Electric work machine

Abstract

To properly protect a motor according to the duration of its load state.SOLUTION: An electric work machine includes a time measurement unit, a heat estimation unit, and a protection unit. The time measurement unit continuously or cumulatively measures a load time. The load time is the period during which a load of a predetermined level or higher (It0 or higher) is applied to a motor 10. The heat estimation unit calculates, based on a motor current value, a heat estimation value by using a parameter. The heat estimation value is an estimation value of an amount of heat generation of the motor 10. The heat estimation unit changes the parameter according to the load time measured by the time measurement unit (time t11). The protection unit performs a protection operation in response to the heat estimation value having reached a heat threshold value (A0).SELECTED DRAWING: Figure 4

Description

[Technical Field]

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

[0002] Patent Document 1 discloses an electric work machine configured to detect the load on a motor and estimate the heat generation amount of the motor based on the detected load. Specifically, in this electric work machine, when the motor is under load (for example, when the load is equal to or greater than a set value), a counter is counted up sequentially. The count value of the counter corresponds to the estimated heat generation amount. When the count value exceeds a threshold, the motor is protected (for example, stopped). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6789834 Summary of the Invention [Problem to be solved by the invention]

[0004] A motor that generates heat during a load state cools down when it enters a low-load state. A low-load state corresponds, for example, to a state in which the load is less than a set value or is zero. The lower the ratio of the time during a load state to the time during a low-load state (i.e., the value obtained by dividing the time during a load state by the time during a low-load state), or the shorter the duration of the load state, the less likely the motor temperature will rise. In other words, the lower the ratio, the easier it is for the motor to cool down during a low-load state.

[0005] Therefore, if the counter is set to a relatively large value, assuming that the ratio is high or the duration of the load state is long, excessive protection may occur. In other words, if the ratio is low or the duration of the load state is short, the count value may exceed the threshold and the motor may be protected, even if there is a temperature margin.

[0006] It is desirable to be able to appropriately protect the motor depending on the duration of the load condition. [Means for solving the problem]

[0007] An electric work machine according to one aspect of the present disclosure includes a manual switch. The manual switch is manually operated by a user of the electric work machine. The electric work machine includes a motor. The motor is driven in response to whether the manual switch has been manually operated or has been manually operated. The electric work machine includes a current detection unit. The current detection unit detects a current value. The current value corresponds to the value of current supplied from a power source to the motor. The electric work machine includes a timing unit. The timing unit continuously or cumulatively measures load time. The load time is the time during which a load equal to or greater than a predetermined level is applied to the motor.

[0008] The electric operating machine includes a heat estimation unit. The heat estimation unit calculates a heat estimation value using parameters based on a current value detected by a current detection unit. The heat estimation value is an estimate of the amount of heat generated by the motor. The heat estimation unit changes the parameters according to the load time measured by the timing unit. The electric operating machine includes a protection unit. The protection unit executes a protection operation to reduce the temperature of the motor in response to the heat estimation value calculated by the heat estimation unit reaching a heat threshold.

[0009] In such an electric operating machine, the parameters used to calculate the heat estimation value are changed depending on the load time, which makes it possible to appropriately protect the motor (i.e., to appropriately perform a protective operation) depending on the load time. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a perspective view of an electric working machine according to an embodiment. [Figure 2] FIG. 2 is a block diagram showing the electrical configuration of the electric operating machine. [Figure 3] 4 is a time chart showing a simplified first operation example of the electric operating machine. [Figure 4] 6 is a time chart showing a second operation example of the electric operating machine in a simplified manner. [Figure 5] 4 is a time chart showing a part of a specific example of the operation of the electric working machine. [Figure 6] 10 is a time chart showing another part of a specific example of the operation of the electric operating machine. [Figure 7] 10 is a time chart showing the remaining part of the specific operation example of the electric working machine. [Figure 8] 10 is a flowchart of a main process. [Figure 9] 10 is a flowchart of a motor driving process. [Figure 10] 10 is a flowchart showing an overview of an overload protection process. [Figure 11] 10 is a flowchart showing a part of the details of an overload protection process. [Figure 12] 10 is a flowchart showing another part of the details of the overload protection process. [Figure 13] 10 is a flowchart showing another part of the details of the overload protection process. [Figure 14] 10 is a flowchart showing another part of the details of the overload protection process. [Figure 15] 10 is a flowchart showing the remaining part of the details of the overload protection process. DETAILED DESCRIPTION OF THE INVENTION

[0011] [Summary of the embodiment] In some embodiments, the electric work machine may include a manual switch. The manual switch may be manually operated by a user of the electric work machine. Additionally / alternatively, the electric work machine may include a motor. The motor may be driven in response to the manual switch being manually operated or being manually operated. Additionally / alternatively, the electric work machine may include a drive circuit that drives the motor. The drive circuit may be configured to supply power to the motor. Additionally / alternatively, the electric work machine may include a current detection unit. The current detection unit may detect a current value. The current value may correspond to the value of the current supplied from the power source to the motor.

[0012] Additionally / alternatively, the electric operating machine may include a timing unit. The timing unit may measure the load time continuously or cumulatively. The load time may be the time during which a load equal to or greater than a predetermined level is applied to the motor. A load equal to or greater than a predetermined level may be defined in any way. For example, a state in which a torque equal to or greater than a predetermined value is applied to the motor may be defined as a state in which a load equal to or greater than a predetermined level is applied. Also, for example, a state in which a current value detected by a current detection unit is equal to or greater than a current threshold may be defined as a state in which a load equal to or greater than a predetermined level is applied. In other words, the load time may include the time during which the current value is equal to or greater than the current threshold.

[0013] Additionally / alternatively, the electric operating machine may include a heat estimator. The heat estimator may calculate a heat estimate based on a current value detected by the current detector. The heat estimate is an estimate of the amount of heat generated by the motor. The heat estimator may calculate the heat estimate using parameters. The heat estimator may change the parameters according to the load time measured by the timer. The heat estimate may be any value that directly or indirectly indicates the amount of heat generated by the motor. That is, the heat estimate may be a value having any dimension and expressed in any physical unit.

[0014] Additionally / alternatively, the electric work machine may include a protection unit. The protection unit may execute a protection action in response to the thermal estimation value calculated by the thermal estimator reaching a thermal threshold. The protection action may be an action to reduce the temperature of the motor. The thermal threshold may be a value indicating a predetermined amount of heat. The predetermined amount of heat may be an amount of heat for which further temperature increase should be suppressed or for which it is desirable to suppress it. The thermal threshold may be determined in any manner. The thermal threshold may have the same dimensions as the thermal estimation value or may be a value expressed in the same physical units as the thermal estimation value. The protection action may include slowing down or stopping the motor. Instead of or in addition to slowing down or stopping the motor, the protection action may include any action that can suppress or prevent a temperature increase of the motor.

[0015] In one embodiment, if an electric work machine is equipped with the above-mentioned manual switch, the above-mentioned motor, the above-mentioned current detection unit, the above-mentioned timing unit, the above-mentioned heat estimation unit, and the above-mentioned protection unit, such an electric work machine can appropriately protect the motor (i.e., appropriately perform protection operations) depending on the load time.

[0016] Additionally / alternatively, the parameters may include an increase rate of the thermal estimate, and the thermal estimator may calculate the thermal estimate such that the thermal estimate increases at the increase rate while the current value detected by the current detector is equal to or greater than the current threshold.

[0017] If an electric power tool in an embodiment has both of these features, the electric power tool can easily calculate a heat estimate. Additionally / alternatively, the heat estimator may increase the increase rate in response to the load time measured by the timer reaching a time threshold. The time threshold may be a predetermined time.

[0018] If an electric operating machine in an embodiment is equipped with the heat estimating unit as described above, such an electric operating machine can appropriately estimate a heat estimated value according to the load time. Additionally / alternatively, the heat estimator may include a counter. The counter may periodically count up an additional value while the current value detected by the current detector is equal to or greater than the current threshold. The additional value may correspond to the increase rate. The counter may change the additional value according to the load time measured by the timer. Additionally / alternatively, the heat estimator may include a calculator configured to calculate a heat estimation value based on the count value of the counter.

[0019] If an electric operating machine in an embodiment includes the counter and the calculation unit, the electric operating machine can more easily calculate the heat estimation value. Additionally / alternatively, the counter may use a first additional value or a second additional value as the additional value depending on the load time being measured by the timer unit, the second additional value being greater than the first additional value.

[0020] If an electric operating machine in an embodiment is provided with the counter, such an electric operating machine can easily change the parameter (i.e., change the rate of increase) according to the load time.

[0021] Additionally / alternatively, the counter may use the first additional value as the additional value while the load time being measured by the timer unit is less than the time threshold value, and additionally / alternatively, the counter may use the second additional value as the additional value in response to the load time being measured by the timer unit reaching the time threshold value.

[0022] In one embodiment, if an electric power tool is equipped with a counter configured to change the added value as described above, such an electric power tool can appropriately and easily calculate a heat estimate according to the load time.

[0023] Additionally / alternatively, the heat estimator may include a first counter. The first counter may periodically count up a first additional value while the current value detected by the current detector is equal to or greater than the current threshold. Additionally / alternatively, the heat estimator may include a second counter. The second counter may periodically count up a second additional value while the current value detected by the current detector is equal to or greater than the current threshold. The second additional value is greater than the first additional value. Each of the first additional value and the second additional value corresponds to an increase rate. Additionally / alternatively, the heat estimator may include a calculator. The calculator may activate the first count value or the second count value depending on the load time measured by the timer. The first count value corresponds to the count value of the first counter, and the second count value corresponds to the count value of the second counter. The calculator may calculate the heat estimate based on the activated count value.

[0024] If an electric operating machine in an embodiment includes the first counter, the second counter, and the calculation unit, such an electric operating machine can more easily calculate the heat estimated value.

[0025] Additionally / alternatively, the calculation unit may enable the first count value while the load time measured by the timer unit is less than the time threshold value. Additionally / alternatively, the calculation unit may enable the second count value in response to the load time measured by the timer unit reaching the time threshold value.

[0026] If an electric operating machine in one embodiment is equipped with a calculation unit configured to validate the first count value or the second count value as described above, such an electric operating machine can appropriately and easily calculate a heat estimation value according to the load time.

[0027] Additionally / alternatively, the calculation unit may calculate the enabled count value as the thermal estimate, i.e., the enabled count value itself may be treated as the thermal estimate. If the electric operating machine in an embodiment is equipped with the above-described calculation unit, such an electric operating machine can more easily calculate the heat estimated value.

