Impact tool, and impact tool control method

Abstract

To achieve realization of an accurate fastening operation.SOLUTION: An impact tool 1 comprises a motor 11, a striking rotation mechanism 12, a detection part 13, a control part 15, and a measurement part 14. The motor 11 can perform normal rotation and reverse rotation. The striking rotation mechanism 12 performs a striking operation by rotational inertia force while receiving a torque from the motor 11 and repeating normal rotation and reverse rotation. The detection part 13 detects a rotation amount and an amount of change in the rotation amount of the motor 11 or the striking rotation mechanism 12. The control part 15 controls the motor 11 so that a fastening operation for fastening an object is performed by at least one of a striking impact torque by the striking operation of the striking rotation mechanism 12 and a torque in normal rotation of the motor 11. The measurement part 14 mesures a fastening time of a fastening operation. The control part 15 reversely rotates the motor 11 if reverse rotation conditions concerning at least one of a relationship between the rotation amount and a first threshold, a relationship between the amount of change and a second threshold, and a relationship between the fastening time and a third threshold is satisfied when the motor 11 normally rotates.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to an impact tool and a method for controlling an impact tool, and more particularly to an impact tool that performs a striking action and a method for controlling an impact tool that performs a striking action. [Background technology]

[0002] Patent Document 1 describes an electric power tool having a hammer, an impact mechanism, a control unit, and a rotational position detection means. The hammer is driven by a motor. The impact mechanism is rotatable relative to the hammer and has an anvil that is struck by the hammer. The output shaft is connected to the anvil. The control unit controls the rotation of the motor. The rotational position detection means detects the rotational position of the motor. The control unit controls the rotation of the motor so that the output shaft alternates between forward rotation at a first angle and reverse rotation at a second angle smaller than the first angle. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-157925 Summary of the Invention [Problem to be solved by the invention]

[0004] The power tool described in Patent Document 1 is capable of performing fastening operations with a large torque by using a hammer in the impact mechanism to strike the anvil, but it is not easy to perform fastening operations accurately with a small torque.

[0005] More specifically, when performing a tightening operation with a small torque, it is conceivable to increase the number of strikes per unit time by, for example, making the second angle during reverse rotation smaller than the first angle during forward rotation. However, when the motor is controlled based on the rotation angle of the output shaft, as in the power tool of Patent Document 1, the change in the rotation angle in response to the strikes is delayed due to the inertia of the anvil, and the delay increases as the number of strikes per unit time increases, which may make it difficult to perform an accurate tightening operation.

[0006] An object of the present disclosure is to provide an impact tool that can achieve accurate tightening operations. [Means for solving the problem]

[0007] An impact tool according to one aspect of the present disclosure includes a motor, an impact rotation mechanism, a detection unit, a control unit, and a measurement unit. The motor is capable of rotating in both forward and reverse directions. The impact rotation mechanism receives rotational force from the motor and performs an impact operation using rotational inertia force while repeatedly rotating in both forward and reverse directions. The detection unit detects the rotation amount of the motor or the impact rotation mechanism and the amount of change in the rotation amount. The control unit controls the motor so that a tightening operation is performed to tighten an object using at least one of the impact rotation force generated by the impact operation of the impact rotation mechanism and the rotation force generated by the forward rotation of the motor. The measurement unit measures the tightening time of the tightening operation. When the motor is rotating in the forward direction, the control unit reverses the motor when a reversal condition is satisfied regarding at least one of the relationship between the rotation amount and a first threshold value, the relationship between the change in the rotation amount and a second threshold value, and the relationship between the tightening time and a third threshold value.

[0008] A control method for an impact tool according to one aspect of the present disclosure is a control method for an impact tool including a motor and an impact rotation mechanism. The motor is capable of rotating in both forward and reverse directions. The impact rotation mechanism receives rotational force from the motor and performs an impact operation using rotational inertia force while repeatedly rotating in both forward and reverse directions. The control method for the impact tool includes a detection step, a control step, and a measurement step. In the detection step, the rotation amount and the change in the rotation amount of the motor or the impact rotation mechanism are detected. In the control step, the motor is controlled so that a tightening operation is performed to tighten an object using at least one of the impact rotation force caused by the impact operation of the impact rotation mechanism and the rotation force during forward rotation of the motor. In the measurement step, the tightening time of the tightening operation is measured. In the control step, when the motor is rotating in the forward direction, the motor is reversed if a reversal condition is satisfied regarding at least one of the relationship between the rotation amount and a first threshold value, the relationship between the change in the rotation amount and a second threshold value, and the relationship between the tightening time and a third threshold value. [Effects of the Invention]

[0009] The impact tool and the control method for the impact tool according to the present disclosure have the effect of enabling accurate tightening operations to be achieved. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is an external view of an impact tool according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a block diagram of the impact tool. [Figure 3] FIG. 3 is a flowchart illustrating a part of the operation of the control unit of the impact tool. [Figure 4] FIG. 4 is a flowchart illustrating another part of the operation of the impact tool. [Figure 5] FIG. 5 is a graph showing an output waveform of the measuring unit (magnetostrictive sensor) in the impact tool. [Figure 6]FIG. 6 is a graph showing, for comparison, an output waveform of the detector (encoder) of the impact tool, a waveform of a current command value from a controller to a motor, and a waveform of the rotation speed of the motor. DETAILED DESCRIPTION OF THE INVENTION

[0011] The specific hardware (e.g., magnetostrictive sensors, encoders, etc.) and the specific numerical values ​​of various variables (e.g., time, voltage values, target current values, count values, rotational speeds, etc.) and various constants (e.g., threshold values, predetermined values, target values, etc.) mentioned in the following description are all examples and may be changed as appropriate.

[0012] (1) Main part First, the main parts of the impact tool 1 according to the embodiment of the present disclosure will be described with reference to FIGS. 2, 5 and 6. FIG.

[0013] As shown in FIG. 2, the impact tool 1 includes a motor 11, an impact rotation mechanism 12, a detection unit 13, a control unit 15, and a measurement unit .

[0014] (1-1) Motor The motor 11 is capable of rotating forward and reverse. When a current is supplied to the motor 11 in the forward direction, the motor 11 rotates forward, and when a current is supplied in the reverse direction, the motor 11 rotates reversely. When no current is supplied to the motor 11, the motor 11 can either stop or continue to rotate by inertia.

[0015] (1-2) Impact rotation mechanism The striking rotation mechanism 12 performs striking operation by rotational inertia force while repeatedly rotating forward and backward upon receiving rotational force from the motor 11. The rotational inertia force is the inertia force of a rotating body (for example, an anvil).

[0016] (1-3) Forward and reverse rotation In this embodiment, forward rotation refers to rotation (e.g., clockwise rotation) of the motor 11, etc., around a rotation axis (hereinafter sometimes simply referred to as the "rotation axis") common to the motor 11 and the impact rotation mechanism 12 (and further, the output shaft 101 described below; hereinafter sometimes referred to as the "motor 11, etc.") when a forward current flows through the motor 11. In addition, reverse rotation refers to rotation (e.g., counterclockwise rotation) of the motor 11, etc., around a rotation axis when a reverse current flows through the motor 11.

[0017] Reversing the rotation of the motor 11 includes reversing a stopped motor 11 and reversing a forward rotating motor 11. Similarly, rotating the motor 11 forward includes reversing a stopped motor 11 and reversing a reverse rotating motor 11.

[0018] (1-3-1) Forward and reverse rotation states In this embodiment, a state in which a current flows in the forward direction through the motor 11 (for example, a state in which the direction flag described below is set to "forward") is referred to as a "forward state," and a state in which a current flows in the reverse direction through the motor 11 (for example, a state in which the direction flag is set to "reverse") is referred to as a "reverse state."

[0019] The forward rotation state includes a case where a forward current flows through the motor 11 and the motor 11 is rotating forward, and a case where a forward current flows through the motor 11 and the motor 11 is stopped (i.e., the rotation speed is 0). Similarly, the reverse rotation state includes a case where a reverse current flows through the motor 11 and the motor 11 is rotating in reverse, and a case where a reverse current flows through the motor 11 and the motor 11 is stopped.

[0020] Reversing the rotation of the motor 11 involves setting the direction flag to "reverse" and passing a current in the reverse direction through the motor 11, and the result of reversing the rotation of the motor 11 does not necessarily mean that the motor 11 rotates in the reverse direction. Similarly, rotating the motor 11 forward involves setting the direction flag to "forward" and passing a current in the forward direction through the motor 11, and the result of rotating the motor 11 forward does not necessarily mean that the motor 11 rotates in the forward direction.

[0021] The rotation speed of the motor 11 is controlled by outputting a direction flag and a current command value (which is equal to or greater than 0) to the motor 11 from the control unit 15, which will be described later.

