Working machine

Abstract

To provide a working machine improved in convenience.SOLUTION: The working machine 10 includes the motor 13, the attachment portion 12 that receives a driving force of the motor 13, rotates about the first axis AR1 extending in the first direction AX1, and to which the tip tools T extending along the first axis AX1 are attached, the housing 11 that supports the motor 13 and the attachment portion 12, and the control unit 15 that controls driving of the motor 13. The control unit 15 changes the drive state of the motor 13 when the acceleration applied to the first direction AR1 with respect to the housing 11 satisfies the first condition, and does not change the drive state of the motor 13 even when the acceleration applied to the second direction AR1 intersecting the first direction AR2 satisfies the first condition.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a work machine. [Background technology]

[0002] Impact tools having a mechanism for suppressing the occurrence of cam-out have been known for some time. Patent Document 1 discloses an impact tool that uses a biasing member such as a spring to press and bias an anvil or a tool bit toward a mating material. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2018 / 155074 Summary of the Invention [Problem to be solved by the invention]

[0004] It is desirable to be able to detect the occurrence of come-out without requiring any complex mechanisms or additional parts, thereby improving the workability and convenience of the work machine when in use. [Means for solving the problem]

[0005] A work machine according to one embodiment includes a motor, a mounting portion that receives a driving force from the motor, rotates about an axis extending in a first direction, and has a tool bit attached thereto, the tool bit extending along the axis, a housing that supports the motor and the mounting portion, and a control portion that controls driving of the motor. The control portion changes a driving state of the motor when acceleration applied to the housing in the first direction satisfies a first condition, and does not change the driving state of the motor even when acceleration applied to a second direction intersecting the first direction satisfies the first condition. [Effects of the Invention]

[0006] According to the present invention, it is possible to provide a work machine with improved convenience. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a side view showing the appearance of a work machine according to an embodiment. [Figure 2] FIG. 2 is a cross-sectional view illustrating the structure of the work machine. [Figure 3] FIG. 3 is an enlarged partial cross-sectional view of a part of FIG. 2. [Figure 4] FIG. 2 is a circuit block diagram of the work machine. [Figure 5] FIG. 10 is a diagram schematically illustrating the work machine when a screw is being tightened. [Figure 6] FIG. 10 is a diagram schematically illustrating the work machine when a screw is being tightened. [Figure 7] 10 is a graph showing a change in acceleration detected during screw tightening and an amplitude threshold value. [Figure 8] 10 is a flowchart illustrating a flow of processing by a control unit. [Figure 9] 10 is a flowchart illustrating a flow of processing by a control unit. [Figure 10] 10 is a graph schematically showing the change in acceleration detected during screw tightening and the acceleration threshold value in the first modified example. [Figure 11] 10 is a graph schematically showing the change in the current value detected during screw tightening and the current threshold value in the second modified example. DETAILED DESCRIPTION OF THE INVENTION

[0008] <Embodiment> A working machine according to an embodiment will be described with reference to the drawings. The working machine is, for example, an electric hammer drill. A worker can use the working machine to perform work such as drilling or chipping on a target material such as concrete.

[0009] <Overall structure> FIG. 1 is a side view of a working machine 10 according to an embodiment, and FIG. 2 is a cross-sectional view of the working machine 10. As shown in FIG.

[0010] The work machine 10 includes a housing 11, a mounting portion 12, a motor 13, a transmission portion 14, a control portion 15, and an acceleration sensor 16. Various types of tool bits T are attached to the mounting portion 12. The work machine 10 drives the tool bits T with the driving force of the motor 13 to perform various operations such as drilling.

[0011] In the following description, the direction along the first axis AX1 of the tool bit T shown in Figure 2 is referred to as the first direction AR1. The first direction AR1 is also referred to as the front-to-rear direction. Furthermore, the tip side of the tool bit T is referred to as the front, and the base side of the tool bit T is referred to as the rear.

[0012] <Housing 11> The housing 11 is an outer shell element of the work implement 10. The housing 11 can be broadly divided into a first housing 20, a second housing 21, and a third housing 22. The first housing 20 forms the front part of the outer shell. The first housing 20 extends forward from the second housing 21. The first housing 20 accommodates a transmission unit 14, which will be described later. A sub-handle 11A is attached to the front of the first housing 20, extending in a direction intersecting (perpendicular or nearly perpendicular to) the first direction AR1.

[0013] The second housing 21 forms the middle part of the outer shell. The second housing 21 extends in a direction intersecting (perpendicular or nearly perpendicular to) the first direction AR1. The first housing 20 is connected to one side of the second housing 21 in the direction in which the second housing 21 extends. The second housing 21 accommodates the motor 13, the control unit 15, and the acceleration sensor 16, which will be described later.