[0028] Additionally / alternatively, when the current value detected by the current detection unit becomes less than a predetermined current value, the heat estimator may (i) retain the current heat estimate and (ii) clear the first count value, the second count value, and the load time. The predetermined current value may be equal to or less than a current threshold. Here, "clear" may mean directly changing the value or time to be cleared to zero or a predetermined value. In other words, "clear" does not necessarily mean gradually bringing the current value or time closer to zero or a predetermined value. Additionally / alternatively, the calculator may calculate the heat estimate by adding the enabled count value to the value retained by the heat estimator.

[0029] If an electric work machine in one embodiment is equipped with a heat estimation unit configured as described above, such an electric work machine can appropriately calculate a heat estimation value even if there is a load fluctuation such that the current value fluctuates above or below a predetermined current value.

[0030] Additionally / alternatively, the predetermined current value may be smaller than the current threshold value. When the electric operating machine in one embodiment is configured in this manner, it is possible to prevent the first counter and the second counter from being counted up and cleared too frequently.

[0031] Additionally / alternatively, the motor may be driven while the manual switch is being manually operated. Additionally / alternatively, the protection unit may stop the protection operation in response to the user releasing the manual operation of the manual switch after starting the protection operation.

[0032] In one embodiment, an electric operating machine including the motor and the protection unit can effectively dissipate heat from the motor, and can also prompt the user to avoid using the machine in a way that would cause the protection unit to operate.

[0033] Additionally / alternatively, the protection unit may change the thermal threshold depending on the number of times the protection action is performed. More specifically, the protection unit may lower the thermal threshold as the number of times the protection action is performed increases. If an electric operating machine in a certain embodiment is provided with the above-described protection section, the electric operating machine can more effectively suppress heat generation from the motor.

[0034] Additionally / alternatively, the protection unit may continue the protection operation when the number of times the protection operation has been performed reaches a specified number, even if the manual operation of the manual switch is released. If the electric working machine in a certain embodiment is provided with the above-described protection section, the electric working machine can more effectively protect the motor from overheating.

[0035] Additionally / alternatively, the electric operating machine may include a power supply control circuit configured to supply power to the protection unit for operating the protection unit. Additionally / alternatively, the protection unit may operate while receiving power from the power control circuit.

[0036] Additionally / alternatively, when the power supply to the protection unit is cut off while the protection unit is performing a protection operation, the protection unit may (i) stop the protection operation and (ii) clear the number of times the protection unit has performed the operation. If an electric operating machine in an embodiment is equipped with the above-described power supply control circuit and the above-described protection unit, such an electric operating machine can more effectively protect the motor from overheating. Note that, as described above, the "clear" here may also mean directly changing the value to be cleared (here, the number of times) to zero or a predetermined value.

[0037] In some embodiments, the above features may be combined in any combination. In some embodiments, any of the above features may be omitted. In addition to the electric work machine described above, the present disclosure can also be realized in various forms, such as a system that includes the electric work machine as a component, a program for causing a computer to function as the electric work machine, a non-transient physical recording medium such as a semiconductor memory on which this program is recorded, and a method used in the electric work machine.

[0038] Specific Exemplary Embodiments [1. Embodiment] (1) Overview of electric work equipment Hereinafter, exemplary embodiments of the present disclosure will be described with reference to the drawings.

[0039] The electric working machine 1 of this embodiment shown in FIG. 1 is in the form of, for example, a hand saw (or pruning saw). A hand saw is expected to be used instead of a handsaw, for example, to easily cut relatively thin branches. A hand saw may be considered a miniaturized version of a chainsaw used to cut logs, thick branches, and the like. A user of the electric working machine 1 can use the electric working machine 1 to easily prune, for example, roadside trees, garden trees, fruit trees, and the like.

[0040] As shown in FIG. 1, the electric work machine 1 includes a main body 2 and a work tool 6. The main body 2 includes a motor housing 3, a grip 4, and a battery mounting section 5. The motor housing 3 houses a motor 10 (see FIG. 2) and a controller 20 (see FIG. 2). In this embodiment, the motor 10 is, for example, a brushless motor. Specifically, the motor 10 includes a permanent magnet rotor (not shown) and a stator (not shown).

[0041] The motor accommodating section 3 further accommodates a transmission mechanism (not shown) and a sprocket (not shown). The transmission mechanism transmits the rotational force of the motor 10 to the sprocket. When the motor 10 rotates, the sprocket rotates.

[0042] The grip 4 extends from the motor housing 3. The grip 4 is held by, for example, a user of the electric work machine 1. The grip 4 is provided with a trigger 9. The user can manually operate (for example, pull) the trigger 9 while holding the grip 4.

[0043] In this embodiment, the drive switch 9a (see FIG. 2) is turned on while the trigger 9 is being manually operated. The drive switch 9a is turned off when the trigger 9 is not being manually operated. The trigger 9 may be of a so-called alternate type. When the trigger 9 is of the alternate type, after being turned on by manual operation, the trigger 9 remains in the on state even if the manual operation is released. If the manual operation is once released and then manually operated again, the trigger 9 is turned off. Alternatively, the drive switch 9a may be of the alternate type.

[0044] The battery attachment section 5 extends from the grip 4. A battery pack 100 is removably attached to the bottom of the battery attachment section 5. The battery pack 100 includes a battery 101 (see FIG. 2). The battery 101 may be, for example, a secondary battery. The battery 101 may be, for example, a lithium ion battery. The battery 101 may be, for example, a secondary battery other than a lithium ion battery.

[0045] The work tool 6 includes a guide bar 7 and a chain blade 8. The guide bar 7 and the chain blade 8 are each removably attached to the main body 2. The guide bar 7 has a long plate shape. The guide bar 7 is attached to the main body 2 (more specifically, to the motor housing 3) with one end of the guide bar 7 housed in the motor housing 3.

[0046] The chain blade 8 is attached along the outer periphery of the guide bar 7. Specifically, in this embodiment, a groove is provided on the outer periphery of the guide bar 7. The chain blade 8 is fitted into the groove over almost the entire circumference of the guide bar 7. The chain blade 8 is movable along the groove (i.e., along the outer periphery of the guide bar 7).

[0047] The chain blade 8 is meshed with a sprocket inside the motor housing 3. As a result, when the motor 10 rotates, the rotational force of the motor 10 is transmitted to the chain blade 8 via the transmission mechanism and the sprocket. This causes the chain blade 8 to be driven (i.e., moved) along the outer periphery of the guide bar 7. A user can cut an object by applying the driven chain blade 8 to the object.

[0048] (2) Electrical configuration of electric work equipment 2, the electric work machine 1 includes the motor 10, the drive switch 9a, and a controller 20. The controller 20 receives power from a battery 101 (hereinafter referred to as "battery power") from a battery pack 100 attached to the battery attachment section 5. The motor 10 and the drive switch 9a are electrically connected to the controller 20.

[0049] The motor 10 is supplied with battery power via a drive circuit 21, which will be described later. Specifically, the battery power is converted into three-phase power by the drive circuit 21 and supplied to the motor 10. The motor 10 of this embodiment has three windings. Three-phase power is supplied to the three windings. The motor 10 rotates when the three-phase power is supplied to the three windings.

[0050] As shown in FIG. 2, the electric work machine 1 includes a rotational position sensor 11. The rotational position sensor 11 outputs rotational position information. The rotational position information indicates the rotational position of the motor 10, more specifically, the rotational position of the rotor. In this embodiment, the rotational position information includes three position signals. The rotational position information is input to a rotational position detection circuit 24, which will be described later.

[0051] The rotational position sensor 11 of this embodiment includes three Hall sensors. The three Hall sensors are arranged around the rotor's rotation axis, spaced apart by an electrical angle of 120 degrees along the direction of rotor rotation. The three position signals described above are output from the three Hall sensors, respectively.

[0052] The controller 20 includes a control circuit 30. The control circuit 30 controls the rotation of the motor 10. A first terminal of the drive switch 9a is connected to the controller 20, and a second terminal of the drive switch 9a is connected to the ground line. The voltage at the first terminal of the drive switch 9a functions as a trigger detection signal. The trigger detection signal indicates whether the drive switch 9a is turned on or not (in other words, whether the trigger 9 is being manually operated or not). The trigger detection signal may further indicate the amount of operation of the trigger 9 when it is being manually operated. The trigger detection signal is input to the controller 20.

[0053] The controller 20 includes the aforementioned drive circuit 21. The drive circuit 21 is connected to the motor 10. Specifically, the drive circuit 21 is provided on a power path that runs from the positive terminal of the battery 101 through the motor 10 to the negative terminal of the battery 101. The drive circuit 21 receives battery power from the battery 101. The drive circuit 21 generates three-phase power from the supplied battery power and supplies it to the motor 10.

[0054] The drive circuit 21 of this embodiment includes a three-phase full-bridge circuit. The three-phase full-bridge circuit includes six switches. Each switch may have any configuration. In this embodiment, each switch is, for example, an n-channel metal-oxide-semiconductor field-effect transistor (MOSFET).

[0055] The controller 20 includes a power supply control circuit 22. The power supply control circuit 22 is connected to a power path and receives battery power from the power path. A trigger detection signal is also input to the power supply control circuit 22. A power supply maintenance signal can also be input to the power supply control circuit 22 from the control circuit 30.

[0056] When the power supply control circuit 22 detects from the trigger detection signal that the drive switch 9a has been turned on, it outputs a first voltage to the control circuit 30. The power supply control circuit 22 generates the first voltage from battery power. The first voltage is a DC voltage. The first voltage may have any value. In this embodiment, the first voltage is the same as or approximately equal to the voltage of the battery 101. The power supply control circuit 22 may output the voltage of the battery 101 as the first voltage via a switch (not shown).

[0057] The control circuit 30 is activated and operates by a first voltage supplied from the power supply control circuit 22. The control circuit 30 stops operating when the supply of the first voltage is cut off. When the control circuit 30 is activated by the supply of the first voltage, it outputs a power supply holding signal to the power supply control circuit 22, as described below.

[0058] After starting to output the first voltage in response to the driving switch 9a being turned on, the power supply control circuit 22 continues to output the first voltage as long as the power supply holding signal is being input, even if the driving switch 9a is turned off. When the input of the power supply holding signal from the control circuit 30 is stopped, the power supply control circuit 22 stops outputting the first voltage. When the output of the first voltage is stopped, the operation of the control circuit 30 stops.