[0022] (1-3-2) Inversion In this embodiment, a change from a forward rotation state to a reverse rotation state (e.g., reversing a forward rotating motor 11) and a change from a reverse rotation state to a forward rotation state (e.g., rotating a reverse rotating motor 11 forward) may be collectively referred to as "reversal."

[0023] (1-4) Detection unit The detector 13 detects the amount of rotation of the motor 11. The detector 13 is realized by a rotation sensor such as an encoder, as will be described in detail later.

[0024] (1-4-1) Rotation amount The rotation amount is the amount by which the motor 11 rotates in the normal direction, and more specifically, the number of rotations or the angle of rotation. The number of rotations is the number of times the motor 11 has rotated, for example, n times. The number of rotations is, for example, the number of rotations from the start of the tightening operation (for example, the start time T0 described later: see FIG. 5). The rotation angle is the angle by which the motor 11 has rotated, for example, θ degrees. The rotation angle is, for example, the angle of rotation from the position at the start of the tightening operation (initial position). Note that the number of rotations n and the angle θ have the relationship "n=θ / 360".

[0025] The amount of rotation increases when the motor 11 rotates forward, remains constant when the motor 11 is not rotating, and decreases when the motor 11 rotates reversely.

[0026] (1-4-2) Detection of rotation amount The detection of the rotation amount includes the detection of the rotation amount and the detection of the change in the rotation amount. The change in the rotation amount includes the increase in the rotation amount in the forward rotation (hereinafter, sometimes simply referred to as the "increase") and the decrease in the rotation amount in the reverse rotation (hereinafter, sometimes simply referred to as the "decrease").

[0027] In addition, the change in the amount of rotation is not limited to the change in the amount of rotation in a single tightening operation, but may also be, for example, the difference in the amount of rotation between a first tightening operation and a second tightening operation following the first tightening operation when tightening operations are performed repeatedly.

[0028] (1-4-3) Repetitive detection The detection unit 13 repeatedly detects the amount of rotation. Repeated detection means, for example, repeatedly detecting at a predetermined cycle. The predetermined cycle is, for example, once every 1 / 100th of a second or once every 1 / 10th of a second. However, repeated detection also includes irregular detection. Multiple detection results from repeated detection are temporarily stored in chronological order in an internal memory, for example.

[0029] The above points regarding repeated detection also apply to repeated measurements by the measurement unit 14.

[0030] (1-5) Measurement section The measuring unit 14 measures the tightening time of the tightening operation, which will be described later.

[0031] (1-5-1) Sensor The measurement unit 14 is realized by a sensor. The sensor detects a physical quantity that changes faster than the amount of rotation in response to the tightening operation (particularly, the impact operation). Examples of physical quantities that change faster than the amount of rotation include strain that changes in response to the tightening operation and acceleration that changes in response to the impact operation.

[0032] (1-5-1a) Magnetostrictive sensor The sensor in this embodiment is a magnetostrictive sensor that magnetically detects distortion of the output shaft 101 (described later) in response to the tightening operation, and outputs an output signal (for example, the voltage waveform in FIG. 5) in response to the detected distortion.

[0033] (1-5-2) Closing time The tightening time is the time that has elapsed since the start of the tightening operation, that is, the duration of the tightening operation.

[0034] The measurement unit 14, for example, identifies the start time T0 of the tightening operation based on the output signal (voltage waveform) of the magnetostrictive sensor as shown in FIG. 5, and measures the tightening time Δt1 as shown in FIG. 6 by timing the elapsed time from the identified start time T0.

[0035] As will be described in detail later, the start time T0 of the tightening operation is, for example, the rising time (T0=0.629 seconds) of the first pulse component P1 in the voltage waveform shown in Fig. 5. The tightening time Δt1 is, for example, 10 msec from 150 msec to 160 msec and 10 msec from 490 msec to 500 msec in the count value waveform shown by the dashed line in Fig. 6. The count value is the number of rotations or a value proportional to the number of rotations.

[0036] (1-5-3) No change time In this embodiment, the measurement unit 14 further measures the no-change time, which is the duration of the no-change state from the point in time when the rotation amount changes from an increasing state to a no-change state.

[0037] (1-5-4) Tightening torque In an operation example described later, the measurement unit 14 further measures the tightening torque of the tightening operation. The tightening torque is measured, for example, based on the output signal of a strain sensor. Alternatively, the tightening torque may be estimated based on the amount of rotation or the amount of change in the amount of rotation from the start time T0 of the tightening operation (see "(6-3) Modified example of the tightening torque measurement method" described later).

[0038] (1-5-5) Repeated measurements The measuring unit 14 repeatedly measures the tightening time and the like.

[0039] (1-6) Control unit The control unit 15 performs tightening control to control the motor 11 so that a tightening operation is performed to tighten the object using at least one of the impact rotation force due to the impact operation of the impact rotation mechanism 12 and the rotation force of the motor 11 in the forward rotation.

[0040] (1-6-1) Tightening operation In this embodiment, the tightening operation is performed using two types of force: the impact rotational force of the impact rotation mechanism 12 and the rotational force of the motor 11 in the forward rotation. Specifically, the tightening operation in this embodiment includes a first tightening operation using the impact rotational force, and a second tightening operation using the rotational force of the motor 11 in the forward rotation following the impact rotational force.

[0041] (1-6-1a) First tightening operation The first tightening operation is, for example, a tightening operation corresponding to a first pulse component P1 in the output signal (voltage waveform) of the magnetostrictive sensor shown in Fig. 5. The first pulse component P1 is a pulse component due to the impact rotational force.

[0042] (1-6-1b) Second tightening operation The second tightening operation is, for example, a tightening operation corresponding to the second pulse component P2 in the output signal of the magnetostrictive sensor shown in Fig. 5. The second pulse component P2 is a pulse component due to the torque of the motor 11 in the forward rotation following the impact torque.

[0043] (1-6-1c) Advantages of tightening operation By performing a first tightening operation using the impact rotation force of the impact rotation mechanism 12 and a second tightening operation using the rotation force of the motor 11 in the forward direction following the impact rotation force, it is possible to achieve a more accurate tightening operation.

[0044] (1-6-2) Tightening control Tightening control is control of the motor 11 to achieve a tightening operation with an appropriate tightening torque by using at least one of the impact rotation force of the impact rotation mechanism 12 and the rotation force of the motor 11 in the forward rotation.

[0045] The tightening control in this embodiment is performed using both the impact rotation force of the impact rotation mechanism 12 and the rotation force of the motor 11 during forward rotation. That is, the control unit 15 uses the impact rotation force of the impact rotation mechanism 12 (first pulse component P1: see FIG. 5) and the rotation force of the motor 11 during forward rotation following the impact rotation force (second pulse component P2) to achieve a tightening operation with a more accurate tightening torque. The tightening control includes tightening torque control and termination control.

[0046] (1-6-2a) Tightening torque control The tightening torque control is the control of the tightening torque during the tightening operation. The tightening torque control allows the tightening operation to be performed with an appropriate torque using the impact rotational force and the rotational force of the motor 11 in the forward rotation following the impact rotational force. The tightening torque control also allows the tightening with high torque using the impact rotational force and the tightening with low torque using the rotational force in the forward rotation of the motor 11 to be performed accurately.

[0047] (1-6-2b) Termination control The termination control is a control for terminating the tightening operation. The control unit 15 terminates the tightening operation when, for example, a termination condition is satisfied regarding at least one of the relationship between the rotation amount and the first target value, the relationship between the increase amount and the second target value, and the relationship between the tightening time and the third target value.

[0048] (1-6-2c) How to achieve tightening control The tightening control described above is realized by the control unit 15 using at least one of the measurement results of the measuring unit 14 (e.g., the output signal of the magnetostrictive sensor) and the detection results of the detecting unit 13 (e.g., the amount of rotation and the amount of change in the amount of rotation).

[0049] (1-6-2d) Specific examples of tightening control The control unit 15 of this embodiment performs tightening control, including tightening torque control and termination control, based on the amount of rotation (e.g., the count value of the encoder) and the amount of change in the amount of rotation (e.g., the amount of change in the count value; hereinafter, this may be simply referred to as "amount of change").

[0050] That is, based on the amount of change detected by the detection unit 13, the control unit 15 performs tightening torque control to control the tightening torque of the motor 11 so that a tightening operation to tighten the object is performed using both the impact rotational force due to the impact operation of the impact rotation mechanism 12 and the rotational force of the motor 11 in the forward rotation after the impact operation.

[0051] Then, when the amount of rotation detected by the detection unit 13 reaches a target value (first target value: described later), the control unit 15 performs end control to end the tightening operation.

