Impact tools

Abstract

To provide an impact tool capable of detecting an impact accurately.SOLUTION: An impact tool includes: a motor 3; a spindle 6 which is rotated by the motor; a hammer 7 which can move in an axial direction and a rotation direction relative to the spindle; an anvil 8 which is provided forward of the hammer and struck by the hammer; a trigger switch 9 which instructs actuation and stop of the motor and instructs change of the rotation number of the motor according to the control input; and a control unit which controls rotation of the motor. The control unit is configured to stop the motor when conditions that an electric current flowing through the motor is higher than or equal to a current threshold and a change rate of the control input of the trigger switch is lower than or equal to a change rate threshold are satisfied.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an impact tool. [Background technology]

[0002] An impact tool tightens a fastening member by striking an anvil with a hammer. The impact tool described in Patent Document 1 prevents overtightening of the fastening member by stopping the motor when it detects that the hammer has struck the anvil a predetermined number of times. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-067910 Summary of the Invention [Problem to be solved by the invention]

[0004] The configuration of Patent Document 1 uses an impact detection sensor to detect impacts, which increases the number of parts and increases costs. Therefore, it is possible to detect impacts based on the current flowing through the motor without using an impact detection sensor. However, impact detection based on simple current alone poses the following problems:

[0005] That is, an impact tool has a trigger that is operated by an operator to start the motor. If the trigger is operated (pulled) a predetermined amount that is smaller than the maximum operation amount to drive the motor, and then the trigger is operated (pulled) further from the predetermined amount, a starting current will flow to the motor twice. Therefore, there is a risk that the second starting current will be mistakenly detected as a current caused by an impact.

[0006] SUMMARY OF THE INVENTION An object of the present invention is to provide an impact tool that is capable of accurately detecting an impact. [Means for solving the problem]

[0007] The present invention provides an impact tool comprising a motor, a rotary impact mechanism that rotary impacts a tool bit by rotation of the motor, a trigger switch that instructs starting and stopping of the motor and instructs changing the rotation speed of the motor according to an amount of operation of the trigger switch, and a control unit that controls the rotation of the motor, wherein the control unit is capable of executing impact detection control, and in the impact detection control, detects a rate of change in the operation amount of the trigger switch and a current flowing through the motor, and determines whether a condition is met in which the current flowing through the motor is equal to or greater than a current threshold while the rate of change in the operation amount of the trigger switch is equal to or less than a change rate threshold, or detects the rate of change in the operation amount of the trigger switch and the rotation speed of the motor, and determines whether a condition is met in which the current flowing through the motor is equal to or greater than a current threshold while the rate of change in the operation amount of the trigger switch is equal to or less than a change rate threshold. rate of change is equal to or less than the change rate threshold value, the rotation speed of the motor is The rotation speed of the motor decreases as the When the condition that the rotational speed is equal to or less than the threshold value is satisfied, it is determined that a rotational impact has been generated by the rotational impact mechanism. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide an impact tool that is capable of accurately detecting an impact. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a side cross-sectional view of an impact tool according to an embodiment of the present invention; [Figure 2] 1 is a circuit block diagram of an impact tool according to an embodiment of the present invention; [Figure 3] FIG. 2 is a first waveform diagram according to the embodiment of the present invention. [Figure 4] FIG. 2 is a second waveform diagram according to the embodiment of the present invention. [Figure 5] FIG. 3 is a third waveform diagram according to the embodiment of the present invention. [Figure 6] FIG. 4 is a fourth waveform diagram according to the embodiment of the present invention. [Figure 7] FIG. 5 is a fifth waveform diagram according to the embodiment of the present invention. [Figure 8] FIG. 6 is a sixth waveform diagram according to the embodiment of the present invention. [Figure 9]3 is a control flowchart according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] In the following, identical or equivalent components, members, etc. shown in each drawing are denoted by the same reference numerals, and redundant explanations will be omitted where appropriate. The embodiments are illustrative and do not limit the invention. All features and combinations thereof described in the embodiments are not necessarily essential to the invention.

