Impact tool and control method of impact tool

Abstract

To provide an impact tool capable of facilitating precise control of a motor.SOLUTION: An impact tool 1 includes a motor 11, an impact rotation mechanism 12, a detection part 13, and a control part 15. The motor 11 can perform normal rotation and reverse rotation. The impact rotation mechanism 12 performs an impact motion using a rotational inertia force while receiving a rotation force from the motor 11 and repeating the normal rotation and the reverse rotation. The detection part 13 performs detection regarding a rotation amount of the motor 11 or the impact rotation mechanism 12 in the normal rotation. The control part 15 controls the motor 11 on the basis of at least one of the rotation amount and a change in the rotation amount detected by the detection part 13.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to an impact tool and a method for controlling the impact tool, and more particularly, to an impact tool that performs a striking operation and a method for controlling such an impact tool.

Background Art

[0002] Patent Document 1 describes a power tool including a motor that can rotate forward or backward, a hammer rotated by the motor, an anvil intermittently struck by the hammer with a first impact force, current detection means for detecting a first reverse current value flowing through the motor each time the motor reverses, and control means for controlling the rotation of the motor. In this power tool, the control means determines whether or not a second reverse current value detected by the current detection means by the next reverse rotation of the motor is substantially the same as a predetermined value when the first reverse current value becomes equal to or less than the predetermined value. Thereby, it is possible to confirm whether or not the tightening operation has been performed reliably, and it is possible to avoid misjudgment of the completion of the tightening operation due to a sudden increase in load during the tightening operation.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the power tool described in Patent Document 1, the motor is controlled based on the reverse current value (that is, the current generated by the rotation of the motor by an external force) generated when the motor reverses due to the reaction force during striking. However, since the reverse current value changes with a delay with respect to the change in the rotation speed of the motor during reverse rotation, there is a possibility that a correct determination regarding the tightening operation cannot be made.

[0005] In a conventional impact tool such as the power tool described in Patent Document 1, generally, the rotation of the motor is controlled based on the current value of the motor (or the detection result of a strain sensor that magnetically or electrically detects the strain of the anvil). However, since there is a time difference between the change in the current value (or the detection result of the strain sensor) and the change in the rotation speed, the rotation speed of the motor cannot be accurately detected, and it may be difficult to accurately control the motor. When it becomes difficult to accurately control the motor, for example, variations in tightening torque occur.

[0006] An object of the present disclosure is to provide an impact tool capable of facilitating accurate control of a motor and a control method for the impact tool.

Means for Solving the Problems

[0007] An impact tool according to an aspect of the present disclosure includes a motor, a percussion rotation mechanism, a detection unit, and a control unit. The motor is capable of forward rotation and reverse rotation. The percussion rotation mechanism receives a rotational force from the motor and performs a percussion operation by rotational inertial force while repeating the forward rotation and the reverse rotation. The detection unit detects the amount of rotation during the forward rotation of the motor or the percussion rotation mechanism. The control unit controls the motor based on at least one of the amount of rotation detected by the detection unit and the change in the amount of rotation.

[0008] A control method for an impact tool according to an aspect of the present disclosure is a control method for an impact tool including a motor and a percussion rotation mechanism. The motor is capable of forward rotation and reverse rotation. The percussion rotation mechanism receives a rotational force from the motor and performs a percussion operation by rotational inertial force while repeating the forward rotation and the reverse rotation. The control method for the impact tool includes a detection step and a control step. The detection step detects the amount of rotation during the forward rotation of the motor or the percussion rotation mechanism. The control step controls the motor based on at least one of the amount of rotation detected in the detection step and the change in the amount of rotation.

Effects of the Invention

[0009] The impact tool and the control method of the impact tool according to the present disclosure have an effect of facilitating accurate control of the motor.

Brief Description of Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0011] (1) Overview First, the overview of the impact tool 1 according to the embodiment of the present disclosure will be described with reference to FIGS. 1 and 2.

[0012] The impact tool 1 includes a motor 11, a striking and rotating mechanism 12, a detection unit 13, and a control unit 15.

[0013] (1-1) Motor The motor 11 can rotate forward and backward. The motor 11 rotates forward when supplied with a forward current and rotates backward when supplied with a reverse current. The motor 11 can stop or continue to rotate by inertia when not supplied with current.

[0014] (1-2) Impact Rotation Mechanism The impact rotation mechanism 12 receives the rotational force from the motor 11 and performs an impact operation due to the rotational inertia force while repeatedly rotating forward and backward. The rotational inertia force is the inertia force of a rotating body (for example, an anvil).

[0015] (1-3) Detection Unit The detection unit 13 detects the rotation amount of the motor 11. The detection unit 13 detects the rotation amount.

[0016] The rotation amount is the amount of rotation when the motor 11 rotates forward, and specifically, it is the rotation speed or the rotation angle. The rotation speed is the number of rotations of the motor 11, for example, n rotations. The rotation speed is, for example, the rotation speed from the start point of the tightening operation. The rotation angle is the angle by which the motor 11 rotates, for example, θ degrees. The rotation angle is, for example, the rotation angle from the position (initial position) at the start point of the tightening operation. Note that there is a relationship of "n = θ / 360" between the number of rotations n and the angle θ.

[0017] The rotation amount increases when the motor 11 is rotating forward, is constant when the motor 11 is not rotating, and decreases when the motor 11 is rotating backward.

[0018] The detection unit 13 repeatedly detects the rotation amount at a predetermined period.

[0019] (1-4) Control Unit The control unit 15 controls the motor 11 based on at least one of the rotation amount detected by the detection unit 13 and the change in the rotation amount.

[0020] According to the above configuration, by performing control based on at least one of the rotation amount by which the motor 11 rotates forward and the change in such rotation amount, compared with the case of performing control based on the current value of the motor 11, etc., it is possible to facilitate the accurate control of the motor 11.

