Power tool

Abstract

To suppress a decrease in the rotational speed of a motor caused by an increase in load torque in constant rotation control of the motor.SOLUTION: A power tool includes a motor, a speed detection unit, a torque detection unit, a control circuit, and a drive circuit. The control circuit calculates a drive command value so that the rotational speed of the motor coincides with a target rotational speed. Specifically, the control circuit calculates an initial value for the drive command value in accordance with the difference between the rotational speed of the motor detected by the speed detection unit and the target rotational speed. Further, the control circuit corrects the initial value based on load torque of the motor detected by the torque detection unit. The drive circuit supplies, to the motor, electric power according to the drive command value calculated by the control circuit.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present disclosure relates to power tools.

Background Art

[0002] Patent Document 1 discloses a power tool configured such that a motor is controlled to rotate at a constant speed by a microcomputer. In this power tool, the microcomputer detects the rotational speed of the motor based on a signal (hereinafter referred to as a "hall signal") acquired from a hall sensor. The microcomputer controls the motor based on the detected rotational speed so that the rotational speed of the motor matches a certain target speed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The hall signal is updated each time the motor rotates through a certain rotation angle. The microcomputer detects the rotational speed based on the updated hall signal each time the hall signal is updated. The microcomputer recognizes the detected rotational speed as the current rotational speed of the motor until the hall signal is updated again next time.

[0005] Therefore, during the deceleration of the motor, a situation may continuously occur where the actual rotation speed of the motor is lower than the recognized rotation speed of the microcontroller. If the recognized rotation speed of the microcontroller is higher than the actual rotation speed, there may be insufficient torque generated by the motor. Especially during low-speed rotation, the update interval of the hall signal becomes longer. Therefore, for example, when a large load is applied to the motor during low-speed rotation and the motor decelerates, a situation where the actual rotation speed is lower than the recognized rotation speed of the microcontroller may occur for a long time, resulting in insufficient torque generated by the motor and the possibility of a sudden decrease in the rotation speed of the motor or the motor locking up.

[0006] One aspect of the present disclosure aims to suppress a decrease in the rotation speed of a motor caused by an increase in load torque during constant rotation control of the motor.

Means for Solving the Problems

[0007] The power tool according to one aspect of the present disclosure includes a motor. The power tool includes an output shaft. The output shaft has a tip tool attached thereto. The output shaft is driven by receiving the rotational force of the motor. The power tool includes a speed detection unit. The speed detection unit detects the rotation speed of the motor. The power tool includes a torque detection unit. The torque detection unit detects the load torque of the motor.

[0008] The power tool includes a control circuit. The control circuit calculates a drive command value so that the rotation speed matches the target rotation speed. The drive command value indicates the power to be supplied to the motor. Specifically, the control circuit calculates the drive command value by executing an initial value calculation process and a correction process. The initial value calculation process includes calculating an initial value of the drive command value according to the difference between the detected rotation speed and the target rotation speed. The detected rotation speed is the rotation speed detected by the speed detection unit. The correction process includes correcting the initial value calculated by the initial value calculation process based on the load torque detected by the torque detection unit and calculating the corrected value as the drive command value.

[0009] The power tool is provided with a drive circuit. The drive circuit drives the motor by supplying power corresponding to a drive command value calculated by a control circuit to the motor. In such a power tool, an initial value of the drive command value is calculated according to the difference between the detected rotational speed and the target rotational speed. Although this initial value may be used as the drive command value, in the present disclosure, this initial value is corrected based on the load torque. Therefore, a drive command value considering the load torque, that is, a drive command value that more reflects (i.e., feedbacks) the actual rotation state of the motor is generated. Thereby, in the constant rotation control of the motor, it becomes possible to suppress a decrease in the rotational speed of the motor caused by an increase in the load torque.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Modes for Carrying Out the Invention

[0011] [Summary of the Embodiment] In one embodiment, the power tool may include a motor. Additionally / Alternatively, the power tool may include an output shaft. The output shaft may have a tip tool attached thereto. The output shaft is driven by receiving the rotational force of the motor. Additionally / Alternatively, the power tool may include a speed detection unit. The speed detection unit detects the rotational speed of the motor. Additionally / Alternatively, the power tool may include a torque detection unit. The torque detection unit detects the load torque of the motor. The load torque may be a torque directly applied to the motor or a torque indirectly applied to the motor. That is, the load torque referred to here is not limited to the torque directly applied to the rotor of the motor. When various operations are performed by the tip tool, a torque in a direction that obstructs the movement of the tip tool may be applied from the work object to the tip tool. This torque acts to obstruct the rotation of the output shaft and, consequently, acts to obstruct the rotation of the motor. That is, this torque is transmitted to the motor via the output shaft. The torque detection unit detects this torque as the load torque. The torque detection unit may detect the torque at any part in the torque transmission path from the output shaft to the motor. Additionally / Alternatively, the power tool may include a control circuit. The control circuit calculates a drive command value so that the rotational speed matches the target rotational speed. The drive command value indicates the power to be supplied to the motor. Additionally / Alternatively, the control circuit may execute an initial value calculation process. The initial value calculation process includes calculating an initial value of the drive command value according to the difference between the detected rotational speed and the target rotational speed. The detected rotational speed is the rotational speed detected by the speed detection unit. Additionally / Alternatively, the control circuit may execute a correction process. The correction process includes correcting the initial value calculated by the initial value calculation process based on the load torque detected by the torque detection unit. The correction process includes calculating the corrected value as the drive command value. Additionally / Alternatively, the power tool may include a drive circuit. The drive circuit drives the motor by supplying power corresponding to the drive command value calculated by the control circuit to the motor.

[0012] The output shaft may be configured such that the tip tool can be detachably attached. The initial value may be calculated in any manner based on the difference between the detected rotational speed and the target rotational speed so that the rotational speed matches the target rotational speed. For example, an initial value of a larger value may be calculated as the detected rotational speed is lower than the target rotational speed. The correction process may correct the initial value in any manner based on the load torque. The correction process may correct the initial value, for example, so that a drive command value of a larger value is calculated as the load torque is larger.

[0013] If a power tool in a certain embodiment includes the above motor, the above output shaft, the above speed detection unit, the above torque detection unit, the above control circuit, and the above drive circuit, and the control circuit executes the above initial value calculation process and correction process, such a power tool can suppress a decrease in the rotational speed of the motor caused by an increase in the load torque. Here, the "decrease in the rotational speed of the motor caused by an increase in the load torque" may more specifically mean, for example, that the difference from the target rotational speed increases due to a decrease in the rotational speed of the motor caused by an increase in the load torque. Note that the rotation (and rotational speed) of the motor more specifically means, for example, the rotation (and rotational speed) of the rotor described later.

[0014] In addition / Or, the correction process may include adding a correction value to the initial value. The correction value may increase in response to an increase in the load torque detected by the torque detection unit. If a power tool in a certain embodiment includes a control circuit that executes the above correction process, such a power tool can efficiently suppress a decrease in the rotational speed of the motor caused by an increase in the load torque.