[0011] This embodiment relates to an impact tool 1. First, the configuration of the impact tool 1 will be described with reference to FIGS. 1 and 2. FIG. 1 defines the mutually orthogonal front-rear and up-down directions of the impact tool 1. The front-rear direction is a direction substantially parallel to the central axis of the output shaft 3a of the motor 3. The impact tool 1 is an electric tool, and more specifically, a cordless impact wrench. The impact tool 1 has a housing 2. The housing 2 includes a body portion (cylindrical portion) 2a, a handle portion 2b, and a battery pack attachment portion 2c. The body portion 2a is cylindrical, and its central axis is parallel to the front-rear direction. The handle portion 2b extends downward from the middle portion of the body portion 2a. The battery pack attachment portion 2c is provided at the lower end of the handle portion 2b. The body portion 2a, the handle portion 2b, and the battery pack attachment portion 2c form an impact tool main body.

[0012] The body 2a contains, from rear to rear, a sensor / inverter circuit board 12, a motor 3 (rotor and stator), and a rotary impact mechanism 4. The sensor / inverter circuit board 12 is supported by the body 2a so as to be approximately perpendicular to the front-to-rear direction. Specifically, it is screwed to an insulating member fixed to the stator of the motor 3. The output shaft 3a of the motor 3 extends rearward through a through-hole formed in the approximate center of the sensor / inverter circuit board 12. In this example, the motor 3 is an inner-rotor brushless motor. The rotary impact mechanism 4 rotary-impacts the tool bit 11 by the rotation of the motor 3. The rotary impact mechanism 4 includes, from rear to rear, a planetary gear mechanism (reduction mechanism) 5, a spindle 6, a hammer 7, and an anvil 8. The planetary gear mechanism 5 reduces the speed of the motor 3 and transmits it to the spindle 6. The hammer 7 is movable in the front-to-rear direction (axial direction) relative to the spindle 6 and is rotatable together with or relative to the spindle 6, rotating or rotating and striking the anvil 8 provided in front of the hammer 7. The hammer 7 is biased toward the anvil 8 (forward) by a spring. A tip tool 11 such as a socket is attached to the anvil 8.

[0013] A trigger switch 9 is provided at the front upper end of the handle portion 2b. The trigger switch 9 is an operating part that allows the operator to instruct (switch) the operation and stopping of the motor 3. The rotation speed of the motor 3 can be changed by changing the amount of operation of the trigger switch 9. A battery pack 20 is connected to the battery pack attachment portion 2c. The impact tool 1 is driven by power from the battery pack 20. A control board 10 is provided at the top inside the battery pack attachment portion 2c. An operation panel 30 is provided on the top surface of the battery pack attachment portion 2c. The operation panel 30 is an operating part that can switch the drive mode of the impact tool 1 between a continuous mode and an auto-stop mode.

[0014] The continuous mode is a mode in which the motor 3 continues to be driven as long as the trigger switch 9 is pulled (operated to ON). The auto-stop mode is a mode in which the motor 3 is stopped even if the trigger switch 9 is pulled when an impact is detected, such as when a predetermined time has elapsed since the hammer 7 started to strike the anvil 8 (the tool tip 11) (hereinafter referred to as "start of impact"), or when the hammer 7 has struck the anvil 8 a predetermined number of times. The predetermined number of times may be one, two or more.

[0015] The operation panel 30 is provided with a setting changeover switch 31, an auto-stop changeover switch 32, and a display unit 37.

[0016] The setting changeover switch 31 is, for example, a tactile switch, and functions as a switch to change the power or rotation speed of the motor 3 in the continuous mode, and as a switch to change the auto-stop setting (condition) in the auto-stop mode. Each time the setting changeover switch 31 is pressed, the power or auto-stop setting of the motor 3 is changed.

[0017] The auto-stop changeover switch 32 is, for example, a tactile switch that switches between enabling and disabling the auto-stop mode. Every time the auto-stop changeover switch 32 is pressed, the drive mode of the impact tool 1 is switched between the continuous mode and the auto-stop mode.

[0018] The display unit 37 has an indicator LED that indicates whether the auto-stop function is enabled or disabled, and for example lights up red in auto-stop mode and turns off in continuous mode. The display unit 37 also has an indicator LED that indicates the power or setting, and functions as a power indicator that indicates the power of the motor 3 in continuous mode, and as a setting indicator that indicates the auto-stop setting in auto-stop mode. The color of the power or setting indicator LED is, for example, red. The number of power or setting indicator LEDs can be changed as desired depending on the number of power levels of the motor 3 and the number of auto-stop mode settings.