[0052] (1-6-2e) Current command value The above-described tightening control and reverse rotation control, which will be described later, are realized by the control unit 15 outputting to the motor 11 a current command value that changes, for example, as shown by the dashed-dotted line graph in FIG.

[0053] (1-6-2f) Advantages of tightening control In this embodiment, the tightening control as described above is executed together with the reverse control described below, so that tightening operation with an appropriate tightening torque can be achieved by using both the impact rotational force of the impact rotation mechanism 12 and the rotational force of the motor 11 in forward rotation (particularly, the impact rotational force of the impact rotation mechanism 12 and the rotational force of the motor 11 in forward rotation following the impact rotational force).

[0054] (1-6-3) Reverse control The reverse rotation control is a control for rotating the motor 11 in the reverse direction when a reverse rotation condition is satisfied while the motor 11 is rotating in the forward direction.

[0055] (1-6-3a) Reversal conditions The reverse rotation condition is a condition for rotating the motor 11 in the reverse direction when the motor 11 is rotating in the forward direction (in other words, for reversing the state of the motor 11 from the forward rotation state to the reverse rotation state). The reverse rotation condition is, for example, a condition relating to at least one of the relationship between the rotation amount and the first threshold value, the relationship between the change amount and the second threshold value, and the relationship between the tightening time and the third threshold value. When the motor 11 is rotating in the forward direction, the control unit 15 performs reverse rotation control if at least one of the rotation amount, the change amount, and the tightening time satisfies the reverse rotation condition.

[0056] Specifically, the control unit 15 determines whether at least one of the rotation amount, the change amount, and the tightening time satisfies the reverse rotation condition. If at least one of the rotation amount, the change amount, and the tightening time satisfies the reverse rotation condition, the control unit 15 reverses the rotation of the motor 11 (reverses the state of the motor 11 from the forward rotation state to the reverse rotation state).

[0057] If none of the rotation amount, the change amount, and the tightening time satisfy the reverse rotation conditions, the motor 11 is not reversed (that is, the control unit 15 causes the motor 11 to continue rotating in the forward direction).

[0058] (1-6-3b) Reverse command, direction flag, and current command value When the motor 11 is in a forward rotation state, if the reverse rotation condition is satisfied, the control unit 15 outputs a command (reverse rotation command) to the motor 11 to reverse the motor 11 from the forward rotation state to the reverse rotation state, thereby reversing the state of the motor 11 from the forward rotation state to the reverse rotation state.

[0059] The reverse rotation command is preferably associated with a direction flag indicating reverse rotation and a current command value (e.g., a negative sign and an absolute value of the current) for controlling the amount of rotation of the motor 11 in the reverse rotation. Note that the association of a current command value with a command also includes the case where the command has a current command value.

[0060] (1-6-3c) Advantages of reverse control In this way, the control unit 15 reverses the motor 11 (performs reverse control) when at least one of the rotation amount and change in rotation amount detected by the detection unit 13 and the tightening time measured by the measurement unit 14 satisfies the reversal condition with respect to the threshold value, thereby achieving accurate tightening operation using at least one of the impact rotational force of the impact rotation mechanism 12 and the rotational force of the motor 11 in forward rotation (in particular, the impact rotational force and the rotational force of the motor 11 in forward rotation following the impact rotational force).

[0061] (1-6-4) Continuation of the reversal After the control unit 15 rotates the motor 11 in the reverse direction, the control unit 15 continues the reverse rotation state of the motor 11 until the forward rotation condition is satisfied.

[0062] (1-6-4a) Forward rotation condition The forward rotation condition is a condition for rotating the motor 11 forward when the motor 11 is rotating in reverse (in other words, for reversing the state of the motor 11 from a reverse rotation state to a forward rotation state). The forward rotation condition is a condition relating to at least one of, for example, the relationship between the rotation amount and a first predetermined value, the relationship between the amount of decrease in the rotation amount after the motor 11 is rotated in reverse (hereinafter, may be simply referred to as "decrease amount") and a second predetermined value, and the relationship between the reverse rotation time (hereinafter, may be simply referred to as "reverse rotation time"), which is the elapsed time after the motor 11 is rotated in reverse, and a third predetermined value.

[0063] When at least one of the rotation amount, the reduction amount, and the reverse rotation time satisfies the forward rotation condition, the control unit 15 rotates the motor 11 forward (reverses the state of the motor 11 from the reverse rotation state to the forward rotation state).

[0064] (1-6-4b) Forward command, direction flag, and current command value When the motor 11 is in a reverse rotation state, if the forward rotation condition is satisfied, the control unit 15 outputs a command (forward rotation command) to the motor 11 to reverse the motor 11 from the reverse rotation state to the forward rotation state, thereby reversing the state of the motor 11 from the reverse rotation state to the forward rotation state.

[0065] The forward rotation command is preferably associated with a direction flag indicating forward rotation and a current command value (for example, a positive sign and absolute value of the current) for controlling the amount of rotation of the motor 11 in the forward rotation.

[0066] (2)Details Next, the impact tool 1 will be described in detail with reference to Figures 1, 2, 5 and 6. Note that in the following, descriptions of matters that have already been mentioned will be omitted or simplified.

[0067] 1, the impact tool 1 further includes a tool body 100 and an output shaft 101. The tool body 100 houses the elements shown in FIG. 2, namely, the motor 11, the impact rotation mechanism 12, the detection unit 13, the measurement unit 14, the control unit 15, and a part of the output shaft 101.

[0068] A battery pack 102 is detachably attached to the tool body 100. 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.

[0069] The output shaft 101 outputs a rotational force and an impact rotational force.

[0070] In detail, the tightening operation is performed by applying the impact rotational force output from the output shaft 101 and the subsequent rotational force of the motor 11 in the forward direction to the object to be tightened via the tip tool attached to the output shaft 101.

[0071] The physical quantity to be detected by the sensor described above is the strain of the output shaft 101. The sensor includes a strain sensor. The strain sensor detects the strain of the output shaft 101. The measurement unit 14 identifies the time when the output signal of the strain sensor rises in response to the impact rotational force as the start time T0 of the tightening operation (see FIG. 5).

[0072] By using a strain sensor, the delay time due to inertia can be reduced compared to when an acceleration sensor is used, for example, resulting in faster detection of the impact action and ultimately in more accurate tightening action.

[0073] (2-1) Hardware that realizes each part (2-1-1) Detection unit The detection unit 13 is realized by 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 angle of rotation, detection of the rotation number, which is the number of rotations, detection of the rotation speed, which is the rotation angle or number of rotations per unit time, and detection of the rotation direction (forward or reverse).

[0074] The rotation sensor in this embodiment is an encoder that detects the number of rotations of the motor 11 and outputs a count value. The encoder is, for example, an optical encoder.

[0075] (2-1-2) Measurement section The measurement unit 14 is realized by, for example, a magnetostrictive sensor and a processing circuit. The processing circuit includes, for example, a processor for processing and an internal memory.

[0076] (2-1-3) Control Unit The control unit 15 is realized by, for example, a processor and a memory. The memory stores a program for causing the processor to operate as the control unit 15.

[0077] (2-2) Closing time details As described above, the tightening time Δt1 (see FIG. 6) is the time elapsed from the start time T0 of the tightening operation (see FIG. 5). In this embodiment, the tightening operation is realized by the impact torque caused by the impact operation and the torque of the motor 11 in the forward rotation following the impact torque, so the time elapsed from the start time T0 of the tightening operation is the time elapsed from the start time T0 of the impact operation (start of impact).

[0078] (2-2-1) First tightening time and second tightening time Specifically, the tightening time is the sum of the time during which the impact rotational force due to the impact operation acts on the output shaft 101 (hereinafter, this may be referred to as the "first tightening time") and the time during which the rotational force of the motor 11 in forward rotation acts on the output shaft 101 after the impact operation (i.e., after the impact is completed) (hereinafter, this may be referred to as the "second tightening time").

[0079] The first tightening time is the pulse width of the first pulse component P1 due to the impact torque, as shown in Fig. 5. The second tightening time is the pulse width of the second pulse component P2 due to the torque of the motor 11 in the forward rotation following the impact torque, as shown in Fig. 5.

[0080] (2-2-2) Details of tightening time measurement The measurement unit 14 identifies the time point at which the first pulse component P1 caused by the impact rotational force rises as the start time T0 of the tightening operation, measures the elapsed time from the identified start time T0, and outputs the measured tightening time to the control unit 15.

[0081] (2-3) Details of the change The change amount used in the reverse rotation control is the increase in the amount of rotation in the forward direction from the start time T0 of the tightening operation. The detection unit 13 detects the increase in the amount of rotation in the forward direction of the motor 11 from the start time T0 of the tightening operation identified by the measurement unit 14.