[0015] Additionally / alternatively, the drive circuit may include a switching element provided in the power supply path. The power supply path connects the power source and the motor. Additionally / alternatively, the drive command value may be a duty ratio. Additionally / alternatively, the control circuit may execute a drive process. The drive process includes periodically turning on or off the switching element according to a pulse width modulation signal having a duty ratio. If a power tool in a certain embodiment includes the drive circuit and the control circuit having the above characteristics, in such a power tool, the control circuit can efficiently perform constant rotation control. Further, in the correction process, the control circuit corrects the initial value of the duty ratio based on the load torque. Therefore, the control circuit can easily calculate an appropriate drive command value (i.e., duty ratio) considering the load torque.

[0016] Additionally / alternatively, the control circuit may execute the correction process in response to the correction condition for executing the correction process being satisfied. Additionally / alternatively, the control circuit may avoid the correction process in response to the correction condition not being satisfied. The control circuit may further calculate a drive command value based on the initial value calculated by the initial value calculation process in response to the correction condition not being satisfied. That is, when the correction condition is not satisfied, for example, the initial value may be calculated as the drive command value. If a power tool in a certain embodiment includes the control circuit having the above characteristics, such a power tool enables effective utilization of the resources of the control circuit.

[0017] Additionally / alternatively, the correction condition may be satisfied in response to the target rotational speed being equal to or lower than a threshold value. If a power tool in a certain embodiment includes the control circuit having the above characteristics, such a power tool can suppress a decrease in the rotational speed caused by the load torque in a low-speed range where the rotational speed is likely to decrease due to the load torque.

[0018] Additionally / alternatively, the speed detection unit may include a signal output circuit. The signal output circuit outputs a signal that changes every time the rotor of the motor rotates by a certain angle. Additionally / alternatively, the speed detection unit may include a speed detection circuit. The speed detection circuit detects the rotational speed based on the signal output from the signal output circuit. If a power tool in a certain embodiment includes a speed detection unit having the above characteristics, such a power tool can suppress a decrease in rotational speed caused by an increase in load torque during the period from when the detected rotational speed is updated until it is updated again next (i.e., the period during which the rotor rotates by a certain angle) by correction processing, even if the load torque increases.

[0019] Additionally / alternatively, the control circuit may periodically repeat the correction processing at a predetermined correction execution cycle. Additionally / alternatively, the correction execution cycle may be shorter than the time required for the rotor to rotate by a certain angle when the rotor is rotating at a predetermined rotational speed or less. The torque detection unit may be configured to detect the load torque continuously (in other words, in real time) or discretely. When the load torque is detected discretely, the interval at which the load torque is detected may be shorter than the correction execution cycle. If a power tool in a certain embodiment includes a control circuit having the above characteristics, in such a power tool, in the low-speed range where the rotational speed is likely to decrease due to an increase in load torque, a decrease in rotational speed caused by an increase in load torque can be efficiently suppressed.

[0020] In addition to and / or, the control circuit may execute correction processing when the target rotational speed is equal to or lower than a threshold value. That is, the correction condition may be established according to the target rotational speed being equal to or lower than the threshold value. Further, when executing the correction processing, the control circuit may periodically repeat the correction processing at a predetermined correction execution period. In addition to and / or, the correction execution period may be shorter than the time required for the rotor to rotate by a certain angle when the rotor is rotating at a rotational speed equal to or lower than the threshold value. If a power tool in a certain embodiment includes a speed detection unit having the above signal output circuit and speed detection circuit and also includes a control circuit having the above characteristics, in such a power tool, in a speed range equal to or lower than the threshold value, a decrease in rotational speed due to an increase in load torque can be efficiently suppressed.

[0021] In addition to and / or, the signal output circuit may include a Hall sensor. In addition to and / or, a power tool in a certain embodiment may further include a rotational force transmission unit. The rotational force transmission unit transmits the rotational force of the motor to the output shaft. In addition to and / or, the torque detection unit may include a torque sensor. The torque sensor is provided on the rotational force transmission unit or the output shaft. The torque sensor outputs a signal corresponding to mechanical torsion generated in the rotational force transmission unit or the output shaft due to the load torque. In addition to and / or, the torque detection unit detects the load torque based on the signal output from the torque sensor. If a power tool in a certain embodiment includes a rotational force transmission unit and a torque detection unit having the above characteristics, such a power tool can directly (or almost directly) detect the actual load torque. Therefore, the control circuit can perform highly accurate correction processing according to the actual load torque.

[0022] Additionally / alternatively, the torque detection unit may include a current detection circuit. The current detection circuit detects the current flowing through the motor. Additionally / alternatively, the torque detection unit may include a torque detection circuit. The torque detection circuit detects the load torque based on the value of the current detected by the current detection circuit. If a power tool in a certain embodiment includes a torque detection unit having the above characteristics, such a power tool can detect the load torque without using a torque sensor.

[0023] Additionally / alternatively, the torque detection unit may detect the load torque based on the voltage drop amount at a predetermined position in the power supply path. The drop amount corresponds to the difference between the voltage at the predetermined position when no power is supplied to the motor and the voltage at the predetermined position when power is supplied to the motor. If a power tool in a certain embodiment includes a torque detection unit having the above characteristics, such a power tool can detect the load torque without using a torque sensor and / or a current detection circuit.

[0024] In a certain embodiment, the above characteristics may be combined in any way. In a certain embodiment, any of the above characteristics may be excluded. [2. Specific exemplary embodiments] Hereinafter, exemplary embodiments of the present disclosure will be described with reference to the drawings.

[0025] (2-1) Configuration of the power tool The power tool 1 of the present embodiment shown in FIGS. 1 to 3 is configured as, for example, a rechargeable screwdriver. The rechargeable screwdriver may be used, for example, to rotate fastening parts such as screws. The power tool 1 of the present embodiment is driven by the power of a battery 101 (see FIG. 4) described later.

[0026] As shown in FIGS. 1 and 2, the power tool 1 includes a main body 2. The main body 2 includes a housing 3. The housing 3 includes a first half housing 3a and a second half housing 3b that are split left and right. The first half housing 3a and the second half housing 3b are combined to form the housing 3. FIG. 3 shows the power tool 1 with the first half housing 3a removed.

[0027] The main body 2 includes a first accommodating portion 5, a grip 6, and a second accommodating portion 7. The first accommodating portion 5 accommodates a motor 11 (see FIG. 3) and a drive mechanism 12 (see FIG. 3). The first accommodating portion 5 is further provided with a direction setting switch 9 and a chuck sleeve 10.

[0028] Various tip tools (or tools) can be selectively and detachably attached to the chuck sleeve 10. Each of the various tip tools may have any function. The various tip tools may be, for example, the plus driver bit 10a illustrated in FIG. 1. The tip tool attached to the chuck sleeve 10 is driven (for example, rotated) by receiving the rotational force of the motor 11.