[0014] In the following description, the direction in which the second housing 21 extends may be referred to as the up-down direction. Furthermore, the side of the second housing 21 that is connected to the first housing 20 will be referred to as the upper side, and the side of the second housing 21 that is not connected to the first housing 20 will be referred to as the lower side. Furthermore, the direction that intersects (is perpendicular or nearly perpendicular to) the front-rear direction (first direction AR1) and the up-down direction may be referred to as the left-right direction. The up-down direction and left-right direction together may be referred to as the second direction AR2. In other words, the second direction AR2 is a direction that intersects with the first direction AR1.

[0015] An operation panel 23 that is operated by an operator is provided on the rear side surface of the second housing 21. The operation panel 23 is electrically connected to the control unit 15, which will be described later. The operation panel 23 is operated by the operator when switching the operation control mode of the work machine 10. The operation control modes that can be set on the operation panel 23 include a drill mode (first mode) and a screw mode (second mode). The first mode and the second mode will be described in detail later.

[0016] The third housing 22 forms the rear of the outer shell. The third housing 22 extends rearward from the second housing 21. The upper part of the third housing 22 is connected to the upper part of the second housing 21, and the lower part of the third housing 22 is connected to the lower part of the second housing 21.

[0017] A trigger 24 is provided in the front of the third housing 22. An operator can operate the trigger 24 while holding the third housing 22. A trigger switch 24A is provided inside the third housing 22 and is electrically connected to the control unit 15. The trigger switch 24A outputs an operation signal (ON signal) when an operating force is applied to the trigger 24. When the operating force on the trigger 24 is released, the trigger switch 24A stops outputting the operation signal.

[0018] A battery pack 25 is detachably attached to the bottom end of the third housing 22. The battery pack 25 is a DC power supply having a housing case and a plurality of battery cells housed within the housing case. The battery cells are secondary batteries that can be charged and discharged, and any of lithium-ion batteries, nickel-metal hydride batteries, lithium-ion polymer batteries, and nickel-cadmium batteries can be used.

[0019] <Mounting part 12> The mounting portion 12 is disposed at the front end of the first housing 20 coaxially with a cylinder 42 of the transmission portion 14, which will be described later. That is, the mounting portion 12 is supported by the housing 11. The rear end of the mounting portion 12 is fixed non-rotatably to the front end of the first housing 20. The base end of the tool bit T is inserted into the mounting portion 12, and the mounting portion 12 holds the base end of the inserted tool bit T. That is, the tool bit T is attached to the mounting portion 12.

[0020] A drill bit or a driver bit is attached to the mounting portion 12 as the tool tip T. The tool tip T attached to the mounting portion 12 rotates about a first axis AX1 along a first direction AR1 and extends along the first axis AX1. 1 and 2 show a case where an adapter 12A is attached to the mounting portion 12 and a driver bit is attached as the tool tip T in a front hole of the adapter 12A.

[0021] <Motor 13> The motor 13 is, for example, a three-phase brushless motor, and is housed in the second housing 21. More specifically, the motor 13 is disposed above the control unit 15 and the acceleration sensor 16, which are housed in the lower part of the second housing 21, and is electrically connected to the control unit 15. In other words, the motor 13 is supported by the housing 11.

[0022] The motor 13 includes an output shaft 30. The output shaft 30 has a second axis AX2 as its central axis, which is parallel to the up-down direction and perpendicular to the first direction AR1, and extends along the second axis AX2. The output shaft 30 is supported so as to be rotatable about the second axis AX2. A pinion gear 31 is provided at the tip (i.e., upper end) of the output shaft 30.

[0023] When the trigger 24 is operated and an operation signal is output from the trigger switch 24A and input to the control unit 15, which will be described later, power is supplied from the battery pack 25 to the motor 13. The motor 13 receives the power supply and is driven to rotate.

[0024] <Transmission section 14> The transmission unit 14 transmits the driving force of the motor 13 to the tool tip T. The transmission unit 14 transmits rotational drive or reciprocating drive to the tool tip T according to the operation mode selected by the operator.

[0025] 2. Fig. 3 is an enlarged partial cross-sectional view of the vicinity of the transmission unit 14. The transmission unit 14 includes an intermediate shaft 40, a motion converter 41, a cylinder 42, a ring gear 43, a clutch 44, etc., and is housed in the first housing 20.

[0026] The intermediate shaft 40 extends along a third axis AX3 that is perpendicular to the output shaft 30 of the motor 13, i.e., parallel to the first direction AR1. The intermediate shaft 40 is supported so as to be rotatable about the third axis AX3. A bevel gear that meshes with a pinion gear 31 provided on the output shaft 30 is provided at the rear end of the intermediate shaft 40. A drive gear 400 that meshes with a ring gear 43 (described later) is provided at the tip end of the intermediate shaft 40.

