Work machine

Abstract

Provided is a work machine that is capable of appropriately detecting a state in which a work machine body is swinging. A work machine 1 is provided with a microcomputer 29 that controls the driving of a motor 6. If centrifugal direction acceleration applied to an acceleration sensor 24 exceeds a centrifugal direction acceleration threshold, the microcomputer 29 reduces the rotation speed of the motor 6 or stops the motor 6. The microcomputer 29 requires the meeting of a condition in which a load current of the motor 6 exceeds a current threshold (not in a no-load state) to activate a swing control function.

Description

Work equipment

[0001] The present invention relates to a work machine such as a hammer drill.

[0002] Japanese Patent Application Laid-Open No. 2006-124493 discloses a work machine that has a function to stop a motor when a rotating tool bit gets caught on an opposing material and the work machine body shakes. This work machine is equipped with an acceleration sensor that detects the vibration of the work machine body, and stops driving the motor when the lateral acceleration detected by the acceleration sensor exceeds a threshold value.

[0003] Japanese Patent Application Publication No. 2019-150897

[0004] The lateral acceleration is greatest at the moment the work machine body begins to swing, and tends to decrease over time. Therefore, when detecting the swing of the work machine body based on the lateral acceleration, it is difficult to determine whether the work machine body is not swinging or whether the swing speed has stabilized after a short time has passed since the work machine body began to swing. Also, if the swing speed rises slowly, it is difficult to determine whether the work machine body is swinging or not. While it is possible to calculate the swing speed to detect swing, this requires an integral calculation of the lateral acceleration, which is prone to large errors.

[0005] An object of the present invention is to provide a work machine that can appropriately detect a state in which the work machine body is shaken.

[0006] One aspect of the present invention is a work machine including a motor, a tool bit that rotates around a rotation axis by receiving driving force from the motor, a housing that supports the motor and the tool bit, a controller that controls the drive of the motor, and a detector that is supported by the housing and can detect acceleration occurring in the motor itself, and the controller controls the drive of the motor based on radial acceleration occurring in a radial direction around the rotation axis relative to the detector.

[0007] The present invention may be expressed as an "electric working machine," "electric tool," "electrical equipment," etc., and such expressions are also valid as aspects of the present invention.

[0008] According to the present invention, it is possible to provide a work machine that can appropriately detect a state in which the work machine body is shaken.

[0009] 3A is a right-side cross-sectional view of a work machine 1 according to an embodiment of the present invention; FIG. 3B is a circuit block diagram of the work machine 1; FIG. 3A is a schematic diagram showing an example of the state of the work machine 1 during operation; FIG. 3B is a schematic diagram of the work machine 1 in the state shown in FIG. 3A, viewed from the concrete side; FIG. 3B is a time chart of the load current of the motor 6, the angle of the work machine body, the acceleration value in the X-axis direction detected by the acceleration sensor 24, and the acceleration value in the Z-axis direction detected by the acceleration sensor 24, when the work machine 1 is in high-speed mode and during normal cutting, i.e., when the tool bit 19 is not locked; and FIG. 3C is a time chart of the load current of the motor 6, the angle of the work machine body, the acceleration value in the X-axis direction detected by the acceleration sensor 24, and the acceleration value in the Z-axis direction detected by the acceleration sensor 24, when the work machine 1 is in high-speed mode and during normal cutting, i.e., when the tool bit 19 is not locked. 1 is a time chart showing the load current of the motor 6, the angle of the work machine body, the acceleration value in the X-axis direction detected by the acceleration sensor 24, and the acceleration value in the Z-axis direction detected by the acceleration sensor 24 when the work machine 1 is in low-speed mode and during normal cutting, i.e., when the tool bit 19 is not locked. 2 is a time chart showing the load current of the motor 6, the angle of the work machine body, the acceleration value in the X-axis direction detected by the acceleration sensor 24, and the acceleration value in the Z-axis direction detected by the acceleration sensor 24 when the work machine 1 is in low-speed mode and the tool bit 19 is locked midway and the swing suppression function is not activated. 3 is a control flowchart for the work machine 1.

[0010] Figure 1 is a right-side cross-sectional view of a work machine 1 according to an embodiment of the present invention. Figure 1 defines the mutually orthogonal front-rear and up-down directions of the work machine 1. The direction perpendicular to the front-rear and up-down directions is defined as the left-right direction. The front-rear direction is parallel to the axial direction of the tool bit 19. The up-down direction is parallel to the axial direction of the output shaft 6a of the motor 6. The left-right direction is defined relative to the operator looking forward.