[0029] The motor 11 is, for example, a brushless motor in the present embodiment. 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. The rotor 19 of the present embodiment is a permanent magnet type. The rotation of the motor 11 specifically means 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 the rotational speed of the motor 11 and transmits it to the chuck sleeve 10.

[0030] The direction setting switch 9 is provided to select the rotation direction of the motor 11 (and thus the rotation direction of the chuck sleeve 10). By operating the direction setting switch 9, the user of the power tool can select the first rotation direction (e.g., forward rotation or CW (ClockWise)) or the second rotation direction (e.g., reverse rotation or CCW (Counter-ClockWise)). 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.

[0031] The direction setting switch 9 may be alternatively set to at least one of the first position and the second position, for example, by manual operation of the user. In response to the direction setting switch 9 being set to the first position, the rotation direction of the motor 11 may be set to the first rotation direction. In response to the direction setting switch 9 being set to the second position, the rotation direction of the motor 11 may be set to the second rotation direction. The rotation direction of the motor 11 corresponding to each of 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 the target rotation speed of the motor 11 (and thus the target rotation speed of the chuck sleeve 10) and / or the stop condition of 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.

[0032] The grip 6 extends from the first housing portion 5. The grip 6 is gripped by the user, for example. The grip 6 is provided with a trigger switch 8. While gripping the grip 6, the user can manually operate (e.g., pull) the trigger switch 8. Pulling the trigger switch 8 corresponds to moving the trigger switch 8 in the left direction (or pushing it into the main body 2) in FIG. 3 in this embodiment.

[0033] The trigger switch 8 is turned on by being manually operated. The trigger switch 8 is turned off when it is not manually operated. The trigger switch 8 outputs a trigger detection signal. The trigger detection signal indicates whether the trigger switch 8 is off. The trigger detection signal may further indicate the amount of operation when the trigger switch 8 is manually operated.

[0034] The second housing portion 7 extends from the grip 6. The battery pack 100 is detachably attached to the bottom of the second housing portion 7. As shown in FIG. 3, the second housing portion 7 houses the controller 30.

[0035] As shown in FIG. 3, the first housing portion 5 is further provided with a torque sensor 13. The torque sensor 13 is provided for detecting the load torque directly or indirectly applied to the motor 11. When various operations are performed by the tip tool attached to the chuck sleeve 10, the motor 11 receives the load torque from the work object via the tip tool, the chuck sleeve 10, and the drive mechanism 12. The torque sensor 13 outputs a signal (hereinafter referred to as "torque detection signal") corresponding to this load torque.

[0036] The torque sensor 13 may be provided at a position where the load torque can be detected. The torque sensor 13 may be provided, for example, on the chuck sleeve 10 or the drive mechanism 12. In the present embodiment, the torque sensor 13 is provided on the drive mechanism 12, for example. The torque sensor 13 may generate the torque detection signal in any manner (for example, by any principle). Also, the torque detection signal may be a signal in any form. The torque sensor 13 of the present embodiment generates, for example, an analog voltage corresponding to the mechanical torsional amount of a shaft (not shown) for transmitting the rotation of the motor 11 to the chuck sleeve 10. This voltage is output as the torque detection signal.

[0037] The torque sensor 13 of the present embodiment outputs a torque detection signal corresponding to the actual load torque (i.e., corresponding to the actual torsional amount of the shaft) in real time (i.e., continuously). 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).

[0038] (2-2) Electrical Configuration of the Power Tool The electrical configuration of the power tool 1 will be supplementarily described with reference to FIG. 4. FIG. 4 shows the power tool 1 with the battery pack 100 attached to the main body 2.

[0039] 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 a secondary battery different from a lithium-ion battery.

[0040] The power tool 1 includes the aforementioned motor 11, trigger switch 8, direction setting switch 9, torque sensor 13, display unit 16, and input I / F 17. "I / F" is an abbreviation for interface.

[0041] The motor 11 is driven by battery power supplied from the battery 101 via a drive circuit 31 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.

[0042] The motor 11 includes a first winding 21, a second winding 22, and a third winding 23. In the present 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. The 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.

[0043] The electric 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, 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 described later.

[0044] The rotational position detection unit 25 of the present 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 at an angle corresponding to 120 degrees in the electrical angle along the rotational direction of the rotor 19 with the rotational axis of the rotor 19 as the center.

[0045] The first hall sensor 26 has a first hall element (not shown) and outputs a first position signal Hu. The first position signal Hu changes according to the relative positional relationship between the first hall sensor 26 (specifically, the first hall element) and the rotor 19. The second hall sensor 27 has a second hall element (not shown) and outputs a second position signal Hv. The second position signal Hv changes according to the relative positional relationship between the second hall sensor 27 (specifically, the second hall element) and the rotor 19. The third hall sensor 28 has a third hall element (not shown) and outputs a third position signal Hw. The third position signal Hw changes according to the relative positional relationship between the third hall sensor 28 (specifically, the third hall element) and the rotor 19.

[0046] In the present embodiment, the first to third position signals Hu, Hv, and Hw are each binary digital signals. That is, the first to third position signals Hu, Hv, and Hw are each set to a high level or a low level. The level of each of the first to third position signals Hu, Hv, and Hw changes every time the rotor 19 rotates by an angle corresponding to 180 degrees in the electrical angle. Also, the first to third position signals Hu, Hv, and Hw have a phase difference of 120° from each other. Therefore, in the present embodiment, every time the rotor 19 rotates by 60° in the electrical angle, the level of any one of the first to third position signals Hu, Hv, and Hw changes.

[0047] The electric power tool 1 further includes a controller 30. When the battery pack 100 is mounted on the main body 2, the controller 30 is electrically connected to the battery 101 through the power supply path 50. The controller 30 is supplied with the power of the battery 101 (hereinafter referred to as "battery power") from the battery 101 through 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.

[0048] The controller 30 includes a drive circuit 31. The drive circuit 31 is connected to the 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 the input battery power and supplies it to the motor 11.

[0049] The drive circuit 31 of the present 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 switch. In the present 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).

[0050] The drive circuit 31 includes the aforementioned first to sixth paths 61 to 66. 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). Note that the path from the first terminal 11a to the positive electrode of the battery may be regarded 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). Note that the path from the first terminal 11a to the negative electrode of the battery may be regarded 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). Note that the path from the second terminal 11b to the positive electrode of the battery may be regarded 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). Note that the path from the second terminal 11b to the negative electrode of the battery may be regarded 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). Note that the path from the third terminal 11c to the positive electrode of the battery may be regarded 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). Note that the path from the third terminal 11c to the negative electrode of the battery may be regarded as the sixth path 66.

[0051] The first switch UH is provided in the first path 61. The first switch UH turns on when it receives the first drive signal from the first control circuit 32 and turns off when it does not receive the first drive signal. The first path 61 conducts through the first switch UH when the first switch UH is on. The first path 61 is blocked by the first switch UH when the first switch UH is off. A first diode D1 is connected between the source and the drain of the first switch UH.