[0059] The controller 20 includes a current detection circuit 23. The current detection circuit 23 is provided to detect the value of the current flowing through the motor 10. In this embodiment, the current detection circuit 23 is provided in the path between the drive circuit 21 and the negative electrode of the battery 101 in the aforementioned power path. The current detection circuit 23 outputs a current detection signal corresponding to the value of the current flowing through this path. The current detection circuit 23 may be configured to include, for example, a resistor (not shown) provided in this path and to generate a current detection signal corresponding to the voltage across the resistor. The current detection signal is input to the control circuit 30 (specifically, to the CPU 30a).

[0060] The controller 20 includes a rotational position detection circuit 24. The rotational position detection circuit 24 detects the rotational position of the motor 10 based on the three position signals input from the rotational position sensor 11. The rotational position detection circuit 24 outputs a rotational position signal corresponding to the detected rotational position. The rotational position signal is input to the control circuit 30 (specifically, to the CPU 30a).

[0061] The controller 20 includes a battery voltage detection circuit 25. The battery voltage detection circuit 25 detects the voltage value of the battery 101 and outputs a battery voltage signal indicating the detected voltage value. The battery voltage signal is input to the control circuit 30 (specifically, to the CPU 30a).

[0062] The controller 20 includes a controller temperature detection circuit 26. The controller temperature detection circuit 26 detects the temperature of the controller 20 and outputs a controller temperature signal indicating the detected temperature. The controller temperature signal is input to the control circuit 30 (specifically, to the CPU 30a).

[0063] The control circuit 30 includes a voltage generating circuit 30c. The first voltage input from the power supply control circuit 22 to the control circuit 30 is input to the voltage generating circuit 30c. While receiving the first voltage, the voltage generating circuit 30c generates and outputs a second DC voltage Vcc from the first voltage. The second voltage Vcc may have any value. In this embodiment, the value of the second voltage Vcc is lower than the value of the first voltage. The second voltage Vcc is supplied to each component within the controller 20 and is used as the power supply for each component.

[0064] The control circuit 30 includes a CPU 30a and a memory 30b. The memory 30b may include a semiconductor memory such as a ROM, a RAM, an NVRAM, or a flash memory. That is, the control circuit 30 of this embodiment includes a microcomputer.

[0065] The control circuit 30 realizes various functions by executing a program stored in a non-transitory physical recording medium. In this embodiment, the memory 30b corresponds to the non-transitory physical recording medium storing the program. In this embodiment, the memory 30b stores a program for main processing (see FIG. 8) described later.

[0066] Some or all of the various functions realized by the control circuit 30 may be achieved by executing a program (i.e., by software processing), or may be achieved by one or more pieces of hardware. For example, instead of or in addition to a microcomputer, the control circuit 30 may include a logic circuit including multiple electronic components, an application specific integrated circuit such as an ASIC and / or ASSP, or a programmable logic device such as an FPGA that can configure any logic circuit.

[0067] The trigger detection signal from the drive switch 9a is input to the CPU 30a in the control circuit 30. A second voltage Vcc is applied to a first terminal of the drive switch 9a via a resistor. Therefore, while the second voltage Vcc is being generated, the voltage value of the trigger detection signal changes depending on the state of the drive switch 9a. The CPU 30a can detect the state of the drive switch 9a based on the voltage value of the trigger detection signal.

[0068] The CPU 30a includes a power supply maintenance control unit 31, a switch input determination unit 32, a rotation speed calculation unit 33, a pulse width modulation (PWM) generation unit 34, a motor drive control unit 35, and a protection determination unit 36. Each of these units 31 to 36 is actually a function realized by software. That is, in Fig. 2, a plurality of functions realized by the CPU 30a executing software are illustrated in the form of a block diagram.

[0069] When the CPU 30a is started up as a result of the supply of the first voltage to the control circuit 30, the power supply maintenance control unit 31 outputs a power supply maintenance signal to the power supply control circuit 22. The power supply maintenance control unit 31 basically continues to output the power supply maintenance signal while the CPU 30a is operating. However, after the start of the CPU 30a, if the state in which the drive switch 9a is continuously turned off (i.e., the trigger 9 is continuously turned off) reaches the power-off determination time T0, the power supply maintenance control unit 31 stops outputting the power supply maintenance signal. This stops the supply of the first voltage from the power supply control circuit 22 to the control circuit 30, and the operation of the control circuit 30 stops.

[0070] The switch input determination unit 32 determines whether the drive switch 9a is turned on or not based on the trigger detection signal input to the CPU 30a. The switch input determination unit 32 outputs the determination result to the PWM generation unit .

[0071] The rotation speed calculation unit 33 calculates the rotation speed of the motor 10 based on the rotation position signal input from the rotation position detection circuit 24 to the CPU 30a, and outputs the calculation result to the PWM generation unit .

[0072] The PWM generation unit 34 generates a PWM signal based on the determination result by the switch input determination unit 32 and the rotation position detection signal. The PWM signal is a control signal for driving the motor 10. In other words, the PWM signal is a signal that is pulse-width modulated in accordance with the value of the current supplied to the motor 10. The PWM generation unit 34 outputs the generated PWM signal to the motor drive control unit 35.

[0073] The PWM signal has a duty ratio. That is, the PWM generating unit 34 controls the current to be supplied to the motor 10 by adjusting the duty ratio. The motor drive control unit 35 generates a control command based on the PWM signal output from the PWM generation unit 34. The control command commands each of the six switches included in the drive circuit 21 to turn on or off. The duty ratio indicated by the PWM signal indicates the duty ratio of the duty drive for the switch that should be duty-driven (i.e., the switch that should be turned on or off according to the duty ratio) among the six switches. The control command commands the switch that should be duty-driven to be duty-driven at the duty ratio indicated by the PWM signal.

[0074] The motor drive control unit 35 outputs the generated control command to the drive circuit 21. As a result, the above-mentioned three-phase power is supplied from the drive circuit 21 to the motor 10, causing the motor 10 to rotate. The protection determination unit 36 ​​has a protection function. The protection function monitors the state of the electric work machine 1 and protects the electric work machine 1 (mainly protecting the motor 10) according to the monitoring results. The protection determination unit 36 ​​monitors the battery voltage, for example, based on a battery voltage signal from the battery voltage detection circuit 25. If the battery voltage is below a predetermined voltage value, for example, the protection determination unit 36 ​​forcibly stops the motor 10. Furthermore, for example, the protection determination unit 36 ​​monitors the temperature of the controller 20 based on a controller temperature signal from the controller temperature detection circuit 26. If the temperature of the controller 20 reaches a predetermined temperature, for example, the protection determination unit 36 ​​forcibly stops the motor 10.

[0075] The protection determination unit 36 ​​further has an overload protection function. When the motor 10 is operated under an overload, the temperature of the motor 10 (more specifically, the temperature of the windings, for example) rises, which may cause an abnormality in the motor 10. The overload protection function is a function for suppressing or preventing an abnormality in the motor 10 due to overheating of the motor 10.

[0076] The protection determination unit 36 ​​acquires the value of the current flowing through the motor 10 (hereinafter referred to as the "current detection value") based on the current detection signal input from the current detection circuit 23. The protection determination unit 36 ​​estimates the heat generation amount of the motor 10 based on the current detection value. When the estimated heat generation amount (hereinafter referred to as the "heat estimation value") reaches a predetermined protection threshold, the protection determination unit 36 ​​determines that the motor 10 is in an overload state or is close to an overload state, and executes protection processing. The protection processing may include any processing that can reduce the temperature of the motor 10. The protection processing may include, for example, slowing down or stopping the motor 10. In the present embodiment, as an example, the protection processing includes stopping the motor 10.

[0077] The current detection circuit 23 detects the current flowing in the path between the drive circuit 21 and the negative electrode of the battery 101. Therefore, strictly speaking, the current that actually flows through the motor 10 is not always detected by the current detection circuit 23. For example, the current that circulates between the motor 10 and the drive circuit 21 (hereinafter referred to as "circulating current") is not detected by the current detection circuit 23.

[0078] Therefore, in this embodiment, the protection determination unit 36 ​​calculates the value of the current that actually flows through the motor 10 (hereinafter referred to as the "actual current value") from the current detection signal, as will be described later. Then, the actual current value is used to execute the overload protection function. Note that it is not essential to use the actual current value, and the overload protection function may be executed using the current detection value without calculating the actual current value.

[0079] (3) Overload protection function The overload protection function will be specifically described below. First, the features of the overload protection function will be simply described using Figures 3 and 4. Then, the overload protection function will be described in detail using Figures 5 to 15.

[0080] (3-1) Overview of overload protection function 3 and 4 are simplified and schematic diagrams showing examples of the operation of the overload protection function, with the aim of making it easy to understand the characteristics of the overload protection function.

[0081] As described above, the overload protection function estimates the heat generation amount based on the detected current value (more specifically, in this embodiment, using the actual current value). Specifically, the heat generation amount can be estimated, for example, as follows. That is, as shown by the two-dot chain line in FIG. 3, a counter (hereinafter referred to as the "old counter") is provided to which a predetermined additional value Xp is periodically added. Then, while the actual current value is equal to or greater than a predetermined current threshold It0, the old counter counts up. The count value of this old counter (hereinafter referred to as the "old count value Cp") is treated as the estimated heat value. Then, when the count value of the old counter (estimated heat value) reaches a predetermined protection threshold A0 (time t01), the above-described protection process is executed.

[0082] The current threshold It0 may be, for example, a value at which a continuous flow of current at the current threshold It0 may cause the motor 10 to overheat and cause an abnormality. The protection threshold A0 may be, for example, a value at which, when the count value reaches the protection threshold A0, the motor 10 may be overheated (i.e., in an overload state) or may be heated to a level close to overheating.

[0083] The increment value Xp of the old counter is determined on the assumption that the ratio of the time in a loaded state to the time in a low-load state during a period in which the motor 10 is continuously rotating is relatively large, i.e., the time in a loaded state is relatively longer than the time in a low-load state.

[0084] The loaded state is, for example, a state in which a load equal to or greater than a predetermined level is applied to the motor 10. The loaded state may be, for example, a state in which the actual current value is equal to or greater than a current threshold value It0. The low-load state is, for example, a state in which the load applied to the motor 10 is less than a predetermined level or is zero. The low-load state may be, for example, a state in which the actual current value is less than the current threshold value It0.

[0085] The addition value Xp of the old counter is determined assuming a usage pattern in which there is little time in a low-load state and heat from the motor 10 is not easily dissipated, that is, a usage pattern in which there are periods in a low-load state but the temperature of the motor 10 is relatively likely to rise.