[0021] Specifically, by performing control based on at least one of the rotation amount and the change in the rotation amount, it is possible to easily achieve the uniformization of the rotational impact force and thus suppress the variation in the tightening torque (details will be described later).

[0022] (2) Details Next, the details of the impact tool 1 will be described with reference to FIGS. 1 to 6. However, hereinafter, the description of the existing matters will be omitted or simplified.

[0023] As shown in FIG. 1, the impact tool 1 further includes a tool body 100 and an output shaft 101. A battery pack 102 is detachable from the tool body 100.

[0024] As shown in FIG. 2, the tool body 100 includes a motor 11, a striking and rotating mechanism 12, a detection unit 13, a measurement unit 14, and a control unit 15. The motor 11, the detection unit 13, the measurement unit 14, and the control unit 15 are supplied with power from the battery pack 102 attached to the tool body 100.

[0025] (2-1) Output Shaft and Measurement Unit The output shaft 101 outputs a striking and rotating force. The striking and rotating force is the conversion result of the striking and rotating mechanism 12.

[0026] The measurement unit 14 performs a measurement operation. The measurement operation is an operation of measuring the tightening torque when tightening an object with the striking and rotating force and acquiring a measurement value. The measurement operation is executed every time the striking operation of the striking and rotating mechanism 12 is completed.

[0027] For example, the measurement unit 14 may repeatedly execute the measurement operation at a predetermined cycle and acquire a plurality of measurement values. The plurality of acquired measurement values are stored in chronological order in the internal memory of the measurement unit 14. Then, when the striking operation is completed, the measurement unit 14 may determine the measurement value of the tightening torque related to the striking operation based on the plurality of measurement values held in the internal memory.

[0028] (2-2) Details of the Striking and Rotating Mechanism The impact rotating mechanism 12 alternately receives the rotational force in the forward rotation and the rotational force in the reverse rotation from the motor 11, and performs an impact operation due to the rotational inertia force in the forward rotation while repeating the forward rotation and the reverse rotation. As a result, a part of the rotational force in the forward rotation of the impact rotating mechanism 12 is converted into an impact rotational force, which is an impact force around the axis, and the converted impact rotational force is output via the output shaft 101. Here, the axis mentioned here is a common rotation axis for the motor 11 and the impact rotating mechanism 12 (and further the output shaft 101 described later).

[0029] (2-2-1) Direct connection with the motor The impact rotating mechanism 12 is directly connected to the motor 11. The direct connection mentioned here means being directly connected to the motor 11 without passing through a spring, a gear, or the like. Specifically, for example, the hammer of the impact rotating mechanism 12 is fixed to the rotor of the motor 11, and the rotor of the motor 11 and the hammer of the impact rotating mechanism 12 rotate integrally.

[0030] According to this configuration, compared with the case where the impact rotating mechanism 12 is connected to the motor 11 via a spring, a gear, or the like (refer to the "First Modified Example of the Impact Rotating Mechanism" and the "Second Modified Example of the Impact Rotating Mechanism" described later), the delay in the change of the rotation of the impact rotating mechanism 12 with respect to the change of the rotation of the motor 11 is suppressed. Also, the delay in the measurement result (measurement value of the tightening torque) of the measurement unit 14 with respect to the change of the rotation of the motor 11 is suppressed. Therefore, further facilitation of the accurate control of the motor 11 can be achieved.

[0031] (2-3) Details of the control unit (2-3-1) Control to reverse the motor almost simultaneously with the completion of the impact operation The control unit 15 determines whether the impact operation has been completed based on the change in the rotation amount detected by the detection unit 13.

[0032] Specifically, when the rotation amount is increasing, that is, "the current rotation amount > the previous rotation amount", the control unit 15 determines that the impact operation has not been completed, and when the increase in the rotation amount stops, that is, "the current rotation amount = the previous rotation amount", the control unit 15 determines that the impact operation has been completed.

[0033] Then, when the result of the determination changes from a negative result indicating that the striking operation has not been completed to an affirmative result indicating that the striking operation has been completed, the control unit 15 reverses the motor 11 substantially simultaneously. Note that "substantially simultaneously" may be rephrased as, for example, "in response to the change".

[0034] In this way, by reversing the motor 11 substantially simultaneously with (e.g., in response to) the completion of the striking operation of the striking rotation mechanism 12, the rotational force of the motor 11 following the striking rotational force of the striking rotation mechanism 12 can be suppressed. As a result, it is possible to achieve a tightening operation only with the striking rotational force of the striking rotation mechanism 12, and further facilitate the accurate control of the motor 11.

[0035] (2-3-2) Specific example of "reversing substantially simultaneously": Reversing after the current stop period When the result of the determination as to whether the striking operation has been completed changes from a negative result to an affirmative result, the control unit 15 stops the current (i.e., the forward current) supplied to the motor 11 and then starts supplying a current in the direction opposite to the current (i.e., the reverse current) to reverse the motor 11.

[0036] Specifically, for example, during the current stop period from the stop of the supply of the forward current to the start of the supply of the reverse current, the control unit 15 uses the repulsive force against the striking rotational force to change the rotation of the motor 11 from forward rotation to reverse rotation.

[0037] The end point of the current stop period here is, for example, in the impact tool 1 of the comparative example, immediately after "striking completion", during the series of operations where "the anvil temporarily reverses due to the repulsive force" against the striking rotational force, but "the anvil returns to forward rotation due to the rotational force of the motor that continues to rotate forward", at an appropriate point in time between "the anvil temporarily reverses due to the repulsive force" and "the anvil returns to forward rotation due to the rotational force of the motor 11".

[0038] That is, in the case of the impact tool of the comparative example, the control unit 15 reverses the motor 11 before the anvil returns to the normal rotation state by the rotational force of the motor 11 after the anvil temporarily reverses due to the repulsive force of the striking operation, so as to continue the reverse state.