[0052] The second switch UL is provided in the second path 62. The second switch UL turns on when receiving the second drive signal from the first control circuit 32, and turns off when not receiving the second drive signal. The second path 62 conducts through the second switch UL when the second switch UL is on. The second path 62 is blocked by the second switch UL when the second switch UL is off. A second diode D2 is connected between the source and the drain of the second switch UL.

[0053] The third switch VH is provided in the third path 63. The third switch VH turns on when receiving the third drive signal from the first control circuit 32, and turns off when not receiving the third drive signal. The third path 63 conducts through the third switch VH when the third switch VH is on. The third path 63 is blocked by the third switch VH when the third switch VH is off. A third diode D3 is connected between the source and the drain of the third switch VH.

[0054] The fourth switch VL is provided in the fourth path 64. The fourth switch VL turns on when receiving the fourth drive signal from the first control circuit 32, and turns off when not receiving the fourth drive signal. The fourth path 64 conducts through the fourth switch VL when the fourth switch VL is on. The fourth path 64 is blocked by the fourth switch VL when the fourth switch VL is off. A fourth diode D4 is connected between the source and the drain of the fourth switch VL.

[0055] The fifth switch WH is provided in the fifth path 65. The fifth switch WH turns on when receiving the fifth drive signal from the first control circuit 32, and turns off when not receiving the fifth drive signal. The fifth path 65 conducts through the fifth switch WH when the fifth switch WH is on. The fifth path 65 is blocked by the fifth switch WH when the fifth switch WH is off. A fifth diode D5 is connected between the source and the drain of the fifth switch WH.

[0056] The sixth switch WL is provided in the sixth path 66. The sixth switch WL turns on when receiving the sixth drive signal from the first control circuit 32, and turns off when not receiving the sixth drive signal. The sixth path 66 conducts through the sixth switch WL when the sixth switch WL is on. The sixth path 66 is blocked by the sixth switch WL when the sixth switch WL is off. A sixth diode D6 is connected between the source and drain of the sixth switch WL.

[0057] 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 the first and second switches UH and UL and the first and second paths 61 and 62. The V-phase system includes the third and fourth switches VH and VL and the third and fourth paths 63 and 64. The W-phase system includes the fifth and sixth switches WH and WL and the fifth and sixth paths 65 and 66.

[0058] 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 (hereinafter referred to as the "motor current value"). The current detection unit 33 of the present embodiment 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 corresponding to the current flowing through the negative electrode path 52 (hereinafter referred to as the "current detection signal"). The current detection signal indicates the value of the current flowing through the negative electrode path 52. The current detection signal of the present embodiment has a voltage value corresponding to the value of the current flowing through the negative electrode path 52. The current detection signal is input to the first control circuit 32.

[0059] The controller 30 includes a voltage detection unit 34. The voltage detection unit 34 is provided to detect the voltage value at a predetermined voltage detection point Pv in the power supply path 50. In this embodiment, the voltage detection point Pv exists, for example, within the controller 30. The voltage detection point Pv may be provided in the vicinity of the drive circuit 31 in the positive electrode path 51 within the controller 30. The voltage detection unit 34 outputs a signal corresponding to the voltage at the voltage detection point Pv (hereinafter referred to as the "voltage detection signal"). The voltage detection signal indicates the value of the voltage at the voltage detection point Pv. The voltage detection signal is input to the first control circuit 32.

[0060] 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 have a semiconductor memory such as a ROM, RAM, NVRAM, or flash memory. That is, the first control circuit 32 of this embodiment includes a microcomputer.

[0061] The first control circuit 32 realizes various functions by executing a program stored in a non-transitory tangible recording medium. In this embodiment, the memory 32b corresponds to the non-transitory tangible recording medium storing the program. In this embodiment, the memory 32b stores programs for motor control processing (see FIG. 7) and duty ratio calculation processing (see FIG. 8) described later.

[0062] 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 hardware components. For example, instead of or in addition to the microcomputer, the first control circuit 32 may include a logic circuit including a plurality of electronic components, may include an application-specific integrated circuit such as an ASIC and / or an ASSP, or may include a programmable logic device such as an FPGA capable of constructing an arbitrary logic circuit.

[0063] The first control circuit 32 receives rotational position information (i.e., the first to third position signals Hu, Hv, Hw) from the rotational position detector 25. Each time the level of any one of the first to third position signals Hu, Hv, Hw changes (i.e., each 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 from the timing of the previous level change and / or the timing of the level change further before that to the timing of the current level change.

[0064] More specifically, in this embodiment, each time the level of any one of the first to third position signals Hu, Hv, Hw changes, an interrupt (hereinafter referred to as "Hall sensor interrupt") enters the process of the CPU 32a. When receiving the Hall sensor interrupt, the CPU 32a calculates the rotational speed of the motor 11. Then, until the Hall sensor interrupt enters again, the calculated rotational speed is recognized as the current rotational speed of the motor 11. In the following description, the "recognized rotational speed" means the rotational speed calculated upon receiving the Hall sensor interrupt. That is, in this embodiment, the recognized rotational speed is updated each time the Hall sensor interrupt enters (i.e., each time the rotor 19 rotates by an electrical angle of 60°).

[0065] The first control circuit 32 receives a trigger detection signal from the trigger switch 8. The first control circuit 32 can detect whether the trigger switch 8 is on based on the trigger detection signal.

[0066] The first control circuit 32 receives a direction setting signal from the direction setting switch 9. The first control circuit 32 can detect which of the first rotation direction and the second rotation direction is selected based on the direction setting signal.

[0067] 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 in which the actual load torque is reflected in real time. Therefore, the first control circuit 32 can detect the actual load torque in real time.

[0068] The controller 30 includes a power supply circuit 35. Battery power is input from the battery 101 to the power supply circuit 35. 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 part within the controller 30 including the first control circuit 32. The first control circuit 32 operates by the power supply power. In the present embodiment, the power supply power is also supplied to the rotation position detection unit 25 and is used for generating the aforementioned first to third position signals Hu, Hv, and Hw.

[0069] 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. The input I / F 17 of the present embodiment includes, for example, four switches. The display unit 16 can display various images, texts, and the like.

[0070] The second control circuit 40 determines drive settings used for driving 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 fastening completion condition, and the like. In the present embodiment, as will be described later, constant rotation control is performed. In the constant rotation control, the motor 11 is controlled so that the rotation speed of the motor 11 matches the target rotation speed.

[0071] The fastening completion condition is a condition for stopping the rotating motor 11. More specifically, the fastening completion condition is a condition for starting the braking process of the motor. The braking process is control for stopping the rotation of the motor 11. When the braking process is performed by the first control circuit 32, the rotation of the motor 11 is stopped.