[0027] The motion converting part 41 is provided on the intermediate shaft 40. The motion converting part 41 includes an inner ring 410, an outer ring 411, rolling elements 412, and a connecting rod 413. The inner ring 410 is fixed to the intermediate shaft 40, and the outer ring 411 is disposed around the inner ring 410. The rolling elements 412 are interposed between the inner ring 410 and the outer ring 411. The connecting rod 413 extends from the outer peripheral surface of the outer ring 411 toward the outside in the radial direction of the outer ring 411.

[0028] Grooves that intersect with each other are formed on the outer peripheral surface of the inner ring 410 and the inner peripheral surface of the outer ring 411. A portion of the rolling element 412 fits into the groove formed in the inner ring 410, and another portion of the rolling element 412 fits into a groove formed in the outer ring 411. As a result, the inner ring 410 and the outer ring 411 are connected via the rolling element 412 so as to be capable of relative rotation.

[0029] A clutch 44 is provided on the intermediate shaft 40. The clutch 44 is connected to the switching lever 26 (see FIG. 1 ) and can move back and forth along the intermediate shaft 40 in response to an operator's operation of the switching lever 26. By moving the clutch 44 back and forth, switching is performed between an engaged state in which power is transmitted from the intermediate shaft 40 to the motion conversion unit 41 and an released state in which power is not transmitted from the intermediate shaft 40 to the motion conversion unit 41.

[0030] When the clutch 44 moves backward to a predetermined position (close to the inner ring 410), the intermediate shaft 40 and the inner ring 410 are connected via the clutch 44, and power is transmitted from the intermediate shaft 40 to the inner ring 410. On the other hand, when the clutch 44 moves forward to a predetermined position (away from the inner ring 410), the connection between the intermediate shaft 40 and the inner ring 410 is released, and power transmission from the intermediate shaft 40 to the inner ring 410 is interrupted. Note that Figures 2 and 3 show a state in which the clutch 44 moves forward to a predetermined position and the connection between the intermediate shaft 40 and the inner ring 410 is released.

[0031] The above-described movement of the clutch 44 is realized in response to an operator's operation to switch the operating mode using the switching lever 26. When the intermediate shaft 40 rotates while the clutch 44 is in the engaged state, the inner ring 410 rotates. This causes the outer ring 411 to roll along the surface of the inner ring 410. As a result, the connecting rod 413 swings back and forth.

[0032] The cylinder 42 is provided above the intermediate shaft 40 and in parallel with the intermediate shaft 40. More specifically, the cylinder 42 is centered on the first axis line AX1 and extends along the first axis line AX1.

[0033] The ring gear 43 is provided around the cylinder 42 and is movable back and forth along the cylinder 42. The ring gear 43 can be switched between a connected state in which the rotation of the intermediate shaft 40 is transmitted to the cylinder 42, and a disconnected state in which the rotation of the intermediate shaft 40 is not transmitted to the cylinder 42. In the connected state, the ring gear 43 meshes with the drive gear 400 at the tip of the intermediate shaft 40. The ring gear 43 is switched in response to an operation to switch the operating mode by an operator. In the disconnected state, the ring gear 43 rotates idly on the cylinder 42.

[0034] The cylinder 42 accommodates a piston 420, a striker 421, and an intermediate element 422. The piston 420, the striker 421, and the intermediate element 422 are aligned in this order from rear to front. An air chamber 423 is provided between the piston 420 and the striker 421.

[0035] A connecting rod 413 of the motion converting unit 41 is rotatably connected to the back surface of the piston 420. When the connecting rod 413 swings back and forth, the piston 420 reciprocates back and forth within the cylinder 42, causing fluctuations in the pressure in the air chamber 423. Then, the pressure fluctuations in the air chamber 423 drive the striker 421, which strikes the intermediate element 422, which strikes the tool bit T attached to the attachment unit 12.

[0036] In this embodiment, the operating modes can be selected from a drill mode, a hammer mode, and a hammer drill mode. In the drill mode, the clutch 44 is in a disengaged state and the ring gear 43 is in a connected state. When the intermediate shaft 40 rotates in this state, the inner ring 410 of the motion converting unit 41 does not rotate, but the cylinder 42 rotates. Therefore, only a rotational force is applied to the tool bit T attached to the attachment portion 12. In other words, the drill mode is a rotation mode in which the driving force of the motor 13 is transmitted to the attachment portion 12 as a rotational force centered on the first axis AX1.

[0037] In the hammer mode, the clutch 44 is engaged and the ring gear 43 is disengaged. When the intermediate shaft 40 rotates in this state, the inner ring 410 of the motion converting part 41 rotates, but the cylinder 42 does not rotate. This causes the piston 420 to reciprocate within the stationary cylinder 42. As a result, only an impact force is applied to the tool bit T attached to the attachment part 12.

