JP7040987B2 - Electric tool - Google Patents

Description

The present invention relates to a power tool driven by a motor.

As an electric tool that is rotated by a motor and is configured to apply an intermittent striking force in the direction of rotation when a torque exceeding a predetermined value is applied, screws, nuts, etc. are fastened with a high torque using the striking force. A rotary striking tool called an impact driver is known.

When using an impact driver to fasten a fastened member with a fastening member such as a screw or nut, the worker usually turns off the trigger switch after confirming that the screw or nut is seated by the worker himself / herself. And stopped the motor.

However, when the work is performed on the concrete mold or the like whose predetermined interval is maintained by the separator, which cannot maintain the proper quality due to excessive tightening of the fastening member, the operator's judgment is made. In the configuration in which the rotation of the motor is stopped by the operation according to the above, it is difficult to suppress excessive tightening, and in order to suppress excessive tightening, if the timing for stopping the motor is advanced, the tightening force is insufficient.

Therefore, as a technique for controlling the tightening of the rotary impact tool, a technique for detecting an impact and controlling the rotation of the motor has been proposed. For example, Patent Document 1 describes the maximum value and the minimum value of the rotation speed of the motor. A technique for detecting a blow from a difference has been proposed. Further, in Patent Document 2, an upper limit threshold value and a lower limit threshold value are set for a pulsation value such as a current value, a voltage value, and a motor rotation speed, and when the pulsation value exceeds the upper limit threshold value and then falls below the lower limit threshold value, a blow is applied. Techniques for detection have been proposed.

Japanese Patent No. 5784473 Japanese Patent No. 5841011

Generally, the rotation speed of a motor is determined by detecting the rotation speed of the motor, but the higher the rotation speed of the motor, the worse the detection accuracy. Therefore, in Patent Document 1, an attempt is made to detect an impact from the difference between the maximum value and the minimum value of the rotation speed of the motor, but when the rotation speed of the motor becomes high, it becomes difficult to detect a large extreme value difference. It is difficult to detect hits in a stable manner. In addition, with a power tool that can arbitrarily adjust the rotation speed by operating the trigger switch of the operator, the rotation speed fluctuates regardless of the impact load depending on the rotation speed during driving and the state of acceleration, deceleration, etc. It is difficult to detect the impact stably even under the conditions.

Further, the pulsating value such as the current value, the voltage value, and the rotation speed of the motor greatly fluctuates depending on the rotation speed of the motor and the magnitude of the load due to the member to be fastened. Therefore, in Patent Document 2, an attempt is made to detect an impact by setting an upper limit threshold value and a lower limit threshold value for the pulsation value, but it is difficult to stably detect an impact under any conditions.

The present invention has been made to solve such a problem, and an object of the present invention is to provide a power tool capable of stably detecting an impact.

In order to solve the above-mentioned problems, the present invention has a motor that drives the driven unit, a striking unit that strikes the driven unit, an operation unit that operates the motor, and a control unit that controls the motor by operating the operation unit. The control unit has a current value acquisition unit that acquires the current value flowing through the motor, an extreme value detection unit that detects the extreme value of the current value acquired by the current value acquisition unit, and an extreme value detection unit. When it is detected, it is equipped with a impact detection unit that detects the presence or absence of impact by the impact unit from the current value acquired by the current value acquisition unit after detecting the extreme value , and the control unit is operated by the operation unit to drive the motor. , The current value acquisition unit acquires the current value flowing through the motor, the current value acquisition unit detects the extreme value of the current value, and the current value acquisition unit detects the extreme value, and then the current value acquisition unit acquires the current value. When the impact detection unit detects the presence or absence of an impact, the number of impact detections is added, and when the added number of impact detections reaches the set multiple times, the motor is stopped or decelerated, and the control unit controls the operation unit. When the motor is driven by operation, the current acquisition unit acquires the current value flowing through the motor, and if the fluctuation amount of the current value acquired by the current acquisition unit is less than or equal to the specified value for detecting no impact, no impact is generated. An electric tool that updates the detection counter and resets the number of hit detections when the extreme value is not detected because there is no hit for a predetermined time and the hitless detection counter is greater than or equal to the specified value for resetting the number of hit detections. Is.
Further, the present invention includes a motor for driving the driven unit, a striking unit for striking the driven unit, an operation unit for operating the motor, and a control unit for controlling the motor by operating the operation unit. , The current value acquisition unit that acquires the current value flowing through the motor, the extreme value detection unit that detects the extreme value of the current value acquired by the current value acquisition unit, and the extreme value detection unit that detects the extreme value, the extreme value It is equipped with a striking detection unit that detects the presence or absence of a striking by the striking unit from the current value acquired by the current value acquisition unit after detection. The current value that flows is acquired, the extreme value of the current value acquired by the current value acquisition unit is detected by the extreme value detection unit, and after the extreme value is detected, the impact detection unit detects the current value acquired by the current value acquisition unit. When the presence is detected, the number of impact detections is added, and when the added number of impact detections reaches the set multiple times, the motor is stopped or decelerated, and the control unit responds to the elapsed time from the start of driving the motor. This is an electric tool that changes the number of impact detections for stopping or decelerating the motor .