[0011] The work machine 1 is a drilling tool, specifically a hammer drill. The work machine 1 can perform chipping, drilling, and crushing operations on a mating material (workpiece) such as concrete or stone by applying rotational force and / or impact force to a tool bit 19. The work machine 1 includes a main body 2 and a dust collection unit 3. The main body 2 has a main body housing 4. The dust collection unit 3 is detachably attached to the main body housing 4.

[0012] The main body housing 4 includes a main body 4a that houses and holds the motor 6, reduction gear mechanism 7, intermediate shaft 8, tool holder 12, reciprocating bearing 13, cylinder 14, main circuit board 20, etc., and a handle 4b that is connected to the main body 4a via a vibration-isolating mechanism for relative movement. A battery pack 10, which serves as a power source, is detachably connected to the rear lower portion of the handle 4b. A trigger switch 9 is provided on the handle 4b, allowing the operator to start and stop the motor 6. The main body 4a also includes an operation panel 23 that allows the operator to switch the rotation mode of the motor 6 between high-speed mode and low-speed mode. The configuration of the rotary impact mechanism (power transmission mechanism) that rotates and / or impacts the tool bit 19 using the rotation of the motor 6 is well known, so only a brief description will be provided below.

[0013] The motor 6 is a brushless electric motor. The rotation of the output shaft 6a of the motor 6 is reduced in speed by a reduction gear mechanism 7 located above the motor 6, and the rotation direction is changed by 90 degrees before being transmitted to the intermediate shaft 8. The axial direction of the intermediate shaft 8 is parallel to the front-to-rear direction. A first clutch mechanism 11a switches whether or not the rotation of the intermediate shaft 8 is transmitted to a reciprocating bearing 13. A second clutch mechanism 11b switches whether or not the rotation of the intermediate shaft 8 is transmitted to a cylinder 14. The operator can switch between transmitting and blocking the rotation by the first clutch mechanism 11a and the second clutch mechanism 11b using a change lever (not shown).

[0014] The work machine 1 has three operating modes: impact mode, rotational impact mode, and rotational mode. The operating mode is determined by the operation of the change lever. In the impact mode, rotational transmission by the first clutch mechanism 11a is active, and rotational transmission by the second clutch mechanism 11b is inactive. In the rotational impact mode, rotational transmission by both the first clutch mechanism 11a and the second clutch mechanism 11b is active. In the rotational mode, rotational transmission by the first clutch mechanism 11a is inactive, and rotational transmission by the second clutch mechanism 11b is active.

[0015] A piston 15 is provided within the cylinder 14. In the impact mode or rotary impact mode, the reciprocating bearing 13 converts the rotation of the intermediate shaft 8 into reciprocating motion in the front-to-rear direction and transmits it to the piston 15. An air chamber 16 and a striker (striker) 17 are provided within the piston 15, in that order from rear to front. A second hammer (intermediate element) 18 is provided in front of the striker 17.

[0016] The forward movement of the piston 15 compresses the air in the air chamber 16, and the pressure (positive pressure) of the compressed air moves the striker 17 forward. The forward moving striker 17 strikes the second hammer 18, and the second hammer 18, which is moving forward with this striking force, strikes the tip tool 19.

[0017] The rearward movement of the piston 15 expands the air in the air chamber 16, and the pressure (negative pressure) of the expanded air moves rearward the striker 17. In this way, the striker 17 is driven to reciprocate back and forth by fluctuations (compression / expansion) in the air chamber 16 caused by the reciprocating movement of the piston 15, and the striker 17 strikes the second hammer 18, which in turn strikes the tool bit 19.

[0018] In the rotary impact mode or the rotation mode, the cylinder 14 is rotationally driven by the intermediate shaft 8. The tool holder 12 provided in front of the cylinder 14 rotates together with the cylinder 14. The tool tip 19 is held by the tool holder 12, extends forward from the main housing 4, and rotates together with the tool holder 12. The rotation axis of the tool tip 19 is coaxial with the rotation axis of the cylinder 14, and will be referred to as the "rotation axis" hereinafter. The tool tip 19 receives the driving force of the motor 6 and rotates around the rotation axis.

