Work equipment

Abstract

Provided is a work machine that offers good operability. A work machine 1 comprises: a motor 6; a work unit that is driven by the motor 6 and configured so as to be able to carry out prescribed work; a microcomputer 98 for controlling the motor 6; and an operating unit that is configured so as to be able to instruct the microcomputer 98 to drive / halt the motor 6. The microcomputer 98 is configured to perform control so as to: cause the motor 6 to be driven continuously by normal operation during a single drive operation of the operating unit; lower the output of the motor 6 by reducing the duty with respect to normal operation when the motor 6 enters an overload state; and then, upon detection of the rotation of the motor 6, return to normal operation.

Description

[Technical Field]

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

[0002] The following Patent Document 1 discloses a work machine having an overcurrent protection function that stops the motor when an overcurrent state (overload state) occurs. In order to restart the motor that has stopped due to the overcurrent protection function, it is necessary to pull the trigger again (operate the switch again). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2020-93369 Summary of the Invention [Problem to be solved by the invention]

[0004] A configuration in which the trigger must be pulled again each time an overcurrent state occurs can be inconvenient to operate.

[0005] An object of the present invention is to provide a work machine that is easy to operate. [Means for solving the problem]

[0006] One aspect of the present invention is A motor; a working unit driven by the motor and configured to perform a predetermined task; a controller configured to control the motor; an operation unit configured to instruct the control unit to drive or stop the motor; a rotation detection unit that detects rotation of the motor; In a work machine having the control unit executes a first control for continuously driving the motor during one drive operation of the operation unit, and when the motor is in an overload state, transitions to a second control in which the output of the motor is lower than the first control; In the second control, When the rotation detector detects the rotation of the motor, the output of the motor is shifted to a third control higher than the second control, the control unit is configured to change the output of the motor by a voltage applied to the motor; The effective value of the voltage applied to the motor in the second control is such that the motor rotates in an unloaded state where the working part is not in contact with the work object, but the motor does not rotate in a loaded state where the working part is in contact with the work object, in this work machine. Another aspect of the present invention is a method for producing a semiconductor device comprising: A motor; a working unit driven by the motor and configured to perform a predetermined task; a controller configured to control the motor; an operation unit configured to instruct the control unit to drive or stop the motor; a rotation detection unit that detects rotation of the motor; In a work machine having the control unit executes a first control for continuously driving the motor during one drive operation of the operation unit, and when the motor is in an overload state, transitions to a second control in which the output of the motor is lower than the first control; In the second control, When the rotation detector detects the rotation of the motor, the output of the motor is shifted to a third control higher than the second control, the control unit is configured to change the output of the motor by a voltage applied to the motor; The control unit is configured to set an effective value of the voltage applied to the motor to zero for a predetermined time B when transitioning from the first control to the second control. This is a work machine characterized by the above. Another aspect of the present invention is a method for producing a semiconductor device comprising: A motor; a working unit driven by the motor and configured to perform a predetermined task; a controller configured to control the motor; an operation unit configured to instruct the control unit to drive or stop the motor; a rotation detection unit that detects rotation of the motor; In a work machine having the control unit executes a first control for continuously driving the motor during one drive operation of the operation unit, and when the motor is in an overload state, transitions to a second control in which the output of the motor is lower than the first control; In the second control, When the rotation detector detects the rotation of the motor, the output of the motor is shifted to a third control higher than the second control, the control unit is configured to change the output of the motor by a voltage applied to the motor; the control unit is configured to set an effective value of the voltage applied to the motor to zero when the rotation detection unit does not detect rotation of the motor before the execution time of the second control reaches a predetermined time C. This is a work machine characterized by the above.

[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. [Effects of the Invention]

[0008] According to the present invention, a work machine with good operability can be provided. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a plan view of a work machine 1 according to an embodiment of the present invention. [Figure 2] FIG. [Figure 3] FIG. 2 is a circuit block diagram of the work machine 1. [Figure 4] FIG. 4 is a circuit block diagram of a work machine 1A according to another example of the configuration of the embodiment. [Figure 5] 4 is a flowchart showing a first example of control of the work machines 1, 1A. [Figure 6] 10 is a flowchart showing a second example of control of the work machines 1, 1A. [Figure 7] 6 is a time chart showing an example of the operation of the work machines 1, 1A when the control shown in FIG. 5 is applied. [Figure 8] 6 is a time chart showing an example of the operation of the work machines 1, 1A when another example of the control shown in FIG. 5 (an example in which a return to normal operation from a duty of 2.5%) is applied. [Figure 9] 7 is a time chart showing an example of the operation of the work machines 1, 1A when the control shown in FIG. 6 is applied. DETAILED DESCRIPTION OF THE INVENTION