In the present invention, when the operation unit is operated, the motor rotates. When the motor rotates, the current value flowing through the motor is acquired by the current value acquisition unit, and the extreme value of the current value acquired by the current value acquisition unit is detected by the extreme value detection unit. When the extreme value is detected by the extreme value detection unit, the impact detection unit detects that the impact is generated by the impact unit from the current value acquired by the current value acquisition unit after the extreme value is detected. When it is detected that there is a hit, the number of hits detected is added, and it becomes possible to control the drive of the motor according to the number of hits detected.

In the present invention, by detecting the presence or absence of a hit by the amount of change in the current value from the extreme value of the current flowing through the motor, the detection accuracy according to the rotation speed of the motor arbitrarily operated by the operator and the occurrence for each hit occur. By suppressing the influence of the magnitude of the pulsation of the current value, it becomes possible to stably detect the impact due to the impact load.

It is an overall block diagram which shows an example of the impact driver of this embodiment. It is an external side view which shows an example of the impact driver of this embodiment. It is an external rear view which shows an example of the impact driver of this embodiment. It is a functional block diagram which shows an example of the control function of the impact driver of this embodiment. It is a flowchart which shows an example of the operation of the impact driver of this embodiment. It is a flowchart which shows an example of a blow detection process. It is a graph which shows the change of the current value with a blow. It is a graph which shows the change of the number of times of hitting detection with hitting detection. FIG. 7 is an enlarged view of part A in FIG. It is a flowchart which shows an example of the hitless detection process. It is a graph which shows the change of the current value at the time of starting a motor drive. It is a flowchart which shows an example of the detection completion count update process. It is a graph which shows the change of the current value with the impact when the impact is detected after the lapse of a specified value for updating the number of impact detections. It is a graph which shows the change of the hit detection number with the hit detection when the hit is detected after the hit detection number update specified value elapses.

Hereinafter, an impact driver as a rotary striking tool, which is an example of an embodiment of the power tool of the present invention, will be described with reference to the drawings.

<Structure example of the impact driver of this embodiment>
FIG. 1 is an overall configuration diagram showing an example of an impact driver according to the present embodiment, FIG. 2 is an external side view showing an example of an impact driver according to the present embodiment, and FIG. 3 is an external side view showing an example of the impact driver according to the present embodiment. It is an external rear view which shows an example.

The impact driver 1A of the present embodiment includes a motor 2 and a fan 3 for cooling the motor 2 and the like. Further, the impact driver 1A includes an anvil 6 in which the driving force of the motor 2 is transmitted via the speed reducer 4 and the hammer unit 5.

The motor 2 is composed of a brushless motor in this example, and includes a rotor 20 provided with a permanent magnet 20b on a rotating shaft 20a and a stator 21 provided with a drive coil 21a. The motor 2 causes the rotor 20 to rotate in the forward direction or the reverse direction by passing a current through the plurality of drive coils 21a in a predetermined pattern. The fan 3 is attached to the rotating shaft 20a of the motor 2 and rotates integrally with the rotor 20.

The speed reducer 4 includes an input shaft 40 provided with a sun gear (not shown), an output shaft 41 provided with a planetary gear 41a that meshes with the sun gear, and an outer gear 42 that meshes with the planetary gear 41a. In the speed reducer 4, the input shaft 40 is connected to the rotating shaft 20a of the motor 2.

The hammer unit 5 is an example of a striking portion, and includes a hammer 51a that applies a striking force in a rotational direction to an anvil 6 that is a driven portion, and a compression spring 51b that urges the hammer 51a in a direction approaching the anvil 6. In the hammer unit 5, the hammer 51a is supported by the output shaft 41 of the speed reducer 4, the hammer 51a rotates together with the output shaft 41 of the speed reducer 4, and moves along the axial direction of the output shaft 41.