[0019] The main board 20 is supported by the main housing 4 below the motor 6 in a vertically perpendicular position.

[0020] 2 is a circuit block diagram of the work machine 1. The work machine 1 includes a main board 20 equipped with a current detection circuit 22, an acceleration sensor 24 as a detector, a voltage detection circuit 25, an inverter circuit 26, a rotor position detection circuit 27, a temperature detection circuit 28, and a microcomputer 29 (microcomputer or microcontroller) as a controller. In other words, the acceleration sensor 24 is provided in the main body portion 4a of the main housing 4. However, the acceleration sensor 24 may also be provided in the handle portion 4b.

[0021] The current detection circuit 22 detects the load current (hereinafter referred to as "load current") flowing through the motor 6 and sends it to the microcomputer 29. The current detection circuit 22 and the acceleration sensor 24 form a detection unit. The acceleration sensor 24 is capable of detecting the acceleration occurring in itself. The voltage detection circuit 25 detects the output voltage of the battery pack 10 and sends it to the microcomputer 29. The inverter circuit 26 is a drive circuit that is made up of switching elements such as FETs and IGBTs connected in a three-phase bridge, and supplies drive current to the motor 6.

[0022] The rotor position detection circuit 27 detects the rotor rotation position from an output signal of a magnetic sensor 30 such as a Hall IC that outputs a signal corresponding to the rotation position of the motor 6 (rotor rotation position), and sends the signal to the microcomputer 29. The temperature detection circuit 28 detects the temperature of the inverter circuit 26 and sends the signal to the microcomputer 29.

[0023] The microcomputer 29 controls the inverter circuit 26, for example, by PWM control, in accordance with the mode set by the operation panel 23 and the operation of the trigger switch 9, and controls the driving of the motor 6. The microcomputer 29 controls the illumination LED 21 that illuminates the work area and the panel LED provided on the operation panel 23.

[0024] FIG. 3(A) is a schematic diagram showing an example of the state of the work machine 1 during work. FIG. 3(B) is a schematic diagram of the work machine 1 in the state shown in FIG. 3(A) viewed from the concrete side. The acceleration sensor 24 here is a three-axis acceleration sensor. The X, Y, and Z axes shown in FIGS. 3(A) and 3(B) are three orthogonal axes that correspond to the detection axes of the acceleration sensor 24. The X axis is parallel to the left-right direction, with the +X direction corresponding to the leftward direction and the -X direction corresponding to the rightward direction. The Y axis is parallel to the front-rear direction, with the +Y direction corresponding to the forward direction and the -Y direction corresponding to the backward direction. The Z axis is parallel to the up-down direction, with the +Z direction corresponding to the downward direction and the -Z direction corresponding to the upward direction.

[0025] During operation by the work machine 1, the tool bit 19 may get caught on an opposing material, such as concrete 50. When this happens, the tool bit 19 enters a locked state, and the work machine body (the entire work machine 1 excluding the tool bit 19) rotates around the locked tool bit 19 in the direction shown in FIG. 3B.

[0026] The work machine 1 has a function (also referred to as a "swing suppression function" in this specification) of reducing the rotation speed of the motor 6 or stopping the motor 6 when it detects that the work machine body is being swung. When the swing suppression function is activated, stopping the motor 6 is preferable in terms of the effect of suppressing the work machine body from being swung, but a certain degree of suppression effect can also be obtained when the rotation speed of the motor 6 is reduced without stopping the motor 6.

[0027] The microcomputer 29 detects whether the work machine body is vibrating based on the acceleration detection value in the Z-axis direction of the acceleration sensor 24, i.e., the radial acceleration (centrifugal acceleration) occurring in the radial direction about the rotation axis relative to the acceleration sensor 24. The radial acceleration (centrifugal acceleration) is the acceleration occurring in the direction away from the rotation axis (+Z direction) along an imaginary line (Z axis) connecting the acceleration sensor 24 and the rotation axis (or its extension).

[0028] As an example of the configuration of the swinging suppression function of this embodiment, the microcomputer 29 reduces the rotation speed of the motor 6 or stops the motor 6 when the centrifugal force direction acceleration exceeds a centrifugal force direction acceleration threshold value as a first threshold value.

