power tools

Abstract

To provide an electric power tool which can be quickly braked in a short-circuit manner while suppressing power regeneration from a motor to a battery when stop condition of motor rotation is satisfied.SOLUTION: An electric power tool comprises: a motor; first - fourth switches; and a control circuit. The control circuit executes a low side PWM processing. Specifically, PWM driving of the fourth switch is performed while the first switch is ON. The control circuit executes a first processing according to establishment of the stop condition during the execution of the low side PWM processing. In the first processing, the fourth switch is held to be ON. The control circuit executes a second processing after execution of the first processing. In the second processing, the first switch is held to be OFF. The control circuit executes brake processing after execution of the second processing. In the brake processing, the second switch and the fourth switch are held to be ON.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to power tools. [Background technology]

[0002] Patent Document 1 discloses an electric work machine equipped with a three-phase bridge circuit. In this electric work machine, a motor is driven by a control circuit turning on a switch pair in the three-phase bridge circuit. The switch pair includes a high-side switch and a low-side switch. The control circuit, for example, turns on the high-side switch and drives the low-side switch with a pulse width modulation signal (hereinafter referred to as a "PWM signal"). Driving with a PWM signal is hereinafter referred to as "PWM drive."

[0003] In this electric work machine, when a stop condition is met, the control circuit performs a specific stop control before braking the motor. The specific stop control suppresses regenerative current from flowing from the motor to the battery. The specific stop control includes, for example, continuing to turn on the high-side switch that was turned on when the stop condition was met and keeping off the low-side switch that was PWM-driven when the stop condition was met.

[0004] One method of braking a motor is short circuit braking, which involves electrically shorting the terminals of the motor together. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6884561 Summary of the Invention [Problem to be solved by the invention]

[0006] By performing the stop specific control, it is possible to suppress the regeneration of power to the battery. However, when the stop specific control is performed, the time required from when the stop condition is met until the short circuit brake is applied increases. Specifically, the control circuit continues the stop specific control, for example, until the current flowing through the motor becomes zero (e.g., several milliseconds). After that, before applying the short circuit brake, all switches in the three-phase bridge circuit are turned off for a predetermined time (e.g., several milliseconds). This makes it difficult to quickly apply the short circuit brake after the stop condition is met.

[0007] One aspect of the present disclosure aims to provide an electric power tool that can quickly apply a short-circuit brake while suppressing power regeneration from the motor to the battery when conditions for stopping motor rotation are met. [Means for solving the problem]

[0008] According to one aspect of the present disclosure, there is provided a power tool including a motor having a first terminal and a second terminal. The power tool includes a first path. The first path connects the first terminal and a positive electrode of the DC power supply. The power tool includes a second path. The second path connects the first terminal and a negative electrode of the DC power supply. The power tool includes a third path. The third path connects the second terminal and a positive electrode of the DC power supply. The power tool includes a fourth path. The fourth path connects the second terminal and a negative electrode of the DC power supply.

[0009] The power tool includes a first switch. The first switch is provided in a first path. The first switch connects or disconnects the first path. The power tool includes a second switch. The second switch is provided in a second path. The second switch connects or disconnects the second path. The power tool includes a third switch. The third switch is provided in the third path. The third switch connects or disconnects the third path. The power tool includes a fourth switch. The fourth switch is provided in the fourth path. The fourth switch connects or disconnects the fourth path.

[0010] The power tool includes a control circuit. The control circuit executes a drive process. The drive process includes driving the motor by supplying power from a DC power supply to the motor. The drive process includes low-side PWM process. The low-side PWM process includes PWM driving the fourth switch while the first switch is turned on. The PWM drive periodically turns on or off the switch to be driven (here, the fourth switch) in accordance with a pulse-width modulation signal.

[0011] The control circuit executes a first process, which includes, during execution of the low-side PWM process, holding the fourth switch on in response to a stop condition for stopping the motor being satisfied.

[0012] The control circuit executes a second process, which includes holding the first switch off after executing the first process. The control circuit executes a braking process, which includes holding both the second switch and the fourth switch on after executing the second process, and which applies a short-circuit brake to the motor.

[0013] In such a power tool, if a stop condition is met during execution of the low-side PWM process, the second process holds the first switch off before short-circuit braking (i.e., before the braking process), thereby preventing the braking process from being performed while the first switch is on (and thus preventing both the first switch and the second switch from being on).

[0014] Furthermore, the first process is performed before the second process is performed. The first process disables PWM driving of the fourth switch in the low-side PWM process, and keeps the fourth switch on. This prevents the second process from being performed while the fourth switch is off (and thus prevents the first to fourth switches from all being off, which would result in power regeneration from the motor to the DC power supply).

[0015] The purpose of the first process is to keep the fourth switch on. In the first process, unlike the stop specific control described above, it is not necessary to wait until the current flowing through the motor reaches zero in order to start the subsequent second process. Therefore, the time required for the first process (for example, the time required from the start of the first process to the start of the second process) is sufficient to turn on the fourth switch.

[0016] The purpose of the second process is to keep the first switch off. In the second process, unlike the stop specific control described above, it is not necessary to wait until the current flowing through the motor reaches zero before starting the next braking process. Therefore, the time required for the second process (for example, the time required from the start of the second process to the start of the braking process) is sufficient to keep the first switch off.

[0017] Therefore, when a stop condition is met, such a power tool can quickly apply a short-circuit brake while suppressing power regeneration from the motor to the DC power supply. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a perspective view of a power tool according to an embodiment, seen obliquely from the front. [Figure 2] 1 is a perspective view of a power tool according to an embodiment, seen obliquely from the rear thereof; [Figure 3] FIG. 2 is a side view of the electric operating machine with the first half housing removed. [Figure 4] FIG. 2 is an explanatory diagram showing the electrical configuration of the power tool according to the embodiment. [Figure 5] FIG. 4 is an explanatory diagram showing a first drive pattern according to the first embodiment. [Figure 6] FIG. 4 is an explanatory diagram showing a second drive pattern according to the first embodiment. [Figure 7] FIG. 4 is an explanatory diagram illustrating an example of the operation of low-side PWM processing according to the first embodiment. [Figure 8] FIG. 4 is an explanatory diagram illustrating an example of the operation of high-side PWM processing according to the first embodiment. [Figure 9]FIG. 4 is an explanatory diagram showing an example of the operation of the braking process according to the first embodiment. [Figure 10] FIG. 4 is an explanatory diagram showing an example of the operation of the brake transition process according to the first embodiment. [Figure 11] 4 is a flowchart of a motor control process according to the first embodiment. [Figure 12] 4 is a flowchart of a brake transition process according to the first embodiment. [Figure 13] FIG. 10 is an explanatory diagram showing a third drive pattern according to the second embodiment. [Figure 14] FIG. 10 is an explanatory diagram showing a fourth drive pattern according to the second embodiment. [Figure 15] FIG. 11 is an explanatory diagram showing an operation example of a brake transition process according to the third embodiment. [Figure 16] 10 is a flowchart of a brake transition process according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0019] [Summary of the embodiment] In some embodiments, the power tool may include a motor. The motor has a first terminal and a second terminal. Additionally / alternatively, the power tool may include a first path. The first path connects the first terminal to a positive terminal of the DC power supply. Additionally / alternatively, the power tool may include a second path. The second path connects the first terminal to a negative terminal of the DC power supply. Additionally / alternatively, the power tool may include a third path. The third path connects the second terminal to a positive terminal of the DC power supply. Additionally / alternatively, the power tool may include a fourth path. The fourth path connects the second terminal to a negative terminal of the DC power supply.

[0020] Additionally / alternatively, the power tool may include a first switch. The first switch is provided in the first path. The first switch connects or disconnects the first path. Additionally / alternatively, the power tool may include a second switch. The second switch is provided in the second path. The second switch connects or disconnects the second path. Additionally / alternatively, the power tool may include a third switch. The third switch is provided in the third path. The third switch connects or disconnects the third path. Additionally / alternatively, the power tool may include a fourth switch. The fourth switch is provided in the fourth path. The fourth switch connects or disconnects the fourth path.