When a load equal to or greater than a predetermined load is applied to the anvil 6, the hammer unit 5 retracts while compressing the compression spring 51b, so that the locking between the anvil 6 and the hammer 51a in the rotational direction is temporarily released. .. After the locking of the anvil 6 and the hammer 51a in the rotational direction is temporarily released, the hammer 51a advances by the force restored by the compression spring 51b, and the hammer 51a hits the anvil 6 in the rotational direction.

The driving force of the motor 2 is transmitted to the anvil 6 via the speed reducer 4 and the hammer unit 5 to rotate, and when a predetermined load or more is applied, the anvil 6 is hit by the hammer 51a in the rotational direction. By attaching a bit or socket (not shown) to the anvil 6 in a detachable manner, it is possible to fasten a screw to an object to be fastened while applying a impact in the rotational direction.

The impact driver 1A includes a trigger switch 7 which is an example of an operation unit in which an operation for operating the motor 2 is performed, and a first button switch 8a and a second button switch in which an operation for switching the rotation direction of the motor 2 is performed. 8b is provided. As the first button switch 8a and the second button switch 8b, a momentary switch is used in which a signal can be output only when a push operation is performed, and a momentary switch is used in which a signal is not output and is turned off when the push operation is released.

The trigger switch 7 includes a load sensor 70 and a trigger lever 71 that pushes the load sensor 70. When the load sensor 70 is pushed by the trigger switch 7 via the trigger lever 71, the resistance value changes according to the load, and a predetermined signal is output.

The impact driver 1A includes a battery mounting portion 9 to which a battery 90, which is a power source, can be detachably mounted. Further, the impact driver 1A includes a housing 10 constituting the exterior, and a handle 10H provided with a trigger lever 71, a button 81a of the first button switch 8a, a button 81b of the second button switch 8b, and the like.

The handle 10H extends from the housing 10 in a direction intersecting the axial direction along the rotation shaft 20a of the motor 2 at a predetermined angle. In the impact driver 1A, the direction along the axial direction of the motor 2 is the front-rear direction, and the side where the anvil 6 is provided is the front side. Further, the impact driver 1A has a left-right direction as a direction intersecting the axial direction of the motor 2 and the extending direction of the handle 10H.

The impact driver 1A is provided with a trigger lever 71 of the trigger switch 7 on the upper front surface of the handle 10H, and a button 81a of the first button switch 8a is provided on one of the upper both side surfaces of the handle 10H. On the other hand, the button 81b of the second button switch 8b is provided.

FIG. 4 is a functional block diagram showing an example of the control function of the impact driver of the present embodiment. The impact driver 1A is a motor controlled by a control unit 100 that controls the motor 2 and the like in response to the operation of the trigger switch 7, the operation of the first button switch 8a, and the operation of the second button switch 8b, and the control unit 100. A drive unit 110 for driving 2 is provided.

The control unit 100 includes a current value acquisition unit 100a for acquiring the current value flowing through the motor 2, an extreme value detection unit 100b for detecting the extreme value of the current value acquired by the current value acquisition unit 100a, and an extreme value detection unit 100b. Based on the detected extreme value, the impact detecting unit 100c for detecting the presence or absence of an impact from the current value acquired by the current value acquiring unit 100a after the detection of the extreme value is provided.

Further, the control unit 100 sets various operations such as the rotation direction of the motor 2 set by the first button switch 8a and the second button switch 8b, and detects the current value and the extreme value acquired by the current value acquisition unit 100a. A storage unit 101 is provided for storing the extreme value of the current value detected by the unit 100b and the number of impact detections detected by the impact detection unit 100c. The storage unit 101 retains storage of various operation settings and the like even in a predetermined hibernation state and in a power cutoff state in which the battery 90 is removed from the impact driver 1A and the power supply is cut off.

The current value acquisition unit 100a includes a first filter 120a and a second filter 120b configured by a low-pass filter. The current value acquisition unit 100a acquires the current value flowing through the motor 2 by blocking components higher than the first threshold value with the first filter 120a from the voltage value when the drive unit 110 drives the motor 2. do. Further, the second filter 120b acquires a current value in which a component in a region higher than the second threshold value lower than the first threshold value is cut off.

The control unit 100 uses the current value processed by the first filter 120a for the extreme value detection by the extreme value detection unit 100b and the impact detection by the impact detection unit 100c.