[0072] In this embodiment, when the trigger switch 8 is turned on, the motor 11 starts rotating. Then, when the stop condition is satisfied during the rotation of the motor 11, the braking process is started. The stop condition is satisfied, for example, in this embodiment, when the trigger switch 8 is turned off or when the above-described fastening completion condition is satisfied. Therefore, when the fastening completion condition is satisfied during the rotation of the motor 11, even if the trigger switch 8 is turned on, the stop condition is satisfied and the braking process is started, whereby the motor 11 is stopped.

[0073] The fastening completion condition may be determined in any way. In this embodiment, the fastening completion condition includes, for example, a target torque, a driving time, and / or a fastening rotation angle. When the fastening completion condition includes, for example, a target torque, the fastening completion condition is satisfied when the load torque reaches the target torque after the start of rotation of the motor 11. When the fastening completion condition includes, for example, a driving time, the fastening completion condition is satisfied when the driving time has elapsed since the start of rotation of the motor 11. When the fastening completion condition includes, for example, a target torque and a driving time, the fastening completion condition is satisfied when the load torque reaches the target torque or when the driving time has elapsed since the start of rotation after the start of rotation of the motor 11.

[0074] The user can select various setting items individually or collectively via the input I / F 17. When the various setting items selected by the user are determined as the drive settings, the second control circuit 40 notifies the first control circuit 32 of the determined drive settings.

[0075] The user may, for example, select one of the first to N target rotational speeds as the target rotational speed. "N" is a natural number of 2 or more. Each of the first to N target rotational speeds may be, for example, a rotational speed within the range of 20,000 rpm to 1,000 rpm. At least one of the first to N target rotational speeds may be equal to or less than a threshold value. The threshold value may be, for example, 5,000 rpm.

[0076] 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 each include the first to Nth target rotational speeds. The user can select any one of the options via the input I / F 17. When an option is selected by the user, the second control circuit 40 determines the selected option as the drive setting and notifies the first control circuit 32 of the drive setting. Also, in this embodiment, one specific option is set as the default option. When starting up, as initial processing after startup, the second control circuit 40 determines the default option as the drive setting and notifies the first control circuit 32.

[0077] (2-3) Constant Rotation Control When the trigger switch 8 is turned on, the first control circuit 32 rotates the motor 11 in the rotation direction set by the direction setting switch 9 by executing constant rotation control.

[0078] Specifically, the first control circuit 32 acquires the aforementioned drive setting from the second control circuit 40. The drive setting includes the target rotational speed. The first control circuit 32 controls the power supplied from the drive circuit 31 to the motor 11 so that the rotational speed of the motor 11 matches the target rotational speed.

[0079] The constant rotation control of this embodiment includes rotational speed feedback control and torque feedback control. In the following description, "feedback" is abbreviated as "FB" for short. The rotational speed FB control is performed by, for example, proportional-integral control in this embodiment. The torque FB control is performed by, for example, proportional control in this embodiment.

[0080] In the rotational speed FB control, an initial value calculation process is performed. Specifically, an initial value of the drive command value is calculated so that the rotational speed of the motor 11 matches the target rotational speed. The drive command value indicates the power to be supplied to the motor 11. The drive command value in this embodiment includes a duty ratio. This duty ratio is hereinafter referred to as the "drive duty ratio". That is, the initial value calculation process is, in other words, a process of calculating the initial value of the drive duty ratio. In the initial value calculation process, the initial value of the drive duty ratio is calculated according to the difference between the aforementioned recognized rotational speed calculated based on the rotational position information and the target rotational speed (hereinafter referred to as the "speed difference"). For example, the initial value may be calculated such that the drive duty ratio increases as the speed difference increases. The initial value corresponds to the sum of the speed difference proportional duty ratio SPDu and the speed difference integral duty ratio SIDu, which will be described later.

[0081] In the torque FB control, a correction process is performed. Specifically, the initial value calculated in the rotational speed FB control is corrected based on the load torque detected based on the torque detection signal. One of the main purposes of the correction process is to prevent the rotational speed of the motor 11 from dropping below the target speed or the motor 11 from stopping due to an increase in the load torque.

[0082] That is, in this embodiment, the recognized rotational speed is updated every time the motor 11 rotates by a certain rotational angle (for example, a rotational angle corresponding to an electrical angle of 60° in this embodiment). Therefore, if, for example, a large load torque is applied after the recognized rotational speed is updated at a certain timing and the rotational speed of the motor 11 drops significantly from the recognized rotational speed, the first control circuit 32 regards the rotational speed of the motor 11 as the recognized rotational speed. Therefore, although the situation actually requires increasing the drive duty ratio, a sufficient drive duty ratio corresponding to the actual rotational speed is not calculated. As a result, the output torque of the motor 11 is insufficient, the difference from the target rotational speed becomes large, and ultimately the motor 11 may stop.

[0083] Particularly during low-speed rotation, the update interval of the recognized rotation speed becomes longer. Therefore, for example, when a large load torque is applied to the motor 11 during low-speed rotation and the motor 11 decelerates, a situation where the actual rotation speed is lower than the recognized rotation speed may occur for a long time. Furthermore, the difference between the actual rotation speed and the recognized rotation speed may also increase over time. Therefore, particularly during low-speed rotation, there is a high possibility that the rotation speed of the motor 11 will suddenly decrease or the motor 11 will lock due to the load torque.

[0084] Therefore, in the present embodiment, in addition to the rotation speed FB control, torque FB control is performed to calculate a more appropriate drive duty ratio corresponding to the load torque. In the correction process, for example, the initial value is corrected so that the drive duty ratio increases as the load torque increases. Specifically, in the present embodiment, a correction value is calculated and added to the initial value. The correction value corresponds to the torque proportional duty ratio TPDu described later. The correction value increases as the load torque increases.

[0085] Note that the torque FB control may be always performed during the constant rotation control execution. However, in the present embodiment, it is performed when the correction condition is satisfied. When the correction condition is not satisfied, the torque FB control is not performed. In this case, the initial value calculated by the rotation speed FB control is calculated as the drive duty ratio. When the correction condition is satisfied, the initial value corrected by the torque FB control is calculated as the drive duty ratio.

[0086] The correction condition may be set in any way. For example, the correction condition may be satisfied when the target rotation speed is set to be equal to or lower than the above-mentioned threshold value. The first control circuit 32 periodically repeats the calculation of the drive duty ratio at a predetermined control period. The control period is shorter than the time required for the rotor 19 to rotate by a certain rotation angle when the rotor 19 is rotating at a speed equal to or lower than a predetermined rotation speed. That is, the control period is shorter than the update interval of the recognized rotation speed (in other words, the interval of hall sensor interrupts) when the rotor 19 is rotating at a speed equal to or lower than a predetermined rotation speed. The predetermined rotation speed may be the same as or different from the above-described threshold value. The control period is shorter than the update interval of the recognized rotation speed when the motor 11 is rotating at the maximum value of the target rotation speed at which the correction condition is satisfied. More specifically, the control period may be 1 / 2 or less of the update interval.

[0087] In the constant rotation control, the first control circuit 32 calculates the drive duty ratio for each control period and drives the drive circuit 31 based on the calculated drive duty ratio. The first control circuit 32 drives the drive circuit 31 by low-side PWM processing and / or high-side PWM processing.