[0082] (2-4) Details of the reversal conditions The reversal conditions specifically include a first reversal condition, a second reversal condition, and a third reversal condition.

[0083] (2-4-1) First reversal condition The first reversal condition is a condition relating to the relationship between the amount of rotation and a first threshold value. In this embodiment, the first reversal condition is a condition relating to the magnitude relationship between the amount of rotation and the first threshold value, and specifically, a condition that "the amount of rotation is equal to or greater than the first threshold value." The first threshold value is, for example, 130 times, but is not limited to 130 times.

[0084] (2-4-2) Second reversal condition The second reversal condition is a condition related to the relationship between the increase amount and the second threshold. In this embodiment, the second reversal condition is a condition related to the magnitude relationship between the increase amount and the second threshold, and specifically, a condition that "the increase amount becomes equal to or greater than the second threshold." The second threshold is, for example, 15 times, but is not limited to 15 times.

[0085] (2-4-3) Third reversal condition The third reversal condition is a condition relating to the relationship between the tightening time and the third threshold. In this embodiment, the third reversal condition is a condition relating to the magnitude relationship between the tightening time and the third threshold, and specifically, a condition that "the tightening time is equal to or greater than the third threshold." The third threshold is, for example, 100 msec, but is not limited to 100 msec.

[0086] (2-5) Details of reverse control When the motor 11 is rotating forward (the state of the motor 11 is in the forward rotation state), the control unit 15 reverses the motor 11 (reverses the state of the motor 11 from the forward rotation state to the reverse rotation state) if at least one of the first reverse rotation condition, the second reverse rotation condition, and the third reverse rotation condition is satisfied.

[0087] "When at least one of the first reversal condition, the second reversal condition, and the third reversal condition is satisfied" means, for example, when any one of the first reversal condition to the third reversal condition is satisfied.

[0088] However, "when at least one of the first reversal condition, the second reversal condition, and the third reversal condition is satisfied" may mean, for example, when either the first reversal condition or the second reversal condition and the third condition are satisfied, or when all of the first reversal condition, the second reversal condition, and the third reversal condition are satisfied.

[0089] (2-5-1) First example of reverse control In this specific example, the control unit 15 sequentially makes three determinations corresponding to the first to third reverse rotation conditions. Then, when it is determined that any one of the reverse rotation conditions is satisfied, that is, when the amount of rotation reaches the first threshold, the increase amount reaches the second threshold, or the tightening time reaches the third threshold, the control unit 15 reverses the motor 11.

[0090] (2-5-2) Second example of reverse control In this specific example, the first reverse condition is a condition that the amount of rotation is equal to or greater than a first threshold value, the second reverse condition is a condition that the amount of increase is equal to or greater than a second threshold value, and the third reverse condition is a condition that at least one of the duration of the tightening time during which the first reverse condition is satisfied (first duration) and the duration of the tightening time during which the second reversal condition is satisfied (second duration) is equal to or greater than a third threshold value.

[0091] When the motor 11 is rotating forward, the control unit 15 reverses the rotation of the motor 11 if the duration of at least one of the states in which the rotation amount is equal to or greater than the first threshold value and the increase amount is equal to or greater than the second threshold value reaches a third threshold value.

[0092] (2-6) Advantages of the reversal conditions, including the first to third reversal conditions According to this embodiment, the reversal conditions include the first to third reversal conditions, and when the motor 11 is rotating forward, the control unit 15 reverses the motor 11 (reverses it from the forward rotation state to the reverse rotation state) if at least one of the first to third reversal conditions is satisfied, thereby achieving an accurate tightening operation (for example, tightening operation with torque of different magnitudes depending on the type of object) using at least one of the impact rotational force and the subsequent rotational force of the motor 11 in the forward rotation.

[0093] Furthermore, by having the first reverse condition be a condition regarding the magnitude relationship between the rotation amount and the first threshold value, the second reverse condition be a condition regarding the magnitude relationship between the increase amount and the second threshold value, and the third reverse condition be a condition regarding the magnitude relationship between the tightening time and the third threshold value, it is possible to achieve accurate tightening operation while avoiding the complexity of the reverse control.

[0094] (2-7) Details of forward rotation conditions More specifically, the forward rotation conditions include a first forward rotation condition, a second forward rotation condition, and a third forward rotation condition.

[0095] (2-7-1) First forward rotation condition The first normal rotation condition is a condition regarding the relationship between the rotation amount and a first predetermined value. In this embodiment, the first normal rotation condition is a condition regarding the magnitude relationship between the rotation amount and the first predetermined value, and specifically, a condition that "the rotation amount becomes equal to or less than the first predetermined value." The first predetermined value is, for example, 100 times, but is not limited to 100 times.

[0096] (2-7-2) Second forward rotation condition The second normal rotation condition is a condition relating to the relationship between the amount of decrease and a second predetermined value. In this embodiment, the second normal rotation condition is a condition relating to the magnitude relationship between the amount of decrease and the second predetermined value, and specifically, a condition that "the amount of decrease is equal to or greater than the second predetermined value." The second predetermined value is, for example, 25 times, but is not limited to 25 times.

[0097] (2-7-3) Third forward rotation condition The third forward rotation condition is a condition relating to the relationship between the reverse rotation time and a third predetermined value. In this embodiment, the third forward rotation condition is a condition relating to the magnitude relationship between the reverse rotation time and the third predetermined value, and specifically, a condition that "the reverse rotation time is equal to or greater than the third predetermined value." The third predetermined value is, for example, 100 msec, but is not limited to 100 msec.

[0098] (2-8) Forward rotation control details When the motor 11 is rotating in reverse (the state of the motor 11 is in a reverse rotation state), the control unit 15 rotates the motor 11 in the forward direction (reverses the state of the motor 11 from the reverse rotation state to the forward rotation state) if at least one of the first forward rotation condition, the second forward rotation condition, and the third forward rotation condition is satisfied.

[0099] "When at least one of the first, second, and third forward rotation conditions is satisfied" means, for example, when any one of the first to third forward rotation conditions is satisfied. However, "when at least one of the first, second, and third forward rotation conditions is satisfied" may also mean, for example, when either one of the first and second forward rotation conditions and the third condition are satisfied, or when all of the first to third forward rotation conditions are satisfied.

[0100] In this way, after the reverse rotation control, the reverse rotation state of the motor 11 is continued until the forward rotation condition regarding the relationship between at least one of the rotation amount, the reduction amount, and the reverse rotation time and a predetermined value is satisfied, thereby achieving the tightening operation with an appropriate tightening torque after the state of the motor 11 is reversed from the reverse rotation state to the forward rotation state.

[0101] Furthermore, by changing the predetermined value, it is possible to achieve a tightening operation with a more accurate tightening torque.

[0102] (2-9) Measurement unit details 1 As mentioned above, the sensor that realizes the measuring unit 14 is a magnetostrictive sensor. The magnetostrictive sensor magnetically detects the strain of the output shaft 101 that changes in response to the tightening operation (more specifically, the first tightening operation caused by the impact rotation force of the impact rotation mechanism 12, and the second tightening operation caused by the rotation force of the motor 11 in the forward direction following the impact rotation force).

[0103] (2-9-1) Processing circuit The measurement unit 14 further includes a processing circuit. The processing circuit processes the output signal of the sensor. In this embodiment, the processing circuit identifies the start time T0 of the impact motion (see FIG. 5) based on the output signal of the magnetostrictive sensor, for example, the voltage waveform shown in FIG. 5, and measures the elapsed time from the start time T0.

[0104] The voltage waveform in FIG. 5, with the horizontal axis representing time and the vertical axis representing voltage, shows the time change in the voltage of the output signal from the magnetostrictive sensor in response to the tightening operation, and therefore the time change in the strain occurring in the output shaft 101.

[0105] (2-10) Details of the detection section 1: Detection of increase from the start When the motor 11 is rotating in the forward direction, the detection unit 13 detects the increase in the amount of rotation from the start time T0 of the tightening operation identified by the measurement unit 14 as described above.

[0106] In this way, by using the magnetostrictive sensor to quickly detect the start of the tightening operation (i.e., the start of impact) and identifying the detected point in time when the impact starts as the start point T0 of the tightening operation, it is possible to improve the accuracy of identifying the start point T0 of the tightening operation and, in turn, the accuracy of measuring the tightening time.

[0107] (2-11) Measuring tightening torque The measurement unit 14 repeatedly measures the tightening torque at a predetermined cycle based on the output signal from the magnetostrictive sensor, and acquires a plurality of measurement values. The acquired plurality of measurement values ​​are stored in chronological order in the internal memory of the measurement unit 14. Then, when the reversal condition is satisfied (i.e., the tightening operation is completed), the measurement unit 14 may determine the measurement value of the tightening torque related to the impact operation based on the plurality of measurement values ​​stored in the internal memory.

