Electric working machine and motor control method

Abstract

To provide an electric working machine that is capable of detecting an unloaded condition of a motor with high accuracy.SOLUTION: An electric working machine comprises: a motor; a driving circuit; a physical quantity acquisition unitt; a change amount deriving unit; a total value calculation unit; and a driving control unit. The physical quantity acquisition unit acquires a physical quantity related to an operation state of the motor at each detection timing. The change amount deriving unit derives a change amount of the physical quantity at each detection timing. The total value calculation unit calculates, for each detection timing, a total value of change amounts that have been derived in a first period up to that detection timing. The driving control unit controls the motor on the basis of a first control scheme in response to the total value satisfying an unloaded detection requirement.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a technique for controlling a motor in an electric work machine. [Background technology]

[0002] Patent Document 1 discloses an electric appliance configured to execute soft no-load control. In the soft no-load control, the output of the motor is suppressed from when the motor starts to drive until it is detected that the motor is in a loaded state. When it is detected that the motor is in a loaded state, the soft no-load control is released. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6154242 Summary of the Invention [Problem to be solved by the invention]

[0004] After the soft no-load control is released, the motor may change from a loaded state to a no-load state. For example, assume that an electric machine is configured to be able to cut a workpiece with a saw blade. In this case, while the workpiece is being cut (i.e., in a loaded state), the saw blade may be temporarily removed from the workpiece while the motor is still in a driven state, causing the motor to change to a no-load state.

[0005] When the motor changes from a loaded state to a no-load state, the convenience of the electric machine or device can be improved if appropriate control is performed in response to the change (for example, soft no-load control is executed again). To achieve this, it is desirable to be able to accurately detect the no-load state of the motor.

[0006] An object of one aspect of the present disclosure is to provide an electric operating machine capable of accurately detecting that a motor is in an unloaded state. [Means for solving the problem]

[0007] One aspect of the present disclosure provides an electric operating machine including a motor, a drive circuit, and a control circuit. The motor is configured to drive a driven tool attached to the electric work machine. The drive circuit is configured to drive the motor. The control circuit includes a physical quantity acquisition unit, a change amount derivation unit, a sum value calculation unit, and a drive control unit.

[0008] The physical quantity acquisition unit acquires a physical quantity related to the operating state of the motor at each detection timing. The change amount deriving section derives, for each detection timing, an amount of change from the physical amount acquired at the previous detection timing to the physical amount acquired at the current detection timing.

[0009] The summation value calculation unit calculates, for each detection timing, a summation value of the amounts of change derived by the change amount derivation unit during a first period from a first calculation start timing to the detection timing. The drive control unit controls the motor through the drive circuit based on the first control method in response to the sum value calculated by the sum value calculation unit satisfying the no-load detection requirement. The no-load detection requirement is required to detect that no load is applied to the motor.

[0010] The sum value satisfying the no-load detection requirement corresponds to the motor being in an no-load state in which no load is applied to the motor. The no-load state includes a state in which no load is applied to the motor. The no-load state may also include a state in which a load of a predetermined magnitude or less is applied to the motor.

[0011] In the electric operating machine configured in this manner, the no-load state of the motor is detected based on the sum of the amounts of change, making it possible to accurately detect that the motor is in the no-load state.

[0012] Another aspect of the present disclosure is a motor control method for use in an electric working machine, comprising: Obtaining a physical quantity related to an operating state of a motor provided in an electric operating machine at each detection timing; Deriving, for each detection timing, an amount of change from a physical quantity acquired at a previous detection timing to a physical quantity acquired at a current detection timing; calculating a sum of the amounts of change derived from a calculation start timing to the detection timing for each detection timing; controlling the motor based on a predetermined control method in response to the calculated sum value satisfying a no-load detection requirement for detecting that no load is applied to the motor; The present invention provides a method comprising:

[0013] This method can provide the same effects as the electric operating machine described above. [Brief description of the drawings]

[0014] [Figure 1] 1 is a perspective view of an electric operating machine according to an embodiment. [Diagram 2] FIG. 2 is a diagram showing the electrical configuration of the electric operating machine. [Diagram 3] FIG. 4 is an explanatory diagram showing a first operation example of the electric operating machine. [Figure 4] FIG. 11 is an explanatory diagram showing a second operation example of the electric operating machine. [Diagram 5] 13 is a flowchart of a main process. [Figure 6] 11 is a part of a flowchart of a soft no-load recovery determination process. [Figure 7] 11 is a remaining part of the flowchart of the soft no-load recovery determination process. [Figure 8] 4 is a flowchart of a target rotation speed determination process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] [1. Overview of the embodiment] An embodiment may provide an electric operating machine having at least one of the following features 1 to 6. Feature 1: A motor configured to drive a driven implement attached to an electric work machine. Feature 2: A drive circuit configured to drive a motor. Feature 3: A physical quantity acquisition unit configured to acquire a physical quantity related to the operating state of the motor at each detection timing. Feature 4: A change amount derivation unit configured to derive, for each detection timing, an amount of change from the physical amount acquired at the previous detection timing to the physical amount acquired at the current detection timing. Feature 5: A summation value calculation unit configured to calculate, for each detection timing, a summation value of the amounts of change derived by the change amount derivation unit in a first period from the first calculation start timing to the detection timing. Feature 6: A drive control unit configured to control the motor via the drive circuit based on the first control method in response to the sum value calculated by the sum value calculation unit satisfying a no-load detection requirement for detecting that no load is applied to the motor.

[0016] The electric operating machine may include a control circuit. The control circuit may include at least one of a physical quantity acquisition unit, a change amount derivation unit, a sum value calculation unit, and a drive control unit. The drive circuit may drive the motor by supplying power to the motor. The detection timing may occur periodically or non-periodically.

[0017] The electric operating machine may have a driven tool attached thereto, or may be configured so that the driven tool can be releasably attached thereto. In the following description, a state in which no load is applied to the motor is referred to as an "unloaded state," and a state in which a load is applied to the motor is referred to as a "loaded state." The unloaded state includes a state in which the magnitude of the load applied to the motor is zero. In this case, the loaded state may include a state in which the magnitude of the load applied to the motor is greater than zero. The unloaded state may include a state in which the magnitude of the load applied to the motor is equal to or less than a predetermined magnitude. In this case, the loaded state may include a state in which the magnitude of the load applied to the motor is greater than the predetermined magnitude.

[0018] The sum value satisfying the no-load detection requirement may correspond to the motor being in an no-load state. The sum value not satisfying the no-load detection requirement may correspond to the motor being in a loaded state.

[0019] The load may be applied to the motor from a work object outside the electric work machine via the driven tool. The no-load state may include a state in which the driven tool is not in contact with an object (e.g., a work object) outside the electric work machine. The no-load state may include a state in which the driven tool is in contact with an object but the magnitude of the load applied to the motor via the object is equal to or less than a predetermined magnitude.

[0020] The amount of change may be, for example, an amount obtained by subtracting a physical amount acquired at a previous detection timing from a physical amount acquired at a current detection timing (i.e., a subtraction amount). The amount of change may be an amount indicating a level of the subtraction amount. Specifically, for example, when the amount of change is positive and its absolute value is less than a predetermined value a1, the amount of change may be "+A" (A is a natural number), when the amount of change is positive and its absolute value is a1 or more, the amount of change may be "+2·A" (i.e., twice +A), when the amount of change is negative and its absolute value is less than a1, the amount of change may be "-A", and when the amount of change is negative and its absolute value is a1 or more, the amount of change may be "-2·A" (i.e., twice -A). The amount of change may be an amount indicating a tendency of change in the physical amount (i.e., an increase or decrease). Specifically, for example, when the physical amount increases, the amount of change may be "+A", and when the physical amount decreases, the amount of change may be "-A". In this specification, "amount" is a concept including "value".

[0021] In an electric operating machine having at least features 1 to 6, it is detected that the motor is in an unloaded state based on the sum of the amounts of change. Therefore, it is possible to accurately detect that the motor is in an unloaded state (or that the motor has changed from a loaded state to an unloaded state). Furthermore, it is possible to control the motor based on the first control method at an appropriate timing according to the load.

[0022] An embodiment may include at least one of the following features 7 to 10 in addition to or instead of at least one of the features 1 to 6 described above. Feature 7: The electric work machine further includes at least one switch configured to be manually operated by a user of the electric work machine to set the rotation speed of the motor. Feature 8: The electric operating machine further includes a target setting unit configured to set a target rotation speed of the motor based on a state of the at least one switch. The control circuit may include the target setting unit. Feature 9: The drive control unit is configured to control the motor based on a second control method different from the first control method when the sum value does not satisfy the no-load detection requirement. Feature 10: The second control method includes controlling the motor so that the motor rotates at the target rotation speed set by the target setting unit.