[0088] The low-side PWM processing includes PWM driving any one of the low-side switches (hereinafter referred to as "PWM-driven low-side switch") of a system different from the system to which any one of the three high-side switches (hereinafter referred to as "high-side switch maintained on") belongs while maintaining any one of the three high-side switches on.

[0089] The "high-side switch" refers to each of the first, third, and fifth switches UH, VH, and WH. The "three high-side switches" mean the first, third, and fifth switches UH, VH, and WH. The "low-side switch" refers to each of the second, fourth, and sixth switches UL, VL, and WL. The "three low-side switches" mean the second, fourth, and sixth switches UL, VL, and WL.

[0090] PWM drive means periodically turning on and off the switch to be driven (here, the PWM drive low-side switch) according to a pulse-width modulation signal. The pulse-width modulation signal has the drive duty ratio described above. That is, PWM drive indicates driving the switch to be driven by a pulse-width modulation signal having the calculated drive duty ratio.

[0091] High-side PWM processing includes PWM-driving any one of the high-side switches (hereinafter referred to as "PWM drive high-side switch") of a system different from the system to which the low-side switch (hereinafter referred to as "on-maintained low-side switch") belongs, while maintaining any one of the three low-side switches in the on state.

[0092] When the first control circuit 32 functions the first switch UH as the on-maintained high-side switch, the first control circuit 32 outputs a first drive signal for maintaining the first switch UH in the on state to the first switch UH. When the first control circuit 32 functions the first switch UH as the PWM drive high-side switch, the first control circuit 32 outputs the above-described pulse-width modulation signal as the first drive signal to the first switch UH. The same applies to the cases where the third and fifth switches VH and WH function as the on-maintained high-side switch or the PWM drive high-side switch, respectively.

[0093] When the first control circuit 32 functions the second switch UL as the on-maintained low-side switch, the first control circuit 32 outputs a second drive signal for maintaining the second switch UL in the on state to the second switch UL. When the first control circuit 32 functions the second switch UL as the PWM drive low-side switch, the first control circuit 32 outputs the above-described pulse-width modulation signal as the second drive signal to the second switch UL. The same applies to the cases where the fourth and sixth switches VL and WL function as the on-maintained low-side switch or the PWM drive low-side switch, respectively.

[0094] When the first control circuit 32 is configured to perform low-side PWM processing, the motor 11 is rotated while appropriately switching the combination of the on-maintaining high-side switch and the PWM-driven low-side switch according to the rotational position (i.e., the rotation angle) of the motor 11.

[0095] When the first control circuit 32 is configured to perform high-side PWM processing, the motor 11 is rotated while appropriately switching the combination of the on-maintaining low-side switch and the PWM-driven high-side switch according to the rotational position (i.e., the rotation angle) of the motor 11.

[0096] The first control circuit 32 may rotate the motor 11 while appropriately switching between low-side PWM processing and high-side PWM processing. (2-4) Example of execution of constant rotation control including torque FB control Referring to FIG. 5, an example of the rotational speed, rotational position information, load torque, and drive duty ratio of the motor 11 when constant rotation control including torque FB control is being executed is shown. As illustrated in FIG. 5, the load torque begins to increase at time t1. Therefore, immediately after time t1, the actual rotational speed of the motor (i.e., the actual rotational speed) decreases from the target rotational speed. As a result, the update interval of the rotational position information (i.e., the update interval of the recognized rotational speed) also becomes longer. For example, after the rotational position information is updated at time t1, the interval until the next update at time t2 becomes longer. Therefore, the difference between the recognized rotational speed and the actual rotational speed widens between time t1 and time t2.

[0097] However, by torque FB control, correction of the drive duty ratio according to the load torque is performed for each control cycle. Therefore, even if the difference between the target rotational speed and the recognized rotational speed does not change, the drive duty ratio increases (specifically, the correction value increases) as the load torque increases. As a result, the motor 11 can output torque corresponding to the increase in the load torque. As a result, although the difference between the actual rotational speed and the target rotational speed temporarily increases from time t1, due to the effect of torque FB control, for example, the decrease in the actual rotational speed stops around time t2. And even if the load torque continues to increase, the decrease in the actual rotational speed is suppressed, and the actual rotational speed approaches the target rotational speed.

[0098] FIG. 6 shows an example of the rotational speed, rotational position information, load torque, and drive duty ratio of the motor 11 when torque FB control is not performed for comparison with FIG. 5. As illustrated in FIG. 6, when the load torque starts to increase at time t1, the actual rotational speed of the motor decreases from the target rotational speed. As a result, the update interval of the rotational position information also becomes longer. However, until the rotational position information is updated, the recognized rotational speed does not change, and thus the drive duty ratio also does not change. The drive duty ratio is updated at the update timing of the rotational position information, such as times t2 and t3. Therefore, the increase in the drive duty ratio cannot catch up with the decrease in the actual rotational speed, and an appropriate torque corresponding to the load torque is not output from the motor 11. Therefore, the actual rotational speed decreases as the load torque increases.

[0099] (2-5) Motor control process With reference to FIG. 7, the motor control process executed by the first control circuit 32 (specifically, executed by the CPU 32a) will be described. The aforementioned constant rotational speed control is performed in this motor control process. When starting up, the first control circuit 32 executes the motor control process.

[0100] When the first control circuit 32 starts the motor control process, at S110, it performs initialization processing. The initialization processing includes, for example, the setting of each port in the CPU 32a. The initial setting includes, for example, obtaining a drive setting (such as the aforementioned default option) from the second control circuit 40 and setting the target rotation speed, fastening completion condition, etc. included in the drive setting in the first control circuit 32.

[0101] At S120, the first control circuit 32 determines whether 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 changed drive setting. If the drive setting has not been input, this process proceeds to S140. If the drive setting has been input, this process proceeds to S130.

[0102] At S130, the first control circuit 32 executes drive setting change processing. Specifically, based on the drive setting input at S120, the settings such as the target rotation speed and fastening completion condition in the first control circuit 32 are updated. After the execution of the process at S130, this process proceeds to S140.

[0103] At S140, the first control circuit 32 determines whether the trigger switch 8 is turned on. If the trigger switch 8 is not turned on, this process proceeds to S120. If the trigger switch 8 is turned on, this process proceeds to S150. At S150, the first control circuit 32 drives the motor 11. Specifically, the aforementioned constant rotation control is started. During the execution of the constant rotation control, the duty ratio calculation process shown in FIG. 8 is performed in parallel.

[0104] After starting the constant rotation control (i.e., during the execution of the constant rotation control), at S160, the first control circuit 32 determines whether the stop condition is satisfied. If the stop condition is not satisfied, this process proceeds to S150 and the constant rotation control continues. If the stop condition is satisfied, this process proceeds to S170.