[0038] In the hammer drill mode, the clutch 44 is engaged and the ring gear 43 is connected. When the intermediate shaft 40 rotates in this state, the inner ring 410 of the motion converting unit 41 rotates, and the cylinder 42 also rotates. This causes the piston 420 to reciprocate within the rotating cylinder 42. As a result, both a rotational force and an impact force are applied to the tool bit T attached to the attachment portion 12. In other words, the hammer drill mode is a rotational impact mode in which the driving force of the motor 13 is transmitted to the attachment portion 12 as a rotational force about the first axis AX1 and an impact force in the direction of the first axis AX1.

[0039] <Control unit 15> The control unit 15 is provided on a control board housed in the lower part of the second housing 21. The control unit 15 is a microcomputer having an input port, an output port, an arithmetic processing unit, and a memory unit. The control unit 15 controls the operation of each unit constituting the work machine 10 according to the results of the arithmetic processing. The control unit 15 is electrically connected by wiring to the operation panel 23, the trigger switch 24A, and the acceleration sensor 16 described below.

[0040] In this embodiment, the control unit 15 sets the operation control mode of the work machine 10 to a first mode or a second mode in response to an operation of the operation panel 23 by the worker. In the first mode, the control unit 15 does not change the drive state of the motor 13 based on the detection result of the acceleration sensor 16, which will be described later. In the second mode, the control unit 15 changes the drive state of the motor 13 based on the detection result of the acceleration sensor 16. In other words, the control unit 15 controls the drive of the motor 13. The control of the drive state of the motor 13 in the first mode and the second mode, which is performed by the control unit 15, will be described in detail below.

[0041] <Acceleration sensor 16> The acceleration sensor 16 detects acceleration acting on the housing 11 using various methods, such as piezoelectric or capacitance. The acceleration sensor 16 detects acceleration in three axes: a first direction AR1 (front-rear direction) and a second direction AR2 (up-down and left-right directions). The acceleration sensor 16 generates an electric signal (detection signal) indicating the detected acceleration and the direction of the acceleration, and outputs it to the control unit 15.

[0042] <Control system of work machine 10> 4 is a circuit block diagram of the work machine 10. Note that a description of the configuration already described will be omitted. The work machine 10 has a main circuit 50, and the main circuit 50 receives a supply of power from a battery pack 25.

[0043] In the main circuit 50, the inverter circuit 51 is controlled by the control unit 15, converts the power supplied from the battery pack 25 into drive power, and supplies it to the motor 13. The motor 13 is rotated by the power supplied via the inverter circuit 51, which rotates the intermediate shaft 40 of the transmission unit 14. Three magnetic sensors H detect the rotation state of the rotor of the motor 13.

[0044] The rotor position detection circuit 52 acquires information about the rotation state of the rotor, i.e., information about the rotation state of the motor 13, based on the detection results obtained by the three magnetic sensors H, and outputs this information to the control unit 15. The voltage detection circuit 53 detects a voltage corresponding to the residual power of the battery pack 25 when power is supplied to the motor 13 via the inverter circuit 51. The current detection circuit 54 detects the motor current flowing through the motor 13. The temperature detection circuit 55 detects the temperature near the motor 13.

[0045] The panel LED 56 is an LED for illuminating the operation panel 23. The panel LED 56 is turned on and off under the control of the control unit 15. The lighting LED 57 is an LED for illuminating an area of ​​the counter material G near the tool bit T. The lighting LED 57 is turned on and off under the control of the control unit 15.

[0046] <Processing of the control unit 15> The following describes the processing that the control unit 15 executes when the operation mode of the work machine 10 is switched to the drill mode. In this case, the work machine 10 can tighten screws using a driver bit attached as the tool tip T.

[0047] 5 and 6 are schematic diagrams showing the work implement 10 during screw tightening. As shown in Fig. 5, the work implement 10 is tightening a screw V into a mating material G, such as concrete. When the screw is tightened, the tip of the tool bit T is inserted into a cross-shaped groove V1 formed in the head of the screw V. When the work implement 10 operates in drill mode in this state, the screw V rotates together with the tool bit T, which rotates about the first axis AX1.

[0048] When the tightening torque of the screw exceeds the torque generated by the work machine 10, the tip of the tool bit T rises upward from the groove V1, causing cam-out, as shown in Fig. 6. Since the work machine 10 also moves upward together with the raised tool bit T, the acceleration sensor 16 provided in the work machine 10 detects the upward acceleration in the first direction AR1.

[0049] Thereafter, the tip of the lifted tool bit T enters the groove V1 again, resulting in the state shown in Fig. 5. That is, the work implement 10 moves downward together with the tool bit T. Therefore, the acceleration sensor 16 provided in the work implement 10 detects the acceleration directed downward in the first direction AR1.

[0050] When the tool bit T repeatedly moves up and down from the groove V1 as described above, the cross recess in the head of the screw V may be damaged, or the tip of the tool bit T may be damaged. In the work machine 10 of this embodiment, when the operation control mode is set to the second mode, the control unit 15 performs control to change the drive state of the motor 13 upon determining that cam-out has occurred. Specifically, the control unit 15 stops the rotational drive of the motor 13 when cam-out has occurred. This will be described in detail below.

