Working machine and control method

Abstract

The present invention provides a perforation method and a work machine capable of improving workability. A work machine 1 is provided with a motor 6, a trigger switch 7 for instructing the driving of the motor 6, and a microcontroller 40 which controls the driving of the motor 6. Upon detecting a rapid increase in the motor current, the microcontroller 40 stops the motor without transitioning to a retry mode. The microcontroller 40 transitions to the retry mode upon detecting an overload not accompanied by a rapid increase in the motor current. In the retry mode, the motor 6 is repeatedly started and stopped. When a load applied to a tip tool 31 is removed during the execution of the retry mode, the microcontroller 40 returns to normal mode while the trigger switch 7 remains on.

Description

[Technical field]

[0001] The present invention relates to a work machine such as a vibrating drill and a control It concerns the method. [Background technology]

[0002] The following Patent Document 1 discloses a drilling tool equipped with an unlocking mode for unlocking the tool tip and the processing member when the tool tip and the processing member become locked during operation.The following Patent Document 2 discloses a power tool that increases output when it detects that the tool tip is about to become locked due to a hard member such as a stone during operation, thereby destroying the cause. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2015 / 029660 [Patent Document 2] Japanese Patent Application Publication No. 9-277195 Summary of the Invention [Problem to be solved by the invention]

[0004] In the drilling tool of Patent Document 1, when the drilling tool is locked, the operator must release the lock and resume the work. During this operation, the operator must release the trigger and pull it again at least once, which means that the operator must operate the trigger at least twice, including the trigger operation before the tool is locked, resulting in poor operability.

[0005] In the power tool of Patent Document 2, when it detects that the tip tool is about to lock, the output is increased to overcome the cause, which causes a large torque to act on the hand. In addition, if the tool locks while the output is increased, there is a possibility that a kickback larger than that of the conventional tool may occur. In addition, in order to restart the motor that has stopped due to the lock, it is necessary to operate the trigger again.

[0006] The present invention has been made in recognition of such circumstances, and an object of the present invention is to provide a working machine and control The purpose is to provide a method. [Means for solving the problem]

[0007] One aspect of the present invention is a work machine. A motor; A working unit configured to be driven by the motor and to perform a predetermined task; A controller configured to control the motor; an operation unit configured to instruct the control unit to drive the motor; In a work machine having The control unit is When the operation unit is operated, a normal mode is executed in which the motor is continuously driven; a retry mode is executed in which, when a torque applied to the motor satisfies a first condition while the normal mode is executed, a stop control for stopping the motor and a retry control for driving the motor with a torque smaller than the torque applied when the first condition is satisfied are alternately repeated; When the retry mode is being executed, the torque applied to the motor is Different from the first condition When a second condition is satisfied, the retry mode is stopped and the motor is continuously driven. It is characterized by, It is characterized by.

[0008] The control unit controls the torque applied to the motor to be increased in a predetermined manner. Add The method may be configured to determine that the first condition is satisfied if

[0009] The control unit may be configured to determine that the first condition is satisfied when a torque applied to the motor reaches a first threshold value.

[0010] The control unit may be configured to execute the retry control in the retry mode until the torque applied to the motor reaches a second threshold, and to execute the stop control when the torque applied to the motor reaches the second threshold.

[0011] The second threshold may be configured to be less than the first threshold.

[0012] The control unit may be configured to determine that the second condition is satisfied when a state in which the torque applied to the motor does not reach the second threshold value has elapsed for a predetermined time.

[0013] The control unit may continue the stop control after repeating the retry control a predetermined number of times.

[0014] Another aspect of the present invention is a control method using a work machine, the method comprising: A motor; a tool tip configured to be driven by the motor and to perform a predetermined task; A controller configured to control the motor; an operation unit configured to instruct the control unit to drive the motor; A control method using a work machine having A first step of executing a normal mode in which the control unit continuously drives the motor and rotates the tool tip when an operator operates the operation unit; When the first step is being performed, Motor When a load applied to the motor satisfies a first condition, the control unit performs a stop control to stop the motor; load Less than Heavy Load a second step of executing a retry mode in which the retry control for driving the motor is alternately repeated; When the second step is being performed, the operator MotorWhen the load applied to the tool tip is removed, the control unit stops the retry mode and continuously drives the motor to rotate the tool tip. to carry out a given task. and a third step of returning to the normal mode.

[0015] The above 2 The retry control in step When the first condition is met The motor torque The motor may be driven with a torque smaller than the torque required for the motor to rotate.