[0021] Additionally / alternatively, the power tool may include a control circuit. The control circuit may execute a driving process. The driving process includes driving the motor by supplying power from a DC power supply to the motor. The driving process includes low-side PWM process. The low-side PWM process includes PWM driving the fourth switch while the first switch is turned on. The PWM driving periodically turns on or off a switch to be driven (here, the fourth switch) in accordance with a pulse-width modulation signal. Additionally / alternatively, the control circuit may execute a first process. The first process includes holding the fourth switch on in response to a stop condition for stopping the motor being satisfied during execution of the low-side PWM process. Additionally / alternatively, the control circuit may execute a second process. The second process includes holding the first switch off after execution of the first process. Additionally / alternatively, the control circuit may execute a braking process. The braking process includes holding both the second switch and the fourth switch on after execution of the second process.

[0022] If the second process is performed before short-circuit braking (i.e., before the braking process), the braking process is prevented from being performed while the first switch is on (and thus the first and second switches are both on). Furthermore, if the first process is performed before the second process, the second process is prevented from being performed while the fourth switch is off (and thus the first to fourth switches are all off, which would result in power regeneration from the motor to the DC power supply). Furthermore, neither the first process nor the second process requires waiting until the current flowing through the motor becomes zero, as in the stop specific control described above. In other words, after the stop condition is satisfied, the transition from the first process to the second process and the transition from the second process to the braking process can be performed quickly.

[0023] Therefore, if an electric power tool in one embodiment comprises the above-mentioned motor, the above-mentioned first to fourth paths, the above-mentioned first to fourth switches, and the above-mentioned control circuit, and the control circuit executes the above-mentioned drive process, first process, second process, and braking process, such an electric power tool can quickly apply a short-circuit brake while suppressing power regeneration from the motor to the DC power source when a stop condition is met.

[0024] Additionally / alternatively, the power tool may include a first rectifier element. The first rectifier element is connected to the second path so as to bypass the second switch. The first rectifier element is arranged so that the forward direction is from the negative electrode of the DC power supply to the first terminal. Additionally / alternatively, the power tool may include a second rectifier element. The second rectifier element is connected to the third path so as to bypass the third switch. The second rectifier element is arranged so that the forward direction is from the second terminal to the positive electrode of the DC power supply. When the power tool includes the first rectifier element in one embodiment, a reflux current may flow through the motor, the fourth switch, and the first rectifier element when the second process is performed. When the power tool includes the second rectifier element in one embodiment, a reflux current may flow through the motor, the second rectifier element, and the first switch when the low-side PWM process is performed.

[0025] Additionally / alternatively, the control circuit may execute a third process. The third process includes holding the third switch off before executing the first process in response to a stop condition being satisfied during execution of the low-side PWM process. Additionally / alternatively, the control circuit may execute the first process after executing the third process. By executing the third process before executing the first process, the first process is prevented from being executed while the third switch is on (and thus the third and fourth switches are both on). The purpose of the third process is to hold the third switch off. Therefore, in the third process, it is not necessary to wait until the current flowing through the motor becomes zero in order to start the next first process, as in the stop specific control described above. Therefore, the time required for the third process (e.g., the time required from the start of the third process to the start of the next first process) is sufficient to turn off the third switch. Therefore, when an electric power tool in one embodiment is equipped with a control circuit having the above-described characteristics, such an electric power tool can appropriately and quickly apply a short-circuit brake when a stop condition is met, while suppressing power regeneration from the motor to the DC power source.

[0026] Additionally / alternatively, the control circuit may execute a standby process instead of the third process. The standby process includes waiting until the fourth switch is turned on by the low-side PWM process before executing the first process in response to the stop condition being satisfied when the fourth switch is turned off by the low-side PWM process. Additionally / alternatively, the control circuit may execute the first process after executing the standby process (i.e., while the fourth switch is turned on by the low-side PWM process). Executing the first process after executing the standby process can prevent the first process from being executed while the third switch is on (and thus prevent both the third and fourth switches from being on). Therefore, if a power tool in one embodiment includes a control circuit having the above-described features, such a power tool can appropriately and quickly apply a short-circuit brake while suppressing power regeneration from the motor to the DC power supply when the stop condition is satisfied. In other words, the same effect as when the third process is executed can be achieved in that the first process can be prevented from being executed while the third switch is on.

[0027] Additionally / alternatively, the low-side PWM process may include turning on the third switch during at least a portion of each off-period in which the fourth switch is periodically turned off by PWM driving. When a power tool according to an embodiment is configured to perform low-side PWM process having the above-described characteristics, a reflux current may flow through the motor, the third switch, and the first switch when the fourth switch is turned off. Therefore, for example, in a power tool including the second rectifier element described above, heat generated in the second rectifier element due to the reflux current flowing through the second rectifier element can be reduced. Furthermore, the third process and standby process described above are more effective when low-side PWM process is performed so as to turn on the third switch during at least a portion of the off-period of the fourth switch.

[0028] Additionally / alternatively, the drive process may include high-side PWM process. The high-side PWM process may include PWM driving the third switch while the second switch is turned on, and / or PWM driving the first switch while the fourth switch is turned on. Additionally / alternatively, the control circuit may execute a fourth process. The fourth process may include, in response to a stop condition being satisfied while the high-side PWM process is being performed, holding the first switch or the third switch, which is being PWM driven by the high-side PWM process, off. Additionally / alternatively, after executing the fourth process, the control circuit may execute a braking process without executing the first and second processes. In other words, if a stop condition is satisfied while the high-side PWM process is being performed, the braking process may be executed via the fourth process instead of the first and second processes. By executing the fourth process before the braking process, the first switch or the third switch, which is being PWM driven, is held off. Therefore, the braking process is prevented from being performed while the first switch or the third switch is on (and thus the first switch and the second switch are both on, or the third switch and the fourth switch are both on). The purpose of the fourth process is to keep the PWM-driven first switch or the third switch off. In the fourth process, it is not necessary to wait until the current flowing through the motor becomes zero in order to start the next braking process, as in the above-mentioned specific stop control. Therefore, the time required for the fourth process (for example, the time required from the start of the fourth process to the start of the braking process) is sufficient to be the time necessary to turn off the first switch or the third switch.

[0029] Additionally / alternatively, the power tool may include a torque detection unit that detects the load torque of the motor. Additionally / alternatively, the stop condition may include the load torque detected by the torque detection unit being equal to or greater than a threshold. When a power tool according to an embodiment includes a torque detection unit and a control circuit having the above-described features, such a power tool can prevent the load torque from exceeding the threshold.

[0030] Additionally / alternatively, the motor may be a brushless motor further including a third terminal. Additionally, the power tool may include a fifth path. The fifth path connects the third terminal and a positive electrode of the DC power supply. Additionally / alternatively, the power tool may include a sixth path. The sixth path connects the third terminal and a negative electrode of the DC power supply. Additionally / alternatively, the power tool may include a fifth switch. The fifth switch is provided in the fifth path and connects or disconnects the fifth path. Additionally / alternatively, the power tool may include a sixth switch. The sixth switch is provided in the sixth path and connects or disconnects the sixth path. In an embodiment, when a power tool includes the brushless motor, the fifth and sixth paths, and the fifth and sixth switches, such a power tool can quickly apply short-circuit braking to the brushless motor when a stop condition is met while suppressing power regeneration from the brushless motor to the DC power supply. The short-circuit braking may include holding the second switch, the fourth switch, and the sixth switch on.

[0031] In some embodiments, the above features may be combined in any combination. In some embodiments, any of the above features may be omitted. 2. Specific Exemplary First Embodiment (2-1) Configuration of power tools The power tool 1 of this embodiment shown in Figures 1 to 3 is configured as, for example, a rechargeable screwdriver. The rechargeable screwdriver may be used to rotate fastening parts such as screws. The power tool 1 of this embodiment is driven by power from a battery 101 (see Figure 4), which will be described later.

[0032] As shown in Figures 1 and 2, the power tool 1 includes a main body 2. The main body 2 includes a housing 3. The housing 3 is divided into a first half housing 3a and a second half housing 3b, which are left and right halves. The first half housing 3a and the second half housing 3b are combined to form the housing 3. Figure 3 shows the power tool 1 with the first half housing 3a removed.

[0033] The main body 2 includes a first housing portion 5, a grip 6, and a second housing portion 7. The first housing portion 5 houses a motor 11 (see FIG. 3) and a drive mechanism 12 (see FIG. 3). The first housing portion 5 further includes a direction setting switch 9 and a chuck sleeve 10.