Further, there is a difference between the current value processed by the first filter 120a and the current value processed by the second filter 120b between the case where the fluctuation amount of the current value is large and the case where the fluctuation amount of the current value is small, and the fluctuation amount of the current value becomes large. When it is large, the difference in current value is larger than when it is small. Therefore, the control unit 100 uses the current value processed by the first filter 120a and the current value processed by the second filter 120b to cause fluctuations in the current value due to impact and fluctuations in current values other than impact. To distinguish.

The extreme value detecting unit 100b compares the magnitude of the current value acquired by the current value acquiring unit 100a and detects the extreme value of the current value.

Explaining the extreme value of the current value, when the motor 2 is driven, the current value flowing through the motor 2 changes as the load increases or decreases. The current value at the point where the current value flowing through the motor 2 changes from rising to decreasing, the current value at the point where it changes from decreasing to increasing is called an extreme value, and the value changing from rising to decreasing is called the maximum value, and the value changing from decreasing to increasing is called the maximum value. The value that changes to is called the minimum value.

In the present embodiment, when the control unit 100 detects that the current value flowing through the motor 2 has reached the maximum value by the extreme value detection unit 100b, the operation of hitting the anvil 6 with the hammer 51a is performed. Set to the reference current value to judge whether or not it has been damaged.

The impact detection unit 100c determines that an impact has occurred when the current value drops by a predetermined value with respect to the maximum value which is the reference current value in this example. The amount of current decrease that is judged to have a hit is called the current specified value. For the current specified value, for example, the fluctuation of the current value due to the impact of the hammer 51a on the anvil 6 is obtained in advance by an experiment or the like, and the value is set as the current specified value, for example, a current drop of 3 A or more.

When the control unit 100 determines that there is a hit, the hit detection number stored in the storage unit 101 is updated (added), and when the hit detection number reaches a specified value, the rotation of the motor 2 is stopped or decelerated. The number of hit detections that stop or decelerate the rotation of the motor 2 is referred to as the number of detection completions.

The impact driver 1A includes an output unit 102 that outputs the contents of the setting. The output unit 102 is composed of, for example, a lamp such as an LED, and visually displays and outputs the contents of the setting depending on whether or not the lamp is lit, blinking, and whether or not a plurality of lamps are lit.

The control unit 100 assigns the first button switch 8a and the second button switch 8b an operation of switching between forward rotation and reverse rotation of the motor 2.

In the following description, the state in which the trigger switch 7 is pressed is turned on, and the state in which the trigger switch 7 is not pressed is turned off. Further, the state in which the first button switch 8a and the second button switch 8b are pressed is turned on, and the state in which the first button switch 8a and the second button switch 8b are pressed is turned off.

When the first button switch 8a is turned on, the control unit 100 sets the rotation direction of the motor 2 to normal rotation, and stores the set rotation direction in the storage unit 101. As a result, even if the first button switch 8a is turned off by releasing the finger from the button 81a or the like, the setting of the rotation direction is maintained.

When the second button switch 8b is turned on, the rotation direction of the motor 2 is set to reverse, and the set rotation direction is stored in the storage unit 101. As a result, even if the second button switch 8b is turned off by releasing the finger from the button 81b or the like, the setting of the rotation direction is maintained. The rotation direction settings of the first button switch 8a and the second button switch 8b may be reversed.

When the trigger switch 7 is turned on, the control unit 100 rotates the motor 2 in the rotation direction set by the first button switch 8a or the second button switch 8b. Further, the rotation speed of the motor 2 is controlled by the magnitude of the force applied to the load sensor 70 by the trigger switch 7. The control unit 100 may display and output the set rotation direction of the motor 2 by the output unit 102.

<Operation example of the impact driver of this embodiment>
FIG. 5 is a flowchart showing an example of the operation of the impact driver of the present embodiment, and the embodiment of the operation of stopping the rotation of the motor 2 by detecting the impact will be described below with reference to each figure.

In step SA1 of FIG. 5, the control unit 100 acquires the current value flowing through the motor 2 by the current value acquisition unit 100a when the motor 2 is driven by the drive unit 110. The control unit 100 acquires the current value every predetermined acquisition time and stores it in the storage unit 101. The predetermined acquisition time is set, for example, every 1 msec.

When the trigger switch 7 is turned on in step SA2, the control unit 100 drives the motor 2 by the drive unit 110 in step SA3, and controls the rotation speed of the motor 2 according to the load detected by the trigger switch 7.