[0023] In an electric operating machine having at least the features 1 to 10, the motor can be appropriately controlled both when the motor is in a loaded state and when it is in an unloaded state. An embodiment may include the following feature 11 in addition to or instead of at least one of the features 1 to 10 described above. Feature 11: When the target rotation speed is changed by the at least one switch, the summation value calculation unit is configured to exclude an amount of change during a predetermined second period from the timing of the change from the calculation of the summation value.

[0024] The physical quantity may vary in response to a change in the target rotation speed. Therefore, when the target rotation speed is changed, the no-load detection requirement may be satisfied even when the motor is not in an no-load state. In other words, the motor may be erroneously determined to be in an no-load state even when it is not, and the motor control method may be switched to the first control method.

[0025] In contrast, in an electric operating machine having at least the features 1 to 11, when the target rotation speed is changed, the amount of change within the second period is not included in the total value, so that erroneous detection of the no-load state can be suppressed.

[0026] During the second period, the physical quantity acquisition unit and / or the change amount derivation unit may stop operating. When the physical quantity acquisition unit stops operating during the second period, the change amount derivation unit may not derive the change amount or may set the change amount to a specified amount (e.g., zero) at the first detection timing after the second period has elapsed.

[0027] An embodiment may include at least one of the following features 12 and 13 in addition to or instead of at least one of the features 1 to 11 described above. Feature 12: The sum value calculation unit is configured to switch the start point of the first period from the first calculation start timing to the second calculation start timing when the target rotation speed is changed by the at least one switch. Feature 13: The second calculation start timing corresponds to an end of the second period.

[0028] In an electric operating machine having at least the features 1 to 13, the no-load detection requirement is determined based on the sum of the amount of change from the second calculation start timing, so that the amount of change within the second period can be easily excluded from the calculation of the sum value.

[0029] An embodiment may include at least one of the following features 14 to 16 in addition to or instead of at least one of the features 1 to 13 described above. Feature 14: The control circuit further includes a control rotation speed setting unit configured to: (i) set the control rotation speed based on the target rotation speed; and (ii) when the target rotation speed is changed, gradually change the control rotation speed from the current control rotation speed to the target rotation speed. Feature 15: The second control method includes controlling the motor so that the rotational speed of the motor matches the control rotational speed. Feature 16: The second period includes a period from when the target rotation speed is changed to when the controlled rotation speed is set by the controlled rotation speed setting unit to reach the target rotation speed.

[0030] The control rotation speed setting unit may basically make the control rotation speed coincide with the target rotation speed. When the target rotation speed is changed, the control rotation speed setting unit does not immediately change the control rotation speed to the target rotation speed. When the target rotation speed is changed, the control rotation speed setting unit gradually brings the control rotation speed closer to the target rotation speed. Specifically, the control rotation speed setting unit may, for example, monotonically increase or decrease the control rotation speed toward the target speed.

[0031] In an electric operating machine having at least the features 1 to 11 and 14 to 16, the influence of the fluctuation in the physical quantity caused by the speed change can be efficiently removed from the sum value. An embodiment may include the following feature 17 in addition to or instead of at least one of the features 1 to 16 described above. Feature 17: The second period further includes a period from when the controlled rotation speed is reached by the controlled rotation speed setting unit to when the first time has elapsed.

[0032] In an electric operating machine having at least the features 1 to 11 and 14 to 17, the influence of the fluctuation of the physical quantity accompanying the speed change can be more efficiently excluded from the sum value. Specifically, for example, the influence of the so-called overshoot or undershoot of the actual rotation speed of the motor after the control rotation speed reaches the target rotation speed can be excluded.

[0033] An embodiment may include at least one of the following features 18 and 19 in addition to or instead of at least one of the features 1 to 17 described above. Feature 18: The summation value calculation unit is configured to calculate the summation value by accumulating the amount of change each time a detection timing arrives within the first period. Feature 19: The summation value calculation unit is configured to reset (or initialize) the currently calculated summation value when the at least one switch is moved to change the target rotation speed.

[0034] In an electric operating machine having at least features 1 to 11, 18, and 19, when the target rotation speed is changed, the sum value accumulated up to that point is reset, and the amount of change within the second period is excluded from the calculation of the sum value. In other words, the sum value is kept reset until the second period has elapsed. Therefore, it is possible to suppress erroneous detection of the no-load state. Resetting the sum value may include any aspect. Resetting the sum value may include, for example, changing the sum value to zero or a predetermined initial value.

[0035] An embodiment may include the following features 20 and 21 in addition to or instead of at least one of the features 1 to 19 described above. Feature 20: The at least one switch includes a first switch. Feature 21: The target setting unit is configured to change the target rotation speed depending on the position of the first switch set by the user.

[0036] An electric operating machine having at least the features 1 to 11, 20, and 21 can improve the workability for the user when the motor is under load. An embodiment may include the following features 22 and 23 in addition to or instead of at least one of the features 1 to 21 described above. Feature 22: The at least one switch includes a second switch. Feature 23: The target setting unit is configured to change the target rotation speed, with the maximum rotation speed according to the position of the second switch as the upper limit.

[0037] The second switch is used to set a maximum rotation speed. The target rotation speed is set with the maximum rotation speed set by the second switch as the upper limit. For example, when the first switch is not provided, the target rotation speed may be set to the maximum rotation speed set by the second switch. Also, for example, when the first switch is provided, the target rotation speed may gradually increase to the maximum rotation speed in response to the movement of the first switch.

[0038] An electric operating machine having at least the features 1 to 11 and 20 to 23 can further improve the workability for the user when the motor is under load. An embodiment may include the following feature 24 or feature 25 in addition to or instead of at least one of the features 1 to 23 described above. Feature 24: The no-load detection requirement is satisfied on the basis that the sum calculated by the sum calculation unit is a predetermined magnitude, and the predetermined magnitude corresponds to being equal to or smaller than a predetermined threshold value. Feature 25: The no-load detection requirement is satisfied based on the sum calculated by the sum calculation unit being a predetermined magnitude, the predetermined magnitude corresponding to being equal to or greater than a predetermined threshold value.

[0039] In an electric working machine having at least the features 1 to 6 and 24, and an electric working machine having at least the features 1 to 6 and 25, it is possible to easily determine that the motor is in an unloaded state. For example, if a physical quantity decreases when the load applied to the motor is reduced, it is possible to easily determine that the motor is in an unloaded state by providing the feature 24. Also, for example, if a physical quantity increases when the load applied to the motor is reduced, it is possible to easily determine that the motor is in an unloaded state by providing the feature 25.

[0040] An embodiment may include the following feature 26 in addition to or instead of at least one of the features 1 to 25 described above. Feature 26: The no-load detection requirement is satisfied based on the sum calculated by the sum calculation unit maintaining the predetermined magnitude for a second period of time.

[0041] In an electric operating machine having at least the features 1 to 6, 24, and 26, and in an electric operating machine having at least the features 1 to 6, 25, and 26, it can be easily and accurately determined that the motor is in a no-load state.

[0042] An embodiment may include the following feature 27 in addition to or instead of at least one of the features 1 to 26 described above. Feature 27: The first control method includes controlling the motor so that the motor rotates at a constant first rotational speed.

[0043] In an electric operating machine having at least the features 1 to 6 and 27, the rotation state of the motor can be stabilized when the motor is in a no-load state. An embodiment may include the above feature 27 and the following feature 28 in addition to or instead of at least one of the above features 1 to 26. Feature 28: The first rotation speed is lower than a target rotation speed based on a state of the at least one switch.

[0044] In an electric work machine having at least features 1 to 6, 27, and 28, the rotation state of the motor can be stabilized when the motor is in an unloaded state, and workability can be improved when the motor transitions from an unloaded state to a loaded state.

[0045] An embodiment may include the following feature 29 in addition to or instead of at least one of the features 1 to 28 described above. · Feature 29: Physical quantities include the current flowing through the motor.

[0046] In an electric operating machine having at least the features 1 to 6 and 29, it can be easily and accurately determined that the motor is in a no-load state. The physical quantity acquired by the physical quantity acquisition unit may be any physical quantity that changes depending on the magnitude of the load. The physical quantity may be, for example, the actual rotation speed of the motor. The physical quantity may be, for example, the voltage applied to the motor, or a value indirectly indicating the voltage.

