Reciprocating tool, and method for controlling electric motor in reciprocating tool

Abstract

To provide a technique capable of suppressing halt of a reciprocating member at an improper place when battery voltage reduces in a reciprocating tool.SOLUTION: A reciprocating tool includes a reciprocating member, an electric motor, a transmission device, a drive circuit and a control circuit. The transmission device transmits driving force of the electric motor to the reciprocating member at least in the stroke of the reciprocating member from a second dead point to a first dead point. The drive circuit supplies motor current from a battery to the electric motor in accordance with a received drive signal, to drive the electric motor. Upon establishment of a first condition, the control circuit adjusts the drive signal so that the drive circuit continues to drive the electric motor with reduced motor current. The first condition is established when (i) the drive circuit drives the electric motor and (ii) the battery voltage is lower than a first threshold voltage.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present disclosure relates to a reciprocating tool. [Background technology]

[0002] The following Patent Document 1 discloses a power tool configured to stop the motor when the battery voltage falls below a first threshold voltage while the motor is operating, regardless of the operating state of the trigger switch. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5564690 Summary of the Invention [Problem to be solved by the invention]

[0004] In a reciprocating tool such as an electric nail gun, if the battery voltage falls below a first threshold voltage while the motor is operating and the motor is stopped, a reciprocating member such as a screwdriver may stop in an inappropriate position.

[0005] Therefore, an object of one aspect of the present disclosure is to provide a technique that can prevent a reciprocating member from stopping at an inappropriate position when the battery voltage drops in a reciprocating tool. [Means for solving the problem]

[0006] In this disclosure, terms such as "first" and "second" are intended only to distinguish elements from one another and are not intended to limit the order or number of elements. Thus, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element. In addition, a first element may be included without a second element, and similarly, a second element may be included without a first element.

[0007] One aspect of the present disclosure provides a reciprocating tool including a reciprocating member, an electric motor, a transmission device, a drive circuit, and a control circuit. The reciprocating member is configured to reciprocate between a first dead center and a second dead center.

[0008] The electric motor is configured to generate a driving force. The transmission device is configured to transmit the driving force of the electric motor to the reciprocating member at least during the stroke of the reciprocating member from the second dead center to the first dead center.

[0009] The drive circuit is configured to (i) receive a drive signal for driving the electric motor, and (ii) supply a motor current from the battery to the electric motor in accordance with the received drive signal, thereby driving the electric motor.

[0010] The control circuit is configured to (i) output a drive signal to the drive circuit, and (ii) adjust the drive signal in response to the first condition being satisfied so that the drive circuit reduces the motor current and continues to drive the electric motor.

[0011] The first condition is satisfied when (i) the drive circuit drives the electric motor and (ii) the battery voltage is lower than a first threshold voltage. The battery voltage is output from the battery. The first threshold voltage is lower than the rated voltage of the battery.

[0012] In the reciprocating tool configured in this manner, even if the battery voltage falls below the first threshold voltage while the electric motor is being driven, the electric motor can continue to be driven. Therefore, in this reciprocating tool, the reciprocating member can be prevented from stopping at an inappropriate position when the battery voltage drops.

[0013] Another aspect of the present disclosure is a method for controlling an electric motor in a reciprocating tool, the method comprising: a drive signal for driving the electric motor is output to a drive circuit of the reciprocating tool, and the drive circuit is configured to supply a motor current from a battery to the electric motor in accordance with the drive signal to drive the electric motor; transmitting a driving force of an electric motor to a reciprocating member of a reciprocating tool, the reciprocating member being configured to reciprocate between a first dead center and a second dead center, and the driving force being transmitted at least from the second dead center to the first dead center; (i) the electric motor is being driven, and (ii) in response to the battery voltage being lower than a threshold voltage, the drive circuit adjusts the drive signal to reduce the motor current and continue to drive the electric motor, the battery voltage being output from the battery, and the threshold voltage being lower than the rated voltage of the battery. The present invention provides a method comprising:

[0014] According to this method, in the reciprocating tool, it is possible to prevent the reciprocating member from stopping at an inappropriate position when the battery voltage drops. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is an external view of a reciprocating tool according to an exemplary embodiment; [Figure 2] FIG. 2 is a central longitudinal cross-sectional view of the reciprocating tool. [Figure 3A-3B] 3A is a cross-sectional view taken along line IIIA-IIIA in FIG. 1, and FIG. 3B is a top view of the reciprocating tool including a perspective view of a motor housing portion. [Figures 4A-4D] 1 shows one sequence of mechanical movements in a reciprocating tool. [Figures 5A-5E] 1 illustrates the movement of the holder corresponding to one sequence of mechanical movements in a reciprocating tool. [Figure 6] FIG. 2 is a circuit diagram showing an electrical configuration of the reciprocating tool. [Figure 7] 4 is a timing chart showing an outline of the electrical operation of the reciprocating tool. [Figure 8]10 is a timing chart showing an outline of a low-voltage driving operation. [Figure 9] 10 is a timing chart showing another outline of the low-voltage driving operation. [Figure 10] 4 is a flowchart showing a flow of a main routine executed by a control circuit. [Figure 11] 4 is a flowchart showing the flow of a motor control process executed by a control circuit. [Figure 12] 10 is a flowchart showing the flow of a drive process executed by a control circuit. [Figure 13] 10 is a flowchart showing the flow of a low-voltage drive determination process executed by a control circuit. [Figure 14A] 10 is a flowchart illustrating a part of an output duty ratio setting process executed by a control circuit. [Figure 14B] 10 is a flowchart showing the remaining flow of the output duty ratio setting process. DETAILED DESCRIPTION OF THE INVENTION

[0016] 1. Overview of the embodiment Some embodiments may provide a reciprocating tool comprising at least one of the following: Feature 1: A reciprocating member configured to reciprocate between a first dead center and a second dead center; Feature 2: an electric motor configured to generate a driving force; Feature 3: A transmission device configured to transmit the driving force of the electric motor to the reciprocating member at least during the stroke of the reciprocating member from the second dead center to the first dead center; Feature 4: A drive circuit configured to (i) receive a drive signal for driving an electric motor, and (ii) supply a motor current from a battery to the electric motor in accordance with the received drive signal to drive the electric motor; Feature 5: A control circuit configured (or programmed) to (i) output a drive signal to a drive circuit, and (ii) adjust the drive signal in response to the first condition being satisfied, such that the drive circuit reduces the motor current and continues to drive the electric motor; Feature 6: the first condition is satisfied when (i) the drive circuit drives the electric motor, and (ii) the battery voltage is lower than a first threshold voltage; Feature 7: The battery voltage is output from the battery; and Feature 8: The first threshold voltage is lower than the rated voltage of the battery.

[0017] In a reciprocating tool having at least features 1 to 8, even if the battery voltage falls below the first threshold voltage while the electric motor is being driven, the electric motor can continue to be driven, thereby preventing the reciprocating member from stopping in an inappropriate position.

[0018] Examples of reciprocating tools include electric nail guns, electric rebar tying machines, electric rebar cutting machines, electric oilers, and electric air pumps. Examples of electric oilers include electric grease guns. Examples of electric motors include DC motors, AC motors, and stepper motors. Examples of DC motors include brushless DC motors and brushed DC motors.

[0019] Examples of drive circuits include full-bridge circuits and half-bridge circuits. In some embodiments, the control circuitry may be integrated into a single electronic unit or a single electronic device or a single circuit board.

[0020] In some embodiments, the control circuit may be a combination of two or more electronic circuits or two or more electronic units or two or more electronic devices individually provided on or within the reciprocating tool.

[0021] In some embodiments, the control circuitry may comprise a microcomputer (or microcontroller or microprocessor), hardwired logic, an application specific integrated circuit (ASIC), an application specific general purpose product (ASSP), a programmable logic device (PLD) (e.g., a field programmable gate array (FPGA)), discrete electronic components, and / or combinations thereof.

[0022] Some embodiments may include at least one of the following in addition to or instead of at least one of features 1-8: Feature 9: A power supply circuit configured to generate a power supply voltage for operating a control circuit based on a battery voltage; Feature 10: the first threshold voltage is set higher than the second threshold voltage so that the battery voltage exceeds the second threshold voltage when the control circuit adjusts the drive signal in response to the first condition being satisfied; and Feature 11: The second threshold voltage corresponds to a lower limit of the battery voltage required for the power supply circuit to generate the power supply voltage.

[0023] In a reciprocating tool having at least features 1 to 11, it is possible to prevent the battery voltage from falling below the second threshold voltage while the electric motor is running, causing the control circuit to stop operating and the reciprocating member to stop in an inappropriate position.

[0024] Some embodiments may include at least one of the following in addition to or instead of at least one of features 1-11: Feature 12: The drive signal is in the form of a pulse width modulated signal having an output duty cycle; and Feature 13: The drive circuit is configured to supply a motor current based on the output duty ratio to the electric motor.

[0025] In a reciprocating tool having at least the features 1 to 8, 12, and 13, the motor current can be adjusted by adjusting the output duty ratio. Some embodiments may include, in addition to or instead of at least one of features 1-13, the following: Feature 14: The control circuit is configured (or programmed) to, in response to the first condition being satisfied, reduce the output duty ratio to a duty ratio capable of driving the reciprocating member.

[0026] In a reciprocating tool having at least the features 1 to 8 and 12 to 14, the output duty ratio can be reduced to such a duty ratio, allowing the electric motor to continue to be driven.

[0027] Some embodiments may include at least one of the following in addition to or instead of at least one of features 1-14: Feature 15: The control circuit is configured (or programmed) to gradually increase the output duty cycle at a predetermined rate over time in response to the second condition being satisfied; Feature 16: The second condition is satisfied when (i) the drive circuit drives the electric motor, and (ii) the battery voltage changes from a first magnitude to a second magnitude; Feature 17: The first magnitude is less than a first threshold voltage; and Feature 18: The second magnitude is equal to or greater than the first threshold voltage.