The control unit 100 performs an impact detection process for detecting the presence or absence of an impact on the anvil 6 by the hammer 51a in step SA4 from the current value acquired by the current value acquisition unit 100a. Further, the control unit 100 performs a no-hit detection process in step SA5 so as not to detect the fluctuation of the current value at the start of driving of the motor 2 as a hit. Further, the control unit 100 performs a detection completion number update process for updating the number of hit detections for stopping the drive of the motor 2 in step SA6 from the time for driving the motor 2.

When the control unit 100 determines in step SA7 that the number of hit detections detected in the hit detection process has reached the number of detection completions updated in the detection completion number update process, the control unit 100 stops driving the motor 2 in step SA8.

FIG. 6 is a flowchart showing an example of the hit detection process, and details of the hit detection process in step SA4 will be described below.

In step SA41 of FIG. 6, the control unit 100 detects whether or not the current value acquired by the current value acquisition unit 100a is the maximum value, by the extreme value detection unit 100b. To detect whether or not the current value is the maximum value, the current values acquired at predetermined acquisition times are compared, and when the current value acquired this time is lower than the current value acquired last time, the current value acquired last time becomes Detects that it is a maximum value.

When the extremum detection unit 100b detects that the current value acquired by the current value acquisition unit 100a is the maximum value, the control unit 100 updates the maximum value of the current stored in the storage unit 101 in step SA42.

In step SA43, the control unit 100 determines whether or not the current value acquired by the current value acquisition unit 100a after the detection of the maximum value has decreased from the reference current value by the current specified value or more, with the maximum value as the reference current value.

When the current value acquired after the detection of the maximum value drops by the current specified value or more, the control unit 100 determines that there has been a hit, and adds the number of hit detections in step SA44.

The control unit 100 determines in step SA45 whether the false detection prevention time, which will be described later, has elapsed, and when the false detection prevention time has elapsed, the next maximum value can be updated in step SA46.

FIG. 7 is a graph showing changes in the current value due to impact, with the vertical axis showing the current value and the horizontal axis showing the time. Further, FIG. 8 is a graph showing changes in the number of hits detected with hit detection, with the vertical axis showing the number of hits detected and the horizontal axis showing the time. Further, FIG. 9 is an enlarged view of part A in FIG. 7.

In the impact driver 1A, when the object to be fastened is fastened by the fastening member and the rotation of the fastening member is restricted, the rotation of the motor 2 is continued and a load is applied to the anvil 6. When a load of a predetermined value or more is applied to the anvil 6, the hammer 51a retracts while compressing the compression spring 51b, so that the load applied to the motor 2 increases. When the load applied to the motor 2 increases, the current value increases as shown in FIGS. 7 and 9.

When the hammer 51a retracts while compressing the compression spring 51b to temporarily release the locking of the anvil 6 and the hammer 51a in the rotational direction, the load applied to the motor 2 is reduced and the current value is reduced. ..

Further, after the locking of the anvil 6 and the hammer 51a in the rotational direction is temporarily released, the hammer 51a advances by the force restored by the compression spring 51b, and the hammer 51a hits the anvil 6 in the rotational direction.

In this way, when the anvil 6 is hit by the hammer 51a, the current value flowing through the motor 2 rises, and the current value becomes maximum immediately before the locking of the anvil 6 and the hammer 51a in the rotational direction is temporarily released. After reaching a value, it decreases.

Therefore, it is detected that the current value flowing through the motor 2 has reached the maximum value, the maximum value is set as the reference current value, and the current value acquired by the current value acquisition unit 100a after the detection of the maximum value is defined as the current from the reference current value. When the value drops by more than the value, it is determined that there has been a hit, and the number of hit detections is updated as shown in FIG.

As shown in FIG. 9, the current value increases or decreases due to the fluctuation of the load applied to the motor 2 before the locking of the anvil 6 and the hammer 51a in the rotational direction is temporarily released, and the maximum value increases. May be detected.

In such a case, after the detection of the maximum value (1), the current value acquired by the current value acquisition unit 100a does not decrease from the maximum value (1) by the current specified value or more, and the next maximum value (2) is detected. Ru. As a result, the maximum value is updated. However, even after the detection of the maximum value (2), the current value acquired by the current value acquisition unit 100a does not decrease from the maximum value 2 by the current specified value or more, and the next maximum value (3) is detected. As a result, the maximum value is updated.

Then, after the detection of the maximum value (3), when the current value acquired by the current value acquisition unit 100a drops by the current specified value or more from the maximum value (3), it is determined that there is a hit.