[0047] An embodiment may provide a method for controlling a motor in an electric operating machine, the method including at least one of the following features 30 to 33. Feature 30: A physical quantity related to the operating state of a motor provided in an electric work machine is obtained at each detection timing. Feature 31: For each detection timing, a change amount from a physical quantity acquired at a previous detection timing to a physical quantity acquired at a current detection timing is derived. Feature 32: For each detection timing, a total sum of the amount of change derived from the calculation start timing to the detection timing is calculated. Feature 33: The motor is controlled based on a predetermined control method in response to the calculated sum satisfying a no-load detection requirement for detecting that no load is applied to the motor.

[0048] By using the method having Features 30 to 33 in an electric work machine, it is possible to accurately detect whether the motor is in an unloaded state (or whether the motor has changed from a loaded state to an unloaded state).

[0049] In some embodiments, the above features 1 to 33 may be combined in any combination. In some embodiments, any of the above features 1-33 may be omitted. Examples of electric work machines include various electric tools used at work sites such as for DIY, manufacturing, gardening, construction, etc., specifically, electric tools for masonry, metalworking, woodworking, and gardening, and electric tools for preparing the work site environment, and more specifically, electric jigsaws, electric reciprocating saws, electric chainsaws, electric grinders, electric circular saws, electric cutters, electric hedge trimmers, electric lawnmowers, electric lawn clippers, electric brush cutters, electric screwdrivers, electric drills, electric hammers, electric hammer drills, electric wrenches, electric planes, electric nail guns (including tackers), and the like.

[0050] The electric working machine may receive power for driving the motor in any manner. For example, the electric working machine may be equipped with a battery, or may be configured to have a detachable battery pack equipped with a battery. In this case, the electric working machine may be configured to receive power from the battery.

[0051] In some embodiments, the control circuitry may be integrated into a single electronic unit or a single electronic device or a single circuit board. In some embodiments, the control circuit may be a combination of two or more electronic circuits, or two or more electronic units, or two or more electronic devices, each provided separately within the electric operating machine.

[0052] In some embodiments, the control circuitry may comprise a microcomputer (or microcontroller or microprocessor), hard-wired logic, an application specific integrated circuit (ASIC), an application specific general purpose product (ASSP), a programmable logic device (e.g., a field programmable gate array (FPGA)), discrete electronic components, and / or combinations thereof.

[0053] 2. SPECIFIC EXEMPLARY EMBODIMENTS Exemplary embodiments of the present disclosure will now be described. (2-1) Overview of electric work equipment As shown in Figure 1, the electric work machine 1 of this embodiment is in the form of a jigsaw. The electric work machine 1 comprises a housing 2. The housing 2 supports a driven tool 3. The driven tool 3 is releasably mounted to the housing 2. Figure 1 shows the electric work machine 1 to which the driven tool 3 is mounted. The driven tool 3 is in the form of a saw blade (i.e. a jigsaw blade). The driven tool 3 is supported so as to be capable of reciprocating motion.

[0054] A motor 10 and various circuits (see FIG. 2), which will be described later, are accommodated in the housing 2. The housing 2 further accommodates a transmission mechanism (not shown). The motor 10 is mechanically connected to the driven tool 3 via a transmission mechanism. The transmission mechanism transmits the rotation of the motor 10 to the driven tool 3. When the motor 10 rotates, the rotational force is transmitted to the driven tool 3 via the transmission mechanism, and the driven tool 3 is driven (i.e., reciprocates). The speed of the reciprocating motion of the driven tool 3 changes depending on the rotational speed of the motor 10. When the rotational speed of the motor 10 increases, the speed of the driven tool 3 also increases, and when the rotational speed of the motor 10 decreases, the speed of the driven tool 3 also decreases.

[0055] The housing 2 includes an attachment section 4. A battery pack 100 is removably attached to the attachment section 4. FIG. 1 shows a state in which the battery pack 100 is attached to the attachment section 4. The battery pack 100 includes a battery 101 (see FIG. 2) that can be repeatedly charged and discharged. The battery 101 includes a plurality of battery cells. The battery 101 may be, for example, a lithium ion battery.

[0056] The housing 2 includes a grip portion 5. The grip portion 5 is gripped by a user of the electric operating machine 1. The housing 2 includes a trigger 6. The trigger 6 is configured to be manually moved (e.g., pulled) by a user. When the trigger 6 is pulled by the user, the motor 10 is driven to drive the driven tool 3. The user can use the electric working machine 1 by pulling the trigger 6 while holding the grip portion 5. Specifically, the user can cut the workpiece (e.g., wood, metal, resin member, etc.) with the driven tool 3.

[0057] The housing 2 includes a speed adjustment dial 7. The speed adjustment dial 7 is manually moved by a user to set the maximum value of the rotation speed of the motor 10 (i.e., the maximum rotation speed). The speed adjustment dial 7 in this embodiment is configured to be rotated by the user. The speed adjustment dial 7 allows the user to select one of a plurality of maximum rotation speeds.

[0058] In this embodiment, as described below, the motor 10 is controlled by a first control method or a second control method. The first control method is a control method in which soft no-load control is executed and the motor 10 is controlled according to the soft no-load control. In the following description, the execution of the soft no-load control is synonymous with the motor 10 being controlled by the first control method.

[0059] The soft no-load control is executed when the motor 10 is in an unloaded state. The unloaded state refers to a state in which no load is applied to the motor 10. In this embodiment, the load is applied directly to the driven tool 3, and is applied to the motor 10 via the driven tool 3. The unloaded state may be only a state in which no load is applied at all, or may include a state in which a load of a certain magnitude or less is applied.

[0060] In the soft no-load control, the motor 10 is controlled so that it rotates at a constant first rotation speed, regardless of the pull amount of the trigger 6 and the position of the speed adjustment dial 7 (i.e., the set maximum rotation speed).

[0061] The second control method is executed when the motor 10 is in a loaded state. The loaded state refers to a state in which a load is applied to the motor 10. The loaded state may be a state in which a load greater than zero is applied, or a state in which a load greater than zero and equal to or greater than the aforementioned certain magnitude is applied.

[0062] In the second control method, the soft no-load control is released, and the motor 10 is controlled without using the soft no-load control. Specifically, in the second control method, a target rotation speed is set according to the pull amount of the trigger 6 and the position of the speed adjustment dial 7, and the motor 10 is controlled so that the motor 10 rotates at the target rotation speed (at a controlled rotation speed, which will be described in detail later).

[0063] (2-2) Electrical configuration of electric work machine As shown in Fig. 2, the electric work machine 1 includes a motor 10 and a controller 20. The controller 20 controls the rotational drive of the motor 10, and therefore the reciprocating drive of the driven tool 3. Fig. 2 electrically illustrates a state in which a battery pack 100 is attached to the electric work machine 1. That is, when the battery pack 100 is attached to the electric work machine 1, the battery 101 is electrically connected to the controller 20.

[0064] The motor 10 of this embodiment is in the form of a three-phase brushless motor. The motor 10 has a first terminal 10a, a second terminal 10b, and a third terminal 10c. The motor 10 rotates by receiving three-phase power, which will be described later, via the first to third terminals 10a to 10c. The motor 10 has three windings corresponding to the three phases. In this embodiment, the three windings are, for example, delta-connected.

[0065] The electric work machine 1 further includes a rotation sensor 11. The rotation sensor 11 includes three Hall ICs. The three Hall ICs are arranged at intervals of an electrical angle of 120 degrees along the rotation direction of the motor 10 (specifically, the rotation direction of the rotor). Each of the three Hall ICs outputs a rotation detection signal according to the position of the Hall IC and the rotational position of the rotor. Each rotation detection signal is in the form of a pulse signal, for example. The three rotation detection signals from the rotation sensor 11 are input to the controller 20.

[0066] The electric operating machine 1 further includes a first detection unit 6a. The first detection unit 6a detects that the trigger 6 has been moved and the amount of movement. When the trigger 6 is pulled, the first detection unit 6a outputs a trigger-on detection signal indicating that the trigger 6 has been pulled. The first detection unit 6a further outputs a first detection signal indicating the position of the trigger 6 (i.e., the amount of pulling or movement). The first detection unit 6a of this embodiment includes a variable resistor whose resistance value changes in conjunction with the movement of the trigger 6. The first detection unit 6a outputs a first detection signal corresponding to the resistance value of the variable resistor. The trigger-on detection signal and the first detection signal are input to the controller 20.