[0108] (2-12) Details of the detection section 2: Identifying the time of change The detection unit 13 further identifies the time point of change. The time point of change is the time point after the start time T0 of the tightening operation when the rotation amount changes from an increasing state, in which the rotation amount is increasing, to a no-change state, in which the rotation amount is unchanged. The no-change state is a state in which the change in the rotation amount is equal to or less than a threshold value. The threshold value is a positive value such as 1 / 100 or 1 / 10, but it can also be 0.

[0109] (2-13) Details of the measurement section 2: Measurement of non-change time The measuring unit 14 further measures the no-change time, which is the duration of the no-change state from the point in time of the change identified by the detecting unit 13.

[0110] (2-14) Fourth Reversal Condition The reversal condition in this embodiment further includes a fourth reversal condition. The fourth reversal condition is a condition regarding the relationship between the unchanged time and the fourth threshold. The fourth reversal condition in this embodiment is a condition regarding the magnitude relationship between the unchanged time and the fourth threshold, and specifically, is a condition that "the unchanged time measured by the measurement unit 14 is equal to or greater than the fourth threshold (where the fourth threshold < the third threshold)." The fourth threshold is, for example, 10 msec, but is not limited to 10 msec.

[0111] Even when the fourth reverse rotation condition is satisfied, the control unit 15 reverses the rotation of the motor 11. That is, when at least one of the first reverse rotation condition, the second reverse rotation condition, the third reverse rotation condition, and the fourth reverse rotation condition is satisfied, the motor 11 is reversed.

[0112] In this way, even if the reversal conditions further include a fourth reversal condition, and the fourth reversal condition regarding the relationship between the unchanged time and the reference time is satisfied before the tightening time reaches the third threshold, the motor 11 is reversed, thereby enabling tightening operation with a more appropriate tightening torque.

[0113] (2-15) Details of termination control The termination condition is a condition for terminating the tightening operation. As described above, the termination condition is, for example, a condition relating to at least one of the relationship between the rotation amount and the first target value, the relationship between the increase amount and the second target value, and the relationship between the tightening time and the third target value.

[0114] The termination conditions in this embodiment include a first termination condition relating to the magnitude relationship between the final rotation amount and the first target value, a second termination condition relating to the magnitude relationship between the increase amount and the second target value, and a third termination condition relating to the magnitude relationship between the tightening time and the third target value. The first termination condition is a condition that the rotation amount is equal to or greater than the first target value. The second termination condition is a condition that the increase amount is equal to or greater than the second target value. The third termination condition is a condition that the tightening time is equal to or greater than the third target value.

[0115] The control unit 15 ends the tightening operation when at least one of the first to third end conditions is satisfied.

[0116] Furthermore, when the tightening operation is repeatedly performed, the termination condition may further include a fourth termination condition relating to the relationship between the difference in the amount of rotation between the plurality of tightening operations and a certain value. For example, the fourth termination condition is a condition that "the difference in the amount of rotation between a first tightening operation and a second tightening operation subsequent to the first tightening operation is equal to or less than a certain value." The control unit 15 may terminate the tightening operation even when the fourth termination condition is satisfied.

[0117] This makes it possible to avoid excessive tightening operations and, in turn, to reduce the power consumption of the impact tool 1.

[0118] (3) Example of impact tool operation Next, an example of the operation of the impact tool 1 will be described with reference to Figures 2 to 4. Note that in the following, the description of the matters already mentioned will be omitted or simplified.

[0119] The control unit 15 of the impact tool 1 operates, for example, according to the flowcharts of Figures 3 and 4. The flowcharts of Figures 3 and 4 correspond to tightening control and reverse rotation control. The control unit 15 further executes processing corresponding to termination control in parallel with the processing of the flowcharts of Figures 3 and 4.

[0120] The processes of Figures 3 and 4 are started, for example, in response to the start of a tightening operation using the impact tool 1. The processes of Figures 3 and 4 are repeatedly executed at predetermined intervals. The processes of Figures 3 and 4 are ended, for example, by end control.

[0121] First, the control unit 15 sets an initial value (for example, a predetermined value 110) to a count value, which is a variable indicating the number of rotations of the motor 11 (step S1).

[0122] Next, the control unit 15 sets the direction flag, which indicates the rotation direction of the motor 11, to "normal rotation" (step S2).

[0123] Next, the control unit 15 turns on the motor 11 (step S3), which starts supplying a current to the motor 11 in the forward direction, causing the motor 11 to start rotating in the forward direction.

[0124] Next, the control unit 15 causes the detection unit 13 to start counting the number of rotations of the motor 11 (step S4). In response to the counting result by the detection unit 13, the control unit 15 updates the count value and holds the count value before the update.

[0125] Next, control unit 15 starts calculating the amount of change in the count value, i.e., the difference between the count value before and after the update (step S5). The difference is calculated by subtracting the count value before the update from the count value after the update. Note that if the difference is a positive value, motor 11 is rotating forward, if the difference is 0, motor 11 is stopped, and if the difference is a negative value, motor 11 is rotating reversely.

[0126] Next, the control unit 15 starts processing the output signal of the magnetostrictive sensor (step S6). Next, the control unit 15 determines whether or not the tightening operation has started based on the processing result of step S6 (step S7). If it is determined that the tightening operation has not started (No in step S7), the processing returns to step S7.

[0127] If it is determined in step S7 that the tightening operation has started (Yes), the control unit 15 identifies the start time T0 of the tightening operation (see FIG. 5) and starts measuring the tightening time from the start time T0 (step S8).

[0128] Next, the control unit 15 determines whether to perform a reverse rotation based on at least one of the count value, the amount of change in the count value, and the tightening time (step S9). Then, the control unit 15 determines whether the reverse rotation condition is satisfied (step S10). If it is determined that the reverse rotation condition is not satisfied (No in step S10), the process returns to step S9.

[0129] If it is determined in step S10 that the reverse rotation condition is met (Yes), the control unit 15 causes the measurement unit 14 to measure the tightening torque (step S11). This allows the measurement value of the tightening torque at the time when the reverse rotation condition is met, i.e., immediately before the motor 11 is reversed from the forward rotation state to the reverse rotation state, to be obtained based on the output signal of the magnetostrictive sensor.

[0130] Next, the control unit 15 sets the direction flag to "reverse" (step S12). Then, the control unit 15 determines whether a forward rotation condition (for example, "the amount of rotation has returned to a predetermined value") is satisfied (step S13). If it is determined that the forward rotation condition is not satisfied (No in step S13), the process returns to step S13.

[0131] If it is determined in step S13 that the forward rotation condition is met (Yes), the control unit 15 sets the direction flag to "forward rotation" (step S14). This reverses the state of the motor 11 from the reverse rotation state to the forward rotation state. Then, the process returns to step S9.

[0132] 3 and 4, the measurement of the tightening torque in step S11 may be omitted. Alternatively, in step S11, instead of measuring the tightening torque, the tightening torque may be estimated based on at least one of the rotation amount, the increase amount, and the tightening time.

[0133] (4) Examples of impact tools Next, a specific example of the impact tool 1 will be described with reference to Figures 1, 2, 5 and 6. Note that in the following, descriptions of matters that have already been mentioned will be omitted or simplified.

[0134] (4-1) Specific example of impact rotation mechanism The impact rotation mechanism of this example includes a hammer, an anvil, a spring, gears, etc. The hammer is connected to a motor 11 via a spring, gears, etc., and part of the rotational force of the motor 11 during normal rotation is converted into potential energy of the spring, and then converted into impact rotational force by striking the anvil. The anvil is connected to an output shaft 101, and receives impact rotational force from the hammer and rotates in the normal direction together with the output shaft 101. In this way, an object to be tightened, such as a nut, is tightened by the impact rotational force repeatedly output from the output shaft 101.

[0135] (4-2) Output waveform of magnetostrictive sensor In the graph of Figure 5, the horizontal axis corresponds to time (sec), the vertical axis corresponds to the voltage (V) of the output signal from the measuring unit 14 (magnetostrictive sensor), and the output waveform shows the change in strain over time. The output waveform in Figure 5 includes a first pulse component P1 and a second pulse component P2. The first pulse component P1 corresponds to the strain generated in the anvil in response to the impact torque of the hammer. The second pulse component P2 corresponds to the strain generated in the anvil in response to the torque of the motor 11 in the forward rotation following the impact torque.

[0136] (4-3) Relationship between motor rotation amount, motor current command value, and motor rotation speed The graph in Fig. 6 shows the relationship between the amount of rotation of motor 11 (encoder count value), the current command value to motor 11, and the rotation speed of motor 11. Fig. 6 shows a waveform indicated by a dashed line indicating a change in the count value, a waveform indicated by a dashed line indicating a change in the current command value from control unit 15 to motor 11, and a waveform indicated by a solid line indicating a change in the rotation speed of motor 11.