[0034] Various types of tool bits (or tools) are selectively and removably attached to the chuck sleeve 10. Each of the various tool bits may have any function. For example, the various tool bits may be a Phillips head screwdriver bit 10a as shown in FIG. 1. The tool bit attached to the chuck sleeve 10 is driven (e.g., rotated) by the rotational force of the motor 11.

[0035] In this embodiment, the motor 11 is, for example, a brushless motor. The rotational driving force (rotational force) generated by the motor 11 is transmitted to the drive mechanism 12. As shown in FIG. 3, the motor 11 includes a rotor 19. In this embodiment, the rotor 19 is a permanent magnet type. The rotation of the motor 11 specifically refers to the rotation of the rotor 19. The drive mechanism 12 includes, for example, a speed reduction mechanism (not shown). The speed reduction mechanism reduces the rotational driving force of the motor 11 to a rotational speed lower than that of the motor 11 and transmits it to the chuck sleeve 10.

[0036] The direction setting switch 9 is provided to select the rotation direction of the motor 11 (and therefore the rotation direction of the chuck sleeve 10). A user of the power tool can select a first rotation direction (e.g., forward or CW (ClockWise)) or a second rotation direction (e.g., reverse or CCW (Counter-ClockWise)) by operating the direction setting switch 9. The direction setting switch 9 outputs a direction setting signal. The direction setting signal indicates the rotation direction selected by the direction setting switch 9.

[0037] The direction setting switch 9 may be manually set by a user to at least one of a first position and a second position. When the direction setting switch 9 is set to the first position, the rotation direction of the motor 11 may be set to a first rotation direction. When the direction setting switch 9 is set to the second position, the rotation direction of the motor 11 may be set to a second rotation direction. The rotation directions of the motor 11 corresponding to the first position and the second position may be fixed in advance. Conversely, arbitrary operating conditions may be set for each of the first position and the second position. The operating conditions may include, for example, at least the rotation direction of the motor 11. The operating conditions may further include a target rotation speed of the motor 11 (and thus a target rotation speed of the chuck sleeve 10) and / or a stop condition for the motor 11. In this case, the motor 11 may be driven according to the operating conditions corresponding to the position of the direction setting switch 9.

[0038] The grip 6 extends from the first housing portion 5. The grip 6 is held by, for example, a user. The grip 6 is provided with a trigger switch 8. The user can manually operate (for example, pull) the trigger switch 8 while holding the grip 6. In this embodiment, pulling the trigger switch 8 corresponds to moving the trigger switch 8 leftward in FIG. 3 (or pushing it into the main body 2).

[0039] The trigger switch 8 is turned on when manually operated. The trigger switch 8 is turned off when not manually operated. The trigger switch 8 outputs a trigger detection signal. The trigger detection signal indicates whether the trigger switch 8 is turned off or not. The trigger detection signal may further indicate the amount of operation of the trigger switch 8 when it is manually operated.

[0040] The second housing section 7 extends from the grip 6. The battery pack 100 is removably attached to the bottom of the second housing section 7. As shown in FIG. 3, the second housing section 7 houses the controller 30.

[0041] As shown in Fig. 3, the first housing section 5 is further provided with a torque sensor 13. The torque sensor 13 is provided to detect a load torque that is applied directly or indirectly to the motor 11. When various operations are performed with the tool bit attached to the chuck sleeve 10, the motor 11 receives a load torque from the workpiece via the tool bit, the chuck sleeve 10, and the drive mechanism 12. The torque sensor 13 outputs a signal corresponding to this load torque (hereinafter referred to as a "torque detection signal").

[0042] The torque sensor 13 may be provided at any position where it can detect the load torque. The torque sensor 13 may be provided, for example, in the chuck sleeve 10 or the drive mechanism 12. In this embodiment, the torque sensor 13 is provided, for example, in the drive mechanism 12. The torque sensor 13 may generate the torque detection signal in any manner (for example, by any principle). Furthermore, the torque detection signal may be a signal in any form. The torque sensor 13 in this embodiment generates, for example, an analog voltage corresponding to the amount of mechanical torsion of a shaft (not shown) that transmits the rotation of the motor 11 to the chuck sleeve 10. This voltage is output as the torque detection signal.

[0043] The torque sensor 13 of this embodiment outputs a torque detection signal in real time (i.e., continuously) corresponding to the actual load torque (i.e., corresponding to the actual amount of torsion of the shaft). Therefore, the torque detection signal output from the torque sensor 13 at a certain point in time indicates the actual load torque at that point in time (or approximately at that point in time).

[0044] (2-2) Electrical configuration of power tools The electrical configuration of the power tool 1 will be further described with reference to Fig. 4. Fig. 4 shows the power tool 1 in a state where the battery pack 100 is attached to the main body 2.

[0045] The battery pack 100 includes a battery 101. 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.

[0046] The power tool 1 includes the motor 11, the trigger switch 8, the direction setting switch 9, the torque sensor 13, the display unit 16, and the input I / F 17. "I / F" is an abbreviation for interface.

[0047] The motor 11 is driven by battery power supplied from the battery 101 via a drive circuit 31, which will be described later. The battery power supplied from the battery 101 is converted into three-phase power by the drive circuit 31 and supplied to the motor 11.

[0048] The motor 11 includes a first winding 21, a second winding 22, and a third winding 23. In this embodiment, the first to third windings 21 to 23 are, for example, delta-connected. However, the first to third windings 21 to 23 may be connected by a connection method other than delta connection. The motor 11 includes a first terminal 11a, a second terminal 11b, and a third terminal 11c. Three-phase power is input to the first to third terminals 11a to 11c and supplied to the first to third windings 21 to 23 via the first to third terminals 11a to 11c.

[0049] The power tool 1 further includes a rotational position detection unit 25. The rotational position detection unit 25 outputs rotational position information. The rotational position information indicates the rotational position of the motor 11, more specifically, the rotational position of the rotor 19. The rotational position information includes a first position signal Hu, a second position signal Hv, and a third position signal Hw. The rotational position information is input to a first control circuit 32, which will be described later.

[0050] The rotational position detection unit 25 of this embodiment includes three Hall sensors, namely, a first Hall sensor 26, a second Hall sensor 27, and a third Hall sensor 28. The first to third Hall sensors 26 to 28 are provided around the rotor 19. Specifically, the first to third Hall sensors 26 to 28 are arranged around the rotation axis of the rotor 19 along the rotation direction of the rotor 19, spaced apart by an angle equivalent to 120 electrical degrees.

[0051] The first Hall sensor 26 outputs a first position signal Hu. The first position signal Hu changes depending on the relative positional relationship between the first Hall sensor 26 and the rotor 19. The second Hall sensor 27 outputs a second position signal Hv. The second position signal Hv changes depending on the relative positional relationship between the second Hall sensor 27 and the rotor 19. The third Hall sensor 28 outputs a third position signal Hw. The third position signal Hw changes depending on the relative positional relationship between the third Hall sensor 28 and the rotor 19. In this embodiment, the first to third position signals Hu, Hv, and Hw are each a binary digital signal.

[0052] The power tool 1 further includes a controller 30. When the battery pack 100 is attached to the main body 2, the controller 30 is electrically connected to the battery 101 via a power supply path 50. The controller 30 is supplied with power from the battery 101 (hereinafter referred to as "battery power") from the battery 101 via the power supply path 50. The power supply path 50 includes a positive electrode path 51 extending from the positive electrode of the battery 101 to the drive circuit 31, and a negative electrode path 52 extending from the negative electrode of the battery 101 to the drive circuit 31. The power supply path 50 further includes a first path 61, a second path 62, a third path 63, a fourth path 64, a fifth path 65, and a sixth path 66, which will be described later. The first to sixth paths 61 to 66 are provided in the drive circuit 31.

[0053] The controller 30 includes a drive circuit 31. The drive circuit 31 is connected to first to third terminals 11a to 11c of the motor 11. The drive circuit 31 generates three-phase drive power for driving the motor 11 from input battery power and supplies the three-phase drive power to the motor 11.

[0054] The drive circuit 31 of this embodiment includes a three-phase full-bridge circuit. The three-phase full-bridge circuit includes a first switch UH, a second switch UL, a third switch VH, a fourth switch VL, a fifth switch WH, and a sixth switch WL. Each of the first to sixth switches UH, UL, VH, VL, WH, and WL may be any type of switch. In this embodiment, each of the first to sixth switches UH, UL, VH, VL, WH, and WL is, for example, an n-channel metal-oxide semiconductor field-effect transistor (MOSFET).