[0019] 2 is a circuit block diagram of the impact tool 1. In the impact tool 1, switching elements Q1 to Q6 provided on a sensor / inverter circuit board 12 are three-phase bridge-connected to form an inverter circuit. The switching elements Q1 to Q6 perform switching operations under the control of a calculation unit 40 and supply drive power to the motor 3. A magnetic sensor 13 provided on the sensor / inverter circuit board 12 is used to detect the rotational position of the motor 3 (rotor) and transmits an electrical signal corresponding to the rotational position of the motor 3 to a rotational position detection circuit 44. The control board 10 is provided with the calculation unit 40 as a control unit, a current detection circuit 41, a switch operation detection circuit 42, a control signal circuit (control signal output circuit) 43, a rotational position detection circuit 44, a rotation speed detection circuit 45, and a memory unit 46.

[0020] The current detection circuit 41 detects the current of the motor 3 from the voltage of a resistor R provided in the current path of the motor 3 and sends the detected signal to the calculation unit 40. The switch operation detection circuit 42 detects the operation of the trigger switch 9 and the amount of operation of the trigger switch 9 and sends the detected signal to the calculation unit 40. The control signal circuit 43 applies a control signal (e.g., a PWM signal) to each control terminal of the switching elements Q1 to Q6 under the control of the calculation unit 40. The rotational position detection circuit 44 detects the rotational position of the motor 3 from a signal from the magnetic sensor 13 and sends the detected signal to the calculation unit 40. The rotation speed detection circuit 45 detects the rotation speed of the motor 3 from the signal from the rotational position detection circuit 44 and sends the detected signal to the calculation unit 40.

[0021] The storage unit 46 is a non-volatile memory that can retain stored information even when power is not supplied to the storage unit 46. The storage unit 46 stores information specific to the impact tool 1, usage history information of the impact tool 1, and settings for the auto-stop mode. The storage unit 46 may be separate from the calculation unit 40 or may be incorporated into the calculation unit 40. The calculation unit 40 includes a microcontroller or the like and operates in a drive mode selected by the operator. In the drive mode, the calculation unit 40 controls the on / off (e.g., PWM control) of the switching elements Q1 to Q6 via the control signal circuit 43 in accordance with the operation of the trigger switch 9, the rotational position and rotation speed of the motor 3, and the current of the motor 3, thereby controlling the drive (output) of the motor 3. The calculation unit 40 also controls the display on the display unit 37 in each drive mode.

[0022] The battery pack 20 includes a battery cell group 21, a calculation unit 22, a memory unit 23, and a remaining capacity display unit 26. The battery cell group 21 includes a plurality of battery cells, such as lithium-ion secondary battery cells, connected to one another. The number of series and parallel connections of the plurality of battery cells may be arbitrary. The calculation unit 22 includes a microcontroller or the like, and communicates (wired communication) with the calculation unit 40 of the impact tool 1 via a communication terminal, and controls the remaining capacity display unit 26. The memory unit 23 stores unique information about the battery pack 20, such as the model name, serial number, and history information. The remaining capacity display unit 26 displays the remaining capacity of the battery cell group 21. The remaining capacity display unit 26 includes a plurality of LEDs and a remaining capacity switch that can be operated by an operator. When the operator operates the remaining capacity switch, a number of LEDs corresponding to the remaining capacity (remaining voltage) of the battery cell group 21 are lit for a predetermined period of time. The battery cell group 21 is configured by connecting the battery pack 20 to the electrical device body according to the rated voltage of the electrical device body such as the impact tool 1 to be connected. In this embodiment, the plurality of battery cells are connected in series via the connection terminals of the main body of the electrical device.

[0023] In the continuous mode, if the calculation unit 40 detects that the setting changeover switch 31 is pressed when the power of the motor 3 is other than the strongest (power 4), the calculation unit 40 increases the power of the motor 3 by one level. In the continuous mode, if the calculation unit 40 detects that the setting changeover switch 31 is pressed when the power of the motor 3 is the strongest, the calculation unit 40 changes the power of the motor 3 to the weakest (power 1). The number of power levels of the motor 3 is arbitrary.