[0016] The above 3 Steps The normal mode In Before The motor is driven by the 2 Steps The retry control The motor in torque The motor may be driven with a torque greater than the torque required for the motor to rotate.

[0017] The above 2 Step The retry mode is When the retry control is repeated a predetermined number of times, the stop control may be continued.

[0018] The above 1 In the step, if the increase in the load per unit time is abrupt, the driving of the motor may be stopped without transitioning to the retry mode.

[0019] The second step P In the case where the load applied to the motor is not removed by the operator, the tool bit is stopped after the motor is stopped by the stop control in the second step. ,stop The stopped state may continue.

[0020] Any combination of the above components and conversion of the present invention between devices, systems, etc. are also valid aspects of the present invention. Effect of the Invention

[0021] According to the present invention, a work machine capable of improving workability and control A method can be provided. [Brief description of the drawings]

[0022] [Figure 1] 1 is a side view of a working machine 1 according to an embodiment of the present invention. [Diagram 2] FIG. [Diagram 3] FIG. [Figure 4] FIG. [Diagram 5] FIG. 2 is a circuit block diagram of the work machine 1. [Figure 6] 3 is a control flowchart of the work machine 1. [Figure 7] 4 is a graph showing an example of changes in the current flowing through a motor 6 in a work machine 1, the rotation speed of the motor 6, and the duty of the rotation control of the motor 6; [Figure 8] 4 is a diagram showing measured waveforms of the rotation speed of the motor 6 and the current flowing through the motor 6 during no-load operation of the work machine 1. FIG. [Figure 9] 4 is a graph showing the measured waveforms of the rotation speed of the motor 6 and the current flowing through the motor 6 during normal drilling of a hole by the work machine 1. FIG. [Figure 10] 6 is a diagram showing measured waveforms of the rotation speed of the motor 6 and the current flowing through the motor 6 during an operation in which the motor 6 is stopped without being able to return to normal control after the work machine 1 has entered a retry mode. [Figure 11] 5 is a diagram showing measured waveforms of the rotation speed of the motor 6 and the current flowing through the motor 6 when the work machine 1 repeatedly switches between a normal mode and a retry mode. [Figure 12] 6 is a diagram showing measured waveforms of the rotation speed of the motor 6 and the current flowing through the motor 6 when the motor 6 is stopped due to an overload during normal control in the work machine 1. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] In the following, the same or equivalent components, members, etc. shown in each drawing are given the same reference numerals, and duplicated explanations are omitted as 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.

[0024] This embodiment relates to a working machine 1. The working machine 1 is an impact drill. The mechanical configuration of the working machine 1 will be described with reference to Figs. 1 to 4. Figs. 1 and 3 define the mutually orthogonal front-rear, up-down, and left-right directions of the working machine 1. Fig. 4 also shows a partial cross-sectional view taken along line AOBCD in Fig. 3 to show the meshing configuration of the reduction gear mechanism.

[0025] The work machine 1 includes a housing 3. The housing 3 includes a motor accommodating portion 3a, a handle portion 3b, a fan guide 3c, an intermediate cover 3d, and a gear cover 3e. The handle portion 3b extends from the rear of the motor accommodating portion 3a. The handle portion 3b is D-shaped in side view. The intermediate cover 3d is connected and fixed to the front portion of the motor accommodating portion 3a with the fan guide 3c in between. The gear cover 3e is connected and fixed to the front portion of the intermediate cover 3d.

[0026] The handle portion 3b is provided with a forward / reverse changeover switch 5 and a trigger switch 7. The trigger switch 7 is an operation unit for an operator to switch between driving and stopping the motor 6, and is configured to instruct the microcomputer 40 in FIG. 5 to drive the motor 6 in response to the operator's operation. When the operator pulls the trigger switch 7 (turns it on), the motor 6 is driven, and when the operator releases the operation of the trigger switch 7 (turns it off), the motor 6 is stopped. The forward / reverse changeover switch 5 is configured to be able to switch the rotation direction of the motor 6 when the trigger switch 7 is operated. As shown in FIG. 4, a control board 26 is accommodated in the lower part of the handle portion 3b. A switching element 27 and the like are provided on the control board 26. A battery pack 4, which serves as a power source for the work machine 1, is detachably connected to the lower end of the handle portion 3b.

[0027] As shown in FIG. 4, the motor housing 3a houses the motor 6. The central axis of the rotating shaft 6a of the motor 6 is parallel to the front-rear direction. The rear part of the rotating shaft 6a is supported by a bearing 11. The front part of the rotating shaft 6a of the motor 6 is supported by a bearing 12. The bearings 11 and 12 are, for example, ball bearings. A fan 10 is attached to the front part of the rotating shaft 6a, behind the bearing 12. The fan 10 is surrounded by a fan guide 3c. The fan 10 rotates integrally with the motor 6, and generates an airflow that cools the motor 6 and the like.