[0086] Therefore, the larger the ratio, the more appropriate the overload protection function using the old counter is to provide protection according to the actual temperature of the motor 10. On the other hand, the electric working machine 1 of this embodiment is expected to be used in a manner in which a loaded state and a low-load state are alternately repeated while the motor 10 is rotating, and the time period in the low-load state is relatively long.

[0087] More specifically, for example, when pruning a tree using the electric work machine 1, while the motor 10 is continuously rotating, periods when the tree is actually being cut (loaded periods) may alternate with periods when the motor 10 is simply idling or nearly idling without cutting the tree (low-load periods). Moreover, there is a high possibility that the ratio will be relatively small. In other words, there is a high possibility that the time spent in the low-load state will be relatively long.

[0088] When the motor is used in such a way that the duration of the low-load state is long, the amount of heat dissipated during the low-load state is large, so even if the temperature of the motor 10 rises during the load state, it is relatively unlikely to rise to a level that requires protection processing. Therefore, in the electric operating machine 1 of this embodiment, if the heat estimation value is calculated using the aforementioned old counter, there is a possibility that the motor 10 will be overprotected.

[0089] That is, a temperature higher than the actual temperature of the motor 10 may be estimated, which may result in the protection process being executed even though it is not necessary. For example, in Figure 3, the old counter value Cp reaches the protection threshold value A0 at time t01, but the actual temperature of the motor 10 is likely to be lower than the temperature corresponding to the protection threshold value A0.

[0090] Therefore, in this embodiment, in order to more appropriately calculate the heat estimated value according to the expected usage pattern, the increase rate of the heat estimated value is changed according to the load time. Specifically, the heat estimated value is calculated using a counter (hereinafter referred to as the "new counter") whose added value changes according to the load time. The load time is the time during which the motor 10 is in a loaded state. More specifically, the load time may be the time during which the loaded state continues, or the accumulated value of the time during which the motor 10 has been in a loaded state. Here, as an example, the time during which the loaded state continues is treated as the load time. In other words, the timing when the motor 10 changes from a low-load state to a loaded state is the start of the load time, and the timing when the motor 10 changes from a loaded state to a low-load state is the end of the load time.

[0091] The new counter uses the first addition value X1 as the addition value while the load time is equal to or less than the time threshold value Ts. The first addition value X1 is smaller than the addition value Xp of the old counter. Therefore, as illustrated in FIG. 3, when the load time is used so as not to exceed the time threshold value Ts, the count value of the new counter (hereinafter referred to as the "new count value Cn") is periodically incremented by the first addition value X1 while the load state is in progress (for example, while the actual current value is equal to or greater than the current threshold value It0). Therefore, the new count value Cn (i.e., the thermal estimated value) at time t01 indicates a value close to the actual temperature of the motor 10 and is lower than the protection threshold value A0. Therefore, the protection process has not yet been executed at time t01.

[0092] On the other hand, if the load time is longer than expected, the temperature of the motor 10 may rise more quickly. Therefore, when the load time exceeds the time threshold Ts, the new counter uses a second additional value X2 as the additional value. The second additional value X2 is greater than the first additional value X1.

[0093] In the operation example shown in Fig. 4, the new count value Cn of the new counter is counted up using the first additional value X1 until time t11. On the other hand, when the duration of the loaded state from time t10 reaches the time threshold value Ts at time t11, the additional value is switched to the second additional value X2. Furthermore, at time t11, not only is the additional value switched, but the new count value Cn is also incremented. Specifically, for example, the counter value at time t11 is changed to the counter value when counting up from time t10 using the second additional value X2.

[0094] This means that a new counter using the first additional value X1 (hereinafter referred to as the "first new counter") and a new counter using the second additional value X2 (hereinafter referred to as the "second new counter") can be regarded as coexisting. It can also be regarded that the new count value Cn of the first new counter is used while the load time is equal to or less than the time threshold value Ts, and that the new count value Cn of the second new counter is used after the load time reaches the time threshold value Ts.

[0095] In this way, when the load time reaches the time threshold Ts, the additional value is increased and the new counter value Cn itself is increased, thereby making it possible to appropriately estimate the temperature rise of the motor 10 that accompanies an increase in the load time. Note that when the load time reaches the time threshold Ts, only one of the additional value and the new counter value Cn itself may be increased.

[0096] 4, after the additional value and new count value Cn increase at time t11, the load time continues, and the new count value Cn reaches the protection threshold value A0 at time t12. As a result, the protection process is executed at time t12. In other words, when the load time exceeds the time threshold value Ts, the protection process is executed more quickly than when the count-up using the first additional value X1 continues.

[0097] (3-2) Details of the overload protection function A more detailed example of the operation of the overload protection function of this embodiment will be described with reference to Figures 5 to 7. In Figures 5 to 7, "power supply" refers to the power supply control circuit 22. "ON" in "power supply" refers to a state in which the first voltage is supplied from the power supply control circuit 22 to the control circuit 30, and "OFF" refers to a state in which the first voltage is not supplied to the control circuit 30. In other words, "power supply" can be considered as a power supply maintaining signal.

[0098] Furthermore, in this embodiment, four types of current thresholds are shown for the "actual current." Specifically, a first current threshold It1, a second current threshold It2, a third current threshold It3, and a fourth current threshold Itc are shown. These current thresholds It1, It2, It3, and Itc have a relationship of "It3>It2>It1>Itc." In this embodiment, for example, a state in which the actual current value is equal to or greater than the first current threshold It1 corresponds to the motor 10 being in a loaded state. A state in which the actual current value is less than the first current threshold It1 corresponds to the motor 10 being in a low-load state. A state in which the actual current value is less than the fourth current threshold Itc corresponds to a lighter load state among low-load states (hereinafter referred to as a "no-load state").

[0099] "Number of times of protection" means the number of times the protection process has been executed. Furthermore, the "main counter" is a counter for calculating the heat estimated value. The count value Ca of the main counter means the heat estimated value. In the following description, the count value Ca of the main counter is referred to as the "heat estimated value Ca." Furthermore, in this embodiment, the "main counter" indicates three types of protection thresholds. Specifically, a first protection threshold A1, a second protection threshold A2, and a third protection threshold A3 are indicated. These protection thresholds A1 to A3 have a mutual relationship of "A1>A2>A3." Each of these protection thresholds A1 to A3 indicates a threshold of the heat estimated value at which a protection process should be executed. In this embodiment, as will be described later, one of the protection thresholds A1 to A3 is used as the protection threshold Ta. In this embodiment, the protection threshold Ta decreases as the number of times the protection process is executed increases.

[0100] Furthermore, when the actual current value becomes less than the fourth current threshold value Itc, the "sub-counter" holds the heat estimated value Ca at that time. In the following description, the count value Cb of the sub-counter will be referred to as the "held value Cb."

[0101] The "first counter" and the "second counter" are counters that are the basis for calculating the estimated heat value Ca. The first counter and the second counter are each periodically counted up while the motor 10 is in a loaded state. That is, the specified additional value is added to each counter value.

[0102] The first count value C1, which is the count value of the first counter, is periodically incremented by a specified first increment value while the motor 10 is in a loaded state. The second count value C2, which is the count value of the second counter, is periodically incremented by a specified second increment value while the motor 10 is in a loaded state.

[0103] The second additional value is greater than the first additional value, so the second count value C2 is greater than the first count value C1. In this embodiment, while the load time is less than the first time threshold Tb, the first count value C1 is enabled and the estimated heat value Ca is calculated using the first count value C1. On the other hand, when the load time is equal to or greater than the first time threshold Tb, the second count value C2 is enabled and the estimated heat value Ca is calculated using the second count value C2.

[0104] Here, the first additional value and the second additional value may be fixed regardless of the actual current value, or may vary depending on the actual current value. In this embodiment, the first additional value varies depending on the actual current value. Specifically, in this embodiment, when the actual current value is equal to or greater than the third current threshold It3, a high-level first additional value α1 is used as the first additional value. When the actual current value is less than the third current threshold It3 and equal to or greater than the second current threshold It2, a medium-level first additional value β1 is used as the first additional value. When the actual current value is less than the second current threshold It2 and equal to or greater than the first current threshold It1, a low-level first additional value γ1 is used as the first additional value.

[0105] In this embodiment, the second additional value also changes depending on the actual current value. Specifically, in this embodiment, when the actual current value is equal to or greater than the third current threshold It3, a high-level second additional value α2 is used as the second additional value. When the actual current value is less than the third current threshold It3 and equal to or greater than the second current threshold It2, a medium-level second additional value β2 is used as the second additional value. When the actual current value is less than the second current threshold It2 and equal to or greater than the first current threshold It1, a low-level second additional value γ2 is used as the second additional value.

[0106] The respective added values ​​α1, β1, γ1, α2, β2, and γ2 are determined within ranges that satisfy the interrelationships shown in the following formulas (1) to (5), for example. α1≧β1≧γ1≧0 (1) α1>0 (2) α2>β2>γ2>0 (3) α2 ≥ α1, β2 ≥ β1, γ2 ≥ γ1 (4) α2>α1 and / or β2>β1 and / or γ2>γ1 ···(5) The above formula (5) means that at least one of "α2>α1", "β2>β1", and "γ2>γ1" needs to be satisfied. In the operation examples shown in FIGS. 5 to 7, the first additional values ​​α1, β1, and γ1 are determined according to the following equations (6) and (7).

[0107] α1=α2 (6) β1=γ1=0 (7) 5 to 7, while the motor 10 is in a loaded state, the second count value C2 is counted up, but the first count value C1 may not be counted up as a result. Specifically, even if the actual current value is equal to or greater than the first current threshold It1, while it is less than the third current threshold It3, the middle-level first addition value β1 and the low-level first addition value γ1 used during this period are both 0, so that although a count-up calculation is performed, the first count value C1 does not change.

[0108] 5 to 7, the "load time counter" is a counter that cumulatively measures the time in a loaded state. In this embodiment, the load time tx, which is the count value of the load time counter, is counted up while the motor 10 is in a loaded state. When the motor 10 enters a low-load state, the load time tx is not immediately reset, but is maintained as long as the actual current value is equal to or greater than the fourth current threshold Itc. As will be described later, the load time tx is reset when the actual current value becomes less than the fourth current threshold Itc. The current threshold used as a reference for resetting the load time tx may be the first current threshold It1. The load time tx may also be reset when the actual current value becomes less than the first current threshold It1. The first time threshold Tb shown in the "load time counter" in FIGS. 5 to 7 is used as a reference for determining whether the first counter or the second counter is to be activated.