[0024] In the auto-stop mode, when the calculation unit 40 detects that the setting switch 31 is pressed, it switches the auto-stop setting. For example, there are four auto-stop settings, Settings 1 to 4. For example, Setting 1 stops the motor 3 after a first predetermined time, e.g., 0.5 seconds, has elapsed since the hammer 7 struck the anvil 8. Setting 2 stops the motor 3 after a second predetermined time, e.g., 1.0 seconds, which is longer than the first predetermined time, has elapsed since the hammer 7 struck the anvil 8. Setting 3 stops the motor 3 after a third predetermined time, e.g., 1.5 seconds, has elapsed since the hammer 7 struck the anvil 8. Setting 4 stops the motor 3 after a third predetermined time, e.g., 2.0 seconds, has elapsed since the hammer 7 struck the anvil 8. The strike may be one or two or more times, and the motor 3 may be stopped after a predetermined time has elapsed since the first strike (detection). Alternatively, the motor 3 may be stopped based on the number of strikes rather than a predetermined time. The number of strikes and the time from the occurrence of a strike (strike detection) to the stopping of the motor 3 can be set arbitrarily and are not limited to the above.

[0025] Furthermore, when the calculation unit 40 detects a short press of the auto-stop changeover switch 32 in the continuous mode, it transitions to the auto-stop mode, and when the calculation unit 40 detects a short press of the auto-stop changeover switch 32 in the auto-stop mode, it transitions to the continuous mode.

[0026] Next, the control of the impact tool 1, particularly the control of the auto-stop mode (single-shot mode) in which the motor 3 is automatically stopped after an impact, will be described with reference to Figures 3 to 9. The calculation unit 40 detects the impact of the hammer 7 on the anvil 8 based on both information from the current detection circuit 41 and information from the switch operation detection circuit 42. These two pieces of information make it possible to suppress erroneous detection while the motor 3 is running, thereby enabling accurate impact detection. In the auto-stop mode, after an impact is detected, the motor 3 is stopped under the conditions set by the setting changeover switch 31.

[0027] 3 to 5 show, from top to bottom, the current flowing through motor 3, the operation amount (pull amount, shown by Tr1, Tr2, Tr3, and solid lines) of trigger switch 9, the rate of change of the operation amount of trigger switch 9 (shown by ΔT1, ΔT2, and dashed dotted lines), the duty of the PWM signals of switching elements Q1 to Q6, and the rotation speed of motor 3, when trigger switch 9 is operated a predetermined amount to drive motor 3 and then operated again. The horizontal axis represents time, and the vertical axis represents the current value, the operation amount (pull amount) of the trigger switch, the rate of change of the operation amount of the trigger switch, the duty, and the rotation speed of motor 3, respectively.

[0028] FIG. 3 shows the state where the trigger switch 9 is changed from a first state, in which the amount of operation (pulling amount) is small (for example, about one-quarter of the amount of operation), to a second state, in which the amount of operation is maximized. At time t0, the operator slightly operates the trigger switch 9 to set it to the initial state Tr1. The motor 3 rotates at rotation speed N1 due to duty D1, which corresponds to the amount of operation of the trigger switch 9 (until time t1). Since the motor 3 starts rotating from a stopped state, a starting current flows when the trigger switch 9 is operated at time t0. Although the starting current is greater than the impact detection threshold, this starting current is ignored for a predetermined time after the initial operation of the trigger switch 9. This allows the motor 3 to continue rotating without erroneously detecting the starting current as a current caused by an impact.

[0029] Subsequently, at time t1, when the operator further operates the trigger switch 9 from the initial state Tr1 (operation amount Tr3), the duty and rotation speed increase in response to the operation of the trigger switch 9. At this time, the motor 3 changes from low speed to high speed, and a starting current flows, just as at time t0. This starting current also exceeds the impact detection threshold at time t2, when the trigger switch 9 reaches the operation amount Tr2. Therefore, in a configuration that detects an impact based solely on the current flowing through the motor 3, there is a risk that this second starting current will be mistakenly detected as a current caused by an impact.

[0030] Therefore, in addition to this current, the present invention is configured so that the calculation unit 40 calculates the rate of change of the operation amount (pulling amount) of the trigger switch 9, and determines that the anvil 8 has been struck by the hammer 7 if the two conditions of the current being equal to or greater than the impact detection threshold and the rate of change of the operation amount of the trigger switch 9 being equal to or less than the threshold (ΔT) are met.