[0028] A first pinion 14 is formed on a portion of the rotating shaft 6a in front of the bearing 12. The first pinion 14 meshes with a first gear 15. The first gear 15 is provided at the rear of the intermediate shaft 16 and rotates integrally with the intermediate shaft 16. The central axis of the intermediate shaft 16 is parallel to the front-rear direction. The rear end of the intermediate shaft 16 is supported by a bearing 28. The front end of the intermediate shaft 16 is supported by a bearing 29. The bearings 28 and 29 are, for example, needle bearings.

[0029] A second pinion 17 is provided on the intermediate shaft 16 in front of the first gear 15. The second pinion 17 meshes with a second gear 18. The second gear 18 is provided at the rear of the spindle 19 and rotates together with the spindle 19. The central axis of the spindle 19 is parallel to the front-rear direction. The second gear 18 is spline-fitted to the second pinion 17 so as to be slidable back and forth, so that the spindle 19 can move back and forth relative to the housing 3. The first pinion 14 and the first gear 15, as well as the second pinion 17 and the second gear 18, constitute a reduction mechanism (rotation transmission mechanism). This reduction mechanism is housed inside the intermediate cover 3d and the gear cover 3e. The rotation of the motor 6 is reduced in two stages by this reduction mechanism and transmitted to the spindle 19 and the tool tip 31.

[0030] The rear end of the spindle 19 is supported by a bearing 30. The bearing 30 is, for example, a needle bearing. A steel ball (sphere) 20 is provided at the rear end of the spindle 19. Behind the steel ball 20, the switching shaft 13 is rotatably supported by the intermediate cover 3d. The switching shaft 13 is cylindrical with a central axis perpendicular to the front-rear direction, and has a recess partially cut out on the outer circumferential surface of the middle part. When the recess of the switching shaft 13 faces the steel ball 20, the mode is the impact drill mode, and when the outer circumferential surface of the switching shaft 13 other than the recess faces the steel ball 20, the mode is the drill mode. The mode switching lever 8 provided on the intermediate cover 3d is an operating part for mode switching to rotate the switching shaft 13 around its own central axis. The operator can switch between the impact drill mode and the drill mode by operating the mode switching lever 8 in the left-right direction.

[0031] A first ratchet 21 is provided around the spindle 19 in front of the second gear 18. The first ratchet 21 is fixed to the gear cover 3e and does not rotate together with the spindle 19. A spring 22 is disposed around the spindle 19 so as to bias the spindle 19 forward relative to the first ratchet 21. A second ratchet 23 is provided around the spindle 19 in front of the first ratchet 21. The second ratchet 23 is fixed to the spindle 19 and rotates together with the spindle 19. The front surface of the first ratchet 21 and the rear surface of the second ratchet 23 face each other. A claw is provided on each of the front surface of the first ratchet 21 and the rear surface of the second ratchet 23. The spindle 19 is supported by a bearing 24 in front of the second ratchet 23. The bearing 24 is, for example, a ball bearing. A chuck (drill chuck) 9 is attached to the tip of the spindle 19 that protrudes forward from the gear cover 3e. A bit (drill) 31 serving as a working part can be detachably attached to the chuck 9 as shown in FIG.

[0032] In the drill mode, the outer peripheral surface (cylindrical outer peripheral surface) of the switching shaft 13 other than the recessed portion comes into face-to-face contact with the steel ball 20. As a result, the spindle 19 cannot move in the forward / backward direction relative to the housing 3, and the front surface of the first ratchet 21 and the rear surface of the second ratchet 23 remain separated from each other. Therefore, the spindle 19 continues to rotate without vibrating, and the workpiece (component) is drilled by the drill attached to the chuck 9.

[0033] In the vibration drill mode, the recess of the switching shaft 13 faces the steel ball 20. Therefore, the spindle 19 can move backward with respect to the housing 3 by the depth of the recess. Therefore, when the drill attached to the chuck 9 is pressed against the workpiece, the spindle 19 moves backward with respect to the housing 3 against the bias of the spring 22, and the front surface of the first ratchet 21 and the rear surface of the second ratchet 23 come into contact with each other. Therefore, the engagement between the claw on the front surface of the first ratchet 21 and the claw on the rear surface of the second ratchet 23 applies vibration to the spindle 19. The drill attached to the chuck 9 is also applied with vibration at the same time as it rotates, so that the workpiece can be drilled efficiently.