[0109] 5 to 7, the "no-load time counter" is a counter that measures the no-load time ty. Specifically, the no-load time counter starts measuring the load time tx when the actual current value becomes less than the fourth current threshold Itc after the load time counter starts measuring the load time tx. The second time threshold Tc shown in the "no-load time counter" in FIGS. 5 to 7 is used as a criterion for determining when to clear the load time counter.

[0110] The number of protections, protection flag, main counter, sub-counter, first counter, second counter, load time counter, no-load time counter, and switching flag shown in Figures 5 to 7 are realized, set, used, etc. by software processing of the CPU 30a. In other words, these are all functions realized, set, used, etc. by the protection determination unit 36 ​​shown in Figure 2.

[0111] The operation examples shown in Figures 5 to 7 will be specifically described in chronological order. In Figures 5 to 7, multiple vertical dashed lines are drawn for each control cycle. In other words, it can be understood that the main processing (see Figure 8), which will be described later, is repeatedly (periodically) executed at roughly each timing when a vertical dashed line is drawn.

[0112] At time t1, the trigger 9 is manually operated by the user, turning on the drive switch 9a. This causes a first voltage to be supplied to the control circuit 30, which then starts up and drives the motor 10. At time t1, for example, the motor 10 is rotating, but no work is being performed and the chain blade 8 is rotating idly. Therefore, almost no load is applied to the motor 10, and the actual current value is low (less than the fourth current threshold Itc).

[0113] At time t2, the user actually applies the chain blade 8 to the cutting object and starts work. As a result, the actual current value becomes equal to or greater than the second current threshold It2 and less than the third current threshold It3. As a result, the first and second counters each count up, and the load time counter starts measuring the load time tx. However, in this embodiment, as described above, when the actual current value is equal to or greater than the second current threshold It2 and less than the third current threshold It3, the first additional value of the first counter (more specifically, the medium-level first additional value β1) is 0. Therefore, the first count value C1 remains unchanged, and the second count value C2 is counted up (added) by the medium-level second additional value β2.

[0114] While the load time tx is less than the first time threshold Tb, the first counter is enabled, and the first count value C1 is added to the count value of the main counter (i.e., the heat estimated value Ca). More specifically, the value obtained by adding the first count value C1 to the held value Cb of the sub-counter is held in the main counter as the heat estimated value Ca. However, at time t2, both the first count value C1 and the held value Cb are 0, so the heat estimated value Ca remains unchanged at 0.

[0115] At the control timing next to time t2 (the control timing immediately before time t3), the actual current value is at the same level as at time t2. Therefore, at this control timing, as at time t2, the second count value C2 is counted up and measurement of the load time tx continues.

[0116] At time t3, the user temporarily suspends the selection process while continuing to manually operate the trigger 9. As a result, the motor is in a nearly no-load state, and the actual current value falls below the fourth current threshold Itc. As a result, the first and second count values ​​C1 and C2 and the load time tx are maintained at their current values. Furthermore, since the actual current value falls below the fourth current threshold Itc while the load time tx is being counted, the no-load time counter begins counting the no-load time ty.

[0117] At the control timing next to time t2 (the control timing immediately before time t3), the actual current value is at the same level as at time t2. Therefore, at this control timing, as at time t2, the second count value C2 is counted up and measurement of the load time tx continues.

[0118] At time t3, the user temporarily suspends the selection process while continuing to manually operate the trigger 9. As a result, the motor is in a nearly unloaded state, and the actual current value falls below the fourth current threshold Itc. As a result, the first and second count values ​​C1 and C2 and the load time tx are maintained at their current values.

[0119] At time t4, just as at time t3, the actual current value remains below the fourth current threshold Itc. Therefore, the no-load time ty continues to be counted, and the no-load time ty reaches the second time threshold Tc. This clears the load time tx. At this time, the no-load time ty, the first and second count values ​​C1 and C2, and the switching flag are also cleared. Furthermore, the current estimated heat value Ca is held in the sub-counter as the held value Cb. However, since the estimated heat value Ca is 0 in this case, the held value Cb also remains unchanged at 0.

[0120] At time t5, the user resumes work. As a result, the actual current value becomes equal to or greater than the first current threshold It1 and less than the second current threshold It2. As a result, the first and second counters count up, and measurement of the load time tx begins. Specifically, the first count value C1 remains unchanged, as at time t2, while the second count value C2 is counted up (added) by the low-level second addition value γ2.

[0121] In this manner, each counter is updated, cleared, or maintained based on the actual current value at each control timing that occurs repeatedly in each control period. At time t6, the actual current value falls below the first current threshold It1 but remains above the fourth current threshold Itc, so the no-load time counter does not start counting. At time t7, the actual current value becomes above the third current threshold It3. Therefore, the high-level first addition value α1 is added to the first count value C1, and the high-level second addition value α2 is added to the second count value C2. At time t7, the load time tx has not yet reached the first time threshold Tb. In other words, the load time is still short. Therefore, the main counter receives the value obtained by adding the first count value C1 to the held value Cb as the estimated heat value Ca. At time t8, the actual current value falls below the fourth current threshold Itc, so counting the no-load time ty begins, just as at time t3. When the no-load time ty reaches the second time threshold Tb at time t9, the load time tx, the no-load time ty, the first and second count values ​​C1 and C2, and the switching flag are cleared, just as at time t4. Furthermore, the current heat estimation value Ca is held in the sub-counter as a held value Cb.

[0122] At time t10, the user releases the manual operation of the trigger 9. This turns off the drive switch 9a, stopping the motor 10. When the drive switch 9a is turned off, timing of the trigger-off time begins. The trigger-off time is the duration of the off state from the time the drive switch 9a changes from on to off. When the trigger-off time reaches the power-off determination time T0, the power hold signal is stopped, the supply of the first voltage to the control circuit 30 is stopped, and the control circuit 30 stops operating. If the drive switch 9a is turned on again before the trigger-off time reaches the power-off determination time T0, the trigger-off time is cleared. Even when the drive switch 9a is turned off at time t10, the heat estimation value Ca of the main counter and the hold value Cb of the sub-counter are held.

[0123] At time t11, the drive switch 9a is turned on again, causing the motor 10 to rotate. At time t12, the user resumes pruning and the actual current value becomes equal to or greater than the first current threshold It1. As a result, similar to time t5, the first and second count values ​​C1 and C2 are updated according to the actual current value, and measurement of the load time tx begins.

[0124] As described above, while the actual current value is less than the third current threshold It3, the first count value C1 does not substantially increase. However, when the actual current value becomes equal to or greater than the third current threshold It3 at time t13, the first count value C1 also increases, as at time t7. Also, at time t13, the load time tx has not yet reached the first time threshold Tb. Therefore, the main counter receives the value obtained by adding the first count value C1 to the held value Cb as the estimated heat value Ca.

[0125] At time t14, the load state continues, and the load time tx reaches the first time threshold Tb. This causes the switching flag to be set. While the switching flag is set, the second counter is enabled. Therefore, the main counter receives the estimated heat value Ca, which is the sum of the held value Cb and the second count value C2. As a result, at time t14, the estimated heat value Ca is equal to or greater than the first protection threshold A1. At time t14, when no protection process has been performed yet, the protection threshold Ta is set to the first protection threshold A1. Therefore, at time t14, the protection flag is set and the number of protections is set to 1. Because the protection flag is set, the protection process is performed and the motor 10 is stopped. That is, although the drive switch 9a remains on, the motor 10 is forcibly stopped. As a result, the actual current value becomes 0. Furthermore, all counters and the switching flag except for the protection flag are cleared.

[0126] When the motor 10 is stopped by the protection process, the user will recognize that some kind of protection function has been activated. It is expected that such a user will then temporarily turn off the drive switch 9a.

[0127] At time t15, when the user turns off the drive switch 9a, the protection flag is cleared. As a result, when the drive switch 9a is turned on again at time t16, the motor 10 is driven, as at time t1. Then, at time t17, when the actual current value becomes equal to or greater than the first current threshold It1, the first and second count values ​​C1 and C2 are incremented according to the actual current value, as at time t2, and measurement of the load time tx begins.

[0128] However, at time t17, the number of protections is one. That is, the protection process has already been executed one or more times. Therefore, although the switching flag is cleared, the second counter is enabled. That is, in this embodiment, when (i) the switching flag is cleared and (ii) the number of protections is zero, the first counter, which has a relatively small added value, is enabled. On the other hand, when the switching flag is set or the number of protections is one or more, the second counter, which has a relatively large added value, is enabled. Therefore, at time t17, a value obtained by adding the second count value C2 to the held value Cb is input to the main counter as the heat estimated value Ca.

[0129] The example of operation from time t18 when the actual current value falls below the fourth current threshold Itc until just before time t19 is basically the same as the example of operation from time t3 to time t7, except that the second counter is enabled.

[0130] At time t19, the actual current value increases to or exceeds the third current threshold It3, causing the second count value Ca to increase, and as a result, the estimated heat value Ca becomes equal to or exceeds the second protection threshold A2. The protection threshold Ta at time t19 is set to the second protection threshold A2 because the number of protections is one. Therefore, at time t19, a protection flag is set, and the number of protections is increased to two. With the protection flag set, protection processing is executed, and the motor 10 is stopped. As a result, the motor 10 is forcibly stopped, and the actual current value becomes zero. Furthermore, all counters and switching flags except for the protection flag are cleared. Then, when the drive switch 9a is turned off at time t20, the protection flag is cleared.

[0131] An example of operation after time t21 will be described with reference to Fig. 6. When the drive switch 9a is turned on again at time t21, the motor 10 is driven, as at time t1. Then, when the actual current value becomes equal to or greater than the first current threshold It1 at time t22, the first and second count values ​​C1 and C2 are incremented according to the actual current value, as at time t2, and measurement of the load time tx is started.

[0132] At time t22, the number of protection times is 2. Therefore, although the switching flag is cleared, the second counter is enabled. Therefore, at time t22, the main counter receives the value obtained by adding the second count value C2 to the held value Cb as the estimated heat value Ca.

[0133] The example of operation from time t18 when the actual current value falls below the fourth current threshold Itc until just before time t19 is basically the same as the example of operation from time t3 to time t7, except that the second counter is enabled.

[0134] At time t19, the actual current value increases to or exceeds the third current threshold It3, causing the second count value Ca to increase, and as a result, the estimated heat value Ca becomes equal to or exceeds the second protection threshold A2. The protection threshold Ta at time t19 is set to the second protection threshold A2 because the number of protections is one. Therefore, at time t19, the protection flag is set, and the number of protections is increased to two. As the protection flag is set, protection processing is executed.