[0067] The electric operating machine 1 further includes a second detection unit 7a. The second detection unit 7a detects the position of the speed adjustment dial 7. The second detection unit 7a outputs a second detection signal indicating the position of the speed adjustment dial 7. The second detection signal is input to the controller 20.

[0068] The controller 20 can recognize that the trigger 6 has been pulled based on the trigger-on detection signal, can recognize the position of the trigger 6 based on the first detection signal, and can recognize the position of the speed adjustment dial 7 based on the second detection signal.

[0069] The controller 20 includes a drive circuit 21 and a power supply line 20a. The power supply line 20a connects the drive circuit 21 to the positive electrode of the battery 101. The drive circuit 21 is further connected to ground, and is connected to the negative electrode of the battery 101 via the ground.

[0070] The drive circuit 21 is further connected to the motor 10. More specifically, the drive circuit 21 is connected to the first to third terminals 10a to 10c. The drive circuit 21 receives power from the battery 101, converts the power into three-phase power, and supplies the three-phase power to the motor 10 via the first to third terminals 10a to 10c.

[0071] The drive circuit 21 of this embodiment is in the form of a so-called three-phase full-bridge circuit. That is, the drive circuit 21 includes three positive-side paths that connect the power supply line 20a to the first to third terminals 10a to 10c, respectively, and three negative-side paths that connect the first to third terminals 10a to 10c to ground, respectively. The drive circuit 21 further includes three semiconductor switching elements (so-called high-side switches) provided in the three positive-side paths, respectively, and three semiconductor switching elements (so-called low-side switches) provided in the three negative-side paths, respectively.

[0072] A resistor R1 is provided in the path connecting the drive circuit 21 to ground. The current from the drive circuit 21 to ground flows through the resistor R1. The controller 20 includes a current detection circuit 22. Both ends of the resistor R1 are connected to the current detection circuit 22. The current detection circuit 22 outputs a current detection signal according to the magnitude of the voltage across the resistor R1. The current detection signal indicates the magnitude of the current flowing through the resistor R1. When a current is supplied from the battery 101 to the motor 10, the current (hereinafter referred to as the "motor current") flows through the resistor R1. Therefore, the current detection signal indicates the magnitude of the motor current.

[0073] The controller 20 includes a capacitor C1. The capacitor C1 is connected between the power supply line 20a and the ground. The capacitor C1 has a function of smoothing the power of the battery 101.

[0074] The controller 20 includes a position detection circuit 23. The three rotation detection signals are input to the position detection circuit 23 from the rotation sensor 11. The position detection circuit 23 detects the rotation position of the motor 10 (more specifically, the rotor) based on the three rotation detection signals. The position detection circuit 23 outputs a position signal according to the detected rotation position.

[0075] The controller 20 includes a trigger detection circuit 24. The trigger detection circuit 24 receives a trigger-on detection signal and a first detection signal from the first detection unit 6a. The trigger detection circuit 24 outputs a trigger-on signal indicating that the trigger 6 is pulled while the trigger-on detection signal is being input (i.e., while the trigger 6 is pulled). The trigger detection circuit 24 further outputs a first command signal indicating the amount of pulling of the trigger 6 based on the first detection signal.

[0076] The controller 20 includes a dial detection circuit 25. The dial detection circuit 25 receives a second detection signal from the second detection unit 7a. The dial detection circuit 25 outputs a second command signal indicating the position of the speed adjustment dial 7 based on the second detection signal. In other words, the second command signal indicates the maximum rotation speed selected by the speed adjustment dial 7.

[0077] The controller 20 includes a control circuit 30. The control circuit 30 controls the motor 10 via the drive circuit 21. In this embodiment, the control circuit 30 is in the form of a microcomputer or microcontrol unit (MCU) including a CPU 30a and a memory 30b. The memory 30b includes a semiconductor memory such as a ROM or a RAM.

[0078] The various functions of the control circuit 30 are realized by the CPU 30a executing a program stored in the memory 30b. By executing the program, a method corresponding to the program is performed. The memory 30b corresponds to an example of a non-transient tangible recording medium storing the program.

[0079] The memory 30b stores various motor control programs for controlling the motor 10 (directly controlling the drive circuit 21). The CPU 30a executes the motor control programs to function as the current value acquisition unit 31, the change amount derivation unit 32, the soft no-load determination unit 33, the drive control unit 34, and the rotation speed calculation unit 35 shown in Fig. 2. In other words, the actual entities of the current value acquisition unit 31, the change amount derivation unit 32, the soft no-load determination unit 33, the drive control unit 34, and the rotation speed calculation unit 35 are functions realized by software.

[0080] In other embodiments, some or all of the functions performed by CPU 30a may be accomplished with one or more electronic components, such as discrete elements and integrated circuits (ICs), control circuitry 30 may include one or more additional microcomputers or one or more additional MCUs, or control circuitry 30 may be in the form of hardwired circuitry.

[0081] The control circuit 30 receives as input a current detection signal from the current detection circuit 22, a position signal from the position detection circuit 23, a trigger-on signal and a first command signal from the trigger detection circuit 24, and a second command signal from the dial detection circuit 25. The control circuit 30 controls the drive circuit 21 (and thus the motor 10) based on these signals.

[0082] The control circuit 30 stops the motor 10 while the trigger-on signal is not being input. When the trigger-on signal is input, the control circuit 30 drives the motor 10. At this time, the control circuit 30 sets a target rotation speed of the motor 10 based on the first command signal and the second command signal, and controls the motor 10 according to the target rotation speed.

[0083] The rotation speed calculation unit 35 calculates the actual rotation speed of the motor 10 based on the position signal from the position detection circuit 23. The current value acquisition unit 31 acquires the magnitude of the motor current (hereinafter referred to as the "motor current value") at each detection timing based on the current detection signal from the current detection circuit 22. In this embodiment, the detection timing occurs repeatedly at a predetermined acquisition period. The acquisition period in this embodiment coincides with and is synchronized with a control period described later.

[0084] The change amount derivation unit 32 derives the amount of current change for each detection timing. The amount of current change is the amount of change from the motor current value acquired by the current value acquisition unit 31 at the previous detection timing (hereinafter referred to as the "previous value") to the motor current value acquired by the current value acquisition unit 31 at the current detection timing (hereinafter referred to as the "present value").

[0085] The change amount deriving section 32 may derive the current change amount by, for example, subtracting the previous value from the current value. Alternatively, the change amount deriving unit 32 may convert the amount of change in current into a discrete numerical value and derive the converted numerical value as the amount of change in current. Specifically, the amount of change in current may be set to (i) "0" when the absolute value of the amount of change from the previous value to the current value is less than a predetermined reference value Io, (ii) "+1" when the current value has increased from the previous value and the increase is equal to or greater than the reference value Io, (iii) "+2" when the current value has increased from the previous value and the increase is equal to or greater than twice the reference value Io, (iv) "-1" when the current value has decreased from the previous value and the decrease is equal to or greater than the reference value Io, or (v) "-2" when the current value has decreased from the previous value and the decrease is equal to or greater than twice the reference value Io.

[0086] The soft no-load judgment unit 33 judges whether the motor 10 is in a no-load state or a loaded state, and generates a command indicating execution or release of the soft no-load control based on the judgment result (specifically, sets or clears a soft no-load release judgment flag described later).

[0087] In this embodiment, when the motor 10 starts to drive, the soft no-load determination unit 33 determines that the motor 10 is in a no-load state. If it is determined that the motor 10 is in a no-load state, the soft no-load determination unit 33 performs a determination as to whether to execute soft no-load control. The execution determination is a determination as to whether soft no-load control should be executed. The execution determination includes issuing a command to the drive control unit 34 to execute the soft no-load control.

[0088] When the soft no-load determination unit 33 determines that the motor 10 has changed from a no-load state to a loaded state, it performs a release determination for the soft no-load control. The release determination is a determination that the soft no-load control should be released. The release determination includes issuing a command to the drive control unit 34 to stop the soft no-load control.

[0089] Whether the motor 10 is in a loaded state may be determined by any method. For example, the motor may be determined to be in a loaded state when the motor current value exceeds a predetermined current threshold. Alternatively, the motor may be determined to be in a loaded state by using the method for detecting the loaded state described in the above-mentioned Patent Document 1.