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

[0011] This embodiment relates to a work machine 1. The work machine 1 is a grinder (disc grinder). Figures 1 and 2 define mutually orthogonal front-rear, up-down, and left-right directions of the work machine 1. The front-rear direction is a direction parallel to the output shaft 6a of the motor 6. The up-down direction is a direction parallel to the central axis of the spindle 20.

[0012] As shown in Fig. 2, the work machine 1 has a grinding wheel 2 as a working part (rotary tool). The work machine 1 can perform predetermined operations such as grinding and cutting using the grinding wheel 2 that is rotationally driven by a motor 6 (described later). The work machine 1 has a housing 3 (made of, for example, resin) and a gear case 4.

[0013] The housing 3 is, for example, a resin molded body having a generally cylindrical shape as a whole, and accommodates and holds the motor 6 etc. A battery 7 that serves as the power source for the work machine 1 is detachably attached to the rear end of the housing 3.

[0014] The gear case 4 is made of metal such as aluminum alloy, and is attached and fixed to the front end of the housing 3 by screws or the like. The work machine 1 has a packing gland 11 as a cover member that closes the lower opening of the gear case 4.

[0015] The work machine 1 has a motor 6 in a housing 3. The motor 6 is, for example, a brushless motor of an inner rotor type with a 4-pole, 6-slot configuration. The front end of the output shaft 6a of the motor 6 is located inside the gear case 4, and a first bevel gear 21 is provided at the front end.

[0016] The output shaft 6a is provided with a fan 8 for cooling the motor 6 etc. The fan 8 is located in the housing 3 in front of the main body of the motor 6 (the part of the motor 6 excluding the output shaft 6a).

[0017] The work machine 1 has a switch 5 behind the motor 6 inside the housing 3. When the switch 5 is in the on state, it instructs the microcomputer 98 in Fig. 3 to drive the motor 6. When the switch 5 is in the off state, it instructs the microcomputer 98 to stop the motor 6.

[0018] As shown in Fig. 1, the work machine 1 has an operation unit 10 at the front of the left side surface of the housing 3, which allows the user to turn on and off the switch 5, i.e., to instruct the microcomputer 98 to drive or stop the motor 6. The work machine 1 has a slide bar 17 inside the housing 3 that moves forward and backward in conjunction with forward and backward operation of the operation unit 10.

[0019] When the user performs a drive operation to move the operation unit 10 forward, the slide bar 17 moves forward in conjunction with this and turns on the switch 5. When the user performs a stop operation to move the operation unit 10 backward, the slide bar 17 moves backward in conjunction with this and turns off the switch 5.

[0020] The housing 3 has a locking protrusion 18 at the front of the left side surface. By hooking the operating unit 10 onto the locking protrusion 18, the operating unit 10 is locked in a position where it has moved forward, and the switch 5 can be maintained in the on state even if the operating unit 10 is released.

[0021] As shown in Fig. 2, the work machine 1 has a control board 9 at the rear end portion inside the housing 3. The control board 9 is equipped with elements necessary for driving and controlling the motor 6, such as an inverter circuit 82 and a microcomputer 98 shown in Fig. 3.

[0022] The work machine 1 has a speed setting dial 19 on the upper rear surface of the housing 3. The user can change the set rotational speed of the motor 6 by operating the speed setting dial 19.

[0023] The gear case 4 and the packing gland 11 rotatably support the spindle 20. The gear case 4 is provided with a needle bearing 12 that rotatably supports the upper end of the spindle 20. The packing gland 11 holds a ball bearing 13 that rotatably supports the middle part of the spindle 20.

[0024] The central axis of the spindle 20 is perpendicular to the output shaft 6a of the motor 6. One end of the spindle 20 penetrates the packing gland 11 and protrudes to the outside. A second bevel gear 22 is provided (attached) to the upper part of the spindle 20 located inside the gear case 4. The second bevel gear 22 meshes with the first bevel gear 21.