[0105] In S170, the first control circuit 32 ends the constant rotation control and executes the braking process. Specifically, in this embodiment, for example, a short-circuit brake is applied. The short-circuit brake means short-circuiting any two or all of the first to third terminals 11a to 11c of the motor 11 via the drive circuit 31. Specifically, with all high-side switches fixed in the off state, any two or three low-side switches are fixed in the on state.

[0106] When the motor 11 stops due to the braking process, this process proceeds to S180. In S180, the first control circuit 32 determines whether the trigger switch 8 is off. If the trigger switch 8 is on, the first control circuit 32 continues the braking process in S170. If the trigger switch 8 is off, this process proceeds to S120.

[0107] (2-6) Duty ratio calculation process Referring to FIG. 8, the duty ratio calculation process executed by the first control circuit 32 (specifically, executed by the CPU 32a) will be described. While driving the motor 11 in S150 of FIG. 7 (that is, while executing the constant rotation control), the first control circuit 32 executes the duty ratio calculation process in parallel with the constant rotation control (for example, in multitasking). The first control circuit 32 periodically repeats the duty ratio calculation process at the aforementioned control cycle.

[0108] When the first control circuit 32 starts the duty ratio calculation process, it calculates the speed difference in S210. The speed difference is calculated by subtracting the recognized rotation speed from the target rotation speed. In S220, the first control circuit 32 calculates a speed difference proportional duty ratio SPDu and a speed difference integral duty ratio SIDu based on the speed difference calculated in S210. The speed difference proportional duty ratio SPDu is a duty ratio calculated by a proportional control operation based on the speed difference. To put it very simply, for example, the speed difference proportional duty ratio SPDu is calculated so as to include a component proportional to the speed difference. The speed difference integral duty ratio SIDu is a duty ratio calculated by an integral control operation based on the speed difference. To put it very simply, for example, the speed difference integral duty ratio SIDu is calculated so as to include a component corresponding to the integral value of the speed difference. That is, S220 corresponds to a process corresponding to so-called proportional-integral control. Also, S220 corresponds to a process corresponding to rotational speed FB control.

[0109] In S230, the first control circuit 32 determines whether or not a correction condition is satisfied. If the correction condition is not satisfied, this process proceeds to S260. If the correction condition is satisfied, this process proceeds to S240.

[0110] In S240, the first control circuit 32 acquires the current load torque. For example, the first control circuit 32 calculates the load torque based on the torque detection signal input from the torque sensor 13 at the current time, and acquires that load torque as the current load torque.

[0111] In S250, the first control circuit 32 calculates a torque proportional duty ratio TPDu based on the load torque acquired in S240. The torque proportional duty ratio TPDu is a duty ratio calculated by a proportional control operation based on the load torque. To put it very simply, for example, the torque proportional duty ratio TPDu is calculated so as to include a component proportional to the load torque. That is, S250 corresponds to a process corresponding to so-called proportional control. Also, S250 corresponds to a process corresponding to torque FB control.

[0112] In S260, the first control circuit 32 calculates the drive duty ratio. The drive duty ratio is obtained, for example, by adding the speed difference proportional duty ratio SPDu calculated in S220, the speed difference integral duty ratio SIDu calculated in S220, and the torque proportional duty ratio TPDu calculated in S250. In the process of S260, the process of adding the speed difference proportional duty ratio SPDu and the speed difference integral duty ratio SIDu corresponds to the above-described initial value calculation process. In S260, the process of further adding the torque proportional duty ratio TPDu corresponds to the above-described correction process.

[0113] Note that when the correction condition is not satisfied in S230, that is, when the torque proportional duty ratio TPDu is not calculated, in S260, the value obtained by adding the speed difference proportional duty ratio SPDu and the speed difference integral duty ratio SIDu (that is, the above-described initial value) is calculated as the drive duty ratio. The process of S260 in this case corresponds to the above-described initial value calculation process.

[0114] In S270, the drive duty ratio used in the constant rotation control is updated to the drive duty ratio calculated in S260. (2-7) Correspondence relationship between the embodiment and the present disclosure The chuck sleeve 10 corresponds to an example of the output shaft in the present disclosure. The drive mechanism 12 corresponds to an example of the rotational force transmission unit in the present disclosure. The torque sensor 13 and the first control circuit 32 correspond to an example of the torque detection unit in the present disclosure. The rotational position detection unit 25 and the first control circuit 32 correspond to an example of the speed detection unit in the present disclosure. The first control circuit 32 corresponds to an example of the control circuit in the present disclosure. Each of the first to sixth switches UH to WL corresponds to an example of the switching element in the present disclosure. The PWM drive corresponds to an example of the drive process in the present disclosure. The rotational position detection unit 25, or each of the first to third hall sensors 26 to 28 corresponds to an example of the signal output circuit in the present disclosure. The first control circuit 32 corresponds to an example of the speed detection circuit and the torque detection circuit in the present disclosure. The control period corresponds to an example of the correction execution period in the present disclosure.

[0115] The process of S260 corresponds to an example of the initial value calculation process and the correction process in the present disclosure. When the addition of the torque proportional duty ratio TPDu is not performed in S260, the process of S260 corresponds to an example of the initial value calculation process in the present disclosure.

[0116] [3. Other Embodiments] As described above, the embodiments of the present disclosure have been described. However, the present disclosure is not limited to the above-described embodiments and can be implemented with various modifications.

[0117] (3-1) The first control circuit 32 may obtain the load torque in any manner. For example, the first control circuit 32 may detect the load torque based on the current detection signal input from the current detection unit 33 (that is, based on the motor current value). The motor current value generally changes according to the load torque. That is, as the load torque increases, the motor current value also increases. Therefore, the load torque can be calculated (or estimated) based on the motor current value. Thus, in the process of S240 in FIG. 8, the first control circuit 32 may calculate the load torque based on the current detection signal and obtain the calculated load torque. In this case, the torque sensor 13 may be omitted from the power tool 1. Conversely, if the torque sensor 13 is provided, the current detection unit 33 may be omitted.

[0118] For example, the first control circuit 32 may also detect the load torque based on the voltage detection signal input from the voltage detection unit 34 (that is, based on the voltage value at the voltage detection point Pv). The voltage value at the voltage detection point Pv can vary according to the load torque. That is, the power supply path 50 includes a resistance component. The path from the positive electrode of the battery 101 to the voltage detection point Pv also includes a resistance component. Therefore, when current flows from the battery 101 to the motor 11, the voltage at the voltage detection point Pv will strictly be lower than the voltage at the positive electrode of the battery 101. The potential difference between the positive electrode of the battery 101 and the voltage detection point Pv (that is, the voltage drop amount from the positive electrode of the battery 101 to the voltage detection point Pv) increases as the current supplied to the motor 11 increases. Therefore, the load torque can be calculated (or estimated) based on the voltage value at the voltage detection point Pv. Specifically, for example, based on the voltage value at the voltage detection point Pv when no current is flowing from the battery 101 to the motor 11 as a reference, the current load torque can be calculated (or estimated) based on the difference between the reference voltage value and the current voltage value at the voltage detection point Pv. Thus, in the process of S240 in FIG. 8, the first control circuit 32 may calculate the load torque based on the voltage detection signal and obtain the calculated load torque. In this case too, the torque sensor 13 may be omitted from the power tool 1. Conversely, if the torque sensor 13 is provided, the voltage detection unit 34 may be omitted.