[0028] In a reciprocating tool having at least the features 1 to 8 and 12 to 18, when the second condition is met, the battery voltage can increase while preventing an excessive motor current from flowing through the electric motor.

[0029] Some embodiments may include at least one of the following in addition to or instead of at least one of features 1-18: Feature 19: The control circuit is configured (or programmed) to set the output duty ratio to the lower limit duty ratio when the first condition is satisfied; and Feature 20: The lower limit duty ratio corresponds to the duty ratio at which the electric motor generates the minimum driving force required to drive the reciprocating member.

[0030] In a reciprocating tool having at least the features 1 to 8, 12 to 14, and 20, the motor current flowing from the battery to the electric motor can be quickly reduced without stopping the reciprocating member, and as a result, the battery voltage can be quickly increased.

[0031] Some embodiments may include at least one of the following in addition to or instead of at least one of features 1-20: Feature 21: The control circuit is configured (or programmed) to gradually decrease the output duty cycle at a predetermined rate over time in response to the establishment of the third condition; and Feature 22: The third condition is met in response to the battery voltage falling below the first threshold voltage again after the output duty ratio is set to the lower limit duty ratio.

[0032] In a reciprocating tool including at least the features 1 to 8, 12 to 14, and 20 to 22, the motor current can be gradually reduced when the battery voltage falls below the first threshold voltage again.

[0033] Some embodiments may include at least one of the following in addition to or instead of at least one of features 1-22: Feature 23: The control circuit is configured (or programmed) to inhibit output of a drive signal for an n-th drive of the electric motor (n is an integer equal to or greater than 2) in response to the fourth condition being satisfied; Feature 24: The fourth condition is satisfied when (i) the battery voltage falls below the third threshold voltage before the (n-1)th driving of the electric motor (n is an integer equal to or greater than 2), and (ii) the battery voltage falls below the fourth threshold voltage during the (n-1)th driving of the electric motor; Feature 25: the third threshold voltage is higher than the first threshold voltage; and Feature 26: The fourth threshold voltage is (i) higher than the first threshold voltage and (ii) lower than the third threshold voltage.

[0034] In a reciprocating tool having at least the features 1 to 8 and 23 to 26, if the fourth condition is met in the (n-1)th driving of the electric motor, the nth driving of the electric motor can be prohibited.

[0035] Some embodiments may include at least one of the following in addition to or instead of at least one of features 1-26: Feature 27: The control circuit is configured (or programmed) to permit output of a drive signal for driving the electric motor an n-th time (n is an integer of 2 or greater) in response to the fifth condition being satisfied; and Feature 28: The fifth condition is satisfied when the battery voltage exceeds the third threshold voltage before the (n-1)th driving of the electric motor (n is an integer of 2 or more).

[0036] In a reciprocating tool having at least the features 1 to 8 and 23 to 28, if the fifth condition is met in the (n-1)th driving of the electric motor, the nth driving of the electric motor can be executed.

[0037] Some embodiments may include, in addition to or instead of at least one of features 1-28: Feature 29: The transmission device includes a reducer (i) having a preset reduction ratio, and (ii) configured to convert the driving force of the electric motor into a reduced output and transmit the reduced output to the reciprocating member.

[0038] In a reciprocating tool having at least Features 1 to 8 and 29, the reciprocating member can be driven at least from the second dead center to the first dead center with a torque proportional to the reduction ratio of the reducer, so that even if the motor current is significantly reduced while the electric motor is running, the reciprocating member can continue to be driven.

[0039] Examples of reducers include gear reducers. Examples of gear reducers include parallel-axis gear reducers, right-angle-axis gear reducers, and concentric-axis gear reducers. Examples of concentric-axis gear reducers include planetary gear reducers.

[0040] Some embodiments may include at least one of the following in addition to or instead of at least one of features 1-29: Feature 30: A first manual switch configured to be manually operated by a user of the reciprocating tool; and Feature 31: The control circuit is configured (or programmed) to output a drive signal to the drive circuit in response to manual operation of at least the first manual switch.

[0041] Some embodiments may include at least one of the following in addition to or instead of at least one of features 1-31: Feature 32: A pressing member configured to be pressed against the workpiece by a user; Feature 33: A second manual switch configured to be manually operated by the pressing member being pressed against the workpiece; and Feature 34: The control circuit is configured (or programmed) to output a drive signal to the drive circuit based on whether both the first manual switch and the second manual switch are manually operated.

[0042] In a reciprocating tool having at least features 1 to 8 and 30 to 34, the electric motor can be prevented from being accidentally driven when the pressing member is not pressed against the workpiece, that is, when the user is not processing the workpiece.

[0043] Some embodiments may include at least one of the following in addition to or instead of at least one of features 1-34: · Feature 35: A cylinder (or chamber) containing compressed gas within it; Feature 36: (i) a piston within the cylinder, (ii) urging the reciprocating member toward the second dead center by compressed gas; and Feature 37: The reciprocating member is configured to be driven by the piston from the first dead center to the second dead center.

[0044] In a reciprocating tool having at least Features 1-8 and 35-37, the reciprocating member can be moved from the first dead center to the second dead center by pressure applied to the piston from the compressed gas.

[0045] Examples of compressed gases include compressed air and compressed inert gases. Compressed air may be compressed dry air. Examples of compressed inert gases include compressed nitrogen gas and compressed noble gases.

[0046] Some embodiments may include, in addition to or instead of at least one of features 1-37, the following: Feature 38: The reciprocating member is configured to (i) be positioned at a first dead center in response to the piston being positioned at its top dead center, and (ii) be positioned at a second dead center in response to the piston being positioned at its bottom dead center.

[0047] In a reciprocating tool including at least 1 to 8 and 35 to 38, the maximum pressure of the compressed gas is applied to the reciprocating member, causing the reciprocating member to move from the first dead center to the second dead center. In addition, the reciprocating member moving from the second dead center to the first dead center can be decelerated by the pressure of the compressed gas.

[0048] Some embodiments may include at least one of the following in addition to or instead of at least one of features 1-38: Feature 39: The transmission device includes a cam, (i) having an outer periphery with a plurality of pins arranged in a circumferential direction of the cam, and (ii) configured to rotate by the driving force of the electric motor; Feature 40: The reciprocating member (i) extends between a first dead point and a second dead point, (ii) includes a plurality of racks in its extending direction, and (iii) is configured to be driven from the second dead point to the first dead point by the plurality of racks engaging with each of the plurality of pins.

[0049] In a reciprocating tool having at least Features 1 to 8, 39, and 40, the reciprocating member can be moved by a cam from at least the second dead center to the first dead center. Some embodiments may include, in addition to or instead of at least one of features 1-40: Feature 41: A battery mounting section configured to allow a battery to be removably mounted.

[0050] An embodiment may provide a method comprising at least one of the following: Feature 42: A drive signal for driving the electric motor of the reciprocating tool is output to a drive circuit of the reciprocating tool; Feature 43: The drive circuit is configured to supply a motor current from the battery to the electric motor according to the drive signal to drive the electric motor; Feature 44: Transmitting the driving force of the electric motor to the reciprocating member of the reciprocating tool; Feature 45: The reciprocating member is configured to reciprocate between a first dead center and a second dead center; · Feature 46: The driving force is transmitted at least from the second dead center to the first dead center; Feature 47: (i) the electric motor is being driven, and (ii) in response to the battery voltage being lower than the threshold voltage, the drive circuit adjusts the drive signal to reduce the motor current and continue to drive the electric motor; Feature 48: The battery voltage is output from the battery; and · Feature 49: The threshold voltage is lower than the rated voltage of the battery.

[0051] According to the method including at least the features 41 to 49, in a reciprocating tool, it is possible to prevent the reciprocating member from stopping at an inappropriate position when the battery voltage drops.

[0052] In some embodiments, features 1-49 may be combined in any manner. In some embodiments, any of features 1-49 may be omitted. 2. Specific Exemplary Embodiments A specific exemplary embodiment is described below: This specific exemplary embodiment provides a reciprocating tool 1 as shown in FIG.

[0053] The terms "upper," "lower," "front," "rear," "left," and "right" used in the following description or drawings are used merely to facilitate easy understanding of the structure of the reciprocating tool 1 and are not intended to limit the orientation of the reciprocating tool 1. The reciprocating tool 1 can be oriented in any direction. 2-1. Overall structure of reciprocating tool 1, the reciprocating motion tool 1 in this embodiment is an electric nail gun configured to drive nails into a workpiece. Examples of nails used in the reciprocating motion tool 1 include staples, pin nails, finish nails, and brad nails. In another embodiment, the reciprocating motion tool 1 may be any other type of reciprocating motion tool, such as an electric rebar tying machine, an electric rebar cutting machine, an electric oiler, or an electric air pump.

[0054] The reciprocating tool 1 includes a housing 2. The housing 2 includes a driving assembly receptacle 3 extending from the rear end of the housing 2 to the front end (i.e., in the direction in which the nail is ejected). The reciprocating tool 1 includes an ejection section 4 in front of the driving assembly receptacle 3. The ejection section 4 includes a guide 5 configured to guide the nail ejected from the reciprocating tool 1 to the workpiece. In this embodiment, the guide 5 protrudes from inside the driving assembly receptacle 3 to the front of the reciprocating tool 1. The ejection section 4 includes a pressing member (or contact) 6 configured to be pressed against the workpiece. The pressing member 6 is disposed above the guide 5 and protrudes furthest forward of the reciprocating tool 1. The ejection section 4 includes a link mechanism 7 connected to the pressing member 6.

[0055] The housing 2 has a grip 8 extending downward from approximately the center of the driving assembly receiving portion 3. The grip 8 is configured to be held with one hand of a user of the reciprocating tool 1. The grip 8 has a trigger 9 on its upper front side. The trigger 9 is configured to be pulled by a finger (e.g., index finger) of the user.