[0025] The rotation of the motor 6 is converted in its direction by 90 degrees by the first bevel gear 21 and the second bevel gear 22, and the rotation speed is reduced before being transmitted to the spindle 20. In other words, the spindle 20 is rotationally driven by the motor 6.

[0026] The grinding wheel 2 is fixed to the spindle 20 and rotates integrally with the spindle 20. The wheel guard 14 is attached to the packing gland 11 and covers approximately half of the grinding wheel 2, preventing the scattering of cutting powder, sparks, etc. that are generated during grinding work.

[0027] When the user operates the operating unit 10, power is supplied from the battery 7 to the motor 6, causing the output shaft 6a of the motor 6 to rotate, which in turn causes the spindle 20 to rotate via the first bevel gear 21 and the second bevel gear 22, thereby causing the grinding wheel 2 fixed to the spindle 20 to rotate.

[0028] 3 is a circuit block diagram of the work machine 1. The work machine 1 includes a control circuit unit 80, an inverter circuit 82, and a magnetic sensor 84. The control circuit unit 80 includes a control signal output circuit 83, a rotor position detection circuit 85, a temperature detection circuit 86, a step-down circuit 87, a control system power supply circuit 88, a battery voltage detection circuit 89, an over-discharge detection circuit 90, a current detection circuit 91, a communication circuit 92, a battery temperature detection circuit 93, an acceleration detection circuit 94, a switch detection circuit 95, a set rotation speed detection circuit 96, and a microcomputer 98 (microcontroller) as a control unit.

[0029] The inverter circuit 82 includes semiconductor switching elements Q1 to Q6 connected in a three-phase bridge. The inverter circuit 82 converts the DC power output from the battery 7 into AC power for driving the motor 6 and supplies it to the motor 6. The control signal output circuit 83, under the control of the microcomputer 98, applies a drive signal, for example a PWM (Pulse Width Modulation) signal, to each gate of the switching elements Q1 to Q6.

[0030] The magnetic sensors 84 are, for example, Hall ICs, and are provided at 60° intervals in the rotational direction of the motor 6. The magnetic sensors 84 detect the magnetic field generated by the rotor of the motor 6 and send the signal to a rotor position detection circuit 85. The rotor position detection circuit 85 detects the rotor position of the motor 6 based on a signal from the magnetic sensors 84 and sends the signal to a microcomputer 98. The magnetic sensors 84 and the rotor position detection circuit 85 constitute a rotation detection unit. The temperature detection circuit 86 detects the temperatures of the switching elements Q1 to Q6 and sends the signal to the microcomputer 98.

[0031] The step-down circuit 87 steps down the output voltage of the battery 7 and supplies it to a control system power supply circuit 88. The control system power supply circuit 88 converts the output voltage of the step-down circuit 87 into a power supply voltage for the microcomputer 98, etc. and supplies it to the microcomputer 98, etc. The battery voltage detection circuit 89 detects the output voltage of the battery 7 and sends it to the microcomputer 98.

[0032] The over-discharge detection circuit 90 detects an over-discharge notification signal from the battery 7 and transmits it to the microcomputer 98. The current detection circuit 91 detects the motor current from the voltage of a resistor R provided in the path of the current (motor current) flowing through the motor 6 and transmits it to the microcomputer 98. The resistor R and the current detection circuit 91 form a current detection unit. The communication circuit 92 is a circuit for communication between the battery 7 and the microcomputer 98. The battery temperature detection circuit 93 detects a temperature notification signal from the battery 7 and transmits it to the microcomputer 98.

[0033] An acceleration detection circuit 94 detects the acceleration applied to the work machine 1 and sends it to the microcomputer 98. A switch detection circuit 95 detects the operation of the operation unit 10, i.e., the on / off of the switch 5, and sends it to the microcomputer 98. A set rotation speed detection circuit 96 detects the set rotation speed set by the speed setting dial 19 and sends it to the microcomputer 98.

[0034] The microcomputer 98 is configured to control the inverter circuit 82 via the control signal output circuit 83, for example, by PWM control, in response to the operation of the operation unit 10, i.e., the on / off of the switch 5, and the rotation speed set by the speed setting dial 19, thereby controlling the drive of the motor 6. The microcomputer 98 can change the effective value of the voltage applied to the motor 6 (hereinafter referred to as "motor applied voltage") by changing the duty of the PWM control (hereinafter referred to as "duty"). The microcomputer 98 can change the output of the motor 6 by controlling the effective value of the motor applied voltage.