[0135] At time t23, because the actual current value is still in the load state, the second count value Ca increases, causing the estimated heat value Ca to become equal to or greater than the third protection threshold value A3. The protection threshold value Ta at time t23 is set to the third protection threshold value A3 because the number of protections is two. Therefore, at time t23, the protection flag is set, and the number of protections is increased to three. As the protection flag is set, protection processing is executed, and the motor 10 is stopped. Furthermore, all counters and switching flags except for the protection flag are cleared.

[0136] In this embodiment, once the protection count reaches a predetermined number, the protection flag is not cleared as long as the control circuit 30 continues to operate, even if the drive switch 9a is turned off. Therefore, even if the user repeatedly turns the drive switch 9a on and off, the motor 10 will not be driven. Then, at time t24, when the drive switch 9a remains off for the power-off determination time TO, the power hold signal from the control circuit 30 to the power control circuit 22 is stopped. This stops the supply of the first voltage to the control circuit 30, and the control circuit 30 stops operating. This clears all counters and flags shown in FIG. 6. Specifically, at time t24, the protection count and protection flag are cleared.

[0137] After the control circuit 30 has stopped operating, at time t25 the drive switch 9a is turned on again, and similarly to time t1, the first voltage is supplied to the control circuit 30, causing the control circuit 30 to start up and drive the motor 10. Then, at time t26, when the actual current value becomes equal to or greater than the first current threshold It1, similarly to time t2, the first and second count values ​​C1 and C2 are incremented in accordance with the actual current value, and measurement of the load time tx is started.

[0138] An example of operation after time t26 will be described with reference to Fig. 7. After time t26, the load state continues, so the first and second count values ​​C1 and C2 continue to be counted and the load time tx continues to be measured. However, as described above, the first count value C1 does not substantially increase while the actual current value is less than the second current threshold It2.

[0139] At time t27, the actual current value becomes equal to or greater than the third current threshold It3. Therefore, at time t27, the first count value C1 is also increased by the first addition value (specifically, the high-level first addition value α1). As a result, at time t27, the value obtained by adding the first count value C1 to the held value Cb is input to the main counter as the estimated heat value Ca.

[0140] At time t28, the load time tx reaches the first time threshold Tb. This causes the switching flag to be set. That is, the second counter is enabled. Therefore, the main counter receives the value obtained by adding the second count value C2 to the held value Cb as the estimated heat value Ca.

[0141] At time t29, the user turns off the drive switch 9a, thereby stopping the motor 10. Furthermore, the sub-counter holds the heat estimated value Ca of the main counter at time t29 as a held value Cb.

[0142] Thereafter, when the drive switch 9a continues to be turned off for the power-off determination time T0 (time t30), the supply of the first voltage to the control circuit 30 is stopped, and the control circuit 30 stops operating, as at time t24. This clears all counters and flags shown in Fig. 6. Specifically, at time t30, the main counter and sub-counter are cleared.

[0143] An example of use is shown in which the load time tx does not reach the first time threshold Tb after time t31. Therefore, the first counter is enabled after time t31. Furthermore, an example of use is shown in which the actual current value does not become equal to or greater than the third current threshold It3 after time t31. Therefore, although the first counter counts up after time t31, the first additional value is 0, and therefore the first count value C1 does not actually increase. Therefore, the estimated heat value Ca also remains 0.

[0144] (4) Main processing (4-1) Overview of the main process The above-described overload protection function, particularly the operational examples shown in Figures 5 to 7, are realized by the control circuit 30 (more specifically, the CPU 30a) executing the main processing of Figure 8. When activated, the control circuit 30 periodically and repeatedly executes the main processing of Figure 8 at the aforementioned control cycle.

[0145] When the control circuit 30 starts the main process, in S110, the control circuit 30 counts up a trigger-off time counter. The trigger-off time counter measures the trigger-off time. The trigger-off time corresponds to the time during which the drive switch 9a is continuously turned off.

[0146] In S120, the control circuit 30 determines whether the drive switch 9a is turned on. If the drive switch 9a is turned off, the process proceeds to S140. If the drive switch 9a is turned on, the control circuit 30 clears the trigger-off time counter in S130. Specifically, in this embodiment, the trigger-off time is set to 0.

[0147] In S140, the control circuit 30 executes overload protection processing. Specifically, the control circuit 30 calculates an estimated heat value Ca based on the actual current value. Then, based on the calculated estimated heat value Ca, it determines whether the motor 10 is in an overload state that requires execution of protection processing. If the motor 10 is in an overload state, a protection flag is set. Details of the overload protection processing in S140 will be described later using Figures 10 to 15.

[0148] In S150, the control circuit 30 executes the motor drive process. The details of the motor drive process are as shown in FIG. 9. When the control circuit 30 starts the motor drive process, in S210, it determines whether the drive switch 9a is on. If the drive switch 9a is off, the control circuit 30 executes the motor stop process in S250 to stop the motor 10. Specifically, the generation of the PWM signal is stopped, thereby stopping the output of the control command to the drive circuit 21. After the motor stop process is executed, the process proceeds to S160 (see FIG. 8).

[0149] If the drive switch 9a is turned on in S210, the control circuit 30 determines whether the protection flag is cleared in S220. The protection flag is set in S815 of FIG. 15, which will be described later, when the estimated heat value Ca is equal to or greater than the protection threshold value Ta (i.e., when an overload state occurs).

[0150] If the protection flag is set in S220, the control circuit 30 executes protection processing in S240, which stops the motor 10. After the protection processing is executed, the process proceeds to S160 (see FIG. 8).

[0151] If the protection flag is cleared in S220, the control circuit 30 drives the motor 10 by executing a drive control process in S230. Specifically, the control circuit 30 calculates the duty ratio of the PWM signal. For example, the control circuit 30 may calculate the duty ratio so that the rotation speed of the motor 10 becomes a predetermined target speed. The target speed may be fixed in advance, or may be specified by the user continuously or in stages. For example, the target speed may be specified according to the amount of operation of the trigger 9 by the user. The control circuit 30 outputs a control command according to the calculated duty ratio to the drive circuit 21. After executing the drive control process in S230, the process proceeds to S160 (see FIG. 8).

[0152] In this way, the above-mentioned overload protection function is realized mainly by the overload protection process in S140 and the motor drive process in S150. In S160, the control circuit 30 determines whether the trigger-off time is equal to or greater than the power-off determination time T0. If the trigger-off time is less than the power-off determination time T0, the control circuit 30 ends the main process. If the trigger-off time is equal to or greater than the power-off determination time T0, the control circuit 30 executes power-off processing in S170. Specifically, the control circuit 30 stops outputting the power hold signal to the power supply control circuit 22. This stops the supply of the first voltage from the power supply control circuit 22 to the control circuit 30, and the operation of the control circuit 30 stops. Time t24 in FIG. 6 is an example of the timing at which it is determined in S160 that the trigger-off time is equal to or greater than the power-off determination time T0.

[0153] (4-2) Overview of overload protection Next, the overload protection process of S140 will be outlined with reference to FIG. When the control circuit 30 starts the overload protection process, it determines the driving state of the motor 10 in S300. This determination includes determining whether the motor 10 is being driven (i.e., whether a control command is being output to rotate the motor). Details of S300 will be described later with reference to FIG. 11.

[0154] Next, in S400, the control circuit 30 sets a protection threshold value Ta for the main counter. That is, the control circuit 30 sets one of the above-mentioned first to third protection threshold values ​​A1 to A3 as the protection threshold value Ta. Details of S400 will be described later with reference to FIG.

[0155] Next, the control circuit 30 calculates the actual current value in S500. Details of S500 will be described later with reference to FIG. Next, in S600, the control circuit 30 determines whether the motor 10 is in a loaded state and performs various processes based on the determination result. Details of S600 will be described later with reference to FIG.

[0156] Next, in S700, the control circuit 30 updates the main counter, i.e., updates the heat estimated value Ca. Specifically, if the actual current value calculated in S500 is equal to or greater than the first current threshold It1, the control circuit 30 updates the first and second counters, respectively. Then, the control circuit 30 updates the heat estimated value Ca based on the updated first and second count values ​​C1 and C2 of the first and second counters, the held value Cb of the sub-counter, and the load time tx. Details of S700 will be described later with reference to FIG. 14.

[0157] Next, in S800, control circuit 30 executes a motor protection determination. Specifically, control circuit 30 compares the heat estimation value Ca updated in S700 with the protection threshold value Ta set in S400. If the heat estimation value Ca is equal to or greater than the protection threshold value Ta, control circuit 30 determines that there is a high possibility that motor 10 is in an overload state (i.e., overheated), and sets a protection flag. If the protection flag is set, the next time the motor drive process of S150 (details in FIG. 9) is executed again, motor 10 is stopped by the protection process of S240. Details of S800 will be described later using FIG. 15.

[0158] (4-3) Details of overload protection processing Next, the overload protection process shown schematically in FIG. 10 will be described in more detail with reference to FIGS.

[0159] First, the process of S300 in Fig. 10 will be described in detail with reference to Fig. 11. The processes of S310 to S350 shown in Fig. 11 correspond to the process of S300 in Fig. 10, that is, the process of determining the driving state of the motor 10.

[0160] In S310, the control circuit 30 determines whether the motor 10 is being driven. Specifically, the control circuit 30 determines whether the control circuit 30 is outputting a control command to rotate the motor 10. If the motor 10 is being driven, i.e., if the control circuit 30 is outputting a control command to rotate the motor 10, the process proceeds to S410 (see FIG. 12). If the motor 10 is not being driven, i.e., if the control circuit 30 is not outputting a control command to rotate the motor 10, the process proceeds to S315.

[0161] In S315, the control circuit 30 determines whether or not the protection flag is set. If the protection flag is not set, the process proceeds to S335. If the protection flag is set, the control circuit 30 determines whether or not the drive switch 9a is off in S320. If the drive switch 9a is on, the process proceeds to S335. If the drive switch 9a is off, the control circuit 30 determines whether or not the number of protections is less than three in S325. If the number of protections is less than three, the control circuit 30 clears the protection flag in S330. If the number of protections is three or more, the process proceeds to S335. In other words, if the number of protections is three or more, the protection flag is not cleared.

[0162] In S335, the control circuit 30 inputs the current heat estimation value Ca (i.e., the current value of the main counter) to the sub-counter as the held value Cb. In other words, while the motor 10 is not being driven, the main counter is not updated, and the value of the main counter is held in the sub-counter.