[0034] Fig. 5 is a circuit block diagram of the work machine 1. The inverter circuit 53 and the control circuit unit 60 shown in Fig. 5 are provided on the control board 26 of Fig. 4. The inverter circuit 53 may be provided on a board separate from the control circuit unit 60. The inverter circuit 53 has six switching elements Q1 to Q6, such as FETs or IGBTs, that are three-phase bridge-connected. The switching element 27 shown in Fig. 4 corresponds to the switching elements Q1 to Q6 in Fig. 5. The switching elements Q1 to Q6 are turned on and off under the control of the microcomputer 40, for example, PWM control (duty control), and convert the DC power supplied from the battery pack 4 into AC power for driving the motor 6 and supply it to the motor 6.

[0035] The control circuit section 60 includes a microcomputer (microcontroller) 40 as a control section, a step-down circuit 41, a control system power supply circuit 42, a communication circuit 43, a battery temperature detection circuit 44, an over-discharge detection circuit 45, a current detection circuit 46, a control signal output circuit 47, a rotor position detection circuit 48, a FET temperature detection circuit 49, a battery voltage detection circuit 50, and an LED control circuit 51. The step-down circuit 41 steps down the output voltage of the battery pack 4. The control system power supply circuit 42 converts the output voltage of the step-down circuit 41 to a power supply voltage of the microcomputer 40 and supplies it to the microcomputer 40. The communication circuit 43 is a circuit for communication between the microcomputer 40 and the battery pack 4. The battery temperature detection circuit 44 detects the temperature of the battery pack 4 by a temperature detection signal from the battery pack 4 and transmits it to the microcomputer 40. The over-discharge detection circuit 45 detects over-discharge of the battery pack 4 by an over-discharge detection signal from the battery pack 4 and transmits it to the microcomputer 40.

[0036] The current detection circuit 46 detects the motor current from the voltage of a resistor R provided in the path of the current of the motor 6 (hereinafter also referred to as "motor current") and transmits it to the microcomputer 40. The control signal output circuit 47 applies a control signal to each control terminal (each gate) of the switching elements Q1 to Q6 according to the control of the microcomputer 40. The rotor position detection circuit 48 detects the rotational position of the motor 6 from the output signals of three magnetic sensors 52 (e.g., Hall ICs) provided near the motor 6 and transmits it to the microcomputer 40. The FET temperature detection circuit 49 detects the temperature of the switching elements Q1 to Q6 from the output signal of a temperature sensor (e.g., a thermistor) not shown provided near the switching elements Q1 to Q6 and transmits it to the microcomputer 40. The battery voltage detection circuit 50 detects the output voltage of the battery pack 4 and transmits it to the microcomputer 40. The LED control circuit 51 controls the lighting of an LED not shown according to the control of the microcomputer 40.

[0037] The microcomputer 40 operates on the output voltage of the control system power supply circuit 42. In response to the operation of the trigger switch 7, the microcomputer 40 controls the switching elements Q1 to Q6 via the control signal output circuit 47 to control the drive of the motor 6 (the supply of current to the motor 6). When stopping the motor 6, the microcomputer 40 stops the supply of current to the motor 6. At this time, the microcomputer 40 may perform brake control. The microcomputer 40 has an overload protection function. The overload protection is protection when the load (torque) of the motor 6 becomes excessive, and includes short circuit current protection (SD), overcurrent protection, and motor lock protection. The microcomputer 40 monitors the load of the motor 6 by the motor current.

[0038] The short circuit current protection is to stop the motor 6 when the motor current satisfies a short circuit condition. The short circuit condition is to detect a motor current equal to or greater than a short circuit threshold (e.g., 187 A) for a short circuit judgment time (e.g., 10 μS). The overcurrent protection is to stop the motor 6 when the motor current satisfies a first or second overcurrent condition. The first overcurrent condition is to detect a motor current equal to or greater than a first overcurrent threshold (e.g., 160 A) for a first judgment time (e.g., 1 msec). The second overcurrent condition is to detect a motor current equal to or greater than a second overcurrent threshold (e.g., 60 A) for a second judgment time (e.g., 100 msec). The second overcurrent threshold corresponds to the clutch threshold in FIG. 7. The second overcurrent threshold is an example of the first threshold of the present invention. The motor lock protection is to stop the motor 6 when the rotation speed of the motor 6 (hereinafter also referred to as "motor rotation speed") becomes equal to or less than a threshold.