[0035] This embodiment is characterized by an overcurrent protection function (overload protection function) described later. This overcurrent protection function is not limited to battery-powered work machines 1, but can also be applied to AC-powered work machines 1A as shown in FIG.

[0036] 4 is a circuit block diagram of an AC-driven work machine 1A. Work machine 1A differs from work machine 1 in that it operates on power (100V AC) supplied from an external AC power source 60 such as a commercial power source and that accompanying changes have been made to the circuit configuration, but is the same in all other respects.

[0037] An input voltage from an AC power supply 60 is supplied to an AC / DC conversion circuit 62 via a filter circuit 61. The AC / DC conversion circuit 62 includes a diode bridge 63 (full-wave rectifier circuit), a smoothing capacitor 64, and a control circuit voltage supply circuit 65. The control circuit voltage supply circuit 65 supplies a DC voltage that has been rectified and smoothed by the diode bridge 63 and the smoothing capacitor 64 to a control signal output circuit 83 and a step-down circuit 87.

[0038] The microcomputer 98 of the work machine 1, 1A has an overcurrent protection function. In the case of a typical overcurrent protection function, if an overcurrent state (overload state) occurs, the motor 6 is stopped, and the operating unit 10 must be operated again to restart the motor 6. A configuration in which the operating unit 10 must be operated again every time an overcurrent state occurs can sometimes result in poor operability. Below, we will explain control that improves this point.

[0039] 5 is a flowchart showing a first example of the control of the work implement 1, 1A. When the switch 5 is turned on (S2) in a stopped state (S1), the microcomputer 98 performs normal operation (S3) to drive the motor 6 at the rotation speed set by the speed setting dial 19. Normal operation corresponds to the first control in which the motor 6 is continuously driven. From S2 onwards, the switch 5 is assumed to be consistently on.

[0040] When the motor current satisfies a first condition for overcurrent protection (overload protection) (Yes in S4), the microcomputer 98 stops the inverter circuit 82 and stops the motor 6 (S5). The first condition is, for example, 180 A / 1 ms or 150 A / 1 ms for a DC-driven work machine 1, and is, for example, 100 A / 1 ms for an AC-driven work machine 1A. When the microcomputer 98 stops the motor 6 because the motor current satisfies the first condition, it determines that a necessary condition for restarting the drive of the motor 6 is that the switch 5 is turned off once. Hereinafter, an overload state that satisfies the first condition will be referred to as a "first overload state." Furthermore, the control (S5) that stops the motor 6 due to the first overload state will be referred to as a "first overload protection control."

[0041] When the motor current does not satisfy the first condition for overcurrent protection (No in S4) but satisfies the second condition for overcurrent protection (Yes in S6), the microcomputer 98 starts a timer (S7). Satisfying the second condition corresponds to the motor 6 being in an overload state. In the case of a DC-driven work machine 1, the second condition is set in stages based on the current value and its duration, such as 130 A / 4 ms, 100 A / 500 ms, 90 A / 2 s, 80 A / 4.3 s, 75 A / 6 s, 70 A / 10 s, 65 A / 20 s, and 60 A / 30 s. In the case of an AC-driven work machine 1A, the second condition is, for example, 90 A / 3 ms. Hereinafter, an overload state that satisfies the second condition will be referred to as a "second overload state." Furthermore, the control (S7 to S16) that corresponds to the second overload state will be referred to as a "second overload protection control."

[0042] The microcomputer 98 fixes the duty to 0% for 300 milliseconds from the start of the timer (S7) (No in S8 and S9). 300 milliseconds corresponds to the predetermined time B. When 300 milliseconds have passed since the start of the timer (S7) (Yes in S9), the microcomputer 98 fixes the duty to 2.5% for the next 200 milliseconds, that is, until 500 milliseconds have passed since the start of the timer (S7) (No in S10 and S11). When 500 milliseconds have passed since the start of the timer (S7) (Yes in S11), the microcomputer 98 fixes the duty to 5% (S12).