[0137] In the graph of Fig. 6, the horizontal axis corresponds to time (msec), the left vertical axis corresponds to the count value (times), and the right vertical axis corresponds to the current command value (mA) and rotation speed (rpm). The current command value is associated with a positive sign indicating a forward direction or a negative sign indicating a reverse direction. However, in the graph of Fig. 6, for convenience, the absolute value of the current command value is shown by a dashed-dotted waveform, and the direction of the current is shown by an increase or decrease in the rotation speed of the motor 11 according to the current command value.

[0138] (4-3-1) Relationship between current command value and rotation speed 6, the rotation speed of motor 11 changes according to the change in the current command value, as shown by the waveform indicated by the solid line. Comparing the waveform indicated by the dashed line with the waveform indicated by the solid line, it can be seen that the change in the rotation speed of motor 11 is delayed relative to the change in the current command value.

[0139] Specifically, for example, at 20 msec when the current command value (waveform of the dashed line) first reaches a maximum, the rotational speed of motor 11 (waveform of the solid line) is increasing, and at 80 msec when the current command value is decreasing, the rotational speed reaches a maximum value of 2500 rpm.

[0140] (4-3-2) Relationship between rotation amount, current command value, and rotation speed In the initial state, that is, when the time is 0, the direction flag is "forward rotation," the current command value is 600 mA, the rotation speed is 0, and the count value is the initial value 110. In other words, initially, the motor 11 is in a forward rotation state, but the rotation speed is 0 and the number of rotations is 110.

[0141] At 10 msec, the current command value begins to rise, and the rotation speed begins to increase. At 20 msec, when the current command value reaches its first maximum value of 1500 mA (however, the direction flag is "forward"), the rotation speed of the motor 11 is increasing toward the maximum value of 2500 rpm, and the count value (waveform indicated by the dashed line) begins to rise.

[0142] At 110 ms, when the current command value reaches its second maximum value of 1200 mA, the rotation speed is maintained at the maximum value of 2500 rpm and the count value continues to rise. Then, at 150 ms, when the count value reaches 130 and goes from the rising state to a static state, the current command value begins to rise again.

[0143] Furthermore, at 160 msec after the no-change state continues for 10 msec (i.e., the fourth reverse rotation condition is satisfied), the direction flag changes from "forward rotation" to "reverse rotation" and the current command value reaches the third maximum value of 1500 mA. In response to this, the motor 11 rotates in the reverse direction (i.e., reverses from the forward rotation state to the reverse rotation state), and the count value returns from 130 to the initial value of 110.

[0144] The 10 msec period from the time point of 150 msec to the time point of 160 msec as described above is the tightening time Δt1 of the first tightening operation.

[0145] When the first tightening operation is completed and the count value returns from 130 to the initial value 110 (i.e., the forward rotation condition is satisfied), the direction flag is changed from "reverse" to "forward rotation," while the current command value suddenly drops to 600 mA and the rotation speed becomes 0. As a result, the motor 11 is in the forward rotation state, but the rotation speed is 0 and the number of rotations is 110, i.e., it returns to the initial state.

[0146] Thereafter, the count value remains at 110. At 260 msec, when the fastening time of the fastening operation by the torque of the motor 11 in forward rotation from 160 msec when the motor 11 reverses from reverse rotation to forward rotation reaches 100 msec (i.e., the third reverse rotation condition is satisfied), the direction flag is changed from "forward rotation" to "reverse rotation," and the current command value rises to the fourth maximum value of 1700 mA. In response to this, the motor 11 enters the reverse rotation state, and the rotation speed rises to 1000 rpm.

[0147] Thereafter, the current command value drops to 600 mA, the rotation speed becomes 0, and the count value decreases. Then, at 400 msec, when the count value decreases by the predetermined value of 10 from 110 and returns to 100 (i.e., the forward rotation condition is satisfied), the direction flag changes from "reverse" to "forward rotation," and the current command value rises to the fifth maximum value of 2000 mA. In response, the motor 11 rotates forward (i.e., reverses from reverse rotation to forward rotation), and the rotation speed increases toward 2500 rpm. Thereafter, the current command value decreases, while the count value increases.

[0148] The current command value begins to increase at 490 ms, when the count value reaches 110 and changes from an increasing state to a stationary state. After this stationary state continues for 10 ms (i.e., the fourth reverse rotation condition is met), at 500 ms, the direction flag changes from "forward" to "reverse," and the current command value reaches its sixth maximum value of 2000 mA. Immediately after reaching the sixth maximum value of 2000 mA, the current command value suddenly drops to 600, the rotation speed becomes 0, and the count value remains at 110.

[0149] The 10 msec period from the time point of 490 msec to the time point of 500 msec as described above is the tightening time Δt1 of the second tightening operation.

[0150] Thereafter, the same operations as those performed immediately after the first tightening operation (at 160 msec) and immediately before the second tightening operation (at 490 msec) are repeated.

[0151] Alternatively, instead of repeating the same operation from 160 msec to 490 msec, the count value immediately after the first tightening operation is 110, and the count value immediately after the second tightening operation is also 110, so it is determined that the fourth termination condition is met and the impact tool 1 may stop operating.

[0152] (5) Control method of impact tool The control method for the impact tool 1 includes a detection step, a control step, and a measurement step. The detection step corresponds to steps S1 to S5 in the flowcharts of Figures 3 and 4. In the detection steps S1 to S5, the rotation amount and the change in the rotation amount of the motor 11 or the impact rotation mechanism 12 are detected.

[0153] The control steps correspond to steps S9, S10, and S12 in the flowcharts of Figures 3 and 4. In control steps S9, S10, and S12, the motor 11 is controlled so that a tightening operation is performed to tighten the object using at least one of the impact rotation force generated by the impact operation of the impact rotation mechanism 12 and the rotation force of the motor 11.

[0154] The measurement steps correspond to steps S6 to S8 in the flowcharts of Figures 3 and 4. In the measurement steps S6 to S8, the tightening time of the tightening operation is measured.

[0155] In control steps S9, S10, and S12, when the motor 11 is rotating forward (the state of the motor 11 is in a forward rotation state), if a reversal condition regarding the relationship between at least one of the rotation amount, the increase amount, and the tightening time and a threshold value is satisfied, the motor 11 is reversed (the state of the motor 11 is reversed from the forward rotation state to the reverse rotation state).

[0156] According to the control method of the impact tool 1, in control steps S9, S10, and S12, when at least one of the detection results (e.g., rotation amount and change in rotation amount) of the detection steps S1 to S5 and the measurement results (e.g., tightening time) of the measurement steps S6 to S8 satisfies the reversal condition, reverse control is performed to reverse the motor 11, thereby achieving accurate tightening operation using the impact rotational force of the impact rotation mechanism 12 and the rotational force of the motor 11 in forward rotation following the impact rotational force.

[0157] (6) Variations Next, various modified examples will be described. Note that in the following, explanations of commonalities with the embodiment will be omitted or simplified, and differences will be described in detail.

[0158] (6-1) Modified example of the detection unit In the embodiment, the detector 13 detects the amount of rotation of the motor 11, but in this modification, the detector 13 may detect the amount of rotation of the impact rotation mechanism 12 or the amount of rotation of the output shaft 101.

[0159] In the embodiment, the rotation sensor that realizes the detection unit 13 detects the amount of rotation and the amount of change in the amount of rotation of the motor 11, but in this modified example, it may also detect the amount of rotation and the amount of change in the amount of rotation of the impact rotation mechanism 12, or the amount of rotation and the amount of change in the amount of rotation of the output shaft 101.

[0160] In the embodiment, the rotation sensor is an optical encoder, but in this modification, it may be a magnetic or electric encoder.

[0161] (6-2) Modified example of the measuring unit The measuring unit 14 may be realized by a strain sensor other than a magnetostrictive sensor. A strain sensor other than a magnetostrictive sensor is, for example, a strain gauge that electrically detects strain, but is not limited to a strain gauge.

[0162] Alternatively, the measuring unit 14 may be, for example, an impact sensor (acceleration sensor) that detects an impact (characteristic acceleration) caused by a hitting motion.

[0163] The sensor may or may not be a component of the measuring unit 14. The sensor may, for example, be an internal component of the impact tool 1, separate from the measuring unit 14. Alternatively, the sensor may be an external component attached to the impact tool 1.

[0164] (6-3) Modified method of measuring tightening torque In the embodiment, the tightening torque is measured based on the output signal of the magnetostrictive sensor, but in this modification, the tightening torque may be estimated based on at least one of the rotation amount, the increase amount, and the tightening time.