[0039] Thus, after the control unit 15 stops supplying current to the motor 11 in response to the completion of the striking operation of the striking rotation mechanism 12, it supplies a reverse current. As a result, a current stop period is provided immediately after the striking operation, so that it is possible to easily reverse the motor 11 that is rotating forward due to inertia by utilizing the repulsive force from the striking rotation mechanism 12 to the motor 11 against the rotational force from the motor 11 to the striking rotation mechanism 12. Then, after the current stop period, by supplying a reverse current to the motor 11, the reverse rotation of the motor 11 can be continued.

[0040] (2-3-3) Control for Reversing the Motor until the Rotation Amount Returns to a Predetermined Value The control unit 15 continues to reverse the motor 11 until the rotation amount detected by the detection unit 13 returns to a predetermined value.

[0041] Specifically, the control unit 15 stops the current (forward current) to the motor 11 in response to the result of the determination of whether the striking operation has been completed changing from a negative result to a positive result, and then starts supplying a current in the direction opposite to that current (reverse current) to reverse the motor 11. Then, the control unit 15 continues to reverse the motor 11 by supplying a reverse current until the rotation amount detected by the detection unit 13 returns to a predetermined value, and when the rotation amount returns to the predetermined value, the motor 11 is rotated forward by supplying a forward current.

[0042] In this way, by returning the rotation amount of the motor 11 to a predetermined value and then performing the next striking operation (re-striking), it is possible to facilitate the accurate control of the motor 11 during re-striking.

[0043] Specifically, by controlling the reverse rotation of the motor 11 based on the rotation amount of the motor 11 (reverse rotation control based on the rotation amount), for example, compared with the case of reversing the motor 11 over a predetermined time, the rotation amount during reverse rotation, and thus the time interval of the repetitive striking operation, can be accurately controlled (for example, equalized).

[0044] In addition, by the reverse rotation control based on the rotation amount, it is possible to facilitate the change of the rotation speed of the motor 11 during reverse rotation. In other words, regardless of the rotation speed of the motor 11 during reverse rotation, the rotation amount during reverse rotation can be accurately controlled.

[0045] Furthermore, by the reverse rotation control based on the rotation amount, control can be performed considering also the reverse rotation of the motor 11 by the repulsive force against the rotational striking force of the striking rotation mechanism 12. That is, even when the motor 11 reverses due to the repulsive force against the rotational striking force, control can be performed taking into account the rotation amount due to the repulsive force.

[0046] (2-3-4) Direction flag The forward and reverse rotations of the motor 11 are controlled by, for example, a direction flag. The direction flag is a flag for rotating the motor 11 forward and backward by switching the direction of the current to the motor 11 between the forward direction and the reverse direction. The direction flag is switched to either "forward rotation" or "reverse rotation" under the control of the control unit 15.

[0047] That is, when the control unit 15 rotates the motor 11 forward, it sets "forward rotation" in the direction flag, and when it rotates the motor 11 backward, it sets "reverse rotation" in the direction flag.

[0048] (2-3-5) ON and OFF of the motor The motor 11 is turned on and off under the control of the control unit 15. When the motor 11 is in the on state, it rotates forward or backward according to the direction flag, and when it is in the off state, it stops or continues to rotate by inertia.

[0049] Specifically, when the motor 11 is in the off state and the control unit 15 sets "forward rotation" in the direction flag and turns on the motor 11, the motor 11 receives the supply of current in the forward direction and starts forward rotation. Also, when the motor 11 is rotating forward and the control unit 15 sets "reverse rotation" in the direction flag, the direction of the current supplied to the motor 11 changes from the forward direction to the reverse direction, and the rotation of the motor 11 changes from forward rotation to reverse rotation. Further, when the motor 11 is rotating in reverse and the control unit 15 sets "forward rotation" in the direction flag, the direction of the current supplied to the motor 11 changes from the reverse direction to the forward direction, and the rotation of the motor 11 changes from reverse rotation to forward rotation.

[0050] Similarly, when the motor 11 is in the off state and the control unit 15 sets "reverse rotation" in the direction flag and turns on the motor 11, the motor 11 receives the supply of current in the reverse direction and starts reverse rotation.

[0051] (2-3-6) Striking completion condition Based on the striking completion condition, the control unit 15 determines whether or not the striking operation of the striking rotation mechanism 12 has been completed. The striking completion condition is a condition for determining that the striking operation of the striking rotation mechanism 12 has been completed. The striking completion condition is, for example, "the rotation amount has changed from an increasing state to a constant state".

[0052] Specifically, the striking completion condition may be the condition that "the increase in the count value has stopped". The fact that the increase in the count value has stopped is determined, for example, by the fact that the difference between the current count value and the previous count value has changed from a state indicating a positive value to a state indicating 0.

[0053] When the rotation amount of the motor 11 satisfies the striking completion condition, the control unit 15 determines that the striking operation of the striking rotation mechanism 12 has been completed. When the rotation amount of the motor 11 does not satisfy the striking completion condition, it is determined that the striking operation of the striking rotation mechanism 12 has not been completed yet.

[0054] (2-4) Hardware for realizing each part (2-4-1) Detection unit The detection unit 13 is realized by, for example, a rotation sensor. The rotation sensor is a sensor that performs detection related to rotation. Detection related to rotation includes, for example, detection of the rotation angle which is the rotated angle, detection of the number of rotations which is the number of times of rotation, detection of the rotation speed which is the rotation angle or the number of rotations per unit time, and detection of the rotation direction (forward rotation or reverse rotation), etc.

[0055] The rotation sensor in this embodiment is an encoder that detects the number of rotations of the motor 11. The encoder is, for example, an optical encoder, but may also be an encoder such as a magnetic type or an electric type.

[0056] (2-4-2) Measurement unit The measurement unit 14 is realized by, for example, a magnetostrictive sensor and a processing circuit that processes the output signal of the magnetostrictive sensor to obtain a measured value of the tightening torque.

[0057] (2-4-3) Control unit The control unit 15 is realized by, for example, a processor and a memory. The memory stores a program for operating the processor as the control unit 15.

