

[0130] Instead of comparing the current (instantaneous value) with a current threshold, the amount of change in current per unit time may be compared with a corresponding threshold. For example, if the amount of change in current per unit time exceeds a corresponding threshold, it may be provisionally determined that there is an abnormality in the screw tightening.

[0131] According to this modification 1, even if the object to be fastened (workpiece W1) is soft and no impact action occurs, the motor control unit 115 can determine whether or not there is an abnormality in the fastening of the screw based on the current. This makes it possible to more reliably detect an abnormality in the fastening of the screw.

[0132] The second determination process may be executed only when the impact detection unit 112 determines that no impact motion has occurred.

[0133] (Variation 2) During period T6, as shown in FIG. 6D , the motor control unit 115 rotates the motor M1 in the reverse direction by a fixed rotation angle to loosen the screw B1. In this variation 2, the "fixed rotation angle" during period T6 is determined by the motor control unit 115 in accordance with the length L1 of the threaded portion B12. Information indicating the length L1 of the threaded portion B12 is input by a user operation. For example, the information indicating the length L1 of the threaded portion B12 is input by a user operation of the operation unit 57 (see FIG. 1 ).

[0134] Preferably, the above-mentioned constant rotation angle is determined so that the screw B1 moves a distance L2 obtained by multiplying the length L1 of the threaded portion B12 by a constant ratio (the constant ratio is less than 1, for example, 0.9) between the start and end of the period T6. This prevents the threaded portion B12 from coming loose from the threaded hole W10. Then, during the period T7 in which the motor M1 is rotated forward, the presence or absence of an abnormality can be determined based on the constant distance L2 corresponding to the length L1 of the threaded portion B12. Specifically, during the period T7, for example, it can be determined whether galling has occurred between the screw B1 and the threaded hole W10 within the range of the distance L2.

[0135] (Other Modifications) The robot 50 of the basic example includes a robot arm 51 with six degrees of freedom, but the configuration of the robot arm 51 is not limited to that of the basic example. It is preferable that the robot 50 includes, for example, a multi-joint robot arm having two or more joints.

[0136] In the basic example, one power tool 10 is attached to one robot 50, but multiple power tools 10 may be attached to one robot 50.

[0137] Although the basic example power tool system 100 has only one robot 50 with one power tool 10 attached, the power tool system 100 may have multiple robots 50 with one or more power tools 10 attached to each robot.

[0138] The external device 50 a that issues commands to the motor control unit 115 may be a device separate from the robot 50 .

[0139] 3 is a socket attached to the outer edge of the screw B1, but the shape of the tool 23 can be changed as needed. For example, the tool 23 may be shaped like a Phillips or flathead screwdriver that can be inserted into a hole in the head B11 of the screw B1. The tool 23 may also be attached directly to the output shaft 22 without using the holder 24 and the coil spring 25.

[0140] In the power tool 10 of the basic example, the notification unit 113 notifies the result of the determination process of the motor control unit 115 by both sound and light, but the notification unit 113 may notify by either sound or light alone. Furthermore, the notification unit 113 may notify the result of the determination process of the motor control unit 115 to an external device (for example, a mobile terminal or wearable terminal carried by the operator, or the centralized management unit 40, etc.).

[0141] The power tool 10 may be a portable tool that is held by an operator and operates in response to the operator's operation.

[0142] The power tool 10 may include a shock sensor. The shock sensor outputs an output signal whose magnitude corresponds to the magnitude of vibration applied to the shock sensor. The impact detection unit 112 may detect the presence or absence of an impact operation based on the output signal from the shock sensor. For example, the impact detection unit 112 determines that an impact operation is occurring when the output signal changes from a state below a threshold to a state above the threshold. Then, for example, the impact detection unit 112 determines that an impact operation is not occurring when the output signal remains below the threshold for a predetermined period of time. The shock sensor may be located in a position where vibrations generated by the impact operation are transmitted. For example, the shock sensor may be located near the hammer 74.

[0143] The change in the command rotation speed over time shown in Figure 5 is an example and can be changed as appropriate. For example, at least one of the periods T1, T2, T4, T5, and T7 may be omitted. Whether or not to omit each of the periods T1, T2, T4, T5, and T7 may be determined by a user operation. For example, whether or not to omit each of the periods T1, T2, T4, T5, and T7 may be determined by a user operation of the operation unit 57 (see Figure 1).