[0051] The control unit 15 determines whether or not cam-out has occurred based on the acceleration of the housing 11 in the first direction AR1 detected by the acceleration sensor 16. When cam-out has occurred, the head of the screw at the tip of the tool bit T repeatedly rises up from and falls into the cross recess, as described above.

[0052] When the state shown in FIG. 5 changes to the state shown in FIG. 6, the work implement 10 moves upward together with the lifted tool bit T. Therefore, the acceleration sensor 16 provided in the housing 11 detects upward acceleration in the first direction AR1. When the state shown in FIG. 6 changes to the state shown in FIG. 5, the work implement 10 moves downward together with the tool bit T that has entered the groove V1. Therefore, the acceleration sensor 16 provided in the housing 11 detects downward acceleration in the first direction AR1. In other words, when cam-out occurs, the housing 11 vibrates up and down in a direction along the first axis AX1 of the tool bit T, i.e., along the first direction AR1. Therefore, the vertical acceleration detected by the acceleration sensor 16 becomes larger than when cam-out does not occur.

[0053] Fig. 7 is a graph showing a schematic diagram of a change L1 in acceleration along the first direction AR1 detected by the acceleration sensor 16. In Fig. 7, the vertical axis represents acceleration [G], and the horizontal axis represents time [s] after the motor 13 starts to rotate.

[0054] As shown in Figure 7, from the time when the motor 13 starts to rotate until 0.5 seconds later, the work machine 10 operates in a state where no come-out has occurred (the state shown in Figure 5). Therefore, the increase or decrease in acceleration (amplitude) detected by the acceleration sensor 16 in the period up to 0.5 seconds is about 2.0 [G]. In contrast, come-out occurs around 0.5 seconds later, and the amplitude of acceleration of the housing 11 in the first direction AR1 becomes larger than 2.0 [G] after 0.5 seconds.

[0055] The control unit 15 determines the occurrence of come-out by calculating the amplitude of acceleration using the detection signal output from the acceleration sensor 16. Specifically, the control unit 15 extracts the maximum and minimum values ​​of acceleration within a predetermined time range (e.g., 30 ms) based on the detection signal output from the acceleration sensor 16. Then, the control unit 15 calculates the difference between the maximum and minimum values ​​as the amplitude of acceleration (discrimination value).

[0056] When the judgment value, which is the calculated amplitude of the acceleration, is equal to or greater than a preset amplitude threshold Th1, the control unit 15 determines that the vibration of the housing 11 in the first direction AR1 is large and that cam-out has occurred. When the control unit 15 determines that cam-out has occurred, as described above, the control unit 15 stops the rotation of the motor 13 that is being rotated and changes the drive state of the motor 13. That is, when the acceleration applied to the housing 11 in the first direction AR1 satisfies the first condition, the control unit 15 changes the drive state of the motor 13. More specifically, when the difference between the maximum and minimum values ​​of the acceleration applied to the first direction AR1 within a predetermined time range exceeds the amplitude threshold Th1, the control unit 15 changes the drive state of the motor 13. It can also be said that the control unit 15 changes the drive state of the motor 13 when it detects cam-out of the tool bit T.

[0057] The amplitude threshold value Th1 is a value in the range of 1.1 to 3.0 times the amplitude of acceleration that occurs when a screw is tightened without cam-out occurring. While Fig. 7 shows a case where the amplitude threshold value Th1 is 3.0 [G], a value of 2.2 [G] to 6.0 [G] can be set as the amplitude threshold value Th1.

[0058] The control unit 15 uses only acceleration along the first direction AR1 to determine whether a come-out has occurred. The control unit 15 does not use acceleration in the up-down direction or the left-right direction (second direction AR2) to determine whether a come-out has occurred. That is, the control unit 15 does not stop the rotation of the motor 13 even if the amplitude of the acceleration in the second direction AR2 exceeds the amplitude threshold Th1, satisfying the first condition. In other words, the control unit 15 does not change the driving state of the motor 13 even if the acceleration acting on the housing 11 in the second direction AR2 satisfies the first condition. Furthermore, the control unit 15 determines whether a come-out has occurred when the second mode is set, but does not determine whether a come-out has occurred when the first mode is set.

[0059] 8 and 9 are flowcharts illustrating the processing performed by the control unit 15 when the second mode is set. When the power of the work machine 10 is turned on, the control unit 15 reads out a program stored in the memory unit and executes the program, thereby performing the processing shown in Fig. 8 and 9.