[0039] The microcomputer 40 has a function of suddenly stopping the motor 6. The sudden stop function is a function that stops the motor 6 when a sudden rise (a steep current gradient) of the motor current is detected. The sudden rise of the motor current is when the motor current rises from a first sudden stop threshold (first RFC threshold) (for example, 40 A) to a second sudden stop threshold (second RFC threshold) (for example, 60 A) within a sudden rise determination time (for example, 10 msec). The sudden rise of the motor current occurs when the tip tool 31 is suddenly locked in a hole in the workpiece regardless of the strength of the pressing force of the tip tool 31 against the workpiece. One example of the sudden lock is a lock that occurs when the tip tool 31 unintentionally hits a hard part of the workpiece during a drilling operation. On the other hand, when the tip tool 31 is locked in a hole in the workpiece due to the pressing force of the tip tool 31 against the workpiece being too strong, the rise of the motor current is relatively gradual. As described below, in this embodiment, different controls are implemented depending on whether the increase in motor current when the motor current exceeded the second overcurrent threshold was rapid or not.

[0040] In the work machine 1, the motor 6 is controlled by the microcomputer 40 in one of the following four control modes. 1. Stopped state: In the stopped state, the motor 6 is stopped, and the microcomputer 40 does not control the driving of the motor 6. 2. Start-up state (start-up mode)...The start-up state is the state before a first predetermined time, for example 300 msec, has elapsed since the microcomputer 40 started up the motor 6. In the start-up state, the microcomputer 40 stops the motor 6 if it detects a sudden increase in motor current or an overload. If the motor 6 is stopped in the start-up state, the retry control described below is not performed. If the first predetermined time has elapsed with the motor 6 still driven after starting the motor 6, the microcomputer 40 transitions to the next operating state. 3. Operation state (normal mode)... In the operation state, the control by the microcomputer 40 differs between when a sudden rise in motor current is detected and when an overload is detected. When the microcomputer 40 detects a sudden rise in motor current, it determines that a shock will be applied to the main body due to a sudden lock of the motor 6 (kickback will occur), and stops the motor 6. This suppresses kickback and also suppresses heat generation, thereby suppressing breakdown of the work machine 1. The worker turns off the trigger switch 7 (releases the operation of the trigger switch 7), and the error caused by the sudden rise in motor current is released (pulling the trigger switch 7 makes the motor 6 drivable). When the microcomputer 40 detects an overload without detecting a sudden rise in motor current, it stops the motor 6 and transitions to the next retry state. Detecting an overload without detecting a sudden rise in motor current in the operation state is an example of the torque of the motor 6 increasing in a predetermined manner, and is an example of the first condition of the present invention being satisfied. 4. Retry state (retry mode)... In the retry state, the microcomputer 40 stops the motor 6 (performs stop control) as overcurrent protection even when a third overcurrent condition is satisfied. The third overcurrent condition is to detect a motor current equal to or greater than a third overcurrent threshold (e.g., 30 A) lower than the start state and the operation state for a third judgment time (e.g., 1 msec). The third overcurrent threshold corresponds to the second clutch threshold in FIG. 7. The third overcurrent threshold is an example of the second threshold of the present invention. The purpose of adding the third overcurrent condition is to reduce the reaction caused by a retry. In the retry state, if the microcomputer 40 detects a sudden increase in motor current or an overload within a second predetermined time, e.g., 500 msec, from the start of the motor 6, the microcomputer 40 stops the motor 6 and immediately restarts it (performs a retry). If the second predetermined time has passed since the start of the motor 6 while the motor 6 is still driven, the microcomputer 40 transitions to the operation state described above. In the retry state, the elapse of the second predetermined time while the motor 6 is still driven is an example of satisfying the second condition of the present invention. When the microcomputer 40 repeats the restart (retry control) of the motor 6 after the stop control a predetermined number of times (e.g., 10 times), it does not perform any more retry control and keeps the motor 6 in the stopped state.

[0041] 6 is a control flowchart of the work machine 1. When the trigger switch 7 is turned on (S2) in the stopped state (S1), which is the initial state, the microcomputer 40 starts the motor 6 (S3) and the motor 6 is in the started state (S4). If the microcomputer 40 detects a sudden increase in the motor current or an overload (Yes in S6 or Yes in S7) before 300 msec has elapsed since the start of the motor 6 (No in S5), it stops the motor 6 (S8). After that, the microcomputer 40 does not start the motor 6 even if the trigger switch 7 continues to be on (Yes in S9), and returns to S1 when the trigger switch 7 is turned off (No in S9). If the microcomputer 40 does not detect a sudden increase in the motor current or an overload (No in S6, No in S7) and 300 msec has elapsed since the start of the motor 6 (Yes in S5), the motor 6 is shifted to the operating state (S10).