[0029] Alternatively, when the centrifugal force direction acceleration exceeds a centrifugal force direction acceleration threshold value as a first threshold value and the load current exceeds a current threshold value as a second threshold value, the microcomputer 29 reduces the rotation speed of the motor 6 or stops the motor 6. The current threshold value is set so that the load current exceeds the current threshold value unless the tool bit 19 is in an unloaded state where it is not in contact with the mating material.

[0030] Alternatively, when the centrifugal force direction acceleration exceeds a centrifugal force direction acceleration threshold value as a first threshold value and the acceleration detection value in the X-axis direction of the acceleration sensor 24, i.e., the circumferential acceleration (left-right acceleration) occurring in the circumferential direction about the rotation axis with respect to the acceleration sensor 24, exceeds a left-right acceleration threshold value as a third threshold value, the microcomputer 29 reduces the rotation speed of the motor 6 or stops the motor 6. The left-right acceleration threshold value is a threshold value for confirming that acceleration in the left direction with respect to the acceleration sensor 24, i.e., acceleration in the direction in which the work machine body is swung is occurring due to the recoil when the motor 6 attempts to rotate the tool bit 19 in a locked state.

[0031] Note that "exceeding the threshold" specifically means "maintaining a state in which the threshold is exceeded for a predetermined period of time." For example, even if the centrifugal force direction acceleration momentarily exceeds the first threshold, if it falls below the first threshold again within a predetermined period of time, it is determined that the first threshold has not been exceeded. This allows the phenomenon in which the numerical value momentarily exceeds the threshold due to vibration or the like, even though no actual swinging has occurred, to be ignored as noise. Of course, it is also possible to determine that the threshold has been exceeded if the numerical value exceeds the threshold for even a very short period of time, regardless of the time.

[0032] The microcomputer 29 sets the centrifugal force direction acceleration threshold, current threshold, and left / right direction acceleration threshold to different values ​​in the high speed mode and the low speed mode (the values ​​are set higher in the high speed mode). For example, in the high speed mode, the microcomputer 29 sets the current threshold to 8.0 A, the left / right direction acceleration threshold to 1.0 G, and the centrifugal force direction acceleration threshold to 2.0 G, and in the low speed mode, the microcomputer 29 sets the current threshold to 4.0 A, the left / right direction acceleration threshold to 0.5 G, and the centrifugal force direction acceleration threshold to 0.75 G.

[0033] 4 is a time chart of the load current, the angle of the work machine body, the acceleration value in the X-axis direction (lateral acceleration) detected by the acceleration sensor 24, and the acceleration value in the Z-axis direction (centrifugal force acceleration) detected by the acceleration sensor 24 when the work machine 1 is in high-speed mode and during normal cutting, i.e., when the tool bit 19 is not locked. Note that all of the time charts in Figs. 4 to 7 show the case when the tool bit 19 rotates clockwise, and when the tool bit 19 rotates counterclockwise, the positive and negative values ​​of the lateral acceleration threshold values ​​are reversed.

[0034] In Figure 4, the trigger switch 9 is turned on at time t0. The load current temporarily increases from the time the trigger switch 9 is turned on (around 20 ms) until 200 ms, i.e., when the motor 6 is started, but then settles down to about 10 A. The angle of the work machine body is generally constant, although it fluctuates by about ±1° due to vibrations during work, etc. The lateral acceleration fluctuates within a range of about ±3 G (G is gravitational acceleration) due to vibrations during work, etc., but averages out to approximately zero. The centrifugal force direction acceleration fluctuates within a range of about ±1 G due to vibrations during work, etc., but does not exceed the centrifugal force direction acceleration threshold (2.0 G) and averages out to approximately zero.

[0035] Figure 5 is a time chart of the load current, the angle of the work machine body, the acceleration value detected by the acceleration sensor 24 in the X-axis direction (left-right acceleration), and the acceleration value detected by the acceleration sensor 24 in the Z-axis direction (centrifugal force acceleration) when the work machine 1 is in high-speed mode and the tip tool 19 locks midway and the swing-prevention function is not activated.

[0036] In FIG. 5, the trigger switch 9 is turned on at time t0, the tool tip 19 is fixed to the mating material at time t1 (around 40 ms), the operator begins to press the work machine body at time t3 (around 150 ms), and the work machine body stops at time t5 (around 270 ms) when the vibration of the work machine body has slightly exceeded 40°.