[0058] (2-5) Operation example of the control unit The control unit 15 of the impact tool 1 operates according to, for example, the flowcharts of FIGS. 3 and 4. Note that the processes of FIGS. 3 and 4 are started, for example, in response to the start of the tightening operation with the impact tool 1. Also, the processes of FIGS. 3 and 4 are repeatedly executed at a predetermined cycle. Furthermore, the processes of FIGS. 3 and 4 are ended, for example, in response to the completion of the tightening operation.

[0059] First, the control unit 15 initializes a count value, which is a variable indicating the number of rotations of the motor 11, to "0" (step S1).

[0060] Next, the control unit 15 sets "forward rotation" to a direction flag, which is a flag indicating the rotation direction of the motor 11 (step S2).

[0061] Next, the control unit 15 turns on the motor 11 (step S3). As a result, the supply of forward current to the motor 11 is started, and the motor 11 starts to rotate forward.

[0062] Next, the control unit 15 causes the detection unit 13 to start counting the rotation speed of the motor 11 (step S4). In response to the count result by the detection unit 13, the control unit 15 updates the count value and holds the count value before the update.

[0063] Next, the control unit 15 starts calculating the change in the count value, that is, the difference between the updated count value and the count value before the update (step S5). The difference is calculated by subtracting the count value before the update from the updated count value. When the difference indicates a positive value, the motor 11 is rotating forward; when the difference indicates "0", the motor 11 is stopped; and when the difference indicates a negative value, the motor 11 is rotating in reverse.

[0064] Next, the control unit 15 determines whether the change in the count value satisfies the impact completion condition (step S6). The impact completion condition here is the condition that "the count value has reached a certain value from an increasing state". If it is determined that the change in the count value has not yet satisfied the impact completion condition (No in step S6), the process returns to step S6.

[0065] If it is determined in step S6 that the change in the count value satisfies the impact completion condition (Yes), the control unit 15 turns off the motor 11 (step S7). As a result, the supply of forward current to the motor 11 is stopped, and the motor 11 becomes in a state where it can rotate forward or in reverse by inertia, and changes from forward rotation to reverse rotation due to the repulsive force against the impact rotational force.

[0066] Next, the control unit 15 causes the measurement unit 14 to measure the tightening torque (step S8). As a result, the measured value of the tightening torque at the time when the impact operation is completed is obtained.

[0067] Next, the control unit 15 sets "reverse rotation" in the direction flag (step S9).

[0068] Next, the control unit 15 turns on the motor 11 (step S10). As a result, the supply of the reverse current to the motor 11 is started, and the motor 11 continues to reverse.

[0069] Next, the control unit 15 determines whether the count value has reached a predetermined value (step S11). If it is determined that the count value has not yet reached the predetermined value (No in step S11), the process returns to step S11.

[0070] If it is determined in step S11 that the count value has reached the predetermined value (Yes), the control unit 15 sets "forward rotation" in the direction flag (step S12). As a result, the direction of the current to the motor 11 is changed from the reverse direction to the forward direction, and the motor 11 changes from reverse rotation to forward rotation. Then, the process returns to step S6.

[0071] In addition, in the processes illustrated in FIGS. 3 and 4, the supply of the current to the motor 11 is stopped in response to the completion of the striking operation (S7), and after the supply of the current to the motor 11 is stopped, the measurement operation (S8) is performed. However, the measurement operation (S8) may be performed before the supply of the current is stopped (S7), or may be performed simultaneously with the supply of the current being stopped (S7). The order of the measurement operation (S8) and the supply of the current being stopped (S7) does not matter.

[0072] (3) Specific example Next, a specific example of the impact tool 1 will be described with reference to FIGS. 1, 2, 5, and 6 while comparing it with the impact tool of the comparative example.

[0073] (3-1) Comparison between the striking and rotating mechanism of the comparative example and the striking and rotating mechanism of the embodiment (3-1-1) Striking and rotating mechanism of the comparative example The impact rotation mechanism of the comparative example includes a hammer, an anvil, a spring, gears, etc. The hammer is connected to the motor via a spring, gears, etc. A part of the rotational force during the forward rotation from the motor is converted into the potential energy of the spring and then into an impact rotational force by the impact operation on the anvil. The anvil is connected to the output shaft 101 and rotates forward together with the output shaft 101 upon receiving the impact rotational force from the hammer. In this way, the fastening target such as a nut is tightened by the impact rotational force repeatedly output from the output shaft 101.

[0074] As described above, in the impact rotation mechanism of the comparative example, since the rotational force of the motor is stored in the spring and then output as a rotational impact force, the rotational impact force is delayed with respect to the rotational force of the motor, and as a result, the measurement accuracy of the tightening torque is likely to decrease.

[0075] (3-1-2) Specific example of the impact rotation mechanism of the embodiment The impact rotation mechanism 12 of the present embodiment includes a hammer and an anvil in this specific example. The hammer is directly connected to the motor 11. When the motor 11 rotates forward, the hammer also rotates forward, and when the motor 11 rotates reversely, the hammer also rotates reversely. The hammer alternately receives the rotational force during forward rotation and the rotational force during reverse rotation from the motor 11, and while repeating forward and reverse rotations, performs an impact operation on the anvil by the rotational inertial force during forward rotation, thereby converting a part of the rotational force during forward rotation into an impact rotational force.

[0076] The anvil is connected to the output shaft 101. The connection to the output shaft 101 is, for example, attachment to the output shaft 101 or integral molding with the output shaft 101. The anvil rotates forward together with the output shaft 101 upon receiving the impact rotational force from the hammer. In this way, the fastening target such as a nut is tightened by the impact rotational force repeatedly output from the output shaft 101.

[0077] As described above, in the impact rotation mechanism 12 of the present embodiment, since the rotational inertial force corresponding to the rotational force of the motor 11 is output as a rotational impact force, the delay of the rotational impact force with respect to the rotational force of the motor 11 is suppressed, and a reduction in the measurement accuracy of the tightening torque can be achieved.