[0060] In step S1 shown in Figure 8, the control unit 15 acquires acceleration data along the first direction AR1 based on the detection signal output from the acceleration sensor 16. Then, the process proceeds to step S2. In step S2, the control unit 15 stores the acceleration value indicated by the acceleration data acquired in step S1 in a memory unit within the control unit 15 as an initial acceleration value. The initial acceleration value is the value of the acceleration in the first direction AR1 acting on the work implement 10 before the motor 13 is driven. Then, the process proceeds to step S3.

[0061] In step S3, the control unit 15 determines whether the motor 13 is rotating based on information about the rotation state of the motor 13 acquired by the rotor position detection circuit 52. If the motor 13 is not rotating, the control unit 15 makes a negative determination, and the process returns to step S1. If the motor 13 is rotating, the control unit 15 makes a positive determination, and the process proceeds to step S4.

[0062] In step S4, control unit 15 acquires acceleration data along first direction AR1 based on the detection signal output from acceleration sensor 16, similar to step S1. Then, the process proceeds to step S5. In step S5, control unit 15 calculates the current value of acceleration. Specifically, control unit 15 calculates the current value of acceleration by subtracting the initial acceleration value calculated in step S2 from the acceleration value indicated by the acceleration data acquired in step S4. Then, the process proceeds to step S6.

[0063] In step S6, control unit 15 determines whether the current acceleration value is greater than the maximum acceleration value within a predetermined time range of 30 ms (maximum past acceleration value). If the current acceleration value is greater than the maximum past acceleration value, control unit 15 makes a positive determination, and the process proceeds to step S7. If the current acceleration value is equal to or less than the maximum past acceleration value, control unit 15 makes a negative determination, and the process proceeds to step S9, which will be described later.

[0064] In step S7, control unit 15 sets the current value of acceleration as a new maximum value of acceleration. Then, the process proceeds to step S8. In step S8, control unit 15 sets the minimum value of acceleration within a predetermined time range of 30 ms as the continuing minimum value of acceleration. Then, the process proceeds to step S13 in FIG. 9, which will be described later.

[0065] In step S9, which is reached after a negative determination in step S6, the control unit 15 continues to set the maximum value of acceleration within a 30 ms period of the predetermined time range as the maximum value of acceleration. Thereafter, the process proceeds to step S10. In step S10, the control unit 15 determines whether the current value of acceleration is smaller than the minimum value of acceleration within a 30 ms period of the predetermined time range (the minimum value of past acceleration). If the current value of acceleration is smaller than the minimum value of past acceleration, the control unit 15 makes a positive determination, and the process proceeds to step S11 in FIG. 9. If the current value of acceleration is equal to or greater than the minimum value of past acceleration, the control unit 15 makes a negative determination, and the process proceeds to step S12 in FIG. 9, which will be described later.

[0066] 9, the control unit 15 sets the current value of acceleration as a new minimum value of acceleration. Then, the process proceeds to step S13, which will be described later. In step S12, to which the process proceeds after a negative determination in step S10, the control unit 15 continues to set the minimum value of acceleration within a period of 30 ms in the predetermined time range as the minimum value of acceleration, as in step S8. Then, the process proceeds to step S13.

[0067] In step S13, control unit 15 stores the current value of acceleration in a memory unit within control unit 15. Thereafter, the process proceeds to step S14. In step S14, control unit 15 calculates a discrimination value, which is the amplitude of acceleration. As described above, the discrimination value is calculated by subtracting the minimum value of acceleration from the maximum value of acceleration. Thereafter, the process proceeds to step S15.

[0068] In step S15, the control unit 15 determines whether the calculated discrimination value is equal to or greater than the amplitude threshold value Th1. If the discrimination value is equal to or greater than the amplitude threshold value Th1, that is, if come-out has occurred, the control unit 15 makes a positive determination, and the process proceeds to step S16. If the discrimination value is less than the amplitude threshold value Th1, that is, if come-out has not occurred, the control unit 15 makes a negative determination, and the process returns to step S4 in FIG. 8.

[0069] In step S16, the control unit 15 stops the rotational driving of the motor 13. This completes the processes in the second mode.

[0070] According to the embodiment described above, at least one of the following advantageous effects can be obtained.

[0071] (1) The control unit 15 changes the driving state of the motor 13 when the acceleration applied to the housing 11 in the first direction AR1 satisfies a first condition, and does not change the driving state of the motor 13 even when the acceleration applied to the housing 11 in the second direction AR2 satisfies the first condition. In other words, the control unit 15 changes the driving state of the motor 13 when it detects that the tool bit T has come out.

[0072] This makes it possible to detect come-out, unlike when detecting torque or current to determine come-out, without being affected by the operating state of the work implement 10, such as the remaining voltage of the battery pack 25, the length and shape of the tool bit T, or the material and thickness of the mating workpiece G. In other words, since come-out can be detected with high accuracy, the workability of work using the work implement 10 can be improved.