[0037] The lateral acceleration momentarily jumps up to about 8 G immediately after time t1, then drops to near 0, then rises to about 5 G and drops again, reaching 0 at time t3. After time t3, the lateral acceleration becomes negative due to the force exerted by the operator trying to stop the work machine body, and reaches 0 at time t5.

[0038] The centrifugal force direction acceleration starts to rise from time t1 and reaches a peak value slightly exceeding 2.5 G (a peak value exceeding the centrifugal force direction acceleration threshold) just before the operator starts to hold down the work machine body at time t5, that is, at the timing when the swing angular velocity of the work machine body centered on the tool bit 19 reaches a maximum. After time t3, the centrifugal force direction acceleration decreases in accordance with the deceleration of the swing velocity of the work machine body caused by the operator, and reaches 0 at time t5.

[0039] FIG. 6 is a time chart showing the load current, the angle of the work machine body, the acceleration value detected by the acceleration sensor 24 in the X-axis direction (lateral acceleration), and the acceleration value detected by the acceleration sensor 24 in the Z-axis direction (centrifugal force acceleration) when the work machine 1 is in low-speed mode and during normal cutting, i.e., when the tip tool 19 is not locked.

[0040] In Figure 6, the trigger switch 9 is turned on at time t0. The load current temporarily increases from the time the trigger switch 9 is turned on (around 20 ms) until 320 ms, i.e., when the motor 6 is started, but then settles to a constant value. The angle of the work machine body is generally constant, although it fluctuates by about ±1° due to vibrations during work, etc. The lateral acceleration fluctuates within a range of about ±1.5 G due to vibrations during work, etc., but averages out to approximately zero. The centrifugal force direction acceleration fluctuates within a range of about ±0.7 G due to vibrations during work, etc., but does not exceed the centrifugal force direction acceleration threshold (0.75 G) and averages out to approximately zero.

[0041] Figure 7 is a time chart of the load current, the angle of the work machine body, the acceleration value in the X-axis direction (left-right acceleration) detected by the acceleration sensor 24, and the acceleration value in the Z-axis direction (centrifugal force acceleration) detected by the acceleration sensor 24 when the work machine 1 is in low-speed mode, the tool tip 19 locks midway, and the swing-prevention function is not activated.

[0042] In FIG. 7, the trigger switch 9 is turned on at 0 ms, the tool tip 19 is fixed to the mating material at time t7 (near 40 ms), the operator begins to press the work machine body at time t9 (near 280 ms), and the vibration of the work machine body stops at time t11 (near 400 ms) when it has slightly exceeded 35°.

[0043] The lateral acceleration momentarily jumps up to about 4 G immediately after time t7, then drops to near 0, and then vibrates while gradually rising from 0 on average, returning to 0 at time t9. After time t9, the lateral acceleration becomes negative due to the force exerted by the worker trying to stop the work machine body, and returns to 0 at time t11.

[0044] The centrifugal force direction acceleration starts to rise from time t7 and reaches a peak value slightly exceeding 0.8 G (a peak value exceeding the centrifugal force direction acceleration threshold) just before the operator starts to hold down the work machine body at time t9, that is, at the timing when the swing angular velocity of the work machine body centered on the tool bit 19 reaches a maximum. After time t9, the centrifugal force direction acceleration decreases in accordance with the deceleration of the swing velocity of the work machine body caused by the operator, and reaches 0 at time t11.

[0045] 8 is a control flowchart of the work machine 1. The microcomputer 29 acquires acceleration data, i.e., the acceleration detected by the acceleration sensor 24 (S1). The microcomputer 29 assigns the detected acceleration value in the Z-axis direction (centrifugal force direction acceleration) included in the acceleration data to the initial acceleration value (S3). If the motor 6 is not in an activated state (No in S5), the microcomputer 29 returns to S1. The centrifugal force direction acceleration immediately after activation of the motor 6 is set as the initial acceleration value. Note that the initial acceleration value may be zero.

[0046] If the motor 6 is in an activated state (Yes in S5), the microcomputer 29 acquires acceleration data (S7). The microcomputer 29 subtracts the initial acceleration value set in S3 from the centrifugal force direction acceleration included in the acceleration data and assigns the result to the discrimination value.

[0047] If the discrimination value does not exceed the centrifugal force direction acceleration threshold (No in S11), the microcomputer 29 returns to S7. If the discrimination value exceeds the centrifugal force direction acceleration threshold (Yes in S11), the microcomputer 29 checks whether the load current exceeds the current threshold (S13).