[0056] The housing 2 includes a motor housing 10 extending downward from the front of the driving assembly housing 3. The housing 2 includes a battery attachment section 11 extending from the lower end of the motor housing 10 to the lower end of the grip 8. The battery attachment section 11 is configured so that a battery pack 12 can be detachably attached to the battery attachment section 11.

[0057] The reciprocating tool 1 includes a magazine 13 on the left side of the housing 2, the magazine 13 extending from the bottom of the guide 5 to the bottom end of the reciprocating tool 1. The magazine 13 is configured to feed one or more nails stored therein one by one into the guide 5. In this embodiment, the magazine 13 is inclined backward.

[0058] As shown in FIG. 2, the driving assembly housing 3 houses a driving assembly 14 configured to drive nails. The driving assembly 14 includes a cylinder 15 extending from the rear end of the driving assembly housing 3 to a generally central portion thereof. The cylinder 15 contains compressed gas therein. In this embodiment, the compressed gas is compressed dry air. In other embodiments, the compressed gas may be compressed inert gas, such as compressed nitrogen gas or compressed noble gas.

[0059] The cylinder 15 has a piston 16 therein. The piston 16 is configured to be able to move between the rear end and the front end of the cylinder 15 while sealing the cylinder 15. The driving assembly 14 has a bumper 17 at the front end of the cylinder 15. The bumper 17 is configured to receive the piston 16 when it reaches the front end of the cylinder 15 and stop the piston 16.

[0060] The driving assembly 14 includes a reciprocating member (or driver) 18 that passes through a bumper 17 and is connected to the piston 16. The reciprocating member 18 extends from the piston 16 toward the tip of the guide 5. The reciprocating member 18 is configured to move toward the tip of the guide 5 by pressure applied to the piston 16 by compressed gas. In other words, the piston 16 urges the reciprocating member 18 toward the tip of the guide 5 by the compressed gas. In this embodiment, the reciprocating member 18 has a length such that (i) the tip of the reciprocating member 18 reaches the tip of the guide 5 when the piston 16 reaches the front end of the cylinder 15 (i.e., the bottom dead center of the piston 16), and (ii) the tip of the reciprocating member 18 retracts into the driving assembly housing 3 when the piston 16 reaches the rear end of the cylinder 15 (i.e., the top dead center of the piston 16).

[0061] The link mechanism 7 of the injection unit 4 includes a spring 19 in the driving assembly housing 3. The link mechanism 7 is configured to urge the pressing member 6 forward by the spring 19, and to move the pressing member 6 toward the rear of the reciprocating tool 1 in response to the tip of the pressing member 6 being pressed against the workpiece.

[0062] The driving assembly accommodating portion 3 accommodates a contact switch 20 above the reciprocating member 18. The contact switch 20 is configured to be pressed (i.e., turned on) by the link mechanism 7 when the pressing member 6 is pressed against the workpiece.

[0063] The grip 8 houses a trigger switch 21. The trigger switch 21 is configured to be pressed (i.e., turned on) when the trigger 9 is pulled. The trigger switch 21 is configured to be turned off when the user's finger is released from the trigger 9.

[0064] The battery mounting section 11 houses a connector 22 configured to be detachably connected to the battery pack 12 mounted on the battery mounting section 11. The battery mounting section 11 houses a controller 23 above the connector 22.

[0065] The motor housing 10 houses an electric motor 24 in its lower portion. In this embodiment, the electric motor 24 is a three-phase brushless DC motor. In other embodiments, the electric motor 24 may be a one-phase brushless DC motor, a two-phase brushless DC motor, a four or more phase brushless DC motor, a brushed DC motor, an AC motor, or a stepping motor.

[0066] The motor accommodating section 10 accommodates a transmission device 25 above the electric motor 24. The transmission device 25 is connected to a rotor 26 of the electric motor 24 and is configured to (i) transmit the driving force of the electric motor 24 to the reciprocating member 18.

[0067] More specifically, the transmission device 25 includes a reducer 27 that (i) has a preset reduction ratio and (ii) is configured to convert the driving force of the electric motor 24 into a reduced output and transmit it to the reciprocating member 18. Therefore, the transmission device 25 can transmit a torque proportional to the reduction ratio of the reducer to the reciprocating member 18. In this embodiment, the reducer 27 is a concentric shaft gear reducer, more specifically, a planetary gear reducer. In another embodiment, the reducer 27 may be a parallel shaft gear reducer or a right-angle shaft gear reducer, depending on the structure of the transmission device 25.

[0068] 3A, the transmission device 25 includes a cam 28 above the reducer 27. In this embodiment, the cam 28 is disk-shaped. The cam 28 includes first to ninth pins 29a to 29i arranged on its outer periphery along the circumferential direction. The cam 28 is configured to rotate upon receiving the output of the reducer 27. More specifically, the cam 28 rotates counterclockwise around the rotor 26 of the electric motor 24 when viewed from above the reciprocating tool 1.

[0069] The reciprocating member 18 is provided with first to ninth racks 30a to 30i on its right side. The first to ninth racks 30a to 30i are aligned in a row in the direction in which the reciprocating member 18 extends. The first to ninth racks 30a to 30i correspond to the first to ninth pins 29a to 29i, respectively. The first to ninth pins 29a to 29i engage with the first to ninth racks 30a to 30i, respectively, and transmit the driving force of the electric motor 24 to the reciprocating member 18.

[0070] As shown in FIG. 3B , the transmission device 25 includes a holder 31 above the cam 28. In this embodiment, the holder 31 is disk-shaped. The holder 31 is made of a non-magnetic material. The holder 31 includes a first magnet 32 ​​on its upper surface. In this embodiment, the first magnet 32 ​​is disposed on the upper surface of the holder 31 with its south pole facing radially outward from the holder 31. In another embodiment, the first magnet 32 ​​may be disposed on the upper surface of the holder 31 with its north pole facing radially outward from the holder 31.

[0071] The holder 31 has a second magnet 33 on its upper surface. In this embodiment, the second magnet 33 is arranged on the upper surface of the holder 31 so that its north pole faces radially outward from the holder 31. In another embodiment, the second magnet 33 may be arranged on the upper surface of the holder 31 so that its south pole faces radially outward from the holder 31.

[0072] The holder 31 is configured to rotate by receiving the output of the reducer 27. More specifically, the holder 31 rotates counterclockwise together with the cam 28 around the rotor 26 of the electric motor 24 when viewed from above the reciprocating tool 1.

[0073] The motor housing 10 is provided with a Hall IC 34 on its right inner wall. The Hall IC 34 faces the outer periphery of the holder 31. The Hall IC 34 is configured to (i) detect the south pole of the first magnet 32 ​​when the first magnet 32 ​​approaches the Hall IC 34, and (ii) detect the north pole of the second magnet 33 when the second magnet 33 approaches the Hall IC 34.

[0074] The housing 2 is provided with a main power switch 36 at its rear upper left side, which is configured to be pressed by a user to power the reciprocating tool 1 on or off.

[0075] The housing 2 includes a mode selection switch 37 adjacent to the main power switch 36. The mode selection switch 37 is configured to be pressed by a user to select an operating mode of the reciprocating tool 1.

[0076] The housing 2 is provided with a first indicator 38 between the main power switch 36 and the mode selection switch 37. The first indicator 38 is lit (i) when the reciprocating tool 1 is set to a single-shot mode, which will be described later, or (ii) when a malfunction occurs in the reciprocating tool 1.

[0077] The housing 2 is provided with a second indicator 39 adjacent to the first indicator 38. The second indicator 39 is lit when (i) the reciprocating tool 1 is set to a repeat mode, which will be described later, or (ii) a malfunction occurs in the reciprocating tool 1. 2-2. Mechanical operation of reciprocating tools 2-2-1. Mechanical operation of reciprocating members and cams 4A to 4D, the operation of the reciprocating member 18 and the cam 28 will be described. In many cases, when processing a workpiece, a user uses the reciprocating tool 1 with the front end of the reciprocating tool 1 facing downward, and therefore, in FIGS. 4A to 4D, the front end of the reciprocating tool 1 faces downward.

[0078] As shown in FIG. 4A, the reciprocating member 18 is normally held in a standby position. The standby position is set just before the top dead center of the reciprocating member 18. In this embodiment, the standby position is a position where the reciprocating member is stopped, and also a position where the reciprocating member waits for its next reciprocating motion. At the standby position, the first to eighth pins 29a to 29h of the cam 28 are disengaged from the first to eighth racks 30a to 30h of the reciprocating member 18, and only the ninth pin 29i of the cam 28 is engaged with the ninth rack 30i of the reciprocating member 18. At this time, the piston 16 is positioned just before its top dead center.

[0079] When the electric motor 24 is driven to rotate the cam 28 counterclockwise, the reciprocating member 18 is driven from the standby position to its top dead center, as shown in Fig. 4B. At this time, the piston 16 also reaches its top dead center.

[0080] When the reciprocating member 18 reaches its top dead center and the ninth pin 29i disengages from the ninth rack 30i, the reciprocating member 18 is driven to its bottom dead center by the compressed gas pressure applied by the piston 16, as shown in FIG. 4C. As a result, the nail fed into the guide 5 is struck by the reciprocating member 18 and driven into the workpiece. When the reciprocating member 18 reaches its bottom dead center, the piston 16 also reaches its bottom dead center. The cam 28 continues to rotate even after the ninth pin 29i disengages from the ninth rack 30i, and the first to ninth pins 29a to 29i re-engage with the first to ninth racks 30a to 30i, respectively. Then, as shown in FIG. 4D, the reciprocating member 18 returns to the standby position, and the cam 28 is stopped. 2-2-2.Mechanical operation of the holder When electric motor 24 is driven, holder 31 rotates together with cam 28 as shown in Figures 5A to 5E. Figures 5A to 5C and 5E correspond to Figures 4A to 4D, respectively. Figure 5D shows the rotational position of holder 31 when cam 28 is located between (i) the rotational position of cam 28 shown in Figure 4C and (ii) the rotational position of cam 28 shown in Figure 4D.