[0090] The soft no-load determining unit 33 further determines whether or not to execute soft no-load control when it is determined that the motor 10 has changed from a loaded state to a no-load state. In order to determine whether the motor is in a no-load state, the soft no-load determination unit 33 of this embodiment includes a sum value calculation unit 40. The sum value calculation unit 40 calculates, for each detection timing, the sum value of the current change amount (including the current change amount at the current detection timing) derived by the change amount derivation unit during a first period from the first calculation start timing to the detection timing.

[0091] The summation value calculation unit 40 may calculate the summation value by any method. In this embodiment, the summation value calculation unit 40 calculates the summation value by accumulating (i.e., cumulatively adding) the amount of change in current each time a detection timing arrives within the first period.

[0092] The start of the first period (i.e., the first calculation start timing) may be determined in any manner. In this embodiment, the start of the first period is after the load state of the motor 10 is determined and at least after the controlled rotation speed reaches the target rotation speed. More specifically, the start of the first period in this embodiment is when the first standby time has elapsed after the controlled rotation speed reaches the target rotation speed. The period from when the controlled rotation speed reaches the target rotation speed to when the first standby time has elapsed is referred to as the first load stable period.

[0093] The sum value calculation unit 40 of this embodiment further has the following characteristics. That is, when a gear shift operation is performed, the sum value calculation unit 40 excludes the amount of change in current during a predetermined second period from the timing of the change operation from the calculation of the sum value. A gear shift operation means that the trigger 6 and / or the speed adjustment dial 7 is moved, more specifically, that the target rotation speed is changed by the target setting unit 41.

[0094] More specifically, when a gear shift operation is performed, the sum value calculation unit 40 of this embodiment stops accumulating the current change amount until the second period has elapsed. In this embodiment, the sum value accumulated up to the present time is further reset (or initialized). Then, the sum value calculation unit 40 restarts the accumulation after the second period has elapsed. In this case, accumulation may not be performed at the first detection timing after the second period has elapsed, and accumulation may be started from the second detection timing after the second period has elapsed. Alternatively, the change amount derivation unit 32 may not derive the current change amount at the first detection timing after the second period has elapsed. In other words, zero or a value close to zero may be derived as the current change amount at the first detection timing. Note that resetting (or initializing) the sum value may be, for example, setting the sum value to zero, or may be, for example, setting the sum value to a predetermined initial value.

[0095] The second period may be determined in any manner. In this embodiment, the second period includes (i) a target attainment period from when the target rotation speed is changed by a gear shift operation until the controlled rotation speed reaches the target rotation speed by the controlled rotation speed setting unit 42 described later, and (ii) a second load stable period from when the controlled rotation speed reaches the target rotation speed until a second standby time has elapsed. Immediately after the controlled rotation speed reaches the target rotation speed, the actual rotation speed of the motor 10 may fluctuate. Specifically, a so-called overshoot or undershoot of the actual rotation speed may occur. The second load stable period is provided in consideration of such fluctuations in the actual rotation speed. The same applies to the first load stable period described above. Therefore, the first load stable period and the second load stable period may each be determined in consideration of the time required for the fluctuations in the actual rotation speed to settle below a certain level. In this embodiment, the second standby period is the same as the first standby period. However, the second standby period may be different from the first standby time.

[0096] When the sum calculated by the sum calculation unit 40 satisfies the no-load detection requirement, the soft no-load determination unit 33 determines that the motor 10 is in a no-load state and determines whether to execute the soft no-load control. As a result, the soft no-load control is executed.

[0097] The no-load detection requirement is required to detect that the motor 10 is in an no-load state. The no-load detection requirement may be determined in any manner. In this embodiment, the no-load detection requirement is satisfied based on the calculated sum value being maintained at or below a predetermined current threshold for a predetermined return determination time.

[0098] The drive control unit 34 controls the motor 10 according to the first control method or the second control method. That is, when the motor 10 is in an unloaded state (i.e., when a determination is made to execute the soft no-load control), the drive control unit 34 controls the motor 10 via the drive circuit 21 using the soft no-load control. When the motor 10 is in a loaded state (i.e., when a determination is made to cancel the soft no-load control), the drive control unit 34 controls the motor 10 via the drive circuit 21 according to the second control method (i.e., without using the soft no-load control).

[0099] The drive control unit 34 of the present embodiment includes a target setting unit 41, a control rotational speed setting unit 42, and a motor control unit 43. The target setting unit 41 sets a target rotation speed of the motor 10 based on the first command signal from the trigger detection circuit 24 and the second command signal from the dial detection circuit 25 .

[0100] For example, when the pulling amount of the trigger 6 is equal to or less than the first pulling amount, the target setting unit 41 sets the target rotation speed to a predetermined initial value (for example, zero). The first pulling amount may be, for example, zero. When the pulling amount of the trigger 6 exceeds the first pulling amount, the target setting unit 41 sets the target rotation speed so that the target rotation speed increases continuously or stepwise as the pulling amount of the trigger 6 increases. At this time, the target setting unit 41 sets the target rotation speed with the maximum rotation speed as the upper limit. That is, the target rotation speed is set so that the target rotation speed reaches the maximum rotation speed when the pulling amount of the trigger 6 reaches a second pulling amount that is greater than the first pulling amount. The second pulling amount may be a pulling amount corresponding to the state in which the trigger 6 is pulled to the maximum, or may be a pulling amount less than the state in which the trigger 6 is pulled to the maximum. When the pulling amount of the trigger 6 exceeds the second pulling amount, the target setting unit 41 maintains the target rotation speed at the maximum rotation speed.

[0101] In this embodiment, the soft no-load control is mainly realized by the target setting unit 41. Specifically, the target setting unit 41 switches the method of setting the target rotation speed depending on whether the motor 10 is in a loaded state or an unloaded state (in other words, depending on whether a determination is made to execute the soft no-load control or to cancel the soft no-load control, in other words, depending on whether the drive control unit 34 is instructed by the soft no-load determination unit 33 to execute the soft no-load control or to stop the soft no-load control).

[0102] When the motor 10 is in a loaded state (i.e., when a determination is made to release the soft no-load control), the target setting unit 41 sets the target rotation speed of the motor 10 based on the first command signal from the trigger detection circuit 24 and the second command signal from the dial detection circuit 25, as described above.

[0103] On the other hand, when the motor 10 is in an unloaded state (i.e., when a determination is made as to whether or not to execute the soft no-load control), the target setting unit 41 sets the target rotation speed to a constant first rotation speed. The first rotation speed may be determined in any manner. For example, the first rotation speed may be the same as the target rotation speed set in the second control method when the trigger 6 is pulled by a predetermined amount. In other words, the first rotation speed may be lower than the target rotation speed set in the second control method when the trigger 6 is pulled by more than the predetermined amount.

[0104] The control rotation speed setting unit 42 sets the control rotation speed based on the target rotation speed set by the target setting unit 41. The control rotation speed setting unit 42 basically matches the control rotation speed with the target rotation speed. When the target rotation speed is changed, the control rotation speed is also changed to the changed target rotation speed.

[0105] However, when the target rotation speed is changed, the control rotation speed setting unit 42 does not immediately change the control rotation speed to the target rotation speed. When the target rotation speed is changed, the control rotation speed setting unit 42 gradually approaches the control rotation speed from the current control rotation speed to the target rotation speed at a predetermined change rate. The control rotation speed setting unit 42 may, for example, monotonically increase or decrease the control rotation speed toward the target rotation speed. The predetermined change rate may be constant or may vary. In this embodiment, the predetermined change rate is constant. That is, in this embodiment, when the target rotation speed is changed, the control rotation speed changes linearly toward the target rotation speed.

[0106] The motor control unit 43 generates a drive command for making the actual rotation speed of the motor 10 coincide with the control rotation speed set by the control rotation speed setting unit 42. The drive command is output to the drive circuit 21. The drive command commands each of the six semiconductor switching elements in the drive circuit 21 to turn on or off. The drive circuit 21 converts the battery power into three-phase power in accordance with the drive command.

[0107] The drive command includes a pulse width modulation (PWM) signal for duty driving one of the six semiconductor switching elements in the drive circuit 21. Duty driving includes turning on and off according to a set duty ratio.

[0108] The motor control unit 43 determines the semiconductor switching elements to be turned on based on the position signal from the position detection circuit 23. At this time, the semiconductor switching elements to be duty-driven are also determined. The motor control unit 43 calculates the duty ratio based on the difference between the actual rotation speed detected by the rotation speed calculation unit 35 and the control rotation speed.

[0109] In this embodiment, as described above, when the motor 10 starts to be driven, it is determined that the motor 10 is in a no-load state, and soft no-load control is executed. That is, regardless of the state of the trigger 6 and the speed adjustment dial 7, a constant first rotation speed (for example, a specified low rotation speed corresponding to a duty ratio of 50%) is set as the target rotation speed, and the motor 10 is driven.