[0165] The control unit 15 of this modified example estimates the tightening torque of the tightening operation based on at least one of the rotation amount, the increase amount, and the tightening time (for example, the rotation amount). Specifically, a set of pairs of the rotation amount and the estimated value of the tightening torque is stored in the memory, and the control unit 15 may acquire from the memory the estimated value paired with the rotation amount detected by the detection unit 13 (that is, the estimated value associated with the rotation amount that is closest to the rotation amount detected by the detection unit 13 among the multiple rotation amounts stored).

[0166] (6-4) Modified examples of tightening operation In the embodiment, the tightening operation is performed by the impact rotational force of the impact rotation mechanism 12 and the rotational force of the motor 11 in forward rotation following the impact rotational force, but in this modified example, the tightening operation may be performed by either of two types of force: the impact rotational force of the impact rotation mechanism 12 and the rotational force of the motor 11 in forward rotation.

[0167] In this modified example, specifically, the type of force used for tightening changes depending on the mode. More specifically, in the normal mode, the control unit 15 of this modified example performs the tightening operation using the impact rotational force of the impact rotation mechanism 12 and the rotational force of the motor 11 in the forward rotation following the impact rotational force, as in the control unit 15 of the embodiment, but may perform the tightening operation using only the impact rotational force in the large torque mode and only the rotational force of the motor 11 in the forward rotation in the small torque mode.

[0168] The tightening time in the normal mode may be the sum of the pulse width of the first pulse component P1 and the pulse width of the second pulse component P2, while the tightening time in the large torque mode may be the pulse width of the first pulse component P1, and the tightening time in the small torque mode may be the pulse width of the second pulse component P2.

[0169] (6-5) Modified examples of tightening control The control unit 15 may perform tightening torque control and termination control based on the amount of rotation and the amount of increase. Specifically, the control unit 15 of this modified example performs tightening torque control based on the amount of increase until the amount of rotation reaches a first target value, and performs termination control when the amount of rotation reaches the first target value. Alternatively, the control unit 15 of this modified example may perform tightening torque control based on the amount of increase until the amount of increase reaches a second target value, and performs termination control when the amount of increase reaches the second target value.

[0170] (6-6) Variations of the reversal condition In the embodiment, the reverse rotation conditions include first to third reverse rotation conditions, and when at least one of the first to third reverse rotation conditions is satisfied while motor 11 is rotating forward, control unit 15 reverses motor 11. In contrast, in this modified example, the reverse rotation conditions may include two or one of the first to third reverse rotation conditions, and control unit 15 may reverse motor 11 when at least one of the two or one conditions included in the reverse rotation conditions is satisfied while motor 11 is rotating forward.

[0171] (6-7) Modification of the predetermined value included in the forward rotation condition In the embodiment, the predetermined value included in the forward rotation condition is a fixed value (constant), but in this modified example, it may be a value (variable) that changes depending on the tightening torque. Specifically, the predetermined value when tightening with a large torque (for example, in the large torque mode) may be larger than the predetermined value when tightening with a small torque (for example, in the small torque mode).

[0172] (7) Summary The impact tool (1) according to the first aspect includes a motor (11), an impact rotation mechanism (12), a detection unit (13), a control unit (15), and a measurement unit (14). The motor (11) is capable of rotating in both forward and reverse directions. The impact rotation mechanism (12) receives rotational force from the motor (11) and performs an impact operation using rotational inertia force while repeatedly rotating in forward and reverse directions. The detection unit (13) detects the amount of rotation and the amount of change in the amount of rotation of the motor (11) or the impact rotation mechanism (12). The control unit (15) controls the motor (11) so that a tightening operation is performed to tighten an object using at least one of the impact rotation force generated by the impact operation of the impact rotation mechanism (12) and the rotation force generated by the forward rotation of the motor (11). The measurement unit (14) measures the tightening time (Δt1) of the tightening operation. When the motor (11) is rotating forward, the control unit (15) reverses the rotation of the motor (11) if a reversal condition is satisfied regarding at least one of the relationship between the rotation amount and the first threshold value, the relationship between the change amount and the second threshold value, and the relationship between the tightening time (Δt1) and the third threshold value.

[0173] According to this aspect, the control unit (15) reverses the motor (11) (performs reverse control) when at least one of the amount of rotation and the amount of change in the amount of rotation detected by the detection unit (13) and the tightening time (Δt1) measured by the measurement unit (14) satisfies a reversal condition relative to a threshold value, thereby achieving accurate tightening operation using at least one of the impact rotational force of the impact rotation mechanism (12) and the rotational force of the motor (11) in forward rotation (in particular, the impact rotational force and the rotational force of the motor 11 in forward rotation following the impact rotational force).

[0174] In the impact tool (1) according to the second aspect, in the first aspect, the control unit (15) controls the motor (11) to perform the tightening operation based on at least one of the rotation amount, the change amount, and the tightening time (Δt1).

[0175] According to this aspect, by controlling the motor 11 (performing tightening control) so that the tightening operation described above is performed based on at least one of the rotation amount, the change amount, and the tightening time (Δt1), it is possible to achieve a more accurate tightening operation.

[0176] In the impact tool (1) according to the third aspect, in the second aspect, the tightening operation includes an operation of tightening an object using the impact rotational force due to the impact operation of the impact rotation mechanism (12) and the rotational force of the motor (11) in the forward rotation after the impact operation.

[0177] According to this embodiment, it is possible to achieve a more accurate tightening operation by using the impact rotation force of the impact rotation mechanism (12) and the rotation force of the motor (11) in the forward rotation.

[0178] In the impact tool (1) according to the fourth aspect, in the first to third aspects, the tightening time (Δt1) is the elapsed time from the start time (T0) of the tightening operation. The change amount is the increase in the amount of rotation in forward rotation from the start time (T0). The reverse rotation conditions include one or more of a first reverse rotation condition, a second reverse rotation condition, and a third reverse rotation condition. The first reverse rotation condition is a condition regarding the relationship between the amount of rotation and a first threshold value. The second reverse rotation condition is a condition regarding the relationship between the increase amount and a second threshold value. The third reverse rotation condition is a condition regarding the relationship between the tightening time (Δt1) and a third threshold value. When the motor (11) is rotating forward, the control unit (15) reverses the motor (11) if at least one of the one or more conditions is satisfied.

[0179] According to this aspect, the reversal conditions include the first to third reversal conditions, and when the motor (11) is rotating in the forward direction, the control unit (15) reverses the rotation of the motor (11) (reverses the motor from the forward rotation state to the reverse rotation state) if at least one of the first to third reversal conditions is satisfied, thereby achieving an accurate tightening operation (for example, tightening operation with torque of a magnitude that varies depending on the type of object) using at least one of the impact rotational force and the subsequent rotational force of the motor (11) in the forward rotation.

[0180] In the impact tool (1) according to the fifth aspect, in the fourth aspect, the first reverse rotation condition is that the amount of rotation detected by the detection unit (13) is equal to or greater than a first threshold value, the second reverse rotation condition is that the amount of increase detected by the detection unit (13) is equal to or greater than a second threshold value, and the third reverse rotation condition is that the tightening time (Δt1) measured by the measurement unit (14) is equal to or greater than a third threshold value.

[0181] According to this aspect, the first reverse condition is a condition relating to the magnitude relationship between the rotation amount and the first threshold value, the second reverse condition is a condition relating to the increase amount and the second threshold value, and the third reverse condition is a condition relating to the magnitude relationship between the tightening time (Δt1) and the third threshold value, thereby making it possible to achieve accurate tightening operation while avoiding the complexity of reverse control.

[0182] In the impact tool (1) according to a sixth aspect, in the fourth or fifth aspect, the measuring unit (14) is realized by a sensor. The sensor detects a physical quantity that changes in response to the tightening operation and that changes faster than the amount of rotation. The measuring unit (14) identifies a start time (T0) based on a change in the output signal of the sensor in response to the impact rotational force. The detecting unit (13) detects an increase from the start time (T0) identified by the measuring unit (14).

[0183] According to this aspect, by detecting the impact motion at high speed using a sensor and identifying the time when the impact motion is detected as the start time (T0) of the tightening motion, it is possible to improve the accuracy of identifying the start time (T0) of the tightening motion and therefore the measurement accuracy of the tightening time (Δt1).

[0184] The impact tool (1) according to a seventh aspect is the sixth aspect, further including an output shaft (101). The output shaft (101) outputs a rotational force and an impact rotational force. The physical quantity is a strain of the output shaft (101). The sensor includes a strain sensor. The strain sensor detects the strain of the output shaft (101). The measurement unit (14) identifies the time when the output signal of the strain sensor rises in response to the impact rotational force as a start time (T0).