[0048] If the load current does not exceed the current threshold value (No in S13), the microcomputer 29 returns to S7. This makes it possible to suppress activation of the swinging suppression function when the operator moves the work machine body while the motor 6 is rotating in an unloaded state.

[0049] If the load current exceeds the current threshold (Yes in S13), the microcomputer 29 calculates the swing direction of the work machine body from the detected acceleration value in the X-axis direction (left-right acceleration) included in the acceleration data, and checks whether the swing direction is opposite to the rotation direction of the tool bit (S15). More specifically, if the motor 6 is rotating in a direction that causes the tool bit 19 to rotate counterclockwise when viewed from the rear, the microcomputer 29 checks whether the clockwise acceleration (i.e., leftward acceleration) exceeds the threshold. Also, if the motor 6 is rotating in a direction that causes the tool bit 19 to rotate clockwise when viewed from the rear, the microcomputer 29 checks whether the counterclockwise acceleration (i.e., rightward acceleration) exceeds the threshold.

[0050] The microcomputer 29 calculates the swing direction of the work machine body, and if the swing direction is not opposite to the rotation direction of the tool bit (No in S15), the process returns to S7. This prevents the swing suppression function from erroneously operating when, for example, the operator swings the work machine body in a direction different from the direction in which acceleration is estimated to occur when the tool bit 19 is locked.

[0051] If the swing direction of the work machine body is opposite to the rotation direction of the tool bit (Yes in S15), the microcomputer 29 reduces the rotation speed of the motor 6 or stops the motor 6 (S17).

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

[0053] (1) The microcomputer 29 controls the driving of the motor 6 based on the radial acceleration (centrifugal force direction acceleration) that occurs in the radial direction about the rotation axis relative to the acceleration sensor 24. Specifically, when the centrifugal force direction acceleration exceeds the centrifugal force direction acceleration threshold, the microcomputer 29 reduces the rotation speed of the motor 6 or stops the motor 6. This makes it possible to appropriately detect the state in which the work machine body is being swung, and to appropriately activate the swing suppression function.

[0054] For comparison, consider a case where the vibration of the work machine body is determined based on whether the lateral acceleration exceeds a threshold value. The lateral acceleration exhibits a momentarily large value when the tool bit 19 is locked, but then decreases. This makes it difficult to distinguish the momentarily large value of the lateral acceleration caused by the tool bit 19 being locked from that caused by noise or momentary vibration. Furthermore, if one attempts to make a judgment after the momentarily large value has passed, the lateral acceleration decreases over time, making it difficult to distinguish whether the work machine body is not vibrating or whether the vibration speed has become approximately constant as time passes. Deriving the vibration speed of the work machine body from the lateral acceleration requires an integral calculation of the lateral acceleration, but the error inherent in the detected value of the lateral acceleration itself is also integrated, resulting in a large error.

[0055] In this regard, the centrifugal force direction acceleration becomes large and not instantaneous when the tool bit 19 is locked. Therefore, a large value of the centrifugal force direction acceleration due to the locking of the tool bit 19 is easily distinguishable from a large value due to noise or momentary vibration. Furthermore, because the rotational speed of the work machine body at which the tool bit 19 is swung increases over time, it is not difficult to distinguish whether the work machine body is not being swung or whether the swung speed has become approximately constant over time. Furthermore, the centrifugal force direction acceleration is proportional to the square of the rotational speed of the work machine body at which the tool bit 19 is swung, and directly corresponds to the rotational speed at which the work machine body is swung. Therefore, the rotational speed at which the work machine body is swung can be estimated from the centrifugal force direction acceleration without using integral calculations, resulting in a small error. This embodiment makes it possible to appropriately detect whether the work machine body is being swung by determining whether the work machine body is being swung based on the centrifugal force direction acceleration.

[0056] (2) The microcomputer 29 determines that the load current must exceed the current threshold (i.e., the motor is not in a no-load state) as a necessary condition for activating the swing-back suppression function. Therefore, the activation of the swing-back suppression function can be suppressed when the operator moves the work machine body while the motor 6 is rotating in a no-load state.