Further, after the driving of the motor 2 is started and before the object to be fastened is fastened by the fastening member, the current value may change so that the maximum value is detected. In order not to detect such a change in the current value as the maximum value, the detection start threshold value of the maximum value is set, and after the current value reaches the detection start threshold value, the detection of the maximum value is started. The detection start threshold is set to, for example, 10A.

Further, after detecting that the impact has been made, and then before the locking of the anvil 6 and the hammer 51a in the rotational direction is temporarily released, the load applied to the motor 2 fluctuates, so that the current value is increased. May increase or decrease, and a maximum value may be detected.

Therefore, the false detection prevention time is set according to the hit interval expected when continuous hits are performed, and after detecting that there is a hit, it is determined whether the false detection prevention time has elapsed to prevent false detection. When time elapses, the next maximum value can be updated to prevent erroneous detection of the presence or absence of a hit. The erroneous detection prevention time is determined based on, for example, the time at which the anchor 6 and the hammer 51a are released from being locked in the rotational direction after hitting the anvil 6 with the hammer 51a, and is set to, for example, 10 msec.

FIG. 10 is a flowchart showing an example of the no-battery detection process, and details of the no-battery detection process in step SA5 will be described below. The no-hit detection process indicates a process of resetting the number of hit detections when no hit is detected for a predetermined time.

The control unit 100 acquires the current value processed by the first filter 120a in step SA51 of FIG. 10, and acquires the current value processed by the second filter 120b in step SA52.

In step SA53, the control unit 100 compares the current value processed by the first filter 120a with the current value processed by the second filter 120b, and the current value difference is equal to or less than the specified value for detecting no impact. Judge if there is.

When the control unit 100 determines that the current value difference between the current value processed by the first filter 120a and the current value processed by the second filter 120b is equal to or less than the no-impact detection specified value, in step SA54, Update the no-hit detection counter.

When the control unit 100 determines in step SA55 that the value of the no-hit detection counter is equal to or higher than the specified value for resetting the number of hit detections, the control unit 100 resets the number of hits detected and detects no hits in step SA56.

When the control unit 100 determines in step SA53 that the current value difference between the current value processed by the first filter 120a and the current value processed by the second filter 120b exceeds the no-impact detection specified value, the step The SA57 resets the no-hit detection counter.

FIG. 11 is a graph showing changes in the current value at the start of motor drive, with the vertical axis showing the current value and the horizontal axis showing the time.

At the start of driving the motor 2, a large current called an inrush current flows. In the impact detection process described with reference to FIG. 6, after the maximum value is detected, if the current value drops by or more than the specified current value from the maximum value, it is determined that the impact is an impact. Therefore, the inrush current is recognized as an impact and the number of impact detections is added. ..

On the other hand, after the inrush current flows at the start of driving the motor 2, a current larger than the inrush current does not flow until the first impact is performed. When the fluctuation amount of the current value is large and small, there is a difference between the current value treated by the first filter 120a and the current value processed by the second filter 120b, and the fluctuation amount of the current value is large. The difference in current value is larger in the case of the case where the difference in the current value is larger than that in the case of the smaller value.

As a result, after the inrush current flows at the start of driving of the motor 2, a current having a larger value than the inrush current does not flow until the first impact is performed, so that the current processed by the first filter 120a does not flow. The current value difference between the value and the current value processed by the second filter 120b becomes smaller after the inrush current flows than when the inrush current flows.

Therefore, the difference between the current value processed by the first filter 120a and the current value processed by the second filter 120b, which is assumed from the current value after the inrush current flows, is set as the no-impact detection default value. do. Then, when the current value difference between the current value processed by the first filter 120a and the current value processed by the second filter 120b is equal to or less than the no-hit detection specified value, the no-hit detection counter is updated (added). However, if the maximum value is not detected because there is no hit for a predetermined time, and the hitless detection counter is equal to or more than the specified value for resetting the hit detection count, the hit detection count is reset. As a result, the number of hit detections due to the detection of the inrush current as a hit can be reset.

FIG. 12 is a flowchart showing an example of the detection completion count update process, and details of the detection completion count update process in step SA6 will be described below.