[0078] (3-2) Output waveform comparison of the measurement unit (3-2-1) Output waveform of the measurement unit with the impact tool of the comparative example Fig. 5A shows the output waveform of the magnetostrictive sensor in the impact tool of the comparative example. This impact tool of the comparative example is different from the impact tool 1 of the present embodiment in that the impact rotation mechanism 12 is modified so that the motor can continue to rotate forward at the time of the impact operation, and the control unit does not perform the control to reverse the motor in response to the completion of the impact operation (that is, it has the configuration of a general impact tool).

[0079] In the impact tool of the comparative example, the motor is connected to the hammer via a spring, a gear, etc. Even when the hammer strikes the anvil and the anvil stops or reverses due to the impact rotational force, the motor continues to rotate forward.

[0080] In the graph of Fig. 5A, the horizontal axis corresponds to time (sec), the vertical axis corresponds to the output (volt: V) of the measurement unit (magnetostrictive sensor), and the output waveform shows the time change of the strain. The output waveform of Fig. 5A includes two pulse components P1 and P2 of the first and second. The first pulse component P1 corresponds to the strain generated in the anvil in response to the impact rotational force of the hammer. The second pulse component P2 corresponds to the strain generated in the anvil in response to the rotational force of the motor.

[0081] As can be seen from the output waveform of Fig. 5A, in the impact tool of the comparative example, immediately after the impact rotational force of the hammer (corresponding to the first pulse component P1) acts on the anvil, the rotational force of the motor that continues to rotate forward (corresponding to the second pulse) further acts on the anvil. In this way, following the impact rotational force of the hammer, the rotational force of the motor acting on the anvil contributes to an increase in the tightening torque, but also causes difficulties in accurate control of the motor, and thus variations in the tightening torque.

[0082] (3-2-2) Output waveform of the measurement unit with the impact tool of the embodiment FIG. 5B shows the output waveform of the magnetostrictive sensor in the impact tool of the present embodiment. Also in the graph of FIG. 5B, the horizontal axis corresponds to time (sec), the vertical axis corresponds to the output (V) of the measurement unit (magnetostrictive sensor), and the output waveform shows the time change of strain.

[0083] The output waveform of FIG. 5B, compared with the output waveform of FIG. 5A, contains only the first pulse component P1, with the second pulse component P2 removed from the two pulse components P1 and P2.

[0084] In the impact tool 1 of the present embodiment, the motor 11 causes the striking rotation mechanism 12 to perform a striking operation in the forward rotation under the control of the control unit 15, and reverses almost simultaneously with the completion of the striking operation.

[0085] Therefore, as can be seen from the output waveform of FIG. 5B, in the impact tool 1 of the present embodiment, it is possible to perform the tightening operation only with the striking rotational force (corresponding to the first pulse component P1) caused by the striking operation of the striking rotation mechanism 12. As a result, it is possible to facilitate the accurate control of the motor 11, and thus suppress the variation in the tightening torque.

[0086] (3-3) Relationship between the rotation amount of the motor, the current command value to the motor, and the rotation speed of the motor The graph of FIG. 6 shows the relationship between the rotation amount of the motor 11, the current command value to the motor 11, and the rotation speed of the motor 11. Specifically, in FIG. 6, a broken line waveform showing the change in the encoder count value, a dashed-dotted line waveform showing the change in the current command value from the control unit 15 to the motor 11, and a solid line waveform showing the change in the rotation speed of the motor 11 are shown.

[0087] In the graph of FIG. 6, the horizontal axis corresponds to time (msec), the left vertical axis corresponds to the count value (revolutions), and the right vertical axis corresponds to the current command value (mA) and the rotation speed (rpm).

[0088] Note that it is possible to switch between supplying a forward current and a reverse current to the motor 11, and the current command value includes, for example, a positive sign indicating the forward direction or a negative sign indicating the reverse direction. However, in the graph of FIG. 6, for the sake of convenience, the absolute value of the current command value is shown as a thin-line waveform, and the direction of the current is indicated by the increase or decrease in the rotational speed of the motor 11 according to the current command value.

[0089] (3-3-1) Relationship between current command value and rotational speed When the current command value to the motor 11 changes as shown by the waveform indicated by the dashed-dotted line in FIG. 6, the rotational speed of the motor 11 changes as shown by the waveform indicated by the solid line in response to the change in the current command value. From a comparison between the waveform indicated by the dashed-dotted line and the waveform indicated by the solid line, it can be seen that the rotational speed of the motor 11 changes with a delay in response to the change in the current command value.

[0090] Specifically, for example, at the first time point t1 (20 msec) when the current command value (dashed-dotted line waveform) first reaches a maximum, the rotational speed (solid line waveform) is increasing, and at the second time point t2 (40 msec), 20 msec after the first time point t1 (20 msec), when the current command value reaches a maximum for the second time, the rotational speed (solid line waveform) is still increasing.

[0091] (3-3-2) Relationship between rotation amount, current command value, and rotational speed At the first time point t1 (20 msec) when the current command value reaches the first maximum value (however, the direction flag is "forward"), the motor 11 starts to rotate forward, and the count value (dashed line waveform) rapidly rises from 0 to the reference value (58 times). After that, between the first time point t1 (20 msec) and the third time point t3 (180 msec) when the current command value reaches the third maximum value (however, the direction flag is "forward") via the second time point t2 (40 msec) when it reaches the second maximum value (however, the direction flag is "forward") (20 - 180 msec), the count value gradually rises from the reference value (58 times) to the maximum value (70 times) as shown by the dashed line waveform in FIG. 6.

[0092] Thereafter, the count value is maintained at the maximum value (70 times), and at the fourth point in time t4 (210 msec) when the current command value becomes the fourth maximum value (however, the direction flag is "reverse direction"), it returns to a predetermined value (56 times) slightly below the reference value (58 times).