[0031] 3, at time t2, the current exceeds the impact detection threshold, but because the rate of change ΔT2 of the amount of operation of the trigger switch 9 is greater than the threshold ΔT, it is not detected as an impact. In other words, the calculation unit 40 determines that the increase in current at time t2 is due to a large operation of the trigger switch 9, and does not determine it as an impact.

[0032] After the second startup current flows at time t2, the trigger switch 9 is in the maximum operation state Tr3, and the rotation speed of the motor 3 reaches the maximum rotation speed N3. At this time, the duty also becomes the maximum duty D3, and the current also becomes a value greater than the current up to time t1.

[0033] Until time t3, the hammer 7 and anvil 8 rotate together to tighten a fastener (e.g., a bolt). At time t3, the bolt is tightened, and the rotation of the anvil 8 is prevented. The hammer 7 then moves backward relative to the anvil 8 against the biasing force of the spring. As a result, from time t3 to time t5, the rotation speed of the motor 3 gradually decreases from N4, and the current also increases. At time t5, when the claw of the hammer 7 overcomes the claw of the anvil 8, the hammer 7 rotates while moving forward due to the biasing force of the spring. The rotation speed of the motor 3 increases again from N4 to N3, and the current decreases. At time t6, the hammer 7 (claw) strikes the anvil 8 (claw). At time t4, when the operation transitions to the striking operation, the current exceeds the strike detection threshold, and the amount of operation of the trigger switch 9 is at its maximum. Therefore, the rate of change in the amount of operation of the trigger switch 9 is zero, i.e., is below the threshold ΔT for the amount of change in the amount of operation of the trigger switch 9. Therefore, the calculation unit 40 determines that an impact (start of striking) has occurred at time t4.

[0034] After the first impact is detected, multiple impacts are performed, but detailed waveforms are omitted. Note that the first impact causes the highest current value, and subsequent impacts result in a current that does not generate a current peak as shown in the figure, and may even be higher than the current up to time t3. After detecting the first impact, the calculation unit 40 automatically stops the motor 3 at time t7, a preset time after impact detection time t4. This allows for accurate impact detection. In auto-stop mode, it is possible to prevent over-tightening or under-tightening of bolts, etc.

[0035] The impact detection operation when the auto-stop mode is set will be described using the flowchart in FIG. 9. This is executed by the calculation unit 40. When the calculation unit 40 starts up, it executes the impact detection process of the impact detection control flow (S100). The calculation unit 40 determines whether the trigger switch 9 has been operated by the operator (S101). If the trigger switch 9 has not been operated (NO in S101), the process returns to S100. If the trigger switch 9 has been operated (YES in S101), a starting current flows through the motor 3 as the motor 3 starts up. Therefore, to avoid falsely detecting this starting current as a current due to an impact, the calculation unit 40 does not process the signal from the current detection circuit 41 and does not detect a current for a predetermined time (e.g., 200 milliseconds) after the trigger switch 9 is operated (S102).

[0036] Thereafter, based on the signal from the current detection circuit 41, it is determined whether the current is equal to or greater than the impact detection threshold (S103). If the current is equal to or greater than the impact detection threshold (YES in S103), it is determined whether the rate of change in the amount of operation of the trigger switch 9 is equal to or less than the threshold (S104). If the rate of change in the amount of operation of the trigger switch 9 is equal to or less than the threshold (YES in S104), the calculation unit 40 determines that an impact between the hammer 7 and the anvil 8 has occurred, and proceeds to the auto-stop mode control flow. On the other hand, if the result is NO in S103 or NO in S104, the calculation unit 40 returns to S103.

[0037] In the auto-stop control flow, the calculation unit 40 reads out the auto-stop setting conditions set by the setting switch 31 before driving the impact tool 1, for example, from the storage unit 46, and sets them (S105). Then, it determines whether the conditions set in S105 are met. For example, it determines whether a predetermined set time of 1.0 seconds has elapsed since the first impact was detected (S106). If the set time has not elapsed (NO in S106), S106 is repeated. If the set time has elapsed (YES in S106), the motor 3 is stopped (S107), and the auto-stop process is terminated (S108).