[0073] Furthermore, the operation mode is mechanically set by the operator operating the switching lever 26, but the setting of the operation mode cannot be determined by the control unit 15. However, when acceleration is acting in the first direction AR1 while the operation control mode is set to the second mode, the control unit 15 changes the drive state of the motor 13 and stops it. Therefore, in an operation mode in which acceleration occurs in the first direction AR1, such as the hammer mode or hammer drill mode, the motor 13 stops. As a result, screw tightening that should be performed in drill mode is prevented from being performed when the operator has mistakenly set the operation mode to the hammer mode or hammer drill mode. Therefore, impacts that are unnecessary for screw tightening are applied to the tool bit T, which prevents damage to the tool bit T.

[0074] Furthermore, the control unit 15 does not change the driving state of the motor 13 even if the acceleration in the second direction AR2 satisfies the first condition, so that erroneous detection of cam-out is suppressed when an acceleration different from the acceleration caused by cam-out is applied to the housing 11. In other words, it is possible to accurately detect the occurrence of cam-out.

[0075] When determining whether or not a come-out has occurred, the control unit 15 uses the detection results from the acceleration sensor 16. The acceleration sensor 16 is provided inside the work machine 10 for the purpose of preventing kickback when the work machine 10 rotates around the tool tip T as an axis in hammer drill mode, and for the purpose of providing vertical support to assist in drilling a hole in the opposing material G in a vertical direction. Therefore, there is no need to add a new part to determine whether or not a come-out has occurred, which prevents an increase in the number of parts and manufacturing costs.

[0076] (2) When the difference between the maximum and minimum values ​​of the acceleration in the first direction AR1 within a predetermined time range (e.g., 30 ms) exceeds the amplitude threshold Th1, the control unit 15 changes the driving state of the motor 13. This enables the control unit 15 to determine come-out using the acceleration in the first direction AR1.

[0077] (3) The control unit 15 can set a first mode in which the drive state of the motor 13 is not changed based on acceleration acting in the first direction AR1 relative to the housing 11, and a second mode in which the drive state of the motor 13 is changed based on acceleration acting in the first direction AR1 relative to the housing 11. As a result, when working in an operation mode in which acceleration occurs in the first direction AR1, such as the hammer mode or hammer drill mode, by setting the operation control mode to the first mode, it is possible to prevent the drive state of the motor 13 from being changed based on acceleration in the first direction AR1. Therefore, by setting the operation control mode to the first mode in the hammer mode or hammer drill mode, it is possible to prevent the motor 13 of the working implement 10 from stopping against the operator's intention during operation.

[0078] <First Modification> In the embodiment, the control unit 15 determines whether or not a come-out has occurred by using the amplitude threshold value Th1 of the detected acceleration amplitude, but the present invention is not limited to this example. For example, the control unit 15 may determine whether or not a come-out has occurred when the maximum value of the acceleration detected by the acceleration sensor 16 exceeds the acceleration threshold value Th2.

[0079] Fig. 10 is a graph showing a schematic diagram of a change in acceleration L1 along the first direction AR1 detected by the acceleration sensor 16. In Fig. 10, the vertical axis represents acceleration [G], and the horizontal axis represents time [s] after the motor 13 starts to rotate. Note that Fig. 10 shows a case where the change in acceleration L1 is the same as that in Fig. 7.

[0080] 10, during the period from when the motor 13 starts to rotate until 0.5 seconds, the work machine 10 operates without cam-out occurring. Therefore, the maximum value of acceleration detected by the acceleration sensor 16 during the period up to 0.5 seconds is approximately 2.0 [G]. In contrast, cam-out occurs around 0.5 seconds, and after 0.5 seconds, the maximum value of acceleration of the housing 11 in the first direction AR1 becomes greater than 3.0 [G].

[0081] If the maximum value of the detected acceleration is equal to or greater than a preset acceleration threshold value Th2, the control unit 15 determines that the vibration of the housing 11 in the first direction AR1 is large and that cam-out has occurred. The acceleration threshold value Th2 is, for example, a value in the range of 1.1 to 3.0 times the maximum value of acceleration that occurs during screw tightening when cam-out has not occurred. While FIG. 10 shows a case where the acceleration threshold value Th2 is 3.0 [G], the acceleration threshold value Th2 can be set to a value between 2.2 [G] and 6.0 [G].

[0082] The control unit 15 may determine that come-out has occurred when the minimum value of the acceleration detected by the acceleration sensor 16 is lower than the acceleration threshold value Th2. In other words, the control unit 15 may determine that come-out has occurred when the minimum value of the acceleration exceeds the absolute value of the acceleration threshold value Th2.

[0083] When control unit 15 determines the occurrence of come-out using acceleration threshold value Th2, it stops the rotational driving of motor 13 in the same manner as in the embodiment. That is, in the first modified example, when the acceleration in first direction AR1 exceeds acceleration threshold value Th2, control unit 15 changes the driving state of motor 13. As a result, the first modified example can also achieve the same effects as those achieved by the embodiment.