[0043] The drive control of the motor 6 at a duty of 2.5% and the drive control of the motor 6 at a duty of 5% correspond to the second control. The second control is a control in which the output of the motor 6 is lower than that in normal operation. The effective value of the motor applied voltage at a duty of 2.5% is an example of the second effective value and an example of the 2.1 effective value. The effective value of the motor applied voltage at a duty of 5% is an example of the second effective value and an example of the 2.2 effective value.

[0044] The effective values ​​of the voltage applied to the motor for the duty cycles of 2.5% and 5% are values ​​that cause the motor 6 to rotate in the no-load state but not in the loaded state. The no-load state is a state in which the grinding wheel 2 is not in contact with the workpiece.

[0045] If the return condition described below is satisfied (Yes in S14) (No in S13) before the duty is fixed at 5% for one second, i.e., before 1.5 seconds have elapsed since the timer started (S7), the microcomputer 98 returns to normal operation from the state in which the duty is fixed at 5% (S15) and returns to S4. The normal operation after the return in S15 corresponds to the third control. Note that the duty, motor rotation speed, etc., of the normal operation after the return in S15 may differ from those of the initial normal operation (S3).

[0046] The recovery condition is, for example, that an event in which the three magnetic sensors 84 switch on and off a total of 12 or more times within 100 milliseconds is detected twice. This recovery condition is based on the premise that the rotor of the motor 6 has four poles. When the motor 6 rotates once (the rotor rotates once), the three magnetic sensors 84 switch on and off a total of 12 times. In other words, the recovery condition is that an event in which the motor 6 rotates once or more within 100 milliseconds is detected twice.

[0047] If the return condition is not satisfied (Yes in S13) by the time 1.2 seconds (corresponding to the predetermined time C) have elapsed since the start of control at a duty of 2.5% (S10), i.e., by the time 1.5 seconds have elapsed since the timer started (S7), the microcomputer 98 stops the inverter circuit 82 and stops the motor 6 (S16).

[0048] The control shown in Fig. 5 is an example in which a check (S14) is performed to see if the return condition is met after the duty is fixed to 5% (S12 and thereafter). That is, the control shown in Fig. 5 is an example in which, when the return condition is met with the duty fixed to 2.5%, the control transitions to normal operation after the execution time of control at 2.5% duty reaches 200 milliseconds (corresponding to predetermined time A) or more.

[0049] As another example of the control shown in FIG. 5, after the duty is fixed at 2.5% (after S10) and before the duty is fixed at 5% (before S12), it may be confirmed whether the return condition is met (the same process as S14), and if the return condition is met, normal operation may be resumed.

[0050] Fig. 6 is a flowchart showing a second example of the control of the work machines 1, 1A. The flowchart in Fig. 6 is the same as the flowchart in Fig. 5 except that steps S8 to S11 have been removed. The processing flow from S1 to S7 in Fig. 6 is the same as the processing flow from S1 to S7 in Fig. 5. The control shown in Fig. 6 is an example in which the effective value of the voltage applied to the motor is kept constant in the second control.

[0051] After starting the timer (S7), the microcomputer 98 fixes the duty to 5% (S12). If the return condition is satisfied (Yes in S14) before 1.5 seconds have elapsed since the timer was started (S7) (No in S13), the microcomputer 98 returns to normal operation from the state in which the duty is fixed to 5% (S15) and returns to S4. If the return condition is not satisfied before 1.5 seconds (corresponding to the predetermined time C) have elapsed since the timer was started (S7) (Yes in S13), the microcomputer 98 stops the inverter circuit 82 and stops the motor 6 (S16).

[0052] FIG. 7 is a time chart showing an example of the operation of the work machines 1, 1A when the control shown in FIG. 5 is applied.

[0053] At time t0, the switch 5 is turned on, and the microcomputer 98 starts soft start control of the motor 6. After time t0, the switch 5 is consistently on.

[0054] The period from time t0 to t1 is a soft start control period, during which the duty gradually increases toward 100%, and the motor rotation speed and motor current also gradually increase. The effective value of the motor applied voltage when the duty is 100% is an example of a first effective value.

[0055] The period from time t1 to t2 is a no-load operation period, during which the duty is 100%, the motor rotation speed is the maximum rotation speed of 31,500 rpm, and the motor current is a no-load current.