[0093] Thereafter, the count value is maintained at the predetermined value (56 times) or a value in its vicinity (55 - 57 times), and starts to increase at the fifth point in time t5 (280 msec) when the current command value becomes the fifth maximum value (however, the direction flag is "forward direction"). Then, when the first striking operation of the striking and rotating mechanism 12 is completed, and at the sixth point in time t6 (330 msec) when the current command value becomes the sixth maximum value (however, the direction flag is "forward direction"), the count value reaches the reference value (58 times).

[0094] In response to this, that is, at the sixth point in time t6 (330 msec), the current command value becomes "0", and the count value is maintained at the reference value (58 times). When the current command value becomes the seventh maximum value and the fifth maximum value (however, the direction flag is "reverse direction") at the seventh point in time t7 (380 msec), the count value starts to decrease, and when it returns to the predetermined value (56 times), the decrease of the count value stops.

[0095] Thereafter, the count value is maintained at the predetermined value (56 times) or a value in its vicinity (55 - 57 times), and starts to increase again at the eighth point in time t8 (450 msec) when the current command value becomes the eighth maximum value (however, the direction flag is "forward direction"). Then, at the ninth point in time t9 (500 msec) when the second striking operation of the striking and rotating mechanism 12 is completed, the current command value becomes the ninth maximum value (however, the direction flag is "forward direction"), and the count value reaches the reference value (58 times).

[0096] In response to this, that is, at the ninth point in time t9 (500 msec), the current command value becomes "0", and the count value is maintained at the reference value (58 times). When the current command value becomes the tenth maximum value (however, the direction flag is "reverse direction") at the tenth point in time t10 (550 msec), the count value starts to decrease again, and when it returns to the predetermined value (56 times), the decrease of the count value stops. Thereafter, the count value repeats the same change.

[0097] (4) Variation Next, various variations of the impact tool 1 of the embodiment will be described. In the variations, descriptions of matters common to those of the embodiment are omitted or simplified.

[0098] (4-1) First Variation of Substantially Simultaneous In this variation, the measurement unit 14 performs a measurement operation in response to the result of the determination by the control unit 15 regarding the completion of the striking operation changing from a negative result to an affirmative result. The control unit 15 reverses the motor 11 after the measurement operation is performed.

[0099] In this way, the control unit 15 of this variation causes the measurement unit 14 to measure the tightening torque in response to the completion of the striking operation, and then reverses the motor 11. That is, the difference from the "second variation of substantially simultaneous" to be described next is that the timing of the reversal of the motor 11 with respect to the completion of the striking operation does not have to be predetermined.

[0100] According to this variation, while suppressing the variation in the tightening torque, the tightening torque can be measured at an accurate timing.

[0101] (4-2) Second Variation of Substantially Simultaneous In this variation, the control unit 15 reverses the motor 11 after a predetermined time has elapsed since the result of the determination regarding the completion of the striking operation has changed from a negative result to an affirmative result. The predetermined time here is, for example, a value between 0 and 40 msec. However, the predetermined time may also be a value between 0 and 60 msec, or a value between 0 and 30 msec.

[0102] The measurement unit 14 performs a measurement operation before the control unit 15 reverses the motor 11.

[0103] Thus, in this modification example, the timing of the reverse rotation of the motor 11 with respect to the completion of the striking operation is predetermined, and after the completion of the striking operation, the control unit 15 causes the measurement unit 14 to measure the tightening torque before the timing of the reverse rotation of the motor 11.

[0104] According to this modification example, while suppressing the variation in the tightening torque, the measurement of the tightening torque can be performed at an accurate timing.

[0105] (4-3) First modification example of the striking and rotating mechanism The striking and rotating mechanism 12 does not have to be directly connected to the motor 11. In this modification example, the hammer constituting the striking and rotating mechanism 12 is connected to the rotor of the motor 11 via a spring, a gear, etc. The motor 11 in this modification example is rotating forward when the striking operation of the striking and rotating mechanism 12 is completed, but the control unit 15 forcibly reverses the motor 11 by switching the direction of the current to the motor 11 from the forward direction to the reverse direction substantially simultaneously with the completion of the striking operation of the striking and rotating mechanism 12.

[0106] According to this modification example, since a part of the rotational force of the motor 11 is converted into the striking rotational force of the striking and rotating mechanism 12 via the potential energy of the spring, compared with the embodiment, the delay in the change of the striking operation of the striking and rotating mechanism 12 with respect to the change of the rotation of the motor 11 becomes larger. However, even if the delay becomes larger, by the detection unit 13 detecting the rotation amount of the motor 11 and the control unit 15 performing control based on the detection result of the detection unit 13, compared with the case of performing control based on the current value etc. of the motor 11, the accurate control of the motor 11 can be facilitated.

[0107] (4-4) Second modification example of the striking and rotating mechanism This modification example is a modification of the first modification example in that, instead of the detection unit 13 detecting the rotation amount of the motor 11, the rotation amount during the forward rotation of the striking and rotating mechanism 12 is detected. In this modification example, compared with the first modification example, accurate control of the motor 11 is difficult, but compared with the case of performing control based on the current value of the striking and rotating mechanism 12, the accurate control of the motor 11 can be facilitated.

[0108] (4-5) Variation example of the detection unit In this embodiment, since the motor 11 and the impact rotation mechanism 12 are directly connected and rotate integrally, the detection unit 13 may detect the rotation amount during the forward rotation of the impact rotation mechanism 12 instead of the rotation amount during the forward rotation of the motor 11.

[0109] Also, the output shaft 101 is fixed to the anvil of the impact rotation mechanism 12, and since the output shaft 101 also rotates integrally in addition to the motor 11 and the impact rotation mechanism 12, the detection unit 13 may detect the rotation amount during the forward rotation of the output shaft 101 instead of the rotation amount during the forward rotation of the motor 11 or the rotation amount during the forward rotation of the impact rotation mechanism 12.

[0110] The rotation sensor that realizes the detection unit 13 in this variation example is, for example, an encoder that detects the rotation speed of the impact rotation mechanism 12 or the output shaft 101.