[0081] The Hall IC 34 includes a first Hall element 34a. In this embodiment, the first Hall element 34a is configured to detect the south pole of the first magnet 32. In another embodiment, when the first magnet 32 ​​is disposed on the upper surface of the holder 31 with its north pole facing radially outward from the holder 31, the first Hall element 34a may be configured to detect the north pole of the first magnet 32.

[0082] The Hall IC 34 includes a second Hall element 34b. In this embodiment, the second Hall element 34b is configured to detect the north pole of the second magnet 33. In another embodiment, when the second magnet 33 is disposed on the upper surface of the holder 31 with its south pole facing radially outward from the holder 31, the second Hall element 34b may be configured to detect the south pole of the second magnet 33.

[0083] The first magnet 32 ​​is disposed in front of the second magnet 33 in the rotation direction of the holder 31 (counterclockwise direction in FIGS. 5A to 5E). More specifically, as shown in FIG. 5D, the first magnet 32 ​​is arranged on the upper surface of the holder 31 so that its south pole faces the first hall element 34a when preparations to stop the cam 28 begin.

[0084] As shown in Figures 5A and 5E, the second magnet 33 is arranged on the upper surface of the holder 31 so that its north pole faces the second Hall element 34b when the reciprocating member 18 is in the standby position. 2-3. Electrical configuration of reciprocating tools As shown in FIG. 6, the electric motor 24 includes first to third coils 24a to 24c, each associated with one of the three phases (i.e., U-phase, V-phase, and W-phase) of the electric motor 24. The first to third coils 24a to 24c are configured to be sequentially excited to generate a rotating magnetic field. In this embodiment, the first to third coils 24a to 24c form a delta connection. In another embodiment, the first to third coils 24a to 24c may form a star connection (or a Y-connection). The rotor 26 (i) includes a first pole 26a and a second pole 26b, and (ii) is configured to rotate when the first pole 26a and the second pole 26b receive the rotating magnetic field generated by the first to third coils 24a to 24c.

[0085] The electric motor 24 includes a rotational position detector 24d. The rotational position detector 24d is configured to output first to third pulse signals (or square wave signals) to the controller 23 in accordance with the rotational position of the rotor 26. In this embodiment, the rotational position detector 24d is a Hall sensor. In this embodiment, each of the first to third pulse signals inverts from positive (or HIGH) to negative (or LOW) or from negative (or LOW) to positive (or HIGH) every time the rotor 26 rotates through 180 electrical degrees. The first to third pulse signals have a phase difference of 60 electrical degrees from one another. In another embodiment, the rotational position detector 24d may be configured to output one pulse signal to the controller 23 every time the rotor 26 rotates through 60 electrical degrees, instead of the first to third pulse signals. In yet another embodiment, the rotational position detector 24d may be configured to output first to third sine wave signals to the controller 23, instead of the first to third pulse signals. In this case, the controller 23 may include a waveform conversion circuit configured to convert the first to third sine wave signals into first to third pulse signals. In yet another embodiment, the rotation position detector 24d may be a pulse encoder.

[0086] The reciprocating tool 1 includes a power supply line Lp extending from the positive terminal of the battery pack 12 attached to the battery attachment section 11 to the controller 23. The reciprocating tool 1 includes a ground line Ln extending from the negative terminal of the battery pack 12 attached to the battery attachment section 11 to the controller 23. The ground line Ln is connected to the ground of the reciprocating tool 1 on the controller 23. The battery pack 12 applies its output voltage (hereinafter referred to as battery voltage) between the power supply line Lp and the ground line Ln.

[0087] The controller 23 includes a control circuit 51. In this embodiment, the control circuit 51 includes a microcomputer 51a. The microcomputer 51a includes a CPU (not shown), a ROM (not shown), a RAM (not shown), an analog-to-digital (AD) converter (not shown), an input port (not shown), and an output port (not shown). In another embodiment, the control circuit 51 may include an additional microcomputer. In yet another embodiment, the control circuit 51 may include, in addition to or instead of the microcomputer 51a, a logic circuit (or a wired logic connection) including two or more electronic components. In yet another embodiment, the control circuit 51 may include, in addition to or instead of the microcomputer 51a, an ASIC and / or an ASSP. In yet another embodiment, the control circuit 51 may include, in addition to or instead of the microcomputer 51a, a PLD on which a reconfigurable logic circuit can be configured. An example of a PLD includes an FPGA. The control circuit 51 is connected to the rotational position detector 24d. The control circuit 51 is configured to (i) receive first to third pulse signals from the rotational position detector 24d, and (ii) recognize the rotational position of the rotor 26 based on the received first to third pulse signals.

[0088] The control circuit 51 is connected to the main power switch 36. The main power switch 36 has (i) a first contact connected to the ground of the reciprocating tool 1 and (ii) a second contact connected to the control circuit 51. Therefore, the main power switch 36 is configured to output a first negative logic signal to the control circuit 51 in response to the main power switch 36 being pressed (i.e., turned on). The control circuit 51 is configured to recognize that the main power switch 36 is turned on based on the control circuit 51 receiving the first negative logic signal from the main power switch 36.

[0089] The control circuit 51 is connected to the mode selection switch 37. The mode selection switch 37 has (i) a first contact connected to the ground of the reciprocating tool 1 and (ii) a second contact connected to the control circuit 51. Therefore, the mode selection switch 37 is configured to output a second negative logic signal to the control circuit 51 in response to the mode selection switch 37 being pressed (i.e., turned on). The control circuit 51 is configured to recognize that the mode selection switch 37 is turned on based on the second negative logic signal received from the mode selection switch 37.

[0090] The control circuit 51 is connected to the contact switch 20. The contact switch 20 has (i) a first contact connected to the ground of the reciprocating tool 1 and (ii) a second contact connected to the control circuit 51. Therefore, the contact switch 20 is configured to output a third negative logic signal to the control circuit 51 in response to the contact switch 20 being pressed (i.e., turned on) by the pressing member 6 being pressed against the workpiece. The control circuit 51 is configured to recognize that the contact switch 20 is turned on based on the fact that the control circuit 51 receives the third negative logic signal from the contact switch 20.

[0091] The control circuit 51 is connected to the first Hall element 34a. The first Hall element 34a is configured to output a first position detection signal to the control circuit 51 in response to the first Hall element 34a detecting the south pole of the first magnet 32. In this embodiment, the first position detection signal is a negative logic signal. In another embodiment, the first position detection signal may be a positive logic signal.

[0092] The control circuit 51 is connected to the second Hall element 34b. The second Hall element 34b is configured to output a second position detection signal to the control circuit 51 in response to the second Hall element 34b detecting the north pole of the second magnet 33. In this embodiment, the second position detection signal is a negative logic signal. In another embodiment, the second position detection signal may be a positive logic signal.

[0093] The control circuit 51 is configured to (i) be connected to the first indicator 38, and (ii) output a first lighting signal to the first indicator 38. The first indicator 38 is configured to light up upon receiving the first lighting signal from the control circuit 51.

[0094] The control circuit 51 is configured to (i) be connected to the second indicator 39, and (ii) output a second lighting signal to the second indicator 39. The second indicator 39 is configured to light up upon receiving the second lighting signal from the control circuit 51.

[0095] The controller 23 includes a power supply circuit 52 connected to (i) a first contact of the main power switch 36, (ii) a control circuit 51, (iii) a power supply line Lp, and (iv) ground. The main power switch 36 is configured to output a first negative logic signal to the power supply circuit 52 in addition to the control circuit 51. The control circuit 51 is configured to output a remote control (RC) signal to the power supply circuit 52. In this embodiment, the RC signal is a negative logic signal. In another embodiment, the RC signal may be a positive logic signal.

[0096] The power supply circuit 52 is configured to maintain its ON state (i) while receiving a first negative logic signal from the main power switch 36, or (ii) while receiving an RC signal from the control circuit 51. In its ON state, the power supply circuit 52 is configured to generate a fixed DC voltage (hereinafter referred to as the power supply voltage) Vc based on the battery voltage. The power supply voltage Vc generated by the power supply circuit 52 is supplied to the rotational position detector 24d, the first Hall element 34a, the second Hall element 34b, the first indicator 38, the second indicator 39, and various circuits on the controller 23 via paths not shown.

[0097] The controller 23 includes a voltage measurement circuit 53 configured to (i) measure the battery voltage on the power supply line Lp and (ii) output a battery voltage signal to the control circuit 51. The battery voltage signal is an analog signal having a voltage corresponding to the measured battery voltage.

[0098] The controller 23 includes a first latch circuit 54 connected to (i) the first contact of the contact switch 20 and (ii) the second Hall element 34b. The first latch circuit 54 is configured to (i) hold its output (POS) negative (or LOW) in response to a falling edge of the second position detection signal output from the second Hall element 34b, and (ii) reset its output to positive (or HIGH) in response to a third negative logic signal output from the contact switch 20.

[0099] The controller 23 includes a drive circuit 55 connected to a control circuit 51. The control circuit 51 is configured to output first to sixth pulse width modulation (PWM) signals to the drive circuit 55. The first to sixth PWM signals share the same cycle. The drive circuit 55 is configured to drive the electric motor 24 in accordance with the first to sixth PWM signals received from the control circuit 51.

[0100] More specifically, the drive circuit 55 includes a signal amplifier (or level shifter) 55a configured to amplify the first to sixth PWM signals received from the control circuit 51.

[0101] The drive circuit 55 includes first to sixth switches Q1 to Q6 that form a three-phase full-bridge circuit. The first to third switches Q1 to Q3 function as high-side switches of the three-phase full-bridge circuit and are connected to (i) the power supply line Lp and (ii) the first to third coils 24a to 24c. The fourth to sixth switches Q4 to Q6 function as low-side switches of the three-phase full-bridge circuit and are connected to (i) the first to third coils 24a to 24 and (ii) ground.