[0163] In S340, the control circuit 30 clears the first and second counters. Specifically, the first count value C1 and the second count value C2 are changed to 0. In S345, the control circuit 30 clears the load time counter and the no-load time counter. Specifically, the load time tx and the no-load time ty are changed to 0. In S350, the control circuit 30 clears the switching flag. After the processing of S350, the process proceeds to S150 (see FIG. 8).

[0164] Next, the process of S400 in Fig. 10 will be described in detail with reference to Fig. 12. The processes of S410 to S430 shown in Fig. 12 correspond to the process of S400 in Fig. 10, i.e., the process of setting the protection threshold value Ta of the main counter. As described above, if it is determined in S310 that the motor 10 is being driven, the process proceeds to S410.

[0165] In S410, the control circuit 30 determines whether the number of protections is 0. If the number of protections is 0, that is, if no protection process has been performed since the control circuit 30 was started, the control circuit 30 sets the first protection threshold A1 as the protection threshold Ta in S415. After processing S415, the process proceeds to S510.

[0166] If the number of protections is not 0 in S410, that is, if one or more protection processes have already been performed since the control circuit 30 was started, the process proceeds to S420. In S420, the control circuit 30 determines whether the number of protections is 1. If the number of protections is 1, the control circuit 30 sets the second protection threshold A2 as the protection threshold Ta in S425. After processing S425, the process proceeds to S510.

[0167] If the protection count is not 1 in S420, that is, if two protection processes have already been performed since the control circuit 30 was started, the process proceeds to S430. In S430, the control circuit 30 sets the third protection threshold A3 as the protection threshold Ta. After the process of S430, the process proceeds to S510.

[0168] Continuing to refer to Fig. 12, the process of S500 in Fig. 10 will be described in detail. The processes of S510 to S515 shown in Fig. 12 correspond to the process of S500 in Fig. 10, i.e., the process of calculating the actual current value. As described above, after the process of S415, S425, or S430, the process proceeds to S510.

[0169] In S510, the control circuit 30 acquires a current detection value based on the current detection value from the current detection circuit 23. In S515, the control circuit 30 calculates an actual current value from the current detection value acquired in S510. Specifically, the control circuit 30 calculates the actual current value by calculating "detected current value / duty ratio [%]×100".

[0170] The reason why the actual current value is calculated by such a calculation is described in detail in Patent Document 1, so a detailed explanation will be omitted here and only a brief explanation will be provided. Specifically, the current detection circuit 23 of this embodiment includes the aforementioned resistor on the power path, an amplifier (not shown), and a low-pass filter (not shown). The amplifier amplifies the voltage across the resistor. The low-pass filter smoothes the voltage amplified by the amplifier. The voltage smoothed by the low-pass filter is output as a current detection signal. A current generally flows through the resistor during a period corresponding to the on period of the PWM signal, but no current flows during a period corresponding to the off period. However, a current may flow through the motor 10 even during the off period of the PWM signal. Specifically, the aforementioned circulating current may flow through the motor 10 during the off period of the PWM signal. This circulating current may also cause the motor 10 to generate heat. However, this circulating current is not detected by the current detection circuit 23. Therefore, the current detection value detected by the current detection circuit 23 does not necessarily accurately represent the current actually flowing through the motor 10. Therefore, in this embodiment, the above formula is used to calculate an actual current value that has a small error with respect to the current that actually flows through the motor 10.

[0171] After the actual current value is calculated in S515, the process proceeds to S610 (see FIG. 13). Next, the process of S600 in Fig. 10 will be described in detail with reference to Fig. 13. The processes of S610 to S670 shown in Fig. 13 correspond to the process of S600 in Fig. 10, that is, the process of determining whether or not the motor 10 is in a loaded state. As described above, after the process of S515, this process proceeds to S610.

[0172] In S610, the control circuit 30 determines whether the actual current value calculated in S515 is equal to or greater than the first current threshold It1. That is, the control circuit 30 determines whether the motor 10 is in a loaded state. If the actual current value is equal to or greater than the first current threshold It1 (that is, the motor 10 is in a loaded state), the control circuit 30 clears the no-load time counter in S615. That is, the control circuit 30 changes the no-load time ty to 0.

[0173] In S620, the control circuit 30 determines whether the switching flag is cleared. If the switching flag is cleared, the control circuit 30 counts up the load time counter in S625. That is, the load time tx is measured by counting up a value corresponding to the control period.

[0174] In S630, the control circuit 30 determines whether the load time tx is equal to or greater than the first time threshold Tb. If the load time tx is equal to or greater than the first time threshold Tb, the control circuit 30 sets a switching flag in S635. That is, since the duration of the load state is long, the switching flag is set to enable the second counter. After processing S635, the process proceeds to S710 (see FIG. 14). If the load time tx is less than the first time threshold Tb in S630, the switching flag is not set and the process proceeds to S710. Also, if the switching flag has already been set in S620, the process proceeds to S710.

[0175] If, in S610, the actual current value is less than the first current threshold It1 (i.e., the load state is low), the process proceeds to S640. In S640, the control circuit 30 determines whether the load time tx is greater than 0, i.e., whether the load time tx is currently being counted. If the load time tx is 0, i.e., if the load time tx is not currently being counted, the control circuit 30 ends the overload protection process and proceeds to S150 (see FIG. 8).

[0176] If the load time tx is greater than 0 in S640, i.e., if the load time tx is being counted, the process proceeds to S645. In S645, the control circuit 30 determines whether the actual current value calculated in S515 is less than the fourth current threshold Itc. If the actual current value is equal to or greater than the fourth current threshold Itc, the control circuit 30 terminates the overload protection process. If the actual current value is less than the fourth current threshold Itc, the control circuit 30 increments the no-load time counter in S650. That is, the no-load time ty is counted up by counting up a value corresponding to the control period.

[0177] In S655, the control circuit 30 determines whether the currently measured no-load time ty is equal to or greater than the second time threshold Tc. If the no-load time ty has not yet reached the second time threshold Tc, the control circuit 30 terminates the overload protection process. If the no-load time ty is equal to or greater than the second time threshold Tc, the process proceeds to S660. In S660, the control circuit 30 inputs the current heat estimation value Ca (i.e., the current value of the main counter) into the sub-counter as the hold value Cb, similar to S335. In other words, if the no-load time ty reaches the second time threshold Tc, the value of the main counter is held in the sub-counter.

[0178] In S665, the control circuit 30 clears the first and second counters, as in S340. In S670, the control circuit 30 clears the load time counter and the no-load time counter, as in S345. In S675, the control circuit 30 clears the switching flag. After processing S675, the process proceeds to S150 (see FIG. 8).

[0179] Next, the processing of S700 in Fig. 10 will be described in detail with reference to Fig. 14. The processing of S710 to S760 shown in Fig. 14 corresponds to the processing of S700 in Fig. 10, i.e., the processing of updating the heat estimated value Ca of the main counter. As described above, after the processing of S635 or when it is determined in S620 that the switching flag is set, this processing proceeds to S710.

[0180] In S710, the control circuit 30 determines whether the actual current value is equal to or greater than the third current threshold It3. If the actual current value is equal to or greater than the third current threshold It3, the process proceeds to S715. In S715, the control circuit 30 increments the first counter. Specifically, the control circuit 30 adds a high-level first additional value α1 to the current first count value C1 of the first counter. In addition, in S720, the control circuit 30 increments the second counter. Specifically, the control circuit 30 adds a high-level second additional value α2 to the current second count value C2 of the second counter. Here, the high-level first additional value α1 and the high-level second additional value α2 added to the first and second counters, respectively, are values ​​corresponding to, for example, the amount of heat generated by the motor 10 that would be expected if a current equal to or greater than the third current threshold It3 flows through the motor 10 during the control period. After S720, the process proceeds to S750.

[0181] If the actual current value is less than the third current threshold It3 in S710, the process proceeds to S725. In S725, the control circuit 30 determines whether the actual current value is equal to or greater than the second current threshold It2. If the actual current value is equal to or greater than the second current threshold It2, the process proceeds to S730. In S730, the control circuit 30 increments the first counter. That is, it adds a medium-level first addition value β1 to the current first count value C1 of the first counter. The control circuit 30 further increments the second counter in S735. That is, it adds a medium-level second addition value β2 to the current second count value C2 of the second counter. Here, the medium-level first addition value β1 and the medium-level second addition value β2 added to the first and second counters, respectively, are values ​​corresponding to the amount of heat generated by the motor 10 that is expected to occur when a current equal to or greater than the second current threshold It2 and less than the third current threshold It3 flows through the motor 10 during the control period. After processing S735, the process proceeds to S750.

[0182] If the actual current value is less than the second current threshold It2 in S725, the process proceeds to S740. In S740, the control circuit 30 increments the first counter. That is, it adds a low-level first addition value γ1 to the current first count value C1 of the first counter. Furthermore, in S745, the control circuit 30 increments the second counter. That is, it adds a low-level second addition value γ2 to the current second count value C2 of the second counter. Here, the low-level first addition value γ1 and the low-level second addition value γ2 added to the first and second counters, respectively, are values ​​corresponding to the amount of heat generated by the motor 10 that would be expected if a current greater than or equal to the first current threshold It1 and less than the second current threshold It2 flowed through the motor 10 during the control period. After S745, the process proceeds to S750.

[0183] In S750, the control circuit 30 determines whether the switching flag is cleared and the number of protections is 0. If the switching flag is cleared and the number of protections is 0, the process proceeds to S755. In S755, the control circuit 30 updates the main counter. That is, the control circuit 30 calculates the heat estimated value Ca by adding the first count value C1 to the current held value Cb, and inputs the calculated heat estimated value Ca to the main counter as its count value. That is, in this case, the first counter is enabled, and the heat estimated value Ca is calculated based on the first count value C1. After processing S755, the process proceeds to S810 (see FIG. 15).

[0184] If the switching flag is set or the number of protection times is one or more in S750, the process proceeds to S760. In S760, the control circuit 30 updates the main counter. Specifically, in S760, the control circuit 30 calculates the heat estimated value Ca by adding the second count value C2 to the current held value Cb, and inputs the calculated heat estimated value Ca to the main counter as its count value. That is, in this case, the second counter is enabled, and the heat estimated value Ca is calculated based on the second count value C2. After S760, the process proceeds to S810 (see FIG. 15).