[0056] The period from time t2 to t4 is a load increase period, during which the user presses the grindstone 2 against the workpiece, increasing the load on the motor 6. This increases the motor current and reduces the motor rotation speed. The duty is maintained at 100%.

[0057] At time t3 during the load increase period, the motor current exceeds the overload protection threshold. At time t4, after a predetermined time corresponding to the threshold has elapsed, the microcomputer 98 sets the duty to zero and stops the motor 6. This causes the motor current to become zero.

[0058] The period from time t4 to t5 is a 300 millisecond period with a 0% duty, during which the motor rotation speed and motor current are both zero.

[0059] The period from time t5 to t6 is a 200 millisecond period with a duty of 2.5%. At time t5, the duty is increased to 2.5%, and the motor current also increases accordingly.

[0060] The one-second period from time t6 is a 5% duty period. At time t6, the duty is increased to 5%, and the motor current also increases accordingly. If the recovery condition is met during the 5% duty period, the microcomputer 98 increases the duty and returns to normal operation without waiting for one second to elapse from time t6.

[0061] At time t7, the user moves the grinding wheel 2 away from the workpiece, causing the motor rotation speed to start increasing.

[0062] At time t8, one second before time t6, the microcomputer 98 detects that the recovery condition has been satisfied, and starts the soft start control of the motor 6 again.

[0063] The period from time t8 to t9 is a soft start control period, during which the duty gradually increases toward 100%, and accordingly the motor rotation speed and motor current also gradually increase.

[0064] The period from time t9 is a no-load operation period, during which the duty is 100%, the motor rotation speed is the maximum rotation speed of 31,500 rpm, and the motor current is the no-load current.

[0065] Fig. 8 is a time chart showing an example of the operation of the work machines 1, 1A when another example of the control shown in Fig. 5 (an example in which a return to normal operation from a duty of 2.5%) is applied. The operation during the period t0 to t5 in Fig. 8 is the same as the operation during the period t0 to t5 in Fig. 7.

[0066] The 200 millisecond period from time t5 is a 2.5% duty period. At time t5, the duty is increased to 2.5%, and the motor current also increases accordingly. If the recovery condition is met during the 2.5% duty period, the microcomputer 98 will increase the duty and return to normal operation without waiting for 200 milliseconds to elapse from time t5.

[0067] At time t11, the user moves the grinding wheel 2 away from the workpiece, causing the motor rotation speed to start increasing.

[0068] At time t12, which is 200 milliseconds before the time t5, the microcomputer 98 detects that the recovery condition is satisfied, and starts the soft start control of the motor 6 again.

[0069] The period from time t12 to t13 is a soft start control period, during which the duty gradually increases toward 100%, and accordingly the motor rotation speed and motor current also gradually increase.

[0070] The period from time t13 is a no-load operation period, during which the duty is 100%, the motor rotation speed is the maximum rotation speed of 31,500 rpm, and the motor current is a no-load current.

[0071] Fig. 9 is a time chart showing an example of the operation of the work machines 1, 1A when the control shown in Fig. 6 is applied. The operation in the period from t0 to just before t4 in Fig. 9 is the same as the operation in the period from t0 to just before t4 in Fig. 7.

[0072] At time t4, the microcomputer 98 reduces the duty to 5%, which in turn reduces the motor rotation speed and motor current.

[0073] The 1.5-second period from time t4 is a 5% duty period. If the recovery condition is met during the 5% duty period, the microcomputer 98 increases the duty and recovers to normal operation without waiting for 1.5 seconds to elapse from time t4.

[0074] At time t17, the user moves the grinding wheel 2 away from the workpiece, causing the motor rotation speed to start increasing.

[0075] At time t18, which is 1.5 seconds before time t4, the microcomputer 98 detects that the recovery condition has been satisfied, and starts the soft start control of the motor 6 again.

[0076] The period from time t18 to t19 is a soft start control period, during which the duty gradually increases toward 100%, and accordingly the motor rotation speed and motor current also gradually increase.

[0077] The period from time t19 is a no-load operation period, during which the duty is 100%, the motor rotation speed is the maximum rotation speed of 31,500 rpm, and the motor current is the no-load current.

[0078] According to this embodiment, the following effects can be achieved.