[0110] Then, when it is detected that the motor 10 is in a loaded state after the motor 10 starts to be driven, the soft no-load control is released (i.e., stopped), and the motor 10 is thereby controlled by the second control method.

[0111] Furthermore, if it is detected that the motor 10 is in a no-load state while the control according to the second control method is being performed, the soft no-load control is executed. However, in this embodiment, when the pulling amount of the trigger 6 is less than the above-mentioned predetermined pulling amount, the soft no-load control is not performed and the motor 10 is controlled by the second control method. Therefore, even if the driving of the motor 10 has just started or even if the motor 10 is in an unloaded state, when the pulling amount of the trigger 6 is less than the predetermined pulling amount, a target rotation speed is set according to the pulling amount of the trigger 6 and the maximum rotation speed based on the speed adjustment dial 7, and the motor 10 is driven according to the target rotation speed.

[0112] In this embodiment, in the soft no-load control, feedback control is performed so that the actual rotation speed coincides with a constant first rotation speed. However, in the soft no-load control, the motor 10 may be open-controlled at a duty ratio (e.g., 50%) corresponding to the first rotation speed. In the second control method, the motor 10 may also be open-controlled. Moreover, when a determination is made as to whether to perform the soft no-load control, the soft no-load control may be performed regardless of the pulling amount of the trigger 6.

[0113] (2-3) Example of electric work machine operation Next, an example of the operation of the electric work machine 1 will be described with reference to Fig. 3 and Fig. 4. Both Fig. 3 and Fig. 4 show an example in which the motor 10 changes to a loaded state after the motor 10 starts to be driven, and then changes to an unloaded state. In Fig. 3, a speed change operation is performed to reduce the rotation speed of the motor 10 while in the loaded state. On the other hand, in Fig. 4, a speed change operation is performed to increase the rotation speed of the motor 10 while in the loaded state.

[0114] 3 and 4, "no-load current" refers to the motor current when it is assumed that the motor 10 is maintained in a no-load state. "Detected current" refers to the motor current value actually acquired by the current value acquisition unit 31.

[0115] First, the operation example in Fig. 3 will be described. At time t00, the trigger 6 is pulled and the driving of the motor 10 is started. As described above, when the driving starts, it is determined that there is no load, and the soft no-load control is executed. Therefore, the target rotation speed is limited to a constant first rotation speed.

[0116] At time t01, the driven tool 3 starts working (for example, cutting a workpiece), and the motor 10 changes to a loaded state. However, at time t01, the control circuit 30 has not yet determined that the motor 10 is in a loaded state.

[0117] At time t02, the control circuit 30 judges the load state of the motor 10, and the soft no-load control is released. In Fig. 3 and Fig. 4, "SNL" means soft no-load control. As a result, the target rotation speed changes to a target rotation speed according to a command from the user (i.e., the state of the trigger 6 and the speed adjustment dial 7). As described above, the control rotation speed gradually increases toward the new target rotation speed after the change. At time t03, the control rotation speed reaches the target rotation speed. As the control rotation speed increases, the motor current value also increases.

[0118] At time t04, which is the elapse of the first waiting time from time t03, calculation of the sum value (i.e., accumulation of the amount of change in current) starts. In other words, time t04 corresponds to the first calculation start timing (i.e., the start of the first period).

[0119] At time t05, the user performs a speed change operation to reduce the rotation speed of motor 10. This stops the accumulation of the current change amount. Furthermore, the currently calculated total sum value is reset. The target rotation speed also changes in response to the speed change operation. The control rotation speed gradually changes (here, decreases) toward the changed target rotation speed, and reaches the target rotation speed at time t06. The period from time t05 to t06 corresponds to the target arrival time described above.

[0120] At time t07, when the above-mentioned second standby time has elapsed since time t06, accumulation of the current change amount (that is, calculation of the total sum) is newly started. At time t08, the operation of the driven tool 3 is temporarily interrupted with the trigger 6 still pulled. That is, the driven tool 3 is moved away from the workpiece. This causes the motor 10 to change to an unloaded state. However, at time t08, the control circuit 30 has not yet determined that the motor 10 is in an unloaded state.

[0121] The change to the no-load state at time t08 causes a large drop in the motor current value. As a result, at time t09, the sum value becomes equal to or less than the current threshold value. At time t10, when the aforementioned return determination time has elapsed since time t09, the no-load state is determined. That is, the no-load state of motor 10 is determined based on the fact that the state in which the sum value is equal to or less than the current threshold value has been maintained for the return determination time. As a result, at time t10, the soft no-load control is restored.

[0122] Next, an operation example will be described in Fig. 4. In Fig. 4, an operation example between times t00 and t15 is substantially the same as the operation example between times t00 and t05 in Fig. 3. Therefore, a description of the operation between times t00 and t15 in Fig. 4 will be omitted.

[0123] In FIG. 4, at time t15, a user performs a speed change operation to increase the rotation speed of motor 10. This stops the accumulation of the current change amount. Furthermore, the currently calculated total sum value is reset. The target rotation speed also changes in response to the speed change operation. The control rotation speed gradually changes (increases in this case) toward the changed target rotation speed, and reaches the target rotation speed at time t16. The period from time t15 to time t16 corresponds to the target arrival time described above.

[0124] At time t17, when the above-mentioned second waiting time has elapsed from time t16, accumulation of the current change amount (that is, calculation of the total sum) is newly started. At time t18, the work by the driven tool 3 is temporarily stopped with the trigger 6 still pulled. That is, the driven tool 3 is moved away from the workpiece. This causes the motor 10 to change to an unloaded state. However, at time t18, the control circuit 30 has not yet determined that the motor 10 is in an unloaded state.

[0125] The change to the no-load state at time t18 causes a large drop in the motor current value. As a result, at time t19, the sum value becomes equal to or less than the current threshold value. At time t20, when the aforementioned return determination time has elapsed since time t19, the no-load state is determined. That is, the no-load state of motor 10 is determined based on the fact that the state in which the sum value is equal to or less than the current threshold value has been maintained for the return determination time. As a result, at time t20, the soft no-load control is restored.

[0126] (2-4) Main processing The main processing executed by the control circuit 30 (more specifically, the CPU 30a) will be described with reference to Figs. 4 to 7. The motor 10 is controlled by the main processing. The above-mentioned exemplary operation of the motor 10 is realized by the control circuit 30 executing the main processing. In other words, the current value acquisition unit 31, the change amount derivation unit 32, the soft no-load determination unit 33, the drive control unit 34 and the rotation speed calculation unit 35 shown in Fig. 2 are realized by the main processing. The program for the main processing is stored in, for example, the memory 30b.

[0127] After starting up, the control circuit 30 repeatedly executes the main process at a predetermined control period. When the control circuit 30 starts the main process, it executes a motor information acquisition process in S110. Specifically, the control circuit 30 acquires the pull amount of the trigger 6, the maximum rotation speed selected by the speed adjustment dial 7, the actual rotation speed of the motor 10, the motor current value, the amount of change in current, and the like.

[0128] Although not shown in Fig. 4, after the start of the main process, a predetermined initial process is executed before the process of S110. In this initial process, the motor 10 is treated as being in a no-load state. As a result, soft no-load control is executed.

[0129] In S120, the control circuit 30 performs a soft no-load release determination process. This process determines whether or not the soft no-load control should be released. This process is performed when the soft no-load control is being executed. When the soft no-load control is not being executed (i.e., when the vehicle is under load), the process of S120 is not performed.

[0130] In S120, the control circuit 30 specifically determines whether the motor 10 is in a loaded state. If the control circuit 30 determines that the motor 10 is in a loaded state, it performs a release determination for the soft no-load control. If a release determination for the soft no-load control is performed, the return determination for the soft no-load control, which will be described later, is released.

[0131] In S130, the control circuit 30 performs a soft no-load return judgment process. This process judges whether or not to return to the soft no-load control. This process is performed when the soft no-load control is not being executed. When the soft no-load control is being executed (i.e., when there is no load), the process of S130 is not performed.

[0132] In S130, the control circuit 30 specifically determines whether the motor 10 is in an unloaded state. If the control circuit 30 determines that the motor 10 is in an unloaded state, it performs a return determination of the soft no-load control. The details of the process of S130 are as shown in FIG. 6.