[0084] <Second Modification> In the embodiment and the first modified example, the control unit 15 uses the acceleration detected by the acceleration sensor 16 when determining the occurrence of come-out, but the determination is not limited to using acceleration. For example, the control unit 15 may determine the occurrence of come-out based on the value of the motor current flowing through the rotationally driven motor 13. In this case, the control unit 15 uses the value of the motor current detected by the current detection circuit 54.

[0085] Fig. 11 is a graph showing a schematic diagram of a change L2 in the value of the motor current of the motor 13 detected by the current detection circuit 54. In Fig. 11, the vertical axis represents the current value [A], and the horizontal axis represents the time [s] after the motor 13 starts to rotate.

[0086] As shown in Figure 11, after 0.2 seconds from when the motor 13 starts to rotate, the current value is in the range of approximately 18 A to 25 A. After that, after about 0.455 seconds, the detected current value increases significantly. As shown in Figure 11, the maximum current value exceeds 40 A.

[0087] This is because cam-out has occurred or there is a sign of cam-out occurring. For example, a sudden increase in the load received from the mating workpiece G causes the rotation speed of the tool bit T to decrease. Meanwhile, the motor 13 tries to maintain the rotation speed of the output shaft 30 in order to maintain the rotation speed of the tool bit T. As a result, the value of the motor current flowing through the motor 13 increases.

[0088] If the maximum detected current value is equal to or greater than a preset current threshold Th3, the control unit 15 determines that the vibration of the housing 11 in the first direction AR1 is large and that cam-out has occurred or is a sign of cam-out. The current threshold Th3 is, for example, a value in the range of 1.1 to 3.0 times the maximum current value during screw tightening when cam-out has not occurred. While Fig. 11 shows a case where the current threshold Th3 is 35 [A], the current threshold Th3 can be set to a value between 27.5 [A] and 75 [A].

[0089] When the control unit 15 determines the occurrence of come-out or a sign of the occurrence of come-out using the current threshold value Th3, it stops the rotational driving of the motor 13 in the same manner as in the embodiment. As a result, in the second modified example, the same effects as those obtained by the embodiment can be obtained.

[0090] Although various embodiments and modifications have been described above, the present invention is not limited to these. Other embodiments that are conceivable within the scope of the technical idea of ​​the present invention are also included within the scope of the present invention. [Explanation of symbols]

[0091] 10 work implement, 11 housing, 12 mounting portion, 12A adapter, 13 motor, 14 transmission portion, 15 control portion, 16 acceleration sensor, AR1 first direction, AR2 second direction, AX1 first axis, T tip tool

Claims

1. A motor; a mounting portion that receives a driving force from the motor, rotates about an axis extending in a first direction, and to which a tool bit extending along the axis is attached; a housing that supports the motor and the mounting portion; a control unit that controls the driving of the motor, The control unit changes the drive state of the motor when acceleration applied to the housing in the first direction satisfies a first condition, and does not change the drive state of the motor even when acceleration applied to the housing in a second direction intersecting the first direction satisfies the first condition.

2. The work machine according to claim 1, A work machine, wherein a driver bit is attached to the attachment portion as the tip tool.

3. The work machine according to claim 2, The control unit changes the driving state of the motor when a difference between a maximum value and a minimum value of acceleration applied in the first direction within a predetermined time range exceeds an amplitude threshold.

4. The work machine according to claim 2, The control unit changes the driving state of the motor when the acceleration applied in the first direction exceeds an acceleration threshold.

5. The work machine according to claim 3 or 4, a transmission unit that transmits the driving force of the motor to the mounting unit, The transmission unit is capable of setting a plurality of modes including a rotation mode in which the driving force of the motor is transmitted to the mounting unit as a rotational force centered on the axis, and a rotational impact mode in which the driving force of the motor is transmitted to the mounting unit as a rotational force centered on the axis and an impact force in the axial direction.

6. The work machine according to claim 5, The control unit is capable of setting a plurality of modes including a first mode in which the drive state of the motor is not changed based on the acceleration applied to the housing in the first direction, and a second mode in which the drive state of the motor is changed based on the acceleration applied to the housing in the first direction.

7. A motor; a mounting portion that receives a driving force from the motor, rotates about an axis extending in a first direction, and to which a tool bit extending along the axis is attached; a housing that supports the motor and the mounting portion; a control unit that controls the driving of the motor; a transmission unit that transmits the driving force of the motor to the mounting unit, the transmission unit is capable of setting a plurality of modes, including a rotation mode in which the driving force of the motor is transmitted to the attachment unit as a rotational force about the axis, and a rotational impact mode in which the driving force of the motor is transmitted to the attachment unit as a rotational force about the axis and an impact force in the axial direction, When the control unit detects that the tool bit has come out, the control unit changes the driving state of the motor.

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