When the trigger switch 7 is turned on, the control unit 100 adds the drive time of the motor 2 in step SA61 of FIG. In step SA62, the control unit 100 determines whether the drive time of the motor 2 is equal to or greater than the specified value for updating the number of hit detections for stopping the drive of the motor 2, which is the specified value for updating the number of hits detected. If the drive time is less than the hit detection count update specified value, the hit detection count for stopping the driving of the motor 2 is set to the first detection count in step SA63. The hit detection number specified value is the continuous driving time of the motor 2 after the trigger switch 7 is turned on, and is set to, for example, 100 msec.

When the drive time of the motor 2 is equal to or longer than the hit detection count update specified value, the control unit 100 sets the number of hit detections for stopping the drive of the motor 2 to be less than the first detection count in step SA64. Set to.

FIG. 13 is a graph showing changes in the current value due to a hit when a hit is detected after the hit detection frequency update specified value elapses, and the vertical axis shows the current value and the horizontal axis shows the time. Further, FIG. 14 is a graph showing changes in the number of hits detected with hit detection when a hit is detected after the specified value for updating the number of hits detected, and the vertical axis shows the number of hits detected and the horizontal axis shows the time.

When the drive time of the motor 2 is short after the trigger switch 7 is turned on, the rotation speed does not increase during the acceleration operation of the motor 2 as compared with the case where the drive time is long. The force to fasten is weak. Therefore, if the number of hits for stopping the drive of the motor 2 is small, the fastening force may be insufficient.

On the other hand, when the drive time of the motor 2 is long after the trigger switch 7 is turned on, the rotation speed of the motor 2 is increased during steady operation or the like as compared with the case where the drive time is short, and the fastening member is fastened. Strong power to fasten things. Therefore, if the number of hits for stopping the drive of the motor 2 is large, the fastening force may be excessive.

Therefore, the hit detection number update default value assumed from the drive time and the rotation speed of the motor 2 is set. FIG. 7 described above is a graph showing a change in the current value due to a hit when a hit is detected before the hit detection count update default value elapses, and FIG. 8 shows a hit detected before the hit detection count update default value elapses. It is a graph which shows the change of the number of times of hitting detection with hitting detection in the case.

As shown in FIG. 7, when a hit is detected before the elapse of the hit detection count update specified value, a predetermined m hit is detected, and when the hit detection count shown in FIG. 8 reaches the first detection count, the motor Stop driving 2. The first detection number is set to the number of striking times that the fastening force is not insufficient even if the rotation speed of the motor 2 is not increased, and the insufficient fastening force is suppressed even during the acceleration operation of the motor 2.

As shown in FIG. 13, when a hit is detected after the lapse of the hit detection count update specified value, a predetermined n hits (n <m) hits are detected, and the hit detection count shown in FIG. 14 becomes the second detection count. When it reaches, the drive of the motor 2 is stopped. The second number of detections is set to the number of striking times that the fastening force does not become excessive when the rotation speed of the motor 2 is increasing, and the excessive fastening force is suppressed even during the steady operation of the motor 2. .. The predetermined first detection number (m times) and second detection number (n times) are arbitrarily set depending on the member to be fastened to be worked.

In the example of FIG. 13, the inrush current is generated before the specified value for updating the number of hit detections, but the hit detection number updated by the inrush current is reset by the no-hit detection process described with reference to FIG. As a result, erroneous detection of the number of hit detections is suppressed.

<Example of operation and effect of the impact driver of this embodiment>
In the impact driver 1A of the present embodiment, the presence or absence of an impact is detected by the amount of change in the current value from the maximum value of the current flowing through the motor 2, and is detected by the rotation speed of the motor 2 arbitrarily operated by the operator. By suppressing the influence of accuracy and the magnitude of pulsation for each impact, it becomes possible to stably detect impact due to impact load.

In the prior art, in order to detect a blow, an upper limit threshold value and a lower limit threshold value of the current value that fluctuates depending on the load applied to the motor are set, and if the current value exceeds the upper limit threshold value and then falls below the lower limit threshold value, it is determined that the hitting is performed. The standard of the current value changed greatly depending on the rotation speed of the motor and the magnitude of the load due to the members to be fastened, and it was not possible to stably detect the impact.

On the other hand, in the present embodiment, by storing the maximum value of the current value that can be acquired for each impact, the impact detection is started in which each maximum value is matched to the impact under different conditions such as the rotation speed of the motor 2. It can be set as a point. When the load of the impact is released, the change of the current value above a certain level always occurs. Can be detected stably. Further, by completing the detection of the impact by detecting the impact a plurality of times and stopping the rotation of the motor 2, it is possible to suppress the rotation stop of the motor 2 due to the erroneous detection.