[0144] The relationship between the high-level or low-level signals of the first and second signals and the content of the commands may be reversed from that in the basic example. That is, when the first signal is a low-level signal, the motor control unit 115 may rotate the motor M1, and when the first signal is a high-level signal, the motor control unit 115 may stop the motor M1. Also, when the second signal is a low-level signal, the motor control unit 115 may control the motor M1 to tighten the screw B1, and when the second signal is a high-level signal, the motor control unit 115 may control the motor M1 to loosen the screw B1.

[0145] The power tool system 100, the power tool 10, or the control method for the power tool 10 according to the present disclosure includes a computer system. The computer system is primarily composed of a processor and memory as hardware. At least a portion of the functions of the power tool system 100, the power tool 10, or the control method for the power tool 10 according to the present disclosure are realized by the processor executing a program stored in the memory of the computer system. The program may be pre-stored in the memory of the computer system, provided via a telecommunications line, or provided in a non-transitory recording medium readable by the computer system, such as a memory card, an optical disk, or a hard disk drive. The processor of the computer system is composed of one or more electronic circuits, including a semiconductor integrated circuit (IC) or a large-scale integrated circuit (LSI). The integrated circuits, such as ICs and LSIs, are referred to by different names depending on the degree of integration, and include integrated circuits called system LSIs, very large-scale integration (VLSI), or ultra-large-scale integration (ULSI). Furthermore, a field-programmable gate array (FPGA), which is programmed after the LSI is manufactured, or a logic device capable of reconfiguring the connections within the LSI or the circuit partitions within the LSI, can also be employed as a processor. Multiple electronic circuits may be integrated into a single chip or distributed across multiple chips. Multiple chips may be integrated into a single device or distributed across multiple devices. The computer system referred to here includes a microcontroller having one or more processors and one or more memories. Therefore, the microcontroller is also composed of one or more electronic circuits, including a semiconductor integrated circuit or a large-scale integrated circuit.

[0146] Furthermore, it is not essential for the power tool 10 that multiple functions are concentrated in a single housing, and multiple components of the power tool 10 may be distributed across multiple housings.

[0147] Conversely, in the embodiment, at least some of the functions of the power tool system 100 that are distributed across multiple housings may be consolidated into one housing. For example, multiple functions that are distributed across the centralized management unit 40 and the control device 60 may be consolidated into one housing.

[0148] (Summary) The above-described embodiments and the like disclose the following aspects.

[0149] A power tool (10) according to a first aspect is a power tool (10) for tightening a screw (B1). The power tool (10) includes a motor (M1), a hammer (74), an anvil (75), an output shaft (22), an impact detection unit (112), a motor control unit (115), and a memory unit (117). The hammer (74) rotates by receiving power from the motor (M1). The anvil (75) rotates by receiving an impact force from the hammer (74) in the rotational direction of the hammer (74). The output shaft (22) is configured to hold a tool bit (23) that transmits torque to the screw (B1) and rotates together with the anvil (75). The impact detection unit (112) detects the presence or absence of an impact operation, which is an operation in which the hammer (74) applies an impact force to the anvil (75). The motor control unit (115) controls the operation of the motor (M1) based on commands from an external device (50a) outside the power tool (10). The memory unit (117) stores information for the motor control unit (115) to perform predetermined control of the motor (M1). When the motor control unit (115) receives a predetermined command from the external device (50a), it tightens the screw (B1) by performing predetermined control on the motor (M1). The motor control unit (115) executes a determination process to determine whether or not there is an abnormality in the screw tightening based on the relationship between the rotation angle of the motor (M1) and the detection result of the impact detection unit (112) indicating whether or not there is an impact operation. The predetermined control includes stopping the motor (M1) if it is determined as a result of the determination process that there is an abnormality in the screw tightening.

[0150] According to the above configuration, it is possible to accurately determine whether or not there is an abnormality in screw tightening in the power tool (10) that performs impact operation, and to stop the motor (M1) if there is an abnormality.