[0042] In the operating state, if the microcomputer 40 does not detect a sudden increase in current or an overload (No in S11, No in S12), it continues to drive the motor 6 as long as the trigger switch 7 is on (Yes in S13). If the trigger switch 7 is turned off (No in S13), the microcomputer 40 stops the motor 6 (S14) and returns to S1. If the microcomputer 40 detects a sudden increase in the motor current (Yes in S11), it stops the motor 6 (S15). After that, the microcomputer 40 does not start the motor 6 even if the trigger switch 7 continues to be on (Yes in S16), and if the trigger switch 7 is turned off (No in S16), it returns to S1. If the microcomputer 40 does not detect a sudden increase in the motor current (No in S11) and detects an overload (Yes in S12), it stops the motor 6 (S17) and transitions to a retry state (S20).

[0043] In the retry state, the microcomputer 40 adds a retry threshold for overload protection (S21). The addition of the retry threshold is the addition of the third overcurrent condition (30A x 1 msec) described above. When the trigger switch 7 is off (Yes in S22), the microcomputer 40 stops the motor 6 and returns to S1. When the trigger switch 7 is on (No in S22) and the motor 6 is stopped (Yes in S23), the microcomputer 40 starts the motor 6 (S24). When the motor 6 is not stopped (No in S23), the microcomputer 40 detects a sudden increase in the motor current or an overload (Yes in S26 or Yes in S27) before 500 msec has elapsed since the start of the motor 6 (No in S25), and stops the motor 6 (S28). After that, the microcomputer 40 returns to S22 if the number of retries, i.e., the number of times the motor 6 has been started in S24, is less than 10 (No in S29). When the number of retries is 10 (Yes in S29), the microcomputer 40 does not start the motor 6 even if the trigger switch 7 continues to be on (Yes in S30), and when the trigger switch 7 is turned off (No in S30), the process returns to S1. When the microcomputer 40 does not detect a sudden increase in motor current or an overload while the trigger switch 7 continues to be on (No in S22, No in S23, No in S26, No in S27), and 500 msec has passed since the start of the motor 6 (Yes in S25), the microcomputer 40 returns from the retry state to the operating state (S31). The retry threshold (30 A x 1 msec) added in S21 is erased when the retry state ends.

[0044] FIG. 7 is a graph showing an example of changes in the motor current, motor rotation speed, and rotation control duty of the motor 6 in the work machine 1 (hereinafter also referred to simply as "duty"). Two cases are shown in FIG. 7, with the solid lines in the current graph and the rotation speed graph corresponding to the first case and the dashed line corresponding to the second case. Also, the duty is shown with a dotted line only for the first case. In FIG. 7, the time axis on the horizontal axis and the duty on the vertical axis are enlarged for ease of viewing during the period from time t2 to t3.

[0045] First, the first case will be described. At time t0, the microcomputer 40 starts the motor 6. At this time, the tool tip 31 is not in contact with the workpiece and is in an unloaded state. In starting control of the motor 6, the microcomputer 40 uses soft start control to gradually increase the duty to a target value, gradually increasing the motor current and motor rotation speed. At time t1, the tool tip 31 is pressed against the workpiece and drilling work begins. Then, as the load increases, the motor current increases and the motor rotation speed decreases. At time t2, the tool tip 31 is locked (stopped) in the hole in the workpiece due to the load and the motor current becomes 60A, and the microcomputer 40 reduces the duty to 0. This causes the motor current to become 0 and the motor 6 to stop.

[0046] The microcomputer 40 executes the retry mode after time t2. Specifically, the microcomputer 40 repeats the control of starting the motor 6 again after stopping the motor 6, and stopping the motor 6 when the motor current becomes 30A. The soft start control is also performed when starting the motor 6 in the retry control. During the period from time t2 to t3, the tool tip 31 is locked, and the tool tip 31 does not rotate even when the motor 6 is started. During the same period, even if the motor 6 is started, the motor 6 only rotates slightly due to the play of the gear meshing. When the tool tip 31 is locked, the time from restarting the motor 6 to stopping it is, for example, about 100 msec. In addition, in this case, the duty immediately before the motor 6 stops is, for example, about 20%. At time t3, the operator removes the tool tip 31 from the hole in the workpiece (removes the load applied to the tool tip 31), and when the motor 6 is started thereafter, the motor current does not exceed 30A even at time t4, 500 msec after the start. This causes the microcomputer 40 to end the retry mode and return to normal control (the control of S10 to S17 in FIG. 6) in which the motor 6 is continuously driven. The operator can again perform drilling work on the workpiece while keeping the trigger switch 7 turned on.