[0038] Figure 4 shows waveforms similar to those in Figure 3, showing the case where the initial amount of operation of the trigger switch 9 is larger than in Figure 3, and the trigger switch is changed from the first state, where it is operated by about half the amount of operation, to the second state, where the amount of operation is at its maximum. In this case, as in Figure 3, when the trigger switch 9 is operated again at time t1, a starting current flows to the motor 3, but because the rate of change in the amount of operation of the trigger switch 9 exceeds the threshold value ΔT, it is not determined to be a current caused by an impact. The situation from time t3 onwards is the same as in Figure 3.

[0039] Figure 5 shows the case where the initial amount of operation of the trigger switch 9 is larger than in Figure 4, and the trigger switch is changed from the first state, where it is operated by about three-quarters of the amount of operation, to the second state, where the amount of operation is maximized. Because the motor 3 is already rotating at rotation speed N1, which is close to the maximum rotation speed N3, when the trigger switch 9 is in the first state, even when the trigger switch 9 is changed to the second state at time t1, a starting current flows to the motor 3, but it is below the impact detection threshold. Furthermore, the rate of change in the amount of operation of the trigger switch 9 is also below the threshold ΔT. Therefore, the starting current caused by the second operation of the trigger switch 9 is ignored. The situation from time t3 onwards is the same as in Figures 3 and 4.

[0040] As described above, according to the present invention, an impact is detected not only based on the current flowing through the motor 3, but also based on the rate of change in the amount of operation of the trigger switch 9. Therefore, an impact can be accurately detected without erroneously detecting a second operation of the trigger switch 9 while the motor 3 is running as an impact.

[0041] By detecting the rate of change in the amount of operation of the trigger switch 9, it is possible to detect an impact even when the motor 3 is driven with the trigger switch 9 at its initial operation amount (first state) that is smaller than the maximum amount of operation. In addition to detecting the current of the motor 3, it is also possible to detect the amount of operation of the trigger switch 9. For example, an impact may be detected when the amount of operation is equal to or greater than a predetermined value and the current of the motor 3 is equal to or greater than a threshold value. However, in this case, if the amount of operation is small, such as in the case of Figure 3, the condition that the amount of operation is equal to or greater than a predetermined value is not met, and an impact cannot be detected. On the other hand, it is also possible to detect an impact when the amount of operation of the trigger switch 9 is equal to or less than a predetermined value and the current of the motor 3 is equal to or greater than a threshold value. However, conversely, in the case of Figure 5 or when the amount of operation of the trigger switch 9 is set to its maximum, an impact cannot be detected. Therefore, by detecting the rate of change in the amount of operation of the trigger switch 9, it is possible to accurately detect an impact regardless of the magnitude of the amount of operation of the trigger switch 9.

[0042] Figures 6 to 8 show the waveforms of impact detection in three states where the operation amount of the trigger switch 9 is different. Figure 6 shows the case where the operation amount Tr1 of the trigger switch 9 is small (for example, one-fourth of the maximum operation amount). When the trigger switch 9 is operated at time t0, a starting current flows and the motor 3 begins to operate, rotating at duty D1 and rotation speed N1. Note that the starting current is not detected (ignored) for a predetermined time from the first operation of the trigger switch 9 or the start of the motor 3. At time t1, the bolt is tightened and the rotation of the anvil 8 begins. When the hammer 7 is blocked, it retreats relative to the anvil 8. As a result, from time t1 to time t3, the rotation speed of the motor 3 gradually decreases from N1 to N2, and the current also increases. When the claw of the hammer 7 passes over the claw of the anvil 8 at time t3, the rotation speed of the motor 3 increases again from N2 to N1, and the current decreases. At time t4, the hammer 7 (claw) strikes the anvil 8 (claw). At time t2, when the impact operation begins, the current exceeds the impact detection threshold, and the operation amount of the trigger switch 9 remains unchanged from the initial Tr1. The rate of change in the operation amount of the trigger switch 9 is zero, i.e., it is below the threshold ΔT for the change in the operation amount of the trigger switch 9. Therefore, the calculation unit 40 determines that an impact (start of impact) has occurred at time t4. The operation after the first impact detection is the same as in Figures 3 to 5.