[0119] (3-2) The torque sensor 13 may be configured to generate a torque detection signal based on any principle. The torque detection signal may have any form. The torque detection signal may be an analog signal or a digital signal. The torque detection signal may not be continuous and may be output discretely (for example, periodically). However, in this case, the output period of the torque detection signal is shorter than the update period of the rotational position information.

[0120] (3-3) In the constant rotation control, the rotational speed FB control may be performed by a control method different from the proportional-integral control. The torque FB control may also be performed by a control method different from the proportional control.

[0121] (3-4) The rotational position detection unit 25 may be configured in any way and may output rotational position information in any form. For example, the rotational position detection unit 25 may include a type of sensor different from a Hall sensor. The rotational position detection unit 25 may include, for example, a rotary encoder. The rotational position information may change in any way according to the rotational position of the rotor 19. The rotational position information may include any kind of signal. The rotational position information may include one or more digital signals or one or more analog signals.

[0122] (3-5) The first control circuit 32 may detect the rotational speed of the motor 11 without using the rotational position detection unit 25. For example, the voltages (specifically, the induced voltages) of the first to third terminals 11a to 11c of the motor 11 may be detected, and the rotational position of the motor 11 may be detected based on those voltages. Then, the rotational speed may be calculated based on the change in the rotational position detected in such a manner.

[0123] (3-6) The present disclosure is applicable to various types of power tools different from rechargeable screwdrivers. For example, the present disclosure may be applied to a rechargeable driver drill. Further, the present disclosure is not limited to the application to power tools powered by a battery. The present disclosure is applicable to, for example, power tools configured to be supplied with alternating current power.

[0124] (3-7) A plurality of functions of one component in the above embodiment may be realized by a plurality of components, or one function of one component may be realized by a plurality of components. Also, a plurality of functions of a plurality of components may be realized by one component, or one function realized by a plurality of components may be realized by one component. Further, a part of the configuration of the above embodiment may be omitted. Also, at least a part of the configuration of the above embodiment may be added to or replaced with the configuration of another of the above embodiments.

Description of Reference Numerals

[0125] 1... Electric tool, 8... Trigger switch, 10... Chuck sleeve, 11... Motor, 12... Drive mechanism, 13... Torque sensor, 19... Rotor, 25... Rotation position detection unit, 26... First Hall sensor, 27... Second Hall sensor, 28... Third Hall sensor, 30... Controller, 31... Drive circuit, 32... First control circuit, 33... Current detection unit, 34... Voltage detection unit, 50... Power supply path, 101... Battery, UH... First switch, UL... Second switch, VH... Third switch, VL... Fourth switch, WH... Fifth switch, WL... Sixth switch.

Claims

1. A motor, An output shaft to which a tip tool is attached and which is configured to be driven by receiving the rotational force of the motor, A speed detection unit configured to detect the rotational speed of the rotor each time the rotor of the motor rotates by a certain angle, A torque detection unit configured to detect the load torque of the motor, At each calculation timing that repeatedly arrives at a predetermined control period, (i) A calculation process for calculating a drive command value indicating the electric power to be supplied to the motor so that the rotational speed of the rotor matches the target rotational speed according to the difference between the rotational speed detected by the speed detection unit and the target rotational speed, (ii) A correction process for correcting the drive command value calculated by the calculation process based on the load torque detected by the torque detection unit so that the value becomes larger as the load torque becomes larger, A control circuit configured to execute, A drive circuit configured to drive the motor by supplying drive power, which is electric power corresponding to the drive command value corrected by the correction process, to the motor, Comprising, The control period is shorter than the time required for the rotor to rotate by the certain angle when the rotor is rotating at a rotational speed equal to or lower than a predetermined threshold value, The torque detection unit is configured to detect the load torque continuously or discretely at intervals shorter than the control period, An electric tool.

2. The electric tool according to claim 1, The correction process includes adding a correction value to the drive command value calculated by the calculation process, and the correction value increases in accordance with an increase in the load torque detected by the torque detection unit. An electric tool.

3. The electric tool according to claim 1 or claim 2, The drive circuit includes a switching element provided in a power supply path connecting a power source and the motor, The drive command value is a duty ratio, The control circuit is further configured to execute a drive process of periodically turning on or off the switching element according to a pulse width modulation signal having the duty ratio. An electric tool.

4. The electric tool according to any one of claims 1 to 3, The control circuit, at the calculation timing, Executes the correction process in response to the correction condition for executing the correction process being satisfied. ​ configured to avoid the correction process in response to the correction condition not being satisfied, and the drive circuit is configured to supply the drive power corresponding to the drive command value calculated by the calculation process to the motor when the correction process is avoided. An electric tool. **Claim 5** The electric tool according to claim 4, wherein the correction condition is satisfied in response to the target rotational speed being less than or equal to the threshold value. **Claim 6** The electric tool according to any one of claims 1 to 5, wherein the speed detection unit includes a signal output circuit configured to output a signal that changes each time the rotor rotates by the fixed angle, and a speed detection circuit configured to detect the rotational speed based on the signal output from the signal output circuit. An electric tool comprising the above. **Claim 7** The electric tool according to claim 6, wherein the signal output circuit includes a Hall sensor. **Claim 8** The electric tool according to any one of claims 1 to 7, further comprising a rotational force transmission unit configured to transmit the rotational force of the motor to the output shaft, wherein the torque detection unit includes a torque sensor provided on the rotational force transmission unit or the output shaft, the torque sensor being configured to output a signal corresponding to mechanical torsion generated in the rotational force transmission unit or the output shaft by the load torque, and a torque detection circuit configured to detect the load torque based on the signal output from the torque sensor. An electric tool comprising the above. **Claim 9** The electric tool according to any one of claims 1 to 7, wherein the torque detection unit includes a current detection circuit configured to detect the current flowing through the motor, and a torque detection circuit configured to detect the load torque based on the value of the current detected by the current detection circuit. An electric tool comprising the above. **Claim 10** The electric tool according to any one of claims 1 to 7, wherein the drive circuit is configured such that the power supply power, which is the power of the power source, is input from the power source via a first power path, the drive power is generated from the input power supply power, and the generated drive power is supplied to the motor via a second power path. An electric tool configured as above. The torque detection unit is configured to detect the load torque based on the voltage drop amount at a predetermined portion in the first power path in a state where a voltage corresponding to the power supply power is applied from the power source to the first power path, and the drop amount corresponds to the difference between the voltage at the predetermined portion when the drive power is not supplied from the drive circuit to the motor and the voltage at the predetermined portion when the drive power is supplied from the drive circuit to the motor. Electric tool.

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