[0055] The drive circuit 31 includes the first to sixth paths 61 to 66 described above. The first path 61 connects the first terminal 11a to the positive electrode path 51 (and thus to the positive electrode of the battery 101). The path from the first terminal 11a to the positive electrode of the battery may be considered as the first path 61. The second path 62 connects the first terminal 11a to the negative electrode path 52 (and thus to the negative electrode of the battery 101). The path from the first terminal 11a to the negative electrode of the battery may be considered as the second path 62. The third path 63 connects the second terminal 11b to the positive electrode path 51 (and thus to the positive electrode of the battery 101). The path from the second terminal 11b to the positive electrode of the battery may be considered as the third path 63. The fourth path 64 connects the second terminal 11b to the negative electrode path 52 (and thus to the negative electrode of the battery 101). The path from the second terminal 11b to the negative electrode of the battery may be considered as the fourth path 64. The fifth path 65 connects the third terminal 11c to the positive electrode path 51 (and thus to the positive electrode of the battery 101). The path from the third terminal 11c to the positive electrode of the battery may be considered as the fifth path 65. The sixth path 66 connects the third terminal 11c to the negative electrode path 52 (and thus to the negative electrode of the battery 101). The path from the third terminal 11c to the negative electrode of the battery may be considered as the sixth path 66.

[0056] The first switch UH is provided on the first path 61. The first switch UH is turned on when receiving a first drive signal from the first control circuit 32, and is turned off when not receiving the first drive signal. The first path 61 is made conductive via the first switch UH when the first switch UH is turned on. The first path 61 is cut off by the first switch UH when the first switch UH is turned off.

[0057] The second switch UL is provided on the second path 62. The second switch UL is turned on when the second drive signal is received from the first control circuit 32, and is turned off when the second drive signal is not received. The second path 62 is conductive via the second switch UL when the second switch UL is turned on. The second path 62 is cut off by the second switch UL when the second switch UL is turned off.

[0058] The third switch VH is provided on the third path 63. The third switch VH is turned on when receiving a third drive signal from the first control circuit 32, and is turned off when not receiving the third drive signal. The third path 63 is made conductive via the third switch VH when the third switch VH is turned on. The third path 63 is cut off by the third switch VH when the third switch VH is turned off.

[0059] The fourth switch VL is provided on the fourth path 64. The fourth switch VL is turned on when receiving a fourth drive signal from the first control circuit 32, and is turned off when not receiving the fourth drive signal. The fourth path 64 is conductive via the fourth switch VL when the fourth switch VL is turned on. The fourth path 64 is cut off by the fourth switch VL when the fourth switch VL is turned off.

[0060] The fifth switch WH is provided on the fifth path 65. The fifth switch WH is turned on when receiving a fifth drive signal from the first control circuit 32, and is turned off when not receiving the fifth drive signal. The fifth path 65 is made conductive via the fifth switch WH when the fifth switch WH is turned on. The fifth path 65 is cut off by the fifth switch WH when the fifth switch WH is turned off.

[0061] The sixth switch WL is provided on the sixth path 66. The sixth switch WL is turned on when receiving a sixth drive signal from the first control circuit 32, and is turned off when not receiving the sixth drive signal. The sixth path 66 is made conductive via the sixth switch WL when the sixth switch WL is turned on. The sixth path 66 is cut off by the sixth switch WL when the sixth switch WL is turned off.

[0062] The drive circuit 31 further includes a first diode D1, a second diode D2, a third diode D3, a fourth diode D4, a fifth diode D5, and a sixth diode D6.

[0063] The first diode D1 is connected to the first path 61 so as to bypass the first switch UH. More specifically, the first diode D1 has an anode connected to the source of the first switch UH and a cathode connected to the drain of the first switch UH, such that the forward direction is from the first terminal 11a of the motor 11 toward the positive electrode of the battery 101. The first diode D1 may be provided separately from the first switch UH, or may be a parasitic diode included in the first switch UH.

[0064] The second diode D2 is connected to the second path 62 so as to bypass the second switch UL. More specifically, the second diode D2 has an anode connected to the source of the second switch UL and a cathode connected to the drain of the second switch UL, with the forward direction being from the negative electrode of the battery 101 toward the first terminal 11a of the motor 11. The second diode D2 may be provided separately from the second switch UL, or may be a parasitic diode included in the second switch UL.

[0065] The third diode D3 is connected to the third path 63 so as to bypass the third switch VH. More specifically, the third diode D3 has an anode connected to the source of the third switch VH and a cathode connected to the drain of the third switch VH such that the forward direction is from the second terminal 11b of the motor 11 toward the positive electrode of the battery 101. The third diode D3 may be provided separately from the third switch VH or may be a parasitic diode included in the third switch VH.

[0066] The fourth diode D4 is connected to the fourth path 64 so as to bypass the fourth switch VL. More specifically, the fourth diode D4 has an anode connected to the source of the fourth switch VL and a cathode connected to the drain of the fourth switch VL such that the forward direction is from the negative electrode of the battery 101 toward the second terminal 11b of the motor 11. The fourth diode D4 may be provided separately from the fourth switch VL or may be a parasitic diode included in the fourth switch VL.

[0067] The fifth diode D5 is connected to the fifth path 65 so as to bypass the fifth switch WH. More specifically, the fifth diode D5 has an anode connected to the source of the fifth switch WH and a cathode connected to the drain of the fifth switch WH so that the forward direction is from the third terminal 11c of the motor 11 toward the positive electrode of the battery 101. The fifth diode D5 may be provided separately from the fifth switch WH or may be a parasitic diode included in the fifth switch WH.

[0068] The sixth diode D6 is connected to the sixth path 66 so as to bypass the sixth switch WL. More specifically, the sixth diode D6 has an anode connected to the source of the sixth switch WL and a cathode connected to the drain of the sixth switch WL such that the forward direction is from the negative electrode of the battery 101 toward the third terminal 11c of the motor 11. The sixth diode D6 may be provided separately from the sixth switch WL or may be a parasitic diode included in the sixth switch WL.

[0069] The drive circuit 31 can be divided into, for example, three systems. The three systems include, for example, a U-phase system, a V-phase system, and a W-phase system. The U-phase system includes first and second switches UH and UL and first and second paths 61 and 62. The V-phase system includes third and fourth switches VH and VL and third and fourth paths 63 and 64. The W-phase system includes fifth and sixth switches WH and WL and fifth and sixth paths 65 and 66.

[0070] The controller 30 includes a current detection unit 33. The current detection unit 33 is provided to detect the value of the current flowing through the motor 11. In this embodiment, the current detection unit 33 is provided, for example, in the negative electrode path 52. When power is supplied from the battery 101 to the motor 11, a current flows through the negative electrode path 52. The current detection unit 33 outputs a signal (hereinafter referred to as a "current detection signal") corresponding to the current flowing through the negative electrode path 52. The current detection signal indicates the value of the current flowing through the negative electrode path 52. The current detection signal is input to the first control circuit 32.

[0071] The controller 30 includes a first control circuit 32. The first control circuit 32 includes, for example, a CPU 32a and a memory 32b. The memory 32b may include, for example, a semiconductor memory such as a ROM, a RAM, an NVRAM, or a flash memory. That is, the first control circuit 32 of this embodiment includes a microcomputer.

[0072] The first control circuit 32 realizes various functions by executing a program stored in a non-transitory physical recording medium. In this embodiment, the memory 32b corresponds to the non-transitory physical recording medium storing the program. In this embodiment, the memory 32b stores a program for a motor control process (see FIG. 11) described later.

[0073] Some or all of the various functions realized by the first control circuit 32 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 first control circuit 32 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.

[0074] The first control circuit 32 receives rotational position information (i.e., the first to third position signals Hu, Hv, and Hw) from the rotational position detection unit 25. Every time the level of any of the first to third position signals Hu, Hv, and Hw changes (i.e., every time the rotor 19 rotates by an electrical angle of 60°), the first control circuit 32 detects the rotational speed of the motor 11 based on the time when the previous level change occurred and / or the time when the level change occurred even earlier than the previous one until the time when the current level change occurs.