[0185] Next, the process of S800 in Fig. 10 will be described in detail with reference to Fig. 15. The processes of S810 to S835 shown in Fig. 15 correspond to the process of S800 in Fig. 10, i.e., the process for executing a motor protection determination. As described above, after the process of S755 or S760, this process proceeds to S810.

[0186] In S810, the control circuit 30 determines whether the heat estimate value Ca is equal to or greater than the protection threshold value Ta. The heat estimate value Ca used in S810 is the most recent heat estimate value Ca, i.e., the current value of the main counter, and is the value calculated in the processing of S755 or S760 immediately before S810. The protection threshold value Ta used in S810 is the value set in the immediately preceding S415, S425, or S430.

[0187] If the heat estimation value Ca is less than the protection threshold value Ta, the control circuit 30 determines that the protection process is not yet necessary, terminates the overload protection process, and proceeds to S150. If the heat estimation value Ca is equal to or greater than the protection threshold value Ta, protection processing is required. In this case, the control circuit 30 sets a protection flag in S815. In S820, the control circuit 30 increments the number of protections by one. In S825, the control circuit 30 clears the main counter, sub-counter, first counter, and second counter. That is, the count values ​​of these counters are changed to 0. Similarly, in S830, the control circuit 30 clears the load time counter and the no-load time counter. In S835, the control circuit 30 clears the switching flag. After processing S835, the control circuit 30 ends the overload protection processing and proceeds to S150.

[0188] (5) Correspondence between the embodiments and the present disclosure The trigger 9 corresponds to an example of a manual switch in the present disclosure. The current detection circuit 23 and / or the protection determination unit 36 ​​corresponds to an example of a current detection unit in the present disclosure. The protection determination unit 36 ​​also corresponds to an example of a timer unit, a heat estimation unit, a protection unit, a counter, a first counter, a second counter, and a calculation unit in the present disclosure.

[0189] The first additional value X1 and the second additional value X2 used in the description of Figures 3 and 4, and the high-level first additional value α1, the middle-level first additional value β1, the low-level first additional value γ1, the high-level second additional value α2, the middle-level second additional value β2, and the low-level second additional value γ2 used in the description of Figures 5 and onwards, correspond to examples of parameters and also to examples of increase rates in the present disclosure. In particular, the high-level first additional value α1, the middle-level first additional value β1, and the low-level first additional value γ1 correspond to examples of first additional values ​​in the present disclosure, and the high-level second additional value α2, the middle-level second additional value β2, and the low-level second additional value γ2 correspond to examples of second additional values ​​in the present disclosure.

[0190] The first current threshold It1 corresponds to an example of a current threshold in the present disclosure. The fourth current threshold Itc corresponds to an example of a predetermined current value in the present disclosure. The protection threshold A0 and each of the first to third protection thresholds A1 to A3 correspond to an example of a thermal threshold in the present disclosure. The first time threshold Tb corresponds to an example of a time threshold in the present disclosure. Three times, which is the number of protection times at which the protection flag is no longer cleared, corresponds to an example of a specified number of times in the present disclosure.

[0191] The processes of S250, S320 to S330, S410 to S430, and S810 to S815 correspond to an example of a process by the protection unit in the present disclosure. The processes of S510 to S515 correspond to an example of a process by the current detection unit in the present disclosure. The process of S625 corresponds to an example of a process by the clock unit in the present disclosure. The processes of S630 to S635, S660 to S665, and S750 to S760 correspond to an example of a process by the heat estimator, counter, and calculator in the present disclosure. The processes of S715, S730, and S740 correspond to an example of a process by the first counter in the present disclosure. The processes of S720, S735, and S745 correspond to an example of a process by the second counter in the present disclosure.

[0192] 2. 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.

[0193] (1) In the above embodiment, the middle level first additional value β1 and the low level first additional value γ1 are 0, but one or both of these may be greater than 0. Each additional value α1, β1, γ1, α2, β2, γ2 may be any value that satisfies the above-mentioned formulas (1) to (5).

[0194] (2) In the above embodiment, the addition value of the first counter changes depending on the level of the actual current value. However, the addition value of the first counter may be fixed regardless of the level of the actual current value. Also, in the above embodiment, the addition value of the first counter is determined to be one of three types of addition values ​​depending on the level of the actual current value. However, the addition value of the first counter may be determined to be one of two types of addition values, or one of four or more types of addition values.

[0195] (3) In the above embodiment, the protection threshold Ta is not fixed but varies depending on the number of protections. However, the protection threshold Ta may be fixed. Also, in the above embodiment, the protection threshold Ta is decreased in stages as the number of protections increases, but the protection threshold Ta may be decreased in any manner as the number of protections increases.

[0196] (4) In the above embodiment, the protection flag was not cleared when the number of protection times reached three. However, the protection flag may not be cleared when the number of protection times reaches two, or the protection flag may be cleared until the number of protection times reaches a predetermined number of times, such as four or more.

[0197] (5) The technology of the present disclosure is not limited to application to electric work machines that are expected to perform long periods of low-load work. The technology of the present disclosure may also be applied to various on-site electrical equipment used at work sites, such as DIY, manufacturing, gardening, and construction sites. Specifically, the technology of the present disclosure may be applied to various electric work machines, such as power tools for masonry, metalwork, and woodworking, gardening work machines, and work site environment improvement devices. More specifically, the technology of the present disclosure may be applied to various electric work machines, such as electric hammers, electric hammer drills, electric drills, electric screwdrivers, electric wrenches, electric grinders, electric circular saws, electric reciprocating saws, electric jigsaws, electric cutters, electric chainsaws, electric planers, electric nail guns (including tack guns), electric hedge trimmers, electric lawn mowers, electric lawn clippers, electric brush cutters, electric cleaners, electric blowers, electric sprayers, electric dust collectors, and the like.

[0198] (6) Multiple functions of one component in the above embodiments may be realized by multiple components, or one function of one component may be realized by multiple components. Also, multiple functions of 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]

[0199] 1...electric work machine, 9...trigger, 9a...drive switch, 10...motor, 23...current detection circuit, 30...control circuit, 30a...CPU, 30b...memory, 36...protection determination unit

Claims

1. An electric work machine, a manual switch configured to be manually operated by a user of the electric working machine; a motor configured to be driven in response to the manual switch being manually operated or being operated; a current detection unit configured to detect a current value, the current value corresponding to a value of a current supplied from a power source to the motor; a timer configured to measure a load time, which is a time during which a state in which the current value detected by the current detection unit is equal to or greater than the current threshold, continues each time the current value detected by the current detection unit changes from a state in which the current value is lower than the current threshold to a state in which the current value is equal to or greater than the current threshold; and a heat estimation unit configured to calculate a heat estimation value that is an estimate of a heat generation amount of the motor based on the current value detected by the current detection unit, the heat estimation unit configured to increase the heat estimation value at a predetermined increase rate while the current detection unit detects a current value that is equal to or greater than the current threshold, and configured to increase the increase rate in accordance with the load time measured by the timer unit; a protection unit configured to execute a protection operation to reduce a temperature of the motor in response to the heat estimation value calculated by the heat estimation unit reaching a heat threshold; and An electric work machine equipped with:

2. An electric work machine as described in claim 1, The heat estimation unit is configured to increase the increase rate in response to the load time measured by the timing unit reaching a time threshold.

3. An electric work machine as described in claim 1, The heat estimation unit a counter configured to periodically count up an additional value while the current value detected by the current detection unit is equal to or greater than the current threshold value, the additional value corresponding to the increase rate, and configured to increase the additional value in accordance with the load time being measured by the timer; a calculation unit configured to calculate the thermal estimate based on a count value of the counter; An electric work machine comprising:

4. An electric work machine as described in claim 3, The counter is configured to use a first additional value or a second additional value greater than the first additional value as the additional value depending on the load time being measured by the timing unit.

5. An electric work machine as described in claim 4, The counter The first additional value is used as the additional value while the load time measured by the timing unit is less than a time threshold value; the second additional value is used as the additional value in response to the load time being measured by the timing unit reaching the time threshold value. The electric work machine is configured as follows.

6. An electric work machine as described in claim 1, The heat estimation unit a first counter configured to periodically count up a first additional value corresponding to the increase rate while the current value detected by the current detection unit is equal to or greater than the current threshold; a second counter configured to periodically count up a second additional value that corresponds to the rate of increase and is greater than the first additional value while the current value detected by the current detection unit is equal to or greater than the current threshold value; a calculation unit configured to validate a first count value that is a count value of the first counter, validate a second count value that is a count value of the second counter in place of the first count value in accordance with the load time measured by the timer unit, and calculate the heat estimated value based on the validated count value; An electric work machine comprising:

7. An electric work machine as described in claim 6, The calculation unit The first count value is valid while the load time measured by the timer is less than a time threshold value; validating the second count value in response to the load time being measured by the timer unit reaching the time threshold value; The electric work machine is configured as follows.

8. An electric work machine as described in claim 6, The calculation unit is configured to calculate the enabled count value as the heat estimated value.

9. An electric work machine as described in claim 8, the heat estimation unit is configured to, in response to the current value detected by the current detection unit becoming less than a predetermined current value that is equal to or less than the current threshold, (i) hold the heat estimation value at that time, and (ii) clear the first count value, the second count value, and the load time; the calculation unit is configured to calculate, as the heat estimated value, a value obtained by adding the enabled count value to a value held by the heat estimator. Electric work equipment.

10. An electric work machine as described in claim 9, The predetermined current value is smaller than the current threshold value.

11. An electric work machine as described in claim 1, The motor is configured to be driven while the manual switch is manually operated, The protection unit is configured to stop the protection operation in response to the user canceling the manual operation of the manual switch after the start of the protection operation. Electric work equipment.

12. An electric work machine as described in claim 11, The protection unit is configured to change the thermal threshold value depending on the number of times the protection operation is performed.

13. An electric work machine as described in claim 12, The protection unit is configured to change the thermal threshold value so that the thermal threshold value becomes lower as the number of executions increases.

14. An electric work machine as described in claim 11, The protection unit is configured to continue the protection operation even when manual operation of the manual switch is released, when the number of times the protection operation has been performed reaches a specified number.

15. An electric work machine as described in claim 14, further comprising a power supply control circuit configured to supply power to the protection unit for operating the protection unit; The protective part is Operates while receiving the power from the power supply control circuit; If the power supply is interrupted while the protective operation is being performed, (i) the protective operation is stopped, and (ii) the number of times the protective operation is performed is cleared. The electric work machine is configured as follows.

16. An electric work machine as described in claim 1, The protective action includes slowing down or stopping the motor.

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