[0151] In the power tool (10) according to the second aspect, in the first aspect, the default control includes a first control and a second control. In the first control, the motor (M1) is caused to alternately perform a forward rotation operation in which the motor (M1) rotates in a direction to tighten the screw (B1) and a reverse rotation operation in which the motor (M1) rotates in a direction opposite to the forward rotation operation. In the second control, if it is determined as a result of the determination process that there is no abnormality in the screw tightening in the first control, the motor (M1) is caused to perform the forward rotation operation to tighten the screw (B1).

[0152] According to the above configuration, burrs and dirt on the screw (B1) and the object (workpiece (W1)) to be tightened by the screw (B1) can be removed by the reverse rotation. This reduces the possibility that burrs and dirt will interfere with the tightening of the screw in the second control. Therefore, the occurrence of abnormalities in the tightening of the screw can be suppressed.

[0153] In addition, in the power tool (10) according to the third aspect, in the second aspect, in the first control, when the motor (M1) is performing forward rotation, the motor control unit (115) causes the motor (M1) to perform reverse rotation when the number of times impact operations are detected by the impact detection unit (112) becomes equal to or greater than the switching threshold value.

[0154] According to the above configuration, the screw (B1) is tightened to an appropriate depth according to the switching threshold, and then the reverse operation is performed, thereby removing burrs and dirt to the above depth.

[0155] Furthermore, in the power tool (10) according to the fourth aspect, in any one of the first to third aspects, after the motor (M1) performs a reverse operation in which it rotates in the opposite direction to the direction in which the screw (B1) is tightened, the motor control unit (115) determines in the judgment process that there is an abnormality in the screw tightening if the number of times that the impact operation is detected by the impact detection unit (112) becomes equal to or exceeds a predetermined number during the period until the rotation angle of the motor (M1) when the motor (M1) performs a forward operation in which it rotates in the direction in which the screw (B1) is tightened reaches a certain rotation angle.

[0156] According to the above configuration, the motor control unit (115) can determine whether or not an abnormality such as galling has occurred.

[0157] In addition, in the power tool (10) according to the fifth aspect, in any one of the first to fourth aspects, after the motor (M1) performs a forward rotation operation in which it rotates in the direction to tighten the screw (B1), the motor control unit (115) determines in the judgment process that there is no abnormality in the screw tightening if the number of times that the impact operation is detected by the impact detection unit (112) is less than a predetermined number during the time until the rotation angle of the motor (M1) during the reverse rotation operation in which it rotates in the opposite direction to the forward rotation operation reaches a certain rotation angle.

[0158] According to the above configuration, the motor control unit (115) can determine whether the screw (B1) has been properly loosened by the reverse rotation.

[0159] In addition, in the power tool (10) according to the sixth aspect, in the fifth aspect, the motor control unit (115) determines that there is no abnormality in the screw tightening when performing a reverse operation, which rotates in the opposite direction to the forward operation, and then causes the motor (M1) to perform a reverse operation by a further predetermined rotation angle.

[0160] According to the above configuration, the screw (B1) can be sufficiently loosened.

[0161] In addition, in the power tool (10) according to the seventh aspect, in any one of the first to sixth aspects, when the motor (M1) is performing a forward rotation operation in which it rotates in the direction to tighten the screw (B1) and the screw (B1) is first inserted into the screw hole (W10), if the number of times that the impact operation is detected by the impact detection unit (112) becomes equal to or exceeds a predetermined number before the rotation angle of the motor (M1) reaches a certain rotation angle, the motor control unit (115) determines that there is an abnormality in the screw tightening.

[0162] According to the above configuration, the motor control unit (115) can determine whether or not an abnormality such as galling has occurred.

[0163] Furthermore, the power tool (10) according to an eighth aspect is any one of the first to seventh aspects, further including a current detection unit (116) that detects a current flowing through the motor (M1). The determination process determines that there is an abnormality in the screw tightening when a provisional determination is made in at least one of the first provisional determination process and the second provisional determination process. In the first provisional determination process, the presence or absence of an abnormality in the screw tightening is provisionally determined based on the relationship between the rotation angle of the motor (M1) and the detection result of the impact detection unit (112) as to whether or not an impact motion has occurred. In the second provisional determination process, the presence or absence of an abnormality in the screw tightening is provisionally determined based on the current detected by the current detection unit (116).