[0102] The first to sixth switches Q1 to Q6 are configured to receive the first to sixth PWM signals amplified by the signal amplifier 55a, respectively, and transition to their respective on or off states. In this embodiment, the first to sixth switches Q1 to Q6 are n-channel metal-oxide-semiconductor field-effect transistors (MOSFETs). In another embodiment, at least one of the first to sixth switches Q1 to Q6 may be another type of semiconductor switch, including a junction field-effect transistor (JFET), a bipolar transistor, and an insulated gate bipolar transistor (IGBT). In yet another embodiment, each of or at least one of the first to sixth switches Q1 to Q6 may be a mechanical relay.

[0103] The controller 23 includes a first signal blocking circuit 56 configured to block the first to third PWM signals output from the control circuit 51. More specifically, the first signal blocking circuit 56 is configured to (i) be disabled while the output (POS) of the first latch circuit 54 is positive, and (ii) be enabled while the output of the first latch circuit 54 is negative. When the first signal blocking circuit 56 is disabled, the first to third PWM signals are transmitted to the drive circuit 55 via the first signal blocking circuit 56. When the first signal blocking circuit 56 is enabled, the first to third PWM signals are blocked from the drive circuit 55 by the first signal blocking circuit 56.

[0104] In this embodiment, the first signal blocking circuit 56 includes wired logic. More specifically, the first signal blocking circuit 56 includes first to third AND gates 56a to 56c. The first to third AND gates 56a to 56c are configured to (i) transmit the first to third PWM signals to the drive circuit 55 while the output of the first latch circuit 54 is positive, and (ii) block the first to third PWM signals from the drive circuit 55 by setting their respective outputs to negative (or LOW) while the output of the first latch circuit 54 is negative.

[0105] The controller 23 includes a current measurement circuit 57 (i) interconnected between the drive circuit 55 and ground, and (ii) configured to measure the magnitude of a current (hereinafter referred to as a motor current) flowing through the electric motor 24. The current measurement circuit 57 includes a shunt resistor R1. The shunt resistor R1 has (i) a first end connected to the fourth to sixth switches Q4 to Q6, and (ii) a second end connected to ground.

[0106] The current measurement circuit 57 includes a differential amplifier OP1 configured to (i) measure the magnitude of the motor current flowing through the shunt resistor R1 and (ii) output a current measurement signal. More specifically, the differential amplifier OP1 is configured to amplify the voltage across the shunt resistor R1 to generate the current measurement signal. The current measurement signal is therefore an analog signal having a voltage corresponding to the magnitude of the motor current. The differential amplifier OP1 may be configured in an open-loop configuration without a negative feedback circuit from its output to its input, or in a closed-loop configuration with such a negative feedback circuit. The control circuit 51 is configured to receive the current measurement signal.

[0107] The current measurement circuit 57 includes a comparator CP1 configured to detect when the trigger switch 21 is turned on. More specifically, the comparator CP1 is configured to (i) compare the voltage of the current measurement signal with a preset reference voltage Vref, (ii) set its output to positive (or HIGH) in response to the voltage of the current measurement signal being greater than the reference voltage Vref, and (iii) set its output to negative (or LOW) in response to the voltage of the current measurement signal being equal to or less than the reference voltage Vref. The reference voltage Vref is equal to or approximates the voltage of the current measurement signal when insufficient motor current, as described below, flows through the electric motor 24.

[0108] The controller 23 includes a second latch circuit 58 configured to hold the output (CUR) of the comparator CP1 positive (or HIGH) when the output of the comparator CP1 is positive. The second latch circuit 58 is configured to hold the output of the comparator CP1 positive for a period of time at least equal to or longer than the periods of the first to sixth PWM signals (e.g., 100 milliseconds) each time the output of the comparator CP1 transitions from negative to positive. The control circuit 51 is configured to receive the output of the second latch circuit 58.

[0109] The trigger switch 21 interconnects (i) the power supply line Lp and (ii) the first to third switches Q1 to Q3. More specifically, the trigger switch 21 has (i) a first contact connected to the power supply line Lp and (ii) a second contact connected to the first to third switches Q1 to Q3, and is configured to establish or block conduction between the power supply line Lp and the first to third switches Q1 to Q3.

[0110] The controller 23 includes a seventh switch Q7 connected to (i) the first contact and (ii) the second contact of the trigger switch 21. The seventh switch Q7 is configured to (i) establish electrical continuity between the first and second contacts of the trigger switch 21 in its on state, and (ii) disconnect the first and second contacts of the trigger switch 21 in its off state. Therefore, the seventh switch Q7 is configured to (i) connect the power supply line Lp to the first to third switches Q1 to Q3 via the seventh switch Q7 while the trigger switch 21 is in its off state and the seventh switch Q7 is in its on state, and (ii) disconnect the power supply line Lp from the first to third switches Q1 to Q3 while the trigger switch 21 is in its off state and the seventh switch Q7 is also in its off state. In this embodiment, the seventh switch Q7 is an n-channel MOSFET. In other embodiments, the seventh switch Q7 may be other types of semiconductor switches, including JFETs, bipolar transistors, IGBTs, and SSRs, and in yet other embodiments, the seventh switch Q7 may be a mechanical relay.

[0111] The control circuit 51 is configured to output (i) a switch-on signal for turning on the seventh switch Q7, and (ii) a switch-off signal for turning off the seventh switch Q7. In this embodiment, the switch-on signal is a positive logic signal, and the switch-off signal is a negative logic signal. In another embodiment, the switch-on signal may be a negative logic signal, and the switch-off signal may be a positive logic signal.

[0112] The controller 23 includes a second signal blocking circuit 59 configured to block the switch-on signal output from the control circuit 51. More specifically, the second signal blocking circuit 59 is configured to (i) be disabled while the output (CUR) of the second latch circuit 58 is positive, and (ii) be enabled while the output of the second latch circuit 58 is negative. When the second signal blocking circuit 59 is disabled, the switch-on signal is transmitted to the seventh switch Q7 via the second signal blocking circuit 59. When the second signal blocking circuit 59 is enabled, the switch-on signal is blocked from the seventh switch Q7 by the second signal blocking circuit 59.

[0113] In this embodiment, the second signal blocking circuit 59 includes wired logic. More specifically, the second signal blocking circuit 59 includes a fourth AND gate 59a. The fourth AND gate 59a is configured to (i) transmit a switch-on signal to the seventh switch Q7 while the output of the second latch circuit 58 is positive, and (ii) set the output of the fourth AND gate 59a to negative (or LOW) to block the switch-on signal from the seventh switch Q7 while the output of the second latch circuit 58 is negative.

[0114] The controller 23 includes an electrolytic capacitor C1 configured to supply a stable motor current to the electric motor 24. The electrolytic capacitor C1 has (i) an anode connected to the first contact of the trigger switch 21 and (ii) a cathode connected to ground. In another embodiment, the electrolytic capacitor C1 may be eliminated. 2-4. Electrical operation of reciprocating tools The electrical configuration described above operates as follows.

[0115] As shown in FIG. 7, when the power supply circuit 52 is in the ON state, if the pressing member 6 is pressed against the workpiece and the contact switch 20 is turned ON, the output (POS) of the first latch circuit 54 is held positive (or HIGH), and the first signal blocking circuit 56 is disabled. The control circuit 51 recognizes the rotational position of the rotor 26 based on the first to third pulse signals received from the rotational position detector 24d. The control circuit 51 selects (i) one of the high-side switches and (ii) one of the low-side switches according to a first table stored in ROM, and outputs PWM signals corresponding to the selected switches. The first table specifies the combination of the high-side switch and the low-side switch to be selected in association with the rotational position of the rotor 26. The first table is set to select a combination of the high-side switch and the low-side switch that will cause the rotor 26 to fail to rotate. More specifically, in this embodiment, the first table is set to select (i) a combination of high-side switches and low-side switches that generates a magnetic field that attracts the first pole 26a of the rotor 26 to the coil (any of the first to third coils 24a to 24c) facing the first pole 26a, or (ii) a combination of high-side switches and low-side switches that generates a magnetic field that attracts the second pole 26b to the coil (any of the first to third coils 24a to 24c) facing the second pole 26b of the rotor 26.

[0116] Each of the corresponding PWM signals has an initial duty ratio that is greater than zero but insufficient (e.g., 10%) to start the electric motor 24. Such an initial duty ratio causes the selected high-side switch and the selected low-side switch to supply insufficient motor current to the corresponding one of the first to third coils 24a to 24c. The rotor 26 is configured not to rotate due to the insufficient motor current.

[0117] When the trigger switch 21 is turned on and insufficient motor current flows, the output (CUR) of the second latch circuit 58 is held positive (or HIGH), disabling the second signal blocking circuit 59. When the control circuit 51 recognizes that the trigger switch 21 is turned on based on the positive output of the second latch circuit 58, it transmits a switch-on signal to the seventh switch Q7, turning on the seventh switch Q7. The control circuit 51 then performs a soft start. During the soft start, the control circuit 51 selects (i) one of the high-side switches and (ii) one of the low-side switches according to a second table stored in ROM and outputs PWM signals corresponding to the selected switches. The second table specifies the combination of the high-side switch and the low-side switch to be selected in association with the rotational position of the rotor 26. The second table is configured to select a combination of the high-side switch and the low-side switch that contributes to rotating the rotor 26. During the soft start, the control circuit 51 gradually increases the duty ratio of each of the corresponding PWM signals.

[0118] When the soft start is completed, the control circuit 51 sets the duty ratio of the PWM signal corresponding to the selected high-side switch and the selected low-side switch to 100%.

[0119] When the first Hall element 34a detects that the reciprocating member 18 has reached the stop preparation position, the control circuit 51 starts preparations to stop the electric motor 24. Specifically, the control circuit 51 calculates the remaining drive time of the electric motor 24. When the calculated remaining drive time has elapsed, the control circuit 51 sets the duty ratios of all of the first to sixth PWM signals to 0% and causes the electric motor 24 to transition to a free-run state.