[0079] (1) The microcomputer 98 is configured to continuously drive the motor 6 in normal operation during one drive operation of the operating unit 10, reduce the duty relative to normal operation when the motor 6 enters the second overload state, and perform control to return to normal operation when rotation of the motor 6 is detected. Therefore, if the pressing force of the grinding wheel 2 against the workpiece is too strong and the second overload state occurs and the motor 6 stops, the user can simply move the grinding wheel 2 away from the workpiece and the motor 6 will start driving again, allowing the user to resume work without having to redo the drive operation of the operating unit 10. Therefore, the work machine 1, 1A has good operability and workability.

[0080] (2) In the control shown in FIG. 5, when the second overload state occurs, the microcomputer 98 temporarily reduces the duty to zero and then increases it to 2.5%. Since the heat generated while the duty is at zero is small, the occurrence of high temperature abnormalities can be suppressed. Note that there is a delay of at least the reaction time between the time the user recognizes that the motor 6 has stopped due to the second overload protection control and the time the grinding wheel 2 is removed from the workpiece. Because the stop of the motor 6 due to the second overload protection control is an unexpected event for the user, this delay is considerably longer than the reaction time. Therefore, even if the duty is reduced to zero for a predetermined time corresponding to this delay after the second overload state is detected, the disadvantage of a longer wait time between the time the user removes the grinding wheel 2 from the workpiece and the time the motor 6 is restarted is limited.

[0081] (3) In the case of the control shown in FIG. 5, the microcomputer 98 temporarily sets the duty to zero when the second overload state occurs, then temporarily increases the duty to 2.5% and then to 5%. Therefore, the amount of heat generated while the duty is at 2.5% is small, thereby suppressing the occurrence of high temperature abnormalities.

[0082] (4) In the case of the control shown in FIG. 6, when an overload state (an overcurrent state that satisfies the second condition) occurs, the microcomputer 98 immediately reduces the duty to 5% and then maintains the duty at 5% until the return condition is met or until the return condition is not met and the duty is set to zero. This simplifies the control by the microcomputer 98. Furthermore, when the duty is 5%, the time from when the user releases the grinding wheel 2 from the workpiece to when the return condition is met is shorter than when the duty is 2.5%, so the waiting time from when the user releases the grinding wheel 2 from the workpiece to when the motor 6 resumes driving can be shortened.

[0083] (5) In the second overload control, the microcomputer 98 sets the effective value of the motor applied voltage to a value that causes the motor 6 to rotate in an unloaded state but not in a loaded state. Therefore, the return condition is not met unless the grinding wheel 2 is securely separated from the workpiece. Therefore, work resumes from an unloaded state, which improves operability and workability.

[0084] While the present invention has been described above using the embodiments as examples, it will be understood by those skilled in the art that various modifications can be made to the components and processes of the embodiments within the scope of the claims. Modifications will be discussed below.

[0085] As a variation of the control shown in FIG. 5, the microcomputer 98 may continuously increase the duty from zero to 5% after starting the timer (S7), or may increase the duty stepwise to 5% in three or more stages. The operating unit 10 is not limited to the slide type illustrated in the embodiment, but may also be a paddle type or trigger type. The working machine of the present invention is not limited to the grinder illustrated in the embodiment, but may be another type such as a circular saw. The present invention is suitably applicable to working machines that start work from an unloaded state where the working unit is not in contact with the work object.

[0086] The specific contents of the first and second conditions and the recovery conditions exemplified in the embodiments, as well as the motor rotation speed, duty, motor current, various thresholds, time, etc. exemplified as specific numerical values ​​in the embodiments, do not in any way limit the scope of the invention and can be changed as desired to suit the required specifications. [Explanation of symbols]

[0087] 1, 1A...working machine, 2...grinding wheel (rotary tool), 3...housing, 4...gear case, 5...switch, 6...motor (brushless motor), 6a...output shaft, 7...battery (battery pack), 8...fan, 9...control board, 10...operation unit, 11...packing gland, 12...needle bearing, 13...ball bearing, 14...wheel guard, 17...slide bar, 18...locking protrusion, 19...speed setting dial, 20...spindle, 21...first bevel gear, 22...second bevel gear, 60...AC power supply, 61...filter circuit, 62...AC / DC conversion circuit circuit, 63...diode bridge (full-wave rectifier circuit), 64...smoothing capacitor, 65...control circuit voltage supply circuit, 80...control circuit section, 82...inverter circuit, 83...control signal output circuit, 84...magnetic sensor, 85...rotor position detection circuit, 86...temperature detection circuit, 87...step-down circuit, 88...control system power supply circuit, 89...battery voltage detection circuit, 90...over-discharge detection circuit, 91...current detection circuit, 92...communication circuit, 93...battery temperature detection circuit, 94...acceleration detection circuit, 95...switch detection circuit, 96...set rotation speed detection circuit, 98...microcontroller.