[0075] More specifically, in this embodiment, an interrupt (hereinafter referred to as a "Hall sensor interrupt") occurs in the processing of the CPU 32a every time the level of any one of the first to third position signals Hu, Hv, and Hw changes. When the CPU 32a receives a Hall sensor interrupt, it calculates the rotation speed of the motor 11. Then, until the next Hall sensor interrupt occurs, the CPU 32a recognizes the calculated rotation speed as the current rotation speed of the motor 11. In the following description, the "recognized rotation speed" refers to the rotation speed calculated in response to a Hall sensor interrupt. In other words, in this embodiment, the recognized rotation speed is updated every time a Hall sensor interrupt occurs (i.e., every time the rotor 19 rotates by 60 electrical degrees).

[0076] The first control circuit 32 receives a trigger detection signal from the trigger switch 8. The first control circuit 32 can detect whether or not the trigger switch 8 is turned on based on the trigger detection signal.

[0077] The first control circuit 32 receives a direction setting signal from the direction setting switch 9. Based on the direction setting signal, the first control circuit 32 can detect whether the first rotation direction or the second rotation direction is selected.

[0078] The first control circuit 32 receives a torque detection signal from the torque sensor 13. The first control circuit 32 can detect the load torque based on the torque detection signal. As described above, the torque sensor 13 continuously outputs a torque detection signal that reflects the actual load torque in real time. Therefore, the first control circuit 32 can detect the actual load torque in real time.

[0079] The controller 30 includes a power supply circuit 35. Battery power is input to the power supply circuit 35 from the battery 101. The power supply circuit 35 generates and outputs power supply power having a control voltage Vc from the battery power input to the power supply circuit 35. The control voltage Vc has, for example, a constant voltage value. The power supply power generated by the power supply circuit 35 is supplied to each unit in the controller 30, including the first control circuit 32. The first control circuit 32 operates using this power supply power. In this embodiment, the power supply power is also supplied to the rotational position detection unit 25, and is used to generate the first to third position signals Hu, Hv, and Hw described above.

[0080] The power tool 1 further includes a second control circuit 40. The second control circuit 40 is connected to the input I / F 17 and the display unit 16. The input I / F 17 includes one or more switches operated by the user. In this embodiment, the input I / F 17 includes, for example, four switches. The display unit 16 is capable of displaying various images, text, and the like.

[0081] The second control circuit 40 determines the drive settings used to drive the motor 11 and transmits them to the first control circuit 32. The drive settings include various setting items. The various setting items include, for example, the target rotation speed of the motor 11, the engagement completion condition, etc. In this embodiment, constant rotation control is performed, as will be described later. In constant rotation control, the motor 11 is controlled so that the rotation speed of the motor 11 matches the target rotation speed.

[0082] The engagement completion condition is a condition under which the rotating motor 11 should be stopped. More specifically, the engagement completion condition is a condition under which constant rotation control should be switched to stop control. Stop control is control for stopping the rotation of the motor 11. When stop control is performed by the first control circuit 32, the rotation of the motor 11 is stopped.

[0083] In this embodiment, when the trigger switch 8 is turned on, the motor 11 starts to rotate. If a stop condition is met while the motor 11 is rotating, the brake process is initiated. In this embodiment, the stop condition is met, for example, when the trigger switch 8 is turned off or when the aforementioned engagement completion condition is met. Therefore, if the engagement completion condition is met while the motor 11 is rotating, even if the trigger switch 8 is turned on, the stop condition is met and the brake process is initiated, thereby stopping the motor 11.

[0084] The engagement completion condition may be determined in any manner. In this embodiment, the engagement completion condition includes, for example, a target torque, a drive time, and / or a tightening rotation angle. If the engagement completion condition includes, for example, a target torque, the engagement completion condition is met when the load torque reaches the target torque after the motor 11 starts to rotate. If the engagement completion condition includes, for example, a drive time, the engagement completion condition is met when the drive time has elapsed since the motor 11 started to rotate. If the engagement completion condition includes, for example, a target torque and a drive time, the engagement completion condition is met when the load torque reaches the target torque after the motor 11 starts to rotate, or when the drive time has elapsed since the motor 11 started to rotate.

[0085] The user can select various setting items individually or collectively via the input I / F 17. When the setting items selected by the user are determined as drive settings, the second control circuit 40 notifies the first control circuit 32 of the determined drive settings.

[0086] For example, the user may be able to select one of first to Nth target rotation speeds as the target rotation speed. "N" is a natural number equal to or greater than 2. Each of the first to Nth target rotation speeds may be a rotation speed within a range of 20,000 rpm to 1,000 rpm, for example. At least one of the first to Nth target rotation speeds may be equal to or less than a threshold value. The threshold value may be, for example, 5,000 rpm.

[0087] The second control circuit 40 of this embodiment displays, for example, N types of drive setting options on the display unit 16. The N types of options include the first to Nth target rotation speeds. The user can select any one of the options via the input I / F 17. When the user selects an option, the second control circuit 40 determines the selected option as the drive setting and notifies the first control circuit 32 of the drive setting. In this embodiment, one specific option is set as the default option. When the second control circuit 40 is started, as an initial process after start-up, it determines the default option as the drive setting and notifies the first control circuit 32 of the default option.

[0088] (2-3) Constant speed control When the trigger switch 8 is turned on, the first control circuit 32 executes constant rotation control to rotate the motor 11 in the rotation direction set by the direction setting switch 9.

[0089] Specifically, the first control circuit 32 acquires the drive settings described above from the second control circuit 40. The drive settings include a target rotation speed. The first control circuit 32 controls the power supplied from the drive circuit 31 to the motor 11 so that the rotation speed of the motor 11 matches the target rotation speed.

[0090] The constant rotation control of this embodiment includes rotation speed feedback control. In the following description, "feedback" is abbreviated as "FB." In this embodiment, the rotation speed FB control is performed by, for example, proportional-integral control.

[0091] In the rotation speed FB control, a drive command value is calculated so that the rotation speed of the motor 11 matches the target rotation speed. The drive command value indicates the power to be supplied to the motor 11. In this embodiment, the drive command value includes a duty ratio. This duty ratio is hereinafter referred to as the "drive duty ratio." In the rotation speed FB control, the drive duty ratio is calculated according to the difference between the recognized rotation speed calculated based on the rotation position information and the target rotation speed (hereinafter referred to as the "speed difference"). For example, the drive duty ratio may be calculated so that it increases as the speed difference increases.

[0092] In the constant rotation control, the first control circuit 32 calculates a drive duty ratio for each predetermined control period and drives the drive circuit 31 based on the drive duty ratio. The first control circuit 32 drives the drive circuit 31 by low-side PWM processing and / or high-side PWM processing.

[0093] The low-side PWM processing involves PWM driving one of the three high-side switches (hereinafter referred to as the "on-maintained high-side switch") in a system different from the system to which the high-side switch (hereinafter referred to as the "on-maintained high-side switch") belongs, while maintaining that high-side switch on.

[0094] The "high-side switch" refers to the first, third, and fifth switches UH, VH, and WH, respectively. The "three high-side switches" refer to the first, third, and fifth switches UH, VH, and WH, respectively. The "low-side switch" refers to the second, fourth, and sixth switches UL, VL, and WL, respectively. The "three low-side switches" refer to the second, fourth, and sixth switches UL, VL, and WL, respectively.

[0095] PWM driving means that the switch to be driven (here, a PWM-driven low-side switch) is periodically turned on and off in accordance with a pulse-width modulation signal. The pulse-width modulation signal has the aforementioned drive duty ratio. In other words, PWM driving means driving the switch to be driven by a pulse-width modulation signal having a calculated drive duty ratio.

[0096] The high-side PWM processing involves PWM driving one of the three low-side switches (hereinafter referred to as the "on-maintained low-side switch") in a system different from the system to which the low-side switch (hereinafter referred to as the "on-maintained low-side switch") belongs, while maintaining that low-side switch on.

[0097] When the first switch UH is made to function as an on-maintaining high-side switch, the first control circuit 32 outputs a first drive signal to the first switch UH to maintain the first switch UH on. When the first switch UH is made to function as a PWM-driven high-side switch, the first control circuit 32 outputs the above-mentioned pulse-width modulation signal as the first drive signal to the first switch UH. The same applies when the third and fifth switches VH and WH are made to function as on-maintaining high-side switches or PWM-driven high-side switches, respectively.