[0164] According to the above configuration, even if the object (workpiece (W1)) to be tightened by the screw (B1) is soft and no impact action occurs, the motor control unit (115) can determine whether or not there is an abnormality in the screw tightening based on the current.

[0165] The configurations other than the first aspect are not essential for the power tool (10) and can be omitted as appropriate.

[0166] A power tool system (100) according to a ninth aspect includes the power tool (10) according to any one of the first to eighth aspects and a robot arm (51). The robot arm (51) holds the power tool (10) and controls the position and attitude of the power tool (10).

[0167] According to the above configuration, the screw tightening operation can be automated.

[0168] A power tool system (100) according to a tenth aspect includes the power tool (10) according to any one of the first to eighth aspects and a robot (50). The robot (50) is an external device (50a) that issues commands to the motor control unit (115). The robot (50) includes a robot arm (51). The robot arm (51) holds the power tool (10) and controls the position and posture of the power tool (10).

[0169] According to the above configuration, the screw tightening operation can be automated.

[0170] A control method according to an eleventh aspect is a control method for a power tool (10) for tightening a screw (B1). The power tool (10) includes a motor (M1), a hammer (74), an anvil (75), an output shaft (22), and an impact detection unit (112). The hammer (74) receives power from the motor (M1) and rotates. The anvil (75) receives an impact force from the hammer (74) in the rotational direction of the hammer (74) and rotates. The output shaft (22) is configured to hold a tool bit (23) that transmits torque to the screw (B1), and rotates together with the anvil (75). The impact detection unit (112) detects the presence or absence of an impact operation, which is an operation in which the hammer (74) applies an impact force to the anvil (75). The control method is executed by a computer system. The control method includes, upon receiving a predetermined command from an external device (50a) outside the power tool (10), tightening a screw (B1) by a predetermined control of the motor (M1), and executing a determination process to determine whether or not there is an abnormality in the screw tightening based on the relationship between the rotation angle of the motor (M1) and the detection result of the presence or absence of an impact operation by the impact detection unit (112). The predetermined control includes stopping the motor (M1) when it is determined as a result of the determination process that there is an abnormality in the screw tightening.

[0171] According to the above configuration, it is possible to accurately determine whether or not there is an abnormality in screw tightening in the power tool (10) that performs impact operation, and to stop the motor (M1) if there is an abnormality.

[0172] A program according to a twelfth aspect is a program for causing one or more processors of a computer system to execute the control method according to the eleventh aspect.

[0173] According to the above configuration, it is possible to accurately determine whether or not there is an abnormality in screw tightening in the power tool (10) that performs impact operation, and to stop the motor (M1) if there is an abnormality.

[0174] Not limited to the above aspects, various configurations (including modified examples) of the power tool (10) and power tool system (100) according to the embodiment can be embodied as a control method, a (computer) program, or a non-transitory recording medium on which a program is recorded.

[0175] REFERENCE SIGNS LIST 10 Power tool 22 Output shaft 23 Tip tool 50 Robot 50a External device 51 Robot arm 74 Hammer 75 Anvil 100 Power tool system 112 Impact detection unit 115 Motor control unit 116 Current detection unit 117 Memory unit B1 Screw M1 Motor W10 Screw hole

Claims

1. An electric power tool for tightening a screw, comprising: a motor; a hammer that rotates by receiving power from the motor; an anvil that rotates by receiving an impact force from the hammer in the rotational direction of the hammer; an output shaft configured to hold a tip tool that transmits torque to the screw and rotates together with the anvil; an impact detection unit that detects the presence or absence of an impact motion, which is the operation of the hammer applying the impact force to the anvil; a motor control unit that controls the operation of the motor based on commands from an external device outside the power tool; and a memory unit that stores information for the motor control unit to perform default control on the motor, wherein when the motor control unit receives a predetermined command from the external device, it tightens the screw by controlling the motor by the default control, and the motor control unit executes a judgment process that judges the presence or absence of an abnormality in the screw tightening based on the relationship between the rotation angle of the motor and the detection result of the presence or absence of the impact motion by the impact detection unit, and the default control includes stopping the motor when it is determined as a result of the judgment process that there is an abnormality in the screw tightening.