[0111] (4-6) Variation example of the rotation sensor The rotation sensor may be, for example, an encoder that detects the rotation angle of the impact rotation mechanism 12 or the output shaft 101. In this case, for example, the control unit 15 calculates the rotation speed based on the rotation angle detected by the encoder.

[0112] Alternatively, the rotation sensor may be an encoder that detects the angular velocity of the impact rotation mechanism 12 or the output shaft 101. In this case, for example, the control unit 15 calculates the rotation angle and thus the rotation speed based on the angular velocity detected by the encoder.

[0113] (4-7) Variation example of the measurement unit The measurement unit 14 may be realized by a strain sensor other than the magnetostrictive sensor, for example, a strain gauge that electrically detects strain, or may be realized by a sensor other than the strain sensor (for example, a sensor that optically detects the torsion of the anvil).

[0114] (5) Control method of the impact tool The control method of the impact tool 1 includes step S4 and S5 (hereinafter referred to as "detection step"), and step S6 to S12 (hereinafter referred to as "control step"). In the detection step, the detection unit 13 detects the rotation amount during the forward rotation of the motor 11. Specifically, for example, the processor may detect the rotation amount of the motor 11 or the impact rotation mechanism 12 using the detection result of the rotation sensor.

[0115] In the control step, the control unit 15 controls the motor 11 based on at least one of the rotation amount detected in the detection step and the change in the rotation amount. Specifically, for example, the previously detected rotation amount is stored in the memory, and the processor obtains the change in the rotation amount based on the rotation amount detected this time and the rotation amount stored in the memory, and controls the motor 11 based on at least one of the rotation amount detected this time and the obtained change in the rotation amount.

[0116] In the control step, the control unit 15 (processor and memory) determines whether the impact operation has been completed based on the change in the rotation amount detected in the detection step, and reverses the motor 11 substantially simultaneously with the result of the determination changing from a negative result indicating that the impact operation has not been completed to a positive result indicating that the impact operation has been completed.

[0117] In the control step, the control unit 15 (processor and memory) continues to reverse the motor 11 until the rotation amount detected in the detection step returns to a predetermined value.

[0118] (6) Summary The impact tool (1) according to the first aspect of the present disclosure includes a motor (11), an impact rotation mechanism (12), a detection unit (13), and a control unit (15). The motor (11) can rotate forward and backward. The impact rotation mechanism (12) performs an impact operation by rotational inertial force while receiving a rotational force from the motor (11) and repeating forward and backward rotations. The detection unit (13) detects the rotation amount during the forward rotation of the motor (11) or the impact rotation mechanism (12). The control unit (15) controls the motor (11) based on at least one of the rotation amount detected by the detection unit (13) and the change in the rotation amount.

[0119] According to this aspect, by performing control based on at least one of the amount of rotation when the motor (11) or the impact rotation mechanism (12) rotates forward and the change in such an amount of rotation, compared with the case of performing control based on the current value of the motor (11) or the like, it is possible to facilitate the accurate control of the motor (11).

[0120] In the impact tool (1) according to the second aspect, in the first aspect, the control unit (15) determines whether or not the impact operation has been completed based on the change in the amount of rotation detected by the detection unit (13). Then, the control unit (15) reverses the motor (11) substantially simultaneously with the change of the determination result from a negative result indicating that the impact operation has not been completed to a positive result indicating that the impact operation has been completed.

[0121] According to this aspect, by reversing the motor (11) substantially simultaneously with the completion of the impact operation, it is possible to suppress the rotational force of the motor (11) following the impact rotational force of the impact rotation mechanism (12). Thereby, it is possible to realize the tightening operation only with the impact rotational force of the impact rotation mechanism (12), and further facilitate the accurate control of the motor (11).

[0122] In the impact tool (1) according to the third aspect, in the second aspect, the control unit (15) continues to reverse the motor (11) until the amount of rotation detected by the detection unit returns to a predetermined value.

[0123] According to this aspect, by returning the amount of rotation to a predetermined value and then performing the next impact operation (re - impact), it is possible to facilitate the accurate control of the motor (11) in the re - impact.

[0124] In the impact tool (1) according to the fourth aspect, in the second or third aspect, the control unit (15) stops the current supplied to the motor (11) in response to the change of the determination result from a negative result to a positive result, and then starts supplying a current in the direction opposite to the current to reverse the motor (11).

[0125] According to this aspect, in response to the completion of the striking operation, after stopping the supply of current to the motor (11), a reverse current is supplied, that is, by providing a current stop period immediately after the striking operation, it is possible to easily reverse the motor (11) from normal rotation to reverse rotation by utilizing the repulsive force from the impact rotation mechanism (12) to the rotational force from the motor (11) to the impact rotation mechanism (12). Further, after the current stop period, by supplying a reverse current to the motor (11), the reverse rotation of the motor (11) can be continued.

[0126] The impact tool (1) according to the fifth aspect further includes an output shaft (101) and a measurement unit (14) in any one of the second to fourth aspects. The output shaft (101) outputs an impact rotational force. The impact rotational force is the conversion result of the impact rotation mechanism (12). The measurement unit (14) performs a measurement operation. The measurement operation is an operation of measuring the tightening torque when tightening an object with the impact rotational force. The measurement unit (14) performs the measurement operation in response to the result of the determination changing from a negative result to a positive result. The control unit (15) reverses the motor (11) after the measurement operation is performed.

[0127] According to this aspect, it is possible to accurately measure the tightening torque at the right timing while suppressing variations in the tightening torque.

[0128] The impact tool (1) according to the sixth aspect further includes an output shaft (101) and a measurement unit (14) in any one of the second to fourth aspects. The output shaft (101) outputs an impact rotational force. The impact rotational force is the conversion result of the impact rotation mechanism (12). The measurement unit (14) performs a measurement operation. The measurement operation is an operation of measuring the tightening torque when tightening an object with the impact rotational force. The control unit (15) reverses the motor (11) after a predetermined time has elapsed since the result of the determination changed from a negative result to a positive result. The measurement unit (14) performs the measurement operation before the control unit (15) reverses the motor (11).