[0098] When the first control circuit 32 causes the second switch UL to function as an on-maintaining low-side switch, it outputs a second drive signal to the second switch UL to keep the second switch UL on. When the first control circuit 32 causes the second switch UL to function as a PWM-driven low-side switch, it outputs the above-mentioned pulse-width modulated signal as the second drive signal to the second switch UL. The same applies when the fourth and sixth switches VL and WL are caused to function as an on-maintaining low-side switch or a PWM-driven low-side switch, respectively.

[0099] When the first control circuit 32 is configured to perform low-side PWM processing, it rotates the motor 11 while appropriately switching the combination of the on-maintain high-side switch and the PWM-driven low-side switch depending on the rotational position (i.e., rotational angle) of the motor 11.

[0100] When the first control circuit 32 is configured to perform high-side PWM processing, it rotates the motor 11 while appropriately switching the combination of the on-maintained low-side switch and the PWM-driven high-side switch depending on the rotational position (i.e., rotational angle) of the motor 11.

[0101] The first control circuit 32 may rotate the motor 11 while appropriately switching between low-side PWM processing and high-side PWM processing. In this embodiment, the first to sixth switches UH to WL are driven according to, for example, the first drive pattern illustrated in Fig. 5 or the second drive pattern illustrated in Fig. 6. In Fig. 5 and Fig. 6, "(PWM)" indicates PWM drive. The horizontal axis in Fig. 5 and Fig. 6 represents the rotation angle of the rotor 19.

[0102] In Fig. 5, for example, during period T1, low-side PWM processing is performed. Specifically, the first switch UH is kept on as an on-maintained high-side switch, and the sixth switch WL is PWM-driven as a PWM-driven low-side switch. Fig. 7 schematically shows the current path during this period T1.

[0103] 7 and 8, "on duty" indicates the period during which a switch to be PWM driven is turned on by a pulse width modulation signal. In FIGS. 7 and 8, "off duty" indicates the period during which a switch to be PWM driven is turned off. In FIGS. 7 and 8, "ON" indicates that the switch is turned on. In FIGS. 7 and 8, "OFF" indicates that the switch is turned off. In FIGS. 7 and 8, "PWM ON" indicates that the switch is being PWM driven and is in an on state in PWM driving. In FIGS. 7 and 8, "PWM OFF" indicates that the switch is being PWM driven and is in an off state in PWM driving.

[0104] 7, during on-duty, the first switch UH and the sixth switch WL are turned on, so that current flows from the positive electrode of the battery 101 to the negative electrode of the battery 101 via the first switch UH, the first terminal 11a of the motor 11, the third terminal 11c of the motor 11, and the sixth switch WL.

[0105] On the other hand, during the off-duty period, the sixth switch WL is turned off. Therefore, battery power is no longer supplied to the motor 11, but a return current flows due to the residual energy of the motor 11. Specifically, as shown in FIG. 7, the return current flows from the third terminal 11c of the motor 11 through the fifth diode D5 and the first switch UH to the first terminal 11a of the motor 11.

[0106] In Fig. 6, for example, during period T2, high-side PWM processing is performed. Specifically, the sixth switch WL is kept on as an on-maintained low-side switch, and the first switch UH is PWM-driven as a PWM-driven high-side switch. Fig. 8 schematically shows the current path during this period T2.

[0107] 8, during on-duty, the first switch UH and the sixth switch WL are turned on, so that current flows from the positive electrode of the battery 101 to the negative electrode of the battery 101 via the first switch UH, the first terminal 11a of the motor 11, the third terminal 11c of the motor 11, and the sixth switch WL.

[0108] On the other hand, during the off-duty period, the first switch UH is turned off. Therefore, battery power is no longer supplied to the motor 11, but a return current flows due to the residual energy of the motor 11. Specifically, as shown in FIG. 8, the return current flows from the third terminal 11c of the motor 11 through the sixth switch WL and the second diode D2 to the first terminal 11a of the motor 11.

[0109] In the PWM process of this embodiment, non-complementary driving is performed. In other words, complementary driving is not performed. Complementary driving means that, for each off period in which a switch to be PWM-driven is periodically turned off in accordance with a pulse-width modulation signal, another switch in the same system as the switch to be PWM-driven is turned on for at least a portion of the off period. When complementary driving is performed, for example, in period T1 in FIG. 5, the fifth switch WH is turned on for at least a portion of the off period of the sixth switch WL. Also, for example, in period T2 in FIG. 6, the second switch UL is turned on for at least a portion of the off period of the first switch UH. In this embodiment, such complementary driving is not performed.

[0110] In both the execution of low-side PWM processing and the execution of high-side PWM processing, if the stop condition is satisfied, the constant rotation control is switched to the stop control. Specifically, as simply shown in Figures 7 and 8, if the stop condition is satisfied, the brake transition process is first performed, and then the brake process is performed.

[0111] (2-4) Stop control The stop control will be described with reference to FIGS. First, the braking process executed after the braking transition process will be described with reference to FIG. 9. In the braking process, short-circuit braking is performed. In this embodiment, as described above, for example, three-phase short-circuit braking is performed. Specifically, as shown in FIG. 9, all high-side switches UH, VH, and WH are held off, and all low-side switches UL, VL, and WL are held on. This braking process stops the motor 11.

[0112] If braking processing is performed immediately when the stop condition is met, it is possible to quickly stop the motor 11. However, if the braking processing is performed while constant rotation control is being performed, depending on the timing of the transition, a so-called arm short circuit may occur, in which the high-side switch and the low-side switch of the same system are simultaneously turned on. Specifically, for example, if the braking processing is performed while the first switch UH is turned on by the low-side PWM processing, the second switch UL may be turned on while the first switch UH remains on. In this case, an arm short circuit occurs in the U-phase system.

[0113] To prevent arm short-circuiting, for example, when a stop condition is met, it is conceivable to temporarily turn off all low-side switches and high-side switches before braking. However, if all switches are turned off while current is being supplied to the motor 11, power regeneration occurs from the motor 11 to the battery 101 due to the influence of the inductance components of the first to third windings 21 to 23 of the motor 11. When power regeneration occurs, the voltage of the positive electrode path 51 temporarily rises above the voltage of the battery 101, which may cause a malfunction in the controller 30.

[0114] One technique that can suppress such power regeneration is the technique disclosed in the aforementioned Patent Document 1. However, as mentioned above, when the technique disclosed in Patent Document 1 is adopted, it takes a long time (for example, several milliseconds or more) from the establishment of the stop condition until the start of braking processing, making it difficult to quickly perform braking processing after the stop condition is established.

[0115] In order to be able to start the braking process quickly while suppressing such arm short circuit and power regeneration, in the stop control of this embodiment, a braking transition process is executed before the braking process.

[0116] The brake transition process will be described with reference to FIG. 10. In detail, the brake transition process of this embodiment includes a transition initial process, a transition first process, and a transition second process. If a stop condition is satisfied during execution of low-side PWM processing, the brake transition process is performed in the order of the transition initial process, the transition first process, and the transition second process. If a stop condition is satisfied during execution of high-side PWM processing, the transition initial process is performed, but the transition first process and the transition second process are not performed.

[0117] Fig. 10 schematically shows, as an example, the brake transition process when the stop condition is satisfied during the execution of the low-side PWM process illustrated in Fig. 7. That is, Fig. 10 shows the brake transition process when the stop condition is satisfied while the first switch UH is kept on and the sixth switch WL is PWM-driven.

[0118] In the initial transition process, both switches in the system including the switch that was PWM-driven in the previous constant rotation control (hereinafter referred to as the "PWM system") are kept off. FIG. 10 shows a state in which the fifth and sixth switches WH and WL, which are switches in the PWM system, are kept off by the initial transition process. This initial transition process causes a reflux current to flow between the motor 11 and the drive circuit 31, as shown in FIG. 10. The route of the reflux current in the initial transition process shown in FIG. 10 is the same as the route of the reflux current during off-duty in low-side PWM process shown in FIG. 7.

[0119] If the stop condition is met during the execution of the high-side PWM process shown in Fig. 8, the first and second switches UH and UL of the U-phase system are both kept off during the initial transition process. Therefore, the return current flows through the same path as the return current during the off-duty period shown in Fig. 8.