[0185] According to this aspect, by using a strain sensor, the delay time due to inertia can be reduced compared to when an acceleration sensor is used, for example, thereby increasing the detection speed of the impact motion and ultimately improving the measurement accuracy of the tightening time (Δt1).

[0186] In the impact tool (1) according to an eighth aspect, in any one of the fourth to seventh aspects, the detection unit (13) further identifies a change time point. The change time point is a time point after the start time (T0) when the rotation amount changes from an increasing state, in which the rotation amount is increasing, to an unchanged state, in which the rotation amount is unchanged. The measurement unit (14) then measures an unchanged time point. The unchanged time point is the duration of the unchanged state from the change time point identified by the detection unit (13). The reverse rotation condition further includes a fourth reverse rotation condition. The fourth reverse rotation condition is a condition in which the unchanged time measured by the measurement unit (14) is equal to or greater than a fourth threshold value. The fourth threshold value is a value smaller than the third threshold value. The control unit (15) reverses the motor (11) when at least one of the first reverse rotation condition, the second reverse rotation condition, the third reverse rotation condition, and the fourth reverse rotation condition is satisfied while the motor (11) is rotating forward.

[0187] According to this aspect, even if the fourth reversal condition regarding the magnitude relationship between the unchanged time and the reference time is satisfied before the tightening time (Δt1) reaches the third threshold value, the motor (11) is reversed, thereby enabling tightening operation with a more appropriate tightening torque.

[0188] In the impact tool (1) according to a ninth aspect, in any of the first to eighth aspects, after the control unit (15) reverses the motor (11), it continues the reverse rotation state of the motor until a forward rotation condition is satisfied. The forward rotation condition is a condition related to at least one of the relationship between the rotation amount and a first predetermined value, the relationship between the amount of decrease in the rotation amount after the motor (11) is reversed and a second predetermined value, and the relationship between the reverse rotation time, which is the elapsed time after the motor (11) is reversed, and a third predetermined value.

[0189] According to this aspect, by continuing the reverse rotation state of the motor (11) until the forward rotation condition regarding the relationship between at least one of the rotation amount, the reduction amount, and the reverse rotation time and a predetermined value is satisfied, it is possible to achieve an accurate tightening operation by repeating the forward and reverse rotations.

[0190] A control method for an impact tool (1) according to a tenth aspect is a control method for an impact tool (1) including a motor (11) and an impact rotation mechanism (12). The motor (11) is capable of rotating in both forward and reverse directions. The impact rotation mechanism (12) receives rotational force from the motor (11) and performs an impact operation using rotational inertia force while repeatedly rotating in both forward and reverse directions. The control method includes detection steps (S1 to S5), control steps (S9, S10, S12), and measurement steps (S6 to S8). In the detection steps (S1 to S5), the amount of rotation and the amount of change in the amount of rotation of the motor (11) or the impact rotation mechanism (12) are detected. In the control steps (S9, S10, S12), the motor (11) is controlled so that a tightening operation is performed to tighten an object using at least one of the impact rotation force generated by the impact operation of the impact rotation mechanism (12) and the rotation force of the motor (11). In the measurement steps (S6 to S8), the tightening time (Δt1) of the tightening operation is measured. In the control steps (S9, S10, S12), when the motor (11) is rotating forward, if a reversal condition is satisfied regarding at least one of the relationship between the rotation amount and the first threshold value, the relationship between the change amount and the second threshold value, and the relationship between the tightening time (Δt1) and the third threshold value, the motor (11) is rotated in the reverse direction.

[0191] According to this aspect, in the control steps (S9, S10, S12), when at least one of the detection results (e.g., the amount of rotation and the change in the amount of rotation) in the detection steps (S1 to S5) and the measurement results (e.g., the tightening time Δt1) in the measurement steps (S6 to S8) satisfies the reversal condition, a reverse control is performed to reverse the motor (11), thereby realizing an accurate tightening operation using the impact rotational force of the impact rotation mechanism (12) and the rotational force of the motor (11) in the forward rotation following the impact rotational force. [Explanation of symbols]

[0192] 1 impact tool 11 Motor 12 Impact rotation mechanism 13 Detection unit 14 Measurement section 15 Control Unit 101 Output shaft T0 start time Δt1 Fastening time

Claims

1. a motor capable of rotating forward and backward; an impact rotation mechanism that receives rotational force from the motor, repeatedly rotates forward and backward, and performs an impact operation using rotational inertia force; a detection unit that detects the rotation amount of the motor or the impact rotation mechanism and the amount of change in the rotation amount; a control unit that controls the motor so that a tightening operation is performed by using at least one of an impact rotational force due to the impact operation of the impact rotation mechanism and the rotational force during forward rotation of the motor; and a measuring unit that measures the tightening time of the tightening operation, the control unit reverses the rotation of the motor when a reversal condition is satisfied regarding at least one of the relationship between the rotation amount and a first threshold value, the relationship between the change amount and a second threshold value, and the relationship between the tightening time and a third threshold value, while the motor is rotating in the forward direction. Impact tool.

2. the control unit controls the motor so that the tightening operation is performed based on at least one of the rotation amount, the change amount, and the tightening time. The impact tool according to claim 1 .

3. The tightening operation includes an operation of tightening the object by the impact rotation force due to the impact operation of the impact rotation mechanism and the rotation force due to forward rotation of the motor after the impact operation. The impact tool according to claim 2.

4. The tightening time is the elapsed time from the start of the tightening operation, the change amount is an increase in the rotation amount in the forward direction from the start point, The reversal condition is: a first reversal condition regarding the relationship between the rotation amount and a first threshold value; a second reversal condition regarding the relationship between the increase amount and a second threshold value; and one or more conditions among third reversal conditions regarding the relationship between the tightening time and a third threshold value, the control unit causes the motor to rotate in a reverse direction when at least one of the one or more conditions is satisfied while the motor is rotating in a forward direction; The impact tool according to any one of claims 1 to 3.

5. the first reverse rotation condition is a condition that the rotation amount detected by the detection unit is equal to or greater than the first threshold value, the second reversal condition is a condition that the increase amount detected by the detection unit is equal to or greater than the second threshold value, the third reverse rotation condition is a condition that the tightening time measured by the measurement unit is equal to or greater than the third threshold value; 5. The impact tool according to claim 4.

6. The measurement unit The sensor detects a physical quantity that changes in response to the tightening operation and that changes faster than the amount of rotation, Identifying the start time point based on a change in the output signal of the sensor according to the impact rotational force; The detection unit detects the increase amount from the start time point identified by the measurement unit.

5. The impact tool according to claim 4.

7. an output shaft for outputting the rotational force and the impact rotational force; the physical quantity is a strain of the output shaft, the sensor includes a strain sensor that detects strain of the output shaft, the measurement unit identifies a time point at which the output signal of the strain sensor rises in response to the impact rotational force as the start time point.

7. The impact tool according to claim 6.

8. The detection unit further identifies a change time point after the start time point at which the rotation amount changes from an increasing state where the rotation amount is increasing to a no-change state where the rotation amount is not changing, The measurement unit further measures a no-change time, which is a duration of the no-change state from the change time point identified by the detection unit, the reversal condition further includes a fourth reversal condition that the unchanged time measured by the measurement unit is equal to or greater than a fourth threshold value that is smaller than the third threshold value; the control unit reverses the rotation of the motor when at least one of the first reverse rotation condition, the second reverse rotation condition, the third reverse rotation condition, and the fourth reverse rotation condition is satisfied while the motor is rotating in the forward direction.

5. The impact tool according to claim 4.

9. After the control unit reverses the rotation of the motor, the control unit continues the reverse rotation state of the motor until a forward rotation condition is satisfied regarding at least one of the relationship between the rotation amount and a first predetermined value, the relationship between an amount of decrease in the rotation amount after the motor is reversed and a second predetermined value, and the relationship between a reverse rotation time, which is an elapsed time after the motor is reversed, and a third predetermined value. The impact tool according to claim 1 .

10. A control method for an impact tool including a motor capable of rotating in a forward direction and a reverse direction, and an impact rotation mechanism that receives a rotational force from the motor and performs an impact operation by rotational inertia force while repeatedly rotating in a forward direction and a reverse direction, a detection step of detecting a rotation amount of the motor or the impact rotation mechanism and a change in the rotation amount; a control step of controlling the motor so that a tightening operation is performed by using at least one of an impact rotational force due to the impact operation of the impact rotation mechanism and the rotational force of the motor to tighten the object; a measuring step of measuring a tightening time of the tightening operation, In the control step, when the motor is rotating in the forward direction, the motor is rotated in the reverse direction if a reversal condition is satisfied regarding at least one of the relationship between the rotation amount and a first threshold value, the relationship between the change amount and a second threshold value, and the relationship between the tightening time and a third threshold value. A method for controlling an impact tool.

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