[0129] According to this aspect, while suppressing the variation in the tightening torque, the measurement of the tightening torque can be performed at an accurate timing.

[0130] In the impact tool (1) according to the seventh aspect, in any of the first to sixth aspects, the detection unit (13) detects the amount of rotation during the forward rotation of the motor (11).

[0131] According to this aspect, even when the impact rotation mechanism (12) is not directly connected to the motor (11) (for example, when connected to the motor (11) via a spring, a gear, etc.), it is possible to facilitate the accurate control of the motor (11).

[0132] The control method of the impact tool (1) according to the eighth aspect is a control method of the impact tool (1) including a motor (11) and an impact rotation mechanism (12). The motor (11) can rotate forward and backward. The impact rotation mechanism (12) receives a rotational force from the motor (11) and performs an impact operation due to rotational inertia while repeating forward and backward rotations. The control method of the impact tool (1) includes a detection step (S4, S5) and a control step (S6 to S12). The detection step (S4, S5) detects the amount of rotation during the forward rotation of the motor (11) or the impact rotation mechanism (12). The control step (S6 to S12) controls the motor (11) based on at least one of the amount of rotation detected in the detection step (S4, S5) and the change in the amount of rotation.

[0133] According to this aspect, by performing control based on at least one of the amount of rotation when the motor (11) or the impact rotation mechanism (12) rotates forward and the change in such an amount of rotation, it is possible to facilitate the accurate control of the motor (11) as compared with the case of performing control based on the current value or the like of the motor (11).

[0134] In the control method of the impact tool (1) according to the ninth aspect, in the eighth aspect, in the control steps (S6 to S12), based on the change in the amount of rotation detected in the detection steps (S4, S5), it is determined whether the striking operation has been completed. When the result of the determination changes from a negative result indicating that the striking operation has not been completed to an affirmative result indicating that the striking operation has been completed, the motor (11) is reversed substantially simultaneously.

[0135] According to this aspect, by reversing the motor (11) substantially simultaneously with the completion of the striking operation, the rotational force of the motor (11) following the striking rotational force of the striking rotation mechanism (12) can be suppressed. As a result, it is possible to realize a tightening operation only with the striking rotational force of the striking rotation mechanism (12), and furthermore, to facilitate more accurate control of the motor (11).

[0136] In the control method of the impact tool (1) according to the tenth aspect, in the ninth aspect, in the control steps (S6 to S12), the reverse rotation of the motor (11) is continued until the amount of rotation detected in the detection steps (S4, S5) returns to a predetermined value.

[0137] According to this aspect, by returning the amount of rotation to a predetermined value and then performing the next striking operation (re-striking), it is possible to facilitate more accurate control of the motor (11) in re-striking.

Explanation of Reference Numerals

[0138] 1 Impact tool 11 Motor 12 Striking rotation mechanism 13 Detection unit 14 Measurement unit 15 Control unit 101 Output shaft

Claims

1. A motor capable of forward and reverse rotation, a striking rotation mechanism that receives a rotational force from the motor and performs a striking operation by rotational inertial force while repeating the forward and reverse rotations, a detection unit that detects the amount of rotation during the forward rotation of the motor or the striking rotation mechanism, a control unit that controls the motor based on at least one of the amount of rotation detected by the detection unit and the change in the amount of rotation, An impact tool.

2. The control unit, based on the change in the amount of rotation detected by the detection unit, determines whether the striking operation has been completed, and reverses the motor substantially simultaneously with the result of the determination changing from a negative result indicating that the striking operation has not been completed to a positive result indicating that the striking operation has been completed. The impact tool according to claim 1.

3. The control unit continues to reverse the motor until the amount of rotation detected by the detection unit returns to a predetermined value. The impact tool according to claim 2.

4. The control unit stops the current supplied to the motor in response to the result of the determination changing from the negative result to the positive result, and then starts supplying a current in the direction opposite to the current to reverse the motor. The impact tool according to claim 2 or 3.

5. an output shaft that outputs a striking rotational force that is a conversion result of the striking rotation mechanism, a measurement unit that performs a measurement operation of measuring the tightening torque when tightening an object with the striking rotational force, and further includes, the measurement unit performs the measurement operation in response to the result of the determination changing from the negative result to the positive result, the control unit reverses the motor after the measurement operation has been performed. The impact tool according to claim 2 or 3.

6. an output shaft that outputs a striking rotational force that is a conversion result of the striking rotation mechanism, a measurement unit that performs a measurement operation of measuring the tightening torque when tightening an object with the striking rotational force, and further includes, the control unit reverses the motor after a predetermined time has elapsed since the result of the determination changed from the negative result to the positive result, the measurement unit performs the measurement operation before the control unit reverses the motor. The impact tool according to claim 2 or 3.

7. The detection unit detects the amount of rotation during the forward rotation of the motor. The impact tool according to claim 1.

8. A control method for an impact tool, comprising: a motor capable of forward and reverse rotation; and a striking rotation mechanism that receives a rotational force from the motor and performs a striking operation by rotational inertial force while repeating the forward and reverse rotations. A detection step of detecting a rotation amount that is the amount of rotation when the motor or the striking rotation mechanism rotates forward. A control step of controlling the motor based on at least one of the rotation amount detected in the detection step and a change in the rotation amount. A control method for an impact tool.

9. In the control step, Based on the change in the rotation amount detected in the detection step, it is determined whether the striking operation has been completed. The motor is reversed substantially simultaneously with the result of the determination changing from a negative result indicating that the striking operation has not been completed to a positive result indicating that the striking operation has been completed. The control method for an impact tool according to claim 8.

10. In the control step, the reverse rotation of the motor is continued until the rotation amount detected in the detection step returns to a predetermined value. The control method for an impact tool according to claim 9.

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