[0133] 6, when the control circuit 30 transitions to the soft no-load return determination process, it determines in S210 whether the motor 10 is being driven. Whether the motor 10 is being driven can be determined based on whether or not a predetermined condition is met based on various states of the electric operating machine 1, such as the operation state of the trigger 6 by the user.

[0134] If the motor 10 is stopped, the control circuit 30 ends the soft no-load return determination process and proceeds to S140 (see FIG. 5). If the motor 10 is driving, the control circuit 30 determines in S220 whether the soft no-load application requirements are met. The soft no-load application requirements are requirements for determining whether the soft no-load control is in an executable state. In this embodiment, the soft no-load application requirements are met when the pulling amount of the trigger 6 is equal to or greater than the above-mentioned predetermined pulling amount.

[0135] If the soft no-load application requirements are not met in S220, the control circuit 30 ends the soft no-load return determination process and proceeds to S140. In other words, if the soft no-load application requirements are not met, the soft no-load control is not performed even if the motor 10 changes to a no-load state. If the soft no-load application requirements are met, the process proceeds to S230.

[0136] In S230, the control circuit 30 judges whether or not a release determination of the soft no-load control has been performed. If this release determination has not been performed (i.e., a loaded state has not been detected), the control circuit 30 ends the soft no-load return determination process and proceeds to S140. If a release determination has been performed (i.e., a loaded state has been detected), this process proceeds to S240.

[0137] In S240, the control circuit 30 determines whether a gear shift has occurred. Specifically, the control circuit 30 may determine that a gear shift has occurred when a gear shift operation is performed by the user. Alternatively, the control circuit 30 may determine that a gear shift has occurred when the target rotation speed is actually changed by the gear shift operation.

[0138] If a gear shift occurs, the process proceeds to S330. In S330, the control circuit 30 resets the currently calculated sum value. When the sum value is reset in S330, the calculation of the sum value is stopped until the second period has elapsed. In other words, during the second period after the reset, the current change amount is excluded from the calculation of the sum value, and the current change amount is not accumulated. When the second period has elapsed after the reset, a positive determination is made in S260 (described later), and the calculation of the sum value is resumed in S270. After the process of S330, the process proceeds to S140.

[0139] If no shifting has occurred in S240, the process proceeds to S250. In S250, the control circuit 30 determines whether the control rotation speed matches the target rotation speed. If the control rotation speed does not match the target rotation speed, the process proceeds to S140. When the soft no-load control is released, the control rotation speed gradually approaches the target rotation speed. Even if a shifting has been performed, the control rotation speed gradually approaches the new target rotation speed after the shifting. Therefore, after the soft no-load control is released or after a shifting has been performed, a negative determination is made in S250 until the control rotation speed reaches the target rotation speed. If the control rotation speed matches the target rotation speed, the process proceeds to S260.

[0140] In S260, the control circuit 30 judges whether or not a load stable period has elapsed since the control rotation speed reached the target rotation speed. In other words, in S260, (i) after the soft no-load control is released, it judges whether or not a first standby time has elapsed since the control rotation speed reached the target rotation speed, and (ii) after the gear shift, it judges whether or not a second standby time has elapsed since the control rotation speed reached the target rotation speed. As described above, in this embodiment, the first standby time is the same as the second standby time. If it is determined in S260 that the stable load period has not elapsed, the process proceeds to S140. If the stable load period has elapsed, the process proceeds to S270.

[0141] In S270, the control circuit 30 updates the sum value. That is, it accumulates the amount of change in current. When the process moves to S270 for the first time after a gear shift, the sum value has been reset. Therefore, in this case, the calculation of the sum value is restarted from the reset value (e.g., zero). After the process of S270, the process moves to S280 (see FIG. 7).

[0142] In S280, the control circuit 30 judges whether the currently calculated sum value is equal to or less than the current threshold value. If the sum value is greater than the current threshold value, the control circuit 30 resets (e.g., updates to zero) the no-load maintenance time in S290. The no-load maintenance time is the time during which the sum value is maintained at or less than the current threshold value from the point in time when the judgment result in S280 changes from a negative judgment to a positive judgment (i.e., the point in time when the sum value changes from a state greater than the current threshold value to a state less than the current threshold value). After the processing of S290, the process proceeds to S140.

[0143] If the sum is equal to or greater than the current threshold, the control circuit 30 measures the no-load maintenance time in S300. Specifically, the currently measured no-load maintenance time is increased (counted up) to update the measured value of the no-load maintenance time.

[0144] In S310, the control circuit 30 judges whether the currently measured no-load duration is equal to or longer than the restoration judgment time. If the no-load duration is not yet equal to or longer than the restoration judgment time, the process proceeds to S140. If the no-load duration is equal to or longer than the restoration judgment time, the process proceeds to S320.

[0145] In S320, the control circuit 30 determines that the motor 10 is in a no-load state, and performs a determination as to whether or not to resume the soft no-load control. If a determination as to whether or not to resume the soft no-load control is performed in S320 after a determination as to whether or not to cancel the soft no-load control, the determination as to whether or not to cancel the soft no-load control is canceled. After the processing of S320, the process proceeds to S140.

[0146] In S140 (see FIG. 5), the control circuit 30 performs a target rotation speed determination process. The details of the target rotation speed determination process are as shown in FIG. 8. When the control circuit 30 proceeds to the target rotation speed determination process, in S410, it determines whether or not the soft no-load application requirements are met. This process of S410 is the same as S220. If the soft no-load application requirements are not met, the process proceeds to S440. If the soft no-load application requirements are met, the process proceeds to S420.

[0147] In S420, the control circuit 30 judges whether or not a release determination of the soft no-load control has been performed. If a release determination of the soft no-load control has not been performed, the process proceeds to S450. For example, immediately after the motor 10 starts to drive, or if the motor 10 is determined to be in a no-load state, it is judged in S420 that a release determination has not been performed.

[0148] In S450, the control circuit 30 sets the target rotation speed to a constant first rotation speed. That is, in order to perform soft no-load control, the control circuit 30 sets the target rotation speed for the soft no-load control. After the process of S450, the process proceeds to S150 (see FIG. 5).

[0149] If it is determined in S420 that the soft no-load control has been released, the process proceeds to S430. In S430, the control circuit 30 determines whether it is determined that the soft no-load control has been resumed. If it is determined that the soft no-load control has been resumed, the process proceeds to S450. In this case, the target rotation speed is set to a constant first rotation speed corresponding to the soft no-load control.

[0150] If the soft no-load control return determination has not been performed, the process proceeds to S440. In S440, the control circuit 30 sets the target rotation speed according to the trigger 6 and the speed adjustment dial 7. After the process of S440, the process proceeds to S150.

[0151] At S150 (see FIG. 5), the control circuit 30 executes the motor control process. Specifically, the control circuit 30 sets a control rotation speed based on a set target rotation speed. The control circuit 30 calculates a duty ratio for duty driving based on the control rotation speed and the actual rotation speed. The control circuit 30 outputs a drive command including a PWM signal having the calculated duty ratio to the drive circuit 21. This drives the motor 10.

[0152] (2-5) Correspondence of Wording In the above embodiment, the current value acquisition unit 31 corresponds to an example of a physical quantity acquisition unit in the summary of the embodiments. The trigger 6 and the speed adjustment dial 7 correspond to an example of at least one switch in the summary of the embodiments. The trigger 6 corresponds to an example of a first switch in the summary of the embodiments. The speed adjustment dial 7 corresponds to an example of a second switch in the summary of the embodiments. The second waiting time corresponds to an example of a first time in the summary of the embodiments. The current threshold corresponds to an example of a predetermined threshold in the summary of the embodiments. The recovery judgment time corresponds to an example of a second time in the summary of the embodiments.

[0153] 3. Other embodiments Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments and can be implemented in various modified forms.

[0154] (3-1) In the above embodiment, when a gear shift operation is performed, the currently calculated sum value is reset and accumulation is not performed until the second period has elapsed, thereby excluding the amount of change during the second period from the sum value.

[0155] However, the amount of change in the second period immediately after the gear shift operation may be excluded from the calculation of the sum value by using another method. For example, resetting the sum value is not essential. Specifically, the sum value at the time when the gear shift operation is performed may be maintained for the second period. After the second period has elapsed, accumulation of the current change amount may be restarted from the maintained sum value.

[0156] Alternatively, for example, the calculation of the sum may not be an accumulation, but may involve calculating the sum of the amounts of change during a first period from a first calculation start timing to the detection timing, one by one, for each detection timing. When a gear shift operation is performed, the start of the first period may be changed from the first calculation start timing to a second calculation start timing. The second calculation start timing corresponds to the end of the second period.