[0120] Subsequently, when the second Hall element 34b detects that the reciprocating member 18 has reached the standby position, (i) the output (POS) of the first latch circuit 54 is reset to negative (or LOW), (ii) the first signal cut-off circuit 56 is enabled, and (iii) the first to third PWM signals are cut off from the first to third switches Q1 to Q3 by the first signal cut-off circuit 56. Almost simultaneously, the control circuit 51 outputs PWM signals having a predetermined duty ratio (for example, 100%) to at least two of the fourth to sixth switches Q4 to Q6 so as to generate short-circuit braking (or regenerative braking) in the electric motor 24. This generates short-circuit braking in the electric motor 24, and the electric motor 24 stops.

[0121] When the control circuit 51 recognizes that the electric motor 24 has stopped based on the first to third pulse signals, a switch-off signal is transmitted from the control circuit 51 to the seventh switch Q7, turning off the seventh switch Q7. 2-4-1.Low voltage drive operation The battery voltage may drop significantly if a large motor current flows through the electric motor 24 while the electric motor 24 is running. This may occur when the battery pack 12 has a large internal impedance due to a low temperature of the battery pack 12.

[0122] When such an event occurs, the control circuit 51 of this embodiment drives the electric motor 24 at a low voltage. Specifically, the ROM of the control circuit 51 stores a first threshold voltage Vth1 and a second threshold voltage Vth2. The first threshold voltage Vth1 is lower than the rated voltage of the battery pack 12. The second threshold voltage Vth2 corresponds to the lower limit of the battery voltage required for the power supply circuit 52 to generate the power supply voltage Vc.

[0123] 8, when the electric motor 24 starts to drive and the battery voltage falls below the first threshold voltage Vth1, the control circuit 51 sets the output duty ratio of each of the PWM signals corresponding to the selected high-side switch and the selected low-side switch to a lower limit duty ratio. The lower limit duty ratio corresponds to the duty ratio at which the electric motor 24 generates the minimum driving force required to drive the reciprocating member 18.

[0124] When the motor current decreases due to the lower limit duty ratio and the battery voltage returns to the first threshold voltage Vth1, the control circuit 51 gradually increases the output duty ratio of each corresponding PWM signal at a predetermined rate over time. The gradual increase in the output duty ratio gradually increases the motor current. When the battery voltage falls below the first threshold voltage Vth1 again due to this increase in motor current, the control circuit 51 gradually decreases the output duty ratio of each corresponding PWM signal at a predetermined rate over time.

[0125] The control circuit 51 continues this low voltage driving until the reciprocating member 18 reaches the return position. In this embodiment, the first threshold voltage Vth1 is set higher than the second threshold voltage Vth2 so that the battery voltage exceeds the second threshold voltage Vth2 when the control circuit 51 adjusts the output duty ratio as described above.

[0126] The ROM of the control circuit 51 further stores a third threshold voltage Vth3 and a fourth threshold voltage Vth4. The third threshold voltage Vth3 is (i) higher than the first threshold voltage Vth1 and (ii) lower than the rated voltage of the battery pack 12. The fourth threshold voltage Vth4 is (i) higher than the first threshold voltage Vth1 and (ii) lower than the third threshold voltage Vth3.

[0127] As shown in FIG. 9, the control circuit 51 prohibits output of a PWM signal for the nth drive of the electric motor 24 if (i) the battery voltage falls below the third threshold voltage Vth3 before the (n-1)th drive (n is an integer greater than or equal to 2) of the electric motor 24, and (ii) the battery voltage falls below the fourth threshold voltage Vth during the (n-1)th drive of the electric motor 24.

[0128] If the battery voltage exceeds the third threshold voltage Vth3 before the (n-1)th drive of the electric motor 24, the control circuit 51 allows the output of a PWM signal for the nth drive of the electric motor 24 even if the battery voltage falls below the fourth threshold voltage Vth during the (n-1)th drive of the electric motor 24. 2-5. Operation mode of reciprocating tools As described above, the reciprocating tool 1 is configured to be switched between the single-shot mode and the continuous-shot mode. The operation of the reciprocating tool 1 in the single-shot mode and the continuous-shot mode will be outlined below.

[0129] In the single shot mode, when the trigger 9 is pulled with the pressing member 6 pressed against the workpiece, the reciprocating tool 1 drives one nail into the workpiece. In the single shot mode, the reciprocating tool 1 does not drive a nail when the trigger 9 is pulled and the pressing member 6 is pressed against the workpiece.

[0130] In the continuous firing mode, the reciprocating tool 1 drives one nail into the workpiece each time the pressing member 6 is pressed against the workpiece with the trigger 9 pulled. 2-6. Processing performed by the control circuit The processing executed by the control circuit 51 (more specifically, the microcomputer 51a) will be described in detail below. 2-6-1.Main routine During its operation, the control circuit 51 repeatedly executes a main routine shown in FIG.

[0131] 10, the control circuit 51 first waits until a preset time base has elapsed in S110 (S110: NO). When the time base has elapsed (S110: YES), the control circuit 51 proceeds sequentially from S120 to S170.

[0132] In S120, the control circuit 51 executes AD conversion processing, in which the control circuit 51 converts the battery voltage signal and the current measurement signal into respective digital values, and stores the respective digital values ​​in the RAM.

[0133] In S130, the control circuit 51 executes a switch determination process. In the switch determination process, the control circuit 51 stores in RAM the logic (positive or negative, or HIGH or LOW, or 1 or 0) of the voltages received from the main power switch 36, the mode selection switch 37, the contact switch 20, the first Hall element 34a, the second Hall element 34b, and the second latch circuit 58.

[0134] In S140, the control circuit 51 executes a standby determination process, in which the control circuit 51 determines whether or not to transition the reciprocating tool 1 to a standby state.

[0135] In S150, the control circuit 51 executes a malfunction determination process. In the malfunction determination process, the control circuit 51 determines whether an error flag is set. The error flag is (i) set when a malfunction has occurred, and (ii) cleared when no malfunction has occurred. If the error flag is set, the control circuit 51 executes a predetermined operation corresponding to the malfunction.

[0136] In S160, the control circuit 51 executes a motor control process, the details of which will be described later. In S170, the control circuit 51 executes a display process. In the display process, the control circuit 51 lights up the first indicator 38 or the second indicator 39 depending on the set operation mode. More specifically, when the reciprocating tool 1 is set to the single-shot mode, the control circuit 51 outputs a first lighting signal to the first indicator 38. When the reciprocating tool 1 is set to the continuous-shot mode, the control circuit 51 outputs a second lighting signal to the second indicator 39. In addition, when an error flag is set, the control circuit 51 outputs the first lighting signal and the second lighting signal to the first indicator 38 and the second indicator 39, respectively. 2-6-2.Interrupt processing In addition to the above-described main routine, the control circuit 51 executes an interrupt process (not shown). In this interrupt process, the control circuit 51 stores the logic (positive or negative, or HIGH or LOW, or 1 or 0) of the voltages of the first to third pulse signals in RAM. In this embodiment, the control circuit 51 periodically and repeatedly executes the interrupt process. In another embodiment, the control circuit 51 may execute the interrupt process in response to the edges or voltage levels of the first to third pulse signals or other signals. 2-6-3.Motor control processing As shown in FIG. 11, in the motor control process, the control circuit 51 first determines in S310 whether or not the contact switch 20 is turned on based on the logic of the voltage of the contact switch 20 stored in the RAM.

[0137] If the contact switch 20 is turned off (S310: NO), the control circuit 51 immediately ends the motor control process. If the contact switch 20 is turned on (S310: YES), the control circuit 51 proceeds to S320. In S320, the control circuit 51 outputs corresponding PWM signals to the selected high-side switch and the selected low-side switch (i.e., the combination of the high-side switch and the low-side switch that fails to rotate the rotor 26). The corresponding PWM signals have the initial duty ratio described above.

[0138] In the next step S330, the control circuit 51 determines whether a first predetermined time (for example, 5 seconds) has elapsed since the start of output of the corresponding PWM signal. The first predetermined time is set to prevent a nail from being accidentally ejected when the pressing member 6 is held in a state pressed against an object against the user's intention. If the first predetermined time has elapsed (S330: YES), the control circuit 51 proceeds to step S340, where it stops outputting the corresponding PWM signal and ends the motor control process.

[0139] If the first predetermined time has not elapsed (S330: NO), the control circuit 51 proceeds to S350 and determines whether the trigger switch 21 is on or not based on the logic of the output of the second latch circuit 58 stored in RAM. If the trigger switch 21 is off (S350: NO), the control circuit 51 immediately ends the motor control process.

[0140] If the trigger switch 21 is turned on (S350: YES), the control circuit 51 proceeds to S360 and determines whether the reciprocating tool 1 is set to the continuous mode. More specifically, the control circuit 51 determines whether the continuous mode flag is set. When the control circuit 51 is started, the continuous mode flag is cleared. In the reciprocating tool 1, the operating mode of the reciprocating tool 1 is switched between the single mode and the continuous mode every time the user presses the mode selection switch 37. Therefore, the control circuit 51 sets or clears the continuous mode flag based on the logic of the voltage of the mode selection switch 37 stored in the RAM.

[0141] If the reciprocating tool 1 is set to the continuous mode (S360: YES), the control circuit 51 proceeds to S362 and determines whether the battery voltage before the previous ((n-1)th) driving of the electric motor 24 was below the third threshold voltage Vth3, based on the digital value of the battery voltage stored in the RAM up to that point.

[0142] If the battery voltage before the previous drive of the electric motor 24 was equal to or higher than the third threshold voltage Vth3 (S362: NO), the control circuit 51 proceeds to S370. If the battery voltage before the previous drive of the electric motor 24 was lower than the third threshold voltage Vth3 (S362: YES), the control circuit 51 proceeds to S364.

[0143] In S364, the control circuit 51 determines whether the battery voltage was lower than the fourth threshold voltage Vth4 during the previous driving of the electric motor 24, based on the digital value of the battery voltage stored in the RAM up to that point.