[0047] Next, the second case will be described. In the second case, the tool tip 31 suddenly locks from the no-load state just before time t2. This causes the motor current to suddenly rise from 40A to 60A within 10 msec. In this case, the microcomputer 40 reduces the duty to 0 and stops the motor 6. When the microcomputer 40 stops the motor 6 due to the sudden rise in the motor current, it does not enter the retry mode described above.

[0048] Fig. 8 is a measured waveform diagram of the motor rotation speed and the motor current when the work machine 1 is in no-load operation. In Fig. 8, the upper part shows the motor rotation speed, and the lower part shows the motor current. The same applies to Figs. 9 to 12. The waveform diagram in Fig. 8 corresponds to the case where S1 to S14 in Fig. 6 are performed without the tool tip 31 contacting the workpiece. Fig. 9 is a measured waveform diagram of the motor 6 rotation speed and the current flowing through the motor 6 when the work machine 1 is normally drilling a hole. This waveform diagram corresponds to the case where S1 to S14 in Fig. 6 are performed with the tool tip 31 in contact with the workpiece.

[0049] Fig. 10 is a graph showing measured waveforms of the motor rotation speed and the motor current in an operation to stop the motor 6 without being able to return to normal control after the working machine 1 has entered the retry mode. This waveform diagram corresponds to a case where S1 to S13, S11, S12, S17, and S20 to S30 in Fig. 6 are executed with the tool tip 31 in contact with the workpiece.

[0050] Fig. 11 is a diagram showing measured waveforms of the rotation speed of the motor 6 and the current flowing through the motor 6 when the normal mode and the retry mode are repeatedly performed in the work machine 1. This waveform diagram corresponds to the case where S1 to S13, S11, S12, S17, S20 to S29, S22 to S25, and S31 in Fig. 6 are repeatedly performed with the tool tip 31 in contact with the workpiece.

[0051] Fig. 12 is a graph showing measured waveforms of the motor rotation speed and motor current when the motor 6 is stopped due to an overload during normal control in the work machine 1. This waveform diagram corresponds to the case where S1 to S13, S11, and S15 in Fig. 6 are executed with the tool tip 31 in contact with the workpiece. The waveforms in Figs. 9 to 12 are the results when a core drill with a diameter of 120 mm is used as the tool tip 31.

[0052] According to this embodiment, the following effects can be obtained.

[0053] (1) The microcomputer 40 executes a retry mode for locking of the tip tool 31 when the force pressing the tip tool 31 against the workpiece (hereinafter, "pressing force") is too strong, and if the pressing force of the tip tool 31 is weakened while the retry mode is being executed, the microcomputer 40 returns to the normal mode even if the trigger switch 7 remains on. Therefore, the operator does not need to re-operate the trigger switch 7 after the tip tool 31 is locked, improving operability.

[0054] (2) In the retry mode, the microcomputer 40 repeatedly stops and restarts the motor. This notifies the worker that the pressing force is too strong, and encourages the worker to reduce the pressing force. In other words, the retry mode allows the worker to know that the pressing force is too strong and gives him an opportunity to reduce the pressing force, improving workability.

[0055] (3) When the microcomputer 40 detects a sudden increase in the motor current, it stops the motor 6 without switching to the retry mode. On the other hand, when the microcomputer 40 detects an overload without a sudden increase in the motor current, it switches to the retry mode. This suppresses kickback, which causes the housing 3 to swing around when the tool tip 31 is suddenly locked, while improving operability as described above by executing the retry mode when the tool tip 31 is locked due to an excessively strong pressing force.

[0056] (4) In the retry mode, the microcomputer 40 adds a stop condition (30A x 1 msec) with a lower motor current than in the normal mode. This reduces the torque (strain) on the operator's hands in the retry mode, improving workability.

[0057] Although the present invention has been described above using the embodiment as an example, it will be understood by those skilled in the art that various modifications are possible to the components and processes of the embodiment within the scope of the claims. Modifications will be mentioned below.