[0120] In this embodiment, since non-complementary driving is performed, switches other than the switches to be PWM-driven in the PWM system are originally held off. Therefore, when non-complementary driving is performed, the process of holding off switches other than the switches to be PWM-driven may be omitted in the transition initial process.

[0121] Furthermore, the primary purpose of the transition initial process is to prevent arm short circuits from occurring in the PWM system when the first transition process is executed. To achieve this primary purpose, the transition initial process has a secondary purpose of keeping the high-side switches in the PWM system off. When low-side PWM process is being executed and non-complementary drive is being performed, the high-side switches in the PWM system are originally kept off. Therefore, when low-side PWM process is being executed and non-complementary drive is being performed, the transition initial process may be omitted. In other words, in this case, transition to the first transition process may be performed when the stop condition is met.

[0122] The time required for the initial transition process may be sufficient to achieve the main purpose of the initial transition process. That is, the time required for the initial transition process may be equal to or longer than the minimum time (e.g., several microseconds) required to keep the high-side switch in the PWM system off. The first control circuit 32 continues the initial transition process for the required time and then performs the first transition process.

[0123] As described above, the first transition process is executed if low-side PWM process is being executed when the stop condition is met. In the first transition process, the PWM-driven low-side switch is maintained on. Figure 10 shows a state in which the sixth switch WL, which is a PWM-driven low-side switch, is maintained on by the first transition process. This first transition process causes current to flow to the motor 11 through the same path as during on-duty operation.

[0124] The main purpose of the first transition process is to keep the PWM-driven low-side switch on. Therefore, the time required for the first transition process only needs to be long enough (for example, several microseconds or more) to keep the PWM-driven low-side switch on. After executing the first transition process, the first control circuit 32 performs the second transition process.

[0125] In the second transition process, all high-side switches are held off. FIG. 10 shows a state in which the first, third, and fifth switches UH, VH, and WH are held off by the second transition process. This second transition process causes a return current to flow between the motor 11 and the low side of the drive circuit 31. FIG. 10 shows a state in which the return current flows from the third terminal 11c of the motor 11 through the sixth switch WL and the second diode D2 to the motor 11. This return current path is the same as the return current path that occurs when transitioning from high-side PWM processing to initial transition processing.

[0126] The main purpose of the second transition process is to keep all high-side switches off, thereby allowing a reflux current to flow to the low side of the drive circuit 31. Therefore, the time required for the second transition process only needs to be long enough (for example, several microseconds or more) to keep all high-side switches off. After executing the second transition process, the first control circuit 32 transitions to the braking process.

[0127] In the constant speed control, one of the three high-side switches is turned on, and the other two high-side switches are kept off. Therefore, the high-side switches to be processed in the second transition process may be only the high-side switches that were kept on in the constant speed control or the PWM-driven high-side switches.

[0128] (2-5) Motor control processing The motor control process executed by the first control circuit 32 (specifically, executed by the CPU 32a) will be described with reference to Figure 11. The constant rotation control and stop control described above are performed as part of this motor control process. When the first control circuit 32 is started up, it executes the motor control process.

[0129] When the first control circuit 32 starts the motor control process, it performs initialization processing in S110. The initialization processing includes, for example, setting each port in the CPU 32a. The initial setting includes, for example, acquiring drive settings (such as the aforementioned default options) from the second control circuit 40 and setting the target rotation speed, engagement completion conditions, and the like included in the drive settings in the first control circuit 32.

[0130] In S120, the first control circuit 32 determines whether or not a drive setting has been input from the second control circuit 40. When the drive setting is changed by the user, the second control circuit 40 notifies the user of the changed drive setting. If a drive setting has not been input, the process proceeds to S140. If a drive setting has been input, the process proceeds to S130.

[0131] In S130, the first control circuit 32 executes a drive setting change process. Specifically, the first control circuit 32 updates settings such as the target rotation speed and the engagement completion condition based on the drive setting input in S120. After the process of S130 is executed, the process proceeds to S140.

[0132] In S140, the first control circuit 32 determines whether the trigger switch 8 is turned on. If the trigger switch 8 is not turned on, the process proceeds to S120. If the trigger switch 8 is turned on, the process proceeds to S150. In S150, the first control circuit 32 drives the motor 11. Specifically, the above-mentioned constant rotation control is started.

[0133] After starting the constant speed control (i.e., while the constant speed control is being executed), the first control circuit 32 determines in S160 whether the stop condition is met. If the stop condition is not met, the process proceeds to S150, where the constant speed control is continued. If the stop condition is met, the process proceeds to S170.

[0134] In S170, the first control circuit 32 executes a brake transition process. Details of the brake transition process are as shown in FIG. 12. When the first control circuit 32 starts the brake transition process, the first control circuit 32 stops the constant rotation control in S210. In S220, the first control circuit 32 executes a transition initial process. Specifically, the high-side switch and the low-side switch of the PWM system are kept off. In S230, the first control circuit 32 determines whether or not low-side PWM process was being executed when the stop condition was satisfied. If high-side PWM process was being executed when the stop condition was satisfied, the first control circuit 32 ends the brake transition process and proceeds to S180 (see FIG. 11).

[0135] If the low-side PWM process was being executed when the stop condition was met, the first control circuit 32 executes a first transition process in S240. Specifically, the PWM-driven low-side switches are kept on. In S250, the first control circuit 32 executes a second transition process. Specifically, all high-side switches are kept off. After the process of S250 is executed, the process proceeds to S180 (see FIG. 11).

[0136] In S180, the first control circuit 32 executes the braking process. Specifically, in this embodiment, the first control circuit 32 applies the short-circuit brake as described above. When the motor 11 is stopped by the braking process, the process proceeds to S190. In S190, the first control circuit 32 determines whether the trigger switch 8 is turned off. If the trigger switch 8 is turned on, the first control circuit 32 continues the braking process in S180. If the trigger switch 8 is turned off, the process proceeds to S120.

[0137] (2-6) Correspondence between the embodiments and the present disclosure The first control circuit 32 corresponds to an example of a control circuit in the present disclosure. The second diode D2 corresponds to an example of a first rectifying element in the present disclosure. The third diode D3 corresponds to an example of a second rectifying element in the present disclosure. The torque sensor 13 and the first control circuit 32 correspond to an example of a torque detection unit in the present disclosure. The constant rotation control corresponds to an example of a drive process in the present disclosure. The initial transition process corresponds to an example of a third process and a fourth process in the present disclosure. The first transition process corresponds to an example of a first process in the present disclosure. The second transition process corresponds to an example of a second process in the present disclosure. The brake process corresponds to an example of a braking process in the present disclosure.

[0138] 3. Specific Exemplary Second Embodiment The constant rotation control and stop control when complementary driving is performed will be described as a second embodiment. The second embodiment differs from the first embodiment basically in that complementary driving is performed in the constant rotation control.

[0139] In the second embodiment, the first to sixth switches UH to WL are driven according to, for example, the third drive pattern illustrated in Fig. 13 or the fourth drive pattern illustrated in Fig. 14. In Fig. 13 and Fig. 14, "(complementary)" indicates complementary driving.

[0140] In FIG. 13 , for example, during period T11, low-side PWM processing is performed. Specifically, the first switch UH is maintained on as an on-maintained high-side switch, and the sixth switch WL is PWM-driven as a PWM-driven low-side switch. Furthermore, the fifth switch WH is complementarily driven in response to the PWM driving of the sixth switch WL. The current path during this period T11 is the same as that in FIG. 7 . Note that in FIG. 7 , the fifth switch WH is turned off during off-duty, but when complementary driving is performed, the fifth switch WH is turned on for at least part of the off-duty. During off-duty and while the fifth switch WH is turned on by complementary driving, a reflux current flows through the fifth switch WH.

[0141] In FIG. 14, for example, during period T12, high-side PWM processing is performed. Specifically, the sixth switch WL is maintained on as an on-maintained low-side switch, and the first switch UH is PWM-driven as a PWM-driven high-side switch. Furthermore, the second switch UL is complementarily driven in response to the PWM driving of the first switch UH. The current path during this period T12 is the same as that in FIG. 8. Note that in FIG. 8, the second switch UL is turned off during off-duty, but when complementary driving is performed, the second switch UL is turned on for at least part of the off-duty. During off-duty and while the second switch UL is turned on by complementary driving, a reflux current flows through the second switch UL.