[0043] Fig. 7 shows a case where the operation amount Tr1 of the trigger switch 9 is medium (for example, half the maximum operation amount), while Fig. 8 shows a case where the operation amount Tr1 of the trigger switch 9 is large (for example, the maximum operation amount). In these cases, as in Fig. 6, the operation amount of the trigger switch 9 does not change after the motor 3 is started, so the rate of change in the operation amount of the trigger switch 9 is zero, and as in Fig. 6, if the current of the motor 3 exceeds the impact detection threshold, the calculation unit 40 determines that an impact has occurred.

[0044] 6 to 8, impact detection and auto-stop control are also executed according to the flowchart in Fig. 9. In this case, S104 is always YES, so if the current of motor 3 is equal to or greater than the impact detection threshold in S103 (YES in S103), the process proceeds to the auto-stop control flow. Therefore, by using two conditions, the current of motor 3 and the rate of change in the amount of operation of trigger switch 9, it is possible to accurately detect an impact regardless of the amount of operation of trigger switch 9.

[0045] In this embodiment, an impact wrench has been described as an example of an impact tool, but the present invention can also be applied to devices that drive a tool bit by impact, such as impact drivers and hammer drills. Furthermore, the impact detection may be based on a change in rotation speed rather than current. Since the rotation speed decreases when an impact occurs, an impact may be determined when the decreased rotation speed is equal to or less than a rotation speed threshold and the rate of change in the amount of operation of the trigger switch is equal to or less than a threshold. In S103 of FIG. 9, an impact may be detected based on rotation speed instead of current. [Explanation of symbols]

[0046] 1...impact tool, 2...housing, 3...motor, 4...rotary impact mechanism, 5...reduction mechanism, 6...spindle, 7...hammer, 9...trigger switch, 10...control board, 11...tipped tool, 12...sensor inverter circuit board, 13...magnetic sensor, 20...battery pack, 21...battery cell assembly, 22...calculation unit, 23...storage unit, 26...remaining charge display unit, 30...operation panel, 31...setting changeover switch, 32...auto-stop changeover switch, 37...display unit

Claims

1. A motor; a rotary impact mechanism that rotates and impacts the tool bit by rotation of the motor; a trigger switch that commands the start and stop of the motor and commands the change of the rotation speed of the motor according to the amount of operation; a control unit that controls the rotation of the motor; An impact tool comprising: The control unit is capable of executing impact detection control, and is configured to detect a rate of change in the operation amount of the trigger switch and a current flowing through the motor in the impact detection control, and determine that a rotary impact has occurred by the rotary impact mechanism when a condition is satisfied in which the current flowing through the motor is equal to or greater than a current threshold while the rate of change in the operation amount of the trigger switch is equal to or less than a change rate threshold, or when a condition is satisfied in which the motor rotation speed decreases while the rate of change in the operation amount of the trigger switch is equal to or less than the change rate threshold and the reduced motor rotation speed is equal to or less than a rotation speed threshold.

2. The impact tool according to claim 1, The impact tool is characterized in that the control unit is configured to determine whether or not a rotary impact has occurred by the rotary impact mechanism, regardless of whether the amount of operation of the trigger switch is at its maximum amount or at half of its maximum amount, during the impact detection control.

3. The impact tool according to claim 1, The impact tool is characterized in that the control unit is configured to determine whether or not a rotational impact has occurred by the rotary impact mechanism, regardless of whether the amount of operation of the trigger switch is at its maximum amount or at one-fourth of the maximum amount of operation, during the impact detection control.

4. The impact tool according to claim 1, The impact tool is characterized in that the control unit is configured to determine whether or not a rotary impact has occurred by the rotary impact mechanism, regardless of the amount of operation of the trigger switch, during the impact detection control.

5. The impact tool according to claim 1, The control unit is capable of executing auto-stop control, and is configured to stop the motor in the auto-stop control when a predetermined time has elapsed since the start of rotary impact by the rotary impact mechanism, or when a predetermined number of rotary impacts by the rotary impact mechanism have occurred, even if the trigger switch is operated.

6. The impact tool according to claim 1, The impact tool is characterized in that the rotary impact mechanism includes a reduction mechanism that reduces the rotation of the motor, a spindle to which the rotation of the motor is transmitted from the reduction mechanism, a hammer that is movable in the forward / backward direction and in the rotational direction relative to the spindle, and an anvil that is rotated or rotary impacted by the hammer.

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