[0157] (3-2) The second period not included in the calculation of the sum value may be determined in any manner. For example, the second period does not have to include the second waiting time. (3-3) The summation value calculation unit 40 may calculate the summation value of a change amount other than the current change amount. Then, the soft no-load determination unit 33 may determine the no-load state of the motor 10 based on the summation value of the other change amount.

[0158] The other change amount may be a change amount of a physical quantity related to the operating state of the motor 10 other than the motor current. The physical quantity related to the operating state of the motor 10 may include a parameter used for controlling the motor 10. Examples of the physical quantity related to the operating state of the motor 10 include the actual rotation speed of the motor 10, the voltage applied or being applied to the motor 10, the duty ratio of the PWM signal, and the like.

[0159] (3-4) The target rotation speed set in the soft no-load control does not have to be a constant speed. The target rotation speed may change even when the soft no-load control is executed. For example, the target rotation speed may change according to the change in the pulling amount of the trigger 6. In this case, the target rotation speed may be set to be lower than the target rotation speed set when the soft no-load control is released.

[0160] (3-5) The drive control unit 34 may realize the soft no-load control in any manner. That is, in the above embodiment, the target setting unit 41 plays a substantial role in the soft no-load control. That is, in the above embodiment, in response to the no-load detection requirement being satisfied, the target setting unit 41 sets the target rotation speed to a constant first target speed for the soft no-load control.

[0161] In contrast to this, for example, the control rotational speed setting unit 42 may take on the substantial role of the soft no-load control. Specifically, in response to the no-load detection requirement being satisfied, the control rotational speed setting unit 42 may set the control rotational speed to a constant speed regardless of the set target rotational speed.

[0162] Alternatively, the motor control unit 43 may take on a substantial role of the soft no-load control. Specifically, in response to the no-load detection requirement being satisfied, the motor control unit 43 may generate a drive command for rotating the motor 10 at a constant first rotation speed regardless of the target rotation speed and the control rotation speed.

[0163] (3-6) When the target rotation speed is changed, it is not essential to gradually bring the control rotation speed closer to the target rotation speed. The control rotation speed may always coincide with the target rotation speed. In other words, the control rotation speed setting unit 42 may be omitted, and the motor control unit 43 may control the motor 10 according to the target rotation speed set by the target setting unit 41.

[0164] (3-7) The trigger 6 or the speed adjustment dial 7 may be omitted. The "at least one switch" in the summary of the embodiments may be realized in a form other than the trigger 6 and the speed adjustment dial 7.

[0165] (3-8) The motor 10 in the above embodiment is a three-phase brushless motor. However, the motor of the present disclosure may be a motor of a different form than a three-phase brushless motor (for example, a DC motor with brushes, various AC motors, etc.).

[0166] (3-9) Multiple functions possessed by one component in the above embodiments may be realized by multiple components, or one function possessed by one component may be realized by multiple components. Also, multiple functions possessed by multiple components may be realized by one component, or one function realized by multiple components may be realized by one component. Also, part of the configuration of the above embodiments may be omitted. Also, at least part of the configuration of the above embodiments may be added to or substituted for the configuration of another of the above embodiments. [Explanation of symbols]

[0167] 1...electric work machine, 3...driven implement, 6...trigger, 7...speed adjustment dial, 10...motor, 20...controller, 21...drive circuit, 30...control circuit, 30a...CPU, 30b...memory, 31...current value acquisition unit, 32...change amount derivation unit, 33...soft no-load determination unit, 34...drive control unit, 40...sum value calculation unit, 41...target setting unit, 42...control rotational speed setting unit, 43...motor control unit.

Claims

1. It is an electric work machine, A motor configured to drive a driven device attached to the aforementioned electric work machine, A drive circuit configured to drive the motor, A control circuit, A physical quantity acquisition unit configured to acquire a physical quantity related to the operating state of the motor at each detection timing, A change amount derivation unit configured to derive the amount of change from the physical quantity acquired at the previous detection timing to the physical quantity acquired at the current detection timing, for each of the aforementioned detection timings, A sum value calculation unit is configured to calculate the sum of the change amounts derived by the change amount derivation unit during the first period from the first calculation start timing to the detection timing, for each of the aforementioned detection timings. A drive control unit is configured to control the motor via the drive circuit based on a first control method, in response to the sum value calculated by the sum value calculation unit satisfying the no-load detection requirement for detecting that no load is applied to the motor. A control circuit equipped with, An electric work machine equipped with the following features.

2. An electric work machine according to claim 1, The electric work machine further includes at least one switch configured to be manually operated by the user of the electric work machine to set the rotational speed of the motor, The control circuit further includes a target setting unit configured to set a target rotational speed of the motor based on the state of at least one switch. The drive control unit is configured to control the motor based on a second control method different from the first control method if the sum value does not satisfy the no-load detection requirement. The second control method includes controlling the motor so that it rotates at the target rotation speed set by the target setting unit. Electric work equipment.

3. An electric work machine according to claim 2, The sum value calculation unit is configured such that, when the target rotational speed is changed by at least one switch, the amount of change during a predetermined second period from the timing of the change is excluded from the calculation of the sum value. Electric work equipment.

4. An electric work machine according to claim 3, The sum value calculation unit is configured to switch the start time of the first period from the first calculation start timing to the second calculation start timing when the target rotational speed is changed by the at least one switch. The second calculation start timing corresponds to the end of the second period, Electric work equipment.

5. An electric work machine according to claim 3 or claim 4, The control circuit further includes a control rotation speed calculation unit configured to (i) calculate a control rotation speed based on the target rotation speed, and (ii) gradually change the control rotation speed from the current control rotation speed to the target rotation speed when the target rotation speed is changed. The second control method includes controlling the motor so that its rotational speed matches the controlled rotational speed. The second period includes the period from when the target rotational speed is changed until the control rotational speed reaches the target rotational speed according to the control rotational speed calculation unit. Electric work equipment.

6. An electric work machine according to claim 5, The second period further includes the period from the time the control rotation speed reaches the target rotation speed according to the control rotation speed calculation unit until the first time has elapsed. Electric work equipment.

7. An electric work machine according to claim 3, The sum value calculation unit is configured to calculate the sum value by accumulating the amount of change each time the detection timing occurs within the first period. The sum value calculation unit is configured to reset the currently calculated sum value when at least one switch is activated and thereby changes the target rotational speed. Electric work equipment.

8. An electric work machine according to Claim 2, The at least one switch comprises a first switch, The target setting unit is configured to change the target rotation speed according to the position of the first switch by the user. Electric work equipment.

9. An electric work machine according to claim 8, The at least one switch comprises a second switch, The target setting unit is configured to change the target rotation speed, with the maximum rotation speed corresponding to the position of the second switch as the upper limit. Electric work equipment.

10. An electric work machine according to Claim 1, The no-load detection requirement is satisfied based on the sum value calculated by the sum value calculation unit being of a predetermined magnitude, and the predetermined magnitude corresponds to being less than or equal to a predetermined threshold. Electric work equipment.

11. An electric work machine according to Claim 1, The no-load detection requirement is satisfied based on the sum value calculated by the sum value calculation unit being of a predetermined magnitude, and the predetermined magnitude corresponds to being greater than or equal to a predetermined threshold. Electric work equipment.

12. An electric work machine according to claim 10 or claim 11, The no-load detection requirement is satisfied based on the fact that the sum value calculated by the sum value calculation unit continues to maintain the predetermined magnitude for a second time. Electric work equipment.

13. An electric work machine according to Claim 1, The first control method includes controlling the motor so that it rotates at a constant first rotational speed. Electric work equipment.

14. An electric work machine according to claim 2, The first control method includes controlling the motor so that it rotates at a constant first rotational speed, The first rotational speed is lower than the target rotational speed. Electric work equipment.

15. An electric work machine according to Claim 1, The aforementioned physical quantity includes the current flowing through the motor. Electric work equipment.

16. A motor control method used in electric work machines, At each detection timing, a physical quantity related to the operating state of the motor provided in the electric work machine is acquired, For each detection timing, the amount of change from the physical quantity acquired at the previous detection timing to the physical quantity acquired at the current detection timing is derived, For each detection timing, the sum of the change amounts derived from the calculation start timing to that detection timing is calculated, In accordance with whether the calculated sum value satisfies the no-load detection requirement for detecting that no load is applied to the motor, the motor is controlled based on a predetermined control method. A motor control method comprising the following features.

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