[0142] In the second embodiment, the motor control process (see FIGS. 11 and 12) is executed in the same manner as in the first embodiment. In the second embodiment, complementary driving is performed in S150 of the motor control process.

[0143] 4. Specific Exemplary Third Embodiment A brake transition process different from the brake transition process of the first embodiment will be described as the third embodiment. The third embodiment differs from the first embodiment basically only in the brake transition process. Fig. 15 shows an example of operation when the brake transition process is started while low-side PWM process is being executed and non-complementary driving is being performed. Fig. 15 illustrates an example in which, during low-side PWM process, the first switch UH is held on as an on-maintained high-side switch and the sixth switch WL is PWM-driven as a PWM-driven low-side switch.

[0144] In the third embodiment, when the brake transition process is started due to the satisfaction of the stop condition, the constant speed control is not stopped immediately. Even if the stop condition is satisfied, the constant speed control is continued until the transition to the first transition process is started.

[0145] In the third embodiment, when the first control circuit 32 transitions to the brake transition process due to the satisfaction of the stop condition, the first control circuit 32 waits until the switches to be PWM-driven are brought into the on-duty state by the constant rotation control. In the example of Fig. 15, the first control circuit 32 waits until the sixth switch WL, which is the PWM-driven low-side switch, is turned on by PWM driving.

[0146] When the switch to be PWM-driven enters the on-duty state, the first control circuit 32 executes a first transition process and then executes a second transition process. The content and execution time of the first and second transition processes are the same as those in the first embodiment. The brake transition process of the third embodiment does not include an initial transition process.

[0147] In the third embodiment, the motor control process (see FIG. 11) is executed in the same manner as in the first embodiment. However, the brake transition process at S170 differs from that in the first embodiment. The brake transition process of the third embodiment is shown in FIG. 16.

[0148] 16, the first control circuit 32 determines in S310 whether the currently executing PWM process is high-side PWM process or low-side PWM process. If the currently executing PWM process is high-side PWM process, the process proceeds to S340. If the currently executing PWM process is low-side PWM process, the process proceeds to S320.

[0149] In S320, the first control circuit 32 determines whether or not the motor is in an on-duty state. If the motor is in an off-duty state, the determination in S320 is repeated until the motor changes to an on-duty state. If the motor is in an on-duty state, the process proceeds to S330. The process in S330 corresponds to an example of a standby process in the present disclosure.

[0150] In S330, the first control circuit 32 executes a first transition process. Specifically, the PWM-driven low-side switch is held on. In the on-duty state, the high-side switch of the same system as the PWM-driven low-side switch is held off in both complementary driving and non-complementary driving. Therefore, there is no need to perform a process to hold the high-side switch off. However, the high-side switch may be held off in S330.

[0151] In S340, the first control circuit 32 executes a second transition process. Specifically, all high-side switches are kept off. After the process of S340 is executed, the process proceeds to S180 (see FIG. 11).

[0152] In the third embodiment, complementary driving is performed in S150 of the motor control process. 5. 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.

[0153] (5-1) The present disclosure is also applicable to cases where the drive circuit includes a circuit other than a three-phase full-bridge circuit. The drive circuit may include, for example, an H-bridge circuit. The H-bridge circuit includes four switches. For example, a circuit obtained by omitting the fifth and sixth switches WH and WL from the drive circuit 31 in FIG. 4 corresponds to an H-bridge circuit. The present disclosure is also applicable to cases where the drive circuit includes an H-bridge circuit and a motor that can be driven by the H-bridge circuit.

[0154] (5-2) The present disclosure can be applied to various types of power tools other than rechargeable screwdrivers. For example, the present disclosure may be applied to a rechargeable driver drill. Furthermore, the present disclosure is not limited to application to battery-powered power tools. For example, the present disclosure can also be applied to power tools configured to be supplied with AC power.

[0155] (5-3) Multiple functions possessed by one component in the above embodiments may be realized by multiple components, or one function possessed by one component may be realized by multiple components. Also, multiple functions possessed by multiple components may be realized by one component, or one function realized by multiple components may be realized by one component. Also, part of the configuration of the above embodiments may be omitted. Also, at least part of the configuration of the above embodiments may be added to or substituted for the configuration of another of the above embodiments. [Explanation of symbols]

[0156] 1...power tool, 8...trigger switch, 11...motor, 11a...first terminal, 11b...second terminal, 11c...third terminal, 12...drive mechanism, 13...torque sensor, 19...rotor, 25...rotational position detection unit, 30...controller, 31...drive circuit, 32...first control circuit, 50...power supply path, 61...first path, 62...second path, 63...third path, 64...fourth path, 65...fifth path, 66...sixth path, 101...battery, D1...first diode, D2...second diode, D3...third diode, D4...fourth diode, D5...fifth diode, D6...sixth diode, UH...first switch, UL...second switch, VH...third switch, VL...fourth switch, WH...fifth switch, WL...sixth switch.

Claims

1. a motor having a first terminal and a second terminal; a first path configured to connect the first terminal and a positive electrode of a DC power source; a second path configured to connect the first terminal and a negative electrode of the DC power supply; a third path configured to connect the second terminal and the positive electrode of the DC power supply; a fourth path configured to connect the second terminal and the negative electrode of the DC power supply; a first switch provided in the first path and configured to make or break the first path; a second switch provided in the second path and configured to make or break the second path; a third switch provided in the third path and configured to make or break the third path; a fourth switch provided in the fourth path and configured to make or break the fourth path; a first rectifier element connected to the second path so as to bypass the second switch and provided such that a direction from the negative electrode of the DC power supply toward the first terminal is a forward direction; A control circuit comprising: a drive process for driving the motor by supplying power from the DC power supply to the motor, the drive process including low-side PWM process for PWM driving the fourth switch while the first switch is turned on, the PWM drive periodically turning on or off the switch to be driven in accordance with a pulse width modulation signal; a first process of holding the fourth switch on in response to a stop condition for stopping the motor being satisfied during execution of the low-side PWM process; a second process of holding the first switch off after the first process is executed; a braking process of holding both the second switch and the fourth switch ON after the second process is executed; and a control circuit configured to perform A power tool comprising:

2. The power tool according to claim 1, moreover, a second rectifier element connected to the third path so as to bypass the third switch and provided such that a direction from the second terminal toward the positive electrode of the DC power supply is a forward direction; A power tool comprising:

3. The power tool according to claim 1 or 2, The control circuit further comprises: a third process of holding the third switch off before executing the first process in response to the stop condition being satisfied during execution of the low-side PWM process; is configured to run The control circuit is configured to execute the first process after executing the third process. Power tools.

4. The power tool according to claim 1 or 2, The control circuit further comprises: a waiting process of waiting until the fourth switch is turned on by the low-side PWM process before executing the first process in response to the stop condition being satisfied when the fourth switch is turned off by the low-side PWM process; is configured to run the control circuit is configured to execute the first process after executing the standby process. Power tools.

5. The power tool according to claim 3 or 4, the low-side PWM processing includes turning on the third switch during at least a part of each off period in which the fourth switch is periodically turned off by the PWM driving. Power tools.

6. The power tool according to any one of claims 1 to 5, the driving process includes high-side PWM process, and the high-side PWM process includes performing the PWM driving of the third switch while the second switch is turned on, and / or performing the PWM driving of the first switch while the fourth switch is turned on; The control circuit further comprises: a fourth process of holding off the first switch or the third switch, which is being PWM driven in the high-side PWM process, in response to the stop condition being satisfied while the high-side PWM process is being performed; is configured to run the control circuit is configured to execute the braking process while avoiding execution of the first process and the second process after executing the fourth process. Power tools.

7. The power tool according to any one of claims 1 to 6, Further, a torque detection unit configured to detect a load torque of the motor is provided, the stop condition includes that the load torque detected by the torque detection unit is equal to or greater than a threshold value. Power tools.

8. The power tool according to any one of claims 1 to 7, the motor is a brushless motor further including a third terminal; The power tool further comprises: a fifth path configured to connect the third terminal and the positive electrode of the DC power supply; a sixth path configured to connect the third terminal and the negative electrode of the DC power supply; a fifth switch provided in the fifth path and configured to make or break the fifth path; a sixth switch provided in the sixth path and configured to make or break the sixth path; A power tool comprising:

9. The power tool according to claim 8, The braking process includes keeping the second switch, the fourth switch, and the sixth switch on.

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