[0144] If the battery voltage during the previous drive of the electric motor 24 was below the fourth threshold voltage Vth4 (S364: YES), the control circuit 51 proceeds to S400. If the battery voltage during the previous drive of the electric motor 24 was equal to or higher than the fourth threshold voltage Vth4 (S364: NO), the control circuit 51 proceeds to S370 and sets a driving permission flag. The driving permission flag indicates that driving a nail is permitted. In the following S380, the control circuit 51 outputs a switch-on signal to the seventh switch Q7 to turn on the seventh switch Q7, and proceeds to S410.

[0145] If the reciprocating tool 1 is set to the single-shot mode (S360: NO), the control circuit 51 proceeds to S390 and determines whether a second predetermined time (e.g., 50 milliseconds) has elapsed. The second predetermined time is set to prevent the reciprocating tool 1 from driving a nail when an operation prohibited in the single-shot mode, such as pressing the pressing member 6 against a workpiece while the trigger 9 is pulled, is performed. If the second predetermined time has elapsed (S390: YES), the control circuit 51 proceeds to S370.

[0146] If the second predetermined time has not elapsed (S390: NO), the control circuit 51 proceeds to S400 and clears the driving permission flag. In the next step S410, the control circuit 51 executes a drive process, the details of which will be described later.

[0147] In the following step S420, the control circuit 51 executes a stop process. In the stop process, the control circuit 51 clears the motor stop flag. The motor stop flag indicates that the electric motor 24 is stopped. Next, based on the logic of the voltage of the first Hall element 34a stored in the RAM, it is determined whether the reciprocating member 18 is located in the stop preparation position. If the reciprocating member 18 is located in the stop preparation position, the control circuit 51 calculates the remaining drive time of the electric motor 24. When the calculated remaining drive time has elapsed, the control circuit 51 sets the duty ratios of all of the first to sixth PWM signals to 0% and causes the electric motor 24 to transition to a free-run state.

[0148] Next, the control circuit 51 determines whether the reciprocating member 18 is located at the standby position based on the logic of the voltage of the second Hall element 34b stored in the RAM. If the reciprocating member 18 is located at the standby position, the control circuit 51 outputs PWM signals having a predetermined duty ratio (for example, 100%) to at least two of the fourth to sixth switches Q4 to Q6 so as to generate short-circuit braking in the electric motor 24.

[0149] Next, the control circuit 51 determines whether or not the electric motor 24 is stopped based on the logic of the voltages of the first to third pulse signals stored in the RAM up to that point. If the electric motor 24 is stopped, the control circuit 51 sets a motor stop flag.

[0150] When this stopping process is completed, the control circuit 51 proceeds to S430 and determines whether or not the electric motor 24 is stopped. More specifically, the control circuit 51 determines whether or not a motor stop flag is set.

[0151] If the electric motor 24 is not stopped (i.e., the motor stop flag is cleared) (S430: NO), the control circuit 51 proceeds to S440. In S440, the control circuit 51 outputs a switch-on signal to the seventh switch Q7 to turn on the seventh switch Q7. In other words, the control circuit 51 continues to output the switch-on signal to the seventh switch Q7 to maintain the seventh switch Q7 in its on state.

[0152] If the electric motor 24 is stopped (i.e., the motor stop flag is set) (S430: YES), the control circuit 51 proceeds to S450. In S450, the control circuit 51 outputs a switch-off signal to the seventh switch Q7 to turn off the seventh switch Q7. 2-6-3-1. Drive processing As shown in FIG. 12, in the drive process, the control circuit 51 first executes a soft start process in S510.

[0153] In the soft start process, if the driving permission flag is set, the control circuit 51 executes the soft start described above. When the soft start is completed, the control circuit 51 sets the duty ratio of the PWM signal output to the selected high-side switch and the selected low-side switch (i.e., the high-side switch and the low-side switch that contribute to rotating the rotor 26) to 100%.

[0154] If the drive permission flag is cleared or if the soft start is completed, the control circuit 51 immediately ends the soft start process. In the next step S520, the control circuit 51 executes a low-voltage drive determination process, the details of which will be described later.

[0155] In the next step S530, the control circuit 51 executes an output duty ratio setting process, the details of which will be described later. 2-6-3-1-1. Low voltage drive determination process 13, in the low-voltage drive determination process, the control circuit 51 first determines whether the drive permission flag is set in S600. If the drive determination flag is cleared (S600: NO), the control circuit 51 immediately ends the low-voltage drive determination process.

[0156] If the driving permission flag is set (S600: YES), the control circuit 51 determines whether the electric motor 24 is stopped based on the motor stop flag.

[0157] If the electric motor 24 is stopped (S610: YES), the control circuit 51 proceeds to S640, and if the electric motor 24 is driven (S610: NO), the control circuit 51 proceeds to S620. In S620, the control circuit 51 determines whether the battery voltage is lower than the first threshold voltage Vth1 based on the digital value of the battery voltage stored in RAM.

[0158] If the battery voltage is lower than the first threshold voltage Vth1 (S620: YES), the control circuit 51 proceeds to S630 and sets a low-voltage drive flag, which indicates that low-voltage drive is required.

[0159] If the battery voltage is equal to or higher than the first threshold voltage Vth1 (S620: NO), the control circuit 51 proceeds to S640 and clears the low voltage drive flag. 2-6-3-1-2. Output duty ratio setting process 14A and 14B, in the output duty ratio setting process, the control circuit 51 first determines whether the drive permission flag is set in S700. If the drive permission flag is cleared (S700: NO), the control circuit 51 immediately ends the output duty ratio setting process.

[0160] If the driving permission flag is set (S700: YES), the control circuit 51 proceeds to S710 and determines whether the electric motor 24 is stopped based on the motor stop flag. If the electric motor 24 is stopped (S710: YES), the control circuit 51 immediately ends the output duty ratio setting process.

[0161] If the electric motor 24 is being driven (S710: NO), the control circuit 51 proceeds to S720 and sets the target duty ratio to 100%. Next, in S730, the control circuit 51 determines whether the low voltage drive flag is set. If the low voltage drive flag is cleared (S730: NO), the control circuit 51 proceeds to S740, sets the reduced duty ratio to zero, and proceeds to S800.

[0162] If the low voltage drive flag is set (S730: YES), the control circuit 51 proceeds to S750 and determines whether the set low voltage drive flag is the first low voltage drive flag. If it is the first low voltage drive (S750: YES), the control circuit 51 proceeds to S760 and sets the reduced duty ratio to the upper limit (50% in this embodiment), and then proceeds to S800.

[0163] If the set low voltage drive flag is the second or subsequent low voltage drive flag (S750: NO), the control circuit 51 proceeds to S770 and determines whether the battery voltage is lower than the first threshold voltage Vth1.

[0164] If the battery voltage is lower than the first threshold voltage Vth1 (S770: YES), the control circuit 51 proceeds to S780, where it increases the reduced duty ratio by a predetermined amount (3% in this embodiment), and then proceeds to S800.

[0165] If the battery voltage is equal to or higher than the first threshold voltage Vth1 (S770: NO), the control circuit 51 proceeds to S790 to decrease the reduced duty ratio by a predetermined amount, and then proceeds to S800.

[0166] In S800, the control circuit 51 subtracts the reduced duty ratio from the target duty ratio, and proceeds to S810. In S810, the control circuit 51 determines whether the target duty ratio is less than the lower limit duty ratio. If the target duty ratio is equal to or greater than the lower limit duty ratio (S810: NO), the control circuit 51 proceeds to S830.

[0167] If the target duty ratio is less than the lower limit duty ratio (S810: YES), the control circuit 51 proceeds to S820 and sets the target duty ratio to the lower limit duty ratio.

[0168] In the next step S830, the control circuit 51 determines whether the target duty ratio is greater than the output duty ratio. If the target duty ratio is greater than the output duty ratio (S830: YES), the control circuit 51 proceeds to step S840 and increases the output duty ratio by a preset amount (3% in this embodiment).

[0169] Next, in S850, the control circuit 51 determines whether the target duty ratio is less than the output duty ratio. If the target duty ratio is less than the output duty ratio (S850: YES), the control circuit 51 proceeds to S880. If the target duty ratio is equal to or greater than the output duty ratio (S850: NO), the control circuit 51 ends the output duty ratio setting process.

[0170] In S830, if the target duty ratio is equal to or less than the output duty ratio (S830: NO), the control circuit 51 proceeds to S860 and reduces the output duty ratio by a preset amount (3% in this embodiment).

[0171] Next, in S870, the control circuit 51 determines whether the target duty ratio is greater than the output duty ratio. If the target duty ratio is equal to or less than the output duty ratio (S870: NO), the control circuit 51 ends the output duty ratio setting process. If the target duty ratio is greater than the output duty ratio (S870: YES), the control circuit 51 proceeds to S880.

[0172] In S880, control circuit 51 sets the output duty ratio to the target duty ratio, and ends the output duty ratio setting process. Through the output duty ratio setting process described above, the control circuit 51 sets the output duty ratios of the PWM signals corresponding to the selected high-side switch and the selected low-side switch, and as a result, the PWM signals having the set output duty ratios are supplied to the selected high-side switch and the selected low-side switch. 2-7. Technical Effects of the Embodiments In the reciprocating tool 1 configured as described above, even if the battery voltage falls below the first threshold voltage Vth1 while the electric motor 24 is being driven, the electric motor 24 can continue to be driven, and thus the reciprocating member 18 can be prevented from stopping at an inappropriate position.

[0173] Furthermore, the reciprocating tool 1 can prevent the battery voltage from falling below the second threshold voltage Vth2 while the electric motor 24 is running, causing the control circuit 51 to stop operating and the reciprocating member 18 to stop in an inappropriate position.

[0174] Furthermore, in the reciprocating tool 1, the lower limit duty ratio is set in the first low-voltage driving, so that the motor current flowing from the battery pack 12 to the electric motor 24 can be quickly reduced without stopping the reciprocating member 18. As a result, the battery voltage can be quickly increased.