Claims

1. A motor; a working unit driven by the motor and configured to perform a predetermined task; a controller configured to control the motor; an operation unit configured to instruct the control unit to drive or stop the motor; a rotation detection unit that detects rotation of the motor; In a work machine having the control unit is configured to execute a first control for continuously driving the motor during one drive operation of the operation unit, and when the motor is in an overload state, to transition to a second control in which the output of the motor is lower than the first control, and when rotation of the motor is detected by the rotation detection unit during the second control, to transition to a third control in which the output of the motor is higher than the second control; the control unit is configured to change the output of the motor by a voltage applied to the motor; The effective value of the voltage applied to the motor in the second control is such that the motor rotates in an unloaded state in which the working part is not in contact with the work object, but does not rotate in a loaded state in which the working part is in contact with the work object.

2. The work machine according to claim 1 , wherein the control unit is configured to maintain an effective value of the voltage applied to the motor constant during the second control.

3. an effective value of the voltage applied to the motor in the first control is a first effective value; 2. The work machine according to claim 1, wherein the effective value of the voltage applied to the motor in the second control is a second effective value, and the control unit is configured to change the second effective value within a range lower than the first effective value.

4. The work machine according to claim 3 , wherein the control unit is configured to set the second effective value to a 2.2 effective value that is greater than the 2.1 effective value after setting the second effective value to a 2.1 effective value.

5. The work machine according to claim 4, wherein the control unit is configured to transition to the third control at the timing when the rotation of the motor is detected by the rotation detection unit, both during execution of control using the 2.1 effective value and during execution of control using the 2.2 effective value.

6. 5. The work machine according to claim 4, wherein the control unit is configured to transition to the third control after the execution time of the control using the 2.1 effective value has reached or exceeded a predetermined time A when the rotation detection unit detects rotation of the motor while the control using the 2.1 effective value is being executed.

7. 2. The work machine according to claim 1, wherein the control unit is configured to set the effective value of the voltage applied to the motor to zero for a predetermined time B when transitioning from the first control to the second control.

8. 2. The work machine according to claim 1, wherein the control unit is configured to set the effective value of the voltage applied to the motor to zero if the rotation detection unit does not detect rotation of the motor before the execution time of the second control reaches a predetermined time C.

9. a current detection unit that detects a current flowing through the motor; The work machine according to claim 1 , wherein the control unit detects an overload state of the motor based on a current flowing through the motor.

10. A motor; a working unit driven by the motor and configured to perform a predetermined task; a controller configured to control the motor; an operation unit configured to instruct the control unit to drive or stop the motor; a rotation detection unit that detects rotation of the motor; In a work machine having the control unit is configured to execute a first control for continuously driving the motor during one drive operation of the operation unit, and when the motor is in an overload state, to transition to a second control in which the output of the motor is lower than the first control, and when rotation of the motor is detected by the rotation detection unit during the second control, to transition to a third control in which the output of the motor is higher than the second control; the control unit is configured to change the output of the motor by a voltage applied to the motor; The control unit is configured to set the effective value of the voltage applied to the motor to zero for a predetermined time B when transitioning from the first control to the second control.

11. A motor; a working unit driven by the motor and configured to perform a predetermined task; a controller configured to control the motor; an operation unit configured to instruct the control unit to drive or stop the motor; a rotation detection unit that detects rotation of the motor; In a work machine having the control unit is configured to execute a first control for continuously driving the motor during one drive operation of the operation unit, and when the motor is in an overload state, to transition to a second control in which the output of the motor is lower than the first control, and when rotation of the motor is detected by the rotation detection unit during the second control, to transition to a third control in which the output of the motor is higher than the second control; the control unit is configured to change the output of the motor by a voltage applied to the motor; The control unit is configured to set the effective value of the voltage applied to the motor to zero if the rotation detection unit does not detect rotation of the motor before the execution time of the second control reaches a predetermined time C.

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