[0057] (3) The microcomputer 29 determines that the swing direction of the work machine body is opposite to the rotation direction of the tool bit as a necessary condition for the swing suppression function to operate. Therefore, for example, if the operator swings the work machine body in a direction different from the direction in which acceleration is estimated to occur when the tool bit 19 is locked, the swing suppression function can be prevented from erroneously operating.

[0058] Although the present invention has been described above using the embodiment as an example, various modifications can be made to the components and processes of the embodiment within the scope of the claims. Modifications will be discussed below.

[0059] The work machine of the present invention is not limited to a hammer drill, but may be other types of machine such as a driver drill, a drill, etc. The load current value, acceleration, time, various thresholds, etc., given as specific numerical values ​​in the embodiments do not limit the scope of the invention in any way and can be changed as desired to suit the required specifications.

[0060] 1...Work machine (hammer drill), 2...Main body, 3...Dust collection unit, 4...Main body housing, 6...Motor (electric motor), 6a...Output shaft, 7...Reduction mechanism, 8...Intermediate shaft, 9...Trigger switch, 10...Battery pack, 11a...First clutch mechanism, 11b...Second clutch mechanism, 12...Tool holding portion, 13...Reciprocating bearing, 14...Cylinder, 15...Piston, 16...Air chamber, 17...Striker (impacting element), 18...Second hammer (intermediate element), 19...Tip tool, 20...Main board, 21...Lighting LED, 22...Current detection circuit, 23...Operation panel, 24...Acceleration sensor, 25...Voltage detection circuit, 26...Inverter circuit, 27...Rotor position detection circuit, 28...Temperature detection circuit, 29...Microcomputer (control unit), 30...Magnetic sensor, 50...Concrete (counterpart material).

Claims

1. A motor; a tool tip that rotates around a rotation axis by receiving a driving force from the motor; a housing for supporting the motor and the tool bit; A control unit that controls the driving of the motor; a detection unit supported by the housing and capable of detecting an acceleration occurring therein; The control unit controls the driving of the motor based on radial acceleration occurring in a radial direction about the rotation axis with respect to the detection unit.

2. The work machine according to claim 1 , wherein the control unit reduces a rotation speed of the motor when the radial acceleration exceeds a first threshold value.

3. The work machine according to claim 1 , wherein the control unit stops the motor when the radial acceleration exceeds a first threshold value.

4. The detection unit is also capable of detecting a load current of the motor, The work machine according to claim 1 , wherein the control unit reduces a rotation speed of the motor when the radial acceleration exceeds a first threshold value and the load current exceeds a second threshold value.

5. 2. The work machine according to claim 1, wherein the control unit reduces the rotation speed of the motor when the radial acceleration exceeds a first threshold value and when the circumferential acceleration occurring in a circumferential direction about the rotation axis with respect to the detection unit exceeds a third threshold value.

6. The work machine according to claim 1 , wherein the radial acceleration is an acceleration occurring in a direction along an imaginary line connecting the detection unit and the rotation shaft, and in a direction away from the rotation shaft.

7. A work machine as described in claim 1, wherein the radial acceleration is the acceleration that occurs when the housing is swung in a rotational direction around the rotation axis.

8. A motor, a tool tip that rotates around a rotation axis by receiving a driving force from the motor; a housing for supporting the motor and the tool bit; A control unit that controls the driving of the motor; a detection unit supported by the housing and capable of detecting an acceleration occurring therein; The control unit controls the driving of the motor based on the acceleration that occurs in a direction intersecting the direction in which the housing is swung relative to the detection unit when the tool tip gets caught on an opposing material and enters a locked state, causing the housing to swing.

9. A work machine as described in Claim 8, wherein the control unit controls the driving of the motor based on the acceleration that occurs in a direction intersecting the rotational direction relative to the detection unit when the housing is swung in a rotational direction around the rotation axis.

10. A work machine as described in Claim 9, wherein the control unit controls the driving of the motor based on radial acceleration occurring in a radial direction centered on the rotation axis relative to the detection unit.

11. A motor, a tool tip that rotates around a rotation axis by receiving a driving force from the motor; a housing for supporting the motor and the tool bit; A control unit that controls the driving of the motor; a detection unit supported by the housing and capable of detecting an acceleration occurring therein; The control unit controls the driving of the motor based on centrifugal force directional acceleration generated in a radial direction about the rotation axis relative to the detection unit when the housing is swung in a rotational direction about the rotation axis.