[0175] Furthermore, in the reciprocating tool 1, when the battery voltage changes from less than the first threshold voltage Vth1 to greater than or equal to the first threshold voltage Vth1 while the electric motor is operating, the battery voltage can rise while preventing excessive motor current from flowing to the electric motor 24.

[0176] Furthermore, in the reciprocating tool 1, when the battery voltage falls below the first threshold voltage Vth1 again, the motor current can be gradually reduced. Furthermore, in the reciprocating tool 1, the reciprocating member 18 can be driven from its bottom dead center to its top dead center with a torque proportional to the reduction ratio of the reducer 27. As a result, even if the motor current is significantly reduced while the electric motor 24 is running, the reciprocating member 18 can continue to be driven.

[0177] Furthermore, in the reciprocating tool 1, when the pressing member 6 is not pressed against the workpiece, that is, when the user is not processing the workpiece, it is possible to prevent the electric motor 24 from being erroneously driven. 2-8. Terminology In this embodiment, the top dead center of the reciprocating member 18 corresponds to an example of a first dead center in the generalization of the embodiments, and the bottom dead center of the reciprocating member 18 corresponds to an example of a second dead center in the generalization of the embodiments. Each of the first to sixth PWM signals corresponds to an example of a drive signal in the generalization of the embodiments, the trigger switch 21 corresponds to an example of a first manual switch in the generalization of the embodiments, the contact switch 20 corresponds to an example of a second manual switch in the generalization of the embodiments, and the battery pack 12 corresponds to an example of a battery in the generalization of the embodiments. 2-9. Variations The present disclosure is not limited to the above-described embodiment, and can be implemented in various modifications.

[0178] In some variations, the standby position of the reciprocating member 18 may be different from the position at which the reciprocating member 18 is stopped. 2-10. Supplementary Information In the above embodiments, multiple functions achieved by one component may be achieved by multiple components, and one function achieved by one component may be achieved by multiple components. Furthermore, multiple functions achieved by multiple components may be achieved by one component, and one function achieved by multiple components may be achieved by one component. Furthermore, part of the configuration of the above embodiments may be omitted. Furthermore, at least part of the configuration of one of the above embodiments may be added to or substituted for the configuration of another of the above embodiments. [Explanation of symbols]

[0179] 1... reciprocating tool, 2... housing, 3... driving assembly accommodating section, 4... injection section, 5... guide, 6... pressing member, 7... link mechanism, 8... grip, 9... trigger, 10... motor accommodating section, 11... battery mounting section, 12... battery pack, 13... magazine, 14... driving assembly, 15... cylinder, 16... piston, 17... bumper, 18... reciprocating member, 19... spring, 20... contact switch, 21... trigger switch, 22... connector, 23... controller, 24... electric motor, 24a to 24c... first to third coils, 24d... rotational position detector, 25... transmission device, 26... rotor, 26a... first pole, 26b... second pole, 27... reducer, 28... cam, 29a to 29i... first to ninth pins, 30a to 30i... first to ninth racks , 31...holder, 32...first magnet, 33...second magnet, 34...Hall IC, 34a...first Hall element, 34b...second Hall element, 36...main power switch, 37...mode selection switch, 38...first indicator, 39...second indicator, 51...control circuit, 52...power supply circuit, 53...voltage measurement circuit, 54...first latch circuit, 55...drive circuit, 55a...signal amplifier, 56...first signal blocking circuit, 56a to 56c...first to third AND gates, 57...current measurement circuit, 58...second latch circuit, 59...second signal blocking circuit, 59a...fourth AND gate, C1...electrolytic capacitor, CP1...comparator, Ln...ground line, Lp...power supply line, OP1...differential amplifier, Q1 to Q7...first to seventh switches, R1...shunt resistor.

Claims

1. A reciprocating tool, a reciprocating member configured to reciprocate between a first dead center and a second dead center; an electric motor configured to generate a driving force; a transmission device configured to transmit the driving force of the electric motor to the reciprocating member at least during a stroke of the reciprocating member from the second dead center to the first dead center; a drive circuit configured to (i) receive a drive signal for driving the electric motor, and (ii) supply a motor current from a battery to the electric motor in accordance with the received drive signal to drive the electric motor; a control circuit configured to (i) output the drive signal to the drive circuit and (ii) adjust the drive signal so that the drive circuit reduces the motor current and continues to drive the electric motor in response to a first condition being satisfied, the first condition being satisfied in response to (i) the drive circuit driving the electric motor and (ii) a battery voltage being lower than a first threshold voltage, the battery voltage being output from the battery, and the first threshold voltage being lower than a rated voltage of the battery; A reciprocating tool comprising:

2. The reciprocating tool according to claim 1, further comprising: a power supply circuit configured to generate a power supply voltage for operating the control circuit based on the battery voltage; the first threshold voltage is set higher than the second threshold voltage so that the battery voltage exceeds the second threshold voltage when the control circuit adjusts the drive signal in response to the first condition being satisfied; The second threshold voltage corresponds to a lower limit of the battery voltage required for the power supply circuit to generate the power supply voltage.

3. The reciprocating tool according to claim 1 or 2, the drive signal is in the form of a pulse width modulated signal having an output duty ratio; The drive circuit is configured to supply the motor current based on the output duty ratio to the electric motor.

4. The reciprocating tool according to claim 3, The control circuit is configured to reduce the output duty ratio to a duty ratio capable of driving the reciprocating member when the first condition is satisfied.

5. The reciprocating tool according to claim 4, the control circuit is configured to gradually increase the output duty ratio at a predetermined rate over time in response to a second condition being satisfied; the second condition is satisfied when (i) the drive circuit drives the electric motor, and (ii) the battery voltage changes from a first magnitude to a second magnitude; the first magnitude is less than the first threshold voltage; The second magnitude is greater than or equal to the first threshold voltage.

6. A reciprocating tool according to claim 4 or 5, the control circuit is configured to set the output duty ratio to a lower limit duty ratio when the first condition is satisfied; The reciprocating tool, wherein the lower limit duty ratio corresponds to a duty ratio at which the electric motor generates a minimum driving force required to drive the reciprocating member.

7. The reciprocating tool according to claim 6, the control circuit is configured to gradually decrease the output duty ratio at a predetermined rate over time in response to a third condition being satisfied; The reciprocating tool, wherein the third condition is met when the battery voltage falls below the first threshold voltage again after the output duty ratio is set to the lower limit duty ratio.

8. A reciprocating tool according to any one of claims 1 to 7, the control circuit is configured to prohibit output of the drive signal for an n-th drive of the electric motor (n is an integer of 2 or more) in response to the establishment of a fourth condition, the fourth condition is satisfied when (i) the battery voltage falls below a third threshold voltage before the (n-1)th driving of the electric motor, and (ii) the battery voltage falls below a fourth threshold voltage during the (n-1)th driving of the electric motor; the third threshold voltage is higher than the first threshold voltage; The reciprocating tool, wherein the fourth threshold voltage is (i) higher than the first threshold voltage and (ii) lower than the third threshold voltage.

9. The reciprocating tool according to claim 8, the control circuit is configured to permit output of the drive signal for driving the electric motor for the n-th time in response to a fifth condition being satisfied, The reciprocating tool, wherein the fifth condition is met when the battery voltage exceeds the third threshold voltage before the (n-1)th driving of the electric motor.

10. A reciprocating tool according to any one of claims 1 to 9, The transmission device is (i) a speed reducer having a preset reduction ratio; and (ii) a speed reducer configured to convert the driving force of the electric motor into a reduced output and transmit the reduced output to the reciprocating member. A reciprocating tool comprising:

11. The reciprocating tool according to any one of claims 1 to 10, further comprising: a first manual switch configured to be manually operated by a user of the reciprocating tool; The control circuit is configured to output the drive signal to the drive circuit in response to manual operation of at least the first manual switch.

12. The reciprocating tool according to claim 11, further comprising: a pressing member configured to be pressed against the workpiece by the user; a second manual switch configured to be manually operated by the pressing member being pressed against the workpiece; and Equipped with The control circuit is configured to output the drive signal to the drive circuit based on manual operation of both the first manual switch and the second manual switch.

13. A reciprocating tool according to any one of claims 1 to 12, a cylinder containing compressed gas therein; (i) a piston within the cylinder, (ii) urging the reciprocating member toward the second dead center by the compressed gas; Equipped with A reciprocating tool, wherein the reciprocating member is configured to be driven by the piston from the first dead center to the second dead center.

14. A reciprocating tool according to claim 13, The reciprocating member is configured to (i) be positioned at the first dead center in response to the piston being positioned at its top dead center, and (ii) be positioned at the second dead center in response to the piston being positioned at its bottom dead center.

15. A reciprocating tool according to any one of claims 1 to 14, The transmission device is a cam (i) having an outer periphery with a plurality of pins arranged in a circumferential direction of the cam; and (ii) a cam configured to be rotated by the driving force of the electric motor; The reciprocating member (i) extends between the first dead center and the second dead center, (ii) has a plurality of racks in its extension direction, and (iii) is configured to be driven from the second dead center to the first dead center by the plurality of racks engaging with each of the plurality of pins.

16. The reciprocating tool according to any one of claims 1 to 15, further comprising: A reciprocating tool comprising a battery mounting portion configured to removably mount the battery.

17. 1. A method for controlling an electric motor in a reciprocating tool, comprising: a drive signal for driving the electric motor is output to a drive circuit of the reciprocating tool, and the drive circuit is configured to supply a motor current from a battery to the electric motor in accordance with the drive signal to drive the electric motor; transmitting a driving force of the electric motor to a reciprocating member of the reciprocating tool, the reciprocating member being configured to reciprocate between a first dead center and a second dead center, and the driving force being transmitted at least from the second dead center to the first dead center; (i) the electric motor is being driven, and (ii) in response to a battery voltage being lower than a threshold voltage, the drive circuit adjusts the drive signal to reduce the motor current and continue to drive the electric motor, the battery voltage being output from the battery, and the threshold voltage being lower than a rated voltage of the battery; The method comprises:

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