In the above-described embodiment, the maximum value of the current is set as the reference current value for determining whether or not the impact has been performed. However, after the maximum value is detected, the current value after a predetermined standby time has elapsed is set as the reference current. It may be set to a value. In addition, the maximum value is detected by comparing the current values before and after each acquisition cycle, and when the later current value falls below the previous current value, the previous current value is detected as the maximum value, but this maximum value is detected. The current value after the value drops below the maximum value at the time of the above may be set as the reference current value. Further, a minimum value may be set as a reference current value.

Further, although the current specified value for determining that there is a hit is set to a constant value, the current specified value may be changed based on the reference current value, in this example, the maximum value.

1A ... Impact driver (power tool), 2 ... Motor, 5 ... Hammer unit (striking part), 6 ... Anvil (driven part), 7 ... Trigger switch (operation part), 100 ... Control unit, 100a ... Current value acquisition unit, 100b ... Extreme value detection unit, 100c ... Impact detection unit, 101 ... Storage unit, 102 ... Output unit, 110 ... ·Drive part

Claims (7)

The motor that drives the driven unit and
The striking portion that strikes the driven portion and the striking portion
The operation unit that operates the motor and
A control unit that controls the motor by operating the operation unit is provided.
The control unit
A current value acquisition unit that acquires the current value flowing through the motor,
An extreme value detection unit that detects the extreme value of the current value acquired by the current value acquisition unit, and
When the extreme value is detected by the extreme value detecting unit, the impact detecting unit is provided to detect the presence or absence of an impact by the impacting unit from the current value acquired by the current value acquiring unit after the extreme value is detected .
When the motor is driven by the operation of the operation unit, the control unit acquires the current value flowing through the motor by the current acquisition unit, and obtains the extreme value of the current value acquired by the current value acquisition unit. When the value detection unit detects and the impact detection unit detects the presence or absence of an impact from the current value acquired by the current value acquisition unit after the extreme value is detected, the impact detection count is added and the added impact detection count is calculated. When the set multiple times are reached, the motor is stopped or decelerated, and at the same time,
When the motor is driven by the operation of the operation unit, the control unit acquires the current value flowing through the motor by the current acquisition unit, and the fluctuation amount of the current value acquired by the current acquisition unit does not hit. When it is less than the specified value to detect, the no-hit detection counter is updated, the extreme value is not detected because there is no hit for a predetermined time, and the no-hit detection counter resets the number of hit detections. With the above, the number of hit detections is reset.
Electric tool. The motor that drives the driven unit and
The striking portion that strikes the driven portion and the striking portion
The operation unit that operates the motor and
A control unit that controls the motor by operating the operation unit is provided.
The control unit
A current value acquisition unit that acquires the current value flowing through the motor,
An extreme value detection unit that detects the extreme value of the current value acquired by the current value acquisition unit, and
When the extreme value is detected by the extreme value detecting unit, the impact detecting unit is provided to detect the presence or absence of an impact by the impacting unit from the current value acquired by the current value acquiring unit after the extreme value is detected.
When the motor is driven by the operation of the operation unit, the control unit acquires the current value flowing through the motor by the current acquisition unit, and obtains the extreme value of the current value acquired by the current value acquisition unit. When the value detection unit detects and the impact detection unit detects the presence or absence of an impact from the current value acquired by the current value acquisition unit after the extreme value is detected, the impact detection count is added and the added impact detection count is calculated. When the set multiple times are reached, the motor is stopped or decelerated, and at the same time,
The control unit is a power tool that changes the number of hit detections for stopping or decelerating the motor according to the elapsed time from the start of driving the motor. The control unit acquires the current value in each acquisition cycle by the current value acquisition unit, and detects the presence or absence of an impact when the acquired current value changes by the current specified value or more after the detection of the extreme value.
The power tool according to claim 1 or 2. The extreme value is the maximum value of the current value detected by the current acquisition unit.
The control unit detects the presence or absence of an impact when the current value acquired after detecting the maximum value drops by a specified value or more.
The power tool according to any one of claims 1 to 3 . The extreme value is a minimum value of the current value detected by the current acquisition unit.
The power tool according to any one of claims 1 to 3 , wherein the control unit detects the presence or absence of an impact when the current value acquired after detecting the minimum value rises by a specified value or more . The power tool according to any one of claims 1 to 5 , wherein the control unit changes the number of times of impact detection for stopping or decelerating the motor. 1 . The power tool according to any one of 6.

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