2. The power tool of claim 1, wherein the default control includes: a first control that causes the motor to alternately perform a forward rotation operation in which it rotates in a direction to tighten the screw, and a reverse rotation operation in which it rotates in a direction opposite to the forward rotation operation; and a second control that causes the motor to perform the forward rotation operation to tighten the screw when it is determined as a result of the judgment process that there is no abnormality in the screw tightening in the first control.

3. The power tool of claim 2, wherein in the first control, when the motor is performing the forward rotation operation, the motor control unit causes the motor to perform the reverse rotation operation when the number of times the impact operation is detected by the impact detection unit becomes equal to or greater than a switching threshold value.

4. A power tool as claimed in any one of claims 1 to 3, wherein in the judgment process, after the motor has performed a reverse operation in which it rotates in the opposite direction to the direction in which the screw is tightened, the motor control unit judges that there is an abnormality in the screw tightening if the number of times the impact operation is detected by the impact detection unit becomes equal to or exceeds a predetermined number before the rotation angle of the motor when the motor is performing a forward operation in which it rotates in the direction in which the screw is tightened reaches a certain rotation angle.

5. A power tool as claimed in any one of claims 1 to 4, wherein, in the judgment process, after the motor performs a forward rotation operation in which it rotates in the direction to tighten the screw, if the number of times the impact operation is detected by the impact detection unit is less than a predetermined number before the rotation angle of the motor when performing a reverse rotation operation in which it rotates in the opposite direction to the forward rotation operation reaches a certain rotation angle, the motor control unit judges that there is no abnormality in the screw tightening.

6. The power tool according to claim 5, wherein the motor control unit, when performing the reverse rotation operation in the opposite direction to the forward rotation operation, determines that there is no abnormality in the screw tightening, and then causes the motor to perform the reverse rotation operation for a further predetermined rotation angle.

7. The electric power tool according to any one of claims 1 to 6, wherein when the motor is performing a forward rotation operation rotating in the direction for tightening the screw and the screw is initially inserted into a screw hole, if the number of times the impact operation is detected by the impact detection unit becomes equal to or exceeds a predetermined number before the rotation angle of the motor reaches a certain rotation angle, the motor control unit determines that there is an abnormality in the screw tightening.

8. An electric power tool as claimed in any one of claims 1 to 7, further comprising a current detection unit which detects a current flowing through the motor, and wherein the judgment process comprises: a first tentative judgment process which provisionally judges the presence or absence of an abnormality in the screw tightening based on the relationship between the rotation angle of the motor and the detection result of the presence or absence of the impact operation in the impact detection unit; and a second tentative judgment process which provisionally judges the presence or absence of an abnormality in the screw tightening based on the current detected by the current detection unit, and judges that there is an abnormality in the screw tightening when it is provisionally judged that there is an abnormality in the screw tightening in at least one of the above.

9. A power tool system comprising: a power tool according to any one of claims 1 to 8; and a robot arm that holds the power tool and controls the position and attitude of the power tool.

10. A power tool system comprising: an electric power tool according to any one of claims 1 to 8; and a robot as the external device that gives commands to the motor control unit, wherein the robot includes a robot arm that holds the electric power tool and controls the position and attitude of the electric power tool.

11. A control method for an electric power tool for tightening a screw, the electric power tool comprising: a motor; a hammer that rotates by receiving power from the motor; an anvil that rotates by receiving an impact force from the hammer in the rotational direction of the hammer; an output shaft configured to hold a tip tool that transmits torque to the screw and rotates together with the anvil; and an impact detection unit that detects the presence or absence of an impact motion, which is the motion of the hammer applying the impact force to the anvil, the control method being executed by a computer system, the control method comprising the steps of: upon receiving a predetermined command from an external device outside the electric power tool, tightening the screw by predetermined control of the motor; and executing a judgment process that judges the presence or absence of an abnormality in the screw tightening based on the relationship between the rotation angle of the motor and the detection result of the presence or absence of the impact motion by the impact detection unit, the predetermined control including stopping the motor when it is determined as a result of the judgment process that there is an abnormality in the screw tightening.

12. A program for causing one or more processors of the computer system to execute the control method according to claim 11.

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