[0058] The microcomputer 40 may monitor the load (torque) of the motor 6 by the motor rotation speed. In this case, the microcomputer 40 may transition to a retry mode if the rate at which the motor rotation speed decreases when the motor rotation speed falls below the threshold rotation speed is gentle, and may stop the motor 6 without transitioning to the retry mode if the rate at which the motor rotation speed decreases is rapid. The work machine 1 is not limited to an impact drill, and may be another drilling tool such as a hammer drill, or may be a work machine other than a drilling tool in which the tip tool may be locked. [Explanation of symbols]

[0059] 1...working machine, 3...housing, 3a...motor housing, 3b...handle, 3c...fan guide, 3d...intermediate cover, 3e...gear cover, 4...battery pack, 5...forward / reverse switch, 6...motor (electric motor), 6a...rotating shaft (output shaft), 7...trigger switch, 8...mode switching lever, 9...chuck, 10...fan, 11, 12...bearing, 13...switching shaft, 14...first pinion, 15...first gear, 16...intermediate shaft, 17...second pinion, 18...second gear, 19...spindle, 20...steel ball (sphere), 21...first ratchet, 22...spr Ring, 23...second ratchet, 24...bearing, 26...control board, 27...switching element, 28, 29...bearing, 30...bearing, 31...tip tool (drill bit), 40...microcontroller (control unit), 41...step-down circuit, 42...control system power supply circuit, 43...communication circuit, 44...battery temperature detection circuit, 45...over-discharge detection circuit, 46...current detection circuit, 47...control signal output circuit, 48...rotor position detection circuit, 49...FET temperature detection circuit, 50...battery voltage detection circuit, 51...LED control circuit, 52...magnetic sensor (Hall IC), 53...inverter circuit, 60...control circuit section.

Claims

1. A motor; A working unit configured to be driven by the motor and to perform a predetermined task; A controller configured to control the motor; an operation unit configured to instruct the control unit to drive the motor; In a work machine having The control unit is When the operation unit is operated, a normal mode is executed in which the motor is continuously driven; a retry mode is executed in which, when a torque applied to the motor satisfies a first condition while the normal mode is being executed, a stop control for stopping the motor and a retry control for driving the motor with a torque smaller than the torque applied when the first condition is satisfied are alternately repeated; and when the torque applied to the motor satisfies a second condition different from the first condition while the retry mode is being executed, the retry mode is stopped and the motor is continuously driven. A working machine characterized by:

2. The work machine according to claim 1, The control unit is configured to determine that the first condition is satisfied when the torque applied to the motor increases in a predetermined manner. A working machine characterized by:

3. The working machine according to claim 1 or 2, The control unit is configured to determine that the first condition is satisfied when a torque applied to the motor reaches a first threshold value. A working machine characterized by:

4. The working machine according to claim 3, The control unit is configured to execute the retry control in the retry mode until a torque applied to the motor reaches a second threshold, and execute the stop control when the torque applied to the motor reaches the second threshold. A working machine characterized by:

5. The working machine according to claim 4, The second threshold is configured to be smaller than the first threshold. A working machine characterized by:

6. The work machine according to claim 4, The control unit is configured to determine that the second condition is satisfied when a state in which the torque applied to the motor does not reach the second threshold value has elapsed for a predetermined time. A working machine characterized by:

7. The work machine according to claim 1, The control unit continues the stop control after repeating the retry control a predetermined number of times. A working machine characterized by:

8. A motor; a tool tip configured to be driven by the motor and to perform a predetermined task; A controller configured to control the motor; an operation unit configured to instruct the control unit to drive the motor; A control method using a work machine having a first step of executing a normal mode in which the control unit continuously drives the motor and rotates the tool bit when an operator operates the operation unit; a second step of executing a retry mode in which, when a load applied to the motor satisfies a first condition while the first step is being executed, the control unit alternately repeats a stop control for stopping the motor and a retry control for driving the motor with a load smaller than the load when the first condition is satisfied; a third step of, when an operator removes a load applied to the motor while the second step is being performed, the control unit cancels the retry mode and returns to the normal mode in which the control unit continuously drives the motor and rotates the tool bit to perform a predetermined task; A control method using a work machine, comprising:

9. 9. The control method according to claim 8, The retry control in the second step drives the motor with a torque smaller than the torque of the motor when the first condition is satisfied. A control method comprising:

10. 9. The control method according to claim 8, The driving of the motor in the normal mode in the third step is performed by driving the motor with a torque larger than a torque of the motor in the retry control in the second step. A control method comprising:

11. 9. The control method according to claim 8, The retry mode in the second step continues the stop control when the retry control is repeated a predetermined number of times. A control method comprising:

12. 9. The control method according to claim 8, In the first step, if the increase in the load per unit time is abrupt, the drive of the motor is stopped without transitioning to the retry mode. A control method comprising:

13. 9. The control method according to claim 8, In the second step, if the operator does not remove the load applied to the motor, the tool bit continues to be stopped after the motor is stopped by the stop control in